JP2002302633A - Baked color pencil lead and its manufacture process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a baked color pencil lead having a sufficient color development and line-drawing density and excellent mechanical strength, i.e., flexural strength, tensile strength, impact strength, etc., and its manufacture process, especially a baked color pencil lead suitable for holders of sharp pencils, etc., and its manufacture process. SOLUTION: The baked color pencil comprises a baked lead body and a coloring material filled in the pores of the baked lead body. Here, the baked lead body is obtained by impregnating the pores of a porous baked lead body, which is made of at least a body material and silicon nitride, with a liquid containing a polysiloxane having a structural unit of formula (I) (wherein R1 and R2 are identical to or different from each other and are each an alkyl group, an alkoxy group, hydroxyl group or a siloxane group), and heating this in an oxidative atmosphere and/or nonoxidative atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a baked color pencil lead having sufficient mechanical strength, that is, excellent bending strength, tensile strength, impact strength, etc., while having sufficient coloring properties and drawing density, and a method for producing the same. The present invention relates to a fired colored pencil lead suitable for a holder such as a mechanical pencil and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a baked color pencil lead has used, as a binder, one and / or two or more kinds of clays and the like, and a filler such as boron nitride and, if necessary, a heat-resistant pigment. Add the reaction accelerator, knead the blended composition,
After extruding the kneaded product, a heat treatment was performed to obtain a porous fired core, and the core of the core was filled with an ink composed of a dye and a pigment to form a colored pencil core.

As important characteristics of a color pencil lead generally required, those having high mechanical strength, good coloring properties of drawing lines and high density are required, but the above-mentioned fired color pencil lead has sufficient mechanical strength. In addition, no good density and color developability were obtained. For this reason, there is a need for a colored pencil lead having a large porosity and a high mechanical strength that can contain a sufficient amount of coloring material.

In order to solve the above-mentioned problems, the present inventors impregnate at least pores of a fired core body made of a constitutional material with a perhydropolysilazane-containing liquid and inactivate an inert atmosphere such as a nitrogen atmosphere. An application has been made for a fired colored pencil lead obtained by producing silicon nitride as a binder by heat treatment in an atmosphere or an ammonia gas atmosphere, and filling the pores of the lead with ink (Japanese Patent Application Laid-Open No. Hei 8- 4
No. 8931). In addition, the present inventors proposed a heat treatment after filling the perhydropolysilazane-containing liquid with a temperature of 1200 to 1 as a solution for the core after firing to absorb and deteriorate due to moisture in the air.
Method for producing a fired colored pencil lead at 400 ° C.
Japanese Patent Application Laid-Open No. 95991) and a method for solving the problem that it is difficult to obtain a core having a high color saturation due to carbonization of a trace amount of organic solvent or the like remaining in the core, making it difficult to obtain a core having a high color saturation.
A method for producing a fired pencil lead which is fired at 000 ° C. or higher to generate silicon nitride on the core and then heat-treated at 600 ° C. or higher in an oxidizing atmosphere has been filed (Japanese Patent Laid-Open No. 2000-11).
No. 9582).

[0005] The fired colored pencil lead obtained by the method described in each of these publications has an unprecedented color developing property and drawing line density and is excellent in mechanical strength.
Even if the heat treatment temperature is set to 1200 to 1400 ° C., it is difficult to completely suppress the deterioration due to moisture absorption, and once silicon nitride is generated, carbon atoms chemically bonded to silicon atoms,
In addition, there is a slight problem in that the carbon content of the residual organic solvent and the like covered with silicon nitride is difficult to remove in an oxidizing atmosphere and causes dullness of light-colored drawn lines.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems and the like, and is intended to further improve the prior art of the present inventors. An object of the present invention is to provide a baked color pencil lead having color developability and smooth writing taste and resistant to moisture absorption deterioration, and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned conventional problems and the like. As a result, at least the pores of a porous fired core made of a body material and silicon nitride are formed. By impregnating with a polysiloxane-containing liquid having a specific structural unit and performing heat treatment in an oxidizing atmosphere and / or a non-oxidizing atmosphere, it has been found that the above-mentioned problems can be solved, and the present invention has been completed. It is. That is, the fired color pencil lead of the present invention and the method for producing the same are as follows.
(1) to (3). (1) At least pores of a porous fired core body composed of a body material and silicon nitride are impregnated with a polysiloxane-containing liquid having a structural unit represented by the following general formula (I) to form an oxidizing atmosphere and / or a non-oxidizing atmosphere. A fired pencil lead comprising: a fired core obtained by heat treatment in an oxidizing atmosphere; and a coloring material filled in pores of the fired core.

Embedded image (2) The porous fired core made of the above-mentioned constitutional material and silicon nitride is obtained by kneading a compounding composition containing at least the constitutional material and the organic excipient, extruding, and firing in a non-oxidizing atmosphere. (1) The fired core is further heated in an oxidizing atmosphere to form a second fired core in which the carbon content is oxidized and removed, and the pores of the second fired core are impregnated with a perhydropolysilazane-containing liquid,
The fired pencil lead according to the above (1), which is a porous fired core obtained by firing at 1000 ° C. or more in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere to produce silicon nitride. (3) Kneading, extruding, and sintering in a non-oxidizing atmosphere a compounding composition containing at least a body material and an organic excipient,
A calcined core was obtained, the first calcined core was further heated in an oxidizing atmosphere to obtain a second calcined core from which carbon was oxidized and removed, and perhydropolysilazane was introduced into the pores of the second calcined core. After impregnating with the containing liquid and baking at 1000 ° C. or more in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere to generate silicon nitride, it has a structural unit represented by the following general formula (I) By impregnating with a polysiloxane-containing liquid and performing heat treatment in an oxidizing atmosphere and / or a non-oxidizing atmosphere,
A method for producing a fired colored pencil lead, characterized in that a fired core is obtained and a coloring material is filled in pores of the fourth fired core.

Embedded image The “in an inert atmosphere such as a nitrogen atmosphere” defined in the present invention refers to a nitrogen gas atmosphere or an inert gas atmosphere such as an argon gas atmosphere.

[0008]

Embodiments of the present invention will be described below in detail. The fired colored pencil lead of the present invention is obtained by impregnating at least pores of a porous fired lead body composed of a body material and silicon nitride with a polysiloxane-containing liquid having a structural unit represented by the above general formula (I), and It is characterized by comprising a fired core obtained by heat treatment in an atmosphere and / or a non-oxidizing atmosphere, and a coloring material filled in pores of the fired core.

In the present invention, the porous fired core composed of at least the body material and silicon nitride is prepared by, for example, kneading a compound composition containing at least the body material, silicon nitride and an organic shaping material, extrusion molding, a non-oxidizing atmosphere. The production method and the like are not particularly limited as long as it can be obtained by calcining, and a porous calcined core composed of at least a body material and silicon nitride. Particularly preferably, since the body material is highly oriented, sufficient pores are formed, and silicon nitride can be uniformly present in the entire fired core body, at least the body material and the organic excipient are used. Kneading a blended composition containing
The first fired core obtained by extrusion molding and firing in a non-oxidizing atmosphere is further heated in an oxidizing atmosphere to form a second fired core in which carbon is oxidized and removed. A perhydropolysilazane-containing liquid is impregnated in the pores of the body, and the solution is placed in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere.
A porous fired core composed of at least a body material and silicon nitride obtained as a third fired core by firing at 000 ° C. or higher is desirable.

[0010] The body material used for forming the porous fired core is not particularly limited as long as it has been conventionally used for a fired color pencil lead, and any of them can be used. For example, boron nitride, talc, mica,
Depending on the hue of a white base material such as calcium carbonate or the hue of a colored pencil, a colored base material such as morbutene disulfide can also be used, and of course, a mixture of several types of these can also be used. As a matter to be noted when using this extender, it is necessary to select an extender that does not cause deterioration, alteration (oxidation or the like), sintering, or the like in the atmosphere and temperature used for firing.

The organic excipients include, for example,
Thermoplastic resins such as polyvinyl chloride resin, chlorinated polyvinyl chloride resin, and polyvinyl alcohol; thermosetting resins such as furan resin, phenolic resin and epoxy resin; natural polymer substances such as lignin, cellulose, and tragacanth gum; petroleum asphalt; Pitches such as coal tar pitch, naphtha decomposed pitch, and dry pitch of synthetic resin can be used. Naturally, a mixture of several types of these can also be used.

Further, for the purpose of improving the characteristics at the time of kneading by applying a high shear force and the characteristics of extrusion molding, water, dioctyl phthalate (DOP), dibutyl phthalate (DB)
P), one or more plasticizers or solvents for organic excipients such as tricresyl phosphate (TCP), dioctyl adipate (DOA), propylene carbonate, alcohols, ketones, and esters. You may add according to it.

In the present invention, for example, a compounded composition containing the above constitutional material, organic excipient and the like is sufficiently kneaded with a Henschel mixer, a pressure kneader, a two-roller or the like, and then formed into a fine wire or the like by an extruder. Extrusion molding, and then firing in a non-oxidizing atmosphere such as a nitrogen atmosphere or an inert gas such as argon gas to carbonize the organic excipient to obtain a first fired core using carbon as a binder. Can be In the present invention, the second fired core is obtained by heating the first fired core obtained above in an oxidizing atmosphere to oxidize and remove the carbon binder. Here, the pores of the second calcined core are formed by calcining a kneaded material composed of a constitutional material and an organic excipient in a non-oxidizing atmosphere, and removing the carbon binder. It is composed of both pores obtained. The porosity of the second fired core is adjusted mainly by adjusting the mixing ratio of the body material and the organic shaping material. It may be added.

The perhydropolysilazane-containing liquid to be filled in the second fired core is obtained by dissolving perhydropolysilazane as a ceramic precursor in an organic solvent. The organic solvent to be used is not particularly limited as long as it can be impregnated into the body, and any of them can be used. Examples of the organic solvent that can be used include organic solvents such as benzene, toluene, xylene, ether, THF, methylene chloride, carbon tetrachloride, and the like, and aromatic hydrocarbons, and may be used alone or in combination of two or more. It is possible.

As a method of impregnating the second fired core with a perhydropolysilazane-containing liquid, for example, the second fired core is immersed in a perhydropolysilazane-containing liquid, and if necessary, heated, reduced in pressure, It can be carried out by impregnation under conditions such as pressure.

In the present invention, the second fired core impregnated with the perhydropolysilazane-containing liquid is treated in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere.
The calcined core obtained by calcining at 0 ° C. or more is carbonized due to trace amounts of organic solvent and the like in the perhydropolysilazane-containing liquid remaining in the pores and becomes grayish. Preferably, firing at 600 ° C. or higher, more preferably 650 ° C. or higher, to obtain a porous fired core (third fired core) composed of at least a body material from which residual carbon has been removed and silicon nitride. Is desirable.

According to the present invention, a porous fired core comprising at least a body material and silicon nitride, for example, the third fired core obtained above
The calcined core body is further impregnated with a polysiloxane-containing liquid having a structural unit represented by the following general formula (I), and heat-treated in an oxidizing atmosphere and / or a non-oxidizing atmosphere to obtain the following general formula (I) The polysiloxane having the structural unit represented by I) is changed to silicon oxide, and silicon oxide is formed in the porous fired core made of at least the body material and silicon nitride. Thus, a fired core (fourth fired core) in which silicon nitride and silicon oxide coexist as binder components is obtained.

Embedded image

The polysiloxane having a structural unit represented by the above general formula (I) used in the present invention may be any as long as it can form silicon oxide in a porous fired core composed of at least a body material and silicon nitride. Things. Therefore, as long as the polysiloxane can finally form silicon oxide in the porous fired core, the number of carbon atoms of the functional group, the degree of polymerization, and the like are not particularly limited. The polysiloxane having a structural unit represented by the general formula (I) used in the present invention is:
For example, it can be synthesized by a general polymerization method such as a sol-gel method using an organic compound of silicon or an inorganic compound of silicon as a starting material. The organic compound of silicon and the inorganic compound of silicon as the starting material can be used alone or in combination of two or more. However, the polysiloxane having the structural unit represented by the general formula (I) may be used. It is determined in a form suitable for the polymerization method, and among them, tetraethoxysilane is preferred because it is inexpensive and easy to handle. The degree of polymerization of the polysiloxane used in the present invention is sufficient if it is 2 (n = 2) or more. There is no particular upper limit, and it is appropriately determined from the polymerization reaction and the ease of handling the polysiloxane.

Examples of the organic solvent for dissolving the polysiloxane having the structural unit represented by the above general formula (I) include methanol, ethanol, propanol, and the like.
Examples include alcohols such as butanol, and organic solvents such as ethylene oxide, ethylene glycol, tetraethylene glycol, toluene, xylene, methyl ethyl ketone, and THF. These may be used alone or in combination of two or more. The polysiloxane-containing liquid contains 1
Two or more types can be used without being limited to the types.

A polysiloxane having a structural unit represented by the above general formula (I) is dissolved in an organic solvent in the third fired core, that is, a porous fired core composed of at least a body material and silicon nitride. As a method of impregnating the solution thus obtained, for example, the third fired core can be immersed in the solution, and if necessary, impregnated under conditions such as heating, reduced pressure, and pressurization.

The heat treatment performed after impregnating the third fired core body with a solution in which a polysiloxy having the structural unit represented by the above general formula (I) is dissolved in an organic solvent is performed in an oxidizing atmosphere and / or a non-oxidizing atmosphere. In an oxidizing atmosphere, the temperature is preferably 350 ° C. or more and 850 ° C.
The heat treatment is preferably performed at a temperature below 700 ° C. in a non-oxidizing atmosphere. If the heat treatment in an oxidizing atmosphere is performed at a low temperature of less than 350 ° C. and the heat treatment in a non-oxidizing atmosphere is performed at a low temperature of less than 700 ° C., the polysiloxane is not sufficiently oxidized, or the above-described general formula ( The functional groups represented by R ₁ and R ₂ in I) are not sufficiently eliminated, and the strength as silicon oxide as a binder cannot be sufficiently exhibited. Further, when the heat treatment in an oxidizing atmosphere is performed at a temperature exceeding 850 ° C., the silicon nitride contained in the third fired core is oxidized, or the body material is oxidized, and the core is worn. It is not preferable because it is difficult to remove, and the mechanical strength becomes weak. Also, particularly preferably, in an oxidizing atmosphere, the above temperature range (3.
After the heat treatment at 50 ° C. to 850 ° C.), it is desirable to further perform the heat treatment at a temperature of 850 ° C. or more in a non-oxidizing atmosphere. By the heat treatment in the oxidizing atmosphere and / or the non-oxidizing atmosphere, a fired core body in which silicon nitride and silicon oxide coexist as binder components is formed. .

The fourth fired core of the present invention preferably has a total content of silicon compounds (silicon nitride, silicon oxide) in the range of 5 to 50% by weight with respect to the body material.
It is desirably from 7% by weight to 30% by weight. This fourth
If the total amount of the silicon compounds contained in the fired core is less than 5% by weight based on the body material, the mechanical strength of the fourth fired core is reduced, which is not preferable. On the other hand, if the content exceeds 50% by weight with respect to the constitutional material, the mechanical strength of the fourth fired core body is increased, but it is difficult to wear, the writing taste is hard, and the drawing line is dull. More preferably, it is desirably 30% by weight or less in order to further increase the saturation of the drawn line. In the present invention, in order to obtain a baked color pencil lead having a remarkably excellent mechanical strength, vivid and excellent color developing property and smooth writing taste, and hardly absorbing and deteriorating, and a method for producing the same, preferably a fourth core is used. It is desirable that the weight ratio between the amount of silicon nitride and the amount of silicon oxide in the silicon compound contained in the fired core is 1: 5 to 5: 1. The amount of silicon nitride and the amount of silicon oxide to be contained in the fourth fired core are adjusted mainly by adjusting the conditions for impregnating the second fired core into the perhydropolysilazane-containing liquid. The amount of silicon oxide can be adjusted mainly by changing the conditions for impregnating the third fired core with the above-mentioned polysiloxane solution. As a fired core having an appropriate amount, a fired color pencil lead having markedly excellent mechanical strength, vivid and excellent coloring and smooth writing, and hardly deteriorating by moisture absorption, and a method for producing the same are obtained. Will be

In the present invention, the fired pencil lead is completed by filling the pores of the fourth fired core obtained above with a coloring material such as ink. As the ink to be impregnated into the fourth fired core, any conventionally known ink for color pencils can be used. For example, dyes,
Commonly used coloring materials such as pigments are dissolved and dispersed in animal and vegetable oils, synthetic oils, alcohols, hydrocarbon oils, water, etc., or are further produced by adding resins, surfactants, etc. as necessary. Printing inks, stamp inks, ballpoint pen inks, aqueous writing inks, and the like. Also,
As a method of impregnating the ink, there is a method in which the core is immersed in the ink and filled in the pores under conditions such as heating, decompression, and pressurization. Further, the impregnation may be performed by repeating the above operation.

In the fired color pencil lead and the method for producing the same, the porous fired lead made of the body material and silicon nitride has the structural unit represented by the general formula (I) in the pores. By impregnating with a polysiloxane-containing liquid and performing heat treatment in an oxidizing atmosphere and / or a non-oxidizing atmosphere, silicon nitride and silicon oxide are contained in a porous fired core body as binder components, thereby forming silicon nitride. It becomes possible to reduce the amount compared to the core body using only conventional silicon nitride as a binder, the carbon atoms chemically bonded to silicon atoms, and the residual carbon covered by silicon nitride are reduced, and The deterioration due to moisture absorption is also small. In addition, the porous core body containing silicon nitride and silicon oxide as binder components was colored in a pale color because the conventional binder was a high-strength core body similar to a core made of only silicon nitride and had high whiteness. Even in such a case, the color of the drawn line of the fired color pencil is high and it is vivid.

[0025]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following, “parts” means parts by weight.

Example 1 Composition A: Tetraethoxysilane 35.0 parts Ethanol 16.0 parts 6N hydrochloric acid 0.6 parts Purified water 4.7 parts Nitrogen was passed through composition A having the above composition. While 8
After stirring at 0 ° C. for 5 hours to react, the concentration was adjusted by further adding ethanol to prepare a polysiloxane solution A. Composition B: 41.3 parts of boron nitride 41.3 parts of vinyl chloride resin 16.5 parts of dioctyl phthalate (DOP) 0.9 part of zinc stearate 0.9 part of the above composition B was mixed and dispersed by a hen shell mixer.
After kneading with a pressure kneader and two rolls, extruded into a thin wire, and heat-treated at 180 ° C in air to remove the residual plasticizer, and then, in a nitrogen atmosphere, After the temperature was raised to 1000 ° C., it was fired at 1000 ° C. to obtain a first fired core. The first fired core was heated to an oxidizing atmosphere of 700 ° C., and was heated and fired at 700 ° C. to remove the remaining carbonized resin.
A fired core was obtained.

The second calcined core was impregnated with a liquid containing perhydropolysilazane at room temperature for one day, and then was
After the temperature was raised to 0 ° C and calcined at 1250 ° C, 70
The temperature was lowered to 0 ° C., fired at 700 ° C. in an oxidizing atmosphere, and then cooled to room temperature to obtain a third fired core. Next, the polysiloxane solution A prepared above was impregnated at room temperature for one day, heated to 700 ° C. in an oxidizing atmosphere, baked at 700 ° C., and further heated to 900 ° C. in a nitrogen atmosphere. , 9
By firing at 00 ° C., a white fourth fired core having a diameter of 0.721 mm was obtained. The total content of silicon compounds (silicon nitride, silicon oxide) with respect to the body material of the fourth fired core is 20% by weight.
And the weight ratio between the silicon nitride and the silicon oxide is 1: 1.3.
Met. In addition, this weight ratio is calculated from the second fired core to the third fired core.
The weight increase to the fired core was calculated as silicon nitride, and the weight increase from the third fired core to the fourth fired core was calculated as silicon oxide (the same applies hereinafter). Next, the fourth fired core was immersed in a pink dye ink and left at 70 ° C. for 24 hours. The surface of the fourth fired core filled with the pink ink was washed with alcohol to obtain a pink fired pencil lead.

[Example 2] Composition C: 48.0 parts of tetramethoxysilane 42.1 parts of methanol 0.6 parts of 2% hydrochloric acid 11.9 parts of purified water 11.9 parts of composition C having the above composition in a nitrogen atmosphere After stirring at 35 ° C. for 12 hours, 2 parts of methyltrimethoxysilane was added and the mixture was stirred for 1 hour, and then methanol was added to adjust the concentration, thereby preparing a polysiloxane solution C.
Then, after obtaining the same third fired core as in Example 1 above,
The third fired core was impregnated with the polysiloxane solution C prepared above at room temperature for one day, heated to 700 ° C. in an oxidizing atmosphere, fired at 700 ° C., and further heated to 900 ° C. in a nitrogen atmosphere. And fired at 900 ° C. to obtain a white fourth fired core having a diameter of 0.718 mm. This fourth
The total content of silicon compounds (silicon nitride, silicon oxide) with respect to the body material of the fired core was 21% by weight, and the weight ratio of this silicon nitride to silicon oxide was 1: 1.8. Next, the fourth fired core was dipped in a pink dye ink in the same manner as in Example 1 and left at 70 ° C. for 24 hours. The surface of the fourth fired core filled with the pink ink was washed with alcohol to obtain a pink fired pencil lead.

Comparative Example 1 A second fired core similar to that of Example 1 was obtained, and the second fired core was impregnated with a perhydropolysilazane-containing solution at room temperature for 12 hours. After heating to 650 ° C. and firing at 650 ° C. to obtain a fired core, the fired core is once again impregnated with a perhydropolysilazane-containing liquid and heated to 1250 ° C. in a nitrogen atmosphere. After firing at 1250 ° C., the temperature was lowered to 700 ° C., and then fired at 700 ° C. in an oxidizing atmosphere to lower the temperature to room temperature to obtain a third fired core using silicon nitride as a binder. Further, the third fired core was immersed in a pink dye ink in the same manner as in Example 1 to obtain a dye having a diameter of 0.1 mm.
A 715 mm pink fired colored pencil was obtained. Note that the third
The content of silicon nitride with respect to the body material of the fired core was 18% by weight.

[Comparative Example 2] After a second fired core similar to that of Example 1 was obtained, the second fired core was impregnated with a perhydropolysilazane-containing solution at room temperature for one day, and then an oxidizing atmosphere was obtained. Temperature, and fired at 600 ° C. to obtain a fired core. Then, the fired core was impregnated with the perhydropolysilazane-containing liquid again, and heated to 700 ° C. in an oxidizing atmosphere. Then, the resultant was fired at 700 ° C. to obtain a third fired core using silicon oxide as a binder. Further, the third fired core was immersed in a pink dye ink in the same manner as in Example 1 to obtain a fired pink pencil having a diameter of 0.721 mm. In addition, the content ratio of silicon oxide with respect to the body material of the third fired core was 20% by weight.

[Comparative Example 3] Boron nitride 40 parts Bentonite 35 parts Polyvinyl alcohol 18 parts Polyethylene glycol 7 parts The above composition and the same weight of water were mixed and dispersed with a hen shell mixer, and kneaded with two rolls. After adjusting the water content, it was extruded into a thin wire and dried at 110 ° C., then heated to 1200 ° C. in argon gas and fired at 1200 ° C. Next, the temperature is raised to 700 ° C. in an oxidizing atmosphere to
It was fired at 00 ° C. to obtain a fired core having a diameter of 0.710 mm. Next, the fired core was immersed in a pink dye ink in the same manner as in Example 1 and left at 70 ° C. for 24 hours. The surface of the fired core body filled with the pink dye ink was washed with alcohol to obtain a fired pink pencil lead having a diameter of 0.710 mm.

The appearance and drawing color of the fired cores before ink dyeing obtained in Examples 1 and 2 and Comparative Examples 1 to 3 and the color of pink fired pencil lead were determined according to JIS-S-6005-198.
Flexural strength (MPa) according to No. 9, writing taste by sensory evaluation, coloring of drawing lines, and pink baked color pencil core at a temperature of 50 ° C.
The strength reduction rate when left in a thermo-hygrostat at 100% humidity for one week was evaluated based on the following equation. Strength reduction rate = {1-[(strength after standing for one week in a thermo-hygrostat at a temperature of 50 ° C. and a humidity of 100%) / (initial strength)]}
× 100 These results are shown in Table 1 below.

[0033]

[Table 1]

As is evident from the results in Table 1, the fired pencil lead of Examples 1 and 2 which fall within the scope of the present invention is compared with the fired pencil lead of Comparative Examples 1 and 3 which fall outside the scope of the present invention. Since the appearance and the drawing line color before dyeing with pink ink are extremely white, the coloring of the drawing line of the baked color pencil core dyed with pink ink also becomes extremely clear. This is because silicon oxide produced by heat-treating polysiloxane is an extremely white binder. On the other hand, in Comparative Example 3, since the conventional bentonite was used, the bending strength and the saturation were low, and the writing taste was slightly hard. In addition, a pink baked colored pencil lead was placed at a temperature of 50 ° C. and a humidity of 10
The strength reduction rate when left in a 0% constant temperature / humidity chamber for one week is
In the case of the baked colored pencil lead using silicon nitride and silicon oxide as binders in Examples 1 and 2 of the present invention, it hardly deteriorates to 1%, and only nitrogen silicon of Comparative Example 1 which is out of the scope of the present invention is used. The calcined pencil lead as a binder, the calcined pencil lead of Comparative Example 2 using only silicon oxide as a binder, or the calcined pencil lead of Comparative Example 3 using a bentonite binder was found to be more stable.

[0035]

According to the present invention, there is provided a fired color pencil lead having high strength, good writing quality, extremely vivid drawing line color, and a method for producing the same.

Continued on the front page (72) Inventor Masashi Wakata 1091 Tateishi, Fujioka-shi, Gunma Mitsubishi Pencil R & D Center (72) Inventor Katsunori Kitazawa 1091 Tateishi, Fujioka-shi, Gunma Mitsubishi Pencil R & D Center F term (reference) 4J039 AE11 BA17 BA20 EA42 GA31

Claims (3)

[Claims] An impregnated polysiloxane-containing liquid having a structural unit represented by the following general formula (I) is impregnated into pores of a porous fired core made of at least a body material and silicon nitride, and an oxidizing atmosphere and / or Alternatively, there is provided a fired pencil lead comprising: a fired core obtained by heat treatment in a non-oxidizing atmosphere; and a coloring material filled in pores of the fired core. Embedded image 2. A porous fired core made of the above-mentioned constitutional material and silicon nitride is obtained by kneading a compounded composition containing at least the constitutional material and an organic excipient, extruding and baking in a non-oxidizing atmosphere. The first fired core is further heated in an oxidizing atmosphere to form a second fired core in which carbon is oxidized and removed.
A porous fired core in which perhydropolysilazane-containing liquid is impregnated into pores of the fired core and fired at 1000 ° C. or more in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere to produce silicon nitride. The fired colored pencil lead according to claim 1, wherein 3. A first fired core is obtained by kneading, extruding, and firing in a non-oxidizing atmosphere a kneaded composition containing at least a body material and an organic excipient. To obtain a second fired core in which the carbon content is oxidized and removed by further heating in the inside, impregnated with a perhydropolysilazane-containing liquid in the pores of the second fired core, and in an inert atmosphere such as a nitrogen atmosphere or After baking at a temperature of 1000 ° C. or more in an ammonia gas atmosphere to generate silicon nitride, a polysiloxane-containing liquid having a structural unit represented by the following general formula (I) is impregnated to form an oxidizing atmosphere and / or A method for producing a fired pencil lead, wherein a fourth fired core is obtained by heat treatment in an oxidizing atmosphere, and a coloring material is filled in pores of the fourth fired core. Embedded image