JPH0657298B2 - Complex desiccant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] In the present invention, a deliquescent salt, particularly calcium chloride and / or magnesium chloride, is mixed with fibrous sepiolite powder having excellent water retention and rheological properties. The present invention relates to a drying agent.

[Problems to be solved by conventional techniques and inventions]

Conventionally, deliquescent salts such as calcium chloride and magnesium chloride have been used as desiccants having a large moisture absorption amount (moisture absorption capacity) per unit weight. However, unlike desiccants such as silica gel and zeolite, it dissolves in water of crystallization obtained by absorbing moisture by itself, separates as a saturated aqueous solution, and continues to absorb moisture until it reaches equilibrium with water vapor in the atmosphere and becomes a dilute solution. Its use was limited because of deliquescent.

Therefore, attempts have been made to solve this problem and to use deliquescent salts as a desiccant in a wider range than foods, precision machinery and the like.

One of them is a method of impregnating and drying a salt with a mineral water retention agent such as vermiculite, perlite, or natural zeolite, a super absorbent polymer, etc. in an aqueous solution state, and supporting it (water retention agent supporting method). One is a method of packaging salts in a bag made of a moisture-permeable and water-impervious film (equal-moisture impermeable film packaging method).

In the former method, the water retention of vermiculite, perlite, superabsorbent polymer, etc. was not sufficient, and when external force was applied to the desiccated desiccant, it was observed that the aqueous solution produced by deliquescent leaked to the outside. Moreover, the weight of the salt that can be supported was small, and the expected moisture absorption capacity was not obtained. The latter method is an effective method as long as the packaging is perfect, but there is always the risk of leakage of deliquescent liquid due to damage to the packaging, and it is economical because a special moisture-permeable and water-permeable film is used. Also has a problem.

Further, the conventional deliquescent salt-supporting desiccant has a drawback that its moisture absorption capacity under low humidity is smaller than that of a physical adsorption desiccant such as silica gel or zeolite.

Still another one is a dehumidifying agent (Japanese Unexamined Patent Publication No. 59-127627) characterized in that calcium chloride is attached to the inner walls of numerous tunnel-shaped holes of granular sepiolite. The production of this dehumidifying agent requires high-pressure heat treatment humidity or a decompression facility for supplying a calcium chloride solution, and anhydrous calcium chloride is adhered to granular sepiolite by a complicated method. In this method, the numerous tunnel-shaped pores of granular sepiolite are blocked with liquefied calcium chloride (anhydrous calcium chloride), so that sufficient moisture absorption cannot be obtained,
Further, since calcium chloride adheres to the granular sepiolite, the physical adsorption performance of the sepiolite against water vapor is impaired, and the dehumidification performance in a low humidity atmosphere is small.

[Object of the Invention]

The object of the present invention is to completely eliminate the problems of liquid phase separation and fluidization due to deliquescent and leakage from a moisture-permeable sheet while maintaining a large moisture absorption capacity of deliquescent salts, particularly calcium chloride and / or magnesium chloride. Another object of the present invention is to provide a desiccant capable of achieving an increase in moisture absorption capacity in a low temperature atmosphere, which is inferior to the conventional impregnation-supporting desiccant as compared with the physical adsorption desiccant. In order to obtain such a desiccant, in particular, hygroscopic deliquescent calcium chloride and / or magnesium chloride is mixed with a sustainably disintegrated sepiolite powder having a strong water retention property to form a deliquescent salt, for example, It is important to bring calcium chloride and / or magnesium chloride into contact with each other at a high density and to mix them without impairing the drying performance due to physical adsorption inherent in sepiolite.

[Means / actions for solving problems]

As a result of diligent studies on a composite material excellent in water absorption and water retention, and a composite method, the inventors have found that a deliquescent salt, particularly calcium chloride and / or magnesium chloride, is crushed into a fiber and has a fiber length of 1000 to 1 μm. The present invention has been completed by finding that the composite desiccant obtained by mixing with the sepiolite powder can exhibit excellent characteristics.

Generally, the deliquescent property of calcium chloride and magnesium chloride is one side of the desiccation process, and the deliquescent problem is the complete absorption of the liquid phase that is always separated with deliquescent and the fluidization of the desiccant. There is no choice but to eliminate it by preventing. In order to completely absorb the liquid phase, it is efficient that calcium chloride or magnesium chloride and the water-absorbing material are in high-density contact. On the other hand, sepiolite is a fibrous natural mineral having many hollow tunnel structures in its crystal structure.

According to the present invention, such a sepiolite has a shear force,
When the fibrous sepiolite powder obtained by crushing into a fibrous form by impact force or the like is mixed with deliquescent salts such as calcium chloride and / or magnesium chloride, the above-mentioned leakage problem is solved.

When the fibrous sepiolite powder is mixed with the deliquescent calcium chloride or magnesium chloride powder, it is considered that these powders are held between the fibers to make the contact intimate and prevent the separation between the two. The length of the sepiolite fiber used is 1000 to 1 μm, and preferably 200 to 1
μm. When the sepiolite fiber length is 1000 μm or more, special measures are required to make close contact with calcium chloride or magnesium chloride powder. For example, it is necessary to mix the sepiolite layer in a layered manner so as to be a lower layer of the calcium chloride layer so that the deliquescent liquid flows to the sepiolite layer to make contact. If the length of the sepiolite fiber exceeds 200 μm, mixing and separation may occur depending on the powder properties of calcium chloride, and the deliquescent liquid may not be locally absorbed. Further, when the sepiolite fiber length is 1 μm or less, the viscosity due to the fiber shape at the time of water absorption is somewhat lowered and the water absorption and water retention performance is also deteriorated, which is not preferable.

The crystal structure of sepiolite has a large number of hollow tunnel structures in the length direction of the fiber, and the structure due to the tunnel structure and the entanglement of the fibers is the cause of the water absorption effect. It is considered that the calcium chloride or magnesium chloride aqueous solution produced by the deliquescent is strongly retained because the tunnel structure is guided through the capillaries formed in the gaps of the sepiolite fibers.

Sepiolite usually occurs as a hard, aggregated ore of many sepiolite tension crystals. In order to obtain sepiolite crushed into fibrous form, this rough stone is first crushed by a coarse crusher, and further, a fine crusher having a shearing force and an impact force as the main crushing force, for example, Raymond mill, hammer mill. Using a rigid roller mill or the like, the sepiolite needle crystals in the rough stone are crushed so as to crush the fibers while maintaining the fibrous shape without breaking them. In this way, is it completely disintegrated into needles,
Alternatively, it is possible to obtain a needle-shaped aggregate powder (fibrous sepiolite) in which needle-shaped crystals are bonded relatively slowly. Further, if the fine pulverization is continued, the needle-shaped crystals are cut off,
After that, when the average particle diameter of the acicular sepiolite aggregate powder that is completely fibrillated into needles and has a fiber length of 1 μm or less and is 20 μm or less, the water retention is sharply reduced. It was crushed in this way. The fiber shape of sepiolite is such that the mixture of sepiolite-deliquescent salts (for example, calcium chloride or magnesium chloride) becomes intimate, the separation of the two is prevented, and the role of rheological properties is exerted. By nature, water is retained in the interstices of sepiolite fibers.

The mixed amount of the deliquescent salts (for example, calcium chloride or / and magnesium chloride) is calculated so that the saturated moisture absorption amount is smaller than the water absorption amount of the sepiolite powder to be mixed. Generally, the water absorption of sepiolite is 1μ
When the fiber length is m or more, the fiber length increases as the fiber length decreases, so that the fibrous powder absorbs more than the granular form, and a composite desiccant having a larger moisture absorption capacity can be obtained. As a mixing method, an ordinary mixer may be used, and it is also possible to mix and mix the sepiolite at the time of pulverization. It is apparent from another invention of the present inventors (desiccant, Japanese Patent Application No. 61-64404; Japanese Patent Application Laid-Open No. 62-221421) that heat treatment of sepiolite can bring out a strong hygroscopic ability due to the adsorption of substances inherent to sepiolite. By mixing this heat-treated sepiolite powder with calcium chloride and / or magnesium chloride, the moisture absorption capacity under high humidity increases, and the moisture absorption is higher than either sepiolite alone or deliquescent inorganic salt alone. The capacity was obtained under low humidity.By adopting the compounding method of mixing, the physical adsorption performance of sepiolite was not impaired, and the moisture absorption capacity of calcium chloride, which has a low hygroscopic capacity under low humidity, was activated. It is considered that this is the result of the fact that the hygroscopic ability of magnesium chloride was also reinforced.

When the fibrous sepiolite powder composite desiccant according to the present invention absorbs the deliquescent liquid and becomes a paste, it exhibits a remarkable viscosity derived from the fibrous form, and when left standing, it becomes a solidified state due to its rheological properties. This is a phenomenon not found in conventional water-absorbing materials.

Also, unlike conventional water absorbents, the rheological properties of sepiolite strongly hold the deliquescent liquid between the fibers and in the crystal structure, so the deliquescent liquid can be easily separated against external pressure during use. I can't.

As described above, unlike the conventional desiccants, the problem associated with deliquescent is solved when the desiccant obtained by the present invention is attached to a desired place. It is not necessary to use a moisture-impermeable film and can be laminated with an inexpensive moisture-permeable sheet or simply wrapped in a moisture-permeable sheet, which is inexpensive, has a high absorption capacity, and is highly effective in a low-humidity atmosphere. A performance desiccant was obtained.

The present invention will be described more specifically with reference to the above examples and comparative examples.

Example 1 A fibrous crushed product with a sepiolite hammer mill type pulverizer (average fiber length: 50 μm, adsorbed water: 30)
%) Was dried at a sample temperature of 300 ° C. for 30 minutes, and then a half amount of calcium chloride dihydrate powder (average particle diameter 100 μm) was added to the weight of sepiolite, and the mixture was mixed with a raikai mixer. The mixture was filled in a commercially available moisture-permeable synthetic paper (Unicel) bag to give a product. This desiccant, 20
When moisture was absorbed under conditions of 90 ° C. and 90% RH, the moisture absorption rate after 14 days was 90%, and under the conditions of 20 ° C. and 10% RH, the moisture absorption rate after 14 days was 20%. Further, no leakage of deliquescent liquid was observed even after absorbing moisture.

Example 2 A sepiolite rough (adsorbed water 3
0%) 120 parts and 75 parts of calcium chloride dihydrate of Example 1
Parts and mixed by dry crushing to obtain fibrous sepiolite calcium chloride composite desiccant. (Average particle size of dry product 50μ
m).

This desiccant was filled in a Japanese paper bag and allowed to absorb moisture under the conditions of 20 ° C. and 90% RH. The moisture absorption rate after 14 days was 100%.
Under the conditions of 20 ° C. and 10% RH, the moisture absorption rate after 14 days was 30%.

Comparative Example 1 Sepiolite was roughly crushed with an impeller breaker, and the obtained granular material was divided by a rotary node to prepare granular sepiolite having a particle size of 1.0 mm to 2.0 mm.

After drying this granular sepiolite at a sample temperature of 300 ° C. for 30 minutes, calcium chloride dihydrate powder average particle diameter 100
μm) is added in an amount of half the weight of sepiolite,
The mixture was mixed with a raikai type mixer. The mixture was filled in a commercially available moisture-permeable synthetic paper (Unicel) bag to give a product.

When this desiccant was allowed to absorb moisture at 20 ° C. and 90% RH, leakage of deliquescent liquid was observed at the time when 50% of the desiccant weight was absorbed, and at 20 ° C. 10% R
Under the condition of H, the moisture absorption rate after 14 days was 8%.

Comparative Example 2 Sepiolite was coarsely crushed with an impeller breaker, and the obtained powdery matter was classified by a rotary node to prepare granular sepiolite having a particle size of 1.0 mm to 2.0 mm.

After absorbing 150 g of a 34% aqueous solution of calcium chloride dihydrate with 100 g of this granular sepiolite,
It was dried at 0 ° C. The dried product was heat-treated at 2 atm and 300 ° C. in an autoclave and then packed in a commercially available transparent synthetic paper (UNICEL) bag to obtain a product.

When this desiccant is allowed to absorb moisture at 20 ° C. and 90% RH, the time required to absorb 60% of the moisture is
The invention product of Example 1 was about twice as long as the time required for absorbing 60% of moisture. Moreover, under the conditions of 20 ° C. and 10% RH,
The moisture absorption rate after 14 days was 13%.

Example 3 Fibrous crushed product using a sepiolite hammer mill type pulverizer (average fiber length: 50 μm, adsorbed water: 30)
%) Was dried at a sample temperature of 300 ° C. for 30 minutes, and then magnesium chloride anhydrous salt powder (average particle diameter 100 μm) was added in an amount of half to the weight of sepiolite and mixed with a raikai type mixer. The mixture was filled in a commercially available breathable synthetic paper bag to give a product. This desiccant is 20 ℃, 90% RH
When it was made to absorb moisture under the conditions of, the moisture absorption rate after 14 days was 20
0%, and under the conditions of 20 ° C. and 10% RH, the moisture absorption rate after 14 days was 40%. Further, no leakage of deliquescent liquid was observed even after absorbing moisture.

Example 4 Rough theophyllite (adsorbed water 30
%) 300 parts and anhydrous magnesium chloride 10 of Example 3
The mixture was mixed with 0 parts and dried and crushed to obtain a fibrous sepiolite magnesium chloride composite desiccant (average particle size of dried product: 50μ
m).

When this desiccant was filled in a Japanese paper bag and allowed to absorb moisture at 20 ° C. and 90% RH, the moisture absorption rate after 14 days was 130.
%, And when it was allowed to absorb moisture under the conditions of 20 ° C. and 10% RH, the moisture absorption rate after 14 days was 24%. Further, no leakage of deliquescent liquid was observed even after absorbing moisture.

〔The invention's effect〕

According to the present invention, a composite desiccant having a large moisture absorption capacity, no deliquescent phenomenon observed, and excellent handleability was obtained. Since this composite desiccant has a large moisture absorption capacity, it can be used in a small amount and there is no problem of deliquescent, so it has not been used conventionally. It can also be used for packing and transporting food, precision machinery, etc.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Takasago 1-1-7 Hoyoshu, Koto-ku, Tokyo Onoda Cement Co., Ltd. Cement Research Laboratory (56) References JP-A-63-162022 (JP, A) Special Features Kai 62-221421 (JP, A)

Claims (2)

[Claims] 1. A composite desiccant obtained by mixing a deliquescent salt with fibrous disintegrated sepiolite powder, wherein the fibrous disintegrated sepiolite powder has a fiber length of 1000 to 1 μm. 2. The composite desiccant according to claim 1, which is obtained by mixing calcium chloride and / or magnesium chloride with fibrous crushed sepiolite powder.