Artificial leather with cool surface features

Abstract

The artificial leather has a top layer containing a solid water-insoluble polyurethane elastomer, a solid water-insoluble acrylate elastomer, and embedded particles of encapsulated phase change material. The top layer imparts the required'cool touch 'feature to the artificial leather while also imparting other important physical and tactile characteristics such as soft smoothness.

Description

[0001] The present invention relates to artificial leather and a method for preparing the same.

[0002] Artificial leather is widely used as an inexpensive alternative to natural leather. Recent advancements in artificial leather technology have resulted in products that closely resemble natural leather in appearance, feel, and performance. Artificial leather is widely used in clothing, furniture, and automotive applications such as seat trim materials and interior trim.

[0003] These artificial leather products are typically multi-layer assemblies having one or more polymer coatings on a fibrous substrate. The polymer coatings are typically based on aqueous polyurethane dispersions, which are used to create the top (or "display") surface of the artificial leather product and, in some cases, intermediate layers such as one or more foam layers. Aqueous polyurethane dispersions have environmental and handling advantages over the previous generation of solvent-based polyurethane dispersions used in this application area. By using aqueous polyurethane dispersions, odor problems, exposure to solvents, and other environmental and occupational safety issues are largely avoided.

[0004] Artificial leather often has excellent heat retention. This makes artificial leather a valuable construction material for winter clothing, shoes, and even furniture and automotive seats, where the warmth obtained when the artificial leather retains heat is desired.

[0005] There are applications where this heat retention ability is less desired. An example of such an application is a baby pad. An artificial leather baby pad may make a young child uncomfortably warm, especially during the summer months. Similarly, applications such as automotive seats and furniture may sometimes benefit if the artificial leather has a lower heat retention ability.

[0006] In one aspect, the present invention is an artificial leather comprising a backing layer and a top layer directly or indirectly adhered to the backing layer, the top layer comprising, based on the total weight of the top layer: (i) 25 wt% to 75 wt% of a solid water-insoluble polyurethane elastomer, (ii) 10 wt% to 40 wt% of a solid water-insoluble acrylate elastomer, and (iii) 5 wt% to 30 wt% of encapsulated phase change material embedded particles having a melting or glass transition temperature of 20°C to 37°C.

[0007] Compared to prior artificial leather products, this artificial leather has a reduced heat retention ability but still retains the physical and tactile properties required of an artificial leather product. This artificial leather exhibits excellent surface smoothness, a soft feel, and resistance to damage caused by abrasion and repeated bending.

[0008] In another aspect, the present invention is an aqueous dispersion comprising a continuous aqueous phase having dispersed therein, based on the total weight of the aqueous dispersion: (i) from 15% to 40% by weight of internally stabilized solid particles of a water-insoluble polyurethane elastomer, (ii) from 5% to 20% by weight of particles of a water-insoluble acrylate elastomer, and (iii) from 3% to 15% by weight of particles of an encapsulated phase change material having a melting or glass transition temperature of from 20°C to 37°C, where (i), (ii), and (iii) together account for from 35% to 65% of the total weight of the aqueous dispersion.

[0009] The dispersion cures to form an elastomeric material that can be used as the top layer of the artificial leather of the present invention. The cured material exhibits the desired soft, "cool" touch and has a low modulus and high elasticity.

[0010] The artificial leather of the present invention comprises a backing layer, a top layer, and optionally one or more intermediate layers.

[0011] The backing layer is not particularly limited and can be or include, for example, a fabric, a metal film, a plastic film, an elastomeric sheet or film, or natural leather (such as split leather). The backing layer is preferably a flexible material in the form of a sheet or film having a thickness of from 0.01 mm to 10 mm, especially from 0.1 mm to 5 mm.

[0012] The fabric is a particularly preferred backing layer. The fabric comprises fibers, which can be, for example, woven, knitted, braided, non-woven, heat-bonded, spunbonded, needled, and / or entangled. The fibers can be natural material fibers such as wool, cotton, linen, hemp, etc., and / or can be synthetic fibers such as polyester, polyamide, polyolefin, poly(vinyl chloride), acrylic, poly(vinyl alcohol), etc. Fiber blends can be used.

[0013] Backing layer materials of particular interest include microfibers coated with or embedded with an elastomeric polymer. Such fabrics are conveniently prepared according to the method described in WO 2018 / 045546A1. As described therein, fabrics are prepared using "sea-island" type multicomponent fibers. The fiber comprises a bundle of individual filaments made of materials with different solubility characteristics such that it is possible to selectively dissolve and remove one type of filament without dissolving the filaments of the other material. Polyolefin / polyamide sea-island fibers are an example of a suitable type. The fabric is embedded and / or coated with an elastomeric polymer. The elastomeric polymer is characterized in that, as a bulk material, it has a glass transition temperature of -10 °C or lower measured by differential scanning calorimetry and a breaking elongation of at least 50%, in particular at least 100% or at least 200% measured according to GB / T528-2009. The embedding or coating step can be carried out, for example, by impregnating the fabric with a dispersion of the elastomeric polymer and / or a reaction mixture containing a precursor that cures to produce the elastomeric polymer, and then curing the impregnated fabric to produce the elastomeric polymer. The elastomeric polymer can be, for example, a polyurethane or an acrylate polymer. In a specific embodiment, the fabric is embedded and / or coated by impregnating it with an aqueous polyurethane dispersion. The aqueous polyurethane dispersion can be thermally curable, such as by comprising both a cationic external surfactant and anionic external surfactant and being thermally curable as described in WO 2018 / 045546A1. The embedded and / or coated fabric is then contacted with a solvent to preferentially dissolve and remove some but not all of the filaments in the multicomponent fiber, leaving the insoluble filaments.

[0014] The top layer comprises, by total weight of the top layer: (i) 25 wt% to 75 wt% of a solid water-insoluble polyurethane elastomer, (ii) 10 wt% to 40 wt% of a solid water-insoluble acrylate elastomer and (iii) 5 wt% to 30 wt% of embedded particles of an encapsulated phase change material having a melting or glass transition temperature of 20 °C to 37 °C. Component (i) comprises at least 30% or at least 35% of the total weight of the top layer in some embodiments and can comprise up to 70% of the total weight of the top layer in some embodiments. Component (ii) comprises at least 12% of the total weight of the top layer in some embodiments and can comprise up to 35% thereof in some embodiments.

[0015] Components (i)-(iii) preferably together comprise at least 85%, preferably at least 90% of the total weight of the top layer. The remainder of the top layer weight comprises various optional non-volatile components that may be present in the aqueous dispersion used to prepare the top layer, as described more fully below. The total weight of the top layer generally equals the solid weight of the polyurethane dispersion used to prepare the top layer and can be calculated as the weight of the dispersion multiplied by the solid content. Solids include all non-volatile materials not removed during the curing step.

[0016] The top layer is preferably prepared by forming a film of an aqueous dispersion and curing the formed film. The aqueous dispersion comprises a continuous aqueous phase having dispersed therein, based on the total weight of the aqueous dispersion: (i) 15 wt% to 40 wt%, preferably 18 wt% to 35 wt% of internally stabilized solid particles of a water-insoluble polyurethane elastomer, (ii) 5 wt% to 20 wt%, preferably 7 wt% to 18 wt% of particles of a water-insoluble acrylate elastomer, and (iii) 3 wt% to 15 wt%, preferably 5 wt% to 15 wt% of particles of an encapsulated phase change material having a melting or glass transition temperature of 20 °C to 37 °C, where (i), (ii), and (iii) together account for 35% to 65% of the total weight of the aqueous dispersion.

[0017] As used herein, "curing" is simply meant to indicate that the coating composition forms a solid coating by any mechanism or combination of mechanisms suitable for the particular elastomeric polymer present. It is not necessary for any chemical reaction (such as polymerization, crosslinking, or chain extension) to occur during the curing step, although such reactions may occur in some cases. In a preferred embodiment, curing is effected by drying the film at about room temperature (20 °C - 25 °C) or at an elevated temperature, such as at least 40 °C or at least 60 °C and, for example, up to 160 °C or up to 140 °C.

[0018] The solid water-insoluble polyurethane elastomer preferably exhibits, by itself, an elongation at break of at least 50%, at least 100%, at least 250%, or at least 500% as measured according to GB / T 528-2009. Preferably, it exhibits, by itself, a glass transition temperature of -10 °C or lower, especially -40 °C or lower, as determined by differential scanning calorimetry.

[0019] The solid water-insoluble polyurethane elastomer is prepared, in some embodiments, by forming an isocyanate-terminated prepolymer, dispersing the prepolymer into water, and chain-extending the prepolymer with water and / or other chain extenders to form polyurethane particles dispersed in the aqueous phase. The prepolymer is preferably internally stabilized, meaning that the prepolymer contains covalently bonded hydrophilic groups such as ionic groups and poly(oxyethylene groups) that emulsify the polyurethane particles in the aqueous phase upon chain extension.

[0020] The prepolymer is preferably the reaction product of: at least one polyether polyol having a hydroxyl equivalent weight of from 400 g / equivalent to 8,000 g / equivalent, preferably from 500 g / equivalent to 2,200 g / equivalent; at least one hydroxyl-, primary amine- or secondary amine-containing compound having a hydrophilic group or a precursor of a hydrophilic group; and an excess of at least one polyisocyanate. The equivalent weight is determined by measuring the hydroxyl number using a titration method such as ASTM D4274-21 and converting the hydroxyl number (in mg KOH / g) to the equivalent weight using the following relationship: equivalent weight = 56,100 ÷ hydroxyl number.

[0021] The polyether polyol used to prepare the prepolymer is preferably insoluble in water at 25 °C and can be, for example, a homopolymer of 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, tetrahydrofuran, a copolymer (block and / or random copolymer) of any two or more of them, and / or a copolymer (block and / or random copolymer) of any one or more of these with up to, for example, 20% by weight of ethylene oxide. The polyether polyol nominally can have, for example, from 2 to 8, from 2 to 6, from 2 to 4 or from 2 to 3 hydroxyl groups per molecule.

[0022] The hydroxyl-, primary amine- or secondary amine-containing compound having a hydrophilic group or a precursor of a hydrophilic group contains, in some embodiments, one or more hydroxyl groups and one or more anionic groups such as carboxylate, sulfonate and phosphate groups in the form of alkali metal or ammonium salts. It can contain carboxyl, carboxylic anhydride, sulfonic acid and / or phosphoric acid groups, which can be converted to the corresponding carboxylate, sulfonate and phosphate groups by neutralization with a suitable base and / or hydrolysis followed by neutralization. Specific examples include dimethylolpropionic acid, dimethylolbutyric acid, dihydroxy sulfonic acid, dihydroxy phosphoric acid such as 2,3-dihydroxypropane phosphonic acid, etc.

[0023] In other embodiments, a hydroxyl-, primary amine- or secondary amine-containing compound having a hydrophilic group contains one or more hydroxyl and / or primary amino or secondary amino groups and one or more cationic groups such as protonated tertiary amino groups or quaternary amino groups (e.g., in the form of their phosphates, sulfates, carboxylates, halides, salts), and / or precursors of such groups that can be neutralized to form the corresponding cationic groups. Specific examples include tris(hydroxyalkyl)amine, N,N'-bis(hydroxyalkyl)alkylamine, N-hydroxyalkyldialkylamine, tris(aminoalkyl)amine, N,N'-bis(aminoalkyl)alkylamine, N-aminoalkyldialkylamine, etc. These are tertiary amine compounds that can be converted to ammonium salts by reaction with an acid such as phosphoric acid, sulfuric acid, a hydrohalic acid such as HCl or HBr, or by reaction with a suitable quaternizing agent such as 1-6 alkyl halide or benzyl halide.

[0024] The third type of compound containing hydroxyl, primary amine or secondary amine with a hydrophilic group is a homopolymer of ethylene oxide or a copolymer of ethylene oxide having a poly(ethylene oxide) block with at least 15, preferably at least 20 ethylene oxide units and one or more hydroxyl groups.

[0025] The polyisocyanate used to prepare the prepolymer has an average of at least 2 isocyanate groups per molecule. The isocyanate groups can be covalently bonded to aromatic, aliphatic and / or alicyclic carbon atoms. Examples of available polyisocyanates include diphenylmethane diisocyanate (any isomer or mixture of isomers), p-phenylenediamine, toluene diisocyanate (any isomer or mixture of isomers), polymethylene polyphenylene polyisocyanate having 3 or more phenyl isocyanate groups, the so-called "polymeric MDI" (which is a mixture of diphenylmethane diisocyanate and higher polymethylene polyphenylene polyisocyanates), 1,5-naphthylene diisocyanate, hydrogenated MDI ("H 12 -MDI"), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-diisocyanatocyclohexane, isophorone diisocyanate, hexamethylene diisocyanate, etc.

[0026] The prepolymer can be prepared by reacting various precursors in the absence of a solvent or in a suitable solvent. The precursors can be combined or reacted all at once or in various sequences. Then the prepolymer is dispersed in water in the form of droplets, and in water the prepolymer reacts with water or other chain extenders to produce solid water-insoluble polyurethane elastomer particles. Suitable chain extenders (other than water) include compounds having a formula molecular weight of at most 250, preferably at most 150, and having two or more, preferably exactly two hydroxyl, primary amino and / or secondary amino groups per molecule. Examples include piperazine, amine-terminated polyethers, aminoethyl ethanolamine, monoethanolamine and ethylenediamine.

[0027] The resulting polyurethane dispersion can have a solids content of, for example, 20 wt% to 70 wt%, preferably 25 wt% to 60 wt% or 40 wt% to 60 wt%. The D50 particle size of the dispersed polyurethane particles can be, for example, at least 20 nm or at least 50 nm and at most 2,000 nm or at most 1,000 nm, as measured by laser diffraction.

[0028] In some embodiments, the polyurethane dispersion is free of external surfactants, i.e., surfactants that are not covalently bonded to the polyurethane particles.

[0029] Suitable polyurethane dispersions can be commercially obtained under the Syntegra TM trade name from The Dow Chemical Company, including, for example, Syntegra as more fully described in the Examples sectionTM YS 3076 dispersion, and Syntegra from The Dow Chemical Company TM YF 4000 dispersion. Syntegra TM The YF 4000 dispersion product has a solids content of about 54 wt%; the cured film prepared by self - coagulation of the dispersion has a 100% modulus of about 2.5 MPa and an elongation at break of 600% - 800%.

[0030] The water - insoluble acrylate elastomer is a polymer of one or more acrylate monomers such as methyl acrylate, ethyl acrylate, 2 - hydroxyethyl acrylate, tert - butyl acrylate, n - butyl acrylate, hexyl acrylate, 2 - ethylhexyl acrylate, etc. If desired, various comonomers can be copolymerized with the acrylate monomers in block, random, and / or graft manners to produce the acrylate elastomer. The acrylate elastomer itself preferably exhibits an elongation at break of at least 50%, at least 100%, at least 250%, and preferably has a glass transition temperature of - 10 °C or below, preferably - 25 °C or below or - 40 °C or below as measured by differential scanning calorimetry.

[0031] The water - insoluble acrylate elastomer is preferably provided in the form of an aqueous dispersion. The acrylate elastomer can be produced as an emulsion or dispersion in a liquid phase that includes water and / or one or more other compounds that are liquid at room temperature (23 °C) and have a boiling temperature of 40 °C to 100 °C at standard pressure. Such an emulsion can be produced during an emulsion polymerization process, in which one or more monomers are dissolved or dispersed into the liquid phase and subjected to polymerization conditions until the polymer chains precipitate and are converted into polymer particles or droplets dispersed in the liquid phase.

[0032] Similarly, an emulsion or dispersion of the acrylate elastomer can be produced during a mechanical dispersion process, in which the molten acrylate elastomer is dispersed into such a liquid phase. The liquid phase used in such a mechanical dispersion process can form part or all of the liquid phase of the emulsion or dispersion for coating the polyurethane foam according to the present invention.

[0033] In yet another suitable process, the acrylate elastomer can be ground or otherwise formed into small particles, and then these small particles are dispersed in the liquid phase to form an emulsion or dispersion.

[0034] The particle size of the acrylate elastomer particles is preferably as generally described for the dispersed polyurethane elastomer particles.

[0035] A suitable dispersion of the acrylate elastomer can be commercially obtained under the trade name Rhoplex TM from The Dow Chemical Company, such as Rhoplex TM 3166 dispersion.

[0036] Dispersions of the acrylate elastomer particles prepared in any of the foregoing methods preferably contain at least one external surfactant to stabilize the dispersion and prevent settling. Cationic, nonionic, zwitterionic, and / or anionic surfactants are all suitable.

[0037] The encapsulated phase change material (iii) includes a phase change material having a melting or glass transition temperature of 20°C to 37°C, and the phase change material is included within a shell. The phase change material preferably has a melting temperature of 20°C to 37°C and more preferably has a melting temperature of 25°C to 32°C or 28°C to 32°C. The encapsulated phase change material may exhibit a heat of fusion of at least 50 joules / gram (J / g), at least 100 J / g, or at least 150 J / g in the temperature range of 20°C to 37°C, as measured by differential scanning calorimetry. The heat of fusion can be up to 300 J / g or more, but more typically is up to 250 J / g or up to 200 J / g.

[0038] For the purposes of the present invention, the weight of the phase change material includes the weight of the shell. The shell may account for 5% to 25% of the total weight of the encapsulated phase change material, and the phase change material itself accounts for the remainder, i.e., 75% to 95% by weight.

[0039] The phase change material can be or include, for example, a wax or a mixture of waxes. The wax can be a natural or synthetic wax such as polyethylene wax, beeswax, lanolin, carnauba wax, candelilla wax, ouricury wax, sugarcane wax, jojoba wax, cutin wax, coconut wax, petroleum wax, or paraffin wax, provided that the foregoing waxes having a melting temperature below 20°C or above 37°C are used as a blend or mixture with one or more waxes such that the combination exhibits a melting temperature within the range of 20°C to 37°C.

[0040] The phase change material in some embodiments is an alkane having 14 to 30 carbon atoms, especially 14 to 24 or 16 to 22 carbon atoms, or a mixture of any two or more thereof. In a specific embodiment, the phase change material includes octadecane and / or eicosane.

[0041] The shell material can be, for example, a polymeric material having a melting or decomposition temperature of at least 50°C and preferably at least 100°C. Examples of useful shell materials include crosslinked thermosetting resins such as crosslinked melamine-formaldehyde, crosslinked melamine, crosslinked resorcinol-urea-formaldehyde, and gelatin.

[0042] The encapsulated phase change material is in the form of particles. The particles can have a particle size of 100 nm to 100 μm, as measured by microscopy. In some embodiments, the particles have a particle size of at least 250 nm, at least 500 nm, at least 1 μm, or at least 5 μm and at most 75 μm or at most 50 μm.

[0043] Suitable methods for preparing encapsulated phase change materials are described, for example, in U.S. Patent Nos. 10,221,323 and 10,005,059.

[0044] Suitable encapsulated phase change materials are available from Microtek Laboratories, Dayton, Ohio, US.

[0045] An aqueous dispersion of a polyurethane elastomer, an aqueous dispersion of an acrylic elastomer, and an encapsulated phase change material are combined in any order to produce a coating composition, which is then formed into a top layer. In some embodiments, the encapsulated phase change material is combined with the aqueous dispersion of the acrylic elastomer and then with the dispersion of the polyurethane elastomer. Commercially available aqueous dispersions of acylated elastomers containing dispersed encapsulated phase change materials are available under the trade name Aquachill TM from The Dow Chemical Company and include Aquachill TM HT705, Aquachill TM HT706, and Aquachill TM HT710 dispersions.

[0046] In addition to the materials already described, the coating composition may also contain one or more optional materials. When the coating composition is formed into a film and cured, non-volatile materials are typically incorporated into the top layer.

[0047] Another available optional material is one or more external surfactants, which can be introduced with the polyurethane elastomer dispersion, the acrylate elastomer dispersion, and / or as a separate component, and can perform one or more available functions. Such surfactants can be used as stabilizers for acrylate elastomer particles and / or, less preferably, polyurethane elastomer particles. The surfactant can be used as a wetting agent to facilitate the dispersion of the phase change material particles into the remaining components of the coating composition. The surfactant can be used as an antifoaming or degassing agent to reduce the entrainment of gases in the coating composition and reduce bubbles. Various silicone surfactants as well as various non-silicone surfactants can be used for these purposes, such as sulfates, sulfonates, phosphates, ethoxylates, fatty acid esters, amine oxides, sulfoxides, and phosphine oxides. The surfactant can be nonionic, anionic, cationic, or zwitterionic. Based on the total weight of the coating composition, one or more surfactants can account for, for example, 0.1 wt% to 5 wt%. Any such surfactant is considered part of the solid content of the coating composition for the purposes of the present invention.

[0048] Other useful ingredients include various rheology modifiers such as various thickeners and thixotropic agents. Among these are fumed silica and various water-soluble or water-swellable polymers of acrylic acid containing free acid groups or carboxylate groups (e.g., alkali metal, ammonium (NH4), quaternary ammonium or quaternary phosphonium carboxylates). Particularly useful rheology modifiers include aqueous emulsions of crosslinked acrylic polymers, such as those sold by DuPont under the trade name Available. Specific examples are ASE-60 and Acrysol ASE-95. When present, such rheology modifiers can be present, for example, in an amount of 0.01 wt% to 5 wt% of the coating composition, preferably 0.05 wt% to 1 wt%. Any such rheology modifier is considered to be part of the solids of the coating composition for the purposes of the present invention.

[0049] The coating composition can contain one or more other compounds (other than water) that are liquid at room temperature (23 °C) and have a boiling temperature of 40 °C to 100 °C at standard pressure. If present to a minimal extent, such compounds preferably do not exceed 5 wt%, especially not more than 2 wt%, of the total weight of the coating composition. Since such compounds are typically removed during the curing step, they do not form part of the top layer upon curing, and such compounds are not counted as part of the solid content of the coating composition.

[0050] The coating composition can contain one or more crosslinking agents. A crosslinking agent is a compound having two or more functional groups that react with functional groups on the polyurethane elastomer and / or acrylate elastomer under the conditions of the curing step to form covalent bonds therewith. Examples of crosslinking agents include aziridines; diols such as propylene glycol, ethylene glycol, dipropylene glycol, tripropylene glycol, diethylene glycol, diethanolamine, diisopropanolamine; diamines such as ethylenediamine, diethylenetriamine, monoethanolamine, etc.

[0051] Other components of the coating composition can include, for example, colorants, preservatives, leveling agents, antioxidants, and biocides, and all of these components are considered to be part of the solids of the coating composition.

[0052] The top layer is prepared from the composition by forming the coating composition into a film, metering the film to a predetermined thickness, and curing the film to produce a solid elastomer. In some embodiments, the film of the coating composition is cast onto a release sheet (such as release paper), metered to the desired thickness in any convenient manner, and then cured. As previously described, curing preferably comprises or consists of one or more drying steps in which water and other volatile components of the coating composition are removed. The polyurethane elastomer particles and acrylate particles solidify as part of the curing process to produce a solid elastomer top layer. The top layer is then separated from the release sheet.

[0053] The resulting top layer can have a thickness of, for example, at least 0.01 μm, at least 1 μm or at least 10 μm, and at most 1,000 μm or at most 500 μm.

[0054] In other embodiments, the coating composition is formed into a film on the backing layer or some optional intermediate layer, metered and cured to produce the top layer.

[0055] The artificial leather of the present invention may contain one or more intermediate layers disposed between the backing layer and the top layer. These include (1) an elastomeric foam layer and (2) a barrier layer, which is also preferably elastic. Either or both may be present, as well as additional layers that may be beneficial. In a particular embodiment, the artificial leather includes, from top to bottom, a top layer, a barrier layer adhered to the top layer; a foam layer adhered to the barrier layer; and a backing layer adhered to the foam layer. In other particular embodiments, the artificial leather includes, from top to bottom, A) a top layer, B) a foam layer adhered to the top layer, and C) a backing layer adhered to the foam layer. In still other embodiments, the artificial leather includes, from top to bottom, A) a top layer, B) a barrier layer adhered to the top layer, and C) a backing layer adhered to the barrier layer.

[0056] The elastomeric foam layer is a layer of porous elastomer. If present, the elastomeric foam layer can have a thickness of, for example, at least 0.1 μm, at least 1 μm or at least 10 μm, and at most 2,000 μm or at most 1,000 μm. A preferred type of elastomeric foam layer is a polyurethane foam layer. Such a polyurethane foam layer can be prepared by forming a film of a foamed polyurethane dispersion or a two-component polyurethane foam system, metering the film and curing the film to produce the foam layer. For example, the polyurethane dispersion can be as generally described above and / or as generally described in WO 2020 / 097838, and can be internally and / or externally stabilized. The two-component polyurethane foam system comprises one or more polyisocyanates, one or more isocyanate-reactive materials (which preferably include at least one polyether polyol having a hydroxyl equivalent weight of 400 to 4,000), at least one chemical and / or physical blowing agent (especially water) and optional additional ingredients such as one or more chain extenders, catalysts, foam-stabilizing surfactants, fillers, etc. Suitable two-component polyurethane foam systems include those described in WO 2020 / 097838.

[0057] If present, the barrier layer is preferably an elastomeric polyurethane layer. It is preferably prepared by forming a film of a polyurethane elastomer dispersion, metering the film, and curing the film. The polyurethane elastomer dispersion is preferably an aqueous dispersion. The polyurethane elastomer particles in such a dispersion can be internally and / or externally stabilized. In a particular embodiment, the dispersion is only externally stabilized, preferably stabilized with a mixture of both a cationic surfactant and an anionic surfactant, as described in WO 2020 / 097838. The dispersion can be thermosettable, as described in WO 2020 / 097838.

[0058] If present, the barrier layer can have a thickness of, for example, at least 0.01 μm, at least 1 μm or at least 10 μm, and at most 1,000 μm or at most 500 μm.

[0059] The artificial leather can contain one or more additional layers, such as a protective film layer on the top layer, one or more waterproof layers, one or more UV protective layers, and one or more tactile modification layers.

[0060] The artificial leather can be used in various applications, such as footwear, clothing, handbags, wallets, furniture decoration materials, automotive decoration materials, belts, gloves and other apparel items, strapping tapes, etc. Particularly interesting applications are mats, especially for babies or other young children, fitness mats, etc., where the "cool touch" feature of the top layer is beneficial. The artificial leather can be subjected to various post-treatment steps as needed or desired to adapt it to a specific application. For example, the artificial leather can be subjected to one or more brushing, filling, milling, or ironing steps. The artificial leather can be uniaxially or biaxially stretched, which can improve breathability.

[0061] The following examples are provided to illustrate the invention but are not intended to limit the scope of the invention. Unless otherwise indicated, all parts and percentages are by weight.

[0062] The acrylic / PCM emulsion is an acrylic latex polymer emulsion that contains approximately 32 wt% acrylic latex solids and approximately 23 wt% microencapsulated paraffin wax particles with a particle size of approximately 15 μm - 30 μm. The wax accounts for 85% - 90% of the weight of the microencapsulated paraffin wax particles, and the polymer shell accounts for the remainder of the product weight. The phase change material has a melting point of approximately 28 °C and a melting enthalpy of 180 J / g - 190 J / g. The latex particles are T g an elastomeric polymer that is less than approximately -10 °C. The Brookfield viscosity of the product at 25 °C is 1700 mPa·s - 3000 mPa·s (S64 rotor, 1000 rpm).

[0063] The PU emulsion is an aqueous dispersion of particles of a polyurethane elastomer based on isophorone diisocyanate, available from Dow Chemical Company as SyntegraTM The YS-3076 dispersion is for sale. The solid content is about 50% by weight. The cured film prepared by solidifying the dispersion has a 100% modulus of about 2 MPa and an elongation at break of 900%-1000%. Examples 1-4 of the coating composition and Comparative Samples A-E were prepared by combining the ingredients listed in Table 1 and mixing them in a high-speed laboratory mixer to produce a homogeneous mixture. The viscosity was measured using a Brookfield device equipped with an S64 rotor and operating at 100 rpm. The odor was subjectively evaluated by placing 10 g of the composition into a 50 mL bottle and sealing the bottle under nitrogen. The bottle and its contents were kept at 20 °C - 23 °C for 24 hours. Then the bottle was opened, and the odor was subjectively determined on a scale of 1-10, where 1 indicates no detectable odor, 5 indicates an obvious but tolerable odor, and a higher value indicates a stronger odor.

[0064] Table 1 Top Layer Formulation

[0065]

[0066]

[0067] * Not an example of the present invention. 1 BYK 346 from BYK USA Inc. 2 ROSILK from The Dow Chemical Company TM Silicone emulsion. 3 ZS-100, from Guangzhou Zengmao Chemical Technology Co., Ltd.; 4 Acrysol TM RM-825, from The Dow Chemical Company.

[0068] Preparation and Testing of Test Films . To prepare a film for physical property testing, 5 g of the coating composition sample was spread onto a glass plate with an anti-adhesive coating and dried overnight at 20 °C - 23 °C. Then the film was removed from the glass and further cured in an oven at 60 °C for 2 hours. The sample was cooled to 20 °C - 23 °C for further testing. Tensile strength, elongation at break, and modulus were measured according to GB / T 528-2009.

[0069] Larger films were prepared for evaluating thermal properties by pouring the coating composition onto release paper to produce a 2 mm thick coating, drying the film overnight at 20 °C - 23 °C, removing the film from the release paper, and further curing it at 80 °C for 2 hours. Cooling effect: The cooling effect was measured according to GB / T 36263-2017. Subjectively, the film was warmed to 20 °C - 23 °C, the hand was applied to the film, and the cooling sensation was rated on a scale of 1 - 5, where a rating of 1 indicates no distinguishable cooling effect and a rating of 5 indicates a strong cooling effect.

[0070] The results from these evaluations and the approximate composition of the cured coatings (calculated based on the composition of the coating composition) are shown in Table 2.

[0071] Table 2 Film Sample Characteristics

[0072]

[0073] * Not an example of the present invention.

[0074] Three-Layer Synthetic Leather Each of these coating compositions was used to prepare a film. The coating composition was poured onto release paper and formed into a 100 μm film using a winding rod. The film was dried at 100 °C for five minutes. A 300 μm polyurethane foam layer was applied on top of the dried film and oven-dried at 140 °C for 90 seconds. A fabric substrate was applied to the exposed surface of the foam layer and then further dried at 120 °C for 3 minutes. Then the release paper was removed to expose the surface layer.

[0075] The cooling effect of the artificial leather was evaluated according to GB / T 36263-2017 and subjectively rated as described above. The high-temperature adhesion was determined according to GB / T 8949-2008. Two pieces of each artificial leather were placed surface-to-surface and sandwiched between glass sheets with a 5 kg load placed on top. After heating at 50 °C for 2 hours, the samples were cooled to room temperature for 30 minutes. Then the artificial leather pieces were separated by hand and the difficulty of pulling them apart was subjectively evaluated on a scale of 1 - 5. A rating of 5 indicates that the pieces can be pulled apart with minimal effort; the smaller the number, the greater the difficulty, where a rating of 1 means that the pieces cannot be pulled apart.

[0076] The surface smoothness was subjectively evaluated by folding a piece of artificial leather sample in half so that the epidermal surfaces of the two halves were in contact. Then the sample was rubbed manually to evaluate the ease with which the epidermal surfaces moved past each other. The sample was rated on a scale of 1 - 5, where a value of 5 indicates the highest surface smoothness and a value of 1 indicates that the epidermal surfaces do not move past each other when rubbed.

[0077] The surface softness was subjectively evaluated by rubbing the skin with a finger and rating the softness on a scale of 1 - 5, where a rating of 5 indicates a very soft surface and a rating of 1 indicates a hard surface.

[0078] The peel strength of the top layer and the underlying layer was evaluated according to GB / T 8949 - 2008. A 3 - cm - wide sample was placed with the top layer against the top layer, with a layer of cyanoacrylate adhesive layer in between. The cyanoacrylate adhesive layer was cured by drying at 135 °C for 2 hours. The sample was cooled to room temperature. The two ends of the bonded sample were separated and peeled at a speed of 500 mm / min, while measuring the average load in N / 3 cm.

[0079] The frosting test was performed by cutting the sample into 5 - cm × 5 - cm squares. The squares were immersed in boiling water for 5 minutes, then cooled and dried at room temperature. The frosting appearance on the surface layer of the sample was visually inspected.

[0080] The results of these evaluations are also shown in Table 3.

[0081] Table 3 - Characteristics of Artificial Leather

[0082]

[0083] * Not an embodiment of the present invention.

[0084] Three-Layer Microfiber Artificial Leather The sample was prepared as follows. A fabric made of polyamine / polyethylene sea - island fibers was impregnated with an externally stabilized polyurethane dispersion ( YF - 4000) containing both a cationic surfactant and an anionic surfactant, and then cured by drying in an oven. Then the so - coated fabric was immersed in toluene to dissolve the polyethylene filaments and leach these polyethylene filaments out of the fabric, resulting in a polyurethane - impregnated micro - fabric base layer.

[0085] The aforementioned coating composition was applied to a release paper and formed into a 100 - μm film using a winding rod. The film was dried at 100 °C for 5 minutes. Then a 100 - μm layer of the same polyurethane dispersion ( YF - 4000) used for impregnating the fabric was applied to the dried film and dried at 140 °C for 90 seconds to form an adhesive layer. Then the polyurethane - impregnated base layer was applied to the surface of the adhesive layer, and the assembly was further cured at 120 °C for 5 minutes. Then the release paper was removed to expose the surface layer.

[0086] As described above, surface smoothness, surface softness, cool feeling in hand touch, and peel strength were evaluated. Abrasion resistance was evaluated using a Martindale abrasion test apparatus under an applied pressure of 12 KPa on a 38-mm disc for 20,000 cycles. A "qualified" grade indicates that the surface layer remained unbroken. Flexural resistance was measured on a 7.5 cm × 4.5 cm test sample according to GB / T8949-2008. The test was carried out at a rate of 100 / min at 20 °C - 23 °C for 100,000 cycles. A "qualified" grade indicates that the surface layer remained unbroken. The results are shown in Table 4.

[0087] Table 4 - Characteristics of Microfiber Artificial Leather

[0088]

[0089] As shown by the data in Tables 1 to 4, the coating compositions and artificial leathers of the present invention provide a unique and desired combination of properties. The coating composition containing an acrylate dispersion (Comparative Example * ) itself has an obvious odor. In contrast, the coating compositions of the present invention are odorless, although a significant amount of acrylate dispersion is present in each of them. The free films made from coating compositions 1 - 4 have the desired elongation and modulus properties. The top layers of Examples 1 - 4 provide a significant "cool touch" effect in the free films (Table 2) and two types of artificial leathers (Tables 3 and 4). The artificial leathers of the present invention have excellent surface smoothness and surface softness. The artificial leathers of the present invention have sufficient or better abrasion resistance and flexural resistance. Good adhesion between the top layer and the underlying layer was observed in the artificial leathers prepared using coating compositions 1 - 4, as confirmed by the peel strength test.

Claims

1. An artificial leather, said artificial leather comprising a backing layer and a top layer directly or indirectly adhered to said backing layer, said top layer comprising, based on the total weight of said top layer: (i) 25% to 75% by weight of a solid water-insoluble polyurethane elastomer, (ii) 10% to 40% by weight of a solid water-insoluble acrylate elastomer, and (iii) 1.5% to 30% by weight of embedded particles of an encapsulated phase change material having a melting or glass transition temperature of 20°C to 37°C.

2. The artificial leather according to claim 1, wherein the combined weight of i), ii) and iii) accounts for at least 85% by weight of the total weight of said top layer.

3. The artificial leather according to claim 1, said artificial leather further comprising at least one polyurethane foam layer between said backing layer and said top layer.

4. The artificial leather according to any of the preceding claims, said artificial leather further comprising a barrier layer between said backing layer and said top layer, said barrier layer comprising a cured elastomeric polyurethane coating prepared by forming a film of an externally stabilized aqueous dispersion and curing said film, said externally stabilized aqueous dispersion comprising a continuous aqueous phase having externally stabilized solid particles of said elastomeric polyurethane dispersed therein.

5. The artificial leather according to claim 4, wherein said externally stabilized dispersion comprises both an anionic surfactant and a cationic surfactant.

6. The artificial leather according to any of the preceding claims, wherein said backing layer comprises a fabric.

7. The artificial leather according to claim 6, wherein said fabric comprises microfibers embedded in a polyurethane binder.

8. The artificial leather according to claim 7, wherein said fabric is prepared by the steps of: i) providing a fabric having sea-island type fibers having at least two different filament types, ii) embedding said fabric in a polyurethane binder, and iii) contacting the embedded fabric with a solvent for at least one but less than all of said different filament types of said sea-island type fibers to dissolve at least one but less than all of said different filament types, and (iv) removing the dissolved filaments from the embedded fabric.

9. The artificial leather according to any of the preceding claims, wherein said top layer is prepared by forming a film of an aqueous dispersion and curing said film to produce said top layer, said aqueous dispersion comprising a continuous aqueous phase having dispersed therein: (i) internally stabilized solid particles of said water-insoluble polyurethane elastomer, (ii) particles of said water-insoluble acrylic elastomer, and (iii) said particles of said encapsulated phase change material.

10. An aqueous dispersion, said aqueous dispersion comprising a continuous aqueous phase having dispersed therein, based on the total weight of said aqueous dispersion: (i) from 15% to 40% by weight of internally stabilized solid particles of a water-insoluble polyurethane elastomer, (ii) from 5% to 20% by weight of particles of a water-insoluble acrylate elastomer, and (iii) from 3% to 15% by weight of particles of an encapsulated phase change material having a melting or glass transition temperature of from 20°C to 37°C, (i), (ii) and (iii) together account for from 35% to 65% of the total weight of said aqueous dispersion.

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