JPH0441885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for making a bottomed parison for blow molding.

<Prior art> Polysulfone manufactured by Union Carbide in the United States obtained by polycondensation of cycloldiphenyl sulfone and bisphenol A has a high heat distortion temperature and excellent mechanical properties, especially creep resistance. The molding temperature is as high as 345-400℃. In addition, polyphenylene oxide manufactured by General Electric Company in the United States has the highest heat distortion temperature among general-purpose thermoplastic resins, and is hard, tough, and has excellent creep resistance, but the molding temperature is 290 to 350 °C. expensive. Such resins, which have a high molding temperature, are molded into thick-walled pressure vessels, boilable containers, special chemical containers, etc. by blow molding. A parison with a bottom was made by injection molding.

<Problems to be Solved by the Invention> When molding a large container using the method described above, when trying to extrude a parison suitable for the large container,
As the amount of resin increases, extrusion time takes longer and the weight of the resin also increases, causing sagging due to gravity.
The so-called drawdown could not be adjusted well, and therefore it was extremely difficult to mold to a uniform thickness. Furthermore, when trying to obtain a parison with a bottom by injection molding, the temperature must be higher than the plasticizing temperature of the resin because it is injected through a small injection hole, and the molding temperature must be set at a temperature higher than the plasticizing temperature of the resin because it is injected under high pressure. As a result, there was a drawback that not only thermal deterioration of the resin material occurred but also residual stress was generated.

<Means for Solving the Problems> An object of the present invention is to provide a molding method that can eliminate the above-mentioned drawbacks when molding a bottomed parison by extrusion molding. A mandrel extending downward from the injection cylinder is surrounded by an outer mold having a welding hole at the bottom, and a parison-shaped inner mold space with a bottom is formed through which the outside passes through the welding hole. Then, the front mandrel is turned to extrude the thermoplasticized resin through the die of the injection tube until it travels through the mold space in a tubular shape and is discharged from the fusion hole, thereby forming the closed bottom of the parison. It was designed to do so.

<Function> As mentioned above, by passing the inside of the mold to the outside through the fusion hole, it is possible to form a bottomed parison without fear of drawdown due to low-pressure extrusion, but the fusion hole has a temperature above the appropriate temperature. Not only does this not cause an increase in resin temperature, but it also serves to complete the melting of the closed parison bottom.

<Example> Regarding the apparatus for carrying out this invention, the first
This will be briefly explained according to the diagram.

Reference numeral 1 denotes a mandrel installed in the injection cylinder 2 of the extruder, and the part below the die 3 at the bottom of the injection cylinder 2 is used as an inner mold for forming the inner diameter of the parison. The center of this mandrel 1 is an air passage 4, and the air passage 4 is opened and closed by a check valve 6 provided at the lower end of an operating rod 5 that can be moved slightly up and down. The outer surface of the check valve 6 serves as the bottom mold of the inner mold. By surrounding the outside of the mandrel 1 with the outer mold 7,
A parison-shaped mold space 8 with a bottom is formed. A welding hole 9 is bored in the bottom of the outer mold 7, and a mold inner space 8 is formed.
communicates with the outside world. When the mold inner space 8 has an outer diameter of 80φ, an inner diameter of 60φ, and a length of 300mm, the fusion hole 9
The size is about 20φ in diameter.

Examples using the above apparatus are shown below.

Polysulfone resin, which has been plasticized by heating to a molding temperature of 320°C in an extruder, is extruded at low pressure through a mandrel 1 in an injection cylinder and into a temperature-controlled mold space 8 through a die 3, which takes about 40 seconds. After filling the mold space and allowing the resin to be discharged from the fusion hole 9, 20 seconds were allowed to stabilize the resin in the mold, and a bottomed parison was preformed. The resin extruded at the low pressure described above shapes the bottom of the parison according to the pressure ratio corresponding to the area ratio of the outside diameter of the parison to the area of the bottom where it converges (see Figure 2), and then passes through the fusion hole 9. At the same time, back pressure is applied to the resin due to the pressure increase due to the area ratio of the outer diameter of the parison to the area of the fusion hole, and a bottomed parison is formed (see Figure 3). The fusion at the bottom was complete.

When the outer mold 7 is lowered and removed, a bottomed parison with a convex portion 10, which is the trace of the fusion hole 9, is collected on the mandrel 1 (see FIG. 4). After that,
The split mold 11 for molding the floating container is positioned at the bottom of the injection cylinder while being closed, and the mold is clamped to form the convex portion 1 of the bottomed parison.
0 to bring out the burr 12 and close it, then press the operating rod 5 to open the check valve 6, blow in pressurized air to inflate the bottomed parison (see Figure 5), and after inflating it sufficiently. was cooled in a split mold 11 for 40 seconds. FIG. 6 is a sectional view of a container formed in this manner, having an outer diameter of 230φ, a length of 300 mm, a wall thickness of 3 mm, and an internal capacity of 10. The time required for blow molding the container was 2 minutes and 40 seconds in total, including 60 seconds for moving the outer mold of the parison up and down, opening and closing the split mold, and taking out the container.

In this embodiment, a tapered outer mold is used that can be raised and lowered, but a split mold that can be opened and closed can be raised and lowered. In this case, it is possible to preform a bottomed parison with an uneven outer surface.

<Effects of the Invention> As is clear from the above description, a parison with a bottom is formed by extruding a thermoplasticized resin into a mold space opened by a fusion hole.
The extrusion pressure may be low, and the molding speed may be set so as not to cause drawdown. Furthermore, since no place is created that would cause the resin temperature to rise above an appropriate temperature, thermal deterioration of the resin and residual stress are not caused. Therefore, it is particularly suitable for molding a bottomed parison when blow molding a large container using a resin with high molding humidity and large drawdown. Furthermore, even when it is desired to add glass fibers, carbon fibers, etc. to the resin to give it even more strength, this can be said to be an extremely effective molding method in that it can be carried out without any problems.

[Brief explanation of drawings]

Figures 1 to 4 are explanatory diagrams sequentially showing the process up to forming the bottomed parison in order to make it easier to understand the molding method of the present invention, and Figure 5 shows the process of blow molding using this bottomed parison. The explanatory diagram, FIG. 6, is a sectional view of the molded product. DESCRIPTION OF SYMBOLS 1... Mandrel, 2... Injection cylinder, 3... Dice, 4... Air path, 5... Operating rod, 6... Check valve, 7... Outer mold, 8... Inner mold space, 9... ...fusion hole.

Claims (1)

[Claims] 1. A mandrel extending downward from the injection cylinder is surrounded by an outer mold having a fusion hole in the bottom to form a bottomed parison-like interior space of the mold that communicates with the outside through the fusion hole, and then the above-mentioned The thermoplasticized resin was passed through the mandrel through the die of the injection tube, and was then extruded until it was ejected from the fusion hole after it had progressed into the mold in a tubular shape, making it possible to mold the closed bottom of the parison. A method for forming a bottomed parison for hollow molding, characterized by the following.