JPH0657319B2 - Oxygen absorber, resin composition using the oxygen absorber, film or sheet comprising the resin composition, and packaging container - Google Patents

Description

The present invention relates to an oxygen absorbent, an oxygen-absorbing resin composition using the oxygen absorbent, and an oxygen-absorbing resin composition. The present invention relates to a film or sheet and a packaging container.

[Prior Art] Oxygen absorbers are widely used in fields such as processed foods, agricultural and marine products, metal products, precision parts, and even textile products where quality deterioration due to oxygen is a problem.

Such an oxygen absorbent is obtained by enclosing the oxygen absorbent in a small air-permeable bag separately from the product in a packaging bag or container for storing the products in each of the above fields. The oxygen absorbent absorbs the internal oxygen to enhance the storage effect of the product.

However, such a means is extremely troublesome in packaging the oxygen absorbent in a small bag and packaging it together with the product, and in food packaging, the oxygen absorbent stored in the small bag may be mistakenly eaten or eaten. In order to prevent such accidents, in recent years, a deoxidizing method has been proposed in which an oxygen absorbent is directly carried on the packaging material itself of the product to absorb the internal oxygen, and as an oxygen absorbing sheet to be used for this, Japanese Patent Publication No. 63-
2648 and JP-A-56-26524 exist.

On the other hand, a film or sheet containing an oxygen absorbent is laminated with another sheet containing no oxygen absorbent, and the oxygen barrier is applied under the condition that water and heat act simultaneously, such as under boiling water heating conditions such as retort sterilization. A packaging container having a multi-layered structure that exhibits performance is also disclosed in Japanese Examined Patent Publication No. 62-1824 and Japanese Unexamined Patent Publication No. 63-
137838, JP-A-1-278335, JP-A-1
It is proposed in No. -278344.

[Problems to be Solved by the Invention]

The oxygen-absorbing sheet and the packaging container having a multi-layered structure disclosed in these prior arts all have a characteristic of the sheet or the packaging container itself so that the oxygen-absorbing performance expresses a gas barrier performance. The oxygen absorbent itself used for the above does not have any particular characteristics, and it depends entirely on the oxygen absorption effect of the oxygen absorbents that have been put into practical use.

The inventors of the present invention have known that the above-mentioned known oxygen absorbent used for an oxygen absorbing sheet or a packaging container having a multi-layered structure should be kneaded and dispersed in the thermoplastic resin constituting the material of the sheet or the container. It was found that the oxygen absorption rate decreased due to this, and due to this, sufficient gas barrier properties could not be imparted, and it was necessary to use a large amount of oxygen absorbent to compensate for this. .

As a result, the use of such a large amount of oxygen absorber inevitably results in thick sheets and packaging materials, and at the same time sacrifices strength, flexibility, and lightness, resulting in practical use. Therefore, it has been recognized that there is a fatal drawback that the oxygen absorbing sheet or the gas barrier packaging container needs an oxygen absorbing agent having a performance suitable for the oxygen absorbing sheet or the gas barrier.

As a result of earnest studies on the oxygen absorbent suitable for such a specific application field, the inventors have found that the oxygen absorbent of the present invention having a novel structure and a resin composition having oxygen absorbability using the oxygen absorbent. And a film or sheet using the resin composition and a packaging container.

[Means for Solving the Problems]

The oxygen absorbent forming the basis of this invention has a specific surface area of 0.5.
It is characterized by comprising iron powder having an apparent density of m ² / g or more and 2.2 g / cm ³ or less and a metal halide.

The resin composition using the oxygen absorbent has a specific surface area of 0.
It is characterized by being a thermoplastic resin in which an oxygen absorbent consisting of iron powder having an apparent density of 5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less and a metal halide is dispersed and carried.

This resin composition having oxygen absorbability is used by molding it into a film or sheet, and further into a packaging container. The packaging container is formed by forming the resin composition into a film or sheet. Can also be molded.

Thus, the iron powder the invention which constitutes a component of the oxygen absorbent has a specific surface area of 0.5 m ² / g or more, preferably 1.0 m ² / g or more, more preferably 2.0 m ² / g or more and an apparent density of 2.2 g / cm ³ or less, preferably 2.9 g / cm ³ or less, particularly preferably 1.6 g / cm
³ or less.

The iron powder having such a specific surface area and apparent density is an iron powder obtained by various manufacturing methods such as reduced iron powder, atomized iron powder, and ground iron powder, and has a sponge-like shape with many fine pores from the surface to the inside. It is composed of porous fine particles.

When the iron powder having a specific surface area of less than 0.5 m ² / g is used as an oxygen absorbent, the absorption rate of oxygen decreases, and when applied to a film or sheet or a packaging container, It will not be able to exert sufficient oxygen absorption capacity, making it difficult to maintain the quality of the packaged products.

On the other hand, when the apparent density exceeds 2.2 g / cm ³ , not only the oxygen absorption rate decreases, but also the obtained film or sheet or packaging container decreases in flexibility and lightness, and the strength Also decreases.

As the iron component of the iron powder used for such an oxygen absorbent, metallic iron or iron oxide can be used alone, or those containing iron hydroxide can be used, but metallic iron and iron oxide are substantially It is desirable that they coexist, and the iron content is 80% by weight or more as the total iron (metal iron + iron oxide, etc.) content,
It is desirable that the content of metallic iron is 40% by weight.

In order to improve the dispersibility with the metal halide powder, the average particle size of the iron powder to be used is usually 150μ or less, preferably 100μ or less, but if it is too fine, it is mixed. In addition, since powdering or deterioration of fluidity occurs in a manufacturing process such as filling, an average particle size of 10 μm or more is preferable.

On the other hand, as the metal halide used in combination with the iron powder, there are alkali metals such as sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide, potassium iodide, calcium chloride, magnesium chloride or barium chloride. Alternatively, one or more kinds of halides of alkaline earth metals are preferably used.

The content of the metal halide in the iron powder is preferably 0.05 to 50 parts by weight, and more preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the iron powder.

When the content of the metal halide is less than 0.05 part by weight, excellent oxygen absorption performance is not exhibited, and the content of more than 50 parts by weight is excessive for the oxygen absorption reaction. Such excess metal halide is not preferred because it may exude from the film or sheet carrying the oxygen during the oxygen absorption reaction and adversely affect the product.

When using this metal halide as a powder, it is desirable that the particle size is almost the same as the iron powder in order to improve the dispersibility with the iron powder, and the average particle size is preferably 150 μm or less, more preferably Is used as a fine powder of 100 μm or less.

Oxygen absorbers made of such iron powder and metal halides can be manufactured by simply mixing both the iron powder and the metal halide powder, or by coating the surface of the iron powder with the metal halide powder by various means. Can be done by the method.

In the resin composition having oxygen absorbability using the oxygen absorbent of the present invention, as the thermoplastic synthetic resin for blending the oxygen absorbent into a resin composition, an olefin resin such as low-, medium- , High density polyethylene, polypropylene, propylene-ethylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1
Olefin resins such as copolymers, ethylene-vinyl acetate copolymers, ion-crosslinked olefin copolymers (ionomers) or blends thereof, polystyrene, styrene-butadiene copolymers, styrene-isoprene copolymers, etc. -Based resins, thermoplastic polyesters such as polyethylene terephthalate and polytetramethylene terephthalate, and polyamide-based resins such as nylon-6, nylon 66, nylon 610, nylon 11, nylon 12, metaxylylene adipamide (MX nylon),
Examples thereof include ethylene-vinyl alcohol copolymer, vinyl alcohol, polyacrylic acid, vinyl alcohol-acrylic acid copolymer, polyvinylpyrrolidone, polyethylene oxide and its modified products, and sodium acrylate polymer. Any of these can be used alone or as a blend of a plurality of them.

A resin composition having an oxygen absorbing property composed of these thermoplastic resins and an oxygen absorbing agent is produced by a calendering method or a T-die method,
A film can be formed by a known melt film forming method such as a ring die method, or can be formed into a sheet by a T-die method.

In such a resin composition, the oxygen absorbent is preferably blended in an amount of 80% by weight or less, more preferably 50% by weight or less based on the thermoplastic resin.

If the blending amount exceeds 80% by weight, the moldability of the resin composition is deteriorated, the strength of the obtained film or sheet is reduced, and the weight of the film or sheet obtained by using the heavy iron powder is reduced. Furthermore, handling becomes inconvenient, and it becomes impossible to obtain a suitable film or sheet.

The thickness of the film or sheet formed from this resin composition is not particularly limited, but a range of about 0.1 mm to 3.0 mm is suitable.

The film or sheet molded from the resin composition of the present invention can be used by laminating it with another thermoplastic resin or a metal foil, if necessary.

The thermoplastic resin to be laminated may be the same thermoplastic resin as the one mixed with the oxygen absorbent described above, or a different thermoplastic resin, but from the viewpoint of oxygen permeability, an olefin resin is preferable, and a metal foil is used. In this case, aluminum foil or iron foil is used.

The lamination method can be carried out by using known techniques such as wet lamination, dry lamination and extrusion lamination, but it is also possible to laminate a dispersion liquid of a silicone resin by a coating method as long as the resin is laminated. Then, these resin layers may be provided on only one side or both sides of the resin layer containing the oxygen absorbent.

Further, the packaging container of the present invention is molded by using the oxygen-absorbing resin composition in which the oxygen absorbent is dispersed, and is a method known per se except for the above-mentioned material constitution. Can be manufactured in.

In the present invention, the packaging container is not particularly limited in its shape as long as it can be used for packaging such as cups, trays, tubes, bottles, caps, bags and lids.

In the case of forming a packaging container by multi-layer coextrusion, the kneaded product is melted and kneaded by an extruder corresponding to each resin layer and then formed into a predetermined shape through a multi-layer multiple die such as a T-die and a circular die. Push out.

Also, after melt-kneading with an injection machine corresponding to each resin layer,
A multi-layer container or a preform for the container is manufactured by co-injection or sequential injection into an injection mold.

Furthermore, a lamination method such as dry lamination, sandwich lamination, and extrusion coating can be adopted.

The molded product of the packaging container made of the resin composition may be in the form of a parison for forming a bottle or a tube, a pipe, a preform for forming a bottle or a tube, or the like.

Molding a bottle from a parison, a pipe or a preform can be easily performed by pinching off an extrudate with a pair of split molds and blowing a fluid into the extrudate.

Further, after cooling the pipe or preform, it is heated to the stretching temperature and stretched in the axial direction to obtain a stretch blow bottle or the like.

In addition, a cup-shaped or tray-shaped packaging container can be obtained from the film or sheet obtained from the resin composition by means such as vacuum forming, pressure forming, injection molding or plug assist molding.

Furthermore, in the case of a multi-layer film, it can be stacked or folded in a bag shape and heat-sealed around the periphery to form a bag-shaped packaging container, which is melt-extruded from an extruder into a cap shell and cooled. While embossing to form a liner having a predetermined shape, or by forming pellets or preforms of a resin composition on a lid, embossing under heating, and then cooling to form a liner having a predetermined shape, or a sheet Alternatively, the multi-layer sheet may be punched into a disc shape to form a liner.

[Work]

The oxygen absorbent of the present invention is composed of iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less, and a metal halide. Since the powder has a large specific surface area consisting of spongy porous fine particles with many fine pores from the surface to the inside, it has a large oxygen absorption rate and a marked increase in the oxygen absorption capacity. Combined with metal oxides, they can exhibit excellent oxygen absorption performance even in small amounts, and because the iron powder used has a low apparent density, they are extremely lightweight.

In addition, the resin composition obtained by carrying the oxygen absorbent in a thermoplastic resin in a dispersed manner exhibits extremely excellent oxygen absorbability, and since the dispersibility of the oxygen absorbent in the thermoplastic resin is good, It is possible to obtain a molded product that is highly flexible and lightweight.

Further, the film or sheet obtained by molding the resin composition and the packaging container each have an excellent oxygen-absorbing property, so that they are molded products having excellent gas barrier performance.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The evaluation of the gas barrier performance in Examples 1 to 9 and Comparative Examples 1 to 4 is based on the following method.

<< Evaluation Method of Gas Barrier Performance >> In Examples 1 to 9 and Comparative Examples 1 to 4, an internal volume of 120 ml obtained by using the sheet composed of the multilayer laminate [surface area:
Each cup-shaped packaging container with an internal volume of 1: 1 (cm ² / cm ³ )] was filled with 2 ml of water in a nitrogen atmosphere, and the volume was 12 μm.
A heat-sealable lid made of polyethylene terephthalate, adhesive, 9 μm aluminum foil, and 30 μm polypropylene film was heat-pressed and sealed, then temperature 12
Perform retort treatment at 0 ° C for 30 minutes, store at 22 ° C and humidity of 60% RH, analyze the gas composition in the packaging container with a gas chromatograph at regular intervals, and use it from the outside for packaging. The amount of oxygen permeated into the container was determined, and the degree of oxygen permeation was divided into 1 to 10 levels. The larger the value, the better the gas barrier property, and the smaller the value, the poorer the gas barrier property. It is a thing.

Example 1 Specific surface area 0.79 m ² / g, apparent density 1.33 g
275 parts (weight part; hereinafter the same) of reduced iron powder having an average particle size of 42μ, a total iron content of 90%, and a metallic iron content of 81% at / cm ^3.
Then, 5 parts of sodium chloride powder having an average particle diameter of 30 μm was added and mixed well to obtain an oxygen absorbent.

This oxygen absorbent and an ethylene-vinyl alcohol copolymer (ethylene content 32 mol%, saponification degree 99.6 mol%) were mixed with a batch type high speed stirring blade mixer (Henschel mixer).

The mixing ratio was such that the oxygen absorbent was 30% by weight.

Then, this mixture was pelletized by a pelletizer consisting of an extruder having a screw with a diameter of 50 mm, a strand die, a blower cooling tank and a cutter, and the pelletized ethylene vinyl alcohol copolymer and oxygen absorber mixture (EO) As an intermediate layer, polypropylene (PP) having a melt index of 0.5 g / 10 min (temperature of 230 ° C.) as an inner and outer layer, and a melt index of 1.0 g
Symmetrical 3 type 5 layer sheet with maleic anhydride modified PP (ADH) of / 10 min as an adhesive layer (total thickness 0.9 mm, composition ratio PP: ADH: EO: ADH: PP = 12: 1: 2:
1:12) is a multi-layer sheet molding consisting of an inner and outer layer extruder having a diameter of 50 mm, an adhesive extruder having a diameter of 32 mm, an intermediate layer extruder having a diameter of 32 mm, a feed block, a T-die, a cooling roll and a sheet take-up machine. A multilayer sheet having a gas barrier property was obtained by molding with an apparatus.

The multilayer sheet thus obtained was heated to a temperature of 190 ° C. and then formed into a cup-shaped packaging container having an internal volume of 120 ml by a vacuum forming machine.

Examples 2 to 9 Examples 2 to 9 were performed in the same manner as in Example 1 except that the specific surface area, the apparent density, the average particle size, the iron content, etc. of the iron powder were varied in the oxygen absorbent. Oxygen absorber was obtained.

The oxygen absorbent thus obtained was mixed with a thermoplastic resin in the same manner as in Example 1 to form a resin composition, which was then molded into a multilayer sheet, which was further subjected to cups of Examples 2-9. It was molded into a rectangular packaging container.

Comparative Examples 1 to 4 Comparative Examples 1 to 4 were carried out in the same manner as in Example 1 except that the specific surface area, apparent density, average particle size, iron content, etc. of the iron powder were varied as oxygen absorbers. Oxygen absorbers were obtained, and these oxygen absorbers were used to disperse and mix with a thermoplastic resin in the same manner as in Example 1 to form a multi-layer sheet having a thickness of 0.9 mm. The cup-shaped packaging container shown in 1-4 was obtained.

Table 1 shows the results of evaluating the gas barrier performance of the packaging containers having various physical properties and oxygen absorbing properties of the oxygen absorbents used in Examples 1 to 9 and Comparative Examples 1 to 4.

Example 10 Similar to Example 1, a mixed pellet (EO) of an ethylene vinyl alcohol copolymer and an oxygen absorbent was prepared by the same method as an intermediate layer, and the melt index was 0.5 g /
Polypropylene (PP) of 10min (temperature 230 ℃) is used as inner and outer layers, and melt index is 1.0g / 10min
A three-dimensional, five-layer, three-dimensional container for packaging (surface area: internal volume = 1: using maleic anhydride-modified PP (AD) as an adhesive layer)
7, body thickness 0.4mm, composition ratio is PP: AD: EO: A
D: PP = 8: 1: 2: 1: 8) was obtained by blow molding. The content seat of this three-dimensional container is 75 cm ³ , and the surface area is 125.
It was cm ² .

After filling 2 ml of distilled water into this three-dimensional container in a nitrogen atmosphere, heat sealing with a sealing material composed of aluminum foil and PP and sealing, then heat sterilization treatment at a temperature of 120 ° C. for 30 minutes, and after this sterilization The sample was stored at a temperature of 22 ° C. and a humidity of 60% RH, and the oxygen concentration in the three-dimensional container was measured with a gas chromatograph at regular intervals.

Also, using the oxygen absorbent of Comparative Example 1 as a control,
The same three-dimensional container as in Example 10 was obtained by blow molding, and the same test as above was performed. Table 2 shows the changes over time in the oxygen concentration (%) in the three-dimensional container at this time.

This table shows that the oxygen concentration in the three-dimensional container, which is a molded product of the resin composition using the oxygen absorbent of the present invention, is obviously lower than that of the comparative example.

[Advantages of the Invention] The oxygen absorbent of the present invention comprises iron powder, which is one component of the oxygen absorbent, having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less. Along with the use, a predetermined amount of metal halide is added to this, and with such a structure, oxygen can be quickly captured at a large oxygen absorption rate, and moreover, excellent oxygen absorption capacity enables continuous oxygen absorption. It is possible.

On the other hand, a resin composition having oxygen absorbability using the oxygen absorber can be obtained by supporting the oxygen absorber having the excellent effect on a thermoplastic resin,
The obtained resin composition has an oxygen absorbent uniformly dispersed in the resin and has excellent oxygen absorption.

On the other hand, the film or sheet obtained by molding the resin composition has a strength which the film or sheet itself has because the oxygen absorbent having excellent oxygen absorbing property is uniformly dispersed in the film or sheet. Also, it has an excellent gas barrier property without any loss of flexibility and lightness, and by simply enclosing the obtained film or sheet in a packaging bag or container in which the product is stored, an oxygen absorption function can be obtained. It fully demonstrates the quality of the stored products.

Although such a film or sheet can be used alone, it is used as an inner layer or an intermediate layer of a packaging bag or container having a multi-layer structure to capture oxygen inside and oxygen passing through from the outside. It is possible to accurately block the absorption of water, and by stacking a sheet and another sheet that does not carry an oxygen absorbent to form a multi-layer structure, it is possible to maintain excellent gas barrier properties as well as moisture and heat. It is possible to prevent the deterioration of the gas barrier performance due to such reasons.

Further, a packaging container molded using the resin composition or a film or sheet molded from the resin composition was obtained because it has excellent oxygen absorption property itself. All you have to do is store the product in a packaging container, and if you ever need to fill it with an oxygen absorber,
It has a great advantage in practical use such that the amount thereof is extremely small.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C08K 3/16 KAD 7242-4J C08L 101/00 KAD (72) Inventor Kunihiko Mizutani Funami-cho, Minato-ku, Nagoya-shi, Aichi No. 1 No. 1 Toagosei Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Satoshi Nakamura No. 1 Funami-cho, Minato-ku Nagoya City, Aichi Prefecture No. 1 Toagosei Synthetic Chemical Industry Co., Ltd. Nagoya Research Institute (56 ) Reference JP 56-60642 (JP, A) JP 55-34164 (JP, A) JP 63-214351 (JP, A)

Claims (5)

[Claims] 1. An oxygen absorber comprising iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less, and a metal halide. 2. A thermoplastic resin in which an oxygen absorbent composed of an iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less and a metal halide is dispersed and carried. A resin composition having oxygen absorbability, which is characterized in that: 3. A thermoplastic resin in which an oxygen absorbent composed of iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less and a metal halide is dispersed and carried. A film or sheet formed from a resin composition having oxygen absorbability. 4. A thermoplastic resin in which an oxygen absorbent composed of iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less and a metal halide is dispersed and carried. A packaging container formed of a resin composition having an oxygen absorbing property. 5. A thermal superplastic resin in which an oxygen absorbent consisting of iron powder having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less and a metal halide is dispersed and carried. A packaging container formed of a film or sheet made of a resin composition having oxygen absorption property.