Gas permeable membranes

• US 8,057,872 B2
• Filed: 08/26/2008
• Issued: 11/15/2011
• Est. Priority Date: 08/26/2008
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Chen, John Chu
• Primary Examiner(s): Miggins; Michael C
• Application Number:
  US12/198,650
• Publication Number:
  US 20100055276A1
• Time in Patent Office: 1,176 Days
• Field of Search: 428/35.2, 428/35.7, 428/36.9, 428/36.91, 428/36.1, 428/220, 428/36.5, 426/395
• US Class Current: 428/35.7
• CPC Class Codes: B32B 1/00 Layered products having a non-planar shape
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/30 having particular thermal properties
• CPC Class Codes: B32B 2307/724 Permeability to gases, adsorption
• CPC Class Codes: B32B 2439/00 Containers; Receptacles closures therefor B32B2435/00
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 2553/00 Packaging equipment or accessories not otherwise provided for
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/10 of paper or cardboard
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 27/18 characterised by the use of special additives
• CPC Class Codes: B32B 27/20 using fillers, pigments, thixotroping agents
• CPC Class Codes: B32B 27/283 comprising polysiloxanes
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/306 comprising vinyl acetate or vinyl alcohol (co)polymers
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 27/322 comprising halogenated polyolefins, e.g. PTFE
• CPC Class Codes: B32B 27/327 comprising polyolefins obtained by a metallocene or single-site catalyst
• CPC Class Codes: B32B 27/40 comprising polyurethanes
• CPC Class Codes: B32B 3/266 : characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
• CPC Class Codes: B32B 5/022 : Non-woven fabric
• CPC Class Codes: B32B 5/024 : Woven fabric
• CPC Class Codes: B65D 81/263 : for ventilating the contents B65D5/4295, B65D51/1605 take precedence
• CPC Class Codes: C08K 5/098 : Metal salts of carboxylic acids
• CPC Class Codes: C08L 23/0876 : Neutralised polymers, i.e. ionomers
• CPC Class Codes: Y10T 428/1334 : Nonself-supporting tubular film or bag [e.g., pouch, envelope, packet, etc.]
• CPC Class Codes: Y10T 428/1352 : Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/1362 : Textile, fabric, cloth, or pile containing [e.g., web, net, woven, knitted, mesh, nonwoven, matted, etc.]
• CPC Class Codes: Y10T 428/1376 : Foam or porous material containing
• CPC Class Codes: Y10T 428/139 : Open-ended, self-supporting conduit, cylinder, or tube-type article
• CPC Class Codes: Y10T 428/1393 : Multilayer [continuous layer]
• CPC Class Codes: Y10T 428/249953 : Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249954 : With chemically effective material or specified gas other than air, N, or carbon dioxide in void-containing component
• CPC Class Codes: Y10T 428/249981 : Plural void-containing components
• CPC Class Codes: Y10T 428/249992 : Linear or thermoplastic

Abstract

Disclosed is a multilayer structure comprising a layer of humidity-dependent composition having a ratio of wet cup permeance to dry cup permeance greater than 10 and a layer of crystallizable polymer sufficiently permeable to oxygen, carbon dioxide and water vapor, exhibiting an increase in permeability to at least one of oxygen and carbon dioxide by a factor of at least 2.5 over a temperature range of 10° C. between 0° C. and 40° C. Also disclosed are packaging materials comprising the multilayer structure and methods for storing respiring materials using the packaging materials.

Claims

1. A multilayer structure comprising or produced from at least two layers wherein

The first layer comprises a humidity-dependent composition having a ratio of wet cup permeance to dry cup permeance of at least 10 when measured according to ASTM E 96-00 at a temperature of 23°

C.;

wherein the wet cup permeance is determined at an average relative humidity of 75% and the dry cup permeance is determined at an average relative humidity of 25%; and

The second layer comprises a crystallizable polymer having a first order transition point T_m from 0°

C. to 40°

C. and a heat of fusion of at least 5 J/g, and said crystallizable polymer being sufficiently permeable to oxygen, carbon dioxide and water vapor and the polymeric material exhibiting an increase in permeability to at least one of oxygen and carbon dioxide by a factor of at least 2.5 over a temperature range of 10°

C. between 0°

C. and 40°

C.

2. The multilayer structure of claim 1 wherein the first layer has water vapor transmission rate at 25% relative humidity and 23°

C. lower than 10 mil-g/m²-day, and at 75% relative humidity and 23°

C. greater than 100 mil-g/m²-day.

3. The multilayer structure of claim 2 wherein the first layer has water vapor transmission rate at 25% relative humidity and 23°

C. lower than 20 mil-g/m²-day, and at 75% relative humidity and 23°

C. greater than 200 mil-g/m²-day.

4. The multilayer structure of claim 3 wherein the first layer has water vapor transmission rate at 25% relative humidity and 23°

C. lower than 30 mil-g/m²-day, and at 75% relative humidity and 23°

C. greater than 300 mil-g/m²-day.

5. The multilayer structure of claim 2 wherein the humidity-dependent composition comprises an organic acid-modified ionomer, an organic acid or salt thereof;

and optionally 0.1 to 60%, based on the humidity-dependent composition weight, of an optional polymer wherein

the ionomer is derived from one or more ethylene acid copolymer;

the acid copolymer is derived from ethylene, at least one C₃ to C₈ α

,β

-ethylenically unsaturated carboxylic acid, and optionally a softening comonomer;

the organic acid is one or more carboxylic acids having from 4 to 36 carbon atoms;

at least 50% of the combined acidic groups in the acid copolymer and the organic acid are nominally neutralized with metal ions to the corresponding salts and at least 50% of the metal ions are alkali metal ions; and

the optional polymer includes ethylene-containing polymers, propylene-containing polymers, or combinations of two or more thereof.

6. The multilayer structure of claim 5 wherein the carboxylic acid is acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid;

monoester of fumaric acid, monoester of maleic acid, or combinations of two or more thereof.

7. The multilayer structure of claim 6 wherein the carboxylic acid is acrylic acid or methacrylic acid.

8. The multilayer structure of claim 6 wherein the softening comonomer is present in the acid copolymer and is alkyl acrylate, alkyl methacrylate, vinyl acetate, or combinations of two or more thereof.

9. The multilayer structure of claim 6 wherein the humidity-dependent composition comprises the optional including ethylene homopolymer, ethylene copolymer, propylene homopolymer, propylene copolymer, ethylene/propylene copolymer, or combinations of two or more thereof;

ethylene copolymer includes one or more copolymers of ethylene with an α

-olefin having 3 to 20 carbon atoms or with at least one polar monomer including vinyl acetate, acrylic ester, methacrylic esters, CO, maleic anhydride, or combinations of two or more thereof.

10. The multilayer structure of claim 9 wherein the optional polymer is an ethylene/vinyl acetate copolymer, ethylene/acrylic ester copolymer, ethylene/methacrylic ester copolymer, ethylene/vinyl acetate/CO copolymer, ethylene/acrylic ester/CO copolymer, ethylene/maleic anhydride copolymer, or combinations of two or more thereof.

11. The multilayer structure of claim 2 wherein the crystallizable polymer is a side-chain crystallizable copolymer comprising copolymerized repeat units n-alkyl acrylate, n-alkyl methacrylate, fluoroalkyl acrylate, or methacrylate methacrylate, or combinations of two or more thereof and one or more comonomers including acrylic acid, methacrylic acid, ester of acrylic or methacrylic acid, polar monomer, or combinations of two or more thereof;

and the polar monomer is polyethylene glycol acrylate or methacrylate.

12. An article comprising the multilayer structure of claim 1 wherein the article is container, cover, wrapping, shield, a rigid or semi-rigid or flexible structure, packaging material, monolayer film, multilayer film, sheet, bag, pouch, package, or structure comprising a gas permeable substrate adhered either directly or through an intervening layer to the first layer.

13. The article of claim 12 wherein the gas permeable substrate comprises cellulosic material, synthetic fiber spun fabrics, woven textile, nonwoven textile, microporous film, or perforated film.

14. The article of claim 13 wherein

the article is surrounded by air and is the container comprising one or more control sections that is the only way in which oxygen, carbon dioxide, and/or water vapor enters or leaves the container;

and

within the container, a material which is biologically active or interactive with the atmospheric environment through respiration, metabilization, or complexation;

or contains microorganisms that cause biological changes.

15. The article of claim 13 wherein the article is the bag or the pouch having windows, patches or areas comprising the composition thereon, comprised in part of polymeric materials other than those comprising the multilayer structure.

16. The article of claim 13 wherein the article is the rigid or semi-rigid or flexible structure having one or more windows comprising the composition thereon, comprised in part of polymeric materials other than those comprising the multilayer structure.

17. The article of claim 16 wherein the rigid or semi-rigid or flexible structure is in combination with a lidding material comprising the composition or comprising in part other materials having one or more windows of the multilayer structure thereon.

18. The article of claim 13 wherein the article is the package having patches of the multilayer structure over designed openings in the package.

19. The article of claim 13 wherein the article is the package in which the multilayer structure is covered by a removable protective cover that allows a user to expose the multilayer structure to the environment at an appropriate time.

20. A method of comprising placing a biologically active material inside a container and storing the container in air wherein

the biologically active material includes red meat, sea food, fruit, produce, plants, flower, seed, cheese, pickled food, fermented food, or combinations of two or more thereof;

the container comprises one or more control sections providing the only way in which oxygen, carbon dioxide, and/or water vapor enters or leaves the container and the control section comprise the multilayer structure recited in claim 1; and

the storing is at a temperature T₁, T₁ is between 0°

C. and 40°

C. or at a second temperature T₂;

T₂ is above T₁ and at most 40°

C.; and

at T₂, the permeability of the control section to oxygen or carbon dioxide is at least 2.5 times that at T₁ or the permeability of the control section to moisture is at least 10 times greater at an average relative humidity of 75% than at an average relative humidity of 25%.