JP3035157B2 - Manufacturing method of non-fired 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 method for producing a non-fired pencil lead for pencils and mechanical pencils.

[0002]

2. Description of the Related Art A conventional non-fired pencil lead is prepared by dissolving or swelling an organic polymer substance as a binder with a solvent and / or a plasticizer, if necessary, and kneading it together with a coloring agent, a filler, a lubricant and the like. It is manufactured by drying and removing the solvent and / or plasticizer added as necessary.

[0003] As the binder, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl chloride,
One or more organic polymer substances such as a vinyl chloride copolymer, a cellulose resin, a polystyrene, a styrene copolymer, and an epoxy resin are selectively used.

[0004] Examples of the lubricant include natural waxes such as wood wax and carnauba wax, montan wax, and the like.
Synthetic waxes such as polyethylene wax, higher fatty acids such as stearic acid and lauric acid, metal soaps such as zinc stearate, calcium stearate and lithium myristate are used. Japanese Patent Publication No. 47-48564 discloses a method using metal soap as a lubricant.
Further, Japanese Patent Publication No. 6-6690 discloses a method using lithium myristate as a lubricant.

[0005] In a non-fired pencil lead, a binder is an indispensable material for developing structural strength, and is selected in consideration of chemical affinity for kneading with other compounding compositions and developing strength. Need to be done.

[0006] On the other hand, a lubricant is an indispensable material for smoothing the writing quality at the time of writing and for improving the drawing line density. However, the bending strength is liable to be remarkably reduced. It is necessary to consider the interaction. Generally, nitrocellulose is used as a binder, taking advantage of its toughness and easy processability. It is known that the use of a lubricant having a high softening point of 210 ° C. or higher typified by lithium soap can suppress a decrease in bending strength to some extent.

However, since nitrocellulose is a substance classified as explosives, strict attention must be paid to its handling under the Fire Service Law. Further, the use of a lubricant containing lithium soap alone has disadvantages such as deterioration of coloring properties and the inability to develop a sufficient drawing line density.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a non-fired pencil lead having sufficient bending strength and excellent coloring properties, which cannot be obtained by the conventional methods.

[0009]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, has found that a compounding composition comprising a binder, a coloring agent, a constitutional agent, and a lubricant as main components. In a method for producing a non-fired pencil lead formed by kneading and molding a product,
Celluloid is used as at least a part of the binder, and lithium soap and a fatty acid amide are used in combination as at least a part of the lubricant. Preferably, the fatty acid amide has a softening point of 110 ° C. or less. The present inventors have found that a non-fired pencil lead having both sufficient bending strength and excellent coloring properties can be manufactured, and the present invention has been completed.

Next, the compounding composition of the present invention will be described in detail. Celluloid is used as at least a part of the binder. In general, celluloid is added to nitrocellulose having a nitrification degree of about 11% and a polymerization degree of about 200 to 600.
It is a mixture of 0-35% camphor and has much less explosive properties than nitrocellulose, but has the toughness required as a binder. In the present invention, the type of celluloid is not particularly limited. In the present invention, an organic polymer substance other than celluloid may be used in combination as a binder, if necessary. For example, vinyl acetate copolymer. It is possible to select one or more of organic polymer substances such as cellulose resin, polystyrene, styrene copolymer, epoxy resin, etc. Preferred are those soluble in alcohols, esters, ketones and the like, which are good solvents. The mixing ratio of the combined resin is preferably kept at 30% by weight or less based on the total amount of the binder for the purpose of not losing the excellent properties of celluloid.

As the colorant, either an inorganic pigment or an organic pigment can be used. As the extender, one or more of talc, sericite, kaolinite, bentonite, wollastonite, calcium carbonate, boron nitride, potassium carbonate, etc., which are commonly used in pencil cores, are selected.

In the present invention, lithium soap and fatty acid amide are used as at least a part of the lubricant. It is preferable that a fatty acid amide having a softening point of 110 ° C. or lower be specified and used. Lithium soap is a metal soap having a softening point of more than 210 ° C. represented by lithium stearate, lithium hydroxystearate, lithium myristate and the like. In the present invention, one or two or more thereof are selected and used.

As the fatty acid amide, either a primary amide or a secondary amide can be used, and one or two or more of them can be used. In order to improve the coloring property and increase the drawing density, the softening point is preferably 110 or more. ° C. or lower, more preferably, a softening point of 70 to 100 for balancing bending strength and coloring power.
It is good to select fatty acid amide of ° C. A fatty acid amide having a softening point of 70 ° C. or lower tends to cause a decrease in bending strength, and a fatty acid amide having a softening point of more than 100 ° C. tends to have poor coloring power. Examples of the fatty acid amide having a softening point of 70 to 100 ° C. include lauric amide (80 ° C.), stearic amide (100 ° C.), erucamide (82 ° C.), N-oleyl stearamide (74 ° C.), N-stearyl stearamide (95 ° C.) and the like.

In the present invention, if necessary, general lubricants such as natural waxes, synthetic waxes, higher fatty acids and metal soaps may be used in combination. When the total amount of the lubricant in the composition is 100 parts by weight, lithium soap: 2
0-90 parts by weight, preferably 35-85 parts by weight, fatty acid amide: 10-80 parts by weight, preferably 25-75 parts by weight, lubricant used together: 0-40 parts by weight, preferably 0-0 parts by weight
It is preferable that the mixing ratio is 25 parts by weight.

In order to obtain a non-fired pencil lead from the above composition, first, a predetermined amount is measured, dispersed and kneaded. As a dispersing method, it is easier to dissolve the celluloid in a solvent and then add another compounding material to facilitate the subsequent kneading step. Next, the kneaded material is formed into a predetermined shape using a forming machine, and the solvent is dried to obtain a product.

[0016]

The non-fired pencil lead obtained by the production method of the present invention has a required toughness as a binder, and a celluloid which is highly safe to handle is selected. Lithium soap is a high softening point lubricant having the property of suppressing, in order to improve the coloring power,
By selecting a fatty acid amide having a polar group with high affinity with the nitro group of nitrocellulose in celluloid,
The drawing line density is improved without inducing a significant decrease in bending strength.

[0017]

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

EXAMPLE 1 75% by weight of nitrocellulose having a nitrification degree of 11% and a viscosity of 120 seconds by a falling ball method and camphor 2
After dissolving 30 parts by weight of the celluloid prepared and mixed with 5% by weight in 100 parts by weight of ethyl acetate, 15 parts by weight of phthalocyanine blue, 35 parts by weight of potassium titanate fiber,
13 parts by weight of lithium stearate as a lubricant and 7 parts by weight of erucamide having a softening point of 82 ° C. were put into a Warner mixer, dispersed, kneaded with a three-roll mill and simultaneously adjusted with ethyl acetate, and extruded. After molding using a molding machine,
The ethyl acetate was dried to obtain a blue core having a diameter of 0.5 mm.

Comparative Example 1 A blue core having a diameter of 0.5 mm was the same as the composition of Example 1, except that the fatty acid amide was replaced by xylylene bisstearic acid amide having a softening point of 123 ° C. I got

Comparative Example 2 A blue core having a diameter of 0.5 mm was obtained in the same composition as in Example 1, except that the lubricant was lithium lithium stearate of one kind and 20 parts by weight. .

COMPARATIVE EXAMPLE 3 The same composition as in Example 1 except that the lubricant was one kind of zinc stearate having a softening point of 120 ° C. and 20 parts by weight was used. A blue core was obtained.

(Comparative Example 4) In the composition of Example 1, one kind of erucamide having a softening point of 82 ° C was used.
0 parts by weight and the same composition except that the diameter is 0.5
mm blue core was obtained.

Example 2 75% by weight of nitrocellulose having a nitrification degree of 11% and a viscosity of 120 seconds by a falling ball method and camphor 2
After dissolving 20 parts by weight of the celluloid prepared and mixed with 5% by weight in 100 parts by weight of ethyl acetate, 15 parts by weight of phthalocyanine blue, 20 parts by weight of potassium titanate fiber,
20 parts by weight of talc, 15 parts by weight of lithium hydroxystearate as a lubricant, and 10 parts by weight of N-oleylstearic acid amide having a softening point of 74 ° C. were put into a Warner mixer, dispersed and kneaded with three rolls. At the same time, the content of ethyl acetate was adjusted and molded using an extruder, and then the ethyl acetate was dried to obtain a blue core having a diameter of 3 mm.

Comparative Example 5 A blue core having a diameter of 3 mm was obtained in the same composition as in Example 2, except that the fatty acid amide was replaced with xylylene bisstearic acid amide having a softening point of 123 ° C. Was.

Comparative Example 6 A blue core having a diameter of 3 mm was obtained in the same composition as in Example 2, except that the lubricant was changed to one kind of lithium stearate and 25 parts by weight.

(Comparative Example 7) A blue core having a diameter of 3 mm was prepared in the same manner as in Example 2 except that one kind of zinc stearate having a softening point of 120 ° C. and 25 parts by weight were used as a lubricant. I got

Comparative Example 8 The same composition as in Example 2 except that the lubricant was one kind of N-oleylstearic amide having a softening point of 74 ° C. and 25 parts by weight was used. Blue core was obtained.

Table 1 shows the measurement results of the bending strength and the drawing line density of the non-fired pencil leads obtained in Examples 1 and 2 and Comparative Examples 1 to 8. The bending strength was measured according to JIS S6
According to 005, JIS S
The determination was made visually according to 6005.

[0029]

[Table 1]

[0030]

The unfired pencil lead obtained by the method of the present invention has a sufficient bending strength and excellent coloring properties, which cannot be obtained by the conventional method, as is apparent from the above test results.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 13/00

Claims (2)

(57) [Claims] 1. A method for producing a non-fired pencil lead, comprising kneading and molding a compounding component mainly comprising a binder, a colorant, a constitution agent and a lubricant, wherein at least a part of the binder is celluloid. A method for producing a non-fired pencil lead, comprising using lithium soap and a fatty acid amide as at least a part of a lubricant. 2. The method according to claim 1, wherein the fatty acid amide has a softening point of 110 ° C. or lower.