Method for preparing branched polycarbonate by interfacial polycondensation process and branched polycarbonate

Abstract

The invention belongs to the technical field of polycarbonate preparation, and particularly relates to a method for preparing branched polycarbonate by an interfacial polycondensation process and branched polycarbonate. The method comprises the following steps: mixing and reacting a water phase containing a dihydroxyl compound, an organic phase containing phosgene and a branching agent to prepare an oligomer reaction liquid a which does not contain unreacted phosgene; the absolute value of the difference between the conversion rates of the branching agent and the dihydroxy compound is less than or equal to 10%; adding an end-capping reagent and alkali liquor into the oligomer reaction liquid, and continuously reacting until the conversion rate of the branching agent is more than or equal to 90% and the hydroxyl content of the oligomer in the reaction liquid is less than or equal to 2000ppm to prepare reaction liquid b; adding a catalyst into the obtained reaction liquid b, and continuously reacting until the content of acyl chloride in the reaction liquid is less than or equal to 2ppm; the prepared branched polycarbonate does not contain a gel component which is insoluble in a good solvent, the total nitrogen content is 0-10 ppm, the hydroxyl content is 0-150 ppm, the total nitrogen content and the hydroxyl content are both at a low level, and the product does not have defects such as a crystal point in downstream application.

Description

Technical Field

[0001] The invention belongs to the technical field of polycarbonate preparation, and in particular relates to a method for preparing branched polycarbonate by an interfacial polycondensation process and the branched polycarbonate. Background Art

[0002] Branched polycarbonate is suitable for applications that require good melt fluidity at high shear rates due to its pseudoplasticity. The moderately branched structure also has better impact resistance than linear polymers, and the improved melt strength also makes it more suitable for processing methods such as extrusion and blow molding. The above characteristics make it very suitable for the manufacture of panels such as polycarbonate sheets and endurance panels or containers for liquids.

[0003] Patent document US 5367044 discloses a branched polycarbonate obtained from 1,1,1-tri-(4-hydroxyphenyl)ethane and a preparation method thereof; this branched polycarbonate has been widely used in fields such as drinking water barrels. For the method disclosed in the patent, there is a problem of uneven regulation of branching degree and generation of gel components in its production and manufacturing. The mixing of gel components into molded products will reduce the transparency and impact resistance of the products, as well as leave appearance defects such as crystal points in some downstream application scenarios. For this defect, a part of the gel component can be removed by setting a filter in the production device, but this will result in a decrease in production efficiency. At the same time, the patented method also has the problem of regulating the total nitrogen content in the branched polycarbonate. A total nitrogen content higher than 10 ppm will deteriorate the heat stability (ΔYI) of the product.

[0004] Patent document CN102656207A discloses a manufacturing method for avoiding the production of gel in branched polycarbonate and controlling the total nitrogen content to 0-7ppm; first, a solution of polycarbonate oligomer is prepared, and then a capping agent is added and the reaction liquid is emulsified, and polymerization is completed without stirring, or polymerization is completed at a catalyst dosage of 0.002mol%. This method has the problem of low reaction efficiency. It usually takes several hours of polymerization time without adding a catalyst. At the same time, the capping rate is low, and there is a high hydroxyl residue. The high hydroxyl residue will also affect the thermal stability of the product. If more than 0.002mol% of the catalyst is added to ensure the reaction efficiency and the capping rate, there is still the possibility of gel.

[0005] Patent document CN100349954A discloses a method for continuously preparing branched polycarbonate by interfacial polycondensation. The method adopts a special instrumentation control rate of the catalyst to prevent the dosage of the catalyst from being lower than the minimum amount of 0.012-0.05 mol of catalyst per mol of bisphenol used, so that polycarbonate with a low nitrogen content can be produced; however, the total nitrogen content is still 3-20 ppm, the upper limit is relatively high, the heat stability of the product is still insufficient, and the method does not describe a method for controlling the gel.

[0006] At present, it is still expected that catalysts can be used in the production of branched polycarbonates to ensure production efficiency, while at the same time being able to control the gel component, total nitrogen, and hydroxyl groups in the resulting branched polycarbonate to be at a low level. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing branched polycarbonate by interfacial polycondensation process and branched polycarbonate in view of some technical problems existing in the existing process of producing branched polycarbonate. By controlling the difference in conversion rate of branching agent and dihydroxy compound in step A to be less than or equal to 10%, and controlling the conversion rate of branching agent in step B to be greater than or equal to 90%, and the hydroxyl content of oligomer to be less than or equal to 2000ppm, the obtained branched polycarbonate can be free of gel component and the total nitrogen and hydroxyl content are at a relatively low level. Moreover, the method basically does not need to reduce the amount of catalyst, does not need to prolong the reaction time, and does not lose production efficiency.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, a method for preparing branched polycarbonate by an interfacial polycondensation process is provided, comprising the following steps:

[0010] Step A, dissolving a dihydroxy compound in an alkaline solution to form an aqueous phase, dissolving phosgene in an inert organic solvent to form an organic phase, mixing the obtained aqueous phase, the organic phase and an additionally added branching agent to react, and preparing an oligomer reaction solution a;

[0011] The oligomer reaction solution a does not contain unreacted phosgene;

[0012] The absolute value of the difference between the conversion rate of the branching agent and the dihydroxy compound is less than or equal to 10% (e.g., 9%, 8%, 6%, 5%, 4%, 2%, 1%, 0.5%, 0.1%);

[0013] Step B, adding a capping agent and an alkali solution to the obtained oligomer reaction solution a, and continuing the reaction until the conversion rate of the branching agent is greater than or equal to 90% (for example, 92%, 94%, 95%, 96%, 98%, 99%), and the hydroxyl content of the oligomer in the reaction solution is less than or equal to 2000 ppm (for example, 1950 ppm, 1800 ppm, 1600 ppm, 1500 ppm, 1200 ppm, 1000 ppm, 800 ppm, 600 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm, 100 ppm, 80 ppm, 60 ppm, 50 ppm, 40 ppm, 20 ppm, 10 ppm, 8 ppm, 6 ppm, 5 ppm, 4 ppm, 2 ppm, 1 ppm), to prepare a reaction solution b;

[0014] Step C, adding a catalyst to the obtained reaction solution b, continuing the reaction until the acyl chloride content in the reaction system is less than or equal to 2 ppm (e.g., less than 1.5 ppm, less than 1.0 ppm, less than 0.5 ppm), and terminating the reaction to obtain a reaction solution containing a branched polycarbonate;

[0015] The prepared branched polycarbonate satisfies:

[0016] 1) It does not contain gel components that are insoluble in good solvents;

[0017] 2) a total nitrogen content of 0-10 ppm (e.g., 0.1 ppm, 0.5 ppm, 1.0 ppm, 2.0 ppm, 3.0 ppm, 4.0 ppm, 5.0 ppm, 6.0 ppm, 8.0 ppm, 9.0 ppm);

[0018] 3) The hydroxyl content is 0-150 ppm (e.g., 0.1 ppm, 0.5 ppm, 1.0 ppm, 2.0 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 50 ppm, 80 ppm, 100 ppm, 120 ppm, 140 ppm).

[0019] In the present invention, "does not contain gel components that are insoluble in the good solvent" can be understood as that when the gel component content in the branched polycarbonate is tested using a detection device, substantially no gel components can be detected. The main types of "good solvents" can be halogenated alkanes and halogenated aromatics, such as dichloromethane.

[0020] In the present invention, the dihydroxy compound can be selected from one or more combinations of the structures represented by formula (I).

[0021]

[0022] In the formula, R2 and R3 are independently selected from halogen, C1-C20 alkyl or alkoxy, C4-C20 cycloalkyl, C6-C20 aryl; n and m are independently integers of 0-4; W is a chemical bond, an oxygen atom, a sulfur atom, a carbonyl group, a sulfone group, a sulfoxide group, a C1-C20 aliphatic group, a C6-C20 aryl group, a C6-C20 alicyclic group, an organic residue of polydimethylsiloxane, or a group represented by formula (II):

[0023] In the formula, R4 and R5 are independently selected from hydrogen, C1-C20 alkyl, C4-C20 cycloalkyl or C4-C20 aryl; or R4 and R5 together form a C4-C20 alicyclic ring, which may be optionally substituted by one or more C1-C20 alkyl, C6-C20 aryl, C7-C21 aralkyl, C5-C20 cycloalkyl or a combination thereof.

[0024] According to the method provided by the present invention, in some embodiments, the dihydroxy compound is selected from one or more of hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenylethane, 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis-(4-hydroxyphenyl)fluorene and 9,9-bis-(3-methyl-4-hydroxyphenyl)fluorene, preferably 2,2-bis-(4-hydroxyphenyl)propane.

[0025] In some embodiments, the alkali solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

[0026] In some embodiments, the concentration of the dihydroxy compound in the aqueous phase is 5-30 wt % (eg, 6 wt %, 8 wt %, 12 wt %, 15 wt %, 18 wt %, 25 wt %), preferably 10-20 wt %.

[0027] In some embodiments, the molar ratio of the solute to the dihydroxy compound in the alkali solution is (2.0-3.0):1, for example, 2.1:1, 2.2:1, 2.4:1, 2.5:1, 2.8:1.

[0028] In some embodiments, in the organic phase, the inert organic solvent is selected from one or more of C1-C6 chlorinated or brominated aliphatic hydrocarbons, C4-C6 chlorinated or brominated alicyclic hydrocarbons, C6-C8 aromatic hydrocarbons and C6-C8 chlorinated or brominated aromatic hydrocarbons, preferably dichloromethane.

[0029] In some embodiments, the concentration of phosgene in the organic phase is 3-20 wt% (eg, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 16 wt%, 18 wt%), preferably 5-15 wt%.

[0030] In some embodiments, in the mixed reaction of the aqueous phase and the organic phase, the amount of phosgene used is 100-150 mol% (e.g., 102 mol%, 108 mol%, 110 mol%, 115 mol%, 120 mol%, 125 mol%, 135 mol%, 140 mol%, 145 mol%) relative to the dihydroxy compound. Too high an excess of phosgene is not conducive to controlling the gel in the polymer, preferably 105-130 mol%. During the reaction, a portion of alkali solution may be optionally added to maintain the pH value of the reaction system> 7. The reaction temperature may be, for example, 0-70°C (e.g., 5°C, 15°C, 20°C, 30°C, 50°C, 60°C), preferably 10-40°C.

[0031] In some embodiments, the branching agent is a trivalent or higher polyphenol or its derivatives. Examples include, but are not limited to, 1,1,1-tris(4-hydroxyphenyl)ethane, 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptene-2,4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptane, 1,3,5-tris(4-hydroxyphenyl)benzene, 2,6-bis(2-hydroxy-5-methylbenzyl)-4-methylphenol, tetrakis(4-hydroxyphenyl)methane, trisphenol, bis(2,4-dihydroxyphenyl)ketone, phloroglucinol, etc. They can be used alone or in combination of two or more; preferably, 1,1,1-tris(4-hydroxyphenyl)ethane (THPE).

[0032] In some embodiments, the molar amount of the branching agent relative to the dihydroxy compound is 0.1-5 mol%, for example, 0.2 mol%, 0.3 mol%, 0.4 mol%, 0.5 mol%, 1.0 mol%, 1.5 mol%, 2.0 mol%, 2.5 mol%, 3.0 mol%, 3.5 mol%, 4.0 mol%, 4.5 mol%; preferably 0.2-3 mol%.

[0033] In some embodiments, the branching agent is added at a timing that the branching agent is not mixed with the organic phase for reaction before the aqueous phase is added to the reaction system. Otherwise, the branching agent is added at any time in step A. To improve the conversion rate of the branching agent, the branching agent can be preferably dissolved in an alkaline solution and pre-mixed with the aqueous phase before mixing with the organic phase for reaction.

[0034] In step A, during the mixing reaction, the desired effect can be achieved by increasing the mixing scale of the aqueous phase and the organic phase, adjusting the reaction residence time, etc., so as to ensure that the obtained reaction solution does not contain unreacted phosgene and reduce gel. The mixing scale here can be such that the Shad diameter D32 of the dispersed phase is less than 300 μm (for example, D32 <280 μm, D32 <250 μm, D32 <220 μm, D32 <180 μm), preferably D32 <200 μm; the Shad diameter D32 can usually be reduced by increasing the shear rate, such as selecting a high shear blade, increasing the stirring speed, etc. The reaction residence time here is usually in the range of seconds to minutes (for example, 10 seconds to 10 minutes).

[0035] In step A, during the mixing reaction, in order to reduce gel, it is also necessary to meet the following requirements: the absolute value of the difference in conversion rate between the branching agent and the dihydroxy compound is less than 10%, or the difference in conversion rate between the two is less than 10%. The reaction activities of the branching agent and the dihydroxy compound are usually inconsistent, and the conversion rates in the photochemical reaction stage will be different; this goal can be achieved by adjusting the phosgene excess rate, the pH value of the aqueous phase in the reaction solution, the reaction residence time, the reaction temperature, the mixing scale, etc. Increasing the phosgene excess rate, controlling the pH value of the reaction solution to be neutral, extending the reaction residence time, increasing the reaction temperature, and increasing the mixing scale can reduce the difference in conversion rate between the branching agent and the dihydroxy compound. The reaction residence time can be 1-120 min (for example, 2 min, 5 min, 10 min, 30 min, 60 min, 90 min), the reaction temperature can be 10-100°C (for example, 15°C, 20°C, 25°C, 40°C, 50°C, 60°C, 80°C, 90°C), and the mixing scale is preferably such that the Shad diameter D32 of the dispersed phase is less than 300 μm.

[0036] In some embodiments, the end-capping agent is a monophenolic compound (e.g., phenol, p-tert-butylphenol, isooctylphenol, cumylphenol), or a chloroformate of a monophenolic compound or an acyl chloride of a monocarboxylic acid. The end-capping agent is usually dissolved in an inert organic solvent, and preferably the end-capping agent can be added to the reaction system before the addition of the alkali solution. In step B, the alkali solution is the same as that in step A, and the concentration of the solute in the alkali solution can be 2-40wt% (e.g., 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%); the addition ratio of the alkali solution is preferably to maintain the pH value of the aqueous phase of the reaction solution>12.

[0037] In some embodiments, the molar amount of the capping agent is greater than the product of the molar amount of the branching agent and its functionality.

[0038] From the perspective of further reducing the gel and total nitrogen content, the reaction solution continues to mix and react in step B until the conversion rate of the branching agent is greater than 90%, preferably greater than 95%, and the hydroxyl content of the oligomer is less than 2000ppm, preferably less than 1000ppm, and then it is sent to the next step. This goal can be achieved by increasing the mixing scale of the materials in the reaction solution, extending the reaction residence time, and increasing the reaction temperature. Increasing the mixing scale of the reaction solution can be to make the Shad diameter D32 of the dispersed phase less than 200μm, preferably D32 less than 100μm, for example, a high shear stirring kettle or a dynamic mixer can be used to strengthen the mixing scale; the reaction residence time can be 10-120min (for example, 2min, 5min, 10min, 30min, 60min, 90min); the reaction temperature can be 10-100℃ (for example, 15℃, 20℃, 25℃, 40℃, 50℃, 60℃, 80℃, 90℃).

[0039] In step C, the catalyst may be a tertiary amine or a quaternary ammonium salt. The tertiary amine may be selected from triethylamine, tripropylamine, tributylamine, trioctylamine, N-ethylpiperidine, N-methylpiperidine, N-isopropylpiperidine, N-n-propylpiperidine, etc.; the quaternary ammonium salt may be selected from hydroxides, chlorides, bromides, hydrogen sulfates, tetrafluoroborate, etc. of tetrabutylammonium, tributylbenzylammonium, tetraethylammonium, etc.; preferably a tertiary amine, more preferably triethylamine.

[0040] In some embodiments, the molar amount of the catalyst relative to the dihydroxy compound is 0.002 mol%-2 mol%, for example, 0.003 mol%, 0.004 mol%, 0.005 mol%, 0.01 mol%, 0.02 mol%, 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.5 mol%, 1 mol%, 1.5 mol%.

[0041] In step C, the catalyst may be mixed with the inert organic solvent to form a solution and then added to the reaction system, or may be mixed with the alkali solution to form a solution and then added to the reaction system.

[0042] The reaction solution obtained in step C can be further separated to remove the aqueous phase to obtain an organic phase; then the organic phase solution can be washed with inorganic acid and deionized water to remove residual impurities such as phenolic compounds, catalysts, and inorganic salts. The organic phase after washing and purification can be further removed by a known desolventizing method (such as steam flocculation, spray drying, poor solvent precipitation, etc.) to remove the organic solvent, and continue to dry to remove the residual solvent and water to obtain the final polycarbonate product.

[0043] In a second aspect, a branched polycarbonate prepared by the method as described above is provided. The weight average molecular weight of the branched polycarbonate is 5000-300000 (e.g., 6000, 8000, 10000, 12000, 15000, 20000, 25000, 30000, 40000, 50000, 60000, 70000, 75000), preferably 10000-80000, more preferably 15000-50000.

[0044] The branched polycarbonate of the present invention can meet the requirements of molding processing methods such as extrusion and blow molding.

[0045] Various conventional additives may be added to the polycarbonate of the present invention. The additives are generally added in an amount of 0-5wt% (e.g., 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%), preferably 0-2wt%, relative to the total weight of the polycarbonate. Optional conventional additives include: a release agent, a flow aid, a heat stabilizer, an antioxidant, a UV absorber, an IR absorber, a flame retardant, an antistatic agent, a dye, a pigment, a filler, or a combination of one or more thereof.

[0046] The polycarbonate of the present invention can be optionally blended with other thermoplastic polymers or commonly used additives to prepare a blend. The thermoplastic polymers include but are not limited to linear bisphenol A type PC, ABS, PET, PBT, PMMA, PS, and the additives can generally be glass fibers, glass balls, carbon fibers, inorganic fillers, etc.

[0047] The above blending can be carried out in various known ways, for example, at a temperature of 240°C-350°C, the components are melt-compounded and melt-extruded in a commonly used device (such as an internal mixer, an extruder, a twin-screw kneader), and granulated by a pelletizer.

[0048] The branched polycarbonate prepared by the method of the present invention does not contain gel components that are insoluble in good solvents, and the total nitrogen content and hydroxyl content are kept at low levels, which can meet the needs of molding processing methods such as extrusion and blow molding, avoid the crystal point problem in downstream application scenarios, and effectively solve the defects such as reduced impact resistance and heat resistance stability. At the same time, the method of the present invention basically does not need to reduce the amount of catalyst, does not need to extend the reaction time, and does not cause the problem of loss of production efficiency. DETAILED DESCRIPTION

[0049] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. For those who do not specify specific conditions in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer.

[0050] Source information of main raw materials used in each example:

[0051] Bisphenol A: industrial grade, Wanhua Chemical Group Co., Ltd.;

[0052] Sodium hydroxide: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0053] Phosgene: industrial grade, Wanhua Chemical Group Co., Ltd.;

[0054] Dichloromethane: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0055] p-tert-Butylphenol: industrial grade, purchased from Zibo Xujia Chemical Co., Ltd.;

[0056] Triethylamine: analytical grade, purchased from Tianjin Kemeiou Chemical Reagent Co., Ltd.;

[0057] 1,1,1-Tris(4-hydroxyphenyl)ethane (branching agent THPE): industrial grade, purchased from LANXESS Chemical.

[0058] Test method:

[0059] The weight average molecular weight was determined by gel permeation chromatography. Equipment manufacturer: Agilent Technologies, equipment model: 1260 Infinity II.

[0060] The conversion rates of the dihydroxy compound and the branching agent were determined by high performance liquid chromatography, equipment manufacturer: Agilent Technologies, equipment model: 1260 Infinity II.

[0061] The hydroxyl content in the oligomer or polymer is measured by 1H-NMR.

[0062] The total nitrogen content was tested using a TN-10 trace nitrogen analyzer.

[0063] Gel component detection: The branched polycarbonate to be tested was dissolved in dichloromethane to prepare 200 ml of a 10 wt% solution, filtered with a nylon filter membrane with a filtration accuracy of 10 μm, and the filter membrane was further filtered with 200 ml of pure dichloromethane solution. The solution was then sent to a fluorescence microscope for observation, and basically no fluorescent spots were observed, indicating that there was no gel component in the branched polycarbonate product.

[0064] Example 1

[0065] The method for preparing branched polycarbonate by interfacial polycondensation process is as follows:

[0066] Step A, dissolving bisphenol A in a sodium hydroxide aqueous solution to form an aqueous phase, and introducing an aqueous phase solution having a bisphenol A concentration of 15.3 wt % and a sodium hydroxide concentration of 5.9 wt % into a pipeline with a static mixer at a flow rate of 1430 g / min for premixing; adding an aqueous solution having a branching agent THPE concentration of 7 wt % and a sodium hydroxide concentration of 2.8 wt % into the pipeline with a static mixer at a flow rate of 14.6 g / min before adding the static mixer;

[0067] The aqueous phase obtained by mixing the aqueous solution containing the branching agent and the aqueous solution containing bisphenol A in the pipeline is introduced into a tubular reactor with a dynamic mixer and multiple outlets, and phosgene at a flow rate of 114 g / min and dichloromethane at a flow rate of 1250 g / min are introduced into the tubular reactor; the speed of the dynamic mixer in the tubular reactor is 3500 rpm, the residence time of the reaction liquid obtained by mixing the materials is 1 min, and the system temperature is 30-40° C.; the oligomer reaction liquid a drawn out from the outlet of the tubular reactor is tested to no longer contain phosgene, and the absolute value of the difference in conversion rate between the branching agent and the dihydroxy compound is 4%;

[0068] Step B, introducing the obtained oligomer reaction liquid a into a first overflow stirring kettle with a high-speed dynamic mixer inserted therein and having multiple adjustable overflow ports, the speed of the dynamic mixer is 500 rpm, a dichloromethane solution with a concentration of 15 wt% of p-tert-butylphenol (capping agent) is added to the system at a flow rate of 35 g / min, and a sodium hydroxide aqueous solution with a concentration of 32 wt% is added at a flow rate of 60 g / min. The system temperature is 35° C., and the reaction is continued until the conversion rate of the branching agent is 97%, the hydroxyl content of the oligomer in the reaction liquid is 1162 ppm, and the residence time of the reaction liquid is 20 min. The obtained reaction liquid b is discharged through the overflow port of the first overflow stirring kettle and sent to step C;

[0069] Step C, introducing the obtained reaction liquid b into the second overflow stirring kettle, and adding a dichloromethane solution with a concentration of 3 wt% of triethylamine (catalyst) at a flow rate of 8 g / min, and continuing to stir and react for 10 minutes; the reaction liquid is discharged through the overflow port, and the residual acyl chloride content in the reaction liquid is detected to be less than 1 ppm, indicating that the reaction has basically ended;

[0070] After the reaction is completed, the aqueous phase in the final reaction solution is separated, the organic phase is washed with dilute hydrochloric acid, and then washed with deionized water until the washing liquid is neutral, and then the organic phase is concentrated at 50°C to a solid content of about 18wt%, and then 70°C hot water is added thereto to evaporate and remove the solvent. The obtained gel is crushed by a grinder and then dried in a vacuum oven at 80°C for 6 hours to obtain a branched polycarbonate powder sample.

[0071] Example 2

[0072] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 1, except that:

[0073] In step A, the flow rate of phosgene was adjusted to 118 g / min, and the oligomer reaction liquid a was drawn out from another outlet of the tubular reactor to extend the residence time of the reaction liquid obtained by mixing the materials in the tubular reactor to 2 min;

[0074] In step B, the rotation speed of the dynamic mixer was adjusted to 800 rpm, and the reaction liquid b was drawn out from the high overflow port of the first overflow stirring kettle to extend the reaction residence time to 30 min.

[0075] The remaining steps are the same as those in Example 1.

[0076] Example 3

[0077] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 1, except that:

[0078] Step C, the flow rate of triethylamine (catalyst) in dichloromethane solution was adjusted to 0.8 g / min; the reaction liquid obtained in this step was discharged through the overflow port, and the residual acyl chloride content in the reaction liquid was still less than 2 ppm after detection.

[0079] The remaining steps are the same as those in Example 1.

[0080] Example 4

[0081] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 1, except that:

[0082] In step A, the flow rate of phosgene was adjusted to 112 g / min, and the residence time of the reaction solution obtained by mixing the materials in the tubular reactor was adjusted to 0.5 min;

[0083] In step B, the speed of the dynamic mixer was adjusted to 300 rpm;

[0084] Step C, the flow rate of triethylamine in dichloromethane solution is adjusted to 32 g / min; the reaction liquid obtained in this step is discharged through the overflow port, and the residual acyl chloride content in the reaction liquid is less than 1 ppm after detection.

[0085] The remaining steps are the same as those in Example 1.

[0086] Comparative Example 1

[0087] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 1, except that:

[0088] In step A, an aqueous solution with a concentration of 32% NaOH was additionally added into the pipeline at a flow rate of 40 g / min before the static mixer was added;

[0089] And, the residence time of the reaction solution obtained by mixing the materials in the tubular reactor was adjusted to 0.5 min;

[0090] In step B, the residence time of the reaction liquid in the first overflow stirring tank is adjusted to 10 min.

[0091] The remaining steps are the same as those in Example 1.

[0092] Comparative Example 2

[0093] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 1, except that:

[0094] In step A, the flow rate of phosgene was adjusted to 112 g / min;

[0095] In step B, the rotation speed of the dynamic mixer was adjusted to 200 rpm, and the residence time of the reaction liquid in the first overflow stirring tank was adjusted to 10 min.

[0096] The remaining steps are the same as those in Example 1.

[0097] Comparative Example 3

[0098] The method for preparing branched polycarbonate by interfacial polycondensation process is referred to Example 4, except that:

[0099] Step C, dichloromethane solution of triethylamine, the flow rate of which is adjusted to 0.06 g / min; the reaction liquid obtained in this step is discharged through the overflow port, and the residual content of acyl chloride in the reaction liquid is detected to be greater than 2 ppm, indicating that the reaction is incomplete and the reaction efficiency is reduced.

[0100] During the preparation of the above embodiments and comparative examples, some index results are shown in Table 1.

[0101] Table 1 Process index results of preparation process

[0102]

[0103]

[0104] Please see Table 2 for the test results of the branched polycarbonate samples obtained in various embodiments and comparative examples.

[0105] Table 2 Test results of branched polycarbonate samples

[0106] serial number Does it contain gel? Total nitrogen content (ppm) Hydroxyl content (ppm) Example 1 none 5 113 Example 2 none 2 96 Example 3 none 3 128 Example 4 none 6 107 Comparative Example 1 have 7 122 Comparative Example 2 have 12 165 Comparative Example 3 none 8 278

[0107] It can be seen from the results in Table 1 and Table 2 that the branched polycarbonate product prepared by the method of the present invention does not have the defect of gel, and can make the total nitrogen content and hydroxyl content in the product lower. Since there is no need to reduce the amount of catalyst, it will not cause the problem of reduced production efficiency of branched polycarbonate.

[0108] In step A of comparative example 1, the absolute value of the difference between the conversion rates of the branching agent and bisphenol A is greater than 10%, which results in the generation of a gel component in the obtained branched polycarbonate; in step B of comparative example 2, the conversion rate of the branching agent is relatively low (not exceeding 90%) and the hydroxyl content of the oligomer exceeds 2000 ppm, which results in the generation of a gel component in the obtained branched polycarbonate and a high total nitrogen content and a high hydroxyl content; in comparative example 3, the amount of catalyst used is reduced, the acyl chloride reaction is incomplete, the reaction efficiency is significantly reduced, and the hydroxyl content of the obtained branched polycarbonate is very high.

[0109] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for preparing branched polycarbonate by interfacial polycondensation process, characterized in that: The steps include: Step A, dissolving a dihydroxy compound in an alkaline solution to form an aqueous phase, dissolving phosgene in an inert organic solvent to form an organic phase, mixing the obtained aqueous phase, the organic phase and an additionally added branching agent to react, and preparing an oligomer reaction solution a; The oligomer reaction solution a does not contain unreacted phosgene; The absolute value of the difference between the conversion rate of the branching agent and the dihydroxy compound is less than or equal to 10%; Step B, adding a capping agent and an alkali solution to the obtained oligomer reaction solution a, and continuing the reaction until the conversion rate of the branching agent is greater than or equal to 90%, and the hydroxyl content of the oligomer in the reaction solution is less than or equal to 2000 ppm, to prepare a reaction solution b; Step C, adding a catalyst to the obtained reaction solution b, continuing the reaction until the acyl chloride content in the reaction system is less than or equal to 2 ppm, and then terminating the reaction to obtain a reaction solution containing a branched polycarbonate; The prepared branched polycarbonate satisfies: 1) It does not contain a gel component that is insoluble in a good solvent; 2) Total nitrogen content is 0-10ppm; 3) The hydroxyl content is 0-150ppm.

2. The method according to claim 1, characterized in that The dihydroxy compound is selected from one or more of hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenylethane, 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 1,1-bis-(3-methyl-4-hydroxyphenyl)cyclohexane, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis-(4-hydroxyphenyl)fluorene and 9,9-bis-(3-methyl-4-hydroxyphenyl)fluorene, preferably 2,2-bis-(4-hydroxyphenyl)propane.

3. The method according to claim 1 or 2, characterized in that: The alkali solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide; The concentration of the dihydroxy compound in the aqueous phase is 5-30wt%, preferably 10-20wt%; The molar ratio of the solute to the dihydroxy compound in the alkali solution is (2.0-3.0):

1.

4. The method according to any one of claims 1 to 3, characterized in that In the organic phase, the inert organic solvent is selected from one or more of C1-C6 chlorinated or brominated aliphatic hydrocarbons, C4-C6 chlorinated or brominated alicyclic hydrocarbons, C6-C8 aromatic hydrocarbons and C6-C8 chlorinated or brominated aromatic hydrocarbons, preferably dichloromethane; The concentration of phosgene in the organic phase is 3-20 wt %, preferably 5-15 wt %.

5. The method according to any one of claims 1 to 4, characterized in that In the mixed reaction of the aqueous phase and the organic phase, the amount of phosgene used is 100-150 mol%, preferably 105-130 mol%, relative to the dihydroxy compound.

6. The method according to any one of claims 1 to 5, characterized in that The branching agent is a trivalent or higher polyvalent phenol or a derivative thereof; Preferably, the molar amount of the branching agent is 0.1-5 mol% relative to the dihydroxy compound.

7. The method according to any one of claims 1 to 6, characterized in that The timing of adding the branching agent is as follows: the branching agent is not mixed with the organic phase for reaction before the aqueous phase is added into the reaction system. In addition, the branching agent is added at any time period of step A.

8. The method according to any one of claims 1 to 7, characterized in that The end-capping agent is a monophenol compound, or a chloroformate of a monophenol compound or an acyl chloride of a monocarboxylic acid.

9. The method according to any one of claims 1 to 8, characterized in that The molar amount of the catalyst is 0.002 mol%-2 mol% relative to the dihydroxy compound.

10. The branched polycarbonate obtained by the method according to any one of claims 1 to 9.

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