JP2735963B2 - Method for producing thermoplastic resin particles having easily heat-modifying additives - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic resin foam 1.0 density from 0.2 produced for the purpose of reproduction of g / cc, an average particle diameter of 20mm following amorphous thermoplastic resin particles
About . In particular, in the present invention, a polystyrene-based resin foam containing a halogen-based flame retardant, for example, a Br-based flame retardant is regenerated to form irregular shaped particles having a density of 0.2 to 1.0 g / cc and an average particle diameter of 20 mm or less. The present invention relates to a method for producing thermoplastic resin particles which can be easily carried without being bulky and can be reused.

[0002]

2. Description of the Related Art There are many thermoplastic resin moldings on the market which contain additives which are thermally denatured. Such additives include, for example, colorants, antioxidants, surfactants, and cross-linking agents. Among them, additives that thermally denature and release harmful substances to the environment, such as Br-based flame retardants There are various foams containing For example, for architectural applications, there are low-foam synthetic wood and high-foam insulation materials manufactured by an extrusion molding machine, and for industrial applications, there are casings for weak electric products manufactured by an injection molding machine.

[0003] These molded products, including defective products generated in the manufacturing process and cut loss at construction sites, are incinerated or buried after use, are treated as waste, or are recycled as resin materials again. . In the conventional resin recycling method, an extruder is mainly used. In this method, a product is pulverized, supplied to an extruder, melted at a high temperature, discharged into water through a number of small holes, cooled, and then pulverized into fragments.

[0004]

However, halogen-based flame retardants such as Br generally have poor thermal stability. When the resin is heated to the melting temperature, the additives are decomposed, and the generated Br
Not only does the gas corrode equipment and equipment, but also results in unfavorable environmental health. Furthermore, polystyrene and the like cause depolymerization by melting, and adhere to the water when discharged into water, and the contained water also causes hydrolysis of the Br-based flame retardant. It could not be obtained and could only be used for limited applications.

[0005] An object of the present invention is to provide a thermoplastic resin foam containing, as an additive, a substance having poor heat stability and easily heat denatured as described above, which is suitable for recycling by a method that does not adversely affect the environment. It is an object of the present invention to provide a method for regenerating amorphous particles having a shape and without quality deterioration, and to obtain such irregular particles.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and achieve the object, the present invention is to pulverize a low-density thermoplastic resin foam having a heat-modifying additive, and to pulverize the pulverized particles.
Supplying into a pair of concave discs that are rotating relative to each other while maintaining a small gap, and controlling the temperature of the pulverized grains by supplying a coolant around the concave discs so that the pulverized grains are between the pair of concave discs. Resin softened by friction but not melted when passing through the configured slit, and further densified from the slit while blowing and cooling air when discharged from the slit. <br/> From a density of 0.2 obtained by exfoliating as particles and then leading to a further cooled vessel and crushing with a rotating blade
A method for producing amorphous thermoplastic resin particles having an average particle diameter of 1.0 g / cc and an average particle diameter of 20 mm or less is disclosed and provided.

The heat-modifying additive is a halogen-based flame retardant, and the low-density thermoplastic resin foam has a density of 0.02-0.1 g / cc.
It is a normal polystyrene resin foam that is
This is a particularly preferred embodiment. In the present invention, for example, up to the point of pulverizing a polystyrene-based resin foam having a halogen-based flame retardant is the same as a conventional technique,
By controlling the temperature of a pair of concave discs rotating relatively to each other while maintaining the slit with a suitable refrigerant, the pulverized particles are softened but discharged into the air from the slit without melting, and further air is released. The method differs from the conventional method in that it is blown off toward the discharge port while spraying and cooling, and then pulverized by a rotary blade while performing final cooling in a cooled container.

Accordingly, the resin does not melt and does not come into contact with moisture, so that thermal decomposition or hydrolysis of additives such as halogen-based flame retardants does not occur, which is not only environmentally desirable but also has a molecular weight of the resin. Therefore, very high quality recycled products can be obtained. In addition, the obtained particles contained air bubbles, and the density was increased from 0.2 to 1.0 g / cc .
For those in which, compared with conventional products, not bulky, fluidity, it is also characterized by good handling characteristics.

[0009]

The present invention will be described in more detail with reference to the following examples. The present invention is carried out using a crushing device as shown in FIG. 1 as an example. The device has a cylindrical outer cylinder 1 placed in a horizontal state, and the tip (right end side in the figure) of the outer cylinder 1 is slightly conical and thin. Outer cylinder 1 has outer cylinder 1
The inner cylinder 2 is fitted coaxially with the inner cylinder 2, and the inner cylinder 2 is rotationally driven by an appropriate driving means (not shown). A helical strip 21 is attached to the outer peripheral surface of the inner cylinder 2 so as to rotate integrally with the inner cylinder 2 over substantially the entire length of the outer cylinder 1. A supply port 3 for charging a material is formed at an entrance side end (left end in the figure) of the outer cylinder 1.

A water jacket 11 fitted to the outer peripheral surface of the conical shape and having a cavity 12 therein is attached to the conical tip of the outer cylinder 1. The water jacket 1
The front end surface (right end in the figure) of 1 has a concave shape,
The outer peripheral edge forms a surface 13 perpendicular to the axis of the outer cylinder 1 and the inner cylinder 2. Then, an appropriate refrigerant, for example, water is circulated in the space 12. A plurality of projections 30 extending in the axial direction are provided concentrically on the concave shape portion, and a large number of irregularities are formed on the surface 13 in the perpendicular direction.

At the front end (right end in the figure) of the inner cylinder 2, a member 40 having a similar concave portion and surface portion 24 at a position facing the concave portion and the surface portion of the water jacket 11.
Are fixed by appropriate means. A plurality of protrusions 45 are also formed concentrically on the concave portion of the member 40 at positions close to the protrusions 30 formed on the concave surface of the water jacket, and the right-angled surface 24 is formed.
Many irregularities are also formed.

The pair of surface portions 13 and 24 face each other with the narrow gap 4 maintained. Further, two passages 22 and 22 ′ extending in the axial direction pass through the inner cylinder 2 at a substantially central portion thereof, and a member 40 fixed to the end of the inner cylinder 2 has one of the passages 22. And the circulation passage 23 connected to the other passage 22 ′ after appropriately circulating inside the member 40.
Are formed. The other ends of the two passages 22 and 22 'are connected to a coolant supply source and a reservoir (not shown) so that a coolant such as water can be circulated as appropriate.

Although not particularly shown, the outer peripheral portion of the slit 4 is covered with a hood having a required volume.
The inside of the hood can be sucked by an appropriate suction means. Further, the above-mentioned apparatus has a rotating blade (not shown) and is connected to crushing means having cooling means. The operation of this device is as follows. A resin foam, which is to be subjected to a regeneration treatment, which has been roughly pulverized outside the machine, is charged into the supply port 3 of the outer cylinder 1. The thrown-in coarse pulverized material is transported in the tip direction (right direction in the drawing) by the action of the spiral strip S provided in the inner cylinder 2 with a gap between the outer cylinder 1 and the inner cylinder 2. At the transfer tip, the pulverized material is discharged into a space formed by a concave portion at the tip of the water jacket and a concave portion formed on the member 40 provided at the tip of the rotating shaft. In this case, the pulverized material is finely pulverized by the shearing force of the two projections 30 and 45 located opposite to each other, and is also blown in the peripheral direction by centrifugal force. At the peripheral portion, the powder is further pulverized by a large number of irregularities provided thereon, and finally discharged from the slit 4 to the outside of the machine. In the meantime, the pulverized materials to be transferred and pulverized generate frictional heat by contact with each other or with equipment. In the conventional apparatus, since it was impossible to control the amount of generated frictional heat, the final step in the process of regenerating the thermoplastic resin foam, that is, the finely pulverized material inside the relatively rotating member and its fineness were removed. The resin is melted in the process of being released from the gap, resulting in deterioration of the quality of the resin itself and deterioration of the environment due to decomposition of additives as described above.

In the present invention, the means for circulating a coolant such as water as described above is provided for the purpose of controlling the amount of generated frictional heat. Therefore, by appropriately adjusting the type of refrigerant and the amount of circulation according to the type of resin, the amount of pulverization, the type of additive that is easily thermally denatured, etc., the foam to be treated is softened but not melted. It can be released from the above-mentioned slits in a state where it is pulverized by performing fine pulverization with appropriate control.

However, since the granulated particles at the moment of being released from the slit are still in a high temperature state and in a softened state, if left as they are, the granulated particles released from the slit remain in a state where they adhere to each other. It tends to be in a large lump state, and may be solidified and adhered to the device around the slit, thereby closing the slit. In the present invention, the outer peripheral portion of the slit 4 is covered with a hood having a required volume, and the inside of the hood can be sucked by an appropriate suction unit. As a result, the granulated particles released from the narrow portion receive a certain amount of cooling by the intake airflow immediately after the release, and are separated from the device as resin particles having a high density . The peeled resin particles are sufficiently cooled,
Usually, resin particles which can be sufficiently used as a recycled product can be obtained as they are.

Depending on the type of the resin or the required size of the resin particles, cooling by the intake airflow in the hood is not sufficient, and the particles may be bonded to each other after being discharged to form a mass. As another aspect of the present invention, the resin particles sucked in the hood are guided to a crushing device further having appropriate cooling means, for example, air cooling means and crushing means such as a rotary blade, to be crushed again. As a result, the resin particles that have been formed into a lump after being released from the narrow portion are again cooled and crushed immediately thereafter, whereby it is possible to obtain irregular-shaped resin particles having a desired size as a final product.

[0017]

Example 1 The illustrated apparatus was used. At this time, the surface portion 13 at the tip of the outer cylinder 1 and the surface portion 24 at the tip of the inner cylinder 2 each had a width of 5 mm, and 48 dents having a width of 5 mm and a depth of 2.5 mm were provided radially. Also, the gap between the facing surface portions was kept at 1 mm. As the foamed resin, the Br concentration is 1.1.
%, A low-density flame-retardant polystyrene resin foam having a density of 0.03 g / cc was used. This resin foam was roughly pulverized outside the machine to a particle size of about 10 mm, and supplied from the inlet 3 at a rate of 100 kg for 1 hour. The inner cylinder 2 was rotated at 1500 rotations for one minute, and the coarsely crushed particles were sent out by the spiral strip S toward the forward end. Water was circulated through the water jacket 11 of the outer cylinder and the refrigerant circulation passage of the inner cylinder to adjust the temperature to 70 ° C.

The flame-retardant polystyrene resin foam is finely pulverized by the two projections 30 and 45 located opposite to each other, and is also flung in the peripheral direction by centrifugal force. And finally discharged out of the machine from the slit 4. Under these conditions, the foam was softened but not melted. The discharged resin particles are sucked in by a blower and the diameter is 50c.
The container was guided to an air-cooled container having a height of 60 cm and a height of 60 cm, and the clumps adhering to each other were crushed again by a rotary blade provided on the bottom surface.

The resulting polystyrene resin particles have a high density
The particles were formed into irregular shaped particles having a density of 0.3 g / cc.
%, And the rest had a diameter of 20 mm or less. Further, the amount of Br remaining in the particles and the molecular weight of polystyrene were measured, as shown in Table 1 below, and it was found that the particles were superior to the conventional method (comparative example).

[0020]

Embodiment 2 The supply amount of coarsely pulverized particles was set to 70 kg for one hour, the amount of circulating water in the refrigerant passage was reduced, and the temperature of the outer cylinder and the inner cylinder was set to 80 ° C
The procedure was performed in the same manner as in Example 1, except that The obtained polystyrene resin particles were irregularly-shaped particles having a density of 0.7 g / cc, which had been further densified. According to examination of the particle size distribution by sieving, 50% of the particles had a diameter of 8 mm or less. Also had a diameter of 20 mm or less.

Similarly, when the amount of residual Br in the particles and the molecular weight of polystyrene were measured, the results are as shown in Table 1 below, and it was found that they were superior to the conventional method (comparative example). In Examples 1 and 2, during operation, generation of white smoke or pungent odor due to decomposition of the flame retardant was not observed.
In the comparative example, the same crushed granules were extruded at 200 ° C. using an extruder.
Melted into water, extruded into water as a string from a mold with many pores, and cut into pieces.At this time, near the mold, white smoke and a strong pungent odor probably caused by decomposition of the flame retardant Admitted.

[0022]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a processing apparatus suitable for use in the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder, 2 ... Inner cylinder, 3 ... Supply port, 4 ... Slot, 11 ... Water jacket, 22 ... Passage, 23 ... Circulation passage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 26

Claims (2)

(57) [Claims] 1. A low-density thermoplastic resin foam having an easily heat-modifying additive is pulverized, and the pulverized particles are supplied into a pair of concave discs rotating relatively to each other while maintaining a narrow gap. The disk is supplied with a refrigerant around the disk to control the temperature of the pulverized particles, so that the pulverized particles are softened by friction but do not melt when passing through the slit formed between the pair of concave disks. Amorphous thermoplastic with a density of 0.2 to 1.0 g / cc and an average particle size of 20 mm or less obtained by exfoliating resin particles from the slits as high-density resin while cooling by blowing air when discharged from the gap A method for producing resin particles. 2. The method for producing thermoplastic resin particles according to claim 1, further comprising a step of guiding the resin particles separated from the slits to a further cooled container and crushing them with a rotary blade.