JP2021130792A - Method for producing polyarylene sulfide - Google Patents

Abstract

To provide a method for producing a high molecular weight polyarylene sulfide.SOLUTION: There is provided a method for producing a polyarylene sulfide via the following steps 1 and 2. Step 1: a step of heating a reaction mixture (A) containing at least a sulfidation agent, a dihalogenated aromatic compound and an organic polar solvent as raw material components to generate a polyarylene sulfide. Step 2: a step of cooling a reaction liquid containing the polyarylene sulfide obtained in the step 1 to less than the boiling point of the organic polar solvent, followed by re-heating at the boiling point of the organic polar solvent or more and 225°C or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a high molecular weight polyarylene sulfide.

Polyphenylene sulfide (hereinafter abbreviated as PPS) represented by polyphenylene sulfide (hereinafter abbreviated as PAS) has heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical insulation, moisture heat resistance, dimensional stability, etc. It is an excellent engineering plastic and can be molded into various molded products, films, sheets, fibers, etc. by various molding methods such as injection molding, extrusion molding and compression molding, so it can be molded in a wide range of electrical / electronic equipment and automobile equipment. Widely used in the field.

As a method for producing PAS, Patent Document 1 describes that a sulfidizing agent such as sodium sulfide is reacted with a dihalogenated aromatic compound such as p-dichlorobenzene in an organic amide solvent such as N-methyl-2-pyrrolidone. A method has been proposed.

Further, in order to obtain a high molecular weight PAS at the time of polymerization, various production methods improved from the above methods have been proposed. As a typical method, a method of adding various polymerization aids when reacting a sulfidizing agent with a dihalogenated aromatic compound in an organic amide solvent is typical. For example, an alkali metal carboxylic acid as a polymerization aid. A method using a salt (Patent Document 2), a method using a sodium salt of an aliphatic carboxylic acid (Patent Document 3), and the like have been proposed.

Further, as another method for obtaining a high molecular weight PAS at the time of polymerization, Patent Document 4 proposes a method of adopting a specific two-step polymerization method. In this method, in the prepolymerization step, the dihalogenated aromatic compound is reacted by reacting at a temperature of 180 to 235 ° C. in the presence of 0.5 to 2.4 mol of water per 1 mol of the charged sulfidizing agent. After producing a low-viscosity prepolymer with a conversion rate of 50 to 98 mol%, the reaction system is in a state where 2.5 to 7 mol of water is present per 1 mol of the charged sulfidizing agent in the subsequent polymerization step. It has been proposed to add water to the polymer and raise the temperature to a temperature of 245 to 290 ° C. to continue the reaction.

Special Publication No. 45-3368 Special Publication No. 52-12240 Japanese Unexamined Patent Publication No. 1-161022 Special Publication No. 63-33775

The method described in Patent Document 1 is a method widely used as an industrial production method of PAS, but this method can only obtain PAS having a low molecular weight and a low melt viscosity. Such a low molecular weight PAS can be increased in molecular weight by heating in the presence of air after polymerization and oxidatively curing (curing), but the cured PAS thus obtained has poor mechanical properties. It was difficult to mold into sheets, films, fibers, etc. because it was sufficient and not linear.

The methods described in Patent Documents 2 and 3 can certainly obtain linear and high molecular weight PAS by polymerization, but it is necessary to carry out polymerization using a polymerization aid such as sodium acetate or sodium benzoate. .. Further, this method requires ancillary equipment for separating and recovering the polymerization aid at the time of PAS recovery after the polymerization reaction and a large amount of cost, and there is room for economic improvement.

Since the method described in Patent Document 4 heats to a high temperature in the presence of a large amount of water, equipment corresponding to a high pressure is required, and a considerably long time is required to obtain a sufficiently high molecular weight PAS. This method has room for improvement because it requires a polymerization time of.

That is, it is an object of the present invention to easily provide a high molecular weight polyarylene sulfide resin.

The present invention employs the following means in order to solve such a problem.

That is, the present invention
[1] A method for producing polyarylene sulfide, which undergoes the following steps 1 and 2.
Step 1: A step of heating a reaction mixture (A) containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent as raw material components to generate polyarylene sulfide.
Step 2: A step of cooling the reaction solution containing the polyarylene sulfide obtained in Step 1 to less than the boiling point of the organic polar solvent, and then reheating at 225 ° C. or higher than the boiling point of the organic polar solvent.
[2] The method for producing a polyarylene sulfide according to the above [1], wherein the conversion rate of the dihalogenated aromatic compound is 90% or more in the step 1.
[3] The polyarylene sulfide according to the above [1] or [2], wherein the amount of the organic polar solvent used per mol of the sulfur atom of the sulfidizing agent is in the range of 2.0 mol or more and 6.0 mol or less. Production method.
[4] Any of [1] to [3], wherein the ratio of the weight average molecular weight of the polyarylene sulfide produced in the step 2 to the weight average molecular weight of the polyarylene sulfide produced in the step 2 is more than 1.0 times. The method for producing polyarylene sulfide according to the above.

According to the present invention, a high molecular weight polyarylene sulfide resin can be easily provided.

Hereinafter, embodiments of the present invention will be described.

Regarding the method for producing PAS in the present invention, polyarylene sulfide is first described, and then, a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent, a branching / cross-linking agent, a molecular weight adjusting agent, a polymerization step, a polymer recovery, Other post-treatments and applications of polyarylene sulfide will be described in detail in this order.

(1) Polyarylene sulfide The polyarylene sulfide in the present invention is a compound having a repeating unit of the formula − (Ar—S) − as a main constituent unit, and is preferably a linear compound containing 80 mol% or more of the repeating unit. Is a homopolymer or copolymer of. As Ar, there are units represented by the following formulas (A) to (L), and the formula (A) is particularly preferable.

(However, R1 and R2 in the formula are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group, and R1 and R2 are the same but different. May be good.)

As long as this repeating unit is used as the main constituent unit, a small amount of branching units or cross-linking units represented by the following formulas (M) to (P) and the like can be included. The copolymerization amount of these branching units or cross-linking units is preferably in the range of 0 to 1 mol% with respect to 1 mol of the main constituent unit represented by − (Ar—S) −.

Further, the polyarylene sulfide in the embodiment of the present invention may be any of a random copolymer containing the above repeating unit, a block copolymer and a mixture thereof.

Typical examples thereof include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers thereof, block copolymers thereof and mixtures thereof. Particularly preferred PAS is the p-phenylene sulfide unit as the main building block of the polymer.

Examples thereof include polyphenylene sulfide (hereinafter, may be abbreviated as PPS), polyphenylene sulfide sulfone, and polyphenylene sulfide ketone, which contain 80 mol% or more, preferably 90 mol% or more.

(2) Sulfidating agent The sulfidizing agent used in the preferred embodiment of the present invention may be any one capable of introducing a sulfide bond into the dihalogenated aromatic compound, for example, alkali metal sulfide, alkali metal hydrosulfide, and the like. And hydrogen sulfide.

Specific examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and a mixture of two or more thereof. Of these, lithium sulfide and / or sodium sulfide are preferable, and sodium sulfide is more preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures, or in the form of anhydrides. The aqueous mixture refers to an aqueous solution, a mixture of an aqueous solution and a solid component, or a mixture of water and a solid component. Since generally available inexpensive alkali metal sulfides are hydrates or aqueous mixtures, it is preferable to use such forms of alkali metal sulfides.

Specific examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and a mixture of two or more thereof. Of these, lithium hydrosulfide and / or sodium hydrosulfide are preferable, and sodium hydrosulfide is more preferably used.

Further, an alkali metal sulfide produced in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. It is also possible to use an alkali metal sulfide prepared in advance by bringing the alkali metal hydrosulfide and the alkali metal hydroxide into contact with each other. These alkali metal hydrosulfides and alkali metal hydroxides can be used in the form of compounds selected from hydrates, aqueous mixtures, and anhydrides. Hydrate or aqueous mixture is preferred from the standpoint of availability and cost.

Further, alkali metal sulfides produced in the reaction system from alkali metal hydroxides such as lithium hydroxide and sodium hydroxide and hydrogen sulfide can also be used. Further, an alkali metal sulfide prepared in advance by contacting an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide with hydrogen sulfide can also be used. Hydrogen sulfide may be used in any form of gaseous, liquid, and aqueous solution.

In a preferred embodiment of the present invention, the amount of the sulfidizing agent means a residual amount obtained by subtracting the loss amount from the actual charged amount when a partial loss of the sulfidizing agent occurs before the start of the reaction due to a dehydration operation or the like. It shall be.

It is also possible to use an alkali metal hydroxide and / or an alkaline earth metal hydroxide in combination with the sulfidizing agent. Specific examples of the alkali metal hydroxide include, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture of two or more thereof. Specific examples of the alkaline earth metal hydroxide include calcium hydroxide, strontium hydroxide, barium hydroxide and the like, and sodium hydroxide is preferably used.

When alkali metal hydrosulfide is used as the sulfidizing agent, it is particularly preferable to use alkali metal hydroxide at the same time. In this case, the amount of the alkali metal hydroxide used can be 0.95 mol or more, preferably 1.00 mol or more, and more preferably 1.005 mol with respect to 1 mol of the alkali metal hydrosulfide. That is all. Further, it can be 5.0 mol or less, preferably 4.5 mol or less, and more preferably 4.0 mol or less. When hydrogen sulfide is used as the sulfidizing agent, it is particularly preferable to use an alkali metal hydroxide at the same time. In this case, the amount of the alkali metal hydroxide used can be 2.0 mol or more, preferably 2.01 mol or more, and more preferably 2.04 mol or more with respect to 1 mol of hydrogen sulfide. .. Further, it can be 6.0 mol or less, preferably 5.5 mol or less, and more preferably 5.0 mol or less.

(3) Dihalogenated Aromatic Compound The dihalogenated aromatic compound used in the preferred embodiment of the present invention is an aromatic compound having an arylene group which is a divalent group of an aromatic ring and two halogeno groups. .. One mole of a dihalogenated aromatic compound has 1 mole of an arylene unit and 2 moles of a halogeno group. For example, as a compound having a phenylene group which is a divalent group of a benzene ring as an arylene group and having two halogeno groups, p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene and o-dibromo Benzene, m-dibromobenzene, 1-bromo-4-chlorobenzene, and dihalogenated benzene such as 1-bromo-3-chlorobenzene can be mentioned. Further, examples of the dihalogenated aromatic compound include 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-dichlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene and 1,3-dimethyl. Compounds that also contain substituents other than halogen, such as -2,5-dichlorobenzene and 3,5-dichlorobenzoic acid, can be mentioned. Of these, a dihalogenated aromatic compound containing p-dihalogenated benzene as a main component, typified by p-dichlorobenzene, is preferable. Particularly preferably, it contains 80 to 100 mol% of p-dichlorobenzene, and more preferably 90 to 100 mol%.

(4) Organic Polar Solvent In a preferred embodiment of the present invention, an organic polar solvent is used, and among them, an organic amide solvent is preferable. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, 1, Aprotic organic solvents such as 3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric acid triamide, and mixtures thereof have stable reactions. It is preferably used because it is expensive. Of these, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used.

(5) Branching / Crosslinking Agent, Molecular Weight Adjusting Agent In the present invention, in order to form a branched or crosslinked polymer, a polyhalogenation compound (not necessarily an aromatic compound) having a trihalogenation or higher and an active hydrogen-containing halogenation It is also possible to use a branching / cross-linking agent such as an aromatic compound and a halogenated aromatic nitro compound in combination. Of these, polyhalogenated aromatic compounds are preferable, and specific examples thereof include 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, and 1,4. , 6-Trichloronaphthalene and the like, and among them, 1,3,5-trichlorobenzene and 1,2,4-trichlorobenzene are preferable.

It is also possible to use a monohalogenated compound (not necessarily an aromatic compound) in combination for the purpose of adjusting the molecular weight of PAS. Examples of the monohalogenated compound include monohalogenated benzene, monohalogenated naphthalene, monohalogenated anthracene, a monohalogenated compound containing two or more benzene rings, and a monohalogenated heterocyclic compound. Of these, monohalogenated benzene is preferable from the viewpoint of economy. It is also possible to use two or more different monohalogenated compounds in combination.

(6) Polymerization Step The present invention is a method for producing polyarylene sulfide through the following steps 1 and 2.
Step 1: A step of heating a reaction mixture (A) containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent as raw material components to produce polyarylene sulfide.
Step 2: A step of cooling the reaction solution containing the polyarylene sulfide obtained in Step 1 to less than the boiling point of the organic polar solvent, and then heating the reaction solution at the boiling point of the organic polar solvent or more and 225 ° C. or less.

Hereinafter, steps 1 and 2 will be described.

(6-1) Step 1
Step 1 is a step of heating the reaction mixture (A) containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent as raw material components to generate polyarylene sulfide.

Here, as a method for preparing the reaction mixture (A), it is also possible to mix the respective raw materials at once, or to add a part of the raw material components afterwards. Further, in addition to the essential component, a third component that does not significantly inhibit the reaction can be added to the reaction mixture (A).

If the amount of the dihalogenated aromatic compound in the reaction mixture (A) is too small, the inside of the reaction system becomes an excess sulfur source and tends to cause a decomposition reaction. Therefore, the amount of the dihalogenated aromatic compound used is preferably 95 mol or more and 107 mol or less, more preferably 98 mol or more and 105 mol or less, and further preferably 100 mol or more and 104 mol or less per 100 mol of the sulfidizing agent.

The amount of the organic polar solvent used as the polymerization solvent in the present invention is not particularly limited, but from the viewpoint of stable reactivity and economy, the amount of the organic polar solvent used is 2.0 mol or more per mol of the sulfide agent. It is preferably 6.0 mol or less, more preferably 2.2 mol or more and 5.5 mol or less, and further preferably 2.5 mol or more and 5.0 mol or less.

The reaction temperature in step 1 cannot be uniquely determined because it varies depending on the type and amount of the organic polar solvent, but it is usually preferably the boiling point or higher of the organic polar solvent, and more preferably 220 ° C. or higher. Further, as the upper limit of the reaction temperature in step 1, 350 ° C. or lower can be exemplified, preferably 320 ° C. or lower, more preferably 300 ° C. or lower, and further preferably 280 ° C. or lower. In such a temperature range, the polyarylene sulfide is easily dissolved, so that the reaction tends to be uniform and easy to proceed. The reaction may be a one-step reaction carried out at a constant temperature, a multi-step reaction in which the temperature is raised stepwise, or a reaction in which the temperature is continuously changed.

The reaction time cannot be unconditionally specified because it depends on the type and amount of the raw material used or the reaction temperature, but 0.1 hours or more is preferable, and 0.5 hours or more is more preferable. By setting the time to this preferable time or longer, the unreacted raw material component can be reduced. On the other hand, although there is no particular upper limit to the reaction time, the reaction proceeds sufficiently even within 40 hours, and preferably 20 hours or less, more preferably 10 hours or less can be adopted.

As the reaction method, various known polymerization methods and reaction methods such as a batch method and a continuous method can be adopted. Further, the atmosphere in the production is preferably a non-oxidizing atmosphere, preferably an atmosphere of an inert gas such as nitrogen, helium, and argon, and more preferably a nitrogen atmosphere from the viewpoint of economy and ease of handling. ..

In step 1, from the viewpoint of advancing the reaction to generate polyarylene sulfide, the reaction is preferably carried out until the conversion rate of the dihalogenated aromatic compound is 90% or more, more preferably 92% or more, and further. Is preferably reacted until it reaches 94% or more.

The conversion rate of the dihalogenated aromatic compound (DHA) is a value calculated by the following formula. The residual amount of DHA can usually be determined by gas chromatography.
(A) When the dihalogenated aromatic compound is excessively added to the sulfidizing agent in a molar ratio, conversion rate (%) = [[DHA charge amount (mol) -DHA residual amount (mol)] / [DHA charge amount ( (Mole) -DHA excess (Mole)]] x 100%
(B) In cases other than the above (a) Conversion rate (%) = [[DHA charge amount (mol) -DHA residual amount (mol)] / [DHA charge amount (mol)]] × 100%.

Here, as the weight average molecular weight of the polyarylene sulfide produced in step 1 of the present invention, 2,000 to 1,000,000 can be exemplified, 2,500 to 500,000 can be preferably exemplified, and 3,000 to 100 can be exemplified. 000 can be more preferably exemplified. Here, when the weight average molecular weight of the polyarylene sulfide produced in step 1 is within the above range, it is presumed that a part or most of the polyarylene sulfide is likely to be precipitated in step 2 described later, and the polyarylene sulfide in step 2 is likely to be precipitated. The molecular weight of sulfide tends to improve easily. The weight average molecular weight of polyarylene sulfide can usually be determined by gel permeation chromatography (GPC).

(6-2) Step 2
The step 2 is a step of cooling the reaction solution containing the polyarylene sulfide obtained in the step 1 to less than the boiling point of the organic polar solvent and then reheating it at the boiling point of the organic polar solvent or more and 225 ° C. or less.

In step 2, the reaction solution containing the polyarylene sulfide obtained in step 1 is first cooled to below the boiling point. The temperature after cooling is not limited, and the effect of the present invention can be obtained even when cooled to room temperature, but from the viewpoint of economy, it is preferably 50 ° C. or lower, more preferably 100 ° C. or lower, and further preferably 150 ° C. or lower. Can be adopted.

The cooling method is not particularly limited, and any method such as rapid cooling, slow cooling at a constant speed, and stepwise slow cooling may be used. After cooling to less than the boiling point, it may be reheated immediately, or it may be held for a certain period of time after cooling and then reheated.

Further, in step 2, after cooling to less than the boiling point of the organic polar solvent, reheating is performed at the boiling point of the organic polar solvent or more and 225 ° C. or less. More preferably, after cooling to less than the boiling point of the organic polar solvent, it is reheated at 220 ° C. or higher than the boiling point of the organic polar solvent.

The method of reheating is not particularly limited, and any method such as a constant rate of temperature rise or a stepwise temperature rise may be used. Further, there is no particular limitation on the control of the reaction temperature when the organic polar solvent is reheated at the boiling point or more and 225 ° C. or less, and a reaction carried out at a constant temperature or a reaction in which the temperature is continuously changed can be exemplified. ..

By reheating the reaction solution containing the polyarylene sulfide obtained in the step 1 in such a temperature range, the polyarylene sulfide produced in the step 1 tends to have a high molecular weight. On the other hand, even if reheating is performed, reheating below the boiling point of the organic polar solvent is economically unfavorable because the reaction requires a long time, and the weight average molecular weight is hardly improved above 225 ° C.

As described above, we have found the effect of increasing the molecular weight of polyarylene sulfide when a specific temperature control is satisfied, and have completed the present invention. Although the reason for this effect is not clear, it is presumed that at least a part of the polyarylene sulfide component is precipitated by cooling, and that the reaction while maintaining the precipitated state even after reheating contributes to the increase in molecular weight. There is.

Further, the reheating time cannot be unconditionally specified because it depends on the type and amount of the raw material used or the reaction temperature, but it is preferably 1 hour or more, more preferably 2 hours or more. By setting the time to such a preferable time or longer, there is a strong tendency for the molecular weight to increase. On the other hand, although there is no particular upper limit to the reaction time, the reaction proceeds sufficiently even within 100 hours, and preferably 75 hours or less, more preferably 50 hours or less, still more preferably 25 hours or less can be adopted.

Here, it is also possible to post-add a part of a sulfidizing agent, a dihalogenated aromatic compound, an organic polar solvent, or the like to the reaction solution containing the polyarylene sulfide obtained in step 1. In addition to the above components, it is also possible to add a third component that does not significantly inhibit the reaction.

In this step 2, the amount of the organic polar solvent used as the polymerization solvent is not particularly limited, but the amount of the organic polar solvent used is preferably 2.0 mol or more and 6.0 mol or less per 1 mol of the sulfide agent. It is more preferably .2 mol or more and 5.5 mol or less, and further preferably 2.5 mol or more and 5.0 mol or less. In such a preferable range, the polyarylene sulfide produced in this step tends to have a high molecular weight.

The amount of the dihalogenated aromatic compound used in this step 2 is preferably 95 mol or more and 107 mol or less, more preferably 98 mol or more and 105 mol or less, and further preferably 100 mol or more and 104 mol or less per 100 mol of the sulfidizing agent. In such a preferable range, the polyarylene sulfide produced in this step tends to have a high molecular weight.

Further, the atmosphere in this step 2 is preferably a non-oxidizing atmosphere, preferably an inert gas atmosphere such as nitrogen, helium, and argon, and is in a nitrogen atmosphere from the viewpoint of economy and ease of handling. Is more preferable.

Here, as the weight average molecular weight of the polyarylene sulfide produced in the embodiment of the present step 2, 3,000 to 1,000,000 can be exemplified, 4,000 to 500,000 can be preferably exemplified, and 5,000 to 5,000 to 500,000 can be exemplified. 100,000 can be more preferably exemplified. The weight average molecular weight of polyarylene sulfide can usually be determined by GPC.

The polyarylene sulfide obtained in this step 2 tends to have a higher weight average molecular weight than the polyarylene sulfide produced in step 1. That is, the ratio of the weight average molecular weight of the polyarylene sulfide produced in step 2 to the weight average molecular weight of the polyarylene sulfide produced in step 1 (the weight average molecular weight of the polyarylene sulfide produced in step 2 / the polyarylene produced in step 1). The weight average molecular weight of sulfide) tends to be more than 1.0 times, preferably 1.1 times or more, and more preferably 1.2 times or more.

Further, the ratio of the weight average molecular weight of the polyarylene sulfide produced in the step 2 to the weight average molecular weight of the polyarylene sulfide produced in the step 2 tends to be 10 times or less, and more likely to be 5 times or less.

From the above, according to this step 2, the polyarylene sulfide can be increased in molecular weight without adding a polymerization aid, and can be utilized for each application.

(7) Polymer Recovery In the production of the PAS of the present invention, after the completion of the polymerization step, a post-treatment for recovering the PAS from the reaction product containing the PAS component and the solvent obtained in the polymerization step is performed. The PAS component can be recovered by a known method, for example, reprecipitation of the PAS component in a poor solvent, low solubility in the PAS component and mixing with an organic polar solvent, preferably with respect to a by-product salt. By contacting with a soluble solvent and recovering the PAS component as a mixed solid, the polymerization reaction product is gradually cooled from a high temperature and high pressure state to precipitate the PAS component in the reaction system, and the PAS component is separated by filtration. A method of recovering a solid containing a PAS component (quenching method), a method of flushing a polymerization reaction product from a high temperature and high pressure state into an atmosphere of normal pressure or reduced pressure to recover the solvent and at the same time recovering the polymer in powdery particles (flash method). ), Etc. can be adopted.

(8) Other Post-Treatment The PAS obtained in the present invention may be treated at a temperature of 130 to 260 ° C. in an oxygen-containing atmosphere in order to remove volatile components or to increase the cross-linked high molecular weight. It is possible.

When the dry heat treatment is performed for the purpose of suppressing the increase in the crosslinked high molecular weight and removing the volatile matter, the temperature is preferably 130 to 250 ° C, more preferably 160 to 250 ° C. Further, it is desirable that the oxygen concentration is less than 2% by volume and further less than 1% by volume. Drying under reduced pressure is also one of the preferable methods. The treatment time is preferably 0.5 to 50 hours, more preferably 1 to 20 hours, still more preferably 1 to 10 hours.

When the dry heat treatment is performed for the purpose of increasing the crosslinked molecular weight, the temperature is preferably 160 to 260 ° C, more preferably 170 to 250 ° C. Further, it is desirable that the oxygen concentration is 2% by volume or more, more preferably 8% by volume or more. The treatment time is preferably 1 to 100 hours, more preferably 2 to 50 hours, still more preferably 3 to 25 hours.

The heat treatment device may be a normal hot air dryer or a rotary type or a heating device with a stirring blade, but for efficient and more uniform processing, a rotary type or a heating device with a stirring blade is used. Is more preferable.

Designability is an important factor in developing the PAS obtained by the present invention for a wide variety of uses, which will be described later. In order to provide high designability, the whiteness of PAS is preferably high, and the L value indicating the high whiteness is preferably 80 or more, and more preferably 83 or more. Usually, when the heat treatment is performed in the PAS post-treatment, it tends to be colored due to the heat history and oxidative cross-linking. Therefore, when the post-treatment is performed, it is preferable to carry out the post-treatment within a range in which the whiteness can be maintained.

(9) Applications of polyarylene sulfide The polyarylene sulfide obtained in the present invention is excellent in heat resistance, chemical resistance, flame retardancy, electrical properties and mechanical properties, and is used only for injection molding, injection compression molding, and blow molding. Instead, it can be molded into extruded products such as sheets, films, fibers and pipes by extrusion molding. At this time, PAS may be used alone, or if desired, an inorganic filler such as glass fiber, carbon fiber, titanium oxide, or calcium carbonate, an antioxidant, a heat stabilizer, an ultraviolet absorber, a colorant, or the like. Can be added, and a resin can be blended.

Examples of such applications include electrical / electronic parts, household / office electrical product parts, optical equipment / precision machine-related parts, water-related parts, automobile / vehicle-related parts, and other industrial applications.

Hereinafter, the present invention will be specifically described with reference to examples. These examples are exemplary and not limiting.

<Measurement of conversion rate of dihalogenated aromatic compounds>
The conversion rate of the dihalogen aromatic compound was quantitatively analyzed by gas chromatography (GC) analysis. The measurement conditions of GC are shown below.
Equipment: Shimadzu GC-2010
Column: J & W DB-5 0.32 mm x 30 m (0.25 μm)
Carrier gas: Helium detector: Hydrogen flame ionization detector (FID)

<Molecular weight measurement>
The molecular weight of polyphenylene sulfide was calculated in terms of polystyrene by gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC). The measurement conditions for GPC are shown below.
Equipment: Senshu Science SSC-7100
Column name: Shodex UT-806M
Eluent: 1-Chloronaphthalene detector: Differential refractive index detector Column temperature: 210 ° C
Pre-constant temperature bath temperature: 250 ° C
Pump constant temperature bath temperature: 50 ° C
Detector temperature: 210 ° C
Flow rate: 1.0 mL / min
Sample injection amount: 300 μL (slurry: about 0.2% by weight).

[Reference example 1]
<Polymerization process>
116.8 g of 48% sodium hydrosulfide aqueous solution (1.00 mol as sodium hydrosulfide) and 85.5 g of 48% sodium hydroxide aqueous solution (1.03 mol as sodium hydroxide) in a 1 liter autoclave with a stirrer. , N-Methyl-2-pyrrolidone (NMP) was charged, and gradually heated to 240 ° C. over about 3 hours while passing nitrogen under normal pressure to distill out 102.0 g of water and 2.0 g of NMP, and then a reaction vessel. Was cooled to 160 ° C. At this time, the amount of hydrogen sulfide scattered was 0.015 mol per 1 mol of the charged alkali metal sulfide.

Next, 147.0 g (1.00 mol) of p-dichlorobenzene and 275 g of NMP were added, and the reaction vessel was sealed under nitrogen gas. At this time, the amount of NMP per 1 mol of sodium hydrosulfide is 4.5 mol. While stirring at 240 rpm, the temperature was raised to 250 ° C. at a rate of 0.6 ° C./min, and the reaction was carried out at 250 ° C. for 2 hours (step 1). Then, the reaction solution was rapidly cooled to near room temperature, and the contents were recovered.

As a result of analyzing the obtained contents by GC, the conversion rate of p-DCB of the monomer was 95%.

<Recovery process>
25 g of the obtained content was diluted with about 100 g of ion-exchanged water and then filtered through a glass filter having an average opening of 10 to 16 micrometers. The filter-on component was dispersed in about 100 g of ion-exchanged water, stirred at 70 ° C. for 15 minutes, and the same filtration operation was performed again three times in total to obtain a white solid. This was vacuum dried at 100 ° C. overnight to obtain a dry solid.

As a result of the analysis, from the absorption spectrum in the infrared spectroscopic analysis, this solid was polyphenylene sulfide, and the weight average molecular weight was 20,000.

[Example 1]
Here, the result of preparing a reaction solution containing polyarylene sulfide in step 1, cooling the reaction solution to less than the boiling point of the organic polar solvent, and then heating at the boiling point of the organic polar solvent or more and 225 ° C. or less will be described.

<Polymerization process>
After the reaction was carried out in the same manner as in step 1 of the polymerization step of Reference Example 1, the reaction solution was rapidly cooled to near room temperature. Subsequently, the temperature was raised to 210 ° C. at a rate of 0.6 ° C./min, and the reaction was carried out at 210 ° C. for 6 hours (step 2). Then, it was rapidly cooled to near room temperature, and the contents were recovered.

As a result of analyzing the obtained contents by GC, the conversion rate of p-DCB of the monomer was 96%.

<Recovery process>
Polyphenylene sulfide was recovered from the reaction mixture in the same manner as in the recovery step of Reference Example 1. The weight average molecular weight of the obtained polyphenylene sulfide was 28,000, which was 1.4 times the weight average molecular weight of the polyphenylene sulfide in Reference Example 1.

By comparing with Reference Example 1, it was found that a reaction solution containing polyarylene sulfide was prepared, cooled to less than the boiling point of the organic polar solvent, and then heated to 210 ° C. to increase the molecular weight of polyarylene sulfide. rice field.

[Comparative Example 1]
Here, the result of preparing a reaction solution containing polyarylene sulfide in step 1, cooling the reaction solution to less than the boiling point of the organic polar solvent, and then heating at 250 ° C. is described.

<Polymerization process>
After the reaction was carried out in the same manner as in step 1 of the polymerization step of Reference Example 1, the reaction solution was rapidly cooled to near room temperature. Subsequently, the temperature was raised to 250 ° C. at a rate of 0.6 ° C./min, and the reaction was carried out at 250 ° C. for 2 hours. Then, it was rapidly cooled to near room temperature, and the contents were recovered.

As a result of analyzing the obtained contents by GC, the conversion rate of p-DCB of the monomer was 96%.

<Recovery process>
Polyphenylene sulfide was recovered from the reaction mixture in the same manner as in the recovery step of Reference Example 1. The weight average molecular weight of the obtained polyphenylene sulfide was 20,000, which was 1.0 times the weight average molecular weight of the polyphenylene sulfide in Reference Example 1.

That is, it was found that when a reaction solution containing polyarylene sulfide was prepared, cooled to less than the boiling point of the organic polar solvent, and then heated at 250 ° C., which is the same temperature as in step 1, the molecular weight was not increased.

[Comparative Example 2]
Here, the result of preparing a reaction solution containing polyarylene sulfide in step 1, cooling the reaction solution to less than the boiling point of the organic polar solvent, and then heating at 230 ° C. is described.

<Polymerization process>
After the reaction was carried out in the same manner as in step 1 of the polymerization step of Reference Example 1, the reaction solution was rapidly cooled to near room temperature. Subsequently, the temperature was raised to 230 ° C. at a rate of 0.6 ° C./min, and the reaction was carried out at 230 ° C. for 6 hours. Then, it was rapidly cooled to near room temperature, and the contents were recovered.

As a result of analyzing the obtained contents by GC, the conversion rate of p-DCB of the monomer was 96%.

<Recovery process>
Polyphenylene sulfide was recovered from the reaction mixture in the same manner as in the recovery step of Reference Example 1. The weight average molecular weight of the obtained polyphenylene sulfide was 20,000, which was 1.0 times the weight average molecular weight of the polyphenylene sulfide in Reference Example 1.

That is, it was found that when a reaction solution containing polyarylene sulfide was prepared, cooled to less than the boiling point of the organic polar solvent, and then heated at 230 ° C., the molecular weight did not increase.

Claims (4)

A method for producing polyarylene sulfide, which undergoes the following steps 1 and 2.
Step 1: A step of heating a reaction mixture (A) containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent as raw material components to generate polyarylene sulfide.
Step 2: A step of cooling the reaction solution containing the polyarylene sulfide obtained in Step 1 to less than the boiling point of the organic polar solvent, and then reheating at 225 ° C. or higher than the boiling point of the organic polar solvent. The method for producing a polyarylene sulfide according to claim 1, wherein in the step 1, the conversion rate of the dihalogenated aromatic compound is 90% or more. The method for producing polyarylene sulfide according to claim 1 or 2, wherein the amount of the organic polar solvent used per 1 mol of sulfur atom of the sulfidizing agent is in the range of 2.0 mol or more and 6.0 mol or less. The poly according to any one of claims 1 to 3, wherein the ratio of the weight average molecular weight of the polyarylene sulfide produced in the step 2 to the weight average molecular weight of the polyarylene sulfide produced in the step 2 is more than 1.0 times. Method for producing arylene sulfide.