Hydrolysis-resistant polyester polyol with high bio-based content, polyurethane resin for synthetic leather surface layer and preparation method of hydrolysis-resistant polyester polyol

Abstract

The invention relates to hydrolysis-resistant polyester polyol with high bio-based content, polyurethane resin for a synthetic leather surface layer and a preparation method of the hydrolysis-resistant polyester polyol. The hydrolysis-resistant polyester polyol with high bio-based content comprises the following raw materials: bio-based dihydric alcohol, bio-based dibasic acid, an antioxidant and a catalyst. In the hydrolysis-resistant polyester polyol with high bio-based content, provided by the invention, the bio-based dihydric alcohol not only comprises micromolecular bio-based 1, 3-propylene glycol, but also comprises low-carbon environment-friendly long-chain polypropylene carbonate dihydric alcohol with molecular weight of 1000, so that the crystallinity and hardness of the bio-based polyester polyol are reduced; the hydrolysis resistance and flexibility of the bio-based polyester polyol are improved, the hydrolysis resistance of polyurethane resin for a synthetic leather surface layer prepared from the hydrolysis-resistant polyester polyol with the high bio-based content is synchronously improved, and the stable dispersion performance of pigment is good.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a high-biobased content hydrolysis-resistant polyester polyol and a polyurethane resin for a synthetic leather surface layer and a preparation method thereof. Background Art

[0002] Polyurethane is made by the addition polymerization of polyols (polyethers or polyesters) and isocyanates. Its special molecular structure gives polyurethane materials excellent mechanical properties. It has been widely used in many application fields such as industry, construction, civil, automobiles, and home appliances. Previously, petroleum-based materials were generally used to prepare polyester polyols. Oil prices fluctuated greatly, and global reserves were gradually decreasing. Petroleum-based products were controlled by crude oil and market demand and have been on an upward trend. For the sustainable development of society, bio-based raw materials will gradually replace petroleum-based materials and become their best substitutes. Fermentation as an alternative process for non-renewable energy is gradually forming a scale. Not only is the production cost competitive, but it also reduces dependence on petrochemical raw materials, reduces greenhouse gas emissions, and utilizes agricultural surplus resources. Succinic acid and propylene glycol prepared by fermentation have attracted widespread attention for their advantages of cleanliness, high purity, energy saving, and pollution reduction. As one of the main raw materials for elastomers, the composition of polyester polyols plays a vital role in the performance of elastomers. In order to respond to national policy requirements and truly achieve low-carbon and environmental protection, it is urgent to develop a low-carbon polyester polyol.

[0003] The patent with publication number CN103694458A discloses a bio-based polyester polyol and its preparation method and application. The bio-based content is 35-100%. Bio-based succinic acid is combined with petroleum-based adipic acid or sebacic acid. Part or all of the biomass replaces the petroleum-based raw materials through condensation reaction to synthesize the polyester polyol. The melting point of the polyester polyol is above 40°C. The melting point of the polyester polyol with 100% bio-based content is as high as 60°C. It has strong crystallinity and high hardness. It cannot be used alone for polyurethane for synthetic leather surface layer.

[0004] The patent with publication number CN113549199A discloses a bio-based solvent-resistant polyester polyol, a polyurethane resin and a preparation process thereof, wherein the polyester polyol is synthesized using bio-based succinic acid, bio-based 1,3-propylene glycol and bio-based 1,4-butanediol, and the bio-based content reaches 100%, thereby achieving energy conservation and environmental protection. The polyurethane resin produced using the bio-based polyester polyol of the present invention has obvious advantages in solvent resistance and high temperature resistance.

[0005] Despite ongoing efforts, there remains a need for readily available products, particularly polyurethanes for synthetic leather topsheets derived from renewable resources, which exhibit properties comparable to their petroleum-based analogs used in established industrial processes. In the course of recent studies it was discovered that the hydrolysis resistance of compositions comprising such bio-based compounds leaves much to be desired, particularly at elevated temperatures and in the presence of water. Summary of the invention

[0006] Based on this, the purpose of the present invention is to provide a high-biobased content, hydrolysis-resistant polyester polyol and a polyurethane resin for a synthetic leather surface layer and a preparation method thereof. The polyurethane resin prepared using the high-biobased content, hydrolysis-resistant polyester polyol of the present invention has excellent hydrolysis resistance and pigment stable dispersion properties.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The invention provides a high-biobased content hydrolysis-resistant polyester polyol, which comprises the following component raw materials: bio-based diol, bio-based dibasic acid, antioxidant, and catalyst; the bio-based diol includes 1,3-propylene glycol and polypropylene carbonate diol.

[0009] As a further improvement of the above scheme of the present invention, in the bio-based diol, the molar ratio of 1,3-propylene glycol to polypropylene carbonate diol is 2-5:1.

[0010] As a further improvement of the above scheme of the present invention, the bio-based dibasic acid includes succinic acid and sebacic acid.

[0011] As a further improvement of the above scheme of the present invention, in the bio-based dibasic acid, the mass ratio of succinic acid to sebacic acid is 65:35.

[0012] As a further improvement of the above scheme of the present invention, the weight proportions of the components in the high bio-based content hydrolysis-resistant polyester polyol are: 68-80% bio-based diol, 20-32% bio-based dibasic acid, 0-0.05% antioxidant, and 0-0.02% catalyst.

[0013] The present invention provides a method for preparing the aforementioned high bio-based content hydrolysis-resistant polyester polyol, which comprises the following steps:

[0014] S11. Add the bio-based diol, bio-based dibasic acid and antioxidant into the reactor, stir and mix well, and then introduce nitrogen;

[0015] S12. The top temperature of the distillation tower is controlled not to exceed 100°C, and the temperature is gradually increased to 210°C. After the acid value is detected to be reduced to 10 mgKOH / g, a catalyst is added, the reaction is continued, and a vacuum is started;

[0016] S13. When the acid value is less than 0.8 mgKOH / g, the reactor temperature is set to 220-230°C and secondary vacuuming is started;

[0017] S14. After 4-8 hours of transesterification reaction, the water and small molecular alcohol in the system are extracted, and when the acid value is ≤0.5 mgKOH / g, the hydroxyl value reaches 50-60 mgKOH / g, the water content is ≤0.03%, and the viscosity reaches 900-1100 mPa·s / 75°C, a high bio-based content hydrolysis-resistant polyester polyol is obtained.

[0018] As a further improvement of the above scheme of the present invention, in step S12, the gradient heating includes four stages: the first stage is heating to 135°C for reaction for 2 hours, the second stage is heating to 155°C for reaction for 2 hours, the third stage is heating to 175°C for reaction for 2 hours, and the fourth stage is heating to 210°C for reaction for 2 hours.

[0019] The present invention provides a method for preparing the polyurethane resin for the surface layer of synthetic leather as described above, which comprises the following steps:

[0020] S21. 20 to 30% of the total amount of solvent, dehydrated bio-based chain extender and high bio-based content hydrolysis-resistant polyester polyol are mixed uniformly to obtain a mixture; 80 to 90% of the total amount of diisocyanate is added to the mixture, and the reaction is continued at 60 to 70 ° C for 20 to 30 minutes, and then the catalyst is added, and the reaction is continued for 20 to 30 minutes;

[0021] S22. Add diisocyanate in batches to carry out viscosity-increasing reaction, and each reaction lasts 30 to 40 minutes; add solvent in batches, control the reaction temperature at 60 to 70°C, and react at normal pressure for 7 to 10 hours. When the solid content reaches 25±1% and the viscosity reaches 30 to 70 Pa·s / 25°C, stop adding diisocyanate and add terminator to terminate the reaction.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the high-biobased content, hydrolysis-resistant polyester polyol provided by the present invention, the bio-based diol includes not only small-molecule bio-based 1,3-propylene glycol, but also a low-carbon, environmentally friendly, long-chain polypropylene carbonate diol with a molecular weight of 1000, which reduces the crystallinity and hardness of the bio-based polyester polyol, improves the hydrolysis resistance and flexibility of the bio-based polyester polyol, and simultaneously improves the hydrolysis resistance of the polyurethane resin for the surface layer of synthetic leather prepared by using the high-biobased content, hydrolysis-resistant polyester polyol of the present invention.

[0024] 2. In the high bio-based content hydrolysis-resistant polyester polyol provided by the present invention, the bio-based dibasic acid includes bio-based succinic acid and sebacic acid to adjust the crystallinity and rigidity and flexibility of the polyester polyol, avoiding the defects of excessive crystallinity, high melting point and high hardness when using succinic acid alone.

[0025] 3. The raw materials used in the present invention are almost all derived from biomass, and the synthesized polyester polyol has a high bio-based content. The bio-based content of the polyurethane resin used to prepare the surface layer of synthetic leather is more than 60%.

[0026] 4. The high bio-based content and hydrolysis-resistant polyester polyol of the present invention is used to prepare the polyurethane resin for the surface layer of synthetic leather. Since the ether bond and the ester bond are in the same molecular chain, compared with the polyurethane system synthesized from a single polyester polyether, the slurry is beneficial to the stability and dispersion of the pigment, thereby improving the color stability of the surface layer of the synthetic leather. DETAILED DESCRIPTION

[0027] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0028] 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.

[0029] The raw material information used in the following examples and comparative examples is as follows:

[0030] Bio-based 1,3-PDO: The manufacturer is Chifeng Zhihe Biotechnology Co., Ltd.;

[0031] Polypropylene carbonate diol: model PPCD, manufacturer is Huizhou Daya Bay Dazhi;

[0032] Bio-based succinic acid: The manufacturer is Shandong Landian Biotechnology Co., Ltd.;

[0033] Bio-based sebacic acid: The manufacturer is Hengshui Jinghua Chemical Co., Ltd.

[0034] Bio-based 1,4-butanediol: Yuanli Chemical Group Co., Ltd.

[0035] It should be noted that the above reagents are only for illustrating the sources and components of the reagents used in the experiments of the present invention so as to fully disclose the information, and do not mean that the present invention cannot be achieved by using other similar reagents or reagents provided by other suppliers.

[0036] Example 1

[0037] This embodiment provides a high bio-based content hydrolysis-resistant polyester polyol, the preparation method of which comprises the following steps:

[0038] 1000g of bio-based succinic acid, 538.46g of bio-based sebacic acid, 810g of bio-based 1,3-propylene glycol, 4830g of polypropylene carbonate diol PPCD and 200ppm of antioxidant UHS-8080LF were respectively put into the reactor, and nitrogen was introduced to stir evenly; a distillation tower was connected to the reactor, and the dehydration was controlled by controlling the top temperature of the distillation tower. The top temperature of the distillation tower was controlled not to exceed 100°C, and the temperature was raised to 135°C for reaction for 2h, then raised to 155°C for reaction for 2h, and then raised to 175°C for reaction 2h, and finally raise the temperature to 210℃ for reaction for 2h; take samples to detect the acid value, after the acid value is <10mgKOH / g, add 100ppm catalyst tetrabutyl orthotitanate, react for half an hour, and start vacuuming once; detect the acid value once every hour, when the acid value is less than 0.8mgKOH / g, start vacuuming twice; test the acid value and viscosity of the sample every half hour, when the sample acid value <0.5mgKOH / g, viscosity 900-1100mPa·s / 75℃, hydroxyl value reaches 50-60mgKOH / g, then cool and discharge.

[0039] The polyester polyol obtained in this example has the following indicators: acid value 0.23 mgKOH / g, hydroxyl value 52.42 mgKOH / g, water content 0.027%, viscosity 910 mPa·s / 75°C, and is fluid at room temperature 20°C.

[0040] Example 2

[0041] This embodiment provides a high bio-based content hydrolysis-resistant polyester polyol, the preparation method of which comprises the following steps:

[0042] 1000g of bio-based succinic acid, 538.46g of bio-based sebacic acid, 826g of bio-based 1,3-propylene glycol, 3293g of polypropylene carbonate diol PPCD and 170ppm of antioxidant UHS-8080LF were respectively put into the reactor, and nitrogen was introduced to stir evenly; a distillation tower was connected to the reactor, and the dehydration was controlled by controlling the top temperature of the distillation tower. The top temperature of the distillation tower was controlled not to exceed 100°C, and the temperature was raised to 135°C for reaction for 2h, then raised to 155°C for reaction for 2h, and then raised to 175°C The mixture was reacted for 2 hours, and finally the temperature was raised to 210°C for reaction for 2 hours. Samples were taken to detect the acid value. When the acid value was <10 mgKOH / g, 86 ppm of catalyst tetrabutyl orthotitanate was added. The mixture was reacted for half an hour and vacuumed once. The acid value was detected every hour. When the acid value was less than 0.8 mgKOH / g, a second vacuum was started. The acid value and viscosity of the sample were tested every half an hour. When the acid value of the sample was <0.5 mgKOH / g, the viscosity was 900-1000 mPa·s / 75°C, and the hydroxyl value reached 50-60 mgKOH / g, the temperature was lowered and the material was discharged.

[0043] The polyester polyol obtained in this example has the following indicators: acid value 0.31 mgKOH / g, hydroxyl value 54.19 mgKOH / g, water content 0.019%, viscosity 930 mPa·s / 75°C, and is fluid at room temperature 20°C.

[0044] Example 3

[0045] This embodiment provides a high bio-based content hydrolysis-resistant polyester polyol, the preparation method of which comprises the following steps:

[0046] 1000g of bio-based succinic acid, 538.46g of bio-based sebacic acid, 857g of bio-based 1,3-propylene glycol, 2565g of polypropylene carbonate diol PPCD and 150ppm of antioxidant UHS-8080LF were respectively put into the reactor, and nitrogen was introduced to stir evenly; a distillation tower was connected to the reactor, and the dehydration was controlled by controlling the top temperature of the distillation tower. The top temperature of the distillation tower was controlled not to exceed 100°C, and the temperature was raised to 135°C for reaction for 2 hours, then raised to 155°C for reaction for 2 hours, and then raised to 175°C for reaction for 2 hours. hours, and finally raise the temperature to 210℃ to react for 2 hours, take samples to detect the acid value, after the acid value is <10mgKOH / g, add 76ppm catalyst tetrabutyl orthotitanate, react for half an hour, and vacuumize once; detect the acid value once every hour, when the acid value is less than 0.8mgKOH / g, start secondary vacuuming; test the acid value and viscosity of the sample every half hour, when the sample acid value <0.5mgKOH / g, viscosity 900-1000mPa·s / 75℃, hydroxyl value reaches 50-60mgKOH / g, cool and discharge.

[0047] The polyester polyol obtained in this example has the following indicators: acid value 0.27 mgKOH / g, hydroxyl value 56.13 mgKOH / g, water content 0.021%, viscosity 950 mPa·s / 75°C, and is fluid at room temperature 20°C.

[0048] Example 4

[0049] In this embodiment, the high bio-based content hydrolysis-resistant polyester polyol prepared in the above embodiment 1 is used to prepare the polyurethane resin for the surface layer of synthetic leather, and the preparation steps are as follows:

[0050] (1) 119 g of DMF, 16 g of bio-based 1,4-butanediol and 100 g of high bio-based content hydrolysis-resistant polyester polyol were mixed uniformly to obtain a mixture; 50 g of diphenylmethane diisocyanate was added to the mixture, reacted at 60 to 70° C. for 20 to 30 min, then a catalyst was added, and the reaction was continued for 20 to 30 min;

[0051] (2) Add the remaining 7 g of diisocyanate several times to carry out a viscosity-increasing reaction, with each step reacting for 30 to 40 min. While the viscosity-increasing reaction is being carried out, add the remaining 400 g of solvent several times, strictly control the reaction temperature at 60 to 70°C, and react at normal pressure for 7 to 10 h. When the solid content reaches 25% and the viscosity reaches 61 Pa·s / 25°C, stop adding diisocyanate and add a terminator to terminate the reaction.

[0052] Comparative Example 1

[0053] This comparative example provides a polyester polyol with a high bio-based content, and the preparation method thereof comprises the following steps:

[0054] 1000g of bio-based succinic acid, 538.46g of bio-based sebacic acid, 1020g of bio-based 1,3-propylene glycol and 80ppm of antioxidant UHS-8080LF were respectively put into the reactor, and nitrogen was introduced to stir evenly; a distillation tower was connected to the reactor, and the dehydration was controlled by controlling the top temperature of the distillation tower. The top temperature of the distillation tower was controlled not to exceed 100°C, and the temperature was raised to 135°C for reaction for 2 hours, then raised to 155°C for reaction for 2 hours, then raised to 175°C for reaction for 2 hours, and finally raised to 2 The mixture was reacted at 10°C for 2 hours, and samples were taken to detect the acid value. When the acid value was less than 10 mgKOH / g, 40 ppm of tetrabutyl orthotitanate catalyst was added, and the mixture was reacted for half an hour and vacuumed once. The acid value was detected once every hour. When the acid value was less than 0.8 mgKOH / g, vacuuming was started for the second time. The acid value and viscosity of the sample were tested once every half an hour. When the acid value of the sample was less than 0.5 mgKOH / g, the viscosity was 900-1000 mPa·s / 75°C, and the hydroxyl value reached 50-60 mgKOH / g, the temperature was lowered and the material was discharged.

[0055] The polyester polyol obtained in this comparative example has the following indicators: acid value 0.26 mgKOH / g, hydroxyl value 52.13 mgKOH / g, water content 0.023%, viscosity 980 mPa·s / 75°C, and is fluid at room temperature 25°C.

[0056] Comparative Example 2

[0057] The polyester polyol of the comparative example 1 is used to process the polyurethane resin for the surface layer of synthetic leather, and the processing steps are as follows:

[0058] (1) 119 g of DMF, 16 g of bio-based 1,4-butanediol and 100 g of high bio-based polyester polyol were mixed to obtain a mixture; 50 g of diphenylmethane diisocyanate was added to the mixture, reacted at 60-70° C. for 20-30 min, then a catalyst was added, and the reaction was continued for 20-30 min;

[0059] (2) Add the remaining 7 g of diisocyanate several times to carry out a viscosity-increasing reaction, with each step reacting for 30 to 40 min. While the viscosity-increasing reaction is being carried out, add the remaining 400 g of solvent several times, strictly control the reaction temperature at 60 to 70°C, and react at normal pressure for 7 to 10 h. When the solid content reaches 25% and the viscosity reaches 62 Pa·s / 25°C, stop adding diisocyanate and add a terminator to terminate the reaction.

[0060] Comparative Example 3

[0061] The polyester polyol of the comparative example 1 is combined with polypropylene carbonate diol to be used in processing polyurethane resin for the surface layer of synthetic leather, and the processing steps are as follows:

[0062] (1) 115 g of DMF, 15 g of bio-based 1,4-butanediol, 80 g of high bio-based polyester polyol and 20 g of polypropylene carbonate diol were mixed to obtain a mixture; 50 g of diphenylmethane diisocyanate was added to the mixture, reacted at 60-70° C. for 20-30 min, then a catalyst was added, and the reaction was continued for 20-30 min;

[0063] (2) Add the remaining 6.7 g of diisocyanate in multiple times to carry out a viscosity-increasing reaction, with each step reacting for 30 to 40 min. While the viscosity-increasing reaction is being carried out, add the remaining 400 g of solvent in multiple times, strictly control the reaction temperature at 60 to 70°C, and react at normal pressure for 7 to 10 h. When the solid content reaches 25% and the viscosity reaches 62 Pa·s / 25°C, stop adding diisocyanate and add a terminator to terminate the reaction.

[0064] Test Case

[0065] (1) The polyester polyols prepared in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests: the acid value was measured according to the method of HG / T2708-1995 "Determination of acid value in polyester polyols"; the hydroxyl value was measured according to the method of HG / T2709-1995 "Determination of hydroxyl value in polyester polyols"; the viscosity was measured at 75°C using a NDJ-79 rotary viscometer; the moisture content was measured according to the method specified in GB / T12008.6. The test results are shown in Table 1.

[0066] Table 1 Comparison of physical properties of polyester polyols prepared in Examples 1-3 and Comparative Example 1

[0067]

[0068] From the results in Table 1, it can be seen that the amount of polypropylene carbonate diol introduced in Example 1, Example 2, and Example 3 gradually decreases, and there is no copolymerized polypropylene carbonate diol in Comparative Example 1. The melting points of the four gradually increase. It can be seen that after the copolymerization of polypropylene carbonate diol into polyester polyol, the crystallinity and melting point of polyester polyol are reduced, and the flexibility of polyester polyol is improved.

[0069] (2) The following performance tests were performed on the polyurethane resin for the surface layer of the synthetic leather prepared in Example 4 and Comparative Examples 2 and 3: the tensile performance test was performed according to the method of GB / T1040.1-2018 or GB / T1040.3-2006; the hydrolysis resistance test was performed according to the C method in QB / T 4671-2014 (high temperature alkali solution accelerated method, 70°C, 10% NaOH solution). The test results are shown in Table 2.

[0070] Table 2

[0071]

[0072] From the results in Table 2, it can be seen that after copolymerizing polypropylene carbonate diol in the bio-based polyester molecular chain, the hydrolysis resistance of the polyurethane film synthesized using it is significantly improved, which makes up for the defect of insufficient hydrolysis resistance when using only bio-based polyester to synthesize polyurethane.

[0073] (3) The color stability of the synthetic leather surface layer prepared in Example 4 and Comparative Examples 2 and 3 was tested with polyurethane resin. The test results are shown in Table 3.

[0074] Table 3

[0075] Example 4 Comparative Example 2 Comparative Example 3 Leave to stand for 24 hours No pigment floating No pigment floating No pigment floating Leave to stand for 48 hours No pigment floating No pigment floating A small amount of floating Leave to stand for 72 hours No pigment floating No pigment floating Slurry is coarse

[0076] From the results in Table 3, it can be seen that Comparative Example 3 uses polypropylene carbonate diol in the synthesis of polyurethane, while Example 4 copolymerizes polypropylene carbonate diol into polyester polyol. Example 4 is more conducive to the stable dispersion of the pigment, which is beneficial for the color stability control of the hydrolysis-resistant polyurethane for the surface layer of synthetic leather during use.

[0077] In summary, the raw materials used in the self-made high-biobased content and hydrolysis-resistant polyester polyol of the present application are almost all derived from biomass, which reduces oil consumption and reduces the impact on the environment. The synthesized polyester polyol has a high biobased content, and the biobased mass fraction of the polyurethane film synthesized using it is more than 60%, which meets the requirements of low-carbon and environmental protection; polypropylene carbonate polyol is copolymerized into the polyester polyol chain, which reduces the crystallinity and hardness of the polyester polyol and improves the flexibility and hydrolysis resistance. The hydrolysis resistance of the polyurethane resin for the surface layer of synthetic leather prepared using it is simultaneously improved. Compared with the slurry in which polypropylene carbonate polyol is added during the preparation of polyurethane, the polyurethane slurry of the present invention has improved stability and dispersion of pigments, which is of practical significance for the color diversification of the surface layer of synthetic leather.

[0078] 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.

[0079] 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 high bio-based content hydrolysis-resistant polyester polyol, characterized in that: The invention comprises the following raw materials: bio-based diol, bio-based dibasic acid, antioxidant and catalyst; the bio-based diol comprises 1,3-propylene glycol and polypropylene carbonate diol.

2. The high bio-based content hydrolysis-resistant polyester polyol according to claim 1, characterized in that: In the bio-based diol, the molar ratio of 1,3-propylene glycol to polypropylene carbonate diol is 2-5:

1.

3. The high bio-based content hydrolysis-resistant polyester polyol according to claim 1, characterized in that: The bio-based dibasic acids include succinic acid and sebacic acid.

4. The high bio-based content hydrolysis-resistant polyester polyol according to claim 3, characterized in that: In the bio-based dibasic acid, the mass ratio of succinic acid to sebacic acid is 65:

35.

5. The high bio-based content hydrolysis-resistant polyester polyol according to claim 1, characterized in that: The weight proportions of the components in the high bio-based content hydrolysis-resistant polyester polyol are as follows: 68-80% of bio-based diol, 20-32% of bio-based dibasic acid, 0-0.05% of antioxidant, and 0-0.02% of catalyst.

6. A method for preparing a high bio-based content hydrolysis-resistant polyester polyol as claimed in any one of claims 1 to 5, characterized in that: It includes the following steps: S11. Add the bio-based diol, bio-based dibasic acid and antioxidant into the reactor, stir and mix well, and then introduce nitrogen; S12. The top temperature of the distillation tower is controlled not to exceed 100°C, and the temperature is gradually increased to 210°C. After the acid value is detected to be reduced to 10 mgKOH / g, a catalyst is added, the reaction is continued, and a vacuum is started; S13. When the acid value is less than 0.8 mgKOH / g, the reactor temperature is set to 220-230°C and secondary vacuuming is started; S14. After 4-8 hours of transesterification reaction, the water and small molecular alcohol in the system are extracted, and when the acid value is ≤0.5 mgKOH / g, the hydroxyl value reaches 50-60 mgKOH / g, the water content is ≤0.03%, and the viscosity reaches 900-1100 mPa·s / 75°C, a high bio-based content hydrolysis-resistant polyester polyol is obtained.

7. The method for preparing a high bio-based content hydrolysis-resistant polyester polyol according to claim 6, characterized in that: In step S12, the gradient heating includes four stages: the first stage is heating to 135°C for reaction for 2 hours, the second stage is heating to 155°C for reaction for 2 hours, the third stage is heating to 175°C for reaction for 2 hours, and the fourth stage is heating to 210°C for reaction for 2 hours.

8. A method for preparing the polyurethane resin for synthetic leather surface layer as claimed in claim 8, characterized in that: It includes the following steps: S21. 20 to 30% of the total amount of solvent, dehydrated bio-based chain extender and high bio-based content hydrolysis-resistant polyester polyol are mixed uniformly to obtain a mixture; 80 to 90% of the total amount of diisocyanate is added to the mixture, and the reaction is continued at 60 to 70 ° C for 20 to 30 minutes, and then the catalyst is added, and the reaction is continued for 20 to 30 minutes; S22. Add diisocyanate in batches to carry out viscosity-increasing reaction, and each reaction lasts 30 to 40 minutes; add solvent in batches, control the reaction temperature at 60 to 70°C, and react at normal pressure for 7 to 10 hours. When the solid content reaches 25±1% and the viscosity reaches 30 to 70 Pa·s / 25°C, stop adding diisocyanate and add terminator to terminate the reaction.

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