JPH06107874A - Packaging film - Google Patents

Abstract

PURPOSE:To provide the title film which is good in non-fogging even when used for packaging a moist article and which has hence good display effect, is excellent in transparency, pliability, and heat-sealability, and is useful as a PVC substitute especially suitable for food packaging. CONSTITUTION:The film is formed from a composition comprising 100 pts.wt. ethylene/(meth)acrylic acid copolymer having a (meth)acrylic acid content of 2-20wt.% or lowly ionized ionomer obtained therefrom and 1-10 pts.wt. mixture comprising a polyglycerol/fatty acid ester and a glycerol/fatty acid ester and/or a poly(ethylene glycol)/fatty acid ester in a weight ratio of 1/9 to 9/1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging film excellent in transparency, flexibility, heat sealability and antifogging property.
More specifically, the present invention relates to a packaging film suitable for general wrap packaging such as stretch wrap or shrink wrap and shrink wrap for processed meat.

[0002]

2. Description of the Related Art In the field of food packaging and other general packaging, soft polyvinyl chloride (P) is used because of its good flexibility, transparency, impact resistance, stress and strain characteristics.
VC) film is widely used. However,
Due to the problems that it is difficult to generate a corrosive gas during incineration and it is difficult to recycle it, the movement of PVC removal has become active in recent years. As an alternative material for such PVC, use of an ethylene / (meth) acrylic acid copolymer, which is excellent in transparency, flexibility, heat sealability, adhesion to a packaged object, and low odor, is considered (here. To (meta)
Acrylic acid means acrylic acid or methacrylic acid,
same as below). However, when the ethylene / (meth) acrylic acid copolymer film is used for packaging a moisture-containing package, there is a drawback that the film surface becomes cloudy.

In general, various anti-fog formulations for preventing fogging have been known for polyolefin-based packaging films, and even if they are used for packaging moisture-containing articles, they have no significant industrial problems. . However, since the ethylene / (meth) acrylic acid copolymer has a high polarity and a strong interaction with the antifogging agent, it exhibits a high antifogging property at the initial stage of compounding the antifogging agent, and has a high antifogging property for a long period of time. It has been fairly difficult to find a formulation that maintains haze. For example, fatty acid ester of glycerin and fatty acid ester of sorbitan have hitherto been widely used as antifog agents for polyolefins. However, when these are blended with ethylene / (meth) acrylic acid copolymer, the antifog performance can be achieved in a short period of time. However, it was not a prescription that could be practically adopted. Further, even when using such as polyglycerin fatty acid ester or polyoxyethylene sorbitol fatty acid ester, which is expected to improve antifogging sustaining effect as compared with the above antifogging agent, the similar satisfactory effect can be obtained. There wasn't.

[0004]

Therefore, the present inventors have found that
In an ethylene / (meth) acrylic acid copolymer film with a polymer composition having excellent stretch wrap properties or shrink wrap properties, it is possible to cause problems such as stickiness on the film surface without impairing excellent properties such as transparency. Therefore, a method for effectively increasing the antifogging performance was investigated. As a result, it has been found that the purpose can be achieved when a proper amount of the two specific antifogging agents described later is used. Therefore, an object of the present invention is to provide a non-PVC type wrapping film which is excellent in transparency, antifogging property and the like and has excellent wrapping wrapping characteristics.

[0005]

The present invention provides an ethylene / (meth) acrylic acid copolymer having a (meth) acrylic acid content of 2 to 20% by weight or a low ionized ionomer 100 thereof.
A composition prepared by mixing 1 to 10 parts by weight of a mixed component of 1/9 to 9/1 in terms of a weight ratio of polyglycerin fatty acid ester and glycerin fatty acid ester and / or polyethylene glycol fatty acid ester per part by weight. The present invention relates to a packaging film formed into a film.

The ethylene / (meth) acrylic acid copolymer used in the present invention is generally a random copolymer of ethylene and acrylic acid and / or methacrylic acid under high temperature and high pressure. Further, it is particularly preferable to use a copolymer having a low gel content, which is produced under a polymerization condition exhibiting a homogeneous phase. The copolymerization ratio of (meth) acrylic acid is 2
-20% by weight, particularly 6-12% by weight is desirable. It is not preferable to use one having a low (meth) acrylic acid copolymerization ratio or low-density polyethylene because the film optical properties, flexibility, low temperature heat sealability, impact resistance, etc. are deteriorated. Use of a copolymer having an acid copolymerization ratio higher than the above range is not preferable because the gel content is large and complete deodorization is not easy.

The above ethylene / (meth) acrylic acid copolymer also contains other monomers such as methyl acrylate, ethyl acrylate, isobutyl acrylate, and acrylic acid n.
-Butyl, 2-ethylhexyl acrylate, methyl methacrylate, isobutyl methacrylate, methacrylate n-
It may be a copolymer of (meth) acrylic acid ester such as butyl and vinyl esters such as vinyl acetate. Such a monomer can be contained in the copolymer in an amount of 20% by weight or less, particularly preferably 10% by weight or less. Especially excellent in flexibility and impact resistance,
For applications that require packaging characteristics that are closer to PVC,
It is preferable to use a copolymer containing at least 2% by weight of such another monomer.

In the present invention, the ethylene
An ionomer having a low ionization of a (meth) acrylic acid copolymer can be used. At this time, the allowable degree of neutralization is generally 40 mol% or less, and particularly 30 mol% or less, although it is slightly different depending on the acid content in the copolymer and the kind of metal ion. In particular, when the metal ion is an alkali metal such as sodium or potassium, an excellent antifogging effect cannot be obtained when the degree of neutralization is high, so the degree of neutralization should normally be suppressed to about 20 mol% or less. . On the other hand, when the metal ion is a polyvalent metal such as zinc, calcium or magnesium, the antifogging performance tends not to decrease so much, and therefore the neutralization degree of up to about 40 mol% is acceptable.

As the ethylene / (meth) acrylic acid copolymer or its low ionized ionomer, considering film strength, processability, etc., 190 ° C., 2160 g
Melt flow rate under load 0.1-20g / 1
It is preferably 0 minutes, particularly 2 to 12 g / 10 minutes.

In the present invention, a mixed component of polyglycerin fatty acid ester and glycerin fatty acid ester and / or polyethylene glycol fatty acid ester is blended with ethylene / (meth) acrylic acid copolymer or its ionomer. As the fatty acid component constituting the above ester, those having about 12 to 22 carbon atoms are preferable. These may be linear or branched. It may be either saturated or unsaturated, and may be a fatty acid having a substituent such as a hydroxyl group. More specifically,
Examples thereof include lauric acid, palmitic acid, stearic acid, oleic acid and hydroxystearic acid.

The polyglycerin fatty acid ester is mainly composed of diglycerin fatty acid, but may contain a small amount of other polyglycerin fatty acid ester such as triglycerin fatty acid ester. There are various types of polyglycerin fatty acid ester depending on the type of fatty acid, the esterification rate, etc., and there are various types of polyglycerin fatty acid from liquid to solid at room temperature (23 ° C.), all of which can be used in the present invention. . However, when a large amount of a substance that is solid at room temperature is blended, the surfactant that has migrated to the film surface tends to harden and whiten on the surface, so it is necessary to pay attention to the amount added.

As the polyethylene glycol fatty acid ester, it is generally preferable to use a polyethylene glycol ester having a molecular weight of about 100 to 1000, especially a monoester.

Further, as the glycerin fatty acid ester,
The use of monoesters is generally preferred.

The fatty acid component of each ester does not have to be one type and may be two or more types. The important point is the usage ratio of the glycerin fatty acid ester to the polyglycerin fatty acid ester and / or the polyethylene glycol fatty acid ester and the blending amount thereof. The weight ratio of the former to the latter is 1/9 to 9/1, preferably 3/7 to 7
The range is / 3. Moreover, the blending amount thereof is an ethylene / (meth) acrylic acid copolymer or its ionomer 100.
1 to 10 parts by weight per part by weight, but in the case of ethylene / (meth) acrylic acid copolymer, 100 parts by weight,
It is preferably 1 to 5 parts by weight, particularly preferably 1.5 to 3 parts by weight, and in the case of ionomer, depending on the degree of ionization and the type of ion, 1 to 10 parts by weight, particularly 2 to 10 parts by weight. It is good to set the range.

In order to produce a packaging film, the above-mentioned polymer which is an essential component, an antifogging component and, if necessary, additives such as an antioxidant, an antiblocking agent and a slip agent are added,
Mixing or kneading using a Banbury mixer, an extruder, or the like, and then forming a film by an ordinary film forming method such as an inflation method or a T-die method. It is also possible to knead the antifogging agent component with the polymer at a predetermined ratio in advance to prepare an antifogging agent masterbatch, and add this masterbatch during film formation to form a film. The polymer used for the packaging film of the present invention is preferably used as the polymer for preparing the masterbatch.

The form of the packaging film is not limited to a single layer, but other materials such as various plastics such as polyolefin resin and gas barrier resin, paper,
It is also possible to take the form of a multilayer film in which the composition layer is formed on the outermost layer of a substrate composed of one layer or two or more layers such as a metal foil. In such a multilayer film, the composition layer serves as a layer in contact with the article to be packaged.

[0017]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. First, a method for preparing the antifogging agent masterbatch used in the present invention, a film processing method, and an antifogging evaluation method will be described below.

(1) Method for preparing antifogging agent masterbatch As the antifogging agent, a mixture of two kinds of surfactants (A
~ C) and a single surfactant (DG) for comparison.
Was extruded into the resin of the film material while kneading and mixing with a twin screw extruder (screw diameter 30 mm, L / D = 32) so that the concentration of the surfactant was 5% by weight. A clouding agent masterbatch pellet was prepared. The extrusion conditions are as follows. Resin temperature: 180 ° C Mixing ratio: Ethylene / methacrylic acid copolymer / surfactant = 95/5 (weight ratio) Extrusion rate: 10 kg / hr

[0019]

[Table 1] Antifogging agents used

(2) Film processing method An antifogging agent masterbatch (hereinafter referred to as an antifogging agent MB) or a mixture of a predetermined amount of a film material resin and mixed therein was prepared by an inflation film processing method with a screw diameter of 30 mm. Here, the master batch and the film material resin, ethylene / methacrylic acid copolymer or ionomer resin, are mixed by a method in which the pellets of both are directly mixed at room temperature without melting (hereinafter referred to as a dry blend). It was The inflation process was performed under the following conditions. Processing resin temperature: 180 ° C Processing speed: 5 m / min Processed film thickness: 14 μm

(3) Antifogging Evaluation Method The film prepared by the method (2) was used to evaluate the antifogging property by the following two methods.

Simple method: 9 in a 200 ml glass cup
Fill 150 ml of hot water at 0 ° C. and stretch the film to be evaluated on the mouth of the cup without wrinkles. Film tension 3
The state of water droplets adhering to the film surface after 0 minutes was observed and evaluated according to the following three stages. ○ Water adhering to the surface (condensation water) completely flows on the film surface, and no water droplets are seen. △ Some condensed water is seen as water droplets. × Water droplets are seen on the entire surface of the film.

Low-temperature method: As shown in FIG. 1, a glass cylinder is placed in a thermostatic chamber filled with water kept at 30 ° C. at an ambient temperature of 3-8 ° C., and an upper opening is placed above the water surface. Stand up so that the film to be evaluated is attached to the opening,
The state of water droplets adhering to the film surface was observed after 30 minutes and 6 hours after the film was attached, and the antifogging property at low temperature and its persistence were evaluated according to the following 5 grades. 5 No water droplets adhered 4 〃 Very small portion 3 〃 Some portion 2 Most water droplets adhered 1 Full surface water droplets adhered

[Examples 1 to 3 and Comparative Examples 1 to 3] Methacrylic acid content was 9% by weight and melt flow rate was 10 g /
A dry blend of a 10-minute ethylene / methacrylic acid copolymer and an antifogging agent MB composed of the various surfactants shown in Table 1 prepared by the method (1) above is used (2) A monolayer film having a thickness of 14 μm was obtained by the method (1). The surfactant-containing film thus obtained was evaluated for antifogging property by the method (3). The results are shown in Table 2.

[Comparative Examples 4 to 7] Films were prepared in the same manner as in Examples 1 to 3 except that the single surfactants D, E, F and G were used as the antifogging agent, and the antifogging property was evaluated. did. The results are also shown in Table 2.

The film using the antifogging agent comprising the two kinds of surfactant compositions of the present invention is excellent in antifogging property, and in particular, from the viewpoint of long-lasting antifogging property, a film containing a single surfactant is more preferable. Are better.

[0027]

[Table 2] * 1: Ethylene / methacrylic acid copolymer (methacrylic acid content = 9 wt%, MFR = 10 g / 10 min)

[Examples 4 to 5] As the film material resin, instead of the ethylene / methacrylic acid copolymer, a low ionized ionomer (obtained by neutralizing the ethylene / methacrylic acid copolymer of Example 1 with zinc ions). Using an ionomer and a neutralization degree of 18%), a film was prepared and the antifogging property was evaluated in the same manner as in Example 1 so that the antifogging agent A was added in the amount shown in Table 2. The results are shown in Table 3.
Even when the low ionized ionomer is used, the film to which the antifogging agent comprising the mixture of two kinds of surfactants of the present invention is added exhibits excellent antifogging property.

[0029]

[Table 3] * 2: Low ionized Zn ionomer (ionomer in which the ethylene / methacrylic acid copolymer of * 1 above is neutralized with zinc ions (neutralization degree 18%, MFR = 5 g / 10
Min) * 3: Highly ionized Na ionomer (methacrylic acid content = 10 wt%, MFR = 35 g / 10 min ethylene-methacrylic acid copolymer neutralized ionomer (neutralization degree 50%))

Comparative Examples 8 to 12 Highly ionized ionomers obtained by neutralizing ethylene / methacrylic acid copolymers having a methacrylic acid content of 10 wt% and a melt flow rate of 35 g / 10 min as a film material resin with sodium. A film was prepared and the antifogging property was evaluated in the same manner as in Example 1 using (the degree of neutralization of 50%) so that the amount of the surfactant described in Table 3 would be the amount described in Table 3. . The results are shown in Table 3. When the high ionized Na ionomer was used, the film antifogging performance was poor, and when a large amount of the surfactant was used, the resin could not be extruded.

[0031]

According to the present invention, it is possible to provide a packaging film having excellent transparency, flexibility and antifogging property. Utilizing each of these characteristics, it can be used for packaging various items to be packaged, but especially for packaging food items such as fresh food in trays that contain moisture, such as stretch wrap, shrink wrap, and multilayer shrink wrapping. By using it, it is possible to provide a film for food packaging which is excellent in packaging suitability and has an excellent display effect without clouding of the film.

[Brief description of drawings]

FIG. 1 is an example of an apparatus for evaluating the anti-fogging property at low temperature of the packaging film of the present invention.

[Explanation of symbols]

 1 Constant temperature bath 2 Insulated water 3 Glass container 4 Film 5 Drops of water

Claims (1)

[Claims] 1. A (meth) acrylic acid content of 2 to 20% by weight
Polyethylene / (meth) acrylic acid copolymer or its low ionized ionomer per 100 parts by weight of polyglycerin fatty acid ester, glycerin fatty acid ester and / or
Alternatively, a packaging film obtained by forming a composition containing a polyethylene glycol fatty acid ester in a weight ratio of 1/9 to 9/1 in an amount of 1 to 10 parts by weight.