Gel ink for writing pens without followers

Abstract

The present disclosure relates to a writing instrument having a writing tip, the writing instrument comprising a non-aqueous writing ink contained within a tubular ink cartridge, the tubular ink cartridge having an inner diameter of about 1 mm to about 2.5 mm and two open ends, the first open end being connected to the writing tip and the second open end being connected to an environment external to the writing instrument, the non-aqueous writing ink contained within the tubular ink cartridge being in fluid communication with the writing tip via the first open end and with the environment external to the writing instrument via the second open end, the non-aqueous writing ink comprising a solvent, a resin, a colorant, and a gelling agent, the gelling agent being a mixture of silica particles and a fatty acid amide wax, the resin being used in an amount greater than about 3% by weight based on the total weight of the ink.

Description

[Technical Field]

[0001] This disclosure relates to the field of writing instruments, particularly pens such as ballpoint pens, and writing inks for use in such writing instruments. [Background technology]

[0002] Traditionally, ballpoint pen inks are Newtonian high-viscosity solvent-based inks. Due to the use of low-volatility glycol solvents, ballpoint pen inks are very stable during storage because the ink does not dry out. Therefore, such inks can be used in pens without tip protection. While such glycol solvent-based systems are desirable, they also typically possess high shear viscosity. Again, high shear viscosity is not an undesirable characteristic in itself, as it helps avoid static leakage. Static leakage corresponds to the formation of ink droplets at the tip, especially when the pen is stored upside down in hot and humid conditions. In the Newtonian system, high shear viscosity also correlates with static viscosity and therefore helps reduce the problem of pigment and other solids settling, which can clog the pen tip. However, in the state of high shear viscosity, the writing experience is not as smooth as consumers desire. Balancing these characteristics has proven to be very difficult.

[0003] To solve these problems, compounders turned to gel inks. Gel inks have a pseudoplastic fluid profile. Generally, gel inks are water-based. They offer a good compromise between low static leakage, smoothness, and particle stabilization. However, they still suffer from several drawbacks.

[0004] Water is a lightweight and volatile solvent. If stored without tip protection (cap or hot melt), the ink inside the tip can dry out and clog the tip. Furthermore, it has been found that the cap-off time for gel ink pens is significantly shorter than that for glycol ballpoint pens.

[0005] Despite the use of corrosion inhibitors, water-based inks remain corrosive fluids. Therefore, using brass tips is impossible, and it is essential to use stainless steel tips, which are extremely expensive and difficult to manufacture due to their hardness.

[0006] Furthermore, because water has poor lubrication properties, it is essential to use a strong flow rate at the tip. In the case of a typical pen, it has been found that the flow rate of a ballpoint pen with water-based ink cannot be reduced to less than approximately 300 mg / 200 m. This is disadvantageous compared to glycol-based ink, which has a flow rate of approximately 35 mg / 200 m. As a result, the lifespan (i.e., the total writing distance) of a water-based ink pen is much shorter than that of a glycol-based ink pen.

[0007] Glycol-based inks for ballpoint pens, or more generally, solvent-based inks, have also been described in the prior art. In particular, JP3078172 and JPH07-196972 describe the use of fatty acid amide waxes as thixotropic agents in oil-based ink compositions. However, the use of fatty acid amide waxes alone is not sufficient to avoid static leakage of the ink. In WO2019 / 122017 A1, this technical problem is addressed by using a combination of fatty acid amide waxes and silica particles, which are used as gelling agents.

[0008] However, there is still room for further improvement in solvent-based inks for pens, particularly when trying to balance the rheological properties of the ink to achieve both excellent writing performance and the avoidance of ink leakage from the pen, both after dynamic situations (e.g., by discharging ink from the cartridge while writing) and after static situations (e.g., storing the pen on a shelf or in a pocket under heat and humidity, such as when keeping the pen close to the body).

[0009] Another issue associated with balancing rheological properties is that the ink contained within the pen's cartridge must not be accidentally displaced when the pen is subjected to impact, for example, by dropping it from a certain height. The force exerted on the ink when a falling pen hits the ground, though short-lived, is considerable and can cause the ink reservoir to split into multiple separate reservoirs, disrupting or depleting the continuous flow of ink during writing. This problem also depends on the geometry of the cartridge, as thinner cartridges are subject to different capillary forces and surface tension on the inner wall surface of the cartridge. The problem of drops causing reservoir splitting can be mitigated by providing the cartridge with a so-called follower. The follower is a viscous yet fluid composition provided at the rear end of the ink reservoir within the cartridge. It is primarily provided to prevent ink from leaking out of the open rear end of the cartridge. Thus, the action of the follower can be likened to the action of a movable plug. However, followers may also have additional functions, such as preventing the reservoir from splitting (by eliminating empty ink spaces in the reservoir that could expand in response to the pen being dropped). While it is a solution that meets one criterion, adding followers is an additional manufacturing process and adds cost. In addition, there is a risk that the follower will mix with the ink at high temperatures, and the colorants will migrate to the follower, giving the pen a darker appearance than it actually is. Therefore, it may be preferable not to use followers. [Overview of the project]

[0010] To our surprise, the inventors have found that certain non-aqueous writing ink compositions do not require the use of a follower in certain tubular cartridges, particularly to prevent the ink reservoir from splitting when the aforementioned writing instrument is dropped.

[0011] In a first aspect, the disclosure relates to a writing instrument. The writing instrument may be a pen, in particular a ballpoint pen. The writing instrument may comprise a tubular ink cartridge. The tubular ink cartridge may have an inner diameter of about 1 mm to about 2.5 mm and two open ends. The first open end of the tubular ink cartridge may be connected to the writing tip. The second open end of the tubular ink cartridge may be connected to the external environment of the writing instrument.

[0012] The writing instrument may contain a non-aqueous writing ink. The non-aqueous writing ink may contain a solvent, resin, colorant, and gelling agent. The gelling agent may include a mixture of silica particles and fatty acid amide wax. The resin may be used in an amount exceeding approximately 3% by weight relative to the total weight of the ink.

[0013] In some embodiments, the resin may be selected from polyester resins, polyurethane resins, ketone resins, ether resins, and mixtures thereof. In some embodiments, the resin may be present in an amount of about 3 to about 30%, specifically about 3 to about 25%, and in particular about 5 to about 20%, relative to the total weight of the ink.

[0014] In some embodiments, the non-aqueous writing ink may contain a homo- or copolymer of vinylpyrrolidone. In some embodiments, the homo- or copolymer of vinylpyrrolidone may, advantageously, contain polyvinylpyrrolidone. In some embodiments, the homo- or copolymer of vinylpyrrolidone may be present in an amount of about 0.05 to about 0.8% by weight, more specifically, about 0.1 to about 0.6% by weight, and in particular, about 0.15 to about 0.5% by weight, relative to the total weight of the ink.

[0015] In some embodiments, the vinylpyrrolidone homo or copolymer may be polyvinylpyrrolidone having a weight-average molecular weight greater than about 200 kDa, specifically about 400 to about 2300 kDa, more specifically about 450 to about 2000 kDa, and in particular about 600 to about 1900 kDa.

[0016] In some embodiments, the weight of a homo- or copolymer of vinylpyrrolidone, particularly polyvinylpyrrolidone, may be less than the weight of the mixture of silica particles and fatty acid amide wax.

[0017] In some embodiments, the silica particles may include hydrophilic silica particles. In some embodiments, the hydrophilic silica particles may be present in an amount of about 0.10 to about 0.60% by weight relative to the total weight of the ink.

[0018] In some embodiments, the fatty acid amide wax may include N,N'-ethylene-bis-fatty acid amide. In some embodiments, the fatty acid amide wax is of the following formula (I) [ka] It may be advantageous to include octadecanamide.

[0019] In some embodiments, the gelling agent may be present in an amount of about 0.1 to about 1.2% by weight, more specifically, about 0.15 to about 0.60% by weight, relative to the total weight of the ink.

[0020] In some embodiments, the solvent may be selected from the group consisting of glycol ethers, alcohols, and mixtures thereof. It may be advantageous for the solvent to be selected from polyethylene glycol ether, polypropylene glycol ether, phenoxyethanol, 1-phenoxy-2-propanol, or mixtures thereof.

[0021] In some embodiments, the solvent may be present in an amount of about 35 to about 80% by weight relative to the total weight of the ink. In some embodiments, it may be advantageous for the solvent to be present in an amount of about 45 to about 75% by weight relative to the total weight of the ink.

[0022] In some embodiments, the colorant may be a dye, particularly one selected from the group consisting of azo dyes, triarylmethane dyes, phthalocyanine derivative dyes, xanthene dyes, and mixtures thereof.

[0023] In some embodiments, the colorant may be present in an amount of about 5 to about 30% by weight, particularly about 7 to about 28% by weight, based on the total weight of the ink.

[0024] In some embodiments, the non-aqueous writing ink may further include one or more additives. In some embodiments, the additive may be an additional gelling agent. In some embodiments, it may be advantageous for the non-aqueous writing ink to further include one or more additives selected from the group consisting of thickeners, clear drain agents, tackifiers, lubricants, dispersants, and mixtures thereof.

[0025] In some embodiments, the non-aqueous writing ink may include about 0.1 to about 0.6% by weight of polyvinylpyrrolidone having a weight average molecular weight of about 450 to about 2000 kDa, about 0.15 to about 0.60% by weight of fatty acid amide wax, and about 0.15 to about 0.60% by weight of hydrophilic silica, in amounts based on the total weight of the ink.

[0026] In some embodiments, the non-aqueous writing ink may include a resin selected from polyester resins, polyurethane resins, ketone resins, ether resins, and mixtures thereof. It may be advantageous for the resin to be a ketone resin. Additionally or alternatively, the resin may be present in an amount of about 3 to about 30%, specifically about 3 to about 25%, particularly about 5 to about 20%, based on the total weight of the ink. Alternatively, the ink may include about 55 to about 75% by weight of 1-phenoxy-2-propanol. The fatty acid amide wax of the non-aqueous writing ink is N,N'-ethylene-bis-fatty acid amide, particularly the octadecanamide of the following formula (I)

Chemical formula

[0027] In some embodiments, the ink may have a resting loss coefficient tanδ of about 3 to about 15, more specifically about 4 to about 12, and in particular about 5 to about 10. Additionally or alternatively, the ink may have a post-shear loss coefficient of about 8 to about 60, more specifically about 11 to about 50, and in particular about 15 to about 40.

[0028] In some embodiments, the non-aqueous writing ink may consist of the following components in proportion to the total weight of the ink: about 55 to about 75% by weight of a solvent selected from polyethylene glycol ether, polypropylene glycol ether, phenoxyethanol, 1-phenoxy-2-propanol, or a mixture thereof; about 10 to about 30% by weight of a colorant; about 0.10 to about 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of about 600 to about 1900 kDa; about 0.15 to about 0.60% by weight of a fatty acid amide wax; about 0.15 to about 0.60% by weight of hydrophilic silica; and the remaining components selected from resins and additives.

[0029] In some embodiments, the non-aqueous writing ink comprises the following components in amounts relative to the total weight of the ink: about 55 to about 75% by weight of 1-phenoxy-2-propanol, about 10 to about 30% by weight of a colorant, about 0.10 to about 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of about 600 to about 1900 kDa, and N,N'-ethylene-bis-fatty acid amide, in particular, the following formula (I) [ka] A fatty acid amide wax containing N,N'-ethylene-bis-fatty acid amide having the following properties, in an amount of approximately 0.15 to approximately 0.60% by weight, It may contain, or may consist of, approximately 0.15 to approximately 0.60 wt% hydrophilic silica, approximately 5 to approximately 15 wt% resin, and additives, in particular the remaining components which are additives as defined above.

[0030] In a second aspect, the disclosure relates to a process for preparing a writing instrument according to a first aspect of the disclosure. A non-aqueous writing ink may be prepared by the following steps: a) forming a first premixture containing silica particles in a solvent. The temperature in this step may be about 30 to about 70°C. The first premixture may be mixed at a shear rate of about 20 to about 25 m / s. b) combining the first premixture with the remaining components of the non-aqueous writing ink.

[0031] In some embodiments, a non-aqueous writing ink may be prepared by the following steps: a) forming a first premixture containing silica particles in a solvent. The temperature in this step may be about 30 to about 70°C. The first premixture may be mixed at a shear rate of about 20 to about 25 m / s. b) forming a second premixture containing fatty acid amide wax in a solvent. The temperature in this step may be about 30 to about 70°C. The second premixture may be mixed at a shear rate of about 20 to about 25 m / s. c) combining the first and second premixtures with the remaining components of the non-aqueous writing ink.

[0032] The embodiments described in the first aspect of this disclosure described above can be combined in the same manner as the second aspect of this disclosure described above. [Brief explanation of the drawing]

[0033] [Figure 1] The performance of Examples 1-5 and Comparative Examples 1-6 is summarized below. [Modes for carrying out the invention]

[0034] The present disclosure is described in detail below. Terms or words used in the description and claims of this disclosure should not be constrained to have only common language or dictionary meanings, but should be construed to have their ordinary technical meanings as established in the relevant art, unless specifically defined below. While the detailed description refers to specific embodiments to better illustrate the disclosure, it should be understood that the presented disclosure is not limited to these specific embodiments.

[0035] In a first aspect, the disclosure relates to a writing instrument. The writing instrument may be a pen, in particular a ballpoint pen. The writing instrument may comprise a tubular ink cartridge. The tubular ink cartridge may have an inner diameter of about 1 mm to about 2.5 mm, more specifically about 1.2 mm to about 2.0 mm, and more specifically about 1.4 mm to about 1.8 mm. The tubular ink cartridge may further have two open ends. The first open end of the tubular ink cartridge may be connected to the writing tip. The entire pen may be configured so that ink can exit the tubular ink cartridge through the first open end, which is supplied to the writing tip. The second open end of the tubular ink cartridge may be connected to the external environment of the writing instrument. Alternatively, the second open end of the tubular ink cartridge may be in fluid communication with the outside of the tubular ink cartridge. Alternatively, the tubular ink cartridge may be configured such that the ink or other reference liquid contained within the tubular ink cartridge can exit the cartridge through a second open end of the tubular ink cartridge. Alternatively, the tubular ink cartridge may not contain a follower. Alternatively, the tubular ink cartridge may not contain a fluid composition positioned between the ink reservoir contained within the tubular ink cartridge and its second open end. Alternatively, the contents of the tubular ink cartridge may consist of non-aqueous writing ink and air.

[0036] Writing instruments may contain non-aqueous writing inks. In this context, non-aqueous means that the ink does not contain water as a solvent for the dye / pigment and / or is substantially free (e.g., contains less than about 2% by weight of water relative to the total weight of the ink), or does not contain water at all.

[0037] Non-aqueous writing inks may contain a solvent, a resin, a colorant, and a gelling agent. The gelling agent may include a mixture of silica particles and a fatty acid amide wax. The resin may be used in an amount exceeding about 3% by weight, more specifically exceeding about 4% by weight, and in particular exceeding about 5% by weight, relative to the total weight of the ink.

[0038] Non-aqueous writing inks may contain a resin. The resin can impart viscosity to the ink and / or act as a binder. It may be a natural or synthetic resin. The resin may include polyester resins, polyurethane resins, ketone resins such as ketone-formaldehyde resins such as acetophenone-formaldehyde modified resins, ether resins, vinyl resins such as vinyl chloride copolymers, polyvinyl butyral, vinyl acetate, vinyl acetate copolymers, or polyvinyl alcohol resins, acrylic resins, styrene-acrylic resins, styrene-maleic acid copolymer resins, rosin-maleic acid copolymer resins, phenolic resins, cellulose resins, amide resins, alkyd resins, rosin-modified resins, rosin-modified phenolic resins, xylene resins, polyacetal resins, terpene resins, phenoxy resins, or mixtures thereof. In some embodiments, a resin selected from polyester resins, polyurethane resins, ketone resins, ether resins, and mixtures thereof may be advantageous. It may be particularly advantageous for the resin to be a ketone resin.

[0039] In some embodiments, the resin may be present in an amount of about 3 to about 30%, specifically about 3 to about 25%, and in particular about 5 to about 20%, relative to the total weight of the ink.

[0040] Non-aqueous writing inks may contain a gelling agent. The gelling agent may include a mixture of silica particles and fatty acid amide wax. It should be understood that the presence of further gelling agents is not ruled out, and that one or more further gelling agents may be optionally added to the ink. The term “mixture” is not particularly limited and is intended to refer to any combination containing silica particles and fatty acid amide wax. In some embodiments, it may be advantageous to pre-mix the silica particles and fatty acid amide wax. Preferred processes for doing so are described in more detail below.

[0041] In some embodiments, the silica particles may include silica particles. It may be advantageous for the silica particles to be hydrophilic silica particles. It may be advantageous for the silica particles to be fumed silica particles, in particular hydrophilic fumed silica particles such as the product sold by Evonik under the trade name AEROSIL® 200.

[0042] In some embodiments, the non-aqueous writing ink may contain dispersed silica particles or silica-based gel-like particles, the average particle size of which is less than about 1 μm, specifically less than about 0.9 μm, and in particular less than about 0.8 μm, using dynamic light scattering (DLS) such as Malvern Zetasizer ZS.

[0043] The use of fatty acid amide waxes is well established in the art, particularly as rheological modifiers. Suitable fatty acid residues may include aliphatic carboxylic acids having more than about six carbon atoms, especially about six to about 24 carbon atoms, or about six to about 18 carbon atoms. The aliphatic carboxylic acid may be optionally substituted, especially with a hydroxyl group. Examples of suitable fatty acid residues include residues derived from caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, hydroxystearic acid, arachidic acid, and behenic acid.

[0044] In some embodiments, the fatty acid amide wax is a fatty acid diamide wax. The fatty acid diamide wax may include a fatty acid diamide containing two fatty acid residues having about six or more carbon atoms, particularly about six to about 24 carbon atoms, or about six to about 18 carbon atoms, which may be optionally substituted, in particular, with a hydroxyl group. It may be advantageous for the fatty acid diamide wax to include an N,N'-alkylene moiety having one to about 12 carbon atoms, particularly one to about six carbon atoms, or particularly about two to about four carbon atoms. It may be particularly advantageous for the fatty acid diamide wax to include an N,N'-ethylene-bis-fatty acid amide, in particular, where two fatty acid residues independently contain about six or more carbon atoms, particularly about six to about 24 carbon atoms, or about six to about 18 carbon atoms. Each of the fatty acid residues may further, and independently of each other, be substituted, in particular, with a hydroxyl group.

[0045] In some embodiments, it may be advantageous that the fatty acid amide wax may include 12-hydroxy-N-[2-[(1-oxooctyl)amino]ethyl]octadecanamide, N,N'-1,2-ethylenebis(12-hydroxy-octadecanamide), N,N'-1,2-ethylenebis(12-hydroxyoctadecanamide), N,N'-ethylenebis(12-hydroxystearamide), N,N'-ethylenebis(caprylamide), or a mixture thereof.

[0046] In some embodiments, the fatty acid amide wax is of the following formula (I) [ka] It may be advantageous to include octadecanamide.

[0047] In some embodiments, the gelling agent may be present in an amount of about 0.1 to about 1.2% by weight, more specifically, about 0.15 to about 0.60% by weight, relative to the total weight of the ink.

[0048] In some embodiments, hydrophilic silica particles may be present in an amount of about 0.10 to about 0.60% by weight relative to the total weight of the ink.

[0049] In some embodiments, the fatty acid amide wax may be present in an amount of about 0.10 to about 0.60% by weight relative to the total weight of the ink.

[0050] Non-aqueous writing inks may contain a solvent. The term “solvent” is not intended to be particularly limited and includes, among other things, a medium for dispersing or suspending solid components such as pigments. In some embodiments, the solvent may be selected from the group consisting of glycol ethers, alcohols, and mixtures thereof. It may be advantageous for the solvent to be selected from polyethylene glycol ether, polypropylene glycol ether, phenoxyethanol, 1-phenoxy-2-propanol, or mixtures thereof. In some embodiments, the alcohol is an alcohol having a high boiling point, such as above about 130°C, above about 150°C, or above about 200°C. In some embodiments, the alcohol may be selected from the group consisting of benzyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, glycerin, and mixtures thereof. It may be particularly advantageous for the alcohol to be benzyl alcohol. In another embodiment, the solvent may be a glycol ether having a high boiling point, such as above about 130°C, above about 150°C, or above about 200°C. It may be advantageous for the glycol ether to be selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripylene glycol monomethyl ether, phenoxyethanol, phenoxypropanol, and mixtures thereof. It may be particularly advantageous for the glycol ether to be selected from the group consisting of phenoxyethanol, 1-phenoxy-2-propanol, and mixtures thereof.

[0051] In some embodiments, the solvent may be present in an amount of about 35 to about 80% by weight relative to the total weight of the ink. In some embodiments, it may be advantageous for the solvent to be present in an amount of about 45 to about 75% by weight relative to the total weight of the ink.

[0052] In some embodiments, it may be advantageous for the ink to contain about 55 to about 75% by weight of 1-phenoxy-2-propanol.

[0053] In some embodiments, the colorant may be a dye, a pigment, or a mixture thereof, particularly a dye or pigment selected from the group consisting of azo dyes, triarylmethane dyes, phthalocyanine derivative dyes, xanthene dyes, and mixtures thereof. In some embodiments, the colorant may be a pigment.

[0054] Examples of dyes usable in inks according to this disclosure include: VARIFAST Black 3806 (CISolvent Black 29), 3807 (trimethylbenzylammonium salt of CISolvent Black 29), Spirit Black SB (CISolvent Black 5), SPIRON Black GMH (CISolvent Black 43), Solvent Black 46 (salt forms of CIBasic Violet 3 and Acid Yellow 36), VARIFAST Red 1308 (salt forms of CIBasic Red 1 dye and CIAcid Yellow 23 dye), Solvent Red 49, VARIFAST Yellow AUM (salt forms of CIBasic Yellow 2 dye and CIAcid Yellow 42 dye), SPIRON Yellow C2 GH (organic acid salt of CIBasic Yellow 2), SPIRON Violet CRH (CISolvent Violet 8-1), VARIFAST Violet 1701 (salt forms of CIBasic Violet 1 and CIAcid Yellow 42 dye), SPIRON Red CGH (CIBasic It contains Red1 organic acid salt, SPIRON Pink BH (CISolvent Red82), Nigrosine Base EX (CISolvent Black7), Oil Blue613 (CISolvent Blue5), and Neozapon Blue808 (CISolvent Blue70).

[0055] In some embodiments, the colorant may be a dye and may be selected from salt-forming dyes and mixtures thereof, such as Solvent Black 46 (salt-forming forms of CIBasic Violet 3 and Acid Yellow 36), VARIFAST Red 1308 (salt-forming forms of CIBasic Red 1 dye and CIAcid Yellow 23 dye), VARIFAST Yellow AUM (salt-forming forms of CIBasic Yellow 2 dye and CIAcid Yellow 42 dye), and VARIFAST Violet 1701 (salt-forming forms of CIBasic Violet 1 and CIAcid Yellow 42 dye).

[0056] Examples of pigments usable in inks according to this disclosure include organic, inorganic, and processed pigments. Therefore, pigments may include, for example, inorganic pigments such as carbon black, ultramarine, and titanium dioxide pigments; organic pigments such as azo pigments, phthalocyanine pigments, indigo pigments, thioindigo pigments, surene pigments, quinacridone pigments, anthraquinone pigments, thorone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, perylene pigments, perinone pigments, and isoindolinone pigments; metallic pigments such as aluminum powder or aluminum powder whose surface is treated with a colored resin; metallic luster pigments obtained by forming a metal vapor-deposited film such as aluminum on a transparent or colored transparent film; metallic pigments having a thickness of about 0.01 to about 0.1 μm obtained by peeling off a metal vapor-deposited film such as aluminum formed on a substrate such as a film; colloidal particles having an average particle size of about 5 to about 30 nm selected from gold, silver, platinum, and copper; fluorescent pigments; phosphorescent pigments; naturally occurring mica, synthetic mica, glass flakes, alumina; and pearl pigments obtained by coating the surface of a core, which is a transparent film, with a metal oxide such as titanium dioxide.

[0057] In some embodiments, the colorant may be present in an amount of about 5 to about 30% by weight, and particularly about 7 to about 28% by weight, relative to the total weight of the ink.

[0058] In some embodiments, the non-aqueous writing ink may contain a homo- or copolymer of vinylpyrrolidone. In some embodiments, the homo- or copolymer of vinylpyrrolidone may, advantageously, contain polyvinylpyrrolidone. In some embodiments, it may be advantageous for the homo- or copolymer of vinylpyrrolidone to be present in an amount of about 0.05 to about 0.8% by weight, more specifically, about 0.1 to about 0.6% by weight, and in particular, about 0.15 to about 0.5% by weight, relative to the total weight of the ink.

[0059] In some embodiments, the homo or copolymer of vinylpyrrolidone may have a weight-average molecular weight greater than about 200 kDa, specifically about 400 to about 2300 kDa, more specifically about 450 to about 2000 kDa, and in particular about 600 to about 1900 kDa.

[0060] In some embodiments, the weight of vinylpyrrolidone, particularly polyvinylpyrrolidone homo or copolymer, may be less than the weight of the mixture of silica particles and fatty acid amide wax.

[0061] In some embodiments, the non-aqueous writing ink may further contain one or more additives. In some embodiments, the additives may be further gelling agents. In some embodiments, it may be advantageous for the non-aqueous writing ink to further contain one or more additives. In some embodiments, the additives may be selected from the group consisting of thickeners, clear drainers, viscosity modifiers, lubricants, dispersants, and mixtures thereof.

[0062] In some embodiments, the non-aqueous writing ink may contain, in terms of amount relative to the total weight of the ink, about 0.1 to about 0.6% by weight of polyvinylpyrrolidone having a weight-average molecular weight of about 450 to about 2000 kDa, about 0.15 to about 0.60% by weight of fatty acid amide wax, and about 0.15 to about 0.60% by weight of hydrophilic silica.

[0063] In some embodiments, the non-aqueous writing ink may comprise, in amounts relative to the total weight of the ink, the following components: about 55 to about 75% by weight of a solvent selected from polyethylene glycol ether, polypropylene glycol ether, phenoxyethanol, 1-phenoxy-2-propanol, or a mixture thereof; about 10 to about 30% by weight of a colorant; about 0.10 to about 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of about 600 to about 1900 kDa; about 0.15 to about 0.60% by weight of a fatty acid amide wax; about 0.15 to about 0.60% by weight of hydrophilic silica; and the remaining components selected from resins and additives.

[0064] In some embodiments, the non-aqueous writing ink comprises the following components in amounts relative to the total weight of the ink: about 55 to about 75% by weight of 1-phenoxy-2-propanol, about 10 to about 30% by weight of a colorant, about 0.10 to about 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of about 600 to about 1900 kDa, and N,N'-ethylene-bis-fatty acid amide, in particular, the following formula (I) [ka] A fatty acid amide wax containing N,N'-ethylene-bis-fatty acid amide having the following properties, in an amount of approximately 0.15 to approximately 0.60% by weight, It may contain, or may consist of, approximately 0.15 to approximately 0.60 wt% hydrophilic silica, approximately 5 to approximately 15 wt% resin, and additives, in particular the remaining components which are additives as defined above.

[0065] In some embodiments, the non-aqueous writing ink may have a static viscosity of about 30,000 cps to about 150,000 cps, more specifically, about 40,000 cps to about 120,000 cps, and in particular, about 50,000 cps to about 100,000 cps at about 20°C. The static viscosity is 0.01 seconds -1 At a shear rate of approximately 40 mm, it can be measured at approximately 20°C using a conical plate rheometer, such as a rheometer by Malvern Kinexus, which has a cone of approximately 40 mm and an angle of approximately 4°.

[0066] In some embodiments, the non-aqueous writing ink is heated at approximately 20°C for approximately 100 seconds. -1 Under shear, it can have a viscosity of approximately 1200 cps to approximately 10000 cps, more specifically, approximately 1300 cps to approximately 5000 cps, and in particular, approximately 1500 cps to approximately 4000 cps. The viscosity under shear is 100 seconds -1 At this shear rate, it can be measured at approximately 20°C using a conical plate rheometer such as a Malvern Kinexus rheometer with a cone of approximately 40 mm and an angle of approximately 4°.

[0067] In some embodiments, non-aqueous writing inks may have a resting loss coefficient tanδ of about 3 to about 15, more specifically, about 4 to about 12, and in particular, about 5 to about 10. The resting loss coefficient tanδ can be measured at about 20°C using a conical plate rheometer, such as a rheometer by Malvern Kinexus, which has a cone of about 40 mm and an angle of about 4°, in vibration measurements (frequency = about 1 Hz, shear about 20 Pa).

[0068] In some embodiments, non-aqueous writing inks may have a post-shear loss coefficient tan of about 8 to about 60, more specifically about 11 to about 50, and in particular about 15 to about 40. The post-shear loss coefficient tanδ is about 1000 seconds. -1 After pre-shearing for approximately 30 seconds, vibration measurements (frequency = approximately 1 Hz, shear approximately 20 Pa) can be taken at approximately 20°C using a conical plate rheometer, such as a Malvern Kinexus rheometer, which has a cone of approximately 40 mm and an angle of approximately 4°.

[0069] In a second aspect, the Disclosure relates to a process for preparing a writing instrument according to a first aspect of the Disclosure or a non-aqueous writing ink according to a second aspect of the Disclosure. The process is not particularly limited.

[0070] Therefore, in some embodiments, a non-aqueous writing ink may be prepared by the following steps, in one step, a first premixture containing silica particles in a solvent is formed. The temperature in this step may be about 30 to about 70°C. The first premixture may be mixed at a shear rate of about 20 to about 25 m / s. In another step, a second premixture containing fatty acid amide wax in a solvent is formed. The temperature in this step may be about 30 to about 70°C. It should be understood that the step of forming the first premixture can be carried out with only a portion of the solvent that will be contained in the final writing ink. The first premixture may then be combined with the remaining components of the writing ink.

[0071] However, in some embodiments, it may be advantageous for the fatty acid amide wax to be activated by the formation of a premixture in a solvent (second premixture), preferably in a solvent such as those described above for the ink, particularly in a glycol ether, before being added to the writing ink containing the (remaining) solvent and colorant, silica particles, and optionally, additives. While we do not wish to be bound by theory, it is thought that such activation may allow for the diffusion of the fatty acid amide wax and, therefore, the acquisition of a stronger gel network. Advantageously, the activation step (formation of the premixture) can be carried out under precise temperature and shear stress.

[0072] Therefore, in some embodiments, a non-aqueous writing ink may be prepared by the following steps, in one step, a first premixture containing silica particles in a solvent is formed. The temperature in this step may be about 30 to about 70°C. The first premixture may be mixed at a shear rate of about 20 to about 25 m / s. In another step, a second premixture containing fatty acid amide wax in a solvent is formed. The temperature in this step may be about 30 to about 70°C. The second premixture may be mixed at a shear rate of about 20 to about 25 m / s. It should be understood that the steps of forming the first and second premixtures may be carried out with only a portion of the solvent that will be contained in the final writing ink. The first and second premixtures may then be combined with the remaining components of the writing ink.

[0073] A rotor-stator disperser may be used to obtain a preliminary mixture. The activation of the fatty acid amide wax can be observed by measuring the static viscosity of the preliminary mixture. The static viscosity reaches its maximum when activation is complete (diffusion of the fatty acid amide wax increases the static viscosity).

[0074] The embodiments described in the first aspect of this disclosure described above can be combined in the same manner as the second aspect of this disclosure described above.

[0075] In a third aspect, the Disclosure relates in particular to a non-aqueous writing ink for a writing instrument as defined in the first aspect of the Disclosure, wherein the non-aqueous writing ink may comprise a solvent, a resin, a colorant, and a gelling agent, the gelling agent may comprise a mixture of silica particles and a homo or copolymer of vinylpyrrolidone, in particular polyvinylpyrrolidone.

[0076] The embodiments described in the first aspect of this disclosure described above can be combined in the same manner as the third aspect of this disclosure described above.

[0077] The present disclosure will be explained in more detail below as an example. [Examples]

[0078] Measurement method The measurements of the ink and pen were carried out as follows. 1. Measurement of residual viscosity The viscosity of the ink was measured at 20 °C using a Malvern Kinexus cone and plate rheometer with a 40 mm cone and an angle of 4° at a shear rate of 0.01 s. -1

[0079] 2. Measurement of shear viscosity The viscosity of the ink was measured at 20 °C using a Malvern Kinexus cone and plate rheometer with a 40 mm cone and an angle of 4° at a shear rate of 100 s. -1

[0080] 3. Determination of shear thinning index Formula: Shear thinning index = (Measurement of residual viscosity at 0.01 s at 20 °C, P4° / 40 mm) -1 / (Measurement of residual viscosity at 100 s at 20 °C, P4° / 40 mm) -1

[0081] 4. Measurement of tan delta at rest The measurement was carried out using a Malvern Kinexus cone and plate rheometer with a 40 mm cone and an angle of 4° by vibration measurement (frequency = 1 Hz, shear 20 Pa).

[0082] 5. Measurement of tan delta after shear at 1000 s -1 The measurement was carried out using a Malvern Kinexus cone and plate rheometer with a 40 mm cone and an angle of 4° after pre-shearing the sample for about 1000 s -1 for about 30 s (to simulate the writing process).

[0083] 6. Penetration 23 °C - 24 hour storage ​​​​This test measures the amount of ink that leaks from the tip of a ballpoint pen when it is stored upside down at 23°C for one day. The process was carried out as follows (10 pens were tested): 1. Start with a ballpoint pen: Write with a pen to reduce viscosity. 2. Wipe off the ink from the tip with a piece of paper that is not cotton-like. 3. Store the ballpoint pen with the tip facing downwards at 23°C / 50%RH for 24 hours. 4. Transfer ink droplets from the pen tip to the paper. Rotate the tip of each pen on the test sheet 360° to transfer the ink of any desired type onto the test sheet. 5. Cover the permeable display area with a piece of transparent tape. 6. Use the ceramic roulette to spread the ink stain into a circular pattern. 7. Measure the diameter of each stain (record the minimum diameter that includes the entire spot). Calculate the average spot size (mm) from all samples in 8.10.

[0084] 7. Allow to soak for 1 week, then store at 40°C / 80%RH. This test measures the amount of ink leaking from the tip of a ballpoint pen when it is stored with the tip facing downwards at 40°C / 80%RH for one week. The test simulates keeping the pen in a shirt pocket close to the body. The process was carried out as follows (tested with 10 pens): 1. Start with a ballpoint pen: Write with a pen to reduce viscosity. 2. Wipe off the ink from the tip with a piece of paper that is not cotton-like. 3. Store the ballpoint pen with the tip facing downwards at 40°C / 80%RH for 7 days. 4. Transfer ink droplets from the pen tip to the paper. Rotate the tip of each pen on the test sheet 360° to transfer the ink of any desired type onto the test sheet. 5. Cover the permeable display area with a piece of transparent tape. 6. Use the ceramic roulette to spread the ink stain into a circular pattern. 7. Measure the diameter of each stain (record the minimum diameter that includes the entire spot). Calculate the average spot size (mm) from all samples in 8.10.

[0085] 8. Cleanliness of machine writing This test evaluates the mechanical writing quality of a pen under given test conditions during the first 20 meters of mechanical writing.

[0086] device: 1. Air conditioning and humidity control room: 23℃ (±2°) 50%RH (±5%) 2. Writing instruments that operate according to the following guidelines: a) General conditions: 70° writing angle (0, +10) Circumference 100mm Total weight (pen / holder / additional weight): 140-160 grams ISO 12757 test strips Polished stainless steel writing surface with felt underneath b) Machine parameters: Writing speed of 4.5 m / min (±0.5) Minitek APC circle spacing 0.6mm (±0.2) or position 5 on Mikron Pen rotation in one axial direction per 100 circles Writing length: 20 meters c) Process: 1. Insert the cartridge into the barrel. 2. Draw a loop and start drawing with the pen. 3. Select a position at 0.6 mm intervals and record 20 meters on the counter. 4. Perform the test by pressing the "Pen Rotation" button. 5. Calculate the average score of the pens that were tested, excluding those that were not started. 6. Evaluate the cleanliness, i.e., whether the thickness along the line is nearly uniform (presence of stains).

[0087] 9. Regularity of machine writing This test evaluates the mechanical writing quality of a pen under given test conditions during the first 20 meters of mechanical writing.

[0088] device: 1. Air conditioning and humidity control room: 23℃ (±2°) 50%RH (±5%) 2. Writing instruments that operate according to the following guidelines: a) General conditions: 70° writing angle (0, +10) Circumference 100mm Total weight (pen / holder / additional weight): 140-160 grams ISO 12757 test strips Polished stainless steel writing surface with felt underneath b) Machine parameters: Writing speed of 4.5 m / min (±0.5) Minitek APC circle spacing 0.6mm (±0.2) or position 5 on Mikron Pen rotation in one axial direction per 100 circles Writing length: 20 meters c) Process: 1. Insert the cartridge into the barrel. 2. Draw a loop and start drawing with the pen. 3. Select a position at 0.6 mm intervals and record 20 meters on the counter. 4. Perform the test by pressing the "Pen Rotation" button. 5. Calculate the average score of the pens that were tested, excluding those that were not started. 6. Evaluate regularity, i.e., the nearly uniform color during writing (the presence of white within the lines).

[0089] 10. Complete ink compensation This test reflects the pen's "endurance," that is, its ability to write until it stops writing. If the pen was used until the cartridge was completely empty, the sample was marked "yes." Otherwise, the sample was marked "no."

[0090] 11. Cleanliness of handwritten text This test measures the uniformity of the thickness of drawn lines. The regularity of the thickness of the drawn lines was visually evaluated and rated on a scale of 1. The rating scale was as follows: 10: Very clean, without excess, stain-free. 0: Not clean; there are excess areas and ink stains on the written lines.

[0091] 12. Regularity of handwriting This test measures the uniformity of color during writing. Samples were visually examined for lighter or darker areas and the "channel" in the center of the line. The rating scale, with an interval of 1, was as follows: 10: Very regular, with no white within the lines. 0: Not regular

[0092] 13. Grouping This test evaluates whether ink drips from the tip after manual writing. It is a visual evaluation of the tip after writing a sentence.

[0093] 14. Drop test without a follower This test simulates a user dropping a pen on the floor. The cartridge did not contain any followers. The process and evaluation were carried out as follows: 1. The cartridge is positioned inside the pen body at 23°C / 50%RH. The tip is not retracted and is in the up-tip position. 2.10 drops / height 80cm (dropped into the PVC pipe to avoid the tip becoming completely filled on the floor) 3. Visual evaluation of the ink column after each drop (no ink movement or splitting). 4. After 10 drops, if the ink column appears stable, verify with a handwriting test (the pen must be used for proper writing).

[0094] Example 1 The following non-aqueous writing inks were prepared in accordance with the procedure outlined in the second aspect of this disclosure. [Table 1]

[0095] The rheological properties of the ink produced in Example 1 were as follows: ·Viscosity at rest=74990cP Shear viscosity = 2765 cP • Restful tandelta = 6.9 • Post-shear tandelta = 29.7

[0096] Examples 2-5 and Comparative Examples 1-6 Further non-aqueous writing inks were prepared as described in reference to Example 1, with the ink composition shown below being the only variable. The dyes, defoamers, and clear drain additives remained unchanged. The prepared inks were injected into cartridges. All experimental tests were performed on stabilized cartridges, i.e., after preparation, after being stored at 23°C and 50% RH for at least one week after injection. This point in time is called T=0. The writing system is a retractable cartridge with a 1 mm needle tip. Table 1 below shows the compositions used, including Example 1 for reference. [Table 2]

[0097] The performance of the examples and comparative examples is shown in Figure 1.

[0098] As is evident from the comparison of the comparative examples and examples, non-aqueous writing inks containing a mixture of resin and silica particles with fatty acid amide wax as a gelling agent provide very good results in drop tests while also offering a balance that very well meets other writing performance criteria. However, as is evident from Comparative Example 6, this further depends on the use of a sufficient amount of resin. Comparative Example 1 passed the drop test but showed performance that did not meet the criteria in both penetration tests. The table in Figure 1 further shows that overall performance is best when a homopolymer or copolymer of vinylpyrrolidone is used in addition.

[0099] While certain embodiments of this disclosure are disclosed for illustrative purposes only, those skilled in the art will understand that various modifications and alterations are possible without departing from the spirit of this disclosure. Furthermore, it should be understood that such modifications and alterations will be incorporated into the scope of this disclosure and the appended claims.

Claims

1. A writing instrument having a writing tip, wherein the writing instrument contains non-aqueous writing ink housed in a tubular ink cartridge, the tubular ink cartridge having an inner diameter of 1 mm to 2.5 mm and two open ends, the first open end being connected to the writing tip, and the second open end being connected to the external environment of the writing instrument. The non-aqueous writing ink contained within the tubular ink cartridge is in fluid communication with the writing tip via the first open end and with the external environment of the writing instrument via the second open end. The non-aqueous writing ink comprises a solvent, a resin, a colorant, and a gelling agent, wherein the gelling agent comprises a mixture of silica particles and fatty acid amide wax, and the resin is present in an amount of 5 to 20% by weight relative to the total weight of the ink. A writing instrument wherein the non-aqueous writing ink has a static viscosity of 30,000 cps to 150,000 cps at 20°C, and the non-aqueous writing ink contains a homo or copolymer of vinylpyrrolidone, and the homo or copolymer of vinylpyrrolidone is present in an amount of 0.05 to 0.8% by weight relative to the total weight of the ink.

2. The writing instrument according to claim 1, wherein the resin is selected from polyester resin, polyurethane resin, ketone resin, ether resin, and mixtures thereof.

3. The writing instrument according to claim 2, wherein the polyvinylpyrrolidone has a weight-average molecular weight greater than 200 kDa.

4. The writing instrument according to claim 2 or 3, wherein the weight of the vinylpyrrolidone homo or copolymer is less than the weight of the mixture of silica particles and fatty acid amide wax.

5. The writing instrument according to any one of claims 1 to 4, wherein the silica particles include hydrophilic silica particles.

6. The writing instrument according to any one of claims 1 to 5, wherein the fatty acid amide wax comprises N,N'-ethylene-bis-fatty acid amide.

7. The writing instrument according to any one of claims 1 to 6, wherein the gelling agent is present in an amount of 0.1 to 1.2% by weight relative to the total weight of the ink.

8. The writing instrument according to any one of claims 1 to 7, wherein the solvent is selected from the group consisting of glycol ethers, alcohols, and mixtures thereof.

9. The writing instrument according to any one of claims 1 to 8, wherein the solvent is present in an amount of 35 to 80% by weight relative to the total weight of the ink.

10. The writing instrument according to any one of claims 1 to 9, wherein the coloring agent is a dye.

11. The writing instrument according to any one of claims 1 to 10, wherein the coloring agent is present in an amount of 5 to 30% by weight relative to the total weight of the ink.

12. The writing instrument according to any one of claims 1 to 11, wherein the non-aqueous writing ink further comprises one or more additives.

13. The non-aqueous writing ink contains 0.1 to 0.6% by weight of polyvinylpyrrolidone having a weight-average molecular weight of 450 to 2000 kDa, in proportion to the total weight of the ink. 0.15 to 0.60% by weight of the fatty acid amide wax, and A writing instrument according to any one of claims 1 to 12, comprising 0.15 to 0.60% by weight of hydrophilic silica.

14. The writing instrument according to claim 13, wherein the ink contains 55 to 75% by weight of 1-phenoxy-2-propanol.

15. The writing instrument according to claim 13 or 14, wherein the fatty acid amide wax comprises N,N'-ethylene-bis-fatty acid amide.

16. The writing instrument according to any one of claims 1 to 15, wherein the ink has a static loss coefficient tanδ of 3 to 15 and / or a post-shear loss coefficient of 8 to 60.

17. The non-aqueous writing ink comprises the following components in proportion to the total weight of the ink: The solvent in an amount of 55 to 75% by weight is selected from polyethylene glycol ether, polypropylene glycol ether, phenoxyethanol, 1-phenoxy-2-propanol, or a mixture thereof. 10 to 30% by weight of the coloring agent, 0.10 to 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of 600 to 1900 kDa, 0.15 to 0.60% by weight of fatty acid amide wax, 0.15 to 0.60 wt% hydrophilic silica, A writing instrument according to any one of claims 1 to 16, comprising the resin and the remaining components selected from additives.

18. The non-aqueous writing ink comprises the following components in proportion to the total weight of the ink: 55 to 75% by weight of the 1-phenoxy-2-propanol, 10 to 30% by weight of the coloring agent, 0.10 to 0.60% by weight of polyvinylpyrrolidone having a weight-average molecular weight of 600 to 1900 kDa, 0.15 to 0.60% by weight of fatty acid amide wax, containing N,N'-ethylene-bis-fatty acid amide, 0.15 to 0.60 wt% hydrophilic silica, 5-15% by weight of resin, The writing instrument according to claim 17, comprising the remaining components which are additives.

19. A process for preparing a writing instrument according to any one of claims 1 to 18, wherein the non-aqueous writing ink comprises a solvent, a resin, a colorant, and a gelling agent, wherein the gelling agent comprises a mixture of silica particles and fatty acid amide wax, the resin is present in an amount of 5 to 20% by weight of the total weight of the ink, the non-aqueous writing ink comprises a homo or copolymer of vinylpyrrolidone, the homo or copolymer of vinylpyrrolidone is present in an amount of 0.05 to 0.8% by weight of the total weight of the ink, and the non-aqueous writing ink has a static viscosity of 30,000 cps to 150,000 cps at 20°C, a) Forming a first premixture containing silica particles in a solvent at a temperature of 30 to 70°C and a shear rate of 20 to 25 m / s, b) A process prepared by combining the first premixture with the remaining components.

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