Biodegradable materials from starch-grafted polymers
AssigneeCereplast, Inc.
InventorsZhenhua Sun, Wanjun Liu, Ya-Jane Wang
Life of this patent
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Abstract
Granular starch is added to a polymer in order to decrease the cost of the polymer derivative. Use of granular starch also makes the derivative more biodegradable. The polymer blend has very similar mechanical properties to pure polymer. Furthermore, unlike other starch/polyethylene mixtures, glycerol is not added to the mixture. This reduces the water absorbency of the final product. The polymer and starch are blended together in the presence of an interfacial compatibilizer that binds the two components together.
Claims18
A synthetic polymer and starch blend comprising:
- 1-30 wt. % a granular and unplasticized starch having a moisture content of less than about 1%;
- 1-24 wt. % a compatibilizer comprising a polymer and a grafting compound, wherein said grafting compound is covalently bound to said polymer, and
- the remainder a second polymer.
A method for synthesizing a synthetic polymer and starch blend, comprising:
- mixing 1-30 wt. % granular and unplasticized starch having a moisture content of less than about 1% with 1-24 wt. % compatibilizer comprising a polymer and a grafting compound, wherein said grafting compound is covalently bound to said polymer, and the remainder a second polymer;
- and
- reacting the mixture such that the compatibilizer and the granular starch become covalently bound.
A synthetic polyethylene and starch covalently bound mixture comprising:
- 5-30 wt. % of as granular and unplasticized starch selected from the group consisting of wheat starch, cornstarch, rice starch, potato starch or high amylose starch, wherein said starch is not gelatinized and has a moisture content of less than about 1%;
- a first polymer selected from the group consisting of polyethylene, polypropylene or polyethylene derivatives;
- a compatibilizer comprising a polymer and a grafting compound, the grafting compound being selected from the group consisting of maleic anhydride or chemicals having similar reactive properties, and the polymer being covalently bound to the grafting compound;
- wherein application of heat and pressure to the mixture produces covalent bonds between the compatibilizer and the starch;
- wherein said compatibilizer is covalently bound to said first polymer;
- wherein said starch granules are 10-100 micrometers in diameter;
- wherein about 5 wt. % of monomer units of said compatibilizer have the grafting compound attached;
- wherein the resulting mixture has similar mechanical properties to pure polyethylene;
- and
- wherein said mixture absorbs relatively little water.
Dependencies are inferred from the claim text.