Laminate structure for barrier packaging

Abstract

Laminate structure comprising an alternating stack of layers from polymer blends AC and BD having the sequence -AC-[BD-AC-].sub.n with n from 4 to 36, wherein the layer thickness of layers AC and layers BD is less than 3 μm, wherein A and B are thermoplastic polymers and C and D are thermoplastic elastomers, wherein the thermoplastic polymer B has functional barrier properties, wherein the amount of the thermoplastic elastomers C and D in the polymer blends AC and BD is each from 3 to 45 wt.-%, and polymer B and elastomer D are essentially incompatible.

Claims

1. A laminate structure comprising an alternating stack of layers of different types of polymer blends AC and BD having the sequence -AC-[BD-AC-].sub.n, wherein n is an integer from 4 to 36, wherein a layer thickness of each of the layers AC and layers BD is less than 3 μm, wherein A and B are thermoplastic polymers, wherein the thermoplastic polymer B has functional barrier properties against transmission of oxygen, nitrogen, carbon dioxide, organic vapors and moisture, wherein the polymers A and B are each blended with a thermoplastic elastomer C and D forming the polymer blends AC and BD, wherein the amount of the thermoplastic elastomers C and D in the blends AC and BD is each from 3 to 45 wt.-%, wherein the thermoplastic polymer B and elastomer D are essentially incompatible with one another forming separate phases in the layers BD, and wherein the structure has a water vapor transmission rate of less than 5 g H.sub.2O per m.sup.2 in 24 hours at 23° C. and 85 Vol.-% relative humidity (DIN 53122) and an oxygen transmission rate of less than 10 cm.sup.3 O.sub.2 per m.sup.2 in 24 hours at 23° C. and 50 Vol.-% relative humidity (ASTM D 3985).

2. The laminate structure according to claim 1, wherein polymer A is a polyamide or nucleated polyamide or a polyamide partly based on a renewable source; a blend of a polyamide with an ethylene vinyl alcohol copolymer or a polyalkylene carbonate or a polyketone; a copolymer of an olefin with a carboxylic acid or ester or ionomer or mixture thereof; a maleic anhydride grafted polyolefin or olefin carboxylic acid or ester copolymer or ionomer; a blend of a maleic anhydride grafted polyolefin or olefin carboxylic acid or ester copolymer or ionomer with a not grafted polyolefin or olefin carboxylic acid or ester copolymer or ionomer.

3. The laminate structure according to claim 2, wherein polymer A is a polyamide or a nucleated polyamide, at least partly made from a renewable source.

4. The laminate structure according to claim 2, wherein polymer A is a copolymer of ethylene with a carboxylic acid or ester or ionomer or mixture thereof or a maleic anhydride grafted copolymer of ethylene with a carboxylic acid or ester or ionomer or mixture thereof.

5. The laminate structure according to claim 1, wherein at least one of the monomeric building blocks of polymer A is from a renewable source being glycerol, diols, vanillin, ferulic acid, lactic acid, levulinic acid, adipic acid, azelaic acid, succinic acid, 1,4-butanediamide, bio-1,4 butanediol, diacids, hydroxyacids, furans, esteramides, amides, esters, CO, CO.sub.2, or bio-alkylenes.

6. The laminate structure according to claim 1, wherein polymer B is an ethylene vinyl alcohol copolymer, a polyketone, a polyvinyl alcohol, a polyalkylene carbonate, a poly(1,3 glycerol carbonate), a poly(1,3 glycerol carbonate) mixed with polytetramethylene succinate, or a mixture or blend of polyamide with ethylene vinyl alcohol copolymer or polyvinyl alcohol or polyketone or polyalkylene carbonate.

7. The laminate structure according to claim 1, wherein the thermoplastic elastomer C is a styrene block copolymer of styrene with at least one of butylene, isoprene, hydrogenated butylene, hydrogenated isoprene and isobutylene.

8. The laminate structure according to claim 1, wherein the thermoplastic elastomer D is a styrene block copolymer of styrene with isobutylene.

9. The laminate structure according to claim 1, wherein the thermoplastic elastomer C and/or D is an at least partly renewably sourced elastomer.

10. The laminate structure according to claim 1, wherein polymer A is a maleic anhydride grafted polyolefin and elastomer C is a block copolymer of styrene with at least partially hydrogenated butylene and/or isoprene or an at least partly renewable sourced elastomer.

11. The laminate structure according to claim 1, wherein polymer B is an ethylene vinyl alcohol copolymer, polyketone, polyvinyl alcohol or polyalkylene carbonate, and elastomer D is a styrene block copolymer of styrene with isobutylene, a mixture of styrene block copolymer of styrene with isobutylene and polyamide or polyamide from renewable sources, or any of these with bio-based multiblock elastomers based on ether or etheramide building blocks.

12. The laminate structure according to claim 1, comprising one or more functional layers on either side of the alternating stack.

13. The laminate structure according to claim 12, wherein one functional layer is a sealing layer.

14. The laminate structure according to claim 12 comprising at least two functional layers, wherein one of the functional layers is a tie layer promoting adhesion between the alternating stack and the second functional layer.

15. The laminate structure according to claim 12, wherein one functional layer is at least partly from a polymer which has at least one monomeric building block from a renewable source.

16. The laminate structure according to claim 1, wherein: a tensile modulus, measured according to ISO 527-1,2,3 or ASTM D882 (at 23° C. and 50% RH) is <250 MPa, and/or a tensile strength at break measured according to ISO 527-1,2,3 or ASTM D882 is >10 MPa, and/or an elongation at break measured according to ISO 527-2,3 or ASTM D882 is >200%, and/or an Izod impact strength measured according to ASTM D256 at 23° C. notched/ISO 180 (1A) notched results in no break, and/or a Charpy impact strength measured according to ISO 179 notched results in no break, and/or a tensile impact strength measured according to ISO 8256 A1 notched at 23° C. is above 160 KJ/m.sup.2, and/or a dart impact strength measured according to ASTM D1709 is above 250 g, and/or a Spencer impact strength measured according to ASTM D3420 is above 30 J/mm, and/or an Elmendorf tear strength measured according to ISO 6383-2 or ASTM D1922 of at least about 2 N, and/or a tensile toughness determined by stress strain testing as described in ASTM D638, ASTM D882 and ISO 527 is >15 MJ/m.sup.3, and/or a puncture resistance tested using a method similar to ASTM F1306-90 or DIN EN 14477 is at least 15 J.

17. The laminate structure according to claim 9, wherein the elastomer C and/or D is polytrimethylene carbonate, poly(lactate/butanediol/sebacate/itaconate) with at least 40 mol-% lactic acid, a triblock elastomer poly(L-lactide)-b-polymyrcene-b-poly(L-lactide), a polyester elastomer, poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-b-hydroxyvalerate, a triblock copolymer from polyitaconate and polyitaconic amide, poly(glycerol sebacate), polytetramethylene ether glycol or blends thereof.

18. The laminate structure according to claim 16, wherein: a tensile modulus, measured according to ISO 527-1,2,3 or ASTM D882 (at 23° C. and 50% RH) is in the range from 75-150 MPa, and/or a tensile strength at break measured according to ISO 527-1,2,3 or ASTM D882 is >15 MPa, but less than 40 MPa, and/or an elongation at break measured according to ISO 527-2,3 or ASTM D882 is >300%, but less than 800%, and/or an Elmendorf tear strength measured according to ISO 6383-2 or ASTM D1922 of at least 3 N, and/or a tensile toughness determined by stress strain testing as described in ASTM D638, ASTM D882 and ISO 527 is >40 MJ/m.sup.3, and/or a puncture resistance tested using a method similar to ASTM F1306-90 or DIN EN 14477 is more than 25 J.

19. The laminate structure according to claim 1, wherein the laminate has the following mechanical properties a tensile modulus, measured according to ISO 527-1,2,3 or ASTM D882 (at 23° C. and 50% RH) is in the range from 75-150 MPa, and a tensile strength at break measured according to ISO 527-1,2,3 or ASTM D882 is >15 MPa, but less than 40 MPa, and an elongation at break measured according to ISO 527-2,3 or ASTM D882 is >300%, but less than 800%, and an Elmendorf tear strength measured according to ISO 6383-2 or ASTM D1922 of at least 3 N, and a tensile toughness determined by stress strain testing as described in ASTM D638, ASTM D882 and ISO 527 is >40 MJ/m.sup.3, and a puncture resistance tested using a method similar to ASTM F1306-90 or DIN EN 14477 is more than 25 J.

Description

(1) In the drawings:

(2) FIG. 1 shows a laminate structure according to the invention

(3) FIG. 2 shows a second laminate structure according to the invention

(4) FIG. 3 shows a photograph of a laminate structure according to the invention

(5) FIG. 4 shows a photograph of a comparison laminate structure.

(6) FIG. 1 shows a section through a laminate structure 1 produced by an extrusion line. In this example, the laminate structure 1 comprises an alternating stack of twenty-four sequential layers made from ten polymer layers 2 (polymer blend AC: Polyamide+TPE) and nine polymer layers 3 (polymer blend BD: EVOH+TPE). The alternating stack has an -AC-[BD-AC-].sub.n layer sequence with n=9. The structure 1 also comprises further functional layers: a skin layer 4 of, for example, LLDPE forming the laminate structure sealing layer, an impact strength promoting layer 5 of, for example, polyolefin plastomer, like m-ULDPE; an adhesion-promoting layer 6 of, for example, MAH grafted EMA (MAH-g-EMA) tie resin promoting adhesion of the sealing skin layer 4 and the impact strength promoting layer 5 with the respective adjacent AC layers 2; and a skin layer 7 made of e.g. EVA for printability.

(7) FIG. 2 shows a section through an alternative laminate structure 1. In this example, the laminate structure 1 comprises a skin layer 4 forming the laminate structure sealing layer of, for example, LLDPE, an alternating stack of twenty-four sequential layers made from ten polymer layers 2 (polymer blend AC-EVA+TPE) and nine polymer layers 3 (polymer blend BD-EVOH blended with SiBS rubber). The alternating stack has an -AC-[BD-AC-].sub.n layer sequence with n=9. The structure 1 also comprises further functional layers: an impact strength promoting layer 5 of, for example, polyolefin plastomer; a laminate stiffness promoting layer 8 of, for example, HDPE; and a skin layer 7 made of EVA polymer to enhance printability.

(8) In the laminate structures shown in FIGS. 1 and 2 the polymer resin stack sequence typically has a thickness of from around 4 to around 60 μm while the laminate structure 1 has an overall thickness in the range from 15 μm to 400 μm. The individual layers of polymer blend AC and polymer blend BD comprised in the stack sequence typically each have a thickness of less than 1 μm.

(9) The laminate structures as described in FIGS. 1 and 2 form very effective packaging laminate materials with a highly flex-crack resistant aroma and gas barrier and are suitable for use in medical, food and other packaging applications like bag-in-box liners for use in modern food and liquid food packaging systems, ostomy films, (total) parenteral, enteral, topical, cell culture and storage films and bags, lidding films. They can for example be used on thermoforming machines and in vacuum skin packaging machines. The extruded laminate as described in this invention can, if desired, also be printed at least with an appropriate skin layer included. The flexible laminates are thus preferably used as packaging film with gas, aroma and moisture barrier functions, flexibility, transparency and toughness for medical, food and other substances or items. They are useful as ostomy film; for packaging of (liquid) (total) parenteral, enteral, intravenous (IV), continuous ambulatory peritoneal dialysis (CAPD), and topical medication (e.g. drugs, nutrition); for making cell culture and storage (2D, 3D) single and multi compartment (e.g. multichamber) bags and containers; and for use in food packaging applications like bag-in-box liners and lidding films; and for packaging of cosmetics and personal hygiene articles.

EXAMPLE 1

(10) A laminate structure approximately 80 μm thick according to the invention was made from an alternating stack of twenty-five microlayers of PA+SEBS and EVOH+SiBS each layer being about 0.9 μm thick, and on both sides of the AC, BD stack a tie layer of approximately 3 μm was extruded. As further functional layers one impact layer being approximately 7 μm thick made from ULDPE (POP) (right side of the photo) and two skin layers made from EVA and LLDPE respectively being approximately 25 and 20 μm thick were provided at the other side. For comparison, a laminate structure was made from twenty-five microlayers of PA and EVOH without blending them with elastomer. The further layers are the same. Both laminate structures were prepared as a microtome and then photographed with a Keyence optical microscope. The obtained photos are shown in FIGS. 3 and 4.

(11) It is immediately apparent that the laminate structure according to the invention has continuous microlayers whereas in the comparison structure without elastomer modification of PA and EVOH the microlayers are broken.

EXAMPLE 2

(12) A sealed bag was made from a laminate structure according to the invention as described in example 1 and a bag from a laminate LLDPE/tie/PA/EVOH/PA/tie/EVA was used as comparison. Chopped onions were placed inside the bags and the bags sealed and stored at RT. After a few days the onions in the comparison bag became brown and an onion smell was perceivable. In the bag made from the laminate structure according to the invention the onions remained white for months and no smell was detected. This shows that the novel structure provides a very effective barrier.

(13) Thus, the present invention provides a laminate structure comprising an alternating stack of layers from polymer blends AC and BD having the sequence -AC-[BD-AC-].sub.n with n from 4 to 36, wherein the layer thickness of layers AC and layers BD is less than 3 μm, wherein A and B are thermoplastic polymers and C and D are thermoplastic elastomers, wherein the thermoplastic polymer B has functional barrier properties, wherein the amount of the thermoplastic elastomers C and D in the polymer blends AC and BD is each from 3 to 45 wt.-%, and polymer B and elastomer D are essentially incompatible.