A bio-based polyurethane elastomer and methods of making and degrading the same
By preparing polyurethane materials with non-crystalline soft segments and hyperregular hard segments using bio-based raw materials, the problem of rapid degradation of polyurethane materials was solved, and efficient enzyme-catalyzed degradation was achieved, reaching a degradation rate of 70-88% and good comprehensive performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING UNIV OF CHEM TECH
- Filing Date
- 2024-08-01
- Publication Date
- 2026-04-28
AI Technical Summary
Existing polyurethane materials are difficult to degrade quickly, leading to environmental pollution, and existing enzyme degradation methods are inefficient.
Non-crystalline soft segments and highly regular hard segments were prepared using bio-based raw materials. The randomness of the polyester diol molecular chain was improved by random polycondensation of various bio-based raw materials, reducing the tendency to crystallize. Enzymatic degradation was carried out using potassium dihydrogen phosphate/dipotassium hydrogen phosphate solution and degrading enzymes.
The degradation rate of bio-based polyurethane elastomers reached 70-88% within 20 days, while maintaining good overall performance.
Smart Images
Figure CN118930800B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer materials technology, and more specifically, to a bio-based polyurethane elastomer and its preparation and degradation methods. Background Technology
[0002] Polyurethane is a block copolymer composed of flexible soft segments and rigid hard segments. The soft segments are typically hydroxyl-terminated polyesters or polyether glycols with a molecular weight of 500–5000 g / mol, while the hard segments are diisocyanates and low-molecular-weight chain extenders. Due to the significant difference in solubility parameters between the soft and hard segments, they spontaneously aggregate under thermodynamic conditions to form aggregates with high hard segment content and soft segment content. The island-like structure resulting from microphase separation provides self-reinforcing properties to the polyurethane hard segment aggregates, giving it excellent strength, resilience, abrasion resistance, and oil resistance. Therefore, polyurethane materials are widely used in footwear, conveyor belts, biomedical applications, and sealing products.
[0003] With the gradual depletion of petrochemical raw materials and people's pursuit of a low-carbon and environmentally friendly lifestyle, there are growing calls to use bio-based raw materials to prepare polymer products. Therefore, the use of bio-based raw materials to prepare rapidly degradable bio-based polyurethane elastomers is of great significance to the sustainable development of the polyurethane industry. However, most polyurethane materials currently developed are difficult to degrade, requiring hundreds of years to completely decompose in the environment. Consequently, the large amount of discarded polyurethane materials each year causes serious environmental pollution.
[0004] Polyurethane degradation typically involves various methods such as soil burial, composting, chemical recycling, and enzymatic degradation. Among these, enzymatic degradation, catalyzed by enzymes, involves the decomposition of water and ester / carbamate groups, and is a low-energy-consumption, high-rate degradation method. During enzymatic degradation, the recalcitrant nature of polyurethane is related to the widely distributed crystalline regions in its molecular structure, the degree of phase separation, and the soft-segment chain structure. On the one hand, the hydrophobic crystalline structure hinders the interaction between water and easily degradable ester groups, affecting degradation efficiency. On the other hand, when the degree of phase separation in polyurethane is low, soft segments are more easily dissolved in hard-segment aggregates. The difficult-to-degrade hard segments hinder the interaction between easily degradable soft segments and degradation factors such as water and enzymes, leading to a reduced polyurethane degradation rate. Furthermore, the shielding effect of the side group structure of soft segments hinders the interaction between ester groups and water, acting as a decelerator in the reaction where ester groups decompose into carboxyl and hydroxyl groups.
[0005] It is evident that developing a polyurethane material with excellent overall performance and rapid biodegradability is an urgent problem to be solved. Summary of the Invention
[0006] To address the above problems, this invention provides a bio-based polyurethane elastomer and its preparation method. The bio-based polyurethane elastomer provided by this invention not only has good comprehensive performance, but also excellent biodegradability.
[0007] Firstly, one of the objectives of this invention is to provide a bio-based polyurethane elastomer.
[0008] Specifically, the bio-based polyurethane elastomer comprises soft segments and hard segments, with a mass ratio of soft segments to hard segments of 74–88:12–26; preferably 75–85:15–25; wherein the soft segments are non-crystalline bio-based polyester diol structural units; and the hard segments are structural units composed of isocyanates and bio-based chain extenders.
[0009] This invention reduces the content of crystalline regions in polyurethane by preparing completely non-crystalline soft segments, and improves the degree of microphase separation of polyurethane by using highly regular isocyanates and chain extenders with regular structures. The resulting polyurethane elastomer not only has the property of being rapidly degradable, but also has good comprehensive properties.
[0010] Furthermore, in bio-based polyurethane elastomers, the bio-based polyester diol structural unit is a linear molecular chain segment structure with hydroxyl double-terminated segments and a molecular weight of 500–2000 g / mol; preferably 1000–1500 g / mol. At this point, the hard segment segments of the polyurethane have a better packing density, resulting in better reinforcement of the hard segment aggregates, and for the non-crystalline soft segments, it is more conducive to improving mechanical properties.
[0011] Furthermore, in bio-based polyurethane elastomers, the bio-based polyester diol structural units contain little or no side groups.
[0012] Furthermore, in the bio-based polyurethane elastomer, the content of branched small molecules in the bio-based polyester diol structural unit is less than or equal to 20 wt%.
[0013] Furthermore, in the bio-based polyurethane elastomer, the non-crystalline bio-based polyester diol is obtained by polycondensation of at least two bio-based raw materials, and the molar ratio of carboxyl groups to hydroxyl groups in the bio-based raw materials participating in the polycondensation reaction is 1:1.05 to 2, preferably 1:1.12 to 1.8.
[0014] This invention improves the randomness of bio-based polyester glycol molecular chains by using random polycondensation of various bio-based raw materials to reduce the crystallization tendency of soft segments; at the same time, the bio-based raw materials used do not contain or contain a small number of side groups, and the resulting polyester glycol is in a completely non-crystalline state with a linear structure as the main component.
[0015] Furthermore, the bio-based raw materials are selected from dimethyl oxalate, dimethyl malonate, succinic acid, glutaric acid, adipic acid, sebacic acid, diethylene glycol, terephthalic acid, methyl itaconic acid, tridecanoic acid, tetradecanoic acid, α-hydroxypropionic acid, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butanediol, 2,3-butanediol, pentanediol, and diethylene glycol.
[0016] Furthermore, the isocyanate is selected from at least one of terephthalic diisocyanate, isophthalic diisocyanate, hexamethylene diisocyanate, and 1,5-pentamethylene diisocyanate.
[0017] Furthermore, the bio-based chain extender is selected from at least one of 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol, 1,3-propanediol, and ethylene glycol.
[0018] Secondly, a second objective of this invention is to provide a method for preparing a bio-based polyurethane elastomer, which includes the following steps:
[0019] S1. Add bio-based raw materials to a reaction vessel, heat to 150-200℃, esterify for 2-6 hours, add catalyst, reduce pressure to -0.1--0.08MPa, stop the reaction when the hydroxyl value reaches 50-230mg KOH / g, and obtain bio-based polyester diol.
[0020] S2. Heat the bio-based polyester diol to 45-80°C, add isocyanate, and react for 2-3 hours; add chain extender, stir well, degas, pour into a mold, hot press at 100-160°C, and then cure at 80-130°C for 12-96 hours to obtain the polyurethane elastomer.
[0021] Preferably, in step S1, the catalyst needs to be dissolved in a solvent to prepare a solution before being added to the reaction system. The solvent is selected from at least one of ethylene glycol, 1,2-propanediol, toluene, and xylene. The mass concentration of the catalyst is 5–100 g / L; the amount of catalyst solution used is 0.1–3% of the total amount of the bio-based diacid and diol.
[0022] More specifically, the preparation method includes the following steps:
[0023] S1. Add the bio-based raw material to the reaction vessel, replace the air twice with nitrogen at room temperature, raise the temperature to 150-200℃, and carry out the esterification reaction for 2-6 hours. Add the catalyst solution, reduce the pressure to a vacuum of about -0.1 to -0.08 MPa, and continue until the acid value drops below 1 mg KOH / g and the hydroxyl value reaches 56-224 mg KOH / g. Then stop the reaction to obtain bio-based polyester diol.
[0024] S2. Heat the bio-based polyester diol to 45-80°C, add isocyanate, and react for 2-3 hours. Add chain extender, stir quickly, degas under reduced pressure, pour into a mold, and hot press in a 100-160°C hot press. After 5-10 minutes, remove the sample from the mold and place it in an 80-130°C oven for 12-96 hours to obtain the polyurethane elastomer.
[0025] Furthermore, a third objective of this invention is to provide a method for degrading bio-based polyurethane elastomers, one of the objectives of this invention, the degradation method comprising the following steps:
[0026] After pulverizing the bio-based polyurethane elastomer sample, it was placed in a potassium dihydrogen phosphate / dipotassium hydrogen phosphate solution to prepare a mixed solution. Degrading enzymes were then added to degrade the elastomer, resulting in a degradation solution.
[0027] Preferably, the pH of the potassium dihydrogen phosphate / dipotassium hydrogen phosphate solution is 6.9 to 7.4.
[0028] Preferably, the degradation temperature is 30–60°C.
[0029] Preferably, the mass concentration of polyurethane elastomer in the mixed solution is 50–200 g / L.
[0030] Preferably, the amount of degrading enzyme used is 0.5 to 2 times the mass of the polyurethane elastomer.
[0031] Preferably, the degrading enzyme is selected from Novozymes non-immobilized lipase A, Novozymes non-immobilized lipase B, and porcine pancreatic lipase.
[0032] Preferably, the degradation time is 2 to 40 days.
[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0034] 1. This invention improves the degradation rate of bio-based polyurethane elastomers by reducing the hard segment content and the proportion of difficult-to-degrade urethane bonds. At the same time, to compensate for the decrease in polyurethane strength caused by the reduction in hard segment content and the lack of crystallinity in soft segments, a combination of lower molecular weight soft segments and highly regular hard segments is used to improve the degree of microphase separation of the material, which better improves the physical crosslinking density of the material and plays a supplementary role in its strength. This gives the polyurethane elastomer better comprehensive performance while ensuring rapid degradation performance.
[0035] 2. This invention improves the phase separation of polyurethane materials by using highly regular diisocyanate and chain extender, reduces the compatibility between soft and hard segments, and increases the degradation rate of polyurethane.
[0036] 3. The bio-based polyester glycol and chain extender of the present invention are both prepared from bio-based raw materials, and the bio-based content in the polyurethane elastomer is above 83%.
[0037] 4. This invention designs the soft and hard segment structures of polyurethane elastomers separately, and selects non-crystalline, linear-structured bio-based polyester glycol, highly regular isocyanate, and chain extender to obtain a rapidly degradable bio-based polyurethane elastomer. Under enzyme catalysis, the degradation rate of the bio-based polyurethane elastomer can reach 70-88% within 20 days. Attached Figure Description
[0038] Figure 1 The images show the DSC test results of the bio-based polyester diols prepared in Examples 1-3 of this invention. Detailed Implementation
[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.
[0040] In the following examples and comparative examples, the raw materials were all commercially available products.
[0041] The test methods in the following embodiments are as follows:
[0042] DSC test: In a nitrogen atmosphere, the sample is cooled from room temperature to -80°C at a rate of 10°C / min, held at that temperature for 5 min, and then heated to 100°C at a rate of 10°C / min. The glass transition temperature (T0) of the sample can be obtained from this process. g Information such as melting temperature and crystallization temperature.
[0043] Mechanical property testing: The test is conducted according to the ASTM-D412 method, and the sample is cut into dumbbell-shaped strips that meet the test standard for testing.
[0044] Example 1
[0045] The following describes the preparation process of bio-based polyester glycol:
[0046] Bio-based succinic acid, sebacic acid, 1,3-propanediol, and 1,2-propanediol were mixed in a molar ratio of 7:3:1.3:11.7 (acid-to-alcohol ratio 1:1.3). A total of 350 g of bio-based raw materials was weighed and added to a 500 ml reaction vessel. After purging with nitrogen, the reaction temperature was raised to 170 °C and the reaction was carried out for 4 hours. Then, 4 g of a catalyst solution (tetrabutyl titanate-toluene, catalyst concentration 10 wt%) was added, with the catalyst mass being 0.3% of the reactant mass. After stirring and mixing, the pressure was uniformly reduced to a vacuum of -0.09 MPa over 1 hour. The reaction was then continued for 20 minutes until the hydroxyl value reached 75 mg KOH / g, at which point the reaction was stopped, yielding a bio-based polyester glycol with a molecular weight of 1500 g / mol.
[0047] The following describes the preparation process of bio-based polyurethane elastomers:
[0048] The prepared bio-based polyester glycol was heated to 80°C, and hexamethylene diisocyanate (molar ratio of bio-based polyester glycol to hexamethylene diisocyanate was 1:1.5) was added. The reaction was allowed to proceed for 2.5 hours. Then, 1,4-butanediol (molar ratio of bio-based polyester glycol to 1,4-butanediol was 1:0.5) (mass ratio of soft segment to hard segment was 83:17) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure and poured into a mold. The mold was then hot-pressed in a hot press and the sample was removed from the mold after 5 minutes. The sample was then placed in an 80°C oven for 48 hours to mature. After being left to stand at room temperature for 2 weeks, the sample could be used for testing and practical applications.
[0049] The bio-based content of this formulation sample is 84.0%, and its mechanical properties are detailed in Table 1.
[0050] Example 2
[0051] The following describes the preparation process of bio-based polyester glycol:
[0052] Bio-based glutaric acid, diethylene glycol, and pentylene glycol were mixed in a molar ratio of 1:1:2.5 (acid-to-alcohol ratio 1:1.25), and 350 g of bio-based raw materials were weighed and added to a 500 ml reaction vessel. After purging with nitrogen, the reaction temperature was raised to 200 °C and reacted for 4 h. Then, 6 g of catalyst solution (antimony diethanolate-toluene, catalyst concentration 80 g / L) was added, with the catalyst mass being 0.15% of the total reactants. After stirring and mixing, the pressure was uniformly reduced to a vacuum of -0.09 MPa over 1 h. The reaction was then continued for 15 min, and stopped when the hydroxyl value reached 112 mg KOH / g, yielding a bio-based polyester glycol with a molecular weight of 1000 g / mol.
[0053] The following describes the preparation process of bio-based polyurethane elastomers:
[0054] The prepared bio-based polyester glycol was heated to 80°C, and terephthalic diisocyanate (molar ratio of bio-based polyester glycol to terephthalic diisocyanate was 1:1.5) was added. The reaction was allowed to proceed for 2 hours. Then, 1,3-propanediol (molar ratio of bio-based polyester glycol to 1,3-propanediol was 1:0.5) (mass ratio of soft segment to hard segment was 77:23) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a hot press. After 5 minutes, the sample was removed from the mold. The sample was then placed in a 100°C oven for 48 hours to mature. After being left to stand at room temperature for 2 weeks, the sample could be used for testing and practical applications.
[0055] The bio-based content of this formulation sample is 83.2%, and its mechanical properties are detailed in Table 1.
[0056] Example 3
[0057] The following describes the preparation process of bio-based polyester glycol:
[0058] Bio-based glutaric acid, 1,3-propanediol, and 1,2-propanediol were mixed in a molar ratio of 1:0.91:0.39 (acid-to-alcohol ratio 1:1.3), and a total mass of 350 g of bio-based raw materials was weighed and added to a 500 ml reaction vessel. After purging with nitrogen, the reaction temperature was raised to 200 °C and reacted for 4 h. Then, 3.5 g of a catalyst solution (antimony diethanolate-1,2-propanediol, mass concentration 10%) was added, with the catalyst mass accounting for 0.15% of the total reactants. After stirring and mixing, the pressure was uniformly reduced to a vacuum of -0.09 MPa over 1 h. The reaction was then continued for 30 min, and stopped when the hydroxyl value reached 75 mg KOH / g, yielding a bio-based polyester glycol with a molecular weight of 1500 g / mol.
[0059] The following describes the preparation process of bio-based polyurethane elastomers:
[0060] The prepared bio-based polyester glycol was heated to 60°C, and 1,5-pentamethylene diisocyanate (molar ratio of bio-based polyester glycol to 1,5-pentamethylene diisocyanate was 1:1.75) was added. The reaction was allowed to proceed for 1.5 hours. Then, 1,4-butanediol (molar ratio of bio-based polyester glycol to 1,4-butanediol was 1:0.75) (mass ratio of soft segment to hard segment was 81:19) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure and poured into a mold. The mold was then hot-pressed in a hot press and the sample was removed from the mold after 5 minutes. The sample was then placed in a 130°C oven for 48 hours to mature. After being left to stand at room temperature for 2 weeks, the sample was ready for testing and practical applications.
[0061] The bio-based content of this formulation sample is 100%, and its mechanical properties are detailed in Table 1.
[0062] Figure 1 The DSC test results for Examples 1-3 above show that the bio-based polyester glycols prepared in Examples 1-3 undergo a glass transition process in the range of -80 to 100°C, but there are no obvious melting or crystallization peaks, indicating that the bio-based polyester glycols prepared in Examples 1-3 are completely non-crystallizable polymers.
[0063] Example 4
[0064] The following describes the preparation process of bio-based polyurethane elastomers:
[0065] The bio-based polyester glycol from Example 1 was heated to 60°C, and hexamethylene diisocyanate (molar ratio of bio-based polyester glycol to hexamethylene diisocyanate was 1:1.75) was added. The reaction was allowed to proceed for 1.5 hours. Ethylene glycol (molar ratio of bio-based polyester glycol to ethylene glycol was 1:0.75) (mass ratio of soft segments to hard segments was 81:19) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a hot press. After 5 minutes, the sample was removed from the mold. The sample was then placed in a 110°C oven for 48 hours to mature. After being left at room temperature for 2 weeks, the sample was ready for testing and practical applications.
[0066] The bio-based content of this formulation sample is 83.3%, and its mechanical properties are detailed in Table 1.
[0067] Example 5
[0068] The following describes the preparation process of bio-based polyurethane elastomers:
[0069] The bio-based polyester glycol from Example 1 was heated to 60°C, and 1,5-pentamethylene diisocyanate (molar ratio of bio-based polyester glycol to 1,5-pentamethylene diisocyanate was 1:1.5) was added. The reaction was allowed to proceed for 1.5 hours. Then, 1,5-pentanediol (molar ratio of bio-based polyester glycol to 1,5-pentanediol was 1:0.5) (mass ratio of soft segment to hard segment was 84:16) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a hot press. After 5 minutes, the sample was removed from the mold. The sample was then placed in a 110°C oven for 48 hours to mature. After being left at room temperature for 2 weeks, the sample was ready for testing and practical applications.
[0070] The bio-based content of this formulation sample is 100%, and its mechanical properties are detailed in Table 1.
[0071] Example 6
[0072] The following describes the preparation process of bio-based polyurethane elastomers:
[0073] The bio-based polyester glycol from Example 1 was heated to 60°C, and 1,5-pentamethylene diisocyanate (molar ratio of bio-based polyester glycol to 1,5-pentamethylene diisocyanate was 1:1.5) was added. The reaction was allowed to proceed for 1.5 hours. Then, 1,6-hexanediol (molar ratio of bio-based polyester glycol to 1,6-hexanediol was 1:0.5) (mass ratio of soft segment to hard segment was 83:17) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a hot press. After 5 minutes, the sample was removed from the mold. The sample was then placed in a 110°C oven for 48 hours to mature. After being left at room temperature for 2 weeks, the sample was ready for testing and practical applications.
[0074] The bio-based content of this formulation sample is 100%, and its mechanical properties are detailed in Table 1.
[0075] Comparative Example 1
[0076] The following describes the preparation process of bio-based polyurethane elastomers:
[0077] Polyhexane adipate (molecular weight 1500 g / mol, crystalline) was heated to 80°C, and hexamethylene diisocyanate (molar ratio of polyhexane adipate to hexamethylene diisocyanate was 1:1.5) was added. The reaction was carried out for 2.5 h. Then, 1,4-butanediol (molar ratio of polyhexane adipate to 1,4-butanediol was 1:0.5) (mass ratio of soft segment to hard segment was 84:16) was added, and the mixture was quickly stirred until homogeneous. The mixture was degassed under reduced pressure and poured into a mold. The mold was then hot-pressed in a 110°C hot press and removed from the mold after 5 min. The sample was then cured in an 80°C oven for 48 h. After being left to stand at room temperature for 2 weeks, the sample could be used for testing and practical applications. The mechanical properties are detailed in Table 1.
[0078] Comparative Example 2
[0079] The following describes the preparation process of bio-based polyurethane elastomers:
[0080] The bio-based polyester glycol prepared in Example 1 was heated to 80°C, and dicyclohexylmethane diisocyanate (molar ratio of bio-based polyester glycol to dicyclohexylmethane diisocyanate was 1:1.16) was added, and the reaction was carried out for 2.5 h. Then, 1,4-butanediol (molar ratio of bio-based polyester glycol to bio-based 1,4-butanediol was 1:0.16) (mass ratio of soft segment to hard segment was 83:17) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a 130°C hot press. After 20 min, the sample was removed from the mold. The sample was then placed in a 100°C oven for 48 h to mature. After being left at room temperature for 2 weeks, the sample could be used for testing and practical applications. The mechanical properties are detailed in Table 1.
[0081] Comparative Example 3
[0082] The following describes the preparation process of bio-based polyester glycol:
[0083] Bio-based glutaric acid and 1,2-propanediol were mixed in a molar ratio of 1:1.3 (acid-to-alcohol ratio 1:1.3), and 350 g of bio-based raw materials were weighed and added to a 500 ml reaction vessel. After purging with nitrogen, the reaction temperature was raised to 200 °C and reacted for 4 h. Then, 7 g of catalyst solution (antimony diethanolate-1,2-propanediol, mass concentration 100 g / L) was added, with the catalyst mass being 0.15% of the reactants. After stirring and mixing, the pressure was uniformly reduced to a vacuum of -0.09 MPa over 1 h. The reaction was then continued for 30 min, and stopped when the hydroxyl value reached 75 mg KOH / g, yielding a bio-based polyester glycol with a molecular weight of 1500 g / mol.
[0084] The following describes the preparation process of bio-based polyurethane elastomers:
[0085] The prepared bio-based polyester glycol was heated to 60°C, and 1,5-pentamethylene diisocyanate (molar ratio of bio-based polyester glycol to 1,5-pentamethylene diisocyanate was 1:1.75) was added. The reaction was allowed to proceed for 1.5 h. Then, 1,4-butanediol (molar ratio of bio-based polyester glycol to 1,4-butanediol was 1:0.75) (mass ratio of soft segment to hard segment was 81:19) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure and poured into a mold. The mold was then hot-pressed in a hot press and the sample was removed from the mold after 5 min. The sample was then placed in a 130°C oven for 48 h to mature. After being left to stand at room temperature for 2 weeks, the sample could be used for testing and practical applications. The mechanical properties are detailed in Table 1.
[0086] Comparative Example 4
[0087] eTPU-95a (purchased from Shenzhen Guanghua Weiye Co., Ltd.) is a commercially available, biodegradable, bio-based polyurethane elastomer.
[0088] The molding method of this sample is as follows: eTPU-95a granules are placed into a 2cm mold, preheated in a hot press at 160℃ for 10min, then hot-pressed for 10min, cooled at room temperature for 10min and then removed. After being left to stand for 2 weeks, it is used for testing and practical application. The mechanical properties are detailed in Table 1.
[0089] Comparative Example 5
[0090] The following describes the preparation process of bio-based polyurethane elastomers:
[0091] The bio-based polyester glycol from Example 1 was heated to 80°C, and hexamethylene diisocyanate (molar ratio of bio-based polyester glycol to hexamethylene diisocyanate was 1:2.75) was added. The reaction was allowed to proceed for 2.5 hours. Then, 1,4-butanediol (molar ratio of bio-based polyester glycol to 1,4-butanediol was 1:1.75) (mass ratio of soft segment to hard segment was 70:30) was added, and the mixture was rapidly stirred until homogeneous. The mixture was then degassed under reduced pressure, poured into a mold, and hot-pressed in a hot press. After 5 minutes, the sample was removed from the mold. The sample was then placed in an 80°C oven for 48 hours to mature. After being left at room temperature for 2 weeks, the sample was ready for testing and practical applications.
[0092] The bio-based content of this formulation sample is 77.9%, and its mechanical properties are detailed in Table 1.
[0093] The degradation performance of the polyurethane materials prepared in Examples 1-6 and the polyurethane materials in Comparative Examples 1-5 was tested. The specific degradation performance testing steps are as follows:
[0094] First, the sample is crushed into particles smaller than 4 mm in volume. 3 The sample was pulverized and then mixed with a potassium dihydrogen phosphate / dipotassium hydrogen phosphate solution at 37℃ and pH=7.4 to prepare a mixed solution with a concentration of 50 g / L. Novozymes immobilized lipase CLAB (enzyme activity 5000 LU / g, enzyme solution mass to sample mass ratio 1:1) was then added, and the mixture was stirred until homogeneous. Degradation was continued for 20 days. After degradation, the degradation solution was centrifuged, and the lower layer residue was collected. The residue was then freeze-dried under reduced pressure at 0℃. Finally, the mass of the residue was weighed, and the mass loss rate during the degradation process was calculated, which is the degradation rate. Detailed degradation performance test results are shown in Table 1.
[0095] The mechanical properties and degradation test results of the bio-based polyurethane elastomers of Examples 1-4 and the polyurethane elastomers of Comparative Examples 1-4 are shown in Table 1, as detailed below:
[0096]
[0097] As shown in Table 1, the polyurethane materials prepared in Examples 1 to 6 have good mechanical properties, which can meet the application requirements, and at the same time, they have good degradation properties.
[0098] Comparative Example 1 used crystalline polyhexanediol adipate as the soft segment, and the degradation rate was significantly reduced after 20 days.
[0099] A comparison of Example 1 and Comparative Example 2 shows that Example 1 used hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO), which have better regularity, as the hard segments of the polyurethane, while Comparative Example 2 used dicyclohexylmethane diisocyanate (HMDI), which has poorer regularity, as the hard segments of the polyurethane. The irregular hard segment chains reduce the degree of microphase separation in the polyurethane, resulting not only in poorer mechanical properties but also a significant reduction in its degradation rate. Compared to the polyurethane in Example 1, the tensile strength and degradation rate of the polyurethane in Comparative Example 2 decreased by 95.2% and 87.5%, respectively.
[0100] A comparison of Example 3 (where side-chain small molecules comprise 17.9% of the bio-based polyester diol by mass) and Comparative Example 3 (where side-chain small molecules comprise 42.8% of the bio-based polyester diol by mass) shows that Comparative Example 3 has a higher side-chain content in its soft segment, and the shielding effect of the side-chains makes the polyurethane more difficult to degrade. Compared to Example 3, the 20-day degradation rate of the polyurethane in Comparative Example 3 is reduced by 52.6%.
[0101] As can be seen from Comparative Example 4, when using commercially available biodegradable polyurethane, the bio-based polyurethanes provided in Examples 1-6 have a significant advantage in degradation performance over 20 days.
[0102] As can be seen from the comparison between Example 1 and Comparative Example 5, when the hard segment content in polyurethane is too high, the degradation rate of the material will decrease significantly when the hard segment content in Comparative Example 5 reaches 30%.
[0103] In summary, the bio-based polyester diols provided by this invention, which are mainly linear with no or low side groups as soft segments and combined with regular hard segments, not only improve the mechanical properties of polyurethane but also greatly enhance the degradation performance of the material.
[0104] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A bio-based polyurethane elastomer, comprising soft segments and hard segments, wherein the soft segments are non-crystalline bio-based polyester diol structural units, and the hard segments are structural units composed of isocyanate and bio-based chain extenders, wherein the mass ratio of the soft segments to the hard segments is 74~88:12~26; The molecular weight of the bio-based polyester diol structural unit is 500~1500 g / mol; The content of branched small molecules in the bio-based polyester diol structural unit is less than or equal to 20 wt%; The degradation temperature of the bio-based polyurethane elastomer is 30~60℃.
2. The bio-based polyurethane elastomer according to claim 1, characterized in that, The bio-based polyester diol structural unit is a linear molecular chain segment structure with hydroxyl double-terminated ends.
3. The bio-based polyurethane elastomer according to claim 1, characterized in that, The bio-based polyester diol structural unit contains little or no side groups.
4. The bio-based polyurethane elastomer according to claim 1, characterized in that, The bio-based polyester glycol is obtained by polycondensation of at least two bio-based raw materials, and the molar ratio of carboxyl groups to hydroxyl groups in the bio-based raw materials participating in the polycondensation reaction is 1:1.05~2.
5. The bio-based polyurethane elastomer according to claim 4, characterized in that, The bio-based raw materials are selected from dimethyl oxalate, dimethyl malonate, succinic acid, glutaric acid, adipic acid, sebacic acid, diethylene glycol, terephthalic acid, methyl itaconic acid, tridecanoic acid, tetradecanoic acid, α-hydroxypropionic acid, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butanediol, 2,3-butanediol, and diethylene glycol.
6. The bio-based polyurethane elastomer according to claim 1, characterized in that, The isocyanate is selected from at least one of terephthalic diisocyanate, isophthalic diisocyanate, hexamethylene diisocyanate, and 1,5-pentamethylene diisocyanate.
7. The bio-based polyurethane elastomer according to claim 1, characterized in that, The bio-based chain extender is selected from at least one of 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol, 1,3-propanediol, and ethylene glycol.
8. A method for preparing a bio-based polyurethane elastomer as described in any one of claims 1 to 7, the method comprising the following steps: S1. Add bio-based raw materials to a reaction vessel, heat to 150~200 ℃, esterify for 2~6 h, add catalyst, reduce pressure to -0.1 ~ -0.08 MPa, stop the reaction when the hydroxyl value reaches 50~230 mg KOH / g, and obtain bio-based polyester diol; S2. Heat the bio-based polyester diol to 45~90 ℃, add isocyanate, and react for 2~3 h; add chain extender, stir well, degas, pour into mold, hot press at 100~160 ℃, and then cure at 80~130 ℃ for 12~96 h to obtain the polyurethane elastomer.
9. A method for degrading the bio-based polyurethane elastomer as described in any one of claims 1 to 7, the degradation method comprising the following steps: After pulverizing the polyurethane elastomer sample, it was placed in a potassium dihydrogen phosphate / dipotassium hydrogen phosphate solution to prepare a mixed solution. Degrading enzymes were then added to degrade the sample, resulting in a degradation solution.
10. The degradation method of the bio-based polyurethane elastomer according to claim 9, characterized in that, The pH of potassium dihydrogen phosphate / dipotassium hydrogen phosphate solution is 6.9–7.4; and / or, The degradation temperature is 30~60℃; and / or, The mass concentration of polyurethane elastomer in the mixed solution is 50~200 g / L; and / or, The amount of degrading enzyme used is 0.5 to 2 times the mass of the polyurethane elastomer; and / or, The degrading enzymes are selected from Novozymes immobilized lipase A, Novozymes immobilized lipase B, and porcine pancreatic lipase; and / or The degradation time is 2 to 40 days.