JPH0796092B2 - Desiccant molding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a desiccant molded article.

In the present specification, the term "container shape" means not only the container itself but also a lid of the container and a combination of the container and the lid.

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 caused by moisture absorption. Has been. These desiccants are used in the above-mentioned applications by being packaged in a granular or powder form with paper, non-woven fabric, or the like, or by being enclosed in a container or the like and put into a packaging material together with a product. Therefore, problems such as the excellent moisture absorption effect and the moisture absorption rate inherent in the desiccant are lowered, and the desiccant adheres to and mixes with the product due to damage to the packaging material of the desiccant often occurs.

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

Japanese Unexamined Patent Publication No. 61-227818 proposes prevention of liquid leakage due to a moisture absorption liquefaction phenomenon by using a microporous thermoplastic resin sheet as a packaging material for a desiccant. In addition, a method of incorporating a non-woven fabric and a composite desiccant into a sandwich to form a desiccant has been carried out, but all of them have drawbacks such as an increase in cost.

Means for Solving the Problems As a result of intensive studies to solve or significantly reduce the above problems, the present inventor has kneaded a specific desiccant in a thermoplastic resin to obtain high hygroscopicity and retention. It was found that a desiccant molded product 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 molded product obtained by heating and kneading 5 to 400 parts by weight of magnesium sulfate represented by gSO ₄ · nH ₂ O (where 0 ≦ n ≦ 3).

The greatest feature of the present invention is that the thermoplastic resin is used by kneading with a desiccant, and the desiccant molded product obtained thereby is in the form of a film, a sheet, a plate, a bag, a pellet, 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 (P
E), polypropylene (PP), polycarbonate, polyamide (PA), ethylene-vinyl acetate copolymer (EV
A), ethylene-methacrylate copolymer, polyvinyl chloride, polystyrene, polyester, polyacrylic acid ester, polyvinylidene chloride (PVDC) and the like,
One or more of these may be used.

Further, as a desiccant used together with the thermoplastic resin,
Magnesium sulfate represented by MgSO ₄ · nH ₂ O (where 0 ≦ n ≦ 3) is used. Magnesium sulfate is particularly preferable because it has excellent dispersibility in the resin. The above desiccant (magnesium sulfate) has an average particle size when used.
It is desirable that the powder is about 50 μm or less. 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 is in the range of 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, the dispersibility of the desiccant in the resin is good, it has high hygroscopicity and water retention, and it is excellent in moldability, and the drying target of the present invention is obtained. An agent molded product can be obtained.

In addition to the thermoplastic resin and the desiccant, a foaming agent can be added as a raw material to the desiccant molded article of the present invention. 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 about 0.2 to 10 parts by weight with respect to 0 parts by weight. A desiccant molded product obtained as a foam by adding a foaming agent is lightweight and exerts a higher hygroscopic force because the hygroscopic effect extends to the inside of the foam.

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

The method for producing the desiccant molded article 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 are mixed with a kneading machine such as a mixing roll, a molding machine, or a kneading molding machine for about 10 minutes.
It may be formed by kneading at 0 to 350 ° C for about 5 to 40 minutes.

Further, the present invention also includes a desiccant molded article obtained by laminating at least one kind of laminating material in the desiccant molded article obtained as described above.

Examples of the laminated material include resins such as the above-mentioned thermoplastic resins which are raw materials of the molded product of the present invention, papers, fibers, metals, various paints, various adhesives, and the desiccant molding of the present invention having a different composition. Goods can be used. The type, amount (thickness) and number of layers of the laminated material are not limited as long as the object of the present invention is achieved and can be widely used, and are appropriately selected according to the application (requirement).

The most common example of such lamination is a film, sheet or plate laminated with the above laminated material. Specific examples of this laminated structure are listed below, but the present invention is not limited to these.

LDPE (Low Density Polyethylene) / MDPE (Medium Density Polyethylene) HDPE (High Density Polyethylene) / LDPE / HDPE HDPE / Ioimer PA / Ioimer PP / EVA / PP PP / EVA / LDPE PA / Adhesive PE / LDPE PA / Adhesive PE / Ioimer PA / Adhesive PE / EVA PA / Adhesive PE / HDPE PA / Adhesive PE / LLDPE (linear low-density polyethylene) PA / Adhesive LLDPE / LLDPE PA / Adhesive PP / PP LDPE / PA / EVA EVA / PVDC / EVA EVA / PVDC / Ioimer LDPE / Adhesive PE / PA In the above example of lamination, “adhesiveness” means lamination with an adhesive. The desiccant may be contained in any layer, but it is not necessary to contain it in the outer layer since the main purpose of lamination is to produce the hygroscopic packaging material. Further, an aluminum foil or the like can be attached to block moisture, light, etc. from the outside almost completely. Lamination can be easily performed by extrusion lamination method, coextrusion lamination method, multilayer injection molding method, adhesive method, etc., and the resulting laminate can be easily processed into a bag shape or a container shape. .. As described above, the desiccant molded article of the present invention in which a waterproof material is laminated on the outer layer and a moisture-permeable protective material is laminated on the inner layer as the packaging material has a moisture absorption effect, its life,
The durability, light-shielding property, antistatic property, safety, stability, etc. are improved, the effect of preventing quality deterioration is further excellent, and it is more functional that can be used in all usage environments.

The desiccant molded product of the present invention thus formed is extruded,
It is processed and molded into a film shape, a sheet shape, a plate shape, a bag shape, a pellet shape, a container shape or the like by coextrusion molding, injection molding, hollow molding, extrusion coating molding, cross-linking foam molding or the like.

EFFECTS OF THE INVENTION The desiccant molding of the present invention has the following characteristics.

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 liquefaction. There is. Therefore, quality deterioration due to oxidation of products is effectively prevented.

2) At the time of use, it is not necessary to wrap it like a conventional desiccant, and what is molded as a bag-shaped, 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).

6) It has a light-shielding property and an antistatic property.

The desiccant molded product of the present invention having the above characteristics can be used as a desiccant or a hygroscopic packaging material for quality protection in a wide range of fields such as foods, pharmaceuticals, cosmetics, luxury items, precision machines and machine parts. It is a term.

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 ), 190 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, and the mixture was mixed at 130 ° C. for 15 with an experimental mixing roll. The mixture was heated and kneaded for a minute to form a sheet having a thickness of 2 mm, 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 rate is as high as 65% at 90% humidity and 33% at 50% humidity.
%, And humidity of 20% is as low as 3%. Since humidity and water absorption are in a nearly proportional relationship, it is clear that humidity control is also excellent, and application to this area is also possible.

Example 2 Ethylene-vinyl acetate copolymer (average molecular weight 31000) 100
Parts by weight, 50 parts by weight of anhydrous magnesium sulfate having an average particle diameter of 10 μm, and 1 part by weight of stearic acid as a lubricant were used to fabricate a sheet in the same manner as in Example 1 below. Then, using a press roll, polyethylene (average molecular weight 28000) and aluminum foil were used. Was laminated into a sheet having a thickness of 0.1 mm and heat-sealed to produce a packaging bag. A water absorption test was conducted using this as a sample.

In addition, vegetables such as leeks and broccoli were enclosed 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 was effective in maintaining freshness and preventing moisture absorption. It was confirmed that there was.

Example 3 Ethylene-methyl methacrylate (average molecular weight 35000) 1
00 parts by weight, 10 parts by weight of magnesium sulfate trihydrate having an average particle diameter of about 6 μm, and 1 part by weight of stearic acid as a lubricant were used to prepare pellets in the same manner as in Example 1 below, and then a pellet having a thickness of 0.1 mm was formed with an extruder. A film was prepared, and a water absorption test was conducted using this film as a sample.

Also, irradiate this film with light with a wavelength of 250 to 500 nm,
The result of obtaining the transmittance is 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 diameter of 3.5 μm (see FIG. 2) 5
By weight, and 0.5 parts by weight of azoisobutyl nitrile as a foaming agent, the mixture was kneaded in the same manner as in Example 1 and 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 were used. Example 3
A film having a thickness of 0.1 mm was prepared in the same manner as in 1. and a water absorption test was conducted using this film as a sample.

Comparative Examples 1 and 2 In place of the anhydrous magnesium sulfate used 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 with respect to the weight of the sample before the test.

As a result, those with a humidity of 90% are shown in Table 1, humidity 50%.
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 a pellet-shaped hygroscopic body. Using an inflation molding machine, the outer layer was made of high-density polyethylene (HDPE: density 0.95 g / cm ³ , the same applies below), and the inner layer was made of LDPE as a coextruded three-layer film (HDPE 50 μm / hygroscopic material 50 μm / LDPE 10 μ).
m) was prepared.

Using this three-layer film (50 x 50mm) as a sample, the temperature is 25 ℃,
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.

In addition, a bag formed by heat-sealing this three-layer film is a hygroscopic packaging material that effectively absorbs moisture in the bag and can be stored for a long period in a sealed state.

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 / moisture absorber 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).

Further, the bag formed by heat-sealing this three-layer film was a hygroscopic packaging material that effectively absorbs moisture in the bag and can be stored for a long period in a sealed state.

Example 8 A hygroscopic material, HDPE and LDPE obtained in the same manner as in Example 6 were introduced into one common die in a heat-melted state by using three extruders and brought into contact with each other to bring them into contact with each other. It is a three-layer film. At that time, aluminum foil is further attached to the outer layer HDPE, and Al 7 μm / HDPE 50 μm / hygroscopic material 50 μm / LDPE 10 μ
A 4-layer film of m was prepared.

Two sheets of this 4-layer film are piled up and heat-sealed on the four sides.
A 57 × 88 mm sealed body was used. This was allowed to stand for 8 days at a temperature of 25 ° C. and a humidity of 90%, and the moisture permeability from the outer layer was measured.
As a result, the water vapor transmission rate was 0.28 g / m ² .

Example 9 When a three-layer film was obtained in the same manner as in Example 8, aluminum foil and polyethylene terephthalate (PET) were further bonded to the outer layer of HDPE, and PET 12 μm / Al 9 μm / HDPE 50 μm.
A 5-layer film having a moisture absorbent of 50 μm and LDPE of 10 μm was prepared.
This five-layer film made into a bag by heat sealing is a good hygroscopic packaging material that can keep internal humidity constant even if it is stored for a long time in a sealed state to block external moisture. there were.

Example 10 Using a two-layer injection molding method using an injection molding machine (“DC100-200” manufactured by NISSEI PLASTIC INDUSTRIAL CO., LTD.), The inner layer had a hygroscopic material of 2 mm and the outer layer had a HDPE of 2 mm. , Capacity 100cc
A wide-mouth two-layer container was prepared. The obtained hygroscopic container had good hygroscopicity on the inside, and the effect as a hygroscopic protective packaging material was great.

Example 11 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 size 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 the 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 11, and a water absorption test was performed using this as a sample. The result is shown in FIG.

Example 12 Soft polyvinyl chloride (paste-like, average molecular weight 1650) 10
3 parts by weight of anhydrous magnesium sulfate having an average particle size of 10 μm
0 parts by weight, 80 parts by weight of dioctyl phthalate as a plasticizer and 2 parts by weight of zinc stearate as a stabilizer are mixed,
A desiccant composition was obtained in the same manner as in Example 1. This composition was made into a sheet with a thickness of 0.5 mm, and the width was 50 mm with a punching cutter.
A sheet piece having a length of 100 mm was prepared. 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 result is shown in FIG.

Comparative Examples 4 and 5 Instead of the magnesium sulfate in Example 12, 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. It was produced and a water absorption test was conducted using this as a sample. A comparison with the water absorption in the case of Example 12 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 13 Low Density Polyethylene (LDPE: Density 0.92 g / cm ³ , same hereafter)
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 to obtain a desiccant composition in the same manner as in Example 1, and 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 13, 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. It was produced and a water absorption test was conducted using this as a sample. A comparison with the amount of water absorption in Example 13 (the amount of water absorption per unit area of polyethylene plate) is shown in FIG. In addition, (B) in FIG. 7 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 curve in the water absorption test of Examples 6 and 7. FIG. 5 is a graph of elapsed days-water absorption rate curve in a water absorption test of Example 5, Example 11 and Comparative Example 3. FIG. 6 is a graph showing the elapsed days-water absorption rate curve in the water absorption test of Example 6, Example 12, and Comparative Examples 4 and 5. FIG. 7 is a graph showing the elapsed days-water absorption curve in the water absorption test of Example 7, Example 13, and Comparative Examples 6 and 7.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B65D 81/26 N (72) Inventor Eiji Isomine 4-chome Kitayamadai Kosai-cho Koga-gun Shiga Prefecture 16 (56) Reference JP 61-68119 (JP, A) JP 61-120638 (JP, A) JP 58-163420 (JP, A) JP 3-109916 (JP, A) 52-77956 (JP, U) JP 46-26569 (JP, B1) JP 54-41998 (JP, B2)

Claims (4)

[Claims] 1. A formula of MgSO ₄ .n based on 100 parts by weight of the thermoplastic resin.
A desiccant molded product obtained by heating and kneading 5-400 parts by weight of magnesium sulfate represented by H ₂ O (where 0 ≦ n ≦ 3). 2. The desiccant molded article according to claim 2, wherein the molded article is a foam. 3. The desiccant-molded article according to claim 2, wherein at least one kind of laminated material is laminated. 4. The desiccant molded article according to claim 1, which has a film shape, a sheet shape, a plate shape, a bag shape, a pellet shape, or a container shape.