A method for producing a polyurethane material having a highly compact crosslinked structure

Abstract

The application discloses a preparation method of polyurethane material with high compact crosslinking structure. Biomass seed fiber is extracted by Soxhlet extraction method, electrophilic addition is carried out by introducing an epoxy reagent, O-H in the seed fiber is reserved and hydrophobic regulation is carried out; the seed fiber is mixed with biomass derived polyol by doping method, and high compact crosslinking structure polyurethane material is obtained by polymerization with isocyanate. In the application, the environmentally friendly vegetable oil replaces the petroleum derived polyol, not only the biomass derived polyol mixture containing seed fiber is introduced to generate polyurethane with isocyanate, but also the hydrogen bond is formed between O-H in the seed fiber and the formed polyurethane, the interaction between the matrix and the fiber is ensured, the crosslinking density of the polymer is increased, the overall density is greater than 0.3 g / cm 3 , and the hydrophobicity and thermal insulation of the polymer are improved, the thermal conductivity is less than 0.03 W / (m.K), and the contact angle is greater than 150 degrees.

Description

Technical Field

[0001] This invention relates to a method for preparing a polyurethane material, and more particularly to a method for preparing a polyurethane material with a highly dense cross-linked structure. Background Technology

[0002] Polyurethane is one of the best-performing thermal insulation materials currently available. It is polymerized from isocyanates and hydroxyl compounds, and is a type of polymer whose main chain contains repeating —NHCOO— structural units. Due to the presence of highly polar urethane groups, polyurethane is insoluble in non-polar groups and possesses excellent oil resistance, toughness, abrasion resistance, aging resistance, and adhesion, making it widely applicable.

[0003] Polyols, as one of the two main raw materials for synthesizing polyurethane foam materials, are currently mostly derived from petrochemical resources. However, the dwindling and non-renewable nature of these resources, coupled with the non-degradable nature of the materials produced, makes waste disposal difficult, severely hindering the sustainable development of the polyurethane industry. Therefore, developing bio-based polyols from renewable and degradable biomass raw materials to prepare bio-based polyurethane materials has become a future development direction for the polyurethane industry.

[0004] In the field of polyurethane materials, research on the utilization of biomass mainly focuses on starch, vegetable oil, lignin, wood and agricultural waste, etc. There are two main methods: (1) Biomass is processed into liquefied polyols with multiple hydroxyl groups on the molecular chain segments through a series of reactions, which are used as polyol raw materials for the subsequent production of polyurethane foam materials. Patent CN 113135793A discloses a method for preparing biomass polyurethane, in which biomass is thermally liquefied with organic reagents and concentrated sulfuric acid to obtain modified biomass. Patent 201910687171.9 discloses a method for preparing bio-based polyester polyurethane, in which polyol initiator, alkali metal and γ-butyrolactone are reacted in organic reagents, and acidic substances such as sulfuric acid are added to terminate the reaction to obtain poly(γ-butyrolactone) polyol. Although the preparation method is simple, has fewer steps and the product performance is good, its disadvantage is that it uses strong acid to treat the biomass, which causes environmental pollution. At the same time, the surface treatment of biomass by acidification will inevitably destroy the structure of biomass and reduce the degree of crosslinking of biomass in composite materials. (2) Biomass powder is used as a modified filler for polyurethane foam materials. Patent CN111607062A discloses a biomass polyurethane foam material and its preparation method. With the assistance of polyethylene glycol and acetic acid, the surface of wood fibers is hydroxylated by micro-shearing in a mixer. Although the preparation process does not use strong acid or alkali reagents and is environmentally friendly, its disadvantages are that the preparation requires specific equipment, the process is relatively complex, there are many required raw materials, and the waterproof performance of the product is lacking and the overall performance is unknown.

[0005] Therefore, developing and designing a green, environmentally friendly, and thermally insulating polyurethane insulation material with high hydrophobicity has good social benefits and application prospects. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a method for preparing a green and environmentally friendly fiber-modified polyurethane material with excellent thermal insulation performance, high hydrophobicity, and a highly dense cross-linked structure.

[0007] Technical solution: The preparation method of the polyurethane material with a highly dense cross-linked structure according to the present invention includes the following steps:

[0008] (1) Add biomass seeds to an organic solvent and extract seed fibers using Soxhlet extraction; add an electrophilic epoxy reagent containing hydrophobic groups to conduct an electrophilic addition reaction; after completion, dry to obtain hydrophobic seed fibers;

[0009] (2) The hydrophobic seed fiber was mixed with biomass-derived polyol and stirred to obtain a mixture of biomass-derived polyols; then the mixture was added to isocyanate and a catalyst was added dropwise to carry out the reaction by solution polymerization; after completion, the mixture was washed with alcohol and dried to obtain a polyurethane material with a high density cross-linked structure.

[0010] In step (1), the biomass seed is at least one of mango seed, horned melon seed or raspberry seed, and the organic solvent is at least one of acetone, dichloromethane or petroleum ether.

[0011] In step (1), the conditions for Soxhlet extraction are: heating temperature of 40-80℃ and heating time of 2-4h.

[0012] In step (1), the electrophilic epoxy reagent containing a hydrophobic group is at least one of 1,2-epoxybutane, tetrahydrofuran, or 1,4-dioxane.

[0013] In step (1), the conditions for the electrophilic addition reaction are: heating temperature of 80-100℃, reaction time of 1-4h, drying temperature of 60-80℃, and drying time of 8-12h.

[0014] In step (2), the biomass-derived polyol is at least one of castor oil polyol, soybean oil polyol, and cashew nut shell oil polyol.

[0015] In step (2), the mass ratio of hydrophobic seed fiber to biomass-derived polyol is 1:5 to 1:20; the stirring speed is 500 to 1000 r / min and the stirring time is 15 to 30 min.

[0016] In step (2), the mass ratio of the biomass-derived polyol mixture to isocyanate is 1:1 to 1:2.

[0017] In step (2), the solution polymerization conditions are: the reaction temperature is 70-90℃, the stirring speed is 800-1500r / min, and the time is 2-5h.

[0018] In step (2), the alcohol washing solvent is a mixed solution of methanol and water with a molar ratio of 1:1 to 1:2, the washing is performed 3 to 5 times, the drying temperature is 40 to 60°C, and the drying time is 18 to 28 hours.

[0019] In step (2), the catalyst is a stannous 2-ethylhexanoate solution, and the concentration of the stannous 2-ethylhexanoate solution is 0.5 to 1 mol / L.

[0020] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0021] (1) This invention uses environmentally friendly vegetable oil instead of petroleum-derived polyols, not only introducing a mixture of biomass-derived polyols containing seed fibers and isocyanates to generate polyurethane; but also forming hydrogen bonds between the OH groups in the seed fibers and the resulting polyurethane, ensuring the interaction between the matrix and the fiber, increasing the crosslinking density of the polymer, improving its mechanical properties, and making its overall density greater than 0.3 g / cm³. 3 This also improves the hydrophobicity and thermal insulation of the polymer, making its thermal conductivity less than 0.03 W / (m·K) and its contact angle greater than 150°.

[0022] (2) Add epoxy reagent to modify the seed fiber by electrophilic addition reaction, introduce hydrophobic groups, increase the crosslinking degree of the seed fiber, improve the hydrophobicity of the polymer, and further improve the heat insulation of the polymer.

[0023] (3) The polymer monomer biomass-derived polyols are extracted from vegetable oils. Compared with polyols extracted from petroleum, the use of heating or ventilation systems that consume a lot of energy is reduced, making the polymer generation process more environmentally friendly and more sustainable. Detailed Implementation

[0024] The present invention will now be described in further detail.

[0025] Example 1

[0026] Weigh 10g of mango seeds, crush them in a mortar and pestle, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 100mL of dichloromethane to a distillation flask, and reflux at 40℃ for 2h to obtain seed fiber. Take 100mg of seed fiber and excess 1,2-epoxybutane and add them to a three-necked flask, react at 80℃ for 1h, and dry at 60℃ for 8h to obtain hydrophobically modified seed fiber.

[0027] 20 mg of hydrophobically modified seed fiber was added to 100 mg of castor oil polyol and stirred for 15 min at 500 rpm to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 100 mg of isocyanate, and 0.5 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 70 °C for 2 h with stirring at 800 rpm. The mixture was washed three times in a 1:1 methanol / water mixture and dried at 40 °C for 18 h to obtain a polyurethane material with a highly dense cross-linked structure.

[0028] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0029] The results showed that the polyurethane material had a compressive strength of 0.41 MPa and an overall density of 0.313 g / cm³. 3 It has a thermal conductivity of 0.021 W / (m·K) and a contact angle of 150°.

[0030] Comparative Example 1

[0031] Weigh 10g of mango seeds, crush them in a mortar and pestle, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 100mL of dichloromethane to a distillation flask, and reflux at 40℃ for 2h to obtain seed fiber. Take 100mg of seed fiber and excess 1,2-epoxybutane and add them to a three-necked flask, react at 80℃ for 1h, and dry at 60℃ for 8h to obtain hydrophobically modified seed fiber.

[0032] 20 mg of hydrophobically modified seed fiber was added to 100 mg of castor oil polyol and stirred for 15 min at 500 rpm to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 100 mg of isocyanate, and 0.5 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 60 °C for 1 h with stirring at 500 rpm. The mixture was washed three times in a 1:1 methanol / water mixture and dried at 40 °C for 18 h to obtain the polyurethane material.

[0033] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0034] The results showed that, by comparing Example 1 and Comparative Example 1, when the temperature, time, and stirring rate of the polymerization of the castor oil polyol mixture and isocyanate solution were changed, the esterification of the OH groups in the castor oil polyol mixture with the NH groups of the isocyanate was incomplete, leading to a decrease in the degree of crosslinking of the polyurethane material. This was reflected in the polyurethane material having a compressive strength of 0.23 MPa and an overall density of 0.176 g / cm³. 3 It has a thermal conductivity of 0.034 W / (m·K) and a contact angle of 121°.

[0035] Example 2

[0036] Weigh 10g of horned melon seeds, crush them in a mortar, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 100mL of acetone to a distillation flask, and reflux at 65℃ for 2.5h to obtain seed fiber. Add 100mg of seed fiber and excess tetrahydrofuran to a three-necked flask, react at 85℃ for 1.5h, and dry at 65℃ for 9h to obtain hydrophobically modified seed fiber.

[0037] 20 mg of hydrophobically modified seed fiber was added to 120 mg of soybean oil polyol and stirred for 20 min at 600 r / min to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 120 mg of isocyanate, and 0.7 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 75 °C for 3 h with stirring at 900 r / min. The mixture was washed four times in a 1:1.2 methanol / water mixture and dried at 45 °C for 20 h to obtain a polyurethane material with a highly dense cross-linked structure.

[0038] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0039] The results showed that the polyurethane material had a compressive strength of 0.47 MPa and an overall density of 0.319 g / cm³. 3 It has a thermal conductivity of 0.026 W / (m·K) and a contact angle of 151°.

[0040] Comparative Example 2

[0041] Weigh 10g of horned melon seeds, crush them in a mortar, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 100mL of acetone to a distillation flask, and reflux at 65℃ for 2.5h to obtain seed fiber. Add 100mg of seed fiber and excess peroxyformic acid to a three-necked flask, react at 85℃ for 1.5h, and dry at 65℃ for 9h to obtain modified seed fiber.

[0042] 20 mg of modified seed fiber was added to 120 mg of soybean oil polyol and stirred for 20 min at 600 r / min to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 120 mg of isocyanate, and 0.7 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 75 °C for 3 h with stirring at 900 r / min. The mixture was washed four times in a 1:1.2 methanol / water mixture and dried at 45 °C for 20 h to obtain the polyurethane material.

[0043] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0044] The results showed that, by comparing Example 2 and Comparative Example 2, when the modifying agent of the seed fiber was changed, no hydrophobic groups were introduced onto the surface of the seed fiber, resulting in a decrease in the hydrophobic properties of the polyurethane material, manifested as a compressive strength of 0.24 MPa and an overall density of 0.084 g / cm³. 3 It has a thermal conductivity of 0.041 W / (m·K) and a contact angle of 129°.

[0045] Example 3

[0046] Weigh 10g of raspberry seeds, crush them in a mortar and pestle, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 50mL of petroleum ether and 50mL of dichloromethane to a distillation flask, and reflux at 70℃ for 3h to obtain seed fiber. Take 100mg of seed fiber and excess 1,4-dioxane and add it to a three-necked flask, react at 80℃ for 2h, and dry at 75℃ for 10h to obtain hydrophobically modified seed fiber.

[0047] 20 mg of hydrophobically modified seed fiber was added to 150 mg of cashew nut shell oil polyol and stirred for 25 min at 750 r / min to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 150 mg of isocyanate, and 0.8 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 80 °C for 3.5 h with stirring at 1000 r / min. The mixture was washed four times in a 1:1.5 methanol / water mixture and dried at 50 °C for 22 h to obtain a polyurethane material with a highly dense cross-linked structure.

[0048] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0049] The results showed that the polyurethane material had a compressive strength of 0.55 MPa and an overall density of 0.337 g / cm³. 3 It has a thermal conductivity of 0.024 W / (m·K) and a contact angle of 155°.

[0050] Comparative Example 3

[0051] Weigh 10g of raspberry seeds, crush them in a mortar and pestle, place them in a filter paper tube, put the tube into an extraction tube, install a Soxhlet extraction apparatus, add 50mL of petroleum ether and 50mL of dichloromethane to a distillation flask, and reflux at 70℃ for 3h to obtain seed fiber. Take 100mg of seed fiber and excess 1,4-dioxane and add it to a three-necked flask, react at 120℃ for 5h, and dry at 75℃ for 10h to obtain hydrophobically modified seed fiber.

[0052] 20 mg of hydrophobically modified seed fiber was added to 150 mg of cashew nut shell oil polyol and stirred for 25 min at 750 r / min to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 150 mg of isocyanate, and 0.8 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 80 °C for 3.5 h with stirring at 1000 r / min. The mixture was washed four times in a 1:1.5 methanol / water mixture and dried at 50 °C for 22 h to obtain the polyurethane material.

[0053] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0054] The results showed that, by comparing Example 3 and Comparative Example 3, when the time and temperature of the electrophilic addition reaction between the seed fiber and the epoxy reagent were changed, the OH groups on the surface of the seed fiber were destroyed and the introduction of hydrophobic groups was incomplete, resulting in a decrease in the crosslinking density and hydrophobic properties of the polyurethane material, manifested as a compressive strength of 0.25 MPa and an overall density of 0.075 g / cm³. 3 It has a thermal conductivity of 0.045 W / (m·K) and a contact angle of 125°.

[0055] Example 4

[0056] Take 5g of mango seeds and 5g of raspberry seeds, crush them in a mortar and pestle, put them into a filter paper tube, place them in an extraction tube, install a Soxhlet extraction apparatus, add 100mL of dichloromethane to a distillation flask, and reflux at 80℃ for 4h to obtain seed fiber. Take 100mg of seed fiber and excess 1,4-dioxane and add it to a three-necked flask, react at 100℃ for 4h, and dry at 80℃ for 11h to obtain hydrophobically modified seed fiber.

[0057] 20 mg of hydrophobically modified seed fiber was added to 300 mg of castor oil polyol and stirred for 25 min at 800 rpm to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 180 mg of isocyanate, and 0.9 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 85 °C for 4 h with stirring at 1200 rpm. The mixture was washed five times in a 1:1.8 methanol / water mixture and dried at 55 °C for 24 h to obtain a polyurethane material with a highly dense cross-linked structure.

[0058] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0059] The results showed that the polyurethane material had a compressive strength of 0.50 MPa and an overall density of 0.325 g / cm³. 3 It has a thermal conductivity of 0.029 W / (m·K) and a contact angle of 153°.

[0060] Comparative Example 4

[0061] Take 5g of mango seeds and 5g of raspberry seeds, crush them in a mortar and pestle, put them into a filter paper tube, place them in an extraction tube, install a Soxhlet extraction apparatus, add 100mL of dichloromethane to a distillation flask, and reflux at 80℃ for 4h to obtain seed fiber. Take 100mg of seed fiber and excess 1,4-dioxane and add it to a three-necked flask, react at 100℃ for 4h, and dry at 80℃ for 11h to obtain hydrophobically modified seed fiber.

[0062] 20 mg of hydrophobically modified seed fiber was added to 300 mg of castor oil polyol and stirred for 25 min at 800 rpm to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 180 mg of isocyanate, and 0.9 mol / L N,N-dimethylpyridine solution were added to a three-necked flask and reacted at 85 °C for 4 h with stirring at 1200 rpm. The mixture was washed five times in a 1:1.8 methanol / water mixture and dried at 55 °C for 24 h to obtain the polyurethane material.

[0063] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0064] The results showed that, by comparing Example 4 and Comparative Example 4, changing the catalyst used in the polymerization of the castor oil polyol mixture and isocyanate solution led to incomplete esterification of the castor oil polyol mixture with the isocyanate, resulting in a decrease in the crosslinking density of the polyurethane material and a decline in its hydrophobic and thermal insulation properties. This manifested as a compressive strength of 0.22 MPa and an overall density of 0.082 g / cm³. 3 The thermal conductivity is 0.045 W / (m·K), and the contact angle is 128°.

[0065] Example 5

[0066] Take 5g of raspberry seeds and 5g of horned melon seeds, crush them in a mortar and pestle, put them into a filter paper tube, place them in an extraction tube, install a Soxhlet extraction apparatus, add 100mL of petroleum ether to a distillation flask, and reflux at 70℃ for 4h to obtain seed fiber. Take 100mg of seed fiber and excess tetrahydrofuran, add them to a three-necked flask, react at 100℃ for 3h, and dry at 80℃ for 12h to obtain hydrophobically modified seed fiber.

[0067] 20 mg of hydrophobically modified seed fiber was added to 200 mg of soybean oil polyol and 200 mg of cashew nut shell oil polyol, and stirred for 30 min at 1000 r / min to obtain a castor oil polyol mixture. 100 mg of the castor oil polyol mixture, 200 mg of isocyanate, and 1 mol / L stannous 2-ethylhexanoate solution were added to a three-necked flask and reacted at 90 °C for 5 h with stirring at 1500 r / min. The mixture was washed five times in a 1:2 methanol / water mixture and dried at 60 °C for 28 h to obtain a polyurethane material with a highly dense cross-linked structure.

[0068] Evaluation criteria: The polyurethane materials were subjected to relevant structural characterization tests. The thermal performance was evaluated by testing the thermal conductivity of the composite material using a thermal conductivity meter, and the hydrophobic performance was evaluated by testing the contact angle of the composite material using a contact angle meter.

[0069] The results showed that the polyurethane material had a compressive strength of 0.44 MPa and an overall density of 0.310 g / cm³. 3 It has a thermal conductivity of 0.024 W / (m·K) and a contact angle of 152°.

Claims

1. A method for preparing a polyurethane material with a highly dense cross-linked structure, characterized in that, Includes the following steps: (1) Add biomass seeds to an organic solvent and extract seed fibers using Soxhlet extraction; add an electrophilic epoxy reagent containing hydrophobic groups to conduct an electrophilic addition reaction; after completion, dry to obtain hydrophobic seed fibers; the biomass seeds are at least one of mango seeds, horned melon seeds or raspberry seeds; the conditions for the electrophilic addition reaction are: heating temperature of 80~100 ℃ and reaction time of 1~4 h; (2) The hydrophobic seed fiber is mixed with biomass-derived polyol and stirred to obtain a mixture of biomass-derived polyols; then the mixture is added to isocyanate, and a catalyst is added dropwise to carry out the reaction by solution polymerization; after completion, the mixture is washed with alcohol and dried to obtain a polyurethane material with a high density cross-linked structure; the conditions of the solution polymerization method are: reaction temperature of 70~90 ℃, time of 2~5 h; stirring speed of 800~1500 r / min; the catalyst is 2-ethylhexanoate stannous solution.

2. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (1), the organic solvent is at least one of acetone, dichloromethane, and petroleum ether.

3. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (1), the conditions for Soxhlet extraction are: heating temperature of 40~80 ℃ and heating time of 2~4 h.

4. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (1), the electrophilic epoxy reagent containing a hydrophobic group is at least one of 1,2-epoxybutane, tetrahydrofuran, or 1,4-dioxane.

5. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (1), the drying temperature is 60~80 ℃ and the drying time is 8~12 h.

6. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (2), the biomass-derived polyol is at least one of castor oil polyol, soybean oil polyol and cashew nut shell oil polyol.

7. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (2), the mass ratio of the hydrophobic seed fiber to the biomass-derived polyol is 1:5 to 1:20; the mass ratio of the biomass-derived polyol mixture to the isocyanate is 1:1 to 1:

2.

8. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (2), the stirring speed is 500~1000 r / min and the time is 15~30 min.

9. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (2), the stirring time is 2-5 h; the alcohol washing solvent is a mixture of methanol and water with a molar ratio of 1:1 to 1:2; the drying temperature is 40-60 ℃ and the drying time is 18-28 h.

10. The method for preparing a polyurethane material with a highly dense cross-linked structure according to claim 1, characterized in that, In step (2), the concentration of the 2-ethylhexanoate stannous solution is 0.5~1 mol / L.