Semi-aromatic high-temperature-resistant nylon and preparation method thereof

Abstract

The invention belongs to the field of high polymer materials, and discloses semi-aromatic high-temperature-resistant nylon and a preparation method thereof.The preparation raw materials comprise nylon salt and auxiliaries, the nylon salt comprises semi-aromatic salt with the mole fraction being 60%-100%, and the auxiliaries comprise the semi-aromatic salt with the mole fraction being 10%-30%; the molar fraction of the PA66 salt is 0%-40%; the auxiliary agent comprises a branching agent, a catalyst and desalted water, the branching agent is polyacid amide, and the addition amount of the branching agent is 0.1-1% of the total mass of the nylon salt. According to the semi-aromatic high-temperature-resistant nylon and the preparation method thereof, polybasic acid amide is added into a pre-polymerization system as a high-temperature-resistant branching auxiliary agent and introduced into a main chain of a nylon molecular chain, and after pre-polymerization and solid-phase tackifying, the prepared semi-aromatic high-temperature-resistant nylon is relatively high in relative viscosity, has excellent mechanical properties and also has better toughness and melt flowability, so that the semi-aromatic high-temperature-resistant nylon can be used for preparing the semi-aromatic high-temperature-resistant nylon. And the processability is better. In addition, the preparation method is simple, large-scale production and popularization are easy, and the application field is wide.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to a semi-aromatic high-temperature resistant nylon and a preparation method thereof. Background Art

[0002] Semi-aromatic nylon is a type of high-performance polyamide material that contains both aliphatic and aromatic units in the main chain, combining the flexibility of aliphatic nylon with the heat resistance and mechanical strength of aromatic nylon. Among them, the aliphatic unit provides flexibility and processability; the aromatic unit enhances heat resistance, mechanical strength and chemical stability.

[0003] Semi-aromatic nylon has excellent heat resistance, with a glass transition temperature (Tg) of more than 100°C; small deformation, shrinkage, and creep, and relatively stable dimensions; mechanical properties are better than general aliphatic nylon; low water absorption, and little effect on product size and mechanical properties after water absorption; excellent electrical insulation performance, as well as excellent arc resistance and leakage trace resistance; good solvent resistance and corrosion resistance; small linear expansion coefficient, low warpage, and good processing performance. Semi-aromatic nylon can be widely used in the fields of automobiles, electronics, industrial materials, etc., and future research will further improve its performance and environmental protection.

[0004] Although semi-aromatic high-temperature resistant nylon has excellent performance, it still has certain problems in terms of processability, cost, performance, environmental protection, etc. For example, the melting point of semi-aromatic nylon is usually higher than 300°C, and high-temperature equipment is required for processing, which increases energy consumption and equipment costs; the melt viscosity of semi-aromatic high-temperature resistant nylon is high, the fluidity is poor, and it is difficult to fill the mold during injection molding or extrusion molding; although it has high strength and rigidity, its toughness is relatively poor and it is prone to brittle fracture; semi-aromatic nylon is difficult to biodegrade and may cause environmental pollution after being discarded.

[0005] Chinese patent with publication number CN109575273A discloses a high temperature resistant semi-aromatic copolymer nylon and a preparation method thereof. The nylon comprises the following components in parts by weight: 80-100 parts of terephthalic acid, 40-50 parts of isophthalic acid, 10-15 parts of adipic acid, 90-120 parts of hexamethylenediamine, 0.1-0.3 parts of a catalyst, 0.05-0.2 parts of a nucleating agent, 0.5-2.5 parts of a capping agent, 0.25-0.6 parts of an anti-yellowing agent, and 80-120 parts of deionized water. The synthesized semi-aromatic copolymer nylon has a melting point of about 300±20°C, which is lower than the thermal decomposition temperature, and can be directly melt-extruded.

[0006] A Chinese patent with publication number CN102477219A discloses a semi-aromatic high-temperature resistant nylon and a preparation method thereof. 75-95 parts of nylon salt, 0.2-0.8 parts of a capping agent, 0.1-0.6 parts of a catalyst, 0.5-1 parts of an antioxidant, 0.1-0.5 parts of a lubricant, and 30-50 parts of deionized water are added to a stirred high-pressure polymerization kettle, and a high-temperature resistant nylon prepolymer is synthesized in the high-pressure stirred reactor. The prepolymer is melt-extruded through a twin-screw extruder twice in succession, thereby improving the devolatilization efficiency, shortening the viscosity-increasing time, and enabling the high-viscosity polymer in the reactor to be discharged smoothly; different extrusion temperatures are successively used to prevent the high-temperature degradation of the prepolymer.

[0007] The Chinese patent CN118325071A discloses a method for preparing bio-based semi-aromatic high-temperature resistant nylon PA5T / 56, which uses terephthalic acid PTA and 1,5-pentanediamine as raw materials, adds adipic acid for copolymerization, adds antioxidants and brighteners, and undergoes salt formation, prepolymerization, and solid phase viscosity enhancement to finally obtain bio-based semi-aromatic high-temperature resistant nylon PA5T / 56. Part of the raw materials of this technology come from biomass, reducing dependence on petroleum resources and can be degraded.

[0008] Therefore, the current preparation method of semi-aromatic high-temperature resistant nylon, under the premise of ensuring its excellent mechanical properties, the properties such as toughness and melt fluidity need to be further improved.

[0009] In view of this, the present invention is proposed. Summary of the invention

[0010] The technical problem to be solved by the present invention is to overcome at least one of the deficiencies of the prior art and provide a semi-aromatic high temperature resistant nylon and a preparation method thereof. The semi-aromatic high temperature resistant nylon prepared by the present invention has a high relative viscosity, excellent mechanical properties, good toughness, good fluidity, and better processing performance. In addition, the preparation method has simple steps, is suitable for large-scale production and promotion, and has a wide range of applications.

[0011] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0012] The present invention provides a semi-aromatic high temperature resistant nylon, the preparation raw materials of which include nylon salt and auxiliary agent, wherein:

[0013] The nylon salt includes:

[0014] Semi-aromatic salts, with a molar fraction of 60%-100%;

[0015] PA66 salt, molar fraction 0%-40%;

[0016] The auxiliary agent includes:

[0017] The branching agent is a polyacid amide, and the added amount is 0.1 to 1% of the total mass of the nylon salt;

[0018] Catalyst, the addition amount is 0.01-0.5% of the total mass of nylon salt;

[0019] Desalted water, the amount added is 50-120% of the total mass of nylon salt.

[0020] In the raw material of the semi-aromatic high temperature resistant nylon of the present invention, polyacid amide is added as a branching agent. Polyacid amide is the reaction product of polyacid ester and diamine, wherein the polyacid ester provides an ester group (-COOR), which reacts with the amino group (-NH2) of the diamine in the polycondensation reaction to form an amide bond (-CONH-). The polyacid amide contains a terminal amine group, which can further undergo an amidation reaction with the terminal carboxyl group of the nylon salt in the prepolymerization reaction. On the one hand, the polyacid amide can be introduced into the main chain of the nylon molecular chain to improve the flexibility of the molecular chain, thereby improving the toughness of the semi-aromatic high temperature resistant nylon; on the other hand, the spacing of the high temperature resistant nylon molecular chain can be enlarged, so that the high temperature resistant nylon is easier to disentangle during processing, and its melt fluidity is also improved, thereby improving its processability.

[0021] The nylon salt described in the present invention can be entirely semi-aromatic salt without PA66 salt; or a mixture of semi-aromatic salt and PA66 salt can be used, and the selection can be made according to specific needs. The ratio of semi-aromatic salt to PA66 salt determines the performance of the final polymer. The performance changes when the ratio of the two changes. The ratio of semi-aromatic salt to PA66 salt can be optimized and adjusted according to the requirements of the melting point, mechanical properties and fluidity of the product. In a further embodiment, the polyacid amide is the reaction product of a polyacid ester and a diamine.

[0022] In a further embodiment, the molar ratio of the polyacid ester to the diamine is 1:(3-3.01).

[0023] In the present invention, the polyacid amide uses polyacid ester and diamine as reaction raw materials, the polyacid ester can undergo esteramide exchange reaction with the short-chain diamine, the polyacid ester provides an ester group (-COOR), and reacts with the amino group (-NH2) of the diamine in the polycondensation reaction to form an amide bond (-CONH-). The reaction conditions of the reaction are simple and the yield is high.

[0024] In a further embodiment, the polybasic acid ester is selected from one or more of trimethyl citrate, triethyl citrate, tributyl citrate, triethyl phosphate and tributyl phosphate;

[0025] In a further embodiment, the diamine is selected from one or more of ethylenediamine, 1,3-propylenediamine, and 1,4-butylenediamine.

[0026] As an optional embodiment, the preparation method of polyacid amide includes: adding diamine into a reaction container, starting stirring and heating, and after the temperature reaches 60 to 90°C, slowly adding polyacid ester into the diamine solution, reflux heating and reacting for 4 to 12 hours, and after the mixed reactants are cooled, extracting, separating and drying to obtain polyacid amide.

[0027] It has been found through experiments that when the amount of branching agent added is increased within a certain range, it is helpful to further improve the toughness of high temperature resistant nylon, and its melt index is also improved. In a further solution, the semi-aromatic salt is selected from one or more of PA6T salt, PA6I salt, and PA6F salt.

[0028] In a further embodiment, the catalyst is selected from one or more of phosphoric acid, sodium hypophosphite, triphenyl phosphate, trioctyl phosphite, and sodium pyrophosphate.

[0029] In a further embodiment, the notched impact strength of the semi-aromatic high temperature resistant nylon is 5.8 to 7.1 kJ / m 2 ; Tensile strength is 88~109MPa; Flexural strength is 135~148MPa; Melt index is 68~88g / 10min.

[0030] The present invention also provides a method for preparing semi-aromatic high temperature resistant nylon, comprising the following steps:

[0031] (1) adding a catalyst, nylon salt, branching agent and desalted water into a polymerization kettle, replacing the air in the polymerization kettle with an inert gas, inflating and pressurizing, heating and stirring, and performing a prepolymerization reaction to obtain a prepolymer;

[0032] (2) separating the prepolymer into solid and liquid, and drying and crushing the prepolymer;

[0033] (3) The crushed prepolymer is subjected to a solid phase polycondensation reaction to obtain semi-aromatic high temperature resistant nylon.

[0034] In a further embodiment, in step (1), the prepolymerization conditions include:

[0035] First, heat to 170℃~200℃, react for 0.5h~2h, drain water and keep the pressure stable at 0.5~1.0MPa;

[0036] Continue to raise the temperature to 200℃~240℃, the pressure is 1.8~3.0MPa, and react for 1h~4h;

[0037] Continue to raise the temperature to 250°C to 280°C, react for 1 to 3 hours, and slowly reduce the pressure to normal pressure to obtain a semi-aromatic high-temperature resistant nylon prepolymer.

[0038] In the preparation method of the present invention, the prepolymerization reaction conditions adopt a method of program stage heating, so that the molecular weight of the prepolymer is controllable, and the prepared high temperature resistant nylon resin has good fluidity while maintaining excellent mechanical properties, solving the problem that the semi-aromatic nylon has poor fluidity and is not conducive to subsequent processing. If the direct heating method is adopted, the molecular weight distribution of the polymerization will become wider and the mechanical properties will decrease.

[0039] In a further embodiment, in step (2), the prepolymer is transported to a solid-liquid separator, and solid-liquid separation is performed in the solid-liquid separator.

[0040] In a further embodiment, in step (3), the conditions of the solid phase polycondensation reaction include: under nitrogen protection, the reaction temperature is 230 to 280° C., and the reaction time is 5 to 10 hours;

[0041] Preferably, the solid phase polycondensation reaction is carried out in a solid phase viscosity increasing reaction bed or a vacuum drum.

[0042] In a further embodiment, the relative viscosity of the obtained semi-aromatic high temperature resistant nylon is 1.85 to 3.2.

[0043] After adopting the above technical scheme, the present invention has the following beneficial effects compared with the prior art.

[0044] 1. The semi-aromatic high temperature resistant nylon prepared by the present invention has polyacid amide added to the raw materials as a branching agent. Polyacid amide is the reaction product of polyacid ester and diamine. The preparation method of the branching agent is simple and has high yield. It can be effectively introduced into the main chain of the high temperature resistant nylon molecular chain by copolymerization to improve the flexibility of the molecular chain and the toughness of the semi-aromatic high temperature resistant nylon. On the other hand, after the introduction, the spacing between the high temperature resistant nylon molecular chains can be enlarged, making the high temperature resistant nylon easier to disentangle during processing, and its melt fluidity is also improved, thereby improving its processability.

[0045] In addition, experiments have found that increasing the amount of branching agent added within a certain range can help further improve its toughness; at the same time, the melt index is increased, which is beneficial to subsequent processing.

[0046] 2. In the preparation method of the semi-aromatic high-temperature resistant nylon of the present invention, a program stage heating method is adopted in the prepolymerization reaction, so that the molecular weight of the prepolymer is controllable, and the prepared high-temperature resistant nylon resin has good fluidity while maintaining excellent mechanical properties, thereby solving the problem that the semi-aromatic nylon has poor fluidity and is not conducive to subsequent processing.

[0047] 3. The preparation method of the semi-aromatic high-temperature resistant nylon provided by the present invention has simple operation steps and easy-to-control conditions, which is conducive to large-scale production and market promotion and application, and has broad prospects and application fields. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in combination with the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0049] The test methods for relative viscosity, melting point and mechanical properties in the embodiments of the present invention are as follows:

[0050] 1. Relative viscosity test conditions: Use 98% concentrated sulfuric acid to dissolve high temperature resistant nylon.

[0051] For viscosity, the test temperature is 25°C, the concentration is 0.01g / ml, and the test is carried out in accordance with ISO307 standard.

[0052] 2. Melting point test: Using the DSC method, weigh 5-8 mg of the sample, and in a nitrogen atmosphere, heat from room temperature to 400°C at 20°C / min, hold for 5 minutes, then cool to room temperature at a rate of 20°C / min, and then heat to 400°C at a rate of 10°C / min. The endothermic peak temperature at this time is the melting point of the polymer.

[0053] 3. Mechanical properties test: The prepared high temperature resistant nylon injection molding test specimens were tested for tensile strength according to GB / T1040.2 standard, the flexural strength and flexural modulus were tested according to GB / T9341-2008 standard, and the simply supported beam impact strength was tested according to GB / T1043.1 standard.

[0054] 4. Melt index: tested according to ISO1133, test temperature 330℃, weight 5kg.

[0055] The experimental materials used in the following examples can be purchased from conventional biochemical reagent companies unless otherwise specified. The preparation method of the polyacid amide in the following examples includes: adding a diamine to a reaction container, stirring and heating, and after the temperature reaches 60 to 90° C., slowly adding a polyacid ester to the diamine solution, reflux heating for 4 to 12 hours, and after the mixed reactant is cooled, extracting, separating, and drying to obtain a polyacid amide.

[0056] Example 1

[0057] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0058] (1) In a polymerization kettle, 17 kg (60 mol) of PA6T salt, 10.5 kg (40 mol) of PA66 salt, 70 g of sodium hypophosphite, 80 g of trimethyl citrate-ethylenediamine reactant (the molar ratio of trimethyl citrate:ethylenediamine is 1:3) and 30 kg of desalted water are added, and the air in the polymerization kettle is replaced with inert gas N2, and the pressure is increased to 0.8 MPa, heated and stirred, and the temperature is raised to 180°C for reaction for 1.5 hours, and the pressure is kept stable by draining; the temperature is continued to be raised to 225°C, the pressure is maintained at 2.2 MPa, and the reaction is continued for 3 hours; the temperature is continued to be raised to 275°C, the reaction is continued for 2 hours, and the pressure is slowly reduced to normal pressure to obtain a PA6T / 66 prepolymer;

[0059] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0060] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 260° C. for a residence time of 3 h to obtain high temperature resistant nylon PA6T / 66.

[0061] Example 2

[0062] The formulation process is the same as that of Example 1, except that the amount of the trimethyl citrate-ethylenediamine reactant (the molar ratio of trimethyl citrate:ethylenediamine is 1:3) is 240 g.

[0063] Example 3

[0064] The formulation process is the same as that of Example 1, except that the amount of the tributyl citrate-ethylenediamine reactant (the molar ratio of tributyl citrate:ethylenediamine is 1:3) is 80 g.

[0065] Example 4

[0066] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0067] (1) In a polymerization kettle, add 20 kg (70 mol) of PA6T salt, 7.9 kg (30 mol) of PA66 salt, 70 g of sodium hypophosphite, 80 g of triethyl citrate-ethylenediamine reactant (the molar ratio of triethyl citrate:ethylenediamine is 1:3) and 20 kg of desalted water, then replace the air in the polymerization kettle with inert gas N2, pressurize to 0.8 MPa, heat and stir, raise the temperature to 184°C to react for 1.5 hours, drain and keep the pressure stable; continue to raise the temperature to 230°C, maintain the pressure at 2.2 MPa, react for 3 hours; continue to raise the temperature to 280°C, react for 2 hours, slowly reduce the pressure to normal pressure, and obtain PA6T / 66 prepolymer;

[0068] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0069] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 260° C. for a residence time of 3 h to obtain high temperature resistant nylon PA6T / 66.

[0070] Example 5

[0071] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0072] (1) In a polymerization reactor, 14.7 kg (52 mol) of PA6T salt, 13.5 kg (48 mol) of PA6I salt, 100 g of sodium pyrophosphate, 85 g of triethyl citrate-1,3-propylenediamine reactant (the molar ratio of triethyl citrate:propylenediamine is 1:3) and 15 kg of desalted water are added, and the air in the polymerization reactor is replaced by inert gas N2, and the reactor is pressurized to 0.8 MPa, heated and stirred, and the temperature is raised to 182°C for reaction for 1.5 hours, and the pressure is kept stable by draining water; the temperature is continued to be raised to 232°C, the pressure is maintained at 2.2 MPa, and the reaction is continued for 3 hours; the temperature is continued to be raised to 272°C, the reaction is continued for 1.5 hours, and the pressure is slowly reduced to normal pressure to obtain a PA6T / 6I prepolymer;

[0073] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0074] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 272° C. and a residence time of 0.5 h to obtain high temperature resistant nylon PA6T / 6I.

[0075] Example 6

[0076] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0077] (1) In a polymerization reactor, 17 kg (60 mol) of PA6T salt, 5.6 kg (20 mol) of PA6I salt, 5.2 kg (20 mol) of PA66 salt, 110 g of triphenyl hypophosphite, 200 g of triethyl phosphate-ethylenediamine reactant (the molar ratio of triethyl phosphate:ethylenediamine is 1:3) and 33 kg of desalted water are added, and the air in the polymerization reactor is replaced with inert gas N2, and the reactor is pressurized to 0.8 MPa, heated and stirred, and the temperature is raised to 180°C for reaction for 1.5 hours, and the pressure is kept stable by draining water; the temperature is continued to be raised to 231°C, the pressure is maintained at 2.2 MPa, and the reaction is continued for 3 hours; the temperature is continued to be raised to 263°C, and the reaction is continued for 2.2 hours, and the pressure is slowly reduced to normal pressure to obtain a PA6T / 6I / 66 prepolymer;

[0078] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0079] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 255° C. and a residence time of 4 h to obtain high temperature resistant nylon PA6T / 6I / 66.

[0080] Example 7

[0081] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0082] (1) In a polymerization kettle, 16.3 kg (60 mol) of PA6F salt, 10.5 kg (40 mol) of PA66 salt, 140 g of trioctyl phosphite, 240 g of triethyl phosphate-1,4-butanediamine reactant (the molar ratio of triethyl phosphate: 1,4-butanediamine is 1:3) and 13.5 kg of desalted water are added, and the air in the polymerization kettle is replaced with inert gas N2, and the pressure is increased to 0.8 MPa, heated and stirred, and the temperature is raised to 180°C for reaction for 1.5 hours, and the pressure is kept stable by draining; the temperature is continued to be raised to 231°C, the pressure is maintained at 2.2 MPa, and the reaction is continued for 3 hours; the temperature is continued to be raised to 263°C, and the reaction is continued for 2 hours, and the pressure is slowly reduced to normal pressure to obtain a PA6F / 66 prepolymer;

[0083] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0084] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 280° C. and a residence time of 2.2 h to obtain high temperature resistant nylon PA6F / 66.

[0085] Example 8

[0086] This embodiment adopts the following steps to prepare high temperature resistant nylon:

[0087] (1) In a polymerization kettle, 15.8 kg (58 mol) of PA6F salt, 11.8 (42 mol) of PA6I salt, 40 g of phosphoric acid, 200 g of tributyl phosphate-ethylenediamine reactant (the molar ratio of tributyl phosphate:ethylenediamine is 1:3) and 22 kg of desalted water are added, and the air in the polymerization kettle is replaced by inert gas N2, and the pressure is increased to 0.8 MPa, heated and stirred, and the temperature is raised to 180°C for reaction for 1.5 hours, and the pressure is kept stable by draining; the temperature is continued to be raised to 231°C, the pressure is maintained at 2.2 MPa, and the reaction is continued for 3 hours; the temperature is continued to be raised to 263°C, and the reaction is continued for 2.5 hours, and the pressure is slowly reduced to normal pressure to obtain a PA6F / 6I prepolymer;

[0088] (2) transporting the prepolymer from step (1) to a solid-liquid separator for solid-liquid separation to obtain a solid product. The prepolymer is then dried and crushed;

[0089] (3) The prepolymer powder obtained in step (2) is fed into a vacuum drum for solid phase polymerization at a temperature of 256° C. and a residence time of 3 h to obtain high temperature resistant nylon PA6F / 6I.

[0090] Comparative Example 1

[0091] The formulation and process are the same as those of Example 1, except that no trimethyl citrate-ethylenediamine reactant is added.

[0092] Comparative Example 2

[0093] The formulation and process are the same as in Example 1, except that the trimethyl citrate-ethylenediamine reactant is replaced with trimesic acid.

[0094] The dosage is the same.

[0095] Comparative Example 3

[0096] The formulation and process are the same as those in Example 1, except that the amount of the trimethyl citrate-ethylenediamine reactant is 280 g.

[0097] Comparative Example 4

[0098] The formula is the same as that of Example 1, except that the step (1) does not use a staged heating method, and the high temperature resistant nylon is prepared by the following steps:

[0099] (1) In a polymerization reactor, 17 kg (60 mol) of PA6T salt, 10.5 kg (40 mol) of PA66 salt, 70 g of sodium hypophosphite, 80 g of trimethyl citrate-ethylenediamine copolymer and 30 kg of desalted water were added, and the air in the polymerization reactor was replaced with inert gas N2, and the reactor was pressurized to 0.8 MPa. The reactor was heated and stirred, and the temperature was raised to 275°C. The reaction was carried out for 5 hours to obtain a PA6T / 66 prepolymer.

[0100] Steps (2) and (3) are the same as in Example 1.

[0101] Table 1 Test results of high temperature resistant nylon prepared in Examples and Comparative Examples

[0102]

[0103] Result analysis:

[0104] It can be seen from Table 1 that the polyacid amide prepared in the present invention is introduced into the main chain of the high-temperature nylon molecular chain to improve the flexibility of the molecular chain, thereby improving the notched impact strength. Increasing its content helps to further improve its toughness; at the same time, the melt index is improved, which is beneficial to subsequent processing.

[0105] Compared with Examples 1 and 2, the amount of branching agent (trimethyl citrate-ethylenediamine copolymer) added in Example 2 is greater, and the notched impact strength and melt index are improved.

[0106] Compared with Example 1 and Example 3, in Example 3, the branching agent is tributyl citrate-ethylenediamine. It can be seen that the notched impact strength and the melt index are not much different, indicating that both trimethyl citrate-ethylenediamine and tributyl citrate-ethylenediamine can play a role in improving toughness, and the effects are similar.

[0107] In Example 4, the content of nylon 6T is increased, and the melting point of the copolymer is increased, which is caused by the increase in the melting point; the tensile strength and bending properties are improved, which is caused by the increase in the content of rigid groups in the molecular chain, and the impact strength is significantly reduced.

[0108] Compared with Example 1, no polyacid amide was added in Comparative Example 1, and the tensile strength and flexural strength of the copolymer did not change much, but the notched impact strength and melt index decreased. This is because the addition of the branching agent introduced a flexible segment into the PA6T / 66 segment, which improved the impact resistance of the polymer. At the same time, the special structure of the branching agent increases the distance between the high-temperature nylon molecular chains, making it easier to disentangle during processing, and its fluidity is improved.

[0109] In Comparative Example 2, the same amount of trimesic acid was added, and the notched impact strength and melt index of the polymer decreased. This is because the side chain of trimesic acid is shorter. After adding trimesic acid, the melt index can be slightly increased compared with Comparative Example 1, but it has little effect on its impact strength.

[0110] In Comparative Example 3, an excessive amount of branching agent is added, and its terminal amino group reacts with the terminal carboxyl group of the high temperature resistant nylon chain to play the role of a capping agent, preventing its molecular weight from continuing to grow, resulting in a low relative viscosity and poor mechanical properties.

[0111] In Comparative Example 4, instead of adopting staged temperature increase, the temperature is directly increased to 275°C for high temperature and high pressure reaction to form a prepolymer. Its mechanical properties are significantly reduced. This is because the staged temperature increase polymerization process is adopted. By controlling the temperature and pressure of different polymerization stages, the prepolymerization reaction of nylon salt is effectively controlled, the salt decomposition is inhibited, and the controllable polymerization reaction of polyamide salt solution is achieved, ensuring the stable and controllable growth of polymer viscosity. The direct temperature increase process will lead to a widening of the molecular weight distribution of the polymerization and a decrease in mechanical properties.

[0112] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the present invention can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A semi-aromatic high temperature resistant nylon, characterized in that: The preparation raw materials include nylon salt and auxiliary agents, wherein: The nylon salt includes: Semi-aromatic salts, with a molar fraction of 60%-100%; PA66 salt, molar fraction 0%-40%; The auxiliary agent includes: The branching agent is a polyacid amide, and the added amount is 0.1 to 1% of the total mass of the nylon salt; Catalyst, the addition amount is 0.01-0.5% of the total mass of nylon salt; Desalted water, the amount added is 50-120% of the total mass of nylon salt.

2. The semi-aromatic high temperature resistant nylon according to claim 1, characterized in that: The polyacid amide is the reaction product of a polyacid ester and a diamine.

3. The semi-aromatic high temperature resistant nylon according to claim 2, characterized in that: The polybasic acid ester is selected from one or more of trimethyl citrate, triethyl citrate, tributyl citrate, triethyl phosphate and tributyl phosphate; The diamine is selected from one or more of ethylenediamine, 1,3-propylenediamine and 1,4-butylenediamine.

4. The semi-aromatic high temperature resistant nylon according to any one of claims 1 to 3, characterized in that: The semi-aromatic salt is selected from one or more of PA6T salt, PA6I salt and PA6F salt.

5. The semi-aromatic high temperature resistant nylon according to any one of claims 1 to 3, characterized in that: The catalyst is selected from one or more of phosphoric acid, sodium hypophosphite, triphenyl phosphate, trioctyl phosphite and sodium pyrophosphate.

6. The semi-aromatic high temperature resistant nylon according to any one of claims 1 to 3, characterized in that: The notched impact strength of the semi-aromatic high temperature resistant nylon is 5.8 to 7.1 kJ / m 2 ; Tensile strength is 88~109MPa; Flexural strength is 135~148MPa; Melt index is 68~88g / 10min.

7. A method for preparing the semi-aromatic high temperature resistant nylon according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) adding a catalyst, nylon salt, a branching agent, and desalted water into a polymerization kettle, replacing the air in the polymerization kettle with an inert gas, inflating and pressurizing, heating and stirring, and performing a prepolymerization reaction to obtain a prepolymer; (2) separating the prepolymer into solid and liquid, and drying and crushing the prepolymer; (3) The crushed prepolymer is subjected to a solid phase polycondensation reaction to obtain semi-aromatic high temperature resistant nylon.

8. The preparation method according to claim 7, characterized in that: In step (1), the conditions for the prepolymerization reaction include: First, heat to 170℃~200℃, react for 0.5h~2h, drain water and keep the pressure stable at 0.5~1.0MPa; Continue to raise the temperature to 200℃~240℃, the pressure is 1.8~3.0MPa, and react for 1h~4h; Continue to raise the temperature to 250°C to 280°C, react for 1 to 3 hours, and slowly reduce the pressure to normal pressure to obtain a semi-aromatic high-temperature resistant nylon prepolymer.

9. The preparation method according to claim 7, characterized in that: In step (3), the conditions of the solid phase polycondensation reaction include: under nitrogen protection, the reaction temperature is 230-280° C., and the reaction time is 5 h to 10 h; Preferably, the solid phase polycondensation reaction is carried out in a solid phase viscosity increasing reaction bed or a vacuum drum.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The relative viscosity of the obtained semi-aromatic high temperature resistant nylon is 1.85-3.2.

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