JPH09169844A - Production of polyarylene sulfide by continuous multistage polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyarylene sulfide(PAS) having a high molecular weight by establishing a technique for stably transferring the reaction solution while keeping the polymer to solvent composition ratio among the polymerizers constant. SOLUTION: A polyarylene sulfide is continuously produced by a continuous multistage polymerization process by successively transferring the reaction solution through multistage polymerizers. This process comprises the step (1) of discharging the polymer phase 5 from the bottom of the polymerizer and discharging the solvent phase 6 from its top, the step (2) of mixing the discharged polymer phase 5 with the discharged solvent phase 6 to give a mixture of a specified concentration, the step (3) of feeding the mixture into the next polymerizer 1, and the step (4) of repeating the steps (1) to (3).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a continuous multi-stage polymerization method for polyarylene sulfide (PAS). More specifically, it relates to a continuous multi-stage polymerization method for producing a polyarylene sulfide which is particularly useful in the fields of electricity, electronics, automobiles, and heat resistant materials, with high quality and at low cost.

[0002]

2. Description of the Related Art Conventionally, polyarylene sulfide (PA
Since the S) resin was produced by the batch method, it was not necessary to transfer the polymer and solvent in the polymerization tank at a high temperature, but in recent years, there has been an increasing demand for continuous polymerization in order to improve production efficiency. In the case of continuous polymerization of PAS, the polymerization reaction tank needs to be operated in multiple stages, and the polymerization reaction solution needs to be transferred between the tanks. As a continuous polymerization method of this kind of PAS, for example, US Pat. No. 4,056,515,
Nos. 4,060,520 and 4,066,632 are disclosed.

[0003]

However, in recent years, in the production of PAS, there are many polymerization methods using a phase separating agent (water, sodium acetate, alkali metal salt, etc.) for the purpose of improving the molecular weight of the obtained polymer. It has come to be used. In the case of continuous polymerization using such a phase separating agent, the polymerization reaction liquid is in a state where the polymer phase and the solvent phase are phase-separated in the polymerization tank, and the bottom of the tank or piping that is difficult to be affected by shearing force such as stirring. In some cases, the polymer phase settles due to the difference in specific gravity, and the composition ratio (concentration) of the polymer phase / solvent phase may not be kept constant during the transfer of the polymerization reaction liquid between the tanks. There was a problem that could not be made sufficiently large.

In the methods described in the above-mentioned three US patents, the polymer phase and the solvent phase are not separated into two phases because a phase separating agent is not added, and the molecular weight of PAS obtained is low. There was a problem that I had no choice. Thus, when producing a high molecular weight PAS, the addition of a phase separation agent is indispensable, and in the continuous polymerization using the phase separation agent, the composition ratio (concentration of the polymer phase / solvent phase between the polymerization tanks ) Is required to be stably transferred while being kept constant.

The present invention has been made in view of the above problems, and in the continuous polymerization process of PAS, a method of stably transferring the polymer while keeping the composition ratio of the polymer and the solvent between the polymerization tanks established. However, it is an object of the present invention to provide a continuous multi-stage polymerization method of polyarylene sulfide that enables the production of PAS having a high molecular weight.

[0006]

To achieve the above object, according to the present invention, a polymerization reaction solution is sequentially transferred to a polymerization vessel connected in multiple stages to continuously polymerize polyarylene sulfide. In the multi-stage polymerization method, there is provided a continuous multi-stage polymerization method for polyarylene sulfide, which comprises the following steps (1) to (4). (1) Extracting the polymer phase from the phase-separated polymerization reaction liquid from the bottom of the first-stage polymerization tank, and extracting the solvent phase from the upper part of the polymerization tank, (2) Polymerization reaction in the polymerization tank The extracted polymer phase and all or part of the solvent phase are mixed so that the composition ratio of the liquid phase is the same as that of the polymer phase, and (3) this mixed solution is polymerized in the next step. Supplying to the tank, (4) Regarding the polymerization tank after the next stage and before the final stage, the above (1) to
Repeating the step (3),

In a preferred embodiment, the polymerization tank used in each of the steps (1) to (4) has a polymer phase retention part at the bottom and a solvent phase retention part at the top. A continuous multi-stage polymerization method of polyarylene sulfide is provided.

[0008]

Embodiments of the present invention will be described below. INDUSTRIAL APPLICABILITY The present invention is a continuous multistage polymerization method in which the entire polymerization operation, including the charging of polymerization raw materials, a solvent, etc., and the removal of a production system, is carried out continuously by sequentially transferring the polymerization reaction solution to a polymerization tank connected in multiple stages Is. That is, to explain the case of three stages for convenience, the polymerization raw material is continuously supplied to the first stage (first) polymerization tank, and a part of the product (polymer) and a part of the solvent are continuously supplied. And is transferred to the next (second) polymerization tank. In the second polymerization tank as well, similar to the first polymerization tank, a part of the product (polymer) and a part of the solvent are continuously extracted and transferred to the final (third) polymerization tank.

1. Polyarylene sulfide (PAS)
In the present invention, the method of polymerizing PAS carried out in each polymerization tank is not particularly limited. For example, JP-A-7-20
The method described in Japanese Patent No. 7027 can be cited as a suitable example. That is, a method for producing a polyarylene sulfide, which comprises adding a sulfur compound and a dihalogenated aromatic compound to a mixture containing a solid substance of lithium hydroxide and non-lithium hydroxide in an aprotic organic solvent, a) Injecting a liquid or gaseous sulfur compound into a mixture containing solid lithium hydroxide and non-lithium hydroxide in an aprotic organic solvent to directly react lithium hydroxide with the sulfur compound. B) separating non-lithium hydroxide solids, c) adjusting the sulfur content of the reaction solution, and d) adding a dihalogenated aromatic compound to the reaction solution to cause polycondensation. , And e) mixing a reaction solution containing by-produced lithium chloride with an alkali metal hydroxide or an alkaline earth metal hydroxide to produce lithium hydroxide. Step of, can be exemplified method for producing a polyarylene sulfide which comprises a. Here, it is preferable to use N-methyl-2-pyrrolidone as the aprotic organic solvent, hydrogen sulfide as the sulfur compound, and paradichlorobenzene (PDCB) at 50 mol% or more as the dihalogenated aromatic compound. In the polymerization reaction liquid in the polymerization tank, it is necessary that the polymer phase and the solvent phase are in a phase separated state due to the presence of the phase separation agent. That is, it is necessary that both the polymer phase and the solvent phase are liquid phases and are in a separated state.

[0010] 2. Each step in the present invention In the present invention, the number of stages used in the polymerization tank is not particularly limited, but for convenience, three stages will be described below. (1) Extraction Step of Polymer Phase and Solvent Phase Of the polymerization reaction liquid phase-separated from the first polymerization tank by adding a phase separation agent (water, sodium acetate, alkali metal salt, etc.),
A part of the polymer phase rich in product (polymer) and a part of the solvent phase rich in solvent are continuously withdrawn. The quantitative standard (index) in this case is the reaction rate (monomer conversion rate) in the first polymerization tank, in other words, the reaction rate (monomer conversion rate) in the first polymerization tank is constant. First, the extraction amount of a part of the polymer phase and a part of the solvent phase is determined. Further, the amount of a part of the polymer phase and the amount of a part of the solvent phase extracted in the second polymerization tank are the same, and the reaction rate (conversion rate of the monomer) in the second polymerization tank is made constant. Then, for example, by setting the reaction rate (monomer conversion rate) in the first polymerization tank to 95% and the reaction rate (monomer conversion rate) in the second polymerization phase to 98%,
The capacity of the polymerization tank can be made smaller and the polymerization time can be shortened as compared with a single-stage polymerization.

As a method of extracting a part of the polymer phase and a part of the solvent phase, the polymer phase is extracted from the bottom of the polymerization tank and the solvent phase is extracted from the top of the polymerization tank. If it is extracted only from the bottom of the polymerization tank, what is called a polymer-rich product that contains a large amount of polymer will be extracted, and the extracted product, that is, the feed to the next stage will be different from the contents of the previous stage. However, the balance of continuous polymerization is lost, and a desired polymer having a high molecular weight cannot be obtained. On the other hand, when the solvent is extracted only from the upper part of the polymerization tank, a so-called solvent-rich substance containing a large amount of the solvent is also extracted, and similarly, the balance cannot be maintained and the desired polymer cannot be obtained.

(2) Mixing Step of Polymer Phase and Solvent Phase In the step (1), the polymer-rich material is extracted from the bottom of the polymerization tank, and the solvent-rich material is extracted from the upper portion of the polymerization tank separately, Both are mixed so that the composition is the same as the composition of the polymerization reaction liquid in the first polymerization tank. In this case, all the polymer-rich ones extracted from the bottom of the polymerization tank are used, and all the solvent-rich ones extracted from the top of the polymerization tank are used, but a new solvent may be added.

(3) Mixing Liquid Supplying Step The method of supplying the polymer-rich liquid and the solvent-rich liquid obtained in the step (2) is not particularly limited, but, for example, before supplying to the second polymerization tank. Alternatively, the polymer-rich phase and the solvent-rich phase may be separately supplied to the second polymerization tank and mixed in the second polymerization tank.

Regarding the supply from the second polymerization tank to the third polymerization tank, the above (1) from the first polymerization tank to the second polymerization tank is also performed.
It can be performed in the same manner as the steps (3) to (3).

3. Configuration Example of Polymerization Tank The polymerization tank used in the present invention is not particularly limited, but in order to efficiently perform the withdrawal in the above step (1), as shown in FIG. 1, a stirring blade 2 is provided and a bottom portion is provided. It is preferable to use the polymerization tank 1 having a structure having a polymer phase retention part 3 and a solvent phase retention part 4 at the top. As a specific example of the solvent phase retention section 4, there can be mentioned a cough having a structure in which only the solvent overflows. With such a structure, the polymer-rich polymer phase 5 can be extracted from the polymer phase retention part 3 and the solvent-rich solvent phase 6 can be extracted from the solvent phase retention part, respectively. In addition,
PAS (polymer) in the polymerization tank (1) is dispersed in the solvent phase 6 as polymer droplets 7 in the liquid phase.

[0016]

The present invention will be specifically described below with reference to examples. <Synthesis of PAS> 1. Synthesis of lithium sulfide N-methyl-2-pyrrolidone 3326.4 g (33.6 mol) was placed in a 10 liter autoclave equipped with a stirring blade.
And 287.4 g (12 mol) of lithium hydroxide are charged, and the temperature is raised to 130 ° C. at a stirring rotation speed of 300 rpm. After the temperature was raised, hydrogen sulfide was added to the liquid at 3 liter / min. Was blown for 2 hours to synthesize lithium hydrosulfide. Subsequently, the reaction solution was placed under a nitrogen stream (200 ml / mi).
n. ) The temperature was raised and a part of the reacted hydrogen sulfide was desulfurized. As the temperature increased, the water by-produced with the synthesis of lithium hydrosulfide started to evaporate. This by-product water was condensed by the condenser and extracted outside the system. Although the temperature of the reaction liquid increased as water was distilled out of the system, the temperature rise was stopped at 180 ° C. and the temperature was kept constant. Lithium sulfide synthesis was completed with a holding time of 2 hours, and the mixture was cooled. After the reaction, lithium sulfide was in the state of being precipitated as a solid in the solvent.
The slurry liquid was sampled while stirring, and the sulfur concentration and the lithium concentration were measured by the following methods. Sulfur concentration was analyzed by iodometry (after adding dilute hydrochloric acid to the sample solution, reacting by adding excess iodine solution and back titrating the excess iodine solution with sodium thiosulfate standard solution). It was analyzed by chromatography. The analysis result is S / Li = 0.498 mol ra
It was tio.

2. Prepolymerization Subsequently, 882.0 g (6 mol) of paradichlorobenzene (PDCB) was charged into this autoclave, and 22
The temperature was raised to 0 ° C. and prepolymerization was performed for 2 hours. After the completion of the prepolymerization, the reaction solution was cooled, a part of the obtained polymer was sampled, washed with water and acetone successively, and dried to obtain a polyarylene sulfide. 0.4% of this polyarylene sulfide to α-chlornaphthalene
It melt | dissolved so that it might become the density | concentration of g / dl, and the viscosity was measured using the Ubbelohde viscometer at the temperature of 206 degreeC. As a result, the intrinsic viscosity (η _inh ) of this polyarylene sulfide was 0.09.

<Example> A MONO pump (4NE04H2 manufactured by Hyojin Equipment Co., Ltd.) was connected to the bottom liquid extraction line of the 10 liter autoclave, and the discharge was connected to a 1 liter autoclave. The method of supplying the prepolymerization liquid to the 1 liter autoclave is as follows:
It was controlled by adjusting the rotation speed of the mono pump while observing the ΔP of the pressure of the liter autoclave. 1
Aiming for an average residence time of 3 hours in a liter autoclave of 2.8 ml / min. It was supplied at a supply amount of. The 1-liter autoclave was controlled at a stirring speed of 400 rpm and an internal temperature of 260 ° C. A liquid extraction line is installed at the bottom of the tank of a 1 liter autoclave, and an upper liquid extraction line with an inner diameter of 4 mmφ is inserted into the autoclave from the top for extracting the upper part, and each line is a ribbon heater at 260 ° C. It is kept warm. The withdrawal from the 1-liter autoclave was performed by utilizing the reaction pressure and adjusting the opening degree of the needle valve installed in the bottom liquid withdrawal line. The supply amount to the 1 liter autoclave was 2.8 ml / min. Controlled at 0.7 ml / min. From the bottom liquid extraction line of the 1 liter autoclave. 2.1 ml / min. From the upper liquid extraction line. It was extracted with the goal. As a result, the intrinsic viscosity of the obtained polyarylene sulfide was 0.22. This is considered to be because the polymer concentration in the polymerization tank could always be kept stable by continuously extracting the solvent and the polymer from the upper part and the lower part, respectively, so that the molecular weight of the polymer was improved.

<Comparative Example 1> Using the same continuous polymerization apparatus as in <Example>, extraction from a 1 liter autoclave was carried out from only one location of the bottom liquid extraction line. Withdrawal rate is 2.8 ml / min. When the flow rate is very small, the polymer composition in the withdrawal solution is
gPAS / 1NMP) and the polymer concentration becomes a high value of 400 to 500 gPAS / 1NMP. The intrinsic viscosity of the polyarylene sulfide obtained at this time was 0.11. It is considered that this is because the precipitation of the polymer occurred in the extraction pipe, the composition of the polymerization reaction liquid could not be stably extracted, and as a result, only the polymer was extracted and the residence time of the polymer was insufficient.

Comparative Example 2 The same experimental apparatus as the above continuous polymerization apparatus was used, but the extraction from the 1 liter autoclave was carried out by a needle valve installed in a threadless line having an inner diameter of 4 mmφ inserted from the top of the autoclave. Withdrawal rate is 2.8 ml / min. At the minute flow rate of, only the solvent was extracted this time. 5
The intrinsic viscosity of the polyarylene sulfide remaining in the autoclave after continuous operation for 1 hour was 0.12. It is considered that this is because the polymer phase could not be extracted by extracting from the upper part, the polymer concentration in the reaction vessel gradually increased, and the molecular weight did not rise.

[0021]

As described above, according to the present invention,
It is possible to accurately control the polymer / solvent ratio in each polymerization tank, and it is possible to provide an inexpensive PAS having a high molecular weight.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing one configuration example of a polymerization tank used in the present invention.

[Explanation of symbols]

 1 Polymerization Tank 2 Stirring Blade 3 Polymer Phase Retaining Part 4 Solvent Phase Retaining Part 5 Polymer Phase 6 Solvent Phase 7 Polymer Drop (Liquid Phase)

Claims (2)

[Claims] 1. A continuous multi-stage polymerization method of polyarylene sulfide in which a polymerization reaction solution is sequentially transferred to a polymerization tank connected in multiple stages to continuously polymerize polyarylene sulfide, and each of the following steps (1) to (4) is performed. A method of continuous multi-stage polymerization of polyarylene sulfide, which comprises: (1) Withdrawing the polymer phase of the phase-separated polymerization reaction liquid from the bottom of the first-stage polymerization tank and the solvent phase from the top of the polymerization tank. (2) Mixing the extracted polymer phase and all or part of the solvent phase so that the composition ratio is the same as the composition ratio of the polymer phase and the solvent phase of the polymerization reaction liquid in the polymerization tank. (3) Supply this mixed solution to the next polymerization tank. (4) Repeat the above steps (1) to (3) for the polymerization tanks after the next stage but before the final stage. 2. The polymerization tank used in each of the steps (1) to (4) is characterized by having a polymer phase retention part at the bottom and a solvent phase retention part at the top. Item 2. A continuous multistage polymerization method for polyarylene sulfide according to Item 1.