GB2218377A - Method of manufacture of insole material - Google Patents

Abstract

The invention relates to a method for the manufacture of laminated insole material, in which method two layers of non- woven insole material are laminated together with a layer of adhesive between the two layers. The lamination is carried out in an apparatus (10) in which the insole material (52) is forwarded by engagement between a pair of endless belts (16, 18) and passed through a passage between a first pair of platens (20, 22) provided with heating means and a second pair of platens (32, 34) provided with cooling means, said first pair of platens (20, 22) being held rigidly with a separation at the parallel exit edges equal to or somewhat less than the thickness desired for the total thickness of the material plus the thickness of the endless belts and said second pair of platens being held rigidly parallel with a separation substantially equal to the desired total thickness. The insole material manufactured according to the invention is particularly suitable for use in the manufacture of shoes where a liquid polyurethane material is injection moulded to form a shoe sole on an upper carried by an appropriate foot form. <IMAGE>

Description

METHOD OF MANUFACTURE OF INSOLE MATERIAL This invention relates to a method for the manufacture of shoe insoles, and to the shoe insoles manufactured by this method. The shoe insoles manufactured by the method according to the invention are particularly suitable for use in the known method of manufacture of shoes, which involves injection moulding a liquid polyurethane material to form, on curing, a shoe sole on an upper carried by an appropriate footform.In carrying out this method the insole material used in shoe manufacture must be sufficiently impervious to the liquid urethane composition to prevent leakage of the urethane material to the inside of the shoe, in addition, the insole needs to be flexible but high in tensile strength both along and across the insole, and low in extensibility both along and across the insole, i.e., having good dimensional stability and, furthermore, as the shoe construction may involve stitching the insole to the upper, the insole must be readily stitched.

The term "shoe" where used herein is intended to denote outer footwear generally whether ready-to-wear or in the course of manufacture, as the context permits.

A number of methods of manufacture of shoe insoles have been proposed in order to attempt to overcome the problem of polyurethane penetration.

In the conventional wet-laid cellulose type of insole, there is no polyurethane penetration. However, because the insole material itself has poor laminar strength, and there is no polyurethane penetration and hence no mechanical bonding, the sole produced by direct moulding of polyurethane on the insole also has poor laminar strength.

There is good adhesion between the polyurethane sole and the insole, but not between the individual layers of the insole.

This means that there is a tendency for the polyurethane sole to peel off with the top layer of the insole.

An alternative approach to the problem has been to coat one surface of a non-woven insole material with a coating which is resistant to polyurethane penetration, and then to mould the polyurethane sole onto either this coated surface or the uncoated surface. Where the polyurethane is moulded onto the coated surface, there is the disadvantage that it is difficult to obtain satisfactory adhesion between the polyurethane and the coating and, as with the cellulose wet-laid materials, there is no mechanical strengthening of the insole material by the polyurethane.Where the polyurethane is moulded onto the uncoated surface of the insole material, there is of course excellent bonding between the insole material and the polyurethane, but the surface of the insole which will contact the foot of the wearer in the finished shoe, will be of very low absorbency and not sufficiently comfortable in wear.

A further alternative approach has been to allow the polyurethane to penetrate into the insole material and through to the upper surface, and then to cover the insole with a socking layer in the completed shoe. This method has the disadvantage that it involves extra cost, since the inner sock has to be inserted by hand during manufacture of the shoe, as an additional stage, and the resultant shoe will have reduced absorbency and will be less comfortable in wear.

It has also been proposed, in GB Patent No. 2 132 554, to provide a shoe insole comprising two layers of non-woven fibre fleece adhered to an impermeable plastics film. The plastics film is said to be suitably a film of polypropylene, polyethylene, ethylene-acrylic acid copolymer or polyester, and where necessary, it may be reinforced by a reinforcing fabric, preferably a woven fabric, for example a woven polypropylene tape scrim or a woven net of open weave.

For certain applications, these insoles have the disadvantage that the flexibility of the insole is reduced compared to the flexibility of similar materials without the plastics film.

An object of the present invention is to provide a method for the manufacture of shoe insoles, and shoe insoles manufactured by this method, in which the above disadvantages are reduced or substantially obviated.

The present invention provides a method for the manufacture of a laminated. insole material in which methdd two layers of non-woven insole material are laminated together, with a layer of adhesive between the two layers, characterised in that the lamination is carried out in an apparatus in which the insole material is forwarded by engagement between a pair of endless belts and passed through a passage between a first pair of platens provided with heating means and a second pair of platens provided with cooling means, said first pair of platens being held rigidly with a separation at the parallel exit edges equal to or somewhat less than the thickness desired for the total thickness of the material plus the thickness of the endless belts and said second pair of platens being held rigidly parallel with a separation substantially equal to the desired total thickness.

An apparatus suitable for use in this method of manufacture of a laminated insole material, and its use in the gauge control of a heat-softenable material is described and claimed in European Patent Application No. 204 482, and will be referred to herein as the Double Band Press.

The non-woven insole materials suitable for use in the method according to the invention include non-woven fibre fleeces,-which may be impregnated in known manner to improve their stiffness and other characteristics.

One or both of the layers of insole material to be used in the method according to the invention may comprise a split, prepared by splitting a non-woven insole material into two layers of substantially equal gauge.

Split and non-split insole materials may be used in a variety of combinations in the method according to the invention, depending on the requirements for the laminated insole material to be produced.

In a first advantageous combination, two splits may be relaminated together with the split surfaces adjacent to each other, with the layer of adhesive between the two surfaces. This arrangement is particularly appropriate when using a -coating adhesive where it has the advantage that the surface to be coated is a particularly smooth and uniform surface, which makes it possible to achieve an even and regular coating of adhesive at a relatively low coating weight.

In an alternative combination, the layer which is to be adjacent to the foot of the wearer may be reversed, so that the surface exposed is the split surface, and this layer may then be laminated to a second layer. This second layer may comprise a split or a non-split layer. If the second layer is a non-split layer, then it is possible to produce insole materials of a thicker gauge than is possible without lamination, which materials have an attractive surface on the part of the sole inside the shoe. It is also possible in this combination, to reduce the cost of the insole materials by using as the lower layer a lower quality and cheaper insole material which might not be acceptable for use as the inside layer adjacent to the foot of the wearer.

Depending on the requirements of the intended end,use, the layer to be adjacent to the foot of the wearer in the finished insole material may be chosen so that it is more absorbent, has a particular colour, is smoother or softer or has a more pleasing appearance. Again depending on the requirements of the intended end use, the material for the layer on which the sole is to be moulded may be selected for lower cost, in which case it will generally be of a coarser grade, strength, stiffness or resilience.

The two layers are laminated together with a layer of adhesive, suitably a PVA (polyvinylacetate) based adhesive, a hot melt adhesive, for example an EVA (ethylene vinyl acetate) based adhesive or a dry film adhesive, for example an EAA (ethylene acryl acetate) adhesive.

The adhesive is suitably coated at a coating weight of above 100 grams per square metre, preferably between 100 to 150 grams per square metre.

The invention will now be further described with reference to the accompanying drawing, which is a diagrammatic side view of an example of an apparatus suitable for use in the method according to the invention.

The illustrative apparatus 10 comprises a heated zone 12 and a cooling zone 14 and a pair of endle-ss belts 16,18.

The heated zone 12 comprises two adjustable opposed heating platens 20,22, each having a heating surface 24,26 respectively. The passage between the heating surfaces 24,26 is arranged to taper from inlet 28 of the heated zone to outlet 30 thereof. The separation between the heating surfaces at inlet 28 is typically 1.0 mm greater than outlet 30. The cooling zone comprises two adjustable opposed cooling platens 32,34 each having a cooling surface 36,38 respectively. The cooling surfaces 36,38 are arranged to be parallel. An air gap 25 is located between the heated zone 12 and the cooling zone 14. The endless belts 16,18 comprise woven fibre belts, which are made of glass fibre and/or KEVLAR (RTM) with a PTFE coating. Belt 16 is passed around two guiding rollers 40,41 and a drive roller 42 and is arranged to bear against a tensioning roller 44.The path of the belt 16 is arranged so that the inside surface of the belt bears against heating surface 24 of heating platen 20 and against cooling surface 36 of cooling platen 32. Similarly, 18 passes around guiding rollers 46,47 and drive roller 48 and bears against tensioning roller 50. The path of belt 18 is arranged so that the inside surface of the belt bears against heating surface 26 and against cooling surface 38. Belts 16,18 because of their thickness, have a low heat capacity so that heat from heated zone 12 is quickly transferred to material inserted between the belts 16,18 and rapidly removed from the material of the cooling zone.

In the method"according to the invention, the material 52 comprising two layers of non-woven insole material with an adhesive layer between, which is to be laminated, is interposed between the two belts 16,18 and carried through the heated zone 12 and the cooling zone 14 of the apparatus.

Whilst in the heated zone heat is transferred through belts 16,18 from the heating platens 20,22 to the layers of material 52 to bring the layers to a heat-softened condition throughout their thickness. As it passes through the heated zone its thickness is reduced by the tapering heating surfaces 24,26 until it reaches the final desired thickness at outlet 30. It is maintained at this thickness whilst being passed between cooling platens 32,34 of the cooling zone 14. Heat is removed from the sheet whilst it is in the cooling section so that the temperature of the laminate 54 is reduced to a temperature below its softening point.

In the method according to the invention, the Double Band Press may be operated with the separation at the parallel exit edges of the first set of platens equal to, or less than, the separation at the parallel exit edge of the second set of platens. Where the material being laminated is relatively thin, or has a high resilience, it is preferred to provide a step between the separations of the two sets of platens. The provision of such a step reduces the load on the motor driving the endless belts of the Double Band Press. Typically, for a laminated insole material of 2.00 mm or 2.25 mm gauge, the separation of the first set of platens should be 0.07 mm less than that of the second set of platens.Where the material to be laminated is resilient, there tends to be some recovery between leaving the first set of platens and entering between the second set of platens, and this increases the drag in the cooling section.

The second set of platens is suitably cooled with water, which may be at the temperature of the supply, which may vary with the outside temperature, or may be chilled, typically to 50C.

The invention will now be described with reference to the following specific Examples. In each of the Examples, an allowance is made for the thickness of the endless belts in specifying the separation of the exit edges of the platens and the measurement of the thickness of the laminated material is an average value for the thickness, measured at a number of points across the sheet.

Example 1 Standard Texon T90 2.25 mm insole boards (non-woven polyester needled felt, impregnated with synthetic rubher latex and fillers, having a thickness in the range 2.25 mm 2.5 mm) were split into two layers of equal thickness and turned to expose the split surfaces. A dry adhesive film 200 gauge DAF 709 (EAA type) was positioned between the splits, giving a total thickness before lamination of 2.67 mm. The material was laminated in the Double Band Press, with the first pair of platens set at 1700C to heat the material to a temperature of approximately 1500C, and the second pair of platens cooled with water at 1500 to cool the material to a temperature below 700C. The separation at the exit edges of each of the pairs of platens was 2.52 mm and the laminated material had an average thickness of 2.45 mm.

The laminated insole material showed excellent resistance to polyurethane penetration, the polyurethane penetrating as far as the adhesive layer and thus ensuring good bonding between the polyurethane and the insole material.

Example 2 Bales of 2.25 mm Texon T90 insole material were split in half and one split was coated, on the original surface, using a blade coating system, at a minimum coating weight of 100 gsm of PVA adhesive, and cut in sheets. The coated split sheets were then rejoined to the uncoated splits, which had also been cut into sheets, in the Double Band Press.

The first pair of platens was set to 1950C to heat the laminate to a temperature of approximately 1700C and the second pair of platens was cooled with water at 150C to cool the laminate to a temperature of below 700C. The separation of the first pair of platens was 2.25 mm and of the second pair of platens was 2.32 mm.

The laminated insole material which was produced had an average thickness of 2.28 mm and showed excellent resistance to polyurethane penetration, the polyurethane penetrating as far as the adhesive layer and thus ensuring good bonding between the polyurethane and the insole layer.

Claims (7)

CLAIMS:

1. A method for the manufacture of laminated insole material in which method two layers of non-woven insole material are laminated together, with a layer of adhesive between the two layers, characterised in that the lamination is carried out in an apparatus in which the insole material is forward by engagement between a pair of endless belts and passed through a passage between a first pair of platens provided with heating means and a second pair of platens provided with cooling means, said first pair of platens being held rigidly with a separation at the parallel exit edges equal to or somewhat less than the thickness desired for the total thickness of the material plus the thickness of the endless belts and said second pair of platens being held rigidly parallel with a separation substantially equal to the desired total thickness.

2. A method as claimed in claim 1, characterised in that one or both of the layers of insole material comprises a split, prepared by splitting a non-woven insole material into two layers of substantially equal thickness.

3. A method as -claimed in claim 1 and claim 2, characterised in that the adhesive is a polyvinylacetate adhesive, a hot melt adhesive or a dry film adhesive.

4. A method as claimed in any of claims 1 to 3, characterised in that the adhesive is coated at a coating -weight above 100 grams per square metre.

5. A method as claimed in claim 4, characterised in that the adhesive is coated at a coating weight of from 100 to 150 grams per square metre.

6. A method as claimed in any of claims 1 to 5, characterised in that, in the apparatus in which the material is laminated, the separation at the parallel exit edge of the first pair of platens is less than the separation at the parallel exit edge of the second pair of platens.

7. A laminated insole material when manufactured by a method as claimed in any of claims 1 to 6.