Preparation method of intrinsically flame-retardant and toughened polystyrene copolymer

Abstract

The invention discloses a preparation method of an intrinsically flame-retardant and toughened polystyrene copolymer. The preparation method comprises the following steps: firstly, preparing a phosphorus-nitrogen integrated functional compound from glycine, paraformaldehyde and dimethyl phosphite as raw materials; then carrying out acylating chlorination modification on the phosphorus-nitrogen integrated functional compound by using thionyl chloride; reacting the phosphorus-nitrogen integrated functional compound modified by acylating chlorination with phenolic hydroxyl cardanol to prepare a high-flexibility flame-retardant monomer; and finally, reacting the high-flexibility flame-retardant monomer with styrene to obtain the polystyrene copolymer. The copolymer has the dual advantages of flame retardance and toughening at the same time.

Description

Technical Field

[0001] The invention relates to a method for preparing an intrinsically flame-retardant and toughened polystyrene copolymer. Background Art

[0002] Polystyrene (PS) is one of the top five thermoplastic polymers in the world. In recent years, my country's annual consumption of polystyrene has basically accounted for one-third of the world's total, and it is increasing at an annual rate of 3%-4%. Polystyrene has good chemical resistance, dimensional stability and transparency, and is widely used in optical instruments, decorations, packaging containers, electrical appliances, electronic packaging, and construction industries.

[0003] However, the molecular structure of polystyrene has a high content of carbon and hydrogen elements, which makes it highly flammable. Its limiting oxygen index (LOI) is only 18, and thick black smoke is produced during combustion, which poses a fire safety hazard. In addition, the large number of rigid benzene ring groups on the side chains also make polystyrene brittle and poor in toughness, and it is prone to stress cracking during use. These shortcomings greatly limit the application of polystyrene. Therefore, research on flame retardancy and toughening of polystyrene materials is not only conducive to reducing the harm caused by combustion, but also has important theoretical guidance and practical significance for improving its comprehensive performance and expanding its application areas.

[0004] The most commonly used flame retardant for polystyrene is the traditional additive brominated flame retardant. However, with the increasing pressure on environmental protection, the market is increasingly calling for more environmentally friendly halogen-free flame retardants. Moreover, adding flame retardants by simple physical addition methods will further damage the mechanical properties of polystyrene. In view of this, the present invention provides a halogen-free, environmentally friendly, inherently flame-retardant and self-toughened polystyrene copolymer that does not require any additives. Summary of the invention

[0005] The present invention aims at the shortcomings of traditional polystyrene, namely, being "flammable" and "brittle", and prepares a polystyrene copolymer having both flame retardant and toughening effects.

[0006] To achieve the above-mentioned purpose, the preparation method of the intrinsically flame-retardant and toughened polystyrene copolymer described in the present invention comprises the following steps: firstly, glycine, paraformaldehyde and dimethyl phosphite are used as raw materials to prepare a phosphorus-nitrogen integrated functional compound; then, the phosphorus-nitrogen integrated functional compound is chlorinated with thionyl chloride; then, the chlorinated phosphorus-nitrogen integrated functional compound is reacted with phenolic hydroxy cardanol to prepare a highly flexible flame-retardant monomer; finally, the highly flexible flame-retardant monomer is reacted with styrene to prepare an intrinsically flame-retardant and toughened polystyrene copolymer.

[0007] The preparation method of the intrinsically flame-retardant and toughened polystyrene copolymer of the present invention comprises the following specific steps: (1) Paraformaldehyde, glycine and tetrahydrofuran are mixed and heated to 60-70°C, and then dimethyl phosphite is added dropwise. After the addition is completed, the temperature is kept constant until the reaction is complete. After the reaction is completed, the solvent tetrahydrofuran is removed to obtain a light yellow viscous liquid, which is a phosphorus-nitrogen integrated functional compound. The phosphorus-nitrogen integrated functional compound is code-named HOOC-NP2.

[0008] (2) The phosphorus-nitrogen integrated functional compound is dissolved in a solvent and a catalyst is added, and thionyl chloride is added dropwise at a temperature of 0-15°C; after the addition is completed, the temperature is raised to 70-80°C and the reaction is continued at this temperature until the reaction is complete to obtain a product solution; saturated salt water and sodium hydroxide solution are added to the product solution to wash the product solution, and then the inorganic phase is separated, and anhydrous sodium sulfate is added to the organic phase for drying. After the drying is completed, the solid-liquid separation is performed, and the solvent is removed from the liquid product obtained by the solid-liquid separation to obtain an acyl chloride modified flame retardant functional monomer. The acyl chloride modified flame retardant functional monomer is code-named ClOC-NP2; the mass concentration of the sodium hydroxide solution is 5%. After the washing is completed, the organic phase and the inorganic phase are generally separated by static stratification, and then the inorganic phase is separated and the organic phase is retained.

[0009] (3) Phenolic hydroxy cardanol (CAS: 501-26-8) was mixed with a solvent and triethylamine was added. The chlorinated flame retardant functional monomer was dissolved in the solvent to prepare a flame retardant functional monomer solution. The flame retardant functional monomer solution was added dropwise at a temperature of -5°C. After the addition was completed, a low-temperature reaction was first carried out at a temperature of -10-0°C, and then the reaction was continued at a temperature of 5-15°C until the reaction was complete. After the reaction was completed, a liquid crude product was filtered to obtain a liquid crude product. The liquid crude product was washed with acetic acid solution, NaOH solution, and saturated brine in sequence, and then dried with anhydrous sodium sulfate. After drying, a solid-liquid separation was performed to obtain a product solution. After removing the solvent from the product solution, a light yellow viscous liquid was obtained, which was a highly flexible flame retardant monomer. The mass concentrations of the acetic acid solution and the NaOH solution were 2% and 10%, respectively. The washing and drying operations were as follows: the acetic acid solution was added to the liquid crude product for washing. After the washing was completed, the product was allowed to stand for stratification, and the inorganic phase was separated and the organic phase was retained. Then, NaOH was added to the organic phase. The solution is washed, and after washing, the mixture is allowed to stand and separate, the inorganic phase is separated and the organic phase is retained; saturated salt water is added to the organic phase for washing, and after washing, the mixture is allowed to stand and separate, the inorganic phase is separated and the organic phase is retained; finally, anhydrous sodium sulfate is added to the organic phase for drying, and after drying, solid-liquid separation is performed; (4) Styrene, high-flexibility flame-retardant monomer and solvent are mixed, and an initiator is added dropwise at a temperature of 65-80°C under nitrogen protection. After the addition is completed, the reaction is kept at a temperature of 65-80°C until the reaction is complete. After the reaction is completed, a liquid mixture containing a crude polystyrene copolymer product is obtained. The addition time is 20-40 minutes, and the reaction is generally complete after 4-8 hours of heat preservation. (5) The liquid mixture is added to ethanol to allow the solid product to be fully precipitated; after solid-liquid separation, the solid product is vacuum dried, and the light yellow solid obtained after drying is the intrinsically flame retardant, toughened polystyrene copolymer; the vacuum drying temperature is 70°C.

[0010] The molar ratio of glycine, paraformaldehyde and dimethyl phosphite is 1.0-1.2:2.0-4.0:4.0.

[0011] In the step (1), after removing the solvent tetrahydrofuran, the following treatment is required: first washing with a small amount of water, then drying with anhydrous sodium sulfate, and finally solid-liquid separation. After solid-liquid separation, a light yellow viscous liquid is obtained, which is the phosphorus-nitrogen integrated functional compound. The washing and drying operation is as follows: after washing with water, standing and stratifying, separating the inorganic phase and retaining the organic phase, and then adding anhydrous sodium sulfate to the organic phase for drying.

[0012] In the steps (1), (2) and (3), the speed of dripping is 1-2 seconds per drop; in step (1), the time of continuing the heat preservation reaction after the dripping is completed is 7-9 hours; in step (2), the time of continuing the heat preservation reaction after the dripping is completed is 1-2 hours; in step (3), the time of low-temperature reaction and heat preservation reaction after the dripping is completed are both 7-9 hours.

[0013] In the step (2), the molar ratio of thionyl chloride to the phosphorus-nitrogen integrated functional compound is 1.1-1.2:1.

[0014] In the step (2), the catalyst is N,N-dimethylformamide (DMF), n-dodecyltrimethylammonium chloride, pyridine or triethylamine; the amount of the catalyst is 3-6% of the mass of thionyl chloride.

[0015] In the step (3), the molar ratio of phenolic hydroxy cardanol to the flame retardant functional monomer modified by acyl chloride is 1:1.0-1.2; and the amount of triethylamine used is 0.5-1.2 times the mass of phenolic hydroxy cardanol.

[0016] In the step (4), the mass ratio of styrene to the high-flexibility flame-retardant monomer is 1:0.2-2.

[0017] In the step (4), the initiator is one or a combination of two or more of azobisisobutyronitrile, azobisisoheptanenitrile and dibenzoyl peroxide in any mass ratio, and the amount of the initiator used is 3-10% of the mass of styrene.

[0018] In the step (2), the solvent is dichloroethane or chloroform; in the step (3), the solvent is dichloroethane or chloroform; in the step (4), the solvent is dichloromethane, dichloroethane, chloroform, cyclohexane or 1,4-dioxane, preferably cyclohexane or 1,4-dioxane.

[0019] The amount of tetrahydrofuran used as a solvent in step (1) is limited to completely dissolving the paraformaldehyde and glycine during the reaction. However, in order to ensure smooth flow of the system during stirring and a more balanced reaction in the system, the amount of tetrahydrofuran can be increased appropriately. Similarly, the amount of the solvent in steps (2), (3) and (4) is also limited to completely dissolving the raw materials it dissolves. However, in order to ensure smooth flow of the system during stirring and a more balanced reaction in the system, the amount of the solvent in steps (2), (3) and (4) can be increased appropriately.

[0020] The reaction process of step (1) is shown in the following formula: .

[0021] The reaction process of step (2) and step (3) is shown in the following formula: .

[0022] The reaction process of step (4) is shown in the following formula: .

[0023] The advantage of the present invention is that the prepared product has the dual advantages of flame retardancy and toughening. On the one hand, the flame retardant function of the copolymer comes from the rich flame retardant groups in the high-phosphorus content flame retardant with reactive functional groups. The flame retardant group is rich in phosphorus content, halogen-free and environmentally friendly, and has a high carbonization rate. The toughening effect comes from a large number of flexible groups in the flame retardant functional monomer and a large number of flexible segments contained in cardanol. The intrinsic flame retardant polystyrene copolymer of the present invention can freely adjust the ratio of flame retardant groups, cardanol, and styrene. A reasonable ratio can optimize the performance of the polystyrene copolymer. The product of the present invention can be directly used as a polystyrene product with good flame retardancy and mechanical properties, and can also be used as a flame retardant additive. It has high flame retardant efficiency and lasting effect. There are no problems such as volatility, migration, and precipitation, and it has a wide range of application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the infrared spectrum of the product obtained in step (1) of Example 1; Figure 2This is the nuclear magnetic resonance spectrum of the product obtained in step (1) of Example 1. DETAILED DESCRIPTION

[0025] The feasibility of the technical solution of the present invention is illustrated below by way of examples, but the protection scope of the present invention should not be limited to the following specific examples. Example 1

[0026] (1) In a three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 252 g (2.8 mol) of paraformaldehyde, 152 g (2.0 mol) of glycine and 400 mL of tetrahydrofuran, stir the reaction mixture and heat it to 66°C, then slowly drop 440 g (4.0 mol) of dimethyl phosphite over 1 hour, one drop per 1-2 seconds; after the dropwise addition is completed, continue the reaction at about 66°C for 8 hours, after the reaction is completed, remove the solvent by rotary evaporation to obtain a crude product, wash the crude product with 60 mL of water, let it stand after washing, separate the inorganic phase, add anhydrous sodium sulfate to the organic phase for drying, and filter after drying to obtain 782 g of a light yellow transparent liquid, which is the phosphorus-nitrogen integrated functional compound (HOOC-NP2); (2) In a 500 ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 329 g (1.0 mol) of HOOC-NP2 and 150 mL of dichloroethane, add 6.0 g of DMF as a catalyst, maintain the temperature at about 10 ° C, slowly drop 130.9 g (1.1 mol) of thionyl chloride into the reaction bottle, one drop per 1-2 seconds, after the addition is completed, heat and slowly raise the temperature to 75 ° C while stirring, continue stirring and keep the reaction at 75 ° C for 1.5 hours; after the reaction is completed, a product solution is obtained, saturated salt water and 5% sodium hydroxide solution are added to the product solution for washing, after washing, stand and stratify, separate the inorganic phase and add anhydrous sodium sulfate to the organic phase for drying, filter and obtain a dichloroethane solution of the flame retardant functional monomer modified by acyl chloride, and remove the solvent dichloroethane by rotary evaporation to obtain the flame retardant functional monomer modified by acyl chloride (ClOC-NP2); (3) 30.25g (0.1mol) of commercially available phenolic hydroxycardanol was mixed with 100ml of dichloroethane solvent and added to a reaction flask, and 20.2g (0.2mol) of triethylamine was added. At a constant temperature of -5°C, 34.55g (0.1mol) of the ClOC-NP2 prepared above was dissolved in 50ml of dichloroethane and added to the reaction flask at a drop rate of 2 drops / s. After the addition was completed, the reaction was maintained at a low temperature for 8h, and then the temperature was raised to 10°C and the reaction was continued for 8h until the reaction was fully reacted. After the reaction was completed, the crude liquid product was filtered and washed with 2% acetic acid solution, 10% NaOH solution, and saturated brine in turn, and then dried with anhydrous sodium sulfate. Finally, solid-liquid separation was performed, and the solvent was removed by rotary evaporation to obtain a light yellow viscous liquid, which was a highly flexible flame retardant monomer; (4) In a 500ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 24g of styrene, 12g of a highly flexible flame retardant monomer and 120g of 1,4-dioxane and mix them, pass nitrogen protection, and stir magnetically. During this process, slowly raise the temperature to the set temperature of 65°C. After the temperature reaches the set temperature, slowly drop a mixed solution of azobisisobutyronitrile and azobisisoheptanenitrile initiator (1.5g of initiator dissolved in 15ml of dioxane). The dropwise addition takes about 0.5h. After the dropwise addition is completed, keep the temperature for 6-8h. After the reaction is completed, a liquid mixture containing a crude polystyrene copolymer product is obtained; (5) The liquid mixture is poured into ethanol to allow the solid product to be fully precipitated, the solid-liquid separation is performed, and the precipitated solid product is dissolved in dichloromethane, and then poured into ethanol to allow the solid product to be fully precipitated. The solid product is separated and vacuum dried at 70°C for 5 hours. After drying, a light yellow solid is obtained, which is an intrinsically flame-retardant and toughened polystyrene copolymer, denoted as polystyrene copolymer-I. Example 2

[0027] (1) In a three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 252 g (2.8 mol) of paraformaldehyde, 152 g (2.0 mol) of glycine and 400 mL of tetrahydrofuran, stir the reaction mixture and heat it to 66°C, then slowly drop 440 g (4.0 mol) of dimethyl phosphite over 1 hour, one drop per 1-2 seconds; after the dropwise addition is completed, continue the reaction at about 66°C for 8 hours, after the reaction is completed, remove the solvent by rotary evaporation to obtain a crude product, wash the crude product with 60 mL of water, let it stand after washing, separate the inorganic phase, add anhydrous sodium sulfate to the organic phase for drying, and filter after drying to obtain 782 g of a light yellow transparent liquid, which is the phosphorus-nitrogen integrated functional compound (HOOC-NP2); (2) In a 500 ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 329 g (1.0 mol) of HOOC-NP2 and 100 mL of dichloroethane, add 7.0 g of DMF as a catalyst, maintain the temperature at about 10 ° C, slowly drop 142.8 g (1.2 mol) of thionyl chloride into the reaction bottle, one drop every 1-2 seconds, after the addition is completed, heat and slowly raise the temperature to 75 ° C while stirring, continue stirring and keep the reaction at 75 ° C for 1.5 hours; after the reaction is completed, the product solution is obtained, saturated salt water and 5% sodium hydroxide solution are added to the product solution for washing, after washing, stand and stratify, separate the inorganic phase and add anhydrous sodium sulfate to the organic phase for drying, filter and obtain the dichloroethane solution of the acyl chloride modified flame retardant functional monomer, and remove the solvent dichloroethane by rotary evaporation to obtain the acyl chloride modified flame retardant functional monomer (ClOC-NP2); (3) 30.25 g (0.1 mol) of commercially available phenolic hydroxycardanol was mixed with 100 ml of dichloroethane solvent and added to a reaction flask, and 20.2 g (0.2 mol) of triethylamine was added. At a constant temperature of -5°C, 34.55 g (0.1 mol) of the ClOC-NP2 prepared above was dissolved in 50 ml of dichloroethane and added dropwise to the reaction flask at a drop rate of 2 drops / s. After the addition was completed, the reaction was maintained at a low temperature for 6 hours, and then the temperature was raised to 15°C and the reaction was continued for 6 hours. After the reaction was completed, the crude liquid product was filtered and washed with 2% acetic acid solution, 10% NaOH solution, and saturated brine in turn, and then dried with anhydrous sodium sulfate. Finally, solid-liquid separation was performed, and the solvent was removed by rotary evaporation to obtain a light yellow viscous liquid, which was a highly flexible flame retardant monomer. (4) In a 500ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 28g of styrene, 8g of a highly flexible flame retardant monomer and 120g of 1,4-dioxane and mix them, pass nitrogen protection, and stir magnetically. During this process, slowly raise the temperature to the set temperature of 65°C. After the temperature reaches the set temperature, slowly drop a mixed solution of azobisisobutyronitrile and azobisisoheptanenitrile initiator (1.5g of initiator dissolved in 15ml of dioxane). The dropwise addition takes about 0.5h. After the dropwise addition is completed, keep the temperature for 6-8h. After the reaction is completed, a liquid mixture containing a crude polystyrene copolymer is obtained; (5) The liquid mixture is poured into ethanol to allow the solid product to be fully precipitated, the solid-liquid separation is performed, and the precipitated solid product is dissolved in dichloromethane, and then poured into ethanol to allow the solid product to be fully precipitated. The solid product is separated and vacuum dried at 70°C for 5 hours. After drying, a light yellow solid is obtained, which is an intrinsically flame-retardant and toughened polystyrene copolymer, recorded as polystyrene copolymer-II. Example 3

[0028] (1) In a three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 252 g (2.8 mol) of paraformaldehyde, 152 g (2.0 mol) of glycine and 400 mL of tetrahydrofuran, stir the reaction mixture and heat it to 66°C, then slowly drop 440 g (4.0 mol) of dimethyl phosphite over 1 hour, one drop per 1-2 seconds; after the dropwise addition is completed, continue the reaction at about 66°C for 8 hours, after the reaction is completed, remove the solvent by rotary evaporation to obtain a crude product, wash the crude product with 60 mL of water, let it stand after washing, separate the inorganic phase, add anhydrous sodium sulfate to the organic phase for drying, and filter after drying to obtain 782 g of a light yellow transparent liquid, which is the phosphorus-nitrogen integrated functional compound (HOOC-NP2); (2) In a 500 ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 329 g (1.0 mol) of HOOC-NP2 and 100 mL of dichloroethane, add 7.0 g of DMF as a catalyst, maintain the temperature at about 10 ° C, slowly drop 142.8 g (1.2 mol) of thionyl chloride into the reaction bottle, one drop per 1-2 seconds, after the addition is completed, heat and slowly raise the temperature to 75 ° C while stirring, continue stirring and keep the reaction at 75 ° C for 1.5 hours; after the reaction is completed, the product solution is obtained, saturated salt water and 5% sodium hydroxide solution are added to the product solution for washing, after washing, stand and stratify, separate the inorganic phase and add anhydrous sodium sulfate to the organic phase for drying, filter and obtain the dichloroethane solution of the acyl chloride modified flame retardant functional monomer, and remove the solvent dichloroethane by rotary evaporation to obtain the acyl chloride modified flame retardant functional monomer (ClOC-NP2); (3) 30.25 g (0.1 mol) of commercially available phenolic hydroxycardanol was mixed with 100 ml of dichloroethane solvent and added to a reaction flask, and 20.2 g (0.2 mol) of triethylamine was added. At a constant temperature of -5°C, 34.55 g (0.1 mol) of the ClOC-NP2 prepared above was dissolved in 50 ml of dichloroethane and added dropwise to the reaction flask at a drop rate of 2 drops / s. After the addition was completed, the reaction was maintained at a low temperature for 6 hours, and then the temperature was raised to 15°C and the reaction was continued for 6 hours. After the reaction was completed, the crude liquid product was filtered and washed with 2% acetic acid solution, 10% NaOH solution, and saturated brine in turn, and then dried with anhydrous sodium sulfate. Finally, solid-liquid separation was performed, and the solvent was removed by rotary evaporation to obtain a light yellow viscous liquid, which was a highly flexible flame retardant monomer. (4) In a 500ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 24g of styrene, 24g of a highly flexible flame retardant monomer and 120g of 1,4-dioxane and mix them, pass nitrogen protection, and stir magnetically. During this process, slowly raise the temperature to the set temperature of 65°C. After the temperature reaches the set temperature, slowly drop a mixed solution of azobisisobutyronitrile and azobisisoheptanenitrile initiator (1.5g of initiator dissolved in 15ml of dioxane). The dropwise addition takes about 0.5h. After the dropwise addition is completed, keep the temperature for 6-8h. After the reaction is completed, a liquid mixture containing a crude polystyrene copolymer product is obtained; (5) The liquid mixture is poured into ethanol to allow the solid product to be fully precipitated, the solid-liquid separation is performed, and the precipitated solid product is dissolved in dichloromethane, and then poured into ethanol to allow the solid product to be fully precipitated. The solid product is separated and vacuum dried at 70°C for 5 hours. After drying, a light yellow solid is obtained, which is an intrinsically flame-retardant and toughened polystyrene copolymer, denoted as polystyrene copolymer-III.

[0029] Comparative Example 4 (1) In a 500ml three-necked flask equipped with a stirring device, a thermometer and a reflux condenser, add 36g of styrene and 120g of 1,4-dioxane solvent, mix them, add them to the three-necked flask, pass nitrogen protection, and stir them magnetically. During this process, slowly increase the temperature to the set temperature of 65°C. After the temperature reaches the set temperature, slowly drop azobisisobutyronitrile, azobisisoheptanenitrile and dibenzoyl peroxide initiator mixed solution (1.5g initiator dissolved in 15ml dioxane), and the dropwise addition is completed in about 0.5h. After the dropwise addition is completed, keep the temperature for 6-8h to fully react.

[0030] (2) After the reaction is completed, the viscous mixture solution is poured into excess methanol to precipitate a large amount of light yellow solid. The precipitate is dissolved in chloroform again and precipitated in excess methanol again. The above dissolution, precipitation and washing cycle is repeated twice. The final product is vacuum dried at 70°C to obtain a pure white solid, which is recorded as pure polystyrene. The weight is 35.7 g, and the yield is 95.3%.

[0031] LOI test: According to ISO 4589-2 combustion performance oxygen index test standard. Use a flat vulcanizer to press and mold the polystyrene copolymer and pure polystyrene into 100×100×3.2 mm 3 The standard plate is then cut to prepare 100×6.5×3.2 mm 3 Flame retardant specimens. There are 15 test specimens in each group. The oxygen concentration changes by 0.5% each time. After the sample passes the test at a certain oxygen concentration, it fails to pass when the oxygen concentration is increased by 0.5%, and passes when the oxygen concentration is reduced by 0.5%. This low oxygen concentration is the corresponding oxygen index.

[0032] Impact resistance test: The impact resistance test was conducted by using a pendulum impact tester (ZBC8400-A) (MTS Systems Co., Ltd., China) according to GB / T 1043-93 standard on a 80×10×3.2 mm 3 The impact strength of unnotched specimens was determined using a simple beam and the specimen was impacted by a pendulum.

[0033] The products obtained in Examples 1-3 and Comparative Example 4 were tested according to the above test standards, and the test results are shown in the following table;

[0034] As can be seen from the table, the results of the LOI test and impact resistance test of the product prepared by the present invention are significantly better than those of the comparative example. The flame retardant function of the copolymer prepared by the present invention comes from the rich flame retardant groups in the reactive high-phosphorus content flame retardant, and the toughening effect comes from the large number of flexible groups in the flame retardant functional monomer and the large number of flexible segments in cardanol. A reasonable ratio can optimize the performance of the polystyrene copolymer.

[0035] The above is only a preferred embodiment of the present invention, and does not limit the technical solution of the present invention in any form. Any equivalent replacement or partial improvement made under the technical essence of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing an intrinsically flame-retardant, toughened polystyrene copolymer, characterized in that The following steps are involved: First, a phosphorus-nitrogen integrated functional compound is prepared using glycine, paraformaldehyde and dimethyl phosphite as raw materials; then, the phosphorus-nitrogen integrated functional compound is modified by chlorination using thionyl chloride; then, the phosphorus-nitrogen integrated functional compound modified by chlorination is reacted with phenolic hydroxycardanol to obtain a highly flexible flame-retardant monomer; finally, the highly flexible flame-retardant monomer is reacted with styrene to obtain an intrinsically flame-retardant and toughened polystyrene copolymer.

2. The method for preparing a highly flexible flame retardant monomer according to claim 1, characterized in that The following steps are involved: (1) paraformaldehyde, glycine and tetrahydrofuran are mixed and heated to 60-70°C, and then dimethyl phosphite is added dropwise. After the addition is completed, the temperature is kept constant until the reaction is complete. After the reaction is completed, the solvent tetrahydrofuran is removed to obtain a light yellow viscous liquid, which is a phosphorus-nitrogen integrated functional compound; (2) dissolving the phosphorus-nitrogen integrated functional compound in a solvent and adding a catalyst, and then dripping thionyl chloride at a temperature of 0-15°C; after the dripping is completed, the temperature is raised to 70-80°C and the reaction is continued at this temperature until the reaction is complete to obtain a product solution; saturated salt water and sodium hydroxide solution are added to the product solution to wash the product solution, and then the inorganic phase is separated, and anhydrous sodium sulfate is added to the organic phase for drying. After the drying is completed, solid-liquid separation is performed, and the solvent is removed from the liquid product obtained by solid-liquid separation to obtain an acyl chloride-modified flame retardant functional monomer; (3) Phenolic hydroxy cardanol is mixed with a solvent and triethylamine is added, and the chlorinated flame retardant functional monomer is dissolved in the solvent to prepare a flame retardant functional monomer solution. The flame retardant functional monomer solution is added dropwise at a temperature of -10-0°C. After the addition is completed, a low-temperature reaction is first carried out at a temperature of -10-0°C, and then the reaction is continued at a temperature of 5-15°C until the reaction is complete. After the reaction is completed, a liquid crude product is filtered to obtain the liquid crude product, and the liquid crude product is washed with acetic acid solution, NaOH solution, and saturated brine in sequence, and then dried with anhydrous sodium sulfate. After drying, a solid-liquid separation is performed to obtain a product solution. After removing the solvent from the product solution, a light yellow viscous liquid is obtained, which is a highly flexible flame retardant monomer; (4) mixing styrene, a highly flexible flame retardant monomer and a solvent, adding an initiator dropwise at a temperature of 65-80°C under nitrogen protection, and after the addition is completed, keeping the temperature at 65-80°C for reaction until the reaction is complete; after the reaction is completed, a liquid mixture containing a crude polystyrene copolymer product is obtained; (5) The liquid mixture is added to ethanol to allow the solid product to be fully precipitated; after solid-liquid separation, the solid product is vacuum dried, and the light yellow solid obtained after drying is the intrinsically flame retardant and toughened polystyrene copolymer.

3. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: The molar ratio of glycine, paraformaldehyde and dimethyl phosphite is 1.0-1.2:2.0-4.0:4.

0.

4. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the steps (1), (2) and (3), the speed of dropping is 1-2 seconds per drop; in step (1), the time of continuing the heat preservation reaction after the drop addition is completed is 7-9 hours; in step (2), the time of continuing the heat preservation reaction after the drop addition is completed is 1-2 hours; in step (3), the time of low temperature reaction and heat preservation reaction after the drop addition is completed is 7-9 hours.

5. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (2), the molar ratio of thionyl chloride to the phosphorus-nitrogen integrated functional compound is 1.1-1.2:

1.

6. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (2), the catalyst is N,N-dimethylformamide, n-dodecyltrimethylammonium chloride, pyridine or triethylamine; the amount of the catalyst is 3-6% of the mass of thionyl chloride.

7. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (3), the molar ratio of phenolic hydroxy cardanol to the flame retardant functional monomer modified by acyl chloride is 1:1.0-1.2; and the amount of triethylamine used is 0.5-1.2 times the mass of phenolic hydroxy cardanol.

8. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (4), the mass ratio of styrene to the high-flexibility flame-retardant monomer is 1:0.2-2.

9. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (4), the initiator is one or a combination of two or more of azobisisobutyronitrile, azobisisoheptanenitrile and dibenzoyl peroxide in any mass ratio, and the amount of the initiator used is 3-10% of the mass of styrene.

10. The method for preparing the intrinsically flame retardant and toughened polystyrene copolymer according to claim 2, characterized in that: In the step (2), the solvent is dichloroethane or chloroform; in the step (3), the solvent is dichloroethane or chloroform; in the step (4), the solvent is dichloromethane, dichloroethane, chloroform, cyclohexane or 1,4-dioxane.

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