GB2375732A

GB2375732A - Fabrication of blown film laminate

Info

Publication number: GB2375732A
Application number: GB0107719A
Authority: GB
Inventors: David Jonathan Matthew Madeley
Original assignee: JOHN MADELEY MACHINERY Ltd
Current assignee: JOHN MADELEY MACHINERY Ltd
Priority date: 2001-03-28
Filing date: 2001-03-28
Publication date: 2002-11-27
Anticipated expiration: 2021-03-28
Also published as: GB0107719D0; GB2375732B

Abstract

The blown film is made by extruding a thermoplastic from a heated die 2 and passing the tube 18 through an air ring 16. The extruded material 18 and die 2 rotate relative to each other, preferably by rotating the die and feeds in a controlled way. The tube 18 is then passed through flattening means 26, nip rollers 28, 30 and laminating rollers 28, 30, 36. Preferably the coloured polyethylene is supplied from two hoppers 6, 10 so as to form patterns 20, 22. The laminate 32 is used for producing bags, preferably having gussets.

Description

METHOD AND APPARATUS FOR MANUFACTURING SHEET-FORM PLASTICS MATERIAL This invention concerns a method and apparatus for manufacturing sheet-form plastics material, which sheetform plastics material can be further processed to provide plastics bags, such as carrier bags.

It is known to provide bags, such as carrier bags, made from sheet-form material. However, one problem with such sheet-form material is that it is relatively weak and tends to tear.

It is also known to provide sheet-form plastics material which is highly decorated with patterns, which may be of various colours. Such decorated sheet-form plastics material is manufactured into plastics bags, such as carrier bags.

At the present time, the provision of the decoration patterns is achieved using printing inks that include volatile organic compounds, such as solvents. These are detrimental to the environment and possibly also to the health of workers. Extraction equipment has to be installed to deal with the volatile organic compounds, such equipment being expensive to install and operate.

It is an object of the present invention to overcome or minimise one or more of these problems.

According to one aspect of the present invention there is provided a method of manufacturing laminated sheet-form plastics material comprising: extruding thermoplastic plastics material through a heated die means ; issuing the extruded thermoplastic plastics material from the die means and through an air ring means to form an advancing tube of thermoplastic plastics material, whilst effecting relative rotation between the extruded material and the die means ; and passing the advancing tube through means for flattening the tube, to form two interfacing layers, and through means for laminating together the two interfacing layers.

According to another aspect of the present invention there is provided apparatus for manufacturing laminated sheet-form plastics material comprising: means for extruding thermoplastic plastics material through a heated die means ;

means for issuing the extruded thermoplastic plastics material from the die means and through an air ring means to form an advancing tube of thermoplastic plastics material; means for effecting relative rotation between the issuing extruded material and the die means; means for flattening the advancing tube to form two interfacing layers; and means for laminating together the two interfacing layers.

The thermoplastics material may be extruded from first and second sources. The thermoplastic plastics materials from the first and second sources may be of first and second colours respectively, whereby the advancing tube of the combination of the thermoplastic plastics materials comprises regions of the first and second colours and whereby the two laminated-together interfacing layers comprise regions of the first and second colours.

The two laminated-together interfacing layers may provide one or more regions of a third colour formed by overlapping one or more regions of the first colour in

one of the layers with one or more regions of the second colour in the other of the layers and/or vice-versa, the third colour resulting from optical mixing of the first and second colours in the overlapping one or more regions.

The advancing tube of the combination of the thermoplastic plastics materials may comprise geometric patterns of the first and second colours. Such geometric patterns may comprise alternating bands of the first and second colours. Such alternating bands of the first and second colours may be substantially parallel to one another and may be provided non-parallel to and nonorthogonal to a long axis of the advancing tube from the die means, such that the bands on the two interfacing layers formed by flattening the advancing tube overlyingly intersect one another to produce a pattern of rectangular, or diamond-like, shapes comprising the first, second and third colours.

Alternatively, the advancing tube of the combination of the thermoplastics materials may comprise abstract patterns.

The advancing tube may be arranged with a rate of advancement selectively variable in relation to a rate of

relative rotation between the issuing extruded combination of materials and the die means whereby the form of the shapes in the pattern is variable.

The die means and optionally the first and second sources may be arranged for rotation, preferably about an axis coincident with a long axis of the advancing tube.

The first and second sources may comprise hoppers containing the thermoplastic plastics materials and which may be connected to the die means by extruder feed means.

Frame means may be provided for collapsing the advancing tube and for guiding the resulting collapsed advancing tube to the means for flattening the tube to form the two interfacing layers.

The means for flattening the tube may comprise a pair of nip rollers between which the tube is passed.

The means for laminating together the two interfacing layers may comprise the pair of nip rollers between which the tube is passed at a temperature for lamination. At least one of the nip rollers may be heated.

Alternatively, the means for laminating together the two interfacing layers may comprise heated roller means provided downstream of the pair of nip rollers, the heated roller means receiving the flattened tube and heating it to a temperature for lamination.

The thermoplastic plastics material may comprise polyethylene and the temperature for lamination may comprise 120 to 140 degrees Celsius.

Means may additionally be provided for forming the laminated sheet-form material into at least one bag, such as at least one carrier bag.

Such means may be arranged for folding the laminated sheet-form material along a length thereof to form two overlapping portions thereof joined along an edge, and for providing spaced-apart strip-form seals between the overlapping portions, the seals extending substantially normal to the edge where the overlapping portions are joined.

The spaced-apart strip-form seals may be provided at a plurality of spaced-apart intervals along the length of the folded laminated sheet-form material and such that by severing of the folded laminated sheet-form material,

along and within regions occupied by the strip-form seals, a plurality of bags are isolated.

The strip-form seals may be provided by locally welding together the overlapping portions of the folded laminated sheet-form material.

Folding of the laminated sheet-form material may be arranged whereby one or more gussets are formed, such one or more gussets providing for expansion of, and/or providing reinforcement for, the one or more resulting bags in use. Alternatively, such one or more gussets may be formed internally of the sheet-form material as the sheet-form material is laminated. Such reinforcement may enhance securement of one or more carrying handles which may be provided on the one or more bags.

As a result of the invention, laminated sheet-form plastics material is provided, which may be further processed to form bags, such as carrier bags, and which is highly decorated with patterns of two or three colours without need for the use of coloured printing inks containing volatile organic materials, such as solvents.

For a better understanding of the present invention and to show more clearly how it may be carried into effect,

reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a schematic diagram illustrating the method and apparatus of the present invention; Figure 2A is a plan view of laminated sheet-form plastics material, manufactured according to the invention, for processing into one or more bags; Figure 2B is a plan view of bags produced from the material of Figure 2A; Figures 3A and 3B are front and side views respectively of one embodiment of a gusseted bag produced according to the invention; and Figures 4A and 4B are front and side views respectively of another embodiment of a gusseted bag produced according to the invention.

Referring to Figure 1, a heated die means 2 is supplied with a thermoplastic plastics material of a first colour, such as cyan blue, through an extruder feed means 4, from a hopper 6.

The heated die means 2 is also supplied with a thermoplastic plastics material of a second colour, such as magenta, through an extruder means 8, from a hopper 10.

The thermoplastic plastics materials of the first and second colours suitably comprise appropriately coloured polyethylene.

The die means 2, extruder feed means 4,8 and the hoppers 6,10 are mounted on a support 12 and arranged for rotation about an axis of rotation 14.

The die means 2 is arranged whereby an extruded combination of the thermoplastic plastics materials of the first and second colours issues therefrom, through an air ring 16, to form an advancing tube 18, of balloon form, of the combined materials. The advancing tube 18 suitably has a long axis 24 substantially coincident with the axis of rotation 14 of the die means 2.

Because the die means 2 is rotating, the advancing tube 18 comprises bands 20 of plastics material of the first colour alternating with bands 22 of plastics material of the second colour. The alternating bands 20,22 are substantially parallel to one another and extend non-

parallel to and non-orthogonal to the long axis 24 of the advancing tube 18. The angle of the bands 20,22 on the tube 18 is able to be varied by arranging for the advancing tube 18 to have a rate of advancement which is selectively variable in relation to a rate of relative rotation between the extruded combination of materials issuing from the die means 2, and the die means 2, and hence selectively variable in relation to the rate of rotation of the die means 2, since the tube 18 is nonrotating.

The advancing tube 18 is collapsed by means of a frame 26 and then flattened, by passing it between a pair of nip rollers 28,30, to form two interfacing layers. The two interfacing layers are arranged to be laminated together to form a laminated sheet-form plastics material 32 which issues over a roller 34.

Laminating together of the two interfacing layers requires the material of the layers to be at a temperature between 120 and 140 degrees Celsius. Such temperature may already be attained by the advancing tube 18 issuing from the die means 2, in which case passage through the nip rollers 28,30 will be sufficient to effect the lamination. If such a temperature has not been attained by the material of the advancing tube 18,

it can be arranged for one or both of the nip rollers 28, 30 to be heated in order to supply the necessary heat for lamination to be effected.

Alternatively, one or more heated rollers 36 could be provided downstream of the pair of nip rollers 28,30, to effect the necessary lamination.

The resulting laminated sheet-form plastics material 32 exhibits a pattern of rectangular, or diamond-like, shapes 38 as a result of overlying intersection of the 'coloured bands 20,22 on the two interfacing layers thereof formed by flattening the tube 18. The rectangular, or diamond-like, shapes 38 have three colours, such as producing a harlequin effect, such colours being the first colour cyan blue, the second colour magenta, and a third colour purple.

The third colour purple is provided where the bands of the first colour cyan blue on one interfacing layer overlyingly intersect bands of the second colour magenta on the other interfacing layer, and results from optical mixing of the first and second colours.

Whether the shapes 38 are rectangular or diamond-like depends on the selected rate of advancement of the

advancing tube 18 relative to the rate of rotation of the die means 2. If the rate of advancement of the tube 18 is substantially the same as the rate of rotation of the die means 2, the shapes 38 will be rectangular, particularly square. If the rate of advancement of the advancing tube 18 is different from the rate of rotation of the die means 2, diamond-like shapes 38 will be obtained.

By appropriate selection of material colours, configuration of the die means 2, extrusion rates for the material of each colour, and the rate of advancement of the tube 18 relative to the rate of rotation of the die means 2, a wide variety of geometric patterns of colour can be obtained by laminating together the interfacing layers formed by flattening the tube 18. Indeed, by providing variable differential feed from the hoppers 6, 10 it is possible to form abstract patterns.

The resulting laminated patterned sheet-form plastics material 32 is further processed as shown in Figures 2A and 2B to produce carrier bags therefrom. The sheet-form plastics material 32 is folded along the length thereof along the dotted line 40 to form two overlapping portions 42,44 thereof joined along an edge 46. The overlapping portions 42,44 are sealed together by welding along

strips 48 extending substantially normal to the edge 46 where the overlapping portions 42,44 are joined.

A plurality of carrier bags 50 are thereby formed, which are open along an edge 52 and are connected together along the sealing strips 48. Individual carrier bags 50 are isolated by cutting along the lines of the sealing strips 48 within the boundaries of the sealing strips 48, as shown by the dotted lines 54.

Relative rotation between the extruded tube 18 and the die means 2 and subsequent flattening of the tube gives rise to a stronger carrier bag 50 because the plastics material is stronger in one direction than the other. In the resulting carrier bag 50, the direction in which the plastics material is relatively strong on one face of the laminated material 32 is transverse to the direction in which the plastics material is relatively strong on the other face of the laminated material 32. The intersecting directions result in a stronger bag.

As shown in Figures 3A and 3B, folding of the laminated sheet-form material 32, to produce carrier bags 50, can be arranged whereby one or more gussets 56 is or are provided along the edge 46 which forms the bottom of the carrier bags 50. Such one or more gussets 56 provides or

provide for expansion of the resulting carrier bags 50 in use. One or more gussets 58 can also be provided in the vicinity of the open edge 52 of the carrier bags 50 to provide reinforcement such as for enhancing securement to the carrier bags of one or more carrying handles (not shown) which may be provided on the bags 50.

If desired, the resulting bags could have printed matter, such as a name, subsequently added, using water-based inks.

The carriers bags 50 shown in Figures 4A and 4B are similar to those shown in Figures 3A and 3B in that the laminated sheet-form material 32 is folded in a manner in which one or more gussets 56 is or are provided along the edge 46 which forms the bottom of the carrier bags 50, the gusset (s) providing for expansion of the resulting carrier bags 50 in use. In the case of Figures 4A and 4B gussets 60 are also provided in the vicinity of the open edge 52 of the carrier bags, between the interfacing layers of the laminated material 32. Such an arrangement is produced at the time the tube 18 is flattened and laminated with the result the gussets 60 are simpler to form and stronger than the more conventional gussets 56 because there is no need to attach the gusset to the side of the bag.

Claims

CLAIMS 1. A method of manufacturing laminated sheet-form plastics material comprising: extruding thermoplastic plastics material through a heated die means; issuing the extruded thermoplastic plastics material from the die means and through an air ring means to form an advancing tube of thermoplastic plastics material, whilst effecting relative rotation between the extruded material and the die means; and passing the advancing tube through means for flattening the tube, to form two interfacing layers, and through means for laminating together the two interfacing layers.
2. A method according to claim 1, wherein the thermoplastics material is extruded from first and second sources.
3. A method according to claim 2, wherein the thermoplastic plastics materials from the first and second sources are of first and second colours respectively, whereby the advancing tube of the

<Desc/Clms Page number 16>

combination of the thermoplastic plastics materials comprises regions of the first and second colours and whereby the two laminated-together interfacing layers comprise regions of the first and second colours.
4. A method according to claim 3, wherein the two laminated-together interfacing layers provide one or more regions of a third colour formed by overlapping one or more regions of the first colour in one of the layers with one or more regions of the second colour in the other of the layers and/or vice-versa, the third colour resulting from optical mixing of the first and second colours in the overlapping one or more regions.
5. A method according to any one of claims 2 to 5, wherein the advancing tube of the combination of the thermoplastic plastics materials comprises geometric patterns of the first and second colours.
6. A method according to claim 5, wherein the geometric patterns comprise alternating bands of the first and second colours.
7. A method according to claim 6, wherein the alternating bands of the first and second colours are substantially parallel to one another and are provided

<Desc/Clms Page number 17>

non-parallel to and non-orthogonal to a long axis of the advancing tube from the die means, such that the bands on the two interfacing layers formed by flattening the advancing tube overlyingly intersect one another to produce a pattern of shapes comprising the first, second and third colours.
8. A method according to any one of claims 2 to 5, wherein the advancing tube of the combination of the thermoplastics materials comprises abstract patterns.
9. A method according to any preceding claim, wherein the advancing tube is arranged with a rate of advancement selectively variable in relation to a rate of relative rotation between the issuing extruded combination of materials and the die means whereby the form of the shapes in the pattern is variable.
10. A method according to any preceding claim, wherein the die means is arranged for rotation.
11. A method according to claim 10, wherein the first and second sources are arranged for rotation.

<Desc/Clms Page number 18>
12. A method according to claim 10 or 11, wherein the die means is arranged for rotation about an axis coincident with a long axis of the advancing tube.
13. A method according to any preceding claim, wherein the first and second sources comprise hoppers containing the thermoplastic plastics materials.
14. A method according to claim 13, wherein the hoppers are connected to the die means by extruder feed means.
15. A method according to any preceding claim, wherein frame means is provided for collapsing the advancing tube and for guiding the resulting collapsed advancing tube to the means for flattening the tube to form the two interfacing layers.
16. A method according to any preceding claim, wherein the means for flattening the tube comprises a pair of nip rollers between which the tube is passed.
17. A method according to any preceding claim, wherein the means for laminating together the two interfacing layers comprises the pair of nip rollers between which the tube is passed at a temperature for lamination.

<Desc/Clms Page number 19>
18. A method according to claim 17, wherein at least one of the nip rollers is heated.
19. A method according to any one of claims 1 to 16, wherein the means for laminating together the two interfacing layers comprises heated roller means provided downstream of the pair of nip rollers, the heated roller means receiving the flattened tube and heating it to a temperature for lamination.
20. A method according to any preceding claim, wherein the thermoplastic plastics material comprises polyethylene.
21. A method according to any preceding claim, wherein the temperature for lamination is in the range from 120 to 140 degrees Celsius.
22. A method according to any preceding claim and including the step of forming the laminated sheet-form material into at least one bag, such as at least one carrier bag.
23. A method according to claim 22, wherein the at least one bag is formed by folding the laminated sheet-form material along a length thereof to form two overlapping

<Desc/Clms Page number 20>

portions thereof joined along an edge, and providing spaced-apart strip-form seals between the overlapping portions, the seals extending substantially normal to the edge where the overlapping portions are joined.
24. A method according to claim 23, wherein the spacedapart strip-form seals are provided at a plurality of spaced-apart intervals along the length of the folded laminated sheet-form material such that, by severing of the folded laminated sheet-form material along and within regions occupied by the strip-form seals, a plurality of bags are isolated.
25. A method according to claim 23 or 24, wherein the strip-form seals are provided by locally welding together the overlapping portions of the folded laminated sheetform material.
26. A method according to any one of claims 23 to 25, wherein folding of the laminated sheet-form material is arranged whereby one or more gussets are formed, such one or more gussets providing for expansion of, and/or providing reinforcement for, the one or more resulting bags in use.

<Desc/Clms Page number 21>
27. A method of manufacturing laminated sheet-form plastics material substantially as hereinbefore described with reference to the accompanying drawings.
28. Apparatus for manufacturing laminated sheet-form plastics material comprising: means for extruding thermoplastic plastics material through a heated die means; means for issuing the extruded thermoplastic plastics material from the die means and through an air ring means to form an advancing tube of thermoplastic plastics material; means for effecting relative rotation between the issuing extruded material and the die means; means for flattening the advancing tube to form two interfacing layers; and means for laminating together the two interfacing layers.
29. Apparatus as claimed in claim 28 and including first and second sources from which the thermoplastics material is extruded.

<Desc/Clms Page number 22>
30. Apparatus as claimed in claim 28 or 29 and including means for selectively varying the rate of advancement of tube in relation to a rate of relative rotation between the issuing extruded combination of materials and the die means whereby the form of the shapes in the pattern is variable.
31. Apparatus as claimed in claim 28,29 or 30, wherein the die means is arranged for rotation.
32. Apparatus as claimed in claim 31, wherein the first and second sources are arranged for rotation.
33. Apparatus as claimed in claim 31 or 32, wherein the die means is arranged for rotation about an axis coincident with a long axis of the advancing tube.
34. Apparatus as claimed in any one of claims 28 to 33, wherein the first and second sources comprise hoppers containing the thermoplastic plastics materials.
35. Apparatus as claimed in claim 34, wherein the hoppers are connected to the die means by extruder feed means.

<Desc/Clms Page number 23>
36. Apparatus as claimed in any one of claims 28 to 35, wherein frame means is provided for collapsing the advancing tube and for guiding the resulting collapsed advancing tube to the means for flattening the tube to form the two interfacing layers.
37. Apparatus as claimed in any one of claims 28 to 36, wherein the means for flattening the tube comprises a pair of nip rollers between which the tube is passed.
38. Apparatus as claimed in any one of claims 28 to 37, wherein the means for laminating together the two interfacing layers comprises the pair of nip rollers between which the tube is passed at a temperature for lamination.
39. Apparatus as claimed in claim 38, wherein at least one of the nip rollers is heated.
40. Apparatus as claimed in any one of claims 28 to 37, wherein the means for laminating together the two interfacing layers comprises heated roller means provided downstream of the pair of nip rollers, the heated roller means receiving the flattened tube and heating it to a temperature for lamination.

<Desc/Clms Page number 24>
41. Apparatus as claimed in any one of claims 28 to 40 and including means for forming the laminated sheet-form material into at least one bag, such as at least one carrier bag.
42. Apparatus as claimed in claim 41, wherein forming means is arranged for folding the laminated sheet-form material along a length thereof to form two overlapping portions thereof joined along an edge, and providing spaced-apart strip-form seals between the overlapping portions, the seals extending substantially normal to the edge where the overlapping portions are joined.
43. Apparatus as claimed in claim 42, wherein the forming means is adapted to provide spaced-apart stripform seals at a plurality of spaced-apart intervals along the length of the folded laminated sheet-form material such that, by severing of the folded laminated sheet-form material along and within regions occupied by the stripform seals, a plurality of bags are isolated.
44. Apparatus as claimed in claim 42 or 43 and including means for locally welding together the overlapping portions of the folded laminated sheet-form material to form the strip-form seals.

<Desc/Clms Page number 25>
45. Apparatus as claimed in any one of claims 42 to 44, wherein the folding means is arranged whereby one or more gussets are formed, such one or more gussets providing for expansion of, and/or providing reinforcement for, the one or more resulting bags in use.
46. Apparatus for manufacturing laminated sheet-form plastics material substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.