Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Utilizing diverse solid particles
Reexamination Certificate
1999-03-26
2001-11-27
Theisen, Mary Lynn (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Utilizing diverse solid particles
C264S109000
Reexamination Certificate
active
06322737
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a structural member and to a structure made with the structural member.
2. Description of the Prior Art
In recent years, much effort has been directed to the development of environmentally friendly structural products. Such structural products contain significant percentages of regenerable and/or recycled materials.
A structural product containing a substantial percentage of regenerable material is taught in U.S. Pat. No. 4,947,611. This patent discloses a wall panel containing clay in combination with straw, chaff and palm material. The panel may optionally include hemp.
U.S. Pat. No. 5,177,924 illustrates a structural product which can comprise straw, chaff and/or rice husks. The product further comprises mineral additives as well as cement, lime and/or gypsum.
A box-like structural product with an interior core of sawdust, rubber or waste fiberglass is shown in U.S. Pat. No. 4,301,198. The box-like product has a rigid exterior skin made of a reinforced plastic binder such as fiber-reinforced polyester, epoxy or polyurethane. The binder penetrates the box-like product to contact the core in adhesive relationship.
U.S. Pat. No. 5,241,795 teaches a structural product made from paper sludge, repulped waste paper or virgin paper pulp. This material is mixed with clay or portland cement, or with animal protein adhesives, or with manufactured resins or polymers.
A panel made up of slats composed of recycled pultrusion polyolefin high density polyethylene is disclosed in U.S. Pat. No. 5,367,844. Each slat contains 85 percent or more of the recycled material.
U.S. Pat. No. 5,482,550 discloses a structural product consisting of portland cement, recycled and ground expanded cellular polystyrene, ground cellulosic fiber, fly ash, silica fume, bentonite, water, air entrainer, paraffin wax emulsion and rubber emulsion. The product serves as a roofing material.
A wall panel made up of layers each of which contains a different recycled material is taught in U.S. Pat. No. 5,724,783. The recycled materials in the panel include used fiberglass insulation, recycled polystyrene, rubber tires and old carpets.
The recycled materials are broken down and then mixed with portland cement, microsilica, sand and water before being placed in the panel.
U.S. Pat. No. 5,729,936 teaches the production of a prefabricated panel by compressing a fiber slurry composed of waste paper, waste cardboard, straw, leaves and grass clippings. The slurry, which may contain waterproofing agents, fire retardants, antifungal agents and insecticides, is poured into a press form for compression,
As seen from the preceding overview of the prior art, the use of recycled thermoplastic plastics in structural products is limited. Thermoplastic plastics are those which soften or fuse when heated and which harden and become rigid when cooled. Plastics of this type are in contrast to thermosetting plastics which become permanently hard and rigid when heated or cured and which are thereafter relatively incapable of softening or fusing upon heating.
Although the use of recycled thermoplastic plastics in structural products is limited, items made of such plastics constitute one of the largest sources of raw material from recycled matter. A plastic number coding is utilized to separate categories of plastic according to their chemical composition properties, and recyclability, A large number of recycled plastic items (milk and water jugs, detergent bottles, margarine tubs, bags and yogurt containers) are composed of high and low density polyethylene classified with Codes 2 and 4. Similarly, many items (prescription bottles and plastic lids) consist of polypropylene classified with Code 5.
Accordingly, there is still a need for new ways of utilizing recycled thermoplastic plastics. This disclosure is directed to the utilization of such plastic matter as a major component of structural products.
SUMMARY OF THE INVENTION
One objective of this invention is a method of making structural members and structures utilizing large quantities of recycled thermoplastic plastic.
Another goal of the invention is a method of manufacture of structural members and structures that is primarily based on the utilization of recycled material.
Still another goal is a method with low energy requirements based on conventional steps and directed at producing strong structural members.
A further objective is a method that can be implemented easily and economically with commercially available materials and manufacturing equipment, modified only to the extent necessary to fit the requirements of the invention.
The preceding objectives and goals, as well as others which will become apparent as the description proceeds, are achieved by the invention.
One aspect of the invention resides in a method of making a structural member. The method comprises the steps of mixing plant-fiber particles, particles of thermoplastic plastic and a fire retardant to form a mixture, and heating the particles and the fire retardant before or after the mixture is formed. Each of the particles is heated to a temperature below a flash point thereof. The plant-fiber particles have voids, and the method further comprises the step of pressing the mixture while hot as required to cause penetration of the plastic into the voids.
By employing thermoplastic plastic, the particles of plastic can be softened during the heating step. This, in turn, makes it possible for the plastic to penetrate the voids of the plant-fiber particles during the pressing step. Such penetration allows the plastic to form a strong bond with the plant-fiber particles thereby imparting strength to the structural member. Additional strength is derived from the tendency of the fibers of the plant-fiber particles to orient themselves in a crisscross pattern.
The plastic utilized in making the structural member may include polyethylene and/or polypropylene while the plant-fiber particles may comprise nutshells, fruit pits, grain, straw, grass and particles of wood. The plant-fiber particles can constitute 50 to 90 weight percent of the mixture while the plastic can constitute 10 to 50 weight percent of the mixture. It is preferred that the plant-fiber particles be sized to pass through a 50 mm screen and that the plastic particles be sized to pass through a 5 mm screen.
The plant-fiber particles, plastic particles and fire retardant can be heated to a temperature between 120 and 230 degrees Centigrade (about 250 to 450° F.). The mixture is advantageously pressed at a pressure between 70 and 250 kilograms per square centimeter (about 1,000 to 3,500 psi).
Another aspect of the invention resides in a construction method. The construction method comprises the steps of producing a structural member, and erecting a structure using the structural member. The producing step involves (a) mixing particles of thermoplastic plastic and plant-fiber particles having voids to form a mixture, (b) heating the particles before or after the mixture is formed, and (c) pressing the mixture while hot. Each of the particles is heated to a temperature below a flash point thereof, and the mixture is pressed as required to cause penetration of the plastic into the voids of the plant-fiber particles.
An additional aspect of the invention resides in a structural member. The structural member comprises a mass which contains plant-fiber particles, thermoplastic plastic and a fire retardant. The plant-fiber particles have voids, and the plastic penetrates the voids and forms a binder for the plant-fiber particles.
A further aspect of the invention resides in a structure. The structure has at least one structural member which comprises a mass containing plant-fiber particles and thermoplastic plastic. The plant-fiber particles have voids, and the plastic penetrates the voids and forms a binder for the plant-fiber particles.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features
Durando Antonio R.
Durando Birdwell & Janke
Theisen Mary Lynn
LandOfFree
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