A method for the synthesis of branched polycarbonate prepolymers and branched polycarbonates

Abstract

This invention belongs to the field of polymer synthesis, and particularly relates to a method for synthesizing branched polycarbonate prepolymers and branched polycarbonates. The method for synthesizing branched polycarbonate prepolymers provided by this invention includes the following steps: a) reacting phosgene with sodium bisphenol A to obtain bisphenol A acyl chloride; b) reacting the bisphenol A acyl chloride with sodium 1,1,1-tris(4-hydroxyphenyl)ethane to obtain the branched polycarbonate prepolymer. The synthesis method provided by this invention first synthesizes bisphenol A acyl chloride. Since the molecular structure of bisphenol A acyl chloride has a reactive group at only one end that can undergo chain growth, subsequently reacting the bisphenol A acyl chloride with the branching agent 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) will yield a branched polycarbonate (PC) prepolymer with unidirectional chain growth, minimizing the probability of THPE linkages and reducing the degree of crosslinking in the prepolymer.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis, and particularly relates to a method for synthesizing branched polycarbonate prepolymer and branched polycarbonate. Background Technology

[0002] Polycarbonate (PC), as an engineering plastic with excellent comprehensive properties, occupies an important position in the fields of electronics, automotive industry, and medical devices. However, traditional linear polycarbonate has inherent limitations in processing applications. Its low melt strength and high melt viscosity dependence on shear rate make it prone to sagging and film breakage during blow molding, foaming, and thermoforming processes, resulting in poor uniformity of product wall thickness. This seriously restricts its application expansion in high-end hollow products, lightweight foam materials, and other fields.

[0003] To improve the melt strength of polycarbonate, existing technologies typically employ methods that introduce branched structures. However, the synthesis of existing branched polycarbonates faces the challenge of simultaneously achieving a balance between the degree of branching and molecular weight. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for synthesizing branched polycarbonate prepolymers and branched polycarbonates. The method provided by the present invention is a continuous process that can synthesize polycarbonate prepolymers and polycarbonate products with high branching degree and low crosslinking.

[0005] This invention provides a method for synthesizing branched polycarbonate prepolymers, comprising the following steps:

[0006] a) Phosgene reacts with sodium bisphenol A to yield bisphenol A acyl chloride;

[0007] b) The bisphenol A acyl chloride is reacted with sodium 1,1,1-tris(4-hydroxyphenyl)ethane to obtain a branched polycarbonate prepolymer.

[0008] Preferably, in step a), the molar ratio of phosgene to sodium bisphenol A is (0.8~1.2):1.

[0009] Preferably, in step a), the reaction temperature is 10~40℃ and the time is 0.5~2min.

[0010] Preferably, in step b), the molar ratio of bisphenol A acyl chloride to sodium 1,1,1-tris(4-hydroxyphenyl)ethane is (8~12):3.

[0011] Preferably, in step b), the reaction temperature is 10~40℃ and the time is 10~60s.

[0012] This invention provides a method for synthesizing branched polycarbonate, comprising the following steps:

[0013] A) Synthesize branched polycarbonate prepolymer according to the synthesis method described in the above technical solution;

[0014] B) The branched polycarbonate prepolymer is mixed with sodium bisphenol A, then reacted with phosgene, and subsequently reacted with p-tert-butylphenol, sodium hydroxide, dichloromethane and triethylamine to obtain branched polycarbonate.

[0015] Preferably, in step B), the molar ratio of the sodium bisphenol A salt to the branched polycarbonate prepolymer, calculated based on the sodium 1,1,1-tris(4-hydroxyphenyl)ethane used as the raw material, is (75~1500):3.

[0016] Preferably, in step B), the molar ratio of phosgene to sodium bisphenol A is 1:(1~1.5).

[0017] Preferably, in step B), the molar ratio of tert-butylphenol to sodium bisphenol A is (3~30):100.

[0018] Preferably, in step B), the molar ratio of sodium hydroxide to sodium bisphenol A is (50~200):100.

[0019] Compared with existing technologies, this invention provides a method for synthesizing branched polycarbonate prepolymers and branched polycarbonates. The method for synthesizing branched polycarbonate prepolymers provided by this invention includes the following steps: a) reacting phosgene with sodium bisphenol A to obtain bisphenol A acyl chloride; b) reacting the bisphenol A acyl chloride with sodium 1,1,1-tris(4-hydroxyphenyl)ethane to obtain the branched polycarbonate prepolymer. The synthesis method provided by this invention first synthesizes bisphenol A acyl chloride. Since the molecular structure of bisphenol A acyl chloride has a reactive group at only one end that can undergo chain growth, subsequently reacting bisphenol A acyl chloride with the branching agent 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) will yield a branched polycarbonate (PC) prepolymer with unidirectional chain growth, minimizing the probability of THPE linkages and reducing the degree of crosslinking in the prepolymer. The synthesis method provided by this invention can improve the reaction efficiency of the branching agent THPE and reduce crosslinking, thereby synthesizing polycarbonate prepolymers and polycarbonate products with high branching degree and low crosslinking. Experimental results show that the synthesis method provided by this invention can significantly reduce the number of crystal points in polycarbonate products. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a method for synthesizing branched polycarbonate prepolymers, comprising the following steps:

[0022] a) Phosgene reacts with sodium bisphenol A to yield bisphenol A acyl chloride;

[0023] b) The bisphenol A acyl chloride is reacted with sodium salt of 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) to obtain a branched polycarbonate (PC) prepolymer.

[0024] In the prepolymer synthesis method provided by the present invention, in step a), the molar ratio of phosgene to sodium bisphenol A is preferably (0.8~1.2):1, specifically it can be 0.8:1, 0.82:1, 0.85:1, 0.87:1, 0.9:1, 0.92:1, 0.95:1, 0.97:1, 1:1, 1.02:1, 1.05:1, 1.07:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1 or 1.2:1.

[0025] In the prepolymer synthesis method provided by the present invention, in step a), the specific process of the reaction preferably includes: dissolving phosgene in an organic solvent, and then mixing and reacting it with an aqueous solution of sodium bisphenol A.

[0026] In the prepolymer synthesis method provided by the present invention, in step a), the reaction temperature is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 30s~2min, specifically 30s, 40s, 50s, 1min, 1min10s, 1min20s, 1min30s, 1min40s, 1min50s or 2min.

[0027] In the prepolymer synthesis method provided by this invention, in step a), the chemical structure of the bisphenol A acyl chloride is as follows:

[0028] .

[0029] In the prepolymer synthesis method provided by the present invention, in step b), the molar ratio of bisphenol A acyl chloride to sodium 1,1,1-tris(4-hydroxyphenyl)ethane is preferably (8~12):3, specifically 8:3, 8.2:3, 8.5:3, 8.7:3, 9:3, 9.2:3, 9.5:3, 9.7:3, 10:3, 10.2:3, 10.5:3, 10.7:3, 11:3, 11.2:3, 11.5:3, 11.7:3 or 12:3.

[0030] In the prepolymer synthesis method provided by the present invention, in step b), the specific process of the reaction preferably includes: mixing and reacting a reaction solution containing bisphenol A acyl chloride with an aqueous solution of sodium 1,1,1-tris(4-hydroxyphenyl)ethane.

[0031] In the prepolymer synthesis method provided by the present invention, in step b), the reaction temperature is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 10~60s, specifically 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s.

[0032] This invention also provides a method for synthesizing branched polycarbonate, comprising the following steps:

[0033] A) Synthesize branched polycarbonate prepolymer according to the synthesis method described in the above technical solution;

[0034] B) The branched polycarbonate prepolymer is mixed with sodium bisphenol A, then reacted with phosgene, and subsequently reacted with p-tert-butylphenol (PTBP), sodium hydroxide, dichloromethane and triethylamine to obtain branched polycarbonate.

[0035] In the branched polycarbonate synthesis method provided by the present invention, in step B), the molar ratio of the bisphenol A sodium salt to the branched polycarbonate prepolymer calculated based on the sodium salt of the raw material 1,1,1-tris(4-hydroxyphenyl)ethane is preferably (75~1500):3, more preferably (88~920):3, and specifically can be 88:3, 90:3, 100:3, 120:3, 150:3, 170:3, 200:3, 250:3, 300:3, 350:3, 400:3, 500:3, 600:3, 700:3, 800:3, 900:3 or 920:3.

[0036] In the branched polycarbonate synthesis method provided by the present invention, in step B), the sodium bisphenol A salt is preferably mixed in the form of a sodium bisphenol A salt solution.

[0037] In the branched polycarbonate synthesis method provided by the present invention, in step B), the molar ratio of phosgene to sodium bisphenol A is preferably 1:(1~1.5), more preferably 1:(1.18~1.3), and specifically can be 1:1.18, 1:1.19, 1:1.2, 1:1.21, 1:1.22, 1:1.23, 1:1.24, 1:1.25, 1:1.26, 1:1.27, 1:1.28, 1:1.29 or 1:1.3.

[0038] In the branched polycarbonate synthesis method provided by the present invention, in step B), the phosgene is preferably mixed in the form of a phosgene solution.

[0039] In the branched polycarbonate synthesis method provided by the present invention, in step B), the temperature of the reaction with phosgene is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 3~8min, specifically 3min, 3min30s, 4min, 4min30s, 5min, 5min30s, 5min40s, 6min, 6min30s, 7min, 7min30s or 8min.

[0040] In the branched polycarbonate synthesis method provided by the present invention, in step B), after the reaction with phosgene is completed, it is preferable to react sequentially with p-tert-butylphenol, sodium hydroxide, dichloromethane and triethylamine.

[0041] In the branched polycarbonate synthesis method provided by the present invention, in step B), the molar ratio of tert-butylphenol to sodium bisphenol A is preferably (3~30):100, more preferably (5~15):100, and specifically can be 5:100, 5.5:100, 6:100, 6.5:100, 7:100, 7.5:100, 8:100, 8.5:100, 9:100, 9.5:100, 10:100, 10.5:100, 11:100, 11.5:100, 12:100, 12.5:100, 13:100, 13.5:100, 14:100, 14.5:100 or 1.5:100.

[0042] In the branched polycarbonate synthesis method provided by the present invention, in step B), the tert-butylphenol is preferably mixed in the form of a tert-butylphenol solution.

[0043] In the branched polycarbonate synthesis method provided by the present invention, in step B), the temperature for the reaction with the tert-butylphenol is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 3~8min, specifically 3min, 3min30s, 4min, 4min30s, 5min, 5min30s, 5min55s, 6min, 6min30s, 7min, 7min30s or 8min.

[0044] In the branched polycarbonate synthesis method provided by the present invention, in step B), the molar ratio of sodium hydroxide to sodium bisphenol A is preferably (50~200):100, more preferably (100~150):100, and specifically can be 100:100, 102:100, 105:100, 107:100, 110:100, 112:100, 115:100, 117:100, 120:100, 123:100, 125:100, 127:100, 130:100, 132:100, 135:100, 137:100, 140:100, 142:100, 145:100, 147:100 or 150:100.

[0045] In the branched polycarbonate synthesis method provided by the present invention, in step B), the sodium hydroxide is preferably mixed in the form of a sodium hydroxide solution.

[0046] In the branched polycarbonate synthesis method provided by the present invention, in step B), the temperature for mixing and reacting with the sodium hydroxide is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 2~7min, specifically 2min, 2min30s, 3min, 3min30s, 4min, 4min30s, 4min35s, 5min, 5min30s, 6min, 6min30s or 7min.

[0047] In the branched polycarbonate synthesis method provided by the present invention, in step B), the mass ratio of dichloromethane to bisphenol A sodium salt solution is preferably (1~6):5, more preferably (2~5):5, and specifically can be 2:5, 2.3:5, 2.5:5, 2.7:5, 3:5, 3.2:5, 3.5:5, 3.7:5, 4:5, 4.2:5, 4.5:5, 4.7:5 or 5.

[0048] In the branched polycarbonate synthesis method provided by the present invention, in step B), the temperature for mixing and reacting with the dichloromethane is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 20~60min, specifically 20min, 23min, 25min, 27min, 30min, 32min, 35min, 37min, 40min, 42min, 45min, 47min, 50min, 52min, 55min, 57min or 60min.

[0049] In the branched polycarbonate synthesis method provided by the present invention, in step B), the amount of triethylamine in the mixed system is preferably 500~2500ppm, more preferably 800~1500ppm, and specifically can be 800ppm, 850ppm, 900ppm, 950ppm, 1000ppm, 1050ppm, 1100ppm, 1150ppm, 1200ppm, 1250ppm, 1300ppm, 1350ppm, 1400ppm, 1450ppm or 1500ppm.

[0050] In the branched polycarbonate synthesis method provided by the present invention, in step B), the triethylamine is preferably mixed in the form of a triethylamine solution.

[0051] In the branched polycarbonate synthesis method provided by the present invention, in step B), the temperature for the reaction with the triethylamine is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃; the reaction time is preferably 1~6min, specifically 1min, 1min30s, 2min, 2min30s, 3min, 3min20s, 3min30s, 4min, 4min30s, 5min, 5min30s or 6min.

[0052] The synthesis method provided by this invention first synthesizes bisphenol A acyl chloride. Since the molecular structure of bisphenol A acyl chloride has only one reactive group at one end capable of chain growth, subsequent reaction of bisphenol A acyl chloride with the branching agent 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) yields a branched polycarbonate (PC) prepolymer with unidirectional chain growth, minimizing the probability of THPE linkages and reducing the degree of crosslinking in the prepolymer. The synthesis method provided by this invention can improve the reaction efficiency of the branching agent THPE and reduce crosslinking, thereby synthesizing highly branched, low-crosslinked polycarbonate prepolymers and polycarbonate products. Experimental results show that the synthesis method provided by this invention can significantly reduce the number of crystal points in polycarbonate products.

[0053] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0054] In the following embodiments and comparative examples of the present invention, the bisphenol A sodium salt solution used was prepared according to the following steps: bisphenol A (BPA) was dissolved in a 6 wt% NaOH aqueous solution, with a molar ratio of BPA to NaOH of 1:2.05, to obtain the bisphenol A sodium salt solution.

[0055] In the following embodiments and comparative examples of the present invention, the sodium 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) salt solution used was prepared according to the following steps: THPE was dissolved in a 6 wt% NaOH aqueous solution, with a THPE to NaOH molar ratio of 1:3.15, to obtain the sodium THPE salt solution.

[0056] In the following embodiments and comparative examples of the present invention, unless otherwise specified, the reactions were carried out at 25°C and atmospheric pressure.

[0057] Example 1

[0058] 2.2 g of phosgene was dissolved in 71.1 g of dichloromethane, and then reacted with 30 g of sodium bisphenol A solution at the interface for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A to phosgene was 1:1.18. The bisphenol A acyl chloride was then reacted with 13.6 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:10.

[0059] The above-mentioned branched PC prepolymer was thoroughly mixed with 270g of sodium bisphenol A solution, and then reacted with 150.3g of a 14.5wt% phosgene solution in dichloromethane. After reacting for 5 min 40 s, 17.0g of a 10wt% PTBP solution in dichloromethane was added to the reaction system. After reacting for 5 min 55 s, 28.6g of a 32wt% sodium hydroxide aqueous solution was added. After reacting for 4 min 35 s, 94.8g of dichloromethane was added. After reacting for 40 min, 16.6g of a 6wt% triethylamine solution in dichloromethane was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0060] The prepared branched PC was acid-washed and water-washed until the conductivity of the aqueous phase was less than 10 μS / cm. Then, molecular weight and residual THPE and BPA content in the aqueous reaction phase were measured. The residual THPE and BPA in the aqueous phase were determined using high-performance liquid chromatography (HPLC) with methanol and water in a volume ratio of 7:3 as the mobile phase.

[0061] Example 2

[0062] 1.9 g of phosgene was dissolved in 60.2 g of dichloromethane, and then reacted with 30 g of sodium bisphenol A solution for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A to phosgene was 1:1. The bisphenol A acyl chloride was then reacted with 13.6 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:10.

[0063] The subsequent steps and conditions are the same as in Example 1.

[0064] Example 3

[0065] 1.7 g of phosgene was dissolved in 54.2 g of dichloromethane, and then reacted with 30 g of sodium bisphenol A solution at the interface for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A to phosgene was 1:0.9. The bisphenol A acyl chloride was then reacted with 13.6 g of sodium THPE for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:10.

[0066] The subsequent steps and conditions are the same as in Example 1.

[0067] Example 4

[0068] 1.5 g of phosgene was dissolved in 48.2 g of dichloromethane, and then reacted with 30 g of sodium bisphenol A solution at the interface for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A to phosgene was 1:0.8. Then, bisphenol A acyl chloride was reacted with 13.6 g of sodium THPE for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:10.

[0069] The subsequent steps and conditions are the same as in Example 1.

[0070] Comparative Example 1

[0071] 13.6 g of THPE sodium salt solution was directly mixed with 300 g of bisphenol A sodium salt solution. Then, 167.0 g of 14.5 wt% phosgene dichloromethane solution, 17.0 g of 10 wt% PTBP dichloromethane solution, 31.5 g of 32 wt% sodium hydroxide aqueous solution, 163.7 g of dichloromethane, and 17.3 g of 6 wt% triethylamine dichloromethane solution were added to the reaction system in sequence to prepare branched PC.

[0072] The prepared branched PC was acid-washed and water-washed until the conductivity of the aqueous phase was less than 10 μs / cm, and then molecular weight and residual THPE and BPA content in the reaction aqueous phase were tested.

[0073] The molecular weight and residual content of the branched PC prepared in Examples 1-4 and Comparative Example 1 are shown in Table 1:

[0074] Table 1

[0075]

[0076] As shown in Table 1, Comparative Example 1 exhibited severe cross-linking, resulting in a large amount of gel formation that prevented successful separation of the aqueous and oil phases for washing. Using bisphenol A acyl chloride as an intermediate facilitated the synthesis of highly branched PC. When the ratio of bisphenol A to phosgene was 0.9, THPE residue was minimized, and the reaction rate was maximized, maximizing the utilization of the branching agent. Excessive phosgene usage during the synthesis of bisphenol A acyl chloride led to bisphenol A self-polymerization, affecting the reaction efficiency of the subsequent THPE sodium salt solution; conversely, insufficient bisphenol A acyl chloride generation resulted in inadequate THPE reaction efficiency.

[0077] Example 5

[0078] 6.7 g of phosgene was dissolved in 216.9 g of dichloromethane, and then reacted with 120 g of sodium bisphenol A solution for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A solution to phosgene was 1:0.9. The bisphenol A acyl chloride was then reacted with 67.9 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:8.

[0079] The above-mentioned branched PC prepolymer was thoroughly mixed with 13500g of sodium bisphenol A solution, and then reacted with 8352.7g of a 14.5wt% phosgene dichloromethane solution. After reacting for 5 min 40 s, 495.3g of a 10wt% PTBP dichloromethane solution was added to the reaction system. After reacting for 5 min 55 s, 1584.8g of a 32wt% sodium hydroxide aqueous solution was added. After reacting for 4 min 35 s, 5916.3g of dichloromethane was added. After reacting for 40 min, 757.6g of a 6wt% triethylamine dichloromethane solution was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0080] The prepared branched PC was acid-washed and water-washed until the aqueous phase conductivity was less than 10 μs / cm, then dried, pulverized, and extruded for injection molding.

[0081] Example 6

[0082] 7.5 g of phosgene was dissolved in 244.0 g of dichloromethane, and then reacted with 135 g of sodium bisphenol A solution for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A solution to phosgene was 1:0.9. Then, bisphenol A acyl chloride was reacted with 67.9 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:9.

[0083] The above-mentioned branched PC prepolymer was thoroughly mixed with 13500g of sodium bisphenol A solution, and then reacted with 8352.7g of a 14.5wt% phosgene dichloromethane solution. After reacting for 5 min 40 s, 495.3g of a 10wt% PTBP dichloromethane solution was added to the reaction system. After reacting for 5 min 55 s, 1584.8g of a 32wt% sodium hydroxide aqueous solution was added. After reacting for 4 min 35 s, 5916.3g of dichloromethane was added. After reacting for 40 min, 757.6g of a 6wt% triethylamine dichloromethane solution was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0084] The prepared branched PC was acid-washed and water-washed until the aqueous phase conductivity was less than 10 μs / cm, then dried, pulverized, and extruded for injection molding.

[0085] Example 7

[0086] 8.4 g of phosgene was dissolved in 271.1 g of dichloromethane, and then reacted with 150 g of sodium bisphenol A solution for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A solution to phosgene was 1:0.9. The bisphenol A acyl chloride was then reacted with 67.9 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:10.

[0087] The above-mentioned branched PC prepolymer was thoroughly mixed with 13500g of sodium bisphenol A solution, and then reacted with 8352.7g of a 14.5wt% phosgene dichloromethane solution. After reacting for 5 min 40 s, 495.3g of a 10wt% PTBP dichloromethane solution was added to the reaction system. After reacting for 5 min 55 s, 1585.9g of a 32wt% sodium hydroxide aqueous solution was added. After reacting for 4 min 35 s, 5889.1g of dichloromethane was added. After reacting for 40 min, 758.0g of a 6wt% triethylamine dichloromethane solution was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0088] The prepared branched PC was acid-washed and water-washed until the aqueous phase conductivity was less than 10 μs / cm, then dried, pulverized, and extruded for injection molding.

[0089] Example 8

[0090] 9.2 g of phosgene was dissolved in 298.2 g of dichloromethane, and then reacted with 165 g of sodium bisphenol A solution for 1 min to generate bisphenol A acyl chloride. The molar ratio of sodium bisphenol A solution to phosgene was 1:0.9. Then, bisphenol A acyl chloride was reacted with 67.9 g of sodium THPE solution for 30 s to generate branched PC prepolymer. The molar ratio of sodium THPE to bisphenol A acyl chloride was 3:11.

[0091] The above-mentioned branched PC prepolymer was thoroughly mixed with 13500g of sodium bisphenol A solution, and then reacted with 8352.7g of a 14.5wt% phosgene dichloromethane solution. After reacting for 5 min 40 s, 495.3g of a 10wt% PTBP dichloromethane solution was added to the reaction system. After reacting for 5 min 55 s, 1587.0g of a 32wt% sodium hydroxide solution was added. After reacting for 4 min 35 s, 5962.0g of dichloromethane was added. After reacting for 40 min, 758.4g of a 6wt% triethylamine dichloromethane solution was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0092] The prepared branched PC was acid-washed and water-washed until the aqueous phase conductivity was less than 10 μs / cm, then dried, pulverized, and extruded for injection molding.

[0093] Comparative Example 2

[0094] 67.9 g of THPE sodium salt solution was directly mixed with 15000 g of bisphenol A sodium salt solution. Then, 15491.6 g of 14.5 wt% phosgene dichloromethane solution was added to the reaction system. After reacting for 5 min 40 s, 495.3 g of 10 wt% PTBP dichloromethane solution was added. After reacting for 5 min 55 s, 1575.0 g of 32 wt% sodium hydroxide solution was added. After reacting for 4 min 35 s, 8500.9 g of dichloromethane was added. After reacting for 40 min, 849.8 g of 6 wt% triethylamine solution was added. Finally, the polymerization reaction was completed in 3 min 20 s to produce branched PC.

[0095] The prepared branched PC was acid-washed and water-washed until the aqueous phase conductivity was less than 10 μs / cm, then dried, pulverized, and extruded for injection molding.

[0096] The molecular weight, residual THPE in aqueous phase, number of crystal points, and melt index R value of the branched PC prepared in Examples 5-8 and Comparative Example 2 were tested.

[0097] The method for counting crystal points is as follows: branched PC is made into a 0.2mm film using a casting machine, and then the number of crystal points is counted over a 1m diameter. 2 The number of crystal points with a diameter greater than 100 micrometers.

[0098] The melt flow index (R) test method is as follows: A melt flow index test is conducted under conditions of 300℃ and 1.2kg load, and the test result is recorded as 'a'; a melt flow index test is conducted under conditions of 300℃ and 10kg load, and the test result is recorded as 'b'; the calculation method is as follows:

[0099] Melt index R value = ;

[0100] The melt index R value can characterize the melt strength of branched PC under different shear forces.

[0101] The test results are shown in Table 2:

[0102] Table 2

[0103]

[0104] As shown in Table 2, when using this process to synthesize branched PC with a slightly lower degree of branching, the number of crystal points in the branched PC can still be significantly reduced, thus reducing crosslinking. Furthermore, during the prepolymer synthesis stage, when the molar ratio of THPE to bisphenol A is 3:10, THPE exhibits the best reaction effect and the highest melt index (R value).

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing a branched polycarbonate prepolymer, characterized in that, Includes the following steps: a) Phosgene reacts with sodium bisphenol A to yield bisphenol A acyl chloride; b) The bisphenol A acyl chloride is reacted with sodium 1,1,1-tris(4-hydroxyphenyl)ethane to obtain a branched polycarbonate prepolymer.

2. The synthesis method according to claim 1, characterized in that, In step a), the molar ratio of phosgene to sodium bisphenol A is (0.8~1.2):

1.

3. The synthesis method according to claim 1, characterized in that, In step a), the reaction temperature is 10~40℃ and the time is 0.5~2min.

4. The synthesis method according to claim 1, characterized in that, In step b), the molar ratio of bisphenol A acyl chloride to sodium 1,1,1-tris(4-hydroxyphenyl)ethane is (8~12):

3.

5. The synthesis method according to claim 1, characterized in that, In step b), the reaction temperature is 10~40℃ and the time is 10~60s.

6. A method for synthesizing branched polycarbonate, characterized in that, Includes the following steps: A) Synthesizing branched polycarbonate prepolymers according to the synthesis method of any one of claims 1 to 5; B) The branched polycarbonate prepolymer is mixed with sodium bisphenol A, then reacted with phosgene, and subsequently reacted with p-tert-butylphenol, sodium hydroxide, dichloromethane and triethylamine to obtain branched polycarbonate.

7. The synthesis method according to claim 6, characterized in that, In step B), the molar ratio of the sodium bisphenol A salt to the branched polycarbonate prepolymer, based on the sodium 1,1,1-tris(4-hydroxyphenyl)ethane salt used to prepare the raw material, is (75~1500):

3.

8. The synthesis method according to claim 6, characterized in that, In step B), the molar ratio of phosgene to sodium bisphenol A is 1:(1~1.5).

9. The synthesis method according to claim 6, characterized in that, In step B), the molar ratio of tert-butylphenol to sodium bisphenol A is (3~30):

100.

10. The synthesis method according to claim 6, characterized in that, In step B), the molar ratio of sodium hydroxide to sodium bisphenol A is (50~200):100.

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