Vinylidene chloride polymer composition comprising at least one sorbate ester
The invention pertains to an improved PVDC composition including certain dienophiles qualified for food contact, which possess an optimized balance of effectiveness in preventing discoloration upon exposure to radiation, with no negative impact on the barrier properties, in particular sorbate esters of formula (I), wherein R 1 is a C 1 -C 12 hydrocarbon group, preferably a C 1 -C 6 alkyl group, to layers made therefrom, to multi-layer assemblies comprising the same, and to the use of said assemblies for packaging, in particular for packaging foodstuffs.
1. A composition (C) for the manufacture of flexible films for packaging articles, comprising:
a a vinylidene chloride (VDC) polymer, wherein the amount of recurring units derived from vinylidene chloride in the VDC polymer varies from 50 to 99.5 wt %, with respect to the total weight of the VDC polymer; and
from 0.05 to 3% by weight (wt %), with respect to the weight of VDC polymer, of at least one sorbate ester of formula (I):
wherein
R 1 is a C 1 -C 6 hydrocarbon group.
2. The composition (C) of claim 1 , wherein the VDC polymer is a copolymer comprising recurring units derived from at least one ethylenically unsaturated monomer copolymerisable with vinylidene chloride selected from the group consisting of vinyl chloride, maleic anhydride, itaconic acid, styrene, styrene derivatives, and the acrylic or methacrylic monomers corresponding to the below general formula:
CH 2 =CR 1 R 2
wherein R 1 is chosen from hydrogen and —CH 3 and R 2 is chosen from —CN and —COR 3 ,
wherein R 3 is chosen from —OH, —OR 4 , and —NR 5 R 6 radicals, wherein R 4 is a C 1 -C 18 linear or branched alkyl group optionally bearing one or more —OH groups, a C 2 -C 10 epoxy alkyl group and a C 2 -C 10 alkoxy alkyl group, and wherein R 5 and R 6 , same or different, are chosen from hydrogen and C 1 -C 10 alkyl groups, optionally bearing one or more —OH groups.
3. The composition (C) of claim 2 , wherein the at least one ethylenically unsaturated monomer copolymerisable with vinylidene chloride is selected from the group consisting of maleic anhydride, itaconic acid, acrylic or methacrylic monomers selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide, N-methylolacrylamide, and N,N-di(alkyl)acrylamide.
4. The composition (C) of claim 3 , wherein the at least one ethylenically unsaturated monomer copolymerisable with vinylidene chloride is methyl acrylate (MA).
5. The composition (C) of claim 4 , wherein the VDC polymer has a weight ratio VDC/MA of 90/10 to 94/6.
6. The composition (C) according to claim 1 , wherein said sorbate ester of formula (I) is ethyl sorbate.
7. The composition (C) according to claim 1 , wherein the amount of said sorbate ester of formula (I) in composition (C) is of at least 0.25% wt, with respect to the weight of VDC polymer; and at most 3% wt, with respect to the weight of VDC polymer.
8. The composition (C) according to claim 7 , wherein the amount of said sorbate ester (I) in composition (C) is of at least 0.5% wt, with respect to the weight of VDC polymer; and at most 3% wt, with respect to the weight of VDC polymer.
9. The composition (C) of claim 1 , wherein the amount of recurring units derived from vinylidene chloride in the VDC polymer varies from 60 to 98 wt %, with respect to the total weight of the VDC polymer.
10. The composition (C) of claim 9 , wherein the amount of recurring units derived from vinylidene chloride in the VDC polymer varies from 85 to 95 wt %, with respect to the total weight of the VDC polymer.
11. A method for manufacturing the composition (C) according to claim 1 , wherein the VDC polymer and the sorbate ester of formula (I) are compounded together.
12. A layer (B) made from the composition (C), according to claim 1 .
13. A method for manufacturing the layer (B) of claim 12 by extrusion-blowing process, the method comprising:
supplying the composition (C) to an extruder and bringing the composition (C) into the molten state by simultaneous action of heat and shear forces; and
extruding the the composition (C) which is molten through an annular die to form a tube, and inflating the tube with a gas as it leaves the die surface, so as to obtain the layer (B).
14. A multi-layer assembly (A) comprising at least one layer (B), according to claim 12 , said at least one layer (B) being assembled to at least one additional layer (O).
15. The multi-layer assembly (A) of claim 14 , wherein materials used for providing at least one layer (O) assembled to a layer (B) are selected from the group consisting of polyolefins, polyethylene, polypropylene, polybutylene; polystyrenes; cellulose esters, cellulose acetate, cellulose propionate, cellulose nitrate; polyvinyl acetate; polymethyl methacrylate, polybutyl methacrylate; polyvinyl alcohol; polyvinyl acetal; polyallyl alcohol; polyallyl acetate; polyesters, polyethylene terephthalate; polyamides, and nylon.
16. The multi-layer assembly (A) of claim 15 , wherein at least one layer (O) is made from a thermoplast composition comprising a polyethylene (PE) and/or wherein the at least one layer (O) is made from a thermoplast composition comprising an ethylene-vinyl acetate copolymer (EVA).
17. The multi-layer assembly (A) of claim 14 , wherein the layer (B) of the composition (C) is sandwiched between an outer layer (O) and inner layer (O), optionally through the use of one or more than one additional adhesive or tie-layer (T).
18. A method of making the multi-layer assembly (A) of claim 14 , wherein the layer (B) is incorporated into an assembly created by coextrusion lamination, adhesive lamination, cast sheet extrusion, tubular water quenched extrusion, air blown extrusions or other film-making process.
19. A package made from the multi-layer assembly (A) according to claim 14 , said package being selected from the group consisting of conventional pouches, boil-in-bag pouches, turkey bags, shrinkable pouches, grease resistant pouches, rust and/or mold inhibiting films, pouches and bags, red meat protective film, pouches and bags, moisture control films, vacuum forming raw material, window films, improved weathering films, improved abuse resistant films at a wide range of temperatures, drum and other container liners, bread wraps, wrapping for cheese, containers which are required to be resistant to gas and liquid transmission for medicine, pharmaceuticals, cosmetics, perfumes, pipe line wrapping, floor tiles, bottle cap liners, and crown cap liners.