WO2012032232A1

WO2012032232A1 - Compressible roller for printers

Info

Publication number: WO2012032232A1
Application number: PCT/FR2011/000474
Authority: WO
Inventors: Delphine Blanc; Sébastien LAVANDIER; Nicola Ranieri
Original assignee: Bluestar Silicones France
Priority date: 2010-09-06
Filing date: 2011-08-25
Publication date: 2012-03-15
Also published as: CN103180144A; BR112013005289A2; CN103180144B; MX2013002549A; EP2613942A1

Abstract

The invention relates to a compressible roller (1) comprising: a cylindrical rigid roller core (2); an intermediate layer (3) of silicone foam, which covers the roller core (2); and an outer layer (4) which is formed by a silicone elastomer and which covers the intermediate layer (3).

Description

COMPRESSIBLE ROLL FOR PRINTER

The present invention relates to novel compressible rolls useful for printing or pad printing and comprising a flexible portion of silicone foam.

The term "silicone foam" or "silicone foam" refers to a polyorganosiloxane composition in the form of foam. Silicone foams are well known in the art and their preparations are described in a number of patents.

In most printing techniques, a printing roll is used.

In order to improve print reproducibility, many t

Flexible printing has been developed.

For example, US-A-3467009 discloses the manufacture of a flexible printing roll comprising a roll core, an intermediate layer of polyurethane foam, natural rubber or neoprene, and at least one prepared compressible outer layer from fibrous materials impregnated with elastomeric substances.

EP-A-577920 discloses a compressible roll comprising a roll core, an intermediate layer of nitrile / polyvinyl chloride foam and an outer layer comprising a polyurethane seal.

However, the type of foam employed in these prior art rolls is unsatisfactory for printing applications which are becoming more demanding in terms of print quality and durability of the printing roll. For example, a problem encountered in the manufacture of these rolls relates to manufacturing defects related to an uncontrolled foaming of the foam intermediate layer generating defects related to the presence of bubbles of too large sizes and whose distribution within the material foamed is heterogeneous thus impacting on the mechanical properties of the roll.

In addition, the foams used in the prior art no longer comply with the constraints imposed by new industrial manufacturing processes. for example in a field such as the manufacture of rolls for pad printing, it is common practice to use centrifugation techniques which impose new foaming constraints, thus affecting the size and the distribution of the bubble size of the foamed material, a key element of roll for printing. Indeed, when the sizes of these bubbles are too large and the bubble size distribution within the foamed material is important, this leads to anisotropy of the physical properties of the roll.

Thus for some applications, such as pad printing (or roll printing), specific properties of the foams are sought. Pad printing is an indirect printing process. The pattern to be printed is previously etched on a support, the plate is then fixed on a tampograph machine; then the ink is deposited in the etched portions to transfer the pattern onto the object to be printed by means of a silicone foam pad or roll. In order to achieve quality engraving and printing, it is essential that the silicone foam pad or roll be small sized bubbles and that the bubble size distribution within the material be homogeneous so that the The ink can be uniformly deposited and transferred onto the receiving layer supported by the silicone foam layer while allowing accurate reproduction of the etching. By "small bubbles" is meant bubbles whose width (or diameter) is less than or equal to about 1 mm, with "medium size bubbles" the width (or diameter) is between 1 and 1.5 mm , whereas for "big bubbles" the width (or diameter) is greater than 1, 5 mm. Thus, the need to obtain foams having small bubbles and a uniform distribution of bubble sizes is particularly sought after for this application.

The preparation of the foamed portion of the rolls for flexible printing is therefore the subject of particular attention in the field of printing.

Several techniques for obtaining silicone foams have been described in the prior art. A first technique implements a condensation reaction with release of volatile by-products. This is particularly the case for systems using the SiH-SiOH type condensation reaction which releases hydrogen which then acts as a blowing agent. For example, French Patent No. FR-A-2,589,872 discloses a silicone foam precursor composition comprising an organosilicon polymer comprising siloxane units having silicon-bonded hydroxyl groups, an organosilicon polymer comprising siloxane units having silicon-bonded hydrogen atoms, a catalyst, for example a tin compound , and a finely divided filler comprising silica that has been treated to become hydrophobic. These compositions cure by a polycondensation reaction and, although satisfactory in many respects, the tin-catalyzed compositions described in French Patent No. FR-A-2,589,872 are considered unsatisfactory because of their use of a tin catalyst which can exert certain undesirable toxic effects.

An alternative described in US Pat. No. 3,923,705 has been to provide compositions comprising polydiorganosiloxanes carrying silicon-bonded hydrogen atoms available for condensation reaction with polydiorganosiloxanes bearing silicon-bonded hydroxyl groups (silanols). ) in the presence of a platinum catalyst. This reaction thus makes it possible to build the network while producing hydrogen gas necessary for the formation of a silicone foam. In this type of formulation, the formation of gas is proportional to the rate of crosslinking and consequently the density of the foams obtained is difficult to control, thus explaining the difficulties in obtaining low density foams by this technique. These compositions may further comprise a polydiorganosiloxane carrying silicon-bonded vinyl groups which simultaneously crosslink by polyaddition reactions with polydiorganosiloxanes bearing silicon-bonded hydrogen atoms thereby participating in the construction of the silicone foam network.

According to another variant described in US Pat. No. US-B-4, 189,545, silicone foams are prepared from a composition comprising water, a polydiorganosiloxane carrying silicon-bonded vinyl groups, a polydiorganosiloxane containing hydrogen atoms bonded to silicon and carried by patterns in the chain and not only at the end of the chain to be able to play a role of crosslinking. The water reacts with the hydride functional polysiloxane thus producing hydrogen gas and a silanol. The silanol then reacts with the hydride-functional polydiorganosiloxane by a condensation reaction thus generating a second molecule of hydrogen gas while another polydiorganosiloxane carrying silicon-bonded vinyl groups will simultaneously react with one addition reaction with another. polydiorganosiloxane hydride function, thereby participating in the construction of the network of silicone foam. The main contribution made by this technique is that hydrogen gas is produced without the addition of silanol and with the addition of a small amount of water. In US Pat. No. 4,590,222, silicone foams are prepared from compositions comprising a polydiorganosiloxane, a resin, a platinum-based catalyst, an organohydrogensiloxane, a polyorganosiloxane carrying hydroxyl groups on the end-chain units, a filler and an organic alcohol. However, techniques using silanol as a pore-forming agent source tend to give foams with densities too high for many applications, for example those intended for the printing industry. In addition, when foams of medium density are obtained, this is most often at the expense of mechanical properties (tensile strength, tear resistance, ...).

Another technique is to use porogenic agents or additives, added in the silicone matrix, which, under the action of heat, expand the material:

or by decomposition with gas release, in particular azo-type derivatives, for example azodicarbonamide, which will make it possible to release nitrogen, carbon dioxide and ammonia. This type of blowing agent, despite the fact that it is widely used for other materials, poses serious problems of toxicity (hydrazine release),

- or by phase change (gas liquid) - especially low-boiling solvents.

Another example of a precursor composition of silicone foam is described in reference WO-A-00/46282. The described composition comprises a crosslinking silicone base by a polyaddition reaction (SiH functional polyorganosiloxane oil / Si / vinyl functional polyorganosiloxane oils / Pt catalyst, with Vi = vinyl group), a hydroxyl-functional compound and wollastonite (the examples describe highly charged compositions, about 21 parts by weight of filler relative to the total weight of the composition). It should be noted that the viscosities of the compositions prepared in the examples (Example 1, Table 2) are all greater than 190,000 mPa.s. As indicated above, it is known (see patent US-B-4,418,157 in column 2, lines 13 to 24) that the higher the viscosity of the composition and the lower the density of the resulting foam. It will be noted that the most viscous composition (reference WO-A-00/46282, Table 2, page 13, composition [1-1], viscosity of 274,000 mPa.s) to the least viscous composition [1-3] (viscosity = 198,000 mPa.s) the density of the foam obtained increases (from 0.20 g / cm ³ to 0.25 g / cm ³ ) thus confirming the known teaching concerning the difficulty of obtaining low density foams from low viscosity composition (viscosity less than 30,000 mPa.s) before crosslinking. Except, for reasons of optimization when the implementation of these compositions, either by the end user or by manufacturers using silicone foam production lines, it is vital to have a composition which, before crosslinking, is in a low viscosity form and easily flowing in the appropriate tools.

Thus, in the preparation of printing rolls it is important to obtain low density silicone foams so as to lighten the equipment used in printing and pad printing techniques.

The problematic considered here can therefore be summed up as the search for a technical compromise between specifications, a priori antinomic, for the preparation of a precursor composition of silicone foam having a low viscosity, that is to say less than 30. 000 mPa.s and precursor of a silicone foam which has a low density, that is to say less than 0.25 g / cm ³ , good mechanical properties, bubble sizes less than or equal to 1 mm and a uniform distribution of bubble sizes within the foamed material. In addition, the desired foams should no longer present problems related to the intervention of new techniques, such as centrifugation, in industrial manufacturing processes of the printing rollers.

The present invention therefore aims to provide a new compressible roller useful for printing whose foamed portion is prepared from an organopolysiloxane composition of low viscosity, that is to say less than 30,000 mPa.s, which, after crosslinking and / or hardening, makes it possible to generate a low density silicone foam, that is to say less than 0.25 g / cm ³ , while obtaining silicone foam having good mechanical properties, bubble sizes whose width or diameter is less than or equal to about 1 mm and a uniform distribution of bubble sizes within the material. The present invention therefore aims to provide a new compressible roll (1) comprising:

a cylindrical and rigid roll core (2),

an intermediate layer (3) made of silicone foam and which covers said roll core (2), and

an outer layer (4) consisting of a silicone elastomer and covering said intermediate layer (3),

said roll being characterized in that said an intermediate layer (3) of silicone foam is prepared by cross-linking and / or curing an organopolysiloxane composition X comprising:

at least one polyorganosiloxane A having a viscosity of between 10 and 300,000 mPa.s and having, per molecule, at least two silicon-bonded C ₂ -C ₆ alkenyl groups,

at least one polyorganosiloxane B having a viscosity of between 1 and 5000 mPa.s and having, per molecule, at least two ≡SiH units and preferably at least three SiH units,

a catalytically effective amount of at least one catalyst C which is a compound derived from at least one metal belonging to the platinum group;

at least one porogenic agent D which is water or an aqueous emulsion,

optionally at least one diorganopolysiloxane E oil blocked at each end of its chain by a triorganosiloxy unit whose organic radicals bonded to the silicon atoms, are chosen from alkyl radicals having from 1 to 8 inclusive carbon atoms, such as methyl groups, ethyl, propyl and 3,3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,

optionally at least one mineral and / or metal filler F,

- optionally at least one additive G, and

optionally at least one polyorganosiloxane resin H,

with the additional condition that the choice, the nature and the quantity of the constituents are determined in such a way that the viscosity of said organopolysiloxane composition X is less than 30,000 mPa.s and preferably less than 25,000 mPa.s.

The Applicant has now found, surprisingly and unexpectedly, that a foaming composition according to the invention comprising, as a porogenic agent, water or an aqueous emulsion, makes it possible to prepare rolls for printing. having less defect related to the appearance of large bubbles in its foamed portion thus improving the industrial weakness of the manufacturing processes of these rolls.

This new compressible roller has the advantage of being composed of an intermediate layer (3) made of silicone foam having a density of less than 0.25 g / cm ³ , having good mechanical properties, bubble sizes of which the width or diameter is less than or equal to about 1 mm and whose bubble size distribution within the material is homogeneous. In addition, the organopolysiloxane composition X used for the preparation of this intermediate layer makes it possible to avoid the problems related to the new constraints encountered in the recent processes for manufacturing these printing rolls, such as for example those related to the use of the centrifugation techniques. Indeed, during the foaming step to prepare this layer of the roll, the organopolysiloxane composition X no longer generates defects related to the appearance of large bubbles in certain areas of this layer.

The pore-forming agent D according to the invention is water or an aqueous emulsion. It can be introduced in the form of a direct silicone oil-in-water emulsion or a water-in-oil reverse silicone emulsion comprising a silicone oily continuous phase, an aqueous phase and a stabilizer.

Direct emulsions can be obtained by emulsification processes well known to those skilled in the art, the process consists in emulsifying in an aqueous phase containing a stabilizer, for example a surfactant, a mixture of constituents. An oil-in-water emulsion is then obtained. Then the missing constituents can be added, either directly to the emulsion (case of the water-soluble constituents), or later in the form of emulsion (case of the constituents soluble in the silicone phase). The particle size of the emulsion obtained can be adjusted by conventional methods known to those skilled in the art, in particular by continuing the stirring in the reactor for a suitable period.

Inverse silicone emulsions consist of water droplets in a continuous silicone oil phase. They can be obtained by emulsification processes well known to those skilled in the art and which involve the mixing of a aqueous phase and an oily phase without or with grinding, ie under high shear. The stabilizer is preferably selected from the group consisting of:

nonionic, anionic, cationic or even zwitterionic surfactants;

polyether silicones;

solid particles, preferably silica particles optionally in combination with at least one co-stabilizer, preferably selected from nonionic, anionic, cationic or even zwitterionic surfactants;

- and their mixtures. The surfactants are chosen more generally as a function of the HLB. The term HLB

(hydrophilic lipophilic balance) refers to the ratio of the hydrophilicity of the polar groups of the surfactant molecules to the hydrophobicity of their lipophilic part. In particular, HLB values are reported in various basic manuals such as the "Handbook of Pharmaceutical Excipients, The Pharmaceutical Press, London, 1994". The water / silicone emulsions can also be stabilized via silicone polyethers (Surfactant Silicone - Surfactant Science V86 series Ed Randal M. Hill (1999).

According to one particular embodiment, the organopolysiloxane composition X is prepared from a two-component system P characterized by:

in that it is in two distinct parts P1 and P2 intended to be mixed to form said organopolysiloxane composition X and comprising said constituents A, B, C, D, E, F, G and H as defined above; , and

in that one of the portions P1 or P2 comprises the catalyst C and the porogen D and does not comprise the polyorganosiloxane B.

According to another embodiment of the invention, the outer layer (4) consisting of a silicone elastomer is prepared by crosslinking and / or curing an organopolysiloxane composition X 'comprising:

at least one polyorganosiloxane A 'having, per molecule, at least two silicon-bonded C ₂ -C ₆ alkenyl groups,

at least one polyorganosiloxane B 'having, per molecule, at least two ≡SiH units and preferably at least three SiH units,

a catalytically effective amount of at least one catalyst C which is a compound derived from at least one metal belonging to the platinum group; optionally at least one diorganopolysiloxane E oil blocked at each end of its chain by a triorganosiloxy unit whose organic radicals bonded to the silicon atoms, are chosen from alkyl radicals having from 1 to 8 inclusive carbon atoms, such as methyl groups, ethyl, propyl and 3,3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,

optionally at least one mineral and / or metal filler F,

- optionally at least one additive G, and

- optionally at least one polyorganosiloxane resin H.

Preferably, the roll core (2) is made of metal.

According to a particularly advantageous embodiment, the roll core (2) is cylindrical, rigid, hollow and comprises an orifice network in which the diameter of each orifice is between 0.1 and 50 mm and preferably between 1 and 10mm. In the manufacture of the roll according to the invention, this roll core structure makes it possible to introduce the composition into the hollow core and, when a centrifugal force is applied, to pass the organopolysiloxane compositions X or X 'through the orifices so as to form, after crosslinking, the intermediate layer (3) or the outer layer (4).

According to a particular embodiment, the thickness of the intermediate layer (3) is between 1 and 100 mm, preferably between 1 and 50 mm and even more preferably between 5 and 20 mm.

According to another particular embodiment, the thickness of the outer layer (4) consisting of a silicone elastomer is between 0.1 and 10 mm and preferably between 0.5 and 5 mm. The polyorganosiloxanes A and A ', each having, per molecule, at least two alkenyl groups, C ₂ -C ₆ bonded to silicon, and having a viscosity of between 10 and 300 000 mPa.s, can be formed:

at least two siloxyl units of formula:

Y _d FLSiO (4-de)

2 (I)

in which :

Y is a C ₂ -C ₆ alkenyl, preferably vinyl,

R is a monovalent hydrocarbon group having no adverse effect on the activity of the catalyst and is generally selected from alkyl groups having from 1 to

8 inclusive carbon atoms such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,

d = 1 or 2, e = 0, 1 or 2 and the sum d + e = 1, 2 or 3, and

optionally, units of the following average formula:

R SiO ^

(II)

in which R has the same meaning as above and f = 0, 1, 2 or 3. Examples of polyorganosiloxanes A and A 'are the following compounds: dimethylvinylsilyl-terminated dimethylpolysiloxanes, (methylvinyl) (dimethyl) polysiloxane copolymers with trimethylsilyl ends, (methylvinyl) (dimethyl) polysiloxane copolymers with dimethylvinylsilyl ends. In the most preferred form the polyorganosiloxane A contains terminal vinyl siloxy units.

As an example of polyorganosiloxane B or polyorganosiloxane B 'having, per molecule, at least two silicon-bonded hydrogen atoms and preferably at least three SiH units and having a viscosity of between 1 and 5000 mPa.s are those comprising :

siloxyl units of formula:

H _g X ₍ SiO ^

(III)

in which :

X is a monovalent hydrocarbon group having no adverse effect on the activity of the catalyst and is generally selected from alkyl groups having 1 to 8 carbon atoms inclusive such as methyl, ethyl, propyl and 3, 3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,

- g = 1 or 2, preferably equal to 1, i = 0, 1 or 2, and g + i = 1, 2 or 3, and optionally siloxyl units of average formula

X _j SiO 4-j

(IV)

in which X has the same meaning as above and

Suitable polyorganosiloxanes B or B 'are polymethylhydrogensiloxanes.

Catalyst C composed of at least one metal belonging to the platinum group is also well known. The platinum group metals are those known as platinoids, which includes, in addition to platinum, ruthenium, rhodium, palladium, osmium and iridium. The platinum and rhodium compounds are preferably used. In particular, platinum complexes and an organic product described in US-A-3 159 601, US-A-3 159 602, US-A-3,220,972 and European patents can be used. A-0 057459, EP-A-0 188 978 and EP-A-0 190 530, the complexes of platinum and vinyl organosiloxanes described in US-A-3,419,593. The most preferred catalyst is platinum. The preference is for the Karstedt solution or complex, as described in US-A-3,775,452.

Component E is for example a linear polydimethylsiloxane, non-functionalized, that is to say to repeating units of formula (CH ₃₎ ₂ Si02 / 2 and having at its two ends (CH ₃₎ ₃ SiO / _2.

As mineral filler F include reinforcing and filling charges. However, the nature and amount of the charge will be determined so as to obtain, after mixing all the components, a viscosity of the composition of less than 30,000 mPa.s. Thus some charges will be discarded because of too much viscosity. These fillers can be in the form of very finely divided products whose mean particle diameter is less than 0.1 m. These fillers include, in particular, fumed silicas and precipitated silicas; their specific surface is generally greater than 10 m ² / g and is most often in the range 20-300 m g. These fillers may also be in the form of more coarsely divided products having an average particle diameter greater than 0.1 m. Examples of such fillers include, in particular, the crushed quartz, diatomaceous earth silicas, calcined clay, rutile-type titanium oxide, iron, zinc, chromium, zirconium, magnesium oxides, various forms of alumina (hydrated or not) , boron nitride, lithopone, barium metaborate; their specific surface area is generally less than 30 m ² / g. Fillers may have been surface-modified by treatment with the various organosilicon compounds usually employed for this purpose. Thus, these organosilicon compounds may be organochlorosilanes, diorganocyclopolysiloxanes, hexaorganodisiloxanes, hexaorganodisilazanes or diorganocyclopolysilazanes (French Patents FR-A-1 126 884, FR-A-1 136 885, FR-A-1 236 505, English Patent GB-A-1,024,234). The treated fillers contain, in most cases, from 3 to 30% of their weight of organosilicic compounds. The charges can be treated before or after their incorporation into the formula. The charges may consist of a mixture of several types of charges of different particle sizes.

The presence of a metal filler F may make it possible to improve the resistance to combustion of the foams. As metallic fillers F, for example:

(a) an additive based on a mixture of platinum with a mixed iron oxide or a cerium-IV oxide as described in application FR-A-2 757 869, in particular the following mixtures:

a platinum mixture in the form of a complex or a platinum compound and a FeO / Fe ₂ O ₃ mixture;

a platinum mixture in the form of a complex or a platinum compound and an oxide and / or cerium-IV hydroxide;

a platinum mixture in the form of a complex or a platinum compound and a constituent consisting of a combination of the oxide and / or cerium-IV hydroxide with titanium oxide TiO ₂ ; and

a mixture of platinum in the form of a complex or of a platinum compound and a constituent which consists of a combination of cerium-IV oxide and / or hydroxide, TiO ₂ titanium oxide and a FeO compound / Fe ₂ 0 ₃

(b) a mixture of platinum and a mixed iron oxide of formula (FeO) x, (Fe ₂ O ₃ ) y where the ratio x / y is between 0.05 / 1 and 1/1, as described in patent application JP-A-76/035 501,

(c) a platinum mixture with at least one rare-metal oxide, in particular a platinum mixture with cerium-IV CeO ₂ oxide as described in the applications

FR-A-2 166 313, EP-A-0 347 349, FR-A-2 166 313 and EP-A-0 347 349, (d) titanium oxide, for example the products marketed by Degussa under the appellation Aeroxide ^®, for example the product "Aeroxide ^{® ΤΊ02} PF2", and

(e) hydrated or unhydrated aluminum hydroxides, iron oxides and cerium oxides or hydroxides.

As additive G, it is possible in particular to incorporate a catalyst inhibitor in order to retard the crosslinking. It is possible in particular to use organic amines, silazanes, organic oximes, diesters of dicarboxylic acids, acetylenic ketones and acetylenic alcohols (see, for example, FR-A-1,528,464, 2,372,874 and 2,704,553). . The inhibitor, when one is used, may be employed in an amount of 0.0001 to 5 parts by weight, preferably 0.001 to 3 parts by weight, per 100 parts of polyorganosiloxane A. Phosphines, phosphites and phosphonites are also included inhibitors usable in the invention. Mention may in particular be made of the compounds of formula P (OR) ₃ described in US Pat. _No. 6,300,455. All these compounds are known to those skilled in the art and are commercially available. For example, the following compounds may be mentioned:

polyorganosiloxanes substituted with at least one alkenyl which may optionally be in cyclic form, tetramethylvinyltetrasiloxane being particularly preferred,

pyridine,

phosphines and organic phosphites,

unsaturated amides,

alkylated maleates, and

acetylenic alcohols which have the formula:

(R ') (R ") C (OH) -C≡ CH

formula in which,

- R 'is a linear or branched alkyl radical, or a phenyl radical;

- R "is a hydrogen atom or a linear or branched alkyl radical, or a phenyl radical, the radicals R ', R" and the carbon atom located at a of the triple bond may optionally form a ring; and

the total number of carbon atoms contained in R 'and R "being at least 5, preferably from 9 to 20.

For said acetylenic alcohols, examples that may be mentioned include:

ethynyl-1-cyclohexanol-1;

3-methyl-1-dodecyn-3-ol; trimethyl-3,7,11-dodecyn-1-ol-3;

1-diphenyl-1 propyne-2-ol;

3-ethyl-6-ethyl nonyne-1-ol-3;

2-methyl-3-butyneol-2;

3-methylpentadecyn-1-ol-3. and

diallyl maleate or derivatives of diallyl maleate.

These inhibitors are added in an amount by weight of between 1 and 50,000 ppm relative to the weight of the total silicone composition, especially between 10 and 10,000 ppm, preferably between 20 and 2000 ppm.

Polyorganosiloxane resins H are oligomers or polymers

branched organopolysiloxanes well known and commercially available. They are in the form of solutions, preferably siloxanes. Examples of oligomers or branched organopolysiloxane polymers include resins MQ, resins "MDQ", resins "TD" and resins "MDT", alkenyl functions that can be carried by siloxyl units M, D and / or T. The skilled person in the field of silicones commonly uses this nomenclature which represents the following siloxyl units:

R3S1O1 / 2 (M pattern), RS1O32 (T pattern), R ₂ Si0 ₂₂ (D pattern) and Si0 _4/2 (Q pattern).

The polyorganosiloxane resins H that are particularly useful according to the invention are silicone resins with "Si-alkenyl" functions, that is to say resins with vinyl, allyl and / or hexenyl functional groups. According to a preferred embodiment of the invention, the resins

Polyorganosiloxanes H are vinylated silicone resins. Advantageously, they comprise in their structures from 0.1 to 20% by weight of group (s) alkenyl (s). In these resins, the alkenyl groups may be located on M, D or T siloxyl units. These resins may be prepared, for example, according to the process described in US Pat. No. 2,676,182. A certain number of these resins are available. in commerce, most often in the state of solutions.

For example, the polyorganosiloxane resin H comprises:

at least two different siloxyl units chosen from those of formulas:

W _a Z _b SiO ₍₄ - (a ₊ b)) / 2

(V)

in which : the symbols W, identical or different, each represent an alkenyl group in

the symbols Z, which may be identical or different, each represent a non-hydrolysable monovalent hydrocarbon group, which has no adverse effect on the activity of the optionally halogenated catalyst and is preferably chosen from alkyl groups as well as from aryl groups, and

a is 1 or 2, preferably 1, b is 0, 1 or 2 and the sum a + b is 1, 2 or 3,

and optionally of the following formula:

(VI)

wherein Z has the same meaning as above and c is 0, 1, 2 or 3, with the proviso that at least one of the (V) or (VI) units is a T or Q unit.

In a preferred embodiment of the invention, the polyorganosiloxane resin H is a resin which comprises Si-Vi units (with "Vi" meaning a vynyl group) and is chosen from the group consisting of the following silicone resins:

- MD ^{V |} Q where the vinyl groups are included in the D patterns,

- MD ^Vl TQ where the vinyl groups are included in the patterns D,

- MM ^{V |} Q where the vinyl groups are included in part of the patterns M,

- MM ^{V |} TQ where the vinyl groups are included in part of the patterns M,

MM ^V 'DD ^V ' Q where the vinyl groups are included in the patterns M and D,

- and their mixtures,

with:

M = siloxyl unit of formula R3S1O1 / 2

- M ^Vl = siloxyl unit of formula (R2) (vinyl) SiOi / 2

- D = siloxyl unit of formula R2S1O2 / 2

- D ^{V |} siloxylated unit of formula (R) (vinyl) SiO 2/2

- Q = siloxyl unit of formula S1O4 / 2;

- T = siloxyl unit of formula RS1O3 / 2, and

the groups R, which are identical or different, are monovalent hydrocarbon-based groups chosen from alkyl groups having from 1 to 8 carbon atoms inclusive, such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups and aryl groups such as that xylyl, tolyl and phenyl According to another particular embodiment of the invention, the polyorganosiloxane resin H is added to the composition according to the invention in the form of a mixture in at least one polyorganosiloxane oil.

According to another embodiment of the invention, the vinylated polyorganosiloxane resin H is present in the silicone elastomer composition before crosslinking up to 25%, preferably up to 20% and even more preferentially between 1 and 20% by weight. weight relative to the total weight of the composition according to the invention.

The vinyl polyorganosiloxanes A or A ', the polyorganosiloxane resins H and the polyorganosiloxanes with hydride function B or B', are in such quantities that a molar ratio between the function≡SiH and the functions≡SiVi of between 0.5 is ensured. and 10 and preferably between 1 and 6. According to a particular embodiment of the invention, the composition

Organopolysiloxane X comprises:

(A) 100 parts by weight of at least one polyorganosiloxane A having, per molecule, at least two silicon-bonded C ₂ -C ₆ alkenyl groups, and having a viscosity of between 10 and 300,000 mPa.s,

(B) from 0.5 to 50 parts by weight of at least one polyorganosiloxane B having, per molecule, at least two silicon-bonded hydrogen atoms and preferably at least three SiH units and having a viscosity of between 1 and 5000 mPa.s,

(C) a catalytically effective amount of at least one catalyst C composed of at least one metal belonging to the platinum group,

(D) from 0.05 to 50 parts by weight of at least one porogen D according to the invention and as described above,

(E) from 0 to 50 parts by weight of at least one diorganopolysiloxane E oil blocked at each end of its chain by a triorganosiloxy unit whose organic radicals bonded to the silicon atoms are chosen from alkyl radicals having from 1 to 8 including carbon atoms such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,

(F) from 0.5 to 50 parts of at least one mineral filler F,

(G) from 0 to 10 parts by weight of at least one additive G, and

(H) from 0 to 70 parts by weight of the polyorganosiloxane H. with the additional condition that the choice, the nature and the quantity of the constituents are determined in such a way that the viscosity of said composition is less than 30,000 mPa.s. Another subject of the invention relates to a method of manufacturing a compressible roller (1) according to the invention and as defined above, useful for pad printing, said method comprising the steps of:

A) mounting in a cylindrical mold, preferably stainless steel, a roller core (2) according to the invention and as described above so that the main axis is horizontal;

b) introducing into the mold an organopolysiloxane composition X 'as defined above by means of a static mixer,

C) impose rotations, preferably by centrifugation, around the horizontal main axis of said cylindrical mold and heat the cylindrical mold to a temperature greater than 35 ° C and preferably greater than or equal to 40 ° so as to form the layer exterior (4) on the inner wall of said cylindrical mold,

d) introducing into the mold an amount sufficient to fill the mold with an organopolysiloxane composition X as defined above by means of a dynamic mixer,

e) imposing rotations, preferably by centrifugation, around the horizontal main axis of said cylindrical mold and heating the cylindrical mold to a temperature greater than 35 ° C and preferably greater than or equal to 40 ° so as to form the intermediate layer (3) silicone foam, and

f) removing the cyclindrical mold so as to recover the compressible roller (1).

According to a particularly advantageous embodiment, the method according to the invention comprises the steps of:

a) mounting in a cylindrical mold, preferably in stainless steel, a cylindrical, rigid, hollow cylindrical core (2) comprising an orifice network whose diameter of each orifice is between 0.1 and 50 mm and preferably between 1 and 10 mm, so that the main axis is horizontal;

B) introducing inside the cavity of said roll core (2) an organopolysiloxane composition X 'as defined above by means of a static mixer; c) centrifugally rotating around the main axis; horizontally of said cylindrical mold so that the organopolysiloxane composition X ' through the orifices of said roll core (2) and forms the uncured outer layer (4) on the inner wall of said cylindrical mold,

D) heating at a temperature above 35 ° C and preferably greater than or equal to 40 ° so as to crosslink and / or harden the outer layer (4),

e) introducing into the interior of the cavity of said roll core (2) an organopolysiloxane composition X as defined above by means of a dynamic mixer,

F) centrifugally rotating about the horizontal main axis of said cylindrical mold so that the organopolysiloxane composition X passes through the orifices of said roll core (2) and fills the cylindrical mold,

g) heating at a temperature greater than 35 ° C and preferably greater than or equal to 40 ° in order to foam and crosslink the organopolysiloxane composition X so as to form the intermediate layer (3) of silicone foam, and

h) removing the cyclindrical mold so as to recover the compressible roller (1).

It is recalled that in a static mixer, used mainly for relatively fluid products, the various components are pressed together through a set of baffles to be mixed intimately, while in a dynamic mixer, generally used for more viscous products the various components are introduced into a mixing chamber where an element such as a blade, animated by a stirring movement, is responsible for carrying out the mixing.

Static and dynamic mixers are well known and commercially available.

Another object of the invention relates to a compressible roll (1) obtainable by the methods according to the invention and described above. Finally, the last object of the invention relates to a use of a compressible roll (1) according to the invention and as described above for printing or pad printing.

Description of the single figure:

The attached single figure shows a compressible roll (1) comprising:

a cylindrical and rigid roll core (2), an intermediate layer (3) made of silicone foam and which covers said roll core (2), and

an outer layer (4) consisting of a silicone elastomer and covering said intermediate layer (3).

All the viscosities referred to herein correspond to a dynamic viscosity quantity which is measured, in a manner known per se, at 25.degree. The viscosities are measured using a BROOKFIELD viscometer according to the indications of standard AFNOR NFT 76 106 of May 1982. These viscosities correspond to a dynamic viscosity quantity at 25 ° C called "Newtonian", that is to say ie the dynamic viscosity which is measured, in a manner known per se, at a sufficiently low shear rate gradient so that the measured viscosity is independent of the speed gradient. The present invention will now be described in more detail using embodiments given by way of non-limiting example.

EXAMPLES Two-component compositions are prepared from the following constituents:

Part P1:

- a: a vinylated polyorganosiloxane resin comprising siloxyl units M, D ^{V |} and Q (or "MD" Q ") with Vi = vinyl group, M: (CH ₃₎ ₃ SiO _{/ 2,} Q: S1O4 _{/ 2,} D ^vi:

- b1_: polydimethylsiloxane blocked with units (CH ₃ ) ₂ ViSiOi / ₂ and whose viscosity is 3500 mPa.s at 25 ° C.

b2_: polydimethylsiloxane blocked with (CH ₃ ) ₂ ViSiOi / _{2 units} and whose viscosity is 10,000 mPa.s at 25 ° C.

- b3_: polydimethylsiloxane blocked with units (CH ₃ ) ₂ ViSiOi ₂ and whose viscosity is 60,000 mPa.s at 25 ° C.

b4: polydimethylsiloxane oil blocked at each of the chain ends by a Vi (CH ₃ ) ₂ SiO _{1 2 unit} having a viscosity of 100 000 mPa.s at 25 ° C.

- cl: Silica combustion treated with a silicone oil having a specific surface of 30m ² / g (BET), sold under the trade name AEROSIL ^® RY50. - C2: Diatomaceous earth marketed under the trade name CLARCEL ^® FD marketed by the company CECA.

- Butanol, d2: Silcone / water emulsion containing 58.45% by weight of water or d3: water

- e: Platinum catalyst from Karstedt.

f: Polydimethylsiloxane oil blocked at each chain end with a (CH ₃ ) ₃ SiO _{1 2 unit} and having a viscosity of 1000 mPa.s at 25 ° C.

poly (vinylmethyl) (dimethyl) siloxane oil having a D ^| 2% by weight and in the form M ^{V |} 0.4% by weight (oil with pendant vinyl groups). 2) Part P2:

- a: vinylated polyorganosiloxane resin comprising siloxyl units M, D ^| and Q (or "MD ^Vi Q")

- 1: polydimethylsiloxane blocked with units (CH ₃ ) ₂ (Vi) SiOi _{/ 2} and whose viscosity is 3500 mPa.s.

- b3_: polydimethylsiloxane blocked with units (CH ₃ ) ₂ (Vi) SiO _{1 2} and whose viscosity is 60,000 mPa.s at 25 ° C.

b4: polydimethylsiloxane oil blocked at each of the chain ends by a Vi (CH ₃ ) 2 SiO 1/2 _/ 2 unit having a viscosity of 100 000 mPa.s at 25 ° C.

- f_: polydimethylsiloxane oil terminated at each of the chain ends by a (CH ₃₎ ₃ SiO _{/ 2} having a viscosity of 1000 mPa.s at 25 ° C

- I: polydimethylsiloxane oil blocked at each chain end by a (CH ₃ ) ₂ HSiO _{1 2} motif.

- h: polymethylhydrogensiloxane oil blocked at each chain end by a (CH ₃ ) ₃ SiOi _{/ 2 unit} .

- j_: 1% solution of ethynylcyclohexanol in a polydimethylsiloxane oil blocked with (CH ₃₎ ₂ (Vi) SiO _{/ 2,} having a viscosity of 600 mPa.s at 25 ° C

Table 1 below describes compositions tested. Table 1: Compositions - Parts by weight.

3) Preparation of compressible rolls for tampoaraphy:

To 50 parts by volume of part P1, 50 parts by volume of component P2 are added so as to prepare the organopolysiloxane compositions X precursors of foam which will be tested as follows:

a) a cylindrical mold (length 132 cm, outer diameter 46 cm) of stainless steel is mounted on a cylindrical, rigid, hollow core of roll (2) and comprising an orifice network whose diameter of each orifice is approximately 4 mm so that the main axis is horizontal;

b) an organopolysiloxane composition X 'is introduced inside the cavity of the roll core (2) which is obtained by mixing parts A and B of a polyaddition RTV-2 (sold under the name Rhodorsil or BlueSil for pad printing application by Bluestar Silicones France) using a static mixer, c) centrifugation is rotated around the horizontal main axis of the cylindrical mold so that the organopolysiloxane composition X 'passes through the openings of the core roll (2) and forms the outer layer (4) uncrosslinked on the inner wall of the cylindrical mold,

d) the mold is heated at a temperature of 40 ° C. for 1 to 4 minutes so that the layer formed cross-links,

e) the organopolysiloxane compositions X precursors of foam and described above are introduced inside the cavity of the roll core (2) by means of a dynamic mixer (invention, preparation route 1) or a mixer static (comparative route of preparation 2).

f) centrifugation rotates around the horizontal main axis of the cylindrical mold so that the organopolysiloxane composition X passes through the openings of the roll core (2) and fills the cylindrical mold,

g) heating at a temperature above 40 ° C for about 5 mm in order to foam and crosslink the organopolysiloxane composition X to form the intermediate layer (3) of silicone foam, and

h) removing the cyclindrical mold so as to recover the compressible roller (1). 4) Results

All foams prepared according to Preparation Route 2 (comparative), that is to say using a static mixer to introduce the silicone precursor X composition of a foam in step e) of the process described above, exhibit defects including the presence of large bubbles at the outer surface of the foam layer and a skin on the surface of the thick foam.

When using the preparation route 1 that is to say using a dynamic mixer (Invention) to introduce the silicone precursor X composition of a foam in step e) of the method described above, the rolls prepared from :

a) of Example 1 (Comparative 1, butanol foaming agent), have defects in particular by the presence of large bubbles at the outer surface of the foam layer and a skin on the surface of the thick foam;

b) Examples 2, 3 and 4, no longer present defects, the bubbles of the intermediate layer of foam are homogeneous and small sizes, the skin on the surface is much thinner than that obtained with Example 1. Table 2:

As shown in Table 2, foams used as diapers

Intermediates in the rolls prepared according to the invention meet the requirements for use in the compressible roll for printing or pad printing.

In this presentation:

the abbreviation "R / R" means the breaking strength, in MPa according to the AFNOR NF T 46002 standard,

the abbreviation hardness DS00 means Shore 00 hardness,

the abbreviation "A / R" means the elongation at break in% according to the preceding standard,

- the abbreviation "R / d" means tear strength in N / mm,

Claims

1 - compressible roll (1) comprising:

a cylindrical and rigid roll core (2),

at least one porogenic agent D which is water or an aqueous emulsion,

optionally at least one mineral and / or metal filler F,

- optionally at least one additive G, and

optionally at least one polyorganosiloxane resin H,

with the additional condition that the choice, the nature and the quantity of the constituents are determined in such a way that the viscosity of said organopolysiloxane composition X is less than 30,000 mPa.s and preferably less than 25,000 mPa.s. 2 - silicone foam roller according to claim 1 characterized in that the organopolysiloxane composition X is prepared from a two-component system P characterized:

in that it is in two distinct parts P1 and P2 intended to be mixed to form said organopolysiloxane composition X and comprising said constituents A, B, C, D, E, F, G and H as defined according to the claim 1, and

in that one of the parts P1 or P2 comprises the catalyst C and the pore-forming agent D and does not comprise the polyorganosiloxane B. 3 - compressible roll (1) according to claim 1 characterized in that the outer layer (4 ) consisting of a silicone elastomer is prepared by crosslinking and / or curing an organopolysiloxane composition X 'comprising:

- optionally at least one mineral filler F

- optionally at least one additive G, and

- optionally at least one polyorganosiloxane resin H.

4- compressible roller (1) according to claim 1 characterized in that the roller core (2) is metal.

5 - compressible roller (1) according to claim 1 or 4 characterized in that the roller core (2) is cylindrical, rigid, hollow and comprises an orifice network whose diameter of each orifice is between 0.1 and 50 mm and preferably between 1 and 10 mm. 6 - compressible roller (1) according to claim 1 characterized in that the thickness of the intermediate layer (3) is between 1 and 100 mm, preferably between 1 and 50 mm and preferably between 5 and 20 mm.

7 - compressible roller (1) according to claim 1 characterized in that the thickness of the outer layer (4) consists of a silicone elastomer is between 0.1 and 10 mm and preferably between 0.5 and 5 mm . 8 - A method of manufacturing a compressible roll (1) as defined in any one of the preceding claims and useful for pad printing, said method comprising the steps of:

a) mounting in a cylindrical mold, preferably stainless steel, a roller core (2) as defined in any one of claims 1, 4 and 5 so that the main axis is horizontal;

b) introducing into the mold an organopolysiloxane composition X 'as defined according to claim 3 by means of a static mixer,

c) to impose rotations, preferably by centrifugation, around the horizontal main axis of said cylindrical mold and to heat the cylindrical mold to a temperature greater than 35 ° C and preferably greater than or equal to 40 ° so as to form the outer layer (4) on the inner wall of said cylindrical mold,

d) introducing into the mold an amount sufficient to fill the mold with an organopolysiloxane composition X as defined in claim 1 by means of a dynamic mixer,

f) removing the cyclindrical mold so as to recover the compressible roller (1).

9 - A method of manufacturing a compressible roll (1) according to claim 8 and useful for pad printing, said method comprising the steps of:

a) mounting in a cylindrical mold, preferably in stainless steel, a hollow cylindrical core (2), hollow and comprising an orifice network whose diameter each orifice is between 0.1 and 50 mm, and preferably between 1 and 10 mm, so that the main axis is horizontal;

b) introducing into the interior of the cavity of said roll core (2) an organopolysiloxane composition X 'as defined according to claim 3 by means of a static mixer,

c) centrifugally rotating about the horizontal major axis of said cylindrical mold so that the organopolysiloxane composition X 'passes through the orifices of said roll core (2) and forms the uncured outer layer (4) on the inner wall of said cylindrical mold,

d) heating at a temperature greater than 35 ° C and preferably greater than or equal to 40 ° so as to crosslink and / or harden the outer layer (4),

e) introducing into the interior of the cavity of said roll core (2) an organopolysiloxane composition X as defined in claim 1 by means of a dynamic mixer,

f) centrifugally rotating about the horizontal major axis of said cylindrical mold such that the organopolysiloxane composition X passes through the orifices of said roll core (2) and fills the cylindrical mold,

h) removing the cyclindrical mold so as to recover the compressible roller

(1) ·

10 - compressible roll (1) obtained by the method as described according to claim 8 or 9.

11 - Use of a compressible roller (1) as defined in any one of claims 1 to 7 or 10 for printing or pad printing.