JPH0716577B2 - Gelling agent for dehumidifying agents - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a dehumidifying agent containing a deliquescent hygroscopic substance such as calcium chloride as a main ingredient, for the purpose of preventing deliquescent liquid from flowing out of a container or a package. The present invention relates to a gelling agent suitable for gelling a liquid.

[Prior Art] Conventional deliquescent hygroscopic agents such as calcium chloride are used to remove moisture from closets, chests, shoe boxes, etc.
Most of these hygroscopic agents show deliquescent and are solid at the initial stage, but become liquid as they absorb moisture. In order to prevent the deliquescent liquid from flowing out, a container having a tank at the bottom, or a package in which a mixture of a dehumidifying agent and a gelling agent is packaged with a moisture-permeable waterproof film is used.

However, in the dehumidifying agent of the type that stores the deliquescent liquid in the lower tank, if the liquid is accidentally tumbled during use, the stored liquid may flow out of the container and stain the futon, clothes, and the like. In order to prevent such outflow, a thickener is put in the storage tank of the deliquescent liquid in advance, and the deliquescent liquid dropped into the storage tank causes the thickening agent to swell or dissolve, thereby gelating the stored liquid and causing fluidity. It has been attempted to prevent the deliquescent liquid from flowing out even if the liquid falls.

Sodium polyacrylate, polyvinyl alcohol, polyacrylamide, methyl cellulose, guar gum, pregelatinized starch and the like are used as a thickener for the deliquescent liquid.

[Problems to be Solved by the Invention] The above polymer exhibits a considerably high viscosity when uniformly dispersed in water or an aqueous solution of an inorganic salt such as deliquescent liquid,
Although it has a thickening effect, when these thickeners are placed in the storage tank, so-called "mamako" occurs when the deliquescent liquid and the thickener come into contact with each other, and the thickened part is thickened. The agent loses almost no liquid permeability and does not act as a gelling agent. Therefore, the function of the thickener almost does not work, which makes it difficult to reliably prevent the deliquescent liquid from flowing out. Also, super absorbent polymers seem to meet this purpose, but although they show water absorption capacity several hundred times for water, their water absorption capacity does not decrease for salts such as calcium chloride. In particular, it shows an extremely high ability of about 2 to 4 times and is not suitable as a gelling agent of this kind. The same phenomenon occurs in the case where calcium chloride and a gelling agent are sealed with a moisture-permeable waterproofing film, and although the gelation is partially present, the liquid portion increases as a whole or the viscosity increases slightly. While it is still partially hardened, the saw will float and it will be meaningless at all from the purpose of preventing the outflow of deliquescent liquid.
To avoid this phenomenon, it is necessary to add or mix a larger amount of gelling agent than necessary, but it cannot be said that this problem is essentially improved. Further, when a large amount of the gelling agent is mixed, a hygroscopic agent such as calcium chloride is encased in the gelling agent while it is partially generated, and the contact with the outside air is cut off to hinder the hygroscopic action itself.

[Means for Solving the Problems] In order to prevent the deliquescent liquid of the dehumidifying agent from flowing out of the container, a gelatinized cross-linked pregelatinized starch having a water absorption ratio of 20 times or less is used. It has been found that, by using the gelling agent, when the surface of the gelling agent is wetted by the deliquescent liquid, the gelling agent quickly penetrates into the starch without forming a sardine, and the whole becomes a gel. Further, even if the deliquescent liquid further falls from the gel-like substance, the liquid is absorbed almost uniformly throughout the gel and is not partially liquid.

It was also found that by setting the water absorption ratio to 20 times or less, the hardness of the gel after absorbing moisture becomes strong and a gel showing almost no fluidity is formed. That is, when comparing the gels of the dehumidifying agents that absorbed the same amount of moisture, the pregelatinized starch that has not been cross-linked shows a high viscosity but has a considerable fluidity, and gradually begins to flow when the container is tilted. On the other hand, in the case of a crosslinkable pregelatinized starch having a water absorption capacity of 20 times or less, a hard gel is formed and the gelled product does not move at all even when the container is tilted. For example, when a mixture of 15 parts by weight of calcium chloride and 5 parts by weight of a gelling agent absorbs 30 parts by weight of moisture, when non-crosslinked pregelatinized starch is a gelling agent, it shows a considerably high viscosity. , Tilt the container and it will flow slowly. However, when the pregelatinized starch whose water absorption ratio is 20 times or less is the gelling agent, the gel does not move at all even when tilted or turned upside down. By setting the water absorption ratio to 20 times or less as described above, the strength of the gel gelled by the deliquescent liquid becomes very high, and even if the dehumidifying agent container is accidentally overturned, there is no fear of soiling clothes, futons and the like.

The gelling agent of the present invention may be used in the case of gelatinizing starch, for example, in a drum dryer. When the gelatinizing agent is gelatinized, the granular and crosslinked starch may be slurried into a drum and dried, or the untreated starch slurry may be drum-dried. The drum may be dried by adding a reactive substance capable of performing the above crosslinking reaction. It may also be gelatinized by an extruder. In this case, a cross-linking reaction product may be previously mixed and added, or a cross-linked granular starch may be used.

There is no limitation on the type of starch as a raw material, and common raw starch such as corn starch, potato starch, tapioca starch, rice starch, wheat starch, sweet potato starch, sago starch and the like can be mentioned. Also, various modified starches may be used. For example,
Examples thereof include etherified starch, esterified starch, grafted starch, crosslinked starch, and oxidized starch. Also, a mixture of a plurality of these starches may be used. When the crosslinking reaction is carried out in the form of particles or on a drum, in an extruder, it may be carried out by a method generally known to those skilled in the art, for example, epichlorohydrin and an alkaline catalyst, phosphates and an alkaline catalyst, aldehydes, A polyepoxy compound or the like may be used. It is known to use cross-linking agents which react with two or more hydroxyl groups. The water absorption of the pregelatinized starch thus obtained needs to be adjusted to 20 times or less of its own weight. If the water absorption exceeds 20 times, the spinnability peculiar to starch remains, and if the surface is wet with a liquid such as deliquescent liquid, lumps will be generated and the liquid will not penetrate inside.

EXAMPLES Next, the present invention will be shown by examples.

Example 1 500 kg of potato starch is poured into 600 water to prepare a slurry.
Into this, 10 kg of sodium trimetaphosphate and 5 kg of sodium carbonate are added and sufficiently stirred. This slurry is fed onto a drum dryer having a surface temperature of 150 ° C. to obtain crosslinked pregelatinized starch.

Example 2 10 kg of calcium hydroxide is dispersed in 1200 water and 1000 kg of tapioca is added to this. The internal temperature is adjusted to 40 ° C, 2 kg of epichlorohydrin is added, and the reaction is carried out for 8 hours. After completion of the reaction, the mixture is neutralized to pH 5.0 with hydrochloric acid, and this slurry is supplied onto a drum dryer to obtain crosslinked pregelatinized starch.

Example 3 13 kg of sodium trimetaphosphate and 2.5 kg of sodium carbonate were thoroughly mixed as powder with 500 kg of corn starch. 2 this mixture
Pregelatinize with a shaft extruder to obtain crosslinked pregelatinized starch.

Comparative Example 1 A general pregelatinized starch was obtained without using sodium trimetaphosphate and sodium carbonate in Example 1.

Comparative Example 2 Example 1 using 2 kg of sodium trimetaphosphate of Example 1
A cross-linked pregelatinized starch was obtained in the same manner as in.

Example 4 Water absorption capacity was measured as follows.

A 5.0 g sample of the crosslinked pregelatinized starch obtained in Examples 1 to 3 and Comparative Examples 1 and 2 was taken and dispersed in 500 ml of deionized water.
Stir for 0 minutes. After 30 minutes, this dispersion was poured onto a 200-mesh sieve, and the water absorption capacity of the sample was determined from the amount of water flowing down.

Example 5 A container having a deliquescent liquid storage tank at the bottom and calcium chloride 200 g at the upper part of a container having fine holes in the lower and upper detent plates through which the deliquescent liquid can fall, and Examples 1 to 3 and Comparative Example 1 at the lower storage tank. Each 50 g of the sample prepared in ~ 2 was put and left in a thermo-hygrostat at 30 ° C and 80RH% for 2 weeks to observe the gel state.

Example 6 10 g of the samples prepared in Examples 1 to 3 and Comparative Examples 1 and 2 and 30 g of calcium chloride were mixed, sealed with a moisture-permeable waterproof film, and left in a constant temperature and humidity chamber at 30 ° C. and 80 RH% for 20 days. Then, the state of the gel was observed.

[Effects of the Invention] As is clear from Example 5, in the case of the type in which the deliquescent solution falls, the gelling agent of the present invention does not form any residue and becomes a hard gel with no uniform fluidity. The same can be said in Example 6, but the reason why the moisture absorption amount is higher is that the moisture absorption capacity of calcium chloride can be fully exerted because there is no encapsulation of calcium chloride caused by the leaving. As described above, by using the gelling agent of the present invention which forms a uniform and strong gel without impairing the hygroscopicity of calcium chloride or the like, the dehumidifying agent is accidentally tumbled or the bag is pinhole. It is possible to provide a dehumidifying agent that does not cause stains on clothes, futons, etc. even if such small holes are formed.

Claims (1)

[Claims] 1. A gelling agent for a dehumidifying agent, which uses crosslinked pregelatinized starch having a water absorption capacity of 20 times or less.