JPH0813461B2 - Method for drying rubbery polymer - Google Patents

Description

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

[Prior Art] A method of 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. It is disclosed that the insertion portion is inserted into a cylinder barrel having a dehydration slit at the lower part of the portion, and an extrusion molding die is provided at the tip end discharge port.

The dried material has various shapes, but the extruded material in the form of a strip is convenient because it is easy to handle in the subsequent kneading work and the like and is suitable for automation of factory operation.

In order to extrude in a strip shape, a large number of circular small holes (7) are formed between the die part having the flat rectangular nozzle and the screw tip part in the oblong area having the same shape as the barrel inner shape as shown in FIG.
Attach the breaker plate (6) in which the
The melt is kneaded, rectified and sent to the die.

[Problems to be Solved by the Invention] However, in the case of the above-mentioned twin-screw extruder, the melt temperature becomes higher than necessary due to the back pressure increase due to the breaker plate provided in the die part, and depending on the kind of the material to be dried, Burning occurred 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 at the above-mentioned location. It is unsuitable because it is a hilly hill with a dented central part, and it is inferior in handleability of movement, stacking and kneading, especially operation automation.

[Means for Solving the Problems] If the inventors remove the breaker plate and provide a screen in the vicinity of the discharge port to apply an appropriate back pressure to the molten resin and release the back pressure through the screen. The inventors have found that a flat extrudate can be obtained from a nozzle, and completed the present invention.

Thus, according to the present invention, the biaxial shaft constituted by directly connecting the die having the screen inserted between the inlet side introduction part and the discharge side rectification part of the die having the flat plate-shaped extrusion port according to the present invention. There is provided a method for drying a rubber-like polymer, which comprises drying the rubber-like polymer using an extruder.

That is, the breaker plate between the tip barrel of the twin-screw type extrusion dryer and the die section is removed to avoid the temperature rise in this section, and the back pressure is raised and released near the discharge port.

The tip of the twin-screw extruder is as shown in the longitudinal sectional view of FIG. 1, and the die part (1) and the barrel (2) are directly connected to each other,
A nozzle rectifying section (4) having a flat plate-shaped extrusion port is connected to the die introducing section (3) at the tip of the die section, and between the die introducing section (3) and the nozzle rectifying section (4). The screen (5) is sandwiched between.

The screen mesh is appropriately selected depending on the melting temperature and melt viscosity of the rubber-like polymer to be dried, and the mesh is selected from the range of 4 to 20 mesh (Tyler standard sieve). If it is larger than 4 mesh, sufficient back pressure for kneading cannot be provided, and if it is smaller than 20 mesh, the resistance is too large and the screen may be broken.

As the twin-screw extruder used in the method of the present invention, a known twin-screw extruder may be used. In addition to a single screw suitable for the type of rubber to be dried, a left screw screw element, a right screw screw element, etc. And a kneading disk may be combined to form a screw, and the barrel may also be formed by combining a feed barrel, a standard barrel, a vent barrel, a dewatering barrel, etc. 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 solidifying a polymerized slurry obtained by emulsion polymerization, and crumb obtained by subjecting polymer cement obtained by solution polymerization to hot water treatment. Examples of rubbers include styrene-butadiene rubber, nitrile rubber, and butadiene rubber. Used for drying rubber crumbs such as rubber, isoprene rubber, butyl rubber, and acrylic rubber.

[Operation] In the case of a twin-screw extrusion dryer, when molten rubber is introduced into the die section with the breaker plate removed and extruded, the rubber melt leaving the screw kneading section flows internally at the screw shaft extension. It is considered that the kneading action due to is not sufficiently performed 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 rod-shaped portion is divided by the screen sandwiched between the introduction portion of the die and the nozzle rectifying portion to be extinguished and rectified, and the back pressure generated on the screw side of the screen exits the screen. Since it is released at the site, it expands to lower the temperature due to adiabatic expansion, that is, to be cooled, and at the same time, extinguishing the rod-shaped high-temperature portion gives an extrudate having a flat plate cross section.

[Examples] Hereinafter, the method of the present invention will be specifically described with reference to Examples and Comparative Examples.

Example A standard extrusion dryer comprising a foot barrel, a dewatering barrel, a standard barrel, a vent barrel, and a vacuum barrel was used as the twin-screw extruder, and nitrile rubber (NBR) crumb was used as the 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 in the rubber crumb is dehydrated in the dehydration barrel, and the residual water and vaporized substances are sucked and removed in the vacuum barrel. It is continuously extruded in a strip shape through a die part in which a wire mesh is sandwiched between the rectifying part and the rectifying part, and sent to a blower cooler at room temperature.

As the wire net, a 10-mesh stainless steel wire net was used.

Using this extrusion dryer, it was dried under normal operating conditions.
The average volatile content of the dry extrudate at the cooler outlet is 0.4-0.7%,
The product was sufficiently dried, and the cross-sectional shape of the product was flat and no scorch was observed.

The rubber temperature at the exit of the extruder is 160 ° C and the total length at room temperature is 80 m.
The temperature of the rubber at the inlet of the blast cooling machine is 100 ° C, and the temperature of the rubber at the outlet is 45 ° C, and the cooling effect is good, which means that the inside of the rubber from the extruder has a uniform temperature distribution. Show.

Comparative Example Using the same extrusion dryer and nitrile rubber crumb with the same water content as in the example, the same operating conditions were used.

As the breaker plate, the conventional breaker plate shown in FIG. 2 was used. The thickness of the plate is 35 mm.
A total of 422 6 mmφ through-holes are uniformly distributed in the compartment.

The cross-sectional shape of the dried product is flat and almost filled,
The volatile content was 0.7 to 1.0%, which was larger than that of the example, and many burns were seen.

Further, the rubber temperature at the extruder outlet was 160 ° C, the rubber temperature at the inlet of the same blast cooling machine as in the example was 100 ° C, and the temperature of the rubber at the outlet was as high as 75 ° C. Inferior,
It shows that the inside of the rubber from the extruder has a non-uniform temperature distribution.

[Effect of the Invention] According to the present invention, it is possible to obtain a dry product on a flat plate that prevents the deterioration of quality due to the high temperature in the die portion that has conventionally occurred in a plate-shaped extruded rubber. Further, the cooling capacity of the cooling device for the plate-shaped extruded rubber is positively affected, and the cooling device can be downsized and energy can be saved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a tip portion of an extruder according to the present invention, and FIG. 2 is a front view of a breaker plate. (1) ... Die part, (2) ... barrel, (3) ... die introducing part, (4) ... nozzle rectifying part, (5) ... screen, (6) ... breaker plate, (7 ) …… Circular small hole.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takanori Musha 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Within Nihon Zeon Co., Ltd. (72) Masamichi Soume 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Zeon Co., Ltd.

Claims (1)

[Claims] 1. A twin-screw extruder having a tip barrel directly connected with a die having a screen interposed between the inlet side introduction section and the discharge side rectification section of a die having a flat extrusion port. A method for drying a rubber-like polymer, which comprises drying the rubber-like polymer using the same.