JP2010006995A - Method for preparing aqueous dispersion liquid of polyphenylene sulfide fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing an aqueous dispersion liquid of polyphenylene sulfide (PPS) fine particles, in which the aqueous dispersion liquid of PPS fine particles is prepared by extracting N-methyl-2-pyrrolidone from a dispersion liquid containing water, N-methyl-2-pyrrolidone and PPS fine particles to decrease the N-methyl-2-pyrrolidone content and which is executed industrially by a simple operation. <P>SOLUTION: The method for preparing the aqueous dispersion liquid of polyphenylene sulfide fine particles comprises a step of extracting N-methyl-2-pyrrolidone from the dispersion liquid, which contains water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having 0.05-0.5 μm average particle size, by using an extracting solvent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an aqueous dispersion of polyphenylene sulfide fine particles.

  Polyphenylene sulfide (hereinafter abbreviated as PPS) resin has excellent heat resistance, chemical resistance, solvent resistance, electrical insulation, and other suitable properties for engineering plastics, mainly for injection molding and extrusion molding applications. It is used for various electric / electronic parts, machine parts and automobile parts. As an additive having such various excellent properties, there is a high demand for PPS fine particle dispersions in the paint field, adhesive material field, polymer compound field, etc., but due to the technical limitations described below, the PPS fine particle water dispersion is currently present. It is extremely difficult to produce the liquid industrially.

  Several methods shown below have been proposed as a method for obtaining PPS particles.

  Patent Document 1 discloses a method for obtaining PPS particles having a relatively controlled particle size by controlling the amount of water in the reaction system and the temperature of the gas phase during PPS polymerization. The PPS particles obtained by this method are relatively large particles having an average particle size of several tens to several tens of μm. Patent Document 2 describes a PPS spherical powder having an average particle size of 0.1 μm to 100 μm and a method for producing the same. The production method specifically disclosed is a method of obtaining spherical PPS particles by forming a sea-island structure resin composition using PPS as an island and other thermoplastic polymer as the sea, and then dissolving and washing the sea phase. Even with this method, only relatively large particles of several μm to several tens of μm can be obtained. Patent Document 3 discloses a method in which a resin dispersed in water containing a surfactant is wet pulverized by a pulverizer such as a vibration ball mill to obtain a resin powder. In this patent document, there is no specific disclosure regarding the pulverization of the PPS resin, and the average particle diameter of the obtained resin powder is as large as about 5 to 50 μm. It is difficult. Patent Documents 4 and 5 disclose a method for obtaining fine PPS by dissolving PPS in a high-temperature NMP solvent and then cooling it as it is to precipitate PPS particles. Fine particles of 1 μm or less are not obtained.

  In addition, N-methyl-2-pyrrolidone is often used as the organic solvent used in the process of producing PPS particles, but it is desired to be reused from the economical and environmental aspects. . Several methods for extracting N-methyl-2-pyrrolidone by an extraction method from a nonpolar solvent have been disclosed. Patent Document 6 discloses a method for recovering an aprotic solvent from an aqueous solution containing an inorganic salt and / or an organic salt and an aprotic polar solvent. Patent Document 7 discloses a method of contacting with a non-halogen aliphatic organic compound. However, both methods involve extraction from non-polar solvents after separating the PPS particles. In other words, the method is in the absence of PPS.

Thus, the PPS particles obtained by the prior art are several μm or more, and it was difficult to obtain a stable dispersion with such a particle size. In order to obtain a stable dispersion, it is necessary to obtain PPS fine particles having a smaller particle diameter. However, a so-called submicron-sized PPS fine particle dispersion of 1 μm or less, which is necessary for obtaining a stable PPS fine particle dispersion, is obtained. A method, a method for directly extracting a nonpolar solvent from a PPS fine particle dispersion, and a method for obtaining it simply and efficiently have not yet been established, and development of a practical method for producing such a dispersion has been strongly desired. .
JP-A-6-298937 JP-A-10-273594 JP 2003-183406 A JP 2007-154166 A JP 2007-177155 A JP 2002-1008 A JP 2007-269638 A

  It is an object of the present invention to provide a method for producing an aqueous PPS fine particle dispersion that is industrially feasible and simple.

  Therefore, in order to obtain an aqueous dispersion of PPS fine particles, a PPS resin dissolved in an organic solvent such as N-methyl-2-pyrrolidone is flash-cooled in a dispersion medium such as water, and PPS fine particles are precipitated to form PPS. Although a method for obtaining a fine particle dispersion was found, the obtained PPS fine particle dispersion contained an organic solvent such as N-methyl-2-pyrrolidone together with a dispersion medium such as water. Therefore, it has been desired to develop a method having excellent practicality from the economical and environmental aspects of extracting an organic solvent such as N-methyl-2-pyrrolidone from the above dispersion containing PPS fine particles.

  Therefore, the present invention extracts N-methyl-2-pyrrolidone from the dispersion containing water, N-methyl-2-pyrrolidone and PPS fine particles as described above, and reduces the N-methyl-2-pyrrolidone content. It is an object of the present invention to provide a method for producing a PPS fine particle aqueous dispersion in an industrially practical and simple operation.

  As a result of intensive studies to solve the above problems, the present inventors have found that when the average particle size of the PPS fine particles is 0.05 to 0.5 μm, a dispersion using N-methyl-pyrrolidone and water as a dispersion medium From the above, it was found that by extracting and removing N-methyl-pyrrolidone, it was possible to efficiently obtain an aqueous dispersion of PPS fine particles, and the present invention was achieved.

  That is, the present invention uses an extraction solvent for N-methyl-2-pyrrolidone from a dispersion containing water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having an average particle size of 0.05 to 0.5 μm. Extraction of the polyphenylene sulfide fine particle aqueous dispersion.

  If this invention is used, the industrially difficult PPS microparticles | fine-particles aqueous dispersion can be manufactured simply, and a widely industrially useful material can be provided. Furthermore, it became possible to extract N-methyl-2-pyrrolidone from a dispersion containing PPS fine particles, water, and N-methylpyrrolidone.

  The aqueous PPS fine particle dispersion of the present invention contains N-methyl-2-pyrrolidone from a dispersion containing water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having an average particle size of 0.05 to 0.5 μm. It is manufactured by extracting using an extraction solvent.

  Hereinafter, embodiments of the present invention will be described in detail.

[Raw PPS resin]
The PPS resin in the present invention is a chemical formula (1)

It is a homopolymer or copolymer having a repeating unit as shown in FIG.

  Ar is represented by chemical formulas (2) to (4).

(R ¹ and R ² are one or more groups selected from hydrogen, alkyl groups, alkoxyl groups, and halogen groups).

As long as this repeat is a main structural unit, a branched bond or a cross-linked bond represented by chemical formula (5) or the like, or chemical formulas (6) to (14) (R ¹ and R ² are hydrogen, alkyl group, alkoxyl group, A copolymer component represented by a halogen group) can be contained in a proportion of 30 mol% or less, preferably 10 mol% or less.

  As PPS resin, the main structural unit of the polymer is represented by the chemical formula (15)

PPS containing 70 mol% or more, particularly 90 mol% or more of p-phenylene sulfide represented by the formula is particularly preferably used.

  As such PPS, what was synthesize | combined by the well-known method in the N-alkylamide solvent from a dihalogen aromatic compound and an alkali metal sulfide can be used.

  For example, PPS having a relatively low molecular weight obtained by the production method described in Japanese Patent Publication No. 45-3368 and heating it in an oxygen atmosphere or adding a crosslinking agent such as a peroxide and heating the PPS There is a method for increasing the degree of polymerization. In addition, essentially linear and high molecular weight PPS is preferably used by the production method described in Japanese Patent Publication No. 52-12240. In order to produce high-quality PPS fine particles, a PPS resin having as little inorganic ion content as possible is particularly preferable. Therefore, the PPS resin is preferably used by removing by-products such as inorganic salts by a method such as washing. The cleaning method may be a commonly performed method. The timing for removing the by-product may be performed after the polymerization or in any of the steps described later.

[Dispersion containing fine PPS particles]
The dispersion containing PPS fine particles used in the present invention is a dispersion containing water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having an average particle diameter of 0.05 to 0.5 μm.

[Production of dispersion containing PPS fine particles]
The method for producing a dispersion containing PPS fine particles in the present invention is not particularly limited as long as the dispersion defined in the present invention can be obtained. For example, the step of heating the PPS resin in a solvent to form a solution (dissolution step) ), And a step of precipitating the solution by flash cooling in a dispersion medium (precipitation step).

(Dissolution process)
In the present invention, in the dissolution step, the PPS resin is heated and dissolved in an organic solvent.

  The form of the PPS resin used in the present invention is not particularly limited. If specifically exemplified, powders, granules, pellets, fibers, films, molded products, etc. are mentioned, but the operability and the time required for dissolution are shortened. From the viewpoint of achieving the above, powder, granules and pellets are desirable, and powdered PPS resin is particularly preferred.

  Here, in order to prevent corrosion of the apparatus due to coexisting inorganic ions, such as when the target PPS fine particle dispersion is used in a water-soluble paint, PPS in the form of powder, granules or pellets not containing inorganic ions Resins are particularly preferred.

  The organic solvent used in the present invention is N-methyl-2-pyrrolidone.

  The feed concentration of the PPS resin with respect to the solvent is not particularly limited as long as it is a concentration at which PPS is dissolved at a predetermined temperature. However, since the solubility of the PPS resin is low, it is difficult to prepare a high concentration, usually 0.1 to 10% by mass, preferably Is 0.5 to 5% by mass. This range is particularly suitable for industrial production. In the present invention, a PPS resin is charged into the solvent and dissolved by heating.

  The atmosphere of the dissolution tank may be any of an air atmosphere, an inert gas atmosphere, or a solvent vapor atmosphere. However, in order to suppress the deterioration of the PPS resin, and further to advance the work safely, the oxygen gas concentration is increased. Lowering is preferable. Here, examples of the inert gas include nitrogen gas, carbon dioxide gas, helium gas, argon gas, etc. In consideration of economy and availability, nitrogen gas, argon gas, carbon dioxide gas is preferable, Particularly preferably, nitrogen gas or argon gas is used. Moreover, under the atmosphere of a solvent vapor | steam means making the atmosphere of the vaporized solvent vapor | steam by heating up a reaction tank, after removing air by making a reaction tank into a vacuum.

  The dissolution method is not particularly limited, but a PPS resin and a solvent are charged into a predetermined container and heated and dissolved while stirring. In order to produce PPS coarse particles having a uniform particle size, a method of complete dissolution in a solvent and precipitation is preferable, but some undissolved PPS resin may be present. Since the PPS resin has a low solubility in an organic solvent, it can be precipitated from a dilute solution in which the PPS resin is dissolved at the boiling point of the solvent. However, a method in which the PPS resin is dissolved by heating to a temperature higher than the boiling point of the solvent in a pressure vessel such as an autoclave is preferable. .

  The dissolution temperature varies depending on the type and concentration of the solvent used, but is usually 250 ° C. to 350 ° C., preferably 260 ° C. to 320 ° C. When the temperature is high, the PPS resin is decomposed. Moreover, if it is less than 250 degreeC, in order to melt | dissolve PPS resin, a large amount of solvent will be used and it will become difficult to melt | dissolve.

  The dissolution time varies depending on the type of solvent, the concentration of the PPS resin, and the dissolution temperature, but is the time until the PPS resin is dissolved. The time is usually 10 minutes to 10 hours, preferably 20 minutes to 8 hours, more preferably 30 minutes to 5 hours.

  By the above operation, the PPS resin can be dissolved. Here, when dissolving in a pressure vessel such as an autoclave, the presence or absence of dissolution may not be directly confirmed due to structural reasons, but the coarse particles precipitated in the subsequent precipitation step are shaped with the PPS resin before dissolution. If the particle size and the like are different, it is judged as a result of the dissolution / precipitation of the present invention.

(Precipitation process)
The PPS resin solution dissolved in the dissolution step is flash-cooled in water as a dispersion medium to precipitate PPS fine particles. In the present invention, flash cooling can be performed by flushing and transferring the solution to another container containing water (hereinafter sometimes referred to as a receiving tank). The flush is lower than the pressure of the container in which the lysing solution is placed (either a lysis tank or another container transferred from the lysis tank, but preferably a dissolution tank). It can be performed by discharging by a method such as spraying into a receiving tank containing water under pressure.

  Specifically, the PPS resin solution is preferably flushed from a container held under pressure into a receiving tank containing water at atmospheric pressure (or under reduced pressure). For example, in the melting step, when the melting is performed in a pressure-resistant container such as an autoclave, the inside of the container is pressurized by a self-made pressure by heating. By releasing the pressure from this state and releasing it into a receiving tank under atmospheric pressure, it can be carried out more easily. In addition, when flushing into water, it may be flushed into water via a gas phase or directly into the dispersion medium.

  The amount of water used is preferable in terms of obtaining PPS fine particles having an average particle diameter of 0.05 to 0.5 μm in the range of 1 to 5 parts by mass with respect to 1 part by mass of the organic solvent for dissolving the PPS resin. When the amount is less than 1 part by mass with respect to 1 part by mass of the solvent, the PPS particle diameter becomes too large, and when it exceeds 5 parts by mass, the PPS concentration decreases, which is not industrially preferable.

  The flash cooling method is not particularly limited, but is usually a method of flash cooling a solution at 250 ° C. to 400 ° C., preferably 260 ° C. to 320 ° C. in one step in an atmospheric pressure or vacuum container, or by dissolving a PPS resin. A method of flash cooling in multiple stages in a container having a lower pressure than the organic solvent liquid can be employed. In order to obtain fine PPS fine particles, it is preferable that the pressure difference is large and the temperature difference is large. Specifically, for example, in the melting step, when the melting is performed in a pressure-resistant container such as an autoclave, the inside of the container is pressurized by a self-made pressure by heating. The organic solvent solution in which the PPS resin in a pressurized state is dissolved is flushed in an atmospheric pressure receiving tank charged with water or flushed in a receiving tank under reduced pressure. The pressure (gauge pressure) of the solution for flash cooling is preferably 0.2 to 4 MPa. It is preferred to flush it from this environment, preferably to a vessel under atmospheric pressure, more preferably into a vessel under atmospheric pressure.

  In addition, the receiving tank can be cooled at a stroke below the boiling point of the organic solvent used by a method such as cooling with a refrigerant or cooling in ice water and cooling the water in advance, and ultrafine PPS fine particles can be obtained. Therefore, it is preferable. By this flash cooling, PPS fine particles are precipitated from the solution of the PPS resin, and a liquid in which the PPS fine particles are dispersed or suspended is obtained.

  The method of flushing into the water, which is the dispersion medium, may be either the method of putting the connecting pipe outlet from the dissolution tank into the dispersion medium of the receiving tank and flushing, or the method of flushing into the dispersion medium via the gas phase, In order to surely obtain a dispersion of fine PPS fine particles, a method of flushing by inserting the outlet of the connecting tube in a dispersion medium is preferable.

[Extraction process]
In the extraction step, the dispersion liquid containing water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having an average particle diameter of 0.05 to 0.5 μm is extracted using an extraction solvent.

  For example, the PPS fine particle dispersion obtained in the precipitation step is used as it is, and N-methyl-2-pyrrolidone is extracted to obtain a PPS fine particle aqueous dispersion. The concentration of N-methyl-2-pyrrolidone in the PPS fine particle aqueous dispersion may be a concentration according to the purpose of use, but when it is desired that the dispersion medium is substantially water, it is 1% or less. It is desirable to be able to. In order to reduce the concentration of N-methyl-2-pyrrolidone, the following extraction process may be repeated.

  Extraction can be performed by a conventional method in which an extraction solvent is added to the dispersion and stirred, and the mixture is left to stand until the interface comes out, and the stirring speed and stirring time are not particularly limited.

  The extraction temperature is preferably 40 ° C. or less in view of extraction efficiency and stability of the PPS dispersion. The lower limit may be at or above the temperature at which the dispersion to which the extraction solvent is added does not freeze, but is preferably 10 ° C. or higher, more preferably 20 ° C. to 40 ° C. from the viewpoint of extraction efficiency.

  The extraction solvent dissolves N-methyl-2-pyrrolidone at the extraction temperature, and the amount of water dissolved in 100 g of the extraction solvent is preferably about 1 g or less at 25 ° C. Specifically, halogen solvents such as chloroform (0.08 g of water dissolved in 100 g of chloroform at 25 ° C.) and methylene chloride (0.17 g of water dissolved in 100 g of methylene chloride at 25 ° C.) are preferably used. However, chloroform is preferable because of extraction efficiency. When using methylene chloride, it is preferable to carry out at 30 degrees C or less from the viewpoint of the boiling point.

  Here, surprisingly, when the average particle size of the PPS fine particles is in the range of 0.05 to 0.5 μm, in the preferable extraction solvent, the PPS fine particles are present in the upper water phase and have a higher specific gravity than water. The extraction solvent is in the lower layer with respect to the aqueous phase and is separated into two layers. The separated lower layer component extraction solvent and the organic solvent N-methyl-2-pyrrolidone present in the extraction solvent are separated from the aqueous dispersion containing PPS fine particles. In order to further remove N-methyl-2-pyrrolidone remaining in the aqueous dispersion containing the PPS fine particles, an extraction solvent was added again, and the liquid separation was repeated until the desired NMP concentration was obtained. A PPS fine particle aqueous dispersion having a particle size of 0.05 to 0.5 μm can be obtained. The average particle size here is measured using a laser diffraction / scattering type particle size distribution measuring device. Specifically, the total volume of particles obtained by analyzing the laser scattered light by the microtrack method is defined as 100%. The cumulative curve is obtained, and the particle diameter (median diameter: d50) at the point where the cumulative curve is 50%. However, in an extraction solvent in which the amount of water dissolved in 100 g of the extraction solvent exceeds about 1 g at 25 ° C., the PPS fine particles are distributed between the aqueous phase and the extraction solvent phase, and the entire liquid becomes cloudy and the interface becomes unclear. It becomes difficult. Such a phenomenon occurs when the average particle size of the PPS fine particles is in the range of 0.05 to 0.5 μm, the outer surface area is increased, and the affinity between the PPS fine particles and water is increased. In the case of an extraction solvent in which water is difficult to dissolve, the PPS fine particles are distributed to the solvent phase side together with water in a solvent that is present in the aqueous phase and has a high water dissolution amount. As a result, it is estimated that the whole becomes cloudy, the interface becomes unclear, and separation becomes difficult.

  The aqueous dispersion of fine PPS fine particles prepared in this way can be used as a particularly useful additive in the fields of paint, adhesion and polymer compounds.

[Measurement of average particle size]
The average particle size of PPS fine particles is 0 of Nikkiso laser diffraction / scattering type particle size distribution analyzer MT3300EXII, and polyoxyethylene cumylphenyl ether (trade name: Nonal 912A, manufactured by Toho Chemical Industries, Ltd., hereinafter referred to as Nonal 912A) as a dispersion medium. Measured using a 5% by mass aqueous solution. Specifically, a cumulative curve is obtained by setting the total volume of particles obtained by analyzing laser scattered light by the microtrack method to 100%, and the particle diameter (median diameter: d50) at which the cumulative curve becomes 50% is calculated. The average particle size of the fine particles was used.

Example 1
[Dissolution process]
A connecting pipe that can be opened and closed internally is attached to a 1000 ml autoclave in the dissolution tank. In addition, as a receiving tank for flash cooling, a stirrer, a condenser and a gas vent pipe were attached to a 1000 ml autoclave, and the other end of the connecting pipe of the dissolution tank was attached.

  14.7 g of PPS powder (manufactured by Toray Industries Inc., grade name M3910) and 490 g of N-methyl-2-pyrrolidone (manufactured by Kanto Chemical Co., Inc.) as an organic solvent are placed in the dissolution tank, and the valve of the internal connecting pipe is sealed. Replaced with nitrogen. After raising the internal temperature to 280 ° C. with stirring, stirring was continued for another 2 hours. The internal pressure (gauge pressure) at this time was 0.4 MPa.

[Precipitation process]
490 g of water was placed in the receiving tank, cooled in ice water, and a small amount of nitrogen gas was aerated with stirring. The outlet of the connecting pipe at this time was put in water. The valve of the connecting pipe of the dissolution tank was opened, the dissolved solution was transferred to an atmospheric pressure receiving tank in about 1 minute, stirring was stopped when the liquid temperature was 40 ° C. or lower, and the receiving tank was opened. The obtained PPS fine particle dispersion contains PPS fine particles, N-methyl-2-pyrrolidone and water (N-methyl-2-pyrrolidone: water (mass ratio) = 1: 1). The average particle size of the PPS fine particles was 0.14 μm.

[Extraction process]
100 g of chloroform (at 25 ° C., the amount of water dissolved in 100 g of chloroform was 0.08 g) was added to 100 g of the PPS fine particle dispersion at 30 ° C. and stirred. Stirring was stopped in 10 minutes and allowed to stand until the interface was visible. As a result, the solution was separated into two layers, a white turbid aqueous layer and a clear extraction solvent layer in the lower layer. Since the aqueous layer was cloudy, it was judged that the PPS fine particles were present in the aqueous layer. The upper PPS fine particle aqueous dispersion was recovered. The lower chloroform layer is subjected to gas chromatography (conditions: FID, column DB-WAX 30 m × 0.25 mmΦ × 0.25 μm, Air pressure 50 kPa, H ₂ pressure 50 kPa, He pressure 20 kPa, column temperature 40 to 180 ° C., injection temperature 280 As a result of analysis at a temperature rising rate of 10 ° C./min), it was found that 25.8 g of NMP was present in the chloroform layer. Since the amount of NMP of the PPS fine particle dispersion before addition of chloroform calculated from the charged amount is 49.3 g, it is considered that 23.5 g is present in the aqueous layer. The PPS fine particle aqueous dispersion was repeatedly extracted with chloroform six times, and 48.7 g of NMP could be removed. From this, the NMP concentration in the PPS fine particle aqueous dispersion is determined to be 0.75%. The average particle diameter of the PPS fine particles in the obtained PPS aqueous dispersion was 0.14 μm.

Comparative Example 1
[Dissolution process]
A connecting pipe that can be opened and closed internally is attached to a 1000 ml autoclave in the dissolution tank. In addition, as a receiving tank for flash cooling, a 1000 ml autoclave was equipped with a stirrer, a condenser and a gas vent pipe, and the other end of the connecting pipe of the dissolution tank was installed.

  14.7 g of PPS powder (manufactured by Toray Industries Inc., grade name M3910) and 490 g of N-methyl-2-pyrrolidone (manufactured by Kanto Chemical Co., Inc.) were placed in the dissolution tank, and the valve of the internal connection pipe was sealed, followed by nitrogen replacement. . After raising the internal temperature to 280 ° C. with stirring, stirring was continued for another 2 hours. The internal pressure (gauge pressure) at this time was 0.4 MPa.

[Precipitation process]
294 g of water was put into the receiving tank, cooled in ice water, and a slight amount of nitrogen gas was aerated with stirring. The outlet of the connecting pipe at this time was put in water. The valve of the connecting pipe of the dissolution tank was opened, the dissolved solution was transferred to an atmospheric pressure receiving tank in about 1 minute, stirring was stopped when the liquid temperature was 40 ° C. or lower, and the receiving tank was opened. The obtained PPS fine particle dispersion contains PPS fine particles, N-methyl-2-pyrrolidone and water (N-methyl-2-pyrrolidone: water (mass ratio) = 5: 3). The average particle size of the PPS fine particles was 4.7 μm.

[Extraction process]
100 g of chloroform was added to 100 g of the PPS dispersion at 30 ° C. and stirred. Stirring was stopped and allowed to stand for 10 minutes. However, since the PPS particles had a large particle size of 4.7 μm, the PPS particles were distributed into the aqueous phase and the chloroform phase, and the entire liquid became cloudy, so that the interface became unclear and separation was not possible.

Comparative Example 2
PPS powder (manufactured by Toray Industries, Inc., grade name M3910, average particle size 27 μm) 1.5 g, N-methyl-2-pyrrolidone (manufactured by Kanto Chemical Co., Inc.) 49 g, and water 49 g are added and stirred with a homogenizer to obtain a dispersion ( N-methyl-2-pyrrolidone: water (mass ratio) = 1: 1) was prepared. To this dispersion, 99.5 g of chloroform was added and stirred. When stirring was stopped for 10 minutes and the mixture was allowed to stand, PPS particles settled in the chloroform phase as the lower layer. For this reason, the aqueous dispersion containing PPS particles could not be recovered. This is probably because the particle size is larger than the PPS particles obtained in Example 1.

Comparative Example 3
The dispersion obtained in the dissolution and precipitation step of Example 1 was carried out except that ethyl acetate (the amount of water dissolved in 2.94 g in 100 g of ethyl acetate at 25 ° C.) was used as an extraction solvent in an amount equivalent to that of the dispersion. Extraction was performed in the same manner as in Example 1. The PPS fine particles were distributed into the aqueous phase and the extraction solvent phase, and the whole became cloudy. As a result, the interface became unclear and separation was not possible.

According to the production method of the present invention, an aqueous dispersion of fine PPS fine particles having a reduced particle size with a reduced N-methyl-2-pyrrolidone content can be obtained very easily.

  The PPS fine particle aqueous dispersion thus obtained can be widely used for applications such as adhesives, paints, dispersants in printing inks, magnetic recording media, plastic modifiers, and interlayer insulating film materials. .

Claims (8)

N-methyl-2-pyrrolidone is extracted from a dispersion containing water, N-methyl-2-pyrrolidone and polyphenylene sulfide fine particles having an average particle diameter of 0.05 to 0.5 μm using an extraction solvent. A process for producing an aqueous dispersion of polyphenylene sulfide fine particles. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to claim 1, wherein a dispersion produced by a method comprising the following steps (a) and (b) is used as the dispersion.
(A) A step of heating polyphenylene sulfide resin in N-methyl-2-pyrrolidone to obtain a solution (dissolution step)
(B) A step in which the solution is flash-cooled in water to precipitate polyphenylene sulfide fine particles to form a dispersion (precipitation step) 3. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to claim 2, wherein the solution under pressure (gauge pressure) of 0.2 to 4 MPa is flash-cooled in water. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to claim 2 or 3, wherein in the dissolving step, heating is performed from 250 ° C to 400 ° C. The mass ratio of the solvent N-methyl-2-pyrrolidone in the dissolution step (a) and the water used in the precipitation step (b) is from 1: 1 to 1: 5. The manufacturing method of the polyphenylene sulfide fine particle aqueous dispersion in any one. The extraction solvent used in the extraction step is dissolved at 20 ° C. to 40 ° C. with N-methyl-2-pyrrolidone used in the dissolution step (a), and the amount of water dissolved in 100 g of the extraction solvent is 1 g or less at 25 ° C. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to any one of claims 1 to 5, characterized in that it exists. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to any one of claims 1 to 6, wherein the extraction solvent is a halogen-based solvent selected from chloroform and methylene chloride. The method for producing an aqueous dispersion of polyphenylene sulfide fine particles according to any one of claims 1 to 7, wherein the extraction solvent is chloroform.