JPS61254248A - Sheet shaped moisture absorbent - Google Patents

Abstract

PURPOSE:To enhance hygroscopicity and to improve moisture release property, by using sodium carboxy methyl cellulose having a specific substitution degree as a main component and receiving the basis wt. of a sheet in a specific range. CONSTITUTION:A sheet is formed of 50-10wt% of sodium carboxy methyl cellulose with a substitution degree of 0.1-1.0 and 50-0wt% of cellulose by a papermaking method so as to set the basis wt. of said sheet to 20-200g/m<2>. As a result, a moisture absorbent having a high hygroscopic speed and large hygroscopic capacity and capable of being easily regenerated by air drying at the time of drying and regeneration is obtained. Further, this moisture absorbent is easy to handle because of its sheet like shape and can be used as a tableware shelf even in domestic use. Furthermore, when a cycle of moisture absorption-moisture release-moisture re-absorption-moisture re-release is repeated, a hygroscopic amount enabled in recycle is increased to a large extent to reach 110% of its own wt.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a sheet-like moisture absorbent, and more specifically, carboxymethyl cellulose sodium (hereinafter referred to as CMC).
This refers to a sheet-like moisture absorbent that has moisture absorption and moisture release several times higher than silica gel, and can be easily dried and regenerated by sun drying or air drying. be.

(Prior Art) Silica gel, quicklime, and the like have been known as drying agents for foods and the like, and recently, various super absorbent resins have been developed, and these can also be used as moisture absorbents.

On the other hand, many methods are known in which a water-absorbing powder material is laminated and integrated between other sheet-like materials (for example, Japanese Patent Application Laid-Open Nos. 56-9458, 1983-89839,
JP-A-56-91052, etc.).

(Problem to be solved by the invention) However, in the case of silica gel, etc., although the rate of moisture absorption is high, the amount of moisture absorbed is small, at most about 30% of its own weight, and as shown in the comparative example described later. -The range of moisture absorption a1 that can be recycled by moisture release and recycle is only about 13% of its own weight. In addition, when using so-called super absorbent resins such as starch and acrylic resins as moisture absorbents, the absorbent i! i! Although ffi is relatively large, its water-retaining properties are too strong, so it has the disadvantage that it is very difficult to dry and regenerate it in a short period of time in a general household by methods such as sun drying or air drying. Therefore, a moisture absorbent that has high hygroscopicity and also has moisture releasing properties that can be easily recycled in ordinary households has not yet been developed.

Therefore, as a result of intensive research to develop a material that has high hygroscopicity, that is, a material that has a fast moisture absorption rate and a large amount of moisture absorption, and has an appropriate moisture release property when dried and regenerated, and is in the form of an easy-to-handle sheet, we have developed the present invention. This is what led to the eggplant.

(Another means to solve the problem) That is, the present invention is a paper made from 50 to 100% by weight of carboxymethylcellulose sodium with a degree of substitution of 0.1 to 1.0 and 50 to 0% by weight of cellulose. The present invention is a sheet-like moisture absorbent characterized in that the tsubo 5 is 20 to 2009/m2.

The sheet used in the present invention is obtained by paper-making cotton-like all-acid CMC in water by applying the method disclosed in Japanese Patent Publication No. 42-2925 and Japanese Patent Publication No. 43-1214, and then pre-drying it. is converted into Na salt type CMC using sodium carbonate, etc.
It is manufactured by drying. During this manufacturing process, in the pre-drying process of the all-acid type CMC sheet and the drying process after converting the sheet into Na salt type, the free acid type group R-COOII inside the sheet and the unreacted hydroxyl group R°-Ko is thought to form an ester crosslink of R-CO-0-R by heat, and the presence of this bridge 10Mc provides high hygroscopicity and dehumidification.

The degree of substitution (hereinafter abbreviated as DS) of this CMC is 0.1 to 1.
0 is appropriate; if DS is less than 0.1, hygroscopicity will be poor, and if O8 exceeds 1.0, the water solubility of CMC will be too high, and the CMC fiber surface will partially dissolve during moisture absorption, resulting in a film. This is inconvenient because the moisture release and absorption properties become inferior after that.

Further, regarding the mixing ratio of CMC and cellulose in the sheet, it is appropriate that the CMC is 50 to 100% by weight. This is because from a papermaking perspective, the more cellulose is included, the easier it is to manufacture, but in terms of hygroscopicity, the greater the cellulose content, the poorer the performance.

Furthermore, the basis ω of this sheet is suitably 20 to 200 g/d. Due to the sheet manufacturing process, if it is less than 20g/g, the sheet is too thin and tends to be uneven;
If it exceeds 7/m, it becomes difficult to dry. Also, from the viewpoint of moisture absorption performance, the former case causes variations in performance, and the latter case is not preferable because it increases ventilation resistance.

The sheet-like moisture absorbent of the present invention can be used alone or in the form of a composite sheet laminated with a cellulose or synthetic polymer sheet or powder. It is also possible to use the sheet-like moisture absorbent of the present invention by cutting it into pieces, scattering it on sheets made of other materials, and laminating them.

(Effects of the Invention) Since the sheet-like moisture absorbent of the present invention is in the form of a sheet, it can be pasted, spread, or sealed on part or all of the wall or bottom of a cupboard, chest of drawers, closet, or airtight container in an ordinary household. It can therefore be used as a moisture absorbent.

In addition, by installing the sheet of the present invention at the inlet or outlet of an air conditioner's blower, it is possible to easily remove moisture from the air passing through it, and conversely, if the air becomes abnormally dry, Since the moisture retained in the sheet of the present invention is released to humidify the room, it can also be used as a humidifying agent.

Its moisture absorption effect is extremely large, and for example, 2 g of the sheet made of 100% CMC of the present invention can dehumidify the humidity in a container having a volume of 121 from 70% to 50% in 30 minutes.

Also, the cycle of moisture absorption-moisture release-re-moisture absorption-re-moisture release!
The amount of moisture absorption that can be recycled when returned is about 13% of its own weight for silica gel, whereas the sheet of the present invention has an extremely excellent moisture absorption capacity of about 8 times that of silica gel, which is 110% of its own weight. It is a moisture absorbent and humidity conditioner.

In general, the sheet-like moisture absorbent of the present invention is characterized in that it can be easily dried and reused by a simple drying method such as sun drying or air drying. In other words, Table 1 shows the results of a comparison of its moisture release rate with silica gel, etc., and the sheet has a very high moisture release rate and approaches the saturated moisture absorption amount and has slowed down in moisture absorption, so it can be easily dried and recycled. I can do it.

Table 1 (Examples) The present invention will be explained below with reference to Examples, but the present invention is not limited by these.

In the examples, % represents heavy F%.

Example 1 and Comparative Examples 1 to 2 A flocculent all-acid type CMC with a DS of 0.43 was disintegrated in water, made into paper, and pre-dried at 60°C to produce a sheet-like all-acid type CMC. After immersing in a bath consisting of 10% sodium carbonate, 3% glycerin, and 87% water, the liquid was removed.
The mixture was heated to ℃ and dried to obtain 1 q of sheet-like Na-type CMC.

This sheet-shaped Na-type CMC had a DS of 0.43, a viscosity of 200 CI)S, a sheet thickness of 0.15 m, and a basis weight of 789/m.

Moisture absorption rate and moisture release rate under the same conditions for this sheet, commercially available silica gel for comparison, and commercially available super absorbent resin (starch-based), and the amount of water that can be recycled by repeating moisture absorption-moisture-desorption-re-moisture-absorption-re-moisture release. was measured.

A sealed plastic container with a volume of 270 g was used for the measurement, and 2 ρ of hot water at 80°C was placed in one corner of the container.
The stainless steel container No. 1 was placed and left for about 1 hour to humidify the inside of the plastic container.

Next, the above-described sheet of the present invention (Example 1), silica gel (Comparative Example 1), and super absorbent resin (Comparative Example 2) were placed into a container at the same time. The sheet of the present invention is a circular sheet 2 with a diameter of 8G.
The iJ[ is 0.73
It was V. Further, 3 g of each of silica gel and super absorbent resin were taken and spread on a watch glass with a diameter of 8C11 in order to equalize the moisture absorption area.

Changes in the weight of each of these samples over time were measured to determine the moisture absorption rate.

In addition, the moisture release rate was measured by removing water droplets attached to the plastic container wall, replacing the inside of the container with air with a relative humidity of 40% flowing in from the piping, and then measuring the weight of each sample over time. 1 change was measured. The results of these measurements are shown in FIG. Weight f of the sample dried at 80℃ for 1 hour in advance
flW1g, weight of sample during moisture absorption or dehumidification i) w2g
The water content W% in the sample was determined from the following formula.

In the case of the inventive sheet of Example 1 from FIG.
It is clear that it is possible to absorb and release 0% moisture, and to do so in about 3 hours. On the other hand, in the case of the silica gel of Comparative Example 1, only 30% of its own weight can be absorbed, and moisture release is only 17% of its own weight even after 24 hours, so the amount of water that can be recycled is only 13% of its own weight. Met.

In addition, in the case of the super absorbent resin of Comparative Example 2, the amount of moisture absorbed was 80% of its own weight, but its rate of moisture release was slow, and it took about 10 hours or more for moisture release and regeneration.

Example 2 Using the sheet-like moisture absorbent prepared in Example 1, the dehumidification effect inside a container was measured. Place one meter of wet hair in a desiccator with a capacity of 12 g, add 60 m of hot water at 70°C to a beaker, and leave it in the desiccator for about 1 hour. When the humidity in the desiccator reaches 70%. The hot water was taken out, the sheet 2.23 of the present invention was quickly put in, and the desiccator was sealed, and the humidity change inside the desiccator was measured. The results are shown in Table 2, and it was found that the inside of the desiccator was dehumidified in a short time.

Table 2 Example 3 A wet filter paper with a moisture content of 58% obtained by dropping 0.50 (j) of water onto 0.3 g of filter paper was placed in one corner of a desiccator with a capacity of 12 g, and the filter paper prepared in Example 1 was placed in the other corner. 3.5 g of a sheet-like moisture absorbent was placed and the filter was sealed. After 10 hours, the moisture content of the filter paper was 165%, indicating that the sheet of the present invention has a great dehumidification effect.

[Brief explanation of drawings]

FIG. 1 shows the change in moisture content of a sample over time when moisture absorption and dehumidification are repeated using the sheet-like moisture absorbent, silica gel, and super absorbent resin of the present invention. A shows the results with the sheet-like moisture absorbent of Example 1, B shows the results with the silica gel of Comparative Example 2, and C shows the results with the starch-based super absorbent resin of Comparative Example 3.

Claims (1)

[Claims] 50 to 100% by weight of sodium carboxymethylcellulose with a degree of substitution of 0.1 to 1.0 and 50 to 100% of cellulose
A sheet-like moisture absorbent, which is a sheet made from 0% by weight and has a basis weight of 20 to 200 g/m^2.