JPH0465215A - Method and device for controlling cooling temperature of preformed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a method for adjusting the temperature at which a plastic preform is cooled in a mold when the preform is injection molded, and an apparatus therefor. Regarding.

[Prior art and problems to be solved by the invention] Plastic containers such as bottles for enclosing carbonated drinks and fruit juice drinks are made by injection molding of saturated polyester resin with excellent heat deformation resistance, and then biaxially stretched and blown. Manufactured by molding.

After injection molding and before being subjected to stretch blow molding, the preformed body 2, so-called a parison, has a shape as shown in FIG.
It has a cylindrical shape with a bottom.

In order to biaxially stretch blow mold this preform, for example, the bottom part 8 is pushed vertically with a stretch rod 10 and at the same time heated at a high temperature. Compressed air is blown out from the outlet 12 to stretch the body 6 in the circumferential direction.

Therefore, it is necessary to blow mold the bottom part 8 at a temperature below the stretching temperature so as not to break through, and keep the body part 6 at a temperature above the stretching temperature. Moreover, since the mouth part 4 is held by the mold, it is not necessarily necessary to keep it at a low temperature like the bottom part 8, or it is desirable to keep it at a low temperature so that it is not stretched together with the body part 6.

On the other hand, in order to manufacture a preform having such a shape by injection molding, as shown in FIG. Inject from 22. Cooling water is passed through a passage (not shown) provided inside the injection cavity 14, or a pipe 24 is provided inside the injection core 16, and the cooling water flows into the pipe as shown by the arrow to remove the plastic. Cool and solidify.

The entire preform 2 thus obtained is cooled to a uniform temperature. Therefore, after injection molding and before subjecting it to stretch blow molding, it is necessary to create a temperature difference between the mouth part 4, body part 6, bottom part 8, etc.
By the method shown in No. 5, the preform 2 is placed in the temperature control mold.
was installed to regulate the temperature.

However, with this method, the temperature control mold is complicated, the entire manufacturing equipment is large-scale, and the manufacturing costs are high due to the increased number of steps.

Therefore, an object of the present invention is to provide a method for simply and efficiently controlling the temperature of a preform before it is subjected to stretch blow molding, and an apparatus therefor.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventor provided a pipe inside the hollow injection core that constitutes the injection mold, and first used a portion of the cooling water that flowed through the pipe to prepare the injection molding material. By bringing the injection core into contact with the side wall of the injection core at a position corresponding to the mouth of the preform, and by bringing the remaining cooling water into contact with the bottom of the injection core, it is possible to create a difference in the degree of cooling of each part of the preform. discovered this and completed the present invention.

That is, the method of the present invention is a method for adjusting the cooling temperature of a plastic preform that is injection molded into a bottomed cylindrical shape that includes a mouth at the upper end, a bottom at the lower end, and a body connecting them. A pipe is provided in the hollow part inside the injection core so that the tip thereof is at the bottom of the injection core, and a hole is provided in the pipe at a position corresponding to the mouth of the preform, and resin is injected. At this time, a portion of the cooling water that has flowed into the pipe flows out of the pipe from the hole, and the remaining cooling water is brought into contact with the bottom of the injection core to cool the body of the preform. The feature is that the temperature is adjusted so that the temperature at the mouth and bottom is lower than that at the mouth.

Furthermore, the device of the present invention for performing the above operation adjusts the cooling temperature of a plastic preform injection molded into a bottomed cylindrical shape, which is composed of a mouth portion at the upper end, a bottom portion at the lower end, and a body portion connecting them. The apparatus includes a hollow part for cooling water inflow inside the injection core of an injection mold, a pipe provided in the hollow part so that the tip thereof is near the bottom of the injection core, and , characterized in that a hole is provided at a position corresponding to the mouth of the preform.

〔Example〕

Hereinafter, the method and apparatus of the present invention will be explained with reference to the drawings.

FIG. 1 shows the apparatus of the invention, including an injection mold and a pipe. The injection mold includes an injection cavity 14 that defines the outer contour of the injection molded product, that is, the preform 2 shown in FIG. It is sandwiched between the cores 16 to set the interval therebetween, and the opening 4 of the preform 2
and a lip 18 defining the shape of. 20 is a cavity.

The injection core 16 is hollow, and pipes 26 are provided at intervals inside the core. The pipe 26 is fixed at the upper end of the injection core 16 by a cylindrical bushing 30. Pipes are brass, iron,
Made of aluminum etc. Further, the pipe 26 is provided with a plurality of holes 34 at a position corresponding to the mouth 4 of the preform 2, and a ring 42 is attached to the outer periphery of the pipe 26 at a position directly below the holes 34. There is. Instead of the ring 42, an annular projection may be provided integrally with the pipe 26.

The melted plastic is transferred from the gate 22 to the cavity 20.
At the same time, cooling water is introduced from the upper end of the pipe 26 as shown by the arrow. A portion of the cooling water flows out of the hole 34 to the outside of the pipe 26, and the remaining cooling water descends and contacts the bottom 161 of the injection core. Next, the cooling water that has started to rise rises while contacting the inner wall 162 of the body of the injection core 16, and together with the cooling water flowing out from the holes 34, flows through a plurality of outflows provided around the bushing 30 at the upper end of the injection core 16. It flows out from the hole 40.

The cooling water flowing out from the hole 34 and the cooling water contacting the bottom portion 161 have a low temperature and a high flow rate. Therefore, the portions that will become the mouth portion 4 and bottom portion 8 of the preform are cooled to a large extent. On the other hand, the cooling water that rises while contacting the inner wall 162 of the body absorbs the heat of the injected plastic material when passing through the bottom 161 and becomes somewhat high temperature. The flow rate is low because it is narrowly fitted. Therefore, the portion of the preform that will become the body 6 is cooled to a small degree.

Therefore, the cooled and solidified preform 2 has a mouth part 4 and a bottom part 8.
The temperature becomes low at the body part 6, and the temperature becomes higher at the body part 6.

If the plastic material is polyethylene terephthalate (PET), for example, its melting point is 270°C, which is the glass transition point of 70°C, so the opening 4 and bottom 8 are made lower than 70°C, and the body 6 is made lower than 80°C. It is desirable that the stretching temperature is 260°C. The cooling temperature of each part can be adjusted by changing the amount of cooling water flowing through each part, such as by changing the size of the hole 34, the diameter of the pipe 26, or the diameter of the ring 42. Alternatively, instead of using the ring 42, it is possible to contact the inner wall 162 by increasing the thickness, that is, the outer diameter, of the pipe 26 without changing its inner diameter over the entire position corresponding to the body 6 of the preform. However, the amount of cooling water that rises can be reduced.

Furthermore, in order to adjust the amount of cooling water rising without contacting the inner wall 162, as shown in FIG. 2 and FIG. ring 42
Instead, a ring 44 having a plurality of holes 46 provided on its outer periphery may be attached to the pipe 26 in close contact with the injection core 16 on its outer periphery.

In this case, the effect that the pipe 26 is fixed so that it does not move can also be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, after the preform is injection molded, the cooling temperature of each part can be adjusted in the injection mold so as to be suitable for stretch blow molding.

Therefore, since the preformed body after injection molding can be directly subjected to stretch blow molding, manufacturing costs are reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a cooling temperature control device according to an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view showing another embodiment of the device according to the present invention, and FIG. FIG. 4 is a longitudinal sectional view of the preform, and FIG. 5 is a longitudinal sectional view of a conventional cooling device for the preform. 2... Preformed body 4... Mouth part 6... Body part 8... Bottom part 10... Stretching rod 12... Air outlet 14... Injection cavity 16... Injection core 161.・Injection core bottom 162 ・Injection core body inner wall 18 ・Lip 20 ・Cavity 22 ・Gate 26 ・Pipe 30 ・Bush 32 ・Step 34, 46 ・Hole 40・・Outflow hole 42.44・・Ring

Claims (3)

[Claims] (1) In a method for adjusting the cooling temperature of a plastic preform injection molded into a bottomed cylindrical shape consisting of an opening at the upper end, a bottom at the lower end, and a body connecting them, the injection core of the injection molding mold is A pipe is provided in the internal hollow part so that its tip is at the bottom of the injection core, and a hole is provided in the pipe at a position corresponding to the mouth of the preform, so that when resin is injected, A portion of the cooling water that has flowed into the pipe flows out from the hole to the outside of the pipe, and the remaining cooling water is brought into contact with the bottom of the injection core, so that the opening is lower than the body of the preform. A method characterized by adjusting the temperature so that the temperature at the top and bottom is low. (2) In a device for adjusting the cooling temperature of a plastic preform injection molded into a bottomed cylindrical shape consisting of an upper mouth portion, a lower bottom portion, and a body connecting them, the injection core of the injection mold A hollow part for cooling water to flow in is provided inside, a pipe is provided in the hollow part so that the tip thereof is near the bottom of the injection core, and a position of the pipe corresponds to the mouth of the preform. 1. A cooling temperature control device for a preform, characterized in that a hole is provided in the preform. (3) In the cooling temperature control device according to claim 2, the gap between the pipe and the injection core is reduced by providing an annular projection on the outer periphery of the pipe at a position directly below the hole. A device featuring: