JP3234050B2 - Non-baked colored 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 non-fired color pencil lead suitable mainly for a wooden pencil and a pencil lead for a mechanical pencil, and more particularly, to a novel concentric and similar core embedded inside. The present invention relates to a non-fired color pencil lead having an internal structure, remarkably excellent bending strength and smooth writing taste.

[0002]

2. Description of the Related Art A conventional non-baked color pencil lead uses one or two or more kinds of thermoplastic organic polymer materials or thermosetting organic polymer materials as a binder, and a coloring material,
After adding and compounding a wax and a filler as an inorganic filler, and further, if necessary, a plasticizer or a solvent of an organic polymer substance as a binder, and kneading the compounded composition, and extruding the kneaded material, It is manufactured by volatilizing the plasticizer or the solvent and performing a heat treatment as necessary.

[0003] However, the organic polymer substance as the binder in the non-fired pencil lead has the disadvantage that the mechanical strength is inferior to that of clay or carbide as the binder in the fired pencil lead, and also has a drawback that it is smooth. There is a problem that waxes added for obtaining a good brush feel and adhesion to paper further reduce the mechanical strength of the non-fired colored pencil lead.

Therefore, in order to increase the mechanical strength, ie, bending strength, tensile strength, impact strength, etc., of a non-fired colored pencil lead, conventionally, for example, a method of adding potassium titanate having a short fiber or needle-like crystal structure ( JP-A-52-8841
No. 9), a method of adding a potassium titanate fibrous body (see JP-A-56-163171), a method of adding fibrous graphite, fibrous carbon, or a fibrous pigment (Japanese Patent Publication No. 48-163). 18347) and the like.

[0005] By the way, although the mechanical strength can be increased by including a fibrous substance, there are many cases in which dissatisfaction remains in terms of writing taste. Among many fibrous substances,
Except for fibrous graphite and fibrous carbon, which cannot be used for colored pencil cores in terms of hue, those with colorless color, white or pale color and relatively good balance between mechanical strength and writing taste so that they can be used for colored pencil cores Examples include potassium titanate whiskers.

However, this potassium titanate whisker also has the following disadvantages. That is, potassium titanate whisker has remarkable hygroscopicity, so that potassium is easily eluted as potassium ions, and therefore, pH
And the deterioration of wettability with the binder and the deterioration of other compounding compositions are likely to occur, and the material changes over time after the manufacturing process of the colored pencil lead and the completion of the lead, resulting in a decrease in mechanical strength. There is an adverse effect that leads to

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a material which is excellent in mechanical strength, practically difficult to break, and has good writing taste.
It is still another object of the present invention to provide a non-fired colored pencil lead whose mechanical strength is hardly reduced with time.

[0008]

Means for Solving the Problems The present inventor has conducted intensive studies in order to solve the above-mentioned problems, and as a result, conventionally, plate-like particles have been used for a fired pencil lead or a body material containing scale-like crystals such as graphite. In the case of a non-baked colored pencil lead, we attempted to form this concentric tubular orientation inside the lead, with the hint that these flat particles are oriented concentrically in the outer surface layer and increase the mechanical strength. As a result, they found that this was possible and completed the present invention.

FIGS. 4 and 5 show the cross-sectional structure of a conventional general non-baked color pencil lead. FIG. 4 shows a structure which is often observed in the case where plate-like particles are used as a constitutional material, and FIG. 5 shows a structure which is often observed in cases where a fibrous substance or amorphous particles are used as a constitutional material. It is known that the bending strength of the core is higher in the skin layer at the outer peripheral portion compared to the inside, regardless of the difference between the fired pencil core and the non-fired pencil core. This is because the orientation of the body material in the outer peripheral portion is increased by high shear stress with the die tube wall when the core is extruded.

[0010] In view of this fact, the present inventor has tried to orient the body material even inside the core. In extruding a kneaded material such as graphite, a skeleton-like material, a binder, a plasticizer, and a solvent from a nozzle hole, a continuous flow path is directed toward the nozzle opening before the nozzle hole. A plurality of concentric conical tubular straightening plates with a reduced cross-sectional area were provided, and when extruded with this straightening plate and an extrusion nozzle, it was found that graphite was oriented concentrically in the inside of the core and strength increased. A patent application was filed on September 25 as Japanese Patent Application No. 4-256307.

[0011] Subsequent research has shown that extruded cores using this device do not all have concentric tubular interiors, but that the bodily materials are oriented concentrically at intervals in the radial direction. Has more than one layer,
In the remaining part, it was found that the constitution material was randomly or radially oriented. And by this, it was found that the density at the time of writing did not decrease than when the entire inside of the core was concentric tubular, and the strength and concentration were well balanced while improving the mechanical strength such as bending strength. It turned out that a wick was obtained.

The inventor of the present invention has applied this idea to a non-fired color pencil lead to increase the strength of the color lead and to obtain a satisfactory writing quality. Instead of blending, bright plate-shaped particles were blended, and this was tried, and the present invention was completed by obtaining a non-fired color pencil lead having an excellent balance between the desired strength and concentration and good writing taste.

That is, the present invention is as follows. (1) In the outer peripheral surface portion of the colored pencil core, the body material containing the plate-like particles is oriented concentrically in a tubular shape, and is spaced apart in the radial direction in the space between the core material and the body material. A non-fired colored pencil lead having at least one layer oriented in a non-fired manner, and in the remaining portion, the body material is randomly or radially oriented.

[0014]

[0015]

The method for obtaining the non-fired colored pencil lead of the present invention will be specifically described. A coloring material and wax are mixed with a binder such as a thermoplastic organic polymer material or a thermosetting organic polymer material, and one or more of plate-like particles such as talc and mica are added to part or all of the body material. Seeds are added and blended, and if necessary, a plasticizer of the organic polymer substance as the binder, or a solvent is added, and the blended composition is blended and kneaded. A cross-sectional view (FIG. 6) and a vertical cross-sectional view passing through the central axis (FIG. 7)
An extrusion die is used which is provided with a plurality of concentric conical tubular flow straightening plates whose flow path cross-sectional area continuously decreases toward the nozzle orifice.

When the kneaded material passes through the gap between the flow straightening plates, the body material of the plate-like particles such as talc and mica contained in the kneaded material has an increased orientation in the extrusion direction due to high shear stress with the wall surface of the straightening plate. Further, when the flow of the kneaded material passes through the tapered portion and joins, the portion that comes into contact with the wall surface of the flow straightening plate forms a layer in which the body material is highly oriented in a concentric tubular shape. As shown in the part other than the concentric circles, the constitutional material has a random structure so that the bees gather in the honeycomb, or as shown in the parts other than the concentric circles in FIGS. Form an oriented structure.

The differences in these internal structures are caused by the types of constitutional materials, binders, coloring materials, and lubricants used, the gaps between the straightening plates, the viscosity when the kneaded material passes through the straightening plates, the shear stress, the shear rate, and the like. Depends on. Therefore, in order to obtain a desired structure, predetermined extrusion conditions experimentally obtained in advance may be set. In order to form two or more concentric tubular layered structures in the internal tissue as shown in FIG. 3, it is preferable to increase the number of concentric conical tubular rectifying plates as shown in FIGS. 8 and 9 (FIG. 8). Is a horizontal sectional view, and FIG. 9 is a vertical sectional view passing through the central axis.

The non-fired colored pencil lead of the present invention can be obtained by volatilizing the plasticizer or the solvent from the linear body obtained by extrusion molding in this way and subjecting it to a heat treatment if necessary.

The extender used in the present invention is talc, mica, or nitrided, which is colorless, white, or pale in color and has a relatively good balance of mechanical strength and writing taste so that it can be used for a color pencil lead. One or more plate-like particles such as silicon, fluorinated graphite, fluorocarbon, and alumina are selected, and the average particle diameter in the plane direction is adjusted to 20 μm or less, preferably 10 μm or less. The thickness direction of plate-like particles is 1μ
m, preferably 0.5 μm or less, more preferably 0.3 μm or less.

In the composition of the present invention, one or more of the plate-like particles must be contained as a constitutional material, and it is desirable that all of the constitutional material be the plate-like particles. If necessary, other constitutional materials such as fibrous substances can be used in combination. Even in that case, it is preferable to add the plate-like particles at a ratio of at least 20% by weight or more in the whole material, from the viewpoint of the degree of improvement in mechanical strength.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. (Example 1) CMC 10 parts by weight Caster wax 25 parts by weight Talc 30 parts by weight Boron nitride 15 parts by weight Lake-based red pigment 20 parts by weight Water corresponding to 100 parts by weight was further added to the above-mentioned composition. After mixing and dispersing with a kneader, the water content is adjusted while kneading with two rolls.
Was extruded using an extrusion die equipped with a plurality of concentric conical tubular rectifying plates, and dried at 60 ° C. for 60 hours to evaporate water to obtain a non-fired red pencil lead having a diameter of 3 mm. As shown in FIG. 1, the cross-sectional structure of the obtained colored pencil lead has a layer in which the body material is oriented concentrically in the outer peripheral portion of the core and the body material is also oriented concentrically in the interior. However, the other parts of the internal tissue had a random structure such that the constitutional material was such that bees swarmed in the beehive.

(Example 2) Celluloid 40 parts by weight Magnesium stearate 15 parts by weight Potassium titanate whisker 10 parts by weight Mica 20 parts by weight Lake-based red pigment 15 parts by weight Ethyl acetate corresponding to 100 parts by weight in the above composition As a solvent, and after mixing and dispersing them with a kneader, the amount of the solvent is adjusted while kneading with two rolls, and the kneaded product is extruded with a plurality of concentric conical tubular rectifying plates shown in FIGS. 6 and 7. Extrusion was performed at 80 ° C. using a die for drying, followed by drying at 60 ° C. for 90 hours to evaporate the solvent to obtain a non-fired red pencil lead having a diameter of 0.5 mm for a mechanical pencil. The cross-sectional structure of the obtained colored pencil lead has, as shown in FIG. 2, a layer in which the body material is oriented concentrically at the outer periphery of the core and the body material is further oriented concentrically inside the core. And the rest of the internal organization
The body material had a radially oriented structure.

Example 3 The same material as in Example 2 was used except that extrusion molding was performed using an extrusion die to which a large number of concentric conical tubular current plates shown in FIGS. 8 and 9 were attached. Through a similar process, a non-fired red pencil lead for a mechanical pencil having a diameter of 0.5 mm was obtained. As shown in FIG. 3, the cross-sectional structure of the obtained color pencil lead is such that, as shown in FIG. 3, the body material is oriented concentrically at the outer periphery of the core, and the layer in which the body material is oriented concentrically inside the core. The other portion of the internal tissue had a structure in which the body material was radially oriented.

(Comparative Example 1) An unfired red pencil lead having a diameter of 3 mm was produced through the same steps and using the same material as in Example 1 except that the extrusion was performed using a normal extrusion die shown in FIG. Obtained. The cross-sectional structure of the obtained core had a conventional structure as shown in FIG.

(Comparative Example 2) The same material as in Example 2 was used, except that it was extruded using a normal extrusion die shown in FIG. An unfired red pencil lead was obtained. The cross-sectional structure of the obtained core had a conventional structure as shown in FIG.

The cores of Examples 1, 2, and 3 and Comparative Examples 1 and 2 manufactured as described above were tested for bending strength in accordance with JISS6005. The results are shown in Table 1 below.

[0028]

[Table 1]

[0029]

As is clear from the results of the examples, in the internal structure of the core according to the present invention, the constitutional material is oriented concentrically at the outer peripheral portion of the core, and the constitutional material is also concentrically tubular inside. The non-fired colored pencil lead, which has one or more oriented layers and other parts are randomly or radially oriented, dramatically improves mechanical strength such as bending strength without lowering the concentration at the time of writing. Further, it has an extremely excellent characteristic in which the balance between strength and density is excellent and the writing taste is good.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a core having a layer in which a body material is oriented concentrically at the outer periphery of a core and has a layer in which the body material is oriented concentrically at the inside, and the remaining portion is random.

FIG. 2 is a sectional view of a core in which the remaining part of FIG. 1 is radially oriented;

FIG. 3 is a cross-sectional view of a core having two concentric tubular layers inside of FIG. 1 and a remaining portion radially oriented.

FIG. 4 is a cross-sectional view of a conventional non-fired colored pencil lead having plate-like particles as a constitutional material.

FIG. 5 is a cross-sectional view of a conventional non-fired colored pencil lead having no plate-like particles in a constitutional material.

FIG. 6 is a horizontal sectional view of a plurality of concentric conical tubular current plates.

FIG. 7 is a vertical cross-sectional view of the straightening vane of FIG. 6 passing through the central axis of the nozzle.

FIG. 8 is a horizontal sectional view of a current plate with an increased number of concentric conical tubes of FIG. 6;

FIG. 9 is a vertical cross-sectional view of the current plate of FIG. 8 passing through the center axis of the nozzle.

FIG. 10 is a vertical sectional view of a conventional nozzle having no current plate.

Claims (1)

(57) [Claims] 1. In the outer peripheral surface portion of a colored pencil lead, a body material containing plate-like particles is oriented concentrically in a tubular shape, and is spaced apart in a radial direction in an inner space between the body material and the center material. A non-fired pencil lead having at least one layer oriented in a concentric tubular shape and having the body material randomly or radially oriented in the remaining portion.