JPH0618685B2 - Extruder screen - Google Patents

Description

TECHNICAL FIELD The present invention relates to a screw of an extruder, and more particularly to a screw of an extruder in which a screw blade and an outer portion of a shaft portion are made of ceramic.

[Prior Art] Conventionally, in ceramic manufacturing, a manufacturing machine having a kneading machine and an extrusion molding mechanism by a screw method such as a clay kneading machine or a vacuum clay kneading extrusion molding machine has been used and built in these. As the screw material, steel, cast iron, stainless steel or the like, or those obtained by subjecting these to hard chrome plating, wear resistant metal spraying, ceramic conting, carburizing and quenching, etc. have been widely used. For example,
Plast.Technol.Vol 23, No.10P.17〜19,1977., Surf J.Vo
l 12, No.1 P.2 ~ 5 1981., ire J. Int.Vol 15 No.5 P.94
~ 97,1982., Etc. describe that ceramic screw spraying is applied to the extruder screw.Plast Massy No.8 P.38 ~ 39
For 1975, the use of hard alloys and also Kunstst Ger. Pl
aast. Vol 73. No. 6 P. 291-294 1983 describes that a screw is heat-treated and nitrided.

Further, in recent years, a screw using a wear-resistant plastic material such as MC nylon or high molecular weight polyethylene has been put into practical use.

[Problems to be Solved by the Invention] Of the above-mentioned conventional techniques, a screw made of metal or treated by thermal spraying, carburizing, dipping chamber, etc.
Peeling resistance is not sufficient. Therefore, with the passage of time of operation of the extruder, the function of kneading or extrusion decreases, and foreign substances generated by abrasion or peeling are mixed in the raw material, and there are considerable defects in the characteristics or appearance of the product using this raw material. Generate. In particular, in the case of a coated or sprayed screw, the surface structure of the screw blade has some pores, and the water absorption by these pores causes the phenomenon of winding of the raw material around the screw surface, which causes heat generation and extrusion. There is a drawback that the extreme decrease of

In addition, wear resistant plastic materials such as MC nylon and high molecular weight polyethylene, which have recently begun to be used, show some advantages in wear resistance compared to the above materials, but their characteristics are low wear coefficient and self-lubrication. Due to the property, slippage occurs between the screw blade surface and the raw material, and particularly in an extrusion molding machine or the like, pulsation of the extrusion speed is induced, which makes the extrusion molding unstable.

[Means for Solving the Problems] In order to solve the above problems, the screw of the extruder of the present invention is a screw of an extruder having a shaft portion and a screw blade protruding from the peripheral surface of the shaft portion, The outer part of the shaft part and the screw blade are made of ceramic, and the shaft center part of the shaft part is made of metal, and the inner peripheral surface of the outer part of the shaft part made of ceramic and the shaft of the metal shaft part are made. The screw of an extruder is characterized in that the outer peripheral surface of the core portion is resin-bonded.

FIG. 1 is a partial cross-sectional view showing a preferred embodiment of the present invention, in which a shaft portion 1 and a screw blade 2 protruding from the peripheral surface of the shaft portion 1 (hereinafter, also referred to as screw blade portion 2). Have. The shaft portion 1 includes a shaft center portion 3 made of metal and an outer portion 4 made of ceramic. The screw blade 2 is made of ceramic, and is integrally formed with the outer portion 4 made of ceramic.

Since the peripheral surface of the shaft portion 1 also comes into contact with the raw material, and the labor of attaching the screw blades to the shaft portion can be omitted,
As shown in the figure, the outer portion 4 of the shaft portion 1 and the screw blade portion 2
And are made of an integral ceramic, and the integral body of the ceramic is resin-bonded to the shaft center portion 3. In the resin joining, the joining work is easy, and after joining, the resin layer 5 serves as a buffer layer to reduce the stress due to the difference in thermal expansion between the ceramic outer portion 4 and the metal shaft center portion 3. Or
It has the effect of reducing vibration transfer between the two.

It should be noted that, in order to enhance the bondability (anchoring effect) between the ceramic outer portion 4 and the metal shaft portion 3, a lorette, a plurality of splines, or a screw groove in the direction opposite to the screw rotation direction may be provided. . By doing so, it is possible to prevent distortion during firing due to the key groove processing that has been conventionally performed, and it is possible to accurately match the pitch of the screw blades.

Although many conventional screws have a long axis and an integral shape, in the present invention, the screw blade portion 2 and the outer portion 4 of the screw blade portion 2 and the outer portion 4 are taken into consideration in consideration of formability, difficulty of firing method, and yield of fired products. It is preferable to divide into a plurality of pieces so that the maximum length is 250 mm or less, and insert the metal shaft center portion 3 into the center hole.

Next, the inclinations θ ₁ and θ _{2 of the} screw blades and the root curvatures R ₁ and R ₂ will be described with reference to FIG. 2 which is an enlarged view of FIG.

The screw of the present invention having a ceramic screw blade,
One of the characteristics is that it has less adhesion to the raw material (kneaded clay) compared to metal products such as stainless steel and those obtained by plating these products, so resistance during kneading and extrusion is small. On the contrary, if the inclination angle of the blade and the root curvature are inappropriate, the adhesion of the kneaded raw material (kneaded material) to the screw surface is extremely reduced, and the material (kneaded material) from the screw surface is A peeling phenomenon occurs, and the peeling raw material (kneaded clay) stays at the same place even when the screw is rotating, so that the next raw material (kneaded clay) is caught between the screws. It becomes difficult to lower the biting performance and the transport performance, and particularly in the case of an extruder, the extrusion pressure is likely to decrease. (Note that such a phenomenon easily occurs in the conventional metal screw when the screw blade inclination angles θ ₁ , θ ₂ and the root curvatures R ₁ , R ₂ are excessive.) In the case of the screw of the present invention It is preferable that the inclination angle and the root curvature are smaller than that of a general metal screw. Regarding the inclination angles θ ₁ and θ ₂ , the forward θ ₁ is 0 to 5 °, preferably 0 °. rearward of theta ₂ is 0-8 °, preferably 0-3 ° With respect to the base curvature, _{R 1} in the extrusion direction forward, is, 0.5R～10
R, preferably 2R to 5R, R ₂ behind the extrusion direction is 2R
-15R, preferably 3.5R-6R.

Generally, smaller values of θ ₁ , θ ₂ , R ₁ and R ₂ were advantageous in terms of performance, but too small values may adversely affect the separation of the raw material (kneaded clay) from the screw. There is. (If the raw material (kneaded clay) is not sufficiently separated from the screw, as in the case where the raw material winds around the screw and causes a peeling phenomenon, the biting performance and the conveying performance are deteriorated, and the extrusion characteristics are deteriorated. , Θ ₁ ,
If θ ₂ , R ₁ and R ₂ are too small, the risk of the raw material remaining at the root of the screw blade increases. Further, in the case of ceramics, which is a brittle material, it is disadvantageous to make R ₁ and R ₂ too small from the viewpoint of forcing.

As the ceramic material constituting the screw of the present invention,
Sintered bodies such as alumina, zirconia, and silicon nitride, which have high wear resistance, are preferable, but the Al ₂ O ₃ content is particularly 8
Alumina having a content of 0% by weight or more is preferable, and in particular, the Al ₂ O ₃ content of the wear resistance and impact resistance is 85-85.
It is preferably 96% by weight. Al ₂ O ₃ content is 80
If it is less than wt%, the wear resistance is poor, and if the reverse Al ₂ O ₃ content is too high, the impact resistance and its moldability are poor.

In addition to Al ₂ O ₃ , SiO ₂ , CaO, MgO, T
It may include various oxides such as iO ₂ and ZrO ₂ that are contained in ordinary oxide sintered bodies. Further, a small amount of nitride or boride may be contained.

This alumina-based sintered body preferably has a water absorption of 1% or less, particularly 0.1% or less. If the water absorption is greater than 1%, the phenomenon of winding of the raw material around the screw surface occurs, the screw heats up, and the extrusion function is extremely deteriorated, which is not preferable.

Next, a preferred method for producing the screw of the present invention will be described.

First, a raw material powder such as alumina powder is mixed with a liquid such as water and, if desired, an appropriate amount of a binder, and molded into a screw shape. The raw material powder, especially the alumina powder, preferably has a maximum particle size of 5 μm or less, especially about 1 to 3 μm in order to improve the surface accuracy after firing.

The molding method may be any of pressing, casting, and extrusion molding, but the strain during firing is small, and after press-forming into a hollow rod shape from the viewpoint that post-processing after firing is minimal or unnecessary, A molding method in which machining is then performed is preferable.

The molded body thus obtained is, for example, 1600 to 1800 ° C.
It is fired at about the same temperature to obtain a sintered body. This sintered body is externally fitted to a metal shaft that is knurled or screw grooved in the direction opposite to the screw rotation direction to improve the desired shape and the complex effect during resin bonding, and resin bonding is performed. .
The resin used at this time is preferably a thermosetting resin, and is 80% relative to the resin amount in order to enhance the durability of the resin and the anchoring effect at the joint surface between the ceramic outer portion and the metal shaft center portion.
It is preferred to mix up to 100% by weight of filler.
Abrasive grains (fused alumina crushed product) that have a high hardness and a large scratching effect are effective as this filler, and those obtained by subjecting these abrasive grains to a silane coupling treatment have very good wetting with the resin. The effect described above is particularly high.

[Examples] Examples and comparative examples will be described below.

Example 1 100 parts by weight of an alumina raw material having an alumina purity of 92% by weight and a particle size of 3 μm or less, 65 to 70 parts by weight of water and a cellulose derivative as a binder, P. V. A. Alternatively, 2 to 6 parts by weight of an acrylic resin was added, mixed sufficiently, and granulated with a spray dryer, and then hydropressed into a hollow rod shape having an outer diameter of 6 cm x an inner diameter of 2.5 cm x a length of 15 cm.

Next, cutting and knurling were performed so as to obtain the shape shown in the figure.

(The dimensions of the screw blades after firing are as shown in Table 1.) This molded body was fired at 1650 ° C. for 1 hour to obtain a sintered body. 2.1cm diameter and 50c length for 3 of these sintered bodies
A stainless steel shaft center of m was inserted, and a void between the sintered body and the shaft center was filled with an epoxy resin, and both were joined to form a screw.

This screw was attached to an extruder, and the main component was 100 consisting of α-Al ₂ O ₃ having an average particle size of 35 to 50 μm.
Extrusion of 0 kg of water-containing kneaded clay was carried out, the abrasion degree of the screw was measured, and the extrusion molding state was observed. The results are shown in Table 2.

Comparative Example 1 For comparison, SUS-3 having the same shape as that of Example 1 above.
04 stainless steel screw (A), A with hard chrome plating (B), A with tungsten-
In the same manner as in Example 1 for each screw of cobalt-based wear-resistant metal sprayed (C), A of alumina sprayed on (D) and C-nylon (E), the main component was Α- with an average particle diameter of about 35-50 μm
An extrusion molding-wear test was performed on a hydrated kneaded clay made of Al ₂ O ₃ . The results are shown in Table 2.

From Table 2, it is clear that the screw of the present invention has a small amount of wear and the extrusion molding state is good.

Examples 2 and 3, Comparative Example 2 A screw was manufactured according to the method of Example 1 so that the shape of the screw blade was as shown in Table 3. The material of the sintered body is Al
₂ O ₃ 92%. For comparison, a stainless steel screw made of SUS-304 having the same shape as that of Example 2 was prepared.

With respect to the extruders equipped with these screws, the same kneaded material as in Example 1 was put into each, and the amount of extrusion per unit time was measured and the operating condition was observed.
The results are shown in Table 3.

It is clear from Table 3 that, as in Example 3, by appropriately selecting the shape of the screw blade, extremely excellent extrusion performance can be exhibited.

[Effect] As described in detail above, since the screw of the extruder of the present invention is made of ceramics at least in the screw blade portion,
Excellent abrasion resistance and peeling resistance. Therefore, excellent extrusion characteristics can be stably exhibited over a long period of time, and foreign materials are hardly mixed into the raw material derived from the screw.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a screw of an extruder according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part thereof. 1 ... Shaft portion, 2 ... Screw blade portion, 3 ... Shaft center portion, 4 ... Shaft outer portion, 5 ... Resin layer.

Claims (2)

[Claims] 1. A screw of an extruder having a shaft portion and a screw blade projecting from a peripheral surface of the shaft portion, wherein an outer portion of the shaft portion and the screw blade are made of an integral ceramic, and a shaft of the shaft portion is formed. A screw for an extruder, characterized in that the core part is made of metal, and the inner peripheral surface of the outer part of the ceramic shaft part and the outer peripheral surface of the shaft center part of the metal shaft part are resin-bonded. 2. A screw for an extruder according to claim 1, wherein the ceramic is a sintered body containing 80% by weight or more of Al ₂ O ₃ and having a water absorption rate of 1% or less.