A kind of semi-aromatic polyamide and its prepolymer and preparation method

Abstract

The present invention provides a semi-aromatic polyamide and its prepolymer and preparation method. The discreteness of the semi-aromatic polyamide prepolymer is 0.1-5.0. The preparation method of the semi-aromatic polyamide prepolymer comprises the following steps: spraying the semi-aromatic polyamide prepolymer reaction liquid into a flash evaporation device and simultaneously performing a crushing treatment to obtain particles of the semi-aromatic polyamide prepolymer; wherein the flash evaporation device is provided with a crushing device and / or a shredding device; the crushing device and / or the shredding device is provided with a cutter, and the rotation speed of the cutter is 100-8000 rpm. The present invention also provides a semi-aromatic polyamide prepared based on the above-mentioned semi-aromatic polyamide prepolymer. The technical scheme of the present invention can effectively prevent the yellowing and blackening problems caused by the overheating side reaction inside the prepolymer due to the agglomeration of the prepolymer during the discharging process of the prepolymer, and at the same time, the prepolymer has a low discreteness, which improves the mechanical properties of the subsequent viscosity-enhancing products, and has a very large production and application prospect.

Description

Technical Field

[0001] The invention relates to a semi-aromatic polyamide and a prepolymer thereof and a preparation method thereof, belonging to the technical field of polymer materials. Background Art

[0002] Semi-aromatic polyamide is synthesized by condensation polymerization of aliphatic diamine or dibasic acid and aromatic diamine or dibasic acid, mainly including PA6T, PA9T, PA10T, PA12T and MXD6. This type of polyamide has greatly improved heat resistance and mechanical properties and reduced water absorption due to the addition of benzene ring structure, so it has a high cost performance. Semi-aromatic polyamide is a high temperature resistant polymer with performance between ordinary engineering plastics and high temperature resistant engineering plastic polyether ether copper. It is mainly used in automobile and electronic appliances industries. With the development of science and technology, the demand for this type of polyamide has also greatly increased. I believe that after the breakthrough of hexamethylenediamine synthesis technology, it is bound to usher in a wave of surging development.

[0003] At present, semi-aromatic polyamides are mostly prepared by a two-step method, that is, prepolymerization is first performed to obtain a semi-aromatic polyamide prepolymer, and then viscosity is increased. The viscosity increase is divided into screw viscosity increase and solid phase viscosity increase. At present, the common method for obtaining semi-aromatic polyamide prepolymers is to spray or directly flash evaporate after the prepolymerization. However, the dispersion of the prepolymer solids obtained by the above two methods is usually wide, and this wide dispersion has a greater negative impact on the performance of the final polymer. In the experiment, the inventor of the present invention unexpectedly found that if the crushing is not timely and sufficient during the discharging process, an overheating side reaction will occur inside the agglomerated prepolymer, causing the prepolymer to turn yellow or even black. At the same time, the excessive dispersion of the prepolymer solid has a significant negative impact on the subsequent viscosity increase, especially the performance of the semi-aromatic polyamide product obtained by solid phase viscosity increase. In order to control the dispersion, some manufacturers adopt the post-crushing method, which adds a process and is difficult to eliminate the side reactions during the flash evaporation process. Summary of the invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a semi-aromatic polyamide prepolymer, which is a semi-aromatic polyamide prepolymer solid with relatively low discreteness.

[0005] The present invention also aims to provide a method for preparing the semi-aromatic polyamide prepolymer prepared by the above method and the semi-aromatic polyamide prepared thereby.

[0006] To achieve the above object, the present invention provides a semi-aromatic polyamide prepolymer, which is prepared by the above method for preparing the semi-aromatic polyamide prepolymer.

[0007] According to a specific embodiment of the present invention, preferably, the discreteness of the semi-aromatic polyamide prepolymer is 0.1-5.0, more preferably 0.3-4.1, and further preferably 0.5-3.2. Too high a discreteness will lead to a decrease in the performance of the final polymer product after viscosity increase, and too low a discreteness will place too high requirements on the equipment and increase the preparation cost. The semi-aromatic polyamide prepolymer provided by the present invention has a suitable discreteness, which can avoid the above problems.

[0008] According to a specific embodiment of the present invention, preferably, the relative viscosity of the semi-aromatic polyamide prepolymer is 1.02-1.52, more preferably 1.05-1.40, and further preferably 1.08-1.31. The semi-aromatic polyamide prepolymer provided by the present invention has a suitable relative viscosity, i.e., degree of polymerization, which is beneficial to the control of the discreteness of the semi-aromatic polyamide prepolymer in the synchronous flash pulverization process.

[0009] The present invention also provides a method for preparing the semi-aromatic polyamide prepolymer, wherein the method for preparing the semi-aromatic polyamide prepolymer comprises the following steps:

[0010] The semi-aromatic polyamide prepolymer reaction liquid is sprayed into a flash evaporation device and pulverized at the same time to obtain particles (or powder) of the semi-aromatic polyamide prepolymer;

[0011] Wherein, the flash evaporation device is provided with a crushing device and / or a shredding device; the crushing device and / or the shredding device is provided with a cutter, and the rotation speed of the cutter is 100-8000 rpm.

[0012] The preparation method of the semi-aromatic polyamide prepolymer provided by the present invention is to discharge and crush the semi-aromatic polyamide prepolymer simultaneously, thereby obtaining the required particle size dispersion, thereby obtaining a product with excellent performance.

[0013] In the above method for preparing the semi-aromatic polyamide prepolymer, preferably, the pulverizing equipment comprises a stirring pulverizing equipment and / or a cage pulverizing equipment.

[0014] In the above method for preparing semi-aromatic polyamide prepolymer, the flash evaporation device may also be equipped with accessories or designs that facilitate crushing. Preferably, the flash evaporation device is also provided with one or more structures selected from the group consisting of a baffle, a sieve plate and a perforated plate.

[0015] In the above-mentioned method for preparing a semi-aromatic polyamide prepolymer, preferably, the orifice plate is arranged inside the feed pipe of the flash evaporation device, and the baffle plate and / or sieve plate is arranged inside the body of the flash evaporation device;

[0016] The semi-aromatic polyamide prepolymer reaction liquid first enters the feed pipe of the flash evaporation device, and then is crushed into particles of the semi-aromatic polyamide prepolymer inside the flash evaporation device and output from the flash evaporation device.

[0017] In the above method for preparing a semi-aromatic polyamide prepolymer, preferably, when the baffle is disposed inside the flash evaporation device, the area of ​​the baffle does not exceed three quarters of the cross-sectional area of ​​the flash evaporation device.

[0018] In the above method for preparing the semi-aromatic polyamide prepolymer, preferably, when the sieve plate is arranged inside the flash evaporation device, the total hole area of ​​the sieve plate is not less than one fifth of the cross-sectional area of ​​the flash evaporation device.

[0019] In the above method for preparing semi-aromatic polyamide prepolymer, preferably, when the orifice plate is arranged inside the feed pipe of the flash evaporation device, the total hole area of ​​the orifice plate does not exceed three quarters of the cross-sectional area of ​​the feed pipe.

[0020] In the above method for preparing a semi-aromatic polyamide prepolymer, preferably, the semi-aromatic polyamide prepolymer reaction liquid is sprayed into the flash evaporation device through a spray nozzle or a straight pipe.

[0021] In the above-mentioned method for preparing the semi-aromatic polyamide prepolymer, preferably, the rotation speed of the cutter is 300-5000 rpm, more preferably 600-3000 rpm. By controlling the rotation speed of the cutter within the range provided by the present invention, a better dispersion and crushing effect can be achieved, but too high a rotation speed increases the difficulty of equipment processing, or even makes processing impossible.

[0022] In the above-mentioned method for preparing a semi-aromatic polyamide prepolymer, preferably, the semi-aromatic polyamide prepolymer reaction liquid is prepared by the following steps:

[0023] The raw material of the semi-aromatic polyamide is configured into a 20%wt to 90%wt aqueous solution, the pH value is adjusted to 6 to 11, an additive not exceeding 10%wt of the total raw material is added, and the mixture is heated and concentrated to 50%wt to 95%, and then reacted at a pressure of 1.5MPa to 6MPa for 0.5 hour to 8 hours to obtain the semi-aromatic polyamide prepolymer reaction solution.

[0024] In the above method for preparing the semi-aromatic polyamide prepolymer, preferably, after the reaction is completed, the semi-aromatic polyamide prepolymer reaction liquid is discharged at a pressure between 1.5 MPa and 6 MPa.

[0025] In the above method for preparing a semi-aromatic polyamide prepolymer, preferably, the raw materials of the semi-aromatic polyamide include a dibasic acid and a diamine;

[0026] Wherein, the dibasic acid includes one to four combinations of C5-C18 dibasic acids and / or benzene ring-containing dibasic acids, and the diamine includes one to three combinations of C5-C18 diamines;

[0027] The total amount of the dibasic acid and the diamine accounts for more than 90% of the total weight of the raw materials.

[0028] In the above method for preparing the semi-aromatic polyamide prepolymer, preferably, the C5-C18 dibasic acid is selected from one or a combination of two or more of glutaric acid, adipic acid, sebacic acid, undecanedioic acid and dodecanedioic acid.

[0029] In the above method for preparing the semi-aromatic polyamide prepolymer, preferably, the dibasic acid containing a benzene ring is selected from terephthalic acid and / or isophthalic acid.

[0030] In the above-mentioned method for preparing the semi-aromatic polyamide prepolymer, preferably, the C5-C18 diamine is selected from one or a combination of two or more of pentamethylenediamine, 2-methyl-pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, nonamethylenediamine and decamethylenediamine.

[0031] In the preparation method of the semi-aromatic polyamide prepolymer, preferably, the additive is selected from one or more of a catalyst, an end-capping agent, a defoaming agent, a weathering agent, a nucleating agent, an antistatic agent, a flame retardant, an anti-ultraviolet agent, a matting agent, an antioxidant, a lubricant, etc., or a combination of two or more thereof. Among them, an antioxidant is preferably added. Among them, the catalyst may include organic matter or salts of phosphoric acid, phosphorous acid, and hypophosphorous acid. The end-capping agent may include a monofunctional amine or a monofunctional acid, such as hexylamine, acetic acid, hexanoic acid, benzoic acid, etc., or may be a diamine or a dibasic acid, such as pentamethylenediamine, hexamethylenediamine, adipic acid, terephthalic acid, etc. The defoaming agent may be a silicon-containing compound. The weathering agent may include a hydroquinone compound, a salicylate compound, a benzotriazole compound, a benzophenone compound, a hindered amine compound, etc. The crystallization nucleating agent may include inorganic particles such as talc, silica, kaolin, clay, boron nitride, or metal oxides, high melting point nylon, etc. The antistatic agent may include an alkyl sulfate type anionic antistatic agent, a quaternary ammonium salt type cationic antistatic agent, a nonionic antistatic agent such as polyoxyethylene sorbitan monostearate, a betaine type amphoteric antistatic agent, etc. The flame retardant may include melamine cyanurate, hydroxides (such as magnesium hydroxide, aluminum hydroxide, etc.), ammonium polyphosphate, brominated polystyrene, brominated polyphenylene ether, brominated polycarbonate, brominated epoxy resin, or a combination of these brominated flame retardants and antimony trioxide, etc. The matting agent may be an inorganic substance such as titanium dioxide. The antioxidant may be an antioxidant H10 (German Brueggemann), etc.

[0032] The preparation method of the semi-aromatic polyamide prepolymer of the present invention is a solution to a series of problems, such as the semi-aromatic polyamide prepolymer synthesized by the existing process cannot be timely and fully dispersed during the flash evaporation process, and the solid dispersion of the obtained semi-aromatic polyamide prepolymer is relatively high, which ultimately leads to poor performance of the semi-aromatic polyamide final polymer.

[0033] The present invention also provides a semi-aromatic polyamide, which is obtained by using the semi-aromatic polyamide prepolymer as a raw material through solid phase viscosity enhancement or screw viscosity enhancement.

[0034] According to a specific embodiment of the present invention, preferably, the discreteness of the semi-aromatic polyamide obtained by solid phase thickening is 0.1-5.0, more preferably 0.3-4.1, and further preferably 0.5-3.2. This discreteness is similar to that of the semi-aromatic polyamide prepolymer, because during the solid phase thickening process, the prepolymer has no obvious adhesion and further crushing phenomenon.

[0035] According to a specific embodiment of the present invention, preferably, the relative viscosity of the semi-aromatic polyamide is 1.65-2.92, more preferably 1.70-2.54, and further preferably 1.76-2.38. The semi-aromatic polyamide of the present invention has a suitable relative viscosity, which is conducive to processing while maintaining relatively high mechanical properties.

[0036] The polyamide of the present invention can be formed into a desired shape by injection molding, film molding, melt spinning, blow molding, vacuum molding and the like, and can be used in, for example, injection molded products, films, sheets, monofilaments, ribbons, fibers, etc., and can also be used in adhesives, coatings, etc.

[0037] The present invention provides a semi-aromatic polyamide prepolymer and final polymer with low dispersion, specifically, after the concentrated prepolymer is completed, the semi-aromatic polyamide solid is obtained by synchronous flash pulverization, and the prepolymer is further polymerized to obtain the final polymer. The process can effectively prevent the yellowing and blackening problems caused by the overheating side reaction inside the prepolymer due to the agglomeration of the prepolymer during the prepolymer discharge process, and the prepolymer has low dispersion, which improves the mechanical properties of the subsequent viscosity-enhancing product, and has a very large production and application prospect. DETAILED DESCRIPTION

[0038] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0039] The present invention uses the following characterization methods to characterize performance:

[0040] 1. Relative viscosity

[0041] Ubbelohde viscometer concentrated sulfuric acid method: Accurately weigh 0.45±0.0002 g of the dried semi-aromatic polyamide sample, add 45 mL of concentrated sulfuric acid (96%) to dissolve it, and measure and record the concentrated sulfuric acid flow time t0 and the semi-aromatic polyamide solution flow time t in a 25°C constant temperature water bath.

[0042] Relative viscosity calculation formula: RV = t / t0

[0043] t—solution flow time;

[0044] t0—Solvent flow time.

[0045] 2. Discreteness

[0046] Determined according to JJF 1211-2008 method.

[0047] Discreteness = (D90-D10) / D50

[0048] 3. Tensile strength test method

[0049] Determined according to GB / T 14344-2008 method.

[0050] 4. Yellow index

[0051] Determined according to HG / T 3862-2006 method.

[0052] Example 1 (crushing)

[0053] This embodiment provides a method for preparing semi-aromatic polyamide 6T / 66 (60:40) 50%, comprising the following steps:

[0054] A 20-liter polymerization kettle was used to replace the air therein three times by evacuating and filling with nitrogen, and the air was protected with nitrogen. 5 kg of pure water was added thereto, and then 2.12 kg of hexamethylenediamine was added. Stirring was started, 1.76 kg of terephthalic acid and 1.11 kg of adipic acid were added, and then 4 g of antioxidant sodium hypophosphite and 0.1 g of Dow Corning defoaming agent were added. The mixture was heated to 120°C and dissolved to obtain a nylon brine solution. The pH value of the nylon brine solution was adjusted to 10% with a small amount of hexamethylenediamine or adipic acid. The pH value was 6.24.

[0055] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.3 MPa. After the system concentration was increased to 85%, the oil bath was heated to 310°C. When the pressure in the kettle was increased to 3.0 MPa, exhaust was started. When the temperature in the kettle reached 265°C, the material was sprayed into a flash stirring and crushing kettle, wherein a perforated plate with a hole diameter of 8 mm was installed in the feed pipe, the perforated plate was arranged along the cross section of the feed pipe, and the total hole area of ​​the perforated plate was one third of the cross section area of ​​the feed pipe, the crushing and stirring paddle rotated at 1000 rpm, the crushing and stirring paddle was double-layered, a sieve plate with 7 mm sieve holes was installed inside the flash stirring and crushing kettle, the sieve plate was arranged along the cross section of the flash stirring and crushing kettle, and the total hole area (sieve hole) of the sieve plate was four fifths of the cross section area of ​​the flash stirring and crushing kettle; a semi-aromatic polyamide prepolymer was obtained, and the test results are shown in Table 1.

[0056] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 260°C and kept at 260°C for 4 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0057] Example 2 (crushing)

[0058] This embodiment provides a method for preparing 30% of semi-aromatic polyamide 6T / 66 (50:50), comprising the following steps:

[0059] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 7 kg of pure water was added thereto, followed by 1.28 kg of hexamethylenediamine. Stirring was started, and 0.88 kg of terephthalic acid and 0.83 kg of adipic acid were added. Then, 1.5 g of antioxidant sodium hypophosphite and 0.06 g of Dow Corning defoamer were added. The mixture was heated to 80°C to dissolve the nylon salt solution. The pH value of the nylon salt solution was adjusted to 8.42 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and 20 g of benzoic acid was added.

[0060] A 20-liter polymerization kettle is heated in an oil bath and the pressure is maintained and concentrated when the pressure reaches 0.3 MPa. After the system concentration is increased to 85%, the oil bath is heated to 310°C. When the pressure in the kettle rises to 2.0 MPa, exhaust is started. When the temperature in the kettle reaches 248°C, the material is sprayed into the flash stirring and crushing kettle, wherein a orifice plate with a hole diameter of 6 mm is installed in the feed pipe, the orifice plate is arranged along the cross-section of the feed pipe, and the total hole area of ​​the orifice plate is one-sixth of the cross-sectional area of ​​the feed pipe, the rotation speed of the crushing and stirring paddle is 2000rpm, the crushing and stirring paddle is three-layered, and a baffle is installed under the second-layer stirring paddle, the baffle is arranged along the cross-section of the flash stirring and crushing kettle, and the area of ​​the baffle is one-fourth of the cross-sectional area of ​​the flash stirring and crushing kettle (that is, one side has three-quarters of the opening), and a sieve plate with 5 mm sieve holes is installed inside the flash stirring and crushing kettle, and the total area of ​​the holes (sieve holes) of the sieve plate is one-half of the cross-sectional area of ​​the flash stirring and crushing kettle. The semi-aromatic polyamide prepolymer was obtained, and the test results are shown in Table 1.

[0061] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 270°C and kept at 270°C for 5 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0062] Example 3 (crushing)

[0063] This embodiment provides a method for preparing semi-aromatic polyamide 6T / 66 (60:40) 50%, comprising the following steps:

[0064] A 20-liter polymerization kettle was used to replace the air therein three times by evacuating and filling with nitrogen, and the air was protected with nitrogen. 5 kg of pure water was added thereto, and then 2.12 kg of hexamethylenediamine was added. Stirring was started, 1.76 kg of terephthalic acid and 1.11 kg of adipic acid were added, and then 6 g of antioxidant sodium hypophosphite and 0.1 g of Dow Corning defoamer were added. The mixture was heated to 120°C and dissolved to obtain a nylon brine solution. The pH value of the nylon brine solution was adjusted to 7.65 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and 10 g of acetic acid was added.

[0065] A 20-liter polymerization kettle was heated in an oil bath and concentrated at a pressure of 0.3 MPa. After the system concentration was increased to 75%, the oil bath was heated to 320°C. When the pressure in the kettle was increased to 4.0 MPa, exhaust was started. When the temperature in the kettle reached 274°C, the material was sprayed into a flash stirring and crushing kettle, wherein a perforated plate with a hole diameter of 7 mm was installed in the feed pipe, the perforated plate was arranged along the cross section of the feed pipe, and the total hole area of ​​the perforated plate was two-ninths of the cross-sectional area of ​​the feed pipe. The rotation speed of the crushing and stirring paddle was 600 rpm, the crushing and stirring paddle was a layer, a sieve plate with a sieve hole of 10 mm was installed inside the flash stirring and crushing kettle, the sieve plate was arranged along the cross section of the flash stirring and crushing kettle, and the total hole area (sieve hole) of the sieve plate was three-fifths of the cross-sectional area of ​​the flash stirring and crushing kettle, and a semi-aromatic polyamide prepolymer was obtained. The test results are shown in Table 1.

[0066] The prepolymer was transferred to a twin-screw extruder with a diameter of 26 mm, with the temperature of zone 1 at 240°C, zone 2 at 295°C, zone 3 at 295°C, zone 4 at 300°C, zone 5 at 300°C, zone 6 at 305°C, zone 7 at 305°C, zone 8 at 310°C, zone 9 at 310°C, zone 10 at 310°C, zone 11 at 315°C, and die head at 315°C. It was equipped with two exhaust ports and two vacuum ports. The exhaust ports were protected by nitrogen. The oxygen content at 8 cm above the material at the first exhaust port was 5 ppm, and the oxygen content at 8 cm above the material at the second exhaust port was 7 ppm. The vacuum degree of the first vacuum port was -0.04 MPa, and the vacuum degree of the second vacuum port was -0.06 MPa. The melt was pelletized underwater through a casting belt hole. The semi-aromatic polyamide particles were dried at 120°C and vacuum dried for 12 hours before various performance tests were conducted. The results are shown in Table 1.

[0067] Example 4 (crushing)

[0068] This embodiment provides a method for preparing 30% of semi-aromatic polyamide 6T / 66 (50:50), comprising the following steps:

[0069] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 7 kg of pure water was added thereto, followed by 1.28 kg of hexamethylenediamine. Stirring was started, 0.88 kg of terephthalic acid and 0.83 kg of adipic acid were added, and then 1.5 g of an antioxidant, sodium hypophosphite, was added. The mixture was heated to 80°C to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.99 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and then 12 g of acetic acid was added.

[0070] The 20-liter polymerization kettle was heated in an oil bath and concentrated at a pressure of 0.3 MPa. After the system concentration was raised to 80%, the oil bath was heated to 310°C. When the pressure in the kettle was raised to 3.0 MPa, exhaust was started. When the temperature in the kettle reached 262°C, the material was sprayed into the flash stirring and crushing kettle. A hole plate with a hole diameter of 4 mm was installed in the feed pipeline. The hole plate was arranged along the cross section of the feed pipeline, and the total hole area of ​​the hole plate was one-fourteenth of the cross section area of ​​the feed pipeline. The speed of the crushing stirring paddle was 12 00rpm, the crushing stirring paddles are three-layered, a baffle is installed under the second-layer stirring paddle, the baffle is arranged along the cross section of the flash stirring crushing kettle and the area of ​​the baffle is one-fifth of the cross section area of ​​the flash stirring crushing kettle (that is, there are four-fifths openings on one side), a sieve plate with a sieve hole of 5mm is installed inside the flash stirring crushing kettle, the sieve plate is arranged along the cross section of the flash stirring crushing kettle, and the total area of ​​the holes (sieve holes) of the sieve plate is one-fifth of the cross section area of ​​the flash stirring crushing kettle, and a semi-aromatic polyamide prepolymer is obtained. The test results are shown in Table 1.

[0071] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 240°C and kept at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0072] Example 5 (Spray)

[0073] This embodiment provides a method for preparing semi-aromatic polyamide 6T / 66 (60:40) 50%, comprising the following steps:

[0074] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 5 kg of pure water was added thereto, followed by 2.12 kg of hexamethylenediamine. Stirring was started, 1.76 kg of terephthalic acid and 1.11 kg of adipic acid were added, and then 4 g of antioxidant sodium hypophosphite and 0.1 g of Dow Corning defoamer were added. The mixture was heated to 120°C to dissolve the nylon salt solution. The pH value of the nylon salt solution was adjusted to 8.78 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and 18 g of benzoic acid was added.

[0075] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.3 MPa. After the system concentration was increased to 80%, the oil bath was heated to 300°C. When the pressure in the kettle was increased to 2.5 MPa, exhaust was started. When the temperature in the kettle reached 258°C, the material was sprayed out. The nozzle aperture was 1.0 mm. The spray tower collected the prepolymer. A squirrel cage open crushing device was built in. The cutter speed was 3000 rpm. A sieve plate with 3 mm sieve holes was installed inside. The sieve plate was arranged along the cross section of the flash stirring crushing kettle. The total area of ​​the holes (sieve holes) of the sieve plate was two-fifths of the cross-sectional area of ​​the flash stirring crushing kettle. Semi-aromatic polyamide prepolymer was obtained. The test results are shown in Table 1.

[0076] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 270°C and kept at 270°C for 4 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0077] Example 6 (Spray)

[0078] This embodiment provides a method for preparing semi-aromatic polyamide 6T / DT (50:50) 40%, comprising the following steps:

[0079] A 20-liter polymerization kettle was evacuated and filled with nitrogen to replace the air therein three times, and the mixture was protected by nitrogen. 6 kg of pure water was added thereto, followed by 0.82 kg of hexamethylenediamine and 0.82 kg of 2-methylpentamethylenediamine. Stirring was started, 2.35 kg of terephthalic acid was added, and then 2 g of antioxidant H10 (Brüggemann, Germany) was added. The mixture was heated to 90° C. to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.78 at a concentration of 10% with a small amount of hexamethylenediamine or terephthalic acid.

[0080] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.5 MPa. After the system concentration was increased to 80%, the oil bath was heated to 300°C. When the pressure in the kettle was increased to 2.5 MPa, exhaust was started. When the temperature in the kettle reached 252°C, the material was sprayed out. The nozzle aperture was 1.0 mm. The spray tower collected the prepolymer. A squirrel cage open pulverizing device was built in. The cutter speed was 800 rpm. A sieve plate with 5 mm sieve holes was installed inside. The sieve plate was arranged along the cross section of the flash stirring pulverizing kettle. The total area of ​​the holes (sieve holes) of the sieve plate was three-fifths of the cross section area of ​​the flash stirring pulverizing kettle. Semi-aromatic polyamide prepolymer was obtained. The test results are shown in Table 1.

[0081] The prepolymer was transferred to a vacuum drum, sealed and replaced with nitrogen, and then vacuum was started, and the backflush system was turned on. The backflush system was turned on every 30 minutes for 5 seconds. First, the system was gradually heated to 100°C, and after staying at this temperature for 3 hours, the system was gradually heated to 240°C and stayed at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide obtained was tested for various properties, and the results are shown in Table 1.

[0082] Example 7 (shredding)

[0083] This embodiment provides a method for preparing 30% of semi-aromatic polyamide 6T / 66 (50:50), comprising the following steps:

[0084] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 7 kg of pure water was added thereto, followed by 1.28 kg of hexamethylenediamine. Stirring was started, 0.88 kg of terephthalic acid and 0.83 kg of adipic acid were added, and then 1.5 g of an antioxidant, sodium hypophosphite, was added. The mixture was heated to 80°C to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.98 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and then 12 g of acetic acid was added.

[0085] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.3 MPa. After the system concentration was increased to 80%, the oil bath was heated to 310°C. When the pressure in the kettle was increased to 3.0 MPa, exhaust was started. When the temperature in the kettle reached 260°C, the material was sprayed into a flash evaporation device with a built-in shredding device. A perforated plate with a hole diameter of 4 mm was installed in the feed pipe. The perforated plate was arranged along the cross section of the feed pipe, and the total hole area of ​​the perforated plate was one-fourteenth of the cross-sectional area of ​​the feed pipe. The shredder speed was 1000 rpm. A sieve plate with 5 mm sieve holes was installed inside the flash evaporation kettle. The sieve plate was arranged along the cross section of the flash evaporation stirring and crushing kettle. The total hole area (sieve hole) of the sieve plate was four-fifths of the cross-sectional area of ​​the flash evaporation stirring and crushing kettle. Semi-aromatic polyamide prepolymer was obtained. The test results are shown in Table 1.

[0086] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 240°C and kept at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0087] Comparative Example 1 (crushing)

[0088] This comparative example provides a preparation method of semi-aromatic polyamide 6T / 66 (50:50) 30%, comprising the following steps:

[0089] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 7 kg of pure water was added thereto, followed by 1.28 kg of hexamethylenediamine. Stirring was started, 0.88 kg of terephthalic acid and 0.83 kg of adipic acid were added, and then 1.5 g of an antioxidant, sodium hypophosphite, was added. The mixture was heated to 80°C to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.99 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and then 12 g of acetic acid was added.

[0090] The 20-liter polymerization kettle oil bath was heated and concentrated when the pressure reached 0.3 MPa. After the system concentration was increased to 80%, the oil bath was heated to 310°C. When the pressure in the kettle rose to 3.0 MPa, exhaust was started. When the temperature in the kettle reached 262°C, the material was discharged onto a cooling conveyor belt with a scraper (reference patent CN201911285438.8) to obtain a semi-aromatic polyamide prepolymer. The test results are shown in Table 1.

[0091] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 240°C and kept at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0092] Comparative Example 2 (crushing)

[0093] This comparative example provides a preparation method of semi-aromatic polyamide 6T / 66 (50:50) 30%, comprising the following steps:

[0094] A 20-liter polymerization kettle was placed in a vacuum reactor and filled with nitrogen to replace the air therein three times, and the reactor was protected with nitrogen. 7 kg of pure water was added thereto, followed by 1.28 kg of hexamethylenediamine. Stirring was started, 0.88 kg of terephthalic acid and 0.83 kg of adipic acid were added, and then 1.5 g of an antioxidant, sodium hypophosphite, was added. The mixture was heated to 80°C to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.99 at a concentration of 10% with a small amount of hexamethylenediamine or adipic acid, and then 12 g of acetic acid was added.

[0095] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.3 MPa. After the system concentration was increased to 80%, the oil bath was heated to 310°C. When the pressure in the kettle increased to 3.0 MPa, exhaust was started. When the temperature in the kettle reached 262°C, the material was sprayed into a flash kettle, and the prepolymer solid was crushed and sieved to obtain a semi-aromatic polyamide prepolymer. The test results are shown in Table 1.

[0096] The prepolymer was transferred to a vacuum drum, vacuum was started, and the backflush system was turned on. The backflush system was turned on once every 10 minutes for 2 seconds. The system was gradually heated to 240°C and kept at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide was tested for various properties, and the results are shown in Table 1.

[0097] Comparative Example 3 (Spray)

[0098] This comparative example provides a method for preparing 40% of semi-aromatic polyamide 6T / DT (50:50), comprising the following steps:

[0099] A 20-liter polymerization kettle was evacuated and filled with nitrogen to replace the air therein three times, and the mixture was protected by nitrogen. 6 kg of pure water was added thereto, followed by 0.82 kg of hexamethylenediamine and 0.82 kg of 2-methylpentamethylenediamine. Stirring was started, 2.35 kg of terephthalic acid was added, and then 2 g of antioxidant H10 (Brüggemann, Germany) was added. The mixture was heated to 90° C. to dissolve the nylon salt solution, and the pH value of the nylon salt solution was adjusted to 8.78 at a concentration of 10% with a small amount of hexamethylenediamine or terephthalic acid.

[0100] A 20-liter polymerization kettle was heated in an oil bath and the pressure was maintained and concentrated when it reached 0.5 MPa. After the system concentration was increased to 80%, the oil bath was heated to 300°C. When the pressure in the kettle increased to 2.5 MPa, exhaust was started. When the temperature in the kettle reached 252°C, the material was sprayed out with a nozzle aperture of 1.0 mm. The prepolymer was collected in a spray tower to obtain a semi-aromatic polyamide prepolymer. The test results are shown in Table 1.

[0101] The prepolymer was transferred to a vacuum drum, sealed and replaced with nitrogen, and then vacuum was started, and the backflush system was turned on. The backflush system was turned on every 30 minutes for 5 seconds. First, the system was gradually heated to 100°C, and after staying at this temperature for 3 hours, the system was gradually heated to 240°C and stayed at 240°C for 6 hours. After the system was cooled, the semi-aromatic polyamide obtained was tested for various properties, and the results are shown in Table 1.

[0102] Table 1 Performance data of semi-aromatic polyamide prepared in various embodiments and comparative examples

[0103]

[0104]

[0105] The above embodiments are only explanations of the technical solutions and do not constitute limitations on the technical solutions of the present invention. Those skilled in the art can achieve polyamides (including semi-aromatic polyamides and aromatic polyamides) with different viscosities by adjusting the raw material ratio, temperature, pressure, etc. in the preparation process based on the knowledge of existing polyamide (including semi-aromatic polyamides and aromatic polyamide) preparation methods.

[0106] Although some aspects of the present invention have been shown and discussed, it will be appreciated by those skilled in the art that changes may be made to the above aspects without departing from the principles and spirit of the invention, and the scope of the invention shall be defined by the claims and their equivalents.

Claims

1. A method for preparing a semi-aromatic polyamide prepolymer, characterized in that: The preparation method of the semi-aromatic polyamide prepolymer comprises the following steps: The semi-aromatic polyamide prepolymer reaction liquid is sprayed into a flash evaporation device and pulverized at the same time to obtain particles of the semi-aromatic polyamide prepolymer; Wherein, the flash evaporation device is provided with a crushing device and / or a shredding device; the crushing device and / or the shredding device is provided with a cutter, and the rotation speed of the cutter is 100-8000 rpm.

2. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The discreteness of the semi-aromatic polyamide prepolymer is 0.1-5.

0.

3. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The relative viscosity of the semi-aromatic polyamide prepolymer is 1.02-1.

52.

4. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The pulverizing equipment includes a stirring pulverizing equipment and / or a cage pulverizing equipment.

5. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The flash evaporation device is also provided with one or more structures of a baffle, a sieve plate and a perforated plate.

6. The method for preparing a semi-aromatic polyamide prepolymer according to claim 5, characterized in that: The orifice plate is arranged inside the feed pipe of the flash evaporation device, and the baffle plate and / or the sieve plate are arranged inside the body of the flash evaporation device; The semi-aromatic polyamide prepolymer reaction liquid first enters the feed pipe of the flash evaporation device, and then is crushed into particles of the semi-aromatic polyamide prepolymer inside the flash evaporation device and output from the flash evaporation device.

7. The method for preparing a semi-aromatic polyamide prepolymer according to claim 6, characterized in that: When the baffle is disposed inside the flash evaporation device, the area of ​​the baffle does not exceed three quarters of the cross-sectional area of ​​the flash evaporation device; When the sieve plate is arranged inside the flash evaporation device, the total area of ​​holes of the sieve plate is not less than one fifth of the cross-sectional area of ​​the flash evaporation device; When the orifice plate is arranged inside the feed pipeline of the flash evaporation device, the total area of ​​the holes of the orifice plate does not exceed three quarters of the cross-sectional area of ​​the feed pipeline.

8. The method for preparing a semi-aromatic polyamide prepolymer according to claim 5, characterized in that: The semi-aromatic polyamide prepolymer reaction liquid is sprayed into the flash evaporation device through a spray nozzle or a straight pipe.

9. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The rotation speed of the cutter is 300-5000 rpm.

10. The method for preparing a semi-aromatic polyamide prepolymer according to claim 1, characterized in that: The semi-aromatic polyamide prepolymer reaction solution is prepared by the following steps: The raw material of the semi-aromatic polyamide is configured into a 20%wt to 90%wt aqueous solution, the pH value is adjusted to 6 to 11, an additive not exceeding 10%wt of the total raw material is added, and the mixture is heated and concentrated to 50%wt to 95%, and then reacted at a pressure of 1.5MPa to 6MPa for 0.5 hour to 8 hours to obtain the semi-aromatic polyamide prepolymer reaction solution.

11. The method for preparing a semi-aromatic polyamide prepolymer according to claim 10, characterized in that: The raw materials of the semi-aromatic polyamide include dibasic acid and diamine; Wherein, the dibasic acid includes a dibasic acid containing a benzene ring, or the dibasic acid includes a C5-C18 dibasic acid and a dibasic acid containing a benzene ring, and the diamine includes one to three combinations of C5-C18 diamines; The total amount of the dibasic acid and the diamine accounts for more than 90% of the total weight of the raw materials.

12. The method for preparing a semi-aromatic polyamide prepolymer according to claim 11, characterized in that: The C5-C18 dibasic acid is selected from one or a combination of two or more of glutaric acid, adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid; The benzene ring-containing dibasic acid is selected from terephthalic acid and / or isophthalic acid; The C5-C18 diamine is selected from one or a combination of two or more of pentamethylenediamine, 2-methyl-pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, nonamethylenediamine and decamethylenediamine.

13. A semi-aromatic polyamide, characterized in that The semi-aromatic polyamide prepolymer prepared by the preparation method according to any one of claims 1 to 12 is used as a raw material and is obtained by solid phase viscosity increasing or screw viscosity increasing.

14. The semi-aromatic polyamide according to claim 13, characterized in that The dispersion of the semi-aromatic polyamide is 0.1-5.

0.

15. The semi-aromatic polyamide according to claim 13, characterized in that The relative viscosity of the semi-aromatic polyamide is 1.65-2.92.

Images