Degradable thermoplastic polyurethane material and preparation method thereof

Abstract

The invention relates to a degradable thermoplastic polyurethane material and a preparation method thereof, and belongs to the technical field of polyurethane materials. Modified erythritol is used as a bio-based material, diisocyanate and a chain extender are synthesized to obtain the degradable thermoplastic polyurethane material, vanillin and ethanolamine are synthesized to obtain the chain extender, an imine bond which is irreversible after hydrolysis exists in the chain extender, and the chain extender and the bio-based material jointly improve the degradability of polyurethane, so that the biodegradable thermoplastic polyurethane material is prepared. Meanwhile, the mechanical property of the material can be ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane materials and relates to a degradable thermoplastic polyurethane material and a preparation method thereof. Background Art

[0002] Polyurethanes (PUs) are a special type of polymer material that is fundamentally different from many other types of plastics. These can be incorporated into a variety of items such as paints, liquid coatings, elastomers, insulators, elastic fibers, foams, artificial skin, etc. Isocyanate and polyol molecules must contain two or more isocyanate groups (R-(N=C=O)n≥2) and hydroxyl groups (R'-(OH)n≥2) respectively. The properties exhibited usually depend on the types of polyols and isocyanates used. By adding different additives during polymerization and modifying the processing conditions, it is possible to obtain different characteristics, making it suitable for various applications.

[0003] However, while polyurethanes are widely used in various industries, they also have certain limitations. After being used in various aspects, polyurethanes are incinerated or landfilled as waste, and only a very small number of polyurethanes that meet specific conditions are recycled, which is a huge waste of resources. The incineration of polyurethanes will produce a large amount of toxic and harmful gases, causing secondary pollution, and in the long run, it will aggravate air pollution. The landfill of polyurethanes will increase the burden on the land, and the trace harmful elements in them will be released into the soil, which is extremely harmful to animals, plants and humans. The chemical stability of polyurethanes makes it difficult to degrade quickly even when buried deep in the soil. On the other hand, since the raw materials of polyurethanes are all obtained from petroleum resources, the high cost, energy demand and environmental problems have increased the need for more suitable and environmentally friendly alternatives. Among many green natural polyurethane raw materials, replacing petroleum-based resources with plant-based or bio-based sources has always been a key research topic, but most bio-based resources have many defects compared with petroleum-based resources, such as large molecular weight, unstable internal structure, too many useless groups or branched structures, resulting in obvious disadvantages in the performance of the prepared polyurethanes.

[0004] Current research shows that introducing substances similar to erythritol or other biobased macromolecular polyols into the polyurethane molecule can achieve the purpose of making the polyurethane degradable. However, for the prepared polyurethane, it is difficult to achieve complete biodegradation, and the resulting polyurethane has poor performance due to the unstable biobased macromolecular structure. In addition, Chinese Patent CN 114015003 A discloses a degradable polyurethane elastomer containing an imine structure based on vanillin and its preparation method. The polyurethane prepared in this invention mainly uses renewable resources as raw materials, which are cheap, environmentally friendly, energy-saving, and the whole reaction process is simple and low-toxic. The aldehyde group of vanillin easily forms an imine bond with ethanolamine, enabling the polyurethane elastomer to have mild degradation conditions and a high degradation rate. Although the formation of multiple imine bonds by the dialdehyde structure greatly enhances the degradability of the material, it also has a weakening effect on the mechanical properties. Therefore, based on the above conditions, the present invention further optimizes the preparation method and performance of the polyurethane. Summary of the Invention

[0005] The present invention relates to a degradable thermoplastic polyurethane material, belonging to the technical field of polyurethane materials. The present invention discloses a degradable thermoplastic polyurethane material synthesized from a modified erythritol as a biobased material, a diisocyanate, and a chain extender. The chain extender is obtained by synthesizing vanillin and ethanolamine, and there is an irreversible imine bond after hydrolysis in the chain extender, which together with the biobased material improves the degradable performance of the polyurethane and can ensure the mechanical properties of the material.

[0006] The object of the present invention can be achieved by the following technical solutions: A degradable thermoplastic polyurethane material, the chemical structural formula of the degradable thermoplastic polyurethane material is: , where R is C 17 H 35 .

[0007] The present invention also provides a preparation method of a degradable thermoplastic polyurethane material, including the following steps: (1) Mix erythritol with a straight-chain saturated fatty acid and a solvent, add boric acid, heat, distill, and vacuum dry after condensation to obtain modified erythritol; (2) Take ethanolamine and vanillin in a container, introduce nitrogen and then raise the temperature, reflux through a condenser, then mix the condensate with absolute ethanol and stir, filter, and dry the filtrate under vacuum to form a solid, which is the chain extender; (3) Heat 4,4'-diphenylmethane diisocyanate in a sealed manner, filter to remove insoluble substances, cool to room temperature, add N,N-dimethylformamide, then add modified erythritol, raise the temperature and stir, then add a catalyst and the chain extender and continue to stir, keep the temperature constant, and cool to room temperature when it forms a mucus state to obtain a degradable thermoplastic polyurethane material.

[0008] Further, in the step (1), the molar ratio of erythritol, straight-chain saturated fatty acid, solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is palmitic acid or stearic acid, the heating temperature is 70 - 90°C, and the drying temperature and time are 50 - 60°C and 30 - 60 min, respectively.

[0009] Further, in the step (2), the molar ratio of ethanolamine and vanillin is 1:1, the temperature and time for temperature rise are 80 - 90°C and 2 - 3 h, respectively, and the time for condensation reflux is 2 - 3 h.

[0010] Further, in the step (2), the volume ratio of the condensate to absolute ethanol is 1:1 - 2, and the temperature and time for vacuum drying are 80°C and 10 - 12 h, respectively.

[0011] Further, in the step (3), the temperature and time for sealed heating are 80°C and 2 - 3 h, respectively, and the mass ratio of 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol, catalyst and chain extender is 3:1:1:0.02 - 0.04:0.3 - 0.5.

[0012] Further, in the step (3), the catalyst is dibutyltin dilaurate, the temperature for heating with stirring is 60 - 80°C, and the time for continuous stirring is 1 - 2 h.

[0013] Further, in the step (3), the temperature and time for heat preservation are 70 - 80°C and 1 - 2 h, respectively, and the viscosity of the mucus is 1000 - 1500 cPs.

[0014] Advantages of the present invention: The present invention uses modified erythritol as a bio-based material to synthesize a degradable thermoplastic polyurethane material with diisocyanate and chain extender. The chain extender is obtained by synthesizing vanillin and ethanolamine. There is an irreversible imine bond after hydrolysis in the chain extender. The modified erythritol reduces the hydroxyl content of erythritol by esterifying erythritol and straight-chain saturated fatty acid, thereby reducing the crosslinking strength with diisocyanate, so that the polyurethane material can be completely degraded, and at the same time, the molecular stability is improved; in addition, the introduction of the chain extender not only improves the degradation of the material, but also ensures the mechanical properties of the material. Specific embodiments

[0015] To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following examples are used to describe in detail the specific embodiments, structures, features and their effects according to the present invention. Example 1

[0016] Degradable thermoplastic polyurethane material, the chemical structural formula of the degradable thermoplastic polyurethane material is: , where R is C 17 H 35 .

[0017] The preparation method of the degradable thermoplastic polyurethane material comprises the following steps: (1) Erythritol is mixed with a straight-chain saturated fatty acid and a solvent, boric acid is added, heated, distilled, and after condensation, it is vacuum dried to obtain modified erythritol; (2) Ethanolamine and vanillin are placed in a container, nitrogen is introduced, the temperature is raised, refluxed through a condenser, then the condensate is mixed and stirred with absolute ethanol, filtered, and the filtrate is dried under vacuum to form a solid, which is the chain extender; (3) 4,4'-Diphenylmethane diisocyanate is sealed and heated, the insoluble substances are filtered off, cooled to room temperature, N,N-dimethylformamide is added, then modified erythritol is added, the temperature is raised and stirred, then a catalyst and a chain extender are added and stirring is continued, the temperature is set for heat preservation, and when it forms a mucus state, it is cooled to room temperature to obtain the degradable thermoplastic polyurethane material.

[0018] In the step (1), the molar ratio of erythritol, straight-chain saturated fatty acid, solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is stearic acid, the heating temperature is 70 °C, and the drying temperature and time are 50 °C and 30 min respectively.

[0019] In the step (2), the molar ratio of ethanolamine and vanillin is 1:1, the temperature and time for raising the temperature are 80 °C and 2 h respectively, and the condensation reflux time is 2 h.

[0020] In the step (2), the volume ratio of the condensate to absolute ethanol is 1:1, and the vacuum drying temperature and time are 80 °C and 10 h respectively.

[0021] In the step (3), the sealing heating temperature and time are 80 °C and 2 h respectively, and the mass ratio of 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol, catalyst and chain extender is 3:1:1:0.02:0.3.

[0022] In the step (3), the catalyst is dibutyltin dilaurate, the temperature for raising the temperature and stirring is 60 °C, and the time for continuous stirring is 1 h.

[0023] In the step (3), the heat preservation temperature and time are 70 °C and 1 h respectively, and the viscosity of the mucus is 1000 cPs. Example 2

[0024] A degradable thermoplastic polyurethane material, the chemical structural formula of the degradable thermoplastic polyurethane material is: , where R is C 17 H 35 .

[0025] The preparation method of the degradable thermoplastic polyurethane material comprises the following steps: (1) Mix erythritol with a straight-chain saturated fatty acid and a solvent, add boric acid, heat, distill, and after condensation, dry in vacuum to obtain modified erythritol; (2) Take ethanolamine and vanillin in a container, introduce nitrogen and then raise the temperature, reflux through a condenser tube, then take the condensate and mix and stir it with absolute ethanol, filter, and dry the filtrate under vacuum to form a solid, which is the chain extender; (3) Seal and heat 4,4'-diphenylmethane diisocyanate, filter to remove insoluble substances, cool to room temperature, add N,N-dimethylformamide, then add modified erythritol, raise the temperature and stir, then add a catalyst and the chain extender and continue to stir, keep the temperature constant, and when it forms a mucus state, cool to room temperature to obtain the degradable thermoplastic polyurethane material.

[0026] In the step (1), the molar ratio of erythritol, the straight-chain saturated fatty acid, the solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is stearic acid, the heating temperature is 80 °C, and the drying temperature and time are 55 °C and 45 min respectively.

[0027] In the step (2), the molar ratio of ethanolamine and vanillin is 1:1, the temperature and time for raising the temperature are 85 °C and 2.5 h respectively, and the condensation reflux time is 2.5 h.

[0028] In the step (2), the volume ratio of the condensate to absolute ethanol is 1:1.5, and the vacuum drying temperature and time are 80 °C and 11 h respectively.

[0029] In the step (3), the sealing heating temperature and time are 80 °C and 2.5 h respectively, and the mass ratio of 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol, the catalyst and the chain extender is 3:1:1:0.03:0.4.

[0030] In the step (3), the catalyst is dibutyltin dilaurate, the temperature for raising the temperature and stirring is 70 °C, and the time for continuing to stir is 1.5 h.

[0031] In the step (3), the temperature and time for heat preservation are 75 °C and 1.5 h respectively, and the viscosity of the mucus is 1200 cPs. Example 3

[0032] A degradable thermoplastic polyurethane material, the chemical structural formula of the degradable thermoplastic polyurethane material is: , where R is C 17 H 35 .

[0033] The preparation method of the degradable thermoplastic polyurethane material includes the following steps: (1) Mix erythritol with a straight-chain saturated fatty acid and a solvent, add boric acid, heat, distill, and after condensation, dry under vacuum to obtain modified erythritol; (2) Take ethanolamine and vanillin in a container, introduce nitrogen and then raise the temperature, reflux through a condenser, then take the condensate and mix and stir it with absolute ethanol, filter, and dry the filtrate under vacuum to form a solid, which is the chain extender; (3) Seal and heat 4,4'-diphenylmethane diisocyanate, filter to remove insoluble substances, cool to room temperature, add N,N-dimethylformamide, then add modified erythritol, raise the temperature and stir, then add a catalyst and a chain extender and continue to stir, keep the temperature constant, and when it forms a mucus state, cool to room temperature to obtain the degradable thermoplastic polyurethane material.

[0034] In the step (1), the molar ratio of erythritol, straight-chain saturated fatty acid, solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is stearic acid, the heating temperature is 90 °C, and the drying temperature and time are 60 °C and 60 min respectively.

[0035] In the step (2), the molar ratio of ethanolamine and vanillin is 1:1, the temperature and time for raising the temperature are 90 °C and 3 h respectively, and the condensation reflux time is 3 h.

[0036] In the step (2), the volume ratio of the condensate to absolute ethanol is 1:2, and the vacuum drying temperature and time are 80 °C and 12 h respectively.

[0037] In the step (3), the sealing heating temperature and time are 80 °C and 3 h respectively, and the mass ratio of 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol, catalyst and chain extender is 3:1:1:0.04:0.5.

[0038] In the step (3), the catalyst is dibutyltin dilaurate, the temperature for raising the temperature and stirring is 80 °C, and the time for continuous stirring is 2 h.

[0039] In the step (3), the temperature and time for heat preservation are 80 °C and 2 h respectively, and the viscosity of the mucus is 1500 cPs.

[0040] Comparative Example 1 Based on Example 2, the preparation method of the degradable thermoplastic polyurethane material comprises the following steps: (1) Mix erythritol with a straight-chain saturated fatty acid and a solvent, add boric acid, heat, distill, and after condensation, dry in vacuo to obtain modified erythritol; (2) Seal and heat 4,4'-diphenylmethane diisocyanate, filter to remove insoluble substances, cool to room temperature, add N,N-dimethylformamide, then add modified erythritol, raise the temperature and stir, then add a catalyst and continue to stir, keep the temperature constant, and when it forms a mucus state, cool to room temperature to obtain the degradable thermoplastic polyurethane material.

[0041] In step (1), the molar ratio of erythritol, straight-chain saturated fatty acid, solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is stearic acid, the heating temperature is 80°C, and the drying temperature and time are 55°C and 45 min respectively.

[0042] In step (2), the sealing heating temperature and time are 80°C and 2.5 h respectively, and the mass ratio of 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol and catalyst is 3:1:1:0.03.

[0043] In step (3), the catalyst is dibutyltin dilaurate, the temperature for raising the temperature and stirring is 70°C, and the time for continuing to stir is 1.5 h.

[0044] In step (3), the temperature and time for heat preservation are 75°C and 1.5 h respectively, and the viscosity of the mucus is 1200 cPs.

[0045] Comparative Example 2 Based on Example 2, the preparation method of the degradable thermoplastic polyurethane material comprises the following steps: (1) Take ethanolamine and vanillin in a container, introduce nitrogen and raise the temperature, reflux through a condenser tube, then take the condensate and mix and stir with absolute ethanol, filter, and dry the filtrate under vacuum to form a solid, which is the chain extender; (2) Seal and heat 4,4'-diphenylmethane diisocyanate, filter to remove insoluble substances, cool to room temperature, add N,N-dimethylformamide, then add erythritol, raise the temperature and stir, then add a catalyst and the chain extender and continue to stir, keep the temperature constant, and when it forms a mucus state, cool to room temperature to obtain the degradable thermoplastic polyurethane material.

[0046] In step (1), the molar ratio of ethanolamine to vanillin is 1:1. The temperature and time for heating up are 85°C and 2.5 h respectively, and the time for condensation reflux is 2.5 h.

[0047] In step (1), the volume ratio of the condensate to absolute ethanol is 1:1.5. The temperature and time for vacuum drying are 80°C and 11 h respectively.

[0048] In step (2), the temperature and time for sealed heating are 80°C and 2.5 h respectively. The mass ratio among 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, erythritol, catalyst and chain extender is 3:1:1:0.03:0.4.

[0049] In step (2), the catalyst is dibutyltin dilaurate. The temperature for heating with stirring is 70°C, and the time for continuous stirring is 1.5 h.

[0050] In step (2), the temperature and time for heat preservation are 75°C and 1.5 h respectively. The viscosity of the mucus is 1200 cPs.

[0051] Comparative Example 3 Based on Example 2, the modified erythritol is replaced with erythritol, and the chain extender is not added while other conditions are the same as those in Example 2.

[0052] Comparative Example 4 Based on Example 2, the molar ratio of erythritol to straight-chain saturated fatty acid in step (1) is adjusted to 1:1, and other conditions are the same as those in Example 2.

[0053] Comparative Example 5 The difference between Comparative Example 5 and Example 2 is only that the preparation method of the chain extender in Comparative Example 5 is replaced with the preparation method of the product in Example 2 of Patent CN114015003A, and other conditions are the same as those in Example 2 of the present invention.

[0054] Performance Test Take the polyurethane materials prepared in Examples 1 - 3 and Comparative Examples 1 - 5 as specimens. Biodegradation rate: The specimens are made into film materials with a thickness of 0.15 mm, and the compost degradation experiment is carried out according to the method specified in "GB / T 19277.2 - 2013". After 50 days of compost degradation, the ratio of the carbon dioxide release amount to the theoretical carbon dioxide release amount measured by the gravimetric method is used to evaluate the biodegradation rate of the prepared film material specimens; Mechanical properties: After the specimens are injection molded into specimens (dumbbell shape type 2), the test is carried out according to the method specified in "GB / T 528 - 2009". The test results are shown in Table 2.

[0055] Table 1 Test Results Specimen Biodegradation rate % Tensile strength MPa Elongation at break % Example 1 89 50 680 Example 2 90 52 688 Example 3 89.5 50 679 Comparative Example 1 57 50 660 Comparative Example 2 65 56 540 Comparative Example 3 53 58 489 Comparative Example 4 69 55 560 Comparative Example 5 93 46 430 As can be seen from Table 1, the biodegradation rates of Examples 1-3 are much higher than those of Comparative Examples 1-4, and the biodegradation rate in Comparative Example 5 is the highest. The tensile strengths of Examples 1-3 are slightly lower than those of Comparative Examples 1-4, but the tensile strength in Comparative Example 5 is much lower than that of other specimens. In addition, the elongation at break of Comparative Examples 1-5 is much lower than that of Examples 1-3. No chain extender was added in Comparative Example 1, and the absence of imino bonds reduced the biodegradation rate; in Comparative Example 2, the 4 hydroxyl groups of erythritol added underwent a high crosslinking reaction with isocyanate, reducing the biodegradation rate; in Comparative Example 5, a dialdehyde structure was used to prepare imine bonds, which improved the biodegradability, but the mechanical properties of the material were severely weakened due to the presence of a large number of imine bonds. Therefore, a degradable thermoplastic polyurethane material was synthesized from modified erythritol as a bio-based material, diisocyanate, and a chain extender. The chain extender was obtained by synthesizing vanillin and ethanolamine. There are irreversible imino bonds after hydrolysis in the chain extender. The modified erythritol was esterified with erythritol and straight-chain saturated fatty acids to reduce the hydroxyl content of erythritol, thereby reducing the crosslinking strength with diisocyanate, so that the polyurethane material can be completely degraded while improving the molecular stability; in addition, the introduction of the chain extender not only improves the degradation of the material but also ensures the mechanical properties of the material.

[0056] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes, but as long as they do not depart from the technical content of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A degradable thermoplastic polyurethane material, characterized in that: The chemical structural formula of the degradable thermoplastic polyurethane material is: , where R is C 17 H 35 .

2. A method for preparing a degradable thermoplastic polyurethane material, characterized in that: The steps include: (1) erythritol is mixed with a straight-chain saturated fatty acid and a solvent, and boric acid is added to heat, distill, condense, and then vacuum dry to obtain modified erythritol; (2) Ethanolamine and vanillin are placed in a container, nitrogen is introduced, the temperature is raised, the mixture is refluxed through a condenser, and the condensate is mixed with anhydrous ethanol and stirred, filtered, and the filtrate is dried under vacuum to form a solid, which is a chain extender; (3) 4,4'-diphenylmethane diisocyanate is sealed and heated, and the infusible material is filtered out. After cooling to room temperature, N,N-dimethylformamide is added, followed by modified erythritol, and the temperature is raised with stirring. Subsequently, a catalyst and a chain extender are added and stirring is continued. The temperature is set to maintain the temperature, and when a viscous state is formed, the temperature is lowered to room temperature to obtain a degradable thermoplastic polyurethane material.

3. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: In the step (1), the molar ratio of erythritol, straight-chain saturated fatty acid, solvent and boric acid is 1:2:5:0.005, the solvent is methanol, the straight-chain saturated fatty acid is palmitic acid or stearic acid, the heating temperature is 70-90° C., and the drying temperature and time are 50-60° C. and 30-60 min, respectively.

4. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: In the step (2), the molar ratio of ethanolamine to vanillin is 1:1, the heating temperature and time are 80-90° C. and 2-3 h respectively, and the condensation reflux time is 2-3 h.

5. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: In the step (2), the volume ratio of the condensate to anhydrous ethanol is 1:1-2, and the temperature and time of the vacuum drying are 80° C. and 10-12 h, respectively.

6. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: The temperature and time of the sealed heating in step (3) are 80° C. and 2-3 h, respectively. The mass ratio of the 4,4'-diphenylmethane diisocyanate, N,N-dimethylformamide, modified erythritol, catalyst and chain extender is 3:1:1:0.02-0.04:0.3-0.

5.

7. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: In the step (3), the catalyst is dibutyltin dilaurate, the temperature of the heating and stirring is 60-80° C., and the stirring time is 1-2 hours.

8. The method for preparing a degradable thermoplastic polyurethane material according to claim 2, characterized in that: The temperature and time of the insulation in step (3) are 70-80° C. and 1-2 h respectively, and the viscosity of the mucus is 1000-1500 cPs.

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