GB2361198A

GB2361198A - Producing leather covered articles

Info

Publication number: GB2361198A
Application number: GB0009038A
Authority: GB
Inventors: Andrew Bennion; John Killingley
Original assignee: Magna Interior Systems Ltd
Current assignee: Grupo Antolin UK Ltd
Priority date: 2000-04-12
Filing date: 2000-04-12
Publication date: 2001-10-17
Also published as: GB0009038D0

Abstract

A leather covered article, is produced by providing a leather cover with a polymeric backing, wherein the polymer is applied directly to the leather cover in a liquid or molten state and allowed to harden to from the polymeric backing. The polymeric backing can cover seams (10) between parts of the leather cover. The polymer may be provided in powder form (4) and then melted e.g. with a heated press (2, 8) before or after bringing it into contact with a leather cover layer (6). Alternatively the polymer may be sprayed as a liquid onto the leather cover. A foam may be applied to the polymeric backing.

Description

2361198 1 72551.609 Method of producing leather covered article The

invention relates to a method of producing a leather covered article.

It is known from US-A-4 758 294 to produce a foambacked article having a covering formed of several parts sewn together along joining seams. A sheet of sewn covering material is held to a desired shape on a vacuum mould and a previously prepared polyurethane film with a hot-melt adhesive coating is heated and placed on the covering material. It is sucked into position by vacuum applied by the mould and is adhered to the covering by the hot-melt adhesive coating. The film is airtight and thus seals the back of the joining seams. This sealing prevents leakage of foam in a subsequent foam injection step and is an improvement over the adhesive affixing of a strip-shaped airtight film along each seam.

Another process intended to avoid the strip sealing of seams in a covering material is known from DE-A-195 33 367. In this known method, the use of a vacuum process for applying a film of polyurethane to a leather covering material is avoided. Instead, adhesive is applied to the leather and the polyurethane film is laminated to the leather in a heated moulding tool.

The present invention is concerned with the problem of preventing leather shrinkage. Neither of the above documents is concerned with this problem. Leather is a material which tends to shrink when exposed to heat over a period of time. When it is desired to use leather to cover a vehicle interior panel, such as an instrument panel, the shrinkage can apply large forces to whatever substrate is under it. This can lead to deformation of the panel, which is unsatisfactory. Previous attempts to address the shrinkage problem have been based on preshrinking the leather to reduce later shrinking.

- 2 However, although this reduces the later shrinkage the reduction has not been sufficient to lower the amount of force applied to a substrate to an acceptable level.

It is therefore an object of the invention to reduce the shrinkage of leather used to cover an article.

According to the invention, there is provided a method of producing a leather covered article, comprising providing a leather cover with a polymeric backing, wherein the polymer is applied directly to the leather cover in a liquid or molten state and allowed to harden to from the polymeric backing.

By applying the polymer directly to the leather case in a liquid or molten state it bonds intimately with the leather. It has been found that this has a significant effect on preventing shrinkage of the leather under heat ageing tests. Further, the polymeri backing has the additional benefit of sealing the back surface of the leather, thus preventing the loss of moisture, oils etc. from the leather and helping it to maintain flexibility.

If the leather cover has parts which are joined together at a seam, e.g. by sewing, then the polymeric backing can cover the seam and seal it, avoiding the need for strip seals. Preferably, therefore, the method comprises forming a seam by joining parts of the leather cover together, and applying the polymer at the seam.

Leather can be a difficult material to handle in automated processes. For example it can be problematic to locate a leather cover having one or more seams accurately in relation to a mould so that the seams are positioned correctly relative to the contoured shape of the final product. This may apply when the leather cover is being attached to a substrate. It is therefore advantageous if the leather cover and the polymeric backing are arranged to adopt a desired shape. Preferably, therefore, the method comprises holding the - 3 is leather cover in a non-planar shape when the polymer is applied thereto. A suitable mould may be provided for this purpose.

It may be desired to provide the leather covered article with a foam layer, for example between the polymeric backing and a substrate. The method preferably comprises applying a layer of foam to the polymeric backing. The use of a moulding system in which a f oaming material foams in a mould and bonds to the polymeric backing is particularly facilitated by the polymeric backing making the leather easier to handle and locate. Furthermore, the polymeric backing prevents foam leakage if there are any seams in the leather.

Various polymers, thermoplastic or thermosetting, may be used to form the polymeric backing. One such material is thermoplastic polyurethane (TPU). One preferred embodiment of the invention, comprises providing a polymer in powder form, and melting the powder before or after bringing it into contact with the leather cover. Hence, the polymer is applied to the leather cover in a molten state and is then allowed to cool and harden to form the polymeric backing. The powder may be sprinkled or otherwise distributed on a heated plate, allowed to melt, and the leather cover may then be pressed towards the plate, such that the polymer is applied to the leather cover. Alternatively, the powder may be distributed on the leather cover, and a heated plate may be pressed towards the leather cover, thereby melting the polymer and thus applying it to the leather cover in the desired molten state.

In an alternative embodiment, the polymer may be sprayed as a liquid onto the leather. For example, two components of polyurethane, polyol and isocyanate, may be mixed in a spray gun and directed under pressure at a leather cover. They then complete a reaction to form a polyurethane backing on the leather cover.

A preferred embodiment of the invention will now be 4 - described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a step in the method of the preferred embodiment of the invention; Figure 2 shows a subsequent step in the method; and Figure 3 is a graph showing the results of a heat ageing test on a leather covered article made by the method.

Figure 1 shows a metal plate 2 to which a layer 4 of thermoplastic polyurethane (TPU) in powder form has been applied by a sprinkler (not shown). Figure 2 shows a subsequent step in the method, in which the powdered TPU in layer 4 has been melted and a leather cover layer 6 has been applied and pressed towards the plate 2 by a press 8. The leather cover layer 6 includes a seam 10 where two leather parts have been stitched together prior to the illustrated process.

An example of the method of producing a leather covered article with the apparatus shown in Figures 1 and 2 will now be described. The metal plate 2 is heated in an oven to a temperature of 2200C. It is removed from the oven and TPU powder is sprinkled evenly thereon. The powder melts in about 5-10 seconds. The leather cover 6, including a seam 10, is applied cold to the melted TPU and is pressed towards the plate 2 by the press 8. Pressure is maintained by the press for about 30-60 seconds, whilst the plate 2 cools and the TPU hardens.

No adhesive is used in the process. An intimate bond is formed between the molten TPU and the leather, to the extent that the leather cover 6 cannot be separated from the TPU backing without tearing the leather.

A heat ageing test was carried out on the TPU backed leather article produced by the method and the results are shown in Figure 3. The material was held at 1200C for 400 hours.It shrunk over the f irst approximately 140 hours by approximately 1.2% and then did not shrink any further. By way of comparison a sheet of preshrunk "anti shrink,' leather was subjected to the same test. It shrank by about 4% over the first 20 hours and then continued to shrink more slowly as the test continued, reaching about 5.6% shrinkage after 400 hours. By way of a further comparison a sheet of seating leather was subjected to the same test and showed even more severe shrinkage results.

It will be appreciated that the degree of shrinking of the anti shrink leather will apply significant forces to a substrate to which the leather is attached, for example an instrument panel substrate, possibly leading to deformation. In contrast, the TPU backed leather shrinks by a relatively small amount, so that the tendency to apply deformation forces to a substrate is significantly reduced. Furthermore, the TPU provides a backing which reduces loss of moisture and oils and enables the leather to remain flexible during subsequent manufacturing steps, such as the application of a foam backing, with or without a substrate. Further, the TPU backing provided by the layer 4 seals the seam 10 in the leather, making it suited to a foaming process without foam leakage.

Although the plate 2 shown in Figures 1 and 2 is generally flat, it could alternatively have a contoured shape so that the TPU backed leather produced by the method would have the same shape. This would facilitate subsequent processing steps.

It will be appreciated that the invention is not limited to the features of the preferred embodiment and example described above and modifications could be made without departing from the scope of the invention. In particular, the invention is not limited to the use of a heated plate for melting a polymeric material, but also extends to the use of polymers which are liquid at room temperature and react after e.g. being sprayed onto the - 6 leather to form a material which hardens to form a solid backing.

7

Claims

1. A method of producing a leather covered article, comprising providing a leather cover with a polymeric backing, wherein the polymer is applied directly to the leather cover in a liquid or molten state and allowed to harden to from the polymeric backing.

2. A method as claimed in claim 1, comprising forming a seam by joining parts of the leather cover together, and applying the polymer at the seam.

3. A method as claimed in claim 1 or 2, comprising holding the leather cover in a non-planar shape when the polymer is applied thereto.

is

4. A method as claimed in claim 1, 2 or 3, comprising applying a layer of foam to the polymeric backing.

5. A method as claimed in any preceding claim, wherein the polymer is thermoplastic polyurethane.

6. A method as claimed in any preceding claim, comprising providing a polymer in powder form, and melting the powder before or after bringing it into contact with the leather cover.

7. A method of producing a leather covered article substantially as hereinbefore described with reference to the accompanying drawings.