JP5589747B2 - Firing pencil lead - Google Patents

Description

  The present invention relates to a fired pencil lead obtained by blending at least graphite and a synthetic resin, kneading and extruding into a fine wire, and then heat-treating to a firing temperature.

Common firing pencil cores are graphite, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, chlorinated polyethylene resin, polyvinyl alcohol resin, polyacrylamide resin, chlorinated paraffin resin, phenol resin, furan resin, Synthetic resins such as urea resin and butyl rubber are the main materials, plasticizers such as phthalates, solvents such as methyl ethyl ketone and water, stearates, stearic acid, carbon black, etc. are also used as necessary. After being dispersed and mixed and kneaded, extruded into a thin line, heat treated up to the firing temperature, and if necessary, oils and waxes such as silicone oil, liquid paraffin, spindle oil, squalane, α-olefin oligomer, etc. It is manufactured by appropriately impregnating.

As described above, graphite is used as a part of the constituent material of the pencil lead. Since graphite is flat, the strength of the core is improved by orienting in the extrusion direction when the core is formed into a thin line, and the graphite particles are peeled off due to resistance to the paper due to its cleavage. It becomes a writing line by fixing. However, since the reflection of light is large on the basal surface of the graphite particles, the writing lines appear to be lead color instead of black. In order to reduce the reflection of the light and make the writing line blacker, there is known a method of using ceramic powder such as silica, mica and talc in addition to graphite. This is because these ceramic powders adhere to the surface of graphite and light is irregularly reflected, so that the color of the writing line becomes black instead of lead color. Moreover, by using ceramic powder together with graphite, the wear of the core is promoted, and the writing line concentration is also improved. Examples of ceramic powders used in combination with graphite include natural mica in JP-B-42-007166 (Patent Document 1) and talc in JP-A-54-088423 (Patent Document 2). In Japanese Patent Laid-Open No. 2002-302633 (Patent Document 3), silicon nitride is disclosed. In Japanese Patent Laid-Open No. 7-258594 (Patent Document 4), boron nitride is disclosed. Describes amorphous platy silica, respectively.
It has been confirmed that the ceramic powder used in these prior arts improves the writing line density and blackness in proportion to the amount used, but the strength is lower than when ceramic powder is not used in combination. On the other hand, when the amorphous plate-like silica described in Patent Document 5 is used in combination with graphite, the strength reduction is less than that of other technical properties, and the effect of promoting the wear of the core against the paper surface is high. It has been confirmed that the density and blackness are further improved.

Japanese Patent Publication No.42-007166 Japanese Patent Laid-Open No. 54-088423 JP 2002-302633 A JP-A-7-258594 JP 2009-228002 A

When ceramic powder is used as a part of the constituent material of the fired pencil lead, not only the concentration but also the blackness of the writing line is improved, but the bending strength of the lead is lowered. Therefore, in order to further improve the performance of the fired pencil lead, it is an object to provide a fired pencil lead that maintains the density and blackness and has improved bending strength.
In general, a baked pencil lead reduces the writing line density / black when an attempt is made to improve the bending strength, and conversely, an attempt to improve the writing line density / blackness lowers the bending strength. That is, there is an inverse correlation between bending strength and writing line density / black. Accordingly, it is very important to improve the performance of the baked pencil lead while maintaining either one while maintaining the other.

The gist of the present invention is a fired pencil lead obtained by blending at least titanium silicon carbide and a synthetic resin, kneaded, extruded into a thin wire, and then subjected to heat treatment up to the firing temperature.

Titanium silicon carbide used in the present invention is a plate-like compound having very flexible properties. Titanium silicon carbide has a crystal structure in which two layers, a titanium carbide layer and a silicon monoatomic layer, are stacked on top of each other. The crystal structure is easily distorted between the two layers, and flexibility is developed because external stress is absorbed. To do. The core is in contact with the mechanical pencil in addition to the paper surface at the time of writing, such as the chuck part that has the function of holding the core and the stainless steel pipe that has the function of guiding the core. If the core is broken during writing, the latter contacts It often breaks. Therefore, when titanium silicon carbide is used as a part of the constituent material of the fired pencil core, the titanium silicon carbide is flat in the direction perpendicular to the c-axis direction of the crystal structure (see FIG. 2) during molding. The structure is oriented in the extrusion direction so that the c-axis direction of the structure is the longitudinal direction of the core. Therefore, when a force is applied from the side surface of the core in the core, the flat titanium silicon carbide distorts between the titanium carbide layer and the silicon monoatomic layer as shown in FIG. 1 to absorb the force. As a result, the bending strength of the fired pencil lead can be improved.
In addition, titanium silicon carbide, like the ceramic powder in the prior art property, improves the bending strength because titanium silicon carbide adheres to the surface of graphite and the light is irregularly reflected, so the color of the writing line becomes black instead of lead. Even if it makes it, a writing line with little fall of a density and blackness can be obtained. From the above, by using the titanium silicon carbide of the present invention as a part of the constituent material, it is possible to provide a fired pencil lead with improved bending strength without reducing the writing line density and blackness.

Conceptual diagram showing the behavior of titanium silicon carbide in the core when an external force is applied Crystal structure of titanium silicon carbide

The present invention is described in detail below.
Titanium silicon carbide is represented by the general formula Ti ₃ SiC ₂ and has a crystal structure in which a thin layer composed of a regular octahedral crystal lattice of titanium carbide and a silicon monoatomic layer are stacked in the c-axis direction of the crystal (see FIG. 2). ).
Titanium silicon carbide can be produced by mixing titanium powder, silicon carbide powder, titanium carbide powder and then solidifying and molding under high-temperature and high-pressure conditions using a pulse current pressure sintering machine, or mixed powder of titanium, silicon and carbon However, the production method is not particularly limited, and may be pulverized and used as necessary.

The particle diameter of the titanium silicon carbide used in the present invention is not particularly limited. If the particle size is such that no problem occurs in the blending operation, it is pulverized and uniformly dispersed together with other materials during kneading.
The amount of titanium silicon carbide used is preferably 1% by weight or more based on the total amount of graphite and titanium silicon carbide used, and if the amount used is less than 1% by weight, the effect of improving the blackness of the writing line is hardly exhibited. Further, if the amount exceeds 60% by weight, the writing line density and blackness are improved, but the bending strength is lowered. Therefore, it is necessary to change the usage amount appropriately in consideration of the core diameter and hardness of the baked pencil lead. is there.

Conventionally known materials can be used as materials other than those described above. As the graphite that can be used as a material for the fired pencil core together with titanium silicon carbide, general scale-like graphite, scale-like graphite, earth-like graphite, artificial graphite, and the like can be used. In addition, one or two or more types selected from conventionally known silica, mica, talc and the like can be exemplified.
Synthetic resins used as constituent materials include polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, chlorinated polyethylene resin, polyvinyl alcohol resin, polyacrylamide resin, chlorinated paraffin resin, furan resin, urea resin, butyl rubber Examples thereof include one or more selected from among synthetic resins such as
Furthermore, if necessary, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tricresyl phosphate, dipropylene glycol dibenzoate, dioctyl adipate, propion carbonate, a solvent such as methyl ethyl ketone, water, carbon black, amorphous silica, A stearate, stearic acid, etc. can be used together.

  These raw materials are dispersed and mixed with a Henschel mixer, etc., kneaded with a kneader, three rolls, etc., then extruded into a thin line, heat treated from room temperature to around 300 ° C. in air, and then in an inert atmosphere. A baking pencil lead is obtained by performing a baking treatment at 800 ° C. to 1300 ° C. and, if necessary, impregnating oils such as silicone oil, liquid paraffin, spindle oil, squalane, α-olefin oligomer, and waxes as appropriate. To manufacture. In addition, if necessary, pigments, dyes, and the like may be used in combination to form a colored pencil lead.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further, this invention is not limited to these Examples.

<Example 1>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 0.4 parts by weight Graphite 49.6 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight After kneading, it was extruded into a thin line, heated to 300 ° C. in air, and further heated to 1100 ° C. in an inert atmosphere to obtain a fired core having a nominal diameter of 0.7 mm. This was immersed in liquid paraffin heated to 100 ° C. for 16 hours, and then excess liquid paraffin on the surface was removed to obtain a pencil lead.

<Example 2>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 0.5 parts by weight Graphite 49.5 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 3>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 2 parts by weight Graphite 48 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 4>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 5 parts by weight Graphite 45 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 5>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition was used as in Example 1.

<Example 6>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 25 parts by weight Graphite 25 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 7>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 29 parts by weight Graphite 21 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition was used as in Example 1.

<Example 8>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 30 parts by weight Graphite 20 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 9>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 31 parts by weight Graphite 19 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 10>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 35 parts by weight Graphite 15 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Example 11>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 40 parts by weight Graphite 10 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition was used as in Example 1.

<Example 12>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Titanium silicon carbide 50 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 1>
(Core composition)
Polyvinyl chloride resin 30 parts by weight of amorphous silica (trade name: Sylleaf (Mizusawa Chemical Co., Ltd.))
0.5 parts by weight Graphite 49.5 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative example 2>
(Core composition)
Polyvinyl chloride resin 30 parts by weight of amorphous silica (trade name: Sylleaf (Mizusawa Chemical Co., Ltd.))
5 parts by weight Graphite 45 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 3>
(Core composition)
Polyvinyl chloride resin 30 parts by weight of amorphous silica (trade name: Sylleaf (Mizusawa Chemical Co., Ltd.))
10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative example 4>
(Core composition)
Polyvinyl chloride resin 30 parts by weight of amorphous silica (trade name: Sylleaf (Mizusawa Chemical Co., Ltd.))
25 parts by weight Graphite 25 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 5>
(Core composition)
Polyvinyl chloride resin 30 parts by weight of amorphous silica (trade name: Sylleaf (Mizusawa Chemical Co., Ltd.))
50 parts by weight dioctyl phthalate 10 parts by weight stearic acid 2 parts by weight methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 6>
(Core composition)
Polyvinyl chloride resin 30 parts by weight A500 (Mica, Yamaguchi Mica Industry Co., Ltd.)
10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 7>
(Core composition)
Polyvinyl chloride resin 30 parts by weight CT35 (Talc, Yamaguchi Mica Industry Co., Ltd.)
10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 8>
(Core composition)
Polyvinyl chloride resin 30 parts by weight silicon nitride powder (silicon nitride, manufactured by Denki Kagaku Kogyo Co., Ltd.)
10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 9>
(Core composition)
Polyvinyl chloride resin 30 parts by weight DENKABORON NITRIDE (Boron nitride, manufactured by Denki Kagaku Kogyo)
10 parts by weight Graphite 40 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition as in Example 1 was used.

<Comparative Example 10>
(Core composition)
Polyvinyl chloride resin 30 parts by weight Graphite 50 parts by weight Dioctyl phthalate 10 parts by weight Stearic acid 2 parts by weight Methyl ethyl ketone 30 parts by weight The same composition was used as in Example 1.

Table 1 shows the bending strength measured in accordance with JIS S 6005 of the pencil lead obtained in each of the above examples, the concentration measured in accordance with JIS S 6005, and the Y value measured as representative characteristics of the blackness of the writing line. . The Y value is a value measured with SPECTROTOPOMETER “CM-3700d type” (manufactured by Konica Minolta Holdings Co., Ltd.), which is obtained by uniformly surface-coating fine paper with a load of 500 g using each pencil lead. The higher the value, the lower the reflectivity and the higher the blackness.
By blending titanium silicon carbide as shown in Table 1, the writing lines are more than when blending the same amounts of conventionally used amorphous silica, mica, talc, silicon nitride and boron nitride. The bending strength is improved while maintaining the concentration of. For example, as can be seen by comparing Examples 2, 4, 5, 6, 12 and Comparative Examples 1 to 5, when the same amount of titanium silicon carbide is blended instead of the conventionally used amorphous silica, It can be seen that the writing line density and blackness do not change, but the bending strength is improved.

Claims (2)

A fired pencil lead obtained by blending at least titanium silicon carbide and a synthetic resin, kneaded, extruded into a fine wire, and then heat-treated to a firing temperature. The fired pencil lead according to claim 1, wherein the compounding amount of the titanium silicon carbide is 1 wt% or more and 60 wt% or less with respect to the total compounding amount of graphite and titanium silicon carbide.

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