[0001] The present invention relates to a laminate material, comprising an upper layer and a lower layer which is joined to the upper layer over substantially the entire surface thereof, the upper layer comprising a thin layer of leather material, and the lower layer comprising a layer of material which can be stretched in two directions.
[0002] FR-A-2 680 478 describes a laminate material in which a layer of leather with a thickness of between 0.2 and 1.0 mm is adhesively bonded to a prestressed lower layer of stretchable material. The stretchable material is either a fabric comprising an elastomer or a layer of rubber. The material has a good elasticity and combines a number of advantageous properties of leather and stretchable material, and is used, for example, for shoes.
[0003] However, none of the known laminate materials described is able to simultaneously satisfy the requirements of flexibility, shape-restoring properties, protection for body parts which are to be covered and breathability without eliminating the advantages of the leather layer. These demands are imposed, for example, on shoes or other items of clothing for people with diabetes, deformities or other disorders which impair the circulation or whose skin is very easily damaged otherwise.
[0004] The present invention provides a solution to the above problem, and to this end is characterized in that the lower layer comprises at least one support layer which can be stretched in two directions and comprises at least two sorts of interwoven fibres, at least one type of fibres being produced from an elastic substance, as well as a layer of a compressible substance which has been joined to the support layer over substantially the entire surface thereof and can be stretched in three mutually perpendicular directions.
[0005] In this way it is possible, for the first time, to create a laminate material which is simultaneously flexible, shaperestoring, soft and protective, and also breathable. The support layer comprising interwoven elastic fibres and other fibres is primarily responsible for flexibility and more rapid recovery of the leather material, the layer of compressible substance is responsible primarily for softness and protection, while it is in part the combination of the two which provides the shape-restoring property. The breathability is ensured by suitable selection of breathable substances for the two part-layers of the lower layer.
[0006] In this way, an extremely suitable and comfortable material is created for, for example, shoes for diabetics. Other applications will be dealt with in more detail below.
[0007] The laminate material according to the invention is stretchable and has elastic properties which are comparable to those of the thinnest leather layers. This will be dealt with in more detail in the discussion of the Examples.
[0008] The elastic substance can be selected from the usual elastic substances, for example the substance which bears the trade name Lycra or products of a similar type. Other elastomers are also possible, in which case, if necessary, the ratio to the other fibres used has to be modified on the basis of the elasticity and other mechanical properties of the elastomer.
[0009] The compressible substance advantageously comprises a substantially open-cell cured plastic foam. This material combines softness and flexibility, and therefore also a protective action against external influences, with the required breathability. Moreover, it is extremely lightweight, making it beneficial and comfortable for any body parts which are to be protected by the material.
[0010] In a particular embodiment of the laminate material according to the invention, the plastic foam comprises latex foam. Latex is a suitable material which is very simple to foam and cure to produce a very lightweight yet flexible, resilient and elastic open-cell cured latex foam. Nevertheless, other breathable, lightweight plastics materials are conceivable, such as polyester sponge and the like.
[0011] The open-cell cured latex foam preferably has a density of between 25 and 35 kg/m3. This density gives a good compromise between the weight of the material, flexibility and strength. Nevertheless, other densities are also conceivable. For example, if the requirement or protection is more important, it is possible to use a denser and heavier foam.
[0012] The layer which can be compressed in three mutually perpendicular directions preferably has a thickness of between 0.5 and 2.5 mm, more preferably of between 1.0 and 2.0 mm. At this thickness, a protective action which is sufficient in most instances is obtained. Therefore, partly in combination with the other layers of the laminate material, a material which is suitable for many different applications and is not too thick is formed. Naturally, it is possible, for example to select a different, greater thickness if protection is a more important factor than flexibility. It is also possible to vary the thickness of the material over the surface. This results in the possibility of offering additional protection only where it is desired, by providing a greater thickness of material, while where flexibility is required, for example at the instep of a shoe, there is no additional material, so that there is no adverse effect on the flexibility.
[0013] In addition to the fibres made from elastic materials, it is in principle possible to select numerous types of fibres for the support layer, for example synthetic fibres, such as polyamide fibres, and other standard textile fibres, such as cotton and the like. In an advantageous embodiment, the support layer comprises between 82% and 95% of fibres of a polyester material and between 18% and 5% of fibres of an elastic material. A support layer of this type has particularly good shape-restoring properties in combination with the required flexibility. Moreover, polyester material exhibits unexpectedly good adhesion to latex, so that the combination of polyester material as synthetic fibre for the support layer and latex for the compressible layer is of particular benefit.
[0014] At this point, it should be noted that throughout the entire document percentages relate to ratios by mass, unless expressly stated otherwise.
[0015] In principle, the support layer may be located either between the layer of leather material and the compressible layer or on that side of the compressible layer which is remote from the layer of leather material. It is preferable for the support layer to be situated between the layer of leather material and the layer of the compressible substance. This offers the advantage of providing better protection for the layer of leather material against excessive stresses. Particularly in the event of external influences, for example impacts against a hard object, the layer of leather material could be dented relatively deeply, with the result that it would be greatly stretched and therefore could tear, since it is so thin. As a result of the support layer being applied directly beneath the layer of leather material, for example by means of adhesive bonding using a breathable adhesive layer, an external pressure of this type is distributed over a larger area, so that the layer of leather material is better protected.
[0016] The mass per unit surface area of the support layer is not limited to any particular extent, although it is preferable for the support layer to have a mass per unit surface area of between 140 and 180 g/m2. Within this range, a particularly favourable combination of an overall mass which is not excessively great and a favourable preponderance of the support layer over the layer of leather material is achieved. The intention of this measure is for the shape-restoring properties of the support layer not to be adversely affected, or to be only slightly adversely affected, by the specific resilience of the layer of leather material. Moreover, this level of mass per unit surface area is suitable for offering sufficient protection for the layer of leather material, as described above. If a slightly stronger, less flexible product is desired, it would be possible to select a slightly greater mass per unit surface area, for example 200-220 g/m2.
[0017] The way in which the fibres in the support layer are interwoven may, for example, be in the form of a woven fabric. However, in the case of a woven fabric it is only possible to achieve sufficient elasticity if there is a large number of fibres made from an elastic material in at least one direction. It is preferable for the support layer to have a knitted structure. It is more preferable for the support layer to comprise a fabric having an embroidery structure, which is obtained by warping. By providing the support layer with a structure of this type, this layer is provided with its own flexibility and, above all, elasticity. Consequently, if desired the proportion of fibres of an elastic substance can be reduced, so that the support layer becomes less dependent on the further mechanical properties of the elastic substance.
[0018] The leather material comprises natural leather with a thickness of between 0.2 and 1.0 mm. Natural leather has an excellent combination of flexibility, elasticity, breathability and a good moisture balance. Moreover, natural leather satisfies the visual demands which are imposed on shoes and can be provided with virtually any desired colour.
[0019] It is preferable for the layer of natural leather to be between 0.4 and 0.6 mm thick, if large shoe parts are being produced, such as for example the entire shoe upper. For smaller parts, which may often be somewhat more flexible, thinner material, for example with a thickness of 0.2 mm, is also suitable.
[0020] The natural leather is advantageously selected from the grain layer of a hide. This offers the finest texture and, after tanning, the best flexibility. Nevertheless, a different layer, for example a suede layer from a deeper hide layer, is also possible. It is advantageous to select hair-sheep leather, preferably from small animals. This provides natural leather of optimum flexibility and elasticity. However, other types of animals, such as goats and sheep, are not ruled out.
[0021] In another attractive embodiment, the leather material comprises imitation leather, which comprises a layer of interwoven fibres of a polyester material and fibres of an elastic material. A layer of this type can be given an appearance which strongly resembles natural leather, with the breathability being retained and the elasticity even being slightly better. The imitation leather preferably comprises 92% of polyester and 8% elastane, and the density is approximately 260 g/m2. This ratio and density ensures very good elasticity and strength. One example of a material of this type is "microfibre" material produced by Texpiel. Other ratios, between 88 and 93% of polyester, and a density between approximately 230 and 270 g/m2 can be used where there are different demands with regard to elasticity or strength.
[0022] In an advantageous embodiment of the laminate material according to the invention, the layer of the compressible material is joined, on the side which is remote from the layer of leather material, over substantially its entire surface, to a lower support layer which can stretch in two directions. In this way, the layer of leather material is provided with still further protection against external influences, by an additional support layer on the underside of the compressible layer. Moreover, any influence acting on the compressible layer from the inside is better distributed over this layer. For example, in the case of shoe a deformity or a toe may exert an undesirably high pressure on the compressible layer. The lower support layer allows this pressure to be better distributed.
[0023] The lower support layer is advantageously composed of substantially the same fibres as the support layer, and the lower support layer has a mass per unit surface area of between 100 and 120 g/2. In this way, use is made of the smallest possible number of different materials, with the result that there will be the smallest possible number of compatibility problems and it will be possible to control the mechanical properties very successfully. Moreover, the lower mass per unit surface area ensures that the lower support layer does not become too strong, so that in this way it is possible to prevent any excessive pressure on body parts or other objects covered by the laminate material. However, it is not necessary to select the same type of fibres if certain other demands imposed on the lower support layer are held to be of greater importance.
[0024] The leather material used often has a direction of maximum elasticity. The elasticity in a different direction, for example perpendicular to the direction of maximum elasticity, is then significantly lower. Advantageously, at least one out of the support layer and the lower support layer has a direction of maximum elasticity and a direction of lower elasticity which is perpendicular to the direction of maximum elasticity, the lower elasticity amounting to between 40 and 60% of the maximum elasticity. More advantageously, the lower elasticity is 50% of the maximum elasticity.
[0025] It is preferable for the direction of maximum elasticity of the support layer and/or the lower support layer to coincide with the direction of maximum elasticity of the leather material used. This orientation of directions of maximum elasticity imparts better stretching properties to the laminate material and offers a better distribution of pressure when the material is in use. In the present context, the term coinciding of the direction is intended to mean that the said directions include an angle which is less than 15°, preferable less than 5°.
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[0036] The above combination of layers, namely a layer of open-cell cured latex foam which is adhesively bonded on at least one side to a support layer comprising polyester fibres interwoven with fibres of an elastic substance is also inventive in itself. The combination of layers as described above, i.e. the laminate material according to the invention without the thin layer of leather material may encompass all aspects as described above and indicated in claims 1-21. Generally, it is advantageous for at least one support layer also to be joined to a layer comprising polyamide fibres interwoven with fibres of an elastic material. This combination offers a material which can provide the skin of body parts covered therewith with protection against shear forces which may occur in the event of movements. Moreover, it offers protection and is soft, flexible and breathable, and the layers exhibit unexpectedly good adhesion.
[0037] The invention also relates to a device for protecting a body part of a human or an animal, comprising a laminate material according to the invention.
[0038] In particular, a device of this type is selected from the group consisting of shoes, shin pads, knee pads, elbow pads and slings. A certain degree of flexibility and strength in combination with protection is important for all these examples. With regard to shin pads and knee pads and the like, consideration may be given not only to humans, but also to, for example, horses or other riding animals or pack animals. In particular, consideration should be given to products which are prescribed for a medical condition. In particular, diabetics, for example, have a skin which is very easily damaged and, moreover, particularly in the case of the legs and feet, has relatively little feeling. Consequently, chafing and pinching parts of shoes can quickly cause injuries which, moreover, are often difficult to heal. For these people, but also for people who have, for example, growths or other deformities on the foot, well-fitting and appropriate, i.e. flexible and protective, footwear is extremely important. Nevertheless, anyone can make use of the advantages of the invention, for example for more comfortable footwear.
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[0049] The support layer 3 comprises, for example, a knitted fabric comprising 92% of polyester material and 8% of Lycra and having a mass per unit surface area of 160 g/m2. This support layer 3 is in turn adhesively bonded over substantially its entire surface, by means of a layer 4 (…)