JPH02173169A - Lead of pencil - Google Patents

Abstract

PURPOSE:To obtain a lead of pencil simultaneously satisfying improvement in concentration and grab, comprising a calcined core material and a specific oily substance impregnated into pores of the calcined core material. CONSTITUTION:In lead of pencil comprising a calcined core material and an oily substance impregnated into pores of the calcined core material, a phthalic ester (e.g. phthalic acid dibenzyl ester, phthalic acid dihexadecyl ester, phthalic acid dicyclohexyl ester or phthalic acid diphenyl ester) solid at normal temperature is used at least part of the oily substance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a pencil lead comprising a fired core and an oil impregnated into the pores of the fired core. That is.

This relates to a so-called baked type pencil lead.

(Conventional technology) Baked type pencil leads use clay, various synthetic resins, etc. as binding materials, as well as extenders such as graphite and talc, colorants, pore-forming agents, plasticizers, etc., as necessary. It is manufactured by impregnating a porous fired core with various substances for various purposes, which is obtained by uniformly dispersing it together with a solvent using a pressure kneader, Henschel mixer, three rolls, etc., and then subjecting it to high-temperature heat treatment.

A typical impregnating material here is an oily substance, which is generally useful for increasing concentration. Also.

It is also useful in improving the adhesion to the writing surface, that is, the resistance to staining of handwriting. Incidentally, examples of oily substances include spindle oil, silicone oil, liquid paraffin, microcrystalline wax, montan wax, bohemia wax, paraffin wax, carnauba wax, cotton wax, and beeswax. They have various melting points, boiling points, etc., and some are liquid at room temperature while others are solid.

(Problems to be Solved by the Invention) Improving the density brought about by oily substances and improving fixing properties are not always compatible. That is, there is a general tendency that oily substances with a high degree of improvement in concentration have a low degree of improvement in fixability. in particular,
Those with a low melting point tend to have a high degree of improvement in density, but have a low degree of improvement in fixability, and those with a high melting point have a high degree of improvement in fixability, but have a low degree of improvement in density.

It is an object of the present invention to break this inverse relationship and provide a pencil lead that has an even higher density if the improvement in fixing performance is the same, and a pencil lead that has an even better fixability if the improvement in the density is the same.

(Means for solving the problem) A phthalate ester that is solid at room temperature is used as the oil. This phthalate ester can be used in combination with other oils.

That is, the present invention provides a pencil lead comprising a fired core and an oily substance impregnated into the pores of the fired lead, which contains a phthalate ester that is solid at room temperature as at least a part of the oily substance. The main point is the pencil lead.

The details will be explained below.

Examples of phthalate esters that are solid at room temperature include dibenzyl phthalate, dihexadecyl phthalate, dicyclohexyl phthalate, diphenyl phthalate, monomethyl phthalate, monophthalate monophthalate, and monophthalate. Examples include cyclohexyl ester. Such phthalate esters, which are solid at room temperature, solidify so that the molecular arrangement becomes regular, and also have the property of easily causing peeling between the eyebrows when pressurized.

This phthalate ester is impregnated into a fired core having an appropriate porosity. For impregnation, heat may be applied as appropriate and pressure may be applied if necessary.

Note that other oily substances that can be used in combination are suitable, such as those mentioned above, and the more compatible they are, the easier the impregnation will be.

In addition, there are impregnating substances other than oily substances, and they may be used in combination depending on the purpose of use.

(Example) Hereinafter, "parts" simply indicate "parts by weight."

<Example 1> Vinyl chloride vinyl acetate copolymer 30 parts graphite
50 parts carbon black
5 parts stearate 1
Dioctyl phthalate 10 parts The above materials were thoroughly kneaded with three rolls, extruded into a thin wire, heat-treated in air to 300°C, and then heated to 950°C in an inert atmosphere.
A fired core for a mechanical pencil with a nominal diameter of 0.5++a was obtained. This was immersed in phthalic acid dibenzyl ester heated to 100° C. for 2 hours, and the excess was removed to obtain a pencil lead.

<Examples 2 to 4> In Example 1, the fired core was immersed in dihexadecyl phthalate, dicyclohexyl phthalate, and diphenyl phthalate instead of immersing the fired core in dibenzyl phthalate. The procedure was the same as in Example 1.

<Example 5> In Example 1, the fired core was immersed in phthalic acid monophenyl ester at 130°C instead of immersing it in phthalic acid monophenyl ester at 100°C.
I did the same thing.

<Example 6> Everything was the same as in Example 1, except that instead of immersing the fired core in phthalic acid dibenzyl ester, it was immersed in an equal weight mixture of phthalic acid diphenyl ester and spindle oil. .

<Example 7> In Example 1, instead of immersing the fired core in dibenzyl phthalate, dihexadecyl phthalate and microcrystalline wax were mixed in a ratio of 4:1 (by weight).
The same procedure as in Example 1 was carried out with Suhachi, except that it was immersed in the mixture.

(Examples 8 to 10) For a total of three products, two products with a carbon skeleton commercially available for mechanical pencils and one product with a clay skeleton commercially available for red holders, methyl ethylkene and acetic acid were used. After sufficient deoiling by steps 1 to 1, this was used in place of the fired core in Example 3.
Everything was the same as in Example 3.

Comparative Examples 1 to 4 In Examples 1 and 8 to 10, all the procedures were the same as in Examples 1 and 8 to 10, except that the fired core was immersed in spindle oil instead of immersed in phthalic acid dibenzyl ester.

Comparative Examples 5 to 8> In Examples 1.8 to 10, instead of immersing the fired core in phthalic acid dibenzyl ester at 100 °C,
Everything was the same as in each example except that it was dipped in montan wax.

(Effects of the Invention) Table 1 shows the results of examining the density and fixing properties of the samples obtained on each side.

(Hereafter, blank space) Table 1 (Note) Concentration is measured according to LIS S 6005,
In addition, the fixability is determined by the following formula: (100-β) where α is the reflectance of the writing area drawn on baryta paper with a load of 400 g, and β is the reflectance of the dirty area outside the writing area when the writing area is rubbed under certain conditions. )÷(100-α)X100. Here, the smaller the value, the better the fixing performance.

As can be seen from Table 1, according to the present invention.

A pencil lead with an improved inverse relationship between density and fixability can be obtained.

Claims (1)

[Scope of Claims] A pencil lead consisting of a fired core and an oily substance impregnated into the pores of the fired lead, which contains a phthalate ester that is solid at room temperature as at least a part of the oily substance. Pencil lead.