JPS61171320A - Plastic tank and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the permeability of gasoline and to improve the connecting strength at pinch off portion by a method in which the portion except the pinch off portion of a tank-wall is composed of multilayer structure in which a high density polyethylene layer is caused to adhere to a nylon layer with an adhesive layer, and the pinch off portion is composed of the single layer structure with only high density polyethylene layer. CONSTITUTION:The cylindrical polyethylene receiving chamber, an adhesive receiving chamber and a nylon receiving chamber arranged so as to be connected to an annular pushing outlet and to adjoin mutually and almost concentrically in order, are provided. An extruding head for extruding a cylindrical parison is prepared, and then first, only high density polyethylene is pressurized and a single layer parison is extruded, and next an adhesive and nylon are pressurized almost simultaneously, thereby extruding a multilayer parison. Finally, only high density polyethylene is pressurized, and a single layer parison is extruded, whereby the parison having single layers at upper and lower parts and a multilayer in central part may be molded. Then the mold into which this parison is inserted, is closed, and blow molding is achieved, feeding pressurizing gas into the parison from a blow nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plastic tank used for a vehicle fuel tank, etc., which is capable of reducing the amount of gasoline that permeates, and an efficient method for manufacturing the same.

[Prior art]

Recently, fuel tanks for vehicles have been formed by blow molding using plastics such as high-density polyethylene in order to reduce cost and weight. There is a problem with gasoline permeation, that is, gasoline in the tank seeps out. In order to prevent this gasoline permeation,
Various surface treatment methods have been developed in the past, such as treating the inside of a tank with high-temperature sulfur dioxide gas and neutralizing it with an ammonia-based solution, and exposing it to 100% fluorine gas for 1 to 20 minutes at room temperature. method, and 10% to nitrogen gas
There was a method of blowing with a mixture of the following fluorine gases, but all of these methods are good in terms of reducing the permeability of gasoline! Although good results have been obtained,
Both methods had problems in that they required handling of dangerous substances and required a huge amount of equipment.

Therefore, as a method to reduce gasoline permeability without causing such problems, conventionally, tanks have been blow molded using a multilayer parison made by adhering nylon, which does not allow gasoline to permeate, to the high-density polyethylene layer using an adhesive layer. There is a method of
There is one described in the 0738 publication. This tank wall was composed of five layers of three types: a high-density polyethylene layer, an adhesive layer, a nylon layer, an adhesive layer, and a high-density polyethylene layer in order from the inside.

However, in the conventional example described in this publication, the pinch-off part where the parisons are bonded to each other during blow molding is made of layers of nylon, high-density polyethylene, etc., and the nylon layer is exposed to the outside. Particularly at low temperatures, there is a problem that cranks are likely to occur in this exposed part and the joint strength is insufficient.Also, it is desirable to recycle the Paris waste material in this pinch-off part to reduce costs, but this conventional method In the example, nylon is made from Paris waste wood.

There was a problem in that it was difficult to recycle because the two types of polyethylene were mixed together.

[Purpose of the invention]

Therefore, the first invention of the present application was made in order to solve the above-mentioned conventional problems, and its purpose is to reduce the permeability of gasoline, improve the joint strength of the pinch-off part, and furthermore, to recycle Paris waste material. The purpose is to provide a plastic tank that is easy to use and can reduce costs, and
A second object of the invention of the present application is to provide a method for efficiently manufacturing the above-mentioned plastic tank with strong joint strength through simple steps.

[Structure of the invention]

The first invention of the present application is a plastic tank formed by blow molding, in which a part of the tank wall other than the pinch-off part has a multilayer structure in which a high-density polyethylene layer and a nylon layer are bonded together with an adhesive layer, and a pinch-off part is formed by blow molding. The part has a single-layer structure consisting of only a high-density polyethylene layer, and as a result, in this first invention, the nylon layer prevents gasoline from permeating, and since there is no nylon layer in the pinch-off part, The bonding strength is greatly improved, and the nylon layer is of course not present in the waste material cut from the pinch-off portion, making it easier to recycle the waste material.

Further, the second invention of the present application is a method for manufacturing a plastic tank, in which a single-layer parison portion consisting only of a high-density polyethylene layer is first extruded from an extrusion head, and then a high-density polyethylene layer, an adhesive layer and A multi-layer parison made of nylon layers is extruded, and finally a single-layer parison made of only a high-density polyethylene layer is extruded, forming a parison with a single layer at the top and bottom ends and a multilayer in the center. In this second invention, by simply controlling the extrusion timing of various parison materials, parts of the tank wall other than the pinch-off part have a multilayer structure. Thus, a plastic tank having a single-layer structure consisting of only a high-density polyethylene layer at the pinch-off portion can be easily, reliably, and efficiently obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Figures 1 to 5 are part 1 of the present application. This is for explaining an embodiment of the second invention, and in FIGS. 1 and 2 showing a plastic tank 1 according to this embodiment, this plastic tank 1 has a top wall 2 a + a bottom wall 2 b, and a side wall. It is a nearly rectangular parallelepiped airtight container made of 2C, and the center portions of the left and right portions of this side wall 2C form a pinch-off portion 3 formed by connecting the upper and lower portions of this side wall 2C. The portions of each of the walls 2a to 2C, excluding the pinch-off portion 3, are covered with a first high-density polyethylene layer 4a, a first high-density polyethylene layer 4a, a first high-density polyethylene layer,
It is composed of five layers of three types: an adhesive layer 4b, a nylon layer 4c, a second adhesive layer 4d, and a second high-density polyethylene layer 4e. Furthermore, the pinch-off section 3 is composed of two layers of one type, ie, high-density polyethylene layers 4a and 4e. That is, the pinch-off section 3 includes a nylon layer 4C like the walls of each tank, and an adhesive layer 4b.
, 4d does not exist.

In the plastic tank 1 of this embodiment, a nylon layer 4c that does not allow gasoline to pass through is provided on the side wall 2C excluding the pinch-off portion 3, the top wall 2a, and the bottom wall 2b, so that gasoline does not flow outward. The amount of permeation can be significantly reduced,
Furthermore, since the adhesive layers 4b and 4d and the nylon layer 4c are not present in the pinch-off portion 3, the upper and lower parts of the side wall 2C are firmly joined, and this joint strength will not be insufficient even at low temperatures. . Also, the Paris waste material 3a obtained by cutting the pinch-off portion 3 is of course made up of only the high-density polyethylene layers 4a and 4e, and the adhesive layers 4b and 4d and the nylon layer 4C are not present.
It is easy to recycle.

3 and 4 show an apparatus for manufacturing the plastic tank 1 having tank walls of three types and five layers as described above.1.
First, in FIG. 4, which shows a parison extrusion molding apparatus, the apparatus has an extrusion head 11. It is composed of a parison material supply section 40 and a head drive control section 50.

The extrusion head 11. Mainly includes a cylindrical head body 12 whose outer diameter is gradually increased at the lower end, a disc-shaped die 13 fixed to the lower end of the head body 12, and the die 1.
3 and a rod-shaped core 14 inserted into the center of the head body 12 in the axial direction thereof. A conical extrusion port forming portion 14a is formed at the lower end of the core 14, and an annular extrusion port 15 is formed by the outer peripheral surface of this portion and the inner peripheral surface of the die 13. Further, the gap between the outer circumferential surface of the columnar portion 14b of the core 14 and the inner circumferential surface of the head body 12 forms a cylindrical first polyethylene storage chamber 16. The first adhesive storage chamber 17°, which houses modified polyethylene, etc., and the nylon storage chamber 18. A second adhesive storage chamber 19 that accommodates the modified polyethylene and the like. Second polyethylene storage chambers 20 are arranged concentrically with each other, and each of these storage chambers 17 to 20 communicates with the extrusion port 15 similarly to the first polyethylene storage chamber 16.

And the above 1. 2nd polyethylene storage chamber 16.20
The first thing is. Second polyethylene plunger 16a, 20a
But first. The second adhesive storage chamber 17°19 contains the first adhesive. Second
Adhesive plungers 17a and 19a are inserted into the nylon storage chamber 18, and a nylon plunger 18a is inserted vertically and slidably.

The parison material supply section 40 is a polyethylene supply section 21
．． Adhesive supply section 22. It consists of a nylon supply section 23, and each supply section 21, 22.23 has a supply passage 21a,
22a and 23a, the first and second polyethylene storage chambers 16, 20, and the first and second polyethylene storage chambers 16, 20, 22a and 23a are connected to each other. second adhesive storage chamber 17;
19, connected to the nylon storage chamber 18.

The polyethylene extrusion cylinder 31 of the head drive control device 50 is the first cylinder. Second polyethylene plunger 16a
, 20a, the adhesive extrusion cylinder 32 is connected to the first . The nylon extrusion cylinder 33 is connected to the second adhesive plunger 17a, 19a and the nylon plunger 188, respectively, and a polyethylene switching valve 41. An adhesive switching valve 42 and a nylon switching valve 43 are provided, and each solenoid 41 of each switching valve 41, 42, and 43 is provided.
An excitation signal is input from the parison control circuit 25 to a, 42a, 42b, 43a, and 43b.

Further, a plunger position detection device 24 is connected to the polyethylene extrusion cylinder 31, and this is connected to the first plunger position detection device 24.
Second polyethylene plunger 16a.

A detected position signal corresponding to the position of 20a is input to the parison control circuit 25.

Next, in FIG. 3 showing the blow molding mold 26, this mold 26 consists of left and right molds 26a and 26b disposed below the extrusion head 11.

The right molds 26a and 26b are shown facing each other while sandwiching the parison extruded from the extrusion head 11!
It is arranged to be movable in the left and right direction, and the inner shape of the molding die 26 when the left and right molds 26a and 26b are closed is the same as the outer shape of the plastic tank 1. Note that 27 is a blow nozzle for supplying pressurized air for blowing into the parison, and this is disposed on the axis of the extrusion head 11 and connected to an air source (not shown).

Next, a method of this embodiment for manufacturing the plastic tank 1 using the above-mentioned manufacturing apparatus will be explained.

(I) Before starting the parison extrusion molding process, the parison extrusion molding apparatus is in the state shown in FIG. 4. That is, 1st. The second adhesive plungers 17a, 19a and the nylon plunger 18a are in the raised position, and the first
．． Inside the second adhesive storage chamber 17°19 is an adhesive supply section 22.
The nylon storage chamber 18 is filled with nylon from the nylon supply section 23. Also, the first
．． High-density polyethylene is supplied into the second polyethylene storage chamber 16.20 from a second polyethylene supply section, and along with this, a polyethylene plunger 16a is supplied.

20a rises and the piston rod of the polyethylene extrusion cylinder 31 connected to the plungers 16a, 20a rises to its upper end position, the plunger position detection device 2
4 sends the parison extrusion start signal A1 to the parison control circuit 25.
Output to.

(II) When the extrusion start signal A1 is input, the parison control circuit 25 outputs the polyethylene supply signal B to the solenoid 41a, the solenoid 41a is energized, and the polyethylene switching valve 41 is switched to the opposite state as shown in FIG. is,
This causes the polyethylene extrusion cylinder 31 to extend downward in the drawing, causing the polyethylene plungers 15a, 20a to descend.

This then forms the high-density polyethylene layer 52a.

The lower single-layer parison portion 51a consisting only of 52e is extruded from the extrusion port 15 of the extrusion head 11.

(III) and the polyethylene plunger 16a.

208 is lowered to a predetermined position and the single layer parison portion 51a reaches a predetermined length, the plunger position detection device 24 outputs a multilayer parison start signal A2, and the control circuit 25 receives this signal A2 and outputs an adhesive supply signal. C to solenoid 4
2a, and with a slight delay, a nylon supply signal is output to the solenoid 43a. Then, the adhesive extrusion cylinder 32 expands and the adhesive plungers 17a, 19
a is lowered, and then, after a short delay, the nylon extrusion cylinder 33 is extended and the plunger 18a is lowered, and as a result, the first high-density polyethylene layer 52a is sequentially moved from the inside, following the single layer parison portion 51a. +First adhesive layer 52b, nylon layer 52c.

Second adhesive layer 52d, second high density polyethylene layer 52e
A multilayer parison portion 51b consisting of five layers of three types is extruded.

(IV) and the polyethylene plunger 16a.

20a further lowers and the multilayer parison portion 51b reaches a predetermined length, the plunger position detection device 24 outputs a multilayer parison end signal A3, and the parison control circuit 25 receives this signal A3 and outputs the nylon supply signal. supply will be stopped.

After a short delay, the adhesive supply signal C is stopped.

Then, the nylon extrusion cylinder 33 stops operating, and a little later, the adhesive extrusion cylinder 32 stops operating, thereby stopping the supply of nylon and adhesive, and the above-mentioned parison 51 returns to the first position. The first from the second high-density polyethylene chamber 16.20. Second high density polyethylene layer 52a.

The upper single-layer parison portion 51c consists of only 52e.

In addition, when stopping the supply of nylon and adhesive, the nylon plunger rise signal D' may be output for a short time after the supply of the nylon supply signal C is stopped, and the adhesive plunger rise signal D' may be output after the supply of the adhesive supply signal C is stopped. The rising signal C' may be output for a short time.

(V) When the upper single-layer parison portion 51c reaches a predetermined length, the plunger position detection device 24 outputs the parison extrusion end signal A4, which stops the parison extrusion start signal B, and the polyethylene switching valve 41 switches to the fourth Returning to the state shown in the figure, the polyethylene extrusion cylinder 31 stops, and in this way the upper and lower ends are made of a single layer as shown in FIG.
A multi-layer parison 51 is formed by extrusion in the center.

(Vl) Next, in order to blow mold the parison 51 into the shape of the plastic tank 1, first, the left and right molds 26a,
Close 26b. Then, the upper and lower single-layer parison parts 51C and 51a of the parison 51 become the left and right molds 25, respectively.
They are sandwiched between the opposing surfaces of a and 26 b and bonded to each other, and this bonded portion becomes a pinch-off portion. In this state, blow air is supplied from the blow nozzle 27 to the
When the air is blown into the interior, the parison 51 is formed into a shape that follows the inner surface of the mold 26, and if the burr 3a of the pinch-off portion 3 of the formed tank material is cut off, the air blowing port 3b is connected to the gasoline refueling passage. A plastic tank 1 as shown in FIGS. 1 and 5, which can be used as a plastic tank, is obtained. Note that the pressurized gas may be supplied from the blow nozzle 27 after the mold 26 is closed.

In this way, in the method of this embodiment, by simply controlling the extrusion timing of the high-density polyethylene, adhesive, and nylon materials, a parison 51 having a single layer at the upper and lower ends and a multilayer at the center can be obtained. By blow molding 51 in the same manner as in the conventional method, tank 1 can be manufactured easily, reliably, and efficiently, with the tank wall having a multilayer structure and the pinch-off part having a single-layer structure, and the joint strength of the pinch-off part being increased. In addition, it is possible to improve the efficiency and facilitate the recycling of Paris waste materials.

In addition, in the above embodiment, a plastic tank having a three-type, five-layer structure and a method for manufacturing the same have been described, but the number of layers is of course not limited to five layers, and may be greater or less than this, and the present application 1st. The second invention can be applied to any multilayer structure in which a nylon layer is bonded to a high-density polyethylene layer using an adhesive layer.

For example, from the inside, the high-density polyethylene layer, the adhesive layer,
In the case of a three-layer structure of three types of nylon layers, the second adhesive storage chamber 19 and the second polyethylene storage chamber 20 are unnecessary in the apparatus shown in FIG. is the first polyethylene storage chamber 16. The first adhesive storage chamber 17 becomes unnecessary.

〔Effect of the invention〕

As described above, according to the plastic tank according to the first invention of the present application, the portion of the tank wall other than the pinch-off portion has a multilayer structure in which a high-density polyethylene layer and a nylon layer are bonded together with an adhesive layer, and Since the pinch-off part has a single-layer structure consisting of only a high-density polyethylene layer, the amount of gasoline permeation can be significantly reduced, the joint strength of the pinch-off part can be improved, and Paris waste material can be easily recycled, reducing costs. There is.

Further, according to the method for manufacturing a plastic tank according to the second invention, the single-layer parison portion is first extruded from the extrusion head, then the multi-layer parison portion is extruded, and finally the single-layer parison portion is extruded again. , a parison with a single layer at the top and bottom edges and a multilayer in the center can be easily and reliably obtained. - By simply blow molding this parison in the same way as before, the parts other than the pinch-off part have a multilayer structure, and only the pinch-off part has a multilayer structure. This has the effect of efficiently manufacturing single-layer plastic tanks.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional side view of a plastic tank according to an embodiment of the first invention of the present application, Fig. 2 is an enlarged sectional view of the wall of the tank, and Figs. 3 and 4 are the second invention of the present application. 3 shows a sectional view of the mold part thereof, FIG. 4 is a block diagram of the parison extrusion molding apparatus part, and FIG. 5 shows the apparatus for manufacturing a plastic tank for carrying out the method of the above embodiment. Indicates a plastic tank manufactured by the method,
Figure 5 (a) is its plan view, Figure 5 (middle) is its left side view, and Figure 5 (C) is its front view, Figure 5! d) is its right side view. 1...Plastic tank, 2a, 2b, 2c...
Tank wall, 3...Pinch-off portion, 4a, 4e...High density polyethylene layer, 4b, 4d-...Adhesive layer, 4c
... Nylon layer, 11... Extrusion head, 15...
Extrusion port, 16.20...1st. 2nd polyethylene storage chamber, 17.19...1st. Second adhesive storage chamber, 18.
... Nylon storage chamber, 26 ... Mold (molding mold), 51
...Paris. Son, 51a, 51c=single layer parison part, 51b...
Multilayer parison section. Figure 3 Figure 5

Claims (4)

[Claims] (1) In a plastic tank formed by blow molding, the parts of the tank wall other than the pinch-off part are
It has a multilayer structure in which a high-density polyethylene layer and a nylon layer are bonded together by an adhesive layer, and the pinch-off portion of the tank wall has a single-layer structure consisting of only a high-density polyethylene layer. plastic tank. (2) The part of the tank wall other than the pinch-off part is composed of five layers of three types: a high-density polyethylene layer, an adhesive layer, a nylon layer, an adhesive layer, and a high-density polyethylene layer, in order from the inside. A plastic tank according to claim 1, characterized in that: (3) In the method of manufacturing a plastic tank by blow molding, a cylindrical polyethylene storage chamber, an adhesive storage chamber, each communicating with an annular extrusion port and arranged approximately concentrically and sequentially adjacent to each other; An extrusion head equipped with a nylon storage chamber and for extruding a cylindrical parison is prepared, and when extruding the parison, first, only the high-density polyethylene in the polyethylene storage chamber is pressurized to form a single-layer parison portion consisting only of the high-density polyethylene layer. Then, in this state, the adhesive in the adhesive storage chamber and the nylon in the nylon storage chamber are pressurized almost simultaneously to extrude a multilayer parison consisting of a high-density polyethylene layer, an adhesive layer, and a nylon layer, and finally the above-mentioned Only the high-density polyethylene in the polyethylene storage chamber is pressurized to extrude a single-layer parison made of only high-density polyethylene layers to form a parison with a single layer at the top and bottom ends and a multilayer at the center, and then this parison is inserted. The formed mold is closed, and pressurized gas is supplied from the blow nozzle into the parison to perform blow molding.The part of the tank wall other than the pinch-off part has a multilayer structure, and the pinch-off part consists only of a high-density polyethylene layer. A method for manufacturing a plastic tank, comprising forming a single-layer plastic tank. (4) The extrusion head includes a first polyethylene storage chamber, a first adhesive storage chamber, a nylon storage chamber, a second adhesive storage chamber, and a second polyethylene storage chamber in order from the center of the head to the outside in the radial direction. In extruding the above-mentioned parison, first, only the high-density polyethylene in the first and second polyethylene storage chambers is pressed to extrude the single-layer parison part, and then, in this state, the first and second adhesive storage chambers are further bonded. The material and the nylon in the nylon storage chamber are pressurized almost simultaneously to extrude a multilayer parison part consisting of five layers of three types: a high-density polyethylene layer, an adhesive layer, a nylon layer, an adhesive layer, and a high-density polyethylene layer in order from the inside of the parison. 4. The method of manufacturing a plastic tank according to claim 3, wherein the single-layer parison portion is extruded by pressurizing only the high-density polyethylene in the first and second polyethylene storage chambers.