Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-05-13
2004-10-05
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S430000, C524S445000, C524S446000, C523S214000, C523S215000, C523S210000, C523S216000
Reexamination Certificate
active
06800684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to composite particles, and a tread rubber composition, a paint and a resin composition using the composite particles, and more particularly, to composite particles capable of an excellent dispersibility and an excellent light resistance; a tread rubber composition prepared by blending the composite particles in rubber, which can show a less discoloration upon exposure to light, a low electric resistance, an excellent wear resistance and an excellent tensile strength; and a paint containing the composite particles and a resin composition containing the composite particles.
The composite particles of the present invention can be used as pigments, or colorants, fillers or the like for rubbers, paints and resin compositions.
As white inorganic particles having a refractive index of less than 2.0, there are generally known extender pigments. The extender pigments form a transparent or translucent dispersion when dispersed in vehicles such as oils and varnishes. Therefore, the extender pigments have been conventionally used as non-color pigments, i.e., as extenders for paints, printing inks or the like. With the progress of powder science or technology, the extender pigments have been recently used not only as extenders, but also as function-imparting pigments in extensive industrial fields for the purpose of controlling or improving the processability and physical properties of rubbers, plastics, paints, printing inks, adhesives, sealing materials, papers or the like.
However, although the extender pigments show transparency or translucency in vehicle, paints or resin compositions to which the extender pigments are added as fillers, exhibit a more whitish color than those containing no extender pigments, and fail to show a sufficient blackness required in some application fields.
White inorganic particles having a refractive index of not less than 2.0 such as titanium oxide, zinc oxide and zirconium oxide, have been conventionally used as white pigments for rubbers, plastics, paints or printing inks.
In particular, it is known that titanium oxide and zinc oxide exhibit an ultraviolet light-shielding effect because these pigments can absorb light in ultraviolet region. In recent years, the titanium oxide and zinc oxide are also used as an ultraviolet light absorber for cosmetics or the like.
However, it is also known that the titanium oxide and zinc oxide have a high surface activity. Therefore, when paints or resin compositions using these pigments are exposed to outdoor environments, there arise problems such as chalking of a painted surface and deterioration of resins.
In addition, white inorganic particles are generally non-conductive, for example, silica particles and zinc oxide have volume resistivity values of about 10
6
to 10
8
&OHgr;·cm and about 10
7
&OHgr;·cm, respectively. Therefore, it is known that in the applications requiring a higher or lower volume resistivity value, it is necessary to use an electric resistance-regulating agent such as carbon black or the like in addition to the white inorganic particles.
On the other hand, black pigments such as aniline black, carbon black or the like have been extensively used in various applications such as inks, paints, rubbers and plastics for the purpose of imparting thereto a tinting property, electric properties, a light-absorbing property or the like.
However, it is known that these black pigments, especially carbon black, are fine particles having an average particle diameter as small as about 0.005 to 0.05 &mgr;m and, therefore, it is difficult to disperse carbon black in vehicles or resin compositions. In addition, it is also known that these black pigments are bulky particles having a bulk density as high as about 0.1 g/cm
3
and, therefore, are deteriorated in handling property and workability.
Further, since the paints or resin compositions using such black particles are sometimes used in outdoor applications and exposed to direct sunlight or severe weather conditions such as winds and rains, the black particles are required to maintain a good hue and properties thereof for a long period of time, namely to show excellent light resistance and weather resistance.
Consequently, it has been strongly required to provide black particles capable not only imparting thereto various properties such as electric properties, ultraviolet light-absorbing property or the like according to applications thereof, but also exhibiting excellent light resistance, tinting strength and dispersibility in vehicle.
Hitherto, it is known that silica particles are blended together with carbon black in rubbers for the purposes of reduction in electric resistance of the rubbers as well as reinforcement thereof (Japanese Patent Application Laid-Open (KOKAI) No. 52-93452(1977), and Japanese Patent Nos. 2722077, 2788212 and 3160552).
In addition, it is also known that titanium oxide or zinc oxide is coated with a silica-based substance in order to suppress the surface activity (Japanese Patent Application Laid-Open (KOKAI) Nos. 2000-319128 and 2001-58821).
At present, it has been strongly required to provide composite particles capable of not only imparting thereto various properties such as electric properties, ultraviolet light-shielding property, according to the applications thereof, but also exhibiting excellent light resistance, tinting strength, handling property and dispersibility in vehicle. However, conventional composite particles have failed to satisfy all of these requirements.
Namely, in Japanese Patent Application Laid-Open (KOKAI) No. 52-93452(1977) and Japanese Patent Nos. 2722077 and 3160552, there are described carbon-coated silica particles and a rubber composition containing such coated silica particles which are used for tires. However, in any of these, since a carbon black coat is formed on the surface of the silica particle by thermal decomposition of organic compounds, the adhesion of carbon black onto the surface of the silica particle is very weak. Therefore, when the coated silica particles are kneaded in the rubber composition, the carbon black coated is desorbed or fallen-off from the surface of the silica particle, so that a part of the surface of the silica particles is exposed. This results in non-uniform dispersion of the silica particles in the rubber composition, and failure to exhibit sufficient the above-mentioned effects.
The rubber composition described in Japanese Patent No. 2788212 is a tire tread rubber composition containing carbon black surface-treated with 0.1 to 50% by weight of silica. However, the adhesion of silica onto the surface of carbon black is very weak. Therefore, when the coated carbon black is kneaded in the rubber composition, the silica coated thereon is desorbed or fallen-off from the surface of the carbon black, thereby preventing carbon black from being uniformly dispersed in the composition.
Also, in Japanese Patent Application Laid-Open (KOKAI) Nos. 2000-319128 and 2001-58821, there is described zinc oxide or titanium oxide whose surface is coated with silica, silica-based substances such as alkyl-modified silica, zinc silicate or the like. However, the coating formed on zinc oxide or titanium oxide fails to sufficiently reduce the surface activity thereof.
In Japanese Patent Application Laid-Open (KOKAI) Nos. 11-323174(1999) and 2001-11339, there are described iron-based composite particles comprising black iron oxide particles or black iron oxide hydroxide particles as core particles, a coating layer formed on the surface of the core particle which comprises organosilane compounds obtainable from alkoxysilanes or polysiloxanes, and a carbon black coat coated onto the surface of the coating layer composed of organosilane compounds or polysiloxanes. However, these techniques are related to the method of fixedly coating carbon black onto the black iron compound particles. Since the core particles show a magnetism, the obtained composite particles cannot be used in applications in which such a magnetism is unnecessary and u
Hayashi Kazuyuki
Iwasaki Keisuke
Morii Hiroko
Ohsugi Mineko
Shimohata Yusuke
Cain Edward J.
Nixon & Vanderhye P.C.
Toda Kogyo Corporation
Wyrozebski Katarzyna
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