JPH07112702B2 - Extrusion molding method for polyphenylene sulfide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an extrusion molding method of polyphenylene sulfide, which is carried out at a pre-stage of a manufacturing process of biaxially stretching polyphenylene sulfide to form a film,
In particular, it relates to a method of promoting crystallization of pellets and then performing extrusion molding using a T die or the like.

[Background of the Invention]

Polyphenylene sulfide (hereinafter referred to as PPS) is one in which a benzene ring and sulfur are alternately bonded. For example, a block copolymer of paraphenylene sulfide polymer and metaphenylene sulfide polymer, or a homopolymer state of paraphenylene sulfide. Is processed in. The PPS resin is used without additives, or processed with inorganic or organic additives and stabilizers added depending on its application.

As the application of this type of PPS, it is considered to process it into a film and use it as a magnetic disk, a magnetic tape, or other electronic component material. To process PPS into a film, first feed the pellets from the hopper to the extruder shown in Fig. 2, heat the pellets by the feed zone (l ₁ ) of this extruder, and feed them out in the compression zone (l ₂ ). The pellets are pressed and melted, metered by the metering zone (l ₃ ), and then extruded into a sheet by a T-die. After cooling, it is biaxially stretched to form a film.

[Problems to be solved by the invention]

In the step of forming the film or the like, PPS is supplied as pellets having a length of about 3 mm, for example. When manufacturing these pellets, the raw material is extruded so that the cross section has a circular shape, water-cooled and cut. The pellets produced by this manufacturing method are in an amorphous state as a whole or have a low degree of crystallinity. For example, in JIS K7112-1980, D
The crystallinity is 2% or less as measured by the density gradient tube method which is standardized as a method. The amorphous or low-crystallinity pellets become tacky when heated. For example, in the case of a block copolymer having a molar ratio of para-phenylene sulfide polymer to meta-phenylene sulfide polymer of about 85:15,
When heated to ℃ or more, the pellets become sticky, and the pellets stick to each other and easily aggregate. Therefore, when extrusion is performed by the extruder shown in FIG. 2, the pellets are not fed because the heated pellets are agglomerated with each other in the feed zone (l ₁ ) or adhere to the screw or the inner surface of the barrel of the extruder. It will not be done smoothly. Also, when the pellets are heated in the hopper and supplied to the extruder, the adhered pellets may aggregate near the outlet of the hopper.

The present invention is to solve the above problems, even when using the whole amorphous or low crystallinity pellets, PPS pellets in the material supply section such as the feed zone of the hopper or extruder The object of the present invention is to provide an extrusion molding method in which even when the adhesive adheres, it does not aggregate or stick to a screw or the like.

[Specific means for solving problems]

In the extrusion molding method according to the present invention, pellets of polyphenylene sulfide that is wholly amorphous or have low crystallinity have a crystallinity of 2 measured by, for example, a density gradient tube method.
% Or less of the polyphenylene sulfide pellets are heated for a certain period of time to promote crystallization so that the crystallinity is 20% or more, preferably about 20 to 30%, and the pellets are singly formed by stirring or the like. It is loosened and then transferred to the extrusion process.

Hereinafter, specific means for solving the problem will be described in detail.

FIG. 1 is a process diagram showing an extrusion molding method of PPS according to the present invention.

The pellets are made by extruding PPS, cooling it with water, and cutting it to a length of about 3 mm. The pellets produced by this process are either entirely amorphous or have a very low degree of crystallinity. Crystallization can be promoted by heating the pellets with a crystallization apparatus as shown in FIG. Further, by stirring in the crystallizer, the pellets that have been heated and once agglomerated can be loosened into a single state. The adhesiveness of the pellets in a single state is remarkably lowered, and the pellets are adhered to each other by heating after that so that they do not aggregate. For example, a block copolymer having a molar ratio of para-phenylene sulfide polymer to meta-phenylene sulfide polymer of about 85:15 and a melt viscosity of 4,000 poise measured at a resin temperature of 310 ° C./shear rate of 200 (sec) ⁻¹ , Using a differential scanning calorimeter (DSC) manufactured by METTLER, sample 10 mg under nitrogen,
For materials with a glass transition temperature of about 73 ° C, which is the temperature that indicates the start of endotherm when measured at a heating rate of 10 ° C / min, the crystallinity before being supplied to the crystallizer is the density gradient. It is about 1 to 2% when measured by the tube method. When the pellets are heated and stirred by the crystallizer, the crystallinity increases.
It is accelerated to about 20 to 30%, and in this state it does not stick even if it is subsequently heated.

The PPS pellets whose crystallization has been promoted and whose tackiness has been reduced are fed from a crystallization device through an hopper to an extruder as shown in FIG. In the extruder, the pellets are heated and fed in the feed zone (l ₁ ). If the crystallization of PPS pellets is promoted and the tackiness is reduced, pellets will agglomerate in this feed zone (l ₁ ) or stick to the screw less easily, and smooth pellet feeding will be performed. . Thereafter, the pellets are pressurized and melted in the compression zone (l ₂ ) and further metered in the metering zone (l ₃ ). Then, it is sent to a T-die or the like. In the case of film forming, PPS is extruded into a sheet, and this sheet is cooled and biaxially stretched.

FIG. 3 shows an example of a specific structure of the crystallization device.

In this crystallizer, a perforated plate 2 is installed in a tapered shape on the inner bottom of a chamber 1, and a valve 3 is installed at the lower end of the perforated plate 2.
Is provided. From the air outlet 1a of the chamber 1,
The hot air heated by the heater 4 is supplied, and this hot air is discharged from the exhaust port 1b, and most of it is circulated to the blower port 1a again via the heater 4. The motor M in the chamber 1
The shaft 5 driven by the
A plurality of stirring blades 6a, 6b are fixed to the shaft 5. Further, in the chamber 1, a stirring rod 7a extending vertically is provided.
7b is fixed. A fixed amount of PPS pellets is supplied onto the perforated plate 2 in the chamber 1. Then, the pellets on the perforated plate 2 are heated by the hot air sent from the heater 4, and the pellets are agitated by the stirring blades 6a, 6b driven by the power of the motor M and the fixed stirring rods 7a, 7b.

The present invention can be applied not only to the film forming process using PPS, but also to other extrusion molding such as fiber or pipe molding.

〔Example〕

As the PPS, for example, a block copolymer having a molar ratio of paraphenylene sulfide polymer to metaphenylene sulfide polymer of about 85:15, as disclosed in JP-A No. 61-14228, was used. The PPS material used had a melt viscosity of 4,000 poise measured at a resin temperature of 310 ° C / shear rate of 200 (sec) ^-1 and a glass transition temperature of about 73 ° C.
Is. The temperature of the glass transition point is a value measured by the same measuring method as disclosed in JP-A-61-14228, that is, a differential scanning calorimeter (DS) manufactured by METTLER CORPORATION.
C), sample 10mg under nitrogen, heating rate 10 ℃ / min
It is a value represented by a temperature indicating the start of endotherm when measured by. The block copolymer was extruded, cooled with water, and cut into pellets of about 3 mm.
50 kg was supplied. Hot air of about 150 ° C. was supplied into the chamber 1 by the heater, and the stirring blade was rotated by the motor M at a rotation speed of 24 rpm.

FIG. 4 is a diagram showing changes in the temperature α of the hot air supplied to the blower port 1a of the chamber 1, the exhaust gas temperature β discharged from the discharge port 1b, and the current value γ of the motor M over time. . About 14 to 15 minutes after starting the operation, the temperature in the chamber 1 (exhaust temperature β) becomes about 90 to 100 ° C, at which time the pellets become sticky and the load on the stirring blade increases. , The current value of the motor M suddenly increases. Stirring blade
When the stirring by 6a and 6b is continued, the PPS pellets adhere to each other to form an aggregate with many voids, and the apparent volume thereof expands and rises in the chamber 1. When about 17 to 18 minutes have passed after starting the operation and the temperature in the chamber 1 (exhaust gas temperature β) rises to about 110 to 115 ° C., crystallization of PPS is promoted and the PPS suddenly becomes white. Then, the agglomerates of the pellets are unraveled and become separated by stirring, the apparent volume is reduced, and the bulge contracts. At this time, as indicated by γ in FIG. 4, the load on the motor M suddenly decreases, and the current value further decreases compared to when the rotation is started. About 25 minutes after the start of operation, crystallization of PPS progresses to 20 to 30%. This crystallinity is measured, for example, by the density gradient tube method standardized as the D method in JIS K7112-1980. After stopping the operation, open valve 3 and PP
Discharge S Then, by the extruder shown in FIG.
PS was extruded, but at this time, the tackiness of PPS had already decreased, and pellets did not aggregate in the feed zone (l ₁ ) or pellets did not stick to the screw, and smooth extrusion was performed. It was

It is also possible to use a homopolymer of paraphenylene sulfide as disclosed in, for example, Japanese Patent Application Laid-Open No. 617332 as a material. In the homopolymer of paraphenylene sulfide, the glass transition temperature is about 88 ° C., which is higher than the materials according to the above examples,
The temperature at which the pellets change in the crystallizer is also higher than in the above example.

〔The invention's effect〕

As described above, according to the present invention, by promoting the crystallinity of 20% or more, preferably 20 to 30% by stirring by heating and stirring the pellets of PPS which are amorphous or have low crystallinity as a whole, Since the tackiness is reduced, PPS does not aggregate or adhere to the screw in the material feeding section in the subsequent extrusion step, and stable extrusion can be performed.

[Brief description of drawings]

FIG. 1 is a process diagram of a method for extrusion-molding polyphenylene sulfide according to the present invention, FIG. 2 is a sectional view showing an outline of a structure of an extruder, FIG. 3 is a sectional view showing an outline of a structure of a crystallization device, and FIG. The figure is a diagram showing changes in temperature in the crystallizer and changes in current value of the motor in the example. 1 ... Chamber, 2 ... Perforated plate, 5 ... Shaft, 6a, 6
b …… Stirring blade.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 59-45106 (JP, A) JP 55-154113 (JP, A) JP 61-112009 (JP, A) JP 59- 12805 (JP, A) JP 58-45229 (JP, A) JP 58-47024 (JP, A) JP 59-22926 (JP, A) JP 47-37498 (JP, B1)

Claims (2)

[Claims] 1. A pellet of polyphenylene sulfide, which is amorphous or has low crystallinity, is heated for a certain period of time so that the crystallinity measured by a density gradient method becomes 20% or more and the pellet is loosened. A method for extrusion-molding polyphenylene sulfide, characterized in that the polyphenylene sulfide is transferred to the extrusion step. 2. The method for extrusion-molding polyphenylene sulfide according to claim 1, wherein the pellets are loosened by stirring to become a single substance.