Plastic and nonmetallic article shaping or treating: processes – Orienting or aligning solid particles in fluent matrix material
Reexamination Certificate
2000-11-01
2001-09-18
Friedman, Carl D. (Department: 3635)
Plastic and nonmetallic article shaping or treating: processes
Orienting or aligning solid particles in fluent matrix material
C264S328180, C264S336000, C052S745190
Reexamination Certificate
active
06290885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is generally directed to the field of roofing materials and is more particularly directed to a method of making a molded roofing unit formed from a fiber-reinforced plastic.
2. Description of the Related Art
A number of different roofing products have been developed and used over the years to cover and protect a building. Various factors may be considered in choosing a roofing product including the cost of the product, ease of application or installation, and appearance. Equally important is the performance or weatherability of the roofing product, meaning its ability to withstand cold, rain, hail and wind and to shed snow and endure ice buildup without significant damage. Fire resistance is another important consideration and is increasingly being identified by insurance companies as a desirable attribute for lowering insurance premiums.
Clay tile, concrete, and slate roofs are distinctive and aesthetically pleasing in appearance such that even the “best” neighborhood associations approve the use of these roofing products. Clay, concrete, and slate also generally withstand wide ranging temperatures, rain, snow and wind, and are relatively fire resistant. However, these materials can be expensive, may be susceptible to damage from hail and foot traffic, and the installment is generally labor intensive. Further, slate, concrete, and clay roofing products can be heavy, such that reinforced structures may be required to support their weight.
Wood shakes are also generally approved by most neighborhood associations for residential use and are less expensive than clay, concrete, or slate roofs. Wood shakes are easier to install than clay, concrete, and slate roofs, although measuring and/or squaring of the individual shakes during installation can prove time consuming and the shakes may split during shipment or installation, thereby increasing the overall cost of materials. Wood shakes are also susceptible to hail damage and generally cannot attain a high degree of fire resistance without costly treatment. Wood shakes are often perceived as catching fire relatively easily in the presence of lightening, sparks from fireworks, or other airborne flames. When exposed to water, wood roofing materials may swell or curl along the edges, thereby providing a protruding surface for winds to catch.
Asphalt shingles, also known as composition roofing, are less expensive than wood roofing and are relatively easy-to-install. However, asphalt roofing products generally do not provide the sought after appearance of wood shakes, slate, clay, or tiles, and therefore are not approved for use in some residential areas with high-priced homes. While asphalt roofing is resistant to fire, it is generally prone to hail and wind damage and may need to be replaced over time due to brittling and cracking from exposure to the elements.
Due to the inadequacies of conventional roofing products, various attempts have been made in the past to develop plastic-based roofing materials that possess the desired combination of physical properties, low cost, aesthetic appeal and ease of installation.
For example, U.S. Pat. No. 5,635,125 to Ternes et al. discloses a relatively flat molded shingle formed of ground-up recycled polyvinyl chloride (PVC) particles and wood sawdust particles. U.S. Pat. No. 5,615,523 to Wells et al. discloses a relatively flat shingle panel comprising a resinous plastic material combined with a large amount of filler.
While these prior plastic and/or composite roofing products heretofore developed for replacing conventional roofing products are suitable for such purposes, none of the products developed to date have fully met the desires of the industry. These prior products do not provide the desired aesthetic attributes, nor superior physical properties. Thus, a need remains in the art for an improved plastic composite roofing product that may be made from relatively safe polyolefin materials, recycled and/or virgin, having high impact resistance, wind resistance and fire resistance, with an aesthetically pleasing appearance and that may serve as a drop-in replacement for traditional roofing products at a reasonable cost. To this end, one of the primary objects of this invention is to provide a polyolefin roofing unit reinforced by partially delignified fibers, in which the fibers bind to the plastic to provide a greater degree of wind resistance and impact resistance than previously known in plastic roofing products and with costs comparable to traditional roofing products.
SUMMARY OF THE INVENTION
The present invention is directed to a novel molded roofing product and method of making the same wherein the product is made from a fiber-reinforced plastic composition, is designed to simulate conventional roofing such as wood shakes, slate, concrete, or tile and can be easily installed on the roof of a structure. The roofing product is uniquely configured to provide consistent results in the molding process, low material and production costs, high rigidity and strength, impact resistance, stability in high wind conditions, ease of installation and other functional advantages. The roofing product is inexpensive to manufacture and maintain, while having superior wind, hail and fire resistance over conventional roofing materials such as cedar shakes.
The roofing product consists of discrete roofing units which may be applied to the roof of a building or other structure to protect the structure from rain, snow, ice, wind, hail, sun, wildlife, and other natural elements. The molded roofing units may be installed on the roof in a fashion similar to conventional asphalt shingles or wood shakes wherein the units are secured in place, one above the other, with nails, staples or screws.
The molded roofing units are formed from a fiber-reinforced plastic composition having impact resistance greater than 1.1 ft-lb/in to reduce hail damage, superior flex modulus ranging from 275,000 to 600,000 psi to withstand strong winds, and at least a class C fire rating to reduce the risk of fires.
The fiber-reinforced plastic composition preferably comprises a plastic compounded with partially delignified agricultural or forestry fibers that strongly bind to the plastic and thereby provide superior reinforcement to the roofing product. The plastic is preferably selected from one or more polyolefin plastics recycled from waste materials. The partially delignified fibers preferably are derived from fibers having an aspect ratio (length to diameter×1,000 of the fiber) greater than 60, and most preferably greater than 100, to provide strength and stiffness to the product.
In a preferred embodiment of the invention, a polyolefin plastic comprised of cleaned waste plastics, such as high-density polyethylene (HDPE) and polypropylene, is compounded with partially delignified cellulosic fibers derived from waste forestry or agricultural materials, such as wheat straw, sugar cane bagasse, or wood cellulose. These cellulosic fibers may be partially delignified by any means known in the art to disrupt the lignin holding the individual fibers and fibrils together so as to increase the fiber surface area to which the plastic can bond. Most preferably, the cellulosic fibers are delignified by steam explosion, such as by the method described in U.S. Pat. No. 5,705,216 to Tyson (hereinafter the “Tyson '216 Patent”) or in U.S. Pat. No. 4,966,650 and Canadian Patents Nos. 1,141,376 and 1,096,374 to DeLong (hereinafter the “DeLong Patents”), in a manner to “open” the individual fibers into an expanded fibrous micromesh matrix of fibrils, thereby enabling the plastic to flow into and bind with the fibers and fibrils. The fiber and fibril-plastic binding yields added strength, rigidity, and impact resistance, while providing resistance against chemical attack, insect infestation, and frost damage. Optionally, the delignified fibers may also be mechanically defibrillated to further dissociate the individual fibers and fibrils.
In addition to the polyolefin
Alexander Robert Joseph
Evans Tony J.
Pratt D. Kevin
Roetheli Joseph C.
A Phi Dieu Tran
Friedman Carl D.
Poly Proximates, Inc.
Stinson, Mag & Fizzell, P.C.
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