Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-06-20
2003-11-11
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
Reexamination Certificate
active
06645279
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a baked color pencil lead which is excellent in mechanical strength such as flexural strength while having a vivid coloring property and sufficiently high density in drawn lines and which can readily be erased lines drawn therewith with an eraser and is suited particularly to a color pencil lead for a mechanical pencil and in which a baked lead is impregnated with an ink, and to a process for producing the same.
BACKGROUND ART
High mechanical strength, a good coloring property and high density in drawn lines are required as important characteristics of a color pencil lead.
In a conventional baked color pencil lead, at least one kind of clay and the like is used as a binder, and a filler such as boron nitride and, if necessary, a heat resistant pigment and a reaction accelerating agent are added thereto and blended to prepare a blend composition. The blend composition is kneaded and extrusion-molded. Then, it is subjected to heat treatment to become a porous baked lead, and an ink comprising a dye and a pigment is filled into pores of the lead to prepare a color pencil lead.
However, the existing situation is that conventional baked color pencil leads are not sufficient in mechanical strength and that those which are sufficient in density of drawn lines and a coloring property have not yet been obtained.
A baked lead using clay as a binder has so far been weak in sintering force between a filler such as boron nitride and a binder such as clay, and further clay itself has low strength, so that the resulting baked color pencil lead has not attained practical strength. Further, clay contains impurities, and therefore the resulting baked lead is usually colored and exerts an adverse effect on a coloring property of the drawn lines. In particular, it causes a dull color in the drawn lines of a pale color base. Accordingly, in order to meet the requirement described above, an increased amount of ink is filled into a lead which is allowed to have a large porosity while maintaining satisfactory mechanical strength.
Proposed by the present inventors as a method for solving the problems described above are a baked color pencil lead prepared by impregnating a perhydropolysilazane solution into pores of a specific porous baked lead obtained by subjecting at least a filler to heat treatment, subjecting it to heat treatment in an inert atmosphere such as a nitrogen atmosphere or in an ammonia gas atmosphere to thereby obtain a lead in which silicon nitride is formed as a binder and filling an ink into this lead, and a process for producing the same (Japanese Patent Application Laid-Open No. 48931/1996).
Also, proposed as a method for solving the problems described above are a baked color pencil lead provided with specific pores by using a filler having a specific particle diameter, and a process for producing the same (Japanese Patent Application Laid-Open No. 208878/1997).
Further, proposed by the present inventors are a baked color pencil lead in which pores are impregnated with an ink containing oleyl alcohol, specific polyoxyethylene fatty acid ester, specific polyoxyethylene alkyl ether and polyoxyethylene oleyl ether, and a process for producing the same (Japanese Patent Application Laid-Open No. 237377/1998, Japanese Patent Application Laid-Open No. 237378/1998 and Japanese Patent Application No. 188299/1997).
However, these color pencil leads have the problem that setting a pore diameter small in order to strengthen the lead makes it difficult to charge fine pores of the lead with an ink and as a result, a difference in a density and a hue is produced between the tip part and the middle part.
An object of the present invention is to solve the problems of the conventional baked color pencil leads described above and further improve the prior arts of the present inventors described above and to provide a baked color pencil lead which is free of scattering in a density of the color depending on spots of the lead and has extraordinarily excellent mechanical strength and a vivid and excellent coloring property and which is excellent in writing feeling and can readily be erased lines drawn therewith with an eraser, and a process for producing the same.
DISCLOSURE OF THE INVENTION
Intensive researches repeated by the present inventors in order to solve the problems described above have resulted in finding that the above problems can be solved by impregnating a porous baked lead having a specific pore with a specific dye ink under a specific pressure, and thus the present invention has come to be completed.
That is, the baked color pencil lead of the present invention and the production process for the same are constituted by the following items (1) to (6):
(1) A process for producing a baked color pencil lead, comprising forming a white or pale color porous baked lead having a volume-based median pore diameter of 0.27 &mgr;m or less, dipping it in a dye ink and then applying a pressure of 1.5 MPa or more thereto to impregnate pores of the above baked lead with the above dye ink.
(2) The process for producing a baked color pencil lead as described in the above item (1), wherein the dye ink impregnated into the pores of the porous baked lead is a dye ink using as a solvent at least one of non-volatile solvents represented by the following Formulas (I) to (III):
CH
3
(CH
2
)
7
CH═CH(CH
2
)
7
CH
2
OH (I)
R
1
O(CH
2
CH
2
O)
n
H (II)
in Formula (II), R
1
represents decanoyl, undecanoyl, lauroyl, tridecanoyl or oleoyl, and n is 4.5 to 15; and
R
2
—O—(CH
2
CH
2
O)
m
H (III)
in Formula (III), R
2
represents decyl, undecyl, lauryl, tridecyl or oleyl, and m is 1 to 14.
(3) The process for producing a baked color pencil lead as described in the above item (2), comprising impregnating the pores of the porous baked lead with a dye ink solution using as the solvent 35 to 90% by weight of at least one of the non-volatile solvents represented by Formulas (I) to (III) described above and a low boiling organic solvent by applying pressure and then removing the above low boiling organic solvent by drying.
(4) The process for producing a baked color pencil lead as described in any of the above items (1) to (3), wherein the porous baked lead comprises a colorless or white filler and silicon nitride, which is a binder and is produced by using perhydropolysilazane as a starting material.
(5) A baked color pencil lead obtained by the production process as described in the above item (1). (6) A baked color pencil lead obtained by the production process as described in any of the above items (2) to (4), characterized by involving the dye ink containing 38% by weight or more of at least one of the non-volatile solvents represented by Formulas (I) to (III).
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiment of the present invention shall be explained below in detail.
The baked color pencil lead of the present invention is produced by impregnating pores of a white or pale color porous baked lead having a volume-based median pore diameter of 0.27 &mgr;m or less with a dye ink by applying a pressure of 1.5 MPa or more. The ink to be impregnated preferably uses at least one of the non-volatile solvents represented by the following Formulas (I) to (III) as a solvent:
CH
3
(CH
2
)
7
CH═CH(CH
2
)
7
CH
2
OH (I)
R
1
O(CH
2
CH
2
O)
n
H (II)
in Formula (II), R
1
represents decanoyl, undecanoyl, lauroyl, tridecanoyl or oleoyl, and n is 4.5 to 15; and
R
2
—O—(CH
2
CH
2
O)
m
H (III)
in Formula (III), R
2
represents decyl, undecyl, lauryl, tridecyl or oleyl, and m is 1 to 14.
The baked color pencil lead of the present invention is more preferably produced by forming a white or pale color porous baked lead having a volume-based median pore diameter of 0.27 &mgr;m or less, dipping the above porous baked lead in a dye ink solution prepared by dissolving a dye in a mixed solvent of at least one of the non-volatile solvents described above with a low boiling solvent, then applying a pressure of 1.5 MPa or
Hoshiba Masaaki
Kanba Noboru
Kitazawa Katsunori
Bell Mark L.
Darby & Darby
Faison Veronica F.
Mitsubishi Pencil Kabushiki Kaisha
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