JPH0959440A - Polyethylene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyethylene resin compsn. improved in processibility and heat seal strength by compounding a specific low-density PE with a specific ethylene-α-olefin copolymer. SOLUTION: This compsn. is prepd. by compounding 99-51wt.% low-density PE with 1-49wt.% ethylene-3C or higher α-olefin copolymer. The former polymer is obtd. by a high-pressure free-radical polymn. and has a density (after immersed in 100 deg.C water for 1hr and allowed to cool to room temp.) of 0.910-0.935g/cm<3> and a melt flow rate (at 190 deg.C under a load of 2160g) of 0.1-20g/10min. The latter polymer has a density (after immersed in 100 deg.C water for 1hr and allowed to cool to room temp.) of 0.860-0.920g/cm<3> , a melt flow rate (at 190 deg.C under a load of 2160g) of 1.0-50g/10min, and a ratio of wt. average mol.wt./number average mol.wt. of 3 or lower, satisfies the relation expressed by the formula [wherein Tm is the highest peak temp. ( deg.C) in the endothermic curve obtd. when a test specimen is melted at 200 deg.C for 5min, cooled to 30 deg.C at a temp. down rate of 10 deg.C/min, and heated at a temp. rise rate of 10 deg.C/min with a differential scanning calorimeter; and SCB is the number of short-chain branches per 100 carbon atoms obtd. from an infrared absorption spectrum], and has a Tm ( deg.C) lower than that of the former polymer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyethylene resin composition. More specifically, it is excellent in workability, has a high heat-sealing strength, and can be heat-sealed at a low temperature, that is, as a heat-sealing material for extruded laminated materials that can be heat-sealed at a high speed at a constant heat-sealing temperature. The present invention relates to a suitable polyethylene resin composition.

[0002]

2. Description of the Related Art Low-density polyethylene (hereinafter referred to as HP-LDPE) obtained by a high-pressure radical polymerization method has a long-chain branch in its molecular chain. Therefore, it can be easily extruded with a general extruder, and a very stable molten film can be obtained in a T-die. Furthermore, the melted film has sufficient drawdown properties and good adhesion to the substrate, so it is extruded and laminated on paper, non-woven fabric, plastic film, metal foil, etc., and mainly used for packaging materials and various containers. Widely used in.

However, since HP-LDPE has a small adhesive strength (hereinafter referred to as heat-sealing strength) at the seal portion when heat-sealing resins with each other, HP-LDPE is similar to water-packed products. It could not be used in applications that require high heat-sealing strength, and its range of use was limited despite its excellent processability. In addition, if the number of long-chain branches in the molecular chain is increased in order to reduce the density, the characteristic processing characteristics deteriorate, so the density decreases due to the increase in the number of long-chain branches, which in turn lowers the density. There was a limit to the lowering of the crystal melting point by the method. Therefore, heat sealing at a lower temperature,
That is, there is a limit to heat sealing at a higher speed at a constant heat sealing temperature.

On the other hand, an ethylene / α-olefin copolymer is known as a resin having a high heat seal strength among resins used for extrusion laminate materials and the like. However, since these do not have long chain branching in the molecular chain, they have higher melt shear viscosity and extremely poor extrusion processability as compared with HP-LDPE having the same melt flow rate. Further, the elongational viscosity is very small and the melt tension is small. Therefore, in extrusion lamination processing and the like, a high load is imposed on the extruder, and the film forming property of the T-die is unstable, that is, the stability of the ears is poor and the neck-in becomes large, which is a drawback in terms of processing. There is.

From the above, ethylene / α-olefin copolymer and HP- are used as the heat seal material in the actual extrusion laminate material for the purpose of utilizing their respective characteristics.
A blend of LDPE is used, and when processability is important, HP-LDPE is the main component in the blend. Here, as the ethylene / α-olefin copolymer, conventionally known ones include those polymerized by using a Ziegler catalyst, and these are HP-
When blended with LDPE, it can provide improved heat seal strength. However, with these blends, it was impossible to develop the heat seal strength at a lower temperature, that is, to develop the heat seal strength at a higher speed at a constant heat seal temperature.

Therefore, the ethylene / α-olefin copolymer obtained by the conventionally known Ziegler catalyst and HP-L are used.
The blend with DPE had good processability, high heat-sealing strength, and there was a limit to heat-sealing at a low temperature, that is, high-speed heat-sealing at a constant heat-sealing temperature.

[0007]

According to the present invention, the workability is good, the heat sealing strength is high, and the heat sealing can be performed at a low temperature, that is, the heat sealing can be performed at a high speed at a constant heat sealing temperature. An object of the present invention is to provide a polyethylene resin composition suitable as a heat seal material for extrusion laminate materials.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, as a result of blending HP-LDPE with a specific ethylene / α-olefin copolymer, HP-LDPE in the blended product is obtained. The melting point of the crystal component of the compound moves to the low temperature side, the workability is good, and the heat seal strength is large, and the heat seal can be performed at a lower temperature, that is, the heat seal can be performed at a higher speed at a constant heat seal temperature. We have found a polyethylene resin composition suitable as a heat seal material for extrusion laminate materials.

That is, according to the present invention, (a) the density of 0.91 to 0.935 g / cm ³ is obtained by immersing in hot water at 100 ° C. for 1 hour and then allowing to cool to room temperature.
(B) a low-density polyethylene (hereinafter referred to as [A]) obtained by high-pressure radical polymerization having a melt flow rate (MFR) measured at 190 ° C. under a load of 2160 g in the range of 0.1 to 20 g / 10 min. (C) 1 in hot water at 100 ° C
After being soaked for a time and then allowed to cool to room temperature, the density is 0.86
The range is from 0 to 0.925 g / cm ³ , and (d) 190
The melt flow rate (MFR) measured under a load of 2160 g at a temperature of 1.0 to 50 g / 10 min.
(E) Weight average molecular weight (Mw) and number average molecular weight (Mn)
Ratio (Mw / Mn) of 3 or less, (f) in a differential scanning calorimeter, melting at 200 ° C. for 5 minutes, and then 10
From the measurement of the peak temperature (Tm (° C.)) and the infrared absorption spectrum of the peak located at the highest temperature in the endothermic curve obtained when the temperature of 30 ° C./min cooled to 30 ° C. was again raised at 10 ° C./min The number of short-chain branches (SCB) per 1000 carbon atoms obtained satisfies the relationship represented by the formula (1), and Tm <−1.8 × SCB + 138 (1) (g) Tm (° C.) is the above [A. ] Ethylene having a temperature lower than the Tm (° C) of the low-density polyethylene and α having 3 or more carbon atoms
-Copolymer with olefin (hereinafter referred to as [B]), and (h) [A] / [B] weight ratio is 99/1 to 51.
It relates to a polyethylene resin composition characterized by being / 49.

Low density polyethylene (HP-LDP) obtained by the high pressure radical polymerization method [A] in the present invention.
E) has a density of 0.910 to 0.935 g / cm ³ after being immersed in hot water of 100 ° C. for 1 hour and then allowed to cool to room temperature.
Range. If the density is less than 0.910 g / cm ³ , it may be difficult to manufacture, but the processability is deteriorated, and blocking occurs on the surface of the film when formed into a film, which is not preferable. Further, when the density is higher than 0.935 g / cm ^3, the crystal melting point of HP-LDPE itself is high, and in the composition with the ethylene / α-olefin copolymer of [B], the crystal of HP-LDPE component is Although the melting point moves to the low temperature side, the melting point itself is at a high temperature,
It cannot be heat-sealed at low temperature, that is, at high speed.

The HP-LDPE of the above [A] is 1
The melt flow rate (MFR) measured at 90 ° C. under a load of 2160 g is in the range of 0.1 to 20 g / 10 minutes. If the MFR is less than 0.1 g / 10 minutes, the draw-down property will be poor, and if it is more than 20 g / 10 minutes, neck-in will be large, which is not preferable.

The HP-LDPE of the above [A] can be obtained by a conventionally known high pressure radical polymerization method.

The ethylene / α-olefin copolymer [B] in the present invention has a density of 0.860 to 0.925 g /
It is in the range of cm ³ . When the density exceeds 0.925 g / cm ³ , the melting point of the ethylene / α-olefin copolymer itself becomes high, and in the blending with [A] above,
No migration of the melting point of [A] to the low temperature side was observed, and the intended effect could not be obtained. On the other hand, the density is 0.860 g / cm ³
If it is less than the above range, the self-adhesiveness of the film increases and blocking occurs, which is not preferable.

The ethylene / α-olefin copolymer has a melt flow rate (MFR) measured at 190 ° C. under a load of 2160 g in the range of 1.0 to 50 g / 10 minutes. When the MFR is less than 1.0 g / 10 minutes, the melt shear viscosity is increased, the load on the extruder is increased, and the drawdown property is deteriorated, which is not preferable. On the other hand, when it is more than 50 g / 10 minutes, the stability of the ears is poor and the neck-in is large, resulting in poor film formation stability.

Further, the ethylene / α-olefin copolymer has a weight average molecular weight (Mw) and a number average molecular weight (Mw).
The ratio (Mw / Mn) of n) is 3 or less. When Mw / Mn exceeds 3, the low molecular weight component that causes stickiness increases, which is not preferable. Also, this ethylene / α-
In the olefin copolymer, Tm (° C.) and the number of short chain branches (SCB) per 1000 carbon atoms determined from the measurement of infrared absorption spectrum satisfy the relationship of the formula (1). An ethylene / α-olefin copolymer that does not satisfy this formula has a wide composition distribution and has many low-density (high branch number) components that cause stickiness, which is not preferable.

Tm <−1.8 × SCB + 138 (1) Furthermore, the Tm of this ethylene / α-olefin copolymer
(° C) is the other component of the composition, HP-LDP
It is lower than that of E [A]. Tm (° C) is HP-L
If higher than DPE, HP-LDP in the composition
The melting point of E does not move to a low temperature and the desired effect cannot be obtained.

As described above, the ethylene / α-olefin copolymer [B] can be obtained using, for example, a metallocene catalyst. The catalyst system and the polymerization method are illustrated below, but the method for producing the ethylene / α-olefin copolymer [B] in the present invention is not limited thereto.

Specifically, the metallocene catalyst may be a catalyst system containing a) a metallocene compound, b) an ionic compound, and c) an organoaluminum compound as constituent components.

The a) metallocene compound has the following general formula (2) or (3):

[0020]

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[0021]

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[In the formula, Cp ¹ and Cp ² are each independently a cyclopentadienyl group, an indenyl group, a fluorenyl group or a substitution product thereof, and R ¹ is a lower alkylene group,
A substituted alkylene group, a dialkylsilanediyl group, a dialkylgermandiyl group, an alkylphosphinediyl group or an alkylimino group, wherein R ¹ is Cp ¹ and Cp ²
R ² and R ³ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group or an aryloxy group, and M ¹ is a titanium atom, Zirconium atom or hafnium atom], and specific compounds thereof include bis (cyclopentadienyl) titanium dichloride, bis (methylcyclopentadienyl) titanium dichloride, and bis (butylcyclopentadiene). (Enyl) titanium dichloride, ethylenebis (indenyl) titanium dichloride, dimethylsilanediylbis (2,4,5-trimethylcyclopentadienyl) titaconium dichloride, dimethylsilanediylbis (2,4-dimethylcyclopentadienyl) Titanium dichloride, dimethy Rusilanediylbis (3-methylcyclopentadienyl) titanium dichloride, dimethylsilanediylbis (4-t-butyl-2-methylcyclopentadienyl) titanium dichloride, diethylsilanediylbis (2,4,5-trimethyl Cyclopentadienyl) titanium dichloride, diethylsilanediylbis (2,4-dimethylcyclopentadienyl) titanium dichloride, diethylsilanediylbis (3-methylcyclopentadienyl) titanium dichloride, diethylsilanediylbis (4-t -Butyl-2-methylcyclopentadienyl) titanium dichloride, isopropylidene (cyclopentadienyl)
(Fluorenyl) titanium dichloride, diphenylmethylene (cyclopentadienyl) (fluorenyl) titanium dichloride, methylphenylmethylene (cyclopentadienyl) (fluorenyl) titanium dichloride, isopropylidene (cyclopentadienyl)
(2,7-di-t-butylfluorenyl) titanium dichloride, diphenylmethylene (cyclopentadienyl) (2,7-di-t-butylfluorenyl) titanium dichloride, methylphenylmethylene (cyclopentadienyl) ) (2,7-di-t-butylfluorenyl)
Titanium dichloride, isopropylidene (cyclopentadienyl) titanium dichloride, diphenylmethylene bis (cyclopentadienyl) titanium dichloride, methylphenylmethylene bis (cyclopentadienyl) titanium dichloride, isopropylidene (cyclopentadienyl) (tetramethyl) Cyclopentadienyl) titanium dichloride, diphenylmethylene (cyclopentadienyl) (tetramethylcyclopentadienyl) titanium dichloride, isopropylidene (indenyl) titanium dichloride, diphenylmethylenebis (indenyl) titanium dichloride,
Examples thereof include titanium compounds such as methylphenylmethylene bis (indenyl) titanium dichloride, and compounds in which the titanium is replaced with zirconium or hafnium, but are not limited thereto.

B) The ionic compound is [HL ¹ _l ] [M ² Z ₄ ] (4) [wherein, H is a proton, L ¹ is independently a Lewis base, and l is 0 < 1 ≦ 2, M ² is a boron atom, an aluminum atom or a gallium atom, Z is each independently an alkyl group or an alkoxy group having 1 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aryl group, An alkylaryl group or an arylalkyl group,
A halogen-substituted hydrocarbon group having 1 to 20 carbon atoms or a halogen-substituted alkoxy group, a halogen-substituted aryloxy group having 6 to 20 carbon atoms or a halogen atom], [C] [M ² Z ₄ ] (5) [In the formula, C is a carbonyl cation or tropylium cation, M ² is a boron atom, an aluminum atom or a gallium atom, and Z is independently a carbon number of 1 to 1
20 alkyl or alkoxy groups, 6 to 2 carbon atoms
An aryloxy group having 0, an aryl group, an alkylaryl group or an arylalkyl group, a halogen-substituted hydrocarbon group having 1 to 20 carbon atoms or a halogen-substituted alkoxy group, a halogen-substituted aryloxy group having 6 to 20 carbon atoms, or a halogen atom. ] Or a [M ³ L ² _p ] [M ² Z ₄ ] (6) [wherein M ³ is a group VIII, IA or IB of the periodic table,
It is a cation of a metal selected from the IIA group and the IIB group, M ² is a boron atom, an aluminum atom or a gallium atom, and Z is each independently an alkyl group or an alkoxy group having 1 to 20 carbon atoms or 6 carbon atoms. ~ 20 aryloxy group, aryl group, alkylaryl group or arylalkyl group, C1-20 halogen-substituted hydrocarbon group or halogen-substituted alkoxy group, C6-20 halogen-substituted aryloxy group or halogen atom And L ² is a Lewis base or a cyclopentadienyl group, and p is 0 ≦ p ≦ 2], and specific examples of these compounds include tri (n -Butyl) ammonium tetrakis (p-tolyl) borate, tri (n-butyl) ammonium tetrakis (m-) Tolyl) borate, tri (n-butyl) ammonium tetrakis (2,4-dimethylphenyl) borate, tri (n-butyl) ammonium tetrakis (3,5-dimethylphenyl) borate, tri (n-butyl) ammonium tetrakis (penta) Fluorophenyl) borate, N, N-dimethylanilinium tetrakis (p-tolyl) borate, N, N-dimethylanilinium tetrakis (m-tolyl) borate, N,
N-dimethylanilinium tetrakis (2,4-dimethylphenyl) borate, N, N-dimethylanilinium tetrakis (3,5-dimethylphenyl) borate,
N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate, triphenylcarbenium tetrakis (p-tolyl) borate, triphenylcarbenium tetrakis (m-tolyl) borate, triphenylcarbenium tetrakis (2,4-dimethyl) Phenyl) borate, triphenylcarbenium tetrakis (3,5-dimethylphenyl) borate, triphenylcarbenium tetrakis (pentafluorophenyl) borate, tropylium tetrakis (p-tolyl) borate, tropylium tetrakis (m-tolyl) borate ,
Tropylium tetrakis (2,4-dimethylphenyl)
Borate, tropylium tetrakis (3,5-dimethylphenyl) borate, tropylium tetrakis (pentafluorophenyl) borate, lithium tetrakis (pentafluorophenyl) borate, lithium tetrakis (phenyl) borate, lithium tetrakis (p-tolyl) borate, Lithium tetrakis (m-tolyl) borate, lithium tetrakis (2,4-dimethylphenyl) borate, lithium tetrakis (3,5-dimethylphenyl) borate, lithium tetrafluoroborate, sodium tetrakis (pentafluorophenyl)
Borate, sodium tetrakis (phenyl) borate, sodium tetrakis (p-tolyl) borate, sodium tetrakis (m-tolyl) borate, lithium tetrakis (2,4-dimethylphenyl) borate, lithium tetrakis (3,5-dimethylphenyl) borate , Sodium tetrafluoroborate, potassium tetrakis (pentafluorophenyl) borate, potassium tetrakis (phenyl) borate, potassium tetrakis (p-tolyl) borate, potassium tetrakis (m-tolyl) borate, potassium tetrakis (2,4-dimethylphenyl) Borate, potassium tetrakis (3,5-
Dimethylphenyl) borate, potassium tetrafluoroborate, tri (n-butyl) ammonium tetrakis (p-tolyl) aminate, tri (n-butyl) ammonium tetrakis (m-tolyl) aminate, tri (n)
-Butyl) ammonium tetrakis (2,4-dimethylphenyl) aluminate, tri (n-butyl) ammonium tetrakis (3,5-dimethylphenyl) aluminate, tri (n-butyl) ammonium tetrakis (pentafluorophenyl) aluminate , N, N-dimethylanilinium tetrakis (p-tolyl) aluminate, N, N-dimethylanilinium tetrakis (m-tolyl) aluminate, N, N-dimethylanilinium tetraakis (2,4-dimethylphenyl) Aluminate, N, N-dimethylanilinium tetrakis (3,5
-Dimethylphenyl) aluminate, N, N-dimethylanilinium tetrakis (pentafluorophenyl) aluminate, triphenylcarbenium tetrakis (p
-Tolyl) aluminate, triphenylcarbenium tetrakis (m-tolyl) aluminate, triphenylcarbenium tetrakis (2,4-dimethylphenyl) aluminate, triphenylcarbenium tetrakis (3,5-dimethylphenyl) aluminate , Triphenylcarbenium tetrakis (pentafluorophenyl) aluminate, tropylium tetrakis (p-tolyl) aluminate, tropylium tetrakis (m-tolyl) aluminate, tropylium tetrakis (2,4-)
Dimethylphenyl) aluminate, tropylium tetrakis (3,5-dimethylphenyl) aluminate, tropylium tetrakis (pentafluorophenyl) aluminate, lithium tetrakis (pentafluorophenyl) aluminate, lithium tetrakis (phenyl) aluminate, lithium Tetrakis (p-tolyl) aluminate, lithium tetrakis (m-tolyl) aluminate, lithium tetrakis (2,4-dimethylphenyl)
Aluminate, lithium tetrakis (3,5-dimethylphenyl) aluminate, lithium tetrafluoroaluminate, sodium tetrakis (pentafluorophenyl) aluminate, sodium tetrakis (phenyl) aluminate, sodium tetrakis (p-tolyl) aluminate, Sodium tetrakis (m-tolyl) aluminate, sodium tetrakis (2,4-dimethylphenyl) aluminate, sodium tetrakis (3,5-dimethylphenyl) aluminate, sodium tetrafluoroaluminate, potassium tetrakis (pentafluorophenyl) aluminum Nate, potassium tetrakis (p-phenyl) aluminate, potassium tetrakis (m-tolyl) aluminate, potassium tetrakis (2,4-dimethylphene) Le) aluminate, potassium tetrakis (3,5-dimethylphenyl) aluminate, but potassium tetrafluoro aluminate and the like, but is not limited thereto.

C) The organoaluminum compound is represented by AlR ⁴ R ^{4 ′} R ^{4 ″} (7) [wherein R ⁴ , R ^{4 ′} and R ^{4 ″} are each independently hydrogen, halogen, amino group, alkyl group, An alkoxy group or an aryl group, and at least one is an alkyl group]
In these specific compounds, trimethyl aluminum, triethyl aluminum, triisopropyl aluminum, diisopropyl aluminum chloride, isopropyl aluminum dichloride, tributyl aluminum, triisobutyl aluminum, diisobutyl aluminum chloride, isobutyl aluminum chloride, Tri-t-butylaluminum, di-t-butylaluminum chloride,
Examples thereof include, but are not limited to, t-butyl aluminum dichloride, triamyl aluminum, diamyl aluminum chloride, amyl aluminum dichloride, and the like.

A) The metallocene compound may be one kind or two kinds.
It is possible to mix and use more than one kind, and when mixed and polymerized, the processability of the copolymer is improved, and it is also preferable in the composition.

The method for adjusting the catalyst system is not particularly limited, and examples thereof include a method of mixing each of the metallocene compound, the ionic compound and the organoaluminum compound in an inert solvent.

The ionic compound is generally used in a range of 0.01 to 1000 times mol, preferably 0.2 to 200 times mol, of the metallocene compound.

The amount of organoaluminum used is not particularly limited, but it is usually used in an amount of about 1 to 10000 times the metallocene compound.

Further, the polymerization using the above catalyst system can be carried out in the liquid phase or the gas phase. If the polymerization is carried out in a liquid phase, any organic solvent generally used as a solvent may be used, and specifically, benzene, toluene,
Hexane, methylene chloride and the like can be mentioned. Further, ethylene or α-olefin itself can be used as the solvent.

There are no particular restrictions on the polymerization temperature,
Usually, it is preferably carried out in the range of -100 to 300 ° C.
Also, the polymerization pressure is not particularly limited. Normally, it is carried out at atmospheric pressure to 30 kgf / cm ² , but atmospheric pressure to 350
It is also possible to carry out in the range of 0 kgf / cm ² .

It is also possible to obtain an ethylene / α-olefin copolymer according to the present invention by copolymerizing ethylene and an α-olefin having 3 or more carbon atoms by using the above catalyst system as a solid catalyst supported on a carrier. it can. Such solid catalysts include metallocene compounds, mixtures of metallocene compounds and ionic compounds, reaction products of metallocene compounds and organoaluminum compounds, ionic compounds themselves or organoaluminum compounds themselves, for example silica, alumina, chloride. It can be obtained by deposition on a carrier such as magnesium, styrene-divinylbenzene copolymer or polyethylene.

Further, in the present invention, α-containing 3 or more carbon atoms
As olefins, propylene, butene-1, pentene-1, hexene-1, octene-1,4-methyl-1
-Pentene and the like, and one or two of these
More than one type is used.

The composition of the present invention is HP-LDPE [A].
Ethylene / α-olefin copolymer [B] into [A] /
[B] It can be produced by mixing in a weight ratio of 99/1 to 51/49.

The polyethylene resin composition of the present invention may be mixed by various known methods, for example, a V-blender, a ribbon blender, a Henschel mixer, a tumbler blender, a method of granulating after mixing with an extruder, or the like. Using an appropriate kneading machine such as roll, plastomill, extruder, kneader, Banbury mixer,
It is adjusted by a method of heating and kneading at a temperature equal to or higher than the crystal melting point of both components [A] and [B].

The polyethylene resin composition of the present invention may contain various phenol-based, phosphite-based, thioether-based antioxidants, fatty acid metal salts, hydroxy fatty acid metal salts, and alkyl lactic acid, if necessary. Metal salts, neutralizing agents such as hydrotalcite, benzophenone-based, benzotriazole-based, salicylate-based UV absorbers, hindered amine-based light stabilizers, lubricants, antiblocking agents, antistatic agents, metal salts of organic acids and sorbitol Additives that are generally used for nucleating agents, dispersants, pigments, and polyolefin resins of the system may be added.

Further, the ethylene / α-olefin copolymer in this polyethylene resin composition may be one in which the molecular chain is crosslinked by addition of a peroxide or irradiation with an electron beam.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

The low-density polyethylene [A] used in Examples and Comparative Examples was one obtained by a conventionally known high-pressure radical polymerization method. Specifically, it is Petrosene 205 manufactured by Tosoh Corporation.

Ethylene / α-olefin copolymer [B]
As the two types of copolymers, an ethylene / butene-1 copolymer [B1] and an ethylene / hexene-1 copolymer [B2], were used, and a composition of them and the above [A] was used as an example. . The catalyst system used to obtain these copolymers was diphenylmethylene (cyclopentadienyl) (fluorenyl) zirconium dichloride as the metallocene compound and N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate as the ionic compound. And triisobutylaluminum as the organoaluminum compound, and the amount of the metallocene compound, the ionic compound and the organoaluminum is 1: 2: 2 in a molar ratio (metallocene compound: ionic compound: organoaluminum).
50. Toluene was used for catalyst preparation. The copolymer used here uses the above catalyst system and has a polymerization temperature of 150.
It was obtained by polymerizing at ˜175 ° C. and a polymerization pressure of 900 kgf / cm ² . Polymerization, purification, reaction and solvent purification were all carried out under an inert gas atmosphere.
All the solvents and the like used in the reaction were previously purified, dried and deoxygenated by known methods, and the compounds used in the reaction were those synthesized and identified by known methods.

Comparative Examples 1 and 2 are ethylene / butene-1 copolymer [B1] and ethylene / butene-1 used in Examples 1 and 2.
An ethylene / butene-1 copolymer [Z1] or an ethylene / hexene-1 copolymer [Z2] obtained with a conventionally known Ziegler catalyst having the same density and MFR as hexene-1 copolymer [B2], respectively. And [A]. These do not satisfy the ethylene / α-olefin copolymer defined in the present invention in terms of Mw / Mn and the relationship between density and branch number. Comparative Example 3 is [A] alone which does not mix the ethylene / α-olefin copolymer. Comparative Example 4 is an ethylene / hexene-1 copolymer obtained under the same metallocene catalyst system and polymerization conditions as in Examples 1 and 2, but with a melting point higher than that of [A] and the copolymer specified in the present invention. Ethylene / hexene not filled with polymer
1 A composition consisting of a copolymer [C] and [A]. The copolymers [Z1] and [Z2] used in Comparative Examples 1 and 2 are both manufactured by Tosoh Corporation, and ethylene / [Z2] /
The hexene-1 copolymer is Nipolone-Z ZF210-1.
It is.

The compositions used in Examples and Comparative Examples were obtained by mixing the mixed components in an appropriate composition and adding 1000 ppm of 2,6-di-t-butyl-4-hydroxytoluene (BHT) as an antioxidant. It was added and melt-granulated with a single-screw extruder. Laboplast mill manufactured by Toyo Seiki Co., Ltd. was used for melt granulation.
It was carried out at 50 rpm. The low density polyethylene [A] alone as a comparative example was also melt-granulated under the same conditions.
Various physical properties of the granulated products used in Examples and Comparative Examples were measured by the following methods.

Density (d): JIS K according to JIS K which was immersed in hot water of 100 ° C. for 1 hour and then allowed to cool to room temperature.
According to 6760, it measured using the density gradient tube kept at 23 degreeC.

Melt Flow Rate (MFR): JIS
According to K7210, it measured at 190 degreeC and the load of 2160 g.

Melting point (Tm): The melting point is a differential scanning calorimeter (DSC) [Perkin Elmer Co., Ltd., DSC-7].
It measured using. Endotherm obtained when the sample was melted in DSC for 5 minutes at 200 ° C. and then solidified by lowering the temperature to 30 ° C. at a rate of 10 ° C./minute and heated again at a rate of 10 ° C./minute The peak temperature of the peak located at the highest temperature in the curve was taken as the melting point.

Short chain branching number (SCB): The number of short chain branching (SCB) in the molecular chain was determined by using a Fourier transform infrared absorption spectrometer [FT-IR spectrometer 1760X manufactured by Perkin Elmer Co., Ltd.]. 1378 cm ^-1
It was determined from the intensity of the absorption band corresponding to the bending vibration of the methyl group located at.

Table 1 shows the density, MFR, melting point and short chain branch number of the polyethylene resins used in the examples and comparative examples, which were determined according to the above measuring method.

The heat-sealing strength was measured using a sheet obtained by press-molding the above granulated product with a compression molding machine to a thickness of about 100 μm. A compression molding machine manufactured by Kansai Roll Co., Ltd. is used for molding, and melting is performed at 150 ° C. for 7 minutes,
Immediately, it was transferred to a compression molding machine at 30 ° C. and cooled and solidified.

For heat sealing, a universal heat sealer manufactured by Tester Sangyo Co., Ltd. was used, and a region of 15 mm × 10 mm was heat sealed at a sealing pressure of 2 kgf / cm ² and a sealing time of 5 seconds. The sealing time used here is JIS
It is somewhat longer than the sealing time specified by Z1707, but this was done to reduce the variation in sealing strength as much as possible and improve the reliability of the data, and basically the same behavior as when the sealing time is short. Becomes To measure the seal strength, a tensile tester manufactured by Orientec Co., Ltd. was used, and the heat-sealed portion was pulled at a chuck distance of 40 mm and a pulling speed of 300 mm / min. The peel strength of the seal portion obtained at that time was defined as the heat seal strength. The measurement conditions are JI
It is based on S Z1707.

Example 1 A low density polyethylene [A] and an ethylene / butene-1 copolymer [B1] shown in Table 1 were used, and [A] / [B
1] A composition having a weight ratio of 70/30. Table 2 shows the relationship between heat seal temperature and heat seal strength.

Comparative Example 1 Ethylene obtained with a conventionally known Ziegler catalyst having the same MFR and density as the low density polyethylene [A] shown in Table 1 and the ethylene / butene-1 copolymer used in Example 1. / Butene-1 copolymer [Z1] and [A]
/ [Z1] weight ratio is 70/30. Table 2 shows the relationship between heat seal temperature and heat seal strength.

Example 2 A low density polyethylene [A] shown in Table 1 and an ethylene / hexene-1 copolymer [B2] were used, and [A] / [B
2] A composition having a weight ratio of 70/30. Table 2 shows the relationship between heat seal temperature and heat seal strength.

Comparative Example 2 MFR which is almost the same as the low density polyethylene [A] shown in Table 1 and the ethylene / hexene-1 copolymer used in Example 2
And an ethylene / hexene-1 copolymer [Z2] obtained with a conventionally known Ziegler catalyst having a density of
The composition has a weight ratio [A] / [Z2] of 70/30. Table 2 shows the relationship between heat seal temperature and heat seal strength.

Comparative Example 3 A low-density polyethylene [A] alone which does not contain an ethylene / α-olefin copolymer. Table 2 shows the relationship between heat seal temperature and heat seal strength.

Comparative Example 4 Low density polyethylene [A] shown in Table 1 and Examples 1 and 2
Ethylene / hexene-1 copolymer [C] having a melting point higher than that of [A] obtained under the same metallocene catalyst and polymerization conditions as described above, and the [A] / [C] weight ratio is 70/30.
Is a composition. Table 2 shows the relationship between heat seal temperature and heat seal strength.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

As described above, the polyethylene resin composition of the present invention has good workability, high heat-sealing strength, and can be heat-sealed at a low temperature, that is, at a constant heat-sealing temperature at high speed. It can be heat-sealed.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between heat seal temperature and heat seal strength in Examples and Comparative Examples.

Claims (1)

[Claims] 1. The density of (a) soaked in hot water at 100 ° C. for 1 hour and then allowed to cool to room temperature has a density of 0.910 to 0.935.
g / cm ³ range, (b) 190 ° C., 2160 g
Melt flow rate (MFR) measured under a load of 0.1 to 20 g / 10 min in the low-density polyethylene (hereinafter referred to as [A]) obtained by a high-pressure radical polymerization method and (c) 100 ° C. After being soaked in hot water for 1 hour and allowed to cool to room temperature, the density is 0.860 to 0.925 g / c.
m ³ range, (d) the melt flow rate (MFR) measured under a load of 190 ° C. and 2160 g is 1.0 to
It is in the range of 50 g / 10 minutes, (e) the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 3 or less, and (f) in the differential scanning calorimeter,
In the endothermic curve obtained by melting at 0 ° C. for 5 minutes and then cooling at 10 ° C./minute to 30 ° C. and raising the temperature again at 10 ° C./minute, the peak temperature (Tm (Tm ( ° C)) and the number of short chain branches per 1000 carbon atoms (SC
B) and the relationship represented by the formula (1) are satisfied, and Tm <−1.8 × SCB + 138 (1) (g) Tm (° C.) is lower than the Tm (° C.) of the low density polyethylene of the above [A]. Some ethylene and α with 3 or more carbon atoms
-Copolymer with olefin (hereinafter referred to as [B]), and (h) [A] / [B] weight ratio is 99/1 to 51.
/ 49. A polyethylene resin composition characterized in that it is / 49.