JP7537088B2 - Easy-to-tear, low-gloss film and packaging bags and sheets using the same - Google Patents

Description

The present invention relates to an easily tearable film that has low gloss and excellent impact strength, and to packaging bags and sheets that use the same.

In recent years, against the backdrop of a declining birthrate and aging population, a decrease in the working population, and a reduction in long working hours, there has been a growing demand for user-friendliness in plastic film and sheet products, such as easier opening. In addition, with growing awareness of environmental issues worldwide, efforts are being made not only to improve convenience and ease of use, but also to reduce the volume and thickness of plastic film and sheet products with the aim of reducing the environmental burden.
An example of an application requiring easy opening and tearing properties is the food packaging field. In addition to the above-mentioned easy opening and tearing properties, the performance required for packaging films and sheets in the food packaging field includes strength, heat sealability, design, etc. In particular, with regard to design, while the required needs are generally transparency, gloss, and high visibility of the contents, there are also many cases where a low-gloss, matte appearance is required because it can create a luxurious feel.

As a method for imparting low gloss as described above, for example, Patent Document 1 describes a low gloss polyethylene film made of an ethylene-α-olefin copolymer component obtained by polymerizing ethylene and an α-olefin having 3 to 12 carbon atoms, and an oxygen-containing ethylene copolymer component. Patent Document 2 describes a low reflection sheet having a low reflection resin layer with numerous protrusions on at least one side of a colored substrate.

JP 2002-105252 A JP 2016-29456 A

As described above, means for imparting low gloss to packaging films or sheets have been investigated, but the film described in Patent Document 1 does not have sufficient low gloss, and the high tear strength results in poor ease of opening when used as a packaging bag. The sheet described in Patent Document 2 requires transfer formation using a soft mold to form the protrusions, which is problematic in terms of cost.
An object of the present invention is to provide an easily tearable, low-gloss film which is not only excellent in low gloss but also excellent in tearability and impact strength, and a packaging bag and sheet using the same.

In order to solve the above problems, the present inventors conducted extensive research and found that a film and sheet capable of solving the above problems can be obtained by using a specific raw material composition, thereby completing the present invention.
That is, according to the first invention, there is provided a single-layer or multi-layer, easily tearable, low-gloss film, characterized in that any one of its layers contains a copolymer (a) containing at least ethylene and a functional group-containing monomer, and a cyclic olefin resin (b).
According to a second invention, there is provided the easy-tear, low-gloss film described in the first invention, characterized in that the functional group-containing monomer is at least one selected from the group consisting of vinyl acetate, acrylic acid, acrylic acid esters, and maleic anhydride.
According to the third invention, there is provided an easily tearable low gloss film as described in the first or second invention, characterized in that it is formed by laminating a plurality of resin layers including at least two layers of a resin layer (A) mainly composed of the copolymer (a) and a resin layer (B) containing a cyclic olefin resin (b) and a polyolefin resin (c), and the resin layer (A) is disposed as the outermost layer.
According to the fourth invention, there is provided the easy-tear low-gloss film according to the third invention, characterized in that the concentration of the cyclic olefin resin (b) in the resin layer (b) is 10 to 80% by weight, and the concentration of the polyolefin resin (c) is 20 to 90% by weight.
According to a fifth aspect of the present invention, there is provided the easily tearable low gloss film according to any one of the third and fourth aspects of the present invention, characterized in that the polyolefin resin (c) is a polyethylene resin.
According to a sixth aspect of the present invention, there is provided an easily tearable, low-gloss film according to any one of the first to fifth aspects of the present invention, characterized in that the cyclic olefin resin (b) is an ethylene-cyclic olefin copolymer.
According to a seventh aspect of the present invention, there is provided the easily tearable low gloss film according to the sixth aspect, characterized in that the glass transition point of the ethylene-cyclic olefin copolymer is 60° C. or higher.
According to an eighth aspect of the present invention, there is provided an easily tearable, low gloss film according to any one of the first to seventh aspects, further comprising a branched polyolefin in at least any one of the layers.
According to a ninth aspect of the present invention, there is provided the easily tearable low gloss film according to any one of the third to seventh aspects of the present invention, characterized in that the resin layer (A) further contains a branched polyolefin.
According to a tenth aspect of the present invention, there is provided an easily tearable low gloss film according to any one of the first to ninth aspects of the present invention, characterized in that the tear strength in MD and TD measured by Elmendorf tear strength based on JIS K7128-2 is 20 N/mm or less.
According to an eleventh invention, there is provided an easily tearable low gloss film as described in any one of the first to tenth inventions, characterized in that, in gloss measurement at an incident angle and acceptance angle of 20° based on JIS Z8741, the gloss of at least one outermost surface of the film is 10% or less.
According to a twelfth aspect of the present invention, there is provided an easily tearable, low gloss film according to any one of the first to eleventh aspects of the present invention, characterized in that the impact strength at 70 μm is 300 g or more in a dirt drop impact measurement based on JIS K7124.
According to a thirteenth aspect of the present invention, there is provided an easily tearable, low gloss film according to any one of the first to twelfth aspects, characterized in that the copolymer (a) is a copolymer of ethylene and methyl acrylate.
According to a fourteenth aspect of the present invention, there is provided a packaging bag using the easy-tearable low-gloss film according to any one of the first to thirteenth aspects of the present invention.
According to a fifteenth aspect of the present invention, there is provided a sheet using the easy-tear low-gloss film according to any one of the first to thirteenth aspects of the present invention.

As described above, according to the first invention, the film contains the copolymer (a) containing at least ethylene and a functional group-containing monomer, and the cyclic olefin resin (b), and thus has excellent tearability, low gloss, and impact strength.
According to the second aspect of the present invention, the functional group-containing monomer is at least one selected from the group consisting of vinyl acetate, acrylic acid, acrylic esters, and maleic anhydride, so that the film has low gloss and excellent impact strength.
According to the third invention, the film is formed by laminating a plurality of resin layers including at least two layers of a resin layer (A) mainly composed of the copolymer (a) and a resin layer (B) containing a cyclic olefin resin (b) and a polyolefin resin (c), and the resin layer (A) is disposed as the outermost layer, so that the film has excellent tearability and low gloss.
In addition, according to the fourth invention, the concentration of the cyclic olefin resin (b) in the resin layer (b) is 10 to 80% by weight, and the concentration of the polyolefin resin (c) is 20 to 90% by weight, so that the film has excellent tearability.
According to the fifth aspect of the present invention, the polyolefin resin (c) is a polyethylene resin, so that the film has superior impact strength.
According to the sixth aspect of the present invention, the olefin resin (b) is an ethylene-cyclic olefin copolymer, so that the film has excellent tearability.
According to the seventh aspect of the present invention, the ethylene-cyclic olefin copolymer has a glass transition point of 60° C. or higher, so that the film has excellent tearability.
According to the eighth aspect of the present invention, by further containing a branched polyolefin in at least one of the layers, the low gloss property of the film is further improved.
According to the ninth aspect of the present invention, the resin layer (A) further contains a branched polyolefin, whereby the low gloss property of the film is further improved.
According to the tenth aspect of the present invention, the tear strength in the MD and TD measured by the Elmendorf tear strength based on JIS K7128-2 is 20 N/mm or less, so that the film has further excellent tearability.
According to the eleventh aspect of the present invention, the gloss of at least one outermost surface of the film is 10% or less in gloss measurement at an incident angle and acceptance angle of 20° according to JIS Z8741, so that the film has even better low gloss properties.
According to the twelfth aspect of the present invention, the impact strength at 70 μm in the dirt drop impact measurement based on JIS K7124 is 300 g or more, so that the film has further excellent impact strength.
According to the thirteenth aspect of the present invention, the copolymer (a) is a copolymer of ethylene and methyl acrylate, so that the film has low gloss and excellent impact strength.
Furthermore, according to the fourteenth aspect of the present invention, a packaging bag having low gloss, easy tearability and excellent impact strength is provided.
According to the fifteenth aspect of the present invention, there is provided a sheet having low gloss, easy tearability and excellent impact strength.

Hereinafter, the easy-tear low-gloss film of the present invention will be described in detail for each item. In the present invention, "mainly composed of" a certain component means that the component is the main component in the resin components constituting the composition or layer, and specifically means that the component is contained in 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight of the resin components constituting the layer.

1. Components constituting the easy-tear low-gloss film 1-1. Copolymer (a)
The copolymer (a) of the present invention is a copolymer containing at least ethylene and a functional group-containing monomer. By using the copolymer (a) particularly in the outermost layer of the film, the gloss of the outer surface of the film can be reduced and the impact strength can be increased. The copolymer may be a block copolymer or a random copolymer. The ethylene unit contained in the copolymer (a) may be a low-density polyethylene (LDPE) having a large number of branched chains or a linear low-density polyethylene (LLDPE). As the ethylene, ethylene derived from a petroleum raw material or ethylene derived from a non-petroleum raw material such as a plant raw material can be used.

The functional group-containing monomer means a monomer having at least one functional group other than the group involved in copolymerization with ethylene. Examples of the functional group contained in the functional group-containing monomer include an ether group, a hydroxyl group, an ester group, a carbonyl group, an amino group, and an amide group. From the viewpoint of achieving better low gloss and impact strength, it is preferable to use a functional group-containing monomer having an ester group.

Non-limiting examples of functional group-containing monomers include vinyl acetate, acrylic acid, acrylic acid esters such as methyl acrylate and ethyl acrylate, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, and maleic anhydride. It is preferable to use methyl acrylate from the viewpoint of improving low gloss and impact strength. Only one type of functional group-containing monomer may be used in the copolymer (a), or two or more types of monomers may be used in combination.
When two or more kinds of functional group-containing monomers are used in combination, the ratio of the amounts of each can be determined within any range according to the desired film properties, and is not particularly limited.

The copolymer (a) may be a copolymer further containing a monomer other than ethylene and the functional group-containing monomer. Non-limiting examples of such monomers include α-olefins having 3 to 20 carbon atoms, represented by the structural formula: CH ₂ ═CHR ¹⁸ (wherein R ¹⁸ is a hydrocarbon group having 1 to 18 carbon atoms, and may have a linear structure or a branched structure). The number of carbon atoms of the α-olefin is more preferably 3 to 12. More specifically, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 3-methyl-1-butene, and 4-methyl-1-pentene are included. When a monomer other than ethylene and the functional group-containing monomer is further contained, the content of such a monomer is preferably in the range of 1% by weight to 30% by weight, more preferably in the range of 3% by weight to 25% by weight, based on the entire copolymer (a). By setting it in this range, it is possible to introduce physical properties due to the added monomer while maintaining low gloss and impact strength.

Examples of copolymers (a) include copolymers of ethylene and polar group-containing monomers polymerized with a metal catalyst such as a metallocene catalyst, and ethylene-vinyl acetate copolymers (EVA), ethylene-methyl acrylate copolymers (EMA), ethylene-ethyl acrylate copolymers (EEA), ethylene-methyl methacrylate copolymers (EMMA), ethylene-acrylic acid copolymers (EAA), and ternary copolymers of ethylene, acrylic acid, and maleic anhydride, which are polymerized using an organic peroxide as a reaction initiator.

In the present invention, from the viewpoints of low gloss and impact strength, copolymer (a) is preferably ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA) or ethylene-methyl methacrylate copolymer (EMMA), more preferably ethylene-methyl acrylate copolymer (EMMA).

The quantitative relationship between ethylene and the functional group-containing monomer in copolymer (a) is such that the content of the functional group-containing monomer is preferably in the range of 10% by weight to 30% by weight, and more preferably in the range of 12.5% by weight to 27.5% by weight, relative to the total amount of copolymer (a). If the content of the functional group-containing monomer falls below 10% by weight, low gloss and impact strength may deteriorate, which is undesirable. The content of the functional group-containing monomer can be controlled by adjusting the compounding ratio of each monomer in the preparation process of copolymer (a).

The melt flow rate (MFR) of the copolymer (a) of the present invention at 190°C under a load of 2.16 kg is preferably 0.1 to 20 g/10 min, more preferably 1 to 10 g/10 min. An MFR below 0.1 g/10 min is undesirable because the extrusion characteristics deteriorate, while an MFR above 20 g/10 min is undesirable because the film formation stability deteriorates. The melt flow rate (MFR) is measured by a method conforming to JIS K7210:1999.

Copolymer (a) may be a commercially available product, or may be produced using the monomers described above. Methods of copolymerization using a metal catalyst such as a metallocene catalyst, and copolymerization using an organic peroxide as a reaction initiator are known to those skilled in the art.

Examples of commercially available products that can be used as copolymer (a) include ethylene-methyl acrylate copolymers (EMA), such as "REXPEARL EMA" manufactured by Japan Polyethylene Co., Ltd., ethylene-ethyl acrylate copolymers (EEA), such as "REXPEARL EEA" manufactured by Japan Polyethylene Co., Ltd., and ethylene-methyl methacrylate copolymers (EMMA), such as "Acryft" manufactured by Sumitomo Chemical Co., Ltd.

1-2. Cyclic olefin resin (b)
The cyclic olefin resin (b) of the present invention may be a polymer using at least one type of cyclic olefin as a monomer, and may be a copolymer. For example, norbornene polymer, vinyl alicyclic hydrocarbon polymer, cyclic conjugated diene polymer, etc. are listed. Among these, norbornene polymer is preferred.

［一般式（１）中、Ｒ^１～Ｒ^１２は、それぞれ同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭素数１～２０の炭化水素基からなる群より選ばれるものであり、Ｒ^９及びＲ^１０、並びに、Ｒ^１１及びＲ^１２は、各々一体化して２価の有機基を形成してもよく、Ｒ^９又はＲ^１０と、Ｒ^１１又はＲ^１２とは、互いに環を形成していてもよい。
また、ｎは、０又は正の整数を示し、ｎが２以上の場合には、Ｒ^５～Ｒ^８は、それぞれの繰り返し単位の中で、それぞれ同一でも異なっていてもよい。］ Examples of the cyclic olefin used in the cyclic olefin co-resin (b) include compounds having the following structures.

[In general formula (1), R ¹ to R ¹² may be the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 20 carbon atoms; R ⁹ and R ¹⁰ , and R ¹¹ and R ¹² may each be bonded together to form a divalent organic group; and R ⁹ or R ¹⁰ and R ¹¹ or R ¹² may form a ring together.
Furthermore, n represents 0 or a positive integer, and when n is 2 or more, R ⁵ to R ⁸ may be the same or different in each repeating unit.]

Examples of the cyclic monomer include norbornene-based olefins, such as norbornene, vinylnorbornene, ethylidenenorbornene, norbornadiene, tetracyclododecene, tricyclo[4.3.0.1 ^2,5 ], and tricyclo[4.3.0.1 ^2,5 ]dec-3-ene, and may also include 2-norbornene (NB) and tetracyclo[6.2.1.1 ^3,6 .0 ^2,7 ]dodec-4-ene.

Examples of norbornene-based polymers include ring-opening polymers of norbornene-based monomers (hereinafter also referred to as "COP"), and norbornene-based copolymers (hereinafter also referred to as "COC") obtained by copolymerizing norbornene-based monomers with α-olefins such as ethylene. Hydrogenated products of COP and COC can also be used.

Examples of COC include cyclic olefin copolymers obtained from linear monomers such as α-olefins, such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, and octene-1, and cyclic monomers, such as tetracyclododecene and norbornene. More specifically, the above linear monomers and monocycloalkenes having 3 to 20 carbon atoms, bicyclo[2.2.1]-2-heptene (norbornene) and derivatives thereof, tricyclo[4.3.0.12,5]-3-decene and derivatives thereof, tetracyclo[4.4.0.1.2,5.17,10]-3-dodecene and derivatives thereof, pentacyclo[6.5.1.13,6.02,7.09,13]-4-pentadecene and derivatives thereof, pentacyclo[7.4.0.12,5.19,12.08,13]-3-pentadecene and derivatives thereof, pentacyclo[8.4.0.12,5.19,12.08,13]-3-hexadecene and derivatives thereof, pentacyclo[6.6.1.13,6.02,7.09,14]-4-hexadecene and derivatives thereof, hexacyclo[6.6.1.13,6.110,13.02,7.09,14]-4-hexadecene and derivatives thereof, Putadecene and its derivatives, heptacyclo[8.7.0.12,9.14,7.111,17.03,8.012,16]-5-eicosene and its derivatives, heptacyclo[8.7.0.13,6.110,17.112,15.02,7.011,16]-4-eicosene and its derivatives, heptacyclo[8.8.0.12,9.14,7.111,18.03,8.012,17]-5-heneicosene Examples of the cyclic olefin copolymers include copolymers of cyclic olefins such as octacyclo[8.8.0.12,9.14,7.111,18.113,16.03,8.012,17]-5-docosene and its derivatives, and nonacyclo[10.9.1.14,7.113,20.115,18.02,10.03,8.012,21.014,19]-5-pentacosene and its derivatives. The linear monomers and cyclic monomers can be used alone or in combination of two or more kinds. Such cyclic olefin copolymers can be used alone or in combination. The cyclic olefin resin (b) can also be used in combination with the COP and COC. In that case, different performances of the COP and COC can be imparted.

In the present invention, the cyclic olefin resin (b) is preferably a COC because of its dispersibility in polyethylene. In addition, the COC is preferably an ethylene-cyclic olefin copolymer in which the linear monomer is ethylene. Furthermore, the cyclic monomer is preferably norbornene or the like.

In the present invention, when an ethylene/cyclic olefin copolymer is used as the cyclic olefin resin (b), the ethylene/cyclic olefin content is preferably 15-40/85-60 by weight. More preferably, it is 30-40/70-60. If the ethylene content is less than 15% by weight, the rigidity becomes too high, which is undesirable as it may deteriorate the inflation moldability and bag-making suitability. On the other hand, if the ethylene content is 40% by weight or more, it is undesirable as it may not be possible to obtain sufficient tearability and rigidity. If the content ratio is within this range, it is preferable as the rigidity, tearability, processing stability, and impact strength of the film are improved.

Furthermore, the ethylene-cyclic olefin copolymer preferably has a glass transition point of 60°C or higher. More preferably, it has a glass transition point of 70°C or higher. If the cyclic olefin content is below the above range, the glass transition point will be below the above range, and there is a risk that, for example, the barrier properties for aromatic components will be reduced, sufficient rigidity will not be obtained, and suitability for high-speed packaging machines will be poor. On the other hand, if the cyclic olefin content is above the above range, the glass transition point will be too high, and there is a risk that the melt moldability of the copolymer and its adhesion to olefin-based resins will be reduced, which is undesirable.

As described above, the cyclic olefin resin (b) may contain a monomer with a chain structure such as ethylene as a comonomer. In addition to ethylene, α-olefins having 3 to 20 carbon atoms and the like can also be used as comonomers for the cyclic olefin resin (b). When such a comonomer is used instead of ethylene, the content ratio can be within the range described for ethylene. Also, such a comonomer can be used in addition to the ethylene-cyclic olefin copolymer.

The weight average molecular weight of the cyclic olefin resin (b) is preferably 5,000 to 500,000, and more preferably 7,000 to 300,000.

Commercially available products that can be used as the cyclic olefin resin (b) include ring-opening polymers (COP) of norbornene monomers such as "ZEONOR" manufactured by Zeon Corporation, and norbornene copolymers (COC) such as "APEL" manufactured by Mitsui Chemicals, Inc. and "TOPAS" manufactured by Polyplastics. In the present invention, TOPAS grade 8007 is preferred because the content ratio of norbornene monomers is within the above-mentioned range and because of processability, etc.

1-3. Polyolefin resin (c)
In the film of the present invention, the layer containing the cyclic olefin resin (b) preferably contains a polyolefin resin (c). The polyolefin resin may be either a polyethylene resin or a polypropylene resin, but it is more preferable to use a polyethylene resin.
When the polyolefin resin is a polyethylene resin, examples of the polyolefin resin include homopolyethylene or ethylene-α-olefin copolymer polymerized by a metallocene catalyst, Ziegler catalyst, Phillips catalyst, or the like, or high-pressure low-density polyethylene polymerized using an organic peroxide as a reaction initiator, but from the viewpoint of interface strength with the cyclic olefin resin, an ethylene-α-olefin copolymer having a linear molecular structure (linear low-density polyethylene) is preferred. The density of the polyethylene resin is not particularly limited as long as it is within the density range of 0.800 g/cm ³ to 0.970 g/cm ³ , which is the general density range of polyethylene. Examples of the type of α-olefin copolymerized with ethylene include α-olefins having 3 to 8 carbon atoms, specifically propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, 4-methylpentene-1, and the like. In the present invention, the density is a value measured based on JIS K6922-2.

The melt flow rate (MFR) of the polyethylene resin at 190°C is preferably 20 g/10 min or less from the viewpoint of film formation stability. If the MFR exceeds 20 g/10 min, the film formation stability may deteriorate due to a decrease in melt tension.

When the polyolefin resin is a polypropylene resin, any of the following may be used: a propylene homopolymer, a random copolymer or a block copolymer of propylene with other α-olefins such as ethylene or butene-1. A blend of one or more of the above polymers may be used, but from the viewpoint of interfacial strength with the cyclic olefin resin, it is preferable to use a linear ethylene-propylene random block copolymer obtained from a metallocene catalyst as the main component, such as the Wintech (registered trademark) series manufactured by Japan Polypropylene Corporation.

The melt flow rate (MFR) of the polypropylene resin at 230°C is preferably 15 g/10 min or less from the viewpoint of film-forming stability under high-temperature molding. If the MFR exceeds 15 g/10 min, the film-forming stability may deteriorate due to a decrease in melt tension.

2. Easy-to-tear low-gloss film As described above, the easy-to-tear low-gloss film of the present invention is a film characterized by containing a copolymer (a) containing at least ethylene and a functional group-containing monomer and a cyclic olefin resin (b) in any layer, and may be either a single-layer structure or a multilayer structure. For example, in the case of a single-layer structure, a single-layer film consisting of the copolymer (a) and the cyclic olefin resin (b), or a single-layer film consisting of the copolymer (a), the cyclic olefin resin (b) and a polyolefin resin (c) can be mentioned. In the case of a multi-layer structure, for example, a three-layer film composed of at least a resin layer (A) mainly composed of the copolymer (a) and a resin layer (B) containing a cyclic olefin resin (b) and a polyolefin resin (c), laminated in the order of resin layer (A)/resin layer (B)/resin layer (A) from the outermost layer side, or a five-layer film containing a resin layer (C) mainly composed of a polyolefin resin (c) and laminated in the order of resin layer (A)/resin layer (C)/resin layer (B)/resin layer (C)/resin layer (A) from the outermost layer side. In the case of a multi-layer structure, it is preferable that the resin layer (A) that exhibits low gloss is disposed on one of the outermost layers. That is, it is preferable that at least one of the layers that becomes the surface of the film contains the copolymer (a). There is no particular limit to the number of layers laminated.

When the easy-tear low-gloss film has a single layer structure, the film contains copolymer (a) and cyclic olefin resin (b), and may further contain polyolefin resin (c). The blending amount of copolymer (a) is preferably 10% to 99% by weight, more preferably 15% to 80% by weight, based on the entire film. The blending amount of cyclic olefin resin (b) is preferably 1 to 90% by weight, more preferably 20% to 85% by weight, based on the entire film. The blending amount of polyolefin resin (c) can be arbitrarily designed according to the total amount of copolymer (a) and cyclic olefin resin (b), but is more preferably in the range of 40 parts by weight to 160 parts by weight, based on 100 parts by weight of cyclic olefin resin (b).

When the easy-tear low-gloss film has a multi-layer structure, the resin layer (A) is mainly composed of the above-mentioned copolymer (a). Therefore, the resin layer (A) contains 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more of the copolymer (a). The resin layer (A) may be a layer consisting of only the copolymer (a). When the resin layer (A) contains components other than the copolymer (a), the other components constituting the resin layer (A) include the above-mentioned cyclic olefin resin (b) and polyolefin resin (c). In particular, when the polyolefin resin (c) is contained, a polyethylene resin is preferable from the viewpoint of compatibility with the copolymer (a), and preferably a branched polyolefin is added. Examples of the branched polyethylene include high-pressure low-density polyethylene polymerized using an organic peroxide as a reaction initiator, and linear low-density polyethylene obtained by specific catalytic polymerization and having long-chain branches introduced therein, and more preferably high-pressure low-density polyethylene. The addition of these branched polyolefins, particularly preferably branched polyethylene, further improves the low gloss. In addition, when a branched polyolefin is used, it is preferably blended in the resin layer (A), but as described later, it may be blended in other resin layers, and low gloss can be further improved by including the branched polyolefin in at least one of the layers. The MFR of the branched polyolefin, particularly the branched low density polyethylene, at 190°C and under a load of 2.16 kg is 0.05 to 10 g/10 min, preferably 0.1 to 5.0 g/10 min, and more preferably 0.1 to 2.0 g/10 min. If the MFR is less than 0.05 g/10 min, extrusion processability may deteriorate, which is not preferable, and if the MFR exceeds 10 g/10 min, low gloss may deteriorate, which is not preferable. The density is in the range of 0.900 to 0.935 g/cm ³ , preferably 0.919 to 0.927 g/cm ³ . The amount of these branched polyolefins added is 2 to 50% by weight, preferably 3 to 35% by weight, and more preferably 5 to 30% by weight, based on the total weight of the resin composition constituting the resin layer (A).

When the tearable low gloss film has a multi-layer structure, the resin layer (B) contains a cyclic olefin resin (b) and a polyolefin resin (c). The concentration of the cyclic olefin resin (b) in the resin layer (B) is preferably 10 to 80% by weight, more preferably 20 to 60% by weight. If the concentration of the cyclic olefin resin is less than 10% by weight, this is not preferred because the tearability may deteriorate, and if it exceeds 80% by weight, this is not preferred because the film formation stability may deteriorate. The concentration of the polyolefin resin (c) in the resin layer (B) is preferably 20 to 90% by weight, more preferably 40 to 80% by weight.

The resin layer (B) may contain a resin other than the cyclic olefin resin (b) and the polyolefin resin (c). Examples of such resins include the copolymer (a) or a branched polyolefin. Specific examples of the copolymer (a) or the branched polyolefin are as described above. The amount of such resins is not particularly limited as long as the total amount of the cyclic olefin resin (b) and the polyolefin resin (c) is 30% by weight or more relative to the entire resin layer.

The tearable low gloss film of the present invention may contain a resin layer other than the resin layers (A) and (B). Such a resin layer may be a resin layer (C) such as a layer consisting only of the cyclic olefin resin (b), a layer consisting only of the polyolefin resin (c), or a layer consisting of a branched polyolefin. In addition, other layers known to those skilled in the art, such as an adhesive layer between layers, may be included as long as the object of the present invention is not impaired.

In the present invention, each resin layer constituting the film may contain components such as anti-fogging agents, antistatic agents, heat stabilizers, nucleating agents, antioxidants, lubricants, anti-blocking agents, release agents, UV absorbers, colorants, and foaming agents, to the extent that the object of the present invention is not impaired. In particular, it is preferable to appropriately add lubricants and anti-blocking agents to impart processing suitability during film molding and packaging suitability for filling machines.

The thickness of the easy-to-tear low-gloss film is preferably 20 to 200 μm, and more preferably 30 to 200 μm. If the thickness of the multilayer film is in the range of 30 to 200 μm, the layers exposed on the outermost surface can be heat-sealed to each other, allowing it to be used as a packaging material. Furthermore, if the thickness of the multilayer film is 50 μm or more, excellent secondary formability can be obtained. When the film has a multilayer structure, the thickness of the resin layer (B) is preferably 20 to 70% of the entire film. More preferably, it is 20 to 50%. For example, when a three-layer structure of resin layer (A)/resin layer (B)/resin layer (A) is used, the thickness of each layer can be about 1:0.5:1 to 1:4:1. If the thickness of the resin layer (B) is less than 20% of the total, sufficient easy-to-tear property may not be obtained, which is not preferable. On the other hand, if it is thicker than 70%, the rigidity becomes too high, which may deteriorate the inflation moldability and bag-making suitability, which is not preferable. If the thickness of the resin layer (B) is within this range, it is preferable because it has excellent tearability and is cost-effective.

The easily tearable low-reflection film of the present invention is manufactured by forming into a film or sheet shape by air-cooled inflation, water-cooled inflation, T-die chill roll method, etc. For example, in the case of a single-layer structure, at least the copolymer (a) and the cyclic olefin resin (b) are heated and melted in the same extruder and manufactured by the above-mentioned processing method. In the case of a multilayer structure, for example, the above-mentioned resin layer (A) and resin layer (B) are heated and melted in separate extruders, and laminated in the molten state in the order of resin layer (A) / resin layer (B) / resin layer (A) by a method such as a coextrusion multilayer die method or a feed block method, and then manufactured by the above-mentioned processing method. This coextrusion method is preferable because it is possible to relatively freely adjust the thickness ratio of each layer, and a multilayer film with excellent hygiene and cost performance can be obtained.

The tearable low gloss film produced by the above-mentioned production method is characterized by the fact that it does not require secondary processing such as a general stretching process to impart tearability, and exhibits tearability through film-forming alone. This is because, for example, when a film is produced by inflation molding using the above-mentioned specific raw material composition and layer composition, the cyclic olefin resin forms a dispersion structure in which it is cooled and solidified while being stretched in the machine direction (MD) of the film. Therefore, since the viscosity of the cyclic olefin resin at the processing temperature during extrusion processing has a significant effect on the dispersion structure, it is necessary to select an optimal cyclic olefin resin that is particularly suited to the processing temperature. For example, when the processing temperature is about 170°C to 230°C, the glass transition temperature of the cyclic olefin resin is more preferably 60°C to 140°C.

The easy-tear low-gloss film of the present invention has low tear strength in both MD and TD, and can be made user-friendly by being easy to open, etc. From the viewpoint of obtaining good easy-tear properties, it is preferable that the Elmendorf tear strength is 20 N/mm or less in both MD and TD, and it is more preferable that the Elmendorf tear strength is 15 N/mm or less in both MD and TD. The Elmendorf tear strength can be measured based on JIS K7128-2.

The easy-tear low-gloss film of the present invention has a low surface gloss and can be used as a film with excellent design and a luxurious feel. The gloss is preferably 10% or less, and more preferably 5% or less, when measured at an incident angle and a receiving angle of 20°. The gloss can be measured based on JIS Z8741.

The easily tearable low gloss film of the present invention has high impact strength and can be used in a variety of applications, such as packaging bags and protective sheets. The impact strength is preferably 300 g or more at 70 μm in a dirt drop impact measurement, and more preferably 400 g or more from the standpoint of strength. The impact strength can be measured based on JIS K7124.

3. Packaging Bags Examples of packaging bags made of the easily tearable low gloss film of the present invention include packaging bags and packaging containers used for food, medicines, medical equipment, industrial parts, miscellaneous goods, magazines, etc.
The packaging bag may be formed by overlapping the inner or outer layers of the easy-tear low-gloss film of the present invention and heat sealing them together. Two sheets of the film are cut to the desired size of the packaging bag, overlapped, and heat-sealed at three sides to form a bag, and then the contents are filled from the one side that is not heat-sealed, and then heat-sealed to seal the bag. The bag can also be used as a packaging bag by using one sheet of film in the form of horizontal pillow packaging or vertical pillow packaging.

In order to weaken the initial tear strength and improve the ease of opening, it is preferable to form any tear initiation portion such as a V notch, an I notch, a perforation, or a micropore in the packaging material using the easy-tear low gloss film of the present invention. Examples of the portion where the notch or the like is formed include a sealed portion, the upper and lower ends of the packaging material, the left and right fold portions, the back stretch portion of a pillow package, etc. Depending on the shape of the packaging material and the notch forming portion, a sealed portion having a shape such as a crescent shape can be provided around the notch to ensure internal airtightness.
Further, the packaging container may be a deep drawn product (a base material having an opening at the top) obtained by secondary molding of the film of the present invention, and representative examples thereof include the bottom material of a vacuum packaging bag for food use and the bottom material of a blister pack.
Examples of the secondary forming method include vacuum forming, pressure forming, vacuum pressure forming, etc. Among these, vacuum forming is preferred because it allows a film or sheet to be formed in-line on a packaging machine and filled with contents.

Generally, the machine direction (MD) of a packaging bag is an axis parallel to the line direction during filling and bag making, and corresponds to the machine direction (MD) of the original film. For example, in the case of horizontal pillow packaging material, the long direction of the back lining corresponds to the machine direction (MD) of the packaging bag, and also corresponds to the machine direction (MD) of the film.

4. Sheets Examples of sheets made of the easy-tear low-gloss film of the present invention include protective sheets, release sheets, and low-reflection sheets for use in foods, medicines, medical instruments, industrial parts, miscellaneous goods, magazines, police identification, and the like.
The sheet may be in the form of either a tube film or a flat film, but is more preferably in the form of a flat film during practical use. The flat film in the present invention means a single film obtained by a T-die chill roll method, or a single film obtained by slitting one or both ends of a tubular film obtained by an inflation method.

In the sheet made of the easy-tear low-gloss film of the present invention, it is preferable that the above-mentioned copolymer (a) that exhibits low reflectivity is exposed on at least one outer layer surface of the sheet, and examples of the layer structure include resin layer (A)/resin layer (B), resin layer (A)/resin layer (B)/resin layer (A), etc.
In order to weaken the initial tear strength and improve the ease of tearing, it is preferable to form any tear initiation portion such as a V notch, an I notch, a perforation, or a micropore in the sheet using the easy-tear low gloss film of the present invention. Examples of the portion where a notch or the like is formed include both ends of the sheet.

The present invention will be described in more detail below with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples.
(1) Raw materials used (1-1) Copolymer (a)
"Rexpearl (registered trademark) EMA" manufactured by Japan Polyethylene Corporation, MFR 2.0 g/10 min, density 0.937 g/cm ³ ; ethylene-methyl acrylate copolymer with MA content of 15 wt % (1-2) Cyclic olefin resin (b)
Polyplastics Co., Ltd. "TOPAS (registered trademark) 8007F-600", an ethylene-norbornene copolymer having a glass transition temperature of 78°C (1-3) polyolefin resin (c)
"Novatec (registered trademark) LD LF129" manufactured by Japan Polyethylene Co., Ltd., high-pressure low-density polyethylene with MFR 0.3 g/10 min and density 0.922 g/ ^cm3. "Novatec (registered trademark) LL UF320" manufactured by Japan Polyethylene Co., Ltd., linear low-density polyethylene with MFR 0.9 g/10 min and density 0.922 g/ ^cm3 . "Novatec (registered trademark) LD LF240" manufactured by Japan Polyethylene Co., Ltd., high-pressure low-density polyethylene with MFR 0.7 g/10 min and density 0.924 g/ ^cm3 . "Novatec (registered trademark) LL UF420" manufactured by Japan Polyethylene Co., Ltd., linear low-density polyethylene with MFR 0.9 g/10 min and density 0.924 g/ ^cm3.

(2) Blown film molding (2-1) Multi-layer film molding machine: 5 types, 5 layers, blown film molding machine, die diameter: 150 mmφ
Die lip clearance: 3mm
Processing temperature: 190°C
Layer ratio: 1/1.4/2.4/1.4/1
Blow ratio: 1.5
Take-up speed: 10 m/min
Film thickness: 70 μm

(2-2) Single layer film molding machine: Single layer inflation molding machine Die diameter: 75 mmφ
Die lip clearance: 1mm
Processing temperature: 150°C
Blow ratio: 2.0
Take-off speed: 15 m/min
Film thickness: 50 μm

(3) Physical Property Evaluation Method (3-1) Glossiness Measurement was performed using the following device and conditions based on JIS Z8741. Prior to the measurement, calibration was performed using a black standard plate (angle 20°, glossiness 87.8%).
Equipment: Suga Test Instruments Co., Ltd. UGV-4D
Incident light angle: 20°
Measurement environment: temperature 23℃, humidity 50%

(3-2) Elmendorf tear strength Based on JIS K7128-2, the Elmendorf tear strength was evaluated using the following device, where MD is the film flow direction, and TD is the value in the perpendicular direction thereto.
Equipment: Digital Elmendorf tear tester, model SA (manufactured by Toyo Seiki Seisakusho Co., Ltd.)
Measurement environment: temperature 23℃, humidity 50%

(3-3) Dirt Drop Impact Strength: Measured by Method A in accordance with JIS K7124.
Measurement environment: temperature 23℃, humidity 50%

Example 1
Using the above raw materials, a two-kind, five-layer inflation film was obtained by laminating the above-mentioned materials by the inflation molding method described in (2-1). The concentration of the cyclic olefin resin in the middle layer was 49% by weight. The types and compositions of the resins constituting each layer are shown in Table 1.

Example 2
An inflation film was obtained in the same manner as in Example 1, except that the intermediate layer of Example 1 contained the copolymer (a) in the concentration shown in Table 1.

(Comparative Example 1)
Instead of the copolymer (a), "Novatec (registered trademark) LD LF240" manufactured by Japan Polyethylene Co., Ltd. was used to obtain a two-kind five-layer inflation film by the inflation molding method described in (2-1) above. The concentration of the cyclic olefin resin in the intermediate layer was 49% by weight.

(Comparative Example 2)
All layers were made of Novatec (registered trademark) LD LF240 manufactured by Japan Polyethylene Co., Ltd., and laminated by the inflation molding method described in (2-1) above to obtain a one-kind five-layer inflation film. No cyclic olefin resin was used.

(Comparative Example 3)
All layers were made of Novatec (registered trademark) LL UF420 manufactured by Japan Polyethylene Co., Ltd., and laminated by the inflation molding method described in (2-1) above to obtain a one-kind five-layer inflation film. No cyclic olefin resin was used.

(Comparative Example 4)
A single-layer inflation film was obtained by the inflation molding method described in (2-2) above using the copolymer (a). No cyclic olefin resin was used.

The gloss, Elmendorf tear strength, and dart drop impact strength of the single-layer or multilayer films obtained in each of the Examples and Comparative Examples were measured according to the methods described in (3-1) to (3-3) above. The results are shown in Table 1 below.

As is clear from Table 1, Comparative Example 1 uses a cyclic olefin resin in the intermediate layer, so it has excellent tearability, but the low gloss and impact strength of the outer surface of the film are poor. In addition, Comparative Examples 2 and 3 do not use a cyclic olefin resin, so they are poor not only in tearability but also in low gloss and impact strength. Comparative Example 4 uses a copolymer of ethylene and methyl acrylate, so it has excellent low gloss and impact strength, but does not use a cyclic olefin resin, so it has poor tearability. On the other hand, Examples 1 and 2 use a copolymer of ethylene and methyl acrylate on both outer surfaces of the film, and further use a cyclic olefin resin in the intermediate layer, so they are excellent not only in low gloss on the outer surface of the film, but also in tearability and impact strength. Therefore, it is suitable for films, packaging bags, sheets, etc. that require low gloss, tearability, and high impact strength.

Claims (13)

A multi -layered, easy-tear, low-gloss film comprising a laminate of multiple resin layers including at least two layers of a resin layer (A) whose main component is a copolymer (a) selected from the group consisting of an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene-methyl methacrylate copolymer, and a resin layer (B) containing a cyclic olefin resin (b) and a polyolefin resin (c), the resin layer (A) being disposed as at least the outermost layer, and the copolymer (a) having a methyl acrylate, ethyl acrylate, or methyl methacrylate content of 10% by weight or more relative to the entire copolymer (a) . The resin layer (B) has a concentration of cyclic olefin resin (b) of 10 to 80% by weight, and a concentration of polyolefin resin (c) of 20 to 90% by weight. The tearable low gloss film according to claim 1 . 3. The easily tearable low gloss film according to claim 1 , wherein the polyolefin resin (c) is a polyethylene resin. 4. The easily tearable low gloss film according to claim 1 , wherein the cyclic olefin resin (b) is an ethylene-cyclic olefin copolymer. 5. The easily tearable low gloss film according to claim 4 , wherein the ethylene-cyclic olefin copolymer has a glass transition temperature of 60[deg.] C. or higher. 6. The easily tearable low gloss film according to claim 1 , further comprising a branched polyolefin in at least one of its layers. 7. The easily tearable low gloss film according to claim 1 , wherein the resin layer (A) further contains a branched polyolefin. 8. The easily tearable low gloss film according to claim 1 , characterized in that the tear strength in MD and TD measured by Elmendorf tear strength based on JIS K7128-2 is 20 N/mm or less. The easily tearable low gloss film according to any one of claims 1 to 8 , characterized in that, in gloss measurements at an incident angle and a receiving angle of 20° based on JIS Z8741, the gloss of at least one outermost layer surface of the film is 10% or less. 10. The easily tearable low gloss film according to claim 1 , characterized in that the impact strength at 70 μm is 300 g or more in a dirt drop impact measurement based on JIS K7124. 11. The easily tearable low gloss film according to claim 1, wherein the copolymer (a) is an ethylene-methyl acrylate copolymer . A packaging bag using the easily tearable low gloss film according to any one of claims 1 to 11 . A sheet using the easily tearable low gloss film according to any one of claims 1 to 11 .