Patent Application
20220090315
The present disclosure relates to a multi-layer organic solvent-free synthetic leather. The present disclosure further relates to a method by which such a synthetic leather can be produced.
This section provides background information related to the present disclosure which is not necessarily prior art.
Synthetic leather and generally multi-layered textile structures are widely used and have a wide range of applications. Non-restrictive examples include, for example, the use in the interior construction of motor vehicles.
Synthetic leather is usually made up of a multi-layer non-breathable structure based on polyurethane or polyvinyl chloride. Water vapour permeable synthetic leathers are usually based on a microporous layer, which is achieved by sudden or selective evaporation of solvents. Impact foams based on polyurethane dispersions are also permeable to water vapor, but these materials are not suitable for use with shoe uppers because they do not have sufficient abrasion resistance.
EP 1 887 128 B1 describes a process for the production of a breathable multilayer synthetic leather with a carrier layer of a textile fabric, at least one intermediate layer based on an at least partially open-cell polyurethane impact foam applied to the carrier layer and a top layer based on a polyurethane applied to the at least one intermediate layer, wherein in a first step the top layer is applied to a removable base and consolidated, then the at least one intermediate layer is applied to the top layer and then the carrier layer is placed on top of the at least one intermediate layer and the base is detached from the top layer, wherein an aqueous aliphatic polyurethane dispersion in liquid form is applied to the substrate to form the top layer, and immediately after the application of the polyurethane dispersion the water content of the latter is evaporated by the application of heat within a time interval of less than 5 s, so that the polyurethane dispersion dries on the substrate without forming a film, forming the top layer with micropores.
EP 2 918 629 A1 describes a process for the production of a breathable film based on polyvinyl chloride (PVC), comprising the steps of: 1. providing a pasty mass comprising a first fraction of PVC and a second fraction of a foreign material and a third fraction of auxiliary materials and additives which are mixed together to form the pasty mass, 2. Applying the pasty mass to a substrate, 3. drying and gelling the pasty mass applied to the substrate while supplying heat to the film, whereby pores are formed which proceed from one surface of the film to the other surface of the film, which give the film breathability.
CN 105 951 466 describes water-based screen-touch glove leather and a manufacturing process therefor. The water-based screen-touch glove leather comprises base fabric, and the base fabric is coated with an underlayer and a surface layer, wherein a slurry of the underlayer is prepared by stirring the following raw material components in parts by weight: 100 parts of water-based polyurethane resin, 0.4-1 part of a water-based thickener, 0.3-0.7 part of a defoamer, 0.5-2 parts of a flat former, 0.2-2 parts of a catalyst, and 0.5-5 parts of a hardener; the slurry of the top coat is prepared by stirring the following raw material components in parts by weight: 100 parts of the aqueous polyurethane resin, 2-18 parts of the water-based color paste, 0.5-3 parts of a water-soluble dispersant, 5-15 parts of screen touch powder, 0.4-2 parts of the water-based thickener, 0.2-1 part of the defoamer, and 0.5-2 parts of the flat former. According to the water-based screen-touch glove leather, the screen-touch glove leather is incorporated into the slurry of the surface layer of the glove leather so that the water-based screen-touch glove leather has good conductivity; water-based screen-touch gloves made of the water-based screen-touch glove leather can be used on a touch screen electronic product; the touch screen electronic product can be used by a user wearing the water-based screen-touch gloves.
DE 27 54 603 A1 describes a process for the solvent-free coating of substrates, in particular leather, split leather and textiles, with the aid of a film which is composed of a high-melting layer, a low-melting layer and optionally an additional intermediate layer.
DE 10 2013 021 148 A1 concerns a leather substitute material comprising an upper layer which is external in use, a middle layer bonded thereto and a lower layer bonded thereto. Accordingly, it is provided that the upper layer is formed from a consolidated, cross-linked PU dispersion based on aliphatic polyester and/or polyether, that the middle layer is formed from a knitted fabric or a woven fabric made of polyester fibres, that the knitted fabric or woven fabric has a weight per unit area of 190 to 420 g/m2 and a thickness of 0.30 to 0.60 mm, that the lower layer is formed from a foamed plastic, which has been applied to the middle layer in liquid or pasty form, that both the upper layer and the lower layer are incorporated in the middle layer in a thickness of at least 0.050 mm and are inseparably bonded to the middle layer, and that a layer is formed in the middle layer with a thickness (D) which is free from the plastics used in the upper layer and the lower layer.
WO 02/33001 A1 describes a process for producing a synthetic leather, in which a composition comprising an anionic or cationic aqueous polyurethane dispersion, a water-repellent agent, an emulsifier, a defoamer and an inorganic filler is impregnated into a substrate and applied to the substrate, the impregnated and/or coated substrate then being coagulated to form a synthetic leather which is internally provided with numerous closed cells and has a smooth surface. The aqueous polyurethane-based synthetic leather is obtained by impregnating a composition comprising 100 parts by weight of an aqueous polyurethane dispersion, 0.1 to 5 parts by weight of a water-repellent agent, 0.1 to 8 parts by weight of an emulsifier, 0.1 to 1 part by weight of an antifoam and 0.1 to 5 parts by weight of an inorganic filler into a substrate, coating the foamed or defoamed composition on the substrate and coagulating the coated substrate with a coagulating solution, wherein an aqueous polyurethane dispersion is covalently bonded to anionic groups including carboxyl groups or sulfonate groups or cationic groups including a tertiary amine group, wherein the coagulation solution is selected from the group consisting of an aqueous solution of different salts, a mixed solution of salt and acid, a mixed solution of salt and base, a mixed solution of acid and base, and mixtures thereof.
However, in the state of the art there is still a need for variations of a synthetic leather, whereby the synthetic leather has a high mechanical stability and is still very breathable.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
It is therefore the object of the present disclosure to at least partially overcome the disadvantages known from the prior art. In particular, it is the object of the present disclosure to provide a possibility by which especially a synthetic leather has a high mechanical stability and is still very breathable.
Subject-matter of the present disclosure is a multilayered synthetic leather, comprising at least
a textile arrangement; and
a polyurethane-based foam;
wherein
the polyurethane-based foam is partially fixed to the textile assembly 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 and thus particularly in the plane of the fixing areas.
Such a synthetic leather has significant advantages over state-of-the-art solutions. In particular, this type of synthetic leather can be particularly breathable and still have a high mechanical stability.
For the purposes of the present disclosure, breathability is understood to mean the water vapour permeability of an especially textile material. In general, the better the water vapour transmission rate, the more pleasant the microclimate for the user of the synthetic leather. It is advantageous for the synthetic leather to have a breathability that lies in a range of up to 1000 g/m2/24 h or above, for example in a range of up to 10000 g/m2/24 h or even above, whereby the upper limit can be technically limited by the synthetic leather. “The breathability of functional textiles is generally determined by the MVTR value (Moisture-Vapor-Transmission-Rate-Value), which describes the water vapor permeability, and/or by the RET value (Resistance-Evaporating-Heat-Transfer-Value), which describes the water vapor transmission resistance. If the present disclosure were to be evaluated with regard to its breathability according to the standard DIN EN 343:2010-05 Schutzkleidung—Schutz gegen Regen, a RET value of up to class 4 can be achieved.
In particular, a synthetic leather is understood to be a textile multi-layer arrangement which is similar to real leather in its appearance and/or haptics, especially in both the appearance and the haptics.
Synthetic leather can be used in various areas of leather goods, for example for bags, clothing fabrics, such as coats or jackets, for furniture, such as seating furniture, for example sofas, for home textiles, or also for automotive interiors, for example vehicle seats, or also for sports articles. However, the synthetic leather described here is particularly suitable as a material for shoes, for example as shoe uppers.
The synthetic leather described here has the following configuration or layer structure. In particular, at least one of the layer structure and the substances used in the layer structure, or a combination of the layer structure and the substances present in it, may have beneficial effects compared with state-of-the-art solutions.
First of all, the synthetic leather or its layered structure comprises a textile arrangement. This textile arrangement can basically be designed as desired and is preferably adapted to the desired area of application, as described above without restriction.
As an example, the textile arrangement may have such a textile layer, 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.
Furthermore, it may be provided that the textile arrangement or a textile layer contained therein is based on natural fibres or also on artificial or synthetic fibres. The specific selection of the fibres for the textile layer can again be made in a way that is easily understandable for the person skilled in the art based on the specific desired application.
The advantage of using a textile can be seen, for example, in the fact that this layer gives the entire layer structure or the synthetic leather an extraordinarily high mechanical stability. This stability can be given especially with regard to a good tensile strength and also a good tear resistance.
A further advantage of a textile layer, especially as a carrier layer in the layer structure of the synthetic leather, can also be seen in the fact that by providing a textile layer, a textile feel of the synthetic leather can be achieved, which can significantly improve the acceptance of the synthetic leather.
Finally, the textile layer makes it possible not to deteriorate the elasticity and breathability provided by the other layers of the layer arrangement, or even to make this possible.
From the above it is thus clear that the provision of a textile arrangement comprising in particular at least one textile layer, in particular as a carrier layer in the layer structure, retains the positive properties of the other layers and can also enable further positive properties.
Furthermore, the synthetic leather or the layer arrangement of the synthetic leather comprises a polyurethane-based foam, which can be designed or manufactured as impact foam in particular. For the purposes of the present disclosure, a polyurethane-based foam is to be understood in particular as such a layer which is porous and thus allows water vapour or gases to pass through and is thus breathable. In addition, polyurethane-based shall mean that the foam may consist of polyurethane or at least shall contain polyurethane. For example, the polyurethane-based foam can have a silicone, as described in more detail below.
Basically, the polyurethane-based foam can be in different grammages and/or in different foam litre weights or in different porosities. The specific selection of the polyurethane-based foam used can in turn be made by the person skilled in the art in a suitable manner, especially depending on the specific application of the synthetic leather.
The provision of a foam in the layered structure or in the synthetic leather, in particular in the form of impact foam, may have the advantage, for example, that an elastic basic structure is obtained. This is necessary for many areas of application, so that the provision of a foam can improve the range of applications.
In addition, a foam can also improve the grip or provide a particularly advantageous feel, which can come very close to the feel of real leather.
Furthermore, by providing a foam it is possible to create a structure on the outer surface of the synthetic leather or the layer structure which is very similar to the structure of real leather, which can further improve both the look and the feel of the synthetic leather.
The foam can ensure that the required elasticity on the one hand and the mechanical resistance, in particular abrasion resistance, of the synthetic leather on the other hand, is achieved or the foam may at least can contribute to this.
Another advantage of polyurethane as a base material for the foam is that the foam as such can already exhibit good mechanical resistance without further additives.
In an embodiment with a top layer, as described in more detail below, it may also be preferable for the foam to have no structure, as the top layer is usually the top layer and therefore the layer which is seen when using the synthetic leather and therefore the top layer may have a structure. The incorporation of the structure into the top layer or even the foam can be achieved, for example, by producing the synthetic leather in a reverse process as described below and applying the top layer or the foam to a structured removable base as described below. Alternatively, the structure can be embossed into the top layer.
It is clear from the above that especially the provision of a polyurethane-based foam can be especially beneficial in achieving the desired properties for a synthetic leather.
At the synthetic leather as described here it is further provided that the polyurethane-based foam is partially fixed with the textile arrangement using a first fixing layer in such a way that the first fixing layer has fixing areas formed by a fixing agent and free areas free of the fixing agent in the same plane.
Thus, contrary to the solutions of the state of the art, at the synthetic leather described here it is not intended that a fixing layer, such as basically an adhesive layer, which connects the foam with the textile arrangement, is applied over the entire surface of the foam or the textile arrangement or is present between the textile arrangement and the foam, but rather that the fixing layer or the fixing agent forming it should only be partially provided. As a result of the only partial provision of the fixing agent, fixing areas may thus be present on one side. These fixing areas are areas in which a fixing agent forming the fixing layer is present. In these fixing areas, the foam is thus connected or bonded to the textile arrangement.
Furthermore, there are free areas in the same plane and thus in particular in a plane which is stretched by the width and length of the layer arrangement of the synthetic leather and which is perpendicular to the thickness of the synthetic leather. These free areas are characterised by the fact that no material forming the fixing layer is provided in these areas. This means that in the free areas the foam is in direct contact with the textile arrangement.
In particular this arrangement can offer significant advantages over state-of-the-art solutions.
In particular, the breathability and thus the water vapour permeability can be significantly improved by the only partial provision of a fixing layer, especially compared to the provision of a full-surface application of a fixing layer such as an adhesive layer. This is because in the free areas, for example, water vapour can easily pass from the textile arrangement into the foam, and there is no inhibition by the fixing layer.
In addition, the strength of the textile assembly and the foam against each other cannot be significantly deteriorated, since the fixing layer or the fixing agent forming the fixing layer can be selected with respect to positive fixing properties, for example with respect to positive adhesion properties. A compromise with good breathability and thus water vapour permeability is not necessary. Therefore the partial provision of the fixing layer may be sufficient for good adhesion properties.
Furthermore, the only partial fixation of the textile arrangement to the foam may allow a particularly good adaptability to the textile arrangement or the textile arrangement may be particularly free to be chosen. This is because the partial provision of the fixing layer can be adapted in its structure to a possibly intended structure of the textile arrangement. Thus, textile arrangements with different structures can be fixed with a foam without loss of adhesion.
Furthermore, the only partial fixing of the textile arrangement to the foam allows the fixing layer to be formed with a reduced amount of fixing agent to form the fixing layer. This reduces costs and saves weight.
Finally, the structure of the partial fixing of the foam and textile arrangement or the formation of the fixing areas and the free areas, in particular with regard to their size and optionally arrangement can enable the fixing layer and thus also the entire synthetic leather to be tailor-made, for example with regard to breathability, mechanical resistance, elasticity, water repellency etc. A particularly high degree of adaptivity is thus made possible.
The synthetic leather described here also has the advantage that it can be free of organic solvents, which can significantly reduce unpleasant odours and other nuisances.
Furthermore, further properties that are preferred for textile applications can be achieved. For example, a wash resistance of 5×40° according to the DIN EN ISO 6330 standard is achieved, which allows a wide range of applications.
The synthetic leather also has an air permeability according to EN ISO 9237, which can be at least 3.0 l/m2/s (20 cm2; 100 Pa) or even higher.
With regard to the fixing agent which forms the fixing layer or at least can be a component of it, it may be preferred that this is a hot-melt adhesive based on polyurethane.
Such a fixing agent can also be called a polyurethane-based hotmelt. For example, the hotmelt can be moisture-curing.
Furthermore, it may be provided that the fixing agent is formed from a particularly aliphatic polyester-polyurethane dispersion. In particular, the dispersion for producing the fixing agent can comprise a polyurethane dispersion with a polyurethane polymer which is built up from at least two and in particular exactly two different polyols and at least one polyisocyanate, wherein one polyol of the two different polyols is an aliphatic polyester polyol and a second of the two polyols is a polyether polyol which was produced from hydrophilic alkylene oxides with multifunctional groups, in particular with two to eight functionalities, and furthermore preferably with branched and/or star-shaped structures. Furthermore, the polyisocyanate can also be aliphatic. In particular, the dispersion for the preparation of the fixing agent may be formed as described in U.S. Pat. No. 9,783,701. Both of the above-mentioned variants, i.e. the provision of a polyurethane-based hot-melt adhesive and the formation of the fixing layer from a polyester-polyurethane dispersion, can be used to form the fixing layer in a manner which is particularly advantageous in terms of breathability, mechanical resistance, elasticity and/or water repellency.
It may also be preferable that the first fixing layer is applied or is present in a dotted manner. The advantages described above can be implemented particularly effectively by applying the first fixing layer in points, as the quantity and structure of the fixing agent can be adjusted particularly easily and efficiently if the individual fixing areas are applied in points. This can be easily achieved by varying the size of the dot areas as well as the distance between the dot areas.
In addition, the application of the fixing layer in dot form is efficient and can be implemented in a defined manner by means of a screen printing process, which, like any other application of the fixing layer, can be applied to the foam or also to the textile arrangement.
The same advantages as with a dot application can also be achieved if the fixing layer is applied or is present in the form of rhombuses or bars.
It may also be preferred that the first fixing layer is applied or is present between the foam and the textile arrangement in a quantity in the range of 2 to 50 g/m2, especially in a range of 0 g/m2 to 20 g/m. Compared to state-of-the-art solutions, this embodiment shows a significantly reduced application rate of the fixing layer. The advantages described above can be implemented particularly effectively especially according to this embodiment. For example, the breathability or water vapour permeability can be influenced only minimally by the fixing layer and can therefore be essentially maintained compared to a layer structure without fixing layer.
With regard to the textile arrangement, it may be provided that it consists of a textile layer, that is to say, in particular, a single textile layer. In this configuration, the structure of the synthetic leather, and in particular the layered structure of the synthetic leather, may be particularly simple, which may also simplify the manufacturing process. In addition, costs and weight can be saved, which also has a positive effect on the synthetic leather.
The achievable properties, which can be achieved by a textile arrangement consisting of only one textile layer, can be sufficient for a variety of applications.
Alternatively, it may be provided that the textile arrangement comprises a textile layer and a water-impermeable membrane, wherein the water-impermeable membrane is partially fixed to the textile layer using a second fixing layer in such a way that the second fixing layer has fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane. The second fixing layer can thus be designed as described above with respect to the first fixing layer, in particular with respect to the production or formation, with respect to the chemical composition and with respect to the structure.
In other words, it may be provided that the textile arrangement may also have been previously bonded to a breathable and waterproof membrane to form a two-layer laminate, in particular before bonding with the foam.
In particular, the membrane can ensure that the finished synthetic leather has a high water column in addition to high breathability, or respectively that liquid water does not pass through the membrane and thus the synthetic leather, or only passes through it in very small proportions. The membrane or respectively the membrane system 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. Seam sealing with seam sealing tape is preferably carried out in combination with the membrane used. A hydrostatic pressure of 200 mbar according to DIN EN ISO 811, as required for protective clothing, is achieved at the seam or for seam sealing.
By providing the membrane, the synthetic leather can be produced while maintaining the breathability and also retaining the elasticity in the overall structure.
Basically, a membrane can be understood as a layer which, in comparison to a design without membrane, influences the transport of substances through the synthetic leather, in particular reduces or completely prevents the transport of liquid water through the synthetic leather, or respectively can enable a high water column of up to 10 metres or even more than 10 metres, which can correspond to a hydrostatic pressure of 1000 mbar or more according to DIN EN ISO 811.
It may also be provided that the polyurethane-based foam will also be provided with a top layer that is particularly breathable. In principle, the top layer can result in the synthetic leather having a particularly high abrasion resistance, which can be of great advantage in terms of the application.
Furthermore, it can be an advantage, especially in this embodiment, that the polyurethane-based foam can be formed in the conventional way. This can facilitate production and reduce costs. Furthermore, the top layer can be selected in such a way that the water vapour permeability and also the breathability are not or not significantly negatively affected.
In principle, the top layer can be formed from a hydrophilic material.
It may be particularly preferred that the top layer is formed from an especially aliphatic polyester-polyurethane dispersion. In particular, the dispersion for producing the fixing agent and/or the top layer may comprise a polyurethane dispersion with a polyurethane polymer which is built up from at least two and in particular exactly two different polyols and at least one polyisocyanate, wherein one polyol of the two different polyols is an aliphatic polyester polyol and a second of the two polyols is a polyether polyol which was produced from hydrophilic alkylene oxides with multifunctional groups, in particular with two to eight functionalities, and furthermore preferably with branched and/or star-shaped structures. Furthermore, the polyisocyanate can also be aliphatic. In particular, the dispersion for the preparation of the fixing agent can be formed as described in U.S. Pat. No. 9,783,701.
Advantages of such a top layer include in particular that such a top layer can meet the requirements of a synthetic leather in a particularly advantageous way. The top layer offers excellent mechanical properties, such as particularly good abrasion resistance, which is advantageous for maintaining the structure and for the long life of the synthetic leather. In addition, such a top layer can have particularly pronounced breathability or water vapour permeability, which is also a requirement of a high-quality synthetic leather. In summary, such a top layer can provide a high synergy of the desired properties.
It may be provided that the top layer consists of the aliphatic polyester-polyurethane of the dispersion described above, or that other components are included.
In addition, it may be that the top layer is applied over the entire surface or only partially. If only partially applied, the breathability and water vapour permeability may be improved compared to a full-surface application. With a full-surface application, for example, the mechanical properties can be improved compared to a partial application.
In summary, a top layer may exhibit increased abrasion resistance, but at the same time allow essentially the same or only slightly reduced water vapour permeability or breathability.
In an embodiment with a top layer, it may also be preferable for the top layer to have a structure, as this can usually be the most upper layer and thus the layer which is seen when using the synthetic leather. The incorporation of the structure into the top layer can be achieved, for example, by producing the synthetic leather in a reverse process, as described below, and applying the top layer to a structured removable substrate, as described below. Alternatively, the structure can be embossed into the top layer.
It may also be preferred that the polyurethane based foam comprises a silicone. In this case, the polyurethane dispersion is modified in particular with a combination of OH-functionalized addition-curing aqueous silicone emulsion and a polyhydrogenmethylsiloxane to achieve a particularly high abrasion and buckling resistance.
The basis for the polyurethane-based foam may be a polyurethane dispersion, as described in WO 03/060017 A2 or in WO 02/090413 A1, for example in this embodiment, but in no way limited to this embodiment but generally in the sense of the present disclosure.
According to an exemplary embodiment, the polyurethane-based foam may be formed from a dispersion comprising a polyurethane based on an aliphatic polycarbonate ester. For example, the dispersion used to produce the foam may comprise, in addition to a polyisocyanate, a mixture of polycarbonate and polytetramethylene glycol polyols.
For example, the polyurethane-based foam may have an aliphatic polyester as the polyol.
An advantage of this embodiment, which generally is also achieved in polyurethane-based foam, especially impact foam, is that the foam is elastic and hydrophobic when shown as a film.
For example, the foam can have a density in a range from 500 g/l to 750 g/l.
It may also be provided that polyisocyanate and melamine resin are incorporated into the foam formulation as additional crosslinking components. The mechanical strength of the foam is increased by incorporating additional networks such as polyurea and melamine resin.
To thicken the polyurethane dispersion, an aqueous emulsion of an acrylic copolymer in particular with a viscosity in aqueous solution of less than 16 mPa·s in the process is added to the polyurethane dispersion. The coating paste or foam during application may have a viscosity of approximately 35 to 50 dPas.
It may also be provided that the foam is designed as a breathable lacquer.
Especially in this embodiment, it may be possible to omit the top layer. This is because the special composition of the foam can increase its resistance to abrasion and buckling compared to conventional foams. Thus, especially in this embodiment, the mechanical stability of the foam is sufficient for a multitude of applications.
Furthermore, especially in this embodiment or respectively in an embodiment without a top layer, synergies can be offered with regard to the partial or locally limited, for example doted, fixing of the foam to the textile arrangement. This is because, especially in this embodiment, the foam can exhibit high abrasion resistance and also high water vapour permeability and breathability. These positive properties can be effectively maintained by the arrangement of the first fixing layer, as these are further enhanced by the design of the first fixing layer.
It may further be preferred that the polyurethane-based foam has a solid content of greater than or equal to 40% by volume, for example a solid content of greater than 50% by volume, preferably in a range from greater than or equal to 40% by volume to less than or equal to 70% by volume, for example in a range from greater than or equal to 55% by volume to less than or equal to 68% by volume. In this embodiment, the production of the synthetic leather can be further improved. This is because, especially in the case of a foam of this type, especially impact foam, drying with removal of the solvent can take place particularly quickly due to the high solid content, which can make production particularly effective. For example, the foam can have a solid content of 60% by volume, whereby this value is to be understood with a tolerance of +/−10% by volume.
In addition, the foam in this embodiment can have a particularly high mechanical stability, which can be of great advantage in terms of the application and can also allow a top layer to be omitted.
With regard to further advantages and technical features of the synthetic leather, it is referred to the description of the method, and vice versa.
Further described is a method for the production of a multi-layer synthetic leather as described above, the process comprising the following steps:
(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) partial application of 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 assembly to the polyurethane-based foam; and
(f) removal of the support.
The steps described above may be carried out in the order given or in a different order, as explained below by way of example.
Such a procedure allows forming a synthetic leather in a particularly advantageous way, as described in detail above. Thus, with regard to the advantages and the advantageous embodiments of the synthetic leather produced by the method it is entirely referred to the description of the synthetic leather.
Such a process generally describes the formation of the synthetic leather in a so-called reverse process. According to this revers process, the synthetic leather to be obtained is thus built up from the uppermost layer, i.e. the layer which, when using the synthetic leather, thus produced, is directed furthest outwards or respectively can be visible to a user, to the lowest layer.
To this end, the method comprises the following steps:
First, according to step a), a support is provided. Such a support is in particular removable from the layer subsequently applied to it and therefore, as described below, is not part of the synthetic leather to be produced. Furthermore, the support may be structured, in particular to introduce a structure into the layer applied to the support.
For example, the support may be made of paper and, as grained support paper, may be provided with a structure.
According to process step b), the method optionally further comprises applying a top layer to the support. This can be done, for example, by using a squeegee and a desired thickness of a suitable material of the top layer can be applied. In particular, the top layer may be applied when it is intended to provide improved abrasion resistance through the opt layer. On the other hand, the top layer can be omitted if a subsequently applied foam already has sufficient mechanical strength. In other words, the top layer can be applied depending on the foam applied to the top layer.
Accordingly, the method according to process step c) comprises the application of a polyurethane-based foam to the substrate or, if a top layer is present on the substrate, to the top layer.
Thus, if the top layer is not present, the foam can be applied directly to the support and thus be provided with a structure like described above.
If the top layer is provided, the foam can be applied to the top layer accordingly.
The foam is again applied with a suitable polyurethane based material in a suitable thickness. For example, the foam can be doctored. It may be advantageous, especially when only the foam is provided or when the top layer is omitted, that this process step c) can be carried out in a one-pass coating process, which may bring about process engineering advantages with regard to the periphery for carrying out the process.
Accordingly, if a top layer is provided, process steps b) and c) can be carried out as a two-pass coating process.
In addition, it is understandable for the person skilled in the art that the top layer or the foam in particular can be dried or cured before further processing. Drying may improve the porosity or the pores of the foam may be opened, which has a positive effect on the breathability or respectively the water vapour permeability.
Furthermore, the method according to process step f) comprises the removal of the support. This step can be carried out, for example, after process step c), so that after process step f) a semi-finished product can be produced from a foam film, possibly with a top layer. The removal of the support can be done mechanically, for example. This may result that the top layer or the foam is the most upper layer, depending on the specific embodiment.
Further, according to process step d), a first fixing layer is partially applied to the polyurethane-based foam or to a textile arrangement, forming fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane. In this step, a fixing agent, such as a hot melt adhesive, is thus applied to part of the surface of the foam or textile arrangement.
According to this process step, the foam, which may be in the form of a film after drying, or the textile arrangement is provided with the fixing agent for example by a screen printing process also described as screen printing technology. The screen printing process involves the through doctoring of a fixing agent, for example a polyurethane-based hot-melt adhesive. Adhesive coats in the range of 2-50 g/m2, in particular 10 g/m2 to less than or equal to 20 g/m2, can be realized.
A polyurethane-based hot melt adhesive can be used as a fixing agent, for example. Such fixing agents are adhesives which cross-link with air humidity, the setting time of which depends on the application temperature, amount of adhesive, type of substrate, temperature of the substrate and the ambient conditions.
According to process step e), the process further comprises the application of the textile arrangement to the polyurethane-based foam, which is for example partially provided with the first fixing layer. For example, the textile arrangement, which can serve as a carrier for the finished synthetic leather, is joined or laminated to the foam under pressure. Due to different hole templates, very precise adhesive layouts can be achieved. Due to the technology-related small adhesive layer and an optimal distribution of the adhesive, the breathability of the coating is only minimally affected.
Such a process allows in particular the production of a mechanically stable and breathable synthetic leather, as described above.
Alternatively, a synthetic leather according to the disclosure, for example in a departure from a reversal process, can be produced by at least the following process steps:
g) providing a textile arrangement;
h) providing a polyurethane based foam;
i) partial application of a first fixing layer to the polyurethane-based foam or to the textile arrangement, thereby forming fixing areas formed by a fixing agent and free areas free from the fixing agent in the same plane;
j) Fixing the polyurethane-based foam and the textile assembly; and
(k) optionally, applying a top layer to the polyurethane-based foam.
This process also results in a synthetic leather as described above. In this case, however, the reverse process is not necessarily used, but the synthetic leather can be built up from the textile arrangement as a carrier upwards. However, a reverse process is not excluded also in this embodiment.
With regard to the arrangement and formation of the individual layers, it is referred to the further description.
It should be mentioned, however, that, for example, to produce the foam, it can be produced separately beforehand, for example by applying it to a support, drying and removing the support, or by separating the foam from a larger foam.
With regard to a structure of the foam or the top layer, it may also be intended that the structure is embossed.
It may be especially preferred that the first fixing layer is applied in step d) or i) using a screen printing process. Using a screen printing process, it is possible in a simple and effective way to allow only partial application of the first fixing layer, which can lead to the advantages described above. By adapting the printing process, different patterns of different, for example, dot-shaped fixing areas can be easily achieved.
It may also be provided that the process includes the further process step of: I) hydrophobizing at least one of the top layer and the foam and preferably the respective outer layer.
According to this embodiment, particularly effective waterproofing or repulsion and peraling of water can be achieved without, however, negatively affecting the breathability and thus the water vapour permeability. For the purposes of the present disclosure, hydrophobicity means in particular that the textile arrangement or at least parts thereof or respectively the top layer or at least a part thereof has an improved hydrophobicity compared to that prior to hydrophobicity, or that a treatment with a hydrophobic agent is simply carried out. For example, hydrophobicity can be achieved with fluorocarbons or fluorocarbon-free DWRs (DWR: durable water repellant). In particular, hydrophobing can also be carried out with an outer side of the layer structure.
For example, this process step can be carried out by padding the synthetic leather or the layer structure and thus the laminate on one side in an optional, approximately final process step. In this process, the outer layer and in particular the foam or the top layer can be guided along a rotating roller by means of guide rollers, whereby by dipping the padding roller the fleet contained in a container can be carried along on the surface of the roller and released on one side to the surface of the top layer or the foam.
It may be advantageous that padding is one of the minimum application methods due to the low fleet usage, which may allow low costs.
With regard to further advantages and technical features of the processes, it is explicitly referred to the description of the synthetic leather, and vice versa.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
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.
The disclosure is further explained below by means of the figures and an example of producing the synthetic leather.
Example embodiments will now be described more fully with reference to the accompanying drawings.
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.
In particular, in order to obtain particularly preferred mechanical properties, it is also provided that the polyurethane-based foam 16 also contains a silicone.
The fixing agent can preferably be a polyurethane-based hotmelt adhesive, which can also be called a hotmelt in the technical field.
In the design according to
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.
The embodiment shown in
In the embodiment shown in
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).
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.
With regard to the arrangement of the individual layer or layers, it is referred to the description relating to the synthetic leather 10.
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
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.
Furthermore, as shown in
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.
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.
Then, the layer sequence 50, as described above and shown in
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.
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.
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.
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
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.
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.
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.
The support is adjusted via the gap thickness to the counter roller or release paper.
Target layer (dry): 200±15 g/m2
3.1 Drying+Condensation of the Paste in the Drying Channel
The drying of the paste/foam 16 takes place in a channel with several separately adjustable temperature zones.
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.
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.
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.
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.
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.
Grammage [g/m2]: 200 with a tolerance of +/−15; WVP [mg/cm2/h]: >10; MVTR [g/m2/24 h]: >5,500; abrasion resistance Martindale [tours] >50,000
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.
For the production of the synthetic leather/laminate, adhesive applications in the range of approx. 10-20 g/m2 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.
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.
Chemical Basis: PUR Prepolymer
Consistency: solid; density: approx. 1.10 g/cm3; 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.
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.
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.
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.
Hydrophobing can be done with fluorocarbons or FC-free DRWs.
Subsequently, the fabric is inspected or respectively visually inspected and quality checked in the test laboratory, whereby the following values were achieved:
WVP (mg/cm2/h): >9 (without membrane 11.5-15.0, especially >7, with membrane 2.54-9.0, especially >2); MVTR (g/m2/24 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.
The following standards were used for the tests:
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19153303.3 | Jan 2019 | EP | regional |
This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/EP2020/051358, filed on Jan. 21, 2020, which claims the benefit of European Patent Application No. 19153303.3, filed on Jan. 23, 2019. The entire disclosures of the above applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/051358 | 1/21/2020 | WO | 00 |
