Patent Application
20080197523
Exemplary embodiments of the present invention relate generally to composite products. More particularly, exemplary embodiments of the present invention include systems and methods directed to the control of manufacturing processes used to manufacture composite materials such as cellulosic-filled and/or inorganic-filled plastic composites. Such composite materials have a wide range of application and may, for example, be used in the manufacture of gates, fences, porch and deck skirts, and other similar or suitable structures.
A major problem with the use of wood materials in structural applications is their lack of durability and the degradation in appearance when exposed to the environment. Wood materials are particularly attractive due to their intrinsic beauty of their wood grain. However, in the example of residential decks, rain can infiltrate exposed surfaces of the wood components, which may eventually cause rot and the loss of a pleasing aesthetic appearance. Traditional wood surface treatments, such as paint or lacquers, have limited life and require routine maintenance, which can result in significant expense over time. Additionally, wood decking systems, for example, are typically custom-built on-site, thereby requiring significant amounts of labor to custom-cut and install individual components. More recently, pre-engineered cellulosic-filled and/or inorganic-filled plastic composites have been developed to overcome such deficiencies. As compared to natural woods, a cellulosic composite may offer superior resistance to wear and tear and to degradation caused by adverse weathering effects, which reduces overall maintenance costs. For instance, a cellulosic composite may have an enhanced resistance to moisture. In fact, it is well known that the retention of moisture is a primary cause of the warping, splintering, and discoloration of natural woods as described above. Moreover, a cellulosic composite may be sawed, sanded, shaped, turned, fastened, and finished in a similar manner as natural woods.
The manufacturing process needed to produce such composite materials may, for example, include the mixing and extrusion of a base plastic resin and cellulosic filler, such as polyvinylchloride (PVC) and wood flour, as well as the addition of other components, such as but not limited to, colorants and lubricants. During the process, the components are typically mixed by introduction into a mixer, preheater, and/or extruder to produce a product having desired characteristics, such as strength, rigidity, color, etc. Of particular importance is the production of composite materials that have a consistently and substantially uniform density and color, which are currently maintained by a manual metering of components as they are introduced into the manufacturing process. However, since the production of extruded composite materials is generally a continuous process, undesirable density variation in the final product occurs because density variations of the introduced base components occur over relatively short time periods. In particular, the components cannot be adequately metered real-time for compensation of variations during mixing by manual operator control. For similar reasons, the control of color is difficult as the amounts of colorants cannot be satisfactorily controlled real-time, producing undesirable variation in color in the final product. Consequently, there is a need for a system and method by which to adequately control the characteristics of an extruded composite material in a real-time manner to produce products having substantially uniform density, color, and/or other desired properties.
Exemplary embodiments of the present invention may satisfy some or all of the above needs. Exemplary embodiments of the present invention include systems and methods for manufacturing composite material components having substantially uniform properties comprising means to control the metering of constituent composite material components during manufacture. The resulting composite material components may be used, for example, in the construction of decking systems, railing, porches, fences, stairs, or other similar or suitable applications that may benefit from aesthetically pleasing appearances.
In addition to the novel features and advantages mentioned above, other features and advantages will be readily apparent from the following descriptions of the drawings and exemplary embodiments.
Examples of cellulosic filler materials may include any combination of sawdust, newspapers, alfalfa, wheat pulp, wood chips, wood fibers, wood particles, ground wood, wood flour, wood flakes, wood veneers, wood laminates, paper, cardboard, straw, cotton, rice hulls, coconut shells, peanut shells, bagasse, plant fibers, bamboo fiber, palm fiber, kenaf, flax, or any other similar or suitable materials. Examples of thermoplastic resins may include multilayer films, high density polyethylene (HDPE), polypropylene, polyvinyl chloride (PVC), low density polyethylene (LDPE), chlorinated polyvinyl chloride (CPVC), acrylonitrile butadiene styrene (ABS), ethyl-vinyl acetate, other similar or suitable copolymers, other similar or suitable plastic materials, or formulations that incorporate any of the aforementioned plastic materials.
The use of other materials to make the desired composite product may include one or more materials including, but not limited to, inorganic fillers, cross-linking agents, thermosetting materials, process aids, lubricants, accelerators, inhibitors, enhancers, compatibilizers, stabilizers, acrylic modifiers, pigments, weathering additives, foaming agents, blowing agents, rubber, other plastics, and other similar or suitable materials that may be used in cellulosic and/or thermoplastic compounds.
Stabilizer(s) may be employed to limit or prevent the breakdown of the plastic material during molding. Examples of stabilizers include tin stabilizers, lead and metal soaps such as barium, cadmium, and zinc, and other similar or suitable materials.
Internal or external lubricant(s) may aid in the molding process. Lubricants may be added to the plastic material to assist the reinforced composite through, for example, an extruder, compounder, or other molding machine, and to help facilitate mold release. Examples of lubricants include zinc stearate, calcium stearate, esters, amide wax, paraffin wax, ethylene bis-stearamide, and other similar or suitable materials.
Process aid(s) may aid in the fusion of the compound. Examples of process aids include acrylic process aids and other similar or suitable materials for improving the fusion of the compound. R&H K-120N and R&H K-175 are examples of acrylic process aids that are available from Rohm & Haas.
Acrylic modifier(s) may improve the physical characteristics of the compound. One example of an impact modifier is Arkema P530. Another example of an acrylic modifier is R&H K-400, which is available from Rohm & Haas. R&H K-400 is a high molecular weight acrylic modifier.
Inorganic filler(s) may be used to increase the bulk density of the reinforced composite. The use of inorganic filler may also improve the ability to process the reinforced composite, thereby allowing for higher rates of manufacture (e.g., extrusion). Inorganic filler may also allow the reinforced composite to be molded into articles having reduced moisture sensitivity and reduced flame and smoke spread. Examples of inorganic fillers include talc, calcium carbonate, kaolin clay, magnesium oxide, titanium dioxide, silica, mica, barium sulfate, wollastanite, acrylics, and other similar or suitable materials.
Blowing agent(s) may be used to reduce the cost (e.g., by reducing the amount of polymer used in the composite) and weight of the composite material. A blowing agent may be an endothermic or exothermic blowing agent. An example of a chemical endothermic blowing agent is Hydrocerol BIH (i.e., sodium bicarbonate/citric acid), which is available from Clariant Corp., whereas an example of a chemical exothermic foaming agent is azodicarbonamide, which is available from Uniroyal Chemical Co.
The use of thermosetting materials may, for example, reduce moisture absorption and increase the strength of products manufactured from the reinforced composite material. Examples of thermosetting materials include polyurethanes (e.g., isocyanates), phenolic resins, unsaturated polyesters, epoxy resins, and other similar or suitable materials. Combinations of the aforementioned materials are also examples of thermosetting materials.
Pigments may be used to give the composite a desired color (e.g., white, cedar, gray, and redwood). Examples of pigments include titanium dioxide, iron oxide, and other similar or suitable colorant additives. For instance, components may be molded in any desired color to match the appearance of a fence, deck, or rail, for example, and may also have a pattern or texture formed on the outside face so as to match the texture or pattern of a fence, deck, or rail, for example.
Titanium dioxide is also an example of a weathering additive. Other similar or suitable weathering additives include, but are not limited to, other ultraviolet absorbers. Examples of other ultraviolet absorbers include organic chemical agents such as benzophenone and benzotriazole types.
Exemplary embodiments of the present invention beneficially provide a system and method by which to produce superior composite materials having desired and substantially uniform properties, which may, for example, be useful for making decking, railing, or fencing components including, but not limited to, rails, planks, balusters, squash blocks, support rails, posts, post covers, and other similar or suitable components. Nevertheless, while exemplary embodiments of the present invention may be particularly useful for making decking, fencing, and railing components, it should be recognized that the composite material produced by exemplary embodiments of the present invention may be useful for manufacturing other types of indoor and outdoor components. Examples of components that can be made with exemplary embodiments of the present invention include, but are not limited to, fence components, furniture components, cabinet components, storage device components, lawn edging components, flower box components, floor components, baseboards, roof components, wall covering components, building siding components, basement floor components, basement wall covering components, interior and exterior decorative house molding components, crown molding components, chair rail components, picture frame components, porch components, deck components, railing components, window molding components, window components, window frames, door components, door frames, door moldings, posts, boards, and other suitable indoor and outdoor items.
Any embodiment of the present invention may include any of the optional or preferred features of the other embodiments of the present invention. The exemplary embodiments herein disclosed are not intended to be exhaustive or to unnecessarily limit the scope of the invention. The exemplary embodiments were chosen and described in order to explain the principles of the present invention so that others skilled in the art may practice the invention. Having shown and described exemplary embodiments of the present invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention. Many of those variations and modifications will provide the same result and fall within the spirit of the claimed invention. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.
