JP2011229460A - Freshness retaining packaging material made of plastic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic packaging material useful for retaining the freshness of fresh foods such as vegetables and fruits and fresh flowers, and excellent in the transparency.SOLUTION: The packaging material made of the plastic film includes black silica powder whose average particle diameter is 0.05-10 micrometers (μm) and in which the weight of particles of larger diameters than 10 micrometers (μm) is less than 10 wt.% at the rate from 0.01-0.5 wt.%, and the thickness of the packaging material is from 10-100 micrometers (μm). The packaging material is a laminated film including at least one layer containing black silica powder and at least one layer without containing black silica.

Description

  The present invention relates to a plastic film packaging material useful for maintaining freshness of fresh foods such as fruits and vegetables and fresh flowers.

  Conventionally, various proposals have been made to maintain the freshness of fruits and vegetables and fresh flowers. Among them, as a plant freshness retaining material using black silica (also referred to as graphite silica), ceramics such as moss and flower pots are known (Patent Document 1).

JP-A-2003-250438 Claims Examples

  The present invention relates to a plastic packaging material that is useful for maintaining the freshness of fresh foods such as fruits and vegetables, fresh flowers, and the like, and has excellent transparency.

  The present invention provides a black silica powder having an average particle size of 0.05 to 10 microns (μm) and a weight of particles having a particle size of more than 10 microns (μm) of less than 10% by weight of 0.01 to 0. The present invention relates to a freshness-keeping packaging material made of plastic film which is contained at a ratio of 0.5% by weight and whose thickness is 10 to 100 microns (μm).

  The present invention is also a freshness maintaining material as described above, characterized in that it is a laminated film of at least one layer containing black silica powder and at least one layer not containing black silica. The present invention relates to a plastic film freshness-keeping packaging material.

  Further, the present invention is the above-described freshness-keeping material, which is a laminated film in which a layer not containing black silica is laminated on both sides of a layer containing black silica powder. It relates to packaging materials.

  Furthermore, the present invention relates to a plastic film freshness-keeping packaging material in which the above laminated film is formed into a bag shape.

  According to the present invention, although the proportion of black silica is relatively small, it is possible to efficiently obtain an excellent freshness-keeping effect, and it is possible to provide a plastic film having excellent transparency as a packaging material. .

FIG. 1 is a schematic view showing a state in which three sample peripheral edges of two sample films are heat-sealed by a heat seal bar.

Black silica The black silica compounded in the plastic film in the present invention is conventionally known by names such as black silica, graphite silica, and graphite silica, and these can be used. Among them, the graphite fault breccia produced from Heisenokuni Mine, Yunobukuro Shinmei, Kaminokuni-cho, Kaminoyama-gun, Hokkaido, is preferred.

Such ores are usually characterized by carbon content of 0.1 to 7% by weight, and the main component SiO ₂ is usually contained by 67 to 92% by weight.
In the present invention, these black silicas having an average particle diameter of 0.05 to 10 microns (μm) are used. The average particle diameter can be measured by the method described later.

  Further, the average particle size of black silica is desirably 50% or less of the thickness of the plastic film to be used, especially 30% or less, and more preferably 10% or less. When the plastic film is a laminated film as will be described later, the average particle size of black silica is 50% or less, particularly 30% or less, more preferably 10% of the thickness of the film in which it is blended. % Or less is desirable. Beyond that, the transparency of the film may be impaired.

  Further, black silica having a particle size exceeding 10 microns (μm) is less than 10% by weight, preferably less than 1% by weight. When the average particle size exceeds 10 microns (μm) and the component having a particle size exceeding 10 microns (μm) exceeds 10% by weight, the transparency of the plastic film tends to be inferior.

  Such black silica is preferably subjected to surface treatment with a surface treatment agent in advance. Such surface treatment agents include, for example, stearic acid, higher fatty acids such as calcium, magnesium, and zinc salts of stearic acid and salts thereof, higher alcohols such as stearyl alcohol, stearic acid glyceride, and polyethylene glycol, higher polyhydric alcohols, poly Examples include various fatty acid esters such as oxyethylene sorbitan monostearate. Preferably, in addition to stearic acid glyceride and the like, dimethyl silicone oil, non-reactive silicone oil such as higher fatty acid ester-modified silicone oil, epoxy-modified silicone oil, carbinol-modified silicone oil, reactive silicone oil such as carboxyl-modified silicone oil, Liquid paraffin, N-lauryl-D, L-aspartic acid-β-lauryl ester and the like can be mentioned.

  Further, in the production of the plastic film, in order to prevent the aggregation of the black silica in the raw material of the plastic film, a dispersion aid such as ethyl alcohol or ethylene glycol is blended together with these as necessary. In this case, the mixing ratio of the dispersion aid is usually from 0.1 to 10 weight percent of the weight of the black silica powder (including the amount of the dispersion aid if surface-treated), and in particular 0 .3 to 3% by weight is preferred.

Raw Material for Plastic Film The raw material for the plastic film used in the present invention is not particularly limited as long as it is a polymer that can be formed into a film.
Among such polymers, olefin-based polymers include homopolymers of α-olefins having 10 or less carbon atoms such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and the like α -There are random or block copolymers of olefins, or copolymers of olefins as a main component and vinyl acetate, acrylic acid, methacrylic acid, alkyl acrylate ester, alkyl methacrylate ester and the like. Specifically, for example, high density polyethylene, low density polyethylene, linear low density polyethylene (LLDPE), polypropylene, propylene-ethylene random copolymer, propylene-ethylene rubber, ethylene-butene-1-copolymer, propylene- Ethylene-1-butene random copolymer, propylene-ethylene block copolymer, propylene-ethylene-1-butene block copolymer, poly-4-methyl-pentene polymer, ethylene-vinyl acetate copolymer, propylene- Examples thereof include 1-butene random copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and metal salts thereof. These olefin polymers further include modified polymers such as halogenated polyolefins such as chlorinated polyethylene, acid-modified polyolefins modified with unsaturated carboxylic acids such as acrylic acid and maleic anhydride, Examples thereof include biodegradable resins such as lactic acid, polyester resins, polyamide resins such as 6-nylon, polyurethane elastomers, vinyl chloride resins, fluororesins, polyether ether ketones, polysulfones, styrene resins, polyacrylates, and vinylidene chloride resins. In the present invention, one kind or two or more kinds thereof are used as necessary.

Plastic film The freshness-preserving packaging material made of the plastic film of the present invention is a film containing the above-mentioned black silica powder and using the above plastic as a raw material. Used in the form of a film. Such a single layer film includes both an unstretched film and a film stretched in a uniaxial direction or a biaxial direction.

The stretch ratio in the case of a stretched film is usually about 2 to 10 times in the vertical direction and about 2 to about 10 times in the horizontal direction, and uniaxial stretching and biaxial stretching are performed as necessary.
In addition to the above black silica, the plastic film freshness-keeping material of the present invention may be blended with other known additives blended in plastics. Such additives include, for example, antioxidants, antistatic agents, ultraviolet absorbers, antiblocking agents and the like. As other additives, natural zeolite and synthetic zeolite, silica, titanium dioxide, synthetic mica and the like, and further, a colorant and the like may be blended within a range that does not impair the transparency of the film.

  Among them, as the antioxidant, for example, 3,5-di-t-butyl-4-hydroxytoluene, tetrakis [methylene (3,5-di-t-butyl-4-hydroxy) hydrocinnamate] methane, n-octadecyl-3- (4'-hydroxy-3,5-di-t-butylphenyl) propionate, phenolic antioxidants such as 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2-hydroxy-4-methoxybenzophenone Benzophenone antioxidants such as 2-hydroxy-4-octoxybenzophenone and 2,4-dihydroxybenzophenone, benzotriazole antioxidants such as 2 (2′-hydroxy-5-methylphenyl) benzotriazole and substituted benzotriazole Agent, 2-ethylhexyl-2-cyano-3,3 Diphenylacrylate, ethyl-2-cyano-3,3-diphenyl acrylate, phenyl salicylate, and a 4-t-butylphenyl salicylate and the like.

Examples of the antistatic agent include alkylamines and derivatives thereof, higher alcohols, glycerol esters of higher fatty acids, pyridine derivatives, sulfated oils, soaps, sulfates of olefins, alkyl sulfates, fatty acid ethyl sulfone. Acid salt, alkyl sulfonate, alkyl naphthalene sulfonate, alkyl benzene sulfonate, naphthalene sulfonate, oxalate ester sulfonate, phosphate ester salt, partial fatty acid ester of polyhydric alcohol, ethylene oxide of fatty alcohol Adducts, fatty acid ethylene oxide adducts, fatty amino or fatty acid amide ethylene oxide adducts, alkylphenol ethylene oxide adducts, alkyl naphthol ethylene oxide adducts, polyhydric alcohols Ethylene oxide adducts of partial fatty acid esters of Lumpur, polyethylene glycol, and the like. In addition, a polymer type antistatic agent can also be used. For example, a block of a polyolefin (a) having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm and a hydrophilic polymer ( Examples of the block b) include polymer-type antistatic agents such as alternating polyolefin (a).

  Examples of such polyolefins (a) of repetitive alternating polyolefins include low molecular weight polypropylene, and in particular, low molecular weight polypropylene whose ends are modified with α, β-unsaturated carboxylic acid and / or anhydride thereof, and hydrophilic polymer. (B) includes polyethers, polyether-containing hydrophilic polymers, cationic polymers and anionic polymers.

  Further, examples of the ultraviolet absorber include ethylene-2-cyano-3,3′-diphenyl acrylate, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, and 2- (2′-hydroxy-3). '-T-butyl-5'-methylphenyl) 5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4octoxybenzophenone, etc. It is done.

  In the case of a laminated film, black silica may be blended in any layer, but black silica may be blended only in a part of the layers. In the case of a stretched film, any layer may be an unstretched film, or all layers may be stretched films, and some layers may be stretched films and the remaining layers may be unstretched films. It is a waste.

  Therefore, when the freshness-keeping material of the present invention is a laminated film, there is an aspect of a laminated film of a layer containing black silica powder and at least one or more other layers. There exists the aspect of the laminated | multilayer film which provided the layer which does not contain black silica on both sides of the mix | blended layer.

  A preferred embodiment in the case of a laminated film is a layer composed of the above olefinic polymer containing black silica, particularly a propylene polymer, and a layer substantially free of black silica on both sides thereof, preferably an olefinic polymer, A laminated film in which a propylene-based polymer is laminated is suitable, and it is desirable from the viewpoint of transparency and strength that each of these layers is stretched, and in particular, a film stretched in a biaxial direction.

In these cases, it is desirable to add an anti-blocking agent to the skin layer.
As an antiblocking agent, inorganic antiblocking agents such as silica (synthetic or natural silicon dioxide), magnesium silicate, aluminosilicate, talc, zeolite, aluminum borate, calcium carbonate, calcium sulfate, barium sulfate, calcium phosphate, Examples of the organic anti-blocking agent include polymethyl methacrylate, polymethylsilyltosesquioxane (silicone), polyamide, polytetrafluoroethylene, epoxy resin, polyester resin, benzoguanamine / formaldehyde (urea resin), and phenol resin. Among these, polymethyl methacrylate and synthetic silica are preferable from the balance of dispersibility, transparency, scratching property, antiblocking property and the like. Anti-blocking agents may be surface-treated, and as surface treating agents, surfactants, metal soaps, organic acids such as citric acid, higher alcohols, esters, silicones, silane coupling agents, etc. Can be used. The shape of these anti-blocking agents is not limited, and can be any shape such as spherical, square, columnar, needle-like, plate-like, and indefinite shape, and the average particle size is usually 0.5 to 12 microns ( μm) grade. Among these, silica having an average particle size of 0.1 to 12 microns (μm) is preferable. Commercially available products of these silicas include silicia [manufactured by Fuji Silysia Chemical Co., Ltd., trade name], furex crystallite [manufactured by Tatsumori Co., Ltd., trade name] and the like.

The blending ratio of the antiblocking agent is usually 0.05 to 1 weight percent of the blended layer.
Another preferred embodiment is a laminated film composed of a layer containing black silica and a plastic layer having a gas barrier property substantially free of black silica.

Examples of the layer having gas barrier properties include resins such as polyvinyl alcohol, polyester, and polyamide.
The thickness of the plastic film as the freshness-keeping material is 10 to 100 microns (μm), preferably 15 to 100 microns (μm), whether it is a single layer film or a laminated film. If it is less than 10 microns, sufficient film strength cannot be obtained, and the bag is easily broken when the contents are filled. On the other hand, if it exceeds 100 microns, the film rigidity is high and it becomes difficult to fill the contents.

  Also, in the case of a three-layer film having a skin layer on both sides of the core layer, the core layer is 10 to 98 microns, especially 15 to 97 microns, and the skin layer is 1 to 45 microns, especially 1.5 to 42.5 microns. Is preferred.

Production method of a plastic film freshness-keeping material The freshness-keeping material of the present invention comprises the above-described black silica powder, further dispersing aid, if necessary, other additives and the above polymer by a conventionally known method. It manufactures by mixing and film-forming from the obtained mixture by a conventionally well-known method.

  As a method for forming a film, for example, extrusion molding methods such as a T-die method, a calendering method, an inflation method, a calendering method and the like are common. A stretched film can also be obtained by performing a stretching operation.

  In the case of a laminated film, each layer is extruded and then laminated together to form a laminated film. In addition, a method of extruding and laminating another layer to a part of the layer, or all the layers can be combined. There is a method of forming a laminated film by pressing. Also in this case, any one of the layers is stretched and used, or the obtained unstretched laminated film is further stretched.

Use The plastic film freshness-preserving material of the present invention is in the form of a film, leaves and vegetables such as cabbage, lettuce, leek, broccoli, fruit vegetables such as cucumber, eggplant, tomato, etc. Vegetables such as vegetables, spinach, komatsuna and spring chrysanthemum, mushrooms, melons, bananas, strawberries, peaches, oysters, ume, apples, kiwi, mango and other fruits, fresh fish, sashimi, etc. Seafood, fresh foods such as meat, beans, oils and fats, seeds, bulbs, fresh flowers such as cut flowers, and the like. Moreover, it is processed into a bag shape by a fusing seal or other methods and used as a packaging bag.

Furthermore, it is also possible to improve the performance of maintaining freshness by providing a large number of minute holes in the plastic film, thereby controlling the permeation of oxygen.
Specific examples of the plastic film freshness-keeping material of the present invention are shown below.
(1) First skin layer // core layer // second skin layer (back layer)
(Thickness 2 microns // 21 microns // 2 microns)
Biaxially stretched film Stretch ratio About 5 times in the vertical direction × About 10 times in the horizontal direction
First and second skin layers Polypropylene (MFR (230 ° C.) 2 to 10 g / 10 min)
Core layer Polypropylene (MFR (230 ° C) 2 to 10 g / 10 min)
0.05% by weight of black silica in the core layer
Black silica average particle size 2 microns (μm)
Ratio of component exceeding 10 microns (μm) Less than 1% by weight 0.5 parts by weight of ethyl alcohol is used as a dispersion aid.
(2) First skin layer // Core layer // Second skin layer (back layer)
(Thickness 2 microns // 23 microns // 2 microns)
Uniaxially stretched film Stretch ratio Approx. 10 times in the machine direction
The first and second skin layers and the core layer are the same as (1) above.

The core layer was blended with black silica similar to (1) above.
A dispersing aid was also used in the same manner as (1) above.
The plastic film freshness-keeping material of the present invention formed in this way exhibits a performance of keeping freshness widely for fresh foods and the like, and reduces the economic value of fresh foods and the like even during a period of several days to several tens of days. You can save without letting.

As an example core layer, polypropylene (F153Z manufactured by Prime Polymer Co., Ltd.) and black silica (coal counter manufactured by Coulter Co., Ltd.) had an average particle size of 2.0 microns (μm) and a particle size of 10 microns. Is used in an amount of less than 1% by weight), and a composition containing 0.05% by weight is used as the first and second skin layers on polypropylene (5C30F manufactured by Sun Allomer Co.). Polymethylmethacrylate (PMMA) 0.1% by weight is added as an agent, and a multi-layer T-die film molding machine is used to form an unstretched laminated film consisting of a core layer and skin layers on both sides, A biaxially stretched film (first skin layer / core layer / second skin layer = 2 mix) is obtained by successively biaxially stretching the stretching ratio 5 times in the longitudinal direction and 10 times in the lateral direction. Down the ([mu] m) / 21 micron ([mu] m) / 2 microns ([mu] m)) was molded.

  Cut out a sample film of size 20cm x 30cm from the obtained biaxially stretched film, and heat-seal the three sides of the two sample films with a heat seal bar to create a packaging bag as shown in FIG. did.

Spinach or spring chrysanthemum was put in this bag, the bag was kept at a constant temperature of 10 ° C., and the content was visually observed for wilting and evaluated in the following five stages.
(Good) ○, ○ △, △, △ ×, × (bad)
The amount of transpiration of water vapor (%) is measured by measuring the weight (W1) of spinach or spring chrysanthemum in a bag, measuring the weight again after constant storage (W2), and calculating the decrease by the following formula: It was.
Amount of transpiration (%) = {(W1) − (W2)} / (W1) × 100
It can be determined that the smaller the amount of transpiration, the higher the freshness retention effect. The results are shown in Table 1.

Comparative Example The above example was performed in the same manner except that black silica was not blended. The results are shown in Table 1.

  The freshness-preserving material made of plastic film of the present invention exhibits a performance of keeping freshness widely for fresh foods and the like, and can be stored without reducing the economic value of fresh foods and the like even during a period of several days to several tens of days. Since the period can be extended, the transparency is excellent, and the film strength is sufficient, it is suitable as a packaging material.

Claims (4)

  0.01 to 0.5% by weight of black silica powder having an average particle size of 0.05 to 10 microns (μm) and a particle size of more than 10 microns (μm) and having a weight of less than 10% by weight A plastic film freshness-maintaining packaging material having a thickness of 10 to 100 microns (μm).   2. The plastic film freshness-keeping packaging material according to claim 1, wherein the packaging film is a laminated film of at least one layer containing black silica powder and at least one layer not containing black silica.   3. The plastic film freshness-keeping packaging material according to claim 2, wherein the plastic film is a laminated film in which layers containing no black silica are laminated on both sides of a layer containing black silica powder.   The plastic film freshness-keeping packaging material according to any one of claims 1 to 3, which is formed into a bag shape.

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