JPH0686532B2 - Method for manufacturing a plastic tank having liquid impermeability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to the production of a liquid-impermeable plastic tank made of plastic such as polyethylene and formed by using a molding technique such as blow molding. Regarding the method.

(Prior Art) In recent years, for example, as a fuel tank for vehicles, a plastic tank made of a thermoplastic resin typified by polyethylene and manufactured by blow molding is being used. Such a plastic tank has a greater degree of freedom in shape than a conventional sheet metal tank, is lightweight, has excellent impact resistance, and has advantages such as cost reduction. On the other hand, in the case where a single-layer structure of only a plastic layer is taken, it is stored when the liquid such as gasoline for vehicle is stored for a relatively long time inside. However, there is a risk that the liquid may permeate the wall, permeate it, and leak to the outer surface side.

For this reason, some proposals have been made to provide liquid impermeability to a plastic tank made of thermoplastic and manufactured by blow molding or the like. . For example, JP-A-58-220738 discloses, as one of such proposals, laminating and adhering a high-density polyethylene layer on both sides of a nylon layer that does not allow the permeation of a liquid such as gasoline through an adhesive layer. Shows a multi-layered tubular extruded product, and a plastic tank having a multi-layered structure obtained by blow molding this tubular extruded product. In such a plastic tank having a multi-layered structure, when used as a fuel tank, the nylon layer serves as a barrier layer that blocks the permeation of gasoline, and the leakage of gasoline to the outside is suppressed. .

Further, as a technique for forming a liquid impermeable layer in a plastic tank obtained by blow molding without taking a laminated structure with an adhesive layer as described above, for example, on the inner wall surface of the plastic tank after blow molding. It is also known to perform surface treatment using a surface treatment gas capable of imparting liquid impermeability to plastic such as fluorine gas or sulfurous acid gas.

(Problems to be Solved by the Invention) However, in the case of a plastic tank having a multi-layer structure as described in the above-mentioned publication, a nylon layer and a high-density polyethylene layer are laminated and adhered to each other before the blow molding at the time of manufacturing thereof. In this case, since it is necessary to interpose an adhesive layer between the nylon layer and the high-density polyethylene layer, the material supply means for forming the high-density polyethylene layer, which is the main constituent member, in the manufacturing equipment. In addition to the above, the extrusion head must be provided with means for supplying a material for forming a nylon layer to be a liquid impermeable layer and means for supplying an adhesive for forming an adhesive layer. There is a problem in that the manufacturing cost increases due to the increase in the complexity and size of the nylon layer, and the nylon layer and the high-density polyethylene layer form the adhesive layer. Since the sandwich structure is formed by sandwiching and adhering, the bonding force in the thickness direction of the tank wall is weak, and the mechanical strength tends to be low.

Further, the inner wall surface of the plastic tank obtained by blow molding is subjected to a surface treatment using a surface treatment gas capable of imparting liquid impermeability to plastic, such as fluorine gas, to form a liquid impermeable layer. If formed, an additional step for forming a liquid impermeable layer is required after blow molding, and the handling of the surface treatment gas used is troublesome, leading to deterioration in workability. I have a problem.

In view of such a point, the present invention is made of a plastic material as a raw material and is formed by blow molding or the like, and the tank wall portion has sufficient mechanical strength and the permeation leakage of liquid such as gasoline stored therein is prevented. An object of the present invention is to provide a method for producing a plastic tank having liquid opacity, which makes it possible to obtain a plastic tank that can be substantially prevented, relatively easily, and keep the production cost low. To do.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the method for producing a plastic tank having liquid impermeability according to the present invention is a mixture of a plastic material and a silane coupling agent. The material is heated to obtain a molten mixture, and the obtained molten mixture is shaped to obtain a plastic tank in which a barrier layer portion formed based on a silane coupling agent is dispersed in the wall portion. .

(Function) When the method for producing a liquid-impermeable plastic tank according to the present invention as described above is carried out, a mixed material obtained by mixing a silane coupling agent with a plastic material such as polyethylene is used. Be heated. Thereby, a molten mixture of the plastic material and the silane coupling agent is generated, and the molten mixture is used,
For example, molding by blow molding is performed to form a plastic tank having a predetermined shape.

The silane coupling agent is generally represented by YRSix ₃ (where Y is an organic functional group, R is a hydrocarbon group, and X is a hydrolyzable group bonded to silicon Si) and is mixed with a plastic material. When heated, it is hydrolyzed, the organic functional group Y reacts with the plastic material to firmly bond, and the vitreous portion Are generated in large numbers.

Therefore, the plastic tank obtained by the manufacturing method according to the present invention, the tank wall portion, the glass portion is dispersed, such glass portion does not allow liquids such as gasoline to permeate, It serves as a barrier layer that blocks the passage of liquid that penetrates the tank wall from the inner surface side to the outer surface side. Therefore, the plastic tank manufactured by the manufacturing method according to the present invention can substantially prevent the permeation and leakage of the liquid contained therein.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

FIG. 1 shows a main part of a plastic tank manufacturing apparatus in which an example of a method for manufacturing a liquid-impermeable plastic tank according to the present invention is carried out.

The plastic tank manufacturing apparatus shown in FIG.
An extrusion head 10 for forming a tubular body is provided, and the extrusion head 10 has a core die 12 extending through a central portion thereof and an outer portion arranged around an outer peripheral surface of a conical lower end portion 12a of the core die 12. Mold 14
And have. An annular nozzle portion 16 is formed between the conical lower end portion 12a of the core die 12 and the outer die 14. The annular nozzle portion 16 communicates with a cylindrical reservoir chamber 18 formed concentrically with the outer peripheral side of the columnar portion 12b of the core die 12,
A ring plunger 22 for pressurizing and pushing, which is driven by a hydraulic cylinder 20, is fitted into the storage chamber 18, and
The supply port 24a of the screw feeder 24 is made to communicate.

The screw feeder 24 is supplied from the hopper 26,
A heater 28 is provided to plasticize polyethylene, which is one of the thermoplastic materials. And
In the hopper 26, granular polyethylene (hereinafter pellet P
(Referred to as “P”) is supplied by the pellet feeder 31 in a predetermined amount, and the liquid silane coupling agent Q is supplied by the coupling agent feeder 33 at a predetermined ratio to the pellet P.

When an example of the method for manufacturing a plastic tank having liquid impermeability according to the present invention is carried out using the plastic tank manufacturing apparatus as described above, first, the hydraulic cylinder 20 is controlled to control the ring plunger 22. The tip is the storage chamber 18
The pellet P and the silane coupling agent Q are put into the hopper 26 while being pulled up to the upper position. The silane coupling agent Q used here is represented by YRSiX _{3 as} described above, and as the organic functional group, for example, NH ₂ , NH ₂ C ₂ H ₄ NH, NH ₂ ONH, CH ₂ CH, CH. ₂ CCH ₃ CO, etc., and as the hydrocarbon group R, for example, C _n H _3n-1 etc.,
As the hydrolyzable group X ₃ , for example, (OCH ₃ ) ₃ , (OC ₂ H ₂ CH ₂ OC
H ₃ )) ₃ and the like, and the amount thereof is adjusted so that the weight ratio to the pellet P is about 0.8 to 10%.
Further, if necessary, plasma treatment may be performed in advance before the pellets P are charged into the hopper 26 to be activated.

Then, the hopper 26 and the screw feeder 24 are driven and the heater 28 is operated. As a result, the pellet P and the silane coupling agent Q are mixed and heated to, for example, about 200 ° C. to be in a molten state,
Molten pellets P and silane coupling agent Q
A molten mixture Z of and is supplied to the storage chamber 18. In this way, the molten mixture Z is filled into the storage chamber 18 from the annular nozzle portion 16 formed between the conical lower end portion 12a of the core die 12 and the outer die 14 to the lower end surface of the ring plunger 22. Be in a state of

Next, the hydraulic cylinder 20 is controlled to push down the ring plunger 22, pressurize the molten mixture Z in the storage chamber 18, and continuously push out from the annular nozzle portion 16. As a result, the molten mixture Z that is continuously extruded in the form of a tubular body that gradually extends from the annular nozzle portion 16 forms a tubular extruded body 40 as indicated by a chain double-dashed line in FIG. To be done.

In this way, the pellet P and the silane coupling agent Q
A gradually extruded tubular extruded body 40 formed by a molten mixture Z composed of and is sandwiched between a pair of blow molding dies 34 separated from each other, as shown by a chain double-dashed line in FIG. It is placed in a position where Then, when the ring plunger 22 descends to a position where the tubular extruded body 40 has a predetermined length, the ring plunger 22
Stop descending.

After that, the pair of blow molding dies 34 are moved in the directions indicated by the white arrows in FIG. At this time, as shown in FIG. 2, the tip portion 40a of the tubular extruded body 40 is attached to the blow nozzle 3
6, with the lower end surface of each of the blow molding dies 34 interposed therebetween to bond the abutting inner wall surfaces to each other, and
The upper end portion 40b of the tubular extruded body 40 is attached to a blow molding die 3
The upper end surface portions of 4 sandwich the contacting inner wall surface portions to each other, and the upper end surface portions of the blow molding dies 34 separate the tubular extrusion molded body 40 from the extrusion head 10.

Subsequently, compressed air or pressurized gas is blown into the tubular extruded body 40 from the blow nozzle 36 to blow-mold the tubular extruded body 40. This allows tubular extrudates
40 is molded so that the outer wall surface thereof has a shape along the inner wall surface of the blow molding die 34, thereby forming a sealed plastic tank 50 as shown in FIG. 3A.

When the plastic tank 50 is manufactured in this manner, the pellets P and the silane coupling agent Q are mixed in the hopper.
When mixed by 26 and a screw feeder 24 and heated by a heater 28 to form a molten mixture Z, a pellet P made of polyethylene (CH ₂ CH ₂ ) _n and a silane coupling agent Q represented by YRSiX ₃ are obtained. After reaction, the following reaction product is obtained.

Thus, the molten mixture Z supplied to the storage chamber 18 depends on the mixing ratio of the pellet P and the silane coupling agent Q and the heating temperature. Groups are generated.

here, Is a vitreous part, and thus the molten mixture Z is extruded from the extrusion head 10 and blow-molded to obtain a plastic tank 50 having a tank wall with a vitreous part, as shown in FIG. 5B. A large number of parts 60 are distributed and arranged. The vitreous portion 60 serves as a barrier layer that does not allow liquid fuel such as gasoline to pass therethrough, and the liquid that permeates the tank wall portion from the inner wall surface side to the outer wall surface side is blocked in its course, and this glass Since the quality portions 60 are arranged so as to overlap each other along the thickness direction of the tank wall portion, for example, when liquid fuel such as gasoline is stored in the plastic tank 50 for a relatively long time. Moreover, the stored liquid fuel is substantially prevented from penetrating the tank wall portion from the inner wall surface side and leaking to the outer wall surface side.

Further, since the plastic tank 50 has a single-layer structure in which the tank wall portion is substantially made of a single plastic material, it has sufficient mechanical strength.

As the silane coupling agent, various kinds can be used, but in particular, an aminosilane coupling agent having the same amide bond or imide bond as nylon has a large effect of preventing permeation of liquid fuel such as gasoline. Is preferred.

(Effects of the Invention) As is clear from the above description, according to the method of manufacturing a liquid-impermeable plastic tank of the present invention, the tank wall portion has sufficient mechanical strength and A large number of barrier layers are dispersed and mixed to have impermeability to liquids such as gasoline. Therefore, it is possible to substantially prevent osmotic leakage of liquids such as gasoline stored inside and tough plastic. The tank can be obtained relatively easily and the manufacturing cost thereof can be kept low. The plastic tank obtained by the manufacturing method according to the present invention is suitable for use as a fuel tank for vehicles.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of a plastic tank manufacturing apparatus used for carrying out an example of a method for manufacturing a liquid-impermeable plastic tank according to the present invention;
The figure is a cross-sectional view used for explaining the steps in an example of the manufacturing method according to the present invention which is carried out by using the manufacturing apparatus shown in FIG. 1, and FIGS. It is the side view and partial sectional view of the plastic tank obtained by an example. In the figure, 10 is an extrusion head, 18 is a storage chamber, 24 is a screw feeder, 26 is a hopper, 28 is a heater, 31 is a pellet feeder, 33 is a coupling agent feeder, 34 is a blow molding die, 36 Is a blow nozzle, 40 is a tubular extrudate, 50 is a plastic tank, P is pellets, Q is a silane coupling agent, and Z is a molten mixture.

Claims (1)

[Claims] 1. A mixed material obtained by mixing a plastic material and a silane coupling agent is heated to obtain a molten mixture, the molten mixture is molded, and a wall portion is formed on the basis of the silane coupling agent. A method for producing a plastic tank having liquid impermeability, which comprises obtaining a plastic tank in which barrier layers formed are dispersed.