JP4925593B2 - Polyethylene polymer composition - Google Patents

Description

  The present invention relates to a polyethylene polymer composition. More specifically, the present invention relates to a polyethylene polymer composition excellent in mechanical properties such as strength and rigidity and molding processability, and is suitable for hollow molding, injection molding, extrusion molding, film / sheet molding, various containers, lids The present invention relates to a polyethylene polymer composition that is used for bottles, pipes, films, sheets, packaging materials, and the like, and particularly suitable for large-sized hollow molding applications, and molded articles thereof.

Conventionally, polyethylene polymers produced using chromium-based catalysts (hereinafter referred to as chromium-catalyzed polyethylene) are generally used as polyethylene polymers suitable for hollow molding because of their relatively wide molecular weight distribution. Yes. However, although such chromium-catalyzed polyethylene has an appropriate melt tension and swell that facilitates hollow molding, it has a drawback of insufficient environmental stress crack resistance (hereinafter referred to as ESCR).
On the other hand, in Patent Document 1, Patent Document 2, Patent Document 3, etc., a polyethylene polymer produced by single-stage or multi-stage polymerization using a Ziegler catalyst has a wide molecular weight distribution suitable for hollow molding. It is disclosed as. However, although the polyethylene polymer obtained by such a method has excellent physical properties such as high ESCR, it has the disadvantages that melt tension, swell (described later), draw-down resistance is low, and hollow molding is difficult. .

As a method for improving these disadvantages, it is known that a method of mixing a chromium-based polyethylene and a polyethylene-based polymer produced by multistage polymerization using a titanium-based catalyst is effective, and molding such as hollow, extrusion, etc. Widely used in the field. Polyethylene polymer compositions comprising such a chromium catalyst polyethylene and a polyethylene polymer produced by multistage polymerization using a titanium catalyst include, for example, Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 7. In other words, it is disclosed as a polyethylene polymer composition having excellent physical properties such as ESCR and molding processability.
However, in recent years, there has been an increasing trend toward resource saving due to the response to environmental problems, and there has been an increasing demand for reducing the thickness of a molded body such as a hollow molded body. If the thickness of the molded body is reduced, buckling and deformation are likely to occur when stacking containers and filling the contents, so it is necessary to increase the rigidity and ensure the strength. However, increasing the rigidity decreases the ESCR. There is a problem such as. In particular, in large-scale hollow molding, when thin-wall molding is performed, unevenness called melt fracture occurs on the parison (cylindrical molten resin extruded during hollow molding) surface, and the appearance of the molded body is significantly deteriorated. is there. Therefore, the above-described conventional technology has a drawback that it cannot cope with the demand for thin molding.

JP-A-2-123108 Japanese Patent Laid-Open No. 4-18407 Japanese Patent Laid-Open No. 5-230136 Japanese Patent Publication No. 1-1777 Japanese Examined Patent Publication No. 1-1778 Japanese Examined Patent Publication No. 1-12781 Japanese Patent Laid-Open No. 11-302465

  The present invention improves the drawbacks of the prior art, and in a specific polyethylene polymer composition comprising a chromium catalyst polyethylene and a polyethylene polymer produced using a titanium catalyst, the rigidity and ESCR It is an object of the present invention to provide a polyethylene polymer composition excellent in balance and having a good appearance of a molded body, particularly a polyethylene polymer composition suitable for large-scale hollow molding applications.

As a result of extensive research to improve the drawbacks of the prior art, the present invention is a specific product comprising a polyethylene polymer produced using a chromium catalyst and a polyethylene polymer produced using a titanium catalyst. Surprisingly, it has been found that the polyethylene-based polymer composition has an excellent balance between rigidity and ESCR, has a good appearance of the molded body, and can solve the above-mentioned problems, and has led to the present invention.
That is, this invention is invention of following (1) to ( 4 ).
(1) A polyethylene-based polymer (A) manufactured using a chromium-based catalyst and a polyethylene-based polymer (B) manufactured by two-stage polymerization using a titanium-based Ziegler catalyst. The amount of the polymer (A) is in the range of 5 to 95% by weight, the composition has an HLMFR (described later) of 1 to 15 g / 10 min, a density of 940 to 965 kg / m ³ , gel permeation, The value of the ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn obtained from chromatography (GPC) is 10 to 19, and the comonomer distribution parameter P obtained from GPC-FTIR (described later) is 0 ≦ P ≦ 0. .05, a polyethylene polymer composition,
(2) The polyethylene-based polymer as described in (1) above, wherein the polyethylene-based polymer (A) is produced by a combination of a chromium-based catalyst treated with an organometallic compound and a promoter. Polymer composition,
( 3 ) The polyethylene polymer composition as described in (1) or (2) , which is used for large-scale hollow molding.
( 4 ) A large-sized hollow molded article comprising the polyethylene polymer composition according to ( 3 ).

  The polyethylene-based polymer composition of the present invention has excellent mechanical properties such as rigidity and ESCR, and also has good melt properties such as melt tension and swell. Furthermore, when thin-wall molding is performed by large-scale hollow molding of 20 liters or more, a hollow molded body having a good appearance can be obtained.

Hereinafter, the present invention will be described in detail.
The HLMFR of the polyethylene polymer composition of the present invention is 1 to 15 g / 10 minutes, preferably 2 to 10 g / 10 minutes, more preferably 4 to 8 g / 10 minutes. If the HLMFR is less than 1 g / 10 minutes, the extrudability and the surface skin of the product are deteriorated. If the HLMFR is more than 15 g / 10 minutes, drawdown occurs and molding becomes difficult.
The density of the polyethylene polymer composition of the present invention is 940 to 965 kg / m ³ , preferably 945 to 960 kg / m ³ , more preferably 946 to 951 kg / m ³ , and still more preferably 946 to 949 kg / m ^3. m is ^3. Density insufficient rigidity is less than 940 kg / ^{m 3,} higher than 965 kg / ^{m 3} is insufficient ESCR.

The molecular weight distribution (Mw / Mn) of the polyethylene polymer composition of the present invention is preferably 10-25. If Mw / Mn is less than 10, the extrusion load at the time of molding becomes too high and molding becomes difficult, and if it exceeds 25, the appearance is improved in thick molding, but melt fracture tends to occur in thin molding. The appearance of the molded product becomes worse. Also, the impact resistance is reduced. Mw / Mn is more preferably 15 to 25, and further preferably 15 to 20.
In the polyethylene polymer composition of the present invention, it is desirable that the terminal methyl group concentration observed by GPC-FTIR measurement satisfies a constant or increasing relationship with respect to the increase in molecular weight in the polymer region. This means that a comonomer component is selectively introduced into the high molecular weight component important for the expression of mechanical properties in the polyethylene polymer composition. If the comonomer content of the high molecular weight component is increased, the number of tie molecules connecting between lamellae (crystal parts) increases, and interlamellar breakage hardly occurs, so that ESCR and impact resistance increase. Here, the terminal methyl group concentration is determined by the absorbance I (—CH ₂ —) (absorption wave number: 2,925 cm ⁻¹ ) attributed to the methylene group analyzed by infrared analysis and the absorbance I (—CH ₂ ) attributed to the methyl group. ₃ ) (absorption wave number; 2,960 cm ⁻¹ ) ratio, I (—CH ₃ ) / I (—CH ₂ —) Hereinafter, this ratio at a certain molecular weight M (i) on the GPC curve is defined as C (M (i)).
In the present invention, the comonomer distribution parameter is a least squares approximate linear relationship between C (M (i)) and molecular weight M (i) C (M (i)) = P × log (M (i)) + Q (4 )
The coefficient P in is shown.

In the present invention, 0 ≦ P ≦ 0.05, preferably 0.001 ≦ P ≦ 0.05, and more preferably 0.002 ≦ P ≦ 0.05.
When P is smaller than 0 (that is, negative), it indicates that the comonomer concentration in the polymer region of the polyethylene polymer composition is low, and the ESCR decreases. Even when P is less than 0, if the comonomer content is increased, the ESCR is improved to some extent, but this is not preferable because the density decreases and the rigidity decreases. On the other hand, lowering the MFR also improves the ESCR, but it is not preferable because molding processability decreases. Therefore, in order to increase ESCR without deteriorating rigidity and moldability, it is necessary to set P to 0 or more. Moreover, it is practically difficult to obtain a polyethylene polymer composition in which P exceeds 0.05.

Here, when calculating P, C (M (i)) at the point where the peak value of the GPC curve is small is not used for the calculation because the accuracy decreases. Further, C (M (i)) in the region below the maximum value M (max) of the GPC curve is not used for calculation because the influence of the terminal methyl groups at both ends of the molecule is large. That is, as shown in FIG. 1, the polymer side from M (max) is set as the P calculation region in a range that is 30% or more of the peak value of M (max).
In the present invention, in order to control P to 0 or more, for example, in the production of low molecular weight components of the polyethylene polymer (A) and the polyethylene polymer (B), homopolymerization of ethylene is carried out to produce a polyethylene polymer ( In the production of the high molecular weight component B), copolymerization of ethylene and α-olefin may be performed. Furthermore, in the production of the polyethylene polymer (B), it is desirable to use a catalyst having good copolymerization, that is, a catalyst capable of introducing many comonomers in the high molecular weight region.

The weight average molecular weight (Mw) of the polyethylene polymer composition of the present invention is preferably 150,000 to 300,000, more preferably 180,000 to 280,000, and still more preferably 200,000 to 250,000. If Mw is less than 150,000, the ESCR is insufficient, and if it is higher than 300,000, melt fracture tends to occur in thin-wall molding, and the appearance of the molded article deteriorates.
The swell of the polyethylene polymer composition of the present invention is preferably 35-60. If the swell is less than 35, the pinch-off fusion part (resin junction between the molds) tends to be thin, and if the swell is 60 or more, the time required to extrude the parison of the length required for molding Longer and lower molding cycle. Therefore, the swell of the polyethylene-based polymer composition of the present invention is more preferably 37 to 47, and further preferably 37 to 42.

  In the polyethylene polymer composition of the present invention, the melt tension (MT) and the high load melt index (HLMFR) satisfy the relationship of −25 × Log (HLMFR) + 30 ≦ MT ≦ −25 × Log (HLMFR) +50. Preferably, more preferably −25 × Log (HLMFR) + 35 ≦ MT ≦ −25 × Log (HLMFR) +45, and still more preferably −25 × Log (HLMFR) + 38 ≦ MT ≦ −25 × Log (HLMFR) +40 It is to satisfy the conditions. If the relationship between MT and HLMFR is MT ≦ −25 × Log (HLMFR) +30, drawdown will occur, and if MT ≧ −35 × Log (HLMFR) +50, the resin will not stretch well during molding, both will be molded Becomes difficult.

The melt elongation (ME) of the polyethylene polymer composition of the present invention is preferably 4-20. If ME is less than 4, the uniform stretchability of the molten resin is lowered, and uneven thickness tends to occur in the hollow molded body, which is not preferable. If ME is 20 or more, a problem that the thickness of the pinch-off fusion part becomes thin is likely to occur. Accordingly, the ME of the polyethylene polymer composition of the present invention is more preferably 4-15, and further preferably 6-12.
In the polyethylene-based polymer composition of the present invention, the number of terminal vinyl groups in 10,000 carbon atoms is preferably 10 or less, more preferably 7 or less, and even more preferably 6 or less. . When the number of terminal vinyl groups is more than 10, the thermal stability at the time of molding processing is lowered, and resin degradation products such as crosslinked gel and koge are likely to occur.

The polyethylene polymer composition of the present invention is composed of two types of polyethylene polymers (A) and (B).
The polyethylene polymer (A) is obtained by homopolymerizing ethylene or copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms using a chromium catalyst.
In the present invention, examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-decene, It is selected from the group consisting of dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

Next, a catalyst for producing the polyethylene polymer (A) and a method for producing (A) will be described.
The chromium-based catalyst used for producing the polyethylene-based polymer (A) is a known catalyst such as a solid catalyst in which a chromium compound is supported on an inorganic oxide carrier, or a catalyst in which the solid catalyst and an organometallic compound are combined. Is mentioned. Specifically, JP-B Nos. 44-2996, 47-1365, 44-3827, 44-2337, 47-19985, 45-40902, 49 No. 38986, No. 56-18132, No. 59-5602, No. 59-50242, No. 59-5604, Japanese Patent Publication No. 1-1277, No. 1-112778, No. 1 -12781, JP-A-11-302465, JP-A-9-25312, JP-A-9-25313, JP-A-9-25314, JP 7-503739, US Pat. No. 5,104,841 No. 5,137,997 and the like.

Among these known catalysts, those produced by a combination of a chromium-based catalyst treated with an organometallic compound and a co-catalyst are particularly suitable for melt tension (MT) and melt elongation (ME). ), Swell, draw-down resistance, etc., and therefore suitable as a chromium-based catalyst used in the present invention.
The polyethylene-based polymer (A) of the present invention is a chromium oxide catalyst produced by a method described in JP-A-2001-294613 and the like, supported on a refractory compound and activated by heat treatment in a non-reducing atmosphere. And a solid catalyst component obtained by mixing an organoaluminum compound containing both an alkoxy group and a hydrosiloxy group, and an organoaluminum compound containing an alkoxy group. Is more preferred.

In order to obtain the polyethylene polymer (A) of the present invention, the most preferred polymerization catalyst is a chromium oxide catalyst supported on a refractory compound and activated by heat treatment in a non-reducing atmosphere, and the following general formula (1): And a solid catalyst component obtained by mixing an organoaluminum compound containing both an alkoxy group and a hydrosiloxy group, and an organoaluminum compound containing an alkoxy group represented by the following general formula (2) Is a polymerization catalyst.
_{^{AlR 1 p H q (OR 2}} ) x (OSiHR 3 R 4) y (1)
(Wherein p ≧ 1, 0 ≦ q ≦ 1, x ≧ 0.25, y ≧ 0.15, 0.5 ≦ x + y ≦ 1.5 and p + q + x + y = 3, R ¹ , R ² , R ³ , R ⁴ represents the same or different hydrocarbon group having 1 to 20 carbon atoms.
AlR ⁵ _3-n (OR ⁶ ) _n (2)
(In the formula, 0 <n ≦ 1, R ⁵ and R ⁶ represent the same or different hydrocarbon groups having 1 to 20 carbon atoms.)

The polyethylene polymer (A) of the present invention can be produced by a known method such as suspension polymerization, solution polymerization, or gas phase polymerization.
The HLMFR of the polyethylene polymer (A) is preferably 1 to 100 g / 10 minutes, more preferably 3 to 20 g / 10 minutes, and further preferably 8 to 15 g / 10 minutes.
The density of the polyethylene polymer (A) is preferably 940 to 965 kg / m ³ . If the density is lower than 940 kg / m ³ , the rigidity of the polyethylene polymer composition of the present invention cannot be sufficiently secured, which is not preferable. The density of the polyethylene polymer (A) is more preferably 955 to 965 kg / m ³ , and still more preferably 960 to 964 kg / m ³ .
The polyethylene polymer (B) is a polyethylene polymer produced using a titanium catalyst.

Next, a catalyst for producing the polyethylene polymer (B) and a method for producing (B) will be described.
As the titanium-based catalyst in the present invention, a porous polymer material (however, the matrix is, for example, polyethylene, polypropylene, polystyrene, ethylene-propylene copolymer, ethylene-vinyl ester copolymer, styrene-divinylbenzene copolymer, Polyolefin such as ethylene-vinyl ester copolymer or completely saponified product and modified products thereof, thermoplastic resin such as polyamide, polycarbonate, polyester, thermosetting resin such as phenol resin, epoxy resin, urea resin, melamine resin, etc. Inorganic solid oxides of elements belonging to Group 2 to 4, 13 or 14 of the periodic table (for example, silica, alumina, magnesia, magnesium chloride, zirconia, titania, boron oxide, calcium oxide, zinc oxide, barium oxide) , Vanadium pentoxide, acid Chromium, thorium oxide, or a carrier such as these mixtures or composite oxides of these), it may be mentioned catalysts carrying a titanium compound, a known catalyst

Preferred catalysts in the present invention include, for example, (a) an organomagnesium compound represented by the following general formula (3): M _α Mg _β R ¹ _p R ² _q X _r Y _s (3)
(In the formula, α is 0 or a number greater than 0, p, q, r, s is 0 or a number greater than 0, and p + q + r + s = mα + 2β, and M is Group I to Group III of the Periodic Table) M is a valence of M, R ¹ and R ² are hydrocarbon groups having the same or different number of carbon atoms, X and Y are the same or different groups, halogen, OR ³ , OSiR ⁴ R ⁵ R ⁶ , NR ⁷ R ⁸ and SR ⁹ are represented, R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are hydrogen atoms or hydrocarbon groups, and R ⁹ is a hydrocarbon group) (B) among (a) to (c) of a titanium compound containing at least one halogen atom and (c) a halide compound of Al, B, Si, Ge, Sn, Te, Sb, (a) ) And (b) or (a), (b) and (c) And [A], is made of an organic metal compound [B].

The organometallic compound [B] is a compound of Groups I to III of the periodic table, and is particularly preferably an organoaluminum compound or an organomagnesium compound complex containing an organoaluminum compound.
The reaction of the catalyst component [A] and the organometallic compound component [B] component can be carried out by adding both components in the polymerization system and proceeding with the polymerization under the polymerization conditions. May be.
The reaction ratio of the catalyst component is preferably in the range of 1 to 3000 mmol of the [B] component with respect to 1 g of the [A] component.

Specifically, JP-B-52-36788, 52-36790, 52-36791, 52-35792, 52-50070, 52-36794, 52-36795, 52-36796, 52-36915, 52-36917, 53-6019 Nos. 50-21876, 50-31835, 50-72044, 50-78619, 53-40696, and WO 99/28353.
The polyethylene polymer (B) of the present invention can be produced by a known method such as suspension polymerization, solution polymerization, or gas phase polymerization.
The polyethylene polymer (B) is preferably a polymer comprising a low molecular weight portion and a high molecular weight portion, which is two-stage polymerized using a titanium catalyst, and the MFR of the low molecular weight portion is preferably 1 It is -300g / 10min, More preferably, it is 5-50g / 10min, More preferably, it is 5-20g / 10min. The low molecular weight component preferably has a density of 945 to 975 kg / m ³ , more preferably 950 to 970 kg / m ³ , still more preferably 955 to 965 kg / m ³ , most preferably 960 to 965 kg / m ^3. Can be obtained by homopolymerization or copolymerization of ethylene and an α-olefin having 3 to 20 carbon atoms. When producing by suspension polymerization, the low molecular weight portion is preferably produced in a solvent containing 2.0 mol% or less of an α-olefin. If the density of the low molecular weight portion is low, the ESCR and impact resistance are lowered.

The polyethylene polymer (B) of the present invention is preferably obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms after homopolymerizing ethylene to produce a low molecular weight portion. The weight ratio of the low molecular weight part to the high molecular weight part (high molecular weight part) / (low molecular weight part) is preferably 40/60 to 60/40. The balance between moldability and moldability deteriorates. More preferably, (high molecular weight portion) / (low molecular weight portion) = 45/55 to 60/40, further preferably 50/50 to 60/40, and most preferably 53/47 to 57/43.
The HLMFR of the polyethylene polymer (B) is preferably 1 to 50 g / 10 minutes, more preferably 1 to 20 g / 10 minutes, still more preferably 3 to 15 g / 10 minutes, and most preferably 3 to 8 g / 10. Minutes.

The density of the polyethylene-based polymer (B) is preferably 920 to 950 kg / m ³ , more preferably 930 to 945 kg / m ³ , still more preferably 935 to 945 kg / m ³ , and most preferably 935 to 940 kg / m ³ . is there.
In the present invention, the polyethylene polymers (A) and (B) are mixed to form a target polyethylene polymer composition.
The ratio of (A) to (B) is (A) / (B) = 5/95 to 95/5, preferably 30/70 to 70/30, more preferably 35/65 by weight. ~ 55/45. Most preferably, it is 35/65 to 45/55.

There is no restriction | limiting in particular in the mixing method in the case of manufacturing a polyethylene-type polymer composition, Normal methods, such as a powder state, a slurry state, and a pellet state, are used. When kneading, it is carried out at a temperature of 150 to 300 ° C. with a uniaxial or biaxial extruder, a kneader or the like.
The polyethylene-based polymer composition is usually added to and blended with polyolefins such as heat stabilizers, antioxidants, ultraviolet absorbers, pigments, antistatic agents, lubricants, fillers, other polyolefins, thermoplastic resins, rubbers, etc. The resulting material can be used as needed. It is also possible to perform foam molding by mixing a foaming agent.
Alternatively, crosslinking can be performed using a radical generator or oxygen. As a method of crosslinking the composition comprising (A) and (B), oxygen or a gas containing oxygen, such as air, is used when the polyethylene polymer composition powder is uniformly mixed, or A method of thermal crosslinking at 210 ° C. to 300 ° C. in an atmosphere having an oxygen concentration of less than 0.5 vol% is particularly preferable.

  The polyethylene polymer composition of the present invention is suitable for hollow molding, injection molding, extrusion molding, film / sheet molding, and can be used for various containers, lids, bottles, pipes, films, sheets, packaging materials, and the like. Especially, it is most suitable for large thin hollow molding. The large hollow molding in the present invention means a hollow molding for molding a container having a container volume of 20 liters or more, and the thin hollow molding is a value obtained by dividing the container volume (liter) by the container weight (kg). It means hollow molding that is more than / kg. The polyethylene polymer composition of the present invention molds a container having a value obtained by dividing the container volume (liter) by the container weight (kg), more preferably 40 liters / kg or more, and still more preferably 50 liters / kg or more. Products with good appearance can be molded by thin-wall molding. Specific uses include dangerous goods medium-sized containers (IBC), interior containers for drums, and the like.

The symbols, measurement methods, and measurement conditions shown in the present invention are as follows.
(1) MFR: Melt index, measured according to JIS K7210 under conditions of a temperature of 190 ° C. and a load of 2.16 kg, and the unit is g / 10 minutes.
(2) HLMFR: Represents a high load melt index, measured according to JIS K7210 under conditions of a temperature of 190 ° C. and a load of 21.6 kg, and the unit is g / 10 minutes.
(3) Density: A value measured according to JIS K7112, and the unit is kg / m ³ .
(4) Bending strength: A value measured according to JIS K7171, and the unit is MPa.
(5) Weight average molecular weight (Mw): determined from gel permeation chromatography (GPC) measurement. For GPC measurement, GPCV2000 manufactured by Waters Co., Ltd., column Showa Denko Co., Ltd. UT-807 (one) and Tosoh Co., Ltd. GMHHR-H (S) HT (two) were connected in series, and mobile phase tri The reaction was performed under the conditions of chlorobenzene (TCB), column temperature 140 ° C., flow rate 1.0 ml / min, sample concentration 20 mg / 15 ml (TCB), injection amount 413 μl, sample dissolution temperature 140 ° C., and sample dissolution time 2 hours. The molecular weight was calibrated at 12 points in which Mw of standard polystyrene manufactured by Tosoh Corporation was in the range of 1,050 to 2,060,000. The Mw of each standard polystyrene was multiplied by a coefficient of 0.43 to obtain a molecular weight in terms of polyethylene, and a primary calibration line was created from a plot of elution time and molecular weight in terms of polyethylene to determine the molecular weight of each sample.

(6) Molecular weight distribution: This is the value of the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) determined from GPC measurement.
(7) GPC-FTIR: A detector; Perkin Elmer Co., Ltd. Infrared analyzer FT-IR 1760X is connected to Waters Alliance GPC V2000, and the measurement is performed simultaneously with GPC measurement.
(8) Charpy impact strength: a value measured according to JIS K7111, the unit being kJ / m ² . The shape of the test piece is No. 1 EA type and is measured at 23 ° C.
(9) b-ESCR (constant strain environmental stress cracking test): As an evaluation of environmental stress cracking resistance, b-ESCR was measured in accordance with JIS K6760. As a test solution, a 10% by weight aqueous solution of Antalox CO130 manufactured by Lion Co., Ltd. is used. . The unit is time.

(10) Melt tension (MT): Using a Capillograph manufactured by Instron, the molten resin was extruded under conditions of a temperature of 190 ° C., an orifice diameter of 2.095 mm, an orifice length of 8 mm, and a constant down speed. The load when wound at a speed of 0 m / min. The unit is g. When the HLMFR of the polyethylene polymer composition is 15 or more, the measurement is performed at a down speed of 0.6 cm / min, and when the HLMFR is less than 15, the measurement is performed at a down speed of 2.0 cm / min.
(11) Melt elongation (ME): The molten resin is extruded under the same conditions as in MT measurement, the strand winding speed is increased, and the winding speed at which the strand breaks is defined as the melt elongation (ME). The unit is m / min.

(12) Swell: 20 cm length when extruded using a hollow molding machine with a 50 mm diameter screw (A-50 manufactured by Plako) under the conditions of a die diameter of 16 mm, a core diameter of 10 mm, a cylinder temperature of 180 ° C., and a screw rotation speed of 45 rpm. The parison weight is in g.
(13) Number of terminal vinyl groups: Obtained from the absorbance at 909 cm ⁻¹ of the sheet-like polyethylene polymer composition obtained by hot pressing using a “Fourier transform infrared spectrophotometer” manufactured by JASCO Corporation.
(14) Gel: A pellet of a polyethylene polymer composition obtained by kneading and extruding at an extrusion rate of 25 kg / hr at a temperature of 200 ° C. with a single screw extruder having a screw diameter of 65 mm, a die diameter of 75 mm, and a die gap of 1.0 mm. Inflation molding is performed with a film molding machine (D-50 manufactured by Modern Machinery Co., Ltd.) having a screw diameter of 50 mm equipped with an annular die. The number of gels contained in a 10 cm × 10 cm film was measured, and the number was divided by the weight of the film to obtain the gel value. The unit is pieces / g.

(15) Appearance: Plaque Co. DA65 is used, and by direct blow molding, the molten resin is once accumulated in the accumulator, and then injected by intermittent blow. Molding is performed under the following two conditions. The values of (container volume) / (container weight) under these conditions are 20 liter / kg and 40 liter / kg, respectively. Molding is performed using a convergence type die having a die diameter of 100 mmφ and a core system of 99 mmφ, cylinder part temperature 190 ° C., die part temperature 190 ° C., mold temperature 20 ° C., mold cooling time 100 seconds, injection pressure 13.3 MPa. To do. The appearance of the container is visually confirmed, and the quality is judged according to the following criteria.
○ mark The surface is smooth and glossy.
X mark The entire surface is uneven, rough skin, and not glossy.

Next, the embodiments of the present invention will be described specifically by way of examples.
[Example 1]
(1) Synthesis of chromium oxide catalyst (I) 4 mol of chromium trioxide was dissolved in 80 liters of distilled water, and 20 kg of silica (grade 952 manufactured by WR Grace and Company) was immersed in this solution. After stirring for a period of time, this slurry was heated to distill off water, followed by drying under reduced pressure at 120 ° C. for 10 hours, followed by firing with flowing dry air at 600 ° C. for 5 hours. A chromium oxide catalyst (I) containing 0% by weight was obtained.
(2) Synthesis of organoaluminum compound (II) 100 moles of triethylaluminum, 50 moles of methyl hydropolysiloxane (viscosity at 30 ° C .: 30 centistokes) (Si standard), and 150 liters of n-hexane were weighed in a pressure-resistant container under a nitrogen atmosphere. The mixture was taken and reacted at 50 ° C. for 24 hours with stirring to prepare an Al (C ₂ H ₅ ) _2.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution. Next, 100 mol (Al basis) of this solution was transferred to a 600 liter reactor under a nitrogen atmosphere, and a mixed solution of 50 liters of ethanol and 50 liters of n-hexane was added with stirring at -10 ° C. The reaction was continued for 1 hour at this temperature, and Al (C ₂ H ₅ ) _2.0 (OC ₂ H ₅ ) _0.5 (OSi · H · CH ₃ · C ₂ H ₅ ) _0.5 hexane solution Adjusted.

(3) Synthesis of titanium catalyst (III) A 15-liter reactor fully purged with nitrogen was charged with 3 liters of trichlorosilane as a 2 mol / liter n-heptane solution and kept at 65 ° C. with stirring. _{AlMg 6 (C 2 H 5)} 3 (n-C 4 H 9) 6.4 5 mol _(On-C 4 _{H 9)} the organomagnesium component represented by _5.6 n-heptane solution 7 liters (magnesium terms ) Was added over 1 hour, and the mixture was further reacted with stirring at 65 ° C. for 1 hour. After completion of the reaction, the supernatant was removed and washed 4 times with 7 liters of n-hexane to obtain a solid material slurry. This solid was separated, dried and analyzed, and as a result, it contained 7.45 mmol of Mg per gram of the solid.
Of these, a slurry containing 500 g of solid was reacted with 0.93 liter of n-butyl alcohol 1 mol / liter n-hexane solution at 50 ° C. for 1 hour with stirring. After completion of the reaction, the supernatant was removed and washed once with 7 liters of n-hexane. This slurry was kept at 50 ° C., and 1.3 liters of n-hexane solution of 1 mol / liter of diethylaluminum chloride was added with stirring and reacted for 1 hour. After completion of the reaction, the supernatant was removed and washed twice with 7 liters of n-hexane. This slurry was kept at 50 ° C., 0.2 liter of n-hexane solution of 1 mol / liter of diethylaluminum chloride and 0.2 liter of n-hexane solution of 1 mol / liter of titanium tetrachloride were added and reacted for 2 hours. After completion of the reaction, the supernatant was removed and the solid catalyst was isolated and washed with hexane until no free halogen was detected. The solid catalyst had 2.3 wt% titanium.

(4) Production of polyethylene polymer (A-1) In a single-stage polymerization process, polymerization was carried out in a 230 L polymerization vessel. The polymerization temperature is 78 ° C. and the polymerization pressure is 0.98 MPa. To this polymerizer, 5 g of the organoaluminum compound (II) prepared in (2) (Al standard) was added to 50 g of the chromium oxide catalyst (I) synthesized in (1), and the mixture was reacted at room temperature for 1 hour. The organoaluminum compound obtained by reacting the obtained solid catalyst with ethanol and trihexylaluminum in a molar ratio of 0.98: 1 at a rate of 2 g / hr was 0.08 mmol / L in the polymerization vessel. It was supplied and adjusted. Purified hexane is supplied at a rate of 60 L / hr, ethylene is supplied at a rate of 12 kg / hr, hydrogen is supplied as a molecular weight regulator so that the gas phase concentration is 4.0 mol%, polymerization is performed, and HLMFR is 10 g. / 10 minutes, a polyethylene polymer (A-1) having a density of 961 kg / m ³ was produced.

(5) Production of polyethylene polymer (B-1) First, in order to produce a low molecular weight component in the first stage polymerization, a stainless polymerizer 1 with a reaction volume of 300 liters was used, polymerization temperature 80 ° C., polymerization Under the condition of a pressure of 1 MPa, the catalyst is the above-mentioned solid catalyst (III) at a rate of 1.4 mmol / hr in terms of Ti atom, triisobutylaluminum at 20 mmol / hr in terms of Al atom, and hexane at a rate of 40 liter / hr. Introduced. Hydrogen was used as the molecular weight modifier, and polymerization was carried out by supplying ethylene, hydrogen, and butene-1 so that the gas phase concentration of hydrogen was 65 mol% and the gas phase concentration of butene was 1.0 mol%. The polymer slurry solution in the polymerization vessel 1 was introduced into a flash drum having a pressure of 0.1 MPa and a temperature of 75 ° C., and unreacted ethylene and hydrogen were separated and then introduced into the polymerization vessel 2 having a reaction volume of 250 liters by increasing the pressure with a slurry pump. . In the polymerization vessel 2, triisobutylaluminum was introduced at a rate of 7.5 mmol / hr and hexane was introduced at a rate of 40 l / hr under the conditions of a temperature of 64 ° C. and a pressure of 0.5 MPa. Ethylene, hydrogen and butene-1 were introduced so that the gas phase concentration of hydrogen was 1.0 mol% and the gas phase concentration of butene was 10.0 mol%, and the low molecular weight produced in the polymerization vessel 1 was introduced. The high molecular weight portion was polymerized such that the weight ratio of the high molecular weight portion generated in the polymerizer 2 (high molecular weight portion) / (low molecular weight portion) was 55/45, and the HLMFR was 4.5 g / 10 min. A polyethylene-based polymer (B-1) having a density of 937 kg / m ³ was produced. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 10 g / 10 minutes, and the density was 954 kg / m ³ .

(6) Production of polyethylene polymer composition The polyethylene polymers (A-1) and (B-1) produced as described above were mixed in a weight ratio of 40/60, and then To this mixture, 300 ppm of calcium stearate and Irganox 1076 manufactured by Ciba Specialty Chemicals were added to a concentration of 1000 ppm, and the mixture was stirred and mixed with a mixer. This mixture was extruded using a twin-screw extruder having a cylinder diameter of 44 mm (TEX44HCT-49PW-7V, manufactured by Nippon Steel Co., Ltd.) while kneading under the conditions of a cylinder temperature of 220 ° C. and an extrusion rate of 35 kg / hour to obtain a polyethylene polymer composition. I got a thing. The molecular weight distribution of this polyethylene polymer composition was 19.

[Example 2]
In Example 1, the polyethylene polymer (A-1) and (B-1) were mixed in a weight ratio of 50/50 in the same manner as in Example 1 except that the powder was mixed. A composition was prepared. The molecular weight distribution of this polyethylene polymer composition was 17.

[ Reference example ]
In the production of the polyethylene polymer (B-1) of Example 1, the gas phase concentration of hydrogen and the gas phase concentration of butene-1 in the polymerization vessel 2 are 0.6% and 9.3%, respectively. A polyethylene (B-2) having an HLMFR of 3.5 g / 10 min and a density of 937 kg / m ³ was produced in the same manner as in the polyethylene (B-1) except that the polymer was polymerized. A polyethylene polymer composition was produced in the same manner as in Example 1 except that the powders of the polyethylene polymers (A-1) and (B-2) were mixed at a weight ratio of 40/60. . The polyethylene polymer composition had a molecular weight distribution of 21.
As shown in Table 1, the performances of the polyethylene-based polymer compositions of Examples 1 and 2 and Reference Example are excellent in physical properties such as rigidity and ESCR, the appearance at the time of thin molding is good, and the performance balance is very good.

[Comparative Example 1]
In the production of the polyethylene-based polymer (B-1) of Example 1, the weight ratio of the low molecular weight part to the high molecular weight part (high molecular weight part) / (low molecular weight part) was 52/48. vapor concentration is 75 mol%, the gas phase concentration of butene in the polymerization vessel 2 is polymerized so as to become 9.0 mol%, HLMFR is 4.5 g / 10 min, polyethylene having a density of 940 kg / ^{m 3} A polymer (B-3) was produced. The MFR of the low molecular weight portion produced in the polymerization vessel 1 was 40 g / 10 minutes, and the density was 956 kg / m ³ . A polyethylene polymer composition was produced in the same manner as in Example 1 except that the powders of the polyethylene polymers (A-1) and (B-3) were mixed at a weight ratio of 40/60. . The polyethylene polymer composition had a molecular weight distribution of 29. As shown in Table 1, the performance of this polyethylene-based polymer composition is excellent in rigidity and ESCR, but has a lot of gel and a poor appearance during thin molding.

  The polyethylene polymer composition of the present invention is suitable for hollow molding, injection molding, extrusion molding, film / sheet molding, and can be used for various containers, lids, bottles, pipes, films, sheets, packaging materials and the like. It is particularly suitable for large thin hollow molding applications, and specific applications include medium for dangerous goods (IBC), interior containers for drums, and the like.

It is a GPC-FTIR figure of one example of the polyethylene-type polymer composition of this invention.

Claims (4)

A polyethylene polymer in a composition comprising a polyethylene polymer (A) produced using a chromium catalyst and a polyethylene polymer (B) produced by two-stage polymerization using a titanium Ziegler catalyst ( The amount of A) is in the range of 5 to 95% by weight, the composition has an HLMFR of 1 to 15 g / 10 min, and a density of 940 to 965 kg / m ³ , as determined from gel permeation chromatography (GPC). The ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn is 10 to 19, and the comonomer distribution parameter P determined from GPC-FTIR is 0 ≦ P ≦ 0.05. -Based polymer composition.   The polyethylene polymer composition according to claim 1, wherein the polyethylene polymer (A) is produced by a combination of a chromium catalyst treated with an organometallic compound and a cocatalyst. object. The polyethylene polymer composition according to claim 1 or 2 , which is used for large-scale hollow molding. A large hollow molded article comprising the polyethylene polymer composition according to claim 3 .

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