JPS6331522A - Moisture absorbent - Google Patents

Abstract

PURPOSE:To obtain a reusable moisture absorbent having excellent hydroscopic capacity and generating no exudation of a liquid even after the absorption of moisture, by compounding a water-insoluble water absorbable resin comprising a specific composition of an acidic vinyl monomer and a basic vinyl monomer with deliquescent salts. CONSTITUTION:An acidic vinyl monomer (A) such as an acrylic acid and a basic vinyl monomer (B) such as dimethylaminoethyl acrylate are set to a compositional ratio of A:B=20:80-80:20 and a water-soluble cross-linking agent is added to polymerize both monomers to obtain a water-insoluble water absorbable resin. This water absorbable resin is mechanically mixed with deliquescent salts such as ground calcium chloride to obtain a moisture absorbent.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a moisture absorbent that has excellent moisture absorption ability, does not seep out even when moisture is absorbed, and can efficiently remove moisture in a reusable space. This is related to drugs.

[Conventional technology and its problems]

Conventionally, when food, clothing, and metal machinery are left in a high-humidity atmosphere, harmful phenomena such as the growth of mold, deterioration, rot, and rust occur, so moisture absorbers have been used as a method to prevent this.

Moisture absorbents that retain their shape even after moisture absorption and can be used repeatedly include silica gel, activated alumina, activated carbon,
Inorganic porous materials such as synthetic zeolites have mainly been used. However, these hygroscopic properties absorb moisture by adsorbing into the pores of the inorganic substance, and therefore have the disadvantage that the hygroscopic capacity per unit weight itself is small and the amount used is large.

On the other hand, deliquescent salts such as calcium chloride, magnesium chloride, and phosphorus pentoxide are known as substances with strong hygroscopicity and large hygroscopic capacity, but these salts liquefy when they absorb moisture, and other It has the disadvantage of contaminating the In order to improve this drawback, it has been proposed to mix deliquescent salts with a water-absorbing resin to gel and solidify the deliquescent liquid (see Japanese Patent Laid-Open No. 107042/1982). The water-absorbent resins used are carboxylates such as polyacrylic acid soda and polyoxyethylenes such as polyvinyl alcohol, but their ability to absorb and retain deliquescent liquid to a high degree is not sufficient. Seepage cannot be completely prevented. Furthermore, carboxylates generally form strong bonds with divalent or higher valent metal salts,
It becomes impossible to reuse.

[Means for solving problems]

The present inventors have overcome the drawbacks of conventional moisture absorbents by combining a super absorbent resin that has excellent absorption capacity for any salt or aqueous solution of any salt concentration with an inorganic salt that has deliquescent properties. The present inventors have discovered a reusable moisture absorbent that has excellent moisture absorption ability, does not seep out even after moisture absorption, and has completed the present invention.

That is, the present invention comprises (a) a deliquescent inorganic salt, and (b) an acidic vinyl monomer (component A) and a basic vinyl monomer (component B) in a composition ratio of A:B=20:80 to 8
The present invention provides a moisture absorbent containing a water-insoluble water-absorbing resin having a molar ratio of 0:20.

The super absorbent resin used in the present invention is a crosslinked copolymer consisting of an acidic vinyl monomer and a basic vinyl monomer,
The essential condition is that it is water insoluble.

The acidic vinyl monomer according to the present invention is a compound having an acidic group such as a carboxyl group or a sulfonic acid group and a polymerizable vinyl group in one molecule, such as acrylic acid, methacrylic acid, itacon acid, maleic anhydride, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid,
Examples include methallylsulfonic acid.

The basic vinyl monomer according to the present invention is a compound having a basic group such as a primary amino group, a secondary amino group, or a tertiary amino group and a polymerizable vinyl group in one molecule. , for example, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate dimethylaminopropylmethacrylamide, dimethylaminopropylacrylamide, 2-vinylpyridine, 4-vinylpyridine, dimethylallylamine, diallylmethylamine, etc. I can do it.

In the present invention, the types of monomers are not limited, and a combination of three or more of the above monomers may be used. Acidic vinyl monomer (A) and basic vinyl monomer (
The molar ratio of B) is A:B=20:80 to 80:20
However, considering the physical properties after moisture absorption, A
: B = 3o is preferably in the range of 0 to 70 to 30. Furthermore, resins copolymerized with nonionic water-soluble vinyl monomers such as 2-hydroxyethyl (meth)acrylate and acrylamide can also be used in the method of the present invention to the extent that the performance of the resin is not deteriorated.

When polymerizing these monomers for the purpose of imparting water insolubility, it is necessary to add a water-soluble crosslinking agent. Any water-soluble crosslinking agent may be used as long as it is a water-soluble vinyl compound or a compound having two or more functional groups that can react with an acidic group or a basic group. Examples of water-soluble vinyl compounds include N,N-methylenebisacrylamide, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and functional groups that can react with acidic or basic groups. Examples of compounds having two or more include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycerin triglycidyl ether, herooepoxy compounds such as epichlorohydrin and α-methylchlorohydrin, geltal aldehyde, Examples include polyaldehydes such as glyoxal.

The amount of the crosslinking agent added varies depending on the type of crosslinking agent and the type of polymer, but the appropriate range is usually 0.01 to 5.0% by weight based on the polymer. If the amount of the crosslinking agent added is less than 0.01% by weight, the effect of the addition will not be sufficiently expressed, and when moisture is absorbed, the gel will be in a semi-dissolved state. On the other hand, if the amount is more than 5.0% by weight, the crosslinking density will increase, leading to a decrease in moisture absorption, which is not the intention of the present invention.

The concentration of the monomer aqueous solution containing acidic vinyl monomer, basic vinyl monomer, and nonionic water-soluble vinyl monomer can be varied within a wide range, and is generally 30 to 70%.
Weight%. This upper limit depends, inter alia, on the solubility during the mixing of the two vehicles, but the lower limit will generally not be lower than the above-mentioned value for economic reasons. As a radical polymerization initiator,
Water-soluble initiators such as persulfates are used. The amount of radical polymerization initiator used varies depending on the type of monomer, but -
It is preferable that i be about 0.01 to 5% by weight based on the total monomers.

The polymerization method is not particularly limited, but suspension polymerization is preferred. Suspension polymerization has a large heat removal effect, so it is easy to obtain high-molecular-weight resin, and it is also possible to obtain bead-shaped resin. It is difficult to generate fine powder, so there is no need to take dust countermeasures, and it is possible to achieve uniformity between particles. This method is preferable in terms of the form of the product as a moisture absorbent, since it is possible to obtain a resin with good performance.

The inorganic salts used in the present invention may be any inorganic salts as long as they have deliquescent properties. As a deliquescent inorganic salt,
Examples include calcium chloride, lithium chloride, magnesium chloride, manganese chloride, and phosphorus pentoxide. These inorganic salts are selected depending on the humidity to be absorbed, and it is also possible to use a mixture of two or more kinds. Among them, calcium chloride and/or lithium chloride are preferred.

The mixing ratio of the deliquescent inorganic salt and the water-absorbing resin can be freely selected, but from the viewpoint of preventing the liquid from seeping out after moisture absorption and from the viewpoint of economic efficiency, It is desirable to use 5 to 500 parts by weight of the resin. If it is less than 5 parts by weight, shape retention is observed, but it is not possible to completely prevent the liquid from seeping out after absorbing moisture, and if it exceeds 500 parts by weight, it is unfavorable from the economic point of view.

The water-absorbent resin and the deliquescent inorganic salt can be easily dispersed by mechanical mixing or by adding water and drying the mixture after mixing, but mixing using a water-soluble binder is also recommended. is also preferable.

The moisture absorption rate depends on the total surface area of the moisture absorbent, and known mixing methods such as pulverization and granulation can be preferably used.

The moisture absorbent of the present invention can be used in any form as it does not seep out even after absorbing moisture, such as spreading it on pulp and wrapping it in non-woven fabric, or sandwiching it in paper to form a sheet. Examples include shapes such as a shape and a tablet.

The composition of this invention can be effectively used in living rooms, closets, shoe cabinets, inside shoes, and other places where it is desired to dehumidify. In addition, silica gel, etc. have traditionally been used to package products that are sold in airtight containers because they do not want to absorb moisture, such as glue, rice crackers, biscuits, other foods, other industrial products, and even equipment that does not want to rust. It can be used on previously used items for even more powerful effects.

C Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Water-absorbent resin-1 47.5 g of dimethylaminoethyl acrylate and 30 g of acrylic acid were dissolved in 140 g of ion-exchanged water, and polyoxyethylene diacrylate (product name: A-600,
0.10 g of Shin Nakamura Chemical Co., Ltd.) was added and uniformly dissolved. After that, v-50 (manufactured by Wako Pure Chemical Industries, Ltd.: 2) was used as a radical polymerization initiator.
, 2'-azobis(2-amidinopropane) dihydrochloride)
0.05 g was added, uniformly dissolved, and polymerized at 70° C. under N2 atmosphere. After polymerization, the water-containing resin was dried under reduced pressure and pulverized to obtain a polymer that passed through 42 meshes.

Water Absorbent Resin-2 Into a 500 ml four day round bottom flask equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube were charged 230 ml of cyclohexane and 1.0 g of ethyl cellulose N-200 (manufactured by Vercules) and heated to 75°C. The temperature rose.

Separately, in an Erlenmeyer flask, 12.0 g of acrylic acid and 26.2 g of dimethylanominityl methacrylate were dissolved in 70 g of distilled water, 5 g of 35% hydrochloric acid was added, and further 0.05 g of N,N-methylenebisacrylamide was added. 0.02 g of ammonium persulfate was added and dissolved as an initiator, and this monomer aqueous solution was dropwise polymerized in the above four-layer flask under a nitrogen atmosphere for 1.5 hours.
The polymerization was completed by standing at 5°C for 0.5 hours. After cooling, cyclohexane was removed, and the polymer was dried at 80 to 100°C under reduced pressure to obtain Resin-2.

Moisture absorbent 1-3 Calcium chloride pulverization @! + (200 mesh passed product)
100g and hygroscopic resin-1 10g, 20g, 50
g of the moisture absorbent of the present invention 1.2.
I got 3.

Comparative Moisture Absorbent 1.2 Calcium chloride and water absorbent resin-1 used in Moisture Absorbents 1 to 3 were each used alone to prepare Comparative Moisture Absorbent 1.2.

Moisture absorbent 4.5 Pulverized lithium chloride (passed through 200 mesh) 100
Log and 50 g of Water Absorbent Resin-2 and 50 g of IQ g of water were added and mechanically mixed. Thereafter, it was dried under reduced pressure to obtain moisture absorbent 4.5 of the present invention.

Comparative moisture absorbent 3: Pulverized lithium chloride (passed through 200 meshes) 100
g and crosslinked sodium polyacrylate (product name: Poise 5A
-20, manufactured by Kao) were mechanically mixed to obtain Comparative Moisture Absorbent 3.

50 g of the obtained hygroscopic agent was left in a thermostatic chamber (temperature 30" C1 humidity 95%), and after absorbing moisture, the weight was measured and the morphology was observed. The results are shown in Table 1. Furthermore, the hygroscopic agent 2.3 50 g of the moisture absorbent that had absorbed moisture with Comparative moisture absorbent 3 was dried under reduced pressure and lightly pulverized, and the moisture absorption evaluation was performed again under the same conditions.The results are shown in Table 2.

Claims (1)

[Scope of Claims] 1 (a) a deliquescent inorganic salt, and (b) an acidic vinyl monomer (component A) and a basic vinyl monomer (component B) in a composition ratio of A:B=20: 80-80:
20 (molar ratio) of a water-insoluble water-absorbing resin. 2 The mixing ratio of component (a) and component (b) is (a
):(b)=100:5-500, the moisture absorbent according to claim 1. 3 Acidic vinyl monomer is acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, 2-acrylamide-2-
One or more selected from the group consisting of methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, and methacrylsulfonic acid, and the basic vinyl monomer is dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. , dimethylaminopropyl (
The moisture absorbent according to claim 1, which is one or more selected from the group consisting of meth)acrylamide and vinylpyridine. 4. The moisture absorbent according to claim 1, wherein the deliquescent inorganic salt is calcium chloride and/or lithium chloride.