GB2516431A

GB2516431A - Cushioning material

Info

Publication number: GB2516431A
Application number: GB1312959.8A
Authority: GB
Inventors: Toshihiro Ota
Original assignee: SANSETSU UK Ltd
Current assignee: SANSETSU UK Ltd
Priority date: 2013-07-19
Filing date: 2013-07-19
Publication date: 2015-01-28
Anticipated expiration: 2033-07-19
Also published as: GB201312959D0; GB2516431B

Abstract

A cushioning material 1 comprises sheets 2a, 2b laminated together to form an array of discreet sealed pockets 3 separated from one another by connecting portions 4. The sheets 2a, 2b are formed from a plastics material that includes ionomer or ionised metal particles. The preferred sheets comprise 8-30 (15) wt% zinc or sodium based ionomer derived from ethylene methacrylic acid copolymer, blended with another polymer, for example polyethylene, and an anti-static additive. The cushioning preferably is produced by, extruding 6a, 6b the films, thermoforming or vacuum forming one film 2a and then laminating onto another film 2b, using dies or rollers 7a, 7b.

Description

CUSHIONING MATERIAL

This invention relates generally to cushioning materials, particularly those that incorporate a plurality of sealed pockets, together with methods of manufacturing such materials.

More specifically, although not exclusively, the invention relates to laminated cushioning materials that are adaptable for use in a multitude of different cushioning and shock absorbing applications, such as for the protective packaging of fragile items prior to transport and/or storage.

Laminated cushioning material that includes a plurality of sealed pockets is well known for providing protective packaging for items to be stored or transported. Since its inception, it has become one of the most common packing materials.

US3142599 describes a method of manufacturing such a cushioning material by thermoforming a first plastic film using a female moulding roller having an array of discreet depressions on its outer circumferential surface. The exposed surface of the first plastic film is heated to a temperature in the vicinity of its melting point, as is an opposing surface of a second plastic film and the two opposing surfaces are brought together and fused to form a laminated cushioning material with discreet sealed pockets.

Conventional plastic films are extruded using an extrusion die, which typically incorporates a lip at or adjacent its outlet over which the molten plastic is drawn to produce the thin film. Despite regular maintenance of the extrusion die, the continuous nature of the process generally results in deposits and/or other imperfections resulting, for example, from wear of the edge of the lip. These deposits and imperfections of the lip edge are generally microscopic, but form localised thinning of the film along its length, which results in a natural tendency for the resulting film to tear easily in its longitudinal direction, while being relatively resistant to tearing in the transverse direction.

It is also known to provide a cushioning material formed of a laminated sheet that has a reinforcing layer, such as a polyamide, between two layers of polyethylene to improve puncture resistance. This approach also requires adhesive layers between the nylon reinforcing layer and each of the two films, thereby resulting in a five-layer, laminated sheet. This co-extrusion arrangement adds significant cost and results in a material with less transparency and that is 15% thicker than the arrangement described above.

It is a first non-exclusive object of the invention to provide a laminated cushioning material that at least mitigates the issues associated with known cushioning materials and their processes of manufacture. It is a further non-exclusive object of the invention to provide a laminated cushioning material and associated method of manufacture that facilitates the adaptability of the material.

According to one aspect of the invention, there is provided a cushioning material comprising a sheet having a plurality of discreet sealed pockets separated from one another by connecting portions, which may be substantially planar, the sheet comprising a io plastics material including an ionomer, e.g. a metal ionomer, or ionized metal particles.

The applicant has discovered that the inclusion of a metal ionomer or ionized metal particles produces a cushioning material that can be segmented or torn more easily in the transverse direction, while providing excellent transparency and good puncture is resistance. This enables a user to adapt the size of the cushioning material manually, more easily than was possible with known products and without the need for cutting tools.

As used herein, the term ionomer is intended to mean a polymer that comprises repeat units of both electrically neutral repeating units and a fraction of ionized units normally, but not exclusively, 15 % or less.

The plastics material may comprise a mixture of a first polymer, e.g. a thermoplastic polymer, such as polyethylene (which may comprise high or low density polyethylene, preferably low density polyethylene), and the ionomer and optionally, one or more additives, such as an anti-static additive. Preferably, the mixture comprises between 1% and 50% by weight ionomer, more preferably between 5% and 40% by weight ionomer and most preferably 8% and 30% by weight ionomer, for example between 10% and 20% by weight ionomer, e.g. roughly 15% by weight ionomer. However, the applicant has found that as the ionomer content is increased to more than 30% by weight the properties of the material begin to have an adverse impact on mouldability, with the material becoming sticky and issues arising with pocket formation.

Additionally or alternatively, the ionomer may comprise a random copolymer, for example a poly(ethylene-co-methacrylic acid), which may include approximately 5.4 mol % methacrylic acid (MA) and/or which has been neutralized with a cation or alkali metals or zinc hydroxides. The applicants have found that zinc ionomers provide particularly advantageous properties. An exemplary zinc ionomer is sold by DuPontTM under the trade name Surlyn® 1706.

Alternatively, the ionomer may be one that is produced by the neutralisation of an s ethylene methacrylic acid copolymer, such as that which is sold by INEOSTM under product code M21E760.

The cushioning material, e.g. the sheet, may comprise a multi-layer sheet, for example a pair of sheets laminated together, one or both of which may be formed of or comprise a plastics material and/or ionized metal particles, for example interspersed in or embedded within the plastics material. Preferably the cushioning material comprises one or more e.g. two or more, mono-extended sheets or films, which may be connected or laminated together.

is Preferably, a first of the plastic sheets comprises an array or plurality of dimples on a first surface thereof, which may be a major surface thereof. The first sheet may further comprise an array or plurality of protrusions on a second surface thereof, which may be a further major surface thereof, for example wherein each protrusion corresponds to one of said dimples.

More preferably, a second of the plastics sheets is substantially planar and/or may be secured or adhered or bonded or fused to the first sheet, for example to the first surface of the first sheet, e.g. such that the discreet sealed pockets are defined by the dimples of the first sheet and the opposed surface of the second sheet. The secured or adhered or bonded or fused regions may correspond to the substantially planar portions of the cushioning material.

According to a second aspect of the invention, there is provided a method of manufacturing a cushioning material, for example a cushioning material as described above, the method comprising providing a sheet, which may be a multi-layer sheet, formed at least in part from a plastics material that includes a metal ionomer or ionized metal particles and forming a plurality of discreet sealed pockets in the sheet such that the pockets are separated from one another by connecting portions, which may be substantially planar.

Preferably, the method comprises providing a first sheet of plastics material, which may include a metal ionomer or ionized metal particles. The method may further comprise forming an array or plurality of dimples in or on the first sheet, for example by heating and/or forming the first sheet and/or thermoforming or vacuum forming the sheet, e.g. on or over or across a forming or female die or roller to form an array or plurality of dimples, e.g. on a first surface thereof, which may be a major surface thereof, and/or a corresponding array or plurality of protrusions on a second surface thereof, which may be a further major surface thereof.

More preferably, the method comprises providing a second sheet of plastics material, which may include a metal ionomer or ionized metal particles. The method may further comprise securing or adhering or bonding or fusing the second sheet to the first sheet, for example to the first surface of the first sheet, e.g. such that the discreet sealed pockets are defined by the dimples of the first sheet and the opposed surface of the second sheet.

The step of securing or adhering or bonding or fusing the second sheet to the first sheet may comprise contacting the first surface of the first sheet to a facing surface of the second sheet when the temperature of at least one, preferably both, of the surfaces is at or approaching the melting temperature of the plastics material.

Additionally or alternatively, the step of securing or adhering or bonding or fusing the second sheet to the first sheet may comprise compressing the first sheet against the second sheet, for example using a further or second die or roller, e.g. wherein the first and second sheet are laminated together between the forming or female die or roller and the second die or roller.

The method may further comprise the step of making the first or second sheet, for example by melting one or more elements of the plastics material, e.g. a first polymer, which may be a thermoplastic polymer such as polyethylene, and/or the ionomer.

The method may further comprise mixing between 1% and 50% by weight ionomer, more preferably between 5% and 40% by weight lonomer and most preferably 8% and 30% by weight ionomer, for example between 10% and 20% by weight ionomer, e.g. roughly 15% by weightionomer with the first polymer.

The method may further comprise extruding the plastics material, for example through an extrusion die and/or through and/or over an extrusion die lip, e.g. to form the first and/or the second sheet of plastics material. In some embodiments, the extruded first and/or second sheets of plastics material are fed to the forming or female die or roller and/or the s second die or roller directly, for example while still at a heated temperature, e.g. wherein the step of securing or adhering or bonding or fusing the second sheet to the first sheet involves drawing the first and/or second sheet from the or a respective extrusion die.

Further aspects of the invention provide an apparatus specifically adapted to perform the aforementioned method and/or to produce the aforementioned cushioning material.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: is Figure 1 is a section view of a cushioning material according to one embodiment of the invention; Figure 2 is a schematic diagram illustrating the manufacturing process for making the cushioning material of Figure 1; Figure 3 is a front view of part of one of the extrusion dies from direction A in Figure 2; and Figure 4 is a plan view of part of the forming roller used in the manufacturing process illustrated in Figure 2.

Referring now to Figure 1, there is shown a cushioning material 1 including first and second sheets 2a, 2b laminated together and forming a plurality of discreet sealed pockets 3 therebetween. The pockets 3 are separated from one another by connecting portions 4.

The first sheet 2a includes an array of dimples 20 on a first major surface thereof with a corresponding array of protrusions on its other major surface. The second sheet 2b is substantially planar and is bonded or fused to the first surface of the first sheet 2a such that the discreet sealed pockets 3 are defined by the dimples 20 of the first sheet 2a and the opposed surface of the second sheet 2b.

Each sheet 2a, 2b is formed of a plastics material mixture, which is a mixture of a first polymer, polyethylene in this embodiment, and a metal ionomer, a zinc ionomer in this embodiment sold under the trade name Surlyn® 1706. The mixture includes roughly 85% by weight polyethylene and 15% by weight Surlyn® 1706.

Surlyn® 1706 is a random copolymer consisting of a poly(ethylene-co-methacrylic acid), contains 5.4 mol % methacrylic acid (MA) and has been neutralized with alkali metals or zinc hydroxides.

This mixture results in a cushioning material that can be segmented or torn easily in the transverse direction, while providing excellent transparency and good puncture resistance. This enables a user to adapt the size of the cushioning material manually, without the need for cutting tools.

is Turning now to Figures 2 to 4, there is illustrated an apparatus 10 for manufacturing the cushioning material 1. The apparatus 10 includes an extruder 5, first and second extrusion dies 6a, 6b, a forming roller 7a and second roller 7b. The extruder 5 is of a construction that is known in the art. Each of the first and second extrusion dies 6a, 6b is also of a construction that is known in the art and includes an extrusion lip 60a, 60b over which molten plastics material is drawn in order to form the film 2a, 2b in a known manner. The forming roller 7a has an external circumferential surface 70a with an array of dimples 71a, while the second roller 7b has a smooth external circumferential surface.

The extruder 5, is positioned to feed molten material through a respective one of the first and second extrusion dies 6a, 6b, over the extrusion lip 60a, 60b and onto a respective one of the forming and second rollers 7a, 7b. The sheets 2a, 2b cool as they are drawn through the apparatus by the rollers 7a, 7b and by subsequent rollers (not shown), which cool the finished material 1 and gather it in rolls (not shown) it for storage.

The process involves the following general steps: a) mixing roughly 85% by weight polyethylene with roughly 15% by weight Surlyn® 1706 (not shown); b) extruding the mixture through the extruder 5, and through the first and second extrusion dies 6a, 6b; c) feeding the semi-molten first and second sheets 2a, 2b onto the forming roller 7a, which may be cooled using water cooling channels, and second roller 7b respectively; d) forming an array of dimples 20 in the first sheet 2a by vacuum forming the first s sheet 2a on the external circumferential surface 70a of the forming roller 7a and into an array of dimples 71a thereon; and e) bonding or fusing the connecting portions of the first and second sheets 2a, 2b by compressing them together between the forming roller 7a and the second roller 7b while the temperature of the facing surfaces of each sheet 2a, 2b is near the melting temperature of the sheets, thereby creating discreet sealed pockets 3 defined by the dimples 20 of the first sheet 2a and the opposed surface of the second sheet 2b.

It will be appreciated by those skilled in the art that several variations are envisaged is without departing from the scope of the invention. For example, the metal ionomer need not comprise zinc or sodium and need not be in the concentrations described. An acceptable ionomer has been found to be a sodium ionomer and other metals have also been found to perform satisfactorily.

The manufacturing process may include fewer or more steps and may be performed using any suitable apparatus. For example, the films 2a, 2b, may be formed using separate extruders 5 and/or the metal ionomers or ionized metal particles may be omitted from one of the films. The pockets 3 need not be formed by the above method and the material need not comprise a laminated structure, for example the material may be formed from a molten foam material.

It will also be appreciated by those skilled in the art that the invention may comprise any novel and/or inventive combination of any one or more of the features disclosed herein.

Claims

CLAIMS1. A cushioning material comprising a sheet having a plurality of discreet sealed pockets separated from one another by connecting portions, the sheet comprising a plastics material including an ionomer or a metal ionomer or ionized metal particles.
2. A cushioning material according to claim 1, wherein the sheet comprises a mixture of a polymer and the metal ionomer.
3. A cushioning material according to claim 1 or claim 2, wherein the mixture comprises between 5% and 40% by weight metal ionomer.
4. A cushioning material according to any preceding claim, wherein the mixture comprises between 8% and 30% by weight metal ionomer.
5. A cushioning material according to any preceding claim, wherein the metal comprises zinc.
6. A cushioning material according to any preceding claim, wherein the metal ionomer comprises a random copolymer including a poly(ethylene-co-methacrylic acid) and has been neutralized with a cation or alkali metals or zinc hydroxides.
7. A cushioning material according to any preceding claim, wherein the sheet comprises a multi-layer sheet formed of first and second laminated sheets, one or both of which being formed of or comprising the plastics material including a metal ionomer or ionized metal particles.
8. A cushioning material according to claim 7, wherein the first plastic sheet comprises an array of dimples on a first major surface thereof.
9. A cushioning material according to claim 8, wherein the second sheet is secured to the first surface of the first sheet such that the discreet sealed pockets are defined by the dimples of the first sheet and an opposed surface of the second sheet.
10. A method of manufacturing a cushioning material, the method comprising providing a sheet formed at least in part from a plastics material that includes a metal ionomer or ionized metal particles and forming a plurality of discreet sealed pockets in the sheet such that the pockets are separated from one another by connecting portions.
11. A method according to claim 10, wherein the forming step comprises forming an array of dimples on a first major surface thereof and securing a second sheet of plastics material to the first sheet such that the discreet sealed pockets are defined s by the dimples of the first sheet and an opposed surface of the second sheet.
12. A method according to claim 11, wherein the forming step comprises thermoforming or vacuum forming the first sheet of plastics material on a forming die or roller.
13. A method according to claim 11 or claim 12, wherein the second sheet is secured to the first sheet by contacting the first surface of the first sheet to a facing surface of the second sheet when the temperature of at least one of the surfaces is at or approaching the melting temperature of the plastics material.
14. A method according to any one of claims 11 to 13, wherein the second sheet is secured to the first sheet by laminating the first and second sheet together between the forming die or roller and a second die or roller.
15. A method according to any one of claims 11 to 13 further comprising forming at least one of the first and second sheets by extruding the plastics material that includes a metal ionomer or ionized metal particles.
16. A method according to claim 15 further comprising mixing a polymer with a metal ionomer to provide the plastics material that includes a metal ionomer or ionized metal particles.
17. A method according to claim 16, wherein the mixing step comprises mixing between 5% and 40% by weight metal ionomer with the polymer.
18. A method according to claim 16, wherein the mixing step comprises mixing between 8% and 30% by weight metal ionomer with the polymer.
19. A method according to any one of claims 10 to 18, wherein the metal comprises zinc.
20. A method according to any one of claims 10 to 18, wherein the metal comprises sodium.
21. A method according to any one of claims 10 to 18, wherein the metal ionomer comprises a random copolymer including a poly(ethylene-co-methacrylic acid) and has been neutralized with a cation or alkali metals or zinc hydroxides.