CA2192859A1 - Radiation- and/or moisture-curable silicone compositions - Google Patents

Radiation- and/or moisture-curable silicone compositions

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Publication number
CA2192859A1
CA2192859A1 CA002192859A CA2192859A CA2192859A1 CA 2192859 A1 CA2192859 A1 CA 2192859A1 CA 002192859 A CA002192859 A CA 002192859A CA 2192859 A CA2192859 A CA 2192859A CA 2192859 A1 CA2192859 A1 CA 2192859A1
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Prior art keywords
silicone
radiation
composition
composition according
ethylenically unsaturated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
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CA002192859A
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French (fr)
Inventor
Hsien Kun Chu
Robert P. Cross
Lester D. Bennington
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Henkel Loctite Corp
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Individual
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Publication date
Priority claimed from US08/276,019 external-priority patent/US5498642A/en
Application filed by Individual filed Critical Individual
Publication of CA2192859A1 publication Critical patent/CA2192859A1/en
Abandoned legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00Processes of polymerisation
    • C08F2/46Polymerisation initiated by wave energy or particle radiation
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L83/00Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
    • C08L83/04Polysiloxanes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/68Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
    • B29C70/84Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks by moulding material on preformed parts to be joined
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04Polysiloxanes
    • C08G77/06Preparatory processes
    • C08G77/08Preparatory processes characterised by the catalysts used
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04Polysiloxanes
    • C08G77/14Polysiloxanes containing silicon bound to oxygen-containing groups
    • C08G77/18Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04Polysiloxanes
    • C08G77/20Polysiloxanes containing silicon bound to unsaturated aliphatic groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08KUse of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00Use of organic ingredients
    • C08K5/0008Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0025Crosslinking or vulcanising agents; including accelerators
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D4/00Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04Polysiloxanes
    • C08G77/14Polysiloxanes containing silicon bound to oxygen-containing groups
    • C08G77/16Polysiloxanes containing silicon bound to oxygen-containing groups to hydroxyl groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04Polysiloxanes
    • C08G77/22Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen
    • C08G77/26Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen nitrogen-containing groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/70Siloxanes defined by use of the MDTQ nomenclature
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00Apparatus or processes for manufacturing printed circuits
    • H05K3/22Secondary treatment of printed circuits
    • H05K3/28Applying non-metallic protective coatings
    • H05K3/285Permanent coating compositions
    • H05K3/287Photosensitive compositions

Abstract

A radiation and/or moisture-curable silicone composition, comprising: a silanol-containing silicone; a silane cross-linker for the silicone, such cross-linker having joined directly to a silicon atom thereof an ethylenically unsaturated functional group and at least two hydrolyzable functional groups; and a photoinitiator effective for radiation curing of the silicone composition. Also disclosed is a "liquid potting system" formulation, which is irradiated subsequent to dispensing thereof at the potting locus (64),so that a resulting radiation surface-cured skin layer (102) overlies and contains (cooperatively with the associated bounding surface(s) of the potting locus) the uncured liquid (100), whereby a potted structural element (66) is encapsulated in the uncured liquid (damping) medium.

Description

2 1 9 2 8 ~ 9 PCT/US95/08874 ~ 1 RADIATION- AND/OR MOISTURE-CURABLE SILICONE
COIUIPOSITIONS

DESCRIPTION

Field of the Invention The present invention relates to radiation- and/or moisture-curable silicone culllpo:~ilions, and to a method of making and using same.

Descli.,lion of the Related Art Silicone materials are widely used in industry as well as in consumer markets as sealants, adhesives, coatings, potting compounds, etc.

Such materials include the so-called room temperature vulcanizable (RT\I) silicones which are curable at ambient (room temperature) conditions, in the presence of alllloa~)helic moisture. Typically, RTV silicone materials are manufactured by enclcappi"g a, ~-silanol terminated silicones with various crosslinkers such as alkoxysilanes, oximinosilanes, WO 96/02579 2 ~ 9 2 8 5 9 PCT/US95~0887~

acetoxysilanes, d",i"o~ilanes, and other silanes with hydrolyzable groups attached to the silicon atom(s) thereof.

The resulting RTV silicone materials are stored in moisture 5 i",per",eable COIlld;llel:~ During I, ,1 ." the materials are extruded or otherwise applied and exposed to ambient conditions for curing. The moisture in the air then will hydrolyze the hydrolyzable groups (alkoxy, oximino, acetoxy, amino, etc.) on the silicon atom(s), to form silanol, either with or without the a~ ld"ce of an added catalyst.

The resulting silanol can then further react with remaining unhydrolyzed groups in a col~del,adlion reaction, to form a siloxane linkage resulting in the cure of the silicone material.

The above-discussed reactions are illustrated below:

~-~~~Si-OH + Rnsix4-n ~ ~~~~~Si-OSiRnX3 n + HX

(1) 20 where R=alkyl, aryl etc., X=OR, oximino, acetoxy, amino, amido etc., and n=0-2.

Depending on the X group, the above reaction may or may not require the as~ ,ld"ce of a catalyst.

WO 96/02579 2 1 9 2 8 5 q PCT/US95/08871 _____~;i-OSiRnX3 n + H20 , -~ Si-OSiRnX2 n(0H) + HX

(2) Again, d~ ndi"g on X group, catalyst(s) may or may not be present.

-~---Si-OSiRnX2 n(0H) + __---Si-OSiRnX3-n -~-si-osiRnx2-n-o-siRnx2-no-si----- + HX (3) 10 Although the RTv materials are very reliable and possess superior properties in the d~ ",e"liul)ed end use d~Jp' cdliolls (sealants, adhesives, coatings, potting compounds, etc. ), the R~V materials often are very slow to cure. For example, a typical RTv silicone formulation often requires overnight curing before ~c~ )le cure properties for the 15 intended end use;,, ' ,s can be fully realized.

As a result, there exists a need to "fix," i.e., spatially i""" ' ." , the applied RTv quickly, so that the applied material will not migrate from the locus of intended use, before a full cure of the RTv silicone is achieved.
20 Such migration may be extremely deleterious. For example, if a sealant RTV formulation is applied to a joint to effect vvdL~llJluo~ sealing thereof, migration such as sag or running of the sealant can take place (in the absence of adequate curing of the formulation). The migrated sealant formulation as a result may no longer overlie the joint to be sealed, so that 25 the dupel L.... ,i"g jointed structure may be rendered deficient or even useless for its intended purpose.

WO 96/02579 PCT/I~S95/08874 21 92~59 - o Col1:,ide, i"9 other ;, ~ of silicone materials, silicone conformal coatings are widely used in the protection of delicate electronic co,,,,uol1~llb such as printed circuit boards as well as in abrasion resistant coatings for plastic lenses.

Typically, silicone conformal coatings are heat-cured using hydrosilylation reactions, or else are moisture-cured using conventional room temperature vulcanizing.
In the formulation and use of heat-cured silicone conformal coatings, silicone fluids with vinyl functional groups are reacted with silicone fluids Cullldillill9 silicon-hydrogen bonds in the presence of a transition metal catalyst, as for example ulllulupldlillic acid. The severity of15 the curing conditions required, along with the high cost of transition metal catalysts, has posed a serious obstacle to the use of such heat-cured silicone coatings.

The d~:ri~,iencies of the moisture-cured conformal silicone coatings in 20 respect of their slow rate of cure have already been discussed above. This slow cure puts a severe limitation on the manufacture of coated co"~pu"e"l~, since full cure of the coated components is needed before the cu,,,,uullelll:~ can be used in the next step of the manufacturing process.

2~ Because of the dru,~",t",lioned limitations involved with heat or moisture curable silicone formulations, a third curing mode, ultraviolet light (uv) curing, has gained wide acc~uldllce in recent years. The curin,q of . . .. . . : . .. . _ . .. _ .. . . .. _ . _ . .. _ .. . _ _ .. . _ _ . . _ .... . . .

WO 96/02579 2 l 9 2 8 5 q PCT/US9!i/0887.1 ~ 5 radiation-curable silicones by uv or other actinic radiation is relatively fast and mild to the substrates. In situations where portions of the coated material are shaded during the uv cure, a secondary cure mode, usually moisture cure, can be further i"cu,,uordlt:d.

Typically, uv cure can be achieved by either a thiol-ene cure or by an acrylate cure. In the thiol-ene cure, a thiol functional silicone is reacted with a vinyl functional silicone. The cure is fast and the surface dry to the touch upon the co",~ lioll of the cure. However, the finished coating resists heat aging poorly and the formulation tends to be storage unstable.

On the other hand, acrylate functional silicone is usually storage-stable and the cured coatings exhibit excellent high temperature resistance. However, the acrylate cure typically exhibits oxygen inhibition.
t5 That is, in the presence of dLIIIo:",ht:,i,; oxygen, the surface cure tends to be i"co" I,ul~L~ and the resulting cured coating tends to be tacky.

The art has proposed a wide variety of silicone compositions, but such cor"po~iliu"s have failed to ~dli~du1ul ily overcome the d~ur~",e"liolled d~ ncies of conventional RTv' silicones, heat-cure silicones, and radiation-curable silicones.

U.S. Patent No. 4,526,955 to Bennington et al. describes radiation-pol~""e,i~dul~ colll~oailions including organopolysiloxanes having -N-Si - 25 or N-O-Si linkages.

W096/0~79 2 1 9 2 8 5 9 PCT~S95/08874 Japanese Patent Application No. 4-69901 filed February 12,1992 by Three-Bond Co., Ltd. discloses an ultraviolet-curing, addition-poly,,,e,i~dliul,-type silicone co",l.o~ilion which is curable at room temperature. The disclosed silicone cor"posilioll cul, ~uri~es a pOIydiUl,U,dllOsilu~dlle containing vinyl groups and a poly.liol~dlloailalle in which at least 4 silicon atoms are directly bonded in the formula Rs(Si(R3)(R4))nR6 in which R3-R6 are alkyl or aryl, and n is 4 or greater, with the proviso that P5 and R6 may be directly bonded to one another. An addition poly",eri~dliun catalyst is also included in the Co",,uoSilioll~ such 1 û as a platinum catalyst. The col I I~Joailiun is uv-light curable with the occurrence of radical addition poly",~ dliol-.

Hoffman, V., et al., J. Mol. Struct.. 293, 253-256 (1993) describes oligomers including a vinyl group-cùl,l~J~l;,lg dimethylsiloxane which are 15 thermally as well as phulu~,he~ically ~.lussl;llhdbl~.

Roth, W., et al., Adv. Mater.. 2(10), 497-498 (1990) discloses a methylvinyl-dimethylsiloxane co",,uo~iLion that is devoid of phuloi~liLidlur~, and undergoes radical ulussli~ki~y when exposed to laser radiation.

Barrall, E., et al., J. Polym. Sci.. Polym. Symp.. 71, 189-202 (1984) describes uv-cured polydimethylsiloxal)es containing pendant vinyl groups, wherein the curing involves dicumyl peroxide-mediated vul~.ani~dliu".

W096/0~579 2 l 9 2 8 5 9 PCT~S9~V0887~

~ 7 U.S. Patent No. 4,064,027 to Gant describes a uv-curable co,,,l~osiliun consisting e~enli l'y of a vinyl-corlld;";"g siioxane and siloxane-. ur,l..:.,i"g silicon-bonded hydrogen atoms in which a mercaptofunctional silicone may be employed as a cure accel~ldlur.
U. S. Patent No. 4,742,û92 to Inoue et al. and U. S. Patent No.
4,595,471 to Preiner et al. show UV and dual UV/moisture curable silocones which employ photocurable (meth)acryloxy and isopropenyloxy group containing silicones in culllbilldlio" with mercapto-co"ldi"i"g 1 0 silicones.

EP 0492828 discloses UV curable silicones of alkoxy terminated polydiolydl1oa;lu~dl1es in culllbilldliul1 with an alkoxy silicone compound which is capable of photo reactivity. This patent, however teaches 15 co",~ o~iliuns wherein the silanol l~ lilldl~:d diorganopolysiloxane is firstreacted with solely hydrolyzable groups containing endcdl.pe, ~. As a result, the silicones are not Itllll,i,~ t~ d with UV activatable groups.

EP 0539 234 pertains to a cc r"l,o~iliol1 for a liquid gasket having 20 both an ultraviolet-curing property and a moisture-curing property which is prepared by CO~ J;II;"Y a polysiloxane having at a molecular end at least one group which can be (meth)acryl a polyu,ydno~ilu,.dl,e having silanol groups at both molecular ends an olyd"u~;lane having at least one hydrolyzable group at a molecular end and a photopoly",eri dlion catalyst 25 and a condellsdlio,, catalyst. The co",posiliol1s disclosed in this referenceare highly viscous afford a bulk cure and are thus unsuitable for conformal coatings.

.~

WO 96/02579 PCT/US95/0887~1 21 92~59 8 O

Japanese Patent Appiication No. 92143102 to Tokyo Three Bond Co. Ltd. describes moisture curable and uv-curable compositions of a composition prepared by adding reactive polysiloxane to less equivalent reactive silane compounds having two or three hydrolysable groups, 5 methacryl groups or epoxy groups and reaction of the co""~osilion with compounds having at least one vinyl group and methacryl groups and a moisture curing catalyst.

U.S. Patent No. 5,179,134 to Chu et al. describes an acryloxy-10 functional capped silicone which is formed as a reaction product of a silyl diacrylate compound and a silicone having at least one functionality which is reactive with an acryloxy functionality of the silyl diacrylate compound to yield the acryloxy-functional capped silicone.

Accordingly, it would be a substantial advance in the art, and is correspondingly an object of the present invention, to provide an RTv' silicone cu"" o~iliol1 which is rapidly ''settable" at the a~ locus following F~p' n of the formulation to such locus, so that migration effects (sag, non-bonding, loss of joint seal integrity, exposure of cor"pol e"l:, intended to be en~Apcl~l~tP~I etc.) are minimized or eliminated, but is curable in a conventional manner under ambient ~ lo~,uhe,~ exposure conditions to moisture cure and achieve superior fully cured properties.

It also would be a substantial advance in the art, and is correspondingly an object of the present invention, to provide a dual uv-curable, moisture curable silicone conformal coating coll",o~iliun wherein 'WO 96102579 2 1 9 2 8 5 9 PCT/US9510887~1 ~ 9 uv cure of the composition results in a coating that is dry to the touch without the common tacky surface often ,t~.co~ d with an acrylate cure.

Another object of the present invention is to provide an improved RTV silicone culll,uOailiol1, which is readily formulated in a convenient manner using conventionally available resin and formulation ~.ul~l,uO~ a.

Yet another object of the present invention is to provide an improved room temperature vulcanizing silicone conformal coating composition of such character, which is readily formulated in a convenient manner using conventionally available formulation components.

Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims.
~;UMMARY OF THE INVENTION

The present invention generally relates to radiation- and/or moisture-curable silicone co",,uo:,iliuns.
In one broad aspect, the invention relates to a radiation and/or moisture-curable silicone cu",,uo:,iliu", cu",,uri:,i"~u.

(A) a silicone formed as a reaction product of a silanol-le""i"dl~d - 25 silicone and a silane cross-linker including an ethylenically unsaturated functional group and at least two hydrolyzable functional groups, and (B) a phului~ id~ul effective for radiation curing of the silicone composition;

WO 96/02579 r~
2~ q2859 ~

wherein the silicone (A) is selected from the group consisting of:

(I) silicones (A) whose precursor reactant silanol L~ dl~d silicone 5 has at least 60 mole percent Si-OH terminal groups and a viscosity at room temperature not exceeding 1000 centipoise, and whose precursor silane cross-linker includes as said ethylenically unsaturated functional group a monovalent ethylenically unsaturated functional group and wherein the silicone (A) is present in the silicone Cu""~O~ilioll in cullllJilldlioll with a 10 second silicone fluid having both radiation curable (meth)acryl functional groups and moisture curable hydrolyzable functional groups, wherein the mole raio of the ethylenically unsaturated groups to the (meth)acryl functional groups is from 5:95 to 4:6;

1 5 and (Il) silicones (A) which are endcap,l)ecl with an ethylenically unsaturated functional group which have a number average molecular weight cl~lu""i"ed by nuclear magnetic l~onallce of at least 5000, and 20 whose precursor silane cross-linker is devoid of mercapto functional groups and has said ethylenically unsaturated functional group and said at least two hydrolyzable functional groups directed joined to a silicon atom of said silane cross-linker.

A particular aspect of the above-described broad invention relates to a radiation surface-curable RlV silicone uullluu~iliull which 5llhsequent to WO 96102579 2 1 q 2 8 5 9 PCT/lJS95~0887~1 ~ 11 radiation surface curing thereof is interiorly (beneath the radiation-cured surface or "skin" of the co",uo~ilion) moisture-curable in character.

Such RTV silicone cu" ,~,osilioll of radiation surface-curable 5 sllhsequently interiorly moisture-curable character may suitably comprise:
(i) an ethylenically unsaturated functional group endcapped silicone formed by reacting a silanol-lu""i"dl~d silicone with a non-mercapto-group containing silane cross-linker for the silicone and a phul~,i"ilidlur for effecting radiation surface curing of the silicone Cu~ c-;t;JIl. The cross-10 linker in such co"",osiliun has joined directly to a silicon atom thereof anethylenically unsaturated functional group and at least 2 hydrolyzable groups. The endcapped silicone has a number average molecular weight of at least about 5000 and preferably at least about 10 000 as dt:le""il,ed by nuclear magnetic l~onallce techniques.

The silanol-l~""i"dltld silicone employed in the RTV silicone cor"po:,ilioll preferably is plt:dulllilld,,Uy linear in character with the silanol functionality (-SiOH) located at the terminus of a polysiloxy moiety (-(SiO)x-) in the silicone molecule. The non-mercapto group cor,lai~,i"g 20 silane cross-linker in such composition may advantageously have the formula RaSiXb wherein:

wo96/025~9 21 92859 r~ s ~ 14 R is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C1 - C8 alkyl, C6 - C12 aryl, C7 - C18 arylalkyl, C7 - C18 alkylar,vl, and X;

X is a monovalent functionality imparting moisture-curability to the reaction product of the silanol-fu~n,Liulldli~d silicone and silane cross-linker;

a has a value of 1 or 2;
b has a value of 2 or 3; and a + b = 4 15 with the proviso that when a is 1, R is a monovalent ethylenically unsaturated radical, and that when a is 2, at least one R is a monovalent ethylenically unsaturated radical.

Specific examples of the monovalent ethylenically unsaturated radical R groups of the silane cross-linker include vinyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, allyl, alkenyloxy, alkenylamino, allyloxy, allylamino, furanyl, phenyl. and benzyl groups. Specific illustrative species of the non-mercapto group containing ulussl;~ht!~ include vinyll,i",~Ll,o,~ysilane, vinylL,id",i"o~ila"e, vinylllid,l,iclo~;ld"e, vinyltriox-il l 'il ,o~ildne~ and vinyltriacetoxysilane.

WO 96102579 1' ~ .,,5.'~

In another aspect, the invention relates to a potting material for dis-pensing to an encArsl~lAtion locus. The en~ArslllAtion locus includes a bounding surface delimiting a potting volume in which an encArslllAtion structure may be disposed. By such alldllu~ulllelll, the encArsulAtiQn 5 structure may be potted in a liquid medium overlaid by an enclosure layer adhesively bonded to the bounding surface. Such pottin,q material co,,,ulisea.(a) an ethylenically unsaturated functional group endcapped silicone having (i) no hydrolyzable groups, and (ii) a number average molecular weight of at least about 5000 as dult: u lliued by nuclear magnetic 10 lUSOlldnC.3 technique; and (b) a pl1utuillilidlul effective for radiation surface curing of the silicone co",po~iliun. In the use of such potting co",uosilion, the potting material is surface-curable by irradiation of the material to form the overlying enclosure layer of potting material. Subsequent to the formation of such overlying enclosure layer, the potting material underlying 15 the enclosure layer is non-hydrolyzable and remains in a liquid state.

In yet another broad aspect, the present invention relates to a potted element structural article, co" ,u, i~i"~. structural means defining an encAr~l IlAtion locus including a bounding surface delimiting an 20 ent~ArslllAtion volume; a structural element disposed in the enr:ArsulAtion volume; a potting medium encapsulating the structural element in the encAr~lllAtion volume, wherein the potting medium comprises a silicone liquid medium overlaid by a solid silicone film enclo~i"!~ly and adhesively bonded to the bounding surface, so that the element is potted in the 25 silicone liquid medium, and the silicone liquid medium is contained in the encAr~lllAtion volume by the solid silicone film.

WO 96/02~79 F~ J4 21 9285~ o The potting medium in such potted element structural article suitably comprises a surface-radiation-cured potting composition formed by surface-radiation-curing of a silicone co",,uosilion cu",prisi"g: a vinyl-5 functional silicone devoid of hydrolyzable groups; and a phului, lilidlueflective for radiation surface curing of the silicone co,,,,uosiLiùn, wherein the potting material is surface-curable by irradiation of the material to form the overlying enclosure layer, after the formation of which the potting material underlying the enclosure layer is non-moisture-curable.

Yet another aspect of the present invention relates to a method of potting an element in a structural encAps~ IlAtion locus including a bounding wall surface. Such method .,ul"p,ist~s. disposing said element in the encArslllAtinn locus; dispensing into the ercArslllAtion locus a silicone 15 potting ~:ulll,uOailiull as described hereinabove; and irradiating the silicone potting l,ulll,uosiLion in the encAps~lAtiQn locus, to surface-cure same and form a solid silicone layer of the potting material enclobi, Iyly and adhesively bonded to the bounding surface, and overlying a non-radiation-cured portion of the potting material.

In the above-described potting method, if the vinyl-terminated silicone has no hydrolyzable groups, then the non-radiation-cured potting cu",~ o~ilioll may be uncurable by subsequent moisture exposure. In such instance, the non-radiation-cured potting colll,uo~ilioll is Illdillldin~d in an 25 uncured condition, so that the structural element in the encapsulation locus is potted in the non-radiation-cured potting composition, and the non-W096102579 2 1 92859 I'~ U~

~ 15 radiation-cured potting material in turn is overlaid and physically retained in position by the overlying layer of surface-cured potting material.

Alternatively, the non-radiation-cured potting composition may be moisture-curable, and the appertaining potting or manufacturing process may further comprise moisture-curing the non-radiation-cured potting cu~ .o~iLioll subsequent to the irradiating step.

Another colllposiliol1dl aspect of the present invention relates to dual uv radiation and moisture-curable room temperature vulcanizing silicone cor"pobiliol1s useful as conformal coating cr,,,,~-osiliuns.

Such radiation- and moisture-curable silicone cor,lposiLiun may suitably comprise: (i) a first silicone fluid co",l,ri~ g a monovalent ethylenically unsaturated functional group el1dcd~.ped silicone which is a reaction product of a silanol-l~",li"dlt:d silicone and a silane cross-linker having joined directly to a silicon atom thereof a monovalent ethylenically unsaturated functional group and at least 2 hydrolyzable groups; (ii) a second silicone fluid co",~ i"g a (meth)acryl-fu"~liol1ali~t:d silicone, e.g., a silicone having both radiation-curable (meth)acryl functional groups and moisture-curable hydrolyzable functional groups; and (iii) a phul~i~lilidlur effective for radiation curing of the silicone co",po~iliu".

In such radiation- and moisture-curable silicone culll,uo~ilioll, the ~ 25 mole ratio of the ethylenically unsaturated groups to the (meth)acryl functional groups may be on the order of 5:95 to 4:6.

WO 96/02~79 21 92859 o The silanol-terminated silicone in such radiation- and moisture-curable silicone uG~ o~iliull preferably comprises a linear polyd;orydr,osiluxd"e having a viscosity as measured on a Bluoh:~lield 5viscometer at ambient temperature (about 25 ~C) not exceeding about 1000 cps, preferably not exceeding 750 cps and most preferably not exceeding about 200 cps. In the preferred silanol-l~"";, - silicone of p,~do",i"a"lly linear character the silanol (-SiOH) functionality preferably is located at the terminus of a polysiloxy l-(SiO)x-) moiety in the silicone 1 0molecule.

Other aspects and features of the inventlon will be more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a partially sectioned side view of an electronic fuel flow sensor assembly potted with a silicone .u,,,, ~ according to one e~l~bodi~ l of the present invention.
Figure 2 is a partially sectioned side view of an electronic fuel flow sensor assembly potted wlth a sllicone cull,po~ilion according to another e",bodi"lt,l,l of the present invention.

W096/02579 r~ o.
~ ~721 92859 DETAILED DESCRIPTION. AND PREFERRED MODES OF
CARRYING OUT THE INVENTION

The silicone col",uo~iliu"~ of the present invention utilize polysilane crosslinkers containing olefinically unsaturated group(s) attached to the silicon atom of the u~us~ ker.

Such clus~ k~ by reaction with a silanol-Ler",i"dLe:d silicone (as shown in equation (1) helt:i"above) allows the formulation of RTV silicones for potting, conformal coating, or other ~ ;-I ,s.

However, the present inventors also unexpectedly discovered that the materials thus prepared, upon formulation with common phuluillilidll~rs such as diethox~,dc~lupl1~"ol1e, can undergo light (actinic radiation exposure) cure to form a firm, non-tacky surface "skin" that po~se~ses stnuctural integrity, i.e., is hard and non-migratory in character, and protectsthe uncured RTv silicone co~,uusitiun u~d~ edlh but that does not prevent the moisture cure of the RTv formulation.
Thus, ethylenically-unsaturated silane capping species, such as vinyll~ i" I~Ll ,o~ysilane. vinylll iu~-i" ,i"o~ildn~ and vinyltriacetoxysilane, were used to endcap silanol-terminated fluids, to form vinyl-functional products, such as vinyld;",~llluxy-, vin~ liu,d,,li,luxy- and vinyldiacetoxy- I~IlllMdL~d 2~ fluids, respectively. Such fluids upon the addition of phuluilliLidLur~ were found to undergo surface uv cure to form r,trong, non-tacky films.

W0 96/02579 F~ /4 When exposed to suitable actinic radiation of curingly effective character, the resulting radiation-cured surface film is typically sufficiently strong to protect and support the uncured liquid underneath the film even 5 when the substrate element bearing the radiation-cured silicone layer is inverted in relation to its initial radiation exposure position.

When such vinyl-functional products are added to (meth)acryl fuln,liu~ d silicones, upon the addition of phuluillili.3JI~, such fluids 10 undergo uv cure to form strong, non-tacky films when exposed to suitable actinic radiation of curingly effective character. The resulting radiation-cured conformal coating is typically sufficiently strong to provide the requisite protection to the substrate upon which it is coated.

The inventors also discovered that ambient temperature (typically, from about 0~C to about 30~C), atmospheric moisture (normal relative humidity (RH), e.g., from about 2~ to 100~fO RH) exposure conditions can, .cllh5erluent to the ' u,,,e,,liulled light-induced "skin cure" of the culllluu~ ùll~ be utilized to effect moisture-curing of the RTV silicone 20 material beneath the radiation-cured skin layer, and surprisingly, the initial surface radiation-cured film formation did not change the hardness of the RTV silicone after such final moisture cure.

In conformal coating a,ul ' ~s, the cross-linker/silanol-lur",;"dl~d 25 silicone reaction forms the monovalent ethylenically unsaturated functional group u"d,.d,uped silicone. The composition CU~uli~ g the ethylenically wos6/02579 21 928~9 r~ 4 unsaturated functional group ~ndcdpped silicone and at least one (meth)acryl-fiJ,,.,Iiul,dli~ed silicone provides a dual uv/moisture curable conformal coating co",,uosilion having improved surface tack and relatively fast cure time.
In a preferred embodiment, the radiation- and moisture-curable silicone conformal coating composition of the invention co",,u~i~es a first silicone fluid, a second silicone fluid, and a phului~lilidlur effective for radiation curing of the silicone ~,ur~ o:,iliol1~

Preferably the first silicone fluid comprises a reaction product of a silanol-l~""i"dl~d silicone having at least 6û mole percent Si-OH terminal groups and a viscosity, at ambient temperature, of 1 ûûû centipoise or less, and a silane cross-linker having a monovalent, radiation curable 15ethylenically unsaturated functional group and at least 2 hydrolyzable groups.

The second silicone fluid preferably has both radiation-curable (meth)acryl function groups and moisture-curable hydrolyzable groups.
2ûThe mole ratio of the ethylenically unsaturated groups to the (meth)acryl functional groups is preferably from about 5:95 to about 4:6 and most preferably is from about 1:5 to about 35:65.

The present invention includes silicone ro",poailiol1s wherein the ~ 25first and second silicone fluids are prepared concurrently from a silanol il ,dlt:d silicone having at least 6û mole percent Si-OH terminal groups and a viscosity, at ambient, of 1û00 centipoise or less and at least two 2l 92859 20 ~
silane cross-linkers. One of the cross-linkers has a monovalent, radiation-curable ethylenically unsaturated group and at least two hydrolyzable groups, and at least one other silane has a (meth)acryl functional group and at least two hydrolyzable groups.
It has been unexpectedly discovered that even though the first and second silicone fluids each have a viscosity which is preferably less than or equal to about 1û00 cps and which in and of itself has poor photocuring ability, when present in the silicone conformal coating co,,,,uo:~ilions~ upon 10formulation with common phuIuilliLidLula such as diethoxyacetophenone, such silicone fluids can undergo light (actinic radiation exposure) cure in a relatively short period of time to form a firm, non-tacky surface "skin" that p~5ce ~ c structural integrity.

In such coating:,, ' "~ns, the silicone co,,,,uo~iIions of the invention, as a result of their sll- ,"b."~y to being cured by radiation ,u~ llerll as well as (or alternatively) by R~V moisture curing, thereby permit great flexibility in use, particularly in instances where the geometric or positional character of the substrate(s) to which the co,,,~uosiliulls are 20applied would otherwise cause shading of the silicone co,,,,uosiIiol1 from the actinic radiation source. In such instances, the applied silicone conformal coating ~~ullluosiliun of the invention can be moisture cured via R~V ulussli~hi~g wherein the slow moisture cure can be allowed to take place under normal dL~usphelic moisture exposure conditions.
~ 25 Alternatively, in instances where the applied silicone conformal coating material is not sllcceptihle to shading, phel1u",ena, the material ~VO 96102579 2 l 9 2 8 5 9 r~l~L ~

~ 21 can be fully and solely cured by exposure to actinic radiation. The composition of the present invention is curable at ambient temperature conditions, without any net addition or i~; ' " 1 of heat to such silicone composition .

Thus, silicone formulations of the present invention can be sequentially polymodally cured, by initial actinic radiation, e.g., uv cure, and Cl~hsequ~?nt moisture cure, and such silicone formulations are also curable in toto by moisture cure only. In either event (polymodal curing 10 involving sequential initial radiation surface curing followed by bulk interior volume moisture-curing, or unimodal curing involving only moisture curing of the entire silicone formulation), the physical properties of the respective cured materials are suLaldl lli.- ly the same.

The present invention, as a result of its sl ,c , ~ y to being surface-cured by radiation illl,uil lgt~ l ll as well as (or alternatively) by RTV
moisture curing, thereby permits great flexibility in use, particularly in instances where the geometric or positional character of the substrate(s) to which the ~u~ Jo~ iun is applied would otherwise cause deleterious sagging or migration of the silicone cu~ osiliùn before it is able to be moisture-cured via RTV u, u~blil Ihil ,9.

In such instances, the applied silicone composition of the invention can be selectively surface cured by radiation exposure, in those regions ~ 25 latently susc~ptihlQ to sag or migration or alternatively over the entire surface of the applied colll,uoailiundl mass, and then the slow moisture cure WO 96/02579 I ~,l/U.~ /4 21 92859 ~

can be allowed to take place under normal atmospheric moisture exposure conditions.

Alternatively, in instances where the applied silicone material is not 5 ~ cQptihle to sag or migration phenor"~"a, the material can be fully and solely cured by moisture exposure under normal ambient temperature relative humidity conditions. The co"lposilion of the present invention is curable at ambient temperature conditions, without any net addition or ,, ' 1 of heat to such silicone COIlll~o The invention can be very useful in many d~pli~dlions.

For example, in potting compound dlJpli~,dliuns, after extruding a silicone potting material according to the present invention into the cavity or 15 interior volume of the structure in which component(s) or other material(s) are to be potted for enrArsUlAtion thereof, the applied potting material can be subjected to a quick light irradiation to form a fixed and firm low to non-tacky film of sufficient strength to structurally enclave the uncured RTv' silicone ~,u,,,yo~ilion u"d~",edLh the surface-curing skin. The resulting 20 potted structural article can then be readily lldn~ullt:d, while allowing slow moisture cure to take place during transport and storage of the article.

In this manner, the potting operation can be quickly concluded in the manufacturing facility so that the potted articles are i"""edidlely ready for 25 transport and packaging, thereby avoiding the substantial inventory of uncured potted articles which in prior practice has had to be sub~ld"li~.:!y moisture-cured prior to such transport and packaging.

WO 96/02579 2 1 9 2 8 5 9 PcrlUS95~0887~

~ 23 The present invention can be also useful in forming non-tacky coatings which are not inhibited by the presence of oxygen, as is commonly the case with uv cure involving (meth)acrylate functional groups.
S In silicone compositions according to the invention, in which silicone containing (meth)acryl functionality is present, there may be some inhibition of the (meth)acryl groups, but this pht,no",ellon appears to be masked in such Co",,uo~iliolls by the presence of monovalent ethylenically unsaturated groups, especially vinyl groups.
As used herein, the term "non-tacky'' in reference to the surface of a silicone compositional mass subjected to radiation exposure, means that such surface is d~,fur,,,able, but touch-resilient or non-adherent to, and non-deformed by, the touch, i.e., contact of a human finger with such 1 5 surface.

The present invention also co"L~",,uldl~s the provision of a dual cure silicone co",,~,oaition cu",~.risi"g a uv cure/moisture cure dielectric gel, in .,, ' )ns where ultraviolet radiation used to effect the uv cure is not 20 Ar~:es~;.l,le to the entire surface of the applied dielectric gel mass, so that the exterior of the mass includes radiation-A~c~ssible (direct impingement) regions as well as shadow regions that are blocked to radiation illl,uillyt:lllelll (e.g., by housing or potted cu,,,,uu,,t:,,l structures in potting a~F' ~n~, by mask or other material layer elements in conformal coating 25 ~p, ' IS, etc.).

WO 9C102579 2 1 9 2 8 5 9 PCTIUS9~/08874 In such ''shadow cure" applications of dielectric gels or other silicone compositions of the present invention, both the direct i~,ui~gemel~L
radiation cured/moisture cured regions of the compositional mass, as well as the shadow regions where only moisture-cure took place, would exhibit similar physical properties (e.g., hardness, toughness, thermal resistance, tensile strength, fracture resistance, temperature stability, co",p,~ssive strength, etc.) in the final cured material .

The silicone conformal coatings of the invention may be cured by exposure to any radiation exposure conditions that are curingly effective for the cu",uosiliom In like manner, surface-photocurable silicone CO~ JU~;l;OI1S of the invention may be surface-cured by exposure to any radiation conditions that are surface-curingly-effective for the co",posiIiol1.
Suitable radiant energy types that may be usefuliy employed in the broad practice of the invention include electron beam radiation, ultraviolet radiation, visible light radiation, gamma radiation, X-rays, ~-rays, etc.
Preferably, the photocuring radiation is actinic radiation, i.e., u~au~t,Iic radiation having a wavelength of about 700 nm or less that is capable of effecting the requisite cure, e.g., surface cure of the silicone co,,,,uo:~iIiol1 in the case of potting or other extended depth silicone formulation volumes, or full volume cure (in the case, for example, of thin conformal coatings) of the silicone ~;u"~uo~iIium Most preferably, the photocuring radiation comprises ultraviolet (uv) radiation having a wavelength of for example from about 20û to about 54û nm.

wo s6/02s7s 2 1 9 2 8 5 9 P~

~ 25 It will be recognized that the type and character of the photocuring radiation, e.g., surface-curing radiation that is used to form a cured skin or film on the silicone co",~oailional mass of the present invention after its arF' ~ to the substrate or other locus of use, or the full body curing 5 radiation for curing an extended depth mass of the silicone composition, may be widely varied within the broad scope of the present invention, and that the radiation exposure cure times in any given apj'~ ~ are co"~:" on.li,lyly variable, with respect to and dependi"g on such factors as: the particular silicone formulation employed, type and light-10 responsiveness of the specific phuLuiu ilidlUI employed, the wavelength andflux of the radiation, the col1celllldLiol1 of the phutui~ilidlul in the culll~Josiliull~ and the thickness of the coating or other form of the applied cu,,,~o~iliunal mass.

15Generally, the radiation exposure time is relatively short, that is, less than about 3 minutes. Exposing the composition to excessive amounts of radiation may "overcure'' the co,llpo~iLiol1, resulting in poor physical and pe,~uulldllce properties. The amount of radiation that is excessive varies with the given formulation of the silicone composition, coating thickness, 20radiation source, etc., and may readily be determined by the skilled artisan without undue ~,.pe, i" ,er,ldli- n.

Co,,t::,,uondi,,yly, the thickness of the radiation-cured skin that is efficacious to provide the required structural stability and cul,Ldi"",e"l of ~ 25the underlying uncured (e.g., liquid or flowable (semi)solid) silicone co,,,~.o:,iliùn in a surface-cure system, or to provide the required structural stability and protection of the substrate in a full cure system, are readily d~l~r",i,ldble within the skill of the art by routine and simple ~ ,e,i,,,el,ldliu,l. Generally, conformal coatings are on the order of less than about 15 mils thick, typically from about 3 to about 10 mils in thickness.
For example, the depth of cure required in a given end use n~r'l 1 may be elll,uilic.llly ~Lduli,l,ed by exposure of corresponding amounts of the composition on separate substrate samples to varying amounts of radiation (or other varying pdldlll~Lt~la, e.g., amounts in the respective co,,,,uo~iLiolldl samples of phuLuilliLidLul~ or amounts of filler; or distances between the applied compositional mass and the radiation source; etc.), followed by lldll~ldLiull~ inversion, etc. of the samples to determine which colll,uoaiLion samples sag or migrate, e.g., in the case of potting or high-depth bulk masses of the silicone formulation.
In the case of conformal coatings, such step of motive d~L~ ldLiull of sag or migration c" r " "'y can be replaced by a corresponding step of touching the samples to determine which cu",~o~ilion samples are tacky to the touch.
The silanol-lt:"";"dled silicone utilized in the potting or bulk deposited silicone culll,uosiliol1s of the present invention may suitably comprise a linear poly.lio,yal1osiloxane, or other linear silicone, having a weight average molecular weight which may for example range from about 1,000 to about 300,000, preferably from about 10,000 to about 80,000, and most preferably from about 10,000 to about 50,000.

W096/02579 2 1 928 59 P~

~ 27 The silanol-terminated silicone which preferably is utilized to form the ethylenically unsaturated functional group endcapped silicone in the conformal coating uu~ o:~ilions of the present invention may suitably 5 comprise a linear polydiù,u~anosilu,~d,)e, or other linear silicone, having a weight average molecular weight which may for example range from about 166to about 20,000 preferably from about 500 to about 12,000, and most preferably from about 800 to about 8000. Such silanol~ ""i"dl~d silicone has a viscosity at ambient (about 25 ~C) of less than or equal to about 1000 1 û cps, preferably less than or equal to about 750 cps, and most preferably of less than or equal to about 200 cps.

Although such silicone is preferably linear in cu"iu"".~ion other, 15 non-linear silicones, e.g., branched, cyclic or ",a-,,u",e~ic, may be usefully employed in the broad practice of the present invention. Preferably, the silicone (polysiloxane) is prt,do",;"ar,lly linear in character. The silanol (-SiOH) functionality is located at the terminus of a polysiloxy (-(SiO)x-) moiety in the silicone molecule, e.g., the hydroxy functionality is covalently 20 bonded to a terminal silicon atom of the polysiloxy backbone, in the case of a linear silicone, or to a terminal silicon atom of a main or side chain or other ag~ ydlioll of siloxy repeating units in the case of a branched or otherwise nonlinear silicone molecular colliulllldliull.

25 Preferably, the polysiloxane is a linear molecule both of whose terminal functional groups comprise hydroxy groups. Thus, for example, wo s6/02~7s r~ c /~
2 1 92859 28 = ~ ~

the polysiloxane material may comprise a hydroxy~ "il ldl~d polydimethylsiloxane or a hydroxy-l~""i"dlt:d polydiphenylsiloxane.
Preferably the silicone is an ul yd"uuolysiioxane whose organo substituents are p,~:dor"i"d"lly methyl.
A particularly preferred polysiloxane material which has been usefully employed in the potting or bulk deposited silicone culllluo~ ons of the present invention is a hydroxy-terminated polydimethylsiloxane of linear configuration having a weight average molecular weight as lû determined by gel-pe~"ecLioll ~ hlullldl~yldully technique on the order of 1 û,ûûû to 5û ûûO.

A particularly preferred polysiloxane material which has been usefully employed in conformal coating cor"po:,itiulls according to the 15 present invention is a hydroxy-te""i"al~d polydimethylsiloxane of linear configuration having a weight average molecular weight as determined by nuclear magnetic ll:sonance technique on the order of 4 00û.

The non-mercapto-group-containing silane cross-linker employed in the compositions of the invention for cross-linking of the silanol-terminated silicone as well as the silane cross-linker empioyed in compositions of the invention for endcappi"g of the silanol-terminated silicone to obtain the monovalent ethyienically unsaturated functional group ul)duapped silanol suitably comprises a silane compound having joined directly to a silicon atom thereof an ethylenically unsaturated functional group and at least two hydrolyzable functional groups.

WO 96/02579 2 1 9 2 8 5 9 PCT/USgcl08874 ~ 29 The silane cross-linker may for example have the formula RaSiXb ~ 5 wherein:

R is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C1 - C8 alkyl, C6 - C12 aryl, C7 - C18 arylalkyl, C7 - C1 8 alkylaryl, and X;
X is a monovalent functionality imparting moisture-curability to the reaction product of the silanol-terminated silicone and non-mercapto group ~,UI IIdil li~ 19 silane cross-linker;

a has a value of 1 or 2;

b has a value of 2 or 3; and a + b = 4 with the proviso that when a is 1, R is a monovalent ethylenically unsaturated radical, and that when a is 2, at least one R is a monovalent - ethylenically unsaturated radical.

In such cross-linker formula, the monovalent ethylenically unsaturated radical may for example contain from 2 to 12 carbon atoms.

WO 96/02579 2 1 9 2 8 5 9 PCT/US9~/088~i~

Illustrative monovalent ethylenically unsaturated radicals suitable for the cross-linker include vinyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, allyl, alkenyloxy, alkenylamino, allyloxy, allylamino, furanyl, phenyl and benzyl groups. Preferably, the monovalent ethylenically unsaturated 5 radical is selected from the group consisting of vinyl and allyl groups, and most preferably, the monovalent ethylenically unsaturated radical is vinyl Illustrative silane cross-linker species which may be variously utilized in the broad practice of the present invention include 10 vinyll,i",t:li,uxysilane, vinylllid,l,i"os;idl1e, vinyll,id",i.lo~ila"e, vinyltriox-i",i"os;ld"e, vinyltriisopropenyloxysilane, and vinyltriacetoxysiiane.

As used herein, the term "vinyl" refers to the group CH2=CH-.

The silane cross-linker may be used at any suitabie concer,l~dliun in the silicone ~,u~po:~ilion of the present invention which is cross-linkingly effective for the silicone, as may be ~lui~,h;ullltllriuliiiy determined in a ~lldi~illiui~dld manner within the skili of the art, or as may be readiiy UIlllJiliC~.''y dc:te:""i"ed within the skiil of the art by varying the col1ct:lllldliol1 of the cross-iinker reiative to the siianol-terminated siiicone in the silicone composition, and cross-iinking the Cul l l,uosiliol1 in the presence of moisture, with and/or without initial surface-radiation-curing of the colll,~o~iliom ~ 25 In conformal coating d,UI ' 1S, for exampie, the amount of the cross-iinker is preferabiy less than slightly less to slightly more than the WO 96/02S79 2 1 q 2 s~ 5 9 r~ .,.174 stoichiometric amount based on SiOH with the goal being to endcap all available SiOH's.

By way of example, in the case of potting or bulk deposited co~ osiliulls of the present invention utilizing silane cross-linker species such as vinyllli",~ll,.)~ysilane, vinylllid",i"osild"e, vinyll,iar"idosilane, vinylt, iuxi" ,i"o:,ild"e, and vinyltriacetoxysilane, the cross-linker cc,nce"l, , is generally on the order of from about 1% to 1 0~h by weight, based on the weight of the silanol-l~ll,,i,ldlt,d silicone, and more preferably from about 1.5% to 5~~O by weight, on the same silanol-lt:llllilldLt:d silicone weight basis.

In conformal coating: p, 'i ":ns utilizing the above silane cross-linker species, or species such as vinylldi:,op~u,,)~"jlv,(ysilane, the cross-linker col)u~ dliul1 is generally on the order of from about 1% to 50~/O by weight, based on the weight of the silanol-terminated silicone.

In contrast to the silicone cu""~o:,iliu"s disclosed in Bennington U.S.
Patent 4,526,955, which describes the use of an o,yal " ~n compound having an average of at least two and preferably three or four groups per molecule having Si-N and/or Si-O-N linkages, the u~u~ kel silanes utilized in the present invention comprise compounds having an ethylenically unsaturated functional group directly bonded to a silicon atom of the silane and at least two hydrolyzable functional groups joined directly ~ 25 to a silicon atom of the silane, with such silane, and the resulting silicone (polysiloxane) product formed by reaction of the crosslinker and the silanol-fu~ iol,dli~ed silicone, having Si-C and/or Si-O-C bonded moieties.

In conformal coating:,, " " ms of the invention, as well as in other :, ,1 ls, the cc.,:,,~,o:,iLiu" may further comprise a nonreactive moiety end~.dpped silicone in order to modify the viscosity of the silicone fluid.
5 Suitable nonreactive moiety encapped silicones for use in the present invention include, but are not iimited to, alkyl, aryl, arylalkyl, and alkylaryl endca,u,ued silicone. An example of a specific nonreactive moiety el1d~,dpped silicone suitable for use in the invention is trimethylsilyl endcd,uped polydimethylsiloxane.


In the cor"r n~ of the invention having utility for conformal coating co"lpo:,ilio,1s, the at least one (meth)acryl-fu~uLiol,~ d silicone has a functional group which is selected from the group consisting of acryl, (meth)acryl, propenyl, butenyl, pentenyl, hexenyl, octenyl, allyl, alkenyloxy, 15 alkenylamino, allyloxy, allylamino, furanyl, phenyl, and benzyl groups, and at least one hydrolyzable group which is selected from the same hydrolyzable groups on the monovalent ethylenically unsaturated functional group endcapped silicone.

2û Preferred fu~ liol1ali~_d silicones are the (meth)acryloxy or acryloxy alkyl or (meth)acryloxy or acryloxy alkenyl functionalized silicones.
Suitable (meth)acryl-ful ,uliol1ali~t:d silicones for use in the present invention include, but are not limited to, methacryloxypropyldi"le:ll,oxysilyl te"l:i,ldled silicone, acryloxypropyldi"l~llluxysily tellllilldled silicone or a 25 mixture thereof. (Meth)acryl-ful,liundli~d silicones are known and can be prepared in accu~ .lan.;e with any known method including those exer", ' ' - ~ in U.S. Patent Nos. 4,5û3,208; 4,504,629; 4,575,545;

W0 96/02579 r~ /4 ~ 3321 92859 4,575,546; 4,760~122; 4,290,869 and 4,595,471, the entire disclosures of which are all hereby illcol~.or~t~d herein by reference.

The phutuillilidlùl employed in silicone comuo~iliolls of the present 5 invention may suitably comprise a photui,,ilidlor that may include any phUIUil lilidlUI known in the art that is useful to effect photopoly" ,~ dliOIl of ethylenically unsaturated (e.g., vinyl or allyi) compounds in the presence of curingly effective radiation.

Potentially useful phuiuillilidlul~ may include, by way of example, benzoin, 5llhctitlltPd benzoins such as benzoin ethyl ether, benzophenone, ben~opllellu"e derivatives, Michler's ketone, dialkoxydc~lupllellr nes such diethoxydc~lu,ullellone, act:lupl ,el)one, benzil, and other derivatives (sllhqtitlltQd forms) and mixtures thereof.
A particularly preferred phuloi"ilidlur material is diethoxyd..~,~opllellone. Although any suitable effective amount of phuluillili.~'ul may be employed in the surface photocurable silicone compositions of the invention, generally the, hului"ili..~u, cullc~lllldlion will be usefully employed in the range of about 0.1% to about 1û% by weight, and more a,ueui~ l'y and preferably from about 0.2~h to about 5~h by weight, based on the weight of the hydroxy-functional silicone.

The phuluil lilidlul employed in the photocurable silicone ~ 25 compositions of the present invention may also be polymer bound. Such phuluillilidlu,~ are described in U.S. Patent Nos. 4,477,326 and 4,587,276.
Otherfree radical initiators, such as peroxy thermal initiators may be used W096/02579 2 ~ 928~5 q ~ = P~ 4 in some of the lower molecular weight silicone formulations of the invention.

Suitable moisture cure initiators for use in various silicone 5 co",uo~ io"~ of the present invention include any such initiators known in the art including ollllulild"dl~.

The cu",uo:~ilions of the present invention may also include other i"y,~.iic:r,ts to modify the cured or uncured properties of the co,,luo:,iliun 10 as necessary or desirable for a specific end use r ~ ~

In instances where the non-mercapto group containing silane cross-linker species used in the present invention is vinyll,i",etl,oxysilane a curing catalyst may be necessary. Examples of curing catalysts include 15 but are not limited to, tin, titanium aluminum zirconium and any other suitable curing catalyst known in the art.

Fillers or ,~i,,fu,ui,,g materials may usefully be employed in co,,,posiliuns of the present invention to provide enhanced mechanical 20 u, u,ue, i ~ and in some instances enhanced UV radiation surface curability of the collluo:,iliùn.

Among preferred fillers are It~ u~ g silicas. The reinforcing silicas are fumed silicas which may be untreated (hydrophilic) or treated to 25 render them h~d~uphobic in character.

WO 96/02579 2 ~ 9 2 8 5 9 PCTiUSg~iJo887~

In general, fillers may be employed at any suitable conce,,LIdlioll in the curable silicone composition, but generally are present at conce,,l,dlions of from about 5 to about 45% by weight, based on the weight of the polysiloxane. Generally, any other suitable mineralic, cdrL,ol1aceous~ glass or ceramic fillers may be potentially advantageously be employed. Examples include ground quartz, tabular alumina, didLui"aceous earth, silica balloons, calcium carbonate, carbon black, titanium oxide, aluminum oxide, aluminum hydroxide, zinc oxide, glass fibers, etc.
In addition, the silicone cor"~.o:,iliol,~ of the present invention may also optionally contain an adhesion promotor, to enhance the adhesive character of the cùlll,uosiliol1 for a specific substrate (e.g., metal, glass, ceramic, etc.), when the co",~,o:,iLion is employed as an adhesive for bonding of respective substrate elements or members.

Any suitable adhesion promotor constituents may be employed for such purpose, d~:"tndi,lg on the specific substrate elements or members employed in a given ~ . For example, the adhesion promotor might be selected to enhance the adhesion of the co~,,,uosiliol1 on substrates Culll~.lisi~g materials such as metals, glasses, ceramics, plastics, and mixtures, blends, cor"pci~ s, and culllLJilidLions thereof.

Various oryano~;ldl1e compounds may be usefully employed for ~ 25 such purpose, and such compounds may also feature oxirane functionality, as well as silicon-bonded alkoxy substituents, to provide broad adhesive bonding utility. In such o~dno~ildne compounds, the oxirane functionality WO 96/02579 PCTIUS95108~74 21 q2~59 may be provided by a glycidoxyalkyl substituent on a silicon atom of the silane compound. A particularly preferred adhesion promotor of such type is glycidoxypropylLd"~lhoxysilane.

In addition further additives such as MQ or MDQ resins can be illco,l.o,dled to vary the properties of the silicone colllpoailion as desired.

Besides the constituents identified above as being optionally includable in the silicone Cu",lJos;i;o"s of the present invention further optional constituents include anti-oxidants flame retardants, and pigments, etc., as well as filler adjuvants e.g., filler-treating agents such as hydroxy-l~llllill t~d vinylmethoxysiloxane for filler treatment of quartz or similar fillers when used in the colllpo~iliol1.

In respect of filler colll~-onellla of the silicone compositions of the present invention it will be appr~cidlt:d that the use of filler materials may biulli~icdlllly alter the depth of the surface cure of the col"uosilional mass and fillers may therefore be usefully employed to attain a prt,dtllt"",i"ed desired cured skin thickness on the exterior surface of the compositional mass.

Radiation exposure surface curing of the silicone cor"~o~ilions of the present invention may suitably be carried out in an ambient dll"u:,l,he,~ or in an inert dlllloauhel~ such as nitrogen or argon dl",o:".he,~. Moisture curing of moisture-curable co",posiLio~1~ of the present invention is typically suitably carried out in ambient atmospheric exposure conditions but such curing may alternatively be conducted in an WO 96/02579 2 1 9 2 8 5 9 PCT/U59510887~1 elevated humidity cabinet or other synthetic high humidity environment for the requisite moisture curing period, which may be readily determined within the skill of the art in relation to d~le,,,,i,,dliun of the product final moisture-cured properties.
!;
The silicone compositions of the present invention utilize cor",uu~ that are easily synthesized within the skill of the art, and/or are readily cullllllelui..:ly available.

In making the silicone Culll~Jositiul1s of the present invention, the silanol-l~, l l lil ldl~d silicone cor, ,~u, ,t:, ,l and the non-mercapto group cullld;,lillg silane cross-linker may be reacted with one another at ambient temperature, e.g., at room temperature in the range of 20~C - 30~C, for sufficient time to complete the reaction, typically 0.5 to 4 hours.
15 Alternatively, elevated lt,r"~,e, Ire may be employed to speed the rate of reaction, however, ambient l~"",e, ~re conditions are generally :~dLi~du~uly and preferred for ease of synthesis.

The reaction mixture may optionally, if desired, include a suitable 23 catalyst, such as an ol"u,dllolll~ldllic compound (e.g., butyllithium) to facilitate the reaction between the silanol-l~"";"dlt:d silicone reactant and the silane ~;~us~ hen After the desired extent of reaction, such catalyst may be quenched, for example by addition of acid in the case of organometallic reagents.

WO 96t02579 2 1 9 2 8 5 9 PCT/US95108874 After the reaction between the silanol-terminated silicone reactant and the silane crosslinker has been carried out, the silicone fluid reaction product is simply admixed with the phuluiuilidlul for sl Ihsequent exposure of the resulting Cu",po~iliull to photopolymerizingly effective radiation to (surface, or bulk) cure the .,o",~,o~ ioll.

The silicone fluid reaction product may thus be admixed with the phuluillilidlul under non-radiation-exposure conditions, and the resulting mixed composition may be stored in containers which are non-l,a"a",is~ive 1 û of photopolymerizingly effective radiation, as a single package composition for subsequent use.

Alternatively, the silicone fluid reaction product may be utilized as a two-part or two-package system, in which the silicone fluid reaction product 1~ is admixed with the phuluil lilidLul co" ,poner,l at the time of use, i"""edidl~ly before a" " 1 thereof to the locus of use, and curingly effective irradiation of the applied mixed colll,uo~ilioll.

The at least partially radiation-curable silicone ~,u~,uo~iliolls of the present invention may be variously fonmulated for suitable use in any variety of ,," " ls, including usage as sealants, adhesives, potting compounds, shock or impact damping media, conformal coatings, etc.

In some 1,:' ~s of the present invention, as more fully 2~ described ht~ illd~l~l with reference to Example 7 hereof, it may be desirable to formulate the radiation surface-curable silicone con,,uoDilioll so that the radiation surface-cured film of the cor"uo~iliun will be lldl 1~ ive ... ..... ..

wo 96/02579 2 1 9 2 8 5 9 F~l/-),.. /4 of moisture but the ethylenically unsaturated functional group endcapped silicone has no hydrolyzable groups so that moisture curing of the underlying non-radiation-cured composition does not take place.

Such compositions may for example be utilized for coating potting, or other ~ tk 15, in which it is desired to provide a solid cured silicone film (layer) overlying uncured silicone liquid.

In potting 15 for example such compositional mass, cor,,ud:.i,,g a surface radiation-cured skin capable of retaining the underlying liquid in the potting locus by adhesive bonding of the solid cured silicone skin layer to the bounding surface(s~ of the potting locus can protect the potted element e.g. an ele~L~u,,,e.hd,,icdl ",e.;l,d"is"" in the underlying liquid.
The underlying liquid thus subsequently functions as a fluid damping medium which may in fact be superior to solid potting materials in securing the potted element against damage or di:~ulace~lelll which might otherwise occur in instances where the potted element assembly is subject to impact shock vibration etc.

Figure 1 is a partially sectioned side view of an electronic fuel flow sensor assembly potted with a silicone ~ omuosilion according to one e",bodi",e"l of the present invention.
~ 25 The sensor assembly 62 comprises a housing 64 in which is disposed a solenoidal element 66. The solenoidal element is joined by wo s6/02s7s ~ ~~ /4 suitable electronic coupling means to female connector elements 71 which permit the sensor assembly to be installed in an automotive electronic system for ",or,ik"i"g fuel flow. The sensor assembly comprises intake port 68 and outlet port 70 providing for fuel flow through the device.

In the housing of the sensor assembly there is an interior space 7 2 surrounding the solenoidal element 66 and its a~so,.i..~,d electronic coupling means, to which the potting ~o~l~po~iliol~ of the invention may be introduced and sequentially cured as previously described. The potting 10 mass comprises an upper radiation-cured skin 102 which is a cured silicone solid layer or film, and which at its periphery is adherently joined (bonded) to the side walls of the housing 64.

By such d"dnger"~nl, the radiation-cured skin 102 overlies, and 15 encloses (together with the side walls of the housing), the uncured liquid silicone composition 100. If the skin 102 is moisture-permeable in character, but the liquid silicone is not moisture curable as described more fully helt:illd~ in cor",ecliol1 with Example 7 hereof, then the silicone liquid 100 is p~lllldln::lllly ~"~ Ldi"ed in liquid state, and constitutes a 20 liquid potting medium for the solenoidal element 66 and associated element structure.

Figure 2 is a partially sectioned side view of a corresponding electronic fuel flow sensor assembly, potted with a silicone composition 25 according to another ~",bodi"~e~l of the present invention. The corresponding parts and elements are numbered in Figure 2 with the same reference numerals used in Figure 1. In the Figure 2 embodiment, .. . . ..... . . .. _ .. .. _ W096102579 21 q28 59 r~

~ 41 the potting composition comprises the radiation-surface-cured skin layer 102 overlying the moisture-cured silicone mass 100 surrounding and encapsulating the solenoidal element 66 and AC:ciOt' ' i element structure. In this Figure 2 ~"lbo.li",~"1, the upper layer 100 subsequent to 5 radiation surface-curing formation thereof, remains moisture permeable, so that moisture L,dus,,,i~siun through the upper skin layer 102 has resulted in moisture-cure of the underlying potting material 100 to a solid state.

In the Figures 1 and 2 ~",I,odi",e,ll~, the thickness of the skin layer 1û102 may be on the order of 1û to 60 mils, d~,uendi~lg on the type and character of radiation utilized to effect the cure-formation thereof.

The radiation- and moisture-curable silicone compositions of the present invention thus afford a quick and convenient means for potting an 15 element, in which the initial radiation exposure forms a solid skin layer permitting subsequent moisture-curing of the underlying silicone co,,,~uosilioll~ but which at the same time permits i"""e-lidlt- handling, transport and storage of the skin-cured potted article. If such immediate han " ' ."~y is not required, the entire mass of the composition may be 2û fully moisture-cured, without the expedient of radiation exposure to form the upper skin layer.

The features and advantages of the invention are more fully illustrated in the following non-limiting examples, wherein all parts and ~ 25 p~,t ~ y~ are by weight, unless otherwise expressly stated.

WO 96/02579 2 1 9 2 8 ~ 2 . PCT/US95/08874 EXAMPLE

Five hundred ninety-four grams of a silanol-L~""i"dLt~d polydimethylsiloxane fluid with an average molecular weight of 18,000 (gel-permeation ul,ror,,dluyldully) was reacted with 10 9 of vlnyltrimethoxysilane using a butylithium catalyst for 2 hours. The catalyst was then quenched with acid. The material thus obtained is a vinyl.li, I I~Lhu~y-h, ~ IdL~d silicone fluid .

To 20 9 of the above fluid was added 0.30 9 of diethoxydct:Lupl-~nolle and 0.10 9 of titanium l~l~diso~.,upu~ide and the resulting cu"".osiliun (denoted hel~i"d~l~r as "Base Culll~Jcailioll") was thoroughly mixed.

The Base Coll~,uo~iLiull mixture was separated into 2 equal fractions and poured into aluminum dishes. One of these fractions, denoted here as Sample A, was subjected to uv irradiation using a Fusion System ultraviolet light source with a light intensity of ~75 milliwatts per square c~ l (mw/cm2) for one minute. The irradiated material formed a firm 2û non-tacky surface skin having a pale yellowish tint, and with uncured liquid enclosed ~",del"edll, the skin.

Attempted d~l~llll;,l~2;oll of the hardness of the material using a Durometer (00) gauge failed to register a reading (hardness 0). However, the skin film was firm enough so that the needle of the durometer gauge WO 96102579 r~,l".)~, _.'l /4 ~ 21 q2859 will not penetrate (rupture) the film. Inversion of the aluminum dish did not cause the liquid enclosed by the film to leak through it or rupture the film.

The other of the fractions denoted here as Sample B was not ~ 5surface radiation-cured or otherwise exposed to curingly effective radiation.

Both of the samples then were moisture-cured overnight and Durometer (00) readings were taken the following day for each. The Durometer (00) value measured for Sample A was 70 and the Durometer 10 (00) value measured for Sample B was 67.

As a Cu~ Jd~ ull, the Base Composltion was modified with only 1.5~h diethoxyacetophenone being added and without any titanium di~uurupu~dde therein (hult7illd~L~I denoted "Modified Composition A").
15 Modified Co,,,posiLiull A was uv-curable (using the same irradiation system as described above) to yield a firm layer of non-tacky skin with liquid enclosed therein. The enclosed liquid however would not moisture cure.
Inversion of the aluminum dish did not cause the liquid to leak through the skin.
~0 As a further culll,ùdlison a mixture of 594 9 of the above silanol lilldL~d fluid and 10 9 of the vinyllri"~t:ll,ùxysilane was made. Twenty grams of this mixture was formulated with 0.3û 9 of diethoxydct,lophel1o,1e.
The formulated mixture (he,ui"dil~l denoted "Modified Composition B'') 25 was subjected to the same uv irradiation system as above described and only a very thin layer of tacky skin was obtained. Inversion of the aluminum wos6/~2s7s 21 ~285~ r~i,u~

dish caused the liquid underneath the skin to leak through the thin skin.
The skin was also readily removed by finger touch.

As still a further ~ Ollludlisol1 370.4 9 of the same silanol fluid was 5reacted with 5.6 9 methyllli",~Lhoxysilane using butylithium catalyst for 2 hours. The catalyst was then quenched by acid. The material thus obtained was a methylui,,,~ll,uxy lt.llllilldled silicone fluid. To 20 9 of thisfluid was further added 0.30 9 of diethoxyau~luul~ ol,e. The resulting mixture (her~i"diL~, denoted "Modified Composition C") was subjected to 10the same uv irradiation system as described above.

Only a very thin surface layer of film was formed. Inverting the container of the mixture after uv curing caused the enclosed liquid to flow through the thin film i,,,,,,eu;.A.My. The film itself was so weak that lightly 15touching the film caused the film to be lifted from the liquid.

E)~AMPLE 2 Twenty grams of the silanol It:llllilldll::d fluid with an average molecular weight of 18 000 was mixed with 0.72 9 of vinyltrioximinosilane [CH2=CHSi(ON=CMeEt)3]. The mixture was further formulated with 0.30 9 of diethoxydct:luul1el1une and 0.10 9 of dimethyl tin bis(neodecanodl~).

The mixture was separated into two equal fractions denoted he,ui,ld~l~, as "Sample C'l and ''Sample D " respectively . Sample C was subjected to uv cure as described in Example 1 whereas Sample D was WO 96/02579 r"l/,J,.,e /~J

moisture cured. The uv cured Sample C was an initial pale yellowish gel with a firm, non-tacky surface probably with fluid underlying the gel. The film was firm enough so that when the aluminum dish was inverted, no enclosed liquid leaked through the film.
The hardness of the surface-cured Sample C material was found to be Durometer (00) of zero. Both Sample C and Sample D were exposed to ~I,,,o~,ulle,i,, relative humidity conditions to complete the moisture cure.
Both Sample C and Sample D showed Durometer (00) readings of 62 after 10 final moisture cure.

As a co",pari~u", vinylldu,~i",i"os,lane was replaced by methyll,io,.i",i"osilal,e in the above-described formulation procedure and the resulting CO~ JO~;I;On (Sample E) when irradiated by the same uv 15 curing procedure as Sample C yielded a material with a very thin, tacky skin which was readily lifted away upon lightly touching the surface with fingers. When the dish was attempted to be inverted, the uncured liquid beneath the skin illlllledidlt:dly flowed through the film.

Twenty grams of the silanol Itllll~illdl~d fluid with an average molecular weight of 18,000 was mixed with 0.72 q of vinyltrioximinosilane.
To this mixture was further and sequentially added 0.80 9 ~ 25 ethyltriacetoxysilane, 0.30 9 diethoxyac~lupll~"one, and 0.10 9 dimethyl tin bis(neodecanoate).

WO 96/0~79 2 1 9 2 8 5 9 The formulation was separated into two equal fractions, denoted heleil,d~lel as Sample F and Sample G, respectively. Sample F was subjected to uv curing by the same irradiation procedure as described 5 above for Sample C. The mixture formed a firm, non-tacky skin film layer upon uv cure. No liquid leaked through the film when the aluminum dish containing the surface-cured material was inverted. Both Sample F and Sample G then were moisture-cured for 72 hours, following which Durometer (00) values were determined. Each of the Samples F and G
10 yielded Durometer (00) readings of 60.

As a ~o~,udli~on~ the order of addition of vinyllliuxi,,,;~,osilane and ethyltriacetoxysilane was reversed in the above process, and the resulting material (Sample H) upon uv cure (by the same irradiation procedure as 15 Sample C) formed a very thin tacky film which was readily lifted by the touch of a finger. Inverting the aluminum dish containing this surface-cured material caused an i"""ed;.,~ flow of the liquid through the film. This formulation then was moisture-cured for 72 hours, yielding a cured silicone material having a Durometer (00) hardness value of 60.

Vinyltriacetoxysilane (0.47 g) was added to 20.74 g of silanol dlt:d silicone fluid with an average molecular weight of 20,000. To 25 this mixture was further added 0.30 g of diethoxyacetophenone and 0.10 g dimethyl tin bis(neodecdl,odl~). The formulation was thoroughly mixed and deaerated.

~ .

WO96/02579 P~ .l /4 ~ 47 21 92859 The resulting mixture then was separated into two equal fractions denoted herui"d~ as Sample I and Sample J.

Sample I was uv cured by the same irradiation procedure as described above for Sample C to yield a surface-cured silicone material having a firm non-tacky skin which was strong enough to hold the uncured liquid beneath the skin when the aluminum dish was inverted.

Both Sample I and Sample J then were moisture-cured overnight to form a cured silicone rubber product. Both cured materials (Sample I and Sample J) had the same Durometer (00) hardness value of 73.

Silanol-l~""i"dlt:d polydimethylsiloxane fluids with an average molecular weight of 20,000 were partially endcapped with trimethyl~;l,loru:,ild"e and hu~dlllulll;ldisild~dne. The resulting fluids were filtered and further t:ndl d~,,ued with vinyll~ioxi",;l IOaildlle.

The fluids upon addition of 1.5% diethoxydculupllenone and 0.5C/o dimethyl tin bis(lleodt:~ dllodl~) were found to be uv-surface-curable (by the same irradiation method described for Sample C) to yield an irradiated silicone material having a non-tacky skin. These formulations were also 25 cluler",i"ed to be moisture-curable to form silicone rubbers.

W096102!i79 21 92859 r~l,u~ ~ ,4 The hardness of the fully cured product rubbers was found to be correlated to the levels of trimethylsilyl endgroups. Specifically, the higher the trimethylsilyl level in the formulation, the softer the cured product rubber. The hardness of the cured product rubber samples was found to be unrelated to the mode of cure. Thus, both (uv/moisture) dual cure silicone rubber products and moisture-only cure silicone rubber products exhibited similar hardness levels as shown in Table I below.

TABLE I
HARDNESS VALUES FOR SAMPLES SEQUENTIALLY CURED BY INITIAL UV
EXPOSURE FOLLOWED BY MOISTURE CURE (DUAL CURE), VERSUS SAMPLES
FULLY CURED ONLY BY MOISTURE CURE (MONOCURE) Curino Motiali~y 0%M-3sl- 2ti%M~35i- 40xM-3si ~0%M~351 rio#Mu355 ~co% visl(oxlm~)3 DuaiCure 71 69 43 22 gum Monocur3 72 69 41 23 gum The silicone cu",po~iliun formulation procedure of Example 5 was repeated using the following ~hoLui,~ilidLul~ in place of diethoxydc~Lu,uhenolle:

wo 96/02579 2 1 9 2 8 5 9 F~l/~ S ~4 ~ 49 Darocur 1116 ((CH3)2HC6H4C=OC(CH3)2OH), 1173 (2-hydroxy-2-methyl-1-phenyl-propane-1-one), 1664 (,urup~ ld,y, E.M. Industries), and ~73 (~ruu~ ldly~ E.M. Industries).
In all cases the irradiation of the applied culll,uoailiulls on the substrate (aluminum pan) by the irradiation procedure of Example 1 yielded radiation-surface-cured materials having firm non-tacky surface layer films with chdldult~ lics similar to those obtained using the 1 û phului, lilidlul :~ of Example 5.

A vinyl-L~""i"dl~d silicone polymer having a weight average 15 molecular weight of 93,ûûO was formulated with 1.5%
diethoxydceluiullellolle~ The resulting silicone material upon uv irradiation formed a gel with liquid u"d~r"edlll the surface skin layer. This material however would not moisture cure.

This composition illustrates an ~",L,oui",e"l of the invention that may be useful in instances where formation of a strong and physically continuous film on top of a fluid is desired to prevent the underlying (uncured) fluid from migrating.

~ 25 The silicone conluo:,ilion of this Example may thus be usefully employed as a potting material, in which the silicone composition is WO 96/02579 P~ /4 2~ 9285~9 = ~ :~ o dispensed into a housing containing a "le.il,a,lis,l" structural element, or other material(s) for enr:ArslllAtion thereof. Subsequent to dispensing, the cor"po:,iliun is irradiated with surface-curingly-effective radiation to form a firm, fixedly posilioned and stable skin layer on the upper surface of the 5 potting mass. Below such overlying cured silicone layer, contained by the bounding surfaces of the housing, is the uncured liquid silicone composition.

The underlying liquid, as a result of its co"~il,ell,~:"l by the surface-10 cured skin and bounding cavity surfaces to which the skin is adherentlybonded, thereafter functions as a fluidic en~Ar.sl IlAtion and shock damping system.

As a result of its viscous damping character, the uncured potting 15 material contained by the overlying cured layer o f potting material is markedly superior to solid (fully cured resin) potting compositions of the prior art, in respect of protecting the encArsl IlAtPd structure or material from damage or displacement which otherwise may occur due to shocks, vibration, impact, etc. exerted on the encArsl IlAtinn (potting) system.

Further, the ''liquid potting" formulation of the invention is not subject to differential thermal expansion effects which adversely affect solid potting masses by causing cracking and stress fractures and A~c~ d tensile, cu",,ult:s~ive, and torsional forces on the Illecl,dnis~ or elements being 25 encArs~lAted by the potting medium.

~os6/02s7s 21 72857 r~ /4 For these reasons the liquid potting structure of the present invention co""Jri:.i"y a surface radiation-cured skin and an underlying uncured liquid in a cavity or other ~ullldMlllelll locus is a marked advance in the art of potting and en~rClll~ti~n~

Forty grams of 100 cps (Brooksfield vi~co,~ r) silanol-l~""i"dled polydimethylsiloxane fluid with a number average molecular weight of 105 000 (nuclear magnetic ,t,sonance) was mixed (encapped) with 5.00 9 of vinyltris(methylethyik~lu,~i",i"o)silane. The initially cloudy mixture became clear in a matter of seconds when endca~,,.i"y was complete. To the mixture was further added 0.675 9 of diethoxydc~luph~"one.

15To an aluminum dish with a diameter of 65 mm was added 0.5 9 of the above formulation. The material was allowed to spread to cover the whole dish. The thickness of the coating coverage was ~uplwdllldl~ly 6 mils. UV irradiation of the coating using a Fusion System lamp (medium pressure mercury lamp) at a radiation flux of @ 75 " li~.~tl~/u~l2 for one 2û minute resulted in a soft cured silicone coating that was dry to the touch.
The coating will further moisture cure to give a hard silicone coating.

In contrast when methyltris(methylethylk~Lu~ ;"o)-silane was used in place of vinyltris(methylethyl-k~lwd"li,lo)silane in the above formulation 25 the resulting material showed no uv curing capability under identical curing WO96/025?9 I~,l/u..,~ /4 21 92859 - o conditions. The material remained liquid after attempted uv curing. The material did moisture cure to a silicone coating after a few hours standing.

Six hundred grams of a 40 cps (Brooksfield visco",t:l~,) siiicone fluid 80% of which had silanol terminal ends and 20Yo of which had trimethylsilyl ends was mixed with two hundred fifty-seven grams of methacryloxyprop~,ll,i,,,~ll,uxysilane in a reactor with nitrogen sparge.
Butyllithium catalyst (1 .6M; 0.36 9) was added to the mixture. The mixture was stirred with nitrogen sparge for 90 minutes and then sparged with carbon dioxide for 30 minutes. The mixture was then vacuum stripped at 70 degrees Centigrade for 1 hour to obtain a silicone fluid which was 80%
methacryloxypropyldi",t,ll,oxy l~llllilldl~d and 20Yo trimethylsily terminated 15 and designated as Fluid M.

Two hundred forty one grams of the 40 cps silicone fluid with 80%
20 silanol terminated ends and 20% trimethylsilyl ends was allowed to react with ninety grams ûf acryloxypropyltrimethoxysilane in the presence of 0.5 ml of butyllithium (1.6M) in dCCUIddllce with the procedure set forth in Example 9 to obtain an 80% acryloxypropyldimethoxysilyl lt:llllilldl~d 20%
trimethylsily lt:llllilldll::d silicone fluid designated as Fluid A.

W096/02579 21 92859 r~ 5l /~

~ 53 Two hundred fifty seven grams of the 40 cps silicone fluid with 80%
silanol It~ dl~d ends and 20~h trimethylsilyl ends was allowed to react 5 with 61.7 grams of vinylld"n:lhuxysilane in the presence of 0.2 ml of butyllithium (1.6M) in acco,dallce with the procedure set forth in Example 9 to obtain an 80% vinyldimethoxysilyl It~llllilldl~d, 20% trimethylsily It~llllilldl~:d silicone fluid desi~u"dlt,d as Fluid V.

Two hundred sixty grams of the 40 cps silicone fluid with 80~h silanol It:llllilldl~d ends and 20~h trimethylsilyl ends was allowed to react with 35 grams of methacryloxypropyltrimethoxysilane 33 grams of acryloxypropyl-15 trimethoxysilane and 21 grams of vinyll,i",t~ll,oxysilane in the presence of0.3 ml of butyllithium (1.6M) in auuu,dd"ce with the procedure set forth in Example 9 to obtain a silicone fluid of apl., u,d" Id~ y 27%
methacryloxypropyldimethoxysilyl ends 26% acryloxypropyldimethoxysilyl ends 27 % vinyldi",etl,u,~ysilyl ends and 20 trimethylsilyl ends designated 20 as Fluid MAV.

Example 12 embodies an alternative method for the p~t:ua~dliull of the cu,l,uosilions of the present invention wherein the first and second silicone fluids are prepared concurrently from an appropriate silanol or 25 silanol mixture and first silane having a monovalent radiation curable ethylenically unsaturated group and at least two hydroly~able groups and WO 96/02579 2 1 9 2 8 ~ 9 PCT/US95/08874 at least one other silane having a (meth)acryl functional groups and at least two hydrolyzable groups.

It is lecO~"i~tsd that one silicone fluid may have both a radiation curable ethylenically unsaturated group and a radiation curable (meth)acryl functional group. However, because of the mole ratio of these moieties, at least some of the silicone fluids having the (meth)acryl functional groups will be free of the ethylenically unsaturated group. The mole ratio of silanes is de,~ ldel ll upon the level of monovalent, radiation curable ethylenically unsaturated groups desired with the total amount of silanes being about the stoichiometric amount relative to the SiOH
ful l~,liol~ 'ity of the starting silanol fluid.

Seven sample formulations (Samples 1-7) were prepared wherein the silicone fluids, obtained from the procedures set forth in Examples 9-12, were included in varying ratios as set forth for each sample in Table ll below. Diethoxyacelupl1enol1e in the amount of 6.5% based on weight of total silicones, was added to each sample as the photoinitiator.
Applu~dllldlt:ly 0.5 grams of each sample formulation was poured into an aluminum dish of dlJ,ulu~idllllely 65 mm diameter. The material was spread to coat the whole base of the dish to an du,l~lu~ ldl~ thickness of 5 mil.
The coating was subjected to uv irradiation using a Fusion System ultraviolet light source with a light intensity of ~60 milliwatts per square celllilll~i~, (mw/cm2) for various durations as set forth in Table ll.

~0 96/02s79 2 1 9 2 8 5 9 p~ 4 ~ 55 Tackiness of the resulting uv cured coatings were d~l~r,l,i"ed by lightly touching the coating with a finger. A number of 0-5 was then assigned to each coating. The number grade denotes the tackiness of the 5 surface cure and is defined as below:
0 = no cure 1 = some thickening of the coating fluid, surface remains liquid covered.
2 = significant thickening of the fluid, when touched upon, the fluid " ,or"e, lldl ily 11 Idil lld;l ,ed a fingerprint mark, 10 3 = coating cured to a gum, leaves a fingerprint mark when touched, 4 = coating is cured but tacky, 5 = coating is fully cured with a dry to the touch surface.

The 7 sample formulations used and their tackiness pt~l ~"", Idl ICtlS at 15 different levels of curing are shown in Table 11 below:

Fluid M 93.5% 73.5% 73.5% 73.5% 0% 0~h 0%
Fluid V 0~/O 20% 0% 0% 93.5% 0% 0%
Fluid A 0% 0~/O 20% 0% 0~fO 93.5% 0~h Fluid MAV 0~/O 0~/O 0~/O 20% 0% 0% 93.5%
DEAP 6.5~~'o 6.5% 6.5% 6.5% 6.5% 6.5% 6.5%
UV 60sec 5 5 5 5 0 5 5 30sec 2 3 1 1 0 2 4 25 sec 1 2 2 2 0 1 4 20 sec 1 2 1 1 0 1 3 15 sec 1 2 1 0 0 0 3 10 sec 0 1 0 0 0 0 2 WO96102579 r~ ,t 4 21 9526859 ~ O

The results set forth in Table ll indicate that presence of Fluid V
resulted in a much improved surface cure than of Fluid M by itself (Sample 1) or Fluid A by itself (Sample 6). Fluid V by itself (Sample 5), however, 5 performed poorly. The best pt:l~ulllldrlce was with Fluid MAV (Sample 7).

Seven additional sample formulatiûns (Samples 8-14) were 1 û prepared wherein the silicone fluids obtained from the procedures set forth in Examples 9-12 were included in varying ratios as set forth for each sample in Table lll below. DiethoxyacuLupllenone in the amount of 6.5%
based on weight of total silicones, was added to each sample as the photoinitiator and LuLldiau,~lu,uyl titanate was added as a moisture cure 15 initiator. Each sample formulation coating was subjected to uv cure according to the procedure set forth for samples 1-7 in Example 13 above.
The samples were further allowed to moisture cure to non-tacky coatings.
Surface tack i"""edidLuly after the uv cure, but before the moisture cure were dc~,.",i"ed as setforth in Example 13. The formulations for samples 20 8-14 and the pe, ~u""dnces are set forth in Table lll below.

WO 96/02s~9 2 1 9 2 8 5 9 r ~"J~ s.~ ~4 ~ 57 TABLE lll Fluid M 93.1~h 73.1~h 73.1% 73.1% 0% 0% 0~h Fluid V 0% 20% 0% 0~h 93.1~h 0% 0~h Fluid A 0~h 0~h 20% 0% 0~h 93.1~h 0~h Fluid MAV 0~h 0~h 0% 20~h 0~h 0% 93.1~h DEAP 6.5~h 6.5% 6.5~h 6.5% 6.5% 6.5% 6.5%
TIPT 0.4% 0.4~h 0.4% 0.4% 0.4~h 0.4~h 0.4%
UV 60sec 5 5 5 5 o 5 5 30sec 5 5 5 5 0 5 5 25 sec 2 3 4 4 0 4 4 20 sec 1 2 2 2 0 2 3 15 sec 0 2 2 2 0 2 3 10 sec 0 1 1 1 0 1 2 The results set forth in Table lll indicate that partial r~place",e"l of Fluid M by Fluid V resulted in a much improved surface cure than of Fluid M
by itself even though Fluid V itself would not surface cure (Sample 12).
Overall results were such that presence of vinyl provided a faster to the touch cure. It is believed that the presence of moisture cure catalyst combined with heat of the photocure enhanced surface cure of acrylate and methacrylate co""~usilions. Even though acrylate cu",po~ilion appears to perform nearly as well as vinyl containing compounds, the vinyl resins do not have environmental, health and safety concerns ~co. i~t~d with acryl functional silicone.

WO 96/02579 2 1 9 2 8 5 9 PCT/usgcl08874 INDUSTRIAL APPLICABILITY OF THE INVENTION

The radiation- and/or moisture-curable silicone co",~uosiliuns of the present invention have utility as sealants, adhesives, coatings, potting cor"pobilio,ls, and the like.

In such d,Uf '' " ~115, the radiation curability of the silicone composition permits the ready di~p~l~bil 19 and curing of the silicone material and ~ull~a,uol1dillg ready handling and further plucesbillbl of structural surfaces, parts, and asse",'' with which the silicone composition is employed.

Further, the liquid potting,, " ~., described he,t:i"dl.uve may be employed in the potting of ",e.,l,a"icdl and/or electrical assell' " , in a manner using the uncured potting material as a viscous damping medium.
Such potting d"d"y~",e"l minimizes the su , :' " y of the potted structural element to damage or malfunction from shock, I,dllsldliu,~ and 2û impact of the potted assembly.

.. . ... . .

While the invention has been illustratively described herein with ~ 25 reference to various preferred features, aspects and embodiments, it will be d,upl~cidl~d that the invention is not thus limited, and may be widely varied in respect of alternative variations, Illodilil,dliullb, and other embodiments, .. ..... .. .. .. ... . .. .. .... . .. . . _ _ ... .. . _ wo s6/0~s79 2 1 9 2 8 5 9 r~

~ 59 and therefore the invention is to be broadly construed as including such alternative variations, Illodi~ dliolls and other en,L,odi",e"L~, within the spirit and scope of the invention as claimed.

Claims

What is claimed is:

1. A radiation and/or moisture-curable silicone composition which upon exposure to radiation surface cures to form a firm surface skin layer overlying a bulk interior moisture-curable volume of the composition, said composition comprising:

(A) a silicone formed as a reaction product of a silanol-terminated silicone and a silane cross-linker including an ethylenically unsaturated functional group and at least two hydrolyzable functional groups, and (B) a photoinitiator effective for radiation curing of the silicone composition;

wherein the silicone (A) is selected from the group consisting of:

(I) silicones (A) whose precursor reactant silanol terminated silicons has at least 60 mole percent Si-OH terminal groups and a viscosity at room temperature not exceeding 1000 centipoise, and whose precursor silane cross-linker includes as said ethylenically unsaturated functional group a monovalent ethylenically unsaturated functional group and wherein the silicone (A) is present in the silicone composition, in combination with a second silicone fluid having both radiation curable (meth)acryl functional groups and moisture curable hydrolyzable functional groups, wherein the mole raio of the ethylenically unsaturated groups to the (meth)acryl functional groups is from 5:95 to 4:6;

and (II) silicones (A), which are endcapped with an ethylenically unsaturated functional group, which have a number average molecular weight determined by nuclear magnetic resonance of at least 5000, and whose precursor silane cross-linker is devoid of mercapto functional groups and has said ethylenically unsaturated functional group and said at least two hydrolyzable functional groups directed joined to a silicon atom of said silane cross-linker.

2. A silicone composition according to claim 1, said precursor silane cross-linker has the formula:
RaSiXb wherein:
R is selected from the group consisting of monovalent ethylenically unsaturated radicals, hydrogen, C1 - C8 alkyl, C5 - C12 aryl, C7 - C18 arylalkyl, C7 - C18 alkylaryl, and X.
X is a monovalent functionality imparting moisture-curability to the reaction product of the silanol-terminated silicone and silane cross-linker;
a has a value of 1 or 2;
b has a value of 2 or 3; and a+b=4.

3. A liquid-phase radiation surface-curable RTV silicone composition which upon exposure to radiation forms a solid skin layer overlying uncured liquid of said composition, and which subsequent to radiation surface curing thereof is interiorly moisture-curable in character in said uncured liquid overlaid by said solid skin layer formed by said radiation exposure, said radiation surface-curable subsequently interiorly moisture-curable RTV silicone composition comprising:
an ethylenically unsaturated functional group endcapped silicone wherein said endcapped silicone is formed by reacting a silanol-terminated silicone with a non-mercapto-group containing silane cross-linker for the silicone, such cross-linker having joined directly to a silicon atom thereof an ethylenically unsaturated functional group and at least two hydrolyzable functional groups and said endcapped silicon has a number average molecular weight of at least about 5000 as determined by nuclear magnetic resonance; and a photoinitiator effective for radiation surface curing of the silicone composition.

4. A composition according to claim 3, wherein the endcapped silicone has a number average molecular weight of at least about 10,000.

6. A composition according to claim 3, wherein the silanol-terminated silicone comprises a linear polydiorganosiloxane having a weight average molecular weight of from about 5,000 to about 300,000 as determined by gel-permeation chromatography.

6. A composition according to claim 3, wherein the silanol-terminated silicone is predominantly linear in character, having the silanol (-SiOH) functionality located at the terminus of a polysiloxy (-(SiO)x-) moiety in the silicone molecule.

7. A composition according to claim 3, wherein the silanol-terminated silicone is a linear molecule both of whose terminal functional groups comprise hydroxy groups.

8. A composition according to claim 3, wherein the silanol-terminated silicone is an organopolysiloxane whose organo substituents are predominantly methyl.

9. A composition according to claim 2, wherein the monovalent ethylenically unsaturated radical contains from 2 to 12 carbon atoms.

10. A composition according to claim 2, wherein the monovalent ethylenically unsaturated radical is selected from the group consisting of vinyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, allyl, alkenyloxy, alkenylamino, allyloxy, allylamino, furanyl, phenyl, and benzyl groups.

11. A composition according to claim 2, wherein the monovalent ethylenically unsaturated radical is selected from the group consisting of vinyl and allyl groups.

12. A composition according to claim 2, wherein the monovalent ethylenically unsaturated radical is vinyl.

13. A composition according to claim 3, wherein the silane cross-linker is selected from the group consisting of vinyltrimethoxysilane, vinyltriaminosilane, vinyltriamidosilane, vinyltrioximinosilane, vinyltriiosopropenoxysilane, and vinyltriacetoxysilane.

14. A composition according to claim 1, wherein the photoinitiator is selected from the group consisting of benzoin, benzophenone, Michler's ketone, dialkoxy-acetophenones, acetophenone, benzil, and derivatives and mixtures thereof.

15. A composition according to claim 1, wherein the photoinitiator is diethoxyacetophenone.

16. A composition according to claim 1 wherein the photoinitiator has a concentration of from about 0.1% to about 10% by weight, based on the weight of the silanol-terminated silicone.

17. A liquid phase radiation surface curable silicone potting material for dispensing to an encapsulation locus including a bounding surface delimiting a volume in which an encapsulation structure is disposable for potting in a liquid medium overlaid by an enclosure layer adhesively bonded to the bounding surface, wherein the potting material upon exposure to radiation forms a solid skin layer constituting said enclosure layer, ove-lying uncured liquid of said potting material, and wherein the potting material subsequent to radiation surface curing thereof interiorly comprises uncured liquid as said liquid medium, said potting material comprising:

an ethylenically unsaturated functional group endcapped silicone wherein said endcapped silicone is formed by reacting a silanol-terminated silicone with a non-mercapto-group containing silane cross-linker for the silicone, such cross-linker having joined directly to a silicon atom thereof an ethylenically unsaturated functional group and at least two hydrolyzable functional groups and said endcapped silicon has a number average molecular weight of at least about 5000 as determined by nuclear magnetic resonance; and a photoinitiator effective for radiation surface curing of the silicone composition, wherein the potting material is surface-curable by irradiation of the material to form said overlying enclosure layer and wherein subsequent to formation thereof the potting material underlying the enclosure layer is moisture-curable.

18. A potted element structural article, comprising:

means defining an encapsulation locus including a bounding surface delimiting an encapsulation volume;

an element disposed in the encapsulation volume; and a potting medium encapsulating the element in the encapsulation volume, said potting medium comprising a silicone liquid medium overlaid by a solid silicone film enclosingly and adhesively bonded to the bounding surface, so that the element is potted in the silicone liquid medium, and the silicone liquid medium is contained in the encapsulation volume by the solid silicone film.

19. A potted element structural article according to claim 18, wherein the means defining an encapsulation locus comprise a housing including bounding side walls providing said bounding wall surface.

20. A potted element structural article according to claim 18, wherein the potted element comprises at least one member selected from the group consisting of electrical, mechanical, electronic. optical, acoustic, and material elements.

21. A potted element structural article according to claim 18, wherein the potted element is an electromechanical element.

22. A potted element structural article according to claim 18, wherein the potting medium comprises a surface-radiation-cured potting composition formed by surface-radiation-curing of a silicone composition comprising:

an ethylenically unsaturated functional group endcapped silicone having joined directly to a silicon atom thereof an ethylenically unsaturated functional group and no hydrolyzable groups and said endcapped silicon has a number average molecular weight of at least about 5000 as determined by nuclear magnetic resonance; and a photoinitiator effective for radiation surface curing of the silicone composition, wherein the potting material is surface-curable by irradiation of the material to form said overlying enclosure layer and wherein subsequent to formation thereof the potting material underlying the enclosure layer is non-moisture-curable.

23. A method of potting an element in a structural encapsulation locus including a bounding wall surface, said method comprising:

disposing said element in the encapsulation locus;

dispensing into the encapsulation locus a liquid-phase radiation surface-curable silicone potting composition which upon exposure to radiation forms a solid skin layer overlying uncured liquid of said composition, and which subsequent to radiation surface curing thereof, comprises interiorly uncured liquid overlaid by said solid skin layer formed by said radiation exposure, said radiation surface-curable silicone composition comprising: an ethylenically unsaturated functional group endcapped silicone optionally having at least two hydrolyzable functional groups and said endcapped silicon has a number average molecular .
weight of at least about 5000 as determined by nuclear magnetic resonance; and a photoinitiator effective for radiation surface curing of the silicone composition: and irradiating the silicone potting composition in the encapsulation locus, to surface-cure same and form a solid silicone layer enclosingly and adhesively bonded to the bounding surface, and overlying non-radiation-cured potting composition.

24. A method according to claim 23, wherein said encapped silicone has no hydrolyzable groups and the non-radiation-cured potting composition is uncurable by moisture exposure, and the non-radiation-cured potting composition is maintained in uncured condition, so that the element in the encapsulation locus is potted in the non-radiation-cured potting composition.

25. A method according to claim 23, wherein the non-radiation-cured potting composition is a liquid.

28. A method according to claim 23, wherein the non-radiation-cured potting composition subsequent to said irradiating step is moisture-curable, further comprising moisture-curing the non-radiation-cured potting composition.

27. A radiation- and moisture-curable silicone conformal coating composition which upon exposure to radiation is surface cured to form a firm, non-tacky surface skin overlying a bulk interior uncured volume of the composition, said composition comprising:

a first silicone fluid comprised of a reaction product of a silanol terminated silicone having at least 60 mole percent Si-OH terminal groups and a viscosity, at room temperature, of 1000 centipoise or less and a silane cross-linker having a monovalent, radiation curable ethylenically unsaturated functional group and at least 2 hydrolyzable groups;

a second silicone fluid having both radiation curable (meth)acryl function groups and moisture curable hydrolyzable groups; and a photoinitiator effective for radiation curing of the silicone composition, wherein the mole ratio of the ethylenically unsaturated groups to the (meth)acryl functional groups being from 5.95 to 4:6.

28. A composition according to claim 27, wherein the first and second silicone fluids are prepared concurrently from a silanol terminated silicone having at least 60 mole percent Si-OH terminal groups and a viscosity, at ambient, of 1000 centipoise or less and at least two silane cross-linkers, one of said cross-linkers having a monovalent, radiation curable ethylenically unsaturated group and at least two hydrolyzable groups and said at least one other silane having a (meth)acryl functional group and at least two hydrolyzable groups.

29. A composition according to claim 27, wherein the mole ratio of the ethylenically unsaturated groups to the (meth)acryl functional groups is from 1:5 to 35:65.

30. A composition according to claim 27 wherein the silanol terminated silicone has a viscosity as measured at ambient of less than or equal to about 750 cps.

31. A composition according to claim 30, wherein the silanol terminated silicone has a viscosity as measured at ambient conditions of less than or equal to about 200.

32. A composition according to claim 27, further comprising a nonreactive moiety endcappsd silicone.

33. A composition according to claim 27 further comprising a moisture cure initiator.

34. A composition according to claim 27, wherein the monovalent ethylenically unsaturated functional group contains from 2 to 12 carbon atoms.

35. A composition according to claim 27, wherein the monovalent ethylenically unsaturated radical is selected from the group consisting of vinyl, propenyl and allyl groups.

36. A composition according to claim 27, wherein the monovalent ethylenically unsaturated radical is vinyl.

37. A composition according to claim 36, wherein said silane cross-linker is selected from the group consisting of vinyltrimethoxysilane, vinyltriaminosilane, vinyltriamidosilane, vinyltrioximinosilane, vinyltris-(methylethylketoxlmino)silane, vinyltriisopropenyloxysilane and vinyltriacetoxysilane.

38. A composition according to claim 27, wherein said (meth)acryl functional group is selected from the group consisting of acryl, (meth)acryl, butenyl, pentenyl, hexenyl, octenyl, alkenyloxy, alkenylamino, allyloxy, allylamino, furanyl, phenyl, and benzyl groups.

39. A composition according to claim 27, wherein said second silicone fluid is selected from the group consisting of (meth)acryloxypropyldimethoxysilyl terminated silicone, acryloxypropyl-dimethoxysily terminated silicone and a mixture thereof.

40. A composition according to claim 32, wherein the nonreactive moiety endcapped silicone is selected from the group consisting of alkyl, aryl arylalkyl, and alkylaryl endcapped silicone.

41. A composition according to claim 32, wherein the nonreactive moiety endcapped silicone is trimethylsilyl endcapped silicone.

42. A composition according to claim 27. wherein the photoinitiator is selected from the group consisting of benzoin, benzophenone, Michler's ketons, dialkoxy-acetophenones, acetophenone, benzil, and derivatives and mixtures thereof.

43. A composition according to claim 27, wherein the photoinitiator is diethoxyacetophenone.

44, A composition according to claim 27, wherein the photoinitiator has a concentration of from about 0.1% to about 15% by weight, based on the weight of the silanol-terminated silicone.

45. A composition according to claim 33, wherein the moisture cure initiator is an orthotitanate.

48. A composition according to claim 27, wherein the first silicone fluid is present in an amount of from about 20 to about 35 parts by weight, the second silicone fluid is present in an amount of from about 80 to about 65 parts by weight, and the photoinitiator is present in an amount of from about 1 to about 15 parts by weight.
CA002192859A 1994-07-15 1995-07-14 Radiation- and/or moisture-curable silicone compositions Abandoned CA2192859A1 (en)

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US284,016 1981-07-16
US276,019 1994-07-15
US08/276,019 US5498642A (en) 1992-03-31 1994-07-15 Radiation surface-curable, room temperature vulcanizing silicone compositions
US08/284,016 US5516812A (en) 1992-03-31 1994-08-01 UV-moisture dual cure silicone conformal coating compositions with improved surface tack
PCT/US1995/008874 WO1996002579A1 (en) 1994-07-15 1995-07-14 Radiation- and/or moisture-curable silicone compositions

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WO1996002579A1 (en) 1996-02-01
EP0772636A4 (en) 1997-09-24
US5516812A (en) 1996-05-14
KR970703371A (en) 1997-07-03
EP0772636A1 (en) 1997-05-14
JP2001523274A (en) 2001-11-20
DE69528529D1 (en) 2002-11-14
NO964720L (en) 1996-12-19
ATE225812T1 (en) 2002-10-15
NO964720D0 (en) 1996-11-07
KR100385473B1 (en) 2003-11-28
MX9605612A (en) 1998-05-31
EP0772636B1 (en) 2002-10-09
DE69528529T2 (en) 2003-06-26

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