A modified polystyrene composite containing a flame-retardant rubber and a method for preparing the same

Abstract

The present application relates to the technical field of polystyrene, and discloses a modified polystyrene composite containing flame-retardant rubber and a preparation method thereof.A p-toluenesulfonic acid is used as a catalyst, 5'-phenyl-[1,1':3',1"]-4,4''-terphenyl dicarboxylic acid, double-end hydroxypropyl silicone oil and 2-carboxyethyl phenyl phosphinic acid ethylene glycol ester are used to prepare a flame retardant, which is then added to a mixture of polystyrene and silicone rubber to obtain the modified polystyrene composite containing flame-retardant rubber.The flame retardant contains phosphorus elements, siloxane structures and triphenylbenzene structures, which are beneficial to improving the carbonization capacity of polystyrene during combustion and have high flame-retardant performance.The flame retardant contains multiple side benzene ring structures, and the double-end hydroxypropyl silicone oil has a similar chemical structure to the silicone rubber, so the double-end hydroxypropyl silicone oil can be used as a compatibilizer to improve the compatibility between the silicone rubber and the polystyrene, and the material has better mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polystyrene technology, specifically to a modified polystyrene composite material containing flame-retardant rubber and its preparation method. Background Technology

[0002] Polystyrene is widely used in packaging, electronics, and construction due to its advantages such as being lightweight, easy to process, and low-cost. However, its poor toughness, low impact strength, and flammability limit its application in high-end fields. Currently, research on the modification of polystyrene mainly focuses on two aspects: first, improving its impact strength and toughness by adding rubber; and second, improving its flame retardancy by introducing flame retardants.

[0003] Silicone rubber possesses high toughness, good mechanical properties, and certain flame-retardant characteristics. When added to polymers such as polystyrene, it can improve the materials' mechanical and flame-retardant properties. However, the poor compatibility between silicone rubber and polystyrene easily leads to phase separation, further weakening the material's performance. Developing polystyrene composite materials that combine high flame retardancy, mechanical reinforcement, and environmental friendliness has become a research hotspot. Patent CN117447805B discloses grafting low-phenyl silicone rubber onto the main chain of polystyrene-based thermoplastic elastomers, giving the material good low-temperature resistance, heat resistance, and chemical solvent resistance. However, this patent does not address the problem of polystyrene's poor flame retardancy. Summary of the Invention

[0004] (a) Technical problems to be solved:

[0005] To address the shortcomings of existing technologies, this invention provides a modified polystyrene composite material containing flame-retardant rubber and its preparation method, which solves the problems of poor flame retardancy and low impact strength of polystyrene.

[0006] (II) Technical Solution: A method for preparing a modified polystyrene composite material containing flame-retardant rubber is as follows:

[0007] Step (1): Add tetrahydrofuran, water, an inorganic base in the ratio of (60-80) mmol:10 mmol:(22-24) mmol:(0.36-0.48) mmol, 3,5-dibromobiphenyl, 4-carboxyphenylboronic acid, and tetra(triphenylphosphine)palladium to a flask. Heat to 70-90℃ under a nitrogen atmosphere and reflux for 12-24 h. Dilute with water and extract with dichloromethane. Dry the organic phase with anhydrous sodium sulfate, filter, distill under reduced pressure, wash the product with petroleum ether, and recrystallize in dichloromethane to obtain 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid.

[0008] Step (2): In an ice-water bath, add N,N-dimethylformamide, bihydroxypropyl silicone oil in a ratio of 100g:(6.1-8.5)g:(10-13.8)g:(0.26-0.35)g, ethylene glycol 2-carboxyethylphenylphosphine, 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, and p-toluenesulfonic acid to a flask. Stir at 100-110℃ for 18-24h, reflux during the reaction, then add ethanol, stir to precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0009] Step (3): On a two-roll mill, mix silicone rubber, vulcanizing agent, catalyst, flame retardant and polystyrene in a ratio of (10-25)g:(0.4-1.2)g:(0.01-0.03)g:(6-15)g:100g evenly, granulate with a twin-screw extruder, dry and sample with an injection molding machine to obtain modified polystyrene composite material containing flame retardant rubber.

[0010] Furthermore, in step (1), the inorganic base is sodium carbonate or potassium carbonate.

[0011] Furthermore, in step (2), the temperature of the twin-screw extruder is 150-190℃ and the rotation speed is 300-450rpm.

[0012] Furthermore, in step (2), the temperature of the injection molding machine is 190-200℃ and the pressure is 40-50MPa.

[0013] Furthermore, in step (3), the sulfiding agent is tetraethyl orthosilicate or methyl tribone oxime silane; the catalyst is dibutyltin dilaurate.

[0014] (III) Beneficial technical effects: The present invention uses p-toluenesulfonic acid as a catalyst to carry out esterification reaction of 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, hydroxypropyl silicone oil, and ethylene glycol 2-carboxyethylphenylphosphine to prepare a flame retardant, which is then added to a mixture of polystyrene and silicone rubber to obtain a modified polystyrene composite material containing flame retardant rubber.

[0015] The 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid and the flame retardant prepared therefrom contain multiple side-chain benzene ring structures, which can generate strong π-π interactions with polystyrene and have good compatibility with polystyrene. Furthermore, the double-terminated hydroxypropyl silicone oil has a similar chemical structure to silicone rubber, which allows the flame retardant to act as a compatibilizer, improving the compatibility between silicone rubber and polystyrene and giving the material better mechanical properties.

[0016] The flame retardant of the present invention contains flame-retardant phosphorus and siloxane structures, as well as a highly char-forming triphenylbenzene structure, which is beneficial to improving the char-forming ability of polystyrene and has a high limiting oxygen index and flame-retardant properties. Detailed Implementation

[0017] The following embodiments illustrate practical and currently preferred embodiments of the present invention. However, those skilled in the art will understand, in light of this disclosure, that modifications and improvements can be made within the spirit and scope of the present invention.

[0018] 2-Carboxyethylphenylphosphine glycol ester was prepared according to the method described in the article "Synthetic Study of 2-Carboxyethylphenylphosphine Glycol Ester" published in the June 2021 issue of the journal *Synthetic Technology and Application*, Volume 36, No. 2. The structural formula is as follows: .

[0019] The following dual-hydroxypropyl silicone oil, model YC-0323, with an average molecular weight of 2000, is sourced from Wuhan Yuancheng Chemical Co., Ltd. The silicone rubber is 107 silicone rubber, sourced from Jinan Juyang Chemical Technology Co., Ltd. The polystyrene is model GP33, sourced from Suzhou Tiantao Plastics Co., Ltd.

[0020] Example 1: A method for preparing a modified polystyrene composite material containing flame-retardant rubber is as follows:

[0021] S1. Add 200 mL tetrahydrofuran, 20 mL water, 60 mmol potassium carbonate, 10 mmol 3,5-dibromobiphenyl, 24 mmol 4-carboxyphenylboronic acid, and 0.36 mmol tetra(triphenylphosphine)palladium to a flask. Heat to 90 °C and reflux for 12 h under a nitrogen atmosphere. Dilute with water, then extract with dichloromethane. Dry the organic phase with anhydrous sodium sulfate, filter, and distill under reduced pressure. Wash the product with petroleum ether, then recrystallize in dichloromethane to obtain 5'-phenyl-[1,1':3',1"]-4,4''-triphenyldicarboxylic acid. The reaction formula for preparation is:

[0022] .

[0023] S2. In an ice-water bath, add 2L of N,N-dimethylformamide, 200g of hydroxypropyl silicone oil, 12.2g of ethylene glycol 2-carboxyethylphenylphosphine, 20g of 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, and 0.52g of p-toluenesulfonic acid to a flask. Stir the mixture at 110℃ for 18h, refluxing the mixture during the reaction. Then add ethanol, stir to precipitate the precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0024] S3. Mix 100g of silicone rubber, 12g of tetraethyl orthosilicate, 0.1g of dibutyltin dilaurate, 60g of flame retardant, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 300rpm. After drying, sample the mixture using an injection molding machine with a temperature of 190℃ and a pressure of 50MPa to obtain a modified polystyrene composite material containing flame-retardant rubber.

[0025] Example 2: A method for preparing a modified polystyrene composite material containing flame-retardant rubber is as follows:

[0026] S1. Add 300 mL tetrahydrofuran, 40 mL water, 80 mmol sodium carbonate, 10 mmol 3,5-dibromobiphenyl, 22 mmol 4-carboxyphenylboronic acid, and 0.48 mmol tetra(triphenylphosphine)palladium to a flask. Heat to 70 °C and reflux for 24 h under a nitrogen atmosphere. Dilute with water and extract with dichloromethane. Dry the organic phase with anhydrous sodium sulfate, filter, distill under reduced pressure, wash the product with petroleum ether, and recrystallize in dichloromethane to give 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid.

[0027] S2. In an ice-water bath, add 2.5 L N,N-dimethylformamide, 200 g hydroxypropyl silicone oil, 17 g ethylene glycol 2-carboxyethylphenylphosphine, 25 g 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, and 0.61 g p-toluenesulfonic acid to a flask. Stir the mixture at 100 °C for 24 h, refluxing during the reaction. Then add ethanol, stir to precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0028] S3. Mix 210g of silicone rubber, 4g of methyl tributanone oxime silane, 0.3g of dibutyltin dilaurate, 90g of flame retardant, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 450rpm. After drying, sample the mixture using an injection molding machine with a temperature of 200℃ and a pressure of 40MPa to obtain a modified polystyrene composite material containing flame-retardant rubber.

[0029] Example 3: A method for preparing a modified polystyrene composite material containing flame-retardant rubber is as follows:

[0030] S1. Prepare 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid according to the method of Example 1.

[0031] S2. In an ice-water bath, add 2.3 L N,N-dimethylformamide, 200 g hydroxypropyl silicone oil, 15 g ethylene glycol 2-carboxyethylphenylphosphine, 27.6 g 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, and 0.7 g p-toluenesulfonic acid to a flask. Stir the mixture at 105 °C for 22 h, refluxing during the reaction. Then add ethanol, stir to precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0032] S3. Mix 250g of silicone rubber, 8g of tetraethyl orthosilicate, 0.2g of dibutyltin dilaurate, 120g of flame retardant, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 375rpm. After drying, sample the mixture using an injection molding machine with a temperature of 190℃ and a pressure of 50MPa to obtain a modified polystyrene composite material containing flame-retardant rubber.

[0033] Example 4: A method for preparing a modified polystyrene composite material containing flame-retardant rubber is as follows:

[0034] S1. Prepare 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid according to the method of Example 1.

[0035] S2. In an ice-water bath, add 2.2 L N,N-dimethylformamide, 200 g hydroxypropyl silicone oil, 13.5 g ethylene glycol 2-carboxyethylphenylphosphine, 24 g 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, and 0.65 g p-toluenesulfonic acid to a flask. Stir the mixture at 100 °C for 21 h, refluxing during the reaction. Then add ethanol, stir to precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0036] S3. 160g of silicone rubber, 12g of methyl tributanone oxime silane, 0.2g of dibutyltin dilaurate, 150g of flame retardant, and 1kg of polystyrene were mixed evenly on a two-roll mill. The mixture was then granulated using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 350rpm. After drying, the mixture was sampled using an injection molding machine with a temperature of 200℃ and a pressure of 50MPa to obtain a modified polystyrene composite material containing flame-retardant rubber.

[0037] The difference between Comparative Example 1 and Example 1 is that no flame retardant was added:

[0038] S1. Mix 100g of silicone rubber, 12g of tetraethyl orthosilicate, 0.1g of dibutyltin dilaurate, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 300rpm. After drying, sample the mixture using an injection molding machine with a temperature of 190℃ and a pressure of 50MPa to obtain a polystyrene composite material.

[0039] The difference between Comparative Example 2 and Example 1 is the absence of 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid.

[0040] S1. In an ice-water bath, add 2L of N,N-dimethylformamide, 200g of hydroxypropyl dimethyl silicone oil, 12.2g of ethylene glycol 2-carboxyethylphenylphosphine, and 0.52g of p-toluenesulfonic acid to a flask. Stir the mixture at 110℃ for 18h, refluxing the mixture during the reaction. Then add ethanol, stir to precipitate the precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0041] S2. Mix 100g of silicone rubber, 12g of tetraethyl orthosilicate, 0.1g of dibutyltin dilaurate, 60g of flame retardant, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 300rpm. After drying, sample the mixture using an injection molding machine with a temperature of 190℃ and a pressure of 50MPa to obtain a polystyrene composite material.

[0042] The difference between Comparative Example 3 and Example 1 is that biphenyl dicarboxylic acid is used instead of 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid:

[0043] S1. In an ice-water bath, add 2L of N,N-dimethylformamide, 200g of hydroxypropyl dimethyl silicone oil, 12.2g of ethylene glycol 2-carboxyethylphenylphosphine, 20g of biphenyl dicarboxylic acid (CAS No. 787-70-2, purchased from Zibo Yujin Trading Co., Ltd.), and 0.52g of p-toluenesulfonic acid to a flask. Stir the mixture at 110℃ for 18h, refluxing the mixture during the reaction. Then add ethanol, stir to precipitate the precipitate, filter, wash the filter cake with ethanol, and dry to obtain the flame retardant.

[0044] S2. Mix 100g of silicone rubber, 12g of tetraethyl orthosilicate, 0.1g of dibutyltin dilaurate, 60g of flame retardant, and 1kg of polystyrene evenly on a two-roll mill. Granulate the mixture using a twin-screw extruder with temperatures of 150℃, 170℃, 190℃, 185℃, and 160℃ in each section and a rotation speed of 300rpm. After drying, sample the mixture using an injection molding machine with a temperature of 190℃ and a pressure of 50MPa to obtain a polystyrene composite material.

[0045] The cantilever beam impact strength of polystyrene composite materials was tested according to GB / T 1843-2008. Tensile properties were tested according to GB / T1040.1-2018. Limiting oxygen index was tested according to GB / T 2406.1-2008.

[0046] Table 1 Mechanical and flame retardant properties of polystyrene composites

[0047]

[0048] Compared to Comparative Example 1, Examples 1-4 used 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, hydroxypropyl silicone oil, and ethylene glycol 2-carboxyethylphenylphosphine to prepare flame retardants. These flame retardants were then added to a mixture of polystyrene and silicone rubber, significantly improving the mechanical and flame retardant properties of the polystyrene composite material. For example, the cantilever beam impact strength, elongation at break, and limiting oxygen index were increased. This is mainly because 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid and its prepared flame retardant contain multiple side-chain benzene ring structures, which can generate strong π-π interactions with polystyrene, resulting in good compatibility. Furthermore, the hydroxypropyl silicone oil has a similar chemical structure to silicone rubber, allowing the flame retardant to act as a compatibilizer, improving the compatibility between silicone rubber and polystyrene and giving the material better mechanical properties. Furthermore, the flame retardant contains flame-retardant phosphorus and siloxane structures, as well as highly char-forming triphenylbenzene (…). The structure is beneficial to improving the char formation ability and flame retardant properties of polystyrene, and it has a very high limiting oxygen index.

[0049] Comparative Example 2 did not add 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid, while Comparative Example 3 used biphenyldicarboxylic acid instead of 5'-phenyl-[1,1':3',1"]-4,4''-terphenyldicarboxylic acid. Neither of these flame retardants contained a large number of side-chain benzene rings, resulting in low π-π interactions with polystyrene and poor compatibility. Consequently, they were difficult to use as compatibilizers to improve the compatibility between silicone rubber and polystyrene, leading to lower impact strength and other mechanical properties in both materials. Furthermore, the flame retardants did not contain highly char-forming triphenylbenzene, resulting in weak charring ability during combustion. Both materials had low limiting oxygen indices and poor flame retardant performance.

[0050] Those skilled in the art should understand that the concepts and specific embodiments disclosed in the foregoing specification can be readily used as the basis for modifications or the design of other embodiments that achieve the same purpose as the present invention. Those skilled in the art should also understand that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.

Claims

1. A process for the preparation of a modified polystyrene composite containing a fire-retardant rubber, characterized in that, The preparation method is as follows: Step (1), in an ice water bath, a flask is added with N, N-dimethylformamide, double end hydroxypropyl silicone oil, 2-carboxyethyl phenyl phosphinic acid ethylene glycol ester, intermediate, p-toluene sulfonic acid, 100-110℃ stirring reaction for 18-24h, then added with ethanol, stirring to precipitate, filtration, washing the filter cake, drying to obtain flame retardant; Step (2), the silicone rubber, vulcanizing agent, catalyst, flame retardant are mixed uniformly on a double roller open mill, then mixed with polystyrene in a high speed mixer, granulated by a double screw extruder, dried and then molded by an injection molding machine to obtain modified polystyrene composite material containing flame retardant rubber; In step (1), the preparation method of the intermediate is as follows: a flask is added with tetrahydrofuran, water, inorganic base, 3, 5-dibromobiphenyl, 4-carboxyphenylboronic acid, tetrakis (triphenylphosphine) palladium, heated to 70-90℃ under nitrogen atmosphere, refluxed for 12-24h, extracted, washed the product, recrystallized to obtain the intermediate.

2. The process for the preparation of a modified polystyrene composite containing a fire-retardant rubber according to claim 1, characterized in that, In step (1), the ratio of double end hydroxypropyl silicone oil, 2-carboxyethyl phenyl phosphinic acid ethylene glycol ester, intermediate, p-toluene sulfonic acid is 100g: (6.1-8.5) g: (10-13.8) g: (0.26-0.35) g.

3. The process for the preparation of modified polystyrene composites containing fire- retardant rubber according to claim 1, characterized in that, The ratio of inorganic base, 3, 5-dibromobiphenyl, 4-carboxyphenylboronic acid, tetrakis (triphenylphosphine) palladium is (60-80) mmol: 10mmol: (22-24) mmol: (0.36-0.48) mmol.

4. The process for the preparation of a modified polystyrene composite containing a fire- retardant rubber according to claim 3, characterized in that, The inorganic base is sodium carbonate or potassium carbonate.

5. The process for the preparation of modified polystyrene composites containing fire retardant rubber according to claim 1, characterized in that, In step (2), the vulcanizing agent is tetraethyl orthosilicate or methyltributylketoximosilane; the catalyst is dibutyltin dilaurate.

6. The process for the preparation of modified polystyrene composites containing fire retardant rubber according to claim 1, characterized in that, In step (2), the ratio of silicone rubber, vulcanizing agent, catalyst, flame retardant, polystyrene is (10-25) g: (0.4-1.2) g: (0.01-0.03) g: (6-15) g: 100g.

7. The process for the preparation of modified polystyrene composites containing fire- retardant rubber according to claim 1, characterized in that, In step (2), the temperature of the double screw extruder is 150-190℃, and the double screw rotation speed is 300-450rpm.

8. The process for the preparation of modified polystyrene composites containing fire- retardant rubber according to claim 1, characterized in that, In step (2), the temperature of the injection molding machine is 190-200℃, and the pressure is 40-50MPa.

9. A modified polystyrene composite material containing flame retardant rubber obtained by the preparation method of any one of claims 1-8.

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