JP2003211442A - Pelletizer, and knife and die plate used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the abrasion resistance of a die plate and a knife without generating non-uniform pellets by making it possible to form a liquid holding structure for forming a lubricating film between the slide surfaces of the die plate and the knife without disturbing the shape of the die hole of the die plate or the shape of a knife edge. <P>SOLUTION: This pelletizer is equipped with the die plate 3 having a plurality of die holes 3A, a housing 6 formed so as to surround the cutting surface 4 of the die plate 3, the knife holder 14 housed in the housing 6 in a freely rotatable manner, a drive means 7 for rotating the knife holder 14 in a definite direction and the knife 15 attached to the knife holder 14 and having a cutter surface 19 opposed to the cutting surface 4 of the die plate 3. Numberless fine dimples are formed to the cutting surface 4 of the die plate 3 or the cutter surface 19 of the knife 15 in order to generate the lubricating surface between both surfaces 14 and 19 from the liquid charged in the housing 6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pelletizer used for producing resin pellets and a knife and die plate used for the pelletizer.

[0002]

2. Description of the Related Art An underwater cutting and granulating apparatus, which is a kind of pelletizer, generally has a die plate having a plurality of die holes, a water chamber (housing) formed so as to surround the cut surface of the die plate, A knife holder rotatably housed in the water chamber, a driving means for rotating the knife holder in a fixed direction, and a plurality of knives attached to the knife holder are provided. A water supply device for circulating and supplying cooling water is connected to the water chamber, a resin supply device such as a gear pump is connected to the die, and molten resin from a resin kneader or the like is pressurized into the water chamber. It is being supplied. Therefore, the molten resin extruded from the die into the water chamber is cooled into the water chamber at the same time as being extruded into the water chamber, finely cut by the knife, and cooled in the water chamber to be granulated into hardened pellets.

In such an underwater cutting and granulating apparatus, when the resin is cut by sliding the cutter surface of the knife on the cutting surface of the die plate, it is important to prevent the abrasion of them as much as possible to reduce the maintenance cost. Is. Therefore, conventionally, for the die plate, a hard plate made of cemented carbide, titanium carbide (TiC), or the like is attached to form a cut surface, or the hard metal is pressure-sintered by thermal spraying or HIP. To improve the wear resistance of the cut surface of the die plate (for example, JP-A-5-124035 and JP-A-200).
0-52337 and JP 2001-191326 A).

Regarding the knife, whether a hard metal such as titanium carbide or tool steel is used as a material of the knife itself, or a cutting edge made of titanium carbide is joined to a base material made of general steel such as stainless steel. Alternatively, the wear resistance of the knife is improved by forming a coating layer having high hardness on the surface of the base material (Japanese Patent Laid-Open No. 2000-2000).
-176932).

[0005]

However, even if the cutter surface of the knife and the cutting surface of the die plate are reinforced with hard metal, as long as the both surfaces are in contact with each other and the resin is cut, the space between the two surfaces will be reduced. Friction cannot be avoided, and therefore the knife must be replaced with a new one in about 2 to 6 months, although it depends on the viscosity of the resin to be cut, the rotation speed of the knife, and the like. In the case of a die plate, if the knife sliding part on the cut surface is locally worn and the flatness is impaired, the resin cannot be cut well, so it takes about 6 months to 2 years to restart the cutting. Reprocessing such as polishing, re-spraying, or hard plate replacement is required. In recent years, the size of the granulating apparatus has been increased, and the size of the die plate has been increased accordingly, so that such reprocessing requires a great deal of time and cost.

On the other hand, since the water chamber of the underwater cutting and granulating apparatus is always filled with cooling water, if this cooling water is used as a lubricating liquid between the sliding surface of the knife and the die plate, the durability of both members will be improved. It is thought that the wearability can be improved and a longer life can be achieved. As one of the means, for example, a so-called "cross hatch" (fine slanted lattice groove) adopted on the inner peripheral surface of the engine piston is used. It is conceivable that a) is formed on these sliding surfaces, and thereby a lubricating film in a state close to fluid lubrication is generated between the sliding surfaces. However, if such a crosshatch is formed on the cut surface of the die plate, some of the groove edges that make up the crosshatch will communicate with the die hole and disturb the edge shape of the die hole. There is a risk that pellets with irregular shapes are likely to be generated. Further, when the cross hatch is formed on the cutter surface of the knife, a part of the groove ends of the cross hatch communicates with the edge of the cutter surface and disturbs the shape of the cutting edge. However, the molten resin may not be cut cleanly, and pellets having irregular shapes may be easily generated.

In view of such circumstances, the present invention forms a liquid holding structure for forming a lubricating film between the sliding surfaces of the die plate and the knife without disturbing the shape of the die hole of the die plate or the blade edge of the knife. By doing so, it is intended to improve their wear resistance without producing uneven pellets.

[0008]

In order to achieve the above object, the present invention takes the following technical means. That is, the pelletizer of the present invention forms innumerable fine dimples on the cutting surface of the die plate or the cutter surface of the knife or both of them for generating a lubricating film between the surfaces with the liquid filled in the housing. It was done. Also,
The knife for a pelletizer of the present invention has a myriad of fine dimples on the cutter surface for generating a lubricating film between the cutting surface of the die plate and the cutting surface of the die plate with the liquid filled in the housing forming the pelletizer. It was formed in.

Further, the die plate for a pelletizer according to the present invention has a cutting surface for generating a lubricating film between the cutting surface and the cutter surface of the knife by the liquid filled in the housing constituting the pelletizer. Innumerable fine dimples are formed. According to the present invention, since a myriad of minute dimples formed on the sliding surface of the die plate and the knife generate a lubricating film made of the liquid (for example, cooling water) filled in the housing forming the pelletizer, The wear resistance of the die plate and the knife can be significantly improved. In addition, since a large number of minute dimples are formed as the liquid holding structure for generating such a lubricating film, the shape of the die hole or the cutting edge of the knife is disturbed as in the case of the cross hatch described above. Thus, the occurrence of uneven pellets is prevented in advance.

In the present invention, the size and density of the dimples are not particularly limited as long as the lubricating film can be generated between the sliding surfaces. However, this type of pelletizer shears the resin extruded from the die hole of the die plate with the blade edge of the knife to pelletize it, so that the sliding surface of the die plate and the knife does not hinder the shearing. Smoothness is required. Therefore,
The dimples have a concave shape with a size of several microns (μm) to several tens of microns, and are of the order of several thousand per square millimeter (specifically, 3000 to
6000 pieces / mm2) is recommended, and if the size and density of the dimples are within this range, the smoothness of the resin extruded from the die hole will not be hindered. Can be secured.

In the present invention, the method of forming the dimples is not limited to a particular method, but the formation of fine dimples while ensuring smoothness that does not hinder the shearing of the resin is not limited to this. This can be achieved by subjecting the work to be formed to shot peening with substantially spherical fine particles that are harder than the work. In this case, fine dimples can be formed simply by hitting shots (fine grains) on the work at high speed, so initial processing or reprocessing work when processing dimples on the sliding surface of the die plate or knife can be performed. It will be easier.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an underwater cutting and granulating apparatus (pelletizer) 1 adopting the present invention and a cutter 2 therein. As shown in FIG. 1, the underwater cutting and granulating apparatus 1 of the present embodiment includes a die plate 3 having a large number of die holes 3A and a water chamber 5 formed so as to surround a cut surface 4 of the die plate 3. It is provided with a housing 6 for constituting it, the cutter 2 rotatably accommodated in the housing 6, and a driving means 7 for rotationally driving the cutter 2.

The die plate 3 closes the water chamber 5 so as to form one side wall (the right side wall in FIG. 1) of the water chamber 5. A water supply port 8 to which a water supply device (not shown) is connected is formed in the lower part of the housing 6 that divides the water chamber 5, and a drain port 9 for discharging the water inside with the pellets is formed in the upper part of the housing 6. Is provided. A chamber 10 of an extruder including a twin-screw kneader or a gear pump is connected to one end (right end in FIG. 1) of the housing 6. Therefore, the molten resin extruded from the die hole 3A of the die plate 3 into the water chamber 5 is extruded into the water chamber 5, and at the same time, the skin is cooled and finely cut by the knife 15 described later, and then the water chamber 5 It is then cooled and hardened and pelletized into pellets.

At the other end of the housing 6 (the left end in FIG. 1),
A bearing case 11 to which the driving means 7 composed of an electric motor or the like is connected is connected. This bearing case 1
A rotary shaft 13 is rotatably and rotatably inserted through the bearing 12 via a bearing 12, and the tip of the rotary shaft 13 projects into the water chamber 5. The cutter 2 is fixed to the tip of the rotary shaft 13. As shown in FIG.
This cutter 2 has a disc-shaped knife holder 14 whose center is fixed to a rotary shaft 13, and a knife holder 14
A plurality of knives 15 radially attached to the knife 15. The knife 15 has a fixing portion 16 having a substantially rectangular cross section, which can be bolted to the knife holder 14,
The fixing portion 16 is integrally formed with a cutting portion 17 having a substantially trapezoidal cross section.

FIG. 3 shows a sectional shape of a knife 15 used in the cutter 2 of the underwater cutting and granulating apparatus 1. As shown in FIG. 3, the cutting portion 17 of the knife 15 of the present embodiment includes a cutter surface 19 that faces the cutting surface 4 of the die plate 3 and a cutter surface 19 that gradually separates from the cutting surface 4 toward the rear in the rotation direction. A cutting blade surface 20 that intersects the front edge in the rotation direction of the surface 19 at an acute angle (approximately 50 degrees in this embodiment), and a rake surface that is continuous with the cutting blade surface 20 in the same direction as the cutting blade surface 20. 21 are provided.

Further, the cutting portion 17 has the rake face 2 described above.
Rear surface 22 extending rearward in the rotational direction from rear edge 21A
And a rear surface 23 extending substantially vertically from the rear end edge 22A of the rear surface 22 toward the cutting surface 4, and an inclined portion that rises in a curved shape from the rear end of the cutter surface 19 in the rotational direction. And an inner surface 24 that extends to intersect the lower end 23A of the rear surface 23. As shown in FIG. 3, the cutting surface 4 of the die plate 3 and the cutter surface 19 of the knife 15 are covered with cooling water in the water chamber 5 on both sides 4, 1.
Numerous dimples 25, which are fine depressions for generating a lubricating film, are formed between the nine. The dimples 25 are formed in a concave shape having a size of several microns (μm) to several tens of microns, and are provided with a density of several thousands per square millimeter.

Further, in order to ensure the smoothness of the cutting surface 4 and the cutter surface 19 to the extent that the cutting of the molten resin by the blade edge of the knife 15 is not obstructed, the countless minute dimples 25 form this. A work (die plate 3 or knife 15) that is an object to be formed is formed into a curved concave shape by shot peening fine particles having a substantially spherical shape that is harder than the work, and is approximately 3000.
The density may be in the range of up to 6000 pieces / mm 2. In order to form an infinite number of dimples 25 having such a size, hard fine particles (shots) having a particle size of 10 to 100 μm may be shot on the work at a speed of about 50 m / s or more. In order to obtain such a density, the shot time may be adjusted appropriately. The fine particles may be made of metal or ceramic.

[0018]

[Examples] Next, the tests conducted for demonstrating the effect of the present invention will be described. FIG. 4 shows an outline of the chip-on-disk tester used in this test. Using such a tester and under the conditions shown in the following [Table 1], the wear reduction of both the chip and the disk is shown. Was measured.

[0019]

[Table 1]

That is, as shown in FIG. 4, while a chip like a knife is pressed onto a donut-shaped disk like a die plate, the disk is rotated at a constant speed and the chips and The wear loss of the disc was measured. In this case, in order to approximate the actual operating state of the pelletizer as much as possible, 65
While supplying hot water at ℃ at a flow rate of 200 cc / min,
The surface pressure (pressing pressure) W of the tip is 5.0 kgf / cm2
The disk was rotated at a peripheral speed V of 15 m / s.

The chips and disks were made of titanium carbide which was actually used for the knife and die plate of the pelletizer. The dimples provided on the chip or disk in this test are formed by shot-peening hard fine particles (shots) having a substantially spherical shape and a particle size of 30 to 60 μm at a speed of 80 m / s. The shot time is
The dimple density was adjusted to be about 5000 pieces / mm 2. Also, for each chip and disk,
When the density of the dimples was visually confirmed from the micrograph of the surface, there were some variations, but it was about 30.
It was within the range of about 00 to 6000 pieces / mm 2.

The following [Table 2] and [Table 3] show the measurement results of the above test, and FIGS. 5 (a) and 5 (b) show the measurement results in a line graph.

[0023]

[Table 2]

[0024]

[Table 3]

In these tables and graphs, test number 1 indicates that no dimple was formed on either the chip or the disk, test number 2 indicates that dimples were formed only on the disk, and test number 3 indicates that the chip was formed. And the test results when dimples are formed on both the disk and the disk. [Table 2] is a table in which the measurement results of the wear reduction on the chip side are summarized, and FIG. 5A is a line graph of the measurement results. As is clear from this table and graph,
When the dimples are formed only on the disk (test number 2), the wear reduction of the chip can be reduced to one third or less as compared with the case without dimples (test number 1). Further, when the dimples are formed on both the tip and the disk (test number 3), the wear reduction of the tip is reduced by 5 as compared with the case without dimples (test number 1).
It can be reduced to a factor of 1 or less.

On the other hand, [Table 3] is a table summarizing the measurement results of the wear loss on the disk side, and FIG. 5B is a line graph of the measurement results. As is clear from this table and the graph, when the dimples are formed only on the disc (test number 2), the wear reduction of the disc is reduced to 1/3 or less as compared with the case without dimples (test number 1). Can be reduced. When the dimples are formed on both the chip and the disk (test number 3), the wear reduction of the disk can be reduced to 1/5 or less as compared with the case without dimples (test number 1). .

By the way, the present invention is not limited to the above embodiment. For example, in the above embodiment, the dimples 25 are formed on both the die plate 3 and the knife 15, but the dimples 2 are formed on only one of them.
5 may be formed. Further, the details of the cross-sectional shape of the knife 15, the number of knives 15 attached to the cutter 2, the detailed configuration of the underwater cutting granulator 1, and the like can be changed as appropriate and are not limited to the illustrated case.

[0028]

As described above, according to the present invention,
A liquid holding structure (innumerable minute dimples) that creates a lubricating film between the sliding surface of the die plate and the knife without disturbing the shape of the die hole of the die plate or the knife edge is formed on the sliding surface. Therefore, the wear resistance of the die plate or the knife can be improved without generating uneven pellets.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an underwater cutting granulator according to the present invention.

FIG. 2 is a front view of a cutter used in the same device as seen from a cutting surface side.

FIG. 3 is a transverse cross-sectional view of a cutting portion of a knife used in the device.

FIG. 4 is a schematic configuration diagram of a chip-on-disk tester.

5A is a line graph showing the measurement result of wear loss on the tip side, and FIG. 5B is a line graph showing measurement result of wear loss on the disk side.

[Explanation of symbols]

1 Underwater cutting granulator (pelletizer) 3 die plate 3A die hole 4 cut surface 6 housing 7 Drive means 14 knife holder 15 knives 19 Cutter surface 20 cutting blade surface 25 dimples

Claims (9)

[Claims] 1. A die plate (3) having a plurality of die holes (3A), and a cut surface (4) of the die plate (3).
A housing (6) formed so as to surround the knife holder, a knife holder (14) rotatably accommodated in the housing (6), a driving means (7) for rotating the knife holder (14), A pelletizer equipped with a knife holder (14) and having a cutter surface (19) facing the cutting surface (4) of the die plate (3), the pelletizer of the die plate (3) In order to generate a lubricating film on the cutting surface (4) or the cutter surface (19) of the knife (15) or both of them by the liquid filled in the housing (6) between the both surfaces (4, 19) Pelletizer characterized in that countless minute dimples (25) are formed. 2. The dimple (25) is a concave depression having a size of several microns to several tens of microns,
The pelletizer according to claim 1, wherein the pelletizer is provided at a density of several thousands per square millimeter. 3. The dimple (25) is formed by subjecting a work, which is an object to be formed, to shot peening of substantially spherical fine particles harder than the work. Pelletizer. 4. A cutter surface (19) facing the cutting surface (4) of the die plate (3), and a cutter surface (19) that gradually separates from the cutting surface (4) toward the rear in the rotational direction during cutting. 19) A knife for a pelletizer having a cutting blade surface (20) that intersects the leading edge in the rotational direction of 19), wherein the cutter surface (19) is inside the housing (6) that constitutes the pelletizer (1). Fine dimples (2) for generating a lubricating film between the cut surface (4) of the die plate (3) and the cutter surface (19) with the liquid filled in
5) A knife for a pelletizer, characterized in that it is formed innumerably. 5. The dimple (25) is a concave depression having a size of several microns to several tens of microns,
The pelletizer knife according to claim 4, wherein the knife is provided at a density of several thousands per square millimeter. 6. The dimple (25) according to claim 4 or 5, wherein the knife, which is the object for forming the dimple, is formed by shot peening fine particles of substantially spherical shape harder than the knife. Knife for pelletizer described. 7. A plurality of die holes (3A) and a knife (15).
A die plate for a pelletizer having a cutting surface (4) facing the cutter surface (19) of the above, wherein the cutting surface (4) is cut with a liquid filled in a housing (6) constituting the pelletizer (1). A die plate for a pelletizer, characterized in that innumerable fine dimples (25) for generating a lubricating film are formed between the surface (4) and the cutter surface (19) of the knife (15). 8. The dimple (25) is a concave depression having a size of several microns to several tens of microns,
The die plate for a pelletizer according to claim 7, wherein the die plate is provided at a density of several thousands per square millimeter. 9. The dimple (25) is formed by subjecting the die plate, which is a target for forming the dimple, to shot peening of substantially spherical fine particles harder than the plate. Die plate for pelletizer described in.