JPH04187408A - Manufacture of thermoplastic resin pellet and apparatus therefor - Google Patents

Abstract

PURPOSE:To enable pellets to be manufactured stably even in the case of molten strands not sufficient in its tensile strength by continuously extruding heat melted thermoplastic resin from a die, simultaneously, forming strands, and then severing the strands into a predetermined length through highly pressurized water spouted from minute diameter nozzles. CONSTITUTION:In an extruder 16, when thermoplastic resin strands are extruded from a die 12 into a chamber 17, highly pressurized water spouted from nozzle tips fixed on a rotating hollow shaft 11 strikes at right angles with respect to the advancing direction of the thermoplastic resin strands, and thus the stands are severed into pellets of the order of 1-5mm in its length. Since the highly pressurized water is spouted continuously, when not required to sever the strands, it hits the wall surface of the chamber 17 directly and therefore comes to mist within the chamber 17, and the severed pellets are cooled immediately and then transported out along with water from a transporting hole 18. In this way, even in the case of thermoplastic resin having no large tensile strength of strands, it can be severed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing thermoplastic resin pellets used as molding materials, colorant masterbatches, and the like.

(Prior Art) The following three methods are known for producing resin pellets by molding a molten strand of thermoplastic resin from an extruder and then cutting the strand.

(1) The cold cut method is the most common method, in which a strand of thermoplastic resin extruded from a die is cooled and solidified in a water bath, and then cut using a rotating blade of a cutter.

In terms of equipment, it is the cheapest. However, if the tensile strength during melting is not sufficient, it becomes difficult to form stable strands, which significantly reduces productivity. Conventionally, pellet producers have used an extruder or the like to knead a binder resin such as polyethylene or polypropylene together with pigments and wax in order to obtain this tensile strength when melted. On the other hand, recently, pellet components have been diversified to meet the needs of pellet users. In particular, the production of high-concentration pigment pellets, elastomer-based pellets, and EVA-based pellets has been increasing recently, and there are significant restrictions on the formulation to obtain melting tensile strength, which reduces pellet productivity. There is.

(2) The hot cut method was developed at approximately the same time as the cold cut method. A strand of thermoplastic resin extruded from a die is cut by a rotating blade close to the die surface and pelletized. Since there is no need to form long strands, even if the tensile strength of the molten resin is insufficient, the strands can be cut to produce pellets. However, the pellets immediately after being cut are not sufficiently cooled and cannot be used for materials that easily re-fuse. In this respect, the pellet components that can be produced are considerably limited.

(3) The underwater cutting method was developed later than the above two methods. In this method, molten thermoplastic resin is extruded as strands directly into water from a die in a chamber filled with circulating cooling water, and then cut into pellets using a rotating blade, similar to the hot-cut method. Unlike the hot-cut method, it is possible to rapidly cool the pellets, and it can be applied to a wide range of resins. However, since the die surface is directly placed in cooling water, the cooling of the die itself is significantly reduced.
It may be difficult to maintain uniform extrusion because the die cannot keep up with the heating and the molten resin continues to cool and solidify. In order to maintain good cutting performance, the rotary blade must be replaced before it wears out. Since the degree of progress of wear varies depending on the material of the pellet, the operator has to be constantly careful, which is a nuisance.

(Problems to be Solved by the Invention) The present invention solves the drawback that in the cold cut method, pellets cannot be stably produced if the tensile strength of the molten strand is insufficient, and in the hot cut method, the pellets are remelted after cutting. The present invention provides a thermoplastic resin pellet manufacturing method and apparatus that eliminates the problems of attaching and replacing rotary blades, and the disadvantage that uniform extrusion cannot be maintained by cooling the die itself in the underwater cutting method. be.

[Structure of the invention]

(Means for Solving the Problems) The present invention forms a strand while continuously extruding a heated and molten thermoplastic resin from a die, and at the same time forms the strand into a predetermined length using high-pressure water injected from a micro-diameter nozzle. The present invention relates to a method for producing thermoplastic resin pellets, which is characterized by cutting them, and an apparatus therefor.

An apparatus related to the present invention will be explained based on the drawings.

The apparatus shown in FIG. 1 includes a hollow soya shaft 11 for water supply that rotates around an axis, a plurality of dies 12 arranged at substantially equal intervals from the hollow shaft 11 in the circumferential direction of the hollow shaft 11, and the The nozzle tip 13 is fixed to the hollow shaft 11. Approximately 6 to 10 dies 12 are arranged concentrically with respect to the hollow shaft 11.

The micro-diameter nozzle 14 has a diameter of 0.05 to 0.2 l, and is integrally attached to the hollow shaft 11 in such a positional relationship that the strand extruded from the die 11 can be cut by the high-pressure water jetted from there. It becomes. The hollow part 15 of the hollow shaft 11 serves as a flow path for high-pressure water,
500 kg/cnf or more, preferably 1000 kg/cnf
Pressure greater than CD is applied to the water. Nozzle tip 1
The number 3 may be one, or in practice it may be two or more since it is necessary to rotate the hollow shaft 11 very quickly.
It is preferable to provide 10 pieces. The hollow shaft 11 is
It is designed to rotate around an axis by external power or a drive device (none of which are shown), and the trajectory of the high-pressure water accompanying the movement of the hollow shaft 11 crosses the direction of travel of the strand. .

The apparatus shown in FIG. 3 includes a hollow shaft 21 for water supply that reciprocates along an axis, a plurality of dies 22 arranged parallel to the hollow shaft 21, and a nozzle tip 23 fixed to the hollow shaft 21. It consists of

(Function of the Invention) In the apparatus shown in FIG. 1, when a strand of thermoplastic resin is extruded from an extruder 16 through a die 12 into a chamber 17, a nozzle tip 13 fixed to a rotating hollow shaft 11 The jetted high-pressure water hits the thermoplastic resin strand in a direction perpendicular to its traveling direction, and the strand is cut into pellets having a length of about 1 to 51III+. The high-pressure water is continuously ejected, and when the strand is not cut, it hits the wall of the chamber 17 and becomes a mist inside the chamber 17, and the cut pellets are immediately cooled and water is poured from the outlet 18. It will be carried out with the

In the device shown in FIG. 3, the motion of the hollow shaft 21 is reciprocating, or the direction in which high-pressure water is ejected is perpendicular to the direction in which the thermoplastic resin strand travels, so that the strand is cut in the same manner as above. pellets are obtained.

(Effects of the Invention) Since the present invention essentially does not use a blade to cut the strands, it is possible to cut even thermoplastic resins whose strands do not have a high tensile strength. Further, immediately after cutting, the pellets come into contact with water and are rapidly cooled, and the inside of the chamber is also cooled by the high-pressure water released, which has a remarkable effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the present device, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIGS. 3 and 4 are sectional views of other embodiments of the present device. The symbols in the figure are as follows. 11.21...Hollow shaft 12.22...Die 13.23...Nozzle tip procedure amendment (method) March 7, 1991 1, Indication of case 1990 Patent Application No. 316644 2 , Name of the invention, Method for manufacturing thermoplastic resin pellets and its apparatus 3, Relationship with the amended person case Patent applicant

Claims (1)

[Claims] 1. A strand is formed by continuously extruding heated and melted thermoplastic resin from a die, and the strand is cut into a predetermined length by high-pressure water sprayed from a micro-diameter nozzle. A method for producing thermoplastic resin pellets. 2. A hollow shaft for water supply that rotates around an axis, a plurality of dies arranged at approximately equal intervals from the hollow shaft in the circumferential direction of the hollow shaft, and a plurality of dies fixed to the hollow shaft and arranged at approximately equal intervals from the hollow shaft. 1. An apparatus for producing thermoplastic resin pellets, comprising one or more nozzle chips arranged so that high-pressure water is ejected toward a strand of thermoplastic resin extruded from the strand. 3. A hollow shaft for water supply that reciprocates along the axis;
a plurality of dies arranged parallel to the hollow shaft;
one or more nozzle tips fixed to the hollow shaft and arranged to eject high-pressure water toward the strand of thermoplastic extruded from the die. Equipment for manufacturing resin pellets.