JPH0616905Y2 - Pre-expansion device for expandable thermoplastic resin particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a prefoaming device for expandable thermoplastic resin particles.

[Conventional technology and problems to be solved]

In producing a foamed molded article from the expandable thermoplastic resin particles, usually, the expandable thermoplastic resin particles are pre-expanded to a predetermined ratio in advance, and then the pre-expanded particles are expanded in a mold to be expanded. Manufactures molded products. There are two types of methods for pre-expanding the expandable thermoplastic resin particles: a normal pressure foaming method and a pressure foaming method.

The atmospheric pressure foaming method is a method of prefoaming expandable thermoplastic resin particles under atmospheric pressure. As shown in FIG. 9, in this atmospheric pressure foaming device, the upper part of the foaming tank 1 is open to the atmosphere, and while heating the expandable thermoplastic resin particles in the foaming tank 1, heated steam is supplied from the air supply pipe 2. It is configured to blow and heat the expandable thermoplastic resin particles to foam.
Since the internal pressure of the foaming tank 1 of the atmospheric foaming apparatus is atmospheric pressure, there are no special restrictions on the structure of the foaming tank 1, the manufacturing cost of the apparatus is low, and the inside of the foaming tank 1 is cleaned. There is an advantage that the manhole door 3 can be enlarged. However, since the foaming tank is open to the atmosphere, there is a problem in that the heating temperature of the expandable thermoplastic resin particles becomes uneven and the expansion ratio varies. In particular, the lower the expansion ratio, the greater the variation in the expansion ratio, which is a drawback.

On the other hand, the pressure foaming method is a method of prefoaming the expandable thermoplastic resin particles under pressure. This pressure foaming device is the first
As shown in FIG. 0, while stirring the expandable thermoplastic resin particles in the closed structure foaming tank 4, heated steam is blown from the air supply pipe 2 under pressure to heat and expand the expandable thermoplastic resin particles. It is configured as follows. Since the pressure-foaming device has less unevenness in the heating temperature of the expandable thermoplastic resin particles, pre-expanded particles having a substantially uniform expansion ratio can be obtained. Moreover, since it is possible to foam in a short time, in recent years, the pre-foaming device is becoming the mainstream.

However, the pressure foaming device needs to use the pressure gauge 5 to control the pressure in the foaming tank 4, and to use the pressure regulating valve or the solenoid valve 7 for the air supply pipe 2 and the exhaust pipe 6, which is a pressure control device. However, there is a problem in that the cost of the device is high. Further, since the foaming tank 4 corresponds to a first-class pressure vessel depending on the pressure range used, there is a problem that the law imposes restrictions on the structure and use of the foaming tank 4 and increases the manufacturing cost. It was Moreover, since the foaming tank 4 is configured as a pressure vessel, the manhole door 8 cannot be enlarged due to legal restrictions. For this reason, it is necessary to clean the inside of the foaming tank 4 when changing the color, for example, when pre-foaming using colored resin particles in the same pressure foaming device, but inside the foaming tank 4 through a small manhole. It was very difficult to clean.

[Means for Solving the Problems]

Therefore, the inventors of the present invention have conducted extensive studies to obtain an atmospheric pressure foaming device that takes advantage of the advantages of the pressure foaming device, and as a result, have arrived at the present invention.

The gist of the present invention is that a closed-type foaming tank equipped with a stirring device, an air supply pipe for blowing a heating medium into the foaming tank, and an exhaust pipe for discharging the heating medium blown into the foaming tank. In a pre-expansion device for blowing a heating medium into the foaming tank while stirring a predetermined amount of the expandable thermoplastic resin particles contained in the foaming tank and thermally expanding the resin particles for pre-foaming. The foaming tank is always opened to the atmosphere through the exhaust pipe, and the exhaust piping is provided with an outflow resistance means for generating an outflow resistance in the exhaust gas so that the inside of the foaming tank is kept at a positive pressure. Especially.

In the pre-expansion device for expandable thermoplastic resin particles of the present invention, a pipe resistance in the exhaust pipe or an orifice plate, a baffle plate or a resistor is used as the outflow resistance means.

[Action]

According to the pre-expansion device for expandable thermoplastic resin particles of the present invention, the expandable thermoplastic resin particles are agitated by the agitating device in the closed-type foaming tank while being heated by the heating medium blown from the air supply pipe. It is heated and prefoamed. That is, the heating medium blown from the air supply pipe is filled in the closed type foaming tank to raise the temperature efficiently, and the expandable thermoplastic resin particles being stirred are heated almost uniformly to foam. After that, the heating medium is discharged from the exhaust pipe together with the gas generated from the expandable thermoplastic resin particles. The exhaust pipe is not equipped with a device for closing the pipe such as a valve, and the foaming tank is always open to the atmosphere through the exhaust piping so that the pressure in the foaming tank does not become high. On the other hand, the exhaust pipe is provided with an outflow resistance means which causes an outflow resistance to the exhausted gas, and the outflow resistance keeps the pressure in the foaming tank at a positive pressure to uniformly heat the expandable thermoplastic resin particles. Be contributed.

〔Example〕

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 10 is a foaming tank in the pre-foaming device, and a stirring device (not shown) is provided in the foaming tank 10 so that the expandable thermoplastic resin particles supplied into the foaming tank 10 are substantially uniform. It is configured so that it can be stirred and mixed. Further, the foaming tank 10 is provided with a manhole for cleaning, repairing, inspecting the inside, and the manhole is a door 12
Is closed by. This manhole and its door 1
2 does not have to be a circular one used for a pressure vessel, and a rectangular door 12 can be used as shown in the figure, so that it is easy to enter and exit the foaming tank 10. Furthermore, the foaming tank 10 is provided with an outlet for taking out the expanded pre-expanded particles, and the outlet is closed by a door 16 which is opened and closed by a cylinder 14, so that the foaming tank 10 has a closed structure as a whole. ing. The structure of the foaming tank 10 is not configured as a pressure vessel having a pressure resistant structure having a strength capable of withstanding a high internal pressure, but is configured as a container having normal strength.

An air supply pipe 18 for blowing a heating medium such as high-temperature steam into the inside of the foaming tank 10 is provided in the lower portion of the foaming tank 10 so that a constant flow rate of the heating medium can be supplied into the foaming tank 10. Has been done. On the other hand, an exhaust pipe 20 is provided in the upper part of the foaming tank 10, the inner diameter of the exhaust pipe 20 is a blown heating medium, and a foaming agent for the expandable thermoplastic resin particles thermally foamed by the heating medium. The gas generated from the foaming tank 10 is of a size that can be sufficiently discharged without increasing the internal pressure of the foaming tank 10. As shown in the figure, the exhaust pipe 20 having an inner diameter of such a size has a sufficiently long pipe extending from the upper part to the lower part of the foaming tank 10. The length of the exhaust pipe 20 is set so that the internal pressure in the foaming tank 10 is maintained at a positive pressure as a gauge pressure due to the outflow resistance of the gas flowing out of the exhaust pipe 20. Internal pressure in the foam tank 10 may When set to, for example, 0.005~0.04kg / cm ^2, more preferably is exemplified 0.01~0.03kg / cm ^2, most preferably the commonly frequently used 0.015 kg / cm ² about the front and rear This is a setting, and at least a pressure value at which the foaming tank 10 is not recognized as a first-class pressure vessel is selected, and the internal pressure of the foaming tank 10 is set to a predetermined pressure value by adjusting the length of the exhaust pipe 20.

In the pre-foaming device having such a configuration, the expandable thermoplastic resin particles supplied into the foaming tank 10 are heated by the heating medium blown from the air supply pipe 18 while being stirred by the stirring device to be foamed. The heating medium blown from the air supply pipe 18 almost uniformly fills the foaming tank 10 having a closed structure to efficiently and quickly raise the temperature in the foaming tank 10 so that the foaming heat is generated so that there is no temperature unevenness. The plastic resin particles are heated and discharged from the exhaust pipe 20. The gas generated from the expandable thermoplastic resin particles that are heated and foamed by the heating medium is discharged from the exhaust pipe 20 together with the heating medium. Due to the outflow resistance generated when the discharged gas passes through the long exhaust pipe 20, the pressure in the foaming tank 10 is maintained at a slightly positive pressure and a heated foaming with little temperature unevenness is ensured. It is possible to obtain pre-expanded particles having a substantially uniform particle size with a small expansion ratio.

Further, in operating the pre-foaming device, the pressure in the foaming tank 10 may be measured and controlled, but such a device is costly, so it is convenient not to equip it. The pre-foaming device according to the present invention does not need to perform such control exactly, and the internal pressure of the foaming tank 10 is the exhaust piping
The outflow resistance at maintains a pressure slightly above atmospheric.

Although the embodiments of the present invention have been described in detail above, the present invention can be implemented in other forms.

For example, since the outflow resistance in the pipe is directly proportional to the length of the pipe, a U-shaped pipe 24 is provided in a part of the exhaust pipe 22 as shown in FIG.
The outflow resistance may be changed by sliding with respect to 2 and changing the length of the exhaust pipe 22. Thereby, the pressure in the foaming tank 10 can be changed. Alternatively, a bellows type pipe may be provided in place of the U-shaped pipe 24, and the length of the bellows type pipe may be changed to adjust the outflow resistance.

Further, since the outflow resistance of the pipe is increased by the bent pipe, it is also possible to increase the outflow resistance by inserting an appropriate number of bent pipes 28 in a part of the exhaust pipe 26 as shown in FIG. Is.

Further, as shown in FIG. 4, an orifice plate 32 is constructed so that it can be inserted into the exhaust pipe 30, and the size of the orifice of the orifice plate 32 is appropriately changed to change the outflow resistance of the exhaust gas. The internal pressure may be maintained at a desired positive pressure. The number of the orifice plate 32 provided in the exhaust pipe 30 is not limited to one, and may be appropriately inserted in two or more places as shown in FIG.

Further, as shown in FIG. 6, a baffle plate 34 can be inserted into the exhaust pipe 36 in place of the orifice plate 32, and the baffle plate 34 blocks the flow of exhaust gas in the exhaust pipe 36 to prevent gas outflow resistance. It is also possible to increase. The baffle plate 34 may be provided at only one place, but as shown in FIG. 7, it may be provided at a plurality of places in the exhaust pipe 36.
In this case, the baffle plate 34 is preferably arranged so as to alternately block the flow of the exhaust gas in the exhaust pipe 36.

Besides, in order to increase the outflow resistance of the exhaust gas in the exhaust pipe, as shown in FIG. 8, a plate-shaped or rod-shaped resistor 38 may be inserted into the exhaust pipe 40.

As described above, the outflow resistance of exhaust gas can be increased by interposing a bent pipe, an orifice plate, a baffle plate, or a resistor having various shapes in a part of the exhaust pipe. As a result, the pressure in the foaming tank 10 can be adjusted to a desired value at a value slightly higher than the atmospheric pressure, and the length of the exhaust pipe can be shortened.

The length of the bent pipe, the orifice plate, the baffle plate or the resistor or the exhaust pipe arranged in the exhaust pipe may be fixed after the internal pressure of the foaming tank is set in advance, but the length of the expandable thermoplastic resin particles It may be appropriately set depending on the type, the temperature of the heating medium, the blowing amount, or the like.

In addition, the present invention can be implemented in a form in which various improvements, modifications and variations are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[Effect of device]

The exhaust pipe in the pre-foaming device of the present invention is sufficiently equipped with the heating medium blown into the foaming tank and the gas generated from the expandable thermoplastic resin particles heat-foamed by the heating medium without increasing the internal pressure of the foaming tank. The size of the foaming tank is set to a positive pressure by the outflow resistance of the exhaust gas without the use of a device such as a valve to block the pipeline in the exhaust pipe. Therefore, the foaming tank can be configured with the same structure as the conventional atmospheric pressure foaming tank. That is, since the foaming tank according to the present invention is not a first-class pressure vessel, there is no structural restriction by law, it can be manufactured at low cost, and the manhole can be enlarged. Makes cleaning easier.

In addition, since the foaming tank according to the present invention has a closed structure, the heating medium blown from the air supply pipe is filled into the foaming tank without the outside air flowing in, and the temperature in the foaming tank is efficiently and quickly increased. Can be increased almost uniformly, and pre-expanded particles having a substantially constant expansion ratio can be obtained, and foaming with a high expansion ratio is also possible.

Further, since the pre-foaming device according to the present invention does not require pressure control for measuring and controlling the pressure in the foaming tank, the equipment cost is low and there is no failure of the control equipment, and stable operation is possible. The present invention has an excellent effect.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining a pre-expansion device for expandable thermoplastic resin particles according to the present invention. 2 to 8
Each of the drawings is a view for explaining another embodiment of the outflow resistance means used in the present invention, FIG. 2 is a cross-sectional view of a main part showing an example in which the length of the pipe is variable, and FIG. FIG. 4 is a sectional view showing an example using a bent pipe, FIG. 4 is a sectional view showing an example using an orifice plate, FIG. 5 is a side view showing an example using a plurality of orifice plates, and FIG. FIG. 7 is a sectional view showing an example using a plate, FIG. 7 is a side sectional view showing an example using a plurality of baffle plates, and FIG. 8 is a sectional view showing an example using a resistor. FIG. 9 is an explanatory view showing a conventional atmospheric pressure foaming tank,
The figure is an explanatory view showing a conventional pressure foaming tank. 10; Foaming tank 12; Manhole door 18; Air supply pipe 20, 22, 26, 30, 36, 40; Exhaust pipe 24; Pipe (outflow resistance means) 28; Curved pipe (outflow resistance means) 32; Orifice plate (outflow Resistance means) 34; Baffle plate (outflow resistance means) 38; Resistor (outflow resistance means)

Claims (2)

[Scope of utility model registration request] 1. A closed type foaming tank provided with a stirring device, an air supply pipe for blowing a heating medium into the foaming tank, and an exhaust pipe for discharging the heating medium blown into the foaming tank. In a pre-foaming device for blowing a heating medium into the foaming tank while stirring a predetermined amount of the expandable thermoplastic resin particles contained in the foaming tank to heat-expand the resin particles for pre-foaming, the exhaust pipe The foaming tank is constantly opened to the atmosphere via the air outlet, and outflow resistance means for causing outflow resistance to the exhaust gas is provided in the exhaust pipe so that the inside of the foaming tank is maintained at a positive pressure. Pre-expansion device for expandable thermoplastic resin particles. 2. A pre-expansion device for expandable thermoplastic resin particles, wherein pipe resistance in the exhaust pipe or an orifice plate, a baffle plate, a resistor or the like is used as the outflow resistance means.