Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-11-28
2004-06-08
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S493000, C106S496000, C106S497000, C106S498000
Reexamination Certificate
active
06746524
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing a sintered color pencil lead which can draw lines having excellent light fastness and weatherability while having a vivid coloring property and a sufficiently high density in drawn lines and is excellent in a mechanical strength such as a bending strength and which can readily be erased with an eraser and is particularly suited as a fine size color pencil lead for a mechanical pencil.
BACKGROUND ART
Conventional sintered color pencil leads are used for mechanical pencils in many cases, and a production process therefor includes a principal production process in which a blend composition comprising an filler such as boron nitride and a binder such as clay is kneaded, extruded and then subjected to heat treatment to prepare a porous lead and in which an ink comprising a dye is filled into pores of this lead.
However, since the colorant is a dye, the problem with the dye is that the stability with the passage of time such as light fastness is inferior. Further, if a lead has pores having a size at the level in which the pores can be impregnated with a pigment-dispersed ink, the lead is weak in strength and can not serve as a practical lead for a mechanical pencil.
The present applicant has heretofore filed Japanese Patent Application Laid-Open No. Hei 8-48931, Japanese Patent Application Laid-Open No. Hei 9-67540, Japanese Patent Application Laid-Open No. Hei 2000-17220 and Japanese Patent Application Laid-Open No. Hei 2000-17221 in connection with methods for obtaining a lead having a high strength. In all of these methods, obtained are sintered leads which can be impregnated with a pigment-dispersed ink so as to provide drawn lines with a high density and which is stronger in strength than the practical level applicable to a lead for a mechanical pencil. However, further desired is a sintered lead whose density in drawn lines thereof is further more improved and whose strength is further more than the practical level.
Further, the present inventors have filed Japanese Patent Application Laid-Open No. Hei 8-143810, Japanese Patent Application Laid-Open No. Hei 8-143811, Japanese Patent Application Laid-Open No. Hei 8-143812 and Japanese Patent Application Laid-Open No. Hei 8-259874 in connection with methods for producing organic pigments in pores of a porous lead for a mechanical pencil by chemical reaction. These methods have made it possible to impregnate pores of a lead having a small pore diameter with an organic pigment. However, problems with these methods are that, since the reaction is carried out in the presence of a strong acid or a strong base, the leads are liable to be a little deteriorated and that, since the production process is different according to each pigment, mixing color and producing multiple color are difficult.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the defects of the sintered color pencil leads produced by the conventional techniques described above and further improve the prior art of the present inventors described above and to provide a process for producing a sintered color pencil lead which can draw lines having excellent light fastness and weatherability while having a vivid coloring property and a sufficiently high density in drawn lines and is excellent in a mechanical strength such as a bending strength and which can readily be erased with an eraser.
The present inventors have done intensive researches in order to solve the problems described above. As a result, they have found that the above problems can be solved by filling pores of a white or light-colored porous sintered lead with a specific compound and pigmenting the compound by heating, and thus they have come to complete the present invention.
That is, a process for producing a sintered color pencil lead characterized by forming a white or light-colored porous sintered pencil lead that is pigmented with an organic pigment by treating said porous sintered pencil lead with a solution of at least one compound of the following Formula (I) to be filled with said compound and then by forming said organic pigment within the pores by means of heating,
A(B)x (I)
in which x is an integer from 1 to 8,
A is the radical of a chromophore of the quinacridone, anthraquinone, perylene, indigo, quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo series, phthalocyanine or diketopyrrolopyrrole which is attached to x groups B via one or more heteroatoms selected from the group consisting of N, O and S and forming part of the radical A,
B is hydrogen or a group of the formula
where at least one group B is not hydrogen and, if x is 2 to 8, all the groups B can be identical or different, and L is any suitable solubilizing group.
To be more specific, pores of a white or light-colored porous sintered lead comprising a colorless or white filler and silicon nitride prepared from a starting material of perhydropolysilazane which is a binder may be filled with a solution prepared by dissolving the compound (I) described above in an organic solvent and pigmented by heating.
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiment of the present invention shall be explained below in detail.
A process for producing a sintered color pencil lead characterized by forming a white or light-colored porous sintered pencil lead that is pigmented with an organic pigment by treating said porous sintered pencil lead with a solution of at least one compound of the following Formula (I) to be filled with said compound and then by forming said organic pigment within the pores by means of heating,
A(B)x (I)
in which x is an integer from 1 to 8,
A is the radical of a chromophore of the quinacridone, anthraquinone, perylene, indigo, quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo series, phthalocyanine or diketopyrrolopyrrole which is attached to x groups B via one or more heteroatoms selected from the group consisting of N, O and S and forming part of the radical A,
B is hydrogen or a group of the formula
where at least one group B is not hydrogen and, if x is 2 to 8, all the groups B can be identical or different, and L is any suitable solubilizing group.
In a process for producing a sintered color pencil lead in accordance with the present invention, a white or light-colored porous sintered lead is formed and pores of the white or light-colored porous sintered lead are filled with a solution prepared by dissolving at least the compound (I) described above in an organic solvent and pigmented said compound in said pores by heating.
In the present invention, the porous sintered lead is formed from a colorless or white filler which is a publicly known substance, such as boron nitride, talc and mica and a binder such as silicon nitride, silica, alumina and zirconia and a solid solution thereof or clay. In particular, preferably suitable in terms of strength is a lead comprising a binder of silicon nitride prepared from perhydropolysilazane used as a starting material, which is disclosed in Japanese Patent Application Laid-Open No. Hei 8-48931.
The filler shall not specifically be restricted as long as it has heretofore been used as an filler for a sintered color pencil lead and is colorless or white, and any substances can be used. For example, the filler described above can be used, and it is a matter of course that a mixture of several kinds thereof can be used. Further, silica and alumina can be used as the filler depending on the kind and the sintering temperature of the binder.
A pore diameter of the porous color pencil lead used in the present invention shall not specifically be restricted as long as it can be impregnated with a solution prepared by dissolving the compound of Formula (I) in an organic solvent. However, a minimum value of the pore diameter is considered to be about 0.1 &mgr;m, so that it is preferable to use those in which all pore diameters are 0.1 &mgr;m or more. Taking a distribution of the pores into consideration, if the pores having a
Bell Mark L.
Faison Veronica F.
Mitsubishi Pencil Kabushiki Kaisha
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