JP5204967B2 - Polyethylene resin for injection molded plastic fuel tank and injection molded fuel tank using the same - Google Patents

Description

  The present invention relates to a polyethylene resin for an injection molded plastic fuel tank and an injection molded fuel tank using the same. More specifically, in the injection-molded plastic fuel tank material, the polyethylene-based resin material for the fuel tank, which is excellent in durability, impact resistance, and fire resistance of the obtained molded product while maintaining good injection moldability, and the same are used. Related to injection molded fuel tanks.

  In recent years, in the field of fuel tanks for automobiles, the use of resin for products has been actively promoted for the purpose of reducing the weight and saving energy. As the resin material, polyethylene is generally used as a main material from the viewpoints of low cost, high strength, good weather resistance, good chemical resistance, recyclability, and the like. Also, resin fuel tanks are mainly produced by large blow molding.

However, in large blow molding, the molding machine is dedicated, the productivity decreases due to the generation of waste materials such as burrs, the thickness distribution of the molded product becomes uneven, the fuel permeability from the blow molding pinch part, etc. I have a problem.
In order to solve these problems, a molding method other than blow molding, for example, a plastic fuel tank by an injection molding method has been proposed (for example, see Patent Documents 1 to 4).
However, for example, Patent Document 1 discloses an ethylene-based copolymer suitable for injection molding having a specific density, melt index, molecular weight distribution index, etc., although it is disclosed that it is suitable for large parts. No material suitable for a plastic fuel tank is disclosed.
Further, Patent Document 2 discloses an automobile fuel tank made of polyethylene having a specific density, dispersion index, and melt index, but it is insufficient in terms of fuel oil resistance.
Furthermore, Patent Document 3 discloses a fuel tank part for automobiles in which a resin composition comprising a polyamide resin and a polyphenylene sulfide resin is injection-molded. However, a material suitable as a fuel tank body is not disclosed.
Further, Patent Document 4 proposes a resin molded product obtained by melt-molding (particularly injection molding, injection press molding) of a polyphenylene resin composition. Although it has good properties and fuel permeation resistance, it is insufficient in terms of molding efficiency.
JP 7-278229 A JP 2001-71759 A Japanese Patent Application Laid-Open No. 2002-289991 JP 2004-339478 A

  In view of the above problems, the object of the present invention is a resin for a plastic fuel tank, which is a material for a large container with an excellent balance between moldability and durability, and particularly excellent in balance between injection moldability, durability, and impact resistance. Another object of the present invention is to provide an injection molded plastic fuel tank resin excellent in fire resistance and a molded article using the same.

  The present inventors have intensively studied to solve the above problems, and as a result of studying a material that can sufficiently meet the characteristics required of an injection-molded plastic fuel tank, polyethylene having density, fluidity, orientation, etc. within a specific range. The present inventors have found that a molded product having an excellent balance between moldability and durability can be obtained from a resin, and the present invention has been completed.

That is, according to the first invention of the present invention, it contains 23 to 84% by weight of the following component (a) and 77 to 16% by weight of the component (b), and satisfies the following requirements (1) to (5). There is provided a polyethylene-based resin for injection molded plastic fuel tanks.
Component (a): density is 0.915-0.940 g / cm ³ , high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) is 0.05-10 g / 10 min. Polyethylene Component (b): Polyethylene having a density of 0.940 to 0.970 g / cm ³ and a melt flow rate (MFR) (test conditions: 190 ° C., 2.16 kg load) of 1 to 300 g / 10 min (1 ) Density is in the range of 0.940-0.970 g / cm ³ (2) High load melt flow rate (HLMFR) (Test conditions: 190 ° C., 21.6 kg load) is 15-20 g / 10 min ( 3) The shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ is 10000 poise or less (4) The Charpy impact strength at −40 ° C. is 5 KJ / m ² or more ( 5) The rupture time in a full notch creep test (measured at 80 ° C. and 6 MPa) is 80 hours or more.

According to a second aspect of the present invention, in the first aspect, the component (a) and the component (b) are obtained by a continuous multistage polymerization method. A resin is provided.

Further, according to the third invention of the present invention, it is molded using the polyethylene-based resin for injection molded plastic fuel tank according to the first or second invention, and the orientation ratio by the Charpy impact strength ratio is 50% or more. An injection molded fuel tank is provided.
Furthermore, according to the fourth invention of the present invention, the molded resin is molded using the polyethylene resin for injection molded plastic fuel tank according to the first or second invention and the fuel barrier material, and the orientation ratio by the Charpy impact strength ratio is An injection molded fuel tank characterized by being 50% or more is provided.

As described above, the present invention relates to a polyethylene-based resin for an injection molded plastic fuel tank, and preferred embodiments thereof include the following.
(1) The polyethylene resin for an injection molded plastic fuel tank as described above, wherein the polyethylene resin is an ethylene homopolymer or an ethylene / α-olefin copolymer.
(2) The polyethylene-based resin for an injection-molded plastic fuel tank described above, wherein the polyethylene-based resin is medium density polyethylene (MDPE) or high density polyethylene (HDPE), particularly high density polyethylene (HDPE).
(3) The polyethylene-based resin for an injection-molded plastic fuel tank described above, wherein the polyethylene-based resin is polymerized using a Ziegler catalyst.
(4) The polyethylene-based resin for an injection-molded plastic fuel tank as described above, wherein the component (a) and the component (b) are obtained by a continuous multistage polymerization method.
(5) The fuel barrier material is a polyamide or an ethylene / vinyl alcohol copolymer, an inorganic filler, aluminum or an epoxy paint, particularly a polyamide or an ethylene / vinyl alcohol copolymer. Injection molded fuel tank.

  According to the present invention, a large container excellent in balance between moldability and durability can be obtained, and in particular, an injection molded plastic fuel tank excellent in balance of injection moldability, durability and impact resistance and excellent in fire resistance. Can be obtained.

The resin for injection-molded plastic fuel tanks of the present invention is a polyethylene resin that satisfies the requirements of the following characteristics (1) to (5).
Hereinafter, the resin of the present invention and its use will be described in detail for each item.

1. Characteristic (1): Density The resin for injection molded plastic fuel tanks of the present invention is composed of an ethylene polymer, and the density of the ethylene polymer is 0.940 to 0.970 g / cm ³ , preferably Is 0.942 to 0.965 g / cm ³ , more preferably 0.945 to 0.960 g / cm ³ .
The density is in accordance with JIS K7112 (1999) “Plastics—Method of measuring density and specific gravity of non-foamed plastic”, and the pellets are cooled at a rate of 25 ° C./min. This sheet is formed and conditioned in a room at a temperature of 23 ° C. for 48 hours, and then placed in a density gradient tube and measured.
When the density is less than 0.940 g / cm ³ , a lack of rigidity of the molded product becomes obvious. On the other hand, when the density exceeds 0.970 g / cm ³ , the impact resistance is insufficient.
The density can be adjusted, for example, by changing the amount of α-olefin copolymerized with ethylene, and can be reduced by increasing the amount of α-olefin.

2. Characteristic (2): High load melt flow rate (HLMFR)
The ethylene polymer used as the resin for an injection-molded plastic fuel tank of the present invention has a high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) of 6 g / 10 min or more.
High load melt flow rate (HLMFR) at a temperature of 190 ° C. and a load of 21.6 kg is JIS K6922-1 (1997) “Plastic—Polyethylene (PE) molding and extrusion materials—Part 1: Designation system and specifications In accordance with ISO 1133 under a measurement condition G of 190 ° C. and a load of 21.60 kg (211.83 N) in accordance with the “basic of the notation”, when the HLMFR is less than 6 g / 10 minutes, The fluidity is insufficient and the molding becomes unstable, which is not practical. The upper limit of the high load melt flow rate (HLMFR) at a temperature of 190 ° C. and a load of 21.6 kg is not particularly limited, but is usually 50 g / 10 minutes.
Adjustment of high load melt flow rate (HLMFR) at 190 ° C. and 21.6 kg load is adjusted by changing the amount of chain transfer agent (hydrogen, etc.) coexisting during ethylene polymerization or changing the polymerization temperature. Can be increased by increasing the amount of hydrogen or by raising the polymerization temperature.

3. Characteristic (3): Shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ The ethylene polymer used as the resin for an injection molded plastic fuel tank of the present invention preferably has a shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ of 10,000 poise or less. Is 9000 poise or less, more preferably 8000 poise or less. When the shear viscosity exceeds 10,000 poise, the fluidity at the time of injection molding is insufficient.
The shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ is measured using a nozzle with a diameter of 1.0 mmφ and a length of 40 mm by a capillograph manufactured by Toyo Seiki Co., Ltd.
The shear viscosity can be increased by generally increasing the molecular weight of the ethylene polymer.

4). Characteristic (4): Charpy impact strength at −40 ° C. The ethylene polymer used as the resin for the injection molded plastic fuel tank of the present invention has a Charpy impact strength at −40 ° C. of 5 KJ / m ² or more, preferably 6 KJ / m ² or more, more preferably 7 KJ / m ² or more. When the Charpy impact strength at −40 ° C. is less than 5 KJ / m ² , the shortage of impact strength of the molded product becomes obvious. On the other hand, the upper limit value of the Charpy impact strength at −40 ° C. is not particularly limited, but is usually 100 KJ / m ² .
Here, the Charpy impact strength at −40 ° C. conforms to JIS K6922-2 (1997) “Plastic—Polyethylene (PE) molding and extrusion materials—Part 2: How to make test pieces and various properties”. Thus, a test piece is prepared and measured according to JIS K7111 (1996) “Plastic-Charpy impact strength test method”.
The Charpy impact strength at −40 ° C. can be increased by increasing the molecular weight of the ethylene polymer or narrowing the molecular weight distribution.

5. Characteristic (5): Rupture time in full-notch creep test (measured at 80 ° C., 6 MPa) The ethylene polymer used as the resin for an injection-molded plastic fuel tank of the present invention has a fracture in a full-notch creep test (measured at 80 ° C., 6 MPa). The time is 80 hours or longer, preferably 150 hours or longer, more preferably 200 hours or longer. When the breaking time in the full notch creep test (measured at 80 ° C. and 6 MPa) is less than 80 hours, the durability of the molded product is insufficient.
The rupture time in the full notch creep test (measured at 80 ° C. and 6 MPa) is measured at 80 ° C. and 6 MPa in accordance with the full-notch tensile creep test in Appendix 1 of JIS K6774 (1995) “Polyethylene pipe for gas”. Do. The test piece was prepared under the conditions shown in Table 2 of JIS K6922-2 (1997) “Plastics—Polyethylene (PE) molding and extrusion materials—Part 2: How to make test pieces and various properties”. Cut from a compression-molded sheet at 6 mm and have a notch on the entire circumference (test piece thickness 6 mm, notch depth 1 mm, full circumference).
The breaking time in the full notch creep test (measured at 80 ° C. and 6 MPa) can be increased by reducing the density of the ethylene-based polymer.

6). Types and Components of Polyethylene Resin (Ethylene Polymer) The ethylene polymer used as the resin for the injection molded plastic fuel tank of the present invention is obtained by homopolymerizing ethylene or ethylene and 3 to 20 carbon atoms, preferably 3 It can be obtained by copolymerizing one or more comonomers selected from ˜15, more preferably 3 to 10 α-olefin, to a predetermined density. Examples of the α-olefin to be copolymerized include propylene, butene-1, pentene-1, 3-methylbutene-1, 3-methylpentene-1, 4-methylpentene-1, hexene-1, octene-1 and decene. -1, tetradecene-1, hexadecene-1, octadecene-1, eicosene-1, and the like. From the viewpoint of durability and economy, propylene, butene-1, and hexene-1 are particularly preferable.
Further, vinyl compounds such as vinyl acetate, acrylic acid, methacrylic acid, vinylcyclohexane, styrene or derivatives thereof can be used as a comonomer copolymerized with ethylene.
These α-olefins may be used alone or in combination of two or more.
The content of α-olefin in the ethylene / α-olefin copolymer is 10% by weight or less, preferably 0.1 to 10% by weight, and more preferably 0.1 to 5% by weight. If the α-olefin content is more than 10% by weight, the rigidity decreases, which is not preferable.

  More specifically, examples of specific ethylene polymers include medium density polyethylene (MDPE) and high density polyethylene (HDPE), and high density polyethylene is preferred.

  The ethylene-based polymer of the present invention can be obtained by mainly polymerizing ethylene using known catalysts such as a Ziegler catalyst and a metallocene catalyst. Preferably, polymerization is performed using a Ziegler catalyst comprising a transition metal compound such as titanium or zirconium, or a magnesium compound as a polymerization catalyst.

The ethylene polymer of the present invention may be a single polyethylene, but is preferably composed of a plurality of, for example, polyethylene components having two different physical properties.
The preferable aspect of what is comprised from the polyethylene component which has two different types of physical properties contains the following component (a) 23-84 weight% and component (b) 77-16 weight%.
Component (a): density is 0.915-0.940 g / cm ³ , high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) is 0.05-10 g / 10 min. Polyethylene A component (b) having a density of 0.940 to 0.970 g / cm ³ and a melt flow rate (MFR) (test conditions: 190 ° C., 2.16 kg load) of 1 to 300 g / 10 min.

Those composed of polyethylene components having two different physical properties are preferably polyethylene obtained by a continuous multistage polymerization method. For example, in a plurality of reactors connected in series during polymerization, the density of the first reactor is A high molecular weight polyethylene component (a) having a high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) of 0.05 to 10 g / 10 min of 0.915 to 0.940 g / cm ^3. In a second reactor with a density of 0.940-0.970 g / cm ³ and a melt flow rate (MFR) (test conditions: 190 ° C., 2.16 kg load) Is preferably produced by polymerizing 77 to 16% by weight of a low molecular weight polyethylene component (b) of 1 to 300 g / 10 min.

Contrary to the above, in the first reactor, the density is 0.940 to 0.970 g / cm ³ , and the melt flow rate (MFR) (test condition: 190 ° C., 2.16 kg load) is 1 to 300 g. / 10 minutes of low molecular weight polyethylene component (b) is polymerized 77 to 16 wt%, in the second reactor, the density is 0.915-0940 g / cm ³ , high load melt flow rate (HLMFR) (test Conditions: 190 ° C., 21.6 kg load) may polymerize the high molecular weight polyethylene component (a) of 0.05 to 10 g / 10 min by 23 to 84% by weight.

Further, a mixture obtained by separately polymerizing the predetermined high molecular weight polyethylene component (a) and the low molecular weight polyethylene component (b) and then blending a predetermined amount with a polymer may be called a so-called polyethylene composition. .
In addition, when producing polyethylene by continuous multistage polymerization, the amount of polyethylene produced in the second and subsequent reactors and its properties are determined by determining the amount of polyethylene produced in each stage (which can be determined by analysis of unreacted gas, etc.). The physical properties can be obtained by measuring the physical properties of the resin extracted after each stage and converting from the additivity of the physical properties.

If the density of the high molecular weight polyethylene component (a) according to the present invention is less than 0.915 g / cm ³ , the rigidity may be lowered. On the other hand, when the density exceeds 0.940 g / cm ³ , the durability is insufficient. Moreover, when the high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) of the high molecular weight polyethylene component (a) according to the present invention is less than 0.05 g / 10 minutes, the injection moldability is improved. On the other hand, if HLMFR exceeds 10 g / 10 min, durability and impact resistance are not satisfied.
Furthermore, when the density of the low molecular weight polyethylene component (b) according to the present invention exceeds 0.970 g / cm ³ , the impact resistance and durability are insufficient. On the other hand, if the density is less than 0.940 g / cm ³ , the rigidity cannot be ensured. Further, when the melt flow rate (MFR) (test condition: 190 ° C., 2.16 kg load) of the low molecular weight polyethylene component (b) according to the present invention is less than 1 g / 10 min, a problem occurs in the injection moldability, On the other hand, when MFR exceeds 300 g / 10 min, a problem is caused in durability, and the weld strength is remarkably deteriorated.
When the proportion of the high molecular weight polyethylene component (a) according to the present invention is less than 23% by weight (that is, when the proportion of the low molecular weight polyethylene component (b) according to the present invention exceeds 77% by weight), the durability improving effect When the proportion of the high molecular weight polyethylene component (a) according to the present invention exceeds 84% by weight (that is, when the proportion of the low molecular weight polyethylene component (b) according to the present invention is less than 16% by weight), injection molding Cause problems with sex.

Various known additives, fillers and the like can be added to the resin for injection-molded plastic fuel tanks comprising the ethylene polymer of the present invention in an appropriate amount within a range that does not significantly impair the effects of the present invention. Examples of additives include antioxidants (phenolic, phosphorus, sulfur), lubricants, antistatic agents, light stabilizers, colorants, pigments, dyes, ultraviolet absorbers, nucleating agents, neutralizing agents, and blocking agents. An inhibitor, a dispersant, a fluidity improver, a plasticizer, a mold release agent, a flame retardant, a compatibilizer, an adhesive, and the like can be appropriately used in combination of one or more. Moreover, as a filler, talc, mica, etc. can be used, for example.
Further, maleic anhydride-modified resin, thermoplastic resin, rubber and the like can be added to the resin for injection-molded plastic fuel tank of the present invention, if necessary.
Further, in the resin for injection molded plastic fuel tank of the present invention, for improving fuel permeability, polyamide such as nylon 6 or ethylene / vinyl alcohol copolymer is used as a fuel permeation-resistant resin (or fuel barrier resin). Combined (EVOH) can be used, preferably in combination with EVOH.

  The resin for injection-molded plastic fuel tank of the present invention can be formed into a molded product by a molding method such as an injection molding method, a hollow molding method, an extrusion molding method, etc. if necessary, but is preferably a material suitable for injection molding. Yes, it can be injection-molded at a low temperature and at a high speed.

7). Application As a molded product molded from the resin for injection molded plastic fuel tanks of the present invention, a large container by injection molding is particularly preferred. As the large container, an industrial chemical can, a drum can, a fuel tank or the like corresponds, and a plastic fuel tank is preferable.

The resin for injection-molded plastic fuel tank of the present invention may be injection-molded so that the orientation ratio according to the Charpy impact strength ratio is 50% or more, preferably 70% or more, more preferably 80% or more. Is preferred. When the orientation ratio based on the Charpy impact strength ratio is less than 50%, the impact strength of the molded product is lowered. The orientation ratio based on the Charpy impact strength ratio can be adjusted by appropriately changing the melting temperature of the resin at the time of injection molding according to the target physical properties.
Specifically, the orientation ratio based on the Charpy impact strength ratio can be reduced by increasing the melting temperature of the resin during injection molding.
The orientation ratio according to the Charpy impact strength ratio is determined from JIS K6922-2 (1997) "Plastic-polyethylene (PE) molding and extrusion materials-Part 2: How to make test specimens" In accordance with JIS K7111 (1996) “Plastic-Charpy impact strength test method”, the direction of the long side of the test piece is the flow direction of the resin. The Charpy impact strength value Sm measured with the sample cut out in the same direction and the Charpy impact strength value St measured with the sample cut out so that the direction of the long side of the test piece is perpendicular to the flow direction of the resin It is calculated from the ratio, St / Sm.

  The injection-molded plastic fuel tank according to the present invention can be molded by a known method, and can be obtained, for example, by welding the split molded bodies formed in two by injection molding at the welding portion. The fuel tank has a fuel permeation resistance, for example, a fuel barrier material (for example, the above-mentioned fuel permeation preventive resin) is mixed with the resin of the present invention and injection-molded, and the fuel barrier material is formed into a layer, It can be imparted by making it exist in a molded product in a shape or other shape. In addition, by combining a molded article molded from the resin of the present invention with a separately prepared fuel barrier material by adhesion or the like, and further coating a molded article molded from the resin of the present invention with a fuel barrier coating. Thus, fuel permeation resistance can be imparted. As the fuel barrier material, known materials can be used, such as EVOH (ethylene / vinyl alcohol copolymer) and nylon, resins such as clay, inorganic fillers such as clay, metals such as aluminum, and epoxy paints. Can be mentioned.

The resin for injection molded plastic fuel tank of the present invention is not only a large container, but also small parts attached to the large container, for example, industrial chemical cans, parts such as lids (caps), internal solution supply ports, or takeout ports in drum cans, In the fuel tank, a resin such as a fuel supply port, a valve, or a fuel pump fixing lid (cap) welded to the fuel tank main body can be suitably used. This small part is a hollow pipe-shaped small part that plays a role such as a handle, an internal solution supply port, or a discharge port, which is attached to a large container by welding and welding to the large container, and the opening of the large container. Various parts such as reinforcing parts, inlets, and opening liners can be listed.
Separate from so-called large containers, such as caps with caps on the inner surface for attaching to large container threads, such as caps for large containers, and caps that simply fit into the mouth of large containers. Small parts that have been redesigned into many predetermined shapes that are handled by the body can be targeted.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.
The physical properties of the resin were measured by the following method.

(1) Density: Measured according to JIS K7112 (1999).
(2) High load melt flow rate (HLMFR) (Test conditions: 190 ° C., 21.6 kg load): Measured according to JIS K6922-1 (1997). In addition, melt flow rate (MFR) (test conditions: 190 ° C., 2.16 kg load) was also measured according to JIS K6922-1 (1997).
(3) Shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ : Measured with a capillograph manufactured by Toyo Seiki Co., Ltd. using a nozzle having a diameter of 1.0 mmφ and a length of 40 mm.
(4) Charpy impact strength at −40 ° C .: A test piece was prepared according to JIS K6922-2 (1997) and measured according to JIS K7111 (1996).
(5) Rupture time in full-notch creep test (measured at 80 ° C., 6 MPa): Measured at 80 ° C., 6 MPa in accordance with the all-around notch tensile creep test of Appendix 1 of JIS K6774 (1995). The test piece was cut from a compression molded sheet with a thickness of 6 mm prepared under the conditions of JIS K6922-2 (1997) Table 2, and notched all around (test piece thickness 6 mm, notch depth 1 mm, full circumference). It was used.

(6) Injection moldability: Using an injection molding machine (IS150E manufactured by Toshiba Machine Co., Ltd.), molding was performed at a molding temperature of 230 ° C., a mold temperature of 40 ° C., and a cooling time of 20 seconds, and the appearance and dimensions of the molded product were measured. . As evaluation criteria, those having a good appearance and low molding shrinkage ratio were rated as ◎, those having no problem in appearance and having a low molding shrinkage ratio were marked as ◯, and those having a poor appearance or a large molding shrinkage ratio as x.
(7) Orientation ratio: A test piece was prepared from a molded article obtained by melting and injecting a resin in accordance with JIS K6922-2 (1997), and the long side of the test piece was in accordance with JIS K7111 (1996). Measured with Charpy impact strength value Sm measured with a sample cut so that the direction is the same as the resin flow direction, and with the sample cut so that the direction of the long side of the test piece is perpendicular to the resin flow direction The ratio of the Charpy impact strength value St was calculated from St / Sm.
(8) Impact resistance of injection-molded product: The resin is melt-mixed at 230 ° C., and using an injection molding machine (IS150E manufactured by Toshiba Machine Co., Ltd.), a molding temperature of 230 ° C., a mold temperature of 40 ° C., and a cooling time of 20 seconds. Under the conditions, it was molded into a rectangular parallelepiped box-shaped concave container having a length of 100 mm, a width of 100 mm, a height of 50 mm, a thickness of 3 mm, a weight of 120 g, and a volume of 500 ml. A rectangular box-shaped concave container having the same shape is manufactured by the same method, and two rectangular parallelepiped box-shaped concave containers are used. A sealed container was produced by welding together.
Next, a hole of about 10 mmφ is made in the upper surface of this sealed container, and a 50 wt% ethylene glycol aqueous solution is put through the hole and sealed, and a drop test is performed at a height of 6 m at −40 ° C. confirmed.
(9) Durability of injection molded product: resin is melt-mixed at 230 ° C., and using an injection molding machine (IS150E manufactured by Toshiba Machine Co., Ltd.), a molding temperature of 230 ° C., a mold temperature of 40 ° C., and a cooling time of 20 seconds. Then, it was molded into a rectangular parallelepiped box-shaped concave container having a length of 100 mm, a width of 100 mm, a height of 50 mm, a thickness of 3 mm, a weight of 120 g and a volume of 500 ml. A rectangular box-shaped concave container having the same shape is manufactured by the same method, and two rectangular parallelepiped box-shaped concave containers are used. A sealed container was produced by welding together. The molded container was stored at 80 ° C. for 1000 hours, and the presence or absence of abnormality was confirmed.
(10) Fuel permeation resistance of injection-molded product: resin is melt-mixed at 230 ° C., and molding temperature is 230 ° C., mold temperature is 40 ° C., and cooling time is 20 seconds using an injection molding machine (IS150E manufactured by Toshiba Machine Co., Ltd.). Under these conditions, a rectangular box-shaped concave container having a length of 100 mm, a width of 100 mm, a height of 50 mm, a thickness of 3 mm, a weight of 120 g, and a volume of 500 ml was formed. A rectangular box-shaped concave container having the same shape is manufactured by the same method, and two rectangular parallelepiped box-shaped concave containers are used. A sealed container was produced by welding together.
Next, a hole of about 10 mmφ was made in the upper surface of this sealed container, 700 ml of gasoline containing 10% by volume of ethanol was injected from the hole and sealed, and the change in weight after leaving at 40 ° C. for 200 hours was measured.

[Example 1]
(1) Preparation of solid catalyst component 20 g of magnesium ethylate (average particle size: 860 μm) commercially available in a nitrogen atmosphere in a 1 L pot (pulverization vessel) containing about 700 magnetic balls having a diameter of 10 mm. 1.66 g of aluminum trichloride and 2.72 g of diphenyldiethoxysilane were added. These were co-ground using a vibrating ball mill for 3 hours under conditions of an amplitude of 6 mm and a frequency of 30 Hz. After co-grinding, the contents were separated from the magnetic balls in a nitrogen atmosphere.
5 g of the co-ground product obtained as described above and 20 ml of n-heptane were added to a 200 ml three-necked flask. While stirring, 10.4 ml of titanium tetrachloride was added dropwise at room temperature, the temperature was raised to 90 ° C., and stirring was continued for 90 minutes. Then, after cooling the reaction system, the supernatant was extracted and n-hexane was added. This operation was repeated three times. The obtained pale yellow solid was dried at 50 ° C. under reduced pressure for 6 hours to obtain a solid catalyst component.

(2) Production of polyethylene (I) In a first polymerization liquid-filled loop reactor having an internal volume of 200 L, dehydrated and purified isobutane is 102 L / hr, triisobutylaluminum is 54 g / hr, and the solid catalyst is 3 Further, ethylene is continuously supplied at a rate of 14 kg / hr, hydrogen is 0.59 g / hr, and 1-hexene as a comonomer is continuously supplied at a rate of 1.38 kg / hr. Copolymerization of ethylene and 1-hexene was performed under conditions of 2 MPa and an average residence time of 0.9 hr.
A part of the polymerization reaction product was collected and measured for physical properties. As a result, HLMFR was 0.16 g / 10 min, and the density was 0.929 g / cm ³ .

Next, the isobutane slurry containing the first step polymerization product was introduced into the second step reactor having an internal volume of 400 L as it was, without adding catalyst and 1-hexene, 86 L / hr of isobutane and 18 kg / hr of ethylene. Hydrogen was continuously supplied at a rate of 36 g / hr, and polymerization in the second step was performed under the conditions of 90 ° C., polymerization pressure 4.1 MPa, and average residence time 1.6 hr. The HLMFR after drying of the polyethylene polymer discharged from the second step reactor was 15 g / 10 min, and the density was 0.948 g / cm ³ . In addition, the ratio of the high molecular weight component (polymer produced in the first step) was 45% by weight.
On the other hand, the MFR and density of the low molecular weight component polyethylene polymer produced in the second step are determined by separately polymerizing under the second stage polymerization conditions. The MFR is 80 g / 10 min and the density is 0.00. It was 946 g / cm ³ .

(3) Evaluation of polyethylene (I) Shear viscosity, Charpy impact strength, and rupture time in a full notch creep test (measured at 80 ° C. and 6 MPa) of this polyethylene (I) were measured.
Moreover, said impact resistance and durability were evaluated using polyethylene (I).
The evaluation results are shown in Table 1. Polyethylene (I) had good injection moldability and good impact resistance, Charpy impact strength, and durability.

[Example 2]
Polyethylene was produced in the same manner as in Example 1 except that the hydrogen supply amount was adjusted, and the density was 0.948 g / cm ³ , high load melt flow rate (HLMFR) (test conditions: 190 ° C., 21.6 kg load) Produced 20 g / 10 min of polyethylene (II).
The polyethylene was evaluated in the same manner as in Example 1 except that polyethylene (II) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (II) had good injection moldability, and all of impact resistance, Charpy impact strength and durability were good.

[Example 3]
Polyethylene was produced in the same manner as in Example 1 except that the hydrogen supply amount was adjusted, and the density was 0.948 g / cm ³ , high load melt flow rate (HLMFR) (test conditions: 190 ° C., 21.6 kg load) Produced polyethylene (III) of 10 g / 10 min.
The polyethylene was evaluated in the same manner as in Example 1 except that polyethylene (III) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (III) had good injection moldability, and all of impact resistance, Charpy impact strength and durability were good.

[Comparative Example 1]
Evaluation was performed in the same manner as in Example 1 except that Novatec HD HB111R (hereinafter referred to as “polyethylene (IV)”) manufactured by Nippon Polyethylene Co., Ltd. was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (IV) lacks fluidity in terms of injection moldability, and has a large shape accuracy and sink (large molding shrinkage ratio) and is not practical. The orientation ratio based on the Charpy impact strength ratio was 30%, and the impact resistance of the container was not satisfactory.

[Comparative Example 2]
A polyethylene was produced in the same manner as in Example 1 except that the 1-hexene supply amount and the hydrogen supply amount were adjusted, and the density was 0.957 g / cm ³ and the high load melt flow rate (HLMFR) (test condition: 190 ° C. 21.6 kg load) produced polyethylene (V) of 22 g / 10 min.
Evaluation was performed in the same manner as in Example 1 except that polyethylene (V) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (V) had a rupture time of 10 hours in a full notch creep test (measured at 80 ° C. and 6 MPa), had insufficient durability, and was in a level where the durability of the container could not be satisfied.

[Comparative Example 3]
Polyethylene was produced in the same manner as in Example 1 except that 1-hexene supply amount and hydrogen supply amount were adjusted, and the density was 0.935 g / cm ³ , high load melt flow rate (HLMFR) (test condition: 190 ° C. 21.6 kg load) produced a polyethylene (VI) of 35 g / 10 min.
Evaluation was performed in the same manner as in Example 1 except that polyethylene (VI) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (VI) was insufficient in impact resistance of the molded product, and was not a satisfactory level as a container.

[Comparative Example 4]
Polyethylene was produced in the same manner as in Example 1 except that the hydrogen supply amount was adjusted, and the density was 0.948 g / cm ³ , high load melt flow rate (HLMFR) (test conditions: 190 ° C., 21.6 kg load) Produced 5 g / 10 min polyethylene (VII).
Evaluation was performed in the same manner as in Example 1 except that polyethylene (VII) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (VII) had a small HLMFR, insufficient injection moldability, and was not a satisfactory level as an injection molding material.

[Comparative Example 5]
Polyethylene was produced in the same manner as in Example 1 except that the hydrogen supply amount was adjusted. The density was 0.948 g / cm ³ , and the high load melt flow rate (HLMFR) (test conditions: 190 ° C., 21.6 kg load) was obtained. 80 g / 10 min of polyethylene (VIII) was produced.
Evaluation was performed in the same manner as in Example 1 except that polyethylene (VIII) was used instead of polyethylene (I) in Example 1.
The evaluation results are shown in Table 1. Polyethylene (VIII) had a large HLMFR, a low Charpy impact strength at −40 ° C., and the impact resistance as a container was not satisfactory.

[Example 4]: Evaluation as a fuel tank 100 parts by weight of polyethylene (I), 1 part by weight of ethylene vinyl alcohol resin (EVOH) manufactured by Kuraray Co., Ltd. and 5 parts by weight of maleic anhydride-modified polyethylene manufactured by Nippon Polyethylene Co., Ltd. at 230 ° C. Melt and mix using an injection molding machine (IS150E manufactured by Toshiba Machine Co., Ltd.) at a molding temperature of 230 ° C., a mold temperature of 40 ° C., and a cooling time of 20 seconds. It was molded into a rectangular parallelepiped box-shaped concave container having a size of 3 mm, a weight of 120 g, and a volume of 500 ml.
A rectangular box-shaped concave container having the same shape is manufactured by the same method, and two rectangular parallelepiped box-shaped concave containers are used. A sealed container was produced by welding together.
For fuel permeation resistance, a hole of about 10 mmφ was made in the upper surface of the sealed container, and 400 ml of gasoline was put into the container through the hole and sealed, and the fuel permeation amount at a temperature of 40 ° C. for 8 weeks was measured by a gravimetric method.
The above injection moldability was good. As a result of evaluating the impact resistance, durability, and fuel permeation resistance of the molded product, there was no abnormality in the impact resistance and durability, and the fuel permeation resistance was 0.01 g / day. The orientation ratio was 53%. The evaluation results are shown in Table 1.

[Comparative Example 6]: Evaluation as a fuel tank Evaluation was performed in the same manner as in Example 4 except that polyethylene (IV) was used instead of polyethylene (I).
As a result, the injection moldability was poor (x). Moreover, as a result of evaluating the impact resistance, durability, and fuel permeation resistance of the molded product, cracks occurred in the impact resistance, the durability was not abnormal, and the fuel permeation resistance was 0.01 g / day. . The orientation ratio was 30%. The evaluation results are shown in Table 1.

[Reference Example 1]: Evaluation as a fuel tank Evaluation was performed in the same manner as in Example 4 except that ethylene vinyl alcohol resin (EVOH) manufactured by Kuraray Co., Ltd. was not used.
As a result, the injection moldability was good. Moreover, as a result of evaluating the impact resistance, durability, and fuel permeability of the molded product, there was no abnormality in the impact resistance and durability, and the fuel permeability was 0.13 g / day. The orientation ratio was 53%. The evaluation results are shown in Table 1.

  The molded product obtained from the resin of the present invention has a good balance between moldability and durability, in particular, a large injection molded plastic fuel tank with a good balance of injection moldability, durability and impact resistance, and excellent durability. And industrially very useful value.

Claims (4)

Polyethylene for injection-molded plastic fuel tanks containing the following component (a) 23 to 84% by weight and component (b) 77 to 16% by weight and satisfying the following requirements (1) to (5) Resin.
Component (a): density is 0.915-0.940 g / cm ³ , high load melt flow rate (HLMFR) (test condition: 190 ° C., 21.6 kg load) is 0.05-10 g / 10 min. Polyethylene Component (b): Polyethylene having a density of 0.940 to 0.970 g / cm ³ and a melt flow rate (MFR) (test conditions: 190 ° C., 2.16 kg load) of 1 to 300 g / 10 min (1 ) Density is in the range of 0.940-0.970 g / cm ³ (2) High load melt flow rate (HLMFR) (Test conditions: 190 ° C., 21.6 kg load) is 15-20 g / 10 min ( 3) The shear viscosity at 230 ° C. and a shear rate of 243 sec ⁻¹ is 10000 poise or less (4) The Charpy impact strength at −40 ° C. is 5 KJ / m ² or more ( 5) The rupture time in a full notch creep test (measured at 80 ° C. and 6 MPa) is 80 hours or more.   The polyethylene resin for an injection-molded plastic fuel tank according to claim 1, wherein the component (a) and the component (b) are obtained by a continuous multistage polymerization method.   An injection-molded fuel tank, which is molded using the polyethylene-based resin for an injection-molded plastic fuel tank according to claim 1 and has an orientation ratio of 70% or more based on a Charpy impact strength ratio.   3. An injection-molded fuel which is molded using the polyethylene-based resin for an injection-molded plastic fuel tank according to claim 1 or 2 and a fuel barrier material and has an orientation ratio of 50% or more according to a Charpy impact strength ratio. tank.