Coated polymer foils with oxygen barrier properties

Abstract

A coated polymer foil is described and can be produced via coating of a polymer foil with an aqueous composition comprising (A) a polymer which is obtained via free-radical polymerization and which is composed of from 10 to 80% by weight of a compound selected from ethylenically unsaturated anhydrides and ethylenically unsaturated dicarboxylic acids, the carboxylic acid groups of which can form an anhydride group, and (B) an alkanolamine having at least two hydroxy groups. The coating gives the polymer foil an oxygen barrier and can in particular be used for producing packaging.

Claims

1. A coated polymer foil produced via coating of a polymer foil in an oxygen permeability-reducing amount with an aqueous composition consisting of water, and: (A) a polymer which is obtained via free-radical polymerization and which comprises from 10 to 80% by weight of at least one compound selected from ethylenically unsaturated anhydrides and ethylenically unsaturated dicarboxylic acids, the carboxylic acid groups of which can form an anhydride group; (B) at least one alkanolamine having at least two hydroxy groups; and (C) optionally at least one selected from the group consisting of a wetting aid, a dye, a pigment, a biocide, a plasticizer, a thickener, an adhesion promoter, a reducing agent, and a transesterification catalyst, wherein the pigment is not a lamellar pigment, wherein the aqueous composition contains a single polymer, which is polymer (A), and wherein the oxygen permeability of the coated polymer foil is less than 30% of the oxygen permeability value of the uncoated polymer foil, measured at 23 C. and 0% relative humidity, according to ASTM D3985.

2. The polymer foil according to claim 1, wherein, after the coating process, the coated polymer foil with the aqueous composition is dried and heated to at least 100 C.

3. The polymer foil according to claim 1, wherein the polymer foil has a coating in which the polymer has been crosslinked by way of ester bonds between acid groups of the polymer (A) and hydroxy groups of the alkanolamine(B).

4. The polymer foil according to claim 1, wherein the polymer (A) is composed of from 10 to 80% by weight of maleic acid or maleic anhydride.

5. The polymer foil according to claim 1, wherein the alkanolamine (B) involves a compound NR.sup.1R.sup.2R.sup.3 in which R.sup.1 is an H atom, a C1-C10-alkyl group, or a C1-C10-hydroxyalkyl group, and R.sup.2 and R.sup.3 are a C1-C10-hydroxyalkyl group.

6. The polymer foil according to claim 1, wherein the alkanolamine (B) involves triethanolamine.

7. The polymer foil according to claim 1, where the molar ratio of the carboxy groups and anhydride groups (where an anhydride group is counted as two carboxy groups) of the polymer (A) to the hydroxy groups of the alkanolamine (B) is from 20:1 to 1:1.

8. The polymer foil according to claim 1, wherein the gel content of the aqueous composition after drying and 15 minutes of curing at 130 C. is greater than 50% by weight.

9. The polymer foil according to claim 1, wherein the thickness of the coating is at least 0.5 m.

10. The polymer foil according to claim 1, wherein the backing material for the polymer film is selected from the group consisting of polyethylene terephthalate, oriented polypropylene, polyethylene, and biodegradable aliphatic-aromatic copolyesters.

11. The polymer foil according to claim 1, wherein the polymer foil is packaging or a portion of packaging.

12. The polymer foil according to claim 1, wherein the polymer foil is further coated with at least one adhesive layer or with at least one sealable layer.

13. The polymer foil according to claim 1, wherein the polymer (A) is composed of from 20 to 40% by weight of maleic acid or maleic anhydride and of from 60 to 80% by weight of acrylic acid and/or methacrylic acid, and from 20 to 40 parts by weight of alkanolamine (B) have been used for every 100 parts by weight of polymer (A).

14. The polymer foil according to claim 1, wherein said oxygen permeability is less than 20% of said oxygen permeability value of the uncoated polymer foil.

15. The polymer foil according to claim 1, wherein said oxygen permeability is less than 10% of said oxygen permeability value of the uncoated polymer foil.

16. The polymer foil according to claim 1, wherein said oxygen permeability is from 1% to 3% of said oxygen permeability value of the uncoated polymer foil.

17. The polymer foil according to claim 1, wherein the polymer (A) consists of 20 to 40% by weight of maleic acid or maleic anhydride and 60 to 80% by weight of acrylic acid and/or methacrylic acid.

18. An oxygen barrier coating on a polymer foil, wherein the oxygen barrier coating is made from an aqueous composition consisting of water, and: (A) a polymer which is obtained via free-radical polymerization and which comprises from 10 to 80% by weight of at least one compound selected from ethylenically unsaturated anhydrides and ethylenically unsaturated dicarboxylic acids, the carboxylic acid groups of which can form an anhydride group; (B) at least one alkanolamine having at least two hydroxy groups; and (C) optionally at least one selected from the group consisting of a wetting aid, a dye, a pigment, a biocide, a plasticizer, a thickener, an adhesion promoter, a reducing agent, and a transesterification catalyst, wherein the pigment is not a lamellar pigment, wherein the aqueous composition contains a single polymer, which is polymer (A), and wherein the oxygen permeability of the coated polymer foil is less than 30% of the oxygen permeability value of the uncoated polymer foil, measured at 23 C. and 0% relative humidity, according to ASTM D3985.

19. A process for producing or reinforcing an oxygen barrier effect on a backing substrate selected from polymer foils, where the backing substrate is directly or indirectly coated with an aqueous composition consisting of water, and: (A) a polymer which is obtained via free-radical polymerization and which comprises from 10 to 80% by weight of at least one compound selected from ethylenically unsaturated anhydrides and ethylenically unsaturated dicarboxylic acids, the carboxylic acid groups of which can form an anhydride group; (B) at least one alkanolamine having at least two hydroxy groups; and (C) optionally at least one selected from the group consisting of a wetting aid, a dye, a pigment, a biocide, a plasticizer, a thickener, an adhesion promoter, a reducing agent, and a transesterification catalyst, wherein the pigment is not a lamellar pigment, wherein, after the coating process, the coated polymer foil with the aqueous composition is dried and heated to at least 130 C., wherein the aqueous composition contains a single polymer, which is polymer (A), and wherein the oxygen permeability of the coated polymer foil is less than 30% of the oxygen permeability value of the uncoated polymer foil, measured at 23 C. and 0% relative humidity, according to ASTM D3985.

Description

EXAMPLES

(1) The aqueous coating compositions can be produced as described in WO 97/31036.

(2) Measurement of Oxygen Barrier Effect:

(3) Oxygen transmission and, respectively, oxygen permeability were determined on coatings on polymer foils at the relative humidity respectively stated. This method begins by measuring oxygen transmission, and then recalculates this on the basis of a layer thickness of 1 m and states it as oxygen permeability with the unit (cm.sup.31 m)/(m.sup.2dbar), where d is the time in days. The determination method is based on ASTM D3985.

Example B1

(Comparison, without Alkanolamine)

(4) Polymer foil: polyethylene terephthalate, thickness 36 m

(5) Aqueous Coating Composition:

(6) Polymer made of 75 parts by weight of acrylic acid and 25 parts by weight of maleic acid

(7) Weight-average molar mass: 80 000 g/mol

(8) Solid content: 50% by weight in water

Example B2

(9) Polymer foil: polyethylene terephthalate, thickness 36 m

(10) Aqueous Coating Composition:

(11) Polymer made of 75 parts by weight of acrylic acid and 25 parts by weight of maleic acid

(12) Weight-average molecular mass: 80 000 g/mol

(13) 30 parts by weight of triethanolamine for every 100 parts by weight of polymer

(14) Solids content: 50% by weight in water

(15) The polymer foils were coated with the aqueous coating compositions, using a layer thickness (after drying) of 6 m (example 1) or 10 m (example 2). The crosslinking was achieved via heating to 160 C. for 30 minutes.

(16) Oxygen barrier effect was in each case measured at 0% and 85% relative humidity. Table 1 collates the results.

(17) TABLE-US-00001 TABLE 1 Oxygen barrier measurement results Oxygen Oxygen Oxygen Oxygen permeability permeability transmission transmission at 0% RH at 85 RH Crosslinking at 0% RH at 85% RH [(cm.sup.3 1 m)/ [(cm.sup.3 1 m)/ agent [cm.sup.3/m.sup.2/d] [cm.sup.3/m.sup.2/d] (m.sup.2 d bar)] (m.sup.2 d bar)] B1 1.5 43.5 9.2 no barrier B2 Triethanolamine 0.1 0.2 1.1 1.6