JPS5962433A - Plastic vessel - 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 The present invention relates to a plastic container, and more particularly to a cup-shaped plastic container having a body wall with molecular orientation.

Conventionally used as a cup-shaped plastic container with a relatively thin body wall (e.g. 0.2 to 0.3 mm) and molecular orientation, improving container properties such as transparency, strength, impact resistance, and gas barrier properties. The main ones known are those in which the barrel wall is cylindrical and has a substantially uniform thickness along the circumference.

This type of plastic container can be used at high temperatures, e.g. 80 to 90°C.
After filling with juice or the like (so-called hot filling or hot gloss), the container is often sealed with a lid member and then cooled to room temperature.

During high-temperature filling, the heated barrel wall undergoes thermal contraction and molecular orientation), and this is accompanied by internal depressurization during cooling, causing the barrel wall to deform unevenly and even after opening. There was a problem in that a localized permanent dent that never recovered occurred, and the location and degree of the permanent dent differed from container to container, resulting in a significant decrease in commercial value. However, in conventional containers of this kind, the wall thickness at the corner portions is extremely thin (for example, approximately 0.5 mm thick).
1) Therefore, there was a problem that large permanent dents were formed in the corner portions, reducing the commercial value.0 The object of the present invention is to solve the problems of the prior art described above.

In order to achieve the above object, the present invention provides a cup-shaped plastic container having a body wall portion with molecular orientation, the body wall portion having a relatively thick wall portion having a large curvature and a relatively thick wall portion extending in the axial direction. The present invention provides a plastic container characterized in that thin-walled portions that are relatively thin and have a small curvature are alternately formed in the circumferential direction.

The present invention will be described below with reference to the drawings which are examples.

In FIGS. 1, 2, 3, and 4, 1 is a cup-shaped plastic container (hereinafter referred to as a container), and has a roughly cylindrical body wall 2 and a bottom wall 3. However, a flange portion 4 is formed at the upper end portion of the body wall portion 2. The upper part 2a of the body wall part 2 is cylindrical, but the part 2b below the upper part 2a has a relatively thick wall (for example, about 0.35 cm) extending in the axial direction and having a large curvature. part 2m, and a thin part 2n that is relatively thin (for example, approximately 0.25 tone) and has a small curvature.
are approximately equally spaced in the circumferential direction and alternately (in the case of the figure, 4
) is formed one by one.

Along with this, the bottom wall part 3 is also connected to the thick part 2m,
A substantially triangular thick-walled protrusion (3) with one side on the peripheral edge is formed. A portion 3n between the thick protrusions 3m and a portion 3p near the center are relatively thin.

The container 1 is made of thermoplastics capable of molecular orientation, such as isotactic polypropylene, crystalline polyolefins such as high-density polyethylene, medium-density polyethylene, and low-density polyethylene, linear polyesters such as polyethylene terephthalate, polycarnate, polyvinyl chloride, Mainly composed of polystyrene, nitrile resins, copolymers or blends thereof, and molecularly orientable thermoplastics, oxygen gas barrier resins such as ethylene-vinyl alcohol copolymers, polyamides, cellulose resins, and I-resin resins are also used. It is formed from a laminate or blend of acrylonitrile, polyvinylidene chloride, polyvinyl alcohol, etc.

Two of the body walls are molecularly oriented to improve container properties such as transparency, strength, and gas barrier properties. Normally, there is no extremely large difference in the degree of molecular orientation between the thick wall portion 2m and the thin wall portion 2n (4).

FIG. 5 shows that after the container 1 of FIG. 1 is filled with orange juice at 90° C. (height of the head wave is 10 arms), a lid member (not shown) is heat-sealed to the 7-run part 4 to seal it. This figure shows the unsealed state after cooling to room temperature. In this case, the container 1 is composed of an outer layer of polyzolopyrene ■, an inner layer of 17 μm thick noethylene-vinyl alcohol II (B), and an adhesive layer of maleic anhydride-modified polyzoropyrene (C) that adheres the outer layer and the inner layer. The upper part 2a of the trunk wall has an outer diameter of 541D11 and a total height of 95m, and an average thickness of the thick part of 2m of 0.5m.
35 tone, curvature radius 24m1, average molecular orientation degree 6.5 times, average thickness of thin part 2n 0.25mm, curvature radius 40fi,
The average molecular orientation was 7.0 times, the average thickness of the 3 m thick protrusion of the bottom wall was 1.5 m, and the average thickness of the 3 nt 3 p portion was 1.0 ym.

In Figure 5, the thick part 2m is slightly (approximately 2m thick) due to heat shrinkage.
m) Although the height is low, since the curvature is large and the wall is thick, it acts as a kind of support, and there is almost no deformation such as dents due to heat shrinkage and depressurization. and thin part 2n
Although a slight concave deformation part 7 occurs, especially in the lower part of the container, the location and extent of the concave deformation part 7 are determined, and the difference from container to container is small. Therefore, the consumer is given the impression that the container with the concave deformation portion 7 has the original shape of a filled and sealed container, so there is almost no decrease in the product value.

Reference numeral 11 in FIG. 6 shows a container in which the body wall 12 has a rectangular cylindrical shape with rounded corners and molecules are oriented. The container 11 is equipped with a bottom wall part 13 and a flange part 14, and the curved corner part of the body wall part 12 is a relatively thick thick part 12m, which is almost flat with almost no curvature. The thin-walled portions 1 and 2n are relatively thin. Note that the portion of the bottom wall portion 13 that is connected to the thick wall portion 12m is relatively thick.

In this case as well, after hot filling, sealing, and cooling, the thick wall portion 12m of the body wall portion 12 is hardly deformed, and the thin wall portion 12n is uniformly depressed and deformed, so that there is almost no decrease in commercial value.

The container 1 of the present invention is manufactured by the inventors of the present invention in a patent application filed in 1983, for example.
- In the method proposed in No. 7701, the bottom wall portion 3
It is manufactured by using a lower plunger having four parts formed on the upper surface portion corresponding to the thick protrusion 3m.

That is, in FIGS. 7 to 12, 21 is an upper plunger, 22 is a lower plunger, 23 is a die, and 24 is a presser foot or a pad. The die 23 is fixed to a holding member (not shown), and has an upper cavity 23a and a lower cavity 23b. Upper cavity 23
a has a short cylindrical shape, and its inner diameter is determined to be approximately equal to the outer diameter of the seven rungs 4 of the container 1 to be formed (FIG. 12) 1, while the lower cavity 23b has a cylindrical shape. , its inner diameter is defined to be substantially equal to the outer diameter of the body wall 2 of the container 1. Inner surface 23a of upper cavity 2, 3a
1 is connected to the lower cavity 2 via the horizontal step portion 23e.
It is connected to the inner surface 23b1 of 3b.

The outer diameter of the upper plunger 21 is equal to the inner diameter 2 of the lower cavity.
3b1 (see FIG. 10) is determined to be larger than the maximum thickness y of the body wall portion 5a of the hollow molded body 5 formed by compression stretch molding, for example, x -
y=Q, which is set at about 2 to 0.8 tan.

As shown in FIG.
7 is formed in the axial direction, and the guide hole is normally closed. The guide hole 27 communicates with a pressurized air source (not shown) via a conduit and a solenoid valve (not shown), and is connected to the upper syringe 21 by a limit switch (not shown).
When the bottom surface 21a is located below the level of the stepped portion 23c, the electromagnetic valve is opened and pressurized air is supplied to the guide hole 27. A heater (not shown) is built in, and the bottom surface 21a and side surfaces 21b are maintained at a temperature close to the temperature at which the molecules of the plastic forming the container 1 can be oriented.

The lower plunger 22 is configured to be able to slide inside the lower cavity 23b, and as shown in FIG.
, the peripheral edge portion of the upper surface 22a forms one side, that is, the four triangular portions 22a1 are open and have a flat bottom surface.

The center portion 221L'2 of the upper surface 22a and the portion 22a'2 between the recesses 22a1 are flat convex portions 22a2.
It becomes. The depth of the four parts 22a1 is usually 0.5 to 2.
It is 0 ■.

The presser foot pad 24 has a hollow portion 24a (FIG. 12), and the upper plunger 2 is inserted along the inner surface of the hollow portion 24a.
-1 is configured to be slidable. Presser foot/IP pad 24
The bottom surface 24b is flat and is disposed to face the stepped portion 23c, and the lower part 24c is movable up and down within the upper cavity 23a, and its outer diameter is approximately the same as the inner diameter of the upper cavity 23a. Equal to or slightly smaller than that. The presser pad 24 is moved up and down via a rod 25 by a drive mechanism (not shown).

(9) The upper syringer 21 and the lower plunger 22 are also moved up and down by a drive mechanism (not shown), and the bottom surface 21a of the upper plunger 21 and the upper surface 22 of the lower syringer 22
During the interval a, the center part 10 of the plastic material piece 10 (hereinafter referred to as the material piece) is pressed so that a controlled compressive force can be applied to the center part 10a when it is introduced into the lower cavity 23b. In order to achieve this, a control mechanism (not shown) controls the lowering speed difference between the upper plunger 21 and the lower plunger 22.

The container 1 is manufactured using the above-mentioned apparatus as follows.

10 pieces of material (usually about 1.5 to 4 mm thick)
is uniformly heated at room temperature or at a temperature lower than the upper limit of molecular orientation temperature, and then placed on the stepped portion 23e as shown in FIG. flange with a predetermined pressing force. Next, the upper plunger 21 and the lower plunger 22 are brought into contact with the center part 10a of the material piece 10, and while compressing the center part 10a, the upper syranger 21 and the lower plunger 22 are simultaneously pressed, as shown in FIG. 9 (10). Lower cavity 23bl; J [lower.

Then, the compression force in the early stage of descent (usually the stage until reaching about 20 to 40 inches in the entire process) is made relatively high to increase the amount of compression in the central part 10a, that is, to extend it between the two syringes. The amount of material is increased so that the body wall portion 5''a formed by the extending material substantially fills the gap between the inner surface 23bl of the lower cavity and the side surface 21b of the upper syringe, as shown in FIG. ie, during said step of descent, material accumulates in said voids.

If the compression force is reduced and the descent continues after passing through the above stage, the amount of material extending from between both norangers will decrease, and tension will be applied to the accumulated material in the trunk wall portion 57a, causing the trunk wall to tighten. The portion 5'a is extended.

At this time, molecular orientation is performed. Therefore, in the latter stage of descent after the above-mentioned stage, the trunk wall portion 5a (FIG. 10)
It is formed by the material supplied by the stretching of the trunk wall portion 5'a during formation and the material extending from between both norangers. Therefore, when the descent is completed, that is, when the hollow molded body 5 is formed, a gap 32 is formed between the body wall portion 5a and the inner surface 23bl of the lower cavity, as shown in FIG.

During molding, the lower cavity inner surface 23b1 and the upper surface 22a of the lower plunger 22 are kept at a temperature slightly lower (usually about 20 to 50 degrees Celsius lower) than the lower limit of molecular orientation humidity of the plastic, for example, about 20 to 50 degrees Celsius in the case of polypropylene, by a built-in heater (not shown). The temperature is maintained at 70-100°C.

After the hollow molded body 5 is formed, when the upper plunger 21 is raised, the plug 28 is lowered by air pressure as shown in FIG. Pressure air is blown out, and the hollow molded body 5 is blow-molded (some molecular orientation is performed at this time).
The bottom wall portion 5b is in close contact with the upper surface 22a of the lower plunger, and the body wall portion 5a is in close contact with the inner surface 23b1 of the lower cavity, and is cooled to a temperature lower than the temperature at which molecular orientation is possible and hardened.

Then, as shown at 1211, a container 1 having seven rungs 4, a trunk wall 2 and a bottom wall 3 is formed. After the upper plunger 21 comes out of the container 1, the presser nod 24 and the lower plunger 22 are raised to extract the container 1 from the die 23.

In the above process, during stretching in the latter stage of molding, the amount of material extending from between the upper plunger 21 and the lower syringe 22 is reduced to the recess 22a on the upper surface of the lower syringe.
1 and the convex portions 22a2 between each concave portion 22a1, and the amount of extension from the former is greater, so the hollow molded body 5
The wall thickness of the portion of the trunk wall portion 5a (FIG. 10) corresponding to the concave portion 22al is thicker than that of the portion corresponding to the convex portion 22a#2. When pressurized air is blown into the hollow molded body 5 and the body wall portion 5a comes into contact with the inner surface 23bl of the lower cavity, the thin portion of the body wall portion 5a corresponding to the convex portion 22a''2 is removed from the body wall portion corresponding to the four portions 22a1. It cools and hardens before the thick part of the portion 5a and contracts in the circumferential direction, and is still in an unhardened state where cooling is slow (that is, at a temperature that allows molecular orientation).
Since the thick part is pulled from both sides in the circumferential direction, the thick part is bent in the circumferential direction and its curvature is larger than that of the thin part (13
) It is presumed that a thick wall portion 2m with a large curvature and a thin wall portion 2n with a small curvature are formed.

The container 11 shown in FIG. 6 has a body wall portion 12 having a rounded corner cylindrical shape.
Lower plunger and die cavity, FIG.
It can be manufactured by the same method as the container 1 by using a lower syringe 42 having four portions 42a1 extending from each corner toward the center on the upper surface 4.2a as shown in FIG. 14.

The present invention is not limited to the above embodiments,
The bottom wall of the container may be flat. Such a bottom wall portion is formed, for example, as follows. That is, the lower plunger is constructed of a main body extending in the axial direction corresponding to the convex portion, a plurality of sliding members extending in the axial direction corresponding to each of the four parts and capable of sliding along the main body, and the above-mentioned hollow molded body. 5. Until just before the end of the latter stage of forming, molding is performed with the sliding member recessed relative to the main body as described above, and at the final stage, the sliding member is raised along the main body so that the upper surfaces of both (14) are the same. By leveling them, a flat bottom wall can be obtained.

Further, the shape of the seven rung portions can also take various shapes depending on the step portion and the shape of the upper cavity.

The container of the present invention has excellent container properties such as transparency and gas barrier properties because the molecules are oriented in the body wall, and the body wall has a thick part with a large curvature and a thin part with a small curvature in the circumferential direction. Because they are formed alternately, permanent concave deformation that occurs after hot filling, sealing, and cooling occurs uniformly only in the thin-walled parts, which has the effect that there is almost no risk of loss of commercial value. can.

[Brief explanation of the drawing]

FIG. 1 is a front view of a container according to a first embodiment of the present invention, FIG. 2 is a bottom view of the container shown in FIG. 1, and FIG.
Figure 4 is a longitudinal cross-sectional view along line IV-IV in Figure 2, Figure 5 is the state after hot filling the container in Figure 1, sealing and cooling, and opening. 6 is a perspective view of the container according to the second embodiment of the present invention, and FIGS. 7, 9, 10, 11, and 12 are views of the container of FIG. 1. A vertical cross-sectional view showing an example of the manufacturing process, Figure 8 is the same as ■ in Figure 7.
13 is a plan view of an example of the upper plunger used in manufacturing the container shown in FIG. 6; FIG. 14 is a longitudinal sectional view taken along line XIV-XIV in FIG. 13. . ■...Plastic container, 2...Body wall, 2m...
・Thick wall part, 2n... Thin wall part, 11... Plastic container, 12... Trunk wall part, 12m... Thick wall part, 12n
...thin section patent applicant Kishimoto Sho 233 Figure 9 Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] (1) A cup-shaped plastic container having a body wall with molecular orientation, the body wall having a relatively thick wall with a large curvature extending in the axial direction, and a relatively thin wall with a small curvature. A plastic container characterized in that thin-walled portions are formed alternately in the circumferential direction.