Partially cross-linked polyvinyl alcohol
The invention relates to a partially cross-linked polyvinyl alcohol, obtained by reacting a polyvinyl alcohol with a polycarboxylic acid, in particular a hydroxypolycarboxylic acid. The partially cross-linked polyvinyl alcohol can be used to produce foils, which have a good water-solubility or water-swelling capacity. Due to this property, such foils can be used as packing material for detergents, cosmetics and the like. According to the invention, the packing dissolves in water, releases its contents or is suitable for releasing (permeation) chemical compounds or agents.
1. A water-soluble or water-swellable film consisting of a cross-linked polyvinyl alcohol obtained by mixing in water a polyvinyl alcohol with a polycarboxylic acid of formula (1)
ROOC-A-COOR (1)
where A represents one or more, identical or different groups of the formulae
—(CH 2 ) m —; —(CH═CH) n —;
—(C 6 H u X 4-u ) o —; —(C 5 H 3 ) p —; —(C 6 H 10 ) q —; —(CH(OH)) r —; —(CH(COOR)) s —;
—(C(OH)(COOR)) t —, X is H, OH or COOR, R is H, C a H 2a-1 , an alkaline earth or alkali metal atom or NH 4 , a is from 1 to 10, m is from 0 to 20, n is from 0 to 6, o is from 0 to 3, p is from 0 to 3, q is from 0 to 3, r is from 0 to 10, s is from 0 to 5, t is from 0 to 5 and u is from 1 to 4
and heating the mixture to a temperature above 150° C. to cross-link said polyvinyl alcohol.
2. A water-soluble or water-swellable capsule consisting of a cross-linked polyvinyl alcohol obtained by mixing a polyvinyl alcohol with a polycarboxylic acid of formula (1)
ROOC-A-COOR (1)
where A represents one or more, identical or different groups of the formulae
—(CH 2 ) m —; —(CH═CH) n —;
—(C 6 H u X 4-u ) o —; —(C 5 H 3 ) p —; —(C 6 H 10 ) q —; —(CH(OH)) r —; —(CH(COOR)) s —;
—(C(OH)(COOR)) t —, X is H, OH or COOR, R is H, C a H 2a-1 , an alkaline earth or alkali metal atom or NH 4 , a is from 1 to 10, m is from 0 to 20, n is from 0 to 6, o is from 0 to 3, p is from 0 to 3, q is from 0 to 3, r is from 0 to 10, s is from 0 to 5, t is from 0 to 5 and u is from 1 to 4;
and heating the mixture to a temperature above 150° C. to cross-link said polyvinyl alcohol.
3. The water-soluble or water-swellable film of claim 1 , wherein the temperature ranges from 150 to 250° C.
4. The water-soluble or water-swellable film of claim 1 , wherein the polycarboxylic acid of formula (1) is selected from the group consisting of tartaric acid, malic acid, citric acid, and mixtures thereof.
5. The water-soluble or water-swellable film of claim 1 , wherein a ratio of the polyvinyl alcohol to polycarboxylic acid ranges from 100 parts by weight of polyvinyl alcohol: 0.1 part by weight of polycarboxylic acid to 1 part by weight of polyvinyl alcohol: 1 part of polycarboxylic acid.
6. The water-soluble or water-swellable film of claim 1 , wherein the mixing and heating steps take place in the presence or absence of a solvent.
7. The water-soluble or water-swellable film of claim 6 , wherein the solvent is water.
8. A method for preparing a water-soluble or water-swellable film or capsule consisting of cross-linked polyvinyl alcohol and optionally a plasticizer, said method comprising:
a) admixing in the presence or absence of a solvent a polyvinyl alcohol with a polycarboxylic acid of formula (1)
ROOC-A-COOR (1)
where A represents one or more, identical or different groups of the formulae
—(CH 2 ) m —; —(CH═CH) n —;
—(C 6 H u X 4-u ) o —; —(C 5 H 3 ) p —; —(C 6 H 10 ) q —; —(CH(OH)) r —; —(CH(COOR)) s —;
—(C(OH)(COOR)) t —, X is H, OH or COOR, R is H, C a H 2a-1 , an alkaline earth or alkali metal atom or NH 4 , a is from 1 to 10, m is from 0 to 20, n is from 0 to 6, o is from 0 to 3, p is from 0 to 3, q is from 0 to 3, r is from 0 to 10, s is from 0 to 5, t is from 0 to 5 and u is from 1 to 4;
b) heating the mixture to a temperature above 150° C. to provide said cross-linked polyvinyl alcohol; and
c) forming the water-soluble or water-swellable film or capsule from the cross-linked polyvinyl alcohol.
9. The method of claim 8 , wherein said forming step includes extrusion.
10. A water-soluble or water-swellable film prepared by the method of claim 8 .
11. A water-soluble or water-swellable capsule prepared by the method of claim 8 .