Preparation method for m-xylylenediamine-based nylon

Abstract

Disclosed in the present invention is a preparation method for m-xylylenediamine-based nylon. The preparation method for m-xylylenediamine-based nylon of the present invention comprises the following steps: S1, subjecting a mixture containing a diacid and a diamine to a reaction, so as to prepare a salt solution; and S2, subjecting the salt solution to a polymerization reaction. The preparation method for m-xylylenediamine-based nylon of the present invention is simple, and can achieve the effect of regulating and controlling the crystallization performance of m-xylylenediamine-based nylon without adding an extra auxiliary used for regulating and controlling crystallization; and prepared m-xylylenediamine-based nylon has a wide crystallization temperature range and adjustable molecular weight distribution, and can meet use requirements in different application scenarios.

Description

A preparation method of m-phenylenediamine nylon

[0001] This application claims priority to Chinese patent application CN2023117836170, filed on December 22, 2023. This application incorporates the entire text of the aforementioned Chinese patent application. Technical Field

[0002] The invention relates to a preparation method of m-phenylenediamine nylon. Background Art

[0003] Polyamide, also known as nylon, is an engineering plastic with excellent comprehensive performance. Due to its excellent high temperature resistance, corrosion resistance, wear resistance and easy processing, nylon is widely used in many fields such as the automotive industry, electronic appliances, and mechanical processing. Among the many nylon varieties, meta-phenylenediamine-based nylon, especially the representative poly (meta-phenylenediamine adipamide) (MXD6), has relatively excellent performance. MXD6 is a semi-aromatic nylon prepared by condensation polymerization using adipic acid and meta-phenylenediamine as raw materials. Due to its very excellent mechanical properties and weather resistance, it is widely used in engineering plastics, film materials, packaging materials and other fields. However, different application fields also have different requirements for the crystallization performance of meta-phenylenediamine-based nylon. For example, in the field of engineering plastics, during the product molding process, in order to ensure the curing molding rate of the product, the product needs to have strong crystallization ability. Because the two amino groups of the raw material, meta-xylylenediamine, are located at the meta position of the benzene ring, its molecular chain exhibits poor symmetry, resulting in a slow crystallization rate. This increases the curing cycle of the finished product, thereby reducing processing efficiency. Therefore, plastic raw materials with strong crystallization properties are required. However, in the barrier film industry, to ensure film performance during processing, meta-xylylenediamine nylon requires relatively weak crystallization. Therefore, it is crucial to regulate the crystallization capacity of meta-xylylenediamine nylon to accommodate different usage scenarios.

[0004] At present, the conventional method for regulating the crystallization ability of m-phenylenediamine nylon is to add additives during modification and other complex methods, which not only requires complex operating procedures but also increases costs. Summary of the Invention

[0005] To address the drawback of existing technologies that require complex methods such as adding additives or modifying the material to adjust the crystallization capacity of meta-xylylenediamine nylon, the present invention provides a method for preparing meta-xylylenediamine nylon. The method is simple and can adjust the crystallization capacity of meta-xylylenediamine nylon simply through process adjustments, without the need for other additives. The meta-xylylenediamine nylon produced using the method can be used in a variety of applications.

[0006] The present invention mainly solves the above technical problems through the following technical solutions:

[0007] The present invention provides a method for preparing m-xylylenediamine nylon, which comprises the following steps:

[0008] S1. reacting a mixture comprising a diacid and a diamine to prepare a salt solution;

[0009] Wherein, the diacid comprises one or more of adipic acid, sebacic acid, undecanedioic acid and dodecanedioic acid; the diamine is m-xylenediamine; the molar ratio of the diacid to the diamine is (0.95-1.05):1

[0010] S2, subjecting the salt solution to a polymerization reaction; the polymerization reaction steps include: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature by pressure relief, and maintaining constant temperature at normal pressure and negative pressure;

[0011] Wherein, the polymerization reaction temperature is 270°C or below;

[0012] During the constant pressure temperature increase process, the pressure is 0.2 MPa to 2.0 MPa; during the pressure reduction temperature increase process, the pressure reduction endpoint is when the pressure drops to normal pressure; during the pressure reduction temperature increase process, the pressure reduction rate is 0.003 to 0.1 MPa / min.

[0013] In the present invention, in step S1, the molar ratio of the diacid to the diamine is preferably (0.98-1.02):1, for example, 0.99:1, 1:1 or 1.01:1.

[0014] In some preferred embodiments, the molar ratio of the diacid to the diamine may be (1-1.02):1.

[0015] In other preferred embodiments, the molar ratio of the diacid to the diamine may be (0.98-1):1.

[0016] In step S1, the diacid is preferably adipic acid.

[0017] In step S1, the reaction temperature may be 60-150°C.

[0018] In step S1, the reaction time may be 0 to 60 minutes, for example, 20 minutes.

[0019] In step S1, the rate of heating to the reaction temperature may be 1-20°C / min, for example, 10°C / min.

[0020] In step S1 , the reaction atmosphere may be an inert gas, such as nitrogen.

[0021] In step S1, the reaction can be carried out using conventional equipment in the art, for example, in a reactor.

[0022] In step S1, the solvent used in the mixture can be a solvent in the art that can dissolve the diamine and the diacid, such as desalted water. The desalted water generally refers to water in which the easily removable strong electrolytes contained therein are removed or reduced to a certain level. The residual salt content in the desalted water is usually 1 to 5 mg / L.

[0023] In step S1, the method for preparing the mixture preferably comprises the following steps: adding the diamine to a solvent under stirring, and then slowly adding a diacid to obtain the mixture.

[0024] In step S1, the reaction preferably includes the following steps: heating the mixture to 60-150° C. at a rate of 5° C. / min under an inert gas; and continuing stirring for 0-60 min after the temperature stabilizes to allow the material to completely form a salt.

[0025] The inventors of this invention discovered through extensive research that during nylon polymerization, under high temperature and high pressure, the molecular weight of the reaction system is low, and gradually increases during pressure release. Therefore, the inventors discovered that by manipulating process conditions such as polymerization pressure, temperature, and pressure release rate, it is possible to control the polymer's molecular microstructure, thereby regulating the product's crystallization ability.

[0026] In the present invention, in step S2, during the polymerization reaction, the concentration of the salt solution may be 40-80%, where the percentage is the percentage of the mass of the solute to the mass of the salt solution.

[0027] In step S2, the total heating time of the pressure-raising and temperature-raising and the constant-pressure temperature-raising can be 0.5 to 4 hours.

[0028] In step S2, during the constant pressure heating process, the temperature after heating can be 220-260°C, such as 240°C, 245°C or 250°C.

[0029] In step S2, during the pressure and temperature increasing process, the heating rate may be 1-10°C / min, for example, 5°C / min.

[0030] In step S2, during the constant pressure heating process, the heating rate may be 1-10°C / min, for example, 5°C / min.

[0031] In step S2, during the constant pressure temperature increase process, the pressure is preferably 0.3-2.0 MPa, more preferably 0.5 MPa-1.7 MPa.

[0032] In some preferred embodiments, during the constant pressure temperature increase process, the pressure may be 1.0 MPa to 2.0 MPa.

[0033] In other preferred embodiments, during the constant pressure temperature increase process, the pressure may be 0.5 MPa to 1.0 MPa.

[0034] In step S2, during the constant pressure temperature increase process, when the system pressure exceeds the set value, part of the water vapor can be removed by pressure relief to maintain the system pressure within the target range.

[0035] In step S2, during the pressure relief and temperature raising process, the temperature after the heating can be 230-270°C, preferably 240-265°C, such as 250°C, 255°C or 260°C.

[0036] In step S2, during the pressure relief and temperature increase process, the temperature increase rate may be 0.1-5°C / min.

[0037] In step S2, during the pressure relief and temperature rise process, the pressure relief rate is preferably 0.003 MPa / min to 0.1 MPa / min, preferably 0.005 to 0.05 MPa / min, for example 0.008 MPa / min, 0.01 MPa / min, 0.016 MPa / min or 0.02 MPa / min.

[0038] In some preferred embodiments, during the pressure relief and temperature raising process, the pressure relief rate may be 0.01 to 0.1 MPa / min.

[0039] In other preferred embodiments, during the pressure relief and temperature raising process, the pressure relief rate may be 0.003-0.02 MPa / min.

[0040] In step S2, during the pressure relief and temperature raising process, the pressure relief time may be 10 to 150 minutes, preferably 30 to 70 minutes, such as 34 minutes, 50 minutes, 57 minutes or 62.5 minutes.

[0041] In step S2, the temperature of the constant temperature at normal pressure may be 240-270°C, preferably 245-265°C, such as 250°C, 255°C or 260°C.

[0042] In step S2, the time of constant temperature at normal pressure may be 10 to 90 minutes, for example, 30 minutes.

[0043] In step S2, the temperature of the negative pressure constant temperature can be 240-270°C, preferably 245-265°C, such as 250°C, 255°C or 260°C.

[0044] Those skilled in the art know that the temperature of the constant temperature at normal pressure and the constant temperature at negative pressure are usually slightly higher than the temperature after the pressure relief and temperature increase.

[0045] In step S2, the negative pressure constant temperature time may be 10 to 90 minutes, for example, 10 minutes or 60 minutes.

[0046] In step S2, the pressure during the negative pressure thermostating process can be -30 kPa to -100 kPa, for example, -80 kPa. The pressure of the vacuum reaction affects the molecular weight of the nylon; the lower the pressure, the faster the molecular weight growth rate. A vacuum pump can be used to reduce the pressure of the system to within the target pressure range during the third reaction. The vacuum pumping time can be 30 minutes. During the vacuum pumping process, the pressure can be reduced at a constant rate.

[0047] In step S2, the reaction can be carried out using conventional equipment in the art, for example, in a reactor.

[0048] In the present invention, step S2 may be followed by steps of extrusion, cooling and granulation.

[0049] The extrusion may include the following steps: filling the system with nitrogen and extruding the material from the lower discharge port under the action of pressure.

[0050] The cooling medium may be a conventional medium in the art, such as water.

[0051] In the present invention, the preparation method of the m-phenylenediamine nylon can be prepared without adding an auxiliary agent for regulating crystallization. The auxiliary agent is, for example, a nucleating agent. The nucleating agent is, for example, benzoic acid.

[0052] In a preferred embodiment of the present invention, when the m-xylylenediamine nylon is applied to engineering plastics, the preparation method of the m-xylylenediamine nylon comprises the following steps:

[0053] S1. reacting a mixture comprising a diacid and a diamine to prepare a salt solution;

[0054] Wherein, the molar ratio of the diacid to the diamine is (1-1.02):1;

[0055] S2, subjecting the salt solution to a polymerization reaction;

[0056] The polymerization reaction includes: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature at reduced pressure, increasing temperature at normal pressure and increasing temperature at negative pressure;

[0057] The polymerization reaction temperature is 220-270° C.; during the constant pressure heating process, the pressure is 1.0 MPa-2.0 MPa; the end point of the pressure relief during the pressure relief heating process is when the pressure drops to normal pressure; during the pressure relief heating process, the pressure relief rate is 0.01-0.1 MPa / min.

[0058] In the above preferred embodiment, the molar ratio of the diacid to the diamine is, for example, 1:0.99 or 1:0.995.

[0059] In the above preferred embodiment, the diacid is preferably adipic acid.

[0060] In the above preferred embodiment, during the constant pressure temperature increase process, the pressure may be 1.0 MPa to 1.7 MPa.

[0061] In the above preferred embodiment, during the constant pressure heating process, the temperature after heating can be 220-260°C, preferably 220-255°C.

[0062] In the above preferred embodiment, during the pressure and temperature increasing process, the heating rate may be 1-10°C / min, for example 5°C / min.

[0063] In the above preferred embodiment, the total heating time in the pressure-increasing and constant-pressure-heating process may be 0.5 to 4 hours.

[0064] In the above preferred embodiment, during the pressure relief and temperature increase process, the temperature after the increase can be 230-270°C, preferably 240-265°C, such as 250°C, 255°C or 260°C.

[0065] In the above preferred embodiment, during the pressure relief and temperature increase process, the temperature increase rate may be 0.1 to 5° C. / min.

[0066] In the above preferred embodiment, during the pressure relief and temperature rising process, the pressure relief rate may be 0.016-0.1 MPa / min, for example, 0.05 MPa / min.

[0067] In the above preferred embodiment, during the pressure relief and temperature raising process, the pressure relief time may be 20 to 65 minutes, preferably 30 to 62.5 minutes, for example 34 minutes.

[0068] In the above preferred embodiment, the temperature of the constant temperature at normal pressure may be 240-270°C, preferably 245-265°C, such as 250°C, 255°C or 260°C.

[0069] In the above preferred embodiment, the time of constant temperature at normal pressure may be 10 to 90 minutes, for example, 30 minutes.

[0070] In the above preferred embodiment, the temperature of the negative pressure constant temperature may be 240-270°C, preferably 245-265°C, for example 250°C, 255°C or 260°C.

[0071] In the above preferred embodiment, the pressure of the negative pressure thermostat may be -30 to -100 kPa, for example -80 kPa.

[0072] In the above preferred embodiment, the negative pressure constant temperature time is 10 to 40 minutes, for example, 10 minutes.

[0073] In another preferred embodiment of the present invention, when the m-xylylenediamine nylon is applied to a film, the preparation method of the m-xylylenediamine nylon comprises the following steps:

[0074] S1. reacting a mixture comprising a diacid and a diamine to prepare a salt solution;

[0075] Wherein, the molar ratio of the diacid to the diamine is (0.98-1):1;

[0076] S2, subjecting the salt solution to a polymerization reaction;

[0077] The polymerization reaction includes: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature at reduced pressure, increasing temperature at normal pressure and increasing temperature at negative pressure;

[0078] The polymerization reaction temperature is 220-270° C.; during the constant pressure heating process, the pressure is 0.5 MPa-1.0 MPa; during the pressure relief heating process, the pressure relief endpoint is when the pressure drops to normal pressure; and the pressure relief rate during the pressure relief heating process is 0.003-0.02 MPa / min.

[0079] In the above preferred embodiment, the molar ratio of the diacid to the diamine is, for example, 1:1.005 or 1:1.01.

[0080] In the above preferred embodiment, the diacid is preferably adipic acid.

[0081] In the above preferred embodiment, during the constant pressure heating process, the temperature after heating can be 220-260°C, for example, 245°C.

[0082] In the above preferred embodiment, during the pressure and temperature increasing process, the heating rate may be 1-10°C / min, for example 5°C / min.

[0083] In the above preferred embodiment, the total heating time in the pressure-increasing and constant-pressure-heating process may be 0.5 to 4 hours.

[0084] In the above preferred embodiment, during the pressure relief and temperature increase process, the temperature after the increase can be 230-270°C, such as 240°C, 250°C, 255°C or 265°C.

[0085] In the above preferred embodiment, during the pressure relief and temperature increase process, the temperature increase rate may be 0.1 to 5° C. / min.

[0086] In the above preferred embodiment, during the pressure relief and temperature raising process, the pressure relief time may be 50 to 120 minutes, preferably 50 to 70 minutes, such as 57 minutes or 60 minutes.

[0087] In the above preferred embodiment, during the pressure relief and temperature raising process, the pressure relief can be performed by one-step pressure relief or two-step pressure relief.

[0088] When the pressure relief in the pressure relief and temperature rise is performed by the one-step pressure relief, the pressure relief rate is 0.003 to 0.02 MPa / min, for example, 0.005 MPa / min or 0.01 MPa / min.

[0089] When the pressure relief in the pressure relief and temperature rise is performed through the two-step pressure relief, the rate of the first pressure relief may be 0.003 to 0.005 MPa / min; the rate of the second pressure relief may be 0.01 to 0.02 MPa / min.

[0090] In the above preferred embodiment, the temperature of the constant temperature at normal pressure may be 240-270°C, such as 245°C, 255°C or 260°C.

[0091] In the above preferred embodiment, the time of constant temperature at normal pressure may be 30 to 90 minutes.

[0092] In the above preferred embodiment, the temperature of the negative pressure constant temperature may be 240-270°C, such as 245°C, 255°C or 260°C.

[0093] In the above preferred embodiment, the pressure of the negative pressure thermostat may be -30 to -100 kPa, for example -80 kPa.

[0094] In the above preferred embodiment, the negative pressure constant temperature time is 30 to 120 minutes, for example, 60 minutes.

[0095] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0096] The reagents and raw materials used in the present invention are commercially available.

[0097] The positive progress effect of the present invention is:

[0098] The preparation method of the meta-xylylenediamine nylon of the present invention is simple, and the effect of regulating the crystallization properties of the meta-xylylenediamine nylon can be achieved without adding additional crystallization regulating additives. The meta-xylylenediamine nylon prepared by the preparation method of the meta-xylylenediamine nylon of the present invention has a wide crystallization temperature range and an adjustable molecular weight distribution, which can meet the use requirements in different application scenarios. DETAILED DESCRIPTION

[0099] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0100] Example 1

[0101] Preparation of MXD6-1 for engineering plastics:

[0102] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5646g of desalted water, add 2724g of m-xylenediamine while stirring at 20r / min, and then slowly add 2923g of adipic acid; the molar ratio of adipic acid to m-xylenediamine is 1:1; replace the air in the reactor with high-purity nitrogen three times, then raise the temperature to 90°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely salt to obtain a salt solution;

[0103] S2. The salt solution prepared in step S1 is subjected to a polymerization reaction. The temperature is gradually raised to 240° C. at a rate of 5° C. / min. At the same time, the pressure in the kettle is raised to 1.0 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 1.0 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 1.0 MPa. The pressure is then released and the temperature is increased. The pressure of the system is released to normal pressure at a rate of 0.016 MPa / min. While releasing the pressure, ensure that the temperature in the kettle gradually rises to 255°C, and the heating rate during the pressure release process is 0.25°C / min; then, keep the temperature at normal pressure for 30 minutes at 255°C; then evacuate the reactor, and reduce the pressure in the reactor to -80 kPa at a uniform rate within 30 minutes, and then keep the temperature at negative pressure for 10 minutes under the vacuum condition; then fill the reactor with nitrogen, and squeeze the material out from the lower discharge port under the action of pressure, obtain cast strips after water cooling and granulate.

[0104] Example 2

[0105] Preparation of MXD6-2 for engineering plastics:

[0106] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 3755g of desalted water, add 2710g of m-xylenediamine while stirring at a speed of 20r / min, and then slowly add 2923g of adipic acid. The molar ratio of adipic acid to m-xylenediamine is 1:0.995; replace the air in the reactor with high-purity nitrogen three times, and then raise the temperature to 80°C at a rate of 10°C / min; continue stirring for 30min after the temperature stabilizes to allow the material to completely salt to obtain a salt solution;

[0107] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 250°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 1.5 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 60%. During the constant pressure heating process, when the pressure in the kettle exceeds 1.5 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 1.5 MPa. Then, the pressure is released and the temperature is increased. The pressure of the system is released to normal pressure at a rate of 0.05 MPa / min. The pressure is increased while ensuring that the temperature in the kettle gradually rises to 260°C, and the heating rate during the pressure relief process is 0.35°C / min; then, constant temperature is maintained at normal pressure for 30 minutes at 260°C, and then the reactor is evacuated to reduce the pressure in the reactor to -80 kPa at a uniform rate within 30 minutes, and then constant temperature is maintained at negative pressure for 10 minutes under the vacuum condition, and then nitrogen is filled into the reactor. Under the action of pressure, the material is extruded from the lower discharge port, and after water cooling, cast strips are obtained and granulated.

[0108] Example 3

[0109] Preparation of MXD6-3 for engineering plastics:

[0110] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5620g of desalted water, add 2697g of m-xylenediamine while stirring at 20r / min, and then slowly add 2923g of adipic acid; the molar ratio of adipic acid to m-xylenediamine is 1:0.99; replace the air in the reactor with high-purity nitrogen three times, then raise the temperature to 95°C at a rate of 10°C / min; after the temperature stabilizes, continue stirring for 30min to allow the material to completely salify to obtain a salt solution;

[0111] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 250°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 1.7 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 1.7 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 1.7 MPa. Then, the pressure is released and the temperature is increased. The pressure is released to normal pressure at a rate of 0.05 MPa / min. Ensure that the temperature in the kettle gradually rises to 265°C, the heating rate during the pressure relief process is 0.45°C / min, and then the normal pressure constant temperature is carried out at 265°C for 30 minutes; then the reactor is evacuated, and the pressure in the reactor is pumped to -80kPa at a uniform rate within 30 minutes, and then negative pressure constant temperature is carried out under the vacuum condition for 10 minutes, and then nitrogen is filled into the reactor. Under the action of pressure, the material is squeezed out from the lower discharge port, and after water cooling, the cast strip is obtained and granulated.

[0112] Example 4

[0113] Preparation of MXD6-4 for engineering plastics:

[0114] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5646g of desalted water, add 2724g of m-xylenediamine while stirring at a speed of 20r / min, and then slowly add 2923g of adipic acid. The molar ratio of adipic acid to m-xylenediamine is 1:1; replace the air in the reactor with high-purity nitrogen three times, and then raise the temperature to 90°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely salify to obtain a salt solution;

[0115] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 240°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 0.5 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 0.5 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 0.5 MPa. Then, the pressure is released and the temperature is increased. The pressure of the system is released to normal pressure at a rate of 0.008 MPa / min. While increasing pressure, ensure that the temperature in the kettle gradually rises to 255°C, the heating rate during the pressure relief process is 0.25°C / min, and then the normal pressure thermostat is carried out at 255°C for 30 minutes; then the reactor is evacuated, and the pressure in the reactor is pumped to -80kPa at a uniform rate within 30 minutes, and then the negative pressure thermostat is carried out under the vacuum condition for 10 minutes, and then nitrogen is filled into the reactor, and the material is squeezed out from the lower discharge port under the action of pressure, and cast strips are obtained after water cooling and granulation.

[0116] Example 5

[0117] Preparation of MXD6-5 for thin films:

[0118] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5646g of desalted water, add 2724g of m-xylenediamine while stirring at 20r / min, and then slowly add 2923g of adipic acid; the molar ratio of adipic acid to m-xylenediamine is 1:1; replace the air in the reactor with high-purity nitrogen three times, then raise the temperature to 80°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely salt to obtain a salt solution;

[0119] S2. The salt solution prepared in step S1 is subjected to a polymerization reaction. The temperature is gradually raised to 250° C. at a rate of 5° C. / min. At the same time, the pressure in the kettle is raised to 1.0 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 1.0 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 1.0 MPa. The pressure is then released and the temperature is increased. The system pressure is released to normal pressure at a rate of 0.02 MPa / min. While releasing the pressure, ensure that the temperature in the kettle gradually rises to 265°C, and the heating rate during the pressure release process is 0.3°C / min; at 265°C and normal pressure, constant temperature is maintained at normal pressure for 30 minutes; then the reactor is evacuated, and the pressure in the reactor is pumped to -80 kPa at a uniform rate within 30 minutes, and then constant temperature is maintained at negative pressure for 60 minutes under the vacuum condition, and then nitrogen is filled into the reactor. Under the action of pressure, the material is squeezed out from the lower discharge port, and after water cooling, cast strips are obtained and granulated.

[0120] Example 6

[0121] Preparation of MXD6-6 for thin films:

[0122] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5660g of desalted water, add 2737g of m-xylenediamine while stirring at 20r / min, and then slowly add 2923g of adipic acid; the molar ratio of adipic acid to m-xylenediamine is 1:1.005; replace the air in the reactor with high-purity nitrogen three times, then raise the temperature to 90°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely salt to obtain a salt solution;

[0123] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 250°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 0.5MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 0.5MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 0.5MPa. Then, the pressure is released and the temperature is increased. The pressure is released to normal pressure at a rate of 0.01MPa / min. The pressure is released at the same temperature. The temperature in the kettle is ensured to gradually rise to 260°C, the heating rate during the pressure relief process is 0.2°C / min, and then constant temperature is carried out at normal pressure for 30 minutes at 260°C; the reactor is then evacuated, and the pressure in the reactor is pumped to -80 kPa at a uniform rate within 30 minutes, and then constant temperature is carried out at negative pressure for 60 minutes under the vacuum condition, and then nitrogen is filled into the reactor. Under the action of pressure, the material is squeezed out from the lower discharge port, and after water cooling, cast strips are obtained and granulated.

[0124] Example 7

[0125] Preparation of MXD6-7 for thin films:

[0126] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5673g of desalted water, add 2751g of m-xylenediamine while stirring at a speed of 20r / min, and then slowly add 2923g of adipic acid. The molar ratio of adipic acid to m-xylenediamine is 1:1.01; replace the air in the reactor with high-purity nitrogen three times, and then raise the temperature to 90°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely form salts to obtain a salt solution;

[0127] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 245°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 0.5 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 0.5 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 0.5 MPa. Then, the pressure is released and the temperature is increased. The system pressure is first released to 0.3 MPa at a rate of 0.005 MPa / min and then released at a rate of 0.01 MPa / min. in, the system pressure is released to normal pressure, and while releasing the pressure, the temperature in the kettle is ensured to gradually rise to 255°C. The heating rate during the pressure release process is 0.1°C / min, and then the normal pressure constant temperature is carried out at 255°C and normal pressure for 30 minutes. Thereafter, the reactor is evacuated, and the pressure in the reactor is pumped to -80 kPa at a uniform rate within 30 minutes. Then, the negative pressure constant temperature is carried out under the vacuum condition for 60 minutes. Then, nitrogen is filled into the reactor, and the material is squeezed out from the lower discharge port under the action of pressure. After water cooling, cast strips are obtained and granulated.

[0128] Example 8

[0129] Preparation of MXD6-8 for thin films:

[0130] S1. Replace the air in a 20L reactor with high-purity nitrogen, then add 5646g of desalted water, add 2724g of m-xylenediamine while stirring at a speed of 20r / min, and then slowly add 2923g of adipic acid. The molar ratio of adipic acid to m-xylenediamine is 1:1. Replace the air in the reactor with high-purity nitrogen three times, then raise the temperature to 80°C at a rate of 10°C / min; continue stirring for 20min after the temperature stabilizes to allow the material to completely salt to obtain a salt solution.

[0131] S2. The salt solution prepared in step S1 is subjected to polymerization reaction. The temperature is gradually raised to 250°C at a rate of 5°C / min. At the same time, the pressure in the kettle is raised to 1.7 MPa. The pressure is increased and the temperature is kept constant. The concentration of the salt solution is 50%. During the constant pressure heating process, when the pressure in the kettle exceeds 1.7 MPa, the water vapor in the kettle is discharged through the pressure relief valve to control the pressure to be maintained at 1.7 MPa. Then, the pressure is released and the temperature is increased. The system pressure is released to normal pressure at a rate of 0.03 MPa / min. While increasing pressure, ensure that the temperature in the kettle gradually rises to 265°C, the heating rate during the pressure relief process is 0.3°C / min, and then constant temperature is carried out at normal pressure for 30 minutes at 265°C; then the reactor is evacuated, and the pressure in the reactor is pumped to -80 kPa at a uniform rate within 30 minutes, and then constant temperature is carried out at negative pressure for 60 minutes under the vacuum condition, and then nitrogen is filled into the reactor. Under the action of pressure, the material is squeezed out from the lower discharge port, and after water cooling, cast strips are obtained and granulated.

[0132] Effect embodiment

[0133] The m-xylylenediamine nylon prepared in Examples 1 to 8 was dried and subjected to the following tests:

[0134] (1) Determination of crystallization temperature: The test was conducted according to ISO 11357. The temperature program of the differential scanning calorimeter (DSC) was as follows: heating to 300°C at a rate of 10°C / min, holding for 5 min, cooling to 25°C at a rate of 10°C / min, holding for another 5 min, and then heating to 300°C at a rate of 10°C / min. The temperature corresponding to the exothermic peak on the curve during the cooling process is the crystallization temperature.

[0135] (2) Determination of relative viscosity: Using concentrated sulfuric acid as the solvent, weigh the dried sample and prepare a polymer solution in concentrated sulfuric acid with a concentration of 0.01 g / mL. Then, at 25°C, use an Ubbelohde viscometer to measure the outflow times t1 and t2 of the polymer solution and the solvent, respectively. The relative viscosity is then calculated according to the following formula: relative viscosity = t1 / t2.

[0136] (3) Determination of molecular weight and molecular weight distribution: GPC was used to measure the weight average molecular weight and number average molecular weight of the sample using hexafluoroisopropanol as solvent, and the molecular weight distribution index (PDI) was calculated.

[0137] The above test results are listed in Table 1.

[0138] Table 1 Performance parameters of m-phenylenediamine nylon obtained in Examples 1-8

[0139] The meta-phenylenediamine nylon prepared in Example 1-4 is suitable for engineering plastics. As can be seen from the above table, the crystallization temperature of the meta-phenylenediamine nylon prepared in Example 1-4 is between 158-170°C, the weight average molecular weight is between 50,000-54,000 g / moL, the number average molecular weight is between 23,000-25,000 g / moL, and the molecular weight distribution index is between 2.00-2.35. By comparing the data results, it can be found that by regulating the polymerization process, the molecular weight and molecular weight distribution of the polymer can be regulated, affecting the microstructure of the polymer, thereby achieving adjustable crystallization performance. The meta-phenylenediamine nylon prepared in Example 1-3 has relatively strong crystallization performance, which is beneficial to the subsequent processing of engineering plastics. The crystallization performance of Example 4 is slightly worse than that of Example 1-3. When used for the preparation of engineering plastics, the performance of Example 4 is worse than that of Example 1-3.

[0140] The meta-phenylenediamine nylon to be prepared in Example 5-8 is suitable for use in thin films. As can be seen from the above table, the crystallization temperature of the meta-phenylenediamine nylon obtained in Example 5-8 is between 156-165°C, the weight average molecular weight is between 87000-93000g / moL, the number average molecular weight is between 37000-40000g / moL, and the molecular weight distribution index is between 2.17-2.51. It can also be found that by regulating the polymerization process, the molecular weight and molecular weight distribution of the polymer can be regulated, affecting the microstructure of the polymer, thereby achieving adjustable crystallization performance. The meta-phenylenediamine nylon obtained in Example 5-7 has relatively weak crystallization performance, which is beneficial to the subsequent processing of the film. Compared with Example 5, the crystallization performance of Example 8 is slightly better, so when used for the preparation of thin films, the performance of Example 8 is worse than that of Example 5.

[0141] The above embodiments are preferred implementations of the invention, but the implementation of the present invention is not limited to the above examples. Any other changes, modifications, substitutions, and combination simplifications made without departing from the spirit and principles of the present invention are equivalent.

Claims

1. A method for preparing meta-xylylenediamine nylon, characterized in that: It includes the following steps: S1, reacting a mixture containing a diacid and a diamine to obtain a salt solution; Wherein, the diacid comprises one or more of adipic acid, sebacic acid, undecanedioic acid and dodecanedioic acid; the diamine is meta-xylylenediamine; the molar ratio of the diacid to the diamine is (0.95-1.05):1; S2, subjecting the salt solution to a polymerization reaction; the steps of the polymerization reaction include: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature by pressure release, and maintaining constant temperature at normal pressure and negative pressure; Wherein, the polymerization reaction temperature is 270°C or below; During the constant pressure temperature increase process, the pressure is 0.2MPa-2.0MPa; during the pressure reduction temperature increase process, the end point of pressure reduction is when the pressure drops to normal pressure; during the pressure reduction temperature increase process, the pressure reduction rate is 0.003-0.1MPa / min.

2. The method for preparing meta-xylylenediamine nylon according to claim 1, characterized in that: The preparation method of the meta-phenylenediamine nylon satisfies one or more of the following conditions: 1) In S1, the molar ratio of the diacid to the diamine is (0.98-1.02):1, for example, 0.99:1, 1:1 or 1.01:1; 2) In S1, the diacid is adipic acid; 3) In S1, the reaction temperature is 60-150°C; 4) In S1, the reaction time is 0 to 60 minutes, for example, 20 minutes; 5) In S1, the rate of heating to the reaction temperature is 1 to 20°C / min, for example, 10°C / min; 6) In S1, the reaction atmosphere is an inert gas, such as nitrogen; and, 7) In S1, the solvent used in the mixture is desalted water.

3. The method for preparing meta-xylylenediamine nylon according to claim 1, characterized in that: The preparation method of the meta-phenylenediamine nylon satisfies one or more of the following conditions: 1) In S2, during the polymerization reaction, the concentration of the salt solution is 40-80%, where the percentage is the mass percentage of the solute in the salt solution; 2) In S2, the total heating time of the pressure increase and the constant pressure heating is 0.5 to 4 hours; 3) In S2, during the constant pressure heating process, the temperature after heating is 220-260°C, for example, 240°C, 245°C or 250°C; 4) In S2, during the pressure and temperature increase process, the heating rate is 1 to 10°C / min, for example, 5°C / min; 5) In S2, during the constant pressure heating process, the heating rate is 1 to 10°C / min, for example, 5°C / min; and 6) In S2, during the constant pressure heating process, the pressure is 0.3-2.0 MPa, preferably 0.5 MPa-1.7 MPa.

4. The method for preparing meta-xylylenediamine nylon according to claim 1, characterized in that: The preparation method of the meta-phenylenediamine nylon satisfies one or more of the following conditions: 1) In S2, during the pressure relief and temperature increase process, the temperature after the temperature increase is 230-270°C, preferably 240-265°C, for example 250°C, 255°C or 260°C; 2) In S2, during the pressure relief and temperature increase process, the temperature increase rate is 0.1-5°C / min; 3) In S2, during the pressure relief and temperature rise process, the pressure relief rate is 0.003-0.1 MPa / min, preferably 0.005-0.05 MPa / min, for example 0.008 MPa / min, 0.01 MPa / min, 0.016 MPa / min or 0.02 MPa / min; and, 4) In S2, during the pressure relief and temperature rise process, the pressure relief time is 10 to 150 minutes, preferably 30 to 70 minutes, such as 34 minutes, 50 minutes, 57 minutes or 62.5 minutes.

5. The method for preparing meta-xylylenediamine nylon according to claim 1, characterized in that: The preparation method of the meta-phenylenediamine nylon satisfies one or more of the following conditions: 1) In S2, the temperature of the constant temperature under normal pressure is 240-270°C, preferably 245-265°C, for example 250°C, 255°C or 260°C; 2) In S2, the constant temperature and pressure time is 10 to 90 minutes, for example, 30 minutes; 3) In S2, the temperature of the negative pressure thermostat is 240-270°C, preferably 245-265°C, for example 250°C, 255°C or 260°C; 4) In S2, the negative pressure constant temperature time is 10 to 90 minutes, for example, 10 minutes or 60 minutes; 5) In S2, the pressure of the negative pressure thermostat is -30 kPa to -100 kPa, for example -80 kPa; 6) After step S2, the step of extrusion, cooling and granulation is also included; and, 7) The preparation method of the meta-phenylenediamine nylon does not require the addition of an auxiliary agent for regulating crystallization, such as a nucleating agent.

6. The method for preparing meta-xylylenediamine nylon according to any one of claims 1 to 5, characterized in that: When the meta-phenylenediamine nylon is applied to engineering plastics, the preparation method of the meta-phenylenediamine nylon comprises the following steps: S1, reacting a mixture containing a diacid and a diamine to obtain a salt solution; Wherein, the molar ratio of the diacid to the diamine is (1-1.02):1; S2, subjecting the salt solution to a polymerization reaction; The steps of the polymerization reaction include: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature by reducing pressure, increasing temperature by constant temperature at normal pressure, and increasing temperature at negative pressure; The polymerization reaction temperature is 220-270°C; during the constant pressure temperature increase, the pressure is 1.0MPa-2.0MPa; the end point of the pressure release during the pressure release temperature increase is when the pressure drops to normal pressure; during the pressure release temperature increase, the pressure release rate is 0.01-0.1MPa / min.

7. The method for preparing meta-xylylenediamine nylon according to claim 6, characterized in that: The preparation method of the meta-xylylenediamine nylon satisfies one or more of the following conditions: 1) During the constant pressure heating process, the pressure is 1.0MPa to 1.7MPa; 2) During the constant pressure heating process, the temperature after heating is 220-260°C, preferably 220-255°C; 3) During the pressure and temperature increase process, the heating rate is 1 to 10°C / min, for example, 5°C / min; 4) The total heating time in the pressure-raising and constant-pressure-raising is 0.5 to 4 hours; 5) During the pressure relief and temperature increase process, the temperature after the temperature increase is 230-270°C, preferably 240-265°C, for example 250°C, 255°C or 260°C; 6) During the pressure relief and temperature rise process, the heating rate is 0.1-5°C / min; 7) During the pressure relief and temperature rise process, the pressure relief rate is 0.016-0.1 MPa / min, for example, 0.05 MPa / min; 8) During the pressure relief and temperature rise process, the pressure relief time is 20 to 65 minutes, preferably 30 to 62.5 minutes, for example 34 minutes; 9) The temperature of the constant temperature at normal pressure is 240-270°C, preferably 245-265°C, for example 250°C, 255°C or 260°C; 10) The time of constant temperature at normal pressure is 10 to 90 minutes, for example 30 minutes; 11) The temperature of the negative pressure thermostat is 240-270°C, preferably 245-265°C, for example 250°C, 255°C or 260°C; 12) The pressure of the negative pressure thermostat is -30 to -100 kPa, for example -80 kPa; and 13) The negative pressure constant temperature time is 10 to 40 minutes, for example 10 minutes.

8. The method for preparing meta-xylylenediamine nylon according to any one of claims 1 to 5, characterized in that: When the meta-xylylenediamine nylon is applied to a film, the preparation method of the meta-xylylenediamine nylon comprises the following steps: S1, reacting a mixture containing a diacid and a diamine to obtain a salt solution; Wherein, the molar ratio of the diacid to the diamine is (0.98-1):1; S2, subjecting the salt solution to a polymerization reaction; wherein the steps of the polymerization reaction include: increasing pressure and temperature, increasing temperature at constant pressure, increasing temperature by pressure release, constant temperature at normal pressure, and constant temperature at negative pressure; The polymerization reaction temperature is 220-270°C; during the constant pressure temperature increase, the pressure is 0.5MPa-1.0MPa; the end point of the pressure release during the pressure release temperature increase is when the pressure drops to normal pressure; during the pressure release temperature increase, the pressure release rate is 0.003-0.02MPa / min.

9. The method for preparing meta-xylylenediamine nylon according to claim 8, characterized in that: The preparation method of the meta-xylylenediamine nylon satisfies one or more of the following conditions: 1) During the constant pressure heating process, the temperature after heating is 220-260°C, for example, 245°C or 250°C; 2) During the pressure and temperature increase process, the heating rate is 1 to 10°C / min, for example, 5°C / min; 3) The total heating time in the pressure-raising and constant-pressure-raising is 0.5 to 4 hours; 4) During the pressure relief and temperature increase process, the temperature after the temperature increase is 230-270°C, preferably 240-265°C, for example 250°C, 255°C or 265°C; 5) During the pressure relief and temperature rise process, the heating rate is 0.1-5°C / min; 6) During the pressure relief and temperature rise process, the pressure relief time is 50 to 120 minutes, preferably 50 to 70 minutes, for example 57 minutes or 60 minutes; 7) During the pressure relief and temperature rising process, the pressure relief is carried out by one-step pressure relief or two-step pressure relief; 8) The temperature of the constant temperature at normal pressure is 240-270°C, for example, 245°C, 255°C or 260°C; 9) The time of constant temperature at normal pressure is 30 to 90 minutes; 10) The temperature of the negative pressure thermostat is 240-270°C, for example, 245°C, 255°C or 260°C; 11) The pressure of the negative pressure thermostat is -30 to -100 kPa, for example -80 kPa; and 12) The negative pressure constant temperature time is 30 to 120 minutes, for example 60 minutes.

10. The method for preparing meta-xylylenediamine nylon according to claim 9, characterized in that: When the pressure relief is performed by the one-step pressure relief, the pressure relief rate is 0.003 to 0.02 MPa / min, for example, 0.005 MPa / min or 0.01 MPa / min; Alternatively, when the pressure relief is performed through the two-step pressure relief, the rate of the first pressure relief is 0.003-0.005 MPa / min; the rate of the second pressure relief is 0.01-0.02 MPa / min.

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