Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-04
2001-04-24
Lipman, Bernard (Department: 1773)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S458000, C524S506000, C524S522000
Reexamination Certificate
active
06221938
ABSTRACT:
BACKGROUND OF THE INVENTION
Conventional organic solvent based polymer compositions have become disfavored due to problems associated with environmental pollution, conservation of resources and providing a safe working environment. Instead, aqueous solution or dispersion type coating compositions have been proposed as alternatives. In particular, much attention has been paid to reactive polymer emulsions and dispersions because of the ease with which they provide improved properties such as water and solvent resistance.
The use of combinations of polymers, aqueous emulsions and dispersions (latices) and epoxy resins or compounds is well known in the art. For example, U.S. Pat. No. 4,049,869 to Long taught a composition including a high acid acrylic latex (5 to 20% by weight), a crosslinking agent (1 to 10%) and an ultraviolet absorber for use in preserving porous inorganic substrates. The crosslinking agent can include an epoxy resin.
Water-soluble silanes as additives in latex systems have also been disclosed in the prior art. For example, U.S. Pat. No. 5,017,632 to Bredow disclosed coating compositions for Portland cement or metal. The coating composition thereof can be mixed from a pair of storage stable components; a dry mix including a fine particle size filler, an epoxy resin and optionally, a coarse aggregate, and a wet mix including a polymer latex, an amine-functional epoxy curing agent, and a water-soluble epoxy- or amino-silane.
U.S. Pat. No. 5,100,955 to Pons disclosed coating and adhesive compositions based on aqueous dispersions of addition polymers of one or more olefinically unsaturated monomers, emulsion stabilizers and/or emulsifiers and a water-soluble epoxysilane. The water-soluble epoxysilane is added preferably after the polymerization of the addition polymer. The shelf life, however, of such compositions is only from two to three days.
EP Patent No. 401,496 to Hahn disclosed aqueous silicon-modified plastic dispersions as adhesives by epoxysilane-treatment of a dispersion of emulsion copolymers containing carboxylic acid, amide and sulfonic acid groups. Water soluble epoxysilanes of the formula R
1
R
2
R
3
R
4
Si are disclosed with R
1
=(cyclo)alkyl with reactive oxirane group; R
2
=(cyclo)alkoxy, (cyclo)alkyl, aryl or aralkyl; R
3
, R
4
=(cyclo)alkoxy, or OH. However, the composition of the synthetic latex is specific. Furthermore, the neat epoxysilane is added directly to the polymer.
In addition to these coating technologies, emulsions of trialkoxysilanes have been previously reported used as waterproofing agents. For example, buffered aqueous silane emulsions are disclosed in U.S. Pat. Nos. 4,877,654 and 5,393,330. Alkylalkoxysilanes are also emulsified with nonionic and anionic emulsifiers for water repellency properties in U.S. Pat. No. 5,226,954.
SUMMARY OF THE INVENTION
The present invention provides shelf stable compositions comprised of epoxysilane, a water dispersible or emulsifiable organic polymer which contains a functional group with an active hydrogen, together with a catalyst for curing the composition. The corresponding method of the present invention for the preparation of a shelf stable composition comprises combining an epoxysilane compound in water with the organic polymer which contains a functional group with an active hydrogen, and adding at any point a catalyst for curing the composition.
One embodiment of the present invention provides shelf stable compositions comprised of water-insoluble or slightly soluble epoxysilanes, emulsifier and a water dispersible or emulsifiable organic polymer which contains a functional group with an active hydrogen, together with a catalyst for curing the composition. The method of the present invention for the preparation of such a shelf stable composition comprises: (a) dispersing a water insoluble or slightly soluble epoxysilane compound in an aqueous solution with emulsifier to yield an aqueous emulsion, and (b) adding the silane emulsion to a water dispersed or emulsified organic polymer which contains a functional group with an active hydrogen, and adding at any point a catalyst for curing the composition.
Another aspect of the present invention is to provide an article coated and cured with any of the aforementioned reactive, aqueous compositions.
The compositions of the present invention are stable for at least about six (6) months. Moreover, improved properties such as solvent resistance, adhesion, smoothness, hardness and mar resistance are achieved with compositions of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides stable epoxy silane containing compositions and methods for the preparation of stable epoxy-silane containing compositions comprising: (I) an epoxysilane, which can be a water soluble, water insoluble or slightly soluble epoxysilane; (II) optional emulsifier; (III) water; (IV) water dispersible or emulsified polymer containing a functional group with an active hydrogen; and (V) a catalyst for cure of the composition. Also provided are two part systems such that an epoxysilane emulsion comprising components (I)-(III) are combined and the components (IV) and (V) may be added upon use of components (I) to (III). Moreover, additional components, such as pH buffers may be added. Contemplated herein are also compositions for the preparation of the above compositions, namely the silane (I), the emulsifier (II), and the catalyst (V).
The present invention provides highly stable epoxysilane containing compositions that do not seed or gel during storage. Generally, they are stable for at least two to three weeks and more preferably two to three months. In fact, these compositions containing less than twenty weight percent epoxysilane last longer than six months of storage. This compares favorably with the prior art which taught silane/polymer compositions which would lose properties, such as adhesion, or even gel after two-three weeks.
The catalyst can be any that permits curing of the composition at lower temperatures, on the order of 150F., than is the case with compositions not containing the catalyst. The presence of the catalyst provides the additional advantage that one can use relatively water-soluble epoxysilanes and catalysts, thus providing greater freedom of operation and permitting the user to avoid having to use an emulsifier where such a component is not desired.
The cured product exhibits very satisfactory to superior properties such as high resistance to chemicals and high resistance to stains.
(I) SILANES
The epoxy functional silanes useful herein are of the general structure R
1
a
R
2
b
Si(OR
3
)
4−a−b
where R
1
is an epoxy substituted alkyl or aralkyl group, where the alkyl may have from four to thirty carbon atoms, R
3
is an alkyl or alkoxy-substituted alkyl, aryl or aralkyl group having from one to ten carbon atoms, R
2
is an alkyl group or alkoxy substituted alkyl, aryl or aralkyl group having from one to ten carbon atoms, a is one to three, and b is zero to two, with the proviso that a+b is 1, 2, or 3. Each R group may be cyclic, branched or linear. Water insoluble or slightly soluble silanes useful in this invention include silanes with solubilities between 0.1 and 8.0 weight percent in water. Water insoluble epoxy silanes are preferred. However, water soluble silanes can be used although compositions made with such silanes may be less stable for extended periods of time, i.e., more than two to three days at ambient conditions.
The preferred epoxy functional silanes include:
where: R is (CH
2
)
m
, where m has a value of zero to six;
R
2
is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms;
R
3
is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms;
R
4
, R
5
, R
6
or R
7
are each hydrogen or an alkyl group having from one to six carbon atoms;
R
8
is an alkyl group having from one to four carbon atoms or aralkyl or aryl group having six to ten
Chen Ming J.
Osterholtz Frederick D.
Lipman Bernard
OSi Specialities Inc.
Scully Scott Murphy & Presser
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