TW202003246A - Multilayer film and food packaging bag - Google Patents

Abstract

This multilayer film is obtained by layering a surface layer (A), an intermediate layer (B), and a seal layer (C). The surface layer (A), the intermediate layer (B), and the seal layer (C) each contain a propylene resin. The intermediate layer (B) additionally contains a plant-derived low-density polyethylene (b1). In addition, the melt flow rate of the low-density polyethylene (b1) is 1-7 g/10 min; as a result, it is possible to select a type of plant-derived ethylene resin and maintain high moldability, and thus achieve the objective of obtaining an environmentally friendly film having suitable characteristics.

Description

Laminated film and food packaging bags

The present invention relates to a laminated film using a plant-derived resin and a food packaging bag.

In recent years, for the purpose of reducing the environmental load, it is being considered to replace part of the materials constituting the resin film used for packaging materials from resins derived from fossil fuels such as petroleum to resins derived from plants (see, for example, Patent Documents 1 and 2 ).

Although plant-derived resins are highly environmentally responsive, they often show properties different from fossil fuel-derived resins. Therefore, if only a part of the material constituting the resin film is replaced with a plant-derived resin, the characteristic of the purpose of the resin film may not be obtained.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2012-167172

Patent Document 2: Japanese Patent Laid-Open No. 2013-151623

In particular, the affinity (miscibility) of the vinyl resin system and the propylene resin is low. Therefore, in a resin film (laminated film) mainly composed of an acrylic resin, when a vinyl resin is used in combination, the moldability of the resin film may decrease depending on the type. In addition, in a heat-sealable resin film (laminated film) mainly composed of an acrylic resin, if plant-derived polyethylene is used, the heat-sealability may decrease.

Therefore, even when vinyl resins derived from resins are used in order to improve environmental response, it is important to select the type.

The problem to be solved by the present invention is to provide a laminated film having a suitable formability and heat sealability in a film structure mainly composed of an acrylic resin, and a food packaging bag using such a laminated film .

The present invention solves the above-mentioned problems through a laminated film which is a laminated film having a surface layer (A), an intermediate layer (B) and a sealing layer (C), the surface layer (A) and the intermediate layer ( B) and the sealing layer (C) each contain an acrylic resin, and the intermediate layer (B) further contains a plant-derived low-density polyethylene (b1).

The laminated film of the present invention is a film mainly composed of a propylene resin, but by selecting the type of plant-derived vinyl resin, high moldability can be maintained, and an environmentally-responsive film having suitable characteristics for the purpose can be produced. In addition, the laminated film of the present invention can be suitably used for packaging food such as bread.

[Form for carrying out the invention]

Hereinafter, the laminated film and the food packaging bag of the present invention will be described in detail based on suitable embodiments.

The laminated film of the present invention has at least a surface layer (A), an intermediate layer (B), and a sealing layer (C), and one of the surface layers is the surface layer (A), and the other surface layer is the sealing layer (C).

In the present invention, the surface layer (A), the intermediate layer (B) and the sealing layer (C) each contain an acrylic resin, and the intermediate layer (B) further contains a plant-derived low-density polyethylene (b1) (hereinafter It is called "biological low-density polyethylene (b1).".

Hereinafter, the structure of each layer (A) to (C) will be described in order.

[Surface layer (A)]

The surface layer (A) is a layer that constitutes the surface layer when the laminated film bag is made into a food packaging bag, and functions as a printed layer to be printed and the like.

This surface layer (A) contains an acrylic resin.

Since it is easy to impart proper fuse sealing and bag-making suitability to the laminated film, the content of the acrylic resin in the resin component contained in the surface layer (A) is preferably 50% by mass or more, and more preferably 70% by mass or more. It is further preferably 80% by mass or more, and particularly preferably 85% by mass or more. In addition, the resin component contained in the surface layer (A) may contain substantially only the propylene-based resin.

For the propylene-based resin, for example, a propylene homopolymer, a propylene-α-olefin copolymer (propylene-α-olefin random copolymer, propylene-α-olefin block copolymer), or the like can be used.

The α-olefin content in the propylene-α-olefin copolymer is preferably 10% by mass or less, more preferably 8% by mass or less, and still more preferably 6% by mass. In addition, since it is easy to impart appropriate impact resistance to the laminated film, the α-olefin content is preferably 2% by mass or more, more preferably 3% by mass or more, and still more preferably 4% by mass or more.

When the laminated film is made into a transparent film, as the propylene-based resin, a propylene-α-olefin random copolymer can be preferably used.

Examples of the propylene-α-olefin random copolymers include propylene-ethylene random copolymers, propylene-1-butene random copolymers, propylene-ethylene-1-butene random copolymers, and the like. These may be used alone or in combination. Among them, the propylene-α-olefin random copolymer is preferably used as the propylene-α-olefin random copolymer because it is easy to impart appropriate transparency to the laminated film.

The melt flow rate (MFR) of the propylene-ethylene random copolymer is not particularly limited as long as it can form a laminated film, and is preferably 0.5 g/10 minutes or more, more preferably 3 g/10 minutes or more, More preferably, it is 5 g/10 minutes or more. In order to obtain good moldability of the laminated film, the MFR is preferably 20 g/10 minutes or less, more preferably 15 g/10 minutes or less, and still more preferably 12 g/10 minutes or less.

In addition, in this specification, unless otherwise stated, MFR is measured in accordance with the provisions of JIS K 7210:1999 under the measurement conditions of a temperature of 230° C. and a load of 21.18 N.

The density of the propylene-ethylene random copolymer is preferably about 0.88 to 0.905 g/cm ³ , and more preferably about 0.89 to 0.9 g/cm ³ .

The melting point of the propylene-ethylene random copolymer is preferably 110° C. or higher, and more preferably 115° C. or higher from the viewpoint of preventing adhesion to the fuse seal knife during bag making. In addition, in the case of fuse sealing during bag making, in order for the laminated film to exhibit fuse sealing, it is necessary to form sufficient fuse balls. Therefore, the melting point is preferably 150°C or lower, and more preferably 145°C or lower.

Since it is easy to impart proper transparency and packaging suitability to the laminated film, the content of the propylene-ethylene random copolymer in the resin component contained in the surface layer (A) is preferably 35% by mass or more, more preferably 45% by mass or more It is further preferably 50% by mass or more. In addition, the content thereof is preferably 75% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less.

In addition, since it is easy to form sufficient fuse balls during fuse sealing, a lower melting point propylene-1-butene random copolymer or propylene-ethylene-1-butene random copolymer is used together with the propylene-ethylene random copolymer It is also better. Among them, a propylene-ethylene-1-butene random copolymer (propylene-ethylene-1-butene terpolymer) can be particularly preferably used.

The ethylene content and 1-butene content in the propylene-ethylene-1-butene random copolymer are preferably 25% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass. In addition, since it is easy to impart suitable low-temperature sealing properties to the laminated film, the ethylene content and the 1-butene content are preferably 0.5% by mass or more, more preferably 1.5% by mass or more, and still more preferably 3% by mass or more.

The MFR of the propylene-ethylene-1-butene random copolymer is not particularly limited as long as it can form a laminated film, and is preferably 0.5 g/10 minutes or more, more preferably 3.0 g/10 minutes or more, and further It is preferably 5.0 g/10 minutes or more. In order to obtain good moldability of the laminated film, the MFR is preferably 20 g/10 minutes or less, more preferably 15 g/10 minutes or less, and still more preferably 12 g/10 minutes or less.

The density of the propylene-ethylene-1-butene random copolymer is preferably about 0.88 to 0.905 g/cm ³ , more preferably about 0.89 to 0.9 g/cm ³ .

The melting point of the propylene-ethylene-1-butene random copolymer is preferably 105° C. or higher, and more preferably 110° C. or higher from the viewpoint of preventing adhesion to the fuse seal knife during bag making. In addition, in the case of fuse sealing during bag making, in order for the laminated film to exhibit fuse sealing, it is necessary to form sufficient fuse balls. Therefore, the melting point is preferably 145°C or lower, and more preferably 140°C or lower.

Since it is easy to impart proper fuse sealing to the laminated film, the content of the propylene-ethylene-1-butene random copolymer in the resin component contained in the surface layer (A) is preferably 15% by mass or more, and more preferably 25% by mass % Or more, further preferably 30% by mass or more. In addition, the content thereof is preferably 55% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

On the other hand, when the laminated film is made into a matte film, as the propylene-based resin, a propylene-based block copolymer, particularly a propylene-α-olefin block copolymer can be preferably used.

Examples of α-olefins include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Among them, since it is possible to impart matte feeling, cold resistance, and rigidity to the laminated film with an excellent balance, the α-olefin is preferably ethylene.

Since the formability of the laminated film is good, and it is easy to impart appropriate impact resistance and matting feeling to the laminated film, the MFR of the propylene-based block copolymer is preferably 0.5 g/10 minutes or more, and more preferably 1 g/10 minutes or more. Moreover, the MFR is preferably 20 g/10 minutes or less, and more preferably 10 g/10 minutes or less.

Since it is easy to impart proper bag-making properties to the laminated film, the melting point of the propylene-based block copolymer is preferably about 155 to 165°C.

The propylene-based block copolymer may be used alone or in combination. When plural types are used in combination, it is preferable to set the total content of the propylene-based block copolymer to the following range.

In addition, since it is easy to impart matt feeling, fuse sealability, and bag-making suitability to the laminated film with an excellent balance, for commercial products of propylene-α-olefin block copolymers, for example, BC8, BC7 (all made by Japan Polypropylene), E150GK, F704V (all made by Prime Polymer), PC480A, PC684S, PC380A, VB370A (all made by SunAllomer), etc.

The content of the propylene-based block copolymer in the resin component contained in the surface layer (A) may be appropriately adjusted in such a manner that it can impart matt feeling, fuse sealability and bag-making suitability to the laminated film with an excellent balance.

The specific content is preferably 50% by mass or more, and more preferably 70% by mass or more. By setting the content in the aforementioned range, the designability of the laminated film is improved, and at the same time, it becomes easy to impart a uniform matt feeling to the laminated film. Among them, when the impact resistance of the laminated film is to be improved, the content is preferably set to about 80 to 100% by mass, and when the matt feeling is to be improved, the content is preferably set to 70 to About 90% by mass.

For the surface layer (A), various olefin-based resins used for packaging films other than the above-mentioned propylene-based resins can also be used. Examples of such olefin-based resins include ethylene-based single polymers, ethylene-based copolymers, and ionomers of ethylene-(meth)acrylic acid copolymers. These may be used alone or in combination.

Examples of the ethylene-based single polymer include ultra low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), and low density polyethylene (LDPE).

Examples of the ethylene-based copolymer include ethylene-1-butene copolymerization, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), and ethylene-ethyl acrylate Copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid Copolymer (EMAA), etc.

Furthermore, the content of these olefin-based resins in the resin component contained in the surface layer (A) is preferably 20% by mass or less.

Among them, ethene-1-based resins other than propylene-based resins can be preferably used because of their flexibility in the wide temperature range that is effective and good dispersibility with propylene-based resins. Butene copolymer (crystalline ethylene-1-butene copolymer). Especially when the laminated film is made into a transparent film, an ethylene-1-butene copolymer can be particularly preferably used.

Since it is easy to impart a suitable low-temperature sealability to the laminated film, the content of the ethylene-1-butene copolymer in the resin component contained in the surface layer (A) is preferably about 1 to 20% by mass, more preferably 5 to 15 About mass%.

The MFR of the ethylene-1-butene copolymer is not particularly limited as long as it can form a laminated film, and is preferably 0.5 g/10 min or more, more preferably 2 g/10 min or more, and still more preferably 3 g /10 minutes or more. In order to obtain good moldability of the laminated film, the MFR is preferably 20 g/10 minutes or less, more preferably 15 g/10 minutes or less, and even more preferably 10 g/10 minutes or less.

The density of the ethylene-1-butene copolymer is preferably about 0.87 to 0.9 g/cm ³ , more preferably about 0.875 to 0.895 g/cm ³ .

In addition, as for the surface layer (A), a plant-derived resin may be used in combination. When the use ratio of the plant-derived resin contained in the laminated film (hereinafter also referred to as "biologicality") is to be increased, it is preferable to derive from the resin component contained in the surface layer (A) The content of the plant resin is set to 10% by mass or more, more preferably 20 to 50% by mass.

On the other hand, when attaching importance to various characteristics such as heat sealability, fuse sealability, and impact resistance of the laminated film, the content of the plant-derived resin in the resin component contained in the surface layer (A) is preferred, It is set to less than 10% by mass, more preferably set to less than 5% by mass, and still more preferably set to substantially 0% by mass.

The surface layer (A) may be composed only of a resin containing a propylene-based resin, and may contain various additives within a range that does not impair the effects of the present invention. Examples of the additives include antioxidants, weather-resistant stabilizers, antistatic agents, anti-fogging agents, anti-caking agents, lubricants, nucleating agents, and pigments.

The surface of the surface layer (A) has a surface roughness (Ra) specified in JIS B 0601:2001 of preferably about 0.2 to 1, more preferably about 0.3 to 0.7. By setting the surface roughness (Ra) to the aforementioned range, even if the additional amount of other additives (such as slipping agent, anti-caking agent, etc.) is reduced, or without the combined use, excellent surface smoothness can be obtained Laminated film. Therefore, while increasing the speed of bag making, it is also possible to achieve alignment after bag making, increase/efficiency of the packaging operation, and to improve workability when packaging by filling the contents with an automatic packaging machine or the like.

The friction coefficient of the surface of the surface layer (A) specified by ASTM D 1894-95 is preferably about 0.05 to 0.7, more preferably about 0.07 to 0.6, and still more preferably about 0.1 to 0.5. By setting the friction coefficient to the aforementioned range, it becomes easy to improve the film transportability at the time of packaging, the alignment after bag making, the packing workability, and the like. In addition, it becomes easy to appropriately suppress film breakage during binding due to the binding tool. Furthermore, the friction coefficient can be adjusted by appropriately adding additives such as a slip material and an anti-caking agent according to the resin component used in the surface layer (A).

[Middle layer (B)]

The intermediate layer (B) is a layer having a function of imparting characteristics to the laminated film, which is a characteristic required when making a food packaging bag and a characteristic required as a food packaging bag.

The intermediate layer (B) contains a propylene-based resin, and further contains bio-low density polyethylene (b1).

By containing the propylene-based resin, it is possible to impart good heat-sealability to the laminated film, suitable fuse-sealing performance in a wide temperature range, and at the same time to impart appropriate impact resistance and bag-break resistance.

In addition, by containing low-density polyethylene, it is possible to prevent or suppress an increase in the pressure (resin pressure) of the forming material of the intermediate layer (B) in the molten state.

As described later, the laminated film is preferably produced by a co-extrusion method. At this time, the molding material of the intermediate layer (B) is heated and melted by an extruder, and after passing the molten molding material through a filter, it is supplied to a molding die. Furthermore, in terms of the filter, foreign substances and the like existing in the molten molding material are removed.

According to the present invention, the pressure of the forming material in the molten state can be suppressed low, so that it can smoothly pass through the filter. Therefore, the film formability and moldability of the intermediate layer (B) can be improved. In addition, the filter is less prone to clogging and can extend the life of the filter, so the productivity of the laminated film is also excellent.

On the other hand, if other polyethylene (especially linear low-density polyethylene) is used instead of low-density polyethylene, the pressure of the forming material in the molten state will increase, and the film formability and moldability of the laminated film will decrease. . Moreover, as a result of clogging of the filter, the filter has to be replaced frequently, and the productivity of the laminated film decreases, and the production cost also rises.

In particular, according to the investigation by the present inventors, it has been known that if bio-low-density polyethylene (b1) is used as the low-density polyethylene, even if it is compared with the case where low-density polyethylene derived from fossil fuels such as petroleum is used, The effect of suppressing the pressure rise of the molten forming material tends to be higher. The inventors believe that this is due to the difference in the branching state and molecular weight of the polymer between the bio-low density polyethylene (b1) and the low-density polyethylene derived from fossil fuels.

In addition, by using bio-low-density polyethylene (b1), the biofilm of the laminated film can be improved, which contributes to the reduction of carbon dioxide emissions and the improvement of environmental response.

Bio-low-density polyethylene (b1) can produce monomer (ethylene) using plants such as sugar cane, corn, sugar beet as raw materials, and can be produced in the same manner as the production method of low-density polyethylene using petroleum-derived monomers. The manufacturing method is not particularly limited, but a known method (for example, radical polymerization reaction) can be used.

In addition, examples of commercially available products of biological low-density polyethylene (b1) include SPB681, SBC818, and STN7006 manufactured by Braskem.

The density of the biological low-density polyethylene (b1) is preferably 0.93 g/cm ³ or less, and more preferably 0.925 g/cm ³ or less.

The MFR of the biological low-density polyethylene (b1) is preferably about 1 to 7 g/10 minutes, more preferably about 2 to 6 g/10 minutes, and even more preferably about 3 to 5 g/10 minutes. By using such MFR bio-low-density polyethylene (b1), the effect of suppressing the pressure rise of the molten forming material can be suitably exerted, and the decrease in the film-forming properties and moldability of the laminated film can be more reliably suppressed.

The content of the bio-low-density polyethylene (b1) in the resin component contained in the intermediate layer (B) is appropriately set in consideration of the following: while maintaining good film-forming properties and moldability of the laminated film, it will properly laminate The film imparts appropriate rigidity, impact resistance, and suitability for bag making. Specifically, the content of the biological low-density polyethylene (b1) is preferably 1% by mass or more, and more preferably 3% by mass or more. In addition, the upper limit may be appropriately adjusted according to the desired characteristics, etc. However, for example, when it is desired to maintain a high fuse seal strength, it is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less.

The intermediate layer (B) may further contain polyethylene (b2) derived from fossil fuels. The propylene-based resin used in the intermediate layer (B) is also a resin derived from fossil fuels, so the affinity (miscibility) of the polyethylene (b2) and the propylene-based resin is high. Therefore, when bio-low-density polyethylene (b1) is used together, it becomes easy to uniformly mix the bio-low-density polyethylene (b1) and the propylene resin due to the presence of polyethylene (b2). As a result, the characteristics of the intermediate layer (B) can be made uniform.

The polyethylene (b2) includes, for example, ethylene-based single polymers, ethylene-based copolymers, and ionomers of ethylene-(meth)acrylic acid copolymers. These may be used alone or in combination.

Examples of ethylene-based single polymers include linear low-density polyethylene (LLDPE), linear medium-density polyethylene (LMDPE), linear high-density polyethylene (LHDPE), and low-density polyethylene. (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE).

Examples of the ethylene-based copolymer include ethylene-butene-rubber copolymer (EBR), ethylene-propylene-rubber copolymer (EPR), ethylene-vinyl acetate copolymer (EVA), and ethylene-methyl Methyl acrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), Ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), etc.

Among them, the polyethylene (b2) is preferably a linear low-density polyethylene. By using linear low-density polyethylene as the polyethylene (b2), the impact resistance of the laminated film can be further improved.

The MFR of polyethylene (b2) is preferably about 2 to 10 g/10 minutes, more preferably about 3 to 5 g/10 minutes. By using such MFR polyethylene (b2), the film-forming property of the laminated film is easily improved, and the dispersibility of polyethylene (b2) in the intermediate layer (B) is also good, so it becomes easy to impart uniformity to the laminated film Characteristics.

The density of polyethylene (b2) is preferably 0.915 g/cm ³ or less, more preferably 0.91 g/cm ³ or less, and still more preferably 0.906 g/cm ³ or less. By using polyethylene (b2) having such a density, it becomes easy to impart suitable fuse sealing, high impact resistance, and bag resistance to the laminated film.

The content of polyethylene (b2) in the resin component contained in the intermediate layer (B) is appropriately set in consideration of the following: while maintaining good film-forming properties and moldability of the laminated film, and appropriately imparting appropriate values to the laminated film Rigidity, impact resistance, suitability for bag making, etc. Specifically, the content of polyethylene (b2) is preferably about 5 to 20% by mass, and more preferably about 5 to 15% by mass.

For the propylene resin of the intermediate layer (B), the same propylene resin as the surface layer (A) can be used, for example, propylene homopolymer, propylene-α-olefin copolymer (propylene-α-olefin random copolymer, Propylene-α-olefin block copolymer), etc.

The propylene-based resin preferably contains a propylene-α-olefin random copolymer, and more preferably contains a propylene-ethylene random copolymer. By using a propylene-based resin containing a propylene-α-olefin random copolymer (especially a propylene-ethylene random copolymer), the propylene-based resin and the biological low-density polyethylene (b1) and/or polyethylene (b2) can be improved Affinity (miscibility).

The α-olefin content in the propylene-α-olefin random copolymer is not particularly limited, but it is preferably about 1 to 20% by mass, and more preferably about 1.5 to 15% by mass.

The MFR of the propylene-α-olefin random copolymer is not particularly limited as long as it can form a laminated film, and is preferably 0.5 g/10 min or more, more preferably 3 g/10 min or more, and still more preferably 5 g /10 minutes or more. In order to obtain good moldability of the laminated film, the MFR is preferably 20 g/10 minutes or less, more preferably 15 g/10 minutes or less, and still more preferably 12 g/10 minutes or less.

The density of the propylene-α-olefin random copolymer is preferably about 0.88 to 0.905 g/cm ³ , and more preferably about 0.89 to 0.9 g/cm ³ .

The melting point of the propylene-α-olefin random copolymer is preferably 110°C or higher, and more preferably 115°C or higher from the viewpoint of preventing adhesion to the fuse-sealing blade during bag making. In addition, in the case of fuse sealing at the time of bag making, in order to exhibit proper fuse sealing performance, it is necessary to form sufficient fuse balls. Therefore, the melting point is preferably 150°C or lower, and more preferably 145°C or lower.

Since it is easy to impart proper bag-making suitability and bag-breaking resistance to the laminated film, the content of the propylene-α-olefin random copolymer in the resin component contained in the intermediate layer (B) is preferably about 10 to 50% by mass , More preferably about 10 to 45% by mass.

When the laminated film is a transparent film, the propylene-based resin preferably contains a propylene homopolymer.

The MFR of the propylene homopolymer is not particularly limited as long as it can form a laminated film, and is preferably 0.5 g/10 minutes or more, more preferably 2 g/10 minutes or more, and still more preferably 3 g/10 minutes or more . In order to obtain good moldability of the laminated film, the MFR is preferably 20 g/10 minutes or less, more preferably 15 g/10 minutes or less, and even more preferably 10 g/10 minutes or less.

The density of the propylene homopolymer is preferably about 0.88 to 0.92 g/cm ³ , more preferably about 0.885 to 0.915 g/cm ³ .

From the viewpoint of sufficiently maintaining the processing suitability of laminated films such as bags, the melting point of the propylene homopolymer is preferably 145°C or higher, and more preferably 150°C or higher.

The content of the propylene homopolymer in the resin component contained in the intermediate layer (B) is preferably about 55 to 85% by mass, more preferably about 60 to 80% by mass, and still more preferably about 65 to 75% by mass. By setting the content of the propylene homopolymer within the aforementioned range, it is possible to impart appropriate rigidity, transparency, and excellent impact resistance to the laminated film.

The resin component contained in the intermediate layer (B) may be used as long as the above-mentioned various resins are used in an appropriate content. However, since it is easy to suppress the reduction in rigidity and impact resistance when the total thickness of the laminated film is designed to be thin, it is Preferably, the content of the propylene-based resin in the resin component contained in the intermediate layer (B) is 55% by mass or more, and the content of the vinyl-based resin is 5 to 45% by mass.

Particularly preferably, the content of the propylene homopolymer in the resin component contained in the intermediate layer (B) is set to 50 to 80% by mass, and the content of the propylene-ethylene random copolymer is set to 5 to 25% by mass. The total amount of low-density polyethylene (b1) and polyethylene (b2) is set to 5 to 45% by mass.

On the other hand, when the laminated film is a matte film, the propylene-based resin preferably contains a propylene-α-olefin block copolymer.

For the propylene-α-olefin block copolymer, the same propylene-α-olefin block copolymer as the surface layer (A) when the matte film is formed can be used. The propylene-α-olefin block copolymer may be used alone or in combination.

The content of the propylene-α-olefin block copolymer in the resin component contained in the intermediate layer (B) is preferably about 20 to 50% by mass, more preferably about 25 to 45% by mass, and still more preferably 30 to 40 About mass%. By setting the content of the propylene-α-olefin block copolymer within the aforementioned range, it is possible to impart suitable impact resistance, matting feeling, and high stability during bag making to the laminated film.

The resin component contained in the intermediate layer (B) may be used as long as the above-mentioned various resins are used in an appropriate content, but it is easy to suppress the reduction in rigidity and impact resistance when the total thickness of the laminated film is designed to be thin, and Preferably, the content of the propylene-based resin in the resin component contained in the intermediate layer (B) is set to 55% by mass or more, and the content of the vinyl-based resin is set to 7 to 45% by mass.

As for the resin component contained in the intermediate layer (B), only bio-low density polyethylene (b1), fossil fuel-derived polyethylene (b2) and propylene-α-olefin block copolymer (b3) are used In the case of the third component, it is preferable to set the ratio of the same content (b1/b2/b3) to 2/3/95 to 30/25/45 in terms of mass ratio, more preferably to 10/5/85 ~25/20/55.

In addition, as the resin component contained in the intermediate layer (B), when the resins b1 to b3 are used in addition to the four components of the propylene-α-olefin random copolymer (b4), the ratio of these contents is preferably ( b1/b2/b3/b4) Set to 2/3/65/30~25/20/15/40 in terms of mass ratio, more preferably set to 10/5/50/35~15/15/30/40 .

By setting the ratio of the resin component contained in the intermediate layer (B) to the aforementioned range, it is possible to obtain a suitable matting hue and at the same time have excellent bag resistance (especially excellent bag resistance and resistance at low temperatures) Friction) laminated film.

The intermediate layer (B) may be composed only of a resin containing a propylene-based resin and a bio-low-density polyethylene (b1), and may contain various additives within a range that does not impair the effects of the present invention. Examples of the additives include antioxidants, weathering stabilizers, antistatic agents, anti-fogging agents, anti-caking agents, lubricants, nucleating agents, and pigments.

[Sealing layer (C)]

The sealing layer (C) is used for adhering the sealing layers (C) of the laminated film to each other, or used for adhering the laminated film to other containers or films.

The sealing layer (C) contains an acrylic resin. By containing the propylene-based resin, high adhesion between the sealing layer (C) and the intermediate layer (B) can be obtained.

Since it is easy to impart suitable sealing properties to the laminated film, the content of the propylene-based resin in the resin component contained in the sealing layer (C) is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass % Or more, in fact, 100% by mass.

In addition, the sealing layer (C) may be determined in such a manner that the type of the resin to be sealed and the object to be sealed are appropriately selected and configured to obtain a suitable sealing strength.

For example, when sealing layers (C) are sealed to each other and used as a packaging bag, from the viewpoint of obtaining a moderate seal strength, the propylene-based resin preferably contains, for example, propylene-ethylene random copolymer, propylene-1 -Propylene-α-olefin random copolymer like butene random copolymer, α-olefin-propylene random copolymer like 1-butene-propylene random copolymer.

Among them, the propylene-based resin preferably includes a butene-based random copolymer such as a propylene-1-butene random copolymer and a 1-butene-propylene random copolymer. This is because, if such a propylene resin containing a butene-based random copolymer is used, it is easy to adjust the heat sealing temperature and strength at the time of easy opening and sealing at a low temperature, and the heat sealing temperature range is large and easy A moderate heat seal strength is obtained in terms of easy-open seal.

Since it is easy to give proper sealing and blocking resistance to the laminated film, the content of 1-butene in the butene-based random copolymer is preferably about 60 to 95 mol%, more preferably about 65 to 95 mol% It is further preferably about 70 to 90 mol%. In addition, since it is easy to impart suitable low-temperature sealing properties to the laminated film, the propylene content is preferably about 2 to 10 mol%, more preferably about 3 to 9 mol%, and even more preferably about 4 to 8 mol%.

The content of the butene-based random copolymer in the resin component contained in the sealing layer (C) is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less. In addition, the content thereof is preferably 10% by mass or more, and more preferably 15% by mass or more. If the content of the butene-based random copolymer is set to the aforementioned range, it is easy to impart a suitable low-temperature sealability, fuse sealability, and crack resistance to the laminated film, and it is also advantageous for cost reduction.

For the butene-based random copolymer, it is preferable to use another propylene-α-olefin random copolymer in combination.

The content of α-olefin in the propylene-α-olefin random copolymer is not particularly limited, but it is preferably about 1 to 20% by mass, and more preferably about 1.5 to 15% by mass. Examples of α-olefins include ethylene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

Among them, as the propylene-α-olefin random copolymer, the same propylene-α-olefin random copolymer as the intermediate layer (B) can be used.

In addition, since it is easy to obtain good moldability of the laminated film, the MFR of the propylene-α-olefin random copolymer is preferably about 0.5 to 20 g/10 minutes, and more preferably about 2 to 10 g/10 minutes.

Since it is easy to impart a suitable low-temperature sealing property to the laminated film, the content of the other propylene-α-olefin random copolymer in the resin component contained in the sealing layer (C) is preferably 90% by mass or less, more preferably 85% by mass %the following. In addition, the content thereof is preferably 50% by mass or more, and more preferably 60% by mass or more.

Especially when a laminated film is used to form a packaging bag, when an easy-to-open seal portion that heat seals the sealing layers (C) with each other is provided, it is preferable to use a butene-based random copolymer/propylene-α-olefin The mass ratio of the random copolymer is about 20/80 to 50/50, and the butene-based random copolymer and the propylene-α-olefin random copolymer are used in combination.

Furthermore, the sealing layer (C) may contain a plant-derived polyolefin (for example, the plant-derived low-density polyethylene (b1) as described above). From the viewpoint of improving the biomass, the content of the plant-derived polyolefin in the resin component contained in the sealing layer (C) is preferably 10% by mass or more, and more preferably 20-50% by mass %about.

On the other hand, when emphasis is placed on characteristics such as fuse sealability and impact resistance of the laminated film, the content of plant-derived polyolefin is preferably less than 10% by mass, more preferably less than 5% by mass, It is further preferably set to substantially 0% by mass.

The sealing layer (C) may be composed only of a resin containing a propylene-based resin, and may contain various additives within a range that does not impair the effects of the present invention. Examples of the additives include antioxidants, weathering stabilizers, antistatic agents, anti-fogging agents, anti-caking agents, lubricants, nucleating agents, and pigments.

The friction coefficient of the surface of the sealing layer (C) specified by ASTM D 1894-95 is preferably about 0.01 to 0.4, more preferably about 0.02 to 0.35, and even more preferably about 0.05 to 0.3. By setting the friction coefficient to the aforementioned range, it becomes easier to improve the workability of the packaging operation due to the film transportability during packaging, the suppression of wrinkles or protrusions after bag making.

In addition, when filling the contents such as bread, even if the contents rub against the inner surface of the laminated film (the surface of the sealing layer (C)), the occurrence of scratches can be suppressed. Further, it is easy to impart abrasion resistance and crack resistance to the laminated film, and it is also possible to appropriately suppress film breakage. Furthermore, the coefficient of friction can be adjusted by appropriately adding additives such as slip materials and anti-caking agents according to the resin component used in the sealing layer (C).

[Laminated Film]

The laminated film of the present invention is a laminated film mainly composed of an acrylic resin laminated with the above surface layer (A), intermediate layer (B) and sealing layer (C), wherein the intermediate layer (B) contains a plant-derived low density Polyethylene (b1). With this configuration, the laminated film of the present invention can achieve suitable moldability without overloading even in a film structure mainly composed of a propylene resin at the time of extrusion molding. In addition, it is possible to achieve suitable heat sealability and suitable impact resistance such as excellent fuse seal strength and heat seal strength.

The average thickness of the laminated film only needs to be adjusted appropriately according to the use and appearance of the bag to be made. However, it is preferably about 25-50 μm because it is easy to take into account volume reduction and bag resistance during delivery. It is preferably about 30 to 45 μm.

The proportion of each layer in the thickness of the laminated film and the specific thickness of each layer are not particularly limited, but can be set as follows.

The proportion of the surface layer (A) is preferably about 1 to 35%, more preferably about 5 to 25%.

The proportion of the intermediate layer (B) is preferably about 45% to 85%, more preferably about 50% to 75%.

The proportion of the sealing layer (C) is preferably about 5 to 20%, more preferably about 10 to 20%.

The specific average thickness of the surface layer (A) is preferably about 0.5 to 15 μm, and more preferably about 1 to 10 μm.

The specific average thickness of the intermediate layer (B) is preferably about 5 to 35 μm, and more preferably about 10 to 25 μm.

The specific average thickness of the sealing layer (C) is preferably about 1 to 20 μm, and more preferably about 5 to 10 μm.

When the laminated film of the present invention is made into a transparent film, the turbidity (haze) of the laminated film is preferably 6% or less, more preferably 5.5% or less, and further preferably 5.0% because the contents of the package are easily recognized Below, particularly good is below 4.5%. In the case of such a high transparency, even though the laminated film has proper packaging suitability, it also becomes less prone to breakage due to friction or rubbing of the contents and the film.

In addition, in order to improve the transparency of the laminated film, it is preferable not to use a resin such as a block copolymer that causes the increase in turbidity in each layer, or to reduce the use amount as much as possible. In this case, the content of the block copolymer in the resin component contained in the entire laminated film is preferably 10% by mass or less, and more preferably 5% by mass or less.

When the laminated film of the present invention is made into a matte tone film, the turbidity of the laminated film is easy to obtain the design property of a suitable matte tone, and its turbidity is preferably 55% or more, and more preferably 60% or more. In addition, when the visibility of the content is to be ensured, the turbidity is preferably 80% or less, and more preferably 70% or less.

Since it is easy to obtain suitable scratch resistance and bag resistance, the laminated film of the present invention preferably has a rigidity (MD) of 450 MPa or more, more preferably 550 MPa or more, and even more preferably 600 MPa or more. In addition, this rigidity is based on ASTM D 882-12, and the 1% tangent modulus of the obtained laminated film at 23° C. was measured using a Tensilon tensile tester (manufactured by A&D Co., Ltd.).

The impact strength of the laminated film of the present invention is preferably 0.10 J or more, and more preferably 0.15 J or more, since it is easy to suppress breakage of bags and leakage of contents when used as packaging materials. Especially in the case of a matte tone film, particularly preferably 0.20J or more. In addition, the impact strength was measured by a film impact method using a spherical metal impact head with a diameter of 1.5 inches after the laminated film was kept in a constant temperature chamber set at 0°C for 6 hours.

The laminated film of the present invention may have any other resin layer other than the surface layer (A), the intermediate layer (B), and the sealing layer (C). However, the thickness of the other resin layer is preferably 20% or less of the overall thickness (total thickness) of the laminated film. The laminated film is particularly preferably composed of the surface layer (A), the intermediate layer (B), and the sealing layer (C) as described above. Furthermore, in such a structure, the intermediate layer (B) can also be composed of a laminated body in which a plurality of layers are laminated.

Specific examples of the layer configuration include a surface layer (A)/intermediate layer (B)/sealing layer (C) in which the intermediate layer (B) is provided between the surface layer (A) and the sealing layer (C) ) Of the three-layer structure, or the four-layer structure of the surface layer (A)/intermediate layer (B1)/intermediate layer (B2)/sealing layer (C) of the intermediate layer (B) using the laminate. Among them, since the adjustment of the characteristics of the laminated film and the production system of the laminated film are easy, it is preferably a three-layer structure composed of a surface layer (A)/intermediate layer (B)/sealing layer (C).

The method for manufacturing the laminated film is not particularly limited, but for example, a co-extrusion method can be used. For the co-extrusion method, the resin or resin mixture used in each layer is heated and melted by separate extruders, and the lamination is carried out in the molten state through the co-extrusion multilayer die method, feed block method, etc. Thereafter, through blow molding (inflation) or T-shaped mold. It is formed into a film shape by a cooling roll method or the like to obtain a laminated film.

According to the co-extrusion method, the ratio of the thickness of each layer can be adjusted relatively freely, and a laminated film with excellent hygiene and excellent cost performance can be obtained.

Furthermore, since the laminated film obtained by the above manufacturing method is obtained as a substantially non-stretched multilayer film, secondary forming such as deep drawing forming by vacuum forming is also possible.

In order to improve the adhesion (adhesion) of the printing ink and the like, it is also preferable to apply surface treatment to the surface of the surface layer (A). As for such surface treatment, for example, corona discharge treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, ozone. Surface oxidation treatment like ultraviolet treatment, surface roughness treatment like sandblasting treatment, etc. These treatments can be used alone or in combination. Among them, corona discharge treatment is suitable in terms of surface treatment.

Examples of the packaging material composed of the laminated film of the present invention include packaging bags, containers, and covering materials for containers used for food, pharmaceuticals, industrial parts, groceries, magazines, and other purposes. In particular, from the viewpoint that the matting feeling is superior to the past, it is possible to provide packaging materials similar to Japanese paper and the like, and can be suitably used for foods to add a sense of quality.

The packaging bag is preferably heat-sealed by superimposing the sealing layers (C) of the laminated film on each other, or by superimposing the surface layer (A) and the sealing layer (C) to perform heat sealing, thereby sealing the sealing layer (C) ) Is formed into a bag shape as the inner side.

For example, after cutting two laminated films to the size of a desired packaging bag, overlapping these and heat-sealing the three sides to form a bag shape, filling the contents from the opening that is not heat-sealed on one side, It can also be used as a packaging bag by heat sealing to seal the opening.

Furthermore, by pulling out the drum-shaped laminated film through an automatic packaging machine and heat-sealing the ends overlapped by the cylindrical shape, the upper end and the lower end are heat-sealed separately, whereby a packaging bag can also be formed.

Also, in the case of a packaging bag for long bread, the printed surface is folded inward and sealed, whereby a bag having a gusset portion (bottom gusset bag) can be made. Specifically, it is processed so that the sealing layer (C) of the laminated film of the present invention becomes the inside of the bag, and is processed by a bag-making machine (for example, "HK-40V" manufactured by Totani Technology Research Co., Ltd.) into Gusset bag at the bottom.

The laminated film of the present invention can be particularly suitably used for gusset bags at the bottom of the bag due to its proper fuse sealing and bag making suitability.

The fuse seal strength of the side edges of the bottom gusset bag and the bottom gusset (the inner fold of the bottom) is preferably 13N/15mm or more, more preferably 14N/15mm or more, and even more preferably 14.5N/15mm or more. Especially good is 16N/15mm or more. The upper limit is not particularly limited, but it is preferably 30 N/15 mm or less. By adjusting the fuse seal temperature and bag making speed during bag making, the fuse seal strength can be set.

The bottom gusset bag obtained is supplied to an automatic baguette filling machine, and after filling the baguette, it is heat-sealed so that it can be easily opened. The heat seal strength at this time is preferably less than 5N/15mm, more preferably 0.1N/15mm or more and less than 5N/15mm, and still more preferably 0.2N/15mm or more and less than 4N/15mm.

Afterwards, if necessary, the upper part of the bag can also be bound by using binding tools such as plastic plates, adhesive tapes, and ropes.

In addition, in the case of assembling packaging of various breads such as cream meal packs, the laminated film is supplied to the horizontal automatic packaging machine in the form of a roll with the sealing layer (C) as the inner side of the bag , Manufactured by FUJI MACHINERY Co., Ltd., "FW-3400αV type", etc.). Since the pillow package is also excellent in heat sealability and easy opening property, the laminated film of the present invention can also be particularly suitably used as a pillow packaging bag.

In the case of a horizontal automatic packaging machine, the sealing surfaces of the sealing layer (C) of the laminated film are stacked and heat-sealed to form a bag on one side and to wrap bread on the inside. The heat-sealing strength of the bottom and back side of the pillow-shaped packaging bag carried out by the packaging machine is preferably about 7.5 to 30 N/15 mm, more preferably about 10 to 30 N/15 mm. By adjusting the heat sealing temperature and packaging speed, the heat sealing strength can be set.

Then, the upper part of the pillow-shaped packaging bag may be heat-sealed to form an easily-openable sealable portion, or it may be bundled by using binding tools such as plastic plates, tapes, and ropes. When an easy-to-open seal portion is formed, the heat seal strength is preferably less than 5N/15mm, more preferably 0.1N/15mm or more and less than 5N/15mm, further preferably 0.2N/15mm or more and less than 4N/15mm .

In addition, it is also possible to form a packaging bag, container or container lid by superimposing and sealing the sealing layer (C) with other films capable of heat sealing.

In this case, for other films, films with relatively low mechanical strength composed of LDPE, EVA, polypropylene, etc. can be used. In addition, as for other films, a laminated film can also be used. The laminated film is a stretched film (for example, biaxially oriented) made of a film composed of LDPE, EVA, polypropylene, etc., and having relatively good tearability. Stretched polyethylene terephthalate film (OPET), biaxially stretched polypropylene film (OPP, etc.) are obtained by laminating.

As described above, since the laminated film of the present invention exerts suitable impact resistance and bag-break resistance, it can be suitably applied to various packaging applications. In particular, since the laminated film of the present invention exhibits excellent impact resistance even at low temperatures, it can be suitably used in food packaging applications where many are packaged and distributed at low temperatures.

Among them, when the laminated film of the present invention is applied to bread packaging such as long bread or confectionary bread using a bundling tool (bundle) with a sharp tip or hook portion, it is not likely to cause bag breakage during bundling, and Even if it comes into contact with the strapping tool or the transport container during transportation, pinholes and cracks are not likely to occur. In addition, pinholes and cracks caused by the rubbing of the food and the inner surface (sealing surface) of the film, the friction with the mixed plastic disc, and puncturing are also unlikely to occur. Furthermore, since the laminated film of the present invention can ensure an appropriate fuse seal strength even when a gusset portion is formed, it is preferably applied to a packaging bag used for bread packaging.

The laminated film and food packaging bag of the present invention have been described above, but the present invention is not limited to the foregoing embodiments.

For example, in the laminated film and the food packaging bag of the present invention, a part of the configuration may be replaced with another configuration that exhibits the same function, and any configuration may be added.

[Example]

Next, the present invention will be described in more detail with examples and comparative examples. Below, unless otherwise specifically stated, "parts" and "%" are quality standards.

1. Fabrication of laminated film

1-1. Production of transparent film

(Example 1)

First, the following resins were used to prepare the surface layer, intermediate layer, and sealing layer forming materials.

Next, each of these resin mixtures was supplied to three extruders for co-extrusion to form a laminated film composed of three layers including a surface layer/intermediate layer/sealing layer. In addition, the average thickness of the surface layer was 7 μm, the average thickness of the intermediate layer was 18 μm, and the average thickness of the sealing layer was 5 μm. Therefore, the average thickness of the entire laminated film is 30 μm.

Thereafter, on the surface of the obtained transparent laminated film (surface layer), corona discharge treatment was performed so that the surface energy became 33 mN/m.

[Formation material of surface layer]

‧Propylene-ethylene random copolymer (COPP(1)): 55 copies

Ethylene content: 2.0%

Density: 0.90g/cm ³

Melt flow rate (MFR): 6.0g/10 minutes

Melting point: 140°C

‧Propylene-ethylene-1-butene terpolymer: 35 parts

Density: 0.90g/cm ³

MFR: 5.4g/10 minutes (190°C, 21.18N)

‧Crystalline ethylene-1-butene copolymer: 10 parts

Density: 0.88g/cm ³

MFR: 4.0g/10 minutes

[Forming material of intermediate layer]

‧Propylene Monopolymer (HOPP): 79 copies

Density: 0.90g/cm ³

MFR: 7.5g/10 minutes

‧Propylene-ethylene random copolymer (COPP(2)): 10 copies

Ethylene content: 5.2%

Density: 0.90g/cm ³

MFR: 5.4g/10 minutes

‧Straight-chain low-density polyethylene (LLDPE): 10 servings

Density: 0.905g/cm ³

MFR: 4.0g/10 minutes

‧Low-density polyethylene (biological LDPE) derived from sugar cane: 1 serving

Product name: Made by Braskem, "SPB681"

Density: 0.922g/cm ³

MFR: 3.8g/10 minutes

[Sealing layer forming material]

‧COPP(2): 70 copies

‧Propylene-1-butene random copolymer (COPP(3)): 30 copies

Density: 0.90g/cm ³

MFR: 4.0g/10 minutes

(Example 2)

A transparent laminated film was obtained in the same manner as in Example 1 except that the composition of the material forming the intermediate layer was changed to the following.

HOPP: 77 parts, COPP(2): 10 parts, LLDPE: 10 parts, biological LDPE: 3 parts

(Example 3)

A laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

HOPP: 75 parts, COPP(2): 10 parts, LLDPE: 10 parts, biological LDPE: 5 parts

(Comparative example 1)

A laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

HOPP: 75 copies, COPP(2): 15 copies, LLDPE: 10 copies

1-2. Production of matting film

(Example 4)

First, the materials for the surface layer, the intermediate layer, and the sealing layer were prepared using the following resins.

Next, each of these resin mixtures was supplied to three extruders and co-extruded to form a laminated film having three layers including a surface layer/intermediate layer/sealing layer. In addition, the average thickness of the surface layer was 7 μm, the average thickness of the intermediate layer was 18 μm, and the average thickness of the sealing layer was 5 μm. Therefore, the average thickness of the entire laminated film is 30 μm.

Thereafter, the surface of the obtained transparent laminated film (surface layer) was subjected to corona discharge treatment so that the surface energy became 35 mN/m.

[Formation material of surface layer]

‧Propylene-ethylene block copolymer (COPP(4)): 100 copies

Density: 0.90g/cm ³

MFR: 8.0g/10 minutes

Melting point: 160℃

[Forming material of intermediate layer]

‧COPP(2): 44 copies

‧COPP(4): 38 copies

‧LLDPE: 14 copies

‧Bio LDPE: 4 servings

[Sealing layer forming material]

‧COPP(2): 70 copies

‧COPP(3): 30 copies

(Example 5)

A transparent laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

COPP(2): 43 parts, COPP(4): 37 parts, LLDPE: 12 parts, biological LDPE: 8 parts

(Example 6)

A laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

COPP(2): 42 copies, COPP(4): 37 copies, LLDPE: 11 copies, bio-LDPE: 10 copies

(Example 7)

A laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

COPP(2): 41 parts, COPP(4): 36 parts, LLDPE: 8 parts, bio LDPE: 15 parts

(Comparative example 2)

A laminated film was obtained in the same manner as in Example 1 except that the composition of the intermediate layer forming material was changed to the following.

COPP(2): 40 copies, COPP(4): 45 copies, LLDPE: 15 copies

2. Measurement and evaluation

Using the laminated films obtained in Examples and Comparative Examples, the following measurements and evaluations were performed.

[Measurement of resin pressure]

The pressure of the intermediate layer forming material prepared in Examples and Comparative Examples in the molten state was measured with a resin pressure gauge (manufactured by Ricoh Co., Ltd., "CZ-200P-HC").

<evaluation criteria>

◎: The resin pressure is less than 8.0MPa.

○: The resin pressure is 8.0 MPa or more and less than 9.0 MPa.

×: The resin pressure is 9.0 MPa or more.

[Measurement of rigidity]

Based on ASTM D 882-12, using a Tensilon tensile tester (manufactured by A&D Co., Ltd.), the 1% tangent modulus at 23° C. of the laminated film obtained in Examples and Comparative Examples was measured.

In addition, the measurement is performed in the extrusion direction (hereinafter referred to as "MD direction") at the time of film production.

[Measurement of Transparency]

Based on JIS K 7105: 1987, the haze of the laminated film obtained by the Example and the comparative example was measured using a haze meter (made by Nippon Denshoku Industries Co., Ltd.).

[Evaluation of suitability for bag making]

The sealing layer of the laminated film obtained in Examples and Comparative Examples was set to the inside, and after folding the laminated film in half, a gusset was made on the bottom, and the sealing portion temperature (bag-making temperature) was 300° C. to perform fusion sealing and bag-making. (Bag making machine: "HK-40V" manufactured by Totani Technical Research Co., Ltd., bag making speed: 120 pieces/minute). By this, a bottom gusset bag (length: 345 mm (side edge portion: 245 mm, gusset portion: 60 mm), width 235 mm) was produced, and the suitability of the bag was evaluated. In addition, 300 pieces were used as a group, aligned into a bundle, and the alignment was evaluated.

<evaluation criteria>

○: Even at a bag-making speed of 120 shots (shot), the laminated film can keep up, and there is no problem with the alignment.

△: Even at a bag-making speed of 120 shots, the laminated film can keep up, but part of the alignment is problematic.

×: There is a laminated film that cannot keep up with the 120-shot (shot) bag-making speed, and the alignment is poor.

[Determination of fuse seal strength]

Using the laminated films obtained in Examples and Comparative Examples, the bottom gusset bags were produced in the same manner as the above-mentioned evaluation of the suitability of bag-making.

From the center of the gussets of the five bottom gusset bags obtained, and the center of the side edges other than the gussets, one piece each was cut to a length of 70 mm so that the fuse seal portion became the center in the longitudinal direction , Test pieces with a width of 15 mm (2 pieces per bag), a total of 10 pieces. Then, each test piece was peeled using a Tensilon tensile tester (manufactured by A&D Co., Ltd.) under the conditions of 23° C. and a tensile speed of 300 mm/min. Let the maximum load measured at this time be the fuse seal strength.

<Evaluation criteria for fuse seal strength>

◎: The fuse seal strength of the gusset part and the side part is 16N/15mm or more.

○: The fuse seal strength of the gusset portion and the side portion is 13 N/15 mm or more and less than 16 N/15 mm.

×: At least one of the gusset portion and the side edge portion has a fuse seal strength of less than 13N/15mm.

[Measurement of heat seal strength]

Using the laminated films obtained in Examples and Comparative Examples, the bottom gusset bags were produced in the same manner as in the evaluation of the suitability of the above-mentioned bags. Using a heat sealer (manufactured by TESTER SANGYO Co., Ltd., pressure: 0.2 MPa, time: 1 second, sealing temperature: upper sealing rod 95°C, lower sealing rod 50°C, sealing rod shape: 300m×10mm flat surface), from The obtained portion of the bottom gusset bag opening 50 mm below the upper end was heat-sealed parallel to the opening.

From the obtained five heat-sealed portions of the bottom gusset bags so that the heat-sealed portion becomes the center portion in the width direction, two test pieces each having a length of 70 mm and a width of 15 mm were cut out (two pieces per bag ), a total of 10 tablets. Then, each test piece was peeled using a Tensilon tensile tester (manufactured by A&D Co., Ltd.) under the conditions of 23° C. and a tensile speed of 300 mm/min. Let the maximum load measured at this time be the heat seal strength.

<evaluation criteria>

○: The heat seal strengths are all less than 5N/15mm, and no film breakage occurs at the time of peeling.

×: The heat seal strength was 5 N/15 mm or more, or the film was broken when peeling off.

[Measurement of impact strength]

After the laminated films obtained in Examples and Comparative Examples were kept in a constant temperature chamber set at 0°C for 6 hours, the impact strength according to the film impact method was measured using a spherical metallic impact head with a diameter of 1.5 inches.

<evaluation criteria>

○: Impact strength is 0.15J or more.

△: Impact strength is 0.10J or more and less than 0.15J.

×: The impact strength is less than 0.10J.

The measurement results and evaluation results are shown in Table 1 below.

It is clear from Table 1 that the laminated film of the present invention obtained in Examples is one that does not easily cause excessive load even when extrusion-molded and has suitable moldability. In addition, the suitability of the bag is also good, and the fuse seal strength and heat sealability are also suitable.

Claims (16)

A laminated film comprising a surface layer (A), an intermediate layer (B) and a sealing layer (C), characterized in that the surface layer (A), the intermediate layer (B) and the sealing layer (C) Each contains a propylene-based resin, and the intermediate layer (B) further contains a plant-derived low-density polyethylene (b1). The laminated film according to claim 1, wherein the melt flow rate of the aforementioned low-density polyethylene (b1) is 1 to 7 g/10 minutes. The laminated film according to claim 1 or 2, wherein the content of the low-density polyethylene (b1) in the resin component contained in the intermediate layer (B) is 1 to 15% by mass. The laminated film according to any one of claims 1 to 3, wherein the intermediate layer (B) further contains 5 to 20% by mass of fossil fuel-derived polyethylene in the resin component contained in the intermediate layer (B) ( b2). The laminated film according to claim 4, wherein the aforementioned polyethylene (b2) is a linear low-density polyethylene. The laminated film according to claim 4 or 5, wherein the melt flow rate of the aforementioned polyethylene (b2) is 2 to 10 g/10 minutes. The laminated film according to any one of claims 1 to 6, wherein the propylene-based resin of the intermediate layer (B) contains 10-50% by mass of propylene-α- in the resin component contained in the intermediate layer (B) Random copolymer of olefins. The laminated film according to any one of claims 1 to 7, wherein the propylene-based resin of the intermediate layer (B) contains 55 to 85% by mass of a propylene homopolymer in the resin component contained in the intermediate layer (B) . The laminated film according to any one of claims 1 to 7, wherein the propylene-based resin of the intermediate layer (B) contains 20 to 50% by mass of propylene-α- in the resin component contained in the intermediate layer (B) Olefin block copolymer. The laminated film according to any one of claims 1 to 9, wherein the content of the propylene-based resin in the resin component contained in each of the surface layer (A) and the sealing layer (C) is 50% by mass or more. The laminated film according to any one of claims 1 to 10, wherein the propylene-based resin of each of the surface layer (A) and the sealing layer (C) includes a propylene-α-olefin copolymer. The laminated film according to any one of claims 1 to 11, wherein in terms of the thickness of the laminated film, the proportion of the surface layer (A) is 10 to 35%, and the proportion of the intermediate layer (B) is 45 ~85%, the proportion of the aforementioned sealing layer (C) is 5~20%. The laminated film according to any one of claims 1 to 12, wherein the average thickness of the laminated film is 25 to 50 μm. A food packaging bag characterized by using the laminated film according to any one of claims 1 to 13. The food packaging bag according to claim 14 has a gusset. If the food packaging bag of claim 14 or 15 is used for bread packaging.