High-temperature-resistant bio-based polyamide and controllable polymerization method and application thereof

Abstract

The application provides a high-temperature-resistant bio-based polyamide and a controllable polymerization method and application thereof, and belongs to the technical field of bio-based polymer materials. Nylon salt is mixed with water, the obtained nylon salt solution is mixed with an additive, a prepolymerization reaction is performed, and a nylon prepolymer is obtained; under the condition of a protective gas, the nylon prepolymer is subjected to solid-phase tackifying polycondensation under at least three vacuum gradient conditions in turn, and a high-temperature-resistant bio-based polyamide is obtained; the nylon salt comprises bio-based nylon 5T salt, bio-based nylon 5I salt, bio-based nylon 52 salt, bio-based nylon 56 salt and bio-based nylon 510 salt. The solid-phase tackifying polycondensation is performed under vacuum gradient conditions in turn, the controllable removal of small molecules of water in the polymerization process is realized, the high-temperature-resistant bio-based polyamide with a narrow molecular weight distribution, good color and excellent mechanical properties is beneficial to be formed, and the problems of unstable polyamide polymerization and high yellow index are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-based high molecular materials, and particularly relates to a high-temperature-resistant bio-based polyamide and a controllable polymerization method and application thereof. BACKGROUND

[0002] Polyamide, commonly known as nylon, is a kind of special engineering plastic with excellent properties such as high-temperature resistance, wear resistance, fatigue resistance, high strength and high impact resistance, and is widely used in the fields of automobile industry, electronics and electrical appliances, and mechanical manufacturing. Since the decomposition temperature of high-temperature-resistant nylon is lower than the melting point, the molding processing of high-temperature-resistant nylon is a big problem. Therefore, in order to improve the processing stability, the high-temperature-resistant nylon is generally copolymerized and modified to partially reduce the melting point of the high-temperature-resistant nylon, so as to realize the formability. Therefore, most of the commercial high-temperature-resistant nylon materials are copolymerized and modified varieties.

[0003] At present, the high-temperature-resistant nylon resin is basically prepared by using petroleum-based monomer technology, for example, the synthetic monomers butanediamine and hexanediamine are all from petroleum-based. With the continuous development of global economy, environment-friendly materials have become the focus of public concern, and low-carbon and environmentally friendly new materials from bio-based are about to become the mainstream trend.

[0004] 1,5-pentanediamine is a compound produced by enzyme-catalyzed decarboxylation of lysine, and the raw material is derived from renewable sugar-based biomass, which is a typical bio-based compound. However, due to the complexity and high cost of its biochemical synthesis method, it has not been paid attention for a long time. In recent years, with the continuous maturity of the synthesis and preparation technology of pentanediamine, its synthesis cost and purity have reached the level of petroleum-based nylon monomers such as hexanediamine. Therefore, developing bio-based high-temperature-resistant nylon 5X based on pentanediamine monomer has great practical significance for reducing carbon emissions.

[0005] At present, the high-temperature-resistant nylon is mostly prepared by two-step method, i.e. pre-polymerization and then melt or solid phase tackification. Melt tackification needs to melt the pre-polymer, and since the melting point of high-temperature-resistant polyamide is generally high, the temperature of melt tackification is generally above 300 DEG C. However, polyamide is prone to various side reactions when the temperature exceeds 280 DEG C, resulting in various color problems and black point problems of high-temperature-resistant polyamide. Solid phase tackification is usually carried out at a temperature of several tens of degrees below the melting point of the polymer, which basically eliminates the black point problem. However, solid phase tackification requires very high vacuum degree, and the equipment is generally in rotating state, and the tackification time is generally long, so it is difficult to ensure that no oxygen enters the system for a long time. In addition, since the high-temperature-resistant polyamide is generally in the form of powder, it is easy to block the vacuum pipeline in the vacuum system. The high-temperature-resistant nylon prepared by solid phase tackification usually has high yellow index, which affects the appearance of the final product and greatly limits its application.

[0006] Meanwhile, if the nylon salt is exposed to moisture during the polymerization process, the nylon material can be yellowed. The yellowing is mainly due to the decomposition of the amide bond of the nylon material at high temperature, which leads to the formation of colored peroxide and further causes yellowing. In addition, nitrogen oxides (NO x ) in the air can also cause oxidation of the nylon amino group and most hindered phenolic antioxidants to form yellow quinone structures, resulting in yellowing. Therefore, moisture control during the polymerization process is crucial to reduce the yellowing of the nylon material. SUMMARY

[0007] The present application aims to provide a high-temperature-resistant bio-based polyamide and its controllable polymerization method and application, which solves the problems of unstable polymerization and high yellow index.

[0008] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0009] The present application provides a controllable polymerization method of a high-temperature-resistant bio-based polyamide, comprising the following steps:

[0010] Mixing the nylon salt with water, mixing the obtained nylon salt solution with additives, and performing a prepolymerization reaction to obtain a nylon prepolymer;

[0011] Under the condition of a protective gas, the nylon prepolymer is subjected to solid-phase tackifying polycondensation under sequentially decreasing vacuum gradients to obtain a high-temperature-resistant bio-based polyamide;

[0012] The sequentially decreasing vacuum gradients include at least three vacuum gradients.

[0013] The nylon salt includes one or more of bio-based nylon 5T salt, bio-based nylon 5I salt, bio-based nylon 52 salt, bio-based nylon 56 salt, and bio-based nylon 510 salt.

[0014] Preferably, the mass fraction of the nylon salt in the nylon salt solution is 10-90%.

[0015] Preferably, the additives include at least one or more of a catalyst, an antioxidant, an antistatic agent, an ultraviolet-resistant agent, a weather-resistant agent, a capping agent, a nucleating agent, a flame retardant, a lubricant, and a matting agent; the amount of the additives is 0.01-1 wt.% of the total mass of the nylon salt solution.

[0016] Preferably, the temperature of the prepolymerization reaction is 200-240℃, the pressure is 1.5-2.3 MPa, and the time is 0.5-5 h.

[0017] Preferably, the protective gas includes one or more of nitrogen, argon, and carbon dioxide.

[0018] Preferably, when the vacuum gradient is sequentially reduced, the three vacuum gradients are low vacuum, medium vacuum and high vacuum, the low vacuum is 101325-3000Pa, the medium vacuum is 3000-500Pa, and the high vacuum is 500-10Pa.

[0019] Preferably, the temperature of the solid-phase adhesion-enhanced polycondensation is 220-300℃, the time is 2-15h, and the stirring speed is 20-120r / min.

[0020] The application provides a high-temperature-resistant bio-based polyamide prepared by the controllable polymerization method.

[0021] The application also provides application of the high-temperature-resistant bio-based polyamide in the automobile industry, the electronic and electrical industry or the machine manufacturing field.

[0022] Beneficial effects:

[0023] The application performs solid-phase adhesion-enhanced polycondensation under the condition of sequentially reduced vacuum gradient, in the vacuum state, the pressure of air and water vapor is reduced, and the boiling point of water is also reduced, so that water is more easily removed from the system; the vacuum gradient is sequentially reduced, so that the vacuum time and process can be strictly controlled, and the thoroughness and controllability of water removal are ensured, thereby realizing controllable removal of small-molecule water in the polymerization process, and facilitating formation of a high-temperature-resistant bio-based polyamide with narrow molecular weight distribution, good color and excellent mechanical properties, and solving the problems of unstable polyamide polymerization and high yellow index.

[0024] The application adopts a method of prepolymerization and solid-phase polymerization under sequentially reduced vacuum gradient to prepare a high-temperature-resistant bio-based polyamide, the polymerization time is short, there is no vacuum pipeline blockage phenomenon, the problems of poor appearance of products caused by the fact that the adhesion time is generally long and it is difficult to ensure that no oxygen enters the system for a long time and the high-temperature-resistant polyamide powder is easy to block the vacuum pipeline in the vacuum system are avoided, the yellow index of the obtained high-temperature-resistant polyamide is less than 15, the quality of downstream engineering plastics, film products and fiber products is greatly improved, the manufacturing cost is reduced, and the application has great industrialization prospects; the polyamide can be formed into a desired shape by using methods such as injection molding, film molding, melt spinning, blow molding, vacuum molding, etc., and can be used in, for example, injection molded products, films, sheets, monofilaments, tapes, fibers, etc., and can also be used in adhesives, coatings, etc.

[0025] Further, by limiting the concentration of the nylon salt aqueous solution, the application can also reduce the fluctuation of the solution position, reduce the probability of gel production, and facilitate black spot control. DETAILED DESCRIPTION

[0026] The application provides a controllable polymerization method of high-temperature-resistant bio-based polyamide, comprising the following steps:

[0027] The nylon salt is mixed with water, the obtained nylon salt solution is mixed with additives, a prepolymerization reaction is performed, and a nylon prepolymer is obtained;

[0028] Under the condition of a protective gas, the nylon prepolymer is subjected to solid-phase tackification polycondensation under sequentially reduced vacuum gradients, and a high-temperature-resistant bio-based polyamide is obtained;

[0029] The sequentially reduced vacuum gradients comprise at least three vacuum gradients;

[0030] The nylon salt comprises one or more of a bio-based nylon 5T salt, a bio-based nylon 5I salt, a bio-based nylon 52 salt, a bio-based nylon 56 salt and a bio-based nylon 510 salt.

[0031] In the application, the nylon salt is mixed with water, the obtained nylon salt solution is subjected to a prepolymerization reaction, and a nylon prepolymer is obtained; the preparation of the nylon salt is not specially limited in the application, and the preparation methods known in the art can be used. In the examples of the application, the preparation method of the nylon salt is specifically as follows: under the condition of normal pressure and a protective atmosphere, bio-based diacid is dissolved in a solvent at 50-100 DEG C to prepare an acid solution with a mass fraction of 30-80%; bio-based diamine is dissolved in the same solvent at 50-100 DEG C to prepare an amine solution with a mass fraction of 30-80%; under the stirring condition of a rotation speed of 200-300 r / min, the amine solution is added to the acid solution, the molar ratio of amine groups to carboxyl groups is 1-1.1:1, the temperature is kept at 40-90 DEG C, the stirring is continuously performed for 0.5-2 h, the obtained mixed solution is cooled to 0-20 DEG C, is left standing for 1-4 h, and crystals are precipitated, and after filtration, washing and drying, the bio-based nylon salt is obtained. The gas used in the protective atmosphere is preferably at least one of nitrogen, argon, helium and carbon dioxide, is further preferably at least one of nitrogen, argon and helium, and is more preferably one of nitrogen and argon; the bio-based diacid and the bio-based diamine are not limited in the application, and can be prepared into the bio-based nylon salt; in the examples of the application, the bio-based diacid is preferably one of terephthalic acid, isophthalic acid, adipic acid, oxalic acid or sebacic acid, and the bio-based diamine is preferably pentanediamine; and the solvent is preferably pure water or anhydrous ethanol.

[0032] Preferably, the nylon salt is put into a 20L stainless steel high-pressure reaction kettle, water is added, the air in the kettle is replaced with nitrogen for 5 times, the nylon salt is completely dissolved under the condition of 70-90 DEG C and 0.5 MPa protective atmosphere and stirring for 1-2 h, a nylon salt solution is prepared, and a prepolymerization reaction is performed.

[0033] In the present application, the mass fraction of the nylon salt in the nylon salt solution is preferably 10-90%, further preferably 20-80%, and more preferably 30-70%. Adjusting the concentration of the nylon salt solution is conducive to controlling black spots, because the reduction of solution position fluctuation reduces the probability of gel production. However, too high a concentration is not conducive to the stability of the oxygen control base solution, and too low a concentration results in high energy consumption, low equipment utilization, and large concentration liquid level difference, which is not conducive to black spot control.

[0034] In the present application, the additive preferably includes at least one or several of a catalyst, an antioxidant, an antistatic agent, a weathering agent, a capping agent, a nucleating agent, a flame retardant, and a matting agent, and further preferably includes a catalyst, an antioxidant, and a capping agent. The amount of the additive is preferably 0.01-1 wt.% of the total mass of the nylon salt solution. The catalyst preferably includes anhydrous sodium hypophosphite, anhydrous potassium hypophosphite, anhydrous sodium phosphite, and / or anhydrous potassium phosphite, etc. The antioxidant preferably includes a hindered phenolic antioxidant (1010, 1076) and an amine antioxidant (naphthylamine, diphenylamine). The antistatic agent preferably includes a quaternary phosphonium salt type cationic antistatic agent, a quaternary ammonium salt type cationic antistatic agent, and / or an alkyl sulfate type anionic antistatic agent, etc. The weathering agent preferably includes a benzenediol compound, a benzotriazole compound, and / or a benzophenone compound. The capping agent preferably includes acetic acid, hexanoic acid, benzoic acid, and / or hexylamine. The nucleating agent preferably includes inorganic microparticles such as silicon dioxide, clay, and boron nitride, and / or high-melting-point nylon and metal oxides. The flame retardant preferably includes magnesium hydroxide, brominated polystyrene, brominated polycarbonate, and / or ammonium polyphosphate, etc. The matting agent preferably includes titanium dioxide and other inorganic substances.

[0035] In the present application, the temperature of the prepolymerization reaction is preferably 200-240°C, and further preferably 220-240°C. The pressure is preferably 1.5-2.3 MPa, and further preferably 1.7-2 MPa. The time is preferably 0.5-5 h, and further preferably 1-4 h.

[0036] In the present application, after the prepolymerization reaction is completed, the pressure is reduced to 0.001 MPa to remove more than 98% of the water in the system. After cooling, a nylon prepolymer is obtained.

[0037] In the present application, the nylon prepolymer is subjected to solid-phase thickening polycondensation under gradually decreasing vacuum gradient conditions under protective gas conditions to obtain a high-temperature-resistant bio-based polyamide; preferably, the nylon prepolymer is added to a solid-phase thickening device, heated to 240-270℃ under stirring at 0.5 MPa for 1-15 h, the valve is opened to slowly release gas for 1 h to reduce the pressure to normal pressure, and then a stage vacuum pumping method is used to keep each step under gradually decreasing vacuum gradient conditions for 10-30 min to obtain the high-temperature-resistant bio-based polyamide; the pressure holding and temperature rising are limited to make the gas and water vapor in the water system more easily volatilize, so that the small molecular water can be removed by subsequent vacuum method; on the other hand, it is to promote the accumulation of some small particle nylon prepolymers during heating to avoid being pumped away and clogging the pipeline.

[0038] Before the solid-phase thickening polycondensation, the solid-phase thickening device is preferably subjected to protective gas replacement, which is preferably achieved by repeatedly pumping vacuum and then filling protective gas or by pressurizing the protective gas and then releasing it to normal pressure; the protective gas preferably includes one or more of nitrogen, argon and carbon dioxide.

[0039] In the present application, when the gradually decreasing vacuum gradient includes three vacuum gradients, the three vacuum gradients are preferably low vacuum degree, medium vacuum degree and high vacuum degree; the low vacuum degree is preferably 101325-3000 Pa, further preferably 8000-3000 Pa, and more preferably 5000-3000 Pa, the vacuum degree being expressed in absolute pressure value; the medium vacuum degree is preferably 3000-500 Pa, further preferably 2000-500 Pa, and more preferably 1000-500 Pa, the vacuum degree being expressed in absolute pressure value; the high vacuum degree is preferably 500-10 Pa, further preferably 100-10 Pa, and more preferably 50-10 Pa, the vacuum degree being expressed in absolute pressure value.

[0040] In the present application, the temperature of the solid-phase thickening polycondensation is preferably 220-300℃, the time is preferably 2-15 h, and the stirring speed is preferably 20-120 r / min, further preferably 40-100 r / min, and more preferably 50-80 r / min.

[0041] The present application provides a high-temperature-resistant bio-based polyamide prepared by the controllable polymerization method described in the above technical solution, and the yellow index of the high-temperature-resistant bio-based polyamide is preferably less than 15, and further preferably less than 10.

[0042] The present application also provides applications of the above high-temperature-resistant bio-based polyamide in the fields of automobile industry, electronic appliances or machine manufacturing.

[0043] The technical solutions provided by the application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the application.

[0044] Example 1

[0045] Under the condition of normal pressure and nitrogen purging, 319.43 g of terephthalic acid was dissolved in pure water at 80℃ to obtain a turbid terephthalic acid suspension with a mass fraction of 60%; 203.17 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 40%; the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 300 r / min, the temperature was maintained at 80℃, and the stirring was continued for 2 h to obtain a mixed solution; the mixed solution was cooled to 10℃, and was allowed to stand for 3 h to precipitate crystals, which were filtered, washed, and dried to obtain nylon 5T salt; according to the above reaction steps, nylon 56 salt was prepared by using adipic acid and pentanediamine as the reaction monomers; 951.45 g of the dried nylon 5T salt and the nylon 56 salt (molar ratio 1:1) were put into a 20 L stainless steel high-pressure reaction kettle, a certain amount of pure water was added to make the mass fraction of the nylon salt 60%, 0.15 wt.% of anhydrous sodium hypophosphite and 0.05 wt.% of antioxidant 1010 were further added, the kettle was replaced with nitrogen for 5 times, and the nylon salt was completely dissolved by stirring at 80℃ under a protective atmosphere of 0.5 MPa for 1.5 h; pre-polymerization was carried out at 220℃ and 1.7 MPa for 2 h, then the pressure was reduced to 0.001 MPa, so that more than 98% of the water in the system was discharged, and the nylon 5T / 56 pre-polymer was obtained after cooling;

[0046] The nylon 5T / 56 pre-polymer was added to a solid-phase tackifying device, the kettle was replaced with nitrogen for 5 times, and the temperature was increased to 250℃ by heating and stirring at a rotation speed of 50 r / min under a pressure of 0.5 MPa, and then the reaction was carried out for 5 h, the valve was slowly opened for 1 h to reduce the pressure to normal pressure, and then a stage vacuum pumping method was adopted, the vacuum degrees (absolute pressure values) were 80000 Pa, 2000 Pa and 100 Pa respectively, and the polymerization temperature was 250℃, each for 10 min, to obtain a high-temperature-resistant bio-based polyamide.

[0047] Example 2

[0048] 326.31 g of isophthalic acid was dissolved in pure water at 80 °C to obtain a turbid isophthalic acid suspension with a mass fraction of 50%; 215.41 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 50%; the clear pentanediamine solution was added to the isophthalic acid solution at a rotation speed of 250 r / min, the temperature was maintained at 80 °C, and stirring was continued for 2 h to obtain a mixed solution; the mixed solution was cooled to 5 °C and stood for 3 h to precipitate crystals, which were filtered, washed, and dried to obtain nylon 5I salt; according to the above reaction steps, nylon 56 salt was prepared using adipic acid and pentanediamine as the reaction monomers; 966.14 g of the dried nylon 5I salt and nylon 56 salt (molar ratio 1:1) were placed in a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 60%, 0.3 wt.% of anhydrous sodium hypophosphite and 0.5 wt.% of the end-capping agent benzoic acid were added, the autoclave was replaced with nitrogen 5 times, and the nylon salt was completely dissolved by stirring at 75 °C under a 0.5 MPa protective atmosphere for 1.5 h; pre-polymerization was carried out at 230 °C and 2 MPa for 3 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and a nylon 5I / 56 pre-polymer was obtained after cooling.

[0049] The nylon 5I / 56 pre-polymer was added to a solid-phase tackifier device, the autoclave was replaced with nitrogen 5 times, and then the temperature was increased to 260 °C under stirring at 80 r / min under a pressure of 0.5 MPa, and the reaction was carried out for 2 h, the valve was opened to slowly release the gas for 1 h to reduce the pressure to normal pressure, and then a stage vacuum was used, the vacuum degrees (absolute pressure values) were 10000 Pa, 3000 Pa, and 400 Pa, respectively, the polymerization temperature was 260 °C, and each was maintained for 30 min to obtain a high-temperature-resistant bio-based polyamide.

[0050] Example 3

[0051] 348.35 g of terephthalic acid was dissolved in pure water at 70 °C to obtain a turbid terephthalic acid suspension with a mass fraction of 50%; 226.78 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 50%; the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 200 r / min, the temperature was maintained at 70 °C, and stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 10 °C, and was allowed to stand for 4 h to precipitate crystals, which were filtered, washed, and dried to obtain nylon 5T salt; nylon 52 salt was prepared according to the above reaction steps using oxalic acid and pentanediamine as the reaction monomers; a total of 948.31 g of the dried nylon 5T salt and the nylon 52 salt (molar mass ratio 1:1) was placed in a 20 L stainless steel autoclave, a certain amount of pure water was added to obtain a nylon salt with a mass fraction of 50%, 0.5 wt.% of anhydrous sodium hypophosphite and 1 wt.% of a capping agent adipic acid were added, the autoclave was replaced with argon 5 times, the nylon salt was completely dissolved by stirring at 70 °C under a protective atmosphere of 0.5 MPa for 2 h; pre-polymerization was performed at 220 °C and 1.8 MPa for 1 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and a nylon 5T / 52 pre-polymer was obtained after cooling.

[0052] The nylon 5T / 52 pre-polymer was added to a solid-phase tackifier device, the autoclave was replaced with argon 5 times, and then the temperature was increased to 250 °C by heating and stirring at 100 r / min under a pressure of 0.5 MPa, and reaction was performed for 8 h, the valve was opened and the pressure was slowly released to normal pressure for 1 h, then a stage vacuum was applied, the vacuum degrees (absolute pressure values) were 6000 Pa, 1000 Pa, and 100 Pa, respectively, the polymerization temperature was 250 °C, and each was maintained for 10 min, to obtain a high-temperature-resistant bio-based polyamide.

[0053] Example 4

[0054] Under the condition of normal pressure and argon purging, 323.48 g of isophthalic acid was dissolved in pure water at 60 °C to obtain a turbid isophthalic acid suspension with a mass fraction of 40%; 212.47 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 60%; then the clear pentanediamine solution was added to the isophthalic acid solution at a rotation speed of 300 r / min, the temperature was maintained at 60 °C, and stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 15 °C and stood for 3 h, and crystals were precipitated, which were filtered, washed, and dried to obtain nylon 5I salt; according to the above reaction steps, oxalic acid and pentanediamine were used as reaction monomers to obtain nylon 52 salt; 963.52 g of dried nylon 5I salt and nylon 52 salt (molar mass ratio 1:1) were put into a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 80%, 0.01 wt.% of anhydrous sodium hypophosphite and 0.1 wt.% of antioxidant 1076 were added, the autoclave was replaced with argon 5 times, the nylon salt was completely dissolved by stirring at 90 °C under a protective atmosphere of 0.5 MPa for 1 h; pre-polymerization was carried out at 210 °C and 2.2 MPa for 5 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and the nylon 5I / 52 pre-polymer was obtained after cooling.

[0055] The nylon 5I / 52 pre-polymer was added to a solid-phase tackifier device, the autoclave was replaced with argon 5 times, and then the temperature was increased to 270 °C under stirring at 120 r / min and a pressure of 0.5 MPa, and the reaction was carried out for 8 h, the valve was slowly opened for 1 h to reduce the pressure to normal pressure, and then a stage vacuum was used, the vacuum degrees (absolute pressure values) were 4000 Pa, 2000 Pa and 80 Pa respectively, the polymerization temperature was 270 °C, and each was maintained for 20 min to obtain a high-temperature-resistant bio-based polyamide.

[0056] Example 5

[0057] 311.04 g of terephthalic acid was dissolved in pure water at 80 °C to obtain a turbid terephthalic acid suspension with a mass fraction of 50%; 200.75 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 50%; then the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 200 r / min, the temperature was maintained at 80 °C, and stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 10 °C and stood for 2 h, and crystals were precipitated, which were filtered, washed, and dried to obtain nylon 5T salt; according to the above reaction steps, decanedioic acid and pentanediamine were used as reaction monomers to obtain nylon 510 salt; 962.81 g of the dried nylon 5T salt and nylon 510 salt (molar mass ratio 1:1) were put into a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 70%, 0.3 wt.% of anhydrous sodium hypophosphite and 0.1 wt.% of antioxidant naphthylamine were added, the autoclave was replaced with nitrogen 5 times, and the nylon salt was completely dissolved by stirring at 70 °C under a protective atmosphere of 0.5 MPa for 2 h; pre-polymerization was carried out at 240 °C and 2.3 MPa for 0.5 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and the nylon 5T / 510 prepolymer was obtained after cooling.

[0058] The nylon 5T / 510 prepolymer was added to a solid-phase tackifying device, the autoclave was replaced with nitrogen 5 times, and then the temperature was increased to 260 °C under stirring at 40 r / min under a pressure of 0.5 MPa, and then the valve was opened and the gas was slowly released for 1 h to reduce the pressure to normal pressure, and then a stage vacuum was used, the vacuum degrees (absolute pressure values) were 4000 Pa, 800 Pa and 100 Pa, respectively, and the polymerization temperature was 260 °C, and each was maintained for 20 min to obtain a high-temperature-resistant bio-based polyamide.

[0059] Example 6

[0060] 304.82 g of isophthalic acid was dissolved in pure water at 70 °C to obtain a turbid isophthalic acid suspension with a mass fraction of 60% under the condition of normal pressure and nitrogen purging; 197.48 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 40%; the clear pentanediamine solution was added to the isophthalic acid solution at a rotation speed of 200 r / min, the temperature was maintained at 70 °C, and stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 10 °C, and was allowed to stand for 4 h to precipitate crystals, which were filtered, washed, and dried to obtain nylon 5I salt; according to the above reaction procedure, decanedioic acid and pentanediamine were used as reaction monomers to obtain nylon 510 salt; 959.03 g of the dried nylon 5I salt and nylon 510 salt (molar mass ratio 1:1) were put into a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 50%, 0.4 wt.% of anhydrous sodium hypophosphite and 0.6 wt.% of a blocking agent hexylamine were added, the autoclave was replaced with nitrogen 5 times, and the nylon salt was completely dissolved by stirring at 70 °C under a protective atmosphere of 0.5 MPa for 2 h; pre-polymerization was carried out at 220 °C and 2.2 MPa for 4 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and a nylon 5I / 510 pre-polymer was obtained after cooling.

[0061] The nylon 5I / 510 pre-polymer was added to a solid-phase tackifier device, the autoclave was replaced with nitrogen 5 times, and the temperature was increased to 260 °C under stirring at 20 r / min under a pressure of 0.5 MPa, and then the reaction was carried out for 8 h, the valve was opened to slowly release the gas for 1 h to reduce the pressure to normal pressure, and then a stage vacuum was used, the vacuum degrees (absolute pressure values) were 5000 Pa, 1000 Pa, and 10 Pa, respectively, the polymerization temperature was 260 °C, and each was maintained for 30 min to obtain a high-temperature-resistant bio-based polyamide.

[0062] Example 7

[0063] The 341.07 g of terephthalic acid was dissolved in pure water at 50 °C to obtain a turbid terephthalic acid suspension with a mass fraction of 40% under the condition of normal pressure and nitrogen purging; 219.20 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 60%; the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 300 r / min, the temperature was maintained at 50 °C, and the stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 20 °C, and the crystallization was precipitated after standing for 2 h; after filtration, washing, and drying, the nylon 5T salt was obtained; the nylon 5I salt was prepared according to the above reaction steps using isophthalic acid and pentanediamine as the reaction monomers; the dried nylon 5T salt and the nylon 5I salt (molar mass ratio 1:1) with a total amount of 955.20 g were put into a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 50%, and then 0.5 wt.% of anhydrous sodium hypophosphite, 0.09 wt.% of the antioxidant diphenylamine, and 0.8 wt.% of the end-capping agent benzoic acid were added; the autoclave was replaced with nitrogen 5 times, the nylon salt was completely dissolved by stirring at 70 °C under a protective atmosphere of 0.5 MPa for 2 h; the pre-polymerization was carried out at 220 °C under 1.5 MPa for 3 h, and then the pressure was reduced to 0.001 MPa, so that more than 98% of the water in the system was discharged, and the nylon 5T / 5I pre-polymer was obtained after cooling.

[0064] The nylon 5T / 5I pre-polymer was added to a solid-phase tackifier device, the autoclave was replaced with nitrogen 5 times, and then the temperature was increased to 240 °C by heating and stirring at 100 r / min under a pressure of 0.5 MPa, and the reaction was carried out for 15 h; the valve was opened and the gas was slowly released for 1 h to reduce the pressure to normal pressure, and then the vacuum was extracted in stages, the vacuum degrees (absolute pressure values) were 3000 Pa, 600 Pa, and 20 Pa, respectively, the polymerization temperature was 240 °C, and each was maintained for 20 min to obtain a high-temperature-resistant bio-based polyamide.

[0065] Example 8

[0066] The terephthalic acid was dissolved in pure water at 80°C to obtain a 50% by mass turbid terephthalic acid suspension; the pentanediamine was dissolved in pure water to obtain a 50% by mass clear pentanediamine solution; the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 300 r / min, the temperature was maintained at 80°C, and the stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 10°C, and was allowed to stand for 4 h to precipitate crystals, which were filtered, washed, and dried to obtain nylon 5T salt; the nylon 56 salt was prepared according to the above reaction procedure using adipic acid and pentanediamine as the reaction monomers; the dried nylon 5T salt and nylon 56 salt (molar mass ratio 1:1) were added to a 20 L stainless steel autoclave, a certain amount of pure water was added to obtain an 80% by mass nylon salt, 0.7% by weight of anhydrous sodium hypophosphite was added, the autoclave was replaced with carbon dioxide 5 times, the nylon salt was completely dissolved by stirring at 80°C and 0.5 MPa for 2 h; the prepolymerization was performed at 240°C and 2.2 MPa for 1 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, to obtain a nylon 5T / 56 prepolymer after cooling;

[0067] The nylon 5T / 56 prepolymer was added to a solid-phase tackifier device, the autoclave was replaced with carbon dioxide 5 times, the temperature was increased to 240°C by heating at a rotation speed of 50 r / min under a pressure of 0.5 MPa, and the reaction was continued for 10 h, the valve was opened, and the pressure was slowly released to normal pressure for 1 h, then a stage vacuum was applied, the vacuum degrees (absolute pressure values) were 3000 Pa, 500 Pa, and 40 Pa, respectively, the polymerization temperature was 240°C, and each was maintained for 10 min, to obtain a high-temperature-resistant bio-based polyamide.

[0068] Comparative Example 1

[0069] Under the condition of normal pressure and nitrogen purging, 314.70 g of terephthalic acid was dissolved in pure water at 80°C to obtain a turbid terephthalic acid suspension with a mass fraction of 50%; 202.53 g of pentanediamine was dissolved in pure water to obtain a clear pentanediamine solution with a mass fraction of 50%; then the clear pentanediamine solution was added to the terephthalic acid solution at a rotation speed of 200 r / min, the temperature was maintained at 80°C, and stirring was continued for 1 h to obtain a mixed solution; the mixed solution was cooled to 10°C, and crystals were precipitated after standing for 2 h; after filtration, washing, and drying, nylon 5T salt was obtained; according to the above reaction steps, decanedioic acid and pentanediamine were used as reaction monomers to obtain nylon 510 salt; a total of 966.29 g of the dried nylon 5T salt and the nylon 510 salt (molar mass ratio 1:1) was put into a 20 L stainless steel autoclave, a certain amount of pure water was added to make the mass fraction of the nylon salt 70%, 0.3 wt.% of anhydrous sodium hypophosphite and 0.1 wt.% of the antioxidant naphthylamine were added, the autoclave was replaced with nitrogen 5 times, and the nylon salt was completely dissolved by stirring at 70°C under a protective atmosphere of 0.5 MPa for 2 h; pre-polymerization was carried out at 240°C and 2.3 MPa for 0.5 h, then the pressure was reduced to 0.001 MPa, and more than 98% of the water in the system was discharged, and after cooling, a nylon 5T / 510 prepolymer was obtained;

[0070] The nylon 5T / 510 prepolymer was added to a solid-phase tackifying device, the autoclave was replaced with nitrogen 5 times, and then the temperature was increased to 260°C by heating and stirring at a rotation speed of 40 r / min under a pressure of 0.5 MPa, and then the reaction was carried out for 15 h; the valve was slowly opened to release the gas for 1 h to reduce the pressure to normal pressure, and then the vacuum degree (absolute pressure value) was 50 Pa, the polymerization temperature was 260°C, and the system was maintained for 20 min to obtain a high-temperature-resistant bio-based polyamide.

[0071] Performance test

[0072] The relative molecular weight (Mw), polydispersity index, relative viscosity, melting point, initial decomposition temperature, yellow index, and tensile strength of the high-temperature-resistant bio-based polyamides prepared in Examples 1-8 and Comparative Example 1 were determined, and the test results are recorded in Table 1, and the test methods are as follows:

[0073] 1. Weight average molecular weight and polydispersity index

[0074] The molecular weight and distribution were tested by gel permeation chromatography (GPC), the mobile phase was hexafluoroisopropanol, and the detector was RI-UV;

[0075] 2. Relative viscosity

[0076] The high-temperature-resistant bio-based polyamide after drying is weighed and dissolved in 96% concentrated sulfuric acid to prepare a solution with a mass concentration of 0.01 g / mL, and the time for the liquid to flow through two scale lines of the Ubbelohde viscometer glass ball is tested in a constant-temperature water bath at 25±0.02℃, and the test is repeated three times, the difference between the three test values is not more than 0.1 s, and the average value is taken; the ratio of the polyamide solution flow-out time t2 to the pure solvent flow-out time t1 is the relative viscosity, and the relative viscosity of the sample is calculated according to the formula η=t2 / t1;

[0077] 3. Melting point

[0078] Under the condition of a nitrogen flow rate of 50 mL / min, the temperature is increased to 350℃ at a temperature increase rate of 10℃ / min, kept constant for 3 min, then decreased to room temperature, and then increased to 350℃ again, and the endothermic peak temperature of the second melting curve is set as the melting point;

[0079] 4. Decomposition temperature

[0080] Under the condition of nitrogen, the temperature increase rate is 10℃ / min, the temperature is set to 30℃ to 800℃, and the initial decomposition temperature is determined by using thermal gravimetric analysis (TGA);

[0081] 5. Yellow index

[0082] The yellow index is determined according to the method of HG / T 3862-2006;

[0083] 6. Tensile properties

[0084] Under the condition of a temperature of 25℃ and a relative humidity of 75%, the tensile property test method is performed according to the national standard GB / T 1040-2008, and the test speed is 50 mm / min.

[0085] Table 1 Determination results of the high-temperature-resistant bio-based polyamide of examples 1-8 and comparative example 1

[0086]

[0087] From the above examples 1-8 and comparative example 1, it can be seen that the present application provides a high-temperature-resistant bio-based polyamide, which is obtained by using the stage vacuumizing method to perform solid-phase tackification and polycondensation on the nylon prepolymer, so that the problem of black spots is basically eliminated, the stage vacuumizing method has a short polymerization time and no vacuum pipeline blockage phenomenon, the controlled removal of small molecular water in the polymerization process is realized, the obtained high-temperature-resistant bio-based polyamide has a yellow index of less than 15, a narrow molecular weight distribution, good color, and excellent mechanical properties, and the problems of unstable polyamide polymerization and high yellow index are solved, so that the high-temperature-resistant bio-based polyamide is better applied in the fields of automobile industry, electronic appliances or mechanical manufacturing.

[0088] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A controlled polymerization method for high-temperature resistant bio-based polyamide, characterized in that, Prepared by the following steps: Nylon salt is mixed with water, and the resulting nylon salt solution is mixed with additives to carry out a prepolymerization reaction to obtain nylon prepolymer; Under protective gas conditions, the nylon prepolymer was subjected to solid-phase thickening polycondensation under successively decreasing vacuum gradient conditions to obtain high-temperature resistant bio-based polyamide. The sequentially decreasing vacuum gradient includes at least three vacuum gradients. When the sequentially decreasing vacuum gradient includes three vacuum gradients, the three vacuum gradients are low vacuum, medium vacuum, and high vacuum. The low vacuum is 101325~3000 Pa, the medium vacuum is 3000~500 Pa, and the high vacuum is 500~10 Pa. The nylon salt includes one or both of bio-based nylon 5T salt and bio-based nylon 5I salt; The prepolymerization reaction is carried out at a temperature of 220~240℃, a pressure of 1.5~2.3MPa, and a time of 0.5~5h.

2. The controllable polymerization method according to claim 1, characterized in that, The nylon salt solution contains 10-90% nylon salt by mass.

3. The controllable polymerization method according to claim 1, characterized in that, The additives include at least one or more of the following: catalysts, antioxidants, antistatic agents, UV stabilizers, weathering agents, end-capping agents, nucleating agents, flame retardants, lubricants, and matting agents; the amount of the additives used is 0.01~1 wt.% of the total mass of the nylon salt solution.

4. The controllable polymerization method according to claim 1, characterized in that, The protective gas includes one or more of nitrogen, argon, and carbon dioxide.

5. The controllable polymerization method according to claim 1, characterized in that, The solid-phase thickening and polycondensation is carried out at a temperature of 220~300℃ for 2~15h and a stirring speed of 20~120r / min.

6. The high-temperature resistant bio-based polyamide prepared by the controlled polymerization method according to any one of claims 1 to 5, characterized in that, The yellow index of the high-temperature resistant bio-based polyamide is less than 15.

7. The application of the high-temperature resistant bio-based polyamide according to claim 6 in the automotive industry, electronics and electrical appliances or machinery manufacturing.

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