JP7824741B2 - Packaging film - Google Patents

Description

The present invention relates to packaging films, particularly food packaging films.

Traditionally, packaging materials have been developed to suit the contents of various product sectors, including food, beverages, pharmaceuticals, and chemicals. Films made from olefin polymers are widely used as packaging materials for a variety of purposes due to their excellent transparency and mechanical properties. One of the functions of packaging materials is to prevent the contents from adhering to the inner surface of the packaging material, i.e., to prevent the contents from remaining on the film surface of the packaged item (adhesion/remaining prevention performance).

Patent Document 1 describes how, in order to impart adhesion and residue prevention properties to packaging materials, water-repellent particles such as resin beads and oxide microparticles are attached to part or all of the outermost layer of the packaging material, allowing the water-repellent particles to be more securely held in place by the unevenness of the resin beads, thereby demonstrating excellent thermal adhesion and non-adhesion properties (water-repellent properties).

Patent Document 2 also describes a lid material that combines a base layer, a sealing layer, and hydrophobic oxide microparticles attached to the surface of the sealing layer, making it possible to prevent the hydrophobic oxide microparticles from falling off and maintaining the effect of preventing yogurt from sticking for a long period of time.

On the other hand, Patent Document 3 describes a packaging material that can prevent contents from adhering or remaining on the film surface by creating an uneven surface without adding modifiers such as fine particles or lubricants to the film surface.

JP 2013-180790 A Japanese Patent Application Laid-Open No. 2020-158146 Japanese Patent Application Laid-Open No. 2017-217866

In conventional packaging materials, the oxide microparticles added as anti-adhesion agents have insufficient affinity with olefin-based polymers, which means that the oxide microparticles may fall off during film formation or secondary processing, potentially preventing adhesion and residue from being fully achieved.

Furthermore, in the resin film disclosed in Patent Document 3, the adhesive strength of the heat-sealed portions of the films is not considered.
Furthermore, when used as a packaging material for food, for example, as a packaging material for retort foods, there is a problem that if the inner walls of the bag in the parts not filled with food adhere to each other during pressure and heat treatment, it becomes difficult to remove the food.

The inventors aimed to provide a packaging material film that has even better anti-adhesion and anti-residue properties, high adhesive strength when the film is heat-sealed, and prevents films from adhering to each other after boiling. In other words, the object of the present invention is to provide a packaging material film that has excellent anti-adhesion and anti-residue properties, high adhesive strength when the film is heat-sealed, and prevents films from adhering to each other after boiling (excellent blocking resistance).

The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved by a packaging material film having the following configuration, thereby achieving the present invention.
That is, the present invention relates to the following [1] to [5].

[1] A packaging material film comprising an olefin polymer (A) and ultra-high molecular weight olefin polymer fine particles (B), wherein the ultra-high molecular weight olefin polymer fine particles (B) are uncrosslinked ultra-high molecular weight olefin polymer fine particles (B1) and/or crosslinked ultra-high molecular weight olefin polymer fine particles (B2) obtained by crosslinking the (B1) by irradiation with radiation, and satisfying the following requirements (i) to (iii):
(i) The intrinsic viscosity [η] measured in decalin solvent at 135°C is in the range of 5 to 50 dl/g.
(ii) The average particle size d50 is in the range of 3 to 45 μm.
(iii) 50% by mass or more passes through a 45 μm mesh sieve.

[2] The packaging material film described in [1] above, wherein at least a portion of the ultra-high molecular weight olefin polymer fine particles (B) is present on the surface of the packaging material film.

[3] The packaging material film described in [1] or [2] above, which is used to package an item to be packaged, has an uneven surface that comes into contact with the item to be packaged, and has an arithmetic mean roughness Sa of 0.1 to 5.0 μm.

[4] The packaging material film according to any one of [1] to [3], wherein the content of the ultra-high molecular weight olefin polymer fine particles (B) is in the range of 0.1 to 20 parts by mass per 100 parts by mass of the total of the olefin polymer (A) and the ultra-high molecular weight olefin polymer fine particles (B).

[5] The packaging material film described in any one of [1] to [4] above, which is used for food packaging.

The present invention provides a packaging material film that has excellent adhesion and residue prevention properties, high adhesive strength when the film is heat-sealed, and excellent blocking resistance after boiling.

1A and 1B are schematic diagrams showing how films are stacked in a blocking resistance evaluation test in the examples ((a) before stacking, (b) after stacking, (c) after sandwiching between metal plates). 1A and 1B are schematic diagrams showing how an aluminum rod is sandwiched between overlapping films in a blocking resistance evaluation test in the Examples ((a) before sandwiching, (b) when sandwiching, (c) after binding the two films at the end of the tester). FIG. 2 is a schematic view showing a state in which a film is fixed to a testing machine in a blocking resistance evaluation test in the examples. FIG. 2 is a schematic diagram showing how overlapping films are peeled off with an aluminum rod in a blocking resistance evaluation test in the Examples.

The packaging material film according to the present invention will be specifically described below.
In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means not less than X and not more than Y. For example, "1.0 to 35.0 μm" means "not less than 1.0 μm and not more than 35.0 μm."

The packaging material film of the present invention contains an olefin polymer (A) and ultra-high molecular weight olefin polymer fine particles (B).

<Olefin Polymer (A)>
Examples of olefin polymers that can be used as the olefin polymer (A) in the present invention include those obtained by polymerizing ethylene and one or more olefins selected from linear or branched α-olefins having 3 to 20 carbon atoms.

Specific examples of linear or branched α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Of these α-olefins, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene are preferred.

In addition to the α-olefins described above, the monomer components constituting the olefin-based polymer in the present invention may also include cyclic olefins, functionalized vinyl compounds, monomers having polar groups (e.g., carbonyl groups, hydroxyl groups, ether bond groups, etc.) and polymerizable carbon-carbon double bonds in the molecule (hereinafter also referred to as polar group-containing monomers), conjugated dienes, non-conjugated polyenes, etc., within the scope of the present invention.

Cyclic olefins include cyclic olefins having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, such as cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, tetracyclododecene, and 2-methyl-1,4:5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene.

The functionalized vinyl compounds include aromatic vinyl compounds and alicyclic vinyl compounds.
Examples of aromatic vinyl compounds include mono- or polyalkylstyrenes such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene; functional group-containing styrene derivatives such as methoxystyrene, ethoxystyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylbenzyl acetate, hydroxystyrene, o-chlorostyrene, and p-chlorostyrene; and 3-phenylpropylene, 4-phenylpropylene, and α-methylstyrene. Examples of alicyclic vinyl compounds include vinylcyclohexane and vinylcycloheptane.

Of the above-mentioned olefin polymers, ethylene polymers, propylene polymers, and 4-methyl-1-pentene polymers are preferably used.
The ethylene-based polymer contains ethylene as a main constituent monomer component, and typically contains 50 mol % or more, preferably 80 mol % or more, of ethylene. Specific examples of the ethylene-based polymer include high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-low-pressure high-density polyethylene (HDPE), and very low-density polyethylene (VLDPE).

More specific examples of ethylene polymers include high-density polyethylene having a density in the range of 940 kg/m ^or more and ^less than 980 kg/m, low-density polyethylene having a density in the range of 900 kg/m ^or more ^and less than 940 kg/m, medium-density polyethylene, linear low-density polyethylene, and very low-density polyethylene, as well as blends thereof. While there are no particular limitations on which of these to employ, low-density polyethylene and linear low-density polyethylene are preferred from the viewpoint of achieving an excellent balance between transparency and processability. The density of the ethylene polymer is measured according to the density gradient tube method of JIS K7112.

The melt flow rate (MFR) of ethylene polymers is typically in the range of 0.01 to 100 g/10 min, preferably 0.02 to 50 g/10 min, and more preferably 0.02 to 30 g/10 min. MFR is measured in accordance with JIS K7210 at 190°C and a test load of 2.16 kg.

The ethylene-based polymer refers to an ethylene homopolymer, a copolymer of ethylene with a small amount of an α-olefin, or a blend thereof. The copolymerization component of the copolymer preferably accounts for 50 mol% or less of all monomer units, and more preferably 20 mol% or less. Examples of copolymerization components of the copolymer are preferably olefins having 3 to 20 carbon atoms, including linear or branched α-olefins, cyclic olefins, functionalized vinyl compounds, polar group-containing monomers, conjugated dienes, and non-conjugated polyenes.

Propylene-based polymers contain propylene as the main constituent monomer, typically at 50 mol% or more, and preferably 80 mol% or more. Specific examples of propylene-based polymers include propylene homopolymers, block copolymers or random copolymers of propylene and the above-mentioned α-olefins other than propylene, and blends thereof. While there are no particular restrictions on which of these to use, homopolymers with high melting points and rigidity are preferred from the perspective of suppressing the stickiness of the olefin-based polymer composition.

The density of the propylene polymer is usually in the range of 895 to 930 kg/m ^3. The density of the polypropylene polymer is measured in accordance with the density gradient tube method of JIS K7112.
The melt flow rate (MFR) of the propylene polymer is usually in the range of 0.01 to 200 g/10 min, preferably 1 to 100 g/10 min, and more preferably 1 to 50 g/10 min. The MFR is measured in accordance with JIS K7210 at 230°C and a test load of 2.16 kg.

4-methyl-1-pentene polymers contain 4-methyl-1-pentene as the main constituent monomer, typically containing 50 mol% or more, and preferably 80 mol% or more, of 4-methyl-1-pentene. Specific examples of 4-methyl-1-pentene polymers include 4-methyl-1-pentene homopolymers, block copolymers or random copolymers of 4-methyl-1-pentene with ethylene and at least one linear or branched α-olefin having 3 to 20 carbon atoms (excluding 4-methyl-1-pentene), and blends thereof.

The density of the 4-methyl-1-pentene polymer is usually in the range of 820 to 850 kg/m ^3. The density of the 4-methyl-1-pentene polymer is measured in accordance with the density gradient tube method of JIS K7112.

The melt flow rate (MFR) of 4-methyl-1-pentene polymers is typically in the range of 0.01 to 200 g/10 min, preferably 1 to 100 g/10 min, and more preferably 1 to 50 g/10 min. MFR is measured in accordance with JIS K7210 at 260°C and a test load of 5.0 kg. When the MFR is within the above range, the 4-methyl-1-pentene polymers have excellent moldability and mechanical strength properties.

<Ultra-high molecular weight olefin polymer fine particles (B)>
The ultra-high molecular weight olefin polymer fine particles (B) (hereinafter also referred to as "fine particles (B)") are uncrosslinked ultra-high molecular weight olefin polymer fine particles (B1) and/or crosslinked ultra-high molecular weight olefin polymer fine particles (B2) obtained by crosslinking the (B1) by irradiation with radiation, which satisfy the following requirements (i) to (iii):

Requirement (i): The intrinsic viscosity [η] measured in decalin solvent at 135° C. is in the range of 5 to 50 dl/g.
In the present invention, the intrinsic viscosity [η] of the fine particles (B1) measured in decalin solvent at 135° C. is in the range of 5 to 50 dl/g, preferably 5 to 40 dl/g, more preferably 5 to 30 dl/g, still more preferably 5 to 20 dl/g, and particularly preferably 5 to 15 dl/g. An intrinsic viscosity in the above range is preferred because it results in excellent abrasion resistance of the packaging material film, resistance to food adhesion to the film, and blocking resistance.

Requirement (ii): The average particle size d50 is in the range of 3 to 45 μm.
In the present invention, the average particle diameter d50 of the fine particles (B1) or (B2) is the value at which the integrated value of the particle shape distribution becomes 50 mass% when the weight-based particle size distribution is measured by the Coulter counter method, and the average particle diameter d50 is in the range of 3 to 45 μm, preferably 3 to 35 μm, more preferably 3 to 25 μm, even more preferably 3 to 15 μm, still more preferably 3 to 10 μm, and particularly preferably 3 to 8 μm.

An average particle size of 45 μm or less is preferable because it prevents a decrease in the strength of the packaging material film. On the other hand, an average particle size of 3 μm or more is preferable because it results in an uneven surface of the packaging material film that comes into contact with the packaged item.

Requirement (iii): 50% by mass or more passes through a 45 μm mesh sieve.
In the present invention, the fine particles (B1) or (B2) are those which pass through a 45 μm mesh sieve (JIS Z 8801 #325) using a vibrating sieve or an ultrasonic vibrating sieve in an amount of 50 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 99 mass% or more.

A passing amount of 50% by mass or more means that the amount of coarse particles present is small. When the amount of coarse particles is small, it is considered preferable to add a crosslinked ultra-high molecular weight olefin polymer produced from the ultra-high molecular weight olefin polymer to the packaging material film, as the added substance (particles) will efficiently contribute to improving adhesion prevention and residue prevention performance.

In the present invention, ultra-high molecular weight olefin polymers include homopolymers such as polyethylene, polypropylene, poly-1-butene, and poly-4-methyl-1-pentene, as well as copolymers of ethylene with small amounts of other α-olefins, such as propylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene. Ethylene polymers are preferred, and ethylene homopolymers are particularly preferred.

Furthermore, the melt flow rate (MFR) of the fine particles (B) is preferably less than 1.0 g/10 min, more preferably 0.01 g/10 min or more and less than 1.0 g/10 min, and even more preferably 0.01 to 0.5 g/10 min. This MFR is measured in accordance with JIS K7210 under conditions of 190°C and a test load of 21.6 kg.

<Method for producing ultra-high molecular weight olefin polymer fine particles (B)>
In the present invention, the method for producing the fine particles (B) is not particularly limited as long as the fine particles (B1) satisfy the above requirements (i) to (iii). For example, the fine particles (B) can be produced by the methods disclosed in the following documents:
(1) International Publication No. 2006/054696 (2) International Publication No. 2008/013144 (3) International Publication No. 2009/011231 (4) International Publication No. 2010/074073 (5) JP 2012-131959 A

The fine particles (B) are preferably crosslinked ultra-high molecular weight olefin polymer fine particles (B2) (hereinafter also referred to as "fine particles (B2)") obtained by irradiating uncrosslinked ultra-high molecular weight olefin polymer fine particles (B1) with radiation to crosslink them, as this can prevent re-agglomeration of particles and reduce fisheyes, making it easier to mold the olefin polymer composition into a shape such as a film.

The term "fisheye" refers to agglomerated particles formed when molten particles come into contact with each other during extrusion molding, and when the film is viewed visually, these agglomerated particles appear as large fisheyes.
The fine particles (B2) can be obtained by irradiating the above-mentioned ultra-high molecular weight olefin polymer with radiation.

By irradiating the fine particles (B1), molecular chains are broken and crosslinked, resulting in the molecular chains being linked together at the crosslinking points. This prevents the molecular chains from flowing freely even above the glass transition temperature or melting point, improving high-temperature properties. Furthermore, the shape can be maintained even when subjected to stress, allowing the mechanical properties to be maintained.

Radiation includes alpha rays, beta rays, gamma rays, electron beams, heavy ion beams, etc., and any of these can be used, but electron beams or gamma rays are more suitable.
The radiation exposure dose varies depending on the type of monomer constituting the ultrahigh molecular weight olefin polymer used, but is usually 20 to 700 kGy, preferably 100 to 500 kGy, more preferably 200 to 500 kGy, and even more preferably 250 to 500 kGy.

When the irradiation dose is within the above range, the crosslinking reaction of the ultra-high molecular weight olefin polymer proceeds efficiently, and when the crosslinked ultra-high molecular weight olefin polymer fine particles (B2) obtained in this manner are used in packaging film, fisheyes can be suppressed.

On the other hand, if the irradiation dose exceeds 700 kGy, the polymer may deteriorate rapidly, and if the irradiation dose is less than 20 kGy, cross-linking of the polymer chains may not proceed or may proceed slowly.

[Packaging material film]
The packaging material film of the present invention contains an olefin polymer (A) and fine particles (B). Specifically, the packaging material film of the present invention contains fine particles (B) in a film made of the olefin polymer (A).

The upper limit for the content of olefin polymer (A) in the packaging material film is preferably 99.9% by mass, and the lower limit for the content of fine particles (B) is preferably 0.1% by mass.

In the packaging material film of the present invention, it is preferred that at least a portion (for example, 0.1 to 20% by mass) of the fine particles (B) is present on the surface of the packaging material film.
When at least a part of the fine particles (B) is present on the surface of the packaging material film, a packaging material film having excellent adhesion and residue prevention properties can be produced.

The content of the fine particles (B) is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 5.0 parts by mass, and particularly preferably 0.3 to 1.5 parts by mass, per 100 parts by mass of the total of the olefin polymer (A) and the fine particles (B). A content above the lower limit is preferred in terms of the adhesion and residue prevention performance of the resulting film, while a content below the upper limit is preferred in terms of the mechanical properties of the resulting film and the shedding resistance of the fine particles (B) contained as an adhesion and residue prevention agent.

The presence of fine particles (B) on the surface of the packaging material film can be confirmed, for example, by observing the film surface and cross section using a scanning electron microscope or the like.

In the phase-separated structure observed under an electron microscope, the olefin polymer (A) forms a continuous phase (sea phase), and the fine particles (B) are dispersed in the continuous phase to form a dispersed phase (island phase).
The packaging material film of the present invention is a packaging material film for packaging an article to be packaged, and preferably has an uneven shape on the surface that comes into contact with the article to be packaged.

The arithmetic mean roughness Sa of the uneven surface is preferably 0.1 μm to 5.0 μm, and more preferably 0.2 to 3.0 μm. By having such an uneven surface on the surface of the packaging material film facing the packaged item, when used as packaging material, it is possible to prevent the contents, particularly food, from adhering to or remaining behind.

This is thought to be because the uneven surface of the packaging film reduces the contact area between the film and the contents, resulting in the formation of gaps.
The packaging material film of the present invention may be a film consisting of only the olefin polymer (A) and the fine particles (B), or may be a laminate containing at least one adherend selected from a sheet-like substrate, a barrier layer, and other layers. It may also have an adhesive layer for laminating various layers.

Known materials can be used as the sheet-like substrate. For example, paper, synthetic paper, resin film, resin film with a vapor-deposited layer, aluminum foil, other metal foil, etc. can be used alone or as composite or laminated materials of these.

The sheet-like substrate can be laminated using known methods such as dry lamination, extrusion lamination, wet lamination, and heat lamination.

The barrier layer is preferably made of an inorganic substance or inorganic oxide, and more preferably made of a vapor-deposited film of an inorganic substance or inorganic oxide or a metal foil. The vapor-deposited film can be formed by a conventionally known method using a conventionally known inorganic substance or inorganic oxide, and its composition and formation method are not particularly limited. The laminate having a barrier layer can impart or improve gas barrier properties that prevent the transmission of oxygen gas, water vapor, etc., and light-blocking properties that prevent the transmission of visible light, ultraviolet light, etc. The laminate may have two or more barrier layers. When two or more barrier layers are present, the layers may have the same composition or different compositions.

Examples of the deposited film that can be used include deposited films of inorganic substances or inorganic oxides such as silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), lead (Pb), zirconium (Zr), and yttrium (Y).

Particularly suitable for packaging materials (bags) and the like are vapor-deposited films of aluminum metal, or vapor-deposited films of silicon oxide, aluminum metal, or aluminum oxide.
Examples of methods for forming the vapor-deposited film include physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

In another embodiment, the barrier layer may be a metal foil obtained by rolling a metal. Any conventional metal foil can be used as the metal foil. Aluminum foil is preferred from the standpoint of gas barrier properties that prevent the transmission of oxygen gas, water vapor, etc., and light-blocking properties that prevent the transmission of visible light, ultraviolet light, etc.

Other layers may include layers used in known packaging materials, laminated at any position, for the purpose of imparting various properties (moisture permeability resistance, oxygen permeability resistance, light blocking properties, heat insulation properties, impact resistance, etc.). Examples include a print layer, a print protection layer (so-called OP layer), a colored layer, an adhesive layer, an adhesion-reinforcing layer, a primer coat layer, an anchor coat layer, an anti-slip agent layer, a lubricant layer, and an anti-fogging agent layer.

The thickness of the packaging material film is not particularly limited.
When the packaging material film is a laminate, the thickness may vary depending on the type of adherend and may be selected appropriately depending on the application, but is, for example, 10 to 200 μm, preferably 20 to 100 μm.

<Method of manufacturing packaging material film>
The packaging material film of the present invention can be obtained by melt-extruding an olefin polymer composition obtained by mixing the above-mentioned olefin polymer (A) and fine particles (B) components, and, if necessary, additives described below, usually at a temperature in the range of 160 to 320°C. The packaging material film of the present invention may also be obtained by uniaxially or biaxially stretching a molded product obtained by molding into a film or sheet by a T-die extrusion molding method or the like. The film of the present invention can be molded by any conventional method without any particular limitation, but a cast molding method is preferred from the viewpoint of reducing the dynamic friction coefficient of the resulting film.

In the present invention, the term "film" is used for convenience to indicate the external structure of an olefin polymer, and "film" is a general term for flat molded objects, and includes not only films but also sheets, membranes, tapes, and the like.

The components can be mixed using a variety of known methods, such as multi-stage polymerization, mixing using a plastomill, Henschel mixer, V-blender, ribbon blender, tumbler, blender, or kneader/ruder, or by melt-kneading the components after mixing using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, or the like, followed by granulation or pulverization. This method allows for the production of a high-quality olefin polymer composition in which the components and additives are uniformly dispersed and mixed.

<Additives>
The olefin polymer composition of the present invention may further contain, as necessary, a nucleating agent, a heat stabilizer, an antioxidant, a weather stabilizer, an antistatic agent, a slip agent, an antifogging agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, a wax, a filler, an antiblocking agent other than the crosslinked ultra-high molecular weight olefin polymer, and the like, within the scope of not impairing the object of the present invention.

Nucleating agents that can be used include dibenzylidene sorbitol-based nucleating agents, phosphate ester salt-based nucleating agents, rosin-based nucleating agents, metal benzoate salt-based nucleating agents, fluorinated polyethylene, sodium 2,2-methylenebis(4,6-di-t-butylphenyl)phosphate, pimelic acid and its salts, and 2,6-naphthalene dicarboxylic acid dicyclohexylamide. There are no particular restrictions on the amount of nucleating agent used, but it is preferably about 0.1 to 1 part by mass per 100 parts by mass of the olefin polymer composition. There are no particular restrictions on the timing of addition, and the agent can be added during or after polymerization, or during molding.

Known antioxidants can be used as the antioxidant. Specifically, hindered phenol compounds, sulfur-based antioxidants, lactone-based antioxidants, organic phosphite compounds, organic phosphonite compounds, or combinations of these can be used.

Lubricants include, for example, sodium, calcium, and magnesium salts of saturated or unsaturated fatty acids such as lauric acid, palmitic acid, oleic acid, and stearic acid, which can be used alone or in combination of two or more. The amount of such lubricants added is typically 0.1 to 3 parts by mass, and preferably 0.1 to 2 parts by mass, per 100 parts by mass of the olefin polymer composition.

As the slip agent, it is preferable to use an amide of a saturated or unsaturated fatty acid such as lauric acid, palmitic acid, oleic acid, stearic acid, erucic acid, or hebenic acid, or a bisamide of these saturated or unsaturated fatty acids. Of these, erucic acid amide and ethylene bisstearamide are particularly preferred. These fatty acid amides are preferably blended in an amount of 0.01 to 5 parts by mass per 100 parts by mass of the olefin polymer composition.

<Applications of packaging film>
The film of the present invention contains the above-mentioned fine particles (B) as an adhesion/remaining preventing component and antiblocking agent. Therefore, when the packaging material film comes into contact with the contents, adhesion or remaining of food or the like on the film surface can be suppressed, and the film also has excellent blocking resistance after boiling. Furthermore, since the adhesion between the olefin polymer (A) and the fine particles (B) is excellent, there is little possibility that the fine particles (B) will fall off from the olefin polymer (A) and become mixed into the packaged contents. Furthermore, this packaging material film is easy to heat-seal together, and the adhesive strength of the sealed portions is high.

Specific examples of applications of such films include food packaging films (outer layer, inner layer, sealant, single layer), medical packaging film, pharmaceutical packaging film, industrial packaging film, stretch film, cling film, oriented film, breathable film, moisture-proof sheet, anti-slip sheet, light-shielding film, film for laminate substrate, foam film, building material skin material, release film, for example, release film for flexible printed circuit boards, release film for rigid boards, release film for rigid-flexible boards, release film for advanced composite materials, release film for curing carbon fiber composites, release film for curing glass fiber composites, release film for curing aramid fiber composites, release film for curing nanocomposite materials, Examples of suitable applications include release films for curing, release films for filler materials, release films for semiconductor encapsulation, cushioning films for release films, release films for fuel cells, release films for various rubber sheets, release films for urethane curing, release films for epoxy curing, surface protective films, such as protective films for resin plates, protective films for polarizing plates, protective films for liquid crystal panels, protective films for optical components, protective films for lenses, protective films for electrical components and electrical appliances, protective films for mobile phones, protective films for personal computers, protective films for mirrored panels, protective films for sheets, office supplies, sanitary products, and garbage bags, and are preferably used for food packaging.

The packaging material film of the present invention can be used as is or after processing. The processing method can be the same as that used for known packaging materials. For example, embossing, half-cutting, notching, etc. are acceptable. The packaging material of the present invention can also be suitably used for molded containers, wrapping paper, trays, tubes, and bags such as pillow bags, gusset bags, and pouches. More specifically, bags can be suitably produced by heat-sealing the packaging material of the present invention together. Such bags can be used for retort packs, etc.

The present invention will be described below with reference to examples, but the present invention is not intended to be limited to these examples.
The methods for measuring various physical properties are as follows.

<Intrinsic viscosity [η]>
The intrinsic viscosity [η] was measured at 135° C. by dissolving the fine particles used in the production of the fine particles (B-1), (B-2) or (B-3) in decalin.

<Average particle diameter d50>
The average particle diameter d50 was calculated from the weight-based particle size distribution by the Coulter counter method using a precision particle size distribution measuring device (Multisizer Three, manufactured by Beckman).

<Proportion of particles passing through a 45 μm mesh sieve>
The proportion of particles passing through a 45 μm mesh sieve was determined by measuring the mass of particles passing through a 45 μm mesh sieve (JIS Z 8801 #325).

[Olefin polymer (A)]
In the examples and comparative examples, the following olefin polymers were used as the olefin polymer (A).
LLDPE...Evolue (registered trademark) SP2040 manufactured by Prime Polymer Co., Ltd. (density = 918 kg/m ³ , MFR (190°C, 2.16 kg load) = 3.8 g/10 min)
LDPE: Mirason (registered trademark) 12, manufactured by Dow Mitsui Polychemicals Co., Ltd. (density = 927 kg/m ³ , MFR (190°C, 2.16 kg load) = 3.0 g/10 min)

[Fine particles (B-1)]
Ultra-high molecular weight polyethylene fine particles (Mitsui Chemicals, Inc., Mipelon (registered trademark) PM-200, intrinsic viscosity [η] = 13.0 dl/g, MFR (190°C, 21.6 kg load) = 0.020 g/10 min, average particle size d50 = 10.5 μm, 45 μm mesh sieve passage rate = 100% by mass) were irradiated with an electron beam at an exposure dose of 200 kGy to obtain ultra-high molecular weight polyethylene fine particles (B-1).

[Fine particles (B-2)]
Ultra-high molecular weight polyethylene fine particles (Mitsui Chemicals, Inc., Mipelon XM-220, intrinsic viscosity [η] = 14.5 dl/g, MFR (190°C, 21.6 kg load) = 0.015 g/10 min, average particle diameter d50 = 32 μm, 45 μm mesh sieve passage rate = 90% by mass) were irradiated with an electron beam at an exposure dose of 200 kGy to obtain ultra-high molecular weight polyethylene fine particles (B-2).

[Fine particles (B-3)]
[Synthesis Example 1]
(Preparation of magnesium-containing microparticles (a))
According to the method described in Synthesis Example 1 of WO 2006/054696, a xylene solvent was used instead of a toluene solvent, and the operating conditions were adjusted to prepare a xylene slurry of magnesium-containing microparticles (a). The magnesium concentration of the prepared magnesium-containing microparticle (a) slurry was 0.23 mmol/mL, and the aluminum concentration was 0.026 mmol/mL.

[Synthesis Example 2]
(Synthesis of solid catalyst component (b))
69.4 ml of xylene was placed in a nitrogen-purged 200 mL glass reactor, and 30.6 ml of the xylene slurry of the magnesium-containing microparticles (a) prepared in the above [Synthesis Example 1] (7.05 mmol in terms of magnesium atoms) was added under stirring. Next, 33.6 mg of the transition metal compound (c) of the following formula (1) (0.0391 mmol in terms of zirconium atoms) was added, and the reaction was carried out at room temperature for 1 hour. The reaction product was then filtered, washed three times with 500 mL of xylene and twice with 500 mL of decane, filtered, and then 120 mL of decane was added to prepare a decane slurry of the solid catalyst component (b). A portion of the obtained slurry of the solid catalyst component (b) was sampled and the concentration was examined. The zirconium concentration was 0.000307 mmol/mL, and the magnesium concentration was 0.0576 mmol/mL.
(1)

[Synthesis Example 3]
(Synthesis of ultra-high molecular weight polyethylene particles)
A 1 L stainless steel autoclave was charged with 500 mL of heptane and thoroughly purged with nitrogen. Ethylene was passed through the autoclave at room temperature at 0.4 NL/min for 15 minutes to saturate the liquid and gas phases. The autoclave was then heated to 65°C, and while continuing to pass ethylene through at 0.4 NL/min, 1.25 mL of a decane solution of triethylaluminum (1.0 mmol/mL in terms of aluminum atoms) and 13.4 mL of solid catalyst component (b) (0.16 mmol in terms of magnesium atoms) were added. The mixture was stirred for 5 minutes while maintaining the temperature. Subsequently, 6 mL of a toluene solution (15 mg/mL) of Emulgen 108 (manufactured by Kao Corporation) was added. The ethylene flow was stopped, 1 mL of hydrogen was added, and the autoclave was then heated to 70°C. Ethylene was then introduced at a rate of 0.1 NL/min until the pressure reached 0.35 MPaG. After reaching 0.35 MPaG, polymerization was continued while maintaining the temperature and pressure until the ethylene feed rate reached 56 NL. The autoclave was then cooled, and the ethylene was depressurized. The resulting slurry containing a white solid was filtered, washed with heptane, and dried under reduced pressure at 80°C for 10 hours, yielding 69.5 g of ultra-high molecular weight polyethylene microparticles.

The physical properties of the resulting ultra-high molecular weight polyethylene fine particles were as follows:
Intrinsic viscosity [η] = 10.8 dl/g, MFR (190°C, 21.6 kg load) = 0.030 g/10 min, average particle size d50 = 6.2 μm, 45 μm mesh sieve passage rate = 100 mass%

The ultra-high molecular weight polyethylene microparticles obtained above were irradiated with an electron beam at a dose of 200 kGy to obtain microparticles (B-3).

[Other fine particles]
The following fine particles were used as fine particles that do not fall under the category of fine particles (B).

[Zeolite]
EAZ-10 (a composition containing 10% by mass of synthetic zeolite as an antiblocking agent and 90% by mass of low-density polyethylene) manufactured by Prime Polymer Co., Ltd. was used.

[silica]
TME172AB (a composition containing 20% by mass of spherical silica and 80% by mass of low-density polyethylene as an anti-blocking agent) manufactured by Toho Co., Ltd. was used.

[Reference example 1-1]
90 parts by mass of LDPE and 10 parts by mass of the fine particles (B-1) were added, and the mixture was melt-kneaded at 190° C. using a twin-screw extruder (manufactured by Technovel Co., Ltd., KZW15-30MG) to obtain a mixture.

The resulting polymer mixture and LLDPE were placed in a cast film molding machine (Toyo Seiki Co., Ltd., D2028) in a mass ratio of 2.5:97.5, and extrusion molding was performed at a cylinder and die temperature of 190°C and a take-up speed of 2.0 m/min to obtain a 40 μm thick cast film made of an olefin polymer composition.

[Reference examples 1-2, 1-3]
A cast film was obtained in the same manner as in Reference Example 1-1, except that the blending amounts of each component were changed as shown in Table 1.

[Reference examples 2-1 to 2-3]
A cast film was obtained in the same manner as in Reference Example 1-1, except that the fine particles (B-1) were changed to fine particles (B-2) so that the blending amounts of the respective components were as shown in Table 1.

[Examples 3-1 to 3-3 ]
A cast film was obtained in the same manner as in Reference Example 1-1, except that the fine particles (B-1) were replaced with the fine particles (B-3) so that the blending amounts of the respective components were as shown in Table 1.

[Comparative Examples 1-1 to 1-3]
A cast film was obtained in the same manner as in Reference Example 1-1, except that LDPE was not used and the fine particles (B-1) were changed to EAZ-10 so that the blending amounts of each component were as shown in Table 2.

[Comparative Examples 2-1 to 2-3]
A cast film was obtained in the same manner as in Reference Example 1-1, except that LDPE was not used and the fine particles (B-1) were changed to TME172AB so that the blending amounts of each component were as shown in Table 2.

[Comparative Example 3]
The LLDPE was charged into a cast film molding machine (D2028) and extrusion-molded at a cylinder and die temperature of 190° C. and a take-up speed of 2.0 m/min to obtain a cast film having a thickness of 40 μm.

[Film Evaluation]
The obtained films were evaluated by the following methods. The evaluation results are shown in Tables 1 and 2.

<Arithmetic mean roughness Sa of film surface>
The arithmetic mean roughness Sa of the obtained cast film surface was measured using a laser microscope (Olympus Corporation, LEXT OLS4000) under the following measurement conditions: objective lens: 20x magnification, film measurement area: 1.22 mm x 1.22 mm.

<Dynamic friction coefficient>
The dynamic friction coefficient between films was measured according to JIS K7125 "Test method for friction coefficient of plastic films and sheets." The test conditions were test speed: 100 mm/min, test piece width: 63.5 mm, load: 200 g, and measurement environment temperature: 23°C.

<Heat seal strength>
The resulting cast film was cut into a 15 mm wide piece to obtain a test piece. Two test pieces were overlapped and heat-sealed according to the following conditions, and the heat-seal strength was measured.
In Tables 1 and 2, "-" means that the evaluation was not performed.

(Heat sealing conditions)
A single-sided heat bar sealer was used, and the setting conditions were as follows:
Heat sealing pressure: 0.2 MPa
Heat sealing time: 1.0 second Heat sealing temperature: 110°C, 120°C, 130°C
Seal bar width: 5 mm

(Heat seal strength measurement conditions)
Test piece width: 15 mm
Peeling angle: 180 degrees Peeling speed: 300 mm/min

<Evaluation of Blocking Resistance>
Two films cut out from the obtained cast film were overlapped (Figs. 1(a) and (b)), and the overlapped film was sandwiched between two metal plates measuring 20 cm in length and 20 cm in width, the surfaces of which had been mirror-finished (Fig. 1(c)), and left to stand at a temperature of 50°C under a load of 10 kg for 3 days. Thereafter, the film was cooled to room temperature to prepare a measurement sample.

A 6 mm diameter aluminum rod was sandwiched between the two overlapping films of the measurement sample so that the distance from the aluminum rod to the bottom edge of the overlapping films was 20 cm (Figures 2(a)-(c)), and the film was fixed to an Intesco Universal Material Testing Machine 2001 (Figure 3).

The two overlapping films were pulled upward at a speed of 20 cm/min while being peeled off with a fixed aluminum rod (FIGS. 4(a)-(c)), and the average load (blocking force (mN)) when the films were shear-peeled off was measured. The value obtained by dividing the average load by 20 cm was taken as the blocking coefficient (mN/cm) (hereinafter referred to as "blocking coefficient (mN/cm)").
In Table 1, "no blocking" means that the blocking coefficient is 0, that is, the films are in contact with each other without being in close contact with each other.

<Evaluation of blocking resistance after boiling>
Two 120 mm x 150 mm films cut from the obtained cast film were overlapped, and the film was heat-sealed around the periphery of the film in a width of 10 mm, leaving a filling opening, according to the conditions below to form a bag. The bag was then filled with 50 ml of water, and the filling opening was heat-sealed with a heat sealer to seal it. The obtained package was boiled in water heated to 95°C for 10 minutes, and the area of blocking (non-peeling) between the packages was confirmed. The evaluation criteria were as follows, relative to the blocking area in Comparative Example 3:

(Heat sealing conditions)
Heat sealing pressure: 1 kgf/cm ²
Heat sealing time: 3 seconds Heat sealing temperature: 150±10°C

(Evaluation criteria)
x: The area of blocking is 50% or more and less than 100% of that of Comparative Example 3.
Δ: The area of blocking is 10% or more and less than 50% of that of Comparative Example 3.
◯: The area of blocking is 0% of that of Comparative Example 3 (no blocking).

<Evaluation of food adhesion to film>
Cream cheese (Kiri (registered trademark), manufactured by Bell Japon Co., Ltd.) was sandwiched between two 100 mm x 100 mm pieces of film cut from the obtained film, and the film was sandwiched between two metal plates with mirror-finished surfaces and left to stand for 5 minutes at 23°C under a load of 20 kg. The upper film was peeled off and the amount of cream cheese adhering to the film was confirmed. The evaluation criteria were as follows, relative to the amount of residual adhesion in Comparative Example 3.

(Evaluation criteria)
x: The amount of residual deposits was 75% or more and less than 150% of that of Comparative Example 3.
Δ: The amount of residual deposits is 50% or more and less than 75% of that of Comparative Example 3.
◯: The amount of residual deposits was 25% or more and less than 50% of that of Comparative Example 3.
⊚: The amount of residual deposits is less than 25% of that of Comparative Example 3.

10: Universal material testing machine 14: Aluminum rod 16: Holding means 18: End portion 20: Film 30: Frame 32: Top surface 34: Pulling means 36: Bottom surface 38: Fixing means 40: Metal plate

Claims (4)

The present invention comprises an olefin polymer (A) and ultra-high molecular weight olefin polymer fine particles (B),
The ultra-high molecular weight olefin polymer fine particles (B)
Crosslinked ultra-high molecular weight olefin polymer fine particles (B2) obtained by crosslinking uncrosslinked ultra-high molecular weight olefin polymer fine particles (B1) by irradiation with radiation, which satisfy the following requirements (i) to (iii):
the content of the ultra-high molecular weight olefin polymer fine particles (B) is in the range of 0.25 to 5.0 parts by mass per 100 parts by mass of the total of the olefin polymer (A) and the ultra-high molecular weight olefin polymer fine particles (B);
Packaging material film.
(i) The intrinsic viscosity [η] measured in decalin solvent at 135°C is in the range of 5 to 20 dl/g.
(ii) The average particle size d50 is in the range of 3 to 8 μm.
(iii) 50% by mass or more passes through a 45 μm mesh sieve. The packaging material film according to claim 1, wherein at least a portion of the ultra-high molecular weight olefin polymer fine particles (B) is present on the surface of the packaging material film. The packaging material film according to claim 1 or 2 is a packaging material film for packaging an item to be packaged, the surface that comes into contact with the item to be packaged having an uneven shape, and the arithmetic mean roughness Sa of the surface is 0.1 to 5.0 μm. The packaging material film according to any one of claims 1 to 3 , which is used for packaging food.