JP2014070091A - Inorganic pigment particle containing fluorine in surface of base material particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide pigment particles showing excellent dispersion stability.SOLUTION: Inorganic pigment particles have an inorganic (hydro) oxide layer doped with fluorine on the surface of base material particles, have fluorine in the amount of 14-35 atom%, which exists from the surface of the inorganic pigment particles to the depth of 10 nm and fluorine in the amount of 5.5-14 atom%, which exists from the surface to a depth of 2 nm to 12 nm, and have a water content of 3000 ppm or less in the inorganic pigment particles.

Description

  The present invention relates to inorganic pigment particles suitable for various uses such as printing inks, paints, and inks for inkjet printers.

  Pigment particles such as titanium oxide and titanium black are widely used in industrial applications such as gravure printing. However, these pigment particles have poor dispersibility, and if added directly to the dispersion, there arises a problem that the pigment particles aggregate.

  As an example of dealing with this problem, for example, there is a technique in which pigment particles are coated with a polymer to stably disperse these pigment particles in a liquid. However, this method is not a simple method because it requires steps and reagents for forming a polymer.

  By the way, the present inventors paid attention to fluorine as a substance that is easily charged with static electricity. In other words, when the pigment particle surface is added to the dispersion medium, the pigment particle surface is charged to induce electrical repulsion between the particles, thereby ensuring dispersion stability of the pigment particles.

  For example, as an example in which fluorine is supported around pigment particles, Patent Document 1 describes pigment particles in which fluoride ions and titanium oxide are bonded. The pigment particles are prepared by first preparing an aqueous slurry in which titanium oxide is dispersed, adding a compound capable of producing a fluorine compound therein, and heating at a low temperature. Patent Document 2 discloses a titanium oxide sphere obtained by applying titania sol to a Teflon (registered trademark) (fluororesin) sheet and then drying it. Patent Documents 3 to 6 describe titanium oxide having a fluorinated surface, which is formed by directly heating titanium oxide particles in a gas containing fluorine.

JP 59-184263 A JP-A-61-2215216 Japanese Patent Laid-Open No. 3-40919 Japanese Patent Laid-Open No. 10-324505 JP 11-292520 A International Publication No. 99/24523 Pamphlet

  However, with the pigment particles described in these documents, the dispersion stability of the particles in the liquid has never been sufficient.

  Under such circumstances, an object of the present invention is to provide pigment particles exhibiting dispersion stability superior to those of the prior art.

  According to the study by the present inventors, in order to improve the dispersibility, the pigment particles need to be fixed with a large amount of fluorine in the outer layer of the particles, and from the particle surface toward the deep part, It has been found that having an inclined structure in which the amount of fluorine to be fixed decreases is an important factor. And it discovered that these structures could be formed by previously forming an inorganic (water) oxide layer having an inorganic substance such as alumina on the surface of the titanium oxide particles, and then doping the particles with fluorine.

  That is, the pigment particles described in Patent Documents 1 and 2 can fix fluorine on the surface of titanium oxide, but it is difficult to form an inclined structure from the surface toward the deep portion, and exhibit desired dispersion stability. Is not done. In addition, although the pigment particles described in Patent Documents 3 to 6 are directly doped with fluorine on the titanium oxide surface, since there is no inorganic (water) oxide layer, a desired amount of fluorine is fixed on the surface. At the same time, it is considered that the dispersion stability was lowered because it was not possible to form a gradient structure in which the amount of fluorine decreased from the particle surface toward the deep part.

As a result of intensive studies to solve the above problems, the inventors of the present invention doped fluorine in the inorganic (water) oxide layer on the surface of the base material particles, so that a large amount of fluorine was fixed to the outer layer of the particles, The inventors have found that an inclined structure in which the amount of fluorine decreases from the particle surface toward the deep part can be formed, and the present invention has been completed.
That is, the inorganic pigment particles according to the present invention have an inorganic (water) oxide layer doped with fluorine on the surface of the substrate particles. Further, the amount of fluorine existing from the surface of the inorganic pigment particle to a depth of 10 nm is 14 to 35 atom%, and the amount of fluorine existing from a depth of 2 nm to a depth of 12 nm from the surface is 5.5 to 14 atom%. Is desirable. Furthermore, it is preferable that the amount of water in the inorganic pigment particles is 3000 ppm or less, and the thickness of the inorganic (water) oxide layer is 20 nm or less. In addition, it is desirable that the amount of fluorine existing from the depth of 8 nm to the depth of 18 nm from the surface is 1.8 atom% or less, and the volume average particle diameter of the inorganic pigment particles is 0.03 to 1.2 μm. Is more preferred.
In the present invention, the inorganic (water) oxide layer refers to a layer containing an inorganic hydroxide and / or an inorganic oxide. That is, the inorganic (water) oxide layer present on the surface of the substrate particles may be entirely composed of inorganic hydroxide, or may be entirely composed of inorganic oxide. Further, the present invention includes an aspect including an inorganic hydroxide as a part of an inorganic (water) oxide layer, an aspect including an inorganic oxide as a part, or an inorganic hydroxide and an inorganic oxide as a part. Embodiments including both are also included.

  According to the present invention, an inorganic pigment particle exhibiting excellent dispersion stability can be obtained by providing an inorganic (water) oxide layer doped with fluorine on the surface of a pigment particle substrate.

  The inorganic pigment particles according to the present invention are subjected to a surface treatment for forming an inorganic (water) oxide layer on the particle surface serving as a substrate, and then contacted with a fluorine gas in a reaction vessel (fluorine gas treatment). It is formed by fixing fluorine to the inorganic (water) oxide layer. That is, the inorganic pigment particle of the present invention has an inorganic (water) oxide layer doped with fluorine on the particle surface serving as a substrate. This is preferable because the dispersion stability of the inorganic pigment particles in the dispersion medium is improved.

<Fluorine>
By doping the inorganic (water) oxide layer with fluorine, the surface of the inorganic pigment particles can be uniformly charged in the dispersion medium. This action makes it possible to stably disperse the inorganic pigment particles in the liquid.

  The inorganic pigment particles are preferably doped with a large amount of fluorine on the outer layer side of the inorganic (water) oxide layer. Specifically, when fluorine is doped from the surface to a depth of 2 nm, the balance of the charge amount of the inorganic pigment particles is improved, and the dispersion of inorganic pigment particles exhibits good dispersion stability.

  The inorganic pigment particles desirably have an inclined structure in which the amount of doped fluorine (degree of fluorination) decreases from the surface of the inorganic pigment particles toward the deep part. With this configuration, the amount of charge in the surface layer portion of the inorganic pigment particles increases, so that the surface of the inorganic pigment particles can be more uniformly charged. The amount of fluorine in the inorganic (water) oxide layer can be measured by, for example, X-ray electron spectroscopy (ESCA, XPS). In the inorganic pigment particles, where the inorganic (water) oxide layer is thin, fluorine may be combined with elements in the substrate particles. For example, when titanium oxide is used as the base particle, a titanium-fluorine bond is formed at a location where the inorganic (water) oxide layer is thin, but the amount of fluorine doped by the titanium-fluorine bond is extremely small. . Therefore, the amount of fluorine doped can include fluorine doped by this titanium-fluorine bond.

  Regarding the amount of fluorine doped in the inorganic (water) oxide layer, for example, the amount of fluorine contained from the surface of the inorganic pigment particles to a depth of 10 nm is desirably 14 to 35 atom%, more preferably. It is 16 to 31 atom%, and more preferably 20 to 30 atom%. If the amount of fluorine is within the above range, the surface of the substrate particles is uniformly doped with fluorine, so that the charging of the inorganic pigment particles is stable, whereby the inorganic pigment particles can be stably present in the dispersion medium. it can.

  Further, the amount of fluorine existing from the depth of 2 nm to the depth of 12 nm from the surface of the inorganic pigment particles is preferably 5.5 to 14 atom%, more preferably 7 to 13 atom%, and more preferably Is 9-13 atom%. Thus, if the amount of fluorine contained in the inorganic (water) oxide layer from the depth of 2 nm to the depth of 12 nm from the surface is within the above range, the charge polarity balance of the inorganic pigment particle surface is improved, Dispersibility in the liquid is also good.

  On the other hand, the amount of fluorine existing from the depth of 4 nm to the depth of 14 nm from the surface of the inorganic pigment particles is desirably 1.8 to 5.5 atom%, and more preferably 3 to 5.3 atom%. More preferably, it is 4.5 to 5.2 atom%. If the amount of fluorine is within the above range, the charge amount on the surface of the inorganic pigment particles tends to be uniform. On the other hand, if the fluorine content exceeds 5.5 atom%, the polarity of the inorganic pigment particles becomes high, and the chargeability of the surface of the inorganic pigment particles becomes non-uniform. For this reason, positive and negative charges are present in a dispersed manner on the surface of the inorganic pigment particles, which is not preferable because the particles may not be dispersed and aggregate.

  Further, the amount of fluorine present from the surface to a depth of 8 nm to 18 nm is preferably 1.8 atom% or less, more preferably 1.5 atom% or less, and even more preferably 1.1 atom% or less. Yes, it is preferably 1 atom% or more, and more preferably 1.05 atom% or more.

  The amount of fluorine existing from the depth of 10 nm to the depth of 20 nm from the surface is preferably 1 atom% or less, more preferably 0.5 atom% or less, and preferably 0 atom% or more, more preferably Is 0.001 atom% or more, and more preferably 0.1 atom% or more.

  As described above, the amount of doped fluorine contained in the inorganic (water) oxide layer can be measured by X-ray electron spectroscopy (ESCA, XPS) or the like. Further, the amount of fluorine existing at a certain depth from the surface may be measured by the X-ray electron spectroscopy after removing a predetermined thickness from the surface of the inorganic pigment particles by performing an etching process or the like. A specific measurement method will be described in detail in the column of Examples.

  In addition, the water content in the inorganic pigment particles of the present invention is desirably 3000 ppm or less, more preferably 2500 ppm or less, further preferably 1500 ppm or less, and more preferably 600 ppm or less. On the other hand, the lower limit of the amount of water in the inorganic pigment particles is not particularly limited, but is preferably 0.1 ppm or more, more preferably 50 ppm or more, and still more preferably 100 ppm or more. A moisture content within the above range is desirable because inorganic pigment particles can be stably present in the dispersion medium without agglomeration.

<Base material particles>
As the base particles, pigment particles are preferably used. The pigment particles are not particularly limited. For example, inorganic pigments such as titanium oxide, barium sulfate, and zinc white are used in the white system; yellow iron oxide, cadmium yellow, titanium yellow, chrome yellow, and yellow are used in the yellow system. Inorganic pigments such as lead; In orange, inorganic pigments such as molybdate orange; In red, inorganic pigments such as Bengala and Cadmium red; In blue, inorganic pigments such as bitumen, ultramarine blue, cobalt blue and cerulean blue; green In the system, inorganic pigments such as emerald green, chrome green, chromium oxide, and viridian; in the black system, inorganic pigments such as carbon black, titanium black, and iron black; These pigment particles may be used alone or in combination of two or more.

  When titanium oxide particles are employed as the base particles, the type thereof is not particularly limited, and any material that is generally used as a white pigment can be used. For example, either a rutile type or an anatase type is suitable. In consideration of fading of the colorant due to the photocatalytic activity of titanium oxide, rutile type titanium oxide having a low photocatalytic activity is preferable.

  The average particle diameter of the substrate particles is preferably 0.03 μm or more, more preferably 0.1 μm or more, further preferably 0.2 μm or more, preferably 1 μm or less, more preferably 0.00. It is 8 μm or less, more preferably 0.5 μm or less. If the average particle size is too small, sufficient chromaticity cannot be obtained and it is not suitable for use as a pigment. On the contrary, if the average particle diameter is too large, the mass of the obtained inorganic pigment particles becomes large, so that the inorganic pigment particles easily settle in the dispersion medium.

  In addition, the average particle diameter of the inorganic pigment particles adopts the nominal value when using a commercial product, and when the nominal value is not clear or prepared by itself, a laser diffraction / scattering type particle size distribution measuring device (For example, “LA-910” manufactured by Horiba, Ltd.) may be used to measure the volume average particle diameter.

<Inorganic (water) oxide layer>
In order to reduce the photocatalytic activity of the base particles, the base particles are subjected to a surface treatment with an inorganic substance such as silica treatment, alumina treatment, silica-alumina treatment, zirconium-alumina treatment, and the like. Si and Al present on the surface are bonded to a hydroxyl group to form an inorganic hydroxide layer containing -Si-OH group and -Al-OH group. And in this invention, the said hydroxyl group remove | excludes a hydroxyl group by the heat processing at the time of dope of fluorine, and a part becomes an inorganic oxide layer.

  The thickness of the inorganic (water) oxide layer is desirably 30 nm or less, more preferably 25 nm or less, further preferably 20 nm or less, and most preferably 18 nm or less. If the thickness of the inorganic (water) oxide layer is within the above range, a desired amount of fluorine is doped into the inorganic (water) oxide layer, so when the resulting inorganic pigment particles are added to the dispersion medium, Inorganic pigment particles are stably dispersed.

  The inorganic (water) oxide layer may cover the surface of the substrate particles with a substantially uniform thickness, or may be formed so that the particle surface after the formation of the inorganic (water) oxide layer has irregularities.

<Inorganic pigment particles>
The inorganic pigment particles according to the present invention are subjected to a surface treatment for forming an inorganic (water) oxide layer on the surface of particles serving as a substrate, and then brought into contact with fluorine gas in a system filled with fluorine gas (fluorine gas). Process).

The volume average particle diameter of the inorganic pigment particles is preferably, for example, 0.03 to 1.2 μm, more preferably 0.2 to 1 μm, and further preferably 0.5 to 0.8 μm. Most preferably, the thickness is 0.55 to 0.7 μm. If the volume average particle diameter of the inorganic pigment particles is within the above range, it is desirable because the inorganic pigment particles can be stably dispersed without settling.
The volume average particle diameter of the inorganic pigment particles is determined by dispersing the sample particles in acetone and using a dynamic light scattering particle size distribution measuring apparatus (for example, “LB-500” manufactured by Horiba, Ltd.). And it is calculated | required by measuring the volume average particle diameter of an aggregate.

  The inorganic pigment particles of the present invention can be stably dispersed in various liquids by doping the surface with fluorine. During dispersion, the particles are uniformly dispersed without requiring high dispersion energy, and thus can be usefully used in various applications. As a use, for example, it is suitable for various uses that require dispersion stability of pigment particles of printing ink, paint, and ink for ink jet printer.

  As the dispersion medium for the inorganic pigment particles, a nonpolar dispersion medium and a polar dispersion medium can be used. Examples of the nonpolar dispersion medium include hydrocarbon nonpolar dispersion media such as hexane, cyclohexane, and cyclopentane; aromatic nonpolar dispersion media such as benzene, toluene, o-xylene, m-xylene, and p-xylene; And silicone oil nonpolar dispersion media such as silicone oil and methylphenyl silicone oil. As polar dispersion media, aprotic polar dispersion media such as acetone, tetrahydrofuran, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide; water, methanol, ethanol, 1-propanol, 2-propanol, n-butanol, formic acid And other protic polar dispersion media.

  In addition, you may add a dispersing agent, dye, a viscosity modifier etc. to the dispersion liquid of an inorganic pigment particle | grain suitably.

  The dispersant that can be added to the dispersion medium is not particularly limited as long as it is a dispersant that can be used to assist the dispersion of the inorganic pigment particles in the dispersion medium. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant, fluorosurfactant, sorbitan fatty acid ester surfactant such as sorbitan sesquiolate, block type Examples thereof include dispersants such as polymers and graft polymers, and various coupling agents. These dispersants may be used alone or in combination of two or more.

  For example, the inorganic pigment particles of the present invention exhibit good dispersion stability with a sedimentation rate of 15 μm / sec or less when dispersed in a toluene dispersion medium containing a titanate-based dispersant having a concentration of 0.2% by mass. In particular, the amount of fluorine existing from the surface of the inorganic pigment particle to a depth of 10 nm is 14 to 35 atom%, and the amount of fluorine existing from a depth of 2 nm to a depth of 12 nm from the surface is 5.5 to 14 atom%. With pigment particles, a sedimentation rate of 5 μm / sec or less can be achieved. The lower limit of the sedimentation rate of the inorganic pigment particles is not limited, but is preferably 0.1 μm / sec, and more preferably 0 μm / sec.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

<Measurement of water content>
About 0.5 g of the sample particles were thoroughly evaluated, and the moisture content in the sample particles was measured using a Karl Fischer moisture meter (“AQV-200” manufactured by Hiranuma Sangyo Co., Ltd.).

<Quantification of elements>
The amount of fluorine was measured by the following method. First, the sample particles are set on a measurement substrate with a double-sided tape, and the detected atoms are identified by ESCA Wide Scan using an X-ray photoelectron spectrometer (“JPS-90 type” manufactured by JEOL Ltd.). Narrow Scan was performed to increase the degree of quantification, and the fluorine content of the sample particle surface layer was measured.
Next, after irradiating with 500 V argon ions for a predetermined time and performing an etching process, ESCA Wide Scan and Narrow Scan were performed, and the amount of fluorine at each depth was determined from the surface of the inorganic pigment particles by a method of measuring the amount of fluorine.

<Evaluation of dispersibility>
1 g of sample particles are put in 10 g of a toluene dispersion medium containing a titanate-based dispersant having a concentration of 0.2% (“Plenact (registered trademark) KR-TTS” manufactured by Ajinomoto Fine Techno Co., Ltd.), and an ultrasonic bath (Nippon Emerson) Using a “BRANSON (registered trademark) 5210” manufactured by the manufacturer, ultrasonic dispersion was performed for 1 hour to prepare a dispersibility test solution. The dispersion state of the sample particles in the dispersibility test liquid was confirmed with an optical microscope ("Digital Microscope VHX-1000" manufactured by Keyence Corporation). The sample particles were evaluated based on the following items.
A: The dispersibility of the sample particles is good, and no aggregates are confirmed at a magnification of 2000 times.
A: The dispersibility of the sample particles is insufficient, and many aggregates are confirmed at a magnification of 1000 times.
Δ: Sample particles are aggregated as a whole and almost no sample particles are dispersed at a magnification of 1000 times.
X: The test solution does not become a dispersion but becomes a paste.

<Measurement of volume average particle diameter>
The volume average particle size of the fluorine-doped titanium oxide is obtained by dispersing sample particles in acetone and using a dynamic light scattering type particle size distribution measuring device (“LB-500” manufactured by Horiba, Ltd.). It calculated | required by measuring a volume average particle diameter.

<Measurement of sedimentation velocity>
The sample particles were added to acetone so that the sample particle concentration was 10% by mass, and the sample particles were sufficiently dispersed using an ultrasonic bath. 0.4 mL of this dispersion was put into a measurement cell made of polycarbonate, and a sedimentation rate measuring device of centrifugal sedimentation type (“LUMiSizer612” manufactured by L.U.M.GmbH). )) And measured under the following conditions. Rotational speed: 2,000 min ⁻¹ , measurement time: 40 minutes, measurement interval: 10 seconds, light factor: white 1, threshold (transmittance defined as interface): 20%.

Example 1
About 5 g of titanium oxide whose surface is alumina-treated (“Typaque (registered trademark) CR60” manufactured by Ishihara Sangyo Co., Ltd., average particle size 0.21 μm (nominal value)) is thinly spread on a nickel tray, and has a cylindrical shape with a capacity of 3 L In a nickel container that can be heated and sealed. The atmosphere in the nickel container was evacuated and purged with nitrogen gas. The inside of the nickel container was heated to 100 ° C. in a vacuum state and held for 2 hours.
Two hours later, the inside of the nickel container was cooled to 40 ° C., and while maintaining this temperature, a mixed gas of fluorine and nitrogen (mixing ratio: F ₂ / N ₂ = 50 vol% / 50 vol%) was flowed from the gas introduction pipe. The mixture was introduced at 5 ml / min, and the inside of the nickel container was filled with a mixed gas. This state was maintained for 1 hour and the titanium oxide was treated with fluorine gas.
After 1 hour, the mixed gas was evacuated and purged with nitrogen gas. A nickel tray was taken out of the nickel container, and about 5 g of fluorine-doped titanium oxide (A-1) was obtained. The moisture content, fluorine content, dispersibility, volume average particle diameter, and sedimentation rate of the fluorine-doped titanium oxide (A-1) were measured by the methods described above. The results are shown in Table 1.
Moreover, the fluorine-doped titanium oxide (A-1) was etched. The amount of each element in the fluorine-doped titanium oxide after the etching treatment was measured by the method described above. The etching process was performed under the condition of a voltage of 500V. The results are shown in Table 2.
The table shows applied voltage, voltage application time, and etched thickness. The “etched thickness” in the table was calculated based on the voltage application time. That is, when silica particles were prepared as a sample, and the particles were etched for 60 seconds under a voltage of 500 V, the silica was removed from the surface to a depth of 20 nm. The voltage application time required for the above was measured, and the etched thickness was calculated by proportional calculation.

Examples 2-4
Fluorine-doped titanium oxide was obtained by the same method as in Example 1 except that the mixing ratio of the fluorine / nitrogen mixed gas was changed as shown in Table 1. The characteristics of the obtained fluorine-doped titanium oxide are shown in each table.

Example 5
The fluorine-doped titanium oxide (A-1) obtained in Example 1 was allowed to stand for 24 hours under conditions of 50 ° C. and 90% RH, and the characteristics of the particles were evaluated. The results are shown in Table 1.

Comparative Example 1
The characteristics of titanium oxide (Typaque CR60) before treatment with fluorine gas were evaluated. In the characteristic evaluation, since titanium oxide (Typaque CR60) was not dispersed in the toluene dispersion medium and acetone, the volume average particle diameter and the sedimentation rate could not be measured.

  In Examples 1 to 5, since the surface of the titanium oxide particles was uniformly doped with fluorine, the surface of the fluorine-doped titanium oxide particles could be uniformly charged and the dispersibility in the solvent was improved. In particular, since the fluorine-doped titanium oxides of Examples 1 and 2 can be repelled efficiently between particles, the dispersibility of the particles is good, and no aggregates were confirmed even at a magnification of 2000 times. In addition, the fluorine-doped titanium oxide dispersions of Examples 1 and 2 exhibited excellent dispersion stability with a sedimentation rate of 6 μm / s or less. In Example 3, since the amount of fluorine on the particle surface is small and the repulsion of the particle is not sufficient, the particles are aggregated. In Example 4, although the reason is not clear, aggregates were confirmed in the dispersion because the amount of fluorine on the particle surface was large. According to the result of Example 5, it seems that the moisture resistance of the titanium oxide particles is improved by the fluorine gas treatment, but the fluorine-treated titanium oxide of Example 1 showing good dispersibility is used. Even if it is a case, when a fixed time passes, it will be understood that the fluorine-doped titanium oxide of the present invention absorbs a large amount of moisture. Then, when the water content in the particles is high in this way, some particles were aggregated.

  In Comparative Example 1, since the surface of the substrate particles was not doped with fluorine, the particles were not dispersed at all.

Claims (6)

  An inorganic pigment particle comprising an inorganic (water) oxide layer doped with fluorine on the surface of a substrate particle. The amount of fluorine existing from the surface of the inorganic pigment particles to a depth of 10 nm is 14 to 35 atom%,
2. The inorganic pigment particle according to claim 1, wherein the amount of fluorine existing from a depth of 2 nm to a depth of 12 nm from the surface is 5.5 to 14 atom%.   The inorganic pigment particles according to claim 1 or 2, wherein the water content in the inorganic pigment particles is 3000 ppm or less.   The inorganic pigment particle according to any one of claims 1 to 3, wherein the inorganic (water) oxide layer has a thickness of 20 nm or less.   The inorganic pigment particle according to any one of claims 1 to 4, wherein an amount of fluorine existing from a depth of 8 nm to a depth of 18 nm from the surface is 1.8 atom% or less.   The inorganic pigment particle according to any one of claims 1 to 5, which has a volume average particle diameter of 0.03 to 1.2 µm.