CA3106090A1

CA3106090A1 - Pencil lead

Info

Publication number: CA3106090A1
Application number: CA3106090A
Authority: CA
Inventors: Takahiro Miura
Original assignee: Pentel Co Ltd
Current assignee: Pentel Co Ltd
Priority date: 2018-08-17
Filing date: 2019-07-30
Publication date: 2020-02-20
Also published as: JP7306398B2; CN112513206B; WO2020036059A1; TW202014484A; DE112019004140T5; JPWO2020036059A1; CN112513206A

Abstract

A pencil lead includes: a fired lead body obtained by subjecting a lead body containing at least a pigment component and an organic binder to a heat treatment; and an impregnating component, in pores of the fired lead body, containing a compound represented by the following general formula (1):

Description

PENCIL LEAD
TECHNICAL FIELD
[0001] The present disclosure relates to a pencil lead including a fired lead body containing at least a pigment component and an organic binder subjected to a heat treatment and an impregnating component in pores of the fired lead body.
BACKGROUND

[0002] Generally, a pencil lead includes a pigment component such as graphite or boron nitride, an extender such as talc, an organic binder such as vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, chlorinated ethylene resin, vinyl alcohol resin, acrylamide resin, chlorinated paraffin, phenolic resin, furan resin, urea resin, carboxymethyl cellulose, nitrocellulose, or butyl rubber, and an inorganic binder such as clay as main components, and optionally includes a plasticizer such as phthalic acid ester, a solvent such as methyl ethyl ketone, acetone, or water, a stabilizer such as stearate, a lubricant such as stearic acid, and a filler such as carbon black. These raw materials are dispersed and mixed, kneaded, formed into a thin rod shape, and then heated to a firing temperature as appropriate. In the lead body after firing (fired lead body), since portions where decomposition products of the organic binder, inorganic binder, plasticizer, and solvent exist become pores, and the compounding materials are highly dispersed during kneading, the fired lead body has numerous pores of a relatively uniform size throughout.
Generally, commercially available pencil leads are manufactured by impregnating the pores with oil such as silicone oil, liquid paraffin, spindle oil, squalane, a-olefin oligomer, paraffin wax, microcrystalline wax, montan wax, or carnauba wax, mainly for the purpose of improving the writability.

[0003] The pencil lead is worn by sliding friction with paper and forms a transfer film on the paper surface as a written line. However, since the written line is merely abrasion powder Date Recue/Date Received 2021-01-08 containing a pigment component such as graphite placed on the paper due to the adhesive wear, when it is rubbed with another paper or hand, the pigment component such as graphite easily moves and stains the paper surface.

[0004] In addition, in recent years, students who are the main users of pencil leads are more likely to prefer a softer and darker pencil lead due to a decrease in writing pressure. However, in the softer and darker pencil lead, there is a correlation between the paper stain and the hardness and/or darkness which increases the degree of paper stain caused by rubbing.
It is thus desired to develop a pencil lead that does not stain the paper surface even when the written line is rubbed.

[0005] The widely known method for suppressing the movement of graphite or the like due to rubbing to reduce stain is to impregnate the pencil lead with an impregnating component such as oil for improving the fixity of the abrasion powder on the paper surface.
In Patent Document 1, the fixity of the written line composed of the abrasion powder is physically improved by using an impregnating component having a high kinematic viscosity. In Patent Document 2, by using a polar fatty acid ester as the impregnating component, the fixity of the written line is improved by the chemical bond between the impregnating component and a functional group on the paper surface.
Citation List Patent Literature

[0006] Patent Document 1: JP2005-213391A (Claims and Examples) Patent Document 2: JP2007-31589A (Claims and Examples) SUMMARY
Problems to be Solved

[0007] However, the impregnating component having a high kinematic viscosity disclosed in Patent Document 1 improves the fixity of a written line, but degrades the erasability by an eraser Date Recue/Date Received 2021-01-08 and makes the lead body difficult to wear, so that the darkness of the written line is decreased compared with the case where a low kinematic viscosity impregnating component, such as general liquid paraffin or silicone oil, is used as the impregnating component of the pencil lead.
The darkness of the written line can be increased by making the lead body softer and easier to wear down, but the soft pencil lead generally has low bending strength and easy to break during writing. On the other hand, the fatty acid ester having a large polarity and a small molecular weight as disclosed in Patent Document 2 chemically reacts with a synthetic resin used in a refill lead case or a lead tank of a mechanical pencil, causing cracks or scratches.

[0008] Further, when the JOB value of the impregnating component is large, the impregnating component absorbs moisture and clouds the inside of the casing during storage, which may cause malfunction in the casing. Therefore, further improvement of the product is required. Here, the JOB value is a value obtained by dividing an inorganic value by an organic value, where the inorganic value is the sum of values determined for a specific group in a chemical structure, and the organic value is a value obtained by multiplying the number of carbon atoms in the chemical structure by 20 and, if there is a specific branch, subtracting a determined value from the multiplied value. For example, the inorganic value of the carboxyl group, which is an inorganic group, is determined to be 150 for each carboxyl group, and the organic value is quantified as 20 per carbon. The JOB value serves as an index indicating the degree of polarity occupying the molecule. Further, since the JOB value x 10 is approximate to the HLB value, it can also be used as a guide for determining hydrophilicity and lipophilicity.

[0009] An object of some embodiments of the present invention is to provide a reliable pencil lead that can draw a dark written line and suppress the movement of the abrasion powder when the written line is rubbed to reduce the paper stain.
Solution to the Problems

[0010] That is, some embodiments of the present invention are directed to a pencil lead Date Recue/Date Received 2021-01-08 comprising: a fired lead body obtained by subjecting a lead body containing at least a pigment component and an organic binder to a heat treatment; and an impregnating component, in pores of the fired lead body, containing a compound represented by the following general formula (1).

[0011] [Chemical formula 1]
HO ¨R H (n 2) R: HE oc WHO icH = CHCH2CHO
(C1-12) 5CH3 Advantageous Effects

[0012] Since the compound represented by the general formula (1) contains unsaturated bonds in the main carbon chain, the compound is a non-drying oil which is liquid at room temperature of 5 to 35 C (JIS Z 8703) and can be easily incorporated in pores of the fired lead body. In addition, since the units are coupled by polar ester bonds, it is easily adsorbed on a solid surface such as graphite particles and resin carbide surfaces having multiple reactive functional groups such as hydroxyl groups, carboxyl groups, and carbon dangling bonds generated by decomposition and recombination of resin at heat treatment. Thus, when the impregnating component containing this compound is used, the compound represented by the general formula (1) is placed between particles as a lubricating film and promotes adhesive wear of the lead body, so that a dark written line can be obtained.

[0013] Further, polar portions of the compound represented by the general formula (1) existing on the abrasion powder surface of the written line, such as the esters and the double bonds of the main chain and the hydroxyl group and the carboxyl group at the terminals, form hydrogen bonds with polar components of cellulose or the like of the paper, while the side carbon chains of the compound represented by the general formula (1) are efficiently adsorbed to the Date Recue/Date Received 2021-01-08 rough surface of the abrasion powder by the anchoring effect, so that the abrasion powder and the paper surface are firmly bonded, which may reduce the movement of the abrasion powder due to rubbing.
DETAILED DESCRIPTION

[0014] Embodiments of the present invention will now be described in detail.

[0015] The compound represented by the general 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 condensation of 12-hydroxy-9-cis-octadecenoic acid). In recent years, the compound represented by the general formula (1) (dehydration condensate of ricinoleic acid) can also be obtained by condensing ricinoleic acid produced using Chaetoceros gracilis as succeeded by Fukuzawa 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-containing monoestolide triacylglycerides in an oleaginous diatom, Chaetoceros gracilis, Scientific reports (2016), 6:36809, (Published: 10 November 2016)).

[0016] Examples of commercially available products of the compound represented by the general formula (1) include dehydration condensates of ricinoleic acid such as K-PON400 series:
K-P0N402, K-P0N403-S, K-P0N404-S, K-P0N405-S, and K-P0N406-S, (manufactured by Kokura Synthetic Industry Co., Ltd.), and MINERASOL PCF series: PCF-90, PCF-45, and PCF-(manufactured by Ito Oil Co., Ltd.).

[0017] The compound represented by the general formula (1) has a viscosity of dimer to hexamer (condensation degree is based on acid value) of 400 mPa-s to 1800 mPa-s (25 C), which is relatively viscous as the impregnating component of the pencil lead. It is thus expected to 25 have an effect of inhibiting the physical movement of the abrasion powder.
Further, the compound is relatively easy to impregnate the fired lead body. In particular, the hexamer is Date Recue/Date Received 2021-01-08 preferable since it has a relatively high temporal chemical stability to oxidation. The hexamer or higher oligomer can provide the effect of embodiments of the present invention when incorporated in the fired lead body with a known technique called pressure impregnation at high temperature and high pressure, for example.

[0018] The compound represented by the general formula (1) can be used alone, but may be used in combination with other components. Examples thereof include conventionally known a-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 based on the total amount of the impregnating component. Further, the impregnation amount (impregnation ratio) 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 based on the total weight of the pencil lead. When the amount is less than 10% by weight, the amount of the impregnating component adsorbed on the surface of the resin carbide or the like in the fired lead body decreases. As a result, the effect as a lubricating film is reduced, and the adhesive wear of the lead body is suppressed, so that a dark handwriting cannot be obtained.
When the amount is more than 30% by weight, the amount of the impregnating component in the fired lead body increases. As a result, the written line is difficult to erase, or the impregnating component permeates the paper surface, and the written line is likely to show through the paper.

[0019] The fired lead body impregnated with the impregnating component may be combined with other compounding materials such as conventionally known pigment components, extenders, organic binders, plasticizers, solvents, lubricants, stabilizers, and fillers.
These materials to be mixed may be one kind or a combination of two or more kinds.

[0020] Examples of the pigment component include graphite such as vein graphite, flake graphite, amorphous graphite, and synthetic graphite, and inorganic particles such as boron nitride and synthetic mica. Examples of the extender include talc, carbon nanotube, carbon fiber, and fibrous potassium titanate. Examples of the organic binder include synthetic resins such as Date Recue/Date Received 2021-01-08 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 copolymers, polyvinyl acetate, polyacrylamide, and butyl rubber, and natural resins such as lignin, cellulose, tragant gum, and arabic gum. 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, and stearic acid. Examples of the stabilizer include stearate, organotins, barium-zinc compounds, and calcium-zinc compounds. Examples of the filler include metals such as iron, aluminum, titanium, and zinc and alloys thereof, oxides of the metals and alloys, metal nitrides, silicon dioxide (silica), carbon black, and fullerene. The filler having a spherical shape, an amorphous granular shape, a needle shape, a fibrous shape, a plate shape, or other shapes can be used as appropriate.

[0021] These compounding materials are uniformly dispersed with a kneader, a Henschel mixer, three rolls or the like, then formed into a thin rod shape, subjected to a heat treatment appropriately according to the used resin, and finally fired at 800 C to 1300 C in a non-oxidizing atmosphere to obtain a fired lead body. When the pore volume of the fired lead body is 0.05 cm3/g to 0.25 cm3/g, a desired impregnation ratio can be obtained. The pore volume of the fired lead body can be measured by a known gas adsorption method or mercury intrusion method.

[0022] As a method of impregnating the fired lead body with the impregnating component, immersing the fired lead body in a heated impregnating component can be adopted. The impregnation rate can be increased by stirring and pressurizing the impregnating component.
The impregnation rate can also be increased by lowering the viscosity of the impregnating component by heating to a higher temperature, but in this case, the impregnating component tends to deteriorate faster due to thermal oxidation of the impregnating component or hydrolysis Date Recue/Date Received 2021-01-08 due to moisture in the air, so that it is necessary to take measures such as blocking the air and moisture. The fired lead body impregnated with the impregnating component may be centrifuged with a centrifugal separator to remove excess impregnating component on the surface of the lead body to obtain the pencil lead.
Some embodiments of the present invention are directed to a pencil lead including a fired lead body obtained by subjecting a lead body containing at least a pigment component and an organic binder to a heat treatment; and an impregnating component, in pores of the fired lead body, containing a compound represented by the general formula (1). Here, the "fired lead body" is obtained through a heat treatment called "firing". Generally, when a composition containing an organic substance (organic binder) such as synthetic resin or natural resin is heated to the firing temperature, the organic substance is irregularly decomposed and condensed while the resin molecules are intricately entangled with a pigment component such as graphite, so that the volume of the entire lead body shrinks in a complicated manner. As a result, the skeletal structure of the lead body after the heat treatment (fired lead body) becomes extremely complicated in fine parts, and the size and the degree of bonding of individual compositions after the heat treatment are varied. Accordingly, performing systematic measurement and analyze that are predominantly related to the above-described effect requires unrealistic number of experiments, and it may be impossible or approximately impractical to directly identify the fired lead body by the structure or properties.

[0023] In the case where the pencil lead according to some embodiments of the present invention is applied to a mechanical pencil body, various conventionally known mechanical pencil bodies can be used as the mechanical pencil body. For example, a pipe slide mechanical pencil as disclosed in JPH8-28182A, which is configured such that, during writing, as the lead wears, the tip surface of the tip member is retreated while being rubbed against the paper surface to prevent the lead from breaking during writing, is effective in protecting the pencil lead obtained by some embodiments of the present invention, and further improves the fixity of the Date Recue/Date Received 2021-01-08 abrasion powder on the paper surface since the tip surface of the tip member presses the abrasion powder against the paper surface. In the case where this pipe slide mechanical pencil is adopted, it is preferable to select the shape and material of the tip member (stainless pipe) which contacts the paper, as disclosed in JP2015-104882A, to make it easier for the abrasion powder of the lead to adhere to the tip member. Further, in the case of using a mechanical pencil as disclosed in JP2018-1685A, which enables writing while the tip member is in contact with the paper surface and continuous writing, it is possible to prevent the lead from breaking due to the impact at the time of knocking. This pencil is thus most suitable as the mechanical pencil to which the pencil lead according to some embodiments of the present invention is applied.
Examples

[0024] The present invention will be described based on Examples, but the present invention is not limited to Examples. The average particle size of graphite of compounding materials is a mean volume diameter measured with a laser diffraction type particle size distribution measuring device SALD-7000 (manufactured by Shimadzu Corporation). Further, the pore volume of the fired lead body core was determined by obtaining nitrogen adsorption isotherm by the constant volume gas adsorption method with a specific surface area/pore distribution measuring device BELSORP-mini II (manufactured by Microtrac Bell Co., Ltd.) using nitrogen as the adsorption gas and calculating adsorption data of the nitrogen adsorption isotherm by the BJH method.
The JOB value of the impregnating component was calculated from the molecular formula. The viscosity was determined as a value of shear rate 1/s measured with a rheometer, Modular Compact Rheometer MCR302 (manufactured by Anton Paar GmbH) at a measuring temperature of 25 C, using a cone plate with a geometry of 1'Ap50mm. The impregnation ratio was determined as a percentage value (% by weight) of (Y-X)/Y where X is the weight of the fired .. lead body before impregnation, and Y is the weight of the pencil lead after impregnation.

[0025] (Production of fired lead body A) Date Recue/Date Received 2021-01-08 45 parts by weight of flake graphite (pigment component: mean volume diameter 15 [tm) 24 parts by weight of polyvinyl chloride (organic binder) 1 part by weight of carbon black (filler) 1.5 parts by weight of stearate (stabilizer) 0.5 parts by weight of stearic acid (lubricant) 18 parts by weight of dioctyl phthalate (plasticizer) parts by weight of methyl ethyl ketone (solvent) The above materials were dispersed and mixed with a Henschel mixer, mixed with three rolls, and then extruded into a fine rod shape with a single-screw extruder.
The resulting 10 product was heated in the air from room temperature to 350 C over about 10 hours, held at 350 C
for about 1 hour, and then fired in a closed container at a maximum of 1100 C, to obtain a fired lead body A having an actual diameter of 0.57 mm. The pore volume was 0.18 cm3/g.

[0026] (Production of fired lead body B) 33 parts by weight of flake graphite (pigment component: mean volume diameter 15 [tm) 15 23 parts by weight of polyvinyl chloride (organic binder) 1 part by weight of carbon black (filler) 1.5 parts by weight of stearate (stabilizer) 0.5 parts by weight of stearic acid (lubricant) 15 parts by weight of dioctyl phthalate (plasticizer) 15 parts by weight of methyl ethyl ketone (solvent) The above materials were dispersed and mixed with a Henschel mixer, mixed with three rolls, and then extruded into a fine rod shape with a single-screw extruder.
The resulting rod was heated in the air from room temperature to 350 C over about 10 hours, held at 350 C for about 1 hour, and then fired in a closed container at a maximum of 1100 C, to obtain a fired lead body B having an actual diameter of 0.57 mm. The pore volume was 0.13 cm3/g.

[0027] <Example 1>
Date Recue/Date Received 2021-01-08 The fired lead body A was immersed for 16 hours in an impregnating component (K-P0N402, compound represented by the general formula (1) (n=2), dehydration condensate of ricinoleic acid, manufactured by Kokura Synthetic Industry Co., Ltd., JOB
value = 0.45, viscosity 520 mPa-s) heated to 120 C, and then centrifuged with a centrifugal separator to remove excess impregnating component on the surface to obtain a pencil lead. The impregnation ratio of the impregnating component was 16.5% by weight.

[0028] <Example 2>
A pencil lead was obtained in the same manner as Example 1 except that K-(compound represented by the general formula (1) (n=4), dehydration condensate of ricinoleic acid, manufactured by Kokura Synthetic Industry Co., Ltd., JOB value = 0.31, viscosity 1068 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.7% by weight.

[0029] <Example 3>
A pencil lead was obtained in the same manner as Example 1 except that K-(compound represented by the general formula (1) (n=6), dehydration condensate of ricinoleic acid, manufactured by Kokura Synthetic Industry Co., Ltd., JOB value = 0.27, viscosity 1589 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.2% by weight.

[0030] <Example 4>
A pencil lead was obtained in the same manner as Example 1 except that PCF-90 (compound represented by the general formula (1) (n=2), dehydration condensate of ricinoleic acid, manufactured by Itoh Oil Chemical Co., Ltd., JOB value = 0.45, viscosity 580 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.2% by weight.

[0031] <Example 5>
A pencil lead was obtained in the same manner as Example 1 except that PCF-45 Date Recue/Date Received 2021-01-08 (compound represented by the general formula (1) (n=4), dehydration condensate of ricinoleic acid, manufactured by Itoh Oil Chemical Co., Ltd., JOB value = 0.31, viscosity 1162 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.5% by weight.

[0032] <Example 6>
A pencil lead was obtained in the same manner as Example 1 except that PCF-30 (compound represented by the general formula (1) (n=6), dehydration condensate of ricinoleic acid, manufactured by Itoh Oil Chemical Co., Ltd., JOB value = 0.27, viscosity 1782 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.5% by weight.

[0033] <Example 7>
The fired lead body B was impregnated under pressure of 2 MPa over 16 hours with an impregnating component (K-P0N402, described above) heated to 150 C, and then centrifuged with a centrifugal separator to remove excess impregnating component on the surface to obtain a pencil lead. The impregnation ratio of the impregnating component was 14.0% by weight.

[0034] <Example 8>
A pencil lead was obtained in the same manner as Example 7 except that K-(described above) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 13.8% by weight.

[0035] <Example 9>
A pencil lead was obtained in the same manner as Example 7 except that K-(described above) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 13.5% by weight.

[0036] <Example 10>
A pencil lead was obtained in the same manner as Example 7 except that PCF-90 (described above) was used as the impregnating component instead of K-P0N402. The impregnation ratio Date Recue/Date Received 2021-01-08 of the impregnating component was 14.2% by weight.

[0037] <Example 11>
A pencil lead was obtained in the same manner as Example 7 except that PCF-45 (described above) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 13.5% by weight.

[0038] <Example 12>
A pencil lead was obtained in the same manner as Example 7 except that PCF-30 (described above) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 13.3% by weight.

[0039] <Comparative Example 1>
A pencil lead was obtained in the same manner as Example 1 except that ricinoleic acid (compound represented by the general formula (1) (n=1), manufactured by Wako Pure Chemical Co., Ltd., JOB value = 0.72, viscosity 342 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 17.6% by weight.

[0040] <Comparative Example 2>
A pencil lead was obtained in the same manner as Example 1 except that K-(glycerin ester of polycondensed castor oil fatty acid, manufactured by Kokura Synthetic Industry Co., Ltd., JOB value = 0.29, viscosity 1574 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 18.3% by weight.

[0041] <Comparative Example 3>
A pencil lead was obtained in the same manner as Example 1 except that heat-dissolved 12-hydro acid (12-hydroxystearic acid, manufactured by Kokura Synthetic Industry Co., Ltd., JOB
value = 0.71, solid at room temperature (melting point 77 C)) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was Date Recue/Date Received 2021-01-08 16.7% by weight.

[0042] <Comparative Example 4>
A pencil lead was obtained in the same manner as Example 1 except that K-P0N306 (12-hydroxyoctadecane acid polycondensate, manufactured by Kokura Synthetic Industry Co., Ltd., IOB value = 0.26, viscosity 3006 mPa-s) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 16.5% by weight.

[0043] <Comparative Example 5>
A pencil lead was obtained in the same manner as Example 1 except that Castor Oil Marutoku A (ricinoleic acid triglyceride, manufactured by Itoh Oil Chemical Co., Ltd., JOB value = 0.43, viscosity 696 mPa-s) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 17.2% by weight.

[0044] <Comparative Example 6>
A pencil lead was obtained in the same manner as Example 1 except that a mixture (JOB
value = 0., viscosity 1430 mPa-s) of Nisseki Polybutene SV-700 (polybutene, manufactured by JXTG Nippon Oil & Energy Corporation) and SYNCELANE 4SP (a-olefin oligomer, manufactured by Nikko Chemicals Co., Ltd.) at a weight ratio of 1:1 was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 15.7% by weight.

[0045] <Comparative Example 7>
A pencil lead was obtained in the same manner as Example 1 except that NIKKOL
Sefsol-218 (propylene glycol monocaprylate, manufactured by Nikko Chemicals Co., Ltd., JOB value =
0.73, viscosity 12.5 mPa-s) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 16.5% by weight.

[0046] <Comparative Example 8>
A pencil lead was obtained in the same manner as Example 7 except that ricinoleic acid (described above) was used as the impregnating component instead of K-P0N402.
The Date Recue/Date Received 2021-01-08 impregnation ratio of the impregnating component was 15.0% by weight.

[0047] <Comparative Example 9>
A pencil lead was obtained in the same manner as Example 7 except that K-(described above) was used as the impregnating component instead of K-P0N402.
The .. impregnation ratio of the impregnating component was 14.8% by weight.

[0048] <Comparative Example 10>
A pencil lead was obtained in the same manner as Example 7 except that heat-dissolved 12-hydro acid (described above) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 12.8% by weight.

[0049] <Comparative Example 11>
A pencil lead was obtained in the same manner as Example 7 except that K-(described above) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 11.7% by weight.

[0050] <Comparative Example 12>
A pencil lead was obtained in the same manner as Example 7 except that Castor Oil Marutoku A (described above) was used as the impregnating component instead of K-P0N402.
The impregnation ratio of the impregnating component was 13.0% by weight.

[0051] <Comparative Example 13>
A pencil lead was obtained in the same manner as Example 7 except that the mixture (described above) of Nisseki Polybutene SV-700 (described above) and SYNCELANE

(described above) at a weight ratio of 1:1 was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 10.9% by weight.

[0052] <Comparative Example 14>
A pencil lead was obtained in the same manner as Example 7 except that NIKKOL
Sefsol-.. 218 (described above) was used as the impregnating component instead of K-P0N402. The impregnation ratio of the impregnating component was 12.7% by weight.
Date Recue/Date Received 2021-01-08

[0053] With respect to the pencil leads obtained in Examples 1 to 12 and Comparative Examples 1 to 14, the darkness of writing and the fixity against rubbing were measured, and the reliability was examined, according to the following methods.

[0054] (Test on darkness of writing) The darkness of writing was examined in accordance with JIS S 6005.

[0055] (Test on fixity against rubbing (stain resistance)) The fixity against rubbing was determined by a percentage value of ((A-B)/A), where A is the darkness of a written portion drawn by the test on darkness of writing, and B is the darkness of a stain portion other than the written portion caused by double-rubbing the written portion 10 times with tissue paper at a vertical load of 500 g. The larger the value, the greater the fixity of the written line against rubbing and the greater the stain resistance.

[0056] (Reactivity test with resin case) The reactivity test with a resin case was performed as follows: 40 pencil leads obtained in Examples 1 to 12 and Comparative Example 1 to 14 were put into a refill lead case (STEIN refill .. lead case, manufactured by pentel Co., Ltd.) made of acrylonitrile-styrene copolymer (AS resin), and the refill lead case was placed on a stainless plate, left still in a thermostatic chamber controlled at 60 C for 16 hours, taken out and left still at room temperature for 1 hour, and then left still in a thermostatic chamber controlled at -30 C for 16 hours. After this cooling/heating cycle test was performed twice, the change of the refill lead case was visually evaluated.

[0057] 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 fired lead body A is impregnated with the impregnating component.

[0058] (Table 1) Date Recue/Date Received 2021-01-08 ,2 i Cim g 73 viscosity Impregnation Darkness of toiling (D) Ficky - Reactway* = 'with gi Impregnating Component 10S (mPa-s) Ratio (Fixity Ratio ,6: Resin Case (%) Z
m o. Example 1 K -PON 402 l=n, rottidc. . 0. 45 520 16. 5 , 0. 59 0. 09 84. 3 No change rg Example 2 K -PON 404-5 .
Vakura sVhebc. Ltd.. .
0. 31 1068 16. 7 0. 56 0.09 84. 4 No change .7Sµ Example 3 K -PON 406-S IndustrM. Ltd.. 0.27 1589 18.2 0.58 0.09 84.3 No change Example 4 PCF- 90 Rob ON Chernkull Co.
Ltd. 0. 46 580 16.2 0. 67 0.09 83.6 No change _ . .
Example 5 PCF-45 Rah Oil Chemical Ca. Ltd. 0. 31 1162 16.5 0.57 0.09 84.2 No change Example 6 PCF- 30 Itch Oil Chemical Co.
Ltd. 0.27 1782 16.5 0.58 0.09 84.1 No change kr rkile 1 Ricinoleic acid Wako Pure Chemical Co. LtdØ 72 342 17. 6 0. 65 0. 12 80. 8 Condensation 0 _ az%le 2 K -PON 406-G Vdkura SathEita. . 0. 29 1574 18. 3 0. 61 0. 11 81. 5 No change ...
..
_ Comp. 12-hydroxystearic acid .,K7k4ttisrtvSlathelp 0. 71 -(Solid) 16. 7 0. 49 0. 08 82. 7 No change 0 Example 3..:. . 1 .
. 0 =cafe 4 K-PON 306 IrinzistSgheil 0. 26 3006 16.5 0.56 0.09 83.6 No change i.

i.
emPExamisis 5 Castor Oil Marutoku A koh Oil Chemical Co.
Ltd. 0. 43 698 17. 2 0. 56 0. 10 82. 2 No change , I-comp of JaXTEG Nippgroiel , Comp.

Example 6 Nisseki Polybutene SV-700 0 1430 15. 7 0. 52 0. 10 80. 8 No change 0 and SYNCELANE 4SP Nikko Chemicals Co. Ltd.
.
.
Comp.
, Example 7 N1KKOL Sefaol-218 ,Nikko Chemicals Co.
Ltd. 0. 73 12. 5 16. 5 0. 56 0. 09 83. 3 Crack As is apparent from the results in Table 1, the pencil leads of Examples 1 to 6 provided dark written lines with little paper stain, compared with the pencil leads of Comparative Examples 1 to 7.

[0059] In Examples 1 to 3, the compounds represented by the general formula (1) used as the impregnating component had different degrees of condensation (dimer in Example 1, tetramer in Example 2, and hexamer in Example 3), and the compound with a higher degree of condensation had a greater molecular weight and a higher viscosity, but with any of the compounds represented by the general formula (1), no decrease in darkness of writing and little paper stain were observed, regardless of the viscosity and JOB value.

[0060] In Example 4, the impregnating component manufactured by a different company from that in Example 1, having a slightly higher viscosity, was used, but no decrease in darkness of writing and little stain on the paper surface were observed with the compound represented by the general formula (1).

[0061] In Example 5, the impregnating component manufactured by a different company from that in Example 1, having a slightly higher viscosity, was used, but no decrease in darkness of writing and little stain on the paper surface were observed with the compound represented by the general formula (1).

[0062] In Example 6, the impregnating component manufactured by a different company from that in Example 3, having a slightly higher viscosity, was used, but no decrease in darkness .. of writing and little stain on the paper surface were observed with the compound represented by the general formula (1).

[0063] In Comparative Examples 1 and 2, the writing was darker than Examples 1 to 6, but the stain on the paper surface increased (the fixity decreased). Meanwhile, in Comparative Examples 3 to 7, the stain on the paper surface increased, and the darkness of writing decreased, so that it cannot be said that the above-described problems are resolved.

[0064] In Comparative Example 1, the impregnating component was ricinoleic acid, which is Date Recue/Date Received 2021-01-08 a substance before condensation of the compound represented by the general formula (1) (n=1).
In this example, it is presumed that the stain on the paper surface was not reduced since the JOB
value is high and the binding between the pigment component and graphite is weak. Further, since ricinoleic acid easily absorbs moisture in the atmosphere, the moisture absorbed in the reactivity test with the resin case condenses in the refill lead case, which makes difficult to remove the leads from the case.

[0065] In Comparative Example 2, the impregnating component was a compound in which the carboxyl group at the terminal of the hexamer of the compound represented by the general formula (1) is replaced with a glyceryl-modified glycerin ester. In this example, it is presumed that the stain on the paper surface was not reduced since the compound has no polar carboxyl group, leading to insufficient interaction with functional groups of the paper surface.

[0066] In Comparative Example 3, the impregnating component (12-hydroxystearic acid) was a saturated fatty acid having no unsaturated bond in the impregnating component (ricinoleic acid) of Comparative Example 1, solid at room temperature, which may reduce the wear of the lead body, resulting in a very light written line (darkness of writing).

[0067] In Comparative Example 4, the impregnating component was a dehydration condensate of the impregnating component (12-hydroxystearic acid) of Comparative Example 3, i.e., a substance having no unsaturated bond of the compound represented by the general formula (1). In this example, it is presumed that since the molecules can easily approach each other and the intermolecular interaction is greater than that of the compound represented by the general formula (1), in which the movement of the molecules is restricted by the intramolecular cis unsaturated bond, the wear of the lead body during writing is inhibited, resulting in the decrease in the darkness of writing.

[0068] In Comparative Example 5, refined castor oil (ricinoleic acid triglyceride), which is a raw material of the compound represented by the general formula (1), was used.
In this example, it is presumed that since ester bonds are unevenly distributed in the molecule, the Date Recue/Date Received 2021-01-08 lubricating effect is lower than that of the compound represented by the general formula (1), and the wear of the lead body is inhibited, resulting in the decrease in the darkness of writing.

[0069] In Comparative Example 6, a saturated hydrocarbon-based impregnating component having a high kinematic viscosity (impregnating component described in Patent Document 1) adjusted to the same viscosity as that of Example 3 was used to obtain the pencil lead. The impregnating component of Comparative Example 6 has a linear region (shear strain 0.1% to 100%) in the dynamic viscoelasticity measurement (frequency 1 Hz, measurement temperature 25 C.) with a rheometer (modular compact rheometer MCR302 (manufactured by Anton Pearl Japan Co., Ltd.)), so that, although the viscosity is substantially the same as that of Example 3, the wear of the lead body during writing is inhibited compared with the impregnating component showing the behavior of the Newtonian fluid having no linear region, and the darkness of writing was reduced.

[0070] In Comparative Example 7, a polar fatty acid ester (impregnating component described in Patent Document 2) was used as the impregnating component to obtain the pencil lead. In this example, in addition to the decrease in the darkness of writing, the impregnating component with a small carbon chain and a large polarity eroded the acrylonitrile-styrene copolymer of the refill lead case and caused cracks.

[0071] 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 fired lead body B is impregnated with the impregnating component.

[0072] (Table 2) Date Recue/Date Received 2021-01-08 o) cT
X
co K, c co o) Fri X mpregnating Componen Viscosity Impregnation Darkness of Writing (D) Fixity Reactivity with co It 10B Ratio o (mPas) (Fixity Ratio %) Resin Case =

co _______________________________________________________________________________ ______________________________ o. Example 7 K¨PON 402 Kokura Synthetic 0.
. , . . 45 520 14 0 0 41 0 07 83 4 No change Inditstry Cr 0 1 td Ag N.) c) Example& K¨PON 404-6 Kokura Smtnetic 0, 31 1068 13, 8 0. 39 0. 07 83, 3 No change NJ tridustQi uo l til O Example 9 K¨PON 406-5 Kokura S nthetic 0, 27 1589 13.5 0.42 0.07 84, 3 No change 1., 1 = =
cb 03 Example 1CI, PCF¨ 90 Itoh Oil Chemical Co. Ltd, 0, 45 580 14. 2 0. 40 0, 07 83, 3 No change Example 11 PCF-45 !toll Oil Chemical Co. Ltd.
0.31 1162 13, 5 0.40 0, 07 83.3 No change , Example 12 PCF-30 . Itch C)il chemical co Lich 0, 27 1782 13. 3 0. 39 0, 06 83, 3 No change _ _______________________________________________________________________________ ________________________________ -Comp. Wako Pure amle 8 Ricinoleic acid Chemical Co Ltd, 0, 72 342 15, 0 O. 43 0, 11 73, 6 Condensation Exp.
Comp. K¨PON 406¨G F.noloc.uusrtvS6not h&c 0, 29 1574 14. 8 0.40 0, 10 75.0 No change P
Example 9 Comp. is 12-hydroxystearic acid tioiLLATJ, Srut.hrtij: 0, 71 - (Solid) 12. 8 0_ 27 0, 06 77. 8 No change 0 ,., Exarli.le Comp. K¨PON 305 Kokura S nthetic O. 25 3005 11. 7 O. 35 0, 08 78. 6 No change t=.) Examrle 11 . J _ _ :' =
II. le, xamve 12 Castor Oil Marutoku A Itoh , . Oil Chemical Co. Ltd. 0 43 696 13 0 0_ 3 , , 6 0 10 73 6 No change E
o 1., ,1 X TG Nippon Oil 1-Mixture of , Comp. 8, Feergy Corp.

Exampe 13 Nisseki Polybutene SV-700 0 1430 10. 9 0, 29 0, 07 77, 6 No change 1-and SYNCELANE 4S1n Nikko Chemicals CO. Ltd, I

a.
are l4 NEKKOL Sefao1-218 Nikko Chemicals Co. Ltd.
0.73 12,5 12, 7 0.41 0, 07 82, 1 Crack Exv As is apparent from the results in Table 2, the pencil leads of Examples 7 to 12 provided dark written lines with little paper stain, compared with the pencil leads of Comparative Examples 8 to 14. This indicates that even if the fired lead body (fired lead body A and fired lead body B) to be impregnated with the compound represented by the general formula (1) is changed, the pencil lead using the compound represented by the general formula (1) as the impregnating component can provide a dark handwriting line with little paper stain even when the amount of wear of the pencil lead varies.

[0073] As described in detail above, by using the pencil leads of Examples 1 to 12, it is possible to obtain the pencil lead that can draw a dark written line (high darkness of writing), and can suppress the movement of the abrasion powder when the written line is rubbed to reduce the paper stain, as compared with the case of using the pencil leads of Comparative Examples 1 to 14.

[0074] Further, in Examples 1 to 12, the impregnating component neither erodes the refill lead case to cause cracks nor absorbs moisture to cause condensation inside the refill lead case, and thus does not inhibit the basic function of removing the pencil lead from the refill lead case.

Date Recue/Date Received 2021-01-08

Claims

1.
A pencil lead, comprising: a fired lead body obtained by subjecting a lead body containing at least a pigment component and an organic binder to a heat treatment; and an impregnating component in pores of the fired lead body, the impregnating component containing a compound represented by the following general formula (1):