METHOD FOR PRODUCING B-EUCRYPTITE FINE PARTICLES

Abstract

The β-eucryptite fine particle production method of the invention includes spraying, into an atmosphere at 50° C. to a temperature lower than 300° C., a solution containing a water-soluble lithium salt, a water-soluble aluminum salt, and colloidal silica, in such amounts that the mole proportions among lithium atoms, aluminum atoms, and silicon atoms (Li:Al:Si) are adjusted to 1:1:1, to thereby dry the solution, and, subsequently, firing the dried product in air at 600 to 1,300° C.

Claims

1-5. (canceled)

6. A method for producing β-eucryptite fine particles, the method comprising: spraying, into an atmosphere at 50° C. to a temperature lower than 300° C., a solution containing a water-soluble lithium salt, a water-soluble aluminum salt, and colloidal silica having a primary particle size, as determined through observation under a transmission electron microscope, of 2 to 50 nm, in such amounts that the mole proportions among lithium atoms, aluminum atoms, and silicon atoms (Li:Al:Si) are adjusted to 1:1:1, to thereby dry the solution, and, subsequently, firing the dried product in air or an oxidizing atmosphere at 600 to 1,300° C.

7. The method according to claim 6, wherein the β-eucryptite fine particles have a crystallite size less than 80 nm and a ratio I.sub.α/I.sub.β less than 0.05, wherein I.sub.α represents an X-ray diffraction peak intensity attributed to a (121) plane of the α phase, and I.sub.β represents an X-ray diffraction peak intensity attributed to a (102) plane of the β phase.

8. The method according to claim 6, wherein the water-soluble lithium salt is a lithium organic acid salt.

9. The method according to claim 7, wherein the water-soluble lithium salt is a lithium organic acid salt.

10. The method according to claim 6, wherein the water-soluble aluminum salt is an aluminum organic acid salt.

11. The method according to claim 7, wherein the water-soluble aluminum salt is an aluminum organic acid salt.

12. The method according to claim 8, wherein the organic acid forming the lithium organic acid salt and/or the aluminum organic acid salt is at least one species selected from the group consisting of citric acid, oxalic acid, glycolic acid, malic acid, tartaric acid, lactic acid, malonic acid, succinic acid, formic acid, and acetic acid.

13. The method according to claim 9, wherein the organic acid forming the lithium organic acid salt and/or the aluminum organic acid salt is at least one species selected from the group consisting of citric acid, oxalic acid, glycolic acid, malic acid, tartaric acid, lactic acid, malonic acid, succinic acid, formic acid, and acetic acid.

14. The method according to claim 10, wherein the organic acid forming the lithium organic acid salt and/or the aluminum organic acid salt is at least one species selected from the group consisting of citric acid, oxalic acid, glycolic acid, malic acid, tartaric acid, lactic acid, malonic acid, succinic acid, formic acid, and acetic acid.

15. The method according to claim 11, wherein the organic acid forming the lithium organic acid salt and/or the aluminum organic acid salt is at least one species selected from the group consisting of citric acid, oxalic acid, glycolic acid, malic acid, tartaric acid, lactic acid, malonic acid, succinic acid, formic acid, and acetic acid.

Description

EXAMPLES

[X-Ray Diffractometry]

[0044] X-ray diffractometry of a sample was performed by means of an X-ray diffractometer RINT Ultima+ (product of Rigaku Corporation) under the following conditions: X-ray source; Cu, voltage; 40 kV, current; 40 mA, step width; 0.04°, cumulative time; 0.5 sec/step, divergence slit 1°, longitudinal divergence limiting slit 10 mm, scattering slit 1°, and light-receiving slit 0.3 mm.

[Determination of Crystallite Size]

[0045] X-ray diffraction data of each sample was analyzed by use of analysis software JADE, and crystallite size was calculated by Scherrer's equation. The crystallite size of α phase was a size orthogonal to the (121) plane, and the crystallite size of β phase was a size orthogonal to the (102) plane.

[X-Ray Diffraction Intensity Ratio]

[0046] The X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was calculated from the X-ray diffraction data of each sample; specifically, the highest diffraction peak intensity I.sub.α attributed to a (121) plane of the α phase observed within a 2θ range from 22.3 to 22.5°, and the highest diffraction peak intensity I.sub.β attributed to a (102) plane of the β phase observed within a 2θ range from 25.2 to 25.4°.

Production Example 1

Production of Aqueous Aluminum Citrate Solution

[0047] Citric acid monohydrate (product of KANTO KAGAKU, special grade, 99.5 mass %) (210.1 g (1 mol)) was dissolved in pure water (750 g). While the thus-prepared aqueous citric acid was stirred, dried aluminum hydroxide gel (Kyoward 200S, product of Kyowa Chemical Industry Co., Ltd., Al.sub.2O.sub.3 53.3 mass %) (95.6 g (0.5 mol)) was added. The mixture was heated at 85° C. for 2 hours. During heating, a part of water was evaporated. Thus, pure water (51 g) was further added thereto, to thereby adjust the weight of the mixture to 1,019.6 g. The resultant mixture was caused to pass through a glass filter (GA-100, product of ADVANTEC) and quantitative filter paper (No. 5C, product of ADVANTEC), to thereby recover clear pale yellow aqueous solution of aluminum citrate. The thus-obtained aqueous aluminum citrate solution was found to have a solid content (as Al.sub.2O.sub.3) of 5.00 mass %.

Production Example 2

Production of Aqueous Lithium Citrate Solution

[0048] Lithium hydroxide monohydrate (product of KANTO, special grade, 98.0 mass %) (37.76 g (0.9 mol)) was dissolved in pure water (734.6 g), and then citric acid monohydrate (product of KANTO KAGAKU, special grade, 99.5 mass %) (63.0 g (0.3 mol)) was added to the solution. The mixture was stirred at room temperature for 10 minutes, to thereby form aqueous lithium citrate solution. The thus-obtained aqueous lithium citrate solution was found to have a solid content (as Li.sub.2O) of 1.60 mass %.

Production Example 3

Production of Aqueous Aluminum Oxalate Solution

[0049] Oxalic acid dihydrate (product of KANTO KAGAKU, special grade, 99.5 mass %) (378.8 g (3 mol)) was dissolved in pure water (1469.6 g). While the thus-prepared aqueous oxalic acid was stirred, dried aluminum hydroxide gel (Kyoward 200S, product of Kyowa Chemical Industry Co., Ltd., Al.sub.2O.sub.3 53.3 mass %) (191.3 g (1 mol)) was added. The mixture was heated at 85° C. for 2 hours. During heating, a part of water was evaporated. Thus, pure water (45 g) was further added thereto, to thereby adjust the weight of the mixture to 2,039.2 g. The resultant mixture was caused to pass through a glass filter (GA-100, product of ADVANTEC) and quantitative filter paper (No. 5C, product of ADVANTEC), to thereby recover clear pale yellow aqueous solution of aluminum oxalate. The thus-obtained aqueous aluminum oxalate solution was found to have a solid content (as Al.sub.2O.sub.3) of 5.00 mass %.

Production Example 4

Production of Aqueous Lithium Oxalate Solution

[0050] Lithium hydroxide monohydrate (product of KANTO, special grade, 98.0 mass %) (42.0 g (1 mol)) was dissolved in pure water (819.1 g), and then oxalic acid dihydrate (product of KANTO KAGAKU, special grade, 99.5 mass %) (63.0 g (0.5 mol)) was added to the solution. The mixture was stirred at room temperature for 10 minutes, to thereby form aqueous lithium oxalate solution. The thus-obtained aqueous lithium oxalate solution was found to have a solid content (as Li.sub.2O) of 1.62 mass %.

Production Example 5

Production of Aqueous Aluminum Malonate Solution

[0051] Malonic acid (product of KANTO KAGAKU, special grade, 99.5 mass %) (156.1 g (1.5 mol)) was dissolved in pure water (767.7 g). While the thus-prepared aqueous malonic acid was stirred, dried aluminum hydroxide gel (Kyoward 200S, product of Kyowa Chemical Industry Co., Ltd., Al.sub.2O.sub.3 53.3 mass %) (95.6 g (0.5 mol)) was added. The mixture was heated at 85° C. for 2 hours. During heating, a part of water was evaporated. Thus, bur e water (45 g) was further added thereto, to thereby adjust the weight of the mixture to 1,019,6 g. The resultant mixture was caused to pass through a glass filter (GA-100, product of ADVANTEC) and quantitative filter paper (No. 5C, product of ADVANTEC), to thereby recover clear pale yellow aqueous solution of aluminum malonate, The thus-obtained aqueous aluminum malonate solution was found to have a solid content (as Al.sub.2O.sub.3) of 5.00 mass %.

Production Example 6

Production of Aqueous Lithium Malonate Solution

[0052] Lithium hydroxide monohydrate (product of KANTO, special grade, 98.0 mass %) (42.0 g (1 mol)) was dissolved in pure water (370.4 g), and then malonic acid (product of KANTO KAGAKU, special grade, 99.5 mass %) (52.0 g (0.5 mol)) was added to the solution. The mixture was stirred at room temperature for 10 minutes, to thereby form aqueous lithium malonate solution. The thus-obtained aqueous lithium malonate solution was found to have a solid content (as Li.sub.2O) of 3.22 mass %.

Example 1

[0053] The aqueous aluminum citrate solution produced in Production Example 1 (917.6 g (Al.sub.2O.sub.3 0.45 mol) and the aqueous lithium citrate solution produced in Production Example 2 (835.4 g) were added to colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm) (515.0 g (SiO.sub.2 0.9 mol)). The resultant mixture was stirred at room temperature for 10 minutes. The thus-obtained liquid mixture was found to have a specific weight of 1.075, a pH of 2.8, and an electric conductivity of 15.0 mS/cm. The liquid mixture was dried by means of a spray dryer (Purvis Mini Spray GB210-A, product of Yamato Scientific Co., Ltd.) under the following conditions: inlet temperature; 185° C., atomizing air pressure; 1.4 kgf/cm.sup.2, aspirator flow; 0.50 m.sup.3/minute, and liquid mixture feeding rate; 4 g/minute. The outlet temperature was 80±3° C. The thus-obtained dry powder (3.0 g) was placed in an alumina crucible and fired in air at 800° C. for 1 hour by means of an electric furnace, to thereby yield a white powder with a pale gray tone (0.7 g). The powder was identified by X-ray diffraction. As a result, the formed phase was found to be substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was less than 0.01. The β phase was found to have a crystallite size of 62 nm. The specific surface area, determined through the nitrogen adsorption method, was 1.6 m.sup.2/g.

Example 2

[0054] The procedure of Example 1 was repeated, except that the unfired powder was calcined in air at 500° C. for 5 hours by means of an electric furnace, before firing in air at 800° C. The obtained white powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was less than 0.01. The β phase was found to have a crystallite size of 61 nm. The specific surface area, determined through the nitrogen adsorption method, was 1.3 m.sup.2/g.

Example 3

[0055] The aqueous aluminum oxalate solution produced in Production Example 3 (1,019.6 g (Al.sub.2O.sub.3 0.5 mol) and the aqueous lithium oxalate solution produced in Production Example 4 (924.1 g (Li.sub.2O 0.5 mol)) were added to colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm) (572.2 g (SiO.sub.2 1 mol)). The resultant mixture was stirred at room temperature for 10 minutes. The thus-obtained liquid mixture was found to have a specific weight of 1.068, a pH of 2.0, and an electric conductivity of 22.3 mS/cm. The liquid mixture was dried by means of a spray dryer (Purvis Mini Spray GB210-A, product of Yamato Scientific Co., Ltd.) under the following conditions: inlet temperature; 185° C., atomizing air pressure; 1.4 kgf/cm.sup.2, aspirator flow; 0.50 m.sup.3/minute, and liquid mixture feeding rate; 4 g/minute. The outlet temperature was 80±3° C. The thus-obtained dry powder (3.0 g) was placed in an alumina crucible and fired in air at 800° C. for 1 hour by means of an electric furnace, to thereby yield a white powder (1.1 g). The powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.02. The β phase was found to have a crystallite size of 46 nm. The specific surface area, determined through the nitrogen adsorption method, was 4.1 m.sup.2/g.

Example 4

[0056] The procedure of Example 1 was repeated, except that the temperature in firing in air for 1 hour was changed to 900° C., after spray drying of a liquid mixture of colloidal silica, aqueous aluminum citrate, and aqueous lithium citrate, to thereby yield a white powder (0.9 g). The obtained white powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was less than 0.01. The β phase was found to have a crystallite size of 65 nm. The specific surface area, determined through the nitrogen adsorption method, was 1.6 m.sup.2/g.

Example 5

[0057] The procedure of Example 3 was repeated, except that the firing in air was performed at 600° C. for 20 hours, after spray drying of a liquid mixture of colloidal silica, aqueous aluminum oxalate, and aqueous lithium oxalate, to thereby yield a white powder (1.1 g). The obtained white powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.03. The β phase was found to have a crystallite size of 44 nm. The specific surface area, determined through the nitrogen adsorption method, was 7.3 m.sup.2/g.

Example 6

[0058] The procedure of Example 1 was repeated, except that colloidal silica (SNOWTEX (registered trademark) OL, product of Nissan Chemical industries, Ltd., silica content: 40.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 42 nm) was used instead of colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm). The thus-obtained pale gray-tone, white powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.03. The β phase was found to have a crystallite size of 24 nm. The specific surface area, determined through the nitrogen adsorption method, was 24.7 m.sup.2/g.

Example 7

[0059] The aqueous aluminum malonate solution produced in Production Example 5 (1,019.6 g (Al.sub.2O.sub.3 0.5 mol) and the aqueous lithium malonate solution produced in Production Example 6 (464.4 g (Li.sub.2O 0.5 mol)) were added to colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm) (572.2 g (SiO.sub.2 1 mol)). The formed mixture was stirred at room temperature for 10 minutes. The resultant liquid mixture was found to have a specific weight of 1.090, a pH of 3.83, and an electric conductivity of 15.6 mS/cm. The liquid mixture was dried by means of a spray dryer (Purvis Mini Spray GE210-A, product of Yamato Scientific Co., Ltd.) under the following conditions: inlet temperature; 185° C., atomizing air pressure; 1.4 kgf/cm.sup.2, aspirator flow; 0.50 m.sup.3/minute, and liquid mixture feeding rate; 4 g/minute. The outlet temperature was 80±3° C. The thus-obtained dry powder (3.0 g) was placed in an alumina crucible and calcined in air at 500° C. for 5 hours by means of an electric furnace. Then, the calcined product was fired in air at 800° C. for 1 hour, to thereby yield a white powder (0.8 g). The white powder was identified by X-ray diffraction. As a result, the formed phase was substantially a single phase composed of β-eucryptite, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.04. The β phase was found to have a crystallite size of 41 nm. The specific surface area, determined through the nitrogen adsorption method, was 2.7 m.sup.2/g.

Comparative Example 1

[0060] The procedure of Example 1 was repeated, except that firing in air was performed by means of the electric furnace at 500° C. for 5 hours. The thus-obtained black powder was identified by X-ray diffraction. As a result, a halo pattern was observed. Thus, a β-eucryptite crystalline phase was not identified.

Comparative Example 2

[0061] The procedure of Example 1 was repeated, except that, instead of carrying out spray drying of the liquid mixture in the drying step, the liquid mixture was placed in an eggplant-shaped flask and subjected to drying under reduced pressure at 30 Torr by means of a rotary evaporator. The thus-obtained pale gray-tone, white powder was identified by X-ray diffraction. As a result, the formed phase was found to he a mixed phase composed of the α phase and the β phase, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.13. The β phase was found to have a crystallite size of 34 nm. The specific surface area, determined through the nitrogen adsorption method, was 10.1 m.sup.2/g.

Comparative Example 3

[0062] The procedure of Example 1 was repeated, except that colloidal silica (SNOWTEX (registered trademark) OLZ, product of Nissan Chemical Industries, Ltd silica content: 35.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 80 nm) was used instead of colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm). The thus-obtained pale gray-tone, white powder was identified by X-ray diffraction. As a result, the formed phase was a mixed phase composed of the α phase and the β phase, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.08. Furthermore, a halo pattern attributed to an amorphous phase was observed. The β phase was found to have a crystallite size of 34 nm. The specific surface area, determined through the nitrogen adsorption method, was 10.1 m.sup.2/g.

Comparative Example 4

[0063] An aqueous solution prepared by dissolving lithium hydroxide monohydrate (4.20 g) in pure water (50 g) was added to colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm) (57.2 g). Subsequently, dried aluminum hydroxide gel (Kyoward 200S, product of Kyowa Chemical Industry Co., Ltd., Al.sub.2O.sub.3 53.3 mass %) (9.57 g) was added thereto. The mixture was stirred for 10 minutes, to thereby prepare a slurry. The slurry-form mixture was placed in an eggplant-shaped flask and subjected to drying under reduced pressure at 30 Torr by means of a rotary evaporator. The thus-obtained white powder was placed in an alumina crucible and fired in air at 800° C. for 1 hour by means of an electric furnace, to thereby yield a white powder. The powder was identified by X-ray diffraction. As a result, the formed phase was a mixed phase composed of the α phase and the β phase, and the X-ray diffraction peak intensity ratio I.sub.α/I.sub.β was 0.17. The β phase was found to have a crystallite size of 24 nm. The specific surface area, determined through the nitrogen adsorption method, was 24.8 m.sup.2/g.

Comparative Example 5

[0064] An aqueous solution prepared by dissolving lithium hydroxide monohydrate (4.20 g) in pure water (50 g) was added to colloidal silica (SNOWTEX (registered trademark) OXS, product of Nissan Chemical Industries, Ltd., silica content: 10.5 mass %, and primary particle size (determined through observation under a transmission electron microscope): 5 nm) (57.2 g). Subsequently, dried aluminum hydroxide gel (Kyoward 200S, product of Kyowa Chemical Industry Co., Ltd., Al.sub.2O.sub.3 53.3 mass %) (9.57 g) was added thereto. The mixture was stirred for 10 minutes, to thereby prepare a slurry. The slurry-form mixture was tried to be dried by means of a spray dryer (Purvis Mini Spray GE210-A, product of Yamato Scientific Co., Ltd.) under the following conditions: inlet temperature; 185° C., atomizing air pressure; 1.4 kgf/cm.sup.2, aspirator flow; 0.50 m.sup.3/minute, and liquid mixture feeding rate; 4 g/minute. However, a nozzle of the dryer was immediately plugged, and spraying was incomplete.

INDUSTRIAL APPLICABILITY

[0065] According to the production method of the present invention, β-eucryptite fine particles can be produced at a firing temperature lower than that employed in a conventional technique. The thus-obtained powder has excellent crushability or disintegrability and serves as a useful filler which can enhance the insulation property of a resin for use in a printed wiring board and a semiconductor sealing material and which can reduce CTE.