TWI837160B - pencil lead - Google Patents

Abstract

The present invention relates to a method of subjecting a core containing at least a coloring component and an organic binder to heat treatment, and then impregnating the pores of the resulting sintered core with a compound represented by the following general formula (Chemical 1).

Description

Pencil refills

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

Generally speaking, pencil refills are made of coloring ingredients such as graphite or boron nitride, base materials such as talc, organic binders such as vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, vinyl chloride resin, vinyl alcohol resin, acrylamide resin, chlorinated wax, phenol resin, furan resin, urea resin, carboxymethyl cellulose, nitrocellulose, butyl rubber, or inorganic binders such as clay as the main materials, and if necessary, plasticizers such as phthalates, solvents such as methyl ethyl ketone, acetone, water, stabilizers such as stearates, lubricants such as stearic acid, fillers such as carbon black, etc. are used in combination. These raw materials are dispersed, mixed, and kneaded to form thin wires, and then heat treated to a suitable firing temperature. It is believed that the decomposed parts of organic or inorganic binders, plasticizers, solvents, etc. that existed in the fired core (fired core) become pores. Since the compound materials are highly dispersed during the mixing and forming, the fired core has a large number of relatively large and uniform pores. The pencil cores generally sold are made by impregnating the pores with oily substances such as polysilicone oil, flowing wax, spindle oil, squalane, α-olefin oligomers, wax wax, microcrystalline wax, monter wax, and carnauba wax, mainly for the purpose of improving the writing feel.

However, the pencil lead is caused by adhesive wear due to sliding friction with the paper, and a transfer film is formed on the paper surface to form writing lines. However, the writing lines are caused by the wear powder containing coloring components such as graphite produced by adhesive wear, which will stick to the paper surface. When rubbed by other papers or hands, the coloring components such as graphite will easily move and dirty the paper surface.

In addition, in recent years, students, who are the main users of pencil refills, have been increasingly preferring pencil refills with softer hardness and thicker handwriting due to the reduction in writing pressure. However, for pencil refills with softer hardness and thicker handwriting, the degree of paper dirt caused by rubbing increases, and there is a correlation between hardness and/or density and paper dirt, so it is necessary to develop pencil refills that leave less dirt on the paper even if the writing line is rubbed.

As a method of reducing dirt by suppressing the movement of graphite and the like caused by rubbing, it is known that the fixation of abrasion powder to the paper surface is improved by impregnating the pencil core with an impregnating component such as an oily substance. Patent document 1 states that the fixation of the writing line containing abrasion powder is physically improved by using an impregnating component with a high dynamic viscosity. Patent document 2 states that by using a polar fatty acid ester as an impregnating component, the fixation of the writing line can be improved by chemical bonding between the impregnating component and the functional group of the paper surface.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2005-213391 (patent application scope, implementation examples)

[Patent Document 2] Japanese Patent Publication No. 2007-31589 (patent application scope, implementation examples)

However, the impregnation component with high dynamic viscosity shown in Patent Document 1 can improve the fixation of the writing line, but it will deteriorate the erasability of the eraser, and the core body becomes less susceptible to wear, and the concentration of the writing line is reduced when compared with the case of the impregnation component with low dynamic viscosity such as general liquid wax or polysilicone oil used as the impregnation component of the pencil core. In addition, although it can make it a higher concentration of the writing line by making it a soft core body, compared with the one with greater wear, the general soft pencil core has a low bending strength, so it is easy to break when writing. On the other hand, the highly polar and low molecular weight fatty acid esters shown in Patent Document 2 will chemically react with synthetic resins used in replacement refill containers or refill tubes of automatic pencils, causing cracks or breaks.

Furthermore, if the IOB value of the impregnated component is large, the impregnated component may absorb moisture, and mist may form in the container during storage, causing a malfunction in the box, so further improvement is required as a product. Here, the so-called IOB value is the sum of the values of specific groups in the chemical structure as the inorganic value, and the value obtained by dividing the inorganic value by the organic value after subtracting the value determined when the number of carbons in the chemical structure is 20 times and there is a specific branch as the organic value. For example, the inorganic value of the carboxyl group of the inorganic group is 150 per carboxyl group, and the organic value is converted to 20 per carbon. The IOB value is an index of the polarity strength occupied in the molecule, and because the IOB value × 10 is close to the HLB value, it is also used as a criterion for judging hydrophilicity and lipophilicity.

The purpose of several embodiments of the present invention is to provide a pencil refill that can obtain a thick writing line, suppress the movement of abrasive powder when rubbing across the writing line, reduce the dirt on the paper surface, and has high reliability.

That is, several embodiments of the present invention are mainly pencil cores, which are characterized by containing at least a coloring component and an organic binder, and having an impregnation component containing a compound represented by the following general formula (Chemical 1) in the pores of the sintered core obtained by heat treatment.

The compound represented by the general formula (chemical 1) is a liquid non-drying oil at room temperature 5~35℃ (JIS Z 8703) because the carbon chain of the main chain contains unsaturated bonds. It is easy to impregnate into the pores of the sintered core, and because it is bonded by polar ester bonds, it is also easy to adsorb on the solid surface of graphite particles or resin carbide surfaces having multiple functional groups such as hydroxyl or carboxyl groups generated by the decomposition and rebonding of the resin during heat treatment, and dangling bonds of carbon. Therefore, by using an impregnation component containing this, the compound represented by the general formula (chemical 1) exists between particles as a lubricating film, and a thick writing line can be obtained by promoting the adhesion and wear of the core.

In addition, it is speculated that the ester and double bond parts of the main chain, the hydroxyl and carboxyl groups at the end of the compound represented by the above general formula (Chemical 1) existing on the surface of the abrasive powder that becomes the writing line, and the polar parts are formed with polar components such as cellulose in the paper. At the same time, the carbon chain that becomes the side chain in the compound represented by the above general formula (Chemical 1) has an anchoring effect on the rough surface of the abrasive powder and can be efficiently adsorbed, so the abrasive powder is strongly bonded to the paper surface, and the abrasive powder is difficult to move even if it is rubbed.

[Form of implementing the invention]

Several implementation forms of the present invention are described in detail below.

The compound represented by the general formula (Chemical 1) used in several embodiments of the present invention is a dehydrated condensate of ricinoleic acid (also known as dehydrated condensate of ricinoleic acid, dehydrated condensate of 12-hydroxy-9-cis-octadecenoic acid) obtained by hydrolyzing purified castor oil as a raw material and further condensing it. In recent years, Fukuzawa et al. have successfully used ricinoleic acid produced by diatom Chaetoceros gracilis (non-patent literature: Masataka Kajikawa, Tatsuki Abe, Kentaro Ifuku, Ken-ichi Furutani, Dongyi Yan, Tomoyo Okuda, Akinori Ando, Shigenobu Kishino, Jun Ogawa & Hideya Fukuzawa., Production of ricinoleic acid-containing monoestolide triacylglycerides in an oleaginous diatom, Chaetoceros gracilis., Scientific reports (2016), 6: 36809, (Published: 10 November 2016)) to condense the compound represented by the above general formula (Chemical 1) (dehydrated condensate of ricinoleic acid).

As the commercial products of the compound represented by the above general formula (Chemical 1), there can be cited dehydrated condensates of ricinoleic acid such as K-PON 402, K-PON 403-S, K-PON 404-S, K-PON 405-S, K-PON 406-S of the K-PON 400 series (manufactured by Kokura Synthetic Industries Co., Ltd.) or PCF-90, PCF-45, PCF-30 of the MINERASOL PCF series (manufactured by Ito Oil Seisakusho Co., Ltd.).

When the viscosity of the compound represented by the general formula (1) is 400mPa.s~1800mPa.s (25°C) in the 2~6 polymer (condensation degree is converted to acid value), as the impregnation component of the pencil core, the viscosity is relatively high, and the physical effect of hindering the movement of abrasive powder is also expected. It is also easier to impregnate the sintered core and is preferred. The 6 polymer is also relatively high in chemical stability over time to oxidation and is particularly preferred. In addition, for polymers exceeding 6 polymers, the effects of the embodiment of the present invention can be obtained by impregnating the sintered core using the so-called pressurized impregnation at high temperature and high pressure, which is a known technology.

The compound represented by the above general formula (Chemical 1) can be used alone, but can also be used in combination with other components. For example, the previously known α-olefin oligomers or fluidized wax can be cited. The concentration of the compound represented by the above general formula (Chemical 1) in the impregnating component is preferably 50% by weight or more relative to the total amount of the impregnating component. In addition, the impregnation amount (impregnation rate) of the impregnating component containing the compound represented by the above general formula (Chemical 1) is preferably 10% by weight or more and 30% by weight or less relative to the total weight of the pencil lead. When it is less than 10% by weight, the amount of adsorption of the impregnating component on the surface of the resin carbide in the sintered core will decrease, and as a result, the effect as a lubricating film will be reduced, and since the adhesion and wear of the core will be suppressed, high handwriting cannot be obtained. Furthermore, if it exceeds 30% by weight, the impregnation components in the fired core will increase, and the writing line will become difficult to disappear, or the impregnation components will penetrate into the paper surface, making it easy for the writing line to penetrate.

The calcined core body impregnated with the impregnation component can be used together with the previously known coloring components, body materials, organic binders, plasticizers, solvents, aggregates, stabilizers, fillers, etc. as other compounding materials. These can be used alone or in combination of two or more.

As coloring components, graphites such as scaly graphite, flaky graphite, soil graphite, and artificial graphite, or inorganic particles such as boron nitride and synthetic mica can be cited. As bulk materials, talc, carbon nanotubes, carbon fibers, and fibrous potassium titanium can be cited. As organic binders, synthetic resins such as polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated wax, furan resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, urea resin, melamine resin, polyester, styrene-butadiene copolymer, polyvinyl acetate, polyacrylamide, and butyl rubber, or natural resins such as lignin, cellulose, tragacanth rubber, and gum arabic can be cited. Examples of plasticizers include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diallyl isophthalate, tricresol phosphate, dioctyl adipate, etc. 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, or fatty acid amides, stearic acid, etc. Examples of stabilizers include stearates, organic tin compounds, barium-zinc compounds, and calcium-zinc compounds. As fillers, metals such as iron, aluminum, titanium, zinc, or their alloys can be cited, as well as oxides or metal nitrides of these metals or alloys, silicon dioxide (SiO2), carbon black, fullerene, etc. These fillers are suitable for shapes such as spheres, amorphous particles, needles, fibers, plates, etc.

These compounding materials can be uniformly dispersed by a kneader, a Henschel mixer, a three-roller, etc. and formed into a thin wire shape. According to the resin used, appropriate heat treatment can be applied, and finally a sintering treatment at 800℃~1300℃ is applied in a non-oxidizing environment to obtain a sintered core. If the pore volume of the sintered core is ^0.05cm3/ g~ ^0.25cm3 /g, the desired impregnation rate can be obtained. In addition, the pore volume of the sintered core can be measured by the known gas adsorption method or mercury penetration method.

As a method of impregnating the calcined core with the impregnation component, a method of impregnating the calcined core with the heated impregnation component can be adopted. The impregnation speed can be accelerated by stirring the impregnation component or applying a pressure treatment. When heating at a higher temperature, the impregnation speed can be accelerated even if the viscosity of the impregnation component is reduced, but the impregnation component tends to deteriorate by hydrolysis due to thermal oxidation of the impregnation component or moisture in the air, so it is necessary to cut off air or moisture and use it. The calcined core impregnated with the impregnation component can be made into a pencil lead by removing excess impregnation components on the surface of the core using a centrifuge or the like.

The subject of several embodiments of the present invention is a pencil core, which is characterized in that it contains at least a coloring component and an organic binder, and the pores of the calcined core obtained by heat-treating the core have an impregnation component containing the compound represented by the above general formula (1). Among them, the "calcined core" is obtained by a heat treatment called "calcination", which is generally when a composition containing organic matter (organic binder) such as synthetic resin or natural resin is heat-treated to a calcination temperature, the resin molecules irregularly cause the decomposition or condensation of the organic matter in a state of complex interweaving with coloring components such as graphite, and the core as a whole undergoes complex volume contraction, and the heat treatment The skeleton structure of the core (sintered core) after heat treatment becomes extremely complex in microscopic parts, so it is believed that the degree of bonding and size of each component after heat treatment are diverse. If you want to conduct systematic measurement and analysis related to the above effects, you must conduct unrealistic experiments, and it is impossible to directly specify the object through its structure or characteristics, or it is impractical.

As the main body of the automatic pencil when using the pencil refill of the embodiments of the present invention, a conventionally known one can be used. For example, as disclosed in Japanese Patent Publication No. 8-282182, when writing, the tip end of the tip member is rubbed against the paper surface while the refill is worn, so as to prevent the refill from breaking during writing. The so-called channel slide type automatic pencil can effectively protect the pencil refill obtained as the embodiments of the present invention, and the tip end of the tip member is pressed against the paper surface with abrasion powder, which can improve the fixation of the abrupt powder to the paper surface. When using the pipe slide type automatic pencil, as disclosed in Japanese Patent Publication No. 2015-104882, the shape or material of the tip member (stainless steel pipe) in contact with the paper is selected, and it is better to make the wear powder of the core easily adhere to the tip member and apply processing. In addition, when using an automatic pencil disclosed in Japanese Patent Publication No. 2018-1685, the tip member can be written in a state of contacting the paper surface, and can be written continuously, because the core can be prevented from breaking due to the impact when pressing, it is most suitable as an automatic pencil using the pencil core of several embodiments of the present invention.

[Implementation example]

The present invention is described below based on the examples, but the present invention is not limited to the examples. In addition, the average particle size of the graphite of the compounding material is the volume average diameter measured by the laser diffraction particle size distribution measuring device SALD-7000 (manufactured by Shimadzu Corporation). In addition, the pore volume of the sintered core is calculated by the BJH method using the specific surface area/pore distribution measuring device BELSORP-miniII (manufactured by Microtrac-bel) of the constant volume gas adsorption method, and the data on the adsorption side of the nitrogen adsorption isotherm obtained by using nitrogen as the adsorption gas. The IOB value of the impregnated component is the calculated value from the molecular formula. The viscosity is the value of the shear rate 1/s measured using a rheometer Modular compact rheometer MCR302 (manufactured by Anton-Paar Japan Co., Ltd.) at a measurement temperature of 25°C and a 1°/Φ50mm cone. The impregnation rate is (Y-X)/Y expressed as a percentage (weight %), with the weight of the sintered core before impregnation as X and the weight of the pencil lead after impregnation as Y.

(Production of fired core A)

The above materials were dispersed and mixed by a Henschel mixer, mixed by three rollers, extruded into thin wires by a single-screw extruder, heated from room temperature to 350°C in air for about 10 hours, kept at 350°C for about 1 hour, and further calcined at a maximum temperature of 1100°C in a sealed container to obtain a calcined core A with an actual diameter of 0.57 mm. The pore volume was 0.18 cm ³ /g.

(Production of fired core B)

The above materials were dispersed and mixed by a Henschel mixer, mixed by three rollers, and extruded into thin wires by a single-screw extruder. The temperature was raised from room temperature to 350°C in air over about 10 hours, maintained at 350°C for about 1 hour, and further calcined at a maximum temperature of 1100°C in a sealed container to obtain a calcined core B with an actual diameter of 0.57 mm. The pore volume was 0.13 cm ³ /g.

<Implementation Example 1>

The above-mentioned calcined core A was impregnated with the impregnation component (K-PON 402. The compound represented by the above general formula (Chemical 1) (n=2), dehydrated condensate of ricinoleic acid, manufactured by Kokura Synthetic Industries, IOB value=0.45, viscosity 520mPa.s) heated at 120°C for 16 hours, and then the excess impregnation component on the surface was removed by a centrifuge to obtain a pencil core. The impregnation rate of the impregnation component was 16.5% by weight.

<Implementation Example 2>

For Example 1, except that 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), a dehydrated condensate of ricinoleic acid, IOB value = 0.31, viscosity 1068mPa.s, manufactured by Ogura Synthetic Industries Co., Ltd.), 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.

<Implementation Example 3>

For Example 1, the impregnation component was changed to K-PON 402, and a pencil lead was obtained in the same manner as in Example 1 except that K-PON 406-S (the compound represented by the above general formula (Chemical 1) (n=6), a dehydrated condensate of ricinoleic acid, manufactured by Ogura Synthetic Industries Co., Ltd., IOB value=0.27, viscosity 1589mPa.s) was used. The impregnation rate of the impregnation component was 16.2% by weight.

<Implementation Example 4>

For Example 1, except that the impregnation component was changed to K-PON 402 and PCF-90 (the compound represented by the above general formula (Chemical 1) (n=2), a dehydrated condensate of ricinoleic acid, produced by Ito Oil Co., Ltd., IOB value=0.45, viscosity 580mPa.s) was used, a pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 16.2% by weight.

<Implementation Example 5>

For Example 1, except that the impregnation component was changed to K-PON 402 and PCF-45 (the compound represented by the above general formula (Chemical 1) (n=4), a dehydrated condensate of ricinoleic acid, produced by Ito Oil Co., Ltd., IOB value=0.31, viscosity 1162mPa.s) was used, a pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 16.5% by weight.

<Implementation Example 6>

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

<Implementation Example 7>

For the sintered core B, the impregnation component (K-PON 402 (mentioned above)) heated at 150°C was impregnated under pressure at 2MPa for 16 hours, and then the excess impregnation component on the surface was removed by a centrifuge to obtain a pencil lead. The impregnation rate of the impregnation component was 14.0% by weight.

<Implementation Example 8>

For Example 7, except that the impregnation component was changed to K-PON 402 and K-PON 404-S (described above) was used, a pencil lead was obtained in the same manner as in Example 7. The impregnation rate of the impregnation component was 13.8% by weight.

<Implementation Example 9>

For Example 7, except that the impregnation component was changed to K-PON 402 and K-PON 406-S (described above) was used, a pencil lead was obtained in the same manner as in Example 7. The impregnation rate of the impregnation component was 13.5% by weight.

<Implementation Example 10>

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

<Implementation Example 11>

For Example 7, the impregnation component was changed to K-PON 402, and the pencil lead was obtained in the same manner as in Example 7 except that PCF-45 (described above) was used. The impregnation rate of the impregnation component was 13.5% by weight.

<Implementation Example 12>

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

<Comparison Example 1>

For Example 1, the impregnation component was changed to K-PON 402, and ricinoleic acid (the substance before condensation of the compound represented by the above general formula (Chemical 1) (n=1), IOB value = 0.72, viscosity 342mPa.s, manufactured by Wako Pure Chemical Industries, Ltd.) was used, and 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.

<Comparison Example 2>

For Example 1, the impregnation component was changed to K-PON 402, and K-PON 406-G (polycondensed castor oil fatty acid glyceride, manufactured by Kokura Synthetic Industries Co., Ltd., IOB value = 0.29, viscosity 1574mPa.s) was used, and the pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 18.3% by weight.

<Comparison Example 3>

For Example 1, except that the impregnation component was changed to K-PON 402 and 12-hydrochloric acid (12-hydroxystearic acid, manufactured by Ogura Synthetic Industries Co., Ltd., IOB value = 0.71, solid at room temperature (melting point 77°C)) dissolved by heating was used, 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.

<Comparison Example 4>

For Example 1, the impregnation component was changed to K-PON 402, and K-PON 306 (12-hydroxyoctadecanoic acid polycondensate, IOB value = 0.26, viscosity 3006mPa.s) was used. The pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 16.5% by weight.

<Comparison Example 5>

For Example 1, the impregnation component was changed to K-PON 402, and castor oil Special Maru A (ricinoleic acid triglyceride, Ito Oil Co., Ltd., IOB value = 0.43, viscosity 696mPa.s) was used, and the pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 17.2% by weight.

<Comparison Example 6>

For Example 1, the impregnation component was changed to K-PON 402, and a mixture of Nippon Polybutene SV-7000 (polybutene, manufactured by JXTG Energy Co., Ltd.) and Synthesizer 4SP (α-olefin oligomer, manufactured by Nikko Chemical Co., Ltd.) was used in a 1:1 (weight ratio, IOB value = 0, viscosity 1430mPa.s), and a pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 15.7% by weight.

<Comparison Example 7>

For Example 1, the impregnation component was changed to K-PON 402, and NIKKOL Sefsol-218 (propylene glycol monooctanoate, manufactured by Nikko Chemical Co., Ltd., IOB value = 0.73, viscosity 12.5 mPa.s) was used, and the pencil lead was obtained in the same manner as in Example 1. The impregnation rate of the impregnation component was 16.5% by weight.

<Comparison Example 8>

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

<Comparison Example 9>

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

<Comparison Example 10>

For Example 7, the impregnation component was changed to K-PON 402, and the pencil lead was obtained in the same manner as in Example 7 except that 12-hydrochloric acid (described above) was used and dissolved by heating. The impregnation rate of the impregnation component was 12.8% by weight.

<Comparison Example 11>

For Example 7, the impregnation component was changed to K-PON 402, and a pencil lead was obtained in the same manner as Example 7 except that K-PON 306 (described above) was used. The impregnation rate of the impregnation component was 11.7% by weight.

<Comparison Example 12>

For Example 7, the impregnation component was changed to K-PON 402, and the castor oil Special Maru A (described above) was used, and the pencil lead was obtained in the same manner as in Example 7. The impregnation rate of the impregnation component was 13.0% by weight.

<Comparison Example 13>

In Example 7, the impregnation component was changed to K-PON 402, and a mixture (described above) of Nippon Polybutene SV-7000 (described above) and Synthesizer 4SP (described above) was used in a 1:1 (weight ratio). A pencil lead was obtained in the same manner as in Example 7. The impregnation rate of the impregnation component was 10.9% by weight.

<Comparison Example 14>

For Example 7, the impregnation component was changed to K-PON 402, and a pencil refill was obtained in the same manner as in Example 7 except that NIKKOL Sefsol-218 (described above) was used. The impregnation rate of the impregnation component was 12.7% by weight.

As described above, the pencil refills obtained in Examples 1 to 12 and Comparative Examples 1 to 14 were tested for writing density and fixation to erasure by the following method, and reliability tests were also performed.

(Test method for writing concentration)

The writing density test is carried out in accordance with JIS S 6005.

(Test method for fixation after rubbing (difficulty in staining))

For the fixation after rubbing, the concentration of the writing part drawn in the writing concentration test is taken as A, the writing part is wiped back and forth 10 times with a tissue paper under a vertical load of 500g under certain conditions, and the concentration of the dirt outside the writing part is taken as B, and the percentage ((A-B)/A) is calculated. The larger the value, the better the fixation of the rubbed writing line, and it can be said that it is difficult to become dirt.

(Reactivity test method with resin containers)

The reactivity test with resin containers is to put 40 pencil refills obtained in Examples 1 to 12 and Comparative Examples 1 to 14 into a replacement refill container made of acrylonitrile-styrene copolymer (AS resin) (STEIN replacement refill container, manufactured by Pentel Co., Ltd.), place them on a stainless steel plate, and place them in a constant temperature bath adjusted to 60°C for 16 hours. Then, take them out and place them at room temperature for 1 hour. Then, place them in a constant temperature bath adjusted to -30°C for 16 hours. The hot and cold cycle test is repeated twice, and the changes in the replacement refill container are visually observed for evaluation.

The test results (evaluation results) of the pencil cores (Examples 1 to 6 and Comparative Examples 1 to 7) impregnated with impregnation components in the fired core A are shown in Table 1.

From the results in Table 1 above, it can be seen that the pencil refills of Examples 1 to 6 are compared with the pencil refills of Comparative Examples 1 to 7, which can produce pencil refills with thicker handwriting lines and less dirt on the paper surface.

In Examples 1 to 3, the condensation degree of the compound represented by the above general formula (Chemical 1) used as the impregnation component is different (Example 1 is a dimer, Example 2 is a tetramer, and Example 3 is a hexamer). The greater the condensation degree, the greater the molecular weight and the higher the viscosity. However, if the impregnation component is the compound represented by the above general formula (Chemical 1), it will not affect the viscosity or IOB value, the writing density will not be reduced, and the dirt on the paper surface will be less.

Example 4 uses an impregnation component produced by a different manufacturer than Example 1. Although the viscosity is slightly increased, if it is a compound represented by the above general formula (Chemical 1), the writing concentration will not decrease, and there will be less dirt on the paper surface.

Example 5 uses an impregnation component from a different manufacturer than Example 2. Although the viscosity is slightly increased, if it is a compound represented by the above general formula (Chemical 1), the writing concentration will not decrease, and there will be less dirt on the paper surface.

Example 6 uses an impregnation component from a different manufacturer than Example 3. Although the viscosity is slightly increased, if it is a compound represented by the above general formula (Chemical 1), the writing concentration will not decrease, and there will be less dirt on the paper surface.

In Comparative Examples 1 and 2, the writing density is thicker than that of Examples 1 to 6, but the dirt on the paper surface becomes more (the fixing rate becomes lower). On the other hand, in Comparative Examples 3 to 7, the dirt on the paper surface is more, and the writing density is also reduced, which cannot solve the above problem.

Comparative Example 1 is a material (n=1) before condensation of the compound represented by the general formula (Chemical 1) with ricinoleic acid as the impregnated component, but it is inferred that the IOB value is high and the bonding with the graphite of the coloring component is weak, so the dirt on the paper surface is not reduced. In addition, ricinoleic acid easily absorbs moisture in the atmosphere, so in the reactivity test with the resin container, the absorbed moisture condenses in the replacement refill container, resulting in the refill being difficult to remove from the outer shell.

Comparative Example 2 is a case where the impregnation component is a glycerol ester modified with a glyceryl group and the terminal carboxyl group of the hexamer of the compound represented by the general formula (Chemical 1) is substituted. However, it is inferred that since it does not have a highly polar carboxyl group, the interaction with the functional groups on the paper surface becomes insufficient, and the dirt on the paper surface is not reduced.

Comparative Example 3 is a saturated fatty acid without unsaturated bonds in the impregnation component (12-hydroxystearic acid) of Comparative Example 1. Since the wear of the solid core at room temperature has been reduced, it becomes a very fine writing line (writing density).

Comparative Example 4 is a dehydrated condensate of the impregnation component (12-hydroxystearic acid) of Comparative Example 3. It is a substance without unsaturated bonds of the compound represented by the above general formula (Chemical 1). However, it is inferred that the interaction between molecules is greater than that of the compound represented by the above general formula (Chemical 1) whose molecular motion is restricted by the cis unsaturated bonds in the molecule because the molecules are easily accessible. Therefore, the core wear during writing is prevented, and the writing concentration is reduced.

Comparative Example 5 is a case where purified castor oil (ricinoleic acid triglyceride) which is the raw material of the compound represented by the above general formula (Chemical 1) is used. It is inferred that because the ester bond in the molecule is localized, the lubrication effect is lower than that of the compound represented by the above general formula (Chemical 1), which hinders the wear of the core and reduces the writing concentration.

Comparative Example 6 is a pencil core that uses a saturated hydrocarbon impregnation component with high dynamic viscosity (impregnation component described in Patent Document 1) and is adjusted to the same viscosity as Example 3. The impregnation component of Comparative Example 6 has a linear region (shear strain 0.1%~100%) in the dynamic viscoelasticity measurement (frequency 1Hz, measurement temperature 25℃) of a rheometer (Modular compact rheometer MCR302 (manufactured by Anton-Paar Japan (Co., Ltd.)). Even if the viscosity is the same as that of Example 3, it is compared with the impregnation component that behaves like a Newtonian fluid without a linear region. It is inferred that the impregnation component will hinder the wear of the core during writing, so it is inferred that the writing concentration is reduced.

Comparative Example 7 is a pencil refill that uses a highly polar fatty acid ester as an impregnation component (the impregnation component described in Patent Document 2). In addition to reducing the writing density, the carbon chain and highly polar impregnation component will corrode the acrylonitrile-styrene copolymer of the replacement refill container and cause cracks.

Next, the test results (evaluation results) of pencil refills (Examples 7 to 12 and Comparative Examples 8 to 14) in which the impregnation components are impregnated in the fired core B are shown in Table 2.

The results in Table 2 above also show that the pencil refills of Examples 7 to 12 have thicker handwriting and less dirt on the paper surface than the pencil refills of Comparative Examples 8 to 14. Even if this is changed to a sintered core body (sintered core body A and sintered core body B) impregnated with the compound represented by the general formula (Chemical 1), if the impregnated component is the compound represented by the general formula (Chemical 1), even if the wear amount of the pencil refill is different, a pencil refill with thicker handwriting and less dirt on the paper surface can still be obtained.

As described above, by using the pencil refills of Examples 1 to 12, compared with the case of using the pencil refills of Comparative Examples 1 to 14, a thick writing line (thick writing density) can be obtained, and the movement of abrasive powder when rubbing across the writing line can be suppressed, and a pencil refill with less dirt on the paper surface can be obtained.

Furthermore, in Examples 1 to 12, the impregnated components will not corrode the replacement refill container to generate cracks, and will not generate condensation in the replacement refill container due to moisture absorption, so it will not hinder the basic function of taking the lead refill out of the replacement refill container.

Claims (1)

A pencil core, characterized in that a core containing at least a coloring component and an organic binder is subjected to heat treatment, and the pores of the sintered core obtained have an impregnation component containing a compound represented by the following general formula (1)