Coating composition and method for coating sheet-like supports by applying curable organopolysiloxanes modified with (Meth) acrylate ester groups

A method is disclosed for coating sheet-like supports by applying curable organopolysiloxanes, which have been modified with (meth)-acrylate ester groups, on the surface of the support and curing the modified organopolysiloxanes by the action of polymerizing high-energy radiation. Polysiloxanes with hydroxy-functional groups are employed for this purpose, which are obtained by reaction with, based on the hydroxyl groups, 0.4 to 0.9 molar amounts of (meth)acrylic acid and up to 0.6 molar amounts of monocarboxylic acids, which are free of double bonds (sum of the acids.ltoreq.1 molar).

FIELD OF INVENTION 
The invention is generally concerned with coating procedures and is 
particularly directed to a method for coating sheet-like supports by 
applying curable organopolysiloxanes, modified with (meth)acrylate ester 
groups to the surface of the support and curing the modified 
organopolysiloxanes by the action of polymerizing high-energy radiation. 
The term, "(meth)acrylate ester group", embraces acrylate ester groups as 
well as methacrylate ester groups. 
Considered from another aspect, the invention discloses novel coating 
compositions. 
BACKGROUND INFORMATION AND PRIOR ART 
Adhesive coating compositions are used on a large scale, especially for 
coating sheet-like materials in order to decrease the tendency of adhesive 
products to adhere to these surfaces. Adhesive coating compositions are 
used, for example, to coat papers or films, which are to serve as supports 
for pressure-sensitive labels. The labels, provided with a 
pressure-sensitive adhesive, adhere to the coated surface to a still 
sufficient extent, to make it possible to handle the support films with 
the pressure-sensitive labels. It must, however, be possible to pull the 
labels from the coated support film without significantly affecting their 
adhesiveness for later use. Other possible applications for adhesive 
coating compositions are wrapping papers, especially for packaging 
adhesive goods. Such adhesive papers or films are used, for example, to 
package foods or technical products such as bitumen. 
Such organopolysiloxanes, modified with (meth)acrylate ester groups, are 
also used to coat printed circuit boards equipped with electronic 
components. For this application, they serve especially as protection 
against mechanical effects and corrosive gases or vapors. 
The German Patent No. 2,948,708 discloses a method for producing 
organopolysiloxanes, which are modified with pentaerythritol triacylate or 
pentaerythritol trimethacrylate esters, from organochloropolysiloxanes, 
optionally with addition of HCl-binding neutralizing agents. In this 
patent, organopolysiloxanes of the formula 
##STR1## 
(R.sup.1 is alkyl with 1 to 4 carbon atoms, vinyl and/or phenyl, with the 
proviso that at least 90 mole percent of the R.sup.1 groups are methyl; a 
is 1.8 to 2.2, b is 0.004 to 0.5) are first reacted with, based on the 
SiCl groups, at least 2 molar amounts of a dialkylamine, the alkyl groups 
of which in each case have 3 to 5 carbon atoms, the carbon atoms adjacent 
to the nitrogen having at most one hydrogen atom each. The reaction 
product is allowed to react with at least equimolar amounts of 
pentaerythritol triacrylate or pentaerythritol methacrylate and the end 
product is then separated from solid components suspended in it by known 
means. 
A coating composition prepared by this method exhibits good adhesive 
properties. Adhesive tapes in contact with the coating composition largely 
retain their adhesiveness towards untreated substrates. It has, however, 
been ascertained that the property of adhesiveness must always be 
considered and evaluated in connection with the chemical constitution and 
structure of the adhesive, towards which the coating agent is to show 
adhesive properties. The adhesive coating material disclosed in the German 
Patent No. 2,948,708 therefore does not provide satisfactory results in 
all cases, since its properties cannot be adapted to the different 
adhesives. 
Improved properties are shown by (meth)acrylate ester-modified 
organopolysiloxane mixtures, which are characterized in that they consist 
of an equilibrated organopolysiloxane with, on the average, &gt;25 to &lt;200 
silicon atoms and 2 to 30% by weight of organopolysiloxanes with, on the 
average, 2 to 25 silicon atoms and 2 to 30% by weight organopolysiloxanes 
with, on the average, 200 to 2,000 silicon atoms. The organopolysiloxanes, 
contained in this ternary mixture, have different tasks. The low molecular 
weight fraction essentially has the task of assuring that the coating 
composition adheres to the substrate. The high molecular weight fraction, 
on the other hand, serves primarily the purpose to attain the desired 
adhesiveness of the coating composition. The middle fraction is the 
curable matrix, which is responsible especially for the physical 
properties of the coating composition. Those skilled in the art will 
understand that this is only a simplified description of the properties 
and tasks of the three different fractions, since the complex properties, 
which an adhesive coating material must have, can only be obtained by the 
united efforts of the three components. With the modified 
organopolysiloxane mixture of the German Patent No. 3,426,087, it has 
become possible to improve, on the one hand, the adhesive properties of 
the mixture towards adhesive surface and, on the other, the adhesive 
properties towards the substrate, on which the coating material is applied 
and on which it is cured. However, even with this coating mass it has 
turned out that the properties cannot be adapted adequately to the 
different adhesives. 
In the European Offenlegungsschrift No. 0 159 683, electron beam-curable 
liquid coating materials are described, which should contain: 
1. 60 to 95 parts of an organopolysiloxane with more than about 25 siloxane 
groups per molecule and 2 to 10 parts of reacted carbinol groups per 
molecule, the rest of the substituents on the silicon being hydrocarbon 
groups with 1 to 20 carbon atoms; the term reacted carbinol groups is 
understood to mean esters of acrylic acid, methacrylic acid or mixtures or 
ethers of a hydroxyalkyl ester of these acids, the alkyl group containing 
2 to 4 carbon atoms; essentially, unreacted carbinol groups should no 
longer be present, so that the hydroxyl number is &lt;10. 
2. 3 to 25 parts of a polyester of a multihydric alcohol with acrylic acid, 
methacrylic acid or mixtures thereof, the multihydric alcohol having 2 to 
4 hydroxyl groups per molecule and a molecular weight of &lt;1,200; 
3. 1 to 10 parts of acrylic acid, methacrylic acid or mixtures of these 
acids. 
The additional use of the (meth)acrylate ester of a polyalcohol increases 
the curing rate, but has a disadvantageous effect on the flexibility and 
adhesiveness of the coating material as a result of the increase in the 
organic portion. The content of free acrylic or methacrylic acid is an 
additional disadvantage, which leads to an annoying odor and makes the 
processing difficult during the application on the material to be coated. 
Because they can be cured by radiation, organopolysiloxanes with acrylate 
ester groups have been described for a series of other possible 
applications. Organopolysiloxanes, modified with acrylate ester groups, 
are thus used as coating lacquers that are to be poured into and around 
electrical and electronic components and also for the manufacture of 
molded objects. The following Offenlegungsschriften, Auslegeschriften and 
patents are cited with regard to the possible structures of such acrylate 
ester group-modified polysiloxanes: 
The German Auslegeschrift No. 2,335,118 relates to optionally substituted 
acrylate group-containing organopolysiloxanes of the general formula 
##STR2## 
(R=hydrogen or univalent hydrocarbon groups with 1 to 12 carbon atoms; 
R'=univalent, optionally halogenated hydrocarbon groups or cyanoalkyl 
groups with 1 to 8 carbon atoms; R"=divalent hydrocarbon groups with 1 to 
18 carbon atoms or C--O--C bonds-containing divalent hydrocarbon groups; 
R'"=R""O.sub.0.5 or R'.sub.3 SiO.sub.0.5 ; Z=OR"", R"" or OSiR'.sub.3 ; 
R""=alkyl group with 1 to 12 carbon atoms; a and b each represent numbers 
from 1 to 20,000; c is a number from 0 to 3; e is a number from 0 to 2; at 
least one of the Z groups is OR"" when c=0). The siloxane polymers can be 
used as intermediates in the synthesis of copolymers, which contain 
organopolysiloxane segments and find use as coating compositions. 
Moreover, these acrylate-functional siloxane polymers can serve as sizes 
and protective coating compositions for paper and fabric. However, these 
products are unsuitable for the preparation of adhesive coating materials. 
Furthermore, the linear, diacrylate-modified polysiloxanes of the German 
Auslegeschrift No. 2,335,118 by definition have alkoxy groups, which can 
be split off hydrolytically and lead to further cross linking of the 
polysiloxanes with a deterioration of the elastic properties, which are 
important for a coating composition. 
The German Offenlegungsschrift No. 3,044,237 discloses polysiloxanes with 
lateral acrylate ester groups, which can be synthesized by the reaction of 
epoxy-functional siloxanes of a particular structure with acrylic acid. 
The products obtained are curable by radiation. They can be used as 
low-viscosity lacquers for application via conventional oil-based printing 
inks. As adhesive coatings compositions, the products can be used only 
with considerable limitations, since there is a hydroxyl group for each 
acrylate ester group. 
In the U.S. Pat. No. 4,568,566, curable silicone preparations are 
described, which comprise: 
(a) 75 to 100 mole percent of chemically bound siloxy units of the formula 
R.sub.3 SiO.sub.0.5, RSiO.sub.1.5 and SiO.sub.2, as well as 
(b) 0 to 25 mole percent of R.sub.2 SiO units, a number of the R units 
having the formula 
##STR3## 
wherein R.sup.1 is a hydrogen group or a hydrocarbon group with 1 to 12 
carbon atoms and R.sup.2 is a divalent hydrocarbon group or an oxyalkylene 
group. These curable preparations are used especially for coating 
electronic components and as a coating material for optical fibers. 
Because the content of R.sub.2 SiO units is too low, they are not suitable 
as adhesive coating materials for sheet-like supports. 
The object of the European Offenlegungsschrift No. 0 152 179 is a silicone 
preparation, which can be cured into an elastomer. This preparation 
comprises (a) a silicone resin with linear structure and, on the average, 
at least 150 siloxane units, as well as terminally linked acrylic acid 
groups, the region in between the terminal groups being free of acrylic 
acid groups; (b) at least 10% of finely divided silica and (c) a 
photoinitiator. These materials are to be used as adhesives and as casting 
compositions. 
Finally, reference is made to the European Offenlegungsschrift No. 0 169 
592, which relates to an optical glass fiber with a synthetic resin 
covering, with a glass fiber and an enveloping layer of artificial rubber 
with a refractive index, which is higher than that of the outer layer of 
the glass fiber, the artificial rubber being formed from a curable 
synthetic resin composition, which has a copolymer that contains, as 
monomeric units, dimethylsiloxane and at least one siloxane from the group 
comprising methylphenylsiloxane and diphenylsiloxane. The siloxane 
copolymer contains at least two acrylate ester groups per molecule. As a 
distinguishing feature, the curable synthetic resin composition 
additionally contains a polyurethane acrylate with an average molecular 
weight of 3,000. The polysiloxane named in the claim may have the 
following formula: 
##STR4## 
It is an essential conditions that these polysiloxanes have phenyl groups 
linked to silicon. The phenyl group content is necessary in order to 
approximate the refractive index of the coating composition to that of the 
glass optical fiber. From the use of these siloxanes in combination with a 
polyurethane acrylate for coating optical glass fibers, it cannot be 
concluded that such compounds can possibly also be used as adhesive 
compositions. 
In the journal "Makromolekulare Chemie" (Macromolecular Chemistry, Rapid 
Communication), 7, (1986), pages 703 to 707, the synthesis of linear 
methylpolysiloxanes with terminal methacrylate ester groups is described. 
For this reaction, an allyl epoxypropyl ether first of all undergoes an 
addition reaction with .alpha.,.omega.-hydrogendimethylpolysiloxane in the 
presence of chloroplatinic acid. The diepoxide formed is subsequently 
reacted with methacrylic acid in the presence of chromium diisopropyl 
salicylate to form the desired methacrylate esters. These esters may be 
present in two isomeric forms: 
##STR5## 
If the (meth)acrylate esters are prepared by methods of the state of the 
art starting out with epoxy-functional siloxanes, the epoxy groups are 
reacted with (meth)acrylic acid. In this reaction, (meth)acrylate 
monoesters with a vicinal hydroxyl group are formed by opening the epoxide 
ring. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide adhesive coating compositions 
based on (meth)acrylate ester-modified organopolysiloxanes, the properties 
of which are improved if compared with those of the coating compositions 
known from the art. 
More particularly, it is an object of the invention to provide coating 
compositions, which can be adapted to differently adhering products 
(adhesives). 
The desired organopolysiloxanes modified with (meth)acrylate ester groups 
should have especially the following combination of properties: 
1. satisfactory adhesion to the particular support that is to be coated 
2. a high rate of curing on the support or substrate 
3. chemical and physical stability of the cured coating 
4. high flexibility of the cured coating 
5. adhesive properties towards adhesive products and adaptability of the 
adhesive coating to the chemical character of the adhesive 
6. adjustability of the desired degree of adhesiveness. 
The modified organopolysiloxanes should, moreover, be suitable for coating 
electronically equipped printed circuit boards and similar electronic 
components. 
SUMMARY OF THE INVENTION 
The inventive method is characterized in that curable organopolysiloxanes 
are used, which are obtained by the reaction of polysiloxanes of the 
general average formula 
##STR6## 
wherein the R.sup.1 groups are the same or different and represent low 
molecular weight alkyl groups with 1 to 4 carbon atoms or phenyl groups, 
the R.sup.2 groups are 
(a) hydroxy-functional groups of the formula --CH.sub.2 
(CR.sup.3.sub.2).sub.n --(OCH.sub.2 CHR.sup.4).sub.m --OH, 
--CH.dbd.CH--CR.sup.3.sub.2 --OH and/or groups of the formula 
##STR7## 
wherein the R.sup.3 groups are the same or different and represent a 
hydrogen group or an alkyl group with 1 to 4 carbon atoms, the R.sup.4 
groups are the same or different and in each case represent a hydrogen or 
alkyl group with 1 to 10 carbon atoms, and the subscripts n=0 to 10 and 
m=0 to 40 and 
(b) unsubstituted or substituted alkyl groups with 2 to 20 carbon atoms 
and/or hydrogen groups and 
(c) R.sup.1 groups with the proviso that at least 1.8 hydroxy functional 
R.sup.2 groups (a) are contained in the average molecule a has a value of 
1 to 1,000 and b a value of 0 to 10, with, based on hydroxyl groups, 0.4 
to 0.9 molar amounts of (meth)acrylic acid and up to 0.6 molar amounts of 
a monocarboxylic acid, which is free of double bonds capable of 
polymerizing, the sum of the molar amounts of the acids being not greater 
than 1.0. The reaction is carried out under the usual esterification 
conditions. 
It is essential that at least 1.8 hydroxy-functional R.sup.2 groups (a) are 
present in the average molecule, although greater amounts may be present. 
As a matter of fact, all R.sup.2 groups may be hydroxy-functional. 
However, once the condition is satisfied that 1.8 hydroxy-functional 
R.sup.2 groups of the species (a) are present, the remainder of the 
R.sup.2 groups may be of the species (b) and/or may be R.sup.1 groups. If 
R.sup.2 groups of the species (b) are present, the further condition 
applies that the lower limit value of the ratio between the 
hydroxy-functional R.sup.2 groups (a) and the R.sup.2 groups of species 
(b) must not be below 70:30. 
The general formula I is the average formula of the hydroxy-functional 
organopolysiloxanes required for the reaction. The individual building 
blocks are distributed randomly (statistically) in the polymer mixture. 
The sum of the functional [R.sup.1 R.sup.2 SiO--] units is 2a+b.times.a. 
The number of trifunctional [R.sup.1 SiO.sub.3/2 --] units is given by the 
subscript b. a has a value of 1 to 1,000 and preferably a value of 5 to 
200, while b has a value of 0 to 10 and preferably of 0 to 2. If b is 0, 
the hydroxy-functional organopolysiloxanes are present in chain form with 
a linear structure. The structure of the hydroxy-functional 
organopolysiloxanes defined by the subscripts a and b is retained even 
after the reaction with the (meth)acrylic acid and the other 
monocarboxylic acid. 
Within the polymeric molecule, R.sup.1 may be the same or different and 
represent a lower alkyl group with 1 to 4 carbon atoms or a phenyl group. 
The alkyl groups may be linear or branched. Preferably, at least 90% of 
the R.sup.1 groups are methyl groups. 
The R.sup.2 groups may partly have the meaning of the R.sup.1 group. The 
remaining R.sup.2 groups are, to the extent of 70 to 100%, 
hydroxy-functional groups of the formula --CH.sub.2 (CR.sup.3.sub.2).sub.n 
--(OCH.sub.2 CHR.sup.4).sub.m --OH and/or the formula 
##STR8## 
and to the extent of 30 to 0% optionally substituted alkyl groups with 2 
to 20 carbon atoms and/or hydrogen groups. 
In these groups, R.sup.3 is the same or different and represents a hydrogen 
or an alkyl group with 1 to 4 carbon atoms, the alkyl group preferably 
being methyl. 
R.sup.4 is the same or different and represents a hydrogen or alkyl group 
with 1 to 10 carbon atoms, linear alkyl groups being preferred. 
n has a value of 0 to 10, a value of 2 to 10, however, being preferred for 
reasons of accessibility. 
m has a value of 0 to 40; preferably, however, m is equal to zero. 
If the meaning of the R.sup.3 and R.sup.4 groups and the value of the 
subscripts is inserted in the --CH.sub.2 (CR.sup.3.sub.2).sub.n 
--(OCH.sub.2 CHR.sup.4).sub.m --OH group or the 
##STR9## 
group, it turns out that the moiety --CH.sub.2 (CR.sup.3.sub.2).sub.n or 
the norbornyl group has the meaning of a bridging element, over which the 
hydroxy-functional group is linked with a silicon atom of the siloxane 
frame. Preferably, the bridge portion --CH.sub.2 (CR.sup.3.sub.2).sub.n 
has the meaning of --(CH.sub.2).sub.3 or 
##STR10## 
The portion of the R.sup.2 group between the bridging element and the 
terminal OH groups with the formula of --(OCH.sub.2 CHR.sup.4).sub.m has 
the meaning of an ether or polyether group. This group may be omitted 
(m=0). 
Preferably, R.sup.4 is a hydrogen group or a methyl group. R.sup.4 may, 
however, also have the meaning of a long-chain alkyl group with up to 10 
carbon atoms. The alkyl group preferably is not branched. 
Preferred hydroxy-functional R.sup.2 groups are --CH.sub.2 OH, 
--(CH.sub.2).sub.3 OH, --(CH.sub.2).sub.4 OH, --(CH.sub.2).sub.11 OH, 
--CH.sub.2 CH(CH.sub.3)CH.sub.2 OH, --CH.sub.2 CH(CH.sub.3)CH.sub.2 
CH.sub.2 OH, --CH.sub.2 CH.sub.2 C(CH.sub.3).sub.2 OH, --CH.sub.2 CH.sub.2 
C(CH.sub.3)HOH and --CH.dbd.CH--CH.sub.2 OH. 
Up to 30% of the R.sup.2 groups can be alkyl groups with 2 to 20 carbon 
atoms or hydrogen groups. The alkyl groups may optionally be substituted 
by halogen or phenyl groups. Examples of suitable and preferred R.sup.2 
alkyl groups are ethyl, propyl, n-butyl, i-butyl, hexyl, octyl, dodecyl, 
octadecyl, 2-phenylpropyl and 3-chloropropyl groups. 
In the selection of the different meanings for the R.sup.2 group, the 
conditions should be noted that at least 1.8 R.sup.2 groups in the average 
molecule are hydroxy-functional groups. The value of 1.8 is to be regarded 
as a mathematical average value of a mixture of polymers. 
It is essential that at least 1.8 hydroxy-functional R.sup.2 groups (a) are 
present in the average molecule, although greater amounts may be present. 
As a matter of fact, all R.sup.2 groups may be hydroxy-functional. 
However, once the condition is satisfied that 1.8 hydroxy-functional 
R.sup.2 groups of the species (a) are present, the remainder of the 
R.sup.2 groups may be of the species (b) and/or may be R.sup.1 groups. If 
R.sup.2 groups of the species (b) are present, the further condition 
applies that the lower limit value of the ratio between the 
hydroxy-functional R.sup.2 groups (a) and the R.sup.2 groups of species 
(b) must not be below 70:30. 
The organopolysiloxanes to be used in the inventive method are obtainable 
by reacting hydroxy-functional organopolysiloxanes of the general formula 
I with (meth)acrylic acid and, optionally, additionally a further 
monocarboxylic acid, which is free of double bonds capable of 
polymerizing. The expression (meth)acrylic acid is intended to imply that 
acrylic acid or methacrylic acid or a mixture of the two acids can be 
used. 
It is a vital proviso of the invention that, based on the hydroxyl groups, 
0.4 to 0.9 molar amounts of (meth)acrylic acid and up to 0.6 molar amounts 
of the additional monocarboxylic acid, which is free of double bonds 
capable of polymerizing, are reacted. Based on the hydroxyl groups, the 
total molar amount of acids may, however, not exceed 1.0. 
Preferably, those polysiloxanes are used, in which all the hydroxyl groups 
of the polysiloxane are esterified. 
Alkyl carboxylic acids and benzoic acids come into consideration as 
monocarboxylic acids, which are free of double bonds capable of 
polymerizing. As alkyl carboxylic acids, those with 2 to 11 carbon atoms 
are preferred. Examples of such monocarboxylic acids are acetic acid, 
propionic acid, butyric acid, valerianic acid, pivalic acid, 
2,2-dimethylbutyric acid, 2,2-dimethylvalerianic acid, acetoacetic acid, 
isooctanecarboxylic acid, isodecanecarboxylic acid, sorbic acid and 
undecylenic acid. 
An especially preferred monocarboxylic acid is acetic acid. 
In the organopolysiloxanes that are to be used in the inventive method, 40 
to 90 mole percent of the hydroxy-functional R.sup.2 groups are present in 
the form of their (meth)acrylate esters. Up to 60 mole percent of the 
hydroxy-functional R.sup.2 groups may be present in the form of the 
monocarboxylate esters that are free of double bonds capable of 
polymerizing. 
Moreover, depending on the proportion of monocarboxylic acid used for the 
esterification, the hydroxy-functional groups may be present unchanged. 
The ratio of the groups derived from the R.sup.2 groups with 
(meth)acrylate ester groups and monocarboxylate ester groups to the 
unchanged hydroxy-functional R.sup.2 groups is a result of the nature and 
amount of the (meth)acrylic acid/monocarboxylic acid mixture used for the 
esterification. 
By these means, those skilled in the art have at their disposal a method 
for adjusting in the desired manner the properties of the 
organopolysiloxanes that are to be used pursuant to the invention: 
1. The adhesiveness of the organopolysiloxanes that are to be used pursuant 
to the invention increases, after they are cured, with the number of 
(meth)acrylate groups in the polymer molecule. As the cross linking 
density increases, the glass transition temperature of the cured coating 
increases and the flexibility of the coating of the coating decreases. At 
the same time, the chemical and physical stability of the cured coating is 
increased. 
2. As the proportion of monocarboxylate ester groups, which are free of 
double bonds capable of polymerizing, increases, the adhesiveness 
decreases and the adhesion to the support improves. This decrease in 
adhesiveness is reinforced additionally by hydroxyl groups of unreacted, 
hydroxy-functional R.sup.2 groups, which may optionally be present. By 
these means, the adhesive coating can also be adapted to the chemical 
character of the adhesive. 
The organopolysiloxanes that are to be used in the inventive method are 
therefore particularly suitable for being adjusted and adapted to the 
particular application. They are therefore especially suitable as a 
radiation-curable adhesive coating material or for coating electrical or 
electronic components. 
In the following, examples are given of polysiloxanes, which are to be used 
pursuant to the invention and have (meth)acrylate ester groups, which are 
linked over SiC groups, and optionally monocarboxylic ester groups. 
##STR11## 
A.sup.1, A.sup.2, n and m are defined as in compound 1. 
##STR12## 
The organopolysiloxanes, which are to be used pursuant to the invention, 
are synthesized by methods known in the art. For example, for the 
synthesis of hydroxy-functional organopolysiloxanes of formula I, 
hydrogenpolysiloxanes can be used, in which R.sup.1 represents hydrogen. 
These hydrogen siloxanes undergo an addition reaction with R.sup.2* 
groups. R.sup.2* groups correspond to R.sup.2 groups, but have an olefinic 
double bond at the end that is intended to be linked to the silicon atom. 
In this reaction unreacted SiH groups may remain in the product, so that 
the inventive polysiloxanes may contain small amounts of hydrogen groups 
as R.sup.2 groups. The hydroxyl groups of the hydroxy-functional 
polysiloxanes of formula I are esterified with (meth)acrylic acid and the 
additional monocarboxylic acid by a procedure that is known. This is 
understood to mean that the esterification is preferably carried out at 
temperatures of 80.degree. to 150.degree. C., optionally in the presence 
of a solvent. Advisably, the solvent should form an azeotrope with the 
water set free during the esterification. It is recommended that an 
esterification catalyst such as sulfuric acid, sulfonic acid or metal 
salts be added to the reaction mixture. 
If necessary, known polymerization inhibitors, such as hydroquinone, can be 
added in effective amounts during the esterification to prevent premature 
polymerization. 
The modified organopolysiloxanes can be used directly as such for the 
inventive method. Only in the case of UV curing is it necessary to add 
free radical initiators to the modified polysiloxanes in amounts of 2 to 
5% by weight, based on the siloxane. 
The selection of the free radical starter should be based on the wavelength 
spectrum of the radiation source used for the curing. Such free radical 
initiators are known. Examples of such free radical initiators are 
benzophenone, its oximes or benzoin ethers. 
It is possible to modify the coating comopositions, so obtained, in a known 
manner by the addition of further products. 
Such known modifying agents are siloxanes with groups, which are 
incorporated chemically into the coating composition, as the latter is 
cured. Especially suitable modifying agents are siloxanes with hydrogen 
atoms linked to silicon atoms. One of the effects that such modifying 
agents can produce is a lowering of the viscosity of the coating 
composition, as a result of which the applicability on the sheet-like 
carrier is improved. 
It is furthermore possible to add additives to the coating materials. These 
additives are then enclosed as inert substances by the coating composition 
during the curing process. Examples of such substances distributed in the 
coating composition are highly disperse silica or polymers of fluorinated 
hydrocarbons. 
In the following examples, the preparation of the modified polysiloxanes to 
be used in the inventive method and their application properties are 
described.

EXAMPLE 1 
To 116 g (2 moles) allyl alcohol, 200 g toluene and 40 mL of a solution of 
4 mg H.sub.2 PtCl.sub.6.6 H.sub.2 O in 3 mL glycol dimethyl ether in a 4 L 
3-neck flask, 1170 g (1 mole) of an SiH group-containing 
polydimethylsiloxane of the average formula 
##STR13## 
is added dropwise at 100.degree. C. After 8 hours at 100.degree. C., 116 g 
(1.6 moles) acrylic acid, 24 g (0.4 moles) acetic acid, 0.3 g 
methylhydroquinone, 2.5 g of 98% sulfuric acid and 200 g of toluene are 
added at 30.degree. C. to the hydroxy-functional polydimethylsiloxane of 
average formula 
##STR14## 
so obtained. The reaction mixture is subsequently heated to the boiling 
point and the resulting reaction water is distilled off azeotropically. 
After 15 hours, the theoretical amount of water of 36 g has been distilled 
over. The excess acid is neutralized with NaHCO.sub.3. After distillation 
(100.degree. C., 40 mbar) and filtration, 1320 g (95% of the theoretical 
amount) of an oil of medium viscosity are obtained which, according to the 
.sup.1 H--NMR spectrum has the general formula 
##STR15## 
A.sup.1 and A.sup.2 are defined as for Compound 1 (R.sup.6 =H) 
m=0.8 
n=0.2 
EXAMPLE 2 
As in Example 1, 11.6 g (0.2 moles) allyl alcohol and 441.9 g (0.05 moles) 
of an SiH group-containing polydimethylsiloxane of the average formula 
##STR16## 
are reacted to form a hydroxy-functional polydimethylsiloxane of the 
average formula 
##STR17## 
Subsequently, the polydimethylsiloxane obtained is esterified with 11.6 g 
(0.16 moles) acrylic acid and 2.4 g (40 mmoles) acetic acid. After 30 
hours, the reaction mixture is neutralized, filtered and distilled, 431 g 
(93% of the theoretical amount) of a moderately viscous oil of average 
formula 
##STR18## 
being obtained, wherein 
A.sup.1, A.sup.2 are as defined in Compound 1 (R.sup.6 =H) 
n=0.8 
m=0.2. 
EXAMPLE 3 
To a mixture of 96.8 g (0.4 moles) of an ethoxylated norborneol having the 
average formula 
##STR19## 
100 g toluene and 8 mL catalyst solution, 200 g (0.1 mole) of an SiH 
group-containing polydimethylsiloxane of the average formula 
##STR20## 
are added dropwise as in Example 1. After 7 hours at 100.degree. C., the 
reaction mixture is cooled to room temperature and 100 g toluene, 2.9 g 
(40 mmoles) propionic acid, 23.1 g (320 mmoles) acrylic acid and 0.8 g of 
98% sulfuric acid are added. The temperature is subsequently raised to the 
boiling point and the reaction water is distilled off azeotropically. 
After 24 hours and a similar working up, 310 g (96%) of an oil of the 
average formula 
##STR21## 
are obtained, wherein 
A.sup.3, A.sup.4, A.sup.5 are defined as in Compound 3 (R.sup.6 =H) 
m=0.8 
n=0.1 
p=0.1 
EXAMPLE 4 
From 1447 g (1.8 moles) of a polyether of the general formula 
##STR22## 
26.3 g (0.2 moles) .alpha.-methylstyrene and 1170 g (1 mole) of an SiH 
group-containing polydimethylsiloxane having the average formula 
##STR23## 
a hydroxy-functional polydimethylsiloxane having the average formula 
##STR24## 
is prepared as in Example 1, wherein 
A.sup.7 is defined as in compound 4 
##STR25## 
m=0.9 
n=0.1 
The product is esterified with 116 g (1.6 moles) of acrylic acid as in 
Example 1. After 30 hours and a similar working up, 2591 g (95% of the 
theoretical amount) of a red-brown oil are obtained, which according to 
the .sup.1 H--NMR spectrum has the average formula 
##STR26## 
wherein 
A.sup.6, A.sup.7 are defined as in compound 4 (R.sup.6 =H) 
##STR27## 
m=0.8 
n=0.1 
p=0.1 
EXAMPLE 5 
From 14.0 g (0.24 moles) allyl alcohol, 5.0 g (0.06 moles) 1-hexene and 
440.5 g (0.05 moles) of an SiH group-containing polydimethylsiloxane 
having the average formula 
##STR28## 
a hydroxy-functional polydimethylsiloxane having the average formula 
##STR29## 
wherein 
A.sup.10 =--(CH.sub.2).sub.5 --CH.sub.3, 
A.sup.11 =--(CH.sub.2).sub.3 --OH, 
m=0.2 
n=0.8 
is prepared as in Example 1. 
The polydimethylsiloxane obtained is subsequently esterified with 13.0 g 
(0.18 moles) acrylic acid and 11.0 g (0.06 moles) undecylenic acid. After 
34 hours, the reaction mixture is neutralized, filtered and distilled, 465 
g (98% of the theoretical amount) of a moderately viscous oil being 
obtained, which according to the .sup.1 H--NMR spectrum has the average 
formula 
##STR30## 
wherein 
A.sup.2 is defined as in Compound 1 (R.sup.6 =H) 
A.sup.10 is defined as in Compound 5 
##STR31## 
m=0.7 
n=0.2 
p=0.1 
TESTING THE APPLICATION 
To check the application properties of the polysiloxanes that are to be 
used pursuant to the invention, the products of the Examples 1 to 5 are 
applied on different sheet-like supports (oriented polypropylene film, 
supercalendered paper) and cured by the action of 1.5 Mrad electron beams. 
The amount applied in each case is about 1.1 g/m.sup.2. 
For the comparison tests, different 30 mm wide adhesive tapes were used, 
namely two adhesive tapes, which are coated with acrylate adhesives and 
commercially obtainable under the names of Tesa.RTM. 154 and Tesa.RTM. 
970, as well as an adhesive tape, which is coated with a rubber adhesive 
and known in the trade under the name of Tesa.RTM. 969. 
To measure the abhesiveness, these adhesive tapes are rolled onto the 
substrate and subsequently stored at 70.degree. in the case of the 
acrylate adhesive tapes and at 40.degree. C. in the case of the rubber 
adhesive tape. After 24 hours, the force is measured, which is required to 
pull the adhesive tape from the substrate at a peel angle of 180.degree.. 
This force is referred to as the release force. In addition, the adhesion 
of the modified polydimethylsiloxane to the substrate is tested by 
vigorous rubbing with the thumb. In the event of defective adhesion, 
rubber-like crumbs are formed (the so-called "rub-off" test). 
TABLE 
__________________________________________________________________________ 
Supercalendered paper 
Oriented Polypropylene 
Tesa .RTM. 
Tesa .RTM. 
Rub 
Tesa .RTM. 
Tesa .RTM. 
Rub 
mod. Siloxane 
154 970 Tesa .RTM. 
off 
154 970 Tesa .RTM. 
off 
Example 
Release 
Force [N] 
969 Test 
Release 
Force [N] 
969 Test 
__________________________________________________________________________ 
1 1.0 2.0 1.8 no 0.9 1.8 1.6 no 
2 0.15 0.4 0.3 no 0.1 0.3 0.3 no 
3 3 6 8 no 3 4 7 no 
4 4 6 6 no 2 5 5 no 
5 0.1 0.4 0.3 no 0.05 0.2 0.2 no 
__________________________________________________________________________ 
It is evident from the Table that the organopolysiloxanes, which are to be 
used pursuant to the invention, have the desired application properties; 
they adhere to the coated support, can be cured rapidly on this and show 
good abhesive properties towards adhesives of chemically different 
structure.