JPH0584813A - Manufacture of plastic bottle - Google Patents

Abstract

PURPOSE:To enhance the strength of a cylindrical part without providing ribs in a mold by a method wherein compressed air is blown in for blow molding under the condition that the temperature of parison is controlled so as to realize high temperature parts and low temperature parts within the temperature domain, which is higher than the mold temperature at stretching and blow molding. CONSTITUTION:By heating a heater built in each temperature controlling block 4 up to the predetermined temperature, heat is radiated through thermal conduction to a parison 1, resulting in heating the parison 1 up to the predetermined temperature. Thus, respective temperature controlling blocks 4 can be heated in advance up to the temperatures, which are different from one another, resulting in setting the temperatures in response to the shape of a bottle. In the parison, which is heated up to the predetermined temperature, low temperature parts and high temperature parts are annually distributed in multiple steps. Stretch blow molding is performed by carrying the resultant parison in a forming tool, which has a cylindrical part with surface as smooth as that of the conventional mold, and then blowing compressed air in the parison. Thus, the low temperature part forms thicker part, since the elongation by the compressed air is small at the low temperature part, annular thicker parts, which protrude over tire inside surface of the cylindrical part and distribute in multiple steps in the cylindrical part, are realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottomed tubular parison made of a resin such as polyethylene terephthalate (hereinafter referred to as PET) by injection molding, and the bottomed tubular parison is directly or cold parisoned. After that, the present invention relates to a method for producing a plastic bottle which is inserted into a molding die in a heated state, clamped, and stretch blow molded.

[0002]

2. Description of the Related Art Conventionally, beverages are produced by stretch blow molding of this kind,
When molding a plastic bottle filled with a liquid such as oil, when the shape of the body of the plastic bottle is a smooth curved surface, for example, the cross section is a circle or an ellipse, it is stretched to reduce the wall thickness. Therefore, there is a problem in that the strength is weakened, and when the contents are filled at a high temperature, the phenomenon of blistering is likely to occur after the filling.

As a means for solving such a problem, as shown in FIG. 4, a method of increasing the strength by providing a number of reinforcing ribs q on a part or the whole of the body of the plastic bottle A is also taken. ing. However, if such reinforcing ribs are provided, the mold processing becomes complicated and the cost becomes high, the position where the label is attached to the body of the plastic bottle after molding is limited, and the label is integrated in the mold. Even when the in-mold label method is adopted, there is a problem in that the appearance design of the bottle is restricted, such as bubbles remaining between the bottle and the label.

[0004]

SUMMARY OF THE INVENTION The present invention thus provides
An object of the present invention is to provide a method for producing a plastic bottle, which is not limited by the appearance design of the plastic bottle in the stretch forming method of the plastic bottle, and which can increase the strength of the body portion without providing ribs on the mold. ..

[0005]

The present invention solves the above problems, and in a method of manufacturing a plastic bottle in which an injection-molded bottomed cylindrical parison is stretch blow-molded in a mold, before inserting the mold. A part of the parison corresponding to the body part after molding is divided into horizontal stripes, and the temperature is adjusted so as to have a high temperature part and a low temperature part in a range higher than the mold temperature during stretch blow molding. The body part is inserted into a mold with a smooth surface, and then compressed air is blown into it to perform blow molding, so that the part where the inner surface of the bottle is set to the low temperature part is thicker than the part set to the high temperature part. It is a method for manufacturing a plastic bottle.

[0006]

In the above-mentioned method of the present invention, the plastic bottle after molding is cooled by the compressed air inserted until the shrinkage becomes stable, and then the plastic bottle is taken out from the mold. Only a bottle with varying wall thickness can be obtained, and a plastic bottle with excellent strength can be obtained.

[0007]

EXAMPLES The method for producing a plastic bottle according to the present invention will be described below with reference to examples.

First, a hot parison method in which a parison in a heated state immediately after injection molding is used as it is will be described.

A cylindrical bottomed parison 1 is molded to a predetermined size from PET resin by an injection molding method, and the parison 1 taken out from the injection molding machine is a temperature control pot 2 as shown in FIG.
And adjust the temperature of this parison 1.

As shown in the sectional view of FIG. 1, the temperature control pot 2 is constructed by stacking temperature control blocks 4 having parison insertion holes 3 in multiple stages with a heat insulating layer 5 interposed therebetween. Here, the numbers of the temperature control blocks 4 and the heat insulation layers 5 are not particularly limited, and the numbers are determined depending on the size and wall thickness of the bottle.

A far infrared ray generating layer 6 is formed on the surface of the parison insertion hole 3 of each temperature control block 4. The far-infrared ray generating layer 6 is composed of, for example, a firing layer of fine ceramic, alumina, etc.
It is formed by firing at a high temperature of 000 ° C.

As the heat insulating layer 5, heat insulating paper may be used, and other materials may be used as long as they have heat insulating properties.

According to the present invention, when a heater (not shown) built in each of the temperature control blocks 4 is heated at a predetermined temperature, heat is radiated to the parison 1 by heat conduction and the parison 1 is heated to a predetermined temperature. To heat. Here, each temperature control block 4 can be heated to a different temperature in advance, and its value is set according to the shape of the plastic bottle.

In this way, the parison 1 heated to a predetermined temperature has a ring-shaped multi-stage distribution of low-temperature parts a and high-temperature parts b, as shown in FIG. (Not shown), and stretch blow molding is performed while blowing compressed air using a molding die having a body having a smooth surface as in the conventional case.

Further, the molded plastic bottle A
After cooling until the shrinkage of the body of the container is stable, when it is taken out of the mold, it has a flat surface such that the outer surface of the bottle matches the inner surface of the mold, as shown in FIG. In the state where the temperature is the low temperature portion a, the expansion due to the compressed air is small.

As described above, since the far-infrared ray generating layer 6 is provided in the temperature control block 4, the influence of the depth is less than the temperature interference in the vertical direction, so that the thickness of the thick portion p can be increased. Becomes

The ring-shaped thick portion p serves as a reinforcing rib, and can prevent bulging when the contents are filled.

In the above description, the hot parison method has been described. However, when using the cold parison method, a preformed parison (preform) is heated to a predetermined temperature by a temperature controller or the like, and then the hot parison method is used. Similarly to the above, a parison may be inserted into the temperature control pot to partially adjust the temperature to a low temperature part and a high temperature part, and stretch blow molding may be performed using the same method as in the above embodiment.

[0019]

EFFECT OF THE INVENTION The present invention is constructed as described above, and the molding die does not have a complicated shape such as a reinforcing rib having irregularities, and the molded bottle has a horizontal wall thickness. Since it is provided with a portion to increase the strength, it is possible to manufacture a bottle capable of preventing dents of hot-filled bottles such as beverages, and when attaching a label, there is no unevenness on the outer surface, so after molding Alternatively, it is an excellent method for producing a plastic bottle, which can be applied simultaneously with molding and can be easily and neatly attached.

[Brief description of drawings]

FIG. 1 is an explanatory view of a temperature control pot and a parison in an example relating to a method for producing a plastic bottle of the present invention.

FIG. 2 is a partially enlarged cross-sectional explanatory view of the heated parison of the present invention.

FIG. 3 is an explanatory cross-sectional view showing a part of a plastic bottle manufactured according to the present invention.

FIG. 4 is an explanatory cross-sectional view showing a part of a plastic bottle manufactured by a conventional method.

[Explanation of symbols]

 1. … Parison 2. … Temperature control pot 3. … Parison insertion hole 4. … Temperature control block 5. … Thermal insulation layer 6. ... Far infrared ray generating layer a. ... Low temperature part b. … High temperature part p. ... Thick part A. … Plastic bottles

Claims (2)

[Claims] 1. A method of manufacturing a plastic bottle in which an injection-molded bottomed tubular parison is stretch blow-molded in a mold, wherein a portion corresponding to a body part of the parison after molding is horizontally oriented before the mold is inserted. Adjust the temperature so that it has a high-temperature part and a low-temperature part in a range that is higher than the mold temperature during stretch blow molding, and insert this parison into a mold whose body has a smooth surface. Then, a method for producing a plastic bottle, in which compressed air is blown into the bottle to blow-mold it so that the inner surface of the bottle is thicker at the low temperature portion than at the high temperature portion. 2. The method for producing a plastic bottle according to claim 1, wherein the high temperature portion is heated via a far infrared ray generating layer.