JP7575974B2 - Polyphenylene sulfide resin and its manufacturing method - Google Patents

Description

The present invention relates to a polyphenylene sulfide resin consisting of specific structural units and a method for producing the same.

Polyarylene sulfide resins (hereinafter also referred to as "PAS resins"), such as polyphenylene sulfide (hereinafter also referred to as "PPS resins"), are engineering plastics that have excellent heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical properties, dimensional stability, etc. PAS resins can be molded into various molded products, films, sheets, fibers, etc., using common melt processing methods such as extrusion molding, injection molding, and compression molding. For this reason, PAS resins are widely used in a wide range of technical fields, such as electrical equipment, electronic equipment, automotive equipment, and packaging materials.

More specifically, for example, the use of PAS resins as materials for parts of refrigerant circulation devices used to cool internal combustion engines, such as automobile engines, is being considered due to their light weight, low cost, and ease of processing. Thermoplastic resins used in refrigerant circulation device parts are required to have excellent properties such as impact resistance, chemical resistance, and water vapor permeability resistance.

As a material for parts of refrigerant circulation devices used to cool such internal combustion engines, for example, a polyphenylene sulfide resin composition has been proposed that is composed of 100 parts by weight of a composition consisting of (A) 45 to 83% by weight of polyphenylene sulfide resin, (B) 15 to 35% by weight of polyethylene resin, and (C) 2 to 20% by weight of a copolymerized polyolefin obtained by copolymerizing ethylene and glycidyl methacrylate, and (D) 30 to 100 parts by weight of glass fiber (see Patent Document 1).

JP 2006-036824 A

However, there is a demand for improved vibration damping in components of refrigerant circulation devices used to cool internal combustion engines in order to reduce noise and improve comfort in the interior of automobiles, etc. This is because the refrigerant circulation devices include a pump for circulating the refrigerant, and vibrations are generated in the refrigerant circulation devices due to the operation of the pump, pulsation of the refrigerant, etc.
In this regard, it is desired that the polyphenylene sulfide resin composition described in Patent Document 1 has a further improved vibration damping property.
In addition, parts of refrigerant circulation devices used around high-temperature internal combustion engines are required to have high heat resistance and excellent mechanical strength so that they are not easily deformed or destroyed by traffic accidents or impacts while driving.

The present invention has been made in consideration of the above problems, and aims to provide a polyarylene sulfide resin having excellent heat resistance, mechanical strength, and vibration damping properties, a preferred method for producing the polyarylene sulfide resin, a polyarylene sulfide resin composition containing the polyarylene sulfide resin, and a molded article made of the polyarylene sulfide resin composition.

The present inventors have found that the above-mentioned problems can be solved by using a polyphenylene sulfide resin which includes a first block consisting of a structural unit (I) represented by the following formula (1) and a second block consisting of a structural unit (II) represented by the following formula (2), and which exhibits a maximum loss factor of 0.15 or more as measured in accordance with dynamic viscoelasticity measurement at a measurement temperature range of 20° C. or more and 200° C. or less, a melting point of 260° C. or more, and an average storage modulus of 4.5 × 10 ^or more in the range of 110° C. or more and 200° C. or less, and have thus completed the present invention.

The polyphenylene sulfide resin according to the present invention comprises a first block composed of a structural unit (I) represented by the following formula (1) and a second block composed of a structural unit (II) represented by the following formula (2):
The maximum loss factor measured according to dynamic viscoelasticity measurement at a measurement temperature in the range of 20° C. to 200° C. is 0.15 or more,
It has a melting point of 260°C or higher,
The average storage modulus in the range of 110° C. or more and 200° C. or less is 4.5×10 ⁸ or more.
-Ph ¹ -S-...(1)
-Ph ² -S-...(2)
(In formula (1), Ph ¹ is a p-phenylene group, and in formula (2), Ph ² is a methyl-p-phenylene group.)

In the polyphenylene sulfide resin, the ratio of the number of moles of structural unit (II) to the total number of moles of structural unit (I) and the number of moles of structural unit (II) may be 1 mol% or more and 30 mol% or less.

The polyphenylene sulfide resin composition of the present invention contains the above-mentioned polyphenylene sulfide resin.

The molded article of the present invention is made of the polyphenylene sulfide resin or the polyphenylene sulfide resin composition.

The method for producing a polyphenylene sulfide resin according to the present invention comprises the steps of:
(1) preparing a feed mixture containing an organic polar solvent, a sulfur source, and p-dichlorobenzene;
(2) a first polymerization step in which the charged mixture is heated to carry out a polymerization reaction;
(3) a second polymerization step in which 2-methyl-p-dichlorobenzene is added to the polymerization reaction mixture after the first polymerization step, and then the polymerization reaction is continued;
Includes.

The present invention provides a polyarylene sulfide resin having excellent heat resistance, mechanical strength, and vibration damping properties, a preferred method for producing the polyarylene sulfide resin, a polyarylene sulfide resin composition containing the polyarylene sulfide resin, and a molded article made of the polyarylene sulfide resin composition.

<Polyphenylene sulfide resin>
Polyphenylene sulfide resin (PPS resin) contains a first block composed of a structural unit (I) represented by the following formula (1) and a second block composed of a structural unit (II) represented by the following formula (2). In other words, polyphenylene sulfide resin is a block copolymer containing the first block and the second block.
-Ph ¹ -S-...(1)
-Ph ² -S-...(2)
(In formula (1), Ph ¹ is a p-phenylene group, and in formula (2), Ph ² is a methyl-p-phenylene group.)

The PPS resin exhibits a maximum loss factor of 0.15 or more as measured according to dynamic viscoelasticity measurement at a measurement temperature range of 20° C. or more and 200° C. or less, has a melting point of 260° C. or more, and exhibits an average storage modulus of 4.5× ^{108 or} more in the range of 110° C. or more and 200° C. or less.

The above PPS resin has excellent heat resistance, mechanical strength, and vibration damping properties due to the inclusion of the above first block and second block. For this reason, the above PPS resin or a PPS resin composition containing the above PPS resin is suitable for use as a molding material in applications requiring excellent heat resistance, mechanical strength, and vibration damping properties, such as components of cooling circulation devices used to cool internal combustion engines in automobiles, etc.

The melting point of the PPS resin can be measured by differential scanning calorimetry (DSC).
Specifically, about 5 mg of a PPS resin sample is sealed in an aluminum pan, and then the sample is heated from 50° C. to 340° C., and then cooled from 340° C. to 50° C. for DSC measurement. The heating rate is 10° C./min, and the cooling rate is 10° C./min.
The melting point is the peak top temperature resulting from the melting of the PPS resin observed during heating.

The melting point of PPS resin can be adjusted, for example, by adjusting the degree of polymerization of the PPS resin or the ratio of the structural units. The melting point tends to be higher as the content of the first block consisting of structural unit (I) in the PPS resin increases. In addition, the melting point tends to be higher as the average molecular weight of the first block increases.

The loss factor and storage modulus of PPS resin are measured according to dynamic viscoelasticity measurement. The loss factor and storage modulus can be adjusted by adjusting the ratio of the structural units of the PPS resin. The greater the content of the second block consisting of structural unit (II) in the PPS resin, the higher the loss factor tends to be. Also, the greater the content of the second block consisting of structural unit (II) in the PPS resin and the smaller the content of the first block consisting of structural unit (I) in the PPS resin, the lower the storage modulus tends to be. However, in the PPS resin containing the above-mentioned first block and second block, the storage modulus is unlikely to decrease even if the content of the second block is increased.

In the above PPS resin, the ratio of the number of moles of the structural unit (I) to the number of moles of the structural unit (II) is not particularly limited as long as the PPS resin exhibits the prescribed loss factor, melting point, and storage modulus.
In the above PPS resin, the ratio of the number of moles of the structural unit (II) to the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) is preferably 1 mol % or more and 30 mol % or less, more preferably 3 mol % or more and 20 mol % or less, and even more preferably 5 mol % or more and 15 mol % or less.

The above PPS resin preferably consists of only a first block consisting of the structural unit (I) and a second block consisting of the structural unit (II). However, as long as the PPS resin exhibits a predetermined loss factor, melting point, and storage modulus, the PPS resin may contain the structural unit (I) and/or the structural unit (II) present randomly, and may contain other structural units other than the structural unit (I) and the structural unit (II). The other structural units may be present randomly or as blocks in the molecular chain of the PPS resin.
The ratio of the total number of moles of the constituent units (I) constituting the first block and the number of moles of the constituent units (II) constituting the second block to the number of moles of all constituent units constituting the PPS resin is preferably 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and particularly preferably 100 mol % or more.

The molecular weight of the PPS resin is preferably 5,000 or more and 200,000 or less, more preferably 10,000 or more and 150,000 or less, and even more preferably 15,000 or more and 100,000 or less, in terms of weight average molecular weight. The weight average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography.

<Polyphenylene sulfide resin composition>
The polyphenylene sulfide resin composition (PPS resin composition) contains the above-mentioned PPS resin.

The PPS resin composition may contain, in addition to the above-mentioned PPS resin, other resins that do not fall under the category of the above-mentioned PPS resins.
The other resin may be either a curable resin or a thermoplastic resin. Since the PPS resin that satisfies the above-mentioned specific requirements can be easily mixed uniformly with the other resin, the other resin is preferably a thermoplastic resin.

As the curable resin, a precursor of the curable resin in an uncured state can also be used. The curable resin may be a thermosetting resin or a photocurable resin, and a thermosetting resin is preferred because it is easy to produce a molded product of a certain size.
As a method for mixing the curable resin with the polyphenylene sulfide resin, a method is exemplified in which the polyphenylene sulfide resin in powder or particulate form is mixed with a liquid or solution-like precursor of the curable resin in an uncured state, and the solvent is removed as necessary after mixing. In this case, a curing agent may be added to the mixture depending on the type of the curable resin.
The mixture thus obtained is cured by heating and/or exposure to light in a manner appropriate for the type of curable resin to form a resin composition.

Specific examples of curable resins include thermosetting resins such as phenolic resins, melamine resins, epoxy resins, and alkyd resins, and photocurable resins such as (meth)acrylic resins.

When the other resin is a curable resin, the ratio of the mass of the aforementioned PPS resin to the total mass of the aforementioned PPS resin and the other resin is, for example, preferably 50 mass% or more, more preferably 70 mass% or more, and even more preferably 90 mass% or more.

When the other resin is a thermoplastic resin, the PPS resin and the other resin are typically mixed using a melt kneading device such as a single screw extruder or a twin screw extruder. The mixing conditions are not particularly limited and are appropriately determined taking into account the melting point, melt viscosity, etc. of the PPS resin and the other resin.

Suitable examples of the other resins that are thermoplastic include polyacetal resins, polyamide resins, polycarbonate resins, polyester resins (polybutylene terephthalate, polyethylene terephthalate, polyarylate resins, liquid crystal polyester resins, etc.), FR-AS resins, FR-ABS resins, AS resins, ABS resins, polyphenylene oxide resins, polyarylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, fluorine-based resins, polyimide resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polybenzoxazole resins, polybenzothiazole resins, polybenzimidazole resins, BT resins, polymethylpentene, ultra-high molecular weight polyethylene, FR-polypropylene, and polystyrene.

Among these thermoplastic resins, PPS resin is preferred because of its excellent compatibility with the above-mentioned PPS resin, and polyparaphenylene sulfide resin, which is a polycondensate of p-dichlorobenzene and a sulfidizing agent (for example, an alkali metal sulfide or an alkali metal hydrosulfide), is preferred.
The PPS resin used as the other resin is not particularly limited as long as it is a PPS resin other than the PPS resin that satisfies the above-mentioned predetermined requirements, and may be appropriately selected from conventionally known PPS resins.
The PPS resin to be mixed with the PPS resin satisfying the above-mentioned specific requirements preferably has a melting point of 270°C to 300°C or less, a weight average molecular weight (Mw) of 1000 to 5000, and a melt viscosity of 100 to 250 Pa·s.
The melt viscosity can be measured using about 20 g of dry polymer with a Capillograph 1-D manufactured by Toyo Seiki Seisakusho Co., Ltd. The capillary can be a die with an inlet angle of 1.000 mmφ×10 mmL, and the set temperature is 310° C. The polymer sample is introduced into the apparatus and held for 5 minutes, and then the measured value measured at a shear rate of 1200 sec ⁻¹ is taken as the melt viscosity value (unit: Pa s).

When the other resin is a thermoplastic resin, the ratio of the mass of the aforementioned PPS resin to the total mass of the aforementioned PPS resin and the thermoplastic resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

The PPS resin composition described above may contain additives or additives that have been conventionally blended into various resin compositions, such as colorants, plasticizers, antioxidants, UV absorbers, flame retardants, release agents, fillers, and reinforcing materials, as necessary. These additives or additives are used in amounts within an appropriate range according to the type of additive or additive.

<Molded products>
The PPS resin or PPS resin composition described above can be molded into various molded articles by a suitable method according to the properties of each resin. Suitable examples of the molded articles include pump housings, pipes for circulating refrigerants, and components of refrigerant circulating devices such as radiator tanks.

When a PPS resin composition containing a curable resin is used, for example, a mold having a recess of a desired shape may be filled with the uncured PPS resin composition, and the PPS resin composition molded into the desired shape in the mold may then be cured.
In addition, when the PPS resin composition containing the uncured curable resin is in a liquid state, a molded article having a desired shape can be produced by a 3D printing method. In this case, the PPS resin composition may be appropriately cured during molding, or the molded article may be cured after obtaining a molded article having a desired shape.

When using the aforementioned PPS resin or a PPS resin composition containing a thermoplastic resin, the aforementioned PPS resin or a PPS resin composition containing a thermoplastic resin is typically molded by a conventional method such as press molding, extrusion molding, or injection molding.

<Production method of polyphenylene sulfide resin>
A preferred example of a method for producing a polyphenylene sulfide resin that satisfies the above-mentioned predetermined requirements will be described below.
The manufacturing method includes:
(1) preparing a charge mixture containing an organic polar solvent, a sulfur source, and p-dichlorobenzene;
(2) a first polymerization in which the charged mixture is heated to carry out a polymerization reaction;
(3) A second polymerization in which 2-methyl-p-dichlorobenzene is added to the reaction mixture after the first polymerization, and then a polymerization reaction is continued;
Includes.

(Organic Polar Solvent, Sulfur Source, and p-Dichlorobenzene)
The organic polar solvent and the sulfur source are not particularly limited, and may be any of those commonly used in the production of PPS resins. Each of the organic polar solvent and the sulfur source may be used alone, or two or more of them may be mixed and used as long as the combination allows the production of a PPS resin having a desired chemical structure.

Examples of organic polar solvents include organic amide solvents; aprotic organic polar solvents made of organic sulfur compounds; and aprotic organic polar solvents made of cyclic organic phosphorus compounds. Examples of organic amide solvents include amide compounds such as N,N-dimethylformamide and N,N-dimethylacetamide; N-alkylcaprolactam compounds such as N-methyl-ε-caprolactam; N-alkylpyrrolidone compounds or N-cycloalkylpyrrolidone compounds such as N-methyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone; N,N-dialkylimidazolidinone compounds such as 1,3-dialkyl-2-imidazolidinone; tetraalkylurea compounds such as tetramethylurea; and hexaalkylphosphoric triamide compounds such as hexamethylphosphoric triamide. Examples of aprotic organic polar solvents made of organic sulfur compounds include dimethyl sulfoxide and diphenyl sulfone. Aprotic organic polar solvents consisting of cyclic organic phosphorus compounds include 1-methyl-1-oxophosphorane, etc. Among them, in terms of availability, ease of handling, etc., organic amide solvents are preferred, N-alkylpyrrolidone compounds, N-cycloalkylpyrrolidone compounds, N-alkylcaprolactam compounds, and N,N-dialkylimidazolidinone compounds are more preferred, NMP, N-methyl-ε-caprolactam, and 1,3-dialkyl-2-imidazolidinone are even more preferred, and NMP is particularly preferred.

From the viewpoint of the efficiency of the polymerization reaction, the amount of the organic polar solvent used is preferably 1 to 30 moles, and more preferably 3 to 15 moles, per mole of the sulfur source.

Examples of the sulfur source include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide, and alkali metal sulfides and alkali metal hydrosulfides are preferred. The sulfur source can be handled, for example, in the form of either an aqueous slurry or an aqueous solution, and from the viewpoint of handling such as measurement and transportability, it is preferred that the sulfur source be in the form of an aqueous solution. Examples of the alkali metal sulfides include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Examples of the alkali metal hydrosulfides include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide.

The amount of p-dichlorobenzene used in preparing the charged mixture is not particularly limited as long as the resulting PPS resin contains the first block and the second block in the desired ratio.
In preparing the charged mixture, the amount of p-dichlorobenzene used is appropriately determined taking into consideration the total amount of monomers including p-dichlorobenzene and 2-methyl-p-dichlorobenzene and the ratio between the number of moles of the structural unit (I) and the number of moles of the structural unit (II) in the resulting PPS resin.
The total amount of the monomers including p-dichlorobenzene and 2-methyl-p-dichlorobenzene used in the production of the PPS resin is preferably 0.90 to 1.50 mol, more preferably 0.92 to 1.10 mol, and even more preferably 0.95 to 1.05 mol, per mol of the charged amount of the sulfur source. When the amount used is within the above range, decomposition reaction is unlikely to occur, stable polymerization reaction is easily carried out, and a high molecular weight polymer is easily produced.

(Dehydration process)
The dehydration step is a step of discharging at least a part of a distillate containing water from a system containing a mixture containing an organic polar solvent and a sulfur source, prior to the charging step. The mixture to be subjected to the dehydration step may contain an alkali metal hydroxide, if necessary. The polymerization reaction between the sulfur source and a monomer such as p-dichlorobenzene or 2-methyl-p-dichlorobenzene is influenced by the amount of water present in the polymerization reaction system, such as being promoted or inhibited. Therefore, it is preferable to reduce the amount of water in the polymerization reaction system by performing a dehydration treatment before polymerization, so that the amount of water does not inhibit the polymerization reaction.

In the dehydration step, it is preferable to carry out the dehydration by heating under an inert gas atmosphere. The moisture to be dehydrated in the dehydration step includes the water contained in each raw material charged in the dehydration step, the aqueous medium of the aqueous mixture, the water produced as a by-product by the reaction between each raw material, etc.

The heating temperature in the dehydration step is not particularly limited as long as it is 300°C or less, and is preferably 100 to 250°C. The heating time is preferably 15 minutes to 24 hours, and more preferably 30 minutes to 10 hours.

In the dehydration step, dehydration is performed until the water content falls within a predetermined range. That is, in the dehydration step, it is desirable to dehydrate until the water content in the charge mixture (described below) is preferably 0.5 to 2.4 moles per 1.0 mole of the sulfur source (hereinafter also referred to as the "charged sulfur source" or "available sulfur source"). If the water content becomes too low in the dehydration step, water can be added in the charge step prior to the first-stage polymerization step described below to adjust the water content to the desired level.

(Preparation process)
The charging step is a step of preparing a mixture containing an organic polar solvent, a sulfur source, and p-dichlorobenzene. The mixture charged in the charging step is also referred to as a "charged mixture."

When a dehydration process is performed, the amount of sulfur source in the charged mixture (hereinafter also referred to as the "amount of charged sulfur source" or the "amount of available sulfur source") can be calculated by subtracting the molar amount of hydrogen sulfide vaporized in the dehydration process from the molar amount of sulfur source charged as a raw material.

When the dehydration step is performed, in the charging step, an alkali metal hydroxide and water can be added as necessary to the mixture remaining in the system after the dehydration step. In particular, the alkali metal hydroxide can be added after taking into consideration the amount of hydrogen sulfide generated during the dehydration step and the amount of alkali metal hydroxide generated during the dehydration step. As the alkali metal hydroxide, one that is usually used in the production of PPS resin can be used. The alkali metal hydroxide may be used alone, or two or more types may be mixed and used as long as the combination allows the production of PPS. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. The number of moles of the alkali metal hydroxide is calculated based on the number of moles of the alkali metal hydroxide added as necessary in the charging step, and, when the dehydration step is performed, the number of moles of the alkali metal hydroxide added as necessary in the dehydration step, and the number of moles of the alkali metal hydroxide generated in the dehydration step due to the generation of hydrogen sulfide. When the sulfur source contains an alkali metal sulfide, the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source) is calculated including the number of moles of alkali metal sulfide. When hydrogen sulfide is used as the sulfur source, the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source) is calculated including the number of moles of alkali metal sulfide produced. However, the number of moles of alkali metal hydroxide added for other purposes, for example, when an organic carboxylic acid metal salt is used as a phase separation agent in the form of a combination of an organic carboxylic acid and an alkali metal hydroxide as described later, is not included in the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source). Furthermore, when at least one acid selected from the group consisting of inorganic acids and organic acids is used for some reason, the number of moles of alkali metal hydroxide required to neutralize the at least one acid is not included in the number of moles of alkali metal hydroxide per mole of the sulfur source (charged sulfur source).

In the feed mixture, the amounts of the organic polar solvent and the dihalo aromatic compound used are set, for example, within the ranges shown above for the organic polar solvent and the dihalo aromatic compound per mole of the sulfur source.

(First Polymerization and Second Polymerization)
In the first polymerization, the charged mixture is heated to carry out a polymerization reaction, and in the second polymerization, 2-methyl-p-dichlorobenzene is added to the reaction mixture after the first polymerization, and then the polymerization reaction is continued.
When other monomers than p-dichlorobenzene and 2-methyl-p-dichlorobenzene are used, the other monomers are added to the reaction mixture after the second polymerization.

The amount of 2-methyl-p-chlorobenzene added before the second polymerization is determined appropriately taking into consideration the total amount of p-dichlorobenzene and monomers including 2-methyl-p-dichlorobenzene, and the ratio of the number of moles of structural unit (I) to the number of moles of structural unit (II) in the resulting PPS resin.

In order to obtain a PPS resin having a higher molecular weight, it is preferable to carry out the polymerization reaction in two or more stages. Specifically, it is preferable to carry out the polymerization reaction in a first polymerization stage and a second polymerization stage in which the polymerization reaction is continued in the presence of a phase separation agent.
In the first polymerization step, the first polymerization and the second polymerization may be carried out. Alternatively, a phase separation agent may be added to the reaction mixture during the first polymerization, and only the first polymerization may be carried out in the first polymerization step, and the first and second polymerizations may be carried out in the second polymerization step. Furthermore, a phase separation agent may be added to the reaction mixture during the second polymerization, and the first and second polymerizations may be carried out in the first polymerization step, and the second polymerization may be carried out in the second polymerization step.

The phase separation agent is added to the reaction mixture in a phase separation agent addition step provided between the first polymerization step and the second polymerization step.
The first-stage polymerization step is a step in which the charged mixture is heated to initiate a polymerization reaction and generate a prepolymer. In the first-stage polymerization step, a sulfur source and p-dichlorobenzene are polymerized in an organic polar solvent, or a sulfur source and p-dichlorobenzene are polymerized and then 2-methyl-p-dichlorobenzene is polymerized. The mixture heated in the first-stage polymerization step and the second-stage polymerization step, the mixture to which a phase separation agent is added in the phase separation agent addition step, and the mixture phase-separated in the phase separation agent addition step are referred to as "reaction mixtures".

When 2-methyl-p-dichlorobenzene is added after the first polymerization, the conversion of p-dichlorobenzene is preferably 30 mol % or more, more preferably 50 mol % or more.
In the first polymerization step, the monomer conversion based on the total number of moles of the monomers used in the production of the PPS resin is preferably 50 to 98 mol%, more preferably 60 to 97 mol%, further preferably 65 to 96 mol%, and particularly preferably 70 to 95 mol%. The monomer conversion can be calculated by determining the amount of monomer remaining in the reaction mixture by gas chromatography, based on the remaining amount, the charged amount of the monomer, and the charged amount of the sulfur source.

In the second polymerization step following the first polymerization step, the degree of polymerization of the prepolymer increases.

As a phase separation agent, water is preferably used. Examples of preferred phase separation agents other than water include at least one selected from the group consisting of organic carboxylate metal salts (e.g., alkali metal salts of aliphatic carboxylic acids such as sodium acetate, and alkaline earth metal salts of aromatic carboxylic acids), organic sulfonate metal salts, alkali metal halides, alkaline earth metal halides, alkali metal phosphates, alcohols, and non-polar solvents. The above salts used as phase separation agents may be in the form of corresponding acids and bases added separately.

The amount of phase separation agent used varies depending on the type of compound used, but may be within the range of 0.01 to 20 moles per kg of organic polar solvent. The amount of water used as a phase separation agent is preferably 0.1 to 5 moles, more preferably 2 to 4 moles, per mole of the sulfur source. Furthermore, the amount of water in the reaction system when water is added as a phase separation agent may be more than 4 moles and not more than 20 moles, 4.1 to 14 moles, or 4.2 to 10 moles, per kg of organic polar solvent.

In the second polymerization step, the amount of alkali metal hydroxide is preferably 1.00 to 1.10 moles, more preferably 1.01 to 1.08 moles, and even more preferably 1.02 to 1.07 moles per mole of the sulfur source. When the amount of alkali metal hydroxide is within the above range, the molecular weight of the resulting PPS resin is more likely to increase, making it easier to obtain a PPS resin with a higher molecular weight. In the second polymerization step, it is preferable to add alkali metal hydroxide to the reaction mixture so that the final amount of alkali metal hydroxide is within the above range, based on the amount of alkali metal hydroxide present in the reaction mixture after the first polymerization step.

In the first and second polymerization steps, from the viewpoint of the efficiency of the polymerization reaction, it is preferable to carry out the polymerization reaction under heating at a temperature of 170 to 300°C. It is more preferable that the polymerization temperature in the first and second polymerization steps is in the range of 180 to 280°C in order to suppress side reactions and decomposition reactions.

The polymerization reactions in the first and second polymerization steps may be carried out batchwise or continuously. For example, the polymerization reaction can be carried out continuously by simultaneously carrying out at least the supply of an organic polar solvent, a sulfur source, and a dihalo aromatic compound, the production of a PPS resin by the reaction of the sulfur source with the dihalo aromatic compound in the organic polar solvent, and the recovery of the reaction mixture containing the PPS resin.

(Cooling process)
The cooling step is a step of cooling the reaction mixture after the polymerization step including the first polymerization and the second polymerization. The specific operation in the cooling step is as described in, for example, Japanese Patent No. 6062924.

(Separation process)
The separation step is a step of separating the PPS resin from the cooled reaction mixture, and is carried out by, for example, sieving using a screen or centrifugal separation using a centrifuge.

The PPS resin separated from the reaction mixture by the method described above is washed with an organic solvent, acid water, water, etc., as necessary, and then dried to produce a product.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed.

The present invention will be described in more detail with reference to the following synthesis examples. Note that the polyphenylene sulfide resin used in the present invention is not limited to the polyphenylene sulfide resin shown in the synthesis examples below.

Comparative Example 1
A 1 L autoclave equipped with a stirrer was charged with 78.0 g of sodium sulfide, 2.4 g of sodium hydroxide, 375 g of N-methyl-2-pyrrolidone (NMP), 134.9 g of p-dichlorobenzene, and 16.4 g of 2-methyl-p-dichlorobenzene. The molar ratio of p-dichlorobenzene and 2-methyl-p-dichlorobenzene charged was 90:10, as p-dichlorobenzene:2-methyl-p-dichlorobenzene. Next, the inside of the autoclave was replaced with a nitrogen gas atmosphere, and the autoclave was sealed. Thereafter, the reaction solution in the autoclave was gradually heated to 240°C over about 30 minutes while stirring. After maintaining 240°C for 2 hours to carry out a polycondensation reaction, 20.3 g of ion-exchanged water was pumped into the autoclave. Then, the temperature was raised to 260°C over 10 minutes. At 260°C, the polycondensation reaction was continued for 3 hours. After the reaction was completed, the reaction solution was cooled to near room temperature.
After removing the contents of the autoclave, 1 L of acetone containing 3% by mass of pure water was added to the contents of the autoclave and washed by stirring at room temperature for 30 minutes. The washed solid matter (crude product) was recovered by filtration, and the above-mentioned washing operation with acetone was repeated twice.
The solid matter washed with acetone was washed in 1 L of pure water at room temperature by stirring for 30 minutes, and then collected by filtration. The collected solid matter was washed three times with pure water, and then the collected solid matter was dried at 120° C. for 4 hours to obtain a purified polyphenylene sulfide resin.
The polyphenylene sulfide resin obtained in Comparative Example 1 was a random copolymer containing 10 mol % of the aforementioned structural unit (II) relative to the total number of moles of the structural unit (I) and the number of moles of the structural unit (II).

Example 1
In a 1 L autoclave equipped with a stirrer, 78.0 g of sodium sulfide, 2.4 g of sodium hydroxide, 375 g of N-methyl-2-pyrrolidone (NMP), and 134.9 g of p-dichlorobenzene were charged. Next, the inside of the autoclave was replaced with a nitrogen gas atmosphere, and the autoclave was sealed. Then, while stirring the reaction liquid in the autoclave, the reaction liquid was gradually heated to 240°C over about 30 minutes. The polycondensation reaction was carried out while maintaining 240°C for 1 hour. Then, 16.4 g of 2-methyl-p-dichlorobenzene was pumped into the autoclave, and the polymerization reaction was continued at 240°C for 1 hour. Next, 20.3 g of ion-exchanged water was pumped into the autoclave. Then, the temperature was raised to 260°C over 10 minutes. The polycondensation reaction was continued at 260°C for 3 hours. After the reaction was completed, the reaction liquid was cooled to near room temperature.
After removing the contents of the autoclave, 1 L of acetone containing 3% by mass of pure water was added to the contents of the autoclave and washed by stirring at room temperature for 30 minutes. The washed solid matter (crude product) was recovered by filtration, and the above-mentioned washing operation with acetone was repeated twice.
The solid matter washed with acetone was washed in 1 L of pure water at room temperature by stirring for 30 minutes, and then collected by filtration. The collected solid matter was washed three times with pure water, and then the collected solid matter was dried at 120° C. for 4 hours to obtain a purified polyphenylene sulfide resin.
The polyphenylene sulfide resin obtained in Comparative Example 1 was a block copolymer containing 10 mol % of the aforementioned structural unit (II), based on the total number of moles of the structural unit (I) and the structural unit (II), and containing a first block composed of the structural unit (I) and a second block composed of the structural unit (II).

Comparative Example 2
Except for changing 16.4 g of 2-methyl-p-dichlorobenzene to 15.0 g of m-dichlorobenzene, a polyphenylene sulfide resin was obtained in the same manner as in Example 1. The obtained polyphenylene sulfide resin is a block copolymer including a first block composed of the structural unit (I) and a block composed of structural units derived from m-dichlorobenzene.

Comparative Example 3
A polyphenylene sulfide resin (W-214A, manufactured by Kureha Corp.), which is a polycondensation product of p-dichlorobenzene and a sulfidizing agent (for example, an alkali metal sulfide or an alkali metal hydrosulfide), was used as the sample of Comparative Example 3.
The polyphenylene sulfide resin of Comparative Example 3 does not contain the aforementioned structural unit (II).

For the polyphenylene sulfide resins of Example 1 and Comparative Examples 1 to 3, sheets were prepared according to the following method, and the loss factor and storage modulus were measured according to the following method. In addition, for the polyphenylene sulfide resins of Example 1 and Comparative Examples 1 to 3, the melting points were measured by DSC measurement according to the above-mentioned method.

Each polyphenylene sulfide resin sample was compression molded at 320°C, 5 MPa, and 1 minute to produce a sheet measuring 55 mm x 55 mm x 1 mm.

From the obtained sheet, a rectangular test piece for DMA measurement was cut out with a cutter knife, and the dynamic viscoelasticity was evaluated by DMA to measure the loss factor and storage modulus. The test piece was annealed at 150°C for 1 hour before the DMA measurement. The DMA measurement conditions are as follows. The measurement results of the loss factor are shown in Table 1.
<DMA measurement conditions>
Sample size: 10 mm x 5 mm x 1 mm
Tensile temperature: 20°C to 240°C
Heating rate: 2°C/min Frequency: 10Hz

The results shown in Table 1 show that the PPS resin of Example 1, which is a block copolymer containing a first block consisting of structural unit (I) and a second block consisting of structural unit (II), exhibits a high melting point, a high loss factor, and a high storage modulus. In other words, the PPS resin of Example 1 can be suitably used as a material for molding molded products that require heat resistance, mechanical strength, and vibration damping properties.

Claims (3)

A polyphenylene sulfide resin comprising a first block composed of a structural unit (I) represented by the following formula (1) and a second block composed of a structural unit (II) represented by the following formula (2):
the ratio of the total number of moles of the structural unit (I) constituting the first block and the number of moles of the structural unit (II) constituting the second block to the number of moles of all structural units constituting the polyphenylene sulfide resin is 80 mol % or more;
the ratio of the number of moles of the structural unit (II) to the total number of moles of the structural unit (I) and the number of moles of the structural unit (II) is 1 mol % or more and 30 mol % or less;
The maximum loss factor measured according to dynamic viscoelasticity measurement at a measurement temperature in the range of 20° C. to 200° C. is 0.15 or more,
The melting point is 260° C. or higher,
A polyphenylene sulfide resin having an average storage modulus of 4.5 x 10 ⁸ or more in the range of 110°C or more and 200°C or less.
-Ph ¹ -S-...(1)
-Ph ² -S-...(2)
(In formula (1), Ph ¹ is a p-phenylene group, and in formula (2), Ph ² is a methyl-p-phenylene group.) A polyphenylene sulfide resin composition comprising the polyphenylene sulfide resin according to claim 1 . A molded article comprising the polyphenylene sulfide resin according to claim 1 or the polyphenylene sulfide resin composition according to claim 2 .