Antistatic polystyrene and a method for preparing the same

Abstract

The application provides antistatic polystyrene and a preparation method thereof, the antistatic polystyrene comprising 100 parts of polystyrene, 5-15 parts of organic anion quaternary ammonium salt modified polystyrene by mass; wherein the organic anion quaternary ammonium salt modified polystyrene is obtained by anion exchange of chloromethyl styrene-styrene copolymer after quaternary ammonization and organic anion metal salt. By introducing the organic anion quaternary ammonium salt modified polystyrene into the polystyrene matrix, the antistatic performance of the material can be significantly improved, and the performance remains stable during long-term use, thereby reducing the problems of dust adsorption, discharge interference and appearance degradation caused by static accumulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to an antistatic polystyrene and a preparation method thereof. BACKGROUND

[0002] Polystyrene (PS) is widely used in packaging materials, electronic and electrical housings, optical elements and daily products due to its good transparency, high rigidity and excellent forming and processing performance. However, polystyrene is a typical electrically insulating material, and its surface resistivity is usually above 10 14 Ω, which easily accumulates static electricity during use. These static charges not only cause dust adsorption, affecting the appearance and cleanliness of the product, but also may cause electronic component malfunction or even electrostatic discharge damage, thereby limiting the application of polystyrene in electronics, optics and clean environments.

[0003] To improve the antistatic performance of polystyrene, the related art mainly adds migration type antistatic agents, dopes conductive fillers and chemically modifies, etc. For example, a surfactant, a quaternary ammonium salt small molecule or a polyether compound is added to polystyrene, so that it migrates to the surface of the material to form a conductive layer during processing or use, thereby reducing the surface resistance. This method can obtain certain antistatic effect at the beginning, but the additives are easily imbalanced in surface migration, washed or removed by abrasion, resulting in rapid attenuation of antistatic performance and short service life. By adding conductive fillers such as carbon black, carbon nanotubes and metal particles, a conductive network is formed in the polystyrene matrix. Although this method can significantly reduce the resistance, it often requires a high filling amount, which easily leads to a decrease in transparency, a darkening of color, and an adverse effect on mechanical properties and processing fluidity, thereby limiting the application in transparent products and high appearance requirement scenarios. In addition, there is also a method of introducing a charged group into the polystyrene chain to obtain more stable antistatic performance, but the existing system is prone to ion re-association or migration, so that the antistatic effect still attenuates in long-term use, and it is difficult to maintain stability.

[0004] Therefore, how to realize long-term stable antistatic effect while ensuring the appearance quality of polystyrene material is still a technical problem to be solved in the field. SUMMARY

[0005] The present application provides an antistatic polystyrene and a preparation method thereof. The antistatic polystyrene is modified by introducing a specific structure of organic anion quaternary ammonium salt into the polystyrene matrix, so as to have good and stable antistatic effect while maintaining the appearance quality of the material.

[0006] In a first aspect, the application provides an antistatic polystyrene, comprising 100 parts by mass of polystyrene and 5-15 parts by mass of organic anion quaternary ammonium salt modified polystyrene; wherein the organic anion quaternary ammonium salt modified polystyrene is obtained by anion exchange of a chloromethylstyrene-styrene copolymer after quaternization with an organic anion metal salt.

[0007] According to the application, by introducing the organic anion quaternary ammonium salt modified polystyrene into the polystyrene matrix, the antistatic performance of the material can be significantly improved, and the performance remains stable during long-term use, thereby reducing the problems of dust adsorption, discharge interference and appearance degradation caused by static accumulation.

[0008] Specifically, polystyrene as the main resin has good transparency, rigidity and processing formability, and can provide a stable physical skeleton and appearance performance; on this basis, chloromethylstyrene units are introduced into the copolymerization with styrene to form a chloromethylstyrene-styrene copolymer, which provides an active benzyl chloride group for subsequent quaternization, ensuring that the cationic group can be fixed on the polymer main chain in a chemical bond. Through quaternization reaction, the chloromethyl structure is converted into a quaternary ammonium salt structure, which gives the polymer a fixed positive charge site. Compared with traditional physical blending type small molecule antistatic agents, the quaternary ammonium salt structure is not migratory or lost, which fundamentally solves the problem of easy scrubbing and dissolution of surface antistatic agents, resulting in decay of effect;

[0009] After the exchange reaction with the organic anion metal salt, the small anion in the quaternary ammonium salt structure is replaced by the organic anion. The introduced organic anion usually has the characteristics of large volume, high degree of charge delocalization, and uniform polarity distribution, which makes its combination with the quaternary ammonium cation in the polymer matrix more loose. This loose ion pair can effectively inhibit strong ion association and prevent the charge from being localized and fixed, and can also reduce the tendency of anion migration and aggregation in the material, so that the material can form a continuous and stable charge dissipation path; as a result, the surface resistance of the material is significantly reduced, and the stable antistatic effect can still be maintained under the conditions of wet heat, cleaning or long-term aging.

[0010] That is, in the antistatic polystyrene provided in the present application, the polystyrene provides a stable skeleton and application performance; the chloromethyl styrene-styrene copolymer structure provides chemically bonded active sites; the quaternization introduces fixed positive charge centers, establishing a stable cationic framework inside the material; the introduction of organic anions enables the persistent existence of charge dissipation paths through delocalization and volume effects; the synergistic design of this "skeleton-cation-large anion" tertiary structure enables the material to have good and stable antistatic effects without the need to add conductive fillers with poor compatibility. Therefore, the antistatic polystyrene provided in the present application realizes persistent and stable antistatic effects while maintaining appearance and mechanical properties.

[0011] In some embodiments, the organic anion quaternary ammonium salt modified polystyrene is prepared by the following steps:

[0012] S1: obtaining a chloromethyl styrene-styrene copolymer by free radical polymerization reaction of chloromethyl styrene and styrene;

[0013] S2: reacting the chloromethyl styrene-styrene copolymer with a tertiary amine compound to cause quaternization of the chloromethyl groups on the chloromethyl styrene-styrene copolymer, obtaining a quaternized chloromethyl styrene-styrene copolymer;

[0014] S3: performing ion exchange reaction of the quaternized chloromethyl styrene-styrene copolymer with an organic anion metal salt to exchange part of the chloride ions in the quaternized chloromethyl styrene-styrene copolymer into organic anions, obtaining an organic anion quaternary ammonium salt modified polystyrene.

[0015] In some of the above embodiments, the step S1 introduces a certain proportion of chloromethyl styrene monomers into styrene, so that the obtained copolymer not only retains the main chain segment of polystyrene, but also has reactive sites distributed in the molecular skeleton, providing uniform and stable reaction sites for subsequent quaternization reaction, thereby ensuring the uniformity of the distribution of quaternization groups in the polymer chain;

[0016] The step S2 converts the chloromethyl structure into a quaternary ammonium salt structure by reaction with a tertiary amine compound. Since the quaternary ammonium salt structure is fixed on the polymer main chain by chemical bonds, it will not migrate or be lost during use like physical blending type antistatic agents, and the polymer surface can maintain charge dissipation ability for a long time, improving the durability of antistatic performance;

[0017] The step S3 introduces organic anions with large volume and delocalized charge distribution by ion exchange with organic anion metal salt. The combination of such anions with quaternary ammonium cations is loose, which can effectively inhibit the strong association of ion pairs and make the charged groups maintain high charge conduction capacity in the polymer matrix. Compared with the traditional small anion system, the introduced large organic anions are not easy to migrate and aggregate in the material, so the stability of the antistatic performance can be further improved, and the problem of resistance rebound after heating, dampening or cleaning of the material can be avoided.

[0018] Therefore, by the above steps S1-S3, the application not only can uniformly introduce cationic functional groups in the molecular skeleton, but also can be stabilized by selecting appropriate organic anions to form an antistatic system of "immobilized quaternary ammonium cation-large volume organic anion" combination, so that the material has more stable and durable antistatic effect.

[0019] In some embodiments, the step S1 comprises:

[0020] 100 parts of styrene, 5-10 parts of chloromethylstyrene, 0.3-1 parts of initiator and 0.1-0.2 parts of chain transfer agent are dispersed in 100-200 parts of toluene, and reacted at 65-75°C under nitrogen atmosphere for 6-10h to obtain a chloromethylstyrene-styrene copolymer.

[0021] In some of the above embodiments, based on 100 parts of styrene, the amount of chloromethylstyrene monomer is controlled to be 5-10 parts, which can introduce a sufficient number of reactive sites in the polymer chain, so that the subsequent quaternization reaction has good uniformity, and at the same time, the increase of polymer brittleness or the decrease of compatibility caused by too high proportion of chloromethyl monomer is avoided; the amount of initiator is in the range of 0.3-1 parts, which can more effectively control the polymerization rate and molecular weight distribution; the addition amount of chain transfer agent is 0.1-0.2 parts, which can further optimize the molecular weight distribution, so that the obtained copolymer is more suitable for subsequent dissolution and modification; at the same time, 100-200 parts of toluene is selected as the solvent, and the reaction is carried out at 65-75°C under nitrogen protection for 6-10h, which is beneficial to ensure that the free radical polymerization proceeds smoothly, reduces side reactions and premature crosslinking, and obtains a chloromethylstyrene-styrene copolymer with uniform distribution and stability, which is more suitable for subsequent quaternization reaction, thereby more conducive to improving the antistatic performance of the material. As an example, p-chloromethylstyrene is used as chloromethylstyrene in an embodiment of the application.

[0022] In some embodiments, the step S2 comprises:

[0023] Disperse 100 parts of chloromethylstyrene-styrene copolymer, 3-10 parts of tertiary amine compound and 0.1-0.5 parts of promoter in 400-1000 parts of N,N-dimethylformamide, and react at 55-65°C for 10-16h under nitrogen atmosphere to obtain the quaternized chloromethylstyrene-styrene copolymer.

[0024] In some of the above embodiments, the chloromethylstyrene-styrene copolymer is used as a reaction substrate, and has uniform benzyl chloromethyl groups distributed in the molecular skeleton, which can undergo nucleophilic substitution reaction with the tertiary amine compound under mild conditions to introduce quaternary ammonium cation groups efficiently; based on 100 parts of chloromethylstyrene-styrene copolymer, the amount of tertiary amine compound is controlled in the range of 3-10 parts, which can ensure efficient quaternization reaction and reduce side reactions or residual problems caused by excessive amine; the amount of promoter is 0.1-0.5 parts, which can significantly accelerate the reaction rate, improve the quaternization efficiency, and make the quaternary ammonium salt structure on the polymer chain more uniform; N,N-dimethylformamide as a high-polarity solvent can fully dissolve the substrate and amine reagent to ensure the reaction to proceed homogeneously; the reaction temperature is controlled at 55-65°C, and the time is 10-16h, which can not only ensure the smooth substitution reaction of chloromethyl group, but also avoid the degradation or crosslinking of polymer chain at high temperature. Through reasonable control of the above conditions, a modified polystyrene structure containing uniform quaternary ammonium cation groups can be obtained, thereby providing a stable precursor for subsequent anion exchange and ensuring the durability and stability of the final material's antistatic performance.

[0025] In some embodiments, the tertiary amine compound includes triethylamine and N-methyl piperidine, and the mass ratio of the triethylamine and N-methyl piperidine is (3-5):1.

[0026] In some of the above embodiments, the inventors found that when triethylamine and N-methyl piperidine are used in combination, and the mass ratio of the two is controlled in the range of (3-5):1, the antistatic performance of the obtained quaternized polystyrene is more stable; the reason may be that the triethylamine molecule has small volume and strong nucleophilicity, which can quickly undergo substitution reaction with the benzyl chloromethyl group, thereby ensuring the conversion rate and reaction efficiency of quaternization; while the N-methyl piperidine molecule has larger volume, and the quaternary ammonium cation formed has stronger steric hindrance effect, which can weaken the strong combination of cation and anion, and avoid excessive association of ion pairs; when the two are used in combination, on the one hand, triethylamine ensures efficient reaction and high degree of substitution, and on the other hand, the appropriate addition of N-methyl piperidine can introduce volume effect, making the quaternary ammonium salt structure more uniform and the ion pairs looser, and finally forming a more stable charge dissipation path, so that the organic anion quaternary ammonium salt modified polystyrene can make the material have better antistatic effect.

[0027] In some embodiments, the step S3 comprises:

[0028] Disperse 100 parts of quaternary ammonium chloromethyl styrene-styrene copolymer and 5-10 parts of organic anion metal salt in 300-600 parts of acetonitrile / N,N-dimethylformamide mixed solvent, and react at 20-40°C for 8-16h to obtain organic anion quaternary ammonium salt modified polystyrene.

[0029] In some of the above embodiments, based on 100 parts of quaternary ammonium chloromethyl styrene-styrene copolymer, the amount of organic anion metal salt is controlled in the range of 5-10 parts, which can effectively introduce the target organic anion while reducing the ion residues in the system caused by excessive salt; the mixed system of acetonitrile and N,N-dimethylformamide is selected as the solvent, which can not only swell or dissolve the modified polymer and the salt, but also facilitate precipitation and purification after the reaction is completed, and obtain organic anion modified products with more uniform structure; reacting at 20-40°C for 8-16h is conducive to the ion exchange process and improves the conversion rate of ion exchange. Through reasonable control of the above conditions, organic anion quaternary ammonium salt modified polystyrene with more uniform anion distribution and higher exchange efficiency can be obtained, so that the antistatic polystyrene has better antistatic effect.

[0030] In some embodiments, the organic anion metal salt comprises an organic anion comprising at least one of bis(trifluoromethane)sulfonimide anion (TFSI - ), trifluoromethanesulfonate anion (OTf - ).

[0031] In some of the above embodiments, the inventors found that, compared with common organic anions such as hexafluorophosphate or tetrafluoroborate, TFSI - and OTf - exhibit more excellent comprehensive advantages in the antistatic polystyrene system; such anions have the characteristics of large volume, high degree of charge delocalization and strong chemical stability, and can form a more loose and uniform ion pair structure with quaternary ammonium cations, so that the material exhibits more durable and stable antistatic effect during use; at the same time, the thermal stability and chemical resistance of TFSI - and OTf - are better than those of other organic anions, and they are not easy to decompose or undergo side reactions under the processing conditions of melt extrusion, avoiding the degradation, discoloration or fluctuation of antistatic performance of the polymer caused by the instability of the anion during processing; thus, the preferred organic anion system of the present application not only improves the stability of the antistatic performance of the final material, but also significantly enhances the adaptability and controllability during processing, and is more suitable for actual industrial application.

[0032] In some embodiments, the organic anion comprises bis(trifluoromethane)sulfonimide anion and triflate anion, and the molar ratio of the bis(trifluoromethane)sulfonimide anion and triflate anion is (2-3):1.

[0033] In some of the above embodiments, the inventors found that when TFSI - and OTf - are compounded in a molar ratio of (2-3):1, the antistatic polystyrene obtained has better antistatic effect; the reason may be that TFSI - has a large volume and a high degree of charge delocalization, which is conducive to the construction of a stable ion dispersion network, but when TFSI - is used alone, the ionic interaction may be too weak, and an excessively loose charge distribution may be formed, resulting in insufficient continuity of the charge dissipation path; OTf - has a relatively small structure and is more likely to be closely coordinated with the quaternary ammonium cation, thereby improving the stability of the ion pair and being more conducive to the formation of a continuous and stable charge dissipation link, but when OTf - is used alone, although the initial antistatic effect is good, an unstable distribution may be formed under humid and hot conditions, resulting in insufficient retention of antistatic performance; thus, when the two are compounded in the above ratio, the volume effect of TFSI - keeps some ion pairs in a loose state, ensuring the freedom of charge migration, and the moderate coordination effect of OTf - allows the ion pairs to form a continuous and stable charge dissipation link, thereby realizing the synergistic enhancement of the antistatic performance and enabling the antistatic polystyrene to have better antistatic effect.

[0034] In some embodiments, the polystyrene has a weight average molecular weight of 100000-1000000. Based on the above embodiments, this molecular weight range can ensure that the material has good mechanical properties while having suitable processing fluidity.

[0035] In some embodiments, the initiator comprises azobisisobutyronitrile. Based on the above embodiments, azobisisobutyronitrile can generate stable free radicals under suitable conditions and can efficiently initiate the copolymerization reaction of styrene and chloromethylstyrene.

[0036] In some embodiments, the chain transfer agent comprises dodecyl mercaptan. Based on the above embodiments, dodecyl mercaptan can effectively control the molecular weight distribution of the polymer, reduce the generation of long-chain polymers, and reduce the problems of excessively high melt strength and poor dispersibility in the processing process.

[0037] In some embodiments, the promoter includes KI. Based on the above embodiments, KI can improve the reactivity of chloromethyl in the nucleophilic substitution reaction, promote the departure of chloride ions, thereby accelerating the quaternary ammonium process and improving the reaction efficiency.

[0038] In some embodiments, the raw material further includes: 0.05-0.5 parts of an antioxidant, the antioxidant including at least one of antioxidant 1076 and antioxidant 1010. Based on the above embodiments, the introduction of the antioxidant can effectively inhibit the chain scission or discoloration problem of the polymer caused by oxidation during high-temperature melt processing and long-term use, thereby improving the appearance stability and the persistence of the antistatic performance of the material during long-term service.

[0039] In a second aspect, the present application provides a method for preparing an antistatic polystyrene, comprising:

[0040] Providing a raw material for the antistatic polystyrene according to any one of the embodiments of the first aspect;

[0041] Melt blending the raw material to obtain the antistatic polystyrene.

[0042] According to the present application, by using melt blending method for preparation, the organic anion quaternary ammonium salt modified polystyrene can be uniformly dispersed in the polystyrene without affecting the mechanical properties and transparency of the polystyrene matrix, thereby ensuring the stable distribution of the antistatic group in the material and avoiding the performance decay problem caused by poor compatibility and easy migration of the traditional small molecule antistatic agent. The method is simple, suitable for conventional extrusion, injection molding and other industrial processing equipment, and has good operability and promotional value.

[0043] Compared with the prior art, the present application has at least the following beneficial effects: by introducing the organic anion quaternary ammonium salt modified polystyrene into the polystyrene matrix, the antistatic performance can be kept stable for a long time, and will not rapidly decay due to the migration, loss or environmental factors of the small molecule antistatic agent; at the same time, the preferred tertiary amine compound is used for quaternary ammonium reaction, which helps to improve the modification effect and enhance the antistatic performance of the material; the preferred organic anion has good thermal stability and chemical resistance during processing, avoiding decomposition or side reactions under melt extrusion conditions, so that the material is suitable for industrial preparation and can maintain excellent antistatic performance in long-term use, and the transparency and mechanical properties of polystyrene itself are maintained. DETAILED DESCRIPTION

[0044] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments.

[0045] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. The exemplary expressions of the above terms in the present specification do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in any one or more embodiments or examples in a suitable manner.

[0046] Further, the terms "first", "second", etc. are used only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Thus, the features defined with "first", "second" can include at least one of the features, explicitly or implicitly. In the description of the present application, the meaning of "plurality" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0047] In the description of the present specification, "parts" means "mass parts" unless otherwise specifically described.

[0048] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are for the purpose of explanation of the present application only and cannot be understood as a limitation of the present application. In the embodiments, the specific techniques or conditions not noted are performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual. The reagents or instruments not noted for the manufacturer are all conventional products that can be obtained by purchase in the market.

[0049] p-Chloromethylstyrene, CAS No. 1592-20-7;

[0050] N-Methylpiperidine, CAS No. 626-67-5;

[0051] Polystyrene, the weight average molecular weight of which is about 300000.

[0052] Preparation Example 1

[0053] Preparation of organic anion quaternary ammonium salt-modified polystyrene:

[0054] S1: In a reactor equipped with a mechanical stirrer, a condenser and a nitrogen protection device, 100 parts of styrene, 8 parts of p-chloromethylstyrene, 0.5 parts of azobisisobutyronitrile and 0.15 parts of dodecyl mercaptan were added, and 150 parts of toluene was added as a solvent. After the system was bubbled for 30 min under a nitrogen atmosphere to remove oxygen, the reaction was carried out at 70°C for 8 h. After the reaction was completed, the reaction solution was poured into excess methanol to precipitate, and was suction filtered and vacuum dried to obtain a chloromethylstyrene-styrene copolymer;

[0055] S2: 100 parts of the above chloromethylstyrene-styrene copolymer was weighed out, dissolved in 500 parts of N,N-dimethylformamide, 6 parts of triethylamine and 1.5 parts of N-methylpiperidine were added, and then 0.3 parts of KI was added as an accelerator. The system was stirred at 60°C for 12 hours under a nitrogen atmosphere. After the reaction was completed, the solution was poured into anhydrous diethyl ether to precipitate, filtered, and vacuum dried to obtain a quaternized chloromethylstyrene-styrene copolymer.

[0056] S3: 100 parts of the above quaternized chloromethylstyrene-styrene copolymer was taken, dispersed in 400 parts of acetonitrile / DMF (volume ratio 4:1) mixed solvent, and 8 parts of organic anion metal salt (organic anion metal salt is a mixture of lithium bis(trifluoromethane)sulfonimide and lithium trifluoromethanesulfonate with a molar ratio of 2.5:1) was added. The reaction system was stirred at 30°C for 12h. After the anion exchange was completed, the solution was poured into anhydrous diethyl ether for further precipitation. The solid was collected, filtered, and vacuum dried to obtain organic anion quaternary ammonium salt modified polystyrene A.

[0057] Preparation Example 2

[0058] Preparation of organic anion quaternary ammonium salt modified polystyrene:

[0059] The same as Preparation Example 1, except that step S2 is different, specifically:

[0060] S2: 100 parts of the above chloromethylstyrene-styrene copolymer was weighed out, dissolved in 500 parts of N,N-dimethylformamide, 6 parts of triethylamine and 1.5 parts of N-methylpiperidine were added, and then 0.3 parts of KI was added as an accelerator. The system was stirred at 60°C for 12 hours under a nitrogen atmosphere. After the reaction was completed, the solution was poured into anhydrous diethyl ether to precipitate, filtered, and vacuum dried to obtain a quaternized chloromethylstyrene-styrene copolymer.

[0061] Preparation Example 3

[0062] Preparation of organic anion quaternary ammonium salt modified polystyrene:

[0063] The same as Preparation Example 1, except that step S2 is different, specifically:

[0064] S2: 100 parts of the above chloromethylstyrene-styrene copolymer was weighed out, dissolved in 500 parts of N,N-dimethylformamide, 6 parts of triethylamine and 1.5 parts of N-methylpiperidine were added, and then 0.3 parts of KI was added as an accelerator. The system was stirred at 60°C for 12 hours under a nitrogen atmosphere. After the reaction was completed, the solution was poured into anhydrous diethyl ether to precipitate, filtered, and vacuum dried to obtain a quaternized chloromethylstyrene-styrene copolymer.

[0065] Preparation Example 4

[0066] Preparation of organic anion quaternary ammonium salt modified polystyrene:

[0067] The preparation example 1 is substantially the same, the difference is only that the step S3 is different, specifically:

[0068] S3: take the above quaternary ammonium chloromethyl styrene-styrene copolymer 100 parts, dispersed in acetonitrile / DMF (volume ratio 4:1) mixed solvent 400 parts, add 8 parts of organic anion metal salt (organic anion metal salt is lithium bis(trifluoromethane)sulfonimide), the reaction system is stirred at 30℃ for 12h, after the anion exchange is completed, the solution is poured into anhydrous ether for further precipitation, the solid is collected, and is filtered and vacuum dried, to obtain organic anion quaternary ammonium salt modified polystyrene D.

[0069] Preparation Example 5

[0070] Preparation of organic anion quaternary ammonium salt modified polystyrene:

[0071] The preparation example 1 is substantially the same, the difference is only that the step S3 is different, specifically:

[0072] S3: take the above quaternary ammonium chloromethyl styrene-styrene copolymer 100 parts, dispersed in acetonitrile / DMF (volume ratio 4:1) mixed solvent 400 parts, add 8 parts of organic anion metal salt (organic anion metal salt is lithium bis(trifluoromethane)sulfonimide), the reaction system is stirred at 30℃ for 12h, after the anion exchange is completed, the solution is poured into anhydrous ether for further precipitation, the solid is collected, and is filtered and vacuum dried, to obtain organic anion quaternary ammonium salt modified polystyrene D.

[0073] Preparation Example 6

[0074] Preparation of organic anion quaternary ammonium salt modified polystyrene:

[0075] The preparation example 1 is substantially the same, the difference is only that the step S3 is different, specifically:

[0076] S3: take the above quaternary ammonium chloromethyl styrene-styrene copolymer 100 parts, dispersed in acetonitrile / DMF (volume ratio 4:1) mixed solvent 400 parts, add 8 parts of organic anion metal salt (organic anion metal salt is lithium bis(trifluoromethane)sulfonimide), the reaction system is stirred at 30℃ for 12h, after the anion exchange is completed, the solution is poured into anhydrous ether for further precipitation, the solid is collected, and is filtered and vacuum dried, to obtain organic anion quaternary ammonium salt modified polystyrene D.

[0077] Comparative Preparation Example 1

[0078] Preparation of quaternary ammonium chloromethylstyrene-styrene copolymer:

[0079] S1: In a reactor equipped with a mechanical stirrer, a condenser and a nitrogen protection device, 100 parts of styrene, 8 parts of p-chloromethylstyrene, 0.5 parts of azobisisobutyronitrile and 0.15 parts of dodecyl mercaptan were added, and 150 parts of toluene were added as a solvent. After the system was bubbled for 30 min under a nitrogen atmosphere to remove oxygen, it was reacted at 70°C for 8 h. After the reaction was completed, the reaction solution was poured into excess methanol to precipitate, and was filtered and vacuum dried to obtain a chloromethylstyrene-styrene copolymer;

[0080] S2: 100 parts of the above chloromethylstyrene-styrene copolymer were weighed, dissolved in 500 parts of N,N-dimethylformamide, 6 parts of triethylamine, 1.5 parts of N-methylpiperidine were added, and 0.3 parts of KI was added as an accelerator. The system was stirred at 60°C for 12 h under a nitrogen atmosphere. After the reaction was completed, the solution was poured into anhydrous diethyl ether to precipitate, filtered and vacuum dried to obtain a quaternary ammonium chloromethylstyrene-styrene copolymer.

[0081] Example 1

[0082] Preparation of antistatic polystyrene:

[0083] After 100 parts of polystyrene, 10 parts of organic anion quaternary ammonium salt modified polystyrene A were dried and pre-mixed with 0.2 parts of antioxidant 1010, they were transferred into a twin-screw extruder for melt extrusion. The temperature of each temperature zone from the feeding section to the die head section was set to 190°C, 200°C, 205°C, 210°C, 210°C and 210°C, respectively, and the rotation speed was 200 rpm. Antistatic polystyrene was obtained by extrusion.

[0084] Example 2

[0085] Preparation of antistatic polystyrene:

[0086] It is substantially the same as Example 1, except that organic anion quaternary ammonium salt modified polystyrene B is used instead of organic anion quaternary ammonium salt modified polystyrene A.

[0087] Example 3

[0088] Preparation of antistatic polystyrene:

[0089] It is substantially the same as Example 1, except that organic anion quaternary ammonium salt modified polystyrene C is used instead of organic anion quaternary ammonium salt modified polystyrene A.

[0090] Example 4

[0091] Preparation of antistatic polystyrene:

[0092] The same as Example 1, except that the organic anion quaternary ammonium salt-modified polystyrene D is used instead of the organic anion quaternary ammonium salt-modified polystyrene A.

[0093] Example 5

[0094] Preparation of antistatic polystyrene:

[0095] The same as Example 1, except that the organic anion quaternary ammonium salt-modified polystyrene E is used instead of the organic anion quaternary ammonium salt-modified polystyrene A.

[0096] Example 6

[0097] Preparation of antistatic polystyrene:

[0098] The same as Example 1, except that the organic anion quaternary ammonium salt-modified polystyrene F is used instead of the organic anion quaternary ammonium salt-modified polystyrene A.

[0099] Comparative Example 1

[0100] Preparation of antistatic polystyrene:

[0101] The same as Example 1, except that the quaternized chloromethylstyrene-styrene copolymer obtained in Comparative Preparation Example 1 is used instead of the organic anion quaternary ammonium salt-modified polystyrene A.

[0102] Test section

[0103] Surface resistivity test: The antistatic polystyrene obtained in each example and comparative example is injection molded to obtain a test sample with a thickness of 2±0.2mm and a size of 100mm×100mm, and after vacuum drying at 50-60℃ for 2h and standing at 23±2℃, 50±5%RH for 48h, the surface resistivity R1 (Ω / □) of the test sample is tested using an ultra-high resistance micro-current tester (using a concentric ring electrode, with an outer ring diameter of 60mm and an inner ring diameter of 30mm), and the results are shown in Table 1.

[0104] Wet heat aging surface resistivity: After the test sample subjected to the surface resistivity test is placed at 85℃±2℃, 85%±5%RH for 72h, it is taken out and placed at 23±2℃, 50±5%RH for 4h, and then the surface resistivity R2 (Ω / □) of the test sample is tested using an ultra-high resistance micro-current tester (using a concentric ring electrode, with an outer ring diameter of 60mm and an inner ring diameter of 30mm), and the results are shown in Table 1.

[0105] Table 1

[0106]

[0107] According to Table 1, each of the embodiments exhibits significantly lower initial surface resistivity R1 and smaller resistivity R2 after hygrothermal aging compared with Comparative Example 1, indicating that the antistatic polystyrene provided by the application can obtain stable and persistent antistatic performance while maintaining transparency and processability; the possible reason is that in Comparative Example 1, only chloride ions are contained in the quaternary ammonium salt structure, and small anions form strong associated ion pairs with quaternary ammonium cations, which not only has insufficient initial charge dissipation capacity, but also has serious chloride ion migration and agglomeration under hygrothermal conditions, resulting in a significant increase in resistivity and a significant attenuation of antistatic performance. In contrast, the large volume and delocalized organic anions in the embodiments of the application replace the chloride ions, significantly weaken the ion pair association, and form a continuous charge dissipation path, thereby significantly improving the antistatic performance of the material.

[0108] According to Examples 1-3, the modification system using triethylamine and N-methyl piperidine as quaternary ammonium reagents (Examples 1 and 3) exhibits lower resistivity and better hygrothermal retention, and the antistatic effect is better than that of the system using only triethylamine (Example 2); this indicates that the ratio of the tertiary amine compound has an important influence on the steric hindrance and uniformity of the quaternary ammonium group, and in addition, when the mass ratio of triethylamine to N-methyl piperidine is close to 4:1 (Example 1), the material obtained has better antistatic effect.

[0109] According to Examples 1, 4-6, the modification effects using different organic anions have obvious differences. Example 4 uses only bis(trifluoromethane) sulfonimide anions, which exhibits the most stable resistivity after hygrothermal aging; Example 6 uses only triflate anions, which has the lowest initial resistivity but a larger increase after hygrothermal aging; Example 5 uses a 1:1 compound of the two, which has better initial performance but still not as good as Example 4 in terms of hygrothermal retention; in contrast, Example 1 uses a 2.5:1 compound of bis(trifluoromethane) sulfonimide and triflate anions, which balances the initial antistatic performance and hygrothermal stability, and has the best comprehensive performance, resulting in a material with better antistatic effect.

[0110] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the application, and are not limiting; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. An antistatic polystyrene, characterized by, The raw materials include the following quality parts: 100 parts of polystyrene, 5-15 parts of organic anion quaternary ammonium salt modified polystyrene; The organic anion quaternary ammonium salt modified polystyrene is prepared by the following steps: S1: chloromethyl styrene and styrene are reacted by free radical polymerization to obtain a chloromethyl styrene-styrene copolymer; S2: the chloromethyl styrene-styrene copolymer is reacted with a tertiary amine compound to quaternize the chloromethyl group on the chloromethyl styrene-styrene copolymer to obtain a quaternized chloromethyl styrene-styrene copolymer; wherein the tertiary amine compound includes triethylamine and N-methyl piperidine, and the mass ratio of the triethylamine and N-methyl piperidine is (3-5):1; S3: the quaternized chloromethyl styrene-styrene copolymer is ion exchanged with an organic anion metal salt to exchange part of the chloride ions in the quaternized chloromethyl styrene-styrene copolymer into organic anions to obtain the organic anion quaternary ammonium salt modified polystyrene; wherein the organic anion metal salt includes an organic anion, and the organic anion includes bis(trifluoromethane) sulfonimide anion and trifluoromethanesulfonate anion, and the molar ratio of the bis(trifluoromethane) sulfonimide anion and trifluoromethanesulfonate anion is (2-3):

1.

2. The antistatic polystyrene according to claim 1, characterized in that, The step S1 includes: 100 parts of styrene, 5-10 parts of chloromethyl styrene, 0.3-1 parts of an initiator, and 0.1-0.2 parts of a chain transfer agent are dispersed in 100-200 parts of toluene, and reacted at 65-75°C under a nitrogen atmosphere for 6-10 hours to obtain a chloromethyl styrene-styrene copolymer.

3. The antistatic polystyrene according to claim 1, characterized in that, The step S2 includes: 100 parts of the chloromethyl styrene-styrene copolymer, 3-10 parts of a tertiary amine compound, and 0.1-0.5 parts of an accelerator are dispersed in 400-1000 parts of N,N-dimethylformamide, and reacted at 55-65°C under a nitrogen atmosphere for 10-16 hours to obtain a quaternized chloromethyl styrene-styrene copolymer.

4. The antistatic polystyrene according to claim 1, characterized in that, The step S3 includes: 100 parts of the quaternized chloromethyl styrene-styrene copolymer and 5-10 parts of an organic anion metal salt are dispersed in 300-600 parts of an acetonitrile / N,N-dimethylformamide mixed solvent, and reacted at 20-40°C for 8-16 hours to obtain the organic anion quaternary ammonium salt modified polystyrene.

5. The antistatic polystyrene according to claim 2, characterized in that, The initiator includes azobisisobutyronitrile; and the chain transfer agent includes dodecyl mercaptan.

6. The antistatic polystyrene according to claim 3, characterized in that, The accelerator includes KI.

7. The antistatic polystyrene according to any one of claims 1 to 6, characterized in that, The weight average molecular weight of the polystyrene is 100000-1000000. The raw materials of the antistatic polystyrene further include: 0.05-0.5 parts of an antioxidant, and the antioxidant includes at least one of antioxidant 1076 and antioxidant 1010.

8. A method of preparing the antistatic polystyrene according to claim 7, characterized in that, The polystyrene, the organic anion quaternary ammonium salt modified polystyrene, and the antioxidant are melt blended to obtain the antistatic polystyrene. ​

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