JP7306398B2 - pencil lead - Google Patents

Description

The present disclosure relates to a pencil lead that contains at least a coloring component and an organic binder, and has an impregnating component in the pores of a fired core obtained by heat treatment.

In general, a pencil lead consists of a coloring component such as graphite and boron nitride, a filler such as talc, and vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, chlorinated ethylene resin, vinyl alcohol resin, acrylamide resin, and chlorinated paraffin. , phenolic resin, furan resin, urea resin, carboxymethylcellulose, nitrocellulose, butyl rubber, and other organic binders, and clay and other inorganic binders as main materials. , methyl ethyl ketone, acetone, water and other solvents, stearate and other stabilizing agents, stearic acid and other lubricants, and carbon black and other fillers are used in combination. After that, heat treatment is appropriately performed up to the firing temperature. In the core body after firing (fired core body), the parts where decomposition products such as organic binders, inorganic binders, plasticizers, and solvents were present become pores, and the compounded materials are highly crushed during kneading and molding. It is considered that the fired core as a whole has a large number of pores of relatively uniform size because they are dispersed. Generally commercially available pencil leads contain silicone oil, liquid paraffin, spindle oil, squalane, α-olefin oligomer, paraffin wax, microcrystalline wax, montan wax, and carnauba in these pores, mainly for the purpose of improving the writing feel. It is manufactured by impregnating it with an oily substance such as wax.

By the way, the pencil lead becomes a writing line by forming a transfer film on the surface of the paper due to adhesive wear caused by sliding friction with the paper. However, since this writing line is only the abrasion powder containing coloring components such as graphite generated by adhesive wear on the paper surface, when rubbed with another paper or hand, the coloring such as graphite Ingredients move easily and stain the paper surface.

In recent years, students, who are the main users of pencil leads, tend to prefer pencil leads with softer hardness and higher handwriting density due to the decrease in writing pressure. However, in a pencil lead with a soft hardness and a high concentration of handwriting, there is a correlation between the hardness and/or density and the staining of the paper surface that the degree of staining of the paper surface due to rubbing increases, so it is difficult to rub the writing line. There was also a demand for the development of a pencil lead that leaves less stains on the paper.

As a method of suppressing the movement of graphite due to rubbing and reducing stains, it is mainly known to improve the fixability of abrasion powder to the paper surface by impregnating components such as oily substances impregnated in the pencil lead. ing. In Patent Document 1, by using an impregnating component having a high kinematic viscosity, the fixability of writing lines made of abrasion powder is physically improved. In Patent Document 2, by using a polar fatty acid ester as an impregnating component, the fixability of writing lines is improved by chemical bonding between the impregnating component and functional groups on the paper surface.

Japanese Patent Application Laid-Open No. 2005-213391 (Claims, Examples) Japanese Patent Application Laid-Open No. 2007-31589 (Claims, Examples)

However, although the impregnating component with high kinematic viscosity disclosed in Patent Document 1 improves the fixability of writing lines, the erasability with an eraser deteriorates, the core is less likely to wear, and the impregnation of the pencil lead The density of the writing line is reduced as compared with the case of using an impregnating component having a low kinematic viscosity such as a common liquid paraffin or silicone oil as the component. In addition, it is possible to increase the density of the writing line by using a softer core that wears more, but in general, a soft pencil lead has a low bending strength and causes another problem that it is easy to break when writing. end up On the other hand, the fatty acid ester with high polarity and low molecular weight disclosed in Patent Document 2 chemically reacts with the synthetic resin used in refill containers and lead tanks of mechanical pencils, resulting in cracks and cracks.

In addition, if the IOB value of the impregnated component is large, the impregnated component absorbs moisture, causing the inside of the container to become cloudy during storage and possibly causing malfunction in the case. Here, the IOB value is defined as the sum of the values determined for a specific group in the chemical structure as an inorganic value, and the number of carbon atoms in the chemical structure is multiplied by 20 to determine when there is a specific branch. It is a value obtained by dividing the inorganic value by the organic value, with the value obtained by subtracting the numerical value obtained as the organic value. and the organicity value is quantified as 20 per carbon. The IOB value serves as an indicator of the strength of polarity in the molecule, and since the IOB value×10 can be approximated to the HLB value, it serves as a criterion for determining hydrophilicity and lipophilicity.

Some embodiments of the present invention provide a highly reliable pencil lead that can obtain a dark writing line, suppress the movement of abrasion powder when the writing line is rubbed, and less stain the paper surface. With the goal.

That is, some embodiments of the present invention contain at least a coloring component and an organic binder, and a compound represented by the following general formula (Formula 1) is placed in the pores of the fired core obtained by heat treatment. The gist of the invention is a pencil lead which has an impregnation component and is characterized in that 2≤n≤6 in the following general formula (Chemical Formula 1) .

The compound represented by the above general formula (Chemical 1) is a non-drying oil that is liquid at room temperature 5 to 35 ° C. (JIS Z 8703) because the carbon chain of the main chain contains an unsaturated bond. It is easily impregnated into pores and is bound by polar ester bonds, so hydroxyl groups, carboxyl groups, and carbon dangling bonds generated by decomposition and recombination of graphite particles and resin during heat treatment. It is also easily adsorbed on a solid surface such as a resin carbide surface having a plurality of reactive functional groups such as. Therefore, by using an impregnating component containing this, the compound represented by the above general formula (Chemical Formula 1) exists as a lubricating film between the particles and promotes adhesive wear of the core, resulting in a thick writing line. can be obtained.

The compound represented by the above general formula (Chem. 1) present on the surface of the wear debris that has become the writing line has polar portions such as esters and double bonds in the main chain, hydroxyl groups and carboxyl groups at the terminals. , along with forming a hydrogen bond with the polar component of the cellulose of paper, etc., the carbon chain, which is a side chain in the compound represented by the above general formula (Chemical Formula 1), effectively anchors the rough surface of abrasion powder. It is presumed that, because of the adsorption, the abrasion powder is hard to move even if the abrasion powder is strongly bound to the paper surface and rubbed.

Several embodiments of the invention are described in detail below.

The compound represented by the general formula (Formula 1) used in some embodiments of the present invention is a dehydration condensate of ricinoleic acid obtained by hydrolyzing and further condensing refined castor oil as a raw material ( Also known as: dehydration condensate of ricinoleic acid, dehydration condensate of 12-hydroxy-9-cis-octadecenoic acid). Moreover, in recent years, ricinoleic acid produced using turmeric, which was successful by Fukuzawa et al. , Shigenobu Kishino, Jun Ogawa & Hideya Fukuzawa., Production of ricinoleic acid-containing monoestolide triacylglycerides in an oleaginous diatom, Chaetoceros gracilis., S scientific reports (2016), 6:36809, (Published: 10 November 2016)), the above general A compound (dehydration condensate of ricinoleic acid) represented by the formula (Chem. 1) is obtained.

Commercial products of the compound represented by the above general formula (Chemical 1) include K-PON 402, K-PON 403-S, K-PON 400 series (manufactured by Ogura Synthetic Industry Co., Ltd.). Dehydration condensation of ricinoleic acid such as PON 404-S, K-PON 405-S, K-PON 406-S, and PCF-90, PCF-45, PCF-30 of the MINERASOL PCF series (manufactured by Ito Oil Co., Ltd.) things are mentioned.

The compound represented by the general formula (Chemical Formula 1) has a viscosity of 2 to 6 mers (condensation degree in terms of acid value) of 400 mPa s to 1800 mPa s (25° C.), and is used as an impregnating component for pencil cores. has a relatively high viscosity, can be expected to have the effect of inhibiting the movement of physical abrasion powder, and is relatively easy to impregnate into the fired core body. is also relatively high, which is particularly preferred. In addition, in the case of more than a hexamer, the effect of the embodiment of the present invention can be obtained by impregnating the sintered core using a known technique such as so-called pressure impregnation at high temperature and high pressure. can get.

The compound represented by the general formula (1) can be used alone, but can also be used in combination with other components. Examples thereof include conventionally known α-olefin oligomers and liquid paraffin. The concentration of the compound represented by the general formula (1) in the impregnating component is preferably 50% by weight or more with respect to the total amount of the impregnating component. The impregnation amount (impregnation rate) of the impregnating component containing the compound represented by the general formula (1) is preferably 10% by weight or more and 30% by weight or less with respect to the total weight of the pencil lead. If it is less than 10% by weight, the amount of the impregnated component adsorbed on the surface of the resin charcoal in the fired core is reduced. No traces can be obtained. On the other hand, if it exceeds 30% by weight, the impregnated component in the fired core increases, and the writing line becomes difficult to erase, or the impregnated component permeates the paper surface, and the set-off of the written line tends to occur.

The sintered core to be impregnated with the impregnating component may contain conventionally known coloring components, extenders, organic binders, plasticizers, solvents, aggregates, stabilizers, fillers, etc. as other compounding materials. These may be used singly or in combination of two or more.

Examples of the coloring component include graphite such as flake graphite, flake graphite, soil graphite, and artificial graphite, and inorganic particles such as boron nitride and synthetic mica. Examples of fillers include talc, carbon nanotubes, carbon fibers, and fibrous potassium titanate. Organic binders include polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated paraffin, furan resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, urea resin, melamine resin, polyester, styrene. Synthetic resins such as butadiene copolymer, polyvinyl acetate, polyacrylamide, and butyl rubber, and natural resins such as lignin, cellulose, gum tragacanth, and gum arabic. Plasticizers include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diallyl isophthalate, tricresyl phosphate, dioctyl adipate, and the like. Examples of solvents include ketones such as methyl ethyl ketone and acetone, alcohols such as ethanol, and water. Examples of lubricants include fatty acids such as stearic acid and behenic acid, fatty acid amides, and stearic acid. Stabilizers include stearates, organotins, barium-zincs, calcium-zincs, and the like. Fillers include metals such as iron, aluminum, titanium and zinc, alloys thereof, oxides and nitrides of these metals and alloys, silicon dioxide (silica), carbon black and fullerene. These fillers can be appropriately used in shapes such as spherical, amorphous granular, needle-like, fibrous, and plate-like.

After uniformly dispersing these blended materials with a kneader, Henschel mixer, three rolls, etc., they are molded into fine wires, subjected to appropriate heat treatment depending on the resin to be used, and finally heated to 800°C to 1300°C in a non-oxidizing atmosphere. A sintering treatment is applied to obtain a sintered core. If the pore volume of the sintered core is 0.05 cm ³ /g to 0.25 cm ³ /g, a desired impregnation rate can be obtained. The pore volume of the fired core can be measured by a known gas adsorption method or mercury intrusion method.

As a method for impregnating the sintered core with the impregnating component, a method of immersing the sintered core in the heated impregnating component and impregnating the impregnating component can be employed. The speed of impregnation can be increased by stirring the impregnation component or applying pressure. The impregnation speed can be increased by lowering the viscosity of the impregnation component by heating at a higher temperature. It is necessary to devise a method such as shutting off air and humidity. The sintered core impregnated with the impregnating component may be used as a pencil lead by removing excess impregnating component on the surface of the core using a centrifuge or the like.
In some embodiments of the present invention, a core containing at least a coloring component and an organic binder is heat-treated, and a compound represented by the general formula (Chemical Formula 1) is contained in the pores of the obtained fired core. A pencil lead characterized by having an impregnating component containing: Here, the "fired core" is obtained through a heat treatment called "fired". In general, when a composition containing an organic substance (organic binder) such as a synthetic resin or a natural resin is heat-treated to a firing temperature, In a state in which resin molecules are intricately entwined with coloring components such as graphite, decomposition and condensation of organic substances occur irregularly, and the core as a whole undergoes complex volumetric shrinkage. The structure becomes extremely complicated in minute parts, and the degree and size of bonding of individual compositions after heat treatment also vary. This requires an unrealistic number of experiments, etc., and there are circumstances where it is impossible or almost impractical to directly identify the product by its structure or characteristics.

Various conventionally known mechanical pencil bodies can be used when using the pencil lead according to some embodiments of the present invention. For example, as disclosed in Japanese Patent Application Laid-Open No. 8-282182, when writing, the tip surface of the tip member retreats while being rubbed against the paper surface as the lead wears, preventing the core from breaking during writing. The so-called pipe slide type mechanical pencil is effective in protecting the pencil lead obtained by some embodiments of the present invention, and the tip surface of the tip member presses abrasion powder against the paper surface, so that the abrasion powder does not reach the paper surface. The fixability of is further improved. When adopting this pipe slide type mechanical pencil, as disclosed in Japanese Patent Application Laid-Open No. 2015-104882, the shape and material of the tip member (stainless pipe) that comes into contact with the paper is selected, and the wear powder of the core is more preferably devised to make it easier to adhere to the tip member. In addition, when using a mechanical pencil that allows writing with the tip member disclosed in Japanese Patent Application Laid-Open No. 2018-1685 in contact with the paper surface and that allows continuous writing, the impact at the time of knocking Since it is possible to prevent breakage of the lead due to excessive force, it is most suitable as a mechanical pencil using a pencil lead according to some embodiments of the present invention.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited only to the examples. The average particle diameter of the graphite compounded is the volume average diameter measured with a laser diffraction particle size distribution analyzer SALD-7000 (manufactured by Shimadzu Corporation). Furthermore, the pore volume of the sintered core was measured by a specific surface area/pore size distribution measuring device BELSORP-miniII (manufactured by Microtrac Bell Co., Ltd.) using a constant volume gas adsorption method. Data on the adsorption side of the adsorption isotherm were calculated by the BJH method. The IOB value of the impregnated component was calculated from the molecular formula. The viscosity was measured using a rheometer of Modular Compact Rheometer MCR302 (manufactured by Anton Paar Japan Co., Ltd.) at a measurement temperature of 25° C. and a cone plate geometry of 1°/Φ50 mm. bottom. The impregnation rate was determined by the percentage (% by weight) of (YX)/Y where X is the weight of the sintered core before impregnation and Y is the weight of the pencil lead after impregnation.

(Production of sintered core A)
Flaky graphite (coloring component: volume average diameter 15 μm) 45 parts by weight polyvinyl chloride (organic binder) 24 parts by weight carbon black (filler) 1 part by weight stearate (stabilizer) 1.5 parts by weight stearic acid ( Lubricant) 0.5 parts by weight Dioctyl phthalate (plasticizer) 18 parts by weight Methyl ethyl ketone (solvent) 15 parts by weight After dispersing and mixing the above materials with a Henschel mixer and mixing with three rolls, they are processed by a single screw extruder. It is extruded into a thin wire shape, heated in air from room temperature to 350°C over about 10 hours, heat-treated by holding at 350°C for about 1 hour, and further heated to 1100°C in a closed container. A sintering treatment was performed to obtain a sintered core A having an actual diameter of 0.57 mm. The pore volume was 0.18 cm ³ /g.

(Production of sintered core B)
Flaky graphite (coloring component: volume average diameter 15 μm) 33 parts by weight polyvinyl chloride (organic binder) 23 parts by weight carbon black (filler) 1 part by weight stearate (stabilizer) 1.5 parts by weight stearic acid ( Lubricant) 0.5 parts by weight Dioctyl phthalate (plasticizer) 15 parts by weight Methyl ethyl ketone (solvent) 15 parts by weight After dispersing and mixing the above materials with a Henschel mixer and mixing with three rolls, they are processed by a single screw extruder. It is extruded into a thin wire shape, heated in air from room temperature to 350°C over about 10 hours, heat-treated by holding at 350°C for about 1 hour, and further heated to 1100°C in a closed container. A sintering treatment was performed to obtain a sintered core B having an actual diameter of 0.57 mm. The pore volume was 0.13 cm ³ /g.

<Example 1>
The impregnation component (K-PON 402, the compound (n = 2) represented by the above general formula (Chemical 1), dehydrated condensate of ricinoleic acid, Ogura Gosei Kogyo Co., Ltd. ( Co., Ltd., IOB value = 0.45, viscosity 520 mPa·s) after immersion for 16 hours, followed by centrifugation to remove excess impregnated components on the surface to obtain a pencil lead. The impregnation rate of the impregnation component was 16.5% by weight.

<Example 2>
In Example 1, the impregnation component was changed to K-PON 402, and K-PON 404-S (the compound represented by the above general formula (Chemical 1) (n = 4), dehydrated condensate of ricinoleic acid, Ogura Synthesis A pencil lead was obtained in the same manner as in Example 1, except for using Kogyo Co., Ltd., IOB value = 0.31, viscosity 1068 mPa·s). The impregnation rate of the impregnation component was 16.7% by weight.

<Example 3>
In Example 1, the impregnation component was changed to K-PON 402, and K-PON 406-S (compound (n = 6) represented by the above general formula (Chemical 1), dehydrated condensate of ricinoleic acid, Ogura synthesis A pencil lead was obtained in the same manner as in Example 1, except for using Kogyo Co., Ltd., IOB value = 0.27, viscosity 1589 mPa·s). The impregnation rate of the impregnation component was 16.2% by weight.

<Example 4>
In Example 1, the impregnation component was changed to K-PON 402, and PCF-90 (the compound represented by the above general formula (Chemical Formula 1) (n = 2), dehydrated condensate of ricinoleic acid, Ito Oil Co., Ltd. A pencil lead was obtained in the same manner as in Example 1, except for using a product with an IOB value of 0.45 and a viscosity of 580 mPa·s. The impregnation rate of the impregnation component was 16.2% by weight.

<Example 5>
In Example 1, the impregnation component was changed to K-PON 402, and PCF-45 (the compound represented by the above general formula (Chemical 1) (n = 4), dehydrated condensate of ricinoleic acid, Ito Oil Co., Ltd. A pencil lead was obtained in the same manner as in Example 1, except for using a product with an IOB value of 0.31 and a viscosity of 1162 mPa·s. The impregnation rate of the impregnation component was 16.5% by weight.

<Example 6>
In Example 1, the impregnation component was changed to K-PON 402, and PCF-30 (the compound represented by the above general formula (Chemical 1) (n = 6), dehydrated condensate of ricinoleic acid, Ito Oil Co., Ltd. A pencil lead was obtained in the same manner as in Example 1, except for using a 0.27 IOB value and a viscosity of 1782 mPa·s. The impregnation rate of the impregnation component was 16.5% by weight.

<Example 7>
The sintered core B was impregnated with the impregnating component (K-PON 402 (described above)) heated to 150° C. for 16 hours under pressure of 2 MPa, and then centrifuged to remove excess on the surface. A pencil lead was obtained by removing the impregnated component. The impregnation rate of the impregnation component was 14.0% by weight.

<Example 8>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 404-S (described above) was used instead of K-PON 402 as the impregnation component. The impregnation rate of the impregnation component was 13.8% by weight.

<Example 9>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 406-S (described above) was used instead of K-PON 402 as the impregnation component. The impregnation rate of the impregnation component was 13.5% by weight.

<Example 10>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and PCF-90 (described above) was used. The impregnation rate of the impregnation component was 14.2% by weight.

<Example 11>
A pencil lead was obtained in the same manner as in Example 7, except that PCF-45 (described above) was used instead of K-PON 402 as the impregnation component. The impregnation rate of the impregnation component was 13.5% by weight.

<Example 12>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and PCF-30 (described above) was used. The impregnation rate of the impregnation component was 13.3% by weight.

<Comparative Example 1>
In Example 1, the impregnation component was changed to K-PON 402, and ricinoleic acid (substance before condensation of the compound represented by the above general formula (Chemical 1) (n = 1), manufactured by Wako Pure Chemical Industries, Ltd. , IOB value = 0.72, viscosity 342 mPa·s), a pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 17.6% by weight.

<Comparative Example 2>
In Example 1, the impregnation component was changed to K-PON 402, and K-PON 406-G (glycerin ester of polycondensed castor oil fatty acid, manufactured by Ogura Synthetic Industry Co., Ltd., IOB value = 0.29, viscosity 1574 mPa s ) was used to obtain a pencil lead in the same manner as in Example 1. The impregnation rate of the impregnation component was 18.3% by weight.

<Comparative Example 3>
In Example 1, the impregnation component was changed to K-PON 402, and heat-dissolved 12-hydroxy acid (12-hydroxystearic acid, manufactured by Ogura Gosei Co., Ltd., IOB value = 0.71, room temperature solid (melting point 77 °C)) was used, and a pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 16.7% by weight.

<Comparative Example 4>
In Example 1, K-PON 306 (12-hydroxyoctadecanoic acid polycondensate, Ogura Synthetic Industry Co., Ltd., IOB value = 0.26, viscosity 3006 mPa s) was used instead of K-PON 402 as the impregnation component. A pencil lead was obtained in the same manner as in Example 1, except that The impregnation rate of the impregnation component was 16.5% by weight.

<Comparative Example 5>
In Example 1, the impregnation component was changed to K-PON 402, except that castor oil Marutoku A (ricinoleic acid triglyceride, manufactured by Ito Oil Co., Ltd., IOB value = 0.43, viscosity 696 mPa s) was used. , to obtain a pencil lead in the same manner as in Example 1. The impregnation rate of the impregnation component was 17.2% by weight.

<Comparative Example 6>
In Example 1, the impregnating component was changed to K-PON 402, and Nisseki Polybutene SV-7000 (polybutene, manufactured by JXTG Energy Co., Ltd.) and Synthlan 4SP (α-olefin oligomer, manufactured by Nikko Chemicals Co., Ltd.) were used. A pencil lead was obtained in the same manner as in Example 1, except that a mixture mixed at a ratio of 1:1 (weight ratio), IOB value=0, viscosity 1430 mPa·s) was used. The impregnation rate of the impregnation component was 15.7% by weight.

<Comparative Example 7>
NIKKOL Sefsol-218 (propylene glycol monocaprylate, manufactured by Nikko Chemicals Co., Ltd., IOB value = 0.73, viscosity 12.5 mPa s) was used instead of K-PON 402 as the impregnation component in Example 1. A pencil lead was obtained in the same manner as in Example 1, except that the The impregnation rate of the impregnation component was 16.5% by weight.

<Comparative Example 8>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and ricinoleic acid (described above) was used. The impregnation rate of the impregnation component was 15.0% by weight.

<Comparative Example 9>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and K-PON 406-G (described above) was used. The impregnation rate of the impregnation component was 14.8% by weight.

<Comparative Example 10>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnating component and 12-hydroxy acid dissolved by heating (described above) was used. The impregnation rate of the impregnation component was 12.8% by weight.

<Comparative Example 11>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 306 (described above) was used instead of K-PON 402 as the impregnation component. The impregnation rate of the impregnation component was 11.7% by weight.

<Comparative Example 12>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and castor oil Marutoku A (described above) was used. The impregnation rate of the impregnation component was 13.0% by weight.

<Comparative Example 13>
In Example 7, the impregnation component was changed to K-PON 402, and Nisseki Polybutene SV-7000 (above) and Syneslan 4SP (above) were mixed at a 1:1 (weight ratio) mixture (above). A pencil lead was obtained in the same manner as in Example 7, except that The impregnation rate of the impregnation component was 10.9% by weight.

<Comparative Example 14>
A pencil lead was obtained in the same manner as in Example 7, except that K-PON 402 was used as the impregnation component and NIKKOL Sefsol-218 (described above) was used. The impregnation rate of the impregnation component was 12.7% by weight.

For the pencil leads obtained in Examples 1 to 12 and Comparative Examples 1 to 14, writing density and fixability against rubbing were measured by the following methods, and a reliability test was also conducted.

(Test method for writing density)
The writing density test was carried out according to JIS S6005.

(Testing method for fixability against rubbing (difficulty in staining))
The fixability against rubbing was determined by setting the density of the writing area streaked in the writing density test to A, and rubbing the writing area with tissue paper 10 times back and forth under a vertical load of 500 g under constant conditions. ((A−B)/A), where B is B, was calculated as a percentage. It can be said that the larger the value, the better the fixability of the written lines against rubbing and the less likely to be stained.

(Reactivity test method with resin container)
In the reactivity test with a resin container, acrylonitrile-styrene copolymer (AS resin) refill container (STEIN refill container, manufactured by Pentel Co., Ltd.), Examples 1 to 12 and Comparative Examples 1 to 14 Put 40 pencil leads obtained in 1. above, place them on a stainless steel plate, leave them in a constant temperature bath adjusted to 60°C for 16 hours, take them out, leave them at room temperature for 1 hour, and then adjust them to -30°C. A change in the refill lead container was visually evaluated after repeating a cooling/heating cycle test in which the container was allowed to stand still for 16 hours in a constant temperature bath twice.

Table 1 shows the test results (evaluation results) of the pencil leads (Examples 1 to 6 and Comparative Examples 1 to 7) in which the sintered core A was impregnated with the impregnation component.

上記表１の結果から明らかなように、実施例１～６の鉛筆芯は、比較例１～７の鉛筆芯に比べ、筆跡線が濃く、且つ、紙面の汚れが少ない鉛筆芯を得られるものである。

As is clear from the results in Table 1 above, the pencil leads of Examples 1 to 6 have darker handwriting lines and less stains on the paper than the pencil leads of Comparative Examples 1 to 7. is.

In Examples 1 to 3, the degree of condensation of the compound represented by the general formula (Chemical Formula 1) used as the impregnation component differs (Example 1 is a dimer, Example 2 is a tetramer, Example 3 is a hexamer), and the higher the degree of condensation, the higher the molecular weight and the higher the viscosity. There is no decrease in writing density, and there is little staining on the paper surface.

Example 4 uses an impregnating component manufactured by a different manufacturer from Example 1. Although the viscosity is slightly higher, the compound represented by the general formula (Chemical Formula 1) reduces the writing density. There is little dirt on the paper surface.

Example 5 uses an impregnating component manufactured by a different manufacturer from Example 2. Although the viscosity is slightly higher, the compound represented by the general formula (Chemical Formula 1) reduces the writing density. There is little dirt on the paper surface.

Example 6 uses an impregnating component manufactured by a different manufacturer from Example 3. Although the viscosity is slightly higher, the compound represented by the general formula (Chemical Formula 1) reduces the writing density. There is little dirt on the paper surface.

Comparative Examples 1 and 2 have higher writing densities than those of Examples 1 to 6, but the paper surface is more soiled (fixing rate is lower). On the other hand, in Comparative Examples 3 to 7, the paper surface was heavily soiled and the writing density was low, so it cannot be said that the above problems have been solved.

In Comparative Example 1, the impregnation component is ricinoleic acid, and the compound represented by the general formula (Chemical Formula 1) before condensation (n=1) has a high IOB value and is associated with graphite as a coloring component. It is presumed that the dirt on the paper surface was not reduced because the Furthermore, since ricinoleic acid easily absorbs moisture in the atmosphere, the absorbed moisture in the reactivity test with the resin container condenses inside the refill lead container, making it difficult to remove the lead from the case.

In Comparative Example 2, the carboxyl group at the end of the hexamer of the compound represented by the above general formula (Chemical Formula 1) was replaced with a glyceryl-modified glycerin ester as the impregnating component, but the carboxyl group with a large polarity was replaced. It is presumed that the interaction with the functional groups on the surface of the paper was insufficient due to the absence of the contamination on the surface of the paper.

In Comparative Example 3, the impregnation component (12-hydroxystearic acid) was a saturated fatty acid without unsaturated bonds in the impregnation component (ricinoleic acid) of Comparative Example 1, and was solid at room temperature, and wear of the core was reduced. It is a thin writing line (writing density).

In Comparative Example 4, the impregnated component is a dehydrated condensate of the impregnated component (12-hydroxystearic acid) of Comparative Example 3, and is a substance without the unsaturated bond of the compound represented by the above general formula (Chemical Formula 1). However, the intermolecular interaction is greater than that of the compound represented by the above general formula (Chemical Formula 1), in which intermolecular cis-unsaturated bonds restrict the movement of molecules, and the intermolecular approach is easy. It is presumed that the abrasion of the core during writing was inhibited, and the writing density was lowered.

In Comparative Example 5, refined castor oil (ricinoleic acid triglyceride), which is a raw material for the compound represented by the general formula (Chemical Formula 1), was used. It is presumed that the effect was lower than that of the compound represented by the above general formula (Chemical Formula 1), that the wear of the core was inhibited, and that the writing density was lowered.

Comparative Example 6 is a pencil lead in which a saturated hydrocarbon-based impregnating component having a high kinematic viscosity (the impregnating component described in Patent Document 1) is adjusted to have a viscosity equivalent to that of Example 3 and used. The impregnated component of Comparative Example 6 has a linear region in dynamic viscoelasticity measurement (frequency 1 Hz, measurement temperature 25 ° C.) with a rheometer (modular compact rheometer MCR302 (manufactured by Anton Paar Japan Co., Ltd.)) ( Shear strain 0.1% to 100%), and even with the same viscosity as in Example 3, compared to the impregnated component that exhibits the behavior of a Newtonian fluid that does not have a linear region, the impregnated component wears the core during writing. It is presumed that the writing density decreased due to the inhibition of

Comparative Example 7 is a pencil lead using a highly polar fatty acid ester as an impregnating component (impregnating component described in Patent Document 2). The impregnated component corrodes the acrylonitrile-styrene copolymer of the refill container, causing cracks.

Next, Table 2 shows the test results (evaluation results) of the pencil leads (Examples 7 to 12 and Comparative Examples 8 to 14) in which the sintered core B was impregnated with the impregnation component.

上記表２の結果においても、実施例７～１２の鉛筆芯は、比較例８～１４の鉛筆芯に比べて、筆跡線が濃く、且つ、紙面の汚れが少ない鉛筆芯を得られるものである。これは上記一般式（化１）にて示される化合物を含浸させる焼成芯体（焼成芯体Ａ及び焼成芯体Ｂ）を変えても、含浸成分が上記一般式（化１）にて示される化合物であれば、鉛筆芯の摩耗量が異なっても、筆跡線が濃く、且つ、紙面の汚れが少ない鉛筆芯を得られるものである。

The results in Table 2 also show that the pencil leads of Examples 7 to 12 give darker handwriting lines and less dirt on the paper than the pencil leads of Comparative Examples 8 to 14. . This is because the impregnated component is represented by the above general formula (Chem. 1) even if the sintered cores (calcined core A and calcined core B) impregnated with the compound represented by the above general formula (Chem. 1) are changed. If it is a compound, even if the wear amount of the pencil lead is different, it is possible to obtain a pencil lead that gives a dark handwriting and less stains on the paper surface.

As detailed above, by using the pencil leads of Examples 1 to 12, darker writing lines (deeper writing density) can be obtained than when the pencil leads of Comparative Examples 1 to 14 are used. When a line is rubbed, the movement of abrasion powder is suppressed, and a pencil lead with less dirt on the paper surface can be obtained.

Further, in Examples 1 to 12, the impregnated component does not corrode the refill container and cause cracks, or absorb moisture and cause condensation in the refill container, so the basic function of taking out the pencil lead from the refill container. nor hinder it.

Claims (1)

A core containing at least a coloring component and an organic binder is heat-treated, and the pores of the obtained fired core contain an impregnation component containing a compound represented by the following general formula (Chemical Formula 1). A pencil lead characterized in that 2≦n≦6 in the general formula (1) .