JPH1158374A - Granulating die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a granulating die in which the problem of clogging of nozzles is not generated, the consumption of quantity of heat is small and a product of high quality can be manufactured despite of the inexpensive manufacturing cost. SOLUTION: A granulating die 1 is provided with a plurality of nozzles 5, 5... communicated with a cylinder of an extruder and a heating means 7 for heating the inside, and an end 6 whereon nozzles 5, 5... are opened is brought into contact with or close to water, and the vicinity of an area on which the nozzles 5, 5... are opened is coated with a porous metal material 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a plurality of nozzles communicating with a cylinder of an extruder, and heating means for heating the inside of the extruder. The present invention relates to a granulating die for forming pellets of a plastic material, which is to be used as such.

[0002]

2. Description of the Related Art An apparatus for forming pellets of a plastic material is conventionally known as a pelletizer, and generally includes an extruder, a die attached to a tip of the extruder, and a cutter. Therefore,
The resin material kneaded and melted by the extruder is extruded from a die, and the extruded resin material is cut into a desired length by a cutter, whereby a pellet having a desired size can be obtained. As such a method of cutting the extruded resin material, a hot cut method and a cold cut method are known.

[0003] The cold cut method is a method in which a resin material extruded from a die is guided into a water tank, cooled to form a strand, and cut. I have. By the way, the hardness of engineering plastics in the solidified state is much higher than that of general-purpose polyolefins, so when cutting with a strand cutter, the state is closer to crushing than when the cutter cuts into the strand and cuts Is broken at As a result, there is a problem that the powdered amount cannot be ignored and the yield is poor. In addition, compounds such as engineering plastics and fillers or glass fibers have higher hardness when solidified, and have a problem of wear of the strand cutter.

Therefore, adoption of a hot cutting method, that is, an underwater cutting method, a watering cutting method, or the like has been attempted. The underwater cutting method is a method in which the tip surface where a plurality of nozzles are open faces the circulating water flow, and the resin extruded into the water flow is cut by a cutter running along the die surface,
Since the resin is cut in a state where it is not sufficiently solidified, powdering of the resin, which is a drawback of the cold cut method, does not occur.
However, there are problems. For example, engineering plastics have a higher melting point than general-purpose polyolefins and the like.In general, a large amount of heat is applied to the inside of the die, but heat is removed because the tip surface of the die is in contact with water. The inside of the die may partially fall to a temperature below the melting point. Then, nozzle holes that cause clogging are also generated. Clogging reduces productivity. In addition, even if clogging does not occur, a nozzle having a small hole diameter may be generated, and the particle diameter of the pellet may be irregular, thereby deteriorating the quality. Furthermore, when clogging increases, extrusion becomes impossible, and the pressure becomes abnormally high, which may adversely affect devices upstream of the die, such as an extruder.

[0005] Such a problem of clogging can be solved by keeping the temperature inside the die high.
However, since the surface is cooled by water, the amount of heat escaping to the surface increases as the temperature difference increases, the applied heat capacity increases, requiring several times the heat capacity of the cold cut method, and the energy loss increases. Another problem arises. Therefore, the present applicant has disclosed in
No. 192423 proposes a granulating die that simultaneously solves the problem of nozzle hole clogging and the problem of energy as described above. The granulation dies proposed by the present applicant have a heating jacket provided inside, and a vacuum heat insulating portion provided on the surface side where the nozzle holes are opened.

[0006]

As described above, the granulating die proposed by the present applicant is provided with a vacuum heat insulating part, so that the surface is cooled by water. The amount of heat conducted from the surface to the low-temperature surface is small. Therefore, even if the amount of heat applied to the heating jacket is small, the inside of the die is maintained at a temperature higher than the melting point of the resin. As a result, clogging of the nozzle does not occur. Further, since the amount of heat to be conducted is small, an excellent effect that energy loss is small can be obtained. By the way, the above-mentioned granulating die proposed by the present applicant is relatively expensive due to the provision of the vacuum heat insulating part. That is, the vacuum heat insulating portion is formed by forming a groove on the surface of the granulating die, securing a predetermined interval in the groove, inserting a filling metal, and electronically welding in a vacuum chamber. Man-hours are high and costs are high. The present invention seeks to provide a granulating die that solves the above-mentioned problems, and specifically, does not have the problem of nozzle clogging, consumes a small amount of heat, and provides a high-quality product. For the purpose of providing a granulating die that can be produced at a low cost despite being obtainable, and is not particularly limited, and is suitable for granulating engineering plastic materials. I have.

[0007]

The above object of the present invention is achieved by covering the vicinity of an opening of a nozzle with a porous metal material. That is, in order to achieve the above object, the present invention has a plurality of nozzles communicating with a cylinder of an extruder, and a heating means for heating the inside, and an end face portion where the nozzles are open is formed by water. What is claimed is: 1. A granulating die for forming pellets of a plastic material, which is adapted to be used in contact with or in close proximity thereto, wherein at least a portion of said die at which a nozzle is open is covered with a porous metal material. Be configured to be The invention according to claim 2 includes a plurality of nozzles communicating with a cylinder of the extruder,
Heating means for heating the inside, wherein the end face portion where the nozzle is open is adapted to be used in contact with or in close proximity to water, for granulating plastic material pellets A die, wherein an end face of the die used near the opening of the nozzle and in contact with or close to water is configured to be covered with a porous metal material.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which an embodiment of the present invention is applied to an underwater cutting method will be described with reference to FIG. Although an extruder is not shown in FIG. 1, a die holder 20 is attached to the tip of a cylinder of the extruder, and a granulating die 1 according to the present embodiment is attached to the die holder 20 in a conventionally well-known manner. It has become. A relatively large-diameter resin passage 21 communicating with the cylinder of the extruder is formed at the center of the die holder 20. The heating jacket 2 surrounds the resin passage 21.
2 are provided.

The granulating die 1 according to the present embodiment includes:
A torpedo 2 protruding toward the resin passage 21 of the die holder 20 is integrally provided at the center thereof. Therefore, as shown in FIG. 1, when the granulating die 1 is attached to the die holder 20, the large-diameter resin passage 21 of the die holder 20 is formed by the outer peripheral surface of the torpedo 2 and the inner peripheral surface of the resin passage 21. A ring-shaped passage 23 is formed. Then, corresponding to the ring-shaped passage 23, a ring-shaped recess 4 is formed on the mounting surface on the left side in FIG.
Are formed. As shown in FIG.
A plurality of nozzles 5 reaching the right cooling surface 6 side,
5,... Are provided. Since such a plurality of nozzles 5, 5,... Are provided in a ring shape with the torpedo 2 at the center, the central portion of the granulating die 1 is sandwiched between these nozzles 5, 5,. The heating jacket 7 is provided on the circumference and the circumference.

According to the present embodiment, these nozzles 5, 5,... Protrude outward from the cooling surface 6 in contact with the circulating water, so that the nozzles 5, 5,. Quality metal material 8 is attached. The thermal conductivity of the porous metal material 8 is smaller than the thermal conductivity of the solid metal material forming the main body of the granulating die 1.
Therefore, the inside of the granulation die 1, that is, the nozzle 5,
Even if there is a large temperature difference between the vicinity of 5,... And the cooling surface 6, the amount of heat transfer is small, and the temperature inside the granulating die 1 falls below the melting point of the resin material. There is no.

Next, a granulating method using the granulating die 1 will be described. A heating medium of a predetermined temperature is flowed through the die holder 20 and the heating jackets 22 and 7 of the granulating die 1 to keep them at a predetermined temperature. As shown by the arrow A, the circulating water flows in a state in contact with the cooling surface 6. The screw of the extruder is rotationally driven to knead and melt the resin material and extrude it. The molten resin is extruded from the ring-shaped passage 23 into the ring-shaped concave portion 4 of the granulating die 1, and is uniformly pressurized from the concave portion 4 and is extruded from a plurality of nozzles 5, 5,. . At this time, the cutter 30 is rotationally driven along the hardened layer 9. Then, the resin material is cut into a predetermined length before being solidified into pellets. The pellets completely solidify while being transported by the water stream. Separate from circulating water. And dry to get the product.

According to the present embodiment, since the porous metal material 8 having a low thermal conductivity is attached near the nozzles 5, 5,... As described above, the temperature inside the granulating die 1 is reduced. That is, the temperature in the vicinity of the nozzles 5, 5,. Therefore, the nozzles 5, 5,... Do not become clogged, and the hole diameter does not become small. Furthermore, the amount of heat escaping to the circulating water is small, and the energy consumption is small. Despite these effects, the porous metal material 8 can be obtained by, for example, sintering a metal powder, and is merely attached and requires no special machining. There is no such thing as.

The present invention can be implemented in various forms without being limited to the above embodiment. For example, in the embodiment shown in FIG.
Although it is mounted only in the vicinity of 5, ..., it can be mounted on the entire cooling surface 6 to further reduce the amount of heat escaping to the circulating water. In addition, a recess for attachment or positioning may be formed in the cooling surface 6 and the porous metal material 8 may be attached to the recess. Obviously, an electric heater can be used instead of the heating jackets 22 and 7. Although the underwater cutting method has been described, it is clear that the granulating die 1 according to the present embodiment can be applied to the water ring cutting method.

[0014]

As described above, according to the present invention, since at least the vicinity of the opening of the nozzle of the granulating die is covered with the porous metal material, the granulation die comes into contact with water from the vicinity of the high-temperature nozzle. The amount of heat that escapes to the adjacent low-temperature end face is small. Therefore, the nozzle does not drop below the melting point of the resin material and the nozzle does not clog. Further, since the hole diameter of the nozzle is not reduced, the particle size is not uniform and the quality of the product is not degraded. Despite these many effects,
Since it is only necessary to cover the vicinity of the opening of the nozzle with a porous metal material, a granulating die can be obtained at low cost.
The effect unique to the present invention is obtained. According to the second aspect of the present invention, since the vicinity of the opening of the nozzle and the end face used in contact with or in close proximity to water are covered with the porous metal material, further effects can be obtained. Can be

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Granulation die 5 Nozzle 6 End part (surface which contacts water) 7 Heating jacket 8 Porous metal material

Claims (2)

[Claims] 1. A plurality of nozzles (5, 5,...) Communicating with a cylinder of an extruder, and heating means (7) for heating the inside of the extruder. A granulating die (1) for forming pellets of plastic material, the end face (6) of which is adapted to be used in contact with or in proximity to water, A granulating die, characterized in that at least the vicinity where the nozzles (5, 5, ...) are open is covered with a porous metal material (8). 2. A plurality of nozzles (5, 5,...) Communicating with a cylinder of the extruder, and a heating means (7) for heating the inside, wherein the nozzles (5, 5,...) A granulating die 81) for molding pellets of plastic material, the end face (6) of which is to be used in contact with or in close proximity to water, the nozzle of said die. The end face portion (6) used in contact with or in proximity to water and near the opening of (5, 5,...) Is covered with a porous metal material (8). Dies for grains.