JPS6186210A - Screw for extruder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

The present invention relates to an extruder screw, and more particularly to an extruder screw in which at least the screw blades are made of ceramic.

[Conventional technology]

Conventionally, in the production of ceramics, manufacturing machines such as clay kneading machines or vacuum clay extrusion molding machines that have a screw-type clay kneading and extrusion molding mechanism have been used, and the screw material built into these machines has been used. is steel, cast iron,
Stainless steel, etc., or those treated with hard chrome plating, wear-resistant metal spraying, ceramic coating, carburizing and quenching, etc., have been widely used. For example, Plast, Dingechno1. Vol 23
．． No, 10 P, 17-19.197? ,, 5u
rf J, Vol 12. No, IP, 2-51
1181,, Wire J, Int, Vol 15
No, 5 P, l114~87°19B2. It is described that ceramic spraying is applied to the screw of an extruder, and Plast Hass I No. 8P, 38-3
91975, it is also possible to use hard alloys.
tst Ger, Plast, Vol 73. N
oJ P, 291~9QIl 1qQ11 Doj+7
h-1-1ru Shufu Taku It is stated that it is given as a master to guest 4. Furthermore, in recent years, screws made of wear-resistant plastic materials such as MC nylon and high molecular weight polyethylene have been put into practical use. [Problems to be solved by the invention]
Products that have been subjected to treatments such as nitriding do not have sufficient wear resistance or peeling resistance. Therefore, as the operating time of the extruder passes, the kneading or extruder functions deteriorate, and foreign matter caused by wear and peeling gets mixed into the raw material, which may affect the characteristics or appearance of products using this raw material. cause defects. In addition, especially in coating or thermal spraying, the structure has some pores, and the water absorption caused by these pores causes the raw material to wrap around the screw surface, causing heat generation and an extreme drop in extrusion function. There are drawbacks. Furthermore, wear-resistant plastic materials such as MC nylon and high-molecular-weight polyethylene, which have begun to be used in recent years, have a slight advantage in wear resistance compared to the above materials, but their characteristics include a low coefficient of wear and self-lubrication. This causes slip between the screw blade surface and the raw material, which has a major drawback in that it induces pulsation in the extrusion speed, especially in extrusion molding machines, making extrusion molding unstable. [Means for Solving the Problems] In order to solve the above-mentioned problems, the screw of the extruder of the present invention has at least the screw blades made of ceramic acid, and has the following features: The present invention provides an extruder screw having a screw blade, characterized in that at least the screw blade is made of ceramic acid. FIG. 1 is a partial sectional view showing a preferred embodiment of the present invention, which has a shaft portion 1 and a screw blade 2 protruding from the circumferential surface of this shaft portion 1. FIG. The shaft part 1 consists of a metal shaft core part 3 and an outer part 4 of ceramic acid. The screw vane 2 is a ceramic acid and is integrally formed with an outer part 4 of the ceramic acid. In the present invention, only the screw blade 2 may be made of ceramic acid, and the entire shaft portion l may be made of metal; however, the shaft portion l may be made of metal.
Since the peripheral surface of the shank also comes into contact with the raw material and the effort of attaching the screw blade to the shaft can be omitted, the outer portion 4 of the shaft 1 and the screw blade 2 are integrated as shown in the figure. Preferably, the ceramic acid is bonded to the shaft portion 3 in one piece of ceramic. The inner circumferential surface of the ceramic acid outer portion 4 and the metal shaft core portion 3 are preferably bonded by resin bonding. Resin bonding facilitates the bonding work, and after bonding, the resin layer 5 serves as a buffer layer to reduce stress due to the difference in thermal expansion between the ceramic outer portion 4 and the metal shaft portion 3. This has the effect of reducing the vibration spacing between the two. In addition, in order to improve the bonding property (anchor effect) between the ceramic acid outer portion 4 and the metal shaft center portion 3. By using a rowland, multiple splines, or splines, it is possible to prevent distortion during firing due to conventional keyway machining, etc., and it is also possible to accurately match the pitch of the screw blades. Most of the conventional screws have an integral shape in the long axis, but in the present invention, the screw blade part 2 and the outer part 4 are designed in consideration of formability, difficulty of the firing method, and yield of the fired product. It is preferable to divide it into a plurality of pieces so that the maximum length is 250 mm or less, and insert the metal shaft portion 3 into the center hole. Next, with reference to FIG. 2, which is an enlarged view of FIG. 1, the inclinations θ1 and θ2 of the screw blades and the root circumference ratios R1 and R2 will be explained. The screw of the present invention having ceramic screw blades includes:
One of its characteristics is that it has less adhesion to the raw material (clay) than metals, such as stainless steel or those that have been plated, so the resistance during kneading and extrusion is lower. On the other hand, the inclination angle and attachment of the blade are inappropriate for the root coverage ratio.
f 11 - The adhesion to the main body is extremely reduced, and the peeling phenomenon of the raw material (clay) from the screw surface occurs, and this peeled raw material (clay) remains the same even though the screw is rotating. By stagnation at a certain point, it becomes difficult for the next raw material (kneaded clay) to be caught between the screws, resulting in a decrease in the jamming performance and a decrease in conveyance performance.Especially in the case of an extrusion molding machine, the extrusion pressure decrease is likely to occur. (In addition, such a phenomenon tends to occur in conventional metal screws when the screw blade inclination angle θ1, θ2 and plate curvature R1, 1, 2 are excessive.) In the case of the screw of the present invention It is preferable that these inclination angles and plate curvatures are smaller than those of general metal screws.As for θ2, 01 at the front in the extrusion direction is □0 to 5°, preferably 0°, 02 at the rear in the extrusion direction is 0 to 8 degrees, preferably 0 to 3 degrees, and the plate curvature is 0 to 8 degrees. R1 at the front in the extrusion direction is 0.5R to 10R1, preferably 2R to 5R1, and R2 at the rear in the extrusion direction is 2R to 15R1, preferably 3.5R to 6R. Generally, these 01, θ2. The smaller the values of R1 and R2, the better in terms of performance, but if they are too small, there is a risk that the raw material (clay) will not be easily separated from the screw. (The separation of the raw material (clay) from the screw is
If it is bad, the extrusion characteristics will deteriorate due to a decrease in the biting performance and conveyance performance, as in the case where the raw material is wrapped around the screw and a peeling phenomenon occurs. ) Also, θ1, θ
2. If RI and R2 are too small, there is a greater risk that raw materials will remain at the root of the threaded blade. Furthermore, in the case of ceramics, which are brittle materials, it is disadvantageous to make R1 and R2 too small from the viewpoint of strength. The ceramic material constituting the screw of the present invention includes:
Sintered bodies made of alumina, zirconia, silicon nitride, etc., which have high wear resistance, are preferred, but alumina with an Al2O3 content of 80% by weight or more is particularly preferred, and has particularly good wear resistance and impact resistance. A fL2O with an excellent Al2O3 content of 85 to 96% by weight is preferred.
If the content of A3 is less than 80% by weight, the wear resistance will be poor;
If the l2O3 content is too high, impact resistance and moldability will be impaired. Besides Nao A l 2O3, 5i02. CaOlMgO
, TiO2, ZrO2, etc., which are included in ordinary oxide sintered bodies. In addition, nitrides and borides may be included in the case of hanging. This alumina sintered body preferably has a water absorption rate of 1% or less, especially 0.1% or less. If the water absorption rate is greater than 1%, a phenomenon in which the raw material wraps around the screw surface occurs, causing heat generation and This is undesirable because it causes an extreme decrease in extrusion function. Next, a preferred method for manufacturing the screw of the present invention will be explained. First, a liquid such as water and, if desired, an appropriate amount of a binder are added to a raw material powder such as alumina powder, and the mixture is molded into a screw shape. The raw material powder, especially the alumina powder, preferably has a maximum particle size of 54 m or more F, particularly about 1 to 3 μm, in order to improve the surface precision after firing. The molding method can be press, casting, or extrusion, but we used booth molding into a hollow bar shape because there is less distortion during firing and post-firing processing is minimal or unnecessary. A molding method in which machining is then performed is preferred. The molded body thus obtained is heated to, for example, 1600 to 1800°C.
A sintered body is produced by firing at a certain temperature. This sintered body is inserted into a metal shaft that has a desired shape and has been knurled or threaded in the direction opposite to the screw rotation direction to improve the anchor effect during resin bonding, and is bonded with resin. The resin used at this time is preferably a thermosetting resin, and the amount of resin is ao-
It is preferable to mix in a filler of 100% by weight.As this filler, abrasive grains (crushed fused alumina products) with high hardness and a large catching effect are effective, and these abrasive grains are further subjected to silane coupling treatment. The wettability with the resin is very good, and the above-mentioned effects are particularly high. [Example] Examples and comparative examples will be described below. Example 1 100 parts by weight of an alumina raw material having a particle size of 3 ILm or less and having an alumina purity of 92% by weight, 65 to 70 parts by weight of water, and 2 to 6 parts by weight of a cellulose derivative, P, V, A, or acrylic resin as a binder. In addition, the mixture was thoroughly mixed and made into granules using a spray dryer, which was then hydropress-molded into a hollow rod shape with an outer diameter of 6 cm, an inner diameter of 2.5 cm, and a length of 15 cm. Next, cutting and knurling were performed to obtain the shape shown in the figure. (The dimensions of the screw blades after firing are as follows.) Pitch 3.8cm Height h 1.3cm 01 0 degrees 02 3 degrees R+ 2R R24R This molded body was fired at 1650°C for 1 hour and sintered. As a body. These three sintered bodies have a diameter of 2.1 cm and a length of 50 cm.
A stainless steel shaft of 1.5 m was inserted, the gap between the sintered body and the shaft was filled with epoxy resin, and the two were joined to form a screw. This screw was attached to an extrusion molding machine, and 1000 kg of hydrated clay, the main component of which was α-A fL 2 O y with an average particle size of about 35 to 50 lm, was extruded, and the degree of wear of the screw was measured. The state of extrusion molding was observed. The results are shown in Table 2. Comparative Example 1 For comparison, a 5US-
304 stainless steel screw (A). From A with hard chrome plating (B), A with tungsten-cobalt wear-resistant metal spraying (C), A with alumina spraying (D), and MC-nylon. Extrusion molding and abrasion tests of hydrous clay, the main component of which is α-A l 2 O 3 with an average particle diameter of approximately 35-50 mm, were conducted on each of the screws (E) in the same manner as in Example 1. The result is the second
Shown in the table. From Table 2, the screw of the present invention has little wear;
It is clear that the extrusion molding condition is also 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 A1.
12O392%. For comparison, 5US-304 stainless steel screws with the same shape as those in Example 2 were prepared.Equal amounts of the same clay as in Example 1 were charged into the extrusion molding machine equipped with these screws. In addition to measuring the amount of extrusion per unit time, the operating conditions were also observed. The results are shown in Table 3. From Table 3, it is clear that, as in Example 3, by appropriately selecting the shape of the screw blades, extremely excellent extrusion performance can be exhibited. [Effects] As detailed above, the screw of the extruder of the present invention has at least the screw blade portion made of ceramic, and therefore has excellent wear resistance and peeling resistance. Therefore, it is possible to stably exhibit excellent extrusion characteristics over a long period of time, and there is almost no possibility that foreign matter will be mixed into the raw material due to the screw.

[Brief explanation of the drawing]

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 the main part thereof. ■...Shaft part, 2...Screw blade part, 3...Axis center part, 4......
Outer portion of the shaft, 5...Resin layer. Agent Patent Attorney Tsuyoshi Shigeno Procedural Amendment December 7, 1980 Patent Application No. 2O9268 2 Name of the invention Extruder screw 3 Relationship to the case of the person making the amendment Name of the patent applicant (429) Noritake Company Limited 4 Agent address: 4-8-19 Akasaka, Minato-ku, Tokyo 107
Akasaka Omotemachi Building No. 502 7 Contents of the amendment' (1) From page 11, page 11, line 14 to page 12, line 1 of the specification, [(after firing...
The dimensions of the screw blade after firing are shown in Table 1. ) Revised as Table 1. (2) Replace r-50JLJ on page 13, line 1 of the specification with “-
50m."that's all

Claims (3)

[Claims] (1) An extruder screw having a shaft portion and screw blades protruding from the circumferential surface of the shaft portion, wherein at least the screw blades are made of ceramic. (2) The outer part of the shaft part and the screw blade are made of integral ceramic, and the axial center part of the shaft part is made of metal, and the inner peripheral surface of the outer part of the ceramic shaft part and the metal shaft are made of metal. The screw for an extruder according to claim 1, characterized in that the outer circumferential surface of the axial center portion of the screw is bonded with a resin. (3) The extruder screw according to claim 1 or 2, wherein the ceramic is a sintered body containing 80% by weight or more of Al_2O_3 and having a water absorption rate of 1% or less.