JP4807347B2 - Method for producing oxide-coated copper fine particles - Google Patents
Method for producing oxide-coated copper fine particles Download PDFInfo
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- JP4807347B2 JP4807347B2 JP2007280012A JP2007280012A JP4807347B2 JP 4807347 B2 JP4807347 B2 JP 4807347B2 JP 2007280012 A JP2007280012 A JP 2007280012A JP 2007280012 A JP2007280012 A JP 2007280012A JP 4807347 B2 JP4807347 B2 JP 4807347B2
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- 239000010949 copper Substances 0.000 title claims description 126
- 229910052802 copper Inorganic materials 0.000 title claims description 124
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims description 117
- 239000010419 fine particle Substances 0.000 title claims description 106
- 238000004519 manufacturing process Methods 0.000 title claims description 25
- 239000011248 coating agent Substances 0.000 claims description 40
- 229910052782 aluminium Inorganic materials 0.000 claims description 39
- 238000000576 coating method Methods 0.000 claims description 39
- 239000011247 coating layer Substances 0.000 claims description 32
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 29
- 239000007771 core particle Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 17
- 239000007900 aqueous suspension Substances 0.000 claims description 16
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 14
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 12
- 239000004202 carbamide Substances 0.000 claims description 12
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 9
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 claims description 7
- 235000019982 sodium hexametaphosphate Nutrition 0.000 claims description 7
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 7
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 claims description 3
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical group [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 claims description 3
- 238000013461 design Methods 0.000 description 29
- 230000003647 oxidation Effects 0.000 description 25
- 238000007254 oxidation reaction Methods 0.000 description 25
- 239000002932 luster Substances 0.000 description 20
- 229910052751 metal Inorganic materials 0.000 description 15
- 239000002184 metal Substances 0.000 description 15
- 239000000049 pigment Substances 0.000 description 14
- 239000002245 particle Substances 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000002411 thermogravimetry Methods 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000003973 paint Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 4
- -1 aluminum compound Chemical class 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 230000001747 exhibiting effect Effects 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000002845 discoloration Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000001639 boron compounds Chemical class 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 230000000640 hydroxylating effect Effects 0.000 description 1
- 230000033444 hydroxylation Effects 0.000 description 1
- 238000005805 hydroxylation reaction Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000000976 ink Substances 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 239000011859 microparticle Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
Description
本発明は、酸化物被覆銅微粒子の製造方法に関し、さらに詳しくは、顔料用金属微粒子として、優れた耐酸化性を有する一方、金属光沢等の銅の意匠性を発現させることができる酸化物被覆銅微粒子の製造方法に関する。 The present invention relates to a method for producing oxide-coated copper fine particles, and more particularly, as an oxide-coated copper fine particle, an oxide coating having excellent oxidation resistance and capable of exhibiting copper design properties such as metallic luster. The present invention relates to a method for producing copper fine particles.
近年、メタリック塗料やメタリックインキは、その独特の意匠から自動車の外装をはじめとして様々な分野で使用されている。ここで用いられるメタリック塗料においては、主に塗料中に含まれる鱗片状の金属顔料が入射光を反射することにより、独特の輝く意匠性が発現されるものである。前記メタリック塗料用の金属顔料としては、表面に形成される自然酸化保護膜による高い耐酸化性や優れた金属光沢から、主としてアルミニウムが広く用いられている。一方、最近の動向としてアルミニウムにはない有色の金属光沢を示す金属顔料として、銅が注目されている。しかしながら、銅においては、アルミニウムのような自然酸化保護膜を形成しないことから、金属の意匠性を維持しつつ耐酸化性を獲得することが求められていた。 In recent years, metallic paints and metallic inks are used in various fields such as automobile exteriors due to their unique design. In the metallic paint used here, a unique shining design is manifested mainly by the scale-like metal pigment contained in the paint reflecting incident light. As the metallic pigment for the metallic paint, aluminum is mainly widely used because of its high oxidation resistance by the natural oxidation protective film formed on the surface and excellent metallic luster. On the other hand, as a recent trend, copper is attracting attention as a metallic pigment exhibiting a colored metallic luster not found in aluminum. However, since copper does not form a natural oxidation protective film such as aluminum, it has been required to obtain oxidation resistance while maintaining the design of the metal.
このための手段として、酸化物被覆の金属微粒子が考えられる。例えば、熱プラズマに原料混合物を供給し、様々な金属微粒子上に様々な酸化物が被覆された酸化物被覆金属微粒子を得る方法として、平均厚みが１〜１０ｎｍの酸化物被覆層が、堅固に、かつ好ましくは全表面に完全に被覆された酸化物被覆金属微粒子が得られることが開示されている（例えば、特許文献１参照。）。しかしながら、この方法では、耐酸化性、金属光沢等についての記述がないため、金属微粒子本来の特性がどの程度維持されているか明らかではない。しかも、ＴＥＭ像によると、粒子の凝集により、被覆層同士が一体化しており、粒度分布の制御が難しい。さらには、装置が高価であり、かつ、装置内壁への酸化物付着量が多いため、低コストで製造するのは困難であるという問題がある。 As means for this purpose, oxide-coated metal fine particles can be considered. For example, as a method of supplying a raw material mixture to thermal plasma and obtaining oxide-coated metal fine particles in which various oxides are coated on various metal fine particles, an oxide coating layer having an average thickness of 1 to 10 nm is firmly formed. It is disclosed that oxide-coated metal fine particles that are completely coated on the entire surface can be obtained (see, for example, Patent Document 1). However, in this method, since there is no description about oxidation resistance, metallic luster, etc., it is not clear how much the original characteristics of the metal fine particles are maintained. Moreover, according to the TEM image, the coating layers are integrated due to aggregation of particles, and it is difficult to control the particle size distribution. Furthermore, since the apparatus is expensive and the amount of oxide attached to the inner wall of the apparatus is large, it is difficult to manufacture at low cost.
また、銅粉に対して無機酸化物を被覆する技術としては、例えば、水系においてアルミニウム化合物とホウ素化合物又はリン化合物ゲルを銅粉表面に析出させる技術が示されている（例えば、特許文献２参照。）。この方法によれば、耐酸化性や設備面の問題を解決できる可能性がある。しかし、基材表面にゲル状の被覆を施すことにより、顔料としての意匠性が損なわれてしまう可能性があり、意匠を維持できるレベルで十分な耐酸化性を付与できるかが不明である。 Moreover, as a technique for coating the copper powder with an inorganic oxide, for example, a technique for depositing an aluminum compound and a boron compound or a phosphorus compound gel on the surface of the copper powder in an aqueous system is shown (for example, see Patent Document 2). .) According to this method, there is a possibility that problems of oxidation resistance and equipment can be solved. However, by applying a gel-like coating to the substrate surface, the design properties as a pigment may be impaired, and it is unclear whether sufficient oxidation resistance can be imparted at a level that can maintain the design.
以上の状況から、有色の金属光沢を持ちかつ耐酸化性に優れた金属顔料を簡易なプロセスで製造する技術が求められている。 From the above situation, there is a demand for a technique for producing a metal pigment having a colored metallic luster and excellent oxidation resistance by a simple process.
本発明の目的は、上記の従来技術の問題点に鑑み、顔料用金属微粒子として、優れた耐酸化性を有する一方、金属光沢等の銅の意匠性を発現させることができる酸化物被覆銅微粒子を効率的に製造する方法を提供することである。 In view of the above-mentioned problems of the prior art, an object of the present invention is an oxide-coated copper fine particle that has excellent oxidation resistance as a metal fine particle for pigments and can exhibit copper design properties such as metallic luster. It is providing the method of manufacturing efficiently.
本発明者らは、上記目的を達成するために、酸化物被覆銅微粒子について、鋭意研究を重ねた結果、特定の条件によりアルミニウム水酸化物からなる被覆層を有する銅微粒子を形成する工程（Ａ）、前記被覆層を有する銅微粒子を固液分離して、乾燥処理を行う工程（Ｂ）、及び特定の条件でアルミニウム水酸化物を熱分解する工程（Ｃ）、を含む方法を用いたところ、金属顔料として用いた場合に、優れた耐酸化性を有する一方、金属光沢等の銅の意匠性を発現させることができる酸化物被覆銅微粒子が得られることを見出し、本発明を完成した。 In order to achieve the above object, the present inventors have conducted extensive research on oxide-coated copper fine particles, and as a result, a process of forming copper fine particles having a coating layer made of aluminum hydroxide under specific conditions (A ), A method including a step (B) of solid-liquid separation of the copper fine particles having the coating layer and performing a drying treatment, and a step (C) of thermally decomposing aluminum hydroxide under specific conditions. When used as a metal pigment, the inventors have found that oxide-coated copper fine particles can be obtained that have excellent oxidation resistance while being able to express the design properties of copper such as metallic luster, thereby completing the present invention.
すなわち、本発明の第１の発明によれば、銅微粒子からなる芯粒子（ａ）と、芯粒子（ａ）の表面上に形成されたアルミニウムを主成分として含む酸化物からなる被覆層（ｂ）とから構成される酸化物被覆銅微粒子の製造方法であって、
下記の工程（Ａ）〜（Ｃ）を含むことを特徴とする酸化物被覆銅微粒子の製造方法が提供される。
工程（Ａ）：銅微粒子を含む水性懸濁液中に、アルミニウム塩と尿素とを含む水溶液を供給して、アルミニウム水酸化物を主成分とする水酸化物からなる被覆層（ｃ）を有する銅微粒子を、下記の要件を満足する被覆量で形成する。
上記被覆量は、質量％の単位で表した前記酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を、［ｍ２・ｇ−１］の単位で表した芯粒子（ａ）の比表面積で除した値が、０．２〜１．２［質量％／（ｍ２・ｇ−１）］であるように制御される。
工程（Ｂ）：前記工程（Ａ）で形成した被覆層（ｃ）を有する銅微粒子を固液分離した後、乾燥処理に付す。
工程（Ｃ）：前記工程（Ｂ）で得た乾燥処理後の銅微粒子を還元雰囲気下に１８０〜３３０℃の温度で加熱処理に付し、前記被覆層（ｃ）を熱分解する。
That is, according to the first invention of the present invention, the core particles (a) made of copper fine particles and the coating layer (b) made of an oxide containing aluminum as a main component formed on the surface of the core particles (a). And a method for producing oxide-coated copper fine particles comprising:
Provided is a method for producing oxide-coated copper fine particles, which comprises the following steps (A) to (C).
Step (A): Supplying an aqueous solution containing an aluminum salt and urea into an aqueous suspension containing copper fine particles, and having a coating layer (c) made of a hydroxide mainly composed of an aluminum hydroxide. Copper fine particles are formed in a coating amount that satisfies the following requirements.
The said coating amount is the core particle which represented the composition ratio of the content of aluminum with respect to the content of the copper in the said oxide covering copper fine particle represented in the unit of the mass% in the unit of [m < 2 > * g <-1 >]. The value divided by the specific surface area of a) is controlled to be 0.2 to 1.2 [mass% / (m 2 · g −1 )].
Step (B): The copper fine particles having the coating layer (c) formed in the step (A) are solid-liquid separated and then subjected to a drying treatment.
Step (C): The copper fine particles after the drying treatment obtained in the step (B) are subjected to a heat treatment at a temperature of 180 to 330 ° C. in a reducing atmosphere to thermally decompose the coating layer (c).
また、本発明の第２の発明によれば、第１の発明において、前記アルミニウム塩と尿素とを含む水溶液を、銅微粒子を含む水性懸濁液中に供給する前に、３０〜１００℃の温度で加熱処理に付すことを特徴とする酸化物被覆銅微粒子の製造方法が提供される。 According to the second invention of the present invention, in the first invention, before supplying the aqueous solution containing the aluminum salt and urea into the aqueous suspension containing copper fine particles, Provided is a method for producing oxide-coated copper fine particles, which is subjected to a heat treatment at a temperature.
また、本発明の第３の発明によれば、第１又は２の発明において、前記アルミニウム塩は、硫酸アルミニウム又は硝酸アルミニウムであることを特徴とする酸化物被覆銅微粒子の製造方法が提供される。 According to a third aspect of the present invention, there is provided the method for producing oxide-coated copper fine particles according to the first or second aspect, wherein the aluminum salt is aluminum sulfate or aluminum nitrate. .
また、本発明の第４の発明によれば、第１〜３いずれかのの発明において、前記水性懸濁液中に、ヘキサメタリン酸ナトリウムを添加することを特徴とする酸化物被覆銅微粒子の製造方法が提供される。 According to a fourth invention of the present invention, in any one of the first to third inventions, sodium hexametaphosphate is added to the aqueous suspension. A method is provided.
本発明の製造方法によれば、顔料用金属微粒子として、優れた耐酸化性を有する一方、金属光沢等の銅の意匠性を発現させることができる酸化物被覆銅微粒子を効率的に製造することができる。さらに、本発明の製造方法によって得られる酸化物被覆銅微粒子は、その金属光沢などの意匠性を維持し、かつ、酸化による変色が緩和されており、金属顔料として好適であり、その工業的価値は極めて大きい。 According to the production method of the present invention, it is possible to efficiently produce oxide-coated copper fine particles that have excellent oxidation resistance and can exhibit copper design properties such as metallic luster, as metal fine particles for pigments. Can do. Furthermore, the oxide-coated copper fine particles obtained by the production method of the present invention maintain its design properties such as its metallic luster, and the discoloration due to oxidation is mitigated, making it suitable as a metal pigment and its industrial value. Is extremely large.
以下、本発明の酸化物被覆銅微粒子の製造方法を詳細に説明する。
本発明の酸化物被覆銅微粒子の製造方法は、銅微粒子からなる芯粒子（ａ）と、芯粒子（ａ）の表面上に形成されたアルミニウムを主成分として含む酸化物からなる被覆層（ｂ）とから構成される酸化物被覆銅微粒子の製造方法であって、下記の工程（Ａ）〜（Ｃ）を含むことを特徴とする。
工程（Ａ）：銅微粒子を含む水性懸濁液中に、アルミニウム塩と尿素とを含む水溶液を供給して、アルミニウム水酸化物を主成分とする水酸化物からなる被覆層（ｃ）を有する銅微粒子を、下記の要件を満足する被覆量で形成する。
上記被覆量は、質量％の単位で表した前記酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を、［ｍ２・ｇ−１］の単位で表した芯粒子（ａ）の比表面積で除した値が、０．２〜１．２［質量％／（ｍ２・ｇ−１）］であるように制御される。
工程（Ｂ）：前記工程（Ａ）で形成した被覆層（ｃ）を有する銅微粒子を固液分離した後、乾燥処理に付す。
工程（Ｃ）：前記工程（Ｂ）で得た乾燥処理後の銅微粒子を還元雰囲気下に１８０〜３３０℃の温度で加熱処理に付し、前記被覆層（ｃ）を熱分解する。
これによって、顔料用金属微粒子として、優れた耐酸化性を有する一方、金属光沢等の銅の意匠性を発現させることができる酸化物被覆銅微粒子を効率的に製造することができる。
Hereinafter, the manufacturing method of the oxide covering copper fine particle of this invention is demonstrated in detail.
The method for producing oxide-coated copper fine particles of the present invention comprises a core particle (a) made of copper fine particles and a coating layer made of an oxide containing aluminum as a main component formed on the surface of the core particles (a) (b ), And the following steps (A) to (C) are included.
Step (A): Supplying an aqueous solution containing an aluminum salt and urea into an aqueous suspension containing copper fine particles, and having a coating layer (c) made of a hydroxide mainly composed of an aluminum hydroxide. Copper fine particles are formed in a coating amount that satisfies the following requirements.
The said coating amount is the core particle which represented the composition ratio of the content of aluminum with respect to the content of the copper in the said oxide covering copper fine particle represented in the unit of the mass% in the unit of [m < 2 > * g <-1 >]. The value divided by the specific surface area of a) is controlled to be 0.2 to 1.2 [mass% / (m 2 · g −1 )].
Step (B): The copper fine particles having the coating layer (c) formed in the step (A) are solid-liquid separated and then subjected to a drying treatment.
Step (C): The copper fine particles after the drying treatment obtained in the step (B) are subjected to a heat treatment at a temperature of 180 to 330 ° C. in a reducing atmosphere to thermally decompose the coating layer (c).
As a result, it is possible to efficiently produce oxide-coated copper fine particles that have excellent oxidation resistance as metal fine particles for pigments and can exhibit copper design properties such as metallic luster.
本発明の製造方法において、工程（Ａ）において銅微粒子を含む水性懸濁液中にアルミニウム塩と尿素とを含む水溶液を供給する際に、最終的に得られる酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を芯粒子（ａ）の比表面積で除した値が所定値になるように、得られる被覆層（ｃ）を有する銅微粒子の被覆量を制御して形成されることが、特に重要である。 In the production method of the present invention, when an aqueous solution containing an aluminum salt and urea is supplied to an aqueous suspension containing copper fine particles in step (A), the copper in the oxide-coated copper fine particles finally obtained is supplied. Formed by controlling the coating amount of the copper fine particles having the resulting coating layer (c) so that the value obtained by dividing the composition ratio of the aluminum content to the content by the specific surface area of the core particle (a) becomes a predetermined value. It is particularly important that
すなわち、上記製造方法の工程（Ａ）は、銅微粒子を含む水性懸濁液中に、アルミニウム塩と尿素とを含む水溶液を供給して、アルミニウム水酸化物を主成分とする水酸化物からなる被覆層（ｃ）を有する銅微粒子を、下記の要件を満足する被覆量で形成する。
上記被覆量は、質量％の単位で表した前記酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を、［ｍ２・ｇ−１］の単位で表した芯粒子（ａ）の比表面積で除した値（以下、Ａｌ含有定数と呼称する場合がある。）が、０．２〜１．２［質量％／（ｍ２・ｇ−１）］、好ましくは０．６〜１．０［質量％／（ｍ２・ｇ−１）］であるように制御される。なお、前記質量％の単位で表した組成割合としては、最終的に生成される酸化物被覆銅微粒子のアルミニウム品位と銅品位から、（アルミニウム品位／銅品位）×１００なる算出式で求められる。
That is, the step (A) of the above production method comprises an hydroxide containing aluminum hydroxide as a main component by supplying an aqueous solution containing an aluminum salt and urea into an aqueous suspension containing copper fine particles. The copper fine particles having the coating layer (c) are formed in a coating amount that satisfies the following requirements.
The said coating amount is the core particle which represented the composition ratio of the content of aluminum with respect to the content of the copper in the said oxide covering copper fine particle represented in the unit of the mass% in the unit of [m < 2 > * g <-1 >]. The value obtained by dividing by the specific surface area of a) (hereinafter sometimes referred to as Al content constant) is 0.2 to 1.2 [mass% / (m 2 · g −1 )], preferably 0. It is controlled to be 6 to 1.0 [mass% / (m 2 · g −1 )]. In addition, the composition ratio expressed in the unit of mass% can be obtained from the aluminum quality and the copper quality of the finally produced oxide-coated copper fine particles by a calculation formula of (aluminum quality / copper quality) × 100.
これにより、芯粒子（ａ）の表面積に応じて、被覆するアルミニウム量を変化させて、芯粒子（ａ）の比表面積あたりの被覆量を所定値に調整して、被覆層の厚さを所望の状態に制御することができる。
すなわち、Ａｌ含有定数が１．２［質量％／（ｍ２・ｇ−１）］を超えると、被覆層が厚すぎるので、芯粒子（ａ）の意匠性が損なわれる。一方、Ａｌ含有定数が０．２［質量％／（ｍ２・ｇ−１）］未満では、被覆粒子に十分な耐酸化性を付与することができない。
Thereby, according to the surface area of the core particles (a), the amount of aluminum to be coated is changed, and the coating amount per specific surface area of the core particles (a) is adjusted to a predetermined value, and the thickness of the coating layer is desired. Can be controlled to the state.
That is, when the Al content constant exceeds 1.2 [% by mass / (m 2 · g −1 )], the coating layer is too thick, so that the design of the core particle (a) is impaired. On the other hand, if the Al content constant is less than 0.2 [% by mass / (m 2 · g −1 )], sufficient oxidation resistance cannot be imparted to the coated particles.
上記工程（Ａ）において、まず、所定のコート液を準備する。前記コート液としては、最終的に得られる酸化物被覆銅微粒子中のＡｌ含有定数が０．２〜１．２［質量％／（ｍ２・ｇ−１）］となるに十分な量のアルミニウム塩と尿素とを含む水溶液を用いる。 In the step (A), first, a predetermined coating solution is prepared. As the coating liquid, an aluminum content sufficient to have an Al content constant of 0.2 to 1.2 [mass / (m 2 · g −1 )] in the finally obtained oxide-coated copper fine particles. An aqueous solution containing salt and urea is used.
ここで、アルミニウム塩は水酸化物となり被覆剤として用いられ、また、尿素は、塩基として用いられるので、アルミニウム塩を水酸化するための十分な量が用いられる。このとき、銅微粒子上への被覆量としては、被覆に際しての反応条件により影響される。例えば、アルミニウムに関しては、銅微粒子の比表面積等の形状要因、尿素の含有量、コート液の供給条件等の反応条件により反応速度が影響されるため、未反応等によって被覆層（ｃ）中、すなわち被覆層（ｂ）中のアルミニウム量がコート液中のアルミニウム量より少なくなる場合があるので、コート液中のアルミニウム量を、上記被覆に際しての反応条件に対して事前に求めておいた、通常は目標とするＡｌ含有定数より求められる値よりも過剰量である添加量にすることにより、Ａｌ含有定数を所定値に制御することが好ましい。なお、後続の工程（Ｂ）、（Ｃ）では、アルミニウムの損失量は実質的に無視できるので、被覆層（ｃ）中に含まれるアルミニウムは、そのまま被覆層（ｂ）中に含有される。 Here, since the aluminum salt becomes a hydroxide and is used as a coating agent, and urea is used as a base, a sufficient amount for hydroxylating the aluminum salt is used. At this time, the amount of coating on the copper fine particles is affected by the reaction conditions during coating. For example, for aluminum, since the reaction rate is affected by the shape factors such as the specific surface area of the copper fine particles, the urea content, and the reaction conditions such as the supply condition of the coating liquid, in the coating layer (c) due to unreacted, That is, since the amount of aluminum in the coating layer (b) may be less than the amount of aluminum in the coating solution, the amount of aluminum in the coating solution has been determined in advance with respect to the reaction conditions for the above coating. It is preferable to control the Al content constant to a predetermined value by setting the addition amount to an excess amount from the value obtained from the target Al content constant. In the subsequent steps (B) and (C), the amount of aluminum loss can be substantially ignored, so the aluminum contained in the coating layer (c) is contained in the coating layer (b) as it is.
また、必要に応じて、コート液を調製する際に、前記コート液を、銅微粒子を含む水性懸濁液中に供給する前に、３０〜１００℃の温度で加熱処理に付すことができる。これにより、コート液中のアルミニウム塩の水酸化を進めることができ、銅微粒子を含む水性懸濁液中に供給したときに被覆層を効率よく形成させることができる。なお、加熱後のコート液は透明であり、微粒子の晶出は認められない。ここで、コート液中のアルミニウム塩と尿素の濃度は、特に限定されるものではないが、例えば、それぞれ、０．００７〜０．１４ｍｏｌ／Ｌ、０．０９〜１８ｇ／Ｌが好ましい。 Moreover, when preparing a coating liquid as needed, before supplying the said coating liquid in the aqueous suspension containing a copper microparticle, it can attach | subject to heat processing at the temperature of 30-100 degreeC. Thereby, the hydroxylation of the aluminum salt in the coating liquid can be promoted, and the coating layer can be efficiently formed when supplied into an aqueous suspension containing copper fine particles. The coating solution after heating is transparent and no crystallization of fine particles is observed. Here, although the density | concentration of the aluminum salt and urea in a coating liquid is not specifically limited, For example, 0.007-0.14 mol / L and 0.09-18 g / L are respectively preferable.
次いで、コート液を懸濁液中に供給すると、銅微粒子上にアルミニウム水酸化物を主成分として含む水酸化物の被覆層を形成する。なお、アルミニウム水酸化物を形成するための水酸基は水から供給される。この際、銅微粒子と水の重量比としては、特に限定されるものではないが、水酸基を供給するのに十分な水が必要である。 Next, when the coating liquid is supplied into the suspension, a hydroxide coating layer containing aluminum hydroxide as a main component is formed on the copper fine particles. In addition, the hydroxyl group for forming aluminum hydroxide is supplied from water. At this time, the weight ratio of the copper fine particles to water is not particularly limited, but sufficient water is required to supply the hydroxyl group.
また、上記方法では、被覆の速度が緩やかであるため、銅微粒子同士の接触部の被覆層による連結も緩やかに進む。したがって、芯粒子（ａ）の分散を十分に行い、かつ、懸濁液の攪拌を十分に行うことにより、連結が破壊され、芯粒子（ａ）と同程度の粒度分布を持った被覆粒子を得ることができる。しかしながら、上記コート液の供給速度が速すぎる場合には、連結が顕著になるとともに均一な被覆が妨げられる場合がある。コート供給速度は、できるだけ遅くすることが好ましいが、生産性を考慮すると、芯粒子（ａ）の表面積あたりのアルミニウム供給量を０．００００５〜０．００１ｇ／分とすることが好ましく、０．００００５〜０．０００５ｇ／分とすることがより好ましい。 Moreover, in the said method, since the speed | rate of coating | cover is slow, the connection by the coating layer of the contact part of copper fine particles also advances moderately. Therefore, by sufficiently dispersing the core particles (a) and sufficiently stirring the suspension, the connection is broken, and the coated particles having the same particle size distribution as the core particles (a) are obtained. Obtainable. However, when the coating liquid supply rate is too high, the connection becomes remarkable and uniform coating may be hindered. The coat supply rate is preferably as slow as possible, but considering the productivity, the aluminum supply amount per surface area of the core particles (a) is preferably 0.00005 to 0.001 g / min. More preferably, it is set to -0.0005 g / min.
上記工程（Ａ）で用いる銅微粒子としては、一般的に得られる銅粒子であればその形状は問われないが、メタリック塗料用の金属顔料として用いる場合には、広い平滑面を有した板状の形状が好ましい。 The shape of the copper fine particles used in the step (A) is not limited as long as it is generally obtained copper particles, but when used as a metal pigment for metallic paint, a plate shape having a wide smooth surface. The shape is preferred.
上記工程（Ａ）で用いるアルミニウム塩としては、特に限定されるものではないが、安価で入手が容易な硫酸アルミニウム又は硝酸アルミニウムが好ましい。 The aluminum salt used in the step (A) is not particularly limited, but is preferably aluminum sulfate or aluminum nitrate which is inexpensive and easily available.
上記工程（Ａ）において、銅微粒子を含む水性懸濁液中の粒子の分散性を向上させるために、特に限定されるものではないが、ヘキサメタリン酸ナトリウムを添加することが好ましい。これにより、ビーカー等の反応容器内壁へのアルミニウム水酸化物の付着も減少するので操作上も好ましい。なお。ヘキサメタリン酸ナトリウムの添加量としては、水に対して０．０１〜０．２重量％が好ましく、特に、０．０１〜０．１重量％が好ましい。 すなわち、０．０１重量％未満では、粒子の分散性の向上効果が不十分であり、一方、０．２重量％を超えると、それ以上の効果の向上がみられず、芯粒子（ａ）へのアルミニウムの吸着を阻害する場合がある。 In the step (A), in order to improve the dispersibility of the particles in the aqueous suspension containing the copper fine particles, it is not particularly limited, but it is preferable to add sodium hexametaphosphate. Thereby, adhesion of aluminum hydroxide to the inner wall of the reaction vessel such as a beaker is also reduced, which is preferable in terms of operation. Note that. The amount of sodium hexametaphosphate added is preferably 0.01 to 0.2% by weight, particularly 0.01 to 0.1% by weight, based on water. That is, when the amount is less than 0.01% by weight, the effect of improving the dispersibility of the particles is insufficient. On the other hand, when the amount exceeds 0.2% by weight, no further improvement in the effect is observed, and the core particle (a) It may inhibit the adsorption of aluminum to the surface.
上記製造方法の工程（Ｂ）は、前記工程（Ａ）で形成した被覆層（ｃ）を有する銅微粒子を固液分離した後、乾燥処理に付す工程である。ここで、固液分離の方法としては、特に限定されるものではなく、通常のろ過方法が用いられる。また、乾燥処理の方法としては、特に限定されるものではないが、特に金属光沢が必要とされる場合、通常の真空乾燥機等により非酸化状態において１００℃以下の温度で水分を除去する方法を用いることが好ましい。 Step (B) of the above production method is a step of subjecting the copper fine particles having the coating layer (c) formed in the step (A) to solid-liquid separation and then subjecting to a drying treatment. Here, the solid-liquid separation method is not particularly limited, and a normal filtration method is used. Further, the method for the drying treatment is not particularly limited, but in particular, when metallic luster is required, a method of removing moisture at a temperature of 100 ° C. or less in a non-oxidized state by a normal vacuum dryer or the like. Is preferably used.
上記製造方法の工程（Ｃ）は、前記工程（Ｂ）で得た乾燥処理後の銅微粒子を還元雰囲気下に１８０〜３３０℃の温度で加熱処理に付し、前記被覆層（ｃ）を熱分解する工程である。これにより、銅微粒子からなる芯粒子（ａ）と、該芯粒子を被覆するアルミニウムを主成分として含む酸化物からなる被覆層（ｂ）とから構成される酸化物被覆銅微粒子が得られる。 In the step (C) of the production method, the copper fine particles after the drying treatment obtained in the step (B) are subjected to a heat treatment at a temperature of 180 to 330 ° C. in a reducing atmosphere, and the coating layer (c) is heated. It is a process of decomposing. As a result, oxide-coated copper fine particles composed of core particles (a) made of copper fine particles and a coating layer (b) made of an oxide mainly containing aluminum covering the core particles are obtained.
ここで、加熱処理は還元雰囲気下で行う必要がある。すなわち、大気又は不活性ガス雰囲気下で加熱処理すると、大気中の酸素及びアルミニウム水酸化物から発生する水蒸気中の酸素により銅が酸化され意匠低下の原因となる。また、加熱処理の温度としては、１８０〜３３０℃の範囲であり、特に２００〜３００℃であることが好ましい。すなわち、温度が１８０℃未満では、アルミニウム水酸化物の分解及び脱水反応が不十分であり、顔料として用いる際に酸化による意匠の変化が大きくなる可能性がある。一方、温度が３３０℃を超えると、被覆層水酸化物の分解時に膜の連続性が損なわれる場合があり、耐酸化性に劣る粒子となる。 Here, the heat treatment needs to be performed in a reducing atmosphere. That is, when heat treatment is performed in the atmosphere or in an inert gas atmosphere, copper is oxidized by oxygen in the atmosphere and oxygen in water vapor generated from aluminum hydroxide, which causes a decrease in design. Moreover, as temperature of heat processing, it is the range of 180-330 degreeC, and it is especially preferable that it is 200-300 degreeC. That is, when the temperature is less than 180 ° C., the decomposition and dehydration reaction of the aluminum hydroxide is insufficient, and there is a possibility that the design change due to oxidation becomes large when used as a pigment. On the other hand, when the temperature exceeds 330 ° C., the continuity of the film may be impaired when the coating layer hydroxide is decomposed, resulting in particles having poor oxidation resistance.
以上の製造方法により、層厚が均一な連続膜からなるアルミニウムを主成分として含む酸化物からなる被覆層と銅微粒子からなる酸化物被覆銅微粒子が得られる。 By the above manufacturing method, a coating layer made of an oxide containing aluminum as a main component, which is a continuous film having a uniform layer thickness, and oxide-coated copper fine particles made of copper fine particles are obtained.
以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によって何ら限定されるものではない。なお、実施例及び比較例で用いた芯粒子（ａ）の比表面積、Ａｌ、Ｃｕの分析、Ａｌ含有定数ならびに耐酸化性の評価方法は、以下の通りである。
（１）芯粒子（ａ）の比表面積の測定：ＢＥＴ多点法により測定した。
（２）Ａｌ、Ｃｕの分析：ＩＣＰ発光分析法で酸化物被覆銅微粒子中のＡｌ、Ｃｕの含有量を求めた。
（３）酸化物被覆銅微粒子のＡｌ含有定数の算出：得られた酸化物被覆銅微粒子中のＡｌ、Ｃｕの含有量から求めたＣｕに対するＡｌの組成割合（質量％）と芯粒子（ａ）の比表面積（ｍ２・ｇ−１）より、Ａｌ含有定数［質量％／（ｍ２・ｇ−１）］を算出した。
（４）酸化物被覆銅微粒子の耐酸化性（重量増加率、ＴＧ測定前後の意匠性）の評価：ＴＧ測定を大気気流中で１６０℃、３０分保持の条件で行い、最小重量と最大重量の差の初期重量に対する割合（以下、この値を重量増加率と称する。）を求めた。なお、この値が少ないほど顔料として使用した場合の意匠変化が少ないことを意味する。一般に、１質量％を超える場合には意匠の変化が著しく、０．５質量％未満の場合には意匠の変化はわずかとなる。また、０．１質量％未満の場合には、目視では意匠の変化がほとんど確認できない。
EXAMPLES The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the specific surface area of the core particle (a) used by the Example and the comparative example, the analysis of Al and Cu, the Al content constant, and the evaluation method of oxidation resistance are as follows.
(1) Measurement of specific surface area of core particle (a): Measured by BET multipoint method.
(2) Analysis of Al and Cu: The contents of Al and Cu in the oxide-coated copper fine particles were determined by ICP emission analysis.
(3) Calculation of Al content constant of oxide-coated copper fine particles: Al in the obtained oxide-coated copper fine particles, Al composition ratio (mass%) to Cu obtained from the Cu content and core particles (a) From the specific surface area (m 2 · g −1 ), the Al content constant [mass% / (m 2 · g −1 )] was calculated.
(4) Evaluation of oxidation resistance (weight increase rate, designability before and after TG measurement) of oxide-coated copper fine particles: TG measurement is performed in an air stream at 160 ° C. for 30 minutes, and the minimum weight and maximum weight The ratio of the difference between the initial weights (hereinafter, this value is referred to as the weight increase rate) was determined. In addition, it means that there are few design changes when it uses as a pigment, so that this value is small. Generally, when the amount exceeds 1% by mass, the change in the design is remarkable, and when it is less than 0.5% by mass, the change in the design becomes slight. When the amount is less than 0.1% by mass, almost no change in the design can be visually confirmed.
（実施例１）
工程（Ａ）、（Ｂ）
まず、Ａｌ２（ＳＯ４）３濃度０．０７ｍｏｌ／Ｌ、及び尿素濃度１８ｇ／Ｌの水溶液からなるコート液を作製し、０．１μｍのメンブレンフィルターで吸引濾過しゴミを取り除いた。次に、比表面積３．１３ｍ２／ｇの板状の銅微粒子５．００ｇと、純水７００ｍＬと、ヘキサメタリン酸ナトリウム０．１４ｇとからなる水性懸濁液を作製した。
次いで、前記水性懸濁液に対して、タービン型ペラを用いた攪拌機で２００ｒｐｍで攪拌しながら、前記コート液３０ｍＬを０．６ｍＬ／分の速度で供給した。このとき、銅微粒子に対するコート液中のアルミニウムの添加割合（単位：質量％）を、銅微粒子の比表面積（単位：ｍ２・ｇ−１）で除した値は、０．７３［質量％／（ｍ２・ｇ−１）］であった。その後、１時間保持した後、吸引ろ過し、得られた水酸化物被覆銅微粒子を真空乾燥機により６０℃で乾燥した。
Example 1
Process (A), (B)
First, a coating solution composed of an aqueous solution having an Al 2 (SO 4 ) 3 concentration of 0.07 mol / L and a urea concentration of 18 g / L was prepared, and suction filtered through a 0.1 μm membrane filter to remove dust. Next, an aqueous suspension composed of 5.00 g of plate-like copper fine particles having a specific surface area of 3.13 m 2 / g, 700 mL of pure water, and 0.14 g of sodium hexametaphosphate was prepared.
Next, 30 mL of the coating solution was supplied to the aqueous suspension at a rate of 0.6 mL / min while stirring at 200 rpm with a stirrer using a turbine type propeller. At this time, the value obtained by dividing the aluminum addition ratio (unit: mass%) in the coating liquid with respect to the copper fine particles by the specific surface area (unit: m 2 · g −1 ) of the copper fine particles is 0.73 [mass% / (M 2 · g −1 )]. Thereafter, after holding for 1 hour, suction filtration was performed, and the obtained hydroxide-coated copper fine particles were dried at 60 ° C. by a vacuum dryer.
工程（Ｃ）
乾燥後の水酸化物被覆銅微粒子を、水素０．２Ｌ／分、及び窒素９．８Ｌ／分の混合ガス気流中で、１０℃／分の速度で２００℃まで昇温し、１時間加熱処理した後、６０℃まで炉内で冷却して、酸化物被覆銅微粒子を得た。
Process (C)
The dried hydroxide-coated copper fine particles are heated to 200 ° C. at a rate of 10 ° C./min in a mixed gas stream of hydrogen 0.2 L / min and nitrogen 9.8 L / min and heat-treated for 1 hour. Then, it was cooled in a furnace to 60 ° C. to obtain oxide-coated copper fine particles.
その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示す。その結果、Ａｌ含有定数は０．６１［質量％／（ｍ２・ｇ−１）］であり、重量増加率は０．６０質量％であった。また、ＴＧ測定後のサンプルは、測定前と同様に金属光沢などの意匠性を維持しており、意匠変化もわずかであった。 Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 0.61 [mass% / (m 2 · g −1 )], and the weight increase rate was 0.60 mass%. Further, the sample after TG measurement maintained the design properties such as metallic luster as before the measurement, and the design change was slight.
（実施例２）
比表面積１．５７ｍ２／ｇの銅微粒子１６ｇと、純水３３６０ｍＬと、ヘキサメタリン酸ナトリウム０．６７ｇとからなる懸濁液を用いたこと、前記コート液６５ｍＬを２ｍＬ／分の速度で供給したこと以外は実施例１と同様にして酸化物被覆銅微粒子を得た。このとき、銅微粒子に対するコート液中のアルミニウムの添加割合（単位：質量％）を、銅微粒子の比表面積（単位：ｍ２・ｇ−１）で除した値は、０．９６［質量％／（ｍ２・ｇ−１）］であった。その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示す。その結果、Ａｌ含有定数は０．９６［質量％／（ｍ２・ｇ−１）］であり、重量増加率は０．０３質量％であった。また、ＴＧ測定後のサンプルは、測定前と同様に金属光沢などの意匠性を維持しており、意匠変化は確認できなかった。
(Example 2)
Using a suspension composed of 16 g of copper fine particles having a specific surface area of 1.57 m 2 / g, 3360 mL of pure water, and 0.67 g of sodium hexametaphosphate, and supplying 65 mL of the coating solution at a rate of 2 mL / min. Except that, oxide-coated copper fine particles were obtained in the same manner as in Example 1. At this time, the value obtained by dividing the aluminum addition ratio (unit: mass%) in the coating liquid with respect to the copper fine particles by the specific surface area (unit: m 2 · g −1 ) of the copper fine particles was 0.96 [mass% / (M 2 · g −1 )]. Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 0.96 [% by mass / (m 2 · g −1 )], and the weight increase rate was 0.03% by mass. Moreover, the sample after TG measurement maintained design properties, such as a metallic luster, similarly to before measurement, and the design change was not able to be confirmed.
（実施例３）
前記コート液を水性懸濁液に供給する前にオーブンを用いて５０℃で２時間保持し、直後に室温まで急冷したこと、比表面積１．５７ｍ２／ｇの板状の銅微粒子１８．０ｇと、純水１７３０ｍＬと、ヘキサメタリン酸ナトリウム０．３４６ｇとからなる水性懸濁液を用いたこと、及び前記コート液７４ｍＬを３．０ｍＬ／分の速度で供給したこと以外は実施例１と同様にして酸化物被覆銅微粒子を得た。このとき、銅微粒子に対するコート液中のアルミニウムの添加割合（単位：質量％）を、銅微粒子の比表面積（単位：ｍ２・ｇ−１）で除した値は、０．９６［質量％／（ｍ２・ｇ−１）］であった。その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示す。その結果、Ａｌ含有定数は０．８３［質量％／（ｍ２・ｇ−１）］であり、重量増加率は０．０７質量％であった。また、ＴＧ測定後のサンプルは、測定前と同様に金属光沢などの意匠性を維持しており、意匠変化は確認できなかった。
(Example 3)
Before supplying the coating solution to the aqueous suspension, it was kept at 50 ° C. for 2 hours using an oven and immediately cooled to room temperature. Plate-shaped copper fine particles having a specific surface area of 1.57 m 2 / g 18.0 g And using an aqueous suspension composed of 1730 mL of pure water and 0.346 g of sodium hexametaphosphate and supplying 74 mL of the coating solution at a rate of 3.0 mL / min. Thus, oxide-coated copper fine particles were obtained. At this time, the value obtained by dividing the aluminum addition ratio (unit: mass%) in the coating liquid with respect to the copper fine particles by the specific surface area (unit: m 2 · g −1 ) of the copper fine particles was 0.96 [mass% / (M 2 · g −1 )]. Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 0.83 [% by mass / (m 2 · g −1 )], and the weight increase rate was 0.07% by mass. Moreover, the sample after TG measurement maintained design properties, such as a metallic luster, similarly to before measurement, and the design change was not able to be confirmed.
（比較例１）
前記コート液の添加量を６０ｍＬとしたこと以外は実施例１と同様にして酸化物被覆銅微粒子を得た。その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示すその結果、Ａｌ含有定数は１．４［質量％／（ｍ２・ｇ−１）］であり、重量増加率は０．０４質量％であった。しかしながら、得られた粒子は金属光沢に乏しく、意匠性が劣るものとなった。
(Comparative Example 1)
Oxide-coated copper fine particles were obtained in the same manner as in Example 1 except that the amount of the coating solution added was 60 mL. Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 1.4 [mass% / (m 2 · g −1 )], and the weight increase rate was 0.04 mass%. However, the obtained particles were poor in metallic luster and poor in design.
（比較例２）
工程（Ｃ）の加熱処理の温度を３５０℃としたこと以外は実施例１と同様にして酸化物被覆銅微粒子を得た。その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示す。その結果、Ａｌ含有定数は０．６１［質量％／（ｍ２・ｇ−１）］であったが、重量増加率が１．０３質量％となった。また、得られた酸化物被覆銅微粒子は、金属光沢を有していたが、ＴＧ測定後のサンプルに意匠の変化が見られた。
(Comparative Example 2)
Oxide-coated copper fine particles were obtained in the same manner as in Example 1 except that the temperature of the heat treatment in the step (C) was 350 ° C. Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 0.61 [mass% / (m 2 · g −1 )], but the weight increase rate was 1.03 mass%. Further, the obtained oxide-coated copper fine particles had a metallic luster, but a design change was observed in the sample after TG measurement.
（比較例３）
工程（Ｃ）の加熱処理の温度を６００℃としたこと以外は実施例１と同様にして酸化物被覆銅微粒子を得た。その後、得られた酸化物被覆銅微粒子のＡｌ、Ｃｕの分析と耐酸化性の評価を行った。結果を表１に示す。その結果、Ａｌ含有定数は０．６１［質量％／（ｍ２・ｇ−１）］であったが、重量増加率が１．９０質量％となった。また、この酸化物被覆銅微粒子は、金属光沢を有していたが、ＴＧ測定後のサンプルに意匠の変化が見られた。
(Comparative Example 3)
Oxide-coated copper fine particles were obtained in the same manner as in Example 1 except that the temperature of the heat treatment in the step (C) was 600 ° C. Thereafter, the obtained oxide-coated copper fine particles were analyzed for Al and Cu and evaluated for oxidation resistance. The results are shown in Table 1. As a result, the Al content constant was 0.61 [mass% / (m 2 · g −1 )], but the weight increase rate was 1.90 mass%. The oxide-coated copper fine particles had a metallic luster, but a design change was observed in the sample after TG measurement.
表１より、実施例１〜３では、酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を芯粒子（ａ）の比表面積で除した値で表したＡｌ含有定数、加熱処理の温度等において本発明の条件にしたがって行われたので、得られた酸化物被覆銅微粒子は、金属光沢を有して意匠性に富んだものであり、加熱による変化もほとんど見られないことが分かる。一方、比較例１では、Ａｌ含有定数が本発明の条件より大きいので、金属光沢に乏しく意匠性が劣るものとなっていることが分かる。また、比較例２又は３は、加熱処理の温度が本発明の範囲より高いので、得られた直後は金属光沢を有しているが、加熱による重量増加が大きく変色も生じていることが分かる。 From Table 1, in Examples 1 to 3, the Al content constant represented by the value obtained by dividing the composition ratio of the aluminum content to the copper content in the oxide-coated copper fine particles by the specific surface area of the core particles (a), Since it was carried out according to the conditions of the present invention at the temperature of the heat treatment, etc., the obtained oxide-coated copper fine particles have a metallic luster and are rich in design, and hardly show changes due to heating. I understand that. On the other hand, in Comparative Example 1, since the Al content constant is larger than the conditions of the present invention, it can be seen that the metallic luster is poor and the design is poor. Moreover, since the temperature of heat processing is higher than the range of this invention, the comparative example 2 or 3 has a metallic luster immediately after being obtained, but it turns out that the weight increase by heating is large and discoloration has also arisen. .
以上より明らかなように、本発明の酸化物被覆銅微粒子の製造方法は、金属顔料として優れた特性を示す金属粒子の製造方法として適している。 As apparent from the above, the method for producing oxide-coated copper fine particles of the present invention is suitable as a method for producing metal particles exhibiting excellent properties as a metal pigment.
Claims (4)
下記の工程（Ａ）〜（Ｃ）を含むことを特徴とする酸化物被覆銅微粒子の製造方法。
工程（Ａ）：銅微粒子を含む水性懸濁液中に、アルミニウム塩と尿素とを含む水溶液を供給して、アルミニウム水酸化物を主成分とする水酸化物からなる被覆層（ｃ）を有する銅微粒子を、下記の要件を満足する被覆量で形成する。
上記被覆量は、質量％の単位で表した前記酸化物被覆銅微粒子中の銅の含有量に対するアルミニウムの含有量の組成割合を、［ｍ２・ｇ−１］の単位で表した芯粒子（ａ）の比表面積で除した値が、０．２〜１．２［質量％／（ｍ２・ｇ−１）］であるように制御される。
工程（Ｂ）：前記工程（Ａ）で形成した被覆層（ｃ）を有する銅微粒子を固液分離した後、乾燥処理に付す。
工程（Ｃ）：前記工程（Ｂ）で得た乾燥処理後の銅微粒子を還元雰囲気下に１８０〜３３０℃の温度で加熱処理に付し、前記被覆層（ｃ）を熱分解する。 Production of oxide-coated copper fine particles comprising core particles (a) made of copper fine particles and a coating layer (b) made of an oxide containing aluminum as a main component formed on the surface of the core particles (a) A method,
The manufacturing method of the oxide covering copper fine particle characterized by including the following process (A)-(C).
Step (A): Supplying an aqueous solution containing an aluminum salt and urea into an aqueous suspension containing copper fine particles, and having a coating layer (c) made of a hydroxide mainly composed of an aluminum hydroxide. Copper fine particles are formed in a coating amount that satisfies the following requirements.
The said coating amount is the core particle which represented the composition ratio of the content of aluminum with respect to the content of the copper in the said oxide covering copper fine particle represented in the unit of the mass% in the unit of [m < 2 > * g <-1 >]. The value divided by the specific surface area of a) is controlled to be 0.2 to 1.2 [mass% / (m 2 · g −1 )].
Step (B): The copper fine particles having the coating layer (c) formed in the step (A) are solid-liquid separated and then subjected to a drying treatment.
Step (C): The copper fine particles after the drying treatment obtained in the step (B) are subjected to a heat treatment at a temperature of 180 to 330 ° C. in a reducing atmosphere to thermally decompose the coating layer (c).
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