JP2001011359A - Pencil lead and manufacturing method thereof - Google Patents

Abstract

(57) [Problem] To obtain a pencil lead having high strength and coloring property. SOLUTION: A non-sintered pencil lead prepared by using an oil-soluble resin and a water-soluble resin in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a binder, a body material,
The present invention relates to a pencil lead obtained by mixing components such as a coloring material with a solvent, kneading with a kneading machine such as a roll or a Hensyl mixer, and extruding without firing.

[0002]

BACKGROUND OF THE INVENTION What gives strength to a pencil lead obtained without firing is a resin called a binder, which binds each composition. In general, water-soluble resin and oil-soluble resin can be used without distinction.However, when a water-soluble resin is used as a binder and shaped into a pencil lead, it absorbs moisture in the air over time and the strength is reduced. Problems such as reduction occur. This is particularly remarkable when a polar solvent such as water or alcohol is used at the time of kneading. The mechanism is that a part of water or alcohol is ionically dissociated and remains in the core after molding, and H +, OH
-Each ion reacts with water molecules in the atmosphere and takes in moisture inside the core. In contrast, an oil-soluble resin using a non-polar solvent during kneading does not cause ion dissociation like water, so that the solvent dissociated ions do not remain in the core and are stable over time, By using a stable oil-soluble resin as the binder, it is possible to have a certain degree of strength as a pencil lead.

By the way, such a mechanism of writing on a pencil lead employs a mechanism in which the pencil lead itself wears due to friction between the pencil lead and the paper surface, so that abrasion powder adheres to the writing surface and is colored. . At this time, how to efficiently remove the colored wear powder adhering on the writing paper surface from the pencil lead determines the vividness and the density of the coloring.

Heretofore, in order to improve the color developability of this pencil lead, microcrystalline wax, montan wax, ketone wax, etc. have been focused on minimizing the decrease in the strength of the pencil lead of the binder used. It is known to use substances having an abrasion promoting action, such as various kinds of waxes and various kinds of metal stearic acids such as aluminum and zinc, including stearic acid.

[0005]

As described above, the known substances having an abrasion promoting effect for peeling the colored constitutional material of the pencil lead from the lead are wax and stearic acid blended in the lead. Are mixed with a constitutional material and a coloring material, and at a glance, agglomerated colored particles are present in a block from the core. Therefore, when worn, the color development is high because the colored particles that peel off in a block are large, but at the same time, the current situation is that the strength as a pencil lead is sacrificed,
A pencil lead having good coloring and strength has not been obtained.

[0006]

That is, according to the present invention, there is provided, as a first gist, a pencil lead obtained by blending at least a body material, a coloring material, an oil-soluble resin, and a water-soluble resin. 2. The pencil lead according to claim 1, wherein the melting point is less than 70 [deg.] C., wherein the water-soluble resin is used in a proportion of 0.1% by weight or more and 3% by weight or less. The pencil lead according to claim 1 or 2, wherein the pencil lead is a third gist, and further, the constitutional material and the coloring material, an oil-soluble resin and a water-soluble resin together with an organic solvent dissolving the oil-soluble resin. And mixing or kneading at a temperature equal to or higher than the melting point of the water-soluble resin.
The fourth aspect of the present invention is a method for manufacturing a pencil lead according to any one of the above.

The details will be described below. Preferred as the resin used as the binder is not a water-soluble resin soluble in a polar solvent such as water or alcohol, but an oil-soluble resin soluble in a non-polar solvent such as acetone, ketone or xylene. For example, polystyrene, polyethylene, polypropylene, polymethylpentene, polybutene, polybutadiene, styrenebutadiene, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyvinylidene chloride, polytetrafluoroethylene, AS resin, A resin
Examples include BS resin, ethylene polytetrafluoroethylene copolymer resin, ethyl cellulose, nitrocellulose, cellulose acetate and the like.

As the water-soluble resin, a polymer which is soluble in a polar solvent is particularly preferable. Konjac, glue, casein, gelatin, brulan, textran, viscose, methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, polyethylene glycol, polypropylene glycol, polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyvinyl ether, polymaleic acid copolymer , Polyester polyol resin, polyester polyether polyol resin, polyethylene oxide, polyethylene imine, poly phosphorus Soda, water glass.

Further, among the above water-soluble resins, the melting point of the water-soluble resin is set to 70 ° C. in order to further disperse it in the core after molding.
It is more preferable to use a resin having less than the above value in order to enhance the effect of cracks generated in the core during writing. This is because the friction between materials is generated by a Hensyl mixer and a roll mill that rotate at high speed in the dispersion kneading process in the process, but if a resin that reduces the viscosity by self-heating due to frictional heat is used at this time, better This is because the dispersion in the core using an oil-soluble resin as a binder can be performed efficiently. Melting point 70
Examples of the water-soluble resin having a temperature lower than 0 ° C. include polyethylene oxide, polyester polyol resin, and polyester polyether polyol resin. These materials may be used alone or in combination of two or more. There is no restriction as long as the material conforms to the above configuration. The amount used is preferably 0.1% by weight or more and 3% by weight or less based on the total amount excluding the volatile solvent. This is because the use of less than 0.1% by weight does not have the effect of increasing the color developability, and the use of more than 3% by weight improves the color developability but lowers the strength.

Other than using the water-soluble resin described above, conventionally known materials can be used. For example, talc, calcium carbonate, mica, bentonite, kaolin clay, N-lauroyl-L-lysine, boron nitride, fluorinated graphite, potassium titanate whisker, calcium carbonate whisker, titanium dioxide whisker, aluminum borate whisker, magnesium sulfate whisker, Natural materials such as carnauba wax, beeswax and wood wax, polyethylene wax, montan wax, paraffin wax, and microcrystalline, provided that the effects of the body material such as calcium sulfate whisker and the water-soluble resin used in the present invention are not impaired. Synthetic waxes such as waxes, various metal stearic acids such as stearic acid, aluminum stearate, calcium stearate, lithium stearate, β-lauri N-lauroyl aspartate Aspartic acid esters such as esters, the use of lubricating materials such as amino acid-based stearate is not permissible,
As a coloring material, organic, various inorganic dyes, coloring materials such as pigments, diallyl phthalate used as needed,
Examples of plasticizers such as dimethyl phthalate, butyl phthalyl butyl glycolate, propylene carbonate, and tricresyl phosphate, and non-polar solvents that dissolve these compounding materials and the oil-soluble resin include petroleum charcoal such as hexane, petroleum, and gasoline. Hydrogen solvents, benzene, xylene,
Examples thereof include aromatic hydrocarbon solvents such as toluene and ketone solvents such as aceketone, methyl ethyl ketone and methyl isobutyl ketone. In producing a pencil lead, these ingredients are dissolved and dispersed in a non-polar solvent, and then kneaded and dispersed with a three-roll mill to form a volatilized solvent while adjusting the amount of the solvent to be volatilized. Is dried in order to completely volatilize.

[0011]

The ideal wear of a pencil lead having strength is sufficient if the size of the colored powder adhering to the paper is the size of the particles of the body material such as talc or calcium carbonate used. In the present invention, the minute cracks generated at the time of writing are transmitted to the vicinity of the body material, thereby facilitating the separation of the colored particles from the core. That is, if a water-soluble resin is added to a non-polar solvent at the stage of compounding, the water-soluble resin causes aggregation in the non-polar solvent to form a macro colony. The colonies are shredded and further dispersed while the resin viscosity decreases and softens due to the heat generated at the time of dispersion due to the shearing of the rolls, and they line up in the direction in which the filler particles such as talc are extruded by the pressure during extrusion molding. At this time, the viscosity of the colony decreases due to the extrusion pressure, the colony becomes soft, and it is oriented together with the extender, so the colony is located near the extender, and in the core after final molding, as a microscopic colony of a water-soluble resin. Exists. This colony surface forms a hydrophilic molecular film on the colony surface by coordinating the OH group of the water-soluble resin to the outside with the nonpolar solvent. This film forms a kind of pore on the surface of the colony by the action of the surface tension repelling the oil-soluble resin component in the core, and micro cracks generated during writing are transmitted to the pores of the colony near the filler, It is presumed that abrasion from the core body is facilitated by assisting the peeling effect of the body material itself through the pores.

[0012]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

<Example 1> Nitrocellulose (oil-soluble resin) 20 parts by weight Talc (building material) 50 parts by weight Stearic acid (lubricant) 8 parts by weight Phthalocyanine blue (coloring material) 20 parts by weight Polyester polyol resin (water-soluble) Resin, melting point 55 ° C) 2 parts by weight Methyl ethyl ketone (non-polar solvent) 100 parts by weight The above ingredients are blended, kneaded with a stirrer, then dispersed and kneaded with three rolls, and extruded into a fine line while adjusting the volatile solvent content. The solvent was removed by drying at 80 ° C. for 8 hours to obtain a blue pencil lead having a nominal diameter of 0.9.

<Examples 2 to 9> In Example 1, the amount of the polyester polyol resin used was 0.05 parts by weight,
When 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2.5 parts by weight, 3 parts by weight, and 3.5 parts by weight, the solid content excluding methyl ethyl ketone is 100 parts by weight. In the same manner as in Example 1 except that the amount of talc used was adjusted so as to obtain a blue pencil lead having a nominal diameter of 0.9.

<Example 10> In Example 1, the polyester polyol resin was replaced with polyvinyl alcohol (melting point 1).
(00 ° C.), except that a blue pencil lead having a nominal diameter of 0.9 was obtained.

Comparative Example 1 The procedure of Example 1 was repeated except that no polyester polyol resin was used.
A blue pencil lead having a nominal diameter of 0.9 was obtained.

<Comparative Example 2> In Example 1, the mixture was replaced with a carboxymethylcellulose resin instead of nitrocellulose and a polyester polyol resin, and methyl ethyl ketone was replaced with 20 parts by weight of water (polar solvent). The mixture was dispersed and kneaded with this roll, extruded into a fine wire, dried at 50 ° C. for about 70 hours to remove water, and a blue pencil lead having a nominal diameter of 0.9 was obtained.

The bending strength (unit: MPa) as a substitute for the strength of the pencil lead obtained in each of the above examples and the density (unit: D) as a substitute for the color developing property were measured based on JIS S6005. . Table 1 shows the measurement results. Also,
As a test for having a stable bending strength over time, a forced humidity test is performed for each of the examples and the comparative examples. The specific test method is based on the saturated salt method, and each prepared pencil lead is opened in an open stainless steel container (length × width × length).
Leave in a depth = 150 × 130 × 25 mm vat, put a saturated aqueous solution of potassium chloride in a Petri dish (φ180, height 25 mm), and use a pot lid desiccator (lid diameter 300 m).
m). Partition with a middle plate, put the stainless steel vat, cover it, and make a constant humidity atmosphere (at this time, the relative humidity of potassium chloride is about 85% to 87% when the normal temperature is about 10 ° C to 20 ° C). become). 24 in this desiccator
After standing for a period of time, the flexural strength was measured based on JIS S 6005 described above, and the results are shown in Table 1.

[0019]

[Table 1]

[0020]

As shown in the above table, according to the present invention, it is possible to obtain a pencil lead excellent in color developability while having a strength that is stable over time.

Claims (4)

[Claims] 1. A pencil lead comprising at least a body material, a coloring material, an oil-soluble resin and a water-soluble resin. 2. The pencil lead according to claim 1, wherein the melting point of the water-soluble resin is less than 70 ° C. 3. The pencil lead according to claim 1, wherein the water-soluble resin is used in a proportion of solid content of not less than 0.1% by weight and not more than 3% by weight. 4. A method comprising mixing or kneading the extender, a coloring material, an oil-soluble resin and a water-soluble resin together with an organic solvent for dissolving the oil-soluble resin at a temperature equal to or higher than the melting point of the water-soluble resin. The method for producing a pencil lead according to any one of claims 1 to 3, wherein: