JPS63319119A - Blow molding equipment - Google Patents

Abstract

PURPOSE:To improve the adhesion of film to the surface of a molded item without lowering productivity by a method wherein porous heat insulating members are arranged to the portions, with which film and parison come into contact for the first time during molding, of molds and, at the late state of molding after the completion of the fusion of the film to the parison, cooling air is blasted through the heat insulating members against the molded item under the condition that the molds are opened by some quantity. CONSTITUTION:A parison 2, the base material of which is thermoplastic resin, is extruded through an extruder head 3 and hung down and, before the disappearance of the moldability of the parison due to the lowering of its temperature, pinched together with films 9 and 9 by the closing of molds 4 and 4 so as to be blow-molded with compressed air blown off through a blow pin 5. Porous heat insulating members 11 and 11 such as ceramic sintered bodies are arranged nearly central parts of molding surfaces 4a and 4a. At the early stage of molding, the quick cooling of the films and the parison in contact with the molds is suppressed by the heat insulating property of the members 11 and 11, resulting in surely fusing the film and the parison each other. At the late stage of molding, the film and the parison are positively cooled by blasting cooling air through a large number of the pores of the heat insulating members. As a result, the shortening of molding cycle time is contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blow molding apparatus, and more specifically, to a molding apparatus for applying a film to the outer peripheral surface of a molded product simultaneously with molding in blow molding.

[Prior Art] As is well known, for example, in a vehicle fuel tank,
In order to reduce manufacturing costs, relatively easily increase capacity, and reduce weight, the conventional press-formed steel plate has been replaced with one that is integrally formed by welding, and has the strength required for tanks. At the same time, tanks have been molded using resins such as high-density polyethylene, which are relatively inexpensive and have excellent moldability.

However, with the resin tanks mentioned above, there is a problem that fuel such as gasoline stored inside the tank leaks out through the tank wall surface while being used for a long period of time. There is a problem that weather resistance deteriorates due to exposure to heat.

For this reason, it has conventionally been possible to prevent fuel from leaking out of the tank through the tank wall and from deteriorating the weather resistance of the tank by pasting a liquid-impermeable film on the outer circumferential surface of the tank. It is being done.

By the way, when molding a hollow product such as a fuel tank for a vehicle using resin as a raw material, a so-called blow molding method is generally often used. This blow molding method involves preforming a thermoplastic resin material into a dupe shape or two sort shapes by extrusion or injection, and then preforming the softened preform product (
The parison is immediately sandwiched between molds to obtain the outer shape of the molded product, and compressed air is blown into the inside of the parison to inflate the parison along the molding surface of the mold and cool and solidify to form a hollow product. It is a molding method that
It has two major advantages: high productivity and low manufacturing costs.

In order to take advantage of the high productivity of the above-mentioned blow molding method, various ideas have been devised to attach a film to the outer circumferential surface of the molded product at the same time as molding rather than post-processing. There is a method in which a film with an adhesive layer is set and the film is pressed against the parison during blow molding, using the heat retained by the parison to fuse the adhesive layer and attach the film. It is well known (for example, see Japanese Patent Laid-Open No. 61-89025).

[Problems to be Solved by the Invention] However, in the above conventional method, the time from when the parison comes into contact with the film until the film comes into contact with the mold and is pressed is short, so that the film does not come out of the parison. The mold removes heat and cools the film before it has sufficiently fused to the surface, resulting in poor adhesion of the film to the outer peripheral surface of the molded product, especially in the area where the film first contacts the mold. There was a problem.

To solve the above problem, by heating the mold appropriately, we can reduce the heat conduction from the film and parison to the mold.
It is possible to improve the adhesion of the film to the surface of the molded product, but in this case, = 3 - The cooling effect of the mold on the molded product decreases, resulting in a longer molding cycle and lower productivity. There was a problem.

[Purpose of the Invention] The present invention was made to solve the above-mentioned problems.In a blow molding device that attaches a film to the outer circumferential surface of a molded product at the same time as the molding, the film is first applied during blow molding. The purpose is to improve the adhesion of the film to the surface of the molded product without reducing the productivity of blow molding by devising the material of the contacting mold part and providing a means to cool the molded product after molding. shall be.

[Means for Solving the Problems] Therefore, in the present invention, with a film set between a mold for obtaining the outer shape of a molded product and a preformed softened parison, In a blow molding device that obtains a blow molded product with a film attached to the outer peripheral surface by blow molding by blowing compressed air into the mold, a porous insulation member is used in the mold part that the film first contacts during blow molding. and a cooling air supply means for supplying cooling air into the mold space through the many holes of the heat insulating member, and in the latter stage of blow molding when the film has finished being fused to the outer peripheral surface of the molded product. The mold is slightly opened and cooling air is blown out from the porous heat insulating member toward the molded product.

"Effects of the Invention" According to the present invention, in a blow molding device for producing a blow molded product with a film pasted on the outer peripheral surface, the film set between the mold and the parison is placed in the mold with which it first comes into contact during blow molding. Since a porous insulation material is installed in the part,
In the early stage of blow molding, its heat insulating properties can suppress rapid cooling of the film and parison due to contact with the mold, ensuring that the two are fused together,
It is possible to improve the adhesion of the film to the outer peripheral surface of the molded product, and in the latter stage of blow molding after the film and the parison are fused, Since cooling air is blown out from the many holes of this heat insulating member towards the molded product using It is possible to compensate for the decrease in the cooling effect from the mold due to the arrangement and shorten the molding cycle time.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

As shown in FIG. 1, a blow molding apparatus 1 according to an embodiment of the present invention includes an extrusion head 3 for extruding a heated and melted thermoplastic resin as a base material into a parison 2 in a softened state;
It includes a pair of left and right molds 4, 4 arranged symmetrically about the center line of the parison 2, and a blow pin 5 for blowing compressed air for blow molding into the inside of the parison 2.

The pair of left and right molds 4.4 are installed so as to be able to move toward and away from the parison 2, and have molds inside them that promote solidification and cooling of the blow-molded product to shorten the molding cycle time. For this purpose, a cooling water passage 6.6 is provided for guiding cooling water for cooling the molds 4,4.

On the upstream side of the cooling water passage 6.6 from the entrance to the inside of the molds 4, 4, there are coolers 7, 7 for appropriately cooling the cooling water introduced into the inside of the molds 4.4. is installed.

The blow pin 5 is arranged coaxially with the center line of the parison 2, and its rear end is connected to a blow air supply device 8 that supplies compressed air for blow molding.

A film 9.9, which is applied to the outer peripheral surface of the molded product at the same time as blow molding, is set between the parison 2 and the left and right molds 4.4.

By the way, in the blow molding apparatus 1 according to this embodiment, a ceramic material, for example, is placed in the mold portion that the film 9.9 comes into contact with first, that is, in the approximate center of the molding surfaces 4a, 4a, which are formed in a concave shape in this embodiment. Porous heat insulating material that has both heat insulating and porous properties like a sintered body + 1.1
+ is placed.

Then, on the side opposite to the molding side of the heat insulating member 11.11, cooling is conducted from the heat insulating member 11.11 toward the molded product in the mold space 12 formed by the left and right molds 4.4. In order to blow out air, a plurality of branched cooling air passages 13, 13 passing through the molds 4, 4 are connected. The cooling air passages 13.13 merge on the second flow side thereof and are connected to the cooler 7.
, 7 to a blow air supply device 8. That is, the blow air supply device 8 is used in common as an air supply source for both blow air for blow molding and cooling air for cooling molded products.

A case in which a resin tank, for example a fuel tank for a vehicle, is molded using the blow molding apparatus I configured as described above will be described below.

As shown in Fig. 2, a parison 2 made of thermoplastic resin is extruded by an extrusion head 3 and hangs between the left and right molds 4.4 which are opened and separated from each other. Films 9, 9 are set between the mold 4.4 and the parison 2, respectively.

The base material used is a thermoplastic resin, such as high-density polyethylene, which has the strength characteristics required for vehicle fuel tanks, is relatively inexpensive, and has excellent moldability. For example, a nylon resin having liquid impermeability is used for the film 9. The film 9 is applied to the outer peripheral surface of the molded product on the surface facing the parison 2.
9, an adhesive layer made of, for example, modified polyethylene is provided. The films 9, 9 are provided with a large number of holes, as will be explained in detail later.

As mentioned above, when the parison 2 hangs down in a softened state, the left and right molds 4 and 4 are pressed together, as shown in FIG. is closed and the parison 2 is sandwiched together with the film 9.9, and at the same time, compressed air is blown into the inside of the parison 2 from the blow pin 5 to perform blow molding.

At this time, the parison 2 expands toward the molding surfaces 4a, 4a of the mold 4.4 due to the increase in internal pressure due to the blowing of compressed air. The films 9, 9 come into contact with the parison 2 at a relatively early stage of the expansion of the parison 2 and transfer their retained heat, and this heat melts the adhesive. Then, the expansion of the parison 2 progresses further and the film 9.9 is exposed to the molds 4 and 4.
The film 9.9 is fused to the outer circumferential surface of the parison 2 until the film 9.9 and the parison 2 are cooled by removing heat from the film 9.9 and the parison 2.

In this embodiment, the porous heat insulating members II and I+ are arranged in the mold part where the films 9 and 9 first come into contact.
Cooling of the films 9, 9 and the parison 2 is suppressed in the above portion where the fusion conditions of the films 9, 9 are the worst.

After blow molding is carried out as described in 1., as shown in FIG. Cooling air is blown out toward the molded product 14 inside, especially the molded product 14.
The portion corresponding to the heat insulating member 11.11 is actively cooled.

At this time, the pressure of the blow air blown from the blow pin 5 is as indicated by the solid line a in FIG.
Immediately before opening 4, the pressure is lowered to an appropriate set pressure that does not cause the molded product 14 to deform, and as already indicated by the solid line in FIG. It is designed to be squirted.

2. As described above, according to this embodiment, in the blow molding apparatus 1 for producing the blow molded product 14 with the film 9 pasted on the outer peripheral surface, there is a gap between the molds 4, 4 and the parison 2. A porous heat insulating member 11.9 is placed on the part of the mold that the set film 9.9 first contacts during blow molding. Since the film 9.9 and the parison 2 are disposed at the initial stage of blow molding, their heat insulating properties can suppress rapid cooling of the film 9.9 and the parison 2 due to contact with the mold 4.4, and the fusion of both can be suppressed. It is possible to reliably adhere the film 9 to the outer circumferential surface of the molded product 14 and improve the adhesion of the film 9 to the outer circumferential surface of the molded product 14, as well as in the latter stage of blow molding after the film 9.9 and the parison 2 have been fused together. In the above-mentioned porous heat insulating member +1.11, this heat insulating member 11.
Since the cooling air is jetted toward the molded product 14 from the large number of holes 11, the molded product 14 after the film 9 has been fused can be actively cooled, and the heat insulating member 1] .

In this embodiment, the film 9 was attached to the outer peripheral surface of the molded product 14 at the same time as the blow molding, but when attaching the film using this method,
In general, air pockets tend to form between the parison and the film, which impairs the adhesion between the film and the molded product, and also causes problems in terms of appearance.

To solve this problem, the film has many stages of fine holes (",
It is possible to prevent the formation of air pockets by discharging air from this hole, but in this case, the permeation of the film that suppresses the leakage of the liquid inside the molded product to the outside through the wall surface of the molded product is necessary. In addition to reducing the reduction effect, there is a problem that it adversely affects the impact resistance such as the drop performance of the molded product because a film having a large number of notches (holes) on the surface of the resin is fused.

The transmission reduction effect of the film described in item 1 and the drop performance of molded articles are greatly influenced by the size and number of holes provided in the film.

In this example, in order to prevent the formation of air pockets between the parison and the film when pasting the film, and to obtain the predetermined transmission reduction effect and drop performance that were set as targets, the film was Optimum conditions are determined for the hole diameter and the total opening area of the holes, respectively, and preferably a film 9 having holes that meet these optimal conditions is used. Therefore, the molded product 14 is
As shown in an enlarged cross-section of a portion of the film 9 in FIG. 5, the film 9 attached to the outer surface has a large number of holes 9a.

The film 9 of this example will be explained below.

In determining the optimal conditions for the hole diameter and total opening area of the holes in the film, we determined the material and thickness of the film and adhesive, and the area of the film to be attached, which is about the size of a typical vehicle's fuel tank. The following materials were used as barrier films for molded products of various sizes.

・Film material: For example, polyamide resin such as nylon ・Film thickness: 10 to 40μ ・Adhesive material Modified polyethylene ・Adhesive layer thickness: 90μ or less *However, the thickness of the adhesive layer may vary depending on the film thickness The total thickness including the thickness was set to be 100 μm or less. This is because if the thickness of the film layer including the adhesive layer becomes thicker than 100 μm, the impact resistance deteriorates.

・Film attachment area: 5 to the total surface area of the molded product
0 to 70% Further, the target values for the permeation reduction effect and drop performance against gasoline were set as follows.

・Gasoline permeability: At most 1/2 degree compared to a single-layer tank without a barrier film ・Drop performance: Same as a single-layer tank, i.e. -40°C
No cracks will occur in the base material when dropped naturally from a height of 6 m or more under the following environmental conditions.

Under the above conditions, the optimum conditions for the hole diameter and the total opening area of the holes were investigated, and the following results were obtained.

・Film hole diameter: 05~! , Omm ・Total opening area of holes: 2 to 8 relative to the total area of the film
%.

In this embodiment, preferably, a large number of holes 9 are formed such that the hole diameter and the total opening area each satisfy the above conditions.
Since we used the film 9 with a, air pockets are formed between the parison 2 and the film 9 when the film 9 is attached without impairing the drop performance compared to a single-layer molded product without a film attached. In addition to preventing
Compared to the case of a single-layer molded product, the amount of gasoline permeating through the wall surface of the molded product I4 can be reduced to at least 1/2 or less.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view of a blow molding apparatus according to an embodiment of the present invention, and FIGS. 2, 3, and 4 show a blow molding apparatus according to an embodiment of the present invention. This is a series of drawings for explaining the blow molding process, in which Figure 2 is a vertical cross section of the blow molding apparatus showing before blow molding, Figure 3 during blow molding, and Figure 4 showing the cooling process after molding. FIG. 5 is an explanatory diagram showing an enlarged part of the cross section of the molded product to which the film according to the present example is attached, and FIG. 6 is a graph showing the pressure of blow air and cooling air. 1...Blow molding device, 2...Parison, 4...Mold, 7...Cooler, 8...Blow air supply device, 9...
Film, 11... Porous heat insulating member, I2... Mold space, 13... Cooling air passage, 14... Molded product.

Claims (1)

[Claims] (1) With a film set between a mold to obtain the outer shape of the molded product and a preformed softened parison, compressed air is blown into the parison for blow molding, so that the outer peripheral surface In a blow molding device for producing a blow molded product with a film pasted on it, a porous heat insulating member is provided in the part of the mold that the film first comes into contact with during blow molding, and a porous heat insulating member is provided in the mold through a large number of holes in the heat insulating member. A cooling air supply means is provided to supply cooling air into the space, and in the latter stage of blow molding when the film has been fused to the outer peripheral surface of the molded product, the mold is slightly opened and the molded product is removed from the porous heat insulating member. A blow molding device characterized in that cooling air is ejected toward the blow molding device.