Polymer compositions with improved barrier properties against the permeation of oxygen
The present invention relates to polymer compositions comprising (a) a polymer containing hydroxyl alkylene repeating units and (b) an additive selected from compounds of the formulae (1) to (6) wherein R a1 , R a2 , R a3 and R a4 can be the same or different and independently represent a group selected from the moieties having formula (A) or formula (B), wherein R b is selected from hydrogen, C 1-6 alkyl, C 1-6 alkoxy and —CO—C 1-4 alkyl.
1. A polymer composition consisting of:
(a) a polymer selected from: polyvinyl alcohol and an ethylene-vinyl alcohol copolymer consisting of ethylene and hydroxyl ethylene repeating units, the polymer comprising hydroxyl ethylene-repeating units in ethylene-vinyl alcohol copolymer are present in the polymer in an amount of at least 50% relative to the total number of repeating units present in the polymer,
(b) 0.2 to 2% by weight relative to said polymer (a) of at least one additive selected from the group consisting of compounds represented by the following formulae (1) to (6)
wherein
R a1 , R a2 , R a3 and R a4 can be the same or different and independently represent a group selected from the moieties having formula (A) or formula (B),
wherein
R b is selected from the group consisting of hydrogen, C 1-6 alkyl, C 1-6 alkoxy, —CO—C 1-4 alkyl and combinations thereof; and
(c) optionally 0.005 to 5% by weight, relative to said polymer (a) of additives selected from the group consisting of stabilizers against thermooxidative and light-induced degradation, fillers, processing additives, colorants and clay-based additives.
2. The composition according to claim 1 , wherein the polymer (a) comprises hydroxyl ethylene repeating units in an amount of at least 65% relative to the total number of repeating units present in the polymer (a).
3. The composition according to claim 1 , wherein said polymer (a) is an ethylene-vinyl alcohol copolymer.
4. The composition according to claim 3 , wherein the polymer (a) is an ethylene-vinyl alcohol copolymer comprising hydroxyl ethylene repeating units in an amount in the range of 75% to less than 100% relative to the total number of repeating units present in the polymer (a).
5. The composition according to claim 1 , wherein the polymer (a) is polyvinyl alcohol.
6. The composition according to claim 1 , wherein said additive is a compound represented by formula (1) or (2), wherein both R a1 and R a2 represent a moiety having formula (A).
7. The composition according to claim 6 , wherein said additive comprises N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,3-benzenedicarboxamide as represented by the following formula
8. The composition according to claim 1 , wherein said additive (b) is present in an amount of 0.3-0.5% by weight relative to said polymer (a).
9. A packaging material comprising a composition according to claim 1 .
10. A packaging material according to claim 9 in a form selected from the group consisting of a film, bag, pouch, tube, cylinder, bottle, and canister.
11. The composition according to claim 1 , wherein the composition has absolute oxygen permeability of less than about 27.1 cm 3 /m 2 /day when measured under pure oxygen at 22° C. and 60% relative humidity.
12. The composition according to claim 1 , wherein the composition has relative oxygen permeability of less than about 63.9% as compared to an identical material lacking the additive (b) when measured under pure oxygen at 22° C. and 60% relative humidity.
13. The composition according to claim 1 , wherein the at least one additive (b) is present in an amount of 0.1 to 0.8% by weight relative to the polymer (a).
14. The composition according to claim 3 , wherein the polymer (a) comprises hydroxyl ethylene repeating units in an amount in the range of 65% to less than 100% relative to the total number of repeating units present in the polymer (a).