JPH0753222B2 - Desiccant composition - Google Patents

Description

FIELD OF THE INVENTION This invention relates to desiccant compositions.

Conventional technology Conventionally, desiccants such as silica gel, calcium chloride, quick lime, and zeolite are used to prevent quality deterioration of products such as foods, pharmaceuticals, electronic parts, precision machinery, etc. due to oxidation due to moisture absorption. Has been. These desiccants are used in the above-mentioned applications by packaging them in the form of granules or powders with paper, non-woven fabric or the like, or enclosing them in a container or the like and putting them in a packaging material together with products. For this reason, there are often problems that the desiccant originally has an excellent hygroscopic effect and a hygroscopic rate, and that the desiccant adheres to and mixes with the product due to damage to the packaging material of the desiccant.

In addition, when using a deliquescent desiccant such as calcium chloride, there are problems such as adverse effects due to the phenomenon of liquefaction by moisture absorption.

Japanese Unexamined Patent Publication No. 61-227818 proposes prevention of liquid leakage due to a hygroscopic liquefaction phenomenon by using a microporous thermoplastic resin sheet as a packaging material for a desiccant. In addition, a method is also practiced in which a nonwoven fabric and a composite desiccant are included and processed into a sandwich to form a desiccant, but all of them have drawbacks such as an increase in cost.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve or remarkably reduce the above problems, and as a result, knead a specific desiccant in a thermoplastic resin to obtain high hygroscopicity and retention. It has been found that a desiccant composition having hydraulic power and free from defects such as liquid leakage due to scattering, hygroscopicity, and deliquescent can be obtained.
The present invention has been completed.

That is, the present invention is based on 100 parts by weight of the thermoplastic resin, the formula M
The present invention relates to a desiccant composition obtained by heating and kneading 5 to 400 parts by weight of gnesium sulfate represented by gSO ₄ · nH ₂ O (where O ≦ n ≦ 3).

The greatest feature of the present invention is that the thermoplastic resin is kneaded together with a desiccant, and the desiccant composition thus obtained has a film shape, a sheet shape, a plate shape, and further a bag shape, a pellet shape, It can be easily processed and molded into any shape depending on the application such as a container. The molded product thus obtained is itself a desiccant and can be a packaging material.

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

Further, as a desiccant used with the thermoplastic resin,
Magnesium sulfate represented by MgSO ₄ · nH ₂ O (where 0 ≦ 2 ≦ 3) is used. Magnesium sulfate is particularly preferable because it has excellent dispersibility in the resin. The desiccant (magnesium sulfate) is preferably a powder having an average particle diameter of about 50 μm or less when used. If necessary, particles having different particle sizes may be mixed and used.

The ratio of the raw materials to be kneaded in the present invention is the thermoplastic resin 10
The drying agent (magnesium sulfate) is in the range of about 5 to 400 parts by weight with respect to 0 parts by weight, and is appropriately selected according to the application. When the proportion of the desiccant is in the above range, it is possible to obtain a desiccant composition having good dispersibility of the desiccant in the resin, high hygroscopicity and water retention, and excellent moldability.

In addition to the above-mentioned thermoplastic resin and desiccant, a foaming agent can be added to the desiccant composition of the present invention as a raw material. The foaming agent is not particularly limited and can be widely used known ones, for example, azoisobutylnitrile, azodicarbonamide, 4,4′-oxybenzenesulfonyl hydrazide and the like, and the amount thereof is thermoplastic. Resin 10
It is preferably 0.2 to 10 parts by weight with respect to 0 parts by weight. The desiccant composition obtained by adding the foaming agent is lighter in weight when processed and molded into a foam, and has a higher hygroscopic force because it has a hygroscopic effect even inside the foam. .

Other known additives such as plasticizers, stabilizers, lubricants, colorants and the like may be appropriately added as needed so long as the objects of the present invention are not impaired.

The method for producing the desiccant composition of the present invention is not particularly limited and can be usually produced by the following method.

The thermoplastic resin, the desiccant, and other additives may be kneaded with a mixing roll or the like at about 100 to 350 ° C. for about 5 to 40 minutes. Further, the composition of the present invention obtained as described above, extrusion molding, co-extrusion molding, injection molding, hollow molding, extrusion coating molding, cross-linking foam molding, etc., can be processed and molded into any shape, It is also possible to form a laminated body in which other laminated materials are laminated.

The desiccant composition of the present invention thus obtained can be used not only as a general desiccant but also as a dehydrating agent for removing water in an organic solvent.

Effect 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 properties.

1) It has high hygroscopicity and water retention, and it is excellent in safety and stability in use as a desiccant because it does not cause corrosiveness, splattering, liquid leakage or water droplets due to moisture absorption and liquefaction. There is.

2) At the time of use, it is not necessary to wrap like a conventional desiccant, and the one molded as a bag-shaped or container-shaped packaging material is a very rational one because the packaging material itself acts as a desiccant. is there.

3) The moisture absorption effect lasts for a long time.

4) It is easy to manufacture and process and has excellent industrial productivity.

5) Excellent in UV absorption (see Fig. 1).

As described above, the molded article of the composition of the present invention is an epoch-making thing that changes the concept of the conventional desiccant, and is a desiccant for quality protection of foods, pharmaceuticals, cosmetics, luxury items, precision machinery, machine parts, etc. Alternatively, it has a wide range of uses as a hygroscopic packaging material and the like.

Examples The following examples are given to further clarify the features of the present invention.

Example 1 100 parts by weight of polyethylene (density 0.92 g / cm ³ ), average particle size
190 parts by weight of anhydrous magnesium sulfate having a size of about 30 μm and 1 part by weight of stearic acid as a lubricant were mixed, and the mixture was heated and kneaded at 130 ° C. for 15 minutes with a mixing roll for experiments to obtain a desiccant composition. A sheet having a thickness of 2 mm was made from this composition, and a pellet having a diameter of 10 mm was produced with a punching cutter. And the water absorption test was done using this as a sample. As a result, the water absorption is
It was as high as 65% at 90%, 33% at 50% humidity, and 3% at 20% humidity, and it was found that humidity control was excellent because the humidity and water absorption were almost proportional. Application to this area is also possible.

Example 2 Ethylene-vinyl acetate copolymer (average molecular weight 31000) 100
Parts by weight, anhydrous magnesium sulfate with an average particle size of about 10 μm
50 parts by weight 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, and a sheet was trial-produced and laminated with polyethylene (average molecular weight 28000) and aluminum foil using a press roll. Thickness 0.1
mm sheet and processed to produce a packaging bag. Using this as a sample, a water absorption test was conducted. Also, vegetables such as leeks and broccoli were sealed in this bag together with carbon dioxide and left at 20 ° C for 1 week, but no phenomena such as water droplets and perspiration were observed inside the bag, and it is effective in maintaining freshness and preventing moisture absorption. Was confirmed.

Example 3 Ethylene-methyl methacrylate (average molecular weight 35,000) 1
00 parts by weight, magnesium sulfate having an average particle size of about 6 μm 3
10 parts by weight of water salt and 1 part by weight of stearic acid as a lubricant were mixed, and a desiccant composition was obtained in the same manner as in Example 1 below.
After making the pellets, a film having a thickness of 0.1 mm was made by an extruder, and a water-absorbing sample was obtained by using this as a sample. The 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) shows the blank and (B) shows the transmittance curve of the sample of Example 3.

Example 4 100 parts by weight of polystyrene (average molecular weight 30,000) and magnesium sulfate monohydrate having an average particle size of 3.5 μm (see FIG. 2) 5
By weight, 0.5 part by weight of azoisobutyl nitrile was mixed as a foaming agent 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 5 100 parts by weight of polyvinyl chloride (paste, average molecular weight 1650), 25 parts by weight of anhydrous magnesium sulfate having an average particle size of 10 μm, 80 parts by weight of dioctyl phthalate as a plasticizer, and 2 parts by weight of zinc stearate as a stabilizer are mixed. Then, a desiccant composition was obtained in the same manner as in Example 3, a film having a thickness of 0.1 mm was prepared, and a water absorption test was conducted using this as a sample.

Comparative Examples 1 and 2 In place of anhydrous magnesium sulfate in Example 5, 25 parts by weight of silica gel (average particle size 13 μm) or zeolite (average particle size 8 μm) was used to prepare a film in the same manner as described below. I went.

A comparison with the water absorption in the case of Example 5 is shown in FIG. In the figure, (A) is Example 5, (B) is Comparative Example 2,
(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 allowed to stand in a constant temperature bath at a temperature of 25 ° C. and a humidity of 90, 50, and 20%, respectively, and 1, 2, 4, 6, and 10. The water absorption was measured after 15 and 20 days.

The water absorption rate is calculated as a percentage of the 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 90% humidity are shown in Table 1, 50% humidity.
Those with a humidity of 20% are shown in Table 2, and those with a humidity of 20% are shown in Table 3.

Example 6 Low-density polyethylene (LDPE: density 0.92 g / cm ³ , the same applies hereinafter)
100 parts by weight and 50 parts by weight of anhydrous magnesium sulfate having an average particle diameter of 4.59 μm were heated and kneaded at 130 ° C. for 15 minutes using a kneading extruder to obtain pellets. Using an inflation molding machine, apply this to the outer layer of high density polyethylene (HD
PE: Density 0.95 g / cm ³ , the same shall apply hereinafter) and a coextruded three-layer film (HDPE 50 μm / 50 μm / LDPE 10 μm) was prepared using LDPE as the inner layer.

This 3-layer film (50 x 50 mm) is used as a sample at a temperature of 25 ° C,
A water absorption test was conducted under the condition of a humidity of 75%. The result is the fourth
It shows in (A) in the figure.

Example 7 100 parts by weight of highly polymerized polyamide (nylon 6, molecular weight 16000) and anhydrous magnesium sulfate having an average particle diameter of 4.59 μm 50
Using 3 parts by weight, a three-layer film (HDPE 50 μm / 50 μm / LDPE 10 μm) was prepared in the same manner as in Example 6 and a water absorption test was conducted. The result is shown in FIG. 4 (B).

Example 8 Low-density polyethylene (LDPE: density 0.92 g / cm ³ , the same applies hereinafter)
100 parts by weight, 43 parts by weight of anhydrous magnesium sulfate having an average particle diameter of about 30 μm and 1 part by weight of stearic acid as a lubricant were mixed, and a desiccant composition was obtained in the same manner as in Example 1. A sheet having a width of 50 mm and a length of 50 mm was produced with a punch cutter using this composition as a sheet having a thickness of 0.5 mm. Using this sheet piece as a sample, a water absorption test was conducted under conditions of a temperature of 25 ° C. and a humidity of 75%. The result is shown in FIG.

Comparative Example 3 A sheet piece was similarly prepared using 43 parts by weight of calcium oxide (average particle diameter 10 μm) instead of magnesium sulfate in Example 8, and a water absorption test was conducted using this as a sample. The result is shown in FIG.

Example 9 Soft polyvinyl chloride (paste-like, average molecular weight 1650) 10
0 parts by weight, anhydrous magnesium sulfate having an average particle size of 10 μm 30
By weight, 80 parts by weight of dioctyl phthalate as a plasticizer and 2 parts by weight of zinc stearate as a stabilizer were mixed, and a desiccant composition was obtained in the same manner as in Example 1. This composition is made into a sheet with a thickness of 0.5 mm, and the width is 50 mm with a punching cutter.
A sheet piece having a length of 100 mm was produced. Using this sheet piece as a sample, a water absorption test was conducted under conditions of a temperature of 25 ° C. and a humidity of 90%. The results are shown in FIG. 6 (A).

Comparative Examples 4 and 5 Instead of magnesium sulfate in Comparative Example 9, 30 parts by weight of silica gel (average particle size 13 μm: Comparative Example 4) or synthetic zeolite (average particle size 8 μm: Comparative Example 5) was used to form a sheet piece in the same manner. A water absorption test was performed using the prepared sample. A comparison with the water absorption in the case of Example 9 is shown in FIG. In FIG. 6, (B) is a comparative example 4, and (C) is a comparative example 5.
The sample was used.

Example 10 Low-density polyethylene (LDPE: Density 0.92 g / cm ³ , the same applies below)
100 parts by weight, 43 parts by weight of anhydrous magnesium sulfate having an average particle size of about 30 μm 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, and then injection molding was performed to obtain a thickness of 2.0. A polyethylene plate of mm × area (length × width) 69.6 cm ² was prepared. Using this polyethylene plate as a sample, a water absorption test was conducted under conditions of a temperature of 25 ° C. and a humidity of 75%. The result is shown in FIG.

Comparative Examples 6 and 7 In place of magnesium sulfate in Example 10, 43 parts by weight of silica gel (average particle size 13 μm: Comparative Example 6) or synthetic zeolite (average particle size 8 μm: Comparative Example 7) was used to prepare a polyethylene plate in the same manner. A water absorption test was performed using the prepared sample. A comparison with the amount of water absorption in Example 10 (the amount of water absorption per unit area of polyethylene plate) is shown in FIG. In addition, in FIG. 7, (B) uses the sample of Comparative Example 6, and (C) uses the sample of Comparative Example 7.

[Brief description of drawings]

FIG. 1 is a curve of light transmittance of the film in Example 3. FIG. 2 is a diagram showing the results of measuring the particle size distribution 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, Comparative Examples 1 and 2. FIG. 4 is a graph of elapsed days-water absorption rate curves in the water absorption tests of Examples 6 and 7. FIG. 5 is a graph of elapsed days-water absorption rate curve in the water absorption test of Example 8 and Comparative Example 3. FIG. 6 is a graph showing the elapsed days-water absorption rate curve in the water absorption test of Example 9 and Comparative Examples 4 and 5. FIG. 7 is a graph of elapsed days-water absorption amount curve in the water absorption test of Example 10, Comparative Examples 6 and 7.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Isojima 4-4-1 Kitayamadai, Kosai-cho, Koga-gun, Shiga Prefecture (56) References JP-A-61-68119 (JP, A) JP-A-61-120638 (JP, A) Actual development Sho 52-77956 (JP, U) Japanese Patent Sho 46-26569 (JP, B1)

Claims (2)

[Claims] 1. A formula MgSO ₄ .multidot.based on 100 parts by weight of a thermoplastic resin.
nH ₂ O (provided that 0 ≦ n ≦ 3) magnesium sulfate is 5 to
A desiccant composition obtained by heating and kneading 400 parts by weight. 2. A desiccant composition according to claim 1, wherein the composition contains a foaming agent.