EP0338048A1 - Polymeric films - Google Patents

Polymeric films

Info

Publication number
EP0338048A1
EP0338048A1 EP88908965A EP88908965A EP0338048A1 EP 0338048 A1 EP0338048 A1 EP 0338048A1 EP 88908965 A EP88908965 A EP 88908965A EP 88908965 A EP88908965 A EP 88908965A EP 0338048 A1 EP0338048 A1 EP 0338048A1
Authority
EP
European Patent Office
Prior art keywords
film according
heat seal
density polyethylene
low density
linear low
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP88908965A
Other languages
German (de)
French (fr)
Inventor
Kenneth Douglas Kendall
Darren William Dean
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Akzo Nobel Films Holding Ltd
Original Assignee
Courtaulds Films and Packaging Holdings Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Courtaulds Films and Packaging Holdings Ltd filed Critical Courtaulds Films and Packaging Holdings Ltd
Publication of EP0338048A1 publication Critical patent/EP0338048A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B32B27/205—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents the fillers creating voids or cavities, e.g. by stretching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2270/00—Resin or rubber layer containing a blend of at least two different polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/31—Heat sealable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/04—Polyethylene
    • B32B2323/046—LDPE, i.e. low density polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/10—Polypropylene

Definitions

  • This invention concerns voided polypropylene films including a heat seal layer.
  • Voided polypropylene films produced by orienting polypropylene homopolymer containing a particulate filler have found wide acceptance as packaging materials.
  • voided and non-voided polyprcpylene homopolymer layers will heat seal to themselves, the temperatures required to effect such seals cause shrinkage of the film in the region of the seal, and a distorted seal results.
  • Various polymer layers have been proposed for voided and non-voided polypropylene homopolymer films which provide the films with heat sealability at lower temperatures, thereby avoiding such shrinkage of the film.
  • layers of polymers containing units derived from at least two of ethylene, propylene and butene It has also been proposed to use blends of polymers to foris heat seal layers, for example to provide increased hot tack strength at lower temperatures.
  • a heat sealable polypropylene film comprising a layer of voided polypropylene homopolymer having a heat seal layer thereon, the heat seal layer comprising a linear low density polyethylene having a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa.
  • Polypropylene films of the present invention in addition to forming good heat seals a: temperatures below those at which distortion of the seal results, have shown other advantages.
  • corona discharge treatment of the film to provide printability can be effected under less stringent conditions, thereby leading to lower odour for the treated film.
  • Heat seals produced with films of the present invention have shown good hot tack combined with good sealability.
  • the heat seal layers have shown good acceptability to cold seal adhesives. Migration of additives, for example slip and anti-static agents, from the voided homopolymer layer, has also been found to be surprisingly substantially unaffected compared with that for hitherto proposed heat seal layers.
  • the linear low density polyethylene of the heat seal layer should have a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa, preferably from 5 to 7. High values of melt flow index can result in the polymer being difficult if not impossible to extrude with the polypropylene homopolymer.
  • the linear low density polyethylene preferably contains units derived from oct-1-ene.
  • the density of the polyethylene will in general be in the range of from 0.917 to 0.924 g/cm 3 .
  • a linear low density polyethylene can be used alone to produce a heat seal layer of a film in accordance with the invention
  • blends thereof with at least one further polymer can be used.
  • Preferred further polymers are ionic polymers, and in particular ionic copolymers and terpolymers. Examples of such further polymers include polymers containing units derived from ethylene, and an acrylic ester and/or maleic anhydride.
  • the weight ratio of linear low density polyethylene to the further polymer or polymers is preferably from 95:5 to 30:70, advantageously from 70:30 to 30:70, and especially about 60:40.
  • the heat seal layer is preferably from 0.5 to 5 microns thick, more particularly from 1 to 2.5 microns thick, and advantageously about 1.5 microns thick. Typical total film thicknesses are from 30 to 60 microns.
  • Heat sealable films of the present invention can, if desired, have a further heat seal layer which can be the same as or different from that already referred to.
  • a further heat seal layer which can be the same as or different from that already referred to.
  • other layers can also be present to provide the films of the present invention with particular properties, for example an adhesive layer can be present to allow the films to be laminated to other films.
  • Films of the present invention can be produced by known methods, for example by coextruding a layer of polypropylene homopolymer containing a voiding agent with a layer of linear low density polyethylene and thereafter orienting the extruded film to cause voiding of the homopolymer layer.
  • a three layer film was co-extruded at 240°C to produce a core of polypropylene homopolymer containing about 6% by weight of chalk with a layer on each side consisting of a 60:40 blend of linear low density polyethylene and an ionic polymer (a terpolymer of ethylene, an acrylic ester and maleic anhydride) to form a chill-cast web.
  • the cast web was then stretched by a ratio of 4.5:1 in the machine direction at temperature of 100°C, and thereafter by a ratio of 9.5:1 in the transverse direction at a temperature of 160°C.
  • the resultant film which had an overall thickness of 43.5 microns with a heat seal layer on each side of a voided core each of 1.5 microns thickness, showed good hot tack at low temperatures combined with good sealability.

Landscapes

  • Laminated Bodies (AREA)

Abstract

The invention concerns heat sealable polypropylene films including a layer of voided polypropylene homopolymer with a heat seal layer. The heat seal layer includes a linear low density polyethylene having a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa. Seals formed with films of the present invention have shown good hot tack combined with good sealability. The heat seal layers have also shown good acceptability to cold seal adhesives.

Description

Polymeric Films
This invention concerns voided polypropylene films including a heat seal layer.
Voided polypropylene films produced by orienting polypropylene homopolymer containing a particulate filler have found wide acceptance as packaging materials. However, although voided and non-voided polyprcpylene homopolymer layers will heat seal to themselves, the temperatures required to effect such seals cause shrinkage of the film in the region of the seal, and a distorted seal results. Various polymer layers have been proposed for voided and non-voided polypropylene homopolymer films which provide the films with heat sealability at lower temperatures, thereby avoiding such shrinkage of the film. In particular it has been proposed to use layers of polymers containing units derived from at least two of ethylene, propylene and butene. It has also been proposed to use blends of polymers to foris heat seal layers, for example to provide increased hot tack strength at lower temperatures.
While such previously proposed heat seal layers can provide satisfactory seals without distortion of the film in the region of the seal, improvements are constantly being sought in the overall properties of heat sealable voided polypropylene films.
According to the present invention there is provided a heat sealable polypropylene film comprising a layer of voided polypropylene homopolymer having a heat seal layer thereon, the heat seal layer comprising a linear low density polyethylene having a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa.
Polypropylene films of the present invention, in addition to forming good heat seals a: temperatures below those at which distortion of the seal results, have shown other advantages. For example, corona discharge treatment of the film to provide printability can be effected under less stringent conditions, thereby leading to lower odour for the treated film. Heat seals produced with films of the present invention have shown good hot tack combined with good sealability. Furthermore, the heat seal layers have shown good acceptability to cold seal adhesives. Migration of additives, for example slip and anti-static agents, from the voided homopolymer layer, has also been found to be surprisingly substantially unaffected compared with that for hitherto proposed heat seal layers.
The linear low density polyethylene of the heat seal layer should have a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa, preferably from 5 to 7. High values of melt flow index can result in the polymer being difficult if not impossible to extrude with the polypropylene homopolymer.
The linear low density polyethylene preferably contains units derived from oct-1-ene. The density of the polyethylene will in general be in the range of from 0.917 to 0.924 g/cm3.
Although a linear low density polyethylene can be used alone to produce a heat seal layer of a film in accordance with the invention, blends thereof with at least one further polymer can be used. Preferred further polymers are ionic polymers, and in particular ionic copolymers and terpolymers. Examples of such further polymers include polymers containing units derived from ethylene, and an acrylic ester and/or maleic anhydride.
The weight ratio of linear low density polyethylene to the further polymer or polymers is preferably from 95:5 to 30:70, advantageously from 70:30 to 30:70, and especially about 60:40.
The heat seal layer is preferably from 0.5 to 5 microns thick, more particularly from 1 to 2.5 microns thick, and advantageously about 1.5 microns thick. Typical total film thicknesses are from 30 to 60 microns.
Heat sealable films of the present invention can, if desired, have a further heat seal layer which can be the same as or different from that already referred to. However, other layers can also be present to provide the films of the present invention with particular properties, for example an adhesive layer can be present to allow the films to be laminated to other films.
Films of the present invention can be produced by known methods, for example by coextruding a layer of polypropylene homopolymer containing a voiding agent with a layer of linear low density polyethylene and thereafter orienting the extruded film to cause voiding of the homopolymer layer.
The following Example is given by way of illustration only. All parts are by weight unless stated otherwise.
EXAMPLE
A three layer film was co-extruded at 240°C to produce a core of polypropylene homopolymer containing about 6% by weight of chalk with a layer on each side consisting of a 60:40 blend of linear low density polyethylene and an ionic polymer (a terpolymer of ethylene, an acrylic ester and maleic anhydride) to form a chill-cast web.
The cast web was then stretched by a ratio of 4.5:1 in the machine direction at temperature of 100°C, and thereafter by a ratio of 9.5:1 in the transverse direction at a temperature of 160°C.
The resultant film, which had an overall thickness of 43.5 microns with a heat seal layer on each side of a voided core each of 1.5 microns thickness, showed good hot tack at low temperatures combined with good sealability.

Claims

1. A heat sealable polypropylene film comprising a layer of voided polypropylene homopolymer having a heat seal layer thereon, the heat seal layer comprising a linear low density polyethylene having a melt flow index of at least 4 as measured by ASTM D1238/73 under condition 240°C and 298.2 KPa.
2. A film according to claim 1 , wherein the linear low density polyethylene has a melt flow index of from 5 to 7.
3. A film according to either of the preceding claims, wherein the linear low density polyethylene contains units derived from oct-1-ene.
4. A film according to any of the preceding claims, wherein the linear low density polyethylene has a density of from 0.917 to 0.924g/cm3.
5. A film according to any of the preceding claims, wherein the heat seal layer comprises a blend of the linear low density polyethylene with at least one further polymer.
6. A film according to claim 5, wherein the further polymer comprises an ionic polymer.
7. A film according to claim 6, wherein the ionic polymer is a copolymer or terpolymer.
8. A film according to claim 6 or claim 7, wherein the ionic polymer contains units derived from ethylene and an acrylic ester and/or maleic anhydride.
9 . A film according to any of claims 5 to 8, wherein the weight ratio of linear low density polyethylene to the further polymer or polymers is from 95:5 to 30:70.
10. A film according to claim 9, wherein the further polymer is a terpolymer, and the weight ratio of linear low density polyethylene to the terpolymer is from 30:70 to 70:30.
11. A film according to claim 10, wherein the weight ratio is about 60:40.
12. A film according to any of the preceding claims, wherein the heat seal layer has a thickness of from 0.5 to 5 microns.
13. A film according to any of the preceding claims, having a further heat seal coating thereon.
EP88908965A 1987-10-12 1988-10-11 Polymeric films Withdrawn EP0338048A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8723897A GB2211464A (en) 1987-10-12 1987-10-12 Heat sealable polypropylene films
GB8723897 1987-10-12

Publications (1)

Publication Number Publication Date
EP0338048A1 true EP0338048A1 (en) 1989-10-25

Family

ID=10625176

Family Applications (2)

Application Number Title Priority Date Filing Date
EP88309477A Pending EP0312288A1 (en) 1987-10-12 1988-10-11 Polymeric films
EP88908965A Withdrawn EP0338048A1 (en) 1987-10-12 1988-10-11 Polymeric films

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP88309477A Pending EP0312288A1 (en) 1987-10-12 1988-10-11 Polymeric films

Country Status (8)

Country Link
EP (2) EP0312288A1 (en)
JP (1) JPH02501553A (en)
KR (1) KR890701362A (en)
AU (1) AU2545888A (en)
BR (1) BR8807242A (en)
DK (1) DK281989A (en)
GB (1) GB2211464A (en)
WO (1) WO1989003310A1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2223446B (en) * 1988-08-26 1993-01-06 Courtaulds Films & Packaging Polymeric films for packaging
GB2224973B (en) * 1988-11-04 1992-08-19 Courtaulds Films & Packaging Polymeric films
AU720652B2 (en) * 1995-12-15 2000-06-08 Cryovac, Inc. Film having excellent ink adhesion in combination with enhanced slip, antifog, and/or antistatic properties
ITMI20011195A1 (en) 2001-06-06 2002-12-06 Veneta Decalcogomme S R L PROCEDURE FOR MAKING A HOT-TRANSFERABLE DECORATIVE FILM ON A FLEXIBLE SUPPORT TAPE
ITMI20040701A1 (en) * 2004-04-08 2004-07-08 Bimo Italia S P A COMPOSITE FILMS
KR102420609B1 (en) * 2015-04-17 2022-07-13 글로벌 스트레터지스 홀딩 코퍼레이션 High Strength Ribbon - Woven Disposable Fabric Product

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1157617A (en) * 1977-12-14 1983-11-29 Milton L. Weiner Oriented polypropylene with linear low density polyethylene copolymer coating
JPS5512008A (en) * 1978-06-29 1980-01-28 Mitsui Petrochemical Ind Packing laminate sack
FR2505731A1 (en) * 1981-05-15 1982-11-19 Charbonnages Ste Chimique COMPLEX THERMOPLASTIC FILMS AND PROCESS FOR OBTAINING THEM
GB2150881A (en) * 1983-11-23 1985-07-10 Bcl Ltd Decorative packaging films
DE3517081A1 (en) * 1985-05-11 1986-11-13 Wolff Walsrode Ag, 3030 Walsrode OPAKE, SEALABLE MULTILAYER FILMS MADE OF POLYOLEFINES

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8903310A1 *

Also Published As

Publication number Publication date
AU2545888A (en) 1989-05-02
WO1989003310A1 (en) 1989-04-20
JPH02501553A (en) 1990-05-31
GB2211464A (en) 1989-07-05
EP0312288A1 (en) 1989-04-19
DK281989A (en) 1989-08-07
GB8723897D0 (en) 1987-11-18
BR8807242A (en) 1990-02-13
KR890701362A (en) 1989-12-20
DK281989D0 (en) 1989-06-09

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XX Miscellaneous

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