Method for removing aluminum from syndiotactic polystyrene

Abstract

The invention belongs to the technical field of polymer purification, and particularly discloses a syndiotactic polystyrene dealumination method. The dealumination method comprises the following steps: washing syndiotactic polystyrene by using a washing solution containing polybasic organic acid, extracting aluminum from a syndiotactic polystyrene product to a liquid phase, and carrying out solid-liquid separation to obtain dealuminated syndiotactic polystyrene and filtrate; and then removing aluminum chelated by the polybasic organic acid in the filtrate through cation exchange resin, so that the polybasic organic acid after aluminum removal is used as a component of the washing liquid to be repeatedly used. According to the method, the washing liquid can be regenerated while aluminum is efficiently removed, so that the washing liquid can be recycled and reused, and the washing liquid is a non-strong-acid and non-strong-alkali organic solution, is non-corrosive to equipment and environment-friendly, and has a very good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer purification, and in particular relates to a method for dealumination of syndiotactic polystyrene. Background Art

[0002] Syndiotactic polystyrene (sPS) is a type of polystyrene that has the good chemical inertness, excellent electrical insulation and moisture resistance of general-purpose polystyrene. Unlike general-purpose polystyrene, the molecular chain configuration of syndiotactic polystyrene is syndiotactic, and the side groups (benzene rings) in the structural units are arranged alternately on both sides of the macromolecular chain. Since syndiotactic polystyrene has high stereoregularity and strong crystallization ability, syndiotactic polystyrene is a crystallizable polymer with a crystalline melting point of about 270°C. The highly crystalline aggregate structure gives syndiotactic polystyrene good heat resistance and corrosion resistance, making its performance comparable to thermoplastic engineering plastics such as nylon, polyester, and polyphenylene sulfide, making it a cost-effective engineering plastic.

[0003] At present, the largest application areas of sPS are automotive connectors, high-frequency communication electronics and other products. There are high requirements for the dielectric properties and electrical insulation of the materials. Due to the shielding interference effect of metal on the signal, such products require that the metal content in the material must be very low (less than 50ppm). However, the synthesis of syndiotactic polystyrene usually requires a large amount of alkyl aluminum as a co-catalyst to assist the main catalyst to produce high activity, resulting in more residual aluminum in the product. The higher aluminum content will affect the excellent electrical properties of syndiotactic polystyrene materials in the fields of high-frequency communication electronics and electrical. Among them, in the syndiotactic polystyrene product, the aluminum-containing additive finally exists in the product in the form of aluminum oxide, which is an insoluble substance like syndiotactic polystyrene. Therefore, it is difficult to simply separate aluminum from the syndiotactic polystyrene product by solvent washing and extraction. The traditional process is to use an organic solvent containing strong acid or strong base to wash, ionize aluminum through the action of strong acid and strong base, and then dissolve aluminum ions in sPS through the good wettability of organic solvents to sPS. Finally, filtration and solid-liquid separation are used to remove aluminum from sPS. However, the use of strong acids and alkalis can cause equipment corrosion, and organic solvents containing waste acids and alkalis are difficult to regenerate and dispose of in an environmentally friendly manner, greatly increasing production costs.

[0004] Therefore, it is currently necessary to solve the problems of using highly corrosive organic solutions in the purification process of syndiotactic polystyrene production, difficulty in treating and regenerating organic waste liquids, and high costs. Summary of the invention

[0005] In view of the problems in the prior art that a highly corrosive organic solution is required in the purification process of syndiotactic polystyrene production, and that the organic waste liquid is difficult to treat and regenerate, the present invention provides a method for dealumination of syndiotactic polystyrene, so as to achieve aluminum ionization, infiltration extraction, solution regeneration and multiple recycling using a method without corrosion of strong acid or strong alkali organic solution.

[0006] To achieve the above purpose, the following technical solutions are specifically included:

[0007] A method for dealumination of syndiotactic polystyrene comprises the following steps:

[0008] (1) dispersing the syndiotactic polystyrene to be dealuminated in a washing liquid to obtain a dispersion; the washing liquid comprises an aqueous solution of a polybasic organic acid;

[0009] (2) the dispersion is subjected to solid-liquid separation, and the solid is washed with water to obtain dealuminated syndiotactic polystyrene and a filtrate;

[0010] (3) The filtrate is dealuminated through a cation exchange resin to obtain a regenerated washing liquid; the cation exchange resin contains a chelating function, and the chelating function includes a group of a polyazaheterocyclic polycarboxylic acid.

[0011] The method of the present invention uses an aqueous washing liquid containing a polybasic organic acid to wash syndiotactic polystyrene. On the one hand, this type of aqueous washing liquid has good wettability for syndiotactic polystyrene; on the other hand, the polybasic organic acid converts alkyl aluminum into aluminum ions, and as a chelating agent for aluminum ions, the aluminum ions are combined through a chelating structure, thereby extracting aluminum from the syndiotactic polystyrene product into a liquid phase, and then obtaining the dealuminated syndiotactic polystyrene and a filtrate through solid-liquid separation; then the aluminum chelated by the polybasic organic acid in the filtrate is removed by a cation exchange resin, so that the dealuminated polybasic organic acid aqueous solution can be repeatedly used as a washing liquid. The method of the present invention can regenerate the washing liquid while efficiently dealuminizing, so that the washing liquid can be recycled and reused, and the washing liquid is an organic solution that is not a strong acid or a strong base, is basically non-corrosive to equipment, is environmentally friendly, and has a good industrial application prospect.

[0012] Preferably, in step (1), the polybasic organic acid in the polybasic organic acid aqueous solution comprises at least one of amine polybasic carboxylic acid, hydroxy polybasic carboxylic acid and polybasic carboxylic acid polymer.

[0013] Further preferably, in step (1), the polybasic organic acid in the polybasic organic acid aqueous solution includes at least one of nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, 3-carboxy-3-hydroxyglutaric acid, 2,3-dihydroxysuccinic acid, hydroxyethylethylenediaminetriacetic acid, dihydroxyethylglycine, polyacrylic acid, and polymethacrylic acid.

[0014] More preferably, the number average molecular weight of the polyacrylic acid is 10,000-1,000,000 g / mol.

[0015] More preferably, the number average molecular weight of the polymethacrylic acid is 10,000-1,000,000 g / mol.

[0016] The above-mentioned polybasic organic acid chelating agent is used to replace conventional inorganic strong acids and bases to convert aluminum oxide into aluminum ions, which is non-corrosive to equipment. The aqueous washing liquid containing the polybasic organic acid has good wettability to syndiotactic polystyrene, making it easy to extract aluminum ions into the liquid phase. Compared with the use of organic solvents, it is cheaper and more environmentally friendly.

[0017] Preferably, in step (1), the pH value of the washing solution is 3-7.

[0018] Preferably, in step (1), the concentration of the polybasic organic acid in the washing liquid is 0.05-1 mol / L, specifically 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 mol / L, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0019] When the washing liquid of the above concentration is used, the content of polybasic organic acid in the washing liquid is low and the acidity is weak, which can reduce the corrosiveness and improve the safety while ensuring the better dealumination effect.

[0020] Preferably, in step (1), the mass ratio of the syndiotactic polystyrene to be dealuminated and the washing liquid is 1:(0.5-12), specifically 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0021] Preferably, in step (1), the aluminum content in the syndiotactic polystyrene to be dealuminated is >10 ppm, more preferably, 20 ppm to 10000 ppm.

[0022] Preferably, in step (1), the average particle size of the syndiotactic polystyrene to be dealuminated is 50-1000 μm.

[0023] Preferably, in step (1), the dispersing method is stirring, and the stirring time is 0.2-2h.

[0024] Preferably, in step (2), the solid-liquid separation method includes at least one of centrifugal separation and filtration separation, and the centrifugal force in the centrifugal separation is 400-800xg.

[0025] Preferably, in step (2), during the solid washing process, the mass ratio of water to solid is 1:(1-15), and the number of washings is ≥1, more preferably 1-3. The washing process transfers the polybasic organic acid in the solid to the water, and whether the washing is complete is determined based on whether the polybasic organic acid remains in the solid after washing. The washed solid is washed with water again, and the residual polybasic organic acid is detected by an ultraviolet spectrophotometer. When the content is lower than the detection limit, the washed solid is considered to be completely washed, that is, no polybasic organic acid remains.

[0026] Preferably, in step (2), the dealuminated syndiotactic polystyrene is further dried, the drying temperature is ≥100°C, more preferably 110-120°C, and the drying time is >2h, more preferably 2-4h.

[0027] The dealuminated syndiotactic polystyrene obtained after drying is washed with water, and is tested by ultraviolet spectrophotometer to determine whether polybasic organic acid remains. When the content is lower than the detection limit, it is considered that the dealuminated syndiotactic polystyrene after drying has no polybasic organic acid residue.

[0028] Preferably, in step (2), the aluminum content in the dealuminated syndiotactic polystyrene is ≤20 ppm.

[0029] The aluminum content in the syndiotactic polystyrene after dealumination by the method of the present invention is ≤20ppm, the residual aluminum content is low, and no polybasic organic acid remains, which has no effect on the dielectric properties and electrical insulation of the syndiotactic polystyrene.

[0030] Preferably, in step (3), the chelating functional group includes at least one of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid group and 1,4,7-triazacyclononane-1,4,7-triacetic acid group.

[0031] The chelating ability of the above-mentioned chelating functional group to aluminum is stronger than that of the polybasic organic acid to aluminum. The cation exchange resin containing the above-mentioned functional group has a stronger chelating ability than the conventional ion exchange resin, and can desorb the aluminum chelated by the polybasic organic acid in the washing liquid, thereby realizing the regeneration of the washing liquid and allowing the washing liquid to be repeatedly used. The process is simple, efficient and low in energy consumption, thereby greatly improving the purification efficiency and reducing the production cost.

[0032] Preferably, in step (3), the matrix of the cation exchange resin comprises polystyrene-divinylbenzene copolymer, the number average molecular weight of the polystyrene-divinylbenzene copolymer is 10000-30000 g / mol, and the crosslinking degree of the polystyrene-divinylbenzene copolymer is 4%-14%.

[0033] Further preferably, the cation exchange resin is a macroporous cation exchange resin, which may specifically include the following types of cation exchange resins: D001, D401, D402, D403, D61, D62, D72, and D751.

[0034] Preferably, in step (3), the mass ratio of the filtrate to the cation exchange resin is 1:(0.1-1), specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, etc., as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0035] Preferably, in step (3), when the filtrate is dealuminated by the cation exchange resin, the residence time is 0.5-2h.

[0036] The present invention also provides a syndiotactic polystyrene, which is obtained by dealumination through the syndiotactic polystyrene dealumination method, and the aluminum content in the syndiotactic polystyrene is ≤20ppm.

[0037] Compared with the prior art, the present invention has the following beneficial effects: the dealumination method of the present invention first uses an aqueous washing liquid containing a polybasic organic acid to wash the syndiotactic polystyrene, extracts aluminum from the syndiotactic polystyrene product into a liquid phase, and then obtains the dealuminated syndiotactic polystyrene and a filtrate through solid-liquid separation; then the aluminum chelated by the polybasic organic acid in the filtrate is removed by a cation exchange resin, so that the dealuminated polybasic organic acid aqueous solution can be repeatedly used as a washing liquid. The method of the present invention can regenerate the washing liquid while efficiently dealuminating, so that the washing liquid can be recycled and reused, and the washing liquid is a non-strong acid and strong alkali solution, non-corrosive to equipment, environmentally friendly, and has a good industrial application prospect. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below through specific comparative examples and embodiments.

[0039] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0040] Ethylenediaminetetraacetic acid (denoted as A1#), hydroxyethylethylenediaminetriacetic acid (denoted as A2#), polyacrylic acid (denoted as A3#), styrene-divinylbenzene cation exchange resin introduced with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid group (denoted as B1#, D401), styrene-divinylbenzene ion exchange resin introduced with 1,4,7-triazacyclononane-1,4,7-triacetate group (denoted as B2#, D402), styrene-divinylbenzene ion exchange resin introduced with porphyrin (denoted as B3#, D403), styrene-divinylbenzene ion exchange resin without chelating agent (denoted as B4#, D001), oxalic acid (denoted as A4#), 36wt.%-38wt.% hydrochloric acid, sodium hydroxide and ethanol are all commercially available, among which B1#, B2# and B3# are Amberlite type ion exchange resins provided by Alfa.

[0041] The syndiotactic polystyrene powder used in the embodiments and comparative examples of the present invention is produced by solution polymerization (it should be noted that the present invention does not limit the production method of the polystyrene powder, and the polystyrene powder produced by bulk polymerization is also applicable to the present invention), and after the volatile matter is removed, the powder is sieved through a sieve with a pore size of 1 mm to obtain a powder with a particle size range of 50-1000 μm.

[0042] Example 1

[0043] A method for dealumination of syndiotactic polystyrene comprises the following steps:

[0044] (1) First, add 1 mol of ethylenediaminetetraacetic acid (denoted as A1#) and 10 L of water into a 30 L stirring tank and stir at room temperature for 0.5 h to prepare a 0.1 mol / L washing solution for use;

[0045] (2) Add 1 kg of syndiotactic polystyrene powder (aluminum content of 1000 ppm) and 10 L of washing liquid into a 30 L washing tank and stir at room temperature for 0.5 h to form a uniform dispersion;

[0046] (3) The dispersion is then subjected to a first centrifugal solid-liquid separation in a centrifugal filtration tank at a centrifugal force of 500 x g to obtain a primary filtrate and a primary filter cake; 10 L of water is then added to rinse the primary filter cake, and a second centrifugal filtration solid-liquid separation is performed, and a secondary filter cake and a secondary filtrate are collected. After the secondary filter cake is dried, a dealuminated syndiotactic polystyrene product is obtained, and no polybasic organic acid remains in the dealuminated syndiotactic polystyrene product;

[0047] (4) The primary filtrate and the secondary filtrate are respectively passed through a packing column filled with a styrene-vinylbenzene copolymer cation exchange resin for regeneration and dealumination. The chelating group introduced into the cation exchange resin is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid group (denoted as B1#), and the desorption residence time is 0.5 h. The regenerated primary filtrate and the secondary filtrate can continue to be used as washing liquid and flushing liquid.

[0048] Embodiments 2 to 5

[0049] The difference between Examples 2 to 5 and Example 1 is the difference in the raw materials and the amounts used, as shown in Table 1 in detail.

[0050] Example 6

[0051] The difference between Example 6 and Example 1 is that in step (2), the aluminum content of the syndiotactic polystyrene powder is 2000 ppm.

[0052] Comparative Example 1

[0053] The difference between this comparative example and Example 1 is that A1# is replaced with an equimolar amount of hydrochloric acid (1 mol / L hydrochloric acid, with a mass concentration of about 3%), and water washing is performed multiple times until the pH value reaches neutral and no polybasic organic acid remains in the solid after water washing. The specific steps are as follows:

[0054] (1) First, add hydrochloric acid solution (the molar amount of hydrochloric acid is the same as the molar amount of 1 mol of ethylenediaminetetraacetic acid) and 10 L of water into a 30 L stirring tank, and stir at room temperature for 0.5 h to prepare a washing solution for use;

[0055] (2) Add 5 kg of syndiotactic polystyrene powder and 10 L of washing liquid into a 30 L washing tank and stir at room temperature for 0.5 h to form a uniform dispersion;

[0056] (3) The dispersion is then centrifuged in a centrifugal filter tank for solid-liquid separation at a centrifugal force of 500 x g to obtain a filtrate and a filter cake; water is then added to rinse the filter cake multiple times, and then centrifuged for solid-liquid separation; the obtained filter cake is the dealuminated syndiotactic polystyrene product.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is that in this comparative example, A1# is replaced by an equal molar amount of hydrochloric acid, and water is replaced by the same volume of ethanol.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 1 is that in this comparative example, A1# is replaced with an equal molar amount of sodium hydroxide, and the number of rinses is based on the pH reaching neutrality.

[0061] Comparative Example 4

[0062] The difference between this comparative example and Example 1 is that in this comparative example, A1# is replaced by an equal molar amount of sodium hydroxide, and water is replaced by the same volume of ethanol.

[0063] Comparative Example 5

[0064] The difference between this comparative example and Example 1 is that in this comparative example, A1# is replaced with an equal molar amount of oxalic acid, recorded as A4#.

[0065] Comparative Example 6

[0066] The difference between this comparative example and Example 1 is that the cation exchange resin in this comparative example does not contain the chelating group 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid group, that is, B4# (D001).

[0067] Comparative Example 7

[0068] The difference between this comparative example and Example 1 is that the chelating group introduced into the cation exchange resin of this comparative example is porphyrin, which is denoted as B3# (D003).

[0069] Table 1

[0070]

[0071] The aluminum content of the syndiotactic polystyrene after dealumination by the dealumination method of each embodiment and comparative example was tested, and the total processing volume and waste liquid volume were calculated at the same time. The testing method is as follows:

[0072] 1. Aluminum content: The syndiotactic polystyrene product with a mass of m is decomposed by microwave digestion in an acidic aqueous solution with a volume of v (an acidic aqueous solution prepared by mixing 3 volumes of concentrated hydrochloric acid with a mass fraction of 36%-38% and 1 volume of concentrated nitric acid with a mass fraction of 65%-68%), and then the mass concentration c of the aluminum element in the acidic aqueous solution is characterized by ICP-OES. In this way, the aluminum content in the product (ppm) = cv / m can be calculated.

[0073] 2. Dealumination efficiency: Dealumination efficiency = aluminum content of the syndiotactic polystyrene after dealumination / aluminum content in the syndiotactic polystyrene powder to be treated * 100%.

[0074] 3. Regeneration capacity of cation exchange resin: The regeneration capacity of the washing liquid of the present invention is evaluated by the ability of the cation exchange resin to repeatedly treat the filtrate. The regeneration capacity (L / Kg) = V (volume of the filtrate) / M (mass of the cation exchange resin), wherein the filtrate includes the primary filtrate and the secondary filtrate, and when the cation exchange resin treats the filtrate, the ability to remove the aluminum element in the filtrate remains substantially unchanged, which is considered normal dealumination, otherwise it is considered to be unable to dealumination normally. For example, when the dealumination rate of the cation exchange resin in removing the aluminum element in the filtrate in the early stage is 98%, and the dealumination amount can still be maintained at 98-±2%, it is considered to be normal dealumination, and the volume V of the treated filtrate under normal dealumination and the mass M of the resin used are recorded; when the dealumination rate is ≤96%, it is considered to be unable to dealumination normally, and it is not included in the above regeneration capacity.

[0075] 4. Organic solvent waste liquid / wastewater volume: The amount of washing liquid that cannot be reused after dealing with 1kg of sPS dealumination, including the waste liquid containing hydrochloric acid or sodium hydroxide aqueous solution, and the waste liquid with high aluminum content generated when using ion exchange resin without chelating agent, which cannot be regenerated and recycled. These disposable washing liquids are all wastewater.

[0076] 5. Equipment corrosion: The presence of corrosion is determined by observing the following phenomena inside the equipment after processing 5 batches: (1) The presence of obvious rust, obvious roughening of the inner surface, and iron filings in the solution are considered severe corrosion; (2) The presence of slightly mild rust, roughening of the inner surface, and no iron filings in the solution are considered moderate corrosion; (3) No rust, no change in the inner surface, and no iron filings in the solution are considered no corrosion.

[0077] The test results are shown in Table 2.

[0078] Table 2

[0079]

[0080]

[0081] The aluminum content of Examples 1 to 6 is all below 20 ppm, the dealumination efficiency is >98%, and the total processing capacity is more than 100 times, there is no corrosion to the equipment, and no organic solution waste is generated, indicating that the process method of the present invention has a good balance between non-corrosion, infiltration extraction, and solution regeneration and multiple use in the dealumination process of producing syndiotactic polystyrene.

[0082] Comparative Examples 1 and 3 respectively used aqueous solutions of hydrochloric acid and sodium hydroxide. Since the aqueous solutions of inorganic acids and bases have poor wettability on sPS, the dealumination effect is very poor, and regeneration is also impossible, resulting in a large amount of wastewater. Comparative Examples 2 and 4 respectively used ethanol solutions of hydrochloric acid and sodium hydroxide. Although a good dealumination effect can be obtained, the organic solvents containing acids and bases will cause great corrosion to the equipment, and organic solvent waste liquid will be formed after solid-liquid separation, which is difficult to regenerate multiple times through ion exchange resins. In addition, the regeneration processing capacity of the cation exchange resin in Comparative Examples 2 and 4 is very small, resulting in a very large consumption of the cation exchange resin. Comparative Example 5 uses oxalic acid as an organic polyacid, and its dealumination ability is very weak, and the dealumination efficiency is only 3%, indicating the high efficiency of dealumination of the organic polyacid selected by the present invention. Comparative Example 6 does not have a chelating group on the ion exchange resin, so it cannot remove aluminum from the washing liquid, resulting in the washing liquid being unable to be regenerated, and a large amount of organic solvent waste liquid is generated; Comparative Example 7 uses porphyrin as a chelating group, but its chelating ability for aluminum is very limited, the regeneration processing capacity of the cation exchange resin is also low, and the consumption of the cation exchange resin is also very large. Comparative analysis of Example 1 and Comparative Examples 6-7 shows that the introduction of a specific type of chelating agent into the cation exchange resin in the present invention can significantly improve the regeneration capacity of the treated filtrate and reduce the consumption of the cation exchange resin. Therefore, the dealumination method of the present invention can produce a low-aluminum content syndiotactic polystyrene product more efficiently, more environmentally friendly, and at a lower cost.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for dealumination of syndiotactic polystyrene, characterized in that: The steps include: (1) dispersing the syndiotactic polystyrene to be dealuminated in a washing liquid to obtain a dispersion; the washing liquid comprises an aqueous solution of a polybasic organic acid; (2) the dispersion is subjected to solid-liquid separation, and the solid is washed with water to obtain dealuminated syndiotactic polystyrene and a filtrate; (3) The filtrate is dealuminated by a cation exchange resin to obtain a regenerated washing liquid; the cation exchange resin contains a chelating functional group, and the chelating functional group includes a group of a polyazaheterocyclic polycarboxylic acid.

2. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (1), the polybasic organic acid in the polybasic organic acid aqueous solution includes at least one of amine polybasic carboxylic acid, hydroxy polybasic carboxylic acid, and polybasic carboxylic acid polymer.

3. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (1), the concentration of the polybasic organic acid in the washing solution is 0.05-1 mol / L.

4. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (1), the mass ratio of the syndiotactic polystyrene to be dealuminated to the washing liquid is 1:(0.5-12).

5. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (3), the matrix of the cation exchange resin includes polystyrene-divinylbenzene copolymer, and the cation exchange resin contains chelating functional groups, and the chelating functional groups include at least one of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracarboxylic acid group and 1,4,7-triazacyclononane-1,4,7-triacetic acid group.

6. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (3), the mass ratio of the filtrate to the cation exchange resin is 1:(0.1-1).

7. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (1), the dispersion method is stirring, and the stirring time is 0.2-2h; in step (2), the solid-liquid separation method includes at least one of centrifugal separation and filtration separation.

8. The method for dealumination of syndiotactic polystyrene according to claim 1, characterized in that: In step (3), when the filtrate is dealuminated by the cation exchange resin, the residence time is 0.5-2h.

9. A syndiotactic polystyrene, characterized in that: The syndiotactic polystyrene is obtained by dealumination by the method for dealumination of syndiotactic polystyrene according to any one of claims 1 to 8, wherein the aluminum content in the syndiotactic polystyrene is ≤20ppm.

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