JPS5850181B2 - Pre-expanding device for expandable thermoplastic resin particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for pre-foaming expandable thermoplastic synthetic resin particles.

Conventionally, foamed resin particles are placed in a foaming tank and heated steam is ejected from the bottom of the foaming tank to create foam, but since the foaming tank is a tall piece of equipment, there is uneven distribution of the heating medium.
There was a problem in that temperature unevenness occurred, the foaming rate of the expanded particles was not averaged, and the particle diameters varied in size.

In addition, volatile gases are emitted from the resin particles and remain in the foaming chamber, and some of the steam condenses in the foaming chamber, making it easier for the resin particles to bond into a solid state, impeding the smoothness of the work. There was a problem.

The present invention allows a heating medium to flow through the foaming chamber to foam the resin particles, and at the same time circulates air inside the foaming chamber to make the internal temperature of the foaming chamber uniform and prevent dew condensation and volatilization within the foaming chamber. It is an object of the present invention to provide a pre-foaming device that can prevent gas filling and produce resin particles of uniform particle size with a uniform expansion ratio.

In the following explanation, steam is used as the heating medium, but
Of course, heated air, hot water, etc. can also be used in the same way.

In the present invention, the expandable thermoplastic resin particles include, for example, polystyrene, copolymers of styrene and a-methylstyrene, chlorstyrene, acrylonitrile, acrylic acid, etc., polyolefins such as polyethylene, polypropylene, etc. Plastic resin particles contain blowing agents such as aliphatic hydrocarbons such as propane, butane, pentane, and hexane, and aliphatic halogenated hydrocarbons such as methyl chloride and dichlorodifluoromethane.

In addition, the shape of the particles can be any shape, but
In particular, spherical ones are most preferably used.

The drawing shows, as an example, a situation in which the present invention is implemented in a pre-foaming device in which a certain amount of particles are introduced into a foaming tank, foamed, and then taken out.
0, a constant weight is measured by a measuring device 12, and the foam is introduced from the upper part of the foaming tank 18 through the inlet 14 by the air cylinder 16.

The foaming tank 18 has a straight cylindrical shape and has an outlet 20 at its lower part, a lid 22 is pivotally fixed to the upper part of the outlet, and the lid 22 is connected to an air cylinder 24 to be opened and closed.

Further, a motor 26 is installed on the upper part of the foaming tank 18, and a rotating shaft 28 connected to the motor is suspended from the center of the foaming tank 18, and is supported by extending to the bottom plate 38 of the tank.

Stirring blades 30 are protruded in multiple stages from the rotating shaft 28, and fixed blades 32 are protruded from the wall of the foaming tank 18 toward the middle height of the stirring blades 30 to stir the foamed particles inside and remove the lumps. Trying to prevent formation.

Inside the foaming tank 18, a phototube, a microswitch, etc. is used to detect the presence of the foaming layer at a position corresponding to the upper surface of the foaming layer when a fixed amount of particles introduced are expanded to a set expansion ratio.
A first detector 78 that stops the ejection of the heating medium and a second detector 80 that reduces the bubbling speed by reducing the ejection amount of the heating medium are provided slightly below the first detector 78.
8.80 can be installed at a height that can be adjusted on the wall of the foaming chamber to accommodate changes in foaming ratio and foaming capacity settings.

An exhaust port 34 is provided in the upper part of the foaming tank 18 and connected to an exhaust device 36 such as an exhaust blower to discharge volatile gas generated inside the foaming tank and circulate air to prevent condensation inside the foaming tank. At the same time, the temperature difference of the steam between the lower part and the upper part is made as small as possible.

On the bottom plate 38 of the foaming tank 18, a perforated plate 41 having a slit-shaped jet port 40 is disposed as shown in FIG. 3, and communicates with a steam chamber 42 provided below the perforated plate 41.

A first steam nozzle 44 and a second steam nozzle 46 are installed in the steam chamber 42 and are connected to a main steam pipe 58 via steam pipes 48 and 50, respectively.
have a gauge 52, a throttle valve 54, and an on-off valve 56 and 57, respectively.
The on-off valve 56 of the first steam pipe 48 is connected to the first detector 7.
The opening and closing valve 5 of the second steam pipe 50 is controlled to open and close in conjunction with the valve 5 of the second steam pipe 50.
7 is connected to the second detector 80 and controlled to open and close.

Therefore, when the foam layer rises and reaches the second detector 80, the on-off valve 57 is activated to stop the steam jetting from the second steam nozzle 46, and then when the foam layer reaches the first detector 78, the on-off valve 57 is activated. 56 stops the steam ejection from the first steam nozzle 44.

Furthermore, a drain pipe 60 is connected to the lower part of the steam chamber 42 to discharge the drain accumulated in the steam chamber 42, and an air nozzle 62 is installed in the steam chamber 42, and an air pipe 64 is connected to the nozzle 6.
2, and an air supply device 68 such as an air compressor is provided upstream of the air pipe 64 via a valve 66 so as to blow air into the steam chamber 42 from small holes opened along the entire length of the air nozzle 62. Eggplant.

A plurality of drain plates 70 each having a drain lower 2 are further provided around the bottom plate 38, and each drain plate 70 is provided with a drain chamber 74 at the lower part of the bottom plate, and the drain collected on the bottom plate 38 is drained from the drain plate. 70, the water is discharged to the outside through a drain pipe 76.

First, a fixed weight of foamed particles is introduced from the inlet 14, and the agitating blades 30 agitate the particles due to the rotation of the rotating shaft 28. At the same time, compressed air is ejected from the air nozzle 62, and the air is ejected from the air outlet 40 of the perforated plate 41. Air is circulated within the foaming chamber through this process.

When flowing into the two steam pipes 4B and 50, a mixed flow of a large amount of steam and air from the air nozzle 62 is ejected into the foaming chamber, passes through the gaps between the particles, and flows upward while rapidly heating the particles. , and are attracted to the exhaust device 36 and discharged outside.

Particles in the foaming chamber begin to heat and foam due to the flow of steam,
Rapid foaming and expansion is carried out while being stirred by stirring blades 30 and fixed blades 32, and the upper surface of the foam layer gradually rises within the foaming chamber.

At this time, since the foamed layer is constantly stirred by the fixed blades 32 and stirring blades 30, the formation of lumps can be almost completely prevented.

Furthermore, even if the steam condenses in the foaming chamber and generates moisture, the air ejected from the air nozzle 62 flows upward within the foaming chamber and is discharged from the exhaust port, so that moisture does not remain in the foaming chamber. Moreover, since there is a constant flow of steam, the temperature difference between the lower and upper parts of the foaming chamber is about 1°C, and uneven heating hardly occurs.

Further, condensed water generated on the upper surface of the perforated plate 41 is forcibly discharged from the drain lower 2 on the outer periphery to the drain chamber 74, thereby preventing moisture from accumulating on the perforated plate 41.

The amount of steam ejected can also be similarly controlled by half-closing the on-off valve of one or more steam nozzles by the operation of the second detector 80 and fully closing by the operation of the first detector 78. It can be implemented.

Furthermore, it is possible to leave the first detector 78 and omit the second detector 80. In this case, the foam layer rapidly expands to the height of the first detector 78, and the detector 78 is activated. When the on-off valves 56 and 57 are closed all at once, and the steam stops, inertial expansion is performed and the steam gradually attenuates until it stops.

However, since the time from when the steam supply stops until the foaming stops is determined experimentally to be approximately constant, if the height of the first detector 78 is set appropriately, the particles can be foamed to the set foaming ratio. .

As described above, in the present invention, since air is circulated in the foaming chamber at the same time as the heating medium is ejected, the temperature in the foaming chamber becomes uniform, and expanded particles having a uniform particle size can be obtained.

Moreover, it is possible to prevent volatile gases from remaining in the foaming chamber and from condensation of steam, allowing safe and smooth work.

Furthermore, since the drain lower 2 is provided on the bottom plate, there are many excellent advantages such as no condensed water collecting on the bottom plate.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of the device used to carry out the present invention, Figure 2 is a cross-sectional view taken along line M-n in Figure 1, and Figure 3 is an enlarged view of part (3) in Figure 1. be. 14... Input port, 18... Foaming tank, 2
0...Outlet port, 34...Exhaust port, 36
...Exhaust device, 38...Bottom plate, 40.
...Ejection port, 42...Steam chamber, 62...
... Air nozzle, 68 ... Air supply device.

Claims (1)

[Claims] 1 It has a built-in stirring device, has an input port 14 for foamable thermoplastic resin particles at the top, and an output port 20 at the bottom, and has a heating medium jet port 40, 40 in the bottom plate 38, and is opposite to the jet port. In a pre-foaming device equipped with a chamber 42 into which a heating medium flows below the foaming tank, an exhaust port 34 is provided at the top of the foaming tank 18.
The foaming tank 1 is opened by connecting the exhaust device 36 to the exhaust port.
Nozzles 44 and 46 for ejecting a heating medium such as steam and air nozzles 62 for ejecting air together with the heating medium from the ejection ports 40 are disposed below the bottom plate 38 of No. 8.
A pre-foaming device for expandable thermoplastic resin particles is equipped with a drain lower 2.