JP6312439B2 - Moisture adsorbent and method for producing the same - Google Patents

Description

  The present invention relates to a moisture adsorbent and a method for producing the same. More specifically, the present invention relates to a moisture adsorbent mainly composed of calcium oxide particles having an aprotic polar solvent layer on the surface, which is particularly useful for an organic EL device, and a method for producing the same.

Organic light-emitting materials used in organic EL elements have a problem that they deteriorate due to moisture and shorten their lifetime. Conventionally, the organic light-emitting materials absorb moisture remaining in the element during manufacturing of the organic EL element and moisture entering from the outside. In addition, a hygroscopic material (moisture getter) is disposed.
Since the moisture getter is required to rapidly adsorb moisture after sealing, barium oxide, strontium oxide, or calcium oxide with an increased moisture adsorption rate is used. And the calcium oxide which accelerated | stimulated the water | moisture-content adsorption | suction speed | rate can be obtained by baking calcium hydroxide on pressure-reduced conditions as disclosed by patent document 1, for example.

Japanese Patent No. 4387870

However, calcium oxide fired under reduced pressure as described in Patent Document 1 is (1) expensive because a vacuum firing furnace is required for production, and (2) highly alkaline and highly organic such as resin. When used in a molecular material, there is a risk of breaking the polymer bond, which can only be used for some resins such as fluororesins. (3) Since calcium oxide is hydrophilic, hydrophobic resins, etc. Organic polymer materials have a problem that they are difficult to fill.
Conventionally, as a method for solving the problems (2) and (3), a method of coating the particle surface with a hydrophobic surface treatment agent such as fatty acid is known. When the hydrophobic coating is applied, the moisture absorption rate is lowered, and the performance as the original moisture absorbent is lowered.

  The present invention has been made in view of the above problems, and provides a moisture adsorbent that can be produced at low cost, has high dispersibility and hydrophobicity, and does not decrease the moisture absorption rate, and a method for producing the same. For the purpose.

  As a result of intensive studies to achieve the above object, the present inventors have found that calcium oxide particles having a thin liquid layer of an aprotic polar solvent on the surface are kept from aggregation and highly dispersible. The present inventors have found that it has a hydrophobic function and a high moisture absorption rate, and has a function suitable as a desiccant for filling a polymer material. That is, the present invention relates to a moisture adsorbent characterized by comprising, as a main component, calcium oxide particles having an aprotic polar solvent layer on the surface.

  In addition, the present inventors have found that by pulverizing calcium oxide in the presence of an aprotic polar solvent, it is possible to obtain calcium oxide particles that are atomized to increase activity and have hydrophobicity and excellent hygroscopicity. The present invention has been reached. That is, the present invention relates to a method for producing a water adsorbent characterized by dry pulverizing calcium oxide in the presence of an aprotic polar solvent. The present invention also relates to a method for producing a water adsorbent characterized by performing solid-liquid separation and / or drying after wet pulverization of calcium oxide in the presence of an aprotic polar solvent.

  As described above, according to the present invention, it is possible to provide a moisture adsorbent that can be produced at low cost, has high dispersibility and hydrophobicity, and does not decrease the moisture absorption rate, and a method for producing the same.

  The water adsorbent according to the present invention is characterized in that the main component is calcium oxide particles having an aprotic polar solvent layer on the surface. The aprotic polar solvent layer is present on the surface of the calcium oxide particles. For example, acetone, acetonitrile, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N, N-dimethylacetamide, tetrahydrofuran, dioxane, Examples include layers such as hexamethylphosphotriamide, ethylene glycol dimethyl ether, propionitrile, methyl ethyl ketone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and N-methylpyrrolidone. In particular, a layer of N-methylpyrrolidone is preferably used. In the moisture adsorbent according to the present invention, the thickness of the aprotic polar solvent layer can be defined as the following formula 1, and is preferably 0.2 to 5 nm.

Moreover, 1-100 m < ² > / g is preferable, as for the BET specific surface area of the moisture adsorption agent which concerns on this invention, 5-100 m < ² > / g is more preferable, and 10-60 m < ² > / g is more preferable. If the BET specific surface area is too small, the moisture adsorption rate is slow, which is not preferable. If the BET specific surface area is too large, the moisture adsorption rate is too fast and handling becomes difficult. Moreover, 0.05-10 micrometers is preferable, as for an average particle diameter, 0.2-5 micrometers is more preferable, and 0.5-3 micrometers is further more preferable. If the average particle size is too small, the adsorption rate is too high and the handling becomes difficult, which is undesirable. If it is too large, the appearance is deteriorated when used as a coating or filling material.

  As a mechanism for expressing the function of the moisture adsorbent according to the present invention, the polarity of the aprotic polar solvent layer present on the surface of calcium oxide gives hygroscopicity and affinity with calcium oxide, and the aproticity is a resin. It is thought that the compatibility (dissolving the resin) with respect to is imparted. Unlike the case of coating an alkoxide layer on the surface of calcium oxide, for example, the aprotic polar solvent layer is a reaction in which the alkoxide is hydrolyzed, decomposed into water and alcohol, and the alkoxide is generated by the reaction between the alcohol and calcium oxide. Therefore, it is considered that hygroscopicity higher than that of the coating involving the reaction can be exhibited. In the moisture adsorbent according to the present invention, the hygroscopicity can be evaluated, for example, from the weight increase rate of the moisture adsorbent after 120 minutes (temperature 24 ° C., relative humidity 55%). 10% or more is preferable and 10 to 30% is more preferable.

  The moisture adsorbent according to the present invention adjusts the thickness of the aprotic polar solvent layer by subjecting calcium oxide to dry pulverization or wet pulverization in the presence of an aprotic polar solvent, followed by drying treatment as necessary. Can be manufactured. When wet pulverization is performed, a drying treatment may be performed after solid-liquid separation by filtration or the like.

In the method for producing a moisture adsorbent according to the present invention, the BET specific surface area of calcium oxide used as a raw material is not particularly limited, but is preferably 0.1 to 60 m ² / g, and preferably 0.5 to 30 m ^2. / G is more preferable. Moreover, the average particle diameter of calcium oxide is not particularly limited, but is preferably 0.1 μm to 5 mm.

  In the production method of the present invention, examples of the aprotic polar solvent used include those similar to the above aprotic polar solvent layer, and these may be used alone or in admixture of two or more. . In the case of dry pulverization, the amount of the aprotic polar solvent used is preferably from 0.1 to 51 mass%, more preferably from 1 to 20 mass%, still more preferably from 1 to 15 mass%, based on calcium oxide. When pulverized using an aprotic polar solvent, the solvent acts as a pulverization aid and can be pulverized into fine and highly active fine particles while maintaining high dispersibility. In the case of wet pulverization, the amount of the aprotic polar solvent used is preferably from 52 to 10000 mass%, more preferably from 500 to 5000 mass%, particularly preferably from 1000 to 2000 mass%, based on calcium oxide. The aprotic polar solvent preferably has a boiling point of 100 ° C. or higher, more preferably 150 ° C. or higher. A boiling point of less than 100 ° C. is not preferable because the aprotic polar solvent layer is likely to volatilize.

  In the present invention, the pulverization method is not particularly limited, and a pulverizing apparatus such as a media mill, a rotating ball mill, a vibration ball mill, a planetary ball mill, a rocking mill, a paint shaker, and an airflow pulverizer can be used. Among the pulverizers, a pulverizer using a metal, resin, or ceramic medium as a medium such as a media mill or a rocking mill is preferable. The material of the medium is preferably made of nylon or zirconia with little wear because of its low contamination. The size of the media can be appropriately selected according to the particle size of the material to be crushed. The pulverization is preferably performed in an inert gas atmosphere. Examples of the inert gas include helium and argon, but it is particularly preferable that the inert gas is performed in a nitrogen gas atmosphere from an economical viewpoint. The pulverization process may be performed in one stage, but the pulverization may be performed in multiple stages by changing the media diameter and the pulverization apparatus.

In the moisture adsorbent according to the present invention, the ratio D ₉₀ / D ₁₀ of 90% particle size (D ₉₀ ) and 10% particle size (D ₁₀ ) of the particle size distribution is in the range of 1.5 to 40. Preferably, the particle size distribution is sharpened so as to be in the range of 1.5 to 5.0.
In that case, the jet mill is particularly preferable among the airflow type pulverizers because a fine and sharp powder having a particle size distribution can be obtained. A sharp particle size distribution is preferable for stabilizing the moisture absorption rate of calcium oxide. Further, in the jet mill, since the particles are pulverized in an air stream, the aprotic polar solvent on the particle surface is partially removed. Therefore, there is an advantage that the drying process can be simplified or omitted. As the pulverization conditions in the jet mill, for example, at a raw material supply rate of 5.0 kg / h, the pulverization pressure is set to 0.3 to 1.5 MPa, more preferably 0.3 to 1.0 MPa. As described above, D ₉₀ / D ₁₀ can be sharpened within a range of 1.5 to 5.0.

  The drying treatment is preferably performed by heat drying, and may be performed under reduced pressure. Examples of the drying device include a shelf dryer, a rotary dryer, a vibration dryer, and a vacuum dryer. Drying of calcium oxide particles having an aprotic polar solvent layer prevents the aprotic polar solvent layer from being decomposed or formed from calcium hydroxide or calcium carbonate by reaction with water vapor or carbon dioxide in the atmosphere. Therefore, it is preferable to carry out the process while introducing an inert gas such as nitrogen gas or argon gas into the dryer. The temperature of the heat drying treatment is not higher than the boiling point of the aprotic polar solvent layer. For example, in the case of N-methylpyrrolidone, 80 to 180 ° C is preferable, and 120 to 170 ° C is more preferable. In addition, when manufacturing by wet crushing, it is desirable to perform a drying process after removing an excess solvent with solid-liquid separators, such as filtration and centrifugation. The thickness of the aprotic polar solvent layer can be adjusted to a predetermined value by appropriately adjusting the drying conditions and removing excess solvent.

  ADVANTAGE OF THE INVENTION According to this invention, the water | moisture-content adsorption agent which has high dispersibility and hydrophobicity, and a moisture absorption rate does not fall compared with normal calcium oxide can be manufactured at low cost. Furthermore, the moisture adsorbent according to the present invention has excellent effects such as high bulk density and easy filling of the resin, low oil absorption and high filling of the resin. The amount of oil absorption is an index for evaluating the filling property of the powder into the resin, and this method can be used for the evaluation of the filling property (magazine "Industrial Materials" vol. 39, No. 1, p116-117 (1991). ). The oil absorption amount of the moisture adsorbent according to the present invention is preferably 45 ml / 100 g or less.

  The moisture adsorbent of the present invention can be used as it is or after being molded into an arbitrary shape. Further, it can be used as a paint filled with an appropriate solvent or polymer material, or a tape or film filled with a polymer material. Therefore, desiccants for electronic devices that repel moisture such as organic EL and liquid crystals, desiccants for heat insulation layers such as refrigerators and double glass, moisture adsorption layers for barrier films, and packing for sealed containers (chemicals, pharmaceuticals, foods) Prevention of deterioration), application to the inner surface of vacuum piping, O-ring use (maintaining high vacuum), and the like.

  Among these, the moisture adsorbent according to the present invention can be suitably used particularly for an organic EL device. For example, the moisture adsorbent for organic EL elements can be used by being dispersed in a synthetic resin and formed into a sheet, pellet, plate, or film. These molded products can be advantageously used as a desiccant for electronic devices such as organic EL displays. As the synthetic resin, polyolefin resin, polyacrylic resin, polyacrylonitrile resin, polyamide resin, polyester resin, epoxy resin, polycarbonate resin, and fluorine resin can be used. Moreover, the water | moisture-content adsorption agent which concerns on this invention can also be accommodated and used for the moisture-permeable bag and container used for the normal moisture absorbent. The moisture adsorbent according to the present invention may be used alone or in combination with other hygroscopic materials (for example, silica gel or molecular sieve).

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, these do not limit the objective of this invention. First, the measuring method of the physical property of the obtained calcium oxide powder is shown below.

[Hygroscopic evaluation: Weight increase after 120 minutes]
The weight of the pre-dried weighing bottle was measured and defined as [A (g)]. About 0.6 g of the powder to be measured was charged into a weighing bottle, and the weight was accurately weighed to obtain [B (g)]. Open the lid of the weighing bottle containing the powder, put it in a constant temperature and humidity chamber maintained at 24 ° C. and relative humidity 55%, measure the weight after 120 minutes, and calculate the weight according to the following formula (1) as [C (g)]. The rate of increase was calculated.

[Measurement method of oil absorption]
JIS K 5101-13-2: 2004 Pigment test method-Part 13: Oil absorption-Section 2: Measurement was carried out according to the oil method. The oil absorption amount (mL / 100 g) was determined from the amount of dripping at the end point at which a sample prepared by dropping oil into boiled sesame and kneading with oil into a predetermined amount of powder sample could be wound into a spiral shape.

[Measuring method of particle size distribution]
Ethanol was used as a dispersion solvent for the sample, and dispersion treatment was performed for 3 minutes with an ultrasonic homogenizer (MODEL US-150T, manufactured by Memoto Seiki Seisakusho). Using a laser diffraction particle size distribution measuring device (MICROTRAC HRA9320-X100, manufactured by Nikkiso Co., Ltd.) or a dynamic light scattering particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) The particle size distribution (D ₁₀ , D ₅₀ , D ₉₀ ) was measured.

[Measurement method of BET specific surface area]
The BET specific surface area was measured by the BET single point method using Monosorb (manufactured by Quantachrome).

[Method for evaluating dispersibility in organic solvents]
Evaluation of dispersibility of the sample in an organic solvent was performed using n-hexane. 5 ml of n-hexane was placed in a glass bottle, about 0.1 g of the sample was added, shaken for 1 minute, allowed to stand, and the state of the solution after 30 seconds was observed. If the sample is dispersed and turbid in hexane, it is evaluated that the sample has good dispersibility in the organic solvent (○). If the sample is agglomerated in hexane and the sample is precipitated while the hexane is transparent, The dispersibility of the sample was evaluated as bad (x).

[Measurement method of bulk density]
The sample was gently packed in a quartz container (bottom 10 mm × 10 mm, height 44 mm) with a volume of 4.4 cm ³ in a nitrogen-filled glove box and filled in piles. The surface of the powder was ground and the sample weight was accurately weighed, and the bulk density was calculated by the following formula (2) as [D (g)].

[Calculation method of coat layer thickness]
The mass of the aprotic polar solvent (N-methylpyrrolidone in Example 1) is calculated from the weight loss from 20 ° C. to 250 ° C. measured by a thermobalance (TG), and the specific gravity of the solvent (in the case of N-methylpyrrolidone, 1 Divided by .028) to calculate the solvent volume per gram of calcium oxide. By dividing this by the surface area per 1 g of calcium oxide determined by BET specific surface area measurement, the layer thickness of the aprotic polar solvent as the coating layer was calculated.

[Measurement method of FT-IR]
Measurement of FT-IR was performed by assembling a Fourier transform infrared spectrophotometer (FT / IR-6100, manufactured by JASCO Corporation) with a single reflection measurement device (ATR PRO470-H). The measured wave number range is 4000 to 400 cm ⁻¹ .

[Example 1]
A high specific surface area calcium oxide granular product (BET) obtained by calcining a granulated product of 120 g of zirconia beads (made by Nikkato Co., Ltd.) having a diameter of 4.0 mm and calcium hydroxide fine powder at 600 ° C. in a 100 mL sealed container (made of polypropylene) 6 g of a specific surface area of 16.5 m ² / g and a particle size of 2 to 3 mm) and 0.45 g of N-methylpyrrolidone were added and sealed. The above operation was performed in a glove box filled with nitrogen so that the sealed container was filled with nitrogen. The closed container taken out from the glove box was pulverized at 700 rpm for 4 hours with a rocking mill (manufactured by Seiwa Giken Co., Ltd.). After the treatment, zirconia beads and calcium oxide powder were separated using a sieve having an opening of 1 mm in a nitrogen-filled glove box. The separated and collected calcium oxide powder was dried in a nitrogen atmosphere in a shelf dryer at 150 ° C. for 18 hours to obtain the calcium oxide powder according to Example 1 in which the particle surface was covered with an aprotic polar solvent layer. It was. The obtained calcium oxide powder had an average particle size of 1.24 μm and a bulk density of 0.77 g / cm ³ . Other physical properties are shown in Table 1.

[Comparative Example 1]
High-purity calcium oxide powder (ultra-high-purity calcia (CSQ), BET specific surface area 2.3 m ² / g, average particle diameter 16.5 μm, manufactured by Ube Materials Co., Ltd.) was used. This calcium oxide powder had an average particle diameter of 16.5 μm and a bulk density of 0.69 g / cm ³ . Other physical properties are shown in Table 1.

[Comparative Example 2]
Sigma-Aldrich calcium oxide (nanopowder particle size <160 nm (BET)) was used. This calcium oxide powder had an average particle size of 0.87 μm and a bulk density of 0.21 g / cm ³ . Other physical properties are shown in Table 1.

[Comparative Example 3]
0.065 g of stearic acid was dissolved in 40 mL of diethyl ether. To this solution, 1.3 g of calcium oxide manufactured by Sigma-Aldrich (nanopowder particle size <160 nm (BET)) was added and mixed for 10 minutes. The mixed solution was vacuum dried at 30 ° C. for 12 hours to remove the solvent. A calcium oxide powder according to Comparative Example 3 was obtained, which was crushed using an agate mortar in a glove box filled with nitrogen with the collected dried powder and surface-treated with a fatty acid. The obtained calcium oxide powder had an average particle size of 0.86 μm and a bulk density of 0.79 g / cm ³ . Other physical properties are shown in Table 1.

[Comparative Example 4]
In a 100 mL sealed container (made of polypropylene), 120 g of zirconia beads (made by Nikkato Co., Ltd.) having a diameter of 4.0 mm and high purity calcium oxide powder (ultra high purity calcia (CSQ), BET specific surface area 2.3 m ² / g, An average particle size of 16.5 μm, 6 g of Ube Materials Co., Ltd.) and 0.45 g of ethanol were added and sealed. The above operation was performed in a glove box filled with nitrogen so that the sealed container was filled with nitrogen. The closed container taken out from the glove box was pulverized at 700 rpm for 4 hours with a rocking mill (manufactured by Seiwa Giken Co., Ltd.). After the treatment, the beads made of zirconia and the calcium oxide powder were separated using a sieve having an opening of 500 μm in a glove box filled with nitrogen. The separated and recovered calcium oxide powder was subjected to a drying treatment at 150 ° C. for 18 hours in a nitrogen atmosphere using a shelf dryer, to obtain a calcium oxide powder according to Comparative Example 4 in which the particle surface was covered with alkoxide. It was confirmed by FT-IR that an alkoxide layer was present on the surface of the obtained calcium oxide powder. The obtained calcium oxide powder had an average particle size of 0.83 μm and a bulk density of 0.86 g / cm ³ . Other physical properties are shown in Table 1.

[Example 2]
Calcium hydroxide fine powder (BET specific surface area 13 m ² / g, average particle size 5.6 μm) calcined at 600 ° C. Calcium oxide powder (BET specific surface area 15 m ² / g, average particle size 5.1 μm) 3000 g and N− 105 g of methylpyrrolidone was uniformly mixed in a nitrogen atmosphere using a mixer having an internal volume of 33 L (Neugra Machine SEG-350, manufactured by Seishin Enterprise Co., Ltd.). Calcium oxide powder recovered from the mixer is pulverized by jet mill (STJ-200 type, manufactured by Seishin Enterprise Co., Ltd.) under the conditions of a raw material supply rate of 5.0 kg / h and a pulverization pressure of 0.7 MPa. A calcium oxide powder according to Example 2 was obtained in which was covered with an aprotic polar solvent layer. During the pulverization process, nitrogen gas was used as the compressed fluid, and the entire pulverizer was surrounded by a booth, and the inside of the booth was set to a nitrogen atmosphere so that the powder and air were not contacted as much as possible. Table 1 shows the physical properties of the obtained calcium oxide powder.

[Example 3]
Except that the amount of N-methylpyrrolidone was 210 g, the calcium oxide powder according to Example 3 was produced by the same method as in Example 2 and the particle surface was covered with an aprotic polar solvent layer. Table 1 shows the physical properties of the obtained calcium oxide powder.

Claims (9)

A water adsorbent characterized by being a powder mainly composed of calcium oxide particles having an aprotic polar solvent layer on the surface. The water adsorbent according to claim 1 , wherein the aprotic polar solvent layer represented by the following formula (1) has a thickness of 0.2 to 5 nm .

The moisture adsorbent according to claim 1 or 2, wherein an average particle diameter is 0.05 to 10 µm. Wherein the aprotic polar solvent is water absorbent according to any one of claims 1 to 3, characterized in that it is N- methyl pyrrolidone. A moisture adsorbent for an organic EL device, wherein the moisture adsorbent according to claim 1 is used.   A method for producing a water adsorbent, comprising dry pulverizing calcium oxide in the presence of an aprotic polar solvent. A method for producing a moisture adsorbent according to any one of claims 1 to 5,
A method for producing a moisture adsorbent, comprising subjecting calcium oxide to wet pulverization in the presence of an aprotic polar solvent, followed by solid-liquid separation and / or drying. The method for producing a moisture adsorbent according to claim 6 or 7, wherein the aprotic polar solvent is N-methylpyrrolidone. The method for producing a moisture adsorbent according to claim 6, wherein the moisture adsorbent is for an organic EL device.