JPH0616719A - Polyethylenic polymer for blow molding - Google Patents

Abstract

PURPOSE:To obtain a polyethylenic polymer for blow molding excellent in molding processing characteristics or low-temperature impact resistance. CONSTITUTION:The polyethylenic polymer is an ethylene homopolymer or a copolymer, composed of ethylene and a >=3C alpha-olefin and having 2-6 (dl/g) intrinsic viscosity, 0.94-0.97 (g/cm<3>) density and 2X10<7> to 1X10<8> (poises) zero- shear viscosity (eta0) at 190 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-based polymer for blow molding, and particularly, in large blow molding, molding processing characteristics such as uniform stretchability and drawdown resistance, and impact resistance of molded products. The present invention relates to a polyethylene polymer for blow molding which is excellent (especially at low temperature).

[0002]

2. Description of the Related Art Hollow molding is a general thermoplastic resin molding method, and is used for small containers such as cosmetic bottles and detergent bottles to medium-sized containers such as kerosene cans and industrial chemical cans, automobile fuel tanks,
Widely used in large containers such as drums. Hollow molding includes a process of extruding a cylindrical molten resin (parison) from an annular die and a process of sandwiching a parison with a mold and blowing compressed air to shape it.

Generally, when a large-sized product is hollow-molded, the parison tends to sag under its own weight (drawdown) and uneven thickness tends to occur during shaping. In order to reduce drawdown and uneven thickness, a method is known in which a resin having a sufficiently high melt tension and a large stress increase during melt drawing is used. In addition, the hollow molded product has environmental stress crack resistance (“ES
Mechanical strength such as impact resistance (CR) is required. Especially for automobile fuel tanks, the impact resistance test at −40 ° C. is defined by the Ministry of Transport technical standard (own vehicle No. 1327).

[0004]

Conventionally, as a method for obtaining polyethylene excellent in molding process characteristics (uniform stretchability, drawdown resistance, etc.) as well as mechanical strength, for example,
Multi-stage polymerization method using Ziegler type catalyst (Japanese Patent Laid-Open No. 2-5
No. 3811, JP-A-2-132109), a method of adding a small amount of a radical generator and a crosslinking aid to a polyethylene resin (Japanese Patent Publication No. 2-52654), and the like are known. However, the polyethylene produced by the above method is insufficient in molding processing characteristics and low temperature impact resistance in order to obtain a large hollow molded article. The present invention has been made in view of the above circumstances, and an object thereof is to overcome the drawbacks of conventional polyethylene and to provide a polyethylene polymer for blow molding which is excellent in molding processing characteristics and low temperature impact resistance. It is in.

[0005]

That is, the gist of the present invention is an ethylene homopolymer or a copolymer composed of ethylene and an α-olefin having 3 or more carbon atoms and having an intrinsic viscosity of 2 to 6 (dl / g) and the density is 0.94 to 0.97 (g /
cm ³ ), the _zero shear viscosity (η ₀ ) at 190 ° C. is 2 × 10
⁷ to 1 × 10 ⁸ (poise), which is a polyethylene polymer for blow molding.

The present invention will be described in detail below. The present invention is an ethylene homopolymer or a copolymer composed of ethylene and an α-olefin having 3 or more carbon atoms, and is a polyethylene-based polymer having a zero shear viscosity (η ₀ ), an intrinsic viscosity and a density adjusted to a specific range. This was achieved based on the finding that the coalescence is excellent in molding processing characteristics such as drawdown resistance and uniform stretchability, and low temperature impact resistance.

The polyethylene polymer for blow molding of the present invention (hereinafter simply referred to as "polymer") is an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 or more carbon atoms. Examples of the α-olefin having 3 or more carbon atoms include propylene, butene, pentene,
Hexene, 4-methylpentene-1, octene, decene and the like can be mentioned.

The polymer of the present invention has a temperature of 130 ° C. in tetralin.
It is necessary that the intrinsic viscosity measured in step 2 is within the range of 2 to 6 (dl / g), preferably 2.3 to 3.6 (dl / g). When the intrinsic viscosity is less than 2 (dl / g), the strength is lowered and the molding processing characteristics such as drawdown resistance are also lowered. On the other hand, when the intrinsic viscosity is higher than 6 (dl / g), the extrudability becomes poor and the molded product also has rough skin.

The polymer of the present invention has a density of 0.94.
~0.97 (g / cm ^3), preferably from 0.95 to 0.9
It must be within the range of 65 (g / cm ³ ). If the density is less than 0.94 (g / cm ³ ), the rigidity will decrease. On the other hand, when the density is higher than 0.97 (g / cm ³ ), the impact strength and the ESCR decrease.

Furthermore, the polymer of the present invention has a _zero shear viscosity (η ₀ ) at 190 ° C. of 2 × 10 ⁷ to 1 × 10 ⁸ (po).
ise), preferably 2.5 × 10 ^{7 to} 6 × 10 ⁷ (p
It must be within the range of (oise). When the zero shear viscosity (η ₀ ) is smaller than 2 × 10 ⁷ (poise), the stress increase during melt drawing is small, and the uniform drawability is lowered, and at the same time, the low temperature impact resistance is lowered. On the other hand, when the _zero shear viscosity (η ₀ ) is larger than 1 × 10 ⁸ (poise), the moldability such as extrudability decreases.

The polymer of the present invention generally comprises a combination of a solid catalyst called a Phillips type (chromium type) catalyst or a Ziegler type (titanium type) catalyst and a cocatalyst organometallic compound depending on the kind of the catalyst component. Manufactured using a catalytic system comprising: Examples of the catalyst component of the chromium-based catalyst include a component in which a chromium compound is supported on silica or silica-alumina. As the catalyst component of the titanium-based catalyst, titanium trichloride, vanadium trichloride, titanium tetrachloride, or a component in which a halo alcoholate of titanium is supported on a magnesium compound-based simple substance, or a coprecipitate or a eutectic of a magnesium compound and a titanium compound, etc. Is mentioned.

[0012] As the co-catalyst is generally an organic aluminum compound, for example, the general formula _{Al · R m · X 3-} m ( wherein, R
Is a hydrocarbon group having up to 20 carbon atoms, X is a halogen atom,
and m represents a number of 1 to 3).

In the present invention, examples of preferable catalysts include a catalyst obtained by combining chromium oxide supported on silica or silica-alumina and an organic aluminum compound, or an oxygen-containing organic compound of magnesium and an oxygen-containing organic compound of titanium. Examples of the catalyst include a reaction product of an aluminum halogen compound and an organoaluminum compound.

The polymerization reaction can be carried out according to a commonly used method such as a slurry polymerization method or a solution polymerization method carried out in an inert hydrocarbon solvent, or a gas phase polymerization method carried out in a gas phase substantially free of a liquid phase. I can. The polymerization reaction may be either a batch polymerization method or a continuous polymerization method.
It is also possible to carry out a multistage polymerization method of more than one step.

[0015]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, the physical property tests were conducted according to the following methods. (1) Intrinsic viscosity [η] Measured in tetralin at 130 ° C. (2) Density The density was measured according to JIS K6760.

(3) Zero Shear Viscosity (η ₀ ) As a measuring device, a stress rheometer (“RSR-M”) manufactured by Rheometrics was used. This device can determine the melt shear viscosity in the low shear rate region from the creep characteristics. 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-mentioned steady value. The fixture was a cone-plate type, and had a diameter of 25 mm and an angle between the cone and the plate of 0.1 rad. As the measurement sample, pellets were molded into a sheet having a thickness of about 1 mm by a press molding machine and used. The measurement temperature is 190 ° C.

(4) Melt tension (MT) A "melt tension tester" manufactured by Toyo Seiki was used. Sample melted at 190 ° C, diameter 1mm, length 5m
m, constant velocity from an orifice with an inflow angle of 60 °: 0.44
The tension when extruded at g / min and taken out at 0.94 m / min was obtained. The draft rate (take-off speed / nozzle linear speed) was 1.25. (5) Izod impact strength It was measured in accordance with JIS K7110. Measurement temperature is 2
3 ° C and -40 ° C.

(6) Drawdown resistance A large blow molding machine of accumulator type (screw diameter: 90 mm, screw L / D: 22, screw compression ratio: 3.8, die diameter 200 mm) was used, and a resin temperature of 190 was used. A parison having a uniform wall thickness was extruded under the conditions of ° C and a weight of 15 kg, and the parison length immediately after the extrusion and after 40 seconds from the extrusion were compared. (7) Uniform stretchability Sumitomo Heavy Industries blow molding machine ("Bekum BA-2")
Was used, the resin temperature was set to 200 ° C., and the maximum depth of the pin that did not cause blowout when molded was determined by a mold having a variable protruding pin with a diameter of 19 mm and a length of 0 to 40 mm.

Example 1 Commercially available silica was impregnated with an aqueous solution of chromium trioxide to obtain 120
After drying at ℃, activated at 800 ℃ dry air to obtain a catalyst component with a carrier containing 1% by weight of chromium. In a 400 liter reactor, 1000 g of the above-mentioned carrier-supported catalyst component,
Triethylaluminum (21.9 g) and n-hexane (200 liters) were charged, and 5 kg of ethylene was supplied at 80 ° C. for 1 hour to carry out reaction while maintaining the hydrogen / ethylene pressure ratio of the reactor at 1.0, thereby catalyzing the catalyst. A polyethylene mixture was obtained. The catalyst-polyethylene mixture was washed by decantation using n-hexane.

The catalyst-polyethylene mixture obtained above was fed to a reactor having a capacity of 1 m ^{3 in} the form of n-hexane slurry. The supply rate is 200 L / n as n-hexane.
hr, and about 3.7 g / hr as a catalyst component. At the same time, 1.8 g of diethyl aluminum monoethoxide /
Feed at a rate of hr. Then, while adjusting the partial pressure ratio of hydrogen / ethylene in the gas phase to 0.6 and the partial pressure ratio of 1-butene / ethylene to 0.004, copolymerization of ethylene and 1-butene was carried out at a polymerization temperature of 85 ° C. .. The physical properties of the obtained polyethylene polymer were measured, and the results are shown in Table 1.

Example 2 In Example 1, the gas phase hydrogen / ethylene partial pressure ratio was 0.1, the 1-butene / ethylene partial pressure ratio was 0.005,
The same operation as in Example 1 was performed except that the polymerization temperature was changed to 90 ° C. The physical properties of the obtained polyethylene polymer were measured, and the results are shown in Table 1.

Example 3 The same conditions as in Example 1 were adopted, and homopolymerization of ethylene was carried out at a gas phase hydrogen / ethylene partial pressure ratio of 0.3.
The physical properties of the obtained polyethylene polymer were measured, and the results are shown in Table 1.

Example 4 115 g of Mg (OC ₂ H ₅ ) ₂ and 151 g of Ti (O
C ₄ H ₉ ) ₃ Cl and 37 g of n-butyl alcohol were mixed at 150 ° C. for 6 hours for homogenization, then cooled, and a predetermined amount of benzene was added to obtain a uniform solution. Next, 457 g of ethylaluminum sesquichloride was added dropwise to the above homogeneous solution at a predetermined temperature, and the mixture was stirred for 1 hour. Further, the solid catalyst 220 is washed by repeating washing with n-hexane.
g was obtained.

Using 5 batches (about 1 kg) of the solid catalyst obtained above, continuous polymerization was carried out using an apparatus in which two 0.6 m ³ reactors were connected in series. In the first polymerization tank, n-hexane was fed at a rate of 53 kg / hr, diethyl aluminum monochloride at 4.5 g / hr, a solid catalyst component at 0.9 g / hr, and ethylene at a rate of 31 kg / hr. At the same time, hydrogen was continuously supplied, the temperature was maintained at 90 ° C., and the hydrogen / ethylene molar ratio in the gas phase was maintained at 0.8 to carry out continuous polymerization.

In the second polymerization tank, the slurry of the polymer obtained in the first polymerization tank was continuously supplied, and n-hexane was 33 kg / hr, 1-butene was 7 kg / hr,
Ethylene was fed at a rate of 13 kg / hr and the temperature was adjusted to 50
Maintained at ℃, hydrogen / ethylene molar ratio in gas phase is 0.03
The continuous polymerization was carried out while purging the gas phase gas at a rate of 8.5 kg / hr so as to be maintained at. And the first
A polyethylene polymer having a polymer fraction of the second and second stages of 85/15 was obtained.

Example 5 In Example 4, the polymer ratio of the first stage and the second stage was 80 /.
Two-step polymerization was carried out in the same manner as in Example 4 except that the number was 20,
A polymer having a [μ] = 4.20 was obtained. The physical property measurement results are shown in Table 1.
It was shown to.

Example 6 In Example 4, the polymer ratio of the first stage and the second stage was 75 /
Two-step polymerization was carried out in the same manner as in Example 4 except that
A polymer having a [μ] = 5.30 was obtained. The physical property measurement results are shown in Table 1.
It was shown to.

Comparative Example 1 The same as Example 1 except that the amount of diethylaluminum monoethoxide supplied was changed to 0.3 g / hr and the partial pressure ratio of vapor phase hydrogen / ethylene was changed to 4.0. Operated. The physical properties of the obtained polyethylene-based polymer were measured, and the results are shown in Table 2.

Comparative Example 2 Continuous polymerization was carried out using the same catalyst and equipment as in Example 4. In the first polymerization tank, the temperature is 77 ° C.
And n-hexane was 83 kg / hr, diethylaluminum was 5.5 kg / hr, and the solid catalyst component was 1.5 g / hr.
hr and ethylene were supplied at a rate of 28 kg / hr. Then, at the same time, hydrogen was continuously supplied. The obtained polymer slurry was continuously supplied to the second polymerization tank. In the second polymerization tank, the temperature was set to 65 ° C and n-hexane was adjusted to 72
kg / hr, 1-butene were fed at a rate of 5.5 kg / hr, and ethylene was fed at a rate of 19 kg / hr. Then, a polyethylene-based polymer having a polymer fraction of the first stage and the second stage of 85/15 was obtained.

Comparative Example 3 A commercially available polyethylene-based polymer (“Showlex 4551H” manufactured by Showa Denko KK) was used.

[0031]

[Table 1] Example 1 2 3 4 5 6 ─────────────────────────────────── Intrinsic viscosity [Η] (dl / g) 2.41 2.35 3.10 3.56 4.20 5.30 Density (g / cm ³ ) 0.953 0.954 0.957 0.954 0.954 0.954 Zero shear viscosity η ₀ (× 10 ⁷ poise) 4.70 3.38 5.85 2.62 4.48 9.00 Melt tension (g) 10.2 10.8 13.0 8.3 11.0 15.0 Izod impact strength (Kg · cm / cm) 23 ℃ 23 20 29 27 ＞ 50 NB -40 ℃ 19 18 24 23 NBNB Drawdown property (cm) 25 shrink 20 shrink 28 shrink 17 shrink 23 shrink 29 uniform Stretchability (mm) 37 29 39 33 37 39 ─────────────────────────────────────

[0032]

[Table 2] Comparative Example 1 2 3 ────────────────────────────── Intrinsic viscosity [η] (dl / g) 2.64 2.95 2.33 Density (g / cm ³ ) 0.951 0.954 0.951 Zero shear viscosity η ₀ (× 10 ⁷ poise) 1.25 1.15 1.47 Melt tension (g) 8.5 5.4 9.7 Izod impact strength (Kg · cm / cm) 23 ° C. 20 20 22 − 40 ° C 12 16 6 Drawdown property (cm) 12 Elongation 5 Elongation 20 Shrinkage Uniform stretchability (mm) 22 19 30 ───────────────────────── ──────

[0033]

According to the present invention described above, there is provided a polyethylene polymer for blow molding which is excellent in molding processing characteristics such as uniform stretchability and drawdown resistance, and particularly in impact resistance at low temperature. . The polyethylene polymer for hollow molding of the present invention can be suitably used as a large hollow molding material for gasoline tanks, drums and the like.

Claims (1)

[Claims] 1. An ethylene homopolymer or a copolymer composed of ethylene and an α-olefin having 3 or more carbon atoms, having an intrinsic viscosity of 2 to 6 (dl / g) and a density of 0.94 to.
0.97 (g / cm ³ ), 190 ° C zero shear viscosity (η
₀ ) is 2 × 10 ⁷ to 1 × 10 ⁸ (poise), a polyethylene polymer for blow molding.