JP2007333673A - Oxygen detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen detector excellent in light resistance, storage stability and responsiveness.
An oxygen detector in which an oxygen detection composition is supported on a porous substrate containing a basic substance.
[Selection figure] None

Description

  The present invention relates to an oxygen detector. More specifically, the present invention relates to an oxygen detector that can identify the presence or absence of oxygen by a color change and is stable against light and heat.

  Conventionally, oxygen detectors using variable organic dyes that change color reversibly by oxidation-reduction have been proposed. For example, solid oxygen detectors composed of thiazine dyes, azine dyes, oxazine dyes and other organic pigments and reducing agents are disclosed (Patent Documents 1 and 2). Also known is an oxygen indicator ink composition in which a thiazine dye or the like, a reducing saccharide, and an alkaline substance are dissolved or dispersed in a resin solution (Patent Document 3).

  A commercially available tablet-type oxygen detector (for example, trade name: Ageless Eye, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and an oxygen detector coated with an ink composition having an oxygen detection function (for example, trade name: Paper Eye, Mitsubishi Gas) (Chemical Co., Ltd.) is a functional product that simply indicates by color change that the oxygen concentration in the transparent packaging container is an oxygen-free state of less than 0.1% by volume. : Ageless, manufactured by Mitsubishi Gas Chemical Co., Ltd.) and used for maintaining the freshness of food and maintaining the quality of medical drugs.

However, conventional oxygen detectors have insufficient light resistance and storage stability, and may fade or discolor under light irradiation, and may turn brown or discolor under high temperatures. For this reason, in order to maintain a vivid color for a long period of time, there is a drawback that it must be stored under light shielding and at a low temperature. This tendency was particularly remarkable in the case of an oxygen detector coated with an oxygen detection ink.
JP-A-53-117495 Japanese Patent Laid-Open No. 53-120493 JP 56-84772 A

  An object of the present invention is to solve the above-described problems in the prior art, and to provide an oxygen detector excellent in light resistance and storage stability and excellent in responsiveness.

As a result of intensive studies in view of the problems of the prior art, the present inventors have achieved excellent light resistance and storage stability by using a base material containing a basic substance, and the atmosphere is in an oxygen-free state. As a result, the inventors have found that the color change responsiveness is excellent when changed to.
That is, the present invention is an oxygen detector in which an oxygen detection composition is supported on a porous substrate containing a basic substance.
In the present invention, the porous substrate is a paper product from a basic substance and a fibrous substance, the basic substance contained in the porous substrate is 5 to 80%, the base The alkaline substance is preferably an alkaline earth metal hydroxide or carbonate, in particular, magnesium hydroxide or magnesium carbonate powder, and the oxygen-sensing composition comprises a dye, a reducing substance, Is an oxygen detector that is an aqueous solution containing no basic substance.

  ADVANTAGE OF THE INVENTION According to this invention, the oxygen detector which is excellent in light resistance and storage stability, and excellent in the responsiveness with respect to oxygen concentration fall is provided.

The present invention uses a porous substrate containing a basic substance. The base material is one in which the aqueous solution exhibits basicity by mixing in water.
As the basic substance of the present invention, any alkaline substance that is solid at room temperature can be used, but hydroxides represented by magnesium hydroxide, calcium hydroxide, sodium hydroxide, potassium hydroxide, or magnesium carbonate, carbonate Preferred examples include carbonates such as calcium, sodium carbonate, and potassium carbonate. In particular, alkaline earth metal hydroxides or carbonates that are hardly soluble or insoluble in water are preferably used.

The porous substrate of the present invention serves as a carrier for a basic substance and has a large contact area with gas in the air. Examples of the porous substrate include paper and cloth using a fibrous substance, and those obtained by making a thermoplastic resin into a fibrous form usually by cold drawing treatment.
First, the fibrous substance serves as a carrier for a basic substance, and is made of natural fiber or synthetic fiber, preferably having a width of 0.2 mm or less and a length of 0.1 to 20 mm. Specific examples include cellulosic fibers such as pulp and cotton, wool, other natural fibers, synthetic fibers made of acrylic, nylon, polyethylene, polypropylene, polyester, etc., and two or more types can be used in combination as appropriate. It is. Preferably, pulp, polyethylene fiber or the like is used.

Examples of the method for using the fibrous material as the porous substrate of the present invention include a papermaking method and a nonwoven fabric manufacturing method, and are usually a film or a sheet.
In the case of the papermaking method, a predetermined amount of a fibrous substance and a basic substance are suspended in water, and are then made into a sheet by the papermaking method, and then the water content is 30% by weight or less, preferably 10% by weight or less. It is manufactured by dehydrating.
The ratio of the fibrous substance to the basic substance is 85/15 to 30/70 (weight ratio), more preferably 70/30 to 35/65 (weight ratio) in the fibrous substance / basic substance.
The proportion of the fibrous material in the aqueous suspension is preferably 0.01 to 15% by weight, more preferably 0.1 to 5% by weight, based on the sum of the fibrous material and the basic material. .

Next, the method of forming a thermoplastic resin composition and drawing it into a porous base material is usually 5 to 80% by weight, more preferably 20 to 50% by weight, of a basic substance in the thermoplastic resin. A mixed resin composition is produced, and is suitably formed into a sheet shape, preferably cold-drawn to obtain a porous substrate.
Here, examples of the thermoplastic resin include the same types of resins as those used for the synthetic fibers described above, and polyethylene and polypropylene are particularly preferable.

The oxygen-sensing composition used in the present invention is a variable organic dye that is a compound that reversibly changes color by oxidation and reduction, and a reduction that is a compound that reduces the above-mentioned variable organic dye under conditions where the oxygen concentration is lower than in the atmosphere. An essential ingredient. And the conventional oxygen detection composition usually plays the role with the basic substance mix | blended with the base material, without mix | blending the basic substance to mix | blend. Thereby, it is estimated that the improvement of the sensitivity as a detection agent was achieved in particular.
The variable organic dye of the present invention is an aromatic compound containing a long conjugated double bond system having π electrons that move easily in the molecule, and the color of the compound changes reversibly by redox. As the variable organic coloring matter of the present invention, a redox indicator, a thiazine dye, an azine dye, an oxazine dye, an indigoid dye, a thioindigoid dye, or the like is preferably used. For example, methylene blue, new methylene blue, methylene green, barrier amine blue B, diphenylamine, ferroin, capri blue, safranin T, indigo, indigo carmine, indigo white, indirubin and the like can be mentioned. Preferred is a thiazine dye typified by methylene blue.

  The reducing agent used in the present invention is a compound that reduces the above-mentioned variable organic dye under a condition in which the oxygen concentration is lower than that in the atmosphere. For example, reducing sugars such as reducing monosaccharides and reducing disaccharides, ascorbine Examples include acids and salts thereof, dithionite and salts thereof, cysteine and salts thereof, and the like. Examples of the reducing monosaccharide include glucose, fructose, xylose, and examples of the reducing disaccharide include maltose. A preferred reducing agent is a reducing sugar, and a more preferred reducing agent is a reducing monosaccharide.

  Furthermore, the color change can be made clear by adding a non-discoloring colorant different from the oxygen detection composition separately to the oxygen detection composition. As such pigments, pigments and dyes that are less susceptible to redox reactions and have colors that contrast with the colors that display the aerobic and non-oxygen states of the variable organic pigments can be used. When blue methylene blue is used as the variable organic coloring matter, acid red and phloxine B, which are red food additives, can be cited as suitable non-discoloring colorants.

  The oxygen detector of the present invention is obtained by supporting an oxygen detection composition on a base material blended with a basic substance, and is appropriately used in the form of a sheet, film, or thread.

  The present invention provides an oxygen detector that is excellent in light resistance and storage stability and excellent in response to a decrease in oxygen concentration. The oxygen detector of the present invention has extremely high utility value in the field of oxygen-free storage such as food preservation and quality maintenance of medical drugs.

Hereinafter, the present invention will be described in detail by way of examples.
Examples 1-4
100 g of pulp mainly composed of cellulose fibers having a length of 2 to 7 mm and a width of 0.03 to 0.05 mm, and a proportion of particles having a particle size of 0.15 mm or less and 0.05 mm or less are 80% by weight 100 g of the basic powder shown in Table 1 was suspended in 10.0 L (liter) of water, and the suspension was subjected to suction filtration. Thereafter, the substrate was dried with a drier to prepare base materials for oxygen detectors having different basic components having a width of 100 cm × 100 cm and a thickness of 0.10 mm.

  An aqueous solution in which 0.003 g of methylene blue and 0.3 g of D-glucose are dissolved is used as an oxygen detector composition, and this aqueous solution is impregnated into a 10 cm × 5 cm sheet cut out from the base material obtained above. A sheet-like oxygen detector was obtained.

A 1 cm × 1 cm square was cut out from this blue sheet-shaped oxygen detector sheet, and the following discoloration test was performed using this.
It was hermetically stored in a gas barrier container together with a commercially available oxygen scavenger (trade name: Ageless SA, manufactured by Mitsubishi Gas Chemical Co., Ltd.), and the oxygen concentration in the container was traced using a zirconia oxygen analyzer.
The time from when the oxygen concentration in the container became less than 0.1% by volume until the color changed to white indicating that the oxygen detector was in a deoxygenated atmosphere was determined as a response time delay at 25 ° C. or 5 ° C. .

After the deoxygenation atmosphere in which the oxygen concentration in the container is less than 0.1% by volume, the oxygen detector shows a white color in almost less than 1 hour under normal temperature conditions of 25 ° C, and under low temperature conditions of 5 ° C, The oxygen detector showed a white color after 10 hours or 12 hours. Under any of the conditions, the blue color quickly indicated that the atmosphere was aerobic again by air exposure by opening.
When the same test as described above was performed again using the oxygen detector used above, the above result was reproduced.

Comparative Example 1
As in Example 1, except that cellulose paper is used as the base material and 0.3 g of sodium carbonate is added as a basic substance to the components used in Example 1 as the oxygen detector composition. A blue sheet-shaped oxygen detector was prepared, and the same test as in Example 1 was performed using this. The results are shown in Table 1.
After the oxygen concentration in the container is less than 0.1% by volume, it takes 8 hours for the oxygen detector to show white indicating the deoxygenated atmosphere under 25 ° C. which is a normal temperature condition. Further, at 5 ° C., which is a low temperature condition, it took 48 hours for the oxygen detecting agent to turn white. In addition, it quickly turned blue due to air exposure by opening.

  The oxygen detectors of the present invention (Examples 1 to 4) show a white color representing a deoxygenated atmosphere following the transition to an oxygen-free atmosphere, and the time delay that turns white even at 5 ° C., which is a low temperature condition, is a comparison. It was short. Further, from the result of Comparative Example 1, the oxygen detector using a base material not containing a basic substance has a time delay in changing to white color indicating a deoxygenated atmosphere after becoming an oxygen-free atmosphere. The conditions caused a significant time delay.

[Table 1]
Response time delay in substrate
Basic substance (25 ° C) (5 ° C)
Example 1 Magnesium hydroxide 0 hour 10 hours Example 2 Calcium hydroxide less than 1 hour 12 hours Example 3 Magnesium carbonate 0 hour 10 hours Example 4 Calcium carbonate Less than 1 hour 12 hours
Comparative Example 1 None 8 hours 48 hours

Example 5
A 1 cm × 1 cm square was cut out from the blue sheet-shaped oxygen detector sheet obtained in Examples 1 to 4, and a light irradiation deterioration acceleration test was performed using the cut sheet.
By irradiating the obtained oxygen detection agent with visible light of 5000 lux using a fluorescent lamp as a light source at 25 ° C. and 60% RH in the air, and following the concentration change of the organic dye component with a visible spectroscopic hardness meter Light resistance was evaluated.
Even after 6 hours of irradiation with the fluorescent lamp, the relative decrease rate of the methylene blue absorbance measured from the maximum absorption wavelength of 650 nm was 0%, and the color of the oxygen detector was not changed at all.
That is, the oxygen detector of the present invention was an oxygen detector that hardly deteriorates even under light irradiation.

Examples 6 and 7
After mixing 1.0 g of methylene blue and 0.8 g of the non-color-changing organic dye Phloxine with 100 g of glycerin, 2.0 g of D-glucose freeze-pulverized using liquid nitrogen is added and mixed. Got.
This oxygen detection ink pigment was mixed with 3.8 g of rosin pentaerythritol ester, 1.3 g of propylene glycol monoethyl ether, 1.3 g of mineral spirit, and 2.0 g of clay to obtain an oxygen detection ink.

Using this oxygen detection ink, an oxygen detection agent sheet was obtained by screen printing on a 10 cm × 5 cm sheet cut out from the base material prepared in Example 1 and Example 3.
A 1 cm × 1 cm square was cut out from this oxygen detector sheet, and this was hermetically stored in a gas barrier container together with the oxygen scavenger Ageless SAPE-A (Mitsubishi Gas Chemical Co., Ltd.) and water-containing cotton cloth. After the deoxygenation atmosphere in which the oxygen concentration in the container is less than 0.1% by volume, the oxygen detector shows a pink color almost at the same time under the normal temperature condition of 25 ° C, and under the low temperature condition of 5 ° C, After 12 hours, the oxygen detector showed a pink color.
When the same test as described above was performed again using the oxygen detector used above, the above result was reproduced.

Example 8
A 1 cm × 1 cm square was cut out from the blue-violet sheet-shaped oxygen detector sheet obtained in Examples 6 and 7, and the light irradiation deterioration acceleration test was performed using a fluorescent light source in the same manner as in Example 5. The visible light of 5000 lux was irradiated at 25 ° C., 60% RH, under air for 6 hours.
Even after irradiation with a fluorescent lamp, the relative decrease in methylene blue absorbance measured from the maximum absorption wavelength of 650 nm was 0%. That is, the oxygen detector of the present invention was an oxygen detector that hardly deteriorates even under light irradiation.

Comparative Example 2
Using the paper eye (Mitsubishi Gas Chemical Co., Ltd.) affixed to the oxygen scavenger Ageless SAPE-A (Mitsubishi Gas Chemical Co., Ltd.), the light irradiation deterioration acceleration test was carried out in the same manner as in Example 5. Carried out.
Six hours after the start of fluorescent lamp irradiation, the relative decrease rate of the methylene blue absorbance measured from the maximum absorption wavelength of 650 nm was 55%. That is, in the conventional oxygen detector, the pigment component was deteriorated by light irradiation.

Example 9
A 1 cm × 1 cm square was cut out from the oxygen detector sheet used in Examples 6 and 7 and Comparative Example 2, and a heat deterioration acceleration test was performed at 60 ° C. and 60% RH in a deoxygenated atmosphere.
The obtained oxygen detector was sealed in a deoxygenated atmosphere having an oxygen concentration of less than 0.1% by volume in a gas barrier container and stored at 60 ° C. and 60% RH to evaluate heat resistance. In the evaluation, after the stored sample was returned to the air, the concentration change of the organic dye component was traced using a visible spectrophotometer.
Even after 3 days from the start of the heat deterioration acceleration test, the relative decrease rate of the methylene blue absorbance measured from the maximum absorption wavelength of 650 nm was 0%. That is, the oxygen detector of the present invention is an oxygen detector that is hardly deteriorated by heat.

Comparative Example 3
Using a paper eye (Mitsubishi Gas Chemical Co., Ltd.) affixed to the oxygen scavenger AGELESS SAPE-A (Mitsubishi Gas Chemical Co., Ltd.), as in Example 9, 60 ° C., 60% RH, deoxygenated It was stored in an atmosphere and an overheat deterioration acceleration test was conducted. In the evaluation, after the stored sample was returned to the air, the concentration change of the organic dye component was traced using a visible spectrophotometer.
The relative decrease rate of the methylene blue absorbance measured from the maximum absorption wavelength of 650 nm was 30% after 3 days. That is, in the conventional oxygen detector, the dye component was deteriorated by heat.

Claims (6)

An oxygen detector in which an oxygen detection composition is supported on a porous substrate containing a basic substance. 2. The oxygen detector according to claim 1, wherein the porous substrate is a paper product made of a basic substance and a fibrous substance. The oxygen detector according to claim 1, wherein the basic substance contained in the porous substrate is 5 to 80%. The oxygen detector according to claim 1, wherein the basic substance is an alkaline earth metal hydroxide or carbonate. The oxygen detector according to claim 1, wherein the basic substance is magnesium hydroxide or magnesium carbonate. 2. The oxygen detector according to claim 1, wherein the oxygen detection composition is an aqueous solution containing a pigment and a reducing substance as essential components and not containing a basic substance.