JP2003261168A - Multi-layered plastic vessel for fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-layered plastic vessel for fuel of excellent permeability resistance against gasoline and oxygen-containing gasoline, and of excellent solvent cracking resistance, swelling resistance, dimensional stability and forming workability. <P>SOLUTION: A high density polyethylene layer is disposed on inner and outer layers, at least one polyglycolic acid layer is disposed as a core layer, and an adhesive resin layer is disposed between layers as necessary. This multi- layered plastic vessel for fuel has considerably excellent permeability resistance against gasoline and oxygen-containing gasoline. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer plastic fuel container having excellent permeation-preventing properties for gasoline and oxygen-containing gasoline and having good solvent crack resistance, swelling resistance, dimensional stability, moldability and the like.

[0002]

2. Description of the Related Art In recent years, in automobiles, effective use of the space inside the vehicle,
There is a growing demand for a large luggage compartment and stable running performance. Also, as seen in 4WD vehicles and the like, the body structure is becoming more complicated. Along with this, only a complicatedly shaped space is left in the fuel tank.

Conventionally, a metal tank has been used as a fuel tank for automobiles. However, the metal tank is (1)
Since steel plates must be manufactured by welding, the processing process is complicated, (2) it is difficult to process into complicated shapes, the degree of freedom in the tank shape is low, and (3) rusting is easy. , (4) It is difficult to reduce the weight, and (5) the impact strength at the time of collision is low.

In order to solve the above problems, it has been proposed to switch the material of the fuel tank for automobiles from metal to plastic, and the adoption of plastic fuel tanks has been increasing. Compared to metal fuel tanks, plastic fuel tanks (1) can be easily molded in a simple process by blow molding, etc. (2) The flexibility of the tank shape is high, so the effective use of limited space It can be used and has a large capacity, (3) no rusting and no need for anti-rust treatment, (4) weight saving, (5) excellent impact resistance It has advantages such as safety at the time of collision and non-explosion at the time of fire.

In the early days of plastic fuel tanks, single-layer tanks made of polyethylene were the mainstream. Polyethylene tends to have improved gasoline permeation resistance and rigidity as the density increases, and impact resistance as the molecular weight increases. Therefore, as the polyethylene for the fuel tank, high density polyethylene (HDPE), particularly ultra high molecular weight high density polyethylene is generally used.

In Japan, in 1987, a technical standard for fuel tanks for passenger cars was established, and each standard of fuel permeability test, impact resistance test, pressure resistance test, fire resistance test, and heat resistance test should be satisfied. It has been demanded. For example, in the fuel permeability test, the gasoline permeation amount under certain conditions was 20 g / 2.
It is set as a standard to be 4 hours or less. A single-layer high-density polyethylene fuel tank satisfies all of these standard values. However, if the shape of the plastic fuel tank is complicated or the capacity is increased, the surface area increases, and the gasoline permeation amount of 20 g / 24
There is a risk of exceeding the reference value of hr.

On the other hand, in the United States, the SHED regulation (Shield Hous) which strictly regulates the amount of hydrocarbon gas generated from the entire vehicle
ing for Evaporative Determinations) has been adopted. In addition, in the state of California in the United States, the total amount of hydrocarbon gas produced must be 2 g / 24 hr or less.
Regulations are stricter than regulations. Therefore,
Plastic fuel tanks are now required to satisfy stricter regulations regarding gasoline permeation than ever. However, it is difficult for the conventional plastic fuel tank technology to comply with such strict regulations.

Furthermore, from the viewpoint of preventing air pollution and saving gasoline consumption, methanol, ethanol, methyl-
Gasoline added with an oxygen-containing compound such as tert-butyl ether (ie, "oxygenated gasoline") is mainly used in the United States. However, when such an oxygen-containing gasoline is used, it is extremely difficult for the conventional plastic fuel tank technology to prevent gasoline permeation.

Conventionally, in order to improve the gasoline permeation-preventing property of a plastic fuel tank, a method of subjecting the surface of a fuel tank made of polyethylene or polypropylene to a sulfonation treatment (Japanese Patent Publication No. 46-23914), and the surface of a polyethylene fuel tank Methods such as fluorination treatment (Japanese Patent Publication No. 47-21877 and Japanese Patent Publication No. 53-15862) have been proposed. Although these methods can reduce the amount of gasoline permeation, they are not sufficient, and the sulfur trioxide and fluorine gas used for these treatments are harmful to the human body.

Therefore, it has been proposed to introduce a multi-layer technology into the technical field of plastic fuel tanks. For example, a multi-layer plastic fuel tank having a layer structure in which a high-density polyethylene layer is arranged in the inner and outer layers and a gas-barrier copolymerized polyamide layer is arranged in the core layer has been proposed (JP-A-4-47938). Further, there has been proposed a fuel tank having a layered structure in which polyamide is dispersed in a discontinuous thin layer in polyolefin. However, the use of polyamide as the barrier layer makes it impossible to meet strict standards for preventing permeation of gasoline, and in particular, has insufficient resistance to alcohol-containing gasoline.

In order to enhance the ability to prevent permeation of alcohol-containing gasoline, the acid-modified polyolefin is used as a compatibilizing agent to allow the high nitrile resin to exist in the high density polyethylene as a discontinuous, parallel, and seamlessly overlapping layer. A method of forming a layered structure has been proposed (JP-A-4-296331). However, it is difficult to find optimum conditions for stable manufacturing of a fuel tank composed of such a special layered structure.

A multi-layer plastic fuel tank having a layer structure in which a high-density polyethylene layer is used as the inner and outer layers and an ethylene-vinyl alcohol copolymer (EVOH) having excellent barrier properties is arranged in the core layer has been proposed (Japanese Patent Laid-Open Publication No. HEI-6 (1994)). -3400
33, JP-A-9-29904, and JP-A-200
0-264326). EVOH has excellent gasoline permeation resistance, and also has better permeation resistance against alcohol-containing gasoline than polyamide.

However, EVOH is inferior in thermal stability to polyamide and is apt to be thermally crosslinked during melt processing to increase its viscosity. Multi-layer plastic fuel tanks are generally manufactured by blow molding with a multi-layer parison. However, if the accumulator method is adopted as the method for forming the multi-layer parison, EVOH is thickened and deteriorated by thermal crosslinking in the accumulator head, and further cured. May damage the accumulator head. Further, in the multilayer blow molding using EVOH for the core layer, sufficient adhesion strength may not be obtained at the pinch-off portion, and the drop impact strength of the obtained fuel tank may be insufficient.

Since EVOH has poor adhesion to high-density polyethylene, an adhesive resin is required.
When molded as a fuel tank, the adhesive strength between the adhesive resin layer and the adhesive resin layer is significantly reduced, and the impact resistance is likely to be reduced. EVOH has insufficient solvent crack resistance. Therefore, the multilayer plastic fuel tank using the EVOH layer as a barrier layer has problems in crack resistance and interlayer adhesive strength during long-term use.

[0015]

An object of the present invention is to provide a multi-layer plastic fuel which is excellent in permeation-preventing properties for gasoline and oxygen-containing gasoline and has good solvent crack resistance, swelling resistance, dimensional stability, molding processability and the like. To provide a container.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a multilayer plastic fuel container having a layer structure in which a high-density polyethylene layer is arranged in the inner and outer layers and a polyglycolic acid layer is arranged in the core layer. Was conceived. Polyglycolic acid, which is known as a biodegradable polymer, is a resin having excellent gas barrier properties. It was found that this polyglycolic acid is superior in permeation resistance to gasoline and oxygen-containing gasoline to polyamide and EVOH.

The high density polyethylene and polyglycolic acid can preferably be molded into a multilayer plastic fuel container by blow molding with a multilayer parison. As a method for forming a multi-layer parison, two methods, an intermittent multi-layer method using an accumulator and a continuous multi-layer method, can be adopted. An adhesive resin layer is preferably arranged between the high-density polyethylene layer and the polyglycolic acid layer. Further, as the intermediate layer, a recovery layer (regrind layer) can be arranged if desired.

The multi-layer plastic fuel container of the present invention is excellent in permeation resistance to gasoline and oxygen-containing gasoline, swelling resistance, and dimensional stability, and also has good moldability, solvent resistance, crack resistance and the like. is there. The present invention is
It was completed based on these findings.

[0019]

According to the present invention, a high-density polyethylene layer is arranged as an inner layer and an outer layer, and at least one polyglycolic acid layer is arranged as a core layer, and if necessary, each interlayer is provided. Provided is a multi-layer plastic fuel container having a layer structure in which an adhesive resin layer is disposed on the.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION 1. Polyglycolic Acid Polyglycolic acid used in the present invention has the following formula (1)

[0021]

[Chemical 1]

It is a homopolymer or a copolymer containing a repeating unit represented by: The content of the repeating unit represented by the formula (1) in the polyglycolic acid is 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and the upper limit thereof is 100% by weight. . If the content ratio of the repeating unit represented by the formula (1) is too low, the gas barrier property and the heat resistance decrease.

In the polyglycolic acid, as the repeating unit other than the repeating unit represented by the formula (1), for example,
At least one repeating unit represented by the following formulas (2) to (6) can be contained.

[0024]

[Chemical 2]

(Where n = 1 to 10 and m = 0 to 10),

[0026]

[Chemical 3]

(Where j = 1 to 10),

[0028]

[Chemical 4]

(In the formula, R ₁ and R ₂ are each independently
It is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. k
= 2-10),

[0030]

[Chemical 5]

And

[0032]

[Chemical 6]

The melting point of the homopolymer of polyglycolic acid can be lowered by introducing the other repeating units represented by the formulas (2) to (6) in a proportion of 1% by weight or more. By lowering the melting point of polyglycolic acid, the processing temperature can be lowered and the thermal decomposition at the time of melt processing can be reduced. Further, the copolymerization can control the crystallization rate of polyglycolic acid to improve the processability. If the content of the other repeating unit in the copolymer is too large, the crystallinity originally possessed by polyglycolic acid may be impaired, and the gas barrier properties may be adversely affected.

Polyglycolic acid can be synthesized by dehydration polycondensation of glycolic acid, dealcohol polycondensation of alkyl glycolic acid ester, ring-opening polymerization of glycolide, and the like. Among these, glycolide is used in the presence of a small amount of a catalyst (for example, a cationic catalyst such as tin organic carboxylate, tin halide and antimony halide) in an amount of about 120.
A method of synthesizing polyglycolic acid (also referred to as "polyglycolide") by a method of heating at a temperature of from ℃ to about 250 ℃ and ring-opening polymerization is preferable. The ring-opening polymerization is preferably performed by a bulk polymerization method or a solution polymerization method.

In order to synthesize a polyglycolic acid copolymer, in each of the above synthesis methods, as a comonomer, for example, ethylene oxalate, lactide, lactones (eg, β-propiolactone, β-butyrolactone, pivalolactone) are used. , Γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, etc.), trimethylene carbonate, and 1,3-
Cyclic monomers such as dioxane; hydroxycarboxylic acids such as lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid or alkyl esters thereof; ethylene glycol, 1,4-butanediol A substantially equimolar mixture of an aliphatic diol such as succinic acid, adipic acid such as adipic acid, or an alkyl ester thereof;
Alternatively, two or more kinds of these may be copolymerized in an appropriate combination with glycolide, glycolic acid, or a glycolic acid alkyl ester.

Of these, cyclic compounds such as lactide, caprolactone and trimethylene carbonate; hydroxycarboxylic acids such as lactic acid are preferable because they are easily copolymerized and a copolymer having excellent physical properties is easily obtained. Comonomers usually account for 45% by weight of all charged monomers
Or less, preferably 30% by weight or less, more preferably 10% by weight or less.
It is used in a proportion of less than or equal to weight%. When the proportion of the comonomer increases, the crystallinity of the polymer produced tends to be impaired. When the crystallinity of polyglycolic acid is lost, heat resistance, gas barrier properties, mechanical strength, etc. are reduced.

The polyglycolic acid used in the present invention is J
The oxygen gas permeation coefficient (PO ₂ ) measured under the conditions of temperature 23 ° C. and relative humidity (RH) 80% according to IS K-7126 is 5.0 × 10 ⁻¹⁴ cm ³ · cm / cm ² · se.
It is preferably c.cmHg or less. The oxygen gas barrier property of polyglycolic acid also serves as an indicator of the barrier property against gasoline and alcohol. The oxygen gas permeability coefficient of polyglycolic acid used in the present invention is 1.0 × 10 ⁻¹⁴ to
5.0 × 10 ^-14 cm ³ · cm / cm ² · sec · cmH
It is preferably within the range of g.

The polyglycolic acid used in the present invention preferably has a melt viscosity of 100 to 2,000 Pa.multidot., Measured under conditions of a temperature of 240.degree. C. and a shear rate of 100 sec.sup.- ^1.
s, more preferably in the range of 300 to 1,500 Pa · s. Polyglycolic acid is 255
When it is melted at a high temperature exceeding ℃, decomposition and accompanying decrease in molecular weight and foaming easily occur. Therefore, the melt processing temperature of polyglycolic acid is around 240 ° C. (for example,
It is desirable to set the temperature within the range of 235 to 245 ° C.

The melting point (Tm) of the polyglycolic acid used in the present invention is preferably 200 ° C. or higher, more preferably 210 ° C. or higher. The melting point of polyglycolic acid is about 22.
0 ° C., glass transition temperature about 38 ° C., crystallization temperature about 91 ° C. However, these thermal properties vary depending on the molecular weight of polyglycolic acid and the copolymerization component.

In the present invention, netoresin of polyglycolic acid can be used alone. However, polyglycolic acid, an inorganic filler, another thermoplastic resin, and a plasticizer can be used within a range not impairing the object of the present invention. A resin composition containing the above can be used. In addition, polyglycolic acid, if necessary, a heat stabilizer, a light stabilizer, a moistureproofing agent, a waterproofing agent, a water repellent, a lubricant, a release agent, a coupling agent,
Various additives such as pigments and dyes can be contained.

In order to improve the melt stability of polyglycolic acid, for example, a phosphoric acid ester having a pentaerythritol skeleton structure, a phosphorus having at least one hydroxyl group and at least one long-chain alkyl ester group is used as a heat stabilizer. It is preferable to add a compound, a heavy metal deactivator, a metal carbonate or the like. These heat stabilizers can be used alone or in combination of two or more kinds.

The phosphoric acid ester used as the heat stabilizer used in the present invention is represented by the following formula (7).

[0043]

[Chemical 7]

A phosphoric acid ester having a pentaerythritol skeleton structure represented by is preferable. Specific examples of such a phosphoric acid ester having a pentaerythritol skeleton structure are represented by the formula (8)

[0045]

[Chemical 8]

Cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite represented by the formula (9)

[0047]

[Chemical 9]

Cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) represented by
Phosphite, formula (10)

[0049]

[Chemical 10]

A phosphite-based antioxidant represented by: and a formula (11)

[0051]

[Chemical 11]

Examples include phosphite type antioxidants represented by:

Among the phosphorus compounds, the formula (12)

[0054]

[Chemical 12]

A phosphorus compound having at least one hydroxyl group represented by the formula (n = 1 or 2) and at least one long-chain alkyl ester group is preferable. The number of carbon atoms of the long chain alkyl is preferably in the range of 8 to 24. Specific examples of such a phosphorus compound include compounds represented by the formula (13):

[0056]

[Chemical 13]

Examples thereof include mono- or di-stearyl acid phosphate represented by the formula (n = 1 or 2).

Examples of the heavy metal deactivator include compounds represented by the formula (1
4)

[0059]

[Chemical 14]

2-hydroxy-N-1H- represented by
1,2,4-triazol-3-yl-benzamide,
And equation (15)

[0061]

[Chemical 15]

Bis [2- (2-hydroxybenzoyl) hydrazine] dodecanedioic acid represented by

Examples of the metal carbonate include calcium carbonate and strontium carbonate. The mixing ratio of these heat stabilizers is usually 0.001 to 5 parts by weight, preferably 0.0 to 100 parts by weight of polyglycolic acid.
It is 03 to 3 parts by weight, more preferably 0.005 to 1 part by weight.

2. High Density Polyethylene The high density polyethylene used in the present invention usually has a density of 0.
935 g / cm ³ or more, preferably 0.940 g / cm ³
Exceeding 0.980 g / cm ³ or less, more preferably 0.9
It is 45 to 0.970 g / cm ³ . The high-density polyethylene used in the present invention has good gasoline permeation-preventing property and rigidity due to its high density.

The high density polyethylene used in the present invention is
Ultra high molecular weight polyethylene is preferred. Generally, the ultrahigh molecular weight polyethylene used in the field of fuel tanks has a weight average molecular weight of usually 110,000 to 500,000, preferably 200,000 to 400,000. The impact resistance of polyethylene increases as the molecular weight increases. Melt flow rate (MFR) of high density polyethylene used in the present invention
When measured at a temperature of 190 ° C. and a load of 2160 g, is preferably 0.01 to 2 g / 10 minutes, more preferably 0.1.
It is 01 to 0.5 g / 10 minutes. The MFR of high-density polyethylene is preferably 0.01 to 0.1 g / 10 minutes when measured at a temperature of 210 ° C. and a load of 2160 g.

By using such high-density polyethylene, it is possible to obtain a multilayer plastic fuel container having excellent rigidity, impact resistance, moldability, drawdown resistance of molten parison, and solvent resistance. Further, by combining the high-density polyethylene layer and the polyglycolic acid layer in multiple layers, it is possible to obtain a multilayer plastic fuel container having excellent gasoline permeation-preventing properties and oxygen-containing gasoline permeation-preventing properties.

The high-density polyethylene used in the present invention is
The following commercial products are included. Lupolen 4261A manufactured by BASF is excellent in impact resistance and creep resistance and is suitable as a resin for fuel containers. Marlex C579 from Philips is an ultra high molecular weight polyethylene (ethylene / hexane-1 copolymer), 21
It can be blow molded at a stock temperature of 1-239 ° C. In addition to these, the following high-density polyethylene can be exemplified.

RIB manufactured by Solvay
714N0060, MS20 manufactured by Fina
1B (black pellet) and MS456 (powder), B5742V manufactured by Tonen Kagaku Co. [ultra high molecular weight high density polyethylene, density = 0.945 g / cm ³ , MFR = 0.2 g /
10 minutes (temperature 210 ° C., load 2160 g)], Hi-Z HZ8200B manufactured by Mitsui Chemicals, Inc. [Density = 0.95]
6 g / cm ³ , MFR = 0.03 g / 10 min (Temperature 21
0 ° C., load 2160 g), melting point = 132 ° C., softening point = 1
23 ° C], Hi-Z HZ7200 manufactured by Mitsui Chemicals, Inc.
B [Density = 0.960 g / cm ³ , MFR = 0.08 g
/ 10 minutes (temperature 210 ° C., load 2160 g), melting point = 1
33 ° C., softening point = 126 ° C.], Novatec HB310 manufactured by Nippon Polychem Co., Ltd. [density = 0.953 g / cm ³ , MF
R = 0.04g / 10 minutes (temperature 210 ° C, load 2160
g), melting point = 134 ° C., softening point = 126 ° C.], J-Rex HD KBX44A manufactured by Nippon Polyolefin Co., Ltd.
[Density = 0.947 g / cm ³ , MFR = 0.03 / H
L5 g / 10 minutes (temperature 210 ° C., load 2160 g), melting point = 130 ° C., softening point = 129 ° C.], Paxson (Pax
on) BA-055 [Density = 0.970 g / cm
³ , MFR = 0.03 g / 10 min (temperature 190 ° C., load 2160 g).

As the high-density polyethylene, those which have been halogenated or treated with a sulfur-based compound can also be used. Carbon black can be added to the outer high-density polyethylene layer. The amount of carbon black added is about 0.5 to 5 parts by weight with respect to 100 parts by weight of high-density polyethylene.

3. Adhesive Resin In the present invention, an adhesive resin layer can be arranged between the layers as necessary. Since the high-density polyethylene layer and the polyglycolic acid layer have insufficient adhesiveness, it is generally preferable to dispose an adhesive resin layer.

The adhesive resin (also simply referred to as "adhesive") is preferably one having a good affinity with both high density polyethylene and polyglycolic acid resins. Further, it is preferable that the adhesive resin is a resin that can be extruded and that matches the melt viscosity of both resins at the time of molding. Specific examples of such an adhesive resin include a maleic anhydride-modified polyolefin resin (MODIC S525 manufactured by Mitsubishi Plastics Co., Ltd.), a glycidyl group-containing ethylene copolymer (Rex Pearl RA3150 manufactured by Nippon Petrochemical Co., Ltd., Bond First 2C manufactured by Sumitomo Chemical Co., Ltd.). Bond First E and Bond First 7B), thermoplastic polyurethane (Kuraray's Kuramilon 1195L), polyamide ionomer (Mitsui DuPont's AM7926), polyacrylimide resin (Rohm & Haas XHT)
A), Admer QF551 manufactured by Mitsui Chemicals, Inc. [acid-modified polypropylene, MFR = 5.7 g / 10 minutes (temperature 230 ° C.,
Load 2160g load), density = 0.890g ・ c
m ³ ], Mitsubishi Chemical Corporation Modic S525, and the like.

The adhesive resin layer may contain a desiccant in order to protect the polyglycolic acid layer of the core layer from hydrolysis due to invasion of water. Examples of the desiccant include inorganic substances such as dibasic sodium phosphate, calcium chloride, sodium chloride, ammonium chloride, potassium carbonate, sodium nitrate, magnesium chloride and magnesium sulfate; sucrose and the like. The amount added is usually in the range of 1 to 40% by weight with respect to the adhesive resin. If the amount of the desiccant added is too large, the adhesiveness will decrease, and if it is too small, the effect of the addition will not be exhibited.

4. Layer Structure The multi-layer plastic container of the present invention has a high-density polyethylene layer as an inner layer and an outer layer, and has at least one core layer.
It has a layer structure in which the polyglycolic acid layer of the layer is arranged, and the adhesive resin layer is arranged between the respective layers as necessary. When manufacturing a multi-layer plastic fuel container having these layer configurations, regrind recovered as burrs or the like can be additionally arranged as a recovery layer.

Specific examples of the layer structure of the multilayer plastic fuel container of the present invention include the following layer structures. The high-density polyethylene layer is represented by HDPE, the polyglycolic acid layer is represented by PGA, the adhesive resin layer is represented by AD, and the recovery layer is represented by RE. The layer structure is expressed as a layer structure from the outer layer to the inner layer of the fuel container.

(1) HDPE / PGA / HDPE, (2) HD
PE / AD / PGA / HDPE, (3) HDPE / AD /
PGA / AD / HDPE, (4) HDPE / AD / PGA
/ AD / PAG / AD / HDPE, (5) HDPE / RE
/ AD / PGA / AD / HDPE, (6) HDPE / RE
/ AD / PGA / AD / HDPE, (7) HDPE / AD
/ RE / AD / PGA / AD / HDPE, (8) HDPE
/ AD / RE / AD / PGA / AD / PGA / AD / H
DPE.

Among these layer structures, three types and five layers of HDPE1 / AD2 / PGA3 / AD4 / HDP shown in FIG.
E5, and 4 types and 6 layers of HDPE21 / RE2 shown in FIG.
A layer structure of 2 / AD23 / PGA24 / AD25 / HDPE26 is preferable.

The thickness of the high density polyethylene (HDPE) layer is generally 100 to 10,000 μm including the inner and outer layers.
m, preferably 500 to 8,000 μm, more preferably 1,000 to 7,000 μm. From the viewpoint of impact strength, the thickness of the high-density polyethylene layer arranged on the outer layer side is preferably thicker than the thickness of the high-density polyethylene layer arranged on the inner layer side. By disposing the recovery layer as the intermediate layer, the thickness of the high-density polyethylene layer can be reduced. When the recovery layer is not used, the total thickness of the high-density polyethylene layer is usually preferably in the range of 80 to 95% based on the total layers. When the recovery layer is arranged, the total thickness of the high-density polyethylene layer and the recovery layer is preferably within the range of 80 to 95% on the basis of all layers.

The thickness of the polyglycolic acid (PGA) layer of the core layer is usually 10 to 500 μm, preferably 50 to 300.
μm, more preferably 100 to 200 μm. The thickness of the polyglycolic acid layer can be appropriately changed depending on the required barrier level. If the thickness of the polyglycolic acid layer is too thin, the fuel permeation resistance (gasoline permeation resistance) becomes insufficient. If the thickness of the polyglycolic acid layer is too large, the impact resistance will decrease. The polyglycolic acid layer is usually one layer, but can be a split barrier layer divided into two or more layers if desired. The polyglycolic acid layer is preferably arranged in the center of all the layers as shown in FIGS. 1 and 2, or slightly on the inner layer side.

The thickness of the adhesive (AD) layer disposed between the layers is usually 10 to 300 μm, preferably 20 to 25 μm.
It is 0 μm, more preferably 30 to 200 μm. If the thickness of the adhesive resin layer is too thin, the interlayer adhesiveness may be insufficient, and if it is too thick, the cost will increase. Further, since the adhesive resin generally has good fuel permeability to gasoline or the like, it is not preferable to increase the thickness of the adhesive resin layer from the viewpoint of gasoline permeation preventive property.

When the recovery layer is provided, it is preferably arranged between the high-density polyethylene layer as the outer layer and the polyglycolic acid layer as the core layer. The high-density polyethylene layer and the recovery layer can be adjacent to each other directly or via an adhesive resin layer. The polyglycolic acid layer and the recovery layer may be directly adjacent to each other, but from the viewpoint of adhesiveness, they are preferably adjacent to each other via an adhesive resin layer. The regrind used for the recovery layer is a recycled material that is crushed or crushed from scraps such as defective moldings and burrs, and contains high-density polypropylene and polyglycolic acid, and depending on the layer structure, contains adhesive resin, etc. .

The thickness of the recovery layer is usually 55% or less, preferably 50% or less on the basis of all layers. The thickness of the recovery layer is 5
If it exceeds 5%, a problem may occur in terms of thermal stability, and the recovery layer may be insufficient due to the balance of the material balance. The polyglycolic acid dispersed in the recovery layer is usually 10 μm or less in size, and it is desirable that the polyglycolic acid be finely dispersed in the matrix from the viewpoint of maintaining the strength of the fuel container.

The thickness (body) of the multilayer plastic fuel container of the present invention depends on the size, but is usually 500 to 12.0.
00 μm, preferably 800 to 9,000 μm, more preferably 1,500 to 8,000 μm.

5. Method for producing multi-layer plastic fuel container In producing the multi-layer plastic fuel container of the present invention, it is preferable to pre-dry polyglycolic acid, which is easily hydrolyzed, to adjust the water content to 50 ppm or less.

The multilayer plastic fuel container of the present invention can usually be manufactured by blow molding with a multilayer parison. As a method for forming a multi-layer parison, there are generally an intermittent multi-layer method using an accumulator and a continuous multi-layer method that does not require an accumulator head. In either method, the multi-layer parison is molded in the shape of the fuel container by direct blow molding in the mold.

In the intermittent multi-layer system, there are extruders for the main material (high-density polyethylene), the adhesive material (adhesive resin), and the barrier material (polyglycolic acid) for forming the multi-layer parison. The adhesive material and the barrier material are respectively stored in the sub accumulator head, and then merge with the main material at a multilayer ring outlet incorporated in the main accumulator head storing the main material. That is, after each material is stored in a predetermined amount in the accumulator head, in accordance with the extrusion of the main material, the barrier material and the adhesive material stored in the sub accumulator head are extruded, in the center of the lower flow path of the main accumulator head. The arranged spidering merges with the main material divided into the inner and outer layers to form a multi-layer parison of 5 layers of 3 types.

In the intermittent multi-layer system, by controlling the timing of injection from each accumulator head, the layer structure of the parison can be made into a single layer / multi-layer / single layer along the longitudinal direction, whereby the fuel container is formed. It is possible to apply a priority multi-layer molding method in which the main body has a multi-layer structure and a single layer is formed from the vicinity of the pinch-offs at the top and bottom of the fuel container to the burr. According to the priority multi-layer molding method, polyglycolic acid, which is easily hydrolyzed in the presence of water, can be wrapped with high-density polyethylene. Further, in the priority multi-layer forming method, the pinch-off portion can be a single layer of high-density polyethylene, so that the problem of lowering the adhesive strength due to defective fusion in the pinch-off portion does not occur. Moreover, since the burr at the pinch-off portion is a high-density polyethylene single layer, it is advantageous for recycling as a recovery layer.

On the other hand, in the continuous multi-layer system, a multi-layer parison is formed in the same manner as the accumulator system (intermittent multi-layer system) except that each layer is continuously extruded without using an accumulator head. The continuous multi-layer system is
Since the injection from the accumulator head is not required, the structure of the device is simple, in addition, it is possible to use a material with poor thermal stability, it is easy to thin the barrier material, and a burr crushed material (Regrind) has the advantage that a recovery layer can be added.
By adding the recovery layer, for example, a four-kind six-layer fuel container can be manufactured.

When the method of forming a multi-layer parison by the continuous multi-layer method is adopted, it is important that the polyglycolic acid layer of the core layer is completely embedded by the high-density polyethylene resin layers of the inner and outer layers in the pinch-off portion. is there. For that purpose, for example, it is preferable to pinch off the pinch-off portion to have a V-shaped pinch-off shape or a T-shaped pinch-off shape.

The multi-layer plastic fuel container of the present invention can be molded by a multi-layer co-injection molding method in addition to the direct blow molding technique as described above.

6. Multi-layer plastic fuel container Polyglycolic acid has excellent permeation resistance to gasoline and oxygen-containing gasoline, and especially permeation resistance to gasoline containing alcohol such as polyamide and EVO.
Remarkably superior to H. Therefore, the multilayer plastic fuel container of the present invention is remarkably excellent in permeation resistance to gasoline and oxygen-containing gasoline, and is excellent in solvent crack resistance, swelling resistance, dimensional stability, molding processability and the like.

The multilayer plastic fuel container of the present invention can be suitably obtained by the multilayer blow molding method. As the multilayer blow molding method, a multilayer coextrusion blow molding method is preferable, and a multilayer coextrusion direct blow molding method is more preferable. In the multi-layer plastic fuel container of the present invention, it is preferable that the polyglycolic acid layer is completely embedded by the high density polyethylene layers of the inner and outer layers, and it is particularly preferable that the polyglycolic acid is not exposed at the pinch-off portion. . A glycidyl group-containing ethylene copolymer is preferable as the adhesive resin disposed between the high-density polyethylene layer and the polyglycolic acid layer. The multilayer plastic fuel container of the present invention is suitable as a fuel tank for automobiles, a fuel storage container, a fuel transport container, and the like.

[0092]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. The methods for measuring various physical properties and characteristics are as follows.

(1) As a melt viscosity sample, an amorphous sheet of each resin having a thickness of about 0.2 mm was prepared and heated at 150 ° C. for 5 minutes to be crystallized, and a capirograph manufactured by Toyo Seiki Co., Ltd. was used. 1C (die = 1
mmφ × 10 mmL) and the resin temperature was 240 ° C. and the shear rate was 100 sec ⁻¹ .

(2) Oxygen Gas Permeability Coefficient According to JIS K-7126, it was measured under the conditions of a temperature of 23 ° C. and a relative humidity of 80% using Oxtran 2/20 manufactured by Modern Control Co.

(3) Swelling degree As gasoline, ordinary gasoline (toluene / isooctane = 50/50 vol%) and methanol-containing gasoline M15 (toluene / isooctane / methanol = 42.
5 / 42.5 / 15 vol%) was used for the swelling degree test. Specifically, each of two types of gasoline was placed in a fuel container and held at 40 ° C. for 120 days, then the gasoline was discharged, and the rate of weight increase (% by weight) relative to the initial value was measured.

(4) Dimensional stability Put each of the two types of gasoline in a fuel container,
After holding at 40 ° C. for 120 days, gasoline was discharged and the rate of dimensional change of the fuel container was measured [longitudinal direction × horizontal direction (%)].

(5) Molding workability When the molding workability was not observed by observation at the time of molding, A
When the heat stability was poor and there was a problem in molding processability, it was evaluated as B.

(6) Put a solvent crack resistant fuel container into each of the two types of gasoline,
After holding at 40 ° C. for 120 days, the body of the fuel container was cut, and the core layer (barrier layer) of the cross section was observed with an optical microscope.
The presence or absence of cracks was examined. The case where no crack was generated was evaluated as A, and the case where there was crack was evaluated as B.

(7) Fuel Permeability For each resin material used in Examples and Comparative Examples, a film sample having a thickness of 20 μm was prepared, and the two types of the above two kinds were prepared under the conditions of a temperature of 40 ° C. and a relative humidity (RH) of 65%. The permeation amount to gasoline (g · 20 μm / m ² · day) was measured.

[Example 1] Polyglycolic acid (PGA)
As a temperature of 240 ° C and a shear rate of 100 sec^-1Measured by
Homopolymer with a melt viscosity of 1000 Pa
Transition temperature = 38 ° C., melting point = 221 ° C., crystallization temperature = 9
1 ° C.) was used. Oxygen gas permeation of this polyglycolic acid
Coefficient (PO₂) Is 2.5 × 10^-14cm³・ Cm / cm²
It was sec.cmHg. Of this polyglycolic acid
Oxygen gas permeability is 0.3 ml / m ²・ Day ・ atm
And the moisture vapor transmission rate (40 ° C, 90% RH) is 20 g / m
²・ It was a day. 100 parts by weight of this polyglycolic acid
To 0.1 parts by weight of PEP-6 [Asahi Denka Kogyo Co., Ltd.
Company-made phosphite type antioxidant represented by the above formula 11
(Stopper) was added.

As high density polyethylene (HDPE),
High-density polyethylene manufactured by Mitsui Chemicals, Inc. [HIZEX H
Z8200B; Density = 0.960 g / cm ³ , MFR =
0.1g / 10 minutes (temperature 210 ° C, load 2160g)]
Was used. As the adhesive resin (AD), a glycidyl group-containing ethylene copolymer (Lexpearl RA3150) manufactured by Nippon Petrochemical was used.

The layer structure is "HDPE / AD /
PGA / AD / HDPE ”, and the thickness and thickness ratio of each layer were adjusted as follows. Outer layer (HDPE) = 2760 μm (46%), adhesive resin layer (AD) = 150 μm (2.5%), core layer (PGA) = 180 μm (3%), adhesive resin layer (AD) = 150 μm (2) 0.5%), inner layer (HDPE) = 2760 μm (46%), total layer thickness = 6000 μm.

Using a continuous multi-layer blow molding machine, the temperature of the molding machine was set to 235 ° C., and a 5-layer fuel container (75 liters) having the above-mentioned layer structure was molded. The temperature of the extruder tip of each resin layer was 235 ° C. in each case. The weight of the fuel container was 8.5 kg. The pinch-off part is
By forming a V-shaped pinch-off shape, it was composed of a single layer of high-density polyethylene, and the polyglycolic acid layer was embedded with high-density polyethylene layers of the inner and outer layers.

[Example 2] By reusing the regrind obtained in Example 1 for the recovery layer (RE), "HDPE / RE / AD / PGA / AD / HDP" was introduced from the outer layer side.
The layer configuration of “E” was used, and the thickness and thickness ratio of each layer were adjusted as follows. Outer layer (HDPE) = 360 μm (6%), Recovery layer (RE) = 2400 μm (40%) Adhesive resin layer (AD) = 150 μm (2.5%), Core layer (PGA) = 180 μm (3%), Adhesive resin layer (AD) = 150 μm (2.5%), inner layer (HDPE) = 2760 μm (46%), total layer thickness = 6000 μm.

Using a multi-layer blow molding machine of 4 types 6 layers continuous multi-layer crosshead die, the preset temperature of the molding machine was 235 ° C.
And a six-layer fuel container (75
Liter). The temperature of the extruder tip of each resin layer was 235 ° C. in each case. The weight of the fuel container is 8.
It was 5 kg. By forming the pinch-off portion in a V-shaped pinch-off shape, the polyglycolic acid layer was filled with the high-density polyethylene layer as the inner and outer layers and the recovery layer.

Comparative Example 1 A single-layer fuel container (75 liters) was molded in the same manner as in Example 1 except that high density polyethylene was used alone.

[Comparative Example 2] The core layer of polyglycolic acid was mixed with P
Adhesive resin made by Mitsui Chemicals, Inc. Admer H on A6 (Novamid 1020 made by Mitsubishi Engineering Plastics)
A layer structure of 3 types and 5 layers (HDPE / AD / PA6 /
A fuel container (75 liters) with AD / HDPE) was molded.

[Comparative Example 3] Polyglycolic acid in the core layer was replaced with E
VOH (EVAL-F104 manufactured by Kuraray Co., Ltd.) and Admer HB500 manufactured by Mitsui Chemicals, Inc. were used as the adhesive resin, respectively. / AD / HDPE) was molded into a fuel container (75 liters).

Table 1 shows the test results of the swelling degree, dimensional stability, moldability, and solvent crack resistance of the fuel containers obtained in the respective Examples and Comparative Examples. The results are shown in Table 2.

[0110]

[Table 1]

(Footnote) (1) Ordinary gasoline: Toluene / isooctane = 50 /
50 vol% (2) M15: toluene / isooctane / methanol =
42.5 / 42.5 / 15 vol%

[0112]

[Table 2]

As is clear from the results shown in Tables 1 and 2,
It can be seen that the multilayer plastic fuel container of the present invention is remarkably excellent in permeation-preventing property against gasoline and oxygen-containing gasoline, and is also excellent in solvent crack resistance, swelling resistance, dimensional stability, molding processability and the like.

[0114]

EFFECTS OF THE INVENTION According to the present invention, a multi-layer plastic fuel container having a remarkably excellent permeation-preventing property with respect to gasoline and oxygen-containing gasoline and having excellent solvent crack resistance, swelling resistance, dimensional stability, molding processability, etc. Will be provided. The multilayer plastic fuel container of the present invention is suitable as a fuel tank for automobiles, a fuel storage container, a fuel transport container, and the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the layer structure of a multilayer plastic fuel container of the present invention.

FIG. 2 is a cross-sectional view showing another example of the layer structure of the multilayer plastic fuel container of the present invention.

[Explanation of symbols]

1: High-density polyethylene layer 2: Adhesive resin layer 3: Polyglycolic acid layer 4: Adhesive resin layer 5: High-density polyethylene layer 21: High-density polyethylene layer 22: Recovery layer 23: Adhesive resin layer 24: Polyglycolic acid layer 25: Adhesive resin layer 26: High-density polyethylene layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daisuke Ito             18-13 Kamitama-ri, Tamazato-mura, Shinji-gun, Ibaraki Prefecture Kure             Haha Chemical Co., Ltd. Resin Processing Technology Center             Within (72) Inventor Koichi Kodama             16 Ochiai, Nishiki-cho, Iwaki-shi, Fukushima Prefecture Kureha Chemical Industry             Nishiki Research Institute, Ltd. (72) Inventor Yoshihiro Matsuko             18-13 Kamitama-ri, Tamazato-mura, Shinji-gun, Ibaraki Prefecture Kure             Haha Chemical Co., Ltd. Resin Processing Technology Center             Within F term (reference) 3E033 BA15 BA30 BB08 CA16 CA20                       FA03 GA02                 3E086 AD30 BA04 BA15 BA24 BA35                       BB05 BB20 BB68 BB74 CA40                 4F100 AK05A AK05D AK41B AK41C                       BA03 BA04 BA05 BA10A                       BA10D BA13 BA15 CB00E                       DA01 GB16 JA02 JD05 JK14                       JL01 JL04 JL11E JL16E

Claims (3)

[Claims] 1. A layer in which a high-density polyethylene layer is arranged as an inner layer and an outer layer, at least one polyglycolic acid layer is arranged as a core layer, and an adhesive resin layer is arranged between the respective layers as required. A multilayer plastic fuel container having a structure. 2. The multilayer plastic fuel container according to claim 1, having a layer structure in which a recovery layer is additionally arranged as an intermediate layer. 3. The multilayer plastic fuel container according to claim 1, which is a multilayer blow-molded container.