Preparation method of polycarbonate

Abstract

The invention provides a preparation method of polycarbonate. The preparation method comprises the following steps: a, adding alkali liquor and an end-capping reagent into a photochemical reaction solution; b, enabling the material obtained in the step a to sequentially pass through first mixing equipment and second mixing equipment; and c, conveying the material treated in the step b into a polycondensation reaction kettle, and adding a catalyst for polymerization. The unit volume reaction liquid input energy ratio of the first mixing equipment to the second mixing equipment is controlled to be 5: 1-1: 2; the terminal hydroxyl group in the polycarbonate polymer in the reaction liquid at the outlets of the first mixing equipment and the second mixing equipment meets the condition that the ratio of OH1 (the content of the terminal hydroxyl group in the polymer at the outlet of the first mixing equipment) to OH2 (the content of the terminal hydroxyl group in the polymer at the outlet of the second mixing equipment) is 1.05-1.50. The polycarbonate product prepared by the process has the characteristics of narrow molecular weight distribution, less phenol residue and low yellowing index after injection molding.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer synthesis, and particularly relates to a preparation method of polycarbonate. BACKGROUND

[0002] Polycarbonate is an important engineering plastic, which has excellent heat resistance, transparency, mechanical strength and electrical insulation, and is widely used in the fields of automobile, electronics, building, etc.

[0003] At present, the application of engineering plastics in the fields of electronics, automobiles, etc. is increasing, especially in the fields of automobile lighting and optical lens, and the requirements for the quality of raw materials are increasingly stringent. For polycarbonate materials, the optical transparency is not only related to the impurity content of the materials, but also the structural characteristics of the materials are a basic parameter affecting the transparency. Especially in the lighting field, under the continuous action of light radiation, the optical properties of the materials will gradually decrease, and due to the temperature rise and long-term radiation, the products will gradually turn yellow, which not only affects the appearance, but also reduces the lighting effect.

[0004] Polycarbonate produced by interfacial phosgene method has unique advantages in optical properties due to the polymerization process, but polycarbonate prepared by interfacial polycondensation method may contain acid-binding agent and sodium ions, potassium ions derived from catalyst, in addition to organic chlorine compounds from solvents and ammonium ions from added impurities. Deionized water is often used to wash polycarbonate solution to remove ionic impurities, and a method of extracting oligomers using polar organic solvents is also used, such as Japanese patent JP1994078429B2 which describes a method of extracting halogenated solvents, monomers, oligomer impurities from polycarbonate using acetone, but the method is complex and only relies on post-processing to improve the structure and performance of polycarbonate is limited.

[0005] The structure of interfacial phosgene polycarbonate is the determining factor of its performance, and the main parameters include molecular weight distribution width and end hydroxyl content. Polycarbonate resin with too wide molecular weight distribution is more prone to chain scission degradation during melt extrusion and shearing due to the increase of high polymer or oligomer content in the bulk. The hydroxyl content is one of the active sites, and once the proportion is not effectively controlled, it will also cause extrusion degradation problem.

[0006] The addition of catalyst in the interfacial polycondensation method for producing polycarbonate will accelerate the polycondensation reaction, and the timing and mixing conditions of the addition of catalyst have important influence on the product structure of polycarbonate such as molecular weight distribution width. How to control the polycondensation reaction before and after the addition of catalyst is the key to the whole interfacial polycondensation production process. The present application takes this as the starting point, adjusts the product structure by controlling the reaction process, and realizes the preparation of high-quality polycarbonate. SUMMARY

[0007] The present application provides a polycarbonate and a preparation method thereof, and the polycarbonate product prepared by using the process has the characteristics of narrow molecular weight distribution, less phenol residue, and low yellowing index after injection molding.

[0008] The present application provides a preparation method of polycarbonate, comprising the following steps:

[0009] a. adding alkali solution and capping agent to the photochemical reaction liquid;

[0010] b. passing the material obtained in step a. through the first mixing device and the second mixing device in sequence;

[0011] c. feeding the material treated in step b. to the second reactor to add catalyst for polycondensation reaction.

[0012] In the synthesis process of the polycarbonate as described above, the photochemical reaction liquid in step a. is the photochemical reaction liquid obtained by mixing halogenated hydrocarbon solution of phosgene and alkaline aqueous solution of bisphenol A and then stirring to carry out interfacial polycondensation reaction.

[0013] The halogenated hydrocarbon includes one or more of dichloromethane, chloroform, and dichloroethane, and is preferably dichloromethane;

[0014] The alkaline aqueous solution of bisphenol A is an aqueous solution of bisphenol A and alkali metal hydroxide, and the alkali metal hydroxide includes one or more of potassium hydroxide, sodium hydroxide, and lithium hydroxide, and is preferably sodium hydroxide and / or potassium hydroxide.

[0015] The concentration of bisphenol A in the alkaline aqueous solution of bisphenol A is generally 10-20 wt%, preferably 13-18 wt%, and the concentration of alkali metal hydroxide is preferably 4.5-6.5 wt%.

[0016] The alkaline aqueous solution of bisphenol A contains a certain amount of reducing agent, which is generally a sulfite substance, preferably sodium hydrosulfite, and the addition amount of sodium hydrosulfite is preferably 0.5-9 wt‰ of the mass of bisphenol A.

[0017] The photochemical reaction liquid is composed of an organic phase and an aqueous phase, and its preparation method refers to the conventional synthesis method of interfacial phosgene method (such as CN118056857A), generally the halogenated hydrocarbon solution and the alkaline aqueous solution of bisphenol A are continuously introduced into the reactor in a certain proportion in advance, then a certain amount of phosgene is introduced, and after the reaction time reaches, the photochemical liquid is discharged to the subsequent process.

[0018] The molar ratio of bisphenol A and phosgene is 1:(1-1.5), preferably 1:(1.05-1.3). In the preparation of the photochemical reaction solution, the temperature is controlled at 10-40℃, preferably 16-40℃, the pressure is normal pressure, and the reaction residence time is 20-80 min. The above reaction conditions can be carried out according to the prior art.

[0019] The organic phase in the photochemical reaction solution contains oligomers with a weight average molecular weight of 1000-3000 g / mol and a solvent halogenated hydrocarbon; the aqueous phase contains inorganic salts, a small amount of bisphenol A sodium salt, sodium hydroxide, etc., and the pH of the aqueous phase is 10-13.

[0020] The preparation method of the present application is a continuous reaction process, and the photochemical reaction solution in step a is transported backward in the pipeline, and the alkali solution and the end-capping agent are added at the front end of the pipeline.

[0021] The alkali solution is a sodium hydroxide or potassium hydroxide solution, preferably a sodium hydroxide solution; the concentration of the alkali solution is 5-15 mol / L, and the molar ratio of sodium hydroxide or potassium hydroxide in the alkali solution to phosgene added in the preparation of the photochemical reaction solution is 1:2-1:4, such as 1:2, 1:2, 5, 1:3, 1:3, 5, 1:4.

[0022] The end-capping agent is a halogenated hydrocarbon solution of a phenol compound, and the solution concentration is 1-15 wt%. The phenol compound includes at least one of p-tert-butyl phenol, phenol, and p-isopropyl phenol. The halogenated hydrocarbon includes one or more of dichloromethane, chloroform, and dichloroethane, preferably dichloromethane. The amount of end-capping agent added is generally 2.5-5% of the total molar amount of bisphenol A monomers added in the preparation of the photochemical reaction solution, according to the melt index design of the polycarbonate product and the application requirements of the polycarbonate.

[0023] In step b of the present application, the first mixing device and the second mixing device are mixers, including one or more of a turbine type stirring mixer, an ultrasonic dispersion device, and a tubular high shear mixer. The first mixing device and the second mixing device can be the same type of mixer or can be used in combination with two different mixers, and preferably both are tubular high shear mixers.

[0024] The energy input ratio of the first mixer to the second mixer per unit volume of reaction solution in step b of the present application satisfies 5:1-1:2; preferably, the first mixing device has an energy input per unit volume of reaction solution of (0.5-10.0)×10 3 kJ / m 3 , and the second mixing device has an energy input per unit volume of reaction solution of (0.05-4)×10 3 kJ / m 3 .

[0025] In the preparation method, the reaction solution after adding the alkali liquor and the end-capping agent is mixed by the first mixing device to form a water-in-oil emulsion, and then enters the second mixing device to complete further mixing.

[0026] In the preparation method, the residence time of the pipeline section between the first mixing device and the second mixing device is 60-600s, and the temperature is 25-40℃, so that the reaction system completes certain conversion, and in order to ensure the stable reaction and uniform reaction rate of the emulsion between the two mixing devices, the flow rate and the pipe diameter of the pipeline section between the two mixing devices are preferably selected to meet the condition that the Reynolds number Re≤1000.

[0027] In the preparation method, the photochemical reaction solution is subjected to the shear of the first mixing device to complete preliminary conversion, and then is further subjected to the shear of the second mixing device, so that the content of the terminal hydroxyl group in the polycarbonate polymer in the reaction solution at the outlet of the first mixing device (OH1) and the content of the terminal hydroxyl group in the polycarbonate polymer at the outlet of the second mixing device (OH2) satisfy the condition that OH1:OH2=1.05-1.50:1, such as 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, 1.5:1.

[0028] Preferably, before the material in step c is transported to the second reactor for polycondensation reaction, the reaction solution at the outlet of the second mixing device is first introduced into the first reactor, and then is introduced into the second reactor for polycondensation reaction after passing through the first reactor.

[0029] In the preparation method, the reaction solution at the outlet of the second mixing device is directly introduced into the first reactor, and the residence time of the reaction solution in the first reactor is 300-1800s, so that the terminal hydroxyl group in the polymer is further converted.

[0030] In the method, the reaction solution in the first reactor is subjected to preliminary polycondensation reaction in the absence of a catalyst, and the pressure is normal pressure. The temperature in the first reactor is controlled to be 10-40℃, and preferably 24-35℃. The content of the terminal hydroxyl group in the polymer at the outlet of the first reactor is OH3, and the content of the terminal hydroxyl group at the outlet of the second mixing device (OH2) satisfies the condition that OH2=(1.5-3.0)×OH3, i.e. OH2:OH3=1.5-3.0:1.

[0031] In the present application, the units of OH1, OH2 and OH3 are all wt%.

[0032] In the present application, the terms "first", "second", "third", "fourth" and the like in the "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity. In the method, the first reactor and the second reactor are tubular or tank reactors.

[0033] In the method, the catalyst is added to the reaction system after passing through the outlet of the first reactor, and the reaction solution enters the second reactor after adding the catalyst to complete the subsequent polycondensation reaction until the chloroformate groups in the reaction system are completely reacted.

[0034] The type of the catalyst includes organic amine substances, specifically including tertiary amines and organic ammonium salts, preferably triethylamine, and the addition amount of the catalyst is preferably 0.5-10‰ of the total moles of bisphenol A monomers added in the photochemical reaction stage.

[0035] In the method, the second reactor is a tank reactor. The subsequent polycondensation reaction described in the present application can be carried out according to the prior art, specifically according to CN118056857A, and the present application does not make special limitations thereon.

[0036] Specifically, the polycondensation reaction time is 0.5-2h, the reaction temperature is 20-40℃, preferably 30-40℃, and the polycondensation process is accompanied by stirring.

[0037] Preferably, after the polycondensation reaction is completed, the steps of demulsification, separation, water washing, powdering, devolatilization and drying are further included.

[0038] The present application also provides a polycarbonate obtained by the above preparation method.

[0039] The polycarbonate described in the present application has a molecular weight distribution index (PDI) ≤2.3, a total amount of residual phenolic monomers in the polycarbonate product ≤100ppm, and a yellowing index ΔYI value ≤0.2.

[0040] The present application has the following beneficial effects:

[0041] The present application provides a preparation method of polycarbonate, in which, in the polycondensation reaction process, by adjusting the energy input ratio of the mixing equipment on the conveying pipeline before entering the polycondensation reaction tank, the residence time of each stage of the reaction, and the hydroxyl end group content of the polymer at the outlet of the mixing equipment and the reactor, the optimization of the structure and other characteristics of the final polycarbonate product is realized. The polycarbonate product prepared by the process has the characteristics of narrow molecular weight distribution, less residual phenolic monomers, and low yellowing index in the product injection test. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 For the synthesis process of polycarbonate in the present application, wherein: 1- photochemical reactor, 2-first mixer, 3-second mixer, 4-first reactor, 5-second reactor; a-alkali liquor adding position, b-end capping agent adding position, c-catalyst adding position. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of the present application, the present application will be further described below in conjunction with examples. It should be understood that the following examples are only for better understanding of the present application, and do not mean that the present application is limited to the following examples only.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The orientation terms such as top, bottom, etc. mentioned or possibly mentioned in the present specification are defined with respect to the structure shown in the drawings, and they are relative concepts, so it is possible that they will change accordingly according to different positions, different use states.

[0045] Main raw material sources

[0046] The chemical substances involved in the reaction process are as follows: dichloromethane (analytical pure, Anjie), deionized water (pH ~ 7.2, conductivity < 5.0), sodium hydroxide aqueous solution (Wanhua product, 20wt%), p-tert-butyl phenol (analytical pure, Wanhua product), triethylamine (Anjie, 99%), phosgene (98%), bisphenol A (analytical pure, Wanhua product).

[0047] Main test method

[0048] The molecular weight of polycarbonate is obtained by Agilent Technologies 1260infinity test, using RI detector, UV detector, dichloromethane as mobile phase, flow rate is 1 mL / min, column temperature and box temperature are both 30℃.

[0049] For OH1, OH2, OH3, take 1.0g of reaction liquid, dissolve in 10ml dichloromethane solution, and further filter to prepare GPC test sample. The molar content of oligomer and polycarbonate end hydroxyl group is characterized: the ratio of peak integration under the conditions of UV detector of GPC chromatogram, analysis wavelength is 288nm (benzene ring end capping) and 264nm (end hydroxyl group peak).

[0050] The yellowing performance test was carried out as follows: the sample was directly injection molded into a sheet at a barrel temperature of 320°C, and then the sample was left in the barrel for 10 min before injection molding. The change in yellowness index YI of the injection molded sheet before and after the test represented the ΔYI value of the sample. The YI test was carried out in accordance with the ASTM E313 standard, and the color difference meter Ultra Scan PRO was used to measure the YI.

[0051] The test method for residual phenolic monomer was as follows: 1 g of polymer powder was dissolved in 10 ml of dichloromethane, then 10 ml of methanol was added for sedimentation, the supernatant was filtered and tested, and the monomer content was analyzed by liquid chromatography using methanol as the eluent.

[0052] Example

[0053] Raw material preparation: 1. Preparation of bisphenol A alkaline aqueous solution (concentration of 14 wt%): the preparation tank was kept at 32°C, and the stirring speed was 200 rpm. 8488 g of bisphenol A monomer, 7 g of reducing agent sodium hydrosulfite, 14235 g of sodium hydroxide aqueous solution (20 wt%), and 37890 g of pure water were added. After 40 min of dissolution, the preparation of bisphenol A alkaline aqueous solution was completed, and multiple tanks were prepared for standby during the implementation process. 2. A measured amount of triethylamine liquid was dissolved in a quantitative dichloromethane solution to prepare a dichloromethane solution of catalyst triethylamine (concentration of 5 wt%).

[0054] Example 1: Reference reaction process flow Figure 1 The bisphenol A alkaline aqueous solution (flow rate of 1000 g / min), phosgene (flow rate of 70 g / min), and organic solvent dichloromethane (600 g / min) were continuously introduced into the photochemical reaction system. After the reaction liquid stayed in the photochemical reaction kettle for 60 min, the reaction liquid was transported backward, and the p-tert-butylphenol solution (concentration of 10 wt%, flow rate of 33 g / min) and the alkali solution (sodium hydroxide aqueous solution, flow rate of 35.3 g / min) were added on the transport pipeline. Figure 1 The first mixing device and the second mixing device were both tubular high-shear mixers. The input power of the first mixing device and the second mixing device was set to ensure that the energy input per unit volume of material of the first mixing device was 10.00 x 10 3 kJ / m 3 , and the energy input per unit volume of material of the second mixing device was 2.00 x 10 3 kJ / m 3; the residence time of the reaction solution in the pipe between the first mixer and the second mixer is 200 s, the Reynolds number of the pipe is about 1000, and the temperature is 25°C. The temperature of the first reactor is 33°C, and the reaction is carried out at normal pressure and with stirring. The residence time in the first reactor is 1000 s, and the ratio of OH1, OH2, and OH3 is shown in Table 1. The catalyst triethylamine is added at the outlet of the first reactor, and the flow rate of the triethylamine solution is 12.5 g / min. After the reaction solution is added into the catalyst, it enters the kettle-type stirred reactor (the second reactor), and the temperature is controlled at about 35°C. The residence time in the second reactor is 60 min, and the chloroformate group is completely reacted. After the completion of the polycondensation reaction, the polycondensation solution is collected, and after demulsification, separation, and washing, the polycarbonate is obtained.

[0055] Example 2: Example 2 is different from Example 1 in that the energy input per unit volume of material of the first mixing device is 4.00 x 10 3 kJ / m 3 , the energy input per unit volume of material of the second mixing device is 1.00 x 10 3 kJ / m 3 , and the other parameters are completely consistent with Example 1.

[0056] Example 3: Example 3 is different from Example 1 in that the flow rate of the alkali solution (sodium hydroxide aqueous solution) added before the reaction solution enters the first mixing device is 47.1 g / min; the energy input per unit volume of material of the first mixing device is 0.6 x 10 3 kJ / m 3 , the energy input per unit volume of material of the second mixing device is 0.12 x 10 3 kJ / m 3 , the residence time of the pipe between the two mixers is 60 s, and the other parameters are completely consistent with Example 1.

[0057] Example 4: Example 4 is different from Example 1 in that the flow rate of the alkali solution (sodium hydroxide aqueous solution) added before the reaction solution enters the first mixing device is 47.1 g / min, the concentration of the end-capping agent solution is 1 wt%, and the flow rate is 350 g / min; the energy input per unit volume of material of the first mixing device is 1.0 x 10 3 kJ / m 3 , the energy input per unit volume of material of the second mixing device is 0.5 x 10 3 kJ / m 3 , the residence time in the first reactor is 300 s, and the other parameters are completely consistent with Example 1.

[0058] Example 5: The difference between Example 5 and Example 1 is that the flow rate of the alkali solution added before the reaction solution enters the first mixing device is 70.7 g / min, the concentration of the end-capping agent solution is 5 wt%, and the flow rate of the end-capping agent solution added is 50 g / min; the energy input per unit volume of material in the first mixing device is 1.0 x 10 3 kJ / m 3 , the energy input per unit volume of material in the second mixing device is 1.0 x 10 3 kJ / m 3 , the residence time of the pipeline between the two mixers is 400 s, the residence time in the first reactor is 600 s, and the other parameters are completely consistent with those of Example 1.

[0059] Example 6: The difference between Example 6 and Example 1 is that the flow rate of the alkali solution added before the reaction solution enters the first mixing device is 70.7 g / min, the concentration of the end-capping agent solution is 15 wt%, and the flow rate of the end-capping agent solution added is 28 g / min; the energy input per unit volume of material in the first mixing device is 1.0 x 10 3 kJ / m 3 , the energy input per unit volume of material in the second mixing device is 2.0 x 10 3 kJ / m 3 , the residence time of the pipeline between the two mixers is 600 s, the residence time in the first reactor is 1800 s, and the other parameters are completely consistent with those of Example 1.

[0060] Comparative Example

[0061] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the energy input per unit volume of material in the first mixing device is 1.0 x 10 3 kJ / m 3 , the energy input per unit volume of material in the second mixing device is 5.0 x 10 3 kJ / m 3 , and the other parameters are completely consistent with those of Example 1.

[0062] Comparative Example 2: The difference between Comparative Example 2 and Example 4 is that the residence time of the pipeline between the first mixing device and the second mixing device is 40 s, the residence time in the first reactor is 250 s, and the other parameters are completely consistent with those of Example 1.

[0063] Table 1: Parameter control during the reaction process of each example and comparative example

[0064]

[0065] Table 2: Polycarbonate structure and performance test of each example and comparative example

[0066]

[0067] It is readily understood that the above-described embodiments are only illustrative of the application and not intended to limit the scope of the application. Other variations and modifications can be made to the embodiments described and illustrated herein, without departing from the spirit of the application, the scope of which is defined by the appended claims.

Claims

1. A process for the preparation of polycarbonate, characterized in that, The method comprises the following steps: a. adding alkali and capping agent into the photochemical reaction solution; b. making the material obtained in step a. pass through the first mixing device and the second mixing device in sequence, wherein the energy input per unit volume of the material of the first mixing device and the second mixing device is controlled to be 5:1-1:2; the content of terminal hydroxyl groups in the polymer in the outlet reaction solution of the first mixing device and the second mixing device satisfies OH1:OH2=1.05-1.50:1; c. delivering the material treated in step b. to the second reactor to add catalyst for polycondensation reaction.

2. The method of claim 1, wherein, In step b, the energy input per unit volume of material in the first mixing device is 0.5 × 10⁻⁶. 3 -10.0×10 3 kJ / m 3 ; and / or, the energy input per unit volume of material in the second mixing device is 0.05 × 10⁻⁶. 3 -4.0×10 3 kJ / m 3 .

3. The method of claim 2, wherein, In step b., the first mixing device and the second mixing device are independently selected from one of a turbine type stirring mixer, an ultrasonic dispersion device and a tubular high shear mixer.

4. The method of claim 3, wherein, In step b., the residence time of the pipeline between the first mixing device and the second mixing device is 60-600 seconds, and the temperature is 25-40℃.

5. The method according to any one of claims 1-4, characterized in that, In step a., the capping agent is a halogenated hydrocarbon solution of phenolic compounds, the phenolic compounds include at least one of p-tert-butyl phenol, phenol and p-isopropyl phenol; and / or the alkali includes a sodium hydroxide or potassium hydroxide solution, preferably the molar ratio of sodium hydroxide or potassium hydroxide in the alkali to the phosgene added in the preparation of the photochemical reaction solution is 1:2-1:

4.

6. The method of claim 1, wherein, In step c., before the material enters the second reactor for polycondensation reaction, the outlet reaction solution of the second mixing device first enters the first reactor, and then enters the second reactor for polycondensation reaction after passing through the first reactor.

7. The method of claim 6, wherein, The first reactor satisfies at least one of the following conditions: (1) the reaction solution stays in the first reactor for 300-1800s, and then enters the second reactor; (2) the temperature of the first reactor is controlled to be 10-40℃, preferably 24-35℃; (3) the content of terminal hydroxyl groups in the polymer at the outlet of the first reactor is OH3, and OH2:OH3=1.5-3.0:1 is satisfied; (4) the first reactor is a tubular reactor or a kettle type reactor.

8. The method of any one of claims 1, 6, or 7, wherein, In step c., the catalyst includes tertiary amine or organic ammonium salt catalyst, and preferably is triethylamine.

9. The method of claim 8, wherein, The second reactor is a tubular reactor or a kettle type reactor.

10. The polycarbonate prepared according to the process of any one of claims 1 to 9, characterized in that, The polycarbonate has a molecular weight distribution index ≤2.3, a total amount of residual phenolic monomers ≤100ppm and a yellowing index ΔYI value ≤0.2.

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