JP2008230251A - Vegetables and fruits packaging film and package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film with sufficient defogging properties and transparency, which is suitable for the packaging of perishables, and a package. <P>SOLUTION: The packaging film is composed of a multilayer laminate which comprises a base layer mainly composed of a polypropylene resin, and a sealing layer mainly composed of a polypropylene resin and formed on both the sides of the base layer. Characteristically, (a) the sealing layer for forming an inside surface of the base layer is mainly composed of a polyolefin resin with a swell ratio of 1.10-1.40, and provided with a surface having the defogging properties; (b) the base layer, in which an defogging agent exists in the resin constituting the base layer, is mainly composed of a polyolefin resin with a swell ratio of 1.42 or less, larger than that of the polyolefin resin of the sealing layer formed on the inside surface of the base layer; and (c) a total thickness of the sealing layer based on all the layers of the film is in the range of 1/50-1/3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a packaging film and a package, and in particular, fresh products made of plants or animals that require high freshness such as vegetables and root vegetables, fruits, flowers, flowers, trees, mushrooms, fish, meat (hereinafter referred to as the present specification). The present invention relates to a film and a package comprising a multilayer laminate having a sealing layer on the inner surface suitable for packaging).

  Conventionally, polypropylene films have been widely used in the packaging field such as food packaging and fiber packaging because they have excellent optical properties, mechanical properties, packaging suitability, and the like. In particular, antifogging films are widely used for packaging vegetables and the like.

  In the conventionally known antifogging film, in order to maintain the antifogging property stably and for a long time, a technique such as kneading an antifogging agent into the resin constituting the film has been adopted. However, in the resin in which these antifogging agents are kneaded, when this is melt-extruded to form a film, the antifogging agent sublimated from the extrusion opening of the molten resin is blown out and the molten resin take-up roll adheres to the molten resin. As a result, there is a problem that transparency is deteriorated by promoting the growth of resin crystals.

  The present invention solves the problems of the conventional polypropylene stretched film having antifogging properties and provides a film and a package suitable for packaging fresh products having sufficient antifogging properties and transparency. With the goal.

In order to achieve the above object, the packaging film of the present invention comprises:
1. A packaging film comprising a multilayer laminate having a base layer mainly composed of a polypropylene resin and a sealing layer mainly composed of a polypropylene resin formed on both side surfaces of the base layer,
a) The sealing layer forming the inner surface of the base layer is mainly composed of a polyolefin resin having a swell ratio in the range of 1.10 to 1.40, and the surface thereof has antifogging properties.
b) The base layer is made of a polyolefin resin having a swell ratio of 1.42 or less, wherein an antifogging agent is present in the resin constituting the base layer, and is larger than the swell ratio of the polyolefin resin of the seal layer formed on the inner surface of the base layer. As the subject,
c) The packaging film, wherein the total thickness of the sealing layer is 1/50 to 1/3 with respect to all layers in the film.
2. The packaging film as described in 1 above, wherein an antifogging agent is present in all layers,
3. The packaging film according to 1 or 2 above, which is biaxially stretched;
4). 4. The packaging film as described in 1, 2 or 3, which is used for packaging fresh products. It consists of a packaging body characterized by using the packaging film described in the above 1, 2, 3 or 4.

  According to the packaging film and package of the present invention, it is possible to provide a packaging film having excellent anti-fogging properties in packaging fresh products and having excellent transparency.

  Hereinafter, embodiments of the packaging film and the package of the present invention will be described. The packaging film used in the present invention comprises a multilayer laminate having a base layer mainly composed of polypropylene resin and biaxially stretched, and a sealing layer mainly composed of polyolefin resin formed on the inner surface of the base layer. Film.

  Such a packaging film is preferably manufactured by a coextrusion method or the like. Moreover, although the base layer of the packaging film constituting the present invention needs to be biaxially stretched, the seal layer formed on the inner surface may be in an unstretched, uniaxially stretched or biaxially stretched state. Good.

  Here, the polypropylene resin suitable for forming the base layer of the packaging film in the present invention has a swell ratio of 1.42 or less than the swell ratio of the polyolefin resin of the seal layer formed on the inner surface. There is a need. Here, the swell ratio means a measure of the size of the die swell (indicating the flow state of the molten resin at the extrusion die outlet), and the larger this value, the greater the expansion at the extrusion die outlet. However, the resistance is large. If it is small, it means that the expansion at the exit of the extrusion die is small and the resistance is small.

  At this time, if the swell ratio of the polypropylene resin forming the base layer is equal to or less than the swell ratio of the polyolefin resin of the sealing layer formed on the inner surface, the sublimation antifogging occurred when the resin was extruded from the extruder outlet. Since the pressure of the agent and the sealing layer resin is directed to the base layer side, the contact with the take-up machine becomes unstable, the resin is crystallized, the transparency is deteriorated, and the swell ratio is 1.42. In the case of exceeding, the pressure at the outlet of the extruder is excessively directed outward, so that the surface of the seal layer resin and the metal are rubbed at the outlet of the extruder and the appearance is deteriorated.

  As described above, the polypropylene resin suitable for forming the base layer is not particularly limited as long as it satisfies the above range. For example, in addition to isotactic polypropylene, propylene / ethylene copolymer, propylene 1 type (s) or 2 or more types, such as a butene-1 copolymer, a propylene-ethylene-butene-1 copolymer, a propylene-pentene copolymer, are used. Further, other polyolefin resins, for example, an ionomer obtained by crosslinking an ethylene / butene-1 copolymer, an ethylene / propylene / butene 1 copolymer, an ethylene / acrylic acid copolymer / ethylene / acrylic acid copolymer with a metal ion. Polybutene-1, butene / ethylene copolymer, etc. may be used in part, and polyester resin, polyamide resin, polycarbonate resin, etc. may be used as long as the properties of the film are not impaired. Moreover, an ultraviolet absorber, antioxidant, etc. can also be arbitrarily mix | blended.

  Moreover, as polyolefin resin suitable for forming the seal layer of the inner surface of the packaging film in the present invention, the swell ratio needs to be in the range of 1.10 to 1.40. Here, when the swell ratio is less than 1.10, when the resin is extruded from the exit of the extruder, it is pushed by the pressure of the sublimated antifogging agent, and the contact with the take-up machine becomes unstable, and the resin If the swell ratio exceeds 1.40, the pressure at the exit of the extruder is too much outward and the sealing layer resin surface at the exit of the extruder. And the metal rub against each other, deteriorating the appearance.

  As described above, the polypropylene resin suitable for forming the seal layer is not particularly limited as long as it satisfies the above range. For example, ethylene-butene-1 copolymer, ethylene-propylene-butene- 1 type, 2 types or more of 1 copolymer, polypropylene, polybutene-1, butene / ethylene copolymer, propylene / propylene / butene-1 copolymer, propylene / pentene copolymer, etc. are used. Resins, polyamide-based resins, polycarbonate-based resins, and the like can also be used as long as the characteristics of the film are not impaired. Moreover, it is preferable to contain fine particles composed of inorganic particles or organic polymers as appropriate.

  The packaging film of the present invention requires that the surface of the sealing layer has antifogging properties. For this reason, an antifogging agent is usually present in the resin constituting the base layer and the sealing layer. During film production, an antifogging agent may be added to both the resin forming the base layer and the resin forming the seal layer, or the film is manufactured by adding the antifogging agent only to the resin forming the base layer. May be. Even in the latter case, the antifogging agent in the resin that forms the base layer during film production and storage after film formation sequentially moves to the seal layer and then bleeds out to the seal layer surface to prevent the seal layer surface. It will be in the state which has cloudiness.

  An anti-fogging agent must be present on the surface of the sealing film in contact with the fresh product in the packaging film so as to exhibit anti-fogging properties during storage or distribution in a state where the fresh product is packaged. That is, in the present invention, the anti-fogging action is extremely important not only for preventing the fogging phenomenon on the inner surface of the packaging body and enhancing the commercial value, but also for preventing water rot of the packaging body contents due to water droplets formed by the progress of clouding. In order to maintain excellent anti-fogging properties for a long time in the distribution process, considering the temperature change during storage or distribution, it continues during the course of repeated temperature changes at 5 to 30 ° C. Thus, it is desired that an antifogging agent exhibiting antifogging properties is present on the surface of the seal layer.

  The present invention is intended for packaging fresh products that maintain their physiological effects even after harvesting, and is desired to be stored in a room temperature atmosphere rather than frozen storage. It is preferable to determine the antifogging property when the temperature change is repeated at a temperature of -30 ° C.

  Typical examples of antifogging agents include fatty acid esters of polyhydric alcohols, higher fatty acid amines, higher fatty acid amides, higher fatty acid amines and amide ethylene oxide adducts, and the like. Can do. The amount of the antifogging agent present in the film is preferably 0.1 to 10% by weight, particularly 0.2 to 5% by weight in terms of all layers, and 5% by weight or less, particularly 0.1% in the constituents of the seal layer. It is preferably -1.0% by weight.

  The thickness ratio of the sealing layer is not particularly limited, but is usually 1/50 to 1/3 of the total layer in the packaging film of the present invention (when the sealing layer is provided on both sides of the base layer, the total thickness). It is. If the thickness ratio is smaller, the sealing strength is insufficient and the reliability as a package is lacking. On the other hand, when the thickness ratio is larger, the ratio of the base layer portion is smaller, so that the whole packaging film is not smooth, and the shape of the package after filling with fresh products is unstable and lacks commercial value. The thickness of the packaging film is not particularly limited, but is about 5 to 250 μm, and the thickness of the seal layer can be appropriately determined within this range.

The characteristic value measurement method used in this specification will be described below.
(1) Swell ratio This is a measure of the size of the die swell. Photograph of molten resin discharge part when measuring melt flow rate based on polypropylene test method (230 ° C., 21.18N) shown in JIS K6758, and ratio of die inner diameter to molten resin strand diameter extruded from die Was measured (see FIG. 1). Swell ratio = molten resin strand diameter / die inner diameter

(2) Transparency (%)
Haze was measured according to JIS K7105.

(3) Anti-fogging property
(1) Put 300 cc of hot water at 50 ° C. into a 500 cc top open container.
(2) Seal the container opening with the film with the antifogging measurement surface of the film inside.
(3) Leave in a cold room at 5 ° C.
(4) Leave in a cold room at 5 ° C for 12 hours, then move to a 30 ° C environment and leave for 12 hours.
(5) After repeating the operation of (4) for 2 days, evaluate the dew adhesion on the film measurement surface in 6 stages.
Evaluation grade 6: No dew on the entire surface (adhesion area 0) Evaluation grade 5: Slight dew adhesion (up to 1/5 adhesion area) Evaluation 4 grade: Slight dew adhesion (up to 1/4 adhesion area) Evaluation grade 3: Approximately 1 / 2 dew adherence (up to 2/4 of adherence area) Evaluation grade 2: Almost dew adherence (up to 3/4 of adherence area) Evaluation 1 grade: Dew adherence over the entire area (adhesion area of 3/4 or more)

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example.

(Example 1)
・ Seal layer forming resin
(1) Propylene / ethylene / butene copolymer (ethylene content 2.5 mol%, butene content 7 mol%, swell ratio 1.24) 100 parts by weight, inert fine particles (Silicia 430, Fuji Silysia Chemical Ltd. ), Particle size 2.5 μm) 0.25 parts by weight and antifogging agent (higher fatty acid ester monoglycerite) 0.45 parts by weight were mixed to obtain a resin for forming a seal layer.

(2) Base layer forming resin
(2) 100 parts by weight of an isotactic polypropylene polymer (swell ratio 1.31) was mixed with 1.0 part by weight of an antifogging agent (higher fatty acid ester monoglycerite) to obtain a base layer forming resin.

(3) Film formation
Resin (1) and resin (2) were melted at a ratio of 1: 9 (weight ratio) at a resin temperature of 260 ° C., and a T-die in a three-layer state in which a sealing layer was laminated on both sides of the base layer. The film was coextruded and cast with a castor crawl at a temperature of 25 ° C., and then stretched 4 times in the machine direction and 9,5 times in the transverse direction.

  Subsequently, the surface of the seal layer of the obtained film was subjected to corona discharge treatment to obtain a three-layer packaging film having a total thickness of 20 μm including a wetting tension of 39 mN / m on the corona discharge treated surface, a base layer of 18 μm, and 1 μm on one side of the seal layer.

  Table 1 shows various properties of the obtained packaging film. As can be seen from this table, it has both excellent anti-fogging properties and transparency.

(Comparative Examples 1 and 2)
In Example 1, the films of Comparative Examples 1 and 2 were obtained by changing the swell ratio of the resins used for the seal layer and the base layer as shown in Table 1, respectively. Table 1 shows various properties of the obtained packaging film.

  In Comparative Example 1, the swell ratio of the seal layer is higher than that of the base layer, and the transparency is poor.

  In Comparative Example 2, since the swell ratio of the base layer exceeded a predetermined range, the transparency was deteriorated.

(Comparative Example 3)
In Comparative Example 1, a packaging film was obtained in the same manner as in Example 1 except that no antifogging agent was added to each of the seal layer and the base layer.

  Table 1 shows various properties of the obtained packaging film. Although the transparency is good, the antifogging property is remarkably bad.

  Since the packaging film of the present invention has sufficient anti-fogging properties and transparency, it is particularly from plants or animals that require high freshness such as vegetables, root vegetables, fruits, flowers, flowering trees, mushrooms, fish and meat. Can be used in the packaging field, and contribute greatly to the industry.

Figure showing swell ratio = melt resin strand diameter / die inner diameter

Claims (5)

A packaging film comprising a multilayer laminate having a base layer mainly composed of a polypropylene resin and a sealing layer mainly composed of a polypropylene resin formed on both side surfaces of the base layer,
a) The sealing layer forming the inner surface of the base layer is mainly composed of a polyolefin resin having a swell ratio in the range of 1.10 to 1.40, and the surface thereof has antifogging properties.
b) The base layer is made of a polyolefin resin having a swell ratio of 1.42 or less, wherein an antifogging agent is present in the resin constituting the base layer, and is larger than the swell ratio of the polyolefin resin of the seal layer formed on the inner surface of the base layer. As the subject,
c) The packaging film, wherein the total thickness of the sealing layer is 1/50 to 1/3 with respect to all the layers in the film.   2. The packaging film according to claim 1, wherein an antifogging agent is present in all layers. The packaging film according to claim 1, which is biaxially stretched.
The packaging film according to claim 1, which is biaxially stretched.   The packaging film according to claim 1, wherein the packaging film is used for packaging fresh products.   A packaging body comprising the packaging film according to claim 1.

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