Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-12-13
2001-09-04
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S032000, C528S015000, C556S408000
Reexamination Certificate
active
06284861
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a silicone rubber composition, and more particularly relates to a silicone rubber composition with excellent adhesion to organic resins even after being cured at a relatively low temperature, and even more particularly relates to a silicone rubber composition that is favorable for use in composite molding, whose adhesion to organic resins and mold release properties are excellent in composite molding, such as insert molding or multi-color molding, of an organic resin and a silicone rubber composition.
A method that has been adopted for bonding a silicone rubber to an organic resin in composite molding such as insert molding or multi-color molding involves priming a pre-molded organic resin and then curing it while it is brought together with a silicone rubber composition. A problem with this method, however, is that a priming step is required, and the adhesion of the silicone rubber decreases if this priming treatment is inadequate. Another problem is that the silicone rubber composition has to be cured at a relatively high temperature in order for this composition to adhere sufficiently to an organic resin, so organic resins with low heat resistance can not be used.
In addition, to bond a silicone rubber securely to an organic resin, there are known methods involving the use of an organic resin containing aliphatic unsaturated groups (Japanese Laid-Open Patent Applications 6-171021, 6-171022, and 6-171023), and methods featuring the use of a silicone rubber composition to which vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyl-trimethoxysilane, or another such adhesion improver has been added. A limitation to the former method, however, was that a special organic resin had to be used, while a problem with the latter method was that the mold release properties decreased, and in extreme cases, the silicone rubber even adhered to the mold.
The inventors arrived at the present invention as a result of diligent study aimed at solving the above problems. Specifically, it is an object of the present invention to provide a silicone rubber composition with excellent adhesion to organic resins even after being cured at a relatively low temperature, and in turn a silicone rubber composition that is favorable for use in composite molding, whose adhesion to organic resins and mold release properties are excellent in composite molding, such as insert molding or multi-color molding, of an organic resin and a silicone rubber composition.
SUMMARY OF INVENTION
A silicone rubber composition comprising (A) 100 weight parts of a polydiorganosiloxane mixture comprising (i) I to 99 wt % polydiorganosiloxane having at least two silicon atom-bonded vinyl groups per molecule and (ii) the remaining percentage of polydiorganosiloxane having at least two non-vinyl silicon atom-bonded alkenyl groups per molecule, (B) a polyorganosiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, (C) 0.1 to 10 weight parts of a silatrane derivative described by general formula
where each R
1
group is independently selected from the group consisting of a hydrogen atom and alkyl groups; each R
2
group is independently selected from the group consisting of a hydrogen atom, alkyl groups, and alkenyloxyalkyl groups described by the general formula
—R
4
O—R
5
where R
4
is an alkylene group, and R
5
is an alkenyl group; at least one R
2
group is an alkenyloxyalkyl group; and R
3
is a group selected from the group consisting of substituted and unsubstituted monovalent hydrocarbon groups, C
1
to C
10
alkoxy groups, glycidoxyalkyl groups, oxiranylalkyl groups, acyloxyalkyl groups, and aminoalkyl groups; and
(D) a platinum type catalyst in an amount sufficient to cure the composition.
DESCRIPTION OF INVENTION
The silicone rubber composition for composite molding of the present invention comprises:
(A) 100 weight parts of a polydiorganosiloxane mixture comprising (i)
1
to 99 wt % polydiorganosiloxane having at least two silicon atom-bonded vinyl groups per molecule and (ii) the remaining percentage of polydiorganosiloxane having at least two non-vinyl silicon atom-bonded alkenyl groups per molecule;
(B) a polyorganosiloxane having at least two silicon atom-bonded hydrogen atoms per molecule in an amount such that the ratio of the number of moles of hydrogen atoms bonded to silicon atoms in this component to the number of moles of alkenyl groups bonded to silicon atoms in component (A) is between 0.5:1 and 20: 1;
(C) 0.1to 10 weight parts of a silatrane derivative described by general formula:
where each R
1
group is independently selected from the group consisting of a hydrogen atom and alkyl groups; each R
2
group is independently selected from the group consisting of a hydrogen atom, alkyl groups, and alkenyloxyalkyl groups described by the general formula —R
4
—O—R
5
, where R
4
is an alkylene group, and R
5
is an alkenyl group; at least one R
2
group is an alkenyloxyalkyl group; and R
3
is selected from the group consisting of substituted and unsubstituted monovalent hydrocarbon groups, C
1
to C
10
alkoxy groups, glycidoxyalkyl groups, oxiranylalkyl groups, acyloxyalkyl groups, and aminoalkyl groups; and
(D) a platinum type catalyst in an amount sufficient to cure the composition.
The silicone rubber composition of the present invention will now be described in detail. Component A is the principal component of the present composition, and is a polydiorganosiloxane mixture comprising (i) a polydiorganosiloxane having at least two silicon atom-bonded vinyl groups per molecule and (ii) a polydiorganosiloxane having at least two non-vinyl silicon atom-bonded alkenyl groups per molecule. This component A is composed of 1 to 99 wt % component (i) and the remaining weight percentage is component (ii), and is preferably composed of 10 to 99 wt % component (i) and the remaining weight percentage of component (ii), and it is particularly favorable for component (i) to account for 50 to 99 wt %, and component (ii) the remaining weight percentage. This is because the adhesion of the silicone rubber to organic resins when cured at a relatively low temperature will tend to decrease if the content of component (i) is below the lower limit of this range, whereas the mechanical properties of the silicone rubber will tend to suffer if the upper limit of this range is exceeded.
Component (i) is a polydiorganosiloxane having at least two silicon atom-bonded vinyl groups per molecule. The molecular structure of component (i) is substantially linear, but part of the molecular chain may be somewhat branched. The bonding position of the vinyl groups in component (i) is not restricted, and may be at the molecular chain terminals, pendant, or both, but the molecular chain terminals is preferred because the mechanical properties of the obtained silicone rubber will be superior. Examples of groups that can be bonded to the silicon atoms besides vinyl groups in component (i) include alkyl groups such as methyl, ethyl, propyl, butyl, and octyl; aryl groups such as phenyl and tolyl; halogenated alkyl groups such as chloromethyl and 3,3,3-trifluoropropyl; and other substituted and unsubstituted monovalent hydrocarbon groups having no aliphatic unsaturated carbon-carbon bonds. There are no restrictions on the viscosity of component (i), but a range of 10 to 1,000,000 mPa·s at 25° C. is preferable.
Examples of the polydiorganosiloxane of component (i) include a dimethylvinylsiloxy group-capped polydimethylsiloxane capped at both ends of the molecular chain, a trimethylsiloxy group-capped dimethylsiloxane.methylvinylsiloxane copolymer capped at both ends of the molecular chain, a dimethylvinylsiloxy group-capped dimethylsiloxane.methylvinylsiloxane copolymer capped at both ends of the molecular chain, a dimethylvinylsiloxy group-capped dimethylsiloxane.methylphenylsiloxane copolymer capped at both ends of the molecular chain, and a dimethylvinylsiloxy group-capped dimethylsiloxane.methyl (3,3,3,-trifluoropropyl)-siloxane copolymer ca
Nakamura Akito
Takuman Osamu
Yoshitake Makoto
Boley William F.
Dawson Robert
Dow Corning Toray Silicone Ltd.
Streu Rick D.
Warren Jennifer S.
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