JPH0455095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a plastic tank used for a vehicle fuel tank, etc., which is capable of reducing the amount of gasoline permeated therethrough, 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 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, conventionally,
Various surface treatment methods have been developed, such as treating the inside of the tank with hot sulfur dioxide gas and neutralizing it with an ammonia-based solution, and exposing the tank to 100% fluorine gas for 1 to 20 minutes at room temperature. , and methods of blowing with a mixture of nitrogen gas and 10% or less fluorine gas, but these methods have all yielded good results in terms of reducing the permeability of gasoline; However, there were problems in that it 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 multilayered parison made by bonding nylon, which does not allow gasoline to permeate, to the high-density polyethylene layer using an adhesive layer. There is a way to
One example of this is described in Japanese Patent Application Laid-Open No. 58-220738. 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 parts where the parisons are bonded to each other during blow molding are made of layers of nylon, high-density polyethylene, etc., and the nylon layer is exposed to the outside. Particularly at low temperatures, cracks are likely to occur in this exposed part, resulting in insufficient joint strength.Also, it is desirable to recycle the burr waste from this pinch-off part to reduce costs, but this In the example, there was a problem that it was difficult to recycle the waste burr because it contained two types, nylon and polyethylene.

[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 burr waste material. It is an object of the present invention to provide a plastic tank that is easy to use and can reduce costs, and a second object of the present invention is to provide a method for efficiently manufacturing the above-mentioned plastic tank with strong bonding strength through simple steps. It is in.

[Structure of the invention]

The first invention of the present application is a plastic tank formed by blow molding, in which a 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. , the pinch-off part has a single-layer structure consisting of only a high-density polyethylene layer, so that in this first invention, the penetration of gasoline is prevented by the nylon layer, and since there is no nylon layer in the pinch-off part, The joint strength of the parts is greatly improved, and the nylon layer is of course not present in the waste material cut from the pin-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.

1 to 5 are for explaining one embodiment of the first and second inventions of the present application, and in FIGS. 1 and 2 showing a plastic tank 1 according to this embodiment, this plastic tank Reference numeral 1 denotes a nearly rectangular sealed container consisting of a top wall 2a, a bottom wall 2b, and a side wall 2c, and the center of the left and right portions of this side wall 2c is a pinch-off portion where the upper and lower parts of this side wall 2c are connected. It's becoming 3. 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 4 in order from the inside of the tank.
a, first adhesive layer 4b, nylon layer 4c, second adhesive layer 4d, and second high-density polyethylene layer 4
It is composed of five layers of three types of e. Further, the pinch-off portion 3 is formed of high-density polyethylene layers 4a and 4e.
In other words, the pinch-off section 3 does not include the nylon layer 4c and the adhesive layers 4b and 4d like the tank wall sections described above.

In the plastic tank 1 of this embodiment, the side wall 2
A nylon layer 4c that does not allow gasoline to permeate is provided on the portions of c other than the pinch-off portion 3, the top wall 2a, and the bottom wall 2b, so that the amount of gasoline that permeates outward can be significantly reduced, and the pinch-off Since the adhesive layers 4b, 4d and the nylon layer 4c are not present in the 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 burr 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 there is no adhesive layer 4b, 4d and nylon layer 4c, so this burr waste material 3a can be easily recycled. It is.

3 and 4 show an apparatus for manufacturing the plastic tank 1 having tank walls of three main five layers. First, in FIG. 4 showing a parison extrusion molding apparatus, the apparatus includes an extrusion head 11, Parison material supply section 40 and head drive control section 50
It consists of

The extrusion head 11 mainly includes a cylindrical head body 12 whose outer diameter gradually increases toward the lower part;
A disk-shaped die 13 is fixed to the lower end of the head body 12, and a rod-shaped core 14 is inserted into the center of the die 13 and the head body 12 in the axial direction thereof.
It is composed of. 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 circumferential surface of this portion and the inner circumferential 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. A first adhesive storage chamber 17, which accommodates modified polyethylene, etc. in this order, a nylon storage chamber 18, a second adhesive storage chamber 19, which accommodates the modified polyethylene, etc., and a second polyethylene storage chamber 20 are arranged concentrically with each other. Each of these storage chambers 17 to 20 communicates with the extrusion port 15 similarly to the first polyethylene storage chamber 16.

Then, the first and second polyethylene storage chambers 1
6 and 20, first and second polyethylene plungers 16a and 20a are connected to the first and second adhesive storage chambers 1.
7 and 19 have first and second adhesive plungers 17
a, 19a, and a nylon plunger 18a is inserted into the nylon storage chamber 18 so as to be able to slide vertically.

The parison material supply section 40 includes a polyethylene supply section 21, an adhesive supply section 22, and a nylon supply section 2.
3, each of the supply sections 21, 22, 23 is connected to the first and second polyethylene storage chambers 16, 20, the first, and
Second adhesive storage chambers 17, 19, nylon storage chamber 1
8 is connected.

The polyethylene extrusion cylinder 31 of the head drive control device 50 is connected to the first and second polyethylene plungers 16a, 20a, and the adhesive extrusion cylinder 32 is connected to the first and second adhesive plungers 17a, 19.
In a, the nylon extrusion cylinders 33 are connected to the nylon plungers 18a, and a polyethylene switching valve 41, an adhesive switching valve 42, and a nylon switching valve are connected between each of the cylinders 31 to 33 and the hydraulic supply device 30. 43 are arranged, and furthermore, each solenoid 41a, 42a, 42b, 43a, 43 of each of these switching valves 41, 42, 43
An excitation signal is input from the parison control circuit 25 to b.

Further, a plunger position detection device 24 is connected to the polyethylene extrusion cylinder 31, and this detects the position of the first and second polyethylene plungers 1.
Detection position signals corresponding to the positions of 6a and 20a are 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, and the left and right molds 26a and 26b are They are disposed so as to be movable in the horizontal direction in the figure, facing each other with the parison extruded from the extrusion head 11 in between, and the inner surface shape when the left and right molds 26a and 26b of this molding mold 26 are closed is , the above plastic tank 1
The external shape is the same as that of . 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, the method of this embodiment for manufacturing the plastic tank 1 using the above-mentioned manufacturing apparatus will be explained.

(I) Before the start of the parison extrusion molding process, the parison extrusion molding apparatus is in the state shown in FIG. 4. That is, the first and second adhesive plungers 17a and 19a and the nylon plunger 18a are in the raised position, and the adhesive is supplied from the adhesive supply section 22 into the first and second adhesive storage chambers 17 and 19. Nylon is supplied and filled into the chamber 18 from a nylon supply section 23 . In addition, the first and second polyethylene storage chambers 1
High-density polyethylene is supplied from the polyethylene supply section 21 into the interiors of the piston rods 6 and 20, and accordingly, the polyethylene plungers 16a and 20a rise, and the piston rod of the polyethylene extrusion cylinder 31 connected to the plungers 16a and 20a moves to its upper end. When the plunger position is raised to this position, the plunger position detection device 24 outputs a parison extrusion start signal A1 to the parison control circuit 25.

() 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 to that shown in FIG.
lower. As a result, the lower single-layer parison portion 51a consisting only of the high-density polyethylene layers 52a and 52e is extruded from the extrusion port 15 of the extrusion head 11.

() And the polyethylene plunger 16
a, 20a is lowered to a predetermined position and the single layer parison portion 51a reaches a predetermined length, a multilayer parison start signal A is sent from the plunger position detection device 24.
2 is output, and the control circuit 25 receives this signal A2 and outputs the adhesive supply signal C to the solenoid 42a, and after a slight delay, the nylon supply signal D is output.
is output to the solenoid 43a. Then, first, the adhesive extrusion cylinder 32 expands and lowers the adhesive plungers 17a and 19a, and then, a little later, the nylon extrusion cylinder 33 expands and lowers the plunger 18a, and as a result, the single layer parison is removed. Following the portion 51a, from the inside, there are three layers: a first high-density polyethylene layer 52a, a first adhesive layer 52b, a nylon layer 52c, a second adhesive layer 52d, and a second high-density polyethylene layer 52e.
A multilayer parison portion 51b consisting of five seed layers is extruded.

() And the polyethylene plunger 16
a, 20a further lowers and the multilayer parison layer 51b reaches a predetermined length, the plunger position detection device 24 outputs a multilayer parison end signal A.
3 is output, and the parison control circuit 25 receives this signal A3 and stops supplying the nylon supply signal D. After a short delay, the control material 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 and second positions. The upper single-layer parison portion 51c consists of only the first and second high-density polyethylene layers 52a and 52e from the two high-density polyethylene storage chambers 16 and 20.

In addition, when stopping the supply of nylon and adhesive, the nylon plunger rising signal D' may be output for a short time after the supply of the nylon supply signal D is stopped, and the adhesive plunger rise signal D' may be output for a short time 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 a parison extrusion end signal A4, thereby stopping 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 is stopped, and in this way, a parison 51 having a single layer at the upper and lower ends and a multilayer at the center is formed by extrusion as shown in FIG.

() Next, in order to blow mold the parison 51 into the shape of the plastic tank 1, the left and right molds 26a and 26b are first closed. Then, the upper and lower single-layer parison parts 51 of the parison 51
c, 51a are left and right type 26a, 26b respectively
are sandwiched between the opposing surfaces of the two and bonded to each other, and this bonded portion becomes a pinch-off portion. When blowing air is blown into the parison 51 from the blow nozzle 27 in this state, the parison 51 is molded into a shape that follows the inner surface of the mold 26, and the burr 3 of the pinch-off portion 3 of the molded tank material is
By cutting the section a, a plastic tank 1 as shown in FIGS. 1 and 5 can be obtained in which the air inlet 3b can be used as a gasoline refueling passage. 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, the upper and lower ends are made of a single layer.
A parison 51 having a multi-layered center part is obtained, and by blow-molding this parison 51 in the same manner as in the conventional method, it is possible to easily and reliably and efficiently form a plastic tank 1 having a multi-layered tank wall structure and a single-layered pinch-off section. This makes it possible to improve the joint strength of the pinch-off part and facilitate the recycling of burr waste.

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 The first and second inventions can be applied to any multilayer structure in which a high-density polyethylene layer and a nylon layer are bonded together by an adhesive layer.
For example, in the case of a three-layer structure consisting of a high-density polyethylene layer, an adhesive layer, and a nylon layer in order from the inside, the second adhesive storage chamber 19 and the second polyethylene storage chamber 20 are unnecessary in the apparatus shown in FIG. 4 above. ,
Contrary to the above, in the case of the above three layers in order from the outside, the first
Polyethylene storage chamber 16, 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 burr waste 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, and 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 is a single layer. This has the effect of efficiently manufacturing a plastic tank with a layered structure.

[Brief explanation of the drawing]

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. A plastic tank manufacturing apparatus for carrying out the method of one embodiment is shown, FIG. 3 is a cross-sectional view of the mold part thereof, FIG. 4 is a block diagram of the parison extrusion molding apparatus part, and FIG. 5 is the above-mentioned embodiment. Indicates a plastic tank manufactured by the method,
FIG. 5a is a plan view thereof, FIG. 5b is a left side view thereof, FIG. 5c is a front view thereof, and FIG. 5d is a right side view thereof. 1...Plastic tank, 2a, 2b, 2c
... Tank wall, 3 ... Pinch-off part, 4a, 4e
...High density polyethylene layer, 4b, 4d...Adhesive layer, 4c...Nylon layer, 11...Extrusion head, 15...Extrusion port, 16, 20...First, second
Polyethylene storage chamber, 17, 19...1st, 2nd
Adhesive storage chamber, 18...Nylon storage chamber, 26...
... Mold (molding mold), 51 ... Parison, 51a,
51c...single layer parison part, 51b...multilayer parison part.

Claims (1)

[Claims] 1. In a plastic tank formed by blow molding, 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. A plastic tank characterized in that the pinch-off portion of the tank wall is constructed of a single-layer structure consisting of only a high-density polyethylene layer. 2. The portion of the tank wall other than the pinch-off portion is comprised 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. 3. A method of manufacturing a plastic tank by blow molding, in which a cylindrical polyethylene storage chamber, an adhesive storage chamber, which are connected to an annular extrusion port and are arranged substantially concentrically and sequentially adjacent to each other; An extrusion head equipped with a nylon storage chamber 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 consisting only of high-density polyethylene layers. Push out the parison part,
Next, 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 polyethylene storage chamber is pressed. Only the high-density polyethylene in the chamber was pressurized to extrude the single-layer parison portion consisting only of the high-density polyethylene layer to form a parison with a single layer at the top and bottom ends and a multilayer at the center, and then this parison was inserted. The 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 is a single layer consisting only of a high-density polyethylene layer. 1. A method for manufacturing a plastic tank, comprising forming a plastic tank with a structure. 4. The extrusion head is equipped with 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 in a radial outward direction, When extruding the 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 extruded. The adhesive material and the nylon in the nylon storage chamber are pressurized almost simultaneously to form a high-density polyethylene layer, an adhesive layer,
Extrude a multi-layer parison part consisting of five layers of three types: a nylon layer, an adhesive layer, and a high-density polyethylene layer, and finally pressurize only the high-density polyethylene in the first and second polyethylene storage chambers to extrude a single-layer parison part. A method for manufacturing a plastic tank according to claim 3, characterized in that: