Erasable colored pencil lead

Abstract

To provide an erasable colored pencil lead having sufficient bending strength and also having such erasability that makes it possible to erase a drawn line with an eraser.SOLUTION: An erasable colored pencil lead contains a smectite clay mineral having a methylene blue adsorption higher than 100 mmol / 100 g, measured by JIS Z 2451:2019 6.3 colorimetric method.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to erasable colored pencil leads that allow lines drawn on a surface such as drawing paper to be erased with an eraser. [Background technology]

[0002] Conventional non-baked colored pencil leads are made by blending wax, oils, lubricants, etc. with coloring materials, binders, and fillers (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 discloses that a solid drawing material containing a colorant, an extender pigment, a clay mineral (such as bentonite), wax, a lubricant, etc., is excellent in erasability when handwriting written on a non-absorbent surface such as a whiteboard is erased with paper, cloth, a whiteboard eraser, etc., by incorporating a non-spherical extender pigment having a predetermined particle size. Furthermore, Patent Document 2 discloses that in the case of colored pencils and other colored cores that contain a fluorescent pigment, an extender, organic bentonite, wax, a lubricant, and the like, by incorporating a predetermined amount of organic bentonite, the coloring properties of the fluorescent pigment are not impaired and sufficient strength can be achieved.

[0004] However, while the incorporation of wax into conventional non-baked colored pencil leads makes writing smoother and improves colorability, the wax adheres strongly to the paper, resulting in poor erasure with an eraser. Furthermore, colored pencil leads that do not contain wax have poor strength (bending strength), which can lead to break when sharpened.

[0005] Therefore, it has been disclosed that by using Nε-lauroyl lysine as an extender, it is possible to obtain non-baked colored pencil leads that are suitable for mechanical pencil leads and that have excellent flexural strength, color development, writing feel, and eraser erasability without blending wax (Patent Document 3). However, the eraser erasability is still insufficient, and colored pencil leads with excellent eraser erasability are desired. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-152071 [Patent Document 2] Japanese Patent Application Publication No. 02-060978 [Patent Document 3] Japanese Patent Application Publication No. 08-120208 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and has as its object to provide an erasable colored pencil lead that has sufficient bending strength and erasability that allows drawn lines to be erased with an eraser. [Means for solving the problem]

[0008] The inventors conducted extensive research to solve the above-mentioned problems, and discovered that the problems can be solved by adding a smectite clay mineral to unbaked colored pencil leads, which has a methylene blue adsorption amount of more than 100 mmol / 100 g as measured by the colorimetric method specified in JIS Z 2451:2019 6.3, and thus arrived at the present invention.

[0009] That is, the present invention is as follows.

[0010] (1) A non-baked color pencil lead with eraser erasability, JIS Z 2451:2019 6.3 Smectite clay minerals with a methylene blue adsorption amount greater than 100 mmol / 100 g as measured by colorimetry; Wax content of 10% by mass or less (including 0%) of the total weight of the colored pencil lead An erasable colored pencil lead characterized by containing (2) The erasable colored pencil lead according to (1) above, wherein the smectite clay mineral is at least one selected from the group consisting of bentonite, hectorite, and stevensite. (3) The lead of the erasable colored pencil according to (1) or (2), wherein the blending amount of the smectite clay mineral is 0.5 to 20 mass % of the total weight of the lead of the erasable colored pencil. (4) The erasable colored pencil lead according to any one of (1) to (3) above, further containing a coloring material, an extender, and a binder. (5) The erasable colored pencil lead according to (4), wherein the coloring material comprises a hiding pigment and a coloring pigment. (6)Furthermore, For all wax-free erasable colored pencil leads Oil 0.5~10% by mass The impregnated (1) to ( 5 ) Erasable colored pencil lead described in any one of the above. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide erasable colored pencil leads that have sufficient bending strength and, compared to conventional non-baked colored pencil leads, are excellent in eraser erasability when erasing drawn lines with an eraser. DETAILED DESCRIPTION OF THE INVENTION

[0012] The erasable colored pencil lead of the present invention is characterized by containing a smectite clay mineral having a methylene blue adsorption amount of more than 100 mmol / 100 g as measured by the colorimetric method specified in JIS Z 2451:2019 6.3.

[0013] [Smectite clay minerals] Examples of smectite clay minerals include bentonite, montmorillonite, hectorite, saponite, stevensite, beidellite, nontronite, sauconite, and acid clay. These may be used alone or in combination of two or more. Examples of such smectite clay minerals include natural products, refined natural products, natural products with modified swelling properties, and synthetic products. The use of smectite clay minerals can impart flexural strength and a smooth writing feel to erasable colored pencil leads.

[0014] Examples of commercially available naturally occurring bentonite include Odoearth (registered trademark) and Odosorb (registered trademark) from Kurosaki Hakudo Kogyo Co., Ltd., bentonite from Hojun Co., Ltd., and Moistnite-U, Moistnite-S, and Moistnite-HC from Kunimine Kogyo Co., Ltd.; and purified bentonite (montmorillonite products with increased purity) such as Kunipia G, Kunipia F, Kunipia G4, and Kunipia G10 from Kunimine Kogyo Co., Ltd. As synthetic smectite products, for example, Sumecton SA, Sumecton ST, Sumecton SWN, Sumecton SWF, etc. manufactured by Kunimine Kogyo Co., Ltd. are commercially available.

[0015] Among smectite clay minerals, bentonite, hectorite, and stevensite are preferred because they can improve the bending strength of the lead, with bentonite being particularly preferred. Among bentonites, Na-type bentonite, which contains a large amount of sodium ions among the cations present between the layers of unit crystals, is desirable because it has excellent swelling properties and suspension stability, resulting in erasable colored pencil leads that have a smooth writing feel and good color retention. The Na-type bentonite referred to here may be, for example, Na-substituted bentonite, in which the calcium ions of Ca-type bentonite have been artificially substituted with sodium ions.

[0016] When selecting a smectite clay mineral, it is necessary to select one with a methylene blue adsorption of greater than 100 mmol / 100 g, as measured by the colorimetric method in JIS Z 2451:2019 6.3. The methylene blue adsorption is preferably 120 mmol / 100 g or greater, and even more preferably 150 mmol / 100 g or greater. If the methylene blue adsorption is greater than 100 mmol / 100 g, the flexural strength of the erasable colored pencil lead will not be insufficient, making it less likely to break or chip during drawing. Furthermore, it is generally best to use a methylene blue adsorption of 170 mmol / 100 g or less.

[0017] The blending amount of smectite clay mineral is preferably 0.5 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 5 to 10% by mass, of the total weight of the erasable colored pencil lead (excluding the impregnated oil, described below; the same applies below). If the blending amount is 0.5% by mass or more, the bending strength of the colored pencil lead will not be insufficient, and a good writing feel can be achieved without breakage or chipping during drawing. Furthermore, if the blending amount is 20% by mass or less, the material will not become too hard, and will not adversely affect roll mixing or molding.

[0018] The form of the smectite clay mineral used in the present invention is not particularly limited, and may be, for example, powder, granules, or flakes. The average particle size of the smectite clay mineral is preferably 10 μm to 300 μm, more preferably 100 μm to 200 μm. The average particle size is measured by laser diffraction.

[0019] [Coloring material] As the coloring material, conventionally known dyes and pigments can be used. By using a coloring material, it is possible to impart hiding power and color to the erasable color pencil lead. Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, and various salt-forming dyes of these. Examples of pigments include inorganic pigments, organic pigments, lake pigments (water-soluble basic dyes or acid dyes made insoluble), pearl pigments, metallic pigments, fluorescent pigments, and opacifying pigments. These can be used alone or in appropriate combinations of two or more. Among these, pigments are preferred in terms of color development and moldability, and it is more preferable to use a color pigment such as an organic pigment or lake pigment in combination with an opacifying pigment. Using both in combination can improve color development on paper.

[0020] Examples of inorganic pigments include white pigments such as titanium oxide (titanium white), zinc oxide (zinc white), basic lead carbonate (lead white), basic lead sulfate, zinc sulfide, lithopone, titanox, white carbon, and precipitated barium sulfate, as well as carbon black, iron black, ultramarine, red iron oxide, Prussian blue, titanium black, black iron oxide, yellow iron oxide, red iron oxide, red iron oxide, red lead, cinnabar, chromium oxide, cobalt blue, chrome green, titanium yellow, cadmium yellow, cadmium red, cadmium orange, barium yellow, aureolin, molybdate orange, and manganese violet. Inorganic pigments come in a limited number of colors, but they have subdued tones and excellent weather resistance. Examples of organic pigments include nitro pigments, azo pigments, thioindigo pigments, quinacridone pigments, anthraquinone pigments, and phthalocyanine pigments. Specific examples include azo pigments such as CI Pigment Red 3, CI Pigment Red 48:3, CI Pigment Red 57:1, CI Pigment Red 53:1, CI Pigment Yellow 3, CI Pigment Yellow 12, and CI Pigment Orange 13; thioindigo pigments such as CI Pigment Violet 38 and CI Pigment Red 88; quinacridone pigments such as CI Pigment Red 122, CI Pigment Red 206, and CI Pigment Red 207; anthraquinone pigments such as CI Pigment Red 83 and CI Pigment Red 177; and phthalocyanine pigments such as CI Pigment Blue 15:1 and CI Pigment Green 7. Organic pigments tend to have vivid colors, a wide variety of colors, excellent coloring power, and excellent transparency. Examples of lake pigments include fast sky blue and methyl violet. The above pigments may be used after being washed with water, dried, surface-treated, and pH-adjusted with a pH adjuster such as alkali.

[0021] The hiding pigment is preferably a titanium oxide pigment, for example, a white pigment made of titanium dioxide with an average particle size of about 0.1 to 0.5 μm. Commercially available hiding pigments available from Titanium Kogyo Co., Ltd., Teikoku Kako Co., Ltd., Furukawa Mining Co., Ltd., Ishihara Sangyo Kaisha, Ltd., etc., can be used. Titanium oxide pigments include anatase type (also known as anatase, refractive index 2.45 to 2.55) and rutile type (also known as rutile, refractive index 2.61 to 2.90). Either anatase type or rutile type can be used in the present invention. The average particle size is measured by laser diffraction.

[0022] The amount of colorant blended is preferably 10 to 50% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass, based on the total weight of the erasable colored pencil lead. When a color pigment and a hiding pigment are used in combination, the ratio of the two (color pigment / hiding pigment) is preferably 0.01 / 99.99 to 90.0 / 10.0 (by mass), although this will vary depending on the desired color of the erasable colored pencil, more preferably 0.05 / 99.95 to 80.0 / 20.0, and even more preferably 0.1 / 99.9 to 70.0 / 30.0. A blending ratio within the above ranges provides excellent color tone and hiding power.

[0023] [Structure material] The filler is not particularly limited, and conventionally known fillers can be used, such as talc, kaolinite, sericite, mica, silica, calcium carbonate, calcium silicate, and barium sulfate. Among these, from the viewpoint of improving the writing feel, talc, kaolinite, and calcium silicate are preferred, talc and kaolinite are more preferred, and talc is even more preferred. These fillers can be used alone or in appropriate combinations of two or more.

[0024] The blending amount of the extender is preferably 40 to 85% by mass, more preferably 50 to 70% by mass, and even more preferably 55 to 65% by mass, based on the total mass of the erasable colored pencil lead. Blending within this range can impart a good writing feel to the erasable colored pencil lead.

[0025] [Binding material] The binder is not particularly limited, and conventionally known binders can be used, such as polyvinyl alcohol, polyvinylpyrrolidone, sodium carboxymethylcellulose, hydroxyethylcellulose, and polyethylene glycol. Among these, sodium carboxymethylcellulose and high-molecular-weight polyethylene glycol are preferred, and sodium carboxymethylcellulose is more preferred, in view of their excellent formability of the core. These binders can be used alone or in appropriate combinations of two or more.

[0026] The blending amount of binder is preferably 2 to 15% by mass, more preferably 3 to 10% by mass, and even more preferably 3 to 7% by mass, based on the total weight of the erasable colored pencil lead. If it is 2% by mass or more, the lead will have excellent moldability, and if it is 15% by mass or less, the writing feel will not be impaired.

[0027] In the present invention, it is preferable not to incorporate wax into the erasable colored pencil lead. The incorporation of wax improves fixation to the paper surface, resulting in good colorability. However, this is undesirable because the core composition adhered between the fibers of the paper cannot be completely removed by the adhesive force of the eraser, leaving written lines behind. Wax may be incorporated within a range that does not impair erasability with an eraser. If wax is incorporated, its amount is preferably 10% by mass or less, more preferably 3% by mass or less, of the total weight of the erasable colored pencil lead.

[0028] Examples of waxes include higher fatty acids such as stearic acid and palmitic acid, higher alcohols or esters thereof, fats and oils or fat derivatives such as hydrogenated castor oil, petroleum waxes such as paraffin wax and microcrystalline wax, vegetable waxes such as carnauba wax and Japan wax, animal waxes such as beeswax and lanolin, and synthetic waxes such as polyethylene wax. These may be used alone or in appropriate combinations of two or more.

[0029] In addition to the above-mentioned components, the erasable colored pencil lead of the present invention may contain, if necessary, antioxidants, ultraviolet absorbers, antifungal agents, preservatives, antibacterial agents, fragrances, etc., within limits that do not impair the effects of the present invention.

[0030] Furthermore, the erasable colored pencil lead of the present invention is preferably impregnated with oil after molding and drying. This improves the smoothness of writing while maintaining the eraser erasability. Examples of oils to be impregnated include animal and vegetable oils such as lard, beef tallow, rapeseed oil, and soybean oil, mineral oils such as spindle oil and liquid paraffin, waxes, and silicone oils. These can be used alone or in appropriate combinations of two or more. Among these, silicone oil is preferred. The amount of oil impregnated is not particularly limited as long as it does not impair erasability with an eraser, and specifically, it may be in the range of 0.5 to 10% by mass relative to the total mass of the erasable colored pencil lead. The amount of oil impregnated was calculated from the mass of the core before and after oil impregnation using the following formula (I). Amount of oil impregnated into the total mass of the erasable colored pencil lead = (mass after impregnation - mass before impregnation) / (mass after impregnation) (I)

[0031] [Erasable colored pencil core] The erasable colored pencil lead of the present invention can be produced by a conventionally known method, namely, by kneading a smectite clay mineral, colorant, extender, binder, and optionally water, solvent, plasticizer, etc., in a triple roll or similar, extruding the mixture in an extruder into a rod of the desired diameter, and then drying and removing the volatile components. When impregnating with oil, the erasable colored pencil core obtained above is immersed in oil at room temperature or heated as necessary for 24 hours, and then the excess oil on the surface is removed using a centrifuge or the like.

[0032] The erasable colored pencil lead of the present invention preferably has a bending strength of 26.0 MPa or more as measured by the method described in JIS S 6006:2020. If the bending strength is 26.0 MPa or more, the lead has sufficient bending strength as a colored pencil lead. On the other hand, if the bending strength is less than 26.0 MPa, the lead may break or chip due to the writing pressure during writing.

[0033] The erasable colored pencil leads of the present invention can be used in a wide range of forms, including for both wooden-barreled pencils and mechanical pencils. In particular, those formed into a rod shape with a diameter of about 0.5 to 5 mm (preferably about 1 to 4 mm) are suitable as leads for wooden-barreled colored pencils.

[0034] [Erasable colored pencils] Erasable colored pencils equipped with the erasable colored pencil leads of the present invention can be manufactured (shafts) by conventionally known methods. In the case of wooden-shaft erasable colored pencils, for example, grooves are made in the upper surface of a wooden board (slat) cut to a predetermined length, width, and thickness, adhesive is applied, the erasable colored pencil leads are placed in the grooves, and a wooden board with a similar groove and adhesive applied to the lower surface is placed on top of the slats, which are then pressed and dried, carved into the desired shape, and painted as necessary. The type of wood used for the wooden board is not limited, but incense cedar, linden, white fir, etc. are preferably used. [Example]

[0035] EXAMPLES The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0036] The methods for measuring the physical properties of the components used in the examples and comparative examples and the methods for evaluating the resulting colored pencil leads are as follows.

[0037] <Methylene blue adsorption amount of smectite clay minerals> In accordance with JIS Z 2451:2019 6.2.4a) Boiling Method and 6.3 Colorimetric Method, methylene blue was added little by little to a suspension of a sample (smectite clay mineral such as bentonite) dispersed in water, and allowed to adsorb onto the sample. The amount of adsorption was calculated from the amount of methylene blue added when the sample could no longer be adsorbed.

[0038] <Bending strength of colored pencil lead> Measurements were performed in accordance with JIS S 6006:2020 using a three-point bending test (support distance 60 mm, load application rate 10 mm / min).

[0039] <Erasability of colored pencil leads> Colored pencils sharpened with an electric pencil sharpener were tested on a record-type line-drawing machine in an environment of 23±2°C and 65±5%RH, with a scale load of 128gf / m 2 A test paper was prepared by drawing a line on Kent paper (marshmallow paper) under conditions of a load of 300 gf and a writing angle of 75°. A 500 gf load was then applied to the drawn portion of the test paper with an eraser (Mono (registered trademark) PE01A, manufactured by Tombow Pencil Co., Ltd.) and the eraser was reciprocated four times. The degree of erasure of the line was visually observed and evaluated based on the following evaluation criteria, with ◯ and △ representing erasure. (Evaluation criteria) 〇: Disappeared △: There is a slight residue ×: Not erased

[0040] <Writing feel of colored pencil lead> A 3cm x 3cm frame was hand-drawn on drawing paper (New TMK Poster (thick paper)) using colored pencils sharpened with an electric pencil sharpener, and the feeling of writing when filling in the frame from all four directions (top, bottom, left, and right) was evaluated based on the following evaluation criteria. (Evaluation criteria) 〇: I never felt any resistance △: I felt a slight resistance ×: I felt something stuck

[0041] (Examples 1 to 18) The ingredients and amounts (by mass) shown in Table 1 were added to a Henschel mixer, and the mixture was stirred and mixed at room temperature with an appropriate amount of water. The mixture was then kneaded using a three-roll mill and then extruded into a thin rod shape using an extruder. The mixture was then thoroughly dried, yielding a lead measuring 180 mm in length and 3 mm in diameter. The lead was then immersed in silicone oil (ELEMENT14® PDMS50-J, manufactured by Momentive Performance Materials Japan, LLC) at room temperature and atmospheric pressure for 24 hours, after which the excess oil was removed from the surface using a centrifuge, yielding a red, unbaked colored pencil lead.

[0042] (Examples 19 to 21) The ingredients and amounts (mass%) shown in Table 1 were charged into a Henschel mixer, and an appropriate amount of water was added. The mixture was stirred and mixed at 70-95°C, then kneaded using a three-roll mill at 30-70°C, and then molded into a thin rod shape using an extruder. After thorough drying, a red, unbaked colored pencil lead measuring 180 mm in length and 3 mm in diameter was obtained.

[0043] (Comparative Example 1) The ingredients and amounts (mass%) shown in Table 1 were charged into a Henschel mixer, and an appropriate amount of water was added. The mixture was stirred and mixed at 70-95°C, then kneaded using a three-roll mill at 30-70°C, and then molded into a thin rod shape using an extruder. After thorough drying, a red, unbaked colored pencil lead measuring 180 mm in length and 3 mm in diameter was obtained.

[0044] (Comparative Examples 2 to 5) The ingredients and amounts (by mass) shown in Table 1 were added to a Henschel mixer, and the mixture was stirred and mixed at room temperature with an appropriate amount of water. The mixture was then kneaded using a three-roll mill and then extruded into a thin rod shape using an extruder. The mixture was then thoroughly dried, yielding a lead measuring 180 mm in length and 3 mm in diameter. The lead was then immersed in silicone oil (ELEMENT14® PDMS50-J, manufactured by Momentive Performance Materials Japan, LLC) at room temperature and atmospheric pressure for 24 hours, after which the excess oil was removed from the surface using a centrifuge, yielding a red, unbaked colored pencil lead.

[0045] The bending strength of the unbaked colored pencil leads obtained above was measured. The unbaked colored pencil leads were then cut into round-shaped colored pencils with a length of 175 mm and a diameter of 8 mm using incense cedar slats, and the erasability and writing feel were evaluated. The evaluation results are shown in Table 1. In Table 1, "MB" stands for methylene blue adsorption amount (unit: mmol / 100 g).

[0046] [Table 1]

[0047] As is clear from Table 1, the erasable colored pencil leads of the present invention (Examples 1 to 21), which use smectite clay minerals with methylene blue adsorption exceeding 100 mmol / 100 g, have a sufficiently high bending strength of 26.0 MPa or more and exhibit excellent erasability with an eraser. In particular, the erasable colored pencil leads (Examples 1 to 18 and 21) with a wax content of 3% by mass or less (including 0) exhibit excellent erasability with an eraser. Furthermore, erasable colored pencil leads (Examples 17 and 18) that blend two types of smectite clay minerals with different methylene blue adsorption capacities, and have a methylene blue adsorption capacity of over 100 mmol / 100 g, calculated by multiplying each methylene blue adsorption capacity by the blending ratio, have a sufficiently high bending strength of 26.0 MPa or more, and are excellent in terms of erasability with an eraser and writing feel.

[0048] On the other hand, the one containing no smectite clay mineral and containing 20% ​​wax by mass (Comparative Example 1) had an excellent writing feel due to the effect of the wax, but the erasability with an eraser was poor.Furthermore, the one containing no smectite clay mineral (Comparative Example 2) and the one containing a smectite clay mineral with a methylene blue adsorption of 100 mmol / 100 g or less (Comparative Examples 3 to 5) had insufficient bending strength. [Industrial Applicability]

[0049] The erasable colored pencil lead of the present invention has sufficient bending strength so that it does not break or chip when drawing, and the written lines can be erased with an eraser.

Claims

1. A non-baked colored pencil lead with eraser erasability, characterized in that it contains a smectite clay mineral having a methylene blue adsorption amount of more than 100 mmol / 100 g as measured by the colorimetric method in accordance with JIS Z 2451:2019 6.3, and 10% by mass or less (including 0%) of wax relative to the total amount of the colored pencil lead.

2. 2. The erasable colored pencil lead according to claim 1, wherein the smectite clay mineral is at least one selected from the group consisting of bentonite, hectorite, and stevensite.

3. The lead of the erasable colored pencil according to claim 1 or 2, wherein the blending amount of the smectite clay mineral is 0.5 to 20 mass % based on the total amount of the lead of the erasable colored pencil.

4. The erasable colored pencil lead according to any one of claims 1 to 3, further comprising a coloring material, an extender, and a binder.

5. 5. The erasable colored pencil lead according to claim 4, wherein the coloring material comprises a hiding pigment and a coloring pigment.

6. Furthermore, the wax-free erasable color pencil core was impregnated with 0.5 to 10% by mass of oil. The erasable colored pencil lead according to any one of claims 1 to 5.

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