JPS58216936A - Humidity indicator - Google Patents

Abstract

PURPOSE:To detect humidity in a space by bringing water released from a humidity absorbing material into contact with a coloring agent. CONSTITUTION:A water permeating sheet 2 carrying a coloring agent 3 is provided tight on the top surface of a sheet-shaped humidity absorbing material 1. The coloring agent 3 is arranged inside or on the surface of the sheet 2. An indicator thus formed is placed on the surface of a drying humidity absorbing bag, covered with a non-steam permeable transparent film whose periphery is bonded on the surface of the drying humidity absorbing bag with an additive to cut the indicator off outside. Here, the indicator is caused to form color or discolor at the relative humidity corresponding to the use limit of drying material in the bag thereby indicating the effectiveness of the drying humidity absorbing bag.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a humidity indicator for easily knowing the humidity of a space by the change in color that occurs when it is installed in a place where humidity is to be measured.

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 deliquescent water flows out from the filter paper, the more the humidity is lower.

The inventors focused on this phenomenon and discovered that when a moisture-absorbing material is placed in an environment with a predetermined humidity, it absorbs moisture exceeding its water-holding capacity, and as a result, moisture is released from the material (in the above example, an aqueous solution of calcium chloride). is brought into contact with the coloring agent to cause the coloring agent to change color,
Alternatively, the present invention was carried out by successfully detecting the release of moisture from the moisture absorbing material by making the coloring material visible.

The present invention is a humidity indicator comprising a hygroscopic material and a coloring agent, and as a result of the hygroscopic material absorbing moisture, the coloring agent becomes visually uniform or the coloring agent causes a visible color change. .

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, sheet-like supports are convenient for supporting these water-soluble hygroscopic substances, such as filter paper, Japanese paper, cloth, etc.
Non-woven fabric or fired expanded vermiculite or
Items with a large capacity to retain liquid such as light and paper, items with a small capacity to retain liquid such as western paper, cardboard, and coated paper, and items with no capacity to retain liquid at all such as plastic plates and glass plates. If the water-soluble hygroscopic substance is solid, it can be impregnated into the support as an aqueous solution and then dried, or if the water-soluble hygroscopic substance is solid, it can be impregnated with the support and then dried. If so, just impregnate the support with an appropriate amount.

If the support has a low or no liquid holding capacity, the water-soluble hygroscopic substance is applied to its surface using a suitable binder and, if necessary, dried. 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 tightly adhere it to the surface of a sheet-like material. Examples of such superabsorbent polymer substances include saponified vinyl acetate-acrylic methyl copolymers, starch-acrylic 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 may include a substance that develops color, browns, or discolors upon contact with water or an aqueous solution of a water-soluble substance (group A), and a substance that is itself a colored substance. They can be divided into substances (group B) that cause migration depending on water or an aqueous solution of a water-soluble substance.

For example, a solid pH indicator can be used as the substance of group A, and in this case, an acidic or alkaline substance compatible with the indicator is made to coexist with the moisture absorbent material.

In addition, a water-permeable sheet carrying a pH indicator is adhered to one side of the sheet-shaped moisture-absorbing material, and a sheet carrying an appropriate acidic or alkaline substance to color, change color, or brown the Senshi pH indicator is attached to 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.

As a typical example of Group B substances, when using the above Group A substances as water-soluble colorants, moisture absorption can be determined by directly observing the coloring or discoloration of the surface of the support on which it is supported. You can tell that the material has released water, that is, the area around the indicator has the humidity specified for the indicator, but if a B group substance is used as a coloring agent, it will not be carried. A water-permeable, colorless (or light-colored), and opaque sheet-like material such as filter paper is placed in close contact with the upper surface of the support, so that the water (or aqueous solution) released from the hygroscopic material when it absorbs moisture is absorbed by the material. Watch as the dissolved dye bleeds onto the top of the opaque notebook and colors it. When using Group A substances, a water-permeable, colorless (or light-colored) and opaque sheet-like material is placed in close contact with the layer carrying the coloring agent, and the appearance of color on the surface is observed. Of course, this is a good thing.

Among the coloring agents that can be used in the present invention, examples of coloring agents in group A include, in addition to the above-mentioned pH indicators, redox indicators,
There are substances that develop or change color due to dioxidation coupling that reacts at room temperature, and these can be combined with corresponding oxidizing or reducing substances, or solid powders such as noazo components or coupling components (these are called toning components). It is used in a mixed state, or the toning component is present within or on the 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 colorants of group B are water-soluble dyes as described above, and other water-insoluble dyes and pigments that can easily flow with water can also be used.

A specific example of the structure of the indicator of the present invention will be described below with reference to the drawings. The humidity indicator shown in FIG.
A water-permeable sheet (2) carrying . At this time, the coloring agent is present inside the water-permeable sheet in FIG. 1(a), and on the surface in FIG. 1(b).

In FIG. 2, a colorant is present on the surface of a moisture absorbent material (1). Figure 3 shows a case in which the coloring agent itself is colored, such as a water-soluble dye (group B), and Figure 3 (a) shows a case in which the colorant is colored by itself, such as a water-soluble dye. A moisture permeable sheet (2) carrying a colorant (3) on one side of the material (1).
) and a water-permeable, colorless or light-colored opaque layer (4).
Figure (B) uses a hygroscopic 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 layer (4). things that are in close contact,
Figure 3 (c) has a structure in which a colorant (3) is sandwiched between a hygroscopic material (1) carrying a water-soluble hygroscopic substance and a water-permeable colorless or light-colored opaque layer (4). It is.

FIG. 4 shows a case where the colorant is a substance (group A) that develops, fades, or changes color when it comes into contact with water or an aqueous solution of a water-soluble substance; It has a structure sandwiched between a layer (5) carrying a substance that causes fading or discoloration and a moisture permeable sheet (2) carrying a colorant.

Figure 5 shows a humidity indicator as shown in Figure 3 (b), which is sandwiched between two thin plastic plates (6) with a hole in the center and fixed with adhesive (7). It is a device in which several humidity indicators, each with a different humidity level, are arranged and sandwiched between two Shirasunak thin plates with holes, and the numbers marked on the plan view (A) (in this case, 40.50) indicates the ambient relative humidity required for these humidity indicators to develop a color. In other words, if O and O are colored, this indicates that the relative humidity of the space where they were placed was approximately 40%.

Next, one example of use of the humidity indicator of the present invention will be explained.

91 The humidity indicator of the present invention is effective for knowing the humidity when installed at any location, and one of its uses is as an indicator for determining the effectiveness of a moisture absorbing bag for drying. That is, for example, a desiccant made of deliquescent salts themselves or a water-retaining porous material (such as calcined expanded vermiculite) supported with deliquescent salts (e.g., calcium chloride) is placed in a film bag that allows water vapor to pass through but not water. The moisture-absorbing bag for drying manufactured by enclosing it has strong hygroscopicity, and even if it absorbs enough moisture, the aqueous solution (calcium chloride aqueous solution) does not ooze out from the bag, so there is no need to worry about staining the surrounding area. However, in the past, it was necessary to measure the increase in weight to determine whether it is still effective as a moisture absorbing device even after long days of use. However, by using the humidity indicator of the present invention, this judgment can be easily made.

That is, the humidity indicator of the present invention is placed on the surface of the moisture-absorbing drying bag, covered with a transparent film that does not transmit water vapor, and the periphery of the film is adhered to the surface of the drying moisture-absorbing bag with an adhesive to form the humidity indicator. 10- Cut off from the outside world. If the humidity indicator used at this time is made so that it develops color, changes color, or fades at a relative humidity that corresponds to the practical use limit of the desiccant material inside the bag, it is possible to The humidity indicator placed in the sealed space that is formed changes color, changes color, or fades when the desiccant material inside the bag absorbs enough moisture and reaches its practical use limit. This allows you to know the effectiveness of the bag.

An example of how the present invention is used in such a case will be explained with reference to FIG. Figure 7 shows a moisture absorbing bag for drying, and the desiccant material (1
2) is housed in a bag made of a water vapor permeable film (11), and the bag is sealed on three sides with heat-treated sealing parts (13). The humidity indicator (9) of the present invention is attached to the surface of a moisture absorbent bag for drying so as to be isolated from the outside air by a water vapor impermeable transparent film (1).

Next, examples of the present invention will be given, but the present invention is not limited thereto.

Example 1 A calcium chloride aqueous solution having the concentration shown in Table 1 was prepared using a 100% aqueous solution of Brilliant Blue FCF (coloring agent). 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 1 These calcium chloride-containing colored filter papers (moisture absorbing material) are layered with untreated filter paper as an opaque layer, and then sandwiched between two glass sheets with a hole in the center and brought into close contact with each other as shown in Figure 5. Table 2 shows the results of observing the coloration of the untreated filter paper after leaving it in a space with a relative humidity (RH) of 40%, □□□, 60.70%, and 90% for 3 days.

Table 2 + 1 Color - 2 No color The color of the untreated filter paper did not disappear even after drying it.

Example 2 Using an aqueous solution of IJ Ant Blue FOF,
Prepare lithium chloride aqueous solutions with the concentrations shown in Table 3, soak filter papers in these aqueous solutions, take them out and dry them. I made a humidity indicator by layering it on top of it. Table 4 shows the blue coloration of the untreated filter paper when these indicators were placed in a space with various relative humidity for 3 days.

Table 4 Example 3 A filter paper was immersed in an aqueous calcium chloride solution as shown in Table 5, taken out and dried to produce a moisture absorbing material made of filter paper containing calcium chloride as shown in Table 5.

According to Table 5, filter paper was soaked in a 1% aqueous solution of Brilliant Blue FOF, taken out and dried.

A humidity indicator was prepared by closely stacking a filter paper containing calcium chloride on a filter paper containing calcium chloride, and then stacking an untreated filter paper on top of the filter paper in close contact [-]. Table 6 shows the coloration of the untreated filter paper when these humidity indicators were placed in a space with various relative humidity for 4 days.

Table 6 1: Coloring - 2 Example 1 without coloring Soak a filter paper in an aqueous calcium chloride solution as shown in Table 7 - 1 Curl 2 and dry 17 - Calcium chloride as shown in Table 7 A moisture-absorbing material made of filter paper was obtained.

Table 7 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 after 3 days, the coloration of the calcium chloride-containing filter paper was observed.

The results are shown in Table 8.3 Table 8 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 a humidity indicator sensitive to various humidity levels. .

These indicators were placed in spaces with various relative humidity, and two days later, the development of a red color on the phenolphthalene-containing filter paper was observed. The results are shown in Table 9.

Table 9 Example 6 A filter paper was immersed in an aqueous solution containing 7 g of sodium chloride and 1 g of Brilliant Blue FOF, taken out and dried to produce a blue kater containing 21.0 f/d of sodium chloride. When the filter was left in a space with a relative humidity of 80% and 90 m2 for 5 days, blue coloration of the untreated filter paper was observed only in the filter paper kept in a space with a relative humidity of 90%. 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 of Nal to Ugly 6 in Example 1 to create six types of humidity indicators as shown in FIG.

When these indicators were observed after the device had been kept in a closed confectionery oven for 3 days, the humidity indicators corresponding to No. 5 and No. 6 had turned blue.

The relative humidity inside this confectionery was approximately 50% (No. 3
(see table).

Reference Example A bag (100 wa x 100 wa x
130 Place the humidity indicator, which is a combination of Na2 calcium chloride-containing filter paper and untreated filter paper in Example 1, on the above bag, overlay the indicator or a large polyvinyl chloride transparent sheet, and wrap the surrounding area in a bag. NF
The indicator was sealed from the outside world by adhering to the R sheet. When the drying moisture-absorbing bag with the humidity indicator attached was placed in a high-humidity space, the indicator turned blue after 26 days. At this time, the moisture absorption bag for drying is 150? The average humidity of the moisture absorbing material inside the bag was measured using a hygrometer AH-1 manufactured by Shibaura Denshi Co., Ltd., and the result was 83.
It was Chi. These numbers indicate that this moisture-absorbing bag has absorbed moisture close to its practical limit. Therefore, the fact that the humidity indicator used here is colored blue indicates that this moisture-absorbing bag has absorbed moisture close to its practical limit. It was a faithful representation of what had been done.

[Brief explanation of the drawing]

5(a) and 6(a) are plan views of the same, and FIGS. 7(a) and 7(b) are sectional views showing specific examples of the humidity indicator of the present invention, respectively. They are a female plan view and a sectional view. 1: Moisture-absorbing material 2: Moisture-permeable sheet 3: Coloring agent 4: Opaque layer 5: Layer carrying a chemical that develops, discolors, or fades the coloring agent 6: Plastic thin plate 7: Adhesive 8: Moisture-absorbing bag for drying 9: Humidity indicator 10: Transparent film impermeable to water vapor 11: Impermeable film permeable to water vapor 12: Drying material Patent applicant Representative of Nippon So Kako Co., Ltd. Haruyuki Ito Eiki Yokoyama Figure 1 Figure 2 Figure 4, Prisoner 5 (a). Figure 6 (a) Figure 7 (b) Written amendment 1, Indication of the case 1983 Patent Application No. 083578 2, Name of the invention Humidity indicator 3, Person making the amendment Relationship with the case Patent applicant Tokyo Kita 3-1-60 Ukima-ku, Nippon Soda Co., Ltd. Representative: Kaname Nakayama 4, Agent: 100 Nippon Soda Co., Ltd., 2-2-1 Otemachi, Chiyoda-ku, Tokyo.'' (2) Correct ``Chota'' in the third line from the second line of the specification to ``exceeded by 1''. (3) "Guarantee" in the third line of page 4 of the specification is corrected to "maintenance." (4) "This substance is" in the fifth line from the bottom of page 4 of the specification.
Correct it to "to this substance." (5) "Aqueous phase" on page 9, line 11 of the specification is "indicated"
I am corrected. (6) 170 and 90 on page 13, line 4 of the specification.”
is corrected to "70.80 and 90". (7) "Adhesive-containing filter paper" in the bottom line of page 16 of the specification is "
"Dye-containing filter paper" is corrected. (8) [Polyvinyl chloride] on page 22, line 9 of the specification
is corrected to ``polyvinylidene chloride''.

Claims (1)

[Claims] (1) Consisting of a hygroscopic material and a coloring agent, and as a result of the hygroscopic material absorbing moisture, the coloring agent becomes visible or the coloring agent undergoes a visible color change. humidity indicator. 2. The humidity indicator according to claim 1, wherein the hygroscopic material comprises a water-soluble hygroscopic substance and a support supporting the hygroscopic substance. 3. The humidity indicator according to claim 2, wherein the support is in the form of a sheet, and a colorant is supported on a water-permeable sheet placed in close contact with one side of the support. 4. The humidity indicator according to claim 2, wherein a water-soluble hygroscopic substance and a colorant are supported on the same sheet-like support. 5. The humidity indicator according to claims 3 and 4, comprising a water-permeable, white or light-colored opaque sheet placed in close contact with the upper surface of a sheet-like support carrying a colorant. .