JP2001172387A - Method for producing polyarylene sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for economically producing a polyarylene sulfide having a high crystallization temperature with no reduction in melt viscosity. SOLUTION: This method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide based solvent comprises adding 0.1-48 mol% oxygen per mole charged alkali metal sulfide fed to the polyarylene sulfide slurry after completion of the reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyarylene sulfide, and more particularly to a method for producing polyarylene sulfide at a high crystallization temperature.

[0002]

2. Description of the Related Art Polyphenylene sulfide (hereinafter referred to as PP)
Polyarylene sulfide (hereinafter sometimes abbreviated as PAS) represented by S) may have heat resistance,
Due to its excellent moldability, chemical resistance, flame retardancy, dimensional stability, etc., in recent years, it has been widely used as a material for electric / electronic equipment parts, automobile equipment parts, chemical equipment parts, and the like. In particular, a PAS, which is called a linear PAS and has a high molecular weight by polymerization, is characterized by having a low impurity content, good hue, and excellent thermal stability. , The utility value is high.

A method for producing the linear PAS includes:
For example, a method in which an alkali metal carboxylate is used as a polymerization aid during the polymerization reaction (Japanese Patent Publication No. 52-12240), the polymerization reaction is performed in two stages, and a large amount of water is positively added in the second stage reaction. Method (JP-A-61-73)
No. 32) or a method in which a gas phase portion of a reaction vessel is cooled during the polymerization reaction to condense a part of the gas phase in the reaction vessel and reflux the liquid phase into a liquid phase (JP-A-5-222).
196 publication).

However, PAs obtained by these methods have
When S is used for injection molding, crystallization may be insufficient depending on molding conditions. Further, in order to shorten the molding cycle, it is necessary that the crystallization speed of PAS is high, that is, the crystallization temperature Tc (° C.) is high. However, the PAS obtained by the above method had a low Tc (° C.) and could not shorten the molding cycle.

As a method for increasing the crystallization temperature Tc (° C.), for example, Japanese Patent Application Laid-Open No. 62-48728 discloses a method in which a PAS polymer produced is separated from a polymerization reaction mixture after the polymerization, and then separated. A method of treating a polymer in a strong acid solution having a pH of less than 2 is disclosed. In addition, JP-A-7-
JP 118389 discloses that the weight ratio of organic solvent: water is 4:
In an organic solvent / water mixture containing an organic acid at a concentration of 0.1 to 5.0% by weight in the range of 1 to 1:10, PA
A method of treating S with an acid is disclosed. However, in these methods, the PAS is treated in a low pH acid solution, and there is a disadvantage that the melt viscosity of the PAS becomes extremely low after the acid treatment.

Further, Japanese Patent Publication No. 6-68025 discloses a method of adding an inorganic acid or an organic acid to a PAS slurry after polymerization, washing the mixture with stirring at a pH of 6 or less, filtering, washing with water, and drying. The method relates to a purification method for removing impurities such as alkali metal ions in PAS. However, the PAS obtained by this method also had a very low melt viscosity of the treated PAS in the same manner as described above.
In any of the above acid treatment methods, the obtained PA
The PA slurry is separated by filtering the S slurry and repeating washing with water. Therefore, most of the solvent used for the polymerization is removed from the PAS by washing and filtering and contained in the filtrate, so that the solvent needs to be recovered. Since the filtrate is composed of water / polymerization solvent / by-product salt, it is complicated. Recovering the solvent was costly. On the other hand, if the solvent is not recovered, the cost is inevitably high, which is not economical. In each method, the polymerization was performed under nitrogen gas during the polymerization of the arylene sulfide or at the completion of the polymerization.

Furthermore, Japanese Patent Application Laid-Open No. 51-144495 discloses a method for producing a low-melt-flow PAS by adding carbon dioxide either during or at the completion of the polymerization of PAS. JP-202222 discloses a method of removing a solvent after PAS polymerization, adding carbon dioxide to a cleaning solution obtained by washing the obtained PAS, and facilitating the recovery of a polymerization aid. No mention is made of high crystallization of PAS.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for economically producing a polyarylene sulfide having a high crystallization temperature and no decrease in melt viscosity.

[0009]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, by adding a specific amount of oxygen to the reaction system immediately after the polymerization reaction of polyarylene sulfide, the melt viscosity is increased. It has been found that polyarylene sulfide having a high crystallization temperature can be obtained without a decrease in the crystallization temperature, and the present invention has been completed.

That is, the present invention relates to a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide-based solvent. 0.1 to 1 mole of metal sulfide
A method for producing polyarylene sulfide, which comprises adding 48 mol% of oxygen.

Further, according to the present invention, the timing for adding oxygen is as follows:
The method for producing polyarylene sulfide described above, wherein the temperature of the polyarylene sulfide slurry after the completion of the reaction is from the reaction temperature to 100 ° C.

Preferred embodiments of the present invention are described below. (1) The method for producing polyarylene sulfide, wherein the amount of added oxygen is 0.1 to 44 mol% based on 1 mol of the charged alkali metal sulfide. (2) The method for producing polyarylene sulfide, wherein the amount of oxygen added is 0.2 to 44 mol% based on 1 mol of the charged alkali metal sulfide. (3) The method for producing polyarylene sulfide described above, wherein the time for adding oxygen is when the temperature of the polyarylene sulfide slurry after the reaction is from 230 to 150 ° C.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for polymerizing a polyarylene sulfide according to the present invention is a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihalo aromatic compound in an organic amide-based solvent. This is intended to increase the crystallization temperature by adding oxygen or an oxygen-containing gas to a polyarylene sulfide slurry and treating the ends of the generated polyarylene sulfide. This will be described in detail below.

1. Production of Polyarylene Sulfide Slurry In the present invention, a method for producing a PAS slurry by reacting an alkali metal sulfide with a dihalo aromatic compound in an organic amide solvent is not particularly limited. For example, a method for producing a PAS by reacting an alkali metal sulfide with a dihaloaromatic compound in an organic amide solvent described in JP-B No. 45-3368, and an alkali metal carboxylic acid described in JP-B No. 52-12240. A method using an acid salt, a method using a polymerization aid such as lithium halide described in U.S. Pat. No. 4,038,263, JP-B-54-871.
No. 9, a method using a cross-linking agent such as a polyhalo aromatic compound, and a method described in Japanese Patent Publication No. 33775/1988 using a multi-step reaction in the presence of different amounts of water.

More preferably, Japanese Patent Application Laid-Open No. 5-222196
In the method described in Japanese Patent Application Publication No. JP-A-2003-260, in which an alkali metal sulfide is reacted with a dihaloaromatic compound in an organic amide solvent to produce a PAS, the reaction vessel is cooled by cooling a gas phase portion of the reaction vessel during the reaction. A method of condensing a part of the gas phase in the inside and refluxing it in a liquid phase can be used.
By using this method, a relatively high melt viscosity of P
AS can be manufactured, and PAS having high mechanical strength such as tensile strength and impact strength can be obtained.

In the method described in JP-A-5-222196, the gas phase portion of the reaction vessel is actively cooled, and a large amount of the reflux liquid rich in water is returned to the upper portion of the liquid phase, whereby the upper portion of the reaction solution is cooled. To form a layer having a high water content. As a result, the remaining alkali metal sulfide (eg, Na
2S), alkali metal halides (eg, NaCl),
The layer contains a large amount of oligomers and the like, so that factors that hinder the reaction can be removed more efficiently than in the conventional method, and a high molecular weight PAS can be obtained. In this method, it is not necessary to add water during the reaction as in the conventional method, but it is preferable to keep the total water content in the polymerization reaction system constant during the reaction.

The gas phase portion of the reaction vessel can be cooled by a known cooling means. A method of flowing a cooling medium through an internal coil installed at an upper portion inside the reaction vessel, an external coil or a jacket wound around the upper portion outside the reaction vessel. A method of flowing a refrigerant to the reactor, a method using a reflux condenser installed on the upper part of the reaction vessel,
Methods such as spraying water or blowing gas (air, nitrogen, etc.) on the upper part outside the reaction vessel and removing the heat insulating material conventionally provided on the upper part of the reaction vessel can be considered. good.

The temperature of the liquid phase bulk is maintained at a predetermined constant temperature or controlled according to a predetermined temperature profile. 230-275 ° C for constant temperature
The reaction is preferably performed at a temperature of 0.1 to 20 hours.
In order to obtain a higher molecular weight PAS, it is preferable to use two or more reaction temperature profiles. When performing this two-step operation, the first step is preferably performed at a temperature of 195 to 240 ° C. If the temperature is low, the reaction rate is too low, which is not practical. If the temperature is higher than 240 ° C., the reaction rate is too high, so that not only a sufficiently high molecular weight PAS cannot be obtained, but also the side reaction rate is significantly increased. The end of the first phase,
It is preferable to carry out the reaction at a time when the residual ratio of the dihaloaromatic compound in the polymerization reaction system is 1 to 40 mol% and the molecular weight is in the range of 3,000 to 20,000. If the residual ratio exceeds 40 mol%, side reactions such as depolymerization tend to occur in the second stage reaction, while if less than 1 mol%, high molecular weight PAS
Hard to get. Thereafter, the temperature is raised, and the reaction in the final stage is preferably performed at a reaction temperature of 240 to 270 ° C. for 1 to 10 hours. If the temperature is low, it is not possible to obtain a PAS having a sufficiently high molecular weight, and if the temperature is higher than 270 ° C., side reactions such as depolymerization are likely to occur, and it is difficult to obtain a stable high molecular weight product.

As an actual operation, first, under an inert gas atmosphere, dehydration or water addition is performed as necessary so that the water content of the polymerization system becomes a predetermined amount. The water content is preferably
It is 0.5 to 1.39 mol per mol of alkali metal sulfide. If the amount exceeds 1.39 mol, the total amount of water added at the time of pH adjustment exceeds 1.4 mol per mol of alkali metal sulfide. , Operation becomes complicated. If the amount is less than 0.5 mol, the reaction rate is too high to obtain a product having a sufficient high molecular weight, and undesirable reactions such as side reactions occur.

In the case of a one-stage reaction at a constant temperature, the cooling of the gas phase during the reaction is preferably carried out from the start of the reaction, but must be carried out at least during the temperature rise to 250 ° C. or lower. In the multi-stage reaction, it is preferable to perform cooling from the first-stage reaction, but it is preferable to perform cooling at the latest after the completion of the first-stage reaction. The degree of the cooling effect is usually the most suitable index of the internal pressure of the reaction vessel, and it is preferable to perform the cooling to such an extent that the internal pressure of the reaction vessel is lower than when no cooling is performed.

The organic amide solvent used in the method is known for PAS polymerization.
-Methylpyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethyl (or diethyl) acetamide, N-methyl (or ethyl) caprolactam, 1,
3-dimethyl-2-imidazolidinone, formamide,
Acetamide, hexamethylphosphoramide, tetramethylurea, N, N'-ethylene-2-pyrrolidone, 2
-Pyrrolidone, ε-caprolactam, diphenylsulfone, and the like, and mixtures thereof can be used, with NMP being preferred. They all have a lower vapor pressure than water.

Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide (Na2S), potassium sulfide, rubidium sulfide, cesium sulfide and a mixture thereof. These hydrates and aqueous solutions may be used.
In addition, hydrosulfides and hydrates corresponding to these, respectively,
It can be used after neutralization with the corresponding hydroxide. Inexpensive sodium sulfide is preferred.

The dihaloaromatic compound can be selected from, for example, those described in JP-B-45-3368, but is preferably p-dichlorobenzene. Further, a copolymer can be obtained by using at least one kind of a small amount (20 mol% or less) of diphenyl ether, diphenyl sulfone, or biphenyl para, meta or ortho dihalo compound. For example, o-dichlorobenzene, p, p′-dichlorodiphenyl ether, m, p′-dichlorodiphenyl ether, m, m′-dichlorodiphenyl ether,
p, p'-dichlorodiphenylsulfone, m, p'-dichlorodiphenylsulfone, m, m'-dichlorodiphenylsulfone, p, p'-dichlorobiphenyl, m,
p'-dichlorobiphenyl and m, m'-dichlorobiphenyl.

In order to increase the molecular weight of PAS,
For example, 1,3,5-trichlorobenzene, 1,2,4-
The polyhalo compound such as trichlorobenzene can be used in an amount of preferably 0.005 to 1.5 mol%, particularly preferably 0.02 to 0.75 mol%, based on 1 mol of the alkali metal sulfide.

2. Oxygen Treatment of Polyarylene Sulfide Slurry In the method of the present invention, oxygen is added to the reacted polyarylene sulfide slurry obtained above and treated. The amount of oxygen added to the PAS slurry after the reaction is:
0.1 to 4 per mol of charged alkali metal sulfide
8 mol% (0.0224 to 10.75 liters), preferably 0.1 to 44 mol% (0.0224 to 9.86 liters), more preferably 0.2 to 44 mol% (0.0
448-9.86 liters). The amount of oxygen is 0.1
If it is less than mol%, the effect of improving the crystallization temperature of the obtained PAS is small, and if it exceeds 48 mol%, the decomposition of the polymer becomes severe, which is not preferable. The oxygen used here can be an oxygen-containing gas such as pure oxygen or a mixture of oxygen and any suitable inert gas. In the oxygen-containing gas, examples of the inert gas include nitrogen, argon, and a mixture thereof, and air is preferably used as the oxygen-containing gas.

In the step of adding and treating oxygen, first, cooling of the PAS slurry after the completion of the PAS polymerization step is started, and the temperature of the PAS slurry is set to a reaction temperature to 100 ° C., preferably 230 to 150 ° C. Alternatively, an oxygen-containing gas is injected into the reaction vessel, and the mixture is treated with stirring for 0.1 to 24 hours. If the temperature of the slurry at the time of adding oxygen exceeds the reaction temperature, the polymer is decomposed. If the temperature is lower than 100 ° C., the effect of improving the crystallization temperature is not obtained, which is not preferable.

In the present invention, it is not clear that the crystallization temperature of PAS can be improved by adding and treating oxygen or an oxygen-containing gas to the reaction slurry at a specific time after the reaction. A sulfur radical is generated at the molecular terminal of the PAS, and the sulfur radical extracts hydrogen from a solvent or the like to form an SH group at the molecular terminal.
It is considered that the crystallization temperature is improved by the presence of PAS having a terminal. Therefore, a PAS having a high crystallization temperature can be easily obtained without going through a complicated treatment step such as an acid treatment as in the conventional method.

3. Recovery of Polyarylene Sulfide (Post-Treatment) In the present invention, recovery of polyarylene sulfide from the PAS slurry subjected to the oxygen treatment as described above can be performed according to a conventional method. For example, the PAS slurry is filtered to obtain a PAS cake containing a solvent, and the PAS cake is placed in a nitrogen gas stream, preferably at 150 to 250 ° C.
At a temperature of preferably 10 minutes to 24 hours, and after repeating water washing and filtration several times on the obtained PAS powder,
PAS can be obtained by a solvent drying treatment method of obtaining PAS by drying. Alternatively, the PAS slurry is filtered,
After removing the solvent, water washing / filtration is repeated several times and then dried to obtain PAS. PAS can be obtained by a direct water washing treatment method.

The PAS produced by the method of the present invention is
It has a high crystallization rate, little decrease in melt viscosity, and mechanical strength. Therefore, it is suitable for injection molding.

When the PAS of the present invention is processed, conventional additives, such as powdered fillers such as carbon black, calcium carbonate, silica and titanium oxide, or carbon fibers, glass fibers, asbestos fibers, polyaramid fibers And other fibrous fillers.

Further, if necessary, additives such as an antioxidant, a heat stabilizer, a lubricant, a releasing agent, and a coloring agent may be added.

[0032]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, the test method in an Example is as follows. (1) Melt viscosity V6: Flow tester CF manufactured by Shimadzu Corporation
300 ° C., load = 1.96 × 10 using T-500C
^{This is} the viscosity (poise) measured after holding at ⁶ Pa and L / D = 10/1 for 6 minutes. (2) Crystallization temperature Tc: The crystallization temperature Tc was measured by DSC. The measurement was performed as follows using a differential scanning calorimeter DSC6200R manufactured by Seiko Instruments. The sample PPS powder was heated at 320 ° C. and 9.8 × 10 ⁵
After pressing for 1 minute at Pa, the film was immersed in cold water and quenched to prepare a film. 5 mg of the film sample was heated from room temperature to 320 ° C. at a temperature rising rate of 20 ° C./min in a nitrogen stream, and then held at 320 ° C. for 5 minutes to melt. Then 1
The exothermic peak temperature when cooled at a rate of 0 ° C./min was taken as the crystallization temperature Tc (° C.). (3) Sodium content: 700 ° C. of the sample PPS powder
After burning in a muffle furnace, the residue was dissolved in hydrochloric acid,
The sodium content (ppm) was measured using AA-670 manufactured by Shimadzu Corporation as an atomic absorption spectrometer.

Example 1 In a 150-liter autoclave, 15.375 kg of flaky sodium sulfide (60.91% by weight Na2S) and N
38.0 kg of -methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) was charged. The temperature was raised to 216 ° C. while stirring under a nitrogen stream to distill 3.740 kg of water (1.05 mol of water per mol of sodium sulfide). Thereafter, the autoclave was closed and cooled to 180 ° C., and 17.700 kg of paradichlorobenzene (hereinafter, sometimes abbreviated as p-DCB) and 16.0 kg of NMP were charged. 9.6 × 10 ⁴ P using nitrogen gas at a liquid temperature of 150 ° C.
The pressure was increased to a, and the temperature was raised. When the liquid temperature reached 260 ° C., watering to the upper part of the autoclave was started. The reaction was carried out by keeping at this temperature for 2 hours. After the completion of the reaction, the water spray was stopped and the system was cooled. When the liquid temperature reached 200 ° C., 44 mol% of oxygen gas per mole of sodium sulfide (9.86 liters of oxygen gas per mole of sodium sulfide) was injected. Then 20
Stirring was performed at 0 ° C. for 30 minutes. Then, it cooled to room temperature. The obtained slurry was filtered to remove the solvent, and then the solvent-containing cake was heated at 220 ° C. for about 6 hours in a nitrogen stream to remove the solvent. Next, the obtained PPS powder is repeatedly washed with water and filtered seven times by a conventional method, and then dried at 120 ° C. for about 8 hours in a hot air circulating drier to obtain a powdery polyphenylene sulfide polymer (P-1). I got Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.

Example 2 The slurry was filtered in the same manner as in Example 1 except that the slurry after the oxygen treatment was filtered to remove the solvent, and then water washing and filtration were repeated seven times by a conventional method. Of polyphenylene sulfide polymer (P-2) was obtained. Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.
Shown in

Example 3 Same as Example 1 except that 0.2 mol% of oxygen gas per mol of sodium sulfide (0.045 liter of oxygen gas per mol of sodium sulfide) was injected into the polymerization reaction slurry. Thus, a powdery polyphenylene sulfide polymer (P-3) was obtained. Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.

Example 4 After the completion of the polymerization reaction, the system was cooled, and air containing 170 mol% of oxygen at 2.0 mol% per mol of sodium sulfide (2.24 liters of air per mol of sodium sulfide) was cooled at 170 ° C. A powdery polyphenylene sulfide polymer (P-4) was obtained in the same manner as in Example 1 except for injecting. Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.

Example 5 A powdery polyphenylene sulfide polymer (P-5) was obtained in the same manner as in Example 1 except that water was not sprayed on the upper part of the autoclave during the polymerization. Melt viscosity of polymer (V
6), crystallization temperature (Tc) and Na content are shown in Table 1.

Comparative Example 1 After the polymerization reaction, the polymerization reaction slurry was cooled,
Powdered polyphenylene sulfide was prepared in the same manner as in Example 1 except that air containing 0.08 mol% of oxygen per mole of sodium sulfide was injected (0.09 liter of air per mole of sodium sulfide). Polymer (PC-
1) was obtained. Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.

Comparative Example 2 55.0 per mol of sodium sulfide was added to the polymerization reaction slurry.
Except that a mole% of oxygen (12.3 liters of oxygen gas per mole of sodium sulfide) was injected in the same manner as in Example 2 except that the powdery polyphenylene sulfide polymer (P
C-2) was obtained. Table 1 shows the melt viscosity (V6), crystallization temperature (Tc), and Na content of the polymer.

[0040]

[Table 1]

[0041]

According to the method of the present invention, polyarylene sulfide having a high crystallization temperature can be easily produced, which is an economically advantageous method. PAS produced by the method of the present invention has a melt viscosity Crystallization rate is fast,
Has high mechanical strength. Therefore, it is suitable for injection molding, can shorten the molding cycle, and is effective in improving productivity.

Claims (2)

[Claims] In a method for producing a polyarylene sulfide by reacting an alkali metal sulfide with a dihalo aromatic compound in an organic amide solvent, the alkali metal sulfide slurry is added to the polyarylene sulfide slurry after the reaction. A method for producing polyarylene sulfide, comprising adding 0.1 to 48 mol% of oxygen to mol. 2. The time when oxygen is added is such that the temperature of the polyarylene sulfide slurry after the reaction is from the reaction temperature to 1
The method for producing a polyarylene sulfide according to claim 1, wherein the temperature is at 00 ° C.