Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-12-11
2003-10-28
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
Reexamination Certificate
active
06638618
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a black composite iron oxide pigment, and a paint and a resin composition using the black composite iron oxide pigment, and more particularly, to a black composite iron oxide pigment capable of exhibiting not only a deep black color, but also excellent acid resistance and light resistance, a paint containing the black composite iron oxide pigment, and a resin composition containing the black composite iron oxide pigment.
Carbon black fine particles and magnetite particles are known as typical black pigments, and have been generally used longtime as colorants for paints, printing inks, cosmetics, rubbers, resin compositions or the like.
Among these conventional black pigments, the carbon black fine particles show a most excellent blackness, and coating films or resin compositions using the carbon black fine particles are also excellent in acid resistance. However, since the carbon black fine particles are particles having an average particle size as small as about 0.005 to 0.05 &mgr;m, it is difficult to uniformly disperse the carbon black fine particles in vehicles or resin compositions. In addition, the carbon black fine particles are bulky fine particles having a bulk density of about 0.1 g/cm
3
and, therefore, are difficult to handle, resulting in deteriorated workability. Further, the carbon black fine particles have hygiene and safety problems such as carcinogenesis.
Specifically, when the carbon black fine particles are used in a larger amount, a higher blackness can be attained. On the other hand, it is more difficult to uniformly disperse such a large amount of the carbon black fine particles in vehicles or resin compositions, resulting in poor workability. Also, the use of a larger amount of the carbon black fine particles is disadvantageous from the viewpoints of hygiene or safety.
The magnetite particles have an appropriate particle size, specifically an average particle size of about 0.08 to 1.0 &mgr;m and, therefore, show an excellent dispersibility in vehicles or resin compositions as well as a good handling property. In addition, the magnetite particles are harmless particles. However, the magnetite particles are insufficient in blackness, and coating films or resin compositions using the magnetite particles are also insufficient in acid resistance.
Further, the magnetite particles tend to be magnetically agglomerated together because of inherent magnetism thereof. For this reason, the use of manganese-containing hematite particles as black iron oxide particles having no magnetism have been proposed from the standpoints of improved dispersibility in vehicles or resin compositions. However, the manganese-containing hematite particles are deteriorated in blackness as compared to that of the magnetite particles.
Thus, it has been strongly required to provide black particles capable of not only showing a good blackness similar to or compatible with that of the carbon black fine particles, an excellent dispersibility in vehicles or resin compositions and a good handling property, but also producing a coating film or a resin composition having excellent acid resistance, light resistance and heat resistance.
Also, in recent years, it has been strongly required to provide black particles exhibiting in addition to the above properties, a less reddish and deep black color.
In order to meet these requirements, various methods have been conventionally attempted for producing composite particles from the carbon black fine particles and magnetite particles, thereby obtaining black particles exhibiting excellent combined properties thereof. For example, there are known 1) the method of adding a water dispersion containing carbon black fine particles to a water suspension containing magnetite particles precipitated from an aqueous solution thereof, and then mixing and stirring the mixed dispersion to absorb the carbon black fine particles onto the surface of the magnetite particles (Japanese Patent Publication (KOKOKU) No. 50-13300(1975)); 2) the method of introducing iron-containing sludge in which high-molecular organic materials such as molasses are dissolved, and a carbon black-containing hot gas into a spray reactor at a temperature of 450 to 850° C. in order to produce magnetite particles from the iron salt and simultaneously bond carbon black on the surface of the magnetite particles using the molasses as a binding accelerator (Japanese Patent Application Laid-Open (KOAKI) No. 49-48725(1974)); 3) the method of suspending carbon black in an aqueous iron salt solution, and co-precipitating the carbon black and magnetite by adding alkali to the suspension, thereby producing co-precipitated particles coated with carbon black (Japanese Patent Publication (KOKOKU) No. 55-39580(1980)); 4) the method of adhering carbon black, etc., onto the surface of fine plate-shaped particles, and fixing the carbon black, etc., on the surface of the particles using an anionic, cationic or nonionic surfactant and an organofunctional organosilane compound (Japanese Patent Application Laid-Open (KOAKI) Nos. 6-145556(1994) and 7-316458(1995)); or the like.
At present, it has been strongly demanded to provide black particles capable of not only showing a blackness similar to or compatible with that of carbon black fine particles, a less reddish and deep black color and excellent dispersibility in vehicles or resin compositions, but also providing a coating film or a resin composition having excellent acid resistance, light resistance and heat resistance. However, such black particles capable of fulfilling these requirements have not been obtained conventionally.
That is, in the above conventional method 1) described in Japanese Patent Publication (KOKOKU) No. 50-13300(1975), since the carbon black fine particles tend to be desorbed from the surface of the magnetite particles when dispersed in vehicles or resin compositions because of high desorption percentage thereof, it is difficult to uniformly disperse the carbon black fine particles in vehicles or resin compositions. In addition, the obtained paints or resin compositions are not sufficiently improved in blackness.
In the above conventional method 2) described in Japanese Patent Application Laid-Open (KOKAI) No. 49-48725(1974), in order to obtain a high blackness similar to or compatible with that obtained by using carbon black fine particles only, it is necessary to use the carbon black fine particles in as large an amount as about 280 parts by weight based on 100 parts by weight of the magnetite particles.
In the above conventional method 3) described in Japanese Patent Publication (KOKOKU) No. 55-39580(1980), in order to obtain a high blackness similar to or compatible with that of obtained by using carbon black fine particles only, it is also necessary to add the carbon black fine particles in as large an amount as about 100 to 400 parts by weight based on 100 parts by weight of the magnetite particles. In addition, the carbon black fine particles adhered onto the surface of the co-precipitated particles tend to be desorbed therefrom.
In the above conventional method 4) described in Japanese Patent Application Laid-Open (KOKAI) Nos. 6-145556(1994) and 7-316458(1995), the carbon black fine particles tend to be desorbed from the obtained particles. In addition, the particles obtained by this method are not black particles.
Further, in Japanese Patent Application Laid-Open (KOKAI) No. 11-323174(1999), there are described black composite iron-based particles, comprising black iron oxide particles or black iron oxide hydroxide particles, a coating layer formed on the surface of the black iron oxide or iron oxide hydroxide particles comprising organosilane compounds obtainable from alkoxysilanes, and a carbon black coat adhered on the surface of the coating layer. However, as shown in Comparative Examples below, the obtained particles fail to show a deep black color.
As a result of the present inventors' earnest studies, it has been found that by forming a coating layer comprisi
Hayashi Kazuyuki
Morii Hiroko
Ohsugi Mineko
Shimohata Yusuke
Le H. Thi
Toda Kogyo Corporation
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