A heat-resistant polycarbonate and its preparation method

Abstract

The present invention relates to a heat-resistant polycarbonate with improved impact resistance and a preparation method thereof. It contains structural units derived from bisphenol compound (I), the polycarbonate has a weight-average molecular weight of 5000 - 300000, the Vicat softening point temperature of the polycarbonate is 170 - 200 °C as measured by ASTM D1525 standard, and its notched impact strength is 400 - 800 J / m as tested by ASTM D256 standard.

Description

Technical Field

[0001] The invention relates to a heat-resistant polycarbonate and a preparation method thereof. The polycarbonate has improved impact toughness. Background Art

[0002] High heat-resistant polycarbonate is very suitable for use in scenes exposed to high temperature loads, such as lenses for automobile headlights, light diffusers for lamps, etc.

[0003] Patent EP 359953 discloses a polycarbonate prepared from dihydroxydiarylcycloalkane, especially polycarbonate prepared from 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (BPTMC), which has outstanding heat resistance and is widely used in fields with higher resistance requirements. However, this type of polycarbonate is very sensitive to notched impact. For products with Vicat softening point temperature of 170°C and above, the notched impact test is basically brittle fracture, which is quite different from the results of bisphenol A PC. Therefore, it is expected to develop polycarbonate that can improve its notched impact performance while retaining heat resistance. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, a heat-resistant polycarbonate with improved impact properties can be prepared by adjusting the molecular weight and distribution of the polycarbonate oligomers that define the structural units during the preparation process, thereby obtaining the present invention.

[0005] Therefore, the present invention provides a heat-resistant polycarbonate and a preparation method thereof, wherein the polycarbonate has improved notched impact toughness.

[0006] The polycarbonate comprises at least one structural unit derived from a bisphenol compound (I), namely bisphenol TMC, or BPTMC.

[0007]

[0008] The polycarbonates according to the invention may additionally contain structural units derived from bisphenol compounds (II), in which Z represents an aromatic or alkylaromatic radical.

[0009] (II)

[0010] Preferably, the bisphenol compound (II) is selected from bisphenol A, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenylethane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 4,4'-dihydroxybiphenyl, more preferably bisphenol A.

[0011] The polycarbonate according to the present invention has a proportion of structural units derived from bisphenol compound (I) of 5-90 mol%, preferably 20-70 mol%, based on all structural units derived from bisphenol compounds.

[0012] As a preferred embodiment, the polycarbonate of the present invention is prepared by the following method:

[0013] Step A: An aqueous solution of an alkali metal hydroxide dissolving bisphenol compound (II) is mixed with an inert organic solvent dissolving phosgene for reaction, the aqueous phase is separated and removed, an organic phase dissolving a polycarbonate oligomer is obtained, and then it is continuously mixed with a poor solvent to obtain a mixed system of an oligomer solid precipitate and an organic phase, and the oligomer solid precipitate is obtained by solid-liquid separation;

[0014] The poor solvent is a solvent in which the polycarbonate is insoluble or hardly soluble, is immiscible with water, and is miscible or partially miscible with the inert organic solvent;

[0015] Step B: An aqueous solution of an alkali metal hydroxide dissolving bisphenol compound (I) is mixed with an inert organic solvent dissolving phosgene for reaction, the aqueous phase is separated and removed, and an organic phase solution dissolving a polycarbonate oligomer is obtained;

[0016] Step C: The oligomer solid precipitate obtained in Step A is continuously mixed and reacted with the organic phase solution from Step B, and a capping agent, a catalyst, and an aqueous solution of an alkali metal hydroxide are added to complete polycondensation to obtain a polycarbonate.

[0017] Among them, the number-average degree of polymerization of the oligomer solid precipitate obtained in Step A is 5-20. In the molecular weight distribution curve with log(M) as the abscissa and dw / dlog(M) as the ordinate measured by gel permeation chromatography, the integral area of the part where log(M) ≤ 3 relative to the integral area of the entire curve is 0-5%, but not equal to 0. The number-average degree of polymerization of the polycarbonate oligomer obtained in Step B is 1-5.

[0018] The polycarbonate prepared according to the present invention can obtain good heat resistance. The Vicat softening point temperature of the polycarbonate measured by ASTM D1525 standard is 170-200 °C. At the same time, the notched impact strength is significantly improved. Its notched impact strength is tested by ASTM D256 standard and is 400-800 J / m, preferably 600-800 J / m.

[0019] The polycarbonate of the present invention can be widely applied to scenarios exposed to high-temperature loads, such as the lenses of automotive headlights, light diffusing plates of lamps, etc. Detailed implementation mode

[0020] In process A of the present invention, an aqueous solution of an alkali metal hydroxide (aqueous phase) dissolving a bisphenol compound (II) is mixed with an inert organic solvent (organic phase) dissolving phosgene for reaction, and the aqueous phase is separated and removed to obtain an organic phase dissolving a polycarbonate oligomer.

[0021] The bisphenol compound (II) is selected from bisphenol A, 1,1-bis-(4-hydroxyphenyl)phenylmethane, 1,1-bis-(4-hydroxyphenyl)phenyl ethane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane, 4,4'-dihydroxybiphenyl, and bisphenol A is more preferred.

[0022] The alkali metal hydroxide can be sodium hydroxide, potassium hydroxide, etc., and sodium hydroxide is preferred. The concentration of the bisphenol compound in the aqueous phase is 5-30 wt%, preferably 10-20 wt%. The molar ratio of the alkali metal hydroxide used to the bisphenol compound is 2.0-3.0:1.

[0023] The inert organic solvent can be one or a combination of two or more of C1-C6 chloro- or bromo-aliphatic hydrocarbons, C4-C6 chloro- or bromo-cycloaliphatic hydrocarbons, C6-C8 aromatic hydrocarbons, and C6-C8 chloro- or bromo-aromatic hydrocarbons. Preferably, it is one or a combination of two or more of dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, chlorobenzene, and chloroform, and dichloromethane is more preferred. The concentration of phosgene in the organic phase is 3-20 wt%, preferably 5-15 wt%.

[0024] In the mixing reaction of the aqueous phase and the organic phase in process A, the ratio of phosgene to the bisphenol compound (II) is generally controlled to be 100-150 mol%. During the reaction process, a part of the alkali metal hydroxide can usually be replenished to maintain the reaction system alkaline. To maintain the reaction rate, the pH of the aqueous phase is generally not lower than 10, and more preferably not lower than 11.

[0025] The number-average degree of polymerization of the polycarbonate oligomer obtained by the reaction should be not less than 5, preferably 5-20. The number-average degree of polymerization can be determined by measuring the number-average molecular weight by gel permeation chromatography and then calculating it in combination with the molecular weight of the structural unit. The degree of polymerization can be regulated by methods such as adjusting the ratio of phosgene to the bisphenol compound, reaction temperature, residence time, mixing scale, and pH value of the reaction aqueous phase. Usually, maintaining the pH value of the reaction aqueous phase not lower than 11, phosgene maintaining a relatively low excess rate, the higher the reaction temperature, the longer the residence time, and the larger the mixing scale, the larger the number-average degree of polymerization of the obtained oligomer. Usually, the ratio of phosgene to the bisphenol compound can be adjusted to 100-120 mol%, the reaction temperature is 20-50 °C. Considering the reaction efficiency, the residence time is preferably about 10-30 min, and the mixing scale is preferably such that the Sauter diameter of the dispersed phase is at the micron scale.

[0026] After the polycarbonate oligomer reaches a predetermined degree of polymerization, phosgene is usually no longer present in the reaction system, and the conversion rate of the aqueous-phase bisphenol compound is usually above 95%, preferably above 99%. The reaction solution is further separated into an organic phase and an aqueous phase. The separation can be carried out by known conventional methods, such as static separation, centrifugal separation, coalescence separation, etc. The aqueous phase is sent to a wastewater treatment unit.

[0027] The separated organic phase is continuously mixed with a poor solvent. Since the solubility of the oligomer in the mixed solvent composed of an inert organic solvent and a poor solvent decreases, a part of the oligomer components precipitate out, obtaining a mixed system of an oligomer solid precipitate and an organic phase.

[0028] The poor solvent is a solvent in which polycarbonate is insoluble or poorly soluble, immiscible with water, and miscible or partially miscible with the inert organic solvent. The solvent includes, but is not limited to, hexane, heptane, toluene, acetone, etc., and can be a combination of one or more of them. For a system where the good solvent is dichloromethane, the inert poor solvent is preferably n-heptane. The mass ratio of the poor solvent to the inert organic solvent is 20 - 300 wt%, preferably 50 - 200 wt%.

[0029] The number-average degree of polymerization of the oligomer solid precipitate is 5 - 20. In addition, the following requirements must also be met: in the molecular weight distribution curve with log(M) as the abscissa and dw / dlog(M) as the ordinate measured by gel permeation chromatography, the integral area of the part where log(M) ≤ 3 relative to the integral area of the entire curve is 0 - 5%. If the above requirements are not met, the impact resistance of the final polymer will be significantly affected.

[0030] By adjusting the proportion of the poor solvent, the integral area of the part where log(M) ≤ 3 can meet the requirement of 0 - 5%. Generally, the larger the dosage proportion of the poor solvent, the smaller the proportion of the integral area of the part where log(M) ≤ 3. The oligomer solid precipitate accounts for about 50 - 95 wt% of the total mass of the oligomer.

[0031] The mixed system is separated by solid-liquid separation to obtain an oligomer solid precipitate. The solid-liquid separation can be carried out by traditional gravity sedimentation. To improve efficiency, a hydrocyclone can also be used for rough solid-liquid separation and then fine separation, or fine separation can be carried out directly. An automatic scraper filter can also be used, and such equipment can achieve automatic and continuous operation. The fine separation equipment can be a solid-liquid centrifuge, a vacuum or pressure drum filter, or a separation form of pressure filtration and backwashing. The filter press can be a plate-and-frame filter press.

[0032] The organic phase separated from the mixed system can be recycled to process A after separating the poor solvent and participate in the reaction cyclically.

[0033] In Step B, an inert organic solvent dissolved with phosgene is mixed and reacted with an aqueous solution of an alkali metal hydroxide dissolved with bisphenol compound (I).

[0034] The usage amount of bisphenol compound (I) should satisfy that in the polycarbonate obtained after the final polycondensation is completed, the structural unit of bisphenol compound (I) accounts for 5-90 mol% of all structural units derived from bisphenol compounds.

[0035] The ratio of phosgene to bisphenol compound (I) is 100-150 mol%. The type of alkali metal hydroxide and its ratio to bisphenol compound (I), the concentration of bisphenol compound in the aqueous phase, the selection of the inert organic solvent, and the concentration of phosgene in the organic phase are all the same as the requirements of Step A.

[0036] The number-average degree of polymerization of the prepared polycarbonate oligomer should be 1-5. Too high a degree of polymerization will also affect the impact resistance of the final polymer. The degree of polymerization can be controlled by increasing the ratio of phosgene, reducing the mixing scale, reducing the reaction residence time, etc. The implementation methods that can be adopted are known to those skilled in the art. The ratio of phosgene to bisphenol compound (I) is preferably 120-150%. The mixing scale can meet the requirements by maintaining the Sauter diameter of the dispersed phase at the millimeter scale. The reaction residence time is about 30 s to 10 min. The reaction temperature is 5-50 °C.

[0037] To improve the usage efficiency of bisphenol compound (I), the conversion rate of bisphenol compound (I) in the aqueous phase after the reaction should be greater than 95%, preferably greater than 99%.

[0038] After the reaction is completed, the aqueous phase is separated and removed to obtain an organic phase solution dissolved with polycarbonate oligomer.

[0039] In Step C, the low-polymer solid precipitate from Step A is mixed and reacted with the organic phase from Step B, and a capping agent, a catalyst, and an aqueous solution of an alkali metal hydroxide are added to complete the polycondensation to obtain polycarbonate. Among them, the ratio of the low-polymer solid precipitate from Step A to the low-polymer component in the organic phase from Step B is roughly in a corresponding relationship with the mass ratio of bisphenol compound in the finally obtained polymer after polycondensation. This ratio should meet the requirement of the proportion of the structural unit of bisphenol compound (I) in the final polymer.

[0040] An inert organic solvent can be additionally added to the reaction. Its first function is to dissolve the low-polymer solid and accelerate the reaction rate; the second function is to adjust the concentration of polycarbonate in the organic phase so that after the reaction in Step C is finally completed, the concentration of polycarbonate in the organic phase is 3-40 wt%, preferably 5-30 wt%.

[0041] Preferably, the oligomer solid precipitate is first mixed with an additionally added inert organic solvent to form a homogeneous phase, and then mixed with the two-phase solution from Process B for reaction.

[0042] The capping agent can be a phenolic compound, such as phenol, p-tert-butylphenol, isooctylphenol, cumylphenol, or a chloroformate of the above phenols or an acyl chloride of a monocarboxylic acid. The capping agent can be added at any time, and preferably, it is added to the reaction before the catalyst. The dosage of the capping agent is designed according to the desired molecular weight to be controlled, and is usually 1-10 mol% of the bisphenol compound.

[0043] The catalyst can be a tertiary amine or a quaternary ammonium salt, preferably a tertiary amine, and more preferably triethylamine. The dosage of the catalyst is 0.001-10 mol%, preferably 0.01-1 mol% relative to all bisphenol compounds used. The catalyst is preferably added to the reaction after the capping agent.

[0044] Generally, the above capping agent and catalyst are preferably mixed with an inert organic solvent respectively to form a solution, and then added to the reaction system.

[0045] The aqueous solution of alkali metal hydroxide added in the reaction is used to maintain the pH value of the aqueous phase above 10, preferably 11-13, so that the chloroformate can end the reaction when in excess. When the pH value exceeds 13, excessive hydrolysis of the chloroformate group will occur, which will also affect the impact resistance of the polymer. The requirements for the alkali metal hydroxide are the same as those in Process A.

[0046] After the polycondensation reaction is completed, an aqueous-oil two-phase mixed reaction solution with at most trace (<2 ppm) chloroformate residue is obtained. The reaction time is 10-100 min, and the reaction temperature is 5-50 °C.

[0047] The reactions of Processes A-C can be carried out in a kettle, a tube, a circulation reactor, or a combination of the above reactors. It can be completed in a batch or continuous manner, and preferably, the continuous manner is used.

[0048] The polycarbonate according to the present invention can also optionally introduce a branched structure, which is introduced by an additionally added branching agent. The branching agent is selected from one or a combination of more of triphenols, tetraphenols, acyl chlorides of tricarboxylic acids, and acyl chlorides of tetracarboxylic acids. The preferred branching agent is 1,1,1-tris(4-hydroxyphenyl)ethane. The branching agent can be added in Processes A and B, and preferably in Process A. The proportion of the branching agent is 0.01-3 mol% relative to all bisphenol compounds used in the preparation.

[0049] The polycarbonate prepared according to the present invention has a weight-average molecular weight of 5,000 - 300,000 (weight-average molecular weight, measured by size-exclusion gel chromatography after pre-calibration with PS or polycarbonate calibration substances), preferably 10,000 - 80,000, more preferably 15,000 - 40,000.

[0050] In the polycarbonate obtained after the final polycondensation is completed, the proportion of the structural unit of bisphenol compound (I) in all the structural units derived from bisphenol compounds is 5 - 90 mol%, preferably 20 - 70 mol%.

[0051] After the polymerization is completed, a disc centrifuge is used to separate the reaction solution to obtain an organic phase, and the organic phase is washed with a 1.5 wt% sodium hydroxide solution and a hydrochloric acid solution respectively to remove residual phenolic compounds and catalysts. Then the organic phase is washed with deionized water to remove impurities such as inorganic salt electrolytes. The organic solvent is removed by high-pressure steam flocculation to obtain a crude powder. Further, a vacuum rake dryer is used to dry at 120 °C for 8 hours to obtain polycarbonate powder.

[0052] After adding additives, the polycarbonate powder is extruded and pelletized, and can be used to further manufacture various molded products. Additives that can be used include but are not limited to heat stabilizers, mold release agents, ultraviolet resistant agents, etc. Other common additives can also be added within the range that does not damage the effects of the present invention.

[0053] Examples

[0054] The following examples are intended to explain the present invention. The present invention is not limited to the scope of the examples and also includes any other changes within the scope of the claims required by the present invention.

[0055] The number-average degree of polymerization is obtained by obtaining the number-average molecular weight result by size-exclusion gel chromatography (GPC) and then dividing by the molecular weight of the structural unit. Analyzer manufacturer: Agilent Technologies, equipment model: 1260 Infinity, column model: Plgel 5μm MIXED-C 300*7.5mm, mobile phase: dichloromethane.

[0056] In the GPC curve of the oligomer solid precipitate, the integral area of the part where log(M) ≤ 3 is defined as Area% relative to the integral area of the entire curve.

[0057] The Vicat softening point temperature is measured according to ASTM D1525 standard, and the test equipment is ZWICK HIT25P

[0058] . The Izod impact strength (IZOD) is tested according to ASTM D256 standard, the thickness of the test piece is 3.2 mm, and the test equipment is ZWICK HDT / Vicat A.

[0059] The raw materials used in the following examples are:

[0060] Bisphenol A: industrial grade, purchased from Jiangsu Changchun Chemical Co., Ltd.; sodium hydroxide: analytical grade, purchased from Tianjin Komeo Chemical Reagent Co., Ltd.; phosgene: industrial grade, Wanhua Chemical Group Co., Ltd.; dichloromethane: analytical grade, purchased from Tianjin Komeo Chemical Reagent Co., Ltd.; p-tert-butylphenol: analytical grade, purchased from Beijing Bailingwei Technology Co., Ltd.; triethylamine: analytical grade, purchased from Tianjin Komeo Chemical Reagent Co., Ltd.; bisphenol TMC, purchased from Jiangsu Yongxing Chemical Co., Ltd.

[0061] Example 1

[0062] Process A:

[0063] A sodium hydroxide aqueous solution containing bisphenol A was added to a tubular reactor with a static mixer and a jacket at a flow rate of 10 kg / h, wherein the concentration of bisphenol A was 15 wt %, and the concentration of sodium hydroxide was 5.8 wt %. A dichloromethane solvent at a flow rate of 10 kg / h and a phosgene at a flow rate of 0.75 kg / h were added to the tubular reactor together. The reaction temperature was controlled at 36° C. by heat exchange of the jacket.

[0064] The outlet liquid of the tubular reactor is introduced into a continuous stirring tank with a high-speed stirring paddle, which is operated at a speed of 500 rpm. A 32 wt% sodium hydroxide aqueous solution is added at a flow rate of 0.7 kg / h. The reaction temperature is maintained at 38°C, and the average residence time in the stirring tank is about 20 minutes.

[0065] A reaction liquid equivalent to the mass flow rate of the added material is drawn out from the continuous stirring tank and sent to a decanter to separate the oil and water phases. The conversion rate of bisphenol A in the separated water phase is detected to be above 99%.

[0066] The organic phase is introduced into a precipitation tank with stirring, and n-heptane solvent is added at the same time. The mass ratio of n-heptane to dichloromethane is 1:1. The treatment time in the precipitation tank is about 20 minutes. The solid-liquid mixed system after precipitation is sent to a solid-liquid centrifuge to separate the oligomer solid precipitate.

[0067] The oligomer solid precipitate was tested by GPC, and the number average degree of polymerization was calculated to be 13. The integral area of ​​the portion with log(M)≤3 relative to the integral area of ​​the entire curve (expressed as Area %) was 3.4%.

[0068] Process B:

[0069] In a tubular reactor with a jacket and an internal static mixer, an aqueous sodium hydroxide solution dissolved with BPTMC is added at a flow rate of 8.2 kg / h, where the concentration of BPTMC is 14.3 wt%, and the alkali concentration is 5 wt%. Methylene chloride with a flow rate of 8 kg / h and phosgene with a flow rate of 0.5 kg / h are added to the tubular reactor together.

[0070] The residence time in the tubular reactor is about 2 min. The reaction temperature is controlled at 28 °C by heat exchange through the jacket. In the organic phase of the outlet reaction liquid, the polycarbonate oligomer component accounts for about 13 wt%, and the conversion rate of BPTMC in the aqueous phase is about 98%. The number-average degree of polymerization of the oligomer in the organic phase of the outlet reaction liquid is tested by GPC, and the calculated result is 3.8.

[0071] The outlet reaction liquid is sent to a disc centrifuge, and the separated organic phase is sent to a storage tank.

[0072] Process C:

[0073] 7 kg of oligomer solid from Process A and 30 kg of methylene chloride solvent are added to a stirring kettle and mixed and dissolved to form a homogeneous solution. 43 kg of organic phase solution is drawn from the storage tank in Process B and also added to the stirring kettle.

[0074] A solution composed of 0.35 kg of p-tert-butylphenol and 4 kg of methylene chloride and a solution composed of 0.03 kg of triethylamine and 4 kg of methylene chloride are continuously added. Then, a 32% sodium hydroxide solution is slowly added dropwise to the stirring kettle, maintaining the pH value of the aqueous phase not exceeding 13.

[0075] The reaction temperature is controlled at about 35 °C by heat exchange through the jacket of the stirring kettle, and the reaction is continuously stirred for about 60 min to confirm the end of the reaction.

[0076] After the reaction ends, the aqueous phase is separated, the organic phase is washed with dilute hydrochloric acid, and then washed with deionized water until the washing liquid is neutral. The organic phase is concentrated at 50 °C, then poured into hot water at 70 °C to remove the solvent, crushed with a pulverizer, and dried in a vacuum oven at 120 °C for 4 h to obtain polycarbonate with a weight-average molecular weight of 31242. The weight ratio of BPTMC is about 44 wt%, and the molar ratio is about 37 mol%.

[0077] Example 2

[0078] Operate with reference to Example 1.

[0079] In Process A, the reaction operation in the tubular reactor is the same as that in Example 1. The outlet liquid of the tubular reactor is introduced into a continuous stirring kettle with a stirring paddle and operated at a rotation speed of 200 rpm. No additional aqueous sodium hydroxide solution is added. The reaction temperature is maintained at 35 °C, and the average residence time in the stirring kettle is about 15 min.

[0080] A reaction solution with a mass flow rate equivalent to that of the added materials is drawn from the continuous stirred tank and fed into a decanter to separate the oil and water phases. In the separated aqueous phase, the conversion rate of bisphenol A is detected to be 98%.

[0081] The organic phase is introduced into a precipitation tank with stirring, and at the same time, n-heptane solvent is added. The mass ratio of n-heptane to dichloromethane is 1.5:1. The treatment time in the precipitation tank is about 20 min. The solid-liquid mixed system after precipitation is fed into a solid-liquid centrifuge to separate out the oligomer solid precipitate.

[0082] The oligomer solid precipitate is tested by GPC, and the number-average degree of polymerization is calculated to be 5.5, and the Area% result is 2.9%.

[0083] In Process B, the residence time in the tubular reactor is about 5 min. The reaction temperature is controlled at 35 °C by jacket heat exchange. In the organic phase of the outlet reaction solution, the polycarbonate oligomer component accounts for about 13 wt%. The conversion rate of BPTMC in the aqueous phase is about 99%. The number-average degree of polymerization of the oligomer is tested by GPC, and the calculated result is 4.5.

[0084] The operation of Process C is the same as that in Example 1.

[0085] The post-treatment after the reaction is the same as that in Example 1. The obtained polycarbonate has a weight-average molecular weight of 30580. The weight ratio of BPTMC is 44 wt%, and the molar ratio is about 37 mol%.

[0086] Example 3

[0087] Operate with reference to Example 1.

[0088] In Process A, the reaction operation in the tubular reactor is the same as that in Example 1. The outlet liquid of the tubular reactor is introduced into a continuous stirred tank with a high-speed stirring paddle and operated at a rotation speed of 800 rpm. An aqueous sodium hydroxide solution with a concentration of 32 wt% is added together at a flow rate of 0.9 kg / h. The reaction temperature is maintained at 38 °C, and the average residence time in the stirred tank is about 30 min.

[0089] A reaction solution with a mass flow rate equivalent to that of the added materials is drawn from the continuous stirred tank and fed into a decanter to separate the oil and water phases. In the separated aqueous phase, the conversion rate of bisphenol A is detected to be 99%.

[0090] The organic phase is introduced into a precipitation tank with stirring, and at the same time, n-heptane solvent is added. The mass ratio of n-heptane to dichloromethane is 1:1. The treatment time in the precipitation tank is about 20 min. The solid-liquid mixed system after precipitation is fed into a solid-liquid centrifuge to separate out the oligomer solid precipitate.

[0091] The oligomer solid precipitate was tested by GPC, and the number-average degree of polymerization was calculated to be 19, and the Area% result was 3.8%.

[0092] In process B, the residence time in the tubular reactor was about 1 min, and the reaction temperature was controlled at 30 °C by jacket heat exchange. In the organic phase of the outlet reaction liquid, the polycarbonate oligomer component accounted for about 13 wt%, and the conversion rate of aqueous-phase BPTMC was about 99%. The number-average degree of polymerization of the oligomer was tested by GPC, and the calculated result was 3.2.

[0093] The operation of process C was the same as that of Example 1.

[0094] The post-treatment after the reaction was the same as that of Example 1. The obtained polycarbonate had a weight-average molecular weight of 29873. The weight ratio of BPTMC was 44 wt%, and the molar ratio was about 37 mol%.

[0095] Example 4

[0096] Processes A and B were carried out with reference to Example 1, and the operation of process C was as follows.

[0097] About 16 kg of the oligomer solid from process A and 80 kg of dichloromethane solvent were added to a stirring kettle and mixed and dissolved to form a homogeneous solution. 43 kg of the organic-phase solution was drawn from the storage tank of process B and also added to the stirring kettle.

[0098] A solution composed of 0.35 kg of p-tert-butylphenol and 4 kg of dichloromethane, and a solution composed of 0.03 kg of triethylamine and 4 kg of dichloromethane were continuously added. Then, a 32% sodium hydroxide solution was slowly added dropwise to the stirring kettle to maintain the pH value of the aqueous phase not exceeding 13.

[0099] The reaction temperature was controlled at about 35 °C by jacket heat exchange of the stirring kettle, and the reaction was continuously stirred for about 60 min to confirm the end of the reaction.

[0100] After the reaction was completed, the aqueous phase was separated, the organic phase was washed with dilute hydrochloric acid, and then washed with deionized water until the washing liquid was neutral. The organic phase was concentrated at 50 °C, then poured into hot water at 70 °C to remove the solvent, crushed with a pulverizer, and dried in a vacuum oven at 120 °C for 4 h to obtain polycarbonate with a weight-average molecular weight of 30655. The molar ratio of BPTMC in the bisphenol compound was about 20 mol%.

[0101] Example 5

[0102] Processes A and B were carried out with reference to Example 4, and the operation of process C was as follows.

[0103] Approximately 1.8 kg of oligomer solid from Process A and 9 kg of dichloromethane solvent were added to a stirred tank and mixed to form a homogeneous solution. 43 kg of organic phase solution was drawn from the storage tank of Process B and also added to the stirred tank.

[0104] A solution composed of 0.1 kg of p-tert-butylphenol and 4 kg of dichloromethane, and a solution composed of 0.03 kg of triethylamine and 4 kg of dichloromethane were continuously added. Then, a 32% sodium hydroxide solution was slowly added dropwise to the stirred tank while maintaining the pH value of the aqueous phase not exceeding 13.

[0105] The reaction temperature was controlled at approximately 35 °C by heat exchange through the jacket of the stirred tank, and the reaction was continuously stirred for about 60 min to confirm the end of the reaction.

[0106] After the reaction ended, the aqueous phase was separated, the organic phase was washed with dilute hydrochloric acid, and then washed with deionized water until the wash liquid was neutral. The organic phase was concentrated at 50 °C, then poured into hot water at 70 °C to remove the solvent, and crushed with a pulverizer, and dried in a vacuum oven at 120 °C for 4 h to obtain polycarbonate with a weight-average molecular weight of 32366. The molar proportion of BPTMC in the bisphenol compound was approximately 70 mol%.

[0107] Comparative Example 1

[0108] The operation was carried out with reference to Example 1.

[0109] In Process A, the reaction operation in the tubular reactor was the same as in Example 1. The liquid at the outlet of the tubular reactor was introduced into a continuous stirred tank with a stirrer and operated at a rotation speed of 100 rpm. No additional sodium hydroxide aqueous solution was added. The reaction temperature was maintained at 25 °C, and the average residence time in the stirred tank was about 5 min.

[0110] A reaction liquid with a mass flow rate equivalent to the added materials was drawn from the continuous stirred tank and sent to a decanter to separate the oil and water phases. In the separated aqueous phase, the conversion rate of bisphenol A was detected to be 96%.

[0111] The organic phase was introduced into a precipitation tank with stirring, and n-heptane solvent was added simultaneously. The mass ratio of n-heptane to dichloromethane was 0.5:1. The treatment time in the precipitation tank was about 20 min, and the solid-liquid mixture system after precipitation was sent to a solid-liquid centrifuge to separate out the oligomer solid precipitate.

[0112] The oligomer solid precipitate was tested by GPC, and the number-average degree of polymerization was calculated to be 4, and the Area% result was 5.6%.

[0113] In Process B, the residence time in the tubular reactor is about 8 min. The reaction temperature is controlled at 38 °C through jacket heat exchange. In the organic phase of the outlet reaction liquid, the polycarbonate oligomer component accounts for about 13 wt%. The conversion rate of BPTMC in the aqueous phase is about 99%. The number-average degree of polymerization of the oligomer is tested by GPC, and the calculated result is 6.

[0114] The operation of Process C is the same as that in Example 1.

[0115] The post-treatment after the reaction is the same as that in Example 1. The obtained polycarbonate has a weight-average molecular weight of 30706, the weight ratio of BPTMC is 44 wt%, and the molar ratio is about 37 mol%.

[0116] Comparative Example 2

[0117] The operations of Processes A and B are referred to Comparative Example 1, and the operation of Process C is referred to Process C of Example 4. The prepared polycarbonate has a molar ratio of BPTMC in the bisphenol compound of about 20 mol%.

[0118] Comparative Example 3

[0119] The operations of Processes A and B are referred to Comparative Example 1, and the operation of Process C is referred to Process C of Example 5. The prepared polycarbonate has a molar ratio of BPTMC in the bisphenol compound of about 70 mol%.

[0120] Comparative Example 4

[0121] Referring to Example 1 of Patent CN 201180029108, the flow rate is reduced by 100 times in proportion, and other steps are referred to the examples. A polycarbonate with a BPTMC weight ratio of 44% and a molar ratio of 37 mol% is obtained.

[0122] The results of the number-average degree of polymerization of the oligomers in the examples and the performance test results of all samples are listed in the following table. By comparison, it can be seen that the polycarbonate prepared by the present invention can improve the heat resistance and at the same time improve the notched impact performance.

[0123] Table 1 Intermediate Product Test Results

[0124]

[0125] Table 2 Heat Resistance and Notched Impact Performance Test

[0126] Vicat softening temperature (°C) Notched impact strength (J / m) Example 1 192℃ 608 Example 2 191℃ 595 Example 3 191℃ 623 Example 4 171℃ 790 Example 5 210℃ 446 Comparative Example 1 188℃ 158 Comparative Example 2 169℃ 177 Comparative Example 3 205℃ 66 Comparative Example 4 188℃ 142

Claims

1. A preparation method of a heat-resistant polycarbonate, characterized in that, The polycarbonate contains structural units derived from bisphenol compound (I). The polycarbonate contains structural units derived from bisphenol compound (II). HO-Z-OH (II) wherein Z represents an aromatic or alkylaromatic residue; The polycarbonate has a weight-average molecular weight of 5,000 - 300,000. The Vicat softening point temperature of the polycarbonate is measured according to ASTM D1525 standard and is 170 - 200 °C. Its notched impact strength is tested according to ASTM D256 standard and is 400 - 800 J / m; The method for preparing the polycarbonate comprises the following steps: Process A: An aqueous alkali metal hydroxide solution dissolving bisphenol compound (II) is mixed with an inert organic solvent dissolving phosgene for reaction. The aqueous phase is separated and removed to obtain an organic phase dissolving the polycarbonate oligomer. It is continuously mixed with a poor solvent to obtain a mixed system of an oligomer solid precipitate and an organic phase. The solid-liquid separation is carried out to obtain the oligomer solid precipitate; Process B: An aqueous alkali metal hydroxide solution dissolving bisphenol compound (I) is mixed with an inert organic solvent dissolving phosgene for reaction. The aqueous phase is separated and removed to obtain an organic phase solution dissolving the polycarbonate oligomer; Process C: The oligomer solid precipitate obtained in Process A is continuously mixed and reacted with the organic phase solution from Process B. A capping agent, a catalyst, and an aqueous alkali metal hydroxide solution are added to complete the polycondensation to obtain the polycarbonate; Among them, the number-average degree of polymerization of the oligomer solid precipitate obtained in Process A is 5 - 20. In the molecular weight distribution curve with log(M) as the abscissa and dw / dlog(M) as the ordinate measured by gel permeation chromatography, the integral area of the part where log(M) ≤ 3 relative to the integral area of the entire curve is 0 - 5%, and it is not 0; The number-average degree of polymerization of the polycarbonate oligomer obtained in Process B is 1 - 5.

2. The preparation method according to claim 1, characterized in that, The bisphenol compound (II) is bisphenol A.

3. The preparation method according to claim 1 or 2, characterized in that, The proportion of the structural units derived from bisphenol compound (I) in all the structural units derived from bisphenol compounds is 5 - 90 mol%.

4. The preparation method according to claim 3, wherein The proportion of the structural units derived from bisphenol compound (I) in all the structural units derived from bisphenol compounds is 20 - 70 mol%.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the poor solvent to the inert organic solvent is 20 - 300 wt%.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the poor solvent to the inert organic solvent is 50 - 200 wt%.

7. According to the preparation method described in claim 1, wherein The inert organic solvent is a chlorinated or brominated alkane or aromatic hydrocarbon. The alkali metal hydroxide is at least one of sodium hydroxide and potassium hydroxide; The poor solvent is one or more of hexane, heptane, toluene, and acetone.

8. The preparation method according to claim 1, characterized in that, The inert organic solvent is dichloromethane.

9. The preparation method according to claim 1 or 7 or 8, characterized in that, In Processes A and B, the molar ratio of the alkali metal hydroxide used to the bisphenol compound is 2.0 - 3.0:

1.

10. The preparation method according to claim 1 or 7 or 8, characterized in that, In Processes A and B, the concentration of the bisphenol compound in the aqueous phase is 5 - 30 wt%.

11. The preparation method according to claim 10, wherein, In Processes A and B, the concentration of the bisphenol compound in the aqueous phase is 10 - 20 wt%.

12. The preparation method according to claim 1 or 7 or 8, characterized in that, In Processes A and B, the concentration of phosgene in the organic phase is 3 - 20 wt%; and / or, the ratio of phosgene to the bisphenol compound is 100 - 150 mol%.

13. The preparation method according to claim 12, characterized in that, In Processes A and B, the concentration of phosgene in the organic phase is 5 - 15 wt%.

14. The preparation method according to claim 1, wherein The reaction temperature of Process A is 20 - 50 °C, and the residence time is 10 - 30 min; and / or, in Process B, the reaction temperature is 5 - 50 °C, and the reaction residence time is 30 s to 10 min.

15. The preparation method according to claim 1, characterized in that, In Process C, an aqueous solution of alkali metal hydroxide added in the reaction is used to maintain the pH value of the aqueous phase above 10.

16. The preparation method according to claim 15, characterized in that, In Process C, an aqueous solution of alkali metal hydroxide added in the reaction is used to maintain the pH value of the aqueous phase at 11 - 13.

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