KR20010044212A - Process for producing linear high molecular weight polyphenylene sulfide - Google Patents

Abstract

PURPOSE: Provided is a process for producing linear polyphenylene sulfide (PPS) having high molecular weight, which controls high pressure caused by decomposing reactants and produces the PPS used as an injection molding material without a heat-crosslinking process. CONSTITUTION: The process comprises the steps of: dehydrating 80-98% of moisture from an alkali metal sulfide hydrate; polymerizing the alkali metal sulfide and a polyhalogen aromatic compound in an organic polar solvent; sealing a reactor hermetically and separating hydrogen sulfide gas which is a decomposed product of the alkali metal sulfide, a non-reacted halogen aromatic compound, and the solvent, from the reactants and the inside of the reactor by self-pressure generated by a reacting temperature of 200-300deg.C in order to increase degree of polymerization.

Description

Method for producing linear high molecular weight polyphenylene sulfide {omitted}

The present invention relates to a process for preparing polyphenylene sulfide (hereinafter referred to as PPS), which is a high-performance engineering plastic, and more particularly, having an alkali metal sulfide such as sodium sulfide and two or more halogen atoms in a benzene ring in an organic polar solvent. The present invention relates to a method of controlling the exothermic and high pressure phenomena caused by decomposition of a reactant generated when polymerizing a polyhalogenated aromatic compound and producing a linear high molecular weight PPS without a separate heat crosslinking process.

In the conventional PPS manufacturing method, in order to control the exothermic and high pressure phenomena due to decomposition of the reactants generated during polymerization, the reaction temperature is decomposed from above a certain temperature while raising the reaction temperature step by step from 150 ° C to 300 ° C for 3 hours. In order to control the exothermic and high pressure phenomena caused by circulating the cooling water through the cooling pipe inside the reactor to forcibly terminate the reaction, the reaction is cooled to 150 ° C and the sludge reactant and the solvent are separated from the filtering device. PPS resin particles pass through the filtration membrane unless the particles of the material PPS are too small to separate into a very dense filtration membrane. In addition, even a very dense filtration membrane is blocked by small resin particles in the filtration passage takes a long time filtration.

Since the PPS thus obtained has a low molecular weight, it cannot be industrially used unless the crosslinking reaction is carried out for at least 5 hours by contacting with air at 250 ° C or higher.

In order to improve the above problems, U.S. Patent No. 4,116,947 discloses a method of adding alkali metal hydroxides to convert hydrogen sulfide, which is a decomposition product of alkali metal sulfides, which triggers decomposition at a predetermined temperature or more during a polymerization reaction, to alkali metal sulfides. Although it has been suggested, this precludes hydrogen sulfide from acting as a reaction catalyst at a predetermined temperature or less. Thus, the reacted PPS should be subjected to a heat crosslinking process after the reaction to improve molecular weight.

The present invention polymerizes alkali metal sulfides and polyhalogen aromatic compounds in organic polar solvents to produce PPS resins, which can be used as injection molding materials without the need for a separate heat crosslinking process after polymerization. By controlling the high pressure phenomena caused by decomposition of the reactants generated during the process, we established a stable production process and created an efficient method of the production process.

The raw material used in this invention is as follows.

The organic polar solvent is N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N = dipropylacetamide, caprolactam, N-methylcaprolactam, N- Ethyl caprolactam, N-isoprolyl caprolactam, N-isobutyl caprolactam, N-propyl caprolactam, N-butyl caprolactam, N-cyclonucleosilcaprolactam, N-methyl-2-pyrrolidinone, N- Ethylpyrrolidinone, N-isopropyl-2-pyrrolidinone, N-isobutyl-2-pyrrolidinone and the like can be used, of which N-methyl-2-pyrrolidinone is suitable.

Alkali metal sulfides include sodium sulfide, potassium sulfide, lithium sulfide and rubidium sulfide, preferably sodium sulfide.

Polyhalogen aromatic compounds include p-dichlorobenzene, p-dibromobenzene, p-diiodinebenzene, 1-chloro-4-bromobenzene, 1-chloro-4-iodobenzene, 1-ethyl-2,5- Dichlorobenzene, 1-ethyl-2,5-dibromobenzene, 1-tripromethylmethyl-2,5-dichlorobenzene, 1-tripromethylmethyl-2,5-dibromobenzene, 1-cyclohexyl -2,5-dichlorobenzene, and the like can be used, of which the use of p-dichlorobenzene is preferred.

The reaction process of the present invention is described as follows.

First, 50 g to 150 g of an organic polar solvent was added to 1 mole of sodium sulfide containing crystalline water in a pressurized reactor, and the reactant was heated to 170 ° C. to 200 ° C. for 1 to 2 hours under nitrogen stream, thereby crystallization of 80 ° C. Dehydrate% to 98%.

At this time, if the dehydration rate is 80% or less, the pressure increases during the reaction.

After dehydrating the above-mentioned dehydrated product at 150 degreeC, 150 g-500 g of organic polar solvents are melt | dissolved in p-dichlorobenzene at 150 degreeC, and are input. The amount of p-dichlorobenzene to be added may be 0.98 to 1.2 moles with respect to 1 mole of sodium sulfide, but preferably 1: 1 is better. Solid content concentration during the reaction can be 20% to 70%, but preferably 30% to 50%. After adding as described above, the reactor is completely sealed and the reaction temperature is gradually raised to 200 ° C. to 300 ° C. for 1 hour to 3 hours.

At this time, the reaction pressure is a solvent, decomposition product hydrogen sulfide, and the self-pressure of p-dichlorobenzene not involved in the reaction to 15kg / ㎠ (absolute pressure).

Under the above pressure and temperature, hydrogen sulfide, unreacted p-dichlorobenzene, and solvent present as gas inside the reactor should be separated by the vaporization temperature and the self pressure of the mesh. Hydrogen sulfide is in the initial 200 ° C to 250 ° C. In addition, it acts as a catalyst to increase the degree of polymerization, but when the reaction temperature is 250 ℃ to 300 ℃ to act to decompose the reactants to reduce the degree of polymerization.

According to the effect of hydrogen sulfide on the polymerization reaction as described above, when the reaction temperature reaches 230 ℃ ~ 270 ℃, the pressure inside the reactor is gradually ejected and separated by hydrogen sulfide and unreacted p-dichlorobenzene in order of the sublimation temperature of the material The reactants no longer decompose and high PPS can be obtained.

In addition, after separating the hydrogen sulfide and the unreacted p-dichlorobenzene, the solvent is separated using the self-pressure remaining in the reactor and the decompression device, and at 200 ° C or higher, the reactant is a virtually homogeneous state, and the particles have a low viscosity with very small particles. As the concentration of the solvent decreases as described above, the particle size of the particles increases, so that a process of washing and filtering sodium chloride, which is a reaction product of PPS performed after the reaction, with water may be facilitated.

Example 1

In order to polymerize the PPS, 314 g 3.3 mol of sodium sulfide (Na ₂ S · 3H ₂ O) containing crystal water and 300 g of organic polar solvent were added to a high-pressure reactor equipped with a thermometer, a pressure gauge, and a distillation column. It heated up at 170 degreeC-200 degreeC, and dehydrated for 1-2 hours. When the amount of dehydration is over 90%, reduce the temperature of the contents to 150 ℃.

After cooling, 3.49.5 g of p-dichlorobenzene was dissolved in 450 g of a solvent and added.

After completion of the addition, the reactor was completely sealed and the internal temperature was gradually raised to 230 ° C. to 270 ° C. for 3 hours, and then hydrogen sulfide and unreacted p-dichlorobenzene, reaction decomposition products existing in the gaseous state were attached to the top of the distillation column. Operate the valve and slowly eject it by the internal pressure. Thereafter, the valve attached to the lower part of the distillation column is operated to separate and recover the solvent by 99% or more by using the pressure of the solvent and the pressure reduction device existing in the reactor. At this time, the heat supply of the reactor is continuously supplied to maintain 220 ℃.

The reaction product obtained as described above contains 50% of PPS resin and 50% of sodium chloride which is a reaction product. Sodium chloride, which is soluble in water, is washed with water at 60 ° C. and separated from the sodium chloride dissolved water in a centrifuge using a filter bag. Let's do it.

Such water washing was performed three times or more so that the remaining sodium chloride content was 0.05% or less.

Comparative Example 1

The reaction was carried out under the same conditions as in Example 1, but after the reaction was heated to 230 ° C. to 270 ° C. for 3 hours, the reactor was immersed in cooling water to cool the internal temperature to 150 ° C., and the sludge reactant was separated from the solvent using a filtration membrane. Washing was carried out to obtain a PPS resin.

Experiment example

◆ Weight average: Molecular weight: Measured under the condition of 210 ℃ and Flow Rate 1.0ml / 1min using 1-naphthalene chloride as a solvent using high temperature gel permeation chromatography (GPC). This was used to evaluate the degree of polymerization of PPS.

◆ Thermal Properties: The glass transition temperature (Tg) and the melting temperature (Tm) were measured using a differential scanning calorimeter, and the measurement conditions were heated at 320 ℃ to 20 ℃ / min for 3 minutes to remove the thermal history. After isothermal treatment, the solution was quenched with liquid nitrogen and heated again at a heating rate of 20 ° C./min.

◆ Crystallinity: In order to measure the crystallinity of the polymer, an X-ray diffractometer (Phillips PW3710) was used, and the X-ray diffraction pattern was irradiated with CuKα rays passing through the Ni filter at 30KV / 20mA to 15 ° <20 <30 It was obtained in the range of °, the crystallinity was obtained from the area ratio of the amorphous pattern and the crystalline pattern.

Melt Index (hereinafter referred to as MI): After preheating PPS at 305 ° C for 5 minutes, the weight of the melt polymer discharged at a load of 2160g was measured to determine the MI value.

As can be seen from the above analysis result, PPS resin having high molecular weight and low crystallinity can be obtained by separating hydrogen sulfide, unreacted p-dichlorobenzene, and solvent which are reaction decomposition products at a certain temperature during the polymerization reaction in the reactor. Since it does not go through the crosslinking process, it is possible to improve the productivity, increase the whiteness of the resin, and increase the particles of the resin to shorten the filtration time during water filtration separation.

Claims (2)

In preparing PPS by polymerizing an alkali metal sulfide as a hydrate and an aromatic compound having two or more halogen atoms in an organic polar solvent, 80% to 98% of the water of the alkali metal sulfide as a hydrate is dehydrated, and then two or more halogen atoms are substituted. After contacting the aromatic compound, the reactor is completely sealed and unreacted halogen aromatic compound and solvent which do not participate in the reaction with hydrogen sulfide which is a decomposition product of alkali metal sulfide existing as gas inside the reactor at a reaction temperature of 200 ° C to 300 ° C. Method to increase the degree of polymerization by separating the reaction material and the inside of the reactor by the pressure of the reaction itself. In the preparation of PPS by the method of claim 1, the solvent is separated using a self-pressure and a pressure reduction device generated in the reaction temperature range of 200 ° C. to 300 ° C. to increase the concentration of solids, thereby increasing the particles of the PPS resin.