JPS6226813B2 - - 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 calcium chloride is impregnated into a continuous porous mineral carrier such as vermiculite or perlite has been proposed (Japanese Patent Application Laid-Open No. 144021/1983). 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 have previously conducted studies aimed at improving desiccants based on conventionally known deliquescent salts as described above, and found that (A) deliquescent salts and (B) vinyl acetate 50 to 99.8
It is a copolymer with a proportion of 50 to 0.2 mol% of unsaturated dicarboxylic acid, and of its vinyl acetate component.
They discovered the novel fact that a desiccant whose main ingredient is a mixture of a saponified copolymer and a saponified copolymer of which 70 mol% or more was saponified can achieve this purpose, and filed a patent application. In this invention, the copolymer which is component (B) has a certain degree of hygroscopic action even by itself, but its hygroscopic ability is much lower than that of component (A).
The mixture of component (B) and component (B) has a synergistic increase in moisture absorption capacity, and even if it absorbs a large amount of water under high humidity, it will not liquefy but will become gel-like, so it is extremely easy to handle, especially in containers. Moreover, such gel-like materials can be dried to their original state by drying them in the sun under normal temperature and humidity conditions, making it possible to reuse them. The economic effects are extremely large. However, upon further study by the present inventors, it became clear that the desiccant can be recycled and reused only about five times at most, and that it is necessary to further increase this number of times for practical use. However, the present inventors continued their intensive research and found that a desiccant made by further mixing (C) short fibrous material with the composition consisting of (A) and (B) above can be recycled and reused more than 10 times. We discovered that this is a highly practical product and completed the present invention. That is, the present invention provides (A) deliquescent salts and (B) vinyl acetate 50~
99.8 mol%, unsaturated dicarboxylic acid 50-0.2 mol%
A desiccant mainly composed of a saponified copolymer in which 70 mol% or more of the vinyl acetate component is saponified and (c) a mixture with short fibrous material. It is something. 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 its methyl, ethyl,
Examples include monoesters and diesters such as propyl ester. 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 short fibrous materials of component (C) include rayon staple cut products, natural fiber cut products such as wool and cotton,
Synthetic fiber cut products such as nylon, polyester, polyvinyl chloride, polyvinylidene chloride, polyolefin, vinylon, etc., other cut products of pulp powder, glass fiber, ceramic fiber, asbestos fiber, iron,
Any material such as copper or other metal fiber cut products, animal hair cut products, etc. can be used. The short fibers have a diameter of 0.1~0.002mm
A length of about 15 to 0.05 mm is preferably used. Component (A)/component (B) are mixed at a weight ratio of 9/1 to 1/9, preferably 7/3 to 1/9. The ratio of both components is
If the amount is more than 9/1, the deliquescent liquid may separate temporarily, and if it is less than 1/9, the water absorption capacity tends to be insufficient at low temperatures and high humidity. Therefore, depending on the purpose, select an appropriate amount from within the above range. The ratio should be chosen accordingly. Further, it is advantageous that the mixing ratio of component (C) is [(A) + (B)]/(C) in a weight ratio of 19/1 to 1/19, preferably 19/1 to 9/11. . A blend of less than 1/19 results in a decrease in hygroscopicity, while a blend of more than 19/1 reduces the number of repeated reuses of the desiccant, reducing its practicality. There are various methods for mixing component (A), component (B), and component (C), such as mixing powders together, and impregnating the powder of component (B) and (C) with an aqueous solution of component (A). Mix with The mixture can also be shaped into sheets, rods, fibers, etc.
It may be molded into various shapes such as spherical or dice-shaped. 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. Moreover, even if it is used ten times or more, there is almost no risk that the moisture absorption ability will decrease. 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) (C) Rayon staple cut product (diameter 0.1
~0.05mm, length 1~1.5mm) Components (A), (B), and (C) were mixed in various weights and placed in a shear dish and left in an atmosphere of 20℃ and 90% relative humidity for 30 hours. The moisture absorption rate (increase in water g/g desiccant x 100%) was measured from the weight increase during the drying period. Thereafter, the desiccant was dried in the sun to bring the moisture absorption rate to 1% or less, and the desiccant was allowed to absorb moisture under the same conditions as above, and the moisture absorption-drying reuse test was repeated 15 times. The results are shown in Table 1.

[Table] Example 2 A saponified monomethyl maleate-vinyl acetate copolymer powder with a vinyl acetate content of 90 mol%, a monomethyl maleate content of 10 mol%, and a saponification degree of the vinyl acetate component of 96% was used as component (B). Implementation 1 except
The same method was used. The results are shown in Table 2.

[Table] Examples 3 to 5 An experiment was conducted according to Example 1 using the component (C) as shown in Table 3. The results are shown in Table 3.

【table】

Claims (1)

[Scope of Claims] 1 A copolymer of (A) deliquescent salts and (B) vinyl acetate in a proportion of 50 to 99.8 mol% and unsaturated dicarboxylic acid in a proportion of 50 to 0.2 mol%, and 70% of the vinyl acetate component thereof. Saponified copolymer whose mole% or more is saponified and (C)
A desiccant whose main ingredient is a mixture with short fibrous materials. 2 (A) deliquescent salts/(B) saponified copolymer in a weight ratio of 9/1 to 1/9, and [(A) deliquescent salts + (B) saponified copolymer]/(C) Weight ratio of short fibrous material is 19/1 to 1/19
The desiccant according to claim 1, characterized in that: