SYNTHETIC LEATHER AND METHOD FOR MANUFACTURING SYNTHETIC LEATHER

Abstract

The present disclosure relates to a multilayer synthetic leather, at least comprising a textile arrangement; and a polyurethane based foam; wherein the polyurethane-based foam is partially fixed to the textile arrangement using a first fixing layer such that the first fixing layer has fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane.

Claims

1. A multilayer synthetic leather, at least comprising a textile arrangement; and a polyurethane based foam; wherein the polyurethane-based foam is partially fixed to the textile arrangement using a first fixing layer such that the first fixing layer has fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane.

2. The synthetic leather according to claim 1, wherein the first fixing layer is applied in a punctiform manner, in the form of rhombusses or in the form of bars.

3. The synthetic leather according to claim 1, wherein the first fixing layer is applied in an amount of ≥2 to ≤50 g/m.sup.2, in particular ≥10 g/m.sup.2 to ≤20 g/m.

4. The synthetic leather according to claim 1, wherein the textile arrangement consists of a textile layer.

5. The synthetic leather according to claim 1, wherein the textile arrangement comprises a textile layer and a water-impermeable membrane, the water-impermeable membrane being partially fixed to the textile layer using a second fixing layer in such a way that the second fixing layer comprises fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane.

6. The synthetic leather according to claim 1, wherein further a top layer is provided on the polyurethane-based foam.

7. The synthetic leather according to claim 6, wherein the top layer is at least in part formed from a particularly aliphatic polyester-polyurethane dispersion.

8. The synthetic leather according to claim 1, wherein at least one of the first fixing layer and the second fixing layer is formed at least partially from a hot-melt adhesive or from a particularly aliphatic polyester-polyurethane dispersion.

9. The synthetic leather according to claim 1, wherein the polyurethane based foam comprises a silicone.

10. The synthetic leather according to claim 1, wherein the polyurethane-based foam has a solid content of ≥40% by volume, preferably in a range from ≥40% by volume to ≤70% by volume.

11. A method of manufacturing a multi-layer synthetic leather according to claim 1, comprising the steps of: a) Providing a support; b) Optionally, applying a top layer to the support; c) Applying a polyurethane-based foam to the support or, if a top layer is present on the support, to the top layer; d) Partially applying a first fixing layer to the polyurethane-based foam or to a textile arrangement to form fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane; e) Applying the textile arrangement to the polyurethane-based foam; and f) Removing the support.

12. A method of manufacturing a multi-layer synthetic leather according to claim 1, comprising the steps of: g) Providing a textile arrangement; h) Providing a polyurethane based foam; i) Partially applying a first fixing layer to the polyurethane-based foam or to the textile arrangement to form fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane; j) Assembling the polyurethane-based foam and the textile arrangement; and k) Optionally, applying a top layer to the polyurethane-based foam.

13. The method according to claim 11, wherein the first fixing layer is applied in process step d) or in process step i) by using a screen printing process.

14. The method according to claim 11, wherein the support is a grained backing paper.

15. The method according to claim 11, wherein the method comprises the further step of: I) hydrophobizing at least one of the top layer and the foam.

16. The method according to claim 12, wherein the first fixing layer is applied in process step d) or in process step i) by using a screen printing process.

17. The method according to claim 12, wherein the method comprises the further step of: I) hydrophobizing at least one of the top layer and the foam.

Description

DRAWINGS

[0120] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0121] The disclosure is further explained below by means of the figures and an example of producing the synthetic leather.

[0122] FIG. 1 schematically shows a sectional view of a first embodiment of a synthetic leather;

[0123] FIG. 2 schematically shows a sectional view of a further embodiment of a synthetic leather;

[0124] FIG. 3 schematically shows a sectional view of a further embodiment of a synthetic leather;

[0125] FIG. 4 schematically shows a process step for the production of a synthetic leather;

[0126] FIG. 5 schematically shows a further process step for the manufacture of a synthetic leather;

[0127] FIG. 6 schematically shows a further process step for the manufacture of a synthetic leather;

[0128] FIG. 7 schematically shows a further process step for manufacturing a synthetic leather; and

[0129] FIG. 8 schematically shows a further process step for the production of synthetic leather.

DETAILED DESCRIPTION

[0130] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0131] FIGS. 1 to 3 show different designs of a synthetic leather 10. Methods and respectively process steps for the production of these designs are shown in FIGS. 4 to 8.

[0132] FIG. 1 shows an embodiment of a multi-layer synthetic leather 10, which has the following structure. The synthetic leather 10 according to FIG. 1 comprises a textile arrangement 12, which can serve in particular as a carrier layer. The textile arrangement 12 consists of a textile layer 14, which is selected from the group consisting of a woven fabric, a knitted fabric, crocheted fabrics, a non-woven fabric or even a 3D spacer fabric. In this context, the present disclosure may in principle include the use of the textile materials described above not only in isolation but also as a suitable mixture comprising at least one of the above examples.

[0133] In addition to the textile arrangement 12 or respectively the textile layer 14, the synthetic leather 10 comprises a polyurethane-based foam 16 which is especially designed as impact foam. The polyurethane-based foam 16 may have an impact foam density in the range of 200-700 g/l, but is not strictly limited to this. It is also provided that the polyurethane-based foam 16 is present on the surface and is provided with a structure 18.

[0134] In particular, in order to obtain particularly preferred mechanical properties, it is also provided that the polyurethane-based foam 16 also contains a silicone.

[0135] FIG. 1 further shows that the polyurethane-based foam 16 is partially fixed to the textile arrangement 12 using a first fixing layer 20 in such a way that the first fixing layer 20 provides fixing areas 22 formed by a fixing agent and free areas 24 free from the fixing agent in the same plane. In particular, it is provided that the first fixing layer 20 is applied in a punctiform manner and thus the fixing areas 22 are punctiform. This allows that a comparatively small amount of fixing agent can be used, for example in an amount of 2-50 g/m.sup.2, in particular 10 g/m.sup.2 to less than or equal to 20 g/m.sup.2.

[0136] The fixing agent can preferably be a polyurethane-based hotmelt adhesive, which can also be called a hotmelt in the technical field.

[0137] FIG. 2 shows an embodiment of a synthetic leather 10 which essentially corresponds to the embodiment in FIG. 1, which is why the differences are discussed in particular.

[0138] In the design according to FIG. 2 it is provided that the textile arrangement 12 does not consist of a textile layer 14, but that the textile arrangement 12 comprises a textile layer 14 and a water non-permeable membrane 26, whereby the water non-permeable membrane 26 is partially fixed to the textile layer 14 using a second fixing layer 28 in such a way that the second fixing layer 28 provides fixing areas 30 formed by a fixing agent and free areas 32 free from the fixing agent are provided in the same plane. With regard to the arrangement of the second fixing layer 28, reference can essentially be made to the design of the first fixing layer 20.

[0139] In summary, the membrane 26 can provide a particularly effective watertightness and can be freely selected according to the respective requirements. Polymer-based membranes may be preferred here. For example, polyether ester (PES), polytetrafluoroethylene (PTFE), and polyurethane (PU) can be processed into membranes and are particularly effective here.

[0140] The embodiment shown in FIG. 3 is again similar to the embodiment shown in FIG. 1, which is why the differences are again essentially discussed.

[0141] In the embodiment shown in FIG. 3, it is provided that on the polyurethane-based foam 16, additionally a top layer 34 is provided. The top layer 34 can, for example, be formed at least partially from a polyester-polyurethane dispersion, especially an aliphatic one. It is shown here that structure 18 is incorporated in the top layer 34 and the top layer 34 forms the most upper or outermost layer. Accordingly, the mechanical requirements to the polyurethane-based foam 16 can be reduced, so that it does not need to contain any additives, such as silicone in particular.

[0142] The production of a synthetic leather 10 as described before is described in the following figures. The production of a synthetic leather 10 is preferably carried out according to the following method or respectively the following steps:

a) Provision of a support 36;
b) optionally, applying the top layer 34 to the support 36;
c) applying the polyurethane-based foam 16 to the support 36 or, if a top layer 34 is present on the support 36, to the top layer 34;
d) partially applying the first fixing layer 20 to the polyurethane based foam 16, thereby forming fixing areas 22 formed by a fixing agent and free areas 24 free from the fixing agent in the same plane;
e) applying the textile arrangement 12 to the polyurethane-based foam 16 partially provided with the first fixing layer 20; and
f) removing the support 36, in particular immediately after process step c).

[0143] From the above it is thus clear that the process is a so-called reverse process in which the synthetic leather 10 is built up from the most upper layer or respectively the outermost layer to the innermost layer or respectively carrier layer.

[0144] With regard to the arrangement of the individual layer or layers, it is referred to the description relating to the synthetic leather 10.

[0145] FIG. 4 shows the application of the polyurethane-based foam 16 is applied to the support 36, which can be a grained underlay paper, for example, for inserting a structure. The polyurethane-based foam 16 can, for example, be applied by a squeegee 38 in a coating process. This creates a layer sequence 40 with the support 36 and the polyurethane-based foam 16, which can be dried and cured preferentially. Now the support 36 can be removed again.

[0146] The layer sequence 40 can then run along an application device 42 in order to partially apply the fixing agent, such as a hot melt, to the polyurethane-based foam 16. For this purpose, the layer sequence 40 can be guided through rollers 44 and passed along the application device, 42 which has a perforated grid 46 through which the fixing agent can be applied to the polyurethane-based foam 16 punctually. This is shown in FIG. 5.

[0147] Afterwards, which is not shown in detail in the figures, the textile arrangement 12, for example the textile layer 14, can be placed on the fixing agent and thus bonded with the polyurethane-based foam 16.

[0148] Furthermore, as shown in FIG. 6, the resulting layer sequence 50 can in turn be guided by rollers 48 through a bath 52 with a hydrophobic liquid 54 to make the layer sequence 50 hydrophobic. This can be done on one side, for example, to make only the top layer 34 or the foam 16 hydrophobic. This process step can also be described as padding.

[0149] Hydrophobing can also be carried out, for example, by treating a composite of top layer 34 and foam 16 or only foam 16 with a hydrophobic liquid 54 in an immersion process using a bath 52 with a hydrophobic liquid.

[0150] FIG. 7 also shows a two-pass coating arrangement. In this case, a top layer 34 is first applied to the support 36. This in turn can be done by means of a squeegee 38, which distributes the corresponding material to a suitable thickness on the support 36, which in turn may be designed as grained underlay paper, for example.

[0151] Then, as already described above, the polyurethane-based foam 16 can be applied, again by means of a squeegee 38. In the embodiment shown here, however, this can be done by applying the foam 16 to the top layer 34.

[0152] Then, the layer sequence 50, as described above and shown in FIG. 8, can pass along an application device 42 to partially apply the fixing agent, such as a hot melt, to the polyurethane based foam 16. For this purpose, the layer sequence 50 can be guided by rollers 44 along the application device 42, which has a perforated grid 46 through which the fixing agent can be applied to the polyurethane-based foam 16.

[0153] Then, which is not shown in detail in the figures, the textile arrangement 12, for example the textile layer 14, can be placed on the fixing agent and thus bonded to the polyurethane-based foam 16. Now, the support 36 can be removed again.

Example

[0154] An example is described below by which a multilayer breathable synthetic leather 10 can be produced, wherein the synthetic leather 10 has a carrier layer of a textile fabric or textile arrangement 12 on which a foam 16 based on a polyurethane and designed as a porous impact foam is arranged. The impact foam is fixed to the textile arrangement 12 as a two-layer laminate by a PUR hot-melt adhesive.

1. Paste Production for the Polyurethane Based Impact Foam

[0155] The paste is produced in a preparation vessel with a stirring dissolver. A polyurethane dispersion is provided and additives are added according to the recipe (additive 1: aqueous silicone emulsion; additive 2: polyhydrogenmethylsiloxane as crosslinking component 1). Further additives: ammonium stearate as foam stabilizer; dispersion of an oxime blocked polyisocyanate cationic/nonionic as crosslinker component 2; HDMI trimer (alternative product: a mixture of MDI and TDI, dry content approx. 30%. Contains 2.5-3.0% blocked isocyanate); melamine resin mixture crosslinker component 3; any arbitrary dispersion.

[0156] The pH is adjusted with 25% ammonia solution to a pH of 9. Thickening was further conducted with an aqueous solution of an acrylic copolymer up to a viscosity of 45 [dPas], with a tolerance of +5/−10. The paste obtained is then pre-filtered by a membrane pump with a 100 μm filter into another preparation vessel.

2. Foaming of the Paste with a Foaming Unit

[0157] The previously obtained paste, which can also be called compound, is now fed through a foaming unit. This is adjusted to the specified parameters, such as in particular compressed air, rotation speed, foam weight and delivery rate. When the filtered compound reaches the feed pump in the mixer, foam production begins in the mixing head. The pre-flow is collected in the container provided. After the consistency of the foam 16 has become even, the litre weight of the foam 16 is weighed and if the result is correct, the application hose is attached to the spreading head and after reaching the template (certain amount before the knife) the production starts.

[0158] The following parameters should be observed in this example: The viscosity of the applied coating mass before foaming should be 45 [dPas], with a tolerance of +5/−10. The foam litre weight of foam 16 should be set to 600 [g/l], with a tolerance of +/−30.

3. Spreading the Paste/Foam 16

[0159] The paste/foam 16 is spread by means of a squeegee roller system in a so-called reverse process onto a grained release paper support 16. The graining can be selected arbitrary depending on the manufacturer.

[0160] The support is adjusted via the gap thickness to the counter roller or release paper.

[0161] Target layer (dry): 200±15 g/m.sup.2

[0162] 3.1 Drying+Condensation of the Paste in the Drying Channel

[0163] The drying of the paste/foam 16 takes place in a channel with several separately adjustable temperature zones.

[0164] A temperature window of 70 to 110° C. is passed through. The condensation, complete cross-linking, of the coating takes place in a second drying channel with several separately adjustable temperature zones. Here, a temperature window of 150 to 190° C. is passed through.

[0165] The dwell time of the coating in the second channel is decisive for complete cross-linking of all fixing components. The dwell time is controlled by the material speed of the coating system.

[0166] The drying process and condensation process are decisive for the formation of a fine foam structure in the coating. Partial bursting of the mechanically foamed foam structure results in a partially open-pored coating. This specifically controlled open porosity must be evenly distributed over the entire layer of the coating.

[0167] After passing the coating over the chill rolls, the coating is delaminated from the release paper in the outgoing section and wound onto a cardboard core as a semi-finished foam film or respectively as a semi-finished product.

[0168] Test samples are taken from the ready assembled rolls. These are tested as foam film in the test laboratory with regard to the coating, MVTR value, WVP value, abrasion and foam structure.

[0169] Grammage [g/m.sup.2]: 200 with a tolerance of +/−15; WVP [mg/cm.sup.2/h]: >10; MVTR [g/m.sup.2/24 h]: >5,500; abrasion resistance Martindale [tours] >50,000

4. Lamination of the Semi-Finished Foam Foil by Means of Screen-Print Technology

[0170] To produce the synthetic leather 10, the foam foil is bonded to the textile using screen-print technology (screen-print application of the adhesive/hotmelt). The screen-print technology involves doctoring the molten adhesive through a hole template on foam foil. Under pressure the textile carrier is joined to the coated foam foil. Due to the different hole templates, very precise adhesive applications can be achieved.

[0171] For the production of the synthetic leather/laminate, adhesive applications in the range of approx. 10-20 g/m.sup.2 are realized. Due to the technology-related low adhesive layer and an optimal distribution of the adhesive, the breathability of the coating is only minimally affected.

[0172] Adhesive technology: PUR-Holtmelt (polyurethane hot-melt adhesives which cross-link with air humidity) The products were specially developed for textile lamination, e.g. for bonding woven and non-woven fibres with PVC, polyester, polyurethane and polyetheramide films. The setting time depends on the application temperature, amount of adhesive, type of substrate, temperature of the substrate and ambient conditions.

[0173] Chemical Basis: PUR Prepolymer

[0174] Consistency: solid; density: approx. 1.10 g/cm.sup.3; melt viscosity (Brookfield). The production of the synthetic leather 10 via screen-print technology offers a unique possibility to vary the textile substrates or respectively the textile layers 14. In this way, a foam film batch can be bonded to a wide variety of textile substrates.

[0175] As an option, the textile or respectively textile layer 14 can also be bonded in advance with a breathable membrane to form a 2-layer laminate, so that the finished synthetic leather/laminate not only has high breathability but also a high water column. The membrane system can be freely selected according to the respective requirements. Polymer-based membranes are the most widely used membranes. Mainly polyether ester (PES), polytetrafluoroethylene (PTFE), and polyurethane (PU) are processed into membranes.

[0176] After an appropriate cross-linking time of the PUR adhesive, the laminates are prepared for hydrophobing on the stenter frame. The last process step 6] should be seen as optional to improve the water repellency of the synthetic leather.

5. Hydrophobing by Means of Finishing on a Stenter Frame

[0177] In the optional last operation, the synthetic leather 10/laminate is not dipped, as is usual for textiles, but rather padded unilaterally. Due to the small amount of fleet used, padding is one of the minimum application methods. Guide rollers guide the fabric web past a rotating roller. The padding roller is immersed and thus the fleet is entrained on the surface of the roller and released on one side to the surface of the foam 16. This operation is carried out by a stenter frame with separately adjustable temperature zones. Afterwards the finished synthetic leather 10 is wound on a dawl and made available to the fabric inspection.

[0178] Hydrophobing can be done with fluorocarbons or FC-free DRWs.

[0179] Subsequently, the fabric is inspected or respectively visually inspected and quality checked in the test laboratory, whereby the following values were achieved:

[0180] WVP (mg/cm.sup.2/h): >9 (without membrane 11.5-15.0, especially >7, with membrane 2.54-9.0, especially >2); MVTR (g/m.sup.2/24 h): >4.500 (without membrane 3.350 to 4.500, especially >2.000, with membrane 1.600-3.750, especially >1.000); abrasion resistance (tours): 55.000; spray test 80.

[0181] The following standards were used for the tests: [0182] Air permeability: EN ISO 9237 [0183] Determination of resistance to penetration by water/Hydrostatic pressure test: DIN EN 20811 [0184] Non-commercial washing and drying methods for testing textiles: DIN EN ISO 6330 [0185] Water vapour permeability: DIN EN ISO 15496 (MVTR [g/m.sup.2 24 h]; Moisture Vapor Transmission Rate (MVTR), also called Water Vapor Transmission Rate (WVTR) [0186] Water vapour permeability: DIN EN ISO 14268:2013 (WVP [mg/cm.sup.2 h]) [0187] Seam sealing: EN 343 20811 [0188] Abrasion: DIN EN ISO 12947-2 [0189] Continuous buckling behaviour: DIN 53359 [0190] permanent bending strength: DIN EN ISO 32100 [0191] Spray test—Determination of the water repellent properties (spray method) of textiles: DIN EN ISO 4920

[0192] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are inter-changeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.