Embossable solvent-free PU sheet, laminate, and synthetic leather containing the same

Abstract

The present invention relates to an embossable solventless polyurethane sheet formed from a solventless polyurethane system comprising a polyol component (a) and an isocyanate component (b), The polyol component (a) comprises (a-1) at least one polyol having a functionality in the range of 1.5 to 2.5, and (a-2) optionally at least one polyol having a functionality in the range of 2.7 to 3.5, wherein the amount of polyol (a-2) is 6 mass% or less based on the total mass of the polyol component (a), and the polyol component (a) has an average functionality of 1.5 to 2.1. The present invention relates to a laminate and synthetic leather containing the sheet, and uses thereof.

Description

[Technical Field]

[0001] The present invention relates to an embossable solvent-free polyurethane sheet formed from a solvent-free polyurethane system containing a polyol component (a) and an isocyanate component (b), as well as to a laminate and synthetic leather comprising the same. [Background technology]

[0002] Solventless PU synthetic leather is one of the environmentally friendly solutions for the synthetic leather industry. Typically, an aqueous dispersion is required to form the top coat layer, and a solventless polyurethane sheet is required to form the base coat layer. Depending on the application, some synthetic leathers require an embossed pattern, and whether or not this pattern can be obtained depends primarily on the properties of the solventless polyurethane sheet. However, the typical thermosetting / crosslinking PU systems commonly used in synthetic leathers are almost impossible to emboss, even at very high embossing temperatures such as 180°C to 220°C.

[0003] WO2006 / 097508 discloses a method for preparing a polyurethane layer for synthetic leather, in which the polyurethane layer comprises an isocyanate component (a), a polyol component (b), a foaming agent (c), and a filler (d). This patent discloses several suitable raw materials for the isocyanate component (a) and the polyol component (b); however, it does not include the reproducibility of the texture of the polyurethane layer.

[0004] CN203938912U discloses an embossable, solvent-free synthetic leather that includes a PU top layer, a thermoplastic polyurethane foam middle layer, and a thermoset polyurethane base layer. Specifically, the patent discloses that the use of a multi-layer structure results in a product with good properties and good processing capabilities.

[0005] CN10403258 discloses a method for producing an embossable solvent-free synthetic leather that includes a PU top layer, a thermoplastic polyurethane foam middle layer, and a thermoset polyurethane base layer. Specifically, this patent discloses that the use of a multi-layer structure results in a product with good texture and feel.

[0006] CN106519177A discloses a method for producing embossable solvent-free PU synthetic leather. Specifically, this patent discloses preparing a semi-finished product using a two-component polyurethane, followed by embossing to obtain synthetic leather. However, this patent does not address the technical problem of how to improve the texture reproducibility of synthetic leather.

[0007] CN111016310A discloses a highly durable, solvent-free embossed grain-sucking polyurethane synthetic leather. Specifically, it discloses a two-component polyurethane foam resin, especially a post-cure embossed grain-sucking polyurethane synthetic leather.

[0008] Therefore, there remains a need to provide a new solvent-free polyurethane sheet that can have a very sharp and clear embossed pattern while imparting a higher texture reproduction, for example, greater than 55%, to synthetic leather based on the sheet. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] WO2006 / 097508 [Patent Document 2] CN203938912U [Patent Document 3] CN10403258 [Patent Document 4] CN106519177A [Patent Document 5] CN111016310A Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to overcome the above-mentioned problems of the prior art and to provide an embossable solvent-free polyurethane sheet formed from a solvent-free polyurethane system containing a polyol component (a) and an isocyanate component (b). The final synthetic leather based on this sheet exhibits improved properties in terms of instant peel strength, curability, and / or flex durability, as well as texture reproduction. Furthermore, the final synthetic leather can be prepared at a low temperature of 160°C to 175°C. [Means for solving the problem]

[0011] Surprisingly, the inventors have found that the above object can be achieved by providing an embossable solvent-free polyurethane sheet obtained from a solvent-free polyurethane system comprising a polyol component (a) and an isocyanate component (b), Here, the polyol component (a) comprises (a-1) at least one polyol having a functionality in the range of 1.5 to 2.5; and optionally (a-2) at least one polyol having a functionality in the range of 2.7 to 3.5; the amount of polyol (a-2) is 6% by mass or less based on the total mass of the polyol component (a); and the polyol component (a) has an average functionality of 1.5 to 2.1.

[0012] In a preferred embodiment of the present invention, the polyol (a-1) is a polyol mixture of at least two polyols having a functionality in the range of 1.5 to 2.5.

[0013] In a preferred embodiment of the present invention, the amount of polyol (a-2) is in the range of 0% by mass to 4% by mass, preferably 0% by mass to 3.5% by mass, and more preferably 1% by mass to 3% by mass, based on the total mass of the polyol component (a).

[0014] In a preferred embodiment of the present invention, at least one polyol of the polyol (a-1) has a functionality in the range of 1.5 to 2.1.

[0015] In a preferred embodiment of the present invention, at least one polyol of polyol (a-2) has a functionality in the range of 2.7 to 3.5, preferably 2.7 to 3.0.

[0016] In a preferred embodiment of the present invention, the polyol component (a) has an average functionality of 1.5 to 2.0, preferably 1.8 to 2.0, more preferably 1.9 to 2.0, especially 1.9 to 1.97.

[0017] In a preferred embodiment of the present invention, at least one polyol of the polyol (a-1) is selected from polyether polyols derived from epoxides or oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms.

[0018] In a preferred embodiment of the present invention, at least one polyol of the polyols (a-2) is selected from polyether polyols derived from epoxides.

[0019] In a preferred embodiment of the present invention, the isocyanate component (b) comprises (b-1) an isocyanate and (b-2) one or more polyols having a functionality in the range of 1.5 to 2.5.

[0020] In a preferred embodiment of the present invention, the polyol (b-2) has a weight average molecular weight in the range of 500 g / mol to 5000 g / mol, preferably 800 g / mol to 3000 g / mol, and an OH value in the range of 20 to 300, preferably 20 to 150.

[0021] Another object of the present invention is to provide an embossable solvent-free PU laminate, the solvent-free PU laminate comprising: A) a topcoat layer based on an aqueous polyurethane dispersion, B) a base coat layer underlying the top coat layer; wherein the base coat layer is made from a sheet according to the present invention.

[0022] In a preferred embodiment of the present invention, the topcoat layer of the laminate further contains a crosslinking agent in a content of 0.5 to 10%, preferably 0.5 to 5%, based on the amount of the aqueous polyurethane dispersion, the crosslinking agent being selected from aromatic or aliphatic polycarbodiimides (PCDIs) with or without hydrophilic modification, or isocyanate trimers.

[0023] In a preferred embodiment of the present invention, the aqueous polyurethane dispersion of the topcoat layer has an onset decomposition temperature measured by TGA in the range of 150 to 250°C, preferably 180 to 230°C.

[0024] Another object of the present invention is to provide a synthetic leather comprising the laminate according to the present invention and a substrate layer, the substrate layer being located beneath a base coat layer of the laminate.

[0025] Another object of the present invention is to provide the use of the sheet, laminate or synthetic leather as an upper or covering material in applications such as apparel, accessories, cases, electronic devices, furniture, automotive upholstery, sporting goods or leisure products.

[0026] Surprisingly, it has been found that the synthetic leather of the present invention has improved properties in terms of texture reproducibility, peel strength, cure property, and / or flex durability by using, as a base coat layer, an innovative embossable solvent-free polyurethane sheet that contains a specific polyol and is formed from a specific polyol and a polyol component (a) having a specific average functionality. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram showing the steps for preparing a two-layer laminate consisting of a top coat layer and a base coat. [Figure 2] FIG. 1 illustrates the preparation process of solvent-free PU synthetic leather. [Figure 3] Figure 1 shows the reproducibility of texture during the preparation of solvent-free PU synthetic leather. DETAILED DESCRIPTION OF THE INVENTION

[0028] Detailed Description of the Invention Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the following terms have the meanings ascribed to them unless specified otherwise.

[0029] As used herein, the articles "a" and "an" refer to one or to more than one (i.e., to at least one) of the grammatical object or component of the article.

[0030] Unless otherwise specified, all percentages (%) are "% by weight".

[0031] Unless otherwise specified, the term "total solids mass" refers to the total mass of the system or dispersion minus the mass of all solvents (including water).

[0032] Unless otherwise specified, for the topcoat layer, all weight percents (%) of additives and / or adjuvants refer to the percentage of "solids weight of additives and / or adjuvants divided by total solids weight of the aqueous polyurethane dispersion."

[0033] Unless otherwise specified, for the basecoat layer, all weight percents (%) of additives and / or adjuvants refer to the percentage of "solids weight of additives and / or adjuvants divided by total solids weight of the solventless polyurethane system."

[0034] Unless otherwise specified, the molecular weight of each component or polymer refers to the weight average molecular weight.

[0035] Unless otherwise specified, temperature refers to room temperature and pressure refers to ambient pressure.

[0036] The present invention provides an embossable solvent-free polyurethane sheet formed from a solvent-free polyurethane system comprising a polyol component (a) and an isocyanate component (b), wherein the polyol component (a) comprises (a-1) at least one polyol having a functionality in the range of 1.5 to 2.5; and optionally (a-2) at least one polyol having a functionality in the range of 2.7 to 3.5; the amount of polyol (a-2) is 6% by weight or less, based on the total weight of the polyol component (a); and the polyol component (a) has an average functionality of 1.5 to 2.1.

[0037] In the present invention, the solventless polyurethane system for producing the embossable solventless polyurethane sheet comprises a polyol component (a), an isocyanate component (b), a chain extender and / or crosslinker (c), and optionally a blowing agent (d), a catalyst (e), a filler (f) and additives and / or auxiliaries (g), such as pigments, thickeners, wetting agents and antioxidants.

[0038] Polyol component (a) In the present invention, the polyol component (a) comprises (a-1) at least one polyol having a functionality in the range of 1.5 to 2.5.

[0039] The polyol used as polyol (a-1) is selected from polyols having a functionality in the range of 1.5 to 2.5, and preferably a polyol having a functionality in the range of 1.5 to 2.1.

[0040] The polyol used as polyol (a-1) preferably has a mass average molecular weight of 500 g / mol to 10,000 g / mol, preferably 800 g / mol to 6,000 g / mol, more preferably 900 g / mol to 4,000 g / mol, and an OH value in the range of 20 to 400 mgKOH / g, preferably 20 to 300 mgKOH / g, more preferably 20 to 200 mgKOH / g.

[0041] The polyol (a-1) may be a single polyol or a mixture of at least two single polyols. Preferably, the polyol (a-1) is a mixture of at least two single polyols. Preferably, a polyether polyol mixture is used as the polyol (a-1).

[0042] Suitable polyether polyols preferably have a weight average molecular weight ranging from 850 g / mol to 1500 g / mol, preferably from 900 g / mol to 1200 g / mol, a functionality ranging from 1.9 to 2.1, and an OH value ranging from 50 to 400 mg KOH / g, preferably from 100 to 200 mg KOH / g. These polyether polyols may be polyether polyols obtained by ring-opening polymerization of oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, such as tetrahydrofuran. Preferably, the polyol is produced by polymerizing tetrahydrofuran as a repeating unit, and is preferably capped with a primary hydroxyl.

[0043] The polyether polyols used also preferably have a weight average molecular weight in the range of 3000 g / mol to 4000 g / mol, preferably 3200 g / mol to 3600 g / mol, a functionality in the range of 1.5 to 2.0, and an OH value in the range of 20 to 200 mg KOH / g, preferably 20 to 60 mg KOH / g. These polyether polyols can be polyether polyols obtained by homopolymerization of diols such as propylene glycol, ethylene glycol or butanediol, or polyether polyols produced by polymerizing epoxides such as ethylene oxide and / or propylene oxide as repeating units and using propylene glycol as a starter, preferably capped with ethylene oxide having primary hydroxyl groups.

[0044] In a preferred embodiment according to the present invention, the polyol (a-1) comprises a mixture of the above tetrahydrofuran-derived polyether polyol and the above epoxide-derived polyether polyol in a mass ratio of 1:1.5 to 3, preferably 1:1.5 to 2.5.

[0045] The polyol used as the polyol (a-1) in the present invention may be one produced by a known method or a commercially available one.

[0046] In the present invention, the polyol component (a) further comprises (a-2) at least one polyol having a functionality in the range of 2.7 to 3.5; wherein the amount of polyol (a-2) is ≦6% by weight based on the total weight of the polyol component (a).

[0047] In a preferred embodiment according to the present invention, the amount of polyol (a-2) is in the range of 0% to 4% by mass, preferably 0% to 3.5% by mass, more preferably 0.5% to 3.0% by mass, and particularly 1.0% to 3.0% by mass, based on the total mass of the polyol component (a).

[0048] The polyol (a-2) is selected from polyols having a functionality in the range of 2.7 to 3.5 or is a mixture of such polyols. The polyol used as polyol (a-2) preferably has a functionality in the range of 2.7 to 3.0.

[0049] The polyol used as polyol (a-2) preferably has a mass average molecular weight in the range of 3000 g / mol to 6000 g / mol, preferably 3500 g / mol to 5000 g / mol, more preferably 4000 g / mol to 4500 g / mol, and an OH value in the range of 20 to 200 mgKOH / g, preferably 20 to 100 mgKOH / g, more preferably 25 to 60 mgKOH / g.

[0050] The polyol (a-2) can be a single polyol or a mixture of single polyols, preferably a polyether polyol, more preferably a polyether polyol based on an epoxide such as ethylene oxide (EO), propylene oxide (PO), and / or butane oxide (BO). These polyether polyols can be polyether polyols produced by polymerizing epoxides such as ethylene oxide and / or propylene oxide as repeating units and using glycerol as a starter, and are preferably capped with ethylene oxide having primary hydroxyl groups. The polyols used as the polyol (a-2) in the present invention can be produced by known methods or commercially available.

[0051] In the present invention, the polyol component (a) consisting of the polyol (a-1) and optionally the polyol (a-2) has an average functionality (FAv) of 1.5 to 2.1. Preferably, the polyol component (a) has an average functionality of 1.8 to 2.0, more preferably 1.9 to 2.0, particularly preferably 1.9 to 1.97, and particularly preferably 1.9 to 1.96 or 1.9 to 1.95.

[0052] In the present invention, FAv means the average Fn of multiple polyols contained in the polyol component (a), and is represented by the following formula: FAv=MR1 * F1+MR2 * F2+MR3 * F3+..., is represented by In the formula, MR1 is the molar ratio of the first polyol in polyol component (a), F1 is the functionality of the first polyol in polyol component (a); MR2 is the molar ratio of the second polyol in polyol component (a), F2 is the functionality of the second polyol in polyol component (a), ...

[0053] In the present invention, the molecular weight of each component was determined using gel permeation chromatography (GPC) according to GB / T21863-2008.

[0054] In the present invention, the OH value of each polyol component was determined according to DIN53240.

[0055] In the present invention, functionality (Fn) means the number of terminal hydroxyl groups per polyol molecule. Functionality is determined by the following formula: F n =M n * (OHv) / 56100 is determined by In the formula, Mn represents the number average molecular weight of the polyol, and OHv represents the OH value of the polyol component.

[0056] Surprisingly, the present inventors have found that the composition of polyol component (a) significantly affects the properties of the solvent-free polyurethane sheet of the present invention. A polyol component (a) having an average functionality (FAv) of 1.5 to 2.1, preferably 1.9 to 2.0, more preferably 1.9 to 1.97, and particularly 1.9 to 1.96 or 1.9 to 1.95, results in excellent properties of the solvent-free polyurethane sheet of the present invention, particularly texture reproducibility of greater than 55%. In particular, by using the specific polyols (a-1) and (a-2) described above, the solvent-free polyurethane sheet of the present invention exhibits excellent properties, such as texture reproducibility, peel strength, curability, and / or flex durability. The present inventors have found that the type and amount of polyol (a-1) and polyol (a-2) significantly affect the properties of the solvent-free polyurethane sheet of the present invention. Specifically, when the amount of polyol (a-2) having a functionality in the range of 2.7 to 3.5 is 6% by mass or less, based on the total mass of the polyol component (a), the solvent-free polyurethane sheet advantageously achieves the above-mentioned excellent properties, i.e., excellent texture reproducibility of more than 55%, while ensuring excellent peel strength, curing properties, and flexural durability. If the amount of polyol (a-2) exceeds 6% by mass, texture reproducibility decreases. Preferably, the amount of polyol (a-2) is in the range of more than 0% to 4% by mass, preferably 1% to 3% by mass, based on the total mass of the polyol component (a).

[0057] Isocyanate component (b) In the present invention, the isocyanate component (b) comprises at least one isocyanate, i.e., (b-1) isocyanate. The isocyanate used to produce the base coat layer of the present invention includes all isocyanates known for producing polyurethanes. These include aliphatic, alicyclic, araliphatic and / or aromatic isocyanates, such as tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), These include cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and / or 2,6-diisocyanate and / or dicyclohexylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate, diphenylmethane 2,2'-, 2,4'- and / or 4,4'-diisocyanate (MDI), polymeric MDI, naphthylene 1,5-diisocyanate (NDI), tolylene 2,4- and / or 2,6-diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate. Diphenylmethane 2,2'-, 2,4'- and / or 4,4'-diisocyanate, and polymeric MDI, especially diphenylmethane 4,4'-diisocyanate, are particularly preferred.

[0058] The amount of the isocyanate component (b) is selected so that the isocyanate index is 100-140, preferably 100-120.

[0059] The isocyanate component (b) may also contain (b-2) at least one polyol.

[0060] The polyol (b-2) is selected from polyols having a functionality in the range of 1.5 to 2.5, or a mixture of such polyols. The polyol used as polyol (b-2) preferably has a functionality in the range of 1.6 to 2.0.

[0061] The polyol used as polyol (b-2) preferably has a mass average molecular weight in the range of 500 g / mol to 5000 g / mol, preferably 800 g / mol to 3000 g / mol, more preferably 1000 g / mol to 2500 g / mol, and an OH value in the range of 20 to 300 mgKOH / g, preferably 20 to 150 mgKOH / g, more preferably 30 to 100 mgKOH / g.

[0062] The polyol (b-2) may be a single polyol or a mixture of single polyols. Preferably, a polyol mixture, in particular a polyether polyol mixture, is used as polyol (b-2).

[0063] The polyether polyols used preferably have a weight average molecular weight of 1000 g / mol to 2500 g / mol, preferably 1800 g / mol to 2300 g / mol, a functionality of 1.9 to 2.1, and an OH value of 20 to 200 mg KOH / g, preferably 30 to 100 mg KOH / g. These polyether polyols may be polyether polyols obtained by ring-opening polymerization of oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, such as tetrahydrofuran. Preferably, the polyol is produced by polymerizing tetrahydrofuran as a repeating unit, and is preferably capped with a primary hydroxyl.

[0064] The polyether polyols used also preferably have a weight average molecular weight in the range of 1000 g / mol to 3000 g / mol, preferably 1500 g / mol to 2500 g / mol, a functionality in the range of 1.8 to 2.0, and an OH number in the range of 20 to 200 mg KOH / g, preferably 30 to 100 mg KOH / g. These polyether polyols may be polyether polyols produced by polymerizing epoxides such as ethylene oxide and / or propylene oxide as repeating units and using propylene glycol as a starter, and are preferably capped with propylene glycol.

[0065] In a preferred embodiment according to the present invention, the polyol (b-2) comprises a mixture of the above polyether polyol derived from tetrahydrofuran and the above polyether polyol derived from epoxide in a mass ratio of 1:0.5 to 2, preferably 1:0.8 to 1.5.

[0066] The polyol used as the polyol (b-2) in the present invention may be one produced by a known method or a commercially available one.

[0067] In a preferred embodiment according to the present invention, the isocyanate component (b) may contain an additive, such as oxydiethylenebis(chloroformate) (DECF), to improve its properties. The amount of the additive is preferably 0.005 to 0.5% by mass, more preferably 0.01 to 0.1% by mass, based on the total mass of the isocyanate component (b).

[0068] Chain extenders and / or crosslinkers (c) Usable chain extenders and / or crosslinkers (c) are preferably substances with a molar mass of less than 500 g / mol, particularly preferably 60 to 400 g / mol, where the chain extenders have two hydrogen atoms reactive with isocyanates and the crosslinkers have three hydrogen atoms reactive with isocyanates. They can be used individually or, preferably, in the form of a mixture. It is preferred to use diols and / or triols with a molecular weight of less than 500, particularly 60 to 400, and especially 60 to 350. Examples of compounds that can be used include aliphatic, cycloaliphatic, and / or aromatic diols having 2 to 14, preferably 2 to 10, carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-, 1,3-, and 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, diethanolamine, or triols such as 1,2,4- or 1,3,5-trihydroxycyclohexane, glycerol, and trimethylolpropane. Ethylene glycol, 1,3-propanediol, or 1,4-butanediol, especially 1,4-butanediol, are preferably used.

[0069] The amount of the chain extender and / or crosslinking agent (c) is preferably 0.5 to 5 mass %, more preferably 1.5 to 4.5 mass %, based on the total mass of the polyol component (a).

[0070] Blowing agent (d) This system may also contain a blowing agent (d). Suitable blowing agents (d) are known to those skilled in the art and are, for example, selected from the group consisting of carbon dioxide, alkanes such as propane, isobutane and pentane, alcohols such as methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol and tert-butanol, ethers such as dimethyl ether, ketones such as acetone or methyl ethyl ketone, halogenated hydrocarbons such as hydrofluoropropene, water, nitrogen and mixtures thereof. Preferably, water is used as the only blowing agent.

[0071] The amount of the blowing agent (d) is preferably 0.1 to 5 mass %, more preferably 0.1 to 1.0 mass %, based on the total mass of the polyol component (a).

[0072] Catalyst (e) As catalyst (e), any compound that accelerates the isocyanate-polyol reaction can be used. Such compounds are known and are described, for example, in "Kunststoffhandbuch, Vol. 7, Polyurethane", Carl Hanser Verlag, 3rd Edition, 1993, Chapter 3.4.1. These include amine-based catalysts and organometallic compound-based catalysts, or mixtures thereof.

[0073] As catalysts based on organometallic compounds, it is possible to use, for example, organotin compounds such as tin(II) salts of organic carboxylic acids, such as tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate, and dialkyltin(IV) salts of organic carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate, as well as Zn or Bi salts, such as zinc octoate, bismuth(III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octoate, or alkali metal salts of carboxylic acids, such as potassium acetate or potassium formate.

[0074] As amine-based catalysts, for example, N,N,N-triethylaminoethoxyethanol, bis(N,N-dimethylaminoethyl)ether, dimethylcyclohexylamine, trimethylhydroxyethylethylenediamine, dimethylbenzylamine, triethylamine, triethylenediamine, pentamethyldipropylenetriamine, dimethylethanolamine, N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine, tris(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylamine, N-ethylmorpholine, diazabicycloundecene, diazabicyclononene, diazabicyclooctane, preferably triethylenediamine or bis(N,N-dimethylaminoethyl)ether can be used.

[0075] The catalyst (e) used in the present invention may be a commercially available product such as Haptex CC 6945 / 92 C-CC manufactured by BASF and Additive CX 93600 manufactured by BASF.

[0076] Typically, the amount of catalyst (e) is preferably 0.05 to 5 mass %, more preferably 0.1 to 1.5 mass %, based on the total mass of polyol component (a).

[0077] Filler (f) According to the invention, if present, the filler that can be used is an inorganic filler selected from calcium carbonate, aluminum hydroxide, barium sulfate, or talc, preferably calcium carbonate or aluminum hydroxide, and the amount of inorganic filler is 0 to 200% by weight, preferably 10 to 50% by weight, based on the total weight of the solventless polyurethane system.

[0078] Additives and / or adjuvants (g) Additives and / or auxiliaries (g) that can be used include surfactants, preservatives, pigments, colorants, antioxidants, silicone oil leveling agents, stabilizers, thickeners, wetting agents, and reinforcing agents. When preparing a solventless polyurethane system, it is common to use one or a mixture of the above additives and / or auxiliaries to improve the physical properties of the resulting polyurethane sheet, such as texture reproducibility, peel strength, flex durability, and curing properties.

[0079] Typically, the amount of additives and / or auxiliaries is preferably 0 to 12% by weight, more preferably 0.1 to 10% by weight, based on the total weight of the solventless polyurethane system.

[0080] According to the present invention, thickeners, wetting agents, and antioxidants are preferably used. Materials that can be used, when present, include all thickeners, wetting agents, and antioxidants commonly used in solventless polyurethane systems. The amount of each of them is preferably 0.1 to 5% by weight, more preferably 0.5 to 1% by weight, based on the total weight of the solventless polyurethane system.

[0081] Further information on the use and mode of action of the abovementioned auxiliaries and additives, as well as further examples, are given by way of example in "Kunststoffhandbuch, Band 7, Polyurethane" ["Plastics handbook, Volume 7, Polyurethanes"], Carl Hanser Verlag, 3rd edition, 1993, Chapter 3.4.

[0082] The invention further provides an embossable solvent-free PU laminate, the solvent-free PU laminate comprising: A) a topcoat layer based on an aqueous polyurethane dispersion, B) a base coat layer underlying the top coat layer; wherein the base coat layer is made from an embossable solvent-free polyurethane sheet according to the present invention.

[0083] Topcoat layer In the present invention, the aqueous polyurethane dispersion used in the top coat skin layer has an onset decomposition temperature, measured by TGA, in the range of 150 to 250° C., preferably 180 to 230° C. Suitable aqueous polyurethane dispersions for use in the top coat skin layer are disclosed, for example, in PCT / CN2020 / 084834, the contents of which are expressly incorporated herein by reference.

[0084] In the present invention, the aqueous polyurethane dispersion used for the topcoat skin layer may be a commercially available product such as Haptex CC 6945 / 90 C-CH from BASF, or may be prepared from an isocyanate component (a') and a polyol component (b'). The method for preparing the aqueous polyurethane dispersion may be any method commonly used in the art and known by those skilled in the art. The isocyanate component (a') includes conventional aliphatic, cycloaliphatic, and aromatic diisocyanates and / or polyisocyanates. It is preferred to use tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and mixtures of diphenylmethane diisocyanate with polyphenylene polymethylene polyisocyanate (polymeric MDI), particularly diphenylmethane diisocyanate (monomeric MDI). Isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and hydrogenated diphenylmethane-4,4'-diisocyanate (H12MDI) are also preferred.

[0085] The isocyanates or isocyanate prepolymers described below may be modified, for example, by the incorporation of uretidione, carbamate, isocyanurate, carbodiimide or allophanate groups. It is also possible to use blends of different isocyanates.

[0086] The polyisocyanate can also be used in the form of a polyisocyanate prepolymer. These prepolymers are known in the art. They are prepared in a conventional manner by reacting the above-mentioned polyisocyanates with the compounds described below having isocyanate-reactive hydrogen atoms to form the prepolymer. The reaction can be carried out, for example, at a temperature of about 80°C. The polyol / polyisocyanate ratio is generally selected so that the NCO content of the prepolymer is in the range of 6% to 25% by weight.

[0087] The polyol component (b') preferably comprises polyetherols and / or polyesterols, which are generally known and are described, for example, in "Kunststoffhandbuch Polyurethane" by Güenter Oertel, Carl-Hanser-Verlag, 2nd edition, 1983, Chapter 3.1.1. Alternative names commonly used in the art are, on the one hand, polyether polyols or polyether alcohols, and, on the other hand, polyester polyols or polyester alcohols.

[0088] In the present application, the polyol component (b') is preferably a polyol mixture. The polyol component (b') includes (b'-1) a polyol having a weight average molecular weight in the range of 500 g / mol to 10,000 g / mol and a functionality in the range of 2 to 4, and (b'-2) a polyol having a weight average molecular weight in the range of 500 g / mol to 3,000 g / mol and a functionality in the range of 2 to 4. For example, the polyol (b'-1) may be a polyester such as XCP-2000N, and the polyol (b'-2) may be a hydrophilic polyether based on polyethylene glycol such as Ymer N120.

[0089] The polyol component (b') includes (b'-3) a chain extender having a molecular weight of less than 400 g / mol, and (b'-4) a hydrophilic chain extender containing a carboxylate group or a sulfonate group.

[0090] Chain extenders (b'-3) that can be used are preferably substances with a molar mass of less than 400 g / mol, particularly preferably 60 to 400 g / mol, which have at least two hydrogen atoms reactive with isocyanates. They can be used individually or, preferably, in the form of a mixture. It is preferred to use diols and / or triols with a molecular weight of 60 to 400, especially 60 to 350. Examples that can be used include aliphatic, cycloaliphatic, and / or aromatic diols having 2 to 10 carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-, 1,3-, and 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, diethanolamine, or triols, such as 1,2,4- or 1,3,5-trihydroxycyclohexane, glycerol, and trimethylolpropane. It is also preferred to use diamines and / or triamines. Examples that can be used include diethylenetriamine or N-(2-hydroxyethyl)ethylenediamine. The amount of chain extender (b'-3) based on the total solids mass of the aqueous polyurethane dispersion is preferably 0.1 to 10 mass%, particularly preferably 0.2 to 8 mass%.

[0091] The hydrophilic chain extenders (b'-4) that can be used are those containing carboxylate or sulfonate groups. These provide hydrophilic groups to the aqueous polyurethane dispersion, ensuring that the dispersion has adequate hydrophilicity. Preferably, AB-salt (sodium 2-[(2-aminoethyl)amino]ethanesulfonate) or DMPA (dimethylolpropionic acid) can be used here. The amount of hydrophilic chain extender (b'-4) is preferably 0.1 to 50% by weight, particularly preferably 0.2 to 35% by weight, based on the total solids weight of the aqueous polyurethane dispersion.

[0092] The aqueous polyurethane dispersion contains 0.5% or less, preferably less than 0.1%, of carboxylate groups, based on the total solids weight of the aqueous polyurethane dispersion, where the carboxylate groups originate from the carboxyl-containing hydrophilic extender and other carboxyl-containing starting materials used to prepare the aqueous polyurethane dispersion. Furthermore, the molar ratio of hydroxyl and / or amino groups to isocyanate groups present in the aqueous polyurethane dispersion is 0.9 to 1.5, preferably 1.10 to 1.25.

[0093] The aqueous polyurethane dispersion optionally contains a gel-reactive amine neutralizing agent to provide the dispersion with a suitable pH range of 6 to 9. The amount of amine neutralizing agent, based on the total solids weight of the aqueous polyurethane dispersion, is preferably 0.01 to 5% by weight, particularly preferably 0.05 to 2% by weight. By way of example, the amine neutralizing agent is selected from the group consisting of triethylenediamine (TEDA), 1,2-dimethylimidazole, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylethylenediamine, and tertiary amines.

[0094] Optionally, the aqueous polyurethane dispersion contains a surfactant. The surfactant may be a nonionic surfactant such as alcohol ethoxylate, alkyl polyglucoside, bisphenol A ethoxylate, ethoxylated natural fat oil, or fatty acid ethoxylate, or / and an anionic surfactant such as fatty alcohol ether sulfate, fatty alcohol sulfate, linear alkyl benzene sulfonate, oleic acid sulfonate, diisodecyl sulfosuccinate, alkyl ether phosphate, or alkyl ether carboxylate, or / and a cationic surfactant such as amine ethoxylate, aminoborol, or quaternary ammonium surfactant.

[0095] In a preferred embodiment of the present invention, the topcoat skin layer based on an aqueous polyurethane dispersion also contains a crosslinking agent. Suitable crosslinking agents can be selected from aromatic or aliphatic polycarbodiimides (PCDIs), with or without hydrophilic modifications, or isocyanates. The crosslinking agents can be used in a mixed or single form, preferably in a mixed form. As an example, Astacin Hardener CA and / or Astacin Hardener CI can be used as crosslinking agents. The amount of crosslinking agent, based on the total solids weight of the aqueous polyurethane dispersion, is preferably 0.1 to 20% by weight, particularly preferably 0.5 to 15% by weight, and particularly preferably 1 to 10% by weight.

[0096] In a preferred embodiment of the present invention, the topcoat skin layer based on an aqueous polyurethane dispersion also contains other additives and / or auxiliaries commonly known to those skilled in the art. Possible additives and / or auxiliaries include surfactants, thickeners, pigments, colorants, antioxidants, reinforcing agents, stabilizers, and wetting agents. In preparing polyurethane dispersions, it is common to use one or a mixture of the above-mentioned additives and / or auxiliaries to improve the properties of the resulting polyurethane dispersion. Typically, the amount of other additives and / or auxiliaries is preferably 0 to 25% by weight, more preferably 0.5 to 15% by weight, based on the total solids weight of the aqueous polyurethane dispersion. Any compound suitable for preparing polyurethane dispersions, such as Permutex PP-39-611, can be used as the pigment. If present, the amount of pigment is preferably 1 to 12% by weight, particularly preferably 5 to 10% by weight, based on the total solids weight of the aqueous polyurethane dispersion. Any compound commonly used in preparing polyurethane dispersions, such as Permutex RM 4456, can be used as the thickener. The amount of thickener, if present, is preferably 0.1 to 8% by weight, particularly preferably 0.5 to 5% by weight, based on the total solids weight of the aqueous polyurethane dispersion. As wetting agents, any compound commonly used in the preparation of polyurethane dispersions, such as BYK 348, can be used. The amount of wetting agent, if present, is preferably 0.1 to 5% by weight, particularly preferably 0.3 to 3% by weight, based on the total solids weight of the aqueous polyurethane dispersion. As antioxidants, any compound suitable for the preparation of polyurethane dispersions can be used. The amount of antioxidant, if present, is preferably 0.1 to 5% by weight, particularly preferably 0.5 to 1% by weight, based on the total solids weight of the aqueous polyurethane dispersion.

[0097] Base coat layer In the present invention, the base coat layer is made of an embossable solvent-free polyurethane sheet according to the present invention, which is formed from the solvent-free polyurethane system defined above.

[0098] The present invention further provides a synthetic leather comprising the laminate defined above and a substrate layer, the substrate layer being located under the base coat layer of the laminate. The top coat layer and the base coat layer are as defined above. The substrate layer is obtained as follows:

[0099] Base material layer In this application, the synthetic leather has a substrate layer below the base coat layer. In principle, the substrate layer can be any layer capable of forming an adhesive bond with the base coat layer. The thickness of the substrate layer is typically in the range of 0.01 mm to 20 mm, preferably in the range of 0.1 mm to 15 mm. The substrate layer is selected from, for example, nonwoven fabric, woven fabric, TPU, genuine leather, wood, plastic, or split leather. In one preferred embodiment, nonwoven fabric or split leather is used as the substrate layer.

[0100] The laminates of the present invention have improved texture reproduction, as well as instantaneous peel strength, hardening properties, and / or flex durability. The laminates of the present invention can be used in apparel and accessories, such as handbags, shoes, boots, gloves, hats, or as upper materials for outerwear items such as jackets, pants, and belts. They can also be used as cases and covers for electronic devices, such as suitcases, briefcases, watch bands, smartphone cases, earphone cases, and camera cases. In the furniture / upholstery field, the laminates can be used as synthetic leather covers for sofas, car seats, car interiors, chairs, cushions, coffee tables, and certain types of decorative items, such as wall hangings. The laminates of the present invention can also be used in sporting goods or leisure products, such as game balls, saddles, toys, and the like. In another aspect, the laminates of the present invention can be used anywhere as a substitute for genuine leather.

[0101] PU sheets / laminates / leather can be processed in many ways, for example: PU sheet / laminate / leather is continuously embossed with a hot embossing roller at 150-250℃ to reproduce the texture / pattern.

[0102] After the PU sheet / laminate / leather is heated to a desired temperature, for example, 150 to 250°C, the leather is continuously embossed by an embossing roller without a heater.

[0103] The PU sheet / laminate / leather is heated to the desired temperature, for example 150-250°C, and the leather is continuously sucked with a vacuum embossing roller that has small indentations and texture.

[0104] The PU sheet / laminate / leather is embossed with a hot plate (150-250°C) rather than in a continuous manner like with an embossing roller.

[0105] The PU sheet / laminate / leather is pressed for a short time by a hot stamper or plate (150-250°C) bearing the designed brand logo or character. [Example]

[0106] The present invention will now be described with reference to examples and comparative examples, but these are not intended to limit the scope of the present invention.

[0107] The following ingredients were used: Polyol #1 was prepared by polymerizing tetrahydrofuran as a repeating unit and capping it with primary hydroxyl groups, and has a functionality of 2 and a hydroxyl number (OHv) of 112.3 mg KOH / g.

[0108] Polyol #2 was prepared by polymerizing ethylene oxide as a repeating unit, using propylene glycol as a starter, and capping with ethylene oxide having a primary hydroxyl group, and has a functionality of 1.76 and a hydroxyl number (OHv) of 29.5 mg KOH / g.

[0109] Polyol #3 was prepared by polymerizing ethylene oxide as a repeating unit, using glycerol as a starter, and capping with ethylene oxide having a primary hydroxyl group, and has a functionality of 2.72 and a hydroxyl number (OHv) of 35 mg KOH / g.

[0110] Polyol #4 was made by polymerizing propylene oxide as the repeating unit, using TDA as the starter, and capping with propylene oxide, and has a functionality of 4 and a hydroxyl number (OHv) of 405 mg KOH / g.

[0111] Polyol #5 was made by polymerizing propylene oxide as a repeating unit, using propylene glycol as a starter, and capping with propylene glycol, and has a functionality of 2 and a hydroxyl number (OHv) of 55 mg KOH / g.

[0112] Polyol #6 was prepared by polymerizing tetrahydrofuran as a repeating unit and capping it with primary hydroxyl groups, and has a functionality of 2 and a hydroxyl number (OHv) of 56.1 mg KOH / g.

[0113] Haptex CC 6945 / 90 C-CH is a water-based PUD from BASF with a solids content of 34.5%. ADDITIVE DECF is a polymerization inhibitor from BASF. Permutex PP-39-611 is a 20.0% solids Pigment Black from Stahl. Permutex RM 4456 is a 28.0% solids thickener from Stahl. BYK 348 is a 100% solids wetting agent from BYK. Astacin Hardener CI is a 70.0% solids crosslinker from BASF. Astacin Hardener CA is a 60.0% crosslinker from BASF. Lupranate MS is an isocyanate from BASF. The additive CX 93600 is a catalyst from BASF. Haptex CC 6945 / 92 C-CC is a catalyst from BASF. Favini B100 is a release paper from Favini.

[0114] Preparation of the topcoat layer: The topcoat layer was prepared using the following ingredients:

[0115] [Table 1]

[0116] Preparation of solvent-free polyurethane sheet as base coat layer: A solvent-free polyurethane sheet was prepared using the following ingredients:

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4]

[0120] Preparation of the laminate Example 1 Preparation of a Laminate Comprising a Topcoat Skin Layer and a Basecoat Layer The formulations in Table 2 were prepared by mixing the ingredients in order, then knife-coating a 100 μm thick coating onto Favini B100 release paper within 4 hours, followed by drying in Oven #1 at 80°C for 2 minutes and 120°C for 2 minutes. The formulations in Table 5 were then mixed in order, then knife-coated onto the dried topcoat formulation at a thickness of 350 μm, followed by heating in Oven #2 at 120-140°C for 5-10 minutes to form the basecoat layer. The resulting laminate was then separated from the release paper to obtain the final laminate product.

[0121] See Figure 1 for method.

[0122] Example 2 Preparation of PU synthetic leather comprising a top coat layer, a base coat layer and a substrate layer The formulations in Table 2 were prepared by mixing the ingredients in order, then knife-coating a 100 μm thick coating onto Favini B100 release paper within 4 hours, followed by drying in oven #1 at 80°C for 2 minutes and 120°C for 2 minutes. The formulations in Table 5 were then mixed in order, then knife-coated onto the dried topcoat formulation at a thickness of 350 μm, followed by heating in oven #2 at 120-140°C for 5-10 minutes. A substrate layer was then applied onto the dried basecoat layer, followed by heating in oven #3 at 140°C for 2-10 minutes, followed by pressing. After peeling off the release paper, the resulting PU synthetic leather was obtained.

[0123] See Figure 2 for method.

[0124] PU synthetic leather physical property testing Peel Strength Test The peel strength test is performed on PU artificial leather immediately after peeling from the release paper after curing, and the test, including specimen preparation and testing, must be completed within 20 minutes. The test is in accordance with the SATRA TM 411 standard.

[0125] Curing properties The curing property of the two-component PU layer was evaluated by pressing the top coat of the laminate (PU synthetic leather) with a fingernail and visually evaluating it according to the following scale: Grade 1: Claw mark rebound >10 seconds or top coat is damaged Grade 2: Claw mark rebound (7-9 seconds); Grade 3: Claw mark rebound (4-6 seconds); Grade 4: Claw mark rebound (1-3 seconds); Grade 5: No obvious claw marks

[0126] Bending durability test The flexural endurance test was carried out according to standard ISO 5402 as follows: The PU synthetic leather test specimens were cut according to ISO 2418, including at least three vertical and three horizontal specimens. The specimens were conditioned according to ISO 2419, and the test was carried out in a conditioned atmosphere. After 25x magnification, the specimens were visually evaluated for cracks, loss of adhesion, and color change. A "pass" indicates no cracks, loss of adhesion, or color change. A "fail" indicates damage to the specimen.

[0127] Embossing characteristics (texture reproducibility): The embossability test was carried out as follows: The embossing machine is model 380 (Nanjing Yueyi Clothing Co. Ltd.), and a custom-made embossing plate is installed. The embossing method is as follows: (1) Set the temperature to 170°C and wait until the embossing plate maintains a constant temperature; (2) Set the embossing / pressing time to 40 seconds; (3) Place the leather sample on the console, press the pressure button, then press the operation button with both hands. When the time is up, the embossing plate will automatically move up and you can remove the sample.

[0128] Using a 3D profile meter measurement system (model: VR-3200), we measured 1) the height difference (ΔHa) of the embossing plate and 2) the height difference (ΔHb) of the laminate embossed with the plate (see Figure 3). The ratio ΔHb / ΔHa is expressed as a percentage indicating what percentage of the embossing plate pattern the laminate replicates. ΔHb = ΔHa means that the embossing plate pattern is reproduced 100%.

[0129] [Table 5]

[0130] The above results show that the PU synthetic leathers obtained in Examples 1 to 4 of the present invention, using the solventless polyurethane system of the present invention as the base coat layer, not only exhibit significant improvements in texture reproducibility but also good peel strength, curing properties, and flexural durability, compared to Comparative Examples 1 and 2. Furthermore, Example 4 of the present invention, which uses a polyol component (a) consisting of a polyol (a-1) with an average functionality of less than 2.1, exhibits excellent texture reproducibility, good flexural durability, and peel strength, but slightly poorer curing properties, while Comparative Example 2, which uses a polyol component (a) consisting of a polyol (a-1) with an average functionality of 2.38, exhibits poor texture reproducibility, flexural durability, and peel strength. Examples 1 to 3 of the present invention, in which the polyol component (a) consisting of polyol (a-1) and polyol (a-2) was used in an amount of 6 mass % or less, exhibited good peel strength, curability, and flexural durability, as well as excellent texture reproducibility, whereas Comparative Example 1, in which a large amount of the polyol component (a) consisting of polyol (a-1) and polyol (a-2) was used, exhibited poor texture reproducibility.

[0131] It will be understood that the structures, materials, compositions, and methods described herein are intended to be representative examples of the present invention, and that the scope of the present invention is not limited by the scope of the examples. Those skilled in the art will recognize that the disclosed structures, materials, compositions, and methods can be modified to practice the present invention, and that such modifications are considered to be within the scope of the present invention. Accordingly, it is intended that the present invention encompass such modifications and variations as come within the scope of the appended claims and their equivalents.

Claims

1. An embossable solventless polyurethane sheet formed from a solventless polyurethane system comprising a polyol component (a) and an isocyanate component (b), The polyol component (a) is (a-1) at least one polyol having a functionality in the range of 1.5 to 2.5; and (a-2) at least one polyol having a functionality in the range of 2.7 to 3.5; Including, the amount of polyol (a-2) is in the range of 1% by weight to 3% by weight based on the total weight of the polyol component (a); the polyol component (a) has an average functionality of 1.5 to 2.1; Embossable solvent-free polyurethane sheet.

2. The sheet according to claim 1, wherein the polyol (a-1) is a mixture of at least two polyols.

3. A sheet as described in claim 1 or 2, wherein the solvent-free polyurethane system consists of the polyol component (a), the isocyanate component (b), a chain extender and / or crosslinker (c), and optionally a blowing agent (d), a catalyst (e), a filler (f) and an additive and / or auxiliary (g).

4. 2. The sheet according to claim 1, wherein the polyol (a-1) has a functionality in the range of 1.5 to 2.

1.

5. 2. The sheet of claim 1, wherein the polyol (a-2) has a functionality in the range of 2.7 to 3.

0.

6. The sheet of claim 1 or 2, wherein the polyol component (a) has an average functionality of 1.8 to 2.

0.

7. The sheet according to claim 1 or 2, wherein at least one polyol of the polyol (a-1) is selected from polyether polyols derived from epoxides or oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms.

8. 2. The sheet according to claim 1, wherein at least one polyol of the polyol (a-2) is selected from polyether polyols derived from epoxides.

9. 2. The sheet of claim 1, wherein the isocyanate component (b) comprises (b-1) an isocyanate and (b-2) at least one polyol having a functionality in the range of 1.5 to 2.

5.

10. The sheet according to claim 9, wherein the polyol (b-2) has a weight average molecular weight in the range of 500 g / mol to 5000 g / mol and an OH value in the range of 20 to 300.

11. A) a topcoat layer based on an aqueous polyurethane dispersion; B) a base coat layer underlying the top coat layer; wherein the base coat layer is made from the sheet according to any one of claims 1 to 10.

12. 12. The laminate according to claim 11, wherein the top coat layer further contains a crosslinking agent in a content of 0.5 to 10%, based on the amount of the aqueous polyurethane dispersion, and the crosslinking agent is selected from aromatic or aliphatic polycarbodiimides (PCDIs) with or without hydrophilic modification, or isocyanate trimers.

13. The laminate of claim 11, wherein the aqueous polyurethane dispersion has an onset decomposition temperature measured by TGA in the range of 150 to 250°C.

14. 14. Synthetic leather comprising the laminate according to any one of claims 11 to 13 and a substrate layer, the substrate layer being located under a base coat layer of the laminate.

15. Use of the sheet according to any one of claims 1 to 10, the laminate according to any one of claims 11 to 13, or the synthetic leather according to claim 14 as an upper or cover material in the applications of apparel, accessories, cases, electronic devices, furniture, automobile interior lining, sporting goods, or leisure products.

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