JP2021133509A - Dual axis extension polypropylene film for producing bag by melting - Google Patents

Abstract

To provide a dual axis extension polypropylene film for producing a bag by melting, comprising excellent transparency, see-through feeling, glossy feeling and melting seal strength.SOLUTION: There is provided a dual axis extension polypropylene film for producing a bag by melting formed of: at least three layers or more layers of an outer face layer 11, an intermediate layer 12 and an inner face layer 13, in which the outer face layer 11 and the inner face layer 13 are respectively formed of a resin composition which is mainly formed of a same or different propylene based polymer. A layer thickness of each of the outer face layer 11 and the inner face layer 13 is greater than 0.8 μm, and the intermediate layer 12 has a composition formed of 85-98 mass% of a propylene based polymer and 2-15 mass% of an ethylene based polymer (E), and the ethylene based polymer (E) has concentration of 0.904-0.945 g/cm3, and has a melt flow rate (190°C and 2.16 kg load) of 1.0 to 8.0 g/10 min.SELECTED DRAWING: Figure 1

Description

The present invention relates to a biaxially stretched polypropylene film that is formed into a bag shape by fusing.

Since biaxially stretched polypropylene film is excellent in transparency and gloss, it is widely used as a packaging material after being processed into various forms. Among them, it is often molded into a bag shape and used, and when it is molded into a bag shape, it may be processed by a fusing seal.

As a polypropylene film that is melt-sealed and molded into a bag shape, a film that is stretched at a low magnification in the MD (flow) direction has been proposed (see, for example, Patent Document 1 and the like). However, since the stretching is performed at a low magnification, uneven stretching may occur. Further, since the film is stretched at a high temperature, there is a concern that the film-forming property and the appearance may be deteriorated due to the adhesion of the sheet to the roll.

In addition, a film having improved sealing properties by laminating a low melting point resin such as an olefin copolymer or a polyethylene resin on the surface layer has been proposed (see, for example, Patent Documents 2 to 4). .. However, by using a resin having a low melting point on the inner surface, the film tends to be sticky, and there is a concern that slipperiness and blocking resistance may be lowered. Further, the deterioration of slipperiness and blocking resistance may cause deterioration of processing suitability and opening property.

By the way, in recent years, there has been an active demand for efforts toward a sound material-cycle society in which the utilization of renewable resources is increased and the environmental load is reduced. Renewable resources are resources that are mainly processed from plants and raw materials derived from plants, and are also called biomass resources. In the case of biomass resources, carbon dioxide in the atmosphere is absorbed as the plants grow. Then, when it is used as a biomass resource for fuel or the like, it is decomposed into water and carbon dioxide again. Therefore, the amount of carbon dioxide does not increase. In other words, biomass resources are resources that need to be largely incorporated in the future from the viewpoint of carbon neutrality.

In the field of plastics, although biomass-derived plastics such as polylactic acid and biodegradable polymers are produced as biomass-derived plastics, the production amount is limited and it cannot be said that they are widely used. On the other hand, regarding polyethylene, which is the most commonly used material among general-purpose plastics, a method of obtaining polyethylene from plant-derived sugar via ethanol has been commercialized and widely used.

As a resin film using biomass-derived polyethylene, a film using only ethylene-based resin has been proposed (see, for example, Patent Document 5). However, since this film is composed of only ethylene-based resin. , Inferior in heat resistance. Further, a film in which biomass-derived polyethylene is added to a polypropylene-based resin has been proposed (see, for example, Patent Document 6). However, these films tend to be inferior in transparency and perspective.

Therefore, the inventors have studied diligently, and are often used in the packaging field. Especially, in a biaxially stretched polypropylene film formed into a bag shape by a fusing seal, biaxially stretched having excellent transparency, glossiness and fusing seal strength. We have developed a polypropylene film, and it has become possible to reduce the environmental load by containing a large amount of resin derived from biomass resources.

Japanese Unexamined Patent Publication No. 9-169050 Japanese Unexamined Patent Publication No. 2004-90543 Japanese Unexamined Patent Publication No. 2007-253349 Japanese Unexamined Patent Publication No. 2013-279777 Japanese Patent No. 5862055 JP-A-2018-65267

The present invention has been proposed in view of the above circumstances, and provides a biaxially stretched polypropylene film for fusing bags having excellent transparency, see-through feeling, glossiness and fusing seal strength. Further, the present invention provides a biaxially stretched polypropylene film for fusing and bag making, which can also reduce the burden on the environment.

That is, the first invention is a biaxially stretched polypropylene film composed of a plurality of at least three or more layers of an outer surface layer, an intermediate layer, and an inner surface layer, which is used for bag making by fusing and sealing, and the outer surface layer. The inner surface layer is composed of a resin composition mainly containing the same or different propylene-based polymer, and the outer surface layer and the inner surface layer are each thicker than 0.8 μm, and the intermediate layer is formed. Is a composition in which the propylene-based polymer is 85 to 98% by weight and the ethylene-based polymer (E) is 2 to 15% by weight, and the ethylene polymer has a (e1) density of 0.904 to 0.945 g. The present invention relates to a biaxially stretched polypropylene film for fusing and bag making, which comprises / cm ³ and (e2) a melt flow rate (190 ° C., 2.16 kg load) of 1.0 to 8.0 g / 10 min.

The second invention relates to a biaxially stretched polypropylene film for fusing and bag making, wherein the ethylene-based polymer (E) is a linear low-density polyethylene in the first invention.

A third invention relates to a biaxially stretched polypropylene film for fusing and bag making, wherein the ethylene-based polymer (E) is produced from a Ziegler-Natta catalyst in the first or second invention.

In the fourth invention, in any of the first to third inventions, the haze value of the biaxially stretched polypropylene film measured in accordance with JIS K 7136 (2000) is 6% or less, and the narrow-angle diffusion transmission is performed. The present invention relates to a biaxially stretched polypropylene film for fusing and bag making, wherein the ratio (LSI) is 50% or less.

The fifth invention is characterized in that, in any one of the first to fourth inventions, the surface glossiness of the biaxially stretched polypropylene film measured in accordance with JIS Z 8741 (1997) is 100% or more. The present invention relates to a biaxially stretched polypropylene film for fusing and bag making.

A sixth invention is a biaxially stretched polypropylene film for fusing bags, wherein the ethylene-based polymer (E) is a biomass-derived ethylene-based polymer in any one of the first to fifth inventions. Related to.

The seventh invention relates to a packaging bag made of a biaxially stretched polypropylene film for fusing bag making according to any one of the first to sixth inventions.

According to the biaxially stretched polypropylene film for fusing bag making of the first invention, it is used for bag making by fusing seal and is biaxially stretched consisting of at least three or more layers of an outer surface layer, an intermediate layer and an inner surface layer. In a polypropylene film, the outer surface layer and the inner surface layer are each composed of a resin composition containing the same or different propylene-based polymer as a main component, and the outer surface layer and the inner surface layer have a thickness of 0. The intermediate layer is thicker than 8 μm and has a composition of 85 to 98% by weight of the propylene polymer and 2 to 15% by weight of the ethylene polymer (E), and the ethylene polymer is (e1). ) The density is 0.904 to 0.945 g / cm ^3, and (e2) the melt flow rate (190 ° C., 2.16 kg load) is 1.0 to 8.0 g / 10 min, so that it has excellent transparency and transparency. It has a feeling, glossiness and fusing seal strength.

According to the biaxially stretched polypropylene film for fusing and bag making of the second invention, in the first invention, since the ethylene-based polymer (E) is a linear low-density polyethylene, it has better transparency and gloss. Have a feeling.

According to the biaxially stretched polypropylene film for fusing and bag making of the third invention, in the first or second invention, the ethylene-based polymer (E) is produced from a Ziegler-Natta catalyst, so that the fusing is more excellent. Has sealing properties.

According to the biaxially stretched polypropylene film for fusing and bag making of the fourth invention, the haze of the biaxially stretched polypropylene film measured in accordance with JIS K 7136 (2000) in any of the first to third inventions. Since the value is 6% or less and the narrow-angle diffusion transmittance (LSI) is 50% or less, it has excellent transparency and a sense of transparency.

According to the biaxially stretched polypropylene film for fusing and bag making of the fifth invention, the surface of the biaxially stretched polypropylene film measured in accordance with JIS Z 8741 (1997) in any of the first to fourth inventions. Since the glossiness is 100% or more, it has excellent glossiness and has a high-class appearance.

According to the biaxially stretched polypropylene film for fusing and bag making of the sixth invention, in any one of the first to fifth inventions, the ethylene polymer (E) is a biomass-derived ethylene polymer, and therefore the environment. The load can be reduced.

According to the packaging bag according to the seventh invention, since it is made of a biaxially stretched polypropylene film for fusing bag making according to any one of the first to sixth inventions, it has excellent transparency, transparency, glossiness and fusing seal. It can be a packaging bag made of a strong film, which has a high-class feel, is durable, and is not easily torn.

It is the schematic sectional drawing of the biaxially stretched polypropylene film of the three-layer structure which concerns on one Example of this invention. It is the schematic which made the biaxially stretched polypropylene film of this invention into a bag-like thing, and shows the cut-out position of the test piece of the bag-like thing used for measuring the fusing seal strength.

The film of the present invention is used for bag making with a fusing seal. A heated rod-shaped heater (fusing blade) is pressed against the half-folded film in the direction orthogonal to the folded portion, which is the bottom, and the film is cut off, so that the film is bonded and sealed by heat. , Molded into a bag shape. Bag making with a fusing seal is appropriately selected from known methods.

FIG. 1 is a schematic cross-sectional view of a biaxially stretched polypropylene film 10 according to an embodiment of the present invention. The film 10 is a laminated film 20 composed of at least three or more layers of an outer surface layer 11, an intermediate layer 12, and an inner surface layer 13. The film 10 is produced by biaxially stretching a sheet in which the raw material resin of each layer is melted, discharged from a T-die or the like to a predetermined thickness, and co-extruded by a known stretching method. The biaxially stretched polypropylene film 10 preferably has a film thickness in the range of 1 to 100 μm from the viewpoint of ease of handling and strength.

The outer surface layer 11 and the inner surface layer 13 of the film 10 are composed of a resin composition mainly composed of a propylene-based polymer, and an appropriate resin such as a propylene homopolypropylene or a propylene-ethylene random copolymer is selected. Will be done. Polypropylene-based polymers are excellent in heat resistance, chemical resistance, and strength. The outer surface layer 11 and the inner surface layer 13 may be the same resin or different resins, and can be appropriately selected depending on the intended use of the film. Additives such as an anti-blocking agent, an antistatic agent, an antioxidant, a neutralizing agent, and a coloring agent are added to the outer surface layer 11 and the inner surface layer 13 as needed.

The outer surface layer 11 and the inner surface layer 13 are configured to have a thickness of more than 0.8 μm, as described in Examples described later. This is because if the thickness of the surface layer is 0.8 μm or less, the transparency and glossiness are impaired.

The intermediate layer is composed of a propylene-based polymer and an ethylene-based polymer (E), and the composition thereof is 85 to 98% by weight of the propylene-based polymer and 2 to 15% by weight of the ethylene-based polymer. Preferably, the propylene-based polymer is 92 to 98% by weight, and the ethylene-based polymer is 2 to 8% by weight. If the amount of the ethylene polymer added is less than 2% by weight, the fusing seal strength of the film may decrease and the desired strength may not be obtained. Further, when the amount of the ethylene polymer added is more than 15% by weight, the transparency and glossiness of the film may be impaired.

The propylene-based polymer used for the intermediate layer may be the same as or different from the propylene-based polymer used for the outer surface layer and the inner surface layer. The propylene-based polymer can be appropriately selected depending on the desired film performance.

The ethylene polymer (E) used in the intermediate layer has a density of 0.904 to 0.945 g / cm ³ (e1), preferably 0.916 to 0.938 g / cm ³ . The melt flow rate (MFR) (190 ° C., 2.16 kg load) is 1.0 to 8.0 g / 10 min (e2), preferably 1.0 to 5.0 g / 10 min. If the density is ^{less than 0.904 g / cm 3} , the transparency and glossiness of the film may be impaired. Even when the density is ^{higher than 0.945 g / cm 3} , the transparency and glossiness of the film may be impaired as well. If the melt flow rate also falls below or exceeds the above range, the transparency and glossiness of the film may be impaired, and the fusing seal strength may also decrease.

Further, the ethylene-based polymer (E) is preferably linear low-density polyethylene. When made into a film, it has excellent transparency and gloss. The ethylene-based polymer (E) is preferably produced by a polymerization method using a Ziegler-Natta catalyst. This is because the fusing seal strength of a film tends to be higher than that of an ethylene-based polymer produced by a polymerization method using a metallocene catalyst.

The ethylene-based polymer (E) is preferably a biomass-derived polyethylene-based resin. The biomass-derived polyethylene-based resin is a polyethylene-based resin obtained by processing a plant raw material. Specifically, ethanol is produced from a sugar solution extracted from a plant material such as sugar cane through alcoholic fermentation with yeast to be ethyleneed, and then polyethylene is produced by a known resinification step. This biomass-derived polyethylene resin contributes to the reduction of the environmental load of the final product.

The haze of the biaxially stretched polypropylene film is preferably 6% or less. Films with a haze of less than 6% have excellent transparency. Haze is measured according to JIS K 7136 (2000) as described in the examples below. Further, the narrow-angle diffusion transmittance (LSI) of the biaxially stretched polypropylene film is 50% or less. If the narrow-angle diffusion transmittance (LSI) exceeds 50%, the transparency may be inferior, and the suitability for the application of the packaging film may be inferior.

The surface glossiness of the biaxially stretched polypropylene film is preferably 100% or more. If the surface gloss exceeds 100%, the appearance of the film will be luxurious. The surface glossiness is measured according to JIS Z 8741 (1997) as described in the following examples.

[Film molding]
The films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2 were molded as follows. Each of the materials described below is kneaded and melted, set to be laminated in the order of the inner surface layer, the intermediate layer, and the outer surface layer, and coextruded from a three-layer coextrusion T-die film molding machine set at 240 degrees to 50 degrees. A sheet-like material was obtained by cooling and solidifying with the cooling roll of the above. Next, the sheet-like material was preheated at a set temperature of 100 to 115 ° C., stretched 4.8 times in the vertical direction (MD direction), and then annealed at a set temperature of 135 ° C. It was preheated with a tenter at a set temperature of 180 ° C., stretched 8.0 times laterally (TD direction) at a set temperature of 155 ° C., and then annealed at a set temperature of 160 ° C. After leaving the tenter, a corona treatment discharge was applied, and the film was wound by a winder to obtain a biaxially stretched polypropylene film. The biaxially stretched polypropylene film was formed so as to have a thickness of 30 μm. The melt flow rate (MFR) is based on JIS K 7210 (2014), and is a melt flow rate measured at 190 ° C. for a polyethylene resin and 230 ° C. for a polypropylene resin.

[Materials used as propylene-based polymers in each layer]
The following resins PP1 and PP2 were used as the polypropylene-based resin constituting the outer surface layer, the resin composition of the inner surface layer, and the intermediate layer. Powdered synthetic silica (manufactured by Fuji Silysia Chemical Ltd., trade name "Silicia 730") was appropriately added to the outer surface layer and the inner surface layer as an anti-blocking agent.
-Resin PP1: Homopolypropylene (manufactured by Japan Polypropylene Corporation, trade name "FL203D", density 0.90 g / cm ³ , MFR: 3.0 g / 10 min)
-Resin PP2: Random polypropylene (manufactured by Japan Polypropylene Corporation, trade name "FX4G", density 0.90 g / cm ³ , MFR: 5.0 g / 10 min)

[Material used as ethylene polymer in the intermediate layer]
In the intermediate layer, the following resins PE1 to PE3 were used as the biomass-derived polyethylene-based resin, and the following resins PE4 to PE10 were used as the non-biomass-derived polyethylene-based resin.
-Resin PE1: Linear low-density polyethylene derived from biomass polymerized using a Ziegler-Natta catalyst (manufactured by Braskem, trade name "SLH118", density: 0.916 ^{g / cm 3} , MFR: 1.0 g / 10 min )
-Resin PE2: Biomass-derived linear low-density polyethylene polymerized using a Ziegler-Natta catalyst (manufactured by Braskem, trade name "SLH218", density: 0.916 ^{g / cm 3} , MFR: 2.3 g / 10 min) )
-Resin PE3: Biomass-derived high-density polyethylene polymerized using a Ziegler-Natta catalyst (manufactured by Braskem, trade name "SGF4960", density: 0.961 ^{g / cm 3} , MFR: 0.34 g / 10 min)
-Resin PE4: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Ube-Maruzen Polyethylene Co., Ltd., trade name "4040FC", density: 0.938 ^{g / cm 3} , MFR: 3.5 g / 10 min)
-Resin PE5: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Ube-Maruzen Polyethylene Co., Ltd., trade name "4540F", density: 0.944 ^{g / cm 3} , MFR: 4.0 g / 10 min)
-Resin PE6: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Ube-Maruzen Polyethylene Co., Ltd., trade name "2040FC", density: 0.919 ^{g / cm 3} , MFR: 5.0 g / 10 min)
-Resin PE7: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Ube-Maruzen Polyethylene Co., Ltd., trade name "022GS", density: 0.904 g / cm ³ , MFR: 8.0 g / 10 min)
-Resin PE8: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Prime Polymer Co., Ltd., trade name "SP2020", density: 0.916 ^{g / cm 3} , MFR: 2.3 g / 10 min)
-Resin PE9: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Prime Polymer Co., Ltd., trade name "SP3010", density: 0.926 ^{g / cm 3} , MFR: 0.8 g / 10 min)
-Resin PE10: Linear low-density polyethylene polymerized using a metallocene catalyst (manufactured by Ube-Maruzen Polyethylene Co., Ltd., trade name "015AN", density: 0.911 g / cm ³ , MFR: 14.0 g / 10 min)

[Prototype example 1]
In Prototype Example 1, resin PP1 is used for the inner surface layer to make the layer thickness 1.0 μm, the composition of the intermediate layer is 98% by weight for resin PP1, 2% by weight for resin PE1, and resin PP2 is used for the outer surface layer. It is a film formed so as to have a layer thickness of 1.2 μm. The corona treatment was applied to the outer surface layer side surface.

[Prototype example 2]
Prototype Example 2 is a film formed in the same manner as Prototype Example 1 except that the composition of the intermediate layer is 96% by weight for the resin PP1 and 4% by weight for the resin PE1.

[Prototype example 3]
Prototype Example 3 is a film formed in the same manner as Prototype Example 1 except that the composition of the intermediate layer is 92% by weight for the resin PP1 and 8% by weight for the resin PE1.

[Prototype example 4]
Prototype Example 4 is a film formed in the same manner as Prototype Example 1 except that the composition of the intermediate layer is 85% by weight for the resin PP1 and 15% by weight for the resin PE1.

[Prototype Example 5]
Prototype Example 5 is a film formed in the same manner as Prototype Example 4 except that the layer thickness of the inner surface layer is 0.8 μm and the layer thickness of the outer surface layer is 0.8 μm.

[Prototype example 6]
Prototype Example 6 is a film formed in the same manner as Prototype Example 5 except that the composition of the intermediate layer is 75% by weight for the resin PP1 and 25% by weight for the resin PE1.

[Prototype example 7]
Prototype Example 7 is a film formed in the same manner as Prototype Example 5 except that the resin PE1 in the intermediate layer is changed to the resin PE2.

[Prototype Example 8]
Prototype Example 8 is a film formed in the same manner as Prototype Example 4 except that the resin PE1 in the intermediate layer is changed to the resin PE4.

[Prototype example 9]
Prototype 9 is a film formed in the same manner as Prototype 4 except that the resin PE1 in the intermediate layer is resin PE5.

[Prototype Example 10]
Prototype Example 10 is a film formed in the same manner as Prototype Example 4 except that the resin PE1 in the intermediate layer is changed to the resin PE6.

[Prototype Example 11]
Prototype Example 11 is a film formed in the same manner as Prototype Example 4 except that the resin PE1 in the intermediate layer is changed to the resin PE7.

[Prototype example 12]
Prototype Example 12 is the same as Prototype Example 1 except that resin PP2 is used for the inner surface layer, the composition of the intermediate layer is 85% by weight for resin PP1, 15% by weight for resin PE2, and resin PP1 is used for the outer surface layer. It is a similarly molded film. The corona treatment was applied to the inner surface layer side surface.

[Prototype example 13]
Prototype 13 is a film formed in the same manner as Prototype 12 except that the resin PE2 in the intermediate layer is resin PE8.

[Prototype Example 14]
Prototype Example 14 is a film formed in the same manner as Prototype Example 4 except that the resin PE1 in the intermediate layer is changed to the resin PE9.

[Prototype Example 15]
Prototype Example 15 is a film formed in the same manner as Prototype Example 4 except that the resin PE1 in the intermediate layer is changed to the resin PE10.

[Prototype Example 16]
Prototype Example 16 is a film formed in the same manner as Prototype Example 1 except that the composition of the intermediate layer is 95.2% by weight for the resin PP1 and 4.8% by weight for the resin PE3.

[Comparative Example 1]
Comparative Example 1 is a film formed in the same manner as in Prototype Example 1 except that the composition of the intermediate layer is 100% by weight of the resin PP1.

[Comparative Example 2]
Comparative Example 2 is a film formed in the same manner as in Comparative Example 1 except that it was produced by exchanging the resins of the inner surface layer and the outer surface layer. The corona treatment was applied to the inner surface layer side surface.

Regarding the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, the resin composition of each layer, the corona-treated layer, and the thicknesses of the inner surface layer and the outer surface layer are shown in Tables 1 to 4.

[Evaluation of film performance]
With respect to the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, each item of haze, narrow-angle diffusion transmittance, surface glossiness (inner surface layer, outer surface layer) and fusing seal strength was measured.

[Measurement of haze]
The haze (%) was measured using a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136 (2000), which is an index of transparency. In the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, the measurement results of 4.0% or less are "◎" as excellent products, and 4.1 to 6.0% are "○" as good products, 6.1%. The above items are designated as "x".

[Measurement of narrow-angle diffusion transmittance]
The narrow-angle diffusion transmittance (LSI) (%) is an index of perspective, and the LSI indicates the ratio of the scattered light amount of the scattered light amount of 0.4 ° or more and 1.2 ° or less to the total light transmitted light amount. .. The LSI is a measure of the fluoroscopic feeling of the naked eye, and the lower the numerical value, the better the fluoroscopic feeling. The LSI was measured using a visual transparency tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). In the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, the measurement result of 35.0% or less was "◎" as a good product, and 35.1 to 50.0% was "○" as a good product, 50.1%. The above items are designated as "x".

[Measurement of surface gloss]
The surface glossiness (%) is an index showing the glossiness of the film surface, and is based on JIS Z 8741 (1997), and a digital gloss meter (manufactured by Nippon Denka Kogyo Co., Ltd., VG-7000) is used. And measured. In the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, 121% or more of the measurement results are regarded as excellent products as "◎", 100 to 120% as good products as "○", and those with 99% or less as "x". bottom.

[Measurement of fusing seal strength]
Using the films of Prototype Examples 1 to 16 and Comparative Examples 1 and 2, the bag was made by fusing the seal so that the inner surface layer was inside the bag. Fold the film flowing in the MD direction in half, and use a fusing seal machine (manufactured by Totani Giken Kogyo Co., Ltd., "HK-40V") to press the fusing blades arranged at right angles to the flow direction to make the fusing seal. The bag-shaped product was formed. As shown in the schematic view of FIG. 2, the bottom side 31 is the folded-back portion 41, and the side portions 32 and 33 are the fusing seal portions 42 and 43. The fusing seal conditions are as follows. Reference numeral 34 in the figure is an opening.
-Seal temperature: 300 ° C, 350 ° C, 400 ° C
・ Hot blade tip angle: 120 degrees ・ Fusing interval: 200 mm
・ Number of shots: 72 shots / minute

Twenty pieces were extracted from the bag-shaped material obtained at each sealing temperature, and the following measurements were performed. As shown in FIG. 2, in the bag-shaped object No. 1, a test piece 50 having a width of 15 mm and a length of 100 mm was cut out from each of the fusing seal portions 42 and 43 on both sides so that the fusing seal portion was arranged in the center. .. The alternate long and short dash line in the figure is the cut-off line 51. The test piece was fixed with a chuck of a tensile tester (manufactured by Shimadzu Corporation, "AUTO GRAPH AGS-X 50N"), and the chuck distance of the test piece was adjusted to 50 mm. It was pulled at 200 mm / min, and the strength at which the fusing seal portion broke was measured. The value obtained by averaging all the measurement results in the fusing seal portion made into a bag at each sealing temperature (300 ° C, 350 ° C and 400 ° C) was taken as the fusing seal strength (N / 15 mm).

[comprehensive evaluation]
In the comprehensive evaluation, "A" is obtained when all the evaluations in each of the items described below are "◎", and "B" is selected if any one item contains "○". However, the one containing "x" was designated as "C". The results are shown in Tables 5 to 8 described later.

[Results and discussion]
As shown in Tables 5 to 8, the overall evaluation was "C" in Prototype Examples 5 to 7, 14 to 16 and Comparative Examples 1 and 2. Prototype Examples 5 and 7 are prototypes in which the thickness of the outer surface layer and the inner surface layer of Prototype Examples 4 and 12, respectively, is reduced. It was found that when the layer thicknesses of the outer surface layer and the inner surface layer were thinner than 0.8 μm, the transparency was lowered and the glossiness was also reduced, so that a film having a desired function could not be obtained. Further, in Prototype Example 6, the proportion of the ethylene-based polymer in the composition of the intermediate layer of Prototype Example 5 is increased, and the transparency and glossiness of the intermediate layer are further inferior to those of Prototype Example 5. It was understood that the upper limit of the ratio of the ethylene polymer was 15% by weight.

Prototype Example 14 is a prototype in which the composition of the intermediate layer of Prototype Example 4 is changed to a resin having a small MFR value of the ethylene polymer. Prototype Example 15 is a prototype in which the composition of the intermediate layer of Prototype Example 4 is changed to a resin having a large MFR value of the ethylene polymer. Since it was found that both of them were inferior in see-through feeling as compared with Prototype Example 4, it was found that the MFR value of the resin used for the intermediate layer needs to be within a predetermined range. Further, looking at Prototype Example 16, it was also understood that when the density of the ethylene-based polymer constituting the intermediate layer exceeds a certain level, the transparency and glossiness are inferior.

In general, the corona-treated surface tends to be difficult to heat-seal, but by containing a specified amount of a specified ethylene polymer in the composition of the intermediate layer, the fusing seal strength can be improved. It has been shown. In particular, in Comparative Examples 1 and 2, the fusing seal strength tends to be poor as compared with other prototype examples.

On the other hand, for the prototype example in which the specified ethylene polymer is contained in the specified amount of the intermediate layer, all the evaluations are excellent or good, and a film having a desired function can be obtained. It has been found that it is possible to provide a film capable of obtaining a bag-like product having sufficient strength, transparency, transparency, functionality with excellent glossiness, and a high-class feeling.

Furthermore, since Prototype Examples 1 to 4 and Prototype 12 using biomass-derived ethylene-based polymers could be made into excellent films with good evaluation, excellent transparency and excellent transparency were achieved while reducing the environmental load. It is possible to obtain a film having a transparent feeling and a glossy feeling, and also having an excellent fusing seal strength.

The biaxially stretched polyolefin film of the fusing bag of the present invention has excellent transparency, transparency, and luster, and also has excellent fusing seal strength, so that it can be used for various purposes as a packaging bag for foods and miscellaneous goods. be. Furthermore, the environmental load can be reduced by containing a large amount of resin derived from biomass resources.

10 Biaxially stretched polypropylene film 11 Outer surface layer 12 Intermediate layer 13 Inner surface layer 20 Laminated film 30 Bag-shaped 31 Bottom 32, 33 Side side 34 Opening 41 Folded seal 42, 43 Fusing seal

Claims (7)

A biaxially stretched polypropylene film composed of at least three or more layers of an outer surface layer, an intermediate layer, and an inner surface layer, which is used for bag making by fusing.
The outer surface layer and the inner surface layer are each composed of a resin composition mainly composed of the same or different propylene-based polymer.
The outer surface layer and the inner surface layer are each thicker than 0.8 μm.
The intermediate layer has a composition of 85 to 98% by weight of the propylene-based polymer and 2 to 15% by weight of the ethylene-based polymer (E).
The ethylene polymer is
(E1) The density is 0.904 to 0.945 g / cm ^3, and the density is set to 0.904 to 0.945 g / cm 3.
(E2) A biaxially stretched polypropylene film for fusing bags, characterized in that the melt flow rate (190 ° C., 2.16 kg load) is 1.0 to 8.0 g / 10 min. The biaxially stretched polypropylene film for fusing and bag making according to claim 1, wherein the ethylene-based polymer (E) is a linear low-density polyethylene. The biaxially stretched polypropylene film for fusing and bag making according to claim 1 or 2, wherein the ethylene-based polymer (E) is produced from a Ziegler-Natta catalyst. Claim 1 is characterized in that the haze value of the biaxially stretched polypropylene film measured in accordance with JIS K 7136 (2000) is 6% or less, and the narrow-angle diffusion transmittance (LSI) is 50% or less. The biaxially stretched polypropylene film for fusing and bag making according to any one of 3 to 3. The fusing bag according to any one of claims 1 to 4, wherein the surface gloss of the biaxially stretched polypropylene film measured in accordance with JIS Z 8741 (1997) is 100% or more. Biaxially stretched polypropylene film. The biaxially stretched polypropylene film for fusing and bag making according to any one of claims 1 to 5, wherein the ethylene-based polymer (E) is a biomass-derived ethylene-based polymer. A packaging bag made of a biaxially stretched polypropylene film for fusing bag according to any one of claims 1 to 7.

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