Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – To form particulate product
Reexamination Certificate
2000-05-11
2002-04-02
Seidleck, James J. (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
To form particulate product
C524S047000, C264S211000, C264S211210, C264S211220, C264S211230
Reexamination Certificate
active
06365079
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for preparing starched-based thermoplastic polymer compositions and the compositions prepared thereby.
U.S. Pat. No. 3,137,592 to Protzman describes a process which comprises mixing starch with about 22 percent to about 67 percent water based on the weight of the starch raw material dry substance. The starch may or may not be modified. The mixture of the starch and water is fed under pressure onto a rotating screw, advanced by means of the rotation of the screw while maintaining an increased temperature by means of external heaters and the shearing action of the screw. The material is mechanically worked in a confining chamber formed by the screw and barrel of the extruder and then transformed into a homogeneous viscous fluid mass.
U.S. Pat. No. 4,673,438 to Wittwer et al. describes a starch/water composition obtained by maintaining a starch/water composition at a water content of 5 percent to 30 percent by weight of the composition under controlled conditions of temperature and pressure, heating the starch/water composition under pressure above its glass transition temperature and melting point while maintaining said water content to form a melt and further heating and plasticizing the molten starch/water composition to dissolve the starch in the water to form a melt as a molecularly dispersed solution of said melt.
U.S. Pat. No. 4,454,268 to Otey describes a process for preparing a starch-based film from a composition of a blend of starch, water and one or more polymers. Otey teaches that the starch should be highly gelatinized, which means that all or substantially all of the starch granules are sufficiently swollen and disrupted, that they form a smooth viscous dispersion in water. The mixture is then processed at 105° C. to 110° C. at elevated pressures and extruded as a film.
Mercier, C., Effect of Extrusion-Cooking,
Die Starke
29. Jahrg. 1977/Nr. 2 S.48-52 (Mercier) describes a process for extruding unmodified potato starch having a moisture content before extrusion of 23 percent by weight using a semi-industrial twin-screw extruder.
Randall et al., “Development of Starch Based Plastics—A Reexamination of Selected Polymer Systems in Historical Perspective,”
Starch/Starke
45 (1993) Nr. 8, S. 276-280, has argued that the concept of “destructurization” is just a new name for an old concept of “gelatinization” of starch that first originated in the food industry. The term “gelatinization” refers to the process of disruption of the granular structure of starch by heating a starch suspension at temperatures in the range of 50° C. to 80° C.
In order to produce a satisfactory extruded article, starch must be combined with other polymers, because extrusion of starch alone produces a brittle, water-sensitive article. U.S. Pat. No. 5,095,054 to Lay et al. describes the preparation of starch-based compositions comprising destructurized starch and water-insoluble polymers.
WO 97/23564 describes a composition comprising a polysaccharide, a modified polysaccharide, or a naturally-occurring fiber or particulate filler and a thermoplastic hydroxy-functional polyether derived from monomers containing 1 or more epoxy groups. The components are brought together and processed in an appropriate melt extruder from which the blend is extruded in the form of powder or strands. The powders or strands are then pelletized or formed into granules for injection molding and other thermal processes.
SUMMARY OF THE INVENTION
The present invention is a process for preparing a starch-based thermoplastic hydroxy-functionalized polyetheramine comprising continuously feeding from about 40 to about 98 weight percent starch and from about 2 to about 60 weight percent of a thermoplastic hydroxy-functionalized polyetheramine into a mixing screw extruder at a temperature of from about 30° C. to about 120° C. while maintaining a water content in the extruder of from about 7 to about 50 weight percent, continuously removing the compounded mixture from the extruder in the form of strands at a rate of from 13.5 to 2725 kg/hour, and forming the strands of compounded mixture into pellets.
The hydroxy-functionalized polyetheramine has been found to adhere strongly to starch. This adhesion, and the generally good physical properties of hydroxy-functionalized polyetheramine, allows for the preparation of hitherto unknown materials with useful physical properties.
The starch-based thermoplastic compositions of the present invention are suitable for use in fabricating molded, extruded or foamed articles, containers, films, film laminates, or coatings using conventional fabricating techniques such as extrusion, compression molding, injection molding, blow molding and similar fabrication techniques commonly used to produce such articles. Examples of such articles include films, foams, sheets, loose fill packaging material, pipes, rods, bags, boxes, meat trays, egg cartons, cups and plates, cutlery, and other disposable consumer items. The compositions of the present invention are also suitable for use as adhesives and encapsulating agents.
DETAILED DESCRIPTION OF THE INVENTION
Preferably, the hydroxy-functionalized polyetheramine employed in the practice of the present invention has repeating units represented by the formula:
wherein R
5
is hydrogen or alkyl, A is an amine moiety or a combination of different amine moieties; B is a divalent organic moiety which is predominantly hydrocarbylene; and m is an integer from 10 to about 1000.
Preferably, A is 2-hydroxyethylimino-, 2-hydroxypropylimino-, piperazenyl, N,N′-bis(2-hydroxyethyl)-1,2-ethylenediimino-, and B is isopropylidenediphenylene, 1,3-phenylene, or 1,4-phenylene, and R
5
is hydrogen.
More preferably, the hydroxy-functionalized polyetheramine has repeating units represented by the formula:
wherein R is 2-hydroxyethyl, phenyl, methyl, ethyl, propyl, 2-hydroxypropyl, 3-hydroxypropyl, cyclohexyl, butyl, aryl, hexyl or combination thereof; and Ar is isopropylidene, diphenylene, oxydiphenylene, sulfonyldiphenylene, methylene diphenylene, 1,4-phenylene, 1,3-phenylene or combination thereof.
The hydroxy-functionalized polyetheramines are prepared by contacting one or more of the diglycidyl ethers of a dihydric phenol with an amine having two amine hydrogens under conditions sufficient to cause the amine moieties to react with epoxy moieties to form a polymer backbone having amine linkages, ether linkages and pendant hydroxyl moieties. These polyetheramines are described in U.S. Pat. No. 5,275,853. These polyetheramines can also be prepared by contacting a diglycidyl ether or an epihalohydrin with a difunctional amine.
The term “starch” as used herein, refers to carbohydrates of natural, vegetable origin, composed mainly of amylose and/or amylopectin, and includes unmodified starches (native starches), physically modified starches, such as thermoplastic, gelatinized or cooked starches, starches with a modified acid value (pH) where acid has been added to lower the acid value of a starch to a range of from 3 to 6, gelatinized starches, ungelatinized starches, cross-linked starches and disrupted starches (starches which are not in particulate form). The starches can be in granular, particulate or powder form. They can be extracted from various plants, such as, for example, potatoes, tapioca, pea, and grains such as corn, rice, rye, oats and wheat.
The composition of the present invention may also contain various additives such as, for example, plasticizers, lubricants, pigments, foaming agents, extenders, stabilizers, chemical modifiers, and flow accelerators. Each of these additives is known and several types of each are commercially available.
While the amounts of hydroxy-functionalized polyetheramines (PHAE) and starch used depend on a variety of factors, including the specific polymer employed and the desired end uses of the composition, in general, the PHAE can be present in an amount of from about 2 to about 60 weight percent, and the starch can be present in an amount of from about 40 to abo
Berry Tricia S.
Kirkpatrick Donald E.
Winkler Marie S.
Dow Chemical Company
Rajguru U. K
Seidleck James J.
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