JP7184624B2 - Aqueous pigment composition and applicator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a highly hiding aqueous white pigment composition.

Titanium oxide (TiO ₂ ) is a pigment capable of imparting whiteness and hiding properties (property to hide substrates) due to its excellent light scattering effect. Aqueous or oily ink compositions in which a masking agent such as titanium oxide or composite particles or hollow particles containing titanium oxide are dispersed are used as correction fluids, inks for writing instruments, and the like.

On the other hand, titanium oxide has a high specific gravity of 3.8 to 4.1, and has the problem of sedimentation or separation in the ink. Therefore, during the drying of the drawn line, the titanium oxide dispersed in the ink agglomerates, reducing the scattering volume and reducing the concealability. In some cases, the titanium oxide sinks between the fibers, exposing the surface of the paper and lowering the concealability.

If the amount of titanium oxide added is increased in order to increase the concealment rate, the titanium oxide particles are more likely to settle and the balance of dispersion deteriorates. In addition, the ink solidifies at the tip of the pen and the drawn line becomes faint (deterioration of non-drying property). Moreover, increasing the amount of titanium oxide compounded leads to high cost.

In ink compositions containing titanium oxide, sedimentation or separation could not be sufficiently suppressed even if the particle size was reduced, for example, due to the high specific gravity of titanium oxide. As the precipitation of titanium oxide progresses, the sediment forms a hard cake, making it difficult to redisperse. In order to solve such problems, an aqueous pigment composition containing titanium oxide having an isoelectric point higher than the pH of the ink, resin particles, a binder, and water has been reported (Patent Document 1). In the water-based pigment composition of Patent Document 1, by using titanium oxide having a higher isoelectric point than the pH of the ink, the resin particles having a lower dielectric constant than water are negatively charged, and the positively charged titanium oxide in the ink is , the negatively charged resin particles are electrically coupled, and even if the titanium oxide and the resin particles settle with the passage of time, the precipitate does not form a hard cake and can be easily redispersed.

However, the particle size and compounding ratio of titanium oxide and resin particles affect the ink performance. The area of contact with the titanium oxide per hit is small, and even if the titanium oxide and the resin particles are electrically bonded, the adsorption force is weak and they are easily detached.

JP-A-11-343443

The present invention is an aqueous white pigment composition containing titanium oxide particles, which has excellent hiding properties by improving the dispersibility of the titanium oxide particles, and can be written well without blurring even when exposed to the air for a long time. It is an object of the present invention to provide a water-based pigment composition that can be used as a water-based pigment composition and an applicator using the water-based pigment composition.

The water-based pigment composition of the present invention comprises titanium oxide (TiO ₂ ) particles and resin particles having a particle diameter smaller than that of the titanium oxide particles and adhering to the surfaces of the titanium oxide particles and covering part or all of the surfaces. Contains composite particles.
In the composite particles, it is preferable that the ratio of the average particle size of the titanium oxide particles and the resin particles is titanium oxide particles/resin particles=1.1-10.
It is preferable that the average particle diameter of the resin particles constituting the composite particles is in the range of 40 to 900 nm.
The applicator uses the water-based pigment composition.

The aqueous pigment composition of the present invention has a high hiding rate and can be written well without blurring. In addition, the non-drying property of the nib, that is, the cap-off property is also excellent.

FIG. 1 is an SEM image of composite particles 1 contained in the aqueous pigment composition of the present invention. FIG. 2 is an enlarged schematic view of the composite particle 1. FIG. FIG. 3 is a schematic diagram showing a state in which the composite particles 1 are uniformly dispersed in the aqueous pigment composition of the present invention.

The aqueous pigment composition of the present invention comprises composite particles of titanium oxide particles and resin particles having a particle size smaller than that of the titanium oxide particles, which adhere to the surfaces of the titanium oxide particles and cover part or all of the surfaces. contains. 1 and 2 show SEM images of the composite particles contained in the aqueous pigment composition and an enlarged view of the composite particles. Hereinafter, the aqueous pigment composition of the present invention will be described in detail with reference to the drawings.

Titanium oxide includes titanium monoxide ₍ TiO), dititanium trioxide (Ti ₂ O ₃ ) and titanium dioxide (TiO ₂ ). In the invention, titanium oxide particles 3 refer to TiO ₂ . TiO ₂ includes rutile type and anatase type, and rutile type is preferred. The titanium oxide particles 3 are hereinafter also simply referred to as titanium oxide 3 or TiO ₂ .
The average particle size of the titanium oxide particles 3 used in the present invention is generally 50-1000 nm, preferably 100-500 nm, more preferably 200-400 nm. The average particle diameter referred to here is a volume-based arithmetic mean diameter based on the Heywood diameters of the titanium oxide 3 and the resin particles 2 from image analysis of the dispersion of the composite particles 1 . Note that the titanium oxide 3 may contain not only primary particles but also secondary particles.

A primary particle is a single particle that cannot be decomposed by considerable mechanical stress, and a secondary particle is an agglomeration of primary particles. Since titanium oxide 3 has cohesiveness, commercial products usually contain not only primary particles but also secondary particles. The average particle size of commercially available titanium oxide is usually 0.15 to 3 μm.
Examples of the titanium oxide 3 used in the present invention include KR-380 (manufactured by Titan Kogyo Co., Ltd., average particle size 0.5 μm, lipophilic treated TiO ₂ ), ITT-2 CR-50 (manufactured by Nikko Chemicals, average particle size 0.3 μm, organic titanate treated TiO ₂ ), and ITT-7 TTO-S-3 (manufactured by Nikko Chemicals, average particle size 0.05 μm, organic titanate treated).

Resin particles 2 having a particle diameter smaller than that of titanium oxide 3 are used. The particle diameter of the resin particles 2 is usually 40-900 nm, preferably 40-500 nm, more preferably 40-300 nm. When the particle diameter of the resin particles 2 is less than 40 nm, the distance between the titanium oxide particles 3 cannot be sufficiently secured during the drying process, and the light scattering volume decreases, resulting in a decrease in concealability. On the other hand, when the particle diameter of the resin particles 2 exceeds 900 nm, the area of contact with the titanium oxide 3 of one resin particle 2 is small, and detachment is likely to occur.
The resin particles 2 include acrylic resins, styrene resins, styrene/acrylic resins, urethane resins, urethane/acrylic resins, polyolefin resins, fluorine resins, nylon resins, melamine resins, benzoguanamine resins, Polyester-based resins, polyphenylene sulfide-based resins, polyamideimide-based resins, and the like are used. These may be used individually by 1 type, and may be used in mixture of 2 or more types.
Among these resin particles 2, the acrylic resin is preferable in the present invention. The acrylic resin may be synthesized, or commercially available products such as Eposter MX series (manufactured by Nippon Shokubai Co., Ltd.) and Finesphere series (manufactured by Nippon Paint Industrial Coatings) may be used.
The shape of the resin particles 2 is not limited as long as the particle diameter is smaller than that of the titanium oxide 3, and may be spherical, irregular, hollow, or the like.

In the aqueous pigment composition of the present invention, titanium oxide 3 and resin particles 2 form composite particles 1 . FIG. 1 shows a composite particle 1 composed of titanium oxide 3 and resin particles 2, with the resin particles 2 adhering to part or all of the surface of the titanium oxide 3. FIG. When the composite particles 1 have such a structure, the titanium oxide 3 does not come into contact with each other and agglomerate, and the composite particles 1 can be effectively dispersed in the aqueous pigment composition, resulting in high hiding power. connected to sex.
In such a composite particle 1, the blending ratio of the titanium oxide 3 and the resin particles 2 is usually 1.5/1.0 to 6.0/1.0, preferably 2.0/1.0 in mass ratio. ~4.0/1.0. If the compounding ratio exceeds 6.0/1.0, the adhesion amount of the resin particles 2 for dispersing the titanium oxide 3 is insufficient, and the dispersion does not proceed sufficiently. Moreover, since the composite particles 1 have a high specific gravity, they may settle. On the other hand, if the blending ratio is less than 1.5/1.0, the excess resin particles 2 that do not participate in the formation of composite particles increase, resulting in an increase in the solid content and an increase in the viscosity of the water-based pigment composition. To increase.
The content of composite particles 1 is usually 1 to 60% by mass with respect to the total amount of the aqueous pigment composition. In the present invention, by improving the dispersibility of the composite particles 1, high hiding power can be maintained even when the content of the composite particles 1 in the aqueous pigment composition is within the above range. When such a water-based pigment composition is used in a writing instrument, the viscosity of the ink is not too high, and blurring does not occur even when writing for a long period of time, which contributes to the improvement of the ink ejection performance. In addition, the water-based pigment composition remaining on the nib of the pen is less likely to solidify, improving the non-drying performance. The content of titanium oxide 3 is usually 0.1 to 35% by mass, preferably 1 to 30% by mass, based on the total amount of the aqueous pigment composition.

The average particle diameter of the composite particles 1 is usually 150-3000 nm, preferably 200-1000 nm, more preferably 300-600 nm. When the composite particles 1 have the above particle diameter, the effects of improved hiding properties, improved ink ejection properties, and improved redispersibility can be obtained. In the composite particles, the ratio of the average particle size of the titanium oxide particles 3 to the average particle size of the resin particles 2 is preferably titanium oxide particles 3/resin particles 2=1.1 to 10, more preferably 2 to 6. .
The average particle diameter is determined from the Heywood diameters of titanium oxide 3 and resin particles 2 from image analysis of composite particle 1 dispersion in the same manner as described above. Note that the titanium oxide 3 may contain not only primary particles but also secondary particles.

In addition to the titanium oxide particles 3 and the resin particles 2, the aqueous pigment composition of the present invention may contain water, a water-soluble organic solvent, a pH adjuster, a surfactant, an antiseptic, an antifungal agent, and the like.
As water, tap water, distilled water, ion-exchanged water, pure water, and the like are used.
Water-soluble organic solvents include glycols such as ethylene glycol, diethylene glycol, propylene glycol and hexylene glycol; glycerins such as glycerin and diglycerin; and propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol. Glycol ether such as is used.

Conventionally known pH adjusters such as aminomethylpropanol and triethanolamine can be used according to the need for pH adjustment.

The surfactant is not limited as long as it lowers the surface tension of the ink, and any of nonionic, cationic and anionic surfactants can be used.
The content of the surfactant is usually 0.001-0.5% by mass relative to the total amount of the aqueous pigment composition.

Halogen, imidazole, thiazole, pyridine, triazine, imide and carboxylic acid compounds are used as antiseptics and antifungal agents.
The content of the antiseptic and antifungal agent is usually 0.01-0.5% by mass relative to the total amount of the aqueous pigment composition.

In addition to the components described above, the water-based pigment composition may optionally contain, for example, a coloring agent, an antifoaming agent, an anti-drying agent, and an oxygen scavenger.

An example of a method for preparing the aqueous pigment composition of the present invention is shown. Titanium oxide 3 , resin particles 2 and, if necessary, a pH adjuster are mixed to cause the resin particles 2 to adsorb to the surface of the titanium oxide 3 . For this purpose, it is necessary to adjust the pH of the dispersion so that the surface potentials of the titanium oxide 3 and the resin particles 2 are different (for example, the titanium oxide 3 is positively charged and the resin particles 2 are negatively charged). The isoelectric point of titanium oxide 3 is greatly affected by the types of surface treatment agents such as alumina and silica, the amount of treatment, and the treatment ratio (for example, the isoelectric point of alumina is pH 9, and the isoelectric point of silica is pH 2). is).
By using such a method, the resin particles 2 are electrically adsorbed to the titanium oxide 3 , and the resin particles 2 cover part or all of the surface of the titanium oxide 3 having a large particle size to form the composite particles 1 . Since the composite particles 1 are kept at a certain distance or more due to electron repulsion, they can maintain good dispersibility as shown in FIG. 3 without forming aggregates. Then, the water-based pigment composition of the present invention can be prepared by adding other components, water, water-soluble organic solvent and surfactant necessary for preparing the water-based pigment composition, and stirring.

The aqueous pigment composition of the present invention has excellent hiding properties due to the good dispersibility of titanium oxide 3 . Moreover, since the masking property is excellent, there is no need to increase the amount of titanium oxide 3 . Therefore, for example, even if it is used as ink for a writing instrument having a polyester nib, such as a felt-tip pen, blurring does not easily occur even when writing is performed while being exposed for a long period of time. Such an aqueous pigment composition can be widely applied not only to ink for writing instruments, but also to cosmetics such as liquid cosmetics, other stationery, and applicators used for daily necessities.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.
[Example 1]
[Preparation of aqueous pigment composition]
Titanium oxide (TiO ₂ ) particles (product name: JR-600A (particle size: 250 nm); manufactured by Tayca) 30% by mass, resin particles (product name: MX030W (acrylic, particle size: 40 nm, 10% dispersion); Nippon Shokubai Co., Ltd. 50% by weight, and treated with a bead mill (DYNO-MILL, KDL type, manufactured by Willie & E. Bakkofen) for 1 hour at 1500 rpm using zirconia beads with a diameter of 0.3 mm as media to obtain titanium oxide particles. resin particles were adsorbed on the surface of the Next, to the mixture, 0.5% by mass of triethanolamine, Surflon S-211 (fluorosurfactant; manufactured by AGC Seimi Chemical Co., Ltd.) 0.2% by mass, Bioden S (preservative; manufactured by Daiwa Chemical Industry Co., Ltd.) 0.3% by mass, 5% by mass of propylene glycol, and 14% by mass of ion-exchanged water were added and mixed to prepare an aqueous pigment composition. As a result of calculating the average particle size from the image of the composite particles, it was 250 nm for titanium oxide and 40 nm for resin particles.

[Evaluation of aqueous pigment composition]
(1) Concealability Black paper (absorbing surface: Nagatoya Shoten color paper medium thickness) is coated with a 50 μm applicator, dried, and then measured with a color computer (SC-P manufactured by Suga Test Instruments Co., Ltd.) for brightness L*. was measured. A to C were evaluated based on the following criteria.
A: L* is over 85% B: L* is 80-85%
C: L* is less than 80%

(2) Ink ejection performance A PC-5M pen body manufactured by Mitsubishi Pencil Co., Ltd. is filled with each water-based pigment composition, and in an environment with a temperature of 25 ° C. and a humidity of 65%, a spiral with a width of 15 mm is written on black paper. The drawn line was evaluated by A to C as follows.
A: Good writing is possible at a writing speed of 8.0 m/min with no blurring.
B: Faintness occurs at a writing speed of 8.0 m/min, but no faintness occurs at 4.0 m/min, and good writing is possible.
C: Scratches occur at a writing speed of 4.0 m/min.

(3) Non-dry performance Each water-based pigment composition was filled in a PC-3M pen body manufactured by Mitsubishi Pencil Co., Ltd., and left for 1 hour after removing the cap made of polypropylene in an environment with a temperature of 25° C. and a humidity of 65%. After that, a 15 mm-wide spiral was drawn on black paper, and the non-drying property was visually evaluated according to the following evaluation criteria A to C.
A: Can be written satisfactorily without fading.
B . . . There is faintness in the first 1-2 laps, but good writing is possible after the 3rd lap.
C: Scratches are observed even after the third round.
Table 1 shows the preparation conditions and evaluation results of the aqueous pigment composition.

[Example 2]
In Example 1, the type of titanium oxide (TiO ₂ ) particles was changed from JR-600A (particle size 250 nm) to JR-301 (particle size 300 nm; manufactured by Tayca), and the type and amount of resin particles were changed to MX030W (acrylic System, particle size 40 nm, 10% dispersion) 50% by mass to FS-101 (acrylic, particle size 100 nm; manufactured by Nippon Paint Industrial Coatings) 15% by mass, and the amount of ion-exchanged water is changed to 14% by mass. % to 49% by mass, and in the same manner as in Example 1 except that, an aqueous pigment composition was prepared.
As a result of calculating the average particle size from the image of the composite particles, it was found to be 300 nm for titanium oxide and 100 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
Table 1 shows the results.

[Example 3]
In Example 1, the type of titanium oxide (TiO ₂ ) particles was changed from JR-600A (particle size: 250 nm) to R-902+ (particle size: 400 nm; manufactured by Chemours), and the type and amount of resin particles were changed to MX030W. (Acrylic, particle size 40 nm, 10% dispersion) MM-101SWA (urethane, particle size 150 nm, 10% dispersion) 60% by mass, and deionized water An aqueous pigment composition was prepared in the same manner as in Example 1 except that the amount was changed from 14% by mass to 4% by mass.
As a result of calculating the average particle size from the image of the composite particles, it was 400 nm for titanium oxide and 150 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
Table 1 shows the results.

[Example 4]
In Example 3, the type and amount of resin particles were changed from MM-101SWA (urethane type, particle size 150 nm, 30% dispersion) to 60% by mass to FS (melamine type, particle size 200 nm; manufactured by Nippon Shokubai Co., Ltd.) to 20% by mass. A water-based pigment composition was prepared in the same manner as in Example 3 except that the amount of ion-exchanged water was changed from 14% by mass to 44% by mass.
As a result of calculating the average particle size from the image of the composite particles, it was 400 nm for titanium oxide and 200 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
Table 1 shows the results.

[Example 5]
In Example 1, the type and amount of the resin particles was changed from 50% by mass of MX030W (particle size 40 nm) to MM-101SWA (urethane type, particle size 150 nm, 30% dispersion; manufactured by Negami Kogyo Co., Ltd.) 60% by mass, An aqueous pigment composition was prepared in the same manner as in Example 1 except that the amount of ion-exchanged water was changed from 14% by mass to 4% by mass.
As a result of calculating the average particle size from the image of the composite particles, it was 250 nm for titanium oxide and 150 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
Table 1 shows the results.

[Example 6]
In Example 3, the type and amount of resin particles were changed from MM-101SWA (urethane type, particle size 150 nm, 30% dispersion) to 60% by mass to MX030W (acrylic type, particle size 40 nm, 10% dispersion; manufactured by Nippon Shokubai Co., Ltd. ) was changed to 40% by mass, and the amount of ion-exchanged water was changed from 4% by mass to 24% by mass.
As a result of calculating the average particle size from the image of the composite particles, it was 400 nm for titanium oxide and 40 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
Table 1 shows the results.

[Comparative Example 1]
In Example 1, the type of resin particles was changed from MX030W (particle size 40 nm) to MX-200W (particle size 350 nm; manufactured by Nippon Shokubai Co., Ltd.), and in the same manner as in Example 1 except that, an aqueous pigment composition was prepared. was prepared. As a result of calculating the average particle size from the image of the composite particles, it was 250 nm for titanium oxide and 350 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
In Comparative Example 1, in which composite particles of titanium oxide particles and resin particles having a particle size larger than that of titanium oxide particles were used, all of the hiding property, ink ejection property, and non-drying property were inferior.
Table 1 shows the results.

[Comparative Example 2]
In Example 2, the type of resin particles was changed from FS-101 (acrylic, particle size 100 nm, powder) to S6 (melamine, particle size 400 nm, powder; manufactured by Nippon Shokubai Co., Ltd.). An aqueous pigment composition was prepared in the same manner as in Example 2.
As a result of calculating the average particle size from the image of the composite particles, it was 300 nm for titanium oxide and 400 nm for resin particles.
The aqueous pigment composition was evaluated in the same manner as in Example 1.
It was found that, similarly to Comparative Example 1, when resin particles having a particle diameter larger than that of titanium oxide particles were used, all of the hiding properties, the ink ejection properties, and the non-drying properties were inferior.
Table 1 shows the results.

1 Composite Particles 2 Resin Particles 3 Titanium Oxide Particles

Claims (4)

Composite particles of titanium oxide particles and resin particles having a particle size smaller than that of the titanium oxide particles adhering to the surfaces of the titanium oxide particles and covering part or all of the surfaces ,
The ratio of the average particle size of the titanium oxide particles and the resin particles in the composite particles is titanium oxide particles/resin particles=1.1 to 10,
An aqueous pigment composition for writing instruments, wherein the content of the composite particles contained in the total amount of the aqueous pigment composition for writing instruments is 1 to 60% by mass. 2. The aqueous pigment composition for writing instruments according to claim 1, wherein the content of titanium oxide contained in the total amount of the aqueous pigment composition for writing instruments is 0.1 to 35% by mass. 3. The water-based pigment composition for a writing instrument according to claim 1, wherein the compounding ratio of titanium oxide and resin particles in said composite particles is 1.5/1.0 to 6.0/1.0 in mass ratio. . The water-based pigment composition for a writing instrument according to any one of claims 1 to 3, wherein the average particle size of the resin particles constituting the composite particles is in the range of 40 to 900 nm.

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