Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
2000-05-03
2001-07-10
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S295000, C051S307000, C051S309000
Reexamination Certificate
active
06258138
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to coated abrasive articles and more particularly, to such articles which incorporate energy curable compositions containing an epoxy resin and an ethylene vinyl acetate copolymer or an epoxy resin, an ethylene vinyl acetate copolymer and an acrylate.
BACKGROUND OF THE INVENTION
Coated abrasives generally comprise a flexible backing upon which a binder supports a coating of abrasive particles. The abrasive particles are typically secured to the backing by a first binder, commonly referred to as a make coat. Additionally, the abrasive particles are generally oriented with their longest dimension perpendicular to the backing to provide an optimum cut rate. A second binder, commonly referred to as a size coat, is then applied over the make coat and the abrasive particles to anchor the particles to the backing.
Porous cloth, fabric and textile materials are frequently used as backings for coated abrasive articles. The make coat precursor is typically applied to the backing as a low viscosity material. In this condition, the make coat precursor can infiltrate into the interstices of the porous backing leaving an insufficient coating thickness making it difficult to bond the subsequently applied abrasive particles to the backing and, on curing, resulting in the backing becoming stiff, hard and brittle. As a result, it has become conventional to employ one or more treatment coats, such as a presize, saturant coat, backsize or a subsize coat, to seal the porous backing.
The presize, saturant coat, backsize and subsize coat typically involve thermally curable resinous adhesives, such as phenolic resins, epoxy resins, acrylate resins, acrylic latices, urethane resins, glue, starch and combinations thereof. A saturant coat saturates the cloth and fills pores, resulting in a less porous, stiffer cloth with more body. An increase in body provides an increase in strength and durability of the article. A presize coat, which is applied to the front side of the backing, may add bulk to the cloth and may improve adhesion of subsequent coatings. A backsize coat, which is applied to the back side of the backing, that is, the side opposite that to which the abrasive grains are applied, adds body to the backing and protects the yams of the cloth from wear. A subsize coat is similar to a saturation coat except that it is applied to a previously treated backing. The drawback of such a presize, saturant coat, backsize and subsize coat is that it entails added processing step(s) which increase the cost and complexity of manufacturing. Similarly, paper backings may be treated to prevent penetration of make adhesives and/or to waterproof.
SUMMARY OF THE INVENTION
This invention generally relates to a coated abrasive article utilizing an improved make coat formulation. The coated abrasive article includes a backing, the improved make coat on the backing, and a plurality of abrasive particles at least partially embedded in the make coat. The make coat also may be referred to herein as the first binder.
The present invention provides a coated abrasive article, comprising:
a) a backing having a front surface and a back surface;
b) a crosslinked first binder on said front surface of said backing,
wherein said first binder is formed from a first binder precursor, said first binder precursor is an energy-curable composition made by mixing the following components
i) about 2 to about 99 weight percent of an epoxy resin, the weight percent being based on the total resin content;
ii) about 1 to about 98 weight percent of an ethylene-vinyl acetate copolymer resin, the weight percent being based on the total resin content;
iii) an effective amount of a curing agent for crosslinking said epoxy resin; and
c) a plurality of abrasive particles, wherein said abrasive particles are at least partially embedded in said first binder.
The above binder precursor compositions of the invention are homogeneous in the molten state and are preferably free from, that is, do not contain, hydrocarbon polyolefin resins. “Hydrocarbon polyolefm resin” refers to a fully prepolymerized uncrosslinked polymeric hydrocarbon bearing essentially no organic functional groups, prepared from homopolymerization and/or copolymerization of an olefinic monomer(s). Such resins can be incompatible with epoxy resins and can cause phase separation of compositions containing an appreciable amount of epoxy resin. Examples of such resins include polyethylene, polypropylene, and the like, and poly(ethylene-co-propylene), poly(propylene-co-1-butene), and the like.
In another aspect, the present invention provides a coated abrasive article, comprising:
a) a backing having a front surface and a back surface;
b) a crosslinked fist binder on said front surface of said backing,
wherein said first binder is formed from a first binder precursor, said first binder precursor is an energy-curable composition made by mixing the following components
i) about 2 to about 98 weight percent of an epoxy resin, the weight percent being based on the total resin content;
ii) about 1 to about 90 weight percent of an ethylene-vinyl acetate copolymer resin, the weight percent being based on the total resin content;
iii) about 0.1 to about 20 weight percent of a polyfunctional acrylate, the weight percent being based on the total resin content;
iv) an effective amount of a curing agent for crosslinking said epoxy resin; and
c) a plurality of abrasive particles, wherein said abrasive particles are at least partially embedded in said first binder.
In another aspect, the present invention provides an energy-curable composition made by mixing components comprising:
a) an epoxy resin;
b) an ethylene-vinyl acetate copolymer resin;
c) a polyfunctional acrylate; and
d) an effective amount of a curing agent for crosslinking said epoxy resin.
In another aspect, the present invention provides a presized backing for a coated abrasive article comprising:
a) a backing suitable for use in a coated abrasive article; and
b) a crosslinked presize layer on the backing formed from a presize binder precursor, wherein the presize binder precursor is an energy curable composition comprising:
i) from about 30 to about 95 weight percent of an epoxy resin, the weight percent being based on the total resin content,
ii) from about 5 to about 70 weight percent an ethylene-vinyl acetate copolymer resin, the weight percent being based on the total resin content, and
iii) an effective amount of a curing agent for crosslinking said epoxy resin.
In another aspect, the present invention provides a presized backing for a coated abrasive article comprising:
a) a backing suitable for use in a coated abrasive article; and
b) a crosslinked presize layer on the backing formed from a presize binder precursor, wherein the presize binder precursor is an energy curable composition comprising:
i) about 2 to about 98 weight percent of an epoxy resin, the weight percent being based on the total resin content,
ii) about 1 to about 90 weight percent of an ethylene-vinyl acetate copolymer resin, the weight percent being based on the total resin content,
iii) about 0.1 to about 20 weight percent of a polyfunctional acrylate component, the weight percent being based on the total resin content, and
iv) an effective amount of a curing agent for crosslinking said epoxy resin.
The above binder precursors of the invention are preferably melt processable.
As used herein, a “hot melt” refers to a composition that is a solid at room temperature (about 20 to 22° C.) but which, upon heating, melts to a viscous liquid that can be readily applied to a coated abrasive article backing. A “melt processable” composition refers to a composition that can transform, for example, by heat and/or pressure, from a solid to a viscous liquid by melting, at which point it can be readily applied to a coated abrasive article backing. Both hot melt and melt processable resin compositions can be in the form of a solid film that is transfer coated to the backing. Desirably, the hot melt compositions of the invention can
Clausen Thomas M.
Dahlke Gregg D.
DeVoe Robert J.
George Clayton A.
Karim Naimul
3M Innovative Properties Company
Bardell Scott A.
Marcheschi Michael
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