Method and device for extracting polycarbonate particles

Abstract

The invention provides an extraction method and an extraction device of polycarbonate particles, and the extraction method of the polycarbonate particles comprises the following steps: 1) washing an organic solution containing polycarbonate to obtain an organic phase and a first water phase; the conductivity of the first water phase is less than or equal to 100 [mu] S / cm, and the pH is 5-10; 2) stirring a mixed solution containing the organic phase and the second water phase to obtain an emulsion; in the emulsified liquid, the number of emulsified liquid drops with the particle size ranging from 50 micrometers to 200 micrometers accounts for 50%-80%; 3, the emulsion is evaporated, and the polycarbonate granules are obtained.By means of the extraction method of the polycarbonate granules, the particle size distribution SPAN of the polycarbonate granules can be smaller than or equal to 2.0, and the quantity proportion of the granules with the particle size smaller than 20 micrometers is smaller than or equal to 10%.

Description

Technical Field

[0001] The invention belongs to the technical field of extraction, and in particular relates to a method and a device for extracting polycarbonate particles. Background Art

[0002] Polycarbonate is an important engineering plastic with excellent heat resistance, transparency, mechanical strength and electrical insulation, and is widely used in the fields of automobiles, electronics, construction, etc. Polycarbonate is usually supplied in granular form.

[0003] The existing polycarbonate particle extraction methods mainly have the following problems: first, the particle size of the obtained polycarbonate particles is uneven, which is not conducive to the subsequent processing technology; second, the large amount of fine powder in the polycarbonate particles will cause the particles to form clusters in the silo during the processing, thereby hindering the feeding. For example, the existing technology adopts a double-axis kneading powder making process, and after obtaining the polycarbonate particles, a pulverizer is used to shear them. Since kneading powder making easily obtains block products and the particle uniformity is poor, after being sheared by the pulverizer, the final product polycarbonate particles contain a certain amount of ultrafine powder.

[0004] Therefore, developing a method for extracting polycarbonate particles with uniform particle size and less fine powder is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for extracting polycarbonate particles, which can extract polycarbonate particles with uniform particle size and less fine powder. Specifically, the particle size distribution SPAN of the polycarbonate particles can be less than or equal to 2.0, and the number of particles with a particle size less than 20 μm accounts for less than or equal to 10%.

[0006] The present invention also provides a device for extracting polycarbonate particles. By using the device to extract polycarbonate particles, polycarbonate particles with uniform particle size and less fine powder can be obtained. Specifically, the particle size distribution SPAN of the polycarbonate particles can be made less than or equal to 2.0, and the number of particles with a particle size less than 20 μm accounts for less than or equal to 10%.

[0007] In a first aspect, the present invention provides a method for extracting polycarbonate particles, comprising the following steps:

[0008] 1) washing an organic solution including polycarbonate to obtain an organic phase and a first aqueous phase; the first aqueous phase has an electrical conductivity of less than or equal to 100 μS / cm and a pH of 5-10;

[0009] 2) stirring a mixed solution including the organic phase and the second aqueous phase to obtain an emulsion; in the emulsion, the number of emulsion droplets with a particle size between 50 μm and 200 μm accounts for 50% to 80%;

[0010] 3) Evaporating the emulsion to obtain the polycarbonate particles.

[0011] In the extraction method as described above, the pH of the first aqueous phase is 6-10, preferably 7-9;

[0012] And / or, the volume ratio of the organic phase to the second aqueous phase is 1:(0.4-2.5), preferably 1:(1.5-2.5).

[0013] In the extraction method as described above, the organic solution comprises an organic solvent, the organic solvent comprises a chlorine-containing organic solvent, and the chlorine-containing organic solvent comprises dichloromethane and / or chlorobenzene.

[0014] The extraction method as described above, wherein a stirring paddle is used to perform the stirring process;

[0015] The linear velocity of the outermost edge of the stirring paddle is greater than or equal to 2 m / s, preferably 3 m / s-9 m / s; the stirring treatment time is greater than or equal to 5 min, preferably 10 min-30 min;

[0016] And / or, the mass percentage of the polycarbonate in the organic solution is 5%-35%, preferably 10%-30%, more preferably 15%-25%.

[0017] In the extraction method as described above, the evaporation treatment of the emulsion comprises:

[0018] The emulsion is jetted into a third aqueous phase, and the organic solvent in the emulsion is evaporated by the third aqueous phase to obtain the polycarbonate particles.

[0019] In the extraction method as described above, the diameter of the jet stream formed by the jet is less than 1 mm, preferably 0.3 mm to 0.7 mm;

[0020] And / or, the jet ejection speed is 3 mL / s-10 mL / s.

[0021] According to the extraction method described above, after all the emulsion is ejected into the third aqueous phase, the evaporation process is started, and the temperature of the third aqueous phase is greater than 35° C., preferably 42° C.-55° C.;

[0022] And / or, the time of the evaporation treatment is 60 min-120 min, and the pressure of the evaporation treatment is 20 KPa-40 KPa.

[0023] The extraction method as described above adopts a horizontal reactor to carry out the evaporation treatment; the volume ratio of the third aqueous phase to the volume of the horizontal reactor is (0.3-0.8):1;

[0024] And / or, the volume ratio of the emulsion to the third aqueous phase is (0.1-0.5):1;

[0025] During the evaporation treatment, the horizontal reactor rotates at a maximum linear velocity of less than 3 m / s, and the maximum linear velocity is preferably 0.2 m / s-1.5 m / s.

[0026] In a second aspect, the present invention provides an extraction device for performing the extraction method as described above, comprising an emulsification unit and an evaporation unit;

[0027] The emulsion outlet of the emulsification unit is communicated with the emulsion inlet of the evaporation unit;

[0028] The emulsification unit includes a stirring paddle;

[0029] The blade of the stirring paddle includes a first edge a and a second edge b, the first edge a is connected to the second edge b through a connecting arc β, the length ratio of the first edge a and the second edge b is (0.5-3.0):1, preferably (0.8-2.0):1; the angle of the connecting arc β is 95°-145°, and the angle α between the blade of the stirring paddle and the axial direction of the stirring paddle is 30°-60°.

[0030] The extraction device as described above, wherein the evaporation unit comprises a horizontal reactor;

[0031] The horizontal reactor comprises a plurality of baffles arranged on the reactor body of the horizontal reactor, the baffles are distributed along the circumference of the horizontal reactor, and the ratio of the width h1 of the baffles in the direction toward the center of the horizontal reactor to the reactor body diameter h of the horizontal reactor is (0.2-0.5):1;

[0032] The ratio of the distance h2 between two adjacent baffles in the circumferential direction of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (0.2-1):1;

[0033] The ratio of the height H of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (2-5):1.

[0034] The method for extracting polycarbonate particles provided by the present invention can fully remove impurities in the organic solution by limiting the conductivity and pH of the first aqueous phase after washing treatment, which is conducive to the subsequent formation of a stable emulsion; and the particle size of the emulsion obtained by stirring treatment is limited, so that the particle size of the finally obtained polycarbonate particles can be uniform and less fine powder, specifically, the particle size distribution SPAN of the polycarbonate particles can be less than or equal to 2.0, and the number of particles with a particle size less than 20 μm accounts for less than or equal to 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A schematic diagram of a device for extracting polycarbonate particles provided by the present invention;

[0037] Figure 2 A schematic diagram of the structure of a stirring paddle provided by the present invention;

[0038] Figure 3 A schematic diagram of the structure of a horizontal reactor provided by the present invention;

[0039] Figure 4 A schematic structural diagram of another horizontal reactor provided by the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0041] Polycarbonate (PC), as an important engineering plastic, has been widely used in many fields, such as automobiles, electronics, and construction, due to its excellent heat resistance, transparency, mechanical strength, and electrical insulation. However, in the production and processing of polycarbonate, how to obtain particles with uniform particle size and less fine powder content has always been a technical challenge faced by the industry.

[0042] Traditional polycarbonate pellet preparation methods, such as the biaxial kneading milling process, often result in uneven pellet size and excessive fine powder content. This uneven pellet size can have an adverse effect on subsequent processing, especially in processes such as injection molding and extrusion, where the uniformity of the pellets directly affects the quality and performance of the product. In addition, the presence of fine powder can easily cause the pellets to form clusters in the silo, which in turn hinders the feeding process and affects production efficiency.

[0043] In the existing technical solutions, the block product obtained by kneading is usually sheared by a pulverizer in order to obtain relatively uniform particles. However, this method often produces a large amount of ultrafine powder, which increases the difficulty and cost of subsequent processing. Therefore, developing a polycarbonate particle extraction method that can effectively control the particle size and reduce the fine powder content is of great significance for improving the processing performance and product quality of polycarbonate.

[0044] In this context, the present invention proposes a new method for extracting polycarbonate particles, which aims to address the deficiencies in the prior art by optimizing processing steps such as washing, stirring and evaporation, and provide polycarbonate particles with uniform particle size and less fine powder content to meet the needs of modern industry for high-performance materials.

[0045] Based on this, in a first aspect, the present invention provides a method for extracting polycarbonate particles, comprising the following steps:

[0046] 1) washing an organic solution including polycarbonate to obtain an organic phase and a first aqueous phase; the conductivity of the first aqueous phase is less than or equal to 100 μS / cm, for example, 10 μS / cm, 20 μS / cm, 30 μS / cm, 40 μS / cm, 50 μS / cm, 60 μS / cm, 70 μS / cm, 80 μS / cm, 90 μS / cm, 100 μS / cm, etc.; the pH is 5-10, for example, 5, 6, 7, 8, 9, 10, etc.

[0047] 2) stirring a mixed solution including an organic phase and a second aqueous phase to obtain an emulsion; in the emulsion, the particle size is 50 μm-200 μm, for example, 50 μm, 70 μm, 90 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, etc., and the number of emulsion droplets between the particle sizes is 50%-80%, for example, 50%, 55%, 60%, 70%, 80%, etc.

[0048] 3) The emulsion is evaporated to obtain polycarbonate particles.

[0049] The method for extracting polycarbonate particles provided by the present invention limits the conductivity and pH of the first aqueous phase obtained after washing treatment, and limits the particle size of the emulsion obtained after stirring treatment, so that the polycarbonate particles finally extracted have uniform particle size and less fine powder.

[0050] Specifically, in step 1), the organic solution including the polycarbonate particles is fully washed with deionized water to remove impurities and excess reaction byproducts in the organic solution, until the conductivity of the washing water, i.e., the first aqueous phase, is less than or equal to 100 μS / cm and the pH is 5-10, which means that the impurities in the organic solution are removed more thoroughly and a pure organic phase can be obtained, which is conducive to the subsequent formation of a stable emulsion and separation of the organic phase and the first aqueous phase. The separation can be performed by centrifugation or coagulation to separate the organic phase and the first aqueous phase, and remove the aqueous phase.

[0051] The present invention does not limit the number of washing treatments, as long as the conductivity of the first water phase after washing is less than or equal to 100 μS / cm and the pH is 5-10.

[0052] In step 2), a certain amount of deionized water, i.e., the second aqueous phase, is added to the organic phase separated in step 1) to form an immiscible mixed solution, and then the mixed solution is stirred, i.e., the mixed solution is shear-mixed, to obtain a long-term stable emulsion, and the number of emulsion droplets with a particle size between 50 μm and 200 μm in the emulsion accounts for 50%-80%, and the uniformity of the particles is high. Since no surfactant is added when forming the emulsion, only stirring is used, oil-in-water emulsion droplets with larger particle sizes can be formed, reducing the formation ratio of emulsion droplets with too small particle sizes, and the distribution of emulsion droplets is relatively uniform, which is conducive to reducing the formation ratio of particles with too small particle sizes, i.e., fine powder, in the final polycarbonate particles, and making the particle size of the final polycarbonate particles more uniform.

[0053] In step 3), after a stable emulsion is obtained, the emulsion is evaporated to remove the organic solvent, that is, the oil phase in the water-in-oil emulsion, to obtain polycarbonate particles.

[0054] The method for extracting polycarbonate particles provided by the present invention can fully remove impurities in the organic solution by limiting the conductivity and pH of the first aqueous phase after washing treatment, which is conducive to the subsequent formation of a stable emulsion; and the particle size of the emulsion obtained by stirring treatment is limited, so that the particle size of the finally obtained polycarbonate particles can be uniform and less fine powder, specifically, the particle size distribution SPAN of the polycarbonate particles can be less than or equal to 2.0, and the number of particles with a particle size less than 20 μm accounts for less than or equal to 10%.

[0055] The organic solution comprising polycarbonate in the present invention can be a qualified polycarbonate solution with qualified structural characteristics prepared by interfacial polycondensation process, or a product dissolved in an organic solvent after recovery. For example, it can be prepared by referring to the preparation method described in the invention application CN117820622A, and specifically, it can be prepared by referring to the preparation method described in Example 1 of the invention application. Exemplarily, the preparation method of the organic solution comprising polycarbonate can include the following steps:

[0056] 1) Bisphenol A monomer undergoes interfacial phosgenation reaction with phosgene to obtain a reaction emulsion containing oligomers;

[0057] 2) After adding alkali solution and end-capping agent into the reaction emulsion, dynamic shearing is performed to obtain a water-in-oil emulsion;

[0058] 3) The oil-in-water emulsion undergoes condensation reaction to synthesize polycarbonate.

[0059] In some embodiments of the present invention, the pH of the first aqueous phase is 6-10, for example, it can be 6, 7, 8, 9, 10 or any two thereof; preferably it is 7-9.

[0060] In some embodiments, the volume ratio of the organic phase to the second aqueous phase is 1:(0.4-2.5), for example, it can be 1:0.4, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or a range consisting of any two thereof; preferably 1:(1.5-2.5).

[0061] In the present invention, the pH of the first aqueous phase is within the above range, which can further remove impurities and excess by-products in the organic solution, improve the purity of the organic phase, and thus further improve the stability of the subsequently formed emulsion.

[0062] The volume ratio of the organic phase to the second aqueous phase in the present invention is within the above range, which can optimize the emulsification process, is beneficial to controlling the size and distribution of droplets in the emulsion, making the droplet size in the emulsion more uniform, reducing the generation of fine powder, and thereby improving the particle size uniformity of the polycarbonate particles and reducing the generation of fine powder.

[0063] In some embodiments of the present invention, the organic solution comprises an organic solvent, the organic solvent comprises a chlorine-containing organic solvent, and the chlorine-containing organic solvent comprises dichloromethane and / or chlorobenzene.

[0064] In the organic solution of polycarbonate in the present invention, the organic solvent used is completely incompatible with water, which means that after sufficient mixing, the amount of water dissolved in the organic phase does not exceed 3%, and the organic solvent is a polar solvent.

[0065] The organic solvent in the present invention includes a chlorine-containing organic solvent, and the chlorine-containing organic solvent includes dichloromethane and / or chlorobenzene, wherein dichloromethane and / or chlorobenzene have excellent solubility for polycarbonate and can dissolve a large amount of polycarbonate. In addition, dichloromethane has high volatility, which helps to quickly remove the solvent in the subsequent evaporation process, reduce residues, and improve the purity of polycarbonate particles. In addition, the low boiling point of dichloromethane makes the recovery and reuse of the solvent more economical and efficient, and reduces the risk of thermal degradation of the polymer during the heat treatment process. Chlorobenzene has good chemical stability, is not prone to side reactions, and ensures the stability of the organic solution.

[0066] In some embodiments of the present invention, a stirring paddle is used for stirring; the outermost edge of the stirring paddle ( Figure 2 The linear speed of the stirring treatment is greater than or equal to 5 min, for example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 50 min or the range consisting of any two thereof; preferably 10 min-30 min.

[0067] In some embodiments, the mass percentage of polycarbonate in the organic solution is 5%-35%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35% or any two thereof; preferably 10%-30%, more preferably 15%-25%.

[0068] The present invention adopts a stirring blade to stir the liquid, and a long-term stable emulsion can be prepared under the shearing action of the blade with a circulating effect. Figure 2 The linear velocity of the organic phase (point A in the figure) is within the above range, which can provide stronger shear force, make the organic phase and the second aqueous phase mix more evenly, form a stable emulsion, prevent agglomeration between droplets, and help control the size distribution of droplets in the emulsion, thereby improving the uniformity of polycarbonate particles. Sufficient stirring time can ensure that the organic phase and the second aqueous phase are fully mixed to form a stable emulsion with uniform particle size.

[0069] The mass percentage of the polycarbonate particles in the organic solution of the present invention is within the above range, which can form a long-term stable emulsion, which is beneficial to controlling the particle size and particle size distribution of the droplets in the emulsion, thereby facilitating the final acquisition of polycarbonate particles with uniform particle size and less fine powder.

[0070] In some embodiments of the present invention, evaporating the emulsion includes: jetting the emulsion into a third aqueous phase, and evaporating the organic solvent in the emulsion using the third aqueous phase to obtain polycarbonate particles.

[0071] In the present invention, the emulsion is introduced into the third aqueous phase in a jet manner, and the third aqueous phase can be deionized water. The organic solvent in the emulsion is evaporated by the third aqueous phase to remove the organic solvent. The presence of the third aqueous phase can accelerate the volatilization of the organic solvent, and the formation of polycarbonate particles can be effectively controlled during the evaporation process, thereby reducing the aggregation and agglomeration of the polycarbonate particles, and pure polycarbonate particles with uniform particle size can be prepared.

[0072] In some embodiments of the present invention, the diameter of the jet stream formed by the jet is less than 1 mm, for example, it can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm or a range consisting of any two of them; preferably 0.3 mm-0.7 mm.

[0073] In some embodiments, the jet ejection speed is 3 mL / s-10 mL / s, for example, it can be 3 mL / s, 4 mL / s, 5 mL / s, 6 mL / s, 7 mL / s, 8 mL / s, 9 mL / s, 10 mL / s or a range consisting of any two thereof.

[0074] The diameter of the jet stream formed by the jet and the jet ejection speed are limited to the above ranges in the present invention, which can make the emulsion contact with the third aqueous phase quickly, reduce the collision and aggregation of emulsion droplets when entering the third aqueous phase, reduce the agglomeration of particles, help to form stable and uniform droplets, reduce the generation of fine powder, thereby improving the uniformity and consistency of polycarbonate particles, and also improve the efficiency of evaporation treatment, so that the solvent evaporates more fully, and obtains relatively pure polycarbonate particles with uniform particle size.

[0075] In some embodiments of the present invention, after all the emulsion is ejected into the third aqueous phase, evaporation treatment is started, and the temperature of the third aqueous phase is greater than 35°C, for example, it can be 35°C, 37°C, 40°C, 42°C, 45°C, 47°C, 50°C, 55°C, 60°C, 70°C or a range consisting of any two of them; preferably 42°C-55°C.

[0076] In some embodiments, the time of the evaporation treatment is 60 min-120 min, for example, it can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min or a range consisting of any two thereof; the pressure of the evaporation treatment is 20 KPa-40 KPa, for example, it can be 20 KPa, 25 KPa, 30 KPa, 35 KPa, 40 KPa or a range consisting of any two thereof.

[0077] In the present invention, after all the emulsion to be evaporated is jetted into the third water phase, the evaporation time starts to be counted.

[0078] The temperature of the third aqueous phase, the time of the evaporation treatment and the pressure of the evaporation treatment in the present invention are within the above ranges, which can accelerate the volatilization rate of the organic solvent, improve the efficiency of the evaporation treatment, and fully remove the organic solvent, reduce the solvent residue in the polycarbonate particles, improve the purity and quality of the product, maintain the stability of the particle morphology, and improve the uniformity and consistency of the particles.

[0079] In some embodiments of the present invention, a horizontal reactor is used for evaporation treatment; the volume ratio of the third aqueous phase to the volume of the horizontal reactor is (0.3-0.8):1, for example, it can be 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1 or a range consisting of any two of them.

[0080] In some embodiments, the volume ratio of the emulsion to the third aqueous phase is (0.1-0.5):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1 or a range consisting of any two thereof.

[0081] During the evaporation process, the horizontal reactor rotates at a maximum linear velocity of less than 3 m / s. For example, the maximum linear velocity may be 0.1 m / s, 0.2 m / s, 0.3 m / s, 0.5 m / s, 1.0 m / s, 1.5 m / s, 2.0 m / s, 2.5 m / s, 3 m / s or a range consisting of any two thereof; the maximum linear velocity is preferably 0.2 m / s-1.5 m / s.

[0082] The use of the horizontal reactor in the present invention is helpful to evenly distribute heat and mix materials, ensure the uniformity of the evaporation process, and thus improve the uniformity of the particle size of the polycarbonate particles.

[0083] On the one hand, the volume ratio of the third aqueous phase to the volume of the horizontal reactor, and the volume ratio of the emulsion to the third aqueous phase are within the above ranges, which allows the emulsion to be fully dispersed in the third aqueous phase, increases the contact area, accelerates the volatilization of the organic solvent, maintains the stability of the operation, and is also conducive to forming uniform polycarbonate particles, thereby improving the consistency and quality of the product.

[0084] On the other hand, the maximum linear speed of the horizontal reactor during rotation, also known as rolling, is within the above range, which can provide sufficient shear force to prevent the polycarbonate particles from agglomerating during the evaporation process, ensure the independence and uniformity of the particles, and also help to continuously mix the materials, ensure the uniform distribution of heat and materials, and improve the evaporation efficiency.

[0085] In a second aspect, the present invention provides an extraction device for performing the extraction method as described above, such as Figure 1 As shown, it includes an emulsification unit 1 and an evaporation unit 2; the emulsion outlet of the emulsification unit 1 is connected to the emulsion inlet of the evaporation unit 2.

[0086] The emulsification unit 1 includes a stirring paddle 11; Figure 2 As shown, the blade of the stirring paddle includes a first edge a and a second edge b, the first edge a is connected to the second edge b by a connecting arc β, and the length ratio of the first edge a to the second edge b is (0.5-3.0):1, for example, it can be 0.5:1, 0.8:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1 or a range consisting of any two thereof, preferably (0.8-2.0):1; the angle of the connecting arc β is 95°-145°, for example, it can be 95°, 100°, 110°, 120°, 130°, 140°, 145° or a range consisting of any two thereof; the angle α between the blade of the stirring paddle and the axial direction of the stirring paddle is 30°-60°, for example, it can be 30°, 35°, 40°, 45°, 50°, 55°, 60° or a range consisting of any two thereof.

[0087] In the present invention, the organic phase obtained by washing treatment and the second aqueous phase are mixed, and the obtained mixed solution is stirred in the emulsification unit 1 to obtain an emulsion, and the emulsion is output through the emulsion outlet of the emulsification unit 1, and enters the evaporation unit 2 through the emulsion inlet of the evaporation unit 2 for evaporation treatment to obtain polycarbonate particles.

[0088] The emulsifying unit 1 includes a stirring paddle 11, and the structure of the stirring paddle 11 is as follows: Figure 2As shown, the length ratio of the first edge a and the second edge b of the blade of the stirring paddle, the connection of the first edge a with the second edge b via the connecting arc β, the angle of the connecting arc β, i.e. the central angle corresponding to the arc β, and the blade of the stirring paddle, i.e. the angle α between the surface of the blade perpendicular to the thickness of the blade and the axial direction of the stirring paddle, within the above range, can increase the mixing effect and ensure the uniform distribution of the liquid during the stirring process, and can also enhance the shear force, improve the emulsification effect, and facilitate the formation of droplets with uniform particle size and reduce agglomeration during the stirring process.

[0089] The device for extracting polycarbonate particles in the present invention can realize the extraction of polycarbonate particles, and the particle size of the extracted polycarbonate particles is relatively uniform and the fine powder is less. Specifically, the particle size distribution SPAN of the polycarbonate particles can be made less than or equal to 2.0, and the number of particles with a particle size less than 20 μm accounts for less than or equal to 10%.

[0090] In addition, the extraction device of the present invention may further include a pump 3, wherein the emulsion outlet of the emulsification unit 1 is connected to the emulsion inlet of the evaporation unit 2 through the pump 3. That is, the emulsion output from the emulsification unit 1 is input into the evaporation unit 2 in a jet shape by the pump 3 for evaporation treatment, wherein the pump 3 may be a diaphragm pump, a rotor pump, etc.

[0091] In some embodiments of the present invention, the evaporation unit 2 includes a horizontal reactor; the horizontal reactor includes a plurality of baffles arranged on the kettle body of the horizontal reactor, the baffles are distributed along the circumference of the horizontal reactor, and the ratio of the width h1 of the baffles in the direction toward the center of the horizontal reactor to the kettle body diameter h of the horizontal reactor is (0.2-0.5):1, for example, it can be 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.5:1 or a range consisting of any two thereof; two adjacent baffles are arranged in the circumference of the horizontal reactor. The ratio of the distance h2 on the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (0.2-1):1, for example, it can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1 or a range consisting of any two thereof; the ratio of the height H of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (2-5):1, for example, it can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 or a range consisting of any two thereof.

[0092] The evaporation unit 2 in the present invention comprises a horizontal reactor, such as Figure 3 and Figure 4As shown, the horizontal reactor includes a plurality of baffles arranged on the kettle body of the horizontal reactor, the baffles are distributed along the circumference of the horizontal reactor, the ratio of the width h1 of the baffles in the direction toward the center of the horizontal reactor to the kettle body diameter h of the horizontal reactor, the ratio of the distance h2 between two adjacent baffles in the circumferential direction of the horizontal reactor to the kettle body diameter h of the horizontal reactor, and the ratio of the height H of the horizontal reactor to the kettle body diameter h of the horizontal reactor are within the above ranges, which can break the rotational flow of the liquid, enhance the turbulence and mixing effects, improve the heat transfer efficiency of the liquid, facilitate the volatilization of the organic solvent, reduce the deposition and agglomeration of the material at the bottom of the kettle, and thus facilitate obtaining polycarbonate particles with uniform particle size and less fine powder.

[0093] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0094] The chemical substances involved in the reaction process are as follows: polycarbonate (commercially available, Wanhua PC product), dichloromethane (analytical grade, Anergy), and deionized water (pH ~ 7.2, conductivity < 5.0).

[0095] The test instruments used for characterizing the droplet size and particle size of particles in the examples are as follows.

[0096] The droplet size test uses a Better BT-2600 laser particle size analyzer. The test medium is dichloromethane. The test temperature is 25°C and the humidity is not higher than 50%.

[0097] The particle size characterization of the particles was tested using the German Sympatec dry particle size analyzer HELOS-RODOS. The test temperature was 25°C and the humidity was not higher than 80%.

[0098] Example 1

[0099] The polycarbonate particle extraction device of this embodiment is as follows Figure 1 As shown, it includes an emulsification unit 1 (emulsification kettle), an evaporation unit 2 (horizontal reaction kettle), and a pump 3 (rotor pump); wherein the emulsion outlet of the emulsification unit 1 is connected to the emulsion inlet of the evaporation unit 2 through the pump 3.

[0100] The method for extracting polycarbonate particles of this embodiment comprises the following steps:

[0101] 1) The interfacial polycondensation process obtains about 1 L of a relatively pure dichloromethane solution of polycarbonate (refer to the preparation method described in Example 1 of the invention application CN117820622A), in which the mass fraction of PC is 18%, which is transferred to a washing kettle, and deionized water is added to the washing kettle for multiple washings. After each washing, the organic phase and the first aqueous phase are separated using a coalescing device until the conductivity and pH of the final washing water, i.e., the first aqueous phase, are reduced to 30 μS / cm and 7.2, respectively.

[0102] 2) The organic phase is then transferred to an emulsification kettle equipped with a double-layer stirring paddle, such as Figure 2 As shown, the diameter of the blade is about 50 mm, that is, the projection of the blade in the direction of the bottom of the emulsifying kettle. The blade of the stirring paddle includes a first edge a and a second edge b, the first edge a is connected to the second edge b through a connecting arc β, the length ratio of the first edge a to the second edge b is 1.4:1, the angle α between the blade of the stirring paddle and the axial direction of the stirring paddle is 45°, and the angle of the connecting arc β is 130°.

[0103] About 0.5 L of deionized water (second aqueous phase) was added to the emulsification kettle, wherein the volume ratio of the organic phase to the second aqueous phase was 1:2.5, and the linear velocity of the outermost edge of the stirring paddle was 8 m / s. After maintaining stirring for 15 minutes, an emulsion that could maintain stability for a short time was prepared. The tested particle size was D50 = 110 μm, and the particle size distribution SPAN = 1.2 (SPAN = (D90-D10) / D50). The number of emulsion droplets with a particle size between 50 μm and 200 μm accounted for 55%, which was recorded as ratio 1.

[0104] 3) The emulsion is pumped into the horizontal reactor in the form of a jet using a rotor pump, wherein the horizontal reactor includes a plurality of baffles arranged on the reactor body of the horizontal reactor, the baffles are distributed along the circumference of the horizontal reactor, the ratio of the width h1 of the baffles in the direction toward the center of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is 0.3:1, the ratio of the distance h2 between two adjacent baffles in the circumferential direction of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is 0.2:1, and the ratio of the height H of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is 4.8:1. The diameter of the jet stream formed by the jet is 0.5 mm, the ejection speed is 3 mL / s, the volume of hot water (third water phase) added to the horizontal reactor is 15 L, the temperature is 45°C, the volume ratio of the third water phase to the volume of the horizontal reactor is 0.6:1, and the volume ratio of the emulsion to the third water phase is 0.5:1. After all the emulsion is jetted into the horizontal reactor, the rotation and vacuum equipment are turned on for evaporation, and the rotation speed of the horizontal reactor is controlled to be 60 rpm, the maximum linear speed is 2.5 m / s, and the vacuum degree is 35 kPa. After maintaining the above operating conditions for about 110 minutes, the powder making operation is stopped, and the slurry is filtered, dried, and other operations are performed to obtain polycarbonate particles.

[0105] Embodiment 2-10

[0106] The extraction devices and extraction methods of the polycarbonate particles in Examples 2-10 are substantially the same as those in Example 1, except that one or more of the extraction devices or extraction methods are changed.

[0107] Comparative Example 1

[0108] The extraction device and extraction method of the polycarbonate particles in Comparative Example 1 are basically the same as those in Example 1, except that the conductivity and pH of the first aqueous phase are reduced to 40 μS / cm and 4.8 respectively, the length ratio of the first edge a and the second edge b of the stirring paddle blade is 4:1, and the angle α between the stirring paddle blade and the axial direction of the stirring paddle is 15°.

[0109] Comparative Example 2

[0110] The extraction device and extraction method of the polycarbonate particles in Comparative Example 2 are substantially the same as those in Example 1, except that the conductivity of the first aqueous phase is 110 μS / cm.

[0111] Comparative Example 3

[0112] The extraction device and extraction method of the polycarbonate particles in Comparative Example 3 are substantially the same as those in Example 1, except that the pH of the first aqueous phase is 12.

[0113] Comparative Example 4

[0114] The extraction device and extraction method of the polycarbonate particles in Comparative Example 4 are basically the same as those in Example 1, except that the linear speed of the outermost edge of the stirring paddle is 15 m / s. After maintaining stirring for 27 minutes, an emulsion that can maintain stability for a short time is prepared, wherein the number of emulsion droplets with a particle size between 50 μm and 200 μm accounts for 40%, which is recorded as Ratio 1.

[0115] Table 1

[0116]

[0117] Table 2

[0118]

[0119] It can be seen from Table 1-2 that, compared with the comparative example, the method for extracting polycarbonate particles provided by the present invention can fully remove impurities in the organic solution by limiting the conductivity and pH of the first aqueous phase after washing treatment, which is beneficial to the subsequent formation of a stable emulsion; and the particle size of the emulsion obtained by stirring treatment is limited, so that the particle size of the finally obtained polycarbonate particles can be uniform and the amount of fine powder is less, specifically, the particle size distribution SPAN of the polycarbonate particles can be less than or equal to 2.0, and the number of particles with a particle size less than 20 μm can account for less than or equal to 10%.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting polycarbonate particles, characterized in that: The following steps are involved: 1) washing an organic solution including polycarbonate to obtain an organic phase and a first aqueous phase; the first aqueous phase has an electrical conductivity of less than or equal to 100 μS / cm and a pH of 5-10; 2) stirring a mixed solution including the organic phase and the second aqueous phase to obtain an emulsion; in the emulsion, the number of emulsion droplets with a particle size between 50 μm and 200 μm accounts for 50% to 80%; 3) Evaporating the emulsion to obtain the polycarbonate particles.

2. The extraction method according to claim 1, characterized in that The pH of the first aqueous phase is 6-10, preferably 7-9; And / or, the volume ratio of the organic phase to the second aqueous phase is 1:(0.4-2.5), preferably 1:(1.5-2.5).

3. The extraction method according to claim 1 or 2, characterized in that The organic solution comprises an organic solvent, the organic solvent comprises a chlorine-containing organic solvent, and the chlorine-containing organic solvent comprises dichloromethane and / or chlorobenzene.

4. The extraction method according to any one of claims 1 to 3, characterized in that Using a stirring paddle to carry out the stirring process; The linear velocity of the outermost edge of the stirring paddle is greater than or equal to 2 m / s, preferably 3 m / s-9 m / s; the stirring treatment time is greater than or equal to 5 min, preferably 10 min-30 min; And / or, the mass percentage of the polycarbonate in the organic solution is 5%-35%, preferably 10%-30%, more preferably 15%-25%.

5. The extraction method according to any one of claims 1 to 4, characterized in that The evaporation treatment of the emulsion comprises: The emulsion is jetted into a third aqueous phase, and the organic solvent in the emulsion is evaporated by the third aqueous phase to obtain the polycarbonate particles.

6. The extraction method according to claim 5, characterized in that The diameter of the jet stream formed by the jet is less than 1 mm, preferably 0.3 mm to 0.7 mm; And / or, the jet ejection speed is 3 mL / s-10 mL / s.

7. The extraction method according to claim 5 or 6, characterized in that After all the emulsion is ejected into the third aqueous phase, the evaporation process is started, and the temperature of the third aqueous phase is greater than 35° C., preferably 42° C.-55° C.; And / or, the evaporation treatment time is 60 min-120 min, and the evaporation treatment is carried out in a negative pressure system with a pressure range of 20 KPa-40 KPa.

8. The extraction method according to any one of claims 5 to 7, characterized in that A horizontal reactor is used for the evaporation treatment; the volume ratio of the third aqueous phase to the volume of the horizontal reactor is (0.3-0.8):1; And / or, the volume ratio of the emulsion to the third aqueous phase is (0.1-0.5):1; During the evaporation treatment, the horizontal reactor rotates at a maximum linear velocity of less than 3 m / s, and the maximum linear velocity is preferably 0.2 m / s-1.5 m / s.

9. An extraction device for performing the extraction method according to any one of claims 1 to 8, characterized in that: It includes an emulsification unit and an evaporation unit; The emulsion outlet of the emulsification unit is communicated with the emulsion inlet of the evaporation unit; The emulsification unit includes a stirring paddle; The blade of the stirring paddle includes a first edge a and a second edge b, the first edge a is connected to the second edge b through a connecting arc β, the length ratio of the first edge a and the second edge b is (0.5-3.0):1, preferably (0.8-2.0):1; the angle of the connecting arc β is 95°-145°, and the angle α between the blade of the stirring paddle and the axial direction of the stirring paddle is 30°-60°.

10. The extraction device according to claim 9, characterized in that The evaporation unit comprises a horizontal reactor; The horizontal reactor comprises a plurality of baffles arranged on the reactor body of the horizontal reactor, the baffles are distributed along the circumference of the horizontal reactor, and the ratio of the width h1 of the baffles in the direction toward the center of the horizontal reactor to the reactor body diameter h of the horizontal reactor is (0.2-0.5):1; The ratio of the distance h2 between two adjacent baffles in the circumferential direction of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (0.2-1):1; The ratio of the height H of the horizontal reactor to the diameter h of the reactor body of the horizontal reactor is (2-5):1.

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