Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-12-08
2002-08-27
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S403000, C428S405000, C523S212000, C427S219000, C106S460000
Reexamination Certificate
active
06440561
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to iron oxide hydroxide composite particles, a pigment composed of the same, a paint containing the pigment, a resin composition containing the pigment and a process for producing the iron oxide hydroxide composite particles. More particularly, the present invention relates to iron oxide hydroxide composite particles containing no harmful elements and exhibiting not only excellent chemical resistances such as acid resistance and alkali resistance, but also excellent heat resistance, a pigment such as a green-based pigment or a orange-based pigment, composed of the iron oxide hydroxide composite particles, a paint containing the pigment, a resin composition containing the pigment and a process for producing the iron oxide hydroxide composite particles.
At present, as green-based pigments, there have been widely used inorganic pigments such as chrome green, chromium oxide and zinc green, and organic pigments such as phthalocyanine green. Also, as orange-based pigments, there have been used chrome vermilion, chrome orange, permanent orange, benzidine orange or the like. These pigments have been extensively applied to colorants of resins, paints, printing inks or the like.
However, it is known that the inorganic pigments such as chrome green, chromium oxide and zinc green tend to be deteriorated in chemical resistances such as acid resistance and alkali resistance though they are excellent in light resistance, and are expensive.
In addition, the inorganic pigments such as chrome green, chromium oxide and zinc green contain harmful elements such as lead and chromium. For this reason, it has been strongly required to develop alternate materials for these green-based pigments from viewpoints of hygiene, safety and environmental protection.
On the other hand, the organic green-based pigments such as phthalocyanine green exhibit a high tinting strength and a clear hue. However, it is known that these organic pigments are deteriorated in light resistance, i.e., suffer from bronze-bleeding (so-called bronzing) upon outdoor exposure.
Chrome vermilion and chrome orange exhibit a very clear hue. However, it is known that these orange-based pigments are deteriorated in chemical resistances such acid resistance and alkali resistance as well as light resistance and heat resistance, and are extensive.
In addition, the inorganic orange-based pigments such as chrome vermilion and chrome orange also contain harmful elements such as lead and chromium. Therefore, it has been strongly required to develop alternate materials for these orange-based pigments from viewpoints of hygiene, safety and environmental protection.
It is also known that the organic orange-based pigments such as permanent orange and benzidine orange exhibit a clear hue, but are deteriorated in light resistance.
Further, resin compositions using thermoplastic resins such as polyolefins, for example, polyethylenes, polypropylenes, styrene polymers or the like, polyamides and ABS resins are usually molded at a temperature as high as not less than 200° C. For this reason, pigments added as colorants to these resin compositions are required to exhibit a good heat resistance.
In consequence, green and orange-based pigments added to these resin compositions are strongly required to have not only excellent chemical resistances and tinting strength but also excellent heat resistance.
Hitherto, in order to improve properties of the pigments, it has been attempted to use inorganic and organic pigments in combination. For example, there have been proposed methods of co-precipitating chrome yellow and phthalocyanine blue together or adhering organic pigments onto the surfaces of inorganic pigments (Japanese Patent Application Laid-Open (KOKAI) Nos. 4-132770(1992), 10-88032(1998) and 11-181329(1999), etc.).
Thus, it has been strongly demanded to provide green and orange-based pigments exhibiting both excellent chemical resistances and excellent heat resistance without containing harmful elements. However, such pigments capable of satisfying these requirements have not been provided until now.
Namely, in the above method of co-precipitating chrome yellow and phthalocyanine blue together, the obtained pigments show a toxicity due to chrome yellow. Further, paints containing such pigments are insufficient in storage stability due to the use of co-precipitated pigments, so that coating films formed therefrom tend to suffer from bleeding.
In the method of precipitating organic pigments in the presence of inorganic pigments as described in Japanese Patent Application Laid-Open (KOKAI) No. 4-132770, the organic pigments are insufficient in adhesion to the inorganic pigments.
In the method of mechanically mixing and milling inorganic and organic pigments together as described in Japanese Patent Application Laid-Open (KOKAI) No. 10-88032(1998), the organic pigments are also insufficient in adhesion to the inorganic pigments.
Further, in Japanese Patent Application Laid-Open (KOKAI) No. 11-181329(1999), there is described the method of adding organic pigments to a solution prepared by dissolving organopolysiloxane in cyclic silicone to disperse therein the pigments as fine particles, impregnating the fine organic pigments with high oil-absorption inorganic pigments, and then evaporating cyclic silicone from the pigments. In this method, the organic pigments are also insufficient in adhesion to the inorganic pigments.
Meanwhile, in Japanese Patent Application Laid-Open (KOKAI) No. 11-323174(1999), there are described iron-based black composite particles obtained by forming an organosilane coating layer on black iron oxide particles or black iron oxide hydroxide particles, and then forming a carbon black coat on the organosilane coating layer. Since the iron-based black composite particles are black iron oxide hydroxide composite particles having the carbon black coat, the iron-based black composite particles are quite different from composite particles having green or orange-based pigments.
As a result of the present inventors' earnest studies, it has been found that by mixing as core particles iron oxide hydroxide particles with at least one compound selected from the group consisting of:
(1) alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes, by using an apparatus capable of applying a shear force to the core particles, thereby coating the surface of the black iron oxide hydroxide particle with the compounds;
mixing the obtained iron oxide hydroxide particles coated with the compounds and organic blue or red-based pigment in an amount of 1 to 30 parts by weight based on 100 parts by weight of the core particles by using an apparatus capable of applying a shear force to the core particles, thereby forming organic blue or red-based pigment coat on the surface of a coating layer comprising the organosilicon compounds, the thus obtained iron oxide hydroxide composite particles are harmless pigments which are excellent not only in chemical resistances such as acid resistance and alkali resistance, but also in heat resistance. The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a harmless pigment such as a harmless green or orange-based pigment exhibiting not only excellent chemical resistances such as acid resistance and alkali resistance, but also high hiding power, high tinting powder and excellent heat resistance.
Another object of the present invention is to provide a fine pigment such as a green or orange-based fine pigment which contains no harmful elements and is improved not only in chemical resistances such as acid resistance and alkali resistance but also in heat resistance, and further is capable of producing a paint and a resin composition exhibiting an excellent transparency.
To accomplish the aim of the present invention, in a first aspect of the present invention, there are provided iron oxide hydroxide composite particles having an average particle diameter (avera
Hayashi Kazuyuki
Morii Hiroko
Ohsugi Mineko
Dawson Robert
Keehan Christopher M
Toda Kogyo Corporation
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