JP3143939B2 - Hollow molded container and method of molding hollow molded container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow molded container whose outer surface is made of a polyester resin and a method for molding the same.

[0002]

2. Description of the Related Art Conventionally, in a molding die for a hollow molded container such as a plastic bottle, a parison having a predetermined length is supplied between a cavity forming wall surface facing each other when the mold is opened. Sometimes, the mold is clamped, and compressed air is supplied to the parison in the mold to press the parison against the cavity forming wall surface, and after the molded product is cured, the mold is opened.

When a molded article is molded by such a method for molding a hollow molded container (hereinafter referred to as blow molding),
If the wall surface of the cavity as a molded product forming space formed at the time of mold clamping is a smooth surface, the parison that expands during blow molding closely adheres to the cavity forming wall surface, and the space between the parison and the cavity forming wall surface becomes tight. Air stays on the outer surface of the molded product, and there is a problem that traces of the air pool remain as recesses on the outer surface of the molded product.

For this reason, the cavity forming wall surface of the blow molding die is provided with such a roughness that air can escape so that air cannot be trapped between the cavity forming wall surface and the parison.

However, such a conventional blow molding has a disadvantage that only a molded article having a low gloss on the outer surface can be formed.

In view of this problem, the present applicant has filed Japanese Patent Application No.
By inventing the mold described in the specification of 74228, it has become possible to obtain a molded article having high gloss without leaving traces of air pockets on the outer surface of the molded article. Generally, polyolefin resins such as ethylene and propylene are employed on the outer surface of such a hollow molded article.

[0007]

By the way, the hollow molded containers formed in this way are guided one after another on a groove-shaped transfer table and transferred to the next step (for example, a washing step). In addition, when the hollow molded containers come into contact with each other during the transfer due to the large friction coefficient of the surface of the polyolefin-based resin, there is a problem that the transfer is delayed without the contact portions sliding.

The present invention has been made in order to solve such a problem, and has a high degree of gloss, and when contacted with each other during the transfer, a hollow portion which allows the contact portions to slide easily without stagnation. It is an object of the present invention to provide a molded article and a molding method thereof.

[0009]

Hollow molded container according to claim 1 SUMMARY OF THE INVENTION The present invention, in order to solve the above problems, as well as constituting a polyester resin an outer surface in contact with at least a cavity formed wall, the outer Surface static friction coefficient
Is 0.45 to 0.66, and the dynamic friction coefficient is 0.30 to 0.4
Has a friction coefficient of 5 and a gloss of 60% or more 90% specular reflection
Having a rate.

[0010] The hollow molded container according to claim 2 of the present invention .
The molding method is such that the outer surface for hollow molding is a polyester between the cavity forming wall surfaces facing each other when the mold is opened.
In a method of molding a hollow molded container in which a parison made of a base resin is positioned and filled with the compressed air into the parison, a center line average roughness of the cavity forming wall surface is set to 0.25 μm or less. , Parting surface
A suction recess for sucking air is formed in the
Between the dent forming recess and the suction recess.
Shallow enough that the parison that expands when tightening does not enter, front
Before filling the parison with compressed air, a mold having a groove formed to communicate with the suction concave portion is used to suck air in a cavity outside the parison.

[0011]

According to the hollow molded container according to the first aspect of the present invention, since at least the outer surface in contact with the cavity forming wall surface is made of a polyester resin having a low friction coefficient, the hollow molded containers come into contact with each other during transfer. If they do, the contact sites will slide.

When the mold is in the open state, the outer surface for hollow molding is made of polyester between the cavity forming wall surfaces facing each other.
In a method of molding a hollow molded container in which a parison made of a base resin is positioned and filled with the compressed air into the parison, a center line average roughness of the cavity forming wall surface is set to 0.25 μm or less. , Parting surface
A suction recess for sucking air is formed in the
Between the dent forming recess and the suction recess.
Shallow enough that the parison that expands when tightening does not enter, front
Before filling the parison with compressed air, the mold is formed with a groove communicating with the suction recess, and the air in the cavity outside the parison is sucked. Even in this case, no air pockets are formed between the cavity forming wall surface and the parison, and the gloss of the outer surface of the hollow molded container can be as high as 90% or more by 60-degree specular reflection. Also, static friction
Coefficient is 0.45 to 0.66, dynamic friction coefficient is 0.30
A hollow molded container having a small friction coefficient of 0.45 can be obtained.
You.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a hollow molded container and a method of hollow molding a hollow molded container according to the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a mold (hereinafter simply referred to as a mold) for the hollow molded container according to the present embodiment. As shown in FIG. When tightened, a cavity 3 is formed. Since the configuration of the mold 2 is the same as the configuration of the mold 1, the description of the mold 1 is referred to for the description of the mold 2.

Before the molds 1 and 2 are clamped to each other, a parison 4 (see FIGS. 4 to 6) is supplied. The parison 4 is of a single-layer type or a laminated type, and the outermost layer is used. 4a is a polyester resin.

The molds 1 and 2 are made of, for example, aluminum and carbon steel, and a concave portion 5 for forming the cavity 3 at the time of mold clamping is formed on the parting surface 1a of the mold 1 which is in close contact with the mold 2. In the present invention, the walls of the recesses 5 of the molds 1 and 2 forming the cavity 3 are
a. The center line average roughness of the cavity forming wall surface 5a is set to 0.25 μm or less.

Suction recesses 6 and 7 are formed on the parting surface 1a so as to surround the periphery of the recess 5. The suction recesses 6 and 7 form air suction holes 8 and 8 when the molds 1 and 2 are clamped. Communication holes 9 and 10 communicating with the outside of the molds 1 and 2 are opened at the bottoms of the suction concave portions 6 and 7. The communication holes 9 and 10 are connected to air suction means 11 which will be described later, which is provided outside the dies 1 and 2.
Grooves 6a and 7a having shallow bottoms are formed between the concave portions 6 and 7 for suction and the concave portion 5 for forming a cavity. This groove 6a,
7a is an air suction hole 8 when the molds 1 and 2 are clamped.
8 is communicated to suck air from the cavity 3. Groove 6
a and 7a have such a depth that the parison 4 which expands when compressed air is blown into the parison 4 does not enter.

The upper end of the recess 5 holds the parison 4 cut off from an extruder (not shown) and a compressed air supply nozzle 21 inserted into the upper end of the parison 4.
Can be held via the parison 4. At the lower end of the recess 5 is provided a blade 13 for cutting off the lower end of the parison 4 supplied from the extruder. Air suction holes 14a, 14a connected to the air suction means 11 are opened in the wall surface 5b on the lower end side of the concave portion 5. Air suction hole
As shown in FIG. 2, thin plugs 15 and 15 made of sintered metal are fitted into openings 14a and 14a on the cavity 3 side,
The air in the cavity 3 is sucked through the stoppers 15 and 15.

As shown in FIG. 3, the air suction means 11 includes a vacuum pump 16, a chamber 17 for vacuum storage, pipes 18a and 18b.
And valves 19 and 20. Vacuum pump 16 is tube 18
connected to the chamber 17 via a
It is connected to the communication holes 9 and 10 and the air suction holes 14a and 14a via 8b. The valve 19 is provided on the pipe 18a, and the valve 20 is provided on the pipe 18b. Vacuum pump 16 and valves 19, 20
Are driven by a driving device (not shown). Until a predetermined length of parison 4 is supplied between the molds 1 and 2,
The valve 19 opens and the valve 20 closes, and the vacuum pump 16 operates to reduce the pressure in the chamber 17. The internal pressure of the chamber 17 is 300m below normal pressure by the operation of the vacuum pump 16.
mHg lower pressure. In this embodiment, before the compressed air supply nozzle 21 is inserted into the parison 4 held by the molds 1 and 2, the valve 19 is closed and the valve 20 is opened to allow the air in the cavity 3 to move into the chamber 17. Is sucked. As a result, the air in the cavity 3 is released from the air suction holes 8, 8,
It is introduced into the chamber 17 through the plugs 12 and 15 of 14a and 14b, and the pressure in the cavity 3 is reduced. When the pressure in the cavity 3 is reduced, the valve 20 is closed, the valve 19 is opened, the vacuum pump 16 is operated, and the pressure in the chamber 17 is reduced again. On the other hand, when the compressed air is supplied from the compressed air supply nozzle 21 in a state where the pressure in the cavity 3 is reduced, the parison 4 expands and comes into close contact with the cavity forming wall surface 5a of the concave portion 5, whereby the molded product 22 is formed.

FIGS. 7 to 10 show an application example of a molding die used in the hollow molding method for a hollow molding container according to claim 2 of the present invention.
Forms a cavity for blow molding by being clamped with a mold (not shown).

The molding die 30 is a split die and is composed of divided portions 31, 32, and 33 which are separably connected. The dividing portion 31 is a mouth forming wall surface 31a that forms the mouth of the hollow molded container.
And a blade portion 31b that cuts off the softened parison is formed above the mouth-forming wall surface 31a. The first opening wall surface 31a at the boundary part of the dividing part 31 separated from the dividing part 32 has the first
The air suction hole 31c is opened. The first air suction hole 31c is formed around the mouth forming wall surface 31a, so that air can be suctioned substantially uniformly from around the parison. A semi-annular plug 31d made of sintered metal is attached to the air suction hole 31c. Instead of attaching the plug 31d, the clearance between the divided portions 31 and 32 may be set so that the expanded parison does not enter. The thickness of the air suction hole 31c and the plug 31d is
If it has d, it is 0.3-1 mm in width, and if it does not have the plug 31d, it is 0.01-0.10 mm,
Unless the boundary between the mouth of the hollow molded container and the main body of the hollow molded container is carefully observed, the thickness is set so that the trace of the plug 31d is not visible. Since this part is a position covered by the end of the cap when the cap is attached to the mouth of the hollow molded container, when displaying with the cap attached, the observer finds a trace of the plug 31d. It is not possible. A lower portion of the air suction hole 31c communicates with an air hole 32f formed in the divided portion 32.

The divided portion 32 is a portion forming the hollow molded container main body portion of the hollow molded container. Since the bottom of the hollow molded container is raised, the divided portion 32 can be separated from the divided portion 33 to facilitate removal of the molded product. It is joined, and is detachably joined to the dividing portion 31 to facilitate the opening of the mouth. A cavity forming wall surface 32b forming a hollow molded container main body portion is formed in the parting surface 32a of the divided portion 32, and a peripheral portion of the cavity forming wall surface 32b is separated from the cavity when the molding die 30 is clamped. A shallow groove 32c for forming a slit for sucking air is formed. An air hole 32d is formed in the shallow groove 32c, and one end of the air hole 32d is open in the shallow groove 32c, and one end of the air hole 32d is made of a sintered metal that can transmit air. A plug 32e is fitted. The other end of the air hole 32d is open at the joint surface between the divided portion 32 and the divided portion 33, and communicates with the air hole 33e of the divided portion 33. The dividing portion 32 is joined to the dividing portion 31 by
An air hole 32f communicating with the first air suction hole 31c is penetrated.

The dividing portion 33 is for forming a protruding portion at the bottom of the hollow molded container, which protrudes into the hollow molded container to improve the strength, and has a curved bottom-forming wall surface having a rounded corner at the bottom. 33a. This bottom forming wall surface 33a
Is a portion corresponding to the boundary between the hollow molded container body and the bottom, and a semi-annular groove 33b as a second air suction hole is formed in the bottom forming wall surface 33a. This groove 33b
Is a second air suction hole formed by joining the divided portions 32 and 33.
Form 33g. A plug 33c made of a sintered metal that can be a semi-annular air lamp is fixed to the groove 33b.
May be set to a clearance such that the expanded parison does not enter. The outer periphery of the plug 33c is a space, which forms a part of the second air suction hole, and communicates with the air hole 33d penetrating through the division 33. The division 33 has air holes 33e and 33f in addition to the air hole 33d. The air hole 33e communicates with the air hole 32d of the division 32, and the air hole 33f communicates with the air hole 32f of the division 32. Pipes (not shown) are connected to the air holes 33d, 33e, and 33f, respectively, and the air in the cavity is sucked when the cavity is formed by controlling the amount of air by an air suction pump connected to each pipe.

In order to form a symmetrical hollow molding container by blow molding, it is necessary to prepare a mold having a shape symmetrical to the mold 30. Since the configuration of the second air suction hole is the same as that of the mold 30, the above description is referred to. 34 is a mold
Mounting plate for fixing 30.

Next, a description will be given of the opening / closing operation of the mold and the air suction control when blow molding is performed by the mold 30.

First, the mold 30 is opposed to the symmetrical mold in an open state so that a cavity can be formed, and a parison is extruded from an extruder into an opposing space of the mold. When the extrusion length of the parison is sufficient, the extrusion is stopped and the molds forming the cavities are closed. While the mold is closed, an air suction pump (not shown) is driven to suck the air in the cavity from the air holes 33d, 33e, and 33f, and the air of the parison in the mold from the blow device. The air in the cavity is supplied to the first air suction holes 3 through sintered metal plugs 31c, 32e, and 33c through which air can pass.
1d, the air hole 32d of the shallow groove 32c, and the second air suction hole 33g.
Air is sucked from the cavity forming wall 31
When the parison extends along a, 32b, and 33a, it is possible to significantly suppress the occurrence of air pockets between the parison and the cavity forming wall surfaces 31a, 32b, and 33a. During the parison air blow, the air suction from the air holes 33d, 33e, and 33f is continued, and the air suction is stopped simultaneously with the completion of the air blow. As a result, the outer surface of the parison in the mold has very few traces of air pockets, that is, very high smoothness. When the parison is cooled and hardened after the air blow to the parison is stopped, the mold is opened and the molded product is dropped into a storage box below the mold.

The material and the like of the hollow molded container suitable for the hollow molding method of the hollow molded container described above will be described.

First, the layer structure of the parison is not limited to a single layer but may be a multilayer as long as at least the outer surface in contact with the cavity is a polyester resin. In this embodiment, polyethylene terephthalate (hereinafter referred to as PET) is generally used as a polyester resin and has a low material cost.
Is adopted).

As a multilayer structure, for example, P
There is a layer structure such as ET, an adhesive resin as an intermediate layer, and a polyolefin resin as an inner layer.

Here, PET is a copolymer containing ethylene glycol and terephthalic acid as main monomers.
As a secondary monomer, “1,4-cyclohexanedimethanol” and “isophthalic acid” may be included.

As the intermediate layer, (1) very low density polyethylene (for example, Admer SE
800, trade name, manufactured by Mitsui Petrochemical Co., Ltd.), (2) Ultra Low Density Polyethylene, (3) Ethylene
Vinyl acetate copolymer (for example, CMPSEX401, trade name of Du Pont-Mitsui Chemicals Co., Ltd.), (4) styrene-butadiene block copolymer (for example, Tufprene 20)
0, trade name manufactured by Asahi Kasei Corporation), (5) styrene-ethylene / butene-styrene block copolymer (for example, Lavalon ME5301C, trade name manufactured by Mitsubishi Yuka Co., Ltd.), (6) ethylene-propylene. There is rubber.

Further, as the polyolefin resin as the inner layer, (1) polypropylene (for example, Hypol B278, trade name of Mitsui Petrochemical Co., Ltd.), (2) low density polyethylene or high density polyethylene (for example, Hyzex 6216B) , Mitsui Petrochemical Co., Ltd.), but as other components, for example, PET and an adhesive resin may be contained as a result of grinding and mixing the hollow molded container itself according to the present embodiment. And resources can be reused.

In the case of a three-layer structure, a preferable layer thickness is 1 to 16% for the outer layer and 1 to 12% for the intermediate layer.
%, And the layer pressure of the inner layer is preferably 72 to 98%.

Table 1 shows experimental data obtained by using the above-mentioned materials in the hollow molding method for a hollow molded container described above.

[0035]

[Table 1]

[0036]

[Table 2]

The symbols A to C in the column of “outer layer” in Table 1 all indicate PET, and the trade names and thicknesses are shown in Table 2. The trade names and thicknesses of the adhesive resin used for the intermediate layer and the polyolefin resin used for the inner layer are those described in Table 1.

In the evaluation of this experiment, the physical properties of the outer surface of the hollow molded container were used. G shown in Table 1 is the gloss (%) of the outer surface of the hollow molded container by 60 ° specular reflection, μs Indicates a static friction coefficient, and μk indicates a dynamic friction coefficient. For example,
Use Unitika PETNEH3060 with a thickness of 40μ for the outer layer, Admar SE800 with a thickness of 30μ for the middle layer, and 500μ for the inner layer.
When a hollow molded container is molded by the method for molding a hollow molded container according to the present embodiment using Hizex 6216B, a glossiness of 99.4% due to 60 ° specular reflection of the outer surface and a static friction coefficient of 0.
A hollow molded container having a dynamic friction coefficient of 0.45 is obtained. Table 1 shows the evaluation results when 40 μm PETG6763 or 40 μm PET9921 was used for the outer layer.

According to the hollow molded container and the molding method according to the embodiment of the present invention, the glossiness due to 60 ° specular reflection is 96.1%.
High gloss of ~ 100% and static friction coefficient of 0.45
A hollow molded container having a small friction coefficient of about 0.66 and a dynamic friction coefficient of 0.30 to 0.45 can be obtained.

[0040]

As described above, according to the hollow molded container and the hollow molded method of the hollow molded container according to the present invention,
Glossiness of 60 degrees specular reflection of hollow molded container after molding is 90
% Or more, and when they come into contact with each other during the transfer, the contact area slips, so that line trouble during the transfer can be avoided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a molding die for a hollow molded container according to a second embodiment of the present invention.

FIG. 2 is an explanatory view of air suction means connected to a molding die of the hollow molded container of FIG.

FIG. 3 is an explanatory diagram illustrating a configuration of an air suction unit.

FIG. 4 is an explanatory view of a step of supplying a parison between the opened molds.

FIG. 5 is an explanatory view showing a step of sucking air while blowing air into a parison in a mold.

FIG. 6 is an explanatory view showing a state in which a parison in a mold is completely filled with air and a vacuum suction step.

FIG. 7 is a perspective view of an application example of a molding die for a hollow molded container according to a second embodiment of the present invention.

FIG. 8 is a partial cross-sectional view showing a configuration of a first air suction hole provided at a boundary between a mouth of the molding die and a container body in FIG.

9 is a partial cross-sectional view illustrating a configuration of a second air suction hole provided between a container body and a bottom of the molding die of FIG. 7;

FIG. 10 is a perspective view showing a schematic configuration of a molding die of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Mold 5a Wall surface of concave part (wall surface on which cavity is formed) 4a Outer surface of parison 4 Parison 3 cavity

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-22339 (JP, A) JP-A-2-22030 (JP, A) Kiyoichi Kobayashi, “Handbook of Plastic Molds”, Seifen Co., Ltd. Doshinkosha, September 25, 1965, p. 337-342 (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 49/00-49/80 B65D 1/00-1/48

Claims (2)

(57) [Claims] 1. A an outer surface in contact with at least a cavity formed wall with constituting a polyester resin, an outer
The coefficient of static friction of the surface is 0.45 to 0.66, and the coefficient of dynamic friction is
Has a coefficient of friction of 0.30 to 0.45, 60 degree specular reflection
A hollow molded container having a gloss ratio of 90% or more . 2. An outer surface for hollow molding between a cavity forming wall surface and a cavity forming wall surface facing each other when the mold is opened.
A method for molding a hollow molded container in which a parison made of a base resin is positioned, and the parison is filled with compressed air to form a hollow molded container, wherein a center line average roughness of the cavity forming wall surface is 0.25 μm.
m and suction to suck air into the parting surface
Notch for cavity formation and the front
Paris that expands when closing the mold between the suction recess
It is shallow enough that the son does not enter and communicates with the suction recess.
A method for forming a hollow molded container, wherein air in a cavity formed outside the parison is sucked before filling the parison with compressed air using a mold having a groove formed therein .