# US 8,772,378 B2 · Thermoplastic starch compositions

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- Number: US 8,772,378 B2
- Document ID: US8772378B2
- Status: Granted
- Kind: B2
- Application number: 13/301,926
- Filed: 2011-11-22
- Published: 2012-06-21
- Granted: 2014-07-08
- Earliest claimed: 2010-11-23
- Assignees: The Procter & Gamble Company
- Applicants: Norman Scott Broyles; Pier-Lorenzo Caruso; Emily Charlotte Boswell; Robert Earl Magness; Ludwig Busam; Jörg Harren; Laurent Wattebled
- Inventors: Norman Scott Broyles; Pier-Lorenzo Caruso; Emily Charlotte Boswell; Robert Earl Magness; Ludwig Busam; Jörg Harren; Laurent Wattebled
- Web page: https://patentgrep.com/patent/US8772378B2

## CPC

- C08L 23/06: Polyethylene
- C08K 3/014: Stabilisers against oxidation, heat, light or ozone
- C08K 3/30: Sulfur-, selenium- or tellurium-containing compounds
- C08K 5/0016: {Plasticisers}
- C08K 5/005: {Stabilisers against oxidation, heat, light, ozone}
- C08K 5/092: Polycarboxylic acids
- C08K 5/098: Metal salts of carboxylic acids
- C08K 5/36: Sulfur-, selenium-, or tellurium-containing compounds {(C08K5/0091 takes precedence)}
- C08K 5/41: Compounds containing sulfur bound to oxygen
- C08L 23/12: Polypropene
- C08L 67/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds (C08L67/06 takes precedence)
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)

## Abstract

The present invention relates to improvements in prevention of discoloration of thermoplastic starch materials and their blends with other thermoplastic materials.

## Claims

### Claim 1

A thermoplastic starch composition comprising,
(a) from about 40% to about 96% starch, by weight of the thermoplastic starch composition;
(b) from about 1% to 40% plasticizer, by weight of the thermoplastic starch composition; and
(c) from about 0.01% to about 5% reducing agent, by weight of the thermoplastic starch composition;
wherein said reducing agent has a redox potential of from about −50 mV to about −1200 mV; and
said redox potential is measured in an aqueous solution at a temperature of about 80° C., wherein said aqueous solution comprises about 1% reducing agent, about 1% citric acid, and about 1% tribasic potassium citrate, by weight of the aqueous solution.

### Claim 2 (depends on 1)

The thermoplastic starch composition of claim 1, wherein the reducing agent is a sulfur-comprising reducing agent.

### Claim 3 (depends on 2)

The thermoplastic starch composition of claim 2, wherein the sulfur-comprising reducing agent is selected from the group consisting of sulfinic acid derivatives or salts thereof, sulfonic acid derivatives or salts thereof, and mixtures thereof.

### Claim 4 (depends on 3)

The thermoplastic starch composition of claim 3, wherein the sulfur-comprising reducing agent is selected from the group consisting of sodium hydroxymethylsulfinate, disodium 2-hydroxy-2-sulfinatoacetic acid, sodium dithionite, thiourea dioxide, disodium 2-hydroxy-2-sulfonatoacetic acid, and mixtures thereof.

### Claim 5 (depends on 4)

The thermoplastic starch composition of claim 4, wherein the sulfur-comprising reducing agent is selected from the group consisting of disodium 2-hydroxy-2-sulfinatoacetic acid, disodium 2-hydroxy-2-sulfonatoacetic acid, and mixtures thereof.

### Claim 6 (depends on 1)

The thermoplastic starch of claim 1, wherein the redox potential of the reducing agent has a value of from about −100 mV to about −1200 mV.

### Claim 7 (depends on 6)

The thermoplastic starch of claim 6, wherein the redox potential of the reducing agent has a value of from about −150 mV to about −1200 mV.

### Claim 8 (depends on 1)

The thermoplastic starch composition of claim 1, wherein the starch is selected from the group consisting of natural starch, modified starch, and mixtures thereof.

### Claim 9 (depends on 8)

The thermoplastic starch composition of claim 8, wherein the starch is a natural starch.

### Claim 10 (depends on 8)

The thermoplastic starch composition of claim 8, wherein the starch is a modified starch.

### Claim 11 (depends on 1)

The thermoplastic starch composition according to claim 1, wherein the thermoplastic starch composition comprises another thermoplastic material.

### Claim 12 (depends on 11)

The thermoplastic starch composition of claim 11, wherein the other thermoplastic material is selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate and mixtures thereof.

### Claim 13 (depends on 1)

A method of preparing the thermoplastic starch composition of claim 1, comprising the steps:
(a) providing ingredients, said ingredients comprising the said starch, said plasticizer, and said reducing agent;
(b) mixing the ingredients to form a mixture;
(c) passing the mixture through a compounder to form a compounded mixture; and
(d) removing excess water from the compounded mixture to form the final thermoplastic starch composition.

### Claim 14 (depends on 13)

The method of claim 13, wherein the ingredients of step (a) additionally comprise added water.

### Claim 15 (depends on 13)

The method of claim 13, wherein the pH of the thermoplastic starch composition is adjusted to less than about 6.

### Claim 16 (depends on 15)

The method of claim 15, wherein the pH of the thermoplastic starch composition is adjusted to less than about 4.