Colored pencil lead and its manufacturing method

Abstract

To provide a colored pencil lead that has excellent handwriting color development and erasability, smooth writing, and excellent storage stability, and to provide a method for producing the same.SOLUTION: The colored pencil lead according to the present invention comprises a body material, an inorganic binder material, a coloring agent soluble in a mixed solvent of a high boiling point organic solvent and a low boiling point organic solvent, and the high boiling point organic solvent. Further, the boiling point difference between the low boiling point organic solvent and the high boiling point organic solvent is 100 degrees or more, and the lead of the colored pencil does not substantially contain the low boiling point organic solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to color pencil leads, and more particularly to color pencil leads that have excellent color development and a smooth writing feel. [Background technology]

[0002] Conventionally, colored pencil leads used in mechanical pencils and the like have been made by extruding a mixture primarily composed of a filler such as boron nitride and a binder such as clay, optionally containing organic polymer compounds, and then firing it at high temperatures to produce a white porous substrate, the pores of which are impregnated with ink containing a dye. To express a wide variety of colors, it is desirable to achieve better color development using a variety of materials and equipment, and there is also a need for improvements in erasability, stability over time, and writing feel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-099633 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a color pencil lead that has excellent color development in handwriting, high stability over time, and smooth writing feel. [Means for solving the problem]

[0005] Body material and an inorganic binder; a colorant soluble in a mixed solvent of a high-boiling point organic solvent and a low-boiling point organic solvent; the high-boiling organic solvent; A colored pencil lead comprising: The boiling point of the low boiling point organic solvent is BP L , the boiling point of the high-boiling organic solvent is BP H When BPH and BP L The difference is 100 degrees or more, The color pencil lead is characterized in that it does not substantially contain the low-boiling organic solvent.

[0006] Further, the method for producing colored pencil leads according to the present invention comprises the steps of: (a) a kneading step of kneading an extender and an inorganic binder to prepare a mixture; (b) extrusion of the mixture to form a linear product; (c) a firing step of firing the linear molding to form a porous substrate; (d) an impregnation step of contacting the porous substrate with a colorant solution containing a colorant and an organic solvent to impregnate the porous substrate; (e) a drying step of heating the porous substrate after the impregnation step to evaporate a portion of the organic solvent and form a porous core; (f) a filling step of bringing the porous core body into contact with a hardly-volatile liquid that cannot dissolve the colorant, thereby filling the voids of the porous core body with the hardly-volatile liquid; A method for producing a colored pencil lead comprising: the organic solvent is a mixed solvent of two or more organic solvents, The boiling point of the low-boiling organic solvent contained in the mixed solvent is expressed as BP L , the boiling point of the high boiling organic solvent is BP H When BP H and BP L The difference is 100 degrees or more, And the heating temperature T in step (e) is BP L More than BP L It is characterized by being +100 or less. [Effects of the Invention]

[0007] By using the colored pencil leads of the present invention, handwriting with excellent color development can be produced. Furthermore, a smooth writing feel can be obtained when writing with the colored pencil leads of the present invention. Furthermore, the colored pencil leads of the present invention have high storage stability and excellent color development and erasability over time. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Colored pencil lead> The structure of the color pencil lead according to the present invention is as follows:

[0009] The porous core used in the colored pencil lead of the present invention comprises a filler and an inorganic binder as its main components. Examples of fillers include white fillers such as titanium oxide, mica, talc, boron nitride, alumina, and calcium carbonate, as well as colored fillers such as molybdenum disulfide, tungsten disulfide, and graphite. It is desirable for the colored pencil lead of the present invention to produce vivid handwriting. Furthermore, when fluorescent colorants are used as colorants to produce fluorescent handwriting, a filler that does not inhibit color development is preferred. Therefore, to produce handwriting with high brightness, it is preferable to use a white filler. Boron nitride is particularly preferred because the filler does not inhibit color development and increases the strength of the colored pencil lead.

[0010] Examples of the inorganic binder include clays such as kaolinites, halloysites, montmorillonites, sericites, and bentonites, ceramics, zeolites, diatomaceous earth, activated clay, silica, aluminum phosphate, silicone resins, and silicone rubbers, and these can be used alone or in combination.

[0011] The blending ratio of the filler material, which is the main component of the porous core, to the inorganic binder is not particularly limited, but is preferably 9:1 to 7:3 by mass ratio.

[0012] In the present invention, the porous core is typically a combination of a colorant and a high-boiling organic solvent on a porous substrate. The colorant may be localized in a portion of the porous substrate, primarily composed of an extender or inorganic binder, or may be uniformly dispersed throughout the porous substrate. However, localization within a portion of the porous core is preferred. Specifically, the colorant is preferably attached or adsorbed within the pores of the porous substrate. The colorant may be in the form of fine particles or dissolved or dispersed in a high-boiling organic solvent, as described below. Presence of the colorant in this state in the final colored pencil lead inhibits penetration of the colorant into the paper during writing, improving color development and erasability. Here, the colorant typically forms a layer or phase within the pores. That is, it generally forms a uniform or non-uniform layer on the inner surface of the pores, or adheres in clumps. In the present invention, "pores" refers to the pores in the base material, e.g., the porous substrate, from which the organic solvent, etc., has been removed from the pencil lead. For example, in the case of a porous core, an organic solvent may penetrate into the pores, and the pores of this porous core refer to the pores after the organic solvent has been removed from the porous core.

[0013] In the present invention, the porous core comprises a filler, an inorganic binder, a colorant, and a high-boiling organic solvent. Pencil leads are generally produced by molding a mixture of the filler and binder and then firing the resulting mixture; a similar method can be applied to the present invention. Specifically, pencil leads can be produced by firing a mixture of the filler and inorganic binder, and then adsorbing or attaching a colorant and a high-boiling organic solvent to the resulting porous substrate (details will be described later). Alternatively, a filler, an inorganic binder, a colorant, and a high-boiling organic solvent may be mixed and fired. In such cases, it is preferable to use a colorant with high heat resistance or a high-boiling organic solvent with a boiling point higher than the firing temperature. On the other hand, the former method allows the use of colorants with low heat resistance or high-boiling organic solvents with a boiling point lower than the firing temperature.

[0014] Alternatively, a porous core can be produced by compressing a mixture containing a filler, an inorganic binder, an inorganic substance, a water-soluble resin, and, if necessary, a colorant at high pressure, and then immersing the mixture in water or a solvent to remove the inorganic substance, water-soluble resin, etc.

[0015] The porosity of the porous core used in the present invention is not particularly limited, but is preferably in the range of 1 to 50%, more preferably 5 to 50%, even more preferably 10 to 40%, and particularly preferably 20 to 40%. If the porosity is less than 1%, the amount of colorant and non-volatile liquid present in the pores will be reduced, tending to result in poor color development and slight resistance to writing. If the porosity is greater than 50%, the resulting porous core will tend to be weaker and more prone to breaking. A porosity in the range of 1 to 50% is preferred because it provides good color development, a smooth writing feel, and maintains the strength of the baked color pencil lead.

[0016] The porosity of the porous substrate used in the present invention can be measured by the following method, with reference to JIS R1634 (1998). First, the dry mass (W1) of the porous substrate is measured. Next, the substrate is immersed in a highly permeable liquid (e.g., benzyl alcohol) and the pores of the porous core are allowed to absorb the liquid until saturated, after which the mass in the liquid (W2) is measured. Next, the porous substrate is removed from the liquid, and the liquid adhering to its surface is removed, after which the mass in the liquid (W3) is measured. Using these measured values, the porosity can be calculated using the following mathematical formula (1).

[0017] Porosity = (W3-W1) / (W3-W2)×100 (1)

[0018] The porosity of colored pencil leads or porous cores can also be measured using a similar method. However, before applying the above-mentioned method for measuring the porosity of porous substrates, it is necessary to remove the organic solvent by heating or reducing the pressure. When measuring the porosity of colored pencil leads or porous cores, even after removing the solvent, some organic solvent may remain in the pores. For this reason, there may be a slight difference between the porosity of the porous substrate and the porosity of the colored pencil leads or porous cores. Taking such differences into consideration, the porosity of the porous substrate is preferably in the range of 5 to 50%, more preferably in the range of 10 to 40%, and particularly preferably in the range of 20 to 40%.

[0019] In the present invention, the colored pencil core contains a high-boiling organic solvent. The high-boiling organic solvent and the low-boiling organic solvent are distinguished by the difference in their boiling points. Specifically, the boiling point of the low-boiling organic solvent is expressed as BP. L , the boiling point of the high boiling organic solvent is BP H When this is done, BP H and BP L The difference between the above is 100 degrees or more, preferably 150 degrees or more. H is preferably 180°C or higher, more preferably 200°C or higher, and particularly preferably 250°C or higher. L The temperature is preferably 100°C or lower, more preferably 90°C or lower, even more preferably 85°C or lower, and even more preferably 80°C or lower. This difference in boiling point between the high-boiling-point organic solvent and the low-boiling-point organic solvent makes it possible to remove only the low-boiling-point organic solvent during the manufacturing process described below. This results in a colored pencil lead that possesses the excellent color development and writing feel brought about by the high-boiling-point organic solvent. Furthermore, the high-boiling-point organic solvent is less likely to volatilize during the manufacturing process or during storage, allowing for stable performance.

[0020] The mixed solvent of the high-boiling organic solvent and the low-boiling organic solvent is capable of dissolving the colorant described below. Preferably, the high-boiling organic solvent and the low-boiling organic solvent are each capable of dissolving the colorant alone, and can be selected in consideration of the solubility.

[0021] Here, a high-boiling point organic solvent or a low-boiling point organic solvent capable of dissolving a colorant means that the solubility of the colorant in that organic solvent is 10 g / 100 g or more at 20° C., that is, 10 g or more of the colorant dissolves in 100 g of organic solvent at 20° C. The higher the solubility of the colorant, the higher the storage stability of the colored pencil lead tends to be; a solubility of 30 g / 100 g or more is more preferable, and 40 g / 100 g or more is even more preferable.

[0022] The high-boiling organic solvent can be selected arbitrarily taking into consideration the solubility of the colorant used, other performance characteristics, etc., but is preferably an aromatic glycol ether or an aliphatic glycol ether. Glycol ethers contain both an ether group and a hydroxyl group in their structure and are generally characterized by high solubility of dyes, resins, etc., and high affinity with other organic solvents, etc.

[0023] Specific examples of such high boiling point organic solvents include Diethylene glycol monophenyl ether (phenyl diglycol, 298°C), Diethylene glycol monobenzyl ether, (302°C), Diethylene glycol monobutyl ether (231°C), Triethylene glycol monobutyl ether (butyl triglycol, 271°C), Ethylene glycol monobenzyl ether (256°C) Triethylene glycol monomethyl ether (249°C), Phenyl cellosolve (245°C), Propylene glycol monophenyl ether (243°C), The numbers in parentheses indicate boiling points (same below).

[0024] Furthermore, as the high-boiling organic solvent, a carboxylic acid ester of a polyalkylene glycol or a carboxylic acid ester of an alcohol can be used.

[0025] Additionally, higher fatty acids and higher alcohols can also be used. Specific examples include carboxylic acids with 10 or more carbon atoms, such as decanoic acid (259°C) and oleic acid (360°C), and alcohols with 12 or more carbon atoms, such as dodecyl alcohol (259°C), myristyl alcohol (292°C), benzyl alcohol (205°C), and 3-methoxy-3-methyl-1-butanol (174°C). Care must be taken when using higher fatty acids, as they may cause corrosion when colored pencil leads are used in mechanical pencils and come into contact with metal parts.

[0026] It should be noted that some organic solvents are liquid at room temperature and pressure, but when heated under normal pressure, they sublimate or are denatured by chemical reactions, making it impossible to measure their boiling points accurately. Even such organic solvents can sometimes be used as high-boiling organic solvents. In such cases, for example, if the weight loss rate after 30 minutes is 10% by mass or less when held at a specific temperature t under normal pressure, the boiling point BP of the high-boiling organic solvent can be determined. H can be set to t°C or higher. By using this temperature t, the temperature difference BP between the high-boiling organic solvent and the low-boiling organic solvent can be calculated. H -BP L The minimum value is determined.

[0027] In addition, the low-boiling organic solvent to be combined with the high-boiling organic solvent is selected so that the difference in boiling point is 100 degrees or more. Specifically, taking into consideration the boiling point, the following solvents are used: Xylene (139°C), Toluene (111°C), n-butanol (117°C), n-propyl alcohol (98°C), Isopropyl alcohol (82°C), Methyl ethyl ketone (79°C), Ethyl alcohol (78°C), ethyl acetate (77°C), or Acetone (56°C) can be selected and used.

[0028] Of these, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, and ethyl acetate are preferred.

[0029] The content of the high-boiling organic solvent contained in the colored pencil lead according to the present invention can be adjusted appropriately depending on the purpose, but the content of the high-boiling organic solvent, based on the total mass of the colored pencil lead, is preferably 0.5 to 20 mass%, more preferably 1 to 15 mass%. Furthermore, the colored pencil lead according to the present invention is substantially free of the low-boiling organic solvent. Specifically, the content of the low-boiling organic solvent, based on the total mass of the colored pencil lead, is preferably less than 1 mass%, more preferably less than 0.1 mass%.

[0030] The colored pencil lead of the present invention may contain an organic solvent other than the high-boiling organic solvent and the low-boiling organic solvent. In other words, in this invention, the high-boiling organic solvent refers to the solvent with the highest boiling point among the solvents contained in the mixed solvent, and the low-boiling organic solvent refers to the solvent with the lowest boiling point among the solvents contained in the mixed solvent. Therefore, an organic solvent whose boiling point is between that of the high-boiling organic solvent and that of the low-boiling organic solvent may be considered an "another organic solvent." Such an organic solvent can be blended into the mixed organic solvent to the extent that it does not impair the effects of the present invention. However, in order to maximize the properties provided by the high-boiling organic solvent, it is preferable not to blend such an organic solvent. Furthermore, if such an organic solvent is blended, it is preferable to use one whose boiling point differs from that of the high-boiling organic solvent by 20°C or less.

[0031] As the colorant, a dye or pigment can be used. It is also possible to use a colored pigment obtained by dyeing a resin with a dye. Although dyes generally have low heat resistance, they easily penetrate porous substrates when dissolved in water, which facilitates the production of pencil leads according to the present invention. Therefore, it is preferable that the colorant be a dye.

[0032] The dyes that can be used in the present invention are not particularly limited as long as they are soluble in the above-mentioned mixed organic solvent, and examples thereof include general dyes and fluorescent dyes.

[0033] Examples of general dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, etc. In addition, examples of salt-forming dyes of these dyes include salt-forming dyes of acid dyes and basic dyes, salt-forming dyes of basic dyes and organic acids, and salt-forming dyes of acid dyes and organic amines. More specifically, Balifast Black 1802, Balifast Black 1805, Balifast Black 1807, Balifast Violet 1701, Balifast Violet 1704, Balifast Violet 1705, Balifast Blue 1601, Balifast Blue 1605, Balifast Blue 1613, Balifast Blue 1621, Balifast Blue 1631, Balifast Red 1320, Balifast Red 1355, Balifast Red 1360, Balifast Yellow 1101, Balifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (Orient Chemical Industry Co., Ltd.), Aizen Spiron Black GMH-Special, Aizen Spiron Violet CRH, Aizen Spiron Blue GNH, Aizenspiron Blue 2BNH, Aizenspiron Blue C-RH, Aizenspiron Red C-GH, Aizenspiron Red C-BH, Aizenspiron Red C-PH, Aizenspiron Yellow C-GNH, Aizenspiron Yellow C-2GH, SPT Blue 111, SPT Blue GLSH-Special, SPT Red 533, SPT Orange 6, SBN Violet 510, SBN Yellow 530, SRC-BH (Hodogaya Chemical Co., Ltd.), etc.

[0034] Examples of fluorescent dyes include Basic Yellow 1, Basic Yellow 40, Basic Red 1, Basic Red 1:1, Basic Red 13, Basic Violet 1, Basic Violet 7, Basic Violet 10, Basic Violet 11:1, Basic Orange 22, Basic Blue 7, Basic Green 1, Acid Yellow 3, Acid Yellow 7, Acid Red 52, Acid Red 77, Acid Red 87, Acid Red 92, Acid Blue 9, Disperse Yellow 121, Disperse Yellow 82, Disperse Yellow 83, Disperse Orange 11, Disperse Red 58, Disperse Blue 7, Direct Yellow 85, Direct Orange 8, Direct Red 9, Direct Blue 22, Direct Green 6, Solvent Yellow 44, Solvent Red 49, Solvent Blue 5, and Solvent Green 7.

[0035] These dyes may be used alone or in combination of two or more to adjust the color of the writing, etc., as long as the performance of the colored pencil lead is not affected. Furthermore, these dyes may be used in combination with other dyes.

[0036] Any pigment may be used as the colorant, and ultrafine pigments, processed pigments, etc. may also be used.

[0037] It is also possible to use a color pigment obtained by dyeing a resin with a dye, etc. Such a color pigment is preferable because it can improve color development.

[0038] The resin constituting the color pigment can be any resin such as an acrylic resin, a styrene-acrylonitrile resin, a styrene resin, a nitrogen-containing resin, a polyethylene resin, or a polypropylene resin. The dye to be combined with these resins can be selected from those listed above.

[0039] Considering the solubility, dispersibility, and dispersion stability in high-boiling organic solvents, and the dyeability with dyes, etc., among these resins, nitrogen-containing resins or styrene-acrylonitrile resins are preferably used, with nitrogen-containing resins being more preferred. Among nitrogen-containing resins, melamine resins, polyamide resins, urethane resins, urea resins, and benzoquanamine resins are preferred. Furthermore, among these, melamine resins or polyamide resins are preferred, with melamine resins being more preferred, from the viewpoint of solubility stability in high-boiling organic solvents.

[0040] Examples of color pigments include the NKS-1000 series, MPI-500 series (manufactured by Nippon Fluorescent Chemical Co., Ltd.), FNP series, and FM series (manufactured by Shinroihi Co., Ltd.).

[0041] These color pigments may be used in combination of two or more kinds, for example, for the purpose of adjusting the color of handwriting, as long as the effects of the present invention are not impaired. Furthermore, these color pigments may be used in combination with dyes.

[0042] In the present invention, it is also preferable to use a fluorescent colorant. By using such a colorant, it is possible to obtain handwriting with fluorescence and more color development. This makes it easy to use not only for leaving letters but also for drawing and making marks.

[0043] The content of the colorant relative to the total mass of the colored pencil lead varies depending on the type of colorant, but is preferably 0.1 to 30 mass%, more preferably 0.2 to 25 mass%, and more preferably 1 to 20 mass%.

[0044] When a porous core is formed by combining a colorant with a porous substrate, the porous core can be easily produced by impregnating a porous substrate containing an extender and an inorganic binder with a colorant solution in which the colorant is dissolved in a mixed organic solvent, and then removing the low-boiling organic solvent (details will be described later).

[0045] In the colored pencil lead of the present invention, the pores of the porous core body are filled with a non-volatile liquid, which further improves the writing feel.

[0046] In the present invention, the term "low-volatility liquid" refers to a liquid that is incapable of dissolving a colorant and that is not likely to volatilize at room temperature. Here, "insoluble" does not mean that the solubility of the colorant is zero, but rather that the colorant is substantially insoluble. By using such a low-volatility liquid, the stability of the colored pencil lead over time can be maintained at a high level. The solubility of the colorant in the low-volatility liquid is preferably lower than the solubility in the high-boiling organic solvent described above. More specifically, the solubility of the colorant in the low-volatility liquid at 20°C is preferably less than 10 g / 100 g, and more preferably 5 g / 100 g or less.

[0047] The boiling point of the hardly volatile liquid is not particularly limited, but it is preferable that the liquid does not volatilize at 250°C or below.

[0048] The use of such a non-volatile liquid maintains the stability of the colored pencil lead over time at a high level and improves the writing feel. Furthermore, if the lead of a replacement lead product contains an organic solvent, there is a possibility that the refill lead and the case will fuse together inside the case. However, by including a non-volatile liquid in the colored pencil lead, it is possible to prevent such fusion.

[0049] Furthermore, the low-volatility liquid preferably has a low viscosity in order to facilitate impregnation into the pores of the porous core.

[0050] Furthermore, the surface tension of the non-volatile liquid is preferably 35 mN / m or less, more preferably 30 mN / m or less, and even more preferably 25 mN / m or less, because this allows for excellent impregnation into the pores of the porous core and allows the non-volatile liquid to impregnate the entire porous core evenly and without unevenness, resulting in a colored pencil lead with excellent writing feel and erasability. Here, the surface tension can be measured at a temperature of 25°C using the method specified in JIS K2241.

[0051] Specific examples of preferred low-volatility liquids include those selected from the group consisting of silicone oil, fluorine-based oil, mineral oil, vegetable oil, and liquid paraffin, with silicone oil being more preferred. Silicone oil exhibits minimal viscosity change with temperature and excellent stability. Therefore, using silicone oil as a low-volatility liquid results in colored pencil leads that are less susceptible to environmental changes and the passage of time. Furthermore, when used in mechanical pencils, the colored pencil leads are less likely to corrode metal components such as the tip opening, zipper, and lead holder of the mechanical pencil. Dimethyl silicone and methylphenyl silicone are particularly preferred silicone oils, with modified silicones also being preferred. Furthermore, silicone oils that do not readily dissolve the colorants described above are preferred. By not readily dissolving colorants, the colorant is prevented from penetrating into the paper along with the low-volatility liquid in the resulting handwriting, thereby improving erasability. Liquid paraffins with a carbon number of 14 or more are also preferred. Alpha-olefins can also be used as low-volatility liquids.

[0052] The content of the low-volatility liquid relative to the total mass of the color pencil lead is preferably 5 to 40 mass %, more preferably 8 to 45 mass %, and even more preferably 10 to 35 mass %.

[0053] The colored pencil lead according to the present invention may contain various additives to the extent that they do not affect the performance of the lead. Specific additives include surfactants, preservatives, antifungal agents, resins, etc.

[0054] The shape of the colored pencil lead according to the present invention is not particularly limited, but is generally a linear body with a circular cross section. For example, for colored pencil leads for mechanical pencils, the cross-sectional diameter is preferably 0.2 to 2.0 mm, more preferably 0.3 to 0.7 mm. The length is preferably 30 to 100 mm, more preferably 40 to 70 mm. When applied to general colored pencils held on a support such as wood, the cross-sectional diameter is preferably 0.5 to 3.0 mm, more preferably 0.8 to 2.0 mm. Since long colored pencil leads are often sandwiched between wood or other materials before being cut during the manufacturing process, the length is not particularly limited, but is generally 1,000 mm or less.

[0055] The colored pencil leads of the present invention can achieve high physical strength when using a porous substrate produced by baking. This is thought to be because the colorant forms a uniform or non-uniform layer on the inner surfaces of the pores, or adheres in clumps. The bending strength of the colored pencil leads of the present invention is preferably 120 MPa or more, and more preferably 180 MPa or more. Here, bending strength can be measured using the method specified in JIS S 6005:2007.

[0056] The colored pencil lead according to the present invention can be configured to be free of acidic components. Colored pencil leads are often used in mechanical pencils and the like, and therefore often come into contact with metal materials. Therefore, by configuring the lead to be free of acidic components, corrosion of the metal parts of the mechanical pencil can be suppressed. Therefore, it is preferable that the colored pencil lead according to the present invention does not contain acidic materials.

[0057] <Manufacturing method of colored pencil lead> The method for producing the colored pencil leads according to the present invention is not particularly limited. (a) a kneading step of kneading an extender and an inorganic binder to prepare a mixture; (b) extrusion of the mixture to form a linear product; (c) a firing step of firing the linear molding to form a porous substrate; (d) an impregnation step of contacting the porous substrate with a colorant solution containing a colorant and an organic solvent to impregnate the porous substrate; (e) a drying step of heating the porous substrate after the impregnation step to evaporate a portion of the organic solvent and form a porous core; (f) a filling step of bringing the porous core body into contact with a hardly-volatile liquid that cannot dissolve the colorant, thereby filling the voids of the porous core body with the hardly-volatile liquid; A method for producing a colored pencil lead comprising: the organic solvent is a mixed solvent of two or more organic solvents, The boiling point of the low-boiling organic solvent contained in the mixed solvent is expressed as BP L , the boiling point of the high boiling organic solvent is BP H When BP H and BP L The difference is 100 degrees or more, And the heating temperature T in step (e) is BP L More than BP L It is preferable to produce it by a method in which the average molecular weight is +100 or less. This method is explained below.

[0058] (a) Mixing process First, the filler and inorganic binder are kneaded to prepare a mixture. This mixture will be the main component of the porous substrate. During mixing, organic solvents, plasticizers, etc. can be added as needed. The organic solvent used here is used to impart fluidity to the raw material mixture and make the mixture homogeneous. It is almost completely removed during the firing process and is separate from the high-boiling organic solvents, low-boiling organic solvents, and non-volatile liquids mentioned above.

[0059] (b) extrusion process; The resulting mixture is then extruded to form a linear product. Since it is generally preferable to form the colored pencil leads according to the present invention into linear bodies having a circular cross section, the linear product is formed by extrusion.

[0060] (c) Firing process The resulting linear molding is dried as needed and then fired to form a porous substrate. The firing removes the organic solvent contained in the mixture, and the filler and inorganic binder are sintered to form a porous substrate. The firing conditions are not particularly limited as long as they allow the materials to be sintered to form a porous substrate; for example, the maximum temperature can be set to 650 to 1000°C. To avoid sudden temperature changes, the firing temperature can be increased continuously or stepwise. In such cases, the temperature increase rate can be set to, for example, 10 to 100°C / hr. After the temperature is increased to a set value, firing at a constant temperature for a certain period of time, for example, 0.5 to 2 hours, is also preferred. Furthermore, these conditions can be arbitrarily combined depending on the purpose. For example, conditions that can be used include increasing the temperature from room temperature to 650°C at a rate of 10°C / hr in an oxygen atmosphere and then maintaining the temperature at 650°C for one hour, or increasing the temperature from room temperature to 1000°C at a rate of 100°C / hr and then maintaining the temperature at 1000°C for one hour.

[0061] (d) Impregnation process The formed porous substrate is cooled as necessary, and then contacted with a solution containing a colorant and an organic solvent. In this process, the colorant solution penetrates into the pores present in the porous substrate. The impregnation method can be atmospheric pressure impregnation or reduced pressure or pressure impregnation.

[0062] The colorant content of the colorant solution is not particularly limited, but is preferably 5 to 50% by mass, more preferably 5 to 45% by mass, and particularly preferably 10 to 40% by mass, based on the total mass of the solution. If the colorant content is less than this range, the colorant content will be low and color development will tend to be poor. If the content is greater than this range, color development will tend not to improve in proportion to the amount of colorant added, and the colorant may precipitate over time, resulting in poor stability of the solution over time. A surfactant may also be added to the solution to improve the solubility and stability of the colorant.

[0063] In addition, a mixed solvent of a high-boiling organic solvent and a low-boiling organic solvent is used as the solvent for the colorant solution. By including a low-boiling organic solvent in the mixed organic solvent, the viscosity of the colorant solution is reduced, facilitating impregnation, and in the subsequent drying process, voids within the pores are more easily formed. In this case, the pores of the core are more easily impregnated with the low-volatility liquid, making it possible to fully achieve the effects of impregnating the low-volatility liquid. As such a low-boiling organic solvent, a solvent that evaporates at 100°C or less is preferred, more preferably 90°C or less, and even more preferably 80°C or less is preferred. An aliphatic alcohol having 1 to 4 carbon atoms is more preferred. The blending ratio of the high-boiling point organic solvent to the low-boiling point organic solvent can be adjusted depending on the difference in boiling points and the solubility of the colorant. For example, the ratio by mass of the high-boiling point organic solvent to the low-boiling point organic solvent is preferably 1:1 to 1:15, more preferably 1:1 to 1:12, even more preferably 1:1.5 to 1:10, and particularly preferably 1:1.5 to 1:7.

[0064] (e) Drying process Subsequently, the porous substrate after the impregnation step is heated to remove a portion of the solvent contained in the solution impregnated in the pores. Here, substantially all of the low-boiling organic solvent contained in the mixed solvent is removed, but a portion of the high-boiling organic solvent may also be removed. On the other hand, a portion of the high-boiling organic solvent remains. Specifically, it is preferable that the weight loss of the high-boiling organic solvent is 50% by weight or less. As a result, the colorant and the high-boiling organic solvent remain in the pores and are adsorbed or attached. Then, as a portion of the solvent is removed by heating and the impregnation of the solvent into the porous substrate progresses, voids are formed in the pores, and a porous core is formed. The heating temperature T during drying is set to BP L More than BP L +100 or less. Here, when the colorant solution contains a solvent with a relatively low boiling point, the drying can be carried out at a lower temperature, for example, 60 to 150°C, and is preferably carried out at 100°C or less. If the drying process can be carried out at a low temperature, it is preferable because energy costs can be reduced.

[0065] (f) Filling process If necessary, the formed porous core is cooled and then contacted with a non-volatile liquid. This process fills the voids formed in the porous core with the non-volatile liquid. The conditions for this process are not particularly limited, but for example, a temperature of 60°C for 6 to 12 hours can be used. Impregnation with the non-volatile liquid can be performed by normal pressure impregnation or reduced pressure / pressure impregnation.

[0066] If necessary, further washing or the like can be carried out to obtain the color pencil lead according to the present invention. [Example]

[0067] Examples of the present invention will be described below, but the present invention is not limited thereto.

[0068] [Example 1] [Kneading process, extrusion process, and firing process] Boron nitride 45 parts by mass Silica 45 parts by mass Polyvinyl alcohol 10 parts by mass 100 parts by mass of water The mixture was heated and kneaded in a kneader and a triple roll while evaporating water, and the resulting mixture was extruded to a predetermined diameter to obtain a linear molded product. This linear molded product was heated to 600°C at a rate of 10°C / hour in an argon gas atmosphere and held for 5 hours, then heated at 100°C / hour in an oxygen atmosphere and fired at 900°C for 1 hour to obtain a porous substrate with a porosity of 25% and a cross-sectional diameter of 0.55 mm.

[0069] [Impregnation process] Colorant (blue dye) 30 parts by weight High boiling point organic solvent (PhDG) 10 parts by mass Low boiling point organic solvent (ethyl alcohol) 50 parts by mass Resin (ketone resin) 10 parts by mass BP in the mixed solvent used here H -BP L The temperature was 205°C. The above mixture was stirred at 30°C until it was uniformly mixed to obtain a colorant solution.

[0070] The porous substrate obtained in the baking step was immersed in the colorant solution heated to 30° C. and held for 6 hours.

[0071] [Drying process] The porous substrate that had undergone the impregnation step was held at 80° C. for 6 hours to substantially completely evaporate and remove the low-boiling organic solvent contained in the porous substrate, thereby obtaining a porous core.

[0072] [Filling process] The porous core obtained in the drying process was immersed in silicone oil heated to 80°C and held for 6 hours to obtain a colored pencil lead. The excess silicone oil adhering to the surface of the colored pencil lead was then removed by centrifugation, yielding a colored pencil lead impregnated with 12.5% ​​by mass of silicone oil. Thermogravimetric analysis of this colored pencil lead confirmed the presence of phenyl diglycol. The content was 1% by mass or more.

[0073] [Examples 2 to 15, Comparative Examples 1 to 3] Colored pencil leads were obtained in the same manner as in Example 1, except that the components were changed to those listed in Table 1. In Comparative Examples 2 and 3, no low-volatility liquid was filled.

[0074] [evaluation] The performance of the resulting colored pencil leads was evaluated by the following method. [Evaluation method for writing feel and handwriting color development] This paper is made from 100% chemical pulp and has a weight range of 40 to 157 g / m². 2 The writing feel at that time was evaluated by a sensory test (writing feel 1). The color development of the resulting handwriting was also evaluated (handwriting color development 1). Furthermore, after production, the baked colored pencil leads were left to stand in a 25°C environment for 4 weeks, and then used to write on the above-mentioned high-quality paper. The writing feel (writing feel 2) and the color development of the resulting writing (writing color development 2) were evaluated by a sensory test. (Evaluation criteria for writing quality 1 and 2) A: It writes very smoothly. B: Smooth writing possible. C: The writing feel is a bit rough and heavy. D: The writing feel is rough and heavy. (Evaluation criteria for handwriting color development 1 and 2) S: Very good color. A: Good color. B: Color is slightly inferior, but good. C: Poor color development. D: Writing is possible, but color development is very poor. E: Unable to write and handwriting is not visible.

[0075] [Evaluation method for erasability of handwriting] The handwriting was erased in accordance with the erasability test for plastic erasers disclosed in JIS S 6050-2008, and the erasability was evaluated by a sensory test (erasability 1). Furthermore, after writing, the written lines were left in a 25°C environment for four weeks, and then the handwriting was erased in accordance with the erasability test for plastic erasers disclosed in JIS S 6050-2008, and the erasability was evaluated by a sensory test (erasability 2). The existing product refers to a mechanical pencil lead manufactured by Pilot Corporation, "Product Name: Neox Color Eno (Yellow)." (Evaluation criteria for erasure 1 and 2) A: Better than existing products. B: Equivalent to existing products. C: Not erasable.

[0076] [Table 1-1]

[0077] [Table 1-2] In the table: Blue dye B: Oil Blue 613 (manufactured by Orient Chemical Industry Co., Ltd.) Red dye R: Spiron Red C-PH (Hodogaya Chemical Co., Ltd.) Pink fluorescent pigment P1: NKS1007 (Nippon Fluorescent Chemical Co., Ltd., a mixture of polyamide resin and CI Basic Violet 11:1) Yellow fluorescent pigment Y: NKS1005 (manufactured by Nippon Fluorescent Chemical Co., Ltd., a mixture of polyamide resin and CI Basic Yellow 40) Pink fluorescent pigment P2: MPI-507C (manufactured by Nippon Fluorescent Chemical Co., Ltd., a mixture of melamine-p-toluenesulfonamide-formaldehyde polycondensate and CI Basic Violet 11:1) Ester A: Adeka Cizer RS-1000 (carboxylic acid ester of polyalkylene glycol, manufactured by ADEKA Corporation, boiling point 250°C or higher) Ester B: Adeka Cizer RS-700 (carboxylic acid ester of polyalkylene glycol, manufactured by ADEKA Corporation, boiling point 250°C or higher) Ester C: Adeka Cizer RS-107 (adipic acid dibutoxyester, manufactured by ADEKA Corporation, boiling point 200°C or higher) Surfactant: Noigen EA-137 (Dai-ichi Kogyo Seiyaku Co., Ltd.) SO1: Dimethyl silicone oil (Shin-Etsu Chemical Co., Ltd., product name: KF-96-50cs, surface tension: 20.8 N / m) SO2: Methylphenyl silicone oil (Shin-Etsu Chemical Co., Ltd., product name: KF-96-100cs) OO: α-olefin oil

Claims

1. (a) a kneading step of kneading an extender and an inorganic binder to prepare a mixture; (b) extrusion of the mixture to form a linear molding; (c) a firing step of firing the linear molding to form a porous substrate; (d) an impregnation step of contacting the porous substrate with a colorant solution containing a colorant and an organic solvent to impregnate the porous substrate; (e) a drying step of heating the porous substrate after the impregnation step to evaporate a part of the organic solvent and form a porous core; (f) a filling step of bringing the porous core body into contact with a hardly-volatile liquid that cannot dissolve the colorant, and filling the voids of the porous core body with the hardly-volatile liquid. A method for producing a colored pencil lead comprising: the organic solvent is a mixed solvent of two or more organic solvents, The boiling point of the low-boiling organic solvent contained in the mixed solvent is expressed as BP. Ｌ , the boiling point of the high boiling point organic solvent is BP Ｈ When BP Ｈ and BP Ｌ The difference between them is 100 degrees or more, And the heating temperature T in step (e) is BP Ｌ More than BP Ｌ +100 or less, the high-boiling organic solvent is an aromatic glycol ether or an aliphatic glycol ether; the low-volatility liquid is selected from the group consisting of silicone oil, fluorine-based oil, mineral oil, vegetable oil, and liquid paraffin; In the step (e), the content of the low-boiling organic solvent is less than 1% by mass based on the total mass of the colored pencil lead. A method characterized by:

2. 2. The method according to claim 1, wherein the weight loss of the high-boiling organic solvent before and after step (e) is 50% by weight or less.

3. 3. The method according to claim 1, wherein the ratio by mass of the high-boiling organic solvent to the low-boiling organic solvent in the mixed solvent is 1:1 to 1:

15.

4. The method according to any one of claims 1 to 3, wherein the heating temperature T is 60°C or higher and 150°C or lower.

5. The method according to claim 1, wherein the BP H is 180° C. or higher.

6. The method according to any one of claims 1 to 5, wherein the low-boiling organic solvent is selected from the group consisting of alcohols having 1 to 5 carbon atoms, ketones having 2 to 5 carbon atoms, and carboxylic acid esters having 2 to 5 carbon atoms.

7. The low-boiling organic solvent is xylene, toluene, n-butanol, n-propyl alcohol, isopropyl alcohol, methyl ethyl ketone, ethyl alcohol, ethyl acetate, and acetone The method according to any one of claims 1 to 6, wherein the compound is selected from the group consisting of:

8. A method according to any one of claims 1 to 7, wherein the solubility of the colorant in the high-boiling point organic solvent and the low-boiling point organic solvent at 20°C is 10 g / 100 g or more.

9. A method described in any one of claims 1 to 8, wherein the solubility of the colorant in the low-volatile liquid at 20°C is lower than the solubility of the colorant in the high-boiling point organic solvent and the low-boiling point organic solvent at 20°C.

10. The method of claim 1, wherein the filler is selected from the group consisting of titanium oxide, mica, talc, boron nitride, alumina, and calcium carbonate.

11. The method according to claim 1, wherein the inorganic binder is selected from the group consisting of clays, ceramics, zeolites, diatomaceous earth, activated clay, silica, aluminum phosphate, silicone resin, and silicone rubber.

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