A polyphenylene sulfide resin and its preparation method

Abstract

This invention belongs to the field of resin preparation technology, specifically relating to a polyphenylene sulfide resin and its preparation method. The preparation method includes the following steps: a composite stabilizer, anhydrous sodium sulfide, and a polar solvent are first mixed; the resulting first mixture undergoes a dehydration reaction to obtain a dehydrated reaction solution; the dehydrated reaction solution is then mixed with p-dichlorobenzene; the resulting second mixture undergoes prepolymerization and postpolymerization sequentially to obtain the polyphenylene sulfide resin; the composite stabilizer includes carbodiimide having the structure of formula I, lithium chloride, and sodium hydroxide; R 1 -(N=C=N) n -R 2 Equation I; n is an integer from 1 to 20; R 1 and R 2 The polymer is independently selected from substituted or unsubstituted alkyl, cycloalkyl, aryl, or aralkyl groups. The composite stabilizer in this invention effectively inhibits excessive hydrolysis by polar solvents, improves reaction efficiency, and controls the polymer molecular structure, thereby obtaining high molecular weight, high yield, and high whiteness PPS resin.

Description

Technical Field

[0001] This invention belongs to the field of resin preparation technology, specifically relating to a polyphenylene sulfide resin and its preparation method. Background Technology

[0002] Polyphenylene sulfide (PPS) is a thermoplastic engineering plastic whose main chain consists of alternating benzene rings and sulfur atoms. It has a highly regular molecular structure and excellent mechanical and chemical properties. For example, it possesses high mechanical strength, high temperature resistance, chemical corrosion resistance (second only to polytetrafluoroethylene), flame retardancy, and excellent electrical insulation properties. Furthermore, PPS exhibits excellent processing performance, low molding shrinkage, radiation resistance, and good dimensional stability. Based on these superior properties, PPS is widely used in the automotive industry, machinery equipment, chemical industry, and electronics.

[0003] Currently, the most common industrial method for preparing PPS is the sodium sulfide method. This method uses sodium sulfide and p-dichlorobenzene as raw materials, and carries out a polycondensation reaction under high temperature and high pressure in a polar solvent (N-methylpyrrolidone). However, when N-methylpyrrolidone is used as a solvent in this process, it will undergo hydrolysis under high temperature and alkaline conditions, which easily leads to solvent loss, the generation of by-products, and affects the stability of the reaction system. This, in turn, results in incomplete PPS reaction (low PPS yield) and a decrease in molecular weight. Summary of the Invention

[0004] The purpose of this invention is to provide a polyphenylene sulfide resin and its preparation method. The preparation method provided by this invention can effectively inhibit excessive hydrolysis of polar solvents, improve reaction efficiency, and increase the yield of PPS.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing polyphenylene sulfide resin, comprising the following steps: The composite stabilizer, anhydrous sodium sulfide and polar solvent are mixed in the first mixture, and the resulting first mixture is subjected to a dehydration reaction to obtain a dehydration reaction solution. The dehydrated reaction solution and p-dichlorobenzene were mixed, and the resulting second mixture was subjected to prepolymerization and postpolymerization in sequence to obtain polyphenylene sulfide resin. The composite stabilizer includes carbodiimide having the structure of Formula I, lithium chloride, and sodium hydroxide; R 1 -(N=C=N) n -R 2 Equation I; n is an integer from 1 to 20; R 1 and R 2 It is independently selected from substituted or unsubstituted alkyl, cycloalkyl, aryl or aralkyl groups.

[0006] Preferably, the carbodiimide is one or more of poly(4,4'-diphenylmethane carbodiimide), poly(1,6-hexamethylene carbodiimide), poly(cyclohexyl carbodiimide), N,N'-diisopropyl carbodiimide, and N,N'-dicyclohexyl carbodiimide.

[0007] Preferably, the composite stabilizer is obtained by mixing a carbodiimide having the structure of Formula I, a solution of lithium chloride, and a solution of sodium hydroxide; the polar solvent includes N-methylpyrrolidone; and the mass ratio of the composite stabilizer to the polar solvent is 1:(1~6).

[0008] Preferably, the molar ratio of carbodiimide to lithium chloride in the composite stabilizer is (0.1~1):(1~2); the molar ratio of sodium hydroxide to lithium chloride in the composite stabilizer is (2~4):(1~2).

[0009] Preferably, the molar ratio of anhydrous sodium sulfide to p-dichlorobenzene is (1~1.2):(1~1.5).

[0010] Preferably, the temperature of the dehydration reaction is 110~130℃; the temperature of the dehydration reaction is 2~3h.

[0011] Preferably, the prepolymerization temperature is 160~240℃, and the prepolymerization time is 2~4h.

[0012] Preferably, the post-polymerization temperature is 240~280℃, and the post-polymerization time is 3~5h.

[0013] Preferably, the first mixing, dehydration reaction, second mixing, prepolymerization, and postpolymerization are all carried out under a protective atmosphere.

[0014] The present invention also provides a polyphenylene sulfide resin prepared by the above-described preparation method, wherein the polyphenylene sulfide resin has a number-average molecular weight of 36,000 to 60,000, a molecular weight distribution index of 2.2 to 5.7, and a whiteness of 81 to 87.

[0015] This invention provides a method for preparing polyphenylene sulfide resin, comprising the following steps: first mixing a composite stabilizer, anhydrous sodium sulfide, and a polar solvent; subjecting the resulting first mixture to a dehydration reaction to obtain a dehydrated reaction solution; second mixing the dehydrated reaction solution with p-dichlorobenzene; and subjecting the resulting second mixture to prepolymerization and postpolymerization sequentially to obtain the polyphenylene sulfide resin; wherein the composite stabilizer comprises carbodiimide having the structure of formula I, lithium chloride, and sodium hydroxide; R 1 -(N=C=N) n -R 2 Equation I; n is an integer from 1 to 20; R 1 and R2 The polymer is independently selected from substituted or unsubstituted alkyl, cycloalkyl, aryl, or aralkyl groups. The composite stabilizer in this invention effectively inhibits excessive hydrolysis by polar solvents, improves reaction efficiency, and controls the polymer molecular structure, thereby obtaining high molecular weight, high yield, and high whiteness PPS resin. Compared with existing technologies, this invention can improve the yield and quality of polyphenylene sulfide resin, reduce preparation costs, and reduce environmental pollution, possessing significant industrial application value and market prospects. Detailed Implementation

[0016] This invention provides a method for preparing polyphenylene sulfide resin, comprising the following steps: The composite stabilizer, anhydrous sodium sulfide and polar solvent are mixed in the first mixture, and the resulting first mixture is subjected to a dehydration reaction to obtain a dehydration reaction solution. The dehydrated reaction solution and p-dichlorobenzene were mixed, and the resulting second mixture was subjected to prepolymerization and postpolymerization in sequence to obtain polyphenylene sulfide resin.

[0017] In this invention, a composite stabilizer, anhydrous sodium sulfide, and a polar solvent are first mixed, and the resulting first mixture is subjected to a dehydration reaction to obtain a dehydration reaction solution.

[0018] In one embodiment of the present invention, the composite stabilizer comprises carbodiimide having the structure of Formula I, lithium chloride, and sodium hydroxide; R 1 -(N=C=N) n -R 2 Equation I; n is an integer from 1 to 20; R 1 and R 2 It is independently a substituted or unsubstituted alkyl, cycloalkyl, aryl or aralkyl group.

[0019] In one embodiment of the present invention, the composite stabilizer is obtained by mixing a carbodiimide having the structure of Formula I, a lithium chloride solution, and a sodium hydroxide solution; the mass concentration of the lithium chloride solution can be 30-60%; the mass concentration of the sodium hydroxide solution can be 40%-60%, specifically 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, or 60%; the mass ratio of the composite stabilizer to the polar solvent is 1:(1-6).

[0020] In one embodiment of the present invention, the carbodiimide is selected from one or more of poly(4,4'-diphenylmethane carbodiimide), poly(1,6-hexamethylene carbodiimide), poly(cyclohexyl carbodiimide), N,N'-diisopropyl carbodiimide, and N,N'-dicyclohexyl carbodiimide.

[0021] In one embodiment of the present invention, the molar ratio of carbodiimide to lithium chloride in the composite stabilizer can be (0.1~1):(1~2), specifically 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 1:1, 0.1:2, 0.2:2, 0.3:2, 0.4:2, 0.5:2, or 1:2; the molar ratio of sodium hydroxide to lithium chloride in the composite stabilizer can be (2~4):( 1~2), specifically, can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 4.0:1, 2.0:2, 2.1:2, 2.2:2, 2.3:2, 2.4:2, 2.5:2, 2.6:2, 2.7:2, 2.8:2, 2.9:2, 3.0:2, or 4.0:2. The mass ratio of the carbodiimide to the polar solvent is 1:(1~5). In one embodiment of the present invention, the molar ratio of anhydrous sodium sulfide to p-dichlorobenzene can be (1~1.2):(1~1.5), specifically 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1.2:1, 1.2:1.1, 1.2:1.3, 1.2:1.4 or 1.2:1.5.

[0022] In one embodiment of the present invention, the dehydration temperature can be 110~130℃, specifically 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃ or 130℃; the dehydration time can be 2~3h, specifically 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h.

[0023] After obtaining the dehydrated reaction solution, the present invention mixes the dehydrated reaction solution with p-dichlorobenzene, and the resulting second mixture is subjected to prepolymerization and postpolymerization in sequence to obtain polyphenylene sulfide resin.

[0024] In one embodiment of the present invention, the molar ratio of anhydrous sodium sulfide to p-dichlorobenzene can be (0.4~1):1, specifically 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1 or 1:1.

[0025] In one embodiment of the present invention, the prepolymerization temperature is 160~240℃, specifically 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃ or 240℃; the prepolymerization temperature time is 2~4h, specifically 2.0h, 2.3h, 2.6h, 2.9h, 3.2h, 3.5h, 3.8h or 4.0h.

[0026] In one embodiment of the present invention, the post-polymerization temperature can be 240~280℃, specifically 240℃, 245℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃ or 280℃; the post-polymerization time can be 3~5h, specifically 3.0h, 3.3h, 3.6h, 3.9h, 4.2h, 4.5h, 4.8h or 5.0h.

[0027] In one embodiment of the present invention, the first mixing, dehydration reaction, second mixing, prepolymerization and postpolymerization are all carried out under a protective atmosphere; the protective atmosphere may be nitrogen.

[0028] The present invention also provides a polyphenylene sulfide resin prepared by the preparation method described above, which has a weight-average molecular weight of 36,000 to 60,000, a molecular weight distribution index of 2.2 to 5.7, and a whiteness of 81 to 87.

[0029] To further illustrate the present invention, the following detailed description of the embodiments is provided in conjunction with the present invention, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 The feedstock consisted of anhydrous sodium sulfide / p-dichlorobenzene / N-methylpyrrolidone / N,N'-diisopropylcarbodiimide / lithium chloride / sodium hydroxide = 9 mol / 9.5 mol / 35 mol / 1.5 mol / 1.5 mol / 4.5 mol. First, diisopropylcarbodiimide, lithium chloride solution (45 wt.%), and sodium hydroxide solution (48 wt.%) were added to a reactor and mixed thoroughly. Then, anhydrous sodium sulfide and N-methylpyrrolidone were added. The air in the reactor was purged with nitrogen, and 0.5 MPa of nitrogen gas was injected. A dehydration reaction was carried out at 120°C for 2 hours. Subsequently, p-dichlorobenzene was added, and the air in the reactor was purged with nitrogen. A prepolymerization reaction was carried out at 225°C for 3 hours. Finally, a post-polymerization reaction was carried out at 260°C. After the reaction was completed, the obtained polyphenylene sulfide resin was washed and treated to obtain white granular polyphenylene sulfide resin.

[0031] Example 2 The feedstock consisted of anhydrous sodium sulfide / p-dichlorobenzene / N-methylpyrrolidone / N,N'-diisopropylcarbodiimide / lithium chloride / sodium hydroxide = 9 mol / 9.5 mol / 35 mol / 1.2 mol / 1.5 mol / 4.5 mol. First, diisopropylcarbodiimide, lithium chloride solution (45 wt.%), and sodium hydroxide solution (48 wt.%) were added to a reactor and mixed thoroughly. Then, anhydrous sodium sulfide and N-methylpyrrolidone were added. The air in the reactor was purged with nitrogen, and 0.5 MPa of nitrogen gas was injected. A dehydration reaction was carried out at 120°C for 2 hours. Subsequently, p-dichlorobenzene was added, and the air in the reactor was purged with nitrogen. A prepolymerization reaction was carried out at 225°C for 3 hours. Finally, a post-polymerization reaction was carried out at 260°C. After the reaction was completed, the obtained polyphenylene sulfide resin was washed and treated to obtain white granular polyphenylene sulfide resin.

[0032] Example 3 The feedstock consisted of anhydrous sodium sulfide / p-dichlorobenzene / N-methylpyrrolidone / N,N'-diisopropylcarbodiimide / lithium chloride / sodium hydroxide = 9 mol / 9.5 mol / 35 mol / 0.9 mol / 1.5 mol / 4.5 mol. First, diisopropylcarbodiimide, lithium chloride solution (45 wt.%), and sodium hydroxide solution (48 wt.%) were added to a reactor and mixed thoroughly. Then, anhydrous sodium sulfide / N-methylpyrrolidone was added, the air in the reactor was purged with nitrogen, and 0.5 MPa of nitrogen gas was injected into the reactor. A dehydration reaction was carried out at 120°C for 2 hours. Subsequently, p-dichlorobenzene was added, and the air in the reactor was purged with nitrogen. A prepolymerization reaction was carried out at 225°C for 3 hours. Finally, a post-polymerization reaction was carried out at 260°C. After the reaction was completed, the obtained polyphenylene sulfide resin was washed and treated to obtain white granular polyphenylene sulfide resin.

[0033] Example 4 The feedstock consisted of anhydrous sodium sulfide / p-dichlorobenzene / N-methylpyrrolidone / N,N'-diisopropylcarbodiimide / lithium chloride / sodium hydroxide = 9 mol / 9.5 mol / 35 mol / 0.6 mol / 1.5 mol / 4.5 mol. First, diisopropylcarbodiimide, lithium chloride solution (45 wt.%), and sodium hydroxide solution (48 wt.%) were added to a reactor and mixed thoroughly. Then, anhydrous sodium sulfide / N-methylpyrrolidone was added, and the air in the reactor was purged with nitrogen. A nitrogen atmosphere of 0.5 MPa was then injected into the reactor. The dehydration reaction was carried out at 120°C for 2 hours. Subsequently, p-dichlorobenzene was added, and the air in the reactor was purged with nitrogen. A prepolymerization reaction was carried out at 225°C for 3 hours. Finally, a post-polymerization reaction was carried out at 260°C. After the reaction was completed, the obtained polyphenylene sulfide resin was washed and treated to obtain white granular polyphenylene sulfide resin.

[0034] Comparative Example 1 The feedstock consisted of anhydrous sodium sulfide / p-dichlorobenzene / N-methylpyrrolidone / lithium chloride / sodium hydroxide = 9 mol / 9.5 mol / 35 mol / 1.5 mol / 4.5 mol. First, lithium chloride solution (45 wt.%) and sodium hydroxide solution (48 wt.%) were added to the reactor and mixed thoroughly. Then, anhydrous sodium sulfide and N-methylpyrrolidone were added. The air in the reactor was purged with nitrogen, and 0.5 MPa of nitrogen gas was injected. A dehydration reaction was carried out at 120°C for 2 hours. Subsequently, p-dichlorobenzene was added, and the air in the reactor was purged with nitrogen. A prepolymerization reaction was carried out at 225°C for 3 hours. Finally, a post-polymerization reaction was carried out at 260°C. After the reaction was completed, the obtained polyphenylene sulfide resin was washed and treated to obtain white granular polyphenylene sulfide resin.

[0035] The present invention tested and calculated the molecular weight and molecular weight distribution index (PD), whiteness, and PPS yield of the products of the examples and comparative examples. The testing and calculation methods are as follows: molecular weight and molecular weight distribution index were tested by high-temperature gel permeation chromatography; whiteness was tested by a whiteness meter; the yield of polyphenylene sulfide resin = actual total product mass / theoretically obtainable total product mass. 100%, results are shown in Table 1.

[0036] Table 1. Statistical data of the products from the examples and comparative examples.

[0037] The comparison between the above examples and comparative examples shows that the yield of polyphenylene sulfide resin increased from 78% to 95% with the addition of the composite stabilizer. This demonstrates that the composite stabilizer can effectively inhibit excessive solvent hydrolysis, improve reaction efficiency, and thus obtain high molecular weight polyphenylene sulfide resin. Furthermore, the effect of the composite stabilizer gradually strengthens with increasing amounts of diisopropylcarbodiimide; however, excessive amounts can over-inhibit NMP hydrolysis, which is detrimental to the reaction.

[0038] In summary, this invention develops a polyphenylene sulfide resin with high yield, high molecular weight, and high whiteness through composite stabilizers, meeting the needs of high-end applications such as fiber grade and electronic grade.

[0039] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyphenylene sulfide resin, comprising the following steps: The composite stabilizer, anhydrous sodium sulfide and polar solvent are mixed in the first mixture, and the resulting first mixture is subjected to a dehydration reaction to obtain a dehydration reaction solution. The dehydrated reaction solution and p-dichlorobenzene were mixed, and the resulting second mixture was subjected to prepolymerization and postpolymerization in sequence to obtain polyphenylene sulfide resin. The composite stabilizer includes carbodiimide having the structure of Formula I, lithium chloride, and sodium hydroxide; R 1 -(N=C=N) n -R 2 Equation I; n is an integer from 1 to 20; R 1 and R 2 It is independently selected from substituted or unsubstituted alkyl, cycloalkyl, aryl or aralkyl groups.

2. The preparation method according to claim 1, characterized in that, The carbodiimide is one or more of poly(4,4'-diphenylmethane carbodiimide), poly(1,6-hexamethylene carbodiimide), poly(cyclohexyl carbodiimide), N,N'-diisopropyl carbodiimide, and N,N'-dicyclohexyl carbodiimide.

3. The preparation method according to claim 1, characterized in that, The composite stabilizer is obtained by mixing a carbodiimide having the structure of Formula I, a solution of lithium chloride, and a solution of sodium hydroxide; the polar solvent includes N-methylpyrrolidone; the mass ratio of the composite stabilizer to the polar solvent is 1:(1~6).

4. The preparation method according to claim 1, characterized in that, The molar ratio of carbodiimide to lithium chloride in the composite stabilizer is (0.1~1):(1~2); the molar ratio of sodium hydroxide to lithium chloride in the composite stabilizer is (2~4):(1~2).

5. The preparation method according to claim 1, characterized in that, The molar ratio of anhydrous sodium sulfide to p-dichlorobenzene is (1~1.2):(1~1.5).

6. The preparation method according to any one of claims 1 to 4, characterized in that, The dehydration reaction is carried out at a temperature of 110~130℃ for 2~3 hours.

7. The preparation method according to claim 1, characterized in that, The prepolymerization temperature is 160~240℃, and the prepolymerization time is 2~4h.

8. The preparation method according to claim 1, characterized in that, The post-polymerization temperature is 240~280℃, and the post-polymerization time is 3~5h.

9. The preparation method according to claim 1, 7 or 8, characterized in that, The first mixing, dehydration reaction, second mixing, prepolymerization, and postpolymerization were all carried out under a protective atmosphere.

10. The polyphenylene sulfide resin prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The polyphenylene sulfide resin has a number-average molecular weight of 36,000 to 60,000, a molecular weight distribution index of 2.2 to 5.7, and a whiteness of 81 to 87.

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