Method for reinforcing a thermoplastic resin composition
The present invention is directed to plant fiber-reinforced thermoplastic compositions and a method for reinforcing thermoplastic resins. The present invention provides a use for the cellulose portion of a plant material, which is the portion left over after processing the selected plant materials to separate the hemi-cellulose and lignin from the cellulose.
1. A method for reinforcing a thermoplastic resin composition comprising:
a) providing an amount of cellulose fibers obtained by the separation of the cellulose fiber fraction from hemi-cellulose and lignin fractions of a natural plant material; and
b) blending from about 1 to about 60 weight percent of the cellulose fibers based on the weight of the composition with a thermoplastic resin, the cellulose fibers having a porous surface obtained by the mechanical shearing and subsequent chemical separation of the cellulose fiber fraction from hemi-cellulose and lignin fractions of a natural plant material.
2. The method of claim 1 wherein the natural plant material is selected from the group consisting of natural fibrous plant materials including a) seed fiber plants, linters, cotton, kapok and poplar down, b) bast fiber plants, sclerenchyma fiber plants, bamboo fiber plants, (stinging) nettles, hemp, jute, linen or flax, and ramie, c) hard fiber plants, sisal, kenaf and manila, d) coir, and e) grasses.
3. The method of claim 1 wherein the cellulose fibers are formed of at least 95% pure cellulose fibers.
4. The method of claim 1 wherein the thermoplastic resin is selected from the group consisting of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyacryl nitrite, polyamides, polyesters, polyacrylates and mixtures thereof.
5. The method of claim 1 wherein the step of providing the cellulose fibers comprises:
a) mechanically separating core tissue fibers from outer plant fibers; and
b) chemically separating the cellulose fibers from hemi-cellulose and lignin fractions of the core tissue fibers.
6. The method of claim 5 wherein the step of mechanically separating the outer plant fibers from the core tissue fibers comprises shearing the outer plant fibers from the core tissue fibers to minimize damage to the core tissue fibers.
7. The method of claim 1 wherein the step of blending the cellulose fibers with the thermoplastic resin comprises mixing the cellulose fibers and the thermoplastic resin in parallel screw mixing device to minimize breakage of the cellulose fibers and the residence time of the fibers and resin in the mixing device.
8. The method of claim 1 wherein the step of blending the cellulose fibers with the thermoplastic resin comprises forming molecular bonds between the cellulose fibers and the thermoplastic resin.