Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-02-28
2003-02-04
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S034000, C528S038000
Reexamination Certificate
active
06515094
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to crosslinked organosilicone systems formed by the reaction of amino-substituted polysiloxanes with epoxy-substituted-polysiloxanes that exhibit excellent adhesion to a variety of substrates. Subject matter cross-linked silicone systems are useful as elastomers, sealants, electronic potting compounds, encapsulants, conformal coatings, foams, shock adsorbing gels, and molds.
PRIOR ART
It is well known in the art that organosilicone polymers, such as dimethylpolysiloxane, phenyl- and trifluoropropyl-substituted dimethylpolysiloxane copolymers, and the like, can be cross-linked to produce elastomers, adhesives, sealants, foams and gels via a number of methods. Perhaps the oldest method of achieving cross-linking of silicone polymers is the use of a peroxide, such as 2,4-dichlorobenzoyl peroxide, and heat to produce the cross-linked mass. Another method is the use of vinyl-substituted organopolysiloxane and peroxide, such a ditertiary-butyl peroxide to form a more uniform and reproducible cross-linked mass. Crosslinked organosilicone polymers can also be prepared by the platinum catalyzed hydrosilation reaction between silanic hydrogen fluids and polysiloxanes modified with the unsaturated groups. Examples of such systems are given in U.S. Pat. No. 4,970,252.
Another widely used method of cross-linking organosilicone copolymers is the condensation of hydroxy-terminated silicone polymers with multi-functional alkoxy silanes using metal soaps, such as dibutyltindilaurate, or stannous octoate.
Yet another method of cross-linking organosilicone polymers is by reacting hydroxy-functionalized fluids with silanic hydrogen fluids in the presence of a base, such as described in U.S. Pat. No. 4,177,176.
Examples of the reactive systems utilizing the reaction of an amine with an epoxy group can be found in the prior art. Most of this prior art, however, relate to amino- or epoxy-functionalized, trialkoxy silanes, or their hydrolyzates cured by themselves or with the organic resins.
U.S. Pat. No. 4,542,174 teaches combination of oxirane compounds and acylamino- or cyano-silane which are stable at room temperature and can be utilized as one-component additives for inorganic fillers employed in filled condensation polymer systems.
U.S. Pat. No. 5,314,980 discloses a coating composition comprising and epoxy component selected from the group consisting of epoxy silane, or epoxy silane hydrolysis/condensation products, an amine hardener selected from organic amines, aminosilane and hydrolyzed aminosilane and a metal component-containing stabilizer to delay crosslinking for more than 3 days. U.S. Pat. No. 4,378,250 teaches coating compositions comprising an organic solvent and a mixture of at least two components derived by partial hydrolysis of precursor epoxy- and amino-functionalized alkoxy silanes. Similar reactive coating compositions are disclosed in U.S. Pat. No. 3,961,977.
U.S. Pat. No. 3,837,876 relates to organosilicone compositions, comprising an organic solvent, a certain aminoalkylalkoxysilane and a certain epoxyalkoxysilane, useful in the improvement of adhesion of sealants and primers.
U.S. Pat. No. 5,703,178 describes heat ablative coating compositions prepared by combining an epoxysilane, an epoxy resin, a silicone intermediate, a silicon-modified polyether, an aminosilane, an organometallic catalyst and other components.
Existing silicone crosslinking technologies, although useful, present several disadvantages in the applications:
Platinum catalyzed addition cure systems are prone to catalyst poisoning, and, without the use of an adhesion promoter that must be applied separately, exhibit poor adhesion to metal, plastic, and glass substrates. These systems are also prone to produce by-product hydrogen gas during the cross-linking reaction; a phenomena that can result in the unintentional entrapment of gas bubbles within the cross-linked mass.
Condensation cure silicone systems produce by-products, such a methyl alcohol and ethyl alcohol, and once mixed, have short working life. Since water is essential to achieve cross-linking in these types of systems, other additives are typically required to achieve depth of cure. In addition, condensation cure silicone systems adhere poorly to substrates without use of an adhesion promoter or primer, and accordingly, their uses are limited to applications where these limitations are not restrictive.
Peroxide cross-linked systems require elevated temperatures to initiate cross-linking, and result in the formation of by-product acid or alcohol products. Post curing is generally required to remove these by-products from the cross-linked mass after initial cure. As with hydrosilation cure and condensation cure systems, an adhesion promoter or primer is generally required to obtain adhesion to metal, plastic, or glass substrates.
SUMMARY OF THE INVENTION
This invention relates to (1) novel reactive compositions comprising an amino-modified organopolysiloxane and an epoxy-modified organopolysiloxane and (2) a method for rapidly curing this composition into elastomers, sealants, electronic potting materials, encapsulants, conformal coatings, foams, shock adsorbing gels, and molds, wherein no by-product is produced during the curing process and the cross-linked material exhibits adhesion to metals, plastics, synthetic fibers, wood, paper, and glass.
The reactive compositions of present invention comprise:
a. an amino-modified organopolysiloxane of the average general formula:
Q
2
RSiO—(SiR
2
O)
x
—(SiRR
1
O)
y
—SiRQ
2
(I)
wherein Q is R or R
1
; R is selected from the group consisting of monovalent hydrocarbon groups having 1 to 10 carbon atoms; R
1
is R
2
NHR
3
; each R
2
is the same or different and is a divalent C
1
-C
6
alkylene group, optionally substituted with a hydroxyl group; R
3
is alkyl of C
1
-C
6
, an alkyl amine of C
1
-C
6
(i.e. a C
1
-C
6
alkyl group substituted with —NH
2
) or an alkanolamine of C
1
-C
6
(i.e. a C
1
-C
6
alkyl group substituted with —OH and with —NH
2
); x is zero or a positive number; y is a positive number and x+y are less than 1,100; and
b. an epoxy-modified organopolysiloxane of the average general formula:
Q′
2
RSiO—(SiR
2
O)
x
—(SiRR
4
O)
y
—SiRQ′
2
(II)
wherein Q′ is R or R
4
; R is as previously defined; R
4
is R
5
—R
6
; R
5
is a divalent hydrocarbon group with at least two carbons, which may be may be interrupted by an oxygen atom; R
6
is an epoxide-containing group.
DETAILED DESCRIPTION OF THE INVENTION
In formulas (I) and (II) above, the monovalent hydrocarbon groups R include alkyl, aryl and aralkyl groups, and may be the same or different from one another. Examples are methyl, ethyl, butyl, hexyl, phenyl, benzyl, and phenethyl. Of these, lower alkyl groups (C
1
-C
4
) are preferred. The most preferable R group is methyl in both formulas.
In formula (I) Q is preferably R, most preferably methyl. In formula (II), Q′ is preferably R
4
. In formula (I) R
2
is preferably ethylene or propylene. R
3
is most preferably, hydrogen, but other examples of R
3
include methyl, ethyl, propyl, aminoethyl, aminopropyl and propanolamino. Specific R
1
groups include propylamine, propanolamine, N-methyl-propylamine and N-propanolamino-aminopropyl.
In formula (II) the R
5
groups may be aliphatic, cycloaliphatic, aromatic or mixed aliphatic/aromatic groups, or (poly)ether groups, for instance ethylene, propylene, ethylenephenylene, propyleneoxyethylene, phenylethylene, ethylhexylene, and the like. Exemplary R
6
groups include glycidoxy, 3-methyl-4,5-cyclohexenyl oxide and 3,4-cyclohexenyl oxide. Exemplary R
4
groups include glycidoxypropyl, 2-(3,4-cyclohexene oxide)ethyl or 2-(3-methyl-4,5-cyclohexene oxide)ethyl.
Preferably x ranges from 20 to 1000 and y ranges from 1 to 50; more preferably x ranges from 50 to 800, most preferably 50 to 500, y ranges from 1 to 20 and x/y ranges from 30:1 to 200:1 in formula (I), and from 5:1 to 30:1 in formula (II).
The composition of the present invention m
Creamer Charles E.
Czech Anna M.
Crompton Corporation
Dilworth Michael P.
Moore Margaret G.
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