JPS642412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a screw for an extruder or a kneader. The term "extruder" used herein refers to all machines, such as so-called extrusion molding machines and injection molding machines, that move the processed material by means of a screw rotating inside a barrel. In addition, the material to be processed by the extruder and the kneader is not particularly limited and may be plastic, ceramic, metal particles, composite materials, etc., but it is particularly suitable for processing hard materials or at least materials containing hard materials. There is.

[Conventional technology]

Various types of extruders or injection molding machines are used in the processes of melt spinning synthetic fibers and molding synthetic resins. In addition, hard fibrous materials such as glass fibers, metal fibers, inorganic fibers, carbon fibers, and various fillers are added to polymers during mixing of pigments, stabilizers, or titanium oxide, etc. prior to spinning, and during premixing and molding of resin composite materials. New materials and composite materials that can be mixed and molded have been developed and put into practical use.

Conventionally, processing machines for such mixing, extrusion, pressurization, molding, etc. have all been made of steel, and in order to improve their wear resistance and salt resistance, they have been made of materials (alloys), plating, etc. Increasing surface hardness by various means such as fusing different materials has been proposed and put into practical use.

[Problem that the invention seeks to solve]

However, as the functionality of composite materials improves, the heat resistance of polymeric materials also improves, and the strength component materials to be mixed become increasingly hard, resulting in the wear resistance of processing machines being lower than that of metals. However, this has reached its limits and is becoming insufficient. Therefore, it becomes necessary to frequently replace mechanical parts within a short period of time.
There are problems such as increased costs due to equipment replacement, decreased productivity, and unstable molding conditions (for example, extrusion pressure fluctuates greatly depending on whether the machine is old or new due to significant wear).

In addition, the mixing of iron and other metals into processed materials due to wear is a problem in recent processing of ultra-high purity materials.

[Means for solving problems]

The present invention provides the above-mentioned method by constructing the part forming the spiral groove existing on the outer circumferential surface of the shaft-shaped screw in whole or in part from a ceramic part, and by attaching the ceramic part to the screw so as to be replaceable. solve the problems.

In order to solve the above problems, it is possible to change the parts of melt extruders, injection molding machines, kneaders, etc. that come into contact with processed materials to materials with excellent wear resistance and heat resistance, but inorganic materials (e.g. Ceramic materials such as metal oxides), glass fibers, metal fibers, etc. have high hardness;
Ceramic materials are the only ones that have wear resistance and can be used industrially at low cost.

On the other hand, although ceramic materials have high hardness, they have low mechanical impact strength, toughness, thermal expansion coefficient, thermal conductivity, etc., so they cannot be used in drive parts, parts that undergo frequent thermal changes, parts that come into contact with solid objects, etc. Must be made of metal. Therefore, only the parts that require particularly high wear resistance and hardness are made of ceramic, and the rest are made of metal.

In addition, ceramics lack toughness, so
In particular, when disassembling a machine for repairs or cleaning, ceramic parts are likely to chip or crack, and in such cases, the damaged parts of the ceramic parts may be individually replaced. It needs to be made easy.

Hereinafter, the structure of the screw according to the present invention will be specifically explained with reference to the drawings. First, an extrusion screw of a melt extruder will be explained as a representative example, but the same is basically applicable to a kneading machine and the like.

FIG. 1 shows a cross-sectional view of an example of an extrusion screw of a melt extruder according to the present invention. This screw 1 includes a plurality of ceramic cylinders 2, 3, 4, 5, 6, 7 having spiral grooves on the outer periphery, a metal cylinder 8 having spiral grooves on the outer periphery, and a metal shaft 9.
It is made into a skewer and fixed with a metal tip presser member 10 which also has a spiral groove on the outer periphery.

FIG. 2 shows a melt extruder equipped with such a screw. In the figure, 1 is Screw, 11
is a barrel, 12 is a hopper, and 13 is a nozzle, and the raw material supplied from the hopper is moved through the barrel 11 by the rotation of the screw 1 as follows: propulsion zone → compression zone → melting zone → metering zone → mixing zone.
During this time, the material is subjected to the actions of propulsion, compression, melting, metering, and mixing in each zone, and is extruded through the squeeze gate 13 to form the desired molded product. In FIG. 2, the die, heating zone, cooling zone, vent, bearing, drive section, measuring hopper, various measuring instruments, etc. are the same as in the case of a conventional melt extruder, so they are omitted.

The part of the screw of this melt extruder that is made of ceramic is the spiral groove part, that is, the outer peripheral part, from the compression zone to the melting zone and the metering zone. The reason why other parts of this screw were not made of ceramic is that, referring also to FIG. This is because both ends are easily damaged when the screw is taken out for cleaning, and the spiral groove 8 of the propulsion band is hit by the solids supplied from the hopper. However, the length of the screw to be made into ceramic is determined by the material of the ceramic, the life of the screw, the type of molded product, etc., and is not limited to this example.

In addition, in this example, the shaft body 9 and the tip presser member 10 are screwed together in order to fix the plurality of spiral grooved ceramic cylinder bodies 2, 3, 4, 5, 6, and 7, but the shaft body 9 and the tip presser member 10 are screwed together. The member 10 may be formed integrally and divided at the rear, for example, at the stopper 14, and then connected by screws or the like. Further, the spirally grooved metal cylinder 8 may be formed integrally with the shaft 9.

In the melt extruder of FIG. 2, a plurality of ceramicized parts 2, 3, 4, 5, 6,
Ceramic parts 1 are also included in the barrel part corresponding to 7.
5, 16, 17, 18, 19, and 20 are used.

FIG. 3 shows the shape of a spirally grooved ceramic or metal cylinder (for example 2). The shape of the spiral groove 21 formed on the outer periphery of the cylindrical body 2 is determined by the processing material and extrusion conditions, but the spiral groove 21 is made to be continuous when a plurality of cylindrical bodies are connected. In the example shown in FIG. 2, the groove 21 gradually becomes deeper along the screw 1 in the → direction.

The cylinders, in particular the ceramic cylinders 2 to 7, are provided with elongated holes along their central axes in order to be connected to the metal shaft 9. In order to prevent the cylindrical bodies 2 to 7 from rotating in the circumferential direction with respect to the shaft body 9, a keyway is provided or the shape of the hole is modified, as shown in FIGS. 3a to 3c.

As the material for the spirally grooved ceramic cylinders 2 to 7, a sintered body of alumina, zirconia, silicon nitride, or the like having high wear resistance and heat resistance is used. In particular, the content of alumina is 80% by weight or more, especially 85~
A 95% by weight sintered body is preferable because it has excellent wear resistance, impact resistance, heat resistance, and formability.
Furthermore, partially reinforced zirconia may be suitable for particularly high loads and shocks encountered during operation.

The ceramic cylindrical body 3 may be manufactured by molding and firing according to a conventional method. However, in order to improve the surface precision after firing, the raw material powder has a particle size of 5 μm.
Below, a thickness of about 1 to 3 μm is particularly preferable. When molding, the dimensions and shape are set in consideration of shrinkage after firing, but if necessary, after firing, the dimensional accuracy is improved by grinding.

FIG. 4 shows a metal shaft 9 and a tip holding member 10.
shows. The shaft body 2 should have sufficient thickness to withstand the maximum torsional stress applied to the screw during processing. The tip holding member 10 is manufactured by machining, but the screw connection with the shaft body 9 is made in the opposite direction to the rotation of the screw. Further, the spirally grooved metal cylindrical body 8 is also produced by machining, but it may be produced integrally with the shaft body 9 as described above.

FIG. 5 illustrates a case in which the screw is made of ceramic parts up to the tip, and inside the spiral grooved ceramic cylinder 22 at the tip,
The ceramic cylindrical body 2 is pressed using the tip holding member 23.
2 and 24 are fixed to a metal shaft body 25.

FIG. 6 shows an alternative screw, which uses a ceramic cylinder 26 with specially shaped grooves near the tip to enhance the mixing effect. As described above, since the screw according to the present invention uses ceramic parts that can be divided and replaced, a screw having a desired tooth profile can be constructed by appropriately combining ceramic parts having spiral grooves of various shapes. It is possible to do so.

In the screw according to the present invention, ceramic and metal have different coefficients of thermal expansion, so in order to absorb thermal changes during operation and to alleviate shock at the start of driving, a gap between the ceramic member and the metal member is added as necessary. Alternatively, a buffer zone may be provided between the ceramic members. As the buffer band, resin such as polyimide, polysulfone, polyamide, heat-resistant synthetic polymer film such as synthetic rubber, or foil such as copper or aluminum may be used, or resin such as epoxy, melamine, or phenol may be used. It may be applied and formed on a metal member or a ceramic member. Particularly preferred are buffer strips made of plastic or the like.

FIG. 7 shows an example of the structure of a screw for a kneading machine.
This screw has a ceramic cylinder body 31, 32 having a spiral groove on its outer periphery, through which a metal shaft body 33 is passed.
It is fixed at both ends with press members 34 and 35. The spiral grooves of the screws for the kneading machine are generally deeper than the grooves of the extruder, but the production and assembly of the ceramic cylinders 31, 32 are the same as in the case of the extruder. 8th
The figure is a sectional view showing a twin-screw kneader constructed with two such screws 36 and 37. The container 38 of this twin-screw kneader has a ceramic lining 39 on its inner surface.
have. The kneading machine can be configured with one shaft, two shafts, or three or more shafts according to a conventional method.

〔Example〕

Example 1 Based on a conventional extruder with L/D = 25, 26 mm having mixing, metering, melting, compression, and thrusting zones, the central part of the 2000 mm screw part is 1680 mm.
In order to ceramicize the length, that is, from the metering zone to the melting zone and the compression zone, six spirally grooved alumina cylinders each having a length of 280 mm were fabricated.

To create an alumina cylinder, 100 parts by weight of alumina powder (purity 92% by weight) with a particle size of 3 μm or less, water
45 to 65 parts by weight, and 2 to 65 parts by weight of polyvinyl alcohol
After thoroughly mixing 6 parts by weight and making it into granules using a spray dryer, the product was made into granules with an outer diameter of 77 mm, an inner diameter of 45 mm, and a length of 333 mm.
A keyway was added to the hollow cylindrical body of the cylindrical body and hydrosless molded. Next, it was cut and knurled into the shape shown in FIG. The spiral grooves of each cylindrical body had the same pitch length (74.7 mm) and the same shape of the peaks, and the depth of the valleys was gradually increased (8.1 mm).
from 20.7mm). This molded body was fired at 1650°C for 1 hour.

A shaft body and a tip holding member as shown in FIG. 4, and a spirally grooved cylindrical body (propelling section) as shown in FIG. 1 were fabricated by machining steel materials. The shaft body has an outer diameter of 37.8 mm at the cylindrical body insertion part and a length of 2001 mm, with a thread cut at the tip and a key groove machined at the cylindrical body insertion part. At the rear of the shaft, a stopper having an outer diameter approximately the same as the inner diameter of the barrel to stop the backward movement of the processed material and a connecting portion with a drive device (not shown) were formed. The surfaces of the shaft body, tip presser member, and cylindrical body thus processed were plated with hard chrome.

Each member thus produced was assembled as shown in FIG. For this assembly, the thickness of the shaft body is 0.25mm.
The same polyimide donut-shaped film as above was inserted between the stopper of the shaft body, each cylindrical body, and the tip pressing member to form a buffer band.

This screw was assembled into a conventional melt extruder as shown in FIG.

Using this melt extruder, we melt-extruded a polyolefin polymer containing short glass fibers and titanium oxide at 30% by weight and 20% by weight, respectively, to form a composite material. There is almost no visible wear and it has withstood more than a year of use.

In contrast, with a conventional extruder using a steel screw with a hard chrome plated surface, when melt extruding a composite material under the same conditions as above, the
Due to continuous operation for hours, the mixing condition of the product deteriorates due to wear of the screw part, and the extrusion rate decreases to less than 80%, making it unusable in three weeks.

The alumina cylinder can be easily replaced by disassembling the screw.

Example 2 A melt extruder similar to that of Example 1 was constructed. However, in this melt extruder, the spiral groove of the screw has a total length of 2190 mm and an outer diameter (maximum diameter) of 65-(0.3~
0.4) mm. An alumina block with a length of 250 mm as a spiral grooved ceramic cylinder6
Two pieces were made of zirconia. These cylindrical bodies were fixed to a hard nickel-plated steel shaft with a zirconia screw disposed at the tip. In this shaft as well, a hard nickel-plated steel member with a spiral groove on the outer periphery was used for the propulsion portion and the tip.

A tube made of alumina with a length of 250 mm and an inner diameter of 65 mm and flanges at both ends is used as the lining of the barrel.3
Two pieces made of silicon nitride were made. When assembling the barrel, the length from the metering zone to the melting zone and compression zone was made up of three alumina barrel linings (750 mm), two silicon nitride barrel linings (500 mm), and a 750 mm portion without ceramic lining. Additionally, three vents were formed near the tip of the barrel.

The inside of the aperture gate at the extrusion tip was made of zirconia, and the outside was protected with a steel member to create the tip gate.

Using this melt extruder, a crosslinkable polyester containing 60% by weight of a mixture of inorganic fine particles such as titanium oxide, magnesium silicate, and aluminum oxide and silicon nitride whiskers was integrally melt-extruded. Even after continuous operation for 6 months, it can be operated well without any change in appearance, extrusion pressure, or other measurements.

On the other hand, when the above composite material is melt-extruded under the same conditions using a melt-extruder made of hard nickel plated steel of the same shape, the wear becomes significant after about a week, and the screws are thickened once a week. It was necessary to grope the barrel once a month.

Example 3 Two screws for a kneader were prepared in the same manner as in Example 1. However, the shape of this screw is as shown in FIG. 7, the effective length of the spiral groove is 600 mm, and the depth of the groove is deeper and constant (about 20 mm) than in the case of a screw for an extruder. The length of the alumina cylinder was 400 mm, and two of them were used to form one screw.

These two alumina screws were assembled into a container having an alumina lining, as shown in FIG. 8, to prepare a screw-type kneading machine. This kneader was used to heat and knead ABS resin containing 50% by weight of magnesium silicate, zinc oxide, glass fiber, and stabilizer, and was used to manufacture premix intermediate products. As a result, the replacement life of the mixing screw was extended by 12 to 15 times compared to the conventional hard nickel plated steel screw. Furthermore, the alumina cylinder can be easily replaced by disassembling the screw.

In addition, in the case of a kneader, the surface finish accuracy does not necessarily have to be high, and it was sufficient to improve the dimensional accuracy before firing.

〔Effect of the invention〕

The present invention provides extruders and kneaders that improve the abrasion resistance and heat resistance of screws for extruders and kneaders, and are suitable for processing hard materials or materials containing hard materials. Even if cracks or chips occur due to this, only the damaged part can be easily replaced.

In explaining the present invention, reference was mainly made to the processing of a composite material in which a hard material is distributed in a resin, but the characteristics of improved wear resistance and heat resistance due to the use of ceramic screws are
It goes without saying that it is effective not only in the molding process of ceramics, but also in the molding process of ceramics, and it has been experimentally confirmed (Japanese Patent Application No. 1983-
(See No. 209268).

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a screw for a ceramic extruder according to the present invention, Fig. 2 is a front view and side view of a spirally grooved ceramic cylinder used in the screw according to the present invention, and Fig. 3 is a schematic cross-sectional view of a screw for a ceramic extruder according to the present invention. A schematic diagram of the metal shaft used for the screw, Figure 4 is another one.
Fig. 5 is a schematic diagram of another screw for a ceramic extruder according to the present invention;
FIG. 6 is a schematic diagram of a screw, and FIG. 7 is a schematic diagram of a screw for a ceramic kneading machine according to the present invention.
FIG. 8 is a schematic sectional view of a two-screw kneader. 1... Screw, 2-7... Ceramic cylindrical body with spiral grooves, 8... Metal cylindrical body with spiral grooves, 9
...Metal shaft body, 10...Tip holding member, 11...
...Barrel, 12...Hopper, 13...Aperture gate, 14...Stopper, 15-20...Ceramic barrel lining, 21...Spiral groove, 22,2
4... Ceramic cylindrical body with a spiral groove at the tip, 2
3...Tip holding member, 25...Metal shaft body, 26
... Ceramic cylindrical body, 31, 32... Ceramic cylindrical body, 33... Metal shaft body, 34, 35
... Pressing member, 38 ... Container, 39 ... Ceramic lining.

Claims (1)

[Scope of Claims] 1. The portion forming the spiral groove existing on the outer circumferential surface of the shaft-like screw is wholly or partially composed of a ceramic part, and the ceramic part is replaceably attached to the screw. A screw for an extruder or kneader characterized by: 2. The screw for an extruder or kneader according to claim 1, further comprising a buffer band made of plastic or the like provided between the ceramic part and the metal part forming the remainder of the screw. 3. For an extruder or kneader according to claim 1 or 2, wherein the ceramic part is composed of a plurality of parts, and a buffer band made of plastic or the like is provided between the plurality of ceramic parts. Screw you.