Abstract:
Polymer composite building materials are provided which contain about 30-80 weight percent resin, 20-70 weight percent fillers and additives, in which the fillers contain at least one bulk filler for reducing the amount of resin needed to make the building material, and at least one aesthetically functional filler for providing the building material with an aesthetic appearance. The bulk filler and the aesthetically functional filler are non toxic, resistant to bacterial attack, and have a Mohs hardness of less than about 5.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a Divisional of U.S. patent application Ser. No. 10/281,795 filed Oct. 28, 2002. The present application is also related to U.S. patent application Ser. No. 09/988,985, filed Nov. 19,  2001 , and is also related to U.S. patent application Ser. No. 10/281,796, filed Oct. 28, 2002, which are all hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a consolidated form of the commingled continuous filaments of glass fibers and polymeric fibers as reinforcement.  
       BACKGROUND OF THE INVENTION  
       [0003]     Most fence and rail materials are either traditional lumber or thermoplastics. Typical plastics in these applications are PVC (polyvinyl chloride) and polyethylene. PVC typically does not have the strength and rigidity of wood and lumber and therefore, the rail for the fence and railing needs the steel or aluminum reinforcement channel inside the rail. These metal reinforcements are prone to corrosion attack, and lose strength in long-term endurance. Also, the problem exists as to the dark color of thermoplastic products. The dark color fence and rail made out of PVC or other polymeric materials has not been successful in the past. The products show bowing due to differences in expansion and contraction between the two different sides of the product upon exposure of sunlight. In addition, the dark color absorbs heat readily and the resultant uneven heat buildup causes this deformation. An additional problem is the lack of long-term stiffness of the products. It has limited the rail span between the posts to less than traditional lumber.  
         [0004]     Thus, synthetic decks, whether composed of plastic or wood-plastic composite materials, do not fully satisfy market needs.  
         [0005]     Wood-plastic composite planks are produced by extrusion, and the extrusion has various limitations. Extrusion uses an embossing roll to create a wood grain surface. The quality of such wood grains is often not particularly high. Furthermore, the wood composite deck planks are heavy, since the wood composite has a lower modulus and flexural strength, needing a thick wall to compensate for these strength levels. In addition, the wood composite deck does not have color fastness; it changes color from natural or gray to silver-gray over time, in a non-uniform manner when exposed to the outdoor environment.  
         [0006]     Stucky et al., U.S. Pat. No. 6,344,268 describes a foamed palmer-fiber composite made of a polyvinyl chloride resonance matrix with fiber and an additive which can include dyes, pigments, fly ash and mixtures hereof. The additives can be designed to provide a weathered appearance to the building material of Stucky et al., such as a grey color, but the suggested fillers have limited aesthetic functionality.  
         [0007]     Accordingly, there remains a need for a building material which more closely simulates wood products, or which has heretofore unavailable aesthetic properties provided by fillers.  
       SUMMARY OF THE INVENTION  
       [0008]     In a first embodiment of this invention a polymer composite building material is provided which contains about 30-80 weight percent resin, and about 20-70 weight percent fillers and additives. The fillers preferable include a bulk filler for reducing the amount of resin needed to make building material and aesthetically functional filler for providing the building material with an aesthetic appearance. The bulk filler and the aesthetically functional filler are non-toxic, resistant to bacterial attack, and have a Mohs hardness of less than about 5.  
         [0009]     The biggest growth in the synthetic building materials market has occurred in composite lumbers for decking, boardwalk and railing applications. The use of wood plastic composite lumbers in place of traditional wood materials is driven by lower maintenance and better appearance customer demands. Color is a key component in the appearance of wood plastic composites (“WPC”). Most successful companies have a product line which includes four colors, namely, red, dark brown, tan and grey, to duplicate main premium woods, for example, mahogany, red cedar, oak, etc. Companies with only one or two colors enjoy only a limited market share. The ideal color mix is estimated to be 70% dark colors such as dark brown or red and 30% clear colors such as grey and tan. The use of industrial pigments to obtain dark colors represents a significant component of the raw material cost. Industrial pigments made of iron oxide usually cost about $1.50 per pound while other pigments can be as expensive as about $4.00 per pound.  
         [0010]     The present invention replaces industrial pigments and dyes to the use of low cost fillers and provides plastic composite building materials with permanent colors relatively inexpensively. In addition, the present invention can provide a grain or surface texture component to the appearance of plastic composite lumbers. While many companies have started to engrave or emboss the plastic composite products to duplicate a wood grain, such techniques are expensive and time consuming. Even so, wood plastic composites with a low wood flower content tend to have a very plastic appearance, while wood plastic composites with a high wood flower content usually have a better touch and appearance due to the wood particles, which appear at the surface of these products. The present invention also attempts to achieve a unique grain, surface texture and touch by using aesthetically functional fillers.  
         [0011]     Wood plastic composites refer to any composite that contains wood such as wood flower or wood fiber and plastic such as polyethylene, polypropylene, polyvinyl or polyvinyl chloride. The WPC industry has grown dramatically in the past ten years in North America. Main applications include decking, railing, boardwalk, porch, park bench seats and wood trim which have accounted for more than about 500 million in sales in 2003. The use of wood plastic composites in place of traditional wood materials is driven by the characteristics of better resistance to moisture and rot, better resistance to insects, less routine maintenance, no cracking, splitting, warping, or splintering.  
         [0012]     Today the main advantages of organic natural filler such as wood flower are their availability, their weight and their cost. Wood flower is also less abrasive to processing equipment than most conventional fillers. For many years the plastic industry was reluctant to use wood or other natural fillers, such as kenaf or flax, due to their low bulk dust density, low thermostability and tendency to absorb moisture. While this perspective has changed in the last ten years due to the success of several wood plastic composite products, wood flower and wood fiber are still sensitive to moisture absorption, fungi attack and decay. This is due to high wood loadings of generally between 30 and 70 weight percent for reducing costs and to the perocity left in the product, which provides a path for water penetration and fungal attack. The surface of wood plastic composites is covered by many unprotected wood particles, which are not encapsulated by plastic and thus are subject to attack by decay, fungi and moisture.  
         [0013]     Complete encapsulation of wood flower by plastic to prevent moisture absorption and fungal attack is not practical for cost reasons, generally, it would require a high percentage of plastic to fully encapsulate the wood particles, and aesthetic reasons, the resulting finish would look too much like a plastic. Wood polymer composites with too much plastic feel more like plastic than wood and are not appreciated by customers. Successful companies have developed wood polymer composites with high wood loading of generally between 50 and 60 weight percent. To account for wood sensitivity to moisture absorption and bacterial growth, manufactures of high wood loading building components rely on the use of extensive anti-bacterial agents to limit the growth of fungi and algae at the surface of these products. The use of these anti-bacterial agents does not guarantee that the products will be maintenance free and does not prevent infiltration of water into the product, physical and photochemical degradation. The product appearance is likely to change within a few months or years and colors may be affected first. The present invention contemplates the replacement or partial replacement of wood flower or fiber by inorganic fillers to develop a more stable plastic composite building material which is less sensitive to moisture absorption, fungal attack, and change in appearance and color.  
         [0014]     The use of mineral fillers and plastic composite lumbers is not new. Century Board, Inc., a licensee of Ecomat, Inc., has developed a plastic composite lumber that contains 70 weight percent fly ash. The resin is a modified polyester-polyurethane thermoset that can be foamed to produce products with similar density, stiffness and toughness of wood products. See U.S. Pat. Nos. 5,604,266; 5,508,315; and 5,369,147, which are hereby incorporated by reference. The Ecomat building materials describe the use of fly ash and several other mineral fillers with a polyester-polyurethane resin to produce foamed plastic composites for building applications. However, fly ash derive from waste incinerators which is some of the most inexpensive fly ash available, is not generally safe and has a high content of heavy metals.  
         [0015]     The present invention therefore employees different fillers which can be blended together to optimize the mechanical properties, color and texture. These fillers can be optimized for loading and machine throughput. For example, clays can be used to significantly improve impact strength and mechanical properties due to their high aspect ratio and limited particle size, for example Dixie® Clay from R T Vanderbilt has an average particle size of less than about 0.5 microns, and is desirable. But the amount of clay in the resin is limited due to its impact on melt viscosity. On the other hand, fly ash can be added, such as Class F fly ash derived from a coal fired power plant can be added to submit any significant percentage to the resin without dramatic increases in viscosity due to spherical shape and wide size distribution. Class F fly ash can act as a ball bearing to improve machine throughput and is desirable.  
         [0016]     In further embodiments of this invention, low cost color fillers can be added to the plastic composite building materials to provide lasting colors similar to premium woods, such as mahogany red cedar, oak or cherry. Such aesthetic fillers can also achieve another purpose, such as to provide a unique grain, and surface texture, that is aesthetically attractive.  
         [0017]     The present invention provides a method for making polymer composite decking including providing commingled glass fibers and thermoplastic fibers, in which the thermoplastic fibers have a melt index of about 2, heating the thermoplastic fibers and the glass fibers to at least partially melt the thermoplastic fibers and consolidate them with the glass fibers, forming the consolidated glass fibers and thermoplastic fibers in a tool deforming shape decking member and cooling the resulting shape decking member wherein the shape decking member has a flexural modulus of at least 400,000 PSI. Other methods are described in which glass fibers and the thermoplastic resin are combined to produce a similar decking member, and a railing component is provided having a thermoplastic matrix containing polyethylene, polypropylene, HMPE or a combination thereof, and a flexural modulus of at least 400,000 PSI. The fencing rail can be a rail or post, for example, and can include a cap stock or a dark color, or both. Biological attack. The mineral fillers used in the composite of this invention can be hydrated, such as hydrous caoline clay such that a vapor is released during the compounding and molding process that can be used to form the composite. Water chemically bound to a mineral filler of this invention can be released when the composite is subject to excess heat and can also act as a fire retardant.  
         [0018]     This invention also provides a process for making a polymer composite building materials which includes the steps of providing a resin and a plurality of fillers and additives, said fillers comprising at least aesthetically functional filler for providing the building material with a desired aesthetic appearance and a bulk filler for reducing the amount of resin needed to make the building material. The method further includes the step of mixing the resin fillers and additives and finally, melt processing the resin fillers and additives into a shaped article useful in making a building material. Several processes such as casting, molding, extrusion, co-extrusion, injection molding, co-injection molding, etc. can be used to produce the plastic composite products according to this invention. If co-extrusion or co-injection processes are used, the surface of the composite, generally a skin layer of about {fraction (1/16)}-¼ inch can have a different composition than the center of the composite, or the core. The plastic composite building material of this invention can be embossed, engraved or cast in a textured mold to duplicate a wood grain.  
         [0019]     As noted above, there is another class of synthetic deck planks available, namely the PVC profile decks. Such decks are produced by profile extrusion. In this type of production, it is often difficult to use an embossing roll to create the wood grain texture in a uniform nature on the deck surface. The pressure imposed by the embossing roll often cannot provide a uniform force, because the surface of a hollow and three-dimensional panel responds in a non-uniform manner to the particular force. As result, a “real wood” grain emulated surface is particularly difficult to achieve. The PVC profile deck also has a significant thermal expansion coefficient; installation requires care in order to accommodate the expansion and contraction of changes in temperature. In this regard, the dark color deck panel materials have not been practical, since the heat build-up on the surface is more pronounced for darker colored panels. Regarding color fastness, the darker color PVC is superior to wood-plastic composites, but still has the tendency to lose its original color to a visible degree. Furthermore, PVC has a tendency to become brittle with aging upon outdoor exposure, resulting in a loss of its impact strength.  
         [0020]     The present invention serves to correct the shortcomings noted above. The deck panel produced in accordance with the present invention has superior resistance to color fading, possesses superior cold impact strength, has a well-defined wood grain surface, and is lightweight.  
         [0021]     One of the objectives of the present invention is the production of a high strength plastic alternative to the traditional wrought iron or aluminum ornamental rail and fence. Metal fences and rails are constantly under the threat of corrosion attack, and need periodic painting. To date, there have not been any non-composite products with the necessary performance properties and aesthetic appearance comparable to these metal products. In that sense, there have not been any thermoplastic composite products in the market. The present invention discloses thermoplastic composite products that resemble wrought iron, and aluminum wrought iron alternative, but are maintenance-free, kink-free, light and perform equally as well.  
         [0022]     An additional objective is to make the dark color thermoplastic post and rail fence (e.g., split post and rails) possible. The fiberglass reinforcement stabilizes the uneven contraction and expansion, in spite of different heat buildup on the surface.  
         [0023]     A further objective of the present invention is providing non-metallic heavy duty rail and fence systems for use in industrial and commercial applications. The metallic railing in an industrial atmosphere is often exposed to chemical gases or acids and is prone to corrosion attack. The integrity of the industrial railing is critical for the safety of those in the workplace. The thermoplastic railing system that is strengthened by reinforcing tapes or rods of fiberglass/thermoplastic polymer composite provides superior strength and rigidity to its metal counterparts.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a front perspective view of a deck construction using the preferred composite.  
         [0025]      FIGS. 2 and 3  are front perspective views of alternative deck constructions. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     The present invention relates to a consolidated form of the commingled continuous filaments of glass fibers and polymeric fibers as reinforcement. The consolidation of the commingled fibers into composite reinforcement may be made in-situ during in-line extrusion of the final end product extrudate, or, alternatively, prepared as a tape or rod and incorporated into an off-line extrusion of final product. In either case, the materials of the present invention are incorporated through a cross-head die into the polymer extrudate. In this way, the matrix polymer encapsulates the inside and outside surface of the hollow profile product.  
         [0027]     Another production process is to subject these commingled fibers through pultrusion and its die, followed by overlay extrusion of a cap stock polymer using a separate extruder, all in-line. In this case, the capstock polymer covers only the outside surface. The commingled fibers are heated prior to entering into the series of forming dies where they are consolidated. In a further embodiment, a helical winding machine may be added in order to enhance the strength in the hoop direction before the die entrance.  
         [0028]     A preferred material for use in the present invention is Twintex™ composite tapes, supplied by the Saint-Gobain Corporation. The Twintex materials are present in various forms, such as commingled roving and fabrics (unidirectional, or multi-axial woven fabric or tapes). The commingled roving is consolidated through a pultrusion die into a thermoplastic composite tape or rod. It contains glass fibers dispersed uniformly in a longitudinal direction. The polymeric fiber that becomes the consolidation matrix may be either polyethylene (PE), polypropylene (PP) or polyesters (PBT or PET). The functional need of the end product and extrusion process will determine the fiberglass contact in the Twintex material and the volume of the consolidated reinforcement. A “standard” Twintex material contains about 40%-75% glass fiber content.  
         [0029]     Although polyethylene and polypropylene Twintex tapes were used in the testing of the present invention, any polymeric materials would be acceptable to be a commingled fiber with glass fiber, as long as they are capable of being fiberized and made compatible to the intended matrix polymers.  
         [0030]     A further aspect of the present invention relates to the compatibility of the commingled polymeric fiber material with the matrix polymer of the final extrusion product. These materials need adhesion with each other in order to be effective. In the testing of the present invention, a polyethylene-glass fiber Twintex reinforcement/HMPE polymer, polypropylene-glass fiber Twintex reinforcement HMPE polymer, polyethylene-glass fiber Twintex reinforcement/polyethylene polymer, and polypropylene glass fiber Twintex reinforcement/polyethylene polymer were used. The combinations of the polymers of the composite reinforcement and the base polymers are numerous, and may be customized in order to meet the needs of the final product performance requirements.  
         [0031]     The Twintex composite reinforcement allows for the base polymeric material with a higher impact in both cold and ambient temperatures, lower heat expansion coefficient, higher tensile and flexural strength, as well as higher rigidity. These Twintex reinforcements (rods, tapes or fabrics) are embedded into strategic locations of the basic polymeric material.  
         [0032]     In a further preferred embodiment of the present invention, a hybrid of Twintex filaments with carbon fibers may be utilized, with the combination providing for higher stiffness and for easier material handling, as well as providing for a lighter weight product as well.  
         [0033]     The materials of the present invention may be manufactured by a pultrusion process, the mechanics of which are familiar to those of skill in the art. The process utilizes continuous Twintex fibers (roving or yarn), and other fiber as necessary, in order to process uniaxially reinforced profiles with exceptional longitudinal strength. Modification of the basic process allows for the incorporation of transverse reinforcements. Important components of the pultrusion process are: (1) heating, wherein the thermoplastic fibers are melted, and (2) the consolidation and shape forming at the tooling die, in which relatively high pressure is involved.  
         [0034]     In a further preferred embodiment, the commingled, continuous filaments of glass fibers and polymeric fibers include from about 40%-80% glass fiber content. These commingled, continuous filaments may further include carbon fibers and/or aramid fibers. Furthermore, a bulk molding compound may be made out of the commingled, continuous filaments of glass fibers and polymeric fibers. This bulk molding compound may be compression molded into particular building products, such as fence, rail, post and deck materials. The commingled, continuous filaments may be added through, e.g., a helical winding machine.  
         [0035]     In a further preferred embodiment of the present invention, the bulk molding compound includes from about 20%-80% glass fiber content, or is diluted with an addition of polymeric pellets to a glass fiber content to 10%-20% in the final product, with a glass fiber content of about 15% preferred. The thermal expansion and contraction of the composite building material is controlled by the use of the bulk molding compound.  
         [0036]     Wood-plastic composite panels commercially available have a stiffness of about 100,000 PSI. In order to match that stiffness, the present inventors incorporated one half inch to one inch long fiberglass of 10% at minimum with a profile height of about 1.25 to 1.5 inches. These dimensions will result in the composite material having a flexural modulus of about 400,000 PSI or higher. In a preferred embodiment, polymeric materials, specifically polypropylene copolymers with a melt index of about ten and higher, and formulated with a UV stabilizer and colorant, were tested. Note that other polymeric materials may be used for the purposes of the present invention, so long as such materials have an adequate melt index. Measurement of melt flow index was described in ASTM D1238. By incorporating fiberglass in the formulation by means of a bulk molding compound, the thermal expansion and contraction was reduced so that the dark brown color was no longer present. The thermal coefficient of linear expansion was reduced by more than ⅙, to about 1×10 −5  inch/inch/° F. for the polypropylene copolymer. In reference to the figures,  FIGS. 1 and 3  and  FIG. 2  demonstrate differing ways by which the panels may be fastened to the substructure. In  FIG. 2 , screw fasteners  21  on the top of composite  20  provide the fastening function; relative to composites  10  and  30  as shown in  FIGS. 1 and 3  respectively, a concealed fastener  14  with pin  11  is formulated to key into the side hole  12  of composite panel  10 , and screwed into the substructure joist by screw  13 . The pins act as spacers, while the concealed fasteners are necessary for the tiles.  
         [0037]     Note that the preferred process for achieving the construction of the present invention is compression molding. The molding process provides a wood grain pattern of high quality. In operation, a fiberglass bulk molding compound is processed through a specially designed plasticator, and the billet is shuttled to a compression mold, and pressed. Note further that the plasticator is merely one type of compounding extruder equipped with a screw, designed to process the fiberglass in the bulk molding compound without breaking the fiberglass. Panel lengths produced by the compression molding process may range up to about 20 feet. The compression molding enables the surface of the panels to have customized patterns, as well as slip resistance called for by various industry codes.  
         [0038]     Thus, the present invention relates to any walking panels or planks which have incorporated fiberglass of at least about V 2  inch long, at about 10% to 40% by weight into a polymeric material of a melt index higher than e.g., about 2, in order to improve the impact strength for both “under room” and cold temperatures. Walking panels or planks with these characteristics may be made into any suitable custom colors, particularly dark colors, and serve to meet relevant building codes, performance criteria, deflection and creep resistance. Furthermore, a quality grain structure is achieved on the surface of the walking panels or planks, thereby controlling slip resistance.  
         [0039]     The fiberglass component of the present invention may be chopped fiberglass, hybridized with other modulus enhancing fibers. In a further preferred embodiment, the walking panels or planks may have incorporated mold-in spacers, for ease of installation. Furthermore, the panels or planks of the present invention may be constructed of fiberglass bulk molding compound, using a compression molding process having a concealed fastener; such materials will make cutting easier by a power driven saw or other related device.  
         [0040]     In a further preferred embodiment of the present invention, a rail of more than an eight foot span between the two posts, on a sixteen foot length encompassing two sections with, e.g., three posts with a Twintex reinforcement, is a possible alternative. The use of a hybrid reinforcement of Twintex commingled fiber and other reinforcement fibers, such as carbon fiber and/or aramid fibers is also possible.  
         [0041]     Thus, the bulk molding compounds used for purposes of the present invention may be employed for compression molding into building products including fence, rail, post, deck, etc.  
         [0042]     While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.