A high-performance polyurethane resin and its applications

Abstract

This invention relates to a high-performance polyurethane resin and its applications. The high-performance polyurethane resin comprises a reaction product of a polyisocyanate, two or more polyols, and a chain extender. The polyols include at least polymeric polyols and polyester polyols; the mass ratio of the polymeric polyol to the polyester polyol is 9:1 to 6:4. This high-performance polyurethane resin possesses excellent resistance to yellowing, solvents, and folding, resolving the contradiction between the yellowing and hydrolysis resistance and the solvent and folding resistance properties of polyurethane synthetic leather products. It is applied to synthetic leather containing this high-performance polyurethane resin as a surface material.

Description

Technical Field

[0001] This invention relates to the field of polyurethane technology, and more specifically to a high-performance polyurethane resin and its application in the field of synthetic leather. Technical Background

[0002] Polyurethane synthetic leather mimics the structure and properties of natural leather, possessing a three-dimensional structure similar to leather, as well as properties such as abrasion resistance, good elasticity, softness, high tensile strength, good gloss, and solvent resistance. It has become the mainstream choice for athletic shoe uppers. Polyurethane resin, as the main raw material for synthetic leather, plays a decisive role in its physical properties. However, currently, due to limitations in key technologies, it is difficult to balance the contradiction between the yellowing and hydrolysis resistance properties of dry-process polyurethane resin and its solvent resistance, folding resistance, and abrasion resistance. This results in a scarcity of dry-process surface layer polyurethane resins on the market that simultaneously possess excellent yellowing resistance, solvent resistance, folding resistance, and hydrolysis resistance. Summary of the Invention

[0003] Technical Problem: The purpose of this invention is to overcome the above-mentioned defects and provide a high-performance polyurethane resin, and its application in the field of synthetic leather. This high-performance polyurethane resin possesses excellent resistance to yellowing, solvent resistance, and folding resistance, thus resolving the contradiction between the yellowing and hydrolysis resistance properties and the solvent resistance and folding resistance properties of polyurethane synthetic leather products.

[0004] Technical solution: The present invention provides a high-performance polyurethane resin comprising a reaction product of polyisocyanate, two or more polyols and chain extender, wherein the polyols include at least polymer polyols and polyester polyols; the mass ratio of the polymer polyols to the polyester polyols is 9:1 to 6:4.

[0005] The polymeric polyols include polyether polyols and / or polyether ester polyols, wherein the polyether polyols include polytetrahydrofuran polyol PTMEG, and the polyether ester polyols include polytetrahydrofuran-caprolactone copolymer polyol PTMEG-PCL.

[0006] The number-average molecular weight of the polymer polyol is greater than 2000 g / mol.

[0007] The polyester polyol comprises a polyol obtained by reacting at least one linear aliphatic diol and at least one linear aliphatic dicarboxylic acid, and the number-average molecular weight of the polyester polyol is 1500-5000 g / mol.

[0008] The straight-chain aliphatic diols include C3 to C8 straight-chain diols, including one or more of propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, and nonanediol.

[0009] The aforementioned straight-chain aliphatic dicarboxylic acids include C2-C8 straight-chain dicarboxylic acids, including one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, and azelaic acid.

[0010] The polyisocyanates include aliphatic polyisocyanates, which include dicyclohexylmethane diisocyanate (HMDI), or at least include dicyclohexylmethane diisocyanate (HMDI) and branched aliphatic polyisocyanates.

[0011] The branched aliphatic polyisocyanate includes at least one of trimethylhexamethylene diisocyanate (TMDI) and isophorone diisocyanate (IPDI); the mass of the branched aliphatic polyisocyanate is calculated based on the total mass of the aliphatic polyisocyanate and accounts for 5%-40%.

[0012] The chain extender comprises small molecule diols and small molecule diamines; the small molecule diols are C2-C6 diols, including one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, neopentanediol, and hexanediol; the small molecule diamines are C2-C10 diamines, including one or more of ethylenediamine, propylenediamine, butanediamine, pentanediamine, methylpentanediamine, hexanediamine, and isophoronediamine; the mass ratio of the small molecule diol to the small molecule diamine is 1:1 to 1:3.

[0013] The molar ratio of isocyanate groups in the polyisocyanate to reactive groups on isocyanate groups in the polyol and chain extender is 1:0.95 to 1:1.

[0014] A synthetic leather is prepared using the high-performance polyurethane resin described above as the surface material.

[0015] Beneficial Effects: The high-performance polyurethane resin of this invention possesses excellent resistance to yellowing, solvents, and folding. When used in the synthetic leather industry, the resulting synthetic leather not only achieves a yellowing resistance rating of 4 or higher, but more importantly, exhibits good folding resistance at both room temperature and low temperatures. Immersion in pure methyl ethyl ketone solution for 3 minutes does not cause delamination, and immersion in 10% NaOH solution at 80°C for 2 hours does not cause cracking. This resolves the contradiction between the yellowing and hydrolysis resistance properties of polyurethane synthetic leather products and their solvent and folding resistance properties. Furthermore, synthetic leather containing this polyurethane resin has a wider range of applications and is less prone to surface peeling and shiny spots during use, greatly expanding the resin's application scope. Detailed Implementation

[0016] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0017] The present invention discloses a high-performance polyurethane resin comprising a reaction product of a polyisocyanate, two or more polyols and a chain extender, wherein the polyols include at least polymer polyols and polyester polyols.

[0018] The mass ratio of the polymer polyol to the polyester polyol is 9:1 to 6:4;

[0019] The polymer polyols include polyether polyols and / or polyether ester polyols, wherein the polyether polyols include polytetrahydrofuran polyol PTMEG, and the polyether ester polyols include polytetrahydrofuran-caprolactone copolyol PTMEG-PCL.

[0020] As an example, the polytetrahydrofuran-caprolactone copolyol can be commercially available, or it can be obtained by copolymerizing ε-caprolactone and tetrahydrofuran, or by copolymerizing low molecular weight polytetrahydrofuran with ε-caprolactone, or by copolymerizing low molecular weight polycaprolactone with tetrahydrofuran.

[0021] The number-average molecular weight of the polymer polyol is greater than 2000 g / mol;

[0022] Furthermore, the number-average molecular weight of the polymer polyol is greater than 2000 g / mol and less than 4000 g / mol;

[0023] The polyester polyol comprises a polyol obtained by reacting at least one linear aliphatic diol and at least one linear aliphatic dicarboxylic acid, wherein the number-average molecular weight of the polyester polyol is 1500-5000 g / mol.

[0024] The straight-chain aliphatic diols include C3 to C8 straight-chain diols, including one or more of propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, and nonanediol.

[0025] In some embodiments of the present invention, the linear aliphatic diol includes one or a mixture of butanediol and hexanediol.

[0026] The aforementioned straight-chain aliphatic dicarboxylic acids include C2-C8 straight-chain dicarboxylic acids, including one or more of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, and azelaic acid.

[0027] In some embodiments of the present invention, the straight-chain aliphatic dicarboxylic acid is adipic acid;

[0028] In some embodiments of the present invention, the polyester polyol comprises one or a mixture of polybutylene adipate polyol PBA and polyhexylene adipate polyol PHA.

[0029] The polyisocyanate is an aliphatic polyisocyanate, which includes dicyclohexylmethane diisocyanate (HMDI).

[0030] Furthermore, the aliphatic polyisocyanates include at least dicyclohexylmethane diisocyanate (HMDI) and branched aliphatic polyisocyanates.

[0031] The branched aliphatic polyisocyanates include at least one of trimethylhexamethylene diisocyanate (TMDI) and isophorone diisocyanate (IPDI).

[0032] In some embodiments of the present invention, the branched aliphatic polyisocyanate is trimethylhexamethylene diisocyanate (TMDI).

[0033] The branched aliphatic polyisocyanate accounts for 5%-40% of the total mass of the aliphatic polyisocyanate.

[0034] The chain extenders include small molecule diols and small molecule diamines;

[0035] Small molecule diols are C2 to C6 diols, including one or more of ethylene glycol EG, diethylene glycol DEG, propylene glycol PG, butanediol BDO, pentanediol PDO, neopentanediol NPG, and hexanediol HDO.

[0036] Small molecule diamines are C2-C10 diamines, including one or more of ethylenediamine (EDA), propylenediamine (PDA), butanediamine, pentanediamine, methylpentanediamine, hexamethylenediamine (HDA), and isophoronediamine (IPDA).

[0037] The mass ratio of the diol to the diamine is 1:1 to 1:3.

[0038] In some examples of the present invention, the high-performance polyurethane resin comprises the reaction product of the following components in parts by weight:

[0039] 25-60 parts by weight of polyisocyanate;

[0040] 25-85 parts by weight of polyols;

[0041] Chain extender 5-25 parts by weight;

[0042] The polyols mentioned above include at least polymer polyols and polyester polyols, wherein the mass ratio of the polymer polyols to polyester polyols is 9:1 to 6:4.

[0043] The polyisocyanate mentioned is an aliphatic polyisocyanate;

[0044] The chain extender comprises a small molecule diol and a small molecule diamine; the mass ratio of the diol to the diamine is 1:1 to 1:3.

[0045] As an example, the molar ratio of isocyanate groups in the polyisocyanate to the isocyanate-reactive groups in the polyol and chain extender is 1:0.95 to 1:1.

[0046] The method for preparing the high-performance polyurethane resin includes: reacting a polyisocyanate, a polyol and a chain extender in the presence of a solvent to obtain a high-performance polyurethane resin solution.

[0047] The solvent includes one or more of dimethylformamide, dimethylacetamide, ethyl acetate, methyl ethyl ketone, and toluene; preferably, dimethylformamide.

[0048] The viscosity of the solution is controlled at 80–150 Pa·s / 25℃;

[0049] Preferably, the high-performance polyurethane resin may also contain additives commonly found in the art, such as one or more of antioxidants, ultraviolet absorbers, light stabilizers, leveling agents, lubricants, and antioxidants.

[0050] In some embodiments of the present invention, the addition of hydroxyl-terminated organosilicon and / or amino-terminated organosilicon allows the organosilicon to participate in the reaction of polyurethane and be grafted into the polyurethane chain segments, thereby promoting microphase separation and further enhancing the basic physical properties of the product.

[0051] The amount of hydroxyl-terminated organosilicon and / or amino-terminated organosilicon added is 0.05-0.5%, calculated based on the mass of the polyurethane resin.

[0052] The method for preparing the low-temperature applicable polyurethane resin can be carried out by integral polymerization or stepwise prepolymerization. For example, in integral polymerization, polyisocyanate, polyol and chain extender are directly added to the solvent and reacted fully to obtain a solution containing low-temperature applicable polyurethane resin; in stepwise prepolymerization, a portion of the polyisocyanate and polyol mixture is first added to the solvent to react and obtain a prepolymer, and then the chain extender and the remaining polyisocyanate are added to the solution to continue the reaction to obtain a solution containing low-temperature applicable polyurethane resin.

[0053] In some embodiments of the present invention, the method for preparing low-temperature applicable polyurethane resin employs a stepwise prepolymerization method:

[0054] ① Add polyol, polyisocyanate, small molecule diol chain extender and solvent to the reaction vessel, control the reaction temperature to 90℃~110℃, and carry out the prepolymerization reaction to obtain the prepolymer, in which the mass content of NCO is 2.5~5%; the amount of solvent added is sufficient to ensure that each component is dissolved.

[0055] ② Reduce the temperature to below 50℃, add solvent and stir evenly, then add small molecule diamine chain extender dropwise to allow the chain growth reaction to proceed. During this process, add more solvent and control the viscosity of the reaction solution to reach 80-150 Pa·s at 25℃, then terminate the reaction.

[0056] Preferably, the polymer polyol and the polyester polyol are mixed together to obtain a polyol mixture, which is then reacted with the polyisocyanate.

[0057] In the above preparation process, catalysts can be selectively added to increase the reaction rate, such as organobismuth catalysts and / or organotin catalysts; in the later stage of the reaction, terminators can be selectively added to adjust the degree of reaction, avoid excessive NCO residue, and control the solution viscosity, such as small molecule monohydric alcohols.

[0058] The synthetic leather used in this invention contains the aforementioned high-performance polyurethane resin as a surface material;

[0059] As an example, the method for preparing the synthetic leather is as follows:

[0060] A high-property polyurethane resin solution is coated onto release paper as a top layer resin. After drying at 130–150°C for 4–6 minutes, a polyurethane resin top layer material is obtained. An intermediate layer resin is coated onto the top layer resin and kept at 100–120°C for 60–90 seconds to obtain a semi-cured intermediate layer. A base fabric is attached to the semi-cured intermediate layer and cured at 120–150°C for 3–7 minutes. The release paper is then separated to obtain a leather product.

[0061] The principles and features of the present invention are described below with reference to implementation examples. The examples are provided to help those skilled in the art better understand the present invention.

[0062] The reaction components of Examples 1-14 are shown in Table 1 below:

[0063] Table 1:

[0064]

[0065] Table 1 (continued):

[0066]

[0067]

[0068] Table 1 (continued):

[0069]

[0070] Comparative Example 1

[0071] The difference from Example 1 is that PTMEG of equal mass is used to replace the original PBA, while everything else remains the same.

[0072] Comparative Example 2

[0073] The difference from Example 1 is that PBA of equal mass is used to replace the original PTMEG, while everything else remains the same.

[0074] Example 1: Preparation method of high-property polyurethane resin:

[0075] ① Add PTMEG, PBA, MDI, HDO and solvent DMF to the reactor, control the reaction temperature at 95℃ to carry out the prepolymerization reaction, and obtain a prepolymer with an NCO mass content of 3%.

[0076] ② Reduce the temperature to below 50℃, continue to add DMF solvent and stir evenly, then add IPDA small molecule diamine chain extender dropwise to allow the chain growth reaction to proceed. During this process, add more DMF solvent, and finally control the solid content of the solution to 30wt%. When the viscosity of the reaction solution reaches 80~150Pa·s at 25℃, terminate the reaction.

[0077] The molar ratio of isocyanate groups in the polyisocyanate to the reactive groups on the isocyanate groups in the polyol and chain extender is 1:0.99.

[0078] The preparation methods of Examples 2 to 14 are the same as those of Example 1. The molar ratio of isocyanate groups in the polyisocyanate to the reactive groups of isocyanate groups in the polyol and chain extender is controlled to be 1:0.99. The solid content and reaction viscosity are kept consistent with those of Example 1.

[0079] The polyurethane resin obtained in the examples and comparative examples was used as the surface material for synthetic leather. The preparation method of the synthetic leather is as follows:

[0080] A polyurethane resin solution is coated onto release paper and dried at 130–150°C for 3–6 minutes. This process is repeated, and the surface layer is coated with two passes to obtain a polyurethane resin surface layer material. An intermediate layer resin (product JF-A-AH5035A from Zhejiang Huafeng Synthetic Resin Co., Ltd.) is coated onto the surface layer resin and kept at 120–140°C for 40–60 seconds to obtain a semi-cured intermediate layer. The base fabric material is then bonded to the semi-cured intermediate layer and cured at 130–150°C for 3–7 minutes. After this process, the release paper is separated to obtain the leather product.

[0081] The following tests were performed on the leather products:

[0082] (1) Yellowing resistance: The yellowing resistance of the leather sample was tested according to Method B of QB / T 4672-2014, with a light exposure time of 4h;

[0083] (2) Solvent resistance: After soaking in methyl ethyl ketone (MEK) for 3 minutes, observe whether delamination occurs on the surface of the leather sample.

[0084] (3) Folding resistance at room temperature: The leather samples were tested for folding resistance at room temperature (23±2℃) using a leather flexing tester. The number of folding tests was recorded when cracks began to appear on the surface of the leather sample.

[0085] (4) Low temperature folding resistance: The leather sample was tested for folding resistance at -15℃ using a vertical cold resistance tester. The number of folding tests was recorded when cracks began to appear on the surface of the leather sample.

[0086] (5) Hydrolysis resistance: After folding the synthetic leather sample in half, immerse it in a 10% NaOH solution at 80℃. After 2 hours, observe whether cracks appear on the surface of the leather sample and at the folded part.

[0087] (6) Bright spots: After drying, peel off the release paper and observe whether there are bright spots on the surface of the leather sample.

[0088]

Claims

1. A high-performance polyurethane resin, characterized in that... The high-performance polyurethane resin comprises a reaction product of polyisocyanate, two or more polyols and chain extender, wherein the polyols include at least polymer polyols and polyester polyols; the mass ratio of the polymer polyol to the polyester polyol is 9:1 to 6:

4. The polyester polyol is polybutylene adipate polyol PBA; The polymer polyol is a polyether polyol and / or a polyether ester polyol, wherein the polyether polyol includes polytetrahydrofuran polyol PTMEG, and the polyether ester polyol includes polytetrahydrofuran-caprolactone copolyol PTMEG-PCL. The polyisocyanates include aliphatic polyisocyanates, and the aliphatic polyisocyanates include at least dicyclohexylmethane diisocyanate (HMDI) and branched aliphatic polyisocyanates. The branched aliphatic polyisocyanate is at least one of trimethyl hexamethylene diisocyanate (TMDI) and isophorone diisocyanate (IPDI); The mass of the branched aliphatic polyisocyanate is calculated based on the total mass of the aliphatic polyisocyanate and accounts for 5%-40% of the total mass. The molar ratio of isocyanate groups in the polyisocyanate to reactive groups on isocyanate groups in the polyol and chain extender is 1:0.95 to 1:

1.

2. The high-performance polyurethane resin according to claim 1, characterized in that, The number-average molecular weight of the polymer polyol is greater than 2000 g / mol.

3. The high-performance polyurethane resin according to claim 1, characterized in that, The number-average molecular weight of the polyester polyol is 1500~5000 g / mol.

4. The high-performance polyurethane resin according to claim 1, characterized in that, The chain extender comprises small molecule diols and small molecule diamines; the small molecule diols are C2-C6 diols, including one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, neopentanediol, and hexanediol; the small molecule diamines are C2-C10 diamines, including one or more of ethylenediamine, propylenediamine, butanediamine, pentanediamine, methylpentanediamine, hexanediamine, and isophoronediamine; the mass ratio of the small molecule diol to the small molecule diamine is 1:1 to 1:3.

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