ANTIMICROBIAL POLYMER COMPOSITION FOR SHELF-LIFE EXTENSION

Abstract

Polymer composition are provided comprising a thermoplastic polymer matrix, 50 to 6000 ppm of zinc pyrithione, 50 to 6000 ppm of silver, 100 to 6000 ppm of a zeolite, and optionally 0 to 5% by weight of one or more polymer additives. The invention also relates to a masterbatch and a method for preparing such polymer composition. The present invention further relates to a food packaging comprising or consisting of such polymer composition and to the use thereof for increasing shelf-life of foodstuff such as baked goods.

Claims

1. A polymer composition comprising: (A) a thermoplastic polymer matrix (component A); (B) 50 to 6000 ppm, related to the polymer composition, of zinc pyrithione (component B); (C) 50 to 6000 ppm, related to the polymer composition, of silver, optionally in uncharged form or in ionic form comprised in a silver salt (component C); (D) 100 to 6000 ppm, related to the polymer composition, of a zeolite (component D); and optionally (E) 0 to 5% by weight, related to the polymer composition, of one or more polymer additives (component E).

2. The polymer composition of claim 1, wherein the polymer matrix A comprises or consists of at least one olefinic polymer.

3. The polymer composition of claim 1, wherein the polymer matrix A is selected from the group consisting of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and blends of two or more thereof.

4. The polymer composition of claim 1, wherein said polymer composition comprises components B:C in a mass ratio in the range of 1.5:1 to 20:1.

5. The polymer composition of claim 1, wherein the zeolite (component D) is a hydrophobic particulate zeolite having a mean average particle size in the range of 0.5 to 50 μm.

6. The polymer composition of claim 1, wherein said polymer composition comprises: (A) a thermoplastic polymer matrix (component A) consisting of an olefinic polymer or a blend of olefinic polymers; (B) 50 to 6000 ppm, related to the polymer composition, of zinc pyrithione (component B); (C) 50 to 1500 ppm, related to the polymer composition, of silver, optionally in uncharged form or in ionic form comprised in a silver salt (component C); (D) 200 to 5000 ppm, related to the polymer composition, of a zeolite (component D); and optionally (E) 0 to 5% by weight, related to the polymer composition, of one or more polymer additives (component E), wherein said polymer composition comprises components B:C is a mass ratio of between 2:1 and 20:1.

7. A masterbatch for preparing a polymer composition of claim 1, comprising or consisting of: 1 to 85% by weight, related to the masterbatch, of zinc pyrithione; 0.5 to 30% by weight, related to the masterbatch, of silver ions comprised in a silver salt; and optionally up to 85% by weight, related to the masterbatch, of a zeolite; and optionally up to 60% by weight of a thermoplastic polymer matrix; and optionally one or more polymer additives; and optionally one or more solvents, wherein the zinc pyrithione:silver ion mass ratio on the masterbatch is in the range of 1.5:1 and 20:1.

8. A method for preparing a polymer composition of claim 1, said method comprising the following steps: (i) providing: a thermoplastic polymer matrix (component A), zinc pyrithione (component B), silver ions (component C), a zeolite (component D), and optionally one or more polymer additives (component E); and (ii) blending components A-D and, optionally, E, at a temperature above the melting temperature of component A.

9. The method of claim 8, wherein in step (i), the components B and C and, optionally, component D, component E or component D and E are provided as a masterbatch.

10. The method of claim 8, wherein blending of step (ii) is performed by coextruding components A-D and, optionally, E.

11. The method of claim 8, wherein said method further comprises step (iii) of preparing a film by a step selected from the list consisting of blow film extrusion, cast film extrusion, and extrusion coating on a solid support.

12. A food packaging comprising or consisting of a polymer composition of claim 1.

13. The food packaging of claim 12, wherein said food packaging is or comprises a film consisting of the polymer composition.

14. The food packaging of claim 12 for increasing shelf-life of foodstuff, wherein said foodstuff is contacted with the polymer composition.

15. The food packaging of claim 14, wherein the foodstuff is a baked good and increasing shelf-life includes preventing or slowing mildewing.

Description

EXAMPLES

[0107] Materials

[0108] Thermoplastic polymer matrix components:

[0109] The low density polyethylene (LDPE) TX7003 has a density of 0.922 g/cm.sup.3 (as determined by ASTM D792) and a melt flow rate (MFR) of 0.27 g/10 min (as determined at 190° C./2.16 kg according to ASTM D1238). LDPE TX7003 was purchased by Braskem S. A. (Sao Paulo, Brazil).

[0110] The linear low density polyethylene (LLDPE) LL318 has a density of 0.918 g/cm.sup.3 (as determined by ASTM D792) and a melt flow rate (MFR) of 2.7 g/10 min (as determined at 190° C./2.16 kg according to ASTM D1238). LLDPE LL318 was purchased by Braskem S. A. (Sao Paulo, Brazil).

[0111] The low density polyethylene (LDPE) BC818 has a density of 0.918 g/cm.sup.3 (as determined by ASTM D1505) and a melt flow rate (MFR) of 8.3 g/10 min (as determined at 190° C./2.16 kg according to ASTM D1238). LDPE BC818 was purchased by Braskem S. A. (Sao Paulo, Brazil).

[0112] The linear low density polyethylene (LLDPE) IC32 has a density of 0.924 g/cm.sup.3 (as determined by ASTM D792) and a melt flow rate (MFR) of 29 g/10 min (as determined at 190° C./2.16 kg according to ASTM D1238). LLDPE IC32 was purchased by Braskem S. A. (Sao Paulo, Brazil).

[0113] Zinc Pyrithione and Silver:

[0114] The antimicrobial composition Life DJ/AM-00-1A contains zinc, pyrithione (as zinc pyrithione), silver and zeolite component, wherein the zinc content is specified as 15% by weight and the silver content as 5% by weight. Life DJ/AM-00-1A was purchased from Life Materials Technologies Ltd (Bangkok, Thailand).

[0115] Zeolite:

[0116] The zeolite ZEOflair 100 is a white powder that has a value average particle size of <7 μm and a loss on ignition (LOI) of <8% by weight. It has a thermal stability of >800° C. ZEOflair 100 was purchased from Zeochem AG (Rüti, Switzerland).

[0117] Preparing the Masterbatches

[0118] Masterbatch 1

[0119] Using the above-defined components, an antimicrobial masterbatch was prepared in a twin screw, co-rotating, 70 mm extruder (L/D 32) in the following ratios: [0120] 86.6% by weight of LDPE BC818, [0121] 10.0% by weight of ZEOflair 100, and [0122] 3.4% by weight of Life DJ/AM-00-1A.

[0123] Masterbatch 2:

[0124] As described for Masterbatch 1 above, Masterbatch 2 was produced using 10% by weight of Life DJ/AM-00-1A and 30% by weight of a ZEOflair 100 in a LLDPE IC32.

[0125] Compounding the Components and Preparing of Films

[0126] Film 1: LDPE TX7003 and LLDPE LL318 were blended with each other in a 1:1 ratio in a single screw extruded equipped with a monolayer blown film extrusion line. Then, 3% by weight of the Masterbatch 1, based on the weight of the entire composition, was added to the (LDPE TX7003/LLDPE LL318) blend. Accordingly, the composition comprises 48.5% by weight of LDPE TX7003, 48.5% by weight of LLDPE LL318 and 3% by weight of the Masterbatch 1. Consequently, the composition comprised: [0127] 2.598% by weight of LDPE BC818, [0128] 0.3% by weight of ZEOflair 100, [0129] 0.102% by weight of DJ/AM-00-1A, [0130] 48.5% by weight of LDPE TX7003, and [0131] 48.5% by weight of LLDPE LL318.

[0132] A film having a thickness of 30 μm was prepared by a blown film line (single screw extruded, monolayer—15 mm screw, L/D 24). The film was fully transparent and had a good visible appearance. The film was odorless.

[0133] Film 2: By the procedural steps as described for Composition 1 above, 1% by weight of Masterbatch 2 was blended with a LDPE resin in the extruder machine. Consequently, the composition comprised: [0134] 2.6% by weight of LLDPE IC32, [0135] 0.3% by weight of ZEOflair 100, [0136] 0.1% by weight of DJ/AM-00-1A, [0137] 48.5% by weight of LDPE TX7003, and [0138] 48.5% by weight of LLDPE LL318.

[0139] A film of a thickness of approximately 30 μm was obtained. The film was fully transparent and had a good visible appearance. The film was odorless.

[0140] Biological Testing of the Films

[0141] Common essentially cuboidal loafs of breads were each wrapped with a film as prepared in the preceding step or comparative films: [0142] Examples E1 and E2 according to the present invention: PE bread packaging prepared as laid out above including the Masterbatch 1 (Example E1) or Masterbatch 2 (Example E2) [0143] Comparative Example C1: Commercially available bread packaging, i.e., a comparable PE film without antimicrobials; [0144] Comparative Example C2: a comparable PE film prepared as laid out above, but without addition of a Masterbatch; [0145] Comparative Example C3: a comparable PE film prepared as laid out above including 1000 ppm silver instead of the Masterbatch

[0146] The wrapped breads were then incubated for 33 days at 23° C. and a relative humidity of 50% under controlled conditions. Appearance of the breads was investigated every few days. Further, the microbiological spore content was determined.

[0147] Technical Results

TABLE-US-00001 TABLE 1 Visual appearance after 20 days of incubation: E1 E2 C1 C2 C3 Fungus visible − − ++ ++ + wherein: − means no fungus visible, + means a slight mildewing was visible (whitishness) ++ means a blue/green/greyish fungus was clearly visible.

[0148] After 33 days of incubation each of comparative examples C1-C3 showed an overall microbial spore density that is increased by >10.sup.5-fold, whereas in Example including the Masterbatch 1 or 2, the spore density is increased by <10-fold.

[0149] These results show that, although only particularly low contents of antimicrobial agents are used, the polymer compositions of the present invention bear a beneficial antimicrobial activity in for packed foodstuff. There is significant synergistic effect of the antimicrobial agents zinc pyrithione and silver with a zeolite. Furthermore, the low contents of antimicrobial agents allow the preparation of transparent films with a beneficial optical appearance. The film was essentially odorless.

[0150] It was found that shelf-life could be extended significantly beyond the expected shelf-life of 10 days. The loaf of bread packed by a film of a polymer composition of the present invention could be extended to more than a month.