Full-bio-based microporous polyurethane foam and preparation method thereof

Abstract

The invention belongs to the field of polyurethane materials, and particularly relates to full-bio-based microporous polyurethane foam and a preparation method thereof. According to the invention, rosin acid and castor oil are used as raw materials, and rosin-castor oil polyol is prepared through an esterification synthetic route. The microporous polyurethane foam with excellent mechanical properties is prepared by utilizing the synergistic effect of the bio-based polyol and the rosin-castor oil polyol in a certain proportion. In addition, the microporous polyurethane foam prepared from the vegetable fat and the abietic acid is simple and low in cost, and meets the requirements of green sustainable development.

Description

Technical Field

[0001] The invention belongs to the field of polyurethane materials, and specifically relates to a fully bio-based microporous polyurethane foam and a preparation method thereof. Background Art

[0002] Microporous polyurethane foam is a special type of polyurethane foam material. Its characteristic is that the pore size is very small. It is neither smooth and dense like elastomers, nor like foam materials, the pores are clearly visible and densely arranged. The pore size of microporous polyurethane foam ranges from 0.1 microns to hundreds of microns. These pores play a full toughening role in the material. By increasing the number of pores and adjusting the pore size, microporous polyurethane foam can effectively dissipate external impacts and reduce energy transfer, thereby achieving impact reduction and vibration absorption. This makes it an ideal material in many fields, such as automobile manufacturing, sports equipment, and protective shells for electronic equipment. However, the current production of microporous polyurethane materials is heavily dependent on petrochemical resources as raw materials, resulting in a significant increase in carbon emissions and ecological hazards. Therefore, researchers have begun to focus on strategies for preparing microporous polyurethane materials using green and sustainable biomass resources.

[0003] Rosin is a brittle, transparent natural resin with two reactive sites, double bonds and carboxyl groups, and has strong reactivity. However, most polyols synthesized by modifying rosin have high viscosity, and the microporous polyurethane foam synthesized using this polyol is brittle and does not achieve ideal mechanical properties.

[0004] Castor oil is a special non-grain renewable resource that can be directly used as polyol in materials, but the added value of the products is low. Therefore, it is an important research direction for the comprehensive utilization of castor oil to modify the ester bonds, hydroxyl groups and double bonds on castor oil molecules to prepare castor oil-based polyols, expand their application range, and increase the added value of products. However, the microporous polyurethane foam synthesized using castor oil or castor oil-modified polyols has certain resilience, but poor hardness and impact resistance. Summary of the invention

[0005] In view of the above problems existing in the prior art, the object of the present invention is to provide a fully bio-based microporous polyurethane foam and a preparation method thereof.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows: a fully bio-based microporous polyurethane foam, the raw materials are composed by weight: 100 parts of total polyol, 3-8 parts of foam leveling agent, 0.1-0.6 parts of catalyst, 0.1-0.5 parts of foaming agent, 1-1.6 parts of small molecule polyol chain extender, 80-130 parts of isocyanate, wherein the polyol is a mixture of rosin-castor oil polyol and bio-based polyether or polyester polyol, and the amount of rosin-castor oil polyol is 3-6 times that of bio-based polyether or polyester polyol; the rosin-castor oil polyol is obtained by reacting rosin acid chloride, castor oil and triethylamine in a solvent.

[0007] The bio-based polyether or polyester polyol includes any one of castor oil polyol, polylactic acid polyol, cardanol polyol, polyoxyethylene castor oil polyol and soybean oil polyol.

[0008] The rosin acid chloride is prepared by esterification reaction of rosin acid, oxalyl chloride and triethylamine at a certain temperature. The obtained product is separated and purified to obtain rosin acid chloride. The molar ratio of rosin acid: oxalyl chloride: triethylamine is 1:1-1.1:1-1.1.

[0009] The isocyanate is 1,5-pentanediisocyanate, MDI, HDI or IPDI; the small molecule polyol chain extender is any one of 1,4-butanediol, ethylene glycol, glycerol and propylene glycol; and the catalyst is an organic tin catalyst or an amine catalyst.

[0010] The molar ratio of the rosin acid chloride to the castor oil is 1:1-1.2.

[0011] The method for preparing the rosin-castor oil-based microporous polyurethane foam comprises the following steps:

[0012] (1) esterification reaction is carried out between rosin acid, oxalyl chloride and triethylamine at a certain temperature, and the obtained product is separated and purified to obtain rosin acid chloride;

[0013] (2) using tetrahydrofuran to dissolve rosin acid chloride and castor oil respectively, mixing castor oil, rosin acid chloride and triethylamine at a certain temperature and stirring, and separating and purifying after a period of time to obtain rosin-castor oil polyol;

[0014] (3) After removing moisture from the rosin-castor oil polyol, the polyol is mixed with bio-based polyether or polyester polyol, isocyanate, a foaming agent, a chain extender, a foam leveling agent and a catalyst, poured into a mold, and cured to obtain a microporous polyurethane foam.

[0015] The esterification reaction conditions in step (1) are to keep the temperature at 5-20°C for 1-2 hours, then raise the temperature to 20-40°C and react for 4-6 hours.

[0016] The esterification reaction conditions in step (2) are 40-60° C. for 4-8 hours.

[0017] The ratio of rosin acid chloride: triethylamine: hydroxyl substance of castor oil in step (2) is 1:1-1.2:1-1.2.

[0018] Beneficial effects:

[0019] Through the esterification reaction of rosin acid, rosin and castor oil were combined to prepare a fully bio-based polyol with both rigid and flexible segments. The microporous polyurethane foam synthesized using this polyol has ideal mechanical properties. At the same time, the foam he synthesized has a smaller pore size, giving it excellent cushioning properties. The rigid groups of rosin can significantly improve the material's cushioning properties, tensile strength, and permanent compression rate, while the long-chain structure of castor oil allows the material to still have good dynamic properties at low temperatures. In addition, the use of bio-based polyols to replace petrochemical polyols is in line with the trend of green and sustainable development, reducing carbon emissions and ecological crises. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an infrared spectrum of the all-biobased polyol of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific embodiments.

[0022] A fully bio-based microporous polyurethane foam and a preparation method thereof, comprising the following steps:

[0023] (1) Abietic acid, oxalyl chloride and triethylamine are fully mixed and stirred in a tetrahydrofuran solution, reacted at a certain temperature for a period of time, and the obtained product is separated and purified to obtain abietic acid chloride;

[0024] (2) dissolving rosin acid chloride, triethylamine and castor oil in tetrahydrofuran respectively, stirring them evenly, reacting them at a certain temperature for a period of time, and separating and purifying the obtained products to obtain rosin-castor oil polyol;

[0025] (3) removing moisture from the rosin-castor oil polyol, mixing it with additives such as polyether or polyester polyol, isocyanate, foaming agent, chain extender, foam leveling agent and catalyst, pouring it into a mold, and curing it to obtain a fully bio-based microporous polyurethane foam;

[0026] The polyether or polyester polyol is composed of bio-based castor oil, polylactic acid polyol and polyoxyethylene castor oil.

[0027] Optionally, in step (3), the total amount of polyol is 100 parts by weight, the catalyst is 0.1-0.6 parts, the foaming agent DC-193 is 3-8 parts, the foaming agent water is 0.01-0.05 parts, the chain extender 1,4-butanediol is 1-1.6 parts, and the isocyanate is 80-130 parts, wherein the amount of rosin-castor oil polyol in the polyol is 3-6 times that of the polyether or polyester polyol.

[0028] Optionally, the esterification reaction conditions of step (1) are to keep the temperature at 5-20°C for 1-2 hours, and then raise the temperature to 20-40°C for reaction for 3-6 hours.

[0029] Optionally, the molar ratio of rosin acid: oxalyl chloride: triethylamine in step (1) is 1:(1-1.1):(1-1.1).

[0030] Optionally, the esterification reaction conditions in step (2) are 40-60° C. for 4-8 hours.

[0031] Optionally, in step (2), the molar ratio of rosin acid chloride to hydroxyl groups of castor oil is 1:(1-1.2).

[0032] Optionally, the polyether or polyester polyol in step (3) is castor oil polyol, polylactic acid polyol, cardanol polyol, polyoxyethylene castor oil polyol and soybean oil polyol; the isocyanate is TDI, MDI, HDI or IPDI; the small molecule polyol chain extender can also be 1,4-butanediol, ethylene glycol, glycerol, propylene glycol, etc.; the catalyst can also be dibutyltin dilaurate, diethylenetriamine, N,N-dimethylcyclohexylamine, etc.

[0033] According to the above method, a fully bio-based microcellular polyurethane foam is obtained.

[0034] In the following examples, bio-based MDI-100 is selected as the isocyanate and 1,4-butanediol is selected as the chain extender diol.

[0035] Example 1

[0036] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 25°C and react for 6 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.05:1.05).

[0037] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 60°C and reacted for 4 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.05:1.05).

[0038] By mass, 80 parts of rosin-castor oil polyol and 20 parts of polyoxyethylene castor oil are stirred and evenly mixed, and then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol. Finally, 110 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0039] Example 2

[0040] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0041] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0042] By mass, 80 parts of rosin-castor oil polyol and 20 parts of cardanol polyol are stirred and evenly mixed, then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol, and finally 105 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0043] Example 3

[0044] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0045] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0046] By mass, 80 parts of rosin-castor oil polyol and 20 parts of castor oil are stirred and evenly mixed, then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol, and finally 105 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0047] Example 4

[0048] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0049] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0050] By mass, 80 parts of rosin-castor oil polyol and 20 parts of polylactic acid polyol are stirred and evenly mixed, then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol, and finally 105 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0051] Comparative Example 1 (addition of cross-linking agent triglycerol)

[0052] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 25°C and react for 6 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.05:1.05).

[0053] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 60°C and reacted for 4 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.05:1.05).

[0054] By mass, 80 parts of rosin-castor oil polyol and 20 parts of polyoxyethylene castor oil are stirred and evenly mixed, and then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, 1 part of glycerol triol and 1.26 parts of 1,4-butanediol, and finally 110 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0055] Comparative Example 2 (Polyether polyol selected non-biobased 330N)

[0056] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0057] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0058] By mass, 80 parts of rosin-castor oil polyol and 20 parts of 330N were stirred and evenly mixed, and then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol. Finally, 105 parts of bio-based MDI-100 ester were added and stirred for 8 seconds at a speed of 2000r / min. The mixture was poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0059] Comparative Example 3 (Polyester polyol selects cardanol polyol)

[0060] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0061] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0062] By mass, 80 parts of rosin-castor oil polyol and 20 parts of cardanol polyol are stirred and evenly mixed, then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1.26 parts of 1,4-butanediol, and finally 105 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0063] Comparative Example 4 (Changing the proportion of chain extender 1,4-butanediol)

[0064] After dissolving rosin acid and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly in an ice-water bath. Then dilute oxalyl chloride with tetrahydrofuran and slowly add it dropwise into the four-necked flask. Maintain the reaction in an ice-water bath for 1 hour. Then heat to 40°C and react for 4 hours. After the reaction is completed, filter out the triethylamine salt, then remove the tetrahydrofuran by rotary evaporation at 60°C to obtain the product rosin acid chloride (rosin acid: triethylamine: oxalyl chloride = 1:1.02:1.02).

[0065] After dissolving rosin acid chloride and triethylamine in tetrahydrofuran, add them into a four-necked flask and stir evenly at room temperature. Then, castor oil dissolved in tetrahydrofuran is slowly added dropwise into the four-necked flask using a constant pressure funnel. The temperature is raised to 50°C and reacted for 6 hours. After the reaction is completed, the triethylamine salt is filtered out, and then the tetrahydrofuran is removed by rotary evaporation at 60°C to obtain the product rosin-castor oil polyol (rosin acid chloride: triethylamine: hydroxyl group of castor oil = 1:1.01:1.01).

[0066] By mass, 80 parts of rosin-castor oil polyol and 20 parts of polylactic acid polyol are stirred and evenly mixed, then mixed with 1 part of DC-193 foaming agent, 0.4 parts of N,N-dimethylcyclohexylamine, 0.03 parts of water, and 1 part of 1,4-butanediol, and finally 105 parts of bio-based MDI-100 are added and stirred for 8 seconds at a speed of 2000r / min. The mixture is poured into a mold and cured at 60°C for one day and then cured in air for three days to obtain a fully bio-based castor oil microporous polyurethane material.

[0067] The mechanical properties of the bio-based microporous polyurethane foams obtained in Examples 1-4 and Comparative Examples 1-4 were tested. The test results are shown in Table 1.

[0068] Table 1 Test results of bio-based microcellular polyurethane foam performance

[0069] Shore hardness / A Tensile strength / MPa Permanent compression rate / % Example 1 65 2.6 2.1 Example 2 70 0.9 5.8 Example 3 68 1.5 1.6 Example 4 80 0.6 10.4 Comparative Example 1 75 1.4 1.6 Comparative Example 2 60 0.7 2.0 Comparative Example 3 75 1.0 6.7 Comparative Example 4 78 0.5 8.7

[0070] It can be seen from the results in Table 1 that the microporous polyurethane foam prepared by the present invention has excellent mechanical properties, the Shore hardness reaches above 60A, the maximum tensile strength reaches 2.6MPa, and the permanent compression rate is mostly below 10%. It has excellent buffering capacity and can be used to replace the microporous polyurethane foam prepared by petrochemical polyols.

Claims

1. A fully bio-based microcellular polyurethane foam, characterized in that: The raw materials are composed of 100 parts by weight of polyol, 3-8 parts of foam leveling agent, 0.1-0.6 parts of catalyst, 0.1-0.5 parts of foaming agent, 1-1.6 parts of small molecule polyol chain extender and 80-130 parts of isocyanate. The polyol is a mixture of rosin-castor oil polyol and bio-based polyether or polyester polyol, and the amount of rosin-castor oil polyol is 3-6 times that of bio-based polyether or polyester polyol. The rosin-castor oil polyol is obtained by reacting rosin acid chloride, castor oil and triethylamine in a solvent.

2. The all-biobased microcellular polyurethane foam according to claim 1, characterized in that: The bio-based polyether or polyester polyol includes any one of castor oil polyol, polylactic acid polyol, cardanol polyol, polyoxyethylene castor oil polyol and soybean oil polyol.

3. The all-biobased microcellular polyurethane foam according to claim 1, characterized in that: The rosin acid chloride is prepared by esterification reaction of rosin acid, oxalyl chloride and triethylamine at a certain temperature. The obtained product is separated and purified to obtain rosin acid chloride. The molar ratio of rosin acid: oxalyl chloride: triethylamine is 1:1-1.1:1-1.

1.

4. The all-biobased microcellular polyurethane foam according to claim 1, characterized in that: The isocyanate is 1,5-pentanediisocyanate, MDI, HDI or IPDI; the small molecule polyol chain extender is any one of 1,4-butanediol, ethylene glycol, glycerol and propylene glycol; and the catalyst is an organic tin catalyst or an amine catalyst.

5. A rosin-castor oil-based microporous polyurethane foam according to claim 1, characterized in that: The molar ratio of the rosin acid chloride to the castor oil is 1:1-1.

2.

6. A method for preparing a rosin-castor oil-based microporous polyurethane foam according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) esterification reaction is carried out between rosin acid, oxalyl chloride and triethylamine at a certain temperature, and the obtained product is separated and purified to obtain rosin acid chloride; (2) using tetrahydrofuran to dissolve rosin acid chloride and castor oil respectively, mixing castor oil, rosin acid chloride and triethylamine at a certain temperature and stirring, and separating and purifying after a period of time to obtain rosin-castor oil polyol; (3) After removing moisture from the rosin-castor oil polyol, the polyol is mixed with bio-based polyether or polyester polyol, isocyanate, a foaming agent, a chain extender, a foam leveling agent and a catalyst, poured into a mold, and cured to obtain a microporous polyurethane foam.

7. The method for preparing a fully bio-based microcellular polyurethane foam according to claim 6, characterized in that: The esterification reaction conditions in step (1) are to keep the temperature at 5-20°C for 1-2 hours, then raise the temperature to 20-40°C and react for 4-6 hours.

8. The method for preparing a fully bio-based microcellular polyurethane foam according to claim 6, characterized in that: The esterification reaction conditions in step (2) are 40-60° C. for 4-8 hours.

9. The method for preparing a fully bio-based microcellular polyurethane foam according to claim 6, characterized in that: The ratio of rosin acid chloride: triethylamine: hydroxyl substance of castor oil in step (2) is 1:1-1.2:1-1.2.

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