Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-01
2003-05-20
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S502000, C524S588000, C524S599000, C524S606000, C524S612000
Reexamination Certificate
active
06566437
ABSTRACT:
The present invention relates to coating compositions and a method for producing wear-resistant coating compositions. In particular, the present invention relates to aqueous coating compositions which include an aqueous emulsion polymer having at least two functional groups reactive with carbodiimide moieties, a polycarbodiimide, and an alkoxysilane which is either part of the polycarbodiimide, reactive with the polycarbodiimide, or reactive with the aqueous emulsion polymer.
Traffic marking paints are applied to roads, parking lots, and the like, typically concrete and asphalt surfaces, to instruct users and to demarcate traffic lanes, parking spaces, and the like. As the replacement of solvent-borne paints continues in order to minimize air pollution, aqueous traffic marking compositions having a useful balance of dried film properties have been sought. One of the most important properties of traffic marking compositions is the wear-resistance of the dried coating under use conditions. The greater the wear-resistance, the longer the useful lifetime of the composition.
U.S. Pat. Nos. 5,047,588, 5,104,928, 4,487,964, 4,649,170, 5,066,705, 5,047,588, World Patent No. 93/22,282, Canadian Patent No. 2,000,607, and EP-B-0,628,582, EP-B-0,277,361, EP-B-0,274,402, EP-B-0,259,511, and EP-B-0,449,143 disclose two-pack aqueous coating compositions which include water-dispersible, carboxylic acid-functional polymers and a polycarbodiimide. However, none of these sources discloses the use of reactive alkoxysilanes in conjunction with polycarbodiimides, which is required to produce the improved durability.
U.S. Pat. No. 5,258,481 discloses two-pack aqueous coating compositions which include water-dispersible carboxylic acid functional polymers and an alkoxysilane-functional polycarbodiimide. However, this reference does not disclose the use of such compositions as traffic markings, nor does it disclose the utility of such coatings when applied to cementitious or mineral surfaces with which the alkoxysilane-functional polycarbodiimides are believed to react.
I have made the surprising finding that combining: a polycarbodiimide having at least two carbodiimide groups; an aqueous emulsion polymer bearing at least two functional groups reactive with carbodiimide and at least one functional group reactive with an alkoxysilane; and an alkoxysilane bearing at least one functional group reactive with the emulsion polymer results in an aqueous coating composition that readily crosslinks during application and drying to form a durable coating. Similarly, I have found that polycarbodiimides, alkoxysilanes reactive with carbodiimide moieties, and aqueous emulsion polymer having multiple functional groups reactive with carbodiimide moieties may be combined to form a coating composition such that, even in the presence of water, the reactive species combine to form crosslinks during application of the composition to and drying of the resultant coating upon the surface of a substrate, thereby hardening the coating and rendering it highly wear resistant. In addition, I have found that polycarbodiimides bearing alkoxysilane groups may be combined with aqueous emulsion polymer bearing multiple groups reactive with carbodiimide to form an aqueous traffic marking composition that crosslinks during application to road surfaces, thereby hardening the traffic marking and rendering it highly wear resistant.
While not wishing to be bound by theory, it is believed that a substantial portion of the enhanced durability observed for the traffic markings of this invention derives from formation of covalent bonds between the alkoxysilane groups and hydroxyl groups resident on cement and asphalt surfaces. Those covalently bound alkoxysilane groups are themselves linked to the binder polymer of the coating, effectively linking the entire coating to the road surface. While the compositions of the present invention are particularly useful as traffic marking compositions and the methods of the present invention are particularly useful for forming traffic markings, the compositions and methods are also generally useful as coating compositions and methods of forming coatings on a wide variety of substrate surfaces.
The first aspect of the present invention relates to an aqueous coating composition including:
(a) a polycarbodiimide having at least two carbodiimide groups;
(b) an aqueous emulsion polymer; and
(c) an alkoxysilane;
wherein the aqueous emulsion polymer has at least two functional groups reactive with the carbodiimide groups and at least one functional group reactive with the alkoxysilane; and
wherein the alkoxysilane has at least one functional group reactive with the aqueous emulsion polymer.
A second aspect of the present invention relates to a method for producing a wear-resistant coating on a surface of a substrate including:
(1) applying to the surface a layer of coating composition including:
(a) a polycarbodiimide having at least two carbodiimide groups;
(b) an aqueous emulsion polymer; and
(c) an alkoxysilane;
wherein the aqueous emulsion polymer has at least two functional groups reactive with the carbodiimide groups and at least one functional group reactive with the alkoxysilane; and
wherein the alkoxysilane has at least one functional group reactive with the aqueous emulsion polymer; and
(2) allowing the coating composition to dry.
A third aspect of the present invention is directed at a method for producing a wear-resistant coating on a surface of a substrate including:
(1) applying to the surface a layer of coating composition including:
(a) a polycarbodiimide having at least two carbodiimide groups;
(b) an aqueous emulsion polymer; and
(c) an alkoxysilane;
wherein the aqueous emulsion polymer has at least two functional groups reactive with the carbodiimide groups; and
wherein the alkoxysilane has least one functional group reactive with the carbodiimide groups; and
(2) allowing the aqueous coating composition to dry.
A fourth aspect of the present invention is a method for producing a wear-resistant traffic marking on a road surface including:
(1) applying to the road surface a layer of a traffic marking composition comprising:
(a) an aqueous emulsion polymer; and
(b) a polycarbodiimide having at least two carbodiimide groups;
wherein the aqueous emulsion polymer has at least two functional groups reactive with the carbodiimide groups; and
wherein the polycarbodiimide has at least one alkoxysilane group; and
(2) allowing the traffic marking composition to dry.
The polymer of the present invention is referred to herein as a “binder polymer”. The specific method by which a binder polymer is prepared is not of particular importance to the present invention. Binder polymers useful in the compositions of the present invention may be prepared via bulk and solution polymerization, and by aqueous dispersion, suspension, and emulsion polymerization, or any other method that would produce the desired polymer dispersed in water, or capable of being dispersed in water. A preferred method for preparing the binder polymers to be used in wear-resistant traffic marking compositions of the present invention is aqueous emulsion polymerization. Polymers thus prepared are usually stabilized by adding anionic, nonionic, cationic, or amphoteric surfactants, or by the incorporation of anionic or cationic moieties into the polymer itself during synthesis. The emulsion polymerization can be carried out by a number processes such as those described in Blackley, D.
C. Emulsion Polymerisation;
Applied Science Publishers: London, 1975; Odian, G.
Principles of Polymerization;
John Wiley & Sons: New York, 1991;
Emulsion Polymerization of Acrylic Monomers;
Rohm and Haas, 1967.
The aqueous emulsion polymer useful in the present invention is an addition polymer having at least two functional groups reactive with carbodiimide, and optionally at least one functional group reactive with the alkoxysilane. The monomers from which the addition polymer is formed are ethylenically-unsaturated. The aqueous emulsion polymer composition
Cheung William
Rohm and Haas Company
Wu David W.
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