Production process of polycarbonate

Abstract

The invention discloses a production process of polycarbonate. The production process comprises the following steps: S1, carrying out prepolymerization reaction on a water-phase solution formed by mixing bisphenol A and sodium hydroxide and a liquid phosgene and dichloromethane solution; s2, carrying out polymerization reaction on the obtained prepolymerization reaction solution under the action of a catalyst to obtain a mixed solution of polycarbonate and water; s3, carrying out water-oil separation on the mixed solution obtained in the step S2 to obtain a polycarbonate solution; and S4, the polycarbonate solution in the step S3 is subjected to reduced pressure flash evaporation, high-concentration polycarbonate is obtained, and the steps S1 to S3 are carried out at high temperature and high pressure. According to the production process of the polycarbonate, the reaction time is shorter, the water-oil separation effect is better, and the obtained polycarbonate has narrower molecular weight distribution and better ground color heat resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material synthesis, and particularly relates to polycarbonate and a production process thereof. Background Art

[0002] Polycarbonate (PC), a high-performance engineering plastic, is widely used in optical materials, electronic appliances, medical devices, and automotive fields due to its excellent transparency, impact resistance, heat resistance, and chemical corrosion resistance. Currently, the industrial production of polycarbonate mainly adopts two processes: phosgene method (interfacial polycondensation) and ester exchange method (melt polycondensation). Among them, the phosgene method uses bisphenol A (BPA) and phosgene (COCl2) as raw materials to produce high molecular weight polymers through interfacial polycondensation reaction. This process has the advantages of strong molecular weight controllability and high product purity, making it particularly suitable for the production of high-end optical-grade products.

[0003] The molecular weight distribution (MWD) of polycarbonate is one of its key performance indicators, usually expressed as the molecular weight distribution coefficient (D = Mw / M n , the ratio of weight-average molecular weight to number-average molecular weight). The narrower the molecular weight distribution (the smaller the D value), the more uniform the polymer chain length, and the better the mechanical properties and processing properties of the material. For example, optical-grade polycarbonate requires a molecular weight distribution coefficient D<2.3 to ensure the stability of its indicators such as transmittance and impact resistance. However, in traditional phosgene production, due to the complex control of reaction conditions and a wide molecular weight distribution (D value is often greater than 2.5), the content of low-molecular-weight components in the product is high, affecting the material's crack resistance and long-term performance. At the same time, the molecular weight distribution will also affect the base color and heat resistance of polycarbonate, affecting its application in optics and other fields.

[0004] In the prior art, CN117801252A discloses a method for producing polycarbonate, which controls the proportion of aromatic dihydroxy compounds in a monodissociated state in an aqueous solution and performs polymerization and polycondensation reactions in a reactor in two steps, thereby achieving a narrowing of the molecular weight distribution to a certain extent. However, the reaction efficiency is low and the overall reaction time is long. CN107207718B discloses an improved method for preparing a heat-resistant polycarbonate comprising 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and bisphenol A. The method reduces the melting point of the monomer mixture by adding a monohydroxyaryl compound to the raw material mixture, further slowing down the polycondensation reaction in the early stage, thereby improving the heat resistance of the polycarbonate. However, the molecular weight distribution is not greatly improved, and the molecular weight of the prepared polycarbonate fluctuates greatly.

[0005] Therefore, developing a safe, efficient and molecular weight distribution controllable polycarbonate production method has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] In response to the above problems, the present invention proposes a production process for phosgenated polycarbonate by optimizing the molecular weight distribution by increasing the temperature and pressure during the reaction stage. By precisely controlling the reaction temperature and pressure, the reaction uniformity and efficiency are improved, and the polymer chain length distribution is made more concentrated, thereby stably obtaining a polycarbonate product with a molecular weight distribution coefficient D<1.8.

[0007] In order to achieve the above object of the invention, the technical solution of the present invention is as follows:

[0008] A production process for polycarbonate comprises the following steps:

[0009] S1, mixing an aqueous solution of bisphenol A and an alkali metal hydroxide with an oily solution of liquid phosgene and a halogenated hydrocarbon to perform a prepolymerization reaction;

[0010] S2, the prepolymerization liquid obtained in step S1 undergoes polymerization reaction under the action of a catalyst to obtain a mixed liquid of polycarbonate and water;

[0011] S3, separating the mixed solution obtained in step S2 into water and oil to obtain a polycarbonate solution;

[0012] S4, flash evaporating the polycarbonate solution in step S3 under negative pressure to obtain high-concentration polycarbonate;

[0013] Among them, steps S1-S3 are all carried out under high temperature and high pressure conditions with a reaction temperature of above 70°C and a reaction pressure of above 3.0 barG.

[0014] In step S1, the mass concentration of bisphenol A in the aqueous solution is 10%-15%, for example, 10%, 11%, 12%, 13%, 14%, 15%, etc.;

[0015] In step S1, the alkali metal hydroxide includes one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide, preferably sodium hydroxide; preferably, the mass concentration of the alkali metal hydroxide is 2%-5%, for example, 2%, 3%, 4%, 5%, etc.;

[0016] In step S1, the molar ratio of bisphenol A to phosgene is 1:(1.2-1.5), for example, 1:1.2, 1:1.3, 1:1.4, 1:1.5, etc.;

[0017] Preferably, the halogenated hydrocarbon is one or more of dichloromethane, chloroform, and dichloroethane, preferably dichloromethane;

[0018] More preferably, the amount of halogenated hydrocarbon added is 75%-125% of the mass of the aqueous solution, for example, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, etc.

[0019] As a preferred embodiment of the present invention, in step S1, the reaction conditions of the prepolymerization reaction are: reaction temperature 70°C-90°C, for example, 75°C, 80°C, 85°C, etc., reaction pressure 3.0-5.0 barG, for example, 3.5 barG, 4.0 barG, 4.5 barG, etc. Preferably, the reactor is a tubular reactor, and the reaction residence time is 3-6 seconds, for example, 4 seconds, 5 seconds, etc.

[0020] As a preferred embodiment of the present invention, in step S2, the catalyst is an ammonium or ammonium salt catalyst, preferably triethylamine or benzyltrimethylammonium chloride, particularly preferably triethylamine. Preferably, the amount of the catalyst is 0.01%-0.03% by mass of bisphenol A, for example 0.02%.

[0021] As a preferred embodiment of the present invention, in step S2, the reaction conditions of the polymerization reaction are: reaction temperature 75°C-95°C, for example, 75°C, 80°C, 85°C, 90°C, etc., reaction pressure 3.0-5.0 barG, for example, 3.5 barG, 4.0 barG, 4.5 barG, etc., reaction time 5-10 min, for example, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0022] As a preferred embodiment of the present invention, in step S3, the separation equipment used for the water-oil separation is one or more of a centrifuge, an inclined plate separator, and a coalescer.

[0023] As a preferred embodiment of the present invention, in step S3, the operating temperature of the water-oil separation is 75°C-95°C, for example, 75°C, 80°C, 85°C, 90°C, etc., and the operating pressure is 3.0-5.0 barG, for example, 3.5 barG, 4.0 barG, 4.5 barG, etc.

[0024] As a preferred embodiment of the present invention, the viscosity of the polycarbonate solution separated in step S3 at room temperature is 10-30 cP, for example, 12 cP, 15 cP, 20 cP, 25 cP, 28 cP, etc., and the water content in the oil phase after separation is 800-1500 ppm, for example, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, etc.

[0025] As a preferred embodiment of the present invention, the operating pressure in step S4 is 50-80 kPaG, for example, 55 kPaG, 60 kPaG, 65 kPaG, 70 kPaG, 75 kPaG, 80 kPaG, etc., and the mass concentration of polycarbonate in the polycarbonate emulsion after flash evaporation is 25%-40%, for example, 30%, 32%, 35%, etc.

[0026] In another aspect of the present invention, the polycarbonate synthesized using the production process of the present invention has a molecular weight distribution of less than 1.8, a base color value YI < 1.5, and a heat resistance ΔYI < 0.2.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The production process of the present invention improves the temperature and pressure during the polycarbonate reaction process, thereby improving the condensation reaction efficiency and narrowing the molecular weight distribution of the polycarbonate. At the same time, it reduces the viscosity of the subsequent agglomeration and separation unit to improve the separation efficiency, ultimately achieving the effect of optimizing the base color and heat resistance of the polycarbonate.

[0029] The method of the present invention not only inherits the advantage of the traditional phosgene method in terms of strong molecular weight controllability, but also breaks through the bottleneck of molecular weight distribution control through process innovation, thus providing a new technical solution for the large-scale production of high-performance polycarbonate. DETAILED DESCRIPTION

[0030] In order to facilitate understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0031] Main raw material sources

[0032] Bisphenol A: industrial grade, Wanhua Chemical;

[0033] Phosgene: industrial grade, Wanhua Chemical;

[0034] Triethylamine: analytical grade, purchased from Tianjin Kemiou Technology Co., Ltd.

[0035] 4-tert-Butylphenol: analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0036] Dichloromethane: analytical grade, purchased from Beijing Yinuokai Chemical Reagent Co., Ltd.;

[0037] Pure water: industrial grade, Wanhua Chemical;

[0038] Sodium hydroxide: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.

[0039] The main equipment information used in the following embodiments of the present invention is as follows:

[0040] Tubular reactor, purchased from Sulzer;

[0041] The kettle polycondensation reactor was purchased from Yantai Keli;

[0042] Water-oil separation coalescer: purchased from Franken Company;

[0043] Centrifuge, purchased from Hitachi;

[0044] Flash evaporator was purchased from Yantai Keli.

[0045] Main test methods:

[0046] The weight-average molecular weight and molecular weight distribution were tested by gel chromatography. The testing equipment model was 1260 Infinity, manufactured by Agilent Technologies, the chromatographic column model was Plgel 5um MIXED-C300*7.5mm, and the mobile phase was dichloromethane.

[0047] The viscosity test was performed using a viscometer, model DV2TLVTJ0, manufactured by Brookfield, USA.

[0048] The water content of the reaction solution was measured using a moisture meter, the equipment model was 875KF, and the manufacturer was Metrohm.

[0049] The concentration of polycarbonate emulsion was tested by evaporation method.

[0050] Example 1

[0051] S1. An aqueous solution containing 10% bisphenol A by mass and 2% sodium hydroxide by mass was introduced into a tubular reactor at a flow rate of 152 g / min; liquid phosgene was introduced into the tubular reactor at a flow rate of 7.9 g / min; and chloroform was introduced into the tubular reactor at a flow rate of 114 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 70°C and the reaction pressure was controlled at 3 bar by electric heating.

[0052] S2. The reaction solution obtained in S1 was introduced into a tank reactor. At the same time, a 3% benzyltrimethylammonium chloride solution was introduced into the tank reactor at a flow rate of 0.152 g / min for polycondensation reaction. The reaction temperature was controlled at 75°C and the reaction pressure was 3 bar. The total reaction time of S1 and S2 was controlled at 8 min.

[0053] S3. The reaction liquid obtained in S2 was passed into a coalescer for water-oil separation. The temperature was controlled at 75° C. and the pressure was 3 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 30 cP and a water content of 1298 ppm.

[0054] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 50 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 27.5%.

[0055] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0056] Example 2

[0057] S1. An aqueous solution containing 12.5% bisphenol A and 3% potassium hydroxide was introduced into a tubular reactor at a rate of 122 g / min; liquid phosgene was introduced into the tubular reactor at a rate of 8.6 g / min; and ethylene dichloride was introduced into the tubular reactor at a rate of 152 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 80°C and the reaction pressure was controlled at 4 bar by electric heating.

[0058] S2. The reaction solution obtained in S1 was introduced into a tank reactor, and 3% triethylamine solution was introduced into the tank reactor at a flow rate of 0.1 g / min for polycondensation reaction. The reaction temperature was controlled at 85°C and the reaction pressure was 4 bar. The total reaction time of S1 and S2 was controlled at 6 min.

[0059] S3. The reaction solution obtained in S2 was passed into a centrifuge for water-oil separation. The temperature was controlled at 85° C. and the pressure was 4 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 22 cP and a water content of 1097 ppm.

[0060] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 70 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 31.3%.

[0061] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0062] Example 3

[0063] S1. An aqueous solution containing 15% bisphenol A by weight and 5% lithium hydroxide was introduced into a tubular reactor at a flow rate of 101 g / min; liquid phosgene was introduced into the tubular reactor at a flow rate of 9.9 g / min; and dichloromethane was introduced into the tubular reactor at a flow rate of 100 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 90°C and the reaction pressure was controlled at 5 bar by electric heating.

[0064] S2. The reaction solution obtained in S1 was introduced into a tank reactor, and 3% triethylamine solution was introduced into the tank reactor at a flow rate of 0.05 g / min for polycondensation reaction. The reaction temperature was controlled at 95°C and the reaction pressure was 5 bar. The total reaction time of S1 and S2 was controlled at 5 min.

[0065] S3. The reaction liquid obtained in S2 was passed into an inclined plate separator for water-oil separation. The temperature was controlled at 95° C. and the pressure was 5 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 10 cP and a water content of 803 ppm.

[0066] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 80 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 38.4%.

[0067] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0068] Comparative Example 1

[0069] S1. An aqueous solution containing 10% bisphenol A by mass and 2% sodium hydroxide by mass was introduced into a tubular reactor at a flow rate of 152 g / min; liquid phosgene was introduced into the tubular reactor at a flow rate of 7.9 g / min; and chloroform was introduced into the tubular reactor at a flow rate of 114 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 30°C and the reaction pressure was controlled at 1 bar by electric heating.

[0070] S2. The reaction solution obtained in S1 was introduced into a tank reactor. At the same time, a 3% benzyltrimethylammonium chloride solution was introduced into the tank reactor at a flow rate of 0.152 g / min for polycondensation reaction. The reaction temperature was controlled at 75°C and the reaction pressure was 3 bar. The total reaction time of S1 and S2 was controlled at 8 min.

[0071] S3. The reaction liquid obtained in S2 was passed into a coalescer for water-oil separation. The temperature was controlled at 75° C. and the pressure was 3 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 41 cP and a water content of 2289 ppm.

[0072] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 50 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 21.4%.

[0073] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0074] Comparative Example 2

[0075] S1. An aqueous solution containing 10% bisphenol A by mass and 2% sodium hydroxide by mass was introduced into a tubular reactor at a flow rate of 152 g / min; liquid phosgene was introduced into the tubular reactor at a flow rate of 7.9 g / min; and chloroform was introduced into the tubular reactor at a flow rate of 114 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 70°C and the reaction pressure was controlled at 3 bar by electric heating.

[0076] S2. The reaction solution obtained in S1 was introduced into a tank reactor, and 3% benzyltrimethylammonium chloride solution was introduced into the tank reactor at a flow rate of 0.152 g / min for polycondensation reaction. The reaction temperature was controlled at 35°C and the reaction pressure was 1 bar. The total reaction time of S1 and S2 was controlled at 8 min.

[0077] S3. The reaction liquid obtained in S2 was passed into a coalescer for water-oil separation. The temperature was controlled at 75° C. and the pressure was 3 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 121 cP and a water content of 4198 ppm.

[0078] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 50 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 17.6%.

[0079] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0080] Comparative Example 3

[0081] S1. An aqueous solution containing 10% bisphenol A by mass and 2% sodium hydroxide by mass was introduced into a tubular reactor at a flow rate of 152 g / min; liquid phosgene was introduced into the tubular reactor at a flow rate of 7.9 g / min; and chloroform was introduced into the tubular reactor at a flow rate of 114 g / min to carry out a prepolymerization reaction. The reaction temperature was controlled at 30°C and the reaction pressure was controlled at 1 bar by electric heating.

[0082] S2. The reaction solution obtained in S1 was introduced into a tank reactor, and 3% benzyltrimethylammonium chloride solution was introduced into the tank reactor at a flow rate of 0.152 g / min for polycondensation reaction. The reaction temperature was controlled at 35°C and the reaction pressure was 1 bar. The total reaction time of S1 and S2 was controlled at 8 min.

[0083] S3. The reaction liquid obtained in S2 was passed into a coalescer for water-oil separation. The temperature was controlled at 75° C. and the pressure was 3 bar during the separation process. The polycarbonate emulsion obtained after separation had a viscosity of 132 cP and a water content of 4232 ppm.

[0084] S4. The PC emulsion obtained in S3 was introduced into a flash evaporator, and the flash pressure was controlled at 50 kPaG. The polycarbonate concentration of the material after flash evaporation was measured to be 16.3%.

[0085] The material obtained in step S4 is dried to obtain polycarbonate powder, and the molecular weight distribution and base color heat resistance are tested.

[0086] The specific test results are shown in Table 1:

[0087] Table 1

[0088] Molecular weight distribution Background color YI Heat-resistant ΔYI Example 1 1.78 1.34 0.08 Example 2 1.65 1.45 0.12 Example 3 1.63 1.37 0.17 Comparative Example 1 2.64 1.87 0.48 Comparative Example 2 2.43 1.64 0.41 Comparative Example 3 2.15 1.55 0.32

[0089] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A production process for polycarbonate, characterized in that: The following steps are involved: S1, mixing an aqueous solution of bisphenol A and an alkali metal hydroxide with an oily solution of liquid phosgene and a halogenated hydrocarbon to perform a prepolymerization reaction; S2, the prepolymerization liquid obtained in step S1 undergoes polymerization reaction under the action of a catalyst to obtain a mixed liquid of polycarbonate and water; S3, separating the mixed solution obtained in step S2 into water and oil to obtain a polycarbonate solution; S4, flash evaporating the polycarbonate solution in step S3 under negative pressure to obtain high-concentration polycarbonate; Among them, steps S1-S3 are all carried out under high temperature and high pressure conditions with a reaction temperature of above 70°C and a reaction pressure of above 3.0 barG.

2. The production process of polycarbonate according to claim 1, characterized in that: In step S1, the mass concentration of bisphenol A in the aqueous solution is 10%-15%, and / or The alkali metal hydroxide includes one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide, preferably sodium hydroxide; preferably, the mass concentration of the alkali metal hydroxide is 2%-5%, and / or The molar ratio of bisphenol A to phosgene is 1:(1.2-1.5); Preferably, the halogenated hydrocarbon is one or more of dichloromethane, chloroform, and dichloroethane, preferably dichloromethane; More preferably, the amount of halogenated hydrocarbon added is 75%-125% of the mass of the aqueous solution.

3. The production process of polycarbonate according to claim 1 or 2, characterized in that: In step S1, the reaction conditions of the prepolymerization reaction are: reaction temperature 70°C-90°C, reaction pressure 3.0-5.0 barG; Preferably, the reactor is a tubular reactor and the reaction residence time is 3-6 seconds.

4. The process for producing polycarbonate according to claim 1 or 2, wherein: In step S2, the catalyst is an ammonium or ammonium salt catalyst, preferably triethylamine or benzyltrimethylammonium chloride, and particularly preferably triethylamine; Preferably, the amount of the catalyst used is 0.01%-0.03% by mass of bisphenol A.

5. The production process of polycarbonate according to claim 4, characterized in that: In step S2, the reaction conditions of the polymerization reaction are: reaction temperature 75° C.-95° C., reaction pressure 3.0-5.0 barG, and reaction time 5-10 min.

6. The process for producing polycarbonate according to any one of claims 1 to 5, characterized in that: In step S3, the separation equipment used for the water-oil separation is one or more of a centrifuge, an inclined plate separator, and a coalescer.

7. The process for producing polycarbonate according to claim 6, wherein: In step S3, the operating temperature of the water-oil separation is 75° C.-95° C., and the operating pressure is 3.0-5.0 barG.

8. The process for producing polycarbonate according to claim 7, wherein: The viscosity of the polycarbonate solution separated in step S3 at room temperature is 10-30 cP, and the water content in the oil phase after separation is 800-1500 ppm.

9. The process for producing polycarbonate according to any one of claims 1 to 8, characterized in that: The operating pressure in step S4 is 50-80 kPaG, and the mass concentration of polycarbonate in the polycarbonate emulsion after flash evaporation is 25%-40%.

10. The polycarbonate prepared by the polycarbonate production process according to any one of claims 1 to 9, characterized in that: The polycarbonate has a molecular weight distribution of less than 1.8, a base color value YI < 1.5, and a heat resistance ΔYI < 0.2.