Siloxane copolymers containing vinyloxy groups, their preparation and their use

The invention relates to organopolysiloxane copolymers having at least one Si-bonded vinyloxy-functional group and their preparation. The compositions of the present compound crosslink particularly rapidly under light.

The invention relates to siloxane copolymers containing vinyloxy groups and 
to a process for their preparation. The invention furthermore relates to 
compositions which can be crosslinked by light and are based on siloxane 
copolymers containing vinyloxy groups. 
Organopolysiloxanes which contain, per molecule, at least one Si-bonded 
vinyloxy-functional group of the formula 
EQU H.sub.2 C=CH--O--G-- 
wherein G is an alkylene radical or an alkylene radical which is 
interrupted by at least one divalent hetero radical, such as --O--, a 
divalent phonylone radical or a substituted divalent phenylene radical, or 
combinations of such hereto radicals, are known from EP-B 105 341. These 
organopolysiloxanes are obtained by preparation of a compound having an 
allyl and a vinyloxy group and addition of this compound onto the SiH 
groups of the organopolysiloxanes, hydrosilylation taking place only on 
the allyl group. EP-B 105 341 furthermore describes compositions which can 
be crosslinked by light and comprise the abovementioned 
organopolysiloxanes, and also onium salts which catalyse the cationic 
polymerisation of these organopolysiloxanes. 
A silane which has one vinyloxypropyl group and at least one 
trimethylsiloxy group and which is obtained by hydrosilylation of allyl 
vinyl ether with a silane containing trimethyisiloxy groups, addition 
taking place on the allyl group, is known for the production of plastic 
lenses from Chemical Abstracts 107, 176221q. 
Organopolysiloxanes which contain propenyloxy groups and siloxane 
copolymers which contain propenyloxy groups are described in U.S. Pat. No. 
5,057,549 and CA-A 20.35 396, these compounds being prepared in a 
two-stage process by addition of compounds having two or more than two 
allyloxy groups onto SiH groups of organopolysiloxanes and subsequent 
conversion of the allyloxy groups into the propenyloxy groups by addition 
on the double bond. 
Siloxane copolymers which are obtained by reaction of hydrocarbons having 
more than two terminal double bonds, such as 1,2,4-trivinylcyclohexane, 
with organopolysiloxanes containing Si-bonded hydrogen atoms in the 
presence of catalysts which promote hydrosilylation are described in the 
German Patent Application of the Applicant Company having the application 
number P 41 23 423.5. 
Organopolysiloxanes which have any number of substituted vinyl ether groups 
and are prepared by hydrosilylation, that is to say by reaction of an 
organopolysiloxane containing SiH groups with a polyoxyalkylene ether, for 
example of the formula 
##STR1## 
addition taking place on the allyl group, are known from U.S. Pat. No. 
5,145,915. 
There was the object of providing siloxane copolymers which contain 
vinyloxy groups and can be prepared in a simple process, the process 
allowing more than one vinyloxy group to be introduced on one silicon atom 
and the process also enabling polyvinyloxy polymers to be obtained when 
divinyl ethers are employed. There was furthermore the object of providing 
siloxane copolymers which contain vinyloxy groups and crosslink 
particularly rapidly under the action of light, in particular ultraviolet 
light, with cationic polymerisation. This object is achieved by the 
invention. 
The invention relates to siloxane copolymers containing vinyloxy groups and 
comprising 
(a) siloxane units of the formula 
##STR2## 
wherein R denotes identical or different, optionally halogenated 
hydrocarbon radicals having 1 to 18 carbon atom(s) per radical, 
R.sup.1 denotes identical or different alkyl radicals having 1 to 4 carbon 
atom(s) per radical, which can be substituted by an ether oxygen atom, 
a is 0, 1, 2 or 3, 
b is 0, 1, 2 or 3 
and the sum of a+b is not greater than 3, 
(b) at least one unit per molecule chosen from the group comprising units 
of the formula 
##STR3## 
wherein R has the meaning given above for this radical, c is 0, 1 or 2, 
G denotes a radical of the formula 
EQU --CH.sub.2 CH.sub.2 OY(OCH=CH.sub.2).sub.x-1 
wherein 
Y denotes a divalent, trivalent or tetravalent hydrocarbon radical having 1 
to 20 carbon atoms per radical, 
which can be substituted by groups of the formula 
--OH 
--OR.sup.3 (wherein R.sup.3 denotes an alkyl radical having 1 to 6 carbon 
atom(s) per radical) 
--OSiR.sub.3.sup.4 (wherein R.sup.4 denotes a methyl, ethyl, isopropyl, 
tert-butyl or phenyl radical) 
##STR4## 
(wherein R.sup.3 has the meaning given above for this radical) or --X 
(wherein X denotes a halogen atom) or can be interrupted by at least one 
oxygen atom, one carboxyl or one carbonyl group, and 
x is 2, 3 or 4, 
G.sup.1 denotes a radical of the formula 
##STR5## 
G.sup.2 denotes a radical of the formula 
##STR6## 
G.sup.3 denotes a radical of the formula 
##STR7## 
wherein Y and x have the meaning given above for these symbols, and 
(c) at least one unit per molecule of the formula 
##STR8## 
wherein R and c have the meaning given above for these symbols and L 
denotes a radical of the formula 
##STR9## 
wherein Z is a divalent, trivalent, tetravalent, pentavalent or hexavalent 
hydrocarbon radical having 2 to 20 carbon atoms per radical, which can be 
substituted by groups of the formula 
--OH 
--OR.sup.3 (wherein R.sup.3 denotes an alkyl radical having 1 to 6 carbon 
atoms per radical) 
--OSiR.sub.3.sup.4 (wherein R.sup.4 denotes a methyl, ethyl, isopropyl, 
tert-butyl or phenyl radical) 
##STR10## 
(wherein R.sup.3 has the meaning given above for this radical) or --X 
(wherein X denotes a halogen atom) or can be interrupted by at least one 
oxygen atom, one carboxyl or one carbonyl group, 
R.sup.2 denotes a hydrogen atom or an alkyl radical having 1 to 6 carbon 
atoms per radical, 
u denotes 0 or 1 and 
y denotes 2, 3, 4, 5 or 6. 
The siloxane copolymers containing vinyloxy groups preferably comprise 
siloxane units of the formula (I), at least one siloxane unit of the 
formula (II) per molecule and at least one unit of the formula (VI) per 
molecule. 
The invention furthermore relates to a process for the preparation of the 
siloxane copolymers containing vinyloxy groups, characterised in that an 
organic compound (1) containing vinyloxy groups, of the general formula 
EQU Y(OCH=CH.sub.2).sub.x ( 1) 
where Y and x have the meaning given above for these symbols, and an 
organic compound (2) containing aliphatic double bonds of the formula 
EQU Z(OCHR.sup.2).sub.u CR.sup.2 =CH.sub.2 !.sub.y ( 2) 
wherein Z, R.sup.2, u and y have the meaning given above for these symbols, 
are reacted with an organopolysiloxane (3) having on average more than one 
Si-bonded hydrogen atom per molecule, in the presence of a catalyst (4) 
which promotes the addition of Si-bonded hydrogen onto an aliphatic double 
bond, the organic compounds (1) and (2) being employed in amounts such 
that the ratio of the sum of aliphatic double bonds in the organic 
compounds (1) and (2) to Si-bonded hydrogen in the organopolysiloxane (3) 
is greater than 1.0, with the proviso that the ratio of aliphatic double 
bond in the organic compound (2) to Si-bonded hydrogen in the 
organopolysiloxane (3) is less than 1.0. 
In the prior art, as in the abovementioned EP-B 105 341, neither are 
siloxane copolymers containing vinyloxy groups described nor was it to be 
expected that such copolymers can be obtained by addition 
(hydrosilylation) of SiH groups onto vinyloxy groups, since according to 
EP-B 105 341, the introduction of a vinyloxy group into an 
organopolysiloxane is achieved only by hydrosilylation of a compound which 
contains an allyl group and a vinyloxy group, the addition taking place on 
the allyl group. 
The organopolysiloxanes according to the invention which contain vinyloxy 
groups preferably have a viscosity of 5 to 5.times.10.sup.5 mPa.multidot.s 
at 25.degree. C., preferably 50 to 50000 mPa.multidot.s at 25.degree. C. 
The siloxane content in the siloxane copolymers according to the invention 
which contain vinyloxy groups is preferably 20 to 90% by weight, based on 
the total weight of siloxane copolymers containing vinyloxy groups. 
Examples of radicals R are alkyl radicals, such as the methyl, ethyl, 
n-propyl, iso-propyl, 1-n-butyl, 2-n-butyl, iso-butyl, tert-butyl, 
n-pentyl, iso-pentyl, neo-pentyl and tert-pentyl radical; hexyl radicals, 
such as the n-hexyl radical; heptyl radicals, such as the n-heptyl 
radical; octyl radicals, such as the n-octyl radical and iso-octyl 
radicals, such as the 2,2,4-trimethylpentyl radical; nonyl radicals, such 
as the n-nonyl radical; decyl radicals, such as the n-decyl radical; 
dodecyl radicals, such as the n-dodecyl radical; octadecyl radicals, such 
as the n-octadecyl radical; cycloalkyl radicals, such as cyclopentyl, 
cyclohexyl and cycloheptyl radicals and methylcyctohexyl radicals; aryl 
radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radical; 
alkaryl radicals, such as o-, m- and p-tolyl radicals; xylyl radicals and 
ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical and 
the .alpha.- and .beta.-phenylethyl radical. The methyl radical is 
preferred. 
Examples of halogenated radicals R are halogenoalkyl radicals, such as the 
3,3,3-trifluoro-n-propyl radical, the 2,2,2,2',2',2'-hexafluoroisopropyl 
radical and the heptafluoroisopropyl radical, and halogenoaryl radicals, 
such as the o-, m- and p-chlorophenyl radical. 
Examples of alkyl radicals R.sup.1 are the methyl, ethyl, n-propyl, 
iso-propyl, 1-n-butyl, 2-n-butyl, iso-butyl and tert-butyl radical. The 
methyl and ethyl radical are preferred. Examples of alkyl radicals R.sup.1 
which are substituted by an ether oxygen atom are the methoxyethyl and 
ethoxyethyl radical. 
Examples of alkyl radicals R.sup.2 are the methyl, ethyl, n-propyl, 
iso-propyl, 1-n-butyl, 2-n-butyl, iso-butyl, tert-butyl, n-pentyl, 
iso-pentyl, neo-pentyl and tert-pentyl radical and hexyl radicals, such as 
the n-hexyl radical. R.sup.2 is preferably a hydrogen atom. 
Examples of alkyl radicals R.sup.3 are the methyl, ethyl, n-propyl, 
iso-propyl, 1-n-butyl, 2-n-butyl, iso-butyl, tert-butyl, n-pentyl, 
iso-pentyl, neo-pentyl and tert-pentyl radical and hexyl radicals, such as 
the n-hexyl radical. 
Preferred siloxane copolymers containing vinyloxy groups are those which 
comprise 
(a) siloxane units of the formula 
EQU R.sub.2 SiO (I'), 
(b) per molecule, at least two siloxane units of the formula 
EQU GR.sub.2 SiO.sub.1/2 (II') and 
(c) per molecule, at least one unit of the formula 
##STR11## 
wherein R, G, G.sup.1 and L have the meaning given above for these 
radicals. 
If divinyl ethers (1), which are readily accessible, are employed, addition 
polymers which are branched by incorporation of polyfunctional 
ene-compounds (2) and are therefore polyfunctional can also be obtained by 
the process according to the invention. 
Examples of the organic compound (1) which contains more than one vinyloxy 
group and is employed in the process according to the invention are those 
of the formula 
##STR12## 
Preferred examples of the organic compound (1) are 
##STR13## 
Examples of the radical Y are therefore those of the formula 
##STR14## 
Processes for the preparation of the organic compound (1) are described, 
for example, in PCT Application WO 91/05756. The basis of the preparation 
is the Reppe vinylation which is known to the expert, in which alcohols 
are reacted catalytically with acetylene. Typical impurities of industrial 
vinyl ethers are vinyl ether-alcohols, which are retained as "intermediate 
stages" due to incomplete vinylation, and, where appropriate, secondary 
products thereof formed by self-cyctisation, such as, for example: 
##STR15## 
Examples of the organic compound (2) which contains aliphatic double bonds 
and is employed in the process according to the invention are 
3,5-dimethyl-4-vinyl-1,6-heptadiene, 
1,2,4-trivinylcyclohexane, 
1,3,5-trivinylcyclohexane and 
1,2,3,4-tetravinylcyclobutane, 
1,2,4-trivinylcyclohexane being preferred, and those of the formula 
##STR16## 
(R.sup.6 denotes hydrogen or a radical of the formula 
##STR17## 
and k is 3), the compound mentioned last and tetraallyloxyethane being 
preferred examples. 
Examples of the radical Z, if u in the radical L is 0, are therefore those 
of the formula 
##STR18## 
the radical of the formula 
##STR19## 
being preferred. 
Examples of the radical Z, if u in the radical L is 1, are therefore those 
of the formula 
##STR20## 
Processes for the preparation of the organic compound (2) are described in 
EP-B 46 731 (published on 3rd October 1984, F. Lohse et al., Ciba-Geigy 
AG). 
The compound of the formula 
EQU (HOCH.sub.2).sub.4-k C(CH.sub.2 OCH.sub.2 CH=CH.sub.2).sub.k 
wherein k is on average 2.9, is commercially obtainable, for example, from 
Shell AG and is marketed as pentaerythritol triallyl ether. The compound 
of the formula 
##STR21## 
is obtained by reaction of the abovementioned compound with acetic 
anhydride or isopropenyl acetate. 
It is possible to employ one type of organic compound (1) or a mixture of 
at least two different types of organic compound (1) in the process 
according to the invention. 
It is likewise possible to employ one type of organic compound (2) or 
mixtures of at least two different types of organic compound (2) in the 
process according to the invention. 
Organopolysiloxanes (3) which have on average more than one Si-bonded 
hydrogen atom per molecule and are preferably employed in the process 
according to the invention are those of the general formula 
##STR22## 
wherein R has the meaning given above for this radical, e is 0 or 1, on 
average 0.005 to 1.0, 
f is 0, 1, 2 or 3, on average 1.0 to 2.5, and the sum of e+f is not greater 
than 3. 
Organopolysiloxanes (3) which are preferably employed in the process 
according to the invention are those of the general formula 
EQU H.sub.d R.sub.3-d SiO(SiR.sub.2 O).sub.o (SiRHO).sub.p SiR.sub.3-d 
H.sub.d(VIII) 
wherein R has the meaning given above for this radical, 
d is identical or different and is 0 or 1, 
o denotes 0 or an integer from 1 to 1000 and 
p denotes 0 or an integer from 1 to 6. 
The organopolysiloxanes (3) employed in the process according to the 
invention particularly preferably contain on average 2 to 4, in particular 
on average 2 to 3, Si-bonded hydrogen atoms per molecule. 
The organopolysiloxanes (3) preferably have a viscosity of 0.5 to 20,000 
mPa.multidot.s at 25.degree. C., preferably 5 to 1000 mPa.multidot.s at 
25.degree. C. 
Preferred examples of organopolysiloxanes (3) of the formula (VIII) are 
copolymers of dimethylhydridosiloxane and dimethylsiloxane units, 
copolymers of dimethylhydridosiloxane, dimethylsiloxane and 
methylhydridosiloxane units, copolymers of trimethylsiloxane and 
methylhydridosiloxane units and copolymers of trimethylsiloxane, 
dimethylsiloxane and methylhydridosiloxane units. 
Processes for the preparation of organopolysiloxanes (3), including those 
of the preferred type, are generally known. 
It is possible to employ one type of organopolysiloxane (3) or a mixture of 
at least two different types of organopolysiloxane (3) in the process 
according to the invention. 
The organic compound (2) is employed in the process according to the 
invention in amounts such that the aliphatic double bond in the organic 
compound (2) is present in a ratio to the Si-bonded hydrogen in the 
organopolysiloxane (3) of preferably 0.10 to 0.95, preferably 0.30 to 
0.80. 
The SiH groups are present in excess in relation to the C=C groups in the 
organic compound (2). The aliphatic double bonds in the organic compound 
(2) react with the SiH groups in the organopolysiloxane (3) far more 
quickly than the vinyloxy groups in the organic compound (1). The SiH 
groups which remain are then required for introduction of the vinyloxy 
groups into the siloxane copolymer, which takes place by reaction with the 
organic compound (1) containing vinyloxy groups, some of the vinyloxy 
groups being consumed by hydrosilylation and the remainder being available 
for cationic crosslinking in the siloxane copolymer. 
The organic compounds (1) and (2) are employed in the process according to 
the invention in amounts such that the sum of the vinyloxy group in the 
organic compound (1) and the aliphatic double bond in the organic compound 
(2) is present in a ratio to the Si-bonded hydrogen in the organic 
polysiloxane (3) of preferably 1.2 to 20, preferably 1.5 to 5. 
Siloxane copolymers which contain vinyloxy groups and have little bridging 
via the organic compound (1) containing vinyloxy groups are preferably 
prepared. 
The siloxane copolymers according to the invention can also be prepared in 
a two-stage process. In a 1st stage of this process, the organic compound 
(2) containing aliphatic double bonds is reacted with the 
organopolysiloxane (3) in the presence of the catalyst (4), and in a 2nd 
stage, the siloxane copolymer obtained in the 1st stage, which contains 
Si-bonded hydrogen atoms, is reacted with the organic compound (1) 
containing vinyloxy groups in the presence of the catalyst (4). In the 
two-stage process, it is also important that the ratio of aliphatic double 
bond in the organic compound (2) to Si-bonded hydrogen in the 
organopolysiloxane (3) in the 1st stage is always less than 1.0, 
preferably 0.10 to 0.95, preferably 0.30 to 0.80. 
Small amounts of free terminal C.dbd.C double bonds from the organic 
compound (2) which have not reacted with the SiH groups may be present in 
the siloxane copolymers according to the invention. These free "ene" 
groups cause no trouble. In the case of allyloxy groups, they can be 
converted into similarly cationically crosslinkable 1-propenoxy groups, as 
described in the abovementioned DE-A 40 02 922. 
The reaction of the organic compound (1), such as triglycol divinyl ether, 
and the organic compound (2), such as tetraallyloxyethane, with the 
organopolysiloxane (3), such as 
.alpha.,.omega.-dihydridodimethytpolysiloxane, in the presence of the 
catalyst (4) proceeds in accordance with the following (idealised) 
equation: 
##STR23## 
Bridging via (1) can be suppressed by an excess of the organic compound 
(1). In real reaction systems, further bridging of (2) via (3) usually 
takes place, so that, for example, units of the formula (VI') are present, 
and bridging of (1) via (3) takes place, so that, for example, units of 
the formula (III) are present. 
Catalysts (4) which promote the addition of Si-bonded hydrogen onto an 
aliphatic multiple bond and which can be employed in the process according 
to the invention are also the same catalysts which it has also been 
possible to employ to date for promoting addition of Si-bonded hydrogen 
onto an aliphatic double bond. The catalysts (4) are preferably a metal 
from the group of platinum metals or a compound or a complex from the 
group of platinum metals. Examples of such catalysts are metallic and 
finely divided platinum, which can be on supports, such as silicon 
dioxide, aluminium oxide or active charcoal, compounds and complexes of 
platinum, such as platinum halides, for example PtCl.sub.4, H.sub.2 
PtCl.sub.6 *6H.sub.2 O or Na.sub.2 PtCl.sub.4 *4H.sub.2 O, platinum-olefin 
complexes, platinum-alcohol complexes, platinum-alcoholate complexes, 
platinum-ether complexes, platinum-aldehyde complexes, platinum-ketone 
complexes, including reaction products of H.sub.2 PtCl.sub.6 *6H.sub.2 O 
and cyclohexanone, platinum-vinylsiloxane complexes, such as 
platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes with or 
without a content of detectable inorganically bonded halogen, 
bis-(gammapicoline)-platinum dichloride, trimethylenedipyridine-platinum 
dichloride, dicyctopentadiene-platinum dichloride, dimethyl 
sulphoxide-ethylene-platinum(II) dichloride and reaction products of 
platinum tetrachloride with an olefin and primary amine or secondary amine 
or a primary and secondary amine according to U.S. Pat. No. 4,292,434, 
such as the reaction product of platinum tetrachloride dissolved in 
t-octene with sec-butylamine, and ammonium-platinum complexes according to 
EP-B 110 370, and compounds and complexes of rhodium, such as the rhodium 
complexes according to EP-A 476 426. 
The catalyst (4) is preferably employed in amounts of 2 to 1000 ppm by 
weight (parts by weight per million parts by weight), preferably in 
amounts of 10 to 50 ppm by weight, in each case calculated as elemental 
platinum and based on the total weight of organic compounds (1) and (2) 
and organopolysiloxane (3). 
The process according to the invention is preferably carried out under the 
pressure of the surrounding atmosphere, that is to say under about 1020 
hPa (absolute), but it can also be carried out under higher or lower 
pressures. Furthermore, the process according to the invention is 
preferably carried out at a temperature of 50.degree. C. to 170.degree. C. 
preferably 80.degree. C. to 150.degree. C. 
Inert, organic solvents can be co-used in the process according to the 
invention, although the co-use of inert organic solvents is not preferred. 
Examples of inert organic solvents are toluene, xylene, octane isomers, 
butyl acetate, 1,2-dimethoxyethane, tetrahydrofuran and cyclohexane. 
Excess organic compound (1) and any inert organic solvent which has been 
co-used are preferably removed by distillation from the siloxane 
copolymers prepared by the process according to the invention and 
containing vinyloxy groups. The excess organic compound (1) can also be 
left in the siloxane copolymer. 
The siloxane copolymers prepared by the process according to the invention 
and containing vinyloxy groups are equilibrated with an organopolysiloxane 
(5), if appropriate. 
Organopolysiloxanes (5) which are used are preferably those chosen from the 
group comprising linear organopolysiloxanes containing terminal 
triorganosiloxy groups, of the formula 
EQU R.sub.3 SiO(SiR.sub.2 O).sub.r SiR.sub.3 
wherein R has the meaning given above for this radical and r is 0 or an 
integer having a value from 1 to 1500, linear organopolysiloxanes 
containing terminal hydroxyl groups, of the formula 
EQU HO(SiR.sub.2 O).sub.s H 
wherein R has the meaning given above for this radical and s is an integer 
having a value from 1 to 1500, cyclic organopolysiloxanes of the formula 
EQU (R.sub.2 SiO).sub.t 
wherein R has the meaning given above for this radical and t is an integer 
from 3 to 12, and copolymers of units of the formula 
EQU R.sub.2 SiO and RSiO.sub.3/2 
wherein R has the meaning given above for this radical. 
The ratio of the amounts of the organopolysiloxane (5) employed in the 
equilibration which is to be carried out if appropriate and the siloxane 
copolymers containing vinyloxy groups is determined merely by the desired 
content of vinyloxy groups in the siloxane copolymers produced by the 
equilibration which is carried out if appropriate and by the desired 
average chain length. 
Basic catalysts which promote the equilibration are preferably employed in 
the equilibration which is carried out if appropriate. Examples of such 
catalysts are alkali metal hydroxides, such as sodium hydroxide and 
potassium hydroxide, trimethylbenzytammonium hydroxide and 
tetramethytammonium hydroxide. Alkali metal hydroxides are preferred. 
Alkali metal hydroxides are preferably used in amounts of 50 to 10,000 ppm 
by weight (=parts per million), in particular 500 to 2000 ppm by weight, 
in each case based on the total weight of siloxane copolymer containing 
vinyloxy groups employed and organopolysiloxane (5) employed. Although it 
is possible to use acid equilibration catalysts, this is not preferred. 
The equilibration which is carried out if appropriate is preferably carried 
out at 100.degree. C. to 150.degree. C. under the pressure of the 
surrounding atmosphere, that is to say at about 1020 hPa (absolute). If 
desired, however, higher or lower pressures can also be used. The 
equilibration is preferably carried out in a concentration of 5 to 20% by 
weight, based on the total weight of the particular siloxane copolymer 
containing vinyloxy groups employed and organopolysiloxane (5) employed, 
in a water-immiscible solvent, such as toluene. The catalyst can be 
rendered inactive before the mixture obtained in the equilibration is 
worked up. 
The process according to the invention can be carried out batchwise, 
semi-continuously or completely continuously. 
The siloxane copolymers according to the invention which contain vinyloxy 
groups can be crosslinked cationically, for example by addition of acids, 
such as hydrochloric acid, sulphuric acid or p-toluenesulphonic acid. The 
siloxane copolymers according to the invention which contain vinyloxy 
groups are preferably crosslinked in a cationic polymerisation initiated 
by light. Catalysts which are used for the crosslinking initiated by light 
are preferably onium salts, such as diaryliodonium salts or 
triarylsulphonium salts, which are known from EP-B 105 341 and the German 
application by the Applicant Company having the application number P 41 42 
327.5. Examples of such onium salts are the bis-(dodecylphenyl)iodonium 
salts described in EP-B 105 341, such as bis-(dodecylphenyl)iodonium 
hexafluoroantimonate or bis-(dodecylphenyl)iodonium hexafluoroarsenate, or 
the iodonium salts of the formula 
##STR24## 
wherein D denotes a radical of the formula 
EQU --O--R.sup.5 --SiR.sub.3.sup.6 
wherein R.sup.5 denotes a divalent hydrocarbon radical having 1 to 18 
carbon atoms per radical, which is optionally interrupted by at least one 
oxygen atom and/or one sulphur atom and/or one carboxyl group, 
R.sup.6 denotes a monovalent hydrocarbon radical having 1 to 18 carbon 
atoms per radical, which is optionally interrupted by at least one oxygen 
atom, and 
X.sup.- is a tosylate anion or a weakly nucleophilic or non-nucleophilic 
anion Y.sup.- chosen from the group comprising CF.sub.3 CO.sub.2.sup.-, 
BF.sub.4.sup.-, PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, 
ClO.sub.4.sup.-, HSO.sub.4.sup.-, CF.sub.3 SO.sub.3.sup.- and C.sub.4 
F.sub.9 SO.sub.3.sup.-, 
which are described in the German application having the application number 
P 41 42 327.5. 
The invention therefore relates to the use of siloxane copolymers 
containing vinyloxy groups, preferably comprising units of the formula 
(I), (II), if appropriate at least one of the units of the formula (III), 
(IV) or (V) and at least one of the units of the formula (VI), preferably 
comprising units of the formula (I'), (II'), (III') and (VI'), in 
compositions which can be crosslinked by light and are based on the 
above-mentioned siloxane copolymers. 
The siloxane copolymers according to the invention which contain vinyloxy 
groups are preferably cross-linked by ultraviolet light, that having 
wavelengths in the range from 200 to 400 nm being preferred. The 
ultra-violet light can be generated, for example, in xenon or low, medium 
or high pressure mercury lamps. Ultraviolet light having a wavelength of 
400 to 600 nm, that is to say so-called "halogen light" is also suitable 
for the crosslinking by light. The siloxane copolymers according to the 
invention which contain vinyloxy groups can be crosslinked by light in the 
visible range if commercially available photosensitisers are also used. 
The cationic polymerisation of the siloxane copolymers according to the 
invention which contain vinyloxy groups can of course also be initiated by 
Bronsted or Lewis acids customary for this purpose. 
Finally, the invention also relates to the use of the siloxane copolymers 
according to the invention which contain vinyloxy groups for the 
preparation of coatings which can be crosslinked by light. 
The siloxane copolymers according to the invention which contain vinyloxy 
groups can be used in radiation-curing printing inks. 
Examples of surfaces onto which the coatings according to the invention can 
be applied are those of paper, wood, cork, films of plastic, for example 
polyethylene films or polypropylene films, ceramic objects, glass, 
including glass fibres, metals, pasteboard, including that of asbestos, 
and woven and non-woven cloth of naturally occurring or synthetic organic 
fibres. 
The application of the siloxane copolymers according to the invention which 
contain vinyloxy groups to the surfaces to be coated can be carried out in 
any desired manner which is suitable and in many cases known for the 
production of coatings from liquid substances, for example by dipping, 
brushing, pouring, spraying, rolling, printing, for example by means of an 
offset gravure coating device, or knife or doctor blade coating.

EXAMPLE 1 
16 g of tetraallyloxyethane and 76 g of triglycol divinyl ether are mixed 
with 238 g of a copolymer of hydridodimethylsiloxane and dimethylsiloxane 
units having a viscosity of 11 mm.sup.2 .multidot.s.sup.-1 at 25.degree. 
C., which contains 0.50 g of Si-bonded hydrogen, and the mixture is heated 
to about 80.degree. C. under a nitrogen atmosphere. The ratio of the allyl 
groups to the SiH groups is 0.5 and the ratio of the sum of the allyl and 
vinyl groups (C.dbd.C) to the SiH groups, C.dbd.C/SiE, is 2.0. 4 mg of 
platinum in the form of hexachloroplatinic acid, dissolved in isopropanol, 
are added to the heated mixture, after which an internal temperature of 
almost 150.degree. C. is reached. A polymer having a viscosity of 220 
mm.sup.2 .multidot.s.sup.-1 at 25.degree. C. is obtained; the amount of 
the content of hydrogen which can be split off shows a conversion of more 
than 99%. The divinyl ether which has not been consumed (about 25 g) is 
separated off in vacuo at 10.degree. C., after which the polymer has a 
viscosity of 450 mm.sup.2 .multidot.s.sup.-1 at 25.degree. C. and the 
.sup.1 H-NMR spectrum shows a ratio of CH.sub.2 =CH-O/SiCH.sub.2 CH.sub.2 
O of 1.04. No free allyloxy groups are detectable. The polymer has a 
double bond equivalent (vinyloxy groups) of about 1200 and a siloxane 
content of about 78% by weight. 
EXAMPLE 2 
6 mg of platinum in the form of a solution of the 
platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex are added to a 
mixture of 56 g of acetylated pentaerythritol triallyl ether and 121 g of 
triglycol divinyl ether, and the mixture is heated to 100.degree. C. under 
a nitrogen atmosphere. 147 g of an 
.alpha.,.omega.-dihydridodimethyl-polysiloxane which contains 0.68% by 
weight of Si-bonded hydrogen are added dropwise to this solution, which 
contains a total of 1.8 mol of C.dbd.C double bonds, and the mixture is 
allowed to react until a conversion of more than 98% is reached. Excess 
divinyl ether is distilled off in vacuo, after which a polymer having a 
viscosity of 290 mm.sup.2 .multidot.s.sup.-1 at 25.degree. C. is obtained. 
The .sup.1 H-NMR spectrum shows a ratio of CH.sub.2 =CHO/SiCH.sub.2 
CH.sub.2 O of 1.06, allyloxy groups no longer being detectable. The 
polymer has a double bond equivalent of about 700 and a siloxane content 
of about 52 % by weight. 
EXAMPLE 3 
10 g of the polymer prepared in Example 2 are mixed with 0.1 g of 
4-2-(3-tributylsilylpropyloxy)ethoxy!phenyl!phenyliodonium 
hexafluoroantimonate (preparation of which is described in the German 
application having the application number P 41 42 327.5) and the mixture 
is spread in a thin layer of about 4 .mu.m onto polyethylene-coated paper 
using a glass rod. Curing is carried out by means of a medium pressure 
mercury lamp (80 watt/cm) at a distance of 10 cm after an exposure time of 
0.2 seconds.