Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1998-11-12
2001-04-03
Weisberger, Richard (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S359000, C428S361000, C428S378000, C428S393000, C428S425100, C428S479300, C428S479600, C428S507000
Reexamination Certificate
active
06210792
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to compatible composite thermoplastic materials used for the fabrication of structural members. The thermoplastic materials comprise a continuous phase of polyvinyl chloride having a discontinuous phase of a cellulosic fiber. The composite material is maintained thermoplastic throughout its useful life by avoiding the use of any substantial concentration of crosslinking agents that would either crosslink cellulosic fibers, polymer molecules or cellulosic fiber to polymer. The physical properties of the thermoplastic material are improved by increasing polymer-fiber compatibility, i.e. the tendency of the polymer and fiber to mix. The improved mixing tendencies improves the coatability of the fiber by polymer, increases the degree the polymer wets the fiber in the melt stage and substantially increases the engineering properties of the materials as a whole. In particular, the improved engineering properties include increased tensile strength when compared to immodified materials (without a compatibilizing composition). The improved engineering properties permit the manufacture of improved structural members. Such members can be any structural unit. Preferably the members are for use in windows and doors for residential and commercial architecture. More particularly, the invention relates to an improved composite material adapted to extrusion or injection molding processes for forming structural members that have improved properties when used in windows and doors. The composite materials of the invention can be made to manufacture structural components such as rails, jambs, stiles, sills, tracks, stop and sash, nonstructural trim elements such as grid, cove, bead, quarter round, etc.
BACKGROUND OF THE INVENTION
Conventional window and door manufacture has commonly used wood and metal components in forming structural members. Commonly, residential windows are manufactured from milled wood products that are assembled with glass to form typically double hung or casement units. Wood windows while structurally sound, useful and well adapted for use in many residential installations, can deteriorate under certain circumstances. Wood windows also require painting and other periodic maintenance. Wooden windows also suffer from cost problems related to the availability of suitable wood for construction. Clear wood products are slowly becoming more scarce and are becoming more expensive as demand increases. Metal components are often combined with glass and formed into single unit sliding windows. Metal windows typically suffer from substantial energy loss during winter months.
Extruded thermoplastic materials have been used in window and door manufacture. Filled and unfilled thermoplastics have been extruded into useful seals, trim, weatherstripping, coatings and other window construction components. Thermoplastic materials such as polyvinyl chloride have been combined with wood members in manufacturing PERMASHIELD® brand windows manufactured by Andersen Corporation for many years. The technology disclosed in Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,883, have been utilized in the manufacturing of plastic coatings or envelopes on wooden or other structural members. Generally, the cladding or coating technology used in making PERMASHIELD® windows involves extruding a thin polyvinyl chloride coating or envelope surrounding a wooden structural member.
Recent advances have made a polyvinyl chloride/cellulosic fiber composite material useful in the manufacture of structural members for windows and doors. Puppin et al., U.S. Pat. No. 5,406,768 comprise a continuous phase of polyvinyl chloride and a particular wood fiber material having preferred fiber size and aspect ratio in a thermoplastic material that provides engineering properties for structural members and for applications in window and door manufacture. These thermoplastic composite materials have become an important part of commercial manufacture of window and door components. While these materials are sufficiently strong for most structural components used in window and door manufacture, certain components require added stiffness, tensile strength, elongation at break or other engineering property not always provided by the materials disclosed in Puppin et al.
We have examined the modification of thermoplastic materials in the continuous polymer phase, the modification of the cellulosic materials in the discontinuous cellulosic phase for improving the structural polymers of these composite materials. The prior art has recognized that certain advantages can be obtained by a judicious modification of the materials. For example, a number of additives are known for use in both thermoplastic and cellulosic materials including molding lubricants, polymer stabilizers, pigments, coatings, etc.
The prior art contains numerous suggestions regarding polymer fiber composites. Gaylord, U.S. Pat. Nos. 3,765,934, 3,869,432, 3,894,975, 3,900,685, 3,958,069 and Casper et al., U.S. Pat. No. 4,051,214 teach a bulk polymerization that occurs in situ between styrene and maleic anhydride monomer combined with wood fiber to prepare a polymer fiber composite. Segaud, U.S. Pat. No. 4,528,303 teaches a composite composition containing a polymer, a reinforcing mineral filler and a coupling agent that increases the compatibility between the filler and the polymer. The prior art also recognizes modifying the fiber component of a composite. Hamed, U.S. Pat. No. 3,943,079 teaches subjecting unregenerated cellulose fiber to a shearing force resulting in mixing minor proportions of a polymer and a lubricant material with the fiber. Such processing improves fiber separation and prevents agglomeration. The processing with the effects of the lubricant tends to enhance receptiveness of the fiber to the polymer reducing the time required for mixing. Similarly, Coran et al., U.S. Pat. No. 4,414,267 teaches a treatment of fiber with an aqueous dispersion of a vinyl chloride polymer and a plasticizer, the resulting fibers contain a coating of polyvinyl chloride and plasticizer and can be incorporated into the polymer matrix with reduced mixing energy. Beshay, U.S. Pat. Nos. 4,717,742 and 4,820,749 teach a composite material containing a cellulose having grafted silane groups. Raj et al., U.S. Pat. No. 5,120,776 teach cellulosic fibers pretreated with maleic or phthalic anhydride to improve the bonding and dispersibility of the fiber in the polymer matrix. Raj et al. teach a high density polyethylene chemical treated pulp composite. Hon, U.S. Pat. No. 5,288,772 discloses fiber reinforced thermoplastic made with a moisture pretreated cellulosic material such as discarded newspapers having a lignant content. Kokta et al., “Composites of Poly(Vinyl Chloride) and Wood Fibers. Part II. Effect of Chemical Treatment”,
Polymer Composites
, April 1990, Volume 11, No. 2, teach a variety of cellulose treatments. The treatments include latex coating, grafting with vinyl monomers, grafting with acids or anhydrides, grafting with coupling agents such as maleic anhydride, abietic acid (See also Kokta, U.K. Application No. 2,192,397). Beshay, U.S. Pat. No. 5,153,241 teaches composite materials including a modified cellulose. The cellulose is modified with an organo titanium coupling agent which reacts with and reinforces the polymer phase. Similarly, the modification of the thermoplastic is also suggested in metal polypropylene laminates, crystallinity of polypropylene has been modified with an unsaturated carboxylic acid or derivative thereof. Such materials are known to be used in composite formation.
Maldas et al. in “Performance of Hybrid Reinforcements in PVC Composites: Part I and Part III”,
Journal of Testing and Evaluation
, Vol. 21, No. 1, 1993, pp. 68-72 and
Journal of Reinforced Plastics and Composites
, Volume II, October 1992, pp. 1093-1102 teach small molecule modification of filler such as glass, mica, etc. in PVC composites. No improvement in physical properties are demonstrated as a result of sample preparation and testing.
Beaverson Neil J.
Deaner Michael J.
Heikkila Kurt E.
Seethamraju Kasyap V.
Andersen Corporation
Merchant & Gould P.C.
Weisberger Richard
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