JPH0740517A - Multi-layer hollow molding - Google Patents

Abstract

PURPOSE:To obtain the excellent reclamation properties of gas barrier properties or burr by forming a polyethylene layer from high mol.wt. polyethylene having specific values produced by using a chrominum catalyst represented by a specific formula and a reducing agent. CONSTITUTION:A multilayered hollow molded object is molded from a multilayered laminating material obtained by laminating a polyethylene layer and a barrier layer constituted of one of a polyamide resin, a saponified ethylene/vinyl acetate copolymer and a thermplastic polyester resin or a mixture of two or more resins through an adhesive layer costituted of a modified polyolefin resin. The polyethylene layer is formed from high mol.wt. polyethylene with a high-load melt flow rate (190 deg.C, 21.6kg load) of 1-10g/10min and density of 0.935g/cm<3> or more produced using a chromium catalyst represented by formula I (wherein R<1> and R<2> are a 1-14C hydrocarbon group) or formula II (wherein R<3> and R<4> are a 70-20C steric hindrance polyalicyclic hydrocarbon group) and a reducing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer hollow molded article, and more particularly to a barrier (permeation) for automobile fuel (gasoline), a mixture of a hydrocarbon and an oxygen-containing organic compound such as alcohol-containing gasoline (gasohol). (Prevention) performance and mechanical strength such as impact resistance,
In addition, the present invention relates to a multi-layer hollow molded article having excellent reusability (reclaim) of burrs and the like in its production.

[0002]

2. Description of the Related Art Fuel tanks for automobiles have heretofore been attempted to be made into plastics by a hollow molding method for the purpose of improving safety at the time of impact and increasing flexibility in shape. Properties required of the resin fuel tank include excellent permeation-preventing performance (gas barrier property) for fuel, and excellent mechanical strength such as impact resistance as a tank. On the other hand, polyolefin is suitable as a plastic material because it is relatively inexpensive and has excellent impact resistance and mechanical strength, but it has a problem of poor gas barrier properties, and various improvements have been proposed.

For example, a method of chemically treating the inner surface of a polyolefin tank with fluorine gas (F ₂ ) or sulfone gas (SO ₃ ), and a modified polyamide obtained by combining a polyamide having a relatively excellent barrier property with an alkylcarboxyl-substituted polyolefin And a laminar method in which these are layered in a continuous matrix phase of polyolefin. However, these methods still do not have sufficient barrier properties for this application, and it is difficult to comply with the stricter regulations in the future for the purpose of environmental protection, and the layered morphology of the modified polyamide formed is stable depending on the molding conditions. There is also a problem that it is difficult to reduce impact resistance, and it cannot be said to be a complete method.

On the other hand, the chemical treatment method has durability of treatment and environmental problems at the time of treatment. In addition, for example, Japanese Patent Publication No. 1-1404
As described in JP-B-9, a material having an excellent gas barrier property such as a polyamide resin, a saponified product of ethylene vinyl acetate copolymer, or a thermoplastic polyester is used as a barrier layer, and this and a polyolefin as a main layer are modified. A multilayer method has been proposed in which the layers are laminated via an adhesive layer made of polyolefin. This method has a very excellent gas barrier property. However, from an economical point of view, a high proportion of recycled materials such as multi-layer burr generated at the time of molding (however, if the mixing ratio of recycled materials exceeds 50% by weight, the recycled material ratio after mixing gradually increases, and the quality is stable. Generally 50% by weight because
Since it needs to be returned to the raw material, the mechanical strength such as impact resistance must be further improved in consideration of the reduction caused by this reclaim.

[0005]

In view of the present situation, the inventors of the present invention can reclaim burrs and the like with a high gas barrier property, which is a condition required for automobile fuel tanks, etc. (% By weight) Even when molded using a reclaim resin, as a result of diligent studies aimed at providing a multilayer hollow body having excellent mechanical strength such as impact resistance at the time of collision, polyethylene as a main layer was found. It has been found that this object is achieved by using high molecular weight polyethylene produced with a specific catalyst as the layer, and completed the present invention.

That is, the multi-layer hollow molded article of the present invention comprises a polyethylene layer and a barrier layer which is a mixture of one or more of a polyamide resin, a saponified ethylene vinyl acetate copolymer and a thermoplastic polyester. A multi-layer hollow molded article formed from a multi-layer laminated material formed by laminating an adhesive layer composed of a modified polyolefin resin layer, wherein the polyethylene layer has the following formula: CrO ₃ ,

[0007]

[Chemical 3]

(In the formula, R ¹ and R ² have 1 to 14 carbon atoms.
Represents a hydrocarbon group of), or

[0009]

[Chemical 4]

(In the formula, R ³ and R ⁴ have 7 to 20 carbon atoms.
The high-load melt flow rate (190 ° C, 21.6 kg load) produced by using a chromium catalyst represented by the sterically hindered polyalicyclic hydrocarbon group) and a reducing agent is 1 to 10
Characterized by being formed of high-molecular-weight polyethylene having a density of g / 10 minutes and a density of 0.935 g / cm ³ or more, and the polyethylene layer containing burrs generated during molding of the material into a multi-layer hollow molded article. It is what

[0011]

DETAILED DESCRIPTION OF THE INVENTION The high molecular weight polyethylene used in the present invention is, for example, JP-B-44-2996 and 44-382.
No. 7, No. 47-1766, No. 47-23176, No. 47-21574 and the like, the following formula: CrO ₃

[0012]

[Chemical 5]

(In the formula, R ¹ and R ² have 1 to 14 carbon atoms.
Represents a hydrocarbon group of), or

[0014]

[Chemical 6]

(In the formula, R ³ and R ⁴ have 7 to 20 carbon atoms.
Of the sterically hindered polyalicyclic hydrocarbon group), and is obtained by polymerizing ethylene using a chromium catalyst and a reducing agent. As a preferable chromium compound,
Formula: CrO ₃ , or

[0016]

[Chemical 7]

## STR3 ## wherein R, R ¹ and R ² represent a hydrocarbon group containing 1 to 14 carbon atoms, preferably 3 to 10 carbon atoms. Examples include bistriphenylsilylchromate, bistrimethylnaphthylsilylchromate, bistriethylphenylsilylchromate, bistrinaphthylsilylchromate, bistrixylsilylchromate, bistritolylsilylchromate, and the like. Among them, the most preferable one is bistriphenylsilyl chromate.

Further, it is a dialkyl chromate represented by the following formula (II), for example, diadamantyl chromate (the following formula (IV)), di-2-alkylbornyl chromate (the following formula (V)), di-2. -Alkylphentyl chromate (the following formula (VI)) and the like can be mentioned. Among them, the most preferable one is diadamantyl chromate.

[0019]

[Chemical 8]

[0020]

[Chemical 9]

[0021]

[Chemical 10]

[0022]

[Chemical 11]

(In the above formula, R ³ and R ⁴ have 7 to 7 carbon atoms.
20 sterically hindered polyalicyclic hydrocarbon groups, R ⁵ , R ⁶ , R ⁷ and R ⁸ represent hydrocarbon groups)

In the chromium catalyst of the present invention, generally, the above-mentioned chromium compound is supported on a porous inorganic oxide such as silica,
It is prepared by reducing with a reducing agent. The reducing agent is represented by the following general formula: R'xAl (OR ") y (x and y are integers of 1 or 2 and the total thereof is 3,
R'and R "represent a hydrocarbon group containing 1 to 14 carbon atoms), and an alkylaluminum alkoxide represented by the formula (I) is preferable. Examples of the hydrocarbon group include an alkyl group, an aralkyl group and an aryl group. Groups, alkaryl groups, alicyclic groups, bicyclic groups, and similar hydrocarbon groups, etc. These reducing agents can be used alone or as a mixture of two or more kinds. Regarding, the molar ratio of aluminum atoms and chromium atoms in the reducing agent (hereinafter abbreviated as Al / Cr ratio) is 100 to 100.
It is 0.5, preferably 15 to 0.5, and particularly preferably 5.0 to 1.0.

As a method for polymerizing ethylene using these catalysts, known methods such as suspension polymerization and solution polymerization, for example, a method of polymerizing in a gas phase as shown in JP-B-60-1882 are used. It is applicable, and copolymerization with one or more α-olefins is possible other than ethylene homopolymerization. The α-olefin has 3 to 10 carbon atoms.
Such as propylene, butene-1, pentene-1, 3-methylbutene-1, hexene-1, 4-methylpentene-1, 4-methylhexene-1,4,4-dimethylpentene-1, heptene -1, octene-1, nonene-1, decene-1, etc., preferably propylene, butene-1, hexene-1, 4-methylpentene-
1, octene-1.

The polyethylene thus obtained has a high load melt flow rate (190 ° C., 21.6 kg load) of 1 to 10 g / 10 minutes, preferably 3 to 8 g / 10.
Minutes. High load melt flow rate is 1g / 10
If it is less than 10 minutes, the moldability (plasticization) at the time of blow molding is poor, and the appearance of the product tends to be poor. If it exceeds 10 g / 10 minutes, the moldability (drawdown property) at the time of blow molding is also poor. Then density of the 0.935 g / cm ³ or more, preferably 0.940 to 0.970 g / cm ^3. When the density is less than 0.935 g / cm ³ , the rigidity (buckling property) of the multilayer hollow molded article becomes low, which is not preferable. Also,
If it exceeds 0.970 g / cm ³ , the impact strength of the multilayer hollow molded article tends to be lowered.

The resin forming the barrier layer in the molded article of the present invention is selected from the group consisting of polyamide resins, saponified ethylene vinyl acetate copolymers and thermoplastic polyesters, or a mixture of two or more thereof. As the polyamide, hexamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4- or 2,4,4-trimethylhexamethylenediamine, 1,3
Or an aliphatic, alicyclic or aromatic diamine such as 1,4-bis (aminomethyl) cyclohexane, bis (p-aminocyclohexylmethane), m- or p-xylylenediamine and adipic acid, suberic acid , Sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid,
A polyamide resin produced from an aliphatic, alicyclic or aromatic dicarboxylic acid such as isophthalic acid; produced from an aminocarboxylic acid such as 6-aminocaproic acid, 11-aminoundecanoic acid or 12-aminododecanoic acid A polyamide resin produced from ε-caprolactam, ω-dodecaractam, ω-laurolactam; and a copolyamide resin containing these components; or a mixture of these polyamide resins.

Specifically, nylon 6, nylon 66,
Examples thereof include copolymers such as nylon 610, nylon 11, nylon 12, nylon 612, nylon 46, nylon MXD · 6 and nylon 6/66. Further, for the purpose of improving adhesion, etc., ethylene is added to these polyamides,
Propylene, butene-1, hexene-1, 4-methyl-
An olefinic elastomer (for example, an ethylene / propylene copolymer or an ethylene / butene copolymer) which is a copolymer rubber of two or more kinds of α-olefins such as pentene is treated with an unsaturated carboxylic acid or an anhydride thereof. It is possible to add a modified product, which is one of the preferred embodiments of the present invention.

The chemical composition of the saponified ethylene vinyl acetate copolymer (saponified EVA) is not limited, but the ethylene content is 2 in view of the fuel barrier property.
What is obtained by saponifying 5 to 50 mol% of ethylene-vinyl acetate copolymer so that the saponification degree is 93% or more, preferably 96% or more is preferable.

The thermoplastic polyester is obtained by a polycondensation reaction of a saturated dibasic acid and a glycol, for example, polyethylene terephthalate obtained from ethylene glycol and terephthalic acid; phthalic acid, isophthalic acid, sebacic acid, adipic acid. , A polyethylene terephthalate copolymer containing a saturated dibasic acid such as azelaic acid, glutaric acid, succinic acid and oxalic acid as a copolymer component;
And a polyethylene terephthalate copolymer containing 1,4-cyclohexanedimethanol, diethylene glycol, propylene glycol, etc. as a diol component; or a reaction of terephthalic acid or dimethyl terphthalate with 1,4-butanediol And polybutylene terephthalate. Furthermore, a combination of a plurality of types selected from these thermoplastic polyesters or a polymer alloy with an ethylene-based polymer or a rubber-like polymer may be used within a range that does not impair the barrier performance and the chemical resistance to the content liquid such as gasoline. it can. Specifically, polyethylene terephthalate and polybutylene terephthalate are preferred.

The modified polyethylene forming the adhesive layer of the multilayer hollow molded article of the present invention is formed of a polyolefin modified with an unsaturated carboxylic acid or its anhydride. Examples of the unsaturated carboxylic acid or anhydride thereof include monocarboxylic acids such as acrylic acid and methacrylic acid, maleic acid, fumaric acid, dicarboxylic acids such as itaconic acid, maleic anhydride, and dicarboxylic acid anhydrides such as itaconic anhydride. Among them, acrylic acid or maleic anhydride is preferable. Maleic anhydride is particularly preferred. Examples of the polyolefin modified with an unsaturated carboxylic acid or an anhydride thereof include ethylene homopolymers, ethylene-α-olefin copolymers, polyolefins such as polypropylene, but the same kind as the polyethylene layer constituting the main layer is used. It is preferable from the viewpoint of enhancing adhesiveness. The content of unsaturated carboxylic acid or its anhydride in the modified polyolefin is preferably such that unsaturated carboxylic acid is added within the range of 0.005 to 10% by weight. And a method of adding the unsaturated carboxylic acid or its anhydride to the polyolefin suspended in an appropriate dispersion medium and stirring with heating.

In the resin of each layer in the present invention, an antioxidant, an ultraviolet absorber, a thermal processing stabilizer, a colorant, a lubricant, a flame retardant, an antistatic agent, a nucleating agent, in a range that does not significantly impair the effects of the present invention, Further, various fillers such as zeolite, talc and calcium carbonate can be added.

The multi-layer hollow molded article of the present invention uses the above-mentioned respective resins, and the polyethylene layer and a layer (barrier layer) selected from a polyamide resin, a saponified ethylene vinyl acetate copolymer or a thermoplastic polyester are modified. A three-layered structure in which at least three layers are bonded via a polyolefin resin layer (adhesive layer) has a multi-layered laminated form that is included in at least the layered structure. Preferable ones are three-kind five-layer bodies constituted in the order of adhesive layer / barrier layer / adhesive layer / polyethylene layer. The layer thickness of each layer is appropriately set according to the purpose of use, gas barrier properties, mechanical strength, and other required performance. For example, in the case of a fuel tank for an automobile, it is general that the barrier layer and the adhesive layer are each set to a layer constitution ratio of about 2 to 4% of the total thickness of the laminated body.
If the layer constitution ratio is less than 2%, the gas barrier property becomes insufficient and the molding process tends to become difficult. Further, if it exceeds 4%, the effect of further improving the gas barrier property cannot be expected, resulting in a decrease in mechanical strength, further increasing the cost of the material, and increasing the proportion of the barrier material at the time of reclaiming. Absent.

The multilayer hollow molded article of the present invention is manufactured by supplying the resins constituting the above-mentioned layers to the respective extruders connected to the blow molding machine, melt-plasticizing it, and then disturbing the layers through the multilayer extrusion die. It can be obtained by extruding a multi-layered molten parison having a uniform layer structure without a layer and performing blow molding in a mold having a desired shape. The burr generated during molding can be reclaimed by adding the burr to any layer of the multilayer molding material or by adding a burr-only layer. Usually, the generated burr is mechanically crushed and then melt-kneaded by a biaxial kneader or the like to be regenerated into pellets. This recycled pellet is 10 to 50 virgin pellet of polyethylene.
It is mixed in the range of wt% and reclaimed as a raw material constituting the polyethylene layer. In particular, since the present invention uses high molecular weight polyethylene produced using a specific catalyst, it is possible to reclaim a large amount of regenerated pellets, for example, 30 wt% to 50 wt%.

The burr generated during the production of the multilayer hollow molded article is usually in the form of a multilayer containing a barrier resin. Therefore, if this is crushed for reclaiming and then melted, the barrier resin is not finely dispersed in the melt, and therefore, In addition, a multilayer hollow molded article made of a resin material in which burrs are reused has a problem that mechanical strength is lowered. If high shear is applied during melt kneading of burrs in order to finely disperse the barrier resin, thermal deterioration of the high molecular weight polyethylene and the barrier resin itself will occur, resulting in deterioration of physical properties. The resin was not finely dispersed into particles having a dispersed particle size of 100 μm or less, which also deteriorated the physical properties, and a complete reclaim has not been achieved in the past. However,
Burrs generated during the production of the multi-layer hollow body of the present invention are crushed, melt-kneaded to finely disperse the barrier resin and made into regenerated pellets, and then continuously reclaimed to the polyethylene layer raw material at a ratio of less than 50% by weight. Even if it is made, the physical properties such as the mechanical strength of the obtained molded product are not significantly deteriorated.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples. Examples 1 to 5 (1) Molding material Polyethylene layer resin The following raw materials were used as the polyethylene layer resin. Manufacture of PE-1 Referring to the example of Japanese Patent Publication No. 47-1766, 4
In liter of dehydrated hexane, 785 g of silica (“952” manufactured by Devison Co., Ltd. was sieved to an average particle size of 50 μm, and 300
(Calcined at 24 ° C. for 24 hours), 20 g of bistriphenylsilylchromate and 6 g of diethylaluminum ethoxide were used to prepare a catalyst composition having an Al / Cr ratio of 1.5 (hereinafter referred to as catalyst 1). This catalyst 1 is used in a fluidized bed gas phase polymerization method known in Japanese Examined Patent Publication No. 60-1882, and the polymerization temperature is 99 ° C. and the ethylene partial pressure is 13 kg / cm ^2.
abs, hydrogen at a partial pressure ratio with ethylene of 0.02, butene-1 as a comonomer with a partial pressure ratio with ethylene of 0.00
Copolymerization with 6 and pelletizing to obtain high molecular weight polyethylene (hereinafter abbreviated as PE-1) which is an ethylene / butene copolymer having a high load melt flow rate of 5 g / 10 min and a density of 0.948 g / cm ^3. It was

Production of PE-2 An Al / Cr ratio of 5. was obtained in the same manner as in Catalyst 1 except that 20 g of diethylaluminum ethoxide was used.
A catalyst composition of 0 (hereinafter referred to as catalyst 2) was prepared. Using this catalyst 2, copolymerization was carried out in the same manner as in the production of PE-1 except that the polymerization temperature was 102 ° C. and the partial pressure ratio of butene-1 as a comonomer and ethylene was 0.007. High load melt flow rate 7 g / 10 minutes, density 0.948g / c
A high molecular weight polyethylene (hereinafter abbreviated as PE-2), which is an m ³ ethylene / butene copolymer, was obtained.

[0038] The following raw materials were used as a barrier layer resin barrier layer resin. Relative viscosity (J
IS K6810) 6.2, melting point [Differential Scanning Calorimetry (DSC method)] 225 ° C. Nylon-6 (hereinafter BR
-1), a relative viscosity of 4.3, a nylon 6/66 copolymer having a melting point of 195 ° C. (hereinafter abbreviated as BR-2), and a melt flow rate (190 ° C., 2.16 k).
g) "Eval" (hereinafter abbreviated as BR-3) manufactured by Kuraray Co., Ltd. having 1.3 g / 10 min and an ethylene content of 32 mol%, and polybutylene terephthalate [having a specific gravity of 1.31 and a melting point of 225 ° C. [ "C7000N" manufactured by Teijin Ltd.] (hereinafter,
(Abbreviated as BR-4) was used.

[0039] The following raw materials were used as an adhesive layer resin adhesive layer resin. High load melt flow rate 10g / 10min, density 0.935g / c
m ³ maleic anhydride modified polyethylene (hereinafter referred to as AD
Abbreviated as -1)

(2) Molding of Multi-layer Hollow Body Using the above-mentioned high-molecular-weight polyethylene, adhesive layer resin and barrier resin, a multi-layer hollow molding machine (manufactured by Japan Steel Works Ltd.) with a combination of layer constitutions shown in Table 1 "NB60G") multi-layer die with (polyethylene layer / adhesive layer / barrier layer / polyethylene layer) co-extruded a multi-layer molten parison and closed the mold to perform hollow molding to obtain an internal volume of 7
A barrier layer of 0 liters and a weight of 6.5 kg (wall thickness of about 150
Five types of multi-layer hollow molded articles having different μm) were obtained. The wall thickness of each molded product was about 5 mm, and the constitution of each layer was polyethylene layer / adhesive layer / barrier layer = 91: 6: 3.

Reclaiming Next, the multi-layered molding burrs that occurred simultaneously were crushed by a crusher (manufactured by Horai Iron Works Co., Ltd., mesh path having a hole diameter of 7 mmφ) to obtain a crushed product having an average crushed particle diameter of about 2 mm. This crushed product is a twin-screw kneader (TEX44mmφ manufactured by Japan Steel Works, Ltd.)
Screw rotation speed 250 rpm, outlet resin temperature 28
Melt-kneading was performed under conditions of 0 ° C., discharge rate of 55 kg / hr, and specific energy of 0.3 to 0.4 to obtain regenerated pellets. In addition,
Observation with an optical microscope revealed that the dispersed particle size of the barrier layer resin in these regenerated pellets was 100 μm or less.

To 50% by weight of each of the regenerated pellets having different barrier materials, 50 parts by weight of the original high molecular weight polyethylene was mixed and then melt-kneaded under the same conditions by the above-mentioned biaxial kneader to obtain pellets 50. After again mixing 50% by weight of the original high-molecular-weight polyethylene with 100% by weight, melt kneading was repeated in the same manner, and a total of 10 pass treatments were carried out. In this way, each of the last 5 types of regenerated pellets is 50
After mixing 50% by weight of the original high-molecular-weight polyethylene with 50% by weight, each was subjected to blow molding to obtain a multilayer blow molded product in which pellets were blended again. As described above, it was obtained for each of the five different types of high molecular weight polyethylene or barrier material,
The following test evaluations were carried out on the multilayer hollow molded article containing no recycled material and the multilayer hollow molded article containing recycled material by repeated pass treatment, and the results are shown in Table 1.

1) Gas barrier test In accordance with the Ministry of Transport standards, first, about 15 kg of regular gasoline and 20% by weight of methanol were added to a multilayer hollow molded article.
Each mixture was filled, and the mouth portion was heat-sealed with a flat plate cut out from the body portion of the same kind of multilayer hollow molded article to perform encapsulation. After encapsulation, the product was left in a steam oven chamber adjusted to 40 ° C. for 20 hours according to the Ministry of Transport standards, and the weight change was measured over time to determine the average permeation amount per day. 2) Low temperature drop impact test A water / ethylene glycol mixed solution was added to the obtained multi-layer hollow molded article to make the total weight 70 kg, and the mouth was closed, -4
After sufficiently cooling at 0 ° C., the multi-layer hollow molded article was dropped from the height shown in Table 1 to the concrete surface with the pinch-off portion facing downward, and the presence or absence of cracks was examined to determine the limit drop height.

Comparative Examples 1 to 3 Production of Polyethylene Layer Resin PE-3 As the polyethylene used in the polyethylene layer of Comparative Example 1, a so-called Phillips-based catalyst prepared by adhering chromium oxide (CrO ₃ ) to a silica carrier was used. -Slurry polymerization using heptane as a solvent, pelletization, high load melt flow rate 5 g / 10 min, density 0.948.
High-molecular-weight polyethylene (hereinafter abbreviated as PE-3), which is an ethylene / butene copolymer having g / cm ³ , was obtained. Production of PE-4 As polyethylene used in the polyethylene layer of Comparative Example 2, n-heptane was used as a solvent by using a highly active Ziegler type catalyst composed of a titanium catalyst component supported on a magnesium halide-containing compound and an organoaluminum compound. After performing multi-tank continuous slurry polymerization, pelletizing, high-load melt flow rate 4.7 g / 10 minutes, density 0.94
High-molecular-weight polyethylene (hereinafter abbreviated as PE-4), which was an ethylene / butene copolymer of 6 g / cm ³ , was obtained. Barrier Layer Resin As the barrier layer resin of Comparative Examples 1 and 2, the above-mentioned BR-1 was used.
It was used. Adhesive Layer Resin The above-mentioned AD-1 was used as the adhesive layer resin of Comparative Examples 1 and 2. Using the above materials, multilayer molding and reclaiming were carried out in the same manner as in Examples to obtain multilayer hollow molded bodies. In addition, as Comparative Example 3, a single-layer hollow molded body containing only PE-1 was obtained. A gas barrier test and a low temperature drop impact test were performed on these as in the examples, and the results are shown in Table 1.

[0045]

[Table 1]

The molded articles of the present invention of Examples 1 to 5 are excellent in gas barrier property, and at the same time, the critical drop height in the low temperature drop impact test is 10 m after reclaiming.
That is all. Judging from the fact that the height is 6 m as a standard in a similar drop test generally performed by automobile manufacturers, it can be seen that the molded product of the present invention has excellent impact resistance.

[0047]

EFFECT OF THE INVENTION The multi-layer hollow molded article of the present invention has excellent gas barrier properties required for automobile fuel tanks and the like, as well as excellent reclaimability of burrs, etc. Since it is a multi-layer hollow body having excellent impact properties, its industrial utility value is extremely useful as a fuel tank for automobiles.

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Claims (2)

[Claims] 1. A polyethylene layer and a polyamide resin,
From a multi-layer laminated material in which a saponified product of ethylene vinyl acetate copolymer and a barrier layer composed of a mixture of one or more kinds of thermoplastic polyester are laminated via an adhesive layer composed of a modified polyolefin resin. In the molded multi-layer hollow molded article, the polyethylene layer has the following formula: CrO ₃ , (In the formula, R ¹ and R ² represent a hydrocarbon group having 1 to 14 carbon atoms), or (In the formula, R ³ and R ⁴ represent a sterically hindered polyalicyclic hydrocarbon group having 7 to 20 carbon atoms) A high-load melt flow rate produced using a chromium catalyst and a reducing agent. (190 ° C, 21.6 kg load) 1-10 g / 10 minutes, density is formed from high molecular weight polyethylene having a density of 0.935 g / cm ³ or more, a multi-layer hollow molded article. 2. The multi-layer hollow molded article according to claim 1, wherein the polyethylene layer contains burrs generated when the multi-layer hollow molded article is molded using the multi-layer molding material.