JP2011174033A - Powder coating comprising cyclic polyarylene sulfide and powder coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyarylene sulfide resin powder coating which produces little amount of gases after being formed into a coating film and can therefore form a coating film having few coating defects (voids) and being excellent in smoothness and uniformity. <P>SOLUTION: There is provided a polyarylene sulfide resin powder coating containing at least 5 wt.% cyclic polyarylene sulfide mixture of general formula (1) (wherein Ar is an arylene group; and m is an integer of 2-50) in 100 wt.% polyarylene sulfide resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyarylene sulfide resin powder coating. More specifically, the present invention relates to a powder coating containing cyclic polyphenylene sulfide and a coating method thereof.

  Polyarylene sulfide (hereinafter sometimes abbreviated as PAS) represented by polyphenylene sulfide (hereinafter also abbreviated as PPS) has excellent heat resistance, barrier properties, chemical resistance, electrical insulation properties, heat and humidity resistance, It is a resin having properties suitable as an engineering plastic such as flame retardancy. Also, it can be molded into various molded parts, films, sheets, fibers, etc. by injection molding and extrusion molding, and widely used in fields requiring heat resistance and chemical resistance such as various electric / electronic parts, mechanical parts, and automotive parts. It has been.

  For this reason, paints based on PAS are used in fields such as rust prevention, corrosion prevention and electrical insulation treatment of metals. As a paint based on this PAS, there is generally known a method in which a powder or slurry paint is applied to the surface of an object to be coated and then thermally melted to form a coating film (for example, patents). Literatures 1-3).

  As a specific method for producing the base resin PAS, an alkali metal sulfide such as sodium sulfide and a polyhaloaromatic compound such as p-dichlorobenzene are mixed in an organic amide solvent such as N-methyl-2-pyrrolidone. A reaction method has been proposed, and this method is widely used as an industrial production method of PAS. However, in this method, only a low molecular weight and low melt viscosity PAS can be obtained, and this PAS contains a large amount of low molecular weight components, and the degree of dispersion represented by the ratio of the weight average molecular weight to the number average molecular weight is very large. Wide distribution. For this reason, when used in powder coatings, there are problems that sufficient mechanical properties are not exhibited, and there are many gas components during heating (baking) of the coating film formation, and voids are likely to occur in the coating film.

  Further, since a large amount of by-product salt such as sodium chloride is produced in this production method, a by-product salt removal step is necessary after the polymerization reaction, but it is difficult to completely remove the by-product salt by a known treatment, and it is commercially available. In general-purpose PPS products, an alkali metal content of about 1000 to 3000 ppm is contained. Thus, when the alkali metal salt remains in the produced polymer, there arises a problem that physical properties such as electrical characteristics are lowered. Therefore, when trying to apply such a molded article using polyarylene sulfide as a raw material to the field of electric / electronic parts, the deterioration of the electrical characteristics due to alkali metal in polyarylene sulfide is a major obstacle, and improvement is desired. It was.

  In order to improve the low melt viscosity, which is a problem of PAS by the above production method, there is a step of forming a crosslinked structure and increasing the molecular weight by performing a gas phase oxidation treatment in an oxidizing atmosphere such as in air. This is necessary, and the process is further complicated and the productivity is reduced (for example, see Patent Document 4).

  As a method for improving one of the problems of the PAS, that is, the PAS having a large amount of low molecular weight components and a wide molecular weight distribution, a mixture of PAS containing impurities is in a state higher than the minimum temperature at which the PAS forms a molten phase. Then, a method of purifying impurities by subjecting them to thermal extraction by phase separation into a polymer melt phase containing PAS and a solvent phase mainly, or a method of precipitating and recovering a granular polymer after cooling is proposed. ing. In these methods, impurities are extracted by the heat extraction effect, so it is expected that the metal content of PAS is reduced and the molecular weight distribution is narrowed, but the effect is insufficient, and an expensive organic solvent is used. The process was complicated due to the method. In addition, the amount of low molecular weight components contained in PAS is certainly reduced by this method, but the effect is insufficient, and especially when the PAS resin powder coating is heated (baked) as in the present invention, the weight reduction rate is reduced. If the gas component is large and contains a large amount of gas, there is a problem that the uniformity and smoothness of the coating film are lowered as described above (for example, Patent Documents 5 and 6).

  Further, as a method for producing a PAS having a narrow molecular weight distribution, a method in which a cyclic arylene sulfide oligomer is heated and subjected to ring-opening polymerization under an ionic ring-opening polymerization catalyst is disclosed. In this method, unlike Patent Documents 5 and 6, it can be expected to obtain a PAS having a narrow molecular weight distribution without performing a complicated organic solvent washing operation, and it can be expected to obtain a PAS having a low low molecular weight component. . However, in this method, since a sulfur alkali metal salt such as a sodium salt of thiophenol is used as a ring-opening polymerization catalyst in the synthesis of PAS, there is a problem that a large amount of alkali metal remains in the obtained PAS. Further, in this method, when an attempt is made to reduce the residual amount of alkali metal in PAS by reducing the amount of ring-opening polymerization catalyst used, there is a problem that the molecular weight of the resulting PAS becomes insufficient. Furthermore, although there is no disclosure about the weight loss rate when the PAS obtained by this method is heated, the initiator used in the method has a lower molecular weight than PAS, so the PAS obtained by the method is heated. The weight loss during the process was large and the amount of gas generated was large, which was a factor that caused a decrease in molding processability and mechanical strength (for example, Patent Documents 7 and 8).

  The problem of PAS obtained by the above method, that is, a method for reducing the residual amount of alkali metal in PAS, is a PAS in which a cyclic aromatic thioether oligomer is subjected to ring-opening polymerization in the presence of a polymerization initiator that generates sulfur radicals by heating. A manufacturing method is disclosed. In this method, since a nonionic compound is used as a polymerization initiator, it is considered that the alkali metal content of the obtained PAS is reduced. However, the glass transition temperature of polyphenylene sulfide obtained by this method is as low as 85 ° C., which is probably because the molecular weight is low and the polyphenylene sulfide contains a large amount of low molecular weight components. Furthermore, although there is no disclosure about the weight reduction rate when the obtained polyphenylene sulfide is heated in the method, the polymerization initiator used in the method has a lower molecular weight than polyphenylene sulfide and also has poor thermal stability. When polyphenylene sulfide obtained by this method is heated, a large amount of gas is generated, and there is still a problem that a uniform coating film cannot be obtained (for example, Patent Document 9).

  Also known is a PPS polymerization method in which a mixture of cyclic PPS and linear PPS is heated as a monomer source (Non-patent Document 1). Although this method is an easy polymerization method of PPS, the degree of polymerization of the obtained PPS is low, and for example, PPS is not suitable for a powder coating as in the present invention. Although this document discloses that the degree of polymerization can be improved by increasing the heating temperature, it still does not reach a molecular weight suitable for practical use, and in this case, the formation of a crosslinked structure is not achieved. It has been pointed out that only PPS having inferior thermal properties cannot be obtained, and a high-quality PPS polymerization method more suitable for practical use has been desired.

  On the other hand, as a method of reducing the weight reduction rate when PAS is heated, many proposals have been made regarding a method of heat-treating PAS. For example, a method of heat-treating polyphenylene sulfide in an oxygen atmosphere below the melting point, polyphenylene sulfide And the like are disclosed in an inert gas atmosphere at a temperature lower than the melting point (for example, Patent Documents 10 and 11). The polyarylene sulfide obtained by these methods certainly has a tendency to reduce the weight loss rate when heated compared to PAS without heat treatment, but the weight loss rate when heated is still satisfactory. It wasn't. Furthermore, the polyphenylene sulfide obtained by this method contains many low molecular weight components, has a very high degree of dispersion expressed by the ratio of the weight average molecular weight to the number average molecular weight, has a wide molecular weight distribution, and has an alkali metal content. The problem of the low purity of the product has not been solved.

  Another method for heat-treating PAS is obtained by performing melt extrusion while purging the vent port with nitrogen and keeping the vent port at a reduced pressure while performing melt extrusion of the PAS resin using an extruder having a vent port. PAS resin pellets are disclosed (for example, Patent Document 12). In this method, since the heat treatment is performed under a reduced pressure condition higher than the melting point of PAS, the degas effect during the heat treatment is excellent, and the PAS obtained by this method can be expected to reduce the weight loss rate when heated. The level was still not satisfactory. Furthermore, the PAS pellets produced by this method also have molecular weight distribution characteristics and alkali metal content characteristics similar to those of the polyphenylene sulfide, and it is difficult to say that the purity is sufficiently high.

  On the other hand, regarding powder coatings made of PAS resin, many powder coatings made of linear PAS resin obtained by the prior art have been disclosed. However, powder coatings containing cyclic PAS having the characteristics of the present invention are known. Therefore, as described above, it is not known at all that a polyarylene sulfide resin powder coating having excellent mechanical strength and reduced gas generation can be obtained.

JP-A-1-297474 JP-A-3-220269 JP-A-5-295301 Japanese Patent Publication No. 1-25493 (page 23) Japanese Patent Publication No. 4-55445 (pages 3-4) Japanese Patent No. 3216228 (pages 7 to 10) Japanese Patent No. 3141459 (pages 5-6) US Pat. No. 5,869,599 (pages 27-28) US Pat. No. 3,793,256 (page 2) JP-A-3-41152 (Claims) JP 2000-246733 A (page 4)

Polymer, vol. 37, no. 14, 1996 (311 pp. 1 to 1116)

  Therefore, in view of the above-mentioned problems, the present invention provides a polyarylene sulfide capable of forming a coating film having a low level of gas generation after the coating film is formed and thus having a smoothness and uniformity with a small number of coating film defects (voids). It is an object to provide a resin powder coating.

  The inventors of the present invention have arrived at the present invention as a result of intensive studies for solving the above problems.

That is, the present invention is 1. A polyarylene sulfide resin powder coating comprising 5% by weight or more of a cyclic polyarylene sulfide mixture represented by the following general formula (1) in 100% by weight of a polyarylene sulfide resin:

(Ar represents an arylene group, and m is an integer of 2 to 50.)
2. 2. The polyarylene sulfide resin powder coating according to 1, comprising at least 50% by weight or more of the cyclic polyarylene sulfide and having a weight average molecular weight of less than 10,000.
3. The polyarylene sulfide resin according to any one of 1 and 2, wherein the cyclic polyarylene sulfide mixture represented by the general formula (1) includes a compound having a repeating number m of 4 to 12 in the formula Powder paint,
4). Furthermore, the polyarylene sulfide resin powder coating according to any one of 1 to 3, comprising a zero-valent transition metal compound,
5. The polyarylene sulfide resin powder coating according to 4, wherein the content of the zero-valent transition metal compound is 0.001 to 20 mol% with respect to sulfur atoms of the polyarylene sulfide resin,
6). The polyarylene sulfide resin powder coating according to any one of 1 to 5, wherein the alkali metal content is 100 ppm or less,
7). The polyarylene sulfide resin powder coating according to 6, wherein the alkali metal is substantially sodium,
8). The polyarylene sulfide resin powder coating material according to any one of 1 to 7, which substantially contains no halogen other than chlorine,
9.1-8 powder coating method characterized in that the polyarylene sulfide resin powder coating according to any one of 9 to 8 is electrostatically coated on a substrate and heated.
10. The powder coating method according to 9, wherein the heating temperature is 250 to 400 ° C,
11. The powder coating method according to any one of 9 and 10, wherein the heating time is 5 to 60 minutes,
A coated product obtained by the coating method according to any one of 12.9 to 11,
Is to provide.

  By using the polyarylene sulfide resin of the present invention as a powder coating material, a coating film free from voids and excellent in surface smoothness and uniformity can be formed.

  Embodiments of the present invention will be described below. In the present invention, “weight” means “mass”.

(1) Polyarylene sulfide (PAS) resin powder coating The PAS resin constituting the powder coating of the present invention has a repeating unit of the formula,-(Ar-S)-as the main structural unit, preferably the repeating unit. A homopolymer or copolymer containing 80 mol% or more of units. Ar includes units represented by the following formulas (A) to (L), among which the formula (A) is particularly preferable.

(R1 and R2 are substituents selected from hydrogen, an alkyl group, an alkoxy group, and a halogen group, and R1 and R2 may be the same or different.)

  As long as this repeating unit is a main structural unit, it can contain a small amount of branching units or crosslinking units represented by the following formulas (M) to (P). The amount of copolymerization of these branched units or cross-linked units is preferably in the range of 0 to 1 mol% with respect to 1 mol of-(Ar-S)-units.

  The PAS in the present invention may be any of a random copolymer, a block copolymer and a mixture thereof containing the above repeating unit.

  Typical examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers thereof, block copolymers, and mixtures thereof. Particularly preferred PASs include p-phenylene sulfide units as the main structural unit of the polymer.

And polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) containing 80 mol% or more, particularly 90 mol% or more.

  Further, the PAS resin used in the powder coating of the present invention is characterized by containing 5% by weight or more of cyclic polyarylene sulfide (hereinafter sometimes referred to as cyclic PAS) described in the next item (2). .

  That is, the present inventors use the property that the cyclic polyarylene sulfide undergoes ring-opening polymerization in a molten state at 300 to 400 ° C. to give a highly polymerized linear PAS resin, and a coating film forming process in powder coating By performing ring-opening polymerization of cyclic PAS (hereinafter sometimes referred to as “baking”), gas generation at the time of coating film formation can be reduced, and thus there is no void-free PAS resin coating with excellent planar smoothness. The inventors have found that a film can be formed and have reached the present invention.

  This is because the PAS resin obtained by the prior art has a wide molecular weight distribution and contains many low molecular weight components, so gas is generated by thermal decomposition of the low molecular weight components during baking, and the resulting coating film is Although a void is generated and a uniform coating cannot be obtained, when the PAS resin containing the cyclic polyarylene sulfide of the present invention is powder coated and baked, as described above, the degree of polymerization is increased during baking. The PAS resin that forms the coating film has a narrow molecular weight distribution and a low content of low molecular weight components, so it is possible to reduce the amount of gas generated, and it is assumed that a highly uniform coating film without voids can be obtained. Yes.

  On the other hand, when the content of cyclic PAS is less than 5% by weight, the amount of gas generated during the formation of the coating film increases, and voids are easily generated, and the object of the present invention cannot be achieved. Moreover, the content rate of cyclic PAS is 30 weight% in a more preferable aspect, More preferably, it is 50 weight%, More preferably, it is 80 weight%, Most preferably, it is 90 weight%.

  The molecular weight of the polyarylene sulfide resin of the present invention is not particularly limited, but the upper limit is preferably a weight average molecular weight of less than 20,000, more preferably less than 10,000, still more preferably 5000 or less, and most preferably 3000 or less. preferable. Further, the lower limit is preferably 300 or more, more preferably 400 or more, and further preferably 500 or more in terms of weight average molecular weight.

  The PAS resin powder coating of the present invention is contained in the PAS resin coating film obtained by baking and increasing the degree of polymerization because the alkali metal content in the cyclic polyarylene sulfide as the main component is small. The alkali metal content is also reduced. In a preferred embodiment, the alkali metal content in the PAS resin powder coating is 100 ppm or less, more preferably 50 ppm or less, more preferably 30 ppm or less, still more preferably 10 ppm or less.

  When the alkali metal content in the PAS resin powder coating exceeds 100 ppm, the reliability of the PAS resin coating film obtained by baking this, for example, in applications where high electrical insulation properties are required is reduced. This is not preferable because the use is limited. Here, the alkali metal content in the PAS resin powder coating in the present invention is a value calculated from the amount of alkali metal in the ash that is a residue obtained by baking the PAS resin powder coating using an electric furnace or the like, for example. The ash content can be quantified by analyzing it by, for example, ion chromatography or atomic absorption. The alkali metal refers to lithium, sodium, potassium, rubidium, cesium, and francium belonging to Group IA of the periodic table, but the PAS of the present invention preferably contains no alkali metal other than sodium. When an alkali metal other than sodium is included, the electrical properties and thermal properties of the coating film tend to be adversely affected. In addition, there is a possibility that the amount of the eluted metal when the coating film comes into contact with various solvents increases, and this tendency becomes strong particularly when the coating film contains lithium.

  Moreover, it is preferable that the PAS resin powder coating material of the present invention does not substantially contain a halogen other than chlorine, that is, fluorine, bromine, iodine, or astatine. When the PAS resin powder paint of the present invention contains chlorine as a halogen, it is stable in the temperature range normally used, so even if it contains a small amount of chlorine, there is little influence on the mechanical properties of the coating film. When these halogens are contained, these unique properties tend to deteriorate the properties of the coating film, such as electrical properties and residence stability. When the PAS resin powder coating material of the present invention contains chlorine as a halogen, the preferable amount is 1% by weight or less, more preferably 0.5% by weight or less, and still more preferably 0.2% by weight or less.

  On the other hand, the PAS resin powder coating of the present invention may contain a zero-valent transition metal compound. This zero-valent transition metal compound is preferable because the ring-opening polymerization reaction of cyclic PAS in the coating film forming step (baking) is promoted and baking is completed at a low temperature and / or in a short time. As a metal seed | species of such a zerovalent transition metal compound, the metal of a periodic table 8th group to 11th group and a 4th period to a 6th period can be illustrated in a preferable aspect. More specifically, nickel, palladium, platinum, iron, ruthenium, rhodium, copper, silver and gold can be exemplified. Various complexes are suitable as the zero-valent transition metal compound. For example, triphenylphosphine, tri-t-butylphosphine, tricyclohexylphosphine, 1,2-bis (diphenylphosphino) ethane, 1 , 1'-bis (diphenylphosphino) ferrocene, dibenzylideneacetone, dimethoxydibenzylideneacetone, cyclooctadiene, and carbonyl complexes. Specifically, bis (dibenzylideneacetone) palladium, tris (dibenzylideneacetone) dipalladium, tetrakis (triphenylphosphine) palladium, bis (tri-t-butylphosphine) palladium, bis [1,2-bis (diphenylphosphine) Fino) ethane] palladium, bis (tricyclohexylphosphine) palladium, [P, P′-1,3-bis (di-i-propylphosphino) propane] [P-1,3-bis (di-i-propyl) Phosphino) propane] palladium, 1,3-bis (2,6-di-i-propylphenyl) imidazol-2-ylidene (1,4-naphthoquinone) palladium dimer, 1,3-bis (2,4 , 6-Trimethylphenyl) imidazol-2-ylidene (1,4-naphthoquinone) palladium dimer, bi (3,5,3 ′, 5′-dimethoxydibenzylideneacetone) palladium, bis (tri-t-butylphosphine) platinum, tetrakis (triphenylphosphine) platinum, tetrakis (trifluorophosphine) platinum, ethylenebis (tri Phenylphosphine) platinum, platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex, tetrakis (triphenylphosphine) nickel, tetrakis (triphenylphosphite) nickel, Examples thereof include bis (1,5-cyclooctadiene) nickel, dodecacarbonyl triiron, pentacarbonyl iron, dodecacarbonyl tetrarhodium, hexadecacarbonyl hexarhodium, dodecacarbonyl triruthenium and the like. These polymerization catalysts may be used alone or in combination of two or more.

  The zero-valent transition metal compound may be added by adding these zero-valent transition metal compounds directly to the PAS resin powder coating material containing the cyclic PAS of the present invention. It may be formed. Here, in order to form a zero-valent transition metal compound in the system as in the latter case, a transition metal compound such as a transition metal salt and a ligand compound are added to form a transition metal complex in the system. And a method of adding a complex formed of a transition metal compound such as a transition metal salt and a compound serving as a ligand. Since transition metal salts other than zero valence do not promote the conversion of cyclic polyarylene sulfide, it is necessary to add a compound serving as a ligand. Examples of transition metal compounds and ligands used in the present invention and complexes formed of transition metal compounds and ligands are given below. Examples of the transition metal compound for forming a zero-valent transition metal compound in the system include acetates and halides of various transition metals. Examples of the transition metal species include nickel, palladium, platinum, iron, ruthenium, rhodium, copper, silver, gold acetate, halide and the like. Specifically, nickel acetate, nickel chloride, nickel bromide. , Nickel iodide, nickel sulfide, palladium acetate, palladium chloride, palladium bromide, palladium iodide, palladium sulfide, platinum chloride, platinum bromide, iron acetate, iron chloride, iron bromide, iron iodide, ruthenium acetate, chloride Examples include ruthenium, ruthenium bromide, rhodium acetate, rhodium chloride, rhodium bromide, copper acetate, copper chloride, copper bromide, silver acetate, silver chloride, silver bromide, gold acetate, gold chloride, and gold bromide. The ligand added simultaneously to form a zero-valent transition metal compound in the system is one that generates a zero-valent transition metal when the cyclic polyarylene sulfide and the transition metal compound are heated. Although not particularly limited, basic compounds are preferable, and examples thereof include triphenylphosphine, tri-t-butylphosphine, tricyclohexylphosphine, 1,2-bis (diphenylphosphino) ethane, 1,1′-bis (diphenylphosphine). Fino) ferrocene, dibenzylideneacetone, sodium carbonate, ethylenediamine and the like. Moreover, as a complex formed with the compound used as a transition metal compound and a ligand, the complex which consists of the above various transition metal salts and a ligand is mentioned. Specifically, bis (triphenylphosphine) palladium diacetate, bis (triphenylphosphine) palladium dichloride, [1,2-bis (diphenylphosphino) ethane] palladium dichloride, [1,1′-bis (diphenylphosphine) Fino) ferrocene] palladium dichloride, dichloro (1,5′-cyclooctadiene) palladium, bis (ethylenediamine) palladium dichloride, bis (triphenylphosphine) nickel dichloride, [1,2-bis (diphenylphosphino) ethane] nickel Examples include dichloride, [1,1′-bis (diphenylphosphino) ferrocene] nickel dichloride, dichloro (1,5′-cyclooctadiene) platinum and the like. These transition metal compounds and ligands may be used alone or in combination of two or more.

  The concentration of the zero-valent transition metal compound used varies depending on the molecular weight of the target PAS resin powder coating and the type of the zero-valent transition metal compound, but is usually 0.001 to the sulfur atom of the PAS resin powder coating. It is 20 mol%, preferably 0.005 to 15 mol%, more preferably 0.01 to 10 mol%. If it is 0.001 mol% or more, the cyclic polyarylene sulfide is sufficiently converted to polyarylene sulfide, and if it is 20 mol% or less, a polyarylene sulfide having the above-described properties can be obtained.

  When the zero-valent transition metal compound is added, it may be added as it is to the PAS resin powder coating material of the present invention. Examples of the uniform dispersion method include a mechanical dispersion method and a dispersion method using a solvent. Specific examples of the mechanical dispersion method include a pulverizer, a stirrer, a mixer, a shaker, and a method using a mortar. Specific examples of the method of dispersing using a solvent include a method of dissolving or dispersing cyclic polyarylene sulfide in an appropriate solvent, adding a predetermined amount of a polymerization catalyst thereto, and then removing the solvent. In addition, when the polymerization catalyst is dispersed, when the polymerization catalyst is a solid, it is preferable that the average particle size of the polymerization catalyst is 1 mm or less because more uniform dispersion is possible.

(2) Cyclic polyarylene sulfide The cyclic polyarylene sulfide constituting the PAS resin used in the powder coating of the present invention is a cyclic compound having a repeating unit of the formula-(Ar-S)-as a main structural unit. And preferably a compound represented by the following general formula (1) containing 80% by weight or more of the repeating unit, more preferably 90% by weight or more, and still more preferably 95% by weight or more. Ar includes units represented by the above formulas (A) to (L), among which the formula (A) is particularly preferable. In this case, the powder coating obtained by the present invention has excellent heat resistance and the like. It is easy to obtain the characteristics.

  In addition, in cyclic polyarylene sulfide, repeating units, such as said Formula (A)-Formula (L), may be included at random, may be included in a block, and any of those mixtures may be sufficient. Typical examples of these are cyclic polyphenylene sulfide (formula (A), formula (B), formula (F) to formula (K)), cyclic polyphenylene sulfide sulfone (formula (D)), cyclic Examples thereof include polyphenylene sulfide ketone (formula (C)), cyclic polyphenylene sulfide ether (formula (E)), cyclic random copolymers, cyclic block copolymers, and mixtures thereof. Particularly preferred cyclic polyarylene sulfides include p-phenylene sulfide units as the main structural unit.

Is a cyclic polyphenylene sulfide (hereinafter, abbreviated as cyclic PPS) containing 80% by weight or more, particularly 90% by weight or more in a cyclic compound having a repeating unit of-(Ar-S)-as a main structural unit. In this case, the powder coating obtained by the present invention is likely to obtain excellent characteristics such as heat resistance.

  Although there is no restriction | limiting in particular in the repeating number m in the said (1) Formula of cyclic polyarylene sulfide, 2-50 are preferable, 2-25 are more preferable, and 4-12 can be illustrated as a still more preferable range. As will be described later, the polyarylene sulfide resin coating film forming step (baking) of the present invention needs to be performed at a temperature higher than the temperature range at which the cyclic polyarylene sulfide is melted. Therefore, it is advantageous to set m to 50 or less in that the polymerization of the polyarylene sulfide prepolymer can be performed at a lower temperature.

  The cyclic polyarylene sulfide may be either a single compound having a single repeating number or a mixture of cyclic polyarylene sulfides having different repeating numbers, but may be a mixture of cyclic polyarylene sulfides having different repeating numbers. However, the melting temperature tends to be lower than that of a single compound having a single repeating number, and it is preferable to use a mixture of cyclic polyarylene sulfides having different repeating numbers because the polymerization temperature can be lowered.

  Such a cyclic PAS compound can be obtained by obtaining a PAS mixture containing PAS and a cyclic PAS compound by a known PAS production method and then extracting the cyclic PAS compound from the PAS mixture. The manufacturing method will be described below.

(3) Manufacturing method of PAS mixture used as raw material of cyclic PAS compound As a manufacturing method of the PAS mixture, a known technique can be used. For example, a polyhalogenated aromatic compound represented by at least p-dichlorobenzene, A mixture containing an alkali metal sulfide typified by sodium sulfide and an organic polar solvent typified by N-methyl-2-pyrrolidone is heated to prepare a reaction solution containing a PAS mixture and an alkali metal halide. Examples thereof include a method of obtaining a PAS mixture (PAS and cyclic PAS compound) by treating the liquid with water or the like, and a method of obtaining a PAS mixture by oxidative polymerization of diphenyl disulfides or thiophenols. However, since the cyclic PAS compound generally contained in the PAS mixture generally obtained by these methods is as low as less than 5% by weight, in order to obtain a PAS mixture containing 5% by weight or more of the cyclic PAS compound, for example, polymerization of the PAS mixture is performed. In this case, a special method such as using a large amount of a polymerization solvent is necessary, and it is economically disadvantageous to obtain a large amount of PAS mixture efficiently by such a method, and it is difficult to establish it industrially. .

  Other methods for producing the PAS mixture include, for example, polyhalogenated aromatic compounds represented by at least p-dichlorobenzene, alkali metal sulfides represented by sodium sulfide, and N-methyl-2-pyrrolidone. At least granular PAS and a PAS mixture other than granular PAS, organic polar solvent, water, and alkali halide obtained by heating and polymerizing the mixture containing the organic polar solvent A preferred example is a method of obtaining a PAS mixture from a recovered slurry obtained when granular PAS is removed from a reaction solution containing a metal salt. Here, granular PAS refers to a PAS component that can be recovered with a standard sieve (80 mesh sieve) having an average aperture of 0.175 mm. The PAS mixture obtained by this method contains a large amount of low molecular weight PAS having a weight average molecular weight of 5,000 or less. For example, the properties such as mechanical properties are significantly inferior to those of the granular PAS. Has been conventionally recognized as being difficult and not worth industrial use. Therefore, the PAS mixture obtained by this method has usually been treated as industrial waste.

  As a result of detailed analysis of the PAS mixture other than the granular PAS, the present inventors include 10% by weight or more of the cyclic PAS (m = 2 to 50) represented by the formula (1). In particular, since these were obtained as a mixture of m = 2 to 50, they were found to be preferable as a raw material for obtaining the cyclic PAS compound of the present invention. This is significant from the viewpoint of recovering a compound having an extremely high industrial utility value from what was conventionally regarded as industrial waste by the method of the present invention.

  As a method for recovering PAS from the recovered slurry, for example, at least 50% by weight or more of an organic polar solvent is removed from the recovered slurry, a residue is obtained, water is added thereto, and then an acid is added as desired. A method in which at least the residual organic polar solvent and the alkali metal halide are removed and the PAS mixture is separated and recovered, or a method in which the PAS mixture is precipitated from the recovered slurry and PAS is recovered as a solid component, such as a recovered slurry. Examples thereof include a method of obtaining PAS as a solid component by a known solid-liquid separation method such as decantation, centrifugation, and filtration after precipitation of PAS by adding water.

(4) Preparation of cyclic PAS compound-containing solution In the present invention, a solution containing a cyclic PAS compound is prepared by bringing the PAS compound into contact with a solvent capable of dissolving the cyclic PAS compound (m = 2 to 50) described in formula (1). Prepare.

  The solvent used here is not particularly limited as long as it is a solvent capable of dissolving the cyclic PAS compound. However, a solvent in which the cyclic PAS compound dissolves in a dissolving environment but PAS is difficult to dissolve, and a solvent in which PAS does not dissolve is preferred. Is more preferable. The pressure of the reaction system when the PAS is brought into contact with the solvent is preferably normal pressure or slight pressure, and particularly preferably normal pressure. The reaction system of such pressure is advantageous in that the components of the reactor for constructing it are inexpensive. There is. From this point of view, it is desirable that the reaction system pressure avoid pressurizing conditions that require an expensive pressure vessel. As the solvent to be used, those which do not substantially cause undesired side reactions such as decomposition and crosslinking of PAS and cyclic PAS compounds are preferable, and as a preferable solvent when the operation of bringing the PAS mixture into contact with the solvent is performed, for example, under atmospheric pressure reflux conditions. Are, for example, hydrocarbon solvents such as benzene, toluene, xylene, halogen solvents such as chloroform, bromoform, methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane, chlorobenzene, 2,6-dichlorotoluene, Ketone solvents such as acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl butyl ketone, acetophenone, ether solvents such as diethyl ether, tetrahydrofuran, diisopropyl ether, N, N-dimethylformamide, N, N-dimethyl Examples include polar solvents such as cetamide, dimethyl sulfoxide, trimethyl phosphoric acid, N, N-dimethylimidazolidinone, among which benzene, toluene, xylene, chloroform, bromoform, methylene chloride, 1,2-dichloroethane, 1,1, 1-trichloroethane, chlorobenzene, 2,6-dichlorotoluene, acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, methyl butyl ketone, diethyl ether, tetrahydrofuran, diisopropyl ether, N, N-dimethylformamide, N, N-dimethylacetamide, Dimethyl sulfoxide, trimethyl phosphate and N, N-dimethylimidazolidinone are preferable, and toluene, xylene, chloroform, methylene chloride and tetrahydrofuran are more preferable. It can be shown.

  There is no particular limitation on the atmosphere in which the PAS is brought into contact with the solvent. However, when the PAS or the solvent is oxidized and deteriorated depending on conditions such as the temperature and time at which the PAS is brought into contact with the solvent, it is desirable to perform in a non-oxidizing atmosphere. . Note that the non-oxidizing atmosphere is an atmosphere having a gas phase oxygen concentration of 5% by volume or less, preferably 2% by volume or less, more preferably an oxygen-free atmosphere such as nitrogen, helium, argon, or the like. Among these, a nitrogen atmosphere is particularly preferable from the viewpoints of economy and ease of handling.

  The temperature at which the PAS mixture is brought into contact with the solvent is not particularly limited, but generally, the higher the temperature, the more the dissolution of the cyclic PAS compound in the solvent tends to be promoted. As described above, since the contact of the PAS mixture with the solvent is preferably performed under atmospheric pressure, the upper limit temperature is preferably set to the reflux condition temperature under atmospheric pressure of the solvent used. For example, 20 to 150 ° C. can be exemplified as a specific temperature range.

  The time for bringing the PAS mixture into contact with the solvent varies depending on the type of solvent used, the temperature, etc., but cannot be uniquely limited. For example, 1 minute to 50 hours can be exemplified, and if it is too short, the cyclic PAS is not sufficiently dissolved in the solvent. If it is too long, dissolution in the solvent reaches a saturated state, and no further effect can be obtained.

  The method of bringing PAS into contact with a solvent is not particularly limited as long as a known general method is used. For example, a method of collecting a PAS mixture and a solvent, stirring the solution as necessary, and then collecting a solution portion, various filters Any method can be used, such as a method in which the PAS mixture is showered with a solvent and at the same time the cyclic PAS is dissolved in the solvent, or a method based on the Soxhlet extraction principle. Although there is no restriction | limiting in particular in the usage-amount of the solvent at the time of making PAS and a solvent contact, For example, the range of 0.5-100 can be illustrated by the bath ratio with respect to PAS weight. When the bath ratio is too small, not only is the mixing of the PAS mixture and the solvent difficult, but the cyclic PAS compound tends to be insufficiently dissolved in the solvent. A larger bath ratio is generally advantageous for dissolving a cyclic PAS compound in a solvent, but if it is too large, no further effect can be expected, and conversely, there may be an economic disadvantage due to an increase in the amount of solvent used. . When the contact between the PAS and the solvent is repeated, a sufficient effect can often be obtained even with a small bath ratio. In addition, the Soxhlet extraction method, in principle, provides an effect similar to the case where the contact between the PAS and the solvent is repeated, and in this case, a sufficient effect can often be obtained with a small bath ratio.

  After the PAS is brought into contact with the solvent, when the solution in which the cyclic PAS compound is dissolved is obtained in the form of a solid-liquid slurry containing the remaining solid PAS, the solution portion is recovered using a known solid-liquid separation method. . Examples of the solid-liquid separation method include separation by filtration, centrifugation, and decantation. For the solution thus separated, the solvent described later is removed. On the other hand, for the remaining solid component, when the cyclic PAS compound still remains, specifically, when 0.05% by weight or more of the cyclic PAS compound remains on a weight basis, A cyclic PAS compound can be obtained with higher yield by repeatedly performing contact and solution recovery. Further, when the cyclic PAS compound hardly remains, specifically, when the cyclic PAS compound remains less than 0.05% by weight, the residual solid PAS is removed by removing the residual solvent. Can be suitably recycled as high-purity PAS.

(5) Removal of solvent from cyclic PAS compound solution In the present invention, the solvent is removed from the solution containing the cyclic PAS compound (m = 2 to 50) represented by the formula (1) obtained as described above. To obtain a cyclic PAS compound. The removal of the solvent can be exemplified by, for example, a method of heating and treating at normal pressure or less, and removal of the solvent using a membrane. However, from the viewpoint of obtaining a cyclic PAS compound with higher yield and efficiency. A method of removing the solvent by heating at a pressure lower than the pressure is preferred. The solution containing the cyclic PAS compound obtained as described above may contain a solid depending on the temperature. In this case, the solid belongs to the cyclic PAS compound. It is desirable to recover together with the soluble component, whereby a cyclic PAS compound can be obtained with good yield.

  In removing the solvent, it is desirable to remove at least 50% by weight, preferably 70% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more. Although the temperature at which the solvent is removed by heating depends on the characteristics of the solvent used, it cannot be limited uniquely. However, the temperature can usually be selected from 20 to 150 ° C, preferably from 40 to 120 ° C. In addition, the pressure for removing the solvent is preferably normal pressure or lower, which makes it possible to remove the solvent at a lower temperature.

(6) Other post-treatments The cyclic PAS compounds obtained by the methods described in (3) to (5) have sufficiently high purity, and can be suitably used as cyclic PAS compounds with m = 2 to 50. Furthermore, it is possible to obtain a cyclic PAS compound with higher purity and a cyclic PAS simple substance with m = 6 by additionally performing post-treatment described below.

  The cyclic PAS compound obtained by the operations (3) to (5) may contain an impurity component contained in PAS depending on the characteristics of the solvent used. Impurities are dissolved in cyclic PAS compounds containing such small amounts of impurities, but cyclic PAS compounds are not dissolved or contacted with a second solvent in which cyclic PAS compounds are difficult to dissolve, thereby selectively removing impurity components. Often it is possible to do.

  The pressure of the reaction system when the cyclic PAS compound is contacted with the second solvent is preferably normal pressure or slight pressure, and particularly preferably normal pressure, and the reaction system having such pressure is inexpensive to construct the members. There is an advantage. From this point of view, it is desirable that the reaction system pressure avoid pressurizing conditions that require an expensive pressure vessel. As the preferred solvent as the second solvent, those which do not substantially cause undesirable side reactions such as decomposition and crosslinking of the target cyclic PAS compound are preferable. For example, methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, Alcohol / phenolic solvents such as propylene glycol, phenol, cresol, polyethylene glycol, hydrocarbon solvents such as pentane, hexane, heptane, octane, cyclohexane, cyclopentane, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl butyl ketone, Ketone solvents such as acetophenone, methyl acetate, ethyl acetate, pentyl acetate, octyl acetate, methyl butyrate, ethyl butyrate, pentyl butyrate, methyl salicylate, ethyl formate, etc. Examples of rubonic acid solvents include methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, pentane, hexane, heptane, octane, cyclohexane, and cyclopentane, and methanol, ethanol, propanol, and ethylene. Glycol, pentane, hexane, heptane, octane, cyclohexane, acetone and ethyl acetate are particularly preferred. These solvents can be used as one kind or a mixture of two or more kinds.

  There is no particular limitation on the temperature at which the cyclic PAS compound is brought into contact with the second solvent, but the upper limit temperature is preferably the reflux condition temperature under normal pressure of the second solvent to be used. When using, 20-100 degreeC can be illustrated as a preferable temperature range, for example, More preferably, 25-80 degreeC can be illustrated.

  The time for contacting the cyclic PAS compound with the second solvent cannot be uniquely limited because it varies depending on the type of solvent used, the temperature, etc., but for example, 1 minute to 50 hours can be exemplified, and if it is too short, impurities in the cyclic PAS compound In this case, the dissolution of the impurities in the second solvent reaches a saturated state, and no further effect can be obtained.

  As a method for bringing the cyclic PAS compound into contact with the second solvent, a method in which the solid cyclic PAS compound and the second solvent are stirred and mixed as necessary, and the second solvent is added to the cyclic PAS compound solid on various filters. A method of dissolving impurities in a second solvent at the same time as showering, a method using Soxhlet extraction of a solid cyclic PAS compound using a second solvent, a cyclic PAS compound slurry containing a solution-like cyclic PAS compound or solvent For example, a method in which the cyclic PAS compound is precipitated in the presence of the second solvent by bringing the compound into contact with the second solvent can be used. In particular, the method of bringing a cyclic PAS compound slurry containing a solvent into contact with the second solvent is an effective method because the cyclic PAS compound obtained after the operation has a high purity.

  After contacting the cyclic PAS compound with the second solvent, a slurry in which the cyclic PAS compound is precipitated in the second solvent is obtained, so that the solid cyclic PAS compound is recovered using a known solid-liquid separation method. To do. Examples of the solid-liquid separation method include separation by filtration, centrifugation, and decantation. If impurities still remain in the cyclic PAS compound obtained after solid-liquid separation, it is also possible to contact the cyclic PAS compound and the second solvent again to further remove the impurities.

(7) Characteristics of Cyclic Polyarylene Sulfide The cyclic PAS compound thus obtained has m in the formula (1) of 2 to 50, and m = 2 to 25 represented by the formula (1). The cyclic PAS compound is preferably a cyclic PAS mixture having m = 4 to 12. When m is in this range, as described later, it was found that the degree of polymerization by melting and heating during the formation of a coating film of a polyarylene sulfide resin composed of cyclic PAS rapidly proceeds, and the present invention has been achieved.
Moreover, although the cyclic PAS compound obtained by the method described in (3) to (6) is sufficiently high in purity, a linear PAS oligomer may be contained as an impurity depending on conditions. Further, as described above, it is difficult to distinguish this linear PAS oligomer from a cyclic PAS compound having m = 13 or more with the latest analysis technique at present. The weight average molecular weight (Mw) of the oligomer component estimated to be a linear PAS oligomer varies depending on the production method of PAS used as the raw material of the cyclic PAS compound described in (3) above, but is usually 5000 or less. Yes, in some cases it is 2000 or less.

  The linear PAS oligomer remaining as an impurity in the cyclic PAS compound has poor thermal stability and increases the amount of volatile gas components as compared with the cyclic PAS compound. If these are contained in a large amount as impurities, there arises a problem that the conversion of the cyclic PAS compound to PAS by melting and heating becomes insufficient.

  Therefore, the amount of linear PAS oligomer in the PAS resin obtained by the method described in (3) to (6) is preferably less than 50% by weight and less than 40% by weight with respect to 100% by weight of the PAS resin. More preferably, it is less than 30% by weight.

  The amount of linear PAS oligomer in the cyclic PAS compound at this time can be quantified by MALDI-TOF-MS as the total amount with the cyclic PAS compound of m = 13 or more according to the present analysis technique. It is.

  Further, as described in JP-A-10-77408, a cyclic PAS compound is subjected to Soxhlet extraction from a crosslinked type PAS, the extract is cooled, and the precipitated white solid is subjected to cyclic PAS by a “recrystallization method”. It is disclosed that a simple substance can be obtained with high purity. Although the recovery amount is smaller than that of cross-linked PAS, it is possible to obtain cyclic PAS with high purity in the same way from linear PAS by the same extraction operation and “recrystallization”. It is.

  That is, according to the method described in (3) to (6), the obtained cyclic PAS compound is a mixture having different m, and the obtained cyclic PAS compound is compared with a single cyclic PA consisting of m, There is a feature that the melting temperature is low, which means that, for example, a cyclic PAS compound can be converted into a high molecular weight polymer at a low melting heating temperature by a simple method. Baking is possible at a lower temperature.

  Further, the cyclic PAS thus obtained has, in a preferred embodiment, an alkali metal content of 100 ppm or less, more preferably 50 ppm or less, further preferably 30 ppm or less, and most preferably 10 ppm. The PAS resin coating film obtained by (coating) has a high purity and is characterized by excellent electrical and mechanical properties of the coating film.

(8) Characteristics of the powder coating material comprising the PAS resin of the present invention Since the powder comprising the PAS resin thus obtained contains the cyclic PAS, it is compared with the powder coating material comprising the conventional linear PAS resin powder. And since the amount of gas generation at the time of baking is small, and generation of voids in the resulting coating film can be suppressed, it is suitable as a powder coating material.

  The powder coating material of the present invention may be a PAS resin alone or, if necessary, other additives such as titanium dioxide, valve stem (iron oxide), carbon black and the like, as long as the object of the present invention is not impaired. An appropriate amount of inorganic pigments such as glass beads, glass powder, short glass fibers, glass flakes, talc, calcium carbonate, and barium sulfate; UV stabilizers; Further, other polymers such as polyamide, polycarbonate, polysulfone, polyethersulfone, polyphenylene oxide, polyimide, polyamideimide, and epoxy resin may be added.

  When the above components are added, the PAS resin of the present invention and the above additives can be uniformly mixed with a stirring device such as a Henschel mixer.

(9) Powder coating method The composition of the present invention is coated on the surface of an object to be coated such as metal, glass or ceramic by a conventional powder coating method, and then heated at a predetermined temperature for a predetermined time (hereinafter baked). Called). Prior to powder coating, an appropriate primer may be primed on the surface of the object to be coated.

  In the PAS resin of the present invention described above, since the cyclic polyarylene sulfide is converted into a high polymerization degree on the coated surface at the time of heating and melting in the baking process, the gas generated during baking of the conventional PAS resin can be reduced. Can suppress the generation of voids in the coating film.

  Accordingly, the baking temperature is preferably a temperature at which the PAS resin, particularly the cyclic PAS as the main component, melts and is not particularly limited as long as it is such a temperature condition. If the baking temperature is lower than the melting temperature of the PAS resin, a long time tends to be required to obtain a coating film.

  Note that the temperature at which the PAS resin of the present invention melts varies depending on the composition, molecular weight, and environment during heating and cannot be uniquely indicated. For example, the PAS resin is analyzed with a differential scanning calorimeter. It is possible to grasp the melting solution temperature. However, if the temperature is too high, undesirable side reactions such as cross-linking reactions and decomposition reactions between cyclic PASs and PASs produced by baking tend to occur, and the properties of the resulting coating film deteriorate. Therefore, it is desirable to avoid a temperature at which such an undesirable side reaction is remarkably generated. Specific examples of the lower limit of the heating temperature include 180 ° C. or higher, preferably 200 ° C. or higher, more preferably 220 ° C. or higher, still more preferably 240 ° C. or higher, and even more preferably 250 ° C. or higher. In this temperature range, the cyclic polyarylene sulfide melts and can be obtained in a short time. On the other hand, if the temperature is too high, undesirable side reactions represented by crosslinking and decomposition reactions between cyclic polyarylene sulfides, between polyarylene sulfides produced by heating, and between polyarylene sulfides and cyclic polyarylene sulfides, etc. Therefore, it is desirable to avoid a temperature at which such undesirable side reactions are remarkably caused, since the characteristics of the resulting polyarylene sulfide may be deteriorated. As an upper limit of heating temperature, 400 degrees C or less can be illustrated, Preferably it is 360 degrees C or less, More preferably, it is 320 degrees C or less, More preferably, it is 300 degrees C or less, More preferably, it is 270 degrees C or less. Under this temperature range, adverse effects on the properties of the polyarylene sulfide obtained by an undesirable side reaction tend to be suppressed, and a polyarylene sulfide having the above-described properties can be obtained.

  In addition, the baking time cannot be uniformly defined because it varies depending on various properties such as the content, m number, and molecular weight of the cyclic polyarylene sulfide in the PAS resin to be used, and the conditions such as the baking temperature. It is preferable to set so that undesirable side reactions do not occur as much as possible. Specific examples of the baking time include 0.05 to 100 hours, preferably 0.1 to 20 hours, and more preferably 0.1 to 10 hours. If it is less than 0.05 hours, the conversion of cyclic PAS to a high degree of polymerization tends to be insufficient, and if it exceeds 100 hours, adverse effects on the properties of the resulting coating due to undesirable side reactions may become apparent. Not only does it tend to be high, it may also be economically disadvantageous.

(10) Properties of the coating film obtained by powder coating of PAS resin The PAS resin coating film obtained by baking the PAS resin powder coating material containing the cyclic polyarylene sulfide of the present invention is used in the baking process as described above. In order to increase the degree of polymerization of the polyarylene sulfide of the formula, in a preferred embodiment, the molecular weight distribution is broadened, that is, the degree of dispersion represented by the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight) is 2.5. Or less, more preferably 2.3 or less, still more preferably 2.1 or less, and even more preferably 2.0 or less, and the content of the low molecular weight component is small. When the degree of dispersion exceeds 2.5, the amount of low-molecular components contained in the PAS coating film increases, which decreases the mechanical properties of the coating film and increases the amount of gas generated during film formation. In this case, voids frequently occur in the coating film, which is not desirable from the viewpoint of uniform smoothness. The weight average molecular weight and number average molecular weight can be determined using, for example, SEC (size exclusion chromatography) equipped with a differential refractive index detector.

  Moreover, since the PAS resin coating film of the present invention has a low alkali metal content in the PAS resin powder coating material containing cyclic polyarylene sulfide as a raw material, it is included in the coating film obtained by baking and increasing the degree of polymerization. The alkali metal content is also reduced. In a preferred embodiment, the alkali metal content in the coating film is 100 ppm or less, more preferably 50 ppm or less, more preferably 30 ppm or less, and still more preferably 10 ppm or less.

  When the alkali metal content in the coating film exceeds 100 ppm, the use is restricted, for example, the reliability in the use requiring high electrical insulation characteristics is lowered. Here, the alkali metal content in the coating film in the present invention means, for example, an alkali in ash that is a residue obtained by peeling the coating film from a coated product obtained by powder coating and firing using an electric furnace or the like. It is a value calculated from the amount of metal, and can be quantified by analyzing the ash by, for example, ion chromatography or atomic absorption. The alkali metal refers to lithium, sodium, potassium, rubidium, cesium, and francium belonging to Group IA of the periodic table, but the PAS of the present invention preferably contains no alkali metal other than sodium. When an alkali metal other than sodium is included, the electrical properties and thermal properties of the coating film tend to be adversely affected. In addition, there is a possibility that the amount of the eluted metal when the coating film comes into contact with various solvents increases, and this tendency becomes strong particularly when the coating film contains lithium.

  The PAS resin coating film of the present invention preferably contains substantially no halogen other than chlorine, that is, fluorine, bromine, iodine, or astatine. When the coating film of the present invention contains chlorine as a halogen, the coating film is stable in the temperature range in which it is normally used. When contained, these unique properties tend to deteriorate the properties of the coating film, such as electrical properties. When the coating film obtained from the powder coating material of the present invention contains chlorine as a halogen, the preferable amount is 1% by weight or less, more preferably 0.5% by weight or less, still more preferably 0.2% by weight or less. In this range, the electrical characteristics and residence stability of PAS tend to be better.

  From the above, the PAS resin coating film of the present invention not only has few voids and excellent surface smoothness, but also has low alkali metal content and low molecular weight components, so it has excellent electrical and mechanical properties. Taking advantage of PAS, which is the base resin of the coating film, the heat insulation / chemical resistance pre-coated board, electrical / electronic parts, electrical insulation coatings such as electric wires, automobile parts, chemical plants, hot water pipes, hot spring pipes, It can be effectively applied to heat / chemical / corrosion-proof coatings for ships, seawater plants, oilfield pipes, etc.

  The present invention will be described more specifically with reference to the following examples. These examples are illustrative and not limiting.

<Molecular weight measurement>
The molecular weight of cyclic polyarylene sulfide and polyarylene 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: Senshu Science GPC3506
Eluent: 1-chloronaphthalene detector: differential refractive index detector Column temperature: 210 ° C
Pre-constant temperature: 250 ° C
Pump 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).

<Quantification of alkali metal content>
The alkali metal content contained in the polyarylene sulfide and the polyarylene sulfide prepolymer was determined as follows.
(A) The sample was weighed in a quartz crucible and incinerated using an electric furnace.
(B) After the ashed product was dissolved with concentrated nitric acid, the volume was adjusted to a constant volume with diluted nitric acid.
(C) The obtained constant volume solution was subjected to ICP gravimetric analysis (apparatus; 4500 manufactured by Agilent) and ICP emission spectroscopic analysis (apparatus; Optima 4300DV manufactured by PerkinElmer).

[Reference Examples, Examples 1 and 2 and Comparative Examples 1 and 2; Production of PAS resin powder coating]
[Reference example]
<Production example of PAS mixture as raw material for cyclic polyarylene sulfide>
Hereinafter, in this reference example, a production example of a PAS mixture as a raw material for the cyclic polyarylene sulfide described in the text (2) will be described.

<Preparation of PAS mixture>
In a 1000 L autoclave with a stirrer, 42.7% sodium hydrosulfide 82.7 kg (700 mol), 96% sodium hydroxide 29.6 kg (710 mol), N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) In some cases, 114.4 kg (1156 mol) of sodium acetate, 17.2 kg (210 mol) of sodium acetate, and 100 kg of ion-exchanged water are gradually heated to about 240 ° C. over about 3 hours while flowing nitrogen at normal pressure. After distilling 143 kg of water and 2.8 kg of NMP through the rectification tower, the reaction vessel was cooled to 160 ° C. In addition, 0.02 mol of hydrogen sulfide per 1 mol of the sulfur component charged during this liquid removal operation was scattered out of the system.

  Next, 103 kg (703 mol) of p-dichlorobenzene and 90 kg (910 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. While stirring at 240 rpm, the temperature was raised to 270 ° C. at a rate of 0.6 ° C./min and held at this temperature for 140 minutes. While 12.6 kg (700 mol) of water was injected over 15 minutes, it was cooled to 250 ° C. at a rate of 1.3 ° C./min. Thereafter, the slurry was cooled to 220 ° C. at a rate of 0.4 ° C./min, and then rapidly cooled to near room temperature to obtain a slurry (A). This slurry (A) was diluted with 200 kg of NMP to obtain a slurry (B).

  200 kg of the slurry (B) heated to 80 ° C. is filtered with a sieve (80 mesh, opening 0.175 mm) at a 50 kg / 1 batch scale, and about 150 kg of the slurry (C) is used as a filtrate component, and the slurry is used as a mesh-on component. 50 kg of granular PAS resin (crude PAS resin (D)) was obtained.

  150 kg of the obtained slurry (C) was charged into a devolatilizer at 50 kg / 1 batch and replaced with nitrogen, and treated at 100 to 150 ° C. under reduced pressure for 1.5 hours, and then 150 ° C. and 1 ° C. in a vacuum dryer. Time treatment gave a solid. After adding 200 kg of ion-exchanged water (1.2 times the amount of slurry (C)) to this solid, it was stirred at 70 ° C. for 30 minutes to make a slurry again. This slurry was subjected to vacuum suction filtration with a filter having an opening of 10 to 16 μm. 200 kg of ion-exchanged water was added to the obtained white cake, and the mixture was stirred again at 70 ° C. for 30 minutes to make a slurry again. Similarly, after suction filtration, vacuum drying was performed at 70 ° C. for 5 hours to obtain 2 kg of the desired PAS mixture.

  Next, production examples of PAS resin powder coatings containing cyclic polyarylene sulfide using the obtained PAS mixture will be described below.

[Example 1]
<Production of PAS resin powder coating material containing cyclic polyarylene sulfide 1 (PAS-1)>
Using 2 kg of the PAS mixture obtained in the above Reference Example and 50 kg of chloroform as a solvent, the PPS mixture and the solvent were contacted by an extraction method at a bath temperature of about 80 ° C. for 3 hours to obtain an extract. The obtained extract was in the form of a slurry partially containing solid components at room temperature. Chloroform was distilled off from the extract slurry using an evaporator and then treated at 70 ° C. for 3 hours in a vacuum dryer to obtain 840 g of white powder (42% yield based on PAS mixture).

  The sodium content of PAS-1 thus obtained was 4 ppm, the chlorine content was 2.2 wt%, and alkali metals other than Na and halogens other than chlorine were below the detection limit. From the absorption spectrum in the infrared spectroscopic analysis of this solid matter, it was found that the solid matter was polyphenylene sulfide.

  Further, from mass spectral analysis of components separated by high performance liquid chromatography and molecular weight information by MALDI-TOF-MS, this PAS-1 has cyclic polyphenylene sulfide having 4 to 11 repeating units and 2 to 11 repeating units. It was a mixture of linear polyphenylene sulfide, and the weight ratio of cyclic polyphenylene sulfide to linear polyphenylene sulfide was found to be about 9: 1. The PAS-1 obtained from this was found to contain 90% by weight of cyclic polyphenylene sulfide and 10% of linear polyphenylene sulfide. As a result of GPC measurement, PAS-1 was completely dissolved in 1-chloronaphthalene at room temperature, and the weight average molecular weight was 900.

[Comparative Example 1]
<Manufacture of PAS resin powder coating 1 by conventional technology (PAS-2)>
About 20 liters of NMP was added to 20 kg of the crude PAS resin (D) obtained in the Reference Example, washed at 85 ° C. for 30 minutes, and filtered through a sieve (80 mesh, opening 0.175 mm). The operation of diluting the obtained solid with 50 liters of ion exchanged water, stirring at 70 ° C. for 30 minutes, and filtering through an 80 mesh sieve to collect the solid was repeated 5 times in total. The solid thus obtained was dried with hot air at 130 ° C. to obtain PAS-2. The absorption spectrum of the obtained polymer by infrared spectroscopic analysis was consistent with the absorption of the PAS mixture obtained in Reference Example.

  As a result of GPC measurement of the obtained PAS-2, it was found that the obtained PAS-2 had a weight average molecular weight of 59600 and a dispersity of 3.78. Further, as a result of elemental analysis, the Na content was 1040 ppm. Furthermore, as a result of analyzing the gas components generated during heating for PAS-2, 618 ppm of γ-butyrolactone and 416 ppm of 4-chloro-N-methylaniline were detected with respect to the weight of PPS before heating. Here, alkali metals other than Na and halogens other than chlorine were not detected.

[Example 2]
<Production of PAS resin powder coating material containing cyclic polyarylene sulfide 2 (PAS-3)>
67 g of the PAS-1 powder obtained in Example 1 and 33 g of the PAS-2 powder obtained in Comparative Example 1 were dry blended to obtain 100 g of PAS-3 powder.

  PAS-3 had a sodium content of 10 ppm and a chlorine content of 2.2 wt%, and alkali metals other than Na and halogens other than chlorine were below the detection limit. From the absorption spectrum in the infrared spectroscopic analysis of this solid matter, it was found that the solid matter was polyphenylene sulfide.

  Further, from the result of high performance liquid chromatography analysis of the obtained PAS-3, it is a mixture composed of cyclic polyarylene sulfide and linear polyarylene sulfide, and the weight ratio of cyclic polyarylene sulfide and linear polyarylene sulfide is It was found to be about 1: 1.5 (cyclic PPS weight / linear PPS weight = 0.67). From these analysis results, it was found that the obtained PAS-3 was a polyarylene sulfide mixture containing 60% by weight of cyclic polyarylene sulfide and 40% of linear polyarylene sulfide. Moreover, as a result of performing GPC measurement, the weight average molecular weight of PAS-3 was 8200.

[Example 3]
<Production of PAS resin powder coating material containing cyclic polyarylene sulfide 3 (PAS-4)>
A stainless steel autoclave equipped with a stirrer was charged with 14.03 g (0.120 mol) of a 48 wt% aqueous solution of sodium hydrosulfide and 12.50 g (0.144 mol) of a 48 wt% aqueous solution prepared using 96% sodium hydroxide. ), 615.0 g (6.20 mol) of N-methyl-2-pyrrolidone (NMP), and 18.08 g (0.123 mol) of p-dichlorobenzene (p-DCB). The reaction vessel was sufficiently purged with nitrogen, and then sealed under nitrogen gas. While stirring at 400 rpm, the temperature was raised from room temperature to 200 ° C. over about 1 hour. At this stage, the pressure in the reaction vessel was 0.35 MPa as a gauge pressure. Next, the temperature was raised from 200 ° C. to 270 ° C. over about 30 minutes. The pressure in the reaction vessel at this stage was 1.05 MPa as a gauge pressure. After maintaining at 270 ° C. for 1 hour, the contents were recovered after quenching to near room temperature.

  500 g of the obtained contents were diluted with about 1500 g of ion-exchanged water, and then filtered through a glass filter having an average opening of 10 to 16 μm. The filter-on component was dispersed in about 300 g of ion-exchanged water, stirred at 70 ° C. for 30 minutes, and filtered again in the same manner three times to obtain a white solid. This was vacuum dried at 80 ° C. overnight to obtain a dry solid.

  The obtained solid was charged into a cylindrical filter paper, and Soxhlet extraction was performed for about 5 hours using chloroform as a solvent to separate low molecular weight components contained in the solid.

  After removing the solvent from the extract obtained by the chloroform extraction operation, about 5 g of chloroform was added to prepare a slurry, which was added dropwise to about 300 g of methanol with stirring. The precipitate thus obtained was collected by filtration and vacuum dried at 70 ° C. for 5 hours to obtain 1.19 g of a white powder. This white powder was confirmed to be a compound composed of phenylene sulfide units from an absorption spectrum in infrared spectroscopic analysis. Moreover, this white powder has p-phenylene sulfide unit as the main constituent unit based on the mass spectrum analysis of the component divided by high performance liquid chromatography (apparatus; M-1200H manufactured by Hitachi) and molecular weight information by MALDI-TOF-MS. It was found to be a cyclic polyphenylene sulfide containing about 99% by weight of a cyclic compound having 4 to 13 repeating units and suitable for use in the PAS resin powder coating material of the present invention. The obtained PAS-4 had a sodium content of 4 ppm and a chlorine content of 2.2 wt%, and alkali metals other than Na and halogens other than chlorine were below the detection limit. As a result of GPC measurement, the cyclic polyphenylene sulfide was completely dissolved in 1-chloronaphthalene at room temperature, and the weight average molecular weight was 900.

[Example 4]
The PAS-1 powder obtained in Example 1 above was dry blended with 1 mol% of tetrakis (triphenylphosphine) palladium with respect to the sulfur atom of PAS-1 to obtain PAS-5. The obtained PAS-5 had a sodium content of 4 ppm and a chlorine content of 2.2 wt%. Alkali metals other than Na and halogens other than chlorine were below the detection limit and were equivalent to PAS-1. Further, from mass spectral analysis of components separated by high performance liquid chromatography and molecular weight information by MALDI-TOF-MS, this PAS-1 is a cyclic polyphenylene sulfide having 4 to 11 repeating units and 2 to 11 repeating units. The weight ratio of cyclic polyphenylene sulfide to linear polyphenylene sulfide was about 9: 1. As a result of GPC measurement, PAS-5 was completely converted into 1-chloronaphthalene at room temperature. The weight average molecular weight was 900 and both were equivalent to PAS-1.

[Example 5]
The PAS-1 powder obtained in Example 1 above was dry blended with 1 mol% of tris (dibenzylideneacetone) dipalladium with respect to the sulfur atom of PAS-1 to obtain PAS-6. The obtained PAS-6 had a sodium content of 4 ppm and a chlorine content of 2.2 wt%. Alkali metals other than Na and halogens other than chlorine were below the detection limit and were equivalent to PAS-1. Further, from mass spectral analysis of components separated by high performance liquid chromatography and molecular weight information by MALDI-TOF-MS, this PAS-1 is a cyclic polyphenylene sulfide having 4 to 11 repeating units and 2 to 11 repeating units. The weight ratio of cyclic polyphenylene sulfide to linear polyphenylene sulfide was about 9: 1. As a result of GPC measurement, PAS-6 was completely converted to 1-chloronaphthalene at room temperature. The weight average molecular weight was 900 and both were equivalent to PAS-1.

[Example 6]
The PAS-1 powder obtained in Example 1 above was dry blended with 1 mol% of tetrakis (triphenylphosphine) nickel with respect to the sulfur atom of PAS-1 to obtain PAS-7. The obtained PAS-7 had a sodium content of 4 ppm and a chlorine content of 2.2 wt%. Alkali metals other than Na and halogens other than chlorine were below the detection limit and were equivalent to PAS-1. Further, from mass spectral analysis of components separated by high performance liquid chromatography and molecular weight information by MALDI-TOF-MS, this PAS-1 is a cyclic polyphenylene sulfide having 4 to 11 repeating units and 2 to 11 repeating units. The weight ratio of cyclic polyphenylene sulfide to linear polyphenylene sulfide was about 9: 1. As a result of GPC measurement, PAS-7 was completely converted to 1-chloronaphthalene at room temperature. The weight average molecular weight was 900 and both were equivalent to PAS-1.

[Example 7]
The PAS-4 powder obtained in Example 3 was dry blended with 1 mol% of tetrakis (triphenylphosphine) palladium with respect to the sulfur atom of PAS-4 to obtain PAS-8. The obtained PAS-8 had a sodium content of 4 ppm and a chlorine content of 2.2 wt%. Alkali metals other than Na and halogens other than chlorine were below the detection limit and were equivalent to PAS-1. Further, from mass spectral analysis of components separated by high performance liquid chromatography and molecular weight information by MALDI-TOF-MS, this PAS-8 is a cyclic polyphenylene sulfide having 4 to 11 repeating units and 2 to 11 repeating units. As a result of GPC measurement, PAS-8 was completely dissolved in 1-chloronaphthalene at a room temperature, and the weight average molecular weight was a mixture of the following linear polyphenylene sulfide. Was 900, both of which were equivalent to PAS-4.

[Comparative Example 2]
<Manufacture of PAS resin powder coating by conventional technology (PAS-9)>
In a 20 liter autoclave with a stirrer and a valve at the bottom, 2383 g (20.0 mol) of 47% sodium hydrosulfide (Sankyo Kasei), 831 g (19.9 mol) of 96% sodium hydroxide, N-methyl-2 -3960 g (40.0 mol) of pyrrolidone (NMP) and 3000 g of ion-exchanged water were charged, gradually heated to 225 ° C over about 3 hours while flowing nitrogen at normal pressure, and after distilling 4200 g of water and 80 g of NMP, The reaction vessel was cooled to 160 ° C. The residual water content in the system per mole of the alkali metal sulfide charged was 0.17 mole. The amount of hydrogen sulfide scattered per mole of the alkali metal sulfide charged was 0.021 mol.

  Next, 2942 g (20.0 mol) of p-dichlorobenzene (Sigma Aldrich) and 1515 g (15.3 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. Then, while stirring at 400 rpm, the temperature was increased from 200 ° C. to 227 ° C. at a rate of 0.8 ° C./min, then increased to 274 ° C. at a rate of 0.6 ° C./min, and held at 274 ° C. for 50 minutes. Then, the temperature was raised to 282 ° C. Open the valve at the bottom of the autoclave, pressurize with nitrogen, flush the contents to a container with a stirrer over 15 minutes, stir at 250 ° C for a while to remove most of NMP, and remove PAS-9 and salts. The containing solid was recovered.

  The obtained solid and 15120 g of ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 70 ° C. for 30 minutes, and suction filtered through a glass filter. Next, 17280 g of ion-exchanged water heated to 70 ° C. was poured into a glass filter, and suction filtered to obtain a cake.

  The obtained cake, 11880 g of ion-exchanged water and 12 g of acetic acid were charged into an autoclave equipped with a stirrer, and the inside of the autoclave was replaced with nitrogen, and then the temperature was raised to 192 ° C. and held for 30 minutes. Thereafter, the autoclave was cooled and the contents were taken out.

  The contents were subjected to suction filtration with a glass filter, and then 17280 g of ion-exchanged water at 70 ° C. was poured into the contents, followed by suction filtration to obtain a cake. The obtained cake was dried with hot air at 80 ° C. and further vacuum-dried at 120 ° C. for 24 hours to obtain dry PAS-9. Subsequently, it processed at 220 degreeC for 5 hours, passing nitrogen through a dryer. The obtained PAS-9 had a weight average molecular weight of 20000 and a degree of dispersion of 3.12. Moreover, Na content of obtained PAS-9 was 980 ppm, and alkali metals other than this were not detected. Furthermore, 420 ppm of γ-butyrolactone (γ-BL) was detected as a lactone type compound that was a generated gas component when heated at 320 ° C. for 60 minutes, and 775 ppm of 4-chloro-N-methylaniline (MeAn) was detected as an aniline type compound. . Further, halogens other than chlorine were not detected.

[Examples 8 to 17 and Comparative Examples 3 and 4; Production of coating film using PAS resin powder coating]
Using the PAS resin powder coating materials obtained in Examples 1 to 7 and Comparative Examples 1 and 2, coating and baking were performed according to the following procedure.

First, the surface of a stainless steel plate (SUS304) having a thickness of 1.0 mm, a length of 50 mm, and a width of 50 mm was degreased with trichlene. The surface was coated with electrostatic powder so as to have a film thickness of 60 to 80 μm. Next, the coating was baked in the ovens set at the temperatures shown in Tables 1 and 2 at the times shown in Tables 1 and 2. Then, it took out from oven and allowed to cool naturally at room temperature, and the coated material of Examples 8-17 and Comparative Examples 3 and 4 was obtained.

  The obtained coating film was evaluated by the following method. The evaluation results are shown in Table 1.

<Void evaluation of coating film>
Five SUS square plates (thickness 1.0 mm, vertical 50 mm, horizontal 50 mm) coated with powder of the above PAS resin were prepared, and the total number of voids in the square plate was counted visually.
◎ Number of voids Less than 5 ○ Number of voids 5 or more, less than 20 × number of voids 20 or more.

<Surface smoothness of coating film>
The SUS square plate (thickness 1.0 mm, length 50 mm, width 50 mm) coated with powder of the PAS resin was visually determined based on the following criteria.
◎ Very good ○ Excellent × Appearance defect (Rough skin, repellency, swelling)

<Molecular weight and molecular weight distribution of PAS coating film>
About the peeled PAS coating film, GPC measurement was performed by the same method as the above-mentioned PAS resin, and the polystyrene conversion molecular weight was measured.

<Quantification of alkali metal content of PAS coating film>
About the peeled PAS coating film, alkali metal content was measured by the following method.
(a) The sample was weighed in a quartz crucible and incinerated using an electric furnace.
(b) After the ashed product was dissolved with concentrated nitric acid, the volume was adjusted to a constant volume with diluted nitric acid.
(c) The obtained constant volume solution was subjected to ICP gravimetric analysis (apparatus; 4500 manufactured by Agilent) and ICP emission spectroscopic analysis (apparatus; Optima 4300DV manufactured by PerkinElmer).

<Gas generation amount of PAS coating film>
The amount of gas generated was measured under the following conditions using a thermogravimetric analyzer. In addition, the sample peeled and used the PAS coating film from the coating material obtained by the said Examples 3-7 and the comparative examples 3 and 4.
Apparatus: Perkin Elmer TGA7
Measurement atmosphere: Sample preparation weight under nitrogen stream: Approximately 10 mg
Measurement condition:
(A) Hold for 1 minute at a program temperature of 50 ° C. (b) Increase the temperature from the program temperature of 50 ° C. to 400 ° C. Temperature increase rate at this time 20 ° C / min

The weight reduction rate ΔWr was calculated from the sample weight (W2) at the time of reaching 330 ° C. using the following equation, based on the sample weight (W1) at the time of 100 ° C. at the temperature rise of (b).
ΔWr = (W1−W2) / W1 × 100 (% by weight).

  As is apparent from the results in Tables 1 and 2, the PAS resin containing the cyclic polyarylene sulfide of the present invention has a high degree of polymerization when the high-purity cyclic polyarylene sulfide is baked in powder coating. It can be seen that the PAS resin that forms the resulting coating film has a low content of low molecular weight components and a coating film with excellent void uniformity. On the other hand, when the PAS resin powder obtained by the prior art is used as a powder coating, it can be seen that the amount of decomposition gas of low molecular weight components is large during baking and the generation of voids is large.

  In addition, the PAS resin coating film obtained by powder coating the cyclic polyarylene sulfide of the present invention is found to have a low alkali metal content, especially heat- and chemical-resistant pre-coated plates, electric / electronic parts, electric wires, etc. It can be seen that it is suitable for heat insulation, chemical resistance and anticorrosion coatings for electrical insulation coatings, automobile parts, chemical plants, hot water supply pipes, hot spring piping, marine / seawater plants, oil field pipes, etc.

Claims (12)

A polyarylene sulfide resin powder coating comprising 5% by weight or more of a cyclic polyarylene sulfide mixture represented by the following general formula (1) in 100% by weight of a polyarylene sulfide resin.

(Ar represents an arylene group, and m is an integer of 2 to 50.) 2. The polyarylene sulfide resin powder coating material according to claim 1, comprising at least 50% by weight or more of the cyclic polyarylene sulfide and having a weight average molecular weight of less than 10,000. The polyarylene sulfide mixture according to any one of claims 1 and 2, wherein the cyclic polyarylene sulfide mixture represented by the general formula (1) includes those having a repeating number m of 4 to 12 in the formula. Sulfide resin powder paint. Furthermore, the polyarylene sulfide resin powder coating material in any one of Claims 1-3 containing a zerovalent transition metal compound. The polyarylene sulfide resin powder coating according to claim 4, wherein the content of the zero-valent transition metal compound is 0.001 to 20 mol% with respect to sulfur atoms of the polyarylene sulfide resin. The polyarylene sulfide resin powder paint according to any one of claims 1 to 5, wherein the alkali metal content is 100 ppm or less. The polyarylene sulfide resin powder coating material according to claim 6, wherein the alkali metal is substantially sodium. The polyarylene sulfide resin powder coating material according to any one of claims 1 to 7, which contains substantially no halogen other than chlorine. A powder coating method comprising electrostatically applying and heating the polyarylene sulfide resin powder paint according to any one of claims 1 to 8 on a substrate. The powder coating method according to claim 9, wherein the heating temperature is 250 to 400 ° C. The powder coating method according to claim 9 or 10, wherein the heating time is 5 to 60 minutes. The coated material obtained by the coating method of any one of Claims 9-11.