JPH01195017A - Manufacture of blow molded object - Google Patents

Abstract

PURPOSE:To prevent the fine hole of the film constituting a barrier layer from increasing its diameter by a method in which the film is stuck to the outer periphery of the parison heated to the temperature nearly equal to the melting point of the film to be laminated in the state where tension is applied to the film, and pressurized gas is blown into the parison pinched in between molds, thereby achieving blow molding. CONSTITUTION:A film 18 is biaxially oriented in the draw ratio by three times, and one surface of this film 18 is coated with an adhesive. Fine holes are dispersively formed on its whole surface, and the film is stretched over in between film holding members 14, 15 under a prescribed tension. The parison 3 molding a tank-main body is extruded in between molds 2 by an extruder 4, and the film 18 stretched in between the film-holding members 14, 15 is positioned on both sides of the parison 3. The molds 2 are closed, and pressurized gas is blown into the pinched parison 3 through a blow pin 4, whereby blow molding is carried out, and the film 18 is brought in close contact with the outer peripheral surface of the parison 3. Then, the temperature of the parison 3 is set at the temperature nearly equal to the melting point of the material to be used for the film 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a blow molded product, and more particularly to a method for manufacturing a blow molded product in which films are laminated.

(Prior Art) In recent years, fuel tanks for vehicles have been blow-molded using plastics such as polyethylene. This plastic tank has the advantage of being lightweight, as well as reducing material and manufacturing costs.

On the other hand, if the SP value (solubility parameter) of a liquid such as gasoline stored inside the tank is similar to the SP value of the tank material, the liquid will permeate the tank wall and leak to the outside. , it has the disadvantage that it must be configured to suppress this.

For this reason, conventionally, as disclosed in JP-A No. 58-22073, for example, a tank body made of high-density polyethylene material and a barrier layer made of nylon resin attached to both the front and back surfaces of the tank body with an adhesive are used. This constitutes a plastic tank, and the barrier layer prevents liquid such as gasoline stored in the tank from permeating to the outside. However, this configuration has the disadvantage that it is necessary to laminate barrier layers on both the front and back surfaces of the tank body via an adhesive, which complicates the molding operation. In order to facilitate the molding work of the plastic tank mentioned above, it is possible to form a barrier layer only on the outer circumferential surface of the tank body, but in this case, the liquid that permeates through the tank body will not interact with the tank body. If the resin accumulates at the interface and the resin in the retention area expands, there is a risk that the barrier layer will peel off from the tank body.

In order to prevent the barrier layer from peeling off from the tank body due to the expansion of the resin as described above, for example, by scattering a large number of micropores in the barrier layer, the liquid that has passed through the wall of the tank body can be prevented from separating from the tank body. The liquid may be gradually vaporized through the micropores, thereby preventing the liquid from remaining at the interface between the tank body and the barrier layer.

(Problem to be Solved by the Invention) However, when forming a laminated blow-molded product by simply using the barrier layer as described above, some corners of the molded product are elongated more than other parts, so the above-mentioned There is a problem in that the diameter of the micropores becomes large and the function as a barrier layer deteriorates in that area.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a blow-molded product that can prevent the diameter of the micropores of the film forming the barrier layer from increasing even in some of the corners. be.

Note that as a method for manufacturing a blow molded product to which a film is attached, the method disclosed in JP-A-61-89025 is known.

(Means for Solving the Problems) The method for producing a blow molded product of the present invention involves attaching the film under tension to the outer periphery of a parison that has been heated near the melting temperature of the film to be laminated. Blow molding is carried out by blowing pressurized gas into the parison which is held between molds in this state.

(Operations and Effects of the Invention) In the method for producing a blow-molded product of the present invention, as described above, the film laminated on the blow-molded product is heated by the parison to near the melting temperature and shrinks when cooled. Therefore, even if the diameter of the micropores once expands in a part of the film, for example, the micropores will also shrink at the same time as the above contraction, and thus the diameter of the micropores provided in the film in the molded product will increase. It's not going to get bigger. Therefore, especially when the blow-molded product is a tank for storing liquid and the film is a barrier layer,
There is no possibility that the diameter of the micropores increases and the barrier effect deteriorates.

(Example) Hereinafter, a method for manufacturing a blow molded product according to the present invention will be described with reference to the accompanying drawings. Note that in the embodiments described below, it is assumed that a tank containing gasoline is formed.

FIG. 1 shows a blow molding apparatus used in the method for producing a blow molded product according to an embodiment of the present invention, and FIG. 9 shows a biaxial stretching device for biaxially stretching a film laminated on the blow molded product. The stretching device is shown.

In FIG. 1, reference numeral 1 indicates a machine frame, and inside the machine frame 1, a pair of molds (molds) 2 are attached so as to be able to come into contact with and be separated from them, and on the top thereof, = 4 - An extruder 4 is installed to extrude a plastic parison 3 that becomes the tank body. Furthermore, a blow pin 4 for blow molding is arranged at the lower part of the mold 2.

Furthermore, a product take-out device 5 is provided on the side of the machine frame 1. This product take-out device 5 has a support frame 6 that is disposed upright at a position apart from the machine frame 1. A guide rail 7 extends from the top of the support frame 6 toward the machine frame 1, and its tip is fixed to the machine frame 1. A sliding member 8 having the shape shown in FIG. 2 is attached to the guide rail 7 so as to be slidable along the guide rail 7. As shown in FIG. On the upper surface of both ends of the guide rail 7,
Pulleys 9 and 10 are attached to each, and these two
A wire 11 is passed between the two pulleys 9 and 10. The sliding member 8 is attached to the wire 11, and when the pulley rotates and the wire 11 moves, the sliding member 8 moves into and out of contact with the mold 2. ing.

The sliding member 8 has a pair of rod-shaped chucks 12.1 facing the mold 2 and extending parallel to the rail.
3 are attached so as to be able to move toward and away from each other, and for this purpose, the sliding member 8 is provided with chucks 12 and 13.
a pair of air cylinders 12a, 13a for each of
is provided. Film holding members 14.15 are provided near both ends of these chucks 12.13, respectively.
It is attached via attachment members 16,17.

A film 18 forming the barrier layer of the tank is stretched between these film holding elements 14, 15 under tension.

The mounting members '16 and 17 are constructed as follows. Note that since the mounting members 16 and 17 are configured symmetrically in FIG. 1, only the mounting member 16 will be described in the following description. Part 16
As shown in FIG. 3, the film holding member 1
4.15 and has one movable member movable along the direction in which the chuck 12 extends. This movable member 1
Attached to 9 is a spring 20 which pulls the film 18 stretched between the film holding members 14, 15 outwardly with a predetermined force for purposes explained later.

Note that FIG. 4 shows a state in which one of the movable members is viewed from the direction of arrow A in FIG. 3.

The film 18 is made of modified PE, nylon-6, modified P
It is desirable that the film be formed of three layers of E and biaxially stretched three times or more. A biaxial stretching machine 30 as shown in FIG. 9 is used for this stretching. This biaxial stretching machine 30 has a ninth
As shown in the figure, a running path 31 on which the film 18 runs
An entrance roller 32 is provided at the entrance thereof, and an exit roller 33 is provided at the exit thereof. These rollers 32 and 33 are for stretching the film 18 in the X-axis direction, and the rotational speed of the exit roller 33 is set higher than that of the entrance roller 32.

A pair of chain conveyors 34 are provided on both sides of the traveling path 31 and are arranged in a V-shape. A large number of film clip rollers 35 are attached to these chain conveyors 34. The film 18 is stretched in the Y-axis direction while moving toward the exit roller 33 while being held by the film clip rollers 35 . As this biaxial stretching machine 30, a conventionally known one may be used, so further detailed explanation will be omitted.

Next, a method for manufacturing a blow molded product according to an embodiment of the present invention will be described. The material for the parison is HD.
PE shall be used.

First, the film 18 is stretched three times in the biaxial direction using the biaxial stretching machine 30, an adhesive is applied to one side of the film 18, and then an adhesive is applied to the entire surface of the film 18, for example, by about 0. 5+n+n micropores are dispersed and formed, and the film 18 is stretched between the film holding members 14 and 15 with a predetermined tension. By applying tension to the film 18 in this manner, the adhesion of the film to the parison is improved. Thereafter, a parison 3 forming a tank body is extruded between the molds 2 by an extruder 4. Next, the pulleys 9 and 10 are operated to move the sliding member 8 in the direction of the mold 2, and as shown in FIG. be located on both sides of the

After this, the mold 2 is closed as shown in FIG.
Blow molding is performed by blowing pressurized gas into the parison 3 held by the parison 3 through the blow pin 4, and at the same time, the film 18 is brought into close contact with the outer peripheral surface of the parison 3. At this time, the temperature of the parison 3 during blow molding is close to the melting point of the material used for the film 18, which is higher than the conventional temperature. For example, when the material of the film 18 is nylon-6 as described above, this temperature is set at 220-240°C.

By doing this, as shown in FIG. 7, there is a part of the blow-molded product B at a corner, and when the part is molded, the film 18 is stretched (FIG. 8), and the micropores 61 are once expanded in diameter. However, due to contraction during cooling, the micropores 61 become the original diameter or smaller, and do not affect the barrier function or the like.

During the shrinkage process, if both ends of the film are simply supported, there is a risk that part of the film will break. However, in this embodiment, as described above, since the film 18 is held via the spring 20, when the film 18 contracts, the film holding members 14 and 15 move in the direction of the contraction, thereby suppressing the contraction to some extent. absorption, thus preventing breakage as described above. Therefore, the tension force of the spring 20 needs to be set to a smaller value than the contraction force of the film 18.

Note that the action of this spring can also prevent the film from breaking due to the blowing pressure of the blow-molded product.

After the molding is completed as described above, the mold 2 is opened, the pulleys 9 and 10 in the product take-out device 5 are rotated in the opposite direction to the above, and the sliding member 8 is moved in a direction away from the mold 2. to remove the product and complete the task.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a blow molding device used in a method for producing a blow molded product according to an embodiment of the present invention, FIG. 2 is a plan view of a product take-out device provided in the blow molding device, and FIG. The figures are a front view of the main parts of the product removal device, FIG. 4 is a view taken from arrow A in FIG. 3, and FIG.
Figure 6 is a horizontal sectional view showing the mold in an open and closed state, respectively, and Figures 7 and 8 show the relationship between the parison, film, and mold before and after blowing. 9 are plan views showing a biaxial stretching device for biaxially stretching the film laminated on the blow-molded product. 1... Machine frame 2... Molding die 3... Parison 4... Extruder 5... Product removal device 14.15...・Film holding member 20...Spring 30...Biaxial stretching machine

Claims (1)

[Claims] An adhesive layer is laminated on the surface to be attached to the outer circumference of the parison,
Then, micropores of a predetermined diameter are dispersed and formed in a stretched film, and a parison is heated to a temperature near the melting point of the film, and the film is attached under tension around the outer periphery of the heated parison. A method for producing a blow-molded article, which comprises blow-molding the parison by blowing pressurized gas into the parison which is clamped by a mold in this state.