JPS60235624A - Humidistat - Google Patents

Abstract

PURPOSE:To increase the moisture absorbing capacity of a humidistat and to make it suitable for several purposes by allowing a water absorptive polymer to contact with a hygroscopic material and covering both with a moisture permeable material or contg. both in the vessel made of a moisture permeable material. CONSTITUTION:A polymer material which forms hydrous gel, such as a water absorbing agent derived from polyacrylic acid, is coated uniformly on a sheet of paper. Another sheet of paper coated with a hygroscopic material such as propylene glycol, glycerol, is heaped thereon. Further, the heaped sheets are held between two sheets of a moisture permeable material such as nonwoven fabric, and the periphery is heat-sealed to obtain thus a moisture conditioning sheet. The humidistat prepd. by this process absorbs moisture when the ambient humidity is higher than the equilibrium humidity but liberates moisture when the ambient moisture is lower than the equilibrium humidity, and keeps the ambient humidity at a constant value. The humidistat is useful for prevention of concrete wall from dew formation or for humidity control in a warehouse for foods.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a humidity control tool. For more details,
The present invention relates to a humidity control tool in which a water-absorbing polymer and a humectant are kept in contact with each other and covered with a moisture-permeable material or housed in a moisture-permeable container.

Water-absorbing polymers have recently attracted a lot of attention because of their high water-absorbing properties, and have been widely used.

However, although water-absorbing polymers such as these have high water-absorbing properties when they come into contact with water or water-containing substances, when left in the atmosphere,
It has the property of exhibiting almost no deprivation or hygroscopicity. Although this property is convenient for handling, it is inconvenient that it cannot be used as a moisture absorbent as it is.

Therefore, these water-absorbing polymers use a method in which a hygroscopic substance is interposed, the water is once absorbed by the water-absorbing polymer, and then the water is transferred to the water-absorbing polymer through this intervening substance. As a result, it has become clear that it exhibits a greater water absorption capacity than those commonly used as moisture absorbents.

Therefore, the humidity control device of the present invention is used by coating a water-absorbing polymer and a moisture-absorbing substance in contact with a moisture-permeable material and sealing the same with a moisture-permeable material, or by storing it in a container made of a moisture-permeable material. .

With a material configured in this way, when the humidity in the space is higher than the equilibrium state, the moisture is absorbed by the moisture-absorbing material through the moisture-permeable material, and then transferred to the water-absorbing polymer to achieve an equilibrium state. It absorbs moisture up to the point where the humidity in the space is lower than the equilibrium state.

This device serves to release moisture and maintain a constant humidity in the space until an equilibrium condition is achieved.

Here, the term "equilibrium state" refers to a state in which moisture equilibrium between two spaces, a hygroscopic substance, and a water-absorbing polymer has been achieved.

Therefore, the humidity control tool of the present invention having the above-mentioned structure can be used for various purposes for controlling humidity, such as for indoor use to prevent dew condensation or over-drying, as well as for fresh food in airtight containers. For example, it can be formed into a sheet to prevent condensation on a concrete wall, or it can be placed in a container and used to control the humidity inside the food storage.

As the polymeric substance forming the hydrogel used in the present invention, any substance that is normally used as a dehydrating agent can be used. , which are commercially used in the fields of soil conditioners, etc., and include polymerizable units that are water-soluble in polysaccharides such as starch, cellulose, etc., or that become water-soluble by hydrolysis, such as acrylic acid. , methacrylic acid, acrylate, methacrylate, acrylic ester, methacrylic ugly ester,
Wood-loving products obtained by graft polymerizing acrylic acid amide, methacrylic amide, acrylonitrile, methacrylonitrile, maleic acid, sulfonated styrene, polyvinylpyridine, etc., or oligomers or cooligomers thereof, and hydrolyzing as necessary. Polymers three-dimensionally polymerized using a crosslinking agent, polyethylene oxide, polypropylene oxide, polyvinylpyrrolidone, sulfonated polystyrene, polyvinylpyridine, polyacrylate, polyacrylic acid amide, polymethacrylate, polymethacrylic It is known that wood-philic polymers such as acid amides are three-dimensionally polymerized using a crosslinking agent. As a commercially available product, Showa Denko Chi's PX
-402A, Sunwet IM-3 manufactured by Sanyo Chemical Industries ■
00, Aqua Keep 10SH manufactured by Seitetsu Kagaku Kogyo ■, etc.

Examples of the crosslinking agent include di- or tri(meth)acrylic acid esters of polyols such as ethylene glycol, trimethylolpropane, glycerin, polyoxyethylene glycol, and polyoxypropylene glycol; Unsaturated polyesters obtained by reacting unsaturated acids such as acids; bisacrylamides such as N,N-methylene-bisacrylamide; Toly(meth)acrylic acid esters; di(meth)acrylic acid carbamyl esters obtained by reacting a polyisocyanate such as tolylene diinocyanate, hexamethylene diisocyanate, etc. with hydroxyethyl (meth)acrylate; allylated Starch: Examples include allylated cellulose, but in some cases, methylolated (meth)acrylamide, glyoxal, ditalic acid,
Difunctional compounds that can be crosslinked under certain reaction conditions such as 7 divic acid, ethylene glycol, etc. or polyvalent metal salts such as calcium oxide, zinc diacetate, etc. may also be used.

Hygroscopic substances used in the present invention include polyhydric alcohols such as ethylene glycol, polyethylene glycol, diethylene glycol monoethyl ether, propylene glycol, 1,3-butylene gelicol, glycerin, and polyglycerin, and sodium carboxymethyl cellulose, xylitol, and nrubitol. Aqueous solutions of hygroscopic polymeric substances such as maltitol can be used alone or in combination.

The rate of moisture absorption can be increased by inserting paper, pulp, cloth, etc. into the water absorbent and moisture absorbent system.

The moisture-permeable materials used in the present invention include sufficiently fine-grained nonwoven fabrics made of thermoplastic materials, thermoplastic films made water-impermeable with communicating holes formed by electron beam irradiation, etc. There are various types of plastic films, such as those that are foamed to have fine continuous pores during film production, and those that have fine continuous pores formed by adding an inorganic substance or a high melting point nucleating agent and then stretching. Currently, it is widely used as a dry battery separator and special mouthpiece.

In the present invention, we chose a heat-sealable water-permeable membrane as the material for the moisture-permeable membrane because in the case of a water-absorbing polymer, when it becomes a water-containing gel, its particle size is several ten times or more than the original particle size. This is because pores on the order of millimicrons are not necessary, and the water permeability improves as the pore size increases. Water-permeable membranes are difficult to adhere effectively and do not have sufficient water resistance.

This is because when the water-permeable film comes into contact with water, water seeps into the adhesive surface.In the present invention, since the base material is continuous and bonded by heat sealing, the water resistance strength is significantly improved. Moreover, heat sealing has the advantage that it can be processed in a shorter time than adhesive bonding, since it will stick if the temperature is below the melting point.

In addition, there are many processing machines that use heat fusion on the market compared to adhesive methods, and there is a great advantage that existing processing machines can be used.

As a moisture-permeable membrane, a non-woven fabric with a fairly coarse mesh can be considered, but it would be inconvenient if the water-absorbing polymer itself permeates through the coarse mesh when it is dry or not absorbing water.
Naturally, there is a limit to its roughness. In addition, it is preferable that the nonwoven fabric's bulk and thickness are not too large for convenience of heat sealing.

In the present invention, even if pulp or inorganic filler that does not permeate the water-permeable film used is added together with the hydrogel-forming material, the principle of operation and function will be exactly the same.

The amount of water-absorbing polymeric substance retained in the moisture permeable material is determined by the balance between the absorption capacity of the substance and the absorption and retention capacity required of the moisture control sheet. In the end, the most appropriate amount should be determined depending on the application and the conditions of use in that application.

The present invention will be explained below with reference to Examples.

Example 1 3.2 g of a polyacrylic acid-based water absorbing agent (PX-402A, manufactured by Showa Denko Co., Ltd.) was evenly sprinkled on a 20 cm square paper (trade name: Kleenex Towel, manufactured by Jujo Kimberly Co., Ltd.), and propylene glycol was sprinkled on top of it. 100cm'9 Ig-coated paper (product name: Kleenex Towel, manufactured by Jujo Kimberly Co., Ltd.) of 20cm square is layered, and the top and bottom are further sandwiched with non-woven* (product name: Nishintex, manufactured by Mitsui Petrochemical Industries, Ltd.). The four circumferences were heat-sealed to obtain a humidity control sheet.

Place this sheet in a desiccator containing 10g of water,
It was left at room temperature for 24 hours. Although all of the water in the desiccator evaporated and did not remain, the humidity in the desiccator showed a constant value of 80% relative humidity.

Example 2 5 g of water was used under the same conditions as in Example 1. The relative humidity in the desiccator was constant at 65%.

Example 3 2.4 g of a polyacrylic acid-based water absorbing agent (PX-402A, manufactured by Showa Denko Co., Ltd.) was evenly sprinkled on a 20 cm square paper (product name: Kleenex Towel, manufactured by Jujo Kimberly Co., Ltd.), and 10 g of glycerin was sprinkled on top of it. was uniformly impregnated, the upper and lower sides were sandwiched between nonwoven fabrics (trade name: Nishintex, manufactured by Mitsui Petrochemical Industries, Ltd.), and the four circumferences were heat-sealed to obtain a humidity control sheet.

This sheet was placed in a desiccator containing a saturated aqueous ammonium chloride solution and left at room temperature for 24 hours.

The relative humidity in the desicage was maintained at 50-60% and the weight of the sheet increased by 6.7 grams.

Applicant: Showa Denko Co., Ltd.

Claims (1)

[Claims] A humidity control tool comprising a water-absorbing polymer and a wetting agent brought into contact with each other, covered with a moisture-permeable material, or housed in a moisture-permeable container.