Aqueous ballpoint pen ink composition

Abstract

Provided is a water-based ink composition for ballpoint pens that maintains a smooth writing feel even when stored for a long time in a state in which the tip is pointing downward, and that is excellent in terms of wear inhibition of the ball socket. As such a water-based ink composition for ballpoint pens, a water-based ink composition for ballpoint pens that contains at least a colorant, microparticles having a new Mohs hardness of 3 or greater and an average particle diameter of 30 μm or less, a polyoxyethylene polycyclic phenyl-based surfactant, and a water-soluble solvent can be cited.

Description

Technical Field

[0001] This instruction manual relates to a water-based ink composition for ballpoint pens that maintains a smooth writing feel even when stored with the nib pointing downwards for extended periods, and that exhibits excellent wear resistance in the ball bearing socket. Background Technology

[0002] In the history of water-based ballpoint pens, ink compositions that reduce wear on the ball bearing caused by the rotation of the ball during writing have been known, for example:

[0003] 1) An ink for ballpoint pens, characterized in that it contains at least: a pigment as a colorant, microparticles with a new Mohs hardness of 4 or higher, and a liquid medium (see, for example, Patent Document 1).

[0004] 2) A water-based ink composition for a fine ballpoint pen, characterized in that, in an ink composition comprising at least water, a colorant, and a water-soluble solvent, one or more ultrafine particles selected from alumina, titanium dioxide, silicon dioxide, silicon carbide, and tungsten carbide with a particle size of less than 0.1 μm are mixed in an amount of 0.002 to 2% by weight in the ink composition (see, for example, Patent Document 2); etc.

[0005] However, in the ink of the aforementioned Patent Document 1, when the pen tip is stored downwards for a long time, pigments, such as dyes, accumulate at the pen tip, resulting in issues such as wear on the ball bearing socket and a stiff writing feel when writing begins.

[0006] Patent Document 2 is excellent at suppressing wear on the ball bearing socket, but sometimes when the pen is stored with the nib facing down for a long time using the above formula, the writing performance and the effect on wear on the ball bearing socket become slightly insufficient.

[0007] On the other hand, as a technology for using polyoxyethylene polycyclic phenyl surfactants in writing inks, for example...

[0008] 3) In order to provide a coloring resin particle dispersion with excellent dispersion stability, and a water-based ink composition for writing instruments with excellent dispersion stability and good handwriting, for example, there are coloring resin particle dispersions and water-based ink compositions for writing instruments containing the same. The coloring resin particle dispersion is made of a specific dispersant such as styrene-acrylonitrile resin particles, colorant, polyoxyethylene polycyclic phenyl surfactant, and water (see, for example, Patent Document 3).

[0009] 4) In order to provide a water-based ballpoint pen ink composition that provides good handwriting, excellent dispersion stability of the colorant, and excellent preservation stability of the ink composition, water-based ballpoint pen ink compositions and water-based ballpoint pens using the same are known. The water-based ballpoint pen ink composition is made by including a colorant, an acrylic copolymer, a polyoxyethylene polycyclic phenyl surfactant, and water (see, for example, Patent Document 4).

[0010] However, the aforementioned patent documents 3 and 4 are water-based ballpoint pen ink compositions with excellent dispersion and storage stability of the colorant, but they do not suppress wear of the ball bearing socket. In addition, they do not recognize the problem of long-term storage with the pen tip pointing downwards when using new microparticles with a Mohs hardness of 3 or higher. The problem and technical concept (structure and its effect) of the invention are different from those of this disclosure.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2002-206066 (claims, embodiments, etc.)

[0014] Patent Document 2: Japanese Patent Publication No. 2007-518838 (claims, embodiments, etc.)

[0015] Patent Document 3: Japanese Patent Application Publication No. 2019-189802 (claims, embodiments, etc.)

[0016] Patent Document 4: Japanese Patent Application Publication No. 2020-180198 (claims, embodiments, etc.) Summary of the Invention

[0017] The problem the invention aims to solve

[0018] This disclosure is made in view of the aforementioned problems and current status of the prior art and with the aim of eliminating them. Its purpose is to provide a water-based ink composition for ballpoint pens that maintains a smooth writing feel even when stored with the nib facing down for a long time and has excellent wear suppression of the ball bearing socket.

[0019] Solution for solving the problem

[0020] In view of the above-mentioned existing problems, the inventors have conducted in-depth research and found that the above-mentioned target water-based ballpoint pen ink composition is obtained by including at least pigments, microparticles with a new Mohs hardness of 3 or above, polyoxyethylene polycyclic phenyl surfactants, and water-soluble solvents, thus completing this disclosure.

[0021] That is, the water-based ballpoint pen ink composition disclosed herein is characterized by comprising at least: a pigment; microparticles with a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less; a polyoxyethylene polycyclic phenyl surfactant; and a water-soluble solvent.

[0022] Preferably, the value obtained by multiplying the new Mohs hardness of the aforementioned particles by the average particle size (μm) of the aforementioned particles is 0.02 to 450.

[0023] Preferably, the content of the aforementioned microparticles is 0.001 to 5% by mass relative to the total amount of the ink composition.

[0024] Preferably, the aforementioned polyoxyethylene polycyclic phenyl surfactant is polyoxyethylene styrene phenyl ether.

[0025] Preferably, the content of the aforementioned polyoxyethylene polycyclic phenyl surfactant is 0.05 to 20% by mass relative to the total amount of the ink composition.

[0026] The preferred viscosity is 50–2000 mPa·s (25°C) at 1 rpm, based on a cone-plate rotational viscometer (1°34′R24 cone).

[0027] The effects of the invention

[0028] According to this disclosure, a water-based ink composition for ballpoint pens is provided, which maintains a smooth writing feel even when stored with the nib facing down for a long time and has excellent wear suppression of the ball bearing socket, and a water-based ballpoint pen equipped with the same.

[0029] The purpose and effects of this disclosure can be recognized and obtained, in particular, by using the features and combinations pointed out in the claims. The foregoing general description and the following detailed description are both exemplary and illustrative, and do not limit the scope of this disclosure as set forth in the claims. Detailed Implementation

[0030] The embodiments of this disclosure will now be described in detail. However, the scope of protection of this disclosure is not limited to the embodiments detailed below, and attention should be paid to aspects relating to the invention as described in the claims and its equivalents.

[0031] The water-based ballpoint pen ink composition disclosed herein is characterized by comprising at least: a pigment; microparticles having a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less; a polyoxyethylene polycyclic phenyl surfactant; and a water-soluble solvent.

[0032] As the pigments used in this disclosure, there can be no limitation on the use of all dyes dissolved or dispersed in water, conventionally known inorganic and organic pigment systems such as titanium dioxide, pigment-containing resin particles, simulated pigments of resin emulsions colored by dyes, white plastic pigments, wax particles, hollow resin particles, pigments based on silica or mica and coated with multiple layers of iron oxide, titanium dioxide, etc., thermochromic pigments, photochromic particles, and composite particles thereof.

[0033] Examples of dyes include acid dyes such as eosin, fluorescent pink, aqua yellow #6-C, acid red, aqua blue #105, brilliant blue FCF, and aniline black NB; direct dyes such as direct black 154, direct sky blue 5B, and violet BB; and basic dyes such as rhodamine and methyl violet.

[0034] Inorganic pigments include, for example, azo lakes, insoluble azo pigments, chelated azo pigments, phthalocyanine pigments, pyrene and violet ketone pigments, and nitroso pigments. More specifically, examples include carbon black, titanium black, zinc oxide, iron oxide red, aluminum, chromium oxide, iron black, cobalt blue, iron oxide yellow, chrome green, zinc sulfide, zinc barium white, cadmium yellow, cinnabar, cadmium red, chrome yellow, molybdenum orange, zinc chromate, strontium chromate, silica, clay, talc, ultramarine, precipitating barium sulfate, barium oxide powder, calcium carbonate, lead white, navy white, deep blue, manganese violet, aluminum powder, brass powder, and other inorganic pigments, as well as CI Pigment Blue 17, CI Pigment Blue 15, CI Pigment Blue 17, CI Pigment Blue 27, CI Pigment Red 5, CI Pigment Red 22, CI Pigment Red 38, CI Pigment Red 48, CI Pigment Red 49, and CI Pigment Red 53. CI Pigment Red 57, CI Pigment Red 81, CI Pigment Red 104, CI Pigment Red 146, CI Pigment Red 245, CI Pigment Yellow 1, CI Pigment Yellow 3, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 17, CI Pigment Yellow 34, CI Pigment Yellow 55, CI Pigment Yellow 74, CI Pigment Yellow 95, CI Pigment Yellow 166, CI Pigment Yellow 167, CI Pigment Orange 5, CI Pigment Orange 13, CI Pigment Orange 16, CI Pigment Violet 1, CI Pigment Violet 3, CI Pigment Violet 19, CI Pigment Violet 23, CI Pigment Violet 50, CI Pigment Green 7, etc.

[0035] As thermochromic pigments, examples of thermochromic pigments manufactured as follows are produced by microencapsulating a thermochromic composition comprising at least a colorless pigment that functions as a color developer, a color developer that has the ability to make the colorless pigment develop color, and a color-changing temperature regulator that controls the color-changing temperature in the color development of the colorless pigment and the color developer, in such a way that the color-changing temperature is a specified average particle size (e.g., 0.1 to 6 μm).

[0036] Examples of photochromic particles include: photochromic particles composed of at least one photochromic pigment (compound), fluorescent pigment, and resin such as terpene phenol resin; and photochromic particles manufactured by microencapsulating a photochromic composition containing at least one photochromic pigment (compound), fluorescent pigment, organic solvent, and additives such as antioxidant, light stabilizer, and sensitizer to a specified average particle size (e.g., 0.1 to 6 μm).

[0037] In this disclosure (including embodiments, etc.), "average particle size" is the D50 value measured using a particle size analyzer [MICROTRAC HRA9320-X100 (Nikkiso Co., Ltd.)].

[0038] Examples of microencapsulation methods for the aforementioned thermochromic pigments include interfacial polymerization, interfacial condensation polymerization, insitu polymerization, liquid-based curing coating, phase separation from aqueous solutions, phase separation from organic solvents, melting-dispersion-cooling, gas-suspended coating, and spray drying. The appropriate method can be selected based on the application. For example, in the phase separation method from aqueous solutions, a colorless pigment, a color developer, and a color-changing temperature regulator are heated and melted, then added to an emulsifier solution and heated and stirred to disperse them in oil droplets. Next, a resin raw material with a wall film such as urethane resin, epoxy resin, or amino resin is used as the encapsulation film agent. This is achieved by slowly adding the resin to various liquids, such as an amino resin solution, specifically an aqueous solution of hydroxymethyl melamine, a urea solution, or a benzoguanamine solution. After the reaction is carried out, the dispersion is filtered, thereby producing a thermochromic microencapsulated pigment. In this thermochromic pigment, by appropriately combining the types and amounts of colorless pigments, color developers, and color-changing temperature regulators, the color development temperature and decolorization temperature of each color can be set to suitable temperatures.

[0039] Furthermore, the microencapsulation method for the aforementioned photochromic particles can be prepared in the same manner as the manufacture of the aforementioned thermochromic resin particles.

[0040] These photochromic particles, by using photochromic pigments (compounds), fluorescent pigments, etc., are colorless in indoor lighting environments (selected from indoor lighting fixtures such as incandescent lamps, fluorescent lamps, lamps, white LEDs, etc.) and can exhibit color development in ultraviolet irradiation environments (irradiation with wavelengths of 200–400 nm, irradiation environments including sunlight with ultraviolet light).

[0041] These pigments can be used alone or in mixtures of two or more. Furthermore, the average particle size of these pigments, including water-dispersed pigments, resin particle pigments, analog pigments, white plastic pigments, multi-layer coated pigments, thermochromic pigments, and photochromic particles, varies depending on spheroid diameter, ink composition, viscosity, etc., but an average particle size of 0.02–6 μm is desirable.

[0042] The content of these pigments can be adjusted according to the line density of the ink, but is expected to be 0.1 to 40% by mass (hereinafter, “mass%” is referred to as “%”), preferably 1 to 10% relative to the total amount of the ink composition.

[0043] The new particles with a Mohs hardness of 3 or higher and an average particle size of 30 μm or less used in this disclosure are included to exert the wear suppression effect of the ball bearing socket.

[0044] The microparticles used can be any microparticles with a new Mohs hardness of 3 or higher and an average particle size of less than 30 μm without any particular restrictions.

[0045] The new Mohs hardness and the modified Mohs hardness have the same meaning. The new Mohs hardness refers to the hardness scale of a mineral, determined by comparing it to 15 benchmark minerals. The benchmark minerals, from softest (new Mohs hardness 1) to hardest (new Mohs hardness 15), are: talc, gypsum, calcite, fluorite, apatite, orthoclase, fused quartz, crystal (quartz), topaz, garnet, fused zirconium oxide, fused alumina, silicon carbide, boron carbide, and diamond. In this specification, the new Mohs hardness is determined by the presence or absence of scratches on a sample material (particles) whose hardness is to be measured by rubbing it against these benchmark minerals. For example, if scratches are caused by fluorite but not by calcite, the new Mohs hardness of that sample material (particles) is 3.5 (meaning between 3 and 4). It should be noted that particles with a new Mohs hardness below 3 are less likely to achieve the sufficient effect required for wear suppression in bearing housings, thus failing to achieve the effects of this disclosure and are not preferred.

[0046] If microparticles with a new Mohs hardness of 3 or higher are used, during writing, as the ink flows out with the rotation of the ball, it is embedded into the ball bearing socket due to the high pressure during writing. As a result, the surface hardness of the socket increases, which can suppress the wear of the socket as the ball rotates. From the perspective of durability and ink flow, it is desirable for the microparticles to have a new Mohs hardness of 3 or higher and 15 or lower.

[0047] As particles with a new Mohs hardness of 3 or higher and 15 or lower, examples include ceramic particles, metal particles, and resin particles such as silicon carbide, alumina, silicon dioxide, tungsten carbide, titanium oxide, and melamine resin. They can be used alone or in mixtures of two or more.

[0048] Furthermore, regarding the microparticles used, from the perspective of further suppressing wear of the ink cartridge and improving dispersibility in the ink, it is desirable for the average particle size to be 30 μm or less, preferably 0.007 to 30 μm, and more preferably 0.01 to 10 μm. If the microparticles have an average particle size exceeding 30 μm, the dispersion stability in the ink and the suppression of microparticle sedimentation will deteriorate, which is not preferred.

[0049] Furthermore, regarding the shape of microparticles with the new Mohs hardness and average particle size specified above, from the perspective of improving writing feel and ink flow, it is desirable for them to be spherical, elliptical, plate-like, or rod-shaped.

[0050] These particles can be any particles that have the new Mohs hardness and average particle size specified above. Commercially available particles can be used. In addition, ceramic particles, metal particles, resin particles, etc., manufactured by known methods can be used.

[0051] Furthermore, in this disclosure, when the particles satisfy the aforementioned new Mohs hardness and the value obtained by multiplying the new Mohs hardness of the particles by their average particle size (μm) (hereinafter referred to as the "multiplication value") is within a specified range, the effect of this disclosure can be further suited to be achieved when the particles are used in a water-based ballpoint pen ink composition, as well as the excellent balance between wear suppression and dispersion stability of the bearing. The specified range of the aforementioned multiplication value is preferably 0.02 to 450, more preferably 0.03 to 150.

[0052] The content of particles with the new Mohs hardness and average particle size specified therefor is expected to be 0.001 to 5%, more preferably 0.1 to 2%, relative to the total amount of the ink composition.

[0053] If the content of this particle is less than 0.001%, sufficient inhibition of bearing wear will not be achieved; on the other hand, if it exceeds 5%, the writing feel will sometimes be reduced.

[0054] The polyoxyethylene polycyclic phenyl surfactants used in this disclosure are ethers that have "a group having at least two monocyclic aromatic hydrocarbon groups (e.g., phenyl, phenylene, etc.)" or "a group having at least one polycyclic aromatic hydrocarbon group (e.g., naphthyl, etc.)" in their molecular backbone.

[0055] The polyoxyethylene polycyclic phenyl surfactant is a component that maintains good dispersion stability even during long-term storage of particles with the above-mentioned physical properties. For example, compounds represented by the following formula (1) can be cited.

[0056]

[0057] [In formula (1) above, X is a polycyclic phenyl group; AO is an alkylene oxide with 2 to 5 carbon atoms; Z is SO3M or a hydrogen atom, M is a hydrogen atom, or an organic or inorganic cation; n is a number from 3 to 120.]

[0058] In the aforementioned formula (1), X is a polycyclic phenyl group. It should be noted that the term "polycyclic phenyl group" here refers to "a group having at least two monocyclic aromatic hydrocarbon groups (e.g., phenyl, phenylene, etc.)" or "a group having at least one polycyclic aromatic hydrocarbon group (specifically, a group with at least two fused benzene rings, such as naphthyl, phenanthrene, etc.)". Examples of "polycyclic phenyl groups" in the aforementioned formula (1) are the following formulas (2) to (5).

[0059]

[0060] In equations (2) to (5) above, R 1 It is a chain-like hydrocarbon group having 1 to 3 carbon atoms. R 2 R 3 It is independently a hydrogen atom or a chain hydrocarbon group having 1 to 3 carbon atoms, or a group shown in formula (6). R 4 R 5 A chain-like hydrocarbon group consisting independently of hydrogen atoms and having 1 to 3 carbon atoms. x is an integer from 1 to 3.

[0061]

[0062] In the above formula (6), R 6 R 7 Independently, it consists of a hydrogen atom or a chain-like hydrocarbon group having 1 to 3 carbon atoms, where y is an integer from 1 to 3.

[0063] The polyoxyethylene polycyclic phenyl surfactants used in this disclosure may also contain bisphenol polycyclic groups as shown in formulas (7) to (8).

[0064]

[0065] In the aforementioned equations (7) to (8), R 8 R 9 Each is independently a hydrogen atom or a chain-like hydrocarbon group having 1 to 3 carbon atoms, and is an integer m ≥ 2.

[0066] In the aforementioned formula (1), X is preferably stilbene phenyl, stilbene methylphenyl, or tristilbene phenyl.

[0067] In the aforementioned formula (1), Z represents SO3M or a hydrogen atom, and M represents a hydrogen atom, or an organic or inorganic cation, preferably a hydrogen atom. Examples of cations represented by M include alkali metal ions, alkaline earth metal ions, ammonium ions, and alkyl-substituted ammonium ions.

[0068] In the aforementioned formula (1), n ​​is preferably 3 to 120, more preferably 3 to 20, and particularly preferably 3 to 10. If the upper and lower limits are within the aforementioned ranges, the stability of the water-based ballpoint pen ink composition and the dispersion stability of the particles with the aforementioned characteristics can be highly balanced.

[0069] The manufacture of this polyoxyethylene polycyclic phenyl surfactant is known, for example, by formalin condensation of stilbeneated phenol in the presence of formaldehyde to obtain a bis(triphenylene oxide), followed by addition polymerization of ethylene oxide in the presence of a catalyst.

[0070] In this disclosure, the length of the ethylene oxide mole in the polyoxyethylene polycyclic phenyl surfactant is preferably 10 to 120 moles to further enhance the effects of this disclosure. Particularly suitable is 20 moles or more.

[0071] Preferred polyoxyethylene polycyclic phenyl surfactants include polyoxyethylene styrene phenyl ether, polyoxyethylene styrene methyl phenyl ether, polyoxyethylene styrene methyl phenyl ether sulfate, polyoxyethylene tristyrene phenyl ether, polyoxyethylene tribenzyl phenyl ether, polyoxyethylene styrene tolyl ether, and polyoxyethylene allyl phenyl ether, with polyoxyethylene styrene phenyl ether being particularly preferred.

[0072] Specific examples of polyoxyethylene polycyclic phenyl surfactants include EMULGEN A-60, EMULGEN A-90, EMULGEN A-500, EMULGEN B-66 (Kao Corporation), Newcol 703, Newcol 704, Newcol 706, Newcol 707, Newcol 708, Newcol 709, Newcol 710, Newcol 711, Newcol 712, Newcol 714, Newcol 719, Newcol 723, Newcol 729, Newcol 733, Newcol 740, Newcol 747, Newcol 780, Newcol 610, Newcol 2604, Newcol 2607, Newcol 2609, Newcol 2614 (Nippon Nyukazai Co., Ltd.), NOIGEN EA-87, and NOIGEN... EA-137, NOIGEN EA-157, NOIGEN EA-167, NOIGEN EA-177, NOIGEN EA-197D, NOIGEN EA-207D (DKS Co., Ltd.).

[0073] These polyoxyethylene polycyclic phenyl surfactants can be used individually or in combination of two or more.

[0074] The content of these polyoxyethylene polycyclic phenyl surfactants varies depending on the type and amount of the microparticles and the type and amount of the pigments, and is 0.05 to 20%, preferably 1 to 10%, relative to the total amount of the ink composition.

[0075] If its content is less than 0.05% relative to the total amount of ink composition, the stability of the particles with the above characteristics will decrease over time. On the other hand, if it exceeds 20%, the ink viscosity will increase, resulting in reduced ink flowability and reduced writing line quality, which is not preferred.

[0076] In this disclosure, the mass ratio (hereinafter sometimes expressed as (A) / (B) ratio) shown as "content of the above-mentioned particles (A) / content of polyoxyethylene polycyclic phenyl surfactant (B)" is preferably 0.005 to 10.0, more preferably 0.05 to 1.5. If the lower and upper limits of this (A) / (B) ratio are within the above range, the abrasion resistance of the water-based ballpoint pen ink composition becomes further improved, and a smooth and stable writing condition can be further formed.

[0077] The water-soluble solvent used in this disclosure is used for various purposes related to ink quality, such as preventing ink freezing at low temperatures and preventing ink drying on the pen nib. Specifically, it may be used alone or in combination with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, 3-butanediol, thiodiethylene glycol, glycerol, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. The content of this water-soluble solvent relative to the total amount of the ink composition is preferably set to 1% to 40%.

[0078] The water-based ballpoint pen ink composition of this disclosure is characterized by comprising at least: the aforementioned pigment; microparticles with a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less; a polyoxyethylene polycyclic phenyl surfactant; and a water-soluble solvent. In addition, apart from water (tap water, purified water, distilled water, ion-exchanged water, pure water, etc.) which is a solvent in the remainder, dispersants, water-soluble resins, lubricants, thickeners, pH adjusters, rust inhibitors, preservatives, or antibacterial agents may be appropriately contained as needed, without impairing the effects of this disclosure.

[0079] As a usable dispersant, nonionic or anionic surfactants other than the aforementioned polyoxyethylene polycyclic phenyl surfactants are used.

[0080] The water-soluble resins used can be suitable for adjusting viscosity and improving adhesion. Specifically, examples include water-soluble resins with hydrophobic parts in the molecule, such as polyacrylic acid, water-soluble styrene-acrylic resin, water-soluble styrene / maleic acid resin, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble maleic acid resin, water-soluble styrene resin, polyvinylpyrrolidone, polyvinyl alcohol, water-soluble ester-acrylic resin, ethylene-maleic acid copolymer, polyethylene oxide, and water-soluble urethane resin, as well as resin emulsions selected from polyolefin emulsions, acrylic emulsions, vinyl acetate emulsions, urethane emulsions, styrene-butadiene emulsions, and styrene-acrylonitrile emulsions. It is desirable to use at least one of these resins, and a total of at least two.

[0081] Examples of usable lubricants include fatty acid esters of polyols, higher fatty acid esters of sugars, higher fatty acid esters of polyoxyethylene, nonionic alkyl phosphates, phosphate esters, anionic alkyl sulfonates and alkyl allyl sulfonates of higher fatty acid amides, derivatives of polyalkylene glycols, and polyether-modified organosilicones.

[0082] As a usable thickener, a known substance may be used. Specifically, at least one of the following can be selected from alkali-swellable associative emulsions, alkali-swellable emulsions, polyvinylpyrrolidone, cellulose derivatives, xanthan gum, polysaccharides such as succinosaccharides, cross-linked acrylic polymers, crystalline cellulose, leozan gum, gellan gum, montmorillonite clay minerals, and other inorganic thickeners.

[0083] Examples of pH adjusters include ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, sodium tripolyphosphate, sodium carbonate and other alkali metal salts of carbonic and phosphoric acids, and hydrates of alkali metals such as sodium hydroxide. Examples of rust inhibitors include benzotriazole, toluenetriazole, dicyclohexammonium nitrite, and saponins. Examples of preservatives or antibacterial agents include phenol, sodium pyrithione, sodium benzoate, thiazoline compounds, and benzimidazole compounds.

[0084] The aforementioned dispersants, lubricants, thickeners, pH adjusters, rust inhibitors, preservatives, or antibacterial agents can be used individually or in combination of two or more. Furthermore, if commercially available products are available, they can be used.

[0085] The water-based ballpoint pen ink composition disclosed herein can be manufactured without any particular change compared to the manufacturing methods of other water-based ink compositions.

[0086] That is, the water-based ballpoint pen ink composition disclosed herein can be manufactured as follows: at least pigments, microparticles with a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less, polyoxyethylene polycyclic phenyl surfactants, water-soluble solvents, and other components are mixed and stirred in a mixer, or even a bead mill, homogenizer, or homogenizer capable of applying strong shearing force, with the stirring conditions set to suitable conditions, and then further removed from the ink composition by filtration or centrifugation as needed, thereby manufacturing the water-based ballpoint pen ink composition.

[0087] Furthermore, regarding the pH (25°C) of the water-based ballpoint pen ink composition disclosed herein, from the perspectives of usability, safety, the stability of the ink itself, and compatibility with the ink reservoir, it is preferably adjusted to 5 to 10 by a pH adjuster or the like, and even more preferably to be set to 6 to 9.5.

[0088] The viscosity of the water-based ballpoint pen ink composition disclosed herein is expected to be 50 to 2000 mPa·s (25°C) at 1 rpm based on a cone-plate rotational viscometer (1°34′R24 cone), preferably 100 to 1000 mPa·s.

[0089] If the viscosity is below 50 mPa·s (25°C), the particles with the above characteristics become more prone to settling, which can easily cause clogging of the pen tip and sometimes worsen the initial writing performance. On the other hand, if the viscosity exceeds 2000 mPa·s (25°C), the flowability decreases and the writing feel sometimes worsens.

[0090] The disclosed water-based ballpoint pen ink composition is applied to a ballpoint pen having a pen tip or other similar part.

[0091] As an example of the water-based ballpoint pen disclosed herein, a water-based ballpoint pen may be constructed by housing the water-based ink composition described above within a ballpoint pen ink reservoir (refill) having a ball with a diameter of 0.18 to 2.0 mm, and simultaneously housing a substance that is incompatible with the water-based ink composition housed within the ink reservoir and has a lower specific gravity than the water-based ink composition, such as polybutene, silicone oil, or mineral oil, as an ink follower. As long as the ball has a diameter within the aforementioned range, the structure of the water-based ballpoint pen used is not particularly limited. It is particularly desirable to fill the aforementioned water-based ink composition into an ink reservoir tube made of polypropylene resin and then finely process it into a refill with a stainless steel tip (the ball being a super-steel alloy).

[0092] Furthermore, it can also be a direct-liquid ballpoint pen with a collector structure (ink retention mechanism) that fills the pen barrel itself, which serves as an ink reservoir, with the water-based ballpoint pen ink composition described above inside the pen barrel.

[0093] In this disclosure, particularly for water-based ballpoint pens with balls having a diameter of 0.18 to 2.0 mm, it is expected that it will be suitable for suppressing wear on the bearing socket.

[0094] The mechanism by which the water-based ballpoint pen ink composition of this disclosure, and the water-based ballpoint pen equipped with it, maintains a smooth writing feel even when stored for a long time with the nib pointing downwards, and effectively inhibits wear of the ball bearing socket, is as follows.

[0095] In other words, it is speculated that in a water-based ballpoint pen ink composition containing at least pigment, by including microparticles with a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less, as well as a polyoxyethylene polycyclic phenyl surfactant, the ink properties remain unchanged during long-term storage. During writing, the ink flows out stably with the rotation of the ball. At the same time, due to the pressure during writing, the microparticles with the above characteristics are embedded in the ball bearing socket. As a result, the surface hardness of the socket increases, thus inhibiting the wear of the socket with the rotation of the ball. Even in a long-term storage state, the microparticles and pigments with the above characteristics are uniformly and stably present in the ink sandwiched between the ball bearing socket during writing. Therefore, it does not hinder the rotation of the ball or the ink properties. Thus, the water-based ballpoint pen ink composition of this disclosure stably inhibits the wear of the ball bearing socket and provides a smooth and stable writing experience without impairing other writing performance.

[0096] The water-based ballpoint pen ink composition and the water-based ballpoint pen containing it exhibit an extremely good sustained effect of the present invention, and the effect is also long-lasting. Furthermore, due to its water-based nature, its stability over time is also excellent.

[0097] Example

[0098] Next, this disclosure will be described in further detail based on Examples 1 to 10 and Comparative Examples 1 to 5 of the water-based ballpoint pen ink composition and the water-based ballpoint pen containing the composition, but this disclosure is not limited to the following examples, etc.

[0099] [Examples 1-10 and Comparative Examples 1-5]

[0100] Based on the formulations shown in Table 1 below, various water-based ballpoint pen ink compositions were prepared using conventional methods.

[0101] For each of the obtained water-based ballpoint pen ink compositions (total mass 100%), the viscosity was determined at 1 rpm using a cone-plate rotational viscometer (1°34′R24 cone) according to the methods described below, and the abrasion resistance test and writing performance were evaluated according to the methods described below.

[0102] These results are shown in Table 1 below.

[0103] (Method for determining the viscosity of ink compositions)

[0104] For viscosity determination based on a cone-plate rotational viscometer, a cone-plate rotational viscometer EMD manufactured by Tokimec Co., Ltd. is used, and the viscosity value is recorded at 25°C, with an st rotor (1°34'R24 cone), and a rotational speed of 1 rpm.

[0105] The tips of ballpoint pens with various ball diameters (0.38mm and 0.5mm) were mounted on the tubes (both PP tubes with an inner diameter of 3.4mm) and polypropylene connectors of Mitsubishi Pencil's UM-151 and UMN-105 models. The water-based ink compositions obtained in the examples and comparative examples were filled with polybutene as an ink follower. After degassing by centrifugation (500G, 5 minutes), the pens were assembled into water-based ballpoint pens with various ball diameters. Then, various writing tests (abrasion resistance test and writing performance test) as shown below were performed.

[0106] For water-based ballpoint pens that were stored for 12 weeks with the nib pointing downwards at a temperature of 50°C and a humidity of 65%, writing tests were conducted using the following method. Evaluation tests were performed on all five ballpoint pens of various nib diameters.

[0107] 1) Abrasion resistance test: The mechanical writing test involves writing 1000m (end of stroke) spiral and is evaluated according to the following evaluation criteria.

[0108] Writing conditions: 100gf, writing angle 75 degrees, writing speed 4.5mm / minute

[0109] Evaluation Criteria:

[0110] A: I can write without any problems.

[0111] B: Slightly blurry, but still able to write until the stroke is finished.

[0112] C: The writing is somewhat blurry, but it is still possible to write until the stroke ends.

[0113] D: At least one or more lines have reduced flow.

[0114] 2) Evaluation methods for handwriting

[0115] Using the various water-based ballpoint pens obtained above, perform "spiral writing" on writing paper freehand, and evaluate the writing feel using the following evaluation criteria.

[0116] Evaluation Criteria:

[0117] A: Smooth and stable writing.

[0118] B: A rather stiff or rigid writing style.

[0119] C: This indicates a stiff or rigid writing style with some broken lines and directional inconsistencies.

[0120] D: This refers to a stiff, rigid writing style with obvious breaks and directionality.

[0121] [Table 1]

[0122]

[0123] The numbers *1 to *3 in Table 1 above are as follows.

[0124] *1: Manufactured by Mitsubishi Chemical Corporation, average particle size 0.1 μm

[0125] *2: Blue colored resin particles, average particle size 1.2μm

[0126] *3: Red thermochromic pigment, average particle size 3.0μm, decolorization temperature 60℃

[0127] The results in Table 1 above confirm that, compared with Comparative Examples 1 to 5 which are not within the scope of this disclosure, the two types of water-based ballpoint pens with different ball diameters equipped with the water-based ballpoint pen ink compositions of Examples 1 to 10 which are within the scope of this disclosure have excellent wear resistance and writing performance even after long-term storage, and can be highly balanced.

[0128] Industrial availability

[0129] A suitable ink composition for water-based ballpoint pens was obtained.

Claims

1. A water-based ballpoint pen ink composition, characterized in that, It contains at least: colorant; microparticles with a new Mohs hardness of 3 or higher and an average particle size of 30 μm or less; polyoxyethylene polycyclic phenyl surfactant; and water-soluble solvent. The ratio of the content of the microparticles to the content of the polyoxyethylene polycyclic phenyl surfactant is 0.005 to 1.

5.

2. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The value obtained by multiplying the new Mohs hardness of the particles by the average particle size (μm) is 0.02 to 450.

3. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The content of the particles is 0.001 to 5% by mass relative to the total amount of the ink composition.

4. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The polyoxyethylene polycyclic phenyl surfactant is polyoxyethylene styrene phenyl ether.

5. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The content of the polyoxyethylene polycyclic phenyl surfactant is 0.05 to 20% by mass relative to the total amount of the ink composition.

6. The water-based ballpoint pen ink composition according to claim 1, wherein the viscosity at 1 rpm based on a cone-plate rotational viscometer (1°34′R24 cone) is 50–2000 mPa·s (25°C).

7. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The ratio of the content of the microparticles to the content of the polyoxyethylene polycyclic phenyl surfactant is 0.05 to 1.

5.

8. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The polyoxyethylene polycyclic phenyl surfactant is represented by formula (1). In the above formula (1), X is a polycyclic phenyl group; AO is an alkylene oxide with 2 to 5 carbon atoms; Z is SO3M or a hydrogen atom, M is a hydrogen atom, or an organic or inorganic cation; and n is a number from 3 to 120.

9. The water-based ballpoint pen ink composition according to claim 1, characterized in that, The polyoxyethylene polycyclic phenyl surfactant is represented by formula (1). In the above formula (1), X is a polycyclic phenyl group; AO is an alkylene oxide with 2 to 5 carbon atoms; Z is a hydrogen atom; n is a number between 3 and 120.

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