Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-03-30
2001-10-02
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S015000, C528S031000, C556S440000
Reexamination Certificate
active
06296944
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 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 has been developed, 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 at least one bis(trialkoxysilylalkyl)hydromuconate.
A further embodiment of the present invention is a method to provide cohesive failure to a silicone composition and metal substrate which comprises the steps of:
(I) applying a silicone composition to a substrate wherein the silicone composition comprises a bis(trialkoxysilylalkyl)hydromuconate, and
(II) curing the silicone composition.
A further embodiment of the present invention provides a bis(trialkoxysilylalkyl)hydromuconate which comprises the formula
wherein R comprises an alkyl radical, aryl radical, aralkyl radical, alkaryl radical, cycloalkyl radical, or bicycloalkyl 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)hydromuconate as an adhesion promoter into silicone compositions provides a room-temperature vulcanizable adhesive formulation which adheres to untreated metal substrates. An “effective amount of a bis(trialkoxysilylalkyl)hydromuconate” as used herein is an amount of the adhesion promoter 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”.
The adhesion promoter is at least one bis(trialkoxysilylalkyl)hydromuconate which has the general formula (I):
wherein “x” has a value in a range between about 3 and about 8. Each R independently represents a monovalent hydrocarbon group such as alkyl radicals, aryl radicals, aralkyl radicals, alkaryl radicals, cycloalkyl radicals, or bicycloalkyl radicals. 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)hydromuconate is used as the adhesion promoter wherein R comprises an alkyl radical with 1 carbon atom and “x” is 3.
The bis(trialkoxysilylalkyl)hydromuconate can be synthesized by first synthesizing an allyl ester by effecting a reaction between hydromuconic acid, a thionyl halide, such as thionyl chloride, and dimethylformamide. The resulting allyl ester can be reacted with trialkoxysilane using a hydrosilylation catalyst, for example, a platinum catalyst to form the bis(trialkoxysilylalkyl)hydromuconate.
In addition to the effective amount of at least one bis(trialkoxysilylalkyl)hydromuconate, the room-temperature vulcanizable adhesive formulation includes
(A) a vinyl-containing polydiorganosiloxane present in a range between about 10% by weight and about 50% by weight of the total composition,
(B) a hydrogen-containing polysiloxane in a range between about 1% by weight and about 15% by weight of the total composition,
(C) a catalytic amount of a hydrosilylation catalyst of at least about 0.1 part per million,
(D) an extending filler in a range between about 0% by weight and about 50% by weight of the total composition, and
(E) a reinforcing filler in a range between about 0% by weight and about 70% by weight of the total composition.
The vinyl-containing polydiorganosiloxane (A) includes (1) a vinyl-containing polydiorganosiloxane and optionally, (2) a vinyl-containing siloxane resin copolymer.
The vinyl-containing polydiorganosiloxane has the general formula (II),
(R)
2
V
i
SiO[(R)
2
SiO]
m
[RV
i
SiO]
n
Si(R)
2
V
i
(II)
wherein “V
i
” is a vinyl radical, “R” 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” are preferably C
1-4
alkyl radicals and more preferably, methyl.
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 comprising,
(R
1
)
3
SiO
1/2
units (“M”) and SiO
4/2
units (“Q”),
wherein “R
1
” 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
1
)
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 siloxane resin copolymer is also referred to as the “vinyl-containing MQ resin” or “M
Vi
Q”.
The vinyl-containing siloxane resin copolymer may further contain (i) R
1
SiO
3/2
units, (ii) (R
1
)
2
SiO
2/2
units, or combinations thereof, where the (R
1
)
2
SiO
2/2
units are present in an amount in a range between about 0 mole percent and about 10 mole percent based on the total number of moles of siloxane units in the vinyl-containing silo
Bennett Bernadette M.
General Electric Company
Johnson Noreen C.
Moore Margaret G.
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