JP2021115857A - Biaxially drawn polyolefin film - Google Patents

Abstract

To provide a biaxially drawn polyolefin film which has excellent transparency and see-through feeling, and elasticity, is also excellent in productivity, and is reduced in load to environment.SOLUTION: A biaxially drawn polyolefin film for packaging that is composed of at least two or more layers of a plurality of layers includes a propylene-based polymer layer composed of a resin composition mainly containing a propylene homopolymer, and a polyethylene resin layer mainly containing a biomass-derived polyethylene resin having a density of 0.900-0.950 g/cm3 on at least one surface of the propylene-based polymer layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a biaxially stretched polyolefin film.

In recent years, there has been an active demand for efforts toward a sound material-cycle society that reduces the environmental burden by increasing the utilization of renewable resources. 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 volume 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 an ethylene-based resin has been proposed (see, for example, Patent Document 1). However, since this film is composed of only an ethylene resin, it is 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 Documents 2 and 3). However, these films tend to be inferior in transparency and perspective.

Therefore, the inventors have made extensive studies, and the biaxially stretched polyolefin film, which is often used in the packaging field, has excellent transparency, transparency, and elasticity, and has an environmental load containing a large amount of resin derived from biomass resources. We have developed a biaxially stretched polyolefin film with excellent productivity while reducing the amount of biomass.

Japanese Patent No. 5862055 JP-A-2018-65267 Japanese Unexamined Patent Publication No. 2019-6461

The present invention has been proposed in view of the above circumstances, and provides a biaxially stretched polyolefin film having excellent transparency, perspective, and elasticity, excellent productivity, and reduced environmental load. offer.

That is, the first invention is a biaxially stretched polyolefin film for packaging composed of a plurality of layers of at least two or more layers, the propylene-based polymer layer composed of a resin composition mainly composed of a propylene homopolymer, and the above-mentioned. The present invention relates to a biaxially stretched polyolefin film, which comprises providing a polyethylene resin layer mainly composed of a biomass-derived polyethylene resin having a ^{density of 0.9000 to 0.950 g / cm 3 on} at least one surface of the propylene-based polymer layer. ..

The second invention relates to a biaxially stretched polyolefin film in which the propylene-based polymer layer and the polyethylene resin layer are alternately laminated to form a laminate of 3 to 5 layers in the first invention.

In the third invention, in the first or second invention, one of the layers constituting the biaxially stretched polyolefin film is the base material layer, and the layer thickness of the base material layer is one. The present invention relates to a biaxially stretched polyolefin film having a thickness larger than that of the polyethylene resin layer.

In the fourth invention, in any of the first to third inventions, the tensile elastic modulus in the winding direction of the biaxially stretched polyolefin film measured in accordance with JIS K 7172 (1999) is 1.0 GPa or more. It relates to a certain biaxially stretched polyolefin film.

In the fifth invention, in any of the first to fourth inventions, the haze of the biaxially stretched polyolefin film measured according to JIS K 7136 (2000) is 9% or less, and the narrow-angle diffusion transmittance is 9% or less. The present invention relates to a biaxially stretched polyolefin film having a content of 15% or less.

The sixth invention relates to a biaxially stretched polyolefin film in which the propylene-based polymer layer and the polyethylene resin layer are integrated without interposing an adhesive layer in any one of the first to fifth inventions. ..

A seventh invention relates to a biaxially stretched polyolefin film in which the biaxially stretched polyolefin film is in the range of 1 μm to 100 μm in any one of the first to sixth inventions.

The eighth invention relates to the biaxially stretched polyolefin film in any one of the first to seventh inventions, wherein the biaxially stretched polyolefin film is formed by co-extruding biaxially stretched film formation.

According to the biaxially stretched polyolefin film according to the first invention, it is a biaxially stretched polyolefin film for packaging composed of at least two or more layers, and is a propylene-based resin composition mainly composed of a propylene homopolymer. Since the polymer layer and the polyethylene resin layer mainly composed of a biomass-derived polyethylene resin having a ^{density of 0.900 to 0.950 g / cm 3} are provided on at least one surface of the propylene-based polymer layer, it is excellently transparent. It is possible to obtain a biaxially stretched polyolefin film which has properties, a sense of transparency, and a feeling of elasticity, is also excellent in productivity, and has a reduced burden on the environment.

According to the biaxially stretched polyolefin film according to the second invention, in the first invention, the propylene-based polymer layer and the polyethylene resin layer are alternately laminated to form a laminate of 3 to 5 layers, which causes an environmental load. An appropriate layer can be used as the surface layer depending on the application of the film, while further reducing the amount of the film.

According to the biaxially stretched polyolefin film according to the third invention, in the first or second invention, one of the layers constituting the biaxially stretched polyolefin film is the base material layer. Since the layer thickness of the base material layer is thicker than the layer thickness of the polyethylene resin layer, the film productivity is excellent.

According to the biaxially stretched polyolefin film according to the fourth invention, in any of the first to third inventions, the tension in the winding direction of the biaxially stretched polyolefin film measured in accordance with JIS K 7172 (1999). Since the elastic modulus is 1.0 GPa or more, it is excellent in processing suitability for film printing and packaging.

According to the biaxially stretched polyolefin film according to the fifth invention, in any of the first to fourth inventions, the haze of the biaxially stretched polyolefin film measured in accordance with JIS K 7136 (2000) is 9% or less. Since the narrow-angle diffusion transmittance is 15% or less, the film is excellent in transparency and transparency, and can be obtained as a film having a high-class appearance.

According to the biaxially stretched polyolefin film according to the sixth invention, in any one of the first to fifth inventions, the propylene-based polymer layer and the polyethylene resin layer are integrated without interposing an adhesive layer. Therefore, the processing process using an adhesive is not required, the productivity is excellent, and since no solvent is used, it is possible to contribute to the reduction of the environmental load.

According to the biaxially stretched polyolefin film according to the seventh invention, in any one of the first to sixth inventions, since the biaxially stretched polyolefin film is in the range of 1 μm to 100 μm, it can be printed or used as a packaging film in a bag. It is possible to obtain a film having excellent processability.

According to the eighth aspect of the invention, in any one of the first to seventh inventions, the biaxially stretched polyolefin film is produced by co-extruding biaxially stretched film formation, thereby facilitating production while increasing the strength of the film. The sex can be improved.

It is the schematic sectional drawing of the biaxially stretched polyolefin film of the bilayer structure which concerns on one Example of this invention. It is the schematic sectional drawing of the biaxially stretched polyolefin film of the three-layer structure which concerns on one Example of this invention. It is the schematic sectional drawing of the biaxially stretched polyolefin film of the four-layer structure which concerns on one Example of this invention. It is the schematic sectional drawing of the biaxially stretched polyolefin film of the five-layer structure which concerns on one Example of this invention.

FIG. 1 is a schematic cross-sectional view of a biaxially stretched polyolefin film 10 according to an embodiment of the present invention. The film 10 is a laminated film composed of a propylene-based polymer layer 11 mainly composed of a propylene homopolymer and a polyethylene resin layer 12 mainly composed of a biomass-derived polyethylene resin. The film 10 is manufactured by a known manufacturing method such as the T-die method 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 forming a film by co-extrusion, it is integrated between each layer without interposing an adhesive layer, so that it is possible to reduce the environmental load while being excellent in productivity, and it is also excellent in transparency and transparency. .. The biaxially stretched polyolefin film 10 preferably has a film thickness in the range of 1 to 100 μm from the viewpoint of printability and processability as a packaging film.

The resin that is the main component of the propylene-based polymer layer 11 is a propylene homopolymer (homopolypropylene), which has high crystallinity and is excellent in heat resistance, chemical resistance, and strength. From this, the propylene-based polymer layer 11 becomes the base material layer. Productivity can be improved by using a layer having high heat resistance as a base material for biaxial stretching. Additives such as an anti-blocking agent, an antistatic agent, an antioxidant, a neutralizing agent, and a coloring agent are added to the propylene-based polymer layer 11 as the base material layer, if necessary.

The polyethylene resin layer 12 is a layer laminated on the propylene-based polymer layer 11, and is composed of a biomass-derived polyethylene-based resin alone or a polyethylene-based resin mainly composed of a biomass-derived polyethylene-based resin. Since the propylene-based polymer layer 11 serves as the base material layer, the layer thickness of the propylene-based polymer layer 11 is thicker than that of the polyethylene resin layer 12. Additives such as an anti-blocking agent, an antistatic agent, an antioxidant, a neutralizing agent, and a coloring agent are appropriately added to the polyethylene resin layer 12.

As shown in FIGS. 2 to 4, the propylene-based polymer layer 11 and the polyethylene resin layer 12 are alternately laminated to form a multi-layer film composed of 3 to 5 layers or more. Can be done. Since the propylene-based polymer layer 11 is mainly composed of a propylene homopolymer, it is excellent in printability. Since the polyethylene resin layer 12 is excellent in heat-sealing property, it is possible to appropriately select which layer is to be the front surface or the back surface depending on the application. Furthermore, by forming the film into multiple layers, it is possible to obtain a film containing a large amount of biomass-derived polyethylene-based resin, so that the environmental load can be further reduced.

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 biomass-derived polyethylene-based resin is composed of a linear low-density polyethylene-based resin, and the density is preferably 0.9000 to 0.950 g / cm ³ . If a resin exceeding this range is used, it becomes difficult to mold and stretch the sheet at the die outlet, and the productivity tends to be inferior.

The tensile elastic modulus in the winding direction of the biaxially stretched polyolefin film is preferably 1.0 GPa or more. If the tensile elastic modulus is smaller than 1.0 GPa, the film will be inferior in processing suitability, and will be easily deformed, which may lead to a decrease in the productivity of printing and packaging. The tensile elastic modulus is measured in accordance with JIS K 7172 (1999) as described in the following examples.

The haze of the biaxially stretched polyolefin film is preferably 9% or less. A film having a haze of more than 9% is inferior in transparency and is not suitable for handling as a transparent film. 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 polyolefin film is preferably 15% or less. When the narrow-angle diffusion transmittance (LSI) is less than 15%, the transparency is significantly improved and there is almost no distortion in what is seen through the film, so that the suitability as a packaging film is improved and the packaging material is high-grade. Have a feeling.

[Production of film]
With respect to the films of Prototype Examples 1 to 9 and Comparative Examples 1 and 2, each material described later was kneaded and melted to form a film by a double-layer coextrusion T-die film molding machine and a subsequent biaxial stretching machine. The stretching ratio was 5 times in the vertical direction (winding direction) and 8 times in the horizontal direction (width direction), and the film was formed by sequential biaxial stretching. The MFR conforms to 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.

[Material used for propylene polymer layer]
In the propylene-based polymer layer, the following resin PP1 was used as the polypropylene-based resin. An appropriate amount of an antistatic agent used for a general film was added.
-Resin PP1: Propylene homopolymer (manufactured by Japan Polypropylene Corporation, trade name "FL100A", MFR: 3.0 g / 10 min)

[Material used for polyethylene resin layer]
In the polyethylene resin layer, the following resins PE1 to PE4 were used as biomass-derived polyethylene-based resins, and the following resins PP2 were used as non-biomass-derived polyethylene-based resins for comparison. An appropriate amount of an anti-blocking agent used for a general film was added.
-Resin PE1: Linear low-density polyethylene (manufactured by Braskem, trade name "SLH218", density: 0.916 ^{g / cm 3} , MFR: 2.3 g / 10 min)
-Resin PE2: High-density polyethylene (manufactured by Braskem, trade name "SGF4960", density: 0.961 ^{g / cm 3} , MFR: 0.3 g / 10 min)
-Resin PE3: Low density polyethylene (manufactured by Braskem, trade name "SEB853", density: 0.923 ^{g / cm 3} , MFR: 2.7 g / 10 min)
-Resin PE4: High-density polyethylene (manufactured by Braskem, trade name "SHE150", density: 0.948 ^{g / cm 3} , MFR: 1.0 g / 10 min)
-Resin PP2: Ethylene-propylene-butene copolymer (manufactured by Japan Polypropylene Corporation, trade name "FX4G", MFR: 5.0 g / 10 min)

[Prototype example 1]
In Prototype 1, the propylene-based polymer layer, which is the base material layer, is composed of 100% by weight of a propylene homopolymer (resin PP1), and the polyethylene resin layer is composed of 100% by weight of linear low-density polyethylene (resin PE1). The film is formed so that the thickness of the propylene-based polymer layer is 19 μm and the thickness of the polyethylene resin layer is 1 μm.

[Prototype example 2]
Prototype Example 2 is a film formed in the same manner as Prototype Example 1 except that the thickness of the propylene-based polymer layer is 17 μm and the thickness of the polyethylene resin layer is 3 μm.

[Prototype example 3]
Prototype Example 3 is a film formed in the same manner as Prototype Example 1 except that the thickness of the propylene-based polymer layer is 11 μm and the thickness of the polyethylene resin layer is 9 μm.

[Prototype example 4]
Prototype Example 4 is a film formed in the same manner as Prototype Example 2 except that the polyethylene resin layer is 100% by weight of low-density polyethylene (resin PE3).

[Prototype Example 5]
Prototype Example 5 is a film formed in the same manner as Prototype Example 4 except that the polyethylene resin layer is 50% by weight of high-density polyethylene (resin PE3) and 50% by weight of high-density polyethylene (resin PE4).

[Prototype example 6]
Prototype Example 6 is a film formed in the same manner as Prototype Example 4 except that the polyethylene resin layer is 20% by weight of high-density polyethylene (resin PE3) and 80% by weight of high-density polyethylene (resin PE4).

[Prototype example 7]
Prototype Example 7 is a film formed in the same manner as Prototype Example 4 except that the polyethylene resin layer is 100% by weight of high-density polyethylene (resin PE4).

[Prototype Example 8]
Prototype Example 8 is a film formed in the same manner as Prototype Example 1 except that high-density polyethylene (resin PE2) is used for the polyethylene resin layer.

[Prototype example 9]
Prototype 9 is a film formed in the same manner as Prototype 2 except that high-density polyethylene (resin PE2) is used for the polyethylene resin layer.

[Comparative Example 1]
Comparative Example 1 is a film formed in the same manner as in Prototype Example 1 except that an ethylene-propylene-butene copolymer (resin PP2) was used for the polyethylene resin layer.

[Comparative Example 2]
In Comparative Example 2, the propylene-based polymer layer was a resin obtained by kneading 85% by weight of the propylene homopolymer (resin PP1) and 15% by weight of the linear low-density polyethylene (resin PE1), and the polyethylene resin layer was made of ethylene-. This film was formed in the same manner as in Prototype Example 1 except that a propylene-butene copolymer (resin PP2) was used.

[Evaluation of film performance]
With respect to the films of Prototype Examples 1 to 9 and Comparative Examples 1 and 2, each item of tensile elastic modulus, haze, narrow-angle diffusion transmittance and productivity was measured. In the comprehensive evaluation, "good (○)" is obtained when good results are obtained in all of the evaluations in each of the items described below, and when one or more unfavorable results are obtained in any of them, or the resin layer derived from biomass is selected. If it is not included, it is marked as "impossible (x)". The results are shown in Tables 1 and 2 described later.

[Measurement of tensile modulus]
The measurement of tensile elastic modulus (GPa) is one of the indexes of workability, and conforms to JIS K 7127 (1999), and uses a tensile tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., V1-D). It was measured. In the films of Prototype Examples 1 to 9 and Comparative Examples 1 and 2, a measurement result of 1.0 GPa or more was regarded as a non-defective product.

[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 9 and Comparative Examples 1 and 2, the measurement result of 9% or less was regarded as a non-defective product.

[Measurement of narrow-angle diffusion transmittance]
The narrow-angle diffusion transmittance (LSI) (%) is an index of transparency, 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. .. LSI is a measure of see-through feeling with the naked eye, and the lower the value, the better the transparency. The LSI was measured using a visual transparency tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). In the films of Prototype Examples 1 to 9 and Comparative Examples 1 and 2, the measurement result of 15% or less was regarded as a non-defective product.

[Evaluation of the physical properties]
In the physical property evaluation, all of the above-mentioned tensile elastic modulus, haze, and narrow-angle diffusion transmittance were evaluated as "○" for non-defective products, and "x" for any non-defective product.

[Productivity evaluation]
The productivity evaluation was "x" for those that could not be biaxially stretched or could not be formed into a sheet, and "△" for those that were difficult to biaxially stretched, and biaxial stretching could be easily performed. The thing was regarded as good and was marked as "○".

[comprehensive evaluation]
As a comprehensive evaluation, those with a physical characteristic evaluation of "○" and productivity of "○" were rated as "good", and those with at least one "x" were rated as "impossible". In addition, Comparative Example 1 containing no biomass-derived polyethylene resin was also rated as "impossible" from the viewpoint of reducing the environmental load.

[Results and discussion]
As shown in Tables 1 to 3, it was Prototype Examples 8 and 9 and Comparative Example 2 that the comprehensive evaluation based on the physical characteristics and productivity evaluation was "impossible". Prototype 8 and Prototype 9 are examples in which a high-density biomass-derived polyethylene resin is used. In general, a film using high-density polyethylene is inferior in tearability as compared with a film using low-density polyethylene. As a result, in Prototype Example 8, although the film was formed even though it was torn during biaxial stretching, the productivity evaluation was set to "△ (OK)" and the haze was higher than the standard, and the overall evaluation was made. It was set as "impossible (x)". Since the prototype example 9 could not be molded into a sheet shape, the productivity evaluation was set to "x (impossible)" and the physical property evaluation could not be performed.

Comparative Example 1 gave good results in terms of film performance, but did not meet the object of the present invention from the viewpoint of reducing the environmental load because it did not contain biomass-derived resin, and the overall evaluation was set to "impossible". .. Comparative Example 2 is an example in which a biomass-derived resin is kneaded into the base material layer. Polyethylene and polypropylene are not completely compatible with each other, and as a result of kneading, a phase-separated structure is formed in the layer and tends to be higher than the LSI standard. Not possible. "

On the other hand, the overall evaluation was "good" in the prototype examples 1 to 7. These prototype examples consist of a propylene-based polymer layer made of a propylene homopolymer and a polyethylene resin layer made of a biomass-derived polyethylene resin, and it was found that the thicker the propylene-based polymer layer, the better the tensile elastic modulus. rice field.

Further, by using a polyethylene resin as a main component of the polyethylene resin layer as ^{a biomass-derived polyethylene resin having a density in the range of 0.9000 to 0.950 g / cm 3} , a film using a biomass-derived resin for reducing the environmental load. Even so, it was found that the haze and narrow-angle diffusion transmittance can be improved, and a film having excellent transparency and transparency can be obtained.

As described above, the biaxially stretched polyolefin film of the present invention comprises a propylene-based polymer layer composed of a resin composition mainly composed of a propylene homopolymer and a polyethylene resin layer mainly composed of a biomass-derived polyethylene resin. In particular, since it has a layer mainly composed of a biomass-derived polyethylene resin, it is possible to obtain a film having excellent transparency, transparency, and elasticity while reducing the environmental load.

By having a layer mainly composed of a biomass-derived polyethylene resin, the biaxially stretched polyolefin film of the present invention can reduce the environmental load while having excellent transparency and a sense of transparency. Therefore, it can be expected to be used for new packaging films and the like, and it is advantageous for the utilization of biomass resources.

10 Biaxially stretched polyolefin film 11 Propylene-based polymer layer 12 Polyethylene resin layer

Claims (8)

A biaxially stretched polyolefin film for packaging, which comprises at least two or more layers.
A propylene-based polymer layer composed of a resin composition mainly composed of a propylene homopolymer, and
A biaxially stretched polyolefin film comprising at least one surface of the propylene-based polymer layer with a polyethylene resin layer mainly composed of a biomass-derived polyethylene resin having a ^{density of 0.9000 to 0.950 g / cm 3.} The biaxially stretched polyolefin film according to claim 1, wherein the propylene-based polymer layer and the polyethylene resin layer are alternately laminated to form a laminate of 3 to 5 layers. Of the layers constituting the biaxially stretched polyolefin film according to claim 1 or 2, one of the propylene-based polymer layers is a base material layer, and the layer thickness of the base material layer is the layer of the polyethylene resin layer. A biaxially stretched polyolefin film that is thicker than it is thick. The biaxially stretched polyolefin according to any one of claims 1 to 3, wherein the tensile elastic modulus in the winding direction of the biaxially stretched polyolefin film measured in accordance with JIS K 7172 (1999) is 1.0 GPa or more. the film. The invention according to any one of claims 1 to 4, wherein the haze of the biaxially stretched polyolefin film measured in accordance with JIS K 7136 (2000) is 9% or less, and the narrow-angle diffusion transmittance is 15% or less. Biaxially stretched polyolefin film. The biaxially stretched polyolefin film according to any one of claims 1 to 5, wherein the propylene-based polymer layer and the polyethylene resin layer are integrated without interposing an adhesive layer. The biaxially stretched polyolefin film according to any one of claims 1 to 6, wherein the biaxially stretched polyolefin film is in the range of 1 μm to 100 μm. The biaxially stretched polyolefin film according to any one of claims 1 to 7, wherein the biaxially stretched polyolefin film is formed by coextruding biaxially stretched film formation.

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