Non-fired pencil lead

Abstract

This non-fired pencil lead contains: an extender material; a pigment; a water-soluble binder composed of a water-soluble polysaccharide, a polycarboxylic acid and a polyvinyl alcohol; and waxes, wherein the content of the water-soluble binder is 1 mass% to 10 mass%, and the content of the waxes is 0.1 mass% to 3 mass%.

Description

Non-fired pencil lead

[0001] This disclosure relates to non-fired pencil leads.

[0002] In Japanese Patent Application Laid-Open No. 5-39449, an organic polymer substance, which is a traditional binder, is dissolved and swollen with solvents such as water and / or plasticizers as needed, kneaded with waxes, extender pigments, colorants, etc., and extruded. After that, a non-fired colored pencil lead manufactured by a wet method of drying and removing the solvents and / or plasticizers is disclosed. For this non-fired colored pencil lead, waxes are not blended when formulating the blending composition of extender pigments, colorants, binders, etc., a water- and oil-repellent substance is added and blended, kneaded with solvents and / or plasticizers, and extruded. After that, the solvents and plasticizers are dried and removed to form open pores due to the water- and oil-repellent substance being difficult to wet. This porous body is impregnated with oils and / or waxes to manufacture a non-fired colored pencil lead that can be easily erased with a rubber.

[0003] In addition, Japanese Patent Application Laid-Open No. 2006-182969 discloses a fired colored pencil lead having excellent water resistance and containing at least a coloring material, an extender pigment, and a water-soluble binder, and further containing a water resistance-imparting material.

[0004] Furthermore, Japanese Patent Application Laid-Open No. 2008-45043 discloses a non-fired colored pencil lead containing a mixture of a glycerin fatty acid ester and / or a pentaerythritol fatty acid ester having a melting point of 65°C or lower and rosin and / or a rosin-modified product as waxes. This non-fired colored pencil lead has a drawing line that can be dissolved in an oil for oil painting such as turpentine oil, enabling oil painting-like drawing. Furthermore, it is a non-fired colored pencil lead in which blooming on the core surface and the drawing surface, which is likely to occur in soft colored cores, is less likely to occur.

[0005] Furthermore, WO2022 / 264643A1 discloses a non-fired pencil lead comprising a water-soluble polymer selected from the group consisting of carboxymethylcellulose salt, starch, polyvinyl alcohol, and xanthan gum, a crosslinking agent selected from the group consisting of acid, polyamide epoxy, polyacrylamide, titanium alkoxide, and glyoxal, and a powder. This non-fired pencil lead is said to have sufficient writing strength even when the tip is sharpened, has little deterioration due to moisture absorption, is erasable, and achieves both improved line density and improved fixation.

[0006] The non-fired colored pencil lead described in Japanese Patent Publication No. 5-39449 takes into consideration bending strength, erasability (non-erasability), and writing feel, but does not take into consideration gloss suppression of drawn lines, blurring, color mixing, and layering. The non-fired colored pencil lead described in Japanese Patent Publication No. 2006-182969 does not leach coloring material from the lead body, does not swell the lead body, and has a good writing feel, but does not take into consideration gloss suppression of drawn lines, blurring, color mixing, and layering. The non-fired colored pencil lead described in Japanese Patent Publication No. 2008-45043 also takes into consideration bending strength, erasability (non-erasability), and writing feel, but does not take into consideration gloss suppression of drawn lines, blurring, color mixing, and layering. The non-fired colored pencil lead described in WO2022 / 264643A1 also does not take into consideration gloss suppression of drawn lines, blurring, color mixing, and layering.

[0007] The present invention aims to provide a non-fired pencil lead that has low gloss on the lines, allows for layering, mixing, and blurring, has high core strength, and provides a good writing feel.

[0008] The non-fired pencil lead of the first embodiment of the present application contains a filler material, a pigment, a water-soluble binder consisting of water-soluble polysaccharides, polycarboxylic acid and polyvinyl alcohol, and waxes, wherein the content of the water-soluble binder is 1% by mass or more and 10% by mass or less, and the content of the waxes is 0.1% by mass or more and 3% by mass or less.

[0009] The non-fired pencil lead of the second embodiment of the present invention, in addition to the configuration of the first embodiment, contains 30% to 85% by mass of particles having a particle diameter of 0.5 μm or more and 20 μm or less, and an aspect ratio of 1.0 or more and 3.0 or less, as the binder material.

[0010] The non-fired pencil lead of the third embodiment of the present application contains, in addition to the configuration of the first or second embodiment, an inorganic pigment in an amount of 5% by mass or more and 20% by mass or less as the pigment.

[0011] Since the embodiment of the present invention is configured as described above, it is possible to provide a non-fired pencil lead that has low gloss on the lines, allows for layering, mixing, and blurring, has high core strength, and provides a good writing feel.

[0012] This is a schematic perspective view showing the appearance of the non-fired pencil lead of the embodiment. This is a scanning electron microscope image of barium sulfate (B-2) particles as a binder contained in the non-fired pencil lead of the example. This is a scanning electron microscope image of barium sulfate (P-30) particles as a binder contained in the non-fired pencil lead of the example. This is a scanning electron microscope image of zinc oxide (zinc oxide type 1) particles as a binder contained in the non-fired pencil lead of the example. This is a scanning electron microscope image of zinc oxide (LPZINC-5) particles as a binder contained in the non-fired pencil lead of the example. This is a scanning electron microscope image of talc particles as a binder contained in the non-fired pencil lead of the example. This is a scanning electron microscope image of calcium carbonate particles as a binder contained in the non-fired pencil lead of the comparative example.

[0013] The non-fired pencil lead of the embodiment of the present invention contains a filler, a pigment, a water-soluble binder consisting of water-soluble cellulose, polycarboxylic acid and polyvinyl alcohol, and waxes, wherein the content of the water-soluble binder is 1% by mass or more and 10% by mass or less, and the content of the waxes is 0.1% by mass or more and 3% by mass or less.

[0014] As for the binder material, there are no particular limitations as long as it is used in conventional non-fired pencil leads, and any of them can be used. For example, white binder materials such as boron nitride, kaolin, talc, mica, or calcium carbonate can be used, and depending on the hue of the solid drawing material, colored binder materials such as graphite can also be used, and of course, mixtures of several of these can also be used. Particularly preferred are graphite, talc, boron nitride, or kaolin, based on their physical properties and shape. However, it is desirable that the binder material contains 30% to 85% by mass of particles with a particle size of 0.5 μm or more and 20 μm or less and an aspect ratio of 1.0 or more and 3.0 or less.

[0015] Examples of pigments include titanium dioxide, iron black, carbon black, Prussian blue, ultramarine blue, Blue No. 1, red iron oxide, yellow iron oxide, chromium oxide, chromium hydroxide, zinc oxide, zirconium oxide, cobalt oxide, fish scale foil, bismuth oxychloride, titanium mica, Blue No. 2, Blue No. 404, Red No. 2, Red No. 3, Red No. 102, Red No. 104, Red No. 105, Red No. 106, DPP Red, Yellow No. 4, Yellow No. 5, or Green No. 3, and these can be used individually or in mixtures of two or more. However, it is desirable that the pigments contain 5% to 20% by mass of inorganic pigments (titanium dioxide, iron black, carbon black, Prussian blue, ultramarine blue, red iron oxide, yellow iron oxide, chromium oxide, chromium hydroxide, zinc oxide, zirconium oxide, cobalt oxide, bismuth oxychloride, or titanium mica, etc.).

[0016] The water-soluble binder is used as a binder and consists of water-soluble polysaccharides, polycarboxylic acids, and polyvinyl alcohol as water-soluble organic polymers. Examples of water-soluble polysaccharides include water-soluble cellulose such as carboxymethylcellulose salt or methylcellulose, or starch, alginate, xanthan gum, guar gum, or carrageenan. Examples of polycarboxylic acids include polyacrylic acid or polymethacrylic acid. The content of the water-soluble binder is 1% by mass or more and 10% by mass or less.

[0017] Any wax commonly used in colored pencil leads can be used. However, the wax content must be between 0.1% and 3% by mass.

[0018] The non-fired pencil lead of this embodiment can be manufactured, for example, by the following manufacturing method. That is, a mixture of a filler material, a pigment, a water-soluble binder consisting of water-soluble cellulose, polycarboxylic acid, and polyvinyl alcohol, and waxes is mixed with an equal amount of water, mixed and dispersed in a kneader, and then the moisture content is adjusted while kneading with a double roll. The mixture obtained by the adjustment is pelletized and extruded into the shape of a pencil lead of the desired thickness using a single-screw extruder. Then, the molded lead is dried to remove the moisture, and a non-fired pencil lead 10 having a substantially cylindrical core body 11, as shown in Figure 1, is obtained.

[0019] (1) Components The components used in the non-fired pencil lead of each example and comparative example described below are as follows:

[0020] (1-1) Consolidating Materials The consolidating materials used are as shown in Table 1 below. Scanning electron microscope images showing the particle shapes of the barium sulfate (B-2), barium sulfate (P-30), zinc oxide (zinc oxide type 1), zinc oxide (LPZINC-5), talc, and calcium carbonate used are shown in Figures 2, 3, 4, 5, 6, and 7, respectively.

[0021]

[0022] (1-2) Pigments The pigments used are as shown in Table 2 below.

[0023]

[0024] (1-3) Water-soluble binders The water-soluble binders used are as shown in Table 3 below.

[0025]

[0026] (1-4) Resins or waxes The resins or waxes used are as shown in Table 4 below.

[0027]

[0028] (2) Examples and Comparative Examples The content of each component in the non-fired pencil lead of Examples 1 to 7 and Comparative Examples 1 and 2 is as shown in Table 5 below. In Table 5 below, "CMC" is an abbreviation for carboxymethylcellulose, "PVA" is an abbreviation for polyvinyl alcohol, "PAA" is an abbreviation for polyacrylic acid, and "PCL" is an abbreviation for polycaprolactone.

[0029]

[0030] (3) Manufacturing of non-fired pencil lead The same mass of water was added to each of the raw materials of Examples 1 to 7 and Comparative Examples 1 and 2 above and mixed in a kneader, and then the moisture content was adjusted while kneading with a double roll. This mixture was pelletized and formed into fine wires using a single-screw extruder, and then dried at 45°C for 24 hours to remove moisture, yielding white non-fired pencil lead (Examples 1 to 4 and Comparative Examples 1 and 2), black non-fired pencil lead (Example 5), yellow non-fired pencil lead (Example 6), and red non-fired pencil lead (Example 7) with a diameter of 2.5 mm.

[0031] (4) Evaluation Items The non-fired pencil leads of Examples 1 to 7 and Comparative Examples 1 and 2 manufactured as described above were tested for the following evaluation items.

[0032] (4-1) Conversion Strength A three-point bending strength test was conducted as specified in JIS S 6006 8.6 "Bending Strength" and the conversion strength (unit: MPa) was calculated.

[0033] (4-2) Amount of wear A record-type mechanical writing measurement was performed as specified in JIS S 6006 8.7.2 "Writing density", and the amount of mechanical writing wear at a load of 300 g was calculated.

[0034] (4-3) Coefficient of Dynamic Friction The coefficient of dynamic friction between the pencil lead and the writing surface during writing was measured. Specifically, the tip of a non-fired pencil lead attached to the wooden shaft of a regular pencil was sharpened into a cone shape at an angle of 17 ± 1°, and the tip was then sharpened into a circle with a diameter of 0.6 ± 0.1 mm, making the whole thing a frustoconical shape. The pencil shaft with the tip shaped in this way was held at a 60° angle with the tip facing downwards using a special fixing jig, and fixed to a dynamic friction measuring machine (TRIBOGEAR, Shinto Kagaku). In this state, a load of 300 g was applied, and the coefficient of dynamic friction was measured when writing at a speed of 10 mm / sec.

[0035] (4-4) Writing feel: The pens were tested on drawing paper to evaluate wear and lubricity. The evaluation criteria were as follows: A: The lead breaks down very smoothly without any snagging. B: The lead breaks down smoothly. C: There is resistance when the lead breaks down. D: There is significant resistance when the lead breaks down.

[0036] (4-5) Glossiness Specular glossiness was measured at 60° glossiness in accordance with JIS Z 8741-1997 "Specular glossiness - Measurement method".

[0037] (4-6) Lines were drawn on drawing paper using pencil leads with different color formulations containing different pigments, and then lines were drawn over these lines with the non-fired pencil leads being evaluated. The color mixing properties were visually assessed. The evaluation criteria were as follows: A: Colors mix very easily. B: Colors mix easily. C: Colors do not mix easily. D: Colors do not mix very well.

[0038] (4-7) Lines drawn on blurred drawing paper were rubbed three times back and forth with a felt pad under a 200g load, and the lines were visually evaluated. The evaluation criteria were as follows: A: The density of the rubbed lines is thick and uniform over a long area. B: The density of the rubbed lines is uniform. C: The density of the rubbed lines is thin. D: The lines hardly spread even when rubbed.

[0039] (4 - 8) Lines were written on drawing paper with a different color combination core for each overwriting pigment, and then written with the non-fired pencil lead to be evaluated on top of the drawn lines, and the overwriting property was visually evaluated. The evaluation criteria were as follows. A: It can be clearly overpainted on top of the drawn line. B: It can be overpainted on top of the drawn line. C: It is difficult to overpaint on top of the drawn line, and the underlying color can be seen. D: It is almost impossible to overpaint on top of the drawn line.

[0040] (5) Results The results of each of the above evaluation items for Examples 1 to 7 and Comparative Examples 1 and 2 are as shown in Table 6 below.

[0041]

[0042] First, as shown in Table 5 above, all of the examples and comparative examples contain a extender and a pigment, and also contain at least one type of water-soluble binder. And all of the examples contain water-soluble polysaccharides, polycarboxylic acids, and polyvinyl alcohol as water-soluble binders. Furthermore, all of the examples contain particles having a particle diameter of 0.5 μm or more and 20 μm or less and an aspect ratio of 1.0 or more and 3.0 or less as an extender in an amount of 30% by mass or more and 85% by mass or less. As a result, none of the examples had an evaluation item with a result of at least D.

[0043] On the other hand, as shown in Table 5 above, Comparative Example 1 (see Table 1) that contains neither polyvinyl alcohol nor polycarboxylic acid (polyacrylic acid) as a water-soluble binder and has an extender with a particle diameter of less than 0.3 μm and 0.5 μm and an aspect ratio of less than 0.6 and 1.0 was inferior with a D in the writing feel item.

[0044] Also, as shown in Table 5 above, Comparative Example 2 that contains neither polyvinyl alcohol nor polycarboxylic acid (polyacrylic acid) as a water-soluble binder and has a wax content exceeding 15% by mass and 3% by mass, combined with a talc content of 60% by mass, had an extremely high glossiness of 10 compared to others, and as a result, the blurring and overwriting results were inferior with a D.

[0045] As described above, the non-fired pencil leads of each embodiment have a low gloss level, enabling overpainting, color mixing, and blurring effects. Additionally, the leads have high core strength and a good writing feel.

[0046] The technology of the present disclosure can be applied to non-fired pencil leads.

Claims

1. A non-fired pencil lead containing a filler, a pigment, a water-soluble binder consisting of water-soluble polysaccharides, polycarboxylic acid and polyvinyl alcohol, and waxes, wherein the water-soluble binder content is 1% by mass or more and 10% by mass or less, and the waxes content is 0.1% by mass or more and 3% by mass or less.

2. The non-fired pencil lead according to claim 1, wherein the binder material contains 30% by mass to 85% by mass of particles having a particle size of 0.5 μm or more and 20 μm or less, and an aspect ratio of 1.0 or more and 3.0 or less.

3. The non-fired pencil lead according to claim 1 or 2, wherein the pigment contains 5% by mass or more and 20% by mass or less of an inorganic pigment.

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