JPH0113529B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a humidity indicator that allows you to easily know the humidity of a space by changing its color. If a filter paper carrying a deliquescent substance such as calcium chloride is placed in a humid space, the calcium chloride will absorb moisture and eventually deliquesce, but as long as the amount of moisture absorbed is small, the deliquescent liquid will remain without flowing out from the filter paper. When the amount of deliquescent liquid increases to the point where it absorbs more moisture and exceeds the water retention capacity of the filter paper, the deliquescent liquid flows out from the filter paper. At this time, the more calcium chloride adheres to the filter paper, the more the deliquescent fluid flows out from the filter paper, the more the humidity is lower. The present invention focuses on this phenomenon, and as a result of absorbing moisture exceeding its water retention capacity when a moisture absorbent material is placed in an environment with a predetermined humidity, moisture is released from the material (in the above example, calcium chloride). Aqueous solution) is brought into contact with a coloring agent to cause a color change, and the moisture released from the moisture absorbent material is soaked into a white or light-colored opaque sheet with water permeability that is in close contact with the moisture absorbent material. It is detected by changing color. That is, in the present invention, the water-permeable sheet 2 carrying the coloring agent 3 is closely attached to the upper surface of the sheet-like moisture absorbing material 1 carrying the coloring agent 3, or the water-permeable sheet 2 carrying the coloring agent 3 is closely attached to one side of the moisture absorbing material 1. This humidity indicator is characterized in that a water-permeable, white or light-colored water-transparent sheet 4 is placed in close contact with the sheet. The hygroscopic material in the present invention may be one in which a water-soluble hygroscopic substance is supported on a support, or it may be a highly water-absorbent polymeric substance which itself has hygroscopic properties. Examples of water-soluble hygroscopic substances include water-absorbing salts (for example, water-soluble salts of alkali metals, alkaline earth metals, magnesium, etc.), phosphoric acid, hygroscopic surfactants, aliphatic polyhydric alcohols, etc. However, it is not limited to these. In addition, the support for supporting these water-soluble hygroscopic substances is conveniently in the form of a sheet, such as filter paper, Japanese paper, cloth, non-woven fabric, or calcined expanded vermiculite or perlite, which retains the liquid inside. Great ability, Western paper, cardboard,
There are materials with a low liquid retention capacity such as coated paper, or materials with no liquid retention capacity such as plastic plates and glass plates.When using a material with a large liquid retention capacity, water-soluble hygroscopic substances are used. If it is solid, it is impregnated into the support as an aqueous solution and then dried, or if the water-soluble hygroscopic substance is liquid, it is directly impregnated into the support in an appropriate amount. If the support has little or no liquid holding capacity, a water-soluble hygroscopic substance can be applied to its surface using a suitable binder;
Dry if necessary. At this time, it is also possible to mix and apply a filler as appropriate. When the hygroscopic material is a highly water-absorbing polymer substance having hygroscopic properties, it can be used as the hygroscopic material itself in the present invention, but this material may further carry a water-soluble hygroscopic substance. This super absorbent polymer material is commercially available in the form of powder or beads, and it is convenient to use a suitable binder to closely adhere it to the surface of a sheet-like material. Examples of such highly water-absorbing polymeric substances include saponified vinyl acetate-acrylic methyl copolymers, starch-acrylic acid copolymers, and vinyl alcohol-acrylic acid copolymers. In the present invention, the coloring agent itself does not necessarily have to be a colored substance, but can include a substance (group A) that causes a color change such as color development, browning, or discoloration when it comes into contact with water or an aqueous solution, and a coloring substance itself. Substances that cause migration when exposed to water or an aqueous solution (Group B) can be classified. For example, a solid PH indicator can be used as the colorant of the A group, and an acidic or alkaline substance compatible with the indicator is supported on the moisture absorbent material. In this case, a water-permeable sheet carrying a PH indicator is closely attached to one side of a sheet-shaped moisture absorbing material, and a sheet carrying an appropriate acidic or alkaline substance that develops, discolors, or fades the PH indicator on the other side. Alternatively, a mixture of a solid PH indicator and a compatible solid acidic or alkaline substance may be used as the colorant. Furthermore, colorants include redox indicators, substances that develop or change color due to diazo coupling that reacts at room temperature, and these include the corresponding oxidizing or reducing substances, diazo components, coupling components, etc. It is used in a mixed state with a solid powder of a toning component (referred to as a toning component), or the toning component is supported inside or on the surface of a moisture-absorbing and water-retaining material. Alternatively, a colorant-carrying sheet may be placed on one side of a sheet-shaped moisture absorbent material, and a toning component-carrying sheet may be placed on the other side in close contact with each other. Typical coloring agents in Group B include water-soluble dyes (preferably those that do not have strong dyeing properties on the material supporting them), and water-insoluble dyes and pigments that can easily flow with water. etc. can also be used. A water-permeable, colorless (or light-colored), and opaque sheet, such as filter paper, is further provided in close contact with the upper surface of the support on which the colorant is supported, so that the water (or aqueous solution) released from the moisture absorbent material due to its absorption of moisture is ), the dye dissolved in the opaque sheet oozes out onto the top surface of the opaque sheet, coloring it. Next, a specific example of the structure of the indicator of the present invention will be explained with reference to the drawings. In Fig. 1A, a water-permeable sheet 2 carrying a coloring agent 3 is closely attached to one side of a moisture-absorbing material 1 carrying a water-soluble hygroscopic substance, and a water-permeable colorless or light-colored opaque sheet 4 is further attached closely. Fig. 1B shows a humidity indicator using a moisture absorbing material 1 in which a colorant 3 and a water-soluble hygroscopic substance are supported on the same support, and a water-permeable colorless or light-colored opaque sheet 4. The one in close contact with the material shown in FIG. It is something. FIG. 2 shows a humidity indicator as shown in FIG.
It is sandwiched between two sheets and fixed with adhesive 7,
Figure 3 shows a configuration in which several humidity indicators indicating different humidity levels are sandwiched between two thin plastic plates with holes. , 50) indicates the ambient relative humidity required for these humidity indicators to develop a color. In other words, if the 〓〓 and 〓〓 parts are colored, it means that the relative humidity of the space where they were placed was approximately 40%. The humidity indicator of the present invention can be installed at any location and is effective for knowing the humidity there, but one of its uses is that it can also be used as a sign to judge the effectiveness of a moisture-absorbing bag for drying. For example, place the humidity indicator of the present invention on the surface of a moisture-absorbing bag for drying, cover it with a transparent film that does not transmit water vapor, and glue the periphery of the film to the surface of the moisture-absorbent bag for drying. Cut off from the outside world. The humidity indicator, placed in the sealed space formed between the surface of the bag and the transparent film, changes color when the desiccant inside the bag absorbs enough moisture to reach its practical use limit. Therefore, the effectiveness of the drying moisture-absorbing bag can be known by displaying the indicator. Next, examples of the present invention will be given, but the present invention is not limited thereto. Example 1 Using a 1% aqueous solution of brilliant blue FCF (coloring agent), an aqueous calcium chloride solution having the concentration shown in Table 1 was prepared. Filter papers were immersed in these aqueous solutions, taken out and dried to obtain moisture absorbing materials made of colored filter papers containing calcium chloride as shown in Table 1.

[Table] These calcium chloride-containing colored filter papers (hygroscopic material) are layered with untreated filter paper as an opaque layer.
As shown in the figure, the relative humidity (RH) is 40%, and the relative humidity (RH) is 40%.
Table 2 shows the results of observing the coloring of the untreated filter paper by broadcasting it in spaces of 50, 60, 70, 80 and 90 for 3 days.

[Table] +: Colored -: No color The color of the untreated filter paper did not disappear even when it was dried. Example 2 Using a 1% aqueous solution of brilliant blue FCF,
Lithium chloride aqueous solutions having the concentrations shown in Table 3 were prepared, filter papers were immersed in these aqueous solutions, taken out and dried to produce hygroscopic materials consisting of lithium chloride-containing colored filter papers as shown in Table 3.

[Table] These lithium chloride-containing colored filter papers were used in Example 1.
In the same manner as above, a humidity indicator was made by stacking the untreated filter paper in close contact with it. Table 4 shows the blue coloring of the untreated filter paper when these indicators were placed in a space with various relative humidity for 3 days.

[Table] +: Colored -: Not colored Example 3 A filter paper was immersed in a calcium chloride aqueous solution as shown in Table 5, taken out and dried to form a moisture absorbing material made of calcium chloride-containing filter paper as shown in Table 5. Tsukutsuta.

[Table] Separately, a filter paper was soaked in a 1% aqueous solution of Brilliant Blue FCF, taken out and dried. A humidity indicator was prepared by closely stacking a dye-containing filter paper on a calcium chloride-containing filter paper, and then closely stacking an untreated filter paper on top of the dye-containing filter paper. When these humidity indicators were placed in a space with various relative humidity for 4 days, the color of the untreated filter paper was 6th.
It was as shown in the table.

【table】

[Table] +: Colored -: Not colored Example 4 A filter paper was soaked in a calcium chloride aqueous solution as shown in Table 7, taken out and dried to obtain a moisture absorbing material made of filter paper containing calcium chloride as shown in Table 7. Ta.

[Table] Various humidity indicators were made by stacking and adhering this calcium chloride-containing filter paper to the same dye-containing filter paper used in Example 3. This indicator was placed in a space with various relative humidity, and the blue coloring of the calcium chloride-containing filter paper was observed after 3 days. The results are shown in Table 8.

[Table] +: Colored -: Not colored Example 5 A filter paper was soaked in a 10% aqueous solution of anhydrous sodium carbonate, taken out, and dried. Further, a filter paper was soaked in a 2% ethanol solution of phenolphthalein, taken out and dried. The various calcium chloride-containing filter papers prepared in Example 3 were layered on top of the sodium carbonate-containing filter paper, and the phenolphthalein-containing filter paper was layered on top of that to make the three layers adhere to each other to create humidity indicators sensitive to various humidity levels. . These indicators were placed in a space with various relative humidity, and two days later, the development of a red color on the phenolphthalein-containing filter paper was observed. The results are shown in Table 9.

[Table] +: Color development -: No color development Example 6 7% sodium chloride and brilliant blue
A filter paper was immersed in an aqueous solution containing 1% FCF, taken out, and dried to obtain a moisture absorbent made of blue filter paper containing 21.0 g/m ² of sodium chloride. A humidity indicator was prepared by closely adhering an untreated filter paper to this filter paper as an opaque layer. When this indicator was placed in a space with relative humidity of 80% and 90% for 5 days, blue coloration of untreated filter paper was observed only in the space with 90% humidity. That is, the relative humidity that causes this indicator to turn blue is approximately 90%. Example 7 An untreated filter paper was layered on each of the calcium chloride-containing colored filter papers No. 1 to No. 6 in Example 1,
Six types of humidity indicators as shown in Figure 3 were created. When these indicators were placed in a closed confectionery oven for 3 days and then observed, No. 5 and No. 6 were observed.
The corresponding humidity indicator had turned blue. That is, the relative humidity inside this confectionery oven was approximately 50%.

[Brief explanation of drawings]

1A, 2B, and 3B are sectional views showing specific examples of the humidity indicator of the present invention, and FIGS. 2A and 3A are plan views. 1: Moisture absorbing material, 2: Water permeable sheet, 3: Colorant,
4: Opaque sheet, 5: Layer carrying a drug that develops, changes color or fades the colorant, 6: Thin plastic plate, 7: Adhesive.

Claims (1)

[Claims] 1 Sheet-like moisture absorbing material 1 on which colorant 3 is supported
A water-permeable sheet 2 carrying a coloring agent is closely adhered to the upper surface or one side of the moisture-absorbing material 1, and a water-permeable white or light-colored opaque sheet 4 is layered in close contact with the sheet. A humidity indicator featuring