Starch compositions
Provided herein are starch compositions, which comprise a first starch having a first weight average molecular weight between about 300,000 and about 4,000,000 Daltons, a second starch having a second weight average molecular weight between about 1,000 and about 290,000 Daltons, and a water-soluble polymer. Also provide herein are articles of manufacture and films comprising the starch composition, and methods of making the starch composition.
1 . A starch composition comprising:
a. from about 60% to about 99% by weight of a first starch, said first starch comprising one or more of unmodified starch and modified starch, said first starch having a first weight average molecular weight between about 300,000 and about 4,000,000 Daltons;
b. from about 0.1% to about 40% by weight of a second starch, said second starch comprising one or more of unmodified and modified starch, said second starch having a second weight average molecular weight between about 1,000 and about 290,000 Daltons; and
c. from about 0.5% to about 40% by weight of at least one water soluble polymer comprising one or more of polyvinyl alcohol, polyvinyl acetate and polyoxyalkylene,
wherein the molecular weight distribution of the starch composition is greater than 6.5.
2 . The starch composition according to claim 1 , wherein the first starch is present in an amount from about 70% to about 99% by weight, and/or the second starch is present in an amount from about 0.1% to about 35% by weight.
3 . The starch composition according to claim 1 , wherein the water-soluble polymer is present in an amount from about 3% to about 30% by weight.
4 . The starch composition according to claim 1 , wherein the water-soluble polymer comprises one or more of polyvinyl alcohol and polyoxyalkylene.
5 . The starch composition according to claim 1 , wherein the first weight average molecular weight is between about 300,000 and about 3,500,000 Daltons.
6 . The starch composition according to claim 1 , wherein the second weight average molecular weight is between about 10,000 and about 290,000 Daltons.
7 . The starch composition according to claim 6 , wherein:
a. the second weight average molecular weight is between about 10,000 and about 50,000 Daltons; or
b. the second weight average molecular weight is between about 100,000 and about 290,000 Daltons.
8 . The starch composition according to claim 1 , wherein the amylose content of the first or second starches is, independently, greater than about 10% by weight.
9 . The starch composition according to claim 8 , wherein the amylose content of the first or second starches is, independently, from about 50% to about 80% by weight.
10 . The starch composition according to claim 1 , wherein the amylose content of the second starch is less than about 20% by weight.
11 . The starch composition according to claim 1 , wherein the second starch is a starch which has been treated with an enzyme or with an acid to reduce molecular weight.
12 . The starch composition according to claim 1 , wherein the modified starch is chemically modified so as to replace hydroxyl functionality with functionality selected from the group consisting of ethers, esters and mixtures thereof.
13 . The starch composition according to claim 1 , wherein the modified starch is chemically modified to include a hydroxyalkyl C 2-6 group or modified by reaction with an anhydride of a carboxylic acid.
14 . The starch composition according to claim 1 , wherein the modified starch is chemically modified so as to have a degree of substitution from 0.01 to 1.5.
15 . The starch composition according to claim 1 , wherein the first starch comprises more than one starches and/or modified starches.
16 . The starch composition according to claim 1 , wherein the second starch comprises more than one starches and/or modified starches.
17 . A film comprising a starch composition according to claim 1 .
18 . The film according to claim 17 , wherein the film has an oxygen permeation coefficient of less than 0.05 cm 3 mm/m 2 ·24 h·atm at 50% relative humidity (RH), when measured according to ASTM F1927.
19 . A method of making a starch composition according to claim 1 , the method comprising the step of contacting the first starch, the second starch and the water-soluble polymer under melt processing conditions.