JPH0470927B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel desiccant using calcium chloride. Specifically, it is a desiccant that has excellent hygroscopicity and prevents the deliquescent solution of calcium chloride from flowing out. [Prior art and problems] Calcium chloride has high hygroscopicity, so
Widely used as a desiccant. For example, the most common method is to fill a container with a lid made of a breathable sheet with the calcium chloride. However, the desiccant using calcium chloride has the problem that once moisture absorption progresses to a certain extent, the moisture absorption rate decreases significantly, and a sufficient drying effect cannot be obtained until the saturated moisture absorption amount is reached. In addition, a deliquescent liquid of calcium chloride was generated, and there were restrictions on handling the outflow of the liquid. [Problems to be Solved by the Invention] The present inventors have conducted extensive research in order to solve these problems. As a result, by using a mixture of dry calcium chloride and a specific powder as a desiccant agent, calcium chloride showed stable hygroscopicity with little decrease in moisture absorption rate, and moreover, The present inventors have discovered that the amount of moisture absorption can be dramatically improved and that the outflow of the deliquescent liquid can be effectively prevented, leading to the completion of the present invention. In the present invention, 80% by weight of particles passing through a 4-mesh sieve
With respect to 100 parts by weight of "pulverized inorganic foam material (hereinafter also referred to as foamed powder)" having a particle size of 50% by weight or less of particles passing through a 100-mesh sieve,
This desiccant is made by dispersing and mixing 20 to 300 parts by weight of calcium chloride powder. In the present invention, the foamed powder is a pulverized inorganic foam whose expansion ratio is generally 10 to 40, such as a foam obtained by firing minerals such as perlite and vermiculite, and a natural foam such as Shirasu balloon. are preferably used. Among these foamed powders, especially crushed pearlite and/or vermiculite foams,
The effect of the present invention is remarkable and preferable. Further, the particle size of the foamed powder is such that the particles passing through a 4-mesh sieve account for 80% by weight, more preferably 90% by weight or more, and
It is desirable that the amount of particles passing through a 100 mesh sieve is not more than 50% by weight, preferably not more than 40% by weight. That is, when the proportion of particles passing through the four-mesh sieve is less than the above range, the diffusivity of liquid between particles decreases, so that the moisture absorption rate and amount of moisture absorption of the resulting desiccant tends to decrease. In addition, if the proportion of particles passing through a 100-mesh sieve is greater than the above range, the diffusion of liquid between particles will decrease, and the moisture absorption rate will similarly decrease, as well as the water retention capacity will decrease.
The amount of moisture absorption of the resulting desiccant also tends to decrease. In addition, calcium chloride can be in the form of powder, granules, flakes, etc., but in the present invention, using powdered calcium chloride increases the surface area of calcium chloride and absorbs moisture. It is preferable that the speed can be improved and that layer separation after dispersion and mixing in the foamed powder described later is small. In the present invention, the mixing ratio of calcium chloride to the foamed powder is 20 to 300 parts by weight, preferably 50 to 300 parts by weight, per 100 parts by weight of the foamed powder.
A proportion of 250 parts by weight is suitable. If the proportion of calcium chloride is higher than the above range, it will be difficult to diffuse and retain the entire amount of calcium chloride deliquescent liquid in the foamed powder, so there will be a tendency for the moisture absorption rate to decrease or for the deliquescent liquid to seep out. be. Further, if the proportion of calcium chloride is less than the above range, there is no particular effect on hygroscopicity, but the volume of the desiccant becomes larger than necessary, and it is not economical. In the present invention, it is important to mix the foamed powder and calcium chloride in a dry state in order to obtain an excellent desiccant, and such mixing is called dispersion mixing. On the other hand, a desiccant obtained by making a monocarboxylic aqueous solution of calcium chloride, absorbing it into a foamed powder, and then drying it does not exhibit the excellent hygroscopicity as in the present invention. That is, in such a desiccant, it is thought that the pores or shape of the foamed powder, which are effective for diffusing the deliquescent liquid of calcium chloride, change depending on the calcium chloride after drying. Also,
In the present invention, the dispersion mixing is most preferably carried out in such a manner that calcium chloride is uniformly dispersed in the foamed powder, but it may also be carried out in such a manner that a portion of the calcium chloride is unevenly distributed in the foamed powder. Even in this case, sufficient effects can be achieved. The manner in which the desiccant of the present invention is used is not particularly limited. Typical usage patterns include filling a container at least partially hygroscopic (including a bag formed of a sheet), filling a closed container such as a desiccator, etc. . Further, it may be molded into an arbitrary shape by adding a molding aid such as calcium silica and the like by a molding method such as compression molding. [Effects and Actions] As can be understood from the above explanation, the desiccant of the present invention has an extremely small decrease in the moisture absorption rate until reaching the saturated moisture absorption amount, and the saturated moisture absorption amount is lower than that of conventional drying using calcium chloride. This value is unexpectedly high for agents. Incidentally, the amount of moisture absorbed is more than twice that of calcium chloride alone.
Furthermore, since the deliquescent liquid is retained in the foamed powder, it also has the characteristic that there is almost no outflow of the deliquescent liquid. Although the mechanism by which the desiccant of the present invention exhibits the above-mentioned excellent hygroscopicity is not clear, the present inventors believe that the unique unevenness and pore structure of the foamed powder makes it possible for the powder to simply retain water. In addition to having a water-diffusing function, the deliquescent liquid that forms on the surface of calcium chloride during moisture absorption is quickly diffused and retained, so that the calcium chloride surface is covered with a layer of deliquescent liquid. It is presumed that this is due to the fact that the surface can always maintain a high calcium chloride concentration without being affected. [Examples] Examples are shown below to specifically explain the present invention, but the present invention is not limited to these Examples. In addition, in the Examples and Comparative Examples, the hygroscopic test was performed by placing 100g of the sample in a room with a temperature of 20°C and a humidity of 80%, and measuring the increase in weight after 7 days, 14 days, 21 days, and 28 days. It is shown as the amount of moisture absorbed. In addition, the above-mentioned increased amount was converted into the amount per 100 g of calcium chloride and was shown as the unit moisture absorption amount. Example 1 Using the foamed powder shown in Table 1, this foamed powder
A desiccant was obtained by mixing 100 parts by weight with an anhydrous calcium chloride powder blender in the proportions shown in Table 2. The results of the moisture absorption test for these desiccants are also shown in Table 2. Incidentally, in No. 6 in Table 2, leaching of deliquescent fluid occurred.

【table】

[Table] Comparative Example 1 As a result of conducting a hygroscopic test on 100g of calcium chloride, the amount of water absorbed was 180g in 7 days and 224g in 14 days.
g, 240 g on the 21st, and 270 g on the 28th. Comparative Example 2 The foamed powder was impregnated with an aqueous calcium chloride solution at a ratio of 100 parts by weight of calcium chloride to 100 parts by weight of the foamed powder A used in Example 1, and then dried. Obtained. A hygroscopicity test was conducted on the obtained desiccant. The results are shown in Table 3.

[Table] Comparative Example 3 The pearlite foam used in Example 1 was used without being crushed, and as in B of Example 1, the particles passing through 4 meshes were 100% by weight and the particles passing through 100 meshes were 30% by weight. 100 parts by weight of anhydrous calcium chloride powder (No. 7 of Example 1) was added to 100 parts by weight of the non-pulverized pearlite foam.
Table 4 shows the results of the moisture absorption test of the desiccant obtained by mixing (same conditions as above) in a blender.

【table】

Claims (1)

[Claims] 1 20 to 300 parts by weight of calcium chloride powder is added to 100 parts by weight of "pulverized inorganic foam" having a particle size of 80% by weight or more of particles passing through a 4-mesh sieve and 50% by weight or less of particles passing through a 100-mesh sieve. A desiccant made by dispersing and mixing.