JPH07137161A - Plastic fuel tank - Google Patents

Abstract

PURPOSE:To obtain a plastic fuel tank having excellent uniform extensibility and excellent impact-resistant strength even in the case of a thin wall thickness by making the tank from a high-density polyethylene resin composition having a specific R value and density, providing a baffle part at a specific size ratio and limiting a minimum wall thickness of the baffle part to the range of a specific ratio against its maximum wall thickness. CONSTITUTION:A plastic fuel tank is made from a high-density polyethylene resin composition wherein zero shear viscosity in a limiting viscosity of 2 to 6dl/g at 190 deg.C is 2X10<7> to 3X10<8> poises, an R value is 2.5 to 4, and density is 0.94 to 0.97g/cm<3>. The tank has a baffle part of L/D=2 to 5 (L denotes height and D denotes width at a position of a height of L/2), and a minimum wall thickness C of the baffle part is in a range of 0.65 to 0.95 against its maximum wall thickness E. The high-density polyolefin resin composition easily presents a curing phenomenon of the material, and blow-up is performed in a state that deformation of parison is made uniform at the curved parts of a mold, whereby a plastic fuel tank having a thicker wall thickness at the curved parts thereof can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic fuel tank, and more particularly to a plastic fuel tank in which the baffle portion is uniformly thinned.

[0002]

2. Description of the Related Art In recent years, in the field of the automobile industry, the plasticization of parts has been actively studied in consideration of weight saving and energy saving. In the movement, some of the plastic fuel tanks using conventional HDPE have been put on the market, but it is common to provide a baffle portion from the viewpoint of preventing ripples. However, in the baffle part, the blow ratio was large and it was easy to become thin. Therefore, conventionally, a method of increasing the thickness of the baffle portion has been used. However, in recent years, it has been further required to reduce the weight of plastic fuel tanks.

As a high-density polyethylene resin having excellent impact resistance, it is proposed to use a high-density polyethylene resin having an intrinsic viscosity of 2 to 6 dl / g and a zero shear viscosity of 2 × 10 ^{7 to} 1.0 × 10 ⁸ poise. (Japanese Patent Laid-Open No. 2-5
3811). By using such a high-density polyethylene resin, it is possible to manufacture a plastic fuel tank having good impact resistance even if it is made thinner than before. However,
Since the wall thickness distribution, particularly the wall thickness distribution of the baffle portion, is difficult to be uniform, and the weight increases when the molded product is manufactured so as to satisfy the minimum wall thickness standard, further improvement has been required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide excellent impact resistance, uniform baffle wall thickness, and lighter weight. It is to provide a plastic fuel tank that can be shortened in cycle such as cooling time and injection time.

[0005]

The present inventors have found that the intrinsic viscosity is 2 to 6 dl / g and the zero shear viscosity is 2 × 10 ^{7 to} 3 ×.
As a result of intensive studies aimed at achieving the intended purpose, paying attention to a high-density polyethylene resin of 10 ⁸ poise, as a result, among the high-density polyethylene resins, those having an R value defined in a specific range as described later are used. As a result, they have found that the intended purpose is achieved, and have completed the present invention.

That is, the gist of the present invention is that the intrinsic viscosity is 2 to 6
dl / g, zero shear viscosity at 190 ° C. is 2 × 10
^{7 to} 3 × 10 ⁸ poise, R value of 2.5 to 4, density of 0.
It is formed from a high density polyethylene resin composition of 94 to 0.97 g / cm ³ , and L / D = 2 to 5 (L is height, D is L
/ 2 means the width at the height position. ), And the minimum thickness of the baffle portion is 0.
It exists in the plastic fuel tank characterized by being in the range of 65 to 0.95.

The present invention will be described in detail below. High of the invention
Density polyethylene resin has a density obtained by a known method.
0.94 to 0.97 g / cm³, Preferably 0.95
5 to 0.97 g / cm³, Particularly preferably 0.96 to
0.97 g / cm³Various high density polyethylene, for example
For example, ethylene homopolymer, ethylene and 10% by weight or less,
Preferably up to 5% by weight of other α-olefins (eg
For example, propylene, butene-1, pentene-1, hexene
-1, octene-1, decene-1, octadecene-1,
4-methylpentene-1,3-methylbutene-1,3-
Methyl pentene-1, vinyl cyclohexane, styrene
Copolymers with 3 to 20 carbon atoms such as α-olefins)
Among them, the intrinsic viscosity is 2 to 6 dl / g, preferably 2.3.
~ 5.5 dl / g, especially 3-5 dl / g, zero shear viscosity
2x10⁷~ 3 x 10⁸Poise, preferably 2.
5 x 10 ⁷~ 2 x 10⁸Poise, especially 3 × 10⁷~ 2x
10⁸Poise ones are used. Furthermore, the high density of the present invention
Degree polyethylene resin, R value is 2.5-4,
Specifically, 2.6 to 3.8, particularly preferably 2.7 to
The one of 3.5 is used.

The above physical properties in the present invention are values measured according to the following methods. Density (ρ) A value measured according to JIS K6760. Intrinsic viscosity ([η]) Value measured at 130 ° C in tetralin.

Zero shear viscosity (η ₀ ) Rheometrics stress rheometer (“RSR
-M ") and the pellets are pressed by a press molding machine to a thickness of about 1 m.
Value measured at 190 ° C. by molding into a sheet of m. The fixture is a cone-plate type and has a diameter of 25.
The angle between the cone and the flat plate was 0.1 rad in mm. Generally, the shear viscosity of a molten polymer takes a steady value in a low shear rate region (10 ⁻³ sec ⁻¹ or less), and decreases as the shear rate increases. Zero shear viscosity (η ₀ ) refers to the above steady value. This device can determine the melt shear viscosity in the low shear rate region from the creep characteristics.

Uniform Stretchability Index (R Value) The R value is an index showing the rate of increase in elongation stress over time under elongation flow, and is defined as R = σ ₂ / σ ₁ . Here, σ ₁ and σ ₂ are elongation strain rates ε = 0.5 se, respectively.
Under the flow of c ⁻¹ , it means the elongation stress when the elongation strain amounts ε = 1 and ε = 2. For σ ₁ and σ ₂ , σ = η _E × ε
(Η _E ; extensional viscosity, ε; extensional strain rate)

[0011]

Σ ₁ = η _E (t = 2.0; ε = 0.5) × 0.5 σ ₂ = η _E (t = 4.0; ε = 0.5) × 0.5 (t ;time)

Can be obtained as The elongation flow characteristic can be estimated by the following method. Extension viscosity is Gie
By solving the sekus constitutive equation for the uniaxial elongation stress at a constant strain rate, it is possible to analytically obtain the equation.

[0013]

[Equation 2]

(Σ ₁ ; Finger tensor, τ _i ;
Relaxation time, H _i ; relaxation spectrum intensity, D; deformation rate tensor, α; nonlinear parameter, subscript i represents the attribution to the i-th Maxwell element in the multimodal analysis,
∇ represents upper-conducted time derivative. )

[0015]

[Equation 3] Where T _i is

[0016]

[Equation 4]

It is Here, the relaxation spectrum H _i (τ
_i ) and the nonlinear parameter α were obtained as follows. (1) Measurement A mechanical spectrometer RMS-800 manufactured by Rheometrics Inc. was used to measure the dynamic viscoelasticity required when obtaining the relaxation spectrum. The measuring jig was a cone-plate type, and had a diameter of 25 mm and an angle between the cone and the plate (hereinafter referred to as a cone angle) of 0.1 rad.
The measurement frequency range is 0.01 to 100 rad / sec.

For measuring a wide range of steady shear viscosity, RSR-M and RMS-800 manufactured by Rheometrics Co., Ltd. and an INTESCO2020 type capillary viscometer manufactured by Intesco Co. were used. The measuring jig of RSR-M has a diameter of 25 m.
m, and the cone angle was 0.1 rad. RMS-8
No. 00 measuring jig has a diameter of 7.9 mm and a cone angle of 0.1.
The one of rad was used. The INTESCO 2020 type capillary viscometer has a diameter of 1.0 mm and a tube length of 50.
It was 0 mm and had an inflow angle of 90 °. Rabinowitch correction was performed as a correction of the shear rate.

RSR-M is mainly shear rate γ = 10 ^-5
Used for measurement at -10 ^-3 sec ^-1 , RMS-800 has γ
= 10 ^-3 to 10 ⁰ sec ^-1 , the INTESCO 2020 type capillary viscometer was used for measurement at γ = 10 ⁰ to 10 ³ sec ^-1 . All of the above measurements were performed at 190 ° C. For the measurement using RSR-M and RMS-800, a press-molded sample piece having a thickness of 1.0 mm was used. INT
A pellet-shaped sample was provided for the ESCO 2020 capillary viscometer.

(2) Calculation of relaxation spectrum H (τ) Among the measurement data of dynamic viscoelasticity, storage elastic modulus G '
(Ω) was subjected to least squares approximation with a regression curve of an arbitrary order (normally quadratic regression), and the relaxation spectrum was calculated by the following formula (Tchoegl quadratic approximation).

[0021]

[Equation 5]

(Ω is an angular frequency and τ is a relaxation time.) The relaxation spectrum obtained by the equation is given as a continuous function. However, when actually applied to a multimode constitutive equation, various calculations are performed. It is necessary to have a discontinuous line spectrum. Therefore, the relaxation spectrum curve is changed from 10 ⁻³ sec on the short time side to 10 ³ to 10 ⁵ se on the long time side.
The histogram was plotted as the isothermic melting point on the natural logarithmic axis in the range of c. Here, in order to confirm that the range of the relaxation time τ selected when performing the line spectrum conversion is appropriate, the obtained line spectrum is measured G ′ by the following equation.
It was confirmed that (ω) was reproduced.

[0023]

[Equation 6] Further, in determining the boundary value on the long time side, it was determined that the zero shear viscosity η ₀ is reproduced by the combination of the obtained line spectra by the following formula.

[0024]

[Equation 7]

The range of the relaxation spectrum obtained directly from the measured dynamic viscoelasticity measurement is τ = √2 × 10 ^{-2 to} √2 × 10 ^2.
Although it is sec, those that deviate from this range were extrapolated from the regression curve of the relaxation spectrum within the measurement range. The order of the regression curve here was the same as that used when the relaxation spectrum was obtained from the storage elastic modulus. (3) Determination of Non-Linear Parameter α When the equation is solved for steady shear flow, the steady shear viscosity η is expressed as the following equation as an analytical solution.

[0026]

[Equation 8]

The relaxation spectrum determined in (2) is
Substituted into the equation, the value of α was determined so as to reproduce the measured steady shear viscosity curve. Such high-density polyethylene can be obtained, for example, by homopolymerizing ethylene or ethylene and carbon number in the presence of a solid catalyst component (A) containing magnesium, titanium and halogen as essential components and a catalyst containing an organoaluminum compound (B) as main components. It can be obtained by copolymerizing with 3 to 20 α-olefins.

The solid catalyst component (A) has, for example, the general formula:
Mg (OR ¹ ) _m X ¹ _2-m (wherein R ¹ is an alkyl group,
It represents an aryl group or a cycloalkyl group, X ¹ represents a halogen atom, and m represents 1 or 2, preferably 2. ) And a magnesium compound (a) represented by the general formula, Ti (OR ² ) _n X ² _4-n (wherein, R ² represents an alkyl group, an aryl group or a cycloalkyl group, and X ² represents a halogen atom). And n is 1 to 4, preferably 3 or 4) and a titanium compound (b) represented by the following general formula:

[0029]

[Chemical 1]

(In the formula, R³ Is an alkyl group or aryl group
Or a cycloalkyl group, which may be the same or different.
May be. p is 2 to 20, preferably 2 to 15
Represent ) A polyalkyl titanate (c) represented by
Is, if necessary, a general formula, R ^Four OH (in the formula, R^Four A
Represents a alkyl group, an aryl group or a cycloalkyl group.
You ) Containing an alcohol compound (d) represented by
By treating the hydrocarbon solution with a halogenating agent,
Obtained as a hydrocarbon solution insoluble solid catalyst.

In the magnesium compound (a),
Examples of the alkyl group for R ¹ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and an octyl group, and an aryl group includes a tolyl group and a xylyl group. Examples of the group include a cyclohexyl group and the like. Further, examples of the halogen atom of X ¹ include a chlorine atom, a bromine atom, an iodine atom and the like. Specific examples of the magnesium compound (a) include dimethoxy magnesium, diethoxy magnesium, ethoxy magnesium chloride, and diphenoxy magnesium.

[0032] The titanium compound (b), the alkyl group, an aryl group R ^2, a cycloalkyl group and X ²
Examples of the halogen atom of are the same as those of R ¹ and X ¹ . Specific examples of such titanium compounds include, for example, tetraethoxy titanium, tetrapropoxy titanium, tetra-n-butoxy titanium, triethoxy dimonochloro titanium, tripropoxy dimonochloro titanium, tri-n-butoxy monochloro titanium, diethoxy dichloro. Titanium, dipropoxydichlorotitanium, di-n
-Butoxydichlorotitanium, ethoxytrichlorotitanium, propoxytrichlorotitanium, n-butoxytrichlorotitanium and the like can be mentioned. Preferably, tetra-n-
Butoxy titanium and tri-n-butoxy monochloro titanium are preferable.

In the above polyalkyl titanate (c), examples of the alkyl group, aryl group and cycloalkyl group of R ³ are the same as those of R ¹ . Specific examples of the polyalkyl titanate include, for example, tetraethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, tetrakis (2-ethylhexyloxy) titanium, tetraalkoxy titanium such as tetrastearyloxy titanium 2 to 20 mer, preferably Include tetrabutoxytitanium 2- to 4-mer and tetrapropoxytitanium 2 to 10-mer. Further, a condensate of tetraalkoxytitanium obtained by reacting tetraalkoxytitanium with a small amount of water may be used. Further, in the alcohol compound (d) which is optionally used, R ⁴
Examples of the alkyl group, aryl group, and cycloalkyl group are the same as those for R ¹ . Specific examples of such alcohols include ethyl alcohol and n-
Propyl alcohol, isopropyl alcohol, n-butyl alcohol, n-octyl alcohol and the like can be mentioned.

In the preparation of the solid catalyst component (A), first, a uniform hydrocarbon solution containing the above (a), (b) and (c) and, if necessary, (d) is prepared. Examples of the hydrocarbon solvent include aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene.

The method for preparing a uniform hydrocarbon solution is not particularly limited, and for example, (a), (b) and (c) and, if necessary, (d) are mixed, and preferably 100 to 170.
A uniform solution can be prepared by adding a hydrocarbon solvent after forming a liquid material or an alcohol solution by heating at 0 ° C. At that time, when (d) is used, the hydrocarbon solvent may be added after distilling off (d). Alternatively, the liquid substances (a) and (b) are formed in advance, and (c)
After adding, a hydrocarbon solvent may be added to prepare a uniform solution. The use ratios of (a), (b) and (c) are molar ratios of each component.

[0036]

## EQU9 ## 0.1 ≦ (b) / (a) ≦ 5 0.3 ≦ (c) / (a) ≦ 8 Preferably

[0037]

## EQU10 ## 0.2 ≦ (b) / (a) ≦ 2 0.5 ≦ (c) / (a) ≦ 4

It is used in the range of. If it deviates from this range, the molding processability such as uniform stretchability and the mechanical strength tend to decrease. (D) is used when it is difficult to form a uniform liquid substance, but the usage ratio also varies depending on the type of catalyst and the like. Generally, it may be added to such an extent that a liquid substance is produced. Then, the obtained uniform hydrocarbon solution is usually added at room temperature to 2
The solid catalyst component (A) is obtained by treating with a halogenating agent at a temperature of 00 ° C.

The halogenating agent is not particularly limited as long as it has a halogenating action, and a compound to which halogen is covalently bonded is usually used. Specifically, for example, boron trichloride, titanium tetrachloride, silicon tetrachloride, tin tetrachloride, vanadium tetrachloride, chlorides such as aluminum chloride,
Examples thereof include chlorine-containing compounds such as hydrogen chloride, thionyl chloride and chlorosulfonic acid, and halogens such as chlorine, bromine and iodine. Titanium tetrachloride and silicon tetrachloride are preferred,
Particularly, titanium tetrachloride is preferable. This treatment with a halogenating agent may be repeated twice or more, and the degree of halogenation is preferably within the following range with respect to the above (a) to (d):

[0040]

[Equation 11] More preferably,

[0041]

[Equation 12]

It is preferable that the range is set to. In the above formula, X represents the number of moles of the halogen atom in the halogenating agent, and X ¹ , X ² , OR ¹ , OR ² , OR ³ and O
R ⁴ represents the number of moles of each group in the above general formula. The solid catalyst component (A) obtained as described above is
Separate from the halogenating agent treatment liquid and wash with a hydrocarbon solvent. As the hydrocarbon solvent, those described above can be used.

Next, as the organoaluminum compound (B) used as a cocatalyst, the general formula: AlR ⁵ _q (O
R ⁶ ) _r X ⁵ _{3- (q + r)} (In the formula, R ⁵ and R ⁶ represent an alkyl group, an aryl group, or a cycloalkyl group, X ⁵ represents a halogen atom, and q represents a number of 2 to 3. And r is a number of 0 to 1). Examples of the alkyl group, aryl group, cycloalkyl group and halogen atom include the same ones as described above.

Specific examples include triethyl aluminum, triisobutyl aluminum, diethyl aluminum monochloride, diisobutyl aluminum monochloride, diethyl aluminum monoethoxide and the like. It is also possible to use the reaction product of a trialkylaluminum and water. You may use these 2 or more types together.

The proportion of the organoaluminum compound (B) used is the concentration of the organoaluminum compound and the ratio of the organoaluminum compound to the solid catalyst component, that is, the product of the Al / Ti atomic ratio [Al] (mmol / l). × (Al / T
i) is 1.2 to 0.02, preferably 1.0 to 0.0
3, more preferably 0.5 to 0.05 is used.

Further, (A) the magnesium compound (a) (Mg (OR ¹ ) _m X ² _2-m ) and the titanium compound (b) (Ti (OR ² ) _n X ² _4-n ), and Obtained by treating a homogeneous hydrocarbon solution containing the alcohol (d), if necessary, with a solution consisting of titanyl chloride (TiOCl ₂ ) (e) and a halogen-containing compound (f) having no reducing ability. It is also possible to use a catalyst system in which a hydrocarbon-insoluble solid catalyst component and the organoaluminum compound (B) are combined. The homogeneous hydrocarbon solution can be prepared in the same manner as in the preparation of the catalyst system described above. The obtained homogeneous hydrocarbon solution contains the titanyl chloride (e) and the halogen-containing compound (f) having no reducing ability.
The treatment is usually carried out at a temperature of room temperature to 200 ° C. At that time, the use ratios of (a), (b) and (e) are

[0047]

## EQU13 ## Used in the range of 0.01 ≦ (b) / (a) ≦ 10 0.1 ≦ (d) / (a) ≦ 50. The usage rate of (f) is
For (a), (b), and (d),

[0048]

[Equation 14]

(In the formula, X represents the number of moles of the halogen atom in (f), and X ¹ , X ² , OR ¹ , OR ² and OR ³ have the same meanings as described above.) Organoaluminum compound (B) The same as above can be used. The usage ratio is the concentration of the organoaluminum compound and the ratio of the organoaluminum compound to the solid catalyst component, that is, the product of the Al / Ti atomic ratio [Al] (mm
ol / l) × (Al / Ti) is used in the range of 2.0 to 0.01, preferably 1.0 to 0.02.

In the present invention, a chromium-based catalyst in which a chromium compound is supported on silica or silica-alumina or a catalyst in which a haloalcolate of titanium trichloride, vanadium trichloride, titanium tetrachloride or titanium is supported on a magnesium compound-based simple substance. Component or a titanium-based catalyst such as a coprecipitate or a eutectic of a magnesium compound and a titanium compound and AlR _l X _{3 -l} (wherein R represents a hydrocarbon group having 20 or less carbon atoms, X represents a halogen atom, 1 represents a number of 1 to 3), and a catalyst system in which an organoaluminum compound represented by the formula is combined may be used.

Copolymerization of ethylene or ethylene with another α-olefin is carried out using the above-mentioned catalyst system, and the polymerization reaction is carried out in an inert solvent, either slurry polymerization, solution polymerization or gas phase polymerization. Method is also acceptable. Examples of the inert solvent include aliphatic hydrocarbons such as butane, hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and toluene. The polymerization reaction is usually at room temperature to 200 ° C. and atmospheric pressure to 100.
It is performed in the range of atmospheric pressure. Also, the molecular weight can be adjusted by introducing hydrogen during the polymerization reaction.

In the present invention, a one-step polymerization method or a multi-step polymerization method can be carried out. Examples of the multistage polymerization method include, for example, a method in which the polymerization reaction is carried out in two steps, that is, in the first reaction zone, and further in the second reaction zone in the presence of the reaction product obtained therein. To be that time,
Homopolymerization of ethylene is carried out in either one of the first and second reaction zones to produce a polymer A having a viscosity average molecular weight of 60 to 150,000 by 60 to 90% by weight based on the total amount of polymer produced,
In the other reaction zone, homopolymerization of ethylene or copolymerization with another α-olefin is carried out, and 40 to 10% by weight of the polymer B having an α-olefin content of 10% by weight or less and a viscosity average molecular weight of 500,000 to 4,000,000. % Generate. The molecular weight ratio of the polymer B and the polymer A is set in the range of 3 to 50.

As long as the effects of the present invention are not impaired,
About 1 part by weight or less of a filler, pigment, heat stabilizer, light stabilizer, flame retardant, plasticizer, antistatic agent, release agent, foaming agent, nucleating agent, etc. You may mix an additive. In the present invention, it can be suitably used as a laminated fuel tank in which a polyethylene layer formed of the above high density polyethylene resin is laminated on at least one side of a barrier layer with an adhesive layer interposed therebetween. The barrier layer is a thermoplastic polyester resin such as polyamide resin, polyethylene terephthalate or polybutylene terephthalate, an ethylene-vinyl acetate copolymer having a saponification degree of 93% or more, preferably 96% or more and an ethylene content of 25 to 50 mol%. It can be formed from an ethylene-vinyl acetate copolymer saponified product such as.

In particular, a polyamide resin is preferable from the viewpoints of stability of formation and gas barrier property, and a polyamide obtained by polycondensation of diamine and dicarboxylic acid, a polyamide obtained by condensation of aminocarboxylic acid, a polyamide obtained from lactam, or these Copolymerized polyamide, etc., usually has a relative viscosity of about 1 to 6 and a melting point of 170 to 2
A temperature of 80 ° C., preferably 200 to 240 ° C. is used. Specifically, for example, nylon-6, nylon-
66, nylon-610, nylon-9, nylon-1
1, nylon-12, nylon-6 / 66, nylon-
66/610, nylon-6 / 11 and the like.
Particularly, nylon-6 is preferable.

In the present invention, the polyamide layer is preferably formed of a modified polyamide resin composition comprising the above polyamide resin and a maleic anhydride modified ethylene-α-olefin copolymer, and a maleic anhydride modified ethylene- The α-olefin copolymer has a crystallinity of 1 to 35%, preferably 1 to 30% and a melt index of 0.01 to 50 g / min, preferably 0.1 to 50%.
Maleic anhydride is added to an ethylene-α-olefin copolymer at 20 g / min in an amount of 0.05 to 1% by weight, preferably 0.1.
Grafted from 2 to 0.6% by weight is used. Examples of the α-olefin of the ethylene-α-olefin copolymer include propylene, butene-1, and hexene-1, and the amount of these α-olefins is 30% by weight or less, preferably 5 to 20% by weight. Copolymerized with ethylene in proportion.

The proportion of the maleic anhydride-modified ethylene-α-olefin copolymer used is 10 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the polyamide resin.
It is selected from the range of parts by weight and, for example, kneaded with an extruder or the like at a temperature of 200 to 280 ° C. before use.

As the adhesive layer, 0.01 to 1% by weight of an unsaturated carboxylic acid or a derivative thereof of a homopolymer or copolymer of α-olefin such as ethylene or propylene, preferably 0.02 to 0. Modified polyolefins grafted with 06% by weight can be used. Especially, the density is 0.94 ~
0.97 g / cm ³ of ethylene homopolymer or ethylene and 3% by weight or less, preferably 0.05 to 0.5% by weight of α-, such as propylene, butene-1, and hexene-1.
Modified products of copolymers with olefins are preferred. Examples of the unsaturated carboxylic acid or its derivative include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and their anhydrides. Maleic anhydride is particularly preferable.

The fuel tank of the present invention can be manufactured by a known blow molding method. For example, a parison of the high density polyolefin resin composition is formed from an extruder through a die. In the mold for molding this parison,
It is manufactured by inflating it from the inside with air pressure, bringing it into close contact with the mold, and cooling at the same time. At that time, pre-blowing is preferable because a molded product having a better wall thickness can be obtained. The high-density polyolefin resin composition of the present invention is liable to cause a hardening phenomenon of the material and has a property of suppressing excessive elongation of the portion, so that in the curved portion of the mold,
Since the parison is blown up in a state where the deformation thereof is uniformized, it is possible to form a molded product having a thicker curved portion than the conventional one. In the fuel tank of the present invention, the minimum thickness of the baffle portion of L / D = 2 to 5 is 0.65 to 0.95, preferably 0.
It is in the range of 75 to 0.95. The meanings of L, D, and minimum / maximum wall thickness are shown in FIG. 1, respectively. Further, in the case of manufacturing a multi-layer fuel tank, for example, the resin composition of each layer is individually plasticized from a plurality of extruders and extruded into the same die having the same circular flow path, and the meat of each layer in the die. The thickness is made uniform, and the respective layers are superposed to form a single parison in appearance, and then the parison is molded in the molding die in the same manner as described above.

As the multilayer fuel tank, it is particularly preferable to use a three-kind five-layer structure in which a high-density polyethylene layer is laminated on both sides of a barrier layer with an adhesive layer interposed therebetween. At that time, the thickness of the barrier layer is 0.01 to 0.5 mm, preferably 0.1.
~ 0.3 mm, the thickness of the adhesive layer is 0.01 ~ 0.5 m
m, preferably 0.1 to 0.3 mm, the thickness of the high-density polyethylene layer is 1 to 10 mm, preferably 1.5 to
It is selected from the range of 5 mm.

[0060]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The following materials were used in the examples.

(1) High Density Polyethylene Resin (HDPE): (a) Preparation of Solid Catalyst Component A 3 liter flask equipped with a condenser was thoroughly dried and purged with nitrogen, and then 133 g of Mg (OEt) ₂ was added.
(1.16 mol), 197 g of Ti (OBu) ₄ .
(0.58 mol) was charged, the temperature was raised to 130 ° C. with stirring, and heat treatment was performed. A uniform viscous liquid was obtained after 4 hours. After cooling to about 80 ° C., 1.0 liter of toluene was added to form a uniform solution. The entire amount of the above solution was transferred to another autoclave of 24 liters which was sufficiently dried and purged with nitrogen. To this toluene solution was added 985 g (1.015 mol) of tetrabutoxytitanium tetramer,
Furthermore, 5.89 liters of toluene were added. While stirring, 2.03 liter (18.49 mol) of TiCl ₄ was diluted with toluene to a concentration of 4.55 mol / l at 40 ° C., and added over 3 hours. Subsequently, the temperature was raised to 105 ° C. over 30 minutes and kept for 1 hour. Then, after cooling, 12.5 liters of the supernatant was extracted by decantation and further washed with 10 liters of toluene.
Then add 4.0 liters of toluene and add another 4.5
A TiCl ₄ -toluene solution having a concentration of 5 mol / liter was added again so that the amount of TiCl ₄ was 18.49 mol. Then, heat treatment was carried out at 105 ° C. for 1 hour, cooling and washing with n-hexane were carried out to obtain a solid catalyst component. The Ti content in the solid catalyst component was 34.0% by weight.

(B) Prepolymerization of ethylene In a container for prepolymerization having a capacity of 300 liters, n-hexane was added.
220 liters and solid catalyst component 7 obtained in (a) above
30g was charged. 2 kg / cm of hydrogen in this ² Introduction
And heated to 80 ° C., and then triethylaluminum 0.52
Initiate prepolymerization by feeding mmol with ethylene
did. Preliminary polymerization for 0.5 hours by continuously introducing ethylene
10 g of polyethylene is added per 1 g of the solid catalyst component.
Obtained. After the prepolymerization is completed, it is cooled and washed with n-hexane.
It was

(C) Polymerization of ethylene Using a continuous polymerization apparatus equipped with a reactor having a capacity of 500 liters, 27 kg of ethylene / 63 kg of n-hexane.
/ Hr and hydrogen are continuously supplied, 2.5 g / hr of the prepolymerization catalyst obtained in (b) above and 2.2 g / hr of triethylaluminum are introduced, and 80 ° C.,
Homopolymerization of ethylene was carried out under the conditions of a total pressure of 25 kg / cm ² and an average residence time of 3 hours. The polyethylene in the reactor was transferred to the degassing tank at a rate of 25 kg / hr, and roughly separated,
After the drying step, ρ 0.961 g / cm ³ , [η] 4.
3 dl / g, η ₀ 5.01 × 10 ⁷ poise, R value 2.8
A polymer powder (HDPE: A) of 3 was obtained. Further, HDPE B and C shown in Table 1 were obtained according to the above method.

[0064]

[Table 1]

(2) Modified polyethylene (APO): Modified polyethylene obtained by grafting maleic anhydride (0.4% by weight) on high density polyethylene of ρ: 0.960 g / cm ³ . Melt index (MI): 0.1 g / 10
(3) Modified polyamide resin composition (MPA): 80 parts by weight of nylon-6 having a relative viscosity of 4.0, and 20 parts by weight of maleic anhydride (0.3% by weight) modified ethylene-butene-
1 copolymer (ethylene-butene-1 (13 mol%) copolymer having a crystallinity of 20% and MI of 3.5 g / 10 min)
Mixture with.

(Examples 1 to 3 and Comparative Examples 1 and 2) Table 1
HDPE full flight type screw (L / D = 2
4, C.I. R. = 3.0) single-screw extruder to granulate (set temperature 280 ℃), then melt in the extruder (cylinder set temperature: 185 to 215 ℃), die (die temperature: 235 ℃) To form a molten cylinder (parison) having a diameter of 530 mm. Adjust the drawdown with the parison controller so that the thickness of the parison just before molding becomes constant in the injection direction, sandwich it with a mold (60L saddle type with 40R corner part, temperature: 20 ° C), and press in air. After (pressure: 6 kg / cm ² ), a fuel tank having a capacity of 60 liters was obtained at a product removal temperature of 80 ° C. In the case of pre-blowing, the lower part of the parison was chucked, and the pre-blow was performed for 3 seconds at a pressure of 1 kg / cm ² before the mold was closed. Baffle part (L / D = 4, R = 30mmφ, L = 6
0 mm) was attached to the bottom of the center of the tank in the injection direction. The minimum / maximum wall thickness ratio of the baffle part of the obtained molded product is shown in Table 2.

[0067]

[Table 2] Table 2 Molded product weight 7 kg ──────────────────────────────────── Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 ──────────────────────────────────── HDPE A B A C C Pre-blown No No Yes Yes No Yes Min / max wall thickness ratio 0.75 0.70 0.85 0.45 0.6 ─────────────────────── ──────────────

(Example 4) HDPE produced in the examples shown in Table 3 and the raw material resins for the respective layers of the adhesive resin (a) and the barrier resin (b) shown in Table 3 were prepared by using different extruders. They were individually melted and extruded into the same die having concentric circular channels, and the layers were superposed within the die (die temperature; 230 ° C.) and coextruded to form a parison with a diameter of 530 mm. Thereafter, in the same manner as in Example 1, a multi-layer (three types, five layers) fuel tank (7 kg) having a capacity of 60 liters was obtained. The minimum / maximum wall thickness ratio of the baffle part of the obtained molded product was 0.75.

[0069]

[Table 3] Table-3 ─────────────────────────── Layer composition Resin used Thickness (μm) ──────── ──────────────────── Outer layer (HDPE) A 2600 Adhesive layer (a) APO 100 Barrier layer (b) MPA 100 Adhesive layer (b) APO 100 Inner layer (HDPE) ) A 2600 ─────────────────────────

(A) Modified polyethylene (APO) A modified polyethylene obtained by grafting maleic anhydride (0.4% by weight) on high-density polyethylene having a density of 0.960 g / cm ³ . Melt index (MI); 0.1 g / 1
0 minutes. (B) Modified polyamide resin composition (MPA) 80 parts by weight of nylon-6 having a relative viscosity of 4.0 and 20% by weight of maleic anhydride (0.3% by weight) modified ethylene-butene-1 copolymer (ethylene ~ Butene-1 (13 mol
%) Crystallinity of copolymer is 20%, MI is 3.5 g / 1
0 min).

[0071]

According to the present invention, uniform stretchability is excellent,
It is possible to obtain a light fuel tank having excellent impact strength even with a thinner wall thickness than before.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a baffle in an embodiment of the present invention.

[Explanation of symbols]

A Start point of rising of baffle B End point of rising of baffle C Minimum wall thickness (means the minimum wall thickness in the range of A to B at which R ¹ rises) D Width of baffle at height L / 2 E Maximum wall thickness (means the maximum wall thickness in the range of A to B where R ¹ rises) F Product L Baffle height R ¹ Baffle rising radius, usually R ¹ = 5
It shows 30 mmφ.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B60K 15/03 C08F 265/00 MQD 267/00 MQG // B29C 49/22 7619-4F C08L 23/04 LDC B29K 23:00 77:00

Claims (5)

[Claims] 1. An intrinsic viscosity of 2 to 6 dl / g, a zero shear viscosity at 190 ° C. of 2 × 10 ^{7 to} 3 × 10 ⁸ poise, an R value of 2.5 to 4, and a density of 0.94 to 0.97 g / g.
formed from a cm ³ high density polyethylene resin composition,
L / D = 2 to 5 (L means height, D means width at L / 2 height position) and has a baffle portion, and the minimum wall thickness of the baffle portion is maximum with respect to the maximum wall thickness. A plastic fuel tank characterized by being in the range of 0.65 to 0.95. 2. A plastic fuel tank comprising a polyethylene layer laminated on at least one side of a barrier layer via an adhesive layer, wherein the polyethylene layer has an intrinsic viscosity of 2 to 6 dl / g and a zero shear at 190 ° C. Viscosity is 2 × 10 ^{7 to} 3 × 10 ⁸ poise, R value is 2.5
˜4, formed from a high density polyethylene resin composition having a density of 0.94 to 0.97 g / cm ³ , L / D = 2 to 5
(L means height and D means width at L / 2 height position.)
2. The plastic fuel tank according to claim 1, wherein said baffle part has a minimum wall thickness of 0.65 to 0.95 with respect to the maximum wall thickness. 3. The plastic fuel tank according to claim 2, wherein the barrier layer is formed of a polyamide resin. 4. An anhydride obtained by grafting an ethylene-α-olefin copolymer having a crystallinity of 1 to 35% and a melt index of 0.01 to 50 with maleic anhydride in an amount of 0.05 to 1% by weight. The plastic fuel tank according to claim 2, which is formed from a composition of a maleic acid-modified ethylene-α-olefin copolymer and a polyamide resin. 5. The plastic fuel tank according to claim 2, wherein the adhesive layer is a high-density polyethylene resin graft-modified with 0.01 to 1% by weight of an unsaturated carboxylic acid or a derivative thereof.