Wet-process polyurethane resin for microporous crease-free mirror leather and preparation method of wet-process polyurethane resin

Abstract

The invention discloses wet-process polyurethane resin for microporous crease-free mirror leather and a preparation method of the wet-process polyurethane resin. The wet-process polyurethane resin for microcellular micro-crease mirror leather is mainly prepared from the following components: diisocyanate, a polyhydric alcohol compound, a micromolecular dihydric alcohol chain extender, a catalyst, an antioxidant, a solvent and a reaction terminator methanol, wherein the polyol compound is polyether glycol and polyester glycol, the polyether glycol is selected from one or two of polytetrahydrofuran glycol or polypropylene oxide glycol, and the polyester glycol is synthesized from adipic acid and small-molecule glycol. In the polyurethane synthesis process, a one-step synthesis process is adopted, so that the condensation speed of the resin is reduced, and bubbles are small and even free. Therefore, the prepared microporous crease-free mirror surface leather resin has the characteristics of micropores and small creases after being formed into leather.

Description

Technical Field

[0001] The invention relates to the field of wet-process polyurethane resins, in particular to a wet-process polyurethane resin for microporous crease-free mirror leather and a preparation method thereof. Background Art

[0002] Polyurethane synthetic leather has good physical and mechanical properties, excellent bonding strength with the substrate, high peel strength, wear resistance, flex resistance, and excellent anti-aging performance. It also has the advantages of good cold resistance, washability, easy processing, and low price. Polyurethane synthetic leather for shoes has the characteristics of good feel, elasticity, and high mechanical properties.

[0003] An important development direction of synthetic leather is imitation leather. Genuine leather is composed of dense connective tissue, with no obvious boundary from top to bottom, elastic and tough, and no obvious wrinkles under external force. However, the base of general polyurethane synthetic leather contains a large number of finger-shaped hole structures, which make the synthetic leather have a full and soft feel, light weight, but poor drape, strong plastic feel, and obvious wrinkles can be seen under external bending, and the product grade is not high.

[0004] To make the wrinkles of synthetic leather closer to genuine leather, the pore structure of synthetic leather must be changed to make the synthetic leather base non-porous. Currently, there are few types of non-porous wet-process polyurethane resins on the market and the amount used is small.

[0005] There are many types of base fabrics for synthetic leather, and the varieties and colors of synthetic leather are countless. Only by developing distinctive products can we seize the market opportunity in time. Elastic leather has good resilience and is comfortable to wear after being made into shoes, and is becoming more and more popular in the market and favored by consumers. Elastic leather refers to polyurethane synthetic leather with elastic base fabric as the base. If a non-porous wrinkle-free mirror leather polyurethane synthetic leather is developed with an elastic cloth base, the mirror surface has good elasticity, strong drape, small wrinkles, good leather surface flatness, and fine velvet on the back, which will definitely attract consumers. This puts forward new requirements for polyurethane resins, and the development of wet-process polyurethane resins for microporous wrinkle-free mirror leather is more strategically significant. Summary of the invention

[0006] The invention provides a wet-process polyurethane resin for microporous crease-free mirror leather and a preparation method thereof, so as to solve the problems of few types of non-porous wet-process polyurethane resins and poor hydrolysis resistance in the prior art industry.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A wet-process polyurethane resin for microporous crease-free mirror leather is prepared from diisocyanate, polyol compound, small molecule diol chain extender, catalyst, antioxidant, solvent, and reaction terminator methanol, and the weight percentage of each component in the total system weight is as follows: Diisocyanate 6-12%, Polyol compounds 15-20%, Small molecule diol chain extender 2-3%, Catalyst 0.01-0.05%, Antioxidant 0.01-0.05%, Solvent 65-75%, The reaction terminator is methanol 0.01-0.05%.

[0008] Furthermore, the molar ratio of isocyanate to active hydrogen in the diisocyanate is (1-1.05):1, and the molar amount of active hydrogen is the sum of the molar amounts of active hydrogen in the polyol compound and the small molecule diol chain extender.

[0009] Furthermore, the diisocyanate is 4,4-diphenylmethane diisocyanate.

[0010] Furthermore, the polyol compound includes polyether diol and polyester diol, and the mass ratio of the polyether diol to the polyester diol is (2-2.4):1.

[0011] Furthermore, the polyether diol in the polyol compound is a mixture of one or two of polytetramethylene glycol and polyoxypropylene glycol, and the polyester diol in the polyol compound is a mixture of one or two of adipic acid and small molecule diol.

[0012] Furthermore, the number average molecular weight of the polyol compound is 1000-3000.

[0013] Furthermore, the small molecule diol chain extender is selected from at least one of ethylene glycol, 1,4-butanediol, and 1,2-propylene glycol.

[0014] Furthermore, the catalyst is an organic bismuth catalyst MB20; the antioxidant is one or a mixture of tetrakis(β-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate) pentaerythritol ester and 2,2'-methylenebis(4-methyl-6-tert-butylphenol); and the solvent is one or a mixture of two of N,N-dimethylformamide and N,N-dimethylacetamide.

[0015] A method for preparing the above-mentioned wet-process polyurethane resin for microporous crease-free mirror leather comprises the following steps: (1) Add polyester polyol, polyether polyol, small molecule diol and antioxidant into the solvent to form a solution with a solid content of 35-40%, and heat it to 75-80°C; (2) After the solution obtained in step (1) is stirred evenly, a portion of diisocyanate and a catalyst are added to make the molar ratio of isocyanate in diisocyanate to hydroxyl in polyester polyol, polyether polyol and small molecule diol be (1.05-1.10):1, and the reaction is carried out at 75-80°C for 2-3 hours in the presence of a catalyst; the viscosity of the polyurethane resin is controlled by continuously adding a solvent, and after the reaction is completed, a reaction terminator, methanol, is added to control the viscosity at 150,000-250,000 cps / 25°C, thereby obtaining a polyurethane resin.

[0016] The total system weight in the present invention is the total weight of the components, namely, diisocyanate, polyol compound, small molecule diol chain extender, catalyst, antioxidant, solvent, and reaction terminator methanol.

[0017] Advantages of the present invention: ① The soft segment uses polyester diol and polyether diol, optimizes the ratio, and adjusts the formula to make the resin non-porous, the finished leather has good processing performance, and has good mechanical properties, hydrolysis resistance and elasticity.

[0018] ② Two chain extenders are selected, one as the main one and the other as the auxiliary one, which can effectively adjust the interaction between the hard segments and ensure good resin fluidity and transparent appearance. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0020] Example 1 Example 1 discloses a wet-process polyurethane resin for microporous crease-free mirror leather, which is prepared from the following components in weight percentage: total system weight is 2835g, diisocyanate is 250g, polyol compound is 500g, small molecule diol chain extender is 75g, catalyst is 5g, antioxidant is 5g, solvent is 2000g, and reaction terminator methanol is 5g. Among them, the diisocyanate specifically uses 4,4-diphenylmethane diisocyanate (MDI) produced by Wanhua Chemical, the polyol compound specifically uses polytetramethylene glycol (PTMG-2000) with a molecular weight of 2000 produced by Sinopec and adipic acid polyester polyol (SP-2000) with a molecular weight of 2000 produced by itself, the small molecule diol chain extender specifically uses 1,4-butanediol (BG) / ethylene glycol (EG), the catalyst specifically uses organic bismuth MB-20, the antioxidant specifically uses I-1010, the solvent specifically uses N,N-dimethylformamide (DMF), and the reaction terminator specifically uses methanol. The details are shown in Table 1: Table 1 Raw material composition

[0021] Example 1 discloses a method for preparing a wet-process polyurethane resin for microporous crease-free mirror leather, comprising the following steps: (1) Synthesis by one-step method: 350 g PTMG-2000, 150 g SP-2000, 70 g BG, 5 g EG and 5 g antioxidant I-1010 were added to 900 g DMF solvent to form a solution with a solid content of 35-40%; (2) After the solution obtained in step (1) is stirred evenly, 240 g of MDI and 5 g of catalyst are added, and the mixture is reacted at 70-80° C. for 1-2 h in the presence of the catalyst; (3) After stirring evenly, add the remaining diisocyanate and react at 75-80°C for 2-5 hours; the viscosity of the polyurethane resin is controlled by continuously adding the remaining solvent DMF. After the reaction is completed, methanol, a reaction terminator, is added to control the viscosity at 150,000-250,000 cps / 25°C to obtain the polyurethane resin.

[0022] Example 2 Example 2 discloses a wet-process polyurethane resin for microporous crease-free mirror leather, which is prepared from the following components in percentage by weight: the total system weight is 2835g, of which the diisocyanate is 250g, the polyol compound is 500g, the small molecule diol chain extender is 75g, the catalyst is 5g, the antioxidant is 5g, the solvent is 2000g, and the reaction terminator methanol is 5g.

[0023] Among them, the diisocyanate specifically uses 4,4-diphenylmethane diisocyanate (MDI) produced by Wanhua Chemical, the polyol compound specifically uses polytetramethylene glycol (PTMG-2000) with a molecular weight of 2000 produced by Sinopec and adipic acid polyester polyol (SP-2000) with a molecular weight of 2000 produced by itself, the small molecule diol chain extender specifically uses 1,4-butanediol (BG) / ethylene glycol (EG), the catalyst specifically uses organic bismuth MB-20, the antioxidant specifically uses I-1010, the solvent specifically uses N,N-dimethylformamide (DMF), and the reaction terminator specifically uses methanol. The details are shown in Table 2: Table 2 Raw material composition

[0024] Example 2 discloses a method for preparing a wet-process polyurethane resin for microporous crease-free mirror leather, comprising the following steps: (1) Synthesis by prepolymerization method: Add 100g solvent DMF, 150g PTMG-2000, 50g SP-2000 and 5g antioxidant I-1010 into a container to form a solution with a solid content of 50%, add the theoretical amount of MDI and catalyst, stir and react at 70-80℃, and gradually add MDI until the high temperature viscosity reaches 60,000-80,000 cps.

[0025] (2) Then add 200g of DMF solvent to dilute and stir evenly, then add 200g of PTMG-2000, 100g of SP-2000, 70g of BG and 5g of EG, add the theoretical amount of MDI, react for 1-2 hours, and then gradually add MDI and solvent DMF to the target viscosity.

[0026] (3) The viscosity of the polyurethane resin is controlled by continuously adding the solvent DMF. After the reaction is completed, methanol, a reaction terminator, is added to control the viscosity at 150,000-250,000 cps / 25°C to obtain the polyurethane resin.

[0027] Example 3 Example 3 discloses a wet-process polyurethane resin for microporous crease-free mirror leather, which is prepared from the following components: the total system weight is 2835g, of which the diisocyanate is 250g, the polyol compound is 500g, the small molecule diol chain extender is 75g, the catalyst is 5g, the antioxidant is 5g, the solvent is 2000g, and the reaction terminator methanol is 5g.

[0028] The diisocyanate specifically uses 4,4-diphenylmethane diisocyanate (MDI) produced by Wanhua Chemical, the polyol compound specifically uses polytetramethylene glycol (PTMG-2000) with a molecular weight of 2000 and polyester polyol with a molecular weight of 2000 produced by Sinopec, the small molecule diol chain extender specifically uses 1,4-butanediol (BG) / ethylene glycol (EG), the catalyst specifically uses organic bismuth MB-20, the antioxidant specifically uses I-1010, the solvent specifically uses N,N-dimethylformamide (DMF), and the reaction terminator specifically uses methanol.

[0029]

[0030] Example 3 discloses a method for preparing a wet-process polyurethane resin for microporous crease-free mirror leather, comprising the following steps: (1) Synthesis by excess prepolymerization method: 100g solvent DMF, 150g PTMG-2000, 50g SP-2000, and 5g antioxidant I-1010 are added into a container to form a solution with a solid content of 50%, and MDI with an R value of 1.2 and 5g catalyst are added, and the mixture is stirred and reacted at 70-80°C for 1 hour.

[0031] (2) Then add 200g of solvent to dilute and stir evenly, then add 200g of PTMG-2000, 100g of PET-200, 70g of BG and 5g of EG, add the theoretical amount of MDI, react for 1-2 hours, and then gradually add MDI and solvent DMF to the target viscosity.

[0032] (3) The viscosity of the polyurethane resin is controlled by continuously adding the solvent DMF. After the reaction is completed, methanol, a reaction terminator, is added to control the viscosity at 150,000-250,000 cps / 25°C to obtain the polyurethane resin.

[0033] The cyanide-hydroxyl ratio (R value) in Implementation Case 2 is 1:1, and the difference from Example 2 is that the cyanide-hydroxyl ratio in Implementation Case 3 is 1:2.

[0034] The microporous crease-free wet-process polyurethane resins prepared in Examples 1, 2 and 3 and ordinary wet-process polyurethane resins were prepared into wet slurries with a resin to filler ratio of 1:1, and coagulated into leather in a 25%-27% (mass fraction) DMF aqueous solution. The pore types of the leather after the leatherification and the wrinkle effects after mirror surface application were compared, as shown in Table 3: Table 3 is the comparison result table

[0035] From Table 3, it can be seen that under the same leather making conditions, the wet-process polyurethane resin prepared in the implementation case has a leather-like cellular layer with no or few pores, which is manifested in that the fold marks on the leather surface disappear quickly without leaving any creases after the blank leather is pasted on the mirror surface. However, because the cellular layer of the ordinary polyurethane wet-process resin is standard finger-shaped cellular, the fold marks on the leather surface are obvious and difficult to disappear after the blank leather is pasted on the mirror surface, leaving obvious crease marks.

[0036] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A wet-process polyurethane resin for microporous crease-free mirror leather, characterized in that: It is prepared from diisocyanate, polyol compound, small molecule diol chain extender, catalyst, antioxidant, solvent, and reaction terminator methanol. The weight percentage of each component in the total system weight is as follows: Diisocyanate 6-12%, Polyol compounds 15-20%, Small molecule diol chain extender 2-3%, Catalyst 0.01-0.05%, Antioxidant 0.01-0.05%, Solvent 65-75%, The reaction terminator is methanol 0.01-0.05%.

2. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 1, characterized in that: The molar ratio of isocyanate to active hydrogen in the diisocyanate is (1-1.05):1, and the molar amount of active hydrogen is the sum of the molar amounts of active hydrogen in the polyol compound and the small molecule diol chain extender.

3. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 2, characterized in that: The diisocyanate is 4,4-diphenylmethane diisocyanate.

4. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 1, characterized in that: The polyol compound comprises polyether diol and polyester diol, and the mass ratio of the polyether diol to the polyester diol is (2-2.4):

1.

5. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 4, characterized in that: The polyether diol in the polyol compound is one or a mixture of polytetrahydrofuran diol and polyoxypropylene diol, and the polyester diol in the polyol compound is one or a mixture of adipic acid and small molecule diol.

6. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 4, characterized in that: The number average molecular weight of the polyol compound is 1000-3000.

7. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 1, characterized in that: The small molecule diol chain extender is selected from at least one of ethylene glycol, 1,4-butanediol and 1,2-propylene glycol.

8. The wet-process polyurethane resin for microporous crease-free mirror leather according to claim 1, characterized in that: The catalyst is an organic bismuth catalyst MB20; the antioxidant is one or a mixture of tetrakis(β-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate) pentaerythritol ester and 2,2'-methylenebis(4-methyl-6-tert-butylphenol); and the solvent is one or a mixture of N,N-dimethylformamide and N,N-dimethylacetamide.

9. A method for preparing a wet-process polyurethane resin for microporous crease-free mirror leather as claimed in any one of claims 1 to 8, characterized in that: The following steps are included: (1) Add polyester polyol, polyether polyol, small molecule diol and antioxidant into the solvent to form a solution with a solid content of 35-40%, and heat it to 75-80°C; (2) After the solution obtained in step (1) is stirred evenly, a portion of diisocyanate and a catalyst are added to make the molar ratio of isocyanate in diisocyanate to hydroxyl in polyester polyol, polyether polyol and small molecule diol be (1.05-1.10):1, and the reaction is carried out at 75-80°C for 2-3 hours in the presence of a catalyst; the viscosity of the polyurethane resin is controlled by continuously adding a solvent, and after the reaction is completed, a reaction terminator, methanol, is added to control the viscosity at 150,000-250,000 cps / 25°C, thereby obtaining a polyurethane resin.

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