JP2017193661A - Polyethylene composition and film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide economically: a polyethylene composition that can provide a film that generates relatively small number of small FE, has strong drape, and generates little fuzz in the cross-section; and, further, a film comprising the polyethylene composition.SOLUTION: A polyethylene composition satisfies the following requirements (1) to (3); requirement (1) the composition has a density according to JIS K 7112 of 940 kg/mto 975 kg/m; requirement (2) the composition has two or more peaks in an elution temperature-elution amount curve obtained by a cross fractionation chromatography measurement; requirement (3) when the lowest temperature peak among the peaks is denoted by peak P, a weight average molecular weight Mwof a component eluted at a peak top temperature Tof the peak Pis 50,000 to 300,000; and requirement (4) when Fourier transformation infrared spectroscopy measurements of areas in a range of 500 μmor more to less than 4000 μmare performed for arbitrary 10 points on the surface of the polyethylene composition, a standard deviation s of a ratio Wof spectrum intensity r(i=1 to 10) observed at 1378 cmto spectrum intensity r(i=1 to 10) observed at 1369 cm, that is, W=r/r(i=1 to 10) is 0.2 or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyethylene composition and a film comprising the composition.

  One of the uses of the polyethylene film is a surface protection (masking) film such as an optical member. The protective film is required to have a firmness in order to improve the handling of the thin film member and / or prevent wrinkles due to sagging during bonding. Further, if the film has fish eyes (hereinafter abbreviated as FE), the member to be protected may be damaged. Therefore, it is also required that the FE is sufficiently small.

  A polyethylene film is more preferable as a protective film because the higher the film density is, the more the film becomes firmer. However, high-density polyethylene generally has a very large amount of FE, and it has not been possible to provide a sufficiently satisfactory performance as a protective film alone. As a method for reducing FE, a method of reducing FE by mixing high-density polyethylene and high-pressure low-density polyethylene is known (for example, see Patent Document 1).

In addition, FE here means the small spherical foreign material and defect structure which exist in a film. There are various causes of FE, but it can be caused by insufficient melt mixing with the base resin, components with different viscosity (molecular weight) from the base resin, gel components, oxidatively deteriorated resins, different resins, packaging materials It is generated by mixing fragments (paper, thread, fiber, etc.), dust, etc. in any of the raw material resin manufacturing process, bagging / transporting process, and film forming process.

JP 2010-248202 A

  In Patent Document 1, in order to sufficiently reduce the FE, 30 to 60% of the polyethylene composition needs to be a high pressure method low density polyethylene. When such a high pressure method low density polyethylene is mixed, the stiffness when formed into a film is lost, and when the thin film member is covered, the whole handling becomes difficult. There is a trade-off relationship that the amount of FE increases if the proportion of high-density polyethylene is increased to produce stiffness. Further, in order to industrially mix 30-60% of high-pressure polyethylene with high-density polyethylene in a high-density polyethylene, a blending hopper that mixes both in advance is required. As a blending method, the melt blend is preferably dispersed more uniformly than the dry blend from the viewpoint of reducing the FE, but there is a problem that the cost is increased because the melt blend is performed once more.

  The present invention has been made in view of the above problems, and a polyethylene composition capable of providing a film having a relatively small number of small FEs, strong stiffness, and less occurrence of fluffing in a cross section, and the polyethylene It aims at providing the film which consists of a composition at low cost.

  As a result of intensive research to develop a film having a moderately low FE and a firmness of the film, the present inventor has the following requirements in a blend system of high-density polyethylene and high-pressure low-density polyethylene. It has been found that the high-pressure low-density polyethylene to be filled is extruded and kneaded under specific conditions, so that the FE of the high-density polyethylene can be sufficiently reduced even with a small amount of addition. Moreover, if it is added in a small amount, it can be kneaded with a side feeder at the time of granulation of high-density polyethylene, and secondary extrusion for melt blending becomes unnecessary, leading to cost reduction.

That is, the present invention relates to the following.
[1]
A polyethylene composition satisfying the following requirements (1) to (3);
Requirement (1): Density at JIS K7112 is, 940 kg / m ³ or more 975 kg / m ³ or less,
Requirement (2): having two or more peaks in the elution temperature-elution amount curve obtained by cross-fractionation chromatography measurement,
Requirement (3): wherein the two or more peaks, when the peak of the lowest temperature side was set to peak P _low, weight-average molecular weight Mw _low of components eluted at a peak top temperature T _low of the peak P _low is 50 , 000 to 300,000,
Requirement (4): When the measurements for area of less than 500 [mu] m ² or more 4000 .mu.m ² Fourier transform infrared spectroscopy was performed on an arbitrary 10 points of the polyethylene composition surface, spectral intensity r observed at 1378 cm ^-1 _{1, i} (i = 1 to 10) and the ratio of spectral intensities r _{2, i} (i = 1 to 10) observed at 1369 cm ⁻¹ W _i = r _{1, i} / r _{2, i} (i = The standard deviation s of 1 to 10) is 0.2 or less.
[2]
Peak top temperature T _low of the peak P _low is, 71 ° C. or higher 84 ° C. or less, the polyethylene composition according to [1].
[3]
The polyethylene composition according to [1] or [2], wherein a ratio w _{low of} a component eluted at the peak P _low is 0.5% or more and 20% or less.
[4]
The ratio Mw _low / Mn _low of the weight average molecular weight Mw _low and the number average molecular weight Mn _low of the component eluted at the peak top temperature T _low of the peak P _low is 3.0 or more and 9.0 or less, [1] to [3] The polyethylene composition according to any one of [3].
[5]
The film containing the polyethylene composition as described in any one of [1]-[4].
[6]
The film according to [5], which is used for a protective film.

  According to the present invention, a polyethylene composition capable of providing a film having a relatively small number of FEs, strong stiffness, and less occurrence of fluffing in a cross section, and a film comprising the polyethylene composition are provided at low cost. be able to.

4 is a graph showing an elution temperature-elution amount curve obtained by cross-fractionation chromatography measurement of Example 3.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not restrict | limited to the following this embodiment, A various deformation | transformation can be implemented within the range of the summary.

[Polyethylene composition]
The polyethylene composition of the present embodiment satisfies the following requirements (1) to (3).
Requirement (1): Density at JIS K7112 is, 940 kg / m ³ or more 975 kg / m ³ or less,
Requirement (2): having two or more peaks in an elution temperature-elution amount curve obtained by cross-fractionation chromatography (hereinafter also referred to as “CFC”) measurement,
Requirement (3): wherein the two or more peaks, when the peak of the lowest temperature side was set to peak P _low, weight-average molecular weight Mw _low of components eluted at a peak top temperature T _low of the peak P _low is 50 , 000 to 300,000,
Requirement (4): When the measurements for area of less than 500 [mu] m ² or more 4000 .mu.m ² Fourier transform infrared spectroscopy was performed on an arbitrary 10 points of the polyethylene composition surface, spectral intensity r observed at 1378 cm ^-1 _{1, i} (i = 1 to 10) and the ratio of spectral intensities r _{2, i} (i = 1 to 10) observed at 1369 cm ⁻¹ W _i = r _{1, i} / r _{2, i} (i = The standard deviation s of 1 to 10) is 0.2 or less.
The above requirements will be described below.

  The polyethylene composition of this embodiment contains at least one selected from the group consisting of high-density polyethylene, high-pressure method low-density polyethylene, linear low-density polyethylene, and other special ultra-low-density polyethylene. Among these, a composition comprising high density polyethylene and high pressure method low density polyethylene is preferable. Such a polyethylene composition tends to reduce FE more. The polyethylene contained in the polyethylene composition of the present embodiment may be a homopolymer of ethylene or a copolymer of ethylene and an α-olefin.

  Moreover, the manufacturing method in particular of polyethylene is not restrict | limited, Even if polyethylene is manufactured by any manufacturing method of the generally used solution method, a high pressure method, a high pressure bulk method, a gas method, and a slurry method. Good. The catalyst used for the production of the high-density polyethylene of this embodiment is not particularly limited, and a metallocene catalyst, a Ziegler-Natta catalyst, a Phillips catalyst, or the like can be used. Among these, a metallocene catalyst that can reduce the low molecular weight component that easily bleeds out is preferably used. Methods for obtaining metallocene catalysts and polymerization methods are known, and are described, for example, in JP-A-2015-89937.

[Requirement (1): Density]
In the polyethylene composition of the present embodiment, the density of the polyethylene compositions are 940 kg / m ³ or more 975 kg / m ³ or less, preferably 945 kg / m ³ or more 975 kg / m ³ or less, more preferably 950 kg / m ³ or more and 974 kg / m ³ or less, more preferably 954 kg / m ³ or more and 973 kg / m ³ or less. When the density is 940 kg / m ³ or more, the stiffness of the film is further improved.

  The density of the polyethylene composition can be measured by the method described in the examples. The density of the polyethylene composition can be controlled by the type of polyethylene used and the mixing ratio thereof.

[Requirement (2): Elution temperature-elution amount curve obtained by CFC measurement]
The polyethylene composition of the present embodiment has two or more peaks in the elution temperature-elution amount curve obtained by CFC measurement.

  Here, “cross fractionation chromatography (CFC)” refers to a temperature-rise elution fractionation part (hereinafter also referred to as “TREF part”) that performs crystalline fractionation and a gel permeation chromatography part (hereinafter referred to as “TRF part”). The GPC unit is also a device that can analyze the mutual relationship between the composition distribution and the molecular weight distribution by directly connecting the TREF unit and the GPC unit.

  The elution amount and integrated elution amount of polyethylene at each temperature can be determined by measuring an elution temperature-elution amount curve as follows using a TREF section. Specifically, first, the column containing the filler is heated to 140 ° C., and a sample solution (for example, concentration: 20 mg / 20 ml) in which polyethylene is dissolved in orthodichlorobenzene is introduced and held for 120 minutes.

  Next, the sample is sequentially deposited on the surface of the filler by lowering the temperature to 40 ° C. at a temperature decrease rate of 0.5 ° C./min. After maintaining at 40 ° C. for 20 minutes, the temperature of the column is sequentially increased at a rate of temperature increase of 20 ° C./min. First, the temperature is increased from 40 ° C. to 60 ° C. at intervals of 10 ° C., the temperature is increased from 60 ° C. to 69 ° C. at intervals of 3 ° C., the temperature is increased from 69 ° C. to 100 ° C. at intervals of 1 ° C., and from 100 ° C. to 120 ° C. The temperature is increased at 10 ° C intervals. In addition, after hold | maintaining at each temperature for 21 minutes, it heats up and the density | concentration of the sample (polyethylene) eluted at each temperature is detected. And the elution temperature-elution amount curve is measured from the value of the elution amount (mass%) of the sample (polyethylene) and the temperature in the column (° C.) at that time, and the elution amount at each temperature is obtained.

[Requirement (3): The weight average molecular weight of components eluted at a peak top temperature T _low peak P _low Mw _low]
Among two or more peaks in the elution temperature-elution amount curve obtained by CFC measurement, the peak at the lowest temperature side is defined as “peak P _low ”, and the peak top temperature of the peak P _low is defined as “peak top temperature T _low ”. To do. At this time, the weight average molecular weight Mw _low of the component eluted at the peak top temperature T _low is 50,000 or more and 300,000 or less, preferably 100,000 or more and 295,000 or less, more preferably 120,000. Above 290,000. When the Mw _low is 300,000 or less, the FE is further reduced. Also, the FE is further reduced when the Mw _low is 50,000 or more.

The weight average molecular weight Mw _low of the component eluting at the peak top temperature T _low is obtained by the above-described CFC measurement, and more specifically can be measured by the method described in the examples. The peak P _low is a peak composed of a component having the lowest crystallinity in the composition, and the weight average molecular weight Mw _low of the component can be controlled when the component is polymerized. For example, when the component is made of high-pressure low-density polyethylene, Mw _low tends to increase by decreasing the polymerization temperature or increasing the polymerization pressure, and decreasing by increasing the polymerization temperature or decreasing the polymerization pressure.

[Peak P peak of the _low top temperature T _low]
The peak top temperature T _low is preferably 71 ° C. or higher and 84 ° C. or lower, more preferably 72 ° C. or higher and 83 ° C. or lower, still more preferably 73 ° C. or higher and 82 ° C. or lower, and particularly preferably 74 ° C. or higher and 81 ° C. or lower. It is below ℃. When the peak top temperature T _low is 71 ° C. or higher, the FE tends to decrease more. Even when the peak top temperature T _low is 84 ° C. or lower, the FE tends to decrease more. The peak P _low is a peak derived from the component having the lowest crystallinity, and the peak top temperature T _low is the elution temperature of the component having the lowest crystallinity.

The peak top temperature T _low can be obtained from the elution temperature-elution amount curve obtained by the above-described CFC measurement, and more specifically can be measured by the method described in the examples. Further, the peak top temperature T _low tends to increase by increasing the density (crystallinity) of the low crystallinity component and decrease by decreasing it.

[Proportion of component eluting at peak P _low w _low ]
The ratio of the components that elute at the peak P _{low is} defined as “ratio w _low ”. At this time, the ratio w _low is preferably 0.5% or more and 20% or less, more preferably 1% or more and 18% or less, still more preferably 3% or more and 15% or less, and still more preferably 4%. % To 14%, particularly preferably 5% to 13%. The component (low temperature side component) eluted at the peak P _low in the elution temperature-elution amount curve substantially represents the amount of the low density component of the blend raw material. Therefore, when the ratio w _low is larger than the above range, it means that the amount of the low density component of the blend raw material to be substantially mixed is large. A small amount of blend is preferable because it can be easily added by adding high-pressure low-density polyethylene to an extruder for granulating high-density polyethylene. It is preferable that the ratio w _low is 20% or less because a dedicated facility can be omitted industrially for mixing the blend raw materials. Further, when the ratio w _low is 0.5% or more, the FE tends to decrease more.

The ratio w _low can be determined as the area of the peak P _low with respect to 100% of the total area of all peaks in the elution temperature-elution amount curve obtained by CFC measurement, and more specifically described in the examples. It can obtain | require by the method of. The ratio w _low tends to increase by increasing the ratio of the low crystallinity component in the composition and decrease by decreasing it.

[Ratio of weight-average molecular weight Mw _low number average molecular weight Mn _low Mw _low / Mn _low]
The ratio between the weight average molecular weight Mw _low and the number average molecular weight Mn _low of the component eluted at the peak top temperature T _low of the peak P _low is defined as “ratio Mw _low / Mn _low ”. The ratio Mw _low / Mn _low is preferably 3.0 or more and 9.0 or less, more preferably 3.0 or more and 8.8 or less, and further preferably 3.0 or more and 8.5 or less. Preferably they are 3.0 or more and 8.1 or less. A large ratio Mw _low / Mn _low means that the molecular weight distribution of the blend raw material to be substantially mixed is wide. It is good that the ratio Mw _low / Mn _low is 9.0 or less, and there are fewer high molecular weight components that can cause FE, and FE tends to decrease more.

The ratio Mw _low / Mn _low is obtained by the above-described CFC measurement, and more specifically can be measured by the method described in the examples. The peak P _low is a peak composed of a component having the lowest crystallinity in the composition, and the ratio Mw _low / Mn _low can be controlled when polymerizing the component. For example, when the component is made of high pressure process low density polyethylene, the ratio Mw _low / Mn _low tends to increase by increasing the agitation during polymerization and decrease by decreasing the agitation.

[Requirement (4): Fourier transform infrared spectroscopy (FT-IR)]
When arbitrary 10 points on the surface of the polyethylene composition of the present embodiment are measured by Fourier transform infrared spectroscopy (FT-IR), the spectrum intensity observed at 1378 cm ⁻¹ is the spectrum intensity r _{1, i} ( i = 1 to 10), and the spectrum intensity observed at 1369 cm ⁻¹ is the spectrum intensity r _{2, i} (i = 1 to 10). At this time, the standard deviation s of the ratio W _i = r _{1, i} / r _{2, i} (i = 1 to 10) is 0.2 or less, preferably 0.18 or less, more preferably 0.8. 15 or less. When the standard deviation s is 0.2 or less, local compositional deviation in the composition is sufficiently small, the physical properties are uniform, and the FE when formed into a film is also reduced.

Here, as the infrared spectrophotometer, it is preferable to use a micro infrared spectrophotometer capable of measuring a minute area. The measurement area per one point to 500 [mu] m ² or more 4000μm less than ^2. Using the line connecting the absorption heights H ₁₃₃₀ and H ₁₃₉₈ of ₁₃₃₀ cm ⁻¹ and 1398 cm ⁻¹ as the baseline, the spectral intensity at the target wave number is evaluated.

The standard deviation can be calculated by the following formula.

  The standard deviation s can be measured more specifically by the method described in the examples. The standard deviation s tends to increase by increasing the kneading strength of the composition and decrease by decreasing it.

[Method for producing polyethylene composition]
The polyethylene composition of the present embodiment can be obtained, for example, by melt kneading by the following method. As kneading, it is preferable to perform melt kneading twice, that is, primary kneading and secondary kneading.

  The primary kneading is preferably strong shear kneading in a low temperature range. For example, the temperature of the extruder is set to 140 ° C. to 180 ° C. (melting point of resin + about 20 ° C.) and the pressure is increased. After starting the extrusion, the set temperature is lowered within a range that does not hinder the operation of the extruder. Since the actual temperature of the resin does not drop below a certain temperature due to heat generation during melting, extrusion and pelletization are carried out with that temperature as the set temperature. By kneading at as low a temperature as possible, a strong shear stress is obtained and the resin is dispersed efficiently. If dispersion seems to be poor, primary kneading may be repeated. However, when extrusion is repeated, there is a concern that FE may increase due to oxidized and deteriorated resin.

  The secondary kneading is preferably kneading of a high melting point component in a high temperature range. For example, the pressure is increased by setting the extruder to 240 ° C. to 280 ° C. (resin melting point + about 120 ° C.). At the time of extrusion, about 0.1 to 1 part by mass of polyethylene wax is added to the composition. This polyethylene wax is preferably produced as a by-product in the production of raw material high-pressure low-density polyethylene and high-density polyethylene from the viewpoint of compatibility, and preferably has a molecular weight of about 1000. By adding polyethylene wax and kneading at a high temperature, the high melting point component present in the raw material resin can be uniformly diffused. At this time, if the dispersion seems to be poor, secondary kneading may be repeated.

  As the melt extruder in the kneading operation, a single screw extruder, a twin screw extruder, a vent extruder, a tandem extruder, or the like can be used.

〔the film〕
The film of this embodiment contains the said polyethylene composition. The film obtained by using the above polyethylene composition has a relatively small number of relatively small FEs, has a firmness of the film, and has less fuzz in the cross section. Although the use of the said film is not specifically limited, For example, it can use suitably in a protective film use.

[Film Formation Method]
A film can be obtained by film-forming the polyethylene composition of this embodiment by various methods. As the molding method, for example, an air-cooled inflation method, a water-cooled inflation method, a T-die method, or the like is suitable.

[Additive]
The polyethylene composition of the present embodiment includes an antioxidant, an anti-blocking agent, a lubricant, an antistatic agent, an antifogging agent, an ultraviolet absorber, an organic or inorganic filler, an organic or inorganic pigment, a structure, if necessary. Known additives such as a nucleating agent and a crosslinking agent can be added.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in more detail, this invention is not limited by these Examples.

[Evaluation method]
Various physical properties of the compositions used in Examples and Comparative Examples were measured by the following methods.

(density)
The density was measured by a density gradient tube method in accordance with JIS K7112.

(Cross fractionation chromatography (CFC) measurement)
CFC measurement was performed using an Automated 3D analyzer CFC-2 manufactured by Polymer ChAR. The column was a stainless steel microball column (3/8 "od x 150 mm), and the eluent was o-dichlorobenzene (for high performance liquid chromatography).

  The column containing the packing was heated to 140 ° C., and a sample solution in which polyethylene was dissolved in orthodichlorobenzene was introduced and held for 120 minutes. Next, the temperature of the column was lowered to 40 ° C. at a temperature lowering rate of 0.5 ° C./min, and then held for 20 minutes. In this step, the sample was deposited on the filler surface.

  The column temperature was adjusted as follows. First, the temperature was raised to 50 ° C. at a rate of temperature rise of 20 ° C./min and held at 50 ° C. for 21 minutes. Then, it heated up to 60 degreeC and hold | maintained at 60 degreeC. Similarly, the temperature was raised while changing the holding temperature. The temperature was raised and held at intervals of 5 ° C. from 60 ° C. to 75 ° C., and the temperature was raised and held at intervals of 3 ° C. from 75 ° C. to 90 ° C. From 110 ° C. to 110 ° C., the temperature was raised / held at 1 ° C. intervals, and from 110 ° C. to 120 ° C., the temperature was raised / held at 5 ° C. intervals. The temperature of each sample was increased at a rate of 20 ° C./min, and the concentration of the sample (polyethylene) eluted after holding at each holding temperature for 21 minutes was detected.

By measurement under the above conditions, an elution temperature-elution amount curve, an elution amount at each temperature, an elution integral amount, and a weight average molecular weight (M _w ) for a sample eluted at each temperature were obtained.

(Film forming)
Using a T-die film forming machine manufactured by Yamaguchi Seisakusho, a cylinder temperature of 200 ° C., a die temperature of 200 ° C., an extrusion rate of 5 kg / h, and a film having a thickness of 40 μm were formed.

(Reduction of large FE)
The number of FE of 0.3 mm or more of the film formed using the T die was visually evaluated. As the FE, those derived from foreign substances other than the composition and colored substances produced by oxidation were excluded from the measurement target. In addition, each component (high density polyethylene (A) and low density polyethylene (B)) which comprises the polyethylene composition of an Example is formed into a film independently, and the number of 0.3 mm or more FE recognized by the said film is counted. did. Of the high-density polyethylene (A) single film and the low-density polyethylene (B) single film, the one with the largest number of FE was used as the reference (1). Next, the number of FEs of 0.3 mm or more in the film obtained from the polyethylene composition of the example was counted, the ratio of the number of FEs with respect to the above criteria was determined, and evaluated as follows.
◎: 0.5 or less ○: 0.5 exceeding 0.7 or less △: 0.7 exceeding 1.0 or less ×: exceeding 1.0

(Reduction of small FE)
The number of FE of 0.1 mm or more and less than 0.3 mm of the film formed using the T-die was visually evaluated. As the FE, those derived from foreign substances other than the composition and those colored by oxidation were excluded from the measurement target. In addition, each component (high density polyethylene (A) and low density polyethylene (B)) which comprises the polyethylene composition of an Example is formed into a film independently, and 0.1-0.3 mm FE recognized by the said film | membrane Counted the number of. Of the high-density polyethylene (A) single film and the low-density polyethylene (B) single film, the one with the largest number of FE was used as the reference (1). Next, the number of FEs of 0.1 mm or more and less than 0.3 mm in the film obtained from the polyethylene composition of the example was counted, and the ratio of the number of FEs with respect to the above criteria was determined and evaluated as follows.
◎: 0.5 or less ○: 0.5 exceeding 0.7 or less △: 0.7 exceeding 1.0 or less ×: exceeding 1.0

(Elastic modulus)
Using the T-die molded film, the tensile secant modulus (specified strain 2%) was measured according to JIS K 7127. The average value of the tensile secant modulus in the machine direction and the transverse direction was used as an index of stiffness, and evaluated according to the following evaluation criteria.
A: 400 MPa or more:
○: 300 or more and less than 400 MPa Δ: 200 or more and less than 300 MPa ×: less than 200 MPa

(State of film cut surface)
The ear trim surface of the above T-die molded film was visually observed. If the cut surface was cut well and there was no fuzz, it was marked as ◯, when fluff was slightly recognized, and when fluff was found in large amounts, it was marked as x. .

(FT-IR measurement)
Using a Fourier transform infrared spectrophotometer FT / IR-4000 manufactured by JASCO Corporation and its associated infrared microscope IRT-3000, microscopic FT-IR measurement of the T-die molded film was performed. The measurement area was 3600 μm ² . For each sample was measured in arbitrary 10 places, the spectral intensity r ₂ observed in the spectral intensity _{r 1, i (i = 1~10} ) and 1369cm ^-1 which is observed in 1378cm ^-1, i (i = The standard deviation s of the ratio W _i = r _{1, i} / r _{2, i} (i = 1 to 10) of 1 to 10) was determined.

[Preparation of components used in Examples and Comparative Examples]
・ High density polyethylene (A)
<Preparation of Ziegler-Natta catalyst (a)>
40 mL of a hexane solution of an organomagnesium compound represented by the formula: AlMg ₆ (C ₄ H ₉ ) ₁₂ (OC ₃ H ₇ ) ₃ in a fully nitrogen-substituted 200 mL stainless steel autoclave (37. 8 mL of hexane containing 2.27 g (37.8 mmol) of methylhydropolysiloxane was added dropwise over 30 minutes while stirring at 25 ° C. After dropping, the mixture was heated to 80 ° C. and reacted with stirring for 3 hours to obtain an organomagnesium compound to be brought into contact with the titanium compound.

Into an 8 L stainless steel autoclave sufficiently purged with nitrogen, 2400 mL of hexane was charged and stirred at −5 ° C., while the organomagnesium compound represented by the formula AlMg ₆ (C ₄ H ₉ ) ₁₂ (OC ₃ H ₇ ) ₃ was used. 1300 mL of hexane solution (corresponding to 521 mmol of magnesium) and 1300 mL of hexane solution of 0.5 mol / L titanium tetrachloride were added dropwise simultaneously over 2 hours. After dropping, the mixture was further aged with stirring at 10 ° C. for 1 hour, and then the supernatant was removed and washed with 3000 mL of hexane four times to prepare a Ziegler-Natta catalyst.

<Preparation of high-density polyethylene resin (A-1)>
The polymerization reaction was conducted in a polymerization vessel having a volume of 230 L. The polymerization temperature was 86 ° C. and the polymerization pressure was 1.0 MPa. The Ziegler-Natta catalyst (a) synthesized in this polymerization vessel was introduced at a rate of 0.3 g / hr, triisobutylaluminum at 24 mmol / hr, and normal hexane at a rate of 48 L / hr. Polymerization was carried out by introducing a mixed gas of ethylene, hydrogen, and 4 mol% of butene-1 to this.

  The polymerization was terminated by depressurizing the mixed gas of ethylene and hydrogen, pressurizing and depressurizing with nitrogen gas three times, and then introducing methanol by 0.5 mass% of normal hexane as a solvent. Thereafter, the ethylene homopolymer was filtered through a 300-mesh wire net and dried in a hot air dryer at 95 ° C. for 3 hours. The obtained high-density polyethylene resin powder was manufactured by Nippon Steel Co., Ltd. extruder (screw diameter 65 mm, L / D = 28, L: distance (m) from the raw material supply port to the discharge port of the extruder, D: extruder. The same is used, and the mixture is extruded and granulated at 200 ° C. to obtain a high-density polyethylene resin (A-1). By carrying out granulation at 160 ° C. or more and 200 ° C. or less, phase separation can be prevented and dispersibility can be improved by kneading under high shear. Table 1 shows the physical properties of the obtained resin.

<Preparation of high-density polyethylene resin (A-2)>
Polymerization was performed in the same manner as A-1 except that butene-1 was not used, to obtain a high-density polyethylene resin (A-2). Table 1 shows the physical properties of the obtained resin.

<Preparation of high-density polyethylene resin (A-3)>
Polymerization was performed in the same manner as the high-density polyethylene resin (A-1) except that the polymerization temperature was 83 ° C. and the amount of butene-1 used was 7.5 mol% to obtain a high-density polyethylene resin (A-3). . Table 1 shows the physical properties of the obtained resin.

<Preparation of metallocene supported catalyst (b)>
Silica P-10 [manufactured by Fuji Silysia Ltd. (Japan)] (trademark) was calcined at 400 ° C. for 5 hours in a nitrogen atmosphere and dehydrated. Ethoxydiethylaluminum was reacted with surface hydroxyl groups to generate ethane gas, and the amount of ethane gas generated was measured using a gas burette. The initial amount of the surface hydroxyl group of dehydrated silica was determined based on the amount of ethane gas generated, and found to be 1.3 mmol / g-SiO ₂ . In a 1.8 L autoclave, 40 g of this dehydrated silica was dispersed in 800 cc of hexane to obtain a slurry. While maintaining the resulting slurry at 50 ° C. with stirring, 60 cc of a hexane solution of triethylaluminum (concentration 1 mol / L) was added, and then stirred for 2 hours to react triethylaluminum with the surface hydroxyl group of silica, and the triethylaluminum treatment In addition, a component (c) containing the silica and the supernatant liquid and having all the surface hydroxyl groups of the silica treated with triethylaluminum being crushed was obtained. Thereafter, the supernatant liquid in the obtained reaction mixture was removed by decantation to remove unreacted triethylaluminum in the supernatant liquid. Thereafter, an appropriate amount of hexane was added to obtain 800 cc of a hexane slurry of silica treated with triethylaluminum.

On the other hand, 200 mmol of [(Nt-butylamide) (tetramethyl-η5-cyclopentadienyl) dimethylsilane] titanium-1,3-pentadiene (hereinafter referred to as “titanium complex”) was added to Isopar E [Exxon Chemical Company (USA) 1) 1 mol / L hexane solution of composition formula AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) ₁₂ dissolved in 1000 cc and previously synthesized from triethylaluminum and dibutylmagnesium 20 cc, hexane was further added to adjust the titanium complex concentration to 0.1 mol / L, and component (d) was obtained.

  Also, 5.7 g of bis (hydrogenated tallow alkyl) methylammonium-tris (pentafluorophenyl) (4-hydroxyphenyl) borate (hereinafter abbreviated as “borate”) was added to 50 cc of toluene and dissolved, A 100 mmol / L toluene solution was obtained. To this toluene solution of borate, 5 cc of a 1 mol / L hexane solution of ethoxydiethylaluminum was added at room temperature, and further hexane was added so that the borate concentration in the toluene solution was 70 mmol / L. Then, it stirred at room temperature for 1 hour and obtained the reaction mixture containing a borate.

  46 cc of this reaction mixture containing borate was added to 800 cc of the slurry of component (c) obtained above with stirring at 15 to 20 ° C., and the borate was supported on silica by physical adsorption. Thus, a slurry of silica carrying borate was obtained. Further, 32 cc of the component (d) obtained above was added and stirred for 3 hours to allow the titanium complex and borate to react. Thus, a metallocene-supported catalyst (b) containing silica and a supernatant liquid and having catalytically active species formed on the silica was obtained.

<Preparation of liquid promoter component (e)>
As organomagnesium compound, using an organic magnesium compound represented by the _{AlMg 6 (C 2 H 5)} 3 (n-C 4 H 9) 12. Methylhydropolysiloxane (viscosity 20 centistokes at 25 ° C.) was used as the siloxane compound to be reacted with this. To a 200 cc flask, 40 cc of hexane and AlMg ₆ (C ₂ H ₅ ) ₃ (n-C ₄ H ₉ ) ₁₂ were added with a total amount of 37.8 mmol of Mg and Al with stirring. Liquid cocatalyst component (e) was prepared by adding 40 cc of hexane containing 2.27 g (37.8 mmol) of siloxane with stirring, then raising the temperature to 80 ° C. and reacting with stirring for 3 hours. .

<Preparation of high-density polyethylene resin (A-4)>
The metallocene-supported catalyst (b) obtained above and the liquid promoter component (e) are brought into contact with hydrogen by supplying a necessary amount of hydrogen as a chain transfer agent to the catalyst transfer line and introduced into the polymerization reactor, Purified hexane was used as a solvent, and ethylene was used as a monomer. High pressure polyethylene resin with a total pressure of 1.0 MPa and a reaction temperature of 80 ° C. and a polymerization reaction in a mixed gas of ethylene and hydrogen (the gas composition is adjusted so that the molar ratio of hydrogen and ethylene + hydrogen is 0.5%). Got. The high-density polyethylene resin powder obtained by polymerization is extruded and granulated at 200 ° C. using an extruder manufactured by Nippon Steel Co., Ltd. (screw diameter 65 mm, L / D = 28). -4) was obtained. Table 1 shows the physical properties of the obtained resin.

<Preparation of high-density polyethylene resin (A-5)>
Similar to the high-density polyethylene resin (A-4), except that the molar ratio of hydrogen is 0.6 mol% with respect to 100 mol% of the total of ethylene and hydrogen, and 0.06 mol% of butene-1 is added as a comonomer. Polymerization was performed to obtain a high-density polyethylene resin (A-5). Table 1 shows the physical properties of the obtained resin.

-Polymerization of low density polyethylene <Preparation of low density polyethylene resins (B-1) to (B-10)>
Under the conditions shown in Table 2, high pressure low density polyethylene resins (B-1) to (B-10) were polymerized using a peroxide as an initiator. Table 2 shows the physical properties of the obtained resin.

[Examples 1 to 11]
High density polyethylene (A) and low density polyethylene (B) were mixed in the ratio shown in Table 3, and melt kneaded and pelletized using an extruder manufactured by Nippon Steel Co., Ltd. The initial temperature was set to 170 ° C., and the temperature was gradually lowered during the preliminary operation, and primary kneading was performed at 150 ° C.

  0.2 parts by mass of polyethylene wax by-produced during the production of high-density polyethylene (A) and 0.1% of polyethylene wax by-produced during the production of low-density polyethylene (B) are added to 100 parts by mass of the obtained pellets. 2 parts by mass was added, and the mixture was put into a blender (container size diameter 770 mm, height 550 mm), and the stirring blade was rotated at 30 rpm and mixed for 5 minutes. The obtained mixture was again charged into an extruder manufactured by Nippon Steel Co., Ltd. set to 260 ° C., and secondary kneading was performed to obtain pellets of polyethylene compositions (C-1) to (C-11). The evaluation results are shown in Table 3.

[Comparative Examples 1-3]
High-density polyethylene (A) and low-density polyethylene (B) are mixed in the proportions shown in Table 4, and primary and secondary kneading are carried out in the same manner as in Examples 1 to 9, and polyethylene compositions (D-1) to ( D-3) pellets were obtained. The evaluation results are shown in Table 4.

[Comparative Examples 4 and 5]
High density polyethylene (A) and low density polyethylene (B) were mixed in the ratio shown in Table 4, and melt kneaded at 200 ° C. using an extruder manufactured by Nippon Steel Co., Ltd., and pelletized. Pellets of the obtained polyethylene compositions (D-4) and (D-5) were obtained. The evaluation results are shown in Table 4.

The graph which shows the elution temperature-elution amount curve obtained by the cross-fractionation chromatography measurement of Example 3 in FIG. The peak P _low and the peak temperature T _low are shown in FIG. As shown in FIG. 3, the ratio w _low of components eluted at a peak P _low is determined as the ratio of the area of the peak P _low to the total peak area. In addition, overlapping peaks can be divided by dividing them with a perpendicular drawn from the peak valley to the time axis.

  Since the polyethylene composition of the present invention does not require secondary extrusion for blending, the production process is reduced. Moreover, since it has sufficient stiffness when it is made into a film, there are few fish eyes, and the fluffing of the cross section of the film can be suppressed, it has high industrial applicability.

Claims (6)

A polyethylene composition satisfying the following requirements (1) to (3);
Requirement (1): Density at JIS K7112 is, 940 kg / m ³ or more 975 kg / m ³ or less,
Requirement (2): having two or more peaks in the elution temperature-elution amount curve obtained by cross-fractionation chromatography measurement,
Requirement (3): wherein the two or more peaks, when the peak of the lowest temperature side was set to peak P _low, weight-average molecular weight Mw _low of components eluted at a peak top temperature T _low of the peak P _low is 50 , 000 to 300,000,
Requirement (4): When the measurements for area of less than 500 [mu] m ² or more 4000 .mu.m ² Fourier transform infrared spectroscopy was performed on an arbitrary 10 points of the polyethylene composition surface, spectral intensity r observed at 1378 cm ^-1 _{1, i} (i = 1 to 10) and the ratio of spectral intensities r _{2, i} (i = 1 to 10) observed at 1369 cm ⁻¹ W _i = r _{1, i} / r _{2, i} (i = The standard deviation s of 1 to 10) is 0.2 or less. Peak top temperature T _low of the peak P _low is at 71 ° C. or higher 84 ° C. or less, the polyethylene composition according to claim 1. The polyethylene composition according to claim 1 or 2, wherein a ratio w _{low of} a component eluting at the peak P _low is 0.5% or more and 20% or less. The ratio Mw _low / Mn _low of the weight average molecular weight Mw _low and the number average molecular weight Mn _low of the component eluted at the peak top temperature T _low of the peak P _low is 3.0 or more and 9.0 or less. The polyethylene composition according to any one of 3 above.   The film containing the polyethylene composition as described in any one of Claims 1-4.   The film according to claim 5, which is used for a protective film.