JPH0924267A - Screw for screw type extrusion granulating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the adhesion even when wet powdery sugar is granulated by manufacturing a screw of stainless steel, removing its crest sections and applying a fluororesin for coating. SOLUTION: A matrix section 10 of a screw is made of stainless steel, and a fluororesin layer 11 coating the surface by the thickness of 2-3mm are formed except crest parts 10a. When wet powder is fed from a hopper by a screw type extrusion granulating machine using the screw and transferred by the screw, it is not feared that a raw material adheres to the surface, as the surface is coated with the fluororesin, and good extrusion can be carried out. The raw material easily adheres to the surface of a casing generally made of stainless steel, and even when the adhered raw material is cured, the resin layer is not damaged and the resin layer is not released, as there is no resin on the end 10a of the screw set close to the casing and the texture of stainless is exposed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw of a screw type extrusion granulator.

[0002]

2. Description of the Related Art A screw-type extrusion granulator has a structure as shown in FIG. 2, in which a wet raw material having plasticity is supplied from a hopper 1 and a screw 4 is driven by a motor 2 through a speed reducer 3. Rotate and feed raw materials from left to right in the drawing. The raw material fed by the rotation of the screw 4 is extruded through the holes 5a of the die 5 and granulated.

[0003]

In such a screw-type extrusion granulator, powder is sometimes attached to a screw used for compressing the powder because the wet powder is used as a raw material. When the wet powder adheres to the screw in this way, the charged raw material is not transported to the extrusion section (die 5) and cannot be granulated. In particular, wet powdered sugar tends to adhere, and granulation often becomes difficult.

According to the present invention, even if a wet powder raw material, particularly a raw material powder which easily adheres such as powdered sugar, is used, the raw material powder does not adhere, and therefore, granulation becomes difficult when used in an extrusion granulator. The present invention provides a screw for extrusion-type granulation that does not occur.

[0005]

Means for Solving the Problems The screw for extrusion granulation of the present invention is made of stainless steel and is coated with a fluororesin excluding its mountain portion. The surface is covered with a fluororesin to prevent the adhesion of the wet powder, and has an adhesion prevention effect even in the case of granulation of the wet powder sugar which is particularly likely to adhere.

The present invention has been made as a result of repeating many experiments using a stainless steel screw as a base material and a screw which has been variously processed.

First, a stainless steel screw was used as a base material, the surface of which was coated with a fluororesin was attached to a granulator, and as a result of an experiment, a sufficient anti-adhesion effect was obtained, but the tip of the screw (mountain) was coated. The fluororesin adheres to the inner surface of the casing of the extruder and comes into contact with the hardened sugar, whereby the fluororesin is scraped off.

Next, similarly, an experiment was carried out using a stainless steel screw as a base material, the surface of which was coated with a fluororesin having a composition having enhanced wear resistance. However, this abrasion-resistant fluororesin does not have much effect of preventing adhesion, and when it is continuously operated for a long time, the raw material adheres and cannot be used.

Further, the result of an experiment using a screw formed by screw-molding a high-molecular polyethylene resin on a stainless shaft is not preferable because the screw tip (ridge) is scraped off.

Based on the above experimental results, the present inventor, as described above, coats the surface of a stainless steel screw with a fluororesin and removes the fluororesin only from the tip (mountain portion) of the screw to form a casing. Even if the sugar attached to the inner surface hardens, the portion that comes into contact with the hardened sugar is stainless steel so that the resin is not scraped off.

The thickness of the coating resin used for the screw of the present invention is several millimeters, and the surface of the stainless steel is left in a range (generally about several millimeters) close to the casing at the tip of the screw.

In the screw of the present invention, the surface of the screw manufactured by using stainless steel as a base material is coated with a fluororesin to form a fluororesin layer having a thickness of about 2 to 3 mm, and then only the mountain portion is made of resin. It was made by scraping off.

As a result of granulating the wet powdered sugar using the screw type extrusion granulator equipped with the screw of the present invention thus produced, no powdered sugar adhered at all. Even if the powdered sugar adheres to the inner wall of the casing and hardens, the hardened sugar comes into contact with the hardened sugar only in the mountain portion where the resin does not exist, so the resin is not scratched and there is a problem in terms of durability etc. There is no.

[0014]

Embodiments of the screw according to the present invention will be described below with reference to the drawings. FIG. 1 is a view showing a screw of the present invention. A base material portion 10 of the screw is made of stainless steel and has the same shape as a screw for a general extrusion granulator. Reference numeral 11 denotes a layer of a fluororesin having a thickness of 2 to 3 mm, which is provided on all of the surface of the stainless screw 10 except the mountain portion 10a (width 2 mm).

When the powder wetted by the screw-type extrusion granulator using the screw of this embodiment is fed from the hopper and fed by the screw, the raw material adheres because the surface is covered with the fluororesin. There is no fear, and therefore good extrusion is possible. In addition, the raw material easily adheres to the surface of the casing 12, which is generally made of stainless steel, and even if the adhered raw material hardens, there is no resin at the tip (mountain portion) 10a of the screw adjacent to the casing 12. Since the surface of stainless steel appears, the resin layer is not damaged and the resin layer is not peeled off. In particular, as a result of the experiment, the resin does not exist continuously in a certain width of the mountain portion 10a, but in the case of the fluororesin, peeling does not occur.

The results of an experiment using powdered sugar as a raw material in the extrusion granulator equipped with the screw of the above-mentioned example are as follows.

Granulation period (number of days) Approximately 10 days Total operating time Approx. 50 hours Longest continuous operating time 17 hours 10 minutes Shortest continuous operating time 3 hours 30 minutes There was no

For comparison, granulation was carried out using the same raw material using an extrusion granulator equipped with a stainless steel screw, and continuous operation for 20 to 30 minutes was the limit.

[0019]

The extrusion granulator using the screw of the present invention can be used for a long period of time without adhering wet raw materials.

[Brief description of drawings]

FIG. 1 is a diagram showing a screw of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional screw-type extrusion granulator.

[Explanation of symbols]

 1 Hopper 2 Motor 3 Reducer 4 Screw 5 Die 5a Die Hole 10 Screw Base Material Part 11 Fluororesin Layer 11a Screw Tip (Mountain) Part 12 Casing

Claims (1)

[Claims] 1. A screw for an extrusion granulator in which the surface of a stainless steel screw is coated with a fluororesin except for the vicinity of the ridge.