GB2047616A - Extruded plastics bags - Google Patents

Extruded plastics bags Download PDF

Info

Publication number
GB2047616A
GB2047616A GB8009280A GB8009280A GB2047616A GB 2047616 A GB2047616 A GB 2047616A GB 8009280 A GB8009280 A GB 8009280A GB 8009280 A GB8009280 A GB 8009280A GB 2047616 A GB2047616 A GB 2047616A
Authority
GB
United Kingdom
Prior art keywords
bag
high density
low density
density polyolefin
carrier
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Withdrawn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
GB8009280A
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.)
DB PLASTICS Manufacturing Ltd
Original Assignee
DB PLASTICS Manufacturing 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 DB PLASTICS Manufacturing Ltd filed Critical DB PLASTICS Manufacturing Ltd
Priority to GB8009280A priority Critical patent/GB2047616A/en
Publication of GB2047616A publication Critical patent/GB2047616A/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Withdrawn legal-status Critical Current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
    • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B70/00—Making flexible containers, e.g. envelopes or bags
    • 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
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/0004—Cutting, tearing or severing, e.g. bursting; Cutter details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D31/00—Bags or like containers made of paper and having structural provision for thickness of contents
    • B65D31/02—Bags or like containers made of paper and having structural provision for thickness of contents with laminated walls
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B2155/00—Flexible containers made from webs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B2155/00—Flexible containers made from webs
    • B31B2155/003—Flexible containers made from webs starting from tubular webs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B2160/00—Shape of flexible containers
    • B31B2160/10—Shape of flexible containers rectangular and flat, i.e. without structural provision for thickness of contents
    • 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
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/402—Coloured
    • 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
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/406—Bright, glossy, shiny surface
    • 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
    • B32B2323/043—HDPE, i.e. high 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
    • B32B2323/04—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
    • B32B2439/00—Containers; Receptacles

Abstract

In a method of manufacturing a bag, a high-density polyolefin, preferably high-density polyethylene, is co-extruded with a low-density polyolefin, preferably a low-density polyethylene, to give a tubular film in which the high density polyolefin constitutes the inner layer, the tubular film being welded and cut to give a series of bags. The bag is coloured, curls outwardly at the edges of the mouth, and may have a handle.

Description

SPECIFICATION Carrier bags The present invention relates to carrier bags.
Carrier bags made from plastics material are widely used, but the manufacturer sometimes has difficulty selecting a suitable plastics material which will give a bag meeting characteristics considered desirable. For example, there are problems in producing a strong carrier bag of brightly coloured plastics material.
A high density polyolefin such as a high density polyethylene can give a strong bag, though this material has a lustre-less appearance which dulls any bright colour. Low density polyethylene has been used to product brightly coloured carrier bags, but such a material tends to stretch under load and accordingly bags of low density polyethylene often lack strength.
We have now found a way in which the respective advantages of high density and low density polyolefins can be combined to permit production of a relatively strong carrier bag which may be brightly coloured.
According to the present invention we provide a method of manufacturing a carrier bag in which a high density polyolefin, preferably a high density polyethylene, is co-extruded by core extrusion with a low density polyolefin, preferably a low density polyethylene, to give a tubular film comprising a layer of high density polyolefin within and bonded to a layer of low density polyolefin, and the tubular film is welded and cut to give a series of carrier bags with or without handles.
The inner layer of high density polyolefin can impart strength to the bag, while the outer layer of low density polyolefin can be brightly coloured and have a glossy finish, the inner layer then also being coloured.
Apart from the advantage of strength and, if desired, bright colour, we find that carrier bags manufactured by the present method typically have a further, unexpected beneficial characteristic.
As produced by the core extrusion process, the tubular film comprises layers of different polyolefins with different properties. It is usually the case that the film has a tendency to curl at its edges, the curling being with the layer of low density polyolefin forming the concave surface and the layer of high density polyolefin forming the convex surface. In that the high density polyolfin layer is inside the low density polyolefin layer, the tendency is thus for the tubular film to curl outwardly at its edges.
This outward curling means that the material at the mouth of a carrier bag of the present invention can readily be grasped to open the mouth. It is a disadvantage of most known plastics material that when used for the manufacture of a carrier bag the bag has major walls which tend to stick together; as a result it is often difficult to open the mouth of the bag. This difficulty in opening is not found with carrier bags of the present invention which exhibit the curl effect at their opening.
The tubular film preferably comprises 50% by weight of high density polyolefin and 50% by weight of low density polyolefin. However, the ratio of the components may be varied and for instant a product with greater strength may be obtained by using up to 70% by weight of high density polyolefin. Equally, if desired one can use up to 70% of low density polyolefin. The film is preferably extruded to a thickness of 25 to 40 microns and can then be processed in a conventional manner to give a series of carrier bags.
The further processing can for example include cutting to give cut-out handles and transverse welding at spaced intervals along the film. The spacing for the welding can be that required to produce a head-to-tail or more preferably a side-by-side series of carrier bags.
There is little difficulty in selecting a welding temperature which is correct for both layers of the plastics material.
In a typical example of the performance of the present invention, a series of carrier bags each with handles was manufactured by core extrusion of equal weights of a high density polyethylene and a low density polyethylene to give a tubular film of thickness 30 microns with the high density polyethylene forming a layer within and bonded to a layer of the low density polyethylene. The tubular film was then cut and welded in a conventional manner. In this particular instance the polyethylenes contained a bright green pigment and the resultant bags had a bright green glossy surface. At the opening of the bag the material was curled back and as such it was easy to open out the opening for insertion of items to be carried.
1. A method of manufacturing a carrier bag in which a high density polyolefin is coextruded by core extrusion with a low density polyolefin to give a tubular film comprising a layer of high density polyolefin within and bonded to a layer of low density polyolefin, and the tubular film is welded and cut to give a series of carrier bags with or without handles.
2. A method according to Claim 1 in which the high density polyolefin is a polyethylene.
3. A method according to Claim 1 or 2 in which the low density polyolefin is a polyethylene.
4. A method according to Claim 1, 2 or 3 in which both layers are coloured to give a bag with a glossy external finish.
5. A method according to any of Claim 1 to 4 in which approximately equal weights of
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Carrier bags The present invention relates to carrier bags. Carrier bags made from plastics material are widely used, but the manufacturer sometimes has difficulty selecting a suitable plastics material which will give a bag meeting characteristics considered desirable. For example, there are problems in producing a strong carrier bag of brightly coloured plastics material. A high density polyolefin such as a high density polyethylene can give a strong bag, though this material has a lustre-less appearance which dulls any bright colour. Low density polyethylene has been used to product brightly coloured carrier bags, but such a material tends to stretch under load and accordingly bags of low density polyethylene often lack strength. We have now found a way in which the respective advantages of high density and low density polyolefins can be combined to permit production of a relatively strong carrier bag which may be brightly coloured. According to the present invention we provide a method of manufacturing a carrier bag in which a high density polyolefin, preferably a high density polyethylene, is co-extruded by core extrusion with a low density polyolefin, preferably a low density polyethylene, to give a tubular film comprising a layer of high density polyolefin within and bonded to a layer of low density polyolefin, and the tubular film is welded and cut to give a series of carrier bags with or without handles. The inner layer of high density polyolefin can impart strength to the bag, while the outer layer of low density polyolefin can be brightly coloured and have a glossy finish, the inner layer then also being coloured. Apart from the advantage of strength and, if desired, bright colour, we find that carrier bags manufactured by the present method typically have a further, unexpected beneficial characteristic. As produced by the core extrusion process, the tubular film comprises layers of different polyolefins with different properties. It is usually the case that the film has a tendency to curl at its edges, the curling being with the layer of low density polyolefin forming the concave surface and the layer of high density polyolefin forming the convex surface. In that the high density polyolfin layer is inside the low density polyolefin layer, the tendency is thus for the tubular film to curl outwardly at its edges. This outward curling means that the material at the mouth of a carrier bag of the present invention can readily be grasped to open the mouth. It is a disadvantage of most known plastics material that when used for the manufacture of a carrier bag the bag has major walls which tend to stick together; as a result it is often difficult to open the mouth of the bag. This difficulty in opening is not found with carrier bags of the present invention which exhibit the curl effect at their opening. The tubular film preferably comprises 50% by weight of high density polyolefin and 50% by weight of low density polyolefin. However, the ratio of the components may be varied and for instant a product with greater strength may be obtained by using up to 70% by weight of high density polyolefin. Equally, if desired one can use up to 70% of low density polyolefin. The film is preferably extruded to a thickness of 25 to 40 microns and can then be processed in a conventional manner to give a series of carrier bags. The further processing can for example include cutting to give cut-out handles and transverse welding at spaced intervals along the film. The spacing for the welding can be that required to produce a head-to-tail or more preferably a side-by-side series of carrier bags. There is little difficulty in selecting a welding temperature which is correct for both layers of the plastics material. In a typical example of the performance of the present invention, a series of carrier bags each with handles was manufactured by core extrusion of equal weights of a high density polyethylene and a low density polyethylene to give a tubular film of thickness 30 microns with the high density polyethylene forming a layer within and bonded to a layer of the low density polyethylene. The tubular film was then cut and welded in a conventional manner. In this particular instance the polyethylenes contained a bright green pigment and the resultant bags had a bright green glossy surface. At the opening of the bag the material was curled back and as such it was easy to open out the opening for insertion of items to be carried. CLAIMS
1. A method of manufacturing a carrier bag in which a high density polyolefin is coextruded by core extrusion with a low density polyolefin to give a tubular film comprising a layer of high density polyolefin within and bonded to a layer of low density polyolefin, and the tubular film is welded and cut to give a series of carrier bags with or without handles.
2. A method according to Claim 1 in which the high density polyolefin is a polyethylene.
3. A method according to Claim 1 or 2 in which the low density polyolefin is a polyethylene.
4. A method according to Claim 1, 2 or 3 in which both layers are coloured to give a bag with a glossy external finish.
5. A method according to any of Claim 1 to 4 in which approximately equal weights of a high density polyethylene and a low density polyethylene are core extruded.
6. A method according to any of Claims 1 to 5 in which the film is extruded to a thickness of 25 to 40 microns.
7. A method according to any of Claims 1 to 6 in which the series of carrier bags are formed from the tubular film by cutting to give cut-out handles and transverse welding at spaced intervals along the film.
8. A carrier bag when manufactured by a process according to any of Claims 1 to 7.
9. A carrier bag according to Claim 8 with outward curling of the material at the mouth of the bag.
GB8009280A 1979-03-19 1980-03-19 Extruded plastics bags Withdrawn GB2047616A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8009280A GB2047616A (en) 1979-03-19 1980-03-19 Extruded plastics bags

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7909507 1979-03-19
GB8009280A GB2047616A (en) 1979-03-19 1980-03-19 Extruded plastics bags

Publications (1)

Publication Number Publication Date
GB2047616A true GB2047616A (en) 1980-12-03

Family

ID=26270940

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8009280A Withdrawn GB2047616A (en) 1979-03-19 1980-03-19 Extruded plastics bags

Country Status (1)

Country Link
GB (1) GB2047616A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0125071A2 (en) * 1983-04-28 1984-11-14 Porter-Lancastrian Limited Coating of plastics materials
US4560598A (en) * 1982-05-20 1985-12-24 Stiksack Sts S.A. Plastics film and bags and sacks therefrom
DE3736236A1 (en) * 1987-10-27 1989-05-11 Nordenia Verpackung Film, in particular for producing a sack, bag or similar package

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4560598A (en) * 1982-05-20 1985-12-24 Stiksack Sts S.A. Plastics film and bags and sacks therefrom
EP0125071A2 (en) * 1983-04-28 1984-11-14 Porter-Lancastrian Limited Coating of plastics materials
EP0125071A3 (en) * 1983-04-28 1985-09-18 Porter-Lancastrian Limited Coating of plastics materials
DE3736236A1 (en) * 1987-10-27 1989-05-11 Nordenia Verpackung Film, in particular for producing a sack, bag or similar package

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Legal Events

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)