JPS6042017B2 - How to make bottles - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a bottle by blow molding Parylin made of a thermoplastic resin material such as PET (polyethylene terephthalate). The present invention relates to a method for producing a bottle which has excellent thermal stability.

(Prior art) In general, to manufacture bottles by blow molding,
A molding method is known in which Parylin is set in a mold having a cavity for bottle molding, a stretching rod is inserted into the Parylin to stretch it in the longitudinal direction, and then compressed fluid is blown into the Parylin to expand it.

Due to the shape of the bottle obtained in this way, the bottom or neck part is naturally thick, which causes problems such as a decrease in strength and deformation when filled with high-temperature substances, especially at the bottom. The phenomenon was severe. For this reason, conventional methods have been used to create a temperature difference in Parylin, that is, at the bottom of the bottle,
Alternatively, a method has been adopted in which the portion corresponding to the mouth and neck is made higher than other portions to promote stretching, or a method is used in which the bottom of the bottle is stretched inward. (Problems to be Solved by the Invention) Among the above-mentioned conventional techniques, it is difficult to set a temperature difference in the former method, and in the latter method, it is difficult to partially stretch only desired areas. There were drawbacks such as 'possible'.

(Means for Solving the Problems) The present invention solves the drawbacks of the conventional methods and provides a method for manufacturing bottles having uniform wall thickness, in which the bottles are manufactured by blow molding Parylin. In the method, in the first step, Parylin, which has been stretched and heated to an appropriate temperature, is blow-molded using a mold with a concave center at the bottom of the mold, so that the center of the bottom of the bottle bulges outward, and in the second step, the periphery of the bottom of the mold is expanded. This is a method of manufacturing a bottle, which is characterized by blow molding using a mold having a concave shape to expand the periphery of the bottom of the bottle outward to form a grounding part.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing blow molding at the first stage of the present invention, and FIG. 2 is a sectional view showing blow molding at the second stage.

In the figure, 1 is a half mold, 2 and 22 are bottom molds, and 3 is a mouth mold.

In the closed state, the molds 1, 2, 22, and 3 constitute a cavity for molding a bottle. The bottom mold 2 has a hemispherical recess in the center, and the bottom mold 22 has a periphery recessed to a depth greater than the depth of the recess. Reference numeral 4 denotes a compressed fluid blowing nozzle, and an extending rod 5 is provided vertically slidably through a blowing port 6 connected to a compressed fluid source.

In the above configuration, the nozzle 4 is attached to the opening of the parison P heated to an appropriate temperature for stretching, and set in the mold. Next, the stretching rod 5 is inserted into the parison P and stretched in the longitudinal direction by protruding in the direction of the arrow shown in FIG. Press it against the wall and inflate it. The inflated parison forms a bottle B shown by a two-dot chain line, the bottom of which is bulged outward along a bottom mold with a concave center. Next, in the second step, the bottle B obtained by the blow molding is removed from the mold, and the bottom of the bottle B is reheated to the stretching temperature.

Next, as shown in FIG. 2, a bottom mold 2 with a concave periphery is formed.
2 is set in the mold that combines them, and the blowing nozzle 42
A compressed fluid is blown into the bottle B from the inlet 62 of the bottle B, and the bottom of the bottle B is inflated until it is pressed against the bottom mold 22, and the periphery of the central bulging part is bulged outward (downward). Forms an annular grounding part.

Note that this second stage blow molding is performed in the first stage shown in Fig. 1.
After the blow molding step, the bottle. Divide B in half 1
It is also possible to replace the bottom mold 2 with a bottom mold 22 as shown in FIG. 2 while holding the bottom mold 2 in place, and then blow compressed fluid into the bottle B to sufficiently stretch the bottom of the bottle.

In this case, the transition from the first stage of blow molding to the second stage of blow molding can be carried out quickly, so there is no need to reheat only the bottom of the bottle, which is insufficiently stretched. Accordingly, the bottom mold 2 may be heated in the first step of blow molding. Furthermore, in the first step of blow molding shown in FIG. 1, even the neck of the bottle, which is insufficiently stretched, can be partially stretched as shown in FIG.

After performing the first and second stages of blow molding as described above, when the mold was opened and the product was taken out, a bottle with uniform wall thickness and an extremely good appearance was obtained. In order to obtain a bottle having the same shape, the bottle is uniformly stretched by the above-mentioned blow molding and heat-set by heating while the bottle is held in the mold, that is, while applying internal pressure to the bottle to maintain its shape.

This heat setting treatment is carried out by maintaining the temperature at or above the crystallization temperature of the resin used in the parison for a predetermined period of time. To explain one example of heat-setting treatment of a bottle made of polyethylene terephthalate resin, the blow molding in the first and second steps results in a birefringence of (10 to 20) x 10-3 and a plane orientation index of ( A bottle blow-stretched to a density of 50 to 100) x 10-3 was pressed against the inner wall of a mold kept at about 140°C, and the bottle was crystallized to have a density of 1.375 or higher.

The bottles heat-fixed in this manner did not shrink due to thermal deformation even when filled with high-temperature substances, nor did they whiten and reduce transparency. (Effects of the Invention) As described above, in the first step, the present invention blow-moldes the parison using a mold with a concave center, thereby causing the center of the bottom part, which is difficult to stretch, to bulge outward. Since the bottle is sufficiently stretched and the periphery of the bottom portion is expanded outward in the second step to form a ground contact portion, the entire bottom portion can be stretched sufficiently uniformly by stepwise stretching, and a bottle with self-supporting properties can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing blow molding at the first stage of the present invention, and FIG. 2 is a sectional view showing blow molding at the second stage. 1...Half mold, 2,22...Bottom mold,
3... Mouth mold.

Claims (1)

[Claims] 1 In a method of manufacturing a bottle by blow molding a parison, the parison heated to an appropriate temperature for stretching in the first step is blow molded using a mold with a concave center at the bottom of the bottle, so that the center of the bottom of the bottle is outwardly shaped. A method for producing a bottle, which comprises: expanding the bottom of the bottle outwardly by blow molding the bottle using a mold that is concave around the bottom of the bottle in a second step, and forming a grounding part.