JPH0815754B2 - Method and apparatus for manufacturing plastic hollow molded article - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a hollow plastic product having a film laminated on an outer peripheral surface by blow molding.

(Prior Art) As one of methods for obtaining a hollow plastic molded product, for example, a cylindrical parison made of a thermoplastic synthetic resin is extruded from an extruder, and the parison is sandwiched by a split mold to seal the upper and lower parts of the parison. A blow molding method in which gas is blown into the parison in this state to expand the parison along the inner surface of the molding die is known.

By the way, when an automobile fuel tank is made of plastic, since the material of the tank is plastic, sufficient consideration must be given to preventing fuel permeation from the tank wall. Therefore, for example, a barrier film is formed on the outer peripheral surface of the tank. A method of sticking is considered.

Thus, when a blow molding method is used to manufacture a plastic hollow molded article such as a plastic fuel tank in which various films such as a barrier film are laminated on the outer peripheral surface, for example, the method described in JP-A-61-51322 is used. It is possible to adopt it.

In the method described in the publication, as shown in FIG. 12, a cylindrical parison 3 is extruded between a pair of molding dies 1 and 2, and the inner surface length of the molding die 2 is between the parison 3 and the molding die 2. The porous sheet 4 having a length sufficient to accommodate the blow pin 5
A gas is blown into the parison 3 to expand the parison 3 along the inner surfaces of the molds 1 and 2, and at the same time, the porous sheet 4 is attached to the outer peripheral surface of the parison.

(Problems to be Solved by the Invention) However, when a porous film is arranged on the outside of the parison 3 by the above-mentioned method and blow molding is performed, an air pocket is partially generated between the parison and the film and the film is formed. There is a problem that I can do it.

Because the parison does not expand with air, it comes into contact with the film and is pressed against the inner surface of the mold, in which case the inner surface of the mold is naturally not a flat surface but a concave surface, and also various complicated shapes. Therefore, the adhesion of the parison and the film is not always performed at the same time, and the time for the local adhesion is changed, and as a result, there is no escape of air, or the film is locally pulled or loosened. This is because the film is wrinkled.

The problem of the air trap can be solved by increasing the number and area of openings of the film, but for example, when the target product is the fuel tank, if they are too large, the effect of preventing permeation of gasoline by the film decreases, which is not preferable. In many cases, such a solution cannot be adopted due to various circumstances.

In view of the above circumstances, an object of the present invention is a method and an apparatus for producing a plastic molded article having a film on the outer peripheral surface by blow molding, which prevents generation of air pockets and wrinkles in the film inside the film. An object of the present invention is to provide a manufacturing method and a device that can be manufactured.

(Means for Solving Problems) The method for producing a plastic hollow molded article according to the present invention comprises:
A heat-shrinkable film is concentrically arranged on the outside of the cylindrical parison, the film is heated before blow molding to bring the film into close contact with the outer peripheral surface of the parison, and then blown. It is characterized by being molded.

An apparatus for manufacturing a plastic hollow molded article according to the present invention,
An extruding machine for extruding a cylindrical parison, and a heat-shrinkable film concentrically with the parison are held outside the cylindrical parison extruded by the extruding machine. Means for holding the film, and a film heating means located outside the film for heating the film to bring it into close contact with the outer peripheral surface of the tubular parison and withdrawing from the film heating position during blow molding of the tubular parison. And a molding die for blow-molding a tubular parison in which the film is closely adhered to the outer peripheral surface, and a blow pin for blowing gas into the tubular parison during the blow-molding.

(Function) Unlike the conventional method in which the parison is inflated toward the inner surface of the molding die and brought into close contact with the film, the cylindrical straight parison is arranged in the same manner as the cylindrical straight film in the same state. When the film is heated to shrink the film, the adhesion conditions between the parison and the film are exactly the same at all locations on the parison, and therefore the adhesion of both is performed simultaneously and uniformly on the entire surface of the parison. Therefore, it is possible to achieve good and perfect adhesion between the parison and the film without the occurrence of air pockets and wrinkles of the film in the case of the conventional method as described above.

(Effect of the invention) The method for producing a plastic hollow molded article according to the present invention is
As described above, a cylindrical heat-shrinkable film is concentrically arranged with respect to the cylindrical parison, and the film is heated and contracted before blow molding to bring it into close contact with the outer surface of the parison. The steps are performed simultaneously and in a single use, so that the two can be completely adhered to each other without causing problems such as air pockets and wrinkles in the film, and a good plastic hollow molded article can be manufactured.

Further, as described above, the apparatus for producing a plastic hollow molded article according to the present invention comprises a film holding means for locating and holding a cylindrical heat-shrinkable film concentrically outside the cylindrical parison, and a film heating device for heating the film. Since it is provided with the means, it is possible to carry out the method for producing a plastic hollow molded article, and as a result, it is possible to produce a good plastic hollow molded article as described above.

(Examples) Examples of the present invention will be described below with reference to the drawings.

A description will be given below of an embodiment of a method and an apparatus for manufacturing a plastic hollow molded article with reference to the illustrated embodiment of the manufacturing apparatus.

FIG. 1 is a conceptual diagram showing an embodiment of a manufacturing apparatus. As shown in the figure, a cylindrical parison 12 made of thermoplastic is extruded from a die 10a of an extruder 10 and concentric with the parison 12 outside the parison 12. The tubular heat-shrinkable barrier film 14 is arranged and held by a barrier film holding device (not shown) in a circular shape, and the barrier film 14 is attached to the film 14.
Barrier film heating means arranged at a position surrounding the outer circumference of
The barrier film 14 is brought into close contact with the outer peripheral surface of the parison 12 by heating and shrinking by 18, and then the barrier film heating means 18 is heated from the heating position (the position where the barrier film 18 is in proximity and the film 18 is heated). Evacuate, then lift the blow pin 20 in the same way as in normal blow molding, match both split molds 22 and seal the upper and lower sides of the parison 12, blow air from the blow pin 20 to form the parison 12 on the inner surface 22a of the mold. A plastic fuel tank is manufactured by expanding the fuel tank.

As the raw material of the parison 12, various thermoplastics such as high density polyethylene can be used.

As a raw material for the barrier film, a material having heat shrinkability, such as nylon or polyamide, can be used. The barrier film has a two-layer structure including, for example, a base layer made of the above polyamide or the like and an adhesive layer made of modified polyethylene or the like formed on the inner surface of the barrier layer. Those that contract can be preferably used. Further, this barrier film is preferably porous in which many openings having a diameter of, for example, several millimeters are formed, but a non-perforated film may be used depending on the size (area) of the barrier film. .

Next, an embodiment of the manufacturing apparatus will be described in more detail with reference to FIGS.

FIG. 2 is a front view and FIG. 3 is a right side view. As shown in these drawings, two divided molding dies 22 each having a concave surface 22a for forming a mold cavity are shown with their mating surfaces 22b. Both of them are opposed to each other, and the barrier film heating means 18 are arranged with a space enough to be located therebetween.
An extruder 10 for pushing out a tubular parison is provided above the space between the barriers 22 and a barrier film holding means 16 for placing and holding a tubular barrier film concentrically with the parison pushed out by the extruder 10 is provided. There is.

The barrier film holding means 16 is an annular holding portion 16 arranged concentrically with the parison pushed out from the extruder 10.
a, a rack-shaped support portion 16b for supporting the holding portion 16a, and a pinion 16c meshed with the support portion.
The holding portion 16a is configured to be movable up and down.

A carriage 24 is located behind the molding die 22, and a barrier film heating means 18 and a barrier film supply means 26 are provided on the carriage 24.
And are placed. The dolly 24 has a fixing piece 24 attached to a part of a chain 28c which is laid between a drive sprocket 28a and a driven sprocket 28b which are rotated by a motor (not shown) or the like.
It is fixed via a, and can be moved back and forth by the movement of the chain 28c.

The barrier film heating means 18 is formed in a cylindrical shape so as to surround the entire surface of the barrier film and uniformly heat the barrier film, and the inner diameter of the barrier film holding means is such that the holding portion 16a of the barrier film holding means can move up and down therein. It is set to be larger than the outer diameter of the portion 16a.

The film supply means 26 has a trumpet-shaped internal cavity film guide 26a, and is covered with a cylindrical barrier film as shown in the drawing and stored in a state in which the film is tucked up. Also, this film guide
26a is a plan view thereof, as shown in FIG.
Has an annular shape that opens upward, and the leading end portion 14a of the barrier film 14 also opens upward in an annular shape along the film guide leading end portion 26b and slightly upward by the film guide leading end portion 26b. It is protruding. Further, the film supply means 26 is the film guide 26a.
It is arranged so that the center of the annular tip portion 26b opened upwardly of the center of the heating portion 18a of the film heating means coincides with the center of the heating portion 18a.

Further, below the molding die 22, a blow pin 30 which is positioned on the central axis of the parison extruded by the extruder 10 and which can be moved up and down is disposed.

In this device, first, from the state shown in Figs.
4 is moved forward by the chain 28c (to the left in the figure),
As shown in the figure, the cylindrical barrier film heating means 18 is positioned between both molds 22 and at a position concentric with the parison extruded from the extruder 10. Then, the barrier film holding portion 16a is also concentric with the annular front end portion of the barrier film guide 26a and thus the front end portion of the tubular barrier film 14 guided by the guide 26.

From this state, as shown in FIG. 4, the barrier film holding part
16a is lowered, and the holding portion 16a holds the tip of the barrier film 14 guided by the film guide 26a. As shown in FIG. 8 which is a plan view and FIG. 9 which is a side view, the holding portion 16a includes a ring portion 16f, a holding piece 16g disposed outside the ring portion 16f, and a bracket protruding from the ring portion 16f. It is composed of an air cylinder 16i which is provided on 16h and moves the holding piece 16g back and forth with respect to the ring portion 16f.The ring portion 16f is lowered and fitted into the opening of the leading end portion 26b of the film guide. Part 16f and four holding pieces 1
The tip end portion 14a of the barrier film located between 6g and 6g is held by the holding piece 16g and the ring portion 16f by operating the cylinder 16i.

When the barrier film 14 is thus held, the barrier film holding portion 16a is raised and the parison is extruded from the extruder 10 so that the cylindrical barrier film 14 is concentrically provided on the outside of the cylindrical parison 12 as shown in FIG. Position, and then activate the heating means 18 to activate the barrier film 14
Is heated and contracted, and the film 14 is adhered onto the outer peripheral surface of the parison 12.

When shrinkage and adhesion of the barrier film 14 is completed, the carriage 24 is retracted (to the right in the drawing) to retract the barrier film heating means 18 from the heating means, and the blow pin 30 is lifted as shown in FIG. 22 is matched with each other to seal the upper and lower sides of the parison 12, air is blown into the sealed parison 12 from the blow pins 30, and the parison 12 is expanded along the inner surface 22a of the molding die to perform blow molding.

The heating means 18 is a plan view of FIG. 10 and FIG.
As shown in FIG. 11 which is a view seen from the direction of arrow XI in FIG. 10, its front part (upper part in the drawing) has two door-shaped heating parts.
18a, and this door-shaped heating part 18a is an air cylinder.
Since it is configured to be rotatable in the direction of arrow B by 18b, it is sufficient to open this door-shaped heating portion 18a and move it back and forth when the carriage 24 moves backward. Further, when the carriage 24 retreats, the barrier film 14 is pressed against the film guide 26a by the film presser 32 including an air cylinder. By doing so, since the perforations are formed in the film 14 at appropriate positions, the film 14 is appropriately cut by the retraction of the carriage 24, and the state shown in the drawing is obtained. Further, although not shown, the forming die 22 is provided with a recess so as to form a blow pin insertion passage during die matching.

As described above, the method and apparatus according to the present invention comprises a straight-extending tubular parison, a straight-extending tubular film, and heat-shrinking the film in this state to bond the two. Therefore, the two are bonded simultaneously and uniformly, and no air pockets or wrinkles of the film are generated between them, and a good molded product can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the apparatus for producing a plastic hollow molded product according to the present invention, and FIGS. 2 and 3 are diagrams specifically showing the apparatus of the embodiment shown in FIG. 2 is a front view, FIG. 3 is a side view, FIGS. 4 to 6 are side views of the apparatus shown in FIGS. 2 and 3, respectively, for showing the manufacturing process, and FIG. 7 is a film guide. FIGS. 8 and 9 are views showing a holding portion of the film holding means, FIG. 8 is a plan view, FIG. 9 is a side view, and FIGS. 10 and 11 are film heating means. Fig. 10 is a plan view, Fig. 11 is a view seen from the direction of arrow XI in Fig. 10, and Fig. 12 is a view showing a conventional blow molding method. 10 …… Extruder, 12 …… Cylindrical parison 14 …… Film, 16 …… Film holding means 18 …… Film heating means, 20 …… Blow pin 22 …… Molding die

Claims (2)

[Claims] 1. A tubular heat-shrinkable film is disposed on the outer side of the tubular parison concentrically with the tubular parison, and the film is heated to be brought into close contact with the outer peripheral surface of the tubular parison. A method for producing a plastic hollow molded article, which comprises blow molding a cylindrical parison. 2. An extruder for extruding a tubular parison, film holding means for disposing and holding a heat-shrinkable film concentrically with the tubular parison on the outside of the tubular parison extruded by the extruder, The film is placed close to the outer peripheral surface of the tubular parison by heating the film so that the film is brought into close contact with the outer peripheral surface of the tubular parison, and the film heating means is retracted from the film heating position during blow molding of the tubular parison. An apparatus for manufacturing a plastic hollow product, comprising: a mold for blow molding a tubular parison and a blow pin for blowing gas into the tubular parison during the blow molding.