JP2900622B2 - Manufacturing method of pencil lead - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pencil lead obtained by kneading, shaping, and firing a material containing at least an organic binder and a body material.

[0002]

2. Description of the Related Art The above-mentioned pencil lead is generally called an organic fired lead, and usually comprises an organic binder such as polyvinyl chloride resin, polyvinyl alcohol and furan resin, and a body material such as graphite and boron nitride. , A plasticizer, a solvent, a stabilizer, and the like, if necessary.
The mixture is uniformly dispersed with a kneader such as a kneader or a three-roll mill, formed into appropriate dimensions, and subjected to a baking treatment to obtain a calcined core having a carbon skeleton. Further, if necessary, silicon oil, spindle oil, It is obtained by appropriately impregnating oily substances such as liquid paraffin, montan wax and microcrystalline wax.

[0003] The organic fired core has an advantage that it has higher strength than a so-called clay sintered core using clay as a binder or a so-called raw core type manufactured without performing high-temperature heat treatment. In addition to being used as a small diameter such as a sharp pencil lead, in recent years,
It has also come to be used as a large-diameter material such as a wooden pencil lead.

Nevertheless, there are still some drawbacks, and various studies have been made on higher strength ones and higher density ones. For example, Japanese Patent Publication No. 51-26849 discloses the use of a material that forms pores by depolymerization as one of means for artificially forming pores, but generally, the use of a pore-forming material improves the concentration. be able to.

[0005]

The use of the above-mentioned pore-forming material is not limited to the use of the above-mentioned pore-forming material, but generally, an increase in the concentration results in a decrease in strength, and an increase in the strength results in a decrease in concentration. That is, there is an inverse correlation between the concentration and the intensity, and there are surprisingly few such relationships that can be improved.

Therefore, an object of the present invention is to provide a method for improving the inverse correlation between the concentration and the intensity.

[0007]

Means for Solving the Problems As one of the materials, an ester compound of a linear fatty acid and a polyhydric alcohol is used. That is, the present invention relates to a method for producing a pencil lead obtained by kneading, molding, and baking a material containing at least an organic binder and a constitutional material as main materials, wherein one of the materials is a linear fatty acid. A method for producing a pencil lead, characterized by using an ester compound of phenol and a polyhydric alcohol.

The ester compounds used in the present invention include, as straight-chain fatty acids, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid,
1.2 Hydroxystearic acid, oleic acid, ricinoleic acid, behenic acid, coconut oil fatty acid, erucic acid, tallow fatty acid, and polyhydric alcohols such as ethylene glycol
, Diethylene glycol, triethylene glycol,
Examples thereof include those obtained by appropriately combining polyethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, glycerin, pentaerythritol, and dipentaerythritol. Particularly preferred are those that are liquid at room temperature and those that become liquid at the temperature at the time of kneading when kneading is possible under heating,
It has a high flash point and smoke point and leaves as little carbon residue as possible.

Here, various ester compounds are commercially available. For example, Edenoa NPG05, PDO, PTO, PEC4, PEC of Henkel Hakusui Co., Ltd.
S, PGDO, PMO, PPE, TMNC, TMP05, TMPC, TMTC, TDO, T
TO, Katsuta Kako Co., Ltd. W-212J, VS-22, A
There are PLO-200, PU-300PL, HL-1000 and the like.

Except for using such an ester compound, a conventionally known method as described above can be used as it is. The amount of the ester compound to be used is appropriately determined according to the type of the binder and the like. However, it is generally preferable to set the amount to about 0.5 to 5% by weight based on the solid content (excluding the evaporation components such as solvents). is there.

[0011]

[Effect] Although it is not clear, the ester compound seems to improve the uniform dispersibility of the material during kneading. This is because the uniform dispersibility of the material is closely related to the inverse correlation between the concentration and the strength of the core after the firing treatment. This is different from making the kneading too long or too vigorous. This is because excessive kneading causes deterioration of the material, and does not improve the uniform dispersibility of the material in the true sense.

[0012]

<Example 1> Polyvinyl chloride 50 parts by weight Graphite 60 parts by weight Dioctyl phthalate 20 parts by weight Neopentyl glycol dioleate 2 parts by weight Stearate 1 part by weight Stabilizer 2 parts by weight Methyl ethyl ketone 100 Parts by weight The above composition was kneaded with three rolls, extruded into a fine wire, and gradually heated to 300 ° C. in air over about 8 hours, and further heated to 1000 ° C. in an inert atmosphere. Heat treatment was performed to obtain a fired core having a diameter of about 0.5 mm, which was impregnated with spindle oil.

<Examples 2 to 5> In Example 1, neopentyl glycodiol dioleate was used.
From 2 parts by weight to 0.5 parts by weight (Example 2), 1 part by weight (Example 3), 4 parts by weight (Example 4),
All operations were the same as in Example 1 except that the weight was changed to 8 parts by weight (Example 5).

<Examples 6 to 8> In Example 1, neopentyl glycol dioleate was used.
Example 1 except that pentaerythritol tetraoleate (Example 6), trimethylolpropane trioleate (Example 7), and propylene glycol dioleate (Example 8) were used in place of toluene. Same as.

<Comparative Example 1> In Example 1, neopentyl glycodiol dioleate was used.
The procedure was the same as in Example 1 except that no metal was used.

<Comparative Example 2> In Example 1, neopentylglycoleate dioleate was used.
All the procedures were the same as in Example 1, except that polymethyl methacrylate was used in place of toluene.

Table 1 shows the results of measuring the flexural strength and the concentration of each of the above examples according to JIS S6005.

[0018]

[Table 1]

[0019]

In Table 1, when the values of Example 2 and Comparative Example 1 are compared, the flexural strength of Example 2 is slightly smaller, but the concentration is much smaller in Comparative Example. . When the values of Examples 3 and 7 are compared with those of Comparative Example 2, the flexural strengths of Examples 3 and 7 are excellent. As can be seen from such an example, according to the present invention, it is possible to manufacture a pencil lead with improved density-intensity inverse correlation.

Claims (1)

(57) [Claims] 1. A method for producing a pencil lead, comprising kneading, molding and baking a material containing at least an organic binder and a building material as main components. A method for producing a pencil lead, comprising using an ester compound with a polyhydric alcohol.