JPS5987364A - Oxygen indicator - Google Patents

Abstract

PURPOSE:To obtain a preservable and stable indicator which is discolored clearly and reversibly in accordance with O2 concentrations by printing or coating with printing inks or paints contg. bis(salicylaldehyde)-3,3'-diiminodipropylamine cobalt or its derivatives on a substrate. CONSTITUTION:In a synthetic resin varnish, a compound expressed by the formula I and its derivatives substituted by F, -OC2H5 or the like at the position there of the benzene ring are dispersed to make inks and paints, which are printed or coated on a supporter such as film made of PE or polyester, paper, metallic foil or the like. In this method, an indicator is obtd. which can be discolored clearly e.g. by the compound shown by the formula in accordance with the O2 concentrations of 0%, 1%, 10%, 20% respectively to yellow, brown, blackbrown, black and used repeatedly due to the reversible discoloration. This indicator is preservable and inexpensive, and can be applied for the comfirmation of the O2 removal at vacuum packagings of packaged foods, clothes, grain or the like, and the detection of the presence or absence of O2 permeation into packagings in a circulation process.

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 check the removal of oxygen when packaging the contents.

Alternatively, even after the contents have been packaged, the container may not be tightly sealed due to poor sealing, pinholes in the packaging container, or damage to the container during transportation, so an oxygen indicator may be enclosed with the contents. It has come to be considered desirable that the presence or absence of oxygen in a container can be easily determined by the end consumer or during the distribution process of the product.

Conventionally, water-based oxygen indicators consisting of caustic soda, glucose, and methylene blue, and solid oxygen indicators containing specific dyes such as methylene blue, alkaline substances, and dithionites have been known as oxygen indicators that can be used. There is.

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 some cases there was a problem of contamination.

In addition, since the reducing agent glucose is easily oxidized in the air, the biggest practical difficulty is that it cannot be stored in the air for a long period 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. However, in order for the oxygen indicator to work, the presence of water or an alcoholic compound is required, and in this respect, the drawbacks of water-based oxygen indicators have not yet been fully resolved. In addition, it is necessary to use it by mechanically mixing it with a water-absorbing powder, or by molding the mixed powder into a tablet.

Industrially, this results in an extremely expensive oxygen indicator. In particular, the high price has hindered the widespread use of this type of oxygen indicator.

The present inventors have conducted extensive 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 printed or coated on a substrate with a printing ink or paint containing bis(salicylaldehyde)-3°3'-diiminodipropylamine cobalt or a derivative thereof.

In the present invention, bis(salicylaldehyde)-3,3-
A derivative of diiminodipropylamine cobalt has a substituent such as a halogen atom, an alkyl group, an alkoxy group, or a nido tetragroup.

Bis(salicylaldehyde)-3,3-diiminodipropylamine cobalt or a derivative thereof of the present invention can be used, for example, by adding salicylaldehyde or a derivative thereof to 3,3-
Diaminodipropylamine and a cobalt salt such as cobalt acetate or cobalt nitrate are refluxed in an alcoholic solvent such as ethanol, or bis(salicylaldehyde)-3,3'-diiminodipropylamine or a derivative thereof, sodium acetate and It can be easily obtained by adding an aqueous solution of cobal chloride (n) to a hot aqueous solution containing sodium hydroxide.

Bis(salicylaldehyde)-3 obtained as powder
, 3-diiminodipropylamine cobalt or its derivatives have weak activity or no reaction to oxygen as they are, so it is preferable to activate them.

Activation can provide sufficient sensitivity to oxygen concentration for use as an oxygen indicator of the present invention.

Treatment operations for activation include methods such as (1) sublimating the powder under heating, (2) pulverizing it, and (3) removing the pyridine by immersing it in pyridine and then heating and degassing it. By the method of 3), bis(salicylaldehyde l-3,3-
Diiminodipropylamine cobalt or a derivative thereof is obtained.

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, polystyrene, polybutadiene, acrylic resin, chlorinated rubber, cyclized rubber, alcohol-soluble phenolic resin , linear polymers such as cellulose derivatives and modified polyolefins such as chlorinated polypropylene, chlorinated ethylene-vinyl acetate copolymers, phenolic resins, alkyd resins, and melamine resins.

These include reactive resins such as epoxy resins, urethane resins, and unsaturated polyester resins. One or more types of binders can be freely selected depending on the type of base material and requirements.

Depending on the type, hue 1 coloring power, discoloration, response speed, etc. will vary slightly.

Base materials that can be used in the present invention include plastics such as polypropylene, polyethylene, polyester, polyvinylidene chloride, polyvinyl chloride, polybutadiene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polystyrene, and polyamide. 9 Paper, cloth, and composite films or sheets 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 aluminum foil or a white-colored opaque film is used as a base material, the color changes from bright yellow to black depending on the oxygen concentration compared to when a transparent film is used. Changes can be clearly observed.

Bis(salicylaldehyde)-3,3- in the present invention
Printing inks or paints containing diiminodipropylamine cobalt or its derivatives.

Preferably activated bis(salicylaldehyde)-
3,3-Diiminodipropylamine cobalt or a derivative thereof, a resin serving as a binder component of printing ink or paint, and an appropriate pigment to achieve a desired hue change. 1 Usually in the presence of a solvent for the resin. Impact type or kneader such as sand mill, attritor, etc.
It can be manufactured by dispersing it in a resin using a shear type dispersing machine such as a roll. In this dispersion process, the bis(salicylaldehyde)-3,3-diiminodipropylamine cobalt or its derivative powder is ground into a finer powder, which significantly increases the surface area of the powder and makes it more sensitive to oxygen. Become sensitive. The dispersion of bis(salicylaldehyde)-3,3'-diiminodipropylamine cobalt or a derivative thereof obtained by the above method is as follows.

Printing or painting can be done on the base material using various printing or painting methods such as gravure method, offset method, silk screen method, roll coating method, spray method, etc. However, from the point of view of oxygen permeability, it is difficult to form a thin film. Possible gravure method.

Offcent printing is advantageous.

The oxygen indicator of the present invention can also be used by printing or coating a substrate and further laminating or coating a film with good oxygen permeability or a porous film.

Although the oxygen indicator of the present invention is in the form of a film or sheet, 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 Activated bis(salicylaldehyde)-3゜3-diiminodipropylamine cobalt N) was dispersed in a sand mill together with a gravure printing face mainly composed of vinyl chloride-vinyl acetate copolymer, and the above A gravure ink with a cobalt complex content of 10% by weight was obtained.

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

(2) The produced trial pieces were placed in atmospheres with different oxygen concentrations at 25°C, and changes in hue were observed after 1 hour. For comparison, bis(salicylaldehyde)-3,
The f-diiminodipropylamine cobalt powder was also observed.

Example 2 Activated bis(3-ethoxysalicylaldehyde)-
3,3'-diiminodipropylamine cobalt (II
) was carried out in the same manner as in Example 1 using a gravure printing face mainly composed of nitrocellulose and polyamide resin to obtain a gravure ink containing 10% by weight of cobalt complex.

This gravure ink was gravure printed on the surface of a polyethylene terephthalate 10-rate 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.

Example 3 Activated bis(3-fluorosalicylaldehyde>-
3, Ryo-diiminodipropylamine cobalt(III)
A gravure ink having a cobalt complex content of 10% by weight was obtained in the same manner as in Example 1 using a gravure ink face containing an ethylene-vinyl acetate copolymer as a main component.

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 I was conducted and almost the same results were obtained.

Example 4 The gravure ink used in Example 2 was used to print on the surface of a polyethylene terephthalate film on which aluminum had been vapor-deposited under the same conditions as in Example 2, and a clear film with the same binder components was further applied on top of this with a film thickness of I had diarrhea and an oxygen indicator was obtained so that it was 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 thus obtained gravure ink, an oxygen indicator was produced in the same manner as in Example 1, and the same performance test as in Example 1 was conducted to observe the change in hue.

13- patent applicant Toyo Ink Manufacturing Co., Ltd. 14-

Claims (1)

[Claims] 1. An oxygen indicator printed or coated on a substrate with a printing ink or paint containing cobalt bis(salicylaldehyde)-3,3-siiminodipropylamine or a derivative thereof.