Mineral-filled coatings having enhanced abrasion resistance and wear clarity and methods for using the same

#The present invention relates to coating compositions that provide enhanced abrasion resistance and wear clarity, and methods for using the same. More specifically, the improved abrasion resistance and wear clarity is achieved by adding a combination of alumina and silica to a coating.

#Floor coverings, such as wood and vinyl flooring, are subject to wear from foot traffic and contact with heavy objects. As such, abrasion resistance is a particularly desired property in a floor covering. Resistance to contamination or staining caused by a variety of sources is also desirable. To provide these desired characteristics, one or more layers of sealers and/or topcoats are typically applied to the flooring. For example, an abrasion resistant layer having hard particles that impart abrasion resistance can be applied. Often, when this layer and particles experience wear, a whitening or clouding of the layer occurs. Thus, abrasion resistant layers having improved wear clarity are desired.

#The present invention is directed to coating compositions generally comprising a combination of alumina and silica. The alumina has been treated or modified with an organosilane, as further described herein; the silica can be modified or unmodified. The particles are typically dispersed in a coating material suitable for use with flooring.

#FIG. 1 illustrates the modification of a silica particle with 3-(trimethoxysilyl)propyl methacrylate.

#FIG. 2 illustrates the modification of an alumina particle with 3-(trimethoxysilyl)propyl methacrylate.

#FIG. 3 illustrates the interaction between silane molecules on the surface of a modified alumina particle.

#The present invention is directed to a coating composition comprising a binder and a mixture of modified alumina and either modified or unmodified silica. Modification is effected through the use of a silane, discussed further below.

#Aluminum oxide (“alumina”) can be used in any of its forms, such as alpha, beta, gamma, delta, pheta, tabular alumina, and the like and can be fused or calcined. Alpha alumina is particularly suitable. The average particle size of the alumina will typically range between about 1 and 40 microns. In one embodiment, the average particle size is between 17 and 25 microns, and in another embodiment is about 3 microns. Typically, the average particle size of the alumina will be about the same as the thickness of the coating layer deposited from the coating composition to which it is added. Sol-gel processed aluminas, such as those described in WO 00/52105, can also be used.

#Suitable alumina products, including those that are silane treated, are widely commercially available. For example, aluminum oxide precision lapping powder is available from Micro Abrasives Corporation in its “WCA” line of products; this alumina is characterized by platelet-shaped particles, each particle being an individual crystallite. The product is available in a number of different average particle sizes. For example, WCA 25 has an average particle size of 17 microns. Tabular alumina is also available from Alcoa as T64-20. DURALUM special white is a fused alumina having a blocky, irregular shape supplied by Washington Mills Electro Minerals Company, and also comes in a variety of sizes including DURALUM 320 (average particle size 29 microns), DURALUM 400 (average particle size 17 microns), and DURALUM 400SK (average particle size about 18 microns).