TW201434531A - Water absorbent and method for producing same - Google Patents

Abstract

Provided are: a water absorbent which can be produced at a low cost, is highly dispersible and hydrophobic, and does not exhibit a decline in moisture-absorption speed and a method for producing the same. This water absorbent is characterized by having, as the principal component thereof, calcium oxide particles having an aprotic polar solvent layer on the surface thereof. The method for producing the water absorbent is characterized by crushing calcium oxide in the presence of an aprotic polar solvent. It is preferable for the aprotic polar solvent to be N-methylpyrrolidone.

Description

Moisture adsorbent and method of manufacturing same

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

The organic light-emitting material used for the organic EL element has a problem of being deteriorated by moisture and has a long life. In order to absorb the moisture remaining in the element during the production of the EL element or the moisture infiltrated from the outside, the hygroscopicity is disposed. Material (water absorbing agent).

Since the water absorbing agent rapidly adsorbs moisture after sealing, calcium oxide having cerium oxide or cerium oxide or accelerating moisture adsorption speed is used. Further, the calcium oxide which accelerates the water adsorption rate is obtained, for example, as disclosed in Patent Document 1, and can be obtained by firing calcium hydroxide under reduced pressure.

Patent Document 1: Japanese Patent No. 4387870

However, the calcium oxide obtained by the calcination calcination described in Patent Document 1 has the following problems: (1) a vacuum furnace is required for production, so that it is expensive; (2) it is strongly alkaline, so it is filled. When it is used in an organic polymer material such as a resin, it may be used to cut a polymer bond, and it may be used only for a part of a resin such as a fluororesin; (3) Calcium oxide is hydrophilic, so it is not easily filled into a hydrophobic resin. Organic polymer materials.

In the prior art, a method of coating the surface of a particle with a hydrophobic surface treatment agent such as a fatty acid is known as a method for solving the problems of the above (2) and (3). However, when the organic EL device or the like is used, it is hydrophobic. When the coating is applied, the moisture absorption rate is lowered, and the performance as a moisture absorbent is lowered.

The present invention has been made in view of the above problems, and its object is to provide a low A moisture adsorbent which is cost-manufactured, has high dispersibility and hydrophobicity, and does not reduce the moisture absorption rate, and a method for producing the same.

The present inventors made efforts to carry out research in order to achieve the above objectives, and the results were Now, the calcium oxide particles having a relatively thin liquid layer with an aprotic polar solvent on the surface can inhibit aggregation and maintain high dispersibility, have hydrophobicity and a high moisture absorption rate, and have a filling as a polymer material. The preferred function of the desiccant is to complete the present invention. That is, the present invention relates to a moisture adsorbent characterized in that calcium oxide particles having an aprotic polar solvent layer on the surface thereof are mainly composed.

Further, the present inventors have found that pulverization is carried out in the presence of an aprotic polar solvent. The present invention has been completed by using calcium oxide to obtain calcium oxide particles which are atomized to improve activity and which are excellent in hydrophobicity and hygroscopicity. That is, the present invention relates to a method for producing a moisture adsorbent characterized by subjecting calcium oxide to dry pulverization in the presence of an aprotic polar solvent. Further, the present invention relates to a method for producing a moisture adsorbent characterized by subjecting calcium oxide to wet pulverization in the presence of an aprotic polar solvent, followed by solid-liquid separation and/or drying.

As described above, according to the present invention, it is possible to provide a product that can be manufactured at low cost. A moisture adsorbent having a high dispersibility and hydrophobicity and a low moisture absorption rate and a method for producing the same.

The moisture adsorbent of the present invention is characterized in that it contains calcium oxide particles having an aprotic polar solvent layer as a main component. An aprotic polar solvent layer is present on the surface of the calcium oxide particles, and examples thereof include acetone, acetonitrile, N,N-dimethylformamide (DMF), dimethylammonium (DMSO), and N,N-di Methylacetamide, tetrahydrofuran, dioxane, hexamethylphosphotriamide, ethylene glycol dimethyl ether, propionitrile, methyl ethyl ketone, diethylene glycol dimethyl ether, triethylene glycol A layer of glyceryl ether, N-methylpyrrolidone or the like, in particular, a layer of N-methylpyrrolidone can be preferably used. In the moisture adsorbent of the present invention, the thickness of the aprotic polar solvent layer can be defined as the following number 1, preferably 0.2 to 5 nm.

Further, the moisture adsorbent of the present invention preferably has a BET specific surface area of from 1 to 100 m ² /g, more preferably from 5 to 100 m ² /g, still more preferably from 10 to 60 m ² /g. When the BET specific surface area is too small, the moisture adsorption rate becomes slow, which is not preferable. If the BET specific surface area is too large, the moisture adsorption rate is too fast and it is difficult to handle it. Further, the average particle diameter is preferably from 0.05 to 10 μm, more preferably from 0.2 to 5 μm, still more preferably from 0.5 to 3 μm. When the average particle diameter is too small, the adsorption rate is too fast, and it becomes difficult to handle it. However, if it is too large, the appearance is deteriorated when applied or used as a filler.

As a mechanism for exhibiting the function of the moisture adsorbent of the present invention, it is considered that the polarity of the aprotic polar solvent layer present on the surface of the calcium oxide imparts hygroscopicity and affinity with calcium oxide, and the aprotic property imparts compatibility with the resin ( Dissolve the resin). Aprotic polar solvent layer and examples When the alkoxide layer is coated on the surface of the calcium oxide, it does not cause a reaction such as "decomposition of alkoxide into water and alcohol, reaction of an alcohol with calcium oxide to form an alkoxide", and thus it can be exerted. It has higher hygroscopicity than coating with the above reaction. In the moisture adsorbent of the present invention, the evaluation of hygroscopicity can be evaluated, for example, based on the weight increase rate of the moisture adsorbent after 120 minutes (temperature: 24 ° C, relative humidity: 55%), and the weight increase rate is preferably 10% or more, and further preferably 10 to 30%.

The moisture adsorbent of the present invention can be obtained by using calcium oxide in an aprotic polar solvent. In the presence of dry pulverization or wet pulverization, it is dried as needed, and the thickness of the aprotic polar solvent layer is adjusted to produce. In the case of wet pulverization, it may be subjected to solid-liquid separation by filtration or the like, followed by drying treatment.

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

In the production method of the present invention, the aprotic polar solvent to be used may be the same as the aprotic polar solvent layer, and these may be used singly or in combination of two or more. In the case of dry pulverization, the amount of the aprotic polar solvent to be used is preferably from 0.1 to 51% by mass, more preferably from 1 to 20% by mass, even more preferably from 1 to 15% by mass, based on the calcium oxide. When pulverization is carried out using an aprotic polar solvent, the solvent functions as a pulverization aid, and can be pulverized to fine particles having high activity and high activity while ensuring high dispersibility. In the case of wet pulverization, the amount of the aprotic polar solvent to be used is preferably from 52 to 10,000% by mass, more preferably from 500 to 5,000% by mass, even more preferably from 1,000 to 2,000% by mass, based on the calcium oxide. Further, the aprotic polar solvent preferably has a boiling point of 100 ° C or higher, more preferably 150 ° C or higher. If the boiling point is not up to At 100 ° C, the aprotic polar solvent layer is less likely to volatilize, which is not preferable.

In the present invention, the method of pulverizing is not particularly limited, and media grinding can be used. Machine, rotary ball mill, vibrating ball mill, planetary ball mill, rocking mill, paint shaker, airflow mill and other pulverizing devices. Among the pulverizing apparatuses, a pulverizing apparatus using a metal or a resin or a 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 zirconia which is made of nylon or which is less abrasive, from the viewpoint of less pollution. Further, the size of the medium can be appropriately selected depending on the particle diameter of the object to be pulverized. Further, the pulverization is preferably carried out in an inert gas atmosphere. Examples of the inert gas include helium gas or argon gas, and it is particularly preferable to carry out the reaction in a nitrogen atmosphere from the viewpoint of economy. Further, the pulverization treatment may be carried out in one stage, or the medium diameter or the pulverization apparatus may be replaced to pulverize in multiple stages.

Further, the ratio of the 90% particle diameter (D ₉₀ ) to the 10% particle diameter (D ₁₀ ) of the particle size distribution of the moisture adsorbent of the present invention D ₉₀ /D _{10 is} preferably in the range of 1.5 to 40, more preferably The particle size distribution becomes sharp in the range of 1.5 to 5.0.

In this case, the jet mill, in particular, the jet mill is preferred because it can obtain a fine and steep particle size distribution. If the particle size distribution is steep, it is preferable because the moisture absorption rate of calcium oxide is stabilized. Further, since the jet mill pulverizes the particles in the gas stream, the aprotic polar solvent on the surface of the particles can be partially removed. Therefore, there is an advantage that the drying process can be simplified or omitted. In addition, as the pulverization conditions by 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 becomes steeper in the range of 1.5 to 5.0.

Further, the drying treatment is preferably carried out by heating and drying, and may be dried under reduced pressure. Examples of the drying apparatus include a shelf type dryer, a rotary dryer, and a vibration. Dynamic dryer, vacuum dryer, etc. The drying of the calcium oxide particles having the aprotic polar solvent layer is preferably carried out while introducing an inert gas such as nitrogen or argon into the dryer to avoid aprotons due to reaction with water vapor or carbon dioxide in the environment. The polar solvent layer decomposes or produces calcium hydroxide or calcium carbonate. The temperature of the heat-drying treatment is not more than the boiling point of the aprotic polar solvent layer. For example, in the case of N-methylpyrrolidone, it is preferably 80 to 180 ° C, more preferably 120 to 170 ° C. Further, in the case of production by wet pulverization, it is preferred to carry out a drying treatment after removing excess solvent by a solid-liquid separation device such as filtration or centrifugation. The thickness of the aprotic polar solvent layer can be adjusted to a specific value by appropriately adjusting the drying conditions to remove excess solvent.

According to the present invention, it is possible to manufacture a high dispersibility and hydrophobicity at low cost and A moisture adsorbent whose moisture absorption rate is not lowered as compared with usual calcium oxide. Further, the moisture adsorbent of the present invention has an effect that the bulk density is large and it is easy to be filled in the resin, and the oil absorption amount is small, and the resin can be highly filled with a resin or the like. Further, the oil absorption amount is an index for evaluating the filling property of the powder with respect to the resin, and the method can be used for evaluation of filling property (Magazine Industrial Materials, vol. 39, No. 1, p116-117 (1991)). The oil adsorbent of the present invention preferably has an oil absorption amount of 45 ml/100 g or less.

The moisture adsorbent of the present invention can be directly used or formed into any shape to make use. Further, it can be used as a coating material filled with a suitable solvent or polymer material, a tape or a film filled with a polymer material, or the like. Therefore, it can be preferably used for a desiccant for electronic equipment such as organic EL and liquid crystal, a desiccant for a heat insulating layer such as a refrigerator or a double glazing, a moisture absorbing layer for a barrier film, and a gasket for a sealed container. (Preventing deterioration of chemicals, pharmaceuticals, and foods), coating of inner surfaces of vacuum piping, O-rings (maintaining high vacuum), etc.

Among them, the moisture adsorbent of the present invention is particularly preferably used as an organic EL element. Used. For example, the moisture adsorbent for an organic EL device can be dispersed in a synthetic resin to form a sheet, a pellet, a plate, or a film. These molded articles can be advantageously used as a desiccant for an electronic device such as an organic EL display. As the synthetic resin, a polyolefin resin, a polyacrylic resin, a polyacrylonitrile resin, a polyamide resin, a polyester resin, an epoxy resin, a polycarbonate resin, and a fluororesin can be used. Further, the moisture adsorbent of the present invention may be used by being contained in a moisture-permeable bag or container used in a usual moisture absorbent. The moisture adsorbent of the present invention may be used alone or in combination with other hygroscopic materials such as silicone or molecular sieves.

Example

Hereinafter, the present invention will be specifically described based on examples, but these are not intended to limit the object of the present invention. First, the measurement method of the physical properties of the obtained calcium oxide powder is shown below.

[Moisture absorption evaluation: weight increase rate after 120 minutes]

The weight of the dry weighing bottle was measured in advance and set to [A(g)]. About 0.6 g of the powder to be measured was placed in a weighing bottle, and the weight was accurately weighed, and it was set to [B (g)]. Open the lid of the weighing bottle containing the powder, place it in a constant temperature and humidity chamber maintained at 24 ° C and a relative humidity of 55%, measure the weight after 120 minutes, set to [C (g)], by the following Formula (1) calculates the weight increase rate.

[Number 2] Weight increase rate (%) = {C(g) - B(g)} / {B(g) - A(g)} × 100 (1)

[Method for measuring oil absorption]

According to JIS K 5101-13-2:2004 Test Method for Pigments - Part 13: Oil absorption - Section 2: Determination by boiling linseed oil method. The boiled linseed oil was added dropwise to a specific amount of the powder sample, and the amount of the oil absorption (mL/100 g) was determined from the amount of the end of the sample which was kneaded with the boiled linseed oil in a state in which the sample was wound into a spiral shape.

[Method for measuring particle size distribution]

Ethanol was used as a dispersion solvent for the sample, and a dispersion treatment was performed for 3 minutes using an ultrasonic homogenizer (MODEL US-150T, manufactured by Mikimoto Seisakusho Co., Ltd.). For the dispersed sample, 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) is available. The company's manufacture) measures the particle size distribution (D ₁₀ , D ₅₀ , D ₉₀ ).

[Method for measuring BET specific surface area]

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

[Method for evaluating the dispersibility of organic solvents]

The evaluation of the dispersibility of the sample to the organic solvent was carried out using n-hexane. 5 ml of n-hexane was placed in a glass bottle, about 0.1 g of the sample was added, and after shaking for one minute, it was allowed to stand, and the solution after 30 seconds was observed. When it was dispersed in hexane and turbid, it was evaluated that the sample had good dispersibility in an organic solvent (○). If hexane was agglomerated and hexane remained transparent and the sample was precipitated, the sample was evaluated as organic. Solvent dispersibility is poor (x).

[Method for measuring body density]

The sample was gently placed in a glove box filled with nitrogen gas to a quartz container having a volume of 4.4 cm ³ (bottom surface 10 mm × 10 mm, height 44 mm), and filled. The surface of the powder was smoothed, and the weight of the sample was accurately weighed, and it was set to [D(g)], and the bulk density was calculated by the following formula (2).

[Number 3] Bulk density (g/cm ³ ) = D (g) / 4.4 (cm ³ ) (2)

[Method of Calculating Coating Thickness]

The mass of the aprotic polar solvent (N-methylpyrrolidone in Example 1) was calculated based on the weight reduced from 20 ° C to 250 ° C as measured by a thermobalance (TG), divided by the specific gravity of the solvent ( In the case of N-methylpyrrolidone, it is 1.028), and the solvent volume per gram of calcium oxide is calculated. This was divided by the surface area per gram of calcium oxide determined by measurement of the BET specific surface area, thereby calculating the layer thickness of the coating, that is, the aprotic polar solvent.

[Measurement method of FT-IR]

The measurement by FT-IR was carried out by a single reflection measuring apparatus (ATR PRO470-H) assembled by a Fourier transform infrared spectrophotometer (FT/IR-6100, manufactured by JASCO Corporation). The measured wave number ranges from 4000 to 400 cm ^-1 .

[Example 1]

A high specific surface area oxidation was carried out by adding 120 g of zirconia beads (manufactured by Nikkato Co., Ltd.) having a diameter of 4.0 mm to a granulated product of calcined calcium hydroxide fine powder at 600 ° C in a 100 mL sealed container (made of polypropylene). Calcium granular material (BET specific surface area: 16.5 m ² /g, particle size: 2 to 3 mm) 6 g, and N-methylpyrrolidone 0.45 g, and sealed. The above operation was carried out in a glove box filled with nitrogen, and the sealed container was filled with nitrogen. The present closed container which was taken out from the glove box was pulverized by a rocking mill (manufactured by SEIWA GIKEN Co., Ltd.) at 700 rpm for 4 hours. After the treatment, the zirconia beads and the calcium oxide powder were separated using a mesh 1 mm sieve in a glove box filled with nitrogen. The separated and recovered calcium oxide powder was dried by a ladle dryer at 150 ° C for 18 hours in a nitrogen atmosphere to obtain a calcium oxide powder of Example 1 in which the surface of the particles was covered with an aprotic polar solvent layer. The obtained calcium oxide powder had an average particle diameter 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 calcium oxide (CSQ), BET specific surface area: 2.3 m ² /g, average particle diameter of 16.5 μm, manufactured by Ube Material Industries, Ltd.) was used. The 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]

Calcium oxide (nano powder particle size <160 nm (BET)) manufactured by Sigma-Aldrich was used. The calcium oxide powder had an average particle diameter 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 (nano powder particle size <160 nm (BET)) manufactured by Sigma-Aldrich was added and mixed for 10 minutes. The mixed solution was vacuum dried at 30 ° C for 12 hours to remove the solvent. The recovered dry powder was crushed in an agate mortar in a glove box filled with nitrogen to obtain a calcium oxide powder of Comparative Example 3 which was surface-treated with a fatty acid. The obtained calcium oxide powder had an average particle diameter 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]

Into a 100 mL sealed container (made of polypropylene), 120 g of zirconia beads (manufactured by Nikkato Co., Ltd.) having a diameter of 4.0 mm and high-purity calcium oxide powder (super high-purity calcium oxide (CSQ), BET specific surface area: 2.3 m ^{2 were added.} / g, an average particle diameter of 16.5 μm, manufactured by Ube Material Industries Co., Ltd., 6 g, and 0.45 g of ethanol were sealed. The above operation was carried out in a glove box filled with nitrogen, and the sealed container was filled with nitrogen. The present closed container which was taken out from the glove box was pulverized by a rocking mill (manufactured by SEIWA GIKEN Co., Ltd.) at 700 rpm for 4 hours. After the treatment, the zirconia beads were separated from the calcium oxide powder using a mesh 500 μm sieve in a glove box filled with nitrogen. The separated and recovered calcium oxide powder was dried at 150 ° C for 18 hours in a nitrogen atmosphere to obtain a calcium oxide powder of Comparative Example 4 in which the surface of the particles was covered with an alkoxide. An alkoxide layer was present on the surface of the obtained calcium oxide powder by FT-IR. The obtained calcium oxide powder had an average particle diameter of 0.83 μm and a bulk density of 0.86 g/cm ³ . Other physical properties are shown in Table 1.

[Embodiment 2]

Calcium oxide powder (BET specific surface area: 15 m ² /g, average particle diameter: 5.1 μm) obtained by calcining calcium hydroxide fine powder (BET specific surface area: 13 m ² /g, average particle diameter: 5.6 μm) at 600 ° C, 3000 g and N - Methylpyrrolidone 105 g was uniformly mixed under a nitrogen atmosphere using a 33 L internal mixer (New-Gra Machine: SEG-350, manufactured by SEISHIN ENTERPRISE CO., LTD.). The calcium oxide powder recovered from the mixer was pulverized by a 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 to obtain an aprotic The polar solvent layer covers the particle surface of the particle of the calcium oxide powder of Example 2. At the time of the pulverization treatment, nitrogen gas is used in the compressed flow system, and the entire pulverization apparatus is surrounded by a small chamber, and the inside of the pulverization chamber is set to a nitrogen atmosphere, thereby preventing the powder from coming into contact with the air as much as possible. The physical properties of the obtained calcium oxide powder are shown in Table 1.

[Example 3]

The calcium oxide powder of Example 3 in which the surface of the particles was covered with an aprotic polar solvent layer was obtained by the same method as in Example 2 except that the amount of N-methylpyrrolidone was 210 g. The physical properties of the obtained calcium oxide powder are shown in Table 1.

Claims (7)

A moisture adsorbent comprising calcium oxide particles having an aprotic polar solvent layer as a main component. The moisture adsorbent according to claim 1, wherein the aprotic polar solvent is N-methylpyrrolidone. A moisture adsorbent for an organic EL device, which uses the moisture adsorbent of claim 1 or 2. A method for producing a moisture adsorbent: dry pulverizing calcium oxide in the presence of an aprotic polar solvent. A method for producing a moisture adsorbent: wet-pulverizing calcium oxide 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 4 or 5, wherein the aprotic polar solvent is N-methylpyrrolidone. The method for producing a moisture adsorbent according to any one of claims 4 to 6, wherein the moisture adsorbent is used for an organic EL device.