Polycarbonate and preparation method thereof

Abstract

The invention provides polycarbonate and a preparation method thereof, the preparation method comprises the following steps: reacting a raw material system comprising bisphenol salt, phosgene and a branching agent to obtain a photochemical liquid, the molecular weight of an oil phase in the photochemical liquid being Mw1; an end-capping reagent and a catalyst are added into the photochemical liquid, a first polycondensation reaction is conducted, a product of the first polycondensation reaction is obtained, the molecular weight of an oil phase in the product of the first polycondensation reaction is Mw2, and the pH of a water phase in the product of the first polycondensation reaction is 4.0-8.0; wherein the ratio of the Mw1 to the Mw2 ranges from 0.067 to 0.500, and the Mw2 ranges from 6000 to 15000; and adding alkali liquor into the product of the first polycondensation reaction to enable the pH value of the water phase to be 10.0-13.0, and then carrying out second polycondensation reaction to obtain the polycarbonate. According to the method, the excessive phosgene rate can be reduced, and the conversion rate of the comonomer, the branching agent, the end-capping reagent and the like can be improved.

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to polycarbonate and a preparation method thereof. Background Art

[0002] Polycarbonate is an engineering plastic with good impact strength and ductility. It is widely used in electronic devices, automotive components and engineering fields.

[0003] In the prior art, high-performance thin-walled transparent flame-retardant polycarbonate is mainly produced by the interfacial phosgene intermittent method, in which the raw materials are put into the reactor at one time, and then phosgene is introduced for reaction to obtain polycarbonate. However, this method generally has the problems of low production efficiency and low conversion rate of raw materials such as comonomers. In order to solve the above problems, most of them use an excess amount of phosgene to promote the conversion of raw materials such as comonomers. For example, there are literature reports on the use of 40% excess phosgene to promote the complete conversion of low-activity comonomers (such as flame-retardant functional monomers such as 1,1,1-tris(4-hydroxyphenyl)ethane (THPE), 4-hydroxybenzonitrile (PHBN) and p-cumylphenol (PCP) monomers), but this will cause the problem of serious excess phosgene.

[0004] In the process of preparing polycarbonate, how to balance reducing the excess rate of phosgene and improving the conversion rate of raw materials such as comonomers is a research focus in this field. Summary of the invention

[0005] The invention provides a polycarbonate and a preparation method thereof, which are helpful to reduce the excess rate of phosgene and improve the conversion rate of comonomers, branching agents and end-capping agents.

[0006] The invention also provides a polycarbonate which has high light transmittance and excellent flame retardancy and impact resistance.

[0007] The invention provides a method for preparing polycarbonate, comprising: reacting a raw material system including bisphenol salt, phosgene and a branching agent to obtain a photochemical liquid, wherein the molecular weight of an oil phase in the photochemical liquid is Mw1; adding a capping agent and a catalyst to the photochemical liquid, and performing a first polycondensation reaction to obtain a product of the first polycondensation reaction, wherein the molecular weight of the oil phase in the product of the first polycondensation reaction is Mw2, and the pH value of an aqueous phase in the product of the first polycondensation reaction is 4.0-8.0; wherein the ratio of Mw1 to Mw2 is 0.067-0.500, and Mw2 is 6000-15000; and adding an alkali solution to the product of the first polycondensation reaction to adjust the pH value of its aqueous phase to 10.0-13.0, and then performing a second polycondensation reaction to obtain the polycarbonate.

[0008] Optionally, the raw material system including bisphenolate, phosgene and branching agent is prepared by the following process: 1 mass part of deionized water, 0.05-0.15 mass parts of alkali metal hydroxide, 0.20-0.30 mass parts of bisphenol compound, and 0.00200-0.00600 mass parts of branching agent are mixed to obtain a solution containing bisphenolate; 1.0-1.5 mass parts of the first oil phase solvent and 0.10-0.20 mass parts of phosgene are mixed to obtain a phosgene oil phase solution; 1.200-1.400 mass parts of the solution containing bisphenolate and 1.30-1.50 mass parts of the phosgene oil phase solution are mixed, and the pH of the mixed solution is adjusted to 10.5-13.0 to obtain the raw material system including bisphenolate, phosgene and branching agent.

[0009] Optionally, the bisphenol salt includes bisphenol A sodium salt; and / or the alkali metal hydroxide includes sodium hydroxide; and / or the bisphenol compound includes 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)sulfide, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)ethane, The invention relates to a novel solvent for preparing an aqueous phase of the present invention, wherein the solvent comprises one or more of bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)oxide, and bis(4-hydroxyphenyl)sulphur; and / or the branching agent comprises one or more of 1,1,1-trihydroxyphenylethane and tetrahydroxyphenylmethane; and / or the first oil phase solvent comprises one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene.

[0010] Optionally, adding the end-capping agent and the catalyst to the photochemical liquid, carrying out the first polycondensation reaction, and obtaining the product of the first polycondensation reaction, comprises: adding an end-capping agent solution and a catalyst solution to the photochemical liquid, carrying out the first polycondensation reaction, and obtaining the product of the first polycondensation reaction; wherein the end-capping agent solution comprises 0.1 to 0.7 parts by mass of the second oil phase solvent, 0.005 to 0.050 parts by mass of the end-capping agent, and the catalyst solution comprises 0.1 to 0.2 parts by mass of the third oil phase solvent, and 0.001 to 0.005 parts by mass of the catalyst.

[0011] Optionally, the method further includes: the capping agent includes one or more of p-tert-butylphenol, phenol, p-cumylphenol, cresol, p-phenylphenol, p-chlorophenol, tribromocresol, pentabromophenol, and p-hydroxybenzonitrile; and / or, the second oil phase solvent includes one or more of dichloromethane, chloroform, monochlorobenzene, and o-dichlorobenzene; and / or, the catalyst includes one or more of triethylamine, tripropylamine, n-butylammonium bromide, and pyridine; and / or, the third oil phase solvent includes one or more of dichloromethane, chloroform, monochlorobenzene, and o-dichlorobenzene.

[0012] Optionally, after the second polycondensation reaction is completed, an oil phase is separated from the product of the second polycondensation reaction, and the oil phase is washed at least once with an acid solution and deionized water in sequence, and then the solvent is removed and then dried to obtain the polycarbonate.

[0013] The present invention provides a polycarbonate, which is obtained according to the preparation method as described above.

[0014] Optionally, the polycarbonate has a weight average molecular weight of 20,000 to 70,000, a total nitrogen content of 1,200 to 3,000 ppm, and a terminal hydroxyl content of 50 to 2,000 ppm.

[0015] Optionally, the polycarbonate comprises a main segment shown in formula I, a branched segment shown in formula II, and a capped segment shown in formula III.

[0016]

[0017] In formula I, R1 and R2 are independently selected from hydrogen, halogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; a and b are independently selected from integers of 0 to 4; X is present or absent, and when X is present, X is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof;

[0018]

[0019] In formula II, R3 is selected from hydrogen (H), an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen group or a nitro group, X1, X2, and X3 are present or absent, and when X1, X2, or X3 is present, X1, X2, and X3 are each independently selected from a carbonyl group, an ether group, a thioether group, a sulfoxide group, a sulfone group, an alkylene group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 20 carbon atoms and derivatives thereof, or an aryl group having 6 to 20 carbon atoms and derivatives thereof, and n1, n2, and n3 are each independently an integer greater than or equal to 0;

[0020]

[0021] In formula III, R4 and R5 are independently selected from hydrogen, halogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; R6 is selected from H, alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 3 carbon atoms, cyano, halogen or nitro; c and d are independently selected from integers of 0 to 4; Y is present or absent, and when Y is present, Y is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof.

[0022] Optionally, in the polycarbonate, the mass percentage of the main segment represented by formula I is 92% to 95%, the mass percentage of the branched segment represented by formula II is 1% to 3%, and the mass percentage of the end-capping segment represented by formula III is 3%-5%.

[0023] The present invention provides a polycarbonate and a preparation method thereof. By synergistically controlling the molecular weight Mw1 of the oil phase in the photochemical liquid, the molecular weight Mw2 of the oil phase in the product of the first polycondensation reaction, the pH value of the water phase and other process conditions to meet the above ranges, it is beneficial to increase the degree of participation of the branching agent and the end-capping agent in the reaction, so that the reaction efficiency is improved, and further it is beneficial to achieve the conversion rate (conversion efficiency) of the bisphenol salt (comonomer), the branching agent and the end-capping agent to be greater than 99%, and reduce the excess rate of phosgene. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0025] Polycarbonate is an engineering plastic with good impact strength and ductility, and is widely used in electronic devices, automotive parts and engineering fields. However, the traditional process for preparing polycarbonate has the problem of serious excess of phosgene and low conversion rate of comonomer, branching agent and end-capping agent. The inventor found in the study that by controlling the addition order (addition position) of end-capping agent, catalyst and alkali solution, and the residence time of the material in the reactor, the molecular weight Mw1 of the oil phase in the photochemical liquid and the molecular weight Mw2 of the oil phase in the product of the first polycondensation reaction can be controlled. When Mw1 and Mw2 meet the specific range, it is conducive to improving the degree of branching agent and end-capping agent participating in the reaction, so that the reaction efficiency is improved, and then it is conducive to improving the conversion rate of comonomer, branching agent and end-capping agent, and effectively solving the problem of serious excess of phosgene.

[0026] Based on this, an embodiment of the present invention provides a method for preparing polycarbonate, comprising: reacting a raw material system including bisphenol salt, phosgene and a branching agent to obtain a photochemical liquid, wherein the molecular weight of the oil phase in the photochemical liquid is Mw1; adding a capping agent and a catalyst to the photochemical liquid, performing a first polycondensation reaction, and obtaining a product of the first polycondensation reaction, wherein the molecular weight of the oil phase in the product of the first polycondensation reaction is Mw2, and the pH of the water phase in the product of the first polycondensation reaction is 4.0-8.0; wherein the ratio of Mw1 to Mw2 is 0.067-0.500, and Mw2 is 6000-15000; adding an alkali solution to the product of the first polycondensation reaction to make the pH of its water phase 10.0-13.0, and then performing a second polycondensation reaction to obtain polycarbonate.

[0027] According to the research and analysis of the inventors: in the preparation system of the polycarbonate of the embodiment of the present invention, by synergistically controlling the molecular weight Mw1 of the oil phase in the photochemical liquid, the molecular weight Mw2 of the oil phase in the product of the first polycondensation reaction and the pH of the aqueous phase and other process conditions to meet the above ranges, it is beneficial to increase the degree of participation of the branching agent and the end-capping agent in the reaction, so that the reaction efficiency is improved, which is beneficial to achieve the conversion rate (conversion efficiency) of bisphenol salt (comonomer), branching agent and end-capping agent greater than 99%, and reduce the excess rate of phosgene.

[0028] Exemplarily, the ratio of Mw1 to Mw2 can be 0.067, 0.070, 0.090, 0.100, 0.200, 0.300, 0.400, 0.500 or a range consisting of any two thereof, Mw2 can be 6000, 8000, 10000, 11000, 13000, 14000, 15000 or a range consisting of any two thereof, the pH of the aqueous phase in the product of the first polycondensation reaction can be 4, 5, 6, 7, 8 or a range consisting of any two thereof, and an alkali solution is added to the product of the first polycondensation reaction so that the pH of the aqueous phase is 10, 11, 12, 13 or a range consisting of any two thereof.

[0029] Some specific fields (such as thin-walled fields with small thickness (less than 3 mm)) have high requirements for the flame retardancy, impact resistance and light transmittance of polycarbonate. Limited by factors such as the preparation process conditions of polycarbonate, the flame retardancy of some polycarbonates (such as bisphenol A-based general-purpose polycarbonates) does not meet the requirements of the thin-walled fields with small thickness (less than 3 mm), resulting in limited applications and reducing its use in transparent thin-walled fields that meet the UL 94 plastic material flammability test standard 5VA grade. Therefore, it is very necessary to improve the flame retardancy of thin-walled polycarbonate. In addition, while improving the flame retardancy of thin-walled polycarbonate, it is also very necessary to maintain its light transmittance and necessary impact resistance. In the prior art, high-performance thin-walled transparent flame-retardant polycarbonate is mainly produced by the interfacial phosgene intermittent method, and a flame retardant functional copolymer structure is added during the synthesis process to improve its flame retardancy. For example, patent document CN102159643B uses polyester-polycarbonate-polysiloxane terpolymer and uses cyanophenol as end capping, and then adds a certain amount of brominated polycarbonate and aromatic sulfone sulfonate in subsequent processing. The final product has good flame retardancy and low smoke performance, but the YI value of the 3.2 mm test piece is 2.5, the haze is 0.78, and the light transmittance is 88%, and the optical performance is relatively poor; in addition, adding flame retardants during the post-processing of polycarbonate can also improve the flame retardancy of polycarbonate (polymer), but this solution can only make the flame retardancy of polycarbonate reach the 3.0 mm level of UL94; patent document CN 102164991B reports the addition of sulfonate flame retardants to polycarbonate, with the addition amount of sulfonate being between 0.01wt% and 0.1wt%. However, when the polycarbonate is injection molded into a 3mm thick extruded sheet, the sheet has a burning length of less than 150mm, a dripping burning time of less than 3 seconds, and a total burning time of less than 15 seconds, and has poor combustion performance.

[0030] In an embodiment of the present invention, under the above-mentioned preparation method system, the amount of raw materials such as bisphenol compounds, branching agents, and end-capping agents, as well as the preparation process of the raw material system and other conditions are further adjusted to improve the structure and content of the main segment, branching segment, and end-capping segment in the polycarbonate structure, which helps to improve the flame retardant properties, light transmittance and impact resistance of the polycarbonate and improve its quality stability.

[0031] In some embodiments, the raw material system comprising bisphenolate, phosgene and a branching agent is prepared by the following process: 1 part by mass of deionized water, 0.05-0.15 parts by mass of an alkali metal hydroxide, 0.20-0.30 parts by mass of a bisphenol compound, and 0.00200-0.00600 parts by mass of a branching agent are mixed to obtain a solution containing bisphenolate (BPA liquid or homogeneous solution); 1.0-1.5 parts by mass of a first oil phase solvent and 0.10-0.20 parts by mass of phosgene are mixed to obtain a phosgene oil phase solution; 1.200-1.400 parts by mass of a solution containing bisphenolate and 1.30-1.50 parts by mass of a phosgene oil phase solution are mixed, and the pH of the mixed solution (the aqueous phase therein) is adjusted to 10.5-13.0 to obtain the raw material system comprising bisphenolate, phosgene and a branching agent. For example, the mass fraction of the alkali metal hydroxide is 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.15 or any two thereof, preferably 0.06 to 0.11; the mass fraction of the bisphenol compound is 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.30 or any two thereof, preferably 0.20 to 0.25; the mass fraction of the branching agent is 0.00200, 0.00285, 0.00300, 0.00400, 0.00500, 0.00600 or any two thereof, preferably 0.00285 to 0.00600; and the first oil phase The mass fraction of the solvent is 1.0, 1.2, 1.25, 1.3, 1.5 or a range consisting of any two thereof, preferably 1.2-1.3, the mass fraction of the above-mentioned phosgene is 0.10, 0.11, 0.15, 0.20 or a range consisting of any two thereof, preferably 0.11-0.20, the mass fraction of the above-mentioned solution containing bisphenol salt (BPA feed solution or homogeneous solution) is 1.200, 1.263, 1.300, 1.350, 1.366, 1.400 or a range consisting of any two thereof, preferably 1.263-1.366, the mass fraction of the above-mentioned phosgene oil phase solution is 1.30, 1.31, 1.40, 1.50 or a range consisting of any two thereof, preferably 1.31-1.50. The invention is helpful to prepare a polycarbonate with excellent flame retardancy, light transmittance and impact resistance and stable quality. The polycarbonate can be used as a thin-walled transparent flame retardant polycarbonate resin in flame retardant electronic devices and other related fields, such as transparent flame retardant fields such as television components.

[0032] The above solution containing bisphenolate may further be added with sodium hydrosulfite (Na2S2O4), and its mass fraction (based on 1 mass fraction of deionized water) may be 0.00003 to 0.00007, such as 0.00003, 0.00004, 0.00005, 0.00006, 0.00007 or any two of them. In addition, during the preparation of the solution containing bisphenolate (BPA feed solution or homogeneous solution), nitrogen may be used for purging, and mechanical stirring may be turned on to stir and mix uniformly to prepare a homogeneous solution, i.e., a solution containing bisphenolate (BPA feed solution).

[0033] The bisphenol salt may include bisphenol A sodium salt.

[0034] The above-mentioned bisphenol compound includes one or more of 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)sulfide, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)oxide, and bis(4-hydroxyphenyl)sulphide, preferably 2,2-bis(4-hydroxyphenyl)propane.

[0035] The above-mentioned alkali metal hydroxide may include sodium hydroxide.

[0036] The branching agent (branching monomer) may include one or more of 1,1,1-trihydroxyphenylethane and tetrahydroxyphenylmethane (tetrahydroxyphenylmethane). In addition, other polyhydroxy branching agents may also be used.

[0037] The first oil phase solvent may include one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene.

[0038] The preparation of the raw material system including bisphenol salt, phosgene and branching agent can be completed by using different batching kettles, such as bisphenol A (BPA) batching kettle, end-capping agent batching kettle and catalyst batching kettle.

[0039] Specifically, a solution containing bisphenolate (such as BPA solution), phosgene, and the first oil phase solvent can be added to a reactor and mixed to obtain a mixed solution, and then the pH of the mixed solution is adjusted to 10.5-13.0 to obtain a raw material system including bisphenolate, phosgene, and a branching agent.

[0040] More specifically, in the process of adjusting the pH of the mixed solution to 10.5-13.0 and obtaining the raw material system comprising bisphenolate, phosgene and branching agent, the pH of the aqueous phase in the mixed solution can be adjusted to 10.5-13.0 by adding alkali solution (such as sodium hydroxide) to the mixed solution, thereby obtaining the raw material system comprising bisphenolate, phosgene and branching agent. Under the preparation method system provided by the embodiment of the present invention, the raw material system helps to prepare a polycarbonate having excellent flame retardancy, light transmittance and impact resistance and stable quality, and the polycarbonate can be used as a thin-walled transparent flame retardant polycarbonate resin in related fields such as flame retardant electronic devices, such as transparent flame retardant fields such as television components.

[0041] Phosgene is generally stored in a phosgene storage tank, and its amount of introduction is controlled by a flow control meter in the form of gas phase and directly introduced into the reactor (reaction liquid).

[0042] The raw material system including bisphenol salt, phosgene and branching agent is reacted to obtain a photochemical liquid.

[0043] In some embodiments, the process of adding a capping agent and a catalyst to the photochemical liquid to carry out a first polycondensation reaction to obtain a product of the first polycondensation reaction includes: adding a capping agent solution and a catalyst solution to the photochemical liquid to carry out a first polycondensation reaction to obtain a product of the first polycondensation reaction; wherein, based on the aforementioned 1 mass part of deionized water, the capping agent solution includes 0.1 to 0.7 mass parts of the second oil phase solvent, 0.005 to 0.050 mass parts of the capping agent, and the catalyst solution includes 0.1 to 0.2 mass parts of the third oil phase solvent, and 0.001 to 0.005 mass parts of the catalyst. It is helpful to prepare a polycarbonate with excellent flame retardancy, light transmittance and impact resistance and stable quality. The polycarbonate can be used as a thin-walled transparent flame retardant polycarbonate resin in related fields such as flame retardant electronic devices, such as transparent flame retardant fields such as television components.

[0044] Illustratively, in the above-mentioned capping agent solution, the mass part of the second oil phase solvent is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or a range consisting of any two thereof, and the mass part of the capping agent is 0.005, 0.010, 0.020, 0.030, 0.040, 0.050 or a range consisting of any two thereof; in the catalyst solution, the mass part of the third oil phase solvent is 0.1, 0.15, 0.2 or a range consisting of any two thereof, and the mass part of the catalyst is 0.001, 0.002, 0.003, 0.004, 0.005 or a range consisting of any two thereof.

[0045] The end-capping agent may include one or more of p-tert-butylphenol, phenol, p-cumylphenol, cresol, p-phenylphenol, p-chlorophenol, tribromocresol, pentabromophenol, and p-hydroxybenzonitrile. In addition, other end-capping agents with amides, nitro groups, etc. may also be used.

[0046] The second oil phase solvent may include one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene.

[0047] The catalyst may include one or more of triethylamine, tripropylamine, n-butylammonium bromide (eg, tetra-n-butylammonium bromide), and pyridine.

[0048] The third oil phase solvent may include one or more of dichloromethane (MC), chloroform, monochlorobenzene and o-dichlorobenzene.

[0049] After adding an alkali solution to the product of the first polycondensation reaction to adjust the pH of the aqueous phase to 10.0 to 13.0, a second polycondensation reaction is performed to obtain a polycarbonate.

[0050] The alkali solution may include sodium hydroxide, such as a sodium hydroxide aqueous solution, wherein the concentration of the sodium hydroxide may be 30.0% to 40.0%, such as 30.0%, 32.2%, 35.0%, 37.0%, 40.0% or a range consisting of any two thereof.

[0051] After the second polycondensation reaction is completed, the oil phase is separated from the product of the second polycondensation reaction (polymerization reaction liquid) (oil-water separation is performed), the oil phase is washed with acid solution and deionized water at least once in sequence, the solvent (the solvent in the oil phase after washing) is removed, and then dried to obtain polycarbonate.

[0052] In a specific implementation, the acid solution may be dilute hydrochloric acid, dilute sulfuric acid or the like. The concentrations of the dilute hydrochloric acid and the dilute sulfuric acid may be 0.08 to 0.12 M, for example, 0.08 M, 0.09 M, 0.10 M, 0.11 M, 0.12 M or any two thereof.

[0053] In addition, after removing the solvent, the material after the solvent is removed can be crushed first, and then the crushed material can be dried, which helps to improve the drying effect.

[0054] In actual production, the process of reacting the raw material system including bisphenol salt, phosgene and branching agent to obtain photochemical liquid can occur in a photochemical reactor, the first polycondensation reaction can occur in a first polycondensation reactor, and the second polycondensation reaction can occur in a second polycondensation reactor.

[0055] Specifically, the process of the preparation method includes: a raw material system including bisphenol salt, phosgene and a branching agent reacts in a photochemical reactor to obtain a photochemical liquid; the photochemical liquid is extracted from the outlet of the photochemical reactor and pumped into a first polycondensation reactor to undergo a first polycondensation reaction to obtain a product of the first polycondensation reaction; the product of the first polycondensation reaction is extracted from the outlet of the first polycondensation reactor and transported to a second polycondensation reactor to undergo a second polycondensation reaction to obtain polycarbonate.

[0056] In order to make the raw material reaction more fully and improve the yield of polycarbonate, a third polycondensation reactor can be connected after the second polycondensation reactor, and the feed port of the third polycondensation reactor is connected to the outlet of the second polycondensation reactor. After the product of the second polycondensation reaction is extracted from the outlet of the second polycondensation reactor, it is transported to the third polycondensation reactor by a peristaltic pump, and then the polycondensation reaction (third polycondensation reaction) is continued in the third polycondensation reactor. The reaction product extracted from the outlet of the third polycondensation reactor is the final polymerization reaction liquid containing polycarbonate. The above reaction process forms a three-stage polycondensation reaction, so that the polycondensation reaction can be fully completed, which helps to improve the yield of polycarbonate.

[0057] The above-mentioned photochemical reactor refers to a reaction device capable of mixed dispersion. The embodiment of the present invention does not specifically limit the type of disperser in the photochemical reactor. It can ensure that the reaction materials are mixed and dispersed and fully reacted. A dynamic disperser or a static mixer (for example, the SMV type or SMX type static mixer of the Swiss Sulze: company (Sulzer Company)) can be selected, preferably a static mixer. The first polycondensation reactor, the second polycondensation reactor, and the third polycondensation reactor can also use a reaction device capable of mixed dispersion. The embodiment of the present invention does not specifically limit it, but these reaction devices need to ensure that the reaction materials have enough mixed dispersion and residence time to ensure sufficient reaction. For example, a dynamic disperser, a static mixer or a stirred reactor can be selected, preferably a stirred reactor.

[0058] In order to further solve the problems of serious excess of phosgene and low production efficiency in the intermittent process in the prior art, the preparation method of the embodiment of the present invention can also realize the continuous production of polycarbonate. Specifically, the above preparation method also includes: continuously introducing a raw material system including bisphenol salt, phosgene and branching agent into a reaction system for reaction to obtain a photochemical liquid, continuously adding a capping agent and a catalyst to the photochemical liquid, performing a first polycondensation reaction, obtaining a product of the first polycondensation reaction, and continuously adding an alkali solution to the product of the first polycondensation reaction to make the pH of its aqueous phase 10.0 to 13.0, and then performing a second polycondensation reaction to continuously obtain polycarbonate, and continuously output the polycarbonate from the reaction system, wherein the amount of polycarbonate output from the reaction system is not less than the amount of polycarbonate newly produced after the reaction of the raw materials input into the reaction system. In the above preparation process, the raw materials are continuously input into the reaction system, and continuously react in the reaction system to produce polycarbonate, and the polycarbonate is continuously output from the reaction system, wherein the amount of polycarbonate output is not less than the amount of polycarbonate newly produced, thereby realizing the continuous production of polycarbonate. Compared with the intermittent process in the prior art, the embodiments of the present invention avoid the problems of low reaction efficiency caused by the aggregation of raw materials and products inside the reaction system in the intermittent process, which in turn causes excessive phosgene and low production efficiency, by continuously inputting raw materials into the reaction system and continuously outputting products from the reaction system. This helps to reduce the excess phosgene rate and improve the utilization rate of comonomers, branching agents, capping agents, etc., thereby improving the yield (output) of polycarbonate.

[0059] In some embodiments, the raw material system including bisphenol salt, phosgene and branching agent is continuously introduced into the reaction system for reaction to obtain a photochemical liquid, including: continuously introducing a solution containing bisphenol salt, phosgene and a first oil phase solvent into the reaction system respectively to obtain a photochemical liquid.

[0060] Wherein, the introduction rate of the solution containing bisphenol salt can be 140.0-150.0 g / min, for example, 140.0 g / min, 142.8 g / min, 145.0 g / min, 148.0 g / min, 150.0 g / min or a range consisting of any two thereof, the introduction rate of phosgene can be 11.00-13.00 g / min, for example, 11.00 g / min, 11.38 g / min, 12.00 g / min, 13.00 g / min or a range consisting of any two thereof, and the introduction rate of the first oil phase solvent can be 140.0-150.0 g / min, for example, 140.0 g / min, 145.0 g / min, 147.6 g / min, 150.0 g / min or a range consisting of any two thereof.

[0061] In some embodiments, in the process of continuously adding a capping agent and a catalyst to the photochemical liquid to carry out a first polycondensation reaction to obtain a product of the first polycondensation reaction, the introduction rate of the capping agent solution can be 20.00 to 30.00 g / min, for example, 20.00 g / min, 22.17 g / min, 25.00 g / min, 30.00 g / min or a range consisting of any two thereof, and the introduction rate of the catalyst solution can be 1.00 to 3.00 g / min, for example, 1.00 g / min, 1.50 g / min, 1.91 g / min, 2.00 g / min, 3.00 g / min or a range consisting of any two thereof.

[0062] In specific implementation, under the preparation method system of the embodiment of the present invention, on the basis of keeping the addition order (addition position) of the end-capping agent, catalyst and alkali solution unchanged, the residence time (fixed liquid level retention time) of the material in the above-mentioned photochemical reactor or the first polycondensation reactor can be controlled, that is, the time from the material entering the photochemical reactor or the first polycondensation reactor until the product formed by it or the remaining material is extracted from the photochemical reactor or the first polycondensation reactor, to control the molecular weight of the oil phase in the photochemical liquid to be Mw1 and the molecular weight of the oil phase in the product of the first polycondensation reaction to be Mw2. It is helpful to prepare a polycarbonate with excellent flame retardancy, light transmittance and impact resistance and stable quality, and the polycarbonate can be used as a thin-walled transparent flame retardant polycarbonate resin in related fields such as flame retardant electronic devices, such as transparent flame retardant fields such as television components.

[0063] In addition, under the preparation method system of the embodiment of the present invention, the order of adding the end-capping agent, the catalyst and the alkali solution (addition position), and the residence time of the material in the above-mentioned photochemical reactor or the first polycondensation reactor (retention time of the fixed liquid level) are kept unchanged. The stirring speed in the photochemical reactor or the first polycondensation reactor is changed to change the mixing scale of the oil-water phase, which will also affect the molecular weight of the oil phase in the photochemical liquid Mw1 and the molecular weight of the oil phase in the product of the first polycondensation reaction Mw2.

[0064] The embodiment of the present invention also provides a polycarbonate, which is obtained according to the above preparation method. The polycarbonate has excellent flame retardancy, light transmittance, impact resistance and stable quality.

[0065] In some embodiments, the polycarbonate has a weight average molecular weight of 20,000 to 70,000, a total nitrogen content of 1,200 to 3,000 ppm, and a terminal hydroxyl content of 50 to 2,000 ppm.

[0066] In some embodiments, the polycarbonate comprises a main segment of formula I, a branched segment of formula II, and a terminal segment of formula III.

[0067]

[0068] In formula I, R1 and R2 are independently selected from hydrogen, halogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; a and b are independently selected from integers of 0 to 4; X is present or absent, and when X is present, X is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof. Illustratively, in R1 and R2, the alkyl group has 1, 2, 3, 4, 5 or 6 carbon atoms, the cycloalkyl group and its derivatives have 5, 7, 10, 15 or 20 carbon atoms, the aryl group and its derivatives have 6, 7, 8, 9, 10, 12, 15, 17, 19 or 20 carbon atoms, and a and b are independently selected from 0, 1, 2, 3 or 4; in X, the alkylene group has 1, 2, 3, 4, 5 or 6 carbon atoms, the cycloalkyl group and its derivatives have 5, 7, 10, 15 or 20 carbon atoms, and the aryl group and its derivatives have 6, 7, 8, 9, 10, 12, 15, 17, 19 or 20 carbon atoms.

[0069]

[0070] In formula II, R3 is selected from hydrogen (H), alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 3 carbon atoms, halogen or nitro, X1, X2, X3 are present or absent, when X1, X2 or X3 are present, X1, X2, X3 are independently selected from carbonyl, ether, sulfide, sulfoxide, sulfone, alkylene with 1 to 6 carbon atoms, cycloalkyl with 5 to 20 carbon atoms and derivatives thereof, or aryl with 6 to 20 carbon atoms and derivatives thereof, n1, n2, n3 are independently integers greater than or equal to 0. It can be understood that the branched fragment shown in the above formula II is a branched structure of three or more arms formed by the reaction of the branching agent in the photochemical liquid.

[0071]

[0072] In formula III, R4 and R5 are independently selected from hydrogen, halogen, alkyl with 1 to 6 carbon atoms, cycloalkyl with 5 to 20 carbon atoms and derivatives thereof, or aryl with 6 to 20 carbon atoms and derivatives thereof; R6 is selected from H, alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 3 carbon atoms, cyano, halogen or nitro; c and d are independently selected from integers of 0 to 4; Y is present or absent, and when Y is present, Y is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene with 1 to 6 carbon atoms, cycloalkyl with 5 to 20 carbon atoms and derivatives thereof, or aryl with 6 to 20 carbon atoms and derivatives thereof. The end-capping fragment shown in formula III is a structure formed by adding an end-capping agent to the photochemical liquid to end-cap the macromolecular chain and control the molecular weight.

[0073] In the above polycarbonate, the mass percentage of the main segment shown in formula I can be 92% to 95%, the mass percentage of the branched segment shown in formula II can be 1% to 3%, and the mass percentage of the end-capping segment shown in formula III can be 3% to 5%. The polycarbonate has excellent flame retardancy, light transmittance and impact resistance, and has stable quality. The polycarbonate can be used as a thin-walled transparent flame retardant polycarbonate resin in flame retardant electronic devices and other related fields, such as transparent flame retardant fields such as television components.

[0074] The present invention is further described below by specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, conventional materials and conventional instruments, which can be commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0075] Example 1

[0076] This embodiment provides a method for preparing polycarbonate, comprising:

[0077] (1) 4736.8 g of deionized water, 1319.3 g of sodium hydroxide solution (wherein the mass percentage of sodium hydroxide is 32.2%), 1083.8 g of bisphenol A, 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent) and 0.33 g of sodium hydrosulfite (Na2S2O4) were mixed to obtain a solution containing bisphenol salt (BPA solution);

[0078] A solution containing bisphenolate is introduced into a photochemical reactor at a rate of 142.8 g / min, phosgene is introduced into the photochemical reactor at a rate of 11.38 g / min, and dichloromethane MC (a first oil phase solvent) is introduced into the photochemical reactor at a rate of 147.6 g / min, and the mixture is stirred and mixed, and sodium hydroxide solution (with a concentration of 32.2%) is added to adjust the pH of the aqueous phase to 10.5-13.0, thereby continuously forming a raw material system including bisphenolate, phosgene and a branching agent in the photochemical reactor; the raw material system including bisphenolate, phosgene and a branching agent is reacted to continuously obtain a photochemical liquid, and the photochemical liquid is continuously output to a first polycondensation reactor; during the process, the residence time of the materials in the photochemical reactor is controlled to be 10 min, and the stirring speed in the reactor is adjusted to make the molecular weight of the oil phase in the photochemical liquid be Mw1;

[0079] (2) 17.1 g of p-hydroxybenzonitrile (capping agent), 27.7 g of p-cumylphenol (capping agent) and 1063.2 g of dichloromethane (second oil phase solvent) were stirred and mixed to form a homogeneous solution to obtain a capping agent solution; 15 g of triethylamine (catalyst) and 485 g of dichloromethane (third oil phase solvent) were fully mixed to form a catalyst solution;

[0080] The end-capping agent solution is added to the first polycondensation reactor (photochemical liquid) at a rate of 22.17 g / min, and the catalyst solution is added to the first polycondensation reactor (photochemical liquid) at a rate of 1.91 g / min to carry out a first polycondensation reaction to obtain a product of the first polycondensation reaction; during the reaction, the residence time of the material in the first polycondensation reactor is controlled to be 10 min and the stirring speed in the reactor is adjusted to control the molecular weight of the oil phase in the product of the first polycondensation reaction to be Mw2, and the pH of the water phase in the product of the first polycondensation reaction is made 4.0 to 8.0; wherein, the ratio of Mw1 to Mw2 is 0.283, and Mw2 is 8290;

[0081] (3) in a second polycondensation reactor, adding a sodium hydroxide solution (with a concentration of 32.2%) to the product of the first polycondensation reaction (transferred from the first polycondensation reactor to the second polycondensation reactor) to adjust the pH of the aqueous phase to 10.0 to 13.0, and then conducting a second polycondensation reaction to obtain a product of the second polycondensation reaction;

[0082] (4) in the third polycondensation reactor, allowing the product of the second polycondensation reaction (transferred from the second polycondensation reactor to the third polycondensation reactor) to continue to react;

[0083] (5) The reaction liquid is taken out from the outlet of the third polycondensation reactor, and the reaction liquid is subjected to oil-water separation. The oil phase is obtained and washed with 0.1M dilute hydrochloric acid and deionized water in sequence, and then crushed and dried to obtain polycarbonate (powder).

[0084] Example 2

[0085] This embodiment is basically the same as Embodiment 1, except that:

[0086] 27.7 g of p-cumylphenol (capping agent) was replaced by 19.2 g of p-tert-butylphenol (capping agent), and the retention time of the material in the first polycondensation reactor was maintained at 20 min; other conditions remained unchanged.

[0087] Example 3

[0088] This embodiment is basically the same as Embodiment 1, except that:

[0089] 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent) was replaced with 26.1 g of tetrahydroxyphenylmethane (branching agent), and the retention time of the material in the first polycondensation reactor was maintained at 20 min; other conditions remained unchanged.

[0090] Example 4

[0091] This embodiment is basically the same as Embodiment 1, except that:

[0092] 15 g of triethylamine (catalyst) was replaced by 20 g of tetra-n-butylammonium bromide (catalyst); other conditions remained unchanged.

[0093] Comparative Example 1

[0094] This comparative example is substantially the same as Example 1, except that the addition position of the alkali solution (sodium hydroxide solution) is different.

[0095] The preparation process of this comparative example specifically includes:

[0096] (1) 4736.8 g of deionized water, 1319.3 g of sodium hydroxide solution (wherein the mass percentage of sodium hydroxide is 32.2%), 1083.8 g of bisphenol A, 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent) and 0.33 g of sodium hydrosulfite (Na2S2O4) were mixed to obtain a solution containing bisphenol salt (BPA solution);

[0097] A solution containing bisphenolate is introduced into a photochemical reactor at a rate of 142.8 g / min, phosgene is introduced into the photochemical reactor at a rate of 11.38 g / min, and dichloromethane MC (a first oil phase solvent) is introduced into the photochemical reactor at a rate of 147.6 g / min, and the mixture is stirred and mixed, and sodium hydroxide solution (with a concentration of 32.2%) is added to adjust the pH of the aqueous phase to 10.5-13.0, thereby continuously forming a raw material system including bisphenolate, phosgene and a branching agent in the photochemical reactor; the raw material system including bisphenolate, phosgene and a branching agent is reacted to continuously obtain a photochemical liquid, and the photochemical liquid is continuously output to a first polycondensation reactor; during the process, the residence time of the materials in the photochemical reactor is controlled to be 10 min, so that the molecular weight of the oil phase in the photochemical liquid is Mw1;

[0098] (2) 17.1 g of p-hydroxybenzonitrile (capping agent), 27.7 g of p-cumylphenol (capping agent) and 1063.2 g of dichloromethane (second oil phase solvent) were stirred and mixed to form a homogeneous solution to obtain a capping agent solution; 15 g of triethylamine (catalyst) and 485 g of dichloromethane (third oil phase solvent) were fully mixed to form a catalyst solution;

[0099] The end-capping agent solution is added to the first polycondensation reactor (photochemical liquid) at a rate of 22.17 g / min, and the catalyst solution is added to the first polycondensation reactor (photochemical liquid) at a rate of 1.91 g / min. A sodium hydroxide aqueous solution (concentration of 32.2%) is added to the first polycondensation reactor (photochemical liquid) to adjust the pH of the aqueous phase to 10.0-13.0, and then a first polycondensation reaction is carried out to obtain a product of the first polycondensation reaction; during the process, the residence time of the material in the first polycondensation reactor is controlled to be 10 min, so as to control the molecular weight of the oil phase in the product of the first polycondensation reaction to be Mw2;

[0100] (3) in a second polycondensation reactor, subjecting the product of the first polycondensation reaction (transferred from the first polycondensation reactor to the second polycondensation reactor) to a second polycondensation reaction to obtain a product of the second polycondensation reaction;

[0101] (4) in the third polycondensation reactor, allowing the product of the second polycondensation reaction (transferred from the second polycondensation reactor to the third polycondensation reactor) to continue to react;

[0102] (5) The reaction liquid is taken out from the outlet of the third polycondensation reactor, and the reaction liquid is subjected to oil-water separation. The oil phase is obtained and washed with 0.1M dilute hydrochloric acid and deionized water in sequence, and then crushed and dried to obtain polycarbonate (powder).

[0103] Comparative Example 2

[0104] This comparative example is substantially the same as Example 1, except that the addition positions of the alkali solution (sodium hydroxide solution) and the triethylamine are different.

[0105] The preparation process of this comparative example specifically includes:

[0106] (1) 4736.8 g of deionized water, 1319.3 g of sodium hydroxide solution (wherein the mass percentage of sodium hydroxide is 32.2%), 1083.8 g of bisphenol A, 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent) and 0.33 g of sodium hydrosulfite (Na2S2O4) were mixed to obtain a solution containing bisphenol salt (BPA solution);

[0107] A solution containing bisphenolate is introduced into a photochemical reactor at a rate of 142.8 g / min, phosgene is introduced into the photochemical reactor at a rate of 11.38 g / min, and dichloromethane MC (a first oil phase solvent) is introduced into the photochemical reactor at a rate of 147.6 g / min, and the mixture is stirred and mixed, and sodium hydroxide solution (with a concentration of 32.2%) is added to adjust the pH of the aqueous phase to 10.5-13.0, thereby continuously forming a raw material system including bisphenolate, phosgene and a branching agent in the photochemical reactor; the raw material system including bisphenolate, phosgene and a branching agent is reacted to continuously obtain a photochemical liquid, and the photochemical liquid is continuously output to a first polycondensation reactor; during the process, the residence time of the materials in the photochemical reactor is controlled to be 10 min, so that the molecular weight of the oil phase in the photochemical liquid is Mw1;

[0108] (2) 17.1 g of p-hydroxybenzonitrile (capping agent), 27.7 g of p-cumylphenol (capping agent) and 1063.2 g of dichloromethane (second oil phase solvent) were stirred and mixed to form a homogeneous solution to obtain a capping agent solution; 15 g of triethylamine (catalyst) and 485 g of dichloromethane (third oil phase solvent) were fully mixed to form a catalyst solution;

[0109] The end-capping agent solution is added to the first polycondensation reactor (photochemical liquid) at a rate of 22.17 g / min, and a sodium hydroxide solution (concentration of 32.2%) is added to make the pH of the aqueous phase 10.0-13.0, and then a first polycondensation reaction is carried out to obtain a product of the first polycondensation reaction; during the process, the residence time of the material in the first polycondensation reactor is controlled to be 10 min, so as to control the molecular weight of the oil phase in the product of the first polycondensation reaction to be Mw2;

[0110] (3) in the second polycondensation reactor, adding the catalyst solution to the product of the first polycondensation reaction (transferred from the first polycondensation reactor to the second polycondensation reactor) at a rate of 1.91 g / min into the first polycondensation reactor (photochemical solution), and performing a second polycondensation reaction to obtain a product of the second polycondensation reaction;

[0111] (4) in the third polycondensation reactor, allowing the product of the second polycondensation reaction (transferred from the second polycondensation reactor to the third polycondensation reactor) to continue to react;

[0112] (5) The reaction liquid is taken out from the outlet of the third polycondensation reactor, and the reaction liquid is subjected to oil-water separation. The oil phase is obtained and washed with 0.1M dilute hydrochloric acid and deionized water in sequence, and then crushed and dried to obtain polycarbonate (powder).

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing polycarbonate, comprising:

[0115] Add 4068 g of dichloromethane to 101.7 g of p-hydroxybenzonitrile and fully dissolve and shake to prepare a capping agent solution;

[0116] Add 6120 g of bisphenol A, 4169.7 g of end-capping agent solution (p-hydroxybenzonitrile solution), 135.0 g of sodium gluconate, 45.0 g of triethylamine, 18.9 kg of deionized water and 55.0 kg of dichloromethane into a 100 L reactor, and start stirring;

[0117] Then, phosgene was continuously introduced into the reactor at a flow rate of 102 g / min. At the same time, sodium hydroxide solution (with a concentration of 32.2%) was introduced into the reactor at a feeding rate of 102 g / min. The total phosgene feeding amount was controlled at 3672 g. The reaction was stopped when the phosgene feeding was completed.

[0118] The reaction solution is washed with 0.1M dilute hydrochloric acid and deionized water in sequence to obtain a polycarbonate solution terminated with p-hydroxybenzonitrile, and the polycarbonate solution is then powdered and dried in sequence to obtain polycarbonate.

[0119] Comparative Example 4

[0120] This comparative example is basically the same as Example 1, except that:

[0121] By real-time controlling the residence time of the material in the first polycondensation reactor and the stirring speed in the reactor, the ratio of Mw1 to Mw2 is made lower than 0.067; other conditions remain unchanged.

[0122] Comparative Example 5

[0123] This comparative example is basically the same as Example 1, except that:

[0124] By real-time controlling the residence time of the material in the first polycondensation reactor and the stirring speed in the reactor, Mw 1 With Mw 2The ratio is higher than 0.500; other conditions remain unchanged.

[0125] Table 1 Relevant parameters in the preparation process of polycarbonate

[0126]

[0127] Test example

[0128] 1. The following parameters of each embodiment and comparative example were tested:

[0129] 1) The weight average molecular weight of polycarbonate, the molecular weight Mw1 of the oil phase in the photochemical liquid, the molecular weight Mw2 of the oil phase in the product of the first polycondensation reaction, and the residual amounts of bisphenol salt (comonomer), branching agent and end-capping agent in polycarbonate: obtained by high performance liquid chromatography (Agilent Technologies 1260 infinity), using a refractive index detector (RI detector), dichloromethane as the mobile phase, a flow rate of 1 mL / min, and a column temperature and a box temperature of 30°C;

[0130] 2) Conversion rate of branching agent and conversion rate of end-capping agent: Take the oil phase and water phase of the final reaction solution (i.e., the reaction solution before oil-water separation), test the content of branching agent and end-capping agent, and calculate their respective conversion rates based on the initial feed amount;

[0131] 3) pH of the aqueous phase in the product of the first polycondensation reaction and adding alkali solution to the product of the first polycondensation reaction to adjust the pH of the aqueous phase: detected by a pH meter;

[0132] 4) Total nitrogen content in polycarbonate: measured using Mitsubishi element analyzer;

[0133] 5) Terminal hydroxyl content in polycarbonate: H 1 -NMR analysis, specifically the proportion of uncapped hydroxyl groups in the total polycarbonate chain;

[0134] 6) Yellowness index (test piece YI value) and light transmittance of polycarbonate: First, a Haitian MA900II1260 injection molding machine was used to injection mold polycarbonate powder into a 100mm×100mm×3mm test piece at a screw temperature of 320°C and a mold temperature of 80°C. The yellowness index (YI value) of the polycarbonate test piece was obtained by testing with a colorimeter UltraScan PRO. The light transmittance of the test piece was tested with a BYK HAZE-GARD PLUS haze meter.

[0135] 7) Vertical burning performance (UL94 flame retardant performance): According to the flame retardant performance test standard of the Underwriters Laboratory of the United States for plastic materials (UL94), specifically, at a screw temperature of 320°C and a mold temperature of 80°C, polycarbonate powder was injection molded into five groups of strips with a length of 125 mm and a width of 13 mm. The thicknesses of the five groups of strips were 1.0 mm, 1.2 mm, 1.5 mm, 2.0 mm and 3.0 mm, respectively. The five groups of strips were subjected to a UL94 flame retardant level test to find the thickness that reached the V0 level;

[0136] 8) Yellowness index (test piece YI value) and light transmittance of polycarbonate: First, a Haitian MA900II1260 injection molding machine was used to injection mold polycarbonate powder into a 100mm×100mm×3mm test piece at a screw temperature of 320°C and a mold temperature of 80°C. The yellowness index (YI value) of the polycarbonate test piece was obtained by testing with a colorimeter UltraScan PRO. The light transmittance of the test piece was tested with a BYK HAZE-GARD PLUS haze meter.

[0137] 9) Izod impact performance: According to ISO 180 standard, at a screw temperature of 320°C and a mold temperature of 80°C, polycarbonate powder was injection molded into a strip with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. The Izod notched impact test was performed at 23°C to test its impact performance;

[0138] 10) Phosgene excess rate: The molar excess rate of phosgene feed relative to bisphenol A feed, which can be calculated based on the feed rates of the two in the formula.

[0139] 2. Test results

[0140] Table 2 Properties of polycarbonate in various embodiments and comparative examples

[0141]

[0142] Analyzing the above data, we can see that:

[0143] The polycarbonate (thin-wall transparent flame-retardant polycarbonate) prepared in the embodiment of the present invention is injection molded into a 1.0 mm test piece, and its flame retardant performance reaches V0; the test piece is injection molded into a 3 mm test piece, and its test piece YI is lower than 1.30, and the transmittance in the range of 360 nm-760 nm is higher than 93%; the injection molded 4 mm test piece, the cantilever beam notch impact is tested at 23 ° C environment 11.2 KJ / m 2 .

[0144] Through the comparison of the above data, it can be seen that the continuous transparent flame-retardant polycarbonate preparation method of the present invention can realize the continuous preparation of transparent flame-retardant polycarbonate, while taking into account a relatively low phosgene excess rate and improving the conversion rate of comonomers, branching agents and end-capping agents. In addition, the flame retardant properties and optical properties of the obtained transparent flame-retardant polycarbonate product are relatively excellent.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polycarbonate, characterized in that: include: A raw material system including bisphenol salt, phosgene and a branching agent is reacted to obtain a photochemical liquid, wherein the molecular weight of the oil phase in the photochemical liquid is Mw1; Adding a capping agent and a catalyst to the photochemical liquid to carry out a first polycondensation reaction to obtain a product of the first polycondensation reaction, wherein the molecular weight of the oil phase in the product of the first polycondensation reaction is Mw2, and the pH of the water phase in the product of the first polycondensation reaction is 4.0 to 8.0; wherein the ratio of Mw1 to Mw2 is 0.067 to 0.500, and Mw2 is 6000 to 15000; After adding an alkali solution to the product of the first polycondensation reaction to make the pH of the aqueous phase be 10.0 to 13.0, a second polycondensation reaction is performed to obtain the polycarbonate.

2. The preparation method according to claim 1, characterized in that: The raw material system including bisphenol salt, phosgene and branching agent is prepared by the following process: 1 mass part of deionized water, 0.05-0.15 mass parts of alkali metal hydroxide, 0.20-0.30 mass parts of bisphenol compound and 0.00200-0.00600 mass parts of branching agent are mixed to obtain a solution containing bisphenol salt; 1.0-1.5 mass parts of the first oil phase solvent and 0.10-0.20 mass parts of phosgene are mixed to obtain a phosgene oil phase solution; 1.200-1.400 mass parts of the solution containing bisphenol salt and 1.30-1.50 mass parts of the phosgene oil phase solution are mixed, and the pH of the mixed solution is adjusted to 10.5-13.0 to obtain the raw material system including bisphenol salt, phosgene and branching agent.

3. The preparation method according to claim 2, characterized in that: The bisphenol salt includes bisphenol A sodium salt; and / or, the alkali metal hydroxide comprises sodium hydroxide; And / or, the bisphenol compound includes one or more of 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, bis(4-hydroxyphenyl)sulfide, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl)oxide, and bis(4-hydroxyphenyl)sulphide; And / or, the branching agent includes one or more of 1,1,1-trihydroxyphenylethane and tetrahydroxyphenylmethane; And / or, the first oil phase solvent includes one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene.

4. The preparation method according to claim 1, characterized in that: Adding the end-capping agent and the catalyst to the photochemical liquid to carry out the first polycondensation reaction to obtain a product of the first polycondensation reaction comprises: Adding a capping agent solution and a catalyst solution to the photochemical liquid to carry out the first polycondensation reaction to obtain a product of the first polycondensation reaction; wherein the capping agent solution comprises 0.1 to 0.7 parts by mass of the second oil phase solvent and 0.005 to 0.050 parts by mass of the capping agent, and the catalyst solution comprises 0.1 to 0.2 parts by mass of the third oil phase solvent and 0.001 to 0.005 parts by mass of the catalyst.

5. The preparation method according to claim 4, characterized in that: The end-capping agent includes one or more of p-tert-butylphenol, phenol, p-cumylphenol, cresol, p-phenylphenol, p-chlorophenol, tribromocresol, pentabromophenol, and p-hydroxybenzonitrile; and / or, the second oil phase solvent comprises one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene; And / or, the catalyst includes one or more of triethylamine, tripropylamine, n-butylammonium bromide, and pyridine; And / or, the third oil phase solvent includes one or more of dichloromethane, chloroform, monochlorobenzene and o-dichlorobenzene.

6. The preparation method according to claim 2, characterized in that: The method further comprises: After the second polycondensation reaction is completed, the oil phase is separated from the product of the second polycondensation reaction, and the oil phase is washed at least once with an acid solution and deionized water in sequence, and then the solvent is removed and then dried to obtain the polycarbonate.

7. A polycarbonate, characterized in that: The polycarbonate is obtained according to the preparation method according to any one of claims 1 to 6.

8. The polycarbonate according to claim 7, characterized in that The polycarbonate has a weight average molecular weight of 20,000 to 70,000, a total nitrogen content of 1,200 to 3,000 ppm, and a terminal hydroxyl content of 50 to 2,000 ppm.

9. The polycarbonate according to claim 7, characterized in that The polycarbonate comprises a main segment shown in formula I, a branched segment shown in formula II, and a terminal segment shown in formula III. In formula I, R1 and R2 are independently selected from hydrogen, halogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; a and b are independently selected from integers of 0 to 4; X is present or absent, and when X is present, X is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; In formula II, R3 is selected from hydrogen (H), an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen group or a nitro group, X1, X2, and X3 are present or absent, and when X1, X2, or X3 is present, X1, X2, and X3 are each independently selected from a carbonyl group, an ether group, a thioether group, a sulfoxide group, a sulfone group, an alkylene group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 20 carbon atoms and derivatives thereof, or an aryl group having 6 to 20 carbon atoms and derivatives thereof, and n1, n2, and n3 are each independently an integer greater than or equal to 0; In formula III, R4 and R5 are independently selected from hydrogen, halogen, alkyl having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof; R6 is selected from H, alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 3 carbon atoms, cyano, halogen or nitro; c and d are independently selected from integers of 0 to 4; Y is present or absent, and when Y is present, Y is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene having 1 to 6 carbon atoms, cycloalkyl having 5 to 20 carbon atoms and derivatives thereof, or aryl having 6 to 20 carbon atoms and derivatives thereof.

10. The polycarbonate according to claim 9, characterized in that In the polycarbonate, the mass percentage of the main segment represented by formula I is 92% to 95%, the mass percentage of the branched segment represented by formula II is 1% to 3%, and the mass percentage of the end-capped segment represented by formula III is 3% to 5%.

Images