JPH0227006B2 - - Google Patents

Description

[Detailed description of the invention]

Deliquescent salts such as calcium chloride and magnesium chloride are conventionally known as desiccants that absorb moisture in the air, but since these deliquesce as a result of absorbing moisture, they must be stored in some kind of container.
There is a problem that if the container is damaged or falls over, the deliquescent liquid will stain the surrounding area, and furthermore, once the container has been deliquesced, it cannot be dried to the point where it can be reused by simply drying it in the sun, so it must be thrown away. Ta. As an improvement to such desiccant agents, a desiccant in which a continuous porous mineral carrier such as vermiculite or pearlite is impregnated with calcium chloride has been proposed (Japanese Patent Application Laid-Open No. 144021/1983), and according to this, Although it has been described that it has the advantage of absorbing a large amount of moisture without reducing the moisture absorption rate, it is difficult to use it in a variety of product formats, and it cannot satisfy the recent demand for commercialization in various formats. Further improvements are required in these areas. The present inventors conducted studies aimed at improving desiccants based on conventionally known deliquescent salts as described above, and found that (A) specific deliquescent salts and (B) vinyl acetate 50
~99.8 mol% copolymer, unsaturated dicarboxylic acid 50~0.2 mol%, and the main ingredient is a mixture with a saponified copolymer in which 70 mol% or more of the vinyl acetate component is saponified. The inventors have discovered the novel fact that a desiccant achieves this purpose, and have completed the present invention. Although the copolymer that is the component (B) of the present invention has a certain degree of hygroscopicity on its own, its hygroscopicity is much lower than that of the (A) component.
The mixture with component (B) has a synergistic increase in moisture absorption ability, and even if it absorbs a large amount of water under high humidity, it will not liquefy, only forming a gel, so it is extremely easy to handle, especially when stored in a container. Furthermore, such a gel-like material can be dried to its original state by drying it in the sun under normal temperature and humidity conditions, making it possible to reuse it and making it economical. The effects are extremely large. Deliquescent salts as component (A) in the present invention include not only calcium chloride alone, but also various salts containing crystal water such as its dihydrate, tetrahydrate, and hexahydrate salts, magnesium chloride, lithium chloride, etc. Among them, calcium chloride is more practical in terms of both performance and cost. As component (B), vinyl acetate is 50 to 99.8 mol%,
It is necessary that the unsaturated dicarboxylic acid is copolymerized in a proportion of 50 to 0.2 mol%, and that 70 mol% or more of the vinyl acetate component is saponified.
Outside this range, there is a problem in that the water absorption capacity decreases. Among these conditions, more preferably vinyl acetate 80 to 99.8 mol%, unsaturated dicarboxylic acid 20 to 99.8 mol%
A saponified copolymer with a saponification degree of 0.2 mol % and a saponification degree of 70 mol % or more has even better performance. Examples of unsaturated dicarboxylic acids include (anhydrous) maleic acid, fumaric acid, itaconic acid, glutaconic acid, allylmalonic acid, and their monoesters and diesters such as methyl, ethyl, and propyl esters. Further, other copolymerizable monomers may be copolymerized as long as the amount is small. Such a saponified copolymer is produced by carrying out ordinary solution polymerization of vinyl acetate and unsaturated dicarboxylic acid to form a copolymer in the above-mentioned ratio, and then subjecting the resulting copolymer to an alkali catalyst such as caustic soda or sodium methylate. It is manufactured by saponifying to a predetermined ratio using Such a saponified copolymer can be imparted with even better performance by further heat treatment. Generally temperature 110~200℃ under air or inert gas atmosphere
Heat-process for 1 to 360 minutes. The obtained resin is a powder, but those with an appropriate particle size are selected and ground to an appropriate particle size for practical use. The weight ratio of component (A)/component (B) is 7/3 or less, preferably 6/4 to 1/9. If the ratio of both components is more than 7/3, the deliquescent liquid may temporarily separate, and if it is less than 1/9, the water absorption capacity tends to be insufficient at low temperatures and high humidity. An appropriate ratio should be selected from the above range according to the above range. Components (A) and (B) can be mixed together in various ways, such as by mixing powders together, or by impregnating the powder of component (B) with an aqueous solution of component (A). Further, the mixture may be molded into various shapes such as a sheet, a rod, a fiber, a sphere, and a dice. The desiccant of the present invention can be used in high-humidity environments such as household storerooms, closets, and chests of drawers, as well as in packages for precision instruments, electronic parts, etc., by utilizing its high hygroscopic power and high hygroscopic capacity. After use, you can restore the desiccant to its original dry state even in winter by exposing it to direct sunlight outside or placing it in a ventilated atmosphere at 25°C or higher, making it possible to recycle it. Become. Next, the present invention will be explained by giving an example. Example 1 Desiccant (A) Powder of calcium chloride dihydrate (B) Monomethyl maleate-vinyl acetate with a vinyl acetate content of 96.1 mol%, a monomethyl maleate content of 3.9 mol%, and a degree of saponification of the vinyl acetate component of 98.1 mol%. Saponified polymer powder (295μ or less) Mix components (A) and (B) in various weight ratios, put 10g in a shear dish, and (a) leave in an atmosphere of 20°C and 90% relative humidity for 8 hours. b) Leave it for 24 hours and determine the moisture absorption rate (increase in water g / desiccant g x 100%) from the weight increase during that time.
was measured. The results are shown in Table 1.

[Table] Incidentally, when a similar experiment was conducted using silica gel A as a control example, the moisture absorption rate after 8 hours was 27%, and the moisture absorption rate after 24 hours was 47%. Practical Example 2 Practical example except that a monomethyl maleate-vinyl acetate copolymer saponified powder containing 90 mol% vinyl acetate, 10 mol% monomethyl maleate, and 96 mol% saponified vinyl acetate component was used as component (B). The same method as 1 was used. The results are shown in Table 2.

【table】

Claims (1)

[Claims] 1 (A) Calcium chloride, calcium chloride hydrated salt,
A copolymer of deliquescent salts selected from magnesium chloride and lithium chloride and (B) vinyl acetate in a ratio of 50 to 99.8 mol% and unsaturated dicarboxylic acid in a proportion of 50 to 0.2 mol%, and 70 mol% of the vinyl acetate component. A desiccant whose main ingredient is a mixture of the saponified copolymer and the saponified product. 2. The desiccant according to claim 1, wherein (A) deliquescent salts/(B) saponified copolymer are mixed in a weight ratio of 7/3 or less.