Method for producing a composite material and a composite material

Abstract

The invention relates to a process for producing a coating film, optionally in the form of sheets or slabs, especially for the coating of a carrier layer (3), optionally textile materials and/or peelable polyurethane foams and/or a textile carrier layer (3), wherein the coating film (100) has an optionally multilayer upper layer (1) and a bonding layer (2) bonded thereto and optionally having multiple layers (2′, 2″) for bonding to the carrier layer (3). It is envisaged in accordance with the invention that the bonding layer (2) creates an uncrosslinked, polyurethane layer having thermoplastic properties and having a thickness between 0.080 and 0.500 mm, preferably between 0.200 and 0.500, especially between 0.120 and 0.180 mm, and is bonded to the upper layer (1), and the upper layer (1) is a polyurethane layer which has a one-layer or preferably two-layer structure with an outer layer (1′) and inner layer (1″) and does not have thermoplastic properties, or a non-thermoplastic polyurethane layer which is amorphous or has a predominantly amorphous structure, said polyurethane layer being thinner than the bonding layer (2).

Claims

1. A process for producing a composite material having an optionally multilayer upper layer, a bonding layer bonded thereto and optionally having multiple layers, and a carrier layer bonded to the bonding layer wherein: the carrier layer used is an optionally coated textile material or an optionally coated leather, and is bonded to the bonding layer; the bonding layer used is an uncrosslinked, thermoplastic polyurethane layer having a thickness between 0.080 and 0.500 mm, and is bonded to the upper layer; and, the upper layer used is a polyurethane upper layer which has a one-layer, or a two-layer structure with an outer layer and inner layer, does not have thermoplastic properties and has an amorphous structure, the polyurethane upper layer being thinner than the bonding layer; wherein the thermoplastic polyurethane bonding layer is applied to the underside of the upper layer or to the topside of the carrier layer; and, has a Kofler bench melting point between 95 and 165° C.; has a Shore A hardness between 70 and 98; is based on aliphatic and/or aromatic polyesterpolyurethane and/or polyetherpolyurethane having a crystalline or semicrystalline structure; contains up to 5% by weight of color pigments or is transparent; and, has fatigue bending characteristics according to DIN EN ISO 5402 of at least 125000 bending operations at standard temperature.

2. The process as claimed in claim 1, wherein the thermoplastic polyurethane bonding layer and the upper layer that has been bonded thereto are applied only to partial regions of the carrier layer which is optionally composed of multiple, optionally stitched pieces, or to the carrier layer in the form of a precut blank.

3. The process as claimed in claim 1, wherein the carrier layer used is a weave, knit, polyester nonwoven or coated leather.

4. The process as claimed in claim 1, wherein the upper layer is applied or attached to the thermoplastic polyurethane bonding layer bonded to the carrier layer, and in that a finish layer is optionally applied to this upper layer after embossment thereof.

5. The process as claimed in claim 1, wherein: textile materials that are free of silicones, waxes or separating agents; and/or, a laid scrim made of synthetic fibers having a basis weight between 5 and 20 g/m.sup.2 is embedded between the thermoplastic bonding layer and the upper layer; and/or, 4% to 20% by weight of flame-retardant additives, optionally aluminum hydroxide, are added to the thermoplastic polyurethane bonding layer and/or the upper layer; and/or, a finish layer having a maximum thickness of 0.010 mm and/or a multicolor print having a thickness of less than 0.010 mm is applied to the outer surface of the upper layer; and/or, the upper layer and the bonding layer are formed with a Shore A hardness which is equal or different by not more than 10%; and/or, the upper layer and an adhesive layer are formed together with a smaller thickness than the thermoplastic polyurethane bonding layer.

6. The process as claimed in claim 1, wherein, for formation of a leather substitute material, the upper layer is applied to a structured substrate, and the thermoplastic polyurethane bonding layer that has optionally already been bonded to the carrier layer is applied thereto, or in that a textile carrier layer in sheet format is bonded to the thermoplastic polyurethane bonding layer with supply of heat and pressure or by use of a contact or pressure-sensitive adhesive, and in that, on the topside thereof, direct coating is effected with a dispersion to form an upper layer which, after solidification, is embossed by removal of water by means of heat, at a temperature between 90 and 160° C. and under pressure, or by means of heat in a vacuum method.

7. The process as claimed in claim 1, wherein the thermoplastic polyurethane bonding layer is applied to the carrier layer together with the upper layer and the layers are bonded with application of heat and/or pressure.

8. The process as claimed in claim 1, wherein the water vapor permeability in the upper layer and the thermoplastic polyurethane bonding layer is adjusted with a laser in the upper layer and the thermoplastic polyurethane bonding layer.

Description

(1) FIG. 1 shows a schematic section through a composite material of the invention.

(2) FIG. 2 shows a top view of a precut blank that has been partly provided with a coating film of the invention.

(3) FIG. 3 shows a section through a composite material of the invention.

(4) FIG. 4 and

(5) FIG. 5 show a detail view of a precut blank with a coating film as usable for a car seat.

(6) FIG. 1 shows a section through an inventive composite material 200 having an upper layer 1, a bonding layer 2 and a carrier layer 3. The upper layer 1 may have multiple layers; it especially comprises two layers 1′ and 1″. The upper layer 1 is bonded to the bonding layer 2 via an adhesive layer 4, which can optionally also be dispensed with. The bonding layer 2 may have a one-layer or multilayer structure, advantageously with 2 layers 2′ and 2″. The carrier layer 3 is a layer of textile material, for example a weave, a knit or a nonwoven composed of polyester fibers. This textile material may comprise cotton fibers.

(7) The upper layer 1 is a layer of a crosslinked solidified polyurethane dispersion created from an aliphatic polycarbonatepolyurethane and/or polyesterpolyurethane and/or polyetherpolyurethane. The individual layers of the upper layer have essentially the same structure.

(8) The upper layer 1 is non-thermoplastic and advantageously thinner than the bonding layer 2.

(9) The bonding layer 2 is at least one polyurethane layer which is not crosslinked and has thermoplastic properties and may be bonded to the upper layer 1 by an adhesive layer 4, likewise composed of polyurethane.

(10) As shown in FIG. 1, a laser can be used to form, by corresponding removal of material, recesses 6, 6′ starting from the surface of the coating film 100 in the composite material 200. Recesses 6′ lead from the surface of the coating film 100 into the interior of the bonding layer 2. The recesses 6 pass through both the upper layer 1 and the bonding layer 2 and extend as far as the carrier layer 3 or into it; more particularly, they extend into the carrier layer 3 when, as shown in FIG. 3, it is filled with material of the bonding layer 2 in an edge region 20. These recesses 6, 6′ serve for passage of air and or water vapor.

(11) FIG. 1 shows in schematic form how a coating film 100 of the invention is placed on a carrier layer 3. FIG. 3 shows how the coating film 100 has penetrated partly into the carrier layer 3. This penetration region 20 results in an inextricable bond between the bonding layer 2 and the carrier layer 3. The upper layer 1 and the bonding layer 2 are bonded to one another either by a direct bond in the course of or after production thereof by means of heat and pressure or via the adhesive layer 4.

(12) FIG. 2 shows a composite material comprising two precut blanks 300 that are stitched to one another or bonded by a seam 110. Across the seam and in the adjoining regions of the two precut blanks 300, a coating film 100 of the invention has been applied, which covers the seam 110 and the parts of the precut blank that are highly stressed in the planned use in this region.

(13) FIG. 4 and FIG. 5 show a detail view of a composite material comprising a precut blank 300 which is covered with a coating film 100, and can form the backrest or seat area of a car seat. The coating film 100 in this case has been provided with different surface structures which may be formed on the template in the production thereof, on which the surface layer 1 or the outer layer 1′ of the surface layer 1 is formed. The application of the coating film 100 to the carrier layer 3 or the precut blank 300 does not disruptively alter the surface structure present, if at all.

(14) It is also possible to structure the precut blank 300 provided with the coating film 100 by hot pressing after bonding of the coating film to the precut blank 300, or to emboss a pattern by hot forming of the thermoplastic bonding layer 2. No change in gloss or fine structure of the upper layer 1 is possible after completion and crosslinking of the coating film 100 since the upper layer is a polyurethane layer that does not have thermoplastic properties, whereas the bonding layer 2 is a polyurethane layer having thermoplastic properties which has advantageously been formed from a pelletized polyurethane material by extrusion. However, the upper layer 1 fits elastically to the form of the bonding layer 2.

(15) For a car seat, it has been found to be advantageous when the bonding layer 2 has a thickness of 0.140 mm and the upper layer 1 a thickness of 0.075 mm. The upper layer 1 is non-thermoplastic and the upper layer 1 and the bonding layer 2 each have a hardness of 80 Shore A. The thin non-thermoplastic upper layer 1 in combination with the thermoplastic bonding layer 2 enables any configuration of the surface by hot embossment by means of an embossing roll. The upper layer 1 and the bonding layer 2 were bonded with an adhesive layer 4 of thickness 0.0080 mm. The bonding layer 2 of the coating film 100 penetrated into the carrier layer 3 by 60% of its thickness. Apart from the fact that the composite material 300 produced in this way has optimal use properties, it has fatigue bending characteristics of more than 160 000 bending operations at room temperature and adhesion between layers 2 and 3 of more than 15 N/cm, even after storage under water for 24 hours.

(16) The film of the invention is used, for example, for partial application or coating of textile carrier materials as used in cars. According to the invention, the layer 2 here has a preferred thickness between 0.10 mm and 0.18 mm and, on plastification by means of pressure and heat, depending on the structure of the textile carrier, penetrates into the carrier layer 3 preferably up 60% of its thickness. In the case of coarse-mesh or open weave structures, the layer 2 may also have a thickness of up to 0.25 mm and can be indented almost completely into the carrier layer 3.

(17) In the case of production of sheet material in which the coating film 100 fully covers the carrier layer 3, the bonding layer 2 may have a higher thickness, preferably between 0.2 mm and 0.5 mm.

(18) In the case of abrasion tests which have been undertaken in the same way for the textile material of the carrier layer 3 without coating and with the coating film 100 of the invention (FIG. 4 and FIG. 5), it has been found that, under the same stress, the textile material already had considerable roughening and worn sites, whereas the surface of the coating film 100 showed virtually no changes. FIG. 4 and FIG. 5 show a polyester weave as used for car seats. The weave has been partly covered with the coating film 100. The thermoplastic bonding layer 2 has a thickness of 0.1 mm and has penetrated into the textile carrier 3 to an extent of 90%. The upper layer 1 has a thickness of 0.065 mm. In a Taber abrasion test (DIN 53109, H18 friction wheel) that was conducted in such a way that half the friction wheel ran over the textile material 3 and half over the coating film 100 of the composite material, i.e. the coated part, the weave showed severe damage after 400 cycles, whereas the coated part has only a slight change in the degree of gloss, but otherwise remained undamaged.

(19) The film of the bonding layer 2 has a softening range from about 80 to 165° C. The film remains soft and pasty up to this temperature and is deformable or indentable by pressure; there is no occurrence of through-melting or mobile, free-flowing characteristics without pressure.

(20) It is advantageous for the invention that there is no change in the non-thermoplastic upper layer 1 at a temperature of 195° C., and likewise not in the carrier layer 3 or in the coating 3.1 either. With regard to their physical properties at 195° C., the behavior of these layers is similar to that at room temperature.

(21) It is a further object of the invention to create a composite material in sheet form or a synthetic leather with a PUR coating in which there are no difficulties with the REACH regulations and where occurrence of CO2 is low or zero.

(22) Problems with synthetic leathers having an outer PU layer, a voluminous middle layer and a carrier are caused by the middle layer which is formed from what are called PUR high-solids, PUR prepolymers or a PUR-forming reaction mixture. These materials are liquid to pasty masses. Consolidation of these masses requires temperatures of more than 100° C. This is not just a process disadvantage; the consolidated masses also cause problems with the REACH regulations and the CO2 regulations. These masses form the middle layer of the composite material, i.e. the layer between the textile carrier and the outer layer. Moreover, these masses are non-thermoplastic and thus can be formed only with difficulty by hot embossing.

(23) It is a further object of the invention to create, in a simple and economically viable manner, a material in sheet form that satisfies the REACH regulations, wherein the bond between the carrier layer 3 and the bonding layer 2 is significantly improved, as are the fatigue bending characteristics and the hydrolysis characteristics of the composite material. The surface 1 of the material can be configured as desired by hot embossing by means of an embossing roll, and thickness thereof can be completely or virtually completely maintained to this operation.

(24) According to the invention, a thermoplastic, extruded PU film is used as bonding layer 2. This film 2 is advantageously created from pelletized polyurethane material containing no emigratable substances. This film 2 is bonded to the carrier layer 3 in the heated state in which it is plastic and can flow under pressure, or after contact with a hot plate or roll, optionally with further application of heat and/or pressure.

(25) Contact heating lasts for between 10 and 30 seconds. This heating operation is of good suitability for precut parts, but comparatively uneconomic for the production of sheet material.

(26) It has been found that a film which is advantageously usable as bonding layer 2 can be made to melt or to bond to a textile carrier layer 3 by means of flame treatment, similarly to the case of flame lamination of a polyurethane foam, or by heating by means of infrared sources without contact with a hot plate or hot roll, i.e. indirectly, within a period of less than 2 seconds. As soon as the film has been plastified or made to melt, it can be bonded to the textile carrier layer 3, optionally by means of rolls.

(27) The penetration depth of the bonding layer 2 or film into the carrier layer 3 (FIG. 3) depends on the structure of the carrier layer 3 and on the temperature of the film and the associated tackiness and the melt viscosity. In addition, the penetration also depends on the pressure with which the film 2 is pressed onto or indented into the carrier layer 3.

(28) According to the invention, it may be the case that the bonding layer 2 or the film after extrusion thereof is placed onto or lies on a temporary, flexible carrier, optionally of thickness less than 1 mm, which advantageously has a higher melting point than the temperatures required or is unmeltable at these temperatures, for example a silicone rubber film, a Teflon film, a polyester film, a coated textile carrier material or a release paper. A material of this kind can be used as often as desired as carrier. From this temporary carrier, the softened film 2 is placed onto the carrier layer 3 and optionally pressed on.

(29) According to the invention, the thermoplastic bonding layer 2 may also at first be formed or produced separately from the non-thermoplastic upper layer 1 and then combined or bonded to the upper layer 1 which consists of an aqueous PUR dispersion or of PUR dispersion mixtures and is not meltable. In this case, it is possible to dispense with a temporary carrier, particularly when the upper layer 1 has a thickness between 0.06 and 0.12 mm and a hardness between 75 and 98 Shore A and hence can stabilize the softened bonding layer 2. The softened film 2 bonded to or coated with the upper layer 1 is placed onto the carrier layer 3.

(30) Advantageously, in the case of performance of such process steps, the film or bonding layer 2 has a thickness of 0.2 to 0.6 mm.

(31) It has been found that it is advantageous in accordance with the invention to use, as carrier layer 3, a textile material, preferably a knit or weave, especially consisting of polyester fibers, having a basis weight of 300 g/m.sup.2 and a thickness of 0.65 mm, and to bond it to a 0.4 mm-thick film as bonding layer 2 which has been heated to 125 to 145° C. by infrared irradiation. The film 2 penetrates between 0.05 and 0.25 mm into the carrier layer 3, or is indented to that degree. An adhesion of 22 N dry and of 18 N wet according to DIN ISO 11644 is achieved. Thus, in an economically viable manner, a firm bond is achieved between the bonding layer 2 and the carrier layer 3, and also an improvement in adhesion. A polyurethane dispersion mixture having a solids content of 40% to 60% by weight of polyurethane is applied as upper layer 1 to the bonding layer 2.

(32) Any PUR primer layer present with a thickness of less than 0.01 mm between the outer layer 1 and the bonding layer 2 is not taken into account in the judgement of layers or judgement.

(33) In the context of the invention, it is also possible first to bond the non-thermoplastic upper layer 1 to the thermoplastic bonding layer 2 and only then to bond the bonding layer 2 and the carrier layer 3.

(34) In this case, the upper layer 1 can be produced with the desired look and then processed, and may have one or two layers. The upper layer 1 may bear a thin, at best non-thermoplastic finish layer 25 of a PUR dispersion having a thickness of less than 0.01 mm.

(35) According to the invention, the film used as bonding layer 2, in the plastic, tacky state after leaving the extruder, may be combined with the desired ultimate carrier layer 3 by placing it on and optionally indented into the carrier 3 in the desired manner by means of one or more rolls optionally having an anti-adhesive finish on their surface. This procedure is not just economically advantageous; it also leads to inextricable bonds, particularly when the melting point of the film 2 is between 125 and 175° C., preferably between 135 and 155° C. The carrier layer 3 is advantageously a textile material, especially a knit or weave made of polyester fibers.

(36) As is well known, inexpensive thermoplastic PUR films based on aromatic polyester are not particularly hydrolysis-stable. According to the invention, however, inexpensive PUR films that have been created entirely or partly on the basis of aromatic PUR also lead to good hydrolysis stability of the finished composite material by providing the carrier 3 with a thin, hydrolysis-resistant coating 3.1 (FIG. 1) having a thickness of 0.05 to 0.3 mm. The hydrolysis-resistant coating 3.1 may consist of aliphatic polyurethane based on polyether or polyester, of polyacrylate, of a layer of mixtures of these two materials, of flexible PVC or of PVC-containing copolymers. This is particularly advantageous for textile material, especially having an open structure. The coating 3.1 prevents the penetration of the film 2 into the carrier layer 3. The coating 3.1 is dry and bonds to the heated film 2. The coating 3.1 consists either of solidified, optionally crosslinked PUR dispersions or PUR mixtures. It is advantageous when the film 2 has a partly crystalline structure. If the coating 3.1 consists of a polymer such as polyacrylate or of a PVC-containing copolymer, an appropriate primer is a thin PUR dispersion adhesive layer.

(37) It is advantageously possible to apply a thin primer layer of less than 0.01 mm of a PUR adhesive dispersion (not shown in the drawing) to the solidified coating 3.1 on the carrier layer 3. The bonding layer 2 can be applied in the manner described above to the carrier 3 thus precoated by plastifying the film or applying the still-soft film immediately after it has left the extruder.

(38) The thin coating 3.1 prevents or makes it difficult for moisture to reach the bonding layer 2 through the carrier layer 3. The upper layer 1 formed with high-quality PUR dispersions prevents the ingress of moisture from this side, and so the composite material does not undergo any significant change in its consolidation properties, if any, even after hydrolysis aging.

(39) It is particularly advantageous when the film 2 has a broad softening point and is not mobile even at the melting point, for example polyamide or polystyrene. At temperatures of 75 to 110° C., its surface does become tacky, but it requires pressure to bond with the layer 3. With increasing temperature, the film 2 becomes tackier and pastier. Before its respective melting point, it is at its tackiest and requires little pressure for bonding to the carrier layer 3.

(40) The invention is illustrated in detail by examples:

EXAMPLE 1 FOR A COMPOSITE MATERIAL AS SLAB MATERIAL

(41) An extruded TPU film 2 based on aliphatic polyester, having a Shore A hardness between 70 and 85 of 78 Shore A and a thickness of 0.4 mm, is heated at a temperature of 130° C. in a heating plate press and pressed at a pressure of 2 bar with a polyester knit as carrier layer 3 having a basis weight of 300 g/m.sup.2. The polyester knit contains 25% by weight of cotton fibers. At the temperature of 130° C., the TPU film becomes tacky and highly viscous/pasty. The pressure and the temperature are used to control the penetration depth into the carrier layer 3 and adjust them to the desired value of 45% of the thickness of the film 2. The residence time in the hot press is 10 to 20 s. After removal from the press, the composite material is dressed in the reverse process, meaning that the upper layer 1 which is then applied is created on a structured substrate, for example on a negatively structured silicone template, on a negatively structured release paper or on a laser-structured Teflon or polypropylene slab, and bonded to the film 2. All surface executions are possible, for example grain leather, velour leather, textiles or a technical appearance such as sandpaper.

EXAMPLE 2

(42) Pelletized TPU material is plastified in an extruder and extruded to a film from a slot and placed onto a textile carrier layer 3, for example onto a knit or weave, in the plastic state, and optionally lightly pressed on. The TPU film has a Shore A hardness of 82, which is thus between 70 and 98 Shore A. It consists of an aromatic polyesterpolyurethane, has a thickness of 0.45 mm and is 20%, optionally 5% to 25%, of its thickness incorporated into the carrier layer 3. On the side opposite the textile carrier 3, the film 2 is bonded to the upper layer 1 which has been formed from a non-thermoplastic polyesterpolyurethane dispersion. The upper layer 1 has a thickness of 0.08 mm and a Shore A hardness of 88. This upper layer 1 is applied to the film 2 by direct application by means of knife-coating or spraying and, after consolidation, it is embossed. For this purpose, it is heated and receives the desired structure with an embossing roll. Optionally, the embossing roll itself has been heated to a temperature between 100 and 180° C. The thin, non-thermoplastic coating can be embossed efficiently by means of heat and pressure in combination with the thicker thermoplastic bonding layer 2.

EXAMPLE 3

(43) A polyester knit of weight 250 g/m.sup.2 with an open knit structure is provided with a thin coating 3.1 having a thickness of 0.05 mm. The coating 3.1 consists of a solidified polyurethane dispersion having a solids content of 50% by weight. The coating 3.1 also contains 40% by weight of polyacrylate having a solids content of 50% by weight. This layer has penetrated into the carrier layer 3 by 0.07 mm, i.e. between 0.05 and 0.1 mm. After it has solidified, it is bonded to the TPU film having a thickness of 0.4 mm in such a way that the TPU film 2 is heated to a temperature of 145° C. by means of infrared rays and the two parts are combined at this temperature. After cooling, the composite material can be provided with the upper layer 1 either directly or indirectly (reverse process).

(44) The most economically viable method is to create the TPU film by extrusion and to combine it, in the still-plastic state, with the carrier 3 desired in each case.

EXAMPLE 4

(45) Leather, especially split leather, is provided in accordance with the invention with a coating 3.1 of maximum thickness 0.15 mm, onto which the TPU film 2 provided with the upper layer 1 is then thermally ironed. This procedure is particularly suitable for safety and athletics footwear.

(46) The TPU film 2 in combination with the non-thermoplastic upper layer 2 has excellent fatigue bending properties at sub-zero temperatures. The composite material is also extremely abrasion-resistant. 4000 cycles in the Taber method for wear resistance with H18 friction wheel (DIN EN ISO 17076-1) are fulfilled easily, whereas conventionally dressed leathers do not withstand more than 400 cycles.

(47) This invention is of particular interest for Tier 1, which manufacture interiors for cars, trucks and buses, especially seats, where textile materials are subject to severe wear at sites under stress.