Hydrophilic modified polysulfone resin with carboxyl side groups and preparation method thereof

Abstract

The invention discloses a hydrophilic modified polysulfone resin with carboxyl side groups and a preparation method thereof, and relates to the technical field of polysulfone. The invention adopts deionized water as a salt-forming solvent to carry out a salt-forming reaction of a bisphenol monomer. After the salt-forming reaction is completed, the salt-forming agent of the system is reacted, and after the alkalinity is weakened, an NMP solvent is added to collect water, thereby reducing the interference of NMP decomposition on the carboxyl group in the salt-forming stage, and the ratio of the diphenolic acid connected to the molecular chain is consistent with the feed ratio, so that the formed hydrophilic modified polysulfone resin component is more stable; at the same time, before the end-capping, the side chain carboxyl group forms a stable coordination complex, so that the diphenolic acid type hydrophilic polysulfone of the invention can be end-capped, greatly reducing the content of the phenolic end group with poor thermal stability, so that the original color can be maintained during extrusion granulation.

Description

Technical Field

[0001] The invention relates to the technical field of polysulfone, in particular to a hydrophilic modified polysulfone resin with carboxyl side groups and a preparation method thereof. Background Art

[0002] Polysulfone resin (PSU) is a non-crystalline special engineering plastic. Because it contains sulfone group, isopropyl group and benzene ring, it has good antioxidant properties, mechanical properties and thermal stability. The presence of ether bond provides it with a certain toughness. Therefore, due to its excellent properties, polysulfone resin is widely used in high-end medical, electronic products, water treatment, aerospace and other fields.

[0003] Polysulfone is usually hydrophobic, and hollow fiber ultrafiltration membranes containing hydrophobic polysulfone have poor wettability, are easy to scale, and are difficult to clean when used for separation and filtration. Therefore, in order to improve the hydrophilicity of polysulfone, manufacturers gradually improve the hydrophilicity of polysulfone by introducing polar groups such as carboxyl, sulfonic acid, and amino groups. Among them, diphenolic acid (4,4-bis (4-hydroxyphenyl) valeric acid, DPA) has achieved large-scale industrial production and is widely used in coatings, cosmetics, surfactants, plasticizers, textile auxiliaries and other industries. It can be used as a polymerization monomer to introduce carboxyl groups into the side chains of polysulfone to achieve the purpose of hydrophilic modification.

[0004] The usual method for synthesizing bisphenolic acid type polysulfone resin is a one-step method, i.e., bisphenol A, bisphenolic acid and 4,4'-dichlorodiphenyl sulfone monomers are subjected to salt formation and nucleophilic substitution polycondensation in the presence of an alkaline nucleophile, the alkaline nucleophile usually being potassium carbonate, and the solvent being N-methylpyrrolidone (NMP); after the polymerization, a polymer solution is obtained, and then water, ethanol or methanol is used as a precipitant, in which polysulfone is separated from the polymer solution; the separated polysulfone is then purified, dried, granulated and packaged to obtain the product.

[0005] Since in the salt-forming stage, the monomer bisphenol A reacts with the alkaline nucleophile to generate bisphenol A salt and water, under the reaction conditions of high temperature and strong alkali, NMP is easily hydrolyzed by the water generated in the salt-forming stage to generate N-methyl-4-aminobutyric acid (reaction formula I); N-methyl-4-aminobutyric acid reacts with part of the bisphenol acid to generate low molecular weight polyamide (reaction formula II), which reduces the activity of the bisphenol acid and makes it difficult to connect to the polysulfone molecular chain, thereby affecting its hydrophilic modification effect.

[0006]

[0007] Reaction formula I;

[0008]

[0009] Reaction formula II.

[0010] In addition, when synthesizing polysulfone by traditional polymerization process, it is necessary to perform end-capping after the polymerization to improve the thermal stability of the resin. The most commonly used end-capping agent is methyl chloride, but for diphenolic acid hydrophilic polysulfone, when methyl chloride caps the phenolic hydroxyl group at the end of the polysulfone molecule, it will react with the carboxyl group of the molecular side chain at the same time to generate hydrophobic esters, resulting in the disappearance of the hydrophilic modification effect:

[0011] .

[0012] Therefore, increasing the proportion of bisphenol acid segments in the molecular chain and avoiding the conversion of carboxyl side groups during the capping stage are issues that must be addressed in the synthesis of bisphenol acid-based polysulfones, which are of great significance for promoting the application of bisphenol acid-based polysulfones. Summary of the invention

[0013] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a hydrophilic modified polysulfone resin with a carboxyl side group and a preparation method thereof. The prepared polysulfone resin can be normally terminated with methyl chloride and maintains its original color during granulation without loss of diphenolic acid components and with a stable content of hydrophilic components, which is conducive to its application in downstream film making.

[0014] The technical solution of the present invention is:

[0015] In one aspect, the present invention provides a method for preparing a hydrophilically modified polysulfone resin having a carboxyl side group, comprising the following steps:

[0016] S1: put bisphenol A, diphenolic acid and salt-forming agent into a salt-forming solvent, pass nitrogen, heat to 90-100°C, keep warm for 2-8h, and perform salt-forming reaction; after the reaction, add N-methylpyrrolidone and 4,4'-dichlorodiphenyl sulfone, continue to heat to 160-180°C for dehydration, heat to 185-200°C after dehydration, and keep warm for nucleophilic polycondensation reaction; after the reaction for 0.5-4h, obtain a polysulfone resin polymerization liquid; wherein the total mole number of bisphenol A and diphenolic acid and the mole number of 4,4'-dichlorodiphenyl sulfone have a ratio of 1:(0.85-1);

[0017] S2: cooling the polysulfone resin polymer solution to 60-150° C., adding calcium salt, reacting for 1-3 hours, and then capping the polysulfone resin polymer solution to obtain a capped polysulfone resin polymer solution;

[0018] S3 cools the blocked polysulfone resin polymer solution to 60-80° C., adds an organic acid after filtering, adjusts the pH to 4-6, stirs for 3-5 hours, and then performs post-treatment to obtain a hydrophilic modified polysulfone resin with a carboxyl side group.

[0019] Preferably, in step S1, the salt-forming agent is a mixture of potassium hydroxide and alkali metal carbonate; and the salt-forming solvent is deionized water.

[0020] Preferably, the alkali metal carbonate is potassium bicarbonate, sodium bicarbonate, cesium carbonate, potassium carbonate or sodium carbonate.

[0021] Preferably, in step S1, the total mass of bisphenol A, diphenolic acid and 4,4'-dichlorodiphenyl sulfone, the mass of the salt-forming solvent, and the mass ratio of N-methylpyrrolidone are 1:(2.5-5):(2.5-5); the molar ratio of bisphenol A to diphenolic acid is 1:(0.05-0.5); the molar number of bisphenol A, the molar number of diphenolic acid, and the molar number of potassium hydroxide meet the following formula: N KOH =0.98×(2N BPA +3N DPA ), where N KOH is the number of moles of potassium hydroxide, N BPA 、N DPA They are the mole number of bisphenol A and the mole number of diphenolic acid respectively; the ratio of the total mole number of bisphenol A and diphenolic acid to the mole number of alkali metal carbonate is 1:(0.01-0.2).

[0022] Preferably, in step S2, the calcium salt is calcium chloride.

[0023] Preferably, the molar ratio of diphenolic acid to calcium salt is 1:(1.1-2).

[0024] Preferably, in step S2, the end-capping treatment of the polysulfone resin polymerization liquid is: introducing methyl chloride into the polysulfone resin polymerization liquid at 160-190° C. and reacting for 1-4 hours.

[0025] Preferably, in step S3, the organic acid is acetic acid, citric acid or oxalic acid.

[0026] Preferably, in step S3, the post-treatment of the blocked polysulfone resin polymerization liquid comprises: cooling, crushing, washing, filtering and drying the blocked polysulfone resin polymerization liquid.

[0027] On the other hand, the present invention provides a hydrophilic modified polysulfone resin with carboxyl side groups, which is prepared by the above-mentioned preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. From the whole polymerization process of polysulfones, the salt-forming stage is the stage with the strongest alkalinity of the system, and NMP decomposes the most seriously in this stage. Therefore, in order to avoid that the NMP hydrolyzate consumes the diphenolic acid monomer, the present invention adopts deionized water as the salt-forming solvent to carry out the salt-forming reaction of the diphenolic monomer. After the salt-forming reaction ends, the salt-forming agent of the system is reacted, and the alkalinity is weakened before adding the NMP solvent to collect water, thereby reducing the decomposition of NMP. Therefore, in the hydrophilic modified polysulfone resin with carboxyl side groups prepared by the present invention, the interference of NMP decomposition to carboxyl in the salt-forming stage is reduced, the diphenolic acid ratio of the access molecular chain is consistent with the feed ratio, and the hydrophilic modified polysulfone resin component formed is more stable.

[0030] 2. After the polymerization reaction is completed, in order to avoid the carboxyl side chain being consumed by methyl chloride, the present invention adds calcium salt, and under the alkaline conditions of the system, the side chain carboxyl is deprotonated in the form of carboxylic acid anions, which can enhance nucleophilicity due to its negative charge. Since the calcium ion has a double positive charge, it can form a stable coordination with the two oxygen atoms of the side chain carboxylic acid anions at the same time, forming a complex that is stable to alkali, and it is not easy to deprotect the carboxyl group during the end-capping process; at the same time, after the end-capping is completed and filtered, an organic acid is added to the system to convert the coordination complex group back into a carboxyl group, thereby restoring the hydrophilicity of the chain segment. Therefore, since the side chain carboxyl forms a stable coordination complex before the end-capping, the bisphenol acid type hydrophilic polysulfone of the present invention can be end-capped, greatly reducing the content of the phenol end group with poor thermal stability, so that it can maintain its original color during extrusion granulation. DETAILED DESCRIPTION

[0031] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0032] Example 1

[0033] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0034] S1: Add 63.45 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 381.55 g of diphenolic acid, 3150.88 g of potassium hydroxide and 38.68 g of potassium carbonate, replace the nitrogen three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 90°C and keep the temperature for 2 hours; after the reaction, add 63.45 kg of N-methylpyrrolidone and 7634.2 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 160°C for water extraction, and after anhydrous extraction, heat up to 190°C and keep the temperature for 1 hour to obtain a polysulfone resin polymerization liquid;

[0035] S2: Cool the polysulfone resin polymer solution to 60°C, add 162.69g of calcium chloride, react for 1h, and then perform end-capping treatment on the polysulfone resin polymer solution: introduce methyl chloride end-capping agent into the polysulfone resin polymer solution, cap at 170°C for 2h, and obtain end-capped polysulfone resin polymer solution;

[0036] S3 cools the blocked polysulfone resin polymer solution to 60°C, adds acetic acid after filtering, adjusts to pH=6, and stirs for 5 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0037] Example 2

[0038] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0039] S1: Add 36.78 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 1144.64 g of diphenolic acid, 3590.54 g of potassium hydroxide and 64.97 g of sodium carbonate. After nitrogen replacement three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 95°C and keep warm for 3 hours; after the reaction is completed, add 36.78 kg of N-methylpyrrolidone and 7481.13 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 170°C for water extraction, and after anhydrous extraction, heat up to 185°C and keep warm for 2 hours to obtain a polysulfone resin polymerization liquid;

[0040] S2: Cool the polysulfone resin polymer solution to 150°C, add 532.44 g of calcium chloride, react for 1 hour, and then perform end-capping treatment on the polysulfone resin polymer solution: introduce methyl chloride end-capping agent into the polysulfone resin polymer solution, cap at 160°C for 2.5 hours, and obtain end-capped polysulfone resin polymer solution;

[0041] S3 cools the blocked polysulfone resin polymer solution to 70°C, adds citric acid after filtering, adjusts to pH=5, and stirs for 4 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0042] Example 3

[0043] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0044] S1: Add 82.53 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 1907.74 g of diphenolic acid, 4030.19 g of potassium hydroxide and 1085.46 g of cesium carbonate, replace the nitrogen three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 100 ° C, and keep the temperature for 3 hours; after the reaction is completed, add 82.53 kg of N-methylpyrrolidone and 8514.33 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 180 ° C for water extraction, and after anhydrous extraction, heat up to 190 ° C, keep the temperature for 3 hours to obtain a polysulfone resin polymerization liquid;

[0045] S2: Cool the polysulfone resin polymer solution to 70°C, add 1109.24g of calcium chloride, react for 1h, and then perform end-capping treatment on the polysulfone resin polymer solution: introduce methyl chloride end-capping agent into the polysulfone resin polymer solution, cap at 165°C for 3h, and obtain end-capped polysulfone resin polymer solution;

[0046] S3 cools the blocked polysulfone resin polymer solution to 80°C, adds acetic acid after filtering, adjusts to pH=4, and stirs for 3 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0047] Example 4

[0048] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0049] S1: Add 61.34 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 2289.28 g of diphenolic acid, 4250.02 g of potassium hydroxide and 520.33 g of potassium bicarbonate, replace the nitrogen three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 90°C and keep the temperature for 4 hours; after the reaction, add 61.34 kg of N-methylpyrrolidone and 9153.39 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 170°C for water extraction, and after anhydrous extraction, heat up to 190°C and keep the temperature for 4 hours to obtain a polysulfone resin polymerization liquid;

[0050] S2: Cooling the polysulfone resin polymer solution to 80°C, adding 1774.79 g of calcium chloride, reacting for 1 hour, and then performing end-capping treatment on the polysulfone resin polymer solution: introducing methyl chloride end-capping agent into the polysulfone resin polymer solution, end-capping at 190°C for 1 hour, to obtain an end-capped polysulfone resin polymer solution;

[0051] S3 cools the blocked polysulfone resin polymer solution to 80°C, adds oxalic acid after filtering, adjusts to pH=6, and stirs for 5 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0052] Example 5

[0053] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0054] S1: Add 67.6 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 3052.38 g of diphenolic acid, 4689.68 g of potassium hydroxide and 626.93 g of sodium bicarbonate, replace the nitrogen three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 90°C and keep the temperature for 5 hours; after the reaction is completed, add 67.6 kg of N-methylpyrrolidone and 10178.93 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 180°C for water extraction, and after anhydrous extraction, heat up to 200°C and keep the temperature for 0.5 hours to obtain a polysulfone resin polymerization liquid;

[0055] S2: Cooling the polysulfone resin polymer solution to 100° C., adding 2366.38 g of calcium chloride, reacting for 2 h, and then performing end-capping treatment on the polysulfone resin polymer solution: introducing methyl chloride end-capping agent into the polysulfone resin polymer solution, end-capping at 160° C. for 4 h, to obtain an end-capped polysulfone resin polymer solution;

[0056] S3 cools the blocked polysulfone resin polymer solution to 60°C, adds acetic acid after filtering, adjusts to pH=5, and stirs for 4 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0057] Example 6

[0058] The preparation method of the hydrophilic modified polysulfone resin with carboxyl side groups of the present embodiment comprises the following steps:

[0059] S1: Add 83.22 kg of deionized water into a 100 L polymerization reactor, then add 6084.34 g of bisphenol A, 3815.47 g of diphenolic acid, 5129.33 g of potassium hydroxide and 1105.06 g of potassium carbonate, replace the nitrogen three times, introduce nitrogen to react at normal pressure, and carry out nitrogen protection throughout the polymerization reaction; heat up to 90°C and keep the temperature for 8 hours; after the reaction is completed, add 83.22 kg of N-methylpyrrolidone and 10906 g of 4,4'-dichlorodiphenyl sulfone, continue to heat up to 160°C for water extraction, and after anhydrous extraction, heat up to 200°C and keep the temperature for 4 hours to obtain a polysulfone resin polymerization liquid;

[0060] S2: Cool the polysulfone resin polymer solution to 120°C, add 2957.98g of calcium chloride, and react for 3h, then perform end-capping treatment on the polysulfone resin polymer solution: introduce methyl chloride end-capping agent into the polysulfone resin polymer solution, and cap at 170°C for 4h to obtain end-capped polysulfone resin polymer solution;

[0061] S3 cools the blocked polysulfone resin polymer solution to 65°C, adds acetic acid after filtering, adjusts to pH=6, and stirs for 3 hours to complete the recovery of the carboxyl side groups; pours the blocked polysulfone resin polymer solution into cold water to cool and precipitate, and after mechanically crushing into powder, boils it in high-temperature water for multiple times, filters, and dries to obtain a white powder of hydrophilic modified polysulfone resin with carboxyl side groups.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that in step S2, calcium chloride is not added, and the polysulfone resin polymerization liquid is directly capped.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that in step S1, deionized water is replaced by NMP, and potassium hydroxide is replaced by potassium carbonate.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that in step S1, potassium hydroxide is replaced with potassium carbonate, and it is found that the viscosity of the system does not increase during the polymerization process, and the polymerization fails. This is because in Comparative Example 3, the salt-forming agent is only potassium carbonate and not potassium hydroxide. Since potassium carbonate has a weak alkalinity, it is difficult to form a salt with diphenolic acid and bisphenol A in water, resulting in difficulty in the reaction.

[0068] Comparative Example 4

[0069] The difference from Example 1 is that in step S3, acetic acid is replaced by hydrochloric acid.

[0070] Comparative Example 5

[0071] The difference from Example 1 is that in step S1, potassium hydroxide is replaced by sodium hydroxide.

[0072] Comparative Example 6

[0073] The difference from Example 1 is that in step S2, the polysulfone resin polymerization liquid is not subjected to methyl chloride end-capping treatment.

[0074] Comparative Example 7

[0075] The difference from Example 1 is that in step S1, potassium carbonate is replaced by potassium hydroxide.

[0076] The polysulfone resin white powder prepared in Examples 1-6 and Comparative Examples 1-2 and Comparative Examples 4-7 was granulated to obtain polysulfone resin particles: the drying temperature was 145°C, the drying time was 3.5h, and the melt temperature was 350°C.

[0077] The following performance tests were performed on the polysulfone resin particles obtained in Examples 1-6 and Comparative Examples 1-2 and Comparative Examples 4-7. The test results are shown in Table 1.

[0078] (1) Proportion of bisphenol acid segments in polysulfone resin

[0079] Diphenolic acid segment ratio 1 H-NMR (CDCl3, 25°C) was used to calculate (chemical shift was based on the CDCl3 peak: 7.26 ppm). The peak in the range of 1.5-2.5 ppm was attributed to the chemical shift of the proton hydrogen on the long fatty chain of the diphenolic acid unit in the polymer.

[0080] (2) Molecular weight of polysulfone resin

[0081] Test instrument: Waters E2695 gel chromatography instrument, equipped with UV detector (wavelength 254nm).

[0082] Test conditions: flow rate 1 mL / min, column temperature 40°C.

[0083] Sample preparation: Dissolve the sample to be tested in THF to make a 1wt.% solution and filter it with a filter.

[0084] Integration method: Use polystyrene standards as standard curve to calculate relative molecular weight.

[0085] (3) Carboxyl content in polysulfone resin

[0086] The polysulfone resin particle sample to be tested is dissolved in N,N-dimethylacetamide (DMAC) to prepare a 1wt.% test solution, hydrochloric acid and p-hydroxybenzoic acid (PHBA) internal standard are added, and titrated with a 0.1M tetrabutylammonium hydroxide methanol solution. The end point is determined by the potential to obtain the total amount of terminal carboxyl groups M of the polysulfone solution; the same amount of hydrochloric acid and PHBA are weighed, dissolved in DMAC to prepare a blank solution, and the blank terminal carboxyl group amount m is tested by potentiometric titration. The difference between the two (Mm) can be used to obtain the carboxyl content of the polysulfone resin.

[0087] (4) Yellowness index of polysulfone resin

[0088] The yellowness index of the polysulfone resin was measured by a colorimeter. The preparation method of a 2 mm thick polysulfone resin sample was as follows: the polysulfone resin was injection molded at a melt temperature of 350° C. and a mold temperature of 180° C., and the sample was cut into 2 mm thick samples.

[0089] (5) Contact angle of polysulfone resin

[0090] The polysulfone resin particles were dissolved in NMP to prepare a casting solution with a solid content of 16%. After being scraped on a scraper, the solution was immersed in desalted water to form a polysulfone flat membrane. The water contact angle of the polysulfone flat membrane was used to characterize its hydrophilicity. The test was carried out on an optical contact angle meter.

[0091] Table 1 Performance test results of polysulfone resins of Examples 1-6 and Comparative Examples 1-2 and Comparative Examples 4-7

[0092]

[0093] It can be seen from the test results in Table 1 that by comparing the data of Example 1 with that of Comparative Example 1, it can be seen that if calcium chloride is not added to protect the carboxyl group before end-capping, the carboxyl content in the polysulfone resin product is significantly reduced from 106.9 mol / t to 0.03 mol / t, resulting in the water contact angle of the polysulfone resin film after film formation increasing from 60.8° to 69.7°, and the hydrophilicity deteriorates. This is because more than 97% of the carboxyl side chains are converted by methyl chloride.

[0094] In Comparative Example 2, the polymerization method is a traditional NMP solvent and potassium carbonate system. Since the decomposition products of NMP react with the diphenolic acid monomers to form small molecular polyamides during the salt formation process, a large amount of diphenolic acid monomers are not connected to the molecular chain, resulting in the actual diphenolic acid segment ratio being much lower than the feed ratio; due to the loss of diphenolic acid, the raw material ratio is unbalanced, resulting in a decrease in the weight average molecular weight of the final polysulfone resin product and a deterioration in color.

[0095] When adjusting the pH value in Comparative Example 4, hydrochloric acid was used as the acid, so that the yellowness index of the prepared polysulfone resin increased to 18. This is because hydrochloric acid is an inorganic strong acid. After hydrochloric acid comes into contact with NMP, NMP is decomposed into color-developing impurities, which are difficult to remove during the post-treatment process, resulting in an increase in the yellowness index of the polysulfone resin.

[0096] In Comparative Example 5, sodium hydroxide was used to replace potassium hydroxide. Since the activity of the sodium salt formed by sodium hydroxide and bisphenol is much lower than that of bisphenol potassium salt, the reaction time was greatly prolonged and the yellowness index of the prepared polysulfone resin increased.

[0097] In Comparative Example 6, the polysulfone resin polymerization liquid was not capped with methyl chloride, resulting in a significant increase in the yellowness index of the polysulfone resin product to 40 after granulation.

[0098] In Comparative Example 7, strong base potassium hydroxide was used as the salt-forming agent. After the salt formation was completed, the excess potassium hydroxide would cause severe decomposition of NMP, and the diphenolic acid was mostly consumed by the decomposition products of NMP, resulting in the amount of diphenolic acid segments connected to the polysulfone molecules in the final product being far lower than the feed amount, and the hydrophilic modification effect was poor.

Claims

1. A method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group, characterized in that: The following steps are involved: S1: put bisphenol A, diphenolic acid and salt-forming agent into a salt-forming solvent, pass nitrogen, heat to 90-100°C, keep warm for 2-8h, and perform salt-forming reaction; after the reaction, add N-methylpyrrolidone and 4,4'-dichlorodiphenyl sulfone, continue to heat to 160-180°C for dehydration, heat to 185-200°C after dehydration, and keep warm for nucleophilic polycondensation reaction; after the reaction for 0.5-4h, obtain a polysulfone resin polymerization liquid; wherein the total mole number of bisphenol A and diphenolic acid and the mole number of 4,4'-dichlorodiphenyl sulfone have a ratio of 1:(0.85-1); S2: cooling the polysulfone resin polymer solution to 60-150° C., adding calcium salt, reacting for 1-3 hours, and then capping the polysulfone resin polymer solution to obtain a capped polysulfone resin polymer solution; S3: cooling the blocked polysulfone resin polymer solution to 60-80° C., filtering, adding an organic acid, adjusting the pH to 4-6, stirring for 3-5 hours, and then post-treating to obtain a hydrophilic modified polysulfone resin with a carboxyl side group; In step S1, the salt-forming agent is a mixture of potassium hydroxide and alkali metal carbonate; the salt-forming solvent is deionized water; In step S2, the calcium salt is calcium chloride; In step S3, the organic acid is acetic acid, citric acid or oxalic acid.

2. The method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group as claimed in claim 1, characterized in that: The alkali metal carbonate is potassium bicarbonate, sodium bicarbonate, cesium carbonate, potassium carbonate or sodium carbonate.

3. The method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group as claimed in claim 1, characterized in that: In step S1, the total mass of bisphenol A, diphenolic acid and 4,4'-dichlorodiphenyl sulfone, the mass of the salt-forming solvent, and the mass ratio of N-methylpyrrolidone are 1:(2.5-5):(2.5-5); the molar ratio of bisphenol A to diphenolic acid is 1:(0.05-0.5); the molar number of bisphenol A, the molar number of diphenolic acid and the molar number of potassium hydroxide meet the following formula: N KOH =0.98×(2N BPA +3N DPA ), where N KOH is the number of moles of potassium hydroxide, N BPA 、N DPA They are the mole number of bisphenol A and the mole number of diphenolic acid respectively; the ratio of the total mole number of bisphenol A and diphenolic acid to the mole number of alkali metal carbonate is 1:(0.01-0.2).

4. The method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group as claimed in claim 1, characterized in that: The molar ratio of diphenolic acid to calcium salt is 1:(1.1-2).

5. The method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group as claimed in claim 1, characterized in that: In step S2, the end-capping treatment of the polysulfone resin polymerization liquid is as follows: at 160-190° C., methyl chloride is introduced into the polysulfone resin polymerization liquid for a reaction of 1-4 hours.

6. The method for preparing a hydrophilic modified polysulfone resin having a carboxyl side group as claimed in claim 1, characterized in that: In step S3, the post-treatment of the blocked polysulfone resin polymerization liquid is as follows: cooling, crushing, washing, filtering and drying the blocked polysulfone resin polymerization liquid.

7. A hydrophilic modified polysulfone resin having carboxyl side groups, characterized in that: The polysulfone resin is prepared by the method for preparing a hydrophilic modified polysulfone resin with carboxyl side groups as described in any one of claims 1 to 6.

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