Silicone resin/silicone rubber composite material

By curing or semi-curing an addition curable silicone resin composition comprising a phenyl-containing organopolysiloxane, placing an addition or peroxide curable silicone rubber composition in close contact with the cured or semi-cured resin, and heat curing the silicone rubber composition, there is prepared a composite material in which silicone resin and silicone rubber are firmly joined together.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to silicone resin/silicone rubber composite 
materials for use in various industrial fields including electric and 
electronic equipment, business machines, automobiles, and precision 
machines. 
2. Prior Art 
A number of methods are known in the art for producing shapes having two 
distinct silicone parts integrated together. Most methods involved 
separately heat molding distinct silicone compositions and adhesively 
joining the molded parts into an integral product. 
These methods, however, suffer from the problem that adhesive joining of 
distinct silicone parts is difficult and time consuming and even when 
possible, the bond is weak, resulting in an integral product having low 
dimensional accuracy. 
In addition to these methods, integral products in which silicone resin is 
integrated with silicone rubber can also be produced by coating silicone 
rubber with silicon resin, for example. The coating method is difficult to 
carry out and finds use only in coating applications. Because of fragility 
of the silicone resin itself and weak bond between silicone resin and 
silicon rubber, the resulting products are inadequate for use as composite 
materials. 
An integral product having combined silicones of different hardnesses has 
been used as a coating on fiber optics. In this proposal, no attention is 
paid to the bond between distinct silicone parts. 
Over the past years, silicone rubber has found a spreading range of 
applications in electric and electronic equipment, business machines and 
automobiles because of its recognized reliability in heat resistance, 
weatherability and electrical characteristics. Currently available 
composite materials of silicone rubber with thermoplastic or thermosetting 
hydrocarbon resins, however, do not take full advantage of the 
characteristics of silicone rubber. There is a need to have an integrally 
molded silicone resin/silicone rubber material in which silicone resin and 
silicone rubber are firmly bonded. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a silicone 
resin/silicone rubber composite material in which silicone resin and 
silicone rubber are firmly bonded. 
We have found that by using a phenyl-containing organopolysiloxane as a 
silicone resin base, curing or semi-curing an addition curable silicone 
resin composition comprising the phenyl-containing organopoly-siloxane, 
placing an addition or peroxide curable silicone rubber composition in 
close contact with the cured or semi-cured resin, and heat curing the 
silicone rubber composition to integrate the rubber to the previously 
cured or semi-cured resin, there is obtained a composite material in which 
silicone resin and silicone rubber are firmly bonded. The order of first 
curing an addition curable silicone resin composition and then curing a 
silicone rubber composition to the cured resin permits the integration of 
silicone resin and silicone rubber to be briefly accomplished in a simple 
manner without an adhesive. There is obtained a silicone resin/silicone 
rubber composite material having a sufficient bonding force for practical 
use. 
According to the present invention, there is provided a silicone 
resin/silicone rubber composite material comprising a cured product of an 
addition curable silicone resin composition having a hardness of at least 
85 as specified in JIS K-6301, entitled Physical Testing Methods for 
Vulcanized Rubber of the Japanese Industrial Standard (JIS K-6301 is 
incorporated herein by reference. The hardness of the silicone resin and 
silicone rubber compositions is measured on a Type A spring hardness 
tester. The tester has a test piece indentor projecting from a hole in the 
center of the loading surface by means of a spring that is pushed back by 
the surface of the test piece. The distance moved by the spring is 
indicated by a pointer on the scale of the tester, which indicates the 
hardness of the test piece. A test piece of not less than 12 mm thickness 
is used. The surface of the test piece should be large enough such that 
the loading surface of the tester is within the boundary thereof), and 
measured on a Type A spring hardness tester, integrated with a cured 
product of an addition or peroxide curable silicone rubber composition 
having a hardness of 20 to 85 as specified in JIS K-6301 and measured on a 
Type A spring hardness tester, that is obtained by curing or semi-curing 
the addition curable silicone resin composition, placing the addition or 
peroxide curable silicone rubber composition in close contact with the 
cured or semi-cured silicone resin composition, and heat curing the 
silicone rubber composition, 
said silicone resin composition comprising an organopolysiloxane of the 
following formula (1): 
EQU R.sub.n (C.sub.6 H.sub.5).sub.m SiO.sub.(4-n-m)/2 ( 1) 
wherein R is independently a substituted or unsubstituted aliphatic or 
alicyclic monovalent hydrocarbon radical having 1 to 20 carbon atoms, 0.1 
to 30 mol % of R being an aliphatic unsaturated hydrocarbon radical, and 
letters n and m are positive numbers satisfying 1.ltoreq.n+m&lt;2 and 
0.05.ltoreq.m/(n+m).ltoreq.0.5.

DETAILED DESCRIPTION OF THE INVENTION 
The silicone resin/silicone rubber composite material of the present 
invention includes an addition curable silicone resin composition and an 
addition or peroxide curable silicone rubber composition which are heat 
cured to form an integral or one-piece product. The silicone resin 
composition is comprised of an organopolysiloxane of the general formula 
(1). 
EQU R.sub.n (C.sub.6 H.sub.5).sub.m SiO.sub.(4-n-m)/2 (1) 
In formula (1), R is independently a substituted or unsubstituted aliphatic 
or alicyclic monovalent hydrocarbon radical, preferably having 1 to 20 
carbon atoms, more preferably 1 to 10 carbon atoms. Exemplary hydrocarbon 
radicals include saturated hydrocarbon radicals, for example, alkyl 
radicals such as methyl, ethyl and propyl and cycloalkyl radicals, 
aliphatic unsaturated hydrocarbon radicals such as vinyl, allyl, propenyl 
and butenyl, halo-substituted hydrocarbon radicals such as 
3,3,3-trifluoropropyl, and cyano-substituted hydrocarbon radicals. It is 
required that 0.1 to 30 mol %, preferably 1 to 20 mol % of R be an 
aliphatic unsaturated hydrocarbon radical, preferably an alkenyl radical. 
If the content of aliphatic unsaturated hydrocarbon radical is less than 
0.1 mol %, the resulting silicone resin is insufficiently hard and poorly 
adhesive to silicone rubber. If the content of aliphatic unsaturated 
hydrocarbon radical is more than 30 mol %, the silicone resin becomes 
brittle because of too many crosslinking sites. Letters n and m are 
positive numbers satisfying 1.ltoreq.n+m&lt;2, and the content of phenyl 
radical is 5 to 50 mol % of the overall organic radicals, that is, 
0.05.ltoreq.m/(n+m).ltoreq.0.5. With a phenyl content outside this range, 
the silicone resin is brittle in molded form. 
These organopolysiloxanes can be prepared by conventional well-known 
methods, for example, by co-hydrolysis of dimethylchlorosilane, 
phenyltrichlorosilane and methylvinyldichlorosilane or by co-hydrolysis of 
dimethyldimethoxysilane, phenyltrimethoxysilane and vinyltrimethoxysilane 
in the presence of an alkali or acid catalyst. 
Preferably the silicone resin composition used herein includes as major 
components, 
(a) an organopolysiloxane of formula (1), 
(b) an organohydrogenpolysiloxane which is liquid at room temperature (for 
example, 5.degree. to 30.degree. C.), and 
(c) an addition reaction catalyst, and optionally, 
(d) an organopolysiloxane containing two or more alkenyl radicals per 
molecule which is liquid or raw rubber at 5.degree. to 30.degree. C.) when 
it is desired to control the hardness of the silicone resin composition to 
the above-defined value or to control the viscosity or the like. 
The organohydrogenpolysiloxane (b) may have the following formula: 
EQU R.sub.a H.sub.b SiO.sub.(4-a-b)/2 
wherein R' represents an unsubstituted or substituted monovalent 
hydrocarbon radical having 1 to 10 carbon atoms excluding an aliphatic 
unsaturated radical, a is a positive number of 1 to 2.1, b is a positive 
number of 0.5 to 1 and a+b is 1.5 to 2.6. 
Examples of the organohydrogenpolysiloxane as component (b) include 
methylhydrogenpolysiloxane blocked with a trimethylsiloxy radical at 
either end, dimethylsiloxanemethylhydrogenpolysiloxane copolymers blocked 
with a trimethylsiloxy radical at either end, dimethylsiloxane blocked 
with a dimethylhydrogensiloxy radical at either end, 
dimethylsiloxane-methylhydrogenpolysiloxane copolymers blocked with a 
dimethylhydrogensiloxy radical at either end, 
methylhydrogenpolysiloxanediphenylsiloxane blocked with a trimethylsiloxy 
radical at either end, methylhydrogenpolysiloxane-dimethylsiloxane blocked 
with a trimethylsiloxy radical at either end, copolymers consisting of 
(CH.sub.3).sub.2 HSiO.sub.1/2 and SiO.sub.4/2 units, copolymers consisting 
of (CH.sub.3).sub.3 SiO.sub.1/2, (CH.sub.3).sub.2 HSiO.sub.1/2 and 
SiO.sub.4/2 units, and copolymers consisting of (CH.sub.3).sub.2 
HSiO.sub.2/1, SiO.sub.4/2 and (C.sub.6 H.sub.5).sub.3 SiO.sub.3/2 units. 
The organohydrogenpolysiloxane (b) is preferably blended in an amount of 
about 1 to 50 parts, more preferably about 5 to 30 parts by weight per 100 
parts by weight of organopolysiloxane (a). With less amounts of 
organohydrogenpolysiloxane, the silicone resin would have low hardness. 
With greater amounts of organohydrogenpolysiloxane, the cured resin would 
become brittle failing to provide satisfactory strength. 
Examples of the addition reaction catalyst (c) include platinum catalysts 
such as platinum black, platinic chloride, chloroplatinic acid, reaction 
products of chloroplatinic acid with monohydric alcohols, complexes of 
chloroplatinic acid with olefins, platinum bisacetoacetate, palladium 
catalysts, and rhodium catalysts. The catalyst may be used in a catalytic 
amount. 
The organopolysiloxane of component (d) preferably has the following 
general compositional formula: 
EQU R".sub.d SiO.sub.(4-d)/2 
wherein R" is an unsubstituted or substituted monovalent hydrocarbon group 
having 1 to 10 carbon atoms such as alkyl, alkenyl, aryl, aralkyl, and 
halogen or cyano substituted alkyl groups, and d is a positive number of 
1.8 to 2.4. 
The organopolysiloxane should have at least two alkenyl radicals preferably 
having 2 to 8 carbon atoms per molecule. Examples of alkenyl radicals 
include vinyl, allyl, propenyl, isopropenyl, butenyl and hexenyl. 
Examples of the organopolysiloxane containing two or more alkenyl radicals 
in a molecule which is liquid or raw rubber at 5.degree. to 30.degree. C. 
of component (d) include dimethylpolysiloxane blocked with a 
dimethylvinylsilyl radical at either end, 
dimethylpolysiloxanemethylvinylsiloxane copolymers blocked with a 
dimethylvinylsilyl radial at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a methylphenylvinylsilyl radical at either end, and 
methyl(3,3,3-trifluoropropyl)polysiloxane blocked with a 
dimethylvinylsilyl radical at either end. The organopolysiloxane (d) is 
preferably blended in an amount of 0 to 100 parts by weight per 100 parts 
by weight of organopolysiloxane (a), more preferably 0 to 50 parts, 
particularly 1 to 50 parts by weight per 100 parts by weight of 
organopolysiloxane (a) so as not to detract from the strength of the 
resin. 
In addition to the above-mentioned components, fillers may be blended in an 
amount of 0 to 200 parts, preferably 0 to 100 parts by weight per 100 
parts by weight of organopolysiloxane (a) in the silicone resin 
composition for adjusting the flow thereof or improving the mechanical 
strength of molded parts. Exemplary fillers include reinforcing fillers 
such as precipitated silica, fumed silica, calcined silica, and fumed 
titanium oxide, and non-reinforcing fillers such as ground quartz, 
diatomaceous earth, asbestos, aminosilicic acid, iron oxide, zinc oxide, 
and calcium carbonate. The fillers may be used with or without surface 
treatment with organic silicon compounds such as hexamethyldisilazane, 
trimethylchlorosilane and polymethylsiloxane. If desired, pigments, heat 
resistance modifiers, flame retardants, plasticizers or the like may be 
blended. 
On the other hand, the silicone rubber composition used herein may be 
either addition reaction curable or peroxide curable. The addition curable 
silicone rubber composition preferably includes as major components, (e) 
an organopolysiloxane containing on average at least two lower alkenyl 
radicals in a molecule, (f) an organohydrogenpolysiloxane having at least 
two hydrogen atoms directly attached to silicon atoms in a molecule, and 
(g) an addition reaction catalyst and is liquid or raw rubber at room 
temperature. 
The organopolysiloxane of component (e) preferably has the following 
general compositional formula: 
EQU R".sub.e SiO.sub.(4-e)/2 
wherein R" is as defined above and e is a positive number of 1.85 to 2.25. 
Examples of the organopolysiloxane (e) include dimethylpolysiloxane blocked 
with a dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-methylvinylsiloxane copolymers blocked with a 
dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a methylphenylvinylsilyl radical at either end, and 
methyl(3,3,3-trifluoropropyl)-polysiloxane blocked with a 
dimethylvinylsilyl radical at either end. These organopolysiloxanes 
preferably have a viscosity of about 100 to about 1,000,000 centipoise at 
25.degree. C. 
The organohydrogenpolysiloxane (f) may have the following formula: 
EQU R.sub.a H.sub.b SiO.sub.(4-a-b)/2 
wherein R represents an unsubstituted or substituted monovalent hydrocarbon 
radical having 1 to 10 carbon atoms excluding an aliphatic unsaturated 
radical, a is a positive number of 1 to 2.1, b is a positive number of 0.5 
to 1 and a+b is 1.5 to 2.6. 
Examples of the organohydrogenpolysiloxane (f) include 
methylhydrogenpolysiloxane blocked with a trimethylsiloxy radical at 
either end, dimethylsiloxane-methylhydrogenpolysiloxane copolymers blocked 
with a trimethylsiloxy radical at either end, dimethylsiloxane blocked 
with a dimethylhydrogensiloxy radical at either end, and 
dimethylsiloxane-methylhydrogenpolysiloxane copolymers blocked with a 
dimethylhydrogensiloxy radical at either end. These 
organohydrogenpolysiloxanes preferably have a viscosity of about 1 to 
about 1,000 centipoise at 25.degree. C. The organohydrogenpolysiloxane (f) 
is preferably blended in an amount of about 0.1 to 50 parts, more 
preferably about 0.5 to 20 parts by weight per 100 parts by weight of 
organopolysiloxane (e). 
Examples of the addition reaction catalyst (g) include platinum catalysts 
such as platinum black, platinic chloride, chloroplatinic acid, reaction 
products of chloroplatinic acid with monohydric alcohols, complexes of 
chloroplatinic acid with olefins, platinum bisacetoacetate, palladium 
catalysts, and rhodium catalysts. The catalyst may be used in a catalytic 
amount. 
In addition to the above-mentioned components, fillers may be blended in an 
amount of 0 to 100 parts, preferably 1 to 80 parts, more preferably 5 to 
60 parts by weight per 100 parts by weight of organopolysiloxane (e) in 
the silicone rubber composition for adjusting the flow thereof or 
improving the mechanical strength of molded parts. In case of using 
reinforcing fillers, they are blended in an amount of 0 to 50 parts, 
preferably 5 to 40 parts, more preferably 10 to 30 parts by weight per 100 
parts by weight of organopolysiloxane (e). Exemplary fillers include 
reinforcing fillers such as precipitated silica, fumed silica, calcined 
silica, and fumed titanium oxide, and non-reinforcing fillers such as 
ground quartz, diatomaceous earth, asbestos, aminosilicic acid, iron 
oxide, zinc oxide, and calcium carbonate. The fillers may be used with or 
without surface treatment with organic silicon compounds such as 
hexamethyl-disilazane, trimethylchlorosilane and polymethylsiloxane. If 
desired, pigments, heat resistance modifiers, flame retardants, 
plasticizers or the like may be blended. 
The peroxide curable silicone rubber composition preferably includes as 
major components, 
(h) an organopolysiloxane containing on average at least two lower alkenyl 
radicals in a molecule and 
(i) an organic peroxide catalyst and is liquid or raw rubber at 5.degree. 
to 30.degree. C. 
The organopolysiloxane of component (h) preferably has the following 
general compositional formula: 
EQU R".sub.h SiO.sub.(4-h)/2 
wherein R" is as defined above and h is a positive number of 1.9 to 2.25. 
Examples of the organopolysiloxane (h) include dimethylpolysiloxane blocked 
with a dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-methylvinylsiloxane copolymers blocked with a 
dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a dimethylvinylsilyl radical at either end, 
dimethylpolysiloxane blocked with a trivinylsiloxy radical at either end, 
dimethylpolysiloxane-methylvinylsiloxane copolymers blocked with a 
trivinylsiloxy radical at either end, 
dimethylpolysiloxane-diphenylsiloxane-methylvinylsiloxane copolymers 
blocked with a methylphenylvinylsilyl radical at either end, and 
methyl(3,3,3-trifluoropropyl)polysiloxane blocked with a 
dimethylvinylsilyl radical at either end. 
Examples of the organic peroxide catalyst (i) include benzoyl peroxide, 
o-monochlorobenzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl 
peroxide, t-butyl benzoate, di-t-butyl peroxide, p-monochlorobenzoyl 
peroxide, t-butylcumyl peroxide, 
1,1,-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 
2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and 
1,6-bis(t-butylperoxycarboxy)hexane. The catalyst may be used in a 
catalytic amount, usually in an amount of 0.1 to 5 parts, preferably 0.5 
to 3 parts by weight per 100 parts by weight of organopolysiloxane (h) 
In addition to the above-mentioned components, fillers may be blended in an 
amount of 0 to 100 parts, preferably 1 to 80 parts, more preferably 5 to 
60 parts by weight per 100 parts by weight of organopolysiloxane (h) in 
the silicone rubber composition for adjusting the flow thereof or 
improving the mechanical strength of molded parts. In case of using 
reinforcing fillers, they are blended in an amount of 0 to 50 parts, 
preferably 5 to 40 parts, more preferably 10 to 30 parts by weight per 100 
parts by weight of organopolysiloxane (e). Exemplary fillers include 
reinforcing fillers such as precipitated silica, fumed silica, calcined 
silica, and fumed titanium oxide, and non-reinforcing fillers such as 
ground quartz, diatomaceous earth, asbestos, aminosilicic acid, iron 
oxide, zinc oxide, and calcium carbonate. The fillers may be used with or 
without surface treatment with organic silicon compounds such as 
hexamethyldisilazane, trimethylchlorosilane and polymethylsiloxane. If 
desired, pigments, heat resistance modifiers, flame retardants, 
plasticizers or the like may be blended. 
For taking full advantage of the characteristics of silicone resin and 
silicone rubber, respectively, it is preferred that a cured product of the 
silicone resin composition have a hardness of at least 85, especially at 
least 90 as specified in JIS K-6301 and measured on a Type A spring 
hardness tester, and a cured product of the silicone rubber composition 
have a hardness of 20 to 85, especially 30 to 70 as specified in JIS 
K-6301 and measured on a Type A spring hardness tester. 
The composite material according to the present invention may have any 
desired construction. Often, a portion or all of one surface of a cured 
product of a silicone rubber composition (simply referred to as silicone 
rubber) overlies a portion or all of one surface of a cured product of a 
silicone resin composition (simply referred to as silicone resin). 
Alternatively, a silicone resin or rubber layer is sandwiched between 
silicone rubber or resin layers. 
The composite material of the invention has silicone resin and silicone 
rubber integrated firmly together without using an adhesive so that it is 
more effective for preventing strain occurrence due to different 
coefficients of thermal expansion as compared with composite materials of 
silicone rubber with other reins. Since both parts have siloxane bonds as 
the backbone, they both have the advantages of heat resistance, 
low-temperature properties and weatherability attributable to the siloxane 
bonds. Therefore, the composite material finds application as connectors, 
gaskets, and insulating parts in electric and electronic equipment, 
business machines, automobiles, and precision machines. 
The silicone resin/silicone rubber composite material of the invention is 
prepared by first molding a silicone resin composition into a desired 
shape by any suitable technique such as casting, compression molding, 
injection molding, extrusion molding and transfer molding, heat curing or 
semi-curing it, then molding a silicone rubber composition in close 
contact with the cured or semi-cured resin by any suitable technique, and 
curing the silicone rubber composition to the cured resin. The semi-cured 
silicone resin should reach at least a curing level capable of forming a 
non-intermixing interface when the silicone rubber composition is molded 
thereover in a close contact relationship. The conditions under which the 
silicone resin and rubber compositions are cured may be suitably 
determined without undue experimentation. After they are cured, they may 
be subject to post-curing if desired. 
EXAMPLE 
Examples of the present invention are given below by way of illustration 
and not by way of limitation. Unless otherwise stated, all parts and 
percents are by weight. 
Example 1 
A silicone resin composition (A) was prepared by mixing 100 parts of an 
organopolysiloxane of the average compositional formula (2) shown below, 
10 parts of an organohydrogenpolysiloxane of the average compositional 
formula (3) shown below, and 1.2 parts of an isopropanol solution of 
chloroplatinic acid (platinum content 0.20%). 
##STR1## 
A silicone rubber composition (B) was prepared by adding 30 parts of dry 
silica having a specific surface area of 200 m.sup.2 /g, 5 parts of 
dimethoxydimethylsilane, and 1 part of water to 100 parts of a 
dimethylpolysiloxane blocked with a dimethylvinylsiloxy radical at either 
end and having a viscosity of 100 poise at 25.degree. C., mixing them 
while heating the mixture at 150.degree. C. for 3 hours, and adding to the 
mixture 50 parts of the same polysiloxane as above, 0.4 parts of a 
dimethylsiloxane copolymer (consisting of 50 mol % of dimethylsiloxane 
units and 50 mol % of methylhydrogensiloxane units) blocked with a 
trimethylsilyl radical at either end and having a viscosity of 10 
centipoise at 25.degree. C., and 0.1 part of an isopropanol solution of 
chloro -platinic acid (platinum content 0.50%). 
Next, silicone resin composition (A) was poured into a cavity 2 of a lower 
mold section 1 to about one half of the cavity volume as shown in FIGURE 1 
and cured therein by heating at 150.degree. C. for 5 minutes. An upper 
mold section 3 was placed on the lower mold section 1 to close the cavity 
2. Silicone rubber composition (B) was injected onto the cured silicone 
resin (A) through a port 4 in the upper mold section 3 at an injection 
pressure of about 60 kg/cm.sup.2 and cured therein by heating at 
150.degree. C. for 5 minutes. There was obtained an integral product in 
which silicone resin and silicone rubber were firmly bonded. The product 
could be removed from the mold without sticking to the mold wall. 
The cured product of silicone resin composition (A) had a hardness of more 
than 95 on the measurement by using a Type A spring hardness tester 
according to the method described in JIS K-6301. The cured product of 
silicone rubber composition (B) had a hardness of 35 on the same Type A 
spring hardness tester measurement. 
For comparison purpose, the following experiment was conducted. 
The cured product of the silicone rubber composition (B) was prepared by 
using the mold shown in FIGURE 1 and injecting the composition (B) into 
the cavity 2 of the lower mold section 1 through the port 4 of the upper 
mold section 3 placing on the lower mold section 1 at an injection 
pressure of about 60 kg/cm.sup.2 to cure the composition (B) by heating at 
150.degree. C. for 5 minutes. Then the cured product was taken out from 
the mold and cut into halves. Next, one half of the cured product was 
inserted in the cavity 2 of the lower mold section 1 so that the cut 
surface of the cured product was positioned as the upper surface. The 
silicone resin composition (A) was poured on the cut surface of the cured 
silicone rubber (B) and cured in the cavity 2 by heating at 150.degree. C. 
for 5 minutes. 
The cured product of the silicone resin composition (A) was not bonded to 
the cured silicone rubber (B) at all. The cured silicone resin (A) was 
easily separated from the cured silicone rubber (B). 
The same result was obtained when the silicone resin composition (A) was 
poured on the non-cut surface of the cured silicone rubber (B). 
Example 2 
A silicone rubber composition (C) was prepared by adding 30 parts of dry 
silica having a specific surface area of 200 m.sup.2 /g, 5 parts of 
dimethoxydimethylsilane, and 1 part of water to 100 parts of a 
dimethylpolysiloxane blocked with a trivinylsiloxy unit at either end and 
having a viscosity of 1,000 poise at 25.degree. C., mixing them while 
heating the mixture at 150.degree. C. for 3 hours, and adding to the 
mixture 50 parts of the same polysiloxane as above and 1.0 part of 
1,6-bis(t-butylperoxy)hexane. 
As in Example 1, silicone resin composition (A) was cured in the mold and 
silicone rubber composition (C) was injected onto the cured silicone resin 
(A) and cured by heating at 150.degree. C. for 5 minutes. There was 
obtained an integral product in which silicone resin and silicone rubber 
were firmly bonded. The product could be removed from the mold without 
sticking to the mold wall. 
The cured product of silicone rubber composition (C) had a hardness of 40 
on the measurement by using a JIS A spring hardness tester according to 
JIS K-6301. 
Comparative Example 
To a mixture of 100 parts of a dimethylpolysiloxane represented by the 
average formula: 
##STR2## 
with a viscosity of 800 cP and 0.7 part of a polymethylhydrogensiloxane 
represented by the average formula: 
##STR3## 
with a viscosity of 100 cP was added a 2-ethylhexanol solution of 
chloroplatinic acid in an amount of 5 ppm, calculated as platinum, based 
on the total amount of the polysiloxanes, followed by mixing uniformly to 
prepare a curable organopolysiloxane composition. The composition was 
poured in an aluminum disk having a diameter of 60 mm and was cured by 
heating at 150.degree. C. for 30 minutes, to be a silicone gel product 
having a diameter of 60 mm and a thickness of 5 mm with a rubber hardness 
of 0 on the measurement by using a JIS A spring hardness tester according 
to JIS K 6301 and a penetration of 80 (ASTMD 1403). 
Next, as in Example 1, silicone resin composition (A) was poured on the 
above silicone gel and cured by heating at 150.degree. C. for 30 minutes. 
The cured product of the silicone resin composition (A) was not bonded to 
the silicone gel and was easily separated from the silicone gel. 
There have been described silicone resin/silicone rubber composite 
materials in which silicone resin and silicone rubber are firmly joined 
together. They are useful in various industrial fields including electric 
and electronic equipment, business machines, automobiles, and precision 
machines. 
Although some preferred embodiments have been described, many modifications 
and variations may be made thereto in the light of the above teachings. It 
is therefore to be understood that within the scope of the appended 
claims, the invention may be practiced otherwise than as specifically 
described.