JP2008224579A - Carbon dioxide detection agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide gas detecting agent that can be discolored within several hours even in a low concentration carbon dioxide gas atmosphere, visually determine the generation of carbon dioxide gas, and can be stored for a long time.
A comprises at least one pH indicator and water retention agent, the added pH indicator is adjusted vapor permeability a base impregnated with an alkaline aqueous solution as an alkaline color 20g ^/ m 2 / 24hrs or less A carbon dioxide gas detecting agent sealed in a small bag, wherein the carbon dioxide gas detecting agent is used by ventilating the atmosphere to be detected and the inside of the small bag.
[Selection figure] None

Description

  The present invention relates to a carbon dioxide gas detection agent using a pH indicator.

  Carbon dioxide detection agents that visually detect the presence of carbon dioxide so far include the carbon dioxide detection ink composition of Patent Document 1, a carbon dioxide indicator using the same, and a package in which the carbon dioxide indicator is disposed, There are carbon dioxide concentration detectors and detectors of Patent Document 2, both of which use a pH indicator.

The carbon dioxide indicator of Patent Document 1 is used in a packaging form filled with carbon dioxide, and shows a certain color in a high carbon dioxide concentration environment, but the carbon dioxide concentration has decreased due to the occurrence of pinholes and the like. In this case, the color can be changed and the leakage of carbon dioxide gas can be determined. However, this carbon dioxide detection agent cannot confirm that carbon dioxide has been generated from the state where there is no carbon dioxide. Further, the carbon dioxide gas detection agent of Patent Document 2 can detect low-concentration carbon dioxide gas, but its discoloration speed is slow, and rapid carbon dioxide gas detection is impossible.
WO01 / 044385 Japanese Patent Laid-Open No. 8-145979

An object of the present invention is to produce a carbon dioxide gas detection agent that can quickly be stored in a long-term storage because the pH indicator discolors rapidly even in a low carbon dioxide gas concentration environment.
A carbon dioxide detector using a pH indicator visually recognizes the presence of carbon dioxide gas by utilizing the color change of the pH indicator as the carbon dioxide dissolves in water and the pH in the system changes to the acidic side. Recognition. Moreover, the color change of the pH indicator due to the pH change is caused by the fact that electron transfer occurs in the molecule and the pH indicator changes to a structure having a different absorption wavelength. Therefore, sufficient water is required for the reaction of the carbon dioxide detection agent using the pH indicator. Further, the pH indicator dissolves in a polar solvent, specifically water or the like, and exhibits an ionic structure to show a visually recognizable color. Therefore, fading occurs in the absence of moisture, and the color cannot be determined.

That is, the present invention includes a base material impregnated with an alkaline aqueous solution containing at least one kind of pH indicator and a water retention agent and adjusted so that the added pH indicator exhibits an alkali color, with a water vapor permeability of 20 g / m ² / A carbon dioxide gas detecting agent sealed in a sachet of 24 hrs or less, wherein the carbon dioxide gas detecting agent is used by ventilating the atmosphere to be detected and the inside of the sachet.

  ADVANTAGE OF THE INVENTION According to this invention, the transpiration | evaporation of the water | moisture content from a base material can be prevented, and the carbon dioxide gas detection agent excellent in the preservability which continues showing an alkali color for a long term can be obtained. Further, by opening one end of the bag at the time of use, it becomes possible to quickly detect carbon dioxide in the atmosphere.

  In the present invention, a pH indicator is used to detect carbon dioxide. Since the carbon dioxide concentration to be detected is low, it is desirable to use an alkali neutralization reaction with carbon dioxide. Therefore, the pH indicator to be used is preferably an indicator having a color change range from neutral to alkaline. An indicator that changes to a distinctly different color is also preferred so that it can be clearly determined. Furthermore, an indicator having high thermal stability is preferable so that it can be used even at high temperatures.

  Examples of pH indicators having a color change range from neutral to alkaline include phenol red, cyanine, α-naphtholphthalein, metacresol purple, thymol blue, o-cresolphthalein, and phenolphthalein. A pH indicator can be selected. Specifically, metacresol purple is optimal because the color change range is alkaline, the color changes from purple to yellow at pH 9.0, the color change is large, and the chemical stability is high. .

In order to use the pH indicator having an alkaline discoloration range selected in this manner as a detection agent, a method of dissolving in a solution and impregnating the water-retaining carrier with the solution can be considered.
The amount of the pH indicator dissolved in the solution does not need to be large, but may be a color that can be clearly colored and the color change can be visually confirmed. Specifically, sufficiently clear coloring can be obtained at 0.1 to 1 wt% with respect to the solvent.

The solvent in which the pH indicator is dissolved needs to be adjusted to be alkaline so that the indicator shows an alkaline color. Examples of alkaline substances that are soluble in water and exhibit alkalinity include silicate metal salts, metal hydroxide salts, metal sulfites, and metal carbonates. However, this inner metal carbonate cannot be used because it is highly stable against carbon dioxide, and the pH does not drop even when carbon dioxide dissolves.
Moreover, the one where the solubility with respect to water is high is preferable. If the solubility in water is low and the undissolved part remains, the clear color necessary for the detection agent may be inhibited.
Therefore, the alkali metal is preferably a metal hydroxide salt from the viewpoint of high solubility in water. In addition, a system adjusted to be alkaline with a metal hydroxide salt is characterized by being easily neutralized with carbon dioxide gas as compared with other alkaline substances. Therefore, sodium hydroxide is most preferable as an alkaline substance that can be added to the carbon dioxide gas detecting agent.
In addition, detection of carbon dioxide using a pH indicator requires the presence and retention of a certain amount of water.

  Examples of the base material impregnated with the carbon dioxide detector composition liquid of the present invention include non-woven fabric, filter paper, cloth, silica gel, diatomaceous earth, zeolite, silicate, and other inorganic water-absorbing carriers.

The nonwoven fabric impregnated with the carbon dioxide gas detector composition liquid is made of fibers such as cellulose, cotton, PET, PE, PP, acrylic, and has a basis weight of 10 to 100 g / m ² and a thickness of 0.1 to 3 mm. The nonwoven fabric is preferred. This non-woven fabric can be folded and enclosed in a sachet to obtain higher water retention. The method of folding into the pouch can be arbitrarily selected from among two-fold, four-fold and even eight-fold.

  The filter paper to be impregnated with the carbon dioxide detector composition liquid may have any thickness and pore size, but if the original pH is acidic, it must be soaked in sodium hydroxide solution and adjusted to be alkaline before impregnation. There is.

  The inorganic water-absorbing carrier impregnated with the carbon dioxide gas detector composition liquid is preferably white so that the color change becomes clear. The pH of the inorganic water-absorbing carrier is preferably neutral to alkaline.

For long-term storage of carbon dioxide detectors, it is necessary to prevent the evaporation of moisture to the outside. Therefore, it is preferable that the carbon dioxide gas detection agent sachet does not release moisture to the outside even when stored for a long time using a packaging material with low moisture permeability. If the water vapor permeability of 20g ^/ m 2 / 24hrs or less of the packaging material, it is possible to prevent the evaporation of moisture to the outside. In order to determine the presence or absence of carbon dioxide by visually confirming the color change from the outside, a storage form in which a transparent packaging material is made and a carbon dioxide detector is enclosed therein is preferred.

Specifically usable transparent packaging materials include biaxially oriented polypropylene (OPP), unstretched polypropylene (CPP), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene ( HDPE), polyethylene terephthalate (PET), packaging material of construction such as polyvinyl alcohol (PVA) water vapor permeability comprising at least one of the following materials 20g / ^{m 2} / 24hrs is preferable.

  In addition, for quick discoloration, it is necessary for carbon dioxide gas to come into contact with the nonwoven fabric, filter paper or inorganic water-absorbing carrier as a base material. Therefore, it is preferable to easily allow the base material and the carbon dioxide gas to contact each other by cutting off one end of the transparent packaging material of the carbon dioxide gas detecting agent at the time of use.

  Even when a packaging material having a low water vapor transmission rate is used, moisture is evaporated from the carbon dioxide detection agent to the outside by cutting off one end and providing a vent hole during use. In order to maintain the water content of the carbon dioxide detection agent even after the vent hole is opened when using the carbon dioxide detection agent, the moisture activity of the detection agent is lowered from the relative humidity of the environment in which it is used, so that moisture transfer from the detection agent to the surroundings It is considered effective to prevent this.

  A water retention agent can be added to reduce the water activity of the carbon dioxide detector and retain moisture. As water retention agents, polymer polymers such as polyethylene glycol and polyacrylate, alcohols such as glycerin, ethylene glycol and propylene glycol, cellulose and the like are considered. The type of the water retention agent is not particularly limited because it can be arbitrarily selected if the effect of reducing the water activity can be confirmed when added to the carbon dioxide detection agent.

  However, excessive addition of these water retention agents leads to a decrease in the color saturation of the carbon dioxide detection agent or a delay in the reaction time. Therefore, it is necessary to select an appropriate amount of the water retention agent. Specifically, no significant reaction time delay is observed up to 20 vol% /% of the total volume of the solvent.

Hereinafter, the present invention will be described in detail by way of examples.
Example 1
900 g of distilled water was mixed with 0.20 g of metacresol purple as a pH indicator, 0.40 g of sodium hydroxide as an alkaline substance, and 100 g of glycerin as a water retention agent to obtain a purple impregnation solution. The impregnation solution 5g of the strip (size 40 × 35 mm) polyethylene nonwoven fabric cut into (basis weight 43 g / ^{m 2,} thickness 0.3 mm) is impregnated with, OPP / PE (water vapor permeability 5~6g / ^{m 2} / 24hrs ) Was folded in two to obtain one purple carbon dioxide detector.

The following tests were conducted using this purple carbon dioxide gas detector.
In other words, the carbon dioxide gas detection agent that cuts off one end of the packaging material to secure the air vent and the gas barrier property together with a commercially available atmosphere conditioner for microaerobic culture (trade name: Aneropack / Microaerobic, manufactured by Mitsubishi Gas Chemical Co., Ltd.) It sealed in the container and preserve | saved in a 35 degreeC thermostat. Aneropack / microaerobic used as an atmosphere control agent for microaerobic culture is an oxygen absorption / carbon dioxide generator for microaerobic culture. It is a product that creates a microaerobic environment with an oxygen concentration of 8-9% and carbon dioxide concentration of 7-8% within 1 hour after application. 30 minutes after application, the sample was taken out from the thermostatic chamber, and the carbon dioxide gas concentration in the container was measured using an infrared CO ₂ analyzer.
30 minutes after application, the carbon dioxide gas detecting agent showed a yellow color. The carbon dioxide concentration in the container was 7.0%. When opened, it turned purple again due to carbon dioxide leakage.

In the same manner as in the above test, a carbon dioxide gas detection agent obtained by cutting off one end of the packaging material of the carbon dioxide gas detection agent and securing a vent was used as a commercial carbon dioxide culture atmosphere conditioner (trade name: Aneropack CO ₂ , Mitsubishi Gas Chemical). The product was sealed in a gas barrier container and stored in a constant temperature bath at 35 ° C. Aneropack CO ₂ used as an atmosphere adjusting agent for carbon dioxide culture is an oxygen absorption / carbon dioxide generator for carbon dioxide cultivation. It is a product that generates 5-6% of CO ₂ in the packaging container and promotes the generation of carbon dioxide-requiring bacteria (hemophilus, Neisseria, etc.). 30 minutes after application, the sample was taken out from the thermostatic chamber, and the carbon dioxide gas concentration in the container was measured using an infrared CO ₂ analyzer.
Thirty minutes after application, the carbon dioxide detector showed a purple to yellow color. The carbon dioxide concentration in the container was 3.0%. Moreover, it turned purple again by the carbon dioxide leak by opening.

  Moreover, when this carbon dioxide gas detection agent was stored at 25 ° C., the purple color at the time of preparation was maintained even after 6 months of storage, and the same carbon dioxide gas detection ability was exhibited even in the evaluation using the same atmosphere modifier as described above.

Example 2
900 g of distilled water was mixed with 0.20 g of metacresol purple, 0.40 g of sodium hydroxide, and 100 g of glycerin to obtain a purple impregnation solution. 5 g of this impregnating solution is impregnated into a polyethylene nonwoven fabric (weighing 43 g / m ² , thickness 0.3 mm) cut into strips (size 40 × 35 mm) and contains PVA / PE (water vapor permeability 4 g / m 2/24 hrs). A purple carbon dioxide detector was obtained by folding the pouch into two.

The following tests were conducted using this purple carbon dioxide gas detector.
That is, in the same manner as in Example 1, a carbon dioxide gas detection agent in which one end of the packaging material was cut off to secure a vent was used as a commercially available atmosphere conditioner for microaerobic culture (trade name: Aneropack / Microaerobic, Mitsubishi Gas Chemical Co., Ltd. )) And sealed in a gas barrier container and stored in a constant temperature bath at 35 ° C. 30 minutes after application, the carbon dioxide gas concentration in the container was measured using an infrared CO ₂ analyzer.
Thirty minutes after the application, the carbon dioxide detector showed a yellow color, and the carbon dioxide concentration in the container was 7.0%. Moreover, it changed to purple again due to carbon dioxide leakage due to opening.

In addition, when the same test was performed using an atmosphere conditioner for carbon dioxide culture (trade name: Aneropack CO ₂ , manufactured by Mitsubishi Gas Chemical Co., Ltd.), the carbon dioxide detector showed yellow after 30 minutes of application. The carbon dioxide concentration in the container was 3.0%. Moreover, it changed to purple again due to carbon dioxide leakage due to opening.

  Moreover, when this carbon dioxide gas detection agent was stored at 25 ° C., the purple color at the time of preparation was maintained even after 6 months of storage, and the same carbon dioxide gas detection ability was exhibited even in the evaluation using the same atmosphere modifier as described above.

Example 3
900 g of distilled water was mixed with 0.20 g of metacresol purple, 0.40 g of sodium hydroxide, and 100 g of glycerin to obtain a purple impregnation solution. 10 g of this impregnating solution was impregnated in 5 g of a calcium silicate granulated product and sealed in an OPP / PE sachet to obtain a purple carbon dioxide detector.
Using this purple carbon dioxide detector, the same evaluation as in Examples 1 and 2 was performed, and the same result was obtained.

Comparative Example 1
900 g of distilled water was mixed with 0.20 g of metacresol purple, 0.40 g of sodium hydroxide, and 100 g of glycerin to obtain a purple impregnation solution. The impregnation solution 5g a strip to cut nonwoven (basis weight 43 g / ^{m 2,} thickness 0.3 mm) is impregnated with, pouch 2 Tsu folding of nylon film (water vapor transmission rate of about 100~200g / ^{m 2} / 24hr) The purple carbon dioxide detector was obtained by folding in.

  When this carbon dioxide detection agent was stored at 25 ° C., discoloration occurred due to the evaporation of moisture after 6 months, and long-term storage was not possible.

Comparative Example 2
A purple impregnating solution was obtained by mixing 1,000 g of distilled water with 0.20 g of metacresol purple as a pH indicator and 0.40 g of sodium hydroxide as an alkaline substance. 5 g of this impregnating solution was impregnated into a strip-shaped non-woven fabric (weighing 43 g / m ² , thickness 0.3 mm) and used alone without being enclosed in a packaging material.
As a result of using together with a commercially available microaerobic culture medium and carbon dioxide culture medium, the determination of carbon dioxide was the same as in each Example. However, on the next day, water transpiration and fading occurred.

Claims (3)

Comprise at least one pH indicator and water retention agent, the added pH indicator a base impregnated with a regulated alkaline aqueous solution as an alkaline color water vapor permeability of 20g ^/ m 2 / 24hrs the following sachet A carbon dioxide gas detection agent which is sealed and used by ventilating the atmosphere to be detected and the inside of the sachet. The carbon dioxide gas detection agent according to claim 1, wherein the pH indicator is metacresol purple. The carbon dioxide gas detection agent according to claim 1, wherein the water retention agent is at least one selected from the group consisting of polyethylene glycol, polyacrylic acid ester, glycerin, and cellulose.