JPH03109916A - Desiccant composition - Google Patents

Abstract

PURPOSE:To obtain a desiccant compsn. having high hygroscopicity, high water retentivity and superior moldability by kneading thermoplastic resin with a specified desiccant. CONSTITUTION:At least one kind of desiccant selected from among magnesium sulfate represented by formula MgSO4.nH2O (where 0<=n<=3), aluminum oxide, barium oxide, calcium oxide and silicon oxide is added to thermoplastic resin by 5-400 pts.wt. per 100 pts.wt. of the resin to give a desiccant compsn. This compsn. has high hygroscopicity and high water retentivity and can be molded into an arbitrary shape. When a blowing agent is added, a desiccant compsn. having higher hygroscopicity and giving a lightweight molded body can be obtd.

Description

[Detailed description of the invention] Industrial applications The present invention relates to desiccant compositions.

Conventional technology Traditionally, desiccant agents such as silica gel, calcium chloride, quicklime, and zeolite have been used in all fields of food, medicine, electronic parts, precision machinery, etc. to prevent quality deterioration of products due to oxidation caused by moisture absorption. It is being In the above-mentioned applications, these desiccants are used in the form of granules or powder, packaged with paper, nonwoven fabric, etc., or sealed in a container, etc., and put into a packaging material together with the product. As a result, problems such as the desiccant's inherent excellent moisture absorption effect and moisture absorption rate are reduced, and the packaging material for the desiccant is damaged, resulting in the desiccant adhering to or contaminating the product, often occur.

Further, when using a deliquescent desiccant such as calcium chloride, there are problems such as adverse effects due to moisture absorption and liquefaction phenomenon.

JP-A-61-227818 proposes preventing liquid leakage due to moisture absorption and liquefaction by using a microporous thermoplastic resin sheet as a packaging material for a desiccant. In addition, methods have been implemented in which a nonwoven fabric and a composite desiccant are incorporated into a sandwich to form a desiccant, but all of these methods have drawbacks such as high costs.

Means for Solving the Problems As a result of extensive research in order to eliminate or significantly reduce the above problems, the present inventor has found that by kneading a specific desiccant into a thermoplastic resin, a thermoplastic resin with high hygroscopicity and retention can be obtained. It has been discovered that a desiccant composition can be obtained that has hydraulic power and does not have drawbacks such as liquid leakage due to scattering, hygroscopicity, and deliquescent properties,
This completes the present invention.

That is, in the present invention, for 100 parts by weight of thermoplastic resin,
Magnesium sulfate, aluminum oxide, barium oxide, represented by the formula MgSO4ΦnH20 (O≦n≦3),
At least one of calcium oxide and silicon oxide 5 to 4
00 parts by weight of the desiccant composition.

The greatest feature of the present invention is that the thermoplastic resin is used by kneading it with a desiccant, and the desiccant composition obtained thereby can be in the form of a film, sheet, plate, bag, pellet, etc. It can be easily processed and molded into any shape depending on the purpose, such as a container shape. The molded product thus obtained is itself a desiccant and can also be used as a packaging material.

The thermoplastic resin in the present invention is not particularly limited and any known one can be used, such as polyethylene, polypropylene, polycarbonate, polyamide, ethylene-vinyl acetate copolymer, ethylene-methacrylate copolymer, polyvinyl chloride, Examples include polystyrene, polyester, polyacrylic ester, polyvinylidene chloride, and one or more of these can be used.

In addition, examples of the desiccant used with the thermoplastic resin include magnesium sulfate, aluminum oxide, barium oxide, calcium oxide, and silicon oxide represented by the formula MgSO4.nH20 (O≦n≦3). One or more of these can be used, with magnesium sulfate being particularly preferred as it has excellent dispersibility in the resin. Further, it is desirable that the desiccant is in the form of a powder with an average particle size of about 50 μm or less when used. If necessary, particles of different particle sizes may be mixed and used.

In the present invention, the ratio of raw materials to be kneaded is 1 part thermoplastic resin, 1 part thermoplastic resin,
00 parts by weight, the desiccant is about 5 to 400 parts by weight, and is appropriately selected depending on the application. When the proportion of the desiccant is within the above range, it is possible to obtain a desiccant composition that has good dispersibility of the desiccant in the resin, has high hygroscopicity and water retention, and has excellent moldability.

In addition to the thermoplastic resin and the desiccant, the desiccant composition of the present invention can also contain a foaming agent as a raw material.

The blowing agent is not particularly limited and a wide variety of known ones can be used, such as azoisobutylnitrile, azodicarbonamide, 4゜4'-oxybenzenesulfonyl hydrazide, etc., and the amount used is determined according to the thermoplastic The amount is preferably about 0.2 to 10 parts by weight per 100 parts by weight of the resin. When the desiccant composition obtained by adding a foaming agent is processed and molded into a foam, it is lightweight and has even higher hygroscopicity because the hygroscopic effect extends to the inside of the foam. .

In addition, known additives such as plasticizers, stabilizers, lubricants, colorants, etc. may be added as necessary to an extent that does not impede the object of the present invention.

There are no particular restrictions on the method for producing the desiccant composition of the present invention, and the desiccant composition can generally be produced by the following method.

The thermoplastic resin, desiccant and other additives are mixed using a mixing roll or the like at about 100 to 350°C for about 5 to 40 minutes.
It is sufficient to knead for 0 minutes. Furthermore, the composition of the present invention obtained in a two-layered manner can be processed and molded into any shape by extrusion molding, coextrusion molding, injection molding, hollow molding, extrusion coating molding, crosslinking foam molding, etc. Furthermore, it is also possible to form a laminate body in which other laminate materials are laminated.

The desiccant composition of the present invention thus obtained can be used not only as a desiccant for ships, but also as a dehydrating agent for removing moisture from organic solvents.

Effects of the Invention The desiccant composition of the present invention is easy to process and can be molded into any shape.

The molded product of the composition of the present invention has the following characteristics.

1) It has high hygroscopic and water-holding power, and is highly safe and stable when used as a desiccant because it is corrosive, scatters, and does not cause liquid leakage or water droplet generation due to moisture absorption and liquefaction phenomena. There is.

2) When used, it does not need to be packaged like conventional desiccant agents, and when it is molded into packaging materials such as bags or containers, the denso itself acts as a desiccant agent, making it extremely rational. be.

3) Moisture absorption effect lasts for a long time.

4) Easy to manufacture and process, and has excellent industrial productivity.

5) Excellent ultraviolet absorption (see Figure 1).

As described above, the molded product of the composition of the present invention is an epoch-making product that changes the concept of conventional desiccants. Also, it has a wide range of uses as a hygroscopic packaging material.

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Example 1 100 parts by weight of polyethylene (density 0.92 g/c),
Anhydrous magnesium sulfate 190 with an average particle size of about 30 μm
parts by weight and 1 part by weight of stearic acid as a lubricant,
A desiccant composition was obtained by heating and kneading at 130° C. for 15 minutes using an experimental mixing roll. This composition was applied to a thickness of 2 m.
A sheet with a diameter of 10 nm was prepared using a punch cutter to produce pellets with a diameter of 10 nm. Then, a water absorption test was conducted using this as a sample.

As a result, the water absorption rate is as high as 65% at 90% humidity, 33% at 50% humidity, and as low as 3% at 20% humidity.Since humidity and water absorption rate are almost proportional, it also improves humidity control. It was found to be excellent, and it is possible to apply it in this field.

Example 2 Ethylene-vinyl acetate copolymer (average molecular weight 31,000
) 100 parts by weight, average particle size 10. 50 parts by weight of anhydrous magnesium sulfate of about czm and 1 part by weight of stearic acid as a lubricant were mixed to obtain a desiccant composition in the same manner as in Example 1. After making a trial sheet, polyethylene (average molecular ff 128,000 ) and aluminum foil to form a sheet with a thickness of 0.1 mm, which was then processed to produce a packaging bag. A water absorption test was conducted using this as a sample. In addition, vegetables such as green onions and broccoli were sealed in this bag with carbon dioxide gas and left at 200C for a week, but no water droplets or sweating were observed inside the bag, indicating that it is effective in maintaining freshness and preventing moisture absorption. was recognized.

Example 3 Ethylene-methyl methacrylate (average molecular weight 3500
0) Mix 100 parts by weight of magnesium sulfate trihydrate with an average particle size of about 6 μm and 1 part by weight of stearic acid as a lubricant to obtain a desiccant composition in the same manner as in Example 1. After production, the thickness is 0.1 mm using an extruder.
A film with a diameter of 1 mm was prepared and used as a sample for a water absorption test.

Further, this film was irradiated with light having a wavelength of 250 to 500 nm, and the transmittance was determined. The results are shown in FIG. In the figure, (A) represents a blank, and (B) represents a transmittance curve of the sample of Example 3.

Example 4 100 parts by weight of polystyrene (average molecular weight 30,000),
Magnesium sulfate monohydrate (secondary
(see figure) and 0.5 parts by weight of azoisobutylnitrile as a blowing agent were mixed and kneaded in the same manner as in Example 1 to obtain a desiccant composition, which was then injection molded to obtain a foam.

A water absorption test was conducted using this as a sample.

Example 5 Polyvinyl chloride (paste, average molecular weight 1650) 1
00 parts by weight, 25 parts by weight of anhydrous magnesium sulfate with an average particle size of 10 μm, and 80 parts by weight of dioctyl phthalate as a plasticizer.
parts by weight and 2 parts by weight of zinc stearate as a stabilizer to obtain a desiccant composition in the same manner as in Example 3.
．． A 1 mm film was prepared and used as a sample for a water absorption test.

Comparative Examples 1 and 2 Films were prepared in the same manner using 25 parts by weight of silica gel (average particle size 13 μm) or zeolite (average particle size 8 μm) instead of anhydrous magnesium sulfate in Example 5, and water absorption tests were conducted using these as samples. I did it.

Further, a comparison with the water absorption rate in the case of Example 5 is shown in FIG. In the figure, (A) is Example 5, (B) is Comparative Example 2, and (C
) uses the sample of Comparative Example 1.

[Water Absorption Test] - The samples prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were left in a constant temperature bath at a temperature of 25°C and a humidity of 90.50.20%, and 1.2.4.6 .10.15.The water absorption rate was measured after 20 days.

The water absorption rate is calculated as the percentage increase in the weight of the sample after the test relative to the weight of the sample before the test.

As a result, those with humidity of 90% are shown in Table 1, ■ ■ For those with humidity of 50%, see Table 2. 20% humidity It is shown in Table 3.

弗Table 3 Z 4 Rabbit 3 Table Example 6 Low density polyethylene (LDPE: density 0.92g /
ci, hereinafter the same) 100 parts by weight and average particle size 4.59
Pellets were obtained by heating and kneading 50 parts by weight of anhydrous magnesium sulfate having a particle diameter of 1.5 μm using a kneading extrusion molding machine at 130° C. for 15 minutes. The outer layer is made of high-density polyethylene (HD) using an inflation molding machine.
PE: Density 0.95g/cnf (same below), inner layer L
Coextruded three-layer film (IIDPE 50 μm
/50μm/LDPE10μm) was created.

A water absorption test was conducted using this three-layer film (50 x 50 mm) as a sample under conditions of a temperature of 25° C. and a humidity of 75%. The results are shown in FIG. 4 (A).

Example 7 High polymerization degree polyamide (nylon 6, molecular weight 16000)
: 100 parts by weight and 50 parts by weight of anhydrous magnesium sulfate with an average particle size of 4.59 μm, a three-layer film (HDPE 50 μm 150 μm/LD
PEIOμm) was prepared and a water absorption test was conducted. The results are shown in FIG. 4 (B).

[Brief explanation of drawings]

FIG. 1 is a curve of light transmittance of the film in Example 3. FIG. 2 is a diagram showing the particle size distribution measurement results of magnesium sulfate used in Example 4. FIG. 3 is a graph of elapsed days-water absorption rate curve in the water absorption test of Example 5 and Comparative Examples 1 and 2. FIG. 4 is a graph of elapsed days versus water absorption rate curve in the water absorption test of Examples 6 and 7. (That's all) 7. A long time ago.

Claims (1)

[Claims] [1] For 100 parts by weight of thermoplastic resin, the formula MgSO_
A desiccant composition containing 5 to 400 parts by weight of at least one of magnesium sulfate, aluminum oxide, barium oxide, calcium oxide, and silicon oxide represented by 4.nH_2O (0≦n≦3). [2] The desiccant composition according to claim [1], wherein the composition contains a foaming agent.