# US 5,705,536 A · Foamed starch polymer

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- Number: US 5,705,536 A
- Document ID: US5705536A
- Status: Granted
- Kind: A
- Application number: 08/586,859
- Filed: 1996-06-27
- Granted: 1998-01-06
- Earliest claimed: 1993-07-28
- Assignees: Bio-Tec Biologische Naturverpackungen GmbH
- Inventors: Ivan Tomka
- Web page: https://patentgrep.com/patent/US5705536A

## CPC

- C08J 9/125: {Water, e.g. hydrated salts}
- C08B 30/12: Degraded, {destructured} or non-chemically modified starch {, e.g. mechanically, enzymatically or by irradiation; Bleaching of starch (preparation of chemical derivatives of starch C08B31/00)}
- C08J 9/0085: {Use of fibrous compounding ingredients (C08J9/0076 takes precedence)}
- C08L 3/02: Starch; Degradation products thereof, e.g. dextrin
- C08J 2303/00: Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C08B: POLYSACCHARIDES; DERIVATIVES THEREOF (polysaccharides containing less than six saccharide radicals attached to each other by glycosidic linkages C07H; fermentation or enzyme-using processes C12P19/00; sugar industry C13; production of cellulose D21)
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

In order to produce a substantially biologically degradable polymer foam, a thermoplastic or disaggregated starch or a polymer mixture of thermoplastic or disaggregated starch with at least one biologically degradable hydrophobic polymer is used. In addition, the material is mixed with a biologically degradable fibrous or capsular material capable of binding water by capillary action, said material being at least partially treated or saturated with water before being mixed with the polymer. The polymer/material mixture thus obtained is processed under controlled pressure and temperature so that the water bound by capillarity in the material is released and causes the polymer to foam.

## Claims

### Claim 1

A process for the production of a substantially biologically degradable polymer foam, characterized by the fact that thermoplastic or disaggregated starch or a polymer mixture of thermoplastic or disaggregated starch with at least one biologically degradable hydrophobic polymer, said starch or polymer mixture having a water content of less than 5 wt % is mixed with a material consisting essentially of a biologically degradable fibrous or capsular material which is capable of binding water by capillary action and which was at least partially treated with water, and the polymer/material mixture is foamed by applying such pressure and temperature that the water bound by capillary action in the material is liberated so as to effect the foaming of the polymer.

### Claim 2 (depends on 1)

A process, according to claim 1, characterized by the fact that thermoplastic starch or the polymer mixture containing thermoplastic starch is mixed with up to 30 wt. % of capillary water-containing fibrous or capsular material.

### Claim 3 (depends on 1)

A process, according to claim 1, characterized by the fact that the mixing of the thermoplastic starch or the thermoplastic starch/polymer mixture with the fibrous or capsular material is effected within a temperature range of 100.degree.-200.degree. C.

### Claim 4 (depends on 1)

A process, according to claim 1, characterized by the fact that the fibrous or capsular material comprises at least one of the following fibers: hemp, jute, sisal, cotton, flax/linen, natural silk and/abaca.

### Claim 5 (depends on 1)

A process, according to claim 1, characterized by the fact that the fibrous or capsular material comprises at least one of the following substances: expanded clay aggregate, silica gel, agarose gel, cephatex gel and/Ceolith.

### Claim 6 (depends on 1)

A process, according to claim 1, characterized by the fact that the fibrous or capsular material comprises ramie fibers.

### Claim 7 (depends on 1)

A process, according to claim 1, characterized by the fact that the polymer mixture contains, in addition to thermoplastic starch, at least one of the following hydrophobic polymers:
cellulose derivative having a degree of substitution less than or equal to 2;
aliphatic polyester;
hydrophobic protein; and
polyvinyl alcohol.

### Claim 8 (depends on 7)

A process, according to claim 7, characterized by the fact that the polymer mixture comprises a polymeric phase mediator or a macromolecular dispersing agent, the phase mediator or the dispersing agent coupling of the starch phase with the hydrophobic polymer phase.

### Claim 9 (depends on 1)

A process according to claim 1, characterized by the fact that the thermoplastically processable starch is starch which has been digested with water removal with at least one of the following substances as swelling or plasticizing agent or as softener:
sorbitol, glycerol, pentaerythritol, trimethyl propane, polyvinyl alcohol, a hydroxy acid or salt thereof, polyvinyl alcohol, and ethoxylated polyalcohol.

### Claim 10 (depends on 1)

A process, according to claim 1, characterized by the fact that the thermoplastic starch or a thermoplastic starch/polymer mixture having a water content of less than 1 wt. % is mixed with 2-20 wt. %, of water-saturated ramie fibers having a fiber length of about 0.3-4.0 mm, within a temperature range of about 120.degree.-180.degree. C.

### Claim 11 (depends on 10)

A process, according to claim 10, characterized by the fact that for the foaming at a temperature of about 200.degree.-210.degree. C. in order to effect the liberation of the water bound by capillary action in the ramie fiber, which water serves as expansion agent for the inflating of the thermoplastic starch.

### Claim 12

A process for the production of a polymer mixture suitable for the production of a biologically degradable polymer foam, characterized by the fact that thermoplastic starch or a polymer mixture containing thermoplastic starch and a hydrophobic polymer having a water content of less than 1 wt. % are mixed with up to 30 wt. % of ramie fibers substantially saturated with water at a temperature range of 130-.degree.170.degree. C.

### Claim 13

A biologically degradable polymer foam, comprising foamed thermoplastic starch containing ramie fibers.

### Claim 14 (depends on 13)

A polymer foam, according to claim 13, comprising 3 to 30 wt. % of ramie fibers based on the total weight of the foam.

### Claim 15 (depends on 13)

A polymer foam, according to claim 13, characterized by comprising 20 to 35 wt. %, based on the weight of the thermoplastic starch, of glycerol, sorbitol or a mixture thereof as plasticizer, as well as 4-8 wt. % of ramie fibers, referred to the total weight of the foam.

### Claim 16

A polymer mixture suitable for the production of a biologically degradable polymer foam, characterized by a thermoplastic starch mixture with ramie fibers substantially saturated with water.

### Claim 17 (depends on 16)

A polymer mixture according to claim 16, characterized by the fact that the thermoplastic starch is from 20 to 35 wt.% based on the weight of the thermoplastic starch of glycerol, sorbitol or a mixture thereof, and the ramie fibers are 4 to 8 wt. % based on the total weight of the polymer mixture.

### Claim 18 (depends on 16)

A polymer mixture according to claim 16, characterized by the fact that it contains at least one hydrophobic polymer.

### Claim 19 (depends on 13)

A biologically degradable polymer foam according to claim 13, characterized by the fact that it contains at least one hydrophobic polymer.

### Claim 20 (depends on 2)

A process according to claim 2 in which said water content is less than one weight percent and the mixture is effected within a temperature range of 130.degree. C.-170.degree. C.

### Claim 21 (depends on 7)

A process according to claim 7, characterized by the fact that the hydrophobic polymer is selected from the group consisting of cellulose ether, cellulose ester, caprolactone, polyhydroxybutyric acid, polyhydroxybutyric acid/hydroxvaleric acid copolymer, polylactic acid, zein and about 88% hydrolyzed polyvinyl acetate.

### Claim 22 (depends on 10)

A process according to claim 10 in which the amount of water-saturated ramie fibers is 4-8 wt. percent and said fibers have a fiber length of about 0.4-0.6 mm and the mixing is effected within a temperature range of 130.degree. C.-170.degree. C.

### Claim 23 (depends on 12)

A process according to claim 12 in which the amount of ramie fibers is about 4-8 wt. percent.