Method for preparing polycarbonate preform and application, polycarbonate preform

Abstract

This invention belongs to the field of polycarbonate preparation technology, specifically relating to a method for preparing and applying polycarbonate feedstock, and the polycarbonate feedstock itself. The polycarbonate produced using this invention via a continuous two-phase interface method achieves a satisfactory conversion rate of diphenols in the initial reaction solution. During the research process, the inventors discovered that using an alkaline solution as the reaction substrate, and continuously introducing diphenol alkaline solution and phosgene into the substrate for a photochemical reaction, can reduce the amount of unreacted BPA in the feedstock without phosgene overflow, thus enabling the production of qualified products in the initial stage of the polycarbonate preparation process.

Description

Technical Field

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

[0002] Polycarbonate is a high-performance engineering plastic widely used in automobiles, electronic devices, construction, office supplies, optical discs, sporting goods, healthcare, computers, aerospace, and other fields. Currently, the main industrial methods for producing polycarbonate are the interfacial phosgene method and the melt transesterification method.

[0003] The interfacial phosgene method involves the reaction of bisphenol salt dissolved in an aqueous solution of an acid acceptor, such as an alkali metal hydroxide, with phosgene dissolved in an inert organic solution at the water-oil interface to prepare polycarbonate. The melt transesterification method is a solvent-free method based on the transesterification between bisphenol and dicarbonate.

[0004] Compared to the melt transesterification method, the interfacial phosgene method has advantages such as being able to complete the reaction at room temperature, easily generating high molecular weight polycarbonates, easily adjusting the molecular weight, and easily obtaining colorless and transparent polymer materials. Currently, the interfacial phosgene method remains the mainstream production process.

[0005] Currently, in industrialized interfacial phosgene processes, to ensure timely reaction of phosgene and the production of high-quality products, an organic inert solvent and bisphenol salt dissolved in an acid acceptor aqueous solution are typically added to the reaction system before phosgene introduction. However, this results in a large amount of unreacted bisphenol at the feedstock. The feedstock is the initial reaction solution in polycarbonate preparation, referring to the intermediate product from the start of raw material introduction until a stable reaction solution is obtained. Furthermore, during polycarbonate preparation, the timing of the capping agent addition coincides with the start-up of the pump from the photochemical stage to the polycondensation stage, and the addition flow rate is consistent with the normal reaction, leading to a large amount of unreacted capping agent at the feedstock. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for preparing polycarbonate feedstock and its application, as well as a polycarbonate feedstock.

[0007] To this end, the present invention provides the following technical solution.

[0008] This invention provides a method for preparing polycarbonate feedstock, comprising the following steps:

[0009] (1) Photochemical reaction: The photochemical reaction is carried out in a photochemical reaction system, which includes a reaction tank and a residence tank that are connected in a circulation manner. The residence tank is provided with a material inlet, and the reactants in the reaction tank enter the residence tank through the material inlet. Before the photochemical reaction, the reaction base liquid covers the material inlet. A diphenol alkaline solution and phosgene are continuously introduced into the reaction base liquid to carry out the photochemical reaction and obtain an oligomer mixture. The reaction base liquid includes an alkaline solution and an organic solvent, and the pH value of the alkaline solution is 11-13.5.

[0010] (2) Polycondensation reaction: Adjust the pH value of the oligomer mixture, add end-capping agent continuously and carry out polycondensation reaction.

[0011] The pH value of the alkaline solution is 11.5-13;

[0012] Preferably, the alkaline substance in the alkaline solution includes at least one of alkali metal hydroxide and alkaline earth metal hydroxide;

[0013] Preferably, the alkaline substance includes at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide;

[0014] Preferably, the mass ratio of the alkaline solution to the organic solvent is (0.3-1.8):1.

[0015] Further, in step (1), the organic solvent includes a haloalkanes;

[0016] Preferably, the halogenated hydrocarbon includes chlorinated hydrocarbons;

[0017] Preferably, the halohydrocarbon includes chlorinated hydrocarbons having 1 to 3 carbon atoms;

[0018] Preferably, the halogenated hydrocarbon includes at least one of dichloromethane, trichloromethane, dichloroethane, and trichloroethane.

[0019] Further, in step (2), during the polycondensation reaction, the content of terminal acyl chloride in the oligomer mixture is tested, and the feed flow rate of the capping agent is determined based on the content of terminal acyl chloride.

[0020] Furthermore, when the content of terminal acyl chlorides in the oligomer mixture changes, the feed flow rate of the capping agent is determined according to Equation 1:

[0021]

[0022] Where: m f : Feed flow rate of end-capping agent, kg / h;

[0023] CF: The content of terminal acyl chlorides in the oligomer mixture entering the polycondensation reaction, in ppm;

[0024] m1: Flow rate of the oligomer mixture entering the polycondensation reaction, kg / h;

[0025] x: The mass ratio of alkaline solution to organic solvent in the reaction substrate;

[0026] m 双酚 : The residual amount of bisphenol in the oligomer mixture entering the polycondensation reaction, in ppm;

[0027] M w Target weight-average molecular weight of polycarbonate;

[0028] M f : Molar mass of capping agent, g / mol.

[0029] Furthermore, the diphenol alkaline solution comprises diphenol and alkali;

[0030] Preferably, the content of diphenol in the diphenol alkaline solution is 14-17 wt%.

[0031] Preferably, the alkali content in the diphenol alkaline solution is 5.5-6.2 wt%.

[0032] Preferably, the diphenol includes aromatic phenolic compounds;

[0033] Preferably, the diphenol comprises 2,2-bis(4-hydroxyphenyl)propane, 4,4-(1-isopropylidene)bis(2,6-dimethylphenol), hydroquinone, resorcinol, 1,1-bis(4-hydroxyphenyl)phenylethane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 1, At least one of 1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclododecane, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfide, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene.

[0034] Further, in step (1), the molar ratio of the diphenol in the diphenol alkaline solution to the phosgene is 1:(1-1.5); and / or,

[0035] The photochemical reaction further includes a step of continuously introducing an organic solvent; the mass ratio of the organic solvent to the diphenol alkaline solution is (0.3-1.2):1; and / or,

[0036] The photochemical reaction is carried out at a temperature not exceeding 40°C for a duration of 0.2-0.6 hours; and / or,

[0037] During the photochemical reaction, the pH of the reaction system is 10.5-13.5.

[0038] Further, in step (2), the pH value of the oligomer mixture is adjusted to 11-13;

[0039] Preferably, the capping agent comprises an aromatic monohydric phenol;

[0040] Preferably, the aromatic monohydric phenol includes at least one of phenol, methylphenol, tert-butylphenol, and p-cumylphenol;

[0041] Preferably, the polycondensation reaction further includes a step of continuously adding a catalyst; the catalyst includes a tertiary amine compound, a quaternary ammonium compound, or a salt of the above compounds;

[0042] Preferably, the amount of catalyst added is 0.01-10 mol% of the amount of diphenol fed into the diphenol alkaline solution;

[0043] Preferably, the temperature of the polycondensation reaction is not higher than 40°C;

[0044] Preferably, the condensation reaction process maintains the pH value of the reaction system at 11.5-12.5.

[0045] The present invention provides a polycarbonate feedstock prepared by the above-described preparation method.

[0046] This invention provides a method for continuous production of polycarbonate, wherein the polycarbonate feedstock is prepared by the above-described preparation method; after the polycarbonate feedstock process is completed, it directly enters the continuous production process of polycarbonate.

[0047] Preferably, after the content of terminal acyl chloride in the oligomer mixture is stabilized, the feed amount of the capping agent is 1-10% of the molar amount of diphenol in the diphenol alkaline solution.

[0048] The technical solution of this invention has the following advantages:

[0049] 1. The present invention provides a method for preparing polycarbonate feedstock. The polycarbonate produced using a continuous two-phase interface method achieves a satisfactory conversion rate of diphenols in the initial reaction solution. Existing technologies require the preparation of a BPA sodium salt solution phase before introducing phosgene to prevent phosgene overflow and potential hazards. However, this method results in a large amount of unreacted BPA in the polycarbonate feedstock. For those skilled in the art, not adding the BPA sodium salt solution phase before introducing phosgene poses a risk of phosgene overflow, while adding it results in a large amount of unreacted BPA residue, leading to waste. The inventors discovered during their research that using an alkaline solution as the reaction substrate, and continuously introducing diphenol alkaline solution and phosgene into the substrate for a photochemical reaction, can reduce the amount of unreacted BPA in the feedstock without phosgene overflow, thus obtaining a qualified product in the initial stage of the reaction.

[0050] 2. The method for preparing polycarbonate feedstock provided by the present invention can reduce the residual amount of end-capping agent by controlling the amount of end-capping agent added at different reaction times. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the preparation process of the polycarbonate feedstock of the present invention;

[0053] Figure Labels

[0054] 1-Reaction vessel; 2-Station tank; 3-Pipeline; 4-Polycondensation reaction vessel; 5-Pump; 6-Heat exchanger. Detailed Implementation

[0055] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0056] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0057] Current techniques for preparing polycarbonate require the addition of bisphenol salts and organic solvents to the reaction system before introducing phosgene to avoid the risk of phosgene overflow. However, adding bisphenol salts in advance results in a large amount of unreacted bisphenols in the reaction system, leading to material waste. If phosgene and bisphenol salts are added to the reaction system simultaneously to prepare polycarbonate, the risk of phosgene overflow is even greater.

[0058] To address the above problems, the present invention provides the following technical solution.

[0059] This invention provides a method for preparing polycarbonate feedstock, comprising the following steps:

[0060] (1) Photochemical reaction: The photochemical reaction is carried out in a photochemical reaction system, which includes a reaction tank and a residence tank connected in a circulation manner. The residence tank is provided with a material inlet, and the reactants in the reaction tank enter the residence tank through the material inlet. Before the photochemical reaction, the reaction base liquid covers the material inlet. An alkaline solution is mixed with an organic solvent to obtain a reaction base liquid. A diphenol alkaline solution and phosgene are continuously introduced into the reaction base liquid to carry out a photochemical reaction, resulting in an oligomer mixture. The pH value of the alkaline solution is 11-13.5.

[0061] (2) Polycondensation reaction: Adjust the pH value of the oligomer mixture to 11-13, preferably 11.5-12.5, add end-capping agent and catalyst, and then perform polycondensation reaction to obtain polycarbonate feedstock.

[0062] It needs to be explained that, for example Figure 1 As shown, the photochemical reaction system includes a reaction tank 1 and a residence tank 2 connected in a circulating manner, and the reaction tank 1 and residence tank 2 are connected by several pipes 3. An alkaline solution mixed with an organic solvent serves as the reaction base liquid, ensuring that the base liquid covers the material inlet in the residence tank 2. This is to ensure that the reaction base liquid fills the reaction tank 1 and the pipes 3, avoiding the risk of overflow when phosgene is introduced during the photochemical reaction stage, and to allow the diphenol alkaline solution and phosgene to fully undergo the photochemical reaction, reducing the residual amount of BPA in the initial reaction solution. Furthermore, the oligomer mixture obtained from the photochemical reaction is discharged from the residence tank 2, with a portion entering the polycondensation reaction tank 4 for polycondensation, and the remaining portion circulating back to the reaction tank 1 via a pump 5 and a heat exchanger 6. This prevents excessive pressure inside the reaction tank due to rapid evaporation of the organic solvent, thus serving a heat exchange function.

[0063] Furthermore, this invention first adds an alkaline solution with a specific pH and a solvent to the reactor to replace the traditional diphenol as the reaction substrate. This avoids the use of diphenol as a padding material, reduces the amount of unreacted diphenol residue, and prevents phosgene from escaping and causing harm. This results in a diphenol conversion rate of more than 98% and a capping agent conversion rate of more than 98.5% in the initial stage of start-up. The conversion rate is qualified, and the molecular weight of the obtained polycarbonate feedstock meets the requirements. The polycarbonate feedstock can be used directly and is beneficial for continuous polycarbonate production.

[0064] In one optional embodiment, the polycondensation reaction is followed by conventional operations such as layering and desalting, acid washing, water washing, concentration, and drying. The polycarbonate obtained by this invention is suitable for electronic products, automobiles, medical fields, and especially for products such as optical discs and films. Furthermore, according to the product requirements, additives such as stabilizers, release agents, fillers, or glass fibers are added to the polycarbonate for processing to obtain molded parts that meet the requirements.

[0065] It should be noted that in step (1), an automatic chloroformate end analyzer and an automatic bisphenol analyzer are installed at the outlet of the photochemical reaction system. When the content of terminal acyl chloride in the oligomer mixture entering the polycondensation reaction changes significantly, it indicates that the polycarbonate obtained at this time belongs to the initial reaction liquid and has not entered the process of continuous and stable production of polycarbonate. The feed flow rate of the end-capping agent is determined according to Equation 1:

[0066]

[0067] Determining the amount of end-capping agent to add based on this relationship can avoid the presence of a large amount of unreacted end-capping agent in the feed head.

[0068] Furthermore, once the terminal acyl chloride content in the oligomer mixture entering the polycondensation reaction stabilizes, it indicates that the continuous polycarbonate production process has commenced. This is relatively easy to understand in the art; significant variations in terminal acyl chloride content are characteristic of the polycarbonate feedstock preparation process, and fluctuations exceeding ±1000 are considered significant. Conversely, when the terminal acyl chloride content stabilizes and becomes less volatile, the continuous polycarbonate production process begins, with fluctuations within ±1000 indicating stable terminal acyl chloride content. It should be noted that the flow rate of the oligomer mixture entering the polycondensation reaction is determined by the production capacity; different production capacity units correspond to different flow rates (m1). The flow rate of the oligomer mixture entering the polycondensation reaction is consistent with the feed rates of the diphenol alkali solution, organic solvent, and phosgene during the phosgene reaction, and those skilled in the art can obtain this value based on actual operation.

[0069] In one optional embodiment, the pH value of the alkaline solution is 11.5-13; as an example, the pH value of the alkaline solution is 11, 11.5, 12, 12.5, or 13; and / or,

[0070] The alkaline substance in the alkaline solution includes at least one of alkali metal hydroxides and alkaline earth metal hydroxides; and / or,

[0071] The alkaline substance includes at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide, preferably sodium hydroxide; and / or,

[0072] The mass ratio of the alkaline solution to the organic solvent is (0.3-1.8):1, preferably (0.6-1.5):1. As an example, the mass ratio of the alkaline solution to the organic solvent is 0.5:1, 0.9:1, 1.3:1, or 1.7:1.

[0073] In one alternative embodiment, in step (1), the organic solvent comprises a haloalkanes;

[0074] Preferably, the halogenated hydrocarbon includes chlorinated hydrocarbons;

[0075] Preferably, the halohydrocarbon includes chlorinated hydrocarbons having 1 to 3 carbon atoms;

[0076] In one optional embodiment, the diphenol alkaline solution comprises diphenol and alkali;

[0077] Preferably, the content of dihydric phenol in the dihydric alkali solution is 14-17 wt%, more preferably 15-16 wt%; as an example, the content of dihydric phenol in the dihydric alkali solution is 14.5 wt%, 15.5 wt%, and 16.5 wt%.

[0078] Preferably, the alkali content in the diphenol alkaline solution is 5.5-6.2 wt%, more preferably 5.7-6.0 wt%; as examples, the alkali content in the diphenol alkaline solution is 5.6 wt%, 5.8 wt%, and 6.1 wt%. The alkali can be an alkaline substance, including at least one of alkali metal hydroxides and alkaline earth metal hydroxides; preferably, the alkaline substance includes at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide.

[0079] Preferably, the diphenol includes aromatic phenolic compounds;

[0080] Preferably, the diphenol comprises 2,2-bis(4-hydroxyphenyl)propane, 4,4-(1-isopropylidene)bis(2,6-dimethylphenol), hydroquinone, resorcinol, 1,1-bis(4-hydroxyphenyl)phenylethane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 1, At least one of 1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclododecane, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfide, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene.

[0081] In an optional embodiment, in step (1), the feed molar ratio of the diphenol in the diphenol alkaline solution to the phosgene is 1:(1-1.5), preferably 1:(1.1-1.2). As an example, the feed molar ratio of phosgene to the diphenol in the diphenol alkaline solution is 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, or 1.5:1; and / or,

[0082] The photochemical reaction further includes a step of continuously introducing an organic solvent; the mass ratio of the organic solvent to the diphenol alkali solution is (0.3-1.2):1, preferably (0.5-0.8):1. For example, the mass ratio of the organic solvent to the diphenol alkali solution is 0.4:1, 0.6:1, 0.8:1, 1.0:1, or 1.2:1. It should be noted that the type of organic solvent is consistent with the organic solvent in the reaction substrate; and / or,

[0083] The photochemical reaction temperature is no higher than 40℃, and the time is 0.2-0.6h; preferably, the photochemical reaction temperature is 19-38℃, more preferably 26-35℃, and the time is preferably 0.3-0.45h; and / or,

[0084] During the photochemical reaction, the pH of the reaction system is 10.5-13.5, preferably 11.5-12.5.

[0085] As an example, the photochemical reaction temperatures were 40°C, 35°C, 30°C, 25°C, 20°C, 15°C, 10°C, 5°C, and 0°C, and the reaction times were 0.2h, 0.3h, 0.4h, 0.5h, and 0.6h. During the photochemical reaction, the pH of the reaction system was 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, and 13.5.

[0086] In one alternative embodiment, the capping agent comprises an aromatic monohydric phenol;

[0087] Preferably, the aromatic monohydric phenol includes at least one of phenol, methylphenol, tert-butylphenol, and p-cumylphenol;

[0088] Preferably, the polymerization reaction further includes a step of continuously adding a catalyst before the polymerization reaction; the catalyst includes a tertiary amine compound, a quaternary ammonium compound, or a salt of the above compounds; more preferably, the catalyst includes at least one selected from triethylamine, tributylamine, trioctylamine, N-methylpiperidine, N-ethylpiperidine, N-n-propylpiperidine, N-isopropylpiperidine, tributylbenzylammonium, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, and tetrabutylammonium.

[0089] Preferably, the amount of catalyst added is 0.01-10 mol% of the amount of diphenol fed into the diphenol alkaline solution, preferably 0.1-1 mol%. Examples include 0.01 mol%, 0.1 mol%, 0.5 mol%, 1.0 mol%, 2.0 mol%, 4.0 mol%, 6.0 mol%, 8.0 mol%, and 10.0 mol%. mol% represents the molar percentage of the amount of catalyst added relative to the amount of diphenol fed into the diphenol alkaline solution.

[0090] Preferably, the temperature of the polycondensation reaction is not higher than 40°C, more preferably 20-39°C, and even more preferably 35-38°C;

[0091] Preferably, the condensation reaction process maintains the pH value of the reaction system at 11.5-12.5, more preferably 11.8-12.2. As an example, the pH value is 11.5, 12.0, or 12.5.

[0092] As an example, the temperatures of the polycondensation reaction are 40°C, 35°C, 30°C, 25°C, 20°C, 15°C, 10°C, 5°C, and 0°C.

[0093] Preferably, in step (2), the reaction time after adding the catalyst is 0.15-0.6h, more preferably 0.25-0.4h.

[0094] It should be noted that when adjusting the pH value, a pH adjuster known in the art, such as an alkaline solution, is used, preferably an aqueous solution of an alkaline hydroxide, is preferred.

[0095] The raw materials used in the following examples:

[0096] Bisphenol A: Industrial grade, produced by Wanhua Chemical; Bisphenol S: Industrial grade, purchased from Chengdu Yuanda Chemical Co., Ltd.; Bisphenol F: Industrial grade, purchased from Chengdu Yuanda Chemical Co., Ltd.; Tetramethylbisphenol A: Industrial grade, purchased from Changzhou Anker Biotechnology Co., Ltd.; Dichloromethane: Analytical grade, purchased from Tianjin Kemei Chemical Reagent Co., Ltd.; p-tert-butylphenol (PTBP): Analytical grade, purchased from Shandong Chemical Research Institute; Phenol: Analytical grade, purchased from Beijing Innocare Technology Co., Ltd.; p-cumylphenol (PCP): Analytical grade, purchased from Beijing Innocare Technology Co., Ltd.; Triethylamine: Analytical grade, purchased from Tianjin Kemei Chemical Reagent Co., Ltd.

[0097] Example 1

[0098] This embodiment provides a method for preparing polycarbonate feedstock, including the following steps:

[0099] (1) Photochemical reaction: The photochemical reaction takes place in a photochemical reaction system, such as Figure 1 As shown, the photochemical reaction system includes a reaction tank 1 and a residence tank 2 connected in a circulating manner, and the reaction tank 1 and residence tank 2 are connected by several pipes 3. An alkaline solution mixed with an organic solvent serves as the reaction base liquid, ensuring that the reaction base liquid covers the material inlet of residence tank 2. Dichloromethane and sodium hydroxide alkaline solution are added to reaction tank 1 as the reaction base liquid, ensuring that the reaction base liquid covers the material inlet of residence tank 2, guaranteeing that reaction tank 1 and the pipes are filled with the reaction base liquid. A NaOH solution containing diphenols, phosgene, and dichloromethane are continuously introduced into reaction tank 1, and the photochemical reaction is carried out at 30°C for 0.3 hours. During this process, the pH value of the reaction system is maintained at 11.5-12.5, yielding an oligomer mixture. The concentration of diphenols in the NaOH aqueous solution containing diphenols is 15.5 wt%, and the concentration of NaOH is 5.85 wt%. The mass ratio of dichloromethane to the NaOH solution containing diphenols is 0.5.

[0100] (2) The polycondensation reaction is carried out in polycondensation reactor 4. An automatic chloroformate end-cap analyzer and an automatic bisphenol analyzer are installed between the photochemical reaction system and polycondensation reactor 4 to monitor the content of terminal acyl chlorides and diphenols in the oligomer mixture entering polycondensation reactor 4. A 32wt% NaOH aqueous solution is added to the oligomer mixture continuously entering polycondensation reactor 4 to adjust the pH to 11.5-12.5. Then, the end-capping agent PTBP and the catalyst triethylamine (catalyst added at 0.1 mol% of the diphenol feed amount) are continuously added and mixed thoroughly. The mixture is then transferred to a reactor and reacted at 35℃ for 0.3 h. During the reaction, the pH of the reaction system is maintained at 11.8-12.2. After the reaction is complete, the aqueous phase is separated to obtain the organic phase. The organic phase is washed and de-dichloromethane solvent is removed to obtain polycarbonate feedstock. The amount of end-capping agent added satisfies Equation 1.

[0101] Examples 2-9

[0102] Examples 2-9 provide a method for preparing polycarbonate, which is basically the same as Example 1, except for the following: the mass ratio of alkaline solution to organic solvent in the reaction substrate (represented by A), the pH value of the alkaline solution in the reaction substrate (represented by B), the type of diphenol, the molar ratio of phosgene to diphenol in the alkaline solution (represented by C), the flow rate m1 of the oligomer mixture entering the polycondensation step from the outlet of the photochemical reaction system (represented by D, kg / h), the terminal acyl chloride content (represented by E, ppm; it should be noted that this is the oligomer mixture without the addition of a capping agent) and the diphenol content (represented by F, ppm) in the oligomer mixture entering the polycondensation step from the outlet of the photochemical reaction system, the type of capping agent, and the amount of solution containing the capping agent added (represented by G, kg / h), wherein the amount of solution containing the capping agent added G is the mass flow rate of the dichloromethane solution containing the capping agent, and the concentration of the capping agent in the solution is 15 wt%. The above parameters for each example are shown in Table 1.

[0103] Table 1 Parameters of each embodiment

[0104]

[0105] Note: The content of terminal acyl chlorides (E) in the oligomer mixture entering the polycondensation step was obtained by testing with a Japanese Hiranuma ALT-1000 fully automatic titrator; the content of diphenols (F) was obtained by testing with a near-infrared spectroscopy instrument.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing polycarbonate, which is basically the same as that in Example 1, except that: the reaction substrate includes an aqueous solution of NaOH containing diphenol and dichloromethane, the NaOH aqueous solution containing diphenol replaces the sodium hydroxide alkaline solution in Example 1 by the same mass, and the amount of diphenol in the NaOH aqueous solution containing diphenol in this comparative example is 15.5 wt%.

[0108] Comparative Example 2

[0109] This comparative example provides a method for preparing polycarbonate, which is basically the same as that in Example 1, except that the amount of end-capping agent added is different. The flow rate of the end-capping agent added in this comparative example is 3.4 kg / h.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing polycarbonate, which is basically the same as that in Example 1, except that in step (1), the pH value of the alkaline solution in the reaction substrate is 9. During the experiment, bisphenol precipitates out, preventing the reaction from proceeding.

[0112] Test case

[0113] This test case provides the performance of the polycarbonate pellets prepared in each embodiment and comparative example.

[0114] Polycarbonate sample molecular weight: Gel permeation chromatography, equipment model: Agilent Technologies 1260 Infinity, 3 separation columns, dichloromethane as mobile phase, PS as standard, flow rate 1 ml / min, column temperature and chamber temperature are both 30℃.

[0115] The contents of bisphenol and capping agent in the polycarbonate feedstocks obtained in each embodiment and comparative example were obtained by high performance liquid chromatography.

[0116] Table 2. Performance test results of polycarbonate feedstocks in each embodiment and comparative example.

[0117]

[0118] The polycarbonate feedstock prepared by this invention has properties such as heat resistance, yellowing resistance, and exudation resistance.

[0119] The results above show that the polycarbonate feedstock prepared using the traditional method in Comparative Example 1 has a high bisphenol residual content. In Comparative Example 2, the addition of excessive end-capping agent resulted in a lower end-capping conversion rate.

[0120] Furthermore, the polycarbonate feedstock prepared by the continuous two-phase interface method of this invention has a low content of end-capping agent and achieves the required diphenol conversion rate; it also avoids problems such as phosgene overflow during the photochemical reaction stage. Furthermore, the amount of end-capping agent added in this invention satisfies Equation 1, which can reduce the residual amount of end-capping agent.

[0121] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a polycarbonate feedstock, characterized in that, Includes the following steps: (1) Photochemical reaction: The photochemical reaction is carried out in a photochemical reaction system, which includes a reaction tank and a residence tank that are connected in a circulation manner. The residence tank is provided with a material inlet, and the reactants in the reaction tank enter the residence tank through the material inlet. Before the photochemical reaction, the reaction base liquid covers the material inlet. A diphenol alkaline solution and phosgene are continuously introduced into the reaction base liquid to carry out the photochemical reaction and obtain an oligomer mixture. The reaction base liquid includes an alkaline solution and an organic solvent, and the pH value of the alkaline solution is 11-13.

5. (2) Polycondensation reaction: Adjust the pH value of the oligomer mixture, add end-capping agent continuously and carry out polycondensation reaction.

2. The preparation method according to claim 1, characterized in that, The pH value of the alkaline solution is 11.5-13; Preferably, the alkaline substance in the alkaline solution includes at least one of alkali metal hydroxide and alkaline earth metal hydroxide; Preferably, the alkaline substance includes at least one selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide; Preferably, the mass ratio of the alkaline solution to the organic solvent is (0.3-1.8):

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the organic solvent includes halogenated hydrocarbons; Preferably, the halogenated hydrocarbon includes chlorinated hydrocarbons; Preferably, the halohydrocarbon includes chlorinated hydrocarbons having 1 to 3 carbon atoms; Preferably, the halogenated hydrocarbon includes at least one of dichloromethane, trichloromethane, dichloroethane, and trichloroethane.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), during the polycondensation reaction, the content of terminal acyl chloride in the oligomer mixture is tested, and the feed flow rate of the capping agent is determined based on the content of terminal acyl chloride.

5. The preparation method according to claim 4, characterized in that, When the content of terminal acyl chlorides in the oligomer mixture changes, the feed flow rate of the capping agent is determined according to Equation 1: Where: m f : Feed flow rate of end-capping agent, kg / h; CF: The content of terminal acyl chlorides in the oligomer mixture entering the polycondensation reaction, in ppm; m1: Flow rate of the oligomer mixture entering the polycondensation reaction, kg / h; x: The mass ratio of alkaline solution to organic solvent in the reaction substrate; m 双酚 : The residual amount of bisphenol in the oligomer mixture entering the polycondensation reaction, in ppm; M w Target weight-average molecular weight of polycarbonate; M f : Molar mass of capping agent, g / mol.

6. The preparation method according to any one of claims 1-5, characterized in that, The diphenol alkaline solution comprises diphenol and alkali; Preferably, the content of diphenol in the diphenol alkaline solution is 14-17 wt%. Preferably, the alkali content in the diphenol alkaline solution is 5.5-6.2 wt%. Preferably, the diphenol includes aromatic phenolic compounds; Preferably, the diphenol comprises 2,2-bis(4-hydroxyphenyl)propane, 4,4-(1-isopropylidene)bis(2,6-dimethylphenol), hydroquinone, resorcinol, 1,1-bis(4-hydroxyphenyl)phenylethane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 1, At least one of 1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)cyclododecane, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, 4,4-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfide, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene.

7. The preparation method according to any one of claims 1-6, characterized in that, In step (1), the molar ratio of the diphenol in the diphenol alkaline solution to the phosgene is 1:(1-1.5); and / or, The photochemical reaction further includes a step of continuously introducing an organic solvent; the mass ratio of the organic solvent to the diphenol alkaline solution is (0.3-1.2):1; and / or, The photochemical reaction is carried out at a temperature not exceeding 40°C for a duration of 0.2-0.6 hours; and / or, During the photochemical reaction, the pH of the reaction system is 10.5-13.

5.

8. The preparation method according to any one of claims 1-7, characterized in that, In step (2), the pH value of the oligomer mixture is adjusted to 11-13; Preferably, the capping agent comprises an aromatic monohydric phenol; Preferably, the aromatic monohydric phenol includes at least one of phenol, methylphenol, tert-butylphenol, and p-cumylphenol; Preferably, the polycondensation reaction further includes a step of continuously adding a catalyst; the catalyst includes a tertiary amine compound, a quaternary ammonium compound, or a salt of the above compounds; Preferably, the amount of catalyst added is 0.01-10 mol% of the amount of diphenol fed into the diphenol alkaline solution; Preferably, the temperature of the polycondensation reaction is not higher than 40°C; Preferably, the condensation reaction process maintains the pH value of the reaction system at 11.5-12.

5.

9. The polycarbonate feedstock prepared by the method according to any one of claims 1-8.

10. A method for continuous production of polycarbonate, characterized in that, The polycarbonate feedstock is prepared by the preparation method according to any one of claims 1-8; Preferably, after the content of terminal acyl chloride in the oligomer mixture is stabilized, the feed amount of the capping agent is 1-10% of the molar amount of diphenol in the diphenol alkaline solution.

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