JPH04312832A - Hollow molded article and manufacture and structure of mold thereof - 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]

0001

[Industrial Application Field] The present invention relates to hollow containers for foods, medicines, cosmetics, etc., industrial hollow molded parts for automobile parts, etc., which require a glossy surface, and the hollow molded products. The present invention relates to a manufacturing method for manufacturing and the structure of a mold used in this manufacturing method.

0002

BACKGROUND OF THE INVENTION In recent years, techniques have been provided for blow-molded products obtained by blow-molding molten parison, etc., to increase the commercial value of the product by imparting gloss to the surface of the molded product. For example, the main methods known include multilayer molding using a glossy resin as an outer layer, and methods in which the surface of the molded product is coated with paint to secondarily impart gloss. Furthermore, a method has been proposed (Japanese Patent Publication No. 2-40498) in which melt fractures and pock patterns caused by residual air in the mold during blow molding are erased and the mold surface is directly transferred. In this method, the mold surface is mirror-finished, the mold temperature is heated above the crystallization temperature of the resin used, and a molten parison with fine irregularities is blown into the mold and pressed against the mold surface using air pressure. In this method, the molded product is brought into complete contact with the mold surface, and then the mold temperature is lowered to below the crystallization temperature to solidify the molded product and then taken out.

0003

[Problems to be Solved by the Invention] However, in the initial multilayer molding, there were restrictions on the resin used,
Since multi-layer molding requires advanced and complex molding equipment and technology, it requires multi-layer molding management and outer layer management that are separate from single-layer molding, and requires less equipment and management compared to single-layer molding. Naturally, each cost is high, and there are disadvantages in that the incidence of defective products in multilayer molded products and the manufacturing cost of multilayer molded products are high.

[0004] In addition, the method of applying the second coating requires secondary processing equipment such as painting in addition to normal molding equipment, so it is necessary to control conditions such as painting that are different from normal molding. However, there were drawbacks such as high incidence of defective products and high manufacturing costs.

Furthermore, in the last method, it is possible to form fine irregularities on the surface of the molten parison in advance to facilitate degassing between the swollen molten parison and the mold surface. However, the air remaining between the swollen molten parison and the mold surface cannot be fundamentally or completely removed, and there is still room for improvement in this respect. In addition, in order to obtain a hollow molded product with a smooth surface from a parison with a rough surface, various molding conditions as described above must be set, and it is not widely applicable to various hollow molded products. Furthermore, it was not a method that could easily provide surface gloss.

The present invention was made in view of the above-mentioned problems, and allows a general-purpose single-layer blow molding machine to be used as is, without requiring secondary processing, and with an excellent surface finish. Hollow molded products that can easily obtain gloss,
The object of the present invention is to provide a manufacturing method for manufacturing this hollow molded product and a structure of a mold used in this manufacturing method.

[0007]

[Means for solving the problem] The invention according to claim 1 includes:
The air interposed between the parison, etc. inflated by blown air and the mold surface passes through the breathable mold surface and escapes to the outside, and the inflated parison, etc. is molded in close contact with the mold surface. It is characterized by:

[0008] The invention as claimed in claim 2, when blow-molding a parison or the like in a mold, allows air interposed between the parison or the like expanded by blown air and the mold surface to pass through a mold surface having air permeability. It is characterized by letting it escape outside.

[0009] The invention according to claim 3 is characterized in that the mold material forming at least a part of the mold surface is made of a porous metal body having air permeability. In this case, the nest inserted into the mold may be made of a porous metal body having air permeability.

0010

[Operation] According to the present invention, pressurized air is blown into the parison, and residual air between the inflated parison and the mold surface passes through the air permeable mold surface and escapes to the outside, so that the parison is inflated. The parison completely adheres to the mold surface. the result,
The mold surface is accurately transferred to the surface of the molded product. therefore,
By setting the mold surface to a predetermined surface roughness such as mirror finishing, a hollow molded product with excellent surface gloss can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show a first embodiment of the present invention, and the purpose of this embodiment is to obtain a hollow molded product (bottle container) with gloss on the entire surface. FIG. 1 shows the structure of a mold used in the manufacturing method. As shown in the figure, the structure of the mold according to the present invention is roughly divided into molds 1 and 2, which are divided into left and right halves (only one is shown in Figure 1).
When these molds 1 and 2 are brought into close contact with each other at a parting surface 7, a cavity 3 for molding a desired hollow molded product is formed.

To explain the specific structure of types 1 and 2, type 1
, 2 is a cavity surface 3a forming the bottom of the hollow molded product.
A body mold 5 having a cavity surface 3b forming the body of the hollow molded product, and a screw mold 6 having a cavity surface 3c forming the mouth of the hollow molded product. From each cavity surface (mold surface) 3a, 3b, 3c of the bottom mold 4, body mold 5, and screw mold 6 to the cavity 3
is formed.

In the mold having the above structure, the bottom mold 4, body mold 5, and screw mold 6 of each mold 1 and 2 are all ventilated in order to obtain a hollow molded product (bottle container) with gloss on the entire surface. It is made of porous metal (hereinafter abbreviated as breathable metal).

The air-permeable metal is a porous sintered metal having air permeability to the extent that air blown into the mold cavity 3 can pass through the mold surface and escape to the outside. The pore diameter of this porous sintered metal is 0.
It is sufficient if it is 3 mm or less. The breathable metal used in this example is made of ferritic stainless steel, and has characteristic values of an average pore diameter of 7 μm, a porosity of about 25%, and a specific gravity of 6.0 to 6.2. ing. Further, the breathable metal is not limited to this, and for example, aluminum-based, copper (alloy)-based, etc. are also possible. Furthermore, the same effect can be obtained by using ceramics (sintered fibers, metal powders, ceramic powders, etc.) instead of breathable metals.

[0016]
Furthermore, the surface roughness of each cavity surface 3a, 3b, and 3c is set to 50 μm or less to give the hollow molded product a surface gloss, and the mold surface is mirror-finished.

In addition, temperature adjustment holes 8 for heating and cooling the molds are provided in the bottom mold 4, body mold 5, and screw mold 6 of each mold 1 and 2, surrounding the cavity 3 to prevent temperature unevenness in the mold. It is provided by appropriate means so as to Temperature-controlled water, oil, or the like is fed into the temperature control hole 8 . Note that in the case of breathable metal, water or oil may penetrate into the cavity 3, so the temperature adjustment hole 8
Coating the inside of the pipe and inserting a pipe for the flow passage. Furthermore, even without these measures, the inside of the temperature adjustment hole 8 may be drawn in by suctioning water or oil under reduced pressure. In this case, there is no risk of water or oil penetrating into the cavity 3 due to the reduced pressure effect.

Next, referring to FIGS. 2 and 3, a procedure for manufacturing a blow molded product using the mold having the above structure will be described.

(1) Pressurized water is fed into the temperature adjustment holes 8 of the molds 1 and 2 to adjust the molds 1 and 2 to a desired temperature. (2) With molds 1 and 2 open, place the parison in mold 1,
Extrusion molding is performed at a predetermined position in the cavity 3 of mold 1, 2.
Close it and put the parison in your mouth. (3) In this state, as shown in FIG. 2, pressurized air is blown into the parison 10 from the opening at the upper end of the mold, and as shown in FIG. , 3c in a molten state. (4) Residual air exists between the parison 9, which expands and is crimped onto each cavity surface 3a, 3b, 3c, and each cavity surface 3a, 3b, 3c as pressurized air is blown into the cavity surface. is released to the outside through a large number of holes in each mold, bottom mold, body mold, and screw mold made of breathable metal. That is, the parison 9 and each cavity surface 3a, 3
b, 3c, the air passes through the surface of each mold and escapes to the outside, and the air interposed between the parison 9 and each cavity surface 3a
, 3b, and 3c. As a result, the parison 9 is accurately brought into close contact with each cavity surface 3a, 3b, 3c, and each cavity surface 3a, 3b, 3c is faithfully transferred to the surface of the molded product. (5) After that, pressurized air is blown into the temperature adjustment hole 8 for a predetermined period of time to cool the hollow molded product, so that the hollow molded product is solidified, and by opening the molds 1 and 2, the surface has the desired gloss. The hollow molded product is taken out.

According to this embodiment, the parison 9 is formed into molds 1 and 2.
By completely adhering to the cavity surfaces 3a, 3b, 3c, it is possible to faithfully transfer the mirror-finished cavity surfaces 3a, 3b, 3c with a surface roughness of 50 μm or less, resulting in an extremely smooth surface condition. It is possible to obtain a hollow molded product with extremely high gloss. The hollow molded product thus obtained has a very beautiful appearance.

Furthermore, the mold of this embodiment has a structure in which the air interposed between the parison and the mold surface is allowed to escape to the outside by passing through the holes in the breathable metal, so that it can be used with the parison with an extremely simple structure. Complete degassing takes place between the mold surface and the mold surface. Therefore, in order to remove air between the parison and the mold surface, it is necessary to form fine irregularities on the surface of the parison, set detailed molding conditions, and make thin air vent holes from the mold surface to molds 1 and 2.
There is no need to make many holes through the hole and towards the outside. As a result, the surface gloss of the blow molded product can be achieved in an extremely simple manner.

Furthermore, the mold has a very simple structure, which is advantageous in production. This reduces the production cost of the mold, making it possible to provide hollow molded products at low cost. Furthermore, the hollow molded product has a very high commercial value because it does not have the problem of leaving traces of air vent holes on the surface, which is the case with glossy molded products.

[0023] In this embodiment, each bottom mold 4 of molds 1 and 2
, the body mold 5 and the screw mold 6 are all made of breathable metal to make the entire surface of the hollow molded product shiny. In this case, only the body mold 5 may be made of breathable metal. This makes it possible to limit the portions where the air-permeable metal is used, for example, to create a pattern on the surface of the hollow molded product.

FIG. 4 shows a second embodiment of the invention. The purpose of this example is to obtain a hollow molded product with gloss only in the upper half. Therefore, the mold used in this embodiment has a structure in which it is divided into upper and lower halves with the parting surface 12 as a boundary, and forms the upper part of the cavity surface 3c of the mouth part and the cavity surface 3b of the body part. It is composed of an upper mold 10 and a lower mold 11 that forms the lower part of the cavity surface 3b of the body and the cavity surface 3a of the bottom.The upper mold 10 is made of breathable metal, and the lower mold 11 is made of a general mold material. It is used.

FIG. 5 shows a third embodiment of the invention. The purpose of this embodiment is to form a glossy part on a part of the body of a hollow molded product. Therefore, the mold used in this embodiment basically has the same structure as the mold used in the first embodiment, and general mold materials are used for these mold materials. The structure is such that a nest 20 made of breathable metal is inserted into a part of the body of the hollow molded product in the cavity 3 where a shiny part is formed.

FIG. 6 shows a fourth embodiment of the invention. In this embodiment, the entire surface of the hollow molded product is made glossy, and the purpose is to form a satin pattern on the lower half of the body. Therefore, the mold used in this embodiment basically has the same structure as the mold used in the first embodiment, and these mold materials are made of breathable metal. Then, a cavity surface 3a corresponding to the part forming the satin pattern of the hollow molded product
, 3b has a structure in which a satin-textured portion 30 is formed by forming a large number of fine irregularities on the surface in advance. In addition, when only the body portion of the hollow molded product has a glossy surface, only the body mold may be made of breathable metal.

The present applicants first evaluated the surface gloss of the blow molded product obtained according to the present invention. The surface gloss of the blow molded article obtained by the present invention was 92.6%. The resin used in this evaluation was HDPE (Hi-Zex6214B manufactured by Mitsui Petrochemicals, Inc.). As a comparison target for evaluation, the surface gloss of a hollow molded product obtained when a steel mold was polished to the same surface roughness as the mold of the present invention was 67.
In the case of two-layer molding, it was 1%, and in the case of two-layer molding, it was 86.5%, and both results showed that the surface gloss was lower than that of the product of the present invention. In addition, in the case of clear top coat, 92
．． A high gloss level of 8% was obtained, and it was demonstrated that the molded article of the present invention can achieve a gloss level equivalent to this level.

The above embodiments show examples in which the present invention is applied to hollow containers for foods, medicines, cosmetics, and the like. However, the present invention is not limited to the above embodiments. For example, when molding automobile parts using the mold of the present invention, conventional problems such as dimensional defects due to poor degassing, undercuts due to gas corrosion, and gas burns occurred, but these problems have been resolved. We were able to. In addition, significant effects were obtained in a wide range of areas, including clarifying the pattern of blow molded products, preventing gas burns and weld lines on ABS resin molded products, preventing gas whiskers, and eliminating burrs.

In the above embodiments, an extrusion blow molding method for blow molding an extruded parison was described, but the present invention can also be applied to other blow molding methods. For example, when applied to an injection molding method in which a bottomed parison is inflated as it is, and a biaxial stretch molding method in which a bottomed parison is expanded while being stretched in the axial direction, excellent results were obtained in both cases. In addition, the parison to be blow-molded according to the present invention refers to the resin to be molded in a softened state immediately before blow-molding, and examples included in this range include extruded parisons, injection parisons, hot parisons, and cold parisons. , melted parison, etc. Blow molded products were obtained according to the present invention using these parisons, and excellent results were obtained with all the parisons.

[0030]

[Effects of the Invention] As explained above, according to the present invention, the following excellent effects can be achieved. When blow molding a parison, etc. in a mold, the air interposed between the parison, etc. inflated by the blown air and the mold surface passes through the breathable mold surface and escapes to the outside. The air interposed between the mold surface and the mold surface can be completely evacuated, the swollen parison etc. can be brought into complete contact with the mold surface, and the mold surface can be faithfully transferred to the surface of the molded product. This results in
It is possible to obtain a blow molded product with extremely excellent surface condition, excellent surface gloss in some or all parts, and furthermore, with extremely high surface gloss in that part. Moreover, such excellent blow-molded products can be easily obtained by one-time blow molding without the need for secondary processing using a general-purpose blow molding machine as is, without setting detailed molding conditions. , can be supplied inexpensively and in large quantities. Further, according to the structure of the mold of the present invention, since the mold material forming at least a part of the mold surface is made of a porous metal body having air permeability, it is possible to obtain the above-mentioned excellent hollow molded product. , the mold can be made to have a very simple structure, which is advantageous in production, and the production cost of the mold can be reduced. Furthermore, it can be applied to all types of blow molding molds, and has excellent versatility.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a mold used in a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a mold showing a procedure for manufacturing a blow molded product using the same mold.

FIG. 3 is a sectional view of a mold showing the same procedure.

FIG. 4 is a diagram showing the structure of a mold used in a second embodiment of the present invention.

FIG. 5 is a diagram showing the structure of a mold used in a third embodiment of the present invention.

FIG. 6 is a diagram showing the structure of a mold used in a fourth embodiment of the present invention.

[Explanation of symbols]

1 type 2 type 3 Cavity 3a Cavity surface (mold surface) 3b Cavity surface (mold surface) 3c Cavity surface (mold surface) 9 Parison 20 Nested.

Claims (7)

[Claims] Claim 1: In a hollow molded product obtained by blow-molding a parison, etc. in a mold, air interposed between the parison, etc. inflated by blown air and the mold surface passes through the breathable mold surface. A hollow molded product characterized in that the swollen parison, etc. is molded in close contact with a mold surface. [Claim 2] When blow-molding a parison, etc. in a mold, the air interposed between the parison, etc. inflated by blown air and the mold surface is allowed to escape to the outside by passing through a mold surface having air permeability. A method for manufacturing a hollow molded product characterized by: 3. A structure of a mold, characterized in that a mold material forming at least a part of the mold surface is made of a porous metal body having air permeability. 4. A structure of a mold, characterized in that a nest inserted into the mold is made of a porous metal body having air permeability. 5. Claim 3 or Claim 4, wherein the metal body is made of porous sintered metal.
The structure of the mold described. 6. The mold structure according to claim 3, wherein the pore diameter of the metal body is set to 0.3 mm or less. 7. The mold structure according to claim 3, wherein the surface roughness of the mold surface is set to 50 μm or less.