JPH04191039A - Packaging body - Google Patents

Abstract

PURPOSE:To prevent oxygen barrier properties from lowering with time by a structure wherein at least one layer of the packaging body contains substance having oxygen adsorbing function under the condition being microencapsulated and sealed with water soluble polymer. CONSTITUTION:The packaging body 10 concerned is a bottle having multilayer structure or consisting of outer layer 1/bonding layer 2/oxygen barrier layer 3/bonding layer 4/inner layer 2. The outer layer 1 and the inner layer 5 are made of hydrophobic resin. The bonding layers 2 and 4 are made of adherent resin and act as protective layers. The oxygen barrier layer 3 is made of moisture sensitive oxygen barrier resin and contains substance 7 having oxygen adsorbing function under the condition being microencapsulated with water soluble polymer 6. Since microencapsulated with the water soluble polymer 6, the substance 7 having oxygen adsorbing function does not absorb the moisture of outer atmosphere at manufacturing and accordingly poor forming due to the containment of moisture at manufacturing does not develop.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a packaging body, and more specifically, it is capable of maintaining good oxygen barrier properties over time and improves the shelf life of contents such as foods and medicines. The present invention relates to packaging bodies that are excellent and useful for various packaging applications such as packaging containers such as bottles, tubes, cups, pouches, bags, and wraps, and films.

Conventional technology Although moisture-sensitive oxygen barrier resins such as saponified ethylene-vinyl acetate copolymers have excellent oxygen barrier properties, they are highly dependent on humidity, so oxygen permeation tends to increase significantly in high humidity regions. It is in. Therefore, in general, as a package, an oxygen barrier resin layer that is highly humidity-dependent is coated with a protective layer of a hydrophobic resin such as polyethylene that has a low water absorption rate. Efforts have been made to avoid contact with moisture and thereby maintain the oxygen barrier properties of the package (for example, Japanese Utility Model Application Publication No. 47-23353).

However, under high humidity and high temperature conditions, such as during sterilization or retort processing (hereinafter referred to as retort treatment in the present invention), the water absorption rate of the polyethylene itself that protects the oxygen barrier resin layer increases. Moisture permeability increases significantly, and as a result, moisture that has permeated through the protective layer transfers to the oxygen barrier resin layer, significantly impairing the oxygen barrier properties of the package. This is generally referred to as "water shock," and the barrier properties deteriorate over several days after the high humidity and high temperature conditions have passed. As a result, a large amount of oxygen enters the package within this period, causing internal damage. It was believed that this would cause oxidation deterioration.

In order to improve these drawbacks, a water-absorbing substance is added to the protective layer, and this water-absorbing substance absorbs moisture that enters the protective layer, thereby reducing moisture transfer to the oxygen barrier resin layer. It is proposed that. For example, in JP-A-57-170748, in a package having a moisture-sensitive barrier resin layer such as a saponified ethylene-vinyl acetate copolymer, dry It has been shown that oxygen barrier properties can be maintained by providing a layer containing an agent to protect a moisture-sensitive barrier resin layer.

Also, JP-A-58-98251 and JP-A-61-11
No. 339 discloses dispersing super absorbent resin particles in a protective layer.

However, in the case of a package containing a desiccant as shown in JP-A-57-170748, since the desiccant itself has poor water absorbency, it is necessary to add a large amount. It has been practically difficult to create packaging that maintains oxygen barrier properties.

Therefore, if an excessive amount of desiccant is added in order to improve the water absorption effect, there is a drawback that the properties of the resin constituting the layer, such as transparency and physical strength, are impaired. Also, JP-A-58-98251 and JP-A-61-113
Super absorbent resins such as those disclosed in Publication No. 39 have superior water absorbency compared to the desiccant described above, but when such super absorbent resin particles are mixed and dispersed in a polyolefin resin protective layer, the dispersion There is almost no decrease in the hardness of the polyolefin resin at the particle interface, and the protective layer suppresses the expansion of the superabsorbent resin particles due to water absorption, significantly inhibiting the inherent water absorbency of the superabsorbent resin. . Therefore, the water absorption swelling property is low and it is difficult to swell, so the swelling due to water absorption of the mixed and dispersed super absorbent resin particles is suppressed,
Therefore, there is a problem in that its water absorption capacity is suppressed. Therefore, it was not possible to obtain the expected effect in preventing deterioration of oxygen barrier properties due to migration of moisture and moisture under high-humidity, high-temperature conditions in retorts for sterilization.

Therefore, in recent years, it has been proposed to mix a substance with an oxygen adsorption function into the layers constituting the package in order to prevent the intrusion of oxygen itself, which causes oxidation and deterioration of the contents. ing. One of them is the Special Table Hei 2-50.
There is one shown in No. 0846. This utilizes the ability to adsorb oxygen when a polymer such as metaxylylene diamine contains a specific metal catalyst such as cobalt.

Still another method, as shown in JP-A-1-278344, is to mix an oxygen scavenger that exhibits oxidizing action in the presence of moisture into the oxygen barrier thermoplastic resin of the intermediate layer.

Problems to be Solved by the Invention In the above-mentioned method, oxygen that reaches a wall made of a polymer such as metaxylylene diamine is adsorbed into the polymer by using a specific metal catalyst such as cobalt due to the oxidizing action of the metal catalyst. It is possible to exhibit the oxygen adsorption function without passing it inside the package, but since this function is developed from the time the metal catalyst is added to the polymer, oxygen has already been absorbed by the time of retorting. Most of the adsorption function may be lost. In addition, in order to give the above-mentioned packaging the ability to adsorb a large amount of oxygen that enters during retorting, a large amount of metal catalyst must be added, especially for packaging in this field where transparency is expected. Not only is this unsuitable, but the moldability and mechanical strength are also reduced.

In the latter method, an oxygen scavenger that exhibits an oxidizing effect in the presence of moisture is mixed into the oxygen-barrier thermoplastic resin. It is certainly possible to overcome the drawback that most of the adsorption function is lost. In other words, during normal conditions until retorting, the protective layer on the surface prevents moisture from entering, so the oxidizing action of the oxygen scavenger does not start and the oxygen adsorption function is not lost, and when retorting, The oxygen absorbing function of the oxygen scavenger is activated by the moisture that passes through the protective layer for the first time. but,
When water is added to the oxygen scavenger, the metal powder, which has a reducing property, becomes activated by the water and undergoes an oxidation reaction with heat generation, which affects the composition of the oxygen barrier thermoplastic resin and deteriorates its physical properties. In particular, the transparency may be reduced, and the color may change. Further, when manufacturing a package using this type of oxygen absorber, there is a problem with how to treat the oxygen absorber. Oxygen scavengers easily absorb moisture in the air and begin to exhibit their oxidizing function, which not only reduces their oxygen adsorption function during manufacturing, but also causes the oxygen barrier resin layer to foam during molding due to the absorbed moisture. There is a drawback that it does.

Therefore, the first object of the present invention is to solve the above-mentioned problems and to prevent the deterioration of oxygen barrier properties over time.
It is therefore an object of the present invention to provide a package with excellent preservability of contents.

The second object of the present invention is to maintain high oxygen barrier properties not only during storage but also under high temperature and high humidity conditions such as heat sterilization and hot filling, without degrading the properties of each constituent layer. To provide a package that is maintained at a relatively low cost.

Furthermore, a third object of the present invention is to provide a package that does not lose most of its oxygen adsorption function before being retorted.

A fourth object of the present invention is to provide a package whose moldability or mechanical strength is not impaired.

Means for Solving the Problems Therefore, the present invention microcapsules a substance with an oxygen adsorption function with a water-soluble polymer and seals it.
The purpose is to control the oxygen adsorption function and efficiently develop the oxygen adsorption function to 100% during retorts that require the adsorption function, thereby solving the above problems. Moreover, by microcapsulating a substance with an oxygen adsorption function with a water-soluble polymer, the oxygen adsorption function of the substance with an oxygen adsorption function can be used efficiently without wasting it during manufacturing or transportation. Moreover, since the material with oxygen adsorption function is manufactured by covering the surface of the material and putting it in one layer of the packaging body, it is not possible to mix it directly into these resins. Unlike other cases, moldability or mechanical strength is not impaired.

The package of the present invention contains a minimum amount of a substance having an oxygen adsorption function that is sufficient to have an oxygen adsorption function only during a period of several days during which water shock occurs.

Therefore, since a large amount of a substance having an oxygen adsorption function is not added, transparency is not impaired. Here, since the water-soluble polymer has reversibility, the oxygen barrier properties of the moisture-sensitive oxygen barrier resin layer are restored by air drying after retorting, and the moisture in the water-soluble polymer is also dried over time. It does not inhibit the restoration of the oxygen barrier properties of the moisture-sensitive oxygen barrier resin layer. A moisture-sensitive oxygen barrier resin layer is essential to the package of the present invention. This moisture-sensitive oxygen barrier resin layer has an oxygen permeability coefficient of 1×1011cc-α/a++・5ec.
- Since a moisture-sensitive oxygen barrier resin with an oxygen barrier property of less than 1g (37℃, R, H, 0%) is used, this oxygen barrier property is basically sufficient under normal conditions. be. However, the purpose of the present invention is to compensate for the decrease in oxygen barrier properties during water shock.

In other words, by backing up the decrease in oxygen barrier properties over several days during water shock caused by retorting with the oxygen adsorption function of a substance that has an oxygen adsorption function, it is possible to maintain good oxygen barrier properties over time.
This provides a packaging body that is useful for various packaging purposes such as packaging containers for foods, medicines, and other items that require long shelf life, such as bottles, tubes, cups, pouches, bags, wraps, and films. There is a particular thing.

Each component of the present invention will be explained in detail below.

Water sensitive oxygen barrier resin.

Oxygen permeability coefficient is 1×10-th cc-an/ad*
sec.

・Resin with αBg (37°C, R, 8.0%) or less,
For example, it is made of saponified ethylene-vinyl acetate copolymer, polyamide, polyvinyl alcohol, and modified products or mixtures thereof.

Among these, saponified ethylene-vinyl acetate copolymers having an ethylene content of 25 to 50 mol% and a saponification degree of 96% or more are preferred. By setting the ethylene content to 25 mol% or more, extrusion moldability, blow moldability, and injection moldability are improved, while by suppressing the ethylene content to 50 mol% or less, good oxygen barrier properties are exhibited, and the degree of saponification is reduced. When the content is 96% or more, the oxygen barrier property becomes good.

Hydrophobic resin A crystalline thermoplastic resin with a melting point of 100°C or higher measured with a differential scanning calorimeter, or a flow start temperature measured with a Koka type flow tester (load 100 kg).

Dice 1 Φ x 10, flow is 2 m'/sec
It is made of amorphous thermoplastic resin with a temperature of 100°C or higher, such as polypropylene, polystyrene, high-density polyethylene, medium-low density polyethylene, linear low-density polyethylene, polyethylene terephthalate, polycarbonate, It consists of an acrylonitrile-styrene-butadiene copolymer, and modified products or mixtures thereof.

Adhesive resin: polyethylene graft-modified with unsaturated carboxylic acids, unsaturated polycarboxylic acids, or their acid anhydrides, polypropylene, modified polyolefins containing polar groups such as ethylene-vinyl acetate copolymers, ethylene-vinyl acetate Copolymers and saponified products thereof, ethylene-ethyl acrylate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ionomers crosslinked with metal ions thereof, or block copolymers of styrene and butadiene. It consists of combinations, etc.

Substances with oxygen adsorption function: Reducing metals such as reducing iron, reducing zinc, etc., and reducing metals such as ferrous oxide, triiron tetroxide, iron carbide, iron hydroxide, ferrous sulfate, etc. metal compounds.

Alkaline modified carbohydrates such as el sorbate, low molecular weight phenols.

water-soluble polymers microorganism-based, plant-based, animal-based natural polymers such as casein and gelatin; cellulose derivatives such as CMC; guar derivatives such as CMG; semi-synthetic polymers such as alginic acid derivatives and starch derivatives; vinyl-based polymers such as polyvinyl alcohol; Synthetic polymers include acrylic polymers such as polyacrylonitrile and amide polymers such as polyacrylamide.

The diameter of the water-soluble polymer needs to be smaller than the thickness of the layer of the package containing it, and is particularly preferably from 2 to 100 microns.

Multilayer structure It is composed of two or more layers by coextrusion or dry lamination, and representative examples of the layer structure are shown below.

2 layers A/ (B: X) (A: X) /B 3 layers A/ (B: X) /A (A: X)/B/ (A: X) (A: X)
/ (B: X) / (A: X) (A:
X) /B/A 4 layers A/B/ (B:X)/A(A:X)
/B/ (B:X) /A(A:X)/B/
(B: X)/(A: X) 5 layers A/C/
(B:X)/C/A(A:X)/C/B/C/
A (A: X)/C/B/C/ (A: X)A/
(C: X)/B/ (C: Indicates a substance that has

The proportion of the substance X microencapsulated with a water-soluble polymer having an oxygen adsorption function mixed in the resin layer constituting the package is preferably 5 to 60% by weight based on the resin constituting the layer.

Packaging - In the present invention, packaging refers to jam, ketchup, mayonnaise, edible oil, fruits, vegetables, cooked foods, soups,
Packaging bodies used for packaging such as bottles, tubes, cups, pouches, bags, and wraps for storing foods such as fruit drinks, pharmaceuticals such as blood, plasma substitutes, and infusions, and other liquids, viscous substances, and powders. be.

Effects of the Invention The effects of the packaging body of the present invention are shown in Figures 1 and 2.
This will be explained with reference to the figures. FIG. 1 is for schematically showing the action of the package of the present invention, and FIG. 2 is a schematic diagram illustrating a substance having an oxygen adsorption function microencapsulated with a water-soluble polymer. This package 10 is a bottle, and its multilayer structure is composed of outer layer 1/adhesive layer 2/oxygen barrier layer 3/adhesive layer 4/inner layer 5. The outer layer 1 and the inner layer 5 are made of hydrophobic resin, and the adhesive layer 2.4
is composed of adhesive resin, and these correspond to the protective layer in the present invention.

The oxygen barrier layer 3 is composed of a water-receptive oxygen barrier resin, and contains a substance 7 having an oxygen adsorption function microencapsulated with a water-soluble polymer 6. Substances with oxygen adsorption function 7
If it is microencapsulated with the water-soluble polymer 6, it will not absorb moisture from the external atmosphere during manufacturing, and therefore, molding defects will not occur due to moisture content during manufacturing. In addition, as mentioned above, under high humidity and high temperature conditions such as during retort processing, the relative humidity outside the container is 100%, so the water absorption rate of the hydrophobic resin itself such as polyethylene increases, and the As shown in , moisture 9 comes to permeate the outer layer 1 made of hydrophobic resin from the outer surface of the multilayer structure, passes through the adhesive layer 2 , and transfers to the oxygen barrier layer 3 . The moisture 9 that has reached the oxygen barrier layer 3 reaches the water-soluble polymer 6 and dissolves the water-soluble polymer 6. This breaks the capsule of the water-soluble polymer 6, removes the sealing property, and causes the substance 7 to absorb oxygen.
is exposed and the oxygen adsorption function is expressed. The oxygen adsorption function can fully exhibit its properties by removing the sealing properties of the microcapsules of the water-soluble polymer 6. In particular, it is preferable when the substance having an oxygen adsorption function is a substance that is reducible by moisture, since the oxygen adsorption function is expressed by the moisture attached to the water-soluble polymer. Furthermore, since the substance is encapsulated with a water-soluble polymer, moisture is directly transmitted to the substance having an oxygen adsorption function, and the reduction is effectively carried out. In FIG. 1, solid line arrows indicate the migration of oxygen 8, and indicate where it is adsorbed by substance 7 having an oxygen adsorption function. A package is one that is manufactured in a packaging form, contains the contents, is sealed, and then retorted, or one that is manufactured in a packaging form (for example, a bottle) and is hot-filled with the contents and then sealed with a cap, etc. There is. This type of packaging is generally exposed to high humidity and high temperature after or during storage of the contents,
This condition impairs the oxygen barrier property at once, but the packaging of the present invention takes advantage of this high humidity and high temperature.
This is the beginning of the oxygen adsorption ability of substances that have an oxygen adsorption function. As mentioned above, the problem with this type of packaging is said to be the amount of oxygen that permeates into the container within several days after retorting. According to the packaging body of the present invention, the oxygen adsorption ability is developed by high humidity and high temperature treatment such as retorting, so the amount of oxygen permeation after several days after retorting is extremely small (and even moreover, the amount of oxygen permeated at the stage before this is extremely low). Oxygen adsorption capacity is not wasted, and contamination with substances having an oxygen adsorption function can be kept to a minimum.

In the present invention, the layer containing the microencapsulated substance having an oxygen adsorption function is applied to at least one of the outer layer, the inner layer, the protective layer such as the adhesive layer or the regeneration layer, and the oxygen barrier layer. Or, when mixed in the adhesive layer adjacent to the inner layer, it exhibits the ability to adsorb oxygen in the case of water-soluble contents, and when mixed in the outer layer or the adhesive layer adjacent to the outer layer, it prevents oxygen from entering from the outside and has high humidity such as in retorts. This will supplement the oxygen barrier properties of the oxygen barrier resin that have decreased due to the high temperature treatment, thereby preventing the oxygen barrier properties from decreasing. Further, when mixed into the oxygen barrier layer, the function becomes exactly intermediate between the above two cases.

These should be appropriately selected depending on the contents to be accommodated and the mode of use.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples and comparative examples.

Examples 1 and 2 The materials shown in Table 1 were used in the composition shown in Table 2, and substances XI and X2 having an oxygen adsorption function were microencapsulated with a water-soluble polymer in oxygen barrier resin B. After mixing at a mixing rate of 30% by weight with respect to 70% by weight of the resin, the materials are melt-kneaded in an extruder, and when fed to the extrusion die, materials A and C are branched into two paths. , A/C/ (B: X+)/C/AA/C in an extrusion die
/ (B: Then, the plasticized parison is placed in a split mold having a cavity for forming a container on the inner surface, and then the split mold is closed, pressure fluid is introduced into the parison for blow molding, and after cooling by the mold, Then, the molded product was taken out, and a multilayer bottle with a capacity of 500 cc as shown in FIG. 3 was obtained. The multilayer bottle 10 obtained by the above molding method has an outer layer 1 and an inner layer 5 consisting of 8 (B:X,) or (B:X2).
Oxygen barrier layer made of the material 3. It is composed of five layers including an adhesive layer 2.4 made of material C. In addition, X is a substance having an oxygen adsorption function microencapsulated with a water-soluble polymer, and CMC is a cellulose derivative.
50 parts by weight of ferrous sulfate was added to 100 parts by weight of a 50 wt % water-soluble emulsion, and the ferrous sulfate was microencapsulated and sealed. Zarani X2
CM is a substance with an oxygen adsorption function that is microencapsulated in a water-soluble polymer, and is a guar derivative.
50 parts by weight of ferrous sulfate was added to 100 parts by weight of a water-soluble emulsion of G 50 wt%, and the ferrous sulfate was nicroencapsulated and sealed.

Comparative Example 1 to Comparative Example 3 Comparative Example 1 is a case containing only oxygen barrier resin, and ferrous sulfate, which is a substance with an oxygen adsorption function, and CMC, which is a cellulose derivative, which is a water-soluble polymer, are mixed in the same ratio. Comparative Example 2 is a mixture in which 30% by weight of the oxygen barrier resin is mixed with 70% by weight of the oxygen barrier resin.
Comparative Example 3 is a bottle in which only 30% by weight of iron is removed from 70% by weight of oxygen barrier resin, and other than this, it is formed using the same method and mold as in Example 1 to produce a multilayer bottle with a 5-layer structure. I got it.

Examples 3 and 4 Substance X having an oxygen adsorption function microencapsulated in oxygen barrier resin B with a water-soluble polymer.

The mixing ratio was the same as in Example 1, except that in Example 3, 60% by weight was mixed in with respect to 40% by weight of oxygen barrier resin, and in Example 4, 5% by weight was mixed in with respect to 95% by weight of oxygen barrier resin. A multilayer bottle with a five-layer structure was obtained by forming using the same method and mold.

Comparative Example 4 and Comparative Example 5 In Comparative Example 4, the mixing ratio of substance x1 having an oxygen adsorption function microencapsulated with a water-soluble polymer in oxygen barrier resin B was 70% by weight relative to 30% by weight of oxygen barrier resin. Comparative Example 5 was formed using the same method and mold as in Example 1, except that 1% by weight was mixed with 99% by weight of the oxygen barrier resin to obtain a multilayer bottle with a 5-layer structure.

Examples 5 to 7 Examples 5 to 7 are examples in which the intermediate layer is made of only oxygen barrier resin B, and in Example 5, the inner layer is made of microcapsules made of a water-soluble polymer based on 90% by weight of polypropylene. 10 of the substance X1 that has an oxygen adsorption function
In Example 6, the outer layer was made of a material Xl having an oxygen adsorption function micro-encapsulated with a water-soluble polymer for 90% by weight of polypropylene.
In addition, in Example 7, 95% by weight of polypropylene was mixed in the inner layer and outer layer.
A substance X having an oxygen adsorption function microencapsulated with a water-soluble polymer is mixed in at a mixing rate of 5% by weight.

(Left below) Table 1: Oxygen permeability (cc/cd・24hr) of the multilayer bottles obtained in the above examples and comparative examples, and after filling the bottles with hot water at 80°C, The bottle was sealed with aluminum, and the oxygen permeability of the bottle immediately after retorting at 120° C. for 30 minutes and the oxygen permeability of the bottle one month after retorting were measured. The results are shown in Table 3.

(Hereinafter, blank space) Table 3 As can be seen from Tables 2 and 3, by microcapsulating and sealing a substance that has an oxygen adsorption function with a water-soluble polymer, it is possible to improve the oxygen barrier properties of the package. It was found that no deterioration occurred even one month after retorting, and that the barrier properties could be stably maintained over time. Further, it can be seen that the mixing ratio of the substance having an oxygen adsorption function microencapsulated with a water-soluble polymer into the resin is preferably in the range of 5 to 60% by weight based on 95 to 40% by weight of the resin.

Effects of the Invention In the present invention, the layer containing the microencapsulated substance having an oxygen adsorption function develops its oxygen adsorption ability through high-humidity treatment such as retorting, so the amount of oxygen permeation after retorting is reduced. The amount of oxygen adsorption becomes extremely small, and furthermore, the oxygen adsorption capacity is not wasted unnecessarily at the stage before this, and the contamination of substances with an oxygen adsorption function can be kept to a minimum.

[Brief explanation of drawings]

Fig. 1 is an enlarged cross-sectional view of the essential parts of a five-layer structure schematically showing the action of the packaging body of the present invention, and Fig. 2 is a mock-up illustrating a substance with an oxygen adsorption function microencapsulated with a water-soluble polymer. FIG. 3 is a partially broken pressure surface view showing an embodiment of the multilayer bottle according to the present invention. DESCRIPTION OF SYMBOLS 1...Outer layer, 3...Oxygen barrier layer, 5...Inner layer, 6...Water-soluble polymer, 7...Substance with oxygen adsorption function

Claims (4)

[Claims] (1) In a two or more layered package having a protective layer mainly made of a hydrophobic resin and a layer of a moisture-sensitive oxygen barrier resin, at least one layer of the package contains a water-soluble substance having an oxygen adsorption function. A packaging body characterized by containing microcapsules in a sealed state with a polymer. (2) The package according to claim 1, wherein the substance having an oxygen adsorption function is a reducing metal and its metal compound, an alkali-denatured carbohydrate, or a low-molecular-weight phenol. (3) The package according to claim 1, wherein the water-soluble polymer is a semi-synthetic polymer such as a cellulose derivative, a guar derivative, an alginic acid derivative, or a starch derivative. (4) The package according to claim 1, wherein the water-soluble polymer is made of a vinyl, acrylic, or amide polymer.