JP4855229B2 - Gas permeation control film and freshness-maintaining packaging film using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polypropylene-based resin film having a high oxygen permeability and carbon dioxide permeability, a high ratio of carbon dioxide permeability/oxygen permeability and excellent freshness retention in packaging vegetables and fruits and flower and ornamental plants. <P>SOLUTION: The gas permeable control film has a layer comprising 54-95 pts.wt. of a polypropylene (A), 4-45 pts.wt. of an ethylene-1-octene random copolymer (B) and 0.1-3 pts.wt. of at least one kind of a surfactant (C) selected from the group consisting of diglycerine oleate, glycerin oleate and a castor oil ethylene oxide adduct. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a gas permeation control film, and more particularly to a gas permeation control film suitable for packaging fruits and vegetables.

  Polyolefin-based resin films are generally excellent in moldability, transparency, moisture resistance and heat sealability, and are widely used as packaging materials for various products such as standard bags and plastic bags, as well as food, daily necessities, and industrial products. It is popular. However, when vegetables and fruits and flowers are sealed and sealed with a film, the transpiration of moisture and the speed of respiration are reduced, so that a certain freshness retention effect can be obtained at the beginning, but oxygen inside the package is consumed by respiration, and carbon dioxide When the concentration of sucrose became high, there was a problem that rot caused by anaerobic breathing began and the freshness rapidly decreased.

  For this reason, low density polyethylene (LDPE and LLDPE) films with relatively high gas permeability are often used for packaging fruits and vegetables, but they are more transparent and rigid than polypropylene and polystyrene films. There was a problem of shortage. Polystyrene films are transparent and rigid, and have a relatively high gas permeability, so they are also used for packaging for the same purpose, but they are broken because they are less stretched than polypropylene or low-density polyethylene films. There was a problem that it was easy and the seal strength was low.

  On the other hand, since a polypropylene film has excellent transparency, rigidity, and sealing strength, for example, a biaxially stretched polypropylene film imparted with antifogging properties is used for packaging fruits and vegetables (for example, Patent Document 1). reference). However, the film made of polypropylene has a lower gas permeability than the film made of low density polyethylene or polystyrene, so that the freshness retention in the case of hermetically wrapping fruits and vegetables and flowers is inferior.

  Therefore, a technique has been proposed in which fruits and vegetables are sealed and packaged with a film provided with gas permeability by opening minute holes (see, for example, Patent Document 2). However, this method is accompanied by equipment and processing costs for punching, and the productivity of the film is reduced, and there is a possibility that contaminants may enter from the outside through the hole.

  Further, a propylene-α-olefin random copolymer having a propylene unit content of 99.1 to 99.9% by weight and a propylene-α-olefin random copolymer having a propylene unit content of 70 to 90% by weight. A film obtained from a resin composition containing a polymer in a specific ratio has been proposed (see, for example, Patent Document 3). Although this film has improved oxygen permeability compared to the propylene homopolymer, it does not specifically mention carbon dioxide permeability.

  On the other hand, by holding a small amount of oxygen taken from the outside of the fruit and vegetables packaging and releasing the carbon dioxide generated inside to the outside, the fruits and vegetables are in a low breathing state, aging is slowed and freshness retention is improved. It is known. In order to realize such an environment for packaging fruits and vegetables, it is necessary to make the ratio of carbon dioxide permeability / oxygen permeability relatively large.

  In addition, a polypropylene composition excellent in rigidity, heat resistance, and impact resistance has been proposed, which is composed of polypropylene and an ethylene-1-butene random copolymer or an ethylene-1-octene random copolymer (see, for example, Patent Document 4). ). However, this patent is basically directed to injection molded products such as automobile bumpers, and has never been envisaged for application to packaging films with improved freshness retention of fruits and vegetables.

  Further, there has been proposed a laminated film obtained by laminating a resin composition composed of a specific syndiotactic polypropylene and an ethylene-octene copolymer on a base material layer composed of isotactic polypropylene (for example, see Patent Document 5). However, since syndiotactic polypropylene generally has a low crystallinity and is soft, its main application has been a heat seal material conventionally, and the proposed composition has also been aimed at improving heat sealability.

  A coextruded laminated film including a resin layer made of an ethylene-1-octene copolymer and an ethylene-propylene copolymer has been proposed (see, for example, Patent Document 6). However, even in this proposal, the function of the resin layer is only heat-sealing, and the thickness ratio of the coextruded laminated film is 40% at the maximum.

  In addition, an olefin-based resin film made of isotactic polypropylene and an ethylene-octene-1 copolymer has been proposed (see, for example, Patent Document 7). However, as shown in the examples, this proposal is a surface cosmetic film that contains 10% calcium carbonate and has a thickness of 0.1 mm, and is a packaging for fruits and flowers that emphasize transparency. It was not suitable for.

  In addition, a biaxially stretched polypropylene film in which an antifogging agent is blended with a mixture of an ethylene-propylene copolymer and an ethylene-α-olefin copolymer composed of an α-olefin having 3 to 8 carbon atoms has been proposed. (For example, refer to Patent Document 8). However, the effect of this proposal is to improve the antifogging property of the polypropylene film by mixing the ethylene-α-olefin copolymer, and mention anything about the superiority of 1-octene as an α-olefin and gas permeability. I did not.

Under such circumstances, the present inventor previously proposed a gas permeation control film composed of polypropylene: 55 to 95 wt% and ethylene-1-octene random copolymer: 5 to 45 wt% (Japanese Patent Application No. 2005-343926). It has been found that there is a need for a film with high gas permeability and a high carbon dioxide permeability / oxygen permeability ratio.
JP 2003-291282 A JP-A-5-153907 JP 2001-106802 A Japanese Patent No. 2618169 JP-A-9-39175 JP 2003-165572 A Japanese Patent Laid-Open No. 10-330551 Japanese Patent No. 3030446

  The present invention provides a gas permeation control film having high oxygen permeability and carbon dioxide permeability and having a large ratio of carbon dioxide permeability / oxygen permeability and excellent freshness retention when packaging fruits and vegetables. Is an issue.

A group consisting of 54 to 95 parts by weight of polypropylene (A), 4 to 45 parts by weight of ethylene-1-octene random copolymer (B), diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct A layer containing at least one surfactant (C) selected from 0.1 to 3 parts by weight (provided that the total of (A), (B) and (C) is 100 parts by weight) The gas permeation control film contained has high oxygen permeability and carbon dioxide permeability, and has a large ratio of carbon dioxide permeability / oxygen permeability, so it has been found that it is extremely suitable for freshness preservation packaging of fruits and vegetables. The present invention has been completed. The polypropylene (A) is preferably a propylene homopolymer (A1) and / or a propylene-α-olefin copolymer (A2), and 1-octene contained in the ethylene-1-octene random copolymer (B). The content of the structural unit derived from is preferably 2 to 20 mol%. The film of the present invention may be a single layer or a multilayer, but in the case of a multilayer, it is preferable that the thickness of the layer having the above composition occupies 50% or more of the total thickness. Further, the gas permeation control film of the present invention is preferably stretched at least in a uniaxial direction, and more preferably stretched in a biaxial direction. The internal haze value of the gas permeation control film of the present invention is preferably less than 1%.

  Such a gas permeation control film of the present invention is high in oxygen permeability and carbon dioxide permeability as compared with a film made of a polypropylene and an ethylene-1-octene random copolymer, as well as a conventional polypropylene film, and Since the ratio of carbon dioxide permeability / oxygen permeability is also large, it is possible to extend the freshness retention period when fruits and vegetables and flowers are sealed and packaged. Moreover, since the internal haze of a film is low, the visibility of the package contents is good. Furthermore, since the gas permeation control film of the present invention can control gas permeation without providing physical holes, entry of contaminants from the outside can be prevented.

  The gas permeation control film according to the present invention comprises 54 to 95 parts by weight of polypropylene (A), 4 to 45 parts by weight of ethylene-1-octene random copolymer (B), diglycerin oleate, and glycerin oleate. , And at least one surfactant (C) selected from the group consisting of castor oil ethylene oxide adduct 0.1 to 3 parts by weight (however, the total of (A), (B) and (C) is 100 A layer (hereinafter also referred to as a gas permeation control layer).

Hereinafter, each component will be described in more detail.
The polypropylene (A) used in the present invention is preferably a propylene homopolymer (A1) and / or a propylene-α-olefin copolymer (A2). The polypropylene (A) is preferably isotactic polypropylene.

Examples of the α-olefin used in the propylene-α-olefin copolymer (A2) include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1- Dodecene, 1-hexadodecene, 4-methyl-1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, diethyl-1-butene, trimethyl-1- Butene, 3-methyl-1-pentene,
Ethyl-1-pentene, propyl-1-pentene, dimethyl-1-pentene, methylethyl-1-pentene, diethyl-1-hexene, trimethyl-1-pentene, 3-
Methyl-1-hexene, dimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, methylethyl-1-heptene, trimethyl-1-heptene, dimethyloctene, ethyl-1-octene, methyl-1- Nonene, vinylcyclopentene, vinylcyclohexane, vinylnorbornane and the like can be mentioned. One or more structural units derived from these α-olefins can be contained in the propylene-α-olefin copolymer (A2) in a proportion of 10 mol% or less in total.

The melt flow rate (JIS K7210, 230 ° C., load 2.16 kg) of the polypropylene (A) used in the present invention is usually 0.5 to 10 g / 10 minutes, preferably 1 to 4 g / 10 minutes, more preferably It is in the range of 1.5 to 3.5 g / min. A melt flow rate in this range is preferable because the moldability and mechanical strength of the film are good. Such polypropylene (A) is 54 to 95 parts by weight, preferably 54 to 90 parts by weight, more preferably 100 parts by weight of the total of (A), (B) and (C) in the gas permeation control layer. Is contained in an amount of 59 to 90 parts by weight. Within this range, the film has good rigidity, which is preferable.

  The ethylene-1-octene random copolymer (B) used in the present invention preferably contains a structural unit derived from 1-octene in an amount of 2 to 20 mol%, and 10 to 20 mol%. More preferably, it is contained in an amount. When the amount of the structural unit derived from 1-octene is in this range, it is preferable because the rigidity and gas permeability of the film are good.

The ethylene-1-octene random copolymer (B) used in the present invention has an intrinsic viscosity [η] measured at 135 ° C. in decalin of 1.5 to 3.5 dl / g, preferably 2. 0-3.0 dl / g. Such an ethylene-1-octene random copolymer (B) can be produced using a known vanadium catalyst or metallocene catalyst.
The ethylene-1-octene random copolymer (B) is 4 to 45 parts by weight, preferably 9 to 45 parts when the total of (A), (B) and (C) is 100 parts by weight in the gas permeation control layer. It is contained in an amount of parts by weight, more preferably 9 to 40 parts by weight.
The surfactant (C) used in the present invention is at least one selected from the group consisting of diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct.

  Diglycerin oleate can be produced by an esterification reaction of diglycerin and oleic acid. Specifically, DG-MO (manufactured by Sakamoto Pharmaceutical Co., Ltd.) and Poem J-2681 (RIKEN Vitamin Co., Ltd.) Manufactured).

Glycerol oleate can be produced by an esterification reaction between glycerin and oleic acid, and specific examples include Rheodor MO-60 (manufactured by Kao Corporation).
The castor oil ethylene oxide adduct is a compound obtained by adding usually 4 to 50 mol of ethylene oxide to castor oil, and examples thereof include SURFRIC CO-10 (ethylene oxide 10 mol adduct; manufactured by Ito Oil Co., Ltd.).

  At least one surfactant (C) selected from the group consisting of such diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct is the gas permeation control layer of the gas permeation control film of the present invention. It may be a constituent of an antifogging agent that can be added to the antifogging agent. Surfactant (C) is 0.1 to 3 parts by weight, preferably 0.2 to 2.5 parts by weight when the total of (A), (B) and (C) is 100 parts by weight in the gas permeation control layer. It is contained in an amount of parts by weight, more preferably 0.5 to 2 parts by weight. Within this range, the film formability and transparency of the film are favorable, which is preferable.

  The gas permeation control film of the present invention includes heat stabilizers, antioxidants, slip agents, antiblocking agents, plasticizers, colorants, nucleating agents, weathering stabilizers, and UV absorbers that are generally used as necessary. In addition to these, an antifogging agent, an antifogging agent, an antibacterial agent, an ethylene removing agent and the like can be contained.

The gas permeation control film of the present invention may be a single layer film comprising only a gas permeation control layer, or may be a multilayer film in which another resin layer or the like is laminated on the gas permeation control layer.
The thickness of the gas permeation control film of the present invention is not particularly limited because it depends on the type of fruits and vegetables to be packaged and the method of use, but is usually 10 to 100 μm, preferably 10 to 60 μm. Further, when a heat sealing layer, a reinforcing layer, a surface protective layer, etc. are laminated on the gas permeation control layer to form a multilayer film, the thickness of the gas permeation control layer is preferably 50% or more of the total thickness More preferably 60% or more, particularly preferably 70% or more. In the case of a multilayer film, the upper limit of the proportion of the gas permeation control layer is not particularly limited as long as the effect of each laminated layer can be obtained, but is usually 95% or less.

  The resin laminated on the gas permeation control layer is not particularly limited. For example, polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate copolymer Examples thereof include polymers, ionomer resins, polypropylene, propylene-α-olefin copolymers, polymethylpentene, polybutene, polybutadiene, and polystyrene.

  The gas permeation control film of the present invention is formed by, for example, a T-die method, an inflation method, a calendar method, or the like. In the case of a multilayer film, for example, the multilayer film is formed by coextrusion, or is formed by laminating another resin layer on the base film by an extrusion lamination method or a dry lamination method.

  Further, the gas permeation control film of the present invention is preferably stretched at least in a uniaxial direction, and more preferably stretched in a biaxial direction. By stretching, a film excellent in strength, optical properties and appearance can be obtained. Examples of the stretching method include a roll method, a tenter method, and a tubular method. Further, in the case of biaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching can be performed. The stretching ratio is preferably in the range of 3 to 8 times in the case of uniaxial stretching and in the range of 10 to 60 times in the case of biaxial stretching.

  The internal haze value (based on JIS K7105, measured in cyclohexanol) of the gas permeation control film of the present invention is less than 1%. When the internal haze value is within this range, transparency is good even when laminated with a heat seal layer, a reinforcing layer, a surface protective layer, or the like to improve the appearance of the packaged vegetables and flowers. The lower limit of the internal haze is not particularly limited, but is usually 0.1% or more.

  In order to produce the gas permeation control film of the present invention, at least one surfactant (C) selected from the group consisting of diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct is added to polypropylene. (A) and ethylene-1-octene random copolymer (B) may be mixed with a Henschel mixer or the like and directly formed into a film, or the mixture may be melt-mixed using a single screw extruder or twin screw extruder. Then, it may be formed into a film. Further, a master batch containing a high concentration of at least one surfactant (C) selected from the group consisting of diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct was prepared. The batch and a mixture of polypropylene (A) and ethylene-1-octene random copolymer (B) may be formed into a film.

[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to this. Gas permeability and internal haze are determined by the following measurement method.
(Gas permeability)
Using a gas permeability measuring device MT-C3 type manufactured by Toyo Seiki Seisakusho Co., Ltd., measurement was performed under the conditions of 23 ° C. and 0% RH in accordance with A method of JIS K7126.
(Internal haze)
Cyclohexanol was put in a glass cell, the film was immersed in the cell, and the measurement was performed according to JIS K7105.

Isotactic polypropylene containing less than 1 wt% ethylene [Prime Polypro (registered trademark) F113G, manufactured by Prime Polymer Co., Ltd., MFR (JIS K7210, 2
30 ° C. load 2.16 kg) = 3 g / 10 min] (hereinafter also referred to as PP) 50 parts by weight,
Ethylene-1-octene random copolymer [content of 1-octene unit 15 mol%, MFR (JIS K7210, 190 ° C., load 2.16 kg) = 1 g / 10 min] (hereinafter referred to as EO
R)) 40 parts by weight and 10 parts by weight of a master batch containing 10 wt% of diglycerin oleate [DG-MO manufactured by Sakamoto Yakuhin Co., Ltd.] in Prime Polypro F113G (dry blending) Thus, a resin composition was obtained.

Next, using this resin composition, a T-die molding machine (die lip width: 200 mm, extruder: 30 mmφ, L / D = 25), extruder set temperature: 230 ° C., die set temperature: 230 ° C., chill roll temperature : 30 ° C., take-up speed: 0.8 m / min, molded on the condition of single-sided air cooling to obtain a 700 μm-thick original film. Next, this raw film was successively stretched 5 times in the longitudinal direction and 7 times in the transverse direction at a stretching speed of 10 m / min in a tenter in which hot air at 150 ° C. was circulated to obtain a biaxially stretched film having a thickness of 20 μm. It was. The film was measured for oxygen permeability [GTR (O ₂ )], carbon dioxide permeability [GTR (CO ₂ )] and internal haze. The results are shown in Table 1.

Glycerol oleate instead of diglycerin oleate [Kao Corporation
A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that Rhedol MO-60] was used. The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.

Thickness 2 as in Example 1 except that castor oil ethylene oxide adduct [SURFRIC CO-10 manufactured by Ito Oil Co., Ltd.] was used instead of diglycerin oleate.
A biaxially stretched film of 0 μm was obtained. The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.

[Comparative Example 1]
A masterbatch was not used, and a biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that 60 parts by weight of Prime Polypro F113G and 40 parts by weight of ethylene-1-octene random copolymer (EOR) were used. . The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.

[Comparative Example 2]
A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that glycerin stearate ester [Rhedol MS-50 manufactured by Kao Corporation] was used instead of diglycerin oleate. The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.
[Comparative Example 3]
A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that diglycerin stearate ester (DG-MS manufactured by Sakamoto Yakuhin Co., Ltd.) was used instead of diglycerin oleate. The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.
[Comparative Example 4]
A biaxially stretched film having a thickness of 20 μm was obtained in the same manner as in Example 1 except that an antifogging agent composed of 61% stearyl diethanolamine stearate and 39% glyceryl stearate was used instead of diglycerin oleate. The film was measured for oxygen permeability, carbon dioxide permeability and internal haze. The results are shown in Table 1.

  The gas permeation control film provided by the present invention has higher oxygen permeability and carbon dioxide permeability than a film made only of polypropylene and an ethylene-1-octene random copolymer, and carbon dioxide permeability / oxygen permeability. The ratio is large. In addition, since no physical hole exists in the gas permeation control film of the present invention, entry of contaminants from the outside can be prevented. Accordingly, the gas permeation control film provided by the present invention is suitable as a freshness-keeping packaging material for fruits and vegetables.

Claims (8)

54 to 95 parts by weight of polypropylene (A),
4 to 45 parts by weight of ethylene-1-octene random copolymer (B);
0.1-3 parts by weight of at least one surfactant (C) selected from the group consisting of diglycerin oleate, glycerin oleate, and castor oil ethylene oxide adduct (provided that (A) and (B ) And (C) as a total of 100 parts by weight).   The gas permeation control film according to claim 1, wherein the polypropylene (A) is a propylene homopolymer (A1) and / or a propylene-α-olefin copolymer (A2).   The gas according to claim 1 or 2, wherein the content of a structural unit derived from 1-octene contained in the ethylene-1-octene random copolymer (B) is 2 to 20 mol%. Transmission control film.   The layer having a multilayer structure and containing the components (A), (B), and (C) occupies 50% or more of the total thickness. The gas permeation control film described in 1.   The gas permeation control film according to any one of claims 1 to 4, wherein the gas permeation control film is stretched in a uniaxial direction.   The gas permeation control film according to any one of claims 1 to 4, which is stretched in a biaxial direction.   The gas permeation control film according to any one of claims 1 to 6, wherein an internal haze value (JIS K7105) is less than 1%.   A freshness-keeping packaging film for fruits and vegetables and / or florets, comprising the gas permeation control film according to claim 1.