JPH11245253A - Gas supply/recovery device for counterpressure molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable recovering and reusing of a pressurized gas and minimize damage even when a corrosive gas is mixed by providing an auxiliary tank and a check valve in that order from a main valve side between a main tank which stores the pressurized gas and a main valve for a gas flow path connected to a sealed die cavity. SOLUTION: An auxiliary valve 13 is closed and a gas source valve 9 is opened, and further, a gas from a gas source 10 is warmed using a warmer 8. In addition, the pressure of the gas is reduced by a reducing valve 7 and the pressurized gas at a required pressure level is stored in a main tank 5 to perform counterpressre molding. An atmospheric air opening valve 18 is closed and the auxiliary valve 13 and a main valve 16 are opened to supply the pressurized gas into a cavity 2 from the main tank 5 through a gas flow path 6 and further, the cavity 2 is sealed. After this sealing procedure, a resin is injected into the cavity 2 while the main valve 16 remains opened. The pressurized gas sealed in the cavity 2 is forced out with the resin, then is checked by a check valve 14 through the gas flow path 6 and is made to flow back into an auxiliary tank 15 to be recovered. The pressurized gas can be recovered and reused, and even when a corrosive gas is mixed, it can be controlled so that its content is at a minimum level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the supply of a pressurized gas to a cavity in a counter pressure molding in which a non-foamable resin is injected into a cavity after a pressurized gas is sealed in a cavity of a sealed mold. And a gas supply / recovery device for recovering the same.

[0002]

2. Description of the Related Art Counter pressure molding is generally used for molding using a foaming resin, but is also used for molding using a non-foaming resin.

For example, Japanese Patent Application Laid-Open No. 62-231715 discloses a method in which counter pressure molding is used for injection molding of a water-containing polymer alloy while suppressing vaporization of water. Japanese Patent Application Laid-Open No. 62-231715
In the publication, a cavity of a sealed mold and a pressure source are connected by a gas flow path having a supply valve interposed therebetween, and a gas supply and a gas supply valve having a pressurized gas release valve connected between the supply valve and the mold. Gas is supplied and discharged using a discharge device. That is, while the pressurized gas release valve is closed, the supply valve is opened to supply the pressurized gas from the pressure source to the cavity, while the pressurized gas pushed out of the cavity by injection of the resin into the cavity is being injected or After the injection is completed,
The supply valve is closed, the pressurized gas release valve is opened, and the gas is released into the atmosphere to supply and discharge the pressurized gas.

[0004]

However, if the pressurized gas supplied to the cavity is released to the atmosphere each time molding is performed, wasteful use of the pressurized gas is generated, and depending on the type of the pressurized gas. It also causes the work environment to deteriorate.

Incidentally, Japanese Patent Application Laid-Open No. 62-231715 describes the above.
Although it is not clear in the publication, if the pressure source is a tank storing a pressurized gas of a predetermined pressure, if the supply valve is kept open without opening the pressurized gas release valve at the time of resin injection,
Pressurized gas that is further compressed by resin injection and pushed out of the cavity can be recovered to some extent by flowing back into the tank that is the pressure source.

However, when such pressurized gas is recovered, the generated corrosive gas is mixed in, for example, counter pressure molding of a resin to which a halogenated flame retardant which generates corrosive gas is added. Since the pressurized gas is recovered, the life of the entire pressurized gas supply system may be shortened.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. In a counter pressure molding using a non-foamable resin, the pressurized gas can be recovered and reused. An object of the present invention is to minimize the range of damage caused by corrosive gas even when corrosive gas is mixed in the pressurized gas.

[0008]

According to the present invention, in order to achieve the above object, a main tank containing a pressurized gas of a predetermined pressure is sealed through a gas flow path in which a main valve is interposed. A gas supply / recovery device for counter pressure molding, characterized in that a sub-tank and a check valve are provided in order from the main valve side in a gas flow path between the main tank and the main valve, which is connected to a mold cavity. Is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is for counter pressure molding using a non-foamable resin. First, counter pressure molding using this non-foamable resin will be described.

In the counter pressure molding of a non-foamable resin, in addition to the method for suppressing the vaporization of water contained in the resin as described in the section of the prior art, the counter pressure molding is performed by dissolving the resin in the resin to increase the solidification temperature of the resin. There is counter pressure molding in which the gas to be reduced is used for the counter pressure. In this counter pressure molding, a gas that dissolves in the resin and lowers the solidification temperature of the resin is sealed in the cavity as a counter pressure at a pressure that easily dissolves in the resin, and the surface layer of the resin injected into the cavity is sealed. By temporarily lowering the solidification temperature and delaying the solidification of the resin surface layer, the mold transferability of the molded product is significantly improved.

Further, the mechanism for improving the mold transferability will be described.

In the injection molding, the resin always flows in a laminar flow in the cavity, and when it comes into contact with the cooled mold surface, a solidified layer is formed at the interface, and the resin to be filled later flows inside the solidified layer. Then, after reaching the resin flow front end (flow front), a flow called a fountain flow flows toward the mold surface. Filling the cavity with gas of appropriate pressure such as carbon dioxide and then filling with resin,
The gas is absorbed by the flow front of the flowing resin or enters the interface between the mold surface and the resin and dissolves in the resin surface layer. The gas dissolved in the resin acts as a plasticizer and selectively lowers the solidification temperature of only the resin surface layer or lowers the melt viscosity of the resin. If the solidification temperature of the thin resin surface decreases and the solidification temperature falls below the mold surface temperature, the resin surface layer does not solidify during resin filling, and the cavity is filled with resin and solidifies while being strongly pressed against the mold. , The mold surface transferability of the molded article can be remarkably improved. The gas dissolved in the resin surface layer diffuses into the resin over time,
Since the solidification temperature of the resin surface layer rises, the surface layer solidifies within the usual resin cooling time and can be taken out as a product.

Hereinafter, counter pressure molding using a gas for lowering the solidification temperature of the resin will be further described.

The applied resin is a thermoplastic resin which can be used for general injection molding and the like. The non-crystalline thermoplastic resin can be suitably applied, but the present invention can also be applied to a thermoplastic polymer alloy containing the non-crystalline resin as a main component or a part of the crystalline thermoplastic resin having low crystallinity. Specifically, styrene resins such as polystyrene, styrene-acrylonitrile copolymer, rubber-reinforced polystyrene, styrene-methyl methacrylate copolymer, ABS resin, styrene-methyl methacrylate-butadiene copolymer, polymethyl methacrylate, methyl methacrylate -Modified polyphenylene ether blended with methacrylic resin such as styrene copolymer, polyvinyl acetate, polycarbonate, polyphenylene ether or polystyrene, polysulfone, polyether sulfone, polyetherimide, polyarylate, polyamideimide, polyvinyl chloride, vinyl chloride- Vinyl chloride resins such as ethylene copolymer and vinyl chloride-vinyl acetate copolymer are preferred. Further, a blend of these resins, a resin in which a part of a crystalline resin is blended with these non-crystalline resins, or a resin in which various fillers such as inorganic and organic substances are blended may be used. In addition, it is preferable to select a resin in which gas is easily dissolved in consideration of a combination with a gas to be used.

The solidification temperature of a resin is a temperature at which a molten resin solidifies in a mold, a glass transition temperature for an amorphous resin, and a crystallization start temperature for a crystalline resin. In the case of the incompatible polymer alloy, it is the glass transition temperature or the crystallization start temperature of the resin constituting the sea having the sea-island structure. Here, the crystallization start temperature of the crystalline resin is set to 20 ° C. after heating and melting the resin to the temperature at the time of molding using a differential calorimeter.
/ Minute, to a temperature at which heat generation due to crystallization of the resin is first recognized.

As the gas, one that dissolves in the resin and lowers the solidification temperature of the resin is used. However, in reality, the gas has a solubility twice or more that of air at the solidification temperature of the resin used. Is a gas having a plasticizing effect on the resin. Specifically, hydrocarbons such as carbon dioxide, methane, ethane, and propane, and those obtained by partially replacing hydrogen with fluorine or the like (such as chlorofluorocarbon), mixtures thereof, and the like, taking into account the solubility in the resin used. Selected. Among them, carbon dioxide is not only best used in terms of safety, price, ease of handling, etc., but also dissolves well in resin to become a plasticizer, and has a great effect of lowering the solidification temperature of the resin. preferable.

The higher the pressure at which the above gas is sealed in the cavity, the more gas is dissolved in the resin, the lower the solidification temperature, and the lower the mold temperature, the more the solidification during the resin filling step can be prevented. Practically, the required gas filling pressure is determined by the required mold transferability, the type of resin and gas, and the mold temperature.Use a gas with high solubility and raise the mold temperature. If set, sufficient transferability can be obtained with a low sealing pressure. The mold temperature may be selected within a temperature range that is equal to or lower than the solidification temperature of the resin before contact with the gas and higher than the solidification temperature of the resin that is lowered by dissolving the gas in the cavity.

Although the lower limit of the sealing pressure is determined by the plasticizer effect of the gas dissolved in the resin, it is preferably a pressure at which the resin is dissolved in the resin in an equilibrium state of 0.1% by weight or more at the solidification temperature of the resin used. More preferably 0.5% by weight
This is the dissolution pressure. The solubility of the gas used in the resin is a value measured by a pressure drop method.

The upper limit of the sealing pressure is not particularly limited. However, if the pressure is too high, problems tend to occur such that the force for opening the mold cannot be ignored and the mold is difficult to seal. , 15 MPa or less is practical, and preferably 10 MPa or less.

The air remaining in the mold when the mold is closed is:
It is preferable to substitute the gas used, but when the pressure of the gas to be filled exceeds 1 MPa, the effect of air can be almost ignored.

In the counter pressure molding as described above, the injection can be completed while maintaining the counter pressure so that the solidification of the resin surface layer is reliably suppressed until the cavity is filled with the resin. preferable. Also, it is possible to collect and reuse the pressurized gas such as carbon dioxide gas, and to minimize the damage caused by corrosive gas even if the collected pressurized gas contains a corrosive gas. We need to be able to do it.
The gas supply / recovery apparatus for molding counter pressure according to the present invention satisfies all of these requirements.

Hereinafter, an example of a gas supply / recovery apparatus for forming counter pressure according to the present invention will be described with reference to FIG.

In the figure, reference numeral 1 denotes a mold, and its cavity 2 is sealed by O-rings 3a to 3d. Further, a gas supply / discharge passage 4 communicating with the cavity 2 is formed in the mold 1.

The gas supply / discharge passage 4 of the mold 1 is connected to the other end of a gas flow path 6 having one end connected to the main tank 5.

The main tank 5 stores pressurized gas for a predetermined pressure for counter pressure and supplies the gas to the cavity 2. A gas source 10 such as a liquefied carbon dioxide cylinder is connected to the main tank 5 via a pressure reducing valve 7, a heater 8 and a gas source valve 9 in this order from the main tank 5 side. The relief valve 11 for releasing the gas pressure when the pressure in the main tank 5 becomes abnormally high and the meter 12 for checking the gas pressure in the main tank 5 are also connected to the main tank 5. .

In the gas flow path 6 connecting the main tank 5 and the mold 1, a sub-valve 13, a check valve 14, a sub-tank 1
5 and the main valve 16 are interposed. A relief valve 17 and an atmosphere release valve 18 are connected to the gas flow path 6 between the main valve 16 and the mold 1.

The above-mentioned gas supply for counter pressure molding
The procedure of counter pressure molding using the recovery device will be described.

First, when the gas source valve 9 is opened with the sub-valve 13 closed, the gas flowing out of the gas source 10 is warmed by the heater 8 and reduced in pressure to the required pressure by the pressure reducing valve 7. 5 Then, counterpressure molding is performed in a state where the pressurized gas of a required pressure is stored in the main tank 5.

The supply of the pressurized gas for the counter pressure to the cavity 2 is performed by opening the main valve 16 with the atmosphere release valve 18 closed and the sub-valve 13 opened. When the main valve 16 is opened, the pressurized gas in the main tank 5 is supplied to the cavity 2 via the gas passage 6.

After the pressurized gas is sealed in the cavity 2 as described above, the resin is injected into the cavity 2 with the main valve 16 opened (the sub-valve 13 is also opened). When the resin is injected into the cavity 2, the cavity 2
The pressurized gas sealed in the inside is pushed by the resin and pushed out to the gas flow path 6, and further, flows back to the sub tank 15 and is collected.

When recovering the pressurized gas, the main tank 5
Since the check valve 14 is interposed between the sub-tank 15 and the sub-tank 15, the collected gas does not flow back to the main tank 5 side beyond the check valve 14. Therefore, even if the recovered gas flowing backward from the cavity 2 contains corrosive gas generated from the resin, the gas exposed to the corrosive gas is from the mold 1 to the check valve 14. And the main tank 5 side from the check valve 14 is not deteriorated by corrosive gas. Also, the main valve 16
In the counter pressure molding using a gas that dissolves in the resin and lowers the solidification temperature of the resin, the resin can be injected until the cavity 2 is filled. The solidification of the surface layer can be reliably suppressed.

When corrosive gas is mixed in the recovered gas,
As described above, the space between the mold 1 and the check valve 14 is exposed. Accordingly, the check valve 14 is used to reduce the gas flow resistance of the pipe portion so that the gas can be supplied to the cavity 2 in a short time so that the gas can be easily replaced when the corrosive gas is damaged. It is preferable to make the gas flow path 6 up to 1 as short as possible, and to provide the sub tank 15 and the main valve 16 as close to the mold 1 as possible. In addition, when the distance from the check valve 14 to the main tank 5 is increased by this method, it is preferable to provide the sub-valve 13 near the main tank 5.
The sub-valve 13 can be omitted if it can be arranged close to the above.

Since the pressure of the recovered gas is increased by injection of the resin and pushed out of the cavity 2, it is preferable to adjust the volume of the sub-tank 15 so that the pressure in the sub-tank 15 for receiving the gas is not excessively increased. . The volume of the sub-tank 15 is 1 of the volume of the cavity 2.
It is preferably at least / 2 and at most 10 times. If the volume of the sub-tank 15 is too small, the pressure in the sub-tank 15 tends to be too high due to the pressure of the collected gas, and the sub-tank 15 having an excessively large volume is disadvantageous in terms of space and equipment cost. The relief valve 17 is for releasing the gas pressure in the gas passage 6 between the check valve 14 and the mold when the gas pressure excessively increases due to the recovered gas pushed out from the cavity 2, and enhances safety. It is preferable to provide it above.

After the injection of the resin and the recovery of the pressurized gas as described above, the main valve 16 is closed, the atmospheric release valve 18 is opened, and the residual pressurized gas between the main valve 16 and the mold 1 is opened. And the resin in the cavity 2 is further cooled.

The molded product is taken out of the mold 1 and again
Is closed and the main valve 16 is opened, the pressurized gas in the main tank 5 can be supplied to the cavity 2 together with the recovered gas in the sub tank 15. Therefore, it is possible to effectively use the recovered gas. Further, since the pressure of the recovered gas is increased, it is possible to quickly supply the recovered gas to the cavity 2.

[0036]

The present invention is as described above. In a counter pressure molding using a non-foamable resin, the pressurized gas can be recovered and reused, and the recovered pressurized gas can be reused. Even if corrosive gas is mixed in the mold 1, the damage caused by the
Up to the minimum range.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a gas supply / recovery device for forming counter pressure according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 mold 2 cavity 3a O-ring 3b O-ring 3c O-ring 3d O-ring 4 gas supply / discharge path 5 main tank 6 gas flow path 7 pressure reducing valve 8 heater 9 gas source valve 10 gas source 11 relief valve 12 meter 13 sub-valve 14 Check valve 15 Sub tank 16 Main valve 17 Relief valve 18 Atmospheric release valve

Claims (2)

[Claims] 1. A main tank containing a pressurized gas of a predetermined pressure is connected to a sealed mold cavity through a gas flow path in which a main valve is interposed. A gas supply / recovery device for forming counter pressure, wherein a sub-tank and a check valve are provided in a gas flow path in order from a main valve side. 2. An air release valve is connected to a gas flow path between the main valve and the mold.
Gas supply and recovery equipment for counter pressure molding.