CA1148690A - Ultraviolet light curable compositions for producing coatings of low gloss - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Films of low gloss may be obtained by exposing to ultraviolet light coatings of a coating composition comprising photoinitiator, photo-sensitizer, quencher and compound having a plurality of acrylyloxy groups.

Description

36~(~

ULTRAVIOLET LIGHT CURABLE COMPOSITIONS
FOR PRODUCING COATINGS OF LOW GLOSS

Coatings of most ultraviolet light curable coating comPositions, when exposed to ultraviolet light, are cured to glossy, crosslinked coatings. In many instances, however, it is desired to obtain crosslinked coatings of low gloss. One way to achieve low gloss coatings is by adding flatting pigment. Unfortunately, when the proportion of flatting pigment is increased in an attempt to produce coatings of lower gloss, the point is reached where the p;gment to binder ratio is so high that there is insufficient binder to firmly hold the pigment. The result is a low gloss coating which lacks hardness and durability. Another method heretofore employed took advantage of the inhibition of polymerization which occurs ~ -when exposure of the film to radiation is conducted in the presence of oxygen. United States Patent Nos. 3,918,393 and 4,048,036 illustrate this approach.
The present invention provides an ultraviolet light curable coating composition comprising at least one photoinitiator, at least one photosensitizer, at least one quencher and at least one compound having a plurality of acrylyloxy groups~and capable of being free radically addition poly~erized by interaction with the photoinltiator and the photosensitizer, wherein upon exposure to ultraviolet light, a coating of~
~;~ 20 the coating composition is cured to a crosslinked film having a lower ~ ~ -: gloss than if the quencher were absent.
As used throughout the instant specification and claims, unless~
otherwise indicated either directly ur by context, acrylyloxy is used in~
its broad sense to mean~unsubstituted acrylyloxy or ~-substituted acrylyloxy -, . : , :

9~

groups such as methacrylyloxy, ethacrylyloxy and ~-chloroacrylyloxy.
Similarly, unless otherwise indicated either directly or by context, acrylic unsaturation is used in its broad sense to mean the unsaturation provided by unsubstituted acrylyl groups or ~-substituted acrylyl groups such as methacrylyl, ethacrylyl and ~-chloroacrylyl.
Photoinitiators absorb photons and thereby obtain energy to form radical pairs. Using alkyl benzoin ether as an example, the absorption of a photon to produce a molecule excited to a higher energy level may be represented by the equat;on:
lo ~ fR r LfR 1 *
~ - CH - ~ ~ hv ~ L ~ CH ~

where ~ is a phenyl group, ~ is an alkyl group and the asterisk indicates an excited molecule of higher energy due to absorption of the photon, hv.
The excited molecule then forms a radical pair :

r ~ R 1 * ~ ~R
~L~ H ~ + H

One or both members of the radical pair are then available to initiate add;tion polymerization of acrylyloxy groups. Because the photoinitiator ~ ;
does not require interaction with another compound to form free radicals, the reaction is termed unimolecular. Hence the photoinitiator used in the ~~
present invention generates a radical pair by way o~ unimolecular homolysis resulting from photoexcitation, at least one member of the radical pair -being capable of initiating addition polymerization of acrylyloxy groups. ~ ~ ~

: :

- 2 -;:

:, .
:

~8~

Free radicals necessary to the photopolymerization of acrylyloxy groups may also be produced by the interaction of two compounds. Such reactions are therefore classed as bimolecular.
One type of bimolecular reaction is hydrogen abstraction. Here3 a photosensitizer, which is a good absorber of photons but which itself is a poor photoinitiator, absorbs photons to produce an excited molecule.
The excited molecule then inter-reacts with a second compound to produce free rad;cals. Using benzophenone as an example of a photosensitizer, the reactions may be represented:

~2C=0 + hv ~ ~2C=O* (III) ~2C=* + A-H -~ ~2C - OH + A (IV) ~here ~ is a phenyl group, A is an organic or organometallic group, A-H
is a monomer, a polymer or an added initiator which interacts ~ith the photosensitizer and the asterisk has the meaning previously defined. In Equation IV, one or both of the free radicals are available to initiate addition polymerization of acrylyloxy groups. In reactions of the hydrogen abstraction type, the photosensitizer is often destroyed in the process of generating free radicals.
Another type of bimolecular reaction is the energy donor type.
Here a photosensitizer molecule absorbs a photon to produce an excited molecule. The~excited molecule then transfers energy to a second molecule which produces radical pairs. Again using benzophenone as an example of a photosensitizer, the reactions may be represented:
.

- 3 -::

::: :

~869~

~2C=O + h v ~ ~2C=0* (V) ~2C=* ~ A-B _~ ~zC=0 ~ [A-B] * (VI) [A-B] * ~ A + B (VII) where ~ , A and the asterisk are as previously defined, B is an organic or inorganic group and A-B is a monomer, polymer or added initiator which interacts with the photosensitizer. In Equation VII, one or both free radicals are available to initiate addition polymerization of acrylic groups. In reactions of the energy donor type, the photosensitizer serves to transfer energy and is not destroyed in the process.
In bimolecular reactions of either the hydrogen abstraction type or the energy donor type, the second compound with which the excited photosensitizer molecule interacts may, depending upon the specific identity of the second compound, be an initiator or a monomer. Photosensitizer employed in the present invention has a triplet energy in the range of from 54 to 72 kilocalories per mole and promotes photopolymerization through bimolecular ~-photochemical reactions.
; Quenchers are compounds or groups that absorb energy from an excited photosensitizer molecule before the sensitizer can inter-react with another compound to produce free radicals. The energy absorbed by ~ ~, the quencher is then dissipated. Again using benzophenone as an example ~ -of a photosensitizer, one quenching sequence may be represented:

~: ::
2C=* + Q ~ ~2C-0 + Q* ~ ~2C= + Q + hv' (VIII) and another may be represented:
, :

- 4 ~:

~869~3 ~2C=0* ~ Q ~ ~2~= + Q + heat (IX) where ~ is a phenyl group, Q is the quencher, hv' is a photon of longer wavelength, and hence of lesser energy, than the absorbed photon, hv, of Equation (III) and the asterisk has the meaning previously assigned.
Quenchers used in ehe present invention are compounds having at least one quenching moiety which quenches the photosensitizer to an extent greater than the extent to which the photosensitizer is quenched by acrylyloxy groups. The quencher is not itself either an effective initiator or an effective inhibitor of free radical polymerization of acrylyloxy groups. It does not produce products during quenching of ~he photosensitizer which are either effective initiators or effective inhibitors of free radical polymerization of acrylyloxy groups. ~oreover, the quencher either doe~s not quench the photoinitiator or it quenches the photoinitiator at a rate much less than the rate at which the photo initiator induces polymerization of acrylyloxy groups so as not to signifi-cantly interfere with initiation of addition polymerization of acrylyloxy groups by a member of the radical pair heretofore discussed. The quenchers used in the present invention have at least one of the following characteristics: (a) a triplet energy in the range of from 35 to 68 kilocalories per mole, but lower than the triplet energy of the photosensitizer employed, (b) an ionization potentia' in the range of from about 6 1/2 to 9 :
electron volts, or (c) an ionization potential in the range of from 10 1/2 to about 12 electron vOles. Quenchers having an ionization potentlal in one or the other of the ranges specified in (b) or (c) may or may not have a triplet energy in the range specified in (a).

- 5 -:

~' ' '.

o Examples of photosensitizers which may be used in the present invention are: benzil, 4-phenylbenzophenone, 4-phenylacetophenone, 3~4-methylenedioxyacetophenone, 4-cyanobenzophenone, 4,4'-dichlorobenzophenone, 4-trifluoromethylbenzophenone, 3-methoxybenzophenone, 4-chlorobenzophenone, 3-chlorobenzophenone, 4-methoxybenzophenone, 3,4-dimethylbenzophenone, 4-methylbenzophenone, benzophenone, 2-methylbenzo~henone, 4,4'-dimethyl-benzophenone, 2,5-dimethylbenzophenone, 2,4-dimethylbenzophenone, 4-cyanoaceto-phenone, 4-fluorobenzophenone, o-benzoylbenzophenone, 4,4'-dimethoxybenzophenone~
3,4,5-trimethylacetophenone, 3,5-dimethylacetophenone, 4-bromoacetophenone, 4-methoxyacetophenone, 3,4-dimethylacetophenone, triphenylmethylacetophenone, anthrone, 4-chloroacetophenone, 4-trifluoro-methylacetophenone, ethyl phenylglyoxylate, o-benzoylbenzoic acid, ethyl benzoylbenzoate, dibenzosuberone,o-benzoylbenzophenone, acrylyloxyethyl benzoylbenzoate, 4-acrylyloxybenzophenone, 2-acrylyloxyethoxybenzophenone, 3,3',4,4'-benzophenonetetracarboxylic dianhydride and esters thereof.
The preferred photosensitizer is benzophenone. Mixtures of photosensitizers may be used if desired.
There are many photoinitiators which may be used in the present invention. In the formulae which follow, ~ represents phenyl which is either unsubstituted or substituted to a minor extent with substituents which either will not substantially interfere with the utility of the compound as a photoinitiator or will enhance such utility. Examples of substituents which may often be employed are halo, lower alkyl, lower alkoxy, carboxy and alkoxycarbonyl.
Many photoinitiators which may be used are compounds falling within the formula:

3-aXa - -9~

where a is 1, 2 or 3 and X is chloro or bromo. Examples are a,,-trichloroacetophenone and _-tert-butyl-a~ -trichloroacetophenone.
Other photoinitiators which may be used fall within the ~ormula:

~H ~ _ where X is chloro or bromo.
Still other photoinitiators fall within the formula:

ORl lo ~ - fH

where Rl and R2 are each independently alkyl usually having from 1 to 4 carbon atoms. Rl and R2 may be the same or different. Examples include ,-diethoxyacetophenone and a,~dibutoxYacetoPhenone.

Still other useful photoinitiaeors fall within the formula:
' ~ j ~ 3 ', ~ ~ f ~

where R3 may be hydrogen, alkyl usually having from 1 to 6 carbon atoms and preferably from 1 to 4 carbon atoms, methylol or alkoxycarbonyl-alkyl where the alkoxy portion usually contains from 1 to 4 carbon atoms :::

_ j _ :

:

/ .' . -': , /
.

8~90 and the alkyl portion usually contains 1 or 2 carbon atoms. R4 is typically alkyl having from 1 to 6 carbon atoms and preferably from I to 4 carbon atoms, tetrahydropyranyl, cycloalkyl usually having from 6 to 8 carbon atoms or substituted or unsubstituted phenyl. Examples are methyl benzoin ether, ethyl benzoin ether, isopropyl benzoin ether3 butyl benzoin ether, isobutyl benzoin ether, phenyl benzoin ether, 2-tetrahydropyranyl benzoin ether, ~-(P3-methoxycarbonylethyl)benzoin ethyl ether and -(~3-ethoxycarbonylethyl)benzoin ethyl ether.
Other photoinitiators which are useful fall within the formula:
.

0 ORs Il I
-;.

where Rs and R6 are each independently alkyl usually having from 1 to 6 carbon atoms and preferably from 1 to 4 carbon atoms. Rs and R6 may be the same or different. Examples are ~,~-diethoxy-X-phenylacetophenone and ,~-dimethoxy-a-phenylacetophenone.
Still other photoinitiators which may be used fall within the formula:

` 20 ~ ~ F - OH

.

where R7 and R8 are each independently alkyl usually containing from 1 to 4 carbon atoms. R7 and R8 may be the same or different.
, o Examples are a,a-dimethyl-a-hydroxyacetophenone and p-isopropyl-a,a-dimethyl-a-hydroxyacetophenone.
Still other useful photoinitiators fall within the formula:

~C - f c ORl O

where Rg, Rlo and Rll are each independently alkyl usually having from 1 to 4 carbon atoms. Rg, Rlo and Rll may be the same or different.
Examples are ethyl ~,~-diethoxy-~-benzoylacetate and methyl ~,~-dimethoxy-~-benzoylacetate.
Other photoinitiators which may be employed fall within the formula:

f l z fl I

R12 ~

_ _ 2 ~.
where ~l is substituted or unsubstituted phenylene (ortho, meta or para), Rl2 is alkyl usually containing from 1 to 4 carbon atoms and Rl3 is alkyl usually containing from 1 to 18 carbon atoms and preferably from 1 to 8 carbon atoms. Examples are benzene-1,4 bis(ethyl ~-oxo~
diethoxypropionate) and benæene-1,4-bis(methyl ~-oxo-~,~-dimethoxypropionate).
Other photoinitiators fall within the formula: ~
~.

_ g _ ~8~;9~

~ C--1 ~ O R15 ~here R14 and Rls are each independently hydrogen or alkyl usually containing from 1 to 4 carbon atoms. R14 and Rls may be the same or different. An example is 2-benzoyl-2-phenyl-1,3-dioxolane.
Still other photoinitiators fall within the formula:

R~6 / R17 ~ _ ~ G -CH2 where R16 and R17 are each independently hydrogen or alkyl usually containing from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms.
R16 and R17 may be the same or different. When R16 is hydrogen, R17 may also be trichloromethyl, p-dimethylaminophenyl, cinnamyl or ~ ~
furyl. Examples are 2-trichloromethyl-4-benzoyl-4-phenyl-1,3-dioxolane, ~ ~;
2-(p-dimethylaminophenyl)-4-benzoyl-4-phenyl-1,3-dioxolane, 2-cinnamyl-4 ~;~ benzoyl-4-phenyl-1,3-dioxolane, 2-fury1-4-benzoyl-4-phenyl-1,3-dioxolane, 4-benzoyl-4-phenyl-1,3-dioxolane, 2,2-dimethyl-4-benzoyl-4-phenyl-1,3-dioxolane, ~~
2-methyl-2-ethyl-4-benzoyl-4-phenyl-1,3-dioxolane and 2-methyl-4-benzoyl-4-phenyl-1,3-dioxolane.
Other photo mitiators which may be used fall within the formula:

' ::
, ~8~9~

R21 ~ g f = NO~ ~ R18 I O ¦ Rlg R22 ~ R24 where Rlg may be alkyl usually having from 1 to about 6 carbon atoms and preferably from 1 to about 4 carbon atoms, alkoxy usually havin~ from 1 to about 6 carbon atoms and preferably from 1 to about 4 carbon atoms, or aryltypically having from 6 to about 12 carbon atoms and preferably from 6 to about 10 carbon atoms. Rlg may be alkyl typically having from 1 to about 4 carbon atoms or aryl generally having from 6 to about 12 carbon atoms. R20, R21~ R22~ R23 and R24 are each independently hydrogen, alkyl usually having from 1 to about 18 carbon atoms and typically from 1 to about 8 carbon atoms, alkoxy usually having from 1 to about 8 carbon atoms and typically from 1 to about 4 carbon atoms, or halo, usually -chloro or bromo. R20 through R24 or any groupings of them, may be the same or different. Examples are l-phenyl-1,2-propanedione-2-(0-ethoxycarbonyl)-oxime and l-phenyl-1,2-propanedione-2-(0-benzoyl)oxime.
Othèr photoinitiators fall within the formula:

R26 ~ ~ ~ ~ ~ ~25 where R2s is hydrogen, alkyl usually containing from 1 to about 22 carbon atoms and preferably from 1 to about 12 carbon atoms, benzyl, unsubstituted phenyl, phenyl substituted with one or more minor substituents : :

_ 1i _ , ~ :

~8~g~

such as lower alkyl, lo~er alkoxy, lower aryloxy, lower alkylthio, lower arylthio or halo ~hich is usually chloro or bromo; hydroxyalkyl usually containing from 1 to about 10 carbon atoms; chloroalkyl containing usually from 1 to about 10 carbon atoms, bromoalkyl usually containing from 1 to about 10 carbon atoms, alkoxy-alkyl where the alkoxy portion usually contains from 1 to about 4 carbon atoms and where the alkyl portion usually contains from 1 to about 10 carbon atoms or phenoxyalkyl where the alkyl portion usually contains from 1 to about 10 carbon atoms. R26 is usually a heterocyclic radical, aryl of from 6 to about 14 carbon atoms, unsubstituted phenyl, phenyl substituted with one or more minor substituents such as lower alkyl, lower alkoxy, lower aryloxy, lower alkylthio, lower arylthio or halo ~hich is usually chloro or bromo. Examples are phenylglyoxylic acid, methyl phenylglyoxylate, ethyl phenylglyoxylate, butyl phenyl-glyoxylate, tert-butyl phenylglyoxylate, benzyl phenylglyoxylate, butoxyethyl phenylglyoxylate, phenoxyethyl phenylglyoxylate, dodecyl phenylglyoxylate, phenyl phenylglyoxvlate, ethyl o-chlorophenylglyoxylate, ethyl p-methyl-thiophenylglyoxylate, ethyl p-phenylthiophenylglyoxylate, ethyl p-methoxy-phenylglyoxylate, ethyl 2-furanglyoxylate and ethyl p-phenoxyphenylglyoxylate.
Mixtures of pnotoinitiators may be used if desired.
Many of the quenchers having ionization potentials in the range of from about 6 1/2 to 9 electron volts or in the range of 10 1/2 to about 12 electron volts are olefins generally having from about 2 to about 18 carbon atoms, preferably from about 4 to about 10 carbon atoms. ~xamples of olefinic quenchers are: l-ethoxy-l-butene, tetraethoxy-ethylene, l,l-diethoxyethylene, ethoxyethylene, 2,3-dimethyl-2-butene, 1,2-dicyanoethylene and tetracyanoethylene.
; Other quenchers having ionization potentials in the range of from about 6 1/2 to 9 electron volts or in the range of from 10 1/2 :

8~

to about 1~ electron volts are conjugated polyenes usually having from about 4 to about 40 carbon atoms, preferably from about 5 to about 10 carbon atoms. Examples of such conjugated polyenic quenchers are: 2,5-dimethyl-2,4-hexadiene, 1,3-pentadiene and ~-carotene.
Still other quenchers having ionization potentials in the range of from about 6 1/2 to 9 eleceron volts are the alkoxy substituted benzenes and the alkoxy substituted naphthalenes. Examples of alkoxy substituted benzenes are compounds represented by the formula:

(RO)n ~

wherein each individual RO on the molecule iS lower alkoxy and n is an integer in the range of from 1 to 6. Usually the alkoxy group contains from 1 to 4 carbon atoms. Other minor substituents which do not interfere with the quenching property may be on the molecule. Examples include: ~
methoxybenzene, o-dimethoxybenzene, m-dimethoxybenzene, p-dimethoxybenzene, ~.
1,3,5-trimethoxybenzene, pentamethoxybenzene, hexamethoxybenzene, ethoxy- ~
benzene, o-diethoxybenzene, m-diethoxybenzene, p-diethoxybenzene, 1,2,4,5-tetraethoxybenzene and l-methoxy-3-ethoxybenzene.
Examples of alkoxy substituted naphthalenes are compounds ~.
- represented by the formula: -(RO ~ OR) wherein each individual RO on the molecule is lower alkoxy, b is an integer in the range of from 1 to 4 and c is an integer in the range of from O to 4. Usually the alkoxy group contains from 1 to 4 carbon atoms.

~ 13 -' Other minor substituents which do not interfere with the quenching property may be on the molecule. Examples include: 1,3-dimethoxy-naphthalene, 1,4-dimethoxynaphthalene, 1,5-dimethoxynaphthalene, 1,6-dimethoxynaphthalene, 1,7-dimethoxynaphthalene, 1,8-dimethoxy-naphthalene, 2,3-d;methoxynaphthalene, 2,6-dimethoxynaphthalene, 2,7-dimethoxynaphthalene, 2,3,6,7-tetramethoxy-naphthalene, 1,3-diethoxy-naphthalene, 1,4-diethoxynaphthalene, 1,5-diethoxy-naphthalene, 1,6-diethoxynaphthalene, 1,7-diethoxynaphthalene, 2,3-diethoxy-naphthalene, Z,6-diethoxynaphthalene, 2,7-diethoxynaphthalene, 2,3,6-triethoxy-naphthalene and 2-methoxy-6-ethoxynaphthalene.
Examples of quenchers having a triplet energy in the range of from 35 to 68 kilocalories per mole include: perylene, 9,10-dichloroanthra-cene, 9,10-diphenylanthracene, 3,4-benzopyrene, l-chloranthracene, adthracene, 1,12-benzperylene, trans-1,3,5-hexatriene, 1,2-benzanthracene, pyrene, pentaphene, diphenyltetraacetylene, trans-stilbene, 1,2,3,4-dibenzanthracene, 1,2,5,6-dibenzanthracene, 1,3-cyclohexadiene, 1,2,7,8-dibenzoanthracene, 1,2-benzopyrene, fluoranthene, 1,2-benzochyrsene, cyclopentadiene, 9-acetyl-phenanthrene, p-terphenyl, l-iodonaphthalene, 2-phenylnaphthalene, l-phenyl-naphthalene, 3,4-benzophenanthrene, 3-acetylphenanthrene, l-bromonaphthalene, l-cbloronaphthalene, 2-naphthonitrile, acenaphthene, trans-1,3-pentadiene, 2-naphthaldehyde, 2-naphthoic acid, l-acetylnaphthalene, 2-acetylnaphthalene, 2-benzoylnaphthalene, 2,4-hexadien-1-ol, l-methylnaphthalene, l-methoxy-naphthalene, 1,3-butadiene, l-fluoronaphthalene, isoprene, tetraacetylene glycol, diethyltetraacetylene, coronene, 3,4-benzofluorene, diphenyltriacetylene, 2,2'-binaphthyl, l-naphthaldehyde, 5,6-benzochry-sene, l-acetylnaphthalene, 3,4,5,6-dibenzophenanthrene, cis-stilbene, chrysene, 1,2-benzofluorene, 2,3-benzofluorene, l-benzoylnaphthalene, l-naphthonitrile, l-naphthoic acid, diphenyldiacetylene, 1,2,6,7-dibenzopyrene, 2-iodonaphthalene, ~8~9I~

2-bromonaphthalene, 2-chloronaphthalene, 2-methylnaphthalene, naphthalene, o-terphenyl, phenanthrene, diphenyl-acetylene, 4,4'-dichlorobiphenyl, triacetylene glycol, 2,4,6-octatriyne, m-terDhenyl, 2-bromobiphenyl, biphenyl and fluorene.
Examples of quenchers which are polymerizable monomers and which have a triplet energy in ehe range of from 35 to 68 kilocalories per mole, an ionization potential in the range of from about 6 1/2 to 9 electron volts or in the range of from 10 1/7 to about 12 electron volts or have both a triplet energy in the stated range and an ionization potential in one of the stated ranges, include: N-vinyl-2-pyrrolidone, N-vinylcaprolactamJ N-vinylcarbazole and styrene.
The quenching moiety may be part of a polymerizable molecule having acrylyloxy functionality, for example: 2-phenoxyethyl acrylate, ~-naphthyl acrylate and ~-naPhthyl acrylate.
Mixtures of quenchers may be used if desired. _ Useful compounds having a plurality of acrylyloxy groups and capable of being free radically addition polymerized by interaction with the photoinitiator and the photosensitizer are numerous and include divalent, trivalent, tetravalent and higher polyvalent organic radicals whose bonds are satisfied with unsubstituted acrylyloxy or ~-substituted acrylyloxy groups. The polyvalent radical may be aliphatic, cycloaliphatic or aromatic. Examples of these compounds are the diacrylates and dimeth-acrylates of ethylene glycol, 1,3-propanediol, propylene glycol, 2,3-butanediol, 1,4-butcmediol, 2-ethylbutane-1,4-diol, 1,5-pentanediol, `` 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, l,9-nonanediol, 1,10-decanediol, 2,10-decanediol, 1,4-cyclohexanediol, 1,4-dimethylolcyclo-hexane, 2,2-diethylpropane-1,3-diol, 2,2-dimethylpropane-1,3-diol, 3-~: i ~ ~8~

methylpentane-1,4-diol, 2,2-diethylbutane-1,3-diol, 4,5-nonanediol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, 5,5-dimethyl-3,7-dioxanonane-1,9-diol, 2,2-dimethyl-3-hydroxypropyl 2,2-dimethyl-3-hydroxypropionate, Bisphenol A diglycidyl ether, 1,4-butanediol diglycidyl ether and neopentyl glycol diglycidyl ether; the triacrylates, trimethacrylates~ diacrylates and dimethacrylates of glycerol, 1,1,1- .
trimethylolpropane and trimethylolethane; and the tetraacrylates, tetra-methacrylates, triacrylates, trimethacrylates, diacrylates and dimetha-crylates, of pentaerythritol and erythritol. The acrylyloxy groups of the molecules are usually the same, but they may be different as exemplified by the compound 2,2-dimethyl-1-acrylyloxy-3-methacrylyloxypropane.
Further examples of satisfactory polyacrylyloxy compounds include polyacrylyloxy functional polyesters, polyamides, polyacrylates, polyethers, polycarbonates or polyurethanes as well as polyacrylyloxy functional compounds of mixed functionality such as polyacrylyloxy functional poly(ester-urethanes), poly(ester-amides) and poly(ether-urethanes).
Nany of the above polyacrylyloxy compounds and others are described in the following United States Patents: 3,455,801; 3,455,802;
3,470,079; 3,471,386; 3,483,104; 3,485,733; 3,509,234; 3,619,260;
3,645,984; 3,647,737; 3,676,398; 3,700,643; 3,968,016; 3,979,426;
4,017,652; 4,024,296; 4,024,297; 4,037,112, 49064,2; 4,108,840 and 4,130,708.
Still other examples of polyacrylyloxy compounds are amide acrylates such as are described in Canadian Application Serial No. 307,235, filed July 12, 1978, amine amide acrylates such as are described in Canadian Application Serial No. 311,599, filed September 19, 1978, and urethane amide acrylates such as are described in U.S. Patent 4,153,776 ; . ' ~ ~ ' ' ' ~:

9~

and in U.S. Patent 4,187,366.
Mixtures of compounds having Q plurality of acrylyloxy groups may be used, if desired.
Monomer having monoacrylic functionality which crosslinks with the compound having polyacrylyloxy functionality may optionally be present in the coating composition. Examples of rnonoacrylic functional monomers which may be used are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate and octyl methacrylate. The preferred monoacrylic functional monomers are liquid compounds miscible with the polyacrylyloxy compound. The use of one or more monoacrylic functional monomers is desirable because the greater mobility of the smaller monomer molecule, as compared to the larger polyacrylyloxy functional molecule, allows crosslinking to proceed faster than if the monoacrylic functional monomer were absent. Another benefit is that the monoacrylic functional monomer usually acts as a reactive solvent for the polyacrylyloxy functional compound thereby providing coating compositions having a satisfactory low viscosity without using an inordinate amount, if any at all, of volatile, nonreactive solvent.
The monoacrylic functional monomer, or mixtures of monoacrylic functional monomers, may be employed over a broad range. At the lower end of the range, no monoacrylic functional monomer need be used. The amount of such monomer when used should be sufficient to provide a liquid, flowable, interpolymeri~able mixture. When used, the monomer will ordinarily be presenl: in the coating composltion in the range of from about 1 to about 80 percenl: by weight of the binder of the coating compositlon.
Typically, .

~ - 17 ~

86~

the monoacrylic functional monomer will ordinarily be present in the ran8e of from about 15 to about 30 percent by weight of the binder.
Pigments are optional ingredients which are often included in the coating composition, Examples oE opacifying pigments include titanium dioxide (rutile or anatase), zinc oxide, zirconium oxide, zinc sulfide and lithopone. Examples of coloring pigments include iron oxides, cadmium sulfide, carbon black, phthalocyanine blue, phthalocyanine green, indanthrone blue, ultramarine blue, chromium oxide, burnt umber, benzidine yellow, toluidine red, aluminum powder and aluminum flakes. Examples of extender pigments include silica, barytes, calcium carbonate, barium sulfate, talc, aluminum silicates, sodium aluminum silicates, potassium aluminum silicates and magnesium silicate. ~ single pigment may be used or mixtures of pigments may be employed. When the pigment is ultraviolet light absorbing, it should be used in amounts which do not preclude curing of the interior of the coating. The maximum amount is therefore related to the thickness of the coating to be cured. Thin coatings may tolerate more ultraviolet light absorbing pigment than thick coatings. When the pigment does not significantly absorb ultraviolet light, there is usually greater latitude in the amounts which may be employed. When pigment is used, it is generally present in an amount in the range of from about ~ -~ 0.1 to about 70 percent by weight of the coating composition. Often it `~ is present in an amount in the range of from about 0.5 to about 50 percent.
Usually it is present in an~amount in the range of from about l to about 35 percent by weight of the coating composition.
Dyes and tints may optionally be included in the coating compo- ~ -sition in conventional amounts. ~ ~ ;

: :

:

Another optional ingredient is resinous pigment dispersant or grinding vehicle. There are many resinous dispersants which are commercially available for that purpose. These dispersants are used in the manner and in amounts known to the art.
Conventional plasticizers such as dibutyl phthalate, butyl benzyl phthalate, diisooctyl phthalate, decyl butyl phthalate, diisooctyl adipate, dibutyl sebacate, butyl benzoate, triisooctyl trimellitate, n-octyl n-decyl trimellitate, and tricresyl phosphates and flow promoters such as phenyl benzoate, dibenzyl ketone, benzyl methyl ketone and the like may also be optionally included in amounts customary in the art.
Any of the conventional viscosity control agents may be optionally employed in the composition. The preferred materials are resinous or polymeric viscosity control agents. Many of these resinous materials are available. Illustrative of such materials are cellulose acetate butyrate and the like. These viscosity control agents are used in the manner and in amounts known to the art.
Another optional ingredient which is often included in the coating composition is an inert volaeile organic solvent. Mixtures of several inert volatile organic solvents may be used when desired. Examples of suitable inert volatile organic solvents are acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, amyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, cellosolve, ethyl cellosolve, cellosolve acetate, 2-ethylhexyl acetate, tetrahydrofuran, and aliphatic naphtha. When solvent of this type is used it is ordinarily present `in the coating composition in the range of from about 0.1 to about 40 percent by weight of the vehicle of the coating composition. From about l to about lS percent is typical. `

8~

The listing of optional ingredients discussed above is by no means exhaustive. Other ingredients may be employed in their customary amounts for their customary purposes so long as they do not seriously interfere with good coatings practice or the obtaining o~ cured coatings of low gloss.
The coating compositions of the invention are usually prepared by simply admixing the various ingredients. The compounds comprising the photocatalyst system may belpremixed and then admixed with the other ingredients of the coating composition or they may be added separately.
Although mixing is usually accomplished at room temperature, elevated temperatures are sometimes used. The maximum temperature which is usable depends upon the heat stability of the ingredients. Temperatures above about 200C. are only rarely employed.
The ultraviolet light curable coating compositions of the invention are generally used to form cured adherent coatings on substrates.
The substrate is coated with the coating composition using substantially any technique known to the art. These include spraying, curtain coating, dipping, roller application, printing, brushing, drawing and extrusion.
The coated substrate is then exposed to ultraviolet light to cure the eoating into a crosslinked film.
The amount of photosensitizer present in tne ultraviolet light curable coating compositions of the invention may be widely varied.
Vsually the photosensitizer is present in an amount in the range of ~rom about 0.01 percent to about 50 percent by weight based on the weight of the binder of the coating composition. More often an amount in the ~~
range of from about 0.1 percent to about 20 percent is employed. From about 0.5 to about 10 percent by weight based on the weight of the binder is preferred.
.

' .. . . .' .

The amount of photoinitiator present in the coating compos;t;on may also be w;dely varied. Ord;nar;ly tlle photo;nitiator is present in an amount in the range of from about 0.01 percent to about 10 percent by weight based on the weight of the binder of the coating composition.
Most often an amount in the range of from about 0.05 percent to about 7 percent is used. From about 0.1 percent to about 5 percent by wei~ht based on the weight of the binder is preferred.
The amount of quencher present in the coating composition is similarly subject to wide variation. Usually the quencher is present in an amount in the range of from about 0.01 percent to about 90 percent by weight based on the weight of binder of the coating composition.
~hen the quencher is not a monomer it is ordinarily present in an amount in the range of from about 0.01 percent to about 20 percent by weight based on the weight of binder of the coating composition. ~ost often an amount in the range of from about 0.02 percent to about 10 percent is used. From about 0.05 percent to about 5 percent by weight based on the weight of the binder is preferred. When the quencher is a monomer, or is a combination of monomer and non-monomer, it is generally present in an amount in the range of from about 0.01 to about 90 percent by weight based on the binder of the coating composition. Typically an amount in the range of from about 0.1 to about 75 percent is used. From-about 1 to about 50 percent by weight of the binder is preferred.
The amount of polymerizable compound having a plurality of acrylyloxy groups present in the coating composition is subject to wide variation. The compound is ordinarily present in an amount in the range of from about 10 to 99 percent by weight based on the weight of the binder of the coating composition. An amount in the range of from about 20 to 97 o percent is typical. From about 30 to 95 percent by weight of the binder is preferred.
Cured coatings of the ultraviolet light curable coating compo-sition of the invention usually have thicknesses in the range of from about 0.1 to about 100 mils. More often they have thicknesses in the range of from about 0.3 to about 10 mils.
Any suitable source which emits ultraviolet light, viz., electro-magnetic radiation having a wavelength in the range of from about 180 to about 400 nanometers, may be used in the practice of this invention.
Suitable sources are mercury arcs, carbon arcs, low pressure mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, swirl-flow plasma arc, ultraviolet light emitting diodes and ultraviolet light emitting lasers. Particularly preferred are ultraviolet light emitting lamps of the medium or high pressure mercury vapor type. Such lamps usually have fused quartz envelopes to withstand the heat and transmlt the ultraviolet radia-tion and are ordinarily in the form of long tubes having an electrode at either end. Examples of these lamps are PPG Models Ç0-2032, 60-0393, 60-0197 and 60-2031 and Hanovla Models 6512A431, 65$2A431, 6565A431 and 6577A431. ~
The time of exposure to ultraviolet light ~and the intensity of ~~
the ultraviolet light to which the coating composition is exposed may vary greatly. Generally the exposure to ultraviolet light should continue until either the film is thermoset throughout or at least cured to the point where subsequent "dark reactions" cause the film to become thermoset throughout. Exposure of the coating to ultraviolet light may be accom- ~ ~
plished in the presence of an inert atmosphere, viz.j an atmosphere either ~ ;
containing no oxygen or only a concentration of oxygen which insignificantly ~ ~

:

- 22 - ~

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inhibits polymerization o~ the coating surface. Gases such as nitrogen, argon, carbon dioxide or mixtures thereof are typically the major com-ponents of inert atmospheres, although other unreactive gases may be used. Nitrogen is generally employed for this purpose. In many cases where the coating composition is such that polymerizati~n is not signifi- -cantly susceptible to oxygen inhibition, exposure to ultraviolet light may be conducted in air.
Substrates which may be coated with the compositions of this invention may vary widely in their properties. Organic substrates such as wood, fiberboard, particle board, composition board, paper, cardboard and various polymers such as polyesters, polyamides, cured phenolic resins, cured aminoplasts, acrylics, polyurethanes and rubber may be used. Inorganic substrates are exemplified by glass, quartz and ceramic materials. Many metallic substrates may be coated. Exemplary metallic substrates are iron, steel, stainless steel, copper, brass, bronze, aluminum, magnesium, titanium, nickel, chronium, zinc and alloys.
Gloss may conveniently be determined by the Standard Method of Test for Specular Gloss, ASTM Designation D-523-67 {Reapproval 1972).
Although it IS not desired to be bound by any theory, it is believed that the enhanced flatting is obtained by a microwrinkling of the surface of the coating. The microwrinkling is thought to be due to -a retardation of cure in the interior of the film relative to cure in the surface layer caused by a preferential and selective quenching of the photosensitizer by the quencher. More specifically, it is believed that this occurs as follows: During exposure of a coating of radiation curable coating co~position to ultraviolet light, the ultraviolet light intensity diminishes in a fashion which is generally exponential with :

depth. There is essentially complete absorption of 2no to 300 nanometer ultraviolet ]ight in the surface layer of the coating where both the photoinitiator and the photosensitizer produce large numbers of free radicals. The quencher reduces the number of free radicals which would be produced in the absence of the quencher, but the net effect is small because of the large excess of available free radicals. In the lower portion of the coating, the concentration of free radicals is many times lower because the remaining 300 to 400 nanometer ultraviolit light is only weakly absorbed by the photoinitiator and photosensitizer. The quencher again reduces the number of free radicals produced by reactions of the photosensitizer, but because the concentration of free radicals is low, the net effect is considerable. Therefore, the quenchable photosensitizer and the substantially non-quenchable photoinitiator both produce significant quantities of free radicals m the surface layer which are available for initiation, whereas in the lower layer, the substantially non-quenchable photoinitiator produces most of the free radicals available for initiation.
The 7arge concentration of free radicals permits the surface layer to be cured at least to the point where it tends to resist flow while the lower portion of the coating is still fluid. Thereafter, as the lower portion cures, it shrinks causing the surface layer to form microwrinkles.
If the lower portion of the coating cures too quickly in relation to the-curing rate of the surface layer, the lower portion shrinks while the surface layer is still fluid and the microwrinkling effect is reduced or eliminated. The quencher and its cooperation with the photosensitizer and the photoinitiator is therefore seen to produce the delay in curing of the lower portion necessary to induce microwrinkling. Nevertheless, because the delay is not gross, films oE low gloss may be produced by a single pass through an ultraviolet light processor at reasonable line speeds which are generally suitable for commercial production.
In the illustrative examples which follow, all parts are parts by weight and percentages are percent by weight unless otherwise specified.

EXAMPLE I
Into a reaction vessel equipped with an agitator, a heater, cooling means, a thermometer and refluxing condenser, there is charged 529 parts N-methylethanolamine. The amine is heated to about 99C. With the temperature of the amine ma;ntained at 96-99C., 615 parts Y-butyro-; 10 lactone is added gradually to the reaction vessel, approximately 9 partsbeing added every minute. The temperature of the reaction mixture is maintained at 99-102C. for about six hours w;th periodic viscosity checks being made on 100 percent samples. A final viscosity of R is obtained after which the amide diol intermediate reaction product is cooled to about 52C. and then placed in a storage container.
Into `a reaction vessel equipped as above, there is charged 809 parts bis(4-isocyanatocyclohexyl)methane ("Hylene W"; DuPont), 618 parts 2-ethylhexyl acrylate, 0.48 part dibutyltin dilaurate ("Niax" catalyst;
Union Carbide Corp.) and 0.05 part phenothiazine. An air sparge is applied below the surface of the reaction mixture and a nitrogen blanket is - -established above the mixture. The reaction mixture is heated from 21C.
to about 40C. in a 55-minute period, after which time the nitrogen blanket and air sparee are removed. Then over a two hour period there is added to the reaction vessel a blend of 663 parts of a polycaprolactone polyol having a hydroxyl value of 216 (PCP 0200, Union Carbide Corporation) and -143 parts of the previously prepared amide diol intermediate. The temperature ~ Tra~ ~ar~ ~
;~:

..:

39~

of the reaction nixture is observed to vary during the two-hour addition period from about 42 C. to about 52 C. The reaction mixture is held at about 52C. for two hours, after which time a viscosity check is made on a sample of the reaction mixture diluted to 75 percent concentration in toluene and is found to be V+. The reaction mixture is then heated to about 63C. and held at that temperature for one hour and 45 minutes, after which time a viscosity of V~ is obtained for a sample taken as before. The reaction mixture is heated to about 68C. during a one hour and 5 minute holding period. Then a blend of 4.5 parts hydroxyethyl O acrylate and 2.3 parts di-t-butyl-p-cresol ('IIonoi~ inhibitin~ agent;
Shell Oil Company) is added to the reaction vessel. Over a 30-minute period 254 parts hydroxyethyl acrylate is added to the reaction mixture, after which time the temperature is observed to be 69C. and a viscosity ., .
measurement of V+ is obtained for a sample taken as before. The reaction mixture is then maintained at 75-76C. for two hours and 45 minutes during which time viscosity measurements of V~ and ~+ are obtained. Then 24.5 parts glacial acrylic acid is added to the reaction mixture and after 45 ~ j minutes a viscosity of Vl is obtained for a sample diluted to 75 percent concentration in 2-ethoxyethanol. The amide urethane acrylate reaction product is cooled to about 52C. and filtered through a nylon bag into a ~ -storage container.
A base composition is prepared by admixing 245 parts of the ~ above amide urethane reaction product, 175 parts of the diacrylate of ; 1,6-hexanediol, 70 parts of the diacrylate of triethyleneglycol, 28 parts benzophenone, 7 parts ~,~-dimethoxy-a-phenylacetophenone and 35 parts silica pigment (Syloid 74; W. R.~Grace & Co.). -~' A plurality of coating compositions is prepared by admixing various amounts of t:he above base composition, 2-(2-ethoxyethoxy)ethyl ~ rr~ MQr~

~' : ' ''~ ' : . ~ '.
.
.

8~9~

acryla~e and naphthalene. A control coating composition is prepared in the same manner, but omitting the naphthalene. Each coating compos;tion is drawn do~n on a printed poly(vinyl chloride) film using a No. 014 wire wound bar. The coatings are then cured by passing the coated films once, in air, through an ultraviolet light processor containing four medium pressure, ultraviolet light emitting, mercury vapor lamps. Ihe 60 and 85 gloss values are then determined generally using the procedure of ASTM
Designation D-523-67 (Reapproval 1972). The proportions of materials, the rates at which the coated films are passed through the processor and the gloss values are shown in Table 1.

Coating Composition _ lB lC lDlE_ _ Base Composition, parts 40 50 50 5050 2-(2-Ethoxyethoxy)ethyl Acrylate, parts 10 10 10 1010 Naphthalene, parts 0 0.05 0.5 1.0 2.5 Conveyor Speed, meters/minute ; 24.4 24.4 24.4 21.3 15.2 ~ ~~
60 Gloss, percent reflectance 30 28 2215 12 85 Gloss, percent reflectance 50 $7 2916 9 `

EXAMPLE II
An intermediate composition is prepared by admixing 122.5 parts of the amide urethane reaction product of Rxample I, 87.5 parts of the ~: :

- 27` -9~

diacrylate of 1,6-he~anediol, 35 parts of the diacrylate of triethylene-glYcol, 14 parts benzophenone, 3.5 parts ~a-dimethoxy-x-phenylacetophenone and 17.5 parts silica pigment (Syloid 74). After dispersing the silica pigment, the intermediate composition is admixed with 56 parts 2-(2-ethoxyethoxy)ethyl acrylate to form a base composition.
A plurality of coating compositions are prepared by admixing portions of the above base composition with various amounts of naphthalene or with naphthalene and styrene. Each coating composition is drawn down on a printed poly(vinyl chloride) film using a No. 014 wire wound bar.
The coatings are then cured, in air, in the manner of Example I and the 60 and 85 gloss values are determined, also in the manner of Example I.
The proportions of materials, the rates at which the coated films are passed through the processor and the gloss values are shown in Table 2.
Coating Composition lA of Example 1 is used as the control.

Coating Composition ~; 2A 2B 2C 2D 2E
Base Composition, parts 60 60 60 60 60 Naphthalene, parts 0 0 0 0 1.0 Styrene, parts ~0.05 0.5 1.0 2.5 1.0 Conveyor Speed, meters/minute 24.4 21.3 18.315.215.2 60~ Gloss, percent reflectance 27 20 18 14 8 85 Gloss, percent reflectance 45 26 23 22 9 .:

;:::

' ~ :
- ' ~ ~ - . . -.. . -, -EXA~IPLE III
A base composition is preparecl by admixing 122.5 parts of the amide urethane reaction product of Exam~le I, 87.5 parts of the diacrylate of 1,6-hexanediol, 35 parts of the diacrylate of triethyleneglycol, 14 5 parts benzophenone, 3.5 parts ~ dimethoxy~X-phenylacetophenone, 17.5 parts silica pigment (Syloid 74) and 56 parts 2-(2-ethoxyethoxy)ethyl acrylate.
A plurality of coating compositions are prepared by admixing 50 parts of the above base composition with 1 part of a quencher. The base composition is used as a control. Each coating composition is drawn down on a printed poly(vinyl chloride) film using a No. 014 wire wound bar. The coatings are then cured by passing the coated films once, in air at 18.3 meters per minute, through two ultraviolet light processors in succession, each containing one medium pressure, ultra-violet light emitting, mercury vapor lamp. The 60 and 85 gloss values -are then determined in the manner of Example I. The identity of the ¦
; quenchers and the gloss vaIues are shown in Table 3.

}
60 Gloss, 85 Gloss, ~uencherpercent reflectancepercent reflectance ~ ~-Benæaldehyde 28 42 ~
~ .
- Fluorene 19 30 Styrene 18 22 Naphthalene 14 14 25 Triphenylene 13 13 ~ -~ Triphenylamine ~ 15 15 : , :

~ ~ ' - 29 - ~ ~

: . . , . : ~ .
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60 Gloss, 85 Gloss, Quencher percent reflectance percent reflectance Maleic Anhydride 16 24 1,2,4,5-Benzenetetra-carboxylic Dianhydride 20 32 None (Control) 36 55 EXA~IPLE IV
A base composition is prepared by admixing 393.3 parts of the amide urethane reaction product of Example I, 280.8 parts of the diacrylate of 1,6-hexanediol, 112.5 parts of the diacrylate of triethyleneglycol, 45.0 parts benzophenone and 4.5 parts ,a-dimethoxy-a-phenylacetophenone.
Three coating compositions are prepared by admixing portions of the above base composition with various materials. Six other coating compositions are prepared by admixing a portion of one of the first three coating compositions with naphthalene or styrene. Each coating -composition is drawn down on printed poly(vinyl chloride) films using a No. 014 wire wound bar. The coatings are then cured by exposing them to ultraviolet light. This is accomplished by passing some of the coated films once, in air at 12.2 meters per minute, through two ultraviolet light processors in succession, each containing two medium pressure, -., :
ultraviolet light emitting, mercury vapor lamps and by passing others of the coated films twice, in a nItrogen atmosphere containing less than 100 parts oxygen per million parts atmosphere by volume and at a speed of 12.2 meters per minute, through one ultraviolet light processor containing two medium pressure, ultraviolet light emitting, mercury vapor lamps. The 60 and 85 gloss values are then determined in the manner of Example I.
The identity of the materials, their proportions and the gloss values are shown in Tables 4 and 5.

.

g~

Coating Composition Base Composition, parts 278.7 278.7 278.7 N-Vinyl-2-pyrrolidone, parts 60.0 0 0 2-(2-Ethoxyethoxy)ethyl Acrylate, parts 0 0 60.0 2-Pheno~yethyl Acrylate~
parts 0 60.0 0 Cured in Air ., 60 Gloss, percent reflectance 53 72 82 85 Gloss, percent reflectance 55 72 86 Cured in Nitrogen 60 Gloss, percent reflectance 74 88 70 85 Gloss, _ percent reflectance 88 93 77 ~;

TABLE 5 ~ ~

Coating Composition ~ j ; 4D 4E 4F 4G 4H 4J :~
Composition 4A, ~~
: ~ parts 50.0 0 0 50 0 0 0 Composition 4B, parts 0 50.0 0 0 50 0 0 Composition 4C, ~ ~ 30 parts 0 0 50.0 0 0 50 0 ~ ~:
:~: Naphthalene, parts 1.0 1.0 1.0 0 0 0 Styrene, parts 0 0 0 1.0 1.0 1.0 ~ ~ ~

:: :~ :

' :. :'' ' ' ' ' Coating Composition _ 4E 4F 4G 4H 4J_ Cured in Air 60~ Gloss, 5percent reflectance 6575 77 34 32 55 85 Gloss, percent reflectance 7079 80 43 43 58 Cured in Nitrogen 60~ Gloss, 10percent reflectance 6580 74 2 1.5 1.5 85~ Gloss, percent reflectance 6184 81 6 3 2.5 EXAMPLE V
.
A base composition is prepared by admixing 509.6 parts of the amide urethane reaction product of Example I, 364.0 parts of the diacrylate of 1,6-hexanediol and 145.6 parts of the diacrylate of triethyleneglycol.
A plurality o coating compositions are prepared by admixing portions of the above base composition with various materials. Each ~oating comPOSition is drawn down on printed poly(vinyl chloride) film using a No. 014 wire wound bar. The coatings are then cured by passing the coated films once, ~in air at 12.2 meters per minute, through two ultraviolet light processors, in succession, each containing two medium pressure, ultraviolet light emitting, mercury vapor lamps. The 60 and 85 gloss values are then determined in the manner of Example I. The ;~
identity of the materials, their proportions and the gloss values are ~~
shown in Table 6. ~~

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U -~ 3 3 ii90 EXAMPLE VI
A base composition is prepared by admixing 72.8 parts of the amide urethane product of Example I, 52.0 parts of the diacrylate of 1,6-hexanediol, 20.8 parts of the diacrylate of triethyleneglycol, 33.2 pa}ts N-vinyl-2-pyrrolidone, 8.4 parts benzophenone and 10.4 parts silica pigment (Syloid 74).
A plurality of coating compositions are prepared by admixing portions of the base composition with various materials. Each coating composition is drawn down on printed poly(vinyl chloride) film using a ~o. 014 wire wound bar. The coatings are then cured by passing the coated films once, in air at 12.2 meters per minute, through an ultraviolet light processor containing four medium pressure, ultraviolet light emitting, mercury vapor lamps. The 60 and 85 gloss values are then determined in the manner of Example I. The identity of the materials, their proportions and the gloss values are shown in Table 7. --Coating Composition -- --Base Composition, .
parts 50 50 50 Methyl Phenylglyoxylate, parts 0.5 0 0 ~; Oxime E~ster Photoinitiator (Q 21 ~ American Cyanamid Co.), parts 0 0.5 0 ~ ~ -Ketone Ph~toinitiator (EM 11731~ EM Laboratories, Inc.), parts ; O 0 0.5 ~ ~ r~Q~ k ~ ~ ~

~ :
~ 34 -3;90 TABLE 7 (Continued) Coating Composition 60 Gloss, percent reflectance 6 26 14 85 Gloss, - percent reflectance 5 46 18 `-- EXAMPLE VII
A reactor equipped with an agitator, a thermometer, a heater, a cooler, a total reflux condenser, a source of air and a source of nitrogen is charged with 1067.5 parts bis~4-isocyanatocyclohexyl)methane, 992.9 parts 2-ethylhexyl acrylate, 0.32 part dibutyl tin dilaurate, 2.2 parts 2,6-di-tert-butyl-4-methylphenol and 19.5 parts methyl isobutyl ketone. A slow stream of air is introduced below the liquid surface 1~ of the charged materials and a slow stream of nitrogen is introduced _ ~i above the liquid surface. The heater is then turned on. One hour later when the temperature has reached 40C., the addition of 1657 parts of a polycaprolactone diol (reaction product of e-caprolactone and diethylene glycol; molecular wei~ht 530; ~iax Polyol PCP-0200, Union Carbide Corporation) is begun. The cooler is used as needed to maintain the temperature in the ; range of from 40C. to 41.1C. during the addition. Three hours after ~; beginning the addition, the~temperature is 41.1C., and the addition is completed. The heater is then turned on and fifteen minutes later the temperature is 48.9C. The temperature is then held in the range of from 48.9C. to 51.7C. for two hours. At the conclusion of this period the ~ ~ temperature is 51.7C. Further heat is applied and forty-five minutes ; later the temperature is 60C. The temperature is then held in the range : :~ ::
:

:~ .

: ' , ' . ' . ' 8~90 of ~rom 60C. to 62.8 C. for one hour. A~ the conclusion of this period the temperature is 62.8 C. mere ;s then added 234.2 parts 2-hydroxyethyl acrylate and 0.32 part 2,6-di-tert-butyl-4-methvlphenol. Further heat is applied and thirty minutes later the temperature is 68.3C. The temperature is held at 68.3C. for thirty minutes after which the addition of 234.5 parts N-vinyl-2-pyrrolidone and 414.0 parts 2-ethylhexyl acrylate is begun.
Twenty minutes later the temperature is 70C. and the addition i5 completed.
Thirty minutes later the temperature is 71.1C. and cooling is applied.
Two hours and forty minutes later the temperature is 51.7C. and the reaction product is filtered to yield a urethane acrylate composition.
A plurality of coating compositions is prepared by admixing various materials. Each coating composition is drawn do~n on printed poly(vinyl chloride) films using a ~o. 014 wire wound bar. The coatings are then cured by exposing them to ultraviolet light. This is accomplished by passing some of the coated films once, in air at 12.2 meters per minute, through two ultraviolet light processors in succession, each ~;
containing two medium pressure, ultraviolet light emitting, mercury vapor lamps and bypassing others of the coated films once, in air at 36.6 meters per minute, through two ultraviolet light processors in succession, each containing two medium pressure, ultraviolet light emitting, mercury vapor lamps. The 60 and 85 gloss values are then determined in the manner of Example 1. The identity of the materials and their proportions are showm in Table 8. The gloss values are shown in Table 9.

69~

Coating Composition Amide Urethane Reaction Product of Example I, parts 32 32 47 32 47 0 Urethane Acrylate Composition, parts 15 15 0 15 0 47 Diacrylate of 1,6-Hexanediol, parts 12 0 15 18 12 12 Tetrahydrofurfuryl Acrylate, parts 0 0 0 12 0 12 N-Vinyl-2-pyrrolidone, parts 12 12 12 12 15 18 Diacrylate of Triethylene-glycol, parts 18 18 0 0 0 0 2-Ethylhexyl Acrylate, parts 0 12 0 0 0 0 2-Phenoxyethyl Acrylate, parts 0 0 15 0 15 0 Benzophenone, parts 4 4 4 4 4 4 a,a-Dimethoxy-~-phenyl- _ i acetophenone, parts Silica Pigment (Syloid 74), parts 5 5 5 5 5 5 ~-Synthetic Wax (S379N;
Shamrock Chemicals Corp.), -parts ~ T~C~ k :

~8~

7A Coating Composition 7F
Conveyor Speed, 12.2 meters/minute 60 Gloss, percent reflectance 23 14 19 17 18 12 85 Gloss, percent reflectance 41 25 36 34 39 17 Conveyor Speed, 36.6 meters/minute 60 Gloss, percent reflectance 21 16 24 20 21 11 85 Gloss, percent reflectance 43 30 45 42 40 20 - 38 - ~ :

:

Claims (18)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An ultraviolet light curable coating composition comprising:
a. at lease one photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation, at least one member of said radical pair being capable of initiating addition polymerization of acrylyloxy groups;
b. at least one photosensitizer which (1) has a triplet energy in the range of from 54 to 72 kilocalories per mole, and (2) promotes photopolymerization through bimolecular photochemical reactions;
c. at least one quencher (1) having at least one quenching moiety which quenches said photosensitizer to an extent greater than the extent to which said photosensitizer is quenched by acrylyloxy groups, (2) which is not itself either an effective initiator or an effective inhibitor of free radical polymerization of acrylyloxy groups, (3) which does not produce products during quenching of said photosensitizer which are either effective initiators or effective inhibitors of free radical polymerization of acrylyloxy groups, (4) which either does not quench said photoinitiator or quenches said photoinitiator at a rate much less than the rate at which said photoinitiator induces polymerization of acrylyloxy groups so as not to significantly interfere with the initiation of free radical polymerization of acrylyloxy groups by said member of said radical pair;

(5) which has at least one of the following characteristics:
(i) a triplet energy in the range of from 35 to 68 kilocalories per mole, but lower than the triplet energy of said photosensitizer, (ii) an ionization potential in the range of from about 6 1/2 to 9 electron volts, (iii) an ionization potential in the range of from 10 1/2 to about 12 electron volts; and d. at least one compound having a plurality of acrylyloxy groups and capable of being free radically addition polymerized by inter-action with said photoinitiator and said photosensitizer;
wherein upon exposure to ultraviolet light, a coating of said coating composition is cured to a crosslinked film having a lower gloss than if said quencher were absent.

2. The coating composition of Claim 1 wherein said photo-sensitizer comprises benzophenone.

3. The coating composition of Claim 1 wherein said photoinitiator comprises .alpha.,.alpha.-dimethoxy-.alpha.-phenylacetophenone.

4. The coating composition of Claim 1 wherein said quencher comprises a polymerizable monomer.

5. The coating composition of Claim 1 wherein said quencher comprises N-vinyl-2-pyrrolidone.

6. The coating composition of Claim 1 wherein said quencher is N-vinylcaprolactam.

7. The coating composition of Claim 1 wherein said quencher comprises 2-phenoxyethyl acrylate.

8. The coating composition of Claim 1 wherein said quencher comprises styrene.

9. The coating composition of Claim 1 wherein said quencher comprises naphthalene.

10. The coating composition of Claim 1 additionally containing pigment.

11. The coating composition of Claim 10 wherein said pigment comprises flatting pigment.

12. The coating composition of Claim 11 wherein said flatting pigment comprises silica flatting pigment.

13. The coating composition of Claim 1 additionally containing monomer having monoacrylic functionality.

14. The coating composition of Claim 1 wherein:
a. said photoinitiator is present in an amount in the range of from about 0.01 percent to about 10 percent by weight based on the weight of the binder of said coating composition;
b. said photosensitizer is present in an amount in the range of from about 0.01 percent to about 50 percent by weight based on the weight of the binder of said coating composition;
c. said quencher is present in an amount in the range of from about 0.01 percent to about 90 percent by weight based on the weight of the binder of said coating composition; and d. said compound having a plurality of acrylyloxy groups is present in an amount in the range of from about 10 to about 99 percent by weight based on the weight of the binder of said coating composition.

15. A method of forming a film of low gloss comprising exposing a coating of the coating composition of Claim 1 to ultraviolet light.

16. The method of Claim15 wherein said exposure is conducted in air.

17. A method of forming a film of low gloss comprising applying to a substrate a coating of the coating composition of Claim 1 and exposing said coating to ultraviolet light.

18. The method of Claim17 wherein said exposure is conducted in air.