Imprintable solventless pu sheet, laminates comprising the same and synthetic leather

Abstract

The present invention relates to a pressable 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 of 1.5 to 2.5; and (a-2) optionally at least one polyol having a functionality of 2.7 to 3.5; wherein the amount of polyol (a-2) is < 6 wt.-%, based on the total weight of the polyol component (a); wherein the average functionality of the polyol component (a) is 1.5 to 2.1. The present invention relates to a laminate and synthetic leather comprising the sheet and uses thereof.

Description

Technical Field

[0001] The present invention relates to embossed solvent-free polyurethane sheets formed from a solvent-free polyurethane system comprising a polyol component (a) and an isocyanate component (b), and to laminates and synthetic leathers comprising the thereof. Background Technology

[0002] Solvent-free PU synthetic leather is an environmentally friendly solution for the synthetic leather industry. It typically requires an aqueous dispersion for forming the top coating and solvent-free polyurethane sheets for forming the base coating. Depending on the application, some synthetic leathers require printed patterns, and the availability of such patterns depends primarily on the properties of the solvent-free polyurethane sheets. However, common thermosetting / crosslinked PU systems typically used for synthetic leather are almost impossible to print even at very high printing temperatures (e.g., 180°C to 220°C).

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

[0004] CN203938912U discloses an embossed solvent-free synthetic leather comprising a PU top layer, a thermoplastic polyurethane foam intermediate layer, and a thermosetting polyurethane bottom layer. Specifically, this patent discloses a product with good performance and favorable processing properties obtained through a multi-layer structure.

[0005] CN10403258 discloses a method for preparing embossed solvent-free synthetic leather, comprising a PU top layer, a thermoplastic polyurethane foam intermediate layer, and a thermosetting polyurethane bottom layer. Specifically, this patent discloses a product with good texture and feel obtained by employing a multi-layer structure.

[0006] CN106519177A discloses a method for preparing embossed solvent-free PU synthetic leather. Specifically, this patent discloses the use of a two-component polyurethane to prepare a semi-finished product, which is then embossed to obtain the synthetic leather. However, this patent does not address the technical issues of how to improve the texture replication properties of the synthetic leather.

[0007] CN111016310A discloses a highly durable solvent-free embossed polyurethane synthetic leather. Specifically, this patent discloses the use of a two-component polyurethane foam resin, particularly a post-cured embossed polyurethane, to prepare the synthetic leather.

[0008] Therefore, there is still a need to provide new solvent-free polyurethane sheets that can give sheet-based synthetic leather higher texture reproducibility, for example, greater than 55%, while having very vivid and clear printed patterns. Summary of the Invention

[0009] The object of this invention is to overcome the problems of the prior art discussed above and to provide an embossed solvent-free polyurethane sheet formed from a solvent-free polyurethane system comprising a polyol component (a) and an isocyanate component (b). Simultaneously, the final synthetic leather based on this sheet achieves improved performance in terms of texture replication, instantaneous peel strength, curing properties, and / or flexural strength. Furthermore, the final synthetic leather can be prepared at a lower temperature of 160°C to 175°C.

[0010] Surprisingly, the inventors discovered that the above objective can be achieved by providing an imprintable solvent-free polyurethane sheet, said imprintable solvent-free polyurethane sheet being obtained from a solvent-free polyurethane system comprising a polyol component (a) and an isocyanate component (b).

[0011] The polyol component (a) comprises (a-1) at least one polyol with a functionality of 1.5 to 2.5; and optionally (a-2) at least one polyol with a functionality 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); and wherein the average functionality of the polyol component (a) is 1.5 to 2.1.

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

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

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

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

[0016] In a preferred embodiment of the invention, the average functionality of the polyol component (a) is 1.5 to 2.0, preferably 1.8 to 2.0, more preferably 1.9 to 2.0, and particularly 1.9 to 1.97.

[0017] In a preferred embodiment of the 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 invention, at least one of the polyols (a-2) is selected from polyether polyols derived from epoxides.

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

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

[0021] Another object of the present invention is to provide an imprintable solvent-free PU laminate comprising...

[0022] A) Top coating based on waterborne polyurethane dispersion, and

[0023] B) The base coating layer beneath the top coating layer.

[0024] The base coating is prepared from the sheet material of this invention.

[0025] In a preferred embodiment of the invention, the top coating of the laminate further includes a crosslinking agent in an amount of 0.5 to 10%, preferably 0.5 to 5%, based on the amount of the aqueous polyurethane dispersion, wherein the crosslinking agent is selected from hydrophilically modified aromatic or aliphatic polycarbodiimide (PCDI) or isocyanate trimer.

[0026] In a preferred embodiment of the present invention, the initial decomposition temperature of the aqueous polyurethane dispersion of the top coating, as determined by TGA, is 150 to 250°C, preferably 180 to 230°C.

[0027] Another object of the present invention is to provide synthetic leather comprising a laminate and a base layer according to the present invention, wherein the base layer is beneath the undercoat of the laminate.

[0028] Another object of the present invention is to provide the use of sheets, laminates or synthetic leather as top or covering materials in applications such as clothing, accessories, bags, electronic devices, furniture, automotive interiors, sporting goods or leisure products.

[0029] Unexpectedly, it was found that by using a novel imprintable solvent-free polyurethane sheet formed from a polyol component (a) containing a specific polyol and having a specific average functionality as a base coating, the synthetic leather of the present invention exhibits improved performance in terms of texture replication, peel strength, curing properties, and / or flexural strength. Attached Figure Description

[0030] Figure 1 A method for preparing a bilayer laminate consisting of a top coating and a bottom coating is shown.

[0031] Figure 2 A method for preparing solvent-free PU synthetic leather is shown.

[0032] Figure 3 The texturing process in the preparation of solvent-free PU synthetic leather is shown. Detailed Implementation

[0033] Unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise stated, as used herein, the following terms have the meanings assigned to them as follows.

[0034] As used in this article, the article “a” and “an” refers to one or more (i.e., at least one) of the grammatical objects of an article or component.

[0035] Unless otherwise stated, all percentages (%) are weight percentages.

[0036] Unless otherwise stated, the term "total solids weight" means the total weight of the system or dispersion minus the weight of all solvents (including water).

[0037] Unless otherwise stated, for topcoat coatings, all weight percentages (%) of additives and / or auxiliaries refer to the percentage of the solid weight of the additives and / or auxiliaries divided by the total solid weight of the aqueous polyurethane dispersion.

[0038] Unless otherwise stated, for the primer layer, all weight percentages (%) of additives and / or auxiliaries refer to the percentage of the solid weight of the additives and / or auxiliaries divided by the total solid weight of the solvent-free polyurethane system.

[0039] Unless otherwise stated, the molecular weight of each component or polymer refers to the weight-average molecular weight.

[0040] Unless otherwise stated, temperature refers to room temperature and pressure refers to ambient pressure.

[0041] The present invention provides an imprintable 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 of 1.5 to 2.5; and (a-2) optionally at least one polyol having a functionality 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); wherein the average functionality of the polyol component (a) is 1.5 to 2.1.

[0042] In this invention, the solvent-free polyurethane system for producing imprintable solvent-free polyurethane sheets comprises: a polyol component (a), an isocyanate component (b), a chain extender and / or crosslinking agent (c), and optionally a foaming agent (d), a catalyst (e), a filler (f), and additives and / or auxiliaries (g) (e.g., pigments, thickeners, wetting agents, and antioxidants).

[0043] Polyol component (a)

[0044] In this invention, the polyol component (a) comprises (a-1) at least one polyol with a functionality of 1.5 to 2.5.

[0045] The polyol used as polyol (a-1) is selected from polyols with a functionality of 1.5 to 2.5, preferably polyols with a functionality of 1.5 to 2.1.

[0046] The polyol used as polyol (a-1) preferably has a weight-average molecular weight of 500 g / mol to 10000 g / mol, more preferably 800 g / mol to 6000 g / mol, and more preferably 900 g / mol to 4000 g / mol, and an OH value of 20 to 400 mg KOH / g, more preferably 20 to 300 mg KOH / g, and more preferably 20 to 200 mg KOH / g.

[0047] The polyol (a-1) can 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 mixture of polyether polyols is used as polyol (a-1).

[0048] Suitable polyether polyols preferably have a weight-average molecular weight of 850 g / mol to 1500 g / mol, more preferably 900 g / mol to 1200 g / mol, a functionality of 1.9 to 2.1, and an OH value of 50 to 400 mg KOH / g, more preferably 100 to 200 mg KOH / g. These polyether polyols can be obtained by ring-opening polymerization of oxygen-containing heterocyclic compounds (e.g., tetrahydrofuran) containing 3 to 6 carbon atoms. Preferably, the polyol is prepared by polymerizing tetrahydrofuran as a repeating unit, preferably with primary hydroxyl end-capping.

[0049] The polyether polyols used preferably have a weight-average molecular weight of 3000 g / mol to 4000 g / mol, more preferably 3200 g / mol to 3600 g / mol, a functionality of 1.5 to 2.0, and an OH value of 20 to 200 mg KOH / g, more preferably 20 to 60 mg KOH / g. These polyether polyols can be polyether polyols obtained by homopolymerization of diols (e.g., propylene glycol, ethylene glycol, or butanediol), or polyether polyols prepared by polymerizing epoxides (e.g., ethylene oxide and / or propylene oxide) as repeating units and using propylene glycol as an initiator, preferably end-capped with ethylene oxide containing primary hydroxyl groups.

[0050] In a preferred embodiment of the invention, the polyol (a-1) comprises a mixture of the above-mentioned polyether polyol derived from tetrahydrofuran and the above-mentioned polyether polyol derived from epoxide, in a weight ratio of 1:1.5 to 3, preferably 1:1.5 to 2.5.

[0051] In this invention, the polyol used as polyol (a-1) is prepared by known methods or may be commercially available.

[0052] In this invention, the polyol component (a) further comprises (a-2) at least one polyol with a functionality 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).

[0053] In a preferred embodiment of the invention, the amount of polyol (a-2) is 0% to 4% by weight, preferably 0% to 3.5% by weight, more preferably 0.5% to 3.0% by weight, and particularly 1.0% to 3.0% by weight, each based on the total weight of the polyol component (a).

[0054] The polyol (a-2) is selected from polyols with a functionality of 2.7 to 3.5, or mixtures of such polyols. The polyol used as polyol (a-2) preferably has a functionality of 2.7 to 3.0.

[0055] The polyol used as polyol (a-2) preferably has a weight-average molecular weight of 3000 g / mol to 6000 g / mol, more preferably 3500 g / mol to 5000 g / mol, and more preferably 4000 g / mol to 4500 g / mol, and an OH value of 20 to 200 mg KOH / g, more preferably 20 to 100 mg KOH / g, and more preferably 25 to 60 mg KOH / g.

[0056] 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 (e.g., ethylene oxide (EO), propylene oxide (PO), and / or butyl oxide (BO)). These polyether polyols can be polyether polyols prepared by polymerizing an epoxide (e.g., ethylene oxide and / or propylene oxide) as a repeating unit and using glycerol as a starting agent, preferably by end-capping with ethylene oxide containing primary hydroxyl groups. In this invention, the polyol used as polyol (a-2) is prepared by known methods or can be commercially available.

[0057] In this invention, the polyol component (a), which is composed of (a-1) polyol and optionally (a-2) polyol, has an average functionality (Fav) of 1.5 to 2.1. Preferably, the average functionality of the polyol component (a) is 1.8 to 2.0, more preferably 1.9 to 2.0, especially 1.9 to 1.97, especially 1.9 to 1.96 or 1.9 to 1.95.

[0058] In this invention, FAv refers to the average Fn value of the various polyols contained in polyol component (a), and is expressed by the following formula:

[0059] FAv=MR1*F1+MR2*F2+MR3*F3+……

[0060] Where MR1 is the molar ratio of the first polyol in polyol component (a), and 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), and F2 is the functionality of the second polyol in polyol component (a)...

[0061] In this invention, the molecular weight of each component was determined by gel permeation chromatography (GPC) according to GB / T 21863-2008.

[0062] In this invention, the OH value of each polyol component is determined according to DIN 53240.

[0063] In this invention, functionality (Fn) refers to the number of terminal hydroxyl groups in each polyol molecule. Functionality is determined according to the following formula:

[0064] F n =M n *(OHv) / 56100

[0065] Where Mn represents the number-average molecular weight of the polyol, and OHv represents the hydroxyl value of the polyol component.

[0066] Unexpectedly, it was found that the composition of the polyol component (a) has a significant impact on the performance of the solvent-free polyurethane sheet of the present invention. The average functionality (FAv) of the polyol component (a) is 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, which gives the solvent-free polyurethane sheet of the present invention excellent properties, especially texture replication, for example, exceeding 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 replication, peel strength, curing performance, and / or flexural strength. The inventors have found that the type and amount of polyols (a-1) and (a-2) have a significant impact on the above-mentioned properties of the solvent-free polyurethane sheet of the present invention. Specifically, based on the total weight of polyol component (a), an amount of polyol (a-2) with a functionality of 2.7 to 3.5 ≤ 6% by weight is beneficial for solvent-free polyurethane sheets to achieve the aforementioned improved performance, namely, excellent texture reproducibility greater than 55%, while ensuring excellent peel strength, curing performance, and flexural strength. If the amount of polyol (a-2) is greater than 6% by weight, texture reproducibility decreases. Preferably, the amount of polyol (a-2) is greater than 0% to 4% by weight, more preferably 1% to 3% by weight, each based on the total weight of polyol component (a).

[0067] Isocyanate component (b)

[0068] In this invention, isocyanate component (b) comprises at least one isocyanate, namely (b-1) isocyanate. The isocyanate used to prepare the base coating of this invention includes all isocyanates known for the preparation of polyurethanes. These include aliphatic, cycloaliphatic, aryliphatic, and / or aromatic isocyanates, such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, and / or octamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyano-3,3,5-trimethyl-5-isocyano-methylcyclohexane (isophorone diisocyanate, IPDI), 1,4-bis(isocyano-methyl)cyclohexane and / or 1,3-bis(isocyano-methyl)cyclohexane (HXDI), cyclohexane-1 4-Diisocyanate, 1-methylcyclohexane 2,4-diisocyanate and / or 1-methylcyclohexane 2,6-diisocyanate, and / or dicyclohexylmethane 4,4'-diisocyanate, dicyclohexylmethane 2,4'-diisocyanate and dicyclohexylmethane 2,2'-diisocyanate, diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate and / or diphenylmethane 4,4'-diisocyanate (MDI), polymeric MDI, naphthalene 1,5-diisocyanate (NDI), toluene 2,4-diisocyanate and / or toluene 2,6-diisocyanate (TDI), 3,3'-dimethylbiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate. Diphenylmethane 2,2'-diisocyanate, diphenylmethane 2,4'-diisocyanate and / or diphenylmethane 4,4'-diisocyanate and polymeric MDI are particularly preferred, especially diphenylmethane 4,4'-diisocyanate.

[0069] The amount of isocyanate component (b) is selected such that the isocyanate index is 100 to 140, preferably 100 to 120.

[0070] The isocyanate component (b) may also contain at least one polyol (b-2).

[0071] The polyol (b-2) is selected from polyols with a functionality of 1.5 to 2.5, or mixtures of such polyols. The polyol used as polyol (b-2) preferably has a functionality of 1.6 to 2.0.

[0072] The polyol used as polyol (b-2) preferably has a weight-average molecular weight of 500 g / mol to 5000 g / mol, more preferably 800 g / mol to 3000 g / mol, and more preferably 1000 g / mol to 2500 g / mol, and an OH value of 20 to 300 mg KOH / g, more preferably 20 to 150 mg KOH / g, and more preferably 30 to 100 mg KOH / g.

[0073] The polyol (b-2) can be a single polyol or a mixture of single polyols. Preferably, a mixture of polyols (especially a mixture of polyether polyols) is used as polyol (b-2).

[0074] The polyether polyols used preferably have a weight-average molecular weight of 1000 g / mol to 2500 g / mol, more 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, more preferably 30 to 100 mg KOH / g. These polyether polyols can be obtained by ring-opening polymerization of oxygen-containing heterocyclic compounds (e.g., tetrahydrofuran) containing 3 to 6 carbon atoms. Preferably, the polyol is prepared by polymerizing tetrahydrofuran as a repeating unit, preferably with primary hydroxyl end-capping.

[0075] The polyether polyols used preferably have a weight-average molecular weight of 1000 g / mol to 3000 g / mol, more preferably 1500 g / mol to 2500 g / mol, a functionality of 1.8 to 2.0, and an OH value of 20 to 200 mg KOH / g, more preferably 30 to 100 mg KOH / g. These polyether polyols can be polyether polyols prepared by polymerizing epoxides (e.g., ethylene oxide and / or propylene oxide) as repeating units and using propylene glycol as an initiator, preferably with propylene glycol end-capping.

[0076] In a preferred embodiment of the invention, the polyol (b-2) comprises a mixture of the above-mentioned polyether polyol derived from tetrahydrofuran and the above-mentioned polyether polyol derived from epoxide, in a weight ratio of 1:0.5-2, preferably 1:0.8-1.5.

[0077] In this invention, the polyol used as polyol (b-2) is prepared by known methods or may be commercially available.

[0078] In a preferred embodiment of the invention, the isocyanate component (b) may further contain additives to improve performance, such as diethylene glycol dichloroformate (DECF). The amount of the additive is preferably 0.005 to 0.5% by weight, more preferably 0.01 to 0.1% by weight, based on the total weight of the isocyanate component (b).

[0079] Chain extenders and / or crosslinking agents (c )

[0080] The chain extenders and / or crosslinking agents (c) that can be used are substances with a molar mass preferably less than 500 g / mol, particularly preferably 60 to 400 g / mol, wherein the chain extender has two hydrogen atoms reactive to isocyanate and the crosslinking agent has three hydrogen atoms reactive to isocyanate. They can be used alone or preferably in mixtures. Diols and / or triols with a molecular weight less than 500, particularly 60 to 400, and especially 60 to 350, are preferred. Examples of usable alcohols are aliphatic, cycloaliphatic, and / or aryliphatic diols having 2 to 14 carbon atoms, preferably 2 to 10 carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol and 1,4-cyclohexanediol, diethylene glycol, dipropylene glycol, tripropylene glycol, diethanolamine, or triols, such as 1,2,4-trihydroxycyclohexane or 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane. Ethylene glycol, 1,3-propanediol, or 1,4-butanediol are preferred, especially 1,4-butanediol.

[0081] The amount of chain extender and / or crosslinker (c) is preferably 0.5 to 5% by weight, more preferably 1.5 to 4.5% by weight, based on the total weight of the polyol component (a).

[0082] Foaming agent (d)

[0083] The system may also include a blowing agent (d). Suitable blowing agents (d) are known to those skilled in the art and are selected from, for example, 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 hydrofluoropropylene, water, nitrogen, and mixtures thereof. Preferably, water is used as the sole blowing agent.

[0084] The amount of foaming agent (d) is preferably 0.1 to 5% by weight, more preferably 0.1 to 1.0% by weight, based on the total weight of the polyol component (a).

[0085] Catalyst (e)

[0086] As catalysts (e), all compounds that accelerate the isocyanate-polyol reaction can be used. These compounds are known and described, for example, in "Kunststoffhandbuch, Vol. 7, Polyurethane", Carl Hanser Verlag, 3rd edition, 1993, Chapter 3.4.1. These compounds include amine-based catalysts and organometallic-based catalysts, or mixtures thereof.

[0087] As catalysts based on organometallic compounds, such as 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, and zinc (Zn) salts or bismuth (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.

[0088] As amine-based catalysts, strong basic amines such as N,N,N-triethylaminoethoxyethanol, bis(N,N-dimethylaminoethyl) ether, dimethylcyclohexylamine, trimethylhydroxyethylethylenediamine, dimethylbenzylamine, triethylamine, triethylenediamine, pentamethyldipropylenetriamine, dimethylethanolamine, N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine, tri(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylamine, N-ethylmorpholine, diazabicycloundecene, diazabicyclononene, diazabicyclooctane, are preferred, with triethylenediamine or bis(N,N-dimethylaminoethyl) ether being preferred.

[0089] The catalyst (e) used in this invention can be commercially available, such as Haptex CC 6945 / 92C-CC and Additive CX 93600 from BASF.

[0090] Typically, the amount of catalyst (e) is preferably 0.05 to 5% by weight, more preferably 0.1 to 1.5% by weight, based on the total weight of the polyol component (a).

[0091] Packing material (f)

[0092] According to the present invention, the filler that can be used (if present) is an inorganic filler selected from calcium carbonate, aluminum hydroxide, barium sulfate or talc, preferably calcium carbonate or aluminum hydroxide. The amount of the inorganic filler is 0 to 200% by weight, preferably 10 to 50% by weight, based on the total weight of the solvent-free polyurethane system.

[0093] Additives and / or auxiliaries (g)

[0094] The additives and / or auxiliaries that may be used include surfactants, preservatives, pigments, colorants, antioxidants, silicone leveling agents, stabilizers, thickeners, wetting agents, and reinforcing agents. In the preparation of solvent-free polyurethane systems, one or more of the above-mentioned additives and / or auxiliaries, or mixtures thereof, are typically used to improve the properties of the obtained polyurethane sheets, such as texture reproduction, peel strength, flexural strength, and curing properties.

[0095] 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 solvent-free polyurethane system.

[0096] According to the invention, thickeners, wetting agents, and antioxidants are preferably used. These materials, if present, include all thickeners, wetting agents, and antioxidants commonly used in solvent-free polyurethane systems. Their respective amounts are preferably 0.1 to 5% by weight, more preferably 0.5 to 1% by weight, each based on the total weight of the solvent-free polyurethane system.

[0097] Further information, as well as further examples, regarding the use and mode of action of the aforementioned adjuvants and additives are given by way of example in "Kunststoffhandbuch, Band 7, Polyurethane" ["Plastics handbook, Volume 7, Polyurethanes"], Carl Hanser Verlag, Third Edition, 1993, Chapter 3.4.

[0098] The present invention also provides an imprintable solvent-free PU laminate comprising:

[0099] A) Top coating based on waterborne polyurethane dispersion, and

[0100] B) The base coating layer beneath the top coating layer.

[0101] The base coating is prepared from the embossed solvent-free polyurethane sheet of the present invention.

[0102] Top Coating

[0103] In this invention, according to TGA measurements, the initial decomposition temperature of the aqueous polyurethane dispersion used in the topcoat surface layer is 150 to 250°C, preferably 180 to 230°C. Suitable aqueous polyurethane dispersions for use in the topcoat surface layer are disclosed, for example, in PCT / CN2020 / 084834, the contents of which are expressly incorporated herein by reference.

[0104] In this invention, the aqueous polyurethane dispersion used for the topcoat layer 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 commonly used aliphatic, cycloaliphatic, and aromatic diisocyanates and / or polyisocyanates. Toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and mixtures of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate (polymeric MDI) are preferred, and diphenylmethane diisocyanate (monomer MDI) is particularly preferred. Isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and hydrogenated diphenylmethane-4,4'-diisocyanate (H12MDI) are also preferred.

[0105] Isocyanates, or isocyanate prepolymers as described below, can also be in a modified state, for example by introducing urea diketone, urethane, isocyanurate, carbodiimide, or urethane groups. Blends of various isocyanates can also be used.

[0106] The polyisocyanate can also be used in the form of polyisocyanate prepolymers. These prepolymers are known in the art. They are prepared in a conventional manner by reacting the aforementioned polyisocyanate with a compound having isocyanate-reactive hydrogen atoms to form a prepolymer. The reaction can be carried out, for example, at a temperature of about 80°C. The polyol / polyisocyanate ratio is typically chosen so that the NCO content of the prepolymer is from 6% to 25% by weight.

[0107] The polyol component (b') preferably comprises polyether alcohols and / or polyester alcohols. These are well-known and described, for example, in "Kunststoffhandbuch Polyurethane," Günter Oertel, Carl-Hanser-Verlag, 2nd edition, 1983, Chapter 3.1.1. Equally common alternative names in the relevant field are, on the one hand, polyether polyol or polyether alcohol, and on the other hand, polyester polyol or polyester alcohol.

[0108] In this invention, preferably, the polyol component (b') is a mixture of polyols. The polyol component (b') comprises (b'-1) a polyol with a weight-average molecular weight of 500 g / mol to 10000 g / mol and a functionality of 2 to 4, and (b'-2) a polyol with a weight-average molecular weight of 500 g / mol to 3000 g / mol and a functionality of 2 to 4. For example, polyol (b'-1) may be a polyester, such as XCP-2000N, and polyol (b'-2) may be a polyether, preferably a hydrophilic polyether based on polyethylene glycol, such as YmerN120.

[0109] The polyol component (b') also includes (b'-3) a chain extender with a molecular weight of less than 400 g / mol and (b'-4) a hydrophilic chain extender containing carboxylic acid ester groups or sulfonate groups.

[0110] The chain extenders (b'-3) that can be used are substances with a molecular weight preferably less than 400 g / mol, particularly preferably 60 to 400 g / mol, wherein the chain extender has at least two hydrogen atoms that are reactive to isocyanates. They can be used alone or preferably in mixtures. Diols and / or triols with a molecular weight of 60 to 400, particularly 60 to 350, are preferred. Examples of them that can be used are aliphatic, cycloaliphatic and / or aryliphatic 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-cyclohexanediol, 1,3-cyclohexanediol and 1,4-cyclohexanediol, diethylene glycol, dipropylene glycol, tripropylene glycol, diethanolamine, or triols, such as 1,2,4-trihydroxycyclohexane or 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane. Diamines and / or triamines are also preferred. Examples of them that can be used are diethylenetriamine or N-(2-hydroxyethyl)ethylenediamine. The amount of chain extender (b'-3) is preferably 0.1 to 10% by weight, particularly preferably 0.2 to 8% by weight, based on the total solids weight of the aqueous polyurethane dispersion.

[0111] The hydrophilic chain extender (b'-4) that can be used is a hydrophilic chain extender having a carboxylic acid group or a sulfonate group. They provide hydrophilic groups to 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. 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.

[0112] The aqueous polyurethane dispersion contains no more than 0.5%, preferably less than 0.1%, of carboxylic acid ester groups based on the total solid weight of the aqueous polyurethane dispersion, wherein the carboxylic acid ester groups are derived from a hydrophilic chain extender having carboxyl groups and other carboxyl-containing starting materials used to prepare the aqueous polyurethane dispersion. Furthermore, the molar ratio of hydroxyl and / or amino groups present in the aqueous polyurethane dispersion to isocyanate groups is 0.9 to 1.5, preferably 1.10 to 1.25.

[0113] The aqueous polyurethane dispersion optionally includes an amine neutralizer with gel-reactive properties, thereby providing a suitable pH range of 6 to 9 for the dispersion. The amount of the amine neutralizer is preferably 0.01 to 5% by weight, particularly preferably 0.05 to 2% by weight, based on the total solids weight of the aqueous polyurethane dispersion. For example, the amine neutralizer is selected from triethylenediamine (TEDA), 1,2-dimethylimidazole, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylethylenediamine, and tertiary amines.

[0114] Optionally, the aqueous polyurethane dispersion includes a surfactant. The surfactant may 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 sulfosuccinate, alkyl ether phosphates, alkyl ether carboxylates, or / and cationic surfactants, such as amine ethoxylates, amino polyols, quaternary ammonium surfactants.

[0115] In a preferred embodiment of the invention, the topcoat layer based on the aqueous polyurethane dispersion further includes a crosslinking agent. Suitable crosslinking agents herein may be selected from hydrophilically modified or unmodified aromatic or aliphatic polycarbodiimide (PCDI), or isocyanates. The crosslinking agent may be used in a mixed manner or alone, preferably in a mixed manner. For example, Astacin Hardener CA and / or Astacin Hardener CI may be used as crosslinking agents. The amount of crosslinking agent is preferably 0.1 to 20% by weight, particularly preferably 0.5 to 15% by weight, especially 1 to 10% by weight, based on the total solids weight of the aqueous polyurethane dispersion.

[0116] In a preferred embodiment of the invention, the topcoat layer based on the aqueous polyurethane dispersion further includes other additives and / or auxiliaries known to those skilled in the art. Applicable additives and / or auxiliaries include surfactants, thickeners, pigments, colorants, antioxidants, reinforcing agents, stabilizers, and wetting agents. In preparing polyurethane dispersions, one of the above-mentioned additives and / or auxiliaries, or a mixture thereof, is typically used to improve the properties of the obtained polyurethane dispersion. Generally, 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. As a pigment, all compounds suitable for preparing polyurethane dispersions can be used, such as Permutex PP-39-611. The amount of pigment (if present) 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. As a thickener, all compounds commonly used in the preparation of polyurethane dispersions can be used, such as Permutex RM 4456. 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 a wetting agent, all compounds commonly used in the preparation of polyurethane dispersions can be used, such as BYK 348. 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 an antioxidant, all compounds suitable for the preparation of polyurethane dispersions can be used. The amount of antioxidant (if present) is preferably 0.1 to 5% by weight, more preferably 0.5 to 1% by weight, based on the total solids weight of the aqueous polyurethane dispersion.

[0117] Primer

[0118] In this invention, the base coating is made of the imprintable solvent-free polyurethane sheet of this invention. The imprintable solvent-free polyurethane sheet is formed from the solvent-free polyurethane system defined above.

[0119] The present invention also provides synthetic leather comprising a laminate and a base layer as defined above, wherein the base layer is beneath an undercoat layer of the laminate. The topcoat and undercoat layers are as defined above. The base layer is obtained as described below:

[0120] basal layer

[0121] In this application, the synthetic leather includes a base layer beneath the primer layer. In principle, the base layer can be any layer capable of bonding with the primer layer. The thickness of the base layer is typically from 0.01 mm to 20 mm, preferably from 0.1 mm to 15 mm. The base layer is selected from, for example, nonwoven fabric, woven fabric, TPU, genuine leather, wood, plastic, or split leather. A preferred embodiment uses nonwoven fabric or split leather as the base layer.

[0122] The laminates according to the present invention have improved texture replication, as well as instantaneous peel strength, curing performance, and / or flexural strength. The laminates of the present invention can be used in clothing and accessories as a top layer material for handbags, shoes, boots, gloves, hats, or outerwear items such as jackets, trousers, and belts. It can also be used as a covering material for bags and electronic devices such as briefcases, suitcases, watch straps, smartphone cases, earphone cases, and camera cases. In the furniture / interior decoration field, the laminates of the present invention can be used as synthetic leather covers for sofas, car seats, car interiors, chairs, cushions, and coffee tables, as well as certain types of decorations, such as hanging ornaments. Furthermore, the laminates of the present invention can also be used in sporting or leisure products, such as play balls, saddles, toys, etc. In another aspect, the laminates of the present invention can be used as a genuine leather substitute anywhere.

[0123] PU sheets / laminates / leather can be processed in various ways, for example:

[0124] PU sheets / laminates / leather are continuously embossed using hot embossing rollers at temperatures of 150 to 250°C to replicate textures / patterns.

[0125] The PU sheet / laminate / leather is heated to the desired temperature, such as 150 to 250°C, and then continuously embossed onto the leather using embossing rollers without a heater.

[0126] The PU sheet / laminate / leather is heated to the desired temperature, such as 150 to 250°C, and then the leather is continuously sucked up through a vacuum embossing roller with tiny indentations and a textured surface.

[0127] PU sheets / laminates / leather are embossed using a hot flat plate (150-250℃), rather than a continuous embossing method like embossing rollers.

[0128] PU sheets / laminates / leather are pressed for a very short time using a hot press mold or hot press plate (150-250℃) with a brand logo or character designed on them.

[0129] Example

[0130] The present invention will now be described with reference to embodiments and comparative embodiments, but is not intended to limit the invention.

[0131] Use the following raw materials:

[0132] Polyol #1 was prepared by polymerizing tetrahydrofuran, which serves as a repeating unit, and end-capped with a primary hydroxyl group, resulting in a functionality of 2 and a hydroxyl value (OHv) of 112.3 mg KOH / g.

[0133] Polyol #2 is prepared by polymerizing ethylene oxide as a repeating unit, using propylene glycol as a starting agent, and end-capping with ethylene oxide having primary hydroxyl groups. It has a functionality of 1.76 and a hydroxyl value (OHv) of 29.5 mg KOH / g.

[0134] Polyol #3 is prepared by polymerizing ethylene oxide as a repeating unit, using glycerol as a starting agent, and end-capping with ethylene oxide containing primary hydroxyl groups. It has a functionality of 2.72 and a hydroxyl value (OHv) of 35 mg KOH / g.

[0135] Polyol #4 was prepared by polymerizing propylene oxide as a repeating unit, using TDA as an initiator, and then end-capping with propylene oxide. It has a functionality of 4 and a hydroxyl value (OHv) of 405 mg KOH / g.

[0136] Polyol #5 is prepared by polymerizing propylene oxide as a repeating unit, using propylene glycol as an initiator, and end-capping with propylene glycol. It has a functionality of 2 and a hydroxyl value (OHv) of 55 mg KOH / g.

[0137] Polyol #6 was prepared by polymerizing tetrahydrofuran, which serves as a repeating unit, and then capping it with a primary hydroxyl group. It has a functionality of 2 and a hydroxyl value (OHv) of 56.1 mg KOH / g.

[0138] Haptex CC 6945 / 90C-CH is a water-based PUD from BASF with a solids content of 34.5%.

[0139] ADDITIVE DECF is a polymerization inhibitor from BASF.

[0140] Permutex PP-39-611 is a pigment black from Stahl with a solid content of 20.0%.

[0141] Permutex RM 4456 is a 28.0% solids thickener from Stahl.

[0142] BYK 348 is a 100% solids wetting agent from BYK.

[0143] Astacin Hardener CI is a crosslinking agent from BASF with a solid content of 70.0%.

[0144] Astacin Hardener CA is a 60.0% crosslinking agent from BASF.

[0145] Lupranate MS is an isocyanate from BASF.

[0146] Additive CX 93600 is a catalyst from BASF.

[0147] Haptex CC 6945 / 92C-CC is a catalyst from BASF.

[0148] Favini B100 is a release paper from Favini.

[0149] Preparation of the top coating:

[0150] The top coating was prepared using the following components:

[0151] Table 2: Formulation of the top coating (parts by weight)

[0152] Comparative Examples 1 to 2 and Examples 1 to 4 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

[0153] Preparation of solvent-free polyurethane sheets as a base coating:

[0154] Solvent-free polyurethane sheets were prepared using the following components:

[0155] Table 3: Formulation (parts by weight) of component (a) of the solvent-free polyurethane system

[0156] Component (a) #1 #2 #3 #4 #5 #6 Polyol #1 30 30 30 30 30 30 Polyol #2 56 60 63 65 60 66 Polyol #3 10 6 3 1 0 0 Polyol #4 0 0 0 0 6 0 BDO 3.8 3.8 3.8 3.8 3.8 3.8 water 0.2 0.2 0.2 0.2 0.2 0.2 gross weight 100 100 100 100 100 100 FAv of component (a) 1.98 1.97 1.96 1.96 2.38 1.95

[0157] Table 4: Formulation (parts by weight) of component (b) of the solvent-free polyurethane system

[0158] Components Polyol #5 Polyol #6 Lupranate MS Additive DECF Total weight 100% 18.99% by weight 20% by weight 61% by weight 0.01% by weight

[0159] Table 5: Formulations of solvent-free polyurethane systems (parts by weight)

[0160]

[0161] Preparation of laminates

[0162] Example 1

[0163] Preparation of laminates comprising a top coating layer and a bottom coating layer

[0164] The formulations in Table 2 were prepared by mixing the components one by one, and applied to Favini B100 release paper at a thickness of 100 μm over 4 hours by scraping. The mixture was then dried in oven #1 at 80°C for 2 minutes, followed by drying at 120°C for 2 minutes. Subsequently, the formulations in Table 5 were prepared by mixing the components one by one, and applied to the top of the dried top coating at a thickness of 350 μm by scraping. The mixture was then heated in oven #2 at 120–140°C for 5–10 minutes to form the base coating. The resulting laminates were then separated from the release paper to obtain the final laminate product.

[0165] See processing Figure 1 .

[0166] Example 2

[0167] Preparation of PU synthetic leather comprising top coating, bottom coating and base layer

[0168] The formulations in Table 2 were prepared by mixing the components one by one, and applied to a thickness of 100 μm on Favini B100 release paper over 4 hours. The mixture was then dried in oven #1 at 80°C for 2 minutes, followed by drying at 120°C for 2 minutes. Subsequently, the formulations in Table 5 were prepared by mixing the components one by one, and applied to a thickness of 350 μm on top of the dried topcoat formulation by scraping. The mixture was then heated in oven #2 at 120–140°C for 5–10 minutes. A base layer was then applied over the dried base coat and heated in oven #3 at 140°C for 2–10 minutes, followed by pressing. After peeling off the release paper, PU synthetic leather was obtained.

[0169] See processing Figure 2 .

[0170] Performance testing of PU synthetic leather

[0171] Peel strength test

[0172] A peel strength test shall be performed on the PU synthetic leather that has just been peeled from the release paper after curing. The test shall be completed within 20 minutes (including sample preparation and testing). The test shall be conducted in accordance with standard SATRA™ 411.

[0173] Curing performance

[0174] The curing performance of the two-component PU layer was evaluated by pressing the top coating of the laminate (PU synthetic leather) with a fingernail, and a visual assessment was performed according to the following grading:

[0175] Level 1: Nail mark bounces back for more than 10 seconds, or the top coat is damaged.

[0176] Level 2: Nail mark bounces back (7 to 9 seconds);

[0177] Level 3: Nail mark bounces back (4 to 6 seconds);

[0178] Level 4: Nail mark bounces back (1 to 3 seconds);

[0179] Level 5: No obvious nail marks

[0180] Bending resistance test

[0181] The flexural strength test is performed according to standard ISO 5402 as follows:

[0182] Test samples of PU synthetic leather were prepared according to ISO 2418, including cutting at least three vertical test samples and at least three horizontal test samples. The test samples were then conditioned according to ISO 2419 and tested in a conditioned atmosphere. The test samples were visually evaluated at 25x magnification based on cracks, loss of adhesion, and color changes. "Pass" is defined as the absence of visible cracks, loss of adhesion, or color changes. "Fail" is defined as the presence of damage on the test sample.

[0183] Embossing performance (texture replication)

[0184] The embossing performance test was conducted according to the following:

[0185] The embossing machine is a Model 380 (Nanjing Yueyi Clothing Co., Ltd.), assembled from specially made embossing sheets. The embossing method is as follows:

[0186] (1) Set the temperature to 170℃ and wait for the embossed board to maintain a constant temperature;

[0187] (2) Set the embossing / pressing time to 40 seconds.

[0188] (3) Place the leather sample on the operating table, first press the pressing button, and then press the operation button with both hands. Once the time is up, the embossing plate will move upward automatically, and then the sample can be removed.

[0189] The following were measured using a 3D profilometer measurement system (model: VR-3200): 1) the height difference of the embossed board (ΔHa), and 2) the height difference of the laminate embossed by the board (ΔHb) (see Figure 3 The ratio ΔHb / ΔHa is expressed as a percentage, indicating how much of the laminate replicates the pattern of the embossed board. ΔHb = ΔHa means 100% replication of the embossed board pattern.

[0190] Table 6: Test Results of PU Synthetic Leather Including Top Coating, Under Coating, and Base Layer

[0191]

[0192] Based on the above results, it can be found that, compared with Comparative Examples 1 to 2, the PU synthetic leather obtained in Examples 1 to 4 of the present invention by using the solvent-free polyurethane system of the present invention as a base coating achieves significantly improved performance in texture replication, as well as good peel strength, curing performance, and flexural strength. It can also be found that Example 4 of the present invention, using polyol component (a) composed of polyols (a-1) with an average functionality of less than 2.1, exhibits excellent texture replication, good flexural strength, and peel strength, with only slightly poor curing performance; however, Comparative Example 2, using polyol component (a) composed of polyols (a-1) with an average functionality of 2.38, shows poorer texture replication, flexural strength, and peel strength. Examples 1-3 of the invention, using a polyol component (a) consisting of polyol (a-1) and ≤6% by weight of polyol (a-2), exhibited excellent texture reproduction, as well as good peel strength, curing performance, and flexural strength; however, Comparative Example 1, using a polyol component (a) consisting of polyol (a-1) and a larger amount of polyol (a-2), showed poor texture reproduction.

[0193] The structures, materials, components, and methods described herein are intended as representative embodiments of the invention, and it should be understood that the scope of the invention is not limited to the scope of these embodiments. Those skilled in the art will recognize that the invention can be practiced with variations of the disclosed structures, materials, components, and methods, and these variations are considered to be within the scope of the invention. Therefore, the invention is intended to cover these modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. An embossed solvent-free polyurethane sheet formed from a solvent-free 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 of 1.5 to 2.5; and optionally (a-2) At least one polyol with a functionality of 2.7 to 3.5; The amount of polyol (a-2) is ≤6% by weight, based on the total weight of the polyol component (a); The average functionality of the polyol component (a) is 1.5 to 1.

98.

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

3. The sheet according to claim 1, wherein the amount of polyol (a-2) is from 0% to 4% by weight, based on the total weight of said polyol component (a).

4. The sheet according to claim 3, wherein the amount of polyol (a-2) is from 0% by weight to 3.5% by weight, based on the total weight of said polyol component (a).

5. The sheet according to claim 4, wherein the amount of polyol (a-2) is 1% to 3% by weight, based on the total weight of said polyol component (a).

6. The sheet according to claim 1, wherein the functionality of the polyol (a-1) is 1.5 to 2.

1.

7. The sheet according to claim 1, wherein the functionality of the polyol (a-2) is 2.7 to 3.

0.

8. The sheet according to claim 1 or 2, wherein the average functionality of the polyol component (a) is 1.8 to 1.

98.

9. The sheet according to claim 8, wherein the average functionality of the polyol component (a) is 1.9 to 1.

98.

10. 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 comprising 3 to 6 carbon atoms.

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

12. The sheet according to any one of claims 1 to 7, wherein the isocyanate component (b) comprises (b-1) an isocyanate and (b-2) at least one polyol having a functionality of 1.5 to 2.

5.

13. The sheet according to claim 12, wherein the polyol (b-2) has a weight-average molecular weight of 500 g / mol to 5000 g / mol and an OH value of 20 to 300.

14. The sheet according to 13, wherein the weight-average molecular weight of the polyol (b-2) is from 800 g / mol to 3000 g / mol.

15. The sheet according to 13, wherein the OH value of the polyol (b-2) is 20 to 150.

16. An imprintable solvent-free PU laminate, comprising... A) Top coating based on waterborne polyurethane dispersion, and B) The base coating layer beneath the top coating layer. The base coating is made of the sheet material according to any one of claims 1 to 15.

17. The laminate of claim 16, wherein the top coating further comprises 0.5 to 10% of a crosslinking agent, based on the amount of the aqueous polyurethane dispersion, wherein the crosslinking agent is selected from hydrophilically modified aromatic or aliphatic polycarbodiimide (PCDI) or isocyanate trimer.

18. The laminate of claim 17, wherein the top coating further comprises 0.5% to 5% of a crosslinking agent, based on the amount of the aqueous polyurethane dispersion.

19. The laminate according to claim 16, wherein the initial decomposition temperature of the aqueous polyurethane dispersion is 150 to 250°C, as determined by TGA.

20. The laminate according to claim 19, wherein the initial decomposition temperature of the aqueous polyurethane dispersion is 180 to 230°C, as determined by TGA.

21. Synthetic leather comprising a laminate according to any one of claims 16 to 20 and a base layer, wherein the base layer is beneath an undercoat layer of the laminate.

22. Use of the sheet according to any one of claims 1 to 15, the laminate according to any one of claims 16 to 20, or the synthetic leather according to claim 21 as a top layer or covering material in applications of clothing, accessories, bags, electronic devices, furniture, automotive interiors, sporting goods, or leisure products.

Images