With the rising cost of wood and the shortage of mature trees, there is a present need to find good quality substitutes for wood which will continue long into the future. Additionally, good quality wood substitutes are more durable and longer lasting than wood since they are less susceptible to termite destruction and wood rot.
Over the past several years a growing market has emerged for the use of polymer-wood composites to replace traditional solid wood products in applications such as decking, windows, fencing, automobile interiors and pallets. One key to achieving a high quality polymer-wood composite is a thorough dispersion of cellulosic fiber in a polymer matrix. To achieve this, many leading producers of polyethylene-wood decking have found lubricants to be essential.
Agricultural residues are the parts of the plant that remain in the fields after a crop is harvested. Examples of such residues include, but are not limited to, those parts of the plant left in the fields after the harvesting of straw, oak, rice, and corn. After harvest, the agricultural residues are usually burned or plowed into the ground as compost. In place of burning or plowing these residues into the ground, these annually renewable lignocellosic fibers or lignocellosics have an outstanding potential of being used as a fiber source in the production of a non-wood fiber composites.
U.S. Pat. No. 6,011,091 teaches a cellulosic composite containing from 60 to 70% cellulosic material, from 30 to 40% polyvinyl chloride material and up to 4% by weight of polar thermosetting material. Common commercial lubricants such as calcium esters, e.g., stearate, paraffin wax and amide wax can be used. However, vinyl-chloride based thermoplastics are generally more difficult to process than olefin based thermoplastics.
U.S. Pat. No. 6,066,680 describes an extruded composite formed from foamable plastic containing a polymer resin and wood flour particles. A two step process is taught wherein the wood flour particles are encapsulated by the resin and pelletized, and then the pelletized pieces are mixed with additional resin and blowing agents. Lubricants such as stearic acid, calcium stearate, ester wax, and AC-629A Oxidized Polyethylene wax can be included.
The polymer resins described are polyvinyl chloride, chlorinated polyvinyl chloride and polystyrene.
U.S. Pat. No. 6,103,791, which is a continuation of U.S. Pat. No. 6,011,091 discloses a cellulosic composite containing from 50 to 65% cellulosic material, from 25 to 30% polyvinyl chloride material and up to 4% by weight of polar thermosetting material. These composites are considered to have improved weatherability. Also, they appear to adhere better to the wood material without the need for adhesives or tie layers.
Therefore, a present need exists for a superior polymer-wood composite based on an easily processable polymer which has better weatherability and dimensional stability than contemporary products on the market.