A polycarbonate and a method for producing the same

Abstract

The application provides a polycarbonate and a preparation method thereof, which comprises the following steps: reacting a raw material system comprising a bisphenol salt, phosgene and a branching agent to obtain a light reaction liquid, wherein the molecular weight of the oil phase in the light reaction liquid is Mw1; adding a capping agent and a catalyst into the light reaction liquid to perform a first polycondensation reaction, so as to obtain a first polycondensation reaction product, wherein the molecular weight of the oil phase in the first polycondensation reaction product is Mw2, and the pH of the water phase in the first polycondensation reaction product 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 into the first polycondensation reaction product to make the pH of the water phase thereof be 10.0-13.0, and then performing a second polycondensation reaction to obtain the polycarbonate. The application is helpful to reduce the excess rate of phosgene and improve the conversion rate of comonomers, branching agents and capping agents.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high molecular materials, in particular to a polycarbonate and a preparation method thereof. BACKGROUND

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

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

[0004] In the preparation of polycarbonate, how to reduce the excess rate of phosgene and improve the conversion rate of comonomers and other raw materials is the research focus in the field. SUMMARY

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

[0006] The present application also provides a polycarbonate, which has high light transmission performance and excellent flame retardance and impact resistance.

[0007] The present application provides a preparation method of polycarbonate, comprising: reacting a raw material system comprising bisphenol salt, phosgene and branching agent to obtain a photochemical liquid, the molecular weight of the oil phase in the photochemical liquid being Mw1; adding an end-capping agent and a catalyst to the photochemical liquid to perform a first polycondensation reaction to obtain a product of the first polycondensation reaction, the molecular weight of the oil phase in the product of the first polycondensation reaction being Mw2, and the pH of the water phase in the product of the first polycondensation reaction being 4.0-8.0; wherein the ratio of Mw1 to Mw2 is 0.067-0.500, and Mw2 is 6000-15000; after adding an alkali liquor to the product of the first polycondensation reaction to make the pH of the water phase thereof 10.0-13.0, performing a second polycondensation reaction to obtain the polycarbonate.

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

[0009] Optionally, the bisphenolate comprises sodium bisphenol A; and / or, the alkali metal hydroxide comprises sodium hydroxide; and / or, the bisphenol compound comprises 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'-dihydroxydiphenyl, 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)sulfone; and / or, the branching agent comprises one or more of 1,1,1-trihydroxyphenylethane, tetrahydroxyphenylmethane; and / or, the first oil phase solvent comprises one or more of dichloromethane, trichloromethane, monochlorobenzene, and o-dichlorobenzene.

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

[0011] Optionally, the method further comprises: the end-capping agent comprises one or more of p-tert-butylphenol, phenol, p-cumylphenol, cresol, p-phenylphenol, p-chlorophenol, tribromophenol, pentabromophenol, p-hydroxybenzonitrile; and / or, the second oil phase solvent comprises one or more of dichloromethane, trichloromethane, monochlorobenzene and o-dichlorobenzene; and / or, the catalyst comprises one or more of triethylamine, tripropylamine, n-butyl ammonium bromide, pyridine; and / or, the third oil phase solvent comprises one or more of dichloromethane, trichloromethane, 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, the oil phase is washed with acid liquid and deionized water at least once in turn, the solvent is removed, and then the oil phase is dried to obtain the polycarbonate.

[0013] The present application provides a polycarbonate obtained according to the preparation method as described above.

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

[0015] Optionally, the polycarbonate comprises a main body fragment represented by Formula I, a branched fragment represented by Formula II, and an end-capping fragment represented by Formula III,

[0016]

[0017] In Formula I, R1 and R2 are each independently selected from hydrogen, halogen, an alkyl group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof; a and b are each independently selected from an integer of 0-4; and X is present or absent, and when X is present, X is selected from a carbonyl group, an ether group, a sulfide group, a sulfoxide group, a sulfone group, an alkylene group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof.

[0018]

[0019] In Formula II, R3 is selected from hydrogen (H), an alkyl group having 1-4 carbon atoms, an alkoxy group having 1-3 carbon atoms, halogen, or a nitro group; X1, X2, X3 are present or absent, and when X1, X2, or X3 is present, X1, X2, X3 are each independently selected from a carbonyl group, an ether group, a sulfide group, a sulfoxide group, a sulfone group, an alkylene group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof; and n1, n2, 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 group with carbon atom number of 1-6, cycloalkyl group with carbon atom number of 5-20 and its derivatives, or aryl group with carbon atom number of 6-20 and its derivatives; R6 is selected from H, alkyl group with carbon atom number of 1-4, alkoxy group with carbon atom number of 1-3, cyano, halogen or nitro; c and d are independently selected from integers of 0-4; Y is present or not, when Y is present, Y is selected from carbonyl, ether group, sulfide group, sulfoxide group, sulfone group, alkylene group with carbon atom number of 1-6, cycloalkyl group with carbon atom number of 5-20 and its derivatives, or aryl group with carbon atom number of 6-20 and its derivatives.

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

[0023] The present application provides a kind of polycarbonate and preparation method thereof, by synergic control photochemical liquid oil phase molecular weight Mw1, the product of first polycondensation reaction oil phase molecular weight Mw2 and water phase pH etc. DETAILED DESCRIPTION

[0024] To make those skilled in the art better understand the scheme of the present application, the present application is further described in detail as follows. The specific embodiments listed below are only to describe the principles and characteristics of the present application, and the examples are only used to explain the present application, not to limit the scope of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] Polycarbonate is an engineering plastic with good impact strength and ductility, which is widely used in electronic devices, automotive parts and engineering fields. However, the traditional preparation process of polycarbonate has the problems of serious excess of phosgene and low conversion rate of comonomer, branching agent and end-capping agent. The inventors found in the research that by controlling the addition sequence (addition position) of end-capping agent and catalyst, alkali liquor and the residence time of materials in the reactor, the molecular weight Mw1 of oil phase in the photochemical liquid and the molecular weight Mw2 of oil phase in the product of the first condensation reaction can be controlled. When Mw1 and Mw2 meet a certain range, it is beneficial to improve the degree of participation of branching agent and end-capping agent in the reaction, so that the reaction efficiency is improved, and then it is beneficial to improve the conversion rate of comonomer, branching agent and end-capping agent, and effectively solve the problem of serious excess of phosgene.

[0026] Based on this, the embodiment of the present application provides a preparation method of polycarbonate, comprising: reacting a raw material system comprising bisphenol salt, phosgene and branching agent to obtain a photochemical liquid, the molecular weight of the oil phase in the photochemical liquid being Mw1; adding end-capping agent and catalyst to the photochemical liquid to carry out the first condensation reaction, and obtaining the product of the first condensation reaction, the molecular weight of the oil phase in the product of the first condensation reaction being Mw2, and the pH of the water phase in the product of the first condensation reaction being 4.0-8.0; wherein the ratio of Mw1 to Mw2 is 0.067-0.500, and Mw2 is 6000-15000; adding alkali liquor to the product of the first condensation reaction to make the pH of the water phase thereof 10.0-13.0, and then carrying out the second condensation 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 application, by synergistically controlling the process conditions such as 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 condensation reaction and the pH of the water phase, which meet the above-mentioned ranges, it is beneficial to improve the degree of participation of branching agent and end-capping agent in the reaction, so that the reaction efficiency is improved, and then it is beneficial to realize that the conversion rate (conversion efficiency) of bisphenol salt (comonomer), branching agent and end-capping agent is greater than 99%, and the excess rate of phosgene is reduced.

[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 formed by any two of them, Mw2 can be 6000, 8000, 10000, 11000, 13000, 14000, 15000 or a range formed by any two of them, the pH of the water phase in the product of the first condensation reaction can be 4, 5, 6, 7, 8 or a range formed by any two of them, and the pH of the water phase of the product of the first condensation reaction after adding alkali liquor thereto can be 10, 11, 12, 13 or a range formed by any two of them.

[0029] Some specific fields (for example, thin-walled fields with small thickness (3 mm or less)) have higher requirements for the flame retardancy, impact resistance and light transmittance of polycarbonates. Due to the limitations of the preparation process conditions of polycarbonates and other factors, the flame retardant properties of some polycarbonates (for example, bisphenol A general polycarbonates) do not meet the requirements of thin-walled fields with small thickness (3 mm or less), which limits their application and reduces their use in transparent thin-walled fields meeting the UL 94 plastic material flammability test standard 5VA level. Therefore, it is necessary to improve the thin-walled flame retardant properties of polycarbonates. In addition, while improving the thin-walled flame retardant properties of polycarbonates, it is also necessary to maintain their light transmittance and necessary impact properties. High-performance thin-walled transparent flame-retardant polycarbonates in the prior art are mainly produced by using interfacial phosgene intermittent method, and adding flame-retardant functional copolymer structures during synthesis to improve their flame retardant properties. For example, patent document CN102159643B uses a polyester-polycarbonate-polysiloxane terpolymer, and uses a cyano phenol end-capping, and then adds a certain amount of brominated polycarbonate and aromatic sulfone sulfonate during subsequent processing. The final product has good flame retardant and low smoke properties, 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 properties are relatively poor. In addition, adding flame retardants during the post-processing of polycarbonates can also improve the flame retardant properties of polycarbonates (polymers), but this scheme can only make the flame retardant properties of polycarbonates reach the level of 3.0 mm of UL94; patent document CN102164991B reports the addition of sulfonate flame retardants in polycarbonates, and the addition amount of sulfonate is between 0.01wt% and 0.1wt%, but when the polycarbonate is injection molded into a 3 mm thick extruded sheet, the sheet has a burning length of less than 150 mm, a drop burning time of less than 3 seconds and a total burning time of less than 15 seconds, and the burning performance is poor.

[0030] In the embodiments of the present application, under the above preparation method system, the amounts of bisphenol compounds, branching agents, end-capping agents and other raw materials are further adjusted, and the preparation process of the raw material system and other conditions are adjusted. The structure and content of the main segment, branching segment and end-capping segment in the polycarbonate structure are improved, 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 branching agent described above is prepared by the following process: 1 part by mass of deionized water, 0.05-0.15 parts by mass of alkali metal hydroxide, 0.20-0.30 parts by mass of bisphenol compound, and 0.00200-0.00600 parts by mass of branching agent are mixed to obtain a solution containing bisphenolate (BPA feed solution 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; after 1.200-1.400 parts by mass of the solution containing bisphenolate and 1.30-1.50 parts by mass of the phosgene oil phase solution are mixed, the pH of the mixed solution (aqueous phase thereof) is adjusted to 10.5-13.0 to obtain the raw material system comprising bisphenolate, phosgene and branching agent described above. Illustratively, the parts by mass of the alkali metal hydroxide described above is 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.15, or a range consisting of any two of them, preferably 0.06-0.11, the parts by mass of the bisphenol compound described above is 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.30, or a range consisting of any two of them, preferably 0.20-0.25, the parts by mass of the branching agent described above is 0.00200, 0.00285, 0.00300, 0.00400, 0.00500, 0.00600, or a range consisting of any two of them, preferably 0.00285-0.00600, the parts by mass of the first oil phase solvent described above is 1.0, 1.2, 1.25, 1.3, 1.5, or a range consisting of any two of them, preferably 1.2-1.3, the parts by mass of the phosgene described above is 0.10, 0.11, 0.15, 0.20, or a range consisting of any two of them, preferably 0.11-0.20, the parts by mass of the solution containing bisphenolate (BPA feed solution or homogeneous solution) described above is 1.200, 1.263, 1.300, 1.350, 1.366, 1.400, or a range consisting of any two of them, preferably 1.263-1.366, the parts by mass of the phosgene oil phase solution described above is 1.30, 1.31, 1.40, 1.50, or a range consisting of any two of them, preferably 1.31-1.50. This helps to prepare a polycarbonate that has excellent flame retardancy, light transmittance and impact resistance, and is stable in quality, which can be used as a thin-walled transparent flame-retardant polycarbonate resin in the field of flame-retardant electronic devices and the like, such as transparent flame-retardant fields of television components and the like.

[0032] The solution containing the bisphenolate can also include sodium dithionite (Na2S2O4) in an amount of 0.00003 to 0.00007 parts by mass (based on 1 part by mass of deionized water), for example, 0.00003, 0.00004, 0.00005, 0.00006, 0.00007, or a range defined by any two of these values. Further, the solution containing the bisphenolate (BPA feed or homogeneous solution) can be prepared by purging with nitrogen gas and agitating the mixture until homogeneous under mechanical agitation.

[0033] The bisphenolate can include sodium bisphenol A.

[0034] The bisphenol compound can include 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'-dihydroxydiphenyl, 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, or bis(4-hydroxyphenyl)sulfone, preferably 2,2-bis(4-hydroxyphenyl)propane.

[0035] The alkali metal hydroxide can include sodium hydroxide.

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

[0037] The first oil phase solvent can include one or more of dichloromethane, trichloromethane, monochlorobenzene, and ortho-dichlorobenzene.

[0038] The preparation of the raw material system including the bisphenolate, the phosgene, and the branching agent can be prepared using different charging tanks, such as a bisphenol A (BPA) charging tank, an end-capping agent charging tank, and a catalyst charging tank.

[0039] Specifically, the solution containing the bisphenolate (e.g., BPA feed), the phosgene, and the first oil phase solvent can be separately added to a reaction tank to form a mixed solution, and then the pH of the mixed solution can be adjusted to 10.5 to 13.0 to form the raw material system including the bisphenolate, the phosgene, and the branching agent.

[0040] More specifically, in the process of adjusting the pH of the mixed solution to 10.5-13.0 to obtain the raw material system comprising the bisphenolate, the phosgene and the branching agent, the pH of the aqueous phase in the mixed solution can be adjusted to 10.5-13.0 by adding an alkali solution (e.g. sodium hydroxide) to the mixed solution, and then the raw material system comprising the bisphenolate, the phosgene and the branching agent is obtained. Under the preparation method system provided in the embodiments of the present application, the raw material system is helpful to prepare the polycarbonate with excellent flame retardant performance, light transmission performance and impact resistance performance and stable quality, which can be used as a thin-walled transparent flame-retardant polycarbonate resin in the related field of flame-retardant electronic devices, such as transparent flame-retardant field of television components.

[0041] The phosgene is generally stored in a phosgene storage tank and is directly introduced into the reaction kettle (reaction liquid) in the form of gas phase by controlling its flow rate through a flow control table.

[0042] After the reaction of the raw material system comprising the bisphenolate, the phosgene and the branching agent, the photochemical liquid is obtained.

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

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

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

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

[0047] The catalyst can include one or more of triethylamine, tripropylamine, n-butyl ammonium bromide (e.g., tetra-n-butyl ammonium bromide), and pyridine.

[0048] The third oil phase solvent can include one or more of dichloromethane (MC), trichloromethane, 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 can include sodium hydroxide, such as an aqueous sodium hydroxide solution, in which the concentration of sodium hydroxide can be 30.0% to 40.0%, such as 30.0%, 32.2%, 35.0%, 37.0%, 40.0%, or a range defined by any two of these values.

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

[0052] In particular implementations, the acid solution can be a dilute acid solution such as dilute hydrochloric acid or dilute sulfuric acid, and the concentration of the dilute hydrochloric acid and the dilute sulfuric acid can each be 0.08 to 0.12 M, such as 0.08 M, 0.09 M, 0.10 M, 0.11 M, 0.12 M, or a range defined by any two of these values.

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

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

[0055] Specifically, the flow of the above preparation method comprises: raw material system comprising bisphenol salt, phosgene and branching agent is reacted in a photochemical reactor to obtain a photochemical liquid; the photochemical liquid is taken out from the outlet of the photochemical reactor and pumped into a first polycondensation reactor to perform a first polycondensation reaction to obtain a first polycondensation reaction product; the first polycondensation reaction product is taken out from the outlet of the first polycondensation reactor and transported to a second polycondensation reactor to perform a second polycondensation reaction to obtain a polycarbonate.

[0056] In order to make the raw material reaction more sufficient and improve the yield of polycarbonate, a third polycondensation reactor can be additionally connected after the second polycondensation reactor, and the feed inlet of the third polycondensation reactor is connected in communication with the outlet of the second polycondensation reactor. The second polycondensation reaction product is taken out from the outlet of the second polycondensation reactor and transported to the third polycondensation reactor by a peristaltic pump, and then the polycondensation reaction (third polycondensation reaction) is continuously performed in the third polycondensation reactor. The reaction product taken out 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 photochemical reactor refers to a reaction device capable of mixing and dispersing. The type of disperser in the photochemical reactor is not specially limited in the embodiments of the present application, and any device capable of ensuring that the reaction materials are mixed and dispersed and fully reacted can be selected, such as a dynamic disperser or a static mixer (for example, SMV type or SMX type static mixer of Sulzer Company in Switzerland), 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 mixing and dispersing, and the embodiments of the present application do not specially limit them, but these reaction devices need to ensure that the reaction materials have sufficient mixing and dispersion time and residence time to ensure that the reaction is sufficient, for example, a dynamic disperser, a static mixer or a stirred reactor can be selected, preferably a stirred reactor.

[0058] To further solve the problems of excessive phosgene and low production efficiency in the existing intermittent process, the preparation method of the embodiment of the present application can also realize continuous production of polycarbonate. Specifically, the above preparation method further comprises: continuously feeding a raw material system comprising bisphenol salt, phosgene and branching agent into the reaction system for reaction to obtain an alysis liquid, continuously adding a capping agent and a catalyst to the alysis liquid to perform a first polycondensation reaction to obtain a first polycondensation reaction product, and then continuously adding an alkali solution to the first polycondensation reaction product to make the pH of the water phase thereof 10.0-13.0, and then performing a second polycondensation reaction to continuously obtain polycarbonate, and continuously outputting the polycarbonate from the reaction system, wherein the amount of polycarbonate output from the reaction system is not less than the amount of newly generated polycarbonate after the reaction of the raw material fed into the reaction system. In the above preparation process, the raw material is continuously fed into the reaction system and continuously reacts in the reaction system to generate polycarbonate, and the polycarbonate is continuously output from the reaction system, wherein the amount of output polycarbonate is not less than the amount of newly generated polycarbonate, thereby realizing continuous production of polycarbonate. Compared with the existing intermittent process, the embodiment of the present application continuously feeds the raw material into the reaction system and continuously outputs the product from the reaction system, avoiding the low reaction efficiency caused by the accumulation of raw materials and products inside the reaction system in the intermittent process, and further causing problems such as excessive phosgene and low production efficiency, which helps to reduce the excessive phosgene rate, and also improves the utilization rate of comonomers, branching agents, capping agents and the like, and improves the yield (output) of polycarbonate.

[0059] In some embodiments, the above continuously feeding a raw material system comprising bisphenol salt, phosgene and branching agent into the reaction system for reaction to obtain an alysis liquid comprises: continuously feeding a solution containing bisphenol salt, phosgene and a first oil phase solvent into the reaction system respectively to obtain an alysis liquid.

[0060] The feeding speed 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 formed by any two of them, the feeding speed 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 formed by any two of them, and the feeding speed 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 formed by any two of them.

[0061] In some embodiments, during the process of continuously adding the end-capping agent and the catalyst to the electrolytic solution to carry out the first polycondensation reaction to obtain the product of the first polycondensation reaction, the end-capping agent solution can be fed at a speed of 20.00-30.00 g / min, such as 20.00 g / min, 22.17 g / min, 25.00 g / min, 30.00 g / min, or a range defined by any two of them, and the catalyst solution can be fed at a speed of 1.00-3.00 g / min, such as 1.00 g / min, 1.50 g / min, 1.91 g / min, 2.00 g / min, 3.00 g / min, or a range defined by any two of them.

[0062] In the preparation method system of the embodiments of the present application, the order of addition (addition position) of the end-capping agent and the catalyst, the alkali solution is kept unchanged, and the residence time of the material in the electrolytic reactor or the first polycondensation reactor (the retention time of the fixed liquid level) is controlled, i.e. the time from the entry of the material into the electrolytic reactor or the first polycondensation reactor to the extraction of the product or the remaining material formed therefrom from the electrolytic reactor or the first polycondensation reactor, to control the molecular weight of the oil phase in the electrolytic solution Mw1 and the molecular weight of the oil phase in the product of the first polycondensation reaction Mw2. This helps to prepare a polycarbonate with excellent flame retardant performance, light transmission performance, and impact resistance, and stable quality, which can be used as a thin-walled transparent flame-retardant polycarbonate resin in the field of flame-retardant electronic devices and other related fields, such as transparent flame-retardant fields of television components.

[0063] In addition, in the preparation method system of the embodiments of the present application, the order of addition (addition position) of the end-capping agent and the catalyst, the alkali solution, and the residence time of the material in the electrolytic reactor or the first polycondensation reactor (the retention time of the fixed liquid level) are kept unchanged, and the stirring speed in the electrolytic reactor or the first polycondensation reactor is changed to change the mixing scale of the oil-water two-phase, which also affects the molecular weight of the oil phase in the electrolytic solution Mw1 and the molecular weight of the oil phase in the product of the first polycondensation reaction Mw2.

[0064] The embodiments of the present application also provide a polycarbonate obtained by the above preparation method. The polycarbonate has excellent flame retardant performance, light transmission performance, impact resistance, and stable quality.

[0065] In some embodiments, the polycarbonate has a weight average molecular weight of 20000-70000, a total nitrogen content of 1200-3000 ppm, and a terminal hydroxyl group content of 50-2000 ppm.

[0066] In some embodiments, the polycarbonate comprises a main segment represented by Formula I, a branched segment represented by Formula II, and an end-capping segment represented by Formula III,

[0067]

[0068] In Formula I, R1and R2are each independently selected from hydrogen, halogen, an alkyl 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; a and b are independently selected from integers from 0 to 4; and X is present or absent, and when X is present, X is selected from a carbonyl group, an ether group, a sulfide 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. Illustratively, in R1and R2, the alkyl group has 1, 2, 3, 4, 5, or 6 carbon atoms, the cycloalkyl group and derivatives thereof have 5, 7, 10, 15, or 20 carbon atoms, the aryl group and derivatives thereof have 6, 7, 8, 9, 10, 12, 15, 17, 19, or 20 carbon atoms, a and b are independently selected from 0, 1, 2, 3, or 4; and in X, the alkylene group has 1, 2, 3, 4, 5, or 6 carbon atoms, the cycloalkyl group and derivatives thereof have 5, 7, 10, 15, or 20 carbon atoms, the aryl group and derivatives thereof have 6, 7, 8, 9, 10, 12, 15, 17, 19, or 20 carbon atoms.

[0069]

[0070] In Formula II, R3is selected from hydrogen (H), an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, halogen, or a nitro group; X1, X2, X3are present or absent, and when X1, X2, or X3are present, each of X1, X2, X3is independently selected from a carbonyl group, an ether group, a sulfide 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 each of n1, n2, n3is independently an integer greater than or equal to 0. It is understood that the branched segment shown in Formula II is a three-arm or more branched structure formed by the reaction of a branching agent in the photochemical solution.

[0071]

[0072] In formula III, R4and R5are independently selected from hydrogen, halogen, alkyl with carbon number of 1-6, cycloalkyl with carbon number of 5-20 and its derivatives, or aryl with carbon number of 6-20 and its derivatives; R6is selected from H, alkyl with carbon number of 1-4, alkoxy with carbon number of 1-3, cyano, halogen or nitro; c and d are independently selected from integers of 0-4; Y is present or not, when Y is present, Y is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene with carbon number of 1-6, cycloalkyl with carbon number of 5-20 and its derivatives, or aryl with carbon number of 6-20 and its derivatives. The end-capping segment shown in formula III is a structure formed by adding an end-capping agent to a photochemical solution for end-capping of a macromolecular chain and control of molecular weight.

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

[0074] The application will be further described below through specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used in the following are conventional reagents, conventional materials and conventional instruments, which are commercially available. The reagents and materials involved can also be obtained by conventional synthesis methods.

[0075] Example 1

[0076] The present embodiment provides a preparation method of polycarbonate, comprising:

[0077] (1) 4736.8 g of deionized water, 1319.3 g of sodium hydroxide solution (with a mass percentage content of 32.2% of sodium hydroxide), 1083.8 g of bisphenol A, and 24.7 g of 1,1,1-trihydroxyphenyl ethane THPE (branching agent) and 0.33 g of sodium hyposulfite (Na2S2O4) are mixed to obtain a solution containing bisphenol salt (BPA solution);

[0078] The solution containing the bisphenolate is fed into the photochemical reactor at a rate of 142.8 g / min, the phosgene is fed into the photochemical reactor at a rate of 11.38 g / min, the dichloromethane MC (first oil phase solvent) is fed into the photochemical reactor at a rate of 147.6 g / min, the mixture is stirred and mixed, and the sodium hydroxide solution (32.2% in concentration) is supplemented to adjust the pH of the aqueous phase to 10.5-13.0, thereby continuously forming a raw material system comprising the bisphenolate, the phosgene and the branching agent in the photochemical reactor; the raw material system comprising the bisphenolate, the phosgene and the branching agent is allowed to react, continuously obtaining the photochemical liquid, and the photochemical liquid is continuously output into the first polycondensation reactor; during the process, the residence time of the material in the photochemical reactor is controlled to be 10 min and the stirring speed in the reactor is adjusted, so that the molecular weight of the oil phase in the photochemical liquid is Mw1.

[0079] (2) 17.1 g of p-hydroxybenzonitrile (end-capping agent), 27.7 g of p-cumylphenol (end-capping agent) and 1063.2 g of dichloromethane (second oil phase solvent) are stirred and mixed uniformly to form a homogeneous solution to obtain an end-capping agent solution; 15 g of triethylamine (catalyst) and 485 g of dichloromethane (third oil phase solvent) are mixed thoroughly 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, and the first polycondensation reaction is carried out to obtain the 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 and the stirring speed in the reactor is adjusted, so that the molecular weight of the oil phase in the product of the first polycondensation reaction is Mw2, and the pH of the aqueous phase in the product of the first polycondensation reaction is 4.0-8.0; wherein the ratio of Mw1 to Mw2 is 0.283, and Mw2 is 8290;

[0081] (3) In the second polycondensation reactor, the product of the first polycondensation reaction (delivered from the first polycondensation reactor to the second polycondensation reactor) is added with the sodium hydroxide solution (32.2% in concentration) to make the pH of the aqueous phase 10.0-13.0, and the second polycondensation reaction is carried out to obtain the product of the second polycondensation reaction;

[0082] (4) In the third polycondensation reactor, the product of the second polycondensation reaction (delivered from the second polycondensation reactor to the third polycondensation reactor) is allowed to continue to react;

[0083] (5) The reaction liquid is taken out from the outlet of the third polycondensation reactor, the oil and water are separated, the oil phase is obtained, and then the oil phase is washed with 0.1 M dilute hydrochloric acid and deionized water, and then the polycarbonate (powder) is obtained after crushing and drying.

[0084] Example 2

[0085] This example is basically identical with Example 1, except that:

[0086] 19.2 g of p-tert-butylphenol (end-capping agent) is used to replace 27.7 g of p-cumylphenol (end-capping agent), and the residence time of the material in the first polycondensation reactor is maintained at 20 min; other conditions remain unchanged.

[0087] Example 3

[0088] This example is basically identical with Example 1, except that:

[0089] 26.1 g of tetrahydroxyphenylmethane (branching agent) is used to replace 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent), and the residence time of the material in the first polycondensation reactor is maintained at 20 min; other conditions remain unchanged.

[0090] Example 4

[0091] This example is basically identical with Example 1, except that:

[0092] 20 g of tetra-n-butylammonium bromide (catalyst) is used to replace 15 g of triethylamine (catalyst); other conditions remain unchanged.

[0093] Comparative Example 1

[0094] This comparative example is basically identical with Example 1, except that the addition position of the lye (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 (with a mass percentage content of sodium hydroxide of 32.2%), 1083.8 g of bisphenol A, and 24.7 g of 1,1,1-trihydroxyphenylethane THPE (branching agent) and 0.33 g of sodium hyposulfite (Na2S2O4) are mixed to obtain a solution containing bisphenol salt (BPA feed solution);

[0097] The solution containing the bisphenolate is fed into the photochemical reactor at a rate of 142.8 g / min, the phosgene is fed into the photochemical reactor at a rate of 11.38 g / min, the dichloromethane MC (first oil phase solvent) is fed into the photochemical reactor at a rate of 147.6 g / min, the mixture is stirred and mixed, and at the same time, the sodium hydroxide solution (concentration of 32.2%) is supplemented to adjust the pH of the aqueous phase to 10.5-13.0, so that a raw material system including the bisphenolate, the phosgene and the branching agent is continuously formed in the photochemical reactor; the raw material system including the bisphenolate, the phosgene and the branching agent is allowed to react, so that the photochemical liquid is continuously obtained and output to the first polycondensation reactor; during the process, the residence time of the material in the photochemical reactor is controlled to be 10 min, so that the molecular weight of the oil phase in the photochemical liquid is Mwl;

[0098] (2) 17.1 g of p-hydroxybenzonitrile (end-capping agent), 27.7 g of p-cumylphenol (end-capping agent) and 1063.2 g of dichloromethane (second oil phase solvent) are stirred and mixed uniformly to form a homogeneous solution to obtain an end-capping agent solution; 15 g of triethylamine (catalyst) and 485 g of dichloromethane (third oil phase solvent) are mixed thoroughly 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, and after the aqueous phase of the first polycondensation reactor (photochemical liquid) is adjusted to have a pH of 10.0-13.0 by adding the sodium hydroxide aqueous solution (concentration of 32.2%), the first polycondensation reaction is allowed to proceed, so that the product of the first polycondensation reaction is obtained; during the process, the residence time of the material in the first polycondensation reactor is controlled to be 10 min, so that the molecular weight of the oil phase in the product of the first polycondensation reaction is controlled to be Mw2;

[0100] (3) The product of the first polycondensation reaction (delivered from the first polycondensation reactor to the second polycondensation reactor) is allowed to undergo the second polycondensation reaction in the second polycondensation reactor, so that the product of the second polycondensation reaction is obtained;

[0101] (4) The product of the second polycondensation reaction (delivered from the second polycondensation reactor to the third polycondensation reactor) is allowed to continue to react in the third polycondensation reactor;

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

[0103] Comparative Example 2

[0104] This comparative example is basically identical with Example 1, except that the addition positions of the alkali solution (sodium hydroxide solution) and 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 (with a mass percentage of sodium hydroxide of 32.2%), 1083.8 g of bisphenol A, and 24.7 g of 1,1,1-trihydroxyphenyl ethane THPE (branching agent) and 0.33 g of sodium dithionite (Na2S2O4) were mixed to obtain a solution containing bisphenolate (BPA solution);

[0107] The solution containing bisphenolate was introduced into the photochemical reactor at a flow rate of 142.8 g / min, the phosgene was introduced into the photochemical reactor at a flow rate of 11.38 g / min, and the dichloromethane MC (first oil phase solvent) was introduced into the photochemical reactor at a flow rate of 147.6 g / min. The mixture was stirred while supplementing the sodium hydroxide solution (concentration of 32.2%) to adjust the pH of the aqueous phase to 10.5-13.0, thereby continuously forming a raw material system including bisphenolate, phosgene and branching agent in the photochemical reactor; the raw material system including bisphenolate, phosgene and branching agent was allowed to react, continuously obtaining a photochemical liquid, and the photochemical liquid was continuously output to the first polycondensation reactor; during this period, by controlling the residence time of the material in the photochemical reactor to be 10 min, the molecular weight of the oil phase in the photochemical liquid was Mw1;

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

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

[0110] (3) In the second polycondensation reactor, the above catalyst solution was added to the product of the first polycondensation reaction (delivered from the first polycondensation reactor to the second polycondensation reactor) at a flow rate of 1.91 g / min to the first polycondensation reactor (photochemical liquid), and the second polycondensation reaction was carried out to obtain the product of the second polycondensation reaction;

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

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

[0113] Comparative Example 3

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

[0115] After 101.7g of p-hydroxybenzonitrile is added into 4068g of dichloromethane, it is fully dissolved and fully shaken to prepare an end-capping agent solution;

[0116] Into a 100L reaction kettle, 6120g of bisphenol A, 4169.7g of the end-capping agent solution (p-hydroxybenzonitrile solution), 135.0g of sodium gluconate, 45.0g of triethylamine, 18.9kg of deionized water and 55.0kg of dichloromethane are added, and stirring is started;

[0117] Then, the reaction kettle is continuously fed with phosgene at a flow rate of 102g / min, and a sodium hydroxide solution (concentration of 32.2%) is also fed into the reaction kettle at the same time, and the feeding speed of the sodium hydroxide solution is kept at 102g / min, the total feeding amount of phosgene is controlled at 3672g, and the reaction is stopped when the feeding of phosgene is completed;

[0118] The reaction liquid is sequentially washed with 0.1M dilute hydrochloric acid and deionized water to obtain a p-hydroxybenzonitrile-terminated polycarbonate solution, and then the polycarbonate solution is sequentially subjected to powdering and drying to obtain polycarbonate.

[0119] Comparative Example 4

[0120] The present comparative example is basically the same as Example 1, and the difference lies in that:

[0121] The residence time of the material in the first polycondensation reactor and the stirring speed in the reactor are controlled in real time, so that the ratio of Mw1 to Mw2 is lower than 0.067; and other conditions remain unchanged.

[0122] Comparative Example 5

[0123] The present comparative example is basically the same as Example 1, and the difference lies in that:

[0124] The residence time of the material in the first polycondensation reactor and the stirring speed in the reactor are controlled in real time, so that the ratio of Mw 1 Mw 2the ratio of the viscosity of the first polycondensation reaction product to the viscosity of the second polycondensation reaction product is higher than 0.500; and other conditions remain unchanged.

[0125] Table 1 Related parameters in polycarbonate preparation process

[0126]

[0127] Test Example

[0128] 1. The following parameters of each example and comparative example were detected

[0129] 1) Weight average molecular weight of polycarbonate, molecular weight Mw1 of oil phase in photochemical solution, molecular weight Mw2 of oil phase in product of first polycondensation reaction, and residual amount of bisphenol salt (comonomer), branching agent and end-capping agent in polycarbonate: obtained by high performance liquid chromatograph (Agilent Technologies 1260 infinity), refractive index detector (RI detector) was selected, dichloromethane was used as mobile phase, flow rate was 1 mL / min, column temperature and box temperature were both 30℃;

[0130] 2) Conversion rate of branching agent and conversion rate of end-capping agent: oil phase and water phase of final reaction liquid (i.e. reaction liquid before oil-water separation) were taken to test the content of branching agent and end-capping agent, and the conversion rates of each were calculated according to the initial feeding amount;

[0131] 3) pH of water phase in product of first polycondensation reaction and pH adjustment of water phase in product of first polycondensation reaction by adding alkali solution: detected by pH meter;

[0132] 4) Total nitrogen content in polycarbonate: determined by Mitsubishi elemental analyzer;

[0133] 5) End hydroxyl content in polycarbonate: analyzed by H 1 -NMR, specifically, the proportion of un-terminated hydroxyl group in total polycarbonate chain;

[0134] 6) Yellow index (test piece YI value) of polycarbonate and light transmittance of polycarbonate: first, Haitian MA900II1260 injection molding machine was used to inject polycarbonate powder into 100mm×100mm×3mm test pieces under the conditions of screw temperature of 320℃ and mold temperature of 80℃, then the yellow index (YI value) of polycarbonate test pieces was obtained by color difference meter UltraScan PRO test, and the light transmittance of the test pieces was tested by HAZE-GARD PLUS haze meter of BYK company;

[0135] 7) Vertical burning performance (UL94 flame retardant performance): according to the flame retardant performance test standard (UL94) of the American Insurance Laboratory plastic material, specifically, under the condition that the screw temperature is 320℃ and the mold temperature is 80℃, the polycarbonate powder is injection molded into five groups of samples with a length of 125mm and a width of 13mm, and the thicknesses of the five groups of samples are 1.0mm, 1.2mm, 1.5mm, 2.0mm and 3.0mm respectively, the five groups of samples are subjected to UL94 flame retardant level test, and the thickness reaching V0 level is found;

[0136] 8) Yellowness index of polycarbonate (test piece YI value) and light transmittance of polycarbonate: first, using Haitian MA900II1260 injection molding machine, under the condition that the screw temperature is 320℃ and the mold temperature is 80℃, the polycarbonate powder is injection molded into a test piece with a size of 100mm*100mm*3mm, the yellowness index (YI value) of the polycarbonate test piece is obtained by color difference meter UltraScan PRO test, and the light transmittance of the test piece is tested by HAZE-GARD PLUS haze meter of BYK company;

[0137] 9) Izod impact performance: according to the standard of ISO 180, under the condition that the screw temperature is 320℃ and the mold temperature is 80℃, the polycarbonate powder is injection molded into a sample with a length of 80mm, a width of 10mm and a thickness of 4mm, and the impact performance is tested by conducting Izod notched impact test at 23℃;

[0138] 10) Excess rate of phosgene: the molar excess rate of phosgene feeding amount relative to bisphenol A feeding amount, which can be calculated according to the feeding rate of the two in the formula.

[0139] 2, Test results

[0140] Table 2 Properties of polycarbonate of each example and comparative example

[0141]

[0142] From the above data, it can be seen that:

[0143] The polycarbonate (thin-walled transparent flame-retardant polycarbonate) prepared in the embodiment of the present application has the following properties: when injection molded into a 1.0mm test piece, the flame retardant performance reaches V0; when injection molded into a 3mm test piece, the test piece YI is lower than 1.30, and the light transmittance in the range of 360nm-760nm is higher than 93%; when injection molded into a 4mm sample, the Izod notched impact is 11.2KJ / m 2 .

[0144] It can be known from the above data comparison that the continuous transparent flame-retardant polycarbonate preparation method can realize continuous preparation of transparent flame-retardant polycarbonate, meanwhile, relatively low excess rate of phosgene can be considered, conversion rates of comonomer, branching agent and end-capping agent and the like are improved, in addition, the prepared transparent flame-retardant polycarbonate product has relatively optimal flame-retardant performance and optical performance.

[0145] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the preparation of polycarbonate, characterized in that, comprising: reacting a raw material system comprising bisphenolate, phosgene and branching agent to obtain a phosgenation liquid, wherein the molecular weight of the oil phase in the phosgenation liquid is Mw1; adding an end-capping agent and a catalyst to the phosgenation liquid to perform a first polycondensation reaction to obtain a first polycondensation reaction product, wherein the molecular weight of the oil phase in the first polycondensation reaction product is Mw2, and the pH of the water phase in the first polycondensation reaction product 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 first polycondensation reaction product to make the pH of the water phase thereof 10.0-13.0, and then performing a second polycondensation reaction to obtain the polycarbonate.

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

3. The production method according to claim 2, wherein the bisphenolate comprises bisphenol A sodium salt; and / or, the alkali metal hydroxide comprises sodium hydroxide; and / or, the bisphenol compound comprises 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'-dihydroxydiphenyl, 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) sulfone; 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, trichloromethane, monochlorobenzene, and o-dichlorobenzene.

4. The method of claim 1, wherein, adding the end-capping agent and the catalyst to the phosgenation liquid to perform the first polycondensation reaction to obtain the first polycondensation reaction product, comprising: The first polycondensation reaction is carried out by adding an end-capping agent solution and a catalyst solution into the photochemical solution, to obtain a product of the first polycondensation reaction; wherein the end-capping agent solution comprises 0.1-0.7 parts by mass of a second oil phase solvent, and 0.005-0.050 parts by mass of the end-capping agent; and the catalyst solution comprises 0.1-0.2 parts by mass of a third oil phase solvent, and 0.001-0.005 parts by mass of the catalyst.

5. The preparation method according to claim 4, wherein the end-capping agent comprises one or more of p-tert-butyl phenol, phenol, p-cumyl phenol, cresol, p-phenyl phenol, p-chlorophenol, tribromophenol, pentabromophenol, and p-hydroxybenzonitrile; and / or the second oil phase solvent comprises one or more of dichloromethane, trichloromethane, monochlorobenzene, and o-dichlorobenzene; and / or the catalyst comprises one or more of triethylamine, tripropylamine, n-butyl ammonium bromide, and pyridine; and / or the third oil phase solvent comprises one or more of dichloromethane, trichloromethane, monochlorobenzene, and o-dichlorobenzene. The method further comprises: After the second polycondensation reaction is completed, an oil phase is separated from the product of the second polycondensation reaction, the oil phase is washed with an acid solution and deionized water at least once in sequence, the solvent is removed, and then the oil phase is dried to obtain the polycarbonate. The polycarbonate is obtained by the preparation method according to any one of claims 1-6. The polycarbonate has a weight average molecular weight of 20,000-70,000, a total nitrogen content of 1,200-3,000 ppm, and a terminal hydroxyl group content of 50-2,000 ppm.

6. The preparation method according to claim 2, characterized in that, The polycarbonate comprises a main segment represented by Formula I, a branched segment represented by Formula II, and an end-capping segment represented by Formula III, In Formula I, R1 and R2 are each independently selected from hydrogen, halogen, an alkyl group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof; a and b are each independently selected from an integer of 0-4; and X is present or absent, and when X is present, X is selected from a carbonyl group, an ether group, a sulfide group, a sulfoxide group, a sulfone group, an alkylene group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof.

7. A polycarbonate characterized by, In Formula II, R3 is selected from hydrogen (H), an alkyl group having 1-4 carbon atoms, an alkoxy group having 1-3 carbon atoms, halogen, 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 sulfide group, a sulfoxide group, a sulfone group, an alkylene group having 1-6 carbon atoms, a cycloalkyl group having 5-20 carbon atoms and derivatives thereof, or an aryl group having 6-20 carbon atoms and derivatives thereof; and n1, n2, and n3 are each independently an integer greater than or equal to 0.

8. The polycarbonate of claim 7, wherein, ​ 9. The polycarbonate of claim 7, wherein, ​ ​ ​ In formula III, R4 and R5 are independently selected from hydrogen, halogen, alkyl with 1-6 carbon atoms, cycloalkyl with 5-20 carbon atoms and derivatives thereof, or aryl with 6-20 carbon atoms and derivatives thereof; R6 is selected from H, alkyl with 1-4 carbon atoms, alkoxy with 1-3 carbon atoms, cyano, halogen or nitro; c and d are independently selected from integers from 0 to 4; Y is present or absent, and when Y is present, Y is selected from carbonyl, ether, thioether, sulfoxide, sulfone, alkylene with 1-6 carbon atoms, cycloalkyl with 5-20 carbon atoms and derivatives thereof, or aryl with 6-20 carbon atoms and derivatives thereof.

10. The polycarbonate of claim 9, wherein, In the polycarbonate, the mass percentage content of the main segment shown in formula I is 92%-95%, the mass percentage content of the branched segment shown in formula II is 1%-3%, and the mass percentage content of the end-capping segment shown in formula III is 3%-5%.

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