JP2720050B2 - Method for producing polyphenylene sulfide - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing polyphenylene sulfide (hereinafter abbreviated as PPS), and more particularly, to a method for producing sodium sulfide as a raw material for producing PPS as an aqueous solution having a specific concentration. The present invention relates to a method for producing a stable and high-quality PPS by improving the productivity by simplifying and facilitating a polymerization operation by using the PPS in a polymerization can.

(Prior Art) A typical method for producing PPS is a method in which a dihalo aromatic compound represented by p-dichlorobenzene is reacted with sodium sulfide in an organic amide solvent such as N-methylpyrrolidone. 52-12240, JP-A-61-7332, etc.).

In this case, the raw material sodium sulfide is usually Na ₂ S
9H ₂ O crystal (Na ₂ S concentration 32.5% by weight), Na ₂ S 5H ₂ O crystal (Na ₂ S concentration 46.4% by weight), or Na ₂ S concentration of about 60% by weight
A solid state material such as a solidified product of the above is used. The reason is that these solid-state sodium sulfides are industrially produced and are easily available.

However, none of these solid sodium sulfides as industrial products have a uniform composition.

For example, Na ₂ S ・ 5H ₂ O crystals are produced by crystallization, but sodium sulfide is easily dissolved in water, so when separating crystals, usually the mother liquor cannot be washed off and dried with the mother liquor attached Product. Therefore, the amount of mother liquor deposited differs depending on the size of the crystal, and the composition of the mother liquor is different from the composition of the crystal.

In addition, about 60% by weight of a consolidated body is produced by cooling a melt having the same composition, and as described later, this is made of Na ₂ S.5H ₂ O
And Na ₂ S.H ₂ O, it does not solidify uniformly during cooling, and the solidified initially has a concentration higher than 60% by weight and a concentration lower than 60% by weight in the latter stage.

For the above reasons, accurate concentration analysis of industrial sodium sulfide is extremely difficult due to its heterogeneity.

Further, when PPS is mass-produced on an industrial scale, it is not always preferable to use sodium sulfide as a raw material in a solid state. Because when storing, transferring or weighing large amounts of sodium sulfide,
This is because it is difficult to handle due to the solid state.

For example, sodium sulfide is susceptible to air oxidation, and as a result, produces oxides such as Na ₂ SO ₃ , Na ₂ S ₂ O ₃ , and Na ₂ S _X ,
These oxides are factors that inhibit the polymerization reaction of PPS. In order to prevent air oxidation, it is necessary to seal with an inert gas such as nitrogen gas. However, if sodium sulfide is in a solid state, it is often difficult to completely seal with sodium gas.

Further, sodium sulfide in a solid state is liable to cause consolidation due to its own weight during transportation and storage, line blockage due to crushing and pulverization during transportation, measurement errors, and the like.

Further, when handling a solid substance, foreign matter may be mixed in, and it is extremely difficult to remove the foreign matter once mixed in a solid state.

Furthermore, when sodium sulfide (hydrous sodium sulfide) in a solid state containing water as water of crystallization is used as a raw material for PPS production, it is heated and dehydrated together with an organic amide solvent in a polymerization vessel to reduce the water content. 0% for sodium.
It is common to react with a dihalo aromatic compound after reducing it to about 3 to 5 molar ratio. The reason is that, in the polymerization of PPS, particularly in the early stage of the polymerization, if more than 5 mol of water is present per 1 mol of sodium sulfide, the polymer during the polymerization is decomposed and the polymerization temperature is lowered.

On the other hand, the water content per mole of sodium sulfide (Na ₂ S)
If the amount is less than 0.3 mol, sodium sulfide will not be dissolved in the organic amide solvent, and it will be difficult to obtain a polymer having a high degree of polymerization. However, when water-containing sodium sulfide is heated in an organic amide solvent to evaporate and remove water, H ₂ S gas dissociates from sodium sulfide equilibrium and volatilizes. As a result, the Na / S ratio (molar ratio, The same applies hereinafter) slightly higher than the Na / S ratio of the raw material. Therefore, as the raw material sodium sulfide,
For example, even when a single crystal of Na ₂ S · 5H ₂ O, that is, one having a Na / S ratio of 2, is used, the Na / S ratio becomes a value larger than 2 and about 2.05 under actual polymerization conditions.

Therefore, sodium sulfide used as a raw material needs to be adjusted so that the Na / S ratio during polymerization falls within a certain range in consideration of an increase in the Na / S ratio during dehydration. However, such adjustment is very difficult with a single crystal of Na ₂ S · 9H ₂ O or Na ₂ S · 5H ₂ O.

The Na ₂ S · 9H ₂ O and Na ₂ S · 5H ₂ O in the single crystal, NaOH (Na / S ratio = ∞) and NaHS (Na / S ratio _{= 1), H 2 S (} Na / S ratio = 0) may be added to control the Na / S ratio,
The operation becomes complicated, and the physical properties of the obtained polymer are often inferior to those obtained by using sodium sulfide whose Na / S ratio is adjusted from the beginning, such as a lower melt viscosity.

Therefore, in the production of PPS, it is preferable to use sodium sulfide whose Na / S ratio has been adjusted to an appropriate range from the beginning as a raw material.

However, sodium sulfide in the solid state, which has been widely used in the past, has the above-mentioned problems, and it is difficult to adjust the Na / S ratio to an appropriate range.

Thus, sodium sulfide in the solid state has problems in handling such as sampling, storage, transfer, measurement, antioxidation, etc. for concentration measurement, and PP due to these problems.
The melt viscosity of S decreases and the melt viscosity of each lot varies.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned problems of the prior art in a method for producing PPS, to improve the productivity by making the polymerization operation simple and easy, to improve the productivity, It is to provide a method for producing quality PPS.

Furthermore, an object of the present invention is to provide a method for using a sodium sulfide aqueous solution which is easy to handle, can prevent oxidation and remove insoluble impurities, and has an appropriate Na / S ratio as a raw material for PPS production. To provide.

The present inventors have conducted intensive studies and produced sodium sulfide, which is a raw material for producing PPS, as a high-concentration aqueous solution, and in the state of the aqueous solution, performed concentration analysis, storage, transfer, measurement, and the like.
It has been found that the above object can be achieved by charging a polymerization can as a raw material for polymerization, and based on this finding, the present invention has been completed.

(Means for Solving the Problems) That is, according to the present invention, in a method for producing polyphenylene sulfide by reacting sodium sulfide with a dihalo aromatic compound in an organic amide solvent, the concentration of sodium sulfide as a raw material for polymerization is reduced. A process for producing polyphenylene sulfide, which is charged into a polymerization can as an aqueous solution of 46 to 60% by weight, is provided.

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

FIG. 1 shows a phase diagram of sodium sulfide (Na ₂ S) and water.

FIG. 1 shows that Na ₂ S can be present as an aqueous solution only at a concentration of 60% by weight or less. Na ₂ S ・ 5H ₂ O
(Na ₂ S concentration 46% by weight) has a maximum melting point of 98 ° C.
It can be seen that in the concentration range of weight%, it exists as an aqueous solution at a temperature lower than 98 ° C., and has a minimum melting point of 86 ° C. at 55% by weight.

In the present invention, the concentration of the aqueous sodium sulfide solution is 46 to 60.
The reason for the weight percentage is based on the dissolution behavior of Na ₂ S in water described above.

The higher the concentration of sodium sulfide, the lower the energy consumption in the dehydration step during PPS production,
At the same time as being economical, it is preferable that the amount of dehydration be small so that the H ₂ S gas is not volatilized during dehydration. In addition, by using a homogeneous solution in which solid components are not mixed, measurement errors can be minimized. It is more economical to keep the aqueous solution at a lower temperature. Therefore, it is preferable that the sodium sulfide aqueous solution has a high concentration and a low temperature at which it can exist as a solution. From that viewpoint, the concentration is more preferably 46 to 60% by weight, and more preferably 54 to 56% by weight.

Note that the Na / S ratio was slightly shifted from 2, that is,
An aqueous sodium sulfide solution containing a small amount of NaOH or NaHS in addition to Na ₂ S can also exist as such an unsaturated aqueous solution. Therefore, the sodium sulfide aqueous solution of the present invention contains a small amount of
NaOH or NaHS may be included.

As a method for producing an aqueous solution of sodium sulfide having a concentration of 46 to 60% by weight, the following various methods can be mentioned.

(A) A crystal of Na ₂ S · 9H ₂ O or Na ₂ S · 5H ₂ O is heated and melted to form a liquid, which is concentrated, and NaOH or NaHS
Is added in a small amount, and the Na / S ratio at the time of polymerization is adjusted to the initially set value.

(B) The aqueous NaHS solution is neutralized with the aqueous NaOH solution and concentrated.

(C) Concentrate the aqueous NaOH solution and absorb H ₂ S gas.

Among these methods, any method may be selected in consideration of the difficulty of obtaining the raw material, the purity of the raw material, etc.
In (a) and (b), it is necessary to use a container made of a material having high corrosion resistance when concentrating a high-concentration Na ₂ S solution, and the H ₂ S gas is volatilized together with the evaporating water. There are many problems.

An example of a preferred production method includes the following method.

A commercially available 48-50% by weight aqueous NaOH solution is concentrated to 73-74% by weight. As shown in FIG. 2, this concentration is industrially
It is the upper limit that can handle NaOH as an aqueous solution.

The aqueous NaOH solution is divided into approximately _two parts, and one of them is allowed to absorb H ₂ S gas until it is saturated, thereby obtaining a 63 to 64% by weight aqueous NaHS solution.
At this time, H ₂ S to be used is preferably of high purity not containing impurities such as carbon dioxide gas and hydrogen polysulfide, and an example of the production method is a method described in JP-A-63-139007. .

When the remaining one of the 73 to 74 wt% NaOH aqueous solution is mixed with this NaHS aqueous solution, a 54 to 55 wt% Na ₂ S aqueous solution is obtained. At this time, the mixing ratio of the NaHS aqueous solution and the NaOH aqueous solution is almost equimolar, but the Na / S ratio can be freely adjusted by slightly changing the mixing ratio as needed.

The aqueous Na ₂ S solution thus produced may contain insoluble solid impurities. Eg, NaCl derived from _{NaOH, Na 2 CO 3, Fe} , Cr, sulphides of heavy metals such as Ni,
Na ₂ by-product in the air oxidation of _{S Na 2 CO 3, Na 2} S 2 O 3, a foreign matter further mixed by the device material and the outside of the system. Since such insoluble impurities adversely affect the physical properties of the obtained PPS, they are removed by solid-liquid separation such as centrifugal sedimentation and used as a clear solution.

Since the aqueous sodium sulfide solution used in the present invention can be stored and transported in a container having a lid, it can be easily sealed or sealed with nitrogen gas. Therefore, as compared with the solid state, the antioxidation is more complete, and even when the measurement is performed, the liquid is a homogeneous liquid and the concentration can be accurately controlled, so that accurate measurement can be easily performed. When an aqueous solution of sodium sulfide is used as a raw material for producing PPS, PPS having a constant viscosity can be produced with little variation among lots.

Here, in the production of PPS, it is as shown in Table 1 which compares the difficulty of handling solid sodium sulfide with the aqueous solution of sodium sulfide having a specific concentration used in the present invention.

(Examples) Hereinafter, the present invention will be specifically described with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to only these Examples.

The method for analyzing sodium sulfide and its impurities was based on JIS K-1435.

Reference Example 1 (Preparation of aqueous sodium sulfide solution) 2.53 kmol of 74.0
A weight% aqueous solution of NaOH is charged. Since the melting point of this liquid was 62 ° C, the liquid temperature was set to 70 ° C.

H ₂ S gas was blown into this from a hydrogen sulfide cylinder until saturation. During this time, the reaction was carried out while cooling the reaction tank so that the liquid temperature did not exceed 110 ° C. Na / S in this state
The ratio was 1.01.

Then, 2.45 kmol of a 74.0% by weight aqueous NaOH solution (liquid temperature 70
C.) to obtain a 55.1% by weight aqueous sodium sulfide solution having a Na / S ratio of 1.99.

The sodium sulfide solution is a was a transparent clear solution, Na ₂ SO ₃ 0.15% by weight as impurities, Na ₂ S ₂ O ₃ 0.06
Wt% was present.

With the aqueous sodium sulfide solution in the reactor,
The solution was stored under a seal with nitrogen gas for 2 months at ℃, but no increase in oxides was observed.

Reference Example 2 (save sodium sulfide solid state) hydrous crystalline sodium sulfide (equivalent to approximately Na ₂ S · 5H ₂ O) Temperature 25 to 35 ° C. in 1 t-filled container back, humidity 70
When stored at 80% for 2 months, the changes shown in Table 2 were observed.

Examples and Comparative Examples (Production of PPS) In order to compare an aqueous sodium sulfide solution with a commercially available hydrous crystalline sodium sulfide, PPS was produced by the following method.

Example 1 The aqueous solution of sodium sulfide (90 ° C.) obtained in Reference Example 1 was used.
354.1 kg (2.50 kmol) and 1000 kg of N-methylpyrrolidone (hereinafter abbreviated as NMP) were charged into a titanium clad autoclave, heated to about 203 ° C., and 96 kg of water was distilled.

Then, 371 kg of p-dichlorobenzene (70 ° C., liquid)
Was charged. The aqueous sodium sulfide solution, NMP, and p-dichlorobenzene were all measured using an integrating flow meter (turbine flow meter). This was further reacted at 220 ° C. for 5 hours, and then 61.8 kg of deionized water was added. And
Polymerization was performed at 255 ° C. for 5 hours.

The reaction solution was sieved with a screen having an opening of 0.1 mm to separate only the granular polymer, and washed with acetone and then with deionized water to obtain a washed polymer.

The washed polymer was immersed in a 2% by weight aqueous solution of ammonium chloride, treated at 40 ° C. for 30 minutes, washed with deionized water, and dried to obtain PPS.

The above operation was repeated 10 times, and the melt viscosity (310 ° C., shear rate 200 sec ⁻¹ ) of each obtained polymer was measured.
It was 0-1850 poise and the average was 1700 poise.

(Comparative Example 1) Hydrous crystalline sodium sulfide of Reference Example 2 (before storage)
Was used to produce PPS in the same manner as in Example 1.

423.3 kg of hydrous crystalline sodium sulfide in a container bag transported to the hopper scale under a nitrogen gas seal
(2.50 mol) was measured and used. Distilled water was 165 kg, and the amount of residual water was the same as in Example 1.

Except for this, PPS was obtained in the same manner as in Example 1. The drying was repeated 10 times, and the melt viscosity of each of the obtained polymers was measured. The average value was 1600 poise, but the melt viscosity of the polymer in each lot varied between 1300 and 1900 poise.

(Comparative Example 2) The same experiment as in Comparative Example 1 was performed three times except that the deteriorated hydrous crystalline sodium sulfide obtained in Reference Example 2 (after storage) was used.

The melt viscosities of the resulting polymers were 700, 900 and 1300 poise, respectively, and varied considerably from lot to lot, and the average value was as low as about 970 poise.

Thus, compared to the case of using sodium sulfide in the solid state, the use of sodium sulfide aqueous solution makes it possible to obtain PPS with less variation in melt viscosity, but the reason is that the measurement accuracy is improved because it is an aqueous solution. It is presumed that this was due to the fact that the oxidation prevention effect was improved.

(Effects of the Invention) According to the present invention, in producing PPS, sodium sulfide as a raw material is prepared as a high-concentration aqueous solution, and this is used as an aqueous solution to measure, store, transport, and measure the concentration of sodium sulfide. In addition, handling such as prevention of air oxidation becomes easy, and stable and high-quality PPS with a high degree of polymerization can be obtained.

[Brief description of the drawings]

FIG. 1 is a phase diagram of sodium sulfide and water. In the figure,
The shaded portion is a solid phase or a solid-liquid coexisting phase. Fig. 2
It is a phase diagram of sodium hydroxide. The meanings of the symbols in FIG. 2 are as follows. 1: Ice + solution, 2: Ice + NaOH ・ 7H ₂ O 3: NaOH ・ 7H ₂ O + solution, 4: NaOH ・ 5H ₂ O + solution 5: NaOH ・ 7H ₂ O + NaOH ・ 5H ₂ O 6: NaOH ・ 4H ₂ O + solution 7: NaOH · 5H ₂ O + NaOH · 4H ₂ O 8: NaOH · 3.5H ₂ O + solution 9: NaOH · 4H ₂ O + NaOH · 3.5H ₂ O 10: NaOH · 3.5H ₂ O + NaOH · 2H ₂ O 11: NaOH · 2H ₂ O 11: NaOH · 2H ₂ O + solution 12: NaOH · H ₂ O + solution _{13: NaOH · 2H 2 O +} NaOH · H 2 O 14: NaOH + solution _{15: NaOH · H 2 O +} NaOH

Claims (3)

(57) [Claims] 1. A method for producing polyphenylene sulfide by reacting sodium sulfide and a dihalo aromatic compound in an organic amide solvent, wherein sodium sulfide as a raw material for polymerization is charged as an aqueous solution having a concentration of 46 to 60% by weight into a polymerization vessel. A method for producing polyphenylene sulfide. 2. The method for producing polyphenylene sulfide according to claim 1, wherein the concentration of the aqueous solution of sodium sulfide is 54 to 56% by weight. 3. The process for producing polyphenylene sulfide according to claim 1, wherein the aqueous solution of sodium sulfide is used as a clarified liquid by solid-liquid separation of insolubles which may be present in the aqueous solution.