GB2400377A

GB2400377A - Moisture vapour permeable leather

Info

Publication number: GB2400377A
Application number: GB0308457A
Authority: GB
Inventors: David O'leary
Original assignee: Pittards PLC
Current assignee: Pittards PLC
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2004-10-13
Also published as: GB0308457D0

Abstract

A balance of static water uptake and moisture vapour permeability is achieved in a leather by providing perforations substantially uniformly over at least 50% of the surface of the leather.

Description

MOISTURE VAPOUR PERMEABLE LEATHER

The present invention relates to a modified leather, particularly useful for articles of clothing such as gloves, that has an excellent balance between water vapour permeability and water resistance.

Such a balance is desirable in order that the leather be breathable but nonetheless prevent the wearer from becoming wet. This is particularly important in gloves and other articles of sports wear. There are many variables to be considered, including the particular nature of the leather, its thickness, the tanning process employed and any subsequent mechanical treatment. It had previously been thought that the presence of perforations in leather would result in excessive liquid water transfer and therefore destroy the leather's water resistance. For this reason, where perforations have been provided in leather they have as a rule been localised over a small portion of the surface of the finished article and have often been added merely for decorative purposes.

I have now found that perforations can provide benefits in certain leathers when provided substantially uniformly over the surface of the leather.

Thus, the present invention provides leather having a static water uptake of 60% or less preferably 40% or less by weight and having perforations substantially uniformly distributed over at least 50%, preferably 75%, preferably over at least 95% and most preferably over substantially all of its surface.

The portion of the surface of the leather over which perforations are provided will be clear in any practical sample of perforated leather. It will generally be possible to draw a line joining up all of the outer most perforations and then to compare the area within the closed line with the total area of the leather. A further variable that is of significance is the total surface area of the leather which is accounted for by the perforations themselves. A suitable range is from 0.5 to 30%, preferably 0.5 to 10%, of the surface over which the pattern of perforations is present.

A static water uptake test is well-known in the leather industry. A sample of leather is weighed dry, and is then immersed for twenty minutes in water at room temperature. The sample size is usually 8 cm2, although this is not critical. The sample is then removed from the water and allowed to drain until free flowing water has run off, and then the sample is re-weighed. The static water uptake is defined as the increased weight of the leather due to water uptake expressed as a percentage of the dry weight.

For an untreated sample of leather uptake would usually be considerably higher than 50% and often about, say, 150%. The leather to be used in the present invention is therefore preferably treated to render it water resistant, and this can be achieved by incorporation into the leather of various materials, generally by l 5 incorporation of hydrophobic agents during the tanning process.

The present leather, although it takes up water in a static water uptake test, is preferably substantially impervious to liquid water when pored onto a surface of the leather. Thus, the leather may be regarded as rain proof.

The density of perforations per unit area is preferably substantially constant over that portion of the leather which is perforated.

Generally, the perforations will pass through the entire thickness of the leather, although for some leathers, particularly thin leathers, a satisfactory increase in breathability may be achieved with perforations that do not penetrate the entire thickness of the leather. In general, I prefer that the leather have a thickness of from 0.25 to 0.8 mm.

For most purposes, the pore size of the perforations will be from 0.01 to 10 mm2, preferably from 0.05 to 5 mm7. The perforations need not be all of the same size, and it may be desirable for perforations of different sizes to be provided at different parts of the finished article. Also, it may be desirable for the number of perforations per unit area to vary over the article. However, for most purposes, I prefer that the pore size and the perforation density do not vary by more than 25%, particularly by more than 10% (based on the smaller value in each case) over the surface of the leather. The preferred pore size given above preferably applies to at least 75%, especially at least 90% and preferably substantially all of the perforations.

The perforations may be produced by removal of material of the leather, for example by drilling, or they may be provided simply by deforming the leather by moving the fibres thereof away from one another, for example by the use of a point that is forced through the leather. Such points may be provided on a plate or on the outside surface of a drum which is forced into contact with the leather.

The present invention may be applied to various leathers, for example bovine, sheep and goat skins. No special tanning process is required, except for that which may be necessary to achieve the static water uptake of 50% or less referred to above. To this end, hydrophobic tanning agents may be employed in the tanning process proper, or in a pre-tanning step or in a subsequent treatment.

A desired, but not essential, characteristic of the tanning process is that which renders the leather soft and allowing predominately plastic deformation of the leather at low levels of mechanical stress. In this way, the leather may be rendered particularly suitable for gloves, particularly sports gloves (particularly golf gloves), and also dress gloves and military gloves.

Other end uses of the leather include shoe leather, other articles of leather clothing, and leather upholstery.

For these uses it would be understood that excellent moisture vapour transmission

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is desirable, but that static water uptake is undesirable. I have found surprisingly that the provision of perforations does not excessively impair the static water uptake properties of the leather. The presence of perforation does, however, improve the moisture vapour permeability often by 50 to 65%. s

The leather that is to be perforated preferably has a moisture vapour permeability before perforation of at least 10 mg cm2 hr- (according to BS EN344 (1992), 5.13).

The perforations may be provided in a pattern that has aesthetic value, although the principal purpose of the perforations is of course to achieve the desired balance between static water uptake and moisture vapour permeability. The pattern may, for example, a linear, non-linear, ordered or random pattern, and when ordered the pattern may be a repeating or non-repeating geometric or other pattern.

The precise shape or shapes of the perforations will not generally be important for functional reasons, although there may be aesthetic reasons for choosing particular shapes. For simple perforation of the leather by means of a drill or by points the perforations will generally be circular. However, elliptical triangular or square or other polygonal shapes may be used.

Claims

1. A leather having a static water uptake of 60% or less by weight and having perforations substantially uniformly distributed over at least 50% of its surface.

2. A leather according to claim 1, in which the perforations penetrate through the entire thickness of the leather.

3. A leather according to claim 1 or 2 in which at least 75% of the penetrations have a pore size of 0.1 to 10 mm2.

4. A leather according to claim 1, 2 or 3, in which the perforations take up from 0.5% to 30% of that region to the surface over which the pattern of perforations is present.

5. A leather according to any preceding claim which is substantially impervious to liquid water.

6. A leather according to any preceding claim which is permeable to moisture vapour.

7. An article of clothing comprising a leather according to any preceding claim.

8. An article according to claim 7 which comprises at least part of a glove.