A method for improving the crystallization ability of a semi-aromatic nylon, a modified semi-aromatic nylon

Abstract

The application discloses a method for improving crystallization ability of semi-aromatic nylon and modified semi-aromatic nylon. The method comprises the following steps: mixing semi-aromatic nylon and an alkaline solution, and preparing the modified semi-aromatic nylon after heat treatment; the mass ratio of the alkali in the alkaline solution to the semi-aromatic nylon is greater than or equal to 0.005:1; the alkali in the alkaline solution comprises hypophosphite, phosphite, phosphate or alkali metal salt; and the temperature of the heat treatment is greater than 60 DEG C. The method can improve the crystallization ability of the semi-aromatic nylon without adding nucleating agents, additives and the like, for example, improving the crystallization ability of the semi-aromatic nylon under the conditions that the polymerization process and the polymer molecular weight are determined.

Description

A method for improving the crystallization ability of semi-aromatic nylon, and modified semi-aromatic nylon. Technical Field

[0001] This invention relates to a method for improving the crystallization ability of semi-aromatic nylon and to modified semi-aromatic nylon. Background Technology

[0002] Semi-aromatic nylons are a class of high-performance polymers with excellent overall properties. Their molecular backbone contains both aromatic rings and aliphatic chains, thus combining the superior properties of aromatic nylons with the good molding and processability of aliphatic nylons. These materials generally possess advantages such as high temperature resistance, corrosion resistance, and low water absorption, and have been widely used in electronics, automotive, and equipment manufacturing in recent years. Among them, poly(m-phenylene adipamide) (MXD6) stands out. Formed through the condensation polymerization of adipic acid and m-phenylene diamine, it is a semi-crystalline polyamide resin. Due to its excellent thermal stability, gas barrier properties, corrosion resistance, mechanical properties, processability, and low water absorption, it is particularly suitable for flexible packaging films, barrier bottles, automotive parts, and electronic products.

[0003] MXD6's high strength, high rigidity, high heat distortion temperature, and ease of molding and manufacturing enable it to be used in engineering plastics fields such as automotive parts and electronic components. However, if the material's crystallization ability is weak, the molding and processing cycle will be longer and the production efficiency will be reduced. To meet processing requirements, its crystallization ability needs to be improved.

[0004] MXD6, due to its excellent barrier properties, is commonly used in multilayer composite packaging materials, primarily as a film. Barrier properties, broadly speaking, refer to the ability to significantly prevent the passage of gas (e.g., vapor) or liquid molecules. Generally, the crystalline regions of polymers, due to their regular molecular chain arrangement and tightly packed molecular structure, have increased density, effectively blocking the permeation of small molecules. Therefore, improving the crystallinity of the polymer also has a significant impact on enhancing barrier performance.

[0005] Currently, existing technologies for improving the crystallinity of MXD6 generally involve complex methods such as adding additives for modification. While this can improve crystallinity, it not only complicates the process but also increases costs.

[0006] Therefore, how to provide a method to improve the crystallinity of semi-aromatic nylon without adding additives is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the fact that the existing methods for improving the crystallinity of semi-aromatic nylon require complex methods such as agent modification, and to provide a method for improving the crystallinity of semi-aromatic nylon and modifying semi-aromatic nylon.

[0008] This invention provides a method for improving the crystallization ability of semi-aromatic nylons such as MXD6 and MXD10, and modifies semi-aromatic nylons accordingly. The method for improving the crystallization ability of semi-aromatic nylons in this invention involves post-treatment with an alkaline solution to improve the crystallization ability of semi-aromatic nylons (e.g., semi-aromatic nylon chips). The semi-aromatic nylon chips are, for example, prepared by solution polymerization.

[0009] The method in this invention can effectively solve the following problems:

[0010] The crystallization ability of semi-aromatic nylon can be improved without the need for modification by adding nucleating agents, auxiliaries, etc. For example, when the polymerization process conditions and polymer molecular weight are determined, the crystallization ability of chip particles can be improved.

[0011] This invention provides a method for improving the crystallization ability of semi-aromatic nylon, comprising the following steps:

[0012] Modified semi-aromatic nylon is prepared by mixing semi-aromatic nylon with an alkaline solution and then heat-treating it.

[0013] The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is ≥0.005:1;

[0014] The base in the alkaline solution includes hypophosphite, phosphite, phosphate or alkali metal salt;

[0015] The heat treatment temperature is greater than 60°C.

[0016] In this invention, the shape of the semi-aromatic nylon is not limited, and conventional shapes in the art are applicable to this invention. When the semi-aromatic nylon has a larger contact area with the alkaline solution, less alkaline solution is needed, which is more conducive to cost savings.

[0017] In some embodiments of the present invention, the semi-aromatic nylon is in granular form. The particle size of the semi-aromatic nylon particles can be a particle size conventional in the art.

[0018] In some embodiments of the present invention, the semi-aromatic nylon is in the form of strips.

[0019] In this invention, the semi-aromatic nylon can be a polyamide, which is conventional in the art and whose main chain contains both aromatic rings and aliphatic chains. Polyamide refers to a polymer whose molecular main chain contains -NHCO- repeating structural units.

[0020] In some embodiments of the present invention, the structural formula of the semi-aromatic nylon is as follows:

[0021] Where a and n are positive integers, and Y is a C6-C8 phenyl group.

[0022] In some embodiments of the present invention, a is a positive integer from 2 to 11, such as 4 or 8.

[0023] In some embodiments of the present invention, Y is

[0024] In some embodiments of the present invention, the structural formula of the semi-aromatic nylon is as follows:

[0025]

[0026] In some embodiments of the present invention, the relative viscosity of the semi-aromatic nylon is 2.0-3.0, for example 2.24 or 2.61.

[0027] In this invention, the method for testing relative viscosity is as follows: the sample is dissolved in concentrated sulfuric acid at a concentration of 0.01 g / mL, and the outflow times t0 and t1 of the concentrated sulfuric acid solvent and polymer solution are measured using a Urumqi viscometer at a temperature of 25°C. The relative viscosity is then calculated according to the formula: relative viscosity = t1 / t0.

[0028] In some embodiments of the present invention, the number-average molecular weight of the semi-aromatic nylon is 10,000-500,000, for example 32701 or 21094.

[0029] In some embodiments of the present invention, the weight-average molecular weight of the semi-aromatic nylon is 10,000-500,000, for example 74,259 or 48,968.

[0030] In this invention, the semi-aromatic nylon can be prepared by solution polymerization in a conventional manner.

[0031] In some embodiments of the present invention, the method for preparing the semi-aromatic nylon includes the following steps:

[0032] In the presence of a catalyst, a diacid, a diamine, and a solvent are mixed to form a solution, and a polymerization reaction is carried out to obtain the semi-aromatic nylon.

[0033] In some embodiments of the present invention, the catalyst is selected from at least one of phosphoric acid, hypophosphoric acid, phosphorous acid, phosphate, hypophosphorous acid, phosphite, phosphite ester, and phosphate ester.

[0034] In some embodiments of the present invention, the amount of catalyst added is 0.01-0.2 wt%, for example 0.03 wt%, based on the total weight of the dicarboxylic acid, the diamine, and the catalyst.

[0035] In some embodiments of the present invention, the diamine is selected from one or more of p-phenylenediamine, m-phenylenediamine, p-phenylenediamine and m-phenylenediamine, preferably m-phenylenediamine.

[0036] In some embodiments of the present invention, the dicarboxylic acid is selected from aliphatic diacids with 4-13 carbon atoms, such as aliphatic diacids with 6 or 10 carbon atoms.

[0037] In some embodiments of the present invention, the dicarboxylic acid includes, but is not limited to, succinic acid, adipic acid, sebacic acid, undecanoic acid, and dodecanoic acid, preferably adipic acid and sebacic acid.

[0038] In some embodiments of the present invention, the molar ratio of the dicarboxylic acid to the diamine is (0.96-1.05):1, preferably (0.98-1.03):1, for example 1.02:1.

[0039] In some embodiments of the present invention, the solvent is desalinated water.

[0040] In this invention, the desalinated water refers to the product obtained by removing chemical salts (cations and anions) from water through a series of processes. This process is called desalination, and the main methods include electrodialysis and reverse osmosis.

[0041] In some embodiments of the present invention, the concentration of the solute in the solution is 50-80 wt%, preferably 55-75 wt%. The solute refers to the catalyst, the dicarboxylic acid, or the diamine.

[0042] In this invention, the temperature of the polymerization reaction can be selected based on the diacid or diamine used.

[0043] In some embodiments of the present invention, the dicarboxylic acid is adipic acid, the diamine is m-phenylenediamine, and the polymerization reaction temperature is 240-290°C, for example, 268°C.

[0044] In some embodiments of the present invention, the dicarboxylic acid is sebacic acid, the diamine is m-phenylenediamine, and the polymerization reaction temperature is 210-260°C, for example, 220°C.

[0045] In some embodiments of the present invention, the polymerization reaction process sequentially includes a positive pressure reaction process, an atmospheric pressure reaction process, and a negative pressure reaction process. The positive pressure condition refers to a pressure higher than atmospheric pressure, i.e., higher than one atmosphere. The negative pressure condition refers to a pressure lower than atmospheric pressure, i.e., lower than one atmosphere.

[0046] During the positive pressure reaction process, the generated byproducts are discharged by venting, and the pressure can be maintained at 400-800 kPa, for example, 600 kPa.

[0047] During the positive pressure reaction process, the duration can be 0.5-2 hours, for example, 1.5 hours.

[0048] During the atmospheric pressure reaction, the holding time can be 20-60 minutes, for example, 25 minutes.

[0049] During the negative pressure reaction process, the vacuum degree can be -100 to -20 kPa, for example -80 kPa.

[0050] During the negative pressure reaction process, the reaction time can be 10-100 minutes, for example, 30 minutes or 60 minutes.

[0051] In some embodiments of the present invention, the method for preparing the semi-aromatic nylon includes the following steps:

[0052] In the presence of a catalyst, diacid, diamine, and solvent are added to a reactor, stirring is turned on, and the temperature is raised to carry out the polymerization reaction. During the process, the by-products generated are discharged by venting. The pressure inside the reactor is adjusted to promote the polycondensation reaction. After polymerization, the material is extruded from the discharge port under pressure, cooled with water, and then processed by a pelletizer to obtain chips.

[0053] In this invention, the crystallization ability of semi-aromatic nylon can be improved by treating it with an alkaline solution.

[0054] In some embodiments of the present invention, the mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is (0.005-0.1):1, for example (0.005-0.05):1, or even (0.005-0.03):1.

[0055] In some embodiments of the present invention, the mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is 0.005:1, 0.03:1, or 0.1:1.

[0056] In some embodiments of the present invention, the alkali in the alkaline solution may be the same type as the catalyst salt used in the semi-aromatic nylon polymerization process, such as an alkali metal hypophosphite.

[0057] In this invention, alkali metals refer to the six metallic elements in Group IA of the periodic table excluding hydrogen (H), including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0058] In this invention, alkaline earth metals refer to the six metallic elements in Group IIA of the periodic table, including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

[0059] In some embodiments of the present invention, the hypophosphite comprises an alkali metal hypophosphite or an alkaline earth metal hypophosphite. The alkali metal hypophosphite may be potassium hypophosphite and / or sodium hypophosphite. The alkaline earth metal hypophosphite may be magnesium hypophosphite.

[0060] In some embodiments of the present invention, the phosphite comprises an alkali metal salt or an alkaline earth metal salt of phosphite. The alkali metal salt of phosphite may be potassium phosphite and / or sodium phosphite. The alkaline earth metal salt of phosphite may be calcium phosphite.

[0061] In some embodiments of the present invention, the phosphate includes an alkali metal phosphate or an alkaline earth metal phosphate. The alkali metal phosphate may be potassium phosphate and / or sodium phosphate. The alkaline earth metal phosphate may be calcium phosphate and / or magnesium phosphate.

[0062] In some embodiments of the present invention, the alkali metal salt is a sodium salt and / or a potassium salt, such as potassium hypophosphite, sodium hypophosphite, potassium phosphite, sodium phosphite, potassium phosphate, sodium phosphate, sodium salts of C1-C5 fatty acids, and potassium salts of C1-C5 fatty acids.

[0063] The C1-C5 fatty acids can be C1-C4 fatty acids, such as formic acid, acetic acid, propionic acid, and butyric acid.

[0064] The sodium salts of fatty acids C1 to C5 may be one or more of sodium formate, sodium acetate, sodium propionate, and sodium butyrate, such as sodium acetate.

[0065] The C1 to C5 fatty acid potassium salts may be one or more of potassium formate, potassium acetate, potassium propionate, and potassium butyrate.

[0066] In some embodiments of the present invention, the alkali in the alkaline solution may be selected from one or more of hypophosphite, phosphite, phosphate and alkali metal salt.

[0067] In some embodiments of the present invention, the alkali in the alkaline solution may be selected from one or more of the following combinations: potassium hypophosphite, sodium hypophosphite, magnesium hypophosphite, potassium phosphite, sodium phosphite, calcium phosphite, potassium phosphate, sodium phosphate, calcium phosphate, magnesium phosphate, sodium formate, potassium formate, sodium acetate, potassium acetate, sodium propionate, potassium propionate, sodium butyrate, and potassium butyrate.

[0068] In some embodiments of the present invention, the alkali in the alkaline solution is selected from one or more of sodium hypophosphite, sodium acetate, potassium phosphite, magnesium phosphate, and sodium formate, such as sodium hypophosphite, sodium acetate, potassium phosphite, magnesium phosphate, or sodium formate.

[0069] In some embodiments of the present invention, the temperature of the heat treatment is 80-150°C, preferably 90-150°C, for example 100-150°C, and also for example 80°C, 100°C, 120°C or 150°C.

[0070] In some embodiments of the present invention, the heat treatment time is 1 to 100 hours, for example 2 to 90 hours, or for example 2 hours, 24 hours, 60 hours or 90 hours.

[0071] In this invention, the heat treatment process can be carried out under normal pressure or under positive pressure. Positive pressure refers to a pressure higher than normal pressure, i.e., higher than one atmosphere.

[0072] In some embodiments of the present invention, the heat treatment process is carried out under normal pressure. When the heat treatment process is carried out under normal pressure, the heat treatment time can be 24 to 90 hours, for example, 24 hours, 60 hours, or 90 hours.

[0073] In some embodiments of the present invention, the heat treatment process is carried out under positive pressure conditions. Under positive pressure conditions, the heat treatment time can be shorter compared to atmospheric pressure. When the heat treatment process is carried out under positive pressure conditions, the heat treatment time can be 1 to 24 hours, for example, 2 to 6 hours.

[0074] The positive pressure condition can be formed by heating in a closed environment.

[0075] In some embodiments of the present invention, the ratio of the mass (g) of the semi-aromatic nylon to the volume (mL) of the alkaline solution is 1:1 to 1:10 g / mL, for example, 1:2 g / mL.

[0076] In some embodiments of the present invention, the solvent in the alkaline solution is water.

[0077] In some embodiments of the present invention, the mass concentration of alkali in the alkaline solution is 0.1 to 10 wt%, for example 0.5 to 5 wt%, for example 3 wt%.

[0078] In this invention, the volume of the alkaline solution can be selected to ensure that the semi-aromatic nylon is fully immersed in the solution. Generally, the same volume of alkaline solution can process more particles, further reducing process costs.

[0079] In one embodiment of the present invention, the mass ratio of the alkali in the alkaline solution to the mass of the semi-aromatic nylon is (0.005-0.05):1, the alkali in the alkaline solution includes hypophosphite, phosphite, phosphate or alkali metal salt, and the temperature of the heat treatment is 80-150°C.

[0080] In one embodiment of the present invention, the mass ratio of the alkali in the alkaline solution to the mass of the semi-aromatic nylon is (0.005-0.05):1, the alkali in the alkaline solution is sodium hypophosphite, and the temperature of the heat treatment is 80-150°C, preferably 100-150°C.

[0081] In one embodiment of the present invention, the mass ratio of the alkali in the alkaline solution to the mass of the semi-aromatic nylon is 0.03:1, the alkali in the alkaline solution is sodium acetate, potassium phosphite, magnesium phosphate or sodium formate, and the heat treatment temperature is 100°C.

[0082] In some embodiments of the present invention, the method for improving the crystallization ability of semi-aromatic nylon includes the following steps:

[0083] Add 50g of semi-aromatic nylon and 100mL of alkaline solution of the corresponding concentration to a container, stir, heat to the specified temperature, maintain the temperature at the specified time, and after the material cools down, perform drying treatment to obtain semi-aromatic nylon with improved crystallization ability.

[0084] In some embodiments of the present invention, the crystallization temperature of the modified semi-aromatic nylon is higher than that of the semi-aromatic nylon.

[0085] In this invention, the crystallization temperature generally refers to the temperature required for a substance to transform from a molten state into a crystal.

[0086] In some embodiments of the present invention, the difference in crystallization temperature between the modified semi-aromatic nylon and the semi-aromatic nylon is ≥0.3℃, for example 0.4~4.5℃, and also for example 0.49℃, 0.76℃, 1.33℃, 1.35℃, 1.69℃, 1.87℃, 1.92℃, 1.95℃, 2.63℃, 2.81℃, 2.92℃, 3.98℃ or 4.03℃.

[0087] In some embodiments of the present invention, the cold crystallization enthalpy of the modified semi-aromatic nylon is lower than that of the semi-aromatic nylon.

[0088] In some embodiments of the present invention, the difference between the cold crystallization enthalpy ΔHc (J / g) of the modified semi-aromatic nylon and the semi-aromatic nylon is ≤-2.0 J / g, for example -2.0 to -15.0 J / g, and further for example -2.03 J / g, -2.85 J / g, -2.86 J / g, -4.02 J / g, -4.32 J / g, -4.67 J / g, -5.06 J / g, -5.27 J / g, -6.38 J / g, -6.7 J / g, -7.16 J / g, -8.5 J / g, -9.18 J / g, -10.4 J / g, or -11.29 J / g.

[0089] In some embodiments of the present invention, the semi-aromatic nylon is poly(m-phenylene adipamide), the crystallization temperature of which is >159.22°C, and the cold crystallization enthalpy ΔHc (J / g) of which is <19.59J / g.

[0090] The crystallization temperature of the poly(m-phenylene adipamide) can be 159.4–163.5°C, for example 159.47°C, 159.74°C, 160.31°C, 160.33°C, 160.67°C, 160.85°C, 160.9°C, 160.93°C, 161.61°C, 161.79°C, 161.9°C, 162.96°C, or 163.01°C.

[0091] The cold crystallization enthalpy ΔHc of the poly(m-phenylene adipamide) can be 8.0–19.0 ​​J / g, for example 8.9 J / g, 9.79 J / g, 11.01 J / g, 11.69 J / g, 13.03 J / g, 13.49 J / g, 13.81 J / g, 14.92 J / g, 15.13 J / g, 15.52 J / g, 15.87 J / g, 16.17 J / g, 17.33 J / g, or 18.16 J / g.

[0092] In some embodiments of the present invention, the semi-aromatic nylon is poly(m-phenylene sebacate), and the cold crystallization enthalpy ΔHc (J / g) of the poly(m-phenylene sebacate) is <12.74 J / g, for example 9.89 J / g.

[0093] The present invention also provides a method for improving the crystallization ability of semi-aromatic nylon, comprising the following steps:

[0094] Modified semi-aromatic nylon is prepared by mixing semi-aromatic nylon with an alkaline solution and then heat-treating it.

[0095] The modified semi-aromatic nylon has a higher crystallization temperature than the semi-aromatic nylon, and the difference between the crystallization temperatures of the modified semi-aromatic nylon and the semi-aromatic nylon is ≥0.3℃; and / or, the modified semi-aromatic nylon has a lower cold crystallization enthalpy than the semi-aromatic nylon, and the difference between the cold crystallization enthalpy ΔHc (J / g) of the modified semi-aromatic nylon and the semi-aromatic nylon is ≤-2.0J / g.

[0096] In some embodiments of the present invention, compared to the semi-aromatic nylon, the modified semi-aromatic nylon is more likely to produce crystallization peaks during the cooling crystallization process. That is, the crystallization peaks of the modified semi-aromatic nylon are more prominent in the spectrum (e.g., DSC spectrum).

[0097] The semi-aromatic nylon can be as described above.

[0098] The alkaline solution can be as described above.

[0099] The alkali in the alkaline solution can be as described above.

[0100] The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution can be as described above.

[0101] The heat treatment process can be as described above.

[0102] The crystallization temperature of the modified semi-aromatic nylon can be as described above.

[0103] The enthalpy of cold crystallization of the modified semi-aromatic nylon can be as described above.

[0104] This invention provides a method for preparing modified semi-aromatic nylon, comprising the following steps:

[0105] The modified semi-aromatic nylon was prepared by mixing semi-aromatic nylon with an alkaline solution and then heat-treating it.

[0106] The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is ≥0.005:1;

[0107] The base in the alkaline solution includes hypophosphite, phosphite, phosphate or alkali metal salt;

[0108] The heat treatment temperature is greater than 60°C.

[0109] The semi-aromatic nylon can be as described above.

[0110] The alkaline solution can be as described above.

[0111] The alkali in the alkaline solution can be as described above.

[0112] The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution can be as described above.

[0113] The heat treatment process can be as described above.

[0114] The crystallization temperature of the modified semi-aromatic nylon can be as described above.

[0115] The enthalpy of cold crystallization of the modified semi-aromatic nylon can be as described above.

[0116] The present invention also provides a modified semi-aromatic nylon, which is prepared by the above method.

[0117] The present invention also provides a poly(m-phenylene adipamide) with a crystallization temperature >159.22℃ and a cold crystallization enthalpy ΔHc (J / g) <19.59J / g.

[0118] The present invention also provides a poly(decanedioylm-phenylene dimethylamine) having a cold crystallization enthalpy ΔHc (J / g) < 12.74 J / g, for example 9.89 J / g.

[0119] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0120] The reagents and raw materials used in this invention are all commercially available.

[0121] The positive and progressive effects of this invention are as follows:

[0122] In this invention, the crystallization ability of semi-aromatic nylon is improved by post-treatment with an alkaline solution. The crystallization temperature of semi-aromatic nylon (e.g., MXD6, MXD10) is increased and the crystallization peak is more obvious; or, although the crystallization peak is not obvious, the cold crystallization enthalpy is significantly reduced. For example, the cold crystallization enthalpy of MXD6 can be reduced from 20 to 8-9. Detailed Implementation

[0123] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0124] In the following embodiments and comparative examples:

[0125] Molecular weight and molecular weight distribution: determined by gel permeation chromatography (GPC) in hexafluoroisopropanol.

[0126] Relative viscosity: The dried sample was dissolved in concentrated sulfuric acid at a concentration of 0.01 g / mL. The outflow times t0 and t1 of the concentrated sulfuric acid solvent and the polymer solution were measured using a viscometer at a temperature of 25℃. The relative viscosity was calculated using the formula: relative viscosity = t1 / t0.

[0127] Normal pressure refers to one atmosphere, and one standard atmosphere is 101325 Pa.

[0128] Desalinated water refers to the product obtained by removing chemical salts (cations and anions) from water through a series of processes. This process is called desalination, and the main methods include electrodialysis and reverse osmosis.

[0129] Preparation Example 1: Preparation of Polyamide MXD6

[0130] Solution polymerization stage: Slowly add 2658g of adipic acid and 1.9g of sodium hypophosphite to the pressure vessel, add 2770g of deionized water, and add 2428g of m-phenylenediamine while stirring; the molar ratio of adipic acid to m-phenylenediamine is 1.02:1; after evacuation, purge with nitrogen, and repeat the evacuation and nitrogen purging process 3 times.

[0131] The mixture was heated to 268℃ with stirring. When the pressure inside the reactor reached 600 kPa, the generated byproducts were discharged by venting the gas over 1.5 hours. The pressure was then adjusted to atmospheric pressure and maintained for 25 minutes. A vacuum was then created inside the reactor at -80 kPa, and the reaction time was 60 minutes. After polymerization, nitrogen gas was introduced into the reactor to extrude the material from the outlet. After water cooling, the material was processed through a pelletizer to obtain chips.

[0132] The polyamide MXD6 chips have a relative viscosity of 2.61, a number-average molecular weight of 32,701, and a weight-average molecular weight of 74,259.

[0133] Preparation Example 2: Preparation of Polyamide MXD10

[0134] Solution polymerization stage: Slowly add 3679g of sebacic acid and 1.9g of sodium hypophosphite to the pressure vessel, add 2770g of deionized water, and add 2428g of m-phenylenediamine while stirring; the molar ratio of sebacic acid to m-phenylenediamine is 1.02:1; after evacuation, nitrogen gas is added, and the evacuation and nitrogen gas filling are repeated 3 times.

[0135] The mixture was heated to 220°C with stirring. When the pressure inside the reactor reached 600 kPa, the byproducts were discharged by venting for 1.5 hours. The pressure was then adjusted to atmospheric pressure and maintained for 25 minutes. The reactor should be evacuated to a pressure of -80 kPa. The reaction time is 30 minutes. After polymerization is complete, the solution is transferred to the reactor. Nitrogen gas is filled inside to expel the material from the outlet. After water cooling, the material is processed through a pelletizer to obtain slices.

[0136] The polyamide MXD10 chips have a relative viscosity of 2.24, a number-average molecular weight of 21094, and a weight-average molecular weight of 48968.

[0137] Example 1

[0138] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0139] Example 2

[0140] Add 50g of MXD6 chip particles obtained from the polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 90h. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0141] Example 3

[0142] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and keep it at 100℃ in a sealed environment for 2 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0143] Example 4

[0144] 50g of MXD6 slices obtained from polymerization in Preparation Example 1 and 3wt% sodium acetate were added. mass percentage This is a percentage of the mass of MXD6 slice particles; MXD6 slice particles: 50g. Add 100 mL of an aqueous solution of 1.5 g sodium acetate (3 wt% sodium acetate) to a container, turn on the stirrer, heat the mixture, and keep it at 100°C in a sealed environment for 2 hours. Then cool the mixture down and dry it to obtain sliced ​​particles with adjustable crystallization ability.

[0145] Example 5

[0146] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and keep it at 120℃ in a sealed environment for 2 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0147] Example 6

[0148] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 60h. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0149] Example 7

[0150] Add 50g of MXD6 chip particles obtained from the polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and keep it at 150℃ in a sealed environment for 2 hours. Then, cool the mixture and dry it to obtain chip particles with controllable crystallization ability.

[0151] Example 8

[0152] 50g of MXD6 slices obtained from polymerization in Preparation Example 1 and 3wt% sodium hypophosphite (hypophosphite) were added. The mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles. 100 mL of an aqueous solution of 50 g of MXD6 chip particles and 1.5 g of sodium hypophosphite (sodium hypophosphite mass percentage is 3 wt%) is added to a container, stirred, heated, and kept at a constant temperature of 120°C for 6 hours in a sealed environment. After cooling, the material is dried to obtain chip particles with adjustable crystallization ability.

[0153] Example 9

[0154] Add 50g of MXD6 chip particles obtained from the polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% potassium phosphite (the mass percentage of potassium phosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of potassium phosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0155] Example 10

[0156] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% magnesium phosphate (the mass percentage of magnesium phosphate is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles, 1.5g of magnesium phosphate, and the mass percentage of magnesium phosphate is 3wt%) to a container, turn on the stir, heat the mixture, and keep it at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0157] Example 11

[0158] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium formate (the mass percentage of sodium formate is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium formate constitute 3wt% of sodium formate) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0159] Example 12

[0160] Add 50g of MXD6 chip particles obtained from the polymerization in Preparation Example 1 and 100mL of an aqueous solution of 0.5wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 0.25g of sodium hypophosphite constitute a mass percentage of 0.5wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0161] Example 13

[0162] Add 50g of MXD10 chips obtained from polymerization in Preparation Example 2 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD10 chips; 50g of MXD10 chips and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chips with adjustable crystallization ability.

[0163] Comparative Example 1

[0164] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 30°C under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain the treated chip particles.

[0165] Comparative Example 2

[0166] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 60°C under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain the treated chip particles.

[0167] Comparative Example 3

[0168] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of deionized water to a container, turn on the stirrer, heat up, and keep the temperature constant for 24 hours when the material temperature reaches 100℃ under normal pressure. Then cool down and dry the material to obtain the processed chip particles.

[0169] Example 14

[0170] Add 50g of MXD6 chip particles obtained from polymerization in Preparation Example 1 and 100mL of an aqueous solution of 10wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 5g of sodium hypophosphite constitute a mass percentage of 10wt% of sodium hypophosphite) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 100℃ under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0171] Example 15

[0172] Add 50g of MXD6 chip particles obtained from the polymerization in Preparation Example 1 and 100mL of an aqueous solution of 3wt% sodium hypophosphite (the mass percentage of sodium hypophosphite is relative to the mass percentage of MXD6 chip particles; 50g of MXD6 chip particles and 1.5g of sodium hypophosphite constitute a mass percentage of 3wt%) to a container, turn on the stirrer, heat the mixture, and maintain the temperature at 80°C under normal pressure for 24 hours. Then, cool the mixture and dry it to obtain chip particles with adjustable crystallization ability.

[0173] Example 1

[0174] Determination of cold crystallization enthalpy and crystallization temperature: According to the testing standard ISO 11357, differential scanning calorimetry (DSC) was used for heating and cooling: under a nitrogen atmosphere, the temperature was increased to 300℃ at a rate of 10℃ / min, held for 5 min, then decreased to 30℃ at a rate of 10℃ / min, held for 5 min, and then increased to 300℃ at a rate of 10℃ / min. The temperature corresponding to the exothermic peak on the cooling curve is the crystallization temperature, and the area of ​​the exothermic peak on the heating curve is the cold crystallization enthalpy.

[0175] The DSC crystallization properties of the sliced ​​particles from Preparation Example 1, Preparation Example 2, Examples 1-15 and Comparative Examples 1-3 were tested, and the test results are shown in Table 1 below.

[0176] Table 1

[0177]

[0178]

[0179] Due to differences in molecular structure, polymers exhibit varying degrees of crystallization ability. Particles with poor crystallization ability show indistinct cooling crystallization peaks, and their crystallization ability can be assessed by comparing their cold crystallization enthalpies. In Preparation Example 1, the untreated MXD6 particles showed indistinct crystallization peaks during DSC cooling, indicating poor crystallization ability. However, after treatment with an alkaline solution, their crystallization temperatures increased, and their cold crystallization enthalpies decreased, indicating that the energy required for chain segment movement decreased, and the crystallization ability of the molecular chains increased.

[0180] A comparison of Examples 1-3, 5-8, 15 and Comparative Examples 1-2 shows that post-treatment at temperatures above 60°C (e.g., 80°C, 100°C, 120°C, or 150°C) can improve the crystallization ability of MXD6. Examples 1 and 15 show that under normal pressure, the increase in crystallization temperature and the decrease in cold crystallization enthalpy of modified MXD6 are more pronounced with increasing temperature. Examples 3, 5, and 7 show that under positive pressure, the increase in crystallization temperature and the decrease in cold crystallization enthalpy of modified MXD6 are also more pronounced with increasing temperature.

[0181] As can be seen from Example 1 and Comparative Example 3, alkaline solution treatment can improve the crystallization ability of MXD6. Examples 1, 12, and 14 show that, under the condition of an alkaline concentration ≥ 0.5 wt%, alkaline solution treatment with different alkaline concentrations can improve the crystallization ability of MXD6. However, as the alkaline concentration in the alkaline solution increases, the crystallization ability of MXD6 does not continuously improve. As shown in Examples 1 and 14, increasing the alkaline concentration in the alkaline solution from 3 wt% to 10 wt% did not significantly change the increase in crystallization temperature or the decrease in cold crystallization enthalpy.

[0182] The crystallization temperature and cold crystallization enthalpy data of untreated MXD6 particles in Examples 1, 4, 9-11 and Preparation Example 1 show that post-treatment with different alkaline solutions can improve their crystallization ability.

[0183] The enthalpy data of cold crystallization of untreated MXD6 particles in Example 1 and Preparation Example 1, and the enthalpy data of cold crystallization of untreated MXD10 particles in Example 13 and Preparation Example 2, show that post-treatment with an alkaline solution can improve the crystallization ability of polyamides obtained by polymerization of m-phenylenediamine with different diacids.

[0184] The scope of protection of this invention is not limited to the following embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept shall be included in this invention and shall be protected by the appended claims.

Claims

1. A method for improving the crystallization ability of semi-aromatic nylon, characterized in that, It includes the following steps: mixing semi-aromatic nylon with an alkaline solution, and then heat-treating to obtain modified semi-aromatic nylon; The mass ratio of the alkali in the alkaline solution to the semi-aromatic nylon is (0.005-0.1):1; the alkali in the alkaline solution includes potassium hypophosphite, sodium hypophosphite, potassium phosphite, sodium phosphite, potassium phosphate, sodium phosphate, magnesium phosphate, sodium salts of C1-C5 fatty acids, or potassium salts of C1-C5 fatty acids; the temperature of the heat treatment is 80-150℃.

2. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: (1) The structural formula of the semi-aromatic nylon is: , where a and n are positive integers, and Y is a C6-C8 phenylene; (2) the relative viscosity of the semi-aromatic nylon is 2.0-3.0; (3) the number average molecular weight of the semi-aromatic nylon is 10000-500000; (4) the weight average molecular weight of the semi-aromatic nylon is 10000-500000; (5) the preparation method of the semi-aromatic nylon includes the following steps: under the presence of a catalyst, a dicarboxylic acid, a diamine and a solvent are mixed to form a solution, and a polymerization reaction is carried out to obtain the semi-aromatic nylon; and, (6) the mass ratio of the alkali in the alkaline solution to the mass of the semi-aromatic nylon is (0.005-0.05):

1.

3. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The method for improving the crystallinity of semi-aromatic nylon satisfies one or more of the following conditions: i. The structural formula of the semi-aromatic nylon is: ii. The relative viscosity of the semi-aromatic nylon is 2.24 or 2.61; iii. The number-average molecular weight of the semi-aromatic nylon is 32701 or 21094; and iv. The weight-average molecular weight of the semi-aromatic nylon is 74259 or 48968.

4. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is (0.005-0.03):

1.

5. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is 0.005:1, 0.03:1, or 0.1:

1.

6. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The mass ratio of the alkali in the alkaline solution to the semi-aromatic nylon is (0.005-0.05):1, the alkali in the alkaline solution is sodium hypophosphite, and the heat treatment temperature is 80~150℃.

7. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 6, characterized in that, The heat treatment temperature is 100~150℃.

8. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The mass ratio of the alkali to the semi-aromatic nylon in the alkaline solution is 0.03:

1. The alkali in the alkaline solution is sodium acetate, potassium phosphite, magnesium phosphate, or sodium formate. The heat treatment temperature is 100°C.

9. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 2, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: (7) a is a positive integer from 2 to 11; Y is 、 、 or (8) The catalyst is selected from at least one of phosphoric acid, hypophosphoric acid, phosphorous acid, phosphate, hypophosphorous acid, phosphite, phosphite ester, and phosphate ester; (9) The amount of catalyst added is 0.01-0.2 wt% based on the total weight of the diacid, the diamine, and the catalyst; (10) The diamine is selected from one or more of p-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and m-phenylenediamine; (11) The diacid is selected from aliphatic diacids with 4-13 carbon atoms; (12) The molar ratio of the diacid to the diamine is (0.96-1.05):1; and, (13) The polymerization reaction process includes, in sequence, a positive pressure reaction process, an atmospheric pressure reaction process, and a negative pressure reaction process.

10. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 9, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: i. a is 4 or 8; ii. the amount of catalyst added is 0.03 wt% based on the total weight of the diacid, the diamine, and the catalyst; iii. the diamine is selected from m-phenylenediamine; iv. the diacid is selected from aliphatic diacids with 6 or 10 carbon atoms; v. the molar ratio of the diacid to the diamine is (0.98-1.03):1; vi. during the positive pressure reaction, the pressure is maintained at 400-800 kPa; vii. during the positive pressure reaction, the holding time is 0.5-2 h; viiii. during the atmospheric pressure reaction, the holding time is 20-60 min; ix. during the negative pressure reaction, the vacuum degree is -100 to -20 kPa; and x. during the negative pressure reaction, the reaction time is 10-100 min.

11. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 9, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: i. the dicarboxylic acid is selected from one or more of succinic acid, adipic acid, sebacic acid, undecanoic acid, and dodecanoic acid; ii. the molar ratio of the dicarboxylic acid to the diamine is 1.02:1; iii. During the positive pressure reaction, the pressure is maintained at 600 kPa; iv. During the positive pressure reaction, the holding time is 1.5 h; v. During the atmospheric pressure reaction, the holding time is 25 min; vi. During the negative pressure reaction, the vacuum degree is -80 kPa; and vii. During the negative pressure reaction, the reaction time is 30 min or 60 min.

12. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 9, characterized in that, The dicarboxylic acid is selected from bisaccharide and / or sebacic acid.

13. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The fatty acids mentioned in C1~C5 are fatty acids from C1 to C4.

14. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The fatty acids in C1 to C5 are formic acid, acetic acid, propionic acid, or butyric acid.

15. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The alkali in the alkaline solution is selected from one or more of sodium hypophosphite, sodium acetate, potassium phosphite, magnesium phosphate, and sodium formate.

16. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The alkali in the alkaline solution is selected from sodium hypophosphite, sodium acetate, potassium phosphite, magnesium phosphate, or sodium formate.

17. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: (14) the heat treatment time is 1 to 100 h; (15) the heat treatment process is carried out under normal pressure or under positive pressure; (16) the ratio of the mass g of the semi-aromatic nylon to the volume mL of the alkaline solution is 1:1 to 1:10 g / mL; (17) the solvent in the alkaline solution is water; And, (18) the mass concentration of alkali in the alkaline solution is 0.1~10wt%.

18. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 17, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: i. the temperature of the heat treatment is 90~150℃; ii. the time of the heat treatment is 2~90h; iii. the ratio of the mass (g) of the semi-aromatic nylon to the volume (mL) of the alkaline solution is 1:2 g / mL; and iv. the mass concentration of the alkali in the alkaline solution is 0.5~5wt%.

19. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 17, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: i. the temperature of the heat treatment is 100~150℃; ii. the time of the heat treatment is 2h, 24h, 60h or 90h; and iii. the mass concentration of alkali in the alkaline solution is 3 wt%.

20. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 17, wherein the temperature of the heat treatment is 80°C, 100°C, 120°C, or 150°C.

21. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 1, characterized in that, The method for improving the crystallization ability of semi-aromatic nylon satisfies one or more of the following conditions: (19) the crystallization temperature of the modified semi-aromatic nylon is higher than that of the semi-aromatic nylon; (20) the cold crystallization enthalpy of the modified semi-aromatic nylon is lower than that of the semi-aromatic nylon.

22. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 21, characterized in that, The difference in crystallization temperature between the modified semi-aromatic nylon and the semi-aromatic nylon is ≥0.3℃; and / or the difference in cold crystallization enthalpy ΔHc J / g between the modified semi-aromatic nylon and the semi-aromatic nylon is ≤-2.0 J / g.

23. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 21, characterized in that, The difference in crystallization temperature between the modified semi-aromatic nylon and the semi-aromatic nylon is 0.4~4.5℃; and / or the difference in cold crystallization enthalpy ΔHc J / g between the modified semi-aromatic nylon and the semi-aromatic nylon is -2.0~-15.0 J / g.

24. The method for improving the crystallization ability of semi-aromatic nylon as described in claim 21, characterized in that, The difference in crystallization temperature between the modified semi-aromatic nylon and the semi-aromatic nylon is 0.49 ℃, 0.76 ℃, 1.33 ℃, 1.35 ℃, 1.69 ℃, 1.87 ℃, 1.92 ℃, 1.95 ℃, 2.63 ℃, 2.81 ℃, 2.92 ℃, 3.98 ℃, or 4.03 ℃; and / or, the difference in cold crystallization enthalpy ΔHc J / g between the modified semi-aromatic nylon and the semi-aromatic nylon is -2.03 J / g, -2.85 J / g, -2.86 J / g, -4.02 J / g, -4.32 J / g, -4.67 J / g, -5.06 J / g, -5.27 J / g, -6.38 J / g, -6.7 J / g, -7.16 J / g, or -8.5 J / g. J / g, -9.18 J / g, -10.4 J / g or -11.29 J / g.

25. A modified semi-aromatic nylon, characterized in that, It is prepared by the method of improving the crystallization ability of semi-aromatic nylon as described in any one of claims 1-24.

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