JP2023139744A - Polyethylene composition, film, and multilayer film - Google Patents

Abstract

To provide a polyethylene composition capable of obtaining a film excellent in easy tearability and capable of improving mechanical strength, a film containing the polyethylene composition, and a multilayer film provided with a layer containing the polyethylene composition.SOLUTION: A polyethylene composition according to the present invention comprises a linear low density ethylene-α-olefin copolymer (component (a)), a styrene homopolymer (component (b)), and a styrene copolymer (component c), and a content of the component (a) is 30 mass% or more and 79.5 mass% or less based on a total of 100 mass% of the components (a), (b) and (c), the content of the component (b) is 20 mass% or more and 50 mass% or less, the content of component (c) is 0.5 mass% or more and 20 mass% or less, and a ratio of a melt flow rate of component (a) to the melt flow rate of the component (c) is 0.2 or more and 5.0 or less.SELECTED DRAWING: None

Description

The present invention relates to a polyethylene composition, a film containing the polyethylene composition, and a multilayer film comprising a layer containing the polyethylene composition.

BACKGROUND ART Films having a laminated structure of a base film and a sealant film are widely used as various packaging materials. A film having such a structure is made into a packaging bag by heat-sealing the bag with the sealant film on the inside to form a storage space. A package is then formed by accommodating the article in such a packaging bag and sealing it.

The film forming such a packaging bag is required to be easily torn in one direction by hand (tearability) when an article is removed from the package. As a film with excellent tearability, for example, Patent Document 1 describes a resin composition containing a styrene resin, an olefin resin, and a hydrogenated product of a styrene/conjugated diene block copolymer in a predetermined ratio. Multilayer films have been proposed that include layers of materials.

Japanese Patent Application Publication No. 2001-179904

Incidentally, the film forming the packaging bag is required to have excellent mechanical strength from the viewpoint of making it difficult to be damaged by impact during transportation, dropping, etc. However, in the film described in Patent Document 1, no consideration has been given to mechanical strength.

The present invention has been made in view of the above circumstances, and provides a polyethylene composition containing the polyethylene composition capable of obtaining a film that is excellent in easy tearability and capable of improving mechanical strength. An object of the present invention is to provide a multilayer film comprising a film and a layer containing the polyethylene composition.

The polyethylene composition according to the present invention comprises a linear low density ethylene-α-olefin copolymer (component (a)), a styrene homopolymer (component (b)), and a styrene copolymer (component (component (b)). c));
Based on a total of 100% by mass of the component (a), the component (b), and the component (c),
The content of the component (a) is 30% by mass or more and 79.5% by mass or less,
The content of the component (b) is 20% by mass or more and 50% by mass or less,
The content of the component (c) is 0.5% by mass or more and 20% by mass or less,
The ratio (MFR(a)/MFR(c)) of the melt flow rate (MFR(a)) of the component (a) to the melt flow rate (MFR(c)) of the component (c) is 0.2 or more and 5 .0 or less.

The film according to the present invention contains the above polyethylene composition.

The multilayer film according to the present invention includes an intermediate resin layer containing the above polyethylene composition,
Containing at least one type of polyethylene selected from the group consisting of a linear low density ethylene-α-olefin copolymer, a branched low density polyethylene, and a high density polyethylene formed on both sides of the intermediate resin layer. a surface resin layer;
Equipped with

Advantageous Effects of Invention According to the present invention, a polyethylene composition capable of obtaining a film having excellent tearability and improved mechanical strength, a film containing the polyethylene composition, and a film containing the polyethylene composition A multilayer film comprising layers can be provided.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[Polyethylene composition]
The polyethylene composition according to the present embodiment includes a linear low density ethylene-α-olefin copolymer (component (a)), a styrene homopolymer (component (b)), and a styrene copolymer (component (c)).

<Linear low-density ethylene-α-olefin copolymer (component (a))>
The linear low density ethylene-α-olefin copolymer (component (a)) is a linear copolymer having a structural unit derived from ethylene and a structural unit derived from α-olefin. .

The content of structural units derived from ethylene in component (a) is preferably 70% by mass or more and 97% by mass or less, more preferably 80% by mass or more and 95% by mass or less. Further, the content of structural units derived from α-olefin is preferably 3% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less.

Examples of α-olefins include α-olefins having 3 to 10 carbon atoms, such as propylene, 1-butene, 1-hexene, 4-methylpentene-1, heptene-1, octene-1, and decene-1. , preferably 1-butene.

Component (a) is preferably an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-butene/1-hexene copolymer, an ethylene/1-octene copolymer, It is an ethylene/4-methyl-1-pentene copolymer.

The melt flow rate (MFR) of component (a) measured at a temperature of 190°C and a load of 2.16 kg is preferably 0.2 g/10 minutes or more and 10 g/10 minutes or less, from the viewpoint of improving the tearability of the film. and more preferably 0.5 g/10 minutes or more and 5 g/10 minutes or less. Note that MFR is measured according to method A specified in JIS K7210-1995.

The density of component (a) is preferably 870 kg/m ³ or more and 940 kg/m ³ or less, more preferably 900 kg/m ³ or more and 930 kg/m ³ or less. Note that the density is measured according to method A specified in JIS K7112-1980 after performing annealing described in JIS K6760-1995.

The content of component (a) is 30% by mass or more and 79.5% by mass or less, preferably 40% by mass, based on the total of 100% by mass of component (a), component (b), and component (c). It is 79.5% by mass or less, more preferably 60% by mass or more and 79.5% by mass or less.

<Styrene homopolymer (component (b))>
The styrene homopolymer (component (b)) is a polymer composed only of structural units derived from styrene.

The melt flow rate (MFR) of component (b) measured at a temperature of 190°C and a load of 2.16 kg is preferably 0.2 g/10 minutes or more and 10 g/10 minutes or less, from the viewpoint of improving the tearability of the film. and more preferably 0.5 g/10 minutes or more and 5 g/10 minutes or less. Note that MFR is measured according to method A specified in JIS K7210-1995.

The ratio of the melt flow rate (MFR(a)) of component (a) to the melt flow rate of component (b) (MFR(b)) (MFR(a)/MFR(b)) improves the mechanical strength of the film. From the viewpoint of achieving this, it is preferably 0.3 or more and 3.0 or less, more preferably 0.5 or more and 2.5 or less. MFR(a)/MFR(b) can be set to 0.3 or more and 3.0 or less by selecting component (a) and component (b) having appropriate MFR.

The content of component (b) is 20% by mass or more and 50% by mass or less, preferably 20% by mass or more and 40% by mass, based on the total of 100% by mass of component (a), component (b), and component (c). It is not more than 20% by mass and not more than 35% by mass.

<Styrenic copolymer (component (c))>
The styrenic copolymer (component (c)) is a block copolymer having a structural unit derived from styrene and a structural unit derived from a conjugated diene, and a hydrogenated product thereof.

The content of structural units derived from styrene in component (c) is preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less. Further, the content of structural units derived from conjugated diene is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 80% by mass or less.

Examples of the conjugated diene include isoprene and butadiene, with butadiene being preferred.

Component (c) is preferably a styrene/butadiene block copolymer, a partially hydrogenated styrene/butadiene block copolymer, or a fully hydrogenated styrene/butadiene block copolymer.

The melt flow rate (MFR) of component (c) measured at a temperature of 190°C and a load of 2.16 kg is preferably 0.1 g/10 minutes or more and 5 g/10 minutes or less, from the viewpoint of improving the tearability of the film. and more preferably 0.2 g/10 minutes or more and 2 g/10 minutes or less. Note that MFR is measured according to method A specified in JIS K7210-1995.

The ratio of the melt flow rate (MFR(a)) of component (a) to the melt flow rate of component (c) (MFR(c)) (MFR(a)/MFR(c)) improves the mechanical strength of the film. From the viewpoint of increasing the temperature, it is 0.2 or more and 5.0 or less, preferably 0.5 or more and 4.5 or less, and more preferably 1.0 or more and 4.0 or less. MFR(a)/MFR(c) can be set to 0.2 or more and 5.0 or less by selecting component (a) and component (c) having appropriate MFR.

The content of component (c) is 0.5% by mass or more and 20% by mass or less, preferably 0.5% by mass, based on the total of 100% by mass of components (a), (b), and (c). It is at least 10% by mass, more preferably at least 0.5% by mass and at most 5% by mass.

The polyethylene composition according to the present embodiment may contain a lubricant, an antiblocking agent, an antistatic agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a pigment, a dye, an antibacterial agent, an antifogging agent, and a plasticizer, as necessary. It may contain additives such as.

<Film>
The film according to this embodiment contains the above polyethylene composition.

The thickness of the film is preferably 20 μm or more and 200 μm or less, more preferably 30 μm or more and 150 μm or less.

The film according to this embodiment includes, for example, a melt-kneading step of melt-kneading the above-mentioned polyethylene composition, an extrusion step of extruding the melt-kneaded composition, and a film-forming step of forming a film from the extruded composition. It can be manufactured by

In the melt-kneading step, a linear low-density ethylene-α-olefin copolymer (component (a)), a styrene homopolymer (component (b)), and a styrene copolymer (component (c)) are and, if necessary, additives, are melt-kneaded.

The melt-kneading can be carried out using conventionally known methods and devices. For example, the above-mentioned materials may be mixed using a mixing device such as a Henschel mixer, a ribbon blender, or a tumble mixer, and then melt-kneaded. In addition, after obtaining a homogeneous mixture by continuously feeding each of the above materials at a fixed rate using a quantitative feeder, the mixture is transferred to a single screw or two or more screw extruder, a Banbury mixer, etc. , a method of melt-kneading using a roll-type kneader or the like.

In the extrusion step, for example, the melt-kneaded composition is extruded from a circular die using an extruder. The extrusion rate can be, for example, 5.0 kg/hour or more and 100 kg/hour or less. Further, the extrusion temperature can be, for example, 150°C or more and 230°C or less.

In the film forming step, for example, the composition extruded from a circular die is stretched with tube nip rolls to form a film to a predetermined thickness.

<Multilayer film>
The multilayer film according to the present embodiment includes an intermediate resin layer containing the above polyethylene composition, a linear low density ethylene-α-olefin copolymer, a branched low and a surface resin layer containing at least one type of polyethylene selected from the group consisting of high-density polyethylene and high-density polyethylene. The surface resin layers formed on both sides of the intermediate resin layer may be made of the same resin, or may be made of different resins.

As the linear low density ethylene-α-olefin copolymer, the same polymer as the above component (a) can be used.

Branched low-density polyethylene is a branched ethylene homopolymer composed only of structural units derived from ethylene, or a branched ethylene homopolymer having structural units derived from ethylene and structural units derived from α-olefin. It is a copolymer of The content of structural units derived from ethylene in the copolymer is preferably 70% by mass or more and 97% by mass or less, more preferably 80% by mass or more and 95% by mass or less. Further, the content of structural units derived from α-olefin is preferably 3% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less. Examples of α-olefins include α-olefins having 3 to 10 carbon atoms, such as propylene, 1-butene, 1-hexene, 4-methylpentene-1, heptene-1, octene-1, and decene-1. , preferably 1-butene.

The density of the branched low density polyethylene is preferably 870 kg/m ³ or more and 940 kg/m ³ or less, more preferably 900 kg/m ³ or more and 930 kg/m ³ or less. Note that the density is measured according to method A specified in JIS K7112-1980 after performing annealing described in JIS K6760-1995.

High-density polyethylene is an ethylene homopolymer composed only of structural units derived from ethylene. The density of the high-density polyethylene is preferably 940 kg/m ³ or more and 980 kg/m ³ or less, more preferably 950 kg/m ³ or more and 970 kg/m ³ or less. Note that the density is measured according to method A specified in JIS K7112-1980 after performing annealing described in JIS K6760-1995.

The thickness of the multilayer film is preferably 20 μm or more and 200 μm or less, more preferably 30 μm or more and 150 μm or less.

Examples of the method for laminating the intermediate resin layer and the surface resin layer formed on both sides of the intermediate resin layer include known film manufacturing methods such as the T-die method and the tubular method, and preferably the T-die method and the tubular method. This is the die method.

Applications of the film and multilayer film according to this embodiment include, for example, packaging applications for foods, textiles, miscellaneous goods, and the like. The film and multilayer film according to the present embodiment may be laminated with a base film made of plastic, aluminum foil, paper, etc., and then formed into a bag shape.

Note that the polyethylene composition, film, and multilayer film according to the present embodiment are not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention.

Hereinafter, the present invention will be explained in more detail using Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Measuring method]
The measured values of each item in Examples and Comparative Examples were measured according to the following method.

<Melt flow rate (MFR, unit: g/10 minutes)>
Measurement was performed according to method A specified in JIS K7210-1995 at a temperature of 190° C. and a load of 2.16 kg.

<Density (unit: kg/m ³ )>
After performing annealing as described in JIS K6760-1995, measurement was performed according to method A specified in JIS K7112-1980.

[Method for evaluating physical properties of film]
The physical properties of the films of Examples and Comparative Examples were evaluated according to the following method.

<Tear strength (unit: kJ/N)>
The Elmendorf test method tear strength was determined based on JIS K7128-2:1998 for the pulling direction (MD) and the direction (TD) perpendicular to the MD direction of the films obtained in each example and comparative example. Ta. Note that the smaller this value is, the better the tearability is.

<Tensile breaking strength (unit: MPa)>
From the formed film, according to the sample collection method for tensile cutting load measurement described in JIS K 6781 6.4, the longitudinal direction is the take-up direction (MD) and the direction perpendicular to the MD direction (TD), respectively. A test piece was prepared. Using the obtained test piece, a tensile test was conducted under the conditions of 80 mm between chucks, 40 mm between marked lines, and a tensile speed of 500 mm/min to determine the tensile strength at break. Note that a film with high tensile strength at break has excellent mechanical strength.

<Tensile elongation at break (unit: %)>
From the formed film, according to the sample collection method for tensile cutting load measurement described in JIS K 6781 6.4, the longitudinal direction is the take-up direction (MD) and the direction perpendicular to the MD direction (TD), respectively. A test piece was prepared. Using the obtained test piece, a tensile test was conducted under the conditions of a chuck distance of 80 mm, a marked line distance of 40 mm, and a tensile speed of 500 mm/min to determine the tensile elongation at break. Note that a film with a high tensile elongation at break has excellent mechanical strength.

The following ethylene-α-olefin copolymer LLDPE was used.
Ethylene-α-olefin copolymer LLDPE-1: Ziegler-Nutter catalyst linear low-density polyethylene Sumikacene L FS150 (manufactured by Sumitomo Chemical Co., Ltd., ethylene-1-butene copolymer, MFR 1.0 g/10 min, density 921. 5kg/ ^m3 )
Ethylene-α-olefin copolymer LLDPE-2: Ziegler-Nutter catalyst linear low-density polyethylene Sumikacene L FS240 (manufactured by Sumitomo Chemical Co., Ltd., ethylene-1-butene copolymer, MFR 2.2 g/10 min, density 919 kg/ ^m3 )
Ethylene-α-olefin copolymer LLDPE-3: Ziegler-Nutter catalyst linear low-density polyethylene Sumikacene L FR152 (manufactured by Sumitomo Chemical Co., Ltd., ethylene-1-butene copolymer, MFR 1.0 g/10 min, density 923. 5kg/ ^m3 )

The following styrene homopolymer was used.
Styrene homopolymer (PS): Toyo Styrene GP G210C (manufactured by Toyo Styrene Co., Ltd., melt flow rate is 1.0 g/10 minutes at a temperature of 190°C and a load of 2.16 kg)

The following styrene copolymers were used.
Styrene/ethylene/butylene/styrene copolymer (SEBS): Tuftec (registered trademark) H1041 (manufactured by Asahi Kasei Corporation, melt flow rate at 190°C and load 2.16 kg is 0.3 g/10 min, styrene content 30 mass%)

[Single layer blown film molding]
<Example 11>
LLDPE-1, PS, and SEBS were mixed in the composition shown in Table 1 using a tumble mixer. Next, the obtained mixture was processed using a blown film molding machine manufactured by Plako Co., Ltd. (Plako Co., Ltd. EXU type single screw extruder, die (die diameter 125 mmφ, lip gap 2.0 mm, single slit air ring with iris). A blown film with a thickness of 50 μm was molded under the processing conditions of a temperature of 190° C., an extrusion rate of 25 kg/hour, and a blow ratio of 2.0.Table 2 shows the physical properties of the obtained single-layer blown film.

<Example 12>
A single-layer blown film was obtained in the same manner as in Example 11, except that LLDPE-1, PS, and SEBS were mixed in the composition shown in Table 1 using a tumble mixer. Table 2 shows the physical properties of the obtained single-layer blown film.

<Example 13>
A single-layer blown film was obtained in the same manner as in Example 11, except that LLDPE-1, PS, and SEBS were mixed in the composition shown in Table 1 using a tumble mixer. Table 2 shows the physical properties of the obtained single-layer blown film.

<Comparative example 11>
A single-layer blown film was obtained in the same manner as in Example 11, except that LLDPE-2, PS, and SEBS were mixed in a tumble mixer at the composition shown in Table 1. Table 2 shows the physical properties of the obtained single-layer blown film.

As can be seen from the results in Table 2, the polyethylene compositions of each example that satisfy all the constituent requirements of the present invention have excellent tearability and can provide films that can improve mechanical strength.

On the other hand, the polyethylene composition of Comparative Example 11 has poor mechanical strength of the film because MFR(a)/MFR(c) does not satisfy the range defined by the present invention.

[Multilayer blown film molding]
<Example 21>
LLDPE-1, PS, and SEBS were mixed in the composition shown in Table 3 using a tumble mixer. Next, the obtained mixture was introduced into an extruder for the middle layer of a 3-layer coextrusion blown film forming machine manufactured by Placo, which was composed of 3 extruders with a screw diameter of 50 mmφ, and LLDPE-3 was introduced into the extruder for the outer layer and the inner layer. using a die (die diameter 150 mmφ, lip gap 2.0 mm), processing temperature 190°C, blow ratio 2.0, extrusion rate of the intermediate layer, inner layer, and outer layer each 10 kg/hour, and take-off speed 11.5 m. A blown film with a thickness of 50 μm was molded under processing conditions of /min. Table 4 shows the physical properties of the obtained multilayer blown film.

Claims (3)

A linear low-density ethylene-α-olefin copolymer (component (a)), a styrene homopolymer (component (b)), and a styrenic copolymer (component (c)),
Based on a total of 100% by mass of the component (a), the component (b), and the component (c),
The content of the component (a) is 30% by mass or more and 79.5% by mass or less,
The content of the component (b) is 20% by mass or more and 50% by mass or less,
The content of the component (c) is 0.5% by mass or more and 20% by mass or less,
The ratio (MFR(a)/MFR(c)) of the melt flow rate (MFR(a)) of the component (a) to the melt flow rate (MFR(c)) of the component (c) is 0.2 or more and 5 .0 or less. A film containing the polyethylene composition according to claim 1. An intermediate resin layer containing the polyethylene composition according to claim 1;
Containing at least one type of polyethylene selected from the group consisting of a linear low density ethylene-α-olefin copolymer, a branched low density polyethylene, and a high density polyethylene formed on both sides of the intermediate resin layer. a surface resin layer;
A multilayer film comprising: