Firing of pencil leads

Abstract

The sintered pencil lead is obtained by sintering a mixture containing a bulk material, an organic binder material, and a polyether-modified polysiloxane.

Description

Technical Field

[0001] This disclosure relates to sintered pencil leads containing at least a bulk material and an organic binder material. Background Technology

[0002] Previously, sintered pencil leads were known to be obtained by the following method: mixing, dispersing, and kneading materials such as graphite, boron nitride, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, chlorinated polyethylene, polyvinyl alcohol, acrylamide resin, chlorinated paraffin resin, phenolic resin, furan resin, urea resin, butyl rubber, etc., clay-based binders such as bentonite and kaolin, plasticizers such as phthalates, solvents such as methyl ethyl ketone and water, stabilizers such as stearates, lubricants such as stearic acid, and fillers such as carbon black, extruding them into fine threads, subjecting the resulting product to heat treatment up to the firing temperature, and impregnating the heat-treated core with oily substances or waxes such as silicone oil, liquid paraffin, spindle oil, squalane, and α-olefin oligomers.

[0003] Generally, the bending strength of fired pencil leads is inversely related to the density of the writing line. If bending strength is increased, the fired pencil lead becomes less prone to wear, resulting in a decrease in the density of the writing line. Conversely, if a fired pencil lead is made to increase the density of the writing line and thus becomes more easily worn, the bending strength decreases. Therefore, various inventions have been disclosed to improve this inverse relationship. As an example of a material for improving the properties of fired pencil leads, as shown in the following patent document, a method for manufacturing a fired pencil lead and the same is disclosed. By adding a silicon compound to a bulk material and an organic binder material and heat-treating it at a firing temperature, the following effect is achieved: not only is the density of the writing line maintained, but bending strength is also increased, and poor appearance is suppressed. Furthermore, as a performance characteristic of fired pencil leads, to obtain a smooth writing feel, a technique for impregnating lubricating components into the pores of the heat-treated lead is disclosed.

[0004] Patent document 1 discloses a method for manufacturing sintered pencil leads with high bending strength by using silicon oxides and / or organic compounds of silicon as additives in sintering pencil leads and performing sintering treatment at a specific temperature and atmosphere.

[0005] In addition, Patent Document 2 discloses a method for manufacturing sintered pencil leads with excellent balance of bending strength and line density without causing appearance defects by using hydrophobic amorphous silica as a co-material for sintered pencil leads.

[0006] Patent Document 3 discloses a method for manufacturing a sintered pencil lead with high bending strength and dense ink marks compared to Patent Document 2, without causing appearance defects in the sintered pencil lead by using silsesquioxane as a co-material for sintering the pencil lead.

[0007] Patent document 4 discloses a method for manufacturing a fired pencil lead, in which carbon nanoparticles and silicon oxide ceramic nanoparticles, which are not used as a co-material for firing the pencil lead but are dispersed in an oily substance impregnated into the heat-treated lead, act as bearings during writing, thereby providing a smooth writing feel.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 63-35672

[0011] Patent Document 2: Japanese Patent Application Publication No. 2004-175900

[0012] Patent Document 3: Japanese Patent Application Publication No. 2011-68796

[0013] Patent Document 4: International Publication No. WO2010 / 123070 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] Typically, for fired pencil leads, increasing bending strength results in a scratchy writing feel. This is because one of the key reasons for increasing bending strength is the bonding of the binder material with resin carbides. These resin carbides are formed by heat-treating organic binders at firing temperatures. However, due to the expansion and contraction process during heat treatment, the expansion and contraction caused by the decomposition / vaporization of organic matter occur irregularly, resulting in complex volume shrinkage of the entire lead. Consequently, the surface of the resin carbides becomes uneven, creating both densely packed areas of resin carbides bonded to the binder material and uneven areas with large gaps. Therefore, these uneven and aggregated areas of the resin carbides are a significant cause of scratching and impaired smooth writing feel. Although inventions have been disclosed that achieve both bending strength and line density by adding silicon compounds, the known silicon compounds are used to enhance bending strength without acting on the resin carbides. Therefore, the problem of reduced writing feel caused by increasing bending strength and line density has not been solved.

[0016] The silicon oxide and / or organic silicon compounds shown in Patent Document 1 do not have an affinity for organic binders and independently play the role of linking the extender materials with the extender materials. However, if heat treatment is performed at the firing temperature, although the strength of the core is improved, it will not be easy to disperse evenly, and the bonding part with the extender material will be uneven. Therefore, the flexural strength is not sufficiently improved, and there is a scratchy writing feel.

[0017] Patent documents 2 and 3 disclose methods to maintain the concentration of pen lines and improve bending strength by surface treatment that improves the dispersion uniformity of organic binder materials or by using silicon compounds with molecular structures. However, as the bending strength increases, the writing experience deteriorates and a smooth writing feel without scratching the paper cannot be obtained.

[0018] Regarding the method of impregnating an oily substance containing dispersed nanoparticles as shown in Patent Document 4, the openings of the pores effective for impregnation in the heat-treated core are blocked by the nanoparticles, resulting in a reduction in the number of pores effective for impregnation. Therefore, the amount of impregnated oily substance retained in the fired pencil lead is reduced, and its effect as a lubricant cannot be fully utilized, impairing the smooth writing feel.

[0019] In view of the above, the object of at least one embodiment of the present invention is to provide a sintered pencil lead that can simultaneously improve bending strength and maintain the density of the writing line, and also has a smooth writing feel.

[0020] Methods for solving problems

[0021] At least one embodiment of the present invention relates to a sintered pencil lead obtained by sintering a mixture comprising a extender material, an organic binder material, and a polyether-modified polysiloxane. In some embodiments, the sintered pencil lead is obtained by compounding, extruding, and heat-treating the mixture up to a sintering temperature, at least combining the extender material, the organic binder material, and the polyether-modified polysiloxane. In some embodiments, the content of the polyether-modified polysiloxane in the mixture is 0.5% by weight or more and 3% by weight or less, relative to the content of the organic binder material in the mixture. In some embodiments, the polyether-modified polysiloxane is a polyether-modified polysiloxane having a molecular structure with a branched polysiloxane chain as the main chain. In some embodiments, the kinematic viscosity of the polyether-modified polysiloxane at 25°C is 100 mmHg. 2 / s or more and 10000mm 2 / s or less.

[0022] At least one embodiment of the present invention relates to a method for manufacturing sintered pencil leads comprising the following steps:

[0023] The process involves at least the step of mixing the extender material, the organic binder material, and the polyether-modified polysiloxane to obtain a mixture.

[0024] The step of shaping the above mixture to obtain a shaped body, and

[0025] The step of firing the above-mentioned molded body to obtain a fired pencil lead.

[0026] Invention Effects

[0027] Through at least one embodiment of the present invention, a sintered pencil lead can be provided that not only improves bending strength and maintains the density of the writing line, but also has a smooth writing feel. Detailed Implementation

[0028] Hereinafter, some embodiments of the present invention will be described. However, the embodiments described below are merely illustrative examples and are not intended to limit the scope of the present invention.

[0029] Some embodiments involve firing pencil leads obtained by firing a mixture comprising a extender material, an organic binder material, and a polyether-modified polysiloxane. In some embodiments, the firing pencil lead is obtained by kneading the mixture comprising the extender material, the organic binder material, and the polyether-modified polysiloxane, extruding it to obtain a shaped body, and then subjecting the shaped body to heat treatment up to the firing temperature.

[0030] Some embodiments of the method for manufacturing sintered pencil leads include the following steps: mixing at least a extender material, an organic binder material and a polyether-modified polysiloxane to obtain a mixture, molding the mixture to obtain a molded body, and sintering the molded body to obtain a sintered pencil lead.

[0031] Polyether-modified polysiloxane is a compound in which at least one methyl group of polydimethylsiloxane is replaced by a polyoxyalkylene group. This polyoxyalkylene group exhibits affinity for organic binders. Therefore, during mixing or compounding, at the interface between the organic binder and other compounding materials, the polyether-modified polysiloxane forms an adsorbed layer adsorbed onto the organic binder. It is believed that subsequent heat treatment (firing) causes the siloxane-linked portions of the polyether-modified polysiloxane adsorbed layer to form a coating of resin carbides, resulting in compounds such as silicon oxides and carbides. Compared to the uncoated form, the coated resin carbides exhibit higher strength, thus improving flexural strength. Furthermore, the low coefficient of thermal expansion of silicon oxides and carbides suppresses the formation of uneven surfaces due to the expansion and contraction of the organic binder, facilitating the formation of a smooth surface. Therefore, not only is a smooth writing feel achieved, but the bonding area of ​​the resin carbides relative to the binder material is smaller than in the uncoated form, thus not hindering wear during writing.

[0032] Therefore, it is possible to obtain fired pencil leads that not only simultaneously improve bending strength and maintain the density of the writing line, but also reduce paper scratching and provide a smooth writing feel due to reduced friction during writing.

[0033] Representative examples of polyether-modified polysiloxanes include side-chain types formed by introducing polyoxyalkylene groups into the side chains of the polysiloxane chain that forms the main chain; single-terminal types formed by introducing polyoxyalkylene groups into a single end of the polysiloxane chain; two-terminal types formed by introducing polyoxyalkylene groups into both ends of the polysiloxane chain; and (AB)n types formed by the copolymerization of alternating polysiloxane chains and polyoxyalkylene groups in the main chain. Furthermore, the side-chain type can be classified into linear and branched types based on the molecular structure of the main chain. Additionally, it is more preferable that the polyoxyalkylene group includes at least polyoxyethylene and / or polyoxypropylene groups because this improves flexural strength and reduces writing resistance.

[0034] The kinematic viscosity of polyether-modified polysiloxane at 25°C is 100 mmHg. 2 / s or more and 10000mm 2 When the viscosity is below a certain value (e.g., s), dispersion in the organic binder becomes easier during mixing, uniformity is improved, and detachment from the organic binder due to low viscosity is effectively suppressed during heat treatment. Furthermore, the aforementioned kinematic viscosity is particularly preferably 500 mm⁻¹. 2 / s or higher and 4500mm 2 / s or less. Furthermore, the ratio of the polyether-modified polysiloxane content in the mixture to the content of the organic binder material in the mixture is preferably 0.5% by weight or more and 3% by weight or less. When the above ratio is 0.5% by weight or more and 3% by weight or less, it is a sufficient content for forming a coating, and it results in an appropriate coating thickness that prevents the fired pencil lead from wearing out easily during writing, thus obtaining a fired pencil lead with excellent balance between bending strength and line density. More preferably, the above ratio is 0.8% by weight or more and 2% by weight or less.

[0035] As an example of a two-terminated polyether-modified polysiloxane, Shin-Etsu Chemical Industry Co., Ltd.'s X-22-4952 (kinematic viscosity at 25°C: 100 mm) is a good example. 2 / s), X-22-4272 (kinematic viscosity at 25℃: 270 mm⁻¹) 2 / s), KF-6123 (kinematic viscosity at 25℃: 420 mm⁻¹) 2 / s), KF-6004 (solid at room temperature).

[0036] As an example of (AB)n type polyether modified polysiloxane, DOWSIL FZ-2203 manufactured by Dow Toray Co., Ltd. (kinematic viscosity at 25°C: 4100 mmHg) is a good example. 2 / s), DOWSIL FZ-2222 (kinematic viscosity at 25℃: 20000 mm³ / ...) 2 / s), DOWSIL FZ-2233 (kinematic viscosity at 25℃: 5000 mm³ / ...). 2 / s), Silsoft 860 (kinematic viscosity at 25°C: 170 mm³ / s) manufactured by Momentive Performance Materials Japan LLC. 2 / s), Silsoft870 (kinematic viscosity at 25°C: 220 mm⁻¹) 2 / s), Silsoft900 (kinematic viscosity at 25°C: 250 mm² / ...) 2 / s).

[0037] As a linear polyether-modified polysiloxane, an example is KF-351A manufactured by Shin-Etsu Chemical Industry Co., Ltd. (kinematic viscosity at 25°C: 70 mm). 2 / s), KF-352A (kinematic viscosity at 25℃: 1600 mm³ / ...) 2 / s), KF-353 (kinematic viscosity at 25℃: 430 mm⁻¹) 2 / s), KF-354L (kinematic viscosity at 25℃: 200mm) 2 / s), KF-355A (kinematic viscosity at 25℃: 150mm) 2 / s), KF-615A (kinematic viscosity at 25℃: 920 mm⁻¹) 2 / s), KF-945 (kinematic viscosity at 25℃: 130 mm²) 2 / s), KF-640 (kinematic viscosity at 25℃: 20mm) 2 / s), KF-642 (kinematic viscosity at 25℃: 50mm) 2 / s), KF-643 (kinematic viscosity at 25℃: 19mm) 2 / s), KF-644 (kinematic viscosity at 25℃: 38mm) 2 / s), KF-6020 (kinematic viscosity at 25℃: 180mm) 2 / s), KF-6204 (kinematic viscosity at 25℃: 70mm) 2 / s), X-22-4515 (kinematic viscosity at 25℃: 4000 mm³ / ...) 2 / s), KF-6011 (kinematic viscosity at 25℃: 130mm) 2 / s), KF-6011P (kinematic viscosity at 25℃: 140mm) 2 / s), KF-6012 (kinematic viscosity at 25℃: 1600 mm⁻¹) 2 / s), KF-6015 (kinematic viscosity at 25℃: 150mm) 2 / s), KF-6017 (kinematic viscosity at 25℃: 600 mm⁻¹) 2 / s), KF-6017P (kinematic viscosity at 25℃: 850 mm⁻¹) 2 / s), KF-6043 (kinematic viscosity at 25℃: 400mm) 2 / s), KF-6048 (co-modified with alkyl groups, kinematic viscosity at 25°C: 2700 mm⁻¹) 2 / s), X-22-2516 (co-modified with alkyl and aralkyl groups, kinematic viscosity at 25°C: 70 mm⁻¹) 2 / s), X-22-3939A (co-modified with amino, kinematic viscosity at 25℃: 3300 mm⁻¹ ...) 2 / s), X-22-4741 (co-modified with epoxy groups, kinematic viscosity at 25℃: 350 mm⁻¹) 2 / s), KF-1002 (co-modified with epoxy groups, kinematic viscosity at 25℃: 4500 mm³ / ... 2 / s), DOWSIL ES-5612 Formulation Aid manufactured by Dow Toray Co., Ltd. (kinematic viscosity at 25°C: 1000 mm³ / s) 2 / s), DOWSIL BY25-337 (kinematic viscosity at 25℃: 3000 mm³ / ...). 2 / s), DOWSIL BY22-008M (kinematic viscosity at 25℃: 2500 mm³ / ...). 2 / s), DOWSIL ES-5373 Formulation Aid (kinematic viscosity at 25°C: 660 mm² / ...). 2 / s), DOWSIL FZ-2123 (kinematic viscosity at 25℃: 90mm) 2 / s), DOWSIL SS-2804 (kinematic viscosity at 25℃: 390 mm³ / ...) 2 / s), DOWSIL SH3771 M Fluid (kinematic viscosity at 25°C: 300 mm³ / s) 2 / s), DOWSIL5200 Formulation Aid (co-modified with alkyl groups, kinematic viscosity at 25°C: 2000 mm⁻¹) 2 / s), TSF4440 manufactured by MomentivePerformance Materials Japan LLC (kinematic viscosity at 25°C: 160 mm⁻¹) 2 / s), SF1188A (kinematic viscosity at 25℃: 1100 mm⁻¹) 2 / s), SF1288 (kinematic viscosity at 25℃: 400 mm⁻¹) 2 / s), Silsoft840 (kinematic viscosity at 25°C: 420 mm⁻¹) 2 / s), Silsoft 875 (kinematic viscosity at 25°C: 400 mm⁻¹) 2 / s), Silsoft880 (kinematic viscosity at 25℃: 600 mm⁻¹) 2 / s).

[0038] As a branched polyether-modified polysiloxane, KF-6028 manufactured by Shin-Etsu Chemical Industry Co., Ltd. (kinematic viscosity at 25°C: 900 mmHg) is an example. 2 / s), KF-6028P (kinematic viscosity at 25℃: 900 mm⁻¹) 2 / s), KF-6038 (co-modified with alkyl groups, kinematic viscosity at 25°C: 700 mm⁻¹) 2 / s).

[0039] Among these, branched polyether-modified polysiloxanes are preferred, especially KF-6028 or KF-6028P. If branched, the intermolecular interactions between the polyether-modified polysiloxanes are weak, thus facilitating homogeneity during mixing and forming a highly smooth coating. Through this method, a smooth writing feel can be obtained by producing a fired pencil lead that does not scratch the paper during writing, significantly reduces friction compared to conventional fired pencil leads.

[0040] Polyether-modified polysiloxanes can be one type or a combination of two or more. Additionally, other polysiloxane compounds can be used in combination. Examples include, but are not limited to, polydimethylsiloxane, polyglycerol-modified polysiloxane, amino-modified polysiloxane, and methylphenyl-modified polysiloxane.

[0041] Examples of suitable filler materials include graphite, boron nitride, mica, and talc. For graphite, either natural or synthetic graphite can be used, but natural graphite with well-developed crystals and good cleavage is preferred. Flake graphite from natural graphite is even more preferred. Flake graphite has well-developed crystals, and its well-developed crystalline layers result in a high aspect ratio and a smooth surface. Therefore, when flake graphite is extruded into fine wire-like cores, its orientation along the extrusion direction improves the core's bending strength. Furthermore, its excellent cleavage provides a smooth writing feel and high line density. Commercially available flake graphite products include the BF series, CPB series, and SC series manufactured by Chuetsu Graphite Industry Co., Ltd., and the FT series and MF series manufactured by Fuji Graphite Industry Co., Ltd. For boron nitride, hexagonal boron nitride (h-BN) is an example. Boron and nitrogen atoms alternately form the vertices of a regular hexagon, resulting in well-developed crystals. These crystals are stacked in multiple layers, constituting a single particle of hexagonal boron nitride (h-BN). Therefore, hexagonal boron nitride (h-BN) particles, like graphite, have a plate-like shape. Furthermore, due to the weak van der Waals forces connecting the layers, hexagonal boron nitride (h-BN) possesses lubricity. Because of these properties, hexagonal boron nitride (h-BN), like graphite, is suitable as a material for fired pencil leads. Fired pencil leads made from hexagonal boron nitride (h-BN) exhibit high bending strength and dense line density. Commercially available products include Denka Boron Nitride SGP, Denka Boron Nitride GP, Denka Boron Nitride HGP, DenkaBoron Nitride SP-2 manufactured by Denka Corporation, and SHP-3, SHP-5, SHP-7, HP-1, HP-2, HP-4W, HP-6, HP-60, HP-P1, FS-1 manufactured by Mizushima Alloy Iron Co., Ltd.

[0042] Examples of organic binders include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), chlorinated PVC, chlorinated polyethylene, chlorinated paraffin, furan resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate (PMMA), urea resin, melamine resin, polyester, styrene-butadiene copolymer, polyvinyl acetate, polyacrylamide, butyl rubber, and other synthetic resins, as well as lignin, cellulose, tragacanth gum, gum arabic, and other natural resins. These organic binders can be one type or a combination of two or more. In particular, thermoplastic resins such as PVC are preferred due to their ease of processing, low cost, and stable supply. Examples of PVC include the TH, TU, TE, and TG series manufactured by Taiyo Vinyl Corporation; the Kanevinyl S, KS, K, M, and HM series manufactured by KANEKACORPORATION; Ryuron Paste manufactured by Tosoh Corporation; and the ZEST series manufactured by Shindai-ichi Vinyl Corporation.

[0043] In some embodiments, sintered pencil leads can be products obtained by sintering a mixture of materials including clay binders, organic binders, and polyether-modified polysiloxanes, as well as other materials and / or various additives.

[0044] Examples of clay-based binders include bentonite and kaolin. Examples of plasticizers include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diallyl isophthalate, tricresyl phosphate, and dioctyl adipate. Examples of solvents include ketones such as methyl ethyl ketone and acetone, alcohols such as ethanol, and water. Examples of stabilizers include stearates, organotin compounds, barium-zinc compounds, and calcium-zinc compounds. Examples of lubricants include fatty acids such as stearic acid and behenic acid, and fatty amides. Examples of fillers include metals such as iron, aluminum, titanium, and zinc, their alloys, as well as oxides and nitrides of these metals and alloys, silicon oxides such as silica and silsesquioxanes, carbon black, and fullerenes. For these fillers, spherical, amorphous granular, needle-like, fibrous, and plate-like shapes can be appropriately used. Alternatively, one type or a combination of two or more types can be used. Among these, plate-shaped particles are preferred because they are oriented in the core along the extrusion direction, similar to graphite, during extrusion molding. Examples include plate-shaped silica and plate-shaped alumina. As plate-shaped silica, amorphous cleavage plate-shaped silica obtained by volume expansion treatment of vermiculite, followed by acid treatment, water washing, drying, pulverizing, and grading is also mentioned. Vermiculite is a mineral mainly composed of sphagnum mica, classified as a vermiculite-type clay mineral or a mica-type clay mineral. The chemical composition of vermiculite varies depending on its origin, but representative compositions are described below.

[0045]

[0046]

[0047] By treating vermiculite with sulfuric acid, hydrochloric acid, nitric acid, etc., colored components such as MgO3 and Fe2O3 are removed, resulting in plate-like silica (amorphous cleavage plate-like silica) that maintains the layered structure of vermiculite. The interlayers of this plate-like silica (amorphous cleavage plate-like silica) are connected by hydrogen bonds based on hydroxyl groups; therefore, cleavage can be easily achieved by applying only a small shear force. Furthermore, even after heat treatment at temperatures up to 1100°C, the layered structure of the plate-like silica (amorphous cleavage plate-like silica) does not change, making it suitable for firing into pencil leads. Commercially available examples include SIL-LEAF manufactured by Mizusawa Chemical Industry Co., Ltd. Examples of plate-like alumina include α-Al2O3, γ-Al2O3, and θ-Al2O3. Because of the smooth surface of plate-shaped alumina particles, the particles have good lubrication, which does not easily damage the density and writing feel of the ink lines. Commercially available products include SERATH FYA00610, FYA02025, and FYA10030 manufactured by Kinsei Matec Co., Ltd., and the Cerasur BMM series manufactured by Kawai Lime Industry Co., Ltd. Additionally, silsesquioxanes with the formula [R(SiO2]2]2... 1.5 ) n The symbol ] indicates a sil-sesquioxane containing 1.5 oxygen atoms in its unit composition, also known as [sil-sesqui-oxane]. Examples of sil-sesquioxanes include octa(dimethylsilyloxy)octasesquioxane (R: OSi(CH3)2H), octavinyloctasesquioxane (R: CH3-CH=CH2), and their derivatives, manufactured by Tokyo Chemical Industry Co., Ltd.

[0048] Some embodiments of the present invention relate to sintered pencil leads obtained by sintering a mixture comprising a extender material, an organic binder material, and a polyether-modified polysiloxane. Here, "sintered pencil lead" refers to a product obtained through a heat treatment called "sintering." Typically, if a composition comprising organic materials (organic binder materials) such as synthetic resins and natural resins is heat-treated up to the sintering temperature, the resin molecules complexly complex with extender materials such as graphite. In this state, the decomposition and condensation of the organic materials occur irregularly, resulting in complex volume shrinkage of the core as a whole. Therefore, the skeletal structure of the heat-treated core becomes very complex in the finer details, and the degree of bonding and size of various compositions after heat treatment are also diverse. It is considered that to conduct systematic measurements and analyses that are advantageous for obtaining the above-mentioned effects, an unlimited number of experiments are required, and it is impossible or completely impractical to directly determine the substance based on its structure or properties.

[0049] As the oil used to impregnate the pores of the heat-treated core, existing known oils can be used. Examples include, but are not limited to, liquid paraffin, α-olefin oligomers, squalane, spindle oil, silicone oil, fatty acid esters, castor oil, and other oily substances, as well as waxes such as paraffin wax, microcrystalline wax, and carnauba wax.

[0050] Example

[0051] The present invention will now be described based on embodiments, but the present invention is not limited to these embodiments. It should be noted that in determining kinematic viscosity, automatic kinematic viscosity measuring devices such as the LAUDA PVS VAS, the Cannon Fenske, and the Ubbelohde manufactured by Shibata Scientific Co., Ltd. can be used, or it can be calculated by dividing the absolute viscosity by the density (specific gravity).

[0052] <Example 1>

[0053]

[0054] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0055] The aforementioned compound materials were dispersed and mixed using a Henschel mixer, then kneaded using a three-roll mill. The resulting fine threads were extruded using a single-screw extruder and subjected to a heat treatment in air, where the temperature was raised from room temperature to 350°C over approximately 10 hours and maintained at 350°C for approximately 1 hour. Subsequently, the threads were fired in a sealed container at a maximum temperature of 1100°C to obtain a heat-treated core with a nominal diameter of 0.5 mm. This heat-treated core was then immersed in liquid paraffin heated to 100°C for 10 hours, after which excess material was removed from the surface, thus obtaining the fired pencil lead.

[0056] <Example 2>

[0057] In Example 1, the amount of KF-6028 was changed from 0.45 parts by weight to 0.06 parts by weight. Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0058] The amount of polyether-modified polysiloxane added is 0.2% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 0.2% by weight relative to the content of organic binder material.

[0059] <Example 3>

[0060] In Example 1, the amount of KF-6028 was changed from 0.45 parts by weight to 0.15 parts by weight. Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0061] The amount of polyether-modified polysiloxane added is 0.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 0.5% by weight relative to the content of organic binder material.

[0062] <Example 4>

[0063] In Example 1, the amount of KF-6028 was changed from 0.45 parts by weight to 0.24 parts by weight. Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0064] The amount of polyether-modified polysiloxane added is 0.8% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 0.8% by weight relative to the content of organic binder material.

[0065] <Example 5>

[0066] In Example 1, the amount of KF-6028 was changed from 0.45 parts by weight to 0.9 parts by weight. Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0067] The amount of polyether-modified polysiloxane added is 3% by weight relative to the amount of organic binder material. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 3% by weight relative to the content of organic binder material.

[0068] <Example 6>

[0069] In Example 1, the amount of KF-6028 was changed from 0.45 parts by weight to 1.2 parts by weight. Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0070] The amount of polyether-modified polysiloxane added is 4% by weight relative to the amount of organic binder material. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 4% by weight relative to the content of organic binder material.

[0071] <Example 7>

[0072] In Example 1, KF-6028 was replaced with KF-6017 (linear polyether modified polysiloxane). Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0073] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0074] <Example 8>

[0075] In Example 1, KF-6028 was changed to KF-6038 (branched polyether modified polysiloxane, co-modified with alkyl groups). Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0076] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0077] <Example 9>

[0078] In Example 1, KF-6028 was changed to KF-6048 (linear polyether modified polysiloxane, co-modified with alkyl groups). Otherwise, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0079] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0080] <Example 10>

[0081] In Example 1, KF-6028 was replaced with FZ-2203 ((AB)n type polyether modified polysiloxane), and otherwise the same operation was performed as in Example 1 to obtain the sintered pencil lead.

[0082] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0083] <Example 11>

[0084] In Example 1, KF-6028 was replaced with FZ-2123 (linear polyether modified polysiloxane), and otherwise the same procedure was followed as in Example 1 to obtain the sintered pencil lead.

[0085] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0086] <Example 12>

[0087] In Example 1, KF-6028 was replaced with FZ-2222 ((AB)n type polyether modified polysiloxane), and otherwise the same operation was performed as in Example 1 to obtain the sintered pencil lead.

[0088] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0089] <Example 13>

[0090] In Example 1, KF-6028 was replaced with Silsoft900 ((AB)n type polyether modified polysiloxane), and otherwise the same procedure was followed as in Example 1 to obtain the sintered pencil lead.

[0091] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0092] <Example 14>

[0093] In Example 1, KF-6028 was replaced with FZ-2233 ((AB)n type polyether modified polysiloxane), and otherwise the same operation was performed as in Example 1 to obtain the sintered pencil lead.

[0094] The amount of polyether-modified polysiloxane added is 1.5% by weight relative to the amount of organic binder material added. That is, the content of polyether-modified polysiloxane in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder material.

[0095] <Comparative Example 1>

[0096] In Example 1, KF-6028 was changed to KF-96-1,000cs (polydimethylsiloxane, kinematic viscosity at 25°C: 1000 mm). 2 / s, manufactured by Shin-Etsu Chemical Industry Co., Ltd., except that, the same procedure as in Example 1 was followed to obtain the sintered pencil lead.

[0097] The amount of polydimethylsiloxane added is 1.5% by weight relative to the amount of organic binder. That is, the content of silicon compound in the above-mentioned mixture of materials is 1.5% by weight relative to the content of organic binder.

[0098] <Comparative Example 2>

[0099] In Example 1, KF-6028 was replaced with Aerosil R972 (hydrophobic amorphous silica (surface substrate: (CH3)2), manufactured by Aerosil Corporation of Japan). Otherwise, the same procedure as in Example 1 was followed to obtain the fired pencil lead.

[0100] The amount of Aerosil R972 added is 1.5% by weight relative to the amount of organic binder. That is, the ratio of the silicon compound content in the above-mentioned mixture to the content of organic binder is 1.5% by weight.

[0101] <Comparative Example 3>

[0102] In Example 1, KF-6028 was replaced with Aerosil R202 (hydrophobic amorphous silica (a product after surface treatment with silicone oil), manufactured by Aerosil Corporation of Japan). Otherwise, the same procedure as in Example 1 was followed to obtain the fired pencil lead.

[0103] The amount of Aerosil R202 added is 1.5% by weight relative to the amount of organic binder. That is, the ratio of the silicon compound content in the above-mentioned mixture to the content of organic binder is 1.5% by weight.

[0104] <Comparative Example 4>

[0105] In Example 1, KF-6028 was replaced with octa(dimethylsilyloxy)octasesquioxane (manufactured by Tokyo Chemical Industry Co., Ltd.), and otherwise the same procedure was followed as in Example 1 to obtain sintered pencil leads.

[0106] The amount of silsesquioxane added is 1.5% by weight relative to the amount of organic binder. That is, the ratio of the silicon compound content in the above-mentioned mixture to the content of organic binder is 1.5% by weight.

[0107] <Comparative Example 5>

[0108] In Example 1, a combination of polyether-modified polysiloxane (KF-6028) without the addition of polyether was compounded, extruded, and then heat-treated up to the firing temperature. The resulting heat-treated core contained dispersed diamond nanoparticles (specific surface area 450 m²). 2 / g, volume average diameter mv value 10nm, dimethyl silicone oil KF96-30CS (kinematic viscosity at 25℃: 30mm) manufactured by Dia Materials Co., Ltd., with a kinematic viscosity of 30mm at 25℃, containing a kinematic viscosity of 10nm at 25℃. 2 / s, refractive index 1.401, manufactured by Shin-Etsu Chemical Industry Co., Ltd. (temperature 100°C), immersed for 10 hours, and then the excess components on the surface are removed, thereby obtaining the sintered pencil lead.

[0109] The sintered pencil leads obtained in Examples 1-14 and Comparative Examples 1-5 above were subjected to measurements of bending strength, line density, and writing resistance using the following method.

[0110] (Test method for bending strength)

[0111] The bending strength was determined in accordance with JIS S 6005.

[0112] (Test method for the density of ink lines)

[0113] The concentration of the pen marks was determined in accordance with JIS S 6005.

[0114] (Test method for writing resistance values)

[0115] The writing resistance value was measured using a Tribo Gear model 40 friction and wear testing machine manufactured by Shin-To Science Co., Ltd. The testing environment was set to a temperature of 23℃ ± 2℃ and a humidity of 65% ± 5%. A Pentel Co., Ltd. P205 mechanical pencil was used, and it was fixed to the friction and wear testing machine using a dedicated writing instrument holder. A stainless steel plate pad and the test paper shown in JIS S 6039 were fixed to the testing stage, and the friction force when writing in a straight line with the mechanical pencil was measured. The test paper was pre-treated in a constant temperature and humidity chamber at 23℃ and 65% humidity for at least 24 hours. The apparatus conditions were set as follows: writing angle: 75 degrees, vertical load: 200g, moving speed: 1cm / s, sampling speed: 1kHz, and measurement time: 10 seconds. During the 10-second measurement period, the average frictional force from 1.5 seconds to 9.5 seconds was taken as the sliding friction force. The writing resistance value (sliding friction coefficient) was calculated by dividing the sliding friction force by the vertical load. It should be noted that the writing resistance value was automatically calculated using the dedicated software Tribosoft6 included with the device.

[0116] The results are shown in Table 1. Table 1 shows that, compared with the fired pencil leads of Comparative Examples 1 to 5, the fired pencil leads of Examples 1 to 14 had the same density of pencil lines, and the bending strength was improved, resulting in a smoother writing feel.

[0117] [Table 1]

[0118]

[0119] In Examples 1-14, due to the inclusion of polyether-modified polysiloxane, the writing resistance was low, resulting in a smooth writing experience with reduced scratching, and improvements in writing density and flexural strength were observed. Furthermore, for Examples 1, 3-5, and 7-14, where the content of polyether-modified polysiloxane was 0.5% to 3% by weight relative to the content of the organic binder, fired pencil leads exhibiting excellent balance between flexural strength and line density, and providing a smooth writing experience, were obtained.

[0120] In Examples 1-6, since polyether-modified polysiloxanes with a molecular structure having a branched polysiloxane chain as the main chain were incorporated, sintered pencil leads exhibiting a particularly smooth writing feel were obtained.

[0121] For polyether-modified polysiloxane with a kinematic viscosity of 100 mm⁻¹ 2 / s or more and 10000mm 2 In Examples 1-10 and 13-14 below, fired pencil leads with excellent balance between bending strength and line density, and exhibiting a smooth writing feel, are obtained.

[0122] In Comparative Example 1, polydimethylsiloxane without polyoxyalkylene groups was added. Although the bending strength was improved, the writing resistance was high, resulting in a writing feel with more paper scratches.

[0123] In Comparative Example 2, hydrophobic amorphous silica with a surface hydrophobicated by methyl groups was added. Although the bending strength was improved, the writing resistance was high, resulting in a writing feel with more scratches.

[0124] In Comparative Example 3, hydrophobic amorphous silica with a surface treated with silicone oil was added. Although the bending strength was improved, the writing resistance was high, resulting in a writing feel with more paper scratches.

[0125] In Comparative Example 4, silsesquioxane was added. Although the bending strength was improved, the writing resistance was high, resulting in a writing feel with more paper scraping.

[0126] In Comparative Example 5, the openings of the pores effective for penetration in the sintered pencil lead were blocked by nanodiamonds, resulting in a reduction in the number of pores effective for penetration. Therefore, the lubricating properties of the oil could not be fully utilized, and thus a smooth writing feel could not be obtained.

[0127] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and also includes modified embodiments and combinations thereof.

[0128] In this specification, expressions such as "same," "equal," and "homogeneous" that indicate that things are in the same state not only indicate a state of strict equivalence, but also indicate a state of difference in the degree to which there is tolerance or the ability to obtain the same function.

[0129] Furthermore, expressions such as "possessing," "comprises," or "have" a constituent element in this specification are not exclusive expressions that exclude the existence of other constituent elements.

Claims

1. A fired pencil lead, which is obtained by kneading a mixture comprising a extender material, an organic binder material and a polyether-modified polysiloxane to obtain a compound, and firing a shaped body of said compound.

2. The fired pencil lead according to claim 1 is obtained by extruding the compound to form the shaped body and subjecting the obtained shaped body to heat treatment up to the firing temperature.

3. The fired pencil lead according to claim 1 or 2, characterized in that, The content of the polyether-modified polysiloxane in the mixture is 0.5% by weight or more and 3% by weight or less, relative to the content of the organic binder material in the mixture.

4. The fired pencil lead according to claim 1 or 2, characterized in that, The polyether-modified polysiloxane is a polyether-modified polysiloxane with a molecular structure having a branched polysiloxane chain as the main chain.

5. The fired pencil lead according to claim 1 or 2, characterized in that, The kinematic viscosity of the polyether-modified polysiloxane at 25°C is 100 mmHg. 2 / s or more and 10000mm 2 / s or less.

6. A method for manufacturing a fired pencil lead, comprising the following steps: The step of at least mixing a mixture comprising extender material, organic binder material and polyether-modified polysiloxane to obtain a compound. The step of shaping the compound to obtain a shaped body, and The step of firing the shaped body to obtain a fired pencil lead.

Images