Layered Material And Method For Producing A Layered Material

Abstract

A method for producing a layered material, which has a substrate layer and a layer of polyurethane bonded to the substrate layer. A leather, preferably a sanded grain leather, a textile material, preferably a woven fabric or a knitted fabric, a bonded leather material, or a microfiber nonwoven is used as the substrate layer and is bonded to the layer. According to the present teaching, at least one, preferably a single, layer of frothed polyurethane foam is applied to the substrate as the layer.

Claims

1. A method for producing a layered material, which has a substrate layer and a layer of polyurethane bonded to the substrate layer, wherein the substrate layer is bonded to the layer, so that at least one layer of foamed polyurethane foam is applied to the substrate as the layer, wherein the liquid polyurethane foam is produced with a polyurethane dispersion compound, so that the individual polyurethane dispersions used to produce the polyurethane dispersion compound display different softening points in the dried state, to produce a polyurethane dispersion compound, a polyurethane dispersion with heat-activatable contact adhesion properties or with a softening point in dry condition of at least 40 C. with a mass of 18 to 52 wt. % of the finished polyurethane compound and a polyurethane dispersion without contact adhesion properties or with a softening point higher than 95 C. with a mass of 38 to 73. wt. % of the finished polyurethane dispersion compound, are mixed together, the layer is applied on the substrate layer at a thickness of 0.030 to 0.60 mm, before or simultaneously with a structuring of the polyurethane foam by a matrix of silicone rubber, an additional layer made of a non-foamed polyurethane foam is applied to the layer, and small-format parts or stamped parts are separated from a large-surface layered material coated with polyurethane foam and are imprinted, or after the polyurethane foam has dried, before further processing the layered material is stamped to fragments and the fragments, independently of one another, are then subjected to stamping or surface structuring under pressure and temperature.

2. The method according to claim 1, wherein: the layer, after it is applied to the substrate layer, is dried to a water content of less than 1.5 wt. % to the point where it is free of water, and/or to produce the polyurethane foam, an aqueous polyurethane dispersion compound based on aliphatic polyether and/or polyester and/or polycarbonate polyurethane is used, and/or the polyurethane dispersions are selected so that the polyurethane dispersion compound possesses thermoplastic properties after it is dried and before it is cross-linked, the polyurethane foam dispersion compound used to produce the polyurethane foam contains 65 to 91 wt. % polyurethane dispersionsbased on the weight of the polyurethane dispersion compoundso that the polyurethane dispersions used to produce the polyurethane foam contain in each case 35 to 52 wt. % solid material based on the weight of the respective polyurethane dispersion, and/or the polyurethane of the polyurethane dispersions being used has at least partially linear and/or at least partial crystalline and/or thermoplastic or amorphous structure.

3. The method according to claim 1, wherein the polyurethane foam is produced by applying a gas or gas bubbles to the polyurethane dispersions or polyurethane dispersion compound, so that in one liter of the polyurethane dispersion or polyurethane dispersion compound, as much gas is introduced or applied so that 1 liter assumes a volume of 1.10 to 1.70 liters.

4. The method according to claim 1, wherein to produce a polyurethane dispersion compound, a polyurethane dispersion with heat-activatable contact adhesion properties or with a softening point in dry condition of at least 40 C. with a mass of 18 to 52 wt. % of the finished polyurethane compound and a polyurethane dispersion without contact adhesion properties or with a softening point higher than 95 C. with a mass of 39 to 73 wt. % of the finished polyurethane dispersion compound, are mixed together.

5. The method according to claim 1, wherein the polyurethane foam is sprayed onto the substrate layer or applied using the silk-screening method or with at least one roller or a squeegee, at uniform thickness, and/or in using a microfiber nonwoven as the substrate layer, the intervals between the fibers of the nonwoven are filled at least partially with coagulated or foamed synthetic foam.

6. The method according to claim 1, wherein, before structuring the surface of the layer of polyurethane foam onto the structure-shaping matrix, the additional layer is configured from a non-foamed polyurethane dispersion at a strength of 0.015 to 0.060 mm, containing at most 1.5 wt. % water, contains no adhesion properties, at least to a temperature of 110 C., and is solidified and/or cross-linked Jo the point where it can be withdrawn from the structured matrix without residual adhesiveness, and this layer that is situated on the matrix warmed to a temperature of 90 to 145 C. is brought in contact with the layer and is pressurized and connected with this layer in the course of the structuring, so that advantageously this layer, after structuring, has a shore A hardness of 55 to 95 and, in some cases, a different color than the layer.

7. The method according to claim 1, wherein the additional layer is applied on the layer in that, before the structuring of the layer with a matrix, the additional layer made of a polyurethane dispersion with, in some cases, a different, preferably greater, hardness and/or color is directly applied to the layer or connected to it, so that the additional layer is formed of a non-foamed polyurethane dispersion and is applied at a strength of 0.015 to 0.060 mm, and, in some cases, is dried to a water content of at most 1.5 wt. % water.

8. The method according to claim 1, wherein to produce a surface-structured layering material, the dried layer, in some cases simultaneously or jointly with the additional layer, is pressurized and in some cases reduced in thickness with a structured matrix which has a temperature of 110 to 155 C., so that for a heated matrix a contact duration of 2 to 18 s and a contract pressure of 0.04 to 1.8 kg/cm2 are maintained, or the layer, in some cases simultaneously or together with the layer, is brought to a temperature of 110 to 155 C., for example with IR radiation, and is pressurized and structured and in some cases reduced in thickness with a matrix that is cold or at most warmed to 75 C., and/or that the thickness of the layer of sprayed polyurethane foam in the course of applying the surface structure or embossing at the pre-established temperature and the pre-established pressure is reduced and thereby the thickness of the layer is such that it remains thicker by 2 to 18% than a comparable layer which is produced from an equally great amount of non-foamed polyurethane dispersion or non-foamed polyurethane dispersion compound of the same composition and is distributed over the same surface as the polyurethane foam, and/or the embossing is conducted by a surface-structured matrix of silicone rubber mass with a shore A hardness of 40 to 85.

9. The method according to claim 1, wherein additives are applied to the polyurethane dispersion or polyurethane dispersion compound, and/or the polyurethane foam is subjected to warming and pressurizing means in such a way that, after structuring with the matrix, the layer has a thickness of 0.80 to 1.030 kg/cm3, and/or cross-linkers with a mass of 0.9 to 4.2 wt. % based on total weight of the polyurethane foam are applied to the polyurethane dispersion or the polyurethane dispersion compounds, and after structuring and cross-linking under pressure and temperature, lose their adhesiveness and are thermoplastic, and/or 8 to 25 wt. %. based on the total weight of the polyurethane foam, undergo a 40 to 60% acrylate dispersion, and/or to produce the polyurethane foam, polyurethane dispersions or polyurethane dispersion compounds are employed in which, after a drying process, a dry layer of the polyurethane foam thereby produced, with a surface of 1 m2 and a thickness of 1.00 mm, weighs 0.78 to 1.03 kg before its structuring.

10. The method according to claim 1, wherein before applying the layer of polyurethane foam to a substrate layer composed of a textile material, such as a woven or knitted fabric, a thin layer is applied to the surface of the textile material, said layer consisting of possibly foamed soft PVC or of a foamed or non-foamed cross-linkable polyurethane dispersion or a non-foamed cross-linkable polyurethane dispersion compound with a polyurethane solid content of 20 to 35 wt. %, and constitutes a connecting layer for the layer of polyurethane foam that is to be applied.

11. A layered material comprising a substrate layer and a layer connected therewith made of polyurethane, wherein the substrate layer is produced according to the method of claim 1, wherein the layer is composed of at least one layer of a polyurethane foam that is not cross-linked or not yet cross-linked or weakly cross-linked and which, in some cases, has a maximum water content of 1.5 wt. %, so that the layer has a softening point above 90 C. and is sticky at a temperature of 90 to 145 C., has thermoplastic properties and is viscous under pressure and/or can be permanently reshaped and, after structuring and cross-linking carried out under pressure and temperature change, loses its stickiness and is thermoplastic, so that an additional layer of a non-foamy polyurethane dispersion is applied to the layer.

12. The layered material according to claim 11, wherein the polyurethane of the layer has a specific weight of 0.8 to 1.03 kg/dm3 and/or the layer of polyurethane foam has a thickness of 0.030 to 0.40 mm, and/or the polyurethanes used for the layer are aliphatic polyurethanes on a polyether or polyester or polycarbonate base and/or the layer of polyurethane foam contains pigments and/or cross-linkers and/or polyacrylates and/or hollow microspheres and/or matting means, and/or the layer of reinforced, dried polyurethane foam has a shore A hardness of 28 to 68.

13. The layered material according to claim 11, wherein, in a substrate layer made of a textile material, between the textile material and the layer a thin layer is configured, which consists of foamed soft PVC or of a cross-linked foam layer of a polyurethane dispersion and the said layer has a thickness of 0.25 to 0.45 mm and constitutes a connecting layer for the layer of polyurethane foam that is to be applied, so that, in some cases, the two layers include a total thickness of 0.3 to 0.5 mm.

14. The layered material according to claim 11, wherein on the layer a thin, heat-structurable, non-foamed layer consisting of a polyurethane dispersion or polyurethane dispersion compound with a thickness of 0.0150 to 0.60 mm, is mounted on or connected to the layer, so that a structure corresponding to the structural embossing in the layer is configured or impressed in the layer of polyurethane foam and so that the layer advantageously includes a greater shore A hardness than the layer or a hardness of more than 70 shore A and, in some cases, contains 1 to 4 wt. % polysiloxane.

15. The layered material according to claim 11, wherein the grain leather is a full-grain steer's leather of which the grain layer has been removed by at least 5% to at most 60% by mechanical means, and/or the fibers of the microfiber nonwoven consist of polyester or polyamide, so that the hollow spaces between fibers are impregnated or filled with a synthetic material, including a foam structure or a coagulated microcellular structure, and/or the polyurethane foam has an open-cellular structure and/or is permeable to air and/or includes a water vapor permeability of more than 0.50 mg/cm.sup.2/h according to DIN EN ISO 14268.

16. Objects produced by using a layered material according to claim 11, such as broadloom, cuttings, stamped parts, shoe parts, sport and work shoes, inlaid shoe soles, pouches, leather goods, steering wheel covers, cushion coverings, inner wall coverings and seat covers for power vehicles, wherein the surface of the objects or the layer includes a structural embossing.

17. The objects according to claim 16, wherein the layer and in some cases also the layer connected with the layer or mounted on the layer is shaped or structured thermoplastically or by using heat and pressure.

18. The objects according to claim 16, wherein a structuring is configured or imprinted on the surface of the layer, and/or the layer of polyurethane foam has a thickness that is only 2 to 18% thicker as a layer that is made of a weight-equalized quantity consisting of a non-foamed polyurethane dispersion or non-foamed polyurethane dispersion compound of the same composition, after this quantity has been distributed in the shape of a layer over an equal-sized surface such as the polyurethane foam.

19. The objects according to claim 16, wherein the polyurethane foam of the layer is not cross-linked or is almost completely cross-linked.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawing shows schematically a section through a layered material constructed according to the present teaching. This layered material is created in such a way that a layer 2 made of a polyurethane foam is attached or applied to the surface of the substrate layer 1. If the substrate layer 1 is a textile material, then this textile material can be provided as base layer for precoating the surface with a layer 5 made of a soft PVC or made of a polyurethane foam from a polyurethane dispersion or polyurethane dispersion compound, in order to connect the layer 2 of polyurethane foam well with the possibly coarse textile material. With a substrate layer 1 which is formed by a textile material, such as woven or knitted fabric, the substrate layer 1 is provided with a layer 5 of polyurethane foam with a thickness of 0.20 to 0.35 mm or a layer 5 of a foamed soft PVC with a thickness of 0.250 to 0.450 mm. As a result, any impressing of the layer 2 into a coarse textile material is excluded. When embossing the layer 2 with the matrix 4 or an embossing roll 10, the layer 2 is reshaped, but does not penetrate into the substrate layer 1.

[0042] A layer 3 of a non-foamed polyurethane dispersion or polyurethane dispersion mixture can be applied to the layer 2 of polyurethane foam prior to its structuring. With a schematically illustrated matrix 4 or an embossing roll 10as shown in FIG. 2the layer 2 or the optionally present layer 3 can be given the indicated surface structure 7. With corresponding presses or pressure rollers 9 and heating devices 8 (infrared heaters), the substrate layer 1 and the matrix 4 are pressed against each other or pressed against the embossing roller 10. The matrix 4 is heated to the required temperature for the embossing process to bring the polyurethane foam to the desired softening temperature. If a cold embossing roller 10 is used, the layer 2 may be heated prior to its contact with the embossing roller 10 or matrix 4, for example with an infrared heater 8. When embossing with a steel roller 10, this roller is not heated, and thus any adhesion of the layer 2 or 3 is safely avoided. The layers 3 and 5 can also be formed with the same polyurethane dispersion compound or compounds as the polyurethane foam.

[0043] Use of a polyurethane foam as opposed to non-foamed coatings offers the advantage that when embossing under strong temperature and pressure, the surface-structured polyurethane foam is permeable to air and water vapor or remains and expands when heated. Air and moisture which, when applied to the layer 2, are present on the matrix 6, can escape, so that the embossing can proceed free of voids and bubbles.

[0044] When the polyurethane foam has dried, the sheet material can be punched into blanks prior to further processing, and the blanks are then subjected to embossing or surface structuring independently of one another, under strong pressure and temperature.

[0045] The layer 3 can either be applied directly to the polyurethane foam layer 2 or it is applied to the matrix 4 and dried on the matrix until anhydrous or almost anhydrous, and optionally pre-cross-linked so that it is removable there and, on embossing with the polyurethane foam layer 2, can be inseparably connected; this is no longer recognizable on the embossed layered material.

[0046] If a conventional unfoamed polyurethane dispersion layer is dried at a temperature of +120 C., a skin forms on its surface and the coating becomes brittle. However, when using a polyurethane foam, drying and embossing can start immediately at a temperature of about 120 C., and no cracks are formed in the pre-dried layer of polyurethane foam, because no skin forms to hinder the removal of water. In addition, unlike non-foam layers, the layer retains almost its original strength after drying.

[0047] The inventive procedure advantageously employs only non-toxic materials, which can also be processed economically and safely by unskilled workers. Furthermore, the embossing of an already dried polyurethane foam helps preserve the matrix, since the cross-linker contained in the polyurethane foam is not wet and does not come into contact with the matrix to the same extent as with conventional coatings because cross-linkers act aggressively and corrosively on silicone matrices.

[0048] When computing the specific gravity of the polyurethane foam, it should be remembered that depending on the application, it may contain pigments or additives of varying specific weight. For example, titanium dioxide is very difficult to use as a white coloring additive, whereas other colored pigments may have significantly lower specific gravity. If the open-pore polyurethane foam also contains hollow micro-spheres filled with gas, which are known to constitute open cells, these must be taken into account and deducted when calculating the density.

[0049] The foamed and thermoplastic layer 2 of polyurethane foam is compressed by means of heat and pressure to accept the negative structure of the matrix 4. The predominantly open-cell microfoam is thus compacted in such a way that some of the microcells are lost and the polyurethane foam still has an open-cell microfoam structure, which then only has a weight of 0.80 to 1.03 kg/dm.sup.3. On the other hand, a non-foamed compact layer produced with the same formulation has a density of 1.050 to 1.12 kg/dm.sup.3. These results, according to the present teaching, in an advantage in weight and material saved. By compressing the polyurethane foam, which can be controlled by embossing, in contrast to non-foamed coatings, deeper structures can be configured and, surprisingly, the softness is retained.

[0050] Because the layer 2 is permeable to water vapor and air, expanding gas or any residual water vapor arising during hot pressing is diverted through the layer 2 into the substrate layer 1 and no voids, bubbles and cracks are formed. When placing the dry layer 2 on the matrix that is hot or to be heated, it is important that the heat-expanding air or residual gases that cannot escape into or through the die, are able to be diverted through the open-cell polyurethane foam or through the substrate layer 1. If the layer did not have an open-celled microstructure, imperfections would result in the intervals between grains of the matrices, which would take the form of undesired pores and shiny patches.

[0051] Structured surfaces by means of heat pressing are mainly used for shoes, steering wheels, bags, leather goods, etc. According to the present teaching, format parts, for example in the dimensions between 0.35 and 0.9 m.sup.2, can be produced easily by punching out sets of format parts with small chads or punch waste. A format part in this case can be large enough to cover the shaft parts, for example for a pair of shoes.

[0052] The complete polyurethane dispersion compound advantageously contains, before foaming, 0.90 to 4.2 wt. % of cross-linker, based on the total weight of the polyurethane dispersion compound. Advantageously, to improve the hydrolysis resistance, the respective polyurethane dispersion compound or compounds can contain from 8 to 25 wt. %. of a 40 to 50% acrylate dispersion, which is advantageously cross-linkable with isocyanate.

[0053] After drying and before the cross-linker takes effect, which at normal temperature begins after about 8 hours, the foamed layer may also be slightly tacky which makes stacking, at least at elevated temperatures, difficult (because of sticking together). To prevent this, optionally after drying and before stacking, the layer 2 can be covered with a polyethylene film or other thin material, such as release paper. Alternatively, according to the present teaching, in a simple and inexpensive manner, a thin layer (about 0.015 to 0.060 mm thick) of a harder polyurethane dispersion can be applied to the surface of the polyurethane foam of the layer 2 and cross-linked or dried; the said layer has a hardness of more than 70 shore A and is not foamed and optionally contains 1 to 4 wt. % of a polysiloxane.

[0054] If a 50% polyurethane dispersion, i.e., 50 parts solid and 50 parts water, is applied to a substrate as a film of, for example, 0.15 mm in thickness, this film shrinks or collapses by approximately 50% upon heat-drying, because of water loss. In addition, during drying (e.g. in the heat-drying channel) at +120 C., the film becomes brittle, because a skin forms on the surface, which makes water removal from the film under the skin difficult. The drying must therefore be done slowly and at low temperature, below 80 C. for a long period of time, which is uneconomical. According to the present teaching, however, a polyurethane foam is used, which does not collapse when drying by heat (e.g. in the drying channel), since no skin forms on the surface, because owing to the largely open microcells, the water or water vapor can continuously escape, even from lower areas, upward through the partially open microcells through the substrate layer. It should be noted that during hot pressing or structuring, the matrix advantageously lies at the bottom and the layered material with the layer 2 of polyurethane foam is placed on it, facing downward. Even with a layer thickness of 0.25 mm and at a drying temperature of 120 C., no cracks occur during drying. Furthermore, the drying time is shortened by more than 60% compared to a non-whipped dispersion layer without open-cell microstructure.

[0055] Furthermore, a compact polyurethane material is not readily embossable at low temperatures, since the material is compacted during embossing and must be able to flow. Here the easily reshapable foam, which is malleable after softening, offers considerable advantages.

[0056] In the context of the present teaching, in the case of a shallow grain, the polyurethane foam with its at least partially open-celled microstructure can be compacted at the surface on a hot matrix or silicone backing so that the surface is as homogeneous as possible at a thickness of 0.010 to 0.020 mm and as a result, it is more resistant to abrasion and more durable.

[0057] At the time of surface shaping, the layer 2 still behaves thermoplastically and becomes so elastic under pressure and heat impact that it also molds the finest microstructures in the surface of the matrix. Nevertheless, the substrate layer 1 with the structured layer 2 can be pulled off the matrix 4 immediately after embossing, that is, while layer 2 is still in the heated state. In the case of particularly difficult surfaces, such as structures in the nanoscale or velour surfaces, it is expedient to apply a non-foamed polyurethane dispersion having a solid content of 30 to 35 wt. % in an amount of 35 to 85 g/m.sup.2 onto the matrix 4 and after drying to connect it with the layer 2.

[0058] The respective polyurethane dispersion compound or compounds contain foaming aids for foaming and for stabilizing the whipped foam, in the simplest case an ammonia-containing foaming agent in an amount from 0.5 to 2 wt. % (based on the total weight of the respective polyurethane dispersion). Thickening agents, e.g. Acronal-based (Wesopret A2), can be added to the respective polyurethane dispersion or the polyurethane dispersion mixture in an amount of 1 to 4 wt. % (based on the total weight of the respective polyurethane dispersion.

[0059] The polyurethane foam is formed by the stirring of gas or air by known agitators, similar to a stirrer for the production of whipped cream or egg whites.

[0060] The polyurethane dispersions used are aqueous polyurethane dispersions.

[0061] The measurement or verification of the softening point takes place on the Kofler bench.

[0062] According to the present teaching, particularly good reshaping properties for the configuration of the surface and an excellent connection between the substrate layer 1 and the foamed layer 2 are obtained if the polyurethane dispersion compound contains 18 to 52 wt. % of a polyurethane dispersion in the form of a heat-activated contact adhesive, which has a polyurethane solid content of 40 to 50% and is heat-activatable and, from a temperature of 4 C., becomes pasty and sticky. Such products are heat-activatable polyurethane-based dispersion contact adhesives, such as, for example, Luphen from BASF. After a cross-linker, such as the product Aquaderm XL 80 from Lanxess AG in Cologne, becomes effective, the polyurethane dispersion compound, which preferably contains the heat-activatable contact adhesive, loses its thermoplastic properties after the dried, anhydrous layer 2 of polyurethane foam, in shaping the surface, has been brought by means of heat and pressure to a temperature above 90 C., preferably above 110 C. Admixed to this polyurethane dispersion is a polyurethane dispersion in the amount of 39 to 73 wt. % based on the weight of the polyurethane dispersion compound whose softening point is higher than 125 C.

[0063] The present teaching also eliminates the known disadvantage that coatings produced with polyurethane dispersions on hydrophobic substrates only achieve insufficient adhesion or bonding. A hydrophobic substrate prevents penetration of polyurethane dispersion, which typically contains more than 40% water, into the surface of the substrate. This disadvantage of polyurethane dispersions for coating, known in the leather industry, is improved according to the present teaching, because the polyurethane foam used according to the present teaching, after drying during structuring, behaves like a heat-activatable adhesive, which penetrates under pressure into the finest depressions of the matrix and in the same way can penetrate the finest depressions of a substrate. The polyurethane foam anchors itself in the carrier like a hot melting adhesive and improves the adhesion.

DETAILED DESCRIPTION

[0064] The present teaching will be explained in more detail below with reference to embodiments.

[0065] To determine whether a polyurethane dispersion compound or a polyurethane foam produced therewith is suitable for structuring, a test is made of the properties required for hot stamping, such as thermoplasticity, tackiness and flow behavior under heat and pressure. This is done by forming a layer with a thickness of 1.0 mm of a dried, not yet cross-linked polyurethane foam and evaluating it with respect to the aforementioned properties in the heating furnace or on the Kofler bench at a temperature between 90 C. and 145 C. In the event of a positive result, this layer of polyurethane foam is pressured in a press with a silicone rubber matrix having the desired surface structure, which has a shore A hardness of 75, at temperatures between 90 C. and 145 C. and press times between 2 and 18 s. At these temperatures, the polyurethane foam film has to be more or less sticky, but must not be liquid, must optimally match the template and must be easily removable from the matrix without deformation and without altering the formed structure. As a rule, the aforementioned commercially available polyurethane dispersions meet this requirement. By a corresponding mixing ratio of such commercial polyurethane dispersions, adjustments to different application purposes or different surface structures and different demands are possible and the softening and embossing temperature can be set or specified.

Embodiment 1

[0066] The grain side of a steer's grain leather was abraded by 0.5 mm using 180-grit abrasive paper. On the abraded side, to form the layer 2, a polyurethane foam was applied at a thickness between 0.090 and 0.110 mm by means of a counter-rotating roller. At a temperature of 110 C. and with circulating air, the water content was reduced in the course of 2.5 minutes to 1.3 wt. %. The polyurethane foam decreased in thickness during drying only by 0.01 mm.

[0067] The foam was prepared from 420 g polyurethane dispersion with heat-activatable contact adhesive properties with a solid content of 40%, 480 g polyurethane dispersion with a high softening point of over +140 C. with a polyester-based amorphous structure and a solid content of 40%, 20 g Melio Foam paste, 30 g thickener, 50 g pigment.

[0068] The polyurethane dispersion mixture, after drying in the heating cabinet, had a softening point or range which allowed excellent embossing at a temperature of 125 C.

[0069] This mixture had a volume of 1.07 l and was whipped up or expanded with a commercial foam beater to a volume of 1.35 l by blowing in air. The foam with its whipped-cream consistency was applied to the abraded side of the grain leather at a thickness of 0.1 mm and dried. After 4 hours, the embossing was carried out, wherein the water content of the polyurethane foam was less than 1 wt. %.

[0070] The embossing was carried out with a matrix temperature of 128 C. and a pressure of 0.08 kg/m2. The pressure was maintained for 7 seconds.

[0071] The structure of the substrate or leather was not visible through the foam or the layer 2. The bonding or the layer formation was free of voids and bubbles; no collapse occurred. A thickness measurement showed that the polyurethane was about 8 to 10% thinner.

[0072] When a further layer 3 was formed on the polyurethane layer 2, which was prepared as indicated above, the water vapor permeability was 0.8 mg/cm2/h. In order to prepare this further layer 3, a layer of polyurethane dispersion mixture, which was not foamed, was applied in a thickness of 0.025 mm to the template 4 used for structuring and dried. Based on its total weight, this polyurethane dispersion mixture was prepared with 60 g polyurethane dispersion based on polycarbonate with a solid content of 32 wt. %. A dried layer of such a polyurethane dispersion has a shore A hardness of 75. To this was mixed 20 g of polyurethane dispersion based on polyester with a solid content of 35 wt. % and a shore A hardness in the dried state of 65. Moreover, this polyurethane dispersion mixture contained 4 g cross-linker, 5 g black pigment paste, 3 g polysiloxane and 1 g matting agent S100.

[0073] This polyurethane dispersion mixture with the specified additives was applied to the matrix 4 unfoamed 10 minutes before the structuring process. It was then dried to less than 1% water content. The connection of this further layer 3 with the polyurethane foam layer 2 that was on top of the carrier 1 as described above took place in the course of contacting the layer 2 with the matrix 4 at the embossing temperature and embossing pressure mentioned above. In this case, this further layer 3 was inseparably connected to the polyurethane foam layer 2.

[0074] The resulting high adhesion of polyurethane dispersion-based layers in hydrophobic substrates, in particular in hydrophobized leathers in combination with the improved water vapor permeability, is a prerequisite, above all, for safety shoes of the class S2 and S3 and is readily met with the inventive layered material.

[0075] It has also been found that when using a foamed soft PVC precoated substrate it is preferable to prepare the polyurethane foam layer only with polyurethane dispersions based on polyester or polycarbonate. In the case of PU dispersions based on polyethers, a plasticizer migration could possibly occur in the polyurethane foam.

[0076] Commercially available polyurethane dispersions are used as polyurethane dispersions for producing the polyurethane foam for layers 2 and 5. These commercial polyurethane dispersions are based on aliphatic polyester or polyether or polycarbonate polyurethanes. Such polyurethane dispersions have a solid content of 35 to 52. The pH of such PU dispersions is between 6.5 and 8.5. After water removal or drying, the film which forms has an elongation at break of between 280 and 650%. These polyurethane dispersions can be cross-linked with XL80. The hardness of a dried and cross-linked unfoamed film of such polyurethane dispersions has a shore A hardness between 35 and 95, preferably 45 to 85. The layers formed are odor-neutral and free of impermissible chemicals.

[0077] Commercially available silicone-rubber impression materials are used for the preparation of the matrixes 4, and the matrices have a shore A hardness between 40 and 85. The density of the matrices is more than 1,150 g/cm3 and are cross-linked by condensation or additive. The created matrices can be engraved by laser or mechanically.

Embodiment 2

[0078] A polyurethane dispersion compound was prepared with:

460 g of commercially available polyurethane contact adhesive dispersion with heat-activatable contact adhesive properties and with a solid content of 40 wt. %,
510 g of commercial polyurethane dispersion based on aliphatic polyether with a solid content of 40% and a softening point of a dried layer (0.5 wt. % water) of 155 C.,
6 g black pigment paste,
4 g compressor in the form of polyacrylate,
2 g MELIO foam paste,
3 g cross-linker,
10 g polyacrylate dispersion having a solid content of 50 wt. %,
5 g hollow microspheres with a diameter of 20 .

[0079] This resulted in a polyurethane dispersion compound with a weight of 1000 g, which occupies a volume of 1.04 l. One liter of such a polyurethane dispersion was whipped to 1.34 l. The whipped polyurethane dispersion mixture has a high viscosity and is virtually thixotropic.

[0080] A layer of 0.13 mm was applied with a counter-rotating applicator roll on a microfiber nonwoven and dried within 3 minutes in a circulating air dryer at a temperature of 115 C. to 1.0 wt. % water content. After 3 hours, shoe upper parts were punched out and pressed and structured at a temperature of 120 C. and a pressure of 0.05 kg/cm2 for 5 seconds with a surface-structured silicone matrix.

[0081] The stamped parts show in the positive the precise structure of the negative matrix, which had the appearance of kangaroo leather. The layer 2 had a thickness of 0.065 mm and the adhesion between the substrate and the layer 2 was 28 N/cm.

Embodiment 3

[0082] A polyurethane foam was applied to a kangaroo leather with sanded grain according to Embodiment 2 by means of a roller at a thickness of 0.09 mm and dried at a temperature of 95 C. to 1 wt. % water. Subsequently, shoe upper blanks for soccer shoes were punched out and structured as shown in Embodiment 2. The thickness of the layer 2 was 0.07 mm and the adhesion between the substrate 1 and the layer 2 was 16.5 N/cm.

Embodiment 4

[0083] A mixture of polyurethane dispersions, but white in color, containing 12 g of titanium oxide, according to Embodiment 2, was foamed and the polyurethane foam was applied to form the layer 2 airlessly at a thickness of 0.12 mm on a microfiber nonwoven and at a temperature dried from 120 C. for 3 minutes to less than 1 wt. % water. Next, shoe upper parts were punched out. A 0.040 mm thick non-foamed polyurethane dispersion was applied to a die with a negative suede structuring. The solid content of this dispersion was 30 wt. %. Furthermore, this dispersion contained 5 wt. % of red pigment paste. The thickness of this layer after drying to 0.5 wt. % water content was 0.018 mm. The stamped parts were placed on the layer 3 on the die 4 and, as in Embodiment 2 described above, pressed, wherein the layers 2 and 3 were inseparably connected to each other.

Embodiment 5

[0084] A substrate made of textile material was coated with a soft PVC foam and another substrate made of textile material was coated with polyurethane foam as a sheet precoated with a thickness of 0.30 mm according to Embodiment 2 to form a layer 2. On each of these precoated substrates, a heat-structurable layer 2 of polyurethane foam was applied with a doctor blade in a thickness between 0.15 mm and dried to a water content of less than 1 wt. %. On this layer 2, an unfoamed layer 3 of a polyurethane dispersion was applied in a thickness of 0.035 mm. This PU dispersion had a solid content of 30 wt. % and a cross-linker as content in the amount of 5 wt. %. After drying the layer 3, the blank or the layers 2 and 3 were structured at a temperature of 145 C. and firmly connected together with the layer 5.

[0085] The present teaching is particularly advantageous for the production of formatted and cut parts, such as for safety shoes or steering wheels. This results in a good full-surface connection between the respective substrate material 1 and the layer 2. At the same time it leads to a temperature resistance up to at least +125 C. It serves to meet the requirement that up to these temperatures, storage for 24 hours can take place, whereby the structure of the surface, its color and the degree of gloss or any expected mattness may not change. Extreme requirements apply in the molding of matrices which have a surface structure obtained by molding a fabric of textile fibers or in the molding of surfaces of carbon fiber fabrics. The structure formed on the layer 2 corresponds exactly to the matrix structure in its three-dimensionality as well as its degree of gloss and mattness. An exact three-dimensional image is obtained particularly well if, on the matrix 4 before the application of the layer 2, a thin polyurethane dispersion of the thickness of 0.025 to 0.06 mm of a cross-linked polyurethane dispersion with a softening point higher than +125 C. is applied. This dispersion contains aliphatic polyester and has a hardness after cross-linking that is greater than 75 shore A. Such a polyurethane dispersion has a solid content of 25 to 32% by weight and as an addition 3% cross-linker, 6% by weight of pigments, 3% by weight of polysiloxane, 0.5 wt. % of matting agent. On the dried polyurethane layer 2, this layer 3 is applied in the manner already described.

[0086] For layered material in the form of sheet material, in particular with a textile substrate made of woven or knitted fabric, a precoating is carried out with a layer 5 of foamed soft PVC or a cross-linkable polyurethane foam. It is advantageous here to apply the foam layer 2 to the layer 5 by means of a doctor blade. After drying, this layer is applied to this layer 3, preferably with a pressure roller. The drying of the applied polyurethane layers 2 and 3 takes place on the web-shaped carrier 1 with the layer 5 in the continuous dryer. The structuring is carried out in such a way that the layer 3 and the layer 2 of polyurethane foam are brought to a temperature between 145 and 165 C. by means of infrared radiators and are embossed under pressure by means of a structured roller. This results in the advantage that the more heat-resistant layer 3 prevents sticking of the polyurethane foam layer 2 on a non-heated patterning roller.

[0087] The embossing speed depends on the type of structuring, in particular on the grain depth, and ranges from 5 to 55 s/m of the layered material.

[0088] In the case of a substrate 1 precoated with soft PVC, it is advantageous to choose the temperature and/or the embossing speed and/or the pressure such that the PVC layer is at least slightly patterned, whereby this layer 5, like the polyurethane foam layer 2, decreases in thickness.

[0089] It has proved advantageous for the structuring of the polyurethane foam layer 2 if, during structuring, a pressurization of at least 6 g/cm2, preferably of at least 12 g/cm2, takes place. Furthermore, the polyurethane foam for structuring should not be thin but pasty and readily malleable under pressure in order to be able to image the fine structures of the matrix; regardless of whether it is sheet-like layered material or layered material in the form of format parts or blanks.

[0090] The polyurethane foam of the layer 2 is at its most advantageous consistency when the polyurethane foam has a similar flowing viscosity as soft PVC at a temperature between 160 and 180 C., so that it is flowable and shapable under pressure. This also applies if, prior to the structuring of the layer 2, an additional layer 3 is applied to this layer 2.

[0091] The formation of a corresponding degree of softening or a desired shapable consistency can also be controlled by the amount of cross-linker used and/or by the mixing ratio of polyurethane dispersions having a low or higher softening point or softening range.

[0092] Matting agents, in particular the matting agent TS100 from Evonik Degussa GmbH used for layers 2 and 3, improve the texture, result in a dry touch and improve water vapor permeability.

[0093] The drying of the layer 2 occurs under heat in the dryer or continuous dryer. A layer of polyurethane foam in accordance with the inventive density range, below tenths of millimeters, takes 2 to 6 minutes at 80 to 120 C., depending on the composition of the dispersion, to be dried until free of water. A wet foam at a thickness of 0.5 mm, dried in a heating or convection oven with circulating air and at a temperature of +120 C., proved to be absolutely anhydrous and dry in 4.5 minutes. At the same temperature for a period of 1.5 to 2.5 minutes, the polyurethane foam layer contains less than 1.5 wt. % water.

[0094] It is advantageous to dry as completely as possible, preferably to freedom from water. The required temperature and time are empirically easy to determine. Since the water content of polyurethane dispersions or of the polyurethane foam is precisely known, it is also possible, for instance by weighing, to determine how much water has already evaporated during drying. In addition, freedom from water can be recognized if no disturbing vapor emerges during the structuring process.

[0095] It is also possible to determine the water content in the dried polyurethane dispersion or polyurethane dispersion compound when exposed to heat, by measuring the residual water content after different time intervals. It is thus easy to obtain a desired residual water content or to set the required temperature and delay time for it. Absence of water can also be obtained in this way, or the required parameters can be set for the process. Advantageously, water is completely or almost completely removed.

[0096] With certain applications, for example shoes, to avoid adverse effects to color pigments from polyurethane dispersions, the layer 2 can be reduced in the course of structuring, under pressure and heat, to a certain thickness. For this purpose, with the same polyurethane dispersion used for the polyurethane foam layer 2, an amount of equivalent weight is applied to the same area as foreseen for the foam, and the thickness of this comparative layer is determined. In structuring, the layer 2 is compressed to a thickness 2 to 18%, preferably 3 to 9%, greater than that of the comparative layer.

[0097] The reduction of the thickness of the layer 2 is mainly appropriate for sanded grain leather and substrate 1 made of microfiber nonwovens, used to make formatting or stamping parts for shoes whose surface is to be structured. The layer 2 is compacted, and thus the load capacity, abrasion resistance and the bending capacity of the layer 2 are improved. In addition, this serves to counteract the lightening of the foam or of the layer 2, which occurs during the foaming up of the polyurethane foam because of the increase in volume while the amount of dyes or pigments remains constant, and also color intensity and color homogeneity are ensured.

[0098] The shaping of the surface by means of heat and pressure and a negative matrix or negative embossing or roller, can also be carried out in a vacuum process, that is, by means of a low-pressure treatment. For example, porous embossing rollers or porous matrixes may be used, or the space between the pressure plates is emptied. Such pressing methods using vacuum or low pressure are known in the art.

[0099] In structuring the polyurethane foam or the layer 2, it is possible, according to the present teaching, to apply reinforcing and/or molded parts to the matrix 4 and/or the layer 2. In the pressuring process with the application of pressure and at elevated temperature, these parts are firmly bound to the layer 2 and, if present, to the layer 3. These reinforcements or molded parts can be designed as desired and can assume the shape of stripes, circles, stars, geometric or other figures, and so on. The most appropriate materials include plastic or all materials usable for the substrate 1, especially in the form of films or thin molded or stamped parts.

[0100] Particularly advantageous values for the layer 2 are obtained when the polyurethane foam is applied to the substrate 1 at a thickness of 0.070 to 0.250 mm.