Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/40—Compounds of aluminium
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
  • C09C3/06—Treatment with inorganic compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/16—Writing inks
  • C09D11/17—Writing inks characterised by colouring agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/16—Writing inks
  • C09D11/18—Writing inks specially adapted for ball-point writing instruments

Definitions

• the present invention relates to an ink coating containing platelet alumina.
• ink compositions containing, for example, a colorant and a solvent such as an organic solvent or water are known, and pigment inks containing a pigment as the colorant are widely used.
• pigment inks containing a pigment as the colorant are widely used.
• inks using titanium oxide as a white pigment, which has excellent hiding power and clarity, are widely used.
• alumina may be added together with a colorant such as titanium oxide (Patent Documents 1 and 2).
• a ballpoint pen tip has a ball and a ball holder, and by adding alumina, it is possible to reduce wear on the ball seat (referring to the contact point between the ball and the ball holder) caused by friction generated by the rotation of the ball during writing.
• the frictional force between the ball and the ball seat is smaller than the frictional force between the paper surface and the ball, preventing skipping of the line.
• alumina has low hiding power, and when added as an additive, there is a risk that the inherent hiding power of the ink composition for writing instruments will be reduced.
• Non-Patent Document 1 shows that plate-like NaNbO 3 of the submicron order has high hiding power, but even when alumina is similarly made to the submicron order, the improvement in hiding power is insufficient.
• the objective of the present invention is to provide an ink coating with excellent hiding power.
• the present invention is as follows.
• the plate-like alumina particles have a volume-based median diameter D50 of 1 ⁇ m or more and 5 ⁇ m or less in laser diffraction particle size distribution measurement, and an aspect ratio of 10 or more and 50 or less.
• the present invention by providing voids between adjacent alumina particles contained in the ink coating, it is possible to provide an ink coating with excellent hiding power.
• the ink coating film of the present invention is characterized in that it contains alumina particles and has voids between adjacent portions of the alumina particles.
• Having voids adjacent to alumina particles means that an air layer is formed between the alumina particles and the resin in the ink coating, and the alumina particles and the resin are not in direct contact with each other.
• the air layer may be formed so as to cover the entire alumina particle, or may be formed so as to cover only a portion of the alumina particle.
• the air layer is formed so as to cover only a portion of the alumina particle, it is preferably formed on the surface side (the surface side of the coating) when the coating is observed in a cross-sectional view.
• the light scattering effect of a coating film can only occur at the interface between the alumina particles and the resin, but by having voids (i.e. air layers), two types of light scattering occur: between the resin and the air layer, and between the air layer and the alumina particles. Because the air layer has a low refractive index, the difference in refractive index between the resin and the alumina particles becomes large, which increases light scattering and is thought to improve hiding power.
• voids i.e. air layers
• the voids adjacent to the alumina particles account for more than half of all voids, and it is particularly preferable that more than 70% of the total voids are in contact.
• the porosity in the ink coating is preferably 2% to 10%, and more preferably 3% to 9%. Being within this range is preferable because it improves the hiding power when made into a coating.
• the presence or absence, location, and porosity of voids can be determined from cross-sectional images of the coating film observed under an electron microscope. The presence or absence of voids can be confirmed using software that distinguishes differences in brightness. The porosity can be calculated as the ratio of the void area to the total cross-sectional area of the coating film.
• the ink coating of the present invention is formed from an ink composition containing alumina particles.
• the alumina particles are not particularly limited, and commercially available alumina particles may be used, such as YFA02050 (plate-shaped alumina, manufactured by Kinsei Matec Co., Ltd.). A known and commonly used manufacturing method may also be used, and the alumina particles may be manufactured by a manufacturing method such as a hydrothermal method or a flux method.
• a manufacturing method for more simply obtaining the desired alumina particles includes the method described in JP 2016-222501 A, in which an aluminum compound is calcined in the presence of a molybdenum compound and a shape control agent.
• the alumina particles are aluminum oxide and may be transition alumina of various crystal forms, such as gamma, delta, theta, and kappa, or may contain alumina hydrate in transition alumina, but it is preferable that they are essentially in the alpha crystal form (alpha type) because of their superior stability.
• the aspect ratio which is the ratio of the average particle diameter (D50) to the thickness of the alumina particles, is from 10 to 50, preferably from 12 to 45, and more preferably from 15 to 40.
• D50 average particle diameter
• the aspect ratio of the alumina particles is within the above range, good hiding performance can be obtained when the alumina particles are made into an ink coating.
• the D50 of the alumina particles is 1 ⁇ m or more and 5 ⁇ m or less, and preferably 1.1 ⁇ m or more and 4 ⁇ m or less.
• the D50 is within the above range, the dry hide effect is easily achieved when a metal oxide layer, which will be described later, is provided, and the hiding power of the ink coating can be improved.
• the inventors have also discovered that by setting D50 to a specific particle size, the location and content of voids can be further controlled, improving the hiding power of the coating film.
• the details are not clear, it is believed that by having the D50 of the alumina particles within the above range, the specific surface area is increased and the amount of resin and solvent contained in the ink composition adsorbed to the alumina particles is increased, making it easier to form voids near the alumina particles. It is also believed that by having the D50 of the alumina particles within the above range, the number of alumina particles contained in the ink composition increases, making it possible to form more voids in the coating film.
• D50 refers to the value calculated as the volume-based median diameter from the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer.
• the alumina particles may further contain molybdenum, and may also contain impurities derived from the raw materials or shape control agents, as long as the effects of the present invention are not impaired.
• the alumina particles contained in the ink coating of the present invention preferably further have a metal oxide layer, more preferably one or more of zinc oxide, silicon dioxide, zirconium dioxide, and titanium oxide, and particularly preferably silicon dioxide.
• a metal oxide layer By having a metal oxide layer, a porous structure is formed, forming many voids in adjacent portions of the alumina particles, and the refractive index difference with the resin is increased, which is preferable.
• the metal oxide layer is preferably a single layer.
• a single layer provides superior hiding power due to the difference in refractive index. Note that a single layer means that it is made of one type of component, and indicates that there are not two types of layers, for example, a zinc oxide layer and a silicon dioxide layer.
• the metal oxide layer may be formed on at least a portion of the surface of the alumina particle, but is more preferably formed on the entire surface of the alumina particle.
• the surface of the alumina particle means the outside of the surface of the alumina particle. Therefore, it is clearly distinguished from the surface layer containing mullite or germanium that is formed on the inside of the surface of the alumina particle.
• the thickness of the metal oxide layer is not particularly limited, but from the standpoint of hiding power and cost, it is 0.1 nm or more, but is thin enough that it cannot be measured in an SEM image.
• the amount of metal oxide in the metal oxide layer relative to the amount of alumina in the alumina particles is not particularly limited, but is preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably more than 0% by mass. Being within the above range is preferable because it provides excellent hiding power when made into an ink composition.
• colorant If used as a colorant, it is preferably 1 to 15% by mass, more preferably 3 to 12% by mass, based on the total mass of the ink composition. Being within this range is preferable because it provides both excellent hiding power and color development.
• the method for forming the metal oxide layer is not particularly limited and may be a known method.
• a porous silicon dioxide layer can be formed by adding a solution of sodium silicate, adjusting the pH with a strong acid, and then drying.
• the ink composition of the present invention may further contain titanium oxide particles.
• the titanium oxide particles are not particularly limited, and either rutile type or anatase type may be used, but it is preferable that the average particle size is 0.01 ⁇ m or more.
• known titanium oxides such as Bayertitan R-FD-1, R-KB-3, and R-CK-20 (all manufactured by Bayer), TIPAQUE R-630, R-615, R-830, and LPT series (all manufactured by Ishihara Sangyo Kaisha, Ltd.), Unitane OR-342 (manufactured by ACC), Ti-pure R-900 and R-901 (manufactured by Chemours), and Luxelene Silk series (manufactured by Sumitomo Chemical Co., Ltd.) may be used.
• the amount added is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less, and particularly preferably 0.02% by mass or more and 4% by mass or less, based on the total mass of the ink composition. If it is within the above range, the resulting coating film will have excellent hiding power and L value, and will also have excellent ink ejection performance, which is preferable.
• the ink composition may contain an organic solvent, for example, aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, etc., aliphatic hydrocarbon solvents such as n-hexane, n-heptane, isoheptane, n-octane, isooctane, etc., cycloparaffin solvents such as methylcyclohexane, ethylcyclohexane, etc., ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, etc., glycol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerin, etc., glycol ether solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, etc., which may be used alone or in combination of two or more.
• the amount of organic solvent contained is not particularly limited, but from the viewpoint of the drying speed of the ink coating, it is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass, based on the total mass of the ink composition.
• the ink composition may contain a resin, such as a polyvinyl butyral resin, a ketone resin, a polyacetal resin, a polyvinyl alcohol resin, a cellulose resin, a terpene resin, an alkyd resin, a phenoxy resin, a polyvinyl acetate resin, a polyvinylpyrrolidone resin, an ethylene oxide polymer, an acrylic resin, a styrene-acrylic resin, or a styrene-maleic acid resin, and these may be used alone or in combination of two or more kinds.
• a resin such as a polyvinyl butyral resin, a ketone resin, a polyacetal resin, a polyvinyl alcohol resin, a cellulose resin, a terpene resin, an alkyd resin, a phenoxy resin, a polyvinyl acetate resin, a polyvinylpyrrolidone resin, an ethylene oxide polymer, an acrylic resin,
• the resin content is preferably 0.05 to 30% by mass, and particularly preferably 0.1 to 25% by mass, based on the total mass of the ink composition.
• the ink composition may contain a dispersant, and examples of such dispersants include nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene methyl ether, polyoxyethylene lanolin alcohol, polyoxyethylene alkylamines, and polyoxyethylene fatty acid amides; anionic surfactants such as alkyl sulfates, N-acylamino acid salts, polyoxyethylene alkyl ether acetates, and alkyl phosphates; cationic surfactants such as alkylamine salts and quaternary ammonium salts; amphoteric surfactants such as alkyl betaines, alkyl amine oxides, and phosphatidylcholines; and polymeric surfactants such as acrylics.
• nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene methyl ether, polyoxyethylene lanolin alcohol, polyoxyethylene alkylamines, and polyoxyethylene fatty acid amides
• the amount of dispersant contained is determined appropriately depending on the solvent and other components used, but from the standpoint of dispersion stability and ink viscosity, it is preferably 0.1 to 30 mass% of the total mass of the ink composition, and particularly preferably 0.5 to 20 mass%.
• additives such as colorants such as organic pigments, inorganic pigments, acid dyes, basic dyes, and direct dyes; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, metal salt compounds, and phosphate compounds; preservatives such as carbolic acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; antifoaming agents such as silicones, mineral oils, polyethers, and fluorine; antioxidants; stabilizers; inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate, and organic basic compounds such as water-soluble amine compounds, and the like, may also be added.
• colorants such as organic pigments,
• the ink composition can be produced by a known method without any particular limitation.
• the above-mentioned components are mixed in appropriate amounts and mixed with various stirrers such as a propeller stirrer, homodisper, or homomixer, or various dispersers such as a bead mill, to produce the ink composition.
• various stirrers such as a propeller stirrer, homodisper, or homomixer, or various dispersers such as a bead mill, to produce the ink composition.
• a disperser such as a bead mill or a paint conditioner.
• the viscosity of the ink composition is not particularly limited, but the ink viscosity at 20°C and a shear rate of 5 sec -1 (at rest) is preferably 30,000 mPa ⁇ s or less, and more preferably 25,000 mPa ⁇ s or less. When it is equal to or less than the upper limit, it is preferable in terms of excellent ink dischargeability and writing comfort. From the viewpoint of suppressing ink leakage, it is preferably 500 mPa ⁇ s or more, and more preferably 1,000 mPa ⁇ s or more.
• the obtained light blue powder was dispersed in 150 mL of 0.5% ammonia water, and the dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, after which the ammonia water was removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 47 g of light blue powder.
• the obtained powder was confirmed to have a plate-like shape by SEM observation. Furthermore, when X-ray diffraction (XRD) measurement was performed, sharp peak scattering due to ⁇ -alumina was observed, and no alumina crystal peaks other than the ⁇ crystal structure were observed, confirming that the particles were plate-like alumina particles (A-1) with a dense crystal structure. The ⁇ conversion rate was 99% or more (almost 100%).
• the obtained plate-like alumina particles (A-1) were dispersed in ion-exchanged water, and No. 3 sodium silicate (Fuji Chemical Industry Co., Ltd.) was added dropwise with stirring so that silicon oxide was added in an amount of 3 parts by mass per 100 parts by mass of alumina. After the dropwise addition, the mixture was stirred for 10 minutes, and 1M sulfuric acid was added dropwise to adjust the pH to 6.0. The mixture was then filtered, washed with ion-exchanged water, and dried at 150° C. for 5 hours to obtain a light blue powder (A-2).
• the resulting light blue powder was then dispersed in 150 mL of 0.5% aqueous ammonia, and the dispersion was stirred at room temperature (25-30°C) for 0.5 hours.
• the aqueous ammonia was then removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 33.5 g of light blue powder.
• SEM observation of the resulting powder confirmed that it was plate-shaped with very few aggregates.
• XRD measurement revealed sharp peak scattering due to ⁇ -alumina, and no alumina crystal peaks other than the ⁇ crystal structure were observed, confirming that the particles were plate-shaped alumina particles (A-3) with a dense crystal structure.
• the ⁇ conversion rate was 99% or more (almost 100%).
• the obtained plate-like alumina particles (A-3) were treated in the same manner as in Production Example 1 to prepare plate-like alumina particles (A-4) having a metal oxide layer formed thereon.
• titanium oxide particles (Typaque R-830, manufactured by Ishihara Sangyo Kaisha, Ltd.) were prepared (T-1).
• the fillers used in the examples and comparative examples are as shown in Table 1.
• the obtained white ink composition was used to form a coating film on colored drawing paper (Koikura, manufactured by PLUS Co., Ltd.) using a bar coater RDS20.
• the coating film was dried at room temperature for one day and the cross section of the coating film was photographed at a magnification of 10,000 times using a JCM7000 (manufactured by JEOL Ltd.).
• the image of the obtained coating film cross section was analyzed using analysis software (WinRoof2018, manufactured by Mitani Shoji Co., Ltd.) to set the brightness threshold of the voids using the automatic setting function, and the presence or absence of voids was confirmed. It was visually confirmed from the image that the voids and the alumina particles were adjacent, and the cases where they were adjacent were marked with ⁇ , and the cases where they were not adjacent were marked with ⁇ .
• the obtained white ink composition was applied to a colored drawing paper (Koikura, manufactured by PLUS Corporation) to form a coating film using a bar coater RDS20.
• the coating film was dried at room temperature for one day and night, and the hiding power of the coating surface was evaluated by the L value.
• the L value was measured using a spectro-guide 45/0 gloss (manufactured by BYK-Gardner GmbH).
• An L value of 86 or more was evaluated as a good coating film that sufficiently hid the coating surface, and an L value below that was evaluated as an X for insufficient hiding power.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

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• 2024
  • 2024-02-29 JP JP2024573337A patent/JPWO2024190433A1/ja active Pending
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