Epoxypolysiloxane release coatings for adhesive materials

This invention relates to cured epoxypolysiloxanes and their blends with epoxy-terminated silanes which are useful as release coatings for adhesive roll and sheet materials.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to cured epoxypolysiloxanes and their blends with 
epoxy-terminated silanes which are useful as release coatings for adhesive 
roll and sheet materials. 
2. Description of the Prior Art 
Coatings having specific release properties toward adhesives are widely 
used. Polydimethylsiloxanes, polymers containing predominantly 
dimethylsiloxane units, provide very low release coatings, e.g., 4 to 16 
g/cm width, for products such as labels or large sheets which contain 
normally tacky and pressure-sensitive adhesives. These polymers are less 
useful as release coatings on the back surface of adhesive tape (back 
surface coating of adhesive tape is known as "low adhesion backsize" 
[LAB]) because their low release force can cause roll instability. LABs 
for tapes in roll form ideally exhibit release toward the adhesive of 
about 60 to 350 g/cm width. Polymers with higher release values make it 
increasingly difficult to use the tape and delamination of the adhesive 
from the substrate often can result. Coatings having release values less 
than 60 g/cm width are useful as components for release liners. Many 
non-silicone polymers, e.g., urethanes, find use as low adhesion backsizes 
for pressure-sensitive tapes because of their much higher release force 
than the polydimethylsiloxanes, typically greater than 200 g/cm width. 
Such non-silicone LAB coatings are exemplified in U.S. Pat. Nos. 
2,532,011, 2,607,711, 2,876,894 and 3,342,625. 
For products such as tapes and liners, coatings having specific release 
properties toward adhesives, which are intermediate between those of the 
polydimethylsiloxanes and conventionally used non-silicone LAB coatings, 
are highly desired. Many previous attempts to provide such coatings by 
modification of polydimethylsiloxanes or blending them with less effective 
release material, as disclosed in, for example, U.S. Pat. Nos. 3,328,482, 
3,527,659, 3,770,687 and 3,891,745, have not met with total success 
because of many problems such as: (1) incompatability of components 
causing extensive migration of the silicone to the surface, (2) 
contamination of the adhesive with low molecular weight components giving 
adhesion loss, (3) nonreproducibility, e.g., inability to consistently 
achieve the desired release level, and (4) use of excessively high cure 
temperatures causing deterioration of the heat-sensitive substrate or tape 
backing. 
One of the best products of the type described in the preceding paragraph 
is disclosed in U.S. Pat. No. 4,171,397, which relates to plural coatings 
presenting areas of (1) fluorochemical polymer and (2) cured silicone 
polymer. 
Coating compositions exhibiting intermediate release properties towards 
adhesives, provided by reaction of an isocyanate with a hydroxyl or 
amine-containing organosiloxane, are described in U.S. Pat. No. 3,997,702. 
Epoxypolysiloxanes have been previously used as polymer components to 
impart water repellency to textile and paper (U.S. Pat. Nos. 4,046,930 and 
3,055,774), treating agents for filling synthetic fiber (U.S. Pat. No. 
4,062,999) and adhesion additives (U.S. Pat. No. 4,033,924). It is 
believed that the use of epoxypolysiloxanes to provide effective release 
coatings with pressure-sensitive adhesives has not been previously 
described. 
SUMMARY OF THE INVENTION 
The present invention provides reliably produced, cured epoxypolysiloxane 
polymers which are crosslinked, polymeric networks and which exhibit 
specific release properties toward tacky and pressure-sensitive adhesives 
throughout and beyond the range represented by the polydimethylsiloxanes 
at the low end and conventional non-silicone low adhesion backsizes at the 
other end. These polymers find utility as coatings for release liners, 
especially differential release liners, and low adhesion backsizes for 
tapes. The present invention provides novel release coatings with 
intermediate release properties, such coatings overcoming many of the 
aforementioned problems of the prior art and do so with a single coating. 
The curable epoxypolysiloxanes useful in the invention can be fluids or 
much higher molecular weight greases or gums, and they can be cured with 
many types of epoxy curing catalysts well-known in the art in conjunction 
with heat or radiation. Although fluids having average molecular weights 
ranging from about 1,000 to 25,000 are preferred because of handling 
performance and versatility of application, e.g., 100% solids or solution 
coatings can be used, polymers having molecular weights up to 10.sup.6 or 
more can be used, especially as solution coatings. Generally, the very 
high molecular weight polymers are less convenient to use because of their 
high solution viscosities. A further disadvantage is that they can exhibit 
lower pot life when mixed in solution with some of the more active 
catalysts. Viscosities of the epoxypolysiloxane ranging from about 50 to 
3,000 centipoises, measured at 23.degree. C. using a Brookfield 
viscometer, are thus best used. 
Epoxy-terminated silanes may be used optionally with the epoxypolysiloxanes 
in the coating formulation of this invention. These are compounds or 
materials having polymerizable epoxy group(s) and a polymerizable silane 
group. 
The cured coating is conveniently obtained by mixing the epoxypolysiloxane 
and catalyst and optionally the epoxy-terminated silane in a solvent, 
coating the solution on the substrate and heating at a suitable curing 
temperature depending on the effectiveness of the catalyst and heat 
sensitivity of the substrate. Mixtures of the epoxypolysiloxanes or 
mixtures of the epoxysilanes may be used. 
The polymers of the invention are best used as coatings upon a solid 
substrate, which may be a sheet, fiber or shaped object. The preferred 
substrate is one that is used for pressure-sensitive adhesive products. 
The substrates of choice are films of thermoplastic resins such as 
polyesters, polyamides, polyolefins, polycarbonates, polyvinylchloride, 
etc. and paper, although any surface requiring release toward adhesives 
can be used. Where the cured epoxypolysiloxane coating does not naturally 
adhere to the substrate, primers known in the art may be used without 
affecting the release performance of the epoxypolysiloxane coating. 
DETAILED DESCRIPTION OF THE INVENTION 
The curable epoxypolysiloxanes essential to this invention are represented 
by the formula, 
##STR1## 
wherein R is a lower alkyl of one to three carbon atoms, R.sup.1 is a 
monovalent hydrocarbon radical of 4 to 20 carbon atoms, E is a monovalent 
epoxy-containing hydrocarbon radical, M is a silyl group R.sub.3 Si--, 
R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, where R, R.sup.1, and E are defined 
above, a is 5 to 200, b is 0 or up to 20% of a, a+b is 5 to 200, c may be 
0 when M is R.sub.2 ESi-- or greater than 0 but less than 20% of the value 
of (a+b) when M is R.sub.3 Si--, R.sub.2 R.sup.1 Si-- or R.sub.2 ESi--, 
and n is 1 to 75. In the above formula, the preferred R group is methyl, 
and the preferred M group is R.sub.2 ESi-- when c is 0, and R.sub.3 Si-- 
when c is greater than 0. Also, when c is 0 and M is R.sub.2 ESi--, n is 1 
to 5, and preferably n is 1 or 2. 
It is apparent from the restrictions placed on the above composition that 
not all types of epoxypolysiloxanes are useful to provide effective 
release coatings. For example, when c is greater than 20% of (a+b), 
release of the cured coating toward adhesives is very high and can be so 
high as to cause delamination of the adhesive from the substrate. When c 
is less than about 0.5% of (a+b) and M is R.sub.3 Si--, curing is more 
difficult to achieve, e.g., very high temperatures and reaction times are 
necessary. Similarly, the value of b can affect release performance. For 
example, when b is greater than 20% of a and R.sup.1 is a long chain 
hydrocarbon radical, e.g., octadecyl or higher alkyl, release can be so 
high as to cause delamination of the adhesive from the substrate. The 
preferred b is 0. 
Illustrative examples of the monovalent hydrocarbon radical, R.sup.1, in 
the above formula are alkyl radicals such as butyl, isobutyl, tert-butyl, 
hexyl, octyl and octadecyl; aryl radicals such as phenyl, naphthyl and 
bisphenylyl; alkaryl radicals such as tolyl and xylyl; aralkyl radicals 
such as phenylmethyl, phenylpropyl and phenylhexyl; and cycloaliphatic 
radicals such as cyclopentyl, cyclohexyl and 3-cyclohexylpropyl; and ether 
oxygen- or ester oxygen-containing radicals such as ethoxypropyl, 
butoxybutyl, and ethoxycarbonylpropyl and the like. The preferred R.sup.1 
is alkyl of 4-8 carbon atoms. 
The siloxane groups, 
##STR2## 
ordered or randomly arranged in the epoxypolysiloxane and the monovalent 
epoxy-containing hydrocarbon radical, E, contains at least one 
polymerizable epoxy group, 
##STR3## 
the remainder being composed of carbon and hydrogen, free of acetylenic 
unsaturation and in addition to the oxirane oxygen can contain ether, 
--O--, or carbonyl oxygen, e.g., 
##STR4## 
Illustrative examples of E are: 
##STR5## 
In the above epoxy-containing hydrocarbon radical, the epoxy group is 
preferably located at the terminal position of the radical, but it need 
not be a terminal group. 
Due to the availability of starting materials, ease of preparation and 
performance, the preferred epoxypolysiloxanes are those where R is methyl, 
b is 0 and E is beta-(3,4-epoxycyclohexyl)ethyl or gamma-glycidoxypropyl. 
The epoxypolysiloxanes can be prepared by many methods known in the art 
such as the chloroplatinic acid catalyzed addition reaction of 
hydrosiloxanes, containing the .tbd.SiH reactive group, with aliphatically 
unsaturated epoxy compounds, epoxidation of vinyl or like unsaturated 
siloxanes and Grignard type reactions as for example described by E. P. 
Plueddemann and G. Fanger, J. Am. Chem. Soc. 81, 2632-35 (1959). A 
convenient method is the hydrosiloxane addition reaction. When this method 
is used, it is preferred that essentially complete reaction of the 
.tbd.SiH sites are accomplished although small amounts of hydrogen 
attached to silicon can be present. It is also preferred for best results 
that the epoxypolysiloxane is essentially free from low molecular weight 
components such as cyclic siloxanes since their presence in the final 
cured coating could adversely affect the adhesion property of the adhesive 
(adhesion loss or buildup). 
As mentioned above, epoxy-terminated silanes can be used optionally with 
the epoxypolysiloxanes in the coating formulation of this invention. Use 
of such epoxy-terminated silanes enables the release performance of the 
coating to be varied. These epoxy-terminated silanes are compounds or 
materials having polymerizable epoxy group(s) and a polymerizable silane 
group, the bridging of these groups being through a non-hydrolyzable 
aliphatic, aromatic or aromatic and aliphatic divalent hydrocarbon linkage 
which may contain ether or carbonyl oxygen linking groups. The 
epoxy-terminated silane is represented by the formula, 
##STR6## 
wherein E is an epoxy-containing monovalent hydrocarbon radical defined 
above, p is 1 to 3 (preferably 3) and R.sup.2 can be an aliphatic 
hydrocarbon radical of less than 10 carbon atoms such as alkyl (methyl, 
ethyl, isopropyl, butyl), an alkenyl such as allyl or vinyl, or an acyl 
radical such as formyl, acetyl, or propionyl. Because of availability and 
performance, the preferred R.sup.2 is a lower alkyl such as methyl or 
ethyl. Many illustrative examples are described in U.S. Pat. No. 
4,049,861. The preferred silane is 
beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 
##STR7## 
In addition to the silane, any hydrolyzate of the above silanes can be 
used. The hydrolyzate is formed by partial or complete hydrolysis of the 
silane OR.sup.2 groups as described further in the above patent. 
The amount of the epoxy-terminated silane or hydrolyzate can range from 0 
to about 98% of the epoxypolysiloxane used, the amount being determined by 
the release performance desired. Generally, the higher amounts give the 
higher release values. Use of amounts greater than about 98% were found to 
be impractical. For example, use of 100% of the silane, i.e., no 
epoxypolysiloxane present, where R.sup.2 is methyl, p=3 and E is 
beta(3,4-epoxycyclohexyl)ethyl, gave a hard abrasion-resistant coating, 
but the release toward an acrylic adhesive was found to be excessively 
high, causing delamination of the adhesive from the substrate. 
Curing of the epoxypolysiloxane-containing compositions of this invention 
can be effected by mixing with conventional epoxy curing catalysts and may 
additionally require heat or radiation. Examples of epoxy curing catalysts 
are tertiary amines, Lewis acids and their complexes, such as BF.sub.3 and 
complexes with ethers and amines; antimony halide-phosphorus containing 
ester complexes, such as with organophosphonates, mentioned below; 
polyaromatic iodonium and sulfonium complex salts (e.g., having SbF.sub.6, 
SbF.sub.5 OH, PF.sub.6, BF.sub.4, or A.sub.s F.sub.6 anions, as disclosed 
in U.S. Pat. No. 4,101,513) and organic acids and their salts or other 
derivatives such as the highly fluorinated sulfonic and sulfonylic acids 
as described in U.S. Pat. No. 4,049,861. The presence of the catalyst in 
the cured composition does not affect its efficacy as a release material. 
Not all catalysts are practical to use, however, because of such 
undesirable characteristics as: (1) high volatility, (2) corrosiveness, 
(3) inability to provide latent coating solutions, (4) inability to 
provide a totally cured coating at reasonable temperatures, e.g., below 
130.degree. C. required for heat-sensitive substrates, and (5) inability 
to provide adequate cure without use of excessive amounts of the catalyst 
which can cause contamination of the adhesive giving adhesive loss. 
The preferred catalysts found useful to provide ideal release coatings for 
pressure-sensitive adhesives are complexes of antimony halides and 
organophosphorus containing esters referred to as the antimony 
halide-phosphorus containing ester catalysts, the sulfonium and iodonium 
catalysts, and the highly fluorinated sulfonic and sulfonylic acids and 
derivatives such as salt derivatives. 
An example of an antimony halide-phosphorus containing ester catalyst is 
SbCl.sub.5.CH.sub.3 P(O)(OCH.sub.3).sub.2 formed by reaction of antimony 
pentachloride and dimethylmethylphosphonate. This and similar catalysts 
are the subject of assignee's copending patent applications, Ser. Nos. 
124,836 and 124,837, filed Feb. 26, 1980, in the names of Robert J. 
Balchunis and Stephen W. Bany. 
Another class of useful catalysts are the highly fluorinated sulfonic acids 
and salts represented by the formula, 
EQU (R.sub.f SO.sub.3).sub.n R.sup.3, 
wherein R.sup.3 is hydrogen, ammonium cation or metal cation, n is the 
valence of R.sup.3, and R.sub.f is a highly fluorinated aliphatic radical 
having 1 to 12 carbon atoms. R.sub.f is preferably a perfluoroalkyl 
radical, e.g. CF.sub.3 CF.sub.2 -- having 1 to 8 carbon atoms. An example 
is CF.sub.3 SO.sub.3 H and its salts. Use of sulfonic acids and salts as 
epoxy curing catalysts is described in U.S. Pat. No. 3,842,019. 
Another class of effective catalysts are the sulfonylic catalysts 
represented by the formula, 
EQU R.sub.f SO.sub.2 --Q--SO.sub.2 R.sub.f, 
wherein R.sub.f is defined above and Q is a divalent radical selected from 
--NH--, 
##STR8## 
wherein R.sup.4 is selected from hydrogen, chlorine, bromine, R.sub.f 
SO.sub.2, alkyl of 1-20 carbon atoms, alkenyl of 3 to 4 carbon atoms, aryl 
or aralkyl from 6 to 20 carbon atoms such as phenyl, naphthyl, 
4-ethylphenyl, benzyl, and the like; R.sup.5 is selected from hydrogen, 
chlorine, and bromine, and R.sup.6 is selected from hydrogen, alkenyl (3 
to 4 carbon atoms), and aryl up to 20 carbon atoms. In the above, R.sup.4 
can also be a substituted alkyl, e.g., substituted with non-basic groups 
such as chlorine, bromine, iodine, perfluoroalkylsulfonyl, nitro, carboxy 
or ester groups such as --CH.sub.2 CH(SO.sub.2 R.sub.f).sub.2, --CH.sub.2 
CBr(CO.sub.2 C.sub.8 H.sub.17).sub.2, --CH.sub.2 CNO.sub.2 (CO.sub.2 
C.sub.2 H.sub.5).sub.2, --CH.sub.2 CHBrCH.sub.2 COOH, and the like, and 
many of these types are very potent catalysts. Likewise, the above aryl 
groups can be substituted, such as 4-nitrophenyl, 3-chlorophenyl, and the 
like. 
Preparation of the above catalysts where Q is --CHR.sup.4 --, --CR.sup.4 
R.sup.5 --, and 
##STR9## 
is further described in U.S. Pat. Nos. 3,704,311, 3,776,960, 3,794,687, 
3,932,526, 3,962,346 and 4,054,596. (See also U.S. Pat. No. 4,049,861). 
All of the above sulfonylic catalysts where Q is the divalent --NH-- and 
--CHR.sup.4 -- are acidic compounds and can be readily converted to 
corresponding metal or ammonium cation salts which afford solutions of the 
epoxypolysiloxane and catalyst that are essentially unreactive at ambient 
temperature but on heating of the coating can rapidly polymerize to useful 
release coatings. "Ammonium cations" as used in the present invention are 
defined as cations of ammonia, primary, secondary, and tertiary amines. 
Use of such salts as epoxy curing catalysts is described in U.S. Pat. Nos. 
3,586,616, 3,632,843, 3,842,019 and 4,031,036. 
In the practice of this invention the epoxypolysiloxane, catalyst, and 
optionally, the epoxy-terminated silane are mixed in a solvent or, where 
possible, without solvent. The amount of catalyst used is about 1 to 5% by 
weight of the epoxy composition. The resultant material is coated on the 
substrate and cured at ambient temperatures or, where necessary, heated to 
temperatures of 25.degree. C. to 150.degree. C. In some cases, curing may 
be effected by radiation. Solvents which can be used include ethyl 
acetate, isopropyl acetate, acetone, methyl ethyl ketone, heptane, 
toluene, and mixtures thereof. The exact coating technique is not 
especially critical and any of several well known procedures can be used. 
Wirewound rods, such as a Meyer bar, or a rotogravure applicator roll 
having, for example, 80 lines per cm, provide uniform coatings. 
Optionally, a mixing spray nozzle having a line for the epoxypolysiloxane 
fluid or solution and a separate line for the catalyst solution can be 
used. 
The initial release performance of the epoxypolysiloxane coating toward 
adhesives can be measured by various methods known in the art depending 
upon whether the final product is in sheet or rolled form such as a tape. 
Various test methods for pressure-sensitive tapes are reported by the 
Pressure Sensitive Tape Council (PSTC), "Test Methods for Pressure 
Sensitive Tapes" (several editions).

Objects and advantages of this invention are further illustrated by the 
following examples, but the particular materials and amounts thereof 
recited in these examples, as well as other conditions and details, should 
not be construed to unduly limit this invention. 
EXAMPLE 1 
This example describes the preparation of an epoxypolysiloxane used in the 
coating formulation. To a solution of 15 g (0.24 mol) of 
polyhydromethylsiloxane (DC 1107 from Dow Corning), 150 g (2.0 mol) of 
octamethylcyclotetrasiloxane and 14 g (0.09 mol) of hexamethyldisiloxane, 
contained in a narrow necked heavy-walled glass bottle, was added 0.3 g of 
conc. sulfuric acid and 2 g of activated carbon. The bottle was sealed and 
agitated in a water bath at 60.degree. C. for 30 hours. The mixture was 
filtered using a filtering aid (Hyflo Suoer-Cel.RTM.) and the solid rinsed 
with petroleum ether. The filtrate was stripped of solvent under reduced 
pressure and volatile silicone compounds were removed by heating at 
160.degree.-175.degree. C. at 0.1 mm (3 hr). A clear fluid residue (158 g) 
having a viscosity of 75 centipoises (cps) at 23.degree. C. and a SiH 
equivalent weight of 780 was obtained. This SiH prepolymer contained an 
average of 36 dimethylsiloxane units, 4 hydromethylsiloxane units, and 2 
trimethylsilyl end groups. 
The reaction of the SiH prepolymer with an olefinic epoxy compound was 
carried out as follows. To a solution of 31 g (0.25 mol) of 
4-vinylcyclohexene monoxide and 75 ml of toluene, stirred under nitrogen 
at 85.degree. C., was added 0.1 ml of a 10% solution of chloroplatinic 
acid catalyst in isopropyl alcohol. A solution of 155 g of the above 
described SiH prepolymer and 100 ml of toluene was then added over a 
period of 3 hr, additional catalyst was added (same amount as above), and 
the mixture stirred at 85.degree. C. for 3 hr. The mixture was cooled and 
0.3 ml of benzothiazole added. The resultant mixture was stirred for 1 hr, 
2 g of activated carbon was added and the mixture then filtered using 
filtering aid and toluene rinse. The solvent was removed from the filtrate 
by distillation and the residue heated at 100.degree. C. at 0.2 mm for 3 
hr to remove any additional volatile components. The epoxypolysiloxane 
residue (176 g) was a fluid having a viscosity of 175 cps at 23.degree. C. 
and an epoxy equivalent weight of 930. The polymer, designated as 
Epoxypolysiloxane A, contained the following average number of 
dimethylsiloxane units, methyl beta(3,4-epoxycyclohexyl)ethylsiloxane 
units and trimethylsiloxy units in the polymer: 
______________________________________ 
Average 
Unit Contained In Epoxypolysiloxane A 
Number of Units 
______________________________________ 
##STR10## 36 
##STR11## 4 
(CH.sub.3).sub.3 SiO 2 
______________________________________ 
Using the above procedures, other epoxypolysiloxanes were prepared by 
reaction of the above olefinic epoxide or other types of olefinic epoxides 
with SiH prepolymers having different SiH content, molecular weights, and 
number of dimethylsiloxane units provided by varying the amounts of 
hexamethyldisiloxane (chain stopper) and octamethylcyclotetrasiloxane used 
in the preparation of the SiH prepolymer. Alternatively, other hydrocarbon 
olefins such as octene-1 in addition to the olefinic epoxide can be 
independently reacted with the SiH prepolymer giving epoxypolysiloxanes 
having the 
##STR12## 
structural unit; e.g., R.sup.1 is octyl. 
The following examples show construction of tapes and their performance. 
EXAMPLES 2-5 
The epoxypolysiloxanes, prepared according to the method of Example 1, 
designated as Epoxypolysiloxanes B to E, given in Table I, were 
trimethylsilyl end blocked and contained dimethylsiloxane units (.about.45 
units) and varying amounts of methyl beta-(3,4-epoxycyclohexyl)ethyl 
siloxane units; the epoxy equivalent weight of each of the polymers is 
given in Table I. These polymers also had similar average molecular 
weights in the range of 3900 to 4300. It is apparent in Table I that by 
varying the epoxy equivalent weight, different release levels can be 
obtained. It is of note that the release force from the adhesive may be 
increased by decreasing the epoxy equivalent weight of the polymer. 
The methods for preparation of tapes having a low adhesion backsize in 
accordance with the invention and the release performance of the tapes 
(Table I) are as follows. To the smooth, shiny side of a pretreated 
(corona discharge) substantially unoriented film (15 cm wide; 90 .mu.m 
thick) of crystalline, pigmented polypropylene was applied a 3% solution 
(80/20 heptane/methyl ethyl ketone) of the epoxypolysiloxane and catalyst 
(antimony pentachloride/dimethylmethylphosphonate complex; 1.8% by weight 
of epoxypolysiloxane; solvent for catalyst, CH.sub.2 Cl.sub.2) using a 
rotorgravure roll having 60 lines/cm. The coated film was heated in an 
oven at 75.degree. C. (one minute residence). In a similar fashion, the 
reverse matte finish side of the polypropylene film was coated with a 
solution of a block copolymer based synthetic rubber/resin adhesive using 
a knife coater. The coated film was again heated at 75.degree. C. for one 
minute, the film was wound, kept at 23.degree. C. for 24 hr, and slit into 
2.54 cm width rolls for testing. 
The data referring to initial release and release after heat aging (Table 
I) were obtained by using Test Method PSTC-4 (11-70) modified as follows. 
A 13 cm length portion of the release tape as prepared above was applied 
to a steel test panel with the adhesive side down. Over this was applied a 
25 cm length portion of a test tape (2.5 cm width, adhesive side down) so 
that overlap occurred, and pressed firmly with a 2 kg mechanically 
operated roller. [The test tape was composed of a 25 .mu.m corona treated 
polyester film (a biaxially oriented polyethylene terephthalate) coated on 
one side with the synthetic rubber/resin adhesive (5 mg/cm.sup.2) 
described above and on the other side with a urethane low adhesion 
backsize]. The free end of the test tape was doubled back one inch at an 
angle of 180.degree. and clamped onto the upper jaw of the tensile test 
machine. The panel, from which the test tape was removed, was clamped onto 
the lower jaw. The lower jaw was operated at 30 cm/min. Release values, 
obtained while the first 3 cm of test tape in contact with the LAB was 
removed, were disregarded. The average release value (grams per 2.5 cm of 
width) obtained during removal of the next 5 cm of test tape are given in 
Table I. 
Heat aging of the roll of release tape was carried out at 50.degree. C. for 
15 days and then at 23.degree. C. (24 hr) at 50% relative humidity. 
The adhesion values given in Table I which measures properties of the 
pressure-sensitive adhesive side of the tape after contact with the 
silicone low adhesion backsize of the invention were obtained by using 
Test Method PSTC-1 (11-70). A 180.degree. peel at 30 cm/min was used. 
TABLE I 
______________________________________ 
Epoxy- Adhesion (steel) 
poly- Release, g/2.5 cm 
kg/2.5 cm 
silo- Epoxy 15 days, 15 days, 
Ex. xane Equiv. Wt. 
Initial 
50.degree. C. 
Initial 
50.degree. C. 
______________________________________ 
2 B 1000 223 228 2.35 2.41 
3 C 1180 135 149 2.58 2.04 
4 D 1650 96 128 2.33 2.33 
5 E 1820 84 109 2.27 2.18 
______________________________________ 
EXAMPLES 6-14 
These examples (Table II) show the release performance using a combination 
of an epoxypolysiloxane and epoxysilane in the coating formulation. The 
epoxypolysiloxane used was Epoxypolysiloxane A (Example 1) and the 
epoxysilane used was beta(3,4-epoxycyclohexyl)ethyl-trimethoxysilane, 
##STR13## 
designated as Epoxysilane A. To a 15 ml solution of the epoxypolysiloxane 
and the epoxysilane in ethyl acetate (15% solids) was added one drop of 
25% L-522 (Union Carbide inert silicone surfactant in ethyl acetate) and 
0.15 g of 25% antimony pentachloride/dimethylmethylphosphonate catalyst in 
methyl ethyl ketone. The solution was coated on 100 .mu.m polyvinylidene 
chloride primed polyester (polyethylene terephthalate) using a No. 8 RDS 
rod (R. D. Specialties, Inc.). The solvent was allowed to evaporate at 
25.degree. C. and the coated film heated at 90.degree. C. for one minute. 
The side of the film containing the cured silicone release coating was 
then coated (.about.200 .mu.m) with a solution (20% in heptane) of acrylic 
adhesive based on a 95/5 isooctylacrylate/acrylic acid copolymer using a 
knife coater. The adhesive coated film was heated to 72.degree. C. for 5 
minutes to remove solvent and the adhesive side laminated with 25 .mu.m 
unprimed polyester by pressing between two rollers. The laminated sample 
was allowed to remain at room temperature for 24 hr, cut into 2.54 cm 
strips, and the strips tested for release using a release testing machine 
having a dial gauge. The release values were measured at 180.degree. peel 
at the rate of 230 cm/min. Adhesion values were obtained by removing the 
adhesive strip and placing the adhesive side on a clean glass surface. A 2 
kg roller was pulled over the strip three times and the adhesion value 
measured at 180.degree. peel at the rate of 230 cm/min. In each case, 
three films were measured; the average release values and adhesion values 
are given in Table II. 
TABLE II 
______________________________________ 
Wt. Ratio, 
Epoxysilane A/ Adhesion 
Epoxy- Release, g/2.5cm 
(glass), kg.sup.a /2.5cm 
Ex. polysiloxane A 
Acrylic Adhesive 
Acrylic Adhesive 
______________________________________ 
6 20/1 709 1.12 
7 10/1 410 1.25 
8 2/1 213 1.24 
9 1/1 156 1.24 
10 1/2 128 1.24 
11 1/4 85 1.24 
12 1/10 71 1.22 
13 1/20 57 1.25 
14 Epoxy- 
polysiloxane A 
99 1.28 
(100%) 
______________________________________ 
.sup.a Aged laminates (72.degree. C./20 hr) gave similar results 
EXAMPLES 15-20 
These examples (Table III) show the use of an epoxypolysiloxane containing 
methyloctylsiloxane units in combination with an epoxysilane to achieve 
variable release performance. The epoxypolysiloxane designated as 
Epoxypolysiloxane G is a trimethylsilyl end-blocked polymer having an 
average of about 40 dimethylsiloxane units, 5 methyloctylsiloxane units, 
and 5 methyl beta(3,4-epoxycyclohexyl)ethyl siloxane units. The 
epoxysilane was beta-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 
designated as Epoxysilane A. The substrate, coating procedures and testing 
procedures were similar to those described in the preceding examples 
(6-14). Releases toward the synthetic rubber/resin adhesive described in 
Examples 2-5 are given in Table III. 
TABLE III 
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Wt. Ratio, Adhesion 
Epoxysilane A/ 
Release, g/2.5cm 
(glass), kg/2.5cm 
Epoxy- Rubber/Resin Rubber/Resin 
Ex. polysiloxane G 
Adhesive Adhesive 
______________________________________ 
15 50/1 454 3.55 
16 20/1 255 3.41 
17 10/1 99 3.35 
18 4/1 71 3.41 
19 1/4 35 3.35 
20 Epoxy- 
polysiloxane G 
14 3.35 
(100%) 
______________________________________ 
EXAMPLES 21-22 
The following examples show the use of other catalysts to provide useful 
release coatings. Coating and testing procedures were similar to those 
described in Examples 6-14. A solution of an epoxypolysiloxane fluid 
(similar to Epoxypolysiloxane A, having an epoxy equivalent weight of 
about 1000) and the ammonium salt of C.sub.4 F.sub.9 SO.sub.2 NHSO.sub.2 
CF.sub.3 (2% by wt., added as a 25% solution in methylene chloride) was 
coated on primed polyester on one side and the film heated at 90.degree. 
C. (1 min.). The cured coating was transparent, tack-free and exhibited an 
initial release toward acrylic adhesive of about 20 g (2.5 cm width). Very 
similar results were obtained using CF.sub.3 SO.sub.2 CH.sub.2 SO.sub.2 
CF.sub.3 and (CF.sub.3 SO.sub.2).sub.2 CHCH.sub.2 CBr(CO.sub.2 C.sub.2 
H.sub.5).sub.2 as catalysts and ethyl acetate (20% solids) as solvent. 
In a similar manner, a solution of the above epoxypolysiloxane fluid and 
triphenylsulfonium hexafluoroantimonate (2% by wt, methyl ethyl ketone as 
carrier) was coated on polyester and exposed to ultraviolet light using a 
UV Processor (PPG Industries, Model QC-1202). A tack-free, cured coating 
having release with acrylic adhesive of about 30 g/2.5 cm width was 
obtained. 
EXAMPLES 23-24 
These examples show the release performance using an epoxypolysiloxane, 
end-blocked with epoxy-containing silyl groups, in the coating 
formulation. An epoxypolysiloxane fluid having an epoxy equivalent weight 
of about 2650 (measured by titration) containing dimethylsiloxane units 
and terminated at each end with a beta(3,4-epoxycyclohexyl)ethyl dimethyl 
silyl group was prepared from the corresponding SiH end-blocked 
polydimethylsiloxane fluid and vinylcyclohexene monoxide using the 
hydrosilation procedure (Example 1). Tapes having the above cured 
epoxypolysiloxane low adhesion backsize (polypropylene as the substrate 
and the antimony pentachloride/dimethyl methylphosphonate complex 
catalyst) were constructed using procedures similar to those described in 
Examples 2-5. Test procedures were also similar except a test tape having 
a more aggressive adhesive was used. The initial release (average of three 
tapes) was 111 g/2.5 cm. 
A similar type polydimethylsiloxane fluid having a lower epoxy equivalent 
weight of about 1475 which was also end-blocked with 
beta(3,4-epoxycyclohexyl)ethyl dimethylsilyl groups was cured and 
evaluated under similar conditions. In this case, the initial average 
release was 260 g/2.5 cm. 
Various modifications and alterations of this invention will become 
apparent to those skilled in the art without departing from the scope and 
spirit of this invention, and it should be understood that this invention 
is not to be unduly limited to the illustrative embodiment set forth 
herein.