Solvent-free polyurethane systems and laminates

Abstract

The present invention relates to a solvent-free polyurethane system comprising (a) a polyol component; (b) an isocyanate component wherein the polyol component (a) comprises 15 wt% to 50 wt% of at least one polyol (a-1) having a weight average molecular weight in the range of 500 g / mol to 2000 g / mol and 50 wt% to 85 wt% of at least one polyol (a-2) having a weight average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a); wherein the isocyanate component (b) has a functionality of from 2.05 to 2.15 and an NCO% in the range of from 16 wt% to 20 wt%; and wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120. The invention also provides the solvent-free PU synthetic leather, the solvent-free PU synthetic leather laminated body and the application of the solvent-free PU synthetic leather laminated body.

Description

Technical Field

[0001] The present invention relates to a solvent-free polyurethane system comprising a polyol component and an isocyanate component, and a laminate comprising the solvent-free polyurethane system. Background Art

[0002] Solvent-free polyurethane (PU) synthetic leather is one of the eco-friendly solutions for the synthetic leather industry, and generally includes a surface coating, a paint layer of solvent-free PU material, and a base layer. However, due to the low thermoforming performance and wrinkle resistance of the solvent-free PU material, the formed solvent-free PU synthetic leather always tends to have shape deformation later, and always easily shows wrinkles after the thermoforming / setting process of the laminated solvent-free PU synthetic leather.

[0003] CN 112195662 A discloses a water-based solvent-free polyurethane synthetic leather for women's shoes and suitcases, which comprises a base fabric layer, a solvent-free foaming layer, an aqueous intermediate layer, and an aqueous surface layer. However, CN 112195662 A does not relate to the thermoforming performance and wrinkle resistance of the water-based solvent-free polyurethane synthetic leather.

[0004] CN 108824017 A discloses an environmentally friendly water-based solvent-free shoe leather, which comprises a water-based PU layer, a solvent-free layer, and a fabric layer. However, CN 108824017 A does not relate to the thermoforming performance and wrinkle resistance of the water-based solvent-free leather.

[0005] In some applications (such as boots and saddles), the PU synthetic leather used should have good shape retention performance and good wrinkle resistance, and can maintain some other conventional properties. However, so far, there is no solvent-free PU synthetic leather or laminate that shows good shape retention performance and good wrinkle resistance, and at the same time maintains some other conventional properties.

[0006] Therefore, there is a need to provide a solvent-free PU synthetic leather laminate that shows good shape retention performance and good wrinkle resistance, and at the same time maintains some other conventional properties. Summary of the Invention

[0007] The object of the present invention is to provide a solvent-free PU synthetic leather laminate that shows good shape retention performance and good wrinkle resistance, and at the same time maintains some other conventional properties.

[0008] Therefore, the present invention provides a solvent-free polyurethane system, which comprises

[0009] (a) a polyol component,

[0010] (b) an isocyanate component,

[0011] wherein the polyol component (a) comprises 15 wt% to 50 wt% of at least one polyol (a-1) having a weight average molecular weight in the range of 500 g / mol to 2000 g / mol and 50 wt% to 85 wt% of at least one polyol (a-2) having a weight average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a);

[0012] wherein the isocyanate component (b) has a functionality (NCO) of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%, and

[0013] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120.

[0014] The present invention also provides a solvent-free PU synthetic leather, which comprises

[0015] (1) a top coat;

[0016] (2) a base coat layer under the top coat; and

[0017] (3) a base layer,

[0018] wherein the base coat layer is made of the solvent-free polyurethane system.

[0019] The present invention further provides a solvent-free PU synthetic leather laminate, which comprises

[0020] (1) the above solvent-free PU synthetic leather; and

[0021] (2) a forming layer,

[0022] wherein the forming layer is on the base layer of the solvent-free PU synthetic leather.

[0023] It has been found that the solvent-free PU synthetic leather laminate of the present invention exhibits good forming retention performance and good wrinkle resistance, and at the same time maintains some other conventional properties, such as curing properties, peel strength and / or fold resistance. Detailed Description of the Invention

[0024] The present invention will be described in detail below. It should be understood that the present invention can be implemented in many different ways and should not be construed as limited to the embodiments set forth herein.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention pertains. As used herein, unless otherwise specified, the following terms have the meanings given to them below.

[0026] As used herein, the article "a / an" refers to one or more (i.e., at least one) of the grammatical object of the article or component.

[0027] As used herein, the terms "comprise / comprising" etc. are used interchangeably with "contain / containing" etc. and shall be interpreted in a non-restrictive, open manner. That is, for example, there may be additional components or elements. The expressions "consisting of" or "consisting essentially of" or cognates may be included in "comprises" or cognates.

[0028] Unless otherwise stated, all percentages (%) are "percentages by weight".

[0029] Unless otherwise stated, the term "total solids weight" refers to the total weight of the system or dispersion minus the weight of all solvents (including water).

[0030] Unless otherwise stated, for the topcoat, the weight percentage (%) of all additives and / or auxiliaries refers to the percentage of "the solid weight of the additives and / or auxiliaries divided by the total solids weight of the aqueous polyurethane dispersion".

[0031] Unless otherwise stated, for the paint layer, the weight percentage (%) of all additives and / or auxiliaries refers to the percentage of "the solid weight of the additives and / or auxiliaries divided by the total solids weight of the solvent-free polyurethane system".

[0032] Unless otherwise stated, the molecular weight of each component or polymer means the weight-average molecular weight.

[0033] In the present invention, the molecular weight of each component is determined by gel permeation chromatography (GPC) according to GB / T 21863-2008.

[0034] In the present invention, the OH value of each polyol component is determined according to DIN 53240.

[0035] In the present invention, the functionality (Fn) of the polyol means the number of terminal hydroxyl groups of each polyol molecule. The functionality is determined by the following formula:

[0036] Fn = M n *(OHv) / 56100

[0037] where M n represents the number-average molecular weight of the polyol and OHv represents the OH value of the polyol.

[0038] In the present invention, the functionality (NCO) of the isocyanate is determined by the following formula:

[0039] Functionality (NCO) = (mol-1 * Fn-1 + mol-2 * Fn-2 + … + mol-n * Fn-n) / (mol-1 + mol-2 + … + mol-n)

[0040] where mol-1 represents the number of moles of the first isocyanate and Fn-1 represents the functionality (NCO) of the first isocyanate, mol-2 represents the number of moles of the second isocyanate and Fn-2 represents the functionality (NCO) of the second isocyanate, and mol-n represents the number of moles of the nth isocyanate and Fn-n represents the functionality (NCO) of the nth isocyanate.

[0041] In the present invention, the isocyanate index of the solvent-free polyurethane system is defined as the ratio of the total number of isocyanate groups of the isocyanate component used in the reaction to the total number of isocyanate-reactive groups (i.e., the number of active hydrogens in the compound having at least two isocyanate-reactive hydrogen groups and the chain extender). An isocyanate index of 100 means that there is one active hydrogen atom for each isocyanate group of the isocyanate component, i.e., the isocyanate-reactive functional groups of the compound having at least two isocyanate-reactive hydrogen groups and the chain extender. An isocyanate index higher than 100 means that there are more isocyanate groups than isocyanate-reactive groups (such as hydroxyl groups).

[0042] Polyol component (a)

[0043] In the present invention, the polyol component (a) comprises at least one polyol (a-1) having a weight-average molecular weight in the range of 500 g / mol to 2000 g / mol.

[0044] The polyol component (a) comprises 15 wt% to 50 wt%, preferably 25 wt% to 40 wt%, such as 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% etc. of the above polyol (a-1) based on the total weight of the polyol component (a).

[0045] The polyol that can be used as the polyol (a-1) preferably has a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol, preferably 800 g / mol to 1200 g / mol, more preferably 1000 g / mol to 1100 g / mol, such as 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1100 g / mol, 1200 g / mol, 1300 g / mol and 1400 g / mol etc.

[0046] The polyol that can be used as polyol (a-1) preferably has an OH value in the range of 60 to 200 mg KOH / g, preferably in the range of 90 to 130 mg KOH / g, more preferably in the range of 100 to 120 mg KOH / g, such as 70 mg KOH / g, 80 mg KOH / g, 90 mg KOH / g, 100 mg KOH / g, 110 mg KOH / g, 120 mg KOH / g, 130 mg KOH / g, 140 mg KOH / g, 150 mg KOH / g, 160 mg KOH / g, 170 mg KOH / g, 180 mg KOH / g, 190 mg KOH / g, etc.

[0047] The polyol that can be used as polyol (a-1) is selected from polyols having a functionality (Fn) in the range of 1.9 to 2.1, preferably a functionality in the range of 1.95 to 2.05, and more preferably a functionality of 2.

[0048] The polyol that can be used as polyol (a-1) is selected from polyether polyols derived from oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, such as 3, 4, 5, or 6 carbon atoms, preferably tetrahydrofuran. Preferably, the polyol is produced by polymerizing tetrahydrofuran as a repeating unit and is preferably terminated with a primary hydroxyl group. More preferably, the polyol is polytetrahydrofuran, which can be produced by polymerizing tetrahydrofuran as a repeating unit and is terminated with a primary hydroxyl group. In a preferred embodiment, the polytetrahydrofuran has a functionality of 2, a weight-average molecular weight (g / mol) of 975 to 1025, and an OH value (OHv) of 109.5 to 115.1 mg KOH / g, such as PTHF1000 from BASF.

[0049] The polyol that can be used as polyol (a-1) in the present invention can be prepared by known methods or can be commercially obtained.

[0050] In the present invention, the polyol component (a) further comprises at least one polyol (a-2) having a weight-average molecular weight in the range of 2500 g / mol to 5000 g / mol.

[0051] The polyol component (a) comprises 50 wt% to 85 wt%, preferably 60 wt% to 75 wt%, more preferably 65 wt% to 70 wt%, such as 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, etc. of the above polyol (a-2) based on the total weight of the polyol component (a).

[0052] The polyol usable as polyol (a-2) preferably has a weight-average molecular weight in the range of 3000 g / mol to 4000 g / mol, preferably 3200 g / mol to 3600 g / mol, such as 3100 g / mol, 3200 g / mol, 3300 g / mol, 3400 g / mol, 3500 g / mol, 3600 g / mol, 3700 g / mol, 3800 g / mol and 3900 g / mol.

[0053] The polyol usable as polyol (a-2) preferably has an OH value in the range of 10 to 50 mg KOH / g, preferably in the range of 20 to 40 mg KOH / g, such as 15 mg KOH / g, 25 mg KOH / g, 30 mg KOH / g, 35 mg KOH / g, 45 mg KOH / g.

[0054] The polyol usable as polyol (a-2) is selected from polyols having a functionality (Fn) in the range of 1.5 to 2.5, preferably a functionality in the range of 1.5 to 2.2, more preferably a functionality in the range of 1.8 to 2.1, still more preferably 2.

[0055] The polyol (a-2) can be a single polyol or a mixture of two or more polyols, preferably a polyether polyol, more preferably a polyether polyol based on epoxides (such as ethylene oxide (EO), propylene oxide (PO) and / or butylene 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 propylene glycol as an initiator, and are preferably capped with ethylene oxide having a primary hydroxyl group.

[0056] The polyol usable as polyol (a-2) in the present invention can be prepared by known methods or can be commercially available.

[0057] Preferably, the polyol (a-2) is poly(ethylene oxide), which can be produced by polymerizing ethylene oxide as a repeating unit and using propylene glycol as an initiator, and is capped with ethylene oxide having a primary hydroxyl group. In a preferred embodiment, the poly(ethylene oxide) has a functionality of 1.76, a weight-average molecular weight of 3350 to 3500 (g / mol) and an OH value (OHv) of 27 to 32 mg KOH / g, such as L2043 from BASF.

[0058] In the present invention, the polyol component (a) contains water in an amount of 0.5 wt% or less, preferably 0.3 wt% or less, based on the weight of the polyol component (a), and even contains no water.

[0059] At least one of the polyols (a-1) and (a-2) has a linear structure. Preferably, both of the polyols (a-1) and (a-2) have a linear structure.

[0060] The amount of the polyol component (a) is preferably 20 wt% to 50 wt% based on the total weight of the solvent-free polyurethane system, such as 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, etc.

[0061] Isocyanate component (b)

[0062] Preferably, the isocyanate component (b) is in a modified state, for example, by incorporating uretdione, carbamate, isocyanurate or urethane groups.

[0063] Preferably, the isocyanate component (b) is in the form of a polyisocyanate prepolymer, which can be prepared in a conventional manner by reacting a polyisocyanate with a compound having isocyanate-reactive hydrogen atoms (such as a polyol) to form a polyisocyanate prepolymer. The reaction can be carried out, for example, at a temperature of about 80 °C, which are commonly known and described, for example, in "Kunststoffhandbuch Polyurethane [Plastic Handbook Polyurethane]" Günter Oertel, Carl-Hanser-Verlag [Carl-Hanser Publishing House], 2nd edition, 1983, Chapter 3.1.1.

[0064] In a preferred embodiment, the isocyanate component (b) comprises or consists of a prepolymer derived from at least one isocyanate (b-1) and at least one polyol (b-2).

[0065] The isocyanates that can be used as the isocyanate (b-1) for producing the prepolymer can include all isocyanates known for producing polyurethanes. These isocyanates include aliphatic, cycloaliphatic, araliphatic, and / or aromatic isocyanates, such as tri-, tetra-, penta-, hexa-, hepta-, and / or octamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butene 1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), 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, naphthalene 1,5-diisocyanate (NDI), toluene 2,4- and / or 2,6-diisocyanate (TDI), 3,3’-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate, and / or phenylene diisocyanate, or mixtures thereof.

[0066] Preferably, the isocyanate used as the isocyanate (b-1) includes 4,4’-diphenylmethane diisocyanate.

[0067] Preferably, the amount of the isocyanate (b-1) is in the range of 50 wt% to 75 wt%, preferably 60 wt% to 70 wt%, based on the total weight of the isocyanate component (b), such as 55 wt%, 65 wt%, etc.

[0068] In the present invention, the polyol (b-2) includes at least one polyol (b-2-1) having a weight average molecular weight in the range of 1000 g / mol to 3000 g / mol, preferably 1500 g / mol to 2500 g / mol, such as 2000 g / mol.

[0069] Preferably, the amount of the polyol (b-2-1) is in the range of 10 wt% to 30 wt%, preferably 15 wt% to 25 wt%, based on the total weight of the isocyanate component (b), such as 20 wt%.

[0070] The polyol that can be used as the polyol (b-2-1) preferably has an OH value in the range of 20 to 100 mgKOH / g, preferably in the range of 40 to 80 mgKOH / g, more preferably in the range of 50 to 70 mgKOH / g, such as 30 mgKOH / g, 40 mgKOH / g, 50 mgKOH / g, 60 mgKOH / g, 70 mgKOH / g, 80 mgKOH / g, 90 mgKOH / g, etc.

[0071] The polyols usable as polyol (b-2-1) are selected from polyols having a functionality (Fn) in the range of 1.9 to 2.1, preferably in the range of 1.95 to 2.05, and more preferably 2.

[0072] The polyols usable as polyol (b-2-1) are selected from polyether polyols derived from oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, such as 3, 4, 5, or 6 carbon atoms, preferably tetrahydrofuran. Preferably, polyol (b-2-1) is produced by polymerizing tetrahydrofuran as a repeating unit and is preferably terminated with a primary hydroxyl group. Preferably, polyol (b-2-1) is polytetrahydrofuran, which can be produced by polymerizing tetrahydrofuran as a repeating unit and is terminated with a primary hydroxyl group. In a preferred embodiment, polyol (b-2-1) is polytetrahydrofuran, such as PTHF2000 from BASF.

[0073] The polyols usable as polyol (b-2-1) in the present invention can be prepared by known methods or can be obtained commercially.

[0074] In the present invention, the polyol component (b-2) may further include at least one polyol (b-2-2) having a weight-average molecular weight in the range of 1000 g / mol to 3000 g / mol, preferably in the range of 1500 g / mol to 2500 g / mol, such as 2000 g / mol.

[0075] Preferably, the amount of polyol (b-2-2) is in the range of 10 wt% to 40 wt%, preferably 15 wt% to 25 wt%, such as 20 wt%, 30 wt%, 35 wt%, etc., based on the total weight of the isocyanate component (b).

[0076] The polyols usable as polyol (b-2-2) preferably have an OH value in the range of 80 to 200 mgKOH / g, preferably in the range of 120 to 180 mgKOH / g, more preferably in the range of 150 to 170 mgKOH / g, such as 90 mgKOH / g, 100 mgKOH / g, 110 mgKOH / g, 120 mgKOH / g, 130 mgKOH / g, 140 mgKOH / g, 150 mgKOH / g, 160 mgKOH / g, etc.

[0077] The polyols usable as polyol (b-2-2) are selected from polyols having a functionality (Fn) in the range of 2.9 to 3.1, preferably in the range of 2.95 to 3.05, and more preferably 3.

[0078] The polyol that can be used as polyol (b-2-2) can be a single polyol or a mixture of two or more polyols, preferably a polyether polyol, more preferably a polyether polyol based on epoxides such as ethylene oxide (EO), propylene oxide (PO) and / or butylene oxide (BO), preferably propylene oxide (PO).

[0079] The polyol that can be used as polyol (b-2-2) in the present invention can be prepared by known methods or can be commercially available.

[0080] At least one of polyol (b-2-1) and polyol (b-2-2) has a linear structure. Preferably, both polyol (b-2-1) and polyol (b-2-2) have a linear structure.

[0081] The isocyanate component (b) has an NCO% in the range of 16 wt% to 20 wt%, preferably in the range of 17 wt% to 19 wt%, such as 18 wt%.

[0082] The isocyanate component (b) has a functionality (Fn) of 2.05 to 2.15, preferably 2.08 to 2.12, such as 2.09, 2.10, etc.

[0083] The amount of polyol (b-2) is in the range of 25 wt% to 50 wt%, preferably 30 wt% to 40 wt%, such as 35 wt%, 45 wt%, etc. based on the total weight of the isocyanate component (b).

[0084] The amount of the isocyanate component (b) is preferably 20 wt% to 50 wt%, such as 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, etc. based on the total weight of the solvent-free polyurethane system.

[0085] Chain extender and / or crosslinking agent (c)

[0086] In the present invention, the solvent-free polyurethane system can contain a chain extender and / or a crosslinking agent (c).

[0087] Chain extenders and / or crosslinking agents (c) which can be used are substances having a molar mass preferably less than 500 g / mol, particularly preferably 60 to 400 g / mol, where the chain extender has 2 hydrogen atoms reactive towards isocyanate and the crosslinking agent has 3 hydrogen atoms reactive towards isocyanate. These chain extenders and / or crosslinking agents can be used individually or preferably in the form of a mixture. Diols and / or triols having a molecular weight less than 500, in particular 60 to 400 and in particular 60 to 350, are preferably used. Examples of those which can be used are aliphatic, cycloaliphatic and / or araliphatic diols having 2 to 14, preferably 2 to 10 carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol (BDO), 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 preferred to use ethylene glycol, 1,3-propanediol or 1,4-butanediol, especially 1,4-butanediol.

[0088] The amount of chain extender and / or crosslinking agent (c) is preferably 0.5 to 5 wt%, more preferably 1.5 to 4.5 wt%, based on the total weight of the polyol component (a).

[0089] Catalyst (d)

[0090] In the present invention, the solvent-free polyurethane system can contain a catalyst (d).

[0091] As the catalyst (d), all compounds which can accelerate the reaction between isocyanate and polyol can be used. Such compounds are known and described, for example, in "Kunststoffhandbuch [Plastic Handbook], Volume 7, Polyurethane [Polyurethane]", Carl Hanser Verlag [Carl Hanser Publishing House], 3rd Edition, 1993, Chapter 3.4.1. These catalysts include amine-based catalysts and organometallic compound-based catalysts or mixtures thereof.

[0092] As amine-based catalysts, for example, strongly basic amines such as N,N,N-triethylaminoethoxyethanol, bis(N,N-dimethylaminoethyl) ether, dimethylcyclohexylamine, trimethylolethylenediamine, dimethylbenzylamine, triethylamine, triethylenediamine, pentamethyldipropylenetriamine, dimethylethanolamine, N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine, tris(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylamine, N-ethylmorpholine, diazabicycloundecene, diazabicyclononene, diazabicyclooctane can be used, preferably triethylenediamine or bis(N,N-dimethylaminoethyl) ether.

[0093] As the catalyst based on organometallic compounds, organotin compounds such as tin(II) salts of organic carboxylic acids, e.g., tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, and tin(II) laurate; and dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate; and Zn salts or Bi salts, e.g., zinc octoate, bismuth(III) neodecanoate, bismuth 2-ethylhexanoate, and bismuth octoate; or alkali metal salts of carboxylic acids, e.g., potassium acetate or potassium formate can be used.

[0094] The catalyst (d) used in the present invention can be commercially available, such as Additive CX93600 and Haptex CC 6945 / 92C-CC from BASF Corporation.

[0095] Typically, the amount of the catalyst (d) is preferably 0.05 to 5 wt%, more preferably 0.1 to 1.5 wt% based on the total weight of the polyol component (a).

[0096] Filler (e)

[0097] In the present invention, the solvent-free polyurethane system can contain a filler (e).

[0098] According to the present invention, the filler (if any) that can be used is an inorganic filler selected from calcium carbonate (CaCO3), kaolin, montmorillonite, aluminum hydroxide, barium sulfate, or talc, preferably calcium carbonate, kaolin, or montmorillonite, more preferably calcium carbonate.

[0099] The amount of the filler is 30 to 55 wt%, preferably 40% to 50 wt%, such as 35 wt%, 45 wt%, etc. based on the total weight of the polyol component (a) and the isocyanate component (b).

[0100] Additive and / or auxiliary agent (f)

[0101] In the present invention, the solvent-free polyurethane system can contain additives and / or auxiliaries (f).

[0102] The additives and / or auxiliaries (f) that can be used include surfactants, preservatives, pigments, colorants, antioxidants, silicone oil leveling agents, stabilizers, thickeners, foaming agents, wetting agents, and reinforcing agents. In the preparation of the solvent-free polyurethane system, it is preferred to use one of the above additives and / or auxiliaries, or a mixture thereof.

[0103] Typically, the amount of the additives and / or auxiliaries is preferably 0 to 12 wt%, more preferably 0.1 to 10 wt% based on the total weight of the solvent-free polyurethane system.

[0104] According to the present invention, thickeners, wetting agents and antioxidants are preferably used. Those materials that can be used (if any) 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 wt%, more preferably 0.5 to 1 wt%, each based on the total weight of the solventless polyurethane system.

[0105] For example, further information on the mode of use and mode of action of the above-mentioned auxiliaries and additives, as well as additional examples, are given in "Kunststoffhandbuch, Band 7, Polyurethane" ["Plastics Handbook, Volume 7, Polyurethane"], Carl Hanser Verlag [Carl Hanser Publishing House], 3rd Edition 1993, Chapter 3.4.

[0106] According to the present invention, the solventless polyurethane system has an isocyanate index in the range of 95 to 120, preferably in the range of 100 to 110, such as 105, 115, etc.

[0107] In the present invention, the solventless polyurethane system is substantially free or free of solvents, especially organic solvents.

[0108] In a preferred embodiment according to the present invention, the solventless polyurethane system comprises:

[0109] (a) a polyol component;

[0110] (b) an isocyanate component,

[0111] wherein the polyol component (a) comprises 15 wt% to 50 wt% of at least one polyol (a-1) having a weight average molecular weight in the range of 500 g / mol to 2000 g / mol and 50 wt% to 85 wt% of at least one polyol (a-2) having a weight average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a);

[0112] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%;

[0113] wherein the solventless polyurethane system has an isocyanate index in the range of 95 to 120; and

[0114] wherein the solventless polyurethane system further comprises 30 to 55 wt% of calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0115] In another specific embodiment according to the present invention, the solventless polyurethane system comprises:

[0116] (a) Polyol component;

[0117] (b) Isocyanate component,

[0118] wherein the polyol component (a) comprises 25 wt% to 40 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 500 g / mol to 2000 g / mol and 60 wt% to 75 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a);

[0119] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%;

[0120] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120; and

[0121] wherein the solvent-free polyurethane system further comprises 40 to 50 wt% of calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0122] In another specific embodiment according to the present invention, the solvent-free polyurethane system comprises:

[0123] (a) Polyol component;

[0124] (b) Isocyanate component,

[0125] wherein the polyol component (a) comprises 25 wt% to 40 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol and 60 wt% to 75 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 3000 g / mol to 4000 g / mol, each based on the total weight of the polyol component (a);

[0126] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%;

[0127] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120; and

[0128] wherein the solvent-free polyurethane system further comprises 40 to 50 wt% of calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0129] In another specific embodiment according to the present invention, the solvent-free polyurethane system comprises:

[0130] (a) a polyol component;

[0131] (b) an isocyanate component,

[0132] wherein the polyol component (a) comprises 25 wt% to 40 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol and 60 wt% to 75 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 3000 g / mol to 4000 g / mol, each based on the total weight of the polyol component (a);

[0133] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%;

[0134] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120;

[0135] wherein the isocyanate component (b) comprises a prepolymer derived from at least one isocyanate (b-1) and at least one polyol (b-2), and

[0136] wherein the solvent-free polyurethane system further comprises 40 to 50 wt% of calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0137] In another specific embodiment according to the present invention, the solvent-free polyurethane system comprises:

[0138] (a) a polyol component;

[0139] (b) an isocyanate component,

[0140] wherein the polyol component (a) comprises 25 wt% to 40 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol and 60 wt% to 75 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 3000 g / mol to 4000 g / mol, each based on the total weight of the polyol component (a);

[0141] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%;

[0142] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120;

[0143] wherein the isocyanate component (b) comprises a prepolymer derived from 60 wt% to 70 wt% diphenylmethane 4,4'-diisocyanate and 30 wt% to 40 wt% polyether polyol, each based on the total weight of the isocyanate component (b), and

[0144] wherein the solvent-free polyurethane system further comprises 40 to 50 wt% calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0145] In another specific embodiment according to the present invention, the solvent-free polyurethane system comprises:

[0146] (a) a polyol component;

[0147] (b) an isocyanate component,

[0148] wherein the polyol component (a) comprises 25 wt% to 40 wt% of at least one polyol (a-1) having a weight average molecular weight in the range of 600 g / mol to 1500 g / mol and 60 wt% to 75 wt% of at least one polyol (a-2) having a weight average molecular weight in the range of 3000 g / mol to 4000 g / mol, each based on the total weight of the polyol component (a);

[0149] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%, and wherein the isocyanate component (b) comprises a prepolymer derived from 60 wt% to 70 wt% diphenylmethane 4,4'-diisocyanate and 30 wt% to 40 wt% polyether polyol, each based on the total weight of the isocyanate component (b);

[0150] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120; and

[0151] wherein the solvent-free polyurethane system further comprises 40 to 50 wt% calcium carbonate based on the total weight of the polyol component (a) and the isocyanate component (b).

[0152] The present invention also provides a solvent-free PU synthetic leather, which comprises

[0153] (1) a top coat;

[0154] (2) a base coat paint layer under the top coat; and

[0155] (3) a base layer,

[0156] wherein the base coat paint layer is made of the solvent-free polyurethane system.

[0157] In the context of the present invention, the topcoat may also be referred to as the topcoat surface layer.

[0158] In the present invention, an aqueous polyurethane dispersion is used to produce the topcoat. The aqueous polyurethane has an initial decomposition temperature in the range of 150 °C to 250 °C, preferably 180 °C to 230 °C, measured by TGA. Suitable aqueous polyurethane dispersions for use in the topcoat are disclosed, for example, in PCT / CN 2020 / 084834, the content of which is hereby expressly incorporated by reference.

[0159] In the present invention, the aqueous polyurethane dispersion for the topcoat can be commercially available, such as Haptex CC 6945 / 90C-CH from BASF, or prepared from an isocyanate component (a') and a polyol component (b'). The method for preparing the aqueous polyurethane dispersion can be any method commonly used in the art and is known to those skilled in the art. The isocyanate component (a') includes conventional aliphatic, cycloaliphatic, and aromatic di- and / or polyisocyanates. Preferably, toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and a mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate (polymeric MDI) are used, and especially diphenylmethane diisocyanate (monomeric MDI). Isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and hydrogenated diphenylmethane-4,4'-diisocyanate (H12MDI) are also preferred.

[0160] The isocyanate or the isocyanate prepolymer described further below may also be in a modified state, for example, by incorporating uretdione, carbamate, isocyanurate, or urethane groups. Further, blends of different isocyanates can be used.

[0161] The polyisocyanate can also be used in the form of a polyisocyanate prepolymer. These prepolymers are known in the prior art. They are prepared in a conventional manner by reacting the above polyisocyanates with compounds having isocyanate-reactive hydrogen atoms described below to form prepolymers. The reaction can be carried out, for example, at a temperature of about 80 °C. Usually, the ratio of polyol / polyisocyanate is selected such that the NCO content of the prepolymer is in the range of 6 wt% to 25 wt%.

[0162] The polyol component (b') preferably comprises a polyether polyol and / or a polyester polyol. These are commonly known and described, for example, in "Kunststoffhandbuch Polyurethane" by Günter Oertel, Carl-Hanser-Verlag, 2nd edition 1983, chapter 3.1.1. Alternative names that are also conventional in the relevant field are polyether polyol or polyether alcohol on the one hand, and polyester polyol or polyester alcohol on the other hand.

[0163] In the present application, preferably, the polyol component (b') is a polyol mixture. The polyol component (b') comprises a polyol (b'-1) 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 a polyol (b'-2) having a weight average molecular weight in the range of 500 g / mol to 3000 g / mol and a functionality in the range of 2 to 4. For example, the polyol (b'-1) can be a polyester, such as XCP-2000N, and the polyol (b'-2) can be a polyether, preferably a hydrophilic polyether based on polyethylene glycol, such as Ymer N120.

[0164] The polyol component (b') further comprises (b'-3) a chain extender having a weight average molecular weight of less than 400 g / mol, and (b'-4) a hydrophilic chain extender containing a carboxylic acid group or a sulfonic acid group.

[0165] The chain extender (b'-3) that can be used is a substance having a molar mass preferably less than 400 g / mol, particularly preferably 60 to 400 g / mol, wherein the chain extender has at least 2 hydrogen atoms reactive to isocyanate. These chain extenders can be used individually or preferably in the form of a mixture. Diols and / or triols having a molecular weight of 60 to 400 and particularly 60 to 350 are preferably used. Examples of those that can be used are aliphatic, cycloaliphatic, and / or aliphatic 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. Diamines and / or triamines are also preferably used. Examples of those that can be used are diethylenetriamine or N-(2-hydroxyethyl)ethylenediamine. The amount of the chain extender (b'-3) is preferably 0.1 wt% to 10 wt%, particularly preferably 0.2 wt% to 8 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0166] The hydrophilic chain extender (b'-4) that can be used is a hydrophilic chain extender having a carboxyl or sulfonic acid group. They provide hydrophilic groups for the aqueous polyurethane dispersion to ensure that the dispersion has appropriate hydrophilicity. Preferably, AB-salt (sodium 2-[(2-aminoethyl)amino]ethanesulfonate) or DMPA (dimethylolpropionic acid) can be used herein. The amount of the hydrophilic chain extender (b'-4) is preferably 0.1 wt% to 50 wt%, particularly preferably 0.2 wt% to 35 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0167] The aqueous polyurethane dispersion contains carboxyl groups not exceeding 0.5%, preferably less than 0.1% based on the total solid weight of the aqueous polyurethane dispersion, wherein the carboxyl groups are derived from the hydrophilic extender having a carboxyl group and other carboxyl-containing starting materials for preparing the aqueous polyurethane dispersion. Additionally, the molar ratio of the hydroxyl and / or amino groups present in the aqueous polyurethane dispersion to the isocyanate groups is 0.9 to 1.5, preferably 1.10 to 1.25.

[0168] The aqueous polyurethane dispersion optionally contains an amine neutralizer having gel reactivity to provide a suitable pH range of 6 to 9 for the dispersion. The amount of the amine neutralizer is preferably 0.01 wt% to 5 wt%, particularly preferably 0.05 wt% to 2 wt% based on the total solid weight of the aqueous polyurethane dispersion. For example, the amine neutralizer is selected from the group consisting of triethylenediamine (TEDA), 1,2-dimethylimidazole, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylethylenediamine, and tertiary amines.

[0169] Optionally, the aqueous polyurethane dispersion contains a surfactant. The surfactant can be nonionic, such as alcohol ethoxylates, alkyl polyglucosides, bisphenol A ethoxylates, ethoxylated natural fats / oils, fatty acid ethoxylates; or / and anionic surfactants, such as fatty alcohol ether sulfates, fatty alcohol sulfates, linear alkylbenzene sulfonates, oleic acid sulfonates, diisodecyl sulfosuccinates, alkyl ether phosphates, alkyl ether carboxylates; or / and cationic surfactants, such as amine ethoxylates, amino polyols, quaternary ammonium surfactants.

[0170] In a preferred embodiment of the present invention, the topcoat based on the aqueous polyurethane dispersion further contains a crosslinking agent. Here, suitable crosslinking agents can be selected from aromatic or aliphatic polycarbodiimides (PCDI), with or without hydrophilic modification, or isocyanates. The crosslinking agent can be used in a mixed or single manner, preferably in a mixed manner. For example, Astacin Hardener CA and / or Astacin Hardener CI can be used as crosslinking agents. The amount of the crosslinking agent is preferably 0.1 wt% to 20 wt%, particularly preferably 0.5 wt% to 15 wt%, and especially 1 wt% to 10 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0171] In a preferred embodiment of the present invention, the topcoat based on the aqueous polyurethane dispersion further contains other additives and / or auxiliaries commonly known to those skilled in the art. Additives and / or auxiliaries that can be used include surfactants, thickeners, pigments, colorants, antioxidants, reinforcing agents, stabilizers, and wetting agents. In the preparation of the aqueous polyurethane dispersion, one or a mixture of the above additives and / or auxiliaries is usually used to improve the properties of the obtained polyurethane dispersion.

[0172] Typically, the amount of other additives and / or auxiliaries is preferably 0 to 25 wt%, more preferably 0.5 wt% to 15 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0173] As the pigment, all compounds suitable for preparing polyurethane dispersions can be used, such as Permutex PP-39-611. The amount of the pigment (if present) is preferably 1 wt% to 12 wt%, particularly preferably 5 wt% to 10 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0174] As the thickener, all compounds commonly used for preparing polyurethane dispersions can be used, such as Permutex RM4456. The amount of the thickener (if present) is preferably 0.1 wt% to 8 wt%, particularly preferably 0.5 wt% to 5 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0175] As the wetting agent, all compounds commonly used for preparing polyurethane dispersions can be used, such as BYK 348. The amount of the wetting agent (if present) is preferably 0.1 wt% to 5 wt%, particularly preferably 0.3 wt% to 3 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0176] As antioxidants, all compounds suitable for the preparation of polyurethane dispersions can be used. The amount of antioxidant (if present) is preferably 0.1 wt% to 5 wt%, more preferably 0.5 wt% to 1 wt% based on the total solid weight of the aqueous polyurethane dispersion.

[0177] Color paint layer

[0178] The colored paint layer is made of the solvent-free polyurethane system according to the present invention.

[0179] The thickness of the colored paint layer ranges from 0.2 mm to 0.5 mm, preferably from 0.3 mm to 0.4 mm.

[0180] Base layer

[0181] For example, the base layer may include a leather fabric in the form of a woven or non-woven fabric, and the leather fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber, and mixtures thereof.

[0182] Preferably, the base layer has a thickness in the range of 0.5 mm to 1 mm.

[0183] Preferably, the base layer has an elongation rate in the range of 60% to 90%, such as 65%, 70%, 75%, 80%, 85%, etc.

[0184] When the base layer has an elongation rate higher than 90%, the wrinkle resistance of the solvent-free PU synthetic leather laminate decreases. When the base layer has an elongation rate lower than 60%, the molding retention performance of the solvent-free PU synthetic leather laminate decreases.

[0185] The present invention further provides a solvent-free PU synthetic leather laminate, which comprises

[0186] (1) the above solvent-free PU synthetic leather; and

[0187] (2) a molding layer,

[0188] wherein the molding layer is on the base layer of the solvent-free PU synthetic leather.

[0189] The solvent-free PU synthetic leather laminate optionally includes an adhesive layer between the base layer of the solvent-free PU synthetic leather and the molding layer.

[0190] Forming layer

[0191] For example, the molding layer may include a molding fabric in the form of a woven or non-woven fabric, and the molding fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber, and mixtures thereof.

[0192] Preferably, the forming layer has a thickness in the range of 1.0 to 1.5 mm.

[0193] Preferably, the forming layer has an elongation rate in the range of 20% to 40%, such as 25%, 30%, 35%, etc. When the elongation rate of the forming layer is higher than 40%, the wrinkle resistance of the solvent-free PU synthetic leather laminate decreases.

[0194] Adhesive layer

[0195] The adhesive layer is formed by an adhesive commonly used in the art. The adhesive can be selected from conventional adhesives such as PVC, PU, TPU, epoxy resin adhesives, etc.

[0196] The present invention also relates to the use of the solvent-free PU synthetic leather laminate as an upper or covering material in the applications of boots, saddles, clothing, accessories, luggage, electronic devices, furniture, automotive interiors, sports items or leisure products, especially in the applications of boots and saddles.

[0197] The present invention also relates to a method for producing a solvent-free PU synthetic leather laminate, especially a method for producing a solvent-free PU synthetic leather laminate used in the applications of boots and saddles.

[0198] The method for producing the solvent-free PU synthetic leather and the solvent-free PU synthetic leather laminate can be any method commonly used in the art and is known to those skilled in the art.

[0199] In a preferred embodiment of the present invention, the method for producing the solvent-free PU synthetic leather includes the following steps: (1) applying a surface coating on a release paper and drying; (2) applying a paint layer on the surface coating and drying; (3) applying a base layer on the paint layer; (4) drying and pressing; and (5) peeling the release paper from the surface coating to form a solvent-free PU leather layer.

[0200] The drying temperature is preferably in the range of 60°C to 160°C, and the drying time is preferably in the range of 1 to 20 minutes.

[0201] In a preferred embodiment of the present invention, the method for producing the solvent-free PU synthetic leather laminate includes the following steps: (1) pasting a forming layer onto the solvent-free PU leather layer through an optional adhesive layer; (2) heat setting; and (3) post setting.

[0202] For example, the heat setting is carried out at a temperature in the range of 70°C to 100°C, preferably in the range of 80°C to 100°C, more preferably in the range of 85°C to 90°C for 3 to 5 seconds.

[0203] For example, the post setting is carried out by placing the formed laminate at room temperature or a lower temperature for cooling and plasticizing.

[0204] In a preferred embodiment of the present invention, the post-shaping is carried out at a temperature of -10 °C to 0 °C, preferably -10 °C to -5 °C, for example in a freezer.

[0205] In all embodiments described herein, based on the total weight of the solvent-free polyurethane system, the sum of the contents of each component in the solvent-free polyurethane system is a total of 100 wt%.

[0206] Examples

[0207] The following various examples are listed. It will be understood that the examples listed below can be combined with all aspects and other embodiments according to the scope of the present invention.

[0208] Example 1. A solvent-free polyurethane system, which comprises

[0209] (a) a polyol component; and

[0210] (b) an isocyanate component,

[0211] wherein the polyol component (a) comprises 15 wt% to 50 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 500 g / mol to 2000 g / mol and 50 wt% to 85 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a);

[0212] wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20%; and

[0213] wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120.

[0214] Example 2. The solvent-free polyurethane system according to Example 1, wherein the polyol component (a) comprises 25 wt% to 40 wt% of the polyol (a-1) and 60 wt% to 75 wt% of the polyol (a-2).

[0215] Example 3. The solvent-free polyurethane system according to Example 1 or 2, wherein the polyol (a-1) has a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol, preferably 800 g / mol to 1200 g / mol.

[0216] Example 4. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-2) has a weight average molecular weight in the range of 3000 g / mol to 4000 g / mol, preferably 3200 g / mol to 3600 g / mol.

[0217] Example 5. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-1) is selected from polyether polyols derived from oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, preferably tetrahydrofuran.

[0218] Example 6. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-2) is selected from polyether polyols derived from epoxides, preferably ethylene oxide, propylene oxide or a mixture thereof.

[0219] Example 7. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-1) has an OH value in the range of 60 to 200 mgKOH / g, preferably in the range of 90 to 130 mgKOH / g.

[0220] Example 8. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-2) has an OH value in the range of 10 to 50 mgKOH / g, preferably in the range of 20 to 40 mgKOH / g.

[0221] Example 9. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-1) has a functionality in the range of 1.9 to 2.1, preferably in the range of 1.95 to 2.05, more preferably 2.

[0222] Example 10. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (a-2) has a functionality in the range of 1.5 to 2.5, preferably in the range of 1.8 to 2.1, more preferably 2.

[0223] Example 11. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the isocyanate component (b) comprises a prepolymer derived from at least one isocyanate (b-1) and at least one polyol (b-2).

[0224] Example 12. The solvent-free polyurethane system according to Example 11, wherein the amount of the isocyanate (b-1) is in the range of 50 wt% to 75 wt%, preferably 60 wt% to 70 wt%, based on the total weight of the isocyanate component (b).

[0225] Example 13. The solvent-free polyurethane system according to Example 11 or 12, wherein the amount of the polyol (b-2) is in the range of 25 wt% to 50 wt%, preferably 30 wt% to 40 wt%, based on the total weight of the isocyanate component (b).

[0226] Example 14. The solvent-free polyurethane system according to any one of Examples 11 to 13, wherein the isocyanate (b-1) comprises diphenylmethane 4,4'-diisocyanate.

[0227] Example 15. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the polyol (b-2) comprises a polyether polyol derived from an oxygen-containing heterocyclic compound having 3 to 6 carbon atoms, especially tetrahydrofuran.

[0228] Example 16. The solvent-free polyurethane system according to Example 15, wherein the polyether polyol has a weight average molecular weight in the range of 1000 g / mol to 3000 g / mol.

[0229] Example 17. The solvent-free polyurethane system according to Example 15 or 16, wherein the polyether polyol has an OH value in the range of 60 to 200 mgKOH / g, preferably in the range of 90 to 130 mgKOH / g.

[0230] Example 18. The solvent-free polyurethane system according to Example 15, wherein the polyol (b-2) comprises an additional polyether polyol derived from an epoxide, preferably ethylene oxide, propylene oxide or a mixture thereof.

[0231] Example 19. The solvent-free polyurethane system according to Example 18, wherein the additional polyether polyol has a weight average molecular weight in the range of 1000 g / mol to 3000 g / mol.

[0232] Example 20. The solvent-free polyurethane system according to Example 18 or 19, wherein the additional polyether polyol has an OH value in the range of 80 to 200 mgKOH / g, preferably in the range of 120 to 180 mgKOH / g.

[0233] Example 21. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the isocyanate component (b) has an NCO% in the range of 17 wt% to 19 wt%.

[0234] Example 22. The solvent-free polyurethane system according to any one of the foregoing examples, wherein the isocyanate component (b) has a functionality of 2.08 to 2.12.

[0235] Example 23. A solvent-free polyurethane system according to any one of the foregoing examples, wherein the solvent-free polyurethane system has an isocyanate index in the range of 100 to 110.

[0236] Example 24. A solvent-free polyurethane system according to any one of the foregoing examples, wherein the solvent-free polyurethane system further comprises a filler.

[0237] Example 25. A solvent-free polyurethane system according to any one of the foregoing examples, wherein the solvent-free polyurethane system further comprises 30 to 55 wt%, preferably 40 to 50 wt%, of a filler based on the total weight of the polyol component (a) and the isocyanate component (b).

[0238] Example 26. A solvent-free polyurethane system according to Example 24 or 25, wherein the filler comprises calcium carbonate, kaolin, montmorillonite, aluminum hydroxide, barium sulfate or talc, preferably calcium carbonate.

[0239] Example 27. A solvent-free PU synthetic leather, which comprises

[0240] (1) a top coat;

[0241] (2) a paint layer under the top coat; and

[0242] (3) a base layer,

[0243] wherein the paint layer is made of a solvent-free polyurethane system according to any one of Examples 1 to 26.

[0244] Example 28. The solvent-free PU synthetic leather according to Example 27, wherein the top coat is based on an aqueous polyurethane dispersion.

[0245] Example 29. The solvent-free PU synthetic leather according to Example 27 or 28, wherein the top coat further contains a crosslinking agent in the range of 0.5 to 10 wt%, preferably 0.5 to 5 wt%, based on the weight of the aqueous polyurethane dispersion.

[0246] Example 30. The solvent-free PU synthetic leather according to Example 29, wherein the crosslinking agent is selected from aromatic or aliphatic polycarbodiimides, with or without hydrophilic modification, or isocyanate trimers.

[0247] Example 31. The solvent-free PU synthetic leather according to any one of Examples 27 to 30, wherein the base layer comprises a leather fabric in the form of a woven or non-woven fabric, and the leather fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber and mixtures thereof.

[0248] Example 32. The solvent-free PU synthetic leather according to any one of Examples 27 to 31, wherein the base layer has a thickness in the range of 0.5 to 1 mm and an elongation at break in the range of 60% to 90%.

[0249] Example 33. A solvent-free PU synthetic leather laminate, comprising

[0250] (1) The solvent-free PU synthetic leather according to any one of Examples 27 to 32; and

[0251] (2) A forming layer,

[0252] wherein the forming layer is on the base layer of the solvent-free PU synthetic leather.

[0253] Example 34. The solvent-free PU synthetic leather laminate according to Example 33, wherein the forming layer comprises a forming fabric in the form of a woven or non-woven fabric, and the forming fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber, and mixtures thereof.

[0254] Example 35. The solvent-free PU synthetic leather laminate according to Example 33 or 34, wherein the forming layer has a thickness in the range of 1.0 to 1.5 mm and an elongation at break in the range of 20% to 40%.

[0255] Example 36. The solvent-free PU synthetic leather laminate according to any one of Examples 33 to 35, wherein the solvent-free PU synthetic leather laminate further comprises an adhesive layer between the base layer of the solvent-free PU synthetic leather and the forming layer.

[0256] Example 37. Use of the solvent-free PU synthetic leather laminate according to any one of Examples 33 to 36 as an upper or covering material in the applications of boots, saddles, clothing, accessories, luggage, electronic devices, furniture, automotive interiors, sports items, or leisure products, especially in the applications of boots and saddles.

[0257] Examples

[0258] The present invention will now be described with reference to examples and comparative examples, which are not intended to limit the present invention.

[0259] Use the following raw materials:

[0260] PTHF1000 is polytetrahydrofuran from BASF.

[0261] PTHF2000 is polytetrahydrofuran from BASF.

[0262] L2043 is a polyether polyol from BASF.

[0263] Lupranate MS is diphenylmethane 4,4'-diisocyanate (MDI) from BASF Corporation.

[0264] TP1000 is polypropylene oxide from BASF Corporation, MW = 1000, Fn = 3, OHv = 168.

[0265] 1,4-Butanediol (BDO) is a chain extender.

[0266] Additive CX 93600 is a catalyst from BASF Corporation.

[0267] Haptex CC 6945 / 92C-CC is a catalyst from BASF Corporation.

[0268] Haptex CC 6945 / 90C-CH is a water-based polyurethane dispersion (PUD) with 34.5% solids content from BASF Corporation

[0269] Permutex PP-39-611 is Pigment Black with 20.0% solids content from Stahl.

[0270] Permutex RM 4456 is a thickener with 28.0% solids content from Stahl.

[0271] Astacin Hardener CI is a crosslinker with 70.0% solids content from BASF Corporation.

[0272] Astacin Hardener CA is a crosslinker with 60.0% solids content from BASF Corporation.

[0273] BYK 348 is a wetting agent with 100% solids content from BYK.

[0274] Favini B100 is a release paper from Favini.

[0275] KL-100 is a water-based EVA adhesive from Dongguan Keli adhesive company.

[0276] Characteristic test

[0277] Peel strength test

[0278] The peel strength of the PU laminate just peeled off from the cured release paper is tested, and the test should be completed within 20 minutes, including sample preparation and testing. This test follows the standard SATRA TM 411.

[0279] Wrinkle characteristics

[0280] Grade 1: More than 5 wrinkles with a length greater than 6 cm;

[0281] Grade 2: 3 - 5 wrinkles with a length of 4 - 6 cm;

[0282] Grade 3: 3 - 5 wrinkles with a length less than 4 cm;

[0283] Grade 4: Less than 3 wrinkles with a length of 2 - 4 cm;

[0284] Grade 5: No wrinkles or less than 3 wrinkles with a length less than 2 cm.

[0285] Curing characteristics

[0286] The curing characteristics of the paint layer are evaluated by pressing the surface coating of the laminate with a fingernail and then visually evaluating according to the following grades:

[0287] Grade 1: The fingernail mark rebounds for more than 10 seconds, or the surface coating is damaged

[0288] Grade 2: The fingernail mark rebounds (7 seconds - 9 seconds);

[0289] Grade 3: The fingernail mark rebounds (4 seconds - 6 seconds);

[0290] Grade 4: The fingernail mark rebounds (1 second - 3 seconds);

[0291] Grade 5: No obvious fingernail mark.

[0292] Forming characteristics

[0293] The forming characteristics indicate the number of days to maintain the arc under the conditions of a temperature of 70 °C and a relative humidity of 95%. The higher the number of days, the better the forming retention performance.

[0294] Preparation of the laminate

[0295] Example 1 of the present invention

[0296] Preparation of PU synthetic leather including topcoat, color paint layer and base layer

[0297] The ingredients were blended according to the order of Table 1 to prepare a formulation for the topcoat, and then applied to Favini B100 release paper at a thickness of 100 μm within 4 hours by knife coating, followed by drying at 80° C. for 2 min and at 120° C. for 2 min in oven #1 to form a dried topcoat. Next, the ingredients were blended according to the order of Table 2 to prepare a formulation for a 2-component solvent-free PU system, and then applied to the dried topcoat at a thickness of 350 μm by knife coating, and heated at 80° C. to 140° C. for 1 to 5 min in oven #2 to form a color paint layer. Then, a base layer (polyester fabric with 75% elongation) was applied to the dried color paint layer and heated at 120° C. to 140° C. for 2 to 10 min in oven #3, followed by pressing. PU synthetic leather was obtained after peeling off the release paper.

[0298] Preparation of laminate including PU synthetic leather and formed fabric

[0299] KL-100 was applied to the forming layer (polyester fabric with 30% elongation) to form an adhesive layer (50 g / m 2 ), and then applying the PU synthetic leather on the adhesive layer, and heating in an oven at 60° C. to 80° C. for 10 min to obtain a laminate including the PU synthetic leather and the formed fabric.

[0300] Comparative Examples 1 to 10

[0301] Comparative Examples 1 to 10 were produced in the same manner as described in Inventive Example 1 according to their corresponding formulations shown in Tables 1 and 2.

[0302] Table 1 Formulation of topcoat

[0303] Component Parts by weight Haptex CC 6945 / 90C-CH 100 Permutex PP-39-611 10 Permutex RM 4456 2.5 Astacin Hardener CI 3 Astacin Hardener CA 1 BYK 348 0.5

[0304] Note: The content of each ingredient in Table 1 is calculated by weight (g).

[0305] Table 2 Formulation of solvent-free polyurethane system and properties of the resulting laminate

[0306]

[0307]

[0308] Table 2 - continued

[0309]

[0310]

[0311] Note: The content of each ingredient in Table 2 is calculated by weight (g).

[0312] As shown in Table 2, Example 1 of the present invention shows excellent performance in terms of molding characteristics, wrinkle resistance, curing characteristics, peel strength, and folding endurance, while the comparative examples show that at least one of the above characteristics is inferior to that of the examples of the present invention.

[0313] Comparative Example 11

[0314] Comparative Example 11 was produced in the same manner as described in Example 1 of the present invention, except that the base layer was a polyester fabric with an elongation of 100% and the molding layer was a polyester fabric with an elongation of 50%.

[0315] Table 3 Comparison of characteristics between Example 1 of the present invention and Comparative Example 11

[0316] Example 1 of the present invention Comparative Example 11 Forming characteristics (days) 7 7 Wrinkle 5 3

[0317] As shown in Table 3, Comparative Example 11 shows excellent molding characteristics but shows poor wrinkle resistance. In contrast, Example 1 of the present invention shows both excellent molding characteristics and excellent wrinkle resistance.

[0318] It will be apparent to those of ordinary skill in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit thereof. The embodiments and examples are intended to be illustrative only. Accordingly, the present invention is intended to cover such modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A solvent - free polyurethane system, which comprises (a) a polyol component; and (b) an isocyanate component, wherein the polyol component (a) comprises 15 wt% to 50 wt% of at least one polyol (a-1) having a weight-average molecular weight in the range of 500 g / mol to 2000 g / mol and 50 wt% to 85 wt% of at least one polyol (a-2) having a weight-average molecular weight in the range of 2500 g / mol to 5000 g / mol, each based on the total weight of the polyol component (a); wherein the isocyanate component (b) has a functionality of 2.05 to 2.15 and an NCO% in the range of 16 wt% to 20 wt%; and wherein the solvent-free polyurethane system has an isocyanate index in the range of 95 to 120.

2. The solvent - free polyurethane system according to claim 1, wherein, The polyol component (a) comprises 25 wt% to 40 wt% of the polyol (a-1) and 60 wt% to 75 wt% of the polyol (a-2).

3. The solvent - free polyurethane system according to claim 1 or 2, wherein, The polyol (a-1) has a weight-average molecular weight in the range of 600 g / mol to 1500 g / mol, preferably 800 g / mol to 1200 g / mol.

4. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-2) has a weight-average molecular weight in the range of 3000 g / mol to 4000 g / mol, preferably 3200 g / mol to 3600 g / mol.

5. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-1) is selected from polyether polyols derived from oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, preferably tetrahydrofuran.

6. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-2) is selected from polyether polyols derived from epoxides, preferably ethylene oxide, propylene oxide or a mixture thereof.

7. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-1) has an OH value in the range of 60 to 200 mgKOH / g, preferably in the range of 90 to 130 mgKOH / g.

8. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-2) has an OH value in the range of 10 to 50 mgKOH / g, preferably in the range of 20 to 40 mgKOH / g.

9. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-1) has a functionality in the range of 1.9 to 2.1, preferably in the range of 1.95 to 2.05, more preferably a functionality of 2.

10. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (a-2) has a functionality in the range of 1.5 to 2.5, preferably in the range of 1.8 to 2.1, more preferably a functionality of 2.

11. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The isocyanate component (b) comprises a prepolymer derived from at least one isocyanate (b-1) and at least one polyol (b-2).

12. The solvent - free polyurethane system according to claim 11, wherein, The amount of the isocyanate (b-1) is in the range of 50 wt% to 75 wt%, preferably 60 wt% to 70 wt%, based on the total weight of the isocyanate component (b).

13. The solvent - free polyurethane system according to claim 11 or 12, wherein, The amount of the polyol (b-2) is in the range of 25 wt% to 50 wt%, preferably 30 wt% to 40 wt%, based on the total weight of the isocyanate component (b).

14. The solvent - free polyurethane system according to any one of claims 11 to 13, wherein, The isocyanate (b-1) includes diphenylmethane 4,4'-diisocyanate.

15. The solvent - free polyurethane system according to any one of the preceding claims, wherein, The polyol (b-2) includes polyether polyols derived from oxygen-containing heterocyclic compounds containing 3 to 6 carbon atoms, especially tetrahydrofuran.

16. The solvent - free polyurethane system according to claim 15, wherein, The polyether polyol has a weight-average molecular weight in the range of 1000 g / mol to 3000 g / mol.

17. The solvent-free polyurethane system according to claim 15 or 16, wherein, The polyether polyol has an OH value in the range of 60 to 200 mg KOH / g, preferably in the range of 90 to 130 mg KOH / g.

18. The solvent-free polyurethane system according to claim 15, wherein, The polyol (b-2) includes an additional polyether polyol derived from an epoxide, preferably ethylene oxide, propylene oxide, or a mixture thereof.

19. The solvent-free polyurethane system according to claim 18, wherein, The additional polyether polyol has a weight average molecular weight in the range of 1000 g / mol to 3000 g / mol.

20. The solvent-free polyurethane system according to claim 18 or 19, wherein, The additional polyether polyol has an OH value in the range of 80 to 200 mg KOH / g, preferably in the range of 120 to 180 mg KOH / g.

21. The solvent-free polyurethane system according to any one of the preceding claims, wherein, The isocyanate component (b) has an NCO% in the range of 17 wt% to 19 wt%.

22. The solvent-free polyurethane system according to any one of the preceding claims, wherein, The isocyanate component (b) has a functionality of 2.08 to 2.

12.

23. The solvent-free polyurethane system according to any one of the preceding claims, wherein, The solvent-free polyurethane system has an isocyanate index in the range of 100 to 110.

24. The solvent-free polyurethane system according to any one of the preceding claims, wherein, The solvent-free polyurethane system further comprises a filler.

25. The solvent-free polyurethane system according to any one of the preceding claims, wherein, The solvent-free polyurethane system further comprises a filler in an amount of 30 to 55 wt%, preferably 40 to 50 wt%, based on the total weight of the polyol component (a) and the isocyanate component (b).

26. The solvent-free polyurethane system according to claim 24 or 25, wherein, The filler includes calcium carbonate, kaolin, montmorillonite, aluminum hydroxide, barium sulfate, or talc, preferably calcium carbonate.

27. A solvent-free PU synthetic leather, which comprises (1) a top coat; (2) a base coat layer under the top coat; and (3) a base layer, wherein the base coat layer is made of the solvent-free polyurethane system according to any one of claims 1 to 26.

28. The solvent-free PU synthetic leather according to claim 27, wherein, The top coat is based on an aqueous polyurethane dispersion.

29. The solvent-free PU synthetic leather according to claim 27 or 28, wherein, The top coat further contains a crosslinking agent in the range of 0.5 to 10 wt%, preferably 0.5 to 5 wt%, based on the weight of the aqueous polyurethane dispersion.

30. The solvent-free PU synthetic leather according to claim 29, wherein, The crosslinking agent is selected from hydrophilic-modified or unmodified aromatic or aliphatic polycarbodiimides, or isocyanate trimers.

31. The solvent-free PU synthetic leather according to any one of claims 27 to 30, wherein, The base layer includes a leather fabric in the form of a woven or non-woven fabric, and the leather fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber, and mixtures thereof.

32. The solvent-free PU synthetic leather according to any one of claims 27 to 31, wherein, The base layer has a thickness in the range of 0.5 to 1 mm and an elongation at break in the range of 60% to 90%.

33. A solvent-free PU synthetic leather laminate, which comprises (1) The solvent-free PU synthetic leather according to any one of claims 27 to 32; and (2) The forming layer, wherein the forming layer is on the base layer of the solvent-free PU synthetic leather.

34. The solvent-free PU synthetic leather laminate according to claim 33, wherein, The forming layer includes a forming fabric in the form of a woven or non-woven fabric, and the forming fabric is selected from cotton, viscose fiber, polyester, elastane, microfiber, and mixtures thereof.

35. The solvent-free PU synthetic leather laminate according to claim 33 or 34, wherein, The forming layer has a thickness in the range of 1.0 to 1.5 mm and an elongation at break in the range of 20% to 40%.

36. The solvent-free PU synthetic leather laminate according to any one of claims 33 to 35, wherein, The solvent-free PU synthetic leather laminate further includes an adhesive layer between the base layer and the forming layer of the solvent-free PU synthetic leather.

37. Use of the solvent-free PU synthetic leather laminate according to any one of claims 33 to 36 in the applications of boots, saddles, clothing, accessories, luggage, electronic devices, furniture, automotive interiors, sports items or leisure products, especially as an upper or covering material in the applications of boots and saddles.

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