JPS5935926A - Production of pre-expanded beads - Google Patents

Abstract

PURPOSE:To obtain pre-expanded beads coated with a coating chemical, by a method wherein a chemical to be applied to resin beads is supplied into a hollow part of a distributor provided in a foaming tank, and the chemical is sprinkled to the resin beads contained in the tank. CONSTITUTION:A solenoid valve 32 and a pump 34 are provided at intermediate parts of a supplying pipe 30 for the chemical sequentially from a distributor 13 side, and a solenoid valve 35 for supplying pressurized air to a measuring container 33 and a check valve 36 are provided. The valve 32 is closed, and a predetermined quantity of the chemical is fed from a chemical tank 31 to the measuring container 33 by the pump 34. Then, the valve 32 is opened, a solenoid valve 35 for pressurized air is changed over to the air side, whereby pressurized air is fed into the container 33 to pressurize the chemical and to feed the chemical into the hollow part 17 of the distributor 13 through the supplying pipe 30, and the chemical is sprinkled to the thermoplastic resin beads contained in the tank through small holes 18. Accordingly, pre-expanded beads coated with optimum quantity of the chemical are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pre-expanded particles, and particularly aims to provide a method suitable for obtaining pre-expanded particles uniformly coated with various coating agents.

Conventionally, foamable resin particles used in so-called foam molding, in which foamed resin particles such as foamed polystyrene are heated and foamed to obtain foamed molded products, are heated and expanded in advance in a foaming tank as appropriate, and are coated with each [i agent]. The use of pre-expanded particles is widely practiced.

The above-mentioned chemicals are intended to shorten the opening time during cooling after molding, improve moldability, etc., and contain paraffin oil, polyethylene wax, etc. as ingredients.

However, the conventional method of coating the above-mentioned chemicals using a blending device before pre-foaming requires extra labor and equipment for the blending process, and the coated expandable resin particles If the foaming is left without immediate pre-foaming treatment, the coated agent may deteriorate or the foamable resin particles may block each other.

For this reason, it has been considered to introduce and mix chemicals at the feeder or hopper outlet of the expandable resin particles in the pre-foaming process, but it is difficult to uniformly coat the entire expandable resin particles, and further improvements are needed. It was wanted.

Therefore, in the method of this invention, the drawbacks of the conventional method of coating the expandable resin particles with a drug are solved,
We have developed a method for producing pre-expanded particles that enables more uniform and efficient coating.The method involves feeding expandable thermoplastic resin particles into a foaming tank and heating the resin particles while stirring. In the method of manufacturing pre-expanded particles by heating and foaming with a medium, a chemical to coat the resin particles is supplied into the hollow part of a baffle rod provided in a foaming tank, and the agent is supplied into the foaming tank through a large number of small holes formed in the baffle rod. It is characterized by spraying the chemical onto the resin particles.

Next, embodiments of the present invention will be illustrated below with reference to the drawings.

+1) indicates the main body of the prefoaming device, of which (lO)
is a foaming tank, (ll) is a stirring blade attached to the central shaft passing through the foaming tank (lO), and a drive unit such as a motor 02)
It is rotatable at . (+3) is a baffle stick,
Stirring blades (II) alternate with multi-stage stirring blades (++)
It is fixedly attached to the outer wall of the foaming tank (lO) across the inside of the foaming tank (lO) at a position that does not come into contact with the foaming tank (lO) or the central axis. Next, the foaming tank (at the top of 101, (3) is a magic loader,
A) is a resin receiving hopper, (5) is a weighing hopper,
Magic loader (foundation) uses expandable resin particles as raw material
), the materials are appropriately sucked up from the raw material supply section and dropped into a resin receiving hopper system, and after the necessary amount of foamable resin particles are weighed with a weighing hopper, they are dropped and supplied into a foaming tank 1till. After the pre-foaming, the pre-foamed particles are stored in a foaming tank (l
O) It is designed to be collected outside the foaming tank (10) from the lower take-out part (14). Also 05) is a foaming tank (10)
This is a steam chamber installed at the bottom. Steam as a heating medium is introduced into this steam chamber (+6), and the steam chamber (+5) and foaming tank (l
Steam is ejected between the foamable resin particles in the foaming tank (10) through a perforated plate 06) provided at the boundary with the foaming tank (10) to heat and foam the resin particles (see Fig. 1).

Regarding the basic structure of the above-mentioned pre-foaming device, 4J% has a structure that is almost the same as a conventional batch-type pre-foaming device, and as a pre-foaming device, the pre-foaming device completes pre-foaming while continuously supplying foamable resin particles as a raw material. The present invention can also be applied to a continuous type pre-foaming device that can sequentially recover the pre-foamed particles from the foaming tank.

A feature of this invention is that a hollow portion 07) is formed in the central axis portion of the baffle rod θ4, and the baffle rod O is formed from this hollow portion αη.
A large number of small holes +181 are bored on the lower surface of the a+ and are concave into the foaming tank (lO). Also, it is a drug supply pipe connected to a baffle rod (attached to one end of the l port, - indicates a hollow portion θ) exposed outside the foaming tank (lO), and is connected to a drug tank (310).

In the structure of the baffle bar, the hollow part (17) and the small hole 08
11 may be formed over the entire length of the baffle bar (1" 4), but this is because most of the foamable resin particles are located near the outer circumference in the foaming tank 11 due to the centrifugal force caused by the stirring action. As shown in the figure, it is preferable that the hollow part 07) and the small hole α barrel are formed only near the end of the baffle bar 03), since the resin particles can be coated sufficiently.

Further, the small holes θ fathom can be formed not only on the lower surface of the baffle bar but also on the side surface and the upper surface.

The size of the small holes can be set to a size that does not allow resin particles to pass through, for example, about 0.4 to 0.5 ff, and one baffle rod (for example, 20 to 3
Although this is carried out by forming 0 small holes (Ill), various changes may be made depending on the conditions such as the type of drug and foamable resin particles, the amount of drug supplied, or the amount of resin particles.

Further, the overall shape of the baffle bar (+1) can be cylindrical, prismatic, etc.

Furthermore, multiple baffle bars 0@ were installed inside the foaming tank (10).
Among them, the hollow part a′? )-b and small hole α barrel can be formed with only one bar such as the bottom part, but if necessary, an appropriate number of baffle bars or all baffle bars may be formed.
A hollow part (17) or a small hole may be formed in the field to enable the spraying of the medicine.

Next, in the illustrated embodiment, solenoid valves 0'4, needle plate container, and
In addition, - is a solenoid valve for supplying pressurized air to the measuring container, - is a check valve, and a method for supplying medicine using the measuring container, etc. To explain this, first, the solenoid valve is closed and a pump is used to deliver a fixed amount of medicine from the medicine tank to the measuring container.At this time, the solenoid valve is set to the atmosphere open side. Next, by opening the solenoid valve 0 and switching the pressurized air solenoid valve (9) to the air side, pressurized air is sent into the measuring container 3) to pressurize the drug and release it into the supply pipe. The medicine is supplied into the hollow part 07 at the end of the baffle rod after being inspected.

According to the drug supply method using the above mechanism, the amount of the drug to be supplied can be accurately measured and coated on the expandable resin particles, which is convenient for obtaining pre-expanded particles that have been optimally coated without excess or deficiency. be.

However, the method for supplying the drug is not limited to the above embodiments, and various known mechanisms and methods can be employed as long as they can supply a certain amount of the drug. Further, when a continuous type device is used instead of a batch type device as a pre-foaming device, a constant amount of the chemical may also be continuously supplied.

As the agent used in this invention, various known agents that have been used in the past, such as molding cycle-up agents, pre-foaming block inhibitors, and fusion promoters, can be freely used, and their ingredients include paraffin oil and polyethylene Consists of wax and other materials.

The timing for dispersing the chemical into the foaming tank (10) is after a certain amount of foamable resin particles have been supplied into the foaming tank (10), and then the chemical is sprayed from the small hole (I → A method of spraying between resin particles and then heating with steam, or a method of spraying a chemical while supplying resin particles and then heating with steam, or a method of supplying resin particles and then heating with steam while spraying a chemical. Any method can be used, such as starting the process.

According to the method of the present invention configured as described above, since the agent is coated on the foamable resin particles in the pre-foaming tank (10), the equipment cost and work time required for the conventional blending device and blending process can be reduced. , it is possible to obtain pre-foamed particles coated with a drug efficiently and at low cost, and at the same time, it does not cause deterioration of the quality of the resin particles such as deterioration of the drug during the period between the blending process and the pre-foaming process. It will be very convenient.

Moreover, in the foaming tank (10), a hollow part θη is provided inside the baffle bar 03) used for stirring action, and the chemical is supplied to this hollow part, and a small hole θ8 formed in the baffle bar (13) is provided. ) into the foaming tank (lO), the sprayed chemicals are immediately stirred and mixed with the resin particles as the stirring blade (0) rotates, and the chemicals are evenly distributed over the entire resin particles. This means that it can be coated.

Therefore, compared to the method of dispersing chemicals in a hopper or screw feeder before supplying the resin particles to the foaming tank (10), the stirring and mixing is more reliable, resulting in a much more uniform coating and higher quality. Pre-expanded particles can be produced, and concerns about blocking due to uneven distribution of chemicals can be completely eliminated.

Furthermore, as is clear from the above description, there is no need for any special blending mechanism, and the method of the present invention can be carried out by only slightly improving the baffle bar (l). It is also easy to modify and use the foaming device.

Furthermore, since no extra processing time is required for spraying chemicals, it is a very effective method for streamlining the entire molding process, and is a method for producing high-quality pre-expanded particles efficiently and at low cost. It has excellent advantages.

[Brief explanation of drawings]

The figures illustrate an embodiment of the present invention, and Fig. 1 is a partially cutaway front view of the entire prefoaming device, and Fig. 2 is the previous I.
A sectional view taken along the line I-II, and FIG. 3 is a schematic diagram of the drug supply mechanism. ■... Pre-foaming device main body, +fil+... Foaming tank,
(1st...stirring blade, vehicle...obstruction bar, 07)...
Hollow part, (18)...small hole, (30)...drug supply pipe, 01)...drug tank, (33)...measuring container.

Claims (1)

[Claims] 1. In a method of producing pre-expanded particles by supplying expandable thermoplastic resin particles into a foaming tank and heating and foaming the resin particles with a heating medium while stirring, the inside of the hollow part of a baffle rod provided in the foaming tank is A method for producing pre-expanded particles, which comprises supplying a chemical to coat resin particles to a baffle rod, and dispersing the chemical onto the resin particles in a foaming tank through a large number of small holes formed in a baffle rod.