Use of aqueous polyanion-polyethyleneimine solutions for producing polymer films with oxygen-barrier properties

Abstract

The use of an aqueous Solution comprising at least one polyanion and at least one high molecular weight polyethyleneimine is described, for providing oxygen barrier properties to a polymer film. The polyanion is a polymer comprising acid groups neutralized with a base selected from the group consisting of inorganic bases and monovalent organic bases and having a weight average molecular weight of at least 10000 g/mol.

Claims

1. A method of providing oxygen barrier properties to a polymer film, comprising: applying an aqueous solution to at least one side of the polymer film, the aqueous solution comprising a polyanion and a polyethylenimine; wherein the polyanion is a polymer comprising acid groups neutralized with at least one base selected from the group consisting of inorganic bases and monovalent organic bases and a weight average molecular weight of the polyanion polymer is at least 10000 g/mol prior to neutralization of the acid groups; and a weight average molecular weight of the polyethyleneimine is at least 25000 g/mol, and wherein the polyanion is selected from polymers obtained by polymerization of at least one monomers selected from the group consisting of monoethylenically unsaturated C.sub.3 to C.sub.10 carboxylic acids, vinylsulfonic acid, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid, and salts of these acids.

2. The method according to claim 1, wherein the aqueous solution comprises: (a) from 10 to 90 wt. %, referring to solids content, of the polyanion and (b) from 10 to 90 wt. %, referring to solids content, of the polyethyleneimine.

3. The method according to claim 1, wherein a weight ratio of the polyanion, calculated without neutralizing agent, to the polyethyleneimine is from 10:2 to 10:5.

4. The method according to claim 1, wherein the weight average molecular weight of the polymer comprising acid groups is from 10,000 to 200,000 g/mol.

5. The method according to claim 1, wherein the polyethyleneimine is branched, and the weight average molecular weight of the polyethyleneimine is from 25000 to 3 million g/mol and the charge density of the polyethyleneimine is from 1 to 35 meq/g.

6. The method according to claim 1, wherein a degree of neutralization of the polyanion is from 30 to 100% and wherein the pH of the aqueous solution is from 6 to 12.

7. The method according to claim 1, wherein the base is selected from the group consisting of ammonia, sodium hydroxide and triethanol amine.

8. A method of forming a polymeric film with enhanced oxygen barrier properties comprising: applying an aqueous solution to at least one side of the polymer film, the aqueous solution comprising: a polyanion and a polyethyleneimine, wherein the polyanion is a polymer comprising acid groups neutralized with at least one base selected from the group consisting of inorganic bases and monovalent organic bases and a weight average molecular weight of the polyanion polymer is at least 10000 g/mol prior to neutralization of the acid groups; and a weight average molecular weight of the polyethyleneimine is at least 25000 g/mol.

Description

EXAMPLES

(1) Measurement of Oxygen-Barrier Action:

(2) Oxygen transmission is determined on coatings on polymer films at a relative humidity (RH) level of 85%. Measurements are done with 100% oxygen gas at a temperature of 23 C.

(3) Carrier material: polymer film of boPP (biaxial oriented polypropylene) with a thickness of 40 m.

(4) Oxygen transmission rate of the uncoated film at 85% RH/23 C.: about 975 cm.sup.3/(m.sup.2*d).

(5) The determination method is based on ASTM D3985, using a coulometric sensor. Each sample is measured twice and the mean result is calculated.

(6) The transmission of a multi-layer system is calculated according to the equation

(7) $\frac{1}{{\mathrm{TR}}_{\mathrm{total}}}=\frac{1}{{\mathrm{TR}}_A}+\frac{1}{{\mathrm{TR}}_B}+\mathrm{.Math.}$
wherein TR.sub.total is the oxygen transmission of the multi-layer film and TR.sub.A and TR.sub.B are the oxygen transmissions of layer A and layer B, respectively.

(8) Polymer Samples:

(9) PEI1 aqueous solution of polyethyleneimine, Mw=750000 g/mol; charge density 17 meq/g, pH=11

(10) PEI2 aqueous solution of polyethyleneimine, Mw=1300 g/mol; charge density 16 meq/g, pH=11

(11) PVA aqueous solution of polyvinylamine, Mw=340000 g/mol; charge density 13 meq/g, pH=7-9

(12) PAS1 copolymer of polyacrylic acid and maleic acid (75:25), Mw=80000 g/mol

(13) PAS2 polyacrylic acid, Mw=3000 g/mol

(14) Samples PAS1 and PAS2 are pre-neutralized with ammonia before combining with the polyethylene imine or polyvinylamine.

(15) The boPP-Film is coated with either a single solutions of polymers according to table 1 for generating a single layer (examples 2-6) or with 4 solutions for generating a 4-layer film (example 1). The compositions and results are summarized in table 1.

(16) TABLE-US-00001 TABLE 1 oxygen transmission rate measurement results; amounts in parts by weight Layer Oxygen transmission thickness rate (85% RH) Example Composition [m] [cm.sup.3/(m.sup.2 * d)] 1 (comparative) Layer structure: about 10 421 1) PEI1 2) PAS1 (+NH3) 3) PEI1 4) PAS1 (+NH3) 2 100 PAS1 4 32 25 NH3 40 PEI1 3 (comparative) 100 PAS1 2 950 25 NH3 40 PVA 4 (comparative) 100 PAS1 8 227 25 NH3 40 PEI2 5 (comparative) 100 PAS2 5 529 25 NH3 40 PEI1 6 (comparative) 100 PAS2 4 540 25 NH3 40 PEI2

(17) The data show that example 2 according to the invention shows the best oxygen barrier properties at high humidity.