JPH0640942B2 - desiccant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a desiccant utilizing a deliquescent dehumidifying agent.

Traditionally, food, clothing, furniture, leather products, musical instruments, precision machinery,
A desiccant is used in a wide range of fields such as industrial use. As the dehumidifying agent, zeolite, molecular sieve, activated alumina, magnesium chloride, lithium chloride, etc. are mainly used, such as quick lime and silica gel. Of these, quicklime is the most widely used because it is cheap, but it is chemically strongly alkaline, so it has the property of strongly attacking it when it comes into contact with the skin. Then it is very dangerous. Further, in terms of physical properties, the dehumidification rate is small and the saturated dehumidification amount per unit weight is not large, so that the dehumidification capacity per unit weight is not necessarily advantageous. On the other hand, silica gel is excellent in the safety of properties and the beautiful appearance, and is widely used in the fields of confectionery, foods, etc., but it has the drawback of being expensive. For these,
Calcium chloride, which is a typical example of a dehumidifying agent having deliquescent properties, has a high dehumidifying rate, a very high dehumidifying capacity per unit weight, and is inexpensive, so it has the best dehumidifying capacity per unit price. There is. Furthermore, calcium chloride has the advantage that it is neither toxic nor polluting. However, since calcium chloride is a deliquescent substance, it becomes a solution when it absorbs more than a certain amount of moisture, so that it has a drawback that it cannot be used as a desiccant in general-purpose fields such as daily foods.

For this reason, it is currently limited to special uses such as for the chemical industry and for chemical experiments, and is not used as a dehumidifying agent for desiccants for general households. In order to solve the disadvantage of liquefaction due to the deliquescent property of calcium chloride, for example, a solution of calcium chloride once impregnated into a porous material,
After that, by heating and drying, an attempt is made to evaporate water to form a solid desiccant (Japanese Patent Laid-Open No. 52-97381, Japanese Patent Laid-Open No. 54-92).
586), or alternatively, an inorganic or organic binder is mixed with calcium chloride, and the mixture is molded and used as a desiccant (JP-A-53-96985). However, in addition to its complexity and high processing cost, the dehumidifying ability in a product state is low, so that it has not been widely used in the field of general daily necessities.

The present invention provides a general-purpose desiccant for general household use, in which such defects of the dehumidifying agent having deliquescent property are improved and the original properties of high dehumidifying ability and low cost are maintained. That is, according to the present invention, calcium chloride as a deliquescent dehumidifying agent has a large number of communicating fine pores having a pore size larger than 1 μm and having breathability without allowing the deliquescent solution of the calcium chloride to leak. Average pore size is larger than 1μ and 20μ
The following microporous thermoplastic resin sheet has a porosity of 3
It is a desiccant characterized by being packaged using a composite material in which 0% or more of reinforcing sheets are laminated. Typical examples of the deliquescent dehumidifying agent include calcium chloride, magnesium chloride, lithium chloride, sodium chloride and the like, but in the present invention, among these deliquescent dehumidifying agents, performance and price are also high. In particular, the most advantageous calcium chloride is selected to obtain a desiccant having a high dehumidification rate, a high dehumidification capacity with a large dehumidification amount per unit weight of the dehumidification agent, and a relatively inexpensive price. It is provided.

The microporous thermoplastic resin sheet which does not leak the deliquescent solution of calcium chloride and has air permeability is preferably obtained by molding a thermoplastic resin containing 35% by weight or more of an inorganic filler into a sheet and then stretching.

Stretching may be performed by a usual uniaxial or biaxial stretching method. The stretching ratio is generally 5% to 700 in terms of volume stretching ratio.
%, Preferably in the range of 200% to 400% is suitable for obtaining a good microporous sheet suitable for use in the present invention.

The thermoplastic resin molded into a sheet containing a large amount of 35% by weight or more of an inorganic filler is stretched as described above to form a void between the thermoplastic resin and the inorganic filler. It is possible to obtain a large number of communicating micropores having a pore size larger than 1 μ, and the average pore size of the communicating micropores is 1
The microporous sheet can be formed to have a size larger than μ and 20 μ or less, which makes it possible to obtain a microporous sheet excellent in air permeability and hence moisture permeability. Therefore, the calcium chloride packaged with the microporous sheet of the present invention exerts a sufficient dehumidifying action through many fine pores which are continuous with the sheet. Moreover, even if the calcium chloride deliquesces and the deliquescent liquid comes into contact with the microporous sheet, the deliquescent liquid does not leak to the outside. It is considered that the thermoplastic resin, such as polyolefin, which is a material of the microporous sheet, has water repellency as well as the micropores having an appropriate pore diameter communicating with the other surface. When the amount of the inorganic filler is less than 35% by weight, even if it is stretched, a good microporous sheet of a thermoplastic resin cannot be obtained and the dehumidifying effect of the packaged calcium chloride cannot be exhibited. On the other hand, when it is as large as 85% by weight or more, the fluidity of the thermoplastic resin is insufficient and it is difficult to obtain a sheet by stretching.

In the present invention, as the thermoplastic resin used for forming the microporous sheet, those generally preferably used include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyester, polyamide and the like. The inorganic filler to be contained in the thermoplastic resin generally has an average particle size of 0.1 to 100 μ, especially 0.5 to
Inorganic compounds such as metal oxides, hydroxides and salts having about 20 μm are preferably used. For example, metal oxides such as calcium oxide, alumina and silica; metal hydroxides such as aluminum hydroxide and calcium hydroxide; metal salts such as calcium carbonate, magnesium chloride, basic magnesium carbonate, calcium sulfate, magnesium sulfate and aluminum sulfate. ; Other calcium silicates; Cements;
Zeolites; clays such as talc can also be used.

The present invention is characterized in that calcium chloride as a deliquescent dehumidifying agent is packaged using a composite material in which an auxiliary sheet is laminated on the above microporous thermoplastic resin sheet. The reinforcing sheet is laminated to reinforce the microporous thermoplastic resin sheet, and a sheet that is more porous and stronger than the microporous thermoplastic resin sheet is used.

In particular, a reinforcing sheet having a porosity of 30% or more is preferably used without impairing the air permeability of the microporous sheet and hence the moisture permeability. A reinforcing sheet having a porosity of less than 30% is preferable because when it is laminated on the microporous sheet by heat fusion or the like, the adhesive portion blocks the pores of the microporous sheet, impairing air permeability and thus moisture permeability. Absent. Examples of such a reinforcing sheet include various reinforcing sheets. Specifically, a paper-like material or a cloth-like material, particularly a perforated sheet-like material made of a synthetic resin or a woven fabric of a film, a fiber or a flat yarn. Alternatively, non-woven fabric is preferable.

These various reinforcing sheets are appropriately laminated. The present invention has found that the composite material in which the reinforcing sheet is laminated on the above-mentioned microporous thermoplastic resin sheet is particularly suitable as a packaging material for calcium chloride of the deliquescent dehumidifying agent,
Not only when the deliquescent dehumidifying agent calcium chloride is used alone, a dehumidifying agent generally used together with the deliquescent dehumidifying agent calcium chloride, such as water-absorbing polymer, water-absorbent paper, water-absorbing pulp, synthetic It may be used in combination with regular silica, synthetic calcium silicate, perlite, anhydrous gypsum, zeolite, quick lime, silica gel and the like. However,
The combined ratio of the deliquescent dehumidifying agent calcium chloride and the general-purpose dehumidifying agent should be appropriately selected in consideration of dehumidifying ability, dehumidifying rate, etc., and is not uniquely determined.

When used in combination with zeolite, activated carbon, etc., it can function not only as a desiccant but also as a deodorant.

It is known that a dehumidifying agent such as quicklime or silica gel is packaged by using at least a part of a thermoplastic resin sheet having holes. However, the thermoplastic resin sheet with pores in this case is complicated because a method of forming a large number of pores after forming the sheet is complicated, and inevitably the diameter of the pores becomes relatively large, and water permeability is increased. Which is also included in the microporous sheet used in the present invention. That is, when the conventional thermoplastic resin sheet having such a hole is used to package a deliquescent dehumidifying agent,
There is a risk of liquid leakage, and the effect of preventing liquid leakage in the present invention cannot be expected.

In the present invention, when calcium chloride is packaged in a composite material in which a reinforcing sheet is laminated on a microporous thermoplastic resin sheet, conventionally known packaging methods and packaging modes are adopted without limitation, but heat sealing (heat sealing) ) Method, and a packaging method of laminating with an adhesive is preferably used, and in many cases, a mode in which the entire packaging is packaged with a microporous thermoplastic resin sheet is adopted.

As described above, the desiccant of the present invention is used in combination with a complex composed of a sheet having a calcium chloride-specific property of a deliquescent dehumidifying agent, and exhibits a high dehumidifying ability, and deliquescent of calcium chloride. Since the liquid does not leak to the outside, it can be widely used as a general-purpose desiccant for food products in general households.

Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples.

Example 1 A blend of 30% by weight polypropylene, 69% by weight calcium carbonate (average particle size 2 microns), 1% by weight polyester plasticizer and a small amount of an antioxidant was uniaxially stretched at 80 ° C. and then 130%. Biaxially stretched at ℃ (300% in volumetric draw ratio) has a large number of communicating micropores with a pore size larger than 1μ, the average pore size of the communicating micropores is 2.1μ, and a micropore of about 0.2mm thickness A sex sheet was obtained. In addition, the average pore diameter represents the average value of the pore diameters obtained by the airflow method measuring method generally used when measuring the pore diameter of the smallest portion of each fine hole that is in communication with the sheet, that is, the pore diameter. Is. A polypropylene mesh having a porosity of 43% was laminated on this sheet to obtain a composite. Using this complex, 2 g of anhydrous calcium chloride was packed,
Heat sealing was performed to obtain a desiccant. Humidity of this desiccant 90
Table 1 shows the results of standing at 23 ° C. for a predetermined time in a desiccator (%).

Example 2 The procedure of Example 1 was repeated, except that talc, magnesium hydroxide, and Portland cement were used in place of calcium carbonate to obtain the polypropylene microporous sheet. The results are shown in Table 1. In addition,
Each of the obtained microporous sheets had a large number of communicating micropores having a pore size larger than 1 μ, and the average pore sizes of the communicating micropores were 1.6 μ, 1.7 μ, and 2.0 μ, respectively. It was

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that the perforated thermoplastic resin sheet, which had been packed with commercially available silica gel (manufactured by Fuji Davison Chemical Co., Ltd.), was packed with anhydrous calcium chloride without laminating the reinforcing sheet. The results are shown in Table 1.

Example 3 When the desiccant prepared in Example 1 in which the dehumidifying agent was anhydrous calcium chloride was left indoors for one month, the inside of the packaging material was completely liquefied, but no leakage of the contents was observed. It was

Comparative Example 2 When tested in the same manner as in Example 3 except that the packaging material used in Comparative Example 1 was used, the contents were completely liquefied and leakage was observed.

 ─────────────────────────────────────────────────── ───Continued from the front page (56) References Microfilm (JP, U) of the detailed description and drawings attached to the application of Japanese Patent Application No. 51-105752 (No. 53-23972). ) Microfilm (JP, U) Practical Application Sho 51-36848 (Practical Development) No. 51-177571 (Practical development Sho 53-93575) Specification attached to the application of Sho 52-129070) and the description attached to the application of Microfilm (JP, U) Actual application Sho 50-143060 (Actual development Sho 52-67060) Microfilm (JP, U) "Polyolefin Times", which is a photograph and the contents of drawings, May 17, 1980, published by Polyolefin Times Co., No. 857, 3rd page

Claims (1)

[Claims] 1. Calcium chloride as a deliquescent dehumidifying agent,
The calcium chloride deliquescent liquid does not leak and has breathability 1
A reinforcing sheet having a porosity of 30% or more is laminated on a microporous thermoplastic resin sheet having a large number of communicating micropores with a pore size larger than μ, and the average pore size of the communicating micropores being 1 μ or more and 20 μ or less. A desiccant characterized by being packaged using a composite material comprising