Multilayer, heat-shrinkable film comprising a plurality of microlayers

• US 8,080,310 B2
• Filed: 07/01/2011
• Issued: 12/20/2011
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Cryovac Incorporated (Sealed Air)
• Original Assignee: Cryovac Incorporated (Sealed Air)
• Inventors: Ramli, Rafizi, Timmons, Anton L., Webster, Bradford E., Wolf, John R., McAllister, Larry Bikle, Brown, Christopher, Wofford, George D
• Primary Examiner(s): Sample, David
• Assistant Examiner(s): KHAN, TAHSEEN
• Application Number:
  US13/175,256
• Publication Number:
  US 20110260354A1
• Time in Patent Office: 172 Days
• Field of Search: 428/213, 428/216, 428/35.2, 428/35.7, 264/173.15, 534/41
• US Class Current: 428/213
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/0019 combined with shaping by flattening, folding or bending
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/10 flexible, e.g. blown foils
• CPC Class Codes: B29C 48/185 comprising six or more components, i.e. each component being counted once for each time it is present, e.g. in a layer
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/32 with annular openings, e.g. for forming tubular articles
• CPC Class Codes: B29C 48/3363 using a layered die, e.g. stacked discs
• CPC Class Codes: B29C 48/3366 using a die with concentric parts, e.g. rings, cylinders
• CPC Class Codes: B29C 48/395 using screws surrounded by a cooperating barrel, e.g. single screw extruders
• CPC Class Codes: B29C 48/49 using two or more extruders to feed one die or nozzle
• CPC Class Codes: B29C 61/0616 layered or partially layered preforms, e.g. preforms with layers of adhesive or sealing compositions B29C61/0625 and B29C61/065 take precedence
• CPC Class Codes: B29L 2023/001 Tubular films, sleeves
• CPC Class Codes: B32B 2250/05 5 or more layers
• CPC Class Codes: B32B 2250/42 Alternating layers, e.g. ABAB(C), AABBAABB(C)
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2272/00 Resin or rubber layer comprising scrap, waste or recycling material
• CPC Class Codes: B32B 2307/40 having particular optical properties light or UV resistant B32B2307/71
• CPC Class Codes: B32B 2307/406 Bright, glossy, shiny surface
• CPC Class Codes: B32B 2307/50 having particular mechanical properties
• CPC Class Codes: B32B 2307/514 : Oriented
• CPC Class Codes: B32B 2307/54 : Yield strength; Tensile strength
• CPC Class Codes: B32B 2307/546 : Flexural strength; Flexion stiffness
• CPC Class Codes: B32B 2307/558 : Impact strength, toughness
• CPC Class Codes: B32B 2307/5825 : Tear resistant
• CPC Class Codes: B32B 2307/736 : Shrinkable
• 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 27/28 : comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
• 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 27/34 : comprising polyamides
• CPC Class Codes: B32B 37/153 : at least one layer is extruded and immediately laminated while in semi-molten state
• CPC Class Codes: B32B 37/28 : involving assembly of non-flat intermediate products which are flattened at a later step, e.g. tubes
• CPC Class Codes: B32B 38/0012 : Mechanical treatment, e.g. roughening, deforming, stretching
• 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 428/2495 : Thickness [relative or absolute]
• CPC Class Codes: Y10T 428/24975 : No layer or component greater than 5 mils thick

Abstract

A multilayer, heat-shrinkable film generally includes at least one bulk layer and a microlayer section comprising a plurality of microlayers. The ratio of the thickness of any of the microlayers to the thickness of the bulk layer ranges from about 1:2 to about 1:40.

Claims

1. A method of making a multilayer, heat-shrinkable film, comprising:

a. extruding a bulk layer;

b. coextruding a plurality of microlayers to form a microlayer section;

c. merging said bulk layer and said microlayer section to form a multilayer film; and

d. stretch-orienting said multilayer film under conditions that impart heat-shrinkability to said film;

wherein, each of said microlayers and said bulk layer have a thickness, the ratio of the thickness of any of said microlayers to the thickness of said bulk layer ranging from about 1;

2 to about 1;

40; and

wherein, said film has a total free shrink (ASTM D2732-03) of at least about 10% at 200°

F., and an Elmendorf Tear value (ASTM D1922-06a) of at least 10 grams, as measured in at least one direction along a length or width dimension of said film.

2. The method of claim 1, wherein, said film has a thickness of less than about 0.7 mil.

3. The method of claim 1, wherein said film is stretch-oriented at a ratio of at least 3 in at least one direction along a length or width dimension of said film.

4. The method of claim 3, wherein said film is stretch-oriented at a ratio of at least 4 in at least one direction along a length or width dimension of said film.

5. The method of claim 1, wherein said film is stretch-oriented at a ratio of at least 5 in at least one direction along a length or width dimension of said film.

6. The method of claim 1, wherein

said microlayers each have a thickness ranging from about 0.001 to 0.015 mil;

and

said bulk layer has a thickness ranging from about 0.03 to 0.5 mil.

7. The method of claim 1, wherein said heat-shrinkable film has an Elmendorf Tear value (ASTM D1922-06a) of at least about 30 grams/mil, as measured in at least one direction along a length or width dimension of said film.

8. The method of claim 1, wherein said microlayer section comprises a repeating sequence of layers represented by the structure:

A/B,

wherein,

A represents a microlayer comprising one or more polymers,

B represents a microlayer comprising a blend of two or more polymers, and

A has a composition that is different from that of B.

9. The method of claim 8, wherein A and B comprise one or more of ethylene/alpha-olefin copolymer, ethylene/vinyl acetate copolymer, polypropylene homopolymer or copolymer, ethylene/methacrylic acid copolymer, maleic-anhydride-grafted polyethylene, polyamide, or low density polyethylene.