Preparation method of polycarbonate

Abstract

The invention provides a preparation method of polycarbonate, which comprises the following steps: firstly, obtaining a polycarbonate oligomer obtained by reacting bisphenol or polyphenol with phosgene, adding an end-capping reagent, continuing to react until the content of acyl chloride is specific, and adding a catalyst until the reaction end point. Wherein when the catalyst is controlled to be added, the reaction system meets the following conditions: (1) 0.1 < = [-COCl]: [-OH] < = N [-COCl]: N [-OH]; and (2) the ratio of the input molar weight of the catalyst to the molar weight of the terminal group acyl chloride in the system is 1: 5-5: 1 when the catalyst is added. By adopting the method, the polycarbonate with excellent quality can be prepared.

Description

Technical Field

[0001] The present invention relates to a method for preparing polycarbonate, belonging to the technical field of polymer materials. Background Art

[0002] Polycarbonate resin is an engineering plastic with excellent properties and is widely used in fields such as automobiles and optics. However, the molecular weight distribution problem of polycarbonate has become one of the key factors restricting the performance of polycarbonate. Therefore, in order to improve the product quality of polycarbonate, the problem of too wide molecular weight distribution has become the first problem to be solved.

[0003] Patent JP2002069168A has requirements for the polycondensation catalyst used in polycarbonate resin. In the invention, an amine with a pKa value below 10 is used, that is, a weakly basic amine catalyst is used. The terminal of the chloroformate molecule is not ionized, and the nucleophilic reaction can preferentially occur from another ionized terminal (-ONa terminal). Its reaction mechanism is different from the conventional polycondensation reaction in the manufacture of polycarbonate resin. Only a single reaction is carried out, and the molecular weight distribution of polycarbonate is within 3, but the molecular weight distribution is still relatively wide.

[0004] Patent US3184431 provides a method for preparing polycarbonate with a low molecular weight distribution, in which the reaction is carried out in the presence of a catalytic amount of a quaternary ammonium compound as a catalyst. About 30% to about 50% of the catalyst is added during the phosgenation reaction, and the remaining catalyst is added after the phosgenation reaction is completed. The invention points out that the molecular weight distribution of polycarbonate can be finally reduced by this method. However, the catalyst added in the phosgenation stage of this invention will undergo a side reaction with phosgene, ultimately resulting in a high total nitrogen content in the product and affecting the product quality.

[0005] In various use scenarios of polycarbonate, relatively high requirements are imposed on the mechanical properties and the like of polycarbonate resin. If the molecular weight distribution is too wide, the performance of polycarbonate will be greatly affected. The catalyst is a reagent that will be used in almost all interfacial polycondensations of polycarbonate. However, the catalytic mechanism of the catalyst and the way it affects the interfacial polycondensation have not been determined. Similarly, there is little research on the influence of the catalyst on the molecular weight distribution. As a key reagent for the interfacial polycondensation reaction of polycarbonate, it is very necessary to study its influence on the molecular weight distribution. Summary of the Invention

[0006] The present invention provides a method for preparing high-quality polycarbonate, which can obtain polycarbonate with a low molecular weight distribution and improve the product quality.

[0007] To achieve the above object, the present invention is prepared by a two-phase interfacial polycondensation process, and the method includes the following steps:

[0008] A method for preparing polycarbonate, including:

[0009] a) First, react an alkali metal salt solution of polyphenol (the molar amount of hydroxyl groups is N [-OH] ) and phosgene dissolved in an inert solvent (the molar amount of acyl chloride groups is N [-COCl] ) in a mixing reactor to obtain a photochemical reaction product;

[0010] b) Add a capping agent to the photochemical reaction product, and then pass the reaction solution through a one-stage reactor. This stage is polycondensation reaction A. Measure the mass concentration of acyl chloride [-COCl] and the mass concentration of hydroxyl [-OH] at the outlet of the reactor;

[0011] c) Add a catalyst to the polycondensate at the outlet of the reactor for polycondensation reaction A, enter a polycondensation reaction kettle, carry out polycondensation reaction B until the reaction ends to obtain a polycarbonate reaction solution, and obtain a polycarbonate resin after washing, devolatilization, and drying.

[0012] In step a) of the method of the present invention, the alkali metal salt solution of polyphenol includes but is not limited to bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(2-hydroxyphenyl)-3,3,5-trimethylcyclohexane, a sodium salt or potassium salt solution of resorcinol, and preferably a sodium salt solution of bisphenol A;

[0013] In step a) of the method of the present invention, the inert solvent is one or any combination of dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, toluene, and chlorobenzene;

[0014] In step a) of the method of the present invention, the molar ratio of acyl chloride groups to phenolic hydroxyl groups is 1≤N [-COCl] :N [-OH] ≤1.2, and preferably 1.05≤N [-COCl] :N [-OH] ≤1.2;

[0015] In step a) of the method of the present invention, the mass concentration ratio of acyl chloride in the photochemical reaction product to the acyl chloride functional groups contained in the initial phosgene is 0.1 - 0.5;

[0016] In step a) of the method of the present invention, the average residence time of the photochemical reaction is 1 s - 5 min;

[0017] In step b) of the method of the present invention, the capping agent is one or more of phenol, p-tert-butylphenol, cumylphenol, p-cyanophenol, or isooctylphenol, and preferably p-tert-butylphenol;

[0018] In step b) of the method of the present invention, the reactor includes, but is not limited to, one or more series combinations of micro-mixing devices such as emulsifiers or high-speed dispersion equipment, tubular reactors, tank reactors, tubular reactors with dynamic or static mixers, etc.;

[0019] In step b) of the method of the present invention, the average residence time of the polycondensation reaction A is between 1 and 25 minutes;

[0020] In step b) of the method of the present invention, the mass concentration ratio of the acyl chloride at the end of the polycondensation reaction A to the acyl chloride functional group contained in the initial phosgene is 10 -5 ~2×10 -3 ;

[0021] In step c) of the method of the present invention, the catalyst is triethylamine, trialkylamine, N-ethylpiperidine, N-isopropylpiperidine, N-ethylmorpholine or other catalysts known in the interfacial polycondensation process of polycarbonate, preferably triethylamine;

[0022] In step c) of the method of the present invention, when adding the catalyst, the following should be satisfied: (1) 0.1 ≤ [-COCl]:[-OH] ≤ N [-COCl] :N [-OH] ; (2) The molar amount of the catalyst input is in the ratio of 1:5 to 5:1, preferably 1:3 to 3:1, to the molar amount of the acyl chloride in the system when adding the catalyst;

[0023] In step c) of the method of the present invention, the washing process of the polycarbonate reaction solution is a combination of pickling and water washing, and each should be at least once;

[0024] In step c) of the method of the present invention, the nitrogen element content of the polycarbonate resin ≤ 30 ppm;

[0025] In step c) of the method of the present invention, the molecular weight distribution of the obtained polycarbonate resin is 1.2 - 2.0, preferably 1.2 - 1.8.

[0026] The beneficial effects of the present invention are as follows:

[0027] From the currently published literature and patents, the catalytic mechanism of the catalyst used in the interfacial polycondensation process of polycarbonate is not yet clear. Therefore, there are few reports on patents that reduce the molecular weight distribution from the catalyst direction. The present invention has studied the possible mechanism of the catalytic process and successfully reduced the molecular weight distribution to 1.2 - 2.0 through precise control of the catalyst metering, improving the product quality. Specific embodiments

[0028] The following is further illustrated by examples, but the scope of the present invention is not limited to the listed examples and should also include any other known changes within the scope of the rights required by the present invention.

[0029] In the following examples or comparative examples, the analysis and evaluation methods are as follows:

[0030] The weight-average molecular weight and molecular weight distribution were obtained by testing with an Agilent Technologies 1260 infinity. Dichloromethane was used as the mobile phase, the flow rate was 1 mL / min, and both the column temperature and the oven temperature were 30 °C. An RI / LS detector was used to obtain the hydroxyl content simultaneously.

[0031] The acyl chloride content was obtained by testing with a Mettler Toledo UV-visible spectrophotometer UV7; the nitrogen element content was obtained by testing with a Thermo Scientific TM Flash Smart TM element analyzer.

[0032] Example 1

[0033] Phosgene (66.2 g) was dissolved in dichloromethane (847.8 g) and then simultaneously introduced into a mixing reactor with a sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) for a photochemical reaction (N [-COCl] :N [-OH] = 1.14). At the end of the photochemical reaction, the acyl chloride group content was 13440 ppm.

[0034] p-tert-Butylphenol (36.31 g, 11% wt) was introduced into the photochemical reaction solution, and then it entered a tubular reactor with a static mixer to start polycondensation reaction A. After reacting for a period of time, the acyl chloride group content was monitored to be 71.94 ppm and the hydroxyl content was 442.77 ppm. At this time, [-COCl]:[-OH] = 0.16. Immediately, triethylamine (6.98 g, 3% wt) as a catalyst was added and the mixture entered a polycondensation reaction kettle until the reaction ended. A polycarbonate reaction solution was obtained, which was subjected to pickling, washed twice with water, then separated from oil and water, and after devolatilization, it was dried in a vacuum oven at 135 °C for 8 h to obtain a polycarbonate resin.

[0035] Example 2

[0036] Phosgene (69.5 g) was dissolved in dichloromethane (847.8 g) and then simultaneously introduced into a mixing reactor with a sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) for a photochemical reaction (N [-COCl] :N [-OH] = 1.2). At the end of the photochemical reaction, the acyl chloride group content was 14461 ppm.

[0037] After introducing p-tert-butylphenol (36.31 g, 11% wt) into the photochemical reaction solution, it enters a tubular reactor with a static mixer to start the polycondensation reaction A. After reacting for a period of time, the acyl chloride group content is monitored to be 75.48 ppm and the hydroxyl group content is 615.63 ppm. At this time, [-COCl]:[-OH] = 0.12. Immediately add the catalyst triethylamine (7.34 g, 3% wt) and enter the polycondensation reaction kettle until the reaction ends. The polycarbonate reaction solution is obtained, and after the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0038] Example 3

[0039] After dissolving phosgene (62.6 g) in dichloromethane (847.8 g), it is simultaneously introduced into the mixing reactor with the sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) to carry out the photochemical reaction (N [-COCl] :N [-OH] = 1.08). At the end of the photochemical reaction, the acyl chloride group content is 12513 ppm.

[0040] After introducing p-tert-butylphenol (36.31 g, 11% wt) into the photochemical reaction solution, it enters a tubular reactor with a static mixer to start the polycondensation reaction A. After reacting for a period of time, the acyl chloride group content is monitored to be 68.06 ppm and the hydroxyl group content is 331.96 ppm. At this time, [-COCl]:[-OH] = 0.21. Immediately add the catalyst triethylamine (6.59 g, 3% wt) and enter the polycondensation reaction kettle until the reaction ends. The polycarbonate reaction solution is obtained, and after the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0041] Example 4

[0042] After dissolving phosgene (66.2 g) in dichloromethane (847.8 g), it is simultaneously introduced into the mixing reactor with the sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) to carry out the photochemical reaction (N [-COCl] :N [-OH] = 1.14). At the end of the photochemical reaction, the acyl chloride group content is 13062 ppm.

[0043] After introducing p-tert-butylphenol (36.31 g, 11% wt) into the photochemical reaction solution, it enters the tubular reactor of the first-stage series emulsifier to start the polycondensation reaction A. After reacting for a period of time, the acyl chloride group content is monitored to be 37.09 ppm and the hydroxyl group content is 286.32 ppm. At this time, [-COCl]:[-OH] = 0.13. Immediately add the catalyst triethylamine (3.60 g, 3% wt) and enter the polycondensation reaction kettle until the reaction ends. The polycarbonate reaction solution is obtained, and after the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0044] Example 5

[0045] After dissolving phosgene (66.2 g) in dichloromethane (847.8 g), it is simultaneously introduced into the mixing reactor with the sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) to carry out the photochemical reaction (N [-COCl] :N [-OH] = 1.14). At the end of the photochemical reaction, the acyl chloride group content is 13285 ppm.

[0046] After introducing p-tert-butylphenol (36.31 g, 11% wt) into the photochemical reaction solution, it enters the tubular reactor with a static mixer in the first stage to start the polycondensation reaction A. After reacting for a period of time, the acyl chloride group content is monitored to be 70.94 ppm and the hydroxyl group content is 436.18 ppm. At this time, [-COCl]:[-OH] = 0.16. Immediately add the catalyst triethylamine (20.65 g, 3% wt) and enter the polycondensation reaction kettle until the reaction ends. The polycarbonate reaction solution is obtained, and after the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0047] Example 6

[0048] After dissolving phosgene (66.2 g) in dichloromethane (847.8 g), it is simultaneously introduced into the mixing reactor with the sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) to carry out the photochemical reaction (N [-COCl] :N [-OH] = 1.14). At the end of the photochemical reaction, the acyl chloride group content is 12097 ppm.

[0049] After introducing p-tert-butylphenol (36.31 g, 11% wt) into the photochemical reaction solution, it enters a tubular reactor with a static mixer to start the polycondensation reaction A. After reacting for a period of time, the acyl chloride group content is monitored to be 68.06 ppm and the hydroxyl group content is 440.23 ppm. At this time, [-COCl]:[-OH] = 0.15. Immediately add the catalyst triethylamine (2.20 g, 3% wt) and enter the polycondensation reaction kettle until the reaction ends. The polycarbonate reaction solution is obtained, and after the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0050] Comparative Example 1

[0051] After dissolving phosgene (66.2 g) in dichloromethane (847.8 g), it is introduced into the mixing reactor simultaneously with the sodium salt solution of bisphenol A (876.8 g, density 1082 kg / m 3 , bisphenol A concentration 165 g / L) for the photochemical reaction (N [-COCl] :N [-OH] = 1.14). At the end of the photochemical reaction, the acyl chloride group content is 13370 ppm and the hydroxyl group content is 5704 ppm. At this time, [-COCl]:[-OH] = 2.34. At this time, p-tert-butylphenol (36.31 g, 11% wt) and the catalyst triethylamine (6.98 g, 3% wt) are introduced into the polycondensation reaction kettle until the reaction ends, and the polycarbonate reaction solution is obtained. After the same post-treatment operation as in Example 1, the polycarbonate resin is obtained.

[0052] Comparative Example 2

[0053] Photochemical stage: Mix recycled brine, fresh make-up water, and 32 wt% NaOH in a stirred storage tank according to a mass ratio of 1.58:2.35:1 to form a NaOH-containing salt solution. Add solid bisphenol A to the NaOH-containing salt solution and stir to dissolve to form a BPA sodium salt aqueous phase, controlling the BPA mass concentration in the aqueous phase to be 14.5 wt%. The BPA sodium salt aqueous phase, dichloromethane, phosgene, and 32 wt% NaOH are respectively fed into a photochemical reactor composed of a group of static mixers at a flow rate of 700 kg / hr, 600 kg / hr, 47 kg / hr, and 24 kg / hr. The reactor diameter is DN40 and the length is 800 mm, controlling the reactor outlet temperature at 35°C.

[0054] Polycondensation stage: Introduce the emulsion obtained in the photochemical stage into two 40 L overflow stirred kettles in series. At the same time, add a 10 wt% end-capping agent p-tert-butylphenol / dichloromethane solution and 32 wt% NaOH into the polycondensation reactor at a flow rate of 20 kg / hr and 2 kg / hr respectively, controlling the temperature in both reactors to be 35°C.

[0055] When the conversion rate of aqueous-phase bisphenol A is about 99.5% and the conversion rate of the end-capping agent is about 99.4%, the content of acyl chloride groups is monitored to be 5 ppm and the content of hydroxyl groups is 151 ppm. At this time, [-COCl]:[-OH] = 0.033. A 5 wt% catalyst triethylamine / dichloromethane solution is added to the polycondensation reactor at a flow rate of 4.5 kg / hr, and the reaction continues for 15 min. The crude reaction product is separated to remove the aqueous phase, and the organic phase is purified by washing and separation respectively, and the dichloromethane solvent is removed to obtain colorless polycarbonate powder.

[0056] Table 1. Summary of experimental data

[0057] PD Total Nitrogen / ppm Example 1 1.39 9.26 Example 2 1.43 10.72 Example 3 1.46 9.04 Example 4 1.28 0.88 Example 5 1.56 16.55 Example 6 1.80 7.17 Comparative Example 1 2.45 33.31 Comparative Example 2 2.23 85.78

[0058] From the comparison of the above data, it can be seen that the polycarbonate preparation method of the present invention can obtain a polymer with a narrow molecular weight distribution and excellent product quality. The above description is only the preferred embodiment of the present invention. It should be noted that for those skilled in the art, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polycarbonate, comprising the following steps: a) First, react an alkali metal salt solution of polyphenol with phosgene dissolved in an inert solvent in a mixing reactor to obtain a photochemical reaction product; wherein, the molar amount of hydroxyl groups is N [-OH] , and the molar amount of acyl chloride groups is N [-COCl] ; b) Adding a capping agent to the photochemical reaction product, and then passing the reaction solution through a first-stage reactor. This stage is polycondensation reaction A, and the mass concentrations of acyl chloride [-COCl] and hydroxyl [-OH] are measured. c) Adding a catalyst to the polycondensate of polycondensation reaction A, entering a polycondensation reactor, and carrying out polycondensation reaction B until the reaction ends to obtain a polycarbonate reaction solution. After washing, devolatilization, and drying, a polycarbonate resin is obtained. Among them, when adding the catalyst in step c), the following conditions should be met: (1) 0.1 ≤ [-COCl]:[-OH] ≤ N [-COCl] :N [-OH] ; (2) The molar amount of the catalyst input is in a ratio of 1:5 to 5:1, preferably 1:3 to 3:1, to the molar amount of acyl chloride in the system when adding the catalyst.

2. The method according to claim 1, wherein In step a), the molar ratio of the acyl chloride group to the phenolic hydroxyl group is 1 ≤ N [-COCl] :N [-OH] ≤ 1.

2.

3. The method according to claim 1 or 2, characterized in that, In step a), the mass concentration ratio of the acyl chloride in the photochemical reaction product to the acyl chloride contained in the initial phosgene is 0.1 to 0.

5.

4. The method according to any one of claims 1-3, characterized in that, In step a), the alkali metal salts of polyphenols include bisphenol A (2,2-bis(4-hydroxyphenyl)propane), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(2-hydroxyphenyl)-3,3,5-trimethylcyclohexane, the sodium salt or potassium salt of resorcinol. The inert solvent is one or more of dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, toluene, and chlorobenzene.

5. The method according to any one of claims 1-4, characterized in that In step b), the capping agent is one or more of phenol, p-tert-butylphenol, cumylphenol, p-cyanophenol, or isooctylphenol.

6. The method according to any one of claims 1-5, characterized in that, In step b), the reactor includes a series combination of one or more of an emulsifier or high-speed dispersion equipment, a tubular reactor, a kettle reactor, and a tubular reactor with a dynamic or static mixer.

7. According to the method described in any one of claims 1-6, characterized in that, In step b), at the end of polycondensation reaction A, the mass concentration ratio of acyl chloride to the acyl chloride contained in the initial phosgene is 10 -5 ~2×10 -3 .

8. The method according to any one of claims 1-7, characterized in that, In step c), the catalyst is selected from triethylamine, trialkylamine, N-ethylpiperidine, N-isopropylpiperidine, and N-ethylmorpholine.

9. The method according to any one of claims 1-8, characterized in that In step c), the nitrogen element content of the polycarbonate resin is ≤ 30 ppm.

10. The method according to any one of claims 1-9, characterized in that, In step c), the molecular weight distribution of the polycarbonate resin is 1.2 - 2.0.