Non-baked porous pencil lead

Abstract

To provide an unfired pencil core that has sufficient tip strength for writing even if the tip is sharpened, is less prone to a deterioration of flexural strength due to moisture absorption, and has erasability, which have been impossible in the conventional methods.SOLUTION: This unfired pencil core comprises a binder, a coloring agent and an extender, where the binder includes a resin emulsion having a glass transition point of 40°C or higher.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention is a non-baked Porous Regarding pencil lead. [Background technology]

[0002] Conventionally, baked pencil leads are made by kneading graphite and clay to form a lead, which is then sintered at a high temperature of around 1000°C, and then impregnating the small pores within the lead with oil or the like to give the lead sufficient bending strength and erasability (see, for example, Patent Document 1). Here, bending strength refers to the strength of the lead that is sufficient for writing without breaking.

[0003] Conventional non-baked pencil leads contain a binder such as wax or resin, which is kneaded with various inorganic or organic pigments, then molded into a lead shape using an extrusion molding machine or the like, and then dried as needed (for example, Patent Document 2).

[0004] Baked pencil leads require heating to around 1000°C to sinter the clay binder, and therefore require more energy to manufacture than non-baked pencil leads. Non-baked pencil leads, when using wax as a binder, do not have sufficient bending strength for writing. Furthermore, non-baked pencil leads that use carboxymethyl cellulose salt as a binder have sufficient bending strength and erasability for writing even when the tip is sharpened, but there is a problem in that bending strength decreases due to moisture absorption (for example, Patent Document 3).

[0005] When a resin is used as a binder, the binder is dissolved by heating or using a solvent before being kneaded with the pigment, etc., so the pigment and resin are firmly bonded together in the core. In this case, the pen has sufficient bending strength for writing, but the pigment and resin are firmly bonded together, resulting in insufficient erasability (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 59-191779 [Patent Document 2] Japanese Patent Application Publication No. 56-116765 [Patent Document 3] Japanese Patent Application Publication No. 5-39449 [Patent Document 4] JP 2015-214633 A Summary of the Invention [Problem to be solved by the invention]

[0007] Each embodiment of the present application provides a non-baked ink that has sufficient bending strength for writing, is less susceptible to deterioration in bending strength due to moisture absorption, and has erasability, which could not be achieved by conventional methods. Porous To provide a pencil lead. [Means for solving the problem]

[0008] The unfired first embodiment of the present application Porous The pencil lead is a non-baked pencil containing a binder, a pigment, and an extender. Porous A pencil lead, wherein the binder has a glass transition temperature of 40°C or higher dry It is characterized by containing a resin emulsion.

[0009] The unfired second embodiment of the present invention Porous The pencil lead is A dried glass transition temperature of 40°C or higher Resin emulsion particle size: 30nm to 500nm dried matter It is characterized in that:

[0010] The unfired third embodiment of the present application Porous The pencil lead is A dried glass transition temperature of 40°C or higher The resin constituting the resin emulsion is characterized in that the basic skeleton of the resin is an acrylic polymer. [Effects of the Invention]

[0011] Since each embodiment of the present application is configured as described above, it is possible to obtain a non-baked ink having sufficient bending strength for writing, little deterioration of bending strength due to moisture absorption, and erasability, which could not be obtained by conventional methods. Porous It is possible to provide pencil leads. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view schematically illustrating the appearance of a non-baked porous pencil lead according to an embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] No-fired embodiments of the present application Porous The pencil lead contains a binder, a pigment, and a filler. Porous The pencil lead contains a resin emulsion with a glass transition temperature of 40°C or higher as a binder. Examples of resin emulsions include acrylic emulsions, which are emulsions of acrylic polymers. When an acrylic emulsion with a glass transition temperature of less than 40°C is used as a binder, the non-baked Porous The bending strength of the pencil lead decreases. Examples of such acrylic emulsions with a glass transition point of 40°C or higher include JE-1056 (glass transition point: 82°C) (both manufactured by Seiko PMC), LX416 (glass transition point: 48°C), V1004 (glass transition point: 87°C), V1008 (glass transition point: 58°C), and LX407BP6 (glass transition point: 73°C) (all manufactured by Nippon Zeon).

[0014] The glass transition point of the resin emulsion is 40° C. or higher, preferably 50° C. or higher, and more preferably 70° C. or higher. There is no particular upper limit to the glass transition point of the resin emulsion as long as the function of the resin emulsion is not impaired, but a temperature of 130° C. does not cause any particular problems.

[0015] Because the resin emulsion is dispersed in water, it can be easily mixed with powder pigments and extenders. Furthermore, because the emulsion diameter is small, between 30 and 500 nm, it can be dispersed efficiently between the powder particles with little energy. Furthermore, since no baking process is required when forming the lead, the resin does not dissolve and surround the powder. This allows the powder and binder to separate well when writing, which is thought to result in good erasability.

[0016] If the particle size of the resin emulsion is less than 30 nm, the bending strength of the core body will decrease. If the particle size of the resin emulsion is more than 500 nm, it will be difficult to knead the resin emulsion with the powder pigment and filler. Therefore, it is desirable that the particle size of the resin emulsion be 30 nm or more and 500 nm or less.

[0017] The binder may consist solely of the resin emulsion described above, but may also contain an auxiliary binder. Examples of auxiliary binders that can be used include water-soluble organic polymers such as sodium carboxymethylcellulose, ammonium carboxycellulose, polyvinyl alcohol, and methylcellulose. Examples of sodium carboxymethylcellulose include Sunrose F10LC, Sunrose F10MC, and Sunrose FJ08HC (all Nippon Paper Industries), as well as 1130, 1260, and 1330 (all Daicel Miraize). The content of the auxiliary binder is determined by the amount of the unbaked binder. Porous A content of 3% by mass or less of the entire pencil lead is sufficient.

[0018] Examples of pigments include graphite, titanium oxide, iron black, carbon black, Prussian blue, ultramarine, Blue No. 1, red iron oxide, yellow iron oxide, chromium oxide, chromium hydroxide, zinc oxide, zirconium oxide, cobalt oxide, fish scale foil, bismuth oxychloride, and titanium mica, as well as azo organic pigments such as Disazo Yellow AAA and Pyrazolone Orange, cyanine organic pigments such as Phthalocyanine Blue and Phthalocyanine Green, high-grade organic pigments such as Quinacridone Red, dye pigments such as Fanal Color, and fluorescent pigments. In addition to pigments, dyes such as Blue No. 2, Blue No. 404, Red No. 2, Red No. 3, Red No. 102, Red No. 104, Red No. 105, Red No. 106, DPP Red, Yellow No. 4, Yellow No. 5, and Green No. 3 can also be used, and these can be used alone or in combination.

[0019] As a filler, conventional non-fired Porous There are no particular limitations on the materials used in pencil leads, and any can be used. For example, white fillers such as boron nitride, kaolin, talc, mica, and calcium carbonate can be used, as well as colored fillers depending on the hue of the solid drawing material, and of course mixtures of several of these can also be used. In particular, boron nitride, kaolin, and talc are preferred due to their physical properties and shape.

[0020] In addition to the above, a metal soap may be blended as a lubricant to adjust the wear amount of the core body. Usable metal soaps include zinc stearate, barium stearate, aluminum stearate, magnesium stearate, zinc lauric acid, and zinc 12-hydroxystearic acid.

[0021] In addition, the non-fired PorousPencil leads can be manufactured, for example, by the following manufacturing method. That is, a binder is added to a mixture of powder pigment and filler, and the mixture is kneaded to prepare a mixture. At this time, a solvent can also be added if necessary. The mixture obtained by this preparation is extruded into the shape of a pencil lead using a plunger or screw extruder. If a solvent is used, it is then removed by drying (at about 40°C for 24 hours). This molding produces an unbaked lead having a roughly cylindrical lead body 11, as shown in Figure 1. Porous A pencil lead 10 is obtained. The formed core is porous, with pores resulting from the microscopic structure of the powder. These pores may be left as they are, or may be impregnated with one or both of fats, oils, and waxes as needed after heating at 60 to 200°C for 12 hours. A lower alcohol such as methanol or ethanol, or water, is used as the solvent.

[0022] Suitable examples of the oils and fats include oils that are liquid at room temperature, such as liquid paraffin, spindle oil, silicone oil, α-olefin oligomers, squalane, vegetable oils such as palm oil and olive oil, and animal oils such as lard. Of these, silicone oils are particularly preferred, and examples include dimethylsilicone oil, methylphenylsilicone oil, methylhydrogensilicone oil, cyclic dimethylsilicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, and alkyl-modified silicone oil.

[0023] Unbaked product prepared as above Porous The pencil lead has sufficient bending strength for writing even when the tip is sharpened, is less susceptible to deterioration in bending strength due to moisture absorption, and has erasability. [Example]

[0024] (1) Raw materials Non-baked samples of Examples 1 to 9 and Comparative Examples PorousThe pencil leads had the following composition. All but Example 10 used graphite (CSP, Nippon Graphite) as the pigment. The filler used was talc (High Micron HE5, Takehara Chemical Industry). Furthermore, acrylic emulsion was used as the resin emulsion binder in all cases, with the grades used being as described in the individual sections.

[0025] (1-1) Example 1 The composition of Example 1 was 60% by mass of graphite, 35% by mass of acrylic emulsion (JE-1056, Seiko PMC), and 5% by mass of talc. The numerical values ​​for the acrylic emulsion composition represent percentages as solids, and the same applies to the percentages of acrylic emulsions in the following Examples and Comparative Examples. The glass transition temperature of JE-1056 was 82°C, and the emulsion particle size was 50 nm.

[0026] (1-2) Example 2 The composition of Example 2 was 60 mass % graphite, 30 mass % acrylic emulsion (JE-1056, Seiko PMC), and 10 mass % talc.

[0027] (1-3) Example 3 The composition of Example 1 was 60 mass% graphite, 25 mass% acrylic emulsion (JE-1056, Seiko PMC), 14 mass% talc, and 1.0 mass% carboxymethyl cellulose (F10MC, Nippon Paper Industries Co., Ltd.) as an auxiliary binder.

[0028] (1-4) Example 4 The composition of Example 4 was 60 mass% graphite, 25 mass% acrylic emulsion (JE-1056, Seiko PMC), 14.5 mass% talc, and 0.5 mass% carboxymethyl cellulose (F10MC, Nippon Paper Industries Co., Ltd.) as an auxiliary binder.

[0029] (1-5) Example 5 The composition of Example 5 was 60 mass % graphite, 25 mass % acrylic emulsion (JE-1056, Seiko PMC), and 15 mass % talc.

[0030] (1-6) Example 6 The composition of Example 6 was 60% by mass of graphite, 5% by mass of acrylic emulsion (LX-407BP6, Zeon Corporation), 20% by mass of acrylic emulsion (QE-1042, Seiko PMC), 14% by mass of talc, and 1.0% by mass of sodium carboxymethylcellulose (CMC3M, Nippon Paper Industries Co., Ltd.) as an auxiliary binder. The glass transition temperature of LX-407BP6 was 73°C, and the emulsion particle size was 208 nm. The glass transition temperature of QE-1042 was 53°C, and the emulsion particle size was 40 nm.

[0031] (1-7) Example 7 The composition of Example 7 was 60% by mass of graphite, 5% by mass of acrylic emulsion (LX-407BP6, Zeon Corporation), 20% by mass of acrylic emulsion (Nipol V1004, Zeon Corporation), 14% by mass of talc, and 1.0% by mass of carboxymethylcellulose ammonium (NA-3L, Nichirin Chemical Industry Co., Ltd.) as an auxiliary binder. The glass transition temperature of Nipol V1004 was 87°C, and the particle size of the emulsion was 314 nm.

[0032] (1-8) Example 8 The composition of Example 8 was 60% by mass of graphite, 25% by mass of acrylic emulsion (JE-1056, Seiko PMC), 11.5% by mass of talc, 0.5% by mass of carboxymethyl cellulose (F10MC, Nippon Paper Industries Co., Ltd.) as an auxiliary binder, and 3% by mass of calcium stearate as a metal soap.

[0033] (1-9) Example 9 The composition of Example 9 was 60% by mass of graphite, 25% by mass of acrylic emulsion (JE-1056, Seiko PMC), 11.5% by mass of talc, 0.5% by mass of carboxymethyl cellulose (F10MC, Nippon Paper Industries Co., Ltd.) as an auxiliary binder, and 3% by mass of barium stearate as a metal soap.

[0034] (1-10) Example 10 The composition of Example 10 was 10% by mass of organic pigment (918 Red M-1, Dainichi Seika) as the pigment, 25% by mass of acrylic emulsion (JE-1056, Seiko PMC), 54.5% by mass of talc as the extender, 10% by mass of titanium oxide (KA-15, Titanium Kogyo) as the extender, and 0.5% by mass of sodium carboxymethylcellulose (F10MC, Nippon Paper Industries) as the auxiliary binder.

[0035] (1-11) Comparative Example 1 The composition of Comparative Example 1 was 60% by mass of graphite, 30% by mass of acrylic emulsion (KE-1148, Seiko PMC), 8% by mass of talc, and 2% by mass of carboxymethyl cellulose (F10MC, Nippon Paper Industries Co., Ltd.) as an auxiliary binder. The glass transition temperature of KE-1148 was 21°C, and the particle size of the emulsion was 80 nm.

[0036] (1-12) Comparative Example 2 The composition of Comparative Example 2 was 60% by mass of graphite, 5% by mass of acrylic emulsion (LX-415M, Zeon Corporation), 20% by mass of acrylic emulsion (Nipol V1004, Zeon Corporation), 14% by mass of talc, and 1.0% by mass of carboxymethylcellulose ammonium (NA-3L, Nichirin Chemical Industry Co., Ltd.) as an auxiliary binder. The glass transition temperature of LX-415M was 26°C, and the particle size of the emulsion was 138 nm.

[0037] (1-13) Comparative Example 3 The composition of Comparative Example 3 was 60 mass% graphite, 25 mass% acrylic emulsion (KE-1148, Seiko PMC), 12 mass% talc, and 3 mass% sodium carboxymethyl cellulose (CMC3M, Nippon Paper Industries Co., Ltd.) as an auxiliary binder.

[0038] (1-14) Comparative Example 4 The composition of Comparative Example 4 was 60% by mass of graphite, 32% by mass of talc, and 8% by mass of sodium carboxymethyl cellulose (CMC3M, Nippon Paper Industries Co., Ltd.) as a co-binder. Note that no resin emulsion was added as a binder.

[0039] (1-15) Comparative Example 5 The composition of Comparative Example 5 was 10% by mass of an organic pigment (918 Red M-1, Dainichiseika Chemicals), 71% by mass of talc as an extender, 10% by mass of titanium oxide (KA-15, Titan Kogyo) as an extender, 5% by mass of boron nitride (HGP: Denka) as an extender, and 4% by mass of sodium carboxymethylcellulose (CMC3M, Nippon Paper Industries) as an auxiliary binder. No resin emulsion was used as a binder.

[0040] (2) Unfired Porous Pencil lead manufacturing The raw materials of each of the above Examples 1 to 10 and Comparative Examples 1 to 5 were each added with the same mass of water and mixed in a planetary mixer, after which the moisture content was adjusted while kneading with a two-roll mill. This mixture was formed into thin wires using a hydraulic plunger extruder, and Examples 1 to 9 and Comparative Examples 1 to 4 were dried at 180°C for 3 hours to remove moisture, while Example 10 and Comparative Example 5 were dried at 120°C for 3 hours to remove moisture, resulting in black pencil lead porous bodies (Examples 1 to 9 and Comparative Examples 1 to 4) and red pencil lead porous bodies (Example 10 and Comparative Example 5) with a diameter of 2.5 mm. These black pencil lead porous bodies and red pencil lead porous bodies were immersed in dimethyl silicone oil at 80°C to impregnate the internal pores with the dimethyl silicone oil, and the non-baked Porous Black non-baked pencil lead Porous Pencil lead and red non-baked Porous I got a pencil lead.

[0041] (3) Bending strength measurement The unfired samples of Examples 1 to 10 and Comparative Examples 1 to 5 were Porous Ten pencil leads were subjected to bending strength tests according to JIS S 6005:2007, and the average value was calculated. Porous A load of 10 mm / min was applied to the center of the pencil lead. PorousThe load (F, unit: N) when the pencil lead broke was measured, and the bending strength (σ, unit: MPa) was calculated using the following formula (1). The tip where the load was applied and the tips of both fulcrums were arc-shaped, and the radius (R) was R = 0.2 ± 0.02 (mm).

[0042] σ=8Fl / πd 3 ...Equation (1)

[0043] In the above formula, "l" is the distance between the supporting points (mm), which is 60 mm in this case. Also, "d" in the above formula is the non-fired Porous The diameter (mm) of the pencil lead is 2.5 mm in this example. The bending strength was measured twice: immediately after production and after leaving the pencil in an environment of 35°C temperature and 80% humidity for 72 hours after production. The results are shown in Table 1 below. The "strength reduction rate" in Table 1 below is the value Z (%) calculated by the following formula (2), where X is the bending strength immediately after production and Y is the bending strength three days after production.

[0044] Z=(XY) / X×100...Equation (2)

[0045] [Table 1]

[0046] First, in Comparative Examples 4 and 5, which did not contain a resin emulsion as a binder, the strength reduction rate exceeded 45%, resulting in a bending strength that was significantly lower than the bending strength immediately after production. In Comparative Examples 1 to 3, which contained a binder with a glass transition point of less than 40°C, the strength reduction rate exceeded 15%, also resulting in a significant decrease in bending strength.

[0047] In contrast, the non-baked Porous The strength reduction rate for all pencil leads was in the single digits or less, which was better than the comparative examples.

[0048] As a result of the above, it is presumed that in each example containing a binder with a glass transition point of 40°C or higher, the binder is easily dispersed evenly in the powder, thereby suppressing moisture absorption by the core body over time and suppressing a decrease in strength. [Industrial Applicability]

[0049] The present invention can be used as a non-baked pencil lead. [Explanation of symbols]

[0050] 10 Unbaked Porous Pencil lead 11 core body

Claims

1. A non-baked porous pencil lead containing a binder, a pigment, and a filler, A non-baked porous pencil lead, characterized in that the binder contains a dried resin emulsion having a glass transition point of 40°C or higher.

2. 2. The non-baked porous pencil lead according to claim 1, wherein the dried resin emulsion having a glass transition point of 40° C. or higher is a dried product of an emulsion of an acrylic polymer.

3. 3. The non-baked porous pencil lead according to claim 1, wherein the dried resin emulsion has a glass transition point of 40° C. or higher and a particle size of 30 nm to 500 nm in a dried product.

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