Method for producing low-chlorine high-crystallization high-melt-index polyphenylene sulfide

Abstract

The invention relates to the technical field of polyphenylene sulfide production, in particular to a method for producing low-chlorine, high-crystallinity and high-melt-index polyphenylene sulfide, which comprises the following steps: dissolving an organic matter containing a carboxyl group in a polar aprotic solvent for later use; the method comprises the following steps: adding sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and N-methyl pyrrolidone into a reaction container, uniformly stirring, and heating and dehydrating under the assistance of nitrogen; adding p-dichlorobenzene into the reaction container; carrying out primary heating reaction on the raw materials in the reaction container, then adding the standby organic matter containing the carboxyl group into the reaction container, maintaining the temperature, reacting for a period of time, and then carrying out secondary heating reaction; according to the method for producing the low-chlorine high-crystallization high-melt-index polyphenylene sulfide, carboxyl groups are introduced into the polymerization reaction, and the adding sequence and the heating mode of the raw materials are regulated and controlled, so that the reaction can be fully carried out, chlorine residues in the product are reduced, side reactions are inhibited, and the crystallization temperature of the polyphenylene sulfide is increased.

Description

Technical Field

[0001] The invention relates to the technical field of polyphenylene sulfide production, in particular to a method for producing low-chlorine, high-crystallization, high-melt index polyphenylene sulfide. Background Art

[0002] The sodium sulfide method is one of the mainstream processes for synthesizing polyphenylene sulfide (PPS). High-performance PPS exhibits excellent chemical resistance and thermal stability at high temperatures, as well as flame retardancy, insulation, radiation resistance, and good mechanical properties. In this field, high-melt-flow PPS refers to PPS with a high melt flow rate (MFR), typically used in processes requiring good fluidity, such as spray coating and injection molding.

[0003] Currently, reducing the chlorine content and increasing the crystallization temperature of high-melt-index polyphenylene sulfide (HMS) can improve its performance, making it suitable for use in electronic and electrical applications, as well as electronic packaging materials. However, existing HMS HMS generally has a high chlorine content and a low crystallization temperature. To address this issue, we propose a method for producing HMS HMS with low chlorine content and high crystallization temperature. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a method for producing low-chlorine, high-crystalline high-melt index polyphenylene sulfide. The method for producing low-chlorine, high-crystalline high-melt index polyphenylene sulfide solves the problem that the existing high-melt index polyphenylene sulfide generally has a high chlorine content and a low crystallization temperature.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for producing low-chloride, high-crystallization, high-melt-index polyphenylene sulfide comprises the following steps: Step 1: dissolving the carboxyl group-containing organic compound in a polar aprotic solvent for later use; Step 2: Add sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and N-methylpyrrolidone into the reaction vessel, stir evenly and then heat and dehydrate under nitrogen assistance; Step 3, adding p-dichlorobenzene into the reaction vessel; Step 4: performing a temperature-raising reaction on the raw materials in the reaction vessel, then adding the reserved carboxyl group-containing organic compound into the reaction vessel, maintaining the temperature for a period of time, and then performing a second temperature-raising reaction; Step 5: After cooling, the reaction slurry is released and filtered, and the filter cake is washed with deionized water, dehydrated, and dried to obtain polyphenylene sulfide.

[0006] By introducing carboxyl groups, the growth of polymer molecular chains is terminated, the end groups are stabilized and the molecular weight is controlled, and the generation of end group chlorine is reduced.

[0007] As a preferred technical solution, the temperature of the first temperature heating reaction is 225°C~235°C, and the temperature is maintained for 1 hour to 3 hours. The temperature of the second temperature heating reaction is 260°C~275°C, and the temperature is maintained for 1 hour to 3 hours.

[0008] As a preferred technical solution, the pressure of the first temperature-raising reaction is 0.3 MPa to 0.5 MPa, and the pressure of the second temperature-raising reaction is 0.8 MPa to 1.0 MPa.

[0009] As a preferred technical solution, the polar aprotic solvent is N-methylpyrrolidone.

[0010] As a preferred technical solution, the molar ratio of N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, and lithium chloride is (3-5):1:1:(0.1-0.12):(0.1-0.5).

[0011] As a preferred technical solution, the molar ratio of the sodium sulfide pentahydrate and the carboxyl group-containing organic matter is 1:0.01~0.1.

[0012] As a preferred technical solution, the carboxyl group-containing organic matter is at least one of terephthalic acid, methyl benzoic acid, 3,5-dichlorobenzoic acid, and 2,5-dichlorobenzoic acid.

[0013] As a preferred technical solution, the temperature after cooling in step five is 120°C.

[0014] As a preferred technical solution, the reaction vessel is a magnetic stirring reactor.

[0015] By means of the above technical solution, the present invention provides a method for producing low-chloride, high-crystallization, high-melt-index polyphenylene sulfide. It has at least the following beneficial effects: (1) The method for producing low-chlorine, high-crystalline high-melt index polyphenylene sulfide can fully carry out the reaction, reduce the residual chlorine in the product, inhibit the occurrence of side reactions, and increase the crystallization temperature of polyphenylene sulfide by introducing carboxyl groups into the polymerization reaction and regulating the addition sequence of raw materials and the heating method.

[0016] (2) The method for producing low-chlorine, high-crystallization, high-melt index polyphenylene sulfide comprises adding an organic substance containing a carboxyl group during the polymerization reaction. As the reaction proceeds, the substance replaces p-dichlorobenzene based on a nucleophilic substitution reaction, terminates the growth of the polymer molecular chain, stabilizes the end group, controls the molecular weight, and reduces the generation of end group chlorine. At the same time, the substance ionizes hydrogen ions, adjusts the pH value of the reaction system, and achieves the effect of increasing the high crystallization temperature of the resin. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0018] The present invention provides a method for producing low-chloride, high-crystallization, high-melt-index polyphenylene sulfide, comprising the following steps: Step 1: dissolving the carboxyl group-containing organic compound in a polar aprotic solvent for later use; Step 2: adding sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and a polar aprotic solvent to a reaction vessel, stirring evenly and then heating and dehydrating under nitrogen assistance; Step 3, adding p-dichlorobenzene into the reaction vessel; Step 4: Heat the reactor to 225°C~235°C, then add the reserved organic compound containing carboxyl groups into the reactor, maintain the temperature range for reaction for 1 hour~3 hours, the reaction pressure is 0.3MPa~0.5MPa, then heat it to 260°C~275°C for a second time, carry out a secondary reaction for 1 hour~3 hours, and the reaction pressure is 0.8MPa~1.0MPa; Step 5: Cooling the mixture to about 120° C., releasing the reaction slurry for filtration, washing the filter cake with deionized water, dehydrating, and drying to obtain a primary polyphenylene sulfide product.

[0019] In the present invention, the carboxyl group-containing organic compound refers to an organic compound that can provide a carboxyl group to the reaction, preferably benzoic acid, terephthalic acid, methylbenzoic acid, and halogenated benzoic acids such as 3,5-dichlorobenzoic acid, 2,5-dichlorobenzoic acid, and 5-chloroisophthalic acid, but not limited thereto.

[0020] In the present invention, a polar aprotic solvent is used to dissolve the reactants, preferably N-methylpyrrolidone.

[0021] The reaction vessel in the present invention refers to a magnetic stirring reactor, but is not limited thereto.

[0022] In the present invention, sodium sulfide pentahydrate is used to provide sulfur anions required for the reaction, sodium hydroxide can neutralize the crystal water in the sodium sulfide pentahydrate, adjust the system H, and inhibit the generation of side reactants; p-dichlorobenzene is used to provide a benzene ring skeleton to undergo nucleophilic substitution polycondensation with the sulfur anions.

[0023] The present invention involves adding an organic compound containing a carboxyl group during the polymerization process. As the reaction proceeds, the compound displaces p-dichlorobenzene through a nucleophilic substitution reaction, terminating the growth of the polymer molecular chain, stabilizing the end groups, controlling the molecular weight, and reducing the generation of terminal chlorine. Simultaneously, the compound ionizes hydrogen ions, regulating the H value of the reaction system, thereby increasing the high crystallization temperature of the resin.

[0024] The final product obtained by the present invention is a primary polyphenylene sulfide product. The chlorine content of the final product is less than 1200 mg / kg, and the melt index is 600-1000 g / 10 min, and the final product can be further purified.

[0025] The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will appreciate that the following examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, conventional conditions were used. Where the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0026] Example 1 The embodiment of the present invention provides a method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide, comprising the following steps: Step 1: Preparation of carboxylic acid dissolution: Calculate the amount of terephthalic acid to be added based on the molar ratio of sodium sulfide pentahydrate to terephthalic acid of 1:0.01, and then dissolve it in N-methylpyrrolidone for later use. Step 2, dehydration reaction: sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and N-methylpyrrolidone are added to a magnetic stirring reactor, stirred evenly, and then heated for dehydration under nitrogen assistance; The molar ratio of N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, and lithium chloride is 4.8:1:1:0.1:0.3; Step 3, polycondensation reaction: Calculate the amount of p-dichlorobenzene to be added, and then add it into the magnetic stirring reactor; Step 4, high temperature polymerization reaction: the magnetic stirring reactor is heated to 225 ° C, and then the spare terephthalic acid is added into the magnetic stirring reactor, and the temperature is maintained for 3 hours. The reaction pressure is 0.5 MPa, and then the temperature is raised to 260 ° C for a second time. The secondary reaction is carried out for 3 hours at a reaction pressure of 1.0 MPa; Step 5: Purification: Cooling to 120° C., releasing the reaction slurry for filtration, washing the filter cake with deionized water, dehydrating, and drying to obtain polyphenylene sulfide.

[0027] Example 2 The only difference from Example 1 is that the molar ratio of sodium sulfide pentahydrate to terephthalic acid is 1:0.1, and the other reaction conditions are the same.

[0028] Example 3 The only difference from Example 1 is that the molar ratio of N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, and lithium chloride is 3:1:1:0.12:0.1, and other reaction conditions are the same.

[0029] Example 4 The only difference from Example 1 is that the molar ratio of N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, and lithium chloride is 5:1:1:0.12:0.5, and the other reaction conditions are the same.

[0030] Example 5 The only difference from Example 1 is that methyl benzoic acid is used as the organic compound containing a carboxyl group, and the other reaction conditions are the same.

[0031] Example 6 The only difference from Example 1 is that the carboxyl group-containing organic compound uses 3,5-dichlorobenzoic acid, and the other reaction conditions are the same.

[0032] Example 7 The only difference from Example 1 is that the carboxyl group-containing organic compound uses 2,5-dichlorobenzoic acid, and the other reaction conditions are the same.

[0033] Comparative Example 1 The only difference from Example 1 is that the carboxyl group-containing organic matter, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and N-methylpyrrolidone are simultaneously added to the reaction vessel for reaction, and other reaction conditions are the same.

[0034] Specifically, the following steps are included: Step 1: Preparation of carboxylic acid dissolution: Calculate the amount of terephthalic acid to be added based on the molar ratio of sodium sulfide pentahydrate to terephthalic acid of 1:0.01, and then dissolve it in N-methylpyrrolidone for later use. Step 2, dehydration and polycondensation reaction: sodium sulfide pentahydrate, sodium hydroxide, lithium chloride, N-methylpyrrolidone, p-dichlorobenzene and spare terephthalic acid are added to the reaction vessel, stirred evenly, and then heated for dehydration under nitrogen assistance; The molar ratio of N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide, and lithium chloride is 4.8:1:1:0.1:0.3; Step 3: High temperature polymerization reaction: heat the reaction vessel to 225°C and maintain the temperature range for 3 hours at a pressure of 0.5 MPa. Then heat the vessel to 260°C for a second time and carry out a secondary reaction for 3 hours at a pressure of 1.0 MPa. Step 5: Purification: Cooling to 120° C., releasing the reaction slurry for filtration, washing the filter cake with deionized water, dehydrating, and drying to obtain polyphenylene sulfide.

[0035] Comparative Example 2 The only difference from Example 1 is that the second temperature-raising reaction step is omitted, and other reaction conditions are the same.

[0036] The products of Examples 1 to 7 and Comparative Examples 1 to 2 were sampled respectively, and then the chlorine content, crystallization temperature and melt index of the products were measured under the same conditions.

[0037] The chlorine content was measured by ion chromatography.

[0038] The crystallization temperature was measured by differential scanning calorimetry (DSC).

[0039] The melt index is measured by a melt indexer.

[0040] The following table is obtained: Combined with the test results of Examples 1 to 4, it can be seen that as long as the molar ratio of the raw materials is controlled within a reasonable range, it has little effect on the chlorine content, crystallization temperature and melt index of the final product.

[0041] Combining the test results of Example 1 and Examples 5 to 7, it can be seen that the range of carboxyl group-containing organic matter that can be selected is relatively wide, and ultimately good results can be obtained. Among them, the carboxyl group-containing organic matter used in Example 6 is 3,5-dichlorobenzoic acid, and the chlorine content in the obtained product is relatively high. The possible reason is that the dichloro substituent in 3,5-dichlorobenzoic acid is directly embedded in the polymer side chain, resulting in residual chlorine.

[0042] Combining the test results of Example 1 and Comparative Example 1, it can be seen that the order of adding the raw materials has a great influence on the chlorine content and crystallization temperature of the final product. The reason for this is that in Comparative Example 1, the raw materials are added to the reaction vessel at one time, and then dehydration and polymerization reactions are carried out. Compared with Example 1, sodium sulfide pentahydrate is not fully dehydrated, resulting in a large amount of chlorine residue during the hydrolysis of dichlorobenzene. The subsequent hydrolysis by-products participate in the polycondensation reaction, resulting in the destruction of the molecular chain structure and a significant decrease in the crystallization temperature.

[0043] Combining the test results of Example 1 and Comparative Example 2, it can be seen that the reaction heating mode has a great influence on the chlorine content and crystallization temperature of the final product. The reason for this is that the reaction temperature in Comparative Example 2 is lower, and compared with the example, the reaction activity of p-dichlorobenzene is insufficient, resulting in an increase in the chlorine content. At the same time, the low-temperature reaction is not sufficient, which affects the crystallization temperature of the final product.

[0044] Combining the test results of Examples 1 to 7 and Comparative Examples 1 to 2, it can be seen that the two-stage heating method, sufficient reaction temperature, and step-by-step addition of raw materials play a key role in the chlorine content and crystallization temperature of the final product.

[0045] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0046] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing low-chloride, high-crystalline, high-melt index polyphenylene sulfide, characterized in that: The following steps are involved: Step 1: dissolving the carboxyl group-containing organic compound in a polar aprotic solvent for later use; Step 2: Add sodium sulfide pentahydrate, sodium hydroxide, lithium chloride and N-methylpyrrolidone into the reaction vessel, stir evenly and then heat and dehydrate under nitrogen assistance; Step 3, adding p-dichlorobenzene into the reaction vessel; Step 4: performing a temperature-raising reaction on the raw materials in the reaction vessel, then adding the reserved carboxyl group-containing organic compound into the reaction vessel, maintaining the temperature for a period of time, and then performing a second temperature-raising reaction; Step 5: After cooling, the reaction slurry is released and filtered, and the filter cake is washed with deionized water, dehydrated, and dried to obtain polyphenylene sulfide.

2. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The temperature of the first temperature-raising reaction is 225° C. to 235° C., and the temperature is maintained for 1 to 3 hours. The temperature of the second temperature-raising reaction is 260° C. to 275° C., and the temperature is maintained for 1 to 3 hours.

3. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The pressure of the first temperature-raising reaction is 0.3 MPa to 0.5 MPa, and the pressure of the second temperature-raising reaction is 0.8 MPa to 1.0 MPa.

4. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The polar aprotic solvent is N-methylpyrrolidone.

5. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 4, characterized in that: The molar ratio of the N-methylpyrrolidone, p-dichlorobenzene, sodium sulfide pentahydrate, sodium hydroxide and lithium chloride is (3-5):1:1:(0.1-0.12):(0.1-0.5).

6. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The molar ratio of the sodium sulfide pentahydrate and the carboxyl group-containing organic matter is 1:0.01-0.

1.

7. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The carboxyl group-containing organic matter is at least one of terephthalic acid, methyl benzoic acid, 3,5-dichlorobenzoic acid, and 2,5-dichlorobenzoic acid.

8. The method for producing low-chloride, high-crystallization, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The temperature after cooling in step 5 is 120°C.

9. The method for producing low-chloride, high-crystalline, high-melt-index polyphenylene sulfide according to claim 1, characterized in that: The reaction vessel is a magnetic stirring reactor.

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