JP2011202189A - Ethylene polymer excellent in processability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ethylene polymer excellent in extrusion molding processability and in the balance between mechanical strength and appearance of an extrusion molded article.SOLUTION: The ethylene polymer is obtained by copolymerizing ethylene and an α-olefin of 5 to 20 carbon atoms, has a melt flow rate (MFR; the unit is g/10 min) of not less than 0.01 and less than 1, in which the relation between the MFR and the melt tension (MT; the unit is cN) at 190°C satisfies formula (1): 2×MFR<MT<3.6×MFR, the relation between the MFR and the intrinsic viscosity ([η]; the unit is dL/g) satisfies formula (2): 1.02×MFR<[η]<1.50×MFR, and the activation energy of flow is not less than 50 kJ/mol and not greater than 100 kJ/mol, and the molecular weight distribution (Mw/Mn) is not less than 5.3 and not greater than 25.

Description

  The present invention relates to an ethylene polymer. More specifically, the present invention relates to an ethylene polymer having an excellent balance between extrudability, mechanical strength, and appearance of an extruded product.

  Ethylene polymers are widely used in many fields as general-purpose resins. The ethylene polymer has, for example, extrusion properties such as extrusion torque, melt tension, and high-speed workability, mechanical properties such as impact strength, surface smoothness of extruded products such as films and sheets, gloss, Appearance such as transparency is required.

  The low-density polyethylene obtained by the high-pressure radical polymerization method, which is an ethylene polymer used as a general-purpose resin, has a good balance between extrusion torque and melt tension, but it is difficult to mold at high speed because the melt tension is too high. Further, the impact strength is low.

  On the other hand, as an ethylene polymer that has been conventionally used as a general-purpose resin in the same way as low-density polyethylene obtained by high-pressure radical polymerization, it is obtained by copolymerizing ethylene and an α-olefin such as 1-butene or 1-hexene. Linear low density polyethylene is known. For conventional linear low density polyethylene, high molecular weight and low density can be considered in order to improve mechanical properties, and high molecular weight can be considered in order to improve moldability such as melt tension. However, when the molecular weight is increased, moldability due to an increase in extrusion torque at the time of molding may be deteriorated, and when the density is decreased, the rigidity and heat resistance of the linear low density polyethylene may be decreased.

  For example, JP-A-4-213309 discloses a polyethylene copolymer having an extremely high melt tension. However, since the melt tension is too high, it is difficult to take up at a high speed, and the processing speed is high. It is limited and cannot be said to meet the requirements.

  JP-A-6-9724 discloses a polyethylene copolymer having a relatively low melt tension, but it is difficult to say that the molecular weight distribution is narrow and the fluidity is sufficiently excellent. Also, the relationship between melt index and intrinsic viscosity shows that it is closer to the conventional linear low density polyethylene than the high pressure method low density polyethylene, which is excellent in processability, and satisfies the conventional requirements for moldability It's hard to say.

Therefore, even when using the ethylene polymer described in the above-mentioned patent publications and the like, the increase in extrusion torque during molding and the decrease in rigidity of the ethylene polymer are suppressed, and the mechanical properties are improved. It is difficult to improve the melt tension to enable high-speed molding.
Therefore, in the situation as described above, the increase in extrusion torque during molding and the decrease in rigidity of the ethylene polymer are suppressed, the mechanical properties are improved, and the melt tension is improved to enable high-speed molding. Development of an ethylene polymer is expected. Furthermore, extrusion products such as films and sheets obtained from such ethylene polymers are required to have excellent appearance such as surface smoothness, gloss and transparency.

JP-A-4-213309 JP-A-6-9724

  An object of the present invention is to provide an ethylene polymer having an excellent balance between extrudability, mechanical strength, and appearance of an extruded product.

The present inventors have found that the present invention can solve the above problems, and have completed the present invention.
In other words, the present invention
It is obtained by copolymerizing ethylene and an α-olefin having 5 to 20 carbon atoms, and has a melt flow rate (MFR; unit is g / 10 minutes) of 0.01 or more and less than 1, and the MFR and 190 ° C. The ethylene tension satisfying the relationship of the following formula (1) with the melt tension (MT; unit of cN) and the relationship of the following formula (2) with the MFR and intrinsic viscosity ([η]; unit of dL / g) This relates to the coalesced resin.
2 × MFR ^−0.59 <MT <3.6 × MFR ^−0.66 Formula (1)
1.02 × MFR ^−0.094 <[η] <1.50 × MFR ^−0.156 Formula (2)

  As described above, according to the present invention, it is possible to obtain an ethylene polymer having an excellent balance between extrudability, mechanical strength, and appearance of an extruded product.

  The ethylene polymer of the present invention is a thermoplastic resin obtained by copolymerizing ethylene and an α-olefin having 5 to 20 carbon atoms, and has a polyethylene crystal structure. The ethylene polymer of the present invention is preferably a thermoplastic ethylene polymer containing 50% by weight or more of repeating units derived from ethylene, wherein ethylene and an α-olefin having 5 to 10 carbon atoms are co-polymerized. It is a coalescence. Examples of the α-olefin include 4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene.

  As the ethylene polymer of the present invention, other monomers may be copolymerized in addition to the α-olefin. Other monomers include propylene, 1-butene, conjugated dienes (eg, butadiene and isoprene), nonconjugated dienes (eg, 1,4-pentadiene), acrylic acid, acrylic acid esters (eg, methyl acrylate and ethyl acrylate), Examples thereof include methacrylic acid, methacrylic acid esters (for example, methyl methacrylate and ethyl methacrylate) and vinyl acetate.

  The ethylene polymer of the present invention is preferably a copolymer of ethylene and an α-olefin having 5 to 20 carbon atoms, more preferably a copolymer weight of ethylene and an α-olefin having 6 to 10 carbon atoms. It is a coalescence. Examples thereof include an ethylene-1-hexene copolymer, an ethylene-4-methyl-1-pentene copolymer, and an ethylene-1-octene copolymer. Among these, an ethylene-1-hexene copolymer is preferable. Further, a terpolymer of ethylene, an α-olefin having 6 to 10 carbon atoms and 1-butene is also preferable, such as an ethylene-1-butene-1-hexene copolymer, ethylene-1-butene-4-methyl. Examples include a -1-pentene copolymer and an ethylene-1-butene-1-octene copolymer, and an ethylene-1-butene-1-hexene copolymer is particularly preferable.

  The melt flow rate (MFR; unit: g / 10 minutes) of the ethylene polymer of the present invention is 0.01 or more and less than 1, preferably 0.05 or more and less than 1, more preferably 0.1 or more and 0. .8 or less, more preferably 0.2 or more and 0.8 or less.

  In the present invention, the melt flow rate (MFR; unit is g / 10 minutes) is a value measured at 190 ° C. under a load of 21.18 N (2.16 Kg) in accordance with the method defined in JIS K7210-1995. . And the polymer which mix | blended 1000 ppm of antioxidant previously is used for the measurement of said melt flow rate (MFR).

It is generally known that there is a relationship between the melt flow rate (MFR) and melt tension of an ethylene polymer, for example, the melt tension decreases as the MFR increases.
The ethylene polymer of the present invention is considered to have a polymer structure such as a long chain branch, and because of having such a polymer structure such as a long chain branch, the melt tension of the ethylene polymer of the present invention is conventionally It is thought that it becomes higher than the ethylene polymer. And, since the polymer structure such as long chain branch considered to be possessed by the ethylene polymer of the present invention is different from the long chain branch polymer structure of low density polyethylene obtained by the high pressure radical polymerization method, It is considered that the melt tension of the ethylene polymer of the present invention is lower than the melt tension of low-density polyethylene obtained by the high-pressure radical polymerization method and falls within an appropriate range.

The melt flow rate (MFR; unit is g / 10 minutes) and the melt tension (MT; unit is cN) at 190 ° C. of the ethylene polymer of the present invention satisfy the relationship of the following formula (1).
2 × MFR ^−0.59 <MT <3.6 × MFR ^−0.66 Formula (1)

The ethylene polymer of the present invention satisfies the relationship of the above formula (1) and is excellent in moldability including moldability at high speed. In the relationship of the above formula (1), if the melt tension is too low and MT and MFR do not satisfy the relationship of 2 × MFR ^−0.59 <MT, the moldability may deteriorate and the melt tension is too high. Thus, when MT and MFR do not satisfy the relationship of MT <3.6 × MFR− ^0.66 , high-speed take-up molding may be difficult.

The relationship between the melt flow rate (MFR) and the melt tension (MT) satisfied by the ethylene polymer of the present invention is more preferably the relationship of the formula (1),
2.2 × MFR ^−0.59 <MT <3.4 × MFR ^−0.66
And more preferably
2.5 × MFR ^−0.59 <MT <3.2 × MFR ^−0.66
It is.

The melt tension (MT; unit is cN) in the above formula (1) is a piston of 190 ° C. and an extrusion speed of 5.5 mm / min using a melt tension tester sold by Toyo Seiki Seisakusho etc. The tension value immediately before the strand breaks when the molten resin strand is extruded from an orifice having a diameter of 09 mm and a length of 8 mm, and the strand is wound up while increasing the rotation speed by 40 rpm per minute using a roller having a diameter of 50 mm. Say.
The maximum winding speed (MTV; unit is m / min) is an index of high-speed workability and refers to the strand winding speed immediately before the strand breaks.

It is generally known that there is a relationship between the MFR and the intrinsic viscosity of an ethylene polymer, for example, the intrinsic viscosity decreases as the MFR increases.
The ethylene polymer of the present invention is considered to have a polymer structure such as a long chain branch, and because of having such a polymer structure such as a long chain branch, the intrinsic viscosity of the ethylene polymer of the present invention is conventionally It is considered that the viscosity is lower than the intrinsic viscosity of the ethylene polymer in an appropriate range.

And the intrinsic viscosity ([η]) and the melt flow rate (MFR) of the ethylene polymer of the present invention satisfy the relationship of the following formula (2).
1.02 × MFR ^−0.094 <[η] <1.50 × MFR ^−0.156 Formula (2)

The ethylene polymer of the present invention satisfies the relationship of the above formula (2), has a low extrusion torque, and is excellent in moldability. In the relationship of the above formula (2), if the intrinsic viscosity is too low and [η] and MFR do not satisfy the relationship of 1.02 × MFR ^−0.094 <[η], the impact strength may decrease. When the intrinsic viscosity is too high and [η] and MFR do not satisfy the relationship [η] <1.50 × MFR ^−0.156 , the extrusion torque is high and the moldability may be poor. In general, the low density polyethylene obtained by the high pressure radical polymerization method satisfies the relationship [η] <1.02 × MFR ^−0.094 , and the conventional ethylene-α-olefin copolymer has [η]> 1. The relationship 50 × MFR ^-0.156 is satisfied.

As the relationship between the intrinsic viscosity ([η]) and the melt flow rate (MFR) satisfied by the ethylene polymer of the present invention, more preferably than the relationship of the formula (2),
1.05 × MFR ^−0.094 <[η] <1.47 × MFR ^−0.156
And more preferably
1.08 × MFR ^−0.094 <[η] <1.42 × MFR ^−0.156
It is.

The intrinsic viscosity ([η]) in the relationship of the above formula (2) is a sample solution prepared by dissolving 100 mg of ethylene polymer resin at 135 ° C. in 100 ml of tetralin containing 5% by weight of BHT as a thermal deterioration inhibitor, After calculating the relative viscosity (ηrel) at 135 ° C. calculated from the falling time of the sample solution and the blank solution using an Ubbelohde viscometer, it is calculated from the following equation.
[Η] = 23.3 × log (ηrel)

The density (unit: kg / m ³ ) of the ethylene polymer of the present invention is usually 890 or more and 970 or less. The density is a value measured by a method defined in JIS K6760-1981. The density is preferably 900 or more and 950 or less, and more preferably 905 or more and 940 or less, from the viewpoint of excellent balance between rigidity and impact strength of a film obtained from the ethylene polymer of the present invention.

  The molecular weight distribution of the ethylene polymer of the present invention is preferably 3.5 or more and 25 or less, from the viewpoint of fluidity, from the viewpoint of lowering extrusion torque and improving moldability, and from preventing smoke generation during molding. More preferably, it is 3.6 or more and 20 or less, More preferably, it is 3.7 or more and 15 or less. The molecular weight distribution is a value (Mw / Mn) obtained by dividing the polystyrene-reduced weight average molecular weight (Mw) obtained by gel permeation chromatography measurement by the number average molecular weight (Mn).

The gel permeation chromatography measurement can be performed under the following conditions (1) to (6).
(1) Apparatus: Waters 150C manufactured by Water
(2) Separation column: TOSOH TSKgelGMH-HT
(3) Measurement temperature: 145 ° C
(4) Carrier: orthodichlorobenzene (5) Flow rate: 1.0 mL / min (6) Injection volume: 500 μL

  The flow activation energy (Ea, unit is kJ / mol) of the ethylene polymer of the present invention is preferably 40 kJ / mol or more, more preferably 45 kJ / mol or more, from the viewpoint of fluidity. Yes, more preferably 50 kJ / mol or more.

The flow activation energy Ea is a dynamic value at each temperature T (K) measured under the following conditions (1) to (4) using a Reometrics Mechanical Spectrometer RMS-800 manufactured by Reometrics. Arrhenius equation for shift factor (a _T ) when shifting viscoelastic data based on temperature-time superposition principle: log (a _T ) = Ea / R (1 / T−1 / T ₀ ) (R is Gas constant, T ₀ is a standard temperature 463K. Calculation software includes Rohms V. from Reometrics. 4.4.4 is used, and the Ea value when the correlation coefficient r ² at the time of linear approximation in the Arrhenius plot log (a _T ) − (1 / T) is 0.99 or more is adopted. In addition, an appropriate amount of 1000 ppm or more of an antioxidant such as Irganox 1076 is blended in advance in the sample, and the measurement is performed under nitrogen.
(1) Geometry: Parallel plate, diameter 25 mm, plate interval: 1.5-2 mm
(2) Strain: 5%
(3) Shear rate: 0.1 to 100 rad / sec
(4) Temperature: 190, 170, 150, 130 ° C

  Furthermore, the ethylene polymer of the present invention is considered to have a polymer structure such as long chain branching, has a higher melt flow rate ratio (MFRR) than conventional ethylene polymers, and is preferable from the viewpoint of fluidity. Is 60 or more.

  The melt flow rate ratio (MFRR) is a value obtained by measuring a melt flow rate value measured at 190 ° C. under a load of 211.82 N (21.60 kg) according to a method defined in JIS K7210-1995 with a load of 21.18 N (2 .16 kg) divided by the melt flow rate value (MFR). A high MFRR of 60 or more means excellent molding processability at a low extrusion torque. For the measurement of the melt flow rate ratio (MFRR), a polymer containing 1000 ppm of an antioxidant in advance is used.

As the melting point (unit is ° C.) of the ethylene polymer of the present invention, when the density is 927 kg / m ³ or less, usually there are at least two melting points, and the maximum melting point (Tmax) is 115 ° C. or more. From the viewpoint of heat resistance, it is preferably 118 ° C. or higher. Even when there is only one melting point and the melting point is 115 ° C. or lower, a melting component of 118 ° C. or higher is present.

  The above melting point is a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, and 8 to 12 mg of sample is packed in an aluminum pan and held at 150 ° C. for 2 minutes, and then up to 40 ° C. at 5 ° C./min. The melting peak temperature observed when the temperature is lowered and held at 40 ° C. for 2 minutes and then raised to 150 ° C. at 5 ° C./min. Among them, the temperature at the highest melting peak position is defined as the maximum melting point Tmax.

The ethylene polymer of the present invention can be obtained by copolymerizing ethylene and α-olefin under hydrogen conditions using a metallocene olefin polymerization catalyst as shown in the Examples.
The metallocene-based olefin polymerization catalyst is a catalyst obtained by contacting a promoter support (A), a crosslinked bisindenyl zirconium complex (B) and an organoaluminum compound (C), and the promoter support (A) Is a support obtained by contacting diethylzinc (a), fluorinated phenol (b), water (c) and silica (d).

The amount of each compound (a), (b), (c) used is not particularly limited, but the molar ratio of the amount of each compound used is (a) :( b) :( c) = 1: y: z It is preferable that y and z satisfy the following formula (3).
| 2-y-2z | ≦ 1 (3)
In the above formula (3), y is preferably a number of 0.01 to 1.99, more preferably a number of 0.10 to 1.80, and still more preferably a number of 0.20 to 1.50. Yes, most preferably a number from 0.30 to 1.00.

  The amount of (d) used for (a) is the amount of zinc atoms derived from (a) contained in the particles obtained by contact between (a) and (d) in 1 g of the obtained particles. The amount of zinc atoms contained is preferably 0.1 mmol or more, more preferably 0.5 to 20 mmol.

Examples of the crosslinked bisindenylzirconium complex (B) include racemic-ethylenebis (1-indenyl) zirconium dichloride and racemic-ethylenebis (1-indenyl) zirconium diphenoxide.
As the organoaluminum compound (C), triisobutylaluminum and trinormaloctylaluminum are preferably used.

The amount of component (B) used is preferably 5 × 10 ^{−6 to} 5 × 10 ⁻⁴ mol per 1 g of component (A). Moreover, it is preferable that the usage-amount of a component (C) is 1-2000 as molar ratio (C) / (B) of the aluminum atom of the component (C) with respect to the zirconium atom of a component (B).

  As the polymerization method, for example, a polymerization method involving formation of ethylene polymer particles such as gas phase polymerization, slurry polymerization, bulk polymerization and the like is preferable. What is necessary is just to follow well-known polymerization conditions as polymerization conditions. Moreover, it is preferable to perform prepolymerization as shown in the Examples before carrying out the main polymerization, and to use the obtained prepolymerized catalyst component as a catalyst component or catalyst for the main polymerization. As the gas phase polymerization reaction apparatus, a fluidized bed type reaction vessel, preferably a fluidized bed type reaction vessel having an enlarged portion is used. A stirring blade may be installed in the reaction vessel.

  As a method for supplying each component to the polymerization tank, a solution or a slurry is usually supplied using an inert gas such as nitrogen or argon, hydrogen, ethylene or the like in the absence of moisture, or dissolved or diluted in a solvent. A method such as supplying in a state can be used. Each catalyst component may be supplied individually, or may be supplied by contacting arbitrary components in advance in an arbitrary order.

  As polymerization conditions, the temperature is less than the temperature at which the polymer melts, preferably 0 ° C. to 150 ° C., particularly preferably 30 ° C. to 100 ° C. Furthermore, hydrogen may be added as a molecular weight modifier for the purpose of adjusting the melt fluidity of the final product. In the polymerization, an inert gas may coexist in the mixed gas.

From the viewpoint of obtaining an extruded product excellent in appearance such as surface smoothness, gloss, transparency, etc., when the ethylene polymer of the present invention is an extruded product such as a film or sheet, Preferably, a logarithm corresponding to a component having the highest molecular weight among lognormal distribution curves obtained by dividing the chain length distribution curve obtained by the gel permeation chromatography measurement into at least two lognormal distribution curves. The chain length A at the peak position of the normal distribution curve and the melt flow rate (MFR; unit is g / 10 minutes) satisfy the relationship of the following formula (3).
3.30 <logA <−0.0815 × log (MFR) +4.05 Formula (3)

  When the ethylene polymer of the present invention satisfies the relationship of the above formula (3), the extrusion torque is low, the extrusion moldability is excellent, and the appearance of an extruded product such as a film is excellent.

As the relationship between the melt flow rate (MFR) and the chain length A (log A) satisfied by the ethylene polymer of the present invention, more preferably than the relationship of the above formula (3),
3.30 <logA <−0.0815 × log (MFR) +4.03
And more preferably
3.30 <logA <−0.0815 × log (MFR) +4.02
It is.

The chain length distribution curve is divided as follows.
First, a chain length distribution curve in which a weight ratio dW / d (logAw) (y value) is plotted against logAw (x value) that is the logarithm of chain length Aw is measured by gel permeation chromatography measurement. The number of plot data is usually at least 300 or more so as to form a continuous distribution curve. Next, four lognormal distribution curves (xy) having a standard deviation of 0.30 and an arbitrary average value (usually corresponding to the chain length A of the peak position) with respect to the above x value. Curve) is added at an arbitrary ratio to create a composite curve. Further, the average value and the ratio are obtained so that the deviation sum of squares of the y value with respect to the same x value of the actually measured chain length distribution curve and the combined curve becomes a minimum value. The minimum value of the deviation sum of squares is usually 0.5% or less with respect to the deviation sum of squares when the ratios of the peaks are all zero. The logarithm corresponding to the component having the highest molecular weight among the lognormal distribution curves obtained by dividing the logarithmic normal distribution curve into four lognormal distribution curves when the average value and the ratio giving the minimum value of the deviation sum of squares are obtained. Log A is calculated from the chain length A at the peak position of the normal distribution curve. The ratio of the peak of the lognormal distribution curve corresponding to the highest molecular weight component is usually 10% or more.

From the viewpoint of obtaining an extruded product excellent in appearance such as surface smoothness, gloss, transparency, etc., when the ethylene polymer of the present invention is an extruded product such as a film or sheet, Preferably, the characteristic relaxation time at 190 ° C. (τ; unit is sec) and the melt flow rate (MFR; unit is g / 10 minutes) satisfy the relationship of the following formula (4).
2 <τ <8.1 × MFR ^-0.746 formula (4)

  When the ethylene polymer of the present invention satisfies the relationship of the above formula (4), the extrusion torque is low, the extrusion moldability is excellent, and the appearance of an extruded product such as a film is excellent.

In general, it is known that there is a relationship between the MFR of an ethylene polymer and the relaxation time, for example, the relaxation time decreases as the MFR increases.
The ethylene polymer of the present invention is considered to have a polymer structure such as a long chain branch, and since it has such a polymer structure such as a long chain branch, the relaxation time of the ethylene polymer of the present invention is conventionally It is considered that the relaxation time is longer than that of the ethylene polymer and is in a preferable range.

As the relationship between the melt flow rate (MFR) and the characteristic relaxation time (τ) satisfied by the ethylene polymer of the present invention, preferably the relationship of the formula (4),
2 <τ <7.9 × MFR ^-0.746
And more preferably
2 <τ <7.8 × MFR ^-0.746
It is.

  The characteristic relaxation time (τ) at 190 ° C. is determined by using the Rheometrics Mechanical Spectrometer RMS-800 manufactured by Rheometrics as a viscoelasticity measuring device, and the dynamic viscosity at each temperature T (K) measured under the above conditions. The elastic data is shifted based on the temperature-time superposition principle, and the shear rate (ω: the unit is rad / sec) of the dynamic viscosity (η; the unit is Pa · sec) at 190 ° C. This is a numerical value calculated when a master curve showing dependency is obtained and the master curve is approximated by the following cross equation.

Cloth's approximate expression η = η0 / [1+ (τ × ω) ⁿ ]
(Η0 and n are constants determined for each ethylene-α-olefin copolymer used in the measurement, similarly to the characteristic relaxation time τ.)
In addition, Rheometrics Rhios V. is used as a calculation software for creating a master curve and cross-type approximation. Use 4.4.4.

  When the ethylene polymer of the present invention is an ethylene polymer that satisfies the relationship of the above formula (3) or formula (4) and is excellent in the appearance of an extrusion-molded product, from the viewpoint of fluidity, the molecular weight distribution is further It is preferably 4.0 to 20, and more preferably 7.5 to 17. Furthermore, the melt flow rate ratio (MFRR) is preferably 80 or more.

When the ethylene polymer of the present invention is an ethylene polymer satisfying the relationship of the above formula (3) or formula (4) and excellent in the appearance of an extruded product, a metallocene olefin polymerization catalyst used for the production thereof Is a catalyst obtained by contacting the co-catalyst support (A ′), the crosslinked bisindenyl zirconium complex (B) and the organoaluminum compound (C), and the co-catalyst support (A ′) is diethyl zinc A carrier obtained by contacting (a), fluorinated phenol (b), water (c), silica (d), and (e) trimethyldisilazane (((CH ₃ ) ₃ Si) ₂ NH). . The amount of (e) used relative to (d) is preferably (e) 0.1 mmol or more per 1 g of (d), more preferably 0.5 to 20 mmol. preferable.

  The ethylene polymer of the present invention is considered to have a polymer structure such as long chain branching. And as a polymer structure like a long chain branch, it is thought that the structure intertwined closely is preferable. Such a tightly intertwined structure can provide a higher flow activation energy than conventional ethylene polymers and further improve the extrusion moldability.

  As described above, the activation energy (Ea; the unit is kJ / mol) of the flow of the ethylene polymer, which is considered to be a structure in which a polymer structure such as long chain branching is closely intertwined, is a low temperature. From the viewpoint of increasing the melt tension and obtaining sufficient moldability, it is preferably 60 kJ / mol or more, more preferably 63 kJ / mol or more, and further preferably 66 kJ / mol or more. From the viewpoint of obtaining sufficient moldability without lowering the melt viscosity at a high temperature, and from the viewpoint of preventing the appearance of the surface of the extrusion-molded product such as a film from being rough and damaged, Ea is preferably 100 kJ / mol or less, more preferably 90 kJ / mol or less.

As described above, the preferred ethylene polymer of the present invention, which is considered to be a structure in which a polymer structure such as a long chain branch is closely entangled, has a swell ratio (SR) and an intrinsic viscosity ([η]; The unit is dL / g) and the relationship of the following formula (5) or formula (6) is satisfied.
If [η] <1.20,
−0.91 × [η] +2.262 <SR <2 Formula (5)
If [η] ≧ 1.20,
1.17 <SR <2 Formula (6)

It is generally known that there is a relationship between the intrinsic viscosity ([η]) and the swell ratio (SR) of an ethylene polymer, for example, the swell ratio increases as the intrinsic viscosity decreases. .
The ethylene polymer of the present invention is considered to have a polymer structure such as a long chain branch, and the preferred ethylene polymer of the present invention has a structure that is closely entangled as a polymer structure such as a long chain branch. It is thought that there is. And, by such a tightly entangled structure, the SR of the ethylene polymer of the present invention is considered to be higher than the conventional ethylene polymer and within a preferable range, and [η] and SR of the ethylene polymer of the present invention Satisfies the above formula (5) or formula (6).

  When the ethylene polymer of the present invention satisfies the relationship of the above formula (5) or formula (6), the extrusion torque is low, the stability at the time of extrusion molding is excellent, and the surface of an extruded product such as a film The appearance is excellent without any roughening.

As the relationship of formula (5) or formula (6) satisfied by the ethylene polymer of the present invention, preferably,
When [η] <1.23, −0.91 × [η] +2.289 <SR <1.9
When [η] ≧ 1.23, 1.17 <SR <1.9
And more preferably
In the case of [η] <1.30, −0.91 × [η] +2.353 <SR <1.8
When [η] ≧ 1.30, 1.17 <SR <1.8
It is.

The swell ratio (SR) in the above formula (5) or formula (6) is 21.18 N (2.16 Kg) at 190 ° C. when measuring the melt flow rate (MFR; unit is g / 10 min). ), A solid strand obtained by extruding into a strand and then cooling in air is determined to obtain a diameter D (unit: mm) at a point in the range of 1 to 6 mm from the tip, and the diameter is the orifice diameter. It is a value (D / D ₀ ) divided by 2.095 mm (D ₀ ). The diameter D was obtained as an average value of three strand samples.

  A preferred ethylene polymer of the present invention, that is, an ethylene polymer having a flow activation energy (Ea) of 60 kJ / mol or more, or an ethylene polymer satisfying the relationship of the above formula (5) or formula (6). Thus, an ethylene polymer that is considered to have a tightly entangled structure as a polymer structure such as a long-chain branch is obtained by using ethylene and α- After copolymerization with olefin, it can be produced by a method of kneading by the following continuous extrusion granulation method.

  One of the methods is to continuously form a strand using an extruder equipped with an extension flow kneading (EFM) die developed by Utracki et al. Described in US Pat. No. 5,451,106. Is continuously cut to produce pellets. In addition, one of the methods is a method in which a strand is continuously formed using an extruder equipped with a different-direction twin screw having a gear pump, and the strand is continuously cut to produce a pellet. . In the latter, it is preferable that there is a staying part between the screw part and the die.

  Since the ethylene polymer of the present invention has excellent properties as described above, it is suitable as a raw material for molded articles such as films or sheets. As a method for obtaining a film by using the ethylene polymer of the present invention as a raw material, in particular, an inflation film molding process for winding the film expanded by extruding the ethylene polymer of the present invention melted from a circular die. Alternatively, a T-die film forming method in which the ethylene polymer of the present invention melted from a linear die is extruded and the film is wound is suitably used.

  The ethylene polymer of the present invention can contain known additives such as antioxidants, weathering agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, drip-free agents, pigments, fillers and the like.

EXAMPLES Next, although this invention is demonstrated based on an Example, this invention is not limited to these Examples at all.
In addition, the tensile impact strength in an Example was measured based on ASTMD1822-68.

  Moreover, about the external appearance of the extrusion molded product in an Example, it evaluated using the film obtained by the following film extrusion molding. The extrusion processability was evaluated by the bubble stability in the following film extrusion molding.

(1) Film processing Using ethylene polymer as a sample, Plako, 30mmφ, L / D = 28, full flight type screw single screw extruder, 50mmφ, lip gap 0.8mm die, double slit air ring Was used to form a film having a thickness of 80 μm under the conditions of a processing temperature of 170 ° C., an extrusion rate of 5.5 kg / hr, a frost line distance (FLD) of 200 mm, and a blow ratio of 1.8.

(2) Haze (degree of itchiness)
According to the method prescribed | regulated to ASTMD1003, the haze value of the film obtained above was measured. It shows that transparency is excellent, so that this value is small.

(3) Bubble stability By visually observing the stability of the inflation bubble, it was marked as ◎ when the stability was extremely excellent, ◯ when it was excellent, △ when it was slightly unstable, and × when it was unstable.

Example 1
[Preparation of catalyst components]
A 5-liter four-necked flask purged with nitrogen was charged with 1.5 liters of tetrahydrofuran and 1.35 liters (2.7 mol) of diethylzinc in hexane (2 mol / liter) and cooled to 5 ° C. A solution prepared by dissolving 0.2 kg (1 mol) of pentafluorophenol in 500 ml of tetrahydrofuran was added dropwise thereto over 60 minutes. After completion of dropping, the mixture was stirred at 5 ° C. for 60 minutes, and the temperature was raised to 45 ° C. over 28 minutes, followed by stirring for 60 minutes. Thereafter, the temperature was lowered to 20 ° C. in an ice bath, and 45 g (2.5 mol) of water was added dropwise over 90 minutes. Thereafter, the mixture was stirred at 20 ° C. for 60 minutes, heated to 45 ° C. over 24 minutes, and stirred for 60 minutes. Thereafter, the solvent was distilled off under reduced pressure for 120 minutes while raising the temperature from 20 ° C. to 50 ° C., and then dried under reduced pressure at 120 ° C. for 8 hours. As a result, 0.43 kg of a solid product was obtained.
0.43 kg of the above solid product and 3 liters of tetrahydrofuran were placed in a 5-liter four-necked flask purged with nitrogen and stirred. Thereto was added 0.33 kg of silica (Sypolol 948 manufactured by Devison; average particle size = 61 μm; pore volume = 1.61 ml / g; specific surface area = 296 m 2 / g) heated at 300 ° C. under nitrogen flow. After heating to 40 ° C. and stirring for 2 hours, the mixture was allowed to stand to settle the solid component, and when the interface between the precipitated solid component layer and the upper slurry portion was seen, the upper slurry portion was removed. . As a washing operation, 3 liters of tetrahydrofuran was added thereto, and after stirring, the mixture was allowed to stand to settle the solid component. Similarly, when the interface was seen, the upper slurry portion was removed. The above washing operation was repeated 5 times in total. Thereafter, drying was performed at 120 ° C. under reduced pressure for 8 hours to obtain 0.52 kg of a promoter support (A).

[Preparation of prepolymerization catalyst]
After charging 80 liters of butane containing triisobutylaluminum at a concentration of 2.5 mmol / liter and 28 liters of hydrogen at normal temperature and pressure into an autoclave with a stirrer with an internal volume of 210 liters that was previously purged with nitrogen, The temperature rose. Further, ethylene was charged by 0.3 MPa as the gas phase pressure in the autoclave, and after the system was stabilized, 200 mmol of triisobutylaluminum, 28 mmol of racemic-ethylenebis (1-indenyl) zirconium diphenoxide, and then the above promoter support (A) 203 g was added to initiate polymerization. For the first hour, 0.9 kg / hour of ethylene and 3.2 liter / hour of hydrogen at ordinary temperature and pressure are supplied, and the polymerization temperature is 30 minutes from the first hour after the above-mentioned promoter support (A) is charged. The temperature was raised from 40 ° C to 50 ° C. Further, from the first hour after the introduction of the component (B), 4.5 kg / hour of ethylene and 9.4 liter / hour of hydrogen at ordinary temperature and pressure were supplied, and polymerization was carried out at 50 ° C. Thus, prepolymerization was carried out for a total of 4 hours. After completion of the polymerization, after purging ethylene, butane and hydrogen gas, the solvent is filtered, and the resulting solid is vacuum-dried at room temperature, so that 55.5 g of polyethylene per 1 g of the above-mentioned promoter support (A) is prepolymerized. A prepolymerized catalyst component was obtained.

[Continuous gas phase polymerization and kneading]
Using the prepolymerization catalyst component obtained above, copolymerization of ethylene and 1-hexene was carried out in a continuous fluidized bed gas phase polymerization apparatus. The polymerization conditions were a temperature of 85 ° C., a total pressure of 2 MPa, a gas linear velocity of 0.24 m / sec, a hydrogen molar ratio to ethylene of 0.28%, and a 1-hexene molar ratio to ethylene of 1.8%. In order to maintain a constant, ethylene, 1-hexene and hydrogen were continuously supplied. The above prepolymerization catalyst component was continuously supplied at a rate of 0.16 kg / hr and triisobutylaluminum at a rate of 75 mmol / hr, and an average polymerization time of 4 hr and 19 kg / hr was maintained so that the total powder weight of the fluidized bed was maintained at 80 kg. An ethylene / 1-hexene copolymer powder was obtained with a production efficiency of The ethylene / 1-hexene copolymer powder thus obtained was blended with 1000 ppm calcium stearate and 1800 ppm Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), Tanabe Plastics Co., Ltd., 40 mmφ, L / D = 28. Then, an ethylene polymer was obtained by granulation with a full flight screw single screw extruder under the conditions of 150 ° C. and screw rotation speed of 80 rpm. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Reference example 2
Using a prepolymerized catalyst component in which 48.2 g of polyethylene was prepolymerized per 1 g of the cocatalyst support (A), a gas linear velocity of 0.34 m / sec, a hydrogen molar ratio to ethylene of 0.10%, and 1-hexene mole to ethylene The ratio was 1.9%, and the copolymerization was carried out in the same manner as in Example 1 except that the copolymerization was carried out by changing the supply rate of the prepolymerization catalyst component to 0.12 kg / hr and the supply rate of triisobutylaluminum to 27 mmol / hr. An ethylene / 1-hexene copolymer was obtained. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Example 3
[Preparation of catalyst components]
(1) Silica treatment Silica heated at 300 ° C. under nitrogen flow in a nitrogen-substituted 3 liter four-necked flask (Sypolol 948 manufactured by Devison; average particle size = 61 μm; pore volume = 1.70 ml / g) Specific surface area = 291 m ² / g) 0.2 kg was added, and then 1.2 liters of toluene was added while washing the silica adhering to the wall of the flask. After cooling to 5 ° C., a mixed solution of 84.4 ml of 1,1,1,3,3,3-hexamethyldisilazane and 115 ml of toluene was added dropwise over 25 minutes. After completion of the dropping, the mixture was stirred at 5 ° C. for 1 hour and then at 95 ° C. for 3 hours and filtered. Thereafter, the filter was washed four times with 1.2 liters of toluene at 95 ° C. Then, after adding 1.2 liters of toluene, it was left still overnight.
(2) Synthesis of promoter support (A ′) 0.550 liter (1.10 mol) of diethylzinc in hexane (2.00 mol / liter) was added to the slurry obtained above and cooled to 5 ° C. A solution prepared by dissolving 105 g (0.570 mol) of pentafluorophenol in 173 ml of toluene was added dropwise thereto over 65 minutes. After completion of dropping, the mixture was stirred at 5 ° C. for 1 hour. Then, it heated at 40 degreeC and stirred for 1 hour. After the temperature was adjusted to 5 ° C. with an ice bath, 14.9 g (0.828 mol) of H ₂ O was added dropwise over 90 minutes. After completion of dropping, the mixture was stirred at 5 ° C. for 1.5 hours and at 40 ° C. for 2 hours. Then, it left still overnight at room temperature. Then, after stirring at 80 ° C. for 2 hours, the mixture is allowed to stand to settle the solid component, and when the interface between the precipitated solid component layer and the upper slurry portion is seen, the upper slurry portion is removed, and then the remaining liquid After filtering the components with a filter, 1.7 liters of toluene was added and stirred at 95 ° C. for 2 hours. Thereafter, the mixture was stirred four times with 1.7 liters of toluene at 95 ° C. and twice with 1.7 liters of hexane at room temperature, and then allowed to stand to precipitate the solid component. When the interface with the slurry portion was seen, the upper slurry portion was removed, and the remaining liquid component was then filtered through a filter. Thereafter, the solid component was dried at room temperature under reduced pressure for 3 hours to obtain 0.39 kg of a promoter support (A ′).

[Preparation of prepolymerization catalyst]
400 g of the promoter support (A ′) obtained above was used, except that hydrogen was changed to 6 liters, ethylene 0.12 MPa, racemic-ethylenebis (1-indenyl) zirconium diphenoxide 60 mmol, and temperature 23 ° C. In the same manner as in Example 1, preliminary polymerization was carried out by raising the temperature to 30 ° C. to obtain a prepolymerized catalyst component in which 34 g of ethylene polymer per 1 g of the cocatalyst support (A) was prepolymerized.

[polymerization]
A continuous fluidized bed was used in the same manner as in Example 1 except that the prepolymerization catalyst component obtained above was used and the hydrogen molar ratio to ethylene was changed to 0.47% and the 1-hexene molar ratio to ethylene was changed to 1.6%. Copolymerization of ethylene and 1-hexene was carried out in a gas phase polymerization apparatus.

[Kneading]
The ethylene / 1-hexene copolymer powder obtained above was blended with 1000 ppm of calcium stearate and 1800 ppm of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.) using an LCM100 extruder manufactured by Kobe Steel, Ltd., at a feed rate of 350 kg / An ethylene / 1-hexene copolymer was obtained by granulation under the conditions of hr, screw rotation speed 450 rpm, gate opening 4.2 mm, gear pump suction pressure 0.2 MPa, and resin temperature 200-230 ° C. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Example 4
Using a prepolymerized catalyst component in which 13 g of polyethylene was prepolymerized per gram of the cocatalyst support (A ′), the temperature was 75 ° C., the hydrogen molar ratio to ethylene was 0.54%, and the 1-hexene molar ratio to ethylene was 0.33%. Further, an ethylene / 1-butene / 1-hexene copolymer was prepared in the same manner as in Example 3 except that 1-butene having a molar ratio to ethylene of 2.4% was used together. Got. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Example 5
Using a prepolymerized catalyst component in which 11 g of polyethylene was prepolymerized per gram of the cocatalyst support (A ′), the hydrogen molar ratio to ethylene was 0.54%, the 1-hexene molar ratio to ethylene was 0.33%, and the molar ratio to ethylene. An ethylene / 1-butene / 1-hexene copolymer was obtained in the same manner as in Example 3 except that the copolymerization was carried out by changing the use of 1-butene at a ratio of 2.4%. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Example 6
Using a prepolymerized catalyst component in which 13 g of polyethylene per 1 g of the cocatalyst support (A ′) was prepolymerized, the hydrogen molar ratio to ethylene was changed to 0.39% and the 1-hexene molar ratio to ethylene was changed to 0.79%. An ethylene / 1-hexene copolymer was obtained in the same manner as in Example 3 except that the polymerization was performed. The obtained ethylene polymer exhibited physical property values and film extrusion moldability as shown in Table 1.

Comparative Example 1
The high pressure method LDPE F102-0 (manufactured by Sumitomo Chemical Co., Ltd.) produced by radical polymerization is excellent in the balance between melt tension and extrusion torque as summarized in Table 1, but the maximum winding speed is extremely high. The mechanical strength was very low.

Comparative Example 2
FA101-0 (manufactured by Sumitomo Chemical), which is a conventional linear low density polyethylene, is relatively excellent in impact strength and maximum winding speed as summarized in Table 1, but has a low melt tension value. Met.

  As shown in Table 1, it can be seen that the ethylene polymer of the present invention is excellent in workability balance between melt tension and maximum winding speed, and is excellent in mechanical strength.

Claims (2)

It is obtained by copolymerizing ethylene and an α-olefin having 5 to 20 carbon atoms, and has a melt flow rate (MFR; unit is g / 10 minutes) of 0.01 or more and less than 1, and the MFR and 190 ° C. The melt tension (MT; unit is cN) satisfies the relationship of the following formula (1), and the MFR and intrinsic viscosity ([η]; unit is dL / g) satisfy the relationship of the following formula (2) An ethylene polymer having an activation energy of 50 kJ / mol to 100 kJ / mol and a molecular weight distribution (Mw / Mn) of 5.3 to 25.
2 × MFR ^−0.59 <MT <3.6 × MFR ^−0.66 Formula (1)
1.02 × MFR ^−0.094 <[η] <1.50 × MFR ^−0.156 Formula (2) The ethylene polymer according to claim 1, wherein the characteristic relaxation time at 190 ° C (τ; the unit is sec) and the melt flow rate (MFR; the unit is g / 10 minutes) satisfy the relationship of the following formula (4). .
2 <τ <8.1 × MFR ^-0.746 formula (4)