JP2002097316A - Polyethylene composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyethylene composition suitable for producing a film excellent in heat-sealing characteristics, antistatic characteristics and easily tearing characteristics. SOLUTION: This polyethylene composition consists of 50-90 pts.wt. of a polyethylene (A), 5-40 pts.wt. of the ionomer (B) of an ethylene.unsaturated carboxylic acid copolymer with an alkali metal and 5-40 pts.wt. of a cyclic olefin polymer (C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat seal,
The present invention relates to a polyethylene composition suitable for producing a film having excellent non-charging properties, easy tearing properties, and the like.

[0002]

2. Description of the Related Art Polyethylene having good heat sealability has been used for a long time as a film material for packaging foods and pharmaceuticals. Among them, recently, transparency, tear resistance, low temperature heat sealability, hot tack, Linear low-density polyethylene having excellent sealability for small articles, heat sealing strength, bag breaking strength, heat resistance, and the like has come to be used frequently. However, in applications in which tear-opening is performed, linear low-density polyethylene has a drawback that tear strength and elongation are high and tear-opening is difficult, and thus, it was not necessarily a suitable material.

[0003] There is a method of uniaxially stretching in order to remedy such drawbacks. However, a stretching step following the film forming is required, which is not economical. In addition, since the film is stretched, linear low-density polyethylene cannot be used. There is a problem that characteristics are impaired. Also, as proposed in Japanese Patent Application Laid-Open Nos. 10-237234 and 11-129415, attempts have been made to improve cutability by forming a multilayer structure. Special equipment was required, and the cost was high.

On the other hand, in the packaging of foods and pharmaceuticals,
To prevent dust from adhering to the film and contents due to electrification, and especially for powder packaging, make sure that the contents adhere to the bag when the contents are taken out after opening. To avoid this, it is required to apply an antistatic prescription. Generally, low-molecular weight antistatic agents are used to address this problem.However, the antistatic agent bleeds out to the film surface over time, causing problems such as stickiness and dirt on the film, or deterioration of the antistatic effect over time. Was sometimes seen.

[0005]

SUMMARY OF THE INVENTION In view of the above situation, the present inventors have found that a single-layer film can easily be torn at the time of opening while maintaining excellent heat-sealing properties, and the contamination by bleed-out can be reduced. We studied a packaging material with excellent anti-static properties without fear. As a result, they have found that a film having desired properties can be produced by blending two kinds of specific polymers described below with polyethylene. Accordingly, an object of the present invention is to provide a polyethylene composition suitable as a packaging film for foods and pharmaceuticals. Especially heat-sealing properties useful for powder packaging,
An object of the present invention is to provide a polyethylene composition suitable for a packaging film having excellent non-charging properties, tear-opening properties and the like.

[0006]

That is, the present invention relates to an alkali metal ionomer (B) 5 of polyethylene (A) 50 to 90 parts by weight and an ethylene / unsaturated carboxylic acid copolymer.
To 40 parts by weight and a cyclic olefin polymer (C) 5 to 40
A polyethylene composition comprising parts by weight.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The polyethylene (A) used in the present invention is a high-density polyethylene, a medium-density polyethylene,
Linear low-density polyethylene, high-pressure low-density polyethylene, and the like. In consideration of film strength, sealing properties, heat resistance, and the like, the density is especially 880 to 940 kg / m ³ ,
In particular, the use of 900 to 930 kg / m ³ linear low density polyethylene is preferred. Linear low-density polyethylene is ethylene and an α-olefin having 3 or more carbon atoms, such as 1-butene, 1-pentene, 1-hexene, 1-octene,
-Decene, 1-dodecene, 4-methyl-1-pentene and the like. Such a linear low-density polyethylene can be produced using a multi-site catalyst system using a highly active titanium catalyst component or the like, or a single site catalyst system using a metallocene catalyst component or the like. It is most preferable to use a catalyst produced by the latter catalyst system having a narrow distribution and excellent mechanical strength, heat sealability, affinity with the ionomer (B), and the like.

Considering workability, film properties, etc., the polyethylene has a melt flow rate of 0.01 to 100 g / 1 at 190 ° C. and a load of 2160 g.
It is preferable to use one for 0 minutes, especially 0.1 to 30 g / 10 minutes.

The alkali metal ionomer (B) of the ethylene / unsaturated carboxylic acid copolymer used in the present invention is:
Some or all of the carboxyl groups in an ethylene copolymer of ethylene and an unsaturated carboxylic acid or, optionally, another monomer are neutralized with an alkali metal ion. Here, as the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic anhydride, monomethyl maleate, monoethyl maleate and the like can be exemplified, and acrylic acid or methacrylic acid is particularly preferable.
Other monomers that can be copolymerized components include vinyl esters such as vinyl acetate and non-polymers such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, and methyl methacrylate. Saturated carboxylic acid esters, carbon monoxide and the like can be exemplified.

The above-mentioned ethylene / unsaturated carboxylic acid copolymer has an unsaturated carboxylic acid content of, for example, 13 to 30% by weight, preferably 15 to 25% by weight in order to impart sufficient antistatic property. Can be mentioned. Alternatively, a blend of two or more copolymers having different unsaturated carboxylic acid contents, wherein the average acid content is 10 to 30% by weight,
It is preferably 11 to 20% by weight, and the difference in acid content between the highest acid content and the lowest acid content is 1% by weight or more, preferably 2 to 20% by weight. The other monomer may be contained, for example, at a ratio of 0 to 30% by weight. Such a copolymer can be easily obtained by radical copolymerization under high temperature and high pressure.

The alkali metal in the alkali metal ionomer (B) includes lithium, sodium, potassium, rubidium, cesium and the like, and potassium is most preferable in consideration of non-charging property and economic efficiency. The degree of neutralization from the viewpoint of non-charging properties (average degree of neutralization when two or more ethylene / unsaturated carboxylic acid copolymers are used)
However, it is desirable to use those having 60% or more, preferably 70% or more. However, in consideration of easiness of production and workability, the upper limit of the degree of neutralization is desirably suppressed to about 90% or less. As the alkali metal ionomer, considering the miscibility with polyethylene (A) and various physical properties of the composition,
The melt flow rate at a load of 190 ° C. and a load of 2160 g is 0.1 to 100 g / 10 min, especially 0.2 to 30 g
It is preferable to use one for about / 10 minutes.

The cyclic olefin polymer (C) used in the present invention is a polymer containing a cyclic olefin as a polymerization unit, and is a homopolymer of a cyclic olefin or a copolymer of a cyclic olefin and an α-olefin. is there. These may be ordinary addition polymers or ring-opening polymers. In the latter ring-opened polymer, its hydride can be used. They may also have been subjected to a chemical modification such as a graft modification with an unsaturated carboxylic acid.

More specifically, cyclic olefins include cycloalkenes such as cyclopentene and cyclohexene, bicyclo [2,2,1] -2-heptene and derivatives thereof, and tricyclo [4,3,0,12 ^{, 5} ] -3-decene and its derivatives, tetracyclo [4,4,0,1
^2,5, 1 ^7,10] -3-dodecene and derivatives thereof, pentacyclo [7,4,0,1 ^4,7, 1 ^10,13, 0 ^3,8] -5-
Pentadecene and its derivatives, pentacyclo [8,4,
0,1 ^4,7, 1 ^11,14, 0 ^3,8] -5-hexadecene and derivatives thereof, hexacyclo [6,6,1,1 ^3,6, 1
^{10 and 13,} 0 ^2,7, 0 ^9,14] -4-heptadecene and its derivatives, octacyclo [8,8,0,1 ^2,9, 1 ^4, 7, 1
^{11, 18,} 1 ^{13, 16,} 0 ^3,8, 0 ^12,17] such as 5-docosenoic and its derivatives can be exemplified. These cyclic olefins may have an aromatic ring as a substituent, such as an adduct of cyclopentadiene / acenaphthene and cyclopentadiene.

Further, α which can be copolymerized with the above-mentioned cyclic olefin
Examples of olefins include, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-
One or more types such as pentene can be used.

Among these cyclic olefin polymers, α-olefins, especially random copolymers of ethylene and cyclic olefins,
It is preferable to use one obtained by copolymerizing a cyclic olefin at a ratio of 80 to 2 mol% with respect to 98 mol%. The cyclic olefin polymer also has a softening temperature of at least 60 ° C. measured with a thermal mechanical analyzer (TMA),
Preferably, the glass transition temperature (Tg) is at least 70 ° C.
° C or more, preferably 60 ° C or more, 260 ° C, 2160 g
The melt flow rate under load is 0.1 to 100 g /
It is desirable to use one for 10 minutes, preferably about 1 to 50 g / 10 minutes.

The polyethylene composition of the present invention contains 50 to 90 parts by weight, preferably 55 to 85 parts by weight of polyethylene (A), 5 to 40 parts by weight, preferably 10 to 30 parts by weight of ionomer (B), and a cyclic olefin polymer. Combined (C) 5-4
0 parts by weight, preferably 5 to 30 parts by weight (100 parts by weight in total). If the compounding amount of the ionomer is less than the above range, sufficient antistatic property cannot be imparted, and if the compounding amount is more than the above range, the excellent properties of polyethylene will be impaired. If the amount of the cyclic olefin polymer is less than the above range, the effect of improving tearability is not sufficient, and if the amount is too large, the toughness is impaired.

In the present invention, it is effective to incorporate a polyhydroxy compound (D) in order to maintain sufficient antistatic properties even in low humidity conditions. Polyhydroxy compound (D) used for such purpose
Is a compound having two or more alcoholic hydroxyl groups, and specifically has various molecular weights, preferably 2000 molecular weight.
Polyhydric alcohols such as the following polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyalkylene glycol such as polyoxyethylene / polyoxypropylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, and ethylene oxides thereof. Examples thereof include adducts and ethylene oxide adducts of various amines and amides. Among them, it is most preferable to use polyethylene glycol or glycerin.

The effective blending ratio of the polyhydroxy compound (D) is 0.1 to 30% by weight of the ionomer (B),
Preferably it is 1 to 20% by weight, more preferably 2 to 15% by weight. That is, by adding a polyhydroxy compound, sufficient antistatic properties can be exhibited even at low humidity, but if added in a large amount, preparation of the composition becomes difficult, and contamination of the molded article surface by bleeding may be concerned. Is not preferred.

Various additives can be added to the polyethylene composition of the present invention, if necessary. As such additives, for example, antioxidants, light stabilizers, heat stabilizers, ultraviolet absorbers, lubricants, anti-blocking agents, pigments,
Dyes and inorganic fillers can be exemplified.

The polyethylene composition of the present invention can be formed by various molding methods such as extrusion molding, injection molding, hollow molding, press molding, vacuum molding, air pressure molding, etc., into films, sheets, tubes, pipes, hollow containers, and other various shapes. It can be used as a molded article. In particular, since it has excellent heat sealing properties, non-charging properties, and tear opening properties, it can be suitably used as a packaging film in various industrial fields.
When the polyethylene composition of the present invention is used as a packaging film, it is generally used after being formed into a film having a thickness of about 5 to 500 μm, preferably about 10 to 100 μm by an inflation method or a T-die method.

In such a packaging film, a single-layer film exhibits the above-mentioned excellent properties, but of course, it may be made of another material as required to add various properties. It can also be used by laminating it with one or more layers. Examples of such other materials include polyolefin, olefin / polar monomer copolymer, polyester, polyamide, polycarbonate, polystyrene, ABS resin, polyvinyl chloride, ethylene
Examples include vinyl alcohol copolymer, aluminum foil, aluminum-deposited film, inorganic oxide-deposited film, and paper.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The types of raw materials used in Examples and Comparative Examples and their physical properties, and methods for measuring physical properties of the obtained films are as follows.

1. Raw Materials (1) Polyethylene Linear low density polyethylene (LLDPE) produced in the presence of a single-site catalyst (trade name: Evolu SP25)
20, density 925 kg / m ³ , MFR 2 g / 10 min, manufactured by Mitsui Chemicals, Inc.) High density polyethylene (HDPE) (trade name: Hyzex 7000F, density 956 kg / m ³ , MFR 0. (2) ionomer A potassium ionomer of an ethylene / acrylic acid copolymer having an acrylic acid content of 21% by weight (neutralization degree: 80%, potassium content: 2.3 g / kg ionomer) MFR0.6g /
(10 minutes) (3) Polyhydroxy compound glycerin (manufactured by Kanto Chemical Co., Ltd.) (4) Cyclic olefin polymer Ethylene / tetracyclododecene copolymer (ETCD) ETCD-1 (trade name: Apel 8008T, TMA80)
° C, Tg70 ° C, density 1020 kg / m ³ , MFR 15
g / 10 minutes (260 ° C., 2160 g load), manufactured by Mitsui Chemicals, Inc.) ETCD-2 (trade names: Apel 6509T, TMA90)
° C, Tg80 ° C, density 1020 kg / m ³ , MFR30
g / 10 minutes (260 ° C, 2160g load), manufactured by Mitsui Chemicals, Inc.)

2. Physical property measurement method (1) Decay time A test specimen left for 24 hours at 26 ° C. and 13% relative humidity was used.
ETS U.S. StaticDecay Meter Model 4060 (Federal
Test 101C 4046)
The decay time to V was measured. (2) Surface resistivity After aging the test specimen at 23 ° C. and a relative humidity of 30%, 40%, 50% and 60% for 24 hours, the surface resistivity was measured by a high resistivity meter (HIRESTA-UP) manufactured by Mitsubishi Chemical Corporation. Was measured. (3) Elmendorf tear strength Measured by a method based on JIS K7128.

[Examples 1 to 6] A mixture of the above LLDPE, ionomer and glycerin in a weight ratio of 90/10.
(IO mixture) and the ethylene / tetracyclododecene copolymer were dry-blended at the ratios shown in Table 1. Next, a film having a thickness of 50 μm was formed from this dry blended product using a single-layer blown film forming machine.
The decay time, surface resistivity and Elmendorf tear strength of the obtained film were measured according to the above-mentioned methods. Table 1 shows the results.

[Examples 7 and 8] The above-mentioned HDPE and IO
The mixture and the ethylene / tetracyclododecene copolymer were dry-blended at the ratios shown in Table 1. Next, a film having a thickness of 50 μm was formed from this dry blended product using a single-layer blown film forming machine. The decay time, surface resistivity and Elmendorf tear strength of the obtained film were measured according to the above-mentioned methods. Table 1 shows the results.

[0027]

[Table 1]

[Comparative Example 1]
A film of LDPE alone was prepared and its physical properties were measured. Table 2 shows the results.

Comparative Example 2 A film was similarly processed from a blend of the above LLDPE and IO mixture at a ratio of 83/17, and the physical properties were measured. Table 2 shows the results
Shown in

Comparative Examples 3 to 5 LLDPE and ethylene
A film was similarly processed from a dry blend of the tetracyclododecene copolymer at the ratio shown in Table 2, and the physical properties were measured. Table 2 shows the results.

[Comparative Example 6]
A film of DPE alone was prepared and its physical properties were measured.
Table 2 shows the results.

[0032]

[Table 2]

As is clear from the comparison between the above Examples and Comparative Examples, the film obtained from the polyethylene composition of the present invention has excellent non-charging properties, low tear strength in both longitudinal and transverse directions, and tear-opening. Is easy.

[0034]

Industrial Applicability The polyethylene composition of the present invention has the excellent characteristics of polyethylene, the excellent non-charging properties, and the ease of tearing and opening when used as a packaging film. . Therefore, powder packaging for powder soup, flour, salt, spices, etc., dry food packaging for snacks, etc., liquid packaging for liquid soups, liquid seasonings, etc., meat packaging for processed meat, chilled beef, etc. It can be used for packaging of medical products such as syringes and infusion bags, packaging of pharmaceuticals, feeds, agricultural chemicals, fertilizers and the like.

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Claims (3)

[Claims] 1. 50 to 90 parts by weight of polyethylene (A),
A polyethylene composition comprising 5 to 40 parts by weight of an alkali metal ionomer (B) of an ethylene / unsaturated carboxylic acid copolymer and 5 to 40 parts by weight of a cyclic olefin polymer (C). 2. The polyhydroxy compound (D) in an amount of 0.1 to 30% by weight based on the alkali metal ionomer (B).
The polyethylene composition according to claim 1, further comprising: 3. The polyethylene composition according to claim 1, wherein the polyethylene (A) is a linear low-density polyethylene produced in the presence of a single-site catalyst.