Preparation method of anhydride curing agent

Abstract

The invention relates to the technical field of anhydride curing agent preparation, in particular to a preparation method of an anhydride curing agent, and relates to drying equipment which comprises a supporting seat, a drying bin fixedly installed on the supporting seat and a pretreatment bin located over the drying bin. And the pretreatment bin and the drying bin are jointly provided with a preheating mechanism for preheating the phthalic anhydride crystals. A stirring, drying and discharging integrated operation model is adopted to complete the drying operation of the phthalic anhydride crystals, and preheating stirring, layered heating and drying and efficient discharging of the phthalic anhydride crystals are achieved, so that heat transfer between the crystals and a heat source is promoted, it is ensured that the crystals are heated evenly, and the quality of the crystals is improved. The risk of crystal damage or decomposition caused by local overheating is reduced, water evaporation is accelerated, the retention time in drying equipment is shortened, meanwhile, crystal discharge is accelerated through vibration discharging, product residues are reduced, and therefore the production efficiency of the anhydride curing agent is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of anhydride curing agents, in particular to a method for preparing anhydride curing agents. Background Art

[0002] Anhydride curing agents are a class of chemical substances commonly used in epoxy resin curing. They react chemically with epoxy resin during the curing process to form a three-dimensional network structure, thereby transforming the epoxy resin from liquid to solid. After filtering and separating the phthalic anhydride crystals in the preparation of the anhydride curing agent, in order to ensure the purity and performance of the phthalic anhydride, the phthalic anhydride crystals need to be dried after the filtration and separation is completed, so as to ensure the stability of the phthalic anhydride.

[0003] At present, there are the following disadvantages in drying phthalic anhydride: when drying phthalic anhydride crystals, the phthalic anhydride crystals after filtration and separation need to be first passed into a drying device, and then the drying device is started to dry and stir the phthalic anhydride crystals to complete the drying process of the phthalic anhydride crystals. However, only using stirring will cause uneven temperature distribution inside the drying device, so that some crystals may overheat and decompose, while other crystals may not reach a sufficient degree of dryness, resulting in uneven drying of the product. In addition, during the drying process, the contact area between the phthalic anhydride crystals and the heat source is small, thereby hindering heat transfer and evaporation of water inside the product, and thus significantly prolonging the drying time of the product.

[0004] Therefore, in order to ensure the purity and performance of phthalic anhydride, the present invention provides a method for preparing anhydride curing agent. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing an anhydride curing agent, which is achieved by the following specific technical means:

[0006] A method for preparing an anhydride curing agent comprises the following steps: S1, dehydration reaction: heating phthalic acid to 250° C. and carrying out a dehydration reaction under the action of a dehydration catalyst, wherein the dehydration catalyst is concentrated sulfuric acid.

[0007] S2. Purification by distillation: distill the reaction product obtained by the dehydration reaction, collect the fraction at about 150° C., and obtain pure phthalic anhydride liquid.

[0008] S3, cooling crystallization: the phthalic anhydride liquid obtained by distillation purification is cooled to room temperature, and the phthalic anhydride will crystallize out.

[0009] S4. Drying: The phthalic anhydride crystals are separated by filtration and dried in a drying device to remove residual moisture.

[0010] S5. Subsequent processing: discharging the phthalic anhydride after drying and conducting quality inspection on the discharged phthalic anhydride.

[0011] Among them, the drying equipment involved in the above-mentioned S4 step includes a support base, on which a drying chamber and a pretreatment chamber located directly above the drying chamber are fixedly installed, and the pretreatment chamber and the drying chamber are jointly provided with a preheating mechanism for preheating the phthalic anhydride crystals; the preheating mechanism includes a main body jointly provided on the pretreatment chamber and the drying chamber, and the main body is provided with a stirring part for stirring the phthalic anhydride crystals.

[0012] The main body is provided with a drying mechanism for cooperating with the preheating mechanism to dry the preheated phthalic anhydride crystals layer by layer; the drying mechanism includes a dispersing part provided on the main body and used to spread and dry the phthalic anhydride crystals, and the main body is also provided with a bulk material part for distributing the phthalic anhydride crystals and a driving part for providing power to the bulk material part.

[0013] The drying bin is provided with a feeding mechanism for vibrating and discharging phthalic anhydride crystals; the feeding mechanism comprises a vibrating part arranged on the dispersing part, and the drying bin is provided with a matching part for providing power to the vibrating part.

[0014] As a preferred technical solution of the present invention, the main body includes a central shaft cylinder, a first motor and a supporting bearing seat. The central shaft cylinder is installed through the bearing at the center of the pretreatment bin and the drying bin. The first motor is fixedly installed on the upper end surface of the pretreatment bin. The output end of the first motor is connected to the central shaft cylinder through a first gear set. The lower end of the drying bin is fixedly installed with a supporting bearing seat connected to the central shaft cylinder through a bearing through a supporting rod.

[0015] As a preferred technical solution of the present invention, the stirring part includes a first fixed ring, a support ring, a second fixed ring, a scraper rod, a V-shaped stirring rod and a discharge hole. The central shaft tube is fixedly sleeved with a first fixed ring located in the pretreatment bin, and the first fixed ring is fixedly installed with a support ring through a support rod. The central shaft tube is fixedly sleeved with a second fixed ring located in the pretreatment bin, and the second fixed ring is located directly below the first fixed ring. A plurality of scraper rods are fixedly installed on the lower end of the support ring in a circular array, and the lower ends of the plurality of scraper rods are fixedly connected to the second fixed ring. V-shaped stirring rods corresponding to the scraper rods are fixedly installed on the central shaft tube, and a plurality of discharge holes are opened on the lower end surface of the pretreatment bin in a circular array, and an electronic valve is arranged in the discharge hole.

[0016] As a preferred technical solution of the present invention, the dispersion part includes a dispersion ring bin, a conical cylinder, a third fixed ring, a tripod, a spreading roller and a heating layer. A number of dispersion ring bins are evenly distributed in an array from top to bottom in the drying bin. The dispersion ring bin is composed of a ring slope at the upper end and a flat ring surface at the lower end. The ring slope and the side wall of the pretreatment bin are provided with a heating layer. A conical cylinder located in the drying bin is fixedly sleeved on the central shaft cylinder. The conical cylinder is located directly above the uppermost dispersion ring bin. A third fixed ring corresponding to the dispersion ring bins is fixedly sleeved on the central shaft cylinder. A left-right symmetrical tripod is fixedly installed on the third fixed ring. A spreading roller is hinged on the end of the tripod away from the central shaft cylinder.

[0017] As a preferred technical solution of the present invention, the bulk material part includes a layered plate, a fan-shaped plate, a connecting rod and a smooth ring. The layered plates corresponding to the dispersion ring bins are fixedly sleeved on the central shaft tube. The layered plates are connected to the corresponding dispersion ring bins through bearings. A number of feed troughs are opened on the layered plates in a circular array. The fan-shaped plates are hinged in the feed troughs. A connecting rod is hinged at the center of the lower end surface of the fan-shaped plate. The lower ends of the connecting rods on the same layered plate are hinged to a smooth ring sleeved on the central shaft tube.

[0018] As a preferred technical solution of the present invention, the driving part includes a limit slide, a limit slider, a connecting disc, a connecting column and an electric push rod. The central shaft tube is penetrated by a limit slide which corresponds to the smooth ring one by one and is symmetrical on the left and right. The limit slide is slidably installed in the limit slide. The ends of the left and right symmetrical limit sliders that are away from each other are fixedly connected to the corresponding smooth ring. The ends of the left and right symmetrical limit sliders that are close to each other are jointly fixedly installed with a connecting disc located in the central shaft tube. A connecting column is jointly fixedly installed at the center of several connecting discs, and an electric push rod with a telescopic end fixedly connected to the connecting column is fixedly installed on the upper end surface of the central shaft tube.

[0019] As a preferred technical solution of the present invention, the vibration part includes a supporting swivel, an impact rod and a rubber column. The supporting swivel is installed on the flat ring surface of the dispersion ring warehouse through a bearing, the outer ring wall of the supporting swivel is fixedly sleeved with a conical gear ring, and a plurality of impact rods are fixedly installed on the upper end surface of the supporting swivel in a circular array. A plurality of rubber columns cooperating with the impact rods are evenly distributed in an array on one side wall of the ring inclined surface of the dispersion ring warehouse close to the flat ring surface.

[0020] As a preferred technical solution of the present invention, the mating part includes a mating shaft, a second motor and a transmission shaft. The mating shaft is installed on the outer ring wall of the drying bin through a bearing seat. The second motor with an output end fixedly connected to the mating shaft is fixedly installed on the outer ring wall of the drying bin. A transmission shaft corresponding to the support swivel is installed on the outer ring wall of the drying bin through a bearing. A first bevel gear meshing with the bevel gear ring is fixedly sleeved on the transmission shaft. The transmission shaft and the mating shaft are connected through a first transmission bevel gear group.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Through the coordinated use of the preheating mechanism, drying mechanism and unloading mechanism, the drying operation of phthalic anhydride crystals is completed by adopting an integrated operation model of stirring, drying and unloading, and the preheating stirring, layered heating and drying and efficient unloading of phthalic anhydride crystals are realized, thereby promoting the heat transfer between the crystals and the heat source, ensuring that the crystals are heated evenly, reducing the risk of crystal damage or decomposition due to local overheating, thereby maintaining the physical and chemical properties of the product, accelerating the evaporation of water, and reducing the residence time in the drying equipment. At the same time, the discharge of crystals is accelerated by vibration unloading, and product residues are reduced, thereby improving the drying efficiency and product quality of phthalic anhydride crystals, and achieving a significant improvement in the production efficiency of anhydride curing agent.

[0023] 2. By using the preheating mechanism and the drying mechanism in coordination with each other, the phthalic anhydride crystals are preheated and stirred before drying, thereby promoting heat transfer between the crystals and the heat source by stirring, so that the crystals can absorb heat faster, and preheating can help the inside and outside of the phthalic anhydride crystals reach a uniform temperature, so that the crystals are partially dried when entering the drying equipment, thereby reducing the residence time of the product in the drying equipment.

[0024] 3. The preheated phthalic anhydride crystals are heated and dried in layers by the drying mechanism, and the phthalic anhydride crystals are spread during the drying process, so that the contact area between the phthalic anhydride crystals and the heat source is increased, which helps to transfer heat to the inside of the crystals faster, thereby accelerating the evaporation of water and improving the drying efficiency. The layered heating helps to evenly distribute the heat, and the spreading ensures that the crystals are heated more evenly, reducing the problem of uneven drying and improving the product quality.

[0025] 4. Through the set unloading mechanism, vibration is used to unload the phthalic anhydride crystals after drying, thereby accelerating the discharge of the crystals from the equipment, and can effectively shake off the crystals adhering to the equipment, ensuring that the crystals can be completely unloaded from the container and avoiding residual phthalic anhydride crystals, thereby achieving rapid unloading and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart of the present invention.

[0027] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention when it is working.

[0028] Figure 3 It is a partial cross-sectional three-dimensional structural schematic diagram of the present invention.

[0029] Figure 4 It is a schematic diagram of the internal sectional three-dimensional structure of the preheating mechanism of the present invention.

[0030] Figure 5 It is a partially cutaway three-dimensional structural schematic diagram of the drying mechanism of the present invention.

[0031] Figure 6 It is a bottom-up stereoscopic structural schematic diagram of the driving part of the present invention.

[0032] Figure 7 It is a cross-sectional three-dimensional structural schematic diagram of the drying mechanism and the feeding mechanism of the present invention.

[0033] In the figure: 1, support seat; 2, drying chamber; 3, pretreatment chamber; 4, preheating mechanism; 41, main body; 411, central shaft cylinder; 412, first motor; 413, support bearing seat; 42, stirring part; 421, first fixing ring; 422, supporting ring; 423, second fixing ring; 424, scraping rod; 425, V-shaped stirring rod; 426, feeding hole; 5, drying mechanism; 51, dispersion part; 511, dispersion ring chamber; 512, conical cylinder; 513, third fixing ring; 514, tripod; 51 5. Spreading roller; 516. Heating layer; 52. Bulk material part; 521. Layering plate; 522. Fan-shaped plate; 523. Connecting rod; 524. Slip ring; 53. Driving part; 531. Limit slideway; 532. Limit slider; 533. Connecting disc; 534. Connecting column; 535. Electric push rod; 6. Unloading mechanism; 61. Vibrating part; 611. Support swivel; 612. Impact rod; 613. Rubber column; 62. Matching part; 621. Matching shaft; 622. Second motor; 623. Drive shaft. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] See also Figure 1 , a method for preparing an anhydride curing agent, comprising the following steps: S1, dehydration reaction: heating phthalic acid to 250° C., and performing a dehydration reaction under the action of a dehydration catalyst, wherein the type of the dehydration catalyst is concentrated sulfuric acid.

[0036] S2. Purification by distillation: distill the reaction product obtained by the dehydration reaction, collect the fraction at about 150° C., and obtain pure phthalic anhydride liquid.

[0037] S3, cooling crystallization: the phthalic anhydride liquid obtained by distillation purification is cooled to room temperature, and the phthalic anhydride will crystallize out.

[0038] S4. Drying: The phthalic anhydride crystals are separated by filtration and dried in a drying device to remove residual moisture.

[0039] S5. Subsequent processing: discharging the phthalic anhydride after drying and conducting quality inspection on the discharged phthalic anhydride.

[0040] See also Figure 2 and Figure 3 The drying equipment involved in the above step S4 includes a support base 1, on which a drying chamber 2 and a pretreatment chamber 3 located directly above the drying chamber 2 are fixedly mounted, and the pretreatment chamber 3 and the drying chamber 2 are jointly provided with a preheating mechanism 4 for preheating the phthalic anhydride crystals; the preheating mechanism 4 includes a main body 41 jointly provided on the pretreatment chamber 3 and the drying chamber 2, and the main body 41 is provided with a stirring portion 42 for stirring the phthalic anhydride crystals.

[0041] See also Figure 2 and Figure 3 The main body 41 is provided with a drying mechanism 5 which cooperates with the preheating mechanism 4 to dry the preheated phthalic anhydride crystals layer by layer; the drying mechanism 5 includes a dispersing portion 51 which is provided on the main body 41 and is used to spread and dry the phthalic anhydride crystals, and the main body 41 is also provided with a bulk material portion 52 which is used to distribute the phthalic anhydride crystals and a driving portion 53 which provides power for the bulk material portion 52.

[0042] See also Figure 2 and Figure 3 The drying bin 2 is provided with a feeding mechanism 6 for vibrating and discharging the phthalic anhydride crystals; the feeding mechanism 6 includes a vibrating portion 61 provided on the dispersing portion 51 , and the drying bin 2 is provided with a matching portion 62 for providing power to the vibrating portion 61 .

[0043] See also Figure 2 , Figure 3 and Figure 4 The main body 41 includes a central shaft cylinder 411, a first motor 412 and a support bearing seat 413. The central shaft cylinder 411 is installed through the bearing at the center of the pretreatment chamber 3 and the drying chamber 2. The first motor 412 is fixedly installed on the upper end surface of the pretreatment chamber 3. The output end of the first motor 412 is connected to the central shaft cylinder 411 through a first gear set. The lower end of the drying chamber 2 is fixedly installed with a support bearing seat 413 connected to the central shaft cylinder 411 through a bearing through a support rod.

[0044] See also Figure 3and Figure 4 The stirring portion 42 includes a first fixed ring 421, a support ring 422, a second fixed ring 423, a scraper rod 424, a V-shaped stirring rod 425 and a discharge hole 426. The first fixed ring 421 located in the pretreatment bin 3 is fixedly sleeved on the central shaft cylinder 411, and the support ring 422 is fixedly installed on the first fixed ring 421 through a support rod. The second fixed ring 423 located in the pretreatment bin 3 is fixedly sleeved on the central shaft cylinder 411. The second fixed ring 423 is located directly below the first fixed ring 421. A plurality of scraper rods 424 are fixedly installed on the lower end of the support ring 422 in a circular array. The lower ends of the plurality of scraper rods 424 are fixedly connected to the second fixed ring 423. V-shaped stirring rods 425 corresponding to the scraper rods 424 are fixedly installed on the central shaft cylinder 411. A plurality of discharge holes 426 are opened on the lower end surface of the pretreatment bin 3 in a circular array, and an electronic valve is arranged in the discharge hole 426.

[0045] See also Figure 3 , Figure 5 , Figure 6 and Figure 7 The dispersion part 51 includes a dispersion ring bin 511, a conical cylinder 512, a third fixed ring 513, a tripod 514, a spreading roller 515 and a heating layer 516. A plurality of dispersion ring bins 511 are evenly distributed in an array from top to bottom in the drying bin 2. The dispersion ring bin 511 consists of an annular slope at the upper end and a flat annular surface at the lower end. A heating layer 516 is provided on the annular slope and the side wall of the pretreatment bin 3. A conical cylinder 512 located in the drying bin 2 is fixedly sleeved on the central shaft cylinder 411. The conical cylinder 512 is located directly above the dispersion ring bin 511 at the upper end. A third fixed ring 513 corresponding to the dispersion ring bin 511 is fixedly sleeved on the central shaft cylinder 411. A left-right symmetrical tripod 514 is fixedly installed on the third fixed ring 513. A spreading roller 515 is hinged at one end of the tripod 514 away from the central shaft cylinder 411.

[0046] During specific operation, when it is necessary to dry the phthalic anhydride crystals, the phthalic anhydride crystals are first introduced into the pretreatment bin 3, and the first motor 412 is started to rotate the central shaft cylinder 411 through the first gear set. At this time, the central shaft cylinder 411 carries the scraper rod 424 and the V-shaped stirring rod 425 to stir the phthalic anhydride crystals in the pretreatment bin 3 to promote heat transfer between the crystals and the heat source, so that the crystals can absorb heat faster. At the same time, the heating layer 516 of the pretreatment bin 3 is started, so that the heating layer 516 preheats the phthalic anhydride crystals in the pretreatment bin 3 to help the inside and outside of the phthalic anhydride crystals reach a uniform temperature. After the phthalic anhydride crystals in the pretreatment bin 3 are heated to a certain temperature, the electronic valve in the discharge hole 426 is opened to discharge the phthalic anhydride crystals into the drying bin 2.

[0047] See also Figure 3 , Figure 5 , Figure 6 and Figure 7 The bulk material part 52 includes a layered plate 521, a fan-shaped plate 522, a connecting rod 523 and a smooth ring 524. The layered plate 521 corresponding to the dispersion ring bin 511 is fixedly sleeved on the central shaft cylinder 411. The layered plate 521 is connected to the corresponding dispersion ring bin 511 through a bearing. A plurality of feed troughs are opened in a circular array on the layered plate 521. The fan-shaped plate 522 is hinged in the feed trough. A connecting rod 523 is hinged at the center of the lower end surface of the fan-shaped plate 522. The lower end of the connecting rod 523 on the same layered plate 521 is hinged with a smooth ring 524 sleeved on the central shaft cylinder 411.

[0048] See also Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 The driving part 53 includes a limiting slide 531, a limiting slider 532, a connecting disc 533, a connecting column 534 and an electric push rod 535. The central shaft tube 411 is penetrated by a limiting slide 531 which corresponds to the smooth ring 524 one by one and is symmetrical on the left and right. The limiting slide 532 is slidably installed in the limiting slide 531. The ends of the symmetrical limiting sliders 532 that are away from each other are fixedly connected to the corresponding smooth ring 524. The ends of the symmetrical limiting sliders 532 that are close to each other are jointly fixedly installed with a connecting disc 533 located in the central shaft tube 411. A connecting column 534 is jointly fixedly installed at the center of several connecting discs 533. An electric push rod 535 with a telescopic end fixedly connected to the connecting column 534 is fixedly installed on the upper end surface of the central shaft tube 411.

[0049] During specific operation, after the preheating mechanism 4 completes the preheating of the phthalic anhydride crystals, the phthalic anhydride crystals entering the drying bin 2 will directly fall onto the conical cylinder 512, and slide through the inclined surface of the conical cylinder 512 to the uppermost dispersion ring bin 511. Since the electric push rod 535 is in an unstarted state at this time, the fan plate 522 will close the feed chute of the stratification plate 521, thereby preventing the fallen phthalic anhydride crystals from directly entering the next layer of dispersion ring bin 511.

[0050] Then, the electric push rod 535 is started to descend with the connecting column 534, and the smooth ring 524 is pulled downward through the connecting disc 533. During the pulling process, the smooth ring 524 will pull the fan plate 522 downward with the hinge point as the center through the connecting rod 523, thereby releasing the discharge chute of the stratification plate 521. At this time, the phthalic anhydride crystals will gradually fall from the discharge chute and accumulate on the next layer of dispersion ring warehouse 511, so as to divide the phthalic anhydride crystals into several layers. After the stratification is completed, the electric push rod 535 is started in the reverse direction to push the fan plate 522 back to close the stratification plate 521 again. At this time, the heating layer 516 on the ring slope can be started to heat and dry the pre-heated phthalic anhydride crystals in layers.

[0051] During the stratification process, the stratification plate 521 will rotate along with the central shaft cylinder 411, and at the same time, the third fixed ring 513 will also rotate along with the central shaft cylinder 411. The third fixed ring 513 will rotate around the central shaft cylinder 411 with the spreading roller 515 through the tripod 514, so as to spread the phthalic anhydride crystals on the dispersion ring bin 511, thereby increasing the contact area between the phthalic anhydride crystals and the heat source, which helps to transfer heat to the inside of the crystal faster, thereby accelerating the evaporation of water and improving the drying efficiency.

[0052] See also Figure 3 , Figure 5 and Figure 7 The vibration part 61 includes a supporting swivel 611, an impact rod 612 and a rubber column 613. The supporting swivel 611 is installed on the flat ring surface of the dispersion ring warehouse 511 through a bearing. The outer ring wall of the supporting swivel 611 is fixed with a conical gear ring. A plurality of impact rods 612 are fixedly installed on the upper end surface of the supporting swivel 611 in a circular array. A plurality of rubber columns 613 cooperating with the impact rod 612 are evenly distributed in an array on one side wall of the annular inclined surface of the dispersion ring warehouse 511 close to the flat ring surface.

[0053] See also Figure 3 , Figure 5 and Figure 7 The mating part 62 includes a mating shaft 621, a second motor 622 and a transmission shaft 623. The mating shaft 621 is installed on the outer ring wall of the drying bin 2 through a bearing seat. The second motor 622 with an output end fixedly connected to the mating shaft 621 is fixedly installed on the outer ring wall of the drying bin 2. A transmission shaft 623 corresponding to the support rotating ring 611 is installed on the outer ring wall of the drying bin 2 through a bearing. A first bevel gear meshing with the bevel gear ring is fixedly sleeved on the transmission shaft 623. The transmission shaft 623 is transmission-connected to the mating shaft 621 through a first transmission bevel gear set.

[0054] During specific operation, after the drying mechanism 5 completes the drying of the phthalic anhydride crystals, the electric push rod 535 is started forward again to open the layering plate 521, and at the same time, the second motor 622 is started to rotate the matching shaft 621, and the transmission shaft 623 is driven by the first transmission bevel gear set to rotate the support swivel 611, so that the support swivel 611 rotates with the impact rod 612 in the dispersion ring bin 511, and the impact rod 612 will continuously hit the rubber column 613 during the rotation process, so that the dispersion ring bin 511 vibrates, so that the phthalic anhydride crystals after drying are discharged by vibration, which not only accelerates the discharge of the crystals from the equipment, but also can effectively shake off the crystals adhering to the equipment, ensuring that the crystals can be completely unloaded from the container.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an anhydride curing agent, characterized in that: The steps include: S1. Dehydration reaction: heating phthalic acid to 250°C and carrying out a dehydration reaction under the action of a dehydration catalyst, wherein the type of the dehydration catalyst is concentrated sulfuric acid; S2, distillation and purification: distilling the reaction product obtained by the dehydration reaction, collecting the fraction at about 150° C., and obtaining pure phthalic anhydride liquid; S3, cooling crystallization: cooling the phthalic anhydride liquid obtained by distillation purification to room temperature, and phthalic anhydride will crystallize out; S4, drying treatment: separating the phthalic anhydride crystals by filtering, and drying them in a drying device to remove residual moisture; S5, subsequent processing: discharging the phthalic anhydride after drying, and performing quality inspection on the discharged phthalic anhydride; The drying device involved in the above step S4 comprises a support base (1), characterized in that: a drying chamber (2) and a pretreatment chamber (3) located directly above the drying chamber (2) are fixedly mounted on the support base (1), and a preheating mechanism (4) for preheating the phthalic anhydride crystals is provided on the pretreatment chamber (3) and the drying chamber (2); The preheating mechanism (4) comprises a main body (41) disposed on the pretreatment chamber (3) and the drying chamber (2), and the main body (41) is provided with a stirring portion (42) for stirring the phthalic anhydride crystals; The main body (41) is provided with a drying mechanism (5) for cooperating with the preheating mechanism (4) to dry the preheated phthalic anhydride crystals layer by layer; The drying mechanism (5) comprises a dispersing portion (51) arranged on the main body (41) and used for spreading and drying the phthalic anhydride crystals. The main body (41) is also provided with a bulking portion (52) for distributing the phthalic anhydride crystals and a driving portion (53) for providing power to the bulking portion (52). The drying bin (2) is provided with a discharge mechanism (6) for discharging phthalic anhydride crystals by vibration. The unloading mechanism (6) comprises a vibration part (61) arranged on the dispersion part (51), and a matching part (62) for providing power to the vibration part (61) is arranged on the drying chamber (2).

2. The method for preparing an anhydride curing agent according to claim 1, characterized in that: The main body (41) comprises a central shaft cylinder (411), a first motor (412) and a support bearing seat (413); the central shaft cylinder (411) is installed through the bearing at the center of the pretreatment chamber (3) and the drying chamber (2); the first motor (412) is fixedly installed on the upper end surface of the pretreatment chamber (3); the output end of the first motor (412) is connected to the central shaft cylinder (411) through a first gear set; and the lower end of the drying chamber (2) is fixedly installed with a support bearing seat (413) connected to the central shaft cylinder (411) through a bearing through a support rod.

3. The method for preparing an anhydride curing agent according to claim 2, characterized in that: The stirring portion (42) comprises a first fixing ring (421), a support ring (422), a second fixing ring (423), a scraping rod (424), a V-shaped stirring rod (425) and a feeding hole (426); the first fixing ring (421) located in the pretreatment bin (3) is fixedly sleeved on the central shaft cylinder (411); the support ring (422) is fixedly mounted on the first fixing ring (421) via a support rod; the second fixing ring (423) located in the pretreatment bin (3) is fixedly sleeved on the central shaft cylinder (411); 3), the second fixed ring (423) is located directly below the first fixed ring (421), a plurality of scraper rods (424) are fixedly installed on the lower end of the support ring (422) in a circular array, the lower ends of the plurality of scraper rods (424) are fixedly connected to the second fixed ring (423), a V-shaped stirring rod (425) corresponding to the scraper rod (424) is fixedly installed on the central shaft tube (411), and a plurality of discharge holes (426) are opened on the lower end surface of the pretreatment bin (3) in a circular array, and an electronic valve is arranged in the discharge hole (426).

4. The method for preparing an anhydride curing agent according to claim 2, characterized in that: The dispersion part (51) comprises a dispersion ring bin (511), a conical cylinder (512), a third fixed ring (513), a tripod (514), a spreading roller (515) and a heating layer (516). A plurality of dispersion ring bins (511) are evenly distributed in an array from top to bottom in the drying bin (2). The dispersion ring bin (511) is composed of an annular bevel at the upper end and a flat annular surface at the lower end. The heating layer (516) is arranged on the annular bevel and the side wall of the pretreatment bin (3). The central shaft cylinder The upper fixed sleeve (411) is provided with a conical cylinder (512) located in the drying chamber (2), and the conical cylinder (512) is located directly above the uppermost dispersion ring chamber (511). The upper fixed sleeve of the central shaft tube (411) is provided with a third fixed ring (513) corresponding one to one with the dispersion ring chamber (511), and the third fixed ring (513) is fixedly mounted with a left-right symmetrical tripod (514), and a spreading roller (515) is hingedly connected to one end of the tripod (514) away from the central shaft tube (411).

5. The method for preparing an anhydride curing agent according to claim 4, characterized in that: The bulk material portion (52) comprises a layered plate (521), a fan-shaped plate (522), a connecting rod (523) and a smooth ring (524); the layered plates (521) corresponding to the dispersion ring bins (511) are fixedly sleeved on the central shaft tube (411); the layered plates (521) are connected to the corresponding dispersion ring bins (511) via bearings; a plurality of material discharge troughs are provided in a circular array on the layered plate (521); a fan-shaped plate (522) is hinged in the material discharge trough; a connecting rod (523) is hinged at the center of the lower end surface of the fan-shaped plate (522); and a smooth ring (524) sleeved on the central shaft tube (411) is hinged at the lower end of the connecting rod (523) on the same layered plate (521).

6. The method for preparing an anhydride curing agent according to claim 5, characterized in that: The driving part (53) comprises a limiting slideway (531), a limiting slider (532), a connecting disc (533), a connecting column (534) and an electric push rod (535). The central shaft tube (411) is provided with a limiting slideway (531) which corresponds to the smooth ring (524) one by one and is symmetrical on both sides. The limiting slider (532) is slidably installed in the limiting slideway (531). The ends of the symmetrical limiting sliders (532) that are away from each other are fixedly connected to the corresponding smooth ring (524). The ends of the symmetrical limiting sliders (532) that are close to each other are fixedly installed with a connecting disc (533) located in the central shaft tube (411). A connecting column (534) is fixedly installed at the center of a plurality of connecting discs (533). An electric push rod (535) whose telescopic end is fixedly connected to the connecting column (534) is fixedly installed on the upper end surface of the central shaft tube (411).

7. The method for preparing an anhydride curing agent according to claim 4, characterized in that: The vibration part (61) comprises a supporting rotating ring (611), an impact rod (612) and a rubber column (613); the supporting rotating ring (611) is installed on the flat ring surface of the dispersion ring chamber (511) via a bearing; a bevel gear ring is fixedly sleeved on the outer ring wall of the supporting rotating ring (611); a plurality of impact rods (612) are fixedly installed on the upper end surface of the supporting rotating ring (611) in a circumferential array manner; and a plurality of rubber columns (613) cooperating with the impact rods (612) are evenly distributed in an array manner on a side wall of the ring inclined surface of the dispersion ring chamber (511) close to the flat ring surface.

8. The method for preparing an anhydride curing agent according to claim 7, characterized in that: The matching part (62) comprises a matching shaft (621), a second motor (622) and a transmission shaft (623); the matching shaft (621) is installed on the outer ring wall of the drying chamber (2) via a bearing seat; the second motor (622) whose output end is fixedly connected to the matching shaft (621) is fixedly installed on the outer ring wall of the drying chamber (2); a transmission shaft (623) corresponding to the support rotating ring (611) is installed on the outer ring wall of the drying chamber (2) via a bearing; a first bevel gear meshing with the bevel gear ring is fixedly sleeved on the transmission shaft (623); the transmission shaft (623) and the matching shaft (621) are connected in transmission via a first transmission bevel gear set.

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