JPS60125544A - Oxygen sensor in hermetic case and packing bag - Google Patents

Abstract

PURPOSE:To simplify the indication of the presence of oxygen by putting a water absorptive member absorbed therein with an aq. soln. of a dye which is discolored by oxidation or reduction into a case and indicating the degree of the oxygen contained in the atmosphere thereof by the oxidation reduction reaction of a dye. CONSTITUTION:A thin fabric 3 such as a porous non-woven fabric is adhered to a thermoplastic resin film 2 opened with holes 1- for passage of air and a highly water absorptive resin 4 absorbed therein with an aq. soln. of an oxidation reduction dye, etc. is coated on such part. A thermoplastic film 5 is adhered thereto by heat-sealing or using an adhesive agent. Such oxygen sensor (a) is adhered to the inside surface of the case 6 by heat-sealing or using an adhesive agent or is charged into the case. The degree of the oxygen contained in the atmosphere is thus made to be displayed from the change owing to the oxidation reduction reaction of the dye and therefore the change in the color tone is visually observable and the inexpensive and simple judgement is made possible for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen sensor for airtight containers and packaging bags, and more specifically, an oxygen sensor that can indicate the presence of element III in the atmosphere inside a container or bag for storing foods. It is related to.

In general, containers used for packaging and preserving food include so-called hard containers such as metal or glass, which reduce the oxygen content within the container by reducing pressure or replacing nitrogen, and containers made of various plastics and paper. So-called soft containers are made of a composite material obtained by combining aluminum foil, etc., and cannot be effectively subjected to depressurization or nitrogen substitution methods like the above-mentioned hard containers.

Therefore, in hard containers made of metal, glass, etc.
It is possible to prevent food deterioration caused by oxidation due to oxygen in the air, but for flexible containers, use aluminum foil, polyvinylidene chloride film, polyacrylonitrile film, or saponified ethylene-vinyl acetate copolymer with high gas barrier properties. When the film is a single layer of the constituent materials of the packaging material, the same method used for rigid containers is used to reduce the oxygen content in the container by reducing pressure or replacing it with nitrogen. Although this method is used for containers of various shapes that are made of raw materials, this method not only hinders productivity considerably in actual operation, but also the equipment for this method is expensive, so it is necessary to compensate for these shortcomings. Therefore, oxygen absorbers mainly composed of inexpensive reduced iron are often used. Also, when oxygen is absorbed, the pressure decreases and the container dents inward.
Products that convert oxygen into the same amount of carbon dioxide gas are also used.

In the containers currently used for food preservation,
There is no inexpensive mechanism to clearly indicate that hard or soft packaging materials, even if they have been treated to reduce oxygen, remain in that state until the consumer opens them. .

Therefore, if an oxygen absorbent is sealed in the container, or if there is a label on the container indicating that high-level depressurization or nitrogen replacement is being performed, and if air enters from a poorly sealed part of the container, If food were to undergo oxidative deterioration, it would lead to a major accident. From this point of view, it is desired to use a so-called oxygen sensor that can indicate the oxygen status within a container with an inexpensive and as simple mechanism as possible.

As a method to indicate the presence of oxygen, (1) a method using a compound that changes color depending on whether oxygen is adsorbed or desorbed in an oxygen carrier; for example, a compound obtained by reacting salicylaldehyde with ethylenediamine and cobalt salts; The cobalt complex salt produced exhibits a blackish-brown color when oxygen is adsorbed, and becomes brownish-brown when oxygen is desorbed.

If this property is applied, it is possible to demonstrate the function as an oxygen sensor, but it is not so clear because the change in color tone is of the same type. This compound turns blackish brown in the presence of about 0.2% oxygen. Since cobalt salts cause food pollution because they are heavy-duty, they need to be covered with polyethylene or the like, which is troublesome.

(Although it is possible to use a two-liquid crystal to indicate oxygen, it is too sensitive and extremely expensive, making it impractical for food containers.

(3) The redox dye used to measure redox potential has a remarkable change in color tone between oxidation and reduction reactions, has a high reaction rate, and is extremely inexpensive, so this indicator is recommended. However, it is desirable as a method of indicating the presence of oxygen. However, the reaction tI of this indicator
The presence of water in structure A is unacceptable.

This inventor uses natural products such as starch/acrylic acid graft polymerization resin, cellulose/acrylic acid graft polymerization resin, and carboxymethylated cellulose as the main raw materials.
A super water absorbent resin whose main raw material is a water absorbent resin and a synthetic polymer obtained by a self-crosslinking method, an ionic crosslinking method, a chemical post-crosslinking method, a radiation crosslinking method, or a combination thereof, has a high magnification of water absorption. Applying this fact, we discovered that redox dyes easily change color depending on the conditions of the atmosphere in which they exist, and that they maintain this color change for a long period of time.

Further, the main redox dyes used in this invention are as follows.

Neutral red, methylene blue, diphenylamine, diphenylbenzine, diphenylamine, sulfonic acid, erioglaucine A15-nitropherroin,
Tris-1,10-7 enanthroline, induline scarlet, tetramethylphenosafranine, phenosafranine, safranin T1 brilliant alizarin blue, gallofenin, indigo-disulfonate, indigo-trisulfonate, methylcapriblue, indigo-tetrasulfonate, Ciba scarlet sulfonate, phenol-m-sulfonate-indo-2,6-dibromophenol, m-chlorophenol-indo-2
, 6-dichlorophenol, m-bromophenol-indophenol, gallocyanine, 2,6-dichlorophenol-indophenol, 1-nat-2-sulfonate-indophenol, 1-nat-2-sulfonate-indophenol 2,6-dichloro-phenol, toluylene blue.

Furthermore, in order to extend the water retention period of the superabsorbent resin as long as possible, polyhydroxy compounds such as glycerin, ethylene glycol, and polyethylene glycol, which have strong water absorption properties, are used as auxiliary additives.

The mechanism for supporting the superabsorbent resin that has absorbed an aqueous solution or dispersion of a redox dye constituting the oxygen sensor of the present invention will be described below with reference to FIG.

A porous thin cloth 3 such as a porous non-woven fabric or gauze is pasted to a thermoplastic resin film 2 with holes 1.1 made to allow air circulation, and a thickness of approximately 11 m is attached to this part.
A super absorbent resin 4 that has absorbed an aqueous solution or aqueous dispersion of a redox dye adjusted to the above is applied, and then a thermoplastic resin film 5, which is the same as the film 2, is bonded by heat sealing or adhesive. The wI oxygen sensor a thus obtained is pasted or placed on the inner surface of a container or packaging bag 6 as shown in FIG. In the case of bonding, if the inner surface of the container is a thermoplastic resin film, heat sealing or an adhesive is used, or if the inner surface of the container cannot be heated and sealed, an adhesive is used.

Next, the invention will be explained with examples.

Example 1 100 parts of a 0.01% methylene blue aqueous solution is added to 5 parts of starch and acrylic acid graft polymerization resin, and the paste-like super absorbent resin 4 obtained by mixing is the thermoplastic resin shown in Fig. 1. Apply to the position of film 5. Polyethylene was used for the thermoplastic film and porous thin cloth 2.3.

The thus obtained oxygen sensor a is heat-sealed to the inner surface of a transparent flexible container having a capacity of 300 cc, which has a polyethylene film on the inner surface and a polyvinylidene chloride film on the outer surface, as shown in FIG. As shown in FIG. 2, the sensor a and the oxygen absorbent 8 are placed in the container 6 together with the contents 7, and the opening is heat-sealed. After about 4 hours, the oxygen in the container 6 was absorbed by the oxygen absorber 8, and the blue color of methylene blue started to gradually disappear, and after about 7 hours, it was clearly observed from the outside that it became colorless.The amount of residual oxygen at this time was 0.1%.

Furthermore, the methylene blue remained in a colorless reduced state even though it was left at room temperature for 3 months. At this point, when the container was opened and air was allowed to flow into the container, the colorless reduced methylene blue remained in the colorless reduced state. Further, in the acid sensor shown in Example 1, even when a pressure of about 4 kg was applied, the moisture inside the sensor a was retained inside without flowing out to the outside.

Example 2 An experiment was conducted in the same manner as in Example 1 except that 10 parts of glycerin was added to 100 parts of 0.01% methylene blue aqueous solution. The effective period at room temperature is 6.5 months, which is approximately twice as long as when using only water.

Example 3 In Example 1, 0.01% methylene blue aqueous solution 1
An experiment was conducted in the same manner as in Example 1 by adding 8 parts of polyethylene glycol having an average molecular weight of 1200 to 00 parts. The effective period at room temperature was approximately 6 months, which was approximately twice as long as when using only water.

Example 4 In Example 2, 0.01% neutral red water W
1 solution was used. In the presence of oxygen, it shows a bright red color, but when the oxygen concentration drops to 0.1% or less, it becomes colorless in a reduced state, and it was possible to indicate the state of the atmosphere inside the container for about 6 months.

Example 5 In Example 4, the atmosphere inside the container was controlled for about 6 months in the same way as in Example 4, in which polyethylene oxide obtained by radiation crosslinking was used as the superabsorbent resin. was completed.

As described above, the present invention involves dissolving or dispersing in water a dye that changes color depending on the degree of oxidation or reduction to create an aqueous dye solution, and placing a water-absorbing member that absorbs this aqueous dye solution in a container or packaging bag. However, since the degree of oxygen content in the atmosphere inside the container or packaging bag is displayed by changes due to oxidation and reduction reactions of the dye, the degree of oxygen content in the contents can be determined by hue or tone due to poor sealing of the container, etc. Changes in the amount of water can be visually observed over a long period of time, can be carried out at low cost, and have the effect of not causing any food hygiene problems.

[Brief explanation of the drawing]

The figures all show one embodiment of the present invention; FIG. 1 is a sectional view of the oxygen sensor, and FIG. 2 is a view showing the oxygen sensor in use. 1... Hole, 2... Thermoplastic resin film, 3...
Porous thin cloth, 4... Super absorbent resin, 6... Container, 7
...Contents, 8...Oxygen absorbent, a...Oxygen sensor. Patent applicant: Kiyoshi Yanagii:

Claims (1)

[Claims] (1) A dye that changes color depending on the degree of oxidation or reduction is dissolved or dispersed in water to create an aqueous dye solution, and a water-absorbing member that absorbs this aqueous dye solution is installed in a container or packaging bag. An oxygen sensor for a sealed container or packaging bag, characterized in that the degree of oxygen content in the atmosphere inside the container or packaging bag is displayed by changes due to oxidation and reduction reactions of the dye. (2) A dye aqueous solution is prepared by dissolving or dispersing a dye that changes color depending on the degree of oxidation or reduction in water, and a water-absorbing member that has absorbed this dye aqueous solution is installed in a container or packaging bag, and the container or packaging bag is An oxygen sensor for airtight containers and packaging bags, characterized in that the degree of oxygen content in the atmosphere inside the container is displayed by a change in hue due to oxidation and reduction reactions of the dye. (3) Dissolving or dispersing the dye. Claims 1 and 1, characterized in that a hygroscopic compound such as glycerin, ethylene glycol, polyethylene glycol, etc. is added to water in advance so that a water-retaining state can be maintained for a long period of time. Oxygen sensor for airtight containers and packaging bags according to item 2. (4) The water-absorbing member is made mainly of natural products such as starch acrylic acid graphite polymer resin, cellulose, acrylic acid graphite polymer resin, carboxymethylated cellulose, etc. An oxygen sensor for an airtight container or packaging bag according to claims 1 or 2, characterized in that the water-absorbing member is formed by a self-crosslinking method, an ion crosslinking method,
Claim 1, characterized in that the main raw material is a polyvinyl alcohol-based or polyoxyethylene-based synthetic polymer material obtained by a chemical post-crosslinking method, a radiation crosslinking method, or a combination thereof; An oxygen sensor for a sealed container or packaging bag according to item 2.