CN113621136B - Method for preparing polyamide material by block copolymerization - Google Patents
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Abstract
The invention discloses a method for preparing a semi-aromatic polyamide material by block copolymerization. The method comprises the following steps: s1, prepolymerizing a first molecular weight regulator and an aliphatic comonomer in a molar ratio of 0.005-0.08: 1 to obtain an aliphatic prepolymer; s2, carrying out block copolymerization on raw materials comprising an aliphatic prepolymer, diamine, aromatic dibasic acid, a composite catalyst and water under the condition of temperature programming to obtain the semi-aromatic polyamide material. The invention can obtain the semi-aromatic polyamide material with good mechanical property and high temperature resistance.
Description
Technical Field
The invention relates to a method for preparing a polyamide material by block copolymerization.
Background
The polyamide has excellent flexibility, elastic resilience, wear resistance, corrosion resistance, hygroscopicity and light weight, is widely applied to the fields of machinery, textile, automobiles, electronic and electric appliances and the like, and becomes one of the engineering materials with the largest use amount at present. Currently, the most widely used and productive polyamide materials are mainly nylon 6 and nylon 66, and these aliphatic polyamide materials have a melting point of less than 250 ℃ and are difficult to use for a long time under high temperature conditions. Researches find that through chemical structure design, the flexibility of a polyamide molecular chain can be effectively reduced by introducing aromatic groups into a molecular main chain, and the high-temperature resistance of a polyamide material is improved. Polyamide materials can be classified into wholly aromatic polyamides (both amines and acids contain aromatic groups) and semi-aromatic polyamides (amines or acids contain aromatic groups) depending on the aromatic group-containing condition of the raw materials. Semi-aromatic polyamides are often used in practical applications because of their high processing temperature and difficulty in processing and molding.
At present, the reported semi-aromatic polyamide is synthesized by feeding once and gradually increasing the temperature. The semi-aromatic polyamide synthesized by the method has poor comprehensive performance due to the fact that the difference of the reactivity of the monomers is large, the chain segments of the copolymerization product are not uniformly distributed, the chain segments of the third monomer are too long, and the too long chain segments of the third monomer are easy to break under the action of heat or external force.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method for preparing a polyamide material by block copolymerization. The polyamide material obtained by the method has good mechanical property and heat resistance.
The invention provides a method for preparing a polyamide material by block copolymerization, which comprises the following steps:
s1, prepolymerizing a first molecular weight regulator and an aliphatic comonomer in a molar ratio of 0.005-0.08: 1 to obtain an aliphatic prepolymer;
s2, carrying out block copolymerization on raw materials comprising an aliphatic prepolymer, diamine, aromatic dibasic acid, a composite catalyst and water under the condition of temperature programming to obtain a polyamide material;
wherein the first molecular weight regulator is selected from one of hexamethylenediamine, nonanediamine, dodecamethylenediamine and adipic acid;
the aliphatic comonomer is selected from one or more of caprolactam, 6-aminobutyric acid, 9-aminononanoic acid, 11-aminoundecanoic acid and laurolactam;
the diamine is selected from aliphatic amine with 5-18 carbon atoms;
the aromatic dibasic acid is selected from one or more of dibasic acid containing a benzene ring structure and dibasic acid containing a heterocyclic structure;
the composite catalyst is selected from at least two of phosphoric acid, phosphate, sodium phosphite, sodium hypophosphite monohydrate, calcium hypophosphite and magnesium hypophosphite;
the conditions for temperature programming were as follows:
1) heating the mixture from room temperature to 60-100 ℃, and then reacting for 0.5-3 h at the temperature of 60-100 ℃;
2) heating from 60-100 ℃ to 200-250 ℃, and then reacting for 2-6 h at 200-250 ℃ and 1.6-1.9 MPa;
3) heating and exhausting for 2-4 h, wherein the temperature is increased from 200-250 ℃ to 300-340 ℃, and the pressure is reduced to be below 0.5MPa after exhausting;
4) and keeping the temperature at 300-340 ℃, and vacuumizing to negative pressure to obtain the polyamide material.
The prior semi-aromatic polyamide copolymers are usually synthesized by one shot. Due to the conjugation effect and steric hindrance effect of the benzene ring, the amidation rate of the aliphatic diamine and the aromatic diacid is lower than the polymerization rate of another copolymer monomer, and the reactivity ratio difference is large, so that the chain segment of the comonomer is rapidly increased, the polymerization rate of the semi-aromatic polyamide is relatively slow, the finally synthesized copolymerization product is uneven in chain segment distribution, the chain segment of the third monomer is too long, and the comprehensive performance of the polyamide material is affected. The invention firstly adopts the molecular weight regulator to pre-polymerize the aliphatic comonomer, controls the molecular chain length to reduce the polymerization activity and reduces the reactivity ratio of the aliphatic comonomer with the semi-aromatic polyamide, thereby obtaining the polyamide material with more uniform distribution of copolymerization chain segments and more excellent performance.
According to one embodiment of the present invention, the first molecular weight regulator and the aliphatic comonomer are dissolved in water, and the mixture is prepolymerized under stirring and under the protection of inert gas to obtain the aliphatic prepolymer. The molar ratio of the first molecular weight regulator to the aliphatic comonomer may be 0.005 to 0.08:1, preferably 0.015 to 0.05: 1. By controlling the molar ratio of the first molecular weight regulator to the aliphatic comonomer, the reactivity of the comonomer can be closer to the polymerization reactivity of the polyamide, which is helpful for improving the distribution uniformity of the copolymerization segments.
In the present invention, the water may be deionized water, distilled water, purified water, preferably deionized water. The aliphatic comonomer may be selected from one or more of caprolactam, 6-aminobutyric acid, 9-aminononanoic acid, 11-aminoundecanoic acid, laurolactam, preferably one or more of caprolactam, 9-aminononanoic acid, laurolactam. The first molecular weight regulator can be one of hexamethylenediamine, nonanediamine, dodecamethylenediamine and adipic acid; preferably one or more of hexamethylene diamine, nonanediamine and dodecanediamine. According to some embodiments of the present invention, the formation of the amino-terminated aliphatic prepolymer is facilitated by the use of hexamethylenediamine, nonanediamine or dodecanediamine as the first molecular weight regulator.
According to the method of the present invention, preferably, step S1 is as follows: dissolving 1-5 parts by weight of a first molecular weight regulator and 60-130 parts by weight of an aliphatic comonomer in 30-60 parts by weight of water, reacting at 150-250 ℃ and 0.5-1.6 MPa for 0.5-3 h under the protection of an inert gas and under the condition of stirring, and drying to obtain the aliphatic prepolymer.
In step S1, the stirring speed may be 50 to 100rpm, preferably 70 to 90 rpm. The heating rate can be 3-15 ℃/min, preferably 5-10 ℃/min. The drying is preferably vacuum drying. The drying temperature can be 30-80 ℃, and preferably 60-80 ℃. The drying time is not particularly limited, and it is sufficient to reduce the amount of water to avoid agglomeration of the particles, for example, drying at 60 to 80 ℃ for 6 to 12 hours.
In step S1, the inert gas may be selected from one or more of nitrogen, argon or helium, preferably nitrogen, argon or helium, and more preferably nitrogen. The inert gas is effective in preventing the amine from being oxidized.
In certain preferred embodiments, step S1 includes: dissolving 1-5 parts by weight of a first molecular weight regulator and 70-130 parts by weight of an aliphatic comonomer in 40-50 parts by weight of water, transferring the mixture into a high-pressure reaction kettle, repeatedly vacuumizing and filling nitrogen for three times to replace air in the kettle, then starting stirring (the stirring speed is 70-90 rpm), heating to 150-200 ℃ at a speed of 5-10 ℃/min under the protection of inert gas, reacting for 0.5-1.0 h under 0.9-1.4 MPa, discharging and drying to obtain the amino-terminated aliphatic prepolymer. The polyamide material prepared by the process has better mechanical property and heat resistance.
In addition, the temperature and pressure conditions of the reaction system are adjusted by temperature programming and strict control of the exhaust rate, so that the polymerization rate of the semi-aromatic polyamide is close to the growth rate of the aliphatic comonomer chain, and the polyamide material with uniformly distributed chain segments is obtained.
In step S2, raw materials including the aliphatic prepolymer, diamine, aromatic dibasic acid, composite catalyst and water are mixed, and temperature programming is performed under stirring and under the protection of inert gas to perform block copolymerization, thereby obtaining a polyamide material.
According to the method of the present invention, preferably, the raw material of step S2 includes the above aliphatic prepolymer, 80-120 parts by weight of diamine, 120-180 parts by weight of aromatic dibasic acid, 0.5-6 parts by weight of composite catalyst, 0.1-3 parts by weight of antioxidant, 0.1-2.5 parts by weight of second molecular weight regulator, 0.2-4 parts by weight of lubricant, and 60-100 parts by weight of water.
In some preferred embodiments, the raw material of step S2 includes the above aliphatic prepolymer, 90-110 parts by weight of diamine, 120-170 parts by weight of aromatic dibasic acid, 0.5-3 parts by weight of composite catalyst, 0.2-1 part by weight of antioxidant, 0.3-2 parts by weight of molecular weight regulator, 0.6-1.8 parts by weight of lubricant and 70-85 parts by weight of water.
According to an embodiment of the present invention, step S2 includes: adding the aliphatic prepolymer, 80-120 parts by weight of diamine, 120-180 parts by weight of aromatic dibasic acid, 0.5-6 parts by weight of composite catalyst, 0.1-3 parts by weight of antioxidant, 0.1-2.5 parts by weight of second molecular weight regulator, 0.2-4 parts by weight of lubricant and 60-100 parts by weight of water into a reaction kettle, and carrying out block copolymerization by temperature programming under the stirring condition and under the protection of inert gas.
According to one embodiment of the present invention, the conditions for temperature programming are as follows:
1) heating the mixture from room temperature to 60-100 ℃, and reacting for 0.5-3 h at the temperature of 60-100 ℃;
2) heating from 60-100 ℃ to 200-250 ℃, and reacting for 2-6 h at 200-250 ℃ and 1.6-1.9 MPa;
3) heating and exhausting for 1-3 h, heating to 260-290 ℃, and maintaining the pressure at the stage to be 1.9-2.2 MPa by controlling the exhaust speed; raising the temperature to 300-340 ℃ after 0.5-2 h of heating and exhausting, exhausting until the pressure is reduced to 90-110 kPa, and controlling the exhausting speed to reduce the pressure by 0.05-0.10 MPa every time the temperature is raised to 5 ℃;
4) keeping the temperature at 300-340 ℃, vacuumizing to the pressure below-0.08 MPa, and reacting for 3-15 min to obtain the polyamide material.
Step S2 is preferably performed in a reaction vessel. Before the block copolymerization reaction, it is preferable to replace the air in the reaction vessel with an inert gas. For example, after replacing the air in the reaction kettle with inert gas, the inert gas is filled until the pressure in the reaction kettle is 0.05-0.5 MPa.
The reaction temperature in the step 1) can be 60-100 ℃, preferably 70-90 ℃, and more preferably 80-85 ℃. The reaction time may be 0.5 to 3 hours, preferably 0.5 to 1.5 hours. The stirring speed may be 70 to 100rpm, preferably 75 to 85 rpm.
The reaction temperature in the step 2) can be 200-250 ℃, preferably 210-230 ℃, and more preferably 210-220 ℃. The pressure may be 1.6 to 1.9MPa, preferably 1.7 to 1.9MPa, and more preferably 1.8 to 1.9 MPa. The stirring speed may be 70 to 100rpm, preferably 75 to 85 rpm. The reaction time can be 2-6 h, preferably 3-5 h, and more preferably 3-4 h. According to some embodiments of the present invention, the reaction temperature in step 1) is controlled to be 80-85 ℃ and the reaction temperature in step 2) is controlled to be 210-220 ℃. Thus, the polymerization rate of the polyamide is close to the chain growth rate of the aliphatic comonomer, and the prepared polyamide material has good mechanical properties.
Step 3) may include one stage and two stages. In the first stage, the temperature is raised to 260-290 ℃ and preferably 275-285 ℃ for 1-3 hours and preferably 1.5-2.5 hours. The stirring speed in the first stage may be 70 to 100rpm, preferably 75 to 85 rpm. The exhaust speed of the first stage is controlled so that the pressure of the first stage is maintained at 1.9 to 2.2MPa, preferably 2 to 2.1 MPa. In the second stage, the temperature is raised to 300-340 ℃ and preferably 300-315 ℃ for 0.5-2 h and preferably 0.5-1.5 h; then the pressure is reduced to below 0.5MPa, preferably to 90-110 kpa. The stirring speed of the two stages may be 30 to 60rpm, preferably 45 to 55 rpm. The exhaust speed in the two stages is controlled to reduce the pressure by 0.05-0.1 MPa at 5 ℃ per liter of temperature, and preferably, the pressure is reduced by 0.07-0.09 MPa at 5 ℃ per liter of temperature.
The invention promotes the reaction balance to move forward by strictly controlling the temperature rise and the exhaust speed. The water content in the first stage is higher, and the water in the system is reduced through the quick exhaust in the first stage, so that the balance is shifted to the right, the system concentration is increased, and the polymerization is accelerated; the two stages are in the later stage of reaction, the viscosity is increased along with the increase of the polymerization degree, the reaction rate is reduced, the thermodynamic equilibrium is gradually shifted to the right by reducing the exhaust speed, and meanwhile, the stirring speed is reduced, so that the prepolymer can be fully contacted and collided, and the molecular weight of the product is further improved.
The reaction temperature in the step 4) is 300-340 ℃, and preferably 300-315 ℃. The speed of vacuum pumping can be 0.01-0.05 MPa/min, preferably 0.01-0.03 MPa/min. The degree of vacuum may be-0.08 MPa or less, preferably-0.08 to-0.09 MPa. And (3) continuing the reaction for 3-15 min, preferably 5-15 min after the vacuum degree reaches-0.08 to-0.09 MPa.
And after the reaction is finished, filling inert gas to restore the pressure in the reaction kettle to normal pressure, and then cooling, discharging, granulating and drying to obtain the polyamide material.
According to the method, the composite catalyst is preferably composed of phosphoric acid, sodium dihydrogen phosphate and sodium hypophosphite in a weight ratio of 1-2: 2-4. According to some embodiments of the present invention, the composite catalyst is composed of phosphoric acid, sodium dihydrogen phosphate and sodium hypophosphite in a weight ratio of 1-2: 3. The invention comprehensively considers the reaction activity of the catalyst and the conditions of polymerization reaction, screens out the catalyst with the compounding ratio, not only ensures that the catalyst with better activity always exists in different reaction stages, but also can ensure that the chain growth rates of two copolymerization structural units are matched, thereby obtaining the block copolymer with high molecular weight and uniform chain segments.
According to the method of the present invention, preferably, the raw material further comprises a lubricant selected from one or more of silicone oil, wax and stearate.
According to the method of the invention, preferably, the raw material also comprises an antioxidant, and the antioxidant is selected from one or more of antioxidant 1098, antioxidant 626, antioxidant 1010, antioxidant 168, antioxidant S-9228 and antioxidant SEED.
According to the method, the antioxidant preferably consists of antioxidant 1098 and antioxidant 626 in a weight ratio of 1-3: 1. According to some embodiments of the present invention, the antioxidant is composed of antioxidant 1098 and antioxidant 626 in a weight ratio of 1 to 2: 1. According to the invention, the antioxidant 1098 is used as a main antioxidant, and the antioxidant 626 is used as an auxiliary antioxidant, so that the thermal degradation resistance of polyamide at high temperature can be obviously enhanced, the yellowing of the product can be effectively prevented, and the photo-thermal stability of the product can be improved.
According to the process of the present invention, preferably, the aliphatic comonomer is selected from one or more of caprolactam, 9-aminononanoic acid, laurolactam; the first molecular weight regulator is selected from one or more of hexamethylenediamine, nonanediamine and dodecamethylenediamine; the diamine is hexamethylene diamine; the aromatic dibasic acid is selected from one or more of terephthalic acid, isophthalic acid and 2, 6-naphthalene dicarboxylic acid.
In the present invention, the second molecular weight regulator may be selected from one or more of acetic acid, benzoic acid, and stearic acid, preferably one or more of stearic acid and benzoic acid. According to some embodiments of the present invention, stearic acid or benzoic acid is used as the second molecular weight regulator to reduce the terminal group content in the molecular chain and improve the stability of the polyamide.
In the present invention, the diamine may be selected from aliphatic amines having 5 to 18 carbon atoms, preferably aliphatic amines having 5 to 12 carbon atoms, and more preferably hexamethylenediamine. The aromatic dibasic acid may be one or more selected from dibasic acids having a benzene ring structure and dibasic acids having a heterocyclic ring structure, preferably one or more selected from terephthalic acid, isophthalic acid, 1, 4-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, and 2, 5-furandicarboxylic acid, and more preferably one or more selected from terephthalic acid, isophthalic acid, and 2, 6-naphthalenedicarboxylic acid. The lubricant may be selected from one or more of silicone oil, wax, stearate, preferably silicone oil. The silicone oil is used as a lubricant, which is beneficial to the movement of molecular chains in the polymerization and processing processes, so that the surface of the polyamide is smoother.
According to the process of the present invention, preferably, the polyamide material has a structure represented by formula (I):
wherein x and y are independently selected from integers of 5-12;m and n are each independently selected from integers greater than zero; r1One selected from the group consisting of formulas (II) to (VI);
according to the method of the present invention, preferably, x is 5 or 6 and y is 6, 9, 11 or 12.
In the present invention, R1May contain one or more of an aromatic ring structure, an aromatic heterocyclic structure, and a carbocyclic ring structure, preferably one of formulas (II) to (VI), and more preferably formula (II) or (III). R containing an aromatic ring structure1The proportion of long chain segments of aliphatic series can be reduced, the rigidity of a macromolecular main chain is increased, the mechanical strength of the molecular chain is improved, the movement of the polyamide molecular chain can be effectively limited by the large steric effect of the aromatic ring, the high-temperature resistance of the material is improved, and in addition, the water absorption of the polyamide material is favorably reduced. R1 containing aromatic heterocyclic structures, such as pyridine rings, furan rings, thiazole rings and the like, can effectively expand the comprehensive performance of the polyamide material.
In the present invention, x may be an integer of 5 to 12, preferably 5, 6, 9, 10, 12. y may be an integer of 5 to 12, preferably 6, 9, 11, 12. m and n are respectively and independently selected from integers larger than zero, preferably from 10 to 1000, preferably from 100 to 1000.
The invention adopts the molecular weight regulator to carry out prepolymerization on the aliphatic comonomer, increases the chain length of the comonomer by controlling the molecular weight of the comonomer, effectively reduces the reactivity of the comonomer, and enables the reactivity to be matched with the chain growth rate of polyamide, thereby obtaining the semi-aromatic polyamide material with evenly distributed chain segments. The polyamide material has better heat resistance, crystallization property and mechanical property.
Drawings
FIG. 1 is a Fourier transform Infrared Spectroscopy (FTIR) plot of the semi-aromatic polyamide material prepared in example 1.
FIG. 2 is a Differential Scanning Calorimetry (DSC) chart of the semi-aromatic polyamide material prepared in example 1.
Fig. 3 is a graph of the thermogravimetric curve (TG) of the semi-aromatic polyamide material prepared in example 1.
Detailed Description
The present invention will be further described with reference to specific embodiments, but the scope of the present invention is not limited thereto.
The test method is described below:
(1) structural test (FTIR) of polyamide material: placing the prepared semi-aromatic polyamide particles at 110 ℃ for vacuum drying for 3h, and injecting a sample strip by adopting a WZS10 micro injection molding machine under the processing conditions that the temperature of a charging barrel is 310 ℃, the mold temperature is 80 ℃ and the pressure is 0.7 MPa; after the sample is cooled, the infrared spectrum of the sample is measured by ATR total reflection. The infrared spectrometer has the following model: agilent (usa) cary 630.
(2) Heat resistance test (DSC, TG) of polyamide material:
DSC test: 10mg of the prepared semi-aromatic polyamide particles are placed in an aluminum crucible for DSC test, the test temperature range is 50-370 ℃, and the heating rate is 10 ℃/min. Heating to 370 deg.C under nitrogen atmosphere, keeping the temperature for 5min, eliminating heat history, cooling to 50 deg.C at 10 deg.C/min, and heating to 370 deg.C. The model of the differential scanning calorimeter is as follows: german stainless steel 200F 3.
TG test: taking 15mg of semi-aromatic polyamide particles, placing the semi-aromatic polyamide particles in a TG crucible, carrying out thermal weight loss measurement (American TA Q50), setting the heating rate of 10 ℃/min, and heating from 50 ℃ to 600 ℃ under the nitrogen atmosphere to obtain the thermal weight loss performance. The model of the thermogravimetric analyzer is as follows: TA Q50 usa.
(3) Mechanical testing of polyamide materials: and (3) placing the prepared semi-aromatic polyamide particles at 110 ℃ for vacuum drying for 3h, performing injection molding by using a WZS10 micro injection molding machine under the processing conditions that the temperature of a charging barrel is 310 ℃, the mold temperature is 80 ℃ and the pressure is 0.7MPa, and then stretching, bending and notch impact sample strips. Using an Instron 5567 universal tester to measure the tensile and bending properties, wherein the tensile rate is 10mm/min, and the temperature is 25 ℃); the bending was carried out at a rate of depression of 5mm/min, a span of 64 and a temperature of 25 ℃. The impact strength was measured using an XJUG-50 cantilever pendulum impact tester.
In the examples and comparative examples of the present invention, parts are by weight unless otherwise specified.
Example 1
S1, weighing 74 parts of caprolactam, 3 parts of hexamethylenediamine and 47 parts of deionized water, and adding the raw materials into a polymerization reaction kettle; and replacing the air in the kettle with nitrogen for three times, starting stirring (the stirring speed is 80rpm), heating to 190 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, maintaining the pressure at 1.4MPa and maintaining the pressure for 1h, discharging, and performing vacuum drying for 12h at the temperature of 80 ℃ to obtain the amino-terminated aliphatic prepolymer.
S2, weighing 100 parts of hexamethylenediamine, 128 parts of terephthalic acid, 0.4 part of phosphoric acid, 0.4 part of sodium dihydrogen phosphate, 0.6 part of sodium hypophosphite monohydrate, 0.4 part of antioxidant 1098, 0.2 part of antioxidant 626, 1 part of stearic acid, 1 part of silicone oil and 80 parts of deionized water; they were added to the reaction vessel together with the above aliphatic prepolymer, and the stirring was started at a stirring speed of 80 rpm.
1) After air in the kettle is fully replaced by nitrogen, the nitrogen is filled to ensure that the pressure in the kettle is 0.1MPa positive pressure; heating to 80 ℃ at the speed of 5 ℃/min, and reacting for 1h at constant temperature to fully salify the terephthalic acid and the hexamethylene diamine.
2) Heating to 210 ℃ at the speed of 5 ℃/min, heating to 1.80MPa, keeping the temperature and the pressure stable, and reacting for 4h to fully pre-polymerize.
3) Gradually raising the temperature in the kettle to 280 ℃ within 2 hours, simultaneously starting to release water vapor in the reaction kettle, collecting the discharged water through a condensing device, adjusting the speed of temperature rise and exhaust through detecting the pressure change and the quality of the discharged water, and maintaining the pressure in the kettle at 2.1 MPa; and continuously heating to 315 ℃ within 0.5h, and slowly exhausting to reduce the pressure in the kettle to normal pressure, wherein the torque of the stirring motor is obviously increased along with the increase of the viscosity of the system.
4) Closing the exhaust valve, slowly vacuumizing at constant temperature, continuing to react for 9min when the vacuum degree reaches-0.09 MPa, and stopping stirring when the torque reaches the maximum value; and (3) recovering to normal pressure by filling nitrogen, and cooling, discharging, granulating and drying to obtain white semi-aromatic polyamide particles.
The semi-aromatic polyamide particles were subjected to structural tests, and the test results are shown in fig. 1. In the infrared spectrum of FIG. 1, 3287cm-1The peak corresponds to the stretching vibration peak of N-H in the amido bond; 2914cm-1And 2860cm-1Then is the stretching vibration peak of C-H in the main chain; 1620cm-1Stretching vibration peak corresponding to C ═ O in amido bond; 1528cm-1Corresponding to the bending vibration peak of N-H in amido bond; 1278cm-1Corresponding to the C-N stretching vibration peak in amido bond. The above results indicate that the semi-aromatic polyamide particles prepared by the present invention are polyamide materials.
The semi-aromatic polyamide particles are subjected to a thermal stability performance test, and the results are shown in figures 2-3. As can be seen from FIG. 2, the melting point of the semi-aromatic polyamide is 307 ℃, and a narrow melting peak exists, which shows that the semi-aromatic polyamide material has uniform distribution of the copolymerization chain segment, does not have too long aliphatic chain segment, and has good high temperature resistance. The crystallization temperature was 268 ℃, indicating the introduction of aromatic groups, which reduced the crystallization rate. As can be seen from figure 3, the semi-aromatic polyamide has no obvious weight loss before 400 ℃, and the weight loss is 5% at 402 ℃, which shows that the material has good heat resistance and relatively uniform molecular chain distribution, and the semi-aromatic polyamide prepared by the technology can meet the application in high temperature environment.
The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
Example 2
S1, weighing 102 parts of 9-aminononanoic acid, 3 parts of nonane diamine and 47 parts of deionized water, and adding the raw materials into a polymerization reaction kettle; and replacing the air in the kettle with nitrogen for three times, starting stirring (the stirring speed is 80rpm), heating to 200 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, maintaining the pressure at 1.4MPa and maintaining the pressure for 1h, discharging, and performing vacuum drying for 12h at the temperature of 80 ℃ to obtain the amino-terminated aliphatic prepolymer.
S2, weighing 100 parts of hexamethylenediamine, 150 parts of terephthalic acid, 0.4 part of phosphoric acid, 0.4 part of sodium dihydrogen phosphate, 0.6 part of sodium hypophosphite monohydrate, 0.4 part of antioxidant 1098, 0.2 part of antioxidant 626, 0.5 part of stearic acid, 1 part of silicone oil and 80 parts of deionized water; they were added to the reaction vessel with the above aliphatic prepolymer, and the stirring was started and adjusted to 90 rpm.
1) After air in the kettle is fully replaced by nitrogen, the nitrogen is filled to ensure that the pressure in the kettle is 0.1MPa positive pressure; heating to 80 ℃ at the speed of 5 ℃/min, and reacting for 1h at constant temperature to fully salify the terephthalic acid and the hexamethylene diamine.
2) Heating to 220 ℃ at the speed of 5 ℃/min, heating to 1.85MPa, keeping the temperature and the pressure stable, and reacting for 4h to fully pre-polymerize.
3) Gradually raising the temperature in the kettle to 280 ℃ within 2 hours, simultaneously starting to release water vapor in the reaction kettle, collecting the drained water through a condensing device, observing and detecting the pressure change and the quality of the drained water, adjusting the heating and exhausting speed, and maintaining the pressure in the kettle at 2.1 MPa; and (3) continuously raising the temperature to 315 ℃ within 1h, and slowly exhausting to reduce the pressure in the kettle to normal pressure, wherein the torque of the stirring motor can be obviously increased along with the increase of the viscosity of the system.
4) Closing the exhaust valve, slowly vacuumizing at constant temperature, continuing to react for 15min after the vacuum degree reaches-0.09 MPa, and stopping stirring when the torque reaches the maximum value; and (3) recovering to normal pressure by filling nitrogen, and cooling, discharging, granulating and drying to obtain white semi-aromatic polyamide particles. The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
Example 3
S1, weighing 129 parts of laurolactam, 1.5 parts of dodecadiamine and 47 parts of deionized water, and adding the raw materials into a polymerization reaction kettle; and replacing the air in the kettle with nitrogen for three times, starting stirring (the stirring speed is 80rpm), heating to 210 ℃ at the speed of 5 ℃/min under the nitrogen atmosphere, maintaining the pressure at 1.6MPa and maintaining the pressure for 1h, discharging, and performing vacuum drying for 12h at the temperature of 80 ℃ to obtain the amino-terminated aliphatic prepolymer.
S2, weighing 100 parts of hexamethylenediamine, 150 parts of terephthalic acid, 0.4 part of phosphoric acid, 0.4 part of sodium dihydrogen phosphate, 0.6 part of sodium hypophosphite, 0.4 part of antioxidant 1098, 0.2 part of antioxidant 626, 0.5 part of stearic acid, 1 part of silicone oil and 80 parts of deionized water; they were added to the reaction vessel with the above aliphatic prepolymer, and the stirring was started and the stirring speed was adjusted to 80 rpm.
1) After air in the kettle is fully replaced by nitrogen, the nitrogen is filled to ensure that the pressure in the kettle is 0.1MPa positive pressure; heating to 90 ℃ at the speed of 5 ℃/min, and reacting for 1 hour at constant temperature to fully salify the terephthalic acid and the hexamethylene diamine.
2) Raising the temperature to 230 ℃ at the speed of 5 ℃/min, raising the pressure to 1.90MPa, keeping the temperature and the pressure stable, and reacting for 4 hours to fully pre-polymerize.
3) Gradually raising the temperature in the kettle to 280 ℃ within 2 hours, simultaneously starting to release water vapor in the reaction kettle, collecting the drained water through a condensing device, observing and detecting the pressure change and the quality of the drained water, adjusting the heating and exhausting speed, and maintaining the pressure in the kettle at 2.1 MPa; and continuously heating to 315 ℃ within 0.5h, and slowly exhausting to reduce the pressure in the kettle to normal pressure, wherein the torque of the stirring motor is obviously increased along with the increase of the viscosity of the system.
4) Closing the exhaust valve, slowly vacuumizing at constant temperature, continuing to react for 15min when the vacuum degree reaches-0.09 MPa, and stopping stirring when the torque reaches the maximum value; and (3) recovering to normal pressure by filling nitrogen, and cooling, discharging, granulating and drying to obtain white semi-aromatic polyamide particles. The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
Comparative example 1
The procedure was as in example 1 except that the prepolymerization step S1 was omitted. In this comparative example, all the raw materials (including the raw materials used in step S1 and step S2) were charged together into a reaction vessel, and a polyamide material was produced by a conventional one-pot method. The discharging process is unstable. The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
Comparative example 2
The procedure was as in example 1 except for the step 3). In this comparative example, step 3) was carried out for 1h with the temperature raised to 305 ℃ and the gas vented for 1h to return the pressure to atmospheric pressure. When discharging, the viscosity of the product is not uniform, and more material remains in the kettle. The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
Comparative example 3
The procedure was as in example 1 except that the composite catalyst was used. In this comparative example, only 0.6 part of sodium hypophosphite monohydrate was added as catalyst. During discharging, the viscosity of the materials in the kettle is low, the discharging process is fast, and the granules are crisp and contain bubbles. The results of the tests for mechanical and heat resistance properties of the semi-aromatic polyamide particles are shown in table 1.
TABLE 1
As can be seen from Table 1, the comprehensive properties (including mechanical properties, heat resistance and processability) of examples 1 to 3 are superior to those of comparative examples 1 to 3. Compared with examples 1-3, comparative example 1 has no prepolymerization, which results in too long third monomer chain segment, and thus poor mechanical properties, low tensile strength and low elongation at break of the polyamide material. Compared with examples 1-3, comparative example 2 does not adopt a gradual temperature rise mode to reduce the reactivity ratio of the comonomer and the semi-aromatic polyamide in the block copolymerization process, and does not regulate and control reaction balance in an exhaust mode, so that the polyamide material has uneven viscosity, smaller molecular weight and poorer mechanical strength. Compared with the examples 1-3, in the comparative example 3, the composite catalyst is not added, and only sodium hypophosphite monohydrate is added as the catalyst, so that the reactants can not be ensured to keep higher reaction activity in the whole reaction process, and the polyamide material has lower viscosity, lower melting point, lower tensile strength, lower elongation at break, lower bending strength, lower bending modulus and lower notch impact strength.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (10)
1. A method for preparing polyamide material by block copolymerization is characterized by comprising the following steps:
s1, prepolymerizing a first molecular weight regulator and an aliphatic comonomer in a molar ratio of 0.005-0.08: 1 to obtain an aliphatic prepolymer;
s2, carrying out block copolymerization on raw materials comprising an aliphatic prepolymer, diamine, aromatic dibasic acid, a composite catalyst and water under the condition of temperature programming to obtain a polyamide material;
wherein the first molecular weight regulator is selected from one of hexamethylenediamine, nonanediamine, dodecamethylenediamine and adipic acid;
the aliphatic comonomer is selected from one or more of caprolactam, 6-aminobutyric acid, 9-aminononanoic acid, 11-aminoundecanoic acid and laurolactam;
the diamine is selected from aliphatic amine with 5-18 carbon atoms;
the aromatic dibasic acid is selected from one or more of dibasic acid containing a benzene ring structure and dibasic acid containing a heterocyclic ring structure;
the composite catalyst is selected from at least two of phosphoric acid, phosphate, sodium phosphite, sodium hypophosphite monohydrate, calcium hypophosphite and magnesium hypophosphite;
the conditions for temperature programming were as follows:
1) heating the mixture from room temperature to 60-100 ℃, and then reacting for 0.5-3 h at the temperature of 60-100 ℃;
2) heating from 60-100 ℃ to 200-250 ℃, and then reacting for 2-6 h at 200-250 ℃ and 1.6-1.9 MPa;
3) heating and exhausting for 2-4 h, heating the temperature from 200-250 ℃ to 300-340 ℃, and exhausting until the pressure is reduced to below 0.5 MPa;
4) and keeping the temperature at 300-340 ℃, and vacuumizing to negative pressure to obtain the polyamide material.
2. The method according to claim 1, wherein step S1 is as follows: dissolving 1-5 parts by weight of a first molecular weight regulator and 60-130 parts by weight of an aliphatic comonomer in 30-60 parts by weight of water, reacting for 0.5-3 h at 150-250 ℃ and 0.5-1.6 MPa under the protection of stirring and inert gas, and drying to obtain the aliphatic prepolymer.
3. The method of claim 2, wherein the raw material of step S2 comprises the aliphatic prepolymer, 80-120 parts by weight of diamine, 120-180 parts by weight of aromatic dibasic acid, 0.5-6 parts by weight of composite catalyst, 0.1-3 parts by weight of antioxidant, 0.1-2.5 parts by weight of second molecular weight regulator, 0.2-4 parts by weight of lubricant and 60-100 parts by weight of water.
4. The method of claim 1, wherein the composite catalyst comprises phosphoric acid, sodium dihydrogen phosphate and sodium hypophosphite in a weight ratio of 1-2: 2-4.
5. The method of claim 1, wherein the feedstock further comprises a lubricant selected from one or more of silicone oil, wax, stearate.
6. The method of claim 1, wherein the feedstock further comprises an antioxidant selected from one or more of the group consisting of antioxidant 1098, antioxidant 626, antioxidant 1010, antioxidant 168, antioxidant S-9228, and antioxidant SEED.
7. The method according to claim 6, wherein the antioxidant consists of antioxidant 1098 and antioxidant 626 in a weight ratio of 1-3: 1.
8. The method according to any one of claims 1 to 7, wherein the aliphatic comonomer is selected from one or more of caprolactam, 9-aminononanoic acid, laurolactam; the first molecular weight regulator is one or more selected from hexamethylenediamine, nonane diamine and dodeca diamine; the diamine is hexamethylene diamine; the aromatic dibasic acid is selected from one or more of terephthalic acid, isophthalic acid and 2, 6-naphthalene dicarboxylic acid.
9. The method of claim 1, wherein the polyamide material has a structure according to formula (I):
wherein x and y are independently selected from integers of 5-12; m and n are each independently selected from integers greater than zero; r1One selected from the group consisting of formulas (II) to (VI);
10. the method of claim 9, wherein x is 5 or 6 and y is 6, 9, 11 or 12.
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| DE68916130D1 (en) * | 1988-08-17 | 1994-07-21 | Mitsubishi Chem Ind | Process for the production of block copolyamide. |
| CN102372922A (en) * | 2010-08-18 | 2012-03-14 | 上海杰事杰新材料(集团)股份有限公司 | Polyesteramide multi-block copolymer and preparation method thereof |
| CN102653594A (en) * | 2011-03-02 | 2012-09-05 | 骏马化纤股份有限公司 | Block type high-temperature-resistant copolyamide and preparation method thereof |
| CN103360599A (en) * | 2013-08-15 | 2013-10-23 | 金发科技股份有限公司 | Semi-aromatic and aliphatic polyamide block copolymer and preparation method thereof |
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| DE68916130D1 (en) * | 1988-08-17 | 1994-07-21 | Mitsubishi Chem Ind | Process for the production of block copolyamide. |
| CN102372922A (en) * | 2010-08-18 | 2012-03-14 | 上海杰事杰新材料(集团)股份有限公司 | Polyesteramide multi-block copolymer and preparation method thereof |
| CN102653594A (en) * | 2011-03-02 | 2012-09-05 | 骏马化纤股份有限公司 | Block type high-temperature-resistant copolyamide and preparation method thereof |
| CN103360599A (en) * | 2013-08-15 | 2013-10-23 | 金发科技股份有限公司 | Semi-aromatic and aliphatic polyamide block copolymer and preparation method thereof |
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