TECHNICAL FIELD

The present invention relates to a fuel container that is excellent in fuel barrier properties and impact resistance, and that enables stable production.

BACKGROUND ART

In recent years, as containers for storing fuels such as hydrocarbons, coextrusion blow-molded containers made of plastic have been used, and examples thereof include fuel containers for automobiles. As fuel containers made of plastic, those of polyethylene single layer have been widely adopted but have a disadvantage of having comparatively high fuel transmittance.

As a method to overcome such a disadvantage, a method of forming a multilayer including an ethylene-vinyl alcohol copolymer (which may be hereinafter abbreviated as EVOH) layer and a polyolefin layer is known (Patent Document 1). Further, in fuel containers having an EVOH layer and a polyolefin layer, a fuel container in which the EVOH layer is disposed on the inner side in order to improve the fuel barrier properties is also known (Patent Document 2).

By the way, when producing fuel containers by coextrusion blow molding or the like, loss parts during molding such as burrs generally occur. Use of a recovered material layer formed by remelting such loss parts during molding, rejected items in molding, or the like as a part of the fuel containers reduces the amount of waste and thus is preferable also in view of environmental protection, and a cost reduction effect is also obtained.

However, there have been cases where foreign matter derived from EVOH occurs in the recovered material layer, thereby reducing the impact resistance or the fuel barrier properties of fuel tanks. In particular, when continuing the production of fuel tanks over a long period of time, such foreign matter tends to occur, which has been a problem.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: US Patent Publication No. 5849376Patent Document 2: JP9-29904 A

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The present invention has been devised in order to solve the aforementioned problem, and it is an object of the present invention to provide a fuel container that is excellent in fuel barrier properties and impact resistance, and that enables stable production.

Means for Solving the Problems

The aforementioned problem is solved by providing a fuel container composed of a multilayer structure containing: an EVOH (A) layer; an adhesive resin (B) layer; a high-density polyethylene (C) layer; and a resin composition (D) layer, wherein the EVOH (A) contains 15 to 44 mol % of ethylene, the adhesive resin (B) is a maleic anhydride-modified polyolefin having an acid value of 0.1 to 10 mgKOH/g and containing 1 to 8.5 μmol/g of magnesium element, calcium element, zinc element, or a combination thereof, the resin composition (D) contains the EVOH (A), the adhesive resin (B), and the high-density polyethylene (C), and the fuel container satisfies formulas (1) to (6) below.
0.05≤Ma/Mb≤40  (1)
2≤Ma/Mc≤1800  (2)

In formulas (1) and (2) above, Ma, Mb, and Mc are respectively as follows: Ma represents a MFR (g/10 min) of the EVOH (A) (measured at 210° C. under a load of 2160 g); Mb represents a MFR (g/10 min) of the adhesive resin (B) (measured at 210° C. under a load of 2160 g); and Mc represents a MFR (g/10 min) of the high-density polyethylene (C) (measured at 210° C. under a load of 2160 g).
0.003≤Ta/Tt≤0.12  (3)
0.0015≤Tb/Tt≤0.12  (4)
0.83≤(Tc+Td)/Tt≤0.99  (5)
0.02≤Td/(Tc+Td)≤0.90  (6)

In formulas (3) to (6) above, Ta represents the total thickness of the (A) layer, Tb represents the total thickness of the (B) layer, Tc represents the total thickness of the (C) layer, Td represents the total thickness of the (D) layer, and Tt represents the overall thickness (Ta+Tb+Tc+Td).

At this time, it is suitable that the resin composition (D) contains 1 to 20 mass % of the EVOH (A), 1 to 20 mass % of the adhesive resin (B), and 60 to 98 mass % of the high-density polyethylene (C). It is also suitable that the resin composition (D) contains 0.001 to 1 μmol/g of magnesium element, calcium element, zinc element, or a combination thereof. It is also suitable that the resin composition (D) contains 0.001 to 5 μmol/g of an alkali metal element.

It is also suitable that the fuel container satisfies formula (7) below.
0.3≤(VA×Ta)/(MT×Tb)≤1000  (7)

In formula (7) above, VA, MT, Ta, and Tb are respectively as follows: VA represents a vinyl alcohol content (mol %) in the EVOH (A); MT represents the total amount (μmol/g) of magnesium element, calcium element, and zinc element in the adhesive resin (B); Ta represents the total thickness (μm) of the EVOH (A) layer; and Tb represents the total thickness (μm) of the adhesive resin (B) layer.

It is also suitable that the EVOH (A) contains 0.04 to 13 μmol/g of an alkali metal element.

It is also suitable that the adhesive resin (B) contains 0.35 to 11.5 μmol/g of aluminum element and 0.5 μmol/g or less of titanium element.

It is also suitable that the total amount of magnesium element, calcium element, and zinc element in the high-density polyethylene (C) is 0.5 μmol/g or less.

It is also suitable that the EVOH (A) layer and the adhesive resin (B) layer are in contact with each other in the fuel container.

Effects of the Invention

The fuel container of the present invention is excellent in fuel barrier properties and impact resistance. Further, even in the case where molding of the fuel container of the present invention is continued over a long period of time, generation of foreign matter derived from the EVOH (A) in the resin composition (D) is suppressed. Accordingly, the fuel container of the present invention is stably produced and thus is excellent in productivity.

