Degradable polymer for low-temperature 3D printing, preparation method and application

Abstract

The invention discloses a degradable polymer for low-temperature 3D printing and a preparation method and application thereof.The preparation method comprises the following steps that S1, under the conditions of normal pressure and inert gas protection, long-chain binary fatty acid and long-chain binary fatty alcohol react under the action of an acid catalyst, and a first precursor is prepared; s2, reacting the first precursor prepared in the step S1 with an end group regulator under the catalytic action of metal Lewis acid to prepare a second precursor; and S3, under heating and pressure reducing conditions, removing the excessive end group regulator from the second precursor prepared in S2 to obtain the high-molecular-weight degradable polymer. The production steps are simplified, the prepared degradable polymer material has the characteristics of low-temperature melting and rapid solidification in the printing process, material degradation and performance loss caused by high temperature can be effectively avoided, meanwhile, the degradable polymer material can be degraded in the natural environment after being used, and the environmental protection requirement is met.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer synthesis, and particularly relates to a degradable polymer for low-temperature 3D printing, a preparation method and application. BACKGROUND

[0002] Low-temperature solidification high-molecular materials for 3D printing refer to high-molecular materials that can be used for 3D printing and can be solidified at a relatively low temperature. The processing of such materials is usually affected by pressure or other external conditions. The materials flow and solidify at a low temperature (e.g., not more than 100 DEG C) to be solidified and formed. Such high-molecular materials can be used in various fields. For example, in the medical field, low-temperature solidification high-molecular materials can be used for printing and manufacturing artificial organs, tissue engineering scaffolds, etc. This requires the materials to maintain good mechanical properties and biocompatibility in a low-temperature environment. For example, in the toy field, the materials are required to be able to be normally printed at a low temperature to avoid scalding children and reduce the release of harmful substances, to ensure the safety of users, and to have a low glass transition temperature below room temperature to have the ability of rapid solidification.

[0003] Currently, the low-temperature solidification materials for 3D printing are mainly polyhydroxyalkanoate polymers, such as polycaprolactone (PCL) and medium-chain-length polyhydroxyalkanoate (PHA). Both PCL and PHA have good flexibility, biodegradability and compatibility, and have been widely used in low-temperature printing fields, such as printing wires, medical stents and flexible models. However, PCL and PHA still face challenges in large-scale production, and the production cost is difficult to reduce. For example, the monomer epsilon-caprolactone of PCL is mainly synthesized by peroxoacetic acid oxidation of cyclohexanone, which has great safety hazards. In addition, the production process is complicated and the reaction time is long, resulting in low production efficiency. Moreover, the synthesis of PCL from epsilon-caprolactone relies on ring-opening polymerization, which requires very high monomer purity (> 99%). Even so, it is difficult to completely realize the conversion, and the subsequent purification process further increases the cost of the end product. Chinese patent CN119859134A discloses a method for preparing epsilon-caprolactone by peroxo acid oxidation. Inorganic acid catalyst is used to catalyze the synthesis of peracetic acid from acetic anhydride and hydrogen peroxide. The peracetic acid solution is oxidized with cyclohexanone to obtain epsilon-caprolactone crude product, which needs to be separated and purified to obtain high-purity product. Chinese patent CN1392176A discloses a cyclic ester ring-opening polymerization initiator, its preparation method and the polymerization method using the initiator. Liquid ammonia, strontium metal and epoxy alkane are used as raw materials to synthesize organic strontium compound initiator. Then, epsilon-caprolactone (CL) is used as a monomer to perform ring-opening polymerization under the catalysis of organic strontium compound to prepare polyepsilon-caprolactone. PHA is a natural polyester produced by microorganisms such as genetically engineered Escherichia coli. Therefore, the synthesis of PHA usually relies on a complex biological fermentation process, which is costly and difficult to accurately control the molecular weight and physical properties of the product. For example, Chinese patent CN113481136A discloses a recombinant halomonas and a construction method, and an application of catalyzing citric acid to prepare itaconic acid. The recombinant halomonas is used to produce P(3HB-co-4HB) by introducing the coding gene into the starting halomonas. Then, the corresponding PHA, i.e. P(3HB-co-4HB), is produced by using glucose and other carbon sources. In summary, the existing methods for preparing low-temperature solidification materials are difficult to meet the requirements of low-cost and large-scale production.

[0004] Compared with the ring-opening polymerization and biosynthesis, the melt polycondensation with easily accessible diacid and diol as raw materials is the main way for the current large-scale synthesis of polyester. In order to maintain the low-temperature solidification property, it is necessary to use long-chain diacid and long-chain diol for polycondensation reaction to construct a molecular chain similar to PCL or medium-long chain PHA structure. However, the existing transesterification method relying on low-boiling and volatile short-chain diol (such as ethylene glycol, 1,3-propanediol, 1,4-butanediol) is not suitable for the system of long-chain diol or diacid with high boiling point and difficult to volatilize. Therefore, it is currently urgent to develop a polycondensation synthesis route suitable for long-chain diacid and long-chain diol, so as to reduce the production cost of low-temperature solidification material for 3D printing and realize large-scale synthesis. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a degradable polymer for low-temperature 3D printing, a preparation method and application, which simplifies the production steps, and the prepared degradable polymer material has low-temperature melting and rapid solidification properties during the printing process, which can effectively avoid material degradation and performance loss caused by high temperature, and can be degraded in the natural environment after use, meeting the environmental protection requirements.

[0006] To achieve the above-mentioned purpose of the application, the technical solutions adopted by the present application are as follows:

[0007] In the first aspect of the present application, a preparation method of a degradable polymer for low-temperature 3D printing is provided as follows:

[0008] S1, under the conditions of normal pressure and inert gas protection, long-chain diacid reacts with long-chain diol under the action of an acidic catalyst to prepare a first precursor;

[0009] S2, the first precursor prepared in S1 reacts with an end group regulator under the catalysis of a metal Lewis acid to prepare a second precursor;

[0010] S3, under the conditions of heating and reducing pressure, the second precursor prepared in S2 is removed from the excess end group regulator to obtain a high molecular weight degradable polymer;

[0011] In step S1, the structure of long-chain diacid is as formula (I):

[0012] The structure of long-chain diol is as formula (II):

[0013] n≥p and n≥4, m≥q and m≥6, R1, R2 are independent of each other, and are both alkyl;

[0014] In step S2, the end-group regulator comprises one or more of monobasic organic acid, monobasic organic alcohol / phenol, dibasic organic acid, dibasic organic alcohol / phenol.

[0015] Preferably, the molar ratio of long-chain dibasic fatty alcohol, long-chain dibasic fatty acid and end-group regulator is (0.90-1) : (0.90-1) : (0.05-2).

[0016] Preferably, in step S1, the acid catalyst comprises one or more of hydrochloric acid, dilute sulfuric acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid.

[0017] Preferably, in step S1, the reaction temperature is 150-250℃.

[0018] Preferably, in step S2, the end-group regulator comprises one or more of monobasic organic acid, monobasic organic alcohol, dibasic organic acid, dibasic organic alcohol, wherein;

[0019] The structure of monobasic organic acid is as formula (III): R3-COOH;

[0020] The structure of monobasic organic alcohol / phenol is as formula (IV): R4-OH;

[0021] The structure of dibasic organic acid is as formula (V):

[0022] The structure of dibasic organic alcohol / phenol is as formula (VI):

[0023] Wherein, x≥k≥0 and x≤5, y>z≥0, y≤5, R3, R4, R5, R6 are independent of each other, hydrogen, alkyl or aryl.

[0024] More preferably, the end-group regulator comprises one or more of formic acid, acetic acid, phenol, benzoic acid, methanol, ethanol, benzyl alcohol, succinic acid, methyl succinic acid, glutaric acid, malonic acid, oxalic acid, ethylene glycol, p-phenol, 1,3-propanediol, 1,4-butanediol and 1,5-pentanediol.

[0025] Preferably, the reaction temperature of step S2 is 100-200℃.

[0026] Preferably, in step S2, the amount of metal Lewis acid added is 0.01-10%, and the metal Lewis acid comprises one or more of tin, antimony, scandium, titanium and corresponding halide, acetate, alcoholate. More preferably, the amount of metal Lewis acid added is 1-5%.

[0027] Preferably, in step S3, the reaction temperature is 200-300℃ and the pressure is 1-1000 Pa.

[0028] In the second aspect of the present application, the present application provides a degradable polymer for low-temperature 3D printing, which is prepared by the above preparation method.

[0029] In the third aspect of the present application, the present application provides an application of the degradable polymer for low-temperature 3D printing, which mixes the degradable polymer with additives to prepare a 3D-printed degradable product.

[0030] Beneficial effects:

[0031] The present application simplifies the production steps, uses specific long-chain binary fatty acids and long-chain binary fatty alcohols as reaction monomers, and synthesizes a polymer material which can be 3D printed under low-temperature conditions and has good mechanical properties and degradability through melt polycondensation under the catalysis of an acid catalyst and a metal Lewis acid. The polymer material has low-temperature melting and rapid solidification characteristics during the printing process, which can effectively avoid material degradation and performance loss caused by high temperature, and can be degraded in the natural environment after use, meeting the environmental protection requirements.

[0032] The present application solves the problem of difficult polycondensation of the long-chain binary fatty alcohol and long-chain dicarboxylic acid system with high boiling point and difficult volatilization by controlling the reaction steps and introducing end group regulators, which is suitable for large-scale production. The degradable polymer prepared by the present application greatly reduces the production cost while ensuring the low-temperature and efficient printing performance. The mechanical and comprehensive properties of the degradable polymer and its 3D-printed product can be flexibly adjusted by changing the preparation conditions, so as to adapt to different product use purposes. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 NMR hydrogen spectrum of the second precursor prepared for Example 1;

[0034] Figure 2 NMR hydrogen spectrum of the high molecular weight degradable polymer prepared for Example 1 and its NMR carbon spectrum;

[0035] Figure 3 NMR hydrogen spectrum of the second precursor prepared for Comparative Example 1;

[0036] Figure 4 NMR hydrogen spectrum of the degradable polymer prepared for Comparative Example 1 and its NMR carbon spectrum. DETAILED DESCRIPTION

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, specific implementations of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative effort, and other embodiments can also be obtained.

[0038] The present application provides a preparation method of degradable polymer for low-temperature 3D printing, wherein the low temperature in the low-temperature 3D printing mentioned in the present application refers to a temperature less than or equal to 100℃, more specifically, the low temperature refers to room temperature to 100℃, and the preparation method steps of the present application are as follows:

[0039] S1, under the conditions of normal pressure and inert gas protection, long-chain dibasic fatty acid and long-chain dibasic fatty alcohol react under the action of an acidic catalyst to prepare a first precursor;

[0040] S2, the first precursor prepared in S1 reacts with an end group regulator under the catalysis of a metal Lewis acid to prepare a second precursor;

[0041] S3, under the conditions of heating and reduced pressure, the second precursor prepared in S2 is removed from the excess end group regulator to obtain a high molecular weight degradable polymer;

[0042] In step S1, the structure of the long-chain dibasic fatty acid is as formula (I):

[0043] The structure of the long-chain dibasic fatty alcohol is as formula (II):

[0044] Wherein, n≥p and n≥4, m≥q and m≥6, R1, R2 are independent of each other, and are both alkyl groups.

[0045] In step S1, inert gas protection can avoid the first precursor from contacting with air to prevent the first precursor from being oxidized and yellowing. The judgment method of complete reaction in step S1 is: according to the mass of the collected by-products such as water, whether the reaction degree in S1 stage reaches the reaction degree is judged, such as the group reaction degree is not less than 90%.

[0046] Preferably, in step S1, the reaction time is 2-8h, more preferably, the reaction time is 2-4h.

[0047] Preferably, in step S1, the acidic catalyst comprises one or more of hydrochloric acid, dilute sulfuric acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid. In the present application, the specific concentration of the acidic catalyst is not limited, as long as it is a concentration capable of catalyzing the reaction, such as commercially available hydrochloric acid, dilute sulfuric acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid, which can be used at a concentration of 30% by mass.

[0048] In the present application, the amount of the acidic catalyst is determined according to the actual reaction requirements, and preferably, the amount of the acidic catalyst is 1-10% of the total mass of the long-chain dibasic fatty acid and the long-chain dibasic fatty alcohol.

[0049] Preferably, in step S1, the reaction temperature is 150-250°C, and a higher reaction temperature helps to remove the water generated in the reaction, promoting the reaction equilibrium to move in the direction of the product.

[0050] In step S2, the end group regulator can be directly added to the first precursor prepared in S1, and the first precursor can be used without purification. The reaction of the end group regulator with the first precursor is to allow the end group regulator to be located at the end of the molecular chain as much as possible. The timing of adding the end group regulator is to add the end group regulator after the reaction in S1 is sufficiently completed.

[0051] The method for determining whether the reaction in step S2 is complete is to determine whether the reaction degree in S2 reaches a certain degree according to the mass of the by-product such as water collected. For example, the reaction degree of the group is not less than 90%.

[0052] Preferably, in step S2, the reaction time is 2-4h.

[0053] Preferably, in step S2, the end group regulator comprises one or more of monobasic organic acid, monobasic organic alcohol / phenol, dibasic organic acid, and dibasic organic alcohol / phenol.

[0054] The structure of the monobasic organic acid is as shown in formula (III): R3-COOH.

[0055] The structure of the monobasic organic alcohol / phenol is as shown in formula (IV): R4-OH.

[0056] The structure of the dibasic organic acid is as shown in formula (V):

[0057] The structure of the dibasic organic alcohol / phenol is as shown in formula (VI):

[0058] wherein x≥k≥0 and x≤5, y>z≥0, y≤5, R3, R4, R5 and R6 are independently of each other hydrogen, alkyl or aryl.

[0059] More preferably, the end group regulator includes one or more of formic acid, acetic acid, phenol, benzoic acid, methanol, ethanol, benzyl alcohol, succinic acid, methyl succinic acid, glutaric acid, malonic acid, oxalic acid, ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol.

[0060] The present application notes that it is difficult to directly melt polycondense long-chain dibasic fatty acids and long-chain dibasic fatty alcohols to prepare products, and according to the principle of polycondensation reaction, in order to obtain a high molecular product, it is necessary to maintain an equimolar ratio state of both long-chain dibasic fatty acids and long-chain dibasic fatty alcohols, however, long-chain dibasic fatty acids are usually derived from bio-based raw materials, purification is difficult, and under the temperature conditions of the reaction, side reactions such as decarboxylation and etherification occur, causing the reaction system to deviate from the equimolar ratio state, in step S1 of the present application, long-chain dibasic fatty acids and long-chain dibasic fatty alcohols are preliminarily reacted to obtain a prepolymer by dehydration, which is not the final product, and in step S2, an end group regulator is added to adjust the molar ratio of fatty acids and fatty alcohols in the reaction system, and after subsequent processing, the final high molecular product can be obtained.

[0061] In the present application, the molar ratio of long-chain dibasic fatty alcohols, long-chain dibasic fatty acids, and end group regulators is (0.90-1):(0.90-1):(0.05-2). Preferably, when long-chain dibasic fatty alcohols are taken as the basis, the molar ratio of long-chain dibasic fatty alcohols, long-chain dibasic fatty acids, and end group regulators is 1:(0.90-0.99):(0.05-2), and when long-chain dibasic fatty acids are taken as the basis, the molar ratio of long-chain dibasic fatty alcohols, long-chain dibasic fatty acids, and end group regulators is (0.90-0.99):1:(0.05-2).

[0062] It should be noted that in the case of slight deviation from the equimolar ratio of long-chain dibasic fatty acids and long-chain dibasic fatty alcohols, such as a molar ratio of 1:(0.90-0.99) or (0.90-0.99):1, the chain ends of the first precursor are mainly composed of a specific group (-COOH or -OH), and precise end capping is achieved by combining the end group regulator, avoiding the chain termination effect caused by monomer excess in step S1, in addition, the presence of short chain / aryl end groups in the reaction process in step S2 can inhibit the crystallization of the product, reducing the melting temperature of the system. The present application uses an end group regulator to limit the excessive polycondensation of the product, ensuring that the molecular chain of the product is adapted to the melt flowability required for low-temperature printing.

[0063] When the end group regulator is used to modify the first precursor, a mild reaction adjustment is adopted to avoid product decomposition, and preferably, the reaction temperature of step S2 is 100-200°C.

[0064] In step S2, the amount of the metal Lewis acid added is determined according to the actual reaction requirement, preferably, the amount of the metal Lewis acid added is 0.01-10% of the total mass of the long-chain dibasic aliphatic acid and the long-chain dibasic aliphatic alcohol. More preferably, the amount of the metal Lewis acid added is 1-5% of the total mass of the long-chain dibasic aliphatic acid and the long-chain dibasic aliphatic alcohol. Preferably, the metal Lewis acid includes one or more of tin, antimony, scandium, titanium and corresponding halide, acetate and alcoholate. More preferably, the metal Lewis acid includes one or more of ethylene glycol antimony, anhydrous stannous chloride, tetraisopropyl titanate and scandium acetate.

[0065] In step S3, the reaction time is 2-8h, the reaction temperature is 200-300℃, and the pressure is 1-1000Pa. A long reaction time in step S3 can cause side reactions and darkening of the product.

[0066] The prepared degradable polymer is mixed with the additive to prepare a 3D-printed degradable product. Specifically, the degradable polymer is blended and extruded with the additive to obtain degradable product particles.

[0067] Preferably, the additive includes one or more of an inorganic filler, a coloring agent, a toughening agent, a solubilizing agent and a plasticizing agent.

[0068] In the use of the inorganic filler, the amount of the inorganic filler is 0.5-5% of the mass of the degradable polymer; in the use of the coloring agent, the amount of the coloring agent is 0.1-0.5% of the mass of the degradable polymer; in the use of the toughening agent, the amount of the toughening agent is 0.1-5% of the mass of the degradable polymer; in the use of the solubilizing agent, the amount of the solubilizing agent is 0.1-5% of the mass of the degradable polymer; and in the use of the plasticizing agent, the amount of the plasticizing agent is 0.1-5% of the mass of the degradable polymer.

[0069] More preferably, the additive includes the inorganic filler, the coloring agent, the toughening agent, the solubilizing agent and the plasticizing agent.

[0070] In the present application, the use of the inorganic filler does not negatively affect the degradable polymer and / or other additives. Specifically, the inorganic filler includes one or more of calcium carbonate, talc, titanium dioxide, silicon dioxide and barium sulfate.

[0071] In the present application, the coloring agent does not negatively affect the degradable polymer and / or other additives. Specifically, the coloring agent includes one or more of titanium dioxide, iron oxide, ultramarine, phthalocyanine and carbon black.

[0072] In the present application, the toughening agent does not negatively affect the degradable polymer and / or other additives. Specifically, the toughening agent includes one or more of polybutylene adipate terephthalate, polyethylene glycol and polypropylene glycol.

[0073] In this invention, the solubilizer does not have a negative impact on the degradable polymer and / or other additives. Specifically, the solubilizer includes one or more of γ-glycidoxypropyltrimethoxysilane, 1-butyl-3-methylimidazolium tetrafluoroborate and hexamethylene diisocyanate.

[0074] In this invention, the plasticizer does not have a negative impact on the biodegradable polymer and / or other additives. Specifically, the plasticizer includes one or more of tributyl citrate, acetylated tributyl citrate, triphenyl phosphate, and dibutyl sebacate.

[0075] The technical solution of the present invention will be described in detail below with specific embodiments.

[0076] Example 1

[0077] S1. Add 40g adipic acid, 31.697g 1,6-hexanediol and 0.037g trifluoromethanesulfonic acid to a reaction vessel, and pass inert argon gas under normal pressure for protection. Stir and heat to 200℃ for 2h to obtain the first precursor.

[0078] S2. Add 8.485g of ethylene glycol (molar ratio of adipic acid, 1,6-hexanediol, and ethylene glycol is 1:0.98:0.5) and 0.037g of antimony glycolate to the first precursor obtained in step S1 above, and stir continuously at 150℃ for 2 hours to obtain the second precursor; as shown in the attached figure. Figure 1 The nuclear magnetic resonance spectrum showed a characteristic peak of the ethylene glycol unit, the end-group regulator, at 3.63 ppm. The integration showed that the molar ratio of adipic acid, 1,6-hexanediol and ethylene glycol units in the second precursor was 1:0.98:0.5, which was the same as the feed ratio.

[0079] S3. The second precursor obtained in step S2 was vacuumed and depressurized in a reaction vessel to a final absolute pressure of 100 Pa. After stirring at 260 °C and 120 r / min for 4 h, a milky white product A1 was obtained. The results of gel permeation chromatography and melting point analysis showed that the number average molecular weight of product A1 prepared in Example 1 was 35 kDa, the molecular weight distribution was 1.9, and the melting point was 58 °C.

[0080] As attached Figure 2 The nuclear magnetic resonance spectrum integration showed that the molar ratio of adipic acid, 1,6-hexanediol and ethylene glycol units in the final biodegradable polymer was 1:0.82:0.18, that is, the ratio of alcohol and acid units in the system was 1:1. Therefore, it met the equimolar ratio of alcohol and acid required to achieve high molecular weight products.

[0081] Example 2

[0082] The preparation method of Example 1 is referred to, and the same process flow is adopted in Example 2, and the difference between the two is that 12.356 g of 1,4-butanediol is used as an end group regulator in S2 step of the present example. The product obtained in Example 2 is named as A2.

[0083] The test results show that the number average molecular weight of the product A2 prepared in Example 2 is 33 kDa, the molecular weight distribution is 1.8, and the melting point is 52°C.

[0084] Example 3

[0085] The preparation method of Example 1 is referred to, and the same process flow is adopted in Example 3, and the difference between the two is that 14.269 g of 1,5-pentanediol is used as an end group regulator in S2 step of the present example. The product obtained in Example 3 is named as A3.

[0086] The test results show that the number average molecular weight of the product A3 prepared in Example 3 is 29 kDa, the molecular weight distribution is 1.6, and the melting point is 48°C.

[0087] Example 4

[0088] The preparation method of Example 1 is referred to, and the same process flow is adopted in Example 4, and the difference between the two is that 12.336 g of oxalic acid is used as an end group regulator in S2 step of the present example. The product obtained in Example 4 is named as A4.

[0089] The test results show that the number average molecular weight of the product A4 prepared in Example 4 is 39 kDa, the molecular weight distribution is 1.9, and the melting point is 67°C.

[0090] Example 5

[0091] The preparation method of Example 1 is referred to, and the same process flow is adopted in Example 5, and the difference between the two is that 16.178 g of succinic acid is used as an end group regulator in S2 step of the present example. The product obtained in Example 5 is named as A5.

[0092] The test results show that the number average molecular weight of the product A5 prepared in Example 5 is 32 kDa, the molecular weight distribution is 1.7, and the melting point is 82°C.

[0093] Example 6

[0094] The preparation method of Example 1 is referred to, and the same process flow is adopted in Example 6, and the difference between the two is that the triflic acid in S1 step of Example 1 is replaced by p-toluenesulfonic acid in Example 6, and the product of Example 6 is marked as A6;

[0095] The test results show that the product A6 prepared in Example 6 has a number average molecular weight of 37 kDa, a molecular weight distribution of 1.8, and a melting point of 51 °C.

[0096] Example 7

[0097] Referring to the preparation method of Example 1, Example 7 adopts the same process flow as Example 1, and the difference between the two is that the antimony glycol in the S2 step of Example 1 is replaced by anhydrous stannous chloride in Example 7, and the product of Example 7 is denoted as A7.

[0098] The test results show that the product A7 prepared in Example 7 has a number average molecular weight of 41 kDa, a molecular weight distribution of 1.7, and a melting point of 52 °C.

[0099] Example 8

[0100] Referring to the preparation method of Example 1, Example 8 adopts the same process flow as Example 1, and the difference between the two is that the molar ratio of adipic acid, 1,6-hexanediol and ethylene glycol in Example 8 is 1:0.98:0.2, and the product of Example 8 is denoted as A8.

[0101] The test results show that the product A8 prepared in Example 8 has a number average molecular weight of 28 kDa, a molecular weight distribution of 1.9, and a melting point of 55 °C.

[0102] Example 9

[0103] Referring to the preparation method of Example 1, Example 9 adopts the same process flow as Example 1, and the difference between the two is that the molar ratio of adipic acid, 1,6-hexanediol and ethylene glycol in Example 9 is 1:0.98:0.4, and the product of Example 8-10 is denoted as A9.

[0104] The test results show that the product A9 prepared in Example 9 has a number average molecular weight of 31 kDa, a molecular weight distribution of 1.7, and a melting point of 56 °C.

[0105] Example 10

[0106] Referring to the preparation method of Example 1, Example 10 adopts the same process flow as Example 1, and the difference between the two is that the molar ratio of adipic acid, 1,6-hexanediol and ethylene glycol in Example 8 is 1:0.98:1, and the product of Example 10 is denoted as A10.

[0107] The test results show that the product A10 prepared in Example 10 has a number average molecular weight of 46 kDa, a molecular weight distribution of 2.1, and a melting point of 45 °C.

[0108] Example 11

[0109] The preparation process of Example 11 is the same as that of Example 1, except that the reaction temperature in Step S1 of Example 11 is 160°C, and the product of Example 11 is denoted as A11.

[0110] The test results show that the number average molecular weight of the product A11 prepared in Example 11 is 25 kDa, the molecular weight distribution is 1.4, and the melting point is 54°C.

[0111] Example 12

[0112] The preparation process of Example 12 is the same as that of Example 1, except that the reaction temperature in Step S1 of Example 12 is 180°C, and the product of Example 12 is denoted as A12.

[0113] The test results show that the number average molecular weight of the product A12 prepared in Example 12 is 30 kDa, the molecular weight distribution is 1.6, and the melting point is 53°C.

[0114] Example 13

[0115] The preparation process of Example 13 is the same as that of Example 1, except that the reaction temperature in Step S1 of Example 13 is 250°C, and the product of Example 13 is denoted as A13.

[0116] The test results show that the number average molecular weight of the product A13 prepared in Example 13 is 38 kDa, the molecular weight distribution is 1.9, and the melting point is 60°C.

[0117] Example 14

[0118] The preparation process of Example 14 is the same as that of Example 1, except that the reaction time in Step S3 of Example 14 is 2 h, and the product of Example 14 is denoted as A14.

[0119] The test results show that the number average molecular weight of the product A14 prepared in Example 14 is 26 kDa, the molecular weight distribution is 1.8, and the melting point is 55°C.

[0120] Example 15

[0121] The preparation process of Example 15 is the same as that of Example 1, except that the reaction time in Step S3 of Example 15 is 8 h, and the product of Example 15 is denoted as A15.

[0122] The test results show that the number average molecular weight of the product A15 prepared in Example 15 is 43 kDa, the molecular weight distribution is 2.4, and the melting point of the product is 62°C.

[0123] Example 16

[0124] Referring to Example 1, the preparation process of Example 16 is the same as that of Example 1, except that in Example 16, step S3 is reacted to a final absolute pressure of 50 Pa, and the product of Example 16 is denoted as A16.

[0125] Test results show that the product A16 prepared in Example 16 has a number-average molecular weight of 42 kDa, a molecular weight distribution of 1.6, and a melting point of 61°C.

[0126] Example 17

[0127] Referring to Example 1, the preparation process of Example 17 is the same as that of Example 1, except that in Example 17, step S3 is reacted to a final absolute pressure of 10 Pa, and the product of Example 17 is denoted as A17.

[0128] Test results show that the product A17 prepared in Example 17 has a number-average molecular weight of 50 kDa, a molecular weight distribution of 1.9, and a melting point of 64°C.

[0129] Comparative Example 1

[0130] S1. Add 40g adipic acid, 35.6g 1,6-hexanediol and 0.038g trifluoromethanesulfonic acid (molar ratio of adipic acid to 1,6-hexanediol is 1:1.1) to a reaction vessel, introduce inert argon gas for protection under normal pressure, stir and heat to 200℃, react at 200℃ for 2h to obtain the first precursor;

[0131] S2. Add 0.0378 g of antimony glycolate to the first precursor obtained in step S1 above, and stir continuously at 150°C for 2 hours to obtain the second precursor; as shown in the attached figure. Figure 3 The nuclear magnetic resonance spectrum integration showed that the molar ratio of adipic acid to 1,6-hexanediol units in the second precursor was 1:1.1, which was the same as the feed ratio.

[0132] S3. The first precursor obtained in step S1 was vacuumed and depressurized to 100 Pa in a reactor, and stirred at 260 °C and 120 r / min for 4 h to obtain product B1. The test results showed that the number average molecular weight of product B1 prepared from comparative example B1 was 13 kDa, the molecular weight distribution was 1.06, and the melting point was 45 °C.

[0133] As attached Figure 4 The nuclear magnetic resonance spectrum integration showed that the molar ratio of adipic acid to 1,6-hexanediol in the final biodegradable polymer was 1:1.06. Therefore, in the absence of end-group regulators, the reaction system of adipic acid and 1,6-hexanediol could not achieve the equimolar ratio of alcohol and acid required for high molecular weight products.

[0134] Comparative Example 2

[0135] S1, 40 g adipic acid, 29.4 g 1,6-hexanediol and 0.035 g trifluoromethanesulfonic acid (molar ratio of adipic acid to 1,6-hexanediol is 1:0.91) were added into a reaction kettle, inert gas argon was introduced under normal pressure for protection, stirring and heating to 200℃, reaction at 200℃ for 2 h, to obtain a first precursor;

[0136] S2, 0.035 g ethylene glycol antimony was added into the first precursor obtained in step S1, stirring at 150℃ for 2 h, to obtain a second precursor;

[0137] S3, the first precursor obtained in step S1 was vacuumed to 100 Pa in a reaction kettle, stirring at 260℃ and 120 r / min for 4 h to obtain product B2;

[0138] The test results show that the number average molecular weight of product B1 prepared by comparative example B2 is 16 kDa, the molecular weight distribution is 1.2, and the melting point is 48℃.

[0139] Comparative example 3

[0140] S1, 40 g adipic acid, 31.7 g 1,6-hexanediol and 0.036 g trifluoromethanesulfonic acid (molar ratio of adipic acid to 1,6-hexanediol is 1:0.98) were added into a reaction kettle, inert gas argon was introduced under normal pressure for protection, stirring and heating to 200℃, reaction at 200℃ for 2 h, to obtain a first precursor;

[0141] S2, 0.036 g ethylene glycol antimony was added into the first precursor obtained in step S1, stirring at 150℃ for 2 h, to obtain a second precursor;

[0142] S3, the first precursor obtained in step S1 was vacuumed to 100 Pa in a reaction kettle, stirring at 260℃ and 120 r / min for 4 h to obtain product B3;

[0143] The test results show that the number average molecular weight of product B1 prepared by comparative example B3 is 8 kDa, the molecular weight distribution is 0.95, and the melting point is 41℃.

[0144] Performance test example

[0145] Performance test example 1

[0146] The degradable polymers A1-A17 of examples 1-17 and products B1-B3 of comparative examples 1-3 were all injection molded into corresponding test strips according to a unified process, and the performance tests were carried out according to the following test standards and conditions, and the results are recorded in Table 1 below.

[0147] Tensile strength: measured according to the measurement method specified in ISO 527-2 Plastic tensile property test method, wherein the tensile rate is 50 mm / min;

[0148] Elongation at break: measured according to the measurement method specified in ISO 527-2 Plastic tensile property test method, wherein the tensile rate is 50 mm / min.

[0149] Table 1 Test results of examples 1-17 and comparative examples 1-3

[0150] Tensile strength (MPa) Elongation at break (%) A1 19.29 1851.07 A2 18.37 2173.42 A3 17.87 2668.08 A4 21.24 1573.68 A5 20.13 1193.58 A6 19.64 1953.81 A7 19.97 2085.79 A8 13.47 1486.87 A9 16.50 1791.83 A10 26.93 2861.94 A11 12.78 1149.28 A12 17.67 1671.30 A13 21.88 2239.77 A14 16.46 1669.25 A15 23.93 2567.39 A16 20.81 2471.83 A17 21.76 2731.75 B1 4.33 38.47 B2 6.16 89.51 B3 1.57 11.42

[0151] The application realizes precise regulation by end group regulator, so that the melting point of the polymer is stable at room temperature, which not only ensures that the material can be melted at a lower temperature (adapted to the printing heating demand), but also avoids the forming defects caused by too low melting point, thereby embodying the applicability to "low temperature printing"; the comparative examples lack effective regulation, and the melting point is either out of control or the performance is not matched, which further proves the key role of the melting point design in low temperature printing in the examples.

[0152] From the data of examples 1-17 in table 1, it can be seen that by selecting the end group regulator, different catalysts, molar ratios, reaction temperatures, reaction times and reaction pressures are adopted to realize the adjustment of the mechanical properties of the degradable polymer, so that the degradable polymer can be applied to different use occasions.

[0153] Among them, the data shows that the type of end group regulator has a more significant impact on the performance of the polymer, for example, in example 3, 1, 5-pentanediol is used as the end group regulator, so that the tensile strength and elongation at break of product A3 are 17.87 MPa and 2668.08%, respectively.

[0154] According to the data, the type of catalyst also has an impact on the performance of the product, but the application has certain flexibility in the selection of catalyst, and the molar ratio of the reactants has a more important influence on the structure and performance of the product, for example, in example 10, when the molar ratio of the reactant raw materials is 1:0.98:0.5, the performance of the product prepared is best.

[0155] The importance of the end group modification step is highlighted by the comparative examples. The tensile strength and elongation at break of product B3 in Comparative Example 3 are greatly reduced due to the omission of this step. At the same time, in Comparative Examples 1 and 2, the initial design ratio of long-chain di-aliphatic alcohols to long-chain di-aliphatic acids is theoretically equimolar (e.g., 1:1) or close to the theoretical equimolar ratio, but due to the decarboxylation and etherification of long-chain raw materials, the molar ratio of the actual reaction system will naturally deviate from the equilibrium; at the same time, due to the lack of the end group regulator of the present application, this deviation cannot be corrected, and the molecular weight distribution and crystallinity cannot be controlled, ultimately resulting in a product performance far lower than that of the examples. This further confirms that the synergistic optimization of various factors in the present method can synthesize degradable polymers with excellent low-temperature printing performance and mechanical properties, while the lack of key steps or improper control of conditions will greatly reduce the performance.

[0156] Compared with the ring-opening polymerization process, the synthesis method of the present application simplifies the synthesis steps, controls the reaction steps and introduces the end group regulator, solves the problem of difficult polycondensation of long-chain di-aliphatic alcohols and long-chain di-carboxylic acids with high boiling point and difficult to volatilize, reduces production cost, and promotes sustainable development of the industry. Secondly, the low-temperature degradable material prepared by the method has multiple selectivity, providing multiple choices. In general, for the prior art, the present application has the following advantages: under the premise of ensuring low-temperature printing, the polymer product of the present application has higher strength and toughness; the degradation speed in the natural environment is faster, and no special degradation conditions are required, the degradation products are harmless to the environment, and meet the requirements of sustainable development.

[0157] The above provides a detailed description of the embodiments of the present application. The principles and implementation methods of the present application are described using specific examples. The above description of the embodiments is only used to help understand the core idea of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, the present application can be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for the preparation of degradable polymers for cryogenic 3D printing, characterized in that, As follows: S1, under the conditions of normal pressure and inert gas protection, long-chain binary fatty acid and long-chain binary fatty alcohol are reacted under the action of an acidic catalyst to prepare a first precursor; S2, the first precursor prepared in S1 is reacted with an end group regulator under the catalysis of a metal Lewis acid to prepare a second precursor; S3, under the conditions of heating and reduced pressure, the second precursor prepared in S2 is subjected to removal of excess end group regulator to obtain a high-molecular-weight degradable polymer; wherein, in step S1, the long-chain dibasic fatty acid has a structure as shown in formula (I): The structure of the long-chain dihydric fatty alcohol is represented by formula (II): n≥p and n≥4, m≥q and m≥6, R1, R2 are independent of each other and are both alkyl; In step S2, the end group regulator includes one or more of monobasic organic acid, monobasic organic alcohol / phenol, dibasic organic acid, and dibasic organic alcohol / phenol.

2. The production method according to claim 1, characterized by, The molar ratio of the long-chain binary fatty alcohol, the long-chain binary fatty acid, and the end group regulator is (0.90-1):(0.90-1):(0.05-2).

3. The preparation method according to claim 1, characterized in that, In step S1, the acidic catalyst includes one or more of hydrochloric acid, dilute sulfuric acid, trifluoromethanesulfonic acid, and p-toluenesulfonic acid.

4. The method of claim 1, wherein, In step S2, the end group regulator includes one or more of monobasic organic acid, monobasic organic alcohol, dibasic organic acid, and dibasic organic alcohol, wherein; The structure of the monobasic organic acid is as formula (III): R3-COOH; The structure of the monobasic organic alcohol / phenol is as formula (IV): R4-OH; The structure of the binary organic acid is shown in formula (V): The structure of the binary organic alcohol / phenol is as formula (VI): Wherein, x≥k≥0 and x≤5, y>z≥0, y≤5, R3, R4, R5, R6 are independent of each other and are hydrogen, alkyl, or aryl.

5. The preparation method according to claim 4, characterized in that, The end group regulator includes one or more of formic acid, acetic acid, phenol, benzoic acid, methanol, ethanol, benzyl alcohol, succinic acid, methyl succinic acid, glutaric acid, malonic acid, oxalic acid, ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol.

6. The method of claim 1, wherein, In step S1, the reaction temperature is 150-250℃, and the reaction time is 2-4h; In step S2, the reaction temperature is 100-200℃, and the reaction time is 2-4h.

7. The method of any one of claims 1-6, wherein, In step S2, the addition amount of the metal Lewis acid is 0.01-10%, and the metal Lewis acid includes one or more of tin, antimony, scandium, titanium, and corresponding halide, acetate, and alcoholate.

8. The method of any one of claims 1-6, wherein, In step S3, the reaction temperature is 200-300℃, and the pressure is 1-1000Pa.

9. A degradable polymer for cryogenic 3D printing, characterized in that, Prepared by the preparation method of any one of claims 1-8.

10. Use of a degradable polymer for cryogenic 3D printing, characterized in that, The degradable polymer prepared by the preparation method of any one of claims 1-8 is mixed with an additive to prepare a 3D-printed degradable product.

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