Biodegradable polyurethane and method for its preparation

Abstract

This invention relates to a biodegradable polyurethane and its preparation method. The biodegradable polyurethane comprises a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is a small molecule monool residue, and the fourth structural unit is a diisocyanate residue. The first structural unit serves as the soft segment of the polyurethane. The first and fourth structural units are linked by a urethane ester. The second and fourth structural units are linked by a urethane ester to form the hard segment of the polyurethane. The third and fourth structural units are linked by a urethane ester to form the end groups of the polyurethane. During preparation, the polyester oligomer diol, a catalyst, lysine diisocyanate, and a portion of the solvent are added to a reactor for reaction. Then, a chain extender and the remaining solvent are added, and finally, a terminator is added to the reaction. This invention has a simple method; the product exhibits excellent degradation performance.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane materials technology, and relates to a biodegradable polyurethane and its preparation method. Background Technology

[0002] Amino acid oligomers have good biocompatibility and biodegradability, and are commonly used in the field of synthetic materials as drug carriers, biomimetic materials, cosmetics and other applications.

[0003] In the field of biodegradable polyurethane, amino acids are a class of compounds with terminal amino and terminal carboxyl groups. Existing technology CN114539505A discloses an amino acid-modified waterborne polyurethane acrylate and its preparation method. The process involves: S1, reacting a polyol with a diisocyanate to obtain a soft polyurethane, then adding a small-molecule chain extender containing carboxylic acid groups to obtain hard polyurethane segments, thus obtaining a waterborne polyurethane prepolymer; S2, adding acrylate to introduce photocurable groups; S3, adding a neutralizing agent to neutralize the carboxylic acid groups; S4, adding an amino acid-based small-molecule chain extender for chain extension, obtaining a waterborne polyurethane dispersion with a solid content of 25-45%; S5, adding a photoinitiator, stirring evenly, and rotary evaporating to remove the organic solvent and triethylamine, thus obtaining the material. This material exhibits excellent hydrolysis resistance, biocompatibility, and mechanical properties; however, its biodegradability is only moderate.

[0004] Patent CN108059706A discloses a biodegradable polyurethane composed of soft segments and hard segments. The soft segments are polycaprolactone, and the hard segments are non-toxic, degradable amino acid diisocyanates, specifically lysine diisocyanate and / or L-lysine diisocyanate. This polyurethane exhibits good biosafety and biocompatibility, which is an improvement over introducing polyurethane as a small-molecule chain extender, but its biodegradability is still not good enough.

[0005] Therefore, it is of great significance to study a biodegradable polyurethane and its preparation method in order to solve the problems existing in the prior art. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of existing biodegradable polyurethane and its preparation methods, and to provide a biodegradable polyurethane and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A biodegradable polyurethane comprising a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit;

[0009] The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is a small molecule monool residue, and the fourth structural unit is a diisocyanate residue.

[0010] The first structural unit serves as the soft segment of the biodegradable polyurethane. The first structural unit and the fourth structural unit are connected by a urethane ester. The second structural unit and the fourth structural unit are connected by a urethane ester to form the hard segment of the biodegradable polyurethane. The third structural unit and the fourth structural unit are connected by a urethane ester to form the end group of the biodegradable polyurethane.

[0011] The molar ratio of the first structural unit to the second structural unit is 7-9:1-3;

[0012] The polyester oligomer diol residues are composed of carboxyl polycaprolactone oligomer diol residues and polycarbonate oligomer diol residues. The molar ratio of carboxyl polycaprolactone oligomer diol residues to polycarbonate oligomer diol residues is 2 to 5:1. In the polyurethane soft segment molecular structure formed during prepolymerization, the two are randomly distributed.

[0013] The polycarbonate oligomer diol residues are polypropylene carbonate diol residues or polyethylene carbonate diol residues;

[0014] The diisocyanate residue is a lysine diisocyanate residue;

[0015] The molar ratio of the total amount of the first and second structural units to the fourth structural unit is 1:1.0 to 1.1;

[0016] The third structural unit is the end group that acts as a capping unit. It accounts for a very small proportion and its impact on degradation can be ignored.

[0017] As a preferred technical solution:

[0018] As described above, in a biodegradable polyurethane, the carboxyl polycaprolactone oligomer diol residue refers to the segment structure that enters the polymer chain after the reaction of carboxyl polycaprolactone oligomer diol with an acid value of 28 mg to 85 KOH / g.

[0019] The biodegradable polyurethane described above has a small molecule diol residue consisting of one or more of the following: 3-methyl-1,5-pentanediol residue, dipropylene glycol residue, 1,3-propanediol residue, methylpropylene glycol residue, and neopentanediol residue. The metabolites of these small molecule diol residues have been experimentally verified to be non-toxic to microorganisms.

[0020] The biodegradable polyurethane described above has an isopropanol residue as a small molecule monohydric alcohol residue.

[0021] The present invention also provides a method for preparing a biodegradable polyurethane as described in any of the preceding claims, comprising the following steps:

[0022] (1) Add polyester oligomer diol, catalyst, lysine diisocyanate and a portion of solvent into a reactor and stir at 40-60°C for 0.5-1 h.

[0023] (2) Raise the temperature of the system after the reaction in step (1) to 70-100℃, then add the chain extender and the remaining solvent, and react until the viscosity of the system is 69.9-129.9 Pa·s / 25℃; the chain extender is a small molecule diol;

[0024] (3) After the reaction in step (2) is completed, the temperature is lowered to below 60°C and a terminator is added. The reaction is carried out for 0.5 to 1 hour to obtain a biodegradable polyurethane with a viscosity of 70 to 130 Pa·s / 25°C. The terminator is a small molecule monohydric alcohol.

[0025] As a preferred technical solution:

[0026] In the preparation method of biodegradable polyurethane described above, the catalyst in step (1) is tetrabutyl titanate or tetraisopropyl titanate. The catalyst used in the preparation process of the present invention is a green and environmentally friendly titanate catalyst, which easily decomposes into titanium dioxide and isopropanol or n-butanol after absorbing water, and will not have an adverse effect on the biodegradation of the invention. Such catalysts hydrolyze into small molecule alcohols and titanium dioxide when exposed to water, and these degradation products will not affect the metabolic activity of microorganisms;

[0027] In step (2), the small molecule diol is one or more of 3-methyl-1,5-pentanediol, dipropylene glycol, 1,3-propanediol, methylpropanediol and neopentanediol;

[0028] In step (3), the small molecule monohydric alcohol is isopropanol, which has been verified to be non-toxic to microorganisms.

[0029] In the preparation method of biodegradable polyurethane as described above, the mass ratio of solvent added in step (1) to step (2) is 3:7;

[0030] The solvent is one or more of ethyl acetate, butyl acetate, and dimethyl sulfoxide;

[0031] Based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, the amount of solvent added is 70 wt%.

[0032] In the preparation method of biodegradable polyurethane as described above, the amount of catalyst is 0.3% to 3% relative to the total mass of reactants excluding solvent; the molar ratio of the total amount of polyester oligomer diol and small molecule diol to lysine diisocyanate is 1:1.0 to 1.1.

[0033] The preparation method of biodegradable polyurethane as described above, based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, has a terminating agent added in an amount of 0.1 to 0.2 wt%.

[0034] Invention Mechanism:

[0035] The development of biodegradable polyurethane typically requires consideration of two factors: the selection of the more difficult-to-degrade polyester oligomer diol and the selection of the isocyanate. Generally, polycaprolactone-type polyester oligomer diols are chosen, while non-toxic isocyanates must be selected to facilitate the biodegradability of the polyurethane structure. This invention is a technical improvement based on existing technology CN108059706A. The inventors discovered that the main reason for the poor degradation ability of existing technologies is the generation of intermediate substances that inhibit microbial activity during the degradation process. Polymer degradation is not instantaneous but depends on the metabolic rate of microorganisms, and the metabolic activity of microorganisms is closely related to the environment.

[0036] Polycaprolactone (PCL) exhibits some biodegradability. In nature, PCL is degraded by Penicillium and Clostridium species (such as Clostridium butyricum), with degradation products including small-molecule carboxylic acids. Lysine isocyanate is currently the only known non-toxic isocyanate suitable for polyurethane degradation, and the degradation products of polyurethanes containing this type of isocyanate include lysine. However, bacterial activity in nature is closely related to the pH of the environment. In polyurethane degradation experiments, a pH range of 6.2–7.5 was found to be suitable for the growth, metabolism, and reproduction of Penicillium and Clostridium butyricum.

[0037] Aqueous solutions of small molecule carboxylic acids are acidic, while aqueous solutions of lysine are alkaline, with a saturated lysine solution having a pH as high as 9.75. Since the degradation rate of polycaprolactone segments is slower than that of isocyanates, the initial degradation environment is usually alkaline. The pH environment created by the resulting lysine solution can make the activity of bacteria decomposing polycaprolactone unsuitable, thus affecting the degradation effect.

[0038] The innovation of this invention lies in the discovery of the relationship between isocyanate degradation products and bacterial metabolism. By selecting a polyurethane molecular chain composition that is more suitable for bacterial metabolism, which includes structures that can be metabolized into acidic small molecules and structures that can be metabolized into alkaline small molecules, the pH value of the environment can be controlled by coordinating the content of the two types of structures and the degradation rate of different structures in the degradation process, thereby improving the biodegradability of polyurethane.

[0039] The degradation of polyurethane typically occurs preferentially in the amorphous polyester polyol soft segments, while simultaneously triggering the degradation of the isocyanate structure connecting the soft segments. The former produces lysine, while the latter produces small molecule acids and small molecule alcohols.

[0040] Compared to conventional polyurethanes, the proportion of polyester oligomer diol residues in this invention is relatively high, and should be controlled to account for 70-90 mol% of the total molar percentage of diol residues. When the proportion of polyester oligomer diol residues is less than 70 mol%, the relatively high proportion of small molecule diol residues leads to an increase in crystalline regions, which severely reduces the overall degradation capacity of the polyurethane. When the proportion of polyester oligomer diol residues is greater than 90 mol%, the insufficient number of small molecule diol residues results in a lower content of hard segments and a reduction in crystalline regions, leading to lower tensile strength of the polyurethane, which fails to meet the requirements of conventional applications.

[0041] The polyester polyol soft segments have relatively long chains, resulting in fewer small-molecule acids produced in the initial decomposition stage. We found that when carboxyl-based polycaprolactone oligomer diols were used instead of traditional polycaprolactone polyester oligomer diols to construct polyurethane soft segments, the pH value decreased in the initial decomposition stage. This is because the decomposition produced more carboxyl groups, resulting in a higher acid value than that of traditional polycaprolactone decomposition. Furthermore, when an appropriate amount of polypropylene carbonate diol or polyethylene carbonate diol was introduced as a third monomer for copolymerization, the resulting polyurethane showed a significantly lower pH value in the initial decomposition stage at the same time. While polycarbonate generally does not exhibit the superior degradation performance of polycaprolactone structures, copolymerization can break the regularity of the soft segments. Introducing appropriate amounts of polypropylene carbonate diol or polyethylene carbonate diol as a third monomer can actually improve the degradation performance of polycaprolactone structures, thereby promoting the degradation of polypropylene carbonate diol or polyethylene carbonate diol residues and producing a relatively larger amount of carboxylic acids in the initial reaction stage.

[0042] The degradation of polyester oligomers begins with the degradation of ester groups, with the metabolic products being alcohols and carboxylic acids. Therefore, as metabolism proceeds, the environmental pH gradually becomes more acidic. The metabolism of carboxyl-based polycaprolactone oligomer diol residues is more conducive to regulating the acidic metabolic environment compared to that of polycaprolactone polyester oligomer diol residues.

[0043] Adding a certain amount of polycarbonate oligomer diol residues to the soft segment alters the regularity of polycaprolactone, reducing its crystallinity and thus increasing the biodegradation rate of the soft segment, leading to the production of more acidic metabolites. The molar ratio of carboxylated polycaprolactone oligomer diol residues to polycarbonate oligomer diol residues should be at least 2:1. Excessive introduction of polycarbonate oligomer diol residues results in excessively long polycarbonate oligomer chains, which in turn significantly reduces the material's degradation capacity, leading to slow degradation and insufficient formation of acidic metabolites. This fails to eliminate the impact of alkaline metabolites on the system's pH, preventing the system's pH from being balanced at a level conducive to bacterial growth. The molar ratio should be at most 5:1. Insufficient polycarbonate oligomer diol residues are insufficient to disrupt the chain regularity of polycaprolactone, resulting in minimal improvement in the polyurethane's biodegradability.

[0044] Beneficial effects:

[0045] (1) A biodegradable polyurethane of the present invention contains a structure in the polyurethane molecular chain that can be metabolized into acidic small molecules and a structure that can be metabolized into alkaline small molecules. By coordinating the content of the two types of structures and the degradation rate of different structures in the degradation process, the pH value of the environment is controlled, thereby improving the biodegradability of the polyurethane.

[0046] (2) A method for preparing biodegradable polyurethane according to the present invention can break the regularity of soft segments by introducing polypropylene carbonate or polyethylene carbonate copolymerized with carboxylated polycaprolactone oligomer diol, thereby improving the degradation performance of polycaprolactone structure, which in turn drives the degradation of polypropylene carbonate diol residues or polyethylene carbonate diol residues. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0048] Terms and definitions:

[0049] (1) The polyester oligomer diols mentioned are polyester diols with an index-average molecular weight of 1000 to 3000.

[0050] (2) The residues refer to the parts that enter the polymer chain after the raw materials are polymerized. For example, after HO-A-OH and NCO-B-NCO are polymerized, the parts that enter the molecular chain are -A- and -B-, respectively. The part of the polyester oligomer diol that enters the polymer chain after polymerization is called polyester oligomer diol residue. The part of the small molecule diol that enters the polymer chain is called small molecule diol residue. The part of the diisocyanate that enters the polymer chain is called diisocyanate residue.

[0051] (3) The carboxyl polycaprolactone oligomer diol is a polycaprolactone polyester oligomer diol containing carboxyl groups. It is usually polymerized by using DMPA as an initiator and caprolactone raw material as a monomer.

[0052] The test methods involved in the performance indicators in the embodiments and comparative examples of this invention are as follows:

[0053] (1) Degradation rate: According to ISO 20200:2023 Plastics - Determination of the degree of disintegration of plastic materials under simulated composting conditions in laboratory-scale testing, the test period is 100 days.

[0054] (2) Tensile strength test method: The tensile strength value of the specimen when the elongation reaches 100% shall be determined in accordance with GB / T13022-1991.

[0055] (3) Acid value: The acid value of the carboxylated polycaprolactone oligomer diol raw material was determined using HG / T 2708-1995;

[0056] (4) Viscosity: The viscosity of polyurethane was tested using a Brookfield LVT dial rotational viscometer with a No. 4 rotor, a rotation speed of 3 rpm, and a test temperature of 25℃.

[0057] Information on some raw materials used in this invention:

[0058] (1) Carboxylated polycaprolactone oligomer diol I: purchased from Perstorp HC1060, acid value 85 mg KOH / g, number average molecular weight 600.

[0059] (2) Carboxylated polycaprolactone oligomer diol II: HC1100 purchased from Perstorp, with an acid value of 53 mg KOH / g and a number-average molecular weight of 1000.

[0060] (3) Carboxylated polycaprolactone oligomer diol III: HC1200 purchased from Perstorp, with an acid value of 28 mg KOH / g and a number-average molecular weight of 2000.

[0061] (4) Polycaprolactone oligomer diol: purchased from Perstorp 2100, acid value 0.3 mg KOH / g.

[0062] (5) Polypropylene carbonate diol: purchased from Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd., brand name PPCD222, with a number average molecular weight of 2000.

[0063] (6) Polypropylene carbonate diol: purchased from Huizhou Daya Bay Dazhi Fine Chemical Co., Ltd., brand name PPCD 231, with a number average molecular weight of 3000.

[0064] (7) Polycarbonate oligomer diol: purchased from Shanghai Shuyu Chemical Co., Ltd., brand name SYPC1000, with a number average molecular weight of 1000.

[0065] (8) 3-Methyl-1,5-pentanediol (CAS No.: 4457-71-0).

[0066] (9) Dipropylene glycol (CAS No.: 25265-71-8).

[0067] (10) 1,3-Propanediol (CAS No.: 504-63-2).

[0068] (11) Methylpropanediol (CAS No.: 2163-42-0).

[0069] (12) Neopentyl glycol (CAS No.: 126-30-7).

[0070] Example 1

[0071] A method for preparing biodegradable polyurethane, comprising the following specific steps:

[0072] (1) Raw material preparation:

[0073] Polyester oligomer diols: Carboxylated polycaprolactone oligomer diol III (HC1200) and polycarbonate oligomer diol (PPCD 231) in a molar ratio of 2:1;

[0074] Catalyst: Tetrabutyl titanate;

[0075] Lysine diisocyanate;

[0076] Solvent: Ethyl acetate;

[0077] Small molecule diol: 3-methyl-1,5-pentanediol;

[0078] Terminator: Isopropanol;

[0079] (2) Add polyester oligomer diol, catalyst, lysine diisocyanate and 30% solvent to the reactor and stir at 40°C for 1 hour.

[0080] The catalyst dosage is 0.30% of the total mass of reactants excluding solvent;

[0081] (3) Raise the temperature of the system after the reaction in step (1) to 70°C, then add the small molecule diol and the remaining 70% solvent, and react until the viscosity of the system is 69.9 Pa·s / 25°C;

[0082] The molar ratio of polyester oligomer diol to small molecule diol is 7:1; the molar ratio of the total amount of polyester oligomer diol and small molecule diol to lysine diisocyanate is 1:1.0; based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, the total amount of solvent added in steps (1) and (2) is 70wt%.

[0083] (4) After the reaction in step (2) is completed, the temperature is lowered to below 60°C and a terminator is added. The reaction is carried out for 0.5 hours to obtain a biodegradable polyurethane with a viscosity of 70 Pa·s / 25°C.

[0084] The amount of terminating agent added is 0.1 wt%, based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent.

[0085] The final biodegradable polyurethane comprises a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is an isopropanol residue, and the fourth structural unit is a lysine diisocyanate residue. The first structural unit serves as the soft segment of the biodegradable polyurethane. The first and fourth structural units are linked by a urethane ester. The second and fourth structural units are linked by a urethane ester to form the hard segment of the biodegradable polyurethane. The third and fourth structural units are linked by a urethane ester to form the end group of the biodegradable polyurethane. The polyester oligomer diol residue is composed of carboxyl polycaprolactone oligomer diol residues and polycarbonate oligomer diol residues. The biodegradable polyurethane has a tensile strength of [missing information]. The tensile strength was 1.5 MPa. During the composting process, the pH of the biodegradable polyurethane system was measured to be 7.5 on day 1, with a degradation rate of 0.01%; on day 3, the pH was 7.4, with a degradation rate of 0.07%; on day 10, the pH was 7.3, with a degradation rate of 0.14%; on day 30, the pH was 7.1, with a degradation rate of 0.93%; on day 60, the pH was 6.8, with a degradation rate of 10.8%; on day 90, the pH was 6.5, with a degradation rate of 37.8%; and on day 100, the pH was 6.3, with a degradation rate of 43.8%.

[0086] Comparative Example 1

[0087] A method for preparing biodegradable polyurethane is basically the same as in Example 1, except that the polyester oligomer diol is polycaprolactone oligomer diol (2100).

[0088] The tensile strength of the prepared biodegradable polyurethane was 1.4 MPa. During the composting process, the pH of the composting system was measured to be 8 on day 1, with a degradation rate of 0%; the pH of the composting system was 7.9 on day 3, with a degradation rate of 0.001%; ​​the pH of the composting system was 7.9 on day 10, with a degradation rate of 0.002%; the pH of the composting system was 7.8 on day 30, with a degradation rate of 0.003%; the pH of the composting system was 7.8 on day 60, with a degradation rate of 0.09%; the pH of the composting system was 7.7 on day 90, with a degradation rate of 0.15%; and the pH of the composting system was 7.8 on day 100, with a degradation rate of 0.21%.

[0089] Comparative Example 2

[0090] A method for preparing biodegradable polyurethane is basically the same as in Example 1, except that the polyester oligomer diol is carboxylated polycaprolactone oligomer diol III (HC1200).

[0091] The tensile strength of the prepared biodegradable polyurethane was 1.4 MPa. During the composting process, the pH of the composting system was measured to be 7.9 on day 1, with a degradation rate of 0.003%; on day 3, the pH was 7.9, with a degradation rate of 0.005%; on day 10, the pH was 7.8, with a degradation rate of 0.01%; on day 30, the pH was 7.7, with a degradation rate of 0.04%; on day 60, the pH was 7.7, with a degradation rate of 0.21%; on day 90, the pH was 7.6, with a degradation rate of 1.01%; and on day 100, the pH was 7.6, with a degradation rate of 1.37%.

[0092] Comparative Example 3

[0093] A method for preparing biodegradable polyurethane is basically the same as in Example 1, except that carboxyl polycaprolactone oligomer diol III (HC1200) is replaced with polycaprolactone oligomer diol (2100).

[0094] The tensile strength of the prepared biodegradable polyurethane was 1.5 MPa. During the composting process, the pH of the composting system was measured to be 7.8 on day 1, with a degradation rate of 0.001%; ​​the pH of the composting system was 7.8 on day 3, with a degradation rate of 0.002%; the pH of the composting system was 7.8 on day 10, with a degradation rate of 0.006%; the pH of the composting system was 7.7 on day 30, with a degradation rate of 0.009%; the pH of the composting system was 7.7 on day 60, with a degradation rate of 0.11%; the pH of the composting system was 7.6 on day 90, with a degradation rate of 0.78%; and the pH of the composting system was 7.6 on day 100, with a degradation rate of 0.82%.

[0095] Comparing Comparative Examples 1-3 with Example 1, it was found that the biodegradable polyurethanes in Comparative Examples 1-3 had lower degradation rates. When carboxyl-based polycaprolactone oligomer diols were used instead of traditional polycaprolactone polyester oligomer diols to construct the polyurethane soft segments, the initial pH value of the environment decreased. This was because the decomposition produced a higher content of carboxyl groups in the small molecule acids, resulting in a higher acid value than that of traditional polycaprolactone polyester oligomer diols. Furthermore, when an appropriate amount of polypropylene carbonate diol or polyethylene carbonate diol was introduced as a third monomer for copolymerization, the resulting polyurethane exhibited a significantly lower pH value under the same decomposition time. In addition, experiments showed that maintaining the initial pH value below 7.5 was more conducive to bacterial growth.

[0096] Example 1 shows that by adding different types of soft segment structures to the polyurethane structure, the regularity of the polyurethane can be reduced, the proportion of crystalline segments of the polyurethane can be reduced, and water can more easily enter the interior of the polyurethane molecule. This makes it easier for the polyurethane to be hydrolyzed from large molecules into small molecules. The small molecules after hydrolysis are more easily decomposed by bacteria into water and carbon dioxide. Therefore, Example 1 has good biodegradability.

[0097] Comparative Example 4

[0098] A method for preparing biodegradable polyurethane is basically the same as in Example 1, except that the molar ratio of carboxylated polycaprolactone oligomer diol III and polycarbonate oligomer diol is 1:1.

[0099] The tensile strength of the prepared biodegradable polyurethane was 1.7 MPa. During the composting process, the pH of the composting system was measured to be 7.8 on day 1, with a degradation rate of 0.002%; on day 3, the pH was 7.8, with a degradation rate of 0.005%; on day 10, the pH was 7.8, with a degradation rate of 0.003%; on day 30, the pH was 7.7, with a degradation rate of 0.008%; on day 60, the pH was 7.7, with a degradation rate of 0.13%; on day 90, the pH was 7.6, with a degradation rate of 0.94%; and on day 100, the pH was 7.7, with a degradation rate of 1%.

[0100] Comparing Comparative Example 4 with Example 1, it can be found that the degradation rate of the biodegradable polyurethane in Comparative Example 4 is low. This is because the introduction of too many polycarbonate oligomer diol residues leads to excessively long polycarbonate oligomer residue chains, which in turn causes a serious decrease in the material's degradation ability, resulting in slow degradation. Consequently, there is insufficient acidic metabolites formed by metabolism, which cannot eliminate the impact of alkaline metabolites on the pH value of the system and cannot balance the pH value of the system to a level conducive to bacterial reproduction.

[0101] Comparative Example 5

[0102] A method for preparing biodegradable polyurethane is basically the same as in Example 1, except that the molar ratio of carboxylated polycaprolactone oligomer diol III and polycarbonate oligomer diol is 6:1.

[0103] The tensile strength of the biodegradable polyurethane was 1.3 MPa. During the composting process, the pH of the composting system was measured to be 7.7 on day 1, with a degradation rate of 0.004%; on day 3, the pH was 7.7, with a degradation rate of 0.01%; on day 10, the pH was 7.7, with a degradation rate of 0.04%; on day 30, the pH was 7.6, with a degradation rate of 0.07%; on day 60, the pH was 7.6, with a degradation rate of 0.44%; on day 90, the pH was 7.5, with a degradation rate of 5.59%; and on day 100, the pH was 7.3, with a degradation rate of 10.62%.

[0104] Comparing Comparative Example 5 with Example 1, it can be found that the degradation rate of the biodegradable polyurethane in Comparative Example 5 is low. This is because too few polycarbonate oligomer diol residues are insufficient to disrupt the chain regularity of polycaprolactone, resulting in a lack of significant improvement in the biodegradability of polyurethane.

[0105] Example 2

[0106] A method for preparing biodegradable polyurethane, comprising the following specific steps:

[0107] (1) Raw material preparation:

[0108] Polyester oligomer diols: Carboxylated polycaprolactone oligomer diol II (HC1100) and polycarbonate oligomer diol (PPCD222) in a molar ratio of 3:1;

[0109] Catalyst: Tetraisopropyl titanate;

[0110] Lysine diisocyanate;

[0111] Solvent: Butyl acetate;

[0112] Small molecule diols: Dipropylene glycol;

[0113] Terminator: Isopropanol;

[0114] (2) Add polyester oligomer diol, catalyst, lysine diisocyanate and 30% solvent into the reactor and stir at 45°C for 0.8 h.

[0115] The catalyst dosage is 2% relative to the total mass of reactants excluding solvent;

[0116] (3) Raise the temperature of the system after the reaction in step (1) to 80°C, then add small molecule diol and the remaining 70% solvent, and react until the viscosity of the system is 92.9 Pa·s / 25°C;

[0117] The molar ratio of polyester oligomer diol and small molecule diol is 7:3; the molar ratio of the total amount of polyester oligomer diol and small molecule diol to lysine diisocyanate is 1:1.02; based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, the total amount of solvent added in steps (1) and (2) is 70wt%.

[0118] (4) After the reaction in step (2) is completed, the temperature is lowered to below 60°C and a terminator is added. The reaction is carried out for 0.7 hours to obtain a biodegradable polyurethane with a viscosity of 93 Pa·s / 25°C.

[0119] The amount of terminating agent added is 0.15 wt%, based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent.

[0120] The final biodegradable polyurethane comprises a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is an isopropanol residue, and the fourth structural unit is a lysine diisocyanate residue. The first structural unit serves as the soft segment of the biodegradable polyurethane. The first and fourth structural units are linked by a urethane ester. The second and fourth structural units are linked by a urethane ester to form the hard segment of the biodegradable polyurethane. The third and fourth structural units are linked by a urethane ester to form the end group of the biodegradable polyurethane. The polyester oligomer diol residue is composed of carboxyl polycaprolactone oligomer diol residues and polycarbonate oligomer diol residues. The biodegradable polyurethane has a tensile strength of [missing information]. The tensile strength was 1.9 MPa. During the composting process, the pH of the biodegradable polyurethane system was measured to be 7.4 on day 1, with a degradation rate of 0.02%; on day 3, the pH was 7.3, with a degradation rate of 0.09%; on day 10, the pH was 7.0, with a degradation rate of 0.23%; on day 30, the pH was 6.8, with a degradation rate of 1.76%; on day 60, the pH was 6.8, with a degradation rate of 18.9%; on day 90, the pH was 6.7, with a degradation rate of 44.5%; and on day 100, the pH was 6.2, with a degradation rate of 55.4%.

[0121] Example 3

[0122] A method for preparing biodegradable polyurethane, comprising the following specific steps:

[0123] (1) Raw material preparation:

[0124] Polyester oligomer diols: Carboxylated polycaprolactone oligomer diol I (HC1060) and polycarbonate oligomer diol (PPCD222) in a molar ratio of 5:1;

[0125] Catalyst: Tetrabutyl titanate;

[0126] Lysine diisocyanate;

[0127] Solvent: Dimethyl sulfoxide;

[0128] Small molecule diols: 1,3-propanediol;

[0129] Terminator: Isopropanol;

[0130] (2) Add polyester oligomer diol, catalyst, lysine diisocyanate and 30% solvent into the reactor and stir at 50°C for 0.75 h.

[0131] The catalyst dosage is 3% relative to the total mass of reactants excluding solvent;

[0132] (3) Raise the temperature of the system after the reaction in step (1) to 90°C, then add small molecule diol and the remaining 70% solvent, and react until the viscosity of the system is 129.9 Pa·s / 25°C;

[0133] The molar ratio of polyester oligomer diol to small molecule diol is 8:2; the molar ratio of the total amount of polyester oligomer diol and small molecule diol to lysine diisocyanate is 1:1.05; based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, the total amount of solvent added in steps (1) and (2) is 70wt%.

[0134] (4) After the reaction in step (2) is completed, the temperature is lowered to below 60℃ and a terminator is added. The reaction is carried out for 1 hour to obtain a biodegradable polyurethane with a viscosity of 130 Pa·s / 25℃.

[0135] The amount of terminating agent added is 0.2 wt%, based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent.

[0136] The final biodegradable polyurethane comprises a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is an isopropanol residue, and the fourth structural unit is a lysine diisocyanate residue. The first structural unit serves as the soft segment of the biodegradable polyurethane. The first and fourth structural units are linked by a urethane ester. The second and fourth structural units are linked by a urethane ester to form the hard segment of the biodegradable polyurethane. The third and fourth structural units are linked by a urethane ester to form the end group of the biodegradable polyurethane. The polyester oligomer diol residue is composed of carboxyl polycaprolactone oligomer diol residues and polycarbonate oligomer diol residues. The biodegradable polyurethane... The tensile strength was 2.2 MPa. During the composting process, the pH of the biodegradable polyurethane system was measured to be 7.3 on day 1, with a degradation rate of 0.05%; on day 3, the pH was 7.1, with a degradation rate of 0.17%; on day 10, the pH was 6.9, with a degradation rate of 1.1%; on day 30, the pH was 6.5, with a degradation rate of 8.9%; on day 60, the pH was 6.3, with a degradation rate of 47.9%; on day 90, the pH was 6.5, with a degradation rate of 93.2%; and on day 100, the pH was 6.6, with a degradation rate of 100%.

[0137] Example 4

[0138] A method for preparing biodegradable polyurethane, comprising the following specific steps:

[0139] (1) Raw material preparation:

[0140] Polyester oligomer diols: Carboxylated polycaprolactone oligomer diol II (HC1100) and polycarbonate oligomer diol (SYPC1000) in a molar ratio of 4:1;

[0141] Catalyst: Tetraisopropyl titanate;

[0142] Lysine diisocyanate;

[0143] Solvent: A mixed solution of ethyl acetate and butyl acetate in a mass ratio of 1:1;

[0144] Small molecule diols: methylpropanediol and neopentyl glycol in a mass ratio of 1:1;

[0145] Terminator: Isopropanol;

[0146] (2) Add polyester oligomer diol, catalyst, lysine diisocyanate and 30% solvent into the reactor and stir at 60°C for 0.5 h.

[0147] The catalyst dosage is 2% relative to the total mass of reactants excluding solvent;

[0148] (3) Raise the temperature of the system after the reaction in step (1) to 100°C, then add small molecule diol and the remaining 70% solvent, and react until the viscosity of the system is 109.9 Pa·s / 25°C;

[0149] The molar ratio of polyester oligomer diol and small molecule diol is 9:3; the molar ratio of the total amount of polyester oligomer diol and small molecule diol to lysine diisocyanate is 1:1.1; based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent, the total amount of solvent added in steps (1) and (2) is 70wt%.

[0150] (4) After the reaction in step (2) is completed, the temperature is lowered to below 60°C and a terminator is added. The reaction is carried out for 0.8 hours to obtain a biodegradable polyurethane with a viscosity of 110 Pa·s / 25°C.

[0151] The amount of terminating agent added is 0.17 wt%, based on the total amount of polyester oligomer diol, small molecule diol, catalyst, lysine diisocyanate and solvent.

[0152] The final biodegradable polyurethane comprises a first structural unit, a second structural unit, a third structural unit, and a fourth structural unit. The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is an isopropanol residue, and the fourth structural unit is a lysine diisocyanate residue. The first structural unit serves as the soft segment of the biodegradable polyurethane. The first and fourth structural units are linked by a urethane ester. The second and fourth structural units are linked by a urethane ester to form the hard segment of the biodegradable polyurethane. The third and fourth structural units are linked by a urethane ester to form the end group of the biodegradable polyurethane. The polyester oligomer diol residue is composed of carboxyl polycaprolactone oligomer diol residues and polycarbonate oligomer diol residues. The biodegradable polyurethane... The tensile strength was 4.2 MPa. During the composting process, the pH of the biodegradable polyurethane system was measured to be 7.4 on day 1, with a degradation rate of 0.035%; on day 3, the pH was 7.2, with a degradation rate of 0.1%; on day 10, the pH was 6.8, with a degradation rate of 0.87%; on day 30, the pH was 6.7, with a degradation rate of 3.3%; on day 60, the pH was 6.6, with a degradation rate of 23%; on day 90, the pH was 6.4, with a degradation rate of 69.1%; and on day 100, the pH was 6.5, with a degradation rate of 81.1%.

Claims

1. A biodegradable polyurethane, characterized by: The first structural unit, the second structural unit, the third structural unit and the fourth structural unit; The first structural unit is a polyester oligomer diol residue, the second structural unit is a small molecule diol residue, the third structural unit is a small molecule mono-alcohol residue, and the fourth structural unit is a diisocyanate residue; The first structural unit is a soft segment of the biodegradable polyurethane, the first structural unit is connected with the fourth structural unit through a urethane group, the second structural unit is connected with the fourth structural unit through a urethane group to form a hard segment of the biodegradable polyurethane, and the third structural unit is connected with the fourth structural unit through a urethane group to form an end group of the biodegradable polyurethane; The molar ratio of the first structural unit to the second structural unit is 7-9:1-3; The polyester oligomer diol residue is composed of a carboxyl polycaprolactone oligomer diol residue and a polycarbonate oligomer diol residue, and the molar ratio of the carboxyl polycaprolactone oligomer diol residue to the polycarbonate oligomer diol residue is 2-5:1; The polycarbonate oligomer diol residue is a polypropylene carbonate diol residue or a polyethylene carbonate diol residue; The diisocyanate residue is a lysine diisocyanate residue; The molar ratio of the total amount of the first structural unit and the second structural unit to the fourth structural unit is 1:1.0-1.

1.

2. The biodegradable polyurethane according to claim 1, wherein, The carboxyl polycaprolactone oligomer diol residue refers to a chain segment structure that is introduced into a polymer segment after a carboxyl polycaprolactone oligomer diol with an acid value of 28-85 mgKOH / g is reacted.

3. The biodegradable polyurethane of claim 1, wherein, The small molecule diol residue is one or more of 3-methyl-1,5-pentanediol, dipropylene glycol, 1,3-propanediol, methylpropanediol and neopentyl glycol.

4. The biodegradable polyurethane of claim 1, wherein, The small molecule mono-alcohol residue is isopropyl alcohol.

5. A process for the preparation of a biodegradable polyurethane according to any one of claims 1 to 4, characterized in that The method comprises the following steps: (1) adding a polyester oligomer diol, a catalyst, a lysine diisocyanate and a part of a solvent into a reactor, stirring and reacting at 40-60℃ for 0.5-1h; (2) increasing the temperature of the system after step (1) to 70-100℃, then adding a chain extender and the remaining solvent, and reacting until the viscosity of the system is 69.9-129.9 Pa·s / 25℃; the chain extender is a small molecule diol; (3) after the reaction in step (2) is completed, cooling to below 60℃, then adding a terminating agent, and reacting for 0.5-1h to obtain a biodegradable polyurethane with a viscosity of 70-130 Pa·s / 25℃; the terminating agent is a small molecule mono-alcohol.

6. The method of claim 5, wherein the biodegradable polyurethane is prepared by reacting a diisocyanate with a diol, a diol having a hydroxyl group and a carboxyl group, or a diol having a hydroxyl group and a thiol group. The catalyst in step (1) is tetrabutyl titanate or tetraisopropyl titanate; The small molecule diol in step (2) is one or more of 3-methyl-1,5-pentanediol, dipropylene glycol, 1,3-propanediol, methylpropanediol and neopentyl glycol; The small molecule mono-alcohol in step (3) is isopropyl alcohol.

7. The method of claim 5, wherein the biodegradable polyurethane is prepared by reacting a diisocyanate with a diol in the presence of a catalyst and a chain extender. The mass ratio of the amount of the solvent added in step (1) to the amount of the solvent added in step (2) is 3:7; The solvent is one or more of ethyl acetate, butyl acetate and dimethyl sulfoxide; The amount of the solvent added is 70wt% based on the total amount of the polyester oligomer diol, the small molecule diol, the catalyst, the lysine diisocyanate and the solvent.

8. The method of claim 5, wherein the biodegradable polyurethane is prepared by reacting a diisocyanate, a diol, and a diol having a hydroxyl group and a carboxyl group. The molar ratio of the total amount of the polyester oligomer diol and the small molecule diol to the lysine diisocyanate is 1:1.0 to 1.

1.

9. The method of claim 5, wherein the biodegradable polyurethane is prepared by reacting a diisocyanate, a diol, and a diol having a hydroxyl group and a carboxyl group. The amount of the terminator added is 0.1 to 0.2 wt% based on the total amount of the polyester oligomer diol, the small molecule diol, the catalyst, the lysine diisocyanate, and the solvent.