Polycarbonate and preparation method thereof

Abstract

According to the polycarbonate and the preparation method thereof, the consumption of phosgene can be reduced by converting a continuous phase and a dispersed phase in a two-phase interface reaction process and controlling a reaction ratio and a reaction degree, and meanwhile, indexes such as phenol residue, hydroxyl content and oligomer content of a polymer are improved.

Description

Technical Field

[0001] This invention belongs to the field of polycarbonate preparation technology, specifically relating to a polycarbonate and its preparation method. Background Technology

[0002] The industrial method of producing polycarbonate using interfacial polycondensation is well known to those skilled in the art. Typically, an alkaline aqueous solution containing bisphenol compounds is mixed with an organic solvent containing phosgene for an interfacial reaction. End-capping agents and catalysts are added during the reaction to ultimately complete the polycondensation reaction and achieve the target molecular weight. Phosgene partially participates in the hydrolysis side reaction; therefore, phosgene must be used in excess compared to bisphenol compounds. Furthermore, the reaction process requires maintaining alkalinity, necessitating the addition of an alkaline solution to neutralize the hydrochloric acid produced by the hydrolysis of excess phosgene.

[0003] Reducing the phosgene excess rate and decreasing alkali consumption is beneficial to the economics of the reaction. However, a reduction in the phosgene excess rate to a certain extent can affect the conversion of bisphenol compounds or end-capping agents, leading to an increase in the residual bisphenol and monophenol (as end-capping agent) in the oil phase of the reaction liquid. These phenol residues are difficult to remove through conventional acid washing and water washing processes. An excessively low phosgene excess rate can also cause an increase in the content of polymer oligomers and terminal hydroxyl groups. Furthermore, the problems of phenol residue, oligomers, and terminal hydroxyl groups can make oil-water phase separation difficult after the reaction, further exacerbating the phenol residue contamination problem and affecting the heat resistance and aging resistance of downstream products. These issues limit the application of interfacial polycondensation polycarbonate in medical, food packaging, and other fields.

[0004] Patent CN101565501B reduces phosgene excess and shortens reaction time by using a disperser to mix the organic and aqueous phases during polycarbonate preparation. This optimizes the problems of phosgene excess and separation difficulties, and improves the preparation efficiency and safety of polycarbonate. However, the optimized phosgene excess rate is still relatively high, and the advantages are not obvious.

[0005] Patent CN113614147B discloses a method for reducing the excess rate of phosgene in a phase interface method by providing a given energy input for dispersing the aqueous and organic phases. Furthermore, this method offers a low oligomer ratio and a low carbonate ratio as a two-chain terminator. However, studies have shown that this method is only applicable to certain reaction scenarios. In reactors with backmixing, such as stirred tanks, or in water-in-oil emulsion systems, the opposite effect occurs. Additionally, this method does not reveal any improvement in phenol residue or oil-water separation issues.

[0006] Patent CN111479845B discloses a method for preparing polycarbonate via a phase interface method in the presence of at least one catalyst. Optionally, after the first addition of the at least one catalyst, a limited amount of mixing energy of 0.01-10 J / kg is introduced into the system containing the at least one catalyst within a given time. This method partially solves the separation difficulties caused by high shear gradients in the phase interface method for preparing polycarbonate and optimizes the problem of phenol residue in the aqueous phase. However, the phenol residue in the organic phase remains at a high level, and the oligomer content level is not disclosed. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the inventors have discovered that by converting the continuous phase and dispersed phase in the two-phase interface reaction process and controlling the reaction ratio and degree of reaction, the consumption of phosgene can be significantly reduced. The prepared polycarbonate has very low bisphenol or monophenol residue, low oligomer content, and high end-capping rate. The resulting polycarbonate product is well-suited to the needs of the food, medical and other industries.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] Firstly, a method for preparing polycarbonate is provided, specifically including the following steps:

[0010] (1) Step A: An alkaline aqueous solution containing bisphenol compounds is mixed with phosgene and organic solvent to react and obtain an oil-in-water oligomer reaction solution. When the reaction solution does not contain unreacted phosgene and the conversion rate of bisphenol compounds is >90%, it is sent to the next step.

[0011] (2) Step B: The oligomer reaction solution is mixed with the end-capping agent and alkali solution at high speed to transform the reaction solution into a water-in-oil system. When the reaction reaches the molar ratio of acyl chloride groups in the oligomer to phosgene in step A of 0.5-8 mol%, the process is transferred to the next step.

[0012] (3) Step C: The reaction solution is converted into an oil-in-water system by demulsification equipment, a catalyst is added, and the reaction continues until the content of acyl chloride groups in the reaction solution is <1ppm.

[0013] Preferably, in the polycarbonate preparation method of the present invention, in step A, the bisphenol compound is selected from one or more compounds with the structure represented by formula (I).

[0014]

[0015] Among them, R2 and R3 are independently selected from halogens and C1-C. 20 Alkyl or alkoxy, C4-C 20 cycloalkyl, C6-C 20aryl group; n and m are independent integers selected from 0 to 4; W is a chemical bond, oxygen atom, sulfur atom, carbonyl group, sulfone group, sulfoxide group, C1-C 20 lipid group, C6-C 20 aryl, C6-C 20 Alicyclic groups, organic residues of polydimethylsiloxane, or groups represented as in formula (II):

[0016]

[0017] Among them, R4 and R5 are independently selected from hydrogen and C1-C. 20 Alkyl, C4-C 20 cycloalkyl or C4-C 20 aryl groups; or R4 and R5 together form C4-C 20 The alicyclic ring, which may optionally be composed of one or more C1-C1 rings. 20 Alkyl, C6-C 20 Aryl, C7-C 21 Aryl alkyl, C5-C 20 Cycloalkyl groups or combinations thereof are substituted.

[0018] Preferably, the bisphenol compound is selected from one or more of 4,4'-dihydroxybiphenyl, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenylethane, 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene, more preferably 2,2-bis-(4-hydroxyphenyl)propane.

[0019] Preferably, in the polycarbonate preparation method of the present invention, in step A, the alkaline aqueous solution is an aqueous solution of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, preferably an aqueous solution of sodium hydroxide. The alkaline aqueous solution containing the bisphenol compound is called the aqueous phase, and the concentration of the bisphenol compound in the aqueous phase is 5-30 wt%, such as 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 23 wt%, 25 wt%, 27 wt%, 30 wt%, preferably 10-20 wt%. Preferably, the molar ratio of the alkali metal hydroxide to the bisphenol compound in the aqueous phase is 2.0-3.0:1, for example, it can be 2.0:1, 2.2:1, 2.5:1, 2.7:1, 2.8:1, 3.0:1, preferably 2.0-2.2:1.

[0020] Preferably, in the polycarbonate preparation method of the present invention, in step A, phosgene can be mixed with an organic solvent to obtain an organic solvent containing phosgene, or phosgene and the organic solvent can be introduced into the reaction system separately, and after entering the reaction system, phosgene and the organic solvent will form an oil phase. The organic solvent can be one or more of the following: C1-C6 chlorinated or brominated aliphatic hydrocarbons, C4-C6 chlorinated or brominated alicyclic hydrocarbons, C6-C8 aromatic hydrocarbons, and C6-C8 chlorinated or brominated aromatic hydrocarbons, preferably dichloromethane or chlorobenzene.

[0021] Preferably, in the polycarbonate preparation method of the present invention, in step A, the mass ratio of organic solvent to alkaline aqueous solution (aqueous phase) is 0.3-0.9:1, for example, it can be 0.3:1, 0.5:1, 0.7:1, or 0.9:1. Reducing the volume of organic solvent is beneficial to forming an oil-in-water system.

[0022] Preferably, in the polycarbonate preparation method of the present invention, in step A, the introduced phosgene and organic solvent form an oil phase in the reaction system, and the concentration of phosgene in the oil phase is 3-20 wt%, for example, it can be 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%.

[0023] Preferably, in the mixed reaction of the aqueous and oil phases, the proportion of phosgene relative to the bisphenol compound is preferably 103-115 mol%, for example, 103 mol%, 105 mol%, 108 mol%, 110 mol%, 112 mol%, 115 mol%, more preferably 105-110 mol%.

[0024] This invention, by reducing the amount of phosgene passing through the gas, and by converting the continuous phase and dispersed phase in the two-phase interface reaction process and controlling the degree of reaction, yields a polycarbonate product that still has a low bisphenol or monophenol residue and oligomer content.

[0025] Preferably, in the polycarbonate preparation method of the present invention, in step A, the reaction temperature is 0-70℃, preferably 10-40℃.

[0026] In step A of this invention, the mixing scale of the reaction process must ensure complete conversion of phosgene and a bisphenol compound conversion rate >90%, while maintaining the reaction system as an oil-in-water emulsion. A suitable mixing scale typically maintains the oil phase as the dispersed phase at the millimeter level. Increasing the mixing scale can further reduce phosgene hydrolysis consumption and improve the bisphenol conversion rate, which is beneficial for reducing phenol and hydroxyl residues. However, an excessively high mixing scale can cause the reaction liquid to transform into an oil-in-water system. In reaction systems with backmixing, this can lead to increased phosgene hydrolysis, which is detrimental to the objectives of this invention. An excessively low mixing scale will result in incomplete phosgene conversion and affect the bisphenol compound conversion rate, leading to an increase in the phenol residue level in the final stage of the reaction, i.e., step C.

[0027] Preferably, the mixing scale can be such that the Sade diameter D32 of the dispersed phase (oil phase) is less than 500 μm (e.g., D32 < 450 μm, D32 < 400 μm, D32 < 350 μm, D32 < 300 μm), preferably D32 < 300 μm; the Sade diameter D32 can usually be adjusted by adjusting the shear rate, for example, by selecting a blade with a suitable shear type or changing the stirring speed.

[0028] In this invention, there are no particular limitations on the mixer used to achieve the mixing scale; both dynamic and static mixers can achieve oil-in-water systems.

[0029] Preferably, in the polycarbonate preparation method of the present invention, in step A, the reaction system further includes a branching agent, which is a ternary or higher polyphenol. Specifically, it includes 1,1,1-tris(4-hydroxyphenyl)ethane, 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptene-2,4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptane, 1,3,5-tris(4-hydroxyphenyl)benzene, 2,6-bis(2-hydroxy-5-methylbenzyl)-4-methylphenol, tetra(4-hydroxyphenyl)methane, triphenol, bis(2,4-dihydroxyphenyl)one, phloroglucinol, etc. These can be used alone or in combination of two or more. The preferred branching agent is 1,1,1-tris(4-hydroxyphenyl)ethane. More preferably, the amount of branching agent relative to the bisphenol compound is 0.1-5 mol%, preferably 0.2-3 mol%.

[0030] Preferably, the branching agent can be added at any time during step A. Preferably, the branching agent is dissolved in an alkaline aqueous solution, premixed evenly with the aqueous phase, and then mixed and reacted with the organic phase.

[0031] Preferably, in the polycarbonate preparation method of the present invention, the highly reactive phosgene has been completely consumed in step A and transformed into low-reactivity chloroformate groups in the oligomer reaction solution. The reaction is affected by interfacial diffusion, and the reaction system is transformed into water-in-oil in step B, which is beneficial to improving the conversion rate of bisphenol compounds and end-capping agents.

[0032] Preferably, the present invention promotes the reaction system in step B to shift to water-in-oil by enhancing the mixing scale (high-speed mixing), maintaining the Sade diameter D32 of the dispersed phase (aqueous phase) < 100 μm (e.g., D32 < 80 μm, D32 < 70 μm), preferably D32 < 50 μm. Specifically, a high-shear stirred tank or a dynamic mixer can be used to enhance the mixing scale.

[0033] Preferably, the enhanced mixing scale (high-speed mixing) of the present invention can be carried out after the addition of the capping agent and alkali solution. After the system is converted into a water-in-oil emulsion through high-speed mixing, a low mixing scale can be maintained to keep the system stable.

[0034] The capping agent described in this invention is typically a monophenolic compound, specifically including at least one of phenol, p-tert-butylphenol, isooctylphenol, and cumylphenol. The capping agent is usually dissolved in an organic solvent and added to the reaction system; preferably, the ratio of the capping agent to the bisphenol compound is 1-10 mol%.

[0035] The alkaline solution described in step B of this invention is the same as that in step A, and is an aqueous solution of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, preferably an aqueous solution of sodium hydroxide, and the concentration of the alkaline solution is preferably 5-40 wt%. The molar ratio of the alkali metal hydroxide used to the bisphenol compound in step A is 0.1-0.4:1, preferably 0.2-0.3:1.

[0036] Preferably, the rate of addition of alkali solution in step B of the present invention can be controlled by maintaining the pH of the aqueous phase of the reaction solution at ≥11.

[0037] In step B of the present invention, the reaction temperature is 0-70°C, preferably 10-40°C. When the reaction solution continues to react until the ratio of the content of acyl chloride groups of the oligomer to the initial phosgene of step A is 0.5-8 mol% (e.g., 0.5 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%), the reaction proceeds to step C.

[0038] In step C of this invention, the reaction solution is transformed into an oil-in-water system by a demulsifier, which can further reduce the residue of bisphenol or monophenol compounds in the oil phase and reduce the hydroxyl content.

[0039] This invention enhances the transformation of the system into an oil-in-water system through demulsification equipment. The purpose of the demulsification equipment is to convert the system from an oil-in-water state to an oil-in-water system. Any equipment that can achieve this purpose without affecting the reaction is suitable for this system. For example, at least one of the following can be used: a transfer pump, a stirred tank, a coalescer, a centrifuge, a settling tank, and a hydrophilic filter, with a transfer pump or a stirred tank being preferred. Preferably, when using a transfer pump or a stirred tank, the reaction solution needs to be supplied with oil for at least 30 seconds. -1 The average shear rate is adjusted to better facilitate system transformation.

[0040] Preferably, in step C, an organic solvent may be added. Adding an organic solvent can reduce the viscosity of the oil phase, which is beneficial for forming and maintaining an oil-in-water system. The selection of the organic solvent can refer to step A.

[0041] Preferably, the mass ratio of the added organic solvent to the aqueous phase (alkaline aqueous solution) in step A is 0-0.6:1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or 0.6:1. More preferably, the cumulative mass ratio of the organic solvent added in steps A and C to the aqueous phase in step A is 0.4-1.5:1.

[0042] In step C of the present invention, the catalyst may be a tertiary amine, including at least one of triethylamine, tripropylamine, tributylamine, trioctylamine, N-ethylpiperidine, N-methylpiperidine, N-isopropylpiperidine, and N-n-propylpiperidine, preferably triethylamine.

[0043] Preferably, the catalyst can be added to the reaction system after being mixed with an organic solvent to form a solution. The amount of catalyst relative to the bisphenol compound is 0.1-3 mol%, for example, 0.1 mol%, 0.3 mol%, 0.5 mol%, 1 mol%, 1.2 mol%, 1.5 mol%, 1.8 mol%, 2 mol%, 2.3 mol%, 2.5 mol%, 2.8 mol%, or 3 mol%, preferably 0.2-2 mol%.

[0044] Preferably, the catalyst is added in step C after the system has become an oil-in-water mixture. Adding the catalyst before the phase transition is complete will result in residual hydroxyl groups and increased oligomer content.

[0045] Preferably, in step C of the present invention, after adding the catalyst, the reaction continues at a reaction temperature of 20-40°C until the content of acyl chloride groups in the reaction solution is <1ppm, and then the reaction ends.

[0046] Preferably, after the reaction in step C of the present invention is completed, the residual phenol in the oil phase of the resulting reaction solution is <10 ppm. The oil phase phenol includes the total amount of bisphenol compounds and monophenol compounds used as capping agents dissolved in the oil phase. The residual phenol in the oil phase is the ratio of the total amount of these phenolic compounds to the weight of the oil phase in the reaction solution. The residual phenol in the oil phase has a relatively linear proportional relationship with the residual phenol in the polymer after solvent evaporation; reducing the residual phenol in the oil phase can directly reduce the residual phenol in the polymer. Preferably, the residual phenol in the oil phase is <5 ppm.

[0047] This invention reduces the amount of phosgene passing through the gas and optimizes the control of reaction ratio and reaction degree by converting the continuous phase and dispersed phase in the two-phase interface reaction process, thereby keeping the residual phenol in the oil phase of the final reaction liquid at a low level.

[0048] Preferably, the reaction solution obtained after the reaction in step C is subjected to post-processing step D, which includes steps such as separating the oil phase, washing, desolventizing, and drying.

[0049] Specifically, post-processing step D includes separating and removing the aqueous phase to obtain the organic phase. Further, the organic phase solution can be washed with inorganic acid and deionized water to remove residual catalysts, inorganic salts, and other impurities. Further, the washed and purified organic phase can be further treated with known desolventizing methods, such as steam flocculation, spray drying, or precipitation of undesirable solvents, to remove the organic solvents. The remaining solvent and water are then removed by further drying to obtain the final polycarbonate product.

[0050] Secondly, the polycarbonate product obtained by the above preparation method is provided.

[0051] The polycarbonate of the present invention has a weight-average molecular weight of 5,000-300,000, preferably 10,000-80,000, and more preferably 15,000-50,000.

[0052] Preferably, the polycarbonate of the present invention has a hydroxyl content of <150ppm and an oligomer content of <3wt%.

[0053] Preferably, the polycarbonate of the present invention may further comprise various conventional additives. The proportion of additives relative to the total weight of the polycarbonate is typically 0-5 wt%, preferably 0-2 wt%. Optional conventional additives include one or more of the following: mold release agents, flow aids, heat stabilizers, antioxidants, UV absorbers, IR absorbers, flame retardants, antistatic agents, dyes, pigments, fillers, etc.

[0054] Preferably, the polycarbonate of the present invention can be optionally blended with other thermoplastic polymers or commonly used additives to prepare blends. The thermoplastic polymers include linear bisphenol A type PC, ABS, PET, PBT, PMMA, PS, etc., and the additives typically include glass fibers, glass beads, carbon fibers, inorganic fillers, etc.

[0055] Preferably, the blending can be carried out by various known methods, for example, at a temperature of 240°C-350°C, the components are melt-blended and melt-extruded in commonly used equipment such as mixers, extruders, twin-screw kneaders, etc., and granulated by pelletizer to obtain polycarbonate products.

[0056] Thirdly, the present invention also provides injection molded articles, extruded articles, blow molded articles, etc., obtained by the aforementioned polycarbonate molding.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] The method of the present invention significantly reduces the consumption of phosgene in the preparation of polycarbonate by interfacial polycondensation, and the polycarbonate prepared by the method of the present invention has excellent indicators such as phenol residue, hydroxyl residue, and oligomer content, which can meet the needs of downstream high-end application scenarios such as medical and food. Detailed Implementation

[0059] The following embodiments are intended to explain the present invention. The present invention is not limited to the scope of the embodiments and includes any other modifications within the scope of the claims of the present invention.

[0060] Source of raw materials

[0061] Bisphenol A: Industrial grade, Wanhua Chemical Group Co., Ltd.; Sodium hydroxide: Analytical grade, purchased from Tianjin Kemio Chemical Reagent Co., Ltd.; Phosgene: Industrial grade, Wanhua Chemical Group Co., Ltd.; Dichloromethane: Analytical grade, purchased from Tianjin Kemio Chemical Reagent Co., Ltd.; p-tert-butylphenol: Industrial grade, purchased from Zibo Xujia Chemical Co., Ltd.; Triethylamine: Analytical grade, purchased from Tianjin Kemio Chemical Reagent Co., Ltd.

[0062] Test methods

[0063] Weight-average molecular weight was determined by gel permeation chromatography. The equipment manufacturer was Agilent Technologies, and the equipment model was 1260 Infinity II.

[0064] Oil phase phenol residue: After the reaction in step C is completed, the oil phase of the reaction solution is taken, methanol is added for precipitation, and the supernatant is taken for determination of bisphenol and monophenol residues by high performance liquid chromatography. Equipment manufacturer: Agilent Technologies, equipment model: 1260InfinityⅡ.

[0065] The content of acyl chloride groups in the oligomers was determined by the NBP colorimetric method. The oil phase was separated from the reaction solution, diluted, and NBP was added to carry out the colorimetric reaction. The concentration of acyl chloride was quantitatively tested by UV-Vis spectrophotometer.

[0066] The hydroxyl content of polycarbonate is determined by... 1 H-NMR determination.

[0067] Oligomer content test: The oligomer components dissolved in acetone in 100g of polymer (polycarbonate) were extracted by 50ml acetone extraction. The extraction was carried out at reflux temperature of acetone for 8h. After the acetone solution was dried, it was weighed. The oligomer mass was divided by the initial mass of the polymer to obtain the oligomer content (wt%).

[0068] Example 1

[0069] In step A, an aqueous solution of 15.5 wt% bisphenol A and 5.9 wt% sodium hydroxide is introduced into a tubular reactor equipped with a static mixer at a flow rate of 143 g / min. Simultaneously, phosgene is introduced into the reactor at a flow rate of 10.3 g / min and dichloromethane at a flow rate of 70 g / min. The Shad diameter (D32) of the dispersed phase (oil phase) is <300 μm. The reactor uses a jacket for heat exchange. The outlet reaction liquid temperature is 34 °C, and the residence time is 1 min. Samples of the outlet reaction liquid are observed to be an oil-in-water system, with the continuous phase being aqueous. Testing shows that the reaction liquid no longer contains phosgene, and the bisphenol A conversion rate is >90%.

[0070] In step B, the reaction solution is fed into a continuous emulsifier at a speed of 600 rpm to convert the reaction solution into a water-in-oil system, ensuring that the Sade diameter D32 of the dispersed phase (aqueous phase) is less than 80 μm. Simultaneously, before the emulsifier inlet, a 15 wt% dichloromethane solution of p-tert-butylphenol is added at a flow rate of 3.5 g / min, and a 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 3.8 g / min to maintain the pH of the aqueous phase of the reaction solution at approximately 11.5.

[0071] The emulsion from the emulsifier was introduced into a continuous stirred tank at a stirring speed of 100 rpm, a reaction temperature of 30°C, and a reaction residence time of 10 min. The reaction solution was discharged through the bottom of the tank, and a sample was taken for observation. It was an emulsion, and after standing, the emulsion remained stable and did not separate into layers, which is a typical water-in-oil system. A portion of the sample was taken for acyl chloride content testing. The ratio of acyl chloride groups in the oligomer to phosgene in process A was 3.4 mol%, and it was then sent to process C.

[0072] In step C, the reaction solution is passed through a small coalescer for demulsification. The aqueous phase in the coalescer outlet solution has coalesced to form a continuous phase. The reaction solution from the coalescer outlet is then introduced into a second continuous stirred tank at 120 rpm. Simultaneously, a 3 wt% triethylamine solution in dichloromethane is added at a flow rate of 3 g / min. Stirring continues at 25°C for 10 min. The reaction solution is then discharged through the bottom of the tank. A sample is taken for observation; the aqueous phase remains continuous, indicating an oil-in-water system. The residual acyl chloride is detected to be <1 ppm, indicating that the reaction is essentially complete.

[0073] After the reaction was completed, the aqueous phase was separated, and the organic phase was washed with dilute hydrochloric acid and then washed with deionized water until the washing solution was neutral. The organic phase was concentrated at 50°C to about 18 wt% solid content, and then the solvent was removed by evaporation in hot water at 70°C. The gel was pulverized by a pulverizer and dried in a vacuum oven at 80°C for 6 hours to obtain a polycarbonate powder sample.

[0074] Example 2

[0075] In process A, an aqueous solution of 15.5 wt% bisphenol A and 5.9 wt% sodium hydroxide is introduced into a tubular reactor equipped with a static mixer at a flow rate of 143 g / min. Simultaneously, phosgene is introduced into the reactor at a flow rate of 10.3 g / min, and dichloromethane at a flow rate of 70 g / min. The Shad diameter (D32) of the dispersed phase (oil phase) is <300 μm. The reactor uses a jacket for heat exchange. The outlet reaction liquid temperature is 36 °C, and the residence time is 1 min. Samples of the outlet reaction liquid are observed to be an oil-in-water system, with the continuous phase being aqueous. Testing shows that the reaction liquid no longer contains phosgene, and the bisphenol A conversion rate is >90%.

[0076] In step B, the reaction solution is fed into a continuous emulsifier at a speed of 1200 rpm to convert the reaction solution into a water-in-oil system, ensuring that the Sade diameter D32 of the dispersed phase (aqueous phase) is less than 40 μm. Simultaneously, before the emulsifier inlet, a 15 wt% dichloromethane solution of p-tert-butylphenol is added at a flow rate of 3.5 g / min, and a 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 3.8 g / min to maintain the pH of the aqueous phase of the reaction solution at approximately 11.5.

[0077] The emulsion from the emulsifier was introduced into a continuous stirred tank at a stirring speed of 150 rpm, a reaction temperature of 30°C, and a reaction residence time of 20 min. The reaction solution was discharged through the bottom of the tank, and a sample was observed to be in emulsion form. The sample was then tested for acyl chloride content; the ratio of acyl chloride groups in the oligomer to phosgene from step A was 1.9 mol%, and the mixture was further fed into step C.

[0078] In step C, the reaction solution is fed into a gear pump for demulsification. The average shear rate of the gear pump is approximately 50 s. -1The aqueous phase in the effluent had coalesced to form a continuous phase. The effluent was then transferred to a second continuous stirred tank at 300 rpm. Simultaneously, a dichloromethane solution was added at a flow rate of 70 g / min, and a 3 wt% triethylamine dichloromethane solution was added at a flow rate of 5 g / min. The reaction was continued at 25°C for 10 min. The reaction solution was drained through the bottom of the tank, and a sample was taken for observation. The aqueous phase was found to be continuous, indicating an oil-in-water system. The residual acyl chloride was detected to be <1 ppm, indicating that the reaction was essentially complete.

[0079] After the reaction was completed, the aqueous phase was separated, and the organic phase was washed with dilute hydrochloric acid and then washed with deionized water until the washing solution was neutral. The organic phase was concentrated at 50°C to about 18 wt% solid content, and then the solvent was removed by evaporation in hot water at 70°C. The gel was pulverized by a pulverizer and dried in a vacuum oven at 80°C for 6 hours to obtain a polycarbonate powder sample.

[0080] Example 3

[0081] In step A, an aqueous solution of 15.5 wt% bisphenol A and 5.9 wt% sodium hydroxide is introduced into a tubular reactor equipped with a static mixer at a flow rate of 143 g / min. Simultaneously, phosgene is introduced into the reactor at a flow rate of 10.2 g / min, and dichloromethane at a flow rate of 70 g / min. The Shad diameter (D32) of the dispersed phase (oil phase) is <500 μm. The reactor uses a jacket for heat exchange. The outlet reaction liquid temperature is 34 °C, and the residence time is 1 min. Samples of the outlet reaction liquid are observed to be an oil-in-water system, with the continuous phase being aqueous. Testing shows that the reaction liquid no longer contains phosgene, and the bisphenol A conversion rate is >90%.

[0082] In step B, the reaction solution is fed into a continuous emulsifier at a speed of 400 rpm to convert the reaction solution into a water-in-oil system, ensuring that the Shad diameter D32 of the dispersed phase (aqueous phase) is less than 100 μm. Simultaneously, before the emulsifier inlet, a 15 wt% dichloromethane solution of p-tert-butylphenol is added at a flow rate of 3.5 g / min, and a 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 3.8 g / min to maintain the pH of the aqueous phase of the reaction solution at approximately 11.5.

[0083] The emulsion from the emulsifier is introduced into a continuous stirred tank at a stirring speed of 100 rpm, a reaction temperature of 30°C, and a reaction residence time of 6 minutes. The reaction solution is discharged through the bottom of the tank, and a sample is observed to be in emulsion form. The sample is then tested for acyl chloride content. When the ratio of acyl chloride groups in the oligomer to phosgene from step A is 6.5 mol%, it is further fed into step C.

[0084] In step C, the reaction solution is passed through a plate and frame filter press for demulsification, using a PTFE hydrophilic modified membrane as the filter media. The aqueous phase in the effluent has polymerized to form a continuous phase. The effluent is then transferred to a second continuous stirred tank at 300 rpm. Simultaneously, dichloromethane solution is added at a flow rate of 70 g / min, and a 3 wt% triethylamine solution in dichloromethane is added at a flow rate of 5 g / min. Stirring continues at 25°C for 10 min. The reaction solution is drained through the bottom of the tank, and a sample is taken for observation. The aqueous phase is continuous, indicating an oil-in-water system. The residual acyl chloride is detected to be <1 ppm, indicating that the reaction is essentially complete.

[0085] After the reaction was completed, the aqueous phase was separated, and the organic phase was washed with dilute hydrochloric acid and then washed with deionized water until the washing solution was neutral. The organic phase was concentrated at 50°C to about 18 wt% solid content, and then the solvent was removed by evaporation in hot water at 70°C. The gel was pulverized by a pulverizer and dried in a vacuum oven at 80°C for 6 hours to obtain a polycarbonate powder sample.

[0086] Comparative Example 1

[0087] Referring to Example 1, in step B, the reaction solution obtained from step A is fed into a continuous emulsifier with a rotation speed of 600 rpm. Simultaneously, before the emulsifier inlet, a 15 wt% dichloromethane solution of p-tert-butylphenol is added at a flow rate of 3.5 g / min; and a 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 3.8 g / min to maintain the pH of the aqueous phase of the reaction solution at approximately 11.5.

[0088] The emulsion outlet liquid was sampled and observed to be in emulsion form (water-in-oil system). At this point, a sample was taken for acyl chloride content testing. The ratio of acyl chloride groups in the oligomer to phosgene in process A was 10.8 mol%. The emulsion outlet liquid was directly fed into process C, with other operations the same as in Example 1.

[0089] Comparative Example 2

[0090] Referring to Example 1, in step B, the reaction solution obtained from step A is directly fed into a continuous stirred tank without passing through an emulsifier. Before being fed into the stirred tank, a 15 wt% dichloromethane solution of p-tert-butylphenol is added at a flow rate of 3.5 g / min; a 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 3.8 g / min to maintain the pH of the aqueous phase of the reaction solution at approximately 11.5. The stirring speed in the stirred tank is 100 rpm, the reaction temperature is 30°C, and the reaction residence time is 10 min. The reaction solution is discharged through the bottom of the tank, and a sample is taken for observation, showing it to be an oil-in-water system. A portion of the sample is taken for acyl chloride content testing. When the ratio of acyl chloride groups in the oligomer to phosgene in step A is 5.2 mol%, it is introduced into a second continuous stirred tank. The stirring speed is 120 rpm, and a 3 wt% dichloromethane solution of triethylamine is added at a flow rate of 3 g / min. The mixture is stirred and reacted at 25°C for 10 min. The reaction solution was drained through the bottom of the vessel, and a sample was taken for observation. The aqueous phase was still a continuous phase, which is an oil-in-water system. The residual acyl chloride was detected to be <1 ppm, indicating that the reaction was basically completed. Other operations were the same as in Example 1.

[0091] Comparative Example 3

[0092] Referring to Example 1, processes A and B are the same as in Example 1, except that process C does not pass through a demulsification device, and the reaction liquid from process B is directly fed into the second continuous stirred tank. Other operations are the same as in Example 1.

[0093] Comparative Example 4

[0094] Referring to Example 1, in step A, an aqueous solution of 15.5 wt% bisphenol A and 5.9 wt% sodium hydroxide was introduced into a tubular reactor equipped with a static mixer at a flow rate of 143 g / min. Simultaneously, phosgene was introduced into the reactor at a flow rate of 10.7 g / min and dichloromethane at a flow rate of 70 g / min. The Shad diameter (D32) of the dispersed phase (oil phase) was <300 μm. The reactor was heat-exchanged via a jacket. The outlet reaction liquid temperature was 22°C, and the residence time was 0.5 min. A sample of the outlet reaction liquid was observed to be an oil-in-water system, with the continuous phase being aqueous. When the reaction liquid was found to be free of phosgene and the bisphenol A conversion rate was 83%, it proceeded to step B, with other operations identical to those in Example 1.

[0095] The test results of the samples from each embodiment and comparative example are listed in Table 1.

[0096] Table 1 Test results of polycarbonate samples

[0097]

[0098] The results show that, under similar or lower phosgene excess rates, by performing the phase transition operation required by this invention and controlling the BPA conversion rate and the proportion of oligomer acyl chloride groups in the corresponding processes, the obtained polycarbonate has significant advantages in terms of oil phase phenol residue, PC hydroxyl content, and oligomer content.

Claims

1. A method for preparing polycarbonate, characterized in that, It includes the following steps: Step A: An alkaline aqueous solution containing bisphenol compounds is mixed with phosgene and an organic solvent to react and obtain an oil-in-water oligomer reaction solution. When the reaction solution does not contain unreacted phosgene and the conversion rate of bisphenol compounds is >90%, it is sent to Step B. Step B: The oligomer reaction solution is mixed with the end-capping agent and alkali solution to convert the reaction solution into a water-in-oil system. When the reaction reaches the point where the molar ratio of the acyl chloride group of the oligomer to the phosgene of Step A is 0.5-8 mol%, the reaction proceeds to Step C. Step C: The reaction solution is converted into an oil-in-water system using a demulsifier, a catalyst is added, and the reaction continues until the acyl chloride content in the reaction solution is <1ppm.

2. The method according to claim 1, characterized in that, In step A, the bisphenol compound is selected from one or more of the following: 4,4'-dihydroxybiphenyl, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenylethane, 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene. And / or, in step A, the alkaline aqueous solution is an aqueous solution of sodium hydroxide or potassium hydroxide, preferably, the molar ratio of sodium hydroxide or potassium hydroxide to bisphenol compound in the alkaline aqueous solution is 2.0-3.0:1; And / or, in step A, the organic solvent is one or more of the following: C1-C6 chloro- or brominated aliphatic hydrocarbons, C4-C6 chloro- or brominated alicyclic hydrocarbons, C6-C8 aromatic hydrocarbons, and C6-C8 chloro- or brominated aromatic hydrocarbons, preferably dichloromethane or chlorobenzene.

3. The method according to claim 2, characterized in that, In process A, the alkaline aqueous solution containing bisphenol compounds is the aqueous phase, and phosgene and organic solvents form the oil phase. The concentration of bisphenol compounds in the aqueous phase is 5-30 wt%. Preferably, the mass ratio of organic solvent to aqueous phase is 0.3-0.9:1; Preferably, the concentration of phosgene in the oil phase is 3-20 wt%. Preferably, the molar ratio of phosgene to bisphenol compound is 103-115 mol%, more preferably 105-110 mol%.

4. The method according to any one of claims 1-3, characterized in that, In processes A and B, the reaction temperature is 0-70℃, preferably 10-40℃.

5. The method according to claim 4, characterized in that, In step B, the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide, and the concentration of the alkaline solution is preferably 5-40 wt%. Preferably, the molar ratio of sodium hydroxide or potassium hydroxide in the alkaline solution to the bisphenol compound in step A is 0.1-0.4:1, and more preferably 0.2-0.3:

1. And / or, the capping agent includes at least one of phenol, p-tert-butylphenol, isooctylphenol, and cumylphenol, and the molar ratio of the capping agent to the bisphenol compound in step A is 1-10 mol.

6. The method according to claim 4, characterized in that, In process C, the demulsification equipment includes at least one of the following: a transfer pump, a mixing tank, a coalescer, a centrifuge, a settling tank, and a hydrophilic filter; And / or, in step C, the catalyst includes at least one of triethylamine, tripropylamine, tributylamine, trioctylamine, N-ethylpiperidine, N-methylpiperidine, N-isopropylpiperidine, and N-n-propylpiperidine, preferably, the amount of catalyst used relative to the bisphenol compound in step A is 0.1-3 mol.

7. The method according to claim 6, characterized in that, When adding the catalyst in step C, an organic solvent is added, and the mass ratio of the added organic solvent to the aqueous phase in step A is 0.1-0.6:1; preferably, the cumulative mass ratio of the organic solvent added in steps A and C to the aqueous phase in step A is 0.4-1.5:

1.

8. The method according to claim 6 or 7, characterized in that, After adding the catalyst in step C, the reaction continues at a temperature of 20-40℃ until the content of acyl chloride groups in the reaction solution is <1ppm, at which point the reaction ends.

9. The method according to claim 8, characterized in that, After the reaction in step C is completed, the residual phenol in the oil phase of the resulting reaction solution is <10 ppm, preferably <5 ppm.

10. The polycarbonate prepared by the method according to any one of claims 1-9, characterized in that, The polycarbonate contains less than 150 ppm of hydroxyl groups and less than 3 wt% of oligomers.

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