JP3466281B2 - Non-erasable 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 pencil lead for a wooden shaft and a pencil lead for a mechanical pencil, in which a drawn line remains when erased with an eraser.

[0002]

2. Description of the Related Art Handwriting drawn with a pencil lead can be easily erased with an eraser. Although this is an excellent feature, it was unsuitable as a writing tool for official documents, preserved documents, etc. because it could be easily erased with an eraser.

As a concrete technique for preventing the line drawn on the pencil lead from being erased with an eraser, a photocurable resin is filled in the pores of the pencil lead, and the line drawn after writing is erased with light energy of a short wavelength such as ultraviolet rays. There is known a method of irradiation (Japanese Patent Laid-Open No. 52-70619). In order to realize this non-erasing expression mechanism, there is a drawback in that it is poor in versatility because it requires an apparatus capable of irradiating light having a short wavelength such as ultraviolet rays.

There is known a method (Japanese Patent Laid-Open No. 60-264296) in which a porous black sintered body having carbon as a binder is impregnated with a colored ink composed of a wettable solvent and a dye soluble in the porous solvent. Has been. In this method, the dye, which is a coloring agent, is an expression mechanism that the drawn line remains even after the eraser is erased by dyeing on the paper surface after writing, so it generally depends on the amount of the coloring agent in the pores of the pencil lead Since the core has a small pore volume and cannot hold a sufficient amount of the coloring agent in the pencil core, it is not possible to leave a drawing line of sufficient density. Further, since the drawn line remaining after the eraser is a dye, the color of the drawn line depends on the color after the coloring of the dye, so that it is not the original color of the pencil lead. Moreover, the remaining drawn line had a defect that the light resistance was weak because it was a dye.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is to have a drawback of the prior art, that is, to give a high energy to a drawing line to fix the drawing line after writing on the paper surface, or to leave a substitute such as a dye as the drawing line. It is an object of the present invention to provide a pencil lead in which the drawn line of the pencil lead can be erased immediately after writing without taking the above means, can be corrected, and the drawn line cannot be erased with an eraser over time.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that the open pores of a pencil lead are impregnated with an organometallic compound represented by the following chemical formula 2. Immediately after writing, the drawn line can be erased with an eraser and the drawn line can be easily corrected, but it contains the organometallic compound shown in Chemical formula 2, and the hydrolyzable group in this compound is in the air. Due to the presence of moisture (moisture), it easily cures via hydrolysis reaction at room temperature over time,
The present invention has been completed by finding that the drawn line is fixed on the paper surface.

That is, the present invention relates to a pencil lead in which firing pores are impregnated with a non-drying liquid, having the following general formula: (However, R ¹ is an amino group of m = 0 or 1, R ² is a monovalent hydrocarbon group of n = 0 or 1 having 1 to 6 carbon atoms, M is silicon or titanium of Group 4 in the periodic table, X Is a non-erasable pencil lead obtained by impregnating the open pores of the pencil lead with an organometallic compound represented by (hydrolyzable group).

In the above general formula, examples of the monovalent hydrocarbon group represented by R ² and having 1 to 6 carbon atoms include alkyl groups such as methyl group, ethyl group, propyl group and butyl group. The hydrolyzable group represented by X is an essential component for expressing the non-erasability of the drawn line of the present invention. Examples of the hydrolyzable group include alkoxy groups such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a methoxyethoxy group, and an ethoxyethoxy group, as well as an acyloxy group, an alkenyloxy group, an iminoxy group, an amide group, and an amino group. ,
An aminooxy group etc. can be illustrated.

Specific examples of the organometallic compound represented by Chemical formula 2 are as follows. That is, when M is silicon, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ -Aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane , Γ-methacryloxypropylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and the like can be exemplified.

When M is titanium, isopropyltriisostearoyl titanate, isopropyltri (N-aminoethylaminoethyl) titanate, di-
n-Butoxy bis (triethanolaminato) titanium, tetra-i-propoxy titanium, tetra-n-butoxy titanium, tetrakis (2-ethylhexyloxy)
Titanium, di-i-propoxy bis (acetylacetonato) titanium, titanium-i-propoxyoctylene glycolate, titanium stearate and the like can be exemplified.

[0011]

Particularly preferably in the present invention, R ¹ in the organometallic compound represented by Chemical formula ² is an amino group, R ² is a methyl or ethyl group, M is silicon, and X is an alkoxy group such as a methoxy group or an ethoxy group. And having at least two hydrolyzable groups represented by X are desirable. That is, as an organometallic compound that satisfies these matters, there is an aminosilane coupling agent, and the following can be specifically exemplified. N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β
(Aminoethyl) γ-aminopropyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β
Examples thereof include (aminoethyl) γ-aminopropyltriethoxysilane.

The organometallic compound represented by Chemical formula 2 can be used alone or in combination of two or more kinds. When two or more kinds are used, at least one kind is an aminosilane coupling agent. desirable.

Further, in the present invention, the non-drying liquid may be used as a mixture with the organometallic compound represented by Chemical formula 2. As the non-drying liquid, soybean oil, sunflower oil, palm oil, rapeseed oil, cottonseed oil, peanut oil, coconut oil, olive oil, linseed oil, castor oil and other fats and oils, hexanoic acid,
Independent fatty acids such as heptanoic acid, oleic acid, linoleic acid, and linolenic acid, saturated hydrocarbon oils, unsaturated hydrocarbon oils, polyhydric alcohols such as glycerin, surfactants, plasticizers, etc. Can be used. Furthermore, these non-drying liquids may be used alone or in combination of two or more.

When these non-drying liquids are used in combination with the organometallic compound represented by Chemical formula 2, the organometallic compound represented by Chemical formula 2 is used in order to maintain the non-erasability of the eraser.
It is desirable that the content is at least wt%. More preferably, it is desirable that the content is 50% by weight or more. More desirably, the organometallic compound represented by Chemical formula 2 contains at least an aminosilane coupling agent.

The present invention will be described in more detail below. As a general method for producing a pencil lead, graphite, boron nitride, talc, mica, an inorganic extender such as carbon black and clay and a surfactant or water as a plasticizer are mixed and kneaded,
After molding, a clay type that is obtained by firing at a high temperature to obtain a sintered body, the inorganic extender and pitches such as synthetic resin or natural resin or asphalt, and a plasticizer or lubricant are mixed, kneaded and molded. After that, it is roughly classified into a carbon type that is obtained by firing in a non-oxidizing atmosphere at 800 to 1400 ° C. to carbonize the resin and obtain a fired body using carbon as a binder. The pencil lead produced in this manner generally has open pores, and a normal pencil lead has the open pores impregnated with fats and oils to increase the line density and smooth writing.

The present invention is characterized in that the open pores of the pencil lead produced by the above-mentioned general method are impregnated with at least a part of the organometallic compound represented by Chemical formula 2. As a method of impregnating the pencil lead with the organometallic compound, a closed system in which the organometallic compound does not come into contact with the atmosphere, preferably, a system in which the closed system is purged with dry air or a dry inert gas at that time A method of dipping the pencil lead in a liquid organometallic compound under normal pressure is preferable, but heating may be performed at that time. Further, when the viscosity of the organometallic compound is high, it can be impregnated into the open pores of the pencil lead by subjecting it to a treatment such as pressure reduction or pressure. After the impregnation treatment is completed, the pencil lead is taken out and the excess organometallic compound on the surface of the pencil lead is wiped off.

[0018]

The thus-obtained pencil lead of the present invention can be written in the same manner as a conventional pencil lead, and the drawn line is mainly composed of an inorganic extender, a binder and an organometallic compound represented by Chemical formula 2. Although it is fixed on the writing surface as a component, it can be erased with an eraser for about 10 to 15 minutes after writing, and the drawn line can be corrected like a normal pencil. After a while after writing, the hydrolyzable group of the organometallic compound shown in Chemical formula 2 is repeatedly hydrolyzed and dehydrated and condensed at room temperature due to the humidity in the atmosphere, so that the organometallic compound shown in Chemical formula 2 is eventually cured. come. As a result, the coloring agent such as graphite is fixed by this resin, and the density of the drawn line is kept sufficiently high even if the volume of the open pores is small. By this, the inorganic extender and the binder constituting the written line are Since it is firmly connected to the writing surface, the writing line can no longer be easily erased with an eraser. Therefore, the writing instrument has both the possibility of correction with an eraser such as a pencil and the possibility of being a non-erased recorded document such as a ballpoint pen and an ink pen.

[0019]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

(Example 1) A pencil lead was prepared by kneading graphite, a synthetic resin and a plasticizer, extruding the kneaded product into a linear shape, and then firing it to 1000 ° C in an inert gas atmosphere.
A 5 mmφ carbon type pencil lead sintered body was obtained. The pencil lead thus obtained was used as KBM-602 (manufactured by Shin-Etsu Chemical Co., Ltd .;
Put it in a container containing N-β (aminoethyl) γ-aminopropyldimethoxysilane, and then shut off the container from the atmosphere to form a closed system.
The mixture was heated to 0 ° C. and impregnated for 24 hours. After the impregnation treatment was completed, as a post-treatment, the pencil lead in the container was taken out and excess KBM-602 adhering to the surface of the pencil lead was wiped off to obtain the pencil lead of the present invention. The obtained pencil lead was writable in the same manner as a usual pencil lead impregnated with oils and fats. This drawn line is erasable immediately after writing and can be easily corrected, but the drawn line of graphite is fixed with resin with the passage of time and cannot be erased by an eraser. The eraser erasability of this pencil lead is shown in Table 1 below.

(Example 2) In the same manner as in Example 1, a pencil lead was kneaded with graphite, a synthetic resin and a plasticizer, the kneaded product was extruded into a linear shape, and then fired to 1000 ° C in an inert gas atmosphere. As a result, a 0.5 mmφ carbon type pencil lead sintered body was obtained. The pencil lead thus obtained was mixed with KR44 (manufactured by Ajinomoto Co .; trade name of isopropyl tri (N-aminoethyl aminoethyl) titanate) and KBE-603 (manufactured by Shin-Etsu Chemical Co., Ltd .; N-β (aminoethyl) γ). -Aminopropyltrimethoxysilane (trade name) was mixed in a weight ratio of 1: 1 to carry out the same impregnation treatment and post-treatment as in Example 1 to obtain a pencil lead of the present invention. The obtained pencil lead was writable in the same manner as a usual pencil lead impregnated with oils and fats. The erasability of the drawn line with the eraser immediately after writing and the non-erasability with the eraser after the passage of time are the same as in Example 1. The same applies to the following examples. The eraser erasability of this pencil lead is shown in Table 1 below.

(Example 3) Graphite, clay and water were mixed and kneaded with a surfactant, and the mixture was extruded into a linear shape, followed by firing to 1000 ° C in a non-oxidizing atmosphere to obtain 2.0.
A sintered body of a pencil lead of a mmφ clay core type was obtained. The thus obtained sintered pencil lead was placed in a container containing KBM-603 (manufactured by Shin-Etsu Chemical Co .; N-β (aminoethyl) γ-aminopropyltrimethoxysilane), and then the container was exposed to the atmosphere. The system was shut off to make a closed system, and the sealed container was heated to 80 ° C. and impregnated for 24 hours. After the impregnation treatment was completed, as a post-treatment, the pencil lead in the container was taken out, and excess KBM-603 attached to the surface of the pencil lead was wiped off to obtain the pencil lead of the present invention. The obtained pencil lead was writable in the same manner as a usual pencil lead impregnated with oils and fats.
The eraser erasability of this pencil lead is shown in Table 1 below.

Example 4 Graphite, clay, water and a surfactant were mixed and kneaded, and the mixture was extruded into a linear shape and then fired to 1000 ° C. in a non-oxidizing atmosphere to obtain 2.0.
A sintered body of a pencil lead of a mmφ clay core type was obtained. The thus obtained pencil lead sintered body is KBM-602 (manufactured by Shin-Etsu Chemical Co .; trade name of N-β (aminoethyl) γ-aminopropyldimethoxysilane) and diethylene glycol in a weight ratio of KBM-602: Diethylene glycol = 9
The solution was placed in a container containing a solution adjusted to 0: 10% by weight, and then the container was isolated from the atmosphere to form a closed system, and the closed container was heated to 80 ° C. and impregnated for 24 hours.
After the impregnation treatment is completed, as a post-treatment, the pencil lead in the container is taken out and extra KBM-60 attached to the surface of the pencil lead is removed.
3 and diethylene glycol were wiped off to obtain the pencil lead of the present invention. The obtained pencil lead was writable in the same manner as a usual pencil lead impregnated with oils and fats. The eraser erasability of this pencil lead is shown in Table 1 below.

(Comparative Example 1) As in Example 1, a pencil lead was kneaded with graphite, a synthetic resin and a plasticizer, and this kneaded product was extruded into a linear shape and then fired up to 1000 ° C in an inert gas atmosphere. As a result, a 0.5 mmφ carbon type pencil lead sintered body was obtained. The thus-obtained pencil lead was impregnated with spindle oil in the same manner as in Example 1 and subjected to the post-treatment to obtain a usual pencil lead. The eraser erasability of this pencil lead is shown in Table 1 below.

(Comparative Example 2) Graphite, clay, water and a surfactant were mixed and kneaded in the same manner as in Example 3, and the kneaded product was extruded into a linear shape and then molded at 1000 ° C in an inert gas atmosphere.
And a clay type pencil lead sintered body of 2.0 mmφ was obtained. Example 3 was obtained by adding pork fat to the pencil lead thus obtained.
An ordinary pencil lead was obtained by carrying out the same impregnation treatment and post-treatment. Table 1 below shows the eraser erasability of this pencil lead.
It was shown to.

The eraser erasability was measured as a non-erasing rate. The definition of the non-erasing rate and its measuring method will be described below. In accordance with the JIS standard density wear test method, a reflection density of a drawn line written on a high-quality paper (Beck smoothness = about 60 to 70 seconds) with a writing load of 300 gf was used as a blank and 1
The non-erasing rate was defined as the ratio with the reflection density of the part erased with the eraser at 0 minutes, 1 hour, and 24 hours. The defined equation is shown in equation (1). However, eraser erasing conditions are 7. ．
A commercially available plastic eraser processed into a cylinder of 2 mmφ was used to rub the writing line 5 times with an eraser load of 1200 gf, and the reflection density of the rubbed portion was measured to obtain the reflection density of the portion erased with the eraser.

[0027]

[Equation 1]

[0028]

[Table 1]

[0029]

The pencil lead of the present invention is obtained by impregnating the organometallic compound represented by Chemical formula 2 with 10 to 1 immediately after writing.
Five minutes can be erased with an eraser, and the drawing line can be corrected in the same manner as a normal pencil lead. Then, the hydrolyzable group of the organometallic compound represented by Chemical formula 2 is easily cured at room temperature in the presence of atmospheric humidity by a curing reaction accompanied by a hydrolysis reaction,
Make it easy to erase the strokes after writing with an eraser. Therefore, with the pencil lead of the present invention, a non-erasable drawing line with an eraser can be easily obtained by moisture in the atmosphere without using a special light source generator as disclosed in JP-A-52-70619. Further, the conventional pencil lead is unsuitable as a writing tool for official documents, stored documents, etc. because it can be easily erased with an eraser, but the pencil lead of the present invention can be erased with an eraser immediately after writing even in such an application. Although it is possible to correct the stroke while maintaining its superiority as a pencil lead, it erases the stroke while keeping the density high over time, and is used for stored documents and recorded documents in the same way as ballpoint pens and felt-tip pens. be able to.

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Claims (2)

(57) [Claims] 1. A pencil lead obtained by impregnating the pores of a sintered body with a non-drying liquid, the following general formula: (However, R ¹ is an amino group of m = 0 or 1, R ² is a monovalent hydrocarbon group of n = 0 or 1 having 1 to 6 carbon atoms, M is silicon or titanium of Group 4 in the periodic table, X Is a hydrolyzable group) is a non-erasable pencil lead obtained by impregnating the open pores of the pencil lead with an organometallic compound. 2. The non-erasable pencil lead according to claim 1, wherein X is an alkoxy group having 1 to 6 carbon atoms.