TW201707981A - Multilayer film and packaging material - Google Patents

Abstract

The present invention relates to a multilayer film which is used for packaging materials for packaging food, sundry goods, magazines and the like, and wherein one surface layer is composed of a print layer and the other surface layer is composed of a seal layer. The surface of the print layer has a wetting tension of 34-40 mN/m; the print layer contains a propylene resin as a main resin component; and a propylene resin having a melting point of 132 DEG C or less is contained in an amount of 25-80% by mass in the propylene resin contained in the print layer. Consequently, this multilayer film is able to achieve excellent print adhesion and adequate fusing seal strength.

Description

Laminated film and packaging materials

The present invention relates to a laminated film for packaging packaging materials for foods, groceries, magazines, and the like, and packaging materials comprising the same.

Conventionally, a laminated film in which a plurality of resins are laminated is used as a film for packaging for packaging bread or other foods. As such a film for packaging, a laminated film using an olefin resin can be widely used from the viewpoint of easily obtaining heat sealability and the like (see, for example, Patent Documents 1 and 2).

The laminated film used for various types of packaging is often provided with printing on the surface layer in order to indicate the content or content, designing property, etc. However, if the adhesion of the printing is low, the printing is detached, so that the surface is corona-treated or the like. Processing to achieve improved print adhesion.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-210897

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-152730

However, in the conventional laminated film, when the printing layer is brought into contact with the surface of the resin sheet such as polyvinyl chloride, the printing may be transferred to the resin sheet, but the printing may fall off. Therefore, it is required to further improve the printing adhesion. Sex. On the other hand, when the surface treatment such as corona treatment is performed to improve the printing adhesion of the surface layer of the laminated film, the printing adhesion is improved, but the melt-sealing strength at the time of melt-cutting the film is lowered.

An object of the present invention is to provide a laminated film which has a preferable melt-cut sealing strength and can achieve excellent printing adhesion.

Further, an object of the present invention is to provide a laminated film having the above-described preferable melt-cut sealing strength and printing adhesion, and having better impact resistance.

The present invention solves the above problems by a laminated film comprising a printed layer on one side and a laminated film comprising a sealing layer on the other side, wherein the surface of the printed layer has a wetting tension of 34 to 40 mN/m; The layer contains a propylene-based resin as a main resin component, and contains a propylene-based resin having a melting point of 132° C. or less, and the content thereof is 25 to 80% by mass in the propylene-based resin contained in the printing layer.

In the present invention, in the case of a printing layer containing a propylene-based resin as a main resin component, even in the case of "containing a predetermined amount of a low-melting propylene-based resin to increase the wetting tension on the surface of the printing layer and further improve the printing adhesion" It is also possible to achieve a better melt cut seal strength. Therefore, the laminated film of the present invention is suitable for use in various packaging applications, in particular It is the packaging use of foods that are mostly packaged or distributed at low temperatures.

In particular, in the case where the contents of the package are long-shaped breads, when the long bread is filled, there is a step of blowing air toward the bag-like package, and the laminated film according to the present invention is not easily blown by the air. The packaging bag is broken, so it is particularly suitable for the packaging of the long bread.

[Formation of the Invention]

The surface layer on one side of the laminated film of the present invention comprises a printed layer, and the other layer has a laminated film comprising a sealing layer, and the surface of the printed layer has a wet tension of 34 to 40 mN/m, and the printed layer contains a propylene resin as a main resin component. Further, the content of the propylene-based resin having a melting point of less than 132 ° C is 25 to 80% by mass in the propylene-based resin contained in the printing layer.

[Printed layer]

The printed layer used for the laminated film of the present invention constitutes a layered body provided with a printed surface layer of a film for packaging. The printing layer contains a propylene resin as a main resin component, and as the propylene resin, for example, a propylene homopolymer, a propylene-α-olefin copolymer, a propylene-α-olefin block copolymer, or the like can be used. In the present invention, among these components, a propylene-α-olefin copolymer is preferably used from the viewpoint of easily obtaining adhesion to the intermediate layer.

The propylene-α-olefin copolymer may, for example, be a propylene-ethylene copolymer, a propylene-1-butene copolymer or a propylene-ethylene-1-butene copolymer, and these copolymers may be used singly or in combination. Combined use. among them, From the viewpoint of easily obtaining preferable transparency, a propylene-ethylene copolymer can be preferably used.

In the propylene-ethylene random copolymer, the ethylene content is preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass. Moreover, from the viewpoint of easily obtaining better impact resistance, the ethylene content is preferably 2% by mass or more, more preferably 3% by mass or more, and still more preferably 4% by mass or more.

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

A propylene - ethylene copolymer has a density preferably 0.880g / cm ³ or more 0.905g / cm ³ or less, more preferably 0.890g / cm ³ or more 0.900g / cm ³ or less.

The propylene-ethylene random copolymer preferably has a melting point of 110 ° C or more, more preferably 115 ° C or more, from the viewpoint of preventing sticking to the melt-cut sealing blade at the time of bag making. Further, in the case of performing the fusion sealing at the time of bag making, it is necessary to form a sufficient melt ball in order to exhibit the melt-sealing strength, and therefore it is preferably 150 ° C or lower, more preferably 145 ° C or lower.

The content of the propylene-based resin in the resin component contained in the printing layer is preferably 50% by mass or more, more preferably 50% by mass or more, based on the resin component contained in the printing layer. 60% by mass or more, particularly preferably 75 to 95% by mass.

In the present invention, as the propylene resin, a melting point is used. The low-melting point propylene-based resin having a content of less than 132 ° C is 25 to 80% by mass in the propylene-based resin contained in the printing layer, whereby a better melt-cut seal can be achieved even when the surface wetting tension is increased. strength. Moreover, a better molten ball can be formed during the melt-cut sealing, and the best melt-sealing strength can be exhibited. The content of the low-melting propylene-based resin is preferably from 30 to 55% by mass, more preferably from 35 to 45% by mass. The melting point of the low melting point propylene resin is preferably from 125 to 131 °C.

In the present invention, in particular, from the viewpoint of easily obtaining a preferable melt-cut seal strength, as the low-melting point propylene-based resin having a melting point of less than 132 ° C, a propylene-ethylene random copolymer is preferably used, and the melting point is used in combination. High melting point propylene-ethylene random copolymer above 134 °C. The melting point of the high melting point propylene-ethylene random copolymer is preferably from 135 to 138 °C.

In the case where two kinds of propylene-ethylene random copolymers having different melting points are used in combination, the content ratio of the copolymer having a low melting point to the copolymer having a high melting point (low melting point copolymer/high melting point copolymer) is preferably in mass ratio. It is 25/75~80/20, more preferably 35/65~45/55. By setting the ratio of the two within this range, it is easy to obtain a preferable melt-cut seal strength at the time of fusion-sealing sealing.

Other resins than the above propylene-based resin may be used in combination in the printed layer. As the other resin, for example, a vinyl resin is preferably used, and examples of the vinyl resin include linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE), and linear high density polyethylene (LHDPE). ), polyethylene resin such as low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE); ethylene-butylene-rubber copolymer (EBR), ethylene-propylene-rubber copolymer (EPR) , ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-acrylic acid Ethylene-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), etc., ethylene copolymer; further, ethylene-acrylic acid copolymer The ionic polymer or the ionic polymer of the ethylene-methacrylic acid copolymer may be used singly or in combination of two or more.

Among them, an ethylene-1-butene copolymer or the like which confirms the effect of the melt-cut seal strength at the bottom of the gusset can be preferably used.

When the resin other than the propylene-based resin is used, the content is preferably 10% by mass or less, more preferably 5 to 10%, based on the resin component contained in the printing layer, in order to prevent deterioration of transparency due to a decrease in the mutual solubility. quality%.

The printing layer used in the present invention has a surface wet tension of 34 to 40 mN/m, preferably 35 to 39 mN/m. By setting the wetting tension within this range, the printing adhesion to the surface of the printing layer can be improved, and the peeling of printing can be suppressed.

The adjustment of the wetting tension on the surface of the printing layer may be, for example, corona discharge treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, surface oxidation treatment such as ozone treatment, or sandblasting. Surface unevenness treatment, wherein corona discharge treatment is preferably used. The method of the corona discharge treatment is not particularly limited. For example, Japanese Patent Publication No. Sho 39-12838, Japanese Patent Laid-Open No. Sho 47-19824, Japanese Patent Laid-Open No. 48-28067, and Japanese Patent Laid-Open No. 52-42114 Each of the bulletins describes a processing method such as a description. As the corona discharge treatment apparatus, a solid corona treatment machine manufactured by Pillar Co., Ltd., a LEPEL type surface treatment machine, a VETAPHON type treatment machine, or the like can be used. It can be processed under normal pressure in air. The discharge frequency during processing is 5kV~40kV, more preferably 10kV~30kV, and the waveform is preferably an alternating current sine wave. The gap between the electrode and the dielectric drum is transparent and the lance is 0.1 mm to 10 mm, more preferably 1.0 mm to 2.0 mm. The discharge system is processed above the dielectric support roller disposed in the discharge zone, and the throughput is 0.34 kV. A. Minutes / m ² ~ 0.4kV. A. Minutes / m ² , more preferably 0.344 kV. A. Minutes / m ² ~ 0.38kV. A. Minutes / m ² .

Further, an antifogging agent, an antistatic agent, a heat stabilizer, a nucleating agent, an antioxidant, a slip agent, an anti-caking agent, and a mold release may be added to the printed layer within a range not impairing the object of the present invention. A component such as a solvent or an ultraviolet absorber is used as a component other than the above resin component.

[sealing layer]

The sealing layer used in the present invention is a layer for adhering the sealing layers of the laminated film to each other or to the laminated film and other containers or films. The sealing layer may be appropriately selected depending on the type of use or the object to be sealed, and a resin type which can obtain a preferable sealing strength can be appropriately selected. For example, in the case where the sealing layers are sealed to each other for use as a packaging bag, it is preferred to use a propylene-ethylene random copolymer or a propylene-1-butene copolymer from the viewpoint of obtaining a moderate sealing strength. A sealing layer of an α-olefin-propylene copolymer such as a propylene-α-olefin copolymer or a 1-butene-propylene copolymer. Among them, from the viewpoint of easily adjusting the heat-sealing temperature or strength at the time of easy opening and sealing at a low temperature, a large heat sealing temperature range, and easy to obtain an appropriate heat-sealing strength of the easy-opening seal, a propylene-1-butene copolymer is preferred. Or a butene-containing copolymer such as a 1-butene-propylene copolymer, particularly preferably used in a sealing layer of propylene - A propylene-1-butene copolymer excellent in mutual solubility of an ethylene copolymer.

In the case of using a propylene-1-butene copolymer, in order to improve the mutual solubility with polypropylene, the 1-butene content in the propylene-1-butene copolymer is preferably from 10 to 50 mol%, more preferably It is 15~35%, and the best is 20~30%.

When a propylene-1-butene copolymer is used, the content of the propylene-1-butene copolymer is preferably 40% by mass or less, more preferably 35% by mass or less, more preferably 35% by mass or less based on the resin component contained in the sealing layer. Preferably, it is 30% by mass or less. Further, it is preferably 10% by mass or more, and more preferably 15% by mass or more. When the content of the 1-butene-propylene copolymer is within this range, it is easy to obtain a preferable low-temperature sealing property and crack resistance, and it is also advantageous in cost reduction.

As the resin to be used in combination with the above-mentioned 1-butene-propylene copolymer, other polyolefin-based resins can be suitably used. However, from the viewpoint of easily adjusting the sealing strength, a propylene-α-olefin copolymer and, preferably, As the ethylene-α-olefin copolymer, a propylene-α-olefin copolymer can be preferably used.

The content of the α-olefin in the propylene-α-olefin copolymer is not particularly limited, but is preferably from 1 to 20% by mass, more preferably from 1.5 to 15% by mass. The α-olefin may, for example, be ethylene, 1-hexene, 4-methyl-1-pentene or 1-octene. Among them, a propylene-ethylene copolymer having the same ethylene content, MFR, density, and melting point as those exemplified as the preferred examples in the above printed layer can be preferably used.

The content of the other olefin-based resin is preferably 90% by mass or less, and more preferably 85% by mass or less, based on the resin component contained in the sealing layer. Further, it is preferably 50% by mass or more, and more preferably 60% by mass or more.

In particular, in the case of forming a packaging bag using the laminated film of the present invention, in the case where an easy-opening portion for heat-sealing the sealing layers is provided, it is preferred to copolymerize 1-butene-propylene copolymer/propylene-α-olefin. The mass ratio represented by the substance is a ratio of 20/80 to 50/50 to use a 1-butene-propylene copolymer and a propylene-α-olefin copolymer.

[middle layer]

The laminated film of the present invention may be a laminated film including the above-mentioned printing layer and sealing layer. However, from the viewpoint of adjusting various film properties and easily achieving better interlayer adhesion, it is preferably used in the printing layer and the sealing layer. Set the middle layer between. As the intermediate layer, a resin for a film for packaging can be used. However, from the viewpoint of easily obtaining adhesion to the layer of the printing layer or the sealing layer, an olefin resin can be preferably used.

As the olefin-based resin, a propylene-based resin or a vinyl-based resin which can be used for the above-mentioned printing layer or sealing layer can be preferably used. From the viewpoint of easily suppressing cracking of the laminated film, propylene-ethylene copolymer can be preferably used. . As the propylene-ethylene random copolymer, a propylene-ethylene copolymer having the same ethylene content, MFR, density, and melting point as those exemplified as the preferred embodiment of the above printed layer can be preferably used.

When a propylene-ethylene copolymer is used, the content of the propylene-ethylene copolymer is preferably 5% by mass or more, more preferably 8% by mass or more, and still more preferably 10% by mass based on the resin component contained in the intermediate layer. the above. Moreover, it is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 40% by mass or less. When the content of the propylene-ethylene random copolymer is within this range, it is easy to obtain better crack resistance and good chip break resistance.

Moreover, as a resin for the intermediate layer, it is easy to obtain From the viewpoint of excellent impact resistance or bag break resistance, particularly at the low temperature, it is possible to use a vinyl resin in combination, and it is preferred to use a linear low density polyethylene as the vinyl system. Resin. In the case of using a linear low-density polyethylene, the content of the linear low-density polyethylene is preferably 5% by mass or more, and more preferably 8% by mass or more, based on the resin component contained in the intermediate layer. Further, it is preferably 20% by mass or less, and more preferably 15% by mass or less.

In the case of using a linear low-density polyethylene, the density thereof is preferably 0.895 g/cm ³ or more and 0.915 g/cm ³ or less, more preferably 0.895 g/cm ³ or more and 0.910 g/cm ³ or less. 0.900g / cm ³ or more 0.907g / cm ³ or less.

Further, as the resin used for the intermediate layer, it is necessary to measure the suitability of the bag to exhibit high rigidity, and therefore it is preferable to use a propylene homopolymer. In the case of using a propylene homopolymer, the propylene homopolymer is preferably from 20 to 85% by mass, more preferably from 30 to 80% by mass, based on the resin component contained in the intermediate layer. By making it into this content, it is easy to obtain favorable transparency.

As the homopolymer of the propylene, the MFR is preferably from 3 to 20 g/10 min, more preferably from 5 to 15 g/10 min. Further, the density thereof is preferably from 0.880 to 0.900 g/cm ³ , more preferably from 0.890 to 0.900 g/cm ³ .

An anti-fogging agent, an antistatic agent, a heat stabilizer, a nucleating agent, an antioxidant, a slip agent, an anti-caking agent, a mold release agent, and the like may be added to the intermediate layer within a range not impairing the object of the present invention. A component such as an ultraviolet absorber is used as a component other than the above resin component.

[Laminated film]

The laminated film of the present invention has at least the above printed layer and seal The laminated film of the layer, and the surface layer on one side of the laminated film includes a printed layer, and the laminated film on the other side including the sealing layer. The laminated film having such a structure has a preferable melt-cut sealing strength, and is suitable for use as a film for various packaging from the viewpoint of excellent impact resistance and bag break resistance.

The layer structure of the laminated film of the present invention is not particularly limited, but a two-layer structure of a printing layer/sealing layer including the printing layer and the sealing layer, and an intermediate layer between the printing layer and the sealing layer are preferably used. The printing layer/intermediate layer/sealing layer is composed of three layers, or the printing layer/intermediate layer 1/intermediate layer 2/sealing layer composed of an intermediate layer of a plurality of layers is formed, and the like. Among them, from the viewpoint of easily adjusting the characteristics of the film and facilitating the production of the film, a three-layer structure including a printing layer/intermediate layer/sealing layer can be preferably used.

The thickness of the laminated film of the present invention may be appropriately adjusted depending on the use or the state to be used, but it is easy to achieve both volume reduction in packaging applications and bag breakability during dispensing. The total thickness is preferably from 20 to 60 μm, more preferably from 25 to 50 μm.

The thickness or thickness ratio of each layer is not particularly limited. For example, the thickness of the printed layer is preferably 2 to 20 μm, more preferably 3 to 15 μm. The thickness of the sealing layer is preferably from 1 to 10 μm, more preferably from 2 to 8 μm. Further, in the case of using the intermediate layer, the thickness of the intermediate layer is preferably from 3 to 30 μm, more preferably from 5 to 20 μm.

The thickness ratio of the printed layer is preferably 20% or more, more preferably 25% or more, of the total thickness of the laminated film from the viewpoint of easily obtaining the melt cut strength of the preferred folded portion and the suitability for bag making. Further, it is preferably 40% or less, more preferably 35% or less. By making the thickness of the printed layer in the range Within the circumference, even when the wetting tension is increased, a better melt-sealing strength is easily obtained. The thickness ratio of the sealing layer is preferably from 5% to 30%, more preferably from 10 to 25%, of the total thickness of the laminated film from the viewpoints of easy availability of the easy-opening property, the fusion strength, and the suitability of the bag. Further, in the case of using the intermediate layer, the thickness ratio of the intermediate layer is preferably 30% or more, more preferably 40%, of the total thickness of the laminated film from the viewpoint of easily obtaining a preferable melt cut strength and suitability for bag making. %the above. Further, it is preferably 70% or less, more preferably 65% or less.

In the laminated film of the present invention, any other resin layer other than the above-mentioned printing layer, intermediate layer, and sealing layer may be laminated. However, the thickness of the other resin layer is preferably 20% or less of the total thickness, and particularly preferably includes the above-mentioned printing layer and the intermediate layer. The composition of the layer and the sealing layer. Further, in this configuration, an intermediate layer in which a plurality of intermediate layers are laminated may be used.

The laminated film of the present invention preferably has a haze of 10% or less, more preferably 8% or less, still more preferably 6% or less, from the viewpoint of easily visually confirming the contents of the package. The laminated film of the present invention can easily achieve better packaging suitability and better printing adhesion even in the case of having such high transparency.

The method for producing the laminated film of the present invention is not particularly limited, and for example, a co-extrusion method in which a resin or a resin mixture for each layer is separately heated and melted by each extruder, and a co-extruded multilayer mold method or After laminating in a molten state by a method such as a feeder method, it is formed into a film shape by a blow method, a T-die, a cooling roll method, or the like. According to the co-extrusion method, the thickness ratio of each layer can be relatively freely adjusted, and a multilayer film excellent in hygienic property and excellent in cost performance can be obtained, and thus it is preferable. . Since the laminated film obtained by the production method can substantially obtain a multilayer film having no elongation, it is also possible to perform secondary molding such as deep drawing by vacuum forming.

In order to improve the adhesion to the printing ink, etc., it is also preferable to carry out surface treatment on the printing layer. Examples of such surface treatment include surface oxidation treatment such as corona treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, ozone/ultraviolet treatment, and surface unevenness treatment such as sandblasting. Good for corona treatment.

The packaging material containing the laminated film of the present invention may, for example, be used for packaging bags, containers, and covering materials for foods, pharmaceuticals, industrial parts, miscellaneous goods, magazines, and the like.

The packaging bag is preferably a packaging bag formed by using a sealing layer of the laminated film of the present invention as a heat sealing layer, and sealing the sealing layers to heat-sealing or overlapping the printing layer and the sealing layer. Heat sealing is performed whereby the sealing layer is used as the inner side. For example, two sheets of the laminated film are cut into a desired bag size, which is overlapped and three sides are heat-sealed to form a bag shape, and the contents are filled with no heat-sealed one side, and then heat-sealed and sealed. This can be used as a packaging bag. Further, the end portion of the roll-shaped film may be sealed into a cylindrical shape by an automatic packaging machine, and then the package may be formed by sealing the upper and lower sides.

Moreover, in the case of forming the packaging bag for the long bread, the packaging bag having the folded portion can be formed by folding and sealing the printing surface inward. Specifically, the sealing layer of the laminated film of the present invention is made to the inside of the packaging bag, and is processed into a bottom hem bag by a bag making machine such as HK-40 manufactured by Totani Techno Co., Ltd. At this time, it is preferred to adjust the melting The sealing temperature and the bag making speed are cut so that the side sealing portion of the bottom hemming bag and the bottom folding portion (the inner folded portion of the bottom portion) have a fusion sealing strength of 7.5N~30N/15mm, preferably 12~30N/15mm. .

The obtained bottom folded bag is supplied to the long bread automatic filling machine, and after being filled with the long bread, it has an easy-opening property and the heat sealing strength is 0.1 to 5 N/15 mm, preferably 0.2 to 4 N/15 mm. Under the condition of heat sealing, forming an easy-opening long bread bag, and further, according to the demand, an easy-opening sealing portion is formed on the upper part of the bag, preferably the upper part of the long bread, or a plastic plate or tape is used. A bundling device such as a rope binds the upper portion of the package to seal it.

Further, the outer cover of the packaging bag, the container, and the container may be formed by overlapping the sealing layer with another heat sealable film and heat sealing. At this time, as another film to be used, a film of LDPE, EVA, or polypropylene having a weak mechanical strength can be used. Further, it is also possible to use a film having a good tearability such as a film of LDPE, EVA or polypropylene, such as a biaxially stretched polyethylene terephthalate film (OPET) or a biaxially oriented polypropylene film (OPP). A laminated film that is laminated.

As described above, the laminated film of the present invention has good packaging suitability, and at the same time, better crack resistance can be achieved, and cracking is less likely to occur when the contents are loaded. Therefore, even in the case where a content having a sharp portion is loaded, particularly in the case where a large amount of contents are continuously and quickly loaded by a packaging machine or the like, a packaging bag which is less likely to be broken can be realized.

Further, the intermediate layer contains a linear low-density polyethylene, and is particularly suitable for use in various packaging applications from the viewpoint of achieving excellent impact resistance and bag break resistance. Especially from low temperatures From the standpoint of achieving excellent impact resistance, it is suitable for food packaging applications that are mostly packaged and distributed at low temperatures.

In particular, even when the laminated film of the present invention is formed into a folded-shaped packaging bag and the bread is placed in the packaging bag, cracking can be preferably suppressed, and from this viewpoint, it is particularly suitable for use. Thinner or less bulky bags require higher bread packaging applications.

[Examples]

Next, the present invention will be described in more detail by way of examples and comparative examples. In addition, "parts" and "%" in the blending of the resin composition and the like are mass standards.

(Example 1)

Each of the following resins was used as a resin component for forming each layer of the printing layer, the intermediate layer, and the sealing layer, and the resin mixture forming each layer was adjusted. The mixture was separately supplied to three extruders so that the ratio of the average thickness of each layer of the laminated film formed by the printing layer/intermediate layer/seal layer was co-extruded to form A laminated film having a thickness of 30 μm. Next, a corona discharge treatment was performed on the printed layer of the obtained laminated film so that the surface energy was 35 mN/m, thereby obtaining a laminated film.

Printing layer: propylene-ethylene copolymer (1) (melting point: 127 ° C, density: 0.90 g/cm ³ , melt index (hereinafter referred to as MI): 5 g/10 min) 40 parts, propylene-ethylene copolymer (2) (melting point: 136 ° C, density: 0.90 g/cm ³ , MI: 8 g/10 min) 52 parts, ethylene-1-butene copolymer (density: 0.886 g/cm ³ , MI: 4 g/10 min) 8 parts

Intermediate layer: propylene homogeneous copolymer (density: 0.90 g/cm ³ , MI: 8 g/10 min) 80 parts, propylene-ethylene copolymer (3) (density: 0.90 g/cm ³ , MI: 5 g/10 min) 10 parts, linear low-density polyethylene (density: 0.905 g/cm ³ , MI: 4 g/10 min) 10 parts

Sealing layer: propylene-1-butene copolymer (density: 0.90 g/cm ³ , MI: 4 g/10 min) 20 parts, propylene-ethylene copolymer (3) (density: 0.90 g/cm ³ , MI: 5 g /10 minutes) 80 copies

(Example 2)

A laminate film was obtained in the same manner as in Example 1 except that the resin component of the resin mixture for the printing layer was changed to the following components.

Printing layer: propylene-ethylene copolymer (1) (melting point: 127 ° C, density: 0.90 g/cm ³ , melt index (hereinafter referred to as MI): 5 g/10 min) 75 parts, propylene-ethylene copolymer (2) (melting point: 136 ° C, density: 0.90 g/cm ³ , MI: 8 g/10 min) 17 parts, ethylene-1-butene copolymer (density: 0.886 g/cm ³ , MI: 4 g/10 min) 8 parts

(Comparative Example 1)

A laminated film was obtained in the same manner as in Example 1 except that the printed layer of the laminated film was subjected to corona discharge treatment to have a surface energy of 33 mN/m.

(Comparative Example 2)

A laminate film was obtained in the same manner as in Example 1 except that the resin component of the resin mixture for the printing layer was changed to the following components.

Printing layer: propylene-ethylene copolymer (2) (melting point: 136 ° C, density: 0.90 g/cm ³ , MI: 8 g/10 min) 92 parts, ethylene-1-butene copolymer (density: 0.886 g/cm ³ , MI: 4g/10 minutes) 8 copies

Using the laminated film obtained in the above examples and comparative examples, the following tests and evaluations were carried out. The results obtained are shown in the table below. this In addition, the numerical value of the resin composition in the table is the content (parts by mass) of the resin component used in each layer.

[Measurement of haze and evaluation of transparency]

The haze (unit: %) of the film obtained in the examples and the comparative examples was measured using a haze meter (manufactured by Nippon Denshi Kogyo Co., Ltd.) in accordance with JIS K7105. The transparency was evaluated on the basis of the following criteria.

◎: The haze is 5% or less

○: Haze is more than 5% and less than 10%

×: haze exceeds 10%

[Measurement of impact strength]

The impact strength of the film obtained in the examples and the comparative examples at 5 ° C was measured by an impact tester (Suga Test Co., Ltd.) according to the method of ASTM D-256.

◎: Impact strength is 0.15J or more

○: Impact strength is 0.1 J or more and less than 0.15 J

△: Impact strength is 0.05 J or more and less than 0.1 J

×: Impact strength is less than 0.05J

[Ease of opening seal evaluation]

The film obtained in the examples and the comparative examples was cut into a length of 10 cm × a width of 10 cm, and then folded into a length of 10 cm × a width of 5 cm so that the surfaces of the sealing layers overlap each other. The top sealing machine (manufactured by Shiga Packaging Machinery Co., Ltd., the upper part of the sealing bar shape: multiple, the lower part: the longitudinal direction, the sealing temperature: 80 ° C, and the sealing width: 1 cm) was sealed from a portion of the curved portion of the film folded at a distance of 5 mm. A test piece having a longitudinal length of 15 mm cut from the sealed film will be distinguished from the other end of the curved portion. The sealing portion was peeled off at 23 ° C and a tensile speed of 300 m/min, and the easy-opening property at this time was evaluated. The easy-opening property was evaluated in the following manner.

○: The sealing surfaces are well adhered to each other during sealing, and peeling can be performed without breaking the film during opening.

X: The sealing faces do not adhere well to each other during sealing, or the film may be broken even after opening.

[Printability (ink adsorption)]

An ink (a urethane type ink, Grossa 709 white; manufactured by DIC Corporation) was applied to the surface of the printed layer of the film obtained in the examples and the comparative examples at a coating amount of 10 g/m ² . The polyvinyl chloride sheet was placed on the coated surface, and a load of 500 g/cm ² was applied thereto, and after standing at 50 ° C for 24 hours, the polyvinyl chloride sheet was peeled off, and the ink peeling on the surface of the film was evaluated by visual observation.

○: The area where the ink is detached is 10% or less of the ground contact surface of the polyvinyl chloride sheet.

△: The area where the ink falls off exceeds 10% of the ground contact surface of the polyvinyl chloride sheet, and is 25% or less.

×: The area where the ink is peeled off exceeds 25% of the grounding surface of the polyvinyl chloride sheet

[Fused seal strength]

Using the film obtained in the examples and the comparative examples, a bottom hem bag was produced in the same manner as the above-described bag suitability evaluation. 10 pieces of each of the center portions of the side portions of the side portions of the five bottom folded pockets and the side portions other than the flanges were cut out so that the melt-cut seal portion was formed at the center portion in the longitudinal direction. a test piece having a width of 15 mm and a length of 7 cm at 23 ° C, The maximum load at the time of stretching was measured by a TENSILON tensile tester (manufactured by A&D Co., Ltd.) under the conditions of a tensile speed of 300 mm/min.

○: The weld strength of the hemmed portion and the side portion are both 18N/15mm or more.

△: The weld strength of the hemmed portion and the side portion are both 15 N/15 mm or more and less than 18 N/15 mm.

×: The weld strength of at least one side of the hemmed portion and the side portion is less than 15 N/15 mm

[bag making evaluation]

The sealing layer of the film obtained in the examples and the comparative examples was inside, and the film was half-folded, and then folded at the bottom, and sealed at a sealing temperature (baking temperature) of 300 ° C to carry out bag making (pocketing) Machine: Tonani Technology Industrial Co., Ltd. HK-40, bag making speed: 120 pieces / min), making 10 bottom hem bags (length: 345mm (side: 245mm, hem: 60mm), width 235mm ), evaluate the suitability of the bag.

○: Suitable for cutting with a sealing blade, the film will not adhere to the blade, suitable for bag making

×: Poor cutting with a sealing blade, or film attached to the sealing blade, resulting in the inability of the bag to be formed

As is clear from the above table, the laminated film of the present invention of Examples 1 to 2 has better melt-sealing strength and excellent printing adhesion. Further, in the case of the melt-cut seal, the molten ball of the melt-cutting blade is formed in a good state, and it has a better bag-making property. On the other hand, the laminated films of Comparative Examples 1 and 2 could not have both good printing adhesion and sealing strength.

Claims (8)

A laminated film comprising a printed layer on one side and a laminated film comprising a sealing layer on the other side, wherein the surface of the printed layer has a wetting tension of 34 to 40 mN/m; and the printed layer contains a propylene system The resin is a main resin component and contains a propylene resin having a melting point of less than 132 ° C, and the content thereof is 25 to 80% by mass in the propylene resin contained in the printing layer. The laminated film according to claim 1, wherein the sealing layer contains a propylene resin as a main resin component and a propylene-1-butene copolymer in an amount of 10 to 40 by mass in the propylene resin contained in the sealing layer. %. The laminated film of claim 1 or 2, wherein the printed layer has a thickness of 20 to 40% of the total thickness. The laminated film according to any one of claims 1 to 3, wherein the printing layer and the sealing layer have an intermediate layer containing a propylene resin as a main resin component. The laminated film according to any one of claims 1 to 4, which has a haze of 10% or less. A laminate film according to any one of claims 1 to 5, which is used for a packaging material. A packaging material comprising the laminated film according to any one of claims 1 to 6. The packaging material of claim 7, which is a packaging bag for food.