JPS6158213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel desiccant that uses dry polyacrylic acid or a salt thereof having an intrinsic viscosity of about 0.1 dl/g or more when measured as a 2N caustic soda solution at 30°C as a hygroscopic component. It is something. When the object to be dried cannot be directly heated, an adsorption drying method is used. Currently, desiccant agents such as calcium chloride, silica gel, lime, bauxite, acid clay, activated carbon, activated alumina, silica alumina, molecular sieve, phosphorus pentoxide, and caustic soda are commercially available and put into practical use, making use of their individual characteristics. but,
Since these substances are all inorganic substances, if they are used in large quantities or disposed of, there is a risk of creating garbage pollution, which may make it difficult to dispose of the desiccant after use, or if it is used as a desiccant for food products. However, since there is a risk of accidents due to accidental ingestion, it has been desired to develop a desiccant with the following qualities. In other words, it is chemically inactive, non-toxic, and should not cause any accidents if ingested by mistake or if it comes into contact with the skin. 2. Must be tasteless and odorless. 3. High drying ability, little change in properties due to moisture absorption, and reusability. 4. Can be incinerated after use.
5. It can be molded for many purposes.

The present inventors have conducted various studies to find a desiccant that satisfies these needs.
We have completed the present invention by discovering that polyacrylic acid and its salts, which have an intrinsic viscosity of about 0.1 dl/g or more when measured as a caustic soda solution at 30°C, have properties as desiccants that meet this need.

In other words, dried polyacrylic acid or its salts are highly hygroscopic and have a very high drying ability, are chemically inactive and non-toxic, and there is no risk of major accidents even if they are accidentally ingested, and they cannot be reused. In addition, it can be incinerated after use, making it an excellent desiccant.

Polyacrylates used in the present invention include metal salts of polyacrylic acid, such as sodium salts,
Examples include alkali metal salts such as potassium salts, aluminum salts, magnesium salts, and cobalt salts, ammonium salts of polyacrylic acid, organic base salts of polyacrylic acid, particularly polymer base salts such as polyethyleneimine salts, and the like.

The polyacrylic acid or its salts used in the present invention usually have a molecular weight of 30,000 or more. Practically, sodium polyacrylate is used from the economic point of view.
It is preferable to have an intrinsic viscosity of about 0.1 dl/g or more as measured by . These polyacrylic acids or their salts are made into various forms such as powder, granules, and porous tablets, and then placed in a suitable container such as paper or cloth and used as a desiccant.

Next, the present invention will be specifically explained using test examples and examples.

Test Example 1 Using sodium polyacrylate as the desiccant of the present invention, and using two commercially available silica gels, activated alumina, sodium polymethacrylate and sodium carboxymethyl cellulose as controls,
100 g of each of these samples was stored in an atmosphere at 25° C. and 51% relative humidity for 25 days, and the moisture absorption rate of the samples was examined over time. The results are shown in Figure 1.

In Figure 1, 1 is sodium polyacrylate, 2 and 3 are commercially available silica gel, 4 is activated alumina, 5 is sodium polymethacrylate, 6 is
represents the hygroscopic water absorption rate of carboxymethyl cellulose sodium.

As is clear from Figure 1, the desiccant of the present invention, sodium polyacrylate, has a moisture absorption rate that is initially inferior to that of commercially available silica gel, but after about a week, it exceeds that of commercially available silica gel.
It can be seen that the moisture absorption rate increases until 25 days have elapsed, whereas the moisture absorption rate of commercially available silica gel becomes constant after approximately 20 days and no further moisture absorption occurs. Note that all control samples other than silica gel were inferior to commercially available silica gel. From the above results, it is clear that sodium polyacrylate has a very large hygroscopic ability, exhibits a hygroscopic effect for a long period of time, and can function as a desiccant for a long period of time.

Test Example 2 Using sodium polyacrylate as the desiccant of the present invention and two types of commercially available silica gel and activated alumina as controls, 100 g of each sample was stored for 20 days at a temperature of 25°C in an atmosphere with various relative humidity. , and its moisture absorption rate was investigated. The results are shown in Figure 2.
In Figure 2, 1 is sodium polyacrylate;
2 and 3 indicate commercially available silica gel, and 3 indicates the moisture absorption rate of activated alumina.

In FIG. 2, sodium polyacrylate exhibits the highest moisture absorption rate compared to the control sample at any humidity, indicating that it has excellent moisture absorption ability.

In both Test Examples 1 and 2, the sodium polyacrylate did not undergo any changes in properties such as deliquescence, and there was no fear of damage due to changes in properties.

Example 1 Dry sodium polyacrylate ([η ³⁰ ° _2NNa
OH =
0.85) (diameter: 5 mm) was placed in a Japanese paper bag and used as a desiccant. Commercially available rice crackers are moistened by leaving this desiccant at 25℃ and 75%RH for one day.
The rice crackers were placed in a bottle containing 200g, sealed, and after 24 hours, the rice crackers were taken out and the weight and texture were examined.The weight decreased to 165g, and the texture was as follows: It was sticky and wet and didn't have the feel of a rice cracker, whereas the one after drying with sodium polyacrylate had the feel of a crispy rice cracker.

Example 2 Instead of the fine particles of dry sodium polyacrylate in Example 1, fine particles of dry polyacrylic acid, granules of dry polyethyleneimine salt of polyacrylate (3 mm diameter), and granules of cobalt salt of dry polyacrylate were used. A desiccant was prepared in the same manner as in Example 1 using granules of dry ammonium salt of polyacrylate and granules of dry ammonium salt of polyacrylate. Tests were conducted in the same manner as in Example 1, and the weights of rice crackers prepared using the desiccant of the present invention were 170 g, 165 g, 161 g, and 160 g, respectively, and the crisp feel of the rice crackers had been restored.

[Brief explanation of the drawing]

Figure 1 shows the moisture absorption rates of various tests at a relative humidity of 51% and a temperature of 25°C. 1 is sodium polyacrylate, 2 and 3 are commercially available silica gel, 4 is activated alumina, and 5 is polymethacrylate. Sodium acid and 6 are for sodium carboxymethylcellulose. Figure 2 shows the hygroscopic water absorption rates of various samples when they were stored for 20 days at a temperature of 25°C and various relative humidity.1 is sodium polyacrylate, 2 and 3 are commercially available silica gel and 4 is the case of activated alumina.

Claims (1)

[Claims] 1. A desiccant containing dry polyacrylic acid or its salt as a moisture-absorbing component and having an intrinsic viscosity of approximately 0.1 dl/g or more when measured as a 2N caustic soda solution at 30°C.