JPS6071955A - Oxygen indicator - Google Patents

Abstract

PURPOSE:To overcome the disadvantage of aq. and solid oxygen indicators and to obtain industrially easily an inexpensive oxygen indicator by using bis-ethylene diimine cobalt or the deriv. thereof. CONSTITUTION:This oxygen indicator is formed by using bis(orthohydroxy acetophenone) ethylene diimine cobalt or the deriv. thereof and printing, coating or vapor deposition of the above-mentioned reagent on, for example, a base material and laminating or coating a film having good oxygen permeability or a porous film thereon. The resultant oxygen indicator reacts only with oxygen in the atmosphere and does not require water and other compd. in the stage of reaction. The above-mentioned reaction with oxygen is extremely sensitive and the discoloration is observed even with 0.1% oxygen concn. in air. The indicator discolors reversibly any number of times and has an excellent shelf life.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen indicator that changes color depending on the presence or absence of oxygen.

In recent years, in order to improve the shelf life of packaged foods, especially to prevent oxidation of oil-based foods, to prevent spoilage and mold growth of wet foods, and to exterminate pests of clothing and grains, vacuum packaging, nitrogen purge packaging, and deoxidizing packaging have been introduced. Oxygen inside the container is removed by sealing the agent together with the contents.

However, to confirm the removal of oxygen when packaging the contents, or even after the contents have been packaged, the container may not be sealed tightly due to poor sealing, pinholes in the packaging container, or damage to the container during transportation. Because it may be insufficient,
It has become considered desirable to encapsulate an oxygen indicator along with the contents so that the presence or absence of oxygen in the container can be easily determined during the product distribution process or by the end consumer.

Conventionally, oxygen indicators that can be used include water-based oxygen indicators consisting of caustic soda, glucose, and methylene blue, and specific dyes such as methylene blue.

Solid oxygen indicators containing alkaline substances and dithionites are known.

The water-based oxygen indicators mentioned above do not change color unless they are used as an aqueous solution, so even if they are used by soaking them into a water-containing base material, they cannot be used when the content is food that dislikes moisture; In this case, there was a problem of contamination. Also, glucose, which is a reducing agent, is easily oxidized in the air.

The biggest practical difficulty was that it could not be stored in air for long periods of time.

The above solid oxygen indicator is disclosed in Japanese Patent Application Laid-Open No. 53-117.
It is disclosed in Japanese Patent No. 495. But for the oxygen indicator to work.

The presence of water or an alcoholic compound is necessary, and in this respect the drawbacks of water-based oxygen indicators have not been fully resolved. Further, it is necessary to use the oxygen indicator by mechanically mixing it with a water-absorbing powder, or by molding the mixed powder into a tablet, making the oxygen indicator industrially extremely expensive. In particular, the high price has hindered the widespread use of this type of oxygen indicator.

The present inventors have conducted intensive studies to overcome the drawbacks of the aqueous and solid oxygen indicators and to develop an industrially very easy and inexpensive oxygen indicator, and as a result, they have arrived at the present invention. That is, the present invention is an oxygen indicator that changes color depending on the presence or absence of oxygen, using bis(orthohydroxyacetophenone)ethylenediimine cobalt or a derivative thereof, and further, the oxygen indicator is vapor-deposited on the surface of a base material or bis(orthohydroxyacetophenone)ethylenediimine. This is an oxygen indicator that is printed or painted on a substrate with a printing ink or paint containing cobalt or a derivative thereof. In addition, in two-color development, the barley is scorched depending on the presence or absence of oxygen. is an expression that also includes discoloration due to changes in the amount of oxygen present.

In the present invention, the bis(orthohydroxyacetophenone)ethylenediimine cobalt derivative has a substituent such as a halogen atom, an alkyl group, an alkoxy group, or a nitro group.

Bis(orthohydroxyacetophenone) ethylenediimine cobalt or a derivative thereof of the present invention is 2, for example, orthohydroxyacetophenone or a derivative thereof,
refluxing in an alcoholic solvent such as ethanol with ethylenediamine and a cobalt salt such as cobalt acetate or cobalt nitrate, or bis(orthohydroxyacetophenone)ethylenediimine or a derivative thereof;
It can be easily obtained by adding an aqueous solution of cobal(II) chloride to a hot aqueous solution containing sodium acetate and sodium hydroxide.

Bis(orthohydroxyacetophenone)ethylenediimine cobalt or its derivatives obtained in the form of powder have weak activity or no reaction with oxygen as it is, so it is preferable to activate it. Activation can provide sufficient sensitivity to oxygen concentration for use as an oxygen indicator of the present invention.

As a processing operation for activation, powder.

Sublimation treatment under +11 heating (2) Fine powder (3
) There are methods such as removing pyridine by immersion in pyridine and then heating degassing, but method (3) can be used to remove cobalt bis(orthohydroxyacetophenone)ethylenediimine, which has a particularly high sensitivity to oxygen. A derivative thereof is obtained.

In the present invention, bis(orthohydroxy)ethylenediimine cobalt or a derivative thereof can be used as a powder, but it is preferably provided on a substrate by printing or painting, or by vapor deposition (including sputtering). This can be formed by printing or vapor deposition.

This is a desirable method not only because it is easy to handle but also because it can increase the sensitivity to oxygen.

The following resins can be used as a binder for printing ink or paint in the present invention.

Natural rubber, shellac, cellulose, protein.

Natural resins such as rosin, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol.

Linear products such as polystyrene, polybutadiene, acrylic resins, chlorinated rubber, cyclized rubber, alcohol-soluble phenol resin, cellulose derivatives and modified polyolefins such as chlorinated polypropylene, chlorinated ethylene-vinyl acetate copolymers, etc. Polymers, phenolic resins, alkyd resins.

Melamine resin, epoxy resin, urethane resin.

These include reactive resins such as unsaturated polyester resins.

The above-mentioned binders can be freely selected from one or more types depending on the type of base material and depending on the requirements.
Depending on the type, the hue 1 coloring strength, width of discoloration, response speed, etc. differ slightly.

Base materials that can be used in the present invention include polypropylene, polyethylene, polyester, polyvinylidene chloride, and polyvinyl chloride.

Plastic films such as polybutadiene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polystyrene, polyamide, metal foils such as aluminum foil, 2 paper, and cloth.

and a composite film or sheet selected from these. Alternatively, it may be made of plastic with a metal such as aluminum or tin or an inorganic material such as alumina deposited on it. In addition, especially when using aluminum foil or a white-colored opaque film as a base material, the color changes from bright yellow to black depending on the oxygen concentration compared to when using a transparent film. Can be clearly observed.

The printing ink or paint containing bis(orthohydroxyacetophenone)ethylenediimine cobalt or a derivative thereof in the present invention is.

Preferably, activated bis(orthohydroxyacetophenone)ethylenediimine cobalt or a derivative thereof, a resin serving as a binder component of a printing ink or paint, and a suitable pigment to achieve a desired hue change are added. Sand mill the resin in the presence of a solvent.

Impact type or kneader such as attritor.

Nodules are produced by dispersing in the resin using a shear type dispersing machine such as a roll. In this dispersion process, the powder of bis(orthohydroxyacetophenone)ethylenediimine cobalt or its derivatives is ground into a finer powder, so that the surface area of the powder increases significantly and it becomes more sensitive to oxygen.

The dispersion of bis(orthohydroxyacetophenone)ethylenediimine cobalt or its derivatives obtained by the above method can be produced by a gravure method, an offset method, or a silk screen method.

The substrate can be printed or painted using various printing or painting methods such as roll coating or spraying, but the gravure method is capable of forming a thin film due to its oxygen permeability.

Offset printing is advantageous.

In addition, the oxygen indicator is produced by vapor deposition.

After drying the obtained bis(orthohydroxyacetophenone)ethylenediimine cobalt or its derivative,
It is preferably obtained by vapor deposition on the surface of a substrate under reduced pressure. When used by vapor deposition on the surface of a substrate, the vapor deposition increases the activity against oxygen, resulting in extremely sensitive discoloration, especially when aluminum foil or a white opaque film is used as the substrate rather than a transparent film. .

A color change from bright yellow to black can be clearly observed depending on the oxygen concentration.

91 The oxygen indicator in the present invention can also be used by printing, painting, or vapor depositing on a base material, and then laminating or coating a film with good oxygen permeability or a porous film.

The oxygen indicator of the present invention is preferably in the form of a film or sheet, but it can be freely cut and used. Alternatively, it is also possible to use the cut material by enclosing it in a film.

The oxygen indicator of the present invention works only with atmospheric oxygen and does not require water or other compounds. The reaction to oxygen is sensitive, and discoloration is observed even at an oxygen concentration of 0.1% in the air. It also has excellent storage stability as it reversibly changes color any number of times.

Examples will be described below.

Example 1 Bis(orthohydroxyacetophenone)ethylenediimine Kobal) (1) activated with pyridine was mixed in a sand mill with a gravure printing face containing vinyl chloride-vinyl acetate copolymer-10- as the main component. This was dispersed to obtain a gravure ink containing 10% by weight of the cobalt complex.

This gravure ink was gravure printed on high quality paper to a film thickness of 10 microns to create an oxygen indicator.

The produced trial pieces were placed in atmospheres with different oxygen concentrations at 25°C, and changes in hue were observed after 1 hour. In addition, activated bis(orthohydroxyacetophenone)
Observations were also made on ethylenediimine cobalt powder.

=11-Example 2 Same as Example 1 using activated bis(2-hydroxy, 3-ethoxyacetophenone) ethylenediimine cobalt (■) using a gravure printing face mainly composed of nitrocellulose and polyamide resin. A gravure ink having a cobalt complex content of 10% by weight was obtained by the above operation.

This gravure ink was gravure printed on the surface of a polyethylene terephthalate film which had been subjected to corona discharge treatment to a film thickness of 10 microns to produce an oxygen indicator.

The prepared prototype piece was placed in an oxygen atmosphere for 1 hour to completely turn black, and then placed in a container with a commercially available oxygen absorber at 25°C.
The color change was observed.

121 Example 3 Activated bis(2-hydroxy, 3-fluoroacetophenone) ethylenediimine cobalt (■) was injected as in Example 1 using a gravure ink face containing ethylene-vinyl acetate copolymer as the main component. A gravure ink having a cobalt complex content of 10% by weight was obtained by the same operation.

This gravure ink was gravure printed on a polyethylene surface to a film thickness of 10 microns to produce an oxygen indicator.

Using the oxygen indicator thus obtained, the same test as in Example 1 was carried out and almost the same results were obtained.

13- Example 4 Printing was carried out on the surface of a polyethylene terephthalate film on which aluminum was vapor-deposited using the gravure ink used in Example 2 under the same conditions as in Example 2, and then a clear film with the same binder components was further applied on top of this. An oxygen indicator was obtained by printing to a thickness of 5 microns. The performance of this oxygen indicator was almost equivalent to that of the oxygen indicator obtained in Example 2.

Example 5 Phthalocyanine blue was further added to the cobalt complex-containing gravure ink used in Example 1 so that the content thereof was 0.2% by weight based on the total amount of ink.

Using the gravure ink thus obtained, an oxygen indicator was produced in the same manner as in Example 1.

The same performance test as in Example 1 was conducted to observe hue changes.

14- Example 6 Polyethylene terephthalate/aluminum foil/polyethylene/unstretched polypropylene An oxygen indicator was prepared by depositing bis(orthomethoxyacetophenone)ethylenediimine cobalt (I) on the unstretched polypropylene surface of the composite film under the following conditions. .

Equipment: Boat using EBH-6 type vacuum evaporation equipment manufactured by Japan Vacuum Technology ■ Tungsten boat Distance to substrate: 9cm Degree of vacuum: I The samples were placed in atmospheres with different concentrations, and changes in hue were observed after 1 hour. For comparison, a powder of bis(orthohydroxyacetophenone) ethylenediimine cobalt was also observed.

Example 6 Bis(2-hydroxy 3-ethoxyacetophenone) ethylenediimine cobalt (II) was deposited on the surface of polyethylene terephthalate under the same conditions as in Example 6 to produce an oxygen indicator.

The prepared prototype piece was placed in an oxygen atmosphere for 1 hour to completely turn black, and then placed in a container with a commercially available deoxidizing material at 25°C.
The color change was observed.

Example 8 Bis(2-hydroxy 3-fluoroacetophenone) ethylenediimine Kobal) (
[1] was deposited under the same conditions as in Example 6 to produce an oxygen indicator. The same test as in Example 6 was conducted and almost the same results were obtained.

17-

Claims (1)

[Claims] 1. An oxygen indicator that changes color depending on the presence or absence of oxygen, characterized by using bis(orthohydroxyacetophenone) ethylenediimine cobalt or a derivative thereof. 2. The oxygen indicator according to claim 1, which comprises bis(orthohydroxyacetophenone)ethylenediimine cobalt or its derivatives deposited on a base material. 3. The oxygen indicator according to claim 1, which is printed or coated on a substrate with a printing ink or paint containing bis(orthohydroxyacetophenone)ethylenediimine cobalt or a derivative thereof.