JPS63137822A - Extrusion molding method for polyphenylene sulfide - Google Patents

Abstract

PURPOSE:To prevent condensation of PPS and adhesion of the same to a screw within a material supply part in an extrusion process, by accelerating crystallization by heating and agitating pellets of polyphenylene sulfide (PPS) the whole of which is amorphous or low in its crystallinity. CONSTITUTION:PPS extruded, water-cooled and cut in a length of about 3mm is used for pellets. The pellets manufactured in this process are amorphous as a whole or crystallinity of the pellets in extremely low. Crystallization of the pellets is accelerated by heating the pellets by a crystallizing equipment. Then the pellet agitated, heated and condensed once within crystallizing equipment is loosened into a state of a simple substance. Adhesion of the pellets turned into the state of the simple substance is dropped drastically and it becomes that the pellets are stuck to each other and not condensed even if the pellets are heated afterward. Then the PPS pellets are supplied to an extruding machine from the crystallizing equipment through a hopper.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an extrusion molding method for polyphenylene sulfide, which is carried out in a pre-stage of a manufacturing process in which polyphenylene sulfide is biaxially stretched to form a film.
In particular, it relates to a method of promoting crystallization of pellets and then extruding them using a T-die or the like.

[Background of the invention]

Polyphenylene sulfite (hereinafter referred to as PPS) is a product in which benzene rings and sulfur are bonded alternately, and is, for example, a polyphenylene sulfide copolymer of para-phenylene sulfide polymer and meta-phenylene sulfide polymer, or a homopolymer of para-phenylene sulfide. It is processed in the state of PPS resins are used without additives or processed with inorganic or organic additives and stabilizers, depending on the application.

As for the use of this type of PPS, it is considered to process it into a film and use it as a magnetic disk, 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 Figure 2, heat the pellets through the feed zone (also 1) of this extruder, send them out, and feed them into the compression zone (text 1). In 2), the pellets are melted under pressure, metered by the metering zone (also 3), and then extruded into a sheet by a T-die. After cooling, it is biaxially stretched and formed into a film.

[Problem that the invention seeks to solve]

In the above-mentioned process of forming into a film or the like, PPS is supplied as pellets having a length of, for example, about 3 mm. When producing these pellets, the raw material is extruded, cooled with water, and cut into circular cross-sections. Pellets produced by this manufacturing method are entirely amorphous or have low crystallinity, such as JIS K7112-1.
The degree of crystallinity measured by the density gradient tube method, which is standardized as the D method in 980, is 2% or less. This amorphous or low crystallinity pellet is
For example, with a block copolymer in which the molar ratio of para-phenylene sulfide polymer and meta-phenylene sulfide polymer is about 85:15, the pellets become sticky when heated to about 80°C or higher. Now you have.

The pellets tend to stick to each other and agglomerate. Therefore, when extrusion is carried out using the extruder shown in Fig. 2, the heated pellets are transferred to the feed zone (
They may aggregate with each other or stick to the screw or inner surface of the barrel of the extruder, making it difficult to feed the pellets smoothly. Also, when heating pellets in a hopper and feeding them to an extruder,
Sticky pellets may aggregate near the hopper outlet.

The present invention solves the above problems, and even when using pellets that are entirely amorphous or have a low degree of crystallinity, PPS< The purpose of the present invention is to provide an extrusion molding method that prevents the particles from sticking and agglomerating or from sticking to screws or the like.

[Specific means for solving the problems] The extrusion molding method according to the present invention produces polyphenylene sulfide pellets that are entirely amorphous or have a low crystallinity, for example, a crystallinity of 2 as measured by density gradient tube method. % or less of polyphenylene sulfide is heated for a certain period of time to promote crystallization, for example, so that the degree of crystallinity is about 20 to 30%, and the pellet is loosened into a single substance by stirring etc., and then This is to move on to the extrusion process.

Hereinafter, specific means for solving the problems will be explained in detail.

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

The pellets used are extruded PPS, cooled in water, and cut into lengths of about 3 cm. The pellets produced by this process are entirely amorphous or have extremely low crystallinity. Crystallization can be promoted by heating this pellet using a crystallization apparatus as shown in FIG. Further, by stirring in the crystallization apparatus, the pellets that have been heated and once agglomerated can be loosened into a single unit. The stickiness of the pellets that have become a single substance has decreased significantly, and even if heated afterwards, the pellets will stick to each other and will not aggregate.For example, if the molar ratio of paraphenylene sulfide polymer and metaphenylene sulfide polymer It is a block copolymer of about 85:15, resin temperature 310 ° C / shear rate 20
Melt viscosity measured at 0 (sec)-1 is 4,000 bois,
In addition, using a differential scanning calorimeter (DSC:) manufactured by Mettler, the sample lovg was measured under nitrogen at a heating rate of 10°C/mi.
For a material whose glass transition temperature, expressed as the temperature at which the endotherm begins when measured in n, is approximately 73°C, the degree of crystallinity before being fed to the crystallization apparatus is 1 when measured by the density gradient tube method. It is about 2%. When this pellet is heated and stirred by a crystallization device, the degree of crystallinity increases from 20 to 30.
%, and in this state it will not stick even if heated afterwards.

The PPS pellet whose crystallization has been promoted and its tackiness has been reduced is supplied from the crystallization device to an extruder as shown in FIG. 2 via a hopper. Inside the extruder, the pellets are heated in a feed zone (Qt) and fed out. P
When the crystallization of the PS pellets is promoted and the adhesion is reduced, the pellets become less likely to aggregate or stick to the screw in this feed zone (Jl+), and smooth pellet feeding becomes possible. The pellet is then pressurized and melted in the compression zone (text 2), and then in the metering zone (text 3).
metered by. They are then sent to T-dai, etc. In the case of film forming, PPS is extruded into a sheet, which is cooled and biaxially stretched.

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

This crystallization apparatus has a perforated plate 2 installed in a tapered shape at the inner bottom of a chamber 1, and a valve 3 at a discharge part at the lower end of the perforated plate 2.
is provided. Hot air heated by the heater 4 is supplied from the air outlet 1a of the chamber 7, and this hot air is discharged from the exhaust port 1b, passes through the heater 4, and most of it is circulated back to the air outlet 1a. A shaft 5 rotationally driven by a motor M is inserted into the chamber 1, and a plurality of stirring blades 6a, 6b are fixed to this shaft 5. Additionally, stirring rods 7a and 7b are fixed in the chamber 1 and extend vertically.

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 stirring 746 a is driven by the power of the motor M.

6b and fixed stirring rods 7a, 7b, the pellets are stirred.

Note that the present invention is applicable not only to the process of forming a film using PPS, but also to other extrusion molding processes such as forming fibers and pipes.

〔Example〕

-PPS has a molar ratio of para-phenylene sulfide polymer and meta-phenylene sulfide polymer of 85, as disclosed in JP-A-81-14228, for example.
: A block copolymer having a molecular weight of about 15 was used. The PPS material used had a melt viscosity of 4,000 voids measured at a resin temperature of 310° C./a shear rate of 200 (seconds) −1 and a glass transition temperature of about 73° C. The temperature of the glass transition point is the value measured by the same measuring method as disclosed in JP-A-81-14228, that is, using a differential scanning calorimeter (DSC:) manufactured by Mettler. Below sample 110ll1, heating rate 10℃/a
It is a value expressed as a temperature indicating the start of endotherm when measured in kin. This block copolymer was extruded, cooled with water, and cut into approximately 311!1 pellets, which weighed about 50 kg, and were fed into a crystallization apparatus shown in FIG. 3. Approximately 15 depending on the heater
Hot air at 0° C. was supplied into the chamber 1, and the stirring blade was rotated by the motor M at a rotation speed of 24 rpm.

FIG. 4 is a diagram showing changes over time in the temperature α of the hot air supplied to the air outlet 1a of the chamber l, the temperature β of the exhaust gas discharged from the outlet 1b, and the electric value γ of the motor M. be. Approximately 14 to 15 minutes after the start of operation, the temperature inside chamber l (exhaust temperature β) reaches approximately 90 to 100°C, and at that time, the pellets become sticky and the load on the stirring blade increases. , the current value of motor M suddenly increases. As the stirring by stirring χ6a and 6b continues,
The PPS pellets adhere to each other to form an aggregate with many voids, and its apparent volume expands and rises northward within the chamber I. Approximately 14 to 15 minutes have passed since the start of operation, and the temperature in chamber 1 (exhaust temperature β) has reached approximately 110 to 1.
When the temperature rises to 15°C, crystallization of PPS is promoted and it suddenly turns white. Then, as a result of stirring, the aggregate of pellets m begins to loosen and break up, the apparent volume decreases, and the bulge shrinks. At this time, as shown by γ in FIG. 4, the load on the motor M suddenly decreases, and the current value further decreases than when the rotation starts. Approximately 25 minutes after the start of operation, crystallization of pps has progressed to 20-30%.

This crystallinity is 1, for example, JIS K7+12-1!38
It was measured by the density gradient tube method, which is standardized as the D method. After the operation is stopped, valve 3 is opened to discharge PPS. Then, PPS was extruded using the extruder shown in Fig. 2, but at this time PPS had already been formed.
The stickiness of PS has decreased and the feed zone (Jlt
) U9 smooth extrusion was performed without the pellets clumping or sticking to the screw.

Note that it is also possible to use a homopolymer of paraphenylene sulfide as disclosed in JP-A No. 81-7332, for example. In the homopolymer of paraphenylene sulfide, the glass transition temperature is about 88°C, which is higher than the material according to the above example, so the temperature at which the pellet changes in the crystallization apparatus is also higher than the above example. .

〔Effect of the invention〕

As described above, according to the present invention, the pellet of PPs, which is entirely amorphous or has a low degree of crystallinity, is heated to open the pellet and promote crystallization, thereby reducing the stickiness. During the extrusion process, PPS does not aggregate in the material supply section or adhere to the screw, and stable extrusion can be performed.

[Brief Description of the Drawings] Fig. 1 is a process diagram of the extrusion molding method for polyphenylene sulfide according to the present invention, Fig. 2 is a cross-sectional view schematically showing the 4XIi structure of the extruder, and Fig. 3 is a schematic diagram of the structure of the crystallization device. A schematic cross-sectional view and FIG. 4 are diagrams showing changes in temperature inside the crystallization apparatus and changes in the current value of the motor in the example. 1... Chan 8, 2... Perforated plate, 5... Shaft, 6a, 6b... Stirring blade.

Claims (3)

[Claims] (1) Polyphenylene sulfide pellets that are entirely amorphous or polyphenylene sulfide pellets with a low degree of crystallinity are heated for a certain period of time to promote crystallization, and after being loosened into individual pellets, the polyphenylene sulfide is transferred to the extrusion process. Sulfide extrusion method. (2) The extrusion molding method for polyphenylene sulfide according to claim 1, wherein the pellets are loosened into single pieces by stirring. (3) The extrusion molding method for polyphenylene sulfide according to claim 1, wherein the pellets after being heated for a certain period of time have a crystallinity of 20% or more as measured by density gradient tube method.