JPH0412211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for cooling a molded article from the inside by injecting liquefied carbon dioxide gas into a synthetic resin blow molding apparatus.

<<Prior Art>> Generally, in a blow molding apparatus, a molded product is cooled from the outside by circulating a coolant such as cooling water within a mold. For this reason, since the molded product is cooled on one side, the cooling rate is slow, and the mold occupancy time becomes long, resulting in low production efficiency.

Therefore, some molded products are cooled from the inside by injecting liquefied carbon dioxide during blow molding. As shown in FIG. 5, a liquefied carbon dioxide gas supply path L is led out from a liquefied carbon dioxide gas storage tank T, and the tip of this liquefied carbon dioxide gas supply path L is passed through a blowing branch path P to a blow molding machine. A configuration in which a flow meter M is interposed in the branch path P, and a constant flow rate of liquefied carbon dioxide gas is blown for a certain period of time by detecting the supply amount with the flow meter M. It was becoming.

<<Problem to be solved>> However, in this case, when the remaining amount of liquid in the liquefied gas storage tank T decreases as liquefied carbon dioxide gas is used, the vapor pressure balance in the storage tank T collapses and the liquefied carbon dioxide gas Vaporization is activated and the liquid temperature decreases. For this reason, even if a fixed amount of liquefied carbon dioxide is injected into the molded product for a set amount of time, the temperature of the supplied liquid will fluctuate, causing the latent heat of vaporization and sensible heat of the liquefied carbon dioxide to fluctuate, making the cooling rate inconsistent. . For this reason, the amount of liquefied gas supplied must be set based on the state of high liquid temperature, which not only wastes the thermal energy of the liquefied gas, but also increases the time that the mold is occupied, and the production line There is a problem in that the operating speed is also slow and production efficiency is low.

Furthermore, since the liquefied gas supply system is configured in an open loop, the liquefied gas is vaporized in the supply path due to the intrusion heat acting on the liquefied gas supply system from the outside, and this vaporized gas becomes liquefied gas. This will cause the mixture to pass through the flow meter, resulting in an error in the amount of liquefied gas supplied. This results in a decrease in production efficiency.

<Means for Solving the Problems> The present invention is configured to send liquefied gas at constant temperature and pressure in an amount larger than the amount consumed by the blow molding machine, and send excess liquefied carbon dioxide gas back to the liquefied carbon dioxide storage tank. The liquefied carbon dioxide gas to be supplied to the blow molding machine is supplied in a fixed amount at constant temperature and pressure.For this purpose, the liquefied carbon dioxide storage tank and the blow molding machine are connected to the liquefied carbon dioxide supply path and the liquefied carbon dioxide return path. The liquefied carbon dioxide gas flow path is connected in a closed loop with the liquefied carbon dioxide gas flow path, and a liquid feeding pump is placed in the liquefied carbon dioxide gas flow path, and the discharge amount from the delivery pop is adjusted to the amount of liquefied carbon gas consumed by the blow molding machine. The feature is that the liquefied carbon dioxide gas is circulated at a rate of 5 times or more.

<<Operation>> In the present invention, since the liquefied carbon dioxide gas flow path is formed in a closed loop to circulate the liquefied carbon dioxide gas, there is a possibility that the liquefied carbon dioxide gas may be gasified in the piping system due to the influence of heat intrusion from the outside. However, the gas components will flow into the liquefied gas return path along with the circulating liquid flow, and the gas will not enter the equipment used, and a certain amount of liquefied gas will be sent to the equipment in its liquefied state. Become. Moreover, since a liquid pump is placed in the liquefied carbon dioxide gas supply path, liquefied carbon dioxide gas is supplied to the blow molding machine at a constant pressure, regardless of pressure fluctuations in the liquefied carbon dioxide gas storage tank. A certain amount of liquefied gas will be supplied to the blow molding machine.

<<Example>> Fig. 1 shows a flowchart in the case where liquefied gas is supplied into the interior of a blow-molded synthetic resin product and used as a cooling medium.

This liquefied gas quantitative supply device supplies liquefied carbon dioxide extracted from a liquefied carbon dioxide storage tank 1 into a blow molding machine 2, and uses the heat of vaporization of the liquefied carbon dioxide to cool a resin molded product from inside. The liquefied gas flow path 3 is configured to supply a fixed amount of liquefied carbon dioxide gas, and the liquefied gas flow passage 3 is connected to the liquefied gas supply path 4 led out from the bottom of the liquefied carbon dioxide storage tank 1 and the liquefied gas supply path 4 that communicates with the upper part of the liquefied carbon dioxide storage tank 1. The return path 5 forms a closed loop. A branch pipe 6 branched from the liquefied gas supply path 4 is connected to a nozzle 8 of the blow molding machine 2.
It is connected to the liquefied gas usage section. A liquid feed pump 9 is disposed in the middle of the liquefied gas supply path 4, and the flow rate of the liquefied gas flowing through the liquefied gas supply path 4 is controlled by a flow rate control valve 10 disposed downstream of the liquid feed pump 9. The flow rate is set to be 5 to 15 times the amount of liquefied gas consumed by the blow molding machine 2. Here, the flow rate of liquefied carbon dioxide is 5 times to 15 times the consumption amount.
The reason for doubling the amount is to ensure that the pressure of the circulating liquefied carbon dioxide gas is not affected by the pressure drop due to consumption of the liquefied carbon dioxide gas or the heat input in the piping system, and so that no economic disadvantage occurs.

On the other hand, the liquefied gas return path 5 is communicated with the liquefied carbon dioxide storage tank 1 via the heat exchanger 11, and the return liquid flowing through the return path 5 is cooled in the heat exchanger 11, and then the liquefied carbon dioxide It is designed to be released in a shower-like manner in the gas phase at the upper part of the storage tank 1. Therefore, a gas-liquid equilibrium state is maintained within the storage tank 1, so that liquefied carbon dioxide gas at a constant temperature and constant pressure is obtained within the storage tank 1.

As a result, most of the liquefied carbon dioxide extracted from the liquefied carbon dioxide storage tank 1 is circulated through the gas flow path 3. In this case, the liquid temperature of the liquefied gas returned to the liquefied gas storage tank 1 is controlled by the heat exchanger 11 so as to be equal to the liquid temperature led out from the liquefied gas storage tank 1.

The heat exchanger 11 uses Freon R22 as a refrigerant, cools the return liquid with this refrigerant, condenses the gas components mixed in the return liquid, and transfers it to the liquefied carbon dioxide gas storage tank 1 in a gas-free state. It is configured to return. The refrigerant that has undergone heat exchange in the heat exchanger 11 is condensed in a refrigerator 12 and is sent into the heat exchanger 11 again.

A branch pipe 6 branched out from the liquefied gas supply path 4
As shown in Figure 2, stainless steel bellows tube 1
The outer surface of the nozzle 3 is covered with a rubber heat insulating layer 14, and the outer surface of the rubber heat insulating layer 14 is covered with a mesh body 15, so that the nozzle 8 can be moved up and down. Further, this branch pipe 6 is formed such that its cross-sectional area becomes smaller as it goes from the outlet base side to the outlet end side. By configuring each branch pipe 6 in this way, even if liquefied carbon dioxide gas is vaporized in the branch pipe 6 and a gas component is generated, the vaporized gas component can escape to the liquefied gas supply path 4 side. No more flowing into the molding machine.

In the liquefied gas quantitative supply device having the above configuration, the liquid feeding pump 9 is disposed in the liquefied gas supply path 4, and a cooling device (heat exchanger) is disposed in the liquefied gas supply system. It is possible to supply a fixed amount of liquefied gas at constant temperature and pressure to gas-using equipment, and maintain the retained heat amount constant.

Additionally, the flow rate of the liquefied carbon dioxide gas flowing through the liquefied carbon dioxide gas flow path is ~5 times the consumption amount in the blow molding machine 2.
15 times, the pressure fluctuation due to liquefied carbon dioxide consumption in the blow molding machine is so small that it can be ignored.
Further, since vaporized gas is also removed by the large flow of liquefied carbon dioxide gas, no gas-containing liquid is supplied into the blow molding machine.

As a result, the liquefied gas supplied to the blow molding machine is kept at a constant temperature, constant pressure, and fixed amount, and its heat content is also stabilized.

<<Effects>> In the present invention, when supplying liquefied carbon dioxide gas to a blow molding machine to cool the molded product from the inside, the liquefied carbon dioxide supply system is formed into a closed loop, and a liquid feeding pump is arranged in the liquefied gas supply path. Since the flow rate of liquefied carbon dioxide flowing through the liquefied gas flow path is set to more than five times the consumption amount in the blow molding machine, liquefied carbon dioxide gas at a constant pressure is supplied to the blow molding machine. Moreover, the gas vaporized in the piping is sent back to the liquefied carbon dioxide storage tank without flowing into the blow molding machine, so it is guaranteed that a certain amount of liquefied carbon dioxide is in a liquid state in the blow molding machine. This makes it possible to keep the cooling rate constant. As a result, the blow-molded product can be properly cooled, and since the cooling time is stabilized, the operating efficiency of the mold can be increased and the product can be molded with high efficiency. Furthermore, since the molding time in the blow molding machine is stabilized, the operating efficiency of the entire production line can be increased, and production efficiency can be increased.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an apparatus for carrying out the method of the present invention;
FIG. 2 is a longitudinal sectional view of a branch pipe, and FIG. 3 is a flowchart of a conventional example. 1...Liquefied carbon dioxide storage tank, 2...Blow molding machine,
3... Liquefied carbon dioxide gas flow path, 4... Liquefied carbon dioxide gas supply path, 8... 2 nozzles, 9... Liquid sending pump.

Claims (1)

[Claims] 1 Connect the nozzle 8 of the blow molding machine 2 in a branched manner to the liquefied gas flow passage 3 led out from the bottom of the liquefied carbon dioxide gas storage tank 1, and connect the terminal end of the liquefied carbon dioxide gas flow passage 3 to the liquefied carbon dioxide storage tank 1. The liquefied carbon dioxide gas supply system is configured as a closed loop by communicating with each other, and the liquid sending pump 9 is disposed in the liquefied carbon dioxide gas supply path 4 between the liquefied carbon dioxide gas storage tank 1 and the blow molding machine 2.
A liquefied carbon dioxide gas injection cooling method for blow molding, characterized in that the liquefied carbon dioxide gas flow rate in the liquefied carbon dioxide gas supply path 4 is set to be five times or more the liquefied carbon dioxide consumption amount in the blow molding machine 2.