Bio-based semi-aromatic nylon PA4T / 46 and preparation method thereof

Abstract

The invention provides a bio-based semi-aromatic nylon PA4T / 46 and a preparation method thereof, which relates to the technical field of polymer materials, and comprises the following steps: adding 1,4-butylene diamine to a mixed solution of terephthalic acid and adipic acid to prepare a PA4T / 46 salt, then prepolymerizing to obtain a prepolymer, and then solid phase thickening to obtain nylon PA4T / 46. The invention uses 1,4-butylene diamine and terephthalic acid as raw materials, and copolymerizes by adding a third monomer adipic acid, and under the condition of no catalyst, through salt formation, prepolymerization, and solid phase thickening steps, the bio-based semi-aromatic nylon PA4T / 46 is prepared. The method does not require a catalyst, and the PA4T / 46 salt formation and prepolymerization are continuously operated to prepare a high temperature resistant nylon, which has a high melting point, low water absorption, high characteristic viscosity, excellent performance, green and environmentally friendly, and can be industrially produced.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a bio-based semi-aromatic nylon PA4T / 46 and a preparation method thereof. Background Art

[0002] The polymer raw materials of semi-aromatic nylon are partly from aromatics. Due to the introduction of the rigid structure of benzene ring in the main chain, it has higher high temperature resistance, mechanical properties and lower water absorption than aliphatic nylon. At the same time, the aliphatic methylene chain structure on the main chain of the molecule makes it easier to process and shape than fully aromatic polyamide, with a higher cost performance. Its physical properties are between high temperature resistant engineering plastics and general engineering plastics, and it has better application prospects.

[0003] Foreign countries started research on the synthesis and modification of semi-aromatic nylon earlier, and have conducted a lot of research work. As early as the 1950s, Lum et al. synthesized crystalline polyamide resin MXD6 by polycondensation reaction using m-phenylenediamine and adipic acid as raw materials. As a crystalline semi-aromatic nylon, it was mainly used to produce fibers in the early stage. In industry, MXD6 is mainly used for packaging materials and engineering structural materials instead of metals. It has low water absorption, high heat deformation temperature, high tensile strength, high bending strength, small shrinkage and excellent gas barrier properties.

[0004] Semi-aromatic nylon PA4T is currently mainly produced by DSM of the Netherlands. PA4T has a melting point of up to 325°C, a glass transition temperature of 125°C, a heat deformation temperature of up to 310°C, and a relative tracking index of 600 (PLC level 0). Therefore, the moisture sensitivity level of the product can reach level 2, and its fluidity is higher than any halogen-free polyphthalamide material. In addition, PA4T has excellent dimensional stability, lead-free reflow soldering compatibility, high rigidity and high mechanical strength during high-temperature operation, as well as excellent mechanical and electronic properties.

[0005] Patent CN115819755A discloses a high-temperature nylon production method based on butanediamine, based on which pure PA4T or pure PA46 is prepared. However, the temperature resistance and mechanical properties of pure PA46 are inferior to those of PA4T, and the thermal decomposition temperature of pure PA4T is lower than its melting point, so it cannot be processed. If copolymerization modification is not performed to lower its melting point, it cannot be commercialized and promotion is also extremely difficult.

[0006] When PA4T is promoted in the market, it generally needs copolymerization modification, and the common method is copolymerization with PA66 and / or PA6 to lower the melting point. Compared with PA66 and PA6, PA46 has stronger mechanical properties, and the performance of PA46 after copolymerization with PA4T is theoretically stronger than that after copolymerization with PA66 / PA6.

[0007] At present, some patents for high-temperature resistant nylon PA4T / 46 have been disclosed in China, but there is no large-scale production of PA4T / 46 in China. The domestic patents that have been disclosed are mainly based on the development of PA6T, PA9T, and PA10T. Although PA4T / 46 is covered, the reaction conditions of these patents are not suitable for the preparation of high-viscosity, high-performance PA4T / 46. This is because the monomer 1,4-butanediamine of PA4T / 46 has poor stability and requires high reaction temperatures for salt formation, prepolymerization, and final polymerization. Excessive temperature will easily cause 1,4-butanediamine to volatilize, decompose, and cyclize. The by-products after cyclization will end the polyamide molecular chain, making it impossible to obtain high-molecular-weight high-temperature resistant nylon, and thus it is impossible to obtain high-performance nylon materials, which limits its application.

[0008] Patent CN115873236A discloses a method and system for preparing high-temperature resistant nylon by continuous polymerization. The method uses a twin-screw process to prepare high-temperature resistant nylon containing a variety of diamines and dibasic acids. However, for the PA4T series of bio-based high-temperature resistant nylon, the intrinsic viscosity of the nylon prepared by the twin-screw process used in this method is usually lower than 2.0, and high-viscosity PA4T / 6T cannot be prepared. The performance of the nylon prepared by the method is not as good as that prepared by the solid phase polycondensation method.

[0009] Patent CN118206741A discloses a method for preparing high temperature resistant nylon by discharging a high molecular weight prepolymer at normal pressure melt. Although this method can make the prepolymer discharged at normal pressure, the prepolymerization temperature reaches 230-280°C, and the prepolymerization pressure is as high as 3.0-6.5MPa. Butanediamine has poor stability and low decomposition temperature. The prepolymerization temperature is usually not higher than 230°C. Too high a prepolymerization temperature will lose a large amount of butanediamine and cause a side reaction of butanediamine cyclization. The by-product acts as a capping agent to cap the polyamide chain, making the molecular weight of the final product low, making it difficult to prepare a high molecular weight, high performance PA4T / 46 product. The prepolymerization pressure is too high, and the equipment requirements are high, and the equipment investment is large. In addition, the molecular weight of the prepolymer is strongly related to the molecular weight of the final polymer. The prepolymer with too high a molecular weight is not conducive to the formation of the high molecular weight final polymer PA4T / 46, further limiting its mechanical properties and significantly reducing the scope of use of the final product.

[0010] Patent CN115197416A discloses a continuous solid phase polycondensation method for producing high temperature resistant nylon, but its salt formation temperature is too high and is not suitable for diaminobenzene system with poor stability; catalyst / auxiliary agent needs to be added during salt formation and the salt needs to be dried and prepolymerized after salt formation, which is cumbersome and inefficient; the temperature during solid phase polycondensation and extrusion polymerization is low, which is not suitable for the preparation of high performance and high viscosity PA4T / 46.

[0011] Cao Hong Chromium prepared PA4T / 46 by low-temperature solution copolymerization. However, this method used N,N-dimethylformamide as a solvent, which is costly, polluting, and difficult to recycle. It also used adipoyl chloride and terephthaloyl chloride as raw materials. The reaction system was sensitive to water, and the operation was cumbersome and costly. The reaction produced hydrogen chloride and required the additional addition of triethylamine as an absorbent. The industrialization prospect of this process was low.

[0012] In view of this, the present invention is proposed. Summary of the invention

[0013] One of the purposes of the present invention is to provide a method for preparing bio-based semi-aromatic nylon PA4T / 46 to at least solve one of the technical problems existing in the prior art. The preparation method of the present invention does not require a catalyst or other additives. The PA4T / 46 prepared by the method has a melting point between 285 and 338°C, excellent performance, high viscosity, good mechanical properties, low production cost, and good industrialization prospects.

[0014] The second object of the present invention is to provide a bio-based semi-aromatic nylon PA4T / 46 prepared by a preparation method of bio-based semi-aromatic nylon PA4T / 46.

[0015] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0016] In a first aspect, the present invention provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, comprising the following steps:

[0017] 1,4-Butanediamine is added to a mixed solution of terephthalic acid and adipic acid to prepare PA4T / 46 salt, which is then prepolymerized to obtain a prepolymer, and then solid phase viscosity enhancement is performed to obtain nylon PA4T / 46.

[0018] Furthermore, the preparation process of the mixed solution of terephthalic acid and adipic acid includes: mixing terephthalic acid, adipic acid and a solvent to obtain a mixed solution, and then heating the mixed solution;

[0019] Preferably, the mixed solution is heated to 40°C to 60°C.

[0020] Furthermore, the adipic acid accounts for 0 to 70% of the total amount of terephthalic acid and adipic acid.

[0021] Further, the solvent includes a mixed solvent of water and alcohol;

[0022] Preferably, the alcohol includes at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0023] Furthermore, the mass ratio of water to alcohol is 0.5-120.

[0024] Furthermore, the molar ratio of 1,4-butanediamine to the sum of terephthalic acid and adipic acid is 1 to 1.1:1.

[0025] Furthermore, the preparation process of the PA4T / 46 salt further includes: after adding 1,4-butanediamine to the mixed solution, adjusting the pH value of the solution to 7.5-8.0;

[0026] Preferably, terephthalic acid and 1,4-butanediamine are used to adjust the pH of the solution.

[0027] Further, the prepolymerization includes: heating the PA4T / 46 salt solution to 105-135° C. under a nitrogen atmosphere, then heating to 205-220° C., stabilizing the pressure to 1.6-2.1 MPa, performing a prepolymerization reaction, and then exhausting the gas to obtain a prepolymer;

[0028] Preferably, the pressure of the nitrogen gas injected is 0.05-0.2 MPa;

[0029] Preferably, the concentration of the heated PA4T / 46 salt solution is 25-65%;

[0030] Preferably, the prepolymerization reaction time is 1 to 2.5 hours;

[0031] Preferably, the exhaust time is 1 to 2 hours.

[0032] Further, the solid phase viscosity enhancement includes: performing a solid phase viscosity enhancement reaction under a range of water vapor and nitrogen;

[0033] Preferably, during the solid phase viscosity increasing process, the flow rate of water vapor is 0.5 to 5 L / min, and the flow rate of nitrogen is 0.1 to 10 L / min;

[0034] Preferably, the solid phase viscosity increasing reaction pressure is less than or equal to 80Pa;

[0035] Preferably, the solid phase viscosity increasing reaction temperature is 265-285° C., and the reaction time is 6-16 hours.

[0036] In a second aspect, the present invention provides a bio-based semi-aromatic nylon PA4T / 46 prepared by the preparation method of the bio-based semi-aromatic nylon PA4T / 46.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The preparation method of bio-based semi-aromatic nylon PA4T / 46 provided by the present invention uses 1,4-diamine and terephthalic acid as raw materials, and copolymerizes by adding a third monomer adipic acid, thereby improving the fluidity of nylon, reducing the melting point of the polymer to below its decomposition temperature, and having usability. The preparation process includes three steps of nylon salt formation, prepolymerization, and solid phase viscosity enhancement, and prepares bio-based semi-aromatic nylon PA4T / 46 with high melting point, good thermal stability, good fluidity, and not easy to yellow. DETAILED DESCRIPTION

[0039] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The first aspect of the present invention provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, comprising the following steps:

[0042] 1,4-Butanediamine is added to a mixed solution of terephthalic acid and adipic acid to prepare PA4T / 46 salt, which is then prepolymerized to obtain a prepolymer, and then solid phase viscosity enhancement is performed to obtain nylon PA4T / 46.

[0043] The preparation method of bio-based semi-aromatic nylon PA4T / 46 provided by the present invention is a preparation method of high-viscosity bio-based semi-aromatic high-temperature resistant nylon PA4T / 46, which uses 1,4-diamine and terephthalic acid as raw materials, and copolymerizes by adding a third monomer 1,6-adipic acid to improve the fluidity of high-temperature resistant nylon, so that the decomposition temperature of the polymer is higher than its melting point, and has usability. The preparation process goes through three steps of nylon salt formation, prepolymerization, and solid phase viscosity enhancement, and no catalyst is required in the reaction process. Finally, a bio-based high-temperature resistant nylon with high melting point, good thermal stability, good fluidity, and not easy to yellow can be prepared, and the nylon has low water absorption, high characteristic viscosity, excellent performance, green and environmentally friendly, and can be industrially produced.

[0044] Furthermore, the present invention does not use a catalyst in the prepolymerization and solid phase polycondensation processes, which can save a certain amount of cost.

[0045] Furthermore, the 1,4-butanediamine used in the present invention is derived from biomass fermentation and is a low-carbon and environmentally friendly material, which reduces the dependence on petroleum resources. The bio-based semi-aromatic high-temperature resistant nylon PA4T / 46 based on 1,4-butanediamine monomer has great environmental significance for reducing carbon emissions.

[0046] In some preferred embodiments, the preparation process of the mixed solution of terephthalic acid and adipic acid comprises: mixing terephthalic acid, adipic acid and a solvent to obtain a mixed solution, and then heating the mixed solution;

[0047] Preferably, the mixed solution is heated to 40°C to 60°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0048] In some preferred embodiments, the adipic acid accounts for 0 to 70% of the total amount of terephthalic acid and adipic acid, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.

[0049] In some preferred embodiments, the solvent comprises a mixed solvent of water and alcohol;

[0050] Preferably, the alcohol includes at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0051] In some preferred embodiments, the mass ratio of the deionized water to the alcohol is 0.5 to 120. For example, it can be 0.5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, etc.

[0052] In the present invention, water / alcohol is selected as the solvent, and a high-temperature solution polycondensation method is adopted to replace the traditional highly polluting and highly polar nitrogen-containing organic solvent solution polycondensation method such as DMF, DEF, NMP, etc. The present invention is green, environmentally friendly, pollution-free, does not require acid absorbent and water absorbent, has low production cost, and has broad prospects for industrial production.

[0053] In some preferred embodiments, the molar ratio of 1,4-butanediamine to the sum of terephthalic acid and adipic acid is 1 to 1.1:1, for example, 1:1, 1.1:1, etc.

[0054] In some preferred embodiments, the preparation process of the PA4T / 46 salt further comprises: adding 1,4-butanediamine to the mixed solution, and adjusting the pH value of the solution to 7.5-8.0;

[0055] Preferably, terephthalic acid and 1,4-butanediamine are used to adjust the pH of the solution.

[0056] In some preferred embodiments, the prepolymerization comprises: heating the PA4T / 46 salt solution to 105-135°C, such as 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, etc., under a nitrogen atmosphere, then heating to 205-220°C, such as 205°C, 210°C, 215°C, 220°C, etc., stabilizing the pressure to 1.6-2.1 MPa, such as 1.6 MPa, 2 MPa, 2.1 MPa, etc., to carry out a prepolymerization reaction, and then exhausting the gas to obtain a prepolymer;

[0057] Preferably, the pressure of the injected nitrogen is 0.05-0.2 MPa, for example, 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, etc.;

[0058] Preferably, the concentration of the heated PA4T / 46 salt solution is 25-65%, for example, it can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, etc.;

[0059] Preferably, the prepolymerization reaction time is 1 to 2.5 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, etc.;

[0060] Preferably, the exhaust time is 1 to 2 hours, for example, 1 hour, 1.5 hours, 2 hours, etc.

[0061] In some preferred embodiments, the solid phase viscosity enhancement comprises: performing a solid phase viscosity enhancement reaction under a range of water vapor and nitrogen;

[0062] In the present invention, the addition of water vapor and nitrogen in the solid phase polycondensation process effectively reduces the degree of yellowing of the high temperature resistant nylon during the solid phase viscosity enhancement and processing process, and the reaction process effectively removes water molecules.

[0063] Preferably, during the solid phase viscosity increasing process, the flow rate of water vapor is 0.5 to 5 L / min, for example, 0.5 L / min, 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, etc., and the flow rate of nitrogen is 0.1 to 10 L / min, for example, 0.1 L / min, 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, etc.;

[0064] Preferably, the solid phase viscosity increasing reaction pressure is less than or equal to 80Pa;

[0065] Preferably, the solid phase viscosity increasing reaction temperature is 265-285°C, for example, it can be 265°C, 270°C, 275°C, 280°C, 285°C, etc., and the reaction time is 6-16h, for example, it can be 6h, 8h, 10h, 12h, 14h, 16h, etc.

[0066] Furthermore, the preparation method of the bio-based semi-aromatic nylon PA4T / 46 specifically comprises the following steps:

[0067] (1) Preparation of PA4T / 46 salt: Add terephthalic acid, adipic acid and solvent in a certain proportion into a high-pressure polymerization reactor, stir and heat the solution to 40°C to 60°C, slowly add a certain amount of 1,4-butanediamine, and then use PTA and 1,4-butanediamine to adjust the pH value of the solution to 7.5 to 8.0 as the reaction end point;

[0068] Wherein, in step (1), the total amine acid molar ratio of 1,4-butanediamine to the sum of terephthalic acid and adipic acid is 1 to 1.1:1; adipic acid accounts for 0 to 70% of the total amount of the two acids;

[0069] Wherein, the solvent is a mixed solvent of water and alcohol, and the mass ratio of water to alcohol is 0.5-120.

[0070] (2) Prepolymerization: The high-pressure polymerization kettle containing the PA4T / 46 salt solution is replaced with nitrogen. After replacement three times, nitrogen gas of 0.05-0.2 MPa is then charged into the polymerization kettle, which is stirred and heated to 105-135° C., and water is gradually removed to concentrate the mixture to a certain concentration. The mixture is then heated to 205-220° C., and the pressure in the kettle is stabilized at 1.6-2.1 MPa. The mixture is reacted for 1-2.5 hours, and then slowly exhausted. The entire exhaust process lasts for 1-2 hours to obtain a prepolymer.

[0071] Wherein, in step (2), the concentration of the PA4T / 46 salt solution is 25-65%;

[0072] (3) Solid phase viscosity enhancement: the prepolymer is placed in a solid phase viscosity enhancement reactor or a vacuum drum, the pressure is reduced to below 80 Pa, and a certain flow of water vapor and nitrogen is continuously introduced, and the reaction is carried out at 265-285°C for 6h-16h, and finally the bio-based semi-aromatic nylon PA4T / 46 is obtained;

[0073] The flow rate of water vapor is 0.5 to 5 L / min, and the flow rate of nitrogen is 0.1 to 10 L / min.

[0074] In the preparation method provided by the present invention, no catalyst is used in step (2) and step (3).

[0075] A second aspect of the present invention provides a bio-based semi-aromatic nylon PA4T / 46 prepared by a preparation method of bio-based semi-aromatic nylon PA4T / 46.

[0076] The bio-based semi-aromatic high-temperature resistant nylon PA4T / 46 material prepared by the present invention has high mechanical strength, good dimensional stability, and enhanced flowability, and solves the problem that fully aromatic nylon is not conducive to subsequent processing. The mechanical properties are stronger than those of fully aliphatic nylon, and can replace part of metal and ceramic materials.

[0077] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0078] The 1,4-butanediamine, adipic acid and terephthalic acid used in the examples and comparative examples of the present invention were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0079] The water used in the following examples is deionized water.

[0080] Example 1

[0081] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, comprising the following steps:

[0082] (1) Preparation of PA4T / 46 salt: Add terephthalic acid (1827.4 g, 11 mol), adipic acid (730.1 g, 5 mol), water (1988 g), and methanol (1988 g) into a reactor, stir and heat the solution to 50°C, slowly add a certain amount of 1,4-butanediamine (1417.45 g, 16.08 mol), and continue stirring until the system is clear. Use PTA and 1,4-butanediamine to adjust the pH value of the solution to 7.5-8.0 as the reaction end point. After the reaction solution is cooled and crystallized, it is filtered, washed, and dried to obtain PA4T / 46 salt;

[0083] (2) Prepolymerization: PA4T / 46 salt was prepared into a 50% concentration salt solution, added to a high-pressure polymerization kettle equipped with a stirring device, replaced with nitrogen three times and then filled with nitrogen at 0.1 MPa, stirred and heated the polymerization kettle to 115°C, gradually removed water and concentrated to a salt concentration of 60%, then heated to 210°C, the pressure in the kettle was stabilized at 1.8 MPa, reacted for 1.5 hours, and then slowly exhausted. The entire exhaust process lasted for 2 hours to obtain a prepolymer;

[0084] (3) Solid phase viscosity enhancement: The prepolymer is placed in a solid phase viscosity enhancement reactor or a vacuum drum, the pressure is reduced to below 80 Pa, and 1.5 L / min of water vapor and 0.5 L / min of nitrogen are continuously introduced, and the reaction is carried out at 275 ° C for 16 hours to finally obtain bio-based semi-aromatic high temperature resistant nylon PA4T / 46.

[0085] Example 2

[0086] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 1 in that only the amounts of terephthalic acid (1329 g, 8.0 mol), adipic acid (1169.12 g, 8 mol) and water (3207.24 g) in step (1) are changed.

[0087] Example 3

[0088] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 1 in that only the amounts of terephthalic acid (996.8 g, 6 mol), adipic acid (1461.4 g, 10 mol) and water (3876.7 g) in step (1) are changed.

[0089] Example 4

[0090] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which differs from embodiment 2 in that only the amount of water vapor introduced in step (3) is changed (the water vapor flow rate is 0);

[0091] The remaining steps were consistent with those in Example 2, and a bio-based semi-aromatic high temperature resistant nylon PA4T / 46 similar to that in Example 2 was obtained, but the color turned significantly yellow.

[0092] Example 5

[0093] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 2 in that only the prepolymerization temperature in step (2) is changed (the prepolymerization temperature is 230° C.);

[0094] The remaining steps are consistent with Example 2.

[0095] Example 6

[0096] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which differs from embodiment 2 in that only the polycondensation temperature in the solid phase viscosity enhancement in step (3) is changed (the polycondensation temperature is 285°C);

[0097] The remaining steps are consistent with Example 2.

[0098] Example 7

[0099] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which differs from Embodiment 2 in that: the solvent used only in step (1) is pure water (3976 g);

[0100] The remaining steps are consistent with Example 2.

[0101] Example 8

[0102] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 2 in that only the amounts of methanol (35.8 g) and water (3940.2 g) in step (1) are changed.

[0103] Example 9

[0104] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 2 in that only the amounts of methanol (2840 g) and water (1136 g) in step (1) are changed.

[0105] Example 10

[0106] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which is different from Example 2 in that only the amounts of methanol (30.4 g) and water (3953 g) in step (1) are changed.

[0107] Embodiment 11

[0108] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, comprising the following steps:

[0109] (1) Preparation of PA4T / 46 salt: Add terephthalic acid (14.4 mol), adipic acid (1.6 mol), methanol (32.9 g), and water (3943.1 g) into a reactor, stir and heat the solution to 40°C, slowly add a certain amount of 1,4-butanediamine (16 mol), and continue stirring until the system is clear. Use PTA and 1,4-butanediamine to adjust the pH value of the solution to 7.5-8.0 as the reaction end point. After the reaction solution is cooled and crystallized, it is filtered, washed, and dried to obtain PA4T / 46 salt;

[0110] (2) Prepolymerization: PA4T / 46 salt was prepared into a 20% concentration salt solution, added to a high-pressure polymerization kettle equipped with a stirring device, replaced with nitrogen three times and then filled with nitrogen at 0.05 MPa, stirred and heated the polymerization kettle to 105°C, gradually removed water and concentrated to a salt concentration of 25%, then heated to 205°C, the pressure in the kettle was stabilized at 2.1 MPa, reacted for 2.5 hours, and then slowly exhausted. The entire exhaust process lasted for 1.5 hours to obtain a prepolymer;

[0111] (3) Solid phase viscosity enhancement: The prepolymer is placed in a solid phase viscosity enhancement reactor or a vacuum drum, the pressure is reduced to below 80 Pa, and 0.5 L / min of water vapor and 10 L / min of nitrogen are continuously introduced, and the reaction is carried out at 265 ° C for 6 hours to finally obtain bio-based semi-aromatic high temperature resistant nylon PA4T / 46.

[0112] Example 12

[0113] This embodiment provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, comprising the following steps:

[0114] (1) Preparation of PA4T / 46 salt: Add terephthalic acid (4.8 mol), adipic acid (11.2 mol), methanol (2650.7 g), and water (1325.3 g) into a reactor, stir and heat the solution to 60°C, slowly add a certain amount of 1,4-butanediamine (17.6 mol), and continue stirring until the system is clear. Use PTA and 1,4-butanediamine to adjust the pH value of the solution to 7.5-8.0 as the reaction end point. After the reaction solution is cooled and crystallized, it is filtered, washed, and dried to obtain PA4T / 46 salt;

[0115] (2) Prepolymerization: PA4T / 46 salt was prepared into a 50% concentration salt solution, added to a high-pressure polymerization kettle equipped with a stirring device, replaced with nitrogen three times and then filled with nitrogen at 0.2 MPa, stirred and heated the polymerization kettle to 135°C, gradually removed water and concentrated to a salt concentration of 65%, then heated to 220°C, the pressure in the kettle was stabilized at 1.6 MPa, reacted for 1 hour, and then slowly exhausted. The entire exhaust process lasted for 1 hour to obtain a prepolymer;

[0116] (3) Solid phase viscosity enhancement: The prepolymer is placed in a solid phase viscosity enhancement reactor or a vacuum drum, the pressure is reduced to below 80 Pa, and 5 L / min of water vapor and 0.1 L / min of nitrogen are continuously introduced, and the reaction is carried out at 280 ° C for 11 hours to finally obtain bio-based semi-aromatic high temperature resistant nylon PA4T / 46.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing bio-based semi-aromatic nylon PA4T / 46, which differs from Example 2 in that: only 0.05% of the catalyst sodium hypophosphite is added in step (2);

[0119] The remaining steps are consistent with Example 2.

[0120] Comparative Example 2

[0121] This comparative example provides a preparation method of nylon PA4T / 6T, which is derived from the master's thesis of Cao Hongkui of Zhejiang University: dry N,N-dimethylacetamide and anhydrous calcium chloride are added to a three-necked flask equipped with a mechanical stirring device, and nitrogen is passed in to purge and replace the air. Repeat the purge more than 3 times to remove the relevant components in the air to avoid their interference with the experiment. The solution is heated to 70°C and stirred for 2 hours. After the calcium chloride solid is completely dissolved, an ice water bath is applied. At the same time, triethylamine and 1,4-butanediamine solution are added under nitrogen protection. After the raw materials are evenly mixed, terephthaloyl chloride and adipic acid chloride solutions are slowly added dropwise, and vigorous stirring is given at the same time. The water bath temperature is maintained at about 0°C for 30 minutes, and then it is kept at room temperature for 6 hours, and a white precipitate appears at the bottom. The solution is poured into deionized water, and all the reaction products are precipitated. The mixture was fully rinsed with methanol and acetone to remove triethylamine hydrochloride impurities and N,N-dimethylacetamide solvent residues, and the product obtained by filtration was placed in a constant temperature drying oven and dried to constant weight to obtain copolyamide PA4T / 6T.

[0122] Test samples: Bio-based semi-aromatic nylon PA4T / 46 prepared by the preparation method of bio-based semi-aromatic nylon PA4T / 46 provided in Examples 1-12 and the nylon obtained in Comparative Examples 1-2 were used as samples.

[0123] Test method:

[0124] The infrared test instrument for PA4T / 46 is Nicoleti S10 Fourier transform infrared spectrometer from Thermo Fisher Scientific.

[0125] The viscosity test adopts the sulfuric acid method: 0.125g of sample is dissolved in 25mL of 96% concentrated sulfuric acid, and the flow time t of the sample is measured by Ubbelohde viscometer in a constant temperature water bath at 25℃. The flow time of pure solvent is t0, and the ratio of t to t0 is the relative viscosity η.

[0126] The melting point test method is in accordance with the national standard GB / T 19466-2004. In a nitrogen atmosphere, 2-3 mg of the test sample is placed in an aluminum crucible. First, the temperature is increased to 350°C at a heating rate of 50°C / min to eliminate the thermal history; then, the temperature is reduced to 50°C at a cooling rate of 10°C / min; finally, the temperature is increased to 35°C at a heating rate of 10°C / min, and the melting temperature of the sample is recorded.

[0127] Conventional mechanical properties tests include tensile properties, bending properties and impact properties. The tensile properties test method is in accordance with the national standard GB / T 1040-2006; the bending properties test method is in accordance with the national standard GB / T 9341-2008.

[0128] The water absorption test is in accordance with the national standard GB / T 1034-2008.

[0129] The test results of the embodiment are shown in Table 1, and the viscosity test was performed on the products of Comparative Examples 1-2, and the test results are shown in Table 1.

[0130] Table 1

[0131]

[0132] Referring to the data in Table 1, it can be seen from the data of Examples 1 to 3 that as the content of PA4T in the product decreases, the melting point, intrinsic viscosity, tensile strength, flexural strength, and flexural modulus of the polymer gradually decrease. This is because as the content of PA4T decreases, the rigid structure of the benzene ring decreases, thereby reducing the melting point. Compared with Examples 1 to 3, the comprehensive performance of the product of Example 2 is better. In Example 1, the content of PA4T is the highest, its melting point is 338°C, and its intrinsic viscosity is 4.27. Compared with Example 1, the melting point of Example 2 at 325°C is more suitable for melt processing. The increase in the content of PA46 can significantly reduce its melting point to a more suitable melt processing temperature. In addition, the water absorption of Examples 1 to 3 gradually increases. This is because the water absorption of the nylon PA4T / 46 polymer is mainly determined by the water-absorbing amide bond density and the hydrophobic benzene ring density in the structure. In Example 1, PA4T has the highest benzene ring density, while the amide bond density is relatively reduced, so the water absorption rate is the lowest; Example 5 has the same preparation conditions as Example 2, and the only difference is the changed prepolymerization temperature. As can be seen from Table 1, the high prepolymerization temperature leads to the decline in mechanical properties of the final PA4T / 46 product of Example 5, while the water absorption rate has no obvious change; Example 6 has the same preparation conditions as Example 2, and the only difference is the different condensation temperature during solid phase viscosity increase. If the condensation temperature is too high, more amine volatilization and cyclization and other side reactions may be induced, thereby resulting in a decline in the performance of the final product. Therefore, appropriate water vapor introduction, prepolymerization temperature and final polymerization temperature play a key role in the performance of the final product; Example 7 uses a single solvent, and the intrinsic viscosity of the final PA4T / 46 is 3.73, which is significantly lower than that of Example 2. This may be because the solvent water is used as the solvent for salt formation and prepolymerization, which significantly affects the prepolymer.

[0133] Referring to the data in Table 1, the intrinsic viscosity of PA4T / 46 finally obtained in Comparative Example 1 is lower than that in Example 2. This may be because the addition of the catalyst makes the molecular weight of the prepolymer too high, which is not conducive to the final polycondensation.

[0134] In summary, the present invention provides a method for preparing a bio-based semi-aromatic high temperature resistant nylon PA4T / 6T, by adding a third monomer adipic acid for copolymerization, and then undergoing salt formation, prepolymerization, and solid phase viscosity enhancement steps to prepare a bio-based high temperature resistant semi-aromatic nylon PA4T / 46. The high temperature resistant nylon prepared by this method has a high melting point, good thermal stabilizer, low water absorption, excellent performance, green and environmentally friendly, and can be industrially produced.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing bio-based semi-aromatic nylon PA4T / 46, characterized in that: The following steps are involved: 1,4-Butanediamine is added to a mixed solution of terephthalic acid and adipic acid to prepare PA4T / 46 salt, which is then prepolymerized to obtain a prepolymer, and then solid phase viscosity enhancement is performed to obtain nylon PA4T / 46.

2. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 1, characterized in that: The preparation process of the mixed solution of terephthalic acid and adipic acid comprises: mixing terephthalic acid, adipic acid and a solvent to obtain a mixed solution, and then heating the mixed solution; Preferably, the mixed solution is heated to 40°C to 60°C.

3. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 2, characterized in that: The adipic acid accounts for 0 to 70% of the total amount of terephthalic acid and adipic acid.

4. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 2, characterized in that: The solvent includes a mixed solvent of water and alcohol; Preferably, the alcohol includes at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

5. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 4, characterized in that: The mass ratio of water to alcohol is 0.5-120.

6. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 1, characterized in that: The molar ratio of 1,4-butanediamine to the sum of terephthalic acid and adipic acid is 1 to 1.1:

1.

7. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 1, characterized in that: The preparation process of the PA4T / 46 salt further includes: adding 1,4-butanediamine to the mixed solution, and adjusting the pH value of the solution to 7.5-8.0; Preferably, terephthalic acid and 1,4-butanediamine are used to adjust the pH of the solution.

8. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 1, characterized in that: The prepolymerization comprises: heating the PA4T / 46 salt solution to 105-135° C. in a nitrogen atmosphere, then heating it to 205-220° C., stabilizing the pressure to 1.6-2.1 MPa, performing a prepolymerization reaction, and then exhausting the gas to obtain a prepolymer; Preferably, the pressure of the nitrogen gas injected is 0.05-0.2 MPa; Preferably, the concentration of the heated PA4T / 46 salt solution is 25-65%; Preferably, the prepolymerization reaction time is 1 to 2.5 hours; Preferably, the exhaust time is 1 to 2 hours.

9. The method for preparing bio-based semi-aromatic nylon PA4T / 46 according to claim 1, characterized in that: The solid phase viscosity enhancement comprises: performing a solid phase viscosity enhancement reaction under the range of water vapor and nitrogen; Preferably, during the solid phase viscosity increasing process, the flow rate of water vapor is 0.5 to 5 L / min, and the flow rate of nitrogen is 0.1 to 10 L / min; Preferably, the solid phase viscosity increasing reaction pressure is less than or equal to 80Pa; Preferably, the solid phase viscosity increasing reaction temperature is 265-285° C., and the reaction time is 6-16 hours.

10. Bio-based semi-aromatic nylon PA4T / 46 prepared by the method for preparing bio-based semi-aromatic nylon PA4T / 46 according to any one of claims 1 to 9.

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