CN112513206B

CN112513206B - Pencil lead

Info

Publication number: CN112513206B
Application number: CN201980050159.5A
Authority: CN
Inventors: 三浦隆博
Original assignee: Pentel Co Ltd
Current assignee: Pentel Co Ltd
Priority date: 2018-08-17
Filing date: 2019-07-30
Publication date: 2023-02-17
Anticipated expiration: 2039-07-30
Also published as: CA3106090A1; TW202014484A; JP7306398B2; CN112513206A; JPWO2020036059A1; DE112019004140T5; WO2020036059A1

Abstract

A fired core obtained by heat-treating a core containing at least a coloring component and an organic binder is impregnated with a compound represented by the following general formula (chemical formula 1). HO-R _n ‑H(n≥2)

Description

Pencil lead

Technical Field

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

Background

Generally, the pencil lead uses a coloring component such as graphite or boron nitride, and an extender (body) such as talc

Materials) and organic binders such as vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, vinyl chloride resin, vinyl alcohol resin, acrylic amide resin, chlorinated paraffin, phenol resin, furan resin, urea resin, carboxymethyl cellulose, nitrocellulose, butyl rubber, or inorganic binders such as clay, and these materials are dispersed, mixed, kneaded, and molded into a fine wire form using plasticizers such as phthalate, solvents such as methyl ethyl ketone, acetone, and water, stabilizers such as stearate, lubricants such as stearic acid, and fillers (fillers) such as carbon black, if necessary, and then subjected to heat treatment to a suitable firing temperature. It is considered that the core after firing (fired core) has many pores which are relatively large and uniform as a whole because the pores are formed in a portion where decomposed substances such as an organic binder, an inorganic binder, a plasticizer, and a solvent exist, and the compounding material is highly dispersed during kneading and molding. A pencil lead that is generally sold is manufactured by: the pores are impregnated with an oily substance such as silicone oil, liquid paraffin, spindle oil, squalane, an α -olefin oligomer, paraffin wax, microcrystalline wax, montan wax, carnauba wax, or the like, mainly for the purpose of improving the writing feeling.

However, the pencil lead forms a transfer adhesive film (transfer film) on the paper surface by adhesive abrasion due to sliding friction with the paper, and becomes a writing line. However, since the writing line is only applied to the paper surface by the abrasion powder containing the coloring component such as graphite generated by the adhesive abrasion, the coloring component such as graphite is easily moved and contaminates the paper surface when rubbed by other paper, hands, or the like.

In recent years, students who are main users of pencil leads tend to prefer pencil leads having a softer hardness and a strong writing density due to a decrease in writing pressure. However, in the case of a pencil lead having a soft hardness and a strong concentration of handwriting, there is a correlation between the paper surface contamination and the hardness and/or concentration, which is said to increase even if the pencil lead is rubbed over the writing line, and the paper surface contamination is small.

As a method for reducing contamination by suppressing movement of graphite or the like due to rubbing, there are mainly known: measures to improve the fixing property of the abrasion powder to the paper surface by an impregnation component such as an oily substance impregnated in the pencil lead. In patent document 1, the fixation of the writing line made of the abrasion powder is physically improved by using an impregnation component having a high dynamic viscosity. In patent document 2, a fatty acid ester having polarity is used as the impregnation component, and the fixation of the writing line is improved by chemical bonding between the impregnation component and the paper surface functional group.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-213391 (claims, examples)

Patent document 2: japanese patent laid-open No. 2007-31589 (claims, examples)

Disclosure of Invention

Problems to be solved by the invention

However, although the impregnation component having a high dynamic viscosity shown in patent document 1 improves the fixability of the writing lines, the erasing property of the eraser is deteriorated, the core is not easily worn, and the concentration of the writing lines is reduced as compared with the case where a low dynamic viscosity impregnation component such as ordinary liquid paraffin or silicone oil is used as the impregnation component of the pencil lead. Further, a core having a high concentration of writing lines can be obtained by making the core soft due to high abrasion, but in general, a soft pencil lead has a low bending strength and has another problem that it is easily broken during writing. On the other hand, the fatty acid ester having a large polarity and a small molecular weight shown in patent document 2 chemically reacts with a synthetic resin for replacing a lead container, a lead groove of a mechanical pencil, or the like, and cracks or fractures are generated.

Further, if the IOB value of the impregnated component is large, the impregnated component may absorb moisture, obscure the container during storage, and cause a failure in the case, and therefore, further improvement is required as a product. Here, the IOB value is a value obtained by dividing an inorganic value by an organic value, a total of values specified by specific groups in a chemical structure is defined as an inorganic value, a number of carbons in the chemical structure is multiplied by 20, and a value obtained by subtracting a value specified when a specific branch is present is defined as an organic value, for example, an inorganic value of a carboxyl group as an inorganic group is defined as 150 for every 1 carboxyl group, and a value of an organic value is defined as 20 for every 1 carbon group. This IOB value indicates an index of the strength of polarity within a molecule, and is a criterion for determining hydrophilicity or lipophilicity because IOB value × 10 is close to HLB value.

Several embodiments of the present invention are directed to provide a pencil lead that can obtain a thick writing line, suppress the movement of abrasion powder when the writing line is rubbed, reduce the contamination of a paper surface, and have high reliability.

Means for solving the problems

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

[ chemical formula 1]

ADVANTAGEOUS EFFECTS OF INVENTION

The compound represented by the general formula (chemical formula 1) is a non-drying oil which is liquid at room temperature from 5 to 35 ℃ (JIS Z8703) because the carbon chain of the main chain contains an unsaturated bond, and is easily impregnated into the pores of the fired core, and is bonded thereto via an ester bond having polarity, and therefore is also easily adsorbed on the solid surface of the graphite particles or the surface of the resin carbide having a plurality of reactive functional groups such as hydroxyl groups, carboxyl groups, and dangling bonds of carbon, which are generated by decomposition and re-bonding of the resin during heat treatment. Therefore, by using the impregnation component containing the compound, the compound represented by the general formula (chemical formula 1) exists between the particles as a lubricating film, and adhesion and abrasion of the core are promoted, so that a thick writing line can be obtained.

It is also assumed that the compound represented by the above general formula (chemical formula 1) present on the surface of the abrasion powder serving as a writing line has an ester of the main chain, a double bond portion, and a portion exhibiting polarity of the terminal hydroxyl group and carboxyl group, and a polar component of cellulose or the like of paper, and that the carbon chain serving as a side chain in the compound represented by the above general formula (chemical formula 1) is efficiently adsorbed by an anchor effect on the rough surface of the abrasion powder, so that the abrasion powder is firmly bonded to the paper surface, and the abrasion powder is hard to move even if rubbed over.

Detailed Description

Several embodiments of the present invention are described in detail below.

The compound represented by the general formula (chemical formula 1) used in some embodiments of the present invention is a dehydration condensate of ricinoleic acid (also referred to as a dehydration condensate of ricinoleic acid or a dehydration condensate of 12-hydroxy-9-cis-octadecenoic acid) obtained by hydrolyzing and further condensing purified castor oil as a raw material. In addition, in recent years, a compound represented by the general formula (formula 1) (a dehydrated condensate of ricinoleic acid) shown above (chemical formula 1) can also be obtained by condensing ricinoleic acid produced by Fuze et al (non-patent document: 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-conjugated monoacylglycerol in an oleaginous dialom, chaetoceros gracilis, scientific rays (2016), 6 36809 [ 10: 2016 ]) successfully used by Chaetomium et al (Nostoc).

As the commercial products of the compounds represented by the above general formula (chemical formula 1), there are ricinoleic acid dehydration condensates such as K-PON 402, K-PON 403-S, K-PON 404-S, K-PON 405-S, K-PON 406-S and MINERASOL PCF series (manufactured by Ivy oil, ltd.), PCF-90, PCF-45 and PCF-30 of K-PON 400 series (manufactured by SMALL SYNTHESIS INDUSTRIAL Co., ltd.).

The compound represented by the above general formula (chemical formula 1) is particularly preferable because the viscosity of the 2-mer to 6-mer (degree of condensation is in terms of acid value) is from 400mPa · s to 1800mPa · s (25 ℃) and the viscosity is relatively high as an impregnation component of the pencil lead, and it is believed that the physical abrasion powder movement-inhibiting effect is also exhibited and the impregnation of the fired core body is relatively easy, and the chemical stability with time of the 6-mer compound against oxidation and the like is also relatively high. In the case of the above-mentioned compound having a more than 6-mer, the fired core is impregnated by a technique such as impregnation under pressure at high temperature and high pressure, which is a known technique, whereby the effects of the embodiment of the present invention can be obtained.

The compound represented by the above general formula (chemical formula 1) may be used alone, but may be used in combination with other components. Examples of the oligomer include conventionally known α -olefin oligomers and liquid paraffin. The concentration of the compound represented by the general formula (chemical formula 1) in the impregnated component is preferably 50% by weight or more relative to the total amount of the impregnated component. The impregnation amount (impregnation rate) of the impregnation component containing the compound represented by the general formula (chemical formula 1) is preferably 10% by weight or more and 30% by weight or less based on the total weight of the pencil lead. If the amount is less than 10% by weight, the amount of the impregnated component adsorbed on the surface of the resin carbide or the like in the fired core is reduced, and as a result, the effect as a lubricant film is reduced, and the adhesive wear of the core is suppressed, so that thick writing cannot be obtained. If the content exceeds 30% by weight, the impregnated component in the fired core becomes large, the writing lines are not easily eliminated, and the impregnated component penetrates the paper surface, which tends to cause smearing of the back surface of the writing lines.

The fired core impregnated with the impregnation component may be used in combination with conventionally known coloring components, extenders, organic binders, plasticizers, solvents, lubricants, stabilizers, fillers, and the like as other compounding ingredients. These can be used in 1 or can also be mixed use of 2 or more.

Examples of the coloring component include graphite such as flake graphite, soil graphite, and artificial graphite, and inorganic particles such as boron nitride and synthetic mica. Examples of the extender include talc, carbon nanotubes, carbon fibers, and fibrous potassium titanate. Examples of the organic binder include synthetic resins such as polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated paraffin, furan resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, urea resin, melamine resin, polyester, styrene-butadiene copolymer, polyvinyl acetate, polyacrylamide, butyl rubber, and natural resins such as lignin, cellulose, tragacanth, and gum arabic. Examples of the plasticizer include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diallyl isophthalate, tricresyl phosphate, and dioctyl adipate. Examples of the solvent include ketones such as methyl ethyl ketone and acetone, alcohols such as ethanol, and water. Examples of the lubricant include fatty acids such as stearic acid and behenic acid, fatty acid amides, stearic acid, and the like. Examples of the stabilizer include stearates, organotin compounds, barium-zinc compounds, and calcium-zinc compounds. Examples of the filler include metals such as iron, aluminum, titanium, and zinc, alloys thereof, oxides or metal nitrides of these metals or alloys, silica (silicon dioxide), carbon black, and fullerenes. As the filler, those having a spherical shape, an amorphous granular shape, a needle shape, a fiber shape, a plate shape, or the like can be suitably used.

These compounding ingredients can be uniformly dispersed by a kneader, henschel mixer, 3 rolls or the like, molded into a fine strand, subjected to heat treatment as appropriate depending on the resin to be used, and finally subjected to a treatment other than kneadingThe core body is obtained by sintering at 800 to 1300 ℃ in an oxidizing atmosphere. Pore volume of 0.05cm ³ /g～0.25cm ³ The impregnation rate per gram is desirably high. 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 fired core with the impregnated component, a method of impregnating the fired core with a heated impregnated component and impregnating the fired core with the impregnated component can be employed. The impregnation speed can be increased by stirring the impregnated components or by applying a pressure treatment. The impregnation speed can be accelerated even if the viscosity of the impregnated component is reduced by heating at a higher temperature, but since there is a tendency that the deterioration of the impregnated component is accelerated by thermal oxidation of the impregnated component or hydrolysis by moisture in the air, a means such as isolating the air or moisture from the impregnated component and using the isolated air or moisture is necessary. The fired core impregnated with the impregnated component can be used to remove excess impregnated component from the surface of the core by a centrifugal separator or the like to form a pencil lead.

The gist of some embodiments of the present invention is a pencil lead characterized in that an impregnated component containing a compound represented by the general formula (chemical formula 1) is contained in pores of a fired core obtained by heat-treating a core containing at least a coloring component and an organic binder. Here, the "fired core" is a core obtained through a heat treatment called "firing", and in general, if a composition containing an organic substance (organic binder) such as a synthetic resin or a natural resin is heat-treated to a firing temperature, decomposition or condensation of the organic substance is irregularly caused in a state where resin molecules are complicatedly mixed with coloring components such as graphite, and the entire core is complicatedly shrunk in volume, so that the skeleton structure of the core (fired core) after the heat treatment has a very complicated structure of fine parts, and the degree of bonding or the size of each composition after the heat treatment is also varied, and it is considered that systematic measurement and analysis which are advantageous in relation to the above-mentioned effects are performed, and it is impossible or completely impractical to directly identify the substance by its structure or characteristics, for example, by performing experiments of unrealistic times.

As the mechanical pencil body in the case of using the pencil lead according to the several embodiments of the present invention, various conventionally known mechanical pencils can be used. For example, as disclosed in japanese patent application laid-open No. 8-282182, a so-called tunnel slide type mechanical pencil, which prevents breakage of a lead during writing, such as when the lead is worn and the tip surface of a tip member is retracted in a state of being wiped by a paper surface, effectively protects a 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, thereby further improving the fixing property of the abrasion powder to the paper surface. In the case of the tunnel slide type mechanical pencil, it is more preferable to apply a means for selecting the shape and material of the tip member (stainless steel tube) to be in contact with the paper and for allowing the abrasion powder of the core to easily adhere to the tip member in the manner disclosed in japanese patent laid-open No. 2015-104882. Further, in the case of using a mechanical pencil which can write in a state where the tip member is in contact with the paper surface and can continuously write as disclosed in japanese patent application laid-open No. 2018-1685, the mechanical pencil is most suitable as a mechanical pencil using the pencil lead according to some embodiments of the present invention because the lead can be prevented from being broken by an impact at the time of pressing.

Examples

The present invention will be described below based on examples, but the present invention is not limited to the examples. The average particle diameter of graphite in the compounding material was measured by a laser diffraction particle size distribution measuring apparatus SALD-7000 (manufactured by Shimadzu corporation). The pore volume of the sintered core was obtained by calculating the adsorption side data of the nitrogen adsorption isotherm obtained by a constant volume gas adsorption method, a specific surface area/pore distribution measuring apparatus BELSORP-miniII (manufactured by Microtrac-bel Co., ltd.) and using nitrogen as an adsorption gas by the BJH method. The IOB value of the impregnation component is a calculated value according to the molecular formula. The viscosity is a value of 1/s of shear rate measured using a rheometer of a Modular compact rheometer MCR302 (manufactured by Anton-Paar Japan, inc.) using a cone plate having a measurement temperature of 25 ℃ and a geometry of 1 °/Φ 50 mm. The impregnation rate is (Y-X)/Y when the weight of the fired core before impregnation is X and the weight of the pencil core after impregnation is Y, which are determined as percentages (% by weight).

(preparation of fired core A)

The above materials were subjected to dispersion mixing treatment by a Henschel mixer, subjected to mixing treatment by 3 rolls, extruded into a fine strand by a single-screw extruder, heated from room temperature to 350 ℃ in air for about 10 hours, subjected to heating treatment for keeping at 350 ℃ for about 1 hour, and further subjected to firing treatment at 1100 ℃ at the maximum in a closed vessel to obtain a fired core A having an actual diameter of 0.57 mm. Pore volume of 0.18cm ³ /g。

(preparation of fired core B)

The above materials were subjected to dispersion mixing treatment by a Henschel mixer, subjected to mixing treatment by 3 rolls, extruded into a fine strand by a single-screw extruder, heated from room temperature to 350 ℃ in air for about 10 hours, subjected to heating treatment for keeping at 350 ℃ for about 1 hour, and further subjected to firing treatment at 1100 ℃ at the maximum in a closed vessel to obtain a fired core B having an actual size diameter of 0.57 mm. Pore volume of 0.13cm ³ /g。

< example 1>

The fired core a was impregnated with an impregnated component (K-PON 402, a dehydration condensation product of a compound represented by the general formula (chemical formula 1) (n = 2), ricinoleic acid, viscosity 520mPa · s, IOB value =0.45, manufactured by mini-synthesis industries, ltd.) heated at 120 ℃ for 16 hours, and then an excess impregnated component on the surface was removed by a centrifugal separator, thereby obtaining a pencil lead. The impregnation rate of the impregnated component was 16.5 wt%.

< example 2>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and K-PON 404-S (a compound represented by the general formula (chemical formula 1) (n = 4), a dehydrated condensate of ricinoleic acid, manufactured by mini-synthesis industries, IOB value =0.31, and viscosity 1068mPa · S) was used. The impregnation rate of the impregnated component was 16.7 wt%.

< example 3>

A pencil lead was obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and that K-PON 406-S (a compound represented by the general formula (chemical formula 1) (n = 6), a dehydrated condensate of ricinoleic acid, manufactured by mini-house synthesis industries, ltd., IOB value =0.27, and viscosity 1589mPa · S) was used. The impregnation rate of the impregnation component was 16.2 wt%.

< example 4>

A pencil lead was obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and PCF-90 (a compound represented by the above general formula (chemical formula 1) (n = 2), a dehydrated condensate of ricinoleic acid, manufactured by itai-kao oil corporation, IOB value =0.45, and viscosity 580mPa · s) was used. The impregnation rate of the impregnated component was 16.2 wt%.

< example 5>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and PCF-45 (a compound represented by the general formula (chemical formula 1) (n = 4), a dehydrated condensate of ricinoleic acid, manufactured by itao corporation, IOB value =0.31, and viscosity 1162mPa · s) was used. The impregnation rate of the impregnation component was 16.5 wt%.

< example 6>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and PCF-30 (a compound represented by the above general formula (chemical formula 1) (n = 6), a dehydrated condensate of ricinoleic acid, manufactured by itao corporation, IOB value =0.27, and viscosity 1782mPa · s) was used. The impregnation rate of the impregnation component was 16.5 wt%.

< example 7>

The impregnated component (K-PON 402 (described above)) heated at 150 ℃ was impregnated into the fired core B under pressure at 2MPa for 16 hours, and then placed in a centrifuge to remove the excess impregnated component on the surface, thereby obtaining a pencil lead. The impregnation rate of the impregnated component was 14.0 wt%.

< example 8>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and K-PON 404-S (described above) was used. The impregnation rate of the impregnation component was 13.8 wt%.

< example 9>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and that K-PON 406-S (as described above) was used. The impregnation rate of the impregnated component was 13.5 wt%.

< example 10>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and PCF-90 (described above) was used. The impregnation rate of the impregnated component was 14.2 wt%.

< example 11>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and PCF-45 (described above) was used. The impregnation rate of the impregnated component was 13.5 wt%.

< example 12>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and PCF-30 (as described above) was used. The impregnation rate of the impregnated component was 13.3 wt%.

< comparative example 1>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and ricinoleic acid (a substance before condensation of the compound represented by the general formula (chemical formula 1) (n = 1), manufactured by wako pure chemical industries, ltd., IOB value =0.72, and viscosity 342mPa · s) was used. The impregnation rate of the impregnation component was 17.6 wt%.

< comparative example 2>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation composition in example 1 was changed to K-PON 402 and K-PON 406-G (glycerol ester of condensed castor oil fatty acid, manufactured by mini-silo synthesis industry, IOB value =0.29 and viscosity 1574mPa · s) was used. The impregnation rate of the impregnation component was 18.3 wt%.

< comparative example 3>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation component in example 1 was changed to K-PON 402, and 12-hydrogen acid (12-hydroxystearic acid, manufactured by mini synthetic industry, IOB value =0.71, room temperature solid (melting point 77 ℃)) dissolved by heating was used. The impregnation rate of the impregnated component was 16.7 wt%.

< comparative example 4>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation composition in example 1 was changed to K-PON 402 and that K-PON 306 (12-hydroxyoctadecanoic acid polycondensate, manufactured by kokusan synthesis industries, IOB value =0.26, viscosity 3006mPa · s) was used. The impregnation rate of the impregnation component was 16.5 wt%.

< comparative example 5>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation composition in example 1 was changed to K-PON 402 and castor oil Special Maru a (ricinoleic acid triglyceride, manufactured by itao oil corporation, IOB value =0.43, viscosity 696mPa · s) was used. The impregnation rate of the impregnated component was 17.2 wt%.

< comparative example 6>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation composition in example 1 was changed to K-PON 402, a mixture obtained by mixing talc polybutene SV-7000 (polybutene, manufactured by JXTG energy corporation) and SYNCELANE4SP (α -olefin oligomer, manufactured by heliochemistry corporation) at a weight ratio of 1: 1 was used, the IOB value =0, and the viscosity was 1430mPa · s. The impregnation rate of the impregnated component was 15.7 wt%.

< comparative example 7>

Pencil leads were obtained in the same manner as in example 1, except that the impregnation composition in example 1 was changed to K-PON 402 and NIKKOL Sefsol-218 (propylene glycol monooctylate, manufactured by heliochemistry, IOB value =0.73, viscosity 12.5mPa · s) was used. The impregnation rate of the impregnation component was 16.5 wt%.

< comparative example 8>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation component in example 7 was changed to K-PON 402 and ricinoleic acid (as described above) was used. The impregnation rate of the impregnation component was 15.0 wt%.

< comparative example 9>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and that K-PON 406-G (described above) was used. The impregnation rate of the impregnated component was 14.8 wt%.

< comparative example 10>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation component in example 7 was changed to K-PON 402 and that 12-hydrogen acid dissolved by heating (as described above) was used. The impregnation rate of the impregnated component was 12.8 wt%.

< comparative example 11>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and that K-PON 306 (as described above) was used. The impregnation rate of the impregnated component was 11.7 wt%.

< comparative example 12>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and castor oil Special Maru a (described above) was used. The impregnation rate of the impregnated component was 13.0 wt%.

< comparative example 13>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and that a mixture (as described above) obtained by mixing talc polybutene SV-7000 (as described above) and syncianane 4SP (as described above) in a weight ratio of 1: 1 was used. The impregnation rate of the impregnated component was 10.9 wt%.

< comparative example 14>

Pencil leads were obtained in the same manner as in example 7, except that the impregnation composition in example 7 was changed to K-PON 402 and NIKKOL Sefsol-218 (described above) was used. The impregnation rate of the impregnated component was 12.7 wt%.

The pencil leads obtained in examples 1 to 12 and comparative examples 1 to 14 were measured for writing density and fixability to rubbing by the following method, and tested for reliability.

(test method of writing Density)

The writing density test was carried out in accordance with JIS S6005.

(test method for fixation of rub-off (contamination degree of difficulty))

With respect to the fixation to rubbing, a percentage ((A-B)/A) was determined, where A represents the density of a written portion drawn in a writing density test, B represents the density of a stain portion other than the written portion, and A represents the density of the stain portion except the written portion when the written portion was rubbed with a Tissue paper (Tissue paper) under a vertical 500g load under a constant condition repeated 10 times. The larger the value, the better the fixability to the rubbed writing line, and it can be said that contamination is difficult.

(method of testing reactivity with resin Container)

Reactivity test with resin container, 40 pencil leads obtained in examples 1 to 12 and comparative examples 1 to 14 were placed in a refill container (STEIN refill container, pentel (manufactured by Ltd)) made of acrylonitrile-styrene copolymer (AS resin), placed on a stainless steel plate, allowed to stand in a thermostatic bath adjusted to 60 ℃ for 16 hours, taken out, allowed to stand at room temperature for 1 hour, allowed to stand in a thermostatic bath adjusted to-30 ℃ for 16 hours, and a cooling-heating cycle test was repeated 2 times, and then the change of the refill container was evaluated visually.

The test results (evaluation results) of the pencil leads (examples 1 to 6 and comparative examples 1 to 7) in which the fired core a was impregnated with the impregnation component are shown in table 1.

[ Table 1]

As is clear from the results of table 1 above, the pencil leads of examples 1 to 6 are pencil leads that can obtain a thicker trace and less contamination of the paper surface than the pencil leads of comparative examples 1 to 7.

Although the compounds represented by the above general formula (chemical formula 1) used as the impregnation components in examples 1 to 3 have different degrees of condensation (2-mer in example 1, 4-mer in example 2, and 6-mer in example 3), the higher the degree of condensation, the higher the molecular weight, and the higher the viscosity, but if the impregnation components are the compounds represented by the above general formula (chemical formula 1), the viscosity and IOB value are not affected, the writing density is not reduced, and the paper surface is less contaminated.

In example 4, although the viscosity was slightly increased by using an impregnation component of a manufacturing company different from that of example 1, the writing density was not decreased and the paper surface was less contaminated if the impregnation component was a compound represented by the general formula (chemical formula 1).

In example 5, although the viscosity was slightly increased by using an impregnation component of a manufacturing company different from that of example 2, the writing density was not decreased and the paper surface was less contaminated if the impregnation component was a compound represented by the general formula (chemical formula 1).

In example 6, although the viscosity was slightly increased by using an impregnation component of a manufacturing company different from that of example 3, the writing density was not decreased and the paper surface was less contaminated by the compound represented by the general formula (chemical formula 1).

Although the writing densities of comparative examples 1 and 2 were thicker than those of examples 1 to 6, the paper surface was more contaminated (the fixation rate was lower). On the other hand, in comparative examples 3 to 7, the paper surface was stained more and the writing density was also reduced, and the above problem could not be solved.

Comparative example 1 the impregnating component was ricinoleic acid, and the compound represented by the general formula (chemical formula 1) was not condensed (n = 1), but the IOB value was high, and the binding with graphite as the coloring component was weak, and therefore it was estimated that the contamination of the paper surface was not reduced. Further, ricinoleic acid readily absorbs moisture in the atmosphere, and therefore moisture absorbed in a reactivity test with a resin container is condensed in a refill container, with the result that the refill is not easily taken out of the cartridge.

Comparative example 2 the impregnation component was obtained by replacing the carboxyl group at the end of the 6-mer of the compound represented by the general formula (chemical formula 1) with a glycerin ester modified with a glycerin group, but it was presumed that the interaction with the functional group on the paper surface was insufficient and the contamination of the paper surface was not reduced because no carboxyl group having a large polarity was present.

Comparative example 3 the impregnated component (12-hydroxystearic acid) was a saturated fatty acid having no unsaturated bond in the impregnated component (ricinoleic acid) of comparative example 1, and the abrasion of the core of the room temperature solid was reduced, resulting in a very light writing line (writing density).

Comparative example 4 the dehydration-condensed product of the impregnation component (12-hydroxystearic acid) of comparative example 3 does not have an unsaturated bond of the compound represented by the above general formula (chemical formula 1), but is easily accessible between molecules, and the intermolecular interaction is larger than that of the compound represented by the above general formula (chemical formula 1) in which the molecular movement is restricted by a cis-unsaturated bond in a molecule, and therefore, it is estimated that the core abrasion at the time of writing is inhibited and the writing density is lowered.

Comparative example 5 uses purified castor oil (ricinoleic acid triglyceride) as a raw material of the compound represented by the above general formula (chemical formula 1), but since the ester bond is unevenly present in the molecule, it is presumed that the lubricating effect is lower than that of the compound represented by the above general formula (chemical formula 1), the abrasion of the core is inhibited, and the writing density is lowered.

Comparative example 6 is a pencil lead used by adjusting a saturated hydrocarbon-based impregnated component having a high dynamic viscosity (impregnated component described in patent document 1) to a viscosity equivalent to that of example 3. In the impregnated composition of comparative example 6, a linear region (shear strain 0.1% to 100%) was present in the dynamic viscoelasticity measurement (frequency 1Hz, measurement temperature 25 ℃) of a rheometer (Modular compact rheometer mcr302 (manufactured by Anton-Paar Japan), and even if the composition had the same viscosity as in example 3, the impregnated composition inhibited the abrasion of the core during writing as compared with the impregnated composition showing the behavior of a newtonian fluid without a linear region, and thus the writing density was estimated to be lowered.

In comparative example 7, a pencil lead was used in which a highly polar fatty acid ester (impregnation component described in patent document 2) was used as the impregnation component, but the writing density was reduced, and in addition, the impregnation component having a small carbon chain and a high polarity corroded the acrylonitrile-styrene copolymer in the refill container, and caused cracks.

Next, the test results (evaluation results) of the pencil leads (examples 7 to 12 and comparative examples 8 to 14) obtained by impregnating the fired core B with the impregnation component are shown in table 2.

[ Table 2]

The results of table 2 above also show that the pencil leads of examples 7 to 12 give pencil leads with thicker pencil lines and less paper surface contamination than the pencil leads of comparative examples 8 to 14. In this way, even if the fired cores (fired core a and fired core B) impregnated with the compound represented by the above general formula (chemical formula 1) are changed, if the impregnated component is the compound represented by the above general formula (chemical formula 1), pencil leads having thick traces and less contamination of the paper surface can be obtained even if the wear amounts of the pencil leads are different.

As described above in detail, by using the pencil leads of examples 1 to 12, pencil leads having a thick writing line (thick writing density) and reduced migration of abrasion powder when the writing line is rubbed and having less contamination on the paper surface can be obtained as compared with the case of using the pencil leads of comparative examples 1 to 14.

Further, the impregnation ingredients of examples 1 to 12 did not corrode the refill container, did not cause cracks, did not absorb moisture, and did not cause dew condensation in the refill container, and thus did not hinder the basic function of taking out the pencil lead from the refill container.

Claims

1. A pencil lead characterized by having an impregnated component containing a compound represented by the following general formula in pores of a fired core obtained by heat-treating a core containing at least a coloring component and an organic binder

HO-R _n -H(n≥2)