GB2110215A - Tearable plastic film - Google Patents

Tearable plastic film Download PDF

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Publication number
GB2110215A
GB2110215A GB08230482A GB8230482A GB2110215A GB 2110215 A GB2110215 A GB 2110215A GB 08230482 A GB08230482 A GB 08230482A GB 8230482 A GB8230482 A GB 8230482A GB 2110215 A GB2110215 A GB 2110215A
Authority
GB
United Kingdom
Prior art keywords
film
plastics
layer
cellular layer
bubbles
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.)
Granted
Application number
GB08230482A
Other versions
GB2110215B (en
Inventor
James William Sinclair
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.)
Metal Closures Venue Packaging Ltd
Original Assignee
Metal Closures Venue Packaging 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 Metal Closures Venue Packaging Ltd filed Critical Metal Closures Venue Packaging Ltd
Priority to GB08230482A priority Critical patent/GB2110215B/en
Publication of GB2110215A publication Critical patent/GB2110215A/en
Application granted granted Critical
Publication of GB2110215B publication Critical patent/GB2110215B/en
Expired legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
    • B29C44/22—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length consisting of at least two parts of chemically or physically different materials, e.g. having different densities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
    • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
    • B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • B29C48/307—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets specially adapted for bringing together components, e.g. melts within the die
    • 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
    • B32B27/065—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 foam
    • 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
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • 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
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • 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
    • B32B2266/00—Composition of foam
    • B32B2266/08—Closed cell foam
    • 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
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/582—Tearability
    • 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
    • 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
    • B32B2439/00—Containers; Receptacles

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

A plastics film which is readily tearable in one direction, the film including a cellular layer of elongate bubbles, the bubbles being closely spaced and aligned with their longitudinal axes extending generally parallel to one another and said direction so as to guide tearing in said direction. The film is made by extruding a sheet of the plastics material while foaming a layer thereof so as to create a layer of the above bubbles which are then elongated as above.

Description

SPECIFICATION A plastic film The present invention relates to a plastics film and its production.
In this specification a film is a single layer or a number of superimposed layers of plastics material(s) having a total thickness of less than about 250 microns.
Bags are commonly made from polyethylene film and are sealed to provide a sealed enclosure for articles contained within the bag.
The problem associated with such bags, and also associated with bags made of a similar material such as polypropylene film, is that they are awkward or difficult to open by tearing since the plastics film does not readily rip in.anyparticsulay,ctirection. This is particularly disadvaritågeousin sltustions where quick access into a bag is required as for instance for bags used in hospitals.
It is a general aim of the present invention to provide a plastics film which readily tears in one direction. Accordingly bags made of such a film can be opened easily and quickly by a tearing action.
Ascording to one aspect of the present invention there is provided a plastics film which is readily tearable in one direction, the film including a cellular layer of elongate bubbles, the bubbles being closely spaced and aligned with their longitudinal axes extending generally parallel to one another and said direction so as to guide tearing in said direction.
Preferably the plastics film is a co-extrusion having at least three layers wherein the central payer is defined by the cellular layer. Conveniently the layers are all formed from the same plastics material although it is envisaged that different plastics material may be used for different layers.
According to another aspect of the present invention there is provided a method of producing a plastics film which is readily tearable in one direction, the method including extruding the plastics material in planar sheet form and during extrusion foaming a layer of plastics material to create a layer of closely spaced bubbles, the extrudate being treated so as to elongate the bubbles so that their longitudinal axes are generally parallel to said direction.
Various aspects of the present invention are hereinafter described with reference to the accompanying drawings in which: Figure 1 is a schematic perspective view of an apparatus arranged to produce a plastics film according to the present invention; Figure 2 is a schematic section through an extrusion die capable of producing a plastics film according to the present invention; Figure 3 is a schematic cross-section through a film according to the present invention; and Figure 4 is a schematic section taken along line IV-IV in Figure 3.
Referring initially to Figures 3 and 4 there is shown a plastics film 10 which is composed of three discrete co-extruded layers 11, 12 and 13. The central layer 12 is a foamed cellular layer having a plurality of closely spaced elongate bubbles or cavities 15.
Preferably the population of bubbles created is such as to give the cellular layer 12 an apparent density of less then 0.7 g/cm3, more preferably in the range of 0.5 to 0.6 g/cm3.
The relative thicknesses of layers 11,12 and 13 are chosen so that the direction of tearing of the film 10 is determined by layer 12. Accordingly since all the cavities 15 have their longitudinal axes aligned in generally the same direction tearing of layer 12 is easier in that direction than any other direction.
When the cellular layer 12 forms part of a multilayered film, as for instance illustrated at 10 in Figure 3, the relative thicknesses of the layers 11, 12 and 13 are chosen so that the combined resistance to tear is substantially less in the direction of elongation of the bubbles than in a direction transverse thereto. For instance, for a 65 micron thick film 10 composed of low density polyethylene the tear strength in the longitudinal direction is in the order of 0.9 Newtons force whereas in the transverse direction it is in the order of 4.0 Newtons force.
The relative thicknesses of the layers are thus chosen so that the tear direction is dictated by the cellular layer. By way of illustration it has been found that if the film 10 has a thickness of 100 microns or less, for example 50 to 100 microns and the film is entirely composed of low density polyethylene then the cellular layer should form at least 35% by weight, preferably 40% or more by weight, of the total weight of the film. If the film is of a thickness in excess of 100 microns, preferably the cellular layer forms at least 50% by weight of the total weight of the film 10.
If, for instance, layers 11 and 13 are formed from a plastics material which is stronger than low density polyethylene, such as polypropylene, the weight of the cellular layer is preferably about 50% of the total weight of the film for a film having a thickness between 50-100 microns.
If the cellular layer 12 is formed from a stronger more resilient material than low density polyethylene, for example an ethylene vinyl acetate co-polymer (9% vinyl acetate) and the outer layers 11,13 are formed from polypropylene it has been found that the cellular layer in such a construction should from at least 75% by weight of the total weight of the film 10 when the film 10 has a thickness ranging between 50-100 microns.
Although film 10 is shown in Figure 1 as a multi-layered film it is envisaged that either layer 11 or 13 or both may be omitted. However it is presently preferred to have a three layered film as shown since layers 11 and 13 isolate layer 12 from the walls of the extruding die which has an advantage of preventing build up of plastics material at the die opening which would otherwise occur.
In Figures 1 and 2 an extruding apparatus 20 capable of producing film 10 is shown schematically.
The apparatus 20 includes an extruding die arrangement 25 which includes a flow combining chamber 24 and a die 26. The die 26 expands in width from the combining chamber 24 to terminate in an elongate orifice 28. The die 26 and flow mixing chamber 24 are conveniently of conventional construction.
The extruded film 10 is directed onto a water cooled roller 29 and is then drawn of roller 29 to be wound into a roll (not shown).
In Figure 2 the relative paths of flow of the plastics material determined by the flow combining chamber are shown. The output from one flow of plastics material enters through port 30 and another flow of plastics material enters through port 31. The flow 33 from port 31 divides into two flows 33a and 33b and meet on either side of flow 34 from port 30 at a location 36 prior to entry into the die 26.
The plastics material entering port 30 has mixed therewith a heat sensitive foaming agent such as an azodicarbonamide. The foaming agent preferably forms between 0.5 to 0.75% by weight of the weight of the cellular layer. The foaming agent is chosen so that it reaches its activation temperature before extrusion from the die 26. When the foaming agent is within flow combining chamber 24 and die 26 although it has reached activation temperature the plastics material does not foam due to the pressure within the flow of plastics material. Accordingly as soon as the plastics material emerges from orifice 28 of die 26 there is a sudden pressure reduction enabling the plastics material to foam.The plastics film 10 is drawn from the die 26 at a controlled rate by roller 29 and the pulling effect created by roller 29 causes the bubbles formed on foaming of the plastics material 12 to elongate in the direction of the pulling.
Accordingly the degree of elongation of the bubbles may be varied by varying the pulling effect created by roller 29. It is presently preferred to have a draw off rate in the range of 10-100 metres per minute.
Layers 11, 12 and 13 as described above may be each formed from the same plastics material such as low density polyethylene or may be of different plastics material.
Although layers 11, 12, 13 are described as being co-extruded it will be appreciated that these layers may be separately extruded and then secured together to form a laminated film.
Additionally it may be appreciated that any desired number of layers may be co-extruded to provide a film according to the present invention, the film including is desired more than one layer of elongate bubbles.

Claims (15)

1. A plastics film which is readily tearable in one direction, the film including a cellular layer of elongate bubbles, the bubbles being closely spaced and aligned with their longitudinal axes extending generally parallel to one another and said direction so as to guide tearing in said direction.
2. A plastics film according to Claim 1 wherein the film is a co-extrusion including said cellular layer and at least one other layer, the layers being constructed so that the combined resistance to tear of said layers is less in said direction than in a direction transverse thereto.
3. A plastics film according to Claim 2 wherein the film is a co-extrusion comprised of three layers, said cellular layer forming the central layer.
4. A plastics film according to Claim 2 or 3 wherein all layers of the co-extrusion are formed from the same plastics material.
5. A plastics film according to Claim 2 or 3 wherein said cellular layer is formed from a plastics material different to the plastics material of at least one of the other layers.
6. A plastics film according to any preceding claim wherein the cellular layer is formed from polyethylene and the density of the cellular layer is less than 0.7 g/cm3.
7. A plastics film according to Claim 6 wherein the density of the cellular layer is in the range of 0.5 to 0.6 g/cm3.
8. A plastics film according to any of Claims 2 to 7 wherein the cellular layer forms at least 35% by weight of the total weight of said film.
9. A plastics film according to Claim 8 wherein the total thickness of said film is up to 100 microns and said cellular layer forms about 40% by weight of the total weight of the film.
10. A plastics film according to Claim 8 wherein the total thickness of said film is between 100 to 250 microns and said cellular layer forms more than 40% by weight of the total weight of said film.
11. A plastics film substantially as described herein with reference to any of the accompanying drawings.
12. A bag or container formed from a plastics film according to any preceding claim.
13. A method of producing a plastics film which is readily tearable in one direction, the method including extruding the plastics material in planar sheetform and during extrusion foaming a layer of plastics material to create a layer of closely spaced bubbles, the extrudate being treated so as to elongate the bubbles so that their longitudinal axes are generally parallel to said direction.
14. A method according to Claim 13 wherein elongation of said bubbles is achieved by stretching the extrudate in the direction of take-off.
15. A method of producing a plastics film substantially as described with reference to any of the drawings.
GB08230482A 1981-10-31 1982-10-26 Tearable plastic film Expired GB2110215B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08230482A GB2110215B (en) 1981-10-31 1982-10-26 Tearable plastic film

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8132916 1981-10-31
GB08230482A GB2110215B (en) 1981-10-31 1982-10-26 Tearable plastic film

Publications (2)

Publication Number Publication Date
GB2110215A true GB2110215A (en) 1983-06-15
GB2110215B GB2110215B (en) 1985-05-30

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08230482A Expired GB2110215B (en) 1981-10-31 1982-10-26 Tearable plastic film

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0962314A1 (en) * 1998-05-27 1999-12-08 Prosyn Polyane S.A. Diffusing and isothermal plastic film for making coverings for greenhouses or sun shading systems
EP1142684A3 (en) * 2000-04-03 2002-06-26 Sumitomo Chemical Company, Limited Thermoplastic resin sheet and container
US7332215B2 (en) * 2003-06-11 2008-02-19 Sony Corporation Resin-molded component and method for manufacturing thereof as well as diaphragm for loudspeaker
US20100112335A1 (en) * 2007-04-10 2010-05-06 Du Pont-Mitsui Polychemicals Co., Ltd Laminated film or sheet having a foamed resin layer and process for producing the same
US9944045B2 (en) 2014-09-02 2018-04-17 Mondi Consumer Packaging Technologies Gmbh Coextruded polyethylene film

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
HUE030040T2 (en) 2014-09-02 2017-04-28 Mondi Consumer Packaging Tech Gmbh Plastic multilayer film

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0962314A1 (en) * 1998-05-27 1999-12-08 Prosyn Polyane S.A. Diffusing and isothermal plastic film for making coverings for greenhouses or sun shading systems
EP1142684A3 (en) * 2000-04-03 2002-06-26 Sumitomo Chemical Company, Limited Thermoplastic resin sheet and container
US6805930B2 (en) 2000-04-03 2004-10-19 Sumitomo Chemical Company, Ltd. Thermoplastic resin sheet and container
US7332215B2 (en) * 2003-06-11 2008-02-19 Sony Corporation Resin-molded component and method for manufacturing thereof as well as diaphragm for loudspeaker
CN1575038B (en) * 2003-06-11 2010-06-16 索尼株式会社 Resin-molded component and method for manufacturing thereof as well as diaphragm for loudspeaker
US20100112335A1 (en) * 2007-04-10 2010-05-06 Du Pont-Mitsui Polychemicals Co., Ltd Laminated film or sheet having a foamed resin layer and process for producing the same
US9944045B2 (en) 2014-09-02 2018-04-17 Mondi Consumer Packaging Technologies Gmbh Coextruded polyethylene film

Also Published As

Publication number Publication date
GB2110215B (en) 1985-05-30

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PCNP Patent ceased through non-payment of renewal fee