JPS595035A - Manufacture of composite layer hollow molded object - Google Patents

Abstract

PURPOSE:To make various means for fluid uniforming in a die unnecessary, by covering the surface of a synthetic resin hollow object with the outer layer object of a thermoplastic resin film, then melting or softening the outer layer object by heating in a mold and blowing an air into the hollow object. CONSTITUTION:The surface of the synthetic resin hollow object molded by an extrusion blow molding method, an injection blow molding method, etc. is covered by the outer layer object shaped with a thermoplastic resin film and the outer layer object is melted or softened by heating both in a mold. Then, the outer layer object and the surface of the hollow object are laminated by contacting integrally and a composite layer hollow mold object is manufactured. Said outer layer object is not necessarily limited to be molded to cover the entirety of the hollow object, but may be in the state to cover only the main part of the hollow object or one part of its surface like a label. The complexation of the hollow object and the outer layer object in a mold is done by heat and pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer hollow molded body using a separately molded synthetic resin hollow body and an outer layer body.

In general, hollow molded bodies with a wall of two or more layers are often used as packaging containers for foods, cosmetics, etc. because they exhibit effects that cannot be obtained with single-layer hollow molded bodies, such as improved gas barrier properties and improved appearance. has been done.

Conventional methods for producing multi-layer hollow molded bodies include a method of blowing an extrusion-molded multi-layer parison into a hollow body, and a method of blowing an injection-molded multi-layer parison with a bottom. Both methods have the disadvantage that they cannot print between layers because they blow a multilayer parison to form hollow objects such as containers and bottles.

Also, in the case of injection blow molding, in which multiple bottomed i41J strips are molded separately to form a multi-layer structure, this is not considered a particular problem; In extrusion blow molding, there are restrictions on the fluidity of the constituent materials in the die, and special techniques are required for pinch-off when blowing multilayers and materials. Problems have arisen, such as the difficulty of reusing Paris.

The above-mentioned problem regarding fluidity within the goo has been solved by adopting a molding head with a specific structure and selecting resins with similar melt viscosity, but regarding the reuse of Paris, since Paris itself is multi-layered, However, except in cases where the same resin is used to create multiple layers, the different resins are inseparably integrated and cannot be reused as in the case of a single layer, so they are treated as molding loss. .

The present inventors have discovered that the drawback of the above-mentioned conventional method lies in the fact that multi-layered Glison is blow-molded into a multi-layered hollow molded body. Therefore, as a result of various attempts to make hollow molded bodies multilayered without using multilayering or jason, a new manufacturing method was invented.

A container-like hollow body made of the synthetic resin of the present invention and an outer layer body made of a thermoplastic resin film are separately molded and placed, and both are brought into close contact with each other in a mold to form a multi-layered body.

The above-mentioned hollow body can be molded using a resin that can be molded by the generally known extrusion blow molding method, injection blow molding method, or even injection stretch blow molding method, and its wall structure is not limited to a single layer. It may be multi-layered.

However, the outer layer body is not limited to being molded to cover the entire hollow body, but may be in a state to cover the main part of the hollow body or a part of the surface such as a label. The resin used for this outer layer body is carefully selected depending on the purpose of making the hollow molded body multi-layered. When the contents are colored to protect them from ultraviolet rays, a film made of the same resin as that forming the hollow body can be used as the outer layer.

Furthermore, the outer layer may be multilayered by laminating a plurality of films made of different resins. The resin used for this multilayer film can be changed in any way depending on the purpose of multilayering the hollow molded product, but in order to improve the adhesion to the hollow product, the innermost layer of the multilayer film should be It is desirable to use a film made of the same resin as the body, or a resin film with good adhesive properties.

The hollow body and the outer layer body are combined in the mold under heat and pressure. If the outer layer is only bonded by melting or softening caused by heating, not only will the adhesion to the surface of the hollow body be incomplete and the finish will be poor.
The outer layer tends to wrinkle.

However, when applying internal pressure to the hollow body to expand it and pressing the outer layer together with the hollow body wall against the mold surface, no wrinkles were generated.
In addition, the adhesion is perfect and the finished state is also improved.

The above-mentioned mold includes a main part of the hollow body, has a mold surface in which the hollow body wall comes into contact with an outer layer, and has heating and cooling means.

Further, pressure is applied to the hollow body using an air nozzle inserted into the neck of the hollow body. The mold is heated to a required temperature by a heating medium during multi-layer molding, and is rapidly cooled by a coolant after molding, thereby shortening the cycle and making it possible to take out the manufactured multi-layer hollow molded body.

In the manufacturing method according to the present invention, a pre-formed single-layer or multi-layer hollow body and an outer layer body made of a single-layer or multi-layer film are integrally multi-layered in a mold.
Various measures for equalizing the flow inside the die, which are required in the conventional multi-layer in-die/non-stick method, are unnecessary or reduced, and even in the case of a structure in which an adhesive layer is interposed in the middle,
There is no difficulty in selecting the melt viscosity. In addition, when the hollow body is a single layer, pinch-off is formed during the initial molding of the single-layer hollow body, so pinch-off formation defects and drop strength reductions that tend to occur in coextrusion multilayer hollow molding do not occur. In addition, the pall produced during the initial single-layer blow molding can be easily reused as in the conventional method, and even if a small amount of pall is generated in the coating film, it can be used for a large amount of multi-layer pall that is difficult to reuse in coextrusion multi-layer blow molding. There's nothing to worry about.

Furthermore, in the present invention, printing can be performed on the inside, outside, or intermediate layer of the outer layer, thereby making it possible to omit subsequent operations such as labeling. Furthermore, for the hollow body that performs most of the mechanical functions as a container or structural material, various types of protection measures can be easily taken by selecting the outer layer, and these protection measures can be applied only to the necessary locations. Therefore, it is economical, takes less time, and can be manufactured at a lower cost than multilayer hollow molded bodies produced by conventional methods.

Examples of this invention are shown below.

Example 1 Blow molding was performed using high-density polyethylene with a melt index of 0.35' 710 min and a density of 0.9459/Crn3 to obtain a 300 CC round bottle.

Separately, the outer layer is a 6-nylon layer with a thickness of 30μ, and the middle layer is 20μ.
A multilayer blown film was prepared in which the adhesive layer was thick and the inner layer was a low density polyethylene layer with a thickness of 30 μm.

This film was placed on the round bottle from which the spout and bottom had been removed, and placed in the mold used for molding the round bottle. A blow pin was inserted into the bottle mouth and an air pressure of 5 kg/crn2 was applied. Then, the mold temperature was raised to 130°C using heated oil, and after heating for about 2 minutes, the process began to cool.
The multilayer container at a temperature of 0 was taken out.

In the product molded as described in Section 2 above, although the cut line at the pinch-off portion of the outer layer film remained, there were no other wrinkles and the adhesion was extremely good.

Example 2 Melt index 0.8 f/IQ min, density 0.921? A cylindrical body with a diameter of 55 mm and a length of 400 mm was molded using low density polyethylene with a diameter of 3 mm, taken out by an extrusion blow molding method, and deburred.

Especially Melt Index 2? /10 min, low density polyethylene with a density of 0.9212/3 was extruded through a T-die and further slit to prepare a black narrow film with a thickness of 50 μm and a width of 50 mm.

This narrow film was spirally wrapped around the cylindrical body, and the film was again set in the mold.

Then, as in Example 1, an air pressure of 5K17cm2 was applied, the mold temperature was raised to 13000C, held for 1 minute, and then cooled, and the multilayer cylindrical body at a temperature of about 50C was taken out.

In the product obtained as described above, the end surfaces of the overlapping films when spirally wound were completely smooth, there were no wrinkles, and the adhesion was extremely good.

This example shows that it is possible to obtain a black product by covering the surface with a black film, but it requires less pigment than when obtaining it by extruding black T4 litho as usual. In addition to this, it also has the advantage of being able to easily change the color, which eliminates material loss when changing the color of the extruder.

Patent applicant: Showa Denko Co., Ltd. ’　　　　　　　　-177

Claims (1)

[Claims] The surface of the synthetic resin hollow body is covered with an outer layer formed from a thermoplastic resin film, both of which are heated in a mold to melt or soften the outer layer, and air is blown into the hollow body. A method for manufacturing a multi-layer hollow molded body, which comprises forming a multi-layered body by integrally adhering an outer layer body and a surface of the hollow body.