JPH0686530B2 - Method for curing polyphenylene sulfide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a controlled curing method for polyphenylene sulfide (hereinafter abbreviated as PPS). More specifically, the curing is stopped by depressurizing and lowering the temperature of a heated atmosphere. And a method for curing PPS, which is particularly useful for various molded articles.

[Conventional technology and problems]

Normally, PPS has a low molecular weight, so it is thickened by curing before being used for molding. Generally, this curing is done in particulate PPS.
Is heated to a temperature equal to or lower than the melting point of PPS in an atmosphere containing oxygen, the viscosity is increased to a desired melt viscosity, and the temperature is lowered to a temperature at which curing does not proceed, whereby the curing is stopped. However, it is difficult to control the viscosity because the viscosity is further increased while the temperature is being lowered simply by lowering the temperature.

In order to solve this problem, US Pat. No. 3,793,256 and JP-A-57-119926 are proposed. In the former, when the curing is stopped, an inert gas such as water vapor is used to replace the atmosphere containing oxygen in the curing container. But,
With this method, the pores of the PPS particles cannot be sufficiently replaced with an inert gas, so that the viscosity tends to increase even when the operation of stopping the curing is started, and it is practically difficult to control. Further, when steam is used, the vapor pressure is high, so that the internal pressure of the curing container is high, and there are structural restrictions such as pressure resistance. On the other hand, in the latter method, when the curing is stopped, liquid water is sprayed into the curing container to rapidly cool the atmosphere temperature to the curing temperature or lower, and the generated steam replaces the atmosphere containing oxygen in the container. Therefore, it can be said that the method for controlling curing is satisfactory. However, since the hardening container is also rapidly cooled, distortion of each part of the device due to heat shock and deterioration of the device due to fatigue become problems, and design restrictions and troubles occur.

[Means for solving problems]

In view of such problems, the present inventors have earnestly studied about a method of stopping curing, and as a result, have found that the above problems can be solved by reducing the temperature of the atmosphere in the curing container to lower the temperature, and arrived at the present invention. .

That is, the present invention, in the atmosphere containing oxygen, the particulate PPS is heated to a temperature equal to or lower than the melting point of the polymer to increase the viscosity to a desired melt viscosity range. In this case, the method for curing polyphenylene sulfide is characterized in that the pressure inside the curing container is reduced to 300 mmHg or lower and the temperature is lowered to 200 ° C. or lower.

The PPS used in the present invention has the general formula It contains 70 mol% or more of the structural unit represented by.

PPS can be polymerized by polymerizing p-dichlorobenzene in the presence of sulfur and sodium carbonate, sodium sulfide or sodium hydrosulfide and sodium hydroxide or hydrogen sulfide and sodium hydroxide or sodium aminoalkano in a polar solvent. Polymerization in the presence of anate, p
Examples include self-condensation of chlorothiophenol, and a method of reacting sodium sulfide with p-dichlorobenzene in an amide solvent such as N-methylpyrrolidone or dimethylacetamide or a sulfone solvent such as sulfolane is suitable. . At this time, it is a preferable method to add an alkali metal salt of carboxylic acid or sulfonic acid or to add an alkali hydroxide in order to adjust the degree of polymerization. If it is less than 30 mol% as a copolymerization component, a meta bond Ortho-join Ether bond Sulfone bond Biphenyl bond Carbonyl bond Substituted phenyl sulfide bond Here, R represents an alkyl group, a nitro group, a phenyl group, an alkoxy group, a carboxylic acid group or a metal carboxylic acid of carboxylic acid), a trifunctional bond It does not matter if it contains such a compound as long as it does not significantly affect the crystallinity of the polymer, but the copolymerization component is preferably 10
It is preferably not more than mol%. Particularly, when a phenyl, biphenyl, naphthyl sulfide bond or the like having a functionality of 3 or more is selected for the copolymerization, the content is preferably 3 mol% or less, more preferably 1 mol% or less.

As a specific method for producing such PPS, for example, (1) a reaction between a halogen-substituted aromatic compound and an alkali sulfide (US Pat. No. 2513188, JP-B-44-27671 and JP-B-45-33)
68), (2) Condensation reaction of thiophenols in the presence of an alkali catalyst or a copper salt (US Pat. No. 327416).
5 and U.S. Pat. No. 1,160,660), (3) A condensation reaction of an aromatic compound with sulfur chloride in the presence of a Lewis acid catalyst (see Japanese Patent Publication No. 46-27255 and Belgian Patent No. 29437), (4) ) JP-B-52-12240, JP-B-54-8719, JP-B-5
3-25588, JP-B-57-334, JP-A-55-43139, USP4350810, U
The production method of high molecular weight PPS described in SP4324886 and the like can be mentioned.

In the present invention, in the above-mentioned uncured PPS, if necessary, cured P
It is also possible to mix and use PS.

The particle size of the particulate PPS used in the present invention and the range of the bulk density are not particularly limited, but from the viewpoint of workability or the yield of the kettle (the charged amount of PPS per kettle volume), the particle diameter is several microns. As described above, the bulk density is preferably 0.20 g / cm ³ or more.

The curing method of the present invention is carried out by heating powdered PPS at a temperature equal to or lower than the melting point of PPS in an oxygen-containing atmosphere until reaching a desired melt viscosity range, and reducing the pressure and temperature. Curing of PPS is performed in an oxygen-containing atmosphere, and for example, oxygen, air, and a mixed gas of these and an inert gas such as nitrogen are used. In the curing method of the present invention, heating must be performed at a temperature below the melting point of PPS, preferably within the range of 5 to 100 ° C below the melting point. If the heating temperature is too high,
It is not preferable because the PPS particles are easily fused with each other and the particle size is significantly increased or adheres to the container wall. On the contrary, if the heating temperature is too low, it takes a long time to cure, which is not economical. The heating time is generally 10 minutes to 3 days, usually 1 hour to 1 day.

The present invention is characterized in that when the curing is stopped, the temperature of the curing container is reduced to lower the temperature. When the curing is stopped, the pressure in the curing container is 300 mmHg or less, preferably 100 mmHg or less, more preferably 20 mmHg or less. The pressure inside the container
If it is higher than 300 mmHg, even if depressurizing and cooling operations are started,
It becomes difficult to stop thickening, which is not preferable from the viewpoint of curing control. In the present invention, it is necessary to reduce the atmosphere temperature to 200 ° C. or lower while depressurizing the curing container. If the temperature is 200 ° C. or lower, the particulate PPS will no longer cure even in an atmosphere containing oxygen, so the reduced pressure may be returned to normal pressure. However, returning from reduced pressure to normal pressure at a temperature higher than 200 ° C. is not appropriate because curing may progress again. It should be noted that the curing of PPS in the present invention is performed by the melt flow rate of PPS (ASTM12
Measured according to 38-70. Measurement temperature 315.6 ℃, load 5Kg, unit g
/ 10 minutes) is 1 to 2000, preferably 50 to 500.

In the curing method of the present invention, a device used for ordinary curing, for example, a forced heating air circulation dryer described in US Pat. No. 3354129, a fluidized bed of US Pat. No. 3793256, US Pat.
7620 No. double spiral type mixing vessel with fixed agitating heating mixer,
A curing device such as the container rotary heating device, the rotary dryer and the vacuum stirring dryer shown in FIG. 1 provided with a device capable of reducing the pressure can be used.

The PPS obtained by the curing method of the present invention contains an optional filler in the composition in order to improve its performance as an engineering plastic such as strength, heat resistance and dimensional stability.
It can be contained in an amount of not more than wt%. Specifically as a filler, glass fiber, carbon fiber, potassium titanate,
Asbestos, silicon carbide, ceramic fiber, metal fiber,
Fibrous reinforcing agents such as silicon nitride barium sulfate, calcium sulfate, kaolin, clay, pyrophyllite, bentonite, sericite, zeolite, mica, mica, nepheline sinite, talc, atharbarugite, wollastonite, PMF, ferrite , Calcium silicate, calcium carbonate, magnesium carbonate, dolomite, antimony trioxide, zinc oxide, titanium oxide, magnesium oxide,
Examples include iron oxide, molybdenum dioxide, graphite, gypsum, glass beads, glass balloons, inorganic fillers such as quartz powder, and organic reinforcing agents such as aramid fibers. When adding these reinforcing agents or fillers, known syrin coupling agents can be used.

Further, PPS obtained by the curing method of the present invention, polyphenylene oxide, polyarylate, polyamide, polybutylene terephthalate, polyether ether ketone, thermoplastic resin such as polyimide, epoxy resin such as novolac type epoxy resin, polyethylene, polypropylene. Polyolefins such as α-olefin copolymers such as maleic acid modified polypropylene, or nylon 11 /
Thermoplastic elastomer SBR such as polyether polyamide elastomer, hydrogenated SBR, etc. may be contained.

The composition of PPS obtained by the present invention can be prepared by various known methods. For example, the raw materials may be uniformly mixed in advance with a mixer such as a tumbler or a Henschel mixer, supplied to a single-screw or twin-screw extruder, melt-kneaded at 230 to 400 ° C, and then pelletized. You can

〔The invention's effect〕

The curing method of the present invention is a curing method that enables strict viscosity control by reducing the pressure and lowering the temperature when the curing of the particulate PPS is stopped, and has great industrial significance.

The PPS obtained by the curing method of the present invention is
In addition to conventional applications such as injection molded products such as machine parts and compression molded products, it is also used in fields requiring strict viscosity control such as extrusion molded products such as fibers, sheets, films, tubes, blow molded products and transfer molded products. Can be used.

〔Example〕

 Next, the present invention will be specifically described with reference to examples.

Example 1 Melt flow rate (hereinafter abbreviated as MFR. Measured according to ASTM 1238-70. Measurement temperature 315.6 ° C., load 5 Kg, unit g / 10 minutes)
3,500 Kg of particulate PPS was charged into a double-convection heating element of a 30-l container rotating type equipped with a gas introducing part, a gas exhausting part and a heat medium circulation type jacket shown in Fig. 1. Next, start the rotation of the container at a rotation speed of 3 RPM, circulate the heat medium in the jacket,
The temperature of the heating medium was raised from room temperature to 260 ° C in 1.5 hours. 260
While introducing air heated to ℃ at a flow rate of 3 l / min into the container, heating at a heating medium temperature of 260 ℃ for 5 hours, PPS powder was sampled from inside the container, and MFR was quickly calculated. Had reached the melt viscosity of. Start depressurizing immediately and
The pressure in the container was lowered to 50 mmHg in a minute, and thereafter the pressure was maintained at 50 mmHg. The heating was stopped at the same time as the depressurization was started, and the atmospheric temperature in the container was lowered to 190 ° C. in 2.0 hours. The reduced pressure was changed to normal pressure at 190 ° C., and after cooling to room temperature, the particulate PPS was taken out and the MFR was determined to be 128. It was found that the method of the present invention is excellent in the control of the curing from the result that the MFR hardly changed as compared with the curing termination operation, that is, the start of the pressure reduction and the temperature reduction.

Comparative Example 1 After measuring the MFR after 5 hours, curing was performed in the same manner as in Example 1 except that the air was switched to nitrogen without depressurizing.
The MFR after 5 hours was 130, and the MFR after cooling to room temperature was 119. Compared to the operation to stop the curing, that is, when the air was switched to nitrogen and the temperature was lowered, the MFR became smaller, which was insufficient for controlling the curing. .

Comparative Example 2 Example 1 except that the pressure in the container due to the reduced pressure was 400 mmHg.
Curing was carried out in the same manner as in. It was found that the MFR after 5 hours was 133, whereas the MFR after cooling at room temperature was 121, which was insufficient for controlling the curing.

Example 2 Curing was performed by setting the pressure in the container due to the reduced pressure in Example 1 to 2 mmHg. MFR after 5 hours is 129, MFR after cooling to room temperature
Was almost the same as 128. According to this result, it is understood that strict melt viscosity control is possible. Also, 340 ℃ × 1
When the volatile matter in time was measured, PPS1.8 before curing
% By weight, and 1.2% by weight of PPS in Example 1, the PP of this Example
It was also found that S was reduced to 0.5% by weight.

[Brief description of drawings]

FIG. 1 is a schematic view of a container rotating type heating device equipped with a gas introducing part and a gas exhausting part used for carrying out the method of the present invention. 1 ... Rotary container, 2 ... Heat medium jacket, 3 ... Heat medium inlet line, 4 ... Heat medium outlet line, 5 ... Rotary joint, 6 ... Bearing, 7 ... Container lid, 8 ... ... filter, 9 ... gas introduction line, 10 ... gas discharge line, 11 ... bush, 12 ... Teflon seal, 13 ... drive gear, 14 ... motor and transmission, 15 ... drive chain, 16 ... … Supports, 17 …… Thermometer, 18 …… Rheometer, 19 ……
Heater, 20 …… Air pump, 21 …… Filter, 22 ……
Switching valve, 23 …… Nitrogen gas line, 24 …… Air line, 25 …… Distillation, 26 …… Filter.

Claims (1)

[Claims] 1. A method for curing polyphenylene sulfide, which comprises heating particulate polyphenylene sulfide to a temperature below the melting point of the polymer in an atmosphere containing oxygen to increase the viscosity to a desired melt viscosity range. In this case, the method for curing polyphenylene sulfide is characterized in that the pressure inside the curing container is reduced to 300 mmHg or lower and the temperature is lowered to 200 ° C or lower.