Preparation method of polycarbonate

Abstract

The invention provides a preparation method of polycarbonate, which comprises the following steps: firstly, obtaining a photochemical product of a polyhydroxy phenol aqueous solution and phosgene reaction, and removing a water phase in the photochemical product; and then, adding a reconfigured water phase into the photochemical product oil phase, continuing the polycondensation reaction, carrying out reinforced mixing after the reaction reaches a certain degree, and finally completing the reaction and refining under the action of the catalyst by controlling the thickness of a mass transfer membrane between the organic phase and the water phase to obtain polycarbonate. According to the method, high-quality polycarbonate is obtained by controlling mass transfer.

Description

Technical Field

[0001] The invention relates to a method for preparing polycarbonate, and belongs to the technical field of polymer materials. Background Art

[0002] Polycarbonate is an engineering plastic with excellent mechanical properties. Due to its impact resistance, easy processing, light transmittance and other characteristics, it is widely used in lenses, light guide plates, automobiles and other fields. However, some polycarbonates currently have low mechanical properties and poor product quality. The main reason for this is the molecular weight distribution problem. Therefore, in order to obtain polycarbonate of better quality, it is necessary to solve the problem of too wide molecular weight distribution.

[0003] The characteristic required by the polycondensation catalyst used in the polycarbonate resin in the patent JP2002069168A is to use an amine with a pKa value of 5.5 or less. That is to say, by using a weakly alkaline amine catalyst, the end of the chloroformate molecule is not ionized, and the nucleophilic reaction can preferentially occur from the other ionized end (-ONa end). Its reaction mechanism is different from the previous polycondensation reaction in the manufacture of polycarbonate resin. Only a single reaction is carried out, and the molecular weight distribution of polycarbonate can only be controlled within 3 in the end, and the distribution is still relatively wide.

[0004] A continuous method for producing polycarbonate resin with improved molecular weight distribution is described in patent US3974126A. In this method, a mixture of chloroformate oligomer, dihydroxy compound and end-capping agent is reacted in a multiphase flow until the viscosity of the polycarbonate resin reaches 10-90% of the final viscosity of 300-4000cps. The method is characterized in that the reaction is carried out in a laminar flow until the polycarbonate reaches its final viscosity. In this method, the molecular weight distribution of aromatic polycarbonate is about 2 by adding end-capping agent to chloroformate oligomer, but the mass transfer is slow under laminar flow, and the molecular weight distribution will gradually increase.

[0005] In the patent JP1991109420A, phosgene bisphenol A is reacted in a first tubular reactor, and after adding a reaction product solution of a capping agent, the reaction product solution is allowed to flow into a tank reactor through the second tubular reactor and further react a polycarbonate oligomer to prepare a polycarbonate oligomer. In this method, a narrow molecular weight distribution of a polycarbonate resin can be obtained by adding a polycarbonate oligomer of bisphenol A for two-step polymerization, but after the second addition of bisphenol A, there is no additional process to improve the conversion rate of bisphenol A, resulting in a high residual phenol in the polycarbonate product, which affects the product quality.

[0006] In patent CN102030895B, 95-99.5 wt% of the formula amount of alkali metal hydroxide aqueous solution dissolved with bisphenol or polyphenol or their mixture is first subjected to photochemical reaction with an organic phase containing phosgene to prepare a polycarbonate oligomer emulsion, and then the remaining part of the alkali metal hydroxide aqueous solution dissolved with bisphenol or polyphenol or their mixture is subjected to coupling reaction to finally prepare a polycarbonate resin. Although the molecular weight distribution of the polycarbonate is reduced in this method, the content of various phenols in the product is relatively high, which affects the product quality.

[0007] In all usage scenarios of polycarbonate, there are high requirements for the mechanical properties of polycarbonate resin. If the molecular weight distribution is too wide, the performance of polycarbonate will be greatly affected. However, the current control methods for molecular weight distribution are mostly focused on process optimization or improvement of end-capping agents and catalysts. In fact, as a property of polycarbonate at the molecular level, molecular weight distribution lacks improvement measures from the perspective of reaction or mechanism. Summary of the invention

[0008] The invention provides a method for preparing high-quality polycarbonate, which can obtain polycarbonate with low molecular weight distribution and improve product quality.

[0009] In order to achieve the above-mentioned object, the present invention adopts a continuous two-phase interfacial polycondensation process, and the scheme is as follows:

[0010] A method for preparing high-quality polycarbonate comprises the following steps:

[0011] a) dissolving polyhydroxyphenol in an alkali metal hydroxide solution to prepare an aqueous phase A;

[0012] Mixing phosgene with an inert organic solvent to prepare oil phase A;

[0013] The molar ratio of the acyl chloride groups of phosgene in the oil phase A to the hydroxyl groups of the polyhydroxyphenol in the water phase A is 1:1 to 3:2.

[0014] b) subjecting the aqueous phase A to a photochemical reaction with the oil phase A, wherein the residence time of the photochemical reaction is 1 s to 5 min, to obtain a photochemical reaction product;

[0015] c) introducing the photochemical reaction product into an oil-water separation device, removing the water phase, and obtaining an oil phase B; at the same time, testing the concentration of residual polyhydroxyphenol in the separated water phase, and preparing an equimolar amount of water phase B with a polyhydroxyphenol concentration of 1.2-2 times that of the separated water phase;

[0016] d) mixing the oil phase B with the water phase B, adding a capping agent, and strengthening the mass transfer of the mixture to form a stable emulsion, wherein the thickness of the mass transfer membrane formed between the organic phase and the water phase of the emulsion is 0.5-1.5 μm;

[0017] e) adding a catalyst to the emulsion to continue the polycondensation reaction, finally forming a polycarbonate polycondensation product, removing the water phase, and obtaining a polycarbonate resin after post-treatment.

[0018] In step a) of the method of the present invention, as one of the preferred embodiments, the mass fraction of the polyhydroxyphenol in the aqueous phase A to the total amount of polyhydroxyphenol added is preferably 80-90%.

[0019] In step a) of the method of the present invention, the mass ratio of the oil phase A to the water phase A is between 0.7 and 1.3, preferably between 0.9 and 1.1.

[0020] In the present invention, the polyhydroxyphenols in aqueous phase A and aqueous phase B include but are not limited to bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(2-hydroxyphenyl)-3,3,5-trimethylcyclohexane, and resorcinol, preferably bisphenol A.

[0021] In step a) of the method of the present invention, the alkali metal hydroxide is potassium hydroxide or sodium hydroxide, and the mass concentration of the alkali metal hydroxide in the aqueous phase A is 5-8wt%, preferably 5.85%;

[0022] The inert organic solvent is dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, toluene, chlorobenzene or any combination thereof, preferably dichloromethane.

[0023] In step c) of the method of the present invention, the oil-water separation device is one or more of an inclined plate separator, a coalescer, and a centrifuge.

[0024] In step c) of the method of the present invention, the water content of the oil phase B is ≤0.5 wt %, preferably, the water content is ≤0.3 wt %.

[0025] In step c) of the method of the present invention, the polyhydroxyphenol concentration of the separated aqueous phase is measured by high performance liquid chromatography, and the ratio of the polyhydroxyphenol concentration of aqueous phase B to that of the separated aqueous phase is 1.2-2, preferably 1.5-2, and the molar amounts are the same.

[0026] In step c) of the method of the present invention, the pH of the prepared aqueous phase B is between 12 and 13, preferably between 12.1 and 12.6.

[0027] In step d) of the method of the present invention, the end-capping agent is one or more of phenol, p-tert-butylphenol, cumylphenol, p-cyanophenol or isooctylphenol.

[0028] In step d) of the method of the present invention, the intensified mass transfer may be carried out by using one or more of a microchannel reactor, a rotating packed bed, an impinging stream reactor, a spray tower, and a high-speed mixing homogenizer.

[0029] In step d) of the method of the present invention, the stable emulsion is of oil-in-water type, the droplet size of the stable emulsion is 5-50 μm, preferably 6-10 μm, and the thickness of the mass transfer membrane formed between the emulsified organic phase and the aqueous phase is 0.5-1.5 μm, preferably 0.8-1.1 μm.

[0030] In step d) of the method of the present invention, the thickness of the mass transfer membrane is measured by online imaging measurement technology (OMIS), wherein OMIS is mainly composed of a high-speed camera, a light source, a high-transmittance borosilicate glass tube, and a computer. When imaging the droplet mass transfer membrane, the image sensor resolution is preferably 2800fps.

[0031] In step e) of the method of the present invention, the catalyst comprises one or more of triethylamine, trialkylamine, N-ethylpiperidine, N-isopropylpiperidine or N-ethylmorpholine, preferably triethylamine or N-ethylpiperidine, and the molar ratio of the added amount of the catalyst to the total polyhydroxyphenol is preferably 1-5‰, more preferably 3‰.

[0032] In step e) of the method of the present invention, after removing the aqueous phase, the content of residual phenolic substances in the oil phase is ≤10 mg / L, and the water content in the oil phase is ≤0.3wt%. Preferably, the content of residual phenolic substances in the oil phase is ≤5 mg / L, and the water content in the oil phase is ≤0.1wt%.

[0033] In step e) of the method of the present invention, the post-treatment process removes impurities in the aqueous phase and removes the organic solvent to obtain the polycarbonate resin.

[0034] The molecular weight distribution of the polycarbonate obtained in step e) of the method of the present invention is 1.5-2.5, preferably 1.5-1.8.

[0035] The present invention first reacts polyhydroxyphenol with phosgene to obtain a photochemical reaction product. After separating the aqueous phase, the product is reacted with the reconfigured polyhydroxyphenol and the end-capping agent. During the reaction, mass transfer is continuously enhanced, and after the molecular weight increases, a catalyst is added to carry out the next stage of polycondensation. Finally, after separation and purification, a polycarbonate of excellent quality is obtained.

[0036] The beneficial effects of the present invention are:

[0037] From the related patents of polycarbonate disclosed so far, the mass transfer process of interfacial polycondensation has not attracted much attention. For the interfacial polycondensation of polycarbonate, a large number of studies have confirmed that the mass transfer rate of polycondensation is an important factor affecting the reaction rate. The present invention improves the mass transfer efficiency by controlling the thickness of the mass transfer membrane in the mass transfer process through the above-mentioned means, and obtains high-quality polycarbonate through an optimized production process. DETAILED DESCRIPTION

[0038] The following is further described by examples, but the scope of the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0039] The raw materials used in the following examples or comparative examples are:

[0040] Bisphenol A: industrial grade, homemade;

[0041] Sodium hydroxide: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0042] Phosgene: industrial grade, homemade;

[0043] Dichloromethane: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0044] p-tert-Butylphenol: analytical grade, purchased from Shanghai Tongcheng New Materials Co., Ltd.;

[0045] Triethylamine: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0046] The analysis and evaluation methods involved in the following examples or comparative examples are as follows:

[0047] The weight average molecular weight and molecular weight distribution were obtained by Agilent Technologies 1260infinity test, using RI detector, dichloromethane as mobile phase, flow rate of 1mL / min, column temperature and box temperature of 30°C.

[0048] Phenol residue was measured by Agilent Technologies 1260 The test obtained that methanol was the mobile phase and the flow rate was 1 mL / min.

[0049] The moisture content was measured using a METTLER TOLEDO Karl Fischer titrator V30S.

[0050] For the convenience of optical imaging test, the polycondensation liquid to be tested is passed through a borosilicate glass with a diameter of 100 mm. The imaging conditions of the OMIS system are: the image sensor resolution is 1920×1200@2800fps, the lens is a customized full-frame 0.5X~2X zoom lens, and the image is kept clear by debugging the light source, camera system and recording system. The thickness of the mass transfer membrane is obtained by processing the image.

[0051] Example 1

[0052] In kettle 1, 118.08 g of bisphenol A and 48.78 g of sodium hydroxide were added to prepare water phase A with a sodium phenolate concentration of 165 g / L. In kettle 2, 67 g of phosgene was dissolved in 860 g of dichloromethane to prepare oil phase A with an oil-water ratio of 1.05.

[0053] The water phase A and the oil phase A are pumped to a static mixer for 1 second for premixing, and then sent to a reactor composed of a static mixer for photochemical reaction. After 1 minute, the photochemical reaction liquid is removed from the water phase through a coalescer to obtain an oil phase B. After testing the water content ≤0.3wt%, the residual bisphenol A concentration in the separated water phase is tested to be 0.097mol / L. Bisphenol A and sodium hydroxide are configured to obtain a water phase B with an equal molar amount of bisphenol A and a concentration of 0.148mol / L, and the pH is controlled at 12.25. The water phase B is mixed with the oil phase B, and 4.41g of p-tert-butylphenol is introduced at the same time, and then enters a high-speed mixing homogenizer. The speed of the high-speed mixing homogenizer is 8000rpm. After staying in the high-speed mixing homogenizer for 1 minute, it enters a high borosilicate glass tube to test the liquid film thickness, and 0.178g of triethylamine is introduced at the outlet. The reaction ends after continuing the reaction for 60 minutes. After removing the water phase, the test phenol residue is 5.0mg / L and the water content is 0.05wt%. After separation and purification, polycarbonate resin is obtained.

[0054] The test data is shown in the table below.

[0055] Example 2

[0056] In kettle 1, 117.76 g of bisphenol A and 48.64 g of sodium hydroxide were added to prepare water phase A with a sodium phenolate concentration of 165 g / L. In kettle 2, 67 g of phosgene was dissolved in 860 g of dichloromethane to prepare oil phase A with an oil-water ratio of 1.05.

[0057] The water phase A and the oil phase A are pumped to a static mixer for 1 second for premixing, and then sent to a reactor composed of a static mixer for photochemical reaction. After 1 minute, the photochemical reaction liquid is removed from the water phase through a coalescer to obtain an oil phase B. After testing the water content ≤0.3wt%, the residual bisphenol A concentration in the separated water phase is tested to be 0.108mol / L. Bisphenol A and sodium hydroxide are configured to obtain a water phase B with an equal molar amount of bisphenol A and a concentration of 0.162mol / L, and the pH is controlled at 12.19. The water phase B is mixed with the oil phase B, and 4.45g of p-tert-butylphenol is introduced at the same time, and then enters a high-speed mixing homogenizer. The speed of the high-speed mixing homogenizer is 8000rpm. After staying in the high-speed mixing homogenizer for 1 minute, it enters a high borosilicate glass tube to test the liquid film thickness, and 0.18g of triethylamine is introduced at the outlet. The reaction ends after continuing the reaction for 60 minutes. After removing the water phase, the test phenol residue is 4.2mg / L, and the water content is 0.07wt%. After separation and purification, polycarbonate resin is obtained.

[0058] The test data is shown in the table below.

[0059] Example 3

[0060] In kettle 1, 117.06 g of bisphenol A and 48.35 g of sodium hydroxide were added to prepare water phase A with a sodium phenolate concentration of 165 g / L. In kettle 2, 67 g of phosgene was dissolved in 860 g of dichloromethane to prepare oil phase A with an oil-water ratio of 1.06.

[0061] The water phase A and the oil phase A are pumped to a static mixer for 1 second for premixing, and then sent to a reactor composed of a static mixer for photochemical reaction. After 1 minute, the photochemical reaction liquid is removed from the water phase through a coalescer to obtain an oil phase B. After testing the water content ≤0.3wt%, the residual bisphenol A concentration in the separated water phase is tested to be 0.099mol / L. Bisphenol A and sodium hydroxide are configured to obtain a water phase B with an equal molar amount of bisphenol A and a concentration of 0.148mol / L, and the pH is controlled at 12.38. The water phase B is mixed with the oil phase B, and 4.38g of p-tert-butylphenol is introduced at the same time, and then enters a high-speed mixing homogenizer. The speed of the high-speed mixing homogenizer is 8000rpm. After staying in the high-speed mixing homogenizer for 1 minute, it enters a high borosilicate glass tube to test the liquid film thickness, and 0.177g of triethylamine is introduced at the outlet. The reaction ends after continuing the reaction for 60 minutes. After removing the water phase, the test phenol residue is 4.0mg / L, and the water content is 0.07wt%. After separation and purification, polycarbonate resin is obtained.

[0062] The test data is shown in the table below.

[0063] Example 4

[0064] In kettle 1, 119.42 g of bisphenol A and 49.32 g of sodium hydroxide were added to prepare water phase A with a sodium phenolate concentration of 165 g / L. In kettle 2, 67 g of phosgene was dissolved in 860 g of dichloromethane to prepare oil phase A with an oil-water ratio of 1.04.

[0065] The water phase A and the oil phase A are pumped to a static mixer for 1 second for premixing, and then sent to a reactor composed of a static mixer for photochemical reaction. After 1 minute, the photochemical reaction liquid is removed from the water phase through a coalescer to obtain an oil phase B. After testing the water content ≤0.3wt%, the residual bisphenol A concentration in the separated water phase is tested to be 0.089mol / L. Bisphenol A and sodium hydroxide are configured to obtain a water phase B with an equal molar amount of bisphenol A and a concentration of 0.143mol / L, and the pH is controlled at 12.22. The water phase B is mixed with the oil phase B, and 4.41g of p-tert-butylphenol is introduced at the same time, and then enters a high-speed mixing homogenizer. The speed of the high-speed mixing homogenizer is 8000rpm. After staying in the high-speed mixing homogenizer for 1 minute, it enters a high borosilicate glass tube to test the liquid film thickness, and 0.178g of triethylamine is introduced at the outlet. The reaction ends after continuing the reaction for 60 minutes. After removing the water phase, the test phenol residue is 3.0mg / L and the water content is 0.08wt%. After separation and purification, polycarbonate resin is obtained.

[0066] The test data is shown in the table below.

[0067] Comparative Example 1

[0068] In kettle 1, 116.06 g of bisphenol A and 47.94 g of sodium hydroxide were added to prepare water phase A with a sodium phenolate concentration of 165 g / L. In kettle 2, 67 g of phosgene was dissolved in 860 g of dichloromethane to prepare oil phase A with an oil-water ratio of 1.07.

[0069] The aqueous phase A and the oil phase A are pumped to a static mixer for 1 second for premixing, and then sent to a reactor composed of a static mixer for photochemical reaction. After 1 minute, the photochemical reaction liquid is removed from the aqueous phase by a coalescer to obtain an oil phase B. After testing the water content ≤0.3wt%, the residual bisphenol A concentration in the separated aqueous phase is tested to be 0.099mol / L. Bisphenol A and sodium hydroxide are configured with equimolar amounts, and the aqueous phase B with a bisphenol A concentration of 0.158mol / L is controlled at pH 12.27. The aqueous phase B is mixed with the oil phase B, and 4.39g of p-tert-butylphenol is introduced at the same time. After entering the static mixer and mixing for 1min, the liquid film thickness is tested in a high borosilicate glass tube. 0.175g of triethylamine is introduced, and the reaction is terminated after continuing the reaction for 60min. After removing the aqueous phase, the test phenol residue is 86mg / L, and the water content is 0.33wt%. After separation and purification, a polycarbonate resin is obtained.

[0070] Comparative Example 2

[0071] 132.83g bisphenol A, water and 54.87g sodium hydroxide were added to a mixing tank, mixed and dissolved to form a water phase with a sodium phenolate concentration of 165g / L; 67g liquid phosgene and 860g dichloromethane were added to another mixing tank, and mixed to form an organic phase. The sodium phenolate salt phase and the organic phase, which accounted for 99% of the total amount of the sodium phenolate salt phase, were respectively injected into a photochemical reactor composed of a static mixer, and after staying for 1min, they were entered into a coupling reactor also composed of a static mixer. At the same time, the remaining sodium phenolate salt phase, 4.41g p-tert-butylphenol and 0.178g triethylamine were injected into the reactor, and the reaction was carried out for 60min. After removing the water phase, the test phenol residue was 94mg / L and the water content was 0.47wt%. After separation and purification, a polycarbonate resin was obtained. The molecular weight distribution of the final polycarbonate resin was 1.81 by GPC analysis.

[0072] The test data is shown in the table below.

[0073] Table. Summary of experimental data

[0074]

[0075] By comparing the above data, it can be seen that the polycarbonate preparation method of the present invention can obtain a polymer with a narrow molecular weight distribution and excellent product quality. The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polycarbonate, The following steps are involved: a) dissolving polyhydroxyphenol in an alkali metal hydroxide solution to prepare an aqueous phase A; Mixing phosgene with an inert organic solvent to prepare oil phase A; b) performing a photochemical reaction on the aqueous phase A and the oil phase A to obtain a photochemical reaction product; preferably, the residence time of the photochemical reaction is 1 s-5 min; c) introducing the photochemical reaction product into an oil-water separation device, removing the water phase, and obtaining an oil phase B; at the same time, testing the concentration of residual polyhydroxyphenol in the separated water phase, and preparing an equimolar amount of water phase B with a polyhydroxyphenol concentration of 1.2-2 times that of the separated water phase; d) mixing the oil phase B with the water phase B, adding a capping agent, and strengthening the mass transfer of the mixture to form a stable emulsion; e) adding a catalyst to the emulsion to continue the polycondensation reaction, finally forming a polycarbonate polycondensation product, removing the water phase, and obtaining a polycarbonate resin after post-treatment.

2. The method according to claim 1, It is characterized in that In step a), the molar ratio of the acyl chloride groups of phosgene in the oil phase A to the hydroxyl groups of the polyhydroxyphenol in the water phase A is 1:1 to 3:2; Preferably, the mass ratio of oil phase A to water phase A is between 0.7 and 1.

3.

3. The method according to claim 1, It is characterized in that The polyhydroxyphenol includes at least one of bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(2-hydroxyphenyl)-3,3,5-trimethylcyclohexane, and resorcinol, preferably bisphenol A; Preferably, the mass fraction of the polyhydroxyphenol in the aqueous phase A accounts for 80-90% of the total added polyhydroxyphenol.

4. The method according to claim 1, It is characterized in that In step a), the alkali metal hydroxide is potassium hydroxide or sodium hydroxide, and the mass concentration of the alkali metal hydroxide in the aqueous phase A is 5-8wt%.

5. The method according to claim 1, It is characterized in that In step c), the water content of the oil phase B is ≤0.5 wt %, preferably, the water content is ≤0.3 wt %.

6. The method according to claim 1, It is characterized in that In step c), the pH of the prepared aqueous phase B is between 12-13.

7. The method according to claim 1, It is characterized in that In step d), the end-capping agent is one or more of phenol, p-tert-butylphenol, cumylphenol, p-cyanophenol or isooctylphenol.

8. The method according to claim 1, It is characterized in that In step d), the thickness of the mass transfer membrane formed between the organic phase and the aqueous phase of the emulsion is 0.5-1.5 μm, preferably 0.8-1.1 μm.

9. The method according to claim 1, It is characterized in that In step e), the catalyst comprises one or more of triethylamine, trialkylamine, N-ethylpiperidine, N-isopropylpiperidine or N-ethylmorpholine, preferably triethylamine or N-ethylpiperidine, and the molar ratio of the added amount of the catalyst to the total polyhydroxyphenol is preferably 1-5‰, more preferably 3‰.

10. The method according to claim 1, It is characterized in that In step e), after removing the water phase, the content of residual phenolic substances in the oil phase is ≤10 mg / L, and the water content in the oil phase is ≤0.3 wt %. Preferably, the content of residual phenolic substances in the oil phase is ≤5mg / L, water content in oil phase ≤0.1wt%; Preferably, the molecular weight distribution of the obtained polycarbonate is 1.5-2.5.

Images