JPH0813460B2 - Method for drying rubbery polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method for drying a rubber-like polymer by a twin-screw extruder, and more particularly to a method for obtaining a rubber-like dried product in a flat plate shape. .

<Prior Art> A method for drying a rubber-like polymer using a twin-screw extruder is as follows.
It is used because the device is compact, requires a small installation area, and can obtain a dried product in a desired shape.

As an example of a twin-screw extruder, for example, as shown in Japanese Patent Laid-Open No. 59-214631, in order to dehydrate the raw material crumb at the feeding stage of the extruder, two screws that mesh with each other and rotate in reverse are used. There is disclosed a cylinder barrel which is provided with a dehydration slit at the lower part of the section and is provided with a die for extrusion molding at the tip end discharge port.

The dried product can take various shapes, but the extruded product in the form of a strip is convenient because it has good handleability in the subsequent kneading work and the like and can be used for automation of process operation.

In order to extrude in a strip shape, a die part having a flat rectangular outlet is attached, and in order to knead and rectify the molten resin, the same shape as the barrel internal shape as shown in Fig. 4 is provided between the die part and the barrel tip. A breaker plate having a large number of circular small holes (7) dispersed therein is installed in the oval area of the. The melt is mixed by the small holes in the breaker plate,
It is rectified and sent to the die section.

<Problems to be Solved by the Invention> However, in the case of the above-mentioned twin-screw extruder, the temperature of the melt becomes unnecessarily high due to the resistance of the breaker plate provided between the die part and the barrel, and depending on the type of the material to be dried. However, burning was caused, and the appearance and physical properties were unfavorable.

The temperature rise can be avoided by removing the breaker plate in order to avoid the temperature rise in the above-mentioned locations, but the extruded one is not a uniform thickness, despite having a flat plate-shaped discharge port, Is a hill and has a constricted shape at the center, which is unsuitable because it is inferior in handling when moving, stacking or kneading, especially in automation of operation.

<Means for Solving the Problems> The inventors found that, when the breaker plate was removed, the raised positions on both sides of the extrudate corresponded to the respective axial extension positions of the twin screw,
By changing the shape of the discharge nozzle, a flat extrudate was successfully obtained from the nozzle, and the present invention was completed.

Thus, according to the present invention, the discharge port cross-sectional shape is constricted at a position corresponding to the axial center extension of each screw of the twin screw extruder, and the flattened discharge port is swollen at both sides of the shaft and the central extension of the two shafts. A method for drying a rubber-like polymer is provided, in which the nozzle portion formed in step 2 is attached to the tip of the die portion of the twin-screw extruder to dry the crumb of the rubber-like polymer.

That is, the twin-screw type extruder / dryer is coupled without a breaker plate provided between the die and the die part, and the nozzle having the special shape according to the present invention is attached to the tip of the die part to compensate the discharge shape by removing the breaker plate. However, an extrudate having a flat plate shape without bulges and constrictions and having no burning or the like is obtained.

As shown in FIG. 1, the tip part of the extruder applied to the present invention is as shown in FIG. 1, in which the die part (1) is connected to the barrel (2), and the breaker plate is not attached between them.

The shape of the nozzle part (4) attached to the tip of the die part (1) is as shown in Fig. 2 (A) front view and (B) vertical sectional view, and the screw (3) when attached to the die part. The shaft center extension has a constriction (5), and both sides of the screw and the biaxial central extension have bulging portions (6), and the contour is wavy. The die-side inlet of the nozzle has a shape corresponding to the inner surface of the die outlet, and gradually changes to the nozzle outlet cross-sectional shape from the barrel-side inlet to the outlet side. And ends with the discharge port at the tip.

FIG. 3 shows a nozzle portion of another embodiment. In this example,
Instead of the waveform curve in FIG. 2, the shape is a series of rhombuses.

As the twin-screw extruder / dryer used in the method of the present invention, a well-known twin-screw / extruder / dryer may be used, and in addition to a single screw, a left screw screw element, a right screw screw element may be used depending on the type of rubber to be dried. Etc. and a kneading disc may be combined to form a screw.
The barrel is also a feed barrel, standard barrel, bent barrel,
A dehydration barrel and the like are combined and configured corresponding to the screw segment.

The method of the present invention is applicable to the drying of various synthetic rubber crumbs. That is, it is suitable for drying crumb obtained by salting out and polymerizing a slurry obtained by emulsion polymerization, and crumb obtained by treating polymer cement obtained by solution polymerization with hot water. Used for drying crumbs such as rubber, isoprene rubber, butyl rubber, and acrylic rubber.

<Operation> In the case of a twin-screw extrusion dryer, when melted rubber is introduced into the die with the breaker plate removed and extruded, the rubber melt leaving the screw kneading part flows internally at the screw shaft extension. It is considered that the rod does not perform a sufficient kneading action, and a high temperature portion is formed in a rod shape, and this portion swells when ejected from the nozzle, and has a bulged shape on both sides as a dried product.

In the present invention, the cross-sectional shape of the nozzle part attached to the discharge port of the die part is narrow and narrow at the part corresponding to the screw shaft center extension part, and both sides of the screw shaft and the central part corresponding to the two screws are outside. It has a shape that bulges toward one side, that is, a shape that is exactly opposite to the bulge and the constriction when the breaker plate is removed and pushed out.

Therefore, the swelling after the discharge is suppressed by reducing the thickness at the constricted part of the discharge port, which is the part where the high temperature part is easily expanded,
The left and right and the middle part where the flow resistance of the melt is large increase the cross-sectional area of the discharge part to reduce the flow resistance and make it easier to flow and swell, as a result, the flow and expansion state of the melt change,
Extruded shape without breaker plate is compensated,
A flat extrudate is obtained.

<Example> Hereinafter, the method of the present invention will be specifically described with reference to Examples and Comparative Examples.

Example A standard type extruder / dryer consisting of a field barrel, a dewatering barrel, a standard barrel, a vent barrel and a vacuum barrel was used as a twin-screw extruder / dryer, and a nitrile rubber (NBR) crumb was used as a rubber-like polymer. .

The water content of the nitrile rubber crumb supplied to the feed port of the extrusion dryer is about 50%, most of the water content of the rubber crumb is dehydrated in the dehydration barrel, and the residual water content and vaporized substances are sucked and removed in the vacuum barrel. The die is continuously extruded in a strip shape through the specially shaped nozzle portion according to the present invention mounted on the die portion, the die portion, and the tip of the die portion, and sent to a blower cooler at room temperature.

As the nozzle portion according to the present invention, the one shown in FIG. 2 was used. Long side 178 mm, slit width of the axial extension of the two twin screws 14 mm 14 mm, slit width of the central extension of the two axes 14 mm
And, the length of the nozzle part is 48 mm.

Using this extrusion dryer, the operating conditions were adjusted so that the volatile matter in the dried product at the outlet of the blower dryer would be 0.4 to 0.7% on average.

No scorch was observed in the dried product, and the cross-sectional shape was as shown in Fig. 5, showing a uniform flat plate shape with a thickness of 24 mm on both sides and a thickness of 25 mm at the center.

Comparative Example 1 The same extrusion dryer and nitrile rubber crumb with the same water content as in Example were used.

As a breaker plate, the conventional breaker plate shown in FIG. 4 was mounted between the extruder tip barrel and a die having a rectangular discharge port and dried.

The operating conditions were adjusted so that the volatile content of the dried product was 0.4 to 0.7% as in the example.

The cross section of the obtained dried product was almost flat, but many burns were observed.

Comparative Example 2 The same extrusion dryer and the same water content nitrile rubber crumb as in Example 1 were used.

Operating conditions of the extruder so that the volatile content of the dried product at the outlet of the blast dryer is 0.4 to 0.7% by connecting the die part directly to the extruder tip barrel without pushing the breaker plate and pushing it out from the die discharge port. Was adjusted.

The cross-sectional shape of the obtained dried product is as shown in FIG.
The thickness of both sides was 29 mm, and the central portion was 18 mm, with severe irregularities.

<Effects of the Invention> According to the present invention, it is possible to obtain a flat plate-shaped product by preventing deterioration of quality due to a high temperature in a die portion such as burning which has conventionally occurred in a plate-shaped extruded rubber.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of the tip of an extruder, FIG. 2 (A) is a front view of a nozzle applied to the present invention, FIG. 2 (B) is a vertical cross-sectional view, and FIG. 4 is a front view of the nozzle embodiment of FIG.
FIG. 5 is a front view of a conventional breaker plate, FIG. 5 is a sectional view of a dry rubber according to an embodiment of the present invention, and FIG. 6 is a sectional view of a dry rubber according to a comparative example 2. (1) …… die part, (2) …… barrel, (3) …… screw, (4) …… nozzle, (5) …… constricted part,
(6) …… Bulging part, (7) …… Circular small hole.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takanori Musha 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Zeon Co., Ltd. (72) In-house Hiroshi Asahina 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Zeon Corporation

Claims (1)

[Claims] 1. A cross-sectional shape of a discharge port is constricted at a position corresponding to an axial extension of each screw of a twin-screw extruder, and a bulging flat discharge port is formed at both sides of the shaft and a central extension of the two shafts. A method for drying a rubber-like polymer, characterized in that the nozzle portion is attached to the tip of a twin-screw extruder die portion to dry the crumb of the rubber-like polymer.