JP4352914B2 - Pencil lead - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a wood pencil lead, a mechanical pencil lead (hereinafter collectively referred to as a pencil lead), graphite as a colorant, a component that binds the colorant, and a pore-forming component that is carbonized by heat treatment. And a pencil lead obtained by firing after kneading and molding.

The pencil core uses clay, various synthetic resins, etc. as a binder, and it is uniform with a kneader, Henschel mixer, three rolls, etc. together with a constitution material and coloring agents, pore forming agents, plasticizers, solvents, etc. It is obtained by dispersing and extruding, followed by high-temperature firing at 800 ° C to 1200 ° C. The pores of the fired core are impregnated with various substances for various purposes. As examples of impregnation components, liquid paraffin, silicone oil, spindle oil (see Patent Document 1), alpha-olefin oligomer (see Patent Document 2), and the like are known. In addition, waxes such as paraffin wax, carnauba wax, and microcrystalline are known.
These impregnating components are obtained by immersing the fired core in pressurized, decompressed, or heated oil, and then removing excess oil from the surface to impregnate the pores of the pencil core.
Japanese Patent Laid-Open No. 55-025368 JP-A-63-135469

Due to the impregnating component, the effect of dark handwriting can be expected. However, the dark handwriting becomes noticeable when the writing line graphite adheres to the hand by rubbing with a hand or the like, or the stain spreads on the paper. Dark handwriting and stain resistance (fixability) tend to be reversed. Dark handwriting and stain resistance do not tend to be compatible. That is, there is a general tendency that impregnated components that produce dark handwriting tend to be dirty. It is an object of the present invention to break this inverse correlation and provide a dark handwriting and a highly resistant (high fixability) pencil lead.
There are several conditions for the impregnation component. For example, it must be liquid when impregnated. That is, at least when the pores of the fired core are impregnated, the viscosity needs to be easily impregnated. And it must be stable and safe over time. Furthermore, it is non-hygroscopic so as not to affect the quality of humidity in the air. It is preferable to satisfy these conditions and contribute greatly to improving density and fixability. However, currently used liquid paraffin, silicone oil, spindle oil, alpha-olefin oligomer, and waxes are also strong. The balance between handwriting and fixability is not satisfactory. Therefore, if a pencil lead that satisfies both the above-described conditions and achieves both a strong handwriting and a fixing property can be obtained, the practical effect becomes enormous.

In the present invention, the component impregnated in the pores of the fired core contains polybutene, and the kinematic viscosity is 3,000 mm2 / sec to 160,000 mm2 / sec at 25 ° C and 27 at 100 ° C. The gist of the pencil lead is from mm2 / sec to 1,300 mm2 / sec.

Impregnation component containing polybutene having a kinematic viscosity of 25 to 3,000 to 160,000 mm2 / sec (c · S · t) and 100 ° C to 27 to 1,300 mm2 / sec (c · S · t) The pencil core impregnated with polybutene wets the surface of an extender (graphite, boron nitride, talc, etc.), forms a film, and can suppress strong reflected light mainly due to graphite. Since the reflected light in the components forming the handwriting is reduced, the handwriting looks dark and black. In addition, such impregnating components are viscous liquids that help bond graphite together and suppress the exfoliation of graphite that is not fixed on the paper at the time of writing (dirt when rubbed by hand), resulting in high fixability. Even if the handwriting is rubbed with a hand or the like, it becomes difficult to get dirty.
The kinematic viscosity can be measured according to JIS K 2283.

Details will be described below.
For the fired core according to the present invention, conventionally used constituent materials and manufacturing methods can be used without limitation. Specifically, synthetic resin such as clay, polyvinyl chloride, polychlorinated polyethylene, furan resin, polyvinyl alcohol, styrene resin, acrylic resin, urea resin, melamine resin, polyester resin is used as a binder, graphite, nitriding Constitutional materials such as boron and talc, coloring materials such as organic pigments and inorganic pigments used as necessary, pore forming agents such as polymethyl methacrylate (PMMA), dioctyl phthalate (DOP), dibutyl phthalate (DBP) Obtained by uniformly dispersing with a kneader, Henschel mixer, 3 rolls, etc. together with a plasticizer such as water, alcohol, ketone, ester, aromatic hydrocarbon, etc. It is done.

The kinematic viscosity of the impregnated component containing polybutene used in the present invention is 3,000 to 160,000 mm2 / sec (c · S · t) at 25 ° C., 27 to 1,300 mm 2 / sec at 100 ° C. ( c · S · t) or less. When the kinematic viscosity is 3,000 mm2 / sec (c · S · t) or less at 25 ° C., the density is improved, but the effect of improving the fixability is not observed. Even if the kinematic viscosity exceeds 160,000 mm2 / sec (c · S · t) at 25 ° C., no further improvement in fixability is observed, and the phenomenon of density reduction is sharply clarified.
An impregnation component having a kinematic viscosity of 3,000 or more and 160,000 mm2 / sec (c · S · t) at 25 ° C. is a viscous liquid and thus tends to be difficult to impregnate the core. Therefore, it is necessary to lower the kinematic viscosity and impregnate the core body by heating. The impregnation temperature is usually about 100 ° C. In order to impregnate the core body, it is necessary that the kinematic viscosity is 100 ° C. and is 27 or more and 1,300 mm 2 / sec (c · S · t) or less. When the kinematic viscosity is 1,300 mm2 / sec (c · S · t) or more at 100 ° C., it is difficult to enter pores in the core body because of high viscosity even when heated.
In order to improve both density and fixability, the kinematic viscosity is 3,000 to 160,000 mm2 / sec (c · S · t) at 25 ° C, and 27 to 1,300 mm2 / sec (c · S · t at 100 ° C). t) Must be less than or equal to It was found that when the oily material was impregnated within this range, a synergistic effect of improving the concentration and fixing property was obtained.

It contains polybutene and has a kinematic viscosity of 3,000 to 160,000 mm2 / sec (c · S · t) at 25 ° C., 27 to 1,300 mm2 / sec (c · S · t) at 100 ° C. The impregnation component can be produced, for example, by the following method.
Kinematic viscosity of 3,000 at 25 ℃ 160,000 mm2 / sec (c · S · t) or less, either alone or mixed with more than 27 1,300 mm2 / sec (c · S · t) following polybutene 100 ° C. Alternatively, the kinematic viscosity may be adjusted by using liquid paraffin, silicone oil, spindle oil, alpha-olefin oligomer, etc., which are conventionally impregnated oils with low kinematic viscosity, as diluent oil. Incidentally, the kinematic viscosity of the conventional impregnating oil is 200 mm 2 / sec (c · S · t) or less at 25 ° C. and 40 mm 2 / sec (c · S · t) or less at 100 ° C.
Typical kinematic viscosity ranges from 3,000 to 160,000 mm2 / sec (c · S · t) at 25 ° C, and 27 to 1,300 mm2 / sec (c · S · t) at 100 ° C. Polybutene includes HV-35, HV-50, HV-100, HV-300: manufactured by Shin Nippon Petrochemical Co., Ltd., 35H, 100H, 300H, 35R, 100R, 300R: manufactured by Idemitsu Petrochemical Co., Ltd.
The kinematic viscosity is outside the range of 3,000 to 160,000 mm2 / sec (c · S · t) at 25 ° C, 27 to 1,300 mm2 / sec (c · S · t) at 100 ° C. However, for example, polybutene HV-3000 (kinematic viscosity is 1,000,000 mm2 / sec (c · S · t) at 25 ° C, and 5,700 mm2 / sec (c · S · t) at 100 ° C is low. The kinematic viscosity may be adjusted by dilution with liquid paraffin, spindle oil, silicone oil, alpha-olefin oligomer or the like conventionally used as impregnation oil, or polybutene having a low kinematic viscosity (eg, polybutene LV-7: kinematic viscosity) May be diluted at 25 ° C. at 40 mm 2 / sec (c · S · t) and at 100 ° C. at 3.6 mm 2 / sec (c · S · t) to adjust the kinematic viscosity.
These can be suitably used as impregnation components in the present invention.

  As a method for impregnating the fired core with such an impregnating component, impregnation is performed by immersing the core in an impregnating component having a reduced kinematic viscosity while maintaining the impregnating oil at around 100 ° C., as in the general impregnation method. The composition material and firing conditions of the fired core to be impregnated may be arbitrary. After the impregnation, an excessive amount of impregnated components on the surface of the fired core body may be appropriately removed with a centrifuge to form a pencil lead.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example.

Example 1
30 parts by weight of vinyl chloride resin 35 parts by weight of graphite 35 parts by weight of talc 15 parts by weight of carbon black 2 parts by weight 10 parts by weight of dioctyl phthalate 2 parts by weight of stearic acid 30 parts by weight Methyl ethyl ketone 30 parts by weight Extruded into a thin line, heated to 300 ° C. in air, and further heated to 800 ° C. in an inert atmosphere to obtain a fired core having a nominal diameter of 0.7 mm. After being immersed in polybutene heated to 100 ° C. (HV-300: 160,000 mm 2 / sec (c · S · t) at 25 ° C., 590 mm 2 / sec (c · S · t) at 100 ° C.) for 16 hours The excess polybutene on the surface was removed to obtain a pencil lead.

(Example 2)
In Example 1, instead of polybutene (LV-300), mixed polybutene (LV-50 and HV-300 weight ratio 50:50, kinematic viscosity at 25 ° C., 3,000 mm 2 / sec (c · S · t), at 100 ° C. A pencil lead was obtained in the same manner as in Example 1 except that 27 mm2 / sec (c · S · t) was used.

(Example 3)
In Example 1, instead of polybutene (LV-300), polybutene (HV-1900: kinematic viscosity at 25 ° C., 650,000 mm 2 / sec (c · S · t), at 100 ° C., 3,800 mm 2 / sec (c · S · t)) and liquid paraffin (Daffney Oil CP 68N, manufactured by Idemitsu Petrochemical Co., Ltd.): kinematic viscosity at 25 ° C. and 140 mm 2 / sec (c · S · t), 100 ° C. and 9 mm 2 / sec (c · S · t) In a ratio of 60:40 by weight ratio (except for using a kinematic viscosity of 10,000 mm2 / sec (c · S · t) at 25 ° C and 100 mm2 / sec (c · S · t) at 100 ° C) A pencil lead was obtained in the same manner as in Example 1.

Example 4
In Example 1, instead of polybutene (LV-300), polybutene (HV-1900: kinematic viscosity at 25 ° C., 650,000 mm 2 / sec (c · S · t), at 100 ° C., 3,800 mm 2 / sec (c · S · t) and polybutene (LV-10: kinematic viscosity at 25 ° C. 40 mm 2 / sec (c · S · t), 100 ° C. 3.6 mm 2 / sec (c · S · t)) at a weight ratio of 90:10 The same as in Example 1 except that a mixture of kinematic viscosity (100,000 mm 2 / sec (c · S · t) at 25 ° C., 1,300 mm 2 / sec (c · S · t) at 100 ° C.) was used. I got a pencil lead.

(Comparative Example 1)
In Example 1, instead of polybutene (LV-300), liquid paraffin (Dafney Oil CP 68N, manufactured by Idemitsu Petrochemical Co., Ltd.): kinematic viscosity: 140 mm 2 / sec (c · S · t) at 25 ° C., 9 mm 2/100 ° C. A pencil lead was obtained in the same manner as in Example 1 except that sec (c · S · t) was used.

(Comparative Example 2)
In Example 1, instead of polybutene (LV-300), polybutene (LV-10: kinematic viscosity at 25 ° C. at 40 mm 2 / sec (c · S · t), at 100 ° C. at 3.6 mm 2 / sec (c · S · t) ) Was used in the same manner as in Example 1 to obtain a pencil lead.

(Comparative Example 3)
In Example 1, instead of polybutene (LV-300), polybutene (HV-1900: kinematic viscosity at 25 ° C., 650,000 mm 2 / sec (c · S · t), at 100 ° C., 3,800 mm 2 / sec (c · S · A pencil lead was obtained in the same manner as in Example 1 except that t)) was used.

The handwriting density and fixability of the pencil lead obtained in the above examples were measured. The results are shown in Table 1.

以上より、本発明の鉛筆芯は、濃い筆跡濃度と高い定着性とを両立しえるものである。

As described above, the pencil lead of the present invention can achieve both high handwriting density and high fixability.

Claims (1)

The component impregnated in the pores of the fired core contains polybutene, and the kinematic viscosity is 3,000 mm2 / sec to 160,000 mm2 / sec at 25 ° C, and 27 mm2 / sec at 100 ° C. A pencil lead of 1,300 mm2 / sec or less.