A short-process polyamide synthesis method

Abstract

The present invention belongs to the technical field of polymer preparation, and relates to a short-process polyamide synthesis method. Synthesis method: using diamine A, dicarboxylic acid A and carrier material as main raw materials, directly prepolymerizing and polycondensing to prepare polyamide; the carrier material is an oligomer generated by the reaction of diamine B and dicarboxylic acid B; the molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 0.5-49.9% of the total mass of diamine A and dicarboxylic acid A. A short-process polyamide synthesis method of the present invention introduces an oligomer composed of dibasic acid and diamine as a carrier material to replace the solvent in the salt-forming step in the existing polyamide synthesis process, which can combine the salt-forming and prepolymerization steps into one, and at the same time eliminates the salt-forming and concentration steps of the existing process, greatly shortening the preparation process; on the other hand, because the concentration and solvent removal steps are reduced, the heat consumption is greatly reduced, and the cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer preparation and relates to a short-process polyamide synthesis method. Background Art

[0002] Polyamide has excellent properties such as light weight, high strength, wear resistance, low temperature resistance, wrinkle resistance, pilling resistance, and good touch, and is widely used in fibers, plastics, etc. Among them, polyamide obtained by polycondensation of diamines and dicarboxylic acids is usually called AABB type polyamide. At present, AABB type polyamide is usually obtained in industry by multiple processes such as salt formation, concentration, prepolymerization, pressure relief, and polycondensation of diamines and dicarboxylic acids.

[0003] For example, patent CN114106319B discloses a method for continuously preparing polyamide with low gel content and narrow molecular weight distribution and its products. The method of this patent includes a salt-forming stage, a melt polymerization stage, and a solid phase polymerization stage. The salt-forming stage uses diacid and diamine as raw materials and pure water as solvent to obtain a nylon salt solution through a salt-forming reaction, and an online potentiometric titration control system is used to online control the concentration and amine-acid ratio of the nylon salt solution.

[0004] For another example, patent CN115806668A discloses a copolymer and a preparation method thereof, and a method for reducing polyamide melt gel. The steps of the method in the patent are: mixing a diamine, a dibasic acid, and water to obtain a polyamide salt solution; copolymerizing the polyamide salt solution to obtain a copolymer melt; and discharging the copolymer melt, water-cooling, and pelletizing.

[0005] For another example, patent CN110857331B discloses a copolymer including polyamide 56 and a preparation method thereof. The steps of the method in the patent are: preparing a mixed solution including polyamide 56 salt; polymerizing the mixed solution to obtain a copolymer; and adding one or more of caprolactam, caprolactam ring-opening product and PA6 polymer in any or all of the aforementioned steps.

[0006] However, the above-mentioned preparation methods of the prior art all have the following problems: (1) the process flow is lengthy, requires a large number of supporting equipment, and has high production costs; (2) a large amount of water needs to be introduced in the salt formation stage to ensure that the polyamide salt is completely dissolved, and a large amount of heat needs to be consumed to remove water in the concentration stage, resulting in a large amount of energy waste and increased production costs.

[0007] Therefore, it is of great practical significance to develop a short-process polyamide synthesis method. Summary of the invention

[0008] The purpose of the invention is to solve the problems existing in the prior art and provide a short-process polyamide synthesis method.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A short-process polyamide synthesis method uses diamine A, dicarboxylic acid A and a carrier material as main raw materials, directly performs prepolymerization and polycondensation reactions to prepare polyamide without undergoing a salt-forming reaction, thereby eliminating the salt-forming and concentration steps and the use of solvents in the prior art, thereby greatly shortening the polyamide synthesis process and significantly reducing energy consumption;

[0011] The carrier material is an oligomer formed by the reaction of diamine B and dicarboxylic acid B;

[0012] The molar ratio of diamine A to dicarboxylic acid A is 1:1; if the molar ratio of diamine A to dicarboxylic acid A is not controlled, it is easy to cause excessive monocarboxylic acid or amino group, which leads to end blocking during the polymerization process, which is not conducive to the preparation of high molecular weight polymers;

[0013] The added amount of the carrier material is 0.5-49.9% of the total mass of the diamine A and the dicarboxylic acid A.

[0014] As the preferred technical solution:

[0015] In the above-mentioned short-process polyamide synthesis method, the number average molecular weight of the carrier material is 3000-5000. If the molecular weight is too high, the viscosity is too high, which is not conducive to the movement of the monomer in the melt, affecting the molecular weight and distribution of the obtained polymer; if the molecular weight is too low, the viscosity is too low, the monomer is easy to volatilize, causing the molar ratio to be destroyed, resulting in the problem of molecular weight not being able to increase and the molecular weight distribution becoming broad.

[0016] In the short-process polyamide synthesis method as described above, diamine A and diamine B are independently selected from one or more of butanediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octanediamine, nonanediamine, decanediamine and a long carbon chain diamine having eleven to eighteen carbon atoms, and dicarboxylic acid A and dicarboxylic acid B are independently selected from one or more of terephthalic acid, isophthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and a long carbon chain dicarboxylic acid having eleven to eighteen carbon atoms.

[0017] The above-mentioned short-process polyamide synthesis method has the following specific steps:

[0018] (1) Prepolymerization reaction;

[0019] Add diamine A and dicarboxylic acid A step by step (diamine A can be added first, or dicarboxylic acid A can be added first, but the two cannot be added together, because if they are added together, there is a problem that the reaction activity of acid and amine is relatively large, and it is easy to react and release heat during the mixing process outside the kettle to volatilize the diamine) to a reaction system composed of a carrier material, trace substances, a catalyst and a thermal oxygen stabilizer, react for 30 to 50 minutes under a nitrogen or carbon dioxide atmosphere at 0.5 to 1.5 MPa and 180 to 260°C, then reduce the pressure to normal pressure within 10 to 40 minutes, and terminate the reaction when the water output reaches more than 98.5% of the theoretical water output to obtain a prepolymer;

[0020] The trace substance is one or more of caprolactam, enantholactam, capryllactam, nonanolactam, decanoic acid, lactams with 11 to 15 carbon atoms, aminocaproic acid, aminoheptanoic acid, aminooctanoic acid, aminononanoic acid, aminodecanoic acid and amino acids with 11 to 15 carbon atoms;

[0021] Based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added does not exceed 0.5wt%;

[0022] The trace substances added in the present invention play a role in adjusting the melting point and fluidity. For example, in the prior art, when polyamide 66 is produced by the salt-forming-concentration-prepolymerization-polycondensation process, caprolactam is added to adjust the melting point, and the amount added is usually about 5wt%, which cannot be called a trace addition. The reason why the prior art adds a large amount is that the system has a large water content. During the concentration and prepolymerization process, caprolactam is easily discharged with water vapor, which reduces the effective concentration. The present invention eliminates the use of solvent water, so that the effective concentration of amino acids generated by caprolactam ring opening is increased, and only a trace amount of addition is needed to achieve the purpose (if the trace substance is not an amide such as caprolactam, but the above-mentioned amino acid, there is no ring opening process).

[0023] If no carrier material is introduced, the prepolymerization time is usually 60 min to 180 min. However, the introduction of the carrier material of the present invention accelerates the dissolution rate of the diamine A and the dicarboxylic acid A in the reaction system. At the same time, the present invention avoids the introduction of a large amount of solvent. The water generated by the reaction of the diamine A and the dicarboxylic acid A can be quickly discharged from the melt into the gas phase, which promotes the reaction to move toward the polymerization direction. The synergistic effect of the above two greatly reduces the time required for the prepolymerization reaction.

[0024] The purpose of adding a catalyst in the present invention is to accelerate the reaction rate, shorten the reaction time, and thus reduce side reactions. The purpose of using a thermal oxygen stabilizer in the present invention is to prevent degradation and color change caused by thermal oxygen. The present invention controls the prepolymerization temperature at 180-260°C because the prepolymerization reaction is an endothermic reaction. Although an excessively high temperature can accelerate the prepolymerization reaction rate, it is also easy to cause thermal degradation of polyamide. An excessively low temperature cannot meet the heat requirements of the prepolymerization reaction and the dissolution process. The prepolymerization process has a certain positive pressure, and the pressure is controlled at 0.5-1.5MPa. This is because the by-product in the prepolymerization process is small molecule water. In addition, a certain positive pressure can increase the boiling point of the monomer and prevent the monomer from escaping into the gas phase to destroy the equimolar ratio. The pressure required for the prepolymerization stage of the present invention is slightly lower than that of the existing conventional process (1.7-1.9MPa), so the present invention can be directly carried out on the existing device and the service life of the equipment components can be extended. The reason why the pressure of the present invention is lower than that of the prior art is that a large amount of water is required in the prior art, and the water generates high pressure at high temperature. The lower pressure of the present invention is because no water is used, and only a small amount of water generated by the polycondensation reaction generates pressure at high temperature, so the pressure in the present invention is lower than that of the prior art.

[0025] (2) Polycondensation reaction;

[0026] The prepolymer obtained in step (1) is reacted at -0.100 to -0.030 MPa and 200 to 280° C. for 10 to 30 minutes to obtain polyamide;

[0027] The polycondensation reaction temperature of the present invention is controlled at 200-280°C, because the reaction cannot be carried out at too low a temperature, and the side reaction is aggravated at too high a temperature, resulting in a deteriorated color, a wider molecular weight distribution, and a higher gel content of the obtained polyamide; the polycondensation pressure of the present invention is controlled at -0.100-0.030MPa, because the polyamide polycondensation reaction rate is relatively fast, and a too high vacuum degree will cause the small molecules with low viscosity to be quickly removed, so that the reaction rate is further increased, resulting in "explosion", and increasing the production cost; if the vacuum degree is too low, the small molecules with low viscosity are difficult to be removed from the system, thereby increasing the reaction time, and the side reaction increases, resulting in a deteriorated color, an increased gel content, and a wider molecular weight distribution of the formed polyamide; the polycondensation time of the present invention is controlled at 10-30min, because if the polycondensation time is too short, the required viscosity cannot be achieved, and if the polycondensation time is too long, the side reaction increases, resulting in a deteriorated color, an increased gel content, and a wider molecular weight distribution of the formed polyamide.

[0028] In the short-process polyamide synthesis method as described above, the degree of polymerization of the prepolymer obtained in step (1) is 10-25.

[0029] A short-process polyamide synthesis method as described above, wherein the catalyst in step (1) is one or more of potassium phosphite, sodium phosphite, magnesium phosphite, aluminum phosphite, calcium phosphite, barium phosphite, zinc phosphite, potassium hypophosphite, sodium hypophosphite, magnesium hypophosphite, calcium hypophosphite, zinc hypophosphite, aluminum hypophosphite and barium hypophosphite, and the thermal oxidation stabilizer is one or more of antioxidant 1010, antioxidant 1096, antioxidant 168, triphenyl phosphite and triphenyl phosphate.

[0030] In the short-process polyamide synthesis method as described above, based on the total mass of diamine A, dicarboxylic acid A and carrier material, the added amount of trace substances is 0.1~0.5wt%, the added amount of catalyst is 0.001~0.05wt%, and the added amount of thermal oxidation stabilizer is 0.001~0.05wt%.

[0031] In the short-process polyamide synthesis method as described above, the polyamide obtained in step (2) has a relative viscosity of 2.2-2.9, a yellowness index ≤-1, a molecular weight distribution range of 1.2-2, and a gel particle content of not more than 0.1wt%.

[0032] According to the short-process polyamide synthesis method as described above, the polyamide can be used to prepare polyamide POY, FDY, DTY or short fibers (in the field of fibers or engineering plastics) after drying.

[0033] Invention mechanism:

[0034] The existing polyamide synthesis process requires first adding dibasic acid and diamine to a solvent to form a salt, then concentrating the salt solution, prepolymerizing under high pressure to form oligomers, and then unloading the pressure to normal pressure or slightly negative pressure to form polyamide by polycondensation. The problems are that the polymerization time is long, side reactions are prone to occur, the final polymer has poor color, wide molecular weight distribution, and poor processability; and the introduction and removal of the solvent consumes a lot of heat, the production process is lengthy, the equipment requirements are complex, and the production cost is high.

[0035] In view of the above problems, the present invention introduces a carrier material instead of a solvent as a base bed for the reaction of a dibasic acid and a diamine (the dibasic acid and the diamine in the present invention are diamine A and dicarboxylic acid A) under the condition of strictly controlling the acid-amine molar ratio. The diamine A and the dicarboxylic acid A can be quickly dissolved and reacted, thereby accelerating the prepolymerization reaction, shortening the time to reach a homogeneous system, and helping to reduce the occurrence of side reactions. Secondly, the heat released by the reaction of the diamine A and the dicarboxylic acid A can be directly used to maintain the prepolymerization reaction, thereby reducing the supply of external heat. Compared with the prior art, the steps of salt formation and concentration are omitted, which not only shortens the process flow but also reduces energy consumption.

[0036] The prior art must first go through the step of salt formation, and use the solvent as the base bed for the reaction of the dibasic acid and the diamine, because the diamine is not easy to volatilize during polymerization after salt formation. However, the present invention does not go through the steps of salt formation, and the diamine A is still not easy to volatilize. This is because the diamine A and the dicarboxylic acid A in the system have high reactivity and react quickly to form salts. The salts are quickly dissolved in the carrier material also composed of amide bonds to undergo dehydration and condensation reactions. The water generated by the reaction is quickly vaporized to generate pressure, which inhibits the volatilization of the diamine A. In addition, the diamine A will dissolve in the carrier material, and the volatilization rate of the diamine A from the carrier material is obviously much lower than the volatilization rate from water, which also inhibits its volatilization to a certain extent.

[0037] Beneficial effects:

[0038] (1) The short-process polyamide synthesis method of the present invention introduces an oligomer composed of a dibasic acid and a diamine as a carrier material to replace the solvent in the salt-forming step in the existing polyamide synthesis process, thereby combining the salt-forming and prepolymerization steps into one, while eliminating the salt-forming and concentration steps of the existing process, thereby greatly shortening the preparation process; on the other hand, because the concentration and solvent removal steps are reduced, the heat consumption is greatly reduced, thereby reducing the cost;

[0039] (2) The short-process polyamide synthesis method of the present invention uses a carrier material as a base bed for the prepolymerization reaction, thereby achieving the purpose of kinetic enhancement, and the reaction enters a homogeneous system faster. Compared with the prior art, the reaction time is shortened, the side reactions are reduced, and the color of the formed polyamide is improved, the molecular weight distribution is narrower, and the processing performance is better;

[0040] (3) A short-process polyamide synthesis method of the present invention, the polyamide obtained by this method has a relative viscosity of 2.2~2.9, a yellow index ≤-1, and a molecular weight distribution range of 1.2~2, and can be used to prepare polyamide POY, FDY, DTY or short fibers (fiber or engineering plastics field). DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0042] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0043] Relative viscosity: Tested with reference to the 96% (mass fraction) sulfuric acid test standard in GB / T12006.1-2009.

[0044] Yellowness Index: Tested in accordance with GB / T39822-2021 standard.

[0045] Molecular weight distribution range: Gel chromatography was used for testing; the testing instrument was Agilent 1260 gel chromatograph, the chromatographic column was Agilent HFIP series, the mobile phase was hexafluoroisopropanol + 0.02M sodium trifluoroacetate, and the testing temperature was 40°C.

[0046] Gel particle content: The formic acid dissolution method is used for testing. The sample is dissolved in a formic acid solution with a mass fraction of 90%. The undissolved part is separated by filtration and weighed after drying.

[0047] Example 1

[0048] A short-process polyamide synthesis method, the specific steps are as follows:

[0049] (1) Preparation of raw materials;

[0050] Diamine A: a mixture of decanediamine and nonanediamine in a molar ratio of 1:1;

[0051] Dicarboxylic acid A: a mixture of azelaic acid and pimelic acid in a molar ratio of 1:1;

[0052] Diamine B: diaminobutane;

[0053] Dicarboxylic acid B: a mixture of undecanedicarboxylic acid (CAS No.: 1852-04-6) and glutaric acid in a molar ratio of 1:1;

[0054] Trace substances: a mixture of caprolactam and aminononanoic acid in a mass ratio of 1:1;

[0055] Catalyst: a mixture of calcium hypophosphite, aluminum hypophosphite and zinc phosphite in a mass ratio of 1:1:1;

[0056] Thermal oxygen stabilizer: Antioxidant 1010, manufactured by BASF of Germany;

[0057] (2) reacting a diamine B and a dicarboxylic acid B in a molar ratio of 1:1 at 230° C. to obtain a carrier material with a number average molecular weight of 3000;

[0058] (3) Diamine A and dicarboxylic acid A are added step by step into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, and reacted for 30 min at 0.5 MPa and 230° C. under a nitrogen atmosphere, and then the pressure is reduced to normal pressure within 10 min. The reaction is terminated when the water output reaches 98.5% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 25;

[0059] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 49.9% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.1wt%, the amount of catalyst added is 0.005wt%, and the amount of thermal oxidation stabilizer added is 0.001wt%;

[0060] (4) The prepolymer obtained in step (3) was reacted at -0.1 MPa and 220° C. for 30 min to obtain polyamide.

[0061] The relative viscosity of the finally prepared polyamide is 2.9, the yellow index is -6, the molecular weight distribution range is 1.8, and there are no gel particles in the polyamide.

[0062] Example 2

[0063] A short-process polyamide synthesis method, the specific steps are as follows:

[0064] (1) Preparation of raw materials;

[0065] Diamine A: a mixture of butanediamine and heptanediamine in a molar ratio of 1:1;

[0066] Dicarboxylic acid A: a mixture of adipic acid and succinic acid in a molar ratio of 1:1;

[0067] Diamine B: a mixture of hexamethylenediamine and tridecanediamine in a molar ratio of 1:1;

[0068] Dicarboxylic acid B: a mixture of octadecanoic acid (CAS No.: 871-70-5) and terephthalic acid in a molar ratio of 1:1;

[0069] Trace substances: a mixture of capryllactam, ω-undecalactam and nonanolactam in a mass ratio of 1:1:1;

[0070] Catalyst: a mixture of calcium phosphite and aluminum phosphite in a mass ratio of 1:1;

[0071] Thermal oxygen stabilizer: Antioxidant 1096, manufactured by BASF of Germany;

[0072] (2) reacting a diamine B and a dicarboxylic acid B at a molar ratio of 1.01:1 at 260° C. to obtain a carrier material having a number average molecular weight of 3500;

[0073] (3) Diamine A and dicarboxylic acid A are added step by step into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, and reacted for 34 min at 1.2 MPa and 250° C. under a nitrogen atmosphere, and then the pressure is reduced to normal pressure within 40 min. The reaction is terminated when the water output reaches 99.1% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 10;

[0074] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 30% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.5wt%, the amount of catalyst added is 0.05wt%, and the amount of thermal oxidation stabilizer added is 0.05wt%;

[0075] (4) The prepolymer obtained in step (3) was reacted at -0.05 MPa and 280° C. for 25 min to obtain polyamide.

[0076] The relative viscosity of the polyamide finally obtained is 2.3, the yellow index is -2, the molecular weight distribution range is 2, and the gel particle content is 0.09wt%.

[0077] Comparative Example 1

[0078] A polyamide synthesis method is basically the same as Example 2, except that step (2) is not performed and no carrier material is added in step (3).

[0079] The relative viscosity of the polyamide finally obtained is 1.7, the yellow index is 10, the molecular weight distribution range is 3.5, and the gel particle content is 10wt%.

[0080] Compared with Example 2, the relative viscosity of Comparative Example 1 is significantly decreased, the yellow index is significantly increased, the molecular weight distribution range is significantly widened, and the gel content is significantly increased. This is because no carrier substance is added to Comparative Example 1, the system viscosity is low during the reaction, the diffusion rate of diamine A in the system is very fast, and the pressure during the reaction is also low, diamine A is easy to escape from the reaction system and destroy the molar ratio. During the polymerization process, excessive carboxylic acid leads to end blocking, resulting in low molecular weight, which is manifested as a significant decrease in relative viscosity; excessive carboxyl groups are prone to cyclization reactions at high temperatures to generate a large amount of cyclic ketone substances, which can undergo cross-linking reactions with polyamide to produce a large amount of gel, and a large amount of gel also causes a significant widening of the molecular weight distribution range; in addition, the gel is usually a yellow or brown substance, resulting in a significant increase in the yellow index.

[0081] Example 3

[0082] A short-process polyamide synthesis method, the specific steps are as follows:

[0083] (1) Preparation of raw materials;

[0084] Diamine A: 1,11-undecanediamine;

[0085] Dicarboxylic acid A: a mixture of isophthalic acid and suberic acid in a molar ratio of 1:1;

[0086] Diamine B: a mixture of 1,11-undecanediamine and heptanediamine in a molar ratio of 1:1;

[0087] Dicarboxylic acid B: a mixture of isophthalic acid and suberic acid in a molar ratio of 1:1;

[0088] Trace substances: a mixture of decanolactam, ω-pentadecanolactam and aminocaproic acid in a mass ratio of 1:1:1;

[0089] Catalyst: a mixture of potassium phosphite, potassium hypophosphite and sodium phosphite in a mass ratio of 1:1:1;

[0090] Thermal oxygen stabilizer: Antioxidant 168, manufactured by BASF of Germany;

[0091] (2) reacting a diamine B and a dicarboxylic acid B at a molar ratio of 1.02:1 at 225° C. to obtain a carrier material having a number average molecular weight of 4500;

[0092] (3) Diamine A and dicarboxylic acid A are added step by step into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, and reacted for 38 min at 0.8 MPa and 180° C. under a nitrogen atmosphere, and then the pressure is reduced to normal pressure within 18 min. The reaction is terminated when the water output reaches 99% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 16;

[0093] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 0.5% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.3wt%, the amount of catalyst added is 0.02wt%, and the amount of thermal oxidation stabilizer added is 0.03wt%;

[0094] (4) The prepolymer obtained in step (3) was reacted at -0.03 MPa and 250° C. for 15 min to obtain polyamide.

[0095] The relative viscosity of the finally prepared polyamide is 2.6, the yellow index is -8, the molecular weight distribution range is 1.5, and there are no gel particles in the polyamide.

[0096] Example 4

[0097] A short-process polyamide synthesis method, the specific steps are as follows:

[0098] (1) Preparation of raw materials;

[0099] Diamine A: a mixture of 1,18-octadecanediamine and hexamethylenediamine in a molar ratio of 1:1;

[0100] Dicarboxylic acid A: a mixture of undecanedicarboxylic acid and glutaric acid in a molar ratio of 1:1;

[0101] Diamine B: a mixture of nonanediamine and decanediamine in a molar ratio of 1:1;

[0102] Dicarboxylic acid B: a mixture of azelaic acid and sebacic acid in a molar ratio of 1:1;

[0103] Trace substances: a mixture of ω-aminoundecanoic acid, aminodecanoic acid and enantholactam in a mass ratio of 1:1:1;

[0104] Catalyst: sodium hypophosphite;

[0105] Thermal oxygen stabilizer: triphenyl phosphite;

[0106] (2) reacting a diamine B and a dicarboxylic acid B at a molar ratio of 1.03:1 at 220° C. to obtain a carrier material having a number average molecular weight of 4500;

[0107] (3) Diamine A and dicarboxylic acid A are added step by step into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, and reacted for 41 minutes at 1 MPa and 220° C. under a carbon dioxide atmosphere, and then the pressure is reduced to normal pressure within 32 minutes. The reaction is terminated when the water output reaches 99.5% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 22;

[0108] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 15% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.4wt%, the amount of catalyst added is 0.03wt%, and the amount of thermal oxidation stabilizer added is 0.02wt%;

[0109] (4) The prepolymer obtained in step (3) was reacted at -0.04 MPa and 200° C. for 10 min to obtain polyamide.

[0110] The relative viscosity of the finally prepared polyamide is 2.2, the yellow index is -6, the molecular weight distribution range is 1.2, and there are no gel particles in the polyamide.

[0111] Example 5

[0112] A short-process polyamide synthesis method, the specific steps are as follows:

[0113] (1) Preparation of raw materials;

[0114] Diamine A: a mixture of pentamethylenediamine and tridecanediamine in a molar ratio of 1:1;

[0115] Dicarboxylic acid A: a mixture of terephthalic acid and sebacic acid in a molar ratio of 1:1;

[0116] Diamine B: 1,18-octadecanediamine;

[0117] Dicarboxylic acid B: pimelic acid;

[0118] Trace substances: a mixture of aminoheptanoic acid, aminooctanoic acid and ω-aminopentadecacarboxylic acid in a mass ratio of 1:1:1;

[0119] Catalyst: a mixture of magnesium phosphite, zinc hypophosphite and barium phosphite in a mass ratio of 1:1:1;

[0120] Thermal oxygen stabilizer: triphenyl phosphate;

[0121] (2) reacting a diamine B and a dicarboxylic acid B at a molar ratio of 1.04:1 at 250° C. to obtain a carrier material with a number average molecular weight of 5000;

[0122] (3) Adding diamine A and dicarboxylic acid A stepwise into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, reacting for 46 min at 1.5 MPa and 260° C. under a carbon dioxide atmosphere, then depressurizing to normal pressure within 26 min, and terminating the reaction when the water output reaches 98.7% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 11;

[0123] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 20% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.5wt%, the amount of catalyst added is 0.04wt%, and the amount of thermal oxidation stabilizer added is 0.04wt%;

[0124] (4) The prepolymer obtained in step (3) was reacted at -0.08 MPa and 270° C. for 10 min to obtain polyamide.

[0125] The relative viscosity of the polyamide finally obtained is 2.3, the yellow index is -1, the molecular weight distribution range is 2, and the gel particle content is 0.1wt%.

[0126] Comparative Example 2

[0127] A polyamide synthesis method is basically the same as Example 5, except that in step (3), the amount of carrier material added is 0.3% of the total mass of diamine A and dicarboxylic acid A.

[0128] The relative viscosity of the polyamide finally obtained is 1.9, the yellow index is 6, the molecular weight distribution range is 3.1, and the gel particle content is 3wt%.

[0129] Compared with Example 5, the yellow index of Comparative Example 2 is significantly increased, the molecular weight distribution range is significantly widened, and the gel content is significantly increased. This is because too little carrier material is added in Comparative Example 2, the system viscosity is low during the reaction, the diffusion rate of diamine A in the system is very fast, and the pressure during the reaction is also low, diamine A is easy to escape from the reaction system and destroy the molar ratio. During the polymerization process, excessive carboxylic acid leads to end blocking, resulting in low molecular weight, which is manifested as a significant decrease in relative viscosity; excessive carboxyl groups are prone to cyclization reactions at high temperatures to generate a large amount of cyclic ketone substances, which can undergo cross-linking reactions with polyamide to produce a large amount of gel, and a large amount of gel also causes a significant widening of the molecular weight distribution range; in addition, the gel is usually a yellow or brown substance, resulting in a significant increase in the yellow index.

[0130] Example 6

[0131] A short-process polyamide synthesis method, the specific steps are as follows:

[0132] (1) Preparation of raw materials;

[0133] Diamine A: octanediamine;

[0134] Dicarboxylic acid A: octadecanoic acid;

[0135] Diamine B: a mixture of pentamethylenediamine and octanediamine in a molar ratio of 1:1;

[0136] Dicarboxylic acid B: a mixture of succinic acid and adipic acid in a molar ratio of 1:1;

[0137] Trace substances: Capryllactam;

[0138] Catalyst: a mixture of barium hypophosphite and magnesium hypophosphite in a mass ratio of 1:1;

[0139] Thermal oxygen stabilizer: a mixture of triphenyl phosphite and triphenyl phosphate in a mass ratio of 1:1;

[0140] (2) reacting a diamine B and a dicarboxylic acid B at a molar ratio of 1.05:1 at 220° C. to obtain a carrier material with a number average molecular weight of 4000;

[0141] (3) Adding diamine A and dicarboxylic acid A stepwise into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, reacting for 50 min at 0.5 MPa and 240° C. under a carbon dioxide atmosphere, then depressurizing to normal pressure within 37 min, and terminating the reaction when the water output reaches 98.6% of the theoretical water output, thereby obtaining a prepolymer with a degree of polymerization of 17;

[0142] The molar ratio of diamine A to dicarboxylic acid A is 1:1; the amount of carrier material added is 35% of the total mass of diamine A and dicarboxylic acid A; based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace material added is 0.2wt%, the amount of catalyst added is 0.001wt%, and the amount of thermal oxidation stabilizer added is 0.02wt%;

[0143] (4) The prepolymer obtained in step (3) was reacted at -0.06 MPa and 260° C. for 20 min to obtain polyamide.

[0144] The relative viscosity of the polyamide finally obtained is 2.5, the yellow index is -4, the molecular weight distribution range is 1.8, and the gel particle content is 0.01wt%.

[0145] Comparative Example 3

[0146] A polyamide synthesis method is basically the same as Example 6, except that in step (3), the amount of carrier material added is 60% of the total mass of diamine A and dicarboxylic acid A.

[0147] The molecular weight distribution range of the finally obtained polyamide is 3.1.

[0148] Compared with Example 6, the molecular weight distribution range of Comparative Example 3 is greatly widened. This is because the amount of carrier material added is too large, the viscosity of the system is relatively large in the early stage of the initial reaction, and the diffusivity of diamine A and dicarboxylic acid A in the system is poor, resulting in a large degree of dispersion of the degree of polymerization, which causes the molecular weight distribution range of the final sample to be greatly widened.

Claims

1. A short-process polyamide synthesis method, characterized in that The specific steps are as follows: (1) Prepolymerization reaction; Adding diamine A and dicarboxylic acid A stepwise into a reaction system consisting of a carrier material, trace materials, a catalyst and a thermal oxidation stabilizer, reacting for 30 to 50 minutes at 0.5 to 1.5 MPa and 180 to 260° C. under a nitrogen or carbon dioxide atmosphere, then unloading the pressure to normal pressure within 10 to 40 minutes, and terminating the reaction when the water output reaches more than 98.5% of the theoretical water output to obtain a prepolymer; The carrier material is an oligomer formed by the reaction of diamine B and dicarboxylic acid B; The number average molecular weight of the carrier material is 3000 to 5000; The molar ratio of diamine A to dicarboxylic acid A is 1:1; The added amount of the carrier material is 0.5 to 49.9% of the total mass of the diamine A and the dicarboxylic acid A; The trace substance is one or more of caprolactam, enantholactam, capryllactam, nonanolactam, decanoic acid, lactams with 11 to 15 carbon atoms, aminocaproic acid, aminoheptanoic acid, aminooctanoic acid, aminononanoic acid, aminodecanoic acid and amino acids with 11 to 15 carbon atoms; Based on the total mass of diamine A, dicarboxylic acid A and carrier material, the amount of trace substances added does not exceed 0.5wt%; (2) polycondensation reaction; The prepolymer obtained in step (1) is reacted at -0.100 to -0.030 MPa and 200 to 280° C. for 10 to 30 minutes to obtain a polyamide; The relative viscosity of the polyamide is 2.2-2.9, the yellow index is ≤-1, the molecular weight distribution range is 1.2-2, and the gel particle content is not higher than 0.1wt%.

2. A short-process polyamide synthesis method according to claim 1, characterized in that: The diamine A and the diamine B are independently selected from one or more of butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine and a long carbon chain diamine having eleven to eighteen carbon atoms. The dicarboxylic acid A and the dicarboxylic acid B are independently selected from one or more of terephthalic acid, isophthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and a long carbon chain dicarboxylic acid having eleven to eighteen carbon atoms.

3. A short-process polyamide synthesis method according to claim 1, characterized in that: The degree of polymerization of the prepolymer obtained in step (1) is 10 to 25.

4. A short-process polyamide synthesis method according to claim 1, characterized in that: In step (1), the catalyst is one or more of potassium phosphite, sodium phosphite, magnesium phosphite, aluminum phosphite, calcium phosphite, barium phosphite, zinc phosphite, potassium hypophosphite, sodium hypophosphite, magnesium hypophosphite, calcium hypophosphite, zinc hypophosphite, aluminum hypophosphite and barium hypophosphite, and the thermal oxidation stabilizer is one or more of antioxidant 1010, antioxidant 1096, antioxidant 168, triphenyl phosphite and triphenyl phosphate.

5. A short-process polyamide synthesis method according to claim 4, characterized in that: Based on the total mass of diamine A, dicarboxylic acid A and carrier material, the added amount of trace substances is 0.1-0.5wt%, the added amount of catalyst is 0.001-0.05wt%, and the added amount of thermal oxidation stabilizer is 0.001-0.05wt%.