JPS61144568A - Oxygen detecting material - Google Patents

Abstract

PURPOSE:To measure easily oxygen concn. by using a paint consisting essentially of a thiazine dye and the org. acid salt of ethanol amine or a sheet coated with said paint. CONSTITUTION:The thiazine dye has the property that the dye is photoreduced and is made colorless by the specific visible ray and restores the original color when the irradiation is ceased. Such reversible reaction is considerably accelerated by the ethanol amine but the ethanol amine forms hardly a coated film when coated together with the dye on a film or the like and even if the coated film is formed, the film absorbs the carbon dioxide in the atm. air and an undesirable change is resulted. The ethanol amine is thereupon preliminarily compounded with the dye and is formed as the org. acid salt into the fast coated film by which the absorptivity of the carbon dioxide is eliminated and the coated film is made stable to the physical and chemical changes. The paint consisting of the thiazine dye and the org. acid salt of the ethanol amine or the sheet coated with such paint is thereupon colored by the oxygen in the air or inert gas by which the colorimetry of the oxygen concn. is made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field and Prior Art] This invention visually detects oxygen in air or inert gas.
Moreover, it relates to an oxygen sensing material that can be quantitatively detected. Specifically, the present invention relates to a paint having the above-mentioned functions or an oxygen sensing material in the form of a test paper coated with the paint.

Techniques for analyzing and quantifying oxygen dissolved in a liquid, oxygen contained in a gas, etc. are known, but measurement requires considerable equipment and operations, and the equipment is expensive.

If visual measurements could be made as easily as with various test strips, it could be used in a wide range of applications. The object of the present invention is to provide an oxygen sensing material that can easily measure oxygen concentration, such as the various test strips mentioned above. The oxygen sensing material of the present invention is a paint containing a thiazine dye and an organic acid salt of ethanolamine as essential components, or a sheet coated with the paint. The coating film on the sheet surface develops color in the presence of oxygen, and is formed so that the oxygen concentration can be measured colorimetrically. One example is that it can be used in conjunction with an oxygen absorber, and if the food, oxygen absorber, and oxygen sensing material of the present application are sealed in a packaging material with low oxygen permeability for food preservation, the packaging can be completed at the desired time. The oxygen concentration contained in the gas inside can be visually detected from outside the package. If the oxygen concentration of the gas inside the package shows a high value, it is due to a poor seal on the package or a decrease in the oxygen scavenging ability of the oxygen scavenger. Inspection becomes possible. Low concentration oxygen content is a problem for food preservation, but the material of the present invention can detect low concentrations and is particularly suitable for use in food packaging. In addition, the material of the present invention can be used by being sealed in a container filled with an inert gas such as nitrogen or carbon dioxide, and can also be used in combination with products other than food.

[Problem that the invention seeks to solve]

Thiazine dyes have the property of forming a shift chromism system when exposed to visible light of 600 to 650 nm. That is, it becomes colorless when irradiated with visible light, and becomes more colored (than K) when placed in a dark place.
recovery) occurs. Generally, attempts have been made to utilize this reaction for image recording and the like.

In this case, the thiazine dye becomes an electron acceptor, accepts electrons from the electron donor, becomes colorless, and the reverse reaction proceeds in the dark, resulting in coloration (recovery). In the absence of, for example, in pure nitrogen,
It was found that no coloration (recovery) occurred even when stored in the dark for several tens of days. In other words, it was found that the reverse reaction rate between the electron acceptor and electron donor in the dark was negligible.

Therefore, we investigated how the coloring (recovery) reaction of colorless pigments is controlled by oxygen concentration, and the results are discussed in the first section.
The figure shows the relationship between the oxygen concentration in nitrogen (expressed in volume t% on a logarithmic scale) and the color density (expressed as color recovery rate). The color recovery rate refers to the ratio of recovered colorimetric density to the color density before light irradiation, and the color density was measured with a Macbeth reflection densitometer. The sample preparation method and experimental method are the same as in the experimental examples described later. As shown in the figure, there is a strong correlation between the oxygen concentration and the color recovery rate. Moreover, it was shown that coloration was observed due to low concentration of oxygen within a short time of about 10 to 30 minutes, and it was recognized that the material is suitable as a material for detecting oxygen concentration by color density.

[Means to try to solve problems]

According to the present invention, there is provided a paint containing a thiazine dye and an organic acid salt of ethanolamine as essential components, or a sheet coated with the paint, which is capable of colorimetrically measuring the oxygen concentration in air or an inert gas. A sensing material is provided.

The inert gas mentioned here is N, s kb? Co
t t Het refers to a gas that is inert to the sensing materials of the present application, such as NelAr, Kr, Xe.

The thiazine dye is a general term for dyes having a thiazine nucleus, and has a structure such as X: halogen t R1-R4: H or an alkyl group, and the following dyes can be exemplified.

Loud violet (thionin); R1~R,=H0
Azusion C: R1=CH@, R1~R,=H0 Azusion B: R, ~R, =CH,, R, =H.

Methylene blue; R1~R, =CH,.

Thionine blue: R1, R1 and R4 = CHa +
R3=C2Hl.

In addition, -OH, -8o are directly attached to the bone core carbon as a side chain, such as neomethylene blue and brilliant alizarin blue.
, )i, etc. are also included, and any thiazine dye having a thiazine nucleus is sufficient.

The organic acid salt of ethanolamine means an organic acid salt such as monoethanolamine, jetanolamine, triethanolamine, etc. The organic acid used here refers to aliphatic, aromatic, etc. that form a salt with ethanolamine. , but also includes saturated, unsaturated, -valent carboxylic acids, polyvalent carboxylic acids, oxy, aldehyde, ketocarboxylic acids, sulfonic acids, etc.

Thiazine dyes have the property of being photoreduced by visible light of 600 to 650 nm (which is also included in large amounts in the light of tungsten lamps), becoming colorless, and restoring the coloring to its original color when the irradiation is stopped. This reversible reaction is significantly promoted by ethanolamines. This is particularly noticeable in triethanolamine. However, since ethanolamines are liquids at room temperature, they are difficult to form into films when coated with pigments, and when they are formed into films, they absorb carbon dioxide gas from the atmosphere, making them undesirable. There will be no change. Therefore, if it is blended in advance as an organic acid salt, the coating film will be more robust.

Therefore, it did not lose its ability to absorb carbon dioxide gas, was stable against physicochemical changes, and did not reduce the effect of promoting the above-mentioned reversible reaction.

The sensing material of the present invention has a thiazine dye and an organic acid salt of ethanolamine as essential components, but the oxygen sensing material that is frequently used in practice is in the form of a coating film, and is preferably coated on a substrate. As for this substrate, porous materials such as cloth or high-quality paper can be used, but finely dense materials such as coated paper, films, metal foils, glass, and ceramic plates are more preferable.

This is because when stored as a detection material, a large contact area with oxygen causes a decrease in detection sensitivity. Usually, a film with low oxygen permeability is used, but if a long time is required for detection, the film can be brought into close contact with the coating surface to delay coloring (recovery). Conversely, depending on the purpose of use, films with high oxygen permeability may be used, or a polymer forming a film having oxygen permeability may be coated on the coating surface.

In addition to the essential components, it is desirable to add binders to the detection material coating to increase its fastness. Since the essential components are soluble in water, lower alcohols, lower ketones, cellosolves, etc., as binders, water-soluble or Water-dispersible polymers or latexes of various polymers such as styrene-butadiene, acrylic esters, vinyl acetate, hinyl chloride, ethylene-vinyl acetate, and various copolymer latexes are used. Polymers soluble in lower alcohols and lower ketones such as methyl cellulose, ethyl cellulose,
Natural products such as propylcellulose, shellac, copal resin, and dammar resin can also be used. In addition, white pigments such as clay, aluminum hydroxide, titanium dioxide, etc. can be blended into the detection material paint to make the hue change clear. In addition to coatings provided on the base material, users can apply detection coatings to desired areas as slow-drying or quick-drying paints containing the above-mentioned binder, white pigment, etc. For example, it is an effective method to apply this detection coating to a part of the outer surface of the oxygen absorber packaging bag. The paint formulation for obtaining a detection coating varies depending on the type of essential components, but the ethanolamine organic acid salt is blended 1 to 50 times as much as the thiazine dye. A desirable range is 10 to 20 times. ≠If the ratio of the organic acid salt of ethanolamine is less than 1x, the detection sensitivity will be significantly reduced, and if it exceeds 50x, the speed of decolorization will be fast, but the speed of coloring (recovery) will decrease and the detection sensitivity will decrease. Not only does this cause a decrease, but also the strength of the coating film deteriorates. The paint intended by the present invention can be obtained by appropriately mixing a binder, a white pigment, etc. with the above-mentioned composition and coating it on a film or the like at a solid content concentration of about 10%.

Note that when a white pigment is blended into a paint, it is necessary to blend a binder in order to prevent it from coming off from the paint film, and the paint blend in this case is exemplified below in parts by weight.

Thiazine dye 1-2 parts M ethanolamine organic acid salt 10-40 parts White pigment
5-10 parts binder
84 to 48 parts Experimental example Ethyl cellulose (Percules, N-50PP) was dissolved in isopropyl alcohol-modified ethyl alcohol to make a 10% solution, and methylene blue lO
Add I and 190 g of triethanolamine laurate and dissolve by stirring gently using a homomixer to avoid foaming. Further add a liquid in which titanium dioxide (rutile type) of cyclohexanone vsog of Father I was uniformly dispersed in advance,
In addition, isopropyl alcohol modified ethyl alcohol 2
200 g was added and homogenized to obtain a paint with a solid content of 10%.

This paint was coated on a 5 0 μm thick polyester film using a Mayer bar and dried.

The drying temperature was 70°0° and the coating was repeated twice to obtain a uniform blue film. The amount of paint applied was 5y/g.

The blue film thus obtained was placed at a distance of 10α from a 200W tungsten lung and irradiated with visible light in the air.
It became colorless. The color density before irradiation was 1.27.

This blue film was placed in a nylon/polyethylene composite film bag, completely degassed, and then heat-sealed. The dimensions of the bag are 15 cm x 155! And so. Next, high-purity nitrogen gas mixed with 0.5, 1.2-5, 5, 7.5, 10, and 15 volumes of oxygen, room air, and Zoo- for any of the above nitrogen gases were mixed with a large syringe. Inject into the above bag, and quickly close the injection needle hole with polyester adhesive tape. The blue film inside the bag was made colorless by light irradiation from the outside of the bag, and the value was determined to be up to 0.1 using a Macbeth reflection densitometer. The blue color of the blue film in the bag that was injected with room air disappeared in 20 seconds, but the lower the oxygen concentration, the faster the blue color disappeared from the blue film in the bag. The blue color in the kyL bag disappeared within seconds.

From the time the light irradiation was stopped, the film was kept at room temperature in a dark place, and after a predetermined period of time, the blue density of the film was colored (recovered) with oxygen and the results are shown in 1st fi.In addition, the color recovery rate was calculated from the color density. As mentioned, it is illustrated in Figure 1. According to Table 1, it can be determined that the coloring does not recover even if left in pure nitrogen for 30 minutes or more, but as the oxygen concentration increases, the color density increases, and the color recovery rate. increased in proportion to the oxygen concentration.A similar tendency was observed in the case of air (oxygen concentration 21.0 volume).

The color recovery rate is a value obtained using a Macbeth reflection densitometer as described above, but by preparing a standard colored print in advance and comparing it with the visual color density, the oxygen concentration could be determined directly.

Example 1 The blue film obtained in the experimental example was sealed together with a bag containing an oxygen absorber in a nylon/polyethylene composite film bag together with room air and left in a dark place. After 24 hours, the blue film became colorless. This indicates that the pigment was rendered colorless by the reducing action of triethanolamine laurate in an oxygen-free gas even without light irradiation. Therefore, in practice, if the blue film of this example is enclosed together with food and an oxygen absorber in a packaging material with low oxygen permeability, it will be a good idea to
1 It is not necessary to previously decolorize the blue film by surface irradiation. In this case, if the film still shows a blue color after 24 hours, it indicates that there is a defect in the heat coolant or that the oxygen absorber is ineffective. It is possible to detect deficiencies as follows. In addition, from the time when the blue film becomes colorless due to light irradiation, the standing time for observing the color density by leaving it in a dark place and determining the oxygen concentration in the gas content is 30 minutes as in the experimental example. Less than a minute was enough.

Example 2 Even when the triethanolamine diurinate in the paint used in the experimental example was replaced with oxalate or tartrate, the results showed the same tendency as in the experimental example and example 1.

Example 3 The results were similar to those in Experimental Example and Example 1 when the methylene blue in the paint used in Experimental Example was replaced with Laud's Violet (thionine). In addition, the nine detection materials using the paint of this example have a colorless ratio by light irradiation, a coloration in the dark (
Recovery) was also about 1.5 times faster, which was advantageous because the detection time could be shortened.

Example 4 When triethanolamine laurate in the paint used in the experimental example was replaced with jetanolamine stearate, both the decolorization and coloring (recovery) rates decreased to about 173.

Depending on the application, slower speeds may be more appropriate, especially in cases where oxygen scavenger is not included and nitrogen-filled packaging is used. Since the detection film is encapsulated, it is preferable that the coloring (recovery) speed of the detection film is slow.

Furthermore, the detection material of this example is suitable when the oxygen concentration is high, that is, when detecting a substance with an oxygen concentration higher than that of air.

〔Effect of the invention〕

The oxygen sensing material obtained by this invention shows an extremely good correlation between the color density and the oxygen concentration at a low concentration (for example, 0.5 volume 1) as shown in Figure 1 above, and the oxygen concentration in the air (21.0 volume s).
The oxygen concentration can be accurately determined from the color density of the coating film, including the color density of the paint film. Another advantage of the present invention is that colorimetric measurements can be carried out within a short period of time. In addition, since this sensing material constitutes a photochromic system, it becomes colorless when exposed to visible light and becomes colored (recovered) by reacting with oxygen in the dark, but this reaction is reversible and can be repeated about 10 times. Sensitivity does not decrease significantly. Therefore, it is easy to store, and depending on the method of use, it is also possible to determine the oxygen concentration by irradiating visible light to color a product that has been colored by the action of oxygen to make it colorless, and then determining the change in color from that point on. In some cases, a color density change needle is used to obtain the color density, but it is also possible to directly determine the oxygen concentration by preparing a standard colored print in advance and comparing it with the visual color density. Oxygen concentration is required. Furthermore, the sensing material of the present invention is extremely easy to store and to attach to the measurement position.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the color recovery rate of a coating film and the oxygen concentration in nitrogen.

Claims (1)

[Claims] A paint containing a thiazine dye and an organic acid salt of ethanolamine as essential components, or a sheet coated with the paint, which is characterized by being capable of colorimetrically measuring the oxygen concentration in air or inert gas. Oxygen sensing material.