JP2002144891A - Fuel tank less in fuel permeation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel tank less in fuel permeation. SOLUTION: The fuel tank less in fuel permeation comprises a permeation inhibiting layer consisting of one or two or more thermoplastic resin layers and one or two or more layers of inorganic materials or inorganic material dispersed thermoplastic resins.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel tank made of a thermoplastic resin and having low fuel permeation.

[0002]

2. Description of the Related Art The advantages of forming a liquid fuel container such as an automobile gasoline tank by hollow molding (blow molding) of a thermoplastic resin are that it has a large degree of freedom in shape, that it can be reduced in weight, and that rust prevention treatment is required. It is unnecessary, the number of processing steps can be reduced, and full automation of manufacturing is possible.

[0003] In particular, in automobile tank applications, it is possible to obtain a tank shape that can secure a sufficient capacity even for a lower structure that has become complicated due to the adoption of four-wheel drive or FF, and the quality of the image can be obtained by fully automatic manufacturing. It is hoped that it will be integrated. As an automotive gasoline tank that can meet such needs, there has been previously an impact-resistant and inexpensive ultra-high-molecular-weight high-density polyethylene (UHMW-HD).
PE) single-layer hollow molded tanks were the mainstream, but in recent years,
Due to the increasing interest in global environmental issues, regulations on gasoline permeation have become stricter, and UHMW-HDPE single layers having a high affinity for hydrocarbons are no longer able to cope.

[0004] Industrial techniques that have been studied to prevent gasoline permeation in UHMW-HDPE tanks include: 1) Fluorination or sulfonation of the tank inner surface with F ₂ gas or SO ₃ gas 2) Hydrocarbon permeation Nylon layer, ethylene-
Multi-layer hollow molding in which a vinyl alcohol copolymer layer or the like is provided as an intermediate layer between HDPE layers. 3) A melt blend of modified nylon and HDPE is hollow-molded under specific molding conditions to form a nylon phase capable of suppressing hydrocarbon permeation. There is a method of dispersing in a layered manner in the HDPE phase.

[0005] Of these, the method 1) has been applied to European vehicles, but it is necessary to ensure safety in handling harmful gases,
Recovery of environmentally hazardous substances in the tank manufacturing process became a problem,
Currently rarely used. Method 2) is the mainstream of the current resin tank manufacturing method, and the introduction of a resin barrier layer can reduce gasoline permeation to some extent. However, since gasoline permeation in resin is essentially unavoidable, it will be further strengthened in the future. It is difficult to sufficiently meet the required transmission amount regulation. In the method 3), as in the case 2), the resin barrier layer cannot sufficiently suppress gasoline permeation, and the molding conditions (shearing of the screw of the extruder screw) must be such that the nylon phase is dispersed in a layered manner throughout the tank having a complicated shape. It is not widely used at present because it is not easy to optimize force and resin temperature.

[0006] In addition to the above methods 1) to 3), there have been developed some related technologies which can be used for preventing gasoline permeation in a resin fuel tank, but there are many problems in industrial application.
None of them has been put to practical use for resin fuel tanks. For example, a method of forming a plasma polymerized film for suppressing liquid permeation on the inner surface of a resin fuel tank is disclosed in Japanese Patent Laid-Open No. 3-10 / 1991.
No. 7458.

In addition to using harmful gases such as fluorinated monomers and organosilicon compounds as the plasma polymerizable monomer, a pretreatment step using an inert gas plasma is required to improve the adhesion of the coating, and the production cost is high and practical. Not. In addition, 5 to 1 on both sides of a metal foil having a thickness of 15 to 200 μm.
A laminated sheet obtained by bonding or thermocompression bonding a thermoplastic resin having a thickness of 000 μm is disclosed in JP-A-58-155944.

A packaging container is obtained by further warm-pressing the laminated sheet as an intermediate product, and has a metal foil between layers, which is useful for preventing gasoline permeation.
Due to the large number of steps, the production cost is high and not practical. As a similar example, Japanese Patent Application Laid-Open No. 8-337244 discloses a liquid container obtained by molding a laminate in which a polyester or polyolefin-based resin layer is provided on one or both sides of an aluminum thin plate having a thickness of 100 μm or more. However, application to a resin fuel tank is difficult for the same reasons as described above.

As described above, various industrial techniques have been tried to prevent gasoline permeation in resin tanks, and related technologies applicable to gasoline permeation prevention have been developed. No technology has been found to meet all the requirements such as gasoline permeation prevention function, excellent tank formability, and small number of processing steps.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in a fuel tank made of a thermoplastic resin, and provides a fuel tank having low environmental permeation and low fuel permeation, and a method of manufacturing the same. That is the challenge.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above-mentioned problems. As a result, the fuel tank has a multilayer structure, and at least one of the layers is made of an inorganic material or an inorganic material. By using a permeation suppression layer made of a dispersed thermoplastic resin to prevent fuel permeation, liquid fuel permeation is low, and no environmentally hazardous substances are discharged in the manufacturing process, processing man-hours are reduced, and the shape is reduced. It has been found that a fuel resin container having a high degree of freedom can be obtained.

The present invention has been completed based on such findings, and the gist thereof is as follows. (1) One or two or more thermoplastic resin layers and one or two or more inorganic substances or a permeation suppression layer made of a thermoplastic resin in which an inorganic substance is dispersed,
Fuel tank with low fuel permeation.

(2) One or both of the inner surface and the outer surface has a permeation suppressing layer made of an inorganic material,
The fuel tank according to (1), wherein at least one of the thicknesses is 0.005 μm or more. (3) The fuel tank according to (1) or (2), wherein a permeation suppression layer made of an inorganic material and having a thickness of 1 μm or more is provided on the outer surface.

(4) The fuel tank according to (1) to (3), wherein the permeation suppression layer is made of an inorganic substance formed by vapor deposition or wet plating. (5) The fuel tank according to any one of (1) to (3), wherein the permeation suppression layer is formed by bonding a film, sheet, or foil made of an inorganic substance.

(6) The fuel according to the above (1), wherein the permeation suppression layer is made of a thermoplastic resin in which an inorganic substance is dispersed, and one or more of the layers have a thickness of 100 μm or more. Low permeation fuel tank. (7) The fuel tank according to (6), wherein the fuel tank has low fuel permeability, and is integrally formed by multilayer hollow molding.

[0016]

Embodiments of the present invention will be described below in detail. The present invention provides a multilayer resin fuel tank having one or more layers having high liquid fuel permeation suppression ability, and a method of manufacturing the same that can be manufactured with as few processing steps as possible. The point of the present invention is that the permeation suppression property is obtained by laminating or mixing inorganic substances.

The permeation suppression layer is provided on any one of the inner surface and outer surface of the container, the inside of the resin constituting the container, or two or more of these portions. In the latter case, for example, one is applied to both the inner and outer surfaces of the container.
A total of two layers are provided for each layer, and one layer is provided for both the inner surface and the inside of the resin. The permeation suppression layer is formed by vapor deposition or wet plating of an inorganic substance on the surface of the container, adhesion of an inorganic substance film or sheet, or a thermoplastic resin-inorganic substance composite (compound of resin and inorganic substance) by UHMW. -H
It is formed by co-extrusion with a container constituting resin such as DPE and hollow-molding a multilayer parison including a resin-inorganic substance composite layer.

In the present invention, the thermoplastic resin constituting the container is excellent in impact resistance, fuel swelling resistance, water resistance, and hollow moldability (such as the drawdown resistance of a molten parison, the prevention of uneven thickness). Although it is not particularly limited as long as it is inexpensive, olefin resins such as ultrahigh molecular weight high density polyethylene (UHMW-HDPE) having a weight average molecular weight of several hundred thousand to several million, low density polyethylene, polypropylene, and nylon 6 and the like are applicable. Among them, it is preferable to use UHMW-HDPE, which has the advantages of preventing the occurrence of extremely uneven wall thickness during blow molding of a fuel tank, which is a large molded body, and of preventing parison breakage due to blow-up. In order to enhance the vapor deposition and plating properties of inorganic substances on the container surface and the adhesion of inorganic substance films and sheets to the container surface, mechanical polishing treatment to increase the bonding area, and to the resin surface that constitutes the container A modification treatment for introducing a polar group, a primer treatment for the resin surface with a primer, and the like may be performed, but the treatment method and the type of the treatment layer are not particularly limited. Among these, the methods of introducing a polar group into the resin surface include, for example, a corona discharge method, which has a lower apparatus cost than the plasma method, an atmospheric pressure plasma method, which can be treated at a relatively low cost among the plasma methods, and a strong acid method. And a chemical treatment method using the same.

The inorganic substance used in the present invention is stable when producing a multilayer hollow container, is solid when the container is used, and does not generate harmful substances during the production and use of the container. There is no particular limitation on these compounds. For example, examples of the metal include aluminum, copper, nickel, tin, zinc, cobalt, titanium, steel, and alloys including these elements. As the metal compound, alumina, magnesia (MgO), rutile (Ti
O ₂ ), tin stone (SnO ₂ ), ilmenite (FeTi
O ₃ ), metal oxides such as potassium titanate, magnesite (MgCO ₃ ), dolomite (CaCO ₃ .MgCO ₃ )
₃ ), carbonates such as calcium carbonate, hydroxides such as magnesium hydroxide and aluminum hydroxide, sulfates such as anhydrous gypsum (calcium sulfate), aluminum nitride (Al
N), titanium nitride (TiN), zirconium nitride (Zr
N), metal nitrides such as tungsten nitride (W ₂ N),
Examples include metal carbides such as titanium carbide (TiC), zirconium carbide (ZrC), and tungsten carbide (WC), and metal borides such as titanium boride (TiB) and nickel boride (NiB). Non-metals include simple carbon (graphite), and non-metallic compounds include silica and carborundum (S).
iC) and the like.

Among the inorganic substances used in the present invention, various silicates can be exemplified as a composite compound of a metal and a nonmetal. For example, wollastonite (calcium silicate), talc (hydrated magnesium silicate), kaolin (hydrated aluminum silicate), clay (aluminum silicate), glass,
Mica (mica), beryl (3BeO.Al ₂ O ₃ .6Si
O ₂ ) and zircon (ZrSiO ₄ ).

In the present invention, when the permeation suppressing layer is formed by vapor deposition on the surface of the resin container after the hollow molding, the inorganic substance may be selected from the above-mentioned metals, non-metals, and compounds thereof by heating in vacuum. There is no particular limitation as long as it can be vaporized by a method such as sputtering and the vapor can be condensed on the resin to form a vapor-deposited layer in close contact with the resin. Further, the vapor deposition method is not particularly limited as long as the vapor deposition layer can be formed without deteriorating and softening the resin surface. The deposition thickness is 0.005 μm or more. When the film thickness is less than 0.005 μm, the effect of suppressing gasoline permeation cannot be sufficiently obtained for many inorganic substances.

When the permeation suppression layer is formed by wet plating, the inorganic material layer is preferably a metal. As a plating method, first, the resin surface is roughened by etching, etc.
Form a thin metal layer adhered to the resin surface by electroless plating,
After that, it is preferable to continue the electroless plating or switch to the electroplating to form the metal layer. The plating layer thickness is 0.005 μm or more. 0.005 layer thickness
If it is less than μm, a sufficient gasoline permeation suppression effect cannot be obtained.

When a film or sheet made of an inorganic material is adhered to the outer surface of the resin container, any of the above-mentioned metals, nonmetals, and compounds thereof may be used as the inorganic material. Mixtures of more than one species may be used. The method of forming the inorganic material into a film or a sheet is not particularly limited. Since many inorganic materials other than metals are difficult to form into films or sheets by themselves, various thermoplastic resins as binders are used as inorganic materials within a range that does not impair the gasoline permeation prevention function of the inorganic materials. A film or sheet may be formed after preparing the thermoplastic resin composite. The type of these thermoplastic resins is not particularly limited as long as the object of the present invention is not impaired, but impact resistance, fuel swelling resistance, water resistance, excellent hollow moldability, and the use of inexpensive olefin-based resins are preferable. . Since the film or sheet is located on the outer surface of the container, a hygroscopic resin such as nylon or polyester whose dimensions are easily changed by moisture is not used. Examples of a method for shaping the inorganic substance-thermoplastic resin composite into a film or sheet include, for example, a method in which an inorganic substance and a thermoplastic resin are mixed in a continuous kneader such as a screw type extruder or a Banbury mixer. After kneading (compounding) with a simple batch-type kneader, the film may be blown or extruded into a sheet.

When a film or sheet made of an inorganic material is adhered to the outer surface of the resin container, the method of adhering the film or sheet to the resin surface is not particularly limited as long as the object of the present invention is not impaired. Examples of applicable bonding methods include thermocompression bonding and bonding with an adhesive.
When the bonding strength of the film or sheet to the resin surface is insufficient, the bonding strength can be improved by, for example, roughening the surface by etching the resin surface. The thickness of the film to be bonded is 1 μm or more. If the film thickness is less than 1 μm, not only is it difficult to handle, but also the effect of defects such as voids and cracks in the film increases, and the gasoline permeation suppression effect cannot be sufficiently obtained.

In the present invention, the permeation suppression layer is a resin-inorganic substance composite layer composed of a thermoplastic resin phase and an inorganic substance phase finely dispersed in the resin phase, and a resin container having the composite layer is provided. When integrally formed by multilayer hollow molding, any of the above-mentioned metals, non-metals, or compounds thereof may be used as the inorganic substance, or a mixture of two or more of these may be used.

There is no particular limitation on the shape and size of the inorganic material, but the shape is such that the plate can be substantially oriented in the direction perpendicular to the thickness direction of the container during multilayer blow molding, and can enhance the gasoline permeation prevention function. Shape, flake shape, needle shape, fiber shape and the like are preferable. Examples of the inorganic substance having such a shape include talc, kaolin, glass flake, mica, and the like in the form of a plate or flake, and potassium titanate, magnesium hydroxide, anhydrous gypsum, wollastonite, or the like in the form of a needle.
In a fibrous state, there are glass fiber, carbon fiber and the like.

The thermoplastic resin is not particularly limited as long as it can easily be compounded with the inorganic substance to be used and has excellent wettability, but is excellent in impact resistance, fuel swelling resistance and hollow moldability. It is preferable to use inexpensive olefin resins, various nylons, various polyesters, polycarbonates and the like. However, when the resin-inorganic substance composite layer is located on the outer surface of the container, it is not preferable to use nylon, polyester, polycarbonate, or the like, whose dimensions easily change due to moisture absorption. The thickness of the resin-inorganic substance composite layer is 100 μm or more. When the thickness is less than 100 μm, it becomes difficult to stably co-extrude the molten composite layer thickened by the dispersion of the inorganic substance together with the other layers.

In the present invention, in addition to the above-described permeation suppression layer, a thermoplastic resin layer having excellent gasoline permeation prevention properties may be provided as an intermediate layer inside the container. Such resins include, for example, various nylons such as nylon 6 and nylon 66 and their modified products, various polyesters such as ethylene-vinyl alcohol copolymer, polyethylene terephthalate, and polybutyrene terephthalate, and melting of two or more of these. Examples thereof include a mixture and a melt mixture (polymer blend) with a polyolefin-based resin. Polyvinylidene chloride, vinylidene chloride copolymer, polyvinylidene fluoride, vinylidene fluoride copolymer and the like also have a certain degree of gasoline permeation prevention properties, but they contain halogen atoms which are environmentally harmful substances, so that it is preferable to avoid using them.

The permeation suppression layer in the present invention may contain various organic or inorganic additives as long as its purpose is not impaired. In particular, when a film or sheet of an inorganic material-thermoplastic resin composite is adhered to a container to form a permeation suppression layer, or a resin-inorganic material composite layer is coextruded with another layer to form a multilayer hollow. When integrally molded by molding, the resin phase contained in these permeation suppression layers contains higher aliphatic alcohols, higher fatty acids, metal soaps, esters of higher fatty acids and other hydrocarbons, polyhydric alcohols and higher fatty acids. Esters, monoamides or bisamides of higher fatty acids, molding lubricants such as paraffin, inorganic sols such as alumina, titania, zirconia, coloring agents such as various pigments and dyes, antioxidants, crosslinking agents, etc. No problem.

[0030]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. [Types of thermoplastic resin] (1) HDPE-1 Ultra high molecular weight high density polyethylene having a weight average molecular weight of 38.8 × 104 (2) HDPE-2 High density polyethylene having a weight average molecular weight of 10.2 × 104 [Inorganic] Kinds of system substances] (1) Aluminum (2) Nickel (3) Mica (size 3 to 10 μm) [Method of forming permeation suppression layer] (1) Vaporized hollow molded resin container (constituent resin: HDPE-1, shape ... Aluminum was vapor-deposited on the inner surface of a rectangular parallelepiped similar to a kerosene tank for home use, having an internal capacity of about 14 liters and an average thickness of 3.3 mm. (2) Wet plating Electroless nickel plating was applied to the inner surface of a hollow molded resin container (constituent resin: HDPE-1, shape, content, average thickness same as in (1)). (3) Thermocompression bonding of metal film An aluminum foil was thermocompression bonded to the outer surface of a hollow molded resin container (constituent resin: HDPE-1, the shape, the content, and the average thickness were the same as in (1)). (4) Multilayer hollow molding including resin-inorganic material composite layer Resin-inorganic material composite (resin: HDPE-2, inorganic material: mica, mass ratio HDPE-2 / mica = 65/3)
5) and HDPE-1 were co-extruded into a parison,
A hollow container having a three-layer structure of -1 / resin-inorganic substance composite / HDPE-1 (shape, content is the same as that of (1), average thickness: 3.8 mm) was formed. [Comparative materials] (1) HDPE single-layer container Single-layer hollow molded container not containing a permeation suppression layer (constituent resin: H
DPE-1, shape: rectangular parallelepiped similar to a kerosene tank for home use, content: about 14 liters, average thickness: 3.3 mm) (2) HDPE / nylon 6 container Multi-layer hollow molded container not including a permeation suppression layer (HDPE-1
/ Adhesive layer / Nylon 6 / Adhesive layer / HDPE-1 Five-layer structure, shape and content are the same as in (1), average thickness ...
(Evaluation of liquid fuel permeability) After putting commercially available regular gasoline, octane, or xylene into a resin container, sealing the contents, and leaving it to stand at room temperature for 2 months. Was reduced to the amount per day per unit surface area of the container, and the liquid permeation amount (g / m ² · day) was determined.

Table 1 summarizes the evaluation results. When the permeation amount of hydrocarbons was very small and clearly lower than 0.02 g / m ² · day, it was described as “<0.02 g / m ² · day”. The multilayer resin container according to the present invention has a much better liquid fuel permeation prevention property than a resin container not satisfying the requirements of the present invention.

[0032]

According to the present invention, it has an excellent liquid fuel permeation prevention function, does not use or discharge environmentally harmful substances during production, and has the advantages of hollow molding (high degree of freedom in container shape, small number of processing steps). Liquid fuel containers, particularly gasoline tanks for automobiles, which can be said to have extremely high industrial value.

[0033]

[Table 1]

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroshi Kanai 20-1 Shintomi, Futtsu-shi, Chiba F-term (Reference) 3D038 CA00 CB01 CC20 4F100 AA00B AA00H AB10B AB16B AB33B AC05B AC05H AK01A AK01B AK05A AK05B CA30B DA01 EH66B EH71B GB32 JA07A JA20 JB16A JB16B JD01B JL01 YY00 YY00B

Claims (7)

[Claims] 1. A fuel comprising one or two or more thermoplastic resin layers and one or two or more layers of an inorganic substance or a permeation suppression layer made of a thermoplastic resin in which an inorganic substance is dispersed. Low permeation fuel tank. 2. The method according to claim 1, wherein one or both of the inner surface and the outer surface has a permeation suppressing layer made of an inorganic material, and at least one of the layers has a thickness of 0.005 μm or more. The fuel tank with low fuel permeation described. 3. The method according to claim 1, wherein the outer surface has a surface of 1 μm made of an inorganic material.
The fuel tank according to claim 1, further comprising a permeation suppression layer having a thickness of not less than m. 4. The fuel tank according to claim 1, wherein the permeation suppression layer is made of an inorganic material formed by vapor deposition or wet plating. 5. The fuel tank according to claim 1, wherein the permeation suppression layer is formed by bonding a film, sheet or foil made of an inorganic substance. 6. The fuel permeation barrier according to claim 1, wherein the permeation suppression layer is made of a thermoplastic resin in which an inorganic substance is dispersed, and one or more of the layers have a thickness of 100 μm or more. Less fuel tank. 7. The fuel tank with low fuel permeation according to claim 6, wherein the fuel tank is formed by integral molding by multi-layer hollow molding.