阅读说明：本技术 一种具有较好加工性能的半芳香族聚酰胺树脂及其制备方法和应用 (Semi-aromatic polyamide resin with good processability and preparation method and application thereof ) 是由 汤锡銮 杨剑停 严海南 康杰 于 2021-08-16 设计创作，主要内容包括：本发明公开了一种具有较好加工性能的半芳香族聚酰胺树脂及其制备方法和应用,其原料按照质量百分比包括：1,4-二氢对苯二甲酸1～50％、二元酸0～40％、二元胺5～50％、封端剂0.1～5％、催化剂0.005～1.5％、去离子水10～70％；本发明通过利用1,4-二氢对苯二甲酸部分或者全部替代对苯二甲酸参与反应,PA6T低聚物含量减少,聚合过程中低聚物的结块倾向减小,从而降低反应压力,降低高压釜的耐压等级,降低设备成本和产品生产成本,提高产品市场竞争力；同时较低的压力使得高压釜可以做成锥底,反应完成后物料残余量少,产成品率高、对后续生产和产品品质影响较小。(The invention discloses a semi-aromatic polyamide resin with better processability, a preparation method and an application thereof, wherein the semi-aromatic polyamide resin comprises the following raw materials in percentage by mass: 1-50% of 1, 4-dihydroterephthalic acid, 0-40% of dibasic acid, 5-50% of diamine, 0.1-5% of end-capping agent, 0.005-1.5% of catalyst and 10-70% of deionized water; according to the invention, 1, 4-dihydroterephthalic acid is used for partially or completely replacing terephthalic acid to participate in the reaction, so that the content of PA6T oligomer is reduced, and the caking tendency of the oligomer in the polymerization process is reduced, thereby reducing the reaction pressure, reducing the pressure-resistant grade of the high-pressure kettle, reducing the equipment cost and the product production cost, and improving the market competitiveness of the product; meanwhile, the high-pressure kettle can be made into a conical bottom under lower pressure, the residual amount of materials after the reaction is finished is small, the yield is high, and the influence on subsequent production and product quality is small.)

1. A semi-aromatic polyamide resin with better processing performance is characterized in that: the semi-aromatic polyamide resin comprises the following raw materials in percentage by mass:

2. the semi-aromatic polyamide resin with better processability as claimed in claim 1, wherein: the semi-aromatic polyamide resin comprises the following raw materials in percentage by mass:

3. the semi-aromatic polyamide resin with better processability as claimed in claim 1, wherein: the dibasic acid is one or more of aromatic dibasic acid, aliphatic dibasic acid and alicyclic dibasic acid.

4. The semi-aromatic polyamide resin with better processability as claimed in claim 1, wherein: the diamine is one or more of aromatic diamine, aliphatic diamine and alicyclic diamine.

5. The semi-aromatic polyamide resin with better processability as claimed in claim 1, wherein: the end capping agent is one or more of monoacid, diacid, polyacid, monoamine, diamine, polyamine, amino acid, piperazine, pyrrolidine, anhydride, isocyanate, acyl chloride, ester, alkali metal salt, monohydric alcohol and dihydric alcohol.

6. The semi-aromatic polyamide resin with better processability as claimed in claim 1, wherein: the catalyst is one or more of phosphoric acid, phosphorous acid, hypophosphorous acid or metal salts or esters thereof.

7. Use of the semi-aromatic polyamide resin having better processability as defined in claim 1.

8. The method for preparing semi-aromatic polyamide resin with better processability according to any one of claims 1 to 7, characterized by comprising the steps of:

(1) weighing 1, 4-dihydroterephthalic acid, dibasic acid, diamine, an end-capping reagent, a catalyst and deionized water according to the mass percentage, adding the weighed materials into a high-pressure reaction kettle, vacuumizing the high-pressure reaction kettle, filling nitrogen, and keeping the micro-positive pressure of 0.03-0.07 MPa;

(2) heating the high-pressure reaction kettle to 200 ℃ and 260 ℃ under the stirring condition of 80-120 r/min, increasing the pressure to 1.5-2.5 MPa, and reacting for 0.1-2 h;

(3) maintaining the constant pressure state, continuously heating to 220-290 ℃, relieving the pressure in the kettle to 0MPa after 0.5-2h, and then reacting at constant temperature and normal pressure for 0.1-1 h;

(4) and (3) extruding the polymerization product from the reaction kettle, and cooling and pelletizing the polymerization product in a water tank to obtain the semi-aromatic polyamide resin with better processability.

9. A method for preparing a modified product by using a semi-aromatic polyamide resin with better processability is characterized by comprising the following steps:

(1) modifying the semi-aromatic polyamide resin by blending modification and adding a modifier to obtain a modified product;

(2) and (3) performing injection molding on the modified product at 170-280 ℃, continuously heating the modified product in a mold at 250-270 ℃ for 10-30 min, cooling the product, taking the product out of the mold, and continuously heating the product at 260-280 ℃ for 2-6h to obtain the final product.

10. The method of claim 9, wherein the modifier is one or more of fibrous or powdery reinforcing filler, antioxidant, light stabilizer, ultraviolet absorber, ultraviolet blocker, lubricant, dye, metallic pigment, nucleating agent, antistatic agent, heat conductive filler, flame retardant, whitening agent, and plasticizer.

Technical Field

The invention belongs to the technical field of synthesis of high polymer materials, and particularly relates to a semi-aromatic polyamide resin with good processability, and a preparation method and application thereof.

Background

Many industrial polymers are prepared by polycondensation, and release micromolecular byproducts while the molecular weight is increased, so that the reaction balance is promoted to move towards the positive reaction direction, the molecular weight of the polymer is increased, and the mechanical and thermal properties are improved. Among them, polyamide is an important polycondensation product, which can be used in many applications, and PA6 and PA66 have moderate melting point and heat resistance, are easy to process, and particularly become the most used nylon varieties after glass fiber reinforcement or mineral filling. However, they have a water absorption of up to 10% when put into water, and cannot be applied to many fields where dimensional stability is strictly required in a humid environment, and the water absorption affects not only dimensional stability but also mechanical properties, resulting in a significant decrease in rigidity and strength, and thus there is a great problem in application in a humid environment. Moreover, the common nylon is difficult to meet the requirements of electronic and electrical reflow soldering process and higher using temperature around the automobile engine. In this case, the semi-aromatic polyamide becomes particularly important due to high temperature stability and low water absorption.

The semi-aromatic polyamide is prepared by condensation polymerization of aliphatic diamine or diacid and diacid with aromatic rings or diamine, the melting point and the heat resistance can be regulated and controlled by adjusting the proportion of monomers in a formula, and the semi-aromatic polyamide with higher melting point and heat resistance needs to be prepared for the reflow soldering process of electronics and electricity, the application fields of automobile engine periphery and the like. The semi-aromatic polyamide products with higher melting points, especially the semi-aromatic polyamide products with higher content of aromatic units, such as PA6T/6I, are easy to agglomerate in the polymerization process, wherein the agglomeration is easy to occur when the content of PA6T is higher. In order to ensure that the prepared semi-aromatic polyamide product has better crystallization performance and heat resistance, the content of PA6T needs to be higher than 65%, and under the formula condition, the semi-aromatic polyamide product is easy to agglomerate and has very high preparation difficulty. Water or small molecules exist in a system, which is helpful for relieving the agglomeration of PA6T oligomer, at a certain reaction temperature, the higher the water or small molecule content in the system is, the less the PA6T oligomer is agglomerated, but at a higher temperature, the saturated vapor pressure of the water or the volatile small molecules is increased rapidly, so that the reaction needs to be carried out at an extremely high pressure to ensure that enough water or small molecules exist in the system, and reaction equipment such as an autoclave and the like is required to have a very high pressure-resistant grade, even more than 4.0 MPa. Under such high pressure conditions, the autoclave cannot be made into a tapered bottom and can only be used for end capping, and after the polymerization of the product is finished, a lot of materials with higher viscosity can be remained, so that the yield of the product is reduced, and more seriously, the residual materials can influence the subsequent production and the quality of the product. Moreover, the effect is more obvious when the pressure grade is increased, the wall thickness of the equipment is sharply increased, and the equipment volume is larger, so that the investment cost of the equipment and the production cost of the product are obviously increased.

Disclosure of Invention

The invention aims to solve the problems that PA6T is easy to agglomerate in the polymerization process, enough water or water molecules are ensured in an agglomeration system to be relieved, so that reaction is carried out under extremely high pressure, and after the product polymerization is finished, a large amount of high-viscosity materials are remained, so that the product yield and the product quality are reduced, and the like in the prior art, and provides a semi-aromatic polyamide resin with good processability and a preparation method thereof. According to the invention, 1, 4-dihydroterephthalic acid is used for partially or completely replacing terephthalic acid to participate in the reaction, so that the content of PA6T oligomer is reduced, and the caking tendency of the oligomer in the polymerization process is reduced, thereby reducing the reaction pressure, reducing the pressure-resistant grade of the high-pressure kettle, reducing the equipment cost and the product production cost, and improving the market competitiveness of the product; meanwhile, the high-pressure kettle can be made into a conical bottom under lower pressure, the residual amount of materials after the reaction is finished is small, the yield is high, and the influence on subsequent production and product quality is small.

In order to achieve the above object, one of the technical solutions of the present invention is to provide a semi-aromatic polyamide resin with good processability, which comprises the following raw materials by mass:

in a preferred embodiment of the present invention, the raw materials of the semi-aromatic polyamide resin include, by mass:

in a preferred embodiment of the present invention, the dibasic acid is selected from all dibasic acids except 1, 4-dihydroterephthalic acid, and is further selected from one or more of aromatic dibasic acid, aliphatic dibasic acid, and alicyclic dibasic acid.

In a preferred embodiment of the present invention, the aromatic dibasic acid is selected from one of substituted or unsubstituted aromatic ring-containing dibasic acids of C8-C20, preferably one or a mixture of two of terephthalic acid and isophthalic acid.

In a preferred embodiment of the present invention, the aliphatic dibasic acid is selected from linear or branched C2-C36 aliphatic dibasic acids, preferably one or a mixture of more of oxalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3-diethylsuccinic acid, glutaric acid, 2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, 2,4, 4-trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, nonadecane dioic acid, eicosanedioic acid, heneicosanedioic acid, and docanedioic acid, and more preferably one or a mixture of more of adipic acid and sebacic acid.

In a preferred embodiment of the present invention, the alicyclic dibasic acid is selected from substituted or unsubstituted aliphatic ring-containing dibasic acids of C8-C20, preferably one or a mixture of two of 1, 4-cyclohexanedicarboxylic acid and 1, 3-cyclohexanedicarboxylic acid.

In a preferred embodiment of the present invention, the diamine is selected from one or a mixture of several of aromatic diamine, aliphatic diamine, and alicyclic diamine.

In a preferred embodiment of the present invention, the aromatic diamine is selected from substituted or unsubstituted aromatic ring-containing C6-C20 diamines, preferably p-xylylenediamine, m-xylylenediamine or a mixture of two thereof.

In a preferred embodiment of the present invention, the aliphatic diamine is selected from linear or branched C2-C36 aliphatic diamines, preferably ethylene diamine, propylene diamine, butylene diamine, pentylene diamine, 2-methyl-1, 5-pentylene diamine, 3-methyl-1, 5-pentylene diamine, hexylene diamine, 2, 4-trimethylhexylene diamine, 2,4, 4-trimethylhexylene diamine, heptylene diamine, octylene diamine, 2-methyl-1, 8-octylene diamine, 3-methyl-1, 8-octylene diamine, nonylene diamine, 5-methyl nonylene diamine, decylene diamine, undecylene diamine, dodecylene diamine, tridecylene diamine, tetradecylene diamine, more preferably butylene diamine, pentylene diamine, 2-methyl pentylene diamine, hexylene diamine, nonylene diamine, nonaethylene diamine, and mixtures thereof, One or more of decamethylenediamine.

In a preferred embodiment of the invention, the alicyclic diamine is selected from substituted or unsubstituted aliphatic ring-containing diamines of C6-C20, preferably one or more of 3-aminomethyl-3, 5, 5-trimethylcyclohexylamine, bis (4-aminocyclohexyl) methane and bis (3-methyl-4-aminocyclohexyl) methane.

In a preferred embodiment of the present invention, the blocking agent is selected from chemicals that can react with amino groups and/or carboxyl groups at the ends of the polyamide molecular chain, and these chemicals may or may not contain aromatic rings. And a mixture of one or more selected from the group consisting of monobasic acids, dibasic acids, polybasic acids, monobasic amines, dibasic amines, polybasic amines, amino acids, piperazine, pyrrolidine, anhydrides, isocyanates, acid chlorides, esters, alkali metal salts, monohydric alcohols, and dibasic alcohols, and further preferably a mixture of one or more selected from the group consisting of acetic acid, benzoic acid, ethylamine, benzylamine, and 2,2,6, 6-tetramethylpiperidin-4-amine. The end capping agent can narrow the molecular weight distribution of the polymer, reduce the deterioration of the catalyst, reduce gas in the forming process, improve the demolding performance and prevent the performance deterioration caused by thermal degradation, photodegradation and oxidative degradation. But the addition amount should be moderate, too much content may cause too low molecular weight and poor mechanical properties of the product, and too little content may cause too high molecular weight, poor processability, broadened molecular weight distribution, and deteriorated properties caused by degradation in use and processing.

In a preferred embodiment of the invention, the catalyst is selected from organic or inorganic compounds having a catalytic effect on the polymerization process of polyamides, preferably phosphoric acid, phosphorous acid, hypophosphorous acid or metal salts or esters thereof. The catalyst has a catalytic action in the system, so that the reaction rate is accelerated, and the product has better quality; the dosage is too small, which can only slightly accelerate, the product can still change color/degrade, and the dosage is too large, the polymerization degree is too large, the gel or the color change is generated, and the processing is difficult.

The second technical scheme adopted by the invention is to provide the application of the semi-aromatic polyamide resin with better processability.

The third technical scheme adopted by the invention is to provide a preparation method of semi-aromatic polyamide resin with better processability, which specifically comprises the following steps:

(1) weighing 1-50% of 1, 4-dihydroterephthalic acid, 0-40% of dibasic acid, 5-50% of diamine, 0.1-5% of end capping agent, 0.005-1.5% of catalyst and 10-70% of deionized water according to the mass percentage, adding the weighed materials into a high-pressure reaction kettle together, vacuumizing the high-pressure reaction kettle, filling nitrogen, repeating the steps for three times to remove residual air in the reaction kettle, and keeping the micro-positive pressure of the high-pressure reaction kettle at 0.03-0.07 MPa after the replacement is finished;

(2) heating the high-pressure reaction kettle to 200 ℃ and 260 ℃ under the stirring condition of 80-120 r/min, increasing the pressure to 1.5-2.5 MPa, and reacting at constant temperature for 0.1-2 h;

(3) continuously heating, simultaneously enabling the high-pressure reaction kettle to be in a constant pressure state by a method of releasing water vapor in the high-pressure reaction kettle, slowly releasing the pressure in the kettle to 0MPa after 0.5-2h when the temperature is increased to 220-290 ℃, and then carrying out constant-temperature reaction at normal pressure for 0.1-1 h;

(4) and (3) extruding the polymerization product from the reaction kettle, and cooling and pelletizing the polymerization product in a water tank to obtain the semi-aromatic polyamide resin with better processability.

After the product is polymerized, the product can be directly used for preparing films, monofilaments, fibers, yarns or textiles, and can also be subjected to melt blending modification by using extrusion equipment and a modifier, so that the mechanical property, the thermal property, the electrical property and the processing property of the product are improved, and the obtained composite material is applied to the fields of electronics, electrics, automobiles and the like.

The fourth technical scheme adopted by the invention is to provide a method for preparing a modified product by using semi-aromatic polyamide resin with better processing performance, which comprises the following steps:

(1) modifying the semi-aromatic polyamide resin by blending modification and adding a modifier to obtain a modified product;

(2) and (3) performing injection molding on the modified product at 170-280 ℃, continuously heating the modified product in a mold at 250-270 ℃ for 10-30 min, cooling the product, taking the product out of the mold, and continuously heating the product at 260-280 ℃ for 2-6h to obtain the final product.

In a preferred embodiment of the present invention, the modifier is selected from one or more of fibrous reinforcing filler or powdered reinforcing filler, antioxidant, light stabilizer, ultraviolet absorbent, ultraviolet blocking agent, lubricant, dye, metal pigment, nucleating agent, antistatic agent, heat conductive filler, flame retardant, whitening agent, and plasticizer.

In a preferred embodiment of the present invention, the extrusion equipment is selected from all equipment capable of melt blending the plastics and the additives, preferably one or more of a single screw extruder, a twin screw extruder, a kneader, and a banbury mixer, and more preferably a twin screw extruder.

In a preferred embodiment of the present invention, the molding method is one or more methods selected from injection molding, multi-component injection molding, injection compression molding, injection blow molding, extrusion molding, pultrusion molding, casting molding, calendaring molding, vacuum molding, closed embossing or expanded embossing, preferably injection molding.

Compared with the background technology, the technical scheme of the invention has the following beneficial effects:

1. the 1, 4-dihydroterephthalic acid is added to be copolymerized with other polyamide monomers to prepare the conventional semi-aromatic polyamide resin, the polymerization temperature of common polyamide can be adopted, and the polymerization difficulty and energy consumption are reduced.

2. The semi-aromatic polyamide resin prepared by the invention can adopt the polymerization temperature of common polyamide, reduces the side reaction of the product at high temperature, and has better quality and appearance.

3. The semi-aromatic polyamide resin prepared by the invention can adopt the polymerization pressure and temperature of common polyamide, can use the existing common polyamide polymerization equipment, reduces the polymerization difficulty, saves the equipment investment, reduces the production cost and increases the market competitiveness of the product.

4. The semi-aromatic polyamide resin prepared by the invention can be subjected to subsequent blending modification, the blending modification temperature before heat treatment can still adopt the processing temperature of common polyamide, the side reaction of the product is reduced, the product quality is improved, and the energy consumption is saved.

5. The semi-aromatic polyamide resin prepared by the invention can freely and flexibly adjust the heat resistance and the processability of the product at any time, not only can increase the heat resistance of the product through heat treatment in the later period of polymerization, but also can be subjected to heat treatment in the modification process, or the product is subjected to heat treatment in the injection molding process of a mold after the modification is finished, so that the final product and a finished product can achieve the required heat resistance, and meanwhile, the product keeps better processability before the heat treatment.

6. Compared with a radiation crosslinking polyamide product, the semi-aromatic polyamide resin prepared by the invention is similar to a semi-aromatic polyamide product prepared by a conventional polymerization method, and the product can be recycled after use and keeps better heat resistance and processability;

7. the invention is different from the prior polymerization method of pre-polymerization and solid phase polycondensation of semi-aromatic polyamide: after the melt polymerization step of the product is completed, the molecular weight of the product is very high, which is obviously different from the lower molecular weight of the prior semi-aromatic polyamide prepolymer, and the molecular weight of the product is not continuously increased by the later heat treatment, but 1, 4-dihydroterephthalic acid in a molecular chain is dehydrogenated and converted into terephthalic acid under the heated condition, so that the heat resistance of the product is improved, and the molecular weight of the prepolymer is increased by the prior semi-aromatic polyamide solid phase polycondensation, and the structure of a molecular chain repeating unit of the product is not changed.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following will describe the contents of the present invention in more detail by way of examples, but the scope of the present invention is not limited to these examples.

The performance tests in the examples of the invention and the comparative examples were carried out according to the following criteria:

melting point Tm: according to ISO 11357: the temperature is raised to 350 ℃ at the speed of 20 ℃/min by a differential scanning calorimeter (German relaxation-resistant DSC214Polyma), and the peak temperature corresponding to the endothermic melting peak on the temperature raising curve is the melting point Tm of the product. It should be noted that if a conventional temperature raising-lowering-re-raising procedure is adopted, it is found that the peak temperature corresponding to the endothermic melting peak of the second temperature raising curve is obviously raised, because in the first temperature raising process, part of 1, 4-dihydroterephthalic acid is dehydrogenated and converted into terephthalic acid under the heated condition, the molecular structure of the product is changed, the melting point is raised, and the product is not the melting point of the test substance.

Tensile strength was according to ISO/CD3167, tensile bars were type TypeA1, 170X 20/10X 4 mm; the test procedure is carried out according to ISO527 standard, tensile speed 5mm/min, temperature 23 ℃.

Flexural modulus was determined according to ISO178 at 23 ℃ at a rate of 2 mm/min.

Example 1

(1) Weighing 2017.6g (12.0mol) of 1, 4-dihydroterephthalic acid, 1169.1g (8.0mol) of adipic acid, 2347.4g (20.2mol) of hexamethylenediamine, 36.6g (0.3mol) of end-capping reagent benzoic acid, 5.6g of catalyst sodium hypophosphite and 2000g of deionized water, adding the materials into a 25L high-pressure reaction kettle, vacuumizing the high-pressure reaction kettle, filling nitrogen, repeating the steps for three times to remove residual air in the reaction kettle, and keeping the micro-positive pressure of the high-pressure reaction kettle to be 0.05MPa after the replacement is finished;

(2) heating the high-pressure reaction kettle to 215 ℃ under the stirring condition of 100r/min, increasing the pressure to 2.0MPa at the same time, and reacting for 1h at constant temperature and constant pressure;

(3) continuously heating, simultaneously enabling the high-pressure reaction kettle to be in a constant pressure state of 2.0MPa by a method of releasing water vapor in the high-pressure reaction kettle, after heating to 280 ℃, slowly releasing the pressure in the kettle to 0MPa after 1h, and then carrying out constant-temperature reaction for 0.2h at normal pressure;

(4) extruding the polymerization product from a reaction kettle, and carrying out bracing, water tank cooling and grain cutting;

(5) and (3) performing injection molding on the polymerization product at 270 ℃, continuously heating the polymerization product in a mold at 260 ℃ for 20min, cooling the polymerization product, taking the polymerization product out of the mold, and continuously heating the polymerization product at 265 ℃ for 3h to obtain a final product.

The raw material monomers and properties thereof of example 1 are shown in Table 1, and the polymerized product, the injection-molded product, and the heat-treated product were separately subjected to DSC tests, and the results are shown in Table 1.

Example 2

(1) Weighing 2522.0g (15.0mol) of 1, 4-dihydroterephthalic acid, 830.7g (5.0mol) of terephthalic acid, 3480.7g (20.2mol) of decamethylene diamine, 36.6g (0.3mol) of end-capping reagent benzoic acid, 6.9g of catalyst sodium hypophosphite and 2000g of deionized water, adding the materials into a 25L high-pressure reaction kettle, vacuumizing the high-pressure reaction kettle, filling nitrogen, repeating the steps for three times to remove residual air in the reaction kettle, and keeping the micro-positive pressure of the high-pressure reaction kettle to be 0.05MPa after the replacement is finished;

(2) heating the high-pressure reaction kettle to 225 ℃ under the stirring condition of 100r/min, increasing the pressure to 2.4MPa at the same time, and reacting for 1h at constant temperature and constant pressure;

(3) and continuously heating, simultaneously enabling the high-pressure reaction kettle to be in a constant pressure state of 2.4MPa by a method of releasing water vapor in the high-pressure reaction kettle, after heating to 280 ℃, slowly releasing the pressure in the kettle to 0MPa after 1 hour, and then carrying out constant-temperature reaction for 0.2 hour at normal pressure.

(4) Extruding the polymerization product from a reaction kettle, and carrying out bracing, water tank cooling and grain cutting;

(5) and (3) performing injection molding on the polymerization product at 275 ℃, continuously heating the polymerization product in a mold at 265 ℃ for 20min, cooling the polymerization product, taking the polymerization product out of the mold, and continuously heating the polymerization product at 270 ℃ for 2.5h to obtain a final product.

The raw material monomers and properties of example 2 are shown in Table 1, and the results of DSC measurement of the polymerized product, the injection-molded product and the heat-treated product are shown in Table 1.

Example 3

2353.8g (14.0mol) of 1, 4-dihydroterephthalic acid, 996.8g (6.0mol) of isophthalic acid, 2347.4g (20.2mol) of hexamethylenediamine, 36.6g (0.3mol) of end-capping reagent benzoic acid, 5.5g of catalyst sodium hypophosphite and 2000g of deionized water are weighed and added into a 25L high-pressure reaction kettle; except for this, semi-aromatic polyamide resins were synthesized in the same manner as in example 1, the proportions of the raw material monomers and the properties thereof in example 3 are shown in Table 1, and the results of DSC measurement of the polymerized products, the products after completion of injection molding and the products after heat treatment are shown in Table 1.

Comparative example 1

(1) Weighing 1993.6g (12.0mol) of terephthalic acid, 1169.1g (8.0mol) of adipic acid, 2347.4g (20.2mol) of hexamethylenediamine, 36.6g (0.3mol) of end-capping reagent benzoic acid, 5.5g of catalyst sodium hypophosphite and 2000g of deionized water, adding the materials into a 25L high-pressure reaction kettle, vacuumizing and filling nitrogen into the high-pressure reaction kettle, repeating the steps for three times to remove residual air in the reaction kettle, and keeping the micro-positive pressure of the high-pressure reaction kettle at 0.05MPa after replacement is finished;

(2) heating the high-pressure reaction kettle to 215 ℃ under the stirring condition of 100r/min, increasing the pressure to 2.0MPa at the same time, and reacting for 1h at constant temperature and constant pressure;

(3) continuously heating, simultaneously enabling the high-pressure reaction kettle to be in a constant pressure state of 2.0MPa by a method of releasing water vapor in the high-pressure reaction kettle, after the temperature is increased to 220 ℃, continuously reacting for 2 hours at constant temperature and constant pressure, stopping the reaction, and taking out the material from the reaction kettle after cooling;

(4) the product is dried in vacuum for 24 hours at the temperature of 80 ℃, and is tackified for 10 hours in solid phase at the temperature of 260 ℃ to obtain a resin product.

The raw material monomers and properties of comparative example 1 are shown in table 1, and the product is melted and prepolymerized, and can only be taken out from the reaction kettle after the product is cooled and crushed because the molecular weight is too small and the viscosity is too low to smoothly brace and cut into particles, and then solid phase polycondensation is carried out.

Comparative example 2

(1) Weighing 1993.6g (12.0mol) of terephthalic acid, 1169.1g (8.0mol) of adipic acid, 2347.4g (20.2mol) of hexamethylenediamine, 36.6g (0.3mol) of end-capping reagent benzoic acid, 5.5g of catalyst sodium hypophosphite and 2000g of deionized water, adding the materials into a 25L high-pressure reaction kettle, vacuumizing and filling nitrogen into the high-pressure reaction kettle, repeating the steps for three times to remove residual air in the reaction kettle, and keeping the micro-positive pressure of the high-pressure reaction kettle at 0.05MPa after replacement is finished;

(2) heating the high-pressure reaction kettle to 215 ℃ under the stirring condition of 100r/min, increasing the pressure to 2.0MPa at the same time, and reacting for 1h at constant temperature and constant pressure;

(3) continuously heating, simultaneously enabling the high-pressure reaction kettle to be in a constant pressure state of 2.0MPa by a method of releasing water vapor in the high-pressure reaction kettle, heating to 280 ℃, and slowly releasing the pressure in the kettle to 0MPa after 1 hour; when the pressure is reduced to 1.0MPa, the materials in the reaction kettle are agglomerated, the stirring is stopped, and the reaction is stopped.

The raw material monomers of comparative example 2 and their properties are shown in table 1.

Example 4

(1) 1400g of the polymerized product obtained in the step (4) of example 1 (without injection molding and heat treatment in the step (5)) was dried at 120 ℃ for 4-6 h, and blended with 2g of antioxidant 1098, 2g of auxiliary antioxidant 168, and 5g of lubricant zinc stearate for 5 min. Adding into main feeding port of twin screw extruder (Kedoulong STS35 series twin screw extruder, length-diameter ratio 40) via weight loss scale;

(2) feeding 600g of glass fiber into a double-screw extruder from the side by a weightless scale in a 5 th zone according to a proportion, wherein the rotation speed of a screw is 300rpm, the temperature of each zone is 250 ℃, 270 ℃, 280 ℃, 290 ℃, 270 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃ and the head temperature is 275 ℃, and the yield is 50 kg/h;

(3) the product is extruded and pulled into strips through an extruder die head, the strips are cut into granules after being cooled by a water tank, and the granules are dried for 4 hours at 120 ℃;

(4) and (3) performing injection molding on the modified product at 280 ℃, continuously heating the modified product in a mold for 20min at 260 ℃, cooling the modified product, taking the modified product out of the mold, and continuously heating the modified product for 3h at 265 ℃ to obtain the final product.

DSC is respectively tested on the modified product, the product after injection molding and the product after heat treatment, the tensile strength and the flexural modulus are tested on the product after heat treatment, and the test results are listed in Table 2.

Example 5

(1) The test specimens from example 4 were crushed with a crusher (Enma Reduire200 series crusher) to give granules of 3X 3mm diameter and the granules were dried at 120 ℃ for 4 h;

(2) the pellets were injection molded at 320 ℃ to give mechanical property test bars, and the pellets were tested for DSC, tensile strength and flexural modulus, and the test results are shown in Table 2.

TABLE 1 raw material formulations and performance test results of examples 1-3 and comparative examples 1-2

Raw materials and Properties	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2
						1, 4-dihydroterephthalic acid/mol	12	15	14	-	-
Terephthalic acid/mol	-	5	-	12	12
						Isophthalic acid/mol	-	-	6	-	-
Adipic acid/mol	8	-	-	8	8
						Hexamethylene diamine per mole	20.2	-	20.2	20.2	20.2
Decamethylenediamine/mol	-	20.2	-	-	-
						Benzoic acid/mol	0.3	0.3	0.3	0.3	0.3
Sodium hypophosphite/%)	0.1	0.1	0.1	0.1	0.1
						Melting Point/. degree.C.of the polymeric product	251	256	260	-	316
Melting Point/. degree.C.of injection-molded product	280	289	291	-	-
						Melting Point/. degree C of Heat-treated product	316	313	325	-	-

Table 2 results of performance testing of examples 4 and 5

Performance of	Melting Point/. degree.C. of modified product	Melting Point/. degree.C.of injection-molded product	Melting Point/. degree C of Heat-treated product	Tensile strength/MPa	Flexural modulus/MPa
						Example 4	272	293	316	174	8100
Example 5	315	-	-	165	7900

As can be seen from the comparison of the experimental procedures and test results of example 1 and comparative example 1, 4-dihydroterephthalic acid was used in example 1 and terephthalic acid was used in comparative example 1, and the polymerization was completed at a lower temperature and pressure by the same polymerization process. Comparative example 1 agglomerated at the late stage of the reaction, and smooth production was not possible; example 1 was able to smoothly polymerize and the melting point of the product was remarkably increased after injection molding and heat treatment to reach the melting point of the resin produced by the prepolymerization + solid phase polycondensation process of comparative example 2, indicating that the product having the predetermined melting point and heat resistance properties could be smoothly produced by the polymerization and heat treatment process of the present invention. But the temperature and pressure in the polymerization process are obviously reduced, and the polymerization difficulty and energy consumption are reduced. The existing common polyamide polymerization equipment can be used, the polymerization difficulty is reduced, the equipment investment is saved, the production cost is reduced, and the market competitiveness of the product is enhanced.

By observing the experimental processes and test results of example 1, example 2 and example 3, it can be seen that the polymerization process is carried out at a lower temperature and pressure close to that of ordinary aliphatic nylon, and the obtained polymer product has better processability, but lower melting point and heat resistance. After the polymerization product is subjected to injection molding heating and subsequent heat treatment, the melting point and the heat resistance of the product are continuously improved, particularly the melting point and the heat resistance of the product after the heat treatment reach the theoretical melting point and the heat resistance of the semi-aromatic polyamide resin under the conventional polymerization process, and the purpose of producing the semi-aromatic polyamide resin by adopting the common polymerization process is realized.

By observing the experimental process and the test results of example 4, it can be seen that the polymer product of example 1 is modified by adding glass fiber at the processing temperature of the conventional polyamide to prepare a glass fiber reinforced product, which is then injection molded and heat treated to obtain the final product. As can be seen from Table 2, the melting point of the modified product was higher than that of the polymerized product of example 1, because a small amount of 1, 4-dihydroterephthalic acid was dehydrogenated to terephthalic acid by the heat and screw shear during the modification, and the melting point of the product was raised. During the subsequent injection molding and heat treatment, more 1, 4-dihydroterephthalic acid was dehydrogenated to terephthalic acid, and the melting point of the product was increased until the same melting point as the heat-treated product of example 1 was reached. At this time, the 1, 4-dihydroterephthalic acid in the product is almost completely dehydrogenated into terephthalic acid, the melting point of the product cannot be continuously increased even if the heat treatment is continued, and even the melting point of the product is slightly reduced due to the breakage of a molecular chain of a side reaction. The mechanical property of the final product also reaches the expectation, which shows that the modified product can be smoothly produced by adopting the polymerization and modification process of the invention, and the mechanical property of the obtained product can meet the use requirement of customers.

As can be seen from the experimental process and test results of example 5, the injection molded product of example 4 was crushed, dried, and re-injection molded, and the molded product was successfully obtained by injection molding. The melting point and the mechanical property of the injection molding product are tested and are basically equivalent to those of the example 4, but a small amount of glass fibers are broken and the length-diameter ratio is reduced due to the crushing and the re-injection molding process, and the mechanical property of the product is slightly reduced. The product of the invention can be recycled after use, and keeps better heat resistance and processability, which is essentially different from the radiation crosslinking polyamide product.

The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.