JPH0469226A - Preliminary molded piece made of resin, biaxially drawn blow molded container using it and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a container with self-standing stability by a method wherein a part corresponding to a heel part of the container after blow molding is formed of a hollow wall consisting of an inside resin layer and an outside resin layer holding a hollow layer between them and the other part is made filled. CONSTITUTION:A bottom part of a preliminary molded piece 1 and the lower end part 4 of a trunk part of the preliminary molded piece 1 to be a heel part 68 are made a hollow wall wherein an outside resin layer 35 and an inside resin layer 34 form a hollow layer 36. Then, biaxially orienting blow molding of the main body of the preliminary molded piece 1 is performed to make the outside resin layer 35 to be a bottom part 66 which is not influenced by the inner pressure of the container 6 and is not deformed therefore and as the result, a container 6 with self-standing stability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resin preform, a biaxial stretch blow molded container using the preform, and a method for manufacturing the same.

[Prior art and problems to be solved by the invention] Resin containers, especially bottles, for enclosing carbonated drinks, fruit juice drinks, etc.
It is generally manufactured by injection molding a saturated polyester resin or the like, followed by stretch blow molding.

Such containers must be rigid enough to withstand impact forces and internal pressures within the container itself, such as those found when containing carbonated beverages, without deformation. In particular, the bottom of the container is a part that is subject to not only internal pressure but also large loads such as the weight of the container itself and the impact force during handling. The bottom part is easily deformed.

To this end, devices have been devised and used in which various regular irregularities are formed on the bottom to increase rigidity. (For example, Japanese Patent Publication No. 48-5708 and Japanese Patent Publication No. 48-9880, etc.).

An example of this is one in which the bottom is formed in a so-called betaroid shape (petal shape). In some cases, a pace cup manufactured in a separate process is attached to the bottom of the container to achieve self-support and resistance to deformation under internal pressure. The latter method is the most widely practiced.

However, the method using a pace cup requires separate processes such as molding the pace cup and assembling it into a bottle, resulting in high costs. In addition, the petaloid type must be thick to increase the strength of the bottom. Furthermore, since the ground contact surface does not cover the entire circumference, the product lacks stability during transportation on molding lines, filling lines, etc. There are also problems such as stress cracks occurring.

Therefore, the object of the present invention is to solve the above-mentioned problems and
It is an object of the present invention to provide a self-supporting and stable container that can be manufactured at low cost and in a simple process, a preform used for manufacturing the same, and a method for manufacturing a container from the preform.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventors have determined that the bottom of the preform and the lower end of the body of the preform, which will serve as the heel of the container, have a hollow structure in which the outer resin layer and the inner resin layer form a hollow layer. By first injecting gas into this hollow layer and stretch blow molding only the outer resin layer, and then biaxial stretch blow molding the main body of the preform, the outer resin layer will deform without being affected by the internal pressure of the container. discovered that it is possible to manufacture containers that are self-sufficient and stable.
The invention has been completed.

That is, the bottomed cylindrical resin preform of the present invention is
Consisting of a mouth, a body, and a bottom, the bottom and the lower end of the body. The part corresponding to the heel part of the container after blow molding is formed by a hollow wall consisting of an inner resin layer and an outer resin layer with a hollow layer in between, and the other parts are solid. , characterized in that the bottom outer resin layer has a gate portion in the form of a narrow opening at the lower end of the outer resin layer.

Further, the biaxially stretched blow-molded container of the present invention has a solid mouth and body, and a bottom consisting of an inner resin layer and an outer resin layer, and the inner resin layer is smoothly continuous with the body. The outer resin layer forms an inner wall of the bottom, and the outer resin layer is in close contact with the inner resin layer at the center of the bottom, and is in contact with the inner resin layer at least at the ground contact portion of the heel located at the periphery of the bottom. It is characterized by forming a part.

Furthermore, the method of the present invention for producing a biaxially stretched blow-molded container from the above-mentioned preform includes (a) heating the preform to a temperature suitable for stretching, and (6) stretching the lower end of the preform. Stretching only the outer resin layer by blowing gas through the gate part with the inner side of the inner resin layer fixed by a core mold using a partial stretching mold,
(c) Place the preform obtained in (c) above in a container stretching mold, sandwich the bottom of the preform from above and below between the tip of the stretching rod and a bottom mold that is driven up and down, and then layer the outer resin layer. The body part and the inner resin layer of the preform are stretch-blow molded while the hollow layer formed by the preform and the inner resin layer is filled with gas.

[Examples and effects]

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

FIG. 1 is a sectional view showing a preform according to an embodiment of the present invention. The preform 1 consists of a mouth part 2, a body part 3, and a bottom part 4.

The mouth part 2 is solid and has a screw fastening part and a support ring part.

The body portion 3 has a wall thickness changing portion 3 corresponding to the shoulder portion of the container to be obtained.
1, a solid wall portion 32 having a substantially uniform thickness and occupying approximately from the top to the bottom of the body portion 3; and a solid wall portion 32 located at the lower end of the body portion;
The outer resin layer 35 and the inner resin layer 34 constitute a hollow wall portion 33 forming a hollow layer 36, and the hollow wall portion 33 continues to the bottom portion 4 with the above-described structure. In addition, this inner wall part 3
3, which will be described in detail later, is a portion that will become a heel portion (including a ground contact portion) located around the bottom of the resulting container.

As described above, the bottom part 4 is continuous with the hollow wall part 33 at the lower end of the body part, and is a hollow wall made of an outer resin layer 35 and an inner resin layer 34. Note that the inner resin layer 34 forms a closed bottom inner wall portion of the preform 1. A gate portion 41 is formed in the center of the outer resin layer 35 in the bottom portion 4 , and the gate portion 41 has a small diameter hole portion 42 communicating with the hollow layer 36 .

In the preform 1 shown in FIG. 1, the solid wall portion 32 of the body has a thickness of 1. The thickness t2 of the hollow wall portion 33 is larger,
A step is provided on the inner surface of the preform to vary the thickness. In addition, as can be seen from FIG. 1, no step is formed on the outer surface from the body part 3 to the bottom part 4.

FIG. 2 is a sectional view showing a preform according to another embodiment of the invention. This preformed body 5 also consists of a mouth part 51, a body part 52 and a bottom part 53, as in the previous embodiment.
The preform 1 shown in FIG.
It has a similar structure. From the lower end 52 a of the body 52 to the bottom 53 , an outer resin layer 54 and an inner resin layer 55 form a hollow wall portion forming a hollow layer 56 . A gate portion 57 is formed at the center of the bottom of the outer resin layer 54.
This gate portion 57 has a small diameter hole portion 58 that communicates with the hollow layer 56 .

As can be seen from FIG. 2, in this preform 5, there is no change in thickness between the solid wall portion of the body and the hollow wall portion 52a of the lower end of the body. Further, the thickness t3 of the bottom portion including the hollow layer 56 is greater than the thickness t of the solid wall portion of the body portion 52.

As shown in Figures 1 and 2, by changing the thickness of the lower part and bottom of the body of the preform and the shape of the hollow layer, it is possible to change the shape of the bottom of the container as appropriate. Become. The shape of the bottom of the container will be described later.

The preforms shown above are manufactured by G, I, P, molding method (Ga
sInjection Process, Mannes
Mann Demag), A.

M, P, method (^ir Mold Process,
Battenfeld Company), or Special Publick 1984-14
It can be molded by the hollow molding method described in No. 968.

FIG. 3 is a partially sectional side view showing a container according to an embodiment of the present invention, which is obtained by biaxial stretch blow molding the preform 1 of FIG. 1 by a method described later.

The container 6 has a mouth portion 61, a shoulder portion 62, a body portion 63, and a bottom portion 6.
It consists of 4. The mouth portion 61 has the same shape as the mouth portion of the preform 1, and the shoulder portion 62 is a portion formed by extending the thickness changing portion 31 of the body portion of the preform 1. Further, the body portion 63 is a portion formed by extending the solid wall portion 32 of the body portion of the preformed body 1. The bottom part 64 is a part formed by extending the hollow wall part 33 and the bottom part 4 from the lower end of the body of the preform 1 to the bottom, and the container bottom wall 65 is a part formed by the extension of the inner resin layer 34 of the preform 1. This is the part that becomes. Further, the stretched portion of the outer resin layer 35 of the preform 1 constitutes an outer bottom portion 66 and a heel portion 68 of the container, and forms a hollow layer 67 between it and the bottom wall 65 of the container.

FIG. 4 is an enlarged partial cross-sectional view of the bottom of the container 6 shown in FIG. 3. In this embodiment, the container bottom wall 65 has a rounded convex surface toward the outside of the container. In this way, by making the bottom of the container convex and smoothly continuous with the body of the container, it is possible to maintain the internal pressure even when the pressure inside the container becomes large (for example, when filled with carbonated drinks, etc.). The bottom part can be made to withstand. Note that it is also possible to make the bottom wall of the container flat.

Outer bottom portion 66 formed from the outer resin layer of the preform
is formed to have a hollow layer 67 between it and the bottom wall 65 of the container as described above, but the vertical width of the hollow layer is large almost at the circumference of the bottom of the container, and the lower part of the heel part 68 becomes the grounding part 69. That is, a circular grounding portion is formed at the periphery of the bottom surface of the container.

As shown in the figure, the central portion of the outer bottom wall 66 is in close contact with the lower surface of the bottom wall 65 of the container, and the hole 70 originating from the small diameter hole of the gate portion of the preform is closed. . Further, the hole 70 is located above the grounding portion 69, and the entire outer bottom surface portion 66 has an upwardly recessed shape.

A container bottom having such a structure has the following advantages.

(1) The outer bottom portion having the ground contact portion is not substantially deformed by the internal pressure of the container. Therefore, the shape of the recess at the center of the outer bottom part is not reversely deformed, and good self-supporting properties are obtained.

(2) Since the bottom wall of the container is smoothly continuous with the container body, there is no area where a particularly large force (stress) is concentrated due to the internal pressure of the container, and stress cracks do not occur.

(3) The hole originating from the gate part of the preform is located at a higher position than the grounding part, and the outer bottom part is in close contact with the bottom wall of the container at that part, so water etc. cannot enter from here. do not have.

Furthermore, in addition to the above-mentioned structural advantages, (4) the container body and the bottom part with the heel part including the ground contact part are integrally formed, so there is no need for a process to attach pace cups, etc. This simplifies the manufacturing process.

(5) The resin of the container body and the bottom of the container, which becomes the base portion, can be the same, and when used containers are recycled, they are advantageous in terms of recyclability because they are made of a single resin.

(6) Compared to petaloid bottle molding, the blow molding has advantages such as the bottom mold can have a shorter removal stroke, and a molding machine with a large mold opening is not required.

FIG. 5 is a partial cross-sectional view of the bottom of a container according to another embodiment of the invention. In this embodiment, most of the outer bottom surface portion 71 is brought into close contact with the lower surface of the container bottom wall 72, and the bottom portion is shaped such that a hollow layer 74 is provided only in the vicinity of the portion that will become the grounding portion 73. In this way, the shape of the bottom of the container can be changed in various ways. Furthermore, the ground contact surface does not extend all the way around, and the outer bottom surface can be provided with a stack of reinforcing ribs such as uneven radial ribs.

Next, a method for manufacturing a container having the above shape from the preform of the present invention will be explained.

FIG. 6 is a sectional view showing a mold (hereinafter referred to as a partial stretch mold) for stretch-molding the outer resin layer of the hollow wall portion located near the bottom of the preform in FIG. A state in which the molded body 1 is installed in the mold is shown.

The partial stretching mold 8 has a body mold 81 , a mouth mold 82 , a bottom mold 83 and a core mold 84 .

The mouth mold 82 holds the mouth of the preform 10, and the body mold 81 has a cavity large enough to tightly contact the outer surface of the solid wall 32 of the preform 1. In the lower hollow wall portion of the preform 1, a cavity portion 86 is formed which bulges out from the surface of the outer resin layer 35 of the preform 1. That is, this bulging cavity portion 86 has a mushroom umbrella shape at the tip portion of the preformed body 1.

The bottom mold 83 has a pipe part 85 in its center for blowing gas, and the upper end of the pipe part 85 receives water from the gate part 41 of the preform 1. That is, the gas flowing in from the pipe portion 85 enters the hollow layer 36 of the preform 1. Note that an O-ring 87 is provided at the portion that contacts the gate portion 41 to maintain airtightness.

The core mold 84 is inserted into the preform 1 from the mouth thereof, and is in tight contact with the inner resin layer 34 that is the bottom surface of the preform 1 . This can prevent the inner resin layer 34 from being deformed during partial stretch molding of the outer resin layer, which will be described later.

As shown in FIG. 6, the preform 1 is placed in a partial stretching mold 8, and after being maintained at a temperature suitable for stretching the resin constituting the preform 1, a gas such as air or nitrogen is passed through the tube 85 into the hollow. By blowing into the layer 36, only the outer resin layer 35 is stretch blow molded. By this partial stretch blow molding, the outer resin layer 35 is molded into the shape shown in FIG. 7. In FIG. 7, 35a is a portion molded from the outer resin layer 35. The shape of the tip of the preform shown by the dotted line in FIG. 7 shows the deformed state immediately before the gas is pressurized from the bottom mold. This deformation occurs because the preform is pushed upwards by the bottom mold 83 to maintain airtightness at the gate.

The above-described partially stretch-blow-molded preform 1a is placed in a container stretch-blow mold 9 as shown in FIG.
Perform stretch molding of the container body.

The container stretch blow molding mold 9 has a body mold 91 having a container-shaped cavity, a mouth mold 92 that grips the mouth, and a bottom mold 93 that is vertically movable.

The preform 1a is placed in the mold 9 with its bottom portion supported by a bottom mold 93 from below.

Here, stretch blow molding is performed using a stretch rod in the same way as normal biaxial stretch blow molding, but in the method of the present invention,
Biaxial stretch blow molding is performed with the bottom portion of the preform 1a being held between the top and bottom of the preform 1a by the tip of the stretching rod 94 and the bottom mold 93. That is, biaxial stretch blow molding is performed by interlocking the entry of the stretching rod 94 and the downward movement of the bottom mold 93. This prevents the bottom portion of the preform, which has been partially stretch-molded, from being irregularly deformed. This is because the outer resin layer 35a is formed by the stretching rod 94 and the bottom mold 93.
and the inner resin layer 34 are in close contact with each other, and the narrow opening of the gate portion is closed. Therefore, stretch blow molding is performed while the hollow layer portion 36a is sealed, and the bottom of the desired structure can be accurately formed. High-pressure gas can be simultaneously blown into the hollow layer portion by the pressure of the gas used to stretch-blow mold the main body, and this may be carried out as appropriate if necessary.

Although the present invention has been described above in detail using the drawings, the present invention is not limited thereto, and it goes without saying that various modifications can be made without departing from the spirit of the present invention. Both a hot parison method in which the above-mentioned steps are performed continuously and a cold parison method in which the steps of preforming and stretch blowing are separated can be applied.

The present invention will be explained in more detail by the following specific examples.

Example 1 Polyethylene terephthalate resin with an intrinsic viscosity of 0.76 (
A preformed body having the shape shown in FIG. 1 was produced using a Mitsui PET) J125 (manufactured by Mitsui Petrochemical Co., Ltd.).

The amount of resin used was 53g, and the wall thickness of the part including the hollow layer (
tz) in FIG. 1 was 5 mm. Moreover, the width of the hollow layer part with respect to the entire thickness of the hollow wall part is 30 to 40
%.

This preform was placed in a partial stretching mold having the shape shown in Fig. 6, and the bottom mold and body mold were heated at 75°C and
The temperature was kept at 0° C., and only the outer resin layer of the hollow wall of the preform was molded as shown in FIG.

Here, the diameter of the stretched portion of the outer resin layer (the diameter of the mushroom umbrella-shaped portion) was 50 mm.

Subsequently, without cooling this preform, the body diameter was reduced to 9.
It had a cylindrical shape of 3 mm and a total height of 300 mm, and was placed in a container forming mold of 1.5 mm, and biaxial stretch blow molding was performed as shown in FIG.

The container thus obtained had a bottom portion having the structure shown in FIG.

This container was filled with carbonated water containing 4.0 gas volume of carbon dioxide and left at 38° C. for 24 hours.

Even after 24 hours of study, no deformation due to protrusion or the like was observed on the bottom. Moreover, the self-supporting property was also good.

Furthermore, when this container was subjected to a 2 m drop test while filled with water, no damage such as bursting was observed at the bottom.

〔Effect of the invention〕

As described in detail above, when a container is manufactured by the method of the present invention using the preform of the present invention, the container can have good self-supporting stability.

In the method of the present invention, since the base portion of the container is formed integrally with the container body, steps such as attaching a base cup etc. can be omitted, and the cost does not increase.

Further, even if the internal pressure of the container becomes high, it will not deform the heel portion including the ground contact portion, and stress cracks will not occur. Therefore, it is also suitable for containers containing items with high content pressure, such as carbonated drinks.

Furthermore, the entire container from the mouth part to the base part can be manufactured in one step using only polyethylene terephthalate resin, for example, resulting in advantages such as simplification of the manufacturing process and improved recyclability.

[Brief explanation of drawings]

1 and 2 are respectively sectional views showing a preform according to an embodiment of the present invention, FIG. 3 is a partially sectional side view showing a container according to an embodiment of the present invention, and FIG. and FIG. 5 are sectional views showing the bottom of a container according to an embodiment of the present invention, and FIG. 6 is a diagram showing an apparatus for stretch-blow molding the outer resin layer near the bottom of the preform by the method of the present invention. FIG. 7 is a partial cross-sectional view showing a state in which the outer resin layer of the preform is stretch-blow molded using the apparatus shown in FIG. 6; FIG. 1 is a schematic cross-sectional view showing an example of an apparatus that can biaxially stretch blow mold a preform to form a container. 1, 5 ・ 2.51 ・ 3, 52 ・ ・ 4.53 ・ ・ 6 ・ ・ ・ ・ 8 ・ 9 ・ 31 ・ ・ ・ 32 ・ 33, 52a 34.55 ・ 35.54 ・ 38, 56i, 6-7 41, 57 ・ 42, 58 ・ 61 ・ 62 ・ Preformed body Mouth part Body bottom Container part Stretch molding mold Container stretch blow molding mold Wall thickness change part Solid wall part Hollow wall part Inner resin layer Outer resin layer Hollow layer gate part Small diameter hole part Container mouth part Container shoulder part 63 ・ ・ ・ 64 ・ 65, 72 ・ 66, 71 ・ 68 ・ 69, 73 ・ 81, 91 ・ ・ 82, 92 ・ 83, 93 ・ 84 ・ 85・ 94 ・ Container body Container bottom Container bottom wall Outer bottom surface Heel portion Ground portion molding mold Body molding mold Mouth molding mold Bottom core mold Gas blowing pipe portion Extension rod

Claims (5)

[Claims] (1) A cylindrical resin preform with a bottom, which has an opening;
Consisting of a body and a bottom, a portion of the bottom and the lower end of the body that corresponds to the heel of the container after blow molding is a hollow wall consisting of an inner resin layer and an outer resin layer with a hollow layer in between. What is claimed is: 1. A preformed article, characterized in that the other part is solid, and has a gate portion in the form of a narrow opening at the lower end of the outer resin layer of the bottom portion. (2) In the preform according to claim 1, the thickness of the hollow wall including the hollow layer at the lower end of the body is substantially equal to the thickness of the solid wall of the body. A hollow wall that is larger than that at the lower end of the body and a solid wall of the body that has a substantially uniform thickness are smoothly continuous with no step on the outside of the preform, and A preformed body characterized by forming a continuous step on the inside of the preformed body. (3) The preform according to claim 1 or 2, wherein the thickness of the hollow wall including the hollow layer at the bottom is larger than the thickness of the solid wall of the body. body. (4) A container formed by biaxially stretch blow molding the preform according to any one of claims 1 to 3, comprising a solid mouth and body, an inner resin layer, and an outer resin layer. the inner resin layer forms a bottom inner wall that is smoothly continuous with the body, the outer resin layer is in close contact with the inner resin layer at a central portion of the bottom, and A biaxial stretch blow-molded container characterized in that a hollow portion is formed with the inner resin layer at least in a ground-contacting portion of a heel portion located at a peripheral portion of the bottom portion. (5) A method for manufacturing the container according to claim 4, comprising (a)
) heating the preform according to claim 1 to a temperature suitable for stretching, (b) using a partial stretching mold for stretching the lower end of the preform, and fixing the inside of the inner resin layer with a core mold. By blowing gas from the gate part in the state,
Stretching only the outer resin layer; (c) placing the preform obtained in (b) above in a container stretching mold; A method characterized by stretching and blow molding the body part and the bottom part of the inner resin layer of the preform while sandwiching the body from above and below and enclosing gas in the hollow layer formed by the outer resin layer and the inner resin layer.