JPS63258954A - Polyphenylene sulfide composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition, having reduced thermal energy cost and improved ready processability and capable of providing a homogeneous solution, by blending polyphenylene sulfide with a specific lactam as a solvent. CONSTITUTION:A composition obtained by blending a polyphenylene sulfide with a lactam having bonds (-NHCO-) as a solvent and capable of being plasticized at a temperature below the melting point of the polyphenylene sulfide. epsilon-Caprolatam or delta-valerolactam is used as the lactam. The amount of the contained polyphenylene sulfide is 8-55wt.%. The temperature at which the composition can be plasticized is 220-280 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyphenylene sulfide composition, which is particularly effective for forming a high-performance separation membrane having good heat resistance and chemical resistance. The present invention relates to a plasticized material composition of polyphenylene sulfide used.

[Prior Art] Polyphenylene sulfide (hereinafter referred to as rPPsJ) has been known as an engineering plastic with excellent heat resistance and chemical resistance (organic solvent resistance).
Attempts have been made to form a film.

However, as shown by its poor organic solvent resistance, there are few suitable solvents for PPS. in many cases.

In addition, as a solution film forming method, one of the few examples is JP-A-57
JP-A-501182 discloses a method for forming a PPS film using benzyl benzoate as a solvent.

As yet another example, it has been proposed to use N-alkylcaprolactam as a solvent when synthesizing PPS from monomers (Japanese Patent Application Laid-Open No. 75812/1983).

[Problems to be Solved by the Invention] However, in the melt film forming method such as that disclosed in JP-A-58-6733, PPS cannot be plasticized unless it is heated above its melting point (approximately 288°C), resulting in excessive thermal energy costs. In addition, the porous membrane obtained by this method is a porous membrane that is homogeneous in the thickness direction, so if you try to reduce the pore size and the molecular weight cutoff of the comb membrane, the permeation rate will decrease dramatically. It had

Furthermore, the solution casting method disclosed in JP-A-57-501182 has the problem that the solvent is toxic and not water-soluble, making the film forming method complicated.

Furthermore, even in the method of synthesizing PPS from monomers using N-alkylcaprolactam as a solvent, as disclosed in JP-A-61-75812@, the processing temperature of the obtained PPS must be 5 to 100°C higher than the melting point of PPS. As a matter of fact (Page 5, lower right Jun, lines 1 to 3 of the same publication, and Examples), a temperature of 300'C or higher was actually required, and it was difficult to lower the above-mentioned plasticizing temperature.

The present invention aims to eliminate the drawbacks of the prior art, and aims to lower the plasticizing temperature of PPS, reduce thermal energy costs, improve processability, and, when applied to separation membranes, for example, provide asymmetrical properties in the thickness direction. Therefore, it is an object of the present invention to provide a PPS composition for solution casting, which has good membrane performance and is easy to form.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

"A composition consisting mainly of polyphenylene sulfide and a solvent, where the solvent is a lactam having a (-NHCO-) bond, and which can be plasticized at a temperature below the melting point of polyphenylene sulfide." Characteristic polyphenylene sulfide composition.'' That is, the present invention is based on the discovery that a specific lactam compound has a dissolving effect on PPS. By controlling the removal of solvent from the roughly obtained homogeneous PPS solution, it is possible to control the porous structure of the membrane.
A high-performance separation membrane can be obtained.

PPS in the present invention is one whose main component is a structural unit represented by the following general formula [I].

The term "main component" means that the above-mentioned repeating unit is contained in an amount of 90 mol % or more, preferably 95 mol % or more.

The remaining structural units may be random copolymerizable units, such as meta bonds (general formula [11] below), ether bonds (general formula [[II] below), sulfone bonds (general formula [IV] below), etc. ), biphenyl bond (the following general formula [V]
), naphthyl bond (general formula [VI] below), substituted phenyl sulfide bond (general formula [■] below), where R represents a substituent such as alkyl, nitrophenyl, alkoxy group, etc.), trifunctional phenyl sulfide Bond (the following general formula [■
]), etc.

In addition, the melt flow value (ASTM D-12
According to 38-70, using a load of 5Kg, 315.6
The value measured in °C and expressed in g/10 min) is 50-2
50, preferably in the range of 70-200.

Specifically, from Phillips Petroleum Company of the United States “
A product commercially available under the trade name "Rydon" can be used. Also, 1q can be easily obtained by the method described in Japanese Patent Publication No. 52-12240, for example.

In the present invention, lactam is an organic cyclic compound in which (
-NHcO-), specifically, β-propiolactam, γ-butyrolactam (
2-pyrrolidone>, δ-valerolactam (2-piperidone), ε-caprolactam, and the like.

Among these, lactams having six or more membered rings, ie, δ-valerolactam and ε-caprolactam, are preferable because they have excellent dissolving power for PPS.

The PPS composition of the present invention may contain other polymer compositions (for example, up to 5% by weight based on the PPS) to the extent that the objects of the present invention are not impaired. Examples include polyarylate, polyester, polyamide, polycarbonate, polysulfone, and the like.

Additionally, additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers can be added to the extent that they are normally added.

Although it depends on the type of lactam used, the PPS composition of the present invention can be uniformly dissolved at any concentration as long as the PPS"a degree is up to about 65% by weight. In particular, 8 to 55% by weight PP The product is suitable for producing flat membranes or hollow fiber membranes.

The PPS composition of the present invention may be prepared by mixing the granules or powder (or liquid) of each composition using a mixing device such as a blender or mixer, and feeding the mixture directly to the melt molding process, or by using an extruder, The materials may be melt-mixed using a kneader or the like, pelletized, and supplied to the melt-molding process.

When melt-mixing, depending on the type of lactam, 280
It is preferable to mix at a temperature below .degree. C., preferably below 260.degree.

If the temperature is too high, the lactam will decompose and become colored during dissolution, which is undesirable.

Furthermore, it is most preferable to seal the system to prevent evaporation of the lactam, which is a solvent, and to purge the inside of the system with an inert gas such as nitrogen to prevent oxidative crosslinking of PPS.

Although the PPS composition of the present invention depends on the type of lactam, 2
20°C to 280'C preferably 230°C to 260'C
It can be spun or extruded at a temperature of

The PPS composition of the present invention is prepared by spinning or extruding into a heated or cold gaseous medium, allowing some or most of the solvent to evaporate, and then casting into a suitable solvent that is a non-solvent for the PPS.
Thereby, the solvent is eluted into the solvent, and if necessary, the remaining solvent can be removed in a separate washing step to obtain the desired high performance hollow fiber membrane or flat membrane.

Here, solvents that are non-solvents for PPS and solvents for lactams include water, methanol, ethanol,
Lower alcohols such as isopropanol, lower aliphatic ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl butyl ketone, cyclic or acyclic ethers such as ethyl ether, butyl ether, tetrahydrofuran, dioxane, etc. are used alone or in combination. It will be done. Among these, water is a particularly suitable solvent, and the temperature of the solvent used in the coagulation bath is preferably kept between room temperature and below the boiling point of the liquid.

The film thus obtained can be heat treated to enhance its heat resistance. The heat treatment temperature is 150℃~
The temperature range is preferably 280°C, and the heat treatment time is 1 to 1
00 seconds is preferred. And the dimensional change before and after heat treatment is ±
It is preferably carried out under conditions such that the concentration is 5% or less.

[Examples] The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 520 parts of PPS granules (melt flow value 164) and ε-
After dry blending 480 parts of caprolactam, the mixture was charged into a pot-type melt spinning machine equipped with a stirrer, and stirred and dissolved at 257°C under a nitrogen blanket to form a uniform transparent dope.

This dope was discharged into the air through a double tube type hollow fiber nozzle. At the same time, nitrogen was injected into the hollow fiber. The spinneret temperature was maintained at 253° C. and the length of the dry section was maintained at 50 m. Then, after immersion in a 50°C warm water bath,
The lactam was extracted and removed by hot water treatment at 5°C for 20 seconds.
After hot air drying and heat treatment at 180'C for 10 seconds,
It was wound up at 5 TIL/min.

The obtained hollow fiber membrane had an outer diameter of 570 μm and an inner diameter of 400 μm.

A small module was fabricated using the obtained hollow fiber membrane, and the ultrafiltration rate was measured using an external pressure method, and it was found to be 15 ml/
It was hr -112-mm11g.

Further, when the cross-sectional structure of the hollow fiber membrane was observed by SEM, it was found that it had a skin layer on the outer surface and a network-like porous structure inside.

Example 2 PPS granules (melt flow value 73.6 > 300 parts and ε
- 700 parts of caprolactam was stirred and dissolved at 255°C under a nitrogen blanket to obtain a uniform transparent dope.

This dope was placed on a support film made of polyimide for 25 minutes.
It was cast in an atmosphere of 5°C and held for 15 seconds. Thereafter, it was introduced into warm water at 50°C. The membrane was further washed with boiling water to extract the lactam, and a translucent membrane with a thickness of 25 μm was obtained.

The gas permeation performance of this membrane was measured at 25°C using gas chromatography using a differential pressure method, and it was found that α: = 5.9
,Po,=1,IX10-”of-cm/
cJ -Sec -CmH (1), which was an excellent performance.

[Effects of the Invention] The PPS composition of the present invention lowers the plasticizing temperature or processing temperature of PPS, reduces thermal energy costs, improves processability, and makes it possible to easily obtain a homogeneous solution of PPS. When applied to separation membranes, it becomes possible to control the porous structure of the membrane, and for example, it becomes possible to produce an asymmetric membrane with a skin layer on the outer surface and a mesh-like porous structure on the inside. This makes it possible to manufacture membranes that require relatively compact membrane structures and have excellent performance as ultrafiltration membranes, gas separation membranes, and even support membranes, which are very useful.

Furthermore, since the lactam used in the present invention is water-soluble and non-toxic, it can be easily formed into a film.

Claims (4)

[Claims] (1) A composition consisting mainly of polyphenylene sulfide and a solvent, where the solvent is a lactam having a (-NHCO-) bond, and which can be plasticized at a temperature below the melting point of the polyphenylene sulfide. A polyphenylene sulfide composition characterized by: (2) The composition according to claim (1), wherein the lactam is one selected from ε-caprolactam and δ-valerolactam. (3) The polyphenylene sulfide composition according to claim (1), which contains 8 to 55% by weight of polyphenylene sulfide. (4) The polyphenylene sulfide composition according to claim (1), wherein the polyphenylene sulfide composition has a plasticizable temperature of 220 to 280°C.