Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2002-03-11
2004-07-27
Robertson, Jeffrey B. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C106S287130, C106S287160, C525S479000, C526S279000, C526S319000, C526S328000, C526S328500, C526S329500, 53, 53
Reexamination Certificate
active
06767642
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to crosslinkable polymers, and more particularly to crosslinkable acrylosilane polymers containing vinyl silane monomers, and a process for preparing the same. It also relates to acid etch resistant high solids solvent borne coating compositions comprising a crosslinkable acrylosilane polymer containing a vinyl silane which can be used for finishing automobile and truck exteriors.
Coating compositions containing crosslinkable film-forming acrylosilane polymers that have excellent resistance to etching from acid rain and other environmental pollutants are described in U.S. Pat. No. 5,162,426 to Hazan et al. issued Nov. 10, 1992. Nowadays, these coatings are widely used for finishing the exteriors of automobile and truck bodies.
While such coatings function very well, the method described for their preparation provides no convenient way for incorporating much less expensive vinyl silane monomers such as vinyl alkoxy silanes into the acrylosilane polymer molecules. Vinyl alkoxy silanes confer certain advantages to these coatings which have gone unrealized up to now. U.S. Pat. No. 5,886,125 to Huybrechts issued Mar. 23, 1999 discloses crosslinkable copolymers comprising vinyl alkoxy silane monomers and vinyl esters of branched fatty acids. While these copolymers produce etch resistant films, it is desirable to obtain copolymers comprising vinyl alkoxy silane monomers without the use of vinyl esters of branched fatty acids.
Therefore, there is still a need for new chemistries and convenient methods to broaden the choice of silane monomers that can be used to optimize the performance of these coating compositions while at the same time significantly reducing their cost.
SUMMARY OF THE INVENTION
The present invention provides a process for preparing crosslinkable acrylosilane polymers useful in forming acid etch resistant coating compositions from vinyl alkoxy silane monomers, which comprises copolymerizing components A, B and optionally C (hereinafter defined) together in the proportions indicated herein.
The crosslinkable acrylosilane polymer compositions made by the above process also are a part of this invention. More particularly, the present invention provides crosslinkable polymeric compositions having a weight average molecular weight below about 40,000 derived from A, B and optionally C, wherein:
(A) is about 5 to 75% by weight, based on the weight of acrylosilane polymer, a vinyl alkoxy silane monomer represented by the general formula
wherein R
1
is an aryl or alkyl group having 1 to 10 carbon atoms, R
2
is a hydrolysable group, m is 0 or 1, and n is 0 or a positive integer from 1 to 10;
(B) is about 25 to 95% by weight, based on the weight of the acrylosilane polymer, of one or more of polymerizable monomers selected from the group consisting of esters of acrylic acid; and,
(C) is about 0 to 70% by weight, based on the weight of the acrylosilane polymer, of one or more ethylenically unsaturated monomers other than (a) and (b) selected from the group consisting of esters of methacrylic acid, styrenic monomers, and combinations thereof.
The polymer compositions of this invention give an excellent balance of solvent resistance, chemical resistance, hardness, flexibility and adherence to a variety of substrates at a much lower cost. More specifically, such compositions are particularly useful in formulating acid etch resistant solvent borne coating compositions used as automotive top coats and in particular clear coating compositions for clear coat/color coat finishes for automobiles and trucks. Also included within the scope of this invention are coating compositions formed from the above polymers and substrates coated with the coating compositions disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
The novel process of this invention provides a convenient way to incorporate vinyl alkoxy silane monomers into an acrylosilane polymer. The acrylosilane polymers so prepared can then be used as the main film-forming component in acid etch resistant coating compositions that are described in U.S. Pat. No. 5,162,426, previously mentioned. That description is incorporated by reference herein in its entirety.
The process of this invention comprises copolymerizing a vinyl alkoxy silane monomer (A) predominantly with acrylate monomers (B) and optionally with other ethylenically unsaturated comonomers (C) such as styrenic or methacrylate monomers. The term “acrylate” as used herein refers to esters of acrylic acid. The term “methacrylate” as used herein refers to esters of methacrylic acid. The term “styrenic” refers to unsubstituted styrene monomers or alkyl substituted styrene monomers having about 1-4 carbon atoms in the alkyl group.
In this invention, it should be understood that the amount of any additional comonomer (C) which is present should not be so great as to adversely affect the desirable polymerization properties such as the polymer conversion rate. Preferably, the weight percentage of any additional comonomer (C) present is not so great as to reduce the polymer conversion rate below about 90%, preferably not below 97%, and even more preferably not below 98-99% conversion. In a typical embodiment, the weight percentage of any additional comonomer (C) present is no greater then the weight percentage of the acrylate monomer (B) present. In one preferred embodiment, only monomers (A) and (B) are present. This ensures almost 100% conversion.
Previously, no convenient way existed to incorporate vinyl alkoxy silane monomers into the acrylosilane polymer, due to poor compolymerization with other monomers, resulting in poor conversion of monomer to polymer. Instead, it had been the standard practice to use (meth)acryloxy silane monomers, such as methacryloxy propyltrimethoxy silane, as the silane monomer. It has now surprisingly been found that when vinyl alkoxy silane is copolymerized predominantly with or, in the alternative, only with acrylate monomers, the conversion is good and the yield is high, thus providing a convenient method to incorporate vinyl alkoxy silanes into the polymer. The acrylosilane polymer so prepared can then be used as the main component in acid etch resistant coating compositions and in particular in clear coating compositions for clear coat/color coat finishes for automobiles and trucks.
Preferably, the acrylosilane polymer prepared in accordance with this invention is the polymerization product of about 5-75%, preferably 10-50%, by weight of ethylenically unsaturated vinyl alkoxy silane monomers and correspondingly about 25-95%, preferably 50-90%, by weight of ethylenically unsaturated acrylate monomers, and optionally 0-70%, preferably 0-40%, by weight of a different ethylenically unsaturated monomer selected from one or both of a styrenic and methacrylate monomer, based on the total weight of the acrylosilane polymer. Illustrative of the vinyl alkoxy silane monomers which can be used to prepare the acrylosilane polymer are represented by the general formula
wherein R
1
is an aryl or alkyl group having 1 to 10 carbon atoms, R
2
is a hydrolysable group, m is 0 or 1, and n is 0 or a positive integer from 1 to 10. Preferably, m is 0, R
2
is CH
3
O, and n is 0.
Typical examples of such vinyl alkoxy silanes are vinyl trimethoxy silane, vinyl methyldimethoxy silane, vinyl triethoxy silane, and vinyl tris (2-methoxyethoxy) silane, and the like.
The acrylate monomers which can be used to prepare the acrylosilane polymer include alkyl acrylates, where the alkyl groups have 1-12 carbon atoms, preferably 3-8 carbon atoms. Typical examples of such alkyl acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, pentyl acrylate, ethyl hexyl acrylate, nonyl acrylate, lauryl acrylate and the like. Cycloaliphatic acrylates can also be used, for example, such as isobornyl acrylate, trimethylcyclohexyl acrylate, t-butyl cyclohexyl acrylate and the like. Aryl acrylates also can be used, for example, such as benzyl acrylate. Polyacrylate monom
Chung Ding-Yu
Hazan Isidor
Paquet, Jr. Donald A.
Benjamin Steven C.
E. I. du Pont Nemours and Company
Robertson Jeffrey B.
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