Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-11-20
2002-09-10
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C427S387000, C528S015000, C528S031000, C524S588000
Reexamination Certificate
active
06447922
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to curable silicone compositions. More specifically, the present invention is related to room temperature vulcanizable (RTV) adhesive formulations which provide adhesion to substrates.
Curable silicone compositions are used as laminates over a variety of substrates and in a wide variety of applications. In order to impart self-bonding adhesive properties to the silicone composition such that a primer is not needed between the silicone composition and a substrate, adhesion promoters in the silicone composition are commonly used.
Mitchell et al., U.S. Pat. No. 5,164,461, discuss an addition-curable silicone composition which includes a vinyl-containing polydiorganosiloxane, a hydrogen-terminated polysiloxane, and an adhesion promoter. The adhesion promoters include silylmaleates, silylmaleimides and silylfumarates. The silicone composition is useful for self-bonding to substrates such as plastics, metals, and glass at a cure temperature in a range between about 100° C. and about 150° C. The silicone composition disclosed has both excellent physical properties and excellent lap shear adhesive properties.
Stein et al., U.S. Pat. No. 5,414,066, is directed to a room-temperature addition-curable silicone adhesive composition which incorporates N-heterocyclic silanes as the adhesion promoter. The addition of the N-heterocyclic silane to a vinyl-containing polydiorganosiloxane and a hydrogen-terminated polysiloxane provides a silicone adhesive composition which cures at room temperature. The composition is directed to providing adhesion to substrates such as glass, plastics and metals.
Although silicone adhesive compositions which have the ability to cure at room temperature have been developed which provides adhesion to plastic and metal substrates, silicone adhesive compositions with new adhesion promoters are constantly being sought which can both cure at room temperature and include desired physical properties.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a silicone composition which comprises a room temperature vulcanizable adhesive formulation which comprises:
(A) at least one bis(trialkoxysilylalkyl)succinate,
(B) a vinyl-containing polydiorganosiloxane,
(C) a hydrogen-containing polysiloxane, and
(D) a catalytic amount of a hydrosilylation catalyst.
A further embodiment of the present invention is a method to provide cohesive failure to a silicone composition and a substrate which comprises the steps of:
(I) applying a silicone composition to a substrate wherein the silicone composition comprises:
(A) at least one bis(trialkoxysilylalkyl)succinate,
(B) a vinyl-containing polydiorganosiloxane,
(C) a hydrogen-containing polysiloxane, and
(D) a catalytic amount of a hydrosilylation catalyst, and
(II) curing the silicone composition.
A further embodiment of the present invention provides a bis(trialkoxysilylalkyl)succinate which comprises the formula
wherein R
3
and R
1
independently at each occurrence is hydrogen, an alkyl radical, aryl radical, aralkyl radical, alkaryl radical, cycloalkyl radical, or bicycloalkyl radical; R
2
comprises hydrogen or an alkyl radical; and “x” is in a range between about 3 and about 8.
DETAILED DESCRIPTION OF THE INVENTION
It has been found that the incorporation of an effective amount of a bis(trialkoxysilylalkyl)succinate as an adhesion promoter into silicone compositions provides a room temperature vulcanizable (RTV) adhesive formulation which adheres to metal substrates and polymer substrates. An “effective amount of a bis(trialkoxysilylalkyl)succinate” as used herein is an amount of the adhesion promoter which promotes adhesion to metal and polymer substrates. Preferably, the amount of adhesion promoter is in a range between about 0.1% by weight and about 5% by weight of the total room temperature vulcanizable adhesive formulation, herein referred to as “total composition” or “silicone composition”.
The adhesion promoter is (A) at least one bis(trialkoxysilylalkyl)succinate which usually has the general formula (I):
wherein “x” has a value in a range between about 3 and about 8. Each R
3
and R
1
independently represents hydrogen or a monovalent hydrocarbon group such as alkyl radicals, aryl radicals, aralkyl radicals, alkaryl radicals, cycloalkyl radicals, or bicycloalkyl radicals. Each R
2
represents hydrogen or an alkyl radical. The term “alkyl radical” is intended to designate both normal alkyl and branched alkyl radicals. Normal and branched alkyl radicals are preferably those containing carbon atoms in a range between about 1 and about 20, and include as illustrative non-limiting examples methyl, ethyl, propyl, isopropyl, butyl, tertiary-butyl, pentyl, neopentyl, hexyl, octyl, decyl, dodecyl. Aryl radicals include examples such as phenyl and tolyl. Cyclo- or bicycloalkyl radicals represented are preferably those containing ring carbon atoms in a range between about 3 and about 12 with a total number of ring carbon atoms less than or equal to about 50. Some illustrative non-limiting examples of these cycloalkyl radicals include cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, and cycloheptyl. Preferred aralkyl radicals are those containing carbon atoms in a range between about 7 and about 14; these include, but are not limited to, benzyl, phenylbutyl, phenylpropyl, and phenylethyl. Most preferably, a bis(trimethoxysilylpropyl)succinate is used as the adhesion promoter wherein R
3
comprises an alkyl radical with 1 carbon atom, R
1
comprises hydrogen, R
2
comprises hydrogen, and “x” is 3.
The bis(trialkoxysilylalkyl)succinate of the present invention can be synthesized by first effecting a reaction between diallylsuccinate and a hydrosilylation catalyst, for example, a platinum catalyst to form a succinate-catalyst mixture. The resulting succinate-catalyst mixture is then reacted with trialkoxysilane to form the bis(trialkoxysilylalkyl)succinate.
In addition to the effective amount of at least one bis(trialkoxysilylalkyl)succinate (A), the room temperature vulcanizable adhesive formulation includes
(B) a vinyl-containing polydiorganosiloxane,
(C) a hydrogen-containing polysiloxane, and
(D) a catalytic amount of a hydrosilylation catalyst.
The vinyl-containing polydiorganosiloxane has the general formula (II),
(R
4
)
2
R
5
SiO[(R
4
)
2
SiO]
m
[R
4
R
5
SiO]
n
Si(R
4
)
2
R
5
(II)
wherein R
5
is an ethylenic unsaturated radical, preferably vinyl; R
4
is selected from the group consisting of C
1-8
alkyl radicals, phenyl radicals, and C
3-10
fluoroalkyl radicals and mixtures thereof, “m”+“n” has a value sufficient to provide a total vinyl-containing composition with a viscosity in a range between about 100 centipoise and about 100,000 centipoise at 25° C., and preferably, in a range between about 3000 centipoise and about 95,000 centipoise at 25° C. and a vinyl content in a range between about 0.02% by weight and about 2.0% by weight of the vinyl-containing polydiorganosiloxane. Radicals represented by R
4
are preferably C
1-4
alkyl radicals and more preferably, methyl. Typically, the vinyl-containing polydiorganosiloxane is present in a range between about 10% by weight and about 50% by weight of the total composition.
The vinyl-containing polydiorganosiloxane (B) includes (1) the vinyl-containing polydiorganosiloxane and may also include (2) a vinyl-containing siloxane resin copolymer.
The vinyl-containing siloxane resin copolymer is present in a range between about 0% by weight and about 70% by weight of the total composition having
(R
6
)
3
SiO
1/2
units (“M”) and SiO
4/2
units (“Q”),
wherein R
6
is a vinyl radical, or a monovalent hydrocarbon radical free of aliphatic unsaturation and containing no more than six carbon atoms, the ratio of (R
6
)
3
SiO
1/2
units to SiO
4/2
units being in a range between about 0.5:1 and about 1.5:1, and the resin having a vinyl content in a range between about 1.5% by weight and about 3.5% by weight of the vinyl-containing siloxane resin copolymer. The vinyl-containing
Stein Judith
Wood Christina Marie Darkangelo
Youssef Eriny Demian
Bennett Bernadette M.
General Electric Company
Johnson Noreen C.
Moore Margaret G.
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