Low-curl high-durability polyurethane bonding layer resin, preparation method thereof and application of low-curl high-durability polyurethane bonding layer resin in TPU (thermoplastic polyurethane) synthetic leather

Abstract

The invention discloses low-curl high-durability polyurethane bonding layer resin, a preparation method thereof and application of the low-curl high-durability polyurethane bonding layer resin in TPU (thermoplastic polyurethane) synthetic leather. According to the invention, hydroxyl-terminated polyethylene glycol is grafted on a polyurethane molecular main chain, and the molecular flexibility of polyethylene is utilized to reduce the shrinkage curl of TPU in the dry production process of a TPU synthetic leather product, so that the product stretching degree is improved, and the smooth processing of subsequent products is ensured; meanwhile, alkane groups of hydroxyl-terminated polyethylene glycol are connected into a polyurethane molecular structure, so that the density of ester bonds in polyurethane is effectively reduced, and the hydrolysis resistance and cold resistance of the product are further improved. In addition, the resin crystallization is further reduced by limiting the use amount of ethylene glycol in the used micromolecular dihydric alcohol and the hydroxyl-containing low-molecular compound. Compared with a common synthetic leather bonding layer, the prepared polyurethane bonding layer enables a TPU synthetic leather product to have high stretching degree, the product quality is improved, and the customer product experience is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane, and in particular relates to a polyurethane resin for synthetic leather, and further relates to a low-curl and high-durability polyurethane adhesive layer resin, a preparation method thereof, and application in TPU synthetic leather. Background Art

[0002] TPU synthetic leather is an environmentally friendly synthetic leather material, which can be achieved by direct dry veneer of TPU substrate. Compared with traditional wet synthetic leather, it has higher durability, the products are healthier and more environmentally friendly, and the shoemaking process is simpler. While the product brings many conveniences, because the TPU substrate lacks the support of the cloth base material compared to traditional synthetic leather products, the whole product is made of polyurethane. During the processing, the polymer material lacks the support of the cloth base, which is prone to curling of the leather product, especially after the TPU synthetic leather is cut before shoemaking, this problem is more prominent. Therefore, traditional adhesive layer resin is not suitable for TPU synthetic leather products. Summary of the invention

[0003] In view of this, the present invention provides a low-curl and high-durability polyurethane adhesive layer resin, a preparation method thereof, and an application in TPU synthetic leather. The present invention provides a polyurethane resin synthesized from terminal hydroxyl polyethylene glycol containing a specific proportion. The terminal hydroxyl polyethylene glycol serves as a soft segment of the polyurethane molecule, which reduces the crystalline rigidity of the resin, better meets the fitting requirements of TPU products, and greatly reduces the curling problem of TPU products, so that it can be applied to the production of various types of TPU synthetic leather.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The first object of the present invention is to provide a method for preparing a low-curl and high-durability polyurethane adhesive layer resin, comprising the following steps:

[0006] Preparation of polyurethane adhesive layer resin: place part of isocyanate, polyol, low molecular weight compound containing hydroxyl group, part of organic solvent, antioxidant and catalyst at 65-85℃ for chain extension reaction, add the remaining isocyanate to the reaction system during the chain extension reaction, add the remaining organic solvent and reaction terminator after the reaction reaches the expected viscosity, and obtain the target product; the polyol includes terminal hydroxyl polyethylene diol and polyester polyol. The molecular formula of terminal hydroxyl polyethylene diol is: HO(C 2 H 4 ) n OH.

[0007] In a further embodiment, the polyol further comprises polyether polyol, the proportion of the polyether polyol in the polyol is less than 35%; the polyether polyol is polytetrahydrofuran diol or polyoxypropylene diol; the number average molecular weight of the polyether polyol is 1000-3000 g / mol. Some products require higher cold resistance requirements, so an appropriate amount of polyether polyol is added according to the requirements, which is achieved by using hydroxyl-terminated polyethylene diol and polyether polyol in coordination.

[0008] In a further embodiment, the number average molecular weight of the hydroxyl-terminated polyethylene glycol is 500-2000 g / mol, and the proportion of the hydroxyl-terminated polyethylene glycol is 3%-25% of the polyol. The number average molecular weight of the polyester polyol is 1000-3000 g / mol, and the polyester polyol is a polyester diol. The polyester diol is obtained by the condensation reaction of a small molecule diol and a small molecule dibasic acid, and the small molecule diol is selected from one or more of ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol; wherein the amount of ethylene glycol is less than 50% of the total mass of the small molecule diol. The small molecule dibasic acid is selected from one or more of adipic acid, isophthalic acid, terephthalic acid, and sebacic acid.

[0009] In a further embodiment, the isocyanate is selected from one or more of MDI-100, MDI-50, IPDI, HDI, HMDI, and XDI;

[0010] The hydroxyl-containing low molecular compound is selected from one or more of ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, wherein the amount of ethylene glycol is less than 50% of the total mass of the hydroxyl-containing low molecular compound.

[0011] The organic solvent is dimethylformamide;

[0012] The antioxidant is selected from at least one of antioxidant 245, antioxidant 1010, antioxidant 1035, antioxidant 1076, antioxidant 1098, and antioxidant 3114;

[0013] The catalyst is selected from BiCAT 8106, BiCAT 8108, BiCAT 8124, BiCAT 3228, Borchi Kat22, Borchi Kat 24, BiCAT 4130, BiCAT 4232, and MB20;

[0014] The reaction terminator is one of methanol, ethanol and isopropanol.

[0015] In a further embodiment, the mass ratio of the isocyanate, polyol, hydroxyl-containing low molecular compound, organic solvent, antioxidant, catalyst and reaction terminator is (25-35):(80-120):(4-8):(160-240):(0.01-0.03):(0.005-0.02):(0.05-0.15).

[0016] The present invention also provides a low curling and high durability polyurethane adhesive layer resin, which is prepared by the preparation method described in the first object. The low curling and high durability polyurethane adhesive layer resin is applied in the production of TPU synthetic leather, which can effectively solve the problems of poor flatness and easy curling of TPU synthetic leather products.

[0017] The present invention has the following beneficial effects:

[0018] The low curl and high durability polyurethane adhesive layer resin disclosed in the present invention grafts hydroxyl-terminated polyethylene glycol onto the main chain of polyurethane molecules, and utilizes the molecular flexibility of polyethylene to reduce the shrinkage and curling of TPU during the dry production of TPU synthetic leather products, thereby improving the stretch of the product and ensuring smooth subsequent product processing; at the same time, by inserting the alkyl group of hydroxyl-terminated polyethylene glycol into the molecular structure of polyurethane, the density of ester bonds in polyurethane is effectively reduced, and the hydrolysis resistance and cold resistance of the product are further improved. This enables TPU synthetic leather products to have a higher stretch, improve product quality, and enhance customer product experience.

[0019] In the formula design, the present invention utilizes the structural adjustment of the terminal hydroxyl polyethylene glycol to improve the molecular flexibility of the resin, and at the same time limits its dosage to optimize the compatibility between the components, and finally limits the dosage of ethylene glycol in the small molecular diol and the low molecular compound containing hydroxyl to further reduce the crystallization of the resin. The present invention can obtain a product with excellent comprehensive performance by using the terminal hydroxyl polyethylene glycol, polyether polyol and polyester polyol in combination. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] The present invention is described below by means of specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used are commercially available; the parts, number of parts, etc., referred to, all refer to parts by mass unless otherwise specified.

[0023] The raw material information and sources involved in the embodiments and comparative examples are as follows:

[0024] Isocyanate MDI-100, MDI-50, Yantai Wanhua Group Co., Ltd.;

[0025] Polytetrahydrofuran diol, Shanxi Sanwei Group Co., Ltd.

[0026] Catalysts BiCAT 8108, BiCAT 322, MB20, Leading Chemicals, USA;

[0027] The following raw material abbreviations are explained as follows:

[0028] PE-X is hydroxyl-terminated polyethylene glycol, where X represents the relative molecular mass, such as 300, 1000.

[0029] SP-XY is polyester diol, X represents relative molecular mass, such as: 1000, 2000. Y represents different structural compositions, such as: 1, 2. For the preparation method, see: Polyurethane Resin and Its Application, Chemical Industry Press (2011.11), Liu Yijun, P62 Production Method and Material Calculation of Polyester Polyol.

[0030] Other materials not mentioned are normal commercially available products.

[0031] Example 1

[0032] A method for preparing a low-curl and high-durability polyurethane adhesive layer resin for TPU synthetic leather comprises the following steps:

[0033] 24 parts of MDI-100, 20 parts of PE-1000, 80 parts of SP-2000-1 (excluding ethylene glycol), 5 parts of 1,4-butanediol, 170 parts of dimethylformamide, 0.02 parts of antioxidant 1010 and 0.01 parts of MB20 were subjected to chain extension reaction at 65°C. During the chain extension reaction, 5 parts of MDI-100 were added to the reaction system. After the reaction reached a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.1 parts of methanol were added to obtain the final product.

[0034] Example 2

[0035] A method for preparing a low-curl and high-durability polyurethane adhesive layer resin for TPU synthetic leather comprises the following steps:

[0036] 17 parts of MDI-100, 2.4 parts of PE-500, 77.6 parts of SP-2000-1 (excluding ethylene glycol), 4 parts of 1,4-butanediol, 130 parts of dimethylformamide, 0.01 parts of antioxidant 1035, and 0.005 parts of BiCAT 3228 were subjected to chain extension reaction at 85°C. During the chain extension reaction, 5 parts of MDI-100 were added to the reaction system. After the reaction reached a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.05 parts of methanol were added to obtain the final product.

[0037] Example 3

[0038] A method for preparing a low-curl and high-durability polyurethane adhesive layer resin for TPU synthetic leather comprises the following steps:

[0039] 27 parts of MDI-50, 30 parts of PE-2000, 70 parts of SP-2000-2 (ethylene glycol accounts for 50% of the total alcohol amount of polyester diol), 20 parts of polytetrahydrofuran diol (Mn=2000, f=2), 8 parts of 1,6-hexanediol, 210 parts of dimethylformamide, 0.03 parts of antioxidant 245, and 0.005 parts of BiCAT 8108 are subjected to chain extension reaction at 85°C. During the chain extension reaction, 5 parts of MDI-50 are added to the reaction system. After the reaction reaches a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.15 parts of methanol are added to obtain the final product.

[0040] Comparative Example 1

[0041] A method for preparing a polyurethane adhesive layer resin comprises the following steps:

[0042] 21 parts of MDI-100, 100 parts of SP-2000-1 (excluding ethylene glycol), 5 parts of 1,4-butanediol, 170 parts of dimethylformamide, 0.02 parts of antioxidant 1010 and 0.01 parts of MB20 were subjected to chain extension reaction at 65°C. During the chain extension reaction, 5 parts of MDI-100 were added to the reaction system. After the reaction reached a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.1 parts of methanol were added to obtain the final product.

[0043] The same preparation method as in Example 1 was adopted, and SP-2000-1 was used instead of PE-1000.

[0044] Comparative Example 2

[0045] A method for preparing a polyurethane adhesive layer resin comprises the following steps:

[0046] 24 parts of MDI-100, 20 parts of PE-1000, 80 parts of SP-2000-3 (ethylene glycol accounts for 80% of the total alcohol amount of polyester diol), 5 parts of 1,4-butanediol, 170 parts of dimethylformamide, 0.02 parts of antioxidant 1010 and 0.01 parts of MB20 are subjected to chain extension reaction at 65°C. During the chain extension reaction, 5 parts of MDI-100 are added to the reaction system. After the reaction reaches a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.1 parts of methanol are added to obtain the final product.

[0047] The same preparation method as in Example 1 was adopted, and SP-2000-3 was used instead of SP-2000-1.

[0048] Comparative Example 3

[0049] A method for preparing a polyurethane adhesive layer resin comprises the following steps:

[0050] 30 parts of MDI-100, 20 parts of PE-1000, 80 parts of SP-2000-1 (excluding ethylene glycol), 5 parts of ethylene glycol, 170 parts of dimethylformamide, 0.02 parts of antioxidant 1010 and 0.01 parts of MB20 were subjected to chain extension reaction at 65°C. During the chain extension reaction, 5 parts of MDI-100 were added to the reaction system. After the reaction reached a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.1 parts of methanol were added to obtain the final product.

[0051] The same preparation method as in Example 1 was adopted, and ethylene glycol was used instead of 1,4-butanediol.

[0052] Comparative Example 4

[0053] A method for preparing a polyurethane adhesive layer resin comprises the following steps:

[0054] 24 parts of MDI-100, 50 parts of PE-1000, 50 parts of SP-2000-1 (excluding ethylene glycol), 5 parts of 1,4-butanediol, 170 parts of dimethylformamide, 0.02 parts of antioxidant 1010 and 0.01 parts of MB20 were subjected to chain extension reaction at 65°C. During the chain extension reaction, 5 parts of MDI-100 were added to the reaction system. After the reaction reached a viscosity of 100 Pa.s / 75°C, 30 parts of dimethylformamide and 0.1 parts of methanol were added to obtain the final product.

[0055] The same method as in Example 1 was used for preparation, and the ratio of PE-1000 and SP-2000-1 was adjusted.

[0056] Test Case

[0057] The resins prepared in the above-mentioned embodiments and comparative examples were used to prepare TPU synthetic leather samples. The method is as follows: the surface layer resin uses LT-68 resin from Hefei Amway Polyurethane New Materials Co., Ltd., and the adhesive layer uses the resins prepared in embodiments 1-3 and comparative examples 1-4, respectively. Two knives and dry lamination process, the surface layer blade thickness is 0.15mm, the adhesive layer blade thickness is 0.2mm, the oven temperature is 135°C, each knife is dried for 15 minutes, and TPU substrate HL-0.95 is used for lamination to obtain leather samples. The test results are shown in Table 1.

[0058] Table 1 Test results of synthetic leather performance with different adhesive layer resins

[0059]

[0060] Note: Numerical rating: 1-poor; 2-average; 3-good

[0061] The tests at 70℃*2H*10%NaOH and -20℃*60,000 times in Table 1 refer to the hydrolysis resistance and cold resistance tests of the industry standards. The transparency of the resin is greatly affected by the different dosage and molecular weight of PE, and most TPU products are semi-transparent or fully transparent products, which have high requirements on the transparency of the resin.

[0062] It can be seen from the test results in Table 1 that the polyurethane adhesive layer resin prepared by the present invention for TPU synthetic leather has excellent leather stretch, hydrolysis resistance and cold resistance. Comparative Example 2 failed to meet the requirements in terms of leather stretch and hydrolysis resistance due to the excessive rigidity of polyester, Comparative Example 3 failed to meet the requirements in terms of leather stretch and cold resistance due to the excessive rigidity of the hard segment, and Comparative Example 4 failed to meet the requirements in terms of resin appearance transparency and adhesion due to excessive PE usage, resulting in failure in hydrolysis resistance and cold resistance tests;

[0063] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a low curl and high durability polyurethane adhesive layer resin, characterized in that: The following steps are involved: Part of isocyanate, polyol, hydroxyl-containing low molecular compound, part of organic solvent, antioxidant and catalyst are placed at 65-85°C for chain extension reaction, and the remaining isocyanate is added to the reaction system during the chain extension reaction. After the reaction reaches the expected viscosity, the remaining organic solvent and reaction terminator are added to obtain the target product; the polyol includes terminal hydroxyl polyethylene diol and polyester polyol.

2. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to claim 1, characterized in that: The number average molecular weight of the terminal hydroxyl polyethylene diol is 500-2000g / mol, and the molar ratio of the terminal hydroxyl polyethylene diol is 3%-25% of the polyol; the number average molecular weight of the polyester polyol is 1000-3000g / mol, and the polyester polyol is a polyester diol, which is obtained by the condensation reaction of a small molecule diol and a small molecule dibasic acid, and the mass ratio of ethylene glycol in the small molecule diol is less than 50%.

3. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to claim 1, characterized in that: The isocyanate is selected from one or more of MDI-100, MDI-50, IPDI, HDI, HMDI, and XDI.

4. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to claim 1, characterized in that: The hydroxyl-containing low molecular compound is selected from one or more of ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, diethylene glycol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, wherein the amount of ethylene glycol is less than 50% of the total mass of the hydroxyl-containing low molecular compound.

5. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to claim 1, characterized in that: The antioxidant is selected from at least one of antioxidant 245, antioxidant 1010, antioxidant 1035, antioxidant 1076, antioxidant 1098, and antioxidant 3114; The catalyst is selected from BiCAT 8106, BiCAT 8108, BiCAT 8124, BiCAT 3228, Borchi Kat 22, Borchi Kat 24, BiCAT 4130, BiCAT 4232, and MB20; The reaction terminator is one of methanol, ethanol and isopropanol.

6. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to any one of claims 1 to 5, characterized in that: The polyol further comprises polyether polyol, the molar ratio of the polyether polyol in the polyol is less than 35%; the polyether polyol is polytetrahydrofuran diol or polyoxypropylene diol; the number average molecular weight of the polyether polyol is 1000-3000 g / mol.

7. The method for preparing the low curl and high durability polyurethane adhesive layer resin according to any one of claims 1 to 5, characterized in that: The mass ratio of the isocyanate, polyol, hydroxyl-containing low molecular compound, organic solvent, antioxidant, catalyst and reaction terminator is (25-35): (80-120): (4-8): (160-240): (0.01-0.03): (0.005-0.02): (0.05-0.15).

8. A low curl and high durability polyurethane adhesive layer resin, characterized in that: The invention discloses a novel nanostructured carbon foam prepared by the preparation method described in any one of claims 1 to 7.

9. The low curl and high durability polyurethane adhesive layer resin as claimed in claim 8 is used in the production of TPU synthetic leather.

Images