Biodegradable packaging foam and method of preparation

• US 5,252,271 A
• Filed: 10/22/1991
• Issued: 10/12/1993
• Est. Priority Date: 10/22/1991
• Status: Expired due to Fees

• Current Assignee: Merizo Enterprises, LLC
• Original Assignee: Bio-Products International, Inc.
• Inventors: Jeffs, Hyrum J.
• Primary Examiner(s): Kuhns, Allan R.
• Application Number:
  US07/781,509
• Time in Patent Office: 721 Days
• Field of Search: 264/51, 264/53, 264/54, 264/148, 106/210, 106/213
• US Class Current: 264/54
• CPC Class Codes: B65D 81/051 using pillow-like elements filled with cushioning material, e.g. elastic foam, fabric
• CPC Class Codes: C08J 2303/00 Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
• CPC Class Codes: C08J 9/08 developing carbon dioxide
• CPC Class Codes: C08L 2201/06 Biodegradable
• CPC Class Codes: C08L 3/02 Starch; Degradation products thereof, e.g. dextrin
• CPC Class Codes: Y02A 40/90 in food processing or handling, e.g. food conservation
• CPC Class Codes: Y02W 90/10 Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Abstract

A closed cell, light weight packaging material having biodegradable properties and being formed initially from a nonmodified starch material which has been modified by reaction within an extrusion barrel with (i) a mild acid selected from the group consisting of malic acid, tartaric acid, citric acid, maleic acid and succinic acid in the presence of water and (ii) a carbonate composition to generate CO2 gas. This modified starch material has decreased molecular weight and a dominant pattern of nonuniformity of hydrogen bonding within and between starch chains, and a dominant pattern of structural randomness of the starch chains. The resultant packaging material has a closed cellular structure with a density less than 0.032 grams per cubic centimeter and with resilient properties which enable substantial return of the compressed structure to its original, expanded shape with structural integrity. Also set forth is a process for preparing this material, as well as modification for enhancing hydrophobicity.

Claims

1. A method for producing a foamed packing material of biodegradable composition, comprising the steps of:

a) selecting a dry, powdered, starch material having no greater than 30% (w) water content;

b) admixing to the starch material a mild acid in dry, powdered form selected from the group consisting of malic acid, tartaric acid, citric acid, maleic acid and succinic acid, said acid being at a composition percentage of 0.2 to 7% (w) of the total starch composition;

c) admixing to the starch material a dry, powdered carbonate composition capable of reacting with acid to generate CO2 gas, said carbonate composition being at a composition percentage of 0.1 to 2% (w) of the total starch composition;

d) introducing the admixed dry materials of steps a), b) and c) within an initial stage of a screw impeller within an extrusion means;

e) adding sufficient water to the dry materials of step d) at the initial stage of the impeller to convert the dry materials to a gelatinous state when subjected to elevated temperatures and pressures within the extrusion means;

f) mixing and advancing the product of step e) within an extrusion barrel of the extrusion means to generate elevated heat and pressure for converting the material to the gelatinous state;

g) concurrently reacting the acid within the extrusion barrel (i) with the starch material for decreasing molecular weight of the starch material while disrupting the uniformity of hydrogen bonding within and between starch chains, and (ii) with the carbonate material to produce CO2 for expanding the starch at reduced molecular weight and increased structural randomness of the starch chains; and

h) discharging the product of step g) through a die opening to generate expansion of the CO2 to form a closed cellular structure having a density less than 0.032 grams per cubic centimeter and with resilient properties which enable substantial return of the compressed structure to its original, expanded shape with structural integrity.

2. A method as defined in claim 1, wherein the mixing step is more specifically defined to include the, steps of successively mixing, kneading and shearing the materials within the extrusion means.

3. A method as defined in claim 1, wherein the initial step of selecting starch comprises the more specific step of selecting a starch composition from the group consisting of potato starch, corn starch, tapioca starch and rice starch.

4. A method as defined in claim 1, comprising the more specific step of admixing to the starch material a mild acid in dry, powdered form selected from the group consisting of malic acid, tartaric acid, citric acid, maleic acid and succinic acid, said acid being at a composition percentage of 0.5 to 5% (w) of the total starch composition.

5. A method as defined in claim 1, comprising the more specific step of admixing to the starch material a dry, powdered carbonate composition which reacts with acid to generate CO2 gas, said carbonate composition being at a composition percentage of 0.2 to 1% (w) of the total starch composition.

6. A method as defined in claim 1, comprising the more specific step of selecting a raw, dry, powdered, nonmodified starch material having no greater than 25% (w) water content.

7. A method as defined in claim 1, comprising the more specific step of admixing to the starch material a dry, powdered form of malic acid within the composition range of 0.5% to 5% (w) of the total starch composition.

8. A method as defined in claim 1, comprising the more specific step of mixing and advancing the combined ingredients of step e) within a twin screw extrusion barrel of the extrusion means to generate elevated heat and pressure for converting the material to the gelatinous state.

9. A method as defined in claim 1, comprising the more specific step of discharging the product of step f) as extrudate through a die opening to generate expansion of the CO2 to form a closed cellular structure and sequentially severing small segments of the extrudate to develop small puffs of foamed starch useful as packing peanuts.

10. A method as defined in claim 1, comprising the more specific step of selecting a raw, dry, powdered, nonmodified starch material.

11. A method as defined in claim 10, comprising the more specific step of selecting a raw, dry, powdered, nonmodified starch material having no greater than 25% (w) water content.

12. A method as defined in claim 1, further comprising the step of adding a fire retardant constituent to the combined ingredients of step e) for the purpose of enhancing resistance of the extrudate against rapid dissolution when in contact with water.