KR19990073050A - Apparatus for manufacturing foamed thermoplastic resin pellets - Google Patents

Abstract

The present invention is a pellet type which can be continuously and inexpensively foamed in a pellet form of thermoplastic resin such as low density polyethylene (PE), polypropylene (PP), etc., in which the structure is simple and no pollution gas is emitted during incineration. The present invention relates to an apparatus for manufacturing a thermoplastic foam, and in particular, a pellet-type thermoplastic foam improved so that continuous cutting of linear foam into pellets can be performed smoothly and uniformly without generating noise, vibration, frictional heat, and airflow. The manufacturing apparatus of this invention relates to.

The present invention is a die 11 in which the thermoplastic resin and the foaming agent are melt-mixed and press-supplied from the inlet side to the inside thereof, and a plurality of radial extrusion holes 23 are formed at the cylindrical outlet side, and the die 11 One end is fixed to the outlet end and the other end is coupled to the top feed 17 is installed so as to extend to the inner center of the die 11, and the outside of the portion where the extrusion port 23 of the die 11 is formed And a cutter 25 rotatably installed to cut the linear foam extruded through the radially extruded holes 23 of the die 11 to form a pellet-shaped resin foam of a predetermined size. The plurality of cutting wires 30 are installed such that the cutter 25 extends in a spiral manner along the outer circumferential surface of the die 25 and the outer circumferential surface of the portion where the radial extrusion holes 23 are formed. It provides an apparatus for manufacturing a foamed thermoplastic resin pellet, characterized in that in consists in comparison.

Description

Apparatus for manufacturing pellet-type thermoplastic resin foam {APPARATUS FOR MANUFACTURING FOAMED THERMOPLASTIC RESIN PELLETS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing pellet-type thermoplastic resin foams, and more particularly, to efficiently and uniformly rotate a die for extruding and foaming a resin material in a radial direction of a cylindrical body and to extrude foams from a die while rotating in contact with the outer peripheral surface of the die. The present invention relates to an apparatus for producing a pellet-type thermoplastic resin foam having a means for cutting to be able to inexpensively and continuously form a relatively large viscosity thermoplastic resin in a small pellet form.

Pellet-type thermoplastic foam has good moldability to products with complex shapes, and features excellent cushioning and durability against repeated impact, hard and smooth surface, excellent chemical resistance and moisture resistance. It is widely used for molding products for various applications such as carrying cases, cushioning materials for shock absorption, cushioning materials for vehicles, buoys, and the like.

Conventionally, such thermoplastic resin foams are usually polystyrene, or a copolymer of polystyrene and other resins is used to cut linear resin melt-extruded into pellets after water cooling to produce foamed resin pellets as intermediate products. It was prepared by a method of foam molding to a final foam through a foam molding process including. This manufacturing method has been commonly used because it is easy to manufacture pellets, but once the foamable resin pellets have to be made through a two-step manufacturing process of foam molding again, the overall process and equipment are complicated, and using The use of these products is increasingly regulated because they emit pollutant gases when incinerated.

Therefore, in recent years, thermoplastic resin pellets are manufactured using materials such as low density polyethylene (LDPE), linear low density polyethylene (L-LDPE), polypropylene (PP), and the like as thermoplastic resin materials that do not emit pollution gas. Doing.

Since the thermoplastic resin pellets have a high viscosity of resin materials such as LDPE and L-LDPE, they are difficult to be manufactured by conventional cutting methods, and the foaming agent is mixed with plastic particles in a small amount of individual reaction method, and foamed after heating and pressing. Was manufacturing.

To explain this in more detail, the resin pellets are made according to the expansion ratio and the size of the foamed particles, and many small resin pellets are put in the drum container to add the foaming agent, and then heated to a temperature below the melting point. At the same time, it is pressurized to high pressure, kneaded for several minutes (5-30 minutes), and foamed particles are obtained in small amounts by opening foaming after the foaming agent has sufficiently infiltrated the resin particles. Therefore, such a small amount of foaming method has a problem that it is difficult to continuously mass-produce the production cost of the foam particles, as well as the size of the foam particles pellets is not uniform.

In general, foams such as polystyrene are not difficult to produce in pellet form, but thermoplastic resins such as low density polyethylene and linear low density polyethylene and polypropylene have high viscosity and are difficult to cut into pellets. The bur is cut in the form of remaining, it is not possible to obtain a good quality pellets and there is a problem that the uniformity is greatly reduced. Therefore, there is a great demand for a means that can economically and practically achieve uniform pelletization while continuously foaming thermoplastic resin having high viscosity.

Accordingly, the present inventors enable continuous foam molding in pellet form while mixing and extruding thermoplastic resin and foaming agent, thereby enabling continuous molding of a desired pellet-type thermoplastic resin foam directly from a resin material without forming a separate foamable intermediate product. The device has been researched and patented as Patent 135899. The present invention further improves the manufacturing performance of the desired foam further.

The patent application is a die in which the thermoplastic resin and the blowing agent are melt-mixed and press-supplied from the inlet side to the inside, and a plurality of radial extrusion holes are formed at the outlet side, and one side is fixed to the outlet side end of the die. And a spindle-shaped top feed coupled to the other side so as to extend to the inner center of the die, and a linear foam that is rotatably coupled to the outer side of the die to be extruded and foamed through radial extrusion holes of the die. And a cutter for forming a resin foam, wherein the cutter includes plate-shaped blades which tangentially contact an outer circumferential surface of a die in which the radial extrusion holes are formed. It is describing.

However, this apparatus has been found to have the following problems in use due to the use of a rotary cutter having a plate-like blades in contact with the length of the die on the outer peripheral surface of the cylindrical die as described above.

First, it is very difficult to install the blades correctly to smoothly perform the required cutting operation because the blades should be installed on the outer circumferential surface of the cylindrical die along the length of the die. If the replacement of the blade is required there is a problem that takes a long time to replace the work.

Secondly, the blade blade structure is rotated along the die surface with the blade blade contacting the die surface without any gap, and the blade blade receives the impact force repeatedly repeatedly when cutting the extrudate by the blade blade. Since the work is made, the blade blades are prone to wear and breakage prematurely, and the noise and vibration are severe.

Third, the use of the plate blades as described above causes severe frictional heat due to the contact rotation between the die and the blades, and at the same time, the air flow due to the rotating plate blades acts on the die and the extrudate through the die, thereby extruded and foaming the resin. Since the conditions are liable to fluctuate unstable, it is difficult to obtain an optimum good foaming condition, and at the same time, the shape of the foam pellets is irregular due to the influence of airflow by the rotating blades.

The present invention has been studied in order to effectively improve the problems and disadvantages of the prior patent invention as described above to provide a device capable of exhibiting the production performance of a more excellent pellet-type thermoplastic resin foam.

1 is a cross-sectional view of a pelletized thermoplastic resin foam manufacturing apparatus according to the present invention,

Figure 2 is an enlarged cross-sectional view of the excerpts in FIG.

* Explanation of code for main part of drawing *

11: die 14: hollow portion

17: top feed 23: extrusion port

25: cutter 26,27: ring portion

28: bearing 29: fixture

30: cutting steel wire

The present invention for achieving the above object is a die that is press-supplied from the inlet side to the inside in a state where the thermoplastic resin and the blowing agent are melt-mixed, and a plurality of radial extrusion holes are formed in the cylindrical outlet side, the outlet side of the die The top feed is fixed to one end and the other side is installed to be coupled so as to extend to the inner center of the die, and rotatably coupled to the outer side is formed radially extruded holes of the die are formed to the radial extruded holes of the die And a cutter for cutting the linear foam that is extruded and foamed through to form pellet-shaped resin foam of a predetermined size, the cutter extending spirally along the outer circumferential surface of the die on the outer circumferential surface of the die in which the radial extrusion holes are formed. Arranging a plurality of cutting steel wires to be installed in close contact It provides an apparatus for manufacturing a foamed thermoplastic resin pellet according to claim.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

First, the thermoplastic resin which can be applied in the present invention is conventional polystyrene, styrene-acrylonitrile interpolymer and styrene-ethylene interpolymer, and the like, low density and linear low density polyethylene, polypropylene, ethylene-propylene interpolymer, ethylene-vinyl acetate hybrid Polymers, polyvinyl chloride, and the like, and those made of interpolymers alone or in combination may be used.

In addition, a blowing agent applied to the present invention may be used a volatile or degradable blowing agent. Examples of the highly volatile blowing agent include aliphatic hydrocarbons such as propane, butane, isobutane, and pentane, substituted aliphatic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, methyl chloride, methylene chloride, dichlorofluoromethane and chlorotri Fluoromethane, dichlorodifluoromethane and the like can be used, and dinitrosopentamethylenetetraamine, trinitrosotrimethylenetriamine, benzene sulfonylhydrazide, azodicarbonamide and the like can be used as the degradable blowing agent. These blowing agents can be used independently or in combination.

The thermoplastic resin, the blowing agent and other additives, etc., are made into a thermoplastic resin foam mixture by passing through an extruder.

That is, in the extruder configured by inserting a mixer between the main extruded part and the cold extruded part, the thermoplastic resin raw material is first supplied to the main extruded part and melted and transferred to the mixer by screw operation. The blowing agent is uniformly dispersed and mixed in the thermoplastic resin by indentation, mixing and stirring.

According to the kind of thermoplastic resin raw material, the main extrusion part is used, for example, in the case of low-density polyethylene, adjusted to a temperature of 100-200 ° C., and the mixer is set at the maximum temperature and pressure.

The foam mixture is then continuously foamed into pellets by the apparatus of the invention as shown in FIG.

As shown in Fig. 1, the apparatus of the present invention has a die 11 having an inlet 13 coupled to an outlet of the extruder 10 and having a hollow portion 14 therein, and an outlet side of the die 11. The top feed 17 is installed in the die 11 so that one side is fixed and the other side extends to the inner center of the hollow portion 14 of the die 11 and rotatable around the cylindrical outlet side of the die 11. And a cutter 25 for cutting and pelletizing linear foams extruded and foamed through a plurality of extruded holes 23 radially perforated at the exit side of the die 11 at a predetermined length. It is composed.

In the illustrated embodiment, the die 11 has a first body in which the inlet 13 is coupled to the outlet side of the extruder 10 and has an inner groove 11B for receiving the centering support 27 of the top feed 17. 11A, a second body 11C coupled to the top feed 17 extending through the inner center thereof, and having a plurality of extruded holes 23 radially drilled into the body in place; The inlet side is inserted into the outlet inner diameter of the first body 11A and the outer protruding flange to connect the body 11A and the second body 11C and at the same time to fix the centering support 27 of the top feed 17. The third body 11D, which is additionally bolted to the outlet side of the first body 11A, the outer periphery of the tip end of the second body 11C, is screwed inside the outlet side, and the outer periphery of the tip end of the first body 11A. It is configured to include a coupling ring 11E screwed to the bolted to the outlet of the extruder 10.

As shown in FIG. 2, the cutter 25 is coupled to the outer side of the cylindrical outlet side of the die 11 through a bearing 28, and is installed in a rotating material and is connected to and fixed to each other by a plurality of stators 29. Extends spirally along the curved surface of the outer circumferential surface between the ring portions 26 and 27 and the cylindrical outlet side outer peripheral surface of the radially extruded holes 23 of the die 11 between the two ring portions 26 and 27. It is configured to include a plurality of cutting steel wires 30 are connected to be installed. In a preferred embodiment, each cutting steel wire 30 is fixed at one end thereof in place of one ring portion 26 and the other end is 180 ° from the wire connection point of the one ring portion 26 at the other ring portion 27. The cutter 25 is installed in a position that is approximately biased, and the cutter 25 is preferably configured by connecting and installing a total of four steel wires 30 between the ring portions 26 and 27 as described above.

The power transmission means 31 for rotating the entire cutter 25 around the second body 11C of the die 11 in accordance with a rotary drive source (not shown), for example, a rotational drive of the motor at the rear end of the cutter 25. ) Is connected and installed.

In operation, when the foam mixture from the extruder 10 is fed through the inlet 13 of the die 11, the foam mixture is compressed, expanded, through a passage between the top feed 17 and the inner circumferential surface of the die 11. It is conveyed to the exit side of the die 11 while undergoing a compression process.

Thereafter, the foam mixture is linearly extruded through a plurality of extruded holes 23 formed radially on the outlet side of the die 11 and simultaneously foamed, and the foam thus extruded is rotated by an unshown rotary drive source. The pellets are cut into pellets by the cutting steel wires 30 of the cutter 25 which is rotationally driven to continuously obtain a pellet-type thermoplastic foam.

In the above, when the cutter 25 is rotated, the cutting steel wires 30 connected as described above between both ring portions 26 and 27 of the cutter 25 are extruded holes 23 of the die 11. Since the foam is continuously cut along the outer circumferential surface of the cylindrical portion with the spiral, the foam extruded through the extruded holes 23 is cut at an angle to the foam without being subjected to the vertical shear pressure on the foam as in the conventional art. Under the shear force acting gradually, it is very smoothly cut. Accordingly, the continuous cutting of the linear foam from the extruder 23 into pellets of a predetermined size is performed in the form of a plate shape that acts perpendicular to the foam as in the prior art. Very quiet and smooth with almost no noise or vibration caused by shear shock from the blade and extremely uniform size and shape Droplets are obtained. In addition, since cutting steel wires 30 having a diameter of about 0.3 to 2.0 mm proceed in a spiral manner, the cutting action is performed as described above, so that friction heat and air flow are not generated as in the case of using conventional plate blades. It is easy to maintain a constant setting of the foaming conditions in an optimal state and has the advantage of minimizing the deformation of the pellets due to airflow.

Therefore, according to the present invention as described above, the desired pellet-type thermoplastic resin foam can be molded continuously in a large quantity without a separate foaming intermediate product molding process, as well as high viscosity foam resin, which has been difficult to foam foam in the prior art Continuous foaming is also possible in the form of pellets, and since the cutter 25 having the cutting wires 30 in the form of wires is used as a means for continuously cutting the foam into pellets, very little noise or vibration is generated. Smooth cutting is achieved and there is little generation of frictional heat and airflow due to the cutting means, which provides an effect of further improving product quality and uniformity.

Claims (1)

A die 11 in which the thermoplastic resin and the blowing agent are melt-mixed and press-supplied from the inlet side to the inside thereof, and a plurality of radial extrusion holes 23 are formed on the cylindrical outlet side, and the outlet end of the die 11; A top feed 17 which is fixed to one end and the other end extends to the inner center of the die 11, and rotatably outside the portion where the extrusion holes 23 of the die 11 are formed. Combination is installed and comprises a cutter 25 for cutting a linear foam extruded through the radial extrusion port 23 of the die 11 to form a pellet-shaped resin foam of a predetermined size, the cutter 25 ) Is provided with a plurality of cutting steel wires (30) are installed to be in close contact with the outer circumferential surface of the portion where the radial extrusion port 23 of the die 11 is formed to extend in a spiral along the outer circumferential surface of the die (11) An apparatus for producing a pellet-type thermoplastic resin foam, characterized in that it is formed.