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
2001-08-01
2002-11-05
Reddick, Judy M. (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...
C524S514000
Reexamination Certificate
active
06476111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to an extrudable highly filled thermoplastic composition that can be used to produce a decorative surface.
2. Description of the Related Art
The preferred use for the composition of this invention is as a decorative surface, for example in production of counter-tops, vanity tops, bath and shower surfaces, sinks, wall panels and furniture surfacing. The use of partially crosslinked acrylic for the production of spas, tubs and showers is well known in the art. Fiberglass reinforced polyester is also well known for being used in showers. These products serve the market well, but have a deficiency in that they cannot be easily repaired if scratched or stained.
Cultured marble and laminate have been used for many years as countertop materials in the kitchen and bath markets. These products serve the market well, but cannot be repaired if scratched or stained.
To overcome the above deficiencies, filled acrylic and filled polyester crosslinked compositions have been used in the past. U.S. Pat. No. 3,847,865 to Duggins refers to a castable composition for making simulated marble, which comprises an acrylic polymer or a mixture of polymers dissolved in a polymerizable constituent and highly filled with alumina trihydrate. This composition is then cast onto a belt or into a mold then cured to give a flat or shaped article with a reproducible simulated marble pattern. These cast sheets are homogeneous from upper surface to lower surface and are commonly known as solid surface. The ability to restore a marred surface by sanding or scrubbing is known in the trade as renewability and is highly preferred by consumers. CORIAN® solid surfaces, sold by E. I. du Pont de Nemours and Company, Wilmington, Del., is a commercially available solid surface material comprising a cast acrylic matrix filled with alumina trihydrate (ATH) and other fillers. Cast solid surface sheets are generally ¼″ to ¾″ thick and are produced in high cost specialized equipment so they are more expensive than laminate or cultured marble.
Thinner sheets are commercially available as a thin continuous cast ATH filled acrylic product called SSV made by Wilsonart International (Temple, Tex., USA). The cost remains much higher than for laminate. A second product developed by Wilsonart called SSL is an extruded wollastonite-filled acrylic product. This product is less expensive to produce than continuous cast sheet; however, it has deficiencies in heat resistance and solvent resistance. A hot object (about 120° C.), placed on a countertop constructed from this sheet, will stick to the countertop because the sheet has become soft. Improved resistance to household chemicals such as nail polish remover is desired.
General Electric Plastics (Pittsfield, Mass, USA) markets a sheet composition for the decorative surface market called Enduran™ semi-crystalline, high density polybutylene terephthalate (PBT) engineering material. Spartech Corporation (St. Louis, Mo., USA) extrudes the composition into a sheet and sells it under the trademark Endurex™. This product is an extruded barium sulfate-filled blend of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and polycarbonate. This product is less expensive to produce than traditional solid surface products. However, increased mar resistance is desired as it mars very easily. Rubbing a fingernail across the surface leaves an area of differing gloss that is objectionable to many customers.
There is a need for an extruded highly filled renewable product that has mar resistance, heat resistance, and solvent (or stain) resistance equal to or at least close to the level normally seen in traditional crosslinked solid surface products.
SUMMARY OF THE INVENTION
The extrudable thermoplastic composition of the invention is formed from a combination by weight of 20-65% glassy polymer, 5-35% semi-crystalline polymer, 0-10% compatibilizing agent for the glassy and semi-crystalline polymers, and 10-70% of a particulate mineral filler wherein the glassy polymer is the major component by a ratio to the semi-crystalline polymer that ranges from 4/1 to 3/2. More preferable is a range from 3/1 to 3/2.
The thermoplastic composite sheet molding composition provided allows the production of thin solid surfacing materials providing the superior properties of conventional thicker solid surfacing with the advantages of handling capabilities and the inexpensive selling cost normally associated with high-pressure decorative laminate. Accordingly, it is a primary object of the invention to provide a highly filled, thermoplastic blended polymeric material having improved resistance to heat, stain, and mar.
It is another object of this invention to provide a highly filled, extruded thermoplastic material which can be extruded into a thin sheet.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to a highly filled thermoplastic sheet composition comprised of a combination of glassy and semi-crystalline polymers. The sheet exhibits improved resistance to heat, stains, and marring.
The terms “glassy” and “semi-crystalline” refer to the crystallinity of a polymer. As used herein, the term “glassy” refers to amorphous polymers that exhibit a glass transition temperature (T
g
) but not a melt temperature (T
m
). Preferably, the T
g
is at least usual room temperature of 25 C. These glassy polymers are capable of being repeatedly melt processed in plastic manufacturing machinery. They are often thought of as substitutes for common glass. Glassy polymers include, but are not limited to acrylics, poly(methacrylates), atactic polystyrene, polycarbonate, styrene-acrylonitrile (SAN) and polyvinylchloride (PVC). Specific examples include 20 to 35% poly(methylmethacrylate), preferably 30 to 35% poly(methylmethacrylate).
As used herein, the term “semi-crystalline” refers to polymers that exhibit both the glass transition phase and a melt temperature (T
m
) Furthermore, the T
m
is greater than the intended maximum operating temperature. Kitchen countertops routinely encounter operating temperatures of at least 65 C. but 95 C. is preferable due to high heat applications such as canning or making candy. Therefore, T
m
is preferably at least 65 C. Semi-crystalline polymers may be thought of as engineering polymers intended as substitutes for metal and ceramic. Semi-crystalline polymers include, but are not limited to polyester, polyamides (such as nylon 6, nylon 6,6, and nylon 6,12), poly(butyl terephthalate), polyethylterephthalate, thermoplastic polyester elastomers (e.g., Hytrel®), polypropylene, stereoregular polystyrene, aramid, and polyketone. Specific examples include 15 to 20% poly(butyl terephthalate) and 10 to 15% nylon 6,12.
It has been found that the ratio of glassy to semi-crystalline in the composition of the present invention is important to a successful countertop or like surface. The ratio should be such to give a balance of properties related to the stressful use in a kitchen or bath. Semi-crystalline polymers have such poor mar resistance they are easily marred by a simple fingernail scratch but have very good heat resistance. When they are first extruded, the surface is mar resistant; however, if a customer uses an abrasive sponge or cleaner on the surface to remove a stain the polymer layer at the surface is removed and the mar performance is reduced to a level unacceptable to consumers, as they desire the ability to renew a stained, scratched, or marred surface. The ability to renew a surface has helped achieve the popularity of solid surface countertops. Addition of minor amounts of glassy polymers will improve the mar resistance of semi-crystalline polymers, but not enough to effectively eliminate mars in a high wear area. Better performance is achieved by crosslinking the resin or chemically modifying the polymer chain with hard and soft copolymers to disrupt crystallinity. Crosslinked polymers cannot be extruded, thus the benefit of low-cost production is lost
Beauchemin Paul Edward
Heitner Barry Jordan
Hutchins Clyde Spencer
Pollak Keith William
Thompson Jennifer Leigh
E. I du Pont de Nemours and Company
Reddick Judy M.
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