JP2001181545A - Sintered pencil lead and its preparation process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pencil lead which hardly breaks at chuck parts of mechanical pencils and yields a sufficient color development and writing performance without any sacrifice of lead wear. SOLUTION: An amorphous anhydrous silica powder is compounded with the pencil lead.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sintered core obtained by kneading at least a clayey binder, an inorganic filler and an organic excipient, extruding and heat-treating the sintered core to impregnate a liquid. The present invention relates to a sintered pencil lead and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a sintered core obtained by kneading a clay-based binder, an inorganic substance, an organic excipient, and the like, extruding, and then heat-treating the material to form a ceramic skeleton by firing. However, a ceramic skeleton is formed while a fine space is formed in the process of bonding the respective materials. These minute spaces (holes) cause the strength of the fired core to become weak. For example, when used in a dedicated holder such as a mechanical pencil, there is a case where a phenomenon such as breakage is caused by a biting pressure at a chuck portion for holding a lead.

[0003] As a material for improving the strength of such a fired core, there is known a material in which boron nitride is used in combination with various inorganic materials and binders in order to improve the denseness of the fired core. . JP-A-9-208879 discloses silicate compounds such as talc and mica, oxides such as silica, alumina and titanium oxide, carbonate compounds such as calcium carbonate, and sulfate compounds such as barium sulfate in addition to boron nitride. It is disclosed that inorganic powders such as the above are used, and Japanese Patent Application Laid-Open No. 9-208880 discloses that boron nitride and potassium hexatitanate fibers are used in combination.

[0004]

The concomitant use with boron nitride shown in the above-mentioned prior art contributes to a certain degree of improvement in the compactness and the strength is found to be improved, but the wear of the core is sacrificed. And the coloring properties were insufficient, for example, the writing lines were blurred.

[0005]

That is, the present invention comprises kneading at least a clayey binder, an inorganic body and an organic excipient,
The gist of the present invention is a fired pencil lead obtained by impregnating an amorphous anhydrous silica powder with a fired pencil lead obtained by impregnating a liquid into pores of a sintered core obtained by heat treatment after extrusion molding.

The details will be described below. The amorphous anhydrous silica powder used in the present invention is defined as a silicon tetrachloride oxyhydrogen flame (10%).
(00 ° C.), containing no water in the structure, being amorphous, and having an average particle size of 7 nm to 4 nm.
0 nm, and the specific surface area is 50 (m2 / g) to 380.
(M2 / g), the bulkiness is high, and due to the action of silanol groups present on the particle surface, it is used as a fluidity or viscosity modifier for various resins from a relatively small amount. Commercially available products include the Aerosil series manufactured by Nippon Aerosil Co., Ltd. as 130, 200, 200V, 200C
F, 300, 300CF, 380, R972, R97
4, R202, R805, R812, OX50, TT6
00, MOX80, MOX170, COK170, CO
K84, etc., as a fine seal series manufactured by Tokuyama Soda Co., Ltd., E50, T32, X37, X70, R
X70, A, B and the like.

In order to obtain the fired pencil lead of the present invention, for example, the following method is used. Amorphous anhydrous silica powder is mixed with blending materials such as boron nitride, clayey binder, and organic excipient, which are constitutional materials, and this mixture is kneaded with a Hensyl mixer, three rolls, etc., and then extruded to form a fine wire. Mold into a shape. Treated in an oxidizing atmosphere to 180 ° C for 10 hours, heated in an inert atmosphere at a rate of 10 ° C / hr to 300 ° C, and further heated to 1000 ° C at a rate of 30 ° C / hr, then fired for 1 hour Then, a first fired core body in which carbon of the organic excipient is a binder is obtained. Next, the first fired core is fired at 700 ° C. in an oxidizing atmosphere to remove carbon as a binder to obtain a white porous second fired core. The second calcined core was dried at 150 ° C. for about 2 hours in advance to prevent hydrolysis, and amorphous anhydrous silica and perhydropolysilazane from which water had been completely removed were mixed with 20 parts.
% Xylene solution is immersed in a mixture for 24 hours, and the mixture is impregnated into the pores of the second fired core. The second sintered core impregnated with the mixed solution is heated to 600 ° C. at a rate of 60 ° C./hr in an inert atmosphere such as a nitrogen atmosphere or an ammonia gas atmosphere, and further treated at 600 ° C. for 1 hour. A firing process is performed. The perhydropolysilazane in the mixed liquid impregnated by this treatment generates a silicon nitride skeleton by a dehydrogenation reaction, and a third fired core body is obtained. Further, for the third fired core, in order to make the silicon nitride skeleton tough, the amorphous anhydrous silica and the above-mentioned mixed solution containing perhydropolysilazane are immersed again, and then fired to perform pores. To obtain a fourth fired core having a silicon nitride skeleton laminated thereon.

An ink is used to color such a core. That is, the third fired core obtained above is immersed in a dye ink (including one in which a pigment is dissolved) to be impregnated and colored. In the case of using a dye ink, a dye solution in which various dyes such as alcohol dye, oil-soluble dye, and basic dye are put in polyethylene glycol fatty acid ester and / or polyoxyethylene alkyl ether is prepared. After immersion for an hour, a drying treatment is performed at 80 ° C. for 5 hours, and a washing treatment is performed with ethyl alcohol.

In the case of using the ink in which the pigment is dissolved, the third fired core is immersed in a solution in which the organic pigment is dissolved in sulfuric acid and the pigment is dissolved for 24 hours, and then immersed in water for 12 hours to be dissolved. The obtained pigment is immobilized and neutralized, washed, washed with water and dried.

[0010] The amount of the amorphous anhydrous silica powder used in the above-mentioned method for producing a white calcined core is 2 to the total amount excluding volatile components with respect to the total amount in the composition before firing.
Not less than 10% by weight and more preferably not more than 5% by weight
The content is preferably at least 8% by weight. If the amount used is less than 2% by weight, the color developability is low and insufficient. If the amount used is more than 10% by weight, the orientation of boron nitride is reduced, so that the color developability is obtained, but there is a concern that the strength may be reduced. That's why.

The amount of the amorphous anhydrous silica used during the immersion treatment may be about 5% based on the solid content of perhydropolysilazane. Although the viscosity slightly increases, it may be diluted with a xylene solution.

[0012] was further described above, the white porous baked lead, but a translation of impregnating a volatile solution dispersed dye ink, such as polyethylene glycol fatty acid esters and or polyoxypropylene ethyl ether, R ₁ of both solutions If the number of carbon atoms is smaller than that of the decyl group, the volatility is increased, so that it becomes difficult to enter the pores of the fired core body. If the number of carbon atoms is larger than the oleyl group, the solubility with various dyes deteriorates.

The amount of both solutions in the ink solution is
The compounding amount varies depending on the type of the dye to be used, but it is preferred from the viewpoint that the content can be obtained in the range of 40% by weight or more for polyethylene glycol fatty acid ester and 35 to 90% by weight for polyoxyethyl ether. In order to promote the effects of polyoxyethyl ether and polyethylene glycol fatty acid ester, both solutions may be used in combination with low-boiling organic solvents such as isopropyl alcohol and ethyl alcohol, which have good compatibility. The solvent, the polyethylene glycol fatty acid ester and the polyoxyethyl ether may be mixed with each other and used.

Examples of the inorganic substance include conventionally known boron nitride, talc, mica, quartz, alumina, calcium carbonate, mica, molybdenum disulfide, tungsten dioxide, and the like. Examples of the clayey binder include bentonite and kaolin clay. And the like, as organic excipients, thermoplastic resins such as vinyl chloride resin, chlorinated vinyl chloride resin, polyvinyl alcohol, thermosetting resins such as furan resin, phenolic resin, epoxy resin, lignin, cellulose,
Natural polymer substances such as tragacanth gum, petroleum asphalt, coal tar pitch, naphtha cracked pitch, dry distilled pitches such as synthetic resin, and water, dioctyl Plasticizers such as phthalate, dibutyl phthalate, butyl phthalyl butyl glycolate, dibutyl phthalate, tricresyl phosphate, and propylene carbonate; lubricants such as metal stearate such as zinc stearate, calcium stearate, and lithium stearate; and various types such as methyl ethyl ketone Organic solvents and the like may be used, and if necessary, a plurality of these may be used in combination.

Next, as a dye to be impregnated into the white sintered core and a coloring agent used in the pigment solution, various kinds of natural and synthetic dyes and various kinds of inorganic and organic pigments can be arbitrarily used. As the dye, Japananol Fast Black D
Conch (CI Direct Black 17), Water Black 100L (19), Water Black L
-200 (19), Water Black # 7 (1)
9), Kayaset Black W9 (19), Direct Fast Black B (22), Direct Fast Black AB (32), Direct Deep Black E
X (38), Direct Deep Black (similar to 38), Direct Fast Black Conch (5
1), Kayaras Sprague-ray VGN (71), Kayak Direct Brilliant Yellow G (CI Direct Arrow 4), Direct Fast Yellow 5GL (2)
6), Aizen Brimura Yellow GCLH (44), Direct Fast Yellow R (50), Aizen Direct Fast Red FH (CI Direct Red 1), Nippon Fast Scarlet GSX (4),
Direct Fast Scarlet 4BS (23), Eisen Direct Durin BH (31), Direct Scarlet B (37), Kayak Direct Scarlet 3B (39), Eisen Buri Malabin Conch 2B
LH (75), Sumilight Red F3B (80),
Aizen Burimura Red 4BH (81) Kayasupurarubin BL (83), Kayasu Light Red F5G
(225), Kayasu Light Red F5B (22)
6), Kayalas Light Rose FR (227) Direct Sky Blue 6B (CI Direct Blue 1),
Direct Sky Blue 5B (15), Benzo Brilliant Sky Blue 8GS (41), Sumilite Supra Blue BRR Conc (71), Diebogen Turquoise Blue S (86), Water Blue # 3 (8)
6), Kayara Star Koizu Blue GL (86), Daiwa Blue 215H (87), Kayara Supra Blue F
F2GL (106), Kayaras Supra Blue FFRL
(Id. 108) Kayasu Splatter Turquoise Blue FBL
(199), Acid Blue Black 10B (CI Acid Black 1), Nigrosine (2), Water Black R455 (2), Water Black R510 (2), Suminol Milling Black 8BX (24), Kayanol milling black VLG (26), Kayanol milling black BR
Conch (31), Mitsui Nylon Black GL (5)
2), Eisen Opal Black WH Extra Conch (52), Sumilan Black WA (52), Ranyl Black BG Extra Conc (107), Kayanol Milling Black TLB (109), Suminol Milling Black B (52) 109), Kayanol Milling Black TLR (110), Eisen Opal Black New Conc (119), Water Black 187
-L (154) Acid Yellow # 10 (CI Acid Yellow 1), Kayak Acid Brilliant Flavin FF (7: 1), Kayasil Yellow GG (17),
Xylene Light Yellow 2G 140% (17), Suminol Leveling Yellow NR (19), Water Yellow # 1 (23), Daiwatrazine (25),
Kayaktor Trazine (23), Suminol Fast Yellow R (25), Diacid Light Yellow 2GP (29), Suminol Milling Yellow O (38), Suminol Milling Yellow MR (42), Water Yellow # 6 (42), Kayanol Yellow NFG (4
9), Suminol Milling Yellow 3G (72), Suminol Fast Yellow G (61), Suminol Milling Yellow G (78), Kayanol Yellow N5G (1)
10), Sumino Milling Yellow 4G 200% (1
41), Kayanol Yellow NG (135), Kayanol Milling Yellow 5GW (127), Kayanol Milling Yellow 6GW (142), Sumitomo Fast Scarlet A (CI Acid Red 8), Kayak Silk Scarlet ( 9), Solar Rubin Extra (14), Daiwa New Koksin (18), Water Scarlet (18), Daiwa Red 102 (18), Eisenbon Saw RH (26), Daiwa Red 2 (No. 27), Suminol Leveling Brilliant Red S3B (No. 35), Kayasil Rubinol 3GS (No. 37), Eisenerythrosine (No. 51), Kayak Acid Rhodamine FB (No. 52), Daiwa Red No. 106 (No. 52) , Suminol Leveling Rubinol 3GP
(57), Diacid Alizarin Rubinol F3G
200% (82), alizarin rubinol 5G (8)
3), Aizen Eosin GH (87), Water Red # 2 (87), Daiwa Red 103WB (8)
7), Water Pink # 2 (92), Eisen Acid Phloxine PB (92), Daiwa Red No. 104 (92), Rose Bengal (94), Kayanol Milling Scarlet FGW (111), Kayanol Milling Rubin 3BW (129), Suminol Milling Brilliant Red 3BN Conc (131), Suminol Milling Brilliant Red BS (138), Eisen Opal Pink BH (186), Suminol Brilliant Red B Conch (249), Kayak Acid Brilliant Red 3BL (254), Kayak Acid Brilliant Red BL (265), Kayanol Milling Red GW (276), Mitsui Acid Violet 6BN (CI Acid Violet 1)
5), Mitsui Acid Violet BN (17), Water Violet # 1 (49), Water Violet # 5 (49), Daiwa Purple No. 1 (49), Ink Violet L10 (49), Sumitomo Patent Pure Blue Blue VX (CI Acid Blue 1), Water Blue # 106 (Same 1), Patent Blue AF
(No. 7), Water Blue # 9 (No. 9), Daiwa Blue No. 1 (No. 9), Ink Blue L20 (No. 9), Spranol Blue B (No. 15), Water Blue # 116
(15), Orient Soluble Blue OBC (2)
2), Orient Soluble-OBX (22), Suminol Leveling Blue 4GL (23), Mitsui Nylon Fast Blue G (25), Kayasil Blue A
GG (40), Kayasil Blue BR (41), Mitsui Alizarin Safirol SE (43), Suminol Leveling Sky Blue R Extra Conc (6)
2), Mitsui Nylon Fast Sky Blue R (7)
8), Sumitomobrilliant indocyanine 6Bh / e
(83), Sandran cyanine N-6B 350% (90), Water Blue # 115 (90), Water Blue # 105 (90), Orient Soluble Blue OBB (93), Spranol Cyanine 7BF
(100), Sumitomo Brilliant Blue 5G (1)
03), Acid Blue (103), Asilane Brilliant Blue FFR (104), Kayanol Milling Ultrasky SE (112), Kayanol Milling Cyanine 5R (113), Eisen Opal Cyanine 2GLH (158), Daiwa Guinea Green B (C.I.
I. Acid Green 3) Acid Brilliant Milling Green (9), Daiwa Green # 70 (1)
6), Kayanol Cyanine Green G (25), Suminol Milling Green G (27), acid dyes such as Water Orange # 17 (CI Acid Orange 56), and Water Yellow # 2 (CI. Food Yellow 3), Food Yellow No. 5 (CI Food Yellow 3) Food Red 3 (CI Food Red 14), Food Blue 2 (CI Acid Blue 74), Food For green 2
No. (CI Acid Green 5), Malachite Green (CI.42000), Victoria Blue FB (CI.44045), Spiron Red (C-GH), Methyl Violet FN (CI. .42
535), Rhodamine F4G (CI. 45160),
Basic dyes such as Rhodamine 6GCP (CI. 45160), VALIFASTCOLORS series 100
No. 0, No. 2000 and No. 3000 alcohol dyes.

As the pigment, Special Blac is used.
k 6, S170, S610, 5, 5, 4,
A, 550, 35, 250, 100, Prin
tex150T, U, V, 140U, 140
V, 95, 90, 85, 80, 75, 5
5, 45, P, XE2, L6, L, 30
0, 30, 30, 35, 25, 200, A,
G (above, manufactured by Degussa Japan Co., Ltd.), # 2400
B, # 2350, # 2300, # 2200B, # 100
0, # 950, # 900, # 850, # MCF88, M
A600, MA100, MA7, MA11, # 50, #
52, # 45, # 44, # 40, # 33, # 32, # 3
0, CF9, # 20B, # 4000B (Mitsubishi Chemical Industries, Ltd.), MONARCH 1300, 110
0, 1000, 900, 880, 800, 7
00, MOGUL L, REGAL 400R, 66
0R, 500R, 330R, 300R, 99
R, ELFTEX 8, 12 and BLACK PEAR
LS 2000 (above, Cabot Co. LTD, USA)
Manufactured), Raven7000, 5750, 5250,
5000, 3500, 2000, 1500, 1255, 1250, 1200, 1170, 1
060, 1040, 1035, 1020, 10
00, 890H, 890, 850, 790, 780, 760, 500, 450, 430, 420, 410, 22, 22, 16, 14, and 825
Oil Beads, H20, C, Conduc
carbon blacks such as tex 975, 900, and SC (all manufactured by Colombian Carbon Japan Co., Ltd.);
KA-10, 10P, 15, 15, 20, 30, 3
5, 60, 80, 90, KR-310, 38
0, 460, 480 (Titanium Industry Co., Ltd.
Titanium oxide such as P25 (manufactured by Nippon Aerosil Co., Ltd.), BS-605, and 607 (manufactured by Toyo Aluminum Co., Ltd.), and bronze powders P-555 and P-77.
7 (above, manufactured by Nakajima Metal Foil Industry Co., Ltd.), bronze powder 3L5, 3L7 (above, manufactured by Fukuda Metal Foil Industry Co., Ltd.)
Metal powder pigments, such as black iron oxide, yellow iron oxide, red iron oxide, ultramarine, navy blue, cobalt blue, chrome green, chromium oxide and other inorganic pigments, Hansa A-10G,
5G, 3G, 4, GR, A, Benzidine Yellow, Permanent Yellow NCG, Tartrazine Lake,
Quinoline yellow, Sudanese 1, permanent orange,
Indus Ren Brilliant Orange GN, Permanent Brown FG, Para Brown, Fire Red, Brilliant Carmine BS, Pyrazolone Red, Lake Red C, Quinacridone Red, Brilliant Carmine 6
B, Bordeaux 5B, thioindigo red, fast violet B, dioxane violet, alkali blue lake, phthalocyanine blue, indigo, acid green lake, phthalocyanine green and the like.

[0017]

The amorphous anhydrous silica is an amorphous isotropic crystal that is not an anisotropic crystal in its particle shape unlike a body material such as talc or boron nitride. For this reason, first, it is not affected by the orientation at the time of the extrusion molding, and exists near the boron nitride particles even after the molding. In the process of sintering the clay particles and perhydropolysilazane by the subsequent sintering process to form a ceramic, the amorphous anhydrous silica, which is located on the surface of boron nitride with a smooth and low reactivity, is used to improve the adhesion between the binders. In order to reduce the fine gaps (holes) to help, it is presumed that the structure becomes difficult to crack even when concentrated force is applied to the core.

Amorphous anhydrous silica is treated with a silanol group (Si-OH) on the silica surface by firing treatment in an oxidizing atmosphere.
Is considered to be agglomerated and globular when hydrolyzed.Since this spherical silica is present on the surface of the boron particle crystal having high slipperiness, it exerts a spike effect on the paper surface to form a core. It is presumed that handwriting with high coloring properties can be obtained since the collapse is promoted. In addition, it is presumed that, by promoting the collapse, the writing feel can be made relatively light while having a dense core.

[0019]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

Example 1 Boron Nitride (Body Material) 48 parts by weight Organic Bentonite (clay binder) 15 parts by weight Stearic acid (lubricant) 1 part by weight Dioctyl phthalate (plasticizer) 10 parts by weight Polymethyl methacrylate (Organic excipient) 20 parts by weight Aerosil 200 (Nippon Aerosil Co., Ltd., amorphous anhydrous silica) 6 parts by weight Methyl ethyl ketone (solvent) 100 parts by weight The above materials are mixed and dispersed by a Hensyl mixer, and kneaded with three rolls. After extruding into a fine wire, heat treatment is performed for 10 hours to 180 ° C. in an oxidizing atmosphere to remove the remaining plasticizer, and then 30 ° C. at 10 ° C./hr in a nitrogen atmosphere.
A first fired core is obtained by heat-treating to 0 ° C., further heat-treating to 30 ° C./hr to 1000 ° C., and firing at 1000 ° C. for 1 hour.

Next, a heat treatment was carried out at 700 ° C. in an oxidizing atmosphere to remove the carbon having the binder as the organic excipient, thereby obtaining a white fired core. This second calcined core is immersed in a perhydropolysilazane-containing liquid (20% xylene solution) to which Aerosil 200 has been added in advance by 2 parts by weight and immersed at room temperature for 24 hours, and then at 60 ° C./hr in a nitrogen gas atmosphere. 6
A baking treatment was performed in which the temperature was raised to 00 ° C. and the baking was further performed for 1 hour to obtain a white third baking core. Further, the third fired core body is again immersed in a perhydropolysilazane-containing liquid (20% xylene solution) to which 2 parts by weight of the above-mentioned Aerosil 200 has been added, and again at 60 ° C./hr in a nitrogen gas atmosphere.
A baking treatment was performed in which the temperature was raised to 0 ° C. and baking was further performed for 1 hour to obtain a white fourth baking core having a nominal size of 0.5.

The fourth fired core was immersed in a red dye ink having the following composition, allowed to stand at room temperature for 24 hours, taken out of the solution, and dried at 80 ° C. for 5 hours to remove isopropyl alcohol and remove a nominal diameter of 0. A red fired pencil lead of 0.5 was obtained. (Red dye ink) VALIFAST COLOR 1335 (manufactured by Orient Chemical Co., Ltd.) 20 parts by weight Isopropyl alcohol 10 parts by weight Polyoxyethylene oleyl ether (n = 2) 70 parts by weight

<Example 2> The fourth fired core of Example 1 was allowed to stand at room temperature for 24 hours in a pigment ink solution having the following composition. (Pigment ink solution) Fastogen Super Red 2Y (quinaglidone pigment, manufactured by Dainippon Ink Industries, Ltd.) 15 parts by weight 98% sulfuric acid 85 parts by weight After leaving still in the above pigment ink solution for 24 hours, the core was taken out and put in water. It was immersed for 12 hours, neutralized with a sodium hydroxide solution or the like, further washed with water, and dried at 100 ° C. for 8 hours to obtain a red fired pencil lead having a nominal diameter of 0.5.

<Examples 3 to 10> In Example 1, the amount of Aerosil 200 used was changed from 6 parts by weight to 1.5 parts by weight (1.6 wt%), 2 parts by weight (2.1 wt%), 4 parts by weight. (4.1 wt%), 5 parts by weight (5.3 wt%), 8 parts by weight (7.8 wt%), 9 parts by weight (8.8 wt%), 1
0 parts by weight (9.6 wt%), 12 parts by weight (11.3 wt%)
%) To obtain a red fired pencil lead in the same manner as in Example 1.

Example 11 The white second fired core of Example 1 was immersed in the same red dye ink as in Example 1 in the same manner as in Example 1, left at room temperature for 24 hours, and removed from the solution. Thereafter, it was dried at 80 ° C. for 5 hours to remove isopropyl alcohol to obtain a red fired pencil lead having a nominal diameter of 0.5.

<Examples 12 to 19> In Example 11, the amount of Aerosil 200 was changed from 6 parts by weight to 1.5 parts by weight (1.6 wt%), 2 parts by weight (2.1 wt%),
Parts by weight (4.1 wt%), 5 parts by weight (5.3 wt%),
8 parts by weight (7.8 wt%), 9 parts by weight (8.8 wt%)
%), 10 parts by weight (9.6 wt%), 12 parts by weight (1
1.3 wt%) to obtain a red fired pencil lead in the same manner as in Example 11.

<Comparative Examples 1 and 2> A red fired pencil lead was obtained in the same manner as in Examples 1 and 11, except that talc was used in place of Aerosil 200.

<Comparative Examples 3 and 4> Example 1 was repeated except that Aerosil 200 was not used.
And 11. A red fired pencil lead was obtained.

With respect to the fired pencil cores obtained in the above Examples and Comparative Examples, bending strength (unit: MPa) was used as a substitute for strength, and writing line density (unit: D) was used as a substitute for color development. Was measured by the test method described in JIS S6005. In addition, the substitute characteristics for the writing taste of the baked pencil lead are as follows: high quality paper (NBS PAPE
R made by Ricoh Co., Ltd.), put the core in a special holder, and put the core about 2 mm from the end of the holder, and then write the core vertically with a weight of 300 g against the writing surface. Was measured as a dynamic friction coefficient. The smaller the value of the dynamic friction coefficient, the better the writing quality, and the higher the numerical value, the worse the writing quality.

Further, the lead is inserted into a mechanical pencil, and the chuck is bitten by the lead.
A drop test is performed in which the core is dropped three times from a height parallel to the ground from a height of m, and each time the core is dropped three times, it is checked whether the core in the chuck part discharges normally without being broken by knocking. confirmed. When the core is discharged normally by knocking without breaking the core even if it is dropped three times (○), when one or two pieces are broken during three drops (△), and when all are broken (×) You rated it on a three-point scale.

[0031]

[Table 1]

As described above, the fired pencil lead of the present invention obtained from the examples has good strength while having strength and not breaking at the chuck biting portion when a dedicated holder such as a mechanical pencil is used. It is possible to obtain a core having writing taste and coloring.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J039 AB01 AB02 AB06 AB07 AD05 AD06 AE01 AE02 AE05 BA04 BA06 BA13 BA16 BA17 BA18 BA20 BA21 BA23 BA24 BA26 BA30 BA32 BA35 BA36 BA37 BA38 BC09 BC12 BC20 BC60 BE01 BE05 BE07 DA03 DA05 DA06 EA15 EA16 EA17 EA19 GA31

Claims (6)

[Claims] 1. A fired pencil lead obtained by kneading at least a binder, an inorganic substance and an organic excipient, extruding and heat-treating a sintered core obtained by impregnating a liquid with a liquid. A fired pencil lead characterized by containing silica powder. 2. The fired pencil lead according to claim 1, wherein at least silicon nitride is used as said binder, and at least boron nitride is used as said inorganic substance. 3. The ink according to claim 1, wherein the liquid to be impregnated into the fired core is an ink in which a dye is dissolved.
The baked pencil lead described in the above. 4. The ink according to claim 1, wherein the ink contains a polyethylene glycol fatty acid ester represented by the following general formula (Formula 1) and / or a polyoxyethylene alkyl ether represented by the following general formula (Formula 2). Claim 3
The baked pencil lead described in the above. (Equation 1) (Equation 2) 5. The amount of the amorphous anhydrous silica powder used is:
The fired color pencil lead according to any one of claims 1 to 3, wherein the content is 2% by weight or more and 10% by weight or less based on the total amount. 6. A first fired core is formed by kneading at least a clayey binder, an inorganic body, and an organic excipient, extruding, and firing in a non-oxidizing atmosphere. The body is heated in an oxidizing atmosphere to form a second fired core body in which the carbide binder has been oxidized and removed, and the pores of the second fired core body are impregnated with a perhydropolysilazane-containing liquid to form an inert gas atmosphere or ammonia. Forming a third fired core in which silicon nitride is generated by heat treatment in a gas atmosphere; and further, in a fired pencil lead obtained by impregnating the pores of the third fired core with ink, at least the first fired core is used. A method for producing a calcined colored pencil lead, wherein amorphous anhydrous silica powder is used in a mixed material to be formed and in a perhydropolysilazane-containing liquid.