JPH0912960A - Colored pencil lead - Google Patents

Abstract

PURPOSE: To obtain a colored pencil lead having a smooth writing touch and having a practical strength without requiring a fibrous reinforcing material by kneading a binder, a extender comprising talc having a specific average particle diameter and produced by a wet grinding method, a coloring agent, a lubricant, etc., and subsequently extruding the mixture into a fine wire-like product. CONSTITUTION: A binder (e.g. nitrocellulose), an extender comprising talc having an average particle diameter of 10-30μm and produced by a wet grinding method, a coloring agent (e.g. copper phthalocyanine blue), a lubricant (e.g. stearic acid) and further a plasticizer (e.g. tricresyl phosphate) are compounded, kneaded with three rolls with the addition of a solvent (e.g. methyl ethyl ketone), extruded into a fine wire-like product, and subsequently dried in a drier at 80 deg.C for approximately 8hr for the removal of the solvent to obtain the objective colored pencil lead having a practical strength and used for mechanical pencils, etc., without deteriorating the writing touch of the colored pencil and further without requiring a fibrous reinforcing material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-sintering type colored pencil lead which uses at least a binder, an extender, a coloring material and a lubricant.

[0002]

2. Description of the Related Art Conventional non-baking type color cores include binders such as polyvinyl chloride, nitrification cotton, and acrylic-styrene copolymers, coloring agents such as inorganic and organic dyes and pigments, and stearic acid. , Natural and synthetic wax, and talc are used as a body material.
It is manufactured by kneading and molding with a solvent.

[0003]

The conventional color core using talc as an extender material has no problem in strength and writing quality when the diameter is 2.0 mm, such as a core for colored pencils. However, in the case of a sharp pencil color core having a thin core diameter, for example, a diameter of 0.9 mm, the strength is remarkably reduced and the core is easily broken during writing.

Various attempts have been made to use a fibrous reinforcing material to overcome this problem. However, when the fibrous reinforcing material is used, the fibers of the reinforcing material are caught on the paper surface during writing. At the present time, the writing quality has to be sacrificed.

[0005]

Therefore, the present invention provides a colored pencil lead having practical strength without needing to use a fibrous reinforcing material, as well as not impairing the smooth writing quality. The purpose is to do.

In the conventional color core, general-purpose talc prepared by a dry pulverization method is used as a body material. When observing the crystals of this talc, firstly, there is a fine crystal talc with a grain size that is not uniform and the surface of the crystal is rough. As a result of diligent research based on the estimation of the present invention, the present invention can improve the drawbacks of using conventional talc by using talc produced by a specific manufacturing method, but at this time, the average particle diameter of talc is extremely important. I found something and completed it.

That is, according to the present invention, in a non-firing type colored pencil lead which uses at least a binder, a body material, a coloring material and a lubricant, talc by the wet pulverization method having an average particle diameter of 10 to 30 μm is used as the body material. The main point is a colored pencil lead that is characterized by being used.

The details will be described below. The talc by the wet pulverization method used in the present invention (hereinafter referred to as the wet pulverization talc) is obtained by subjecting the talc wet pulverized by a rod mill, a ball mill, a pan mill or the like to a wet classification by an elutriation operation. Compared with the one obtained by the conventional talc produced by the dry pulverization and dry classification method,
The crystals are crushed into flakes, the surface of the crystals is smooth, and coarse particles are hardly mixed.

By using this wet pulverized talc having a particle size in a limited range as an extender, it is possible to provide a color core excellent in writing taste and strength.

The particle size of the wet pulverized talc used in the present invention (the particle size means the average particle size, and the average particle size is measured by the Microtrack laser diffraction method) is 1
It is preferable that the thickness falls within 0 to 30 μm. The reason is that if the particle size is less than 10 μm, the strength is improved, but the smooth area that wears is reduced, resulting in poor writing quality and thin handwriting. If the particle size exceeds 30 μm, the bulk and specific surface area are This is because it becomes smaller and the strength decreases.

The use ratio of the wet pulverized talc used as the extender depends on the kind of the binder, but is 20 to 40% by weight with respect to the total amount excluding volatile components such as solvents, and more preferably 25. It is recommended to use ˜35% by weight. If it is less than 20% by weight, the effect of orientation on the binder is reduced, but since the proportion of the binder is increased, there is no reduction in strength.
The writing feels bad. If it is used in an amount of more than 40% by weight, the orientation effect can be obtained, but the proportion of the binder becomes small, resulting in a decrease in strength.

The color core of the present invention can be manufactured in the same manner as the conventional one except that this wet pulverized talc is used as a body material. As the binder, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol are used. Such as cellulose, polymethyl acrylate, polyvinyl butyral, gum arabic, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, cellulose acetate, cellulose derivative such as cellulose nitrate, etc. Examples include fibrin-based resins, polystyrene, acrylic-styrene copolymers, and acrylic-styrene-butadiene copolymers.

Coloring agents include natural and synthetic dyes and inorganics,
Organic pigments can be used arbitrarily, various metal stearic acid, stearic acid, polyethylene wax, distearyl ketone, ketone wax, paraffin wax, beeswax, wood wax, carnauba wax and other lubricants, potassium titanate, Fibrous reinforcing materials such as magnesium sulfate, magnesium silicate and gypsum, and other plasticizers such as tricresyl phosphate, dimethyl phthalate, diallyl phthalate, dibutyl phthalate and dioctyl phthalate, and solvents such as methyl ethyl ketone, if necessary. These are appropriately compounded and mixed and dispersed and kneaded with three rolls, a kneader, and a hensyl mixer, and when a solvent is used, the solvent content is adjusted and molded by an extruder or the like, and a drying treatment is performed if necessary. .
Further, as an extender, any existing extender may be used in combination with the wet pulverized talc.

[0014]

The present invention has a large effect due to the wet grinding talc.
Compared to the talc produced by the conventional dry grinding method, the layer of talc crystals is in the form of flakes, which does not hinder the orientation of the resin when molded into a core and is oriented in the extrusion direction like when using a fibrous reinforcing material. In order to increase the strength, the crystal surface in writing is clean and smooth, and the wettability of the interface with the binder is relatively weak, so that detachment from the core easily occurs,
As a result, it is presumed that it has a smooth writing feel.

[0015]

【Example】

 <Example 1> Nitrocellulose 20 parts by weight Stearic acid 25 parts by weight Wet pulverized talc (particle size 20.1 μm, talc ore was pulverized by a Raymond mill, and further obtained by pulverization and classification in the presence of water. ) 30 parts by weight Tricresyl phosphate 5 parts by weight Copper phthalocyanine blue-20 parts by weight Methyl ethyl ketone (solvent) 100 parts by weight

The above materials were kneaded while adjusting the amount of the solvent with three rolls, extruded into a fine wire and dried in a dryer at 80 ° C. for about 8 hours to remove the solvent, and a nominal diameter of 0.9 A blue core for a sharp pencil was obtained.

<Examples 2 to 7> In Example 1, the amount of the wet pulverized talc used was 16, 18, 24, 37, 46, 5
All were the same as in Example 1 except that the value was changed to 0.

<Examples 8 and 9> The same procedure as in Example 1 was carried out except that the wet pulverized talc having particle sizes of 10.3 μm and 29.8 μm was used in Example 1.

<Comparative Examples 1 and 2> The same procedure as in Example 1 was carried out except that wet pulverized talc having a particle size of 7.1 μm and 39.7 μm was used in Example 1.

<Comparative Examples 3 and 4> Potassium titanate fiber (fiber diameter 0.2
.About.0.5 .mu.m, fiber length 10 to 20 .mu.m) and talc (particle size 19.8 .mu.m) obtained by the dry pulverization method were all used in the same manner as in Example 1.

Regarding the writing quality of the colored pencil lead obtained in each of the above examples, the dynamic friction coefficient was measured, and the bending strength and the density were measured according to JIS.
Table 1 shows the results of measurement according to the measuring method of S6005. Further, a small value of the dynamic friction coefficient means that the writing quality is good, and conversely, a large value means that the writing quality is bad.

[0022]

[Table 1]

[0023]

According to the present invention, by using a wet pulverized talc having an average particle size of 10 to 30 μm as an extender, a colored pencil lead having practical strength without impairing the smooth writing quality as shown in the above table. Can be provided.

Claims (1)

[Claims] 1. A non-baking type colored pencil lead using at least a binder, a body material, a coloring material and a lubricant, wherein talc by a wet grinding method having an average particle size of 10 to 30 μm is used as the body material. A featured colored pencil lead.