High-temperature-resistant nylon block copolymer and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant nylon block copolymer and a preparation method thereof, and belongs to the technical field of high-temperature-resistant nylon. The preparation method provided by the invention comprises the following steps: adding binary acid, diamine, an antioxidant, an end-capping reagent and a catalyst into water, uniformly mixing, and carrying out salt-forming reaction to obtain a salt solution; the method comprises the following steps: adding a salt solution into a polymerization kettle, adding a certain amount of PA56 or PA66 / PA6 copolymer, replacing air in the polymerization kettle with shielding gas, heating, maintaining the pressure when the pressure reaches 2.4-3.0 MPa, carrying out prepolymerization reaction for 1-3 hours when the temperature reaches 240-260 DEG C, continuously heating to 280-300 DEG C, carrying out heat preservation and pressure maintenance for 1-3 hours, continuously heating to 320 DEG C, and releasing the pressure to normal pressure, so as to obtain the PA56 / PA66 copolymer. And discharging and pelletizing to obtain a target product. By improving the preparation process, the high-temperature-resistant nylon block copolymer which is good in appearance, stable in product performance and good in toughness is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature resistant nylon, and in particular relates to a high-temperature resistant nylon block copolymer and a preparation method thereof. Background Art

[0002] Due to the high melting point of high-temperature resistant nylon, its polymerization technology is relatively difficult to master. Heat media is easily degraded during polymerization, and the polymer tends to yellow. Furthermore, the high melting point of high-temperature resistant nylon salts leads to low solubility in aqueous solutions. During the heating process, the solution crystallizes and agglomerates, resulting in an imbalance in the polymerization vessel, ultimately affecting product uniformity. In severe cases, this can also affect discharge, resulting in significant material retention within the reactor.

[0003] Patent publication number CN104774454A discloses a high-temperature resistant nylon PA66T material and its preparation method. This patent involves directly adding dried nylon 6T salt to PA66 for a high-pressure polymerization reaction, producing the PA6T / 66 high-temperature nylon material via a melt process. Due to the high polymerization temperature, the material appears yellowish. Furthermore, the precipitation of high-temperature nylon salt during the heating phase can cause lumps in the product and result in unsmooth discharge.

[0004] The high-temperature resistant nylon copolymers reported in current patents are primarily copolymerized with PA66 or PA6I. These high-temperature nylons produced using a one-step melt polymerization process often exhibit yellowing and rough discharge. This is because the carboxyl groups of adipic acid are easily decarboxylated during copolymerization with PA66, resulting in yellowing, lumps, rough discharge, and breakage. Furthermore, nylon materials produced using existing technologies suffer from poor toughness and low elongation at break. Summary of the Invention

[0005] In view of the problems existing in the production process of high-temperature resistant nylon copolymers in the prior art, the purpose of the present invention is to provide a high-temperature resistant nylon block copolymer and a preparation method thereof. By improving the synthesis process, the present invention prepares a high-temperature resistant nylon material with good appearance, stable product performance, good toughness and easy modification and processing.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: Add a dibasic acid, a diamine, an antioxidant, a capping agent, and a catalyst to water, mix well, and then perform a salt-forming reaction to obtain a salt solution. Preferably, the molar ratio of the dibasic acid to the diamine is (0.98-1.05):1. Based on the total mass of the dibasic acid and the diamine, the amounts of the antioxidant, the capping agent, and the catalyst are 0.01-1%, 1-3%, and 0.01-1%, respectively. Water acts as a solvent and the amount of water used is sufficient to fully disperse the reaction raw materials. Those skilled in the art can reasonably add water according to needs. Preferably, the mass of water is the same as the total mass of the reaction raw materials. A salt solution is added to a polymerization kettle, and 20-40% by weight of a PA56 or PA66 / PA6 copolymer resin is added. The air in the polymerization kettle is replaced with a protective gas, and the temperature is raised. When the pressure reaches 2.4-3.0 MPa, the pressure is maintained. When the temperature reaches 240-260°C, a prepolymerization reaction is carried out for 1-3 hours. The temperature is then raised to 280-300°C and maintained for 1-3 hours. The temperature is then further raised to 320°C, the pressure is released to atmospheric pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer. Preferably, the protective gas is nitrogen or an inert gas. In the present invention, the melting point of high-temperature nylon is adjusted by controlling the addition amount of PA56 or PA66 / PA6 copolymer. Therefore, the addition amount of PA56 or PA66 / PA6 copolymer has a great influence on the performance of the product. When the addition ratio of PA56 or PA66 / PA6 copolymer is too low, the melting point of high-temperature nylon is relatively high and it is not easy to process; when the addition ratio is too high, the melting point of high-temperature nylon is relatively low, it does not have the advantages of high-temperature nylon, and the temperature resistance will be relatively poor.

[0007] As a preferred technical solution, the temperature of the salt-forming reaction is 105-160° C., more preferably 120-150° C.; the reaction time is 1-3 hours, more preferably 1.5-2.5 hours.

[0008] As a preferred technical solution, the relative viscosity of the PA56 or PA66 / PA6 copolymer resin is 2.0-2.7, and a more preferred relative viscosity is 2.4-2.6.

[0009] As a preferred technical solution, the dibasic acid is an aromatic dibasic acid. More preferably, the aromatic dibasic acid is at least one of terephthalic acid and isophthalic acid.

[0010] As a preferred technical solution, the diamine is an aliphatic diamine. More preferably, the aliphatic diamine is at least one of butanediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, decamethylenediamine, dodecanediamine, and dimethylpentamethylenediamine.

[0011] As a preferred technical solution, the antioxidant is at least one of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, and tris[2,4-di-tert-butylphenyl] phosphite.

[0012] As a preferred technical solution, the end-capping agent is at least one of benzoic acid, acetic acid, propionic acid, and phthalic anhydride.

[0013] As a preferred technical solution, the catalyst is at least one of sodium phosphate, magnesium phosphate, calcium phosphate, sodium phosphite, magnesium phosphite, calcium phosphite, zinc phosphite, sodium hypophosphite, magnesium hypophosphite, calcium hypophosphite, and zinc hypophosphite.

[0014] The present invention also provides a high-temperature resistant nylon block copolymer, which is prepared using the above-described preparation method. The high-temperature resistant nylon block copolymer prepared by the present invention has a melting point of 295-330°C, more preferably 305-315°C, and a relative viscosity of 1.9-2.4, more preferably 2.0-2.2.

[0015] Compared with the prior art, the beneficial effects of the present invention are embodied in: In the preparation process of the high-temperature resistant nylon block copolymer of the present invention, a salt-forming reaction is first carried out, and then the obtained salt solution is reacted with a PA56 or PA66 / PA6 copolymer resin under high temperature and high pressure. The PA56 or PA66 / PA6 copolymer will undergo chain scission and rearrangement in a high-temperature water solvent. The resin stability is higher than that of the PA66 salt, and the material uniformity is good, the material discharge is relatively smooth, the prepared product has a good appearance, the product is stable and easy to modify and process. DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to the embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0017] In addition, unless otherwise specified, the preparation processes in the following examples are conventional means in the prior art in the field, and therefore, they are not described in detail.

[0018] Comparative Example 1 A method for preparing a high-temperature resistant nylon copolymer comprises the following steps: 2696 g of hexamethylenediamine, 2203 g of terephthalic acid, 1586 g of adipic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 100 g of benzoic acid and 10 g of sodium phosphite were weighed and added into a polymerization kettle to carry out salt formation reaction at a reaction temperature of 120° C. for 1.5 hours. The salt solution generated by the reaction is pumped into the polymerization kettle, and the air in the polymerization kettle is replaced with nitrogen. Then the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 240°C, a prepolymerization reaction is carried out for 1.5 hours. The temperature is further increased to 290°C and maintained at this temperature and pressure for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, and the pressure is released to normal pressure. The material is discharged and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0019] Comparative Example 2 A method for preparing a high-temperature resistant nylon copolymer comprises the following steps: 1435 g of hexamethylenediamine, 1106 g of pentamethylenediamine, 2203 g of terephthalic acid, 1586 g of adipic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 100 g of benzoic acid and 10 g of sodium phosphite were weighed and added to a polymerization kettle for salt formation reaction at a reaction temperature of 120° C. for 1.5 hours. The salt solution generated by the reaction is pumped into the polymerization kettle, and the air in the polymerization kettle is replaced with nitrogen. Then the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 240°C, a prepolymerization reaction is carried out for 1.5 hours. The temperature is further increased to 290°C and maintained at this temperature and pressure for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, and the pressure is released to normal pressure. The material is discharged and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0020] Comparative Example 3 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2696 g of hexamethylenediamine, 3850 g of terephthalic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 100 g of benzoic acid and 10 g of sodium phosphite were weighed and added into a polymerization kettle to carry out salt formation reaction at a reaction temperature of 120° C. for 1.5 hours. The salt solution generated by the reaction was pumped into the polymerization kettle, and 1860 g of PA56 resin with a relative viscosity of 2.5 was added; The air in the polymerization kettle is replaced with nitrogen, and the temperature is increased. After the pressure reaches 2.6 MPa, the pressure is maintained. The temperature is increased to 290°C and maintained for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is continued to be increased to 320°C, and the pressure is released to normal pressure. The material is discharged and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0021] Example 1 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2696 g of hexamethylenediamine, 3850 g of terephthalic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 100 g of benzoic acid and 10 g of sodium phosphite were weighed and added into a polymerization kettle to carry out salt formation reaction at a reaction temperature of 120° C. for 1.5 hours. The salt solution generated by the reaction was pumped into the polymerization kettle, and 1860 g of PA56 resin with a relative viscosity of 2.5 was added; The air in the polymerization kettle is replaced with nitrogen, the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 240°C, a prepolymerization reaction is carried out for 1.5 hours. The temperature is further increased to 290°C and maintained at this temperature and pressure for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0022] Example 2 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2696 g of hexamethylenediamine, 3850 g of terephthalic acid, 5 g of tris[2,4-di-tert-butylphenyl]phosphite, 150 g of benzoic acid and 15 g of sodium phosphite were weighed and added to a polymerization kettle to carry out salt formation reaction at a reaction temperature of 110° C. for 2 hours. The salt solution generated by the reaction was pumped into the polymerization reactor, and 2200 g of PA56 resin with a relative viscosity of 2.7 was added; The air in the polymerization kettle is replaced with nitrogen, the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 260°C, a prepolymerization reaction is carried out for 2 hours. The temperature is further increased to 290°C and maintained for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0023] Example 3 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2696 g of hexamethylenediamine, 3880 g of terephthalic acid, 15 g of tris[2,4-di-tert-butylphenyl]phosphite, 80 g of benzoic acid and 5 g of sodium phosphite were weighed and added to a polymerization kettle for salt formation reaction at a reaction temperature of 130° C. for 3 hours. The salt solution generated by the reaction was pumped into a polymerization reactor, and 1800 g of PA66 / PA6 copolymer resin with a relative viscosity of 2.5 was added; The air in the polymerization kettle is replaced with nitrogen, the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 260°C, a prepolymerization reaction is carried out for 1 hour. The temperature is further increased to 290°C and maintained for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0024] Example 4 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2750 g of hexamethylenediamine, 3850 g of terephthalic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 100 g of benzoic acid and 10 g of sodium phosphite were weighed and added into a polymerization kettle to carry out salt formation reaction at a reaction temperature of 120° C. for 2 hours. The salt solution generated by the reaction was pumped into a polymerization reactor, and 2000 g of PA66 / PA6 copolymer resin with a relative viscosity of 2.5 was added; The air in the polymerization kettle is replaced with nitrogen, the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 250°C, a prepolymerization reaction is carried out for 3 hours. The temperature is further increased to 290°C and maintained for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0025] Example 5 A method for preparing a high-temperature resistant nylon block copolymer comprises the following steps: 2696 g of hexamethylenediamine, 3850 g of terephthalic acid, 10 g of tris[2,4-di-tert-butylphenyl]phosphite, 150 g of benzoic acid and 10 g of sodium phosphite were weighed and added to a polymerization kettle to carry out salt formation reaction at a reaction temperature of 120° C. for 1.5 hours. The salt solution generated by the reaction was pumped into the polymerization kettle, and 1860 g of PA56 resin with a relative viscosity of 2.5 was added; The air in the polymerization kettle is replaced with nitrogen, the temperature is increased, and the pressure is maintained after reaching 2.6 MPa. When the temperature reaches 245°C, a prepolymerization reaction is carried out for 2.5 hours. The temperature is further increased to 290°C and maintained at this temperature and pressure for 1.5 hours. After the end of the heat preservation and pressure maintenance, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

[0026] The products prepared in the above comparative examples and examples were subjected to performance tests, wherein the tensile strength was tested according to the standard ISO 527-1-2019, the tensile modulus was tested according to the standard ISO 527-1-2019, the flexural strength was tested according to the standard ISO 178-2019, the charpy notched impact strength was tested according to the standard ISO 179-1-2023, the melting point was tested according to the standard ISO 1133, and the yellowness index was tested according to the standard ISO 17223; the test results are shown in Table 1 below: Table 1

[0027] As can be seen from Table 1, the high-temperature resistant nylon block copolymer prepared by the embodiment of the present invention has a better appearance, and the yellow index is all within 10. However, in conventional high-temperature nylon copolymers, the presence of PA66 salt and the insufficient heat resistance of the carboxyl group of adipic acid are easy to decarboxylate, resulting in yellowing of the material. In addition, the process provided by the present invention is to first prepolymerize semi-aromatic nylon at 240-260°C, and then connect the aliphatic nylon at 280-300°C. After reaching 320°C, the pressure is released, and the high-temperature nylon prepolymer is polycondensed with the low-molecular-weight aliphatic nylon that has broken the chain, and polymerizes into a block copolymer. By comparing Example 1 and Comparative Example 3, it can be seen that the product prepared by the process of the present invention has better performance. The high-temperature nylon block copolymer prepared by the present invention not only retains the high strength and high modulus of semi-aromatic nylon, but also has the toughness of aliphatic nylon and has a higher elongation at break.

[0028] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0029] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a high-temperature resistant nylon block copolymer, characterized in that: The following steps are involved: Adding dibasic acid, diamine, antioxidant, end-capping agent and catalyst into water, mixing them evenly and then performing salt formation reaction to obtain a salt solution; The salt solution is added to a polymerization kettle, and 20-40% of the total material mass of PA56 or PA66 / PA6 copolymer resin is added; the air in the polymerization kettle is replaced with protective gas and then the temperature is increased. When the pressure reaches 2.4-3.0 MPa, the pressure is maintained. When the temperature reaches 240-260°C, a prepolymerization reaction is carried out for 1-3 hours. The temperature is further increased to 280-300°C and the temperature is maintained and the pressure is maintained for 1-3 hours. Then, the temperature is further increased to 320°C, the pressure is released to normal pressure, the material is discharged, and pelletized to obtain a high-temperature resistant nylon block copolymer.

2. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The molar ratio of the dibasic acid to the diamine is (0.98-1.05):

1.

3. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The temperature of the salt-making reaction is 105-160° C., and the time is 1-3 hours.

4. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The relative viscosity of the PA56 or PA66 / PA6 copolymer resin is 2.0-2.

7.

5. The method for preparing a high temperature resistant nylon block copolymer according to any one of claims 1 to 4, characterized in that: The dibasic acid is an aromatic dibasic acid.

6. The method for preparing a high temperature resistant nylon block copolymer according to claim 5, wherein: The aromatic dibasic acid is at least one of terephthalic acid and isophthalic acid.

7. The method for preparing a high temperature resistant nylon block copolymer according to any one of claims 1 to 4, characterized in that: The diamine is an aliphatic diamine.

8. The method for preparing a high temperature resistant nylon block copolymer according to claim 7, wherein: The aliphatic diamine is at least one of butanediamine, pentamethylenediamine, hexamethylenediamine, nonanediamine, decamethylenediamine, dodecamethylenediamine, and dimethylpentamethylenediamine.

9. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The antioxidant is at least one of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N,N-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, and tris[2,4-di-tert-butylphenyl] phosphite.

10. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The end-capping agent is at least one of benzoic acid, acetic acid, propionic acid, and phthalic anhydride.

11. The method for preparing a high temperature resistant nylon block copolymer according to claim 1, wherein: The catalyst is at least one of sodium phosphate, magnesium phosphate, calcium phosphate, sodium phosphite, magnesium phosphite, calcium phosphite, zinc phosphite, sodium hypophosphite, magnesium hypophosphite, calcium hypophosphite, and zinc hypophosphite.

12. A high temperature resistant nylon block copolymer, characterized in that: The high temperature resistant nylon block copolymer is prepared by the preparation method according to any one of claims 1 to 11.

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