Quinacridone pigment and method for producing the same

Abstract

To provide a quinacridone pigment which not only reduces the content of phosphorus in the whole pigment but also can suppress elusion of phosphorus from the pigment surface, especially, is useful for inkjet.SOLUTION: There is provided a quinacridone pigment having a phosphorus elution amount of 100 ppm or less and a phosphorus content of 400 ppm or less by the following measurement method. Measurement method: a quinacridone pigment before and after dispersion under the following dispersion condition is measured by a fluorescent X-ray analyzer, and a difference between before and after the dispersion is defined as the phosphorus elution amount. Dispersion condition: 0.1 pts.wt. of IPA and 15.9 pts.wt. of water are added to 1 pts.wt. of a quinacridone pigment and are mixed at 20°C, and are dispersed by a paint conditioner at a frequency of 750 rpm for 1 hour.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to quinacridone pigments.

Background Art

[0002] Quinacridone pigments are used in various applications such as paints, toners, printing inks, and inks for inkjet recording. For example, in magenta ink for inkjet recording, quinacridone pigments such as C.I. Pigment Violet 19 and C.I. Pigment Red 122 are widely used.

[0003] As an inkjet recording method, a thermal method is known in which thermal energy is applied to a part of a thin metal pipe filled with ink to cause foaming in the ink, and the ink is ejected by the pressure. As a phenomenon peculiar to this thermal method, there is adhesion of deposits, so-called "cogging", to the surface of the heater for applying thermal energy to the ink for inkjet recording. This "cogging", also called "cogation", may reduce the thermal efficiency and the ink ejection efficiency. Patent Document 1 describes that an inorganic phosphorus compound in the ink is heated by a heater in the ink nozzle, forms a compound with calcium eluted from the ink or ink contact materials such as nozzles and tanks, and adheres to the heater. This compound of phosphorus and calcium is very hard and hardly soluble, and is said not to be redissolved or peeled off. Further, in Patent Document 1, it is presumed that fine irregularities occur due to the adhesion of the scorch of phosphorus and calcium on the heater, and the sudden decrease in the ejection amount occurs due to the entry of carbon scorch thereinto. Therefore, in the ink described in Patent Document 1, the concentration of phosphorus in the pigment used is set to 500 ppm or less to reduce the amount of phosphorus in the whole pigment in order to suppress cogation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] As described above, quinacridone pigments with a low phosphorus content are in high demand for inkjet ink applications. The inventors have discovered that even with techniques that reduce the phosphorus content in the pigment as described in Patent Document 1, coging can still occur if a large amount of phosphorus leaches from the pigment, particularly from the pigment surface, even after reducing the phosphorus content in the ink. Therefore, the problem that the present invention aims to solve is to provide a quinacridone pigment that not only reduces the phosphorus content in the pigment as a whole, but also suppresses the leaching of phosphorus from the pigment surface, and is particularly useful for inkjet applications. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the inventors of the present invention discovered that quinacridone pigments, which have a specific surface structure, not only have a low phosphorus content in the overall pigment, but also that phosphorus is less likely to leach from the pigment surface, thus completing the present invention.

[0007] In other words, the present invention is Item 1. A quinacridone pigment having a phosphorus elution amount of 100 ppm or less and a phosphorus content of 400 ppm or less in the measurement method described below. Measurement method: The quinacridone pigment was measured before and after dispersion under the following dispersion conditions using an X-ray fluorescence analyzer, and the difference between the pre- and post-dispersion measurements was defined as the phosphorus elution amount. Dispersion conditions: Add 0.1 parts by weight of IPA and 15.9 parts by weight of water to 1 part by weight of quinacridone pigment, mix at 20°C, and disperse in a paint conditioner at a vibration frequency of 750 rpm for 1 hour. Item 2. The quinacridone pigment described in Item 1, comprising CI Pigment Violet 19 and CI Pigment Red 122. [Effects of the Invention]

[0008] According to the quinacridone pigment of the present invention, the phosphorus content in the entire pigment is low, and phosphorus is less likely to leach from the pigment surface. Therefore, in inkjet inks used in thermal systems, the adhesion of "burnt residue," or "coggation," to the ink nozzle can be suppressed. In other words, according to the quinacridone pigment of the present invention, phosphorus compounds formed by phosphorus and calcium are less likely to be generated during ink formation, making it possible to manufacture a good inkjet ink with less occurrence of "coggation." [Modes for carrying out the invention]

[0009] The present invention will be described in detail below.

[0010] <Quinacridone pigment> The quinacridone pigment of the present invention has a phosphorus elution amount of 100 ppm or less and a phosphorus content of 400 ppm or less in the measurement method described below. Measurement method: The quinacridone pigment was measured before and after dispersion under the following dispersion conditions using an X-ray fluorescence analyzer, and the difference between the pre- and post-dispersion measurements was defined as the phosphorus elution amount. Dispersion conditions: Add 0.1 parts by weight of IPA (=isopropyl alcohol) and 15.9 parts by weight of water to 1 part by weight of quinacridone pigment, mix at 20°C, and disperse in a paint conditioner at a vibration frequency of 750 rpm for 1 hour.

[0011] The above dispersion conditions mimic typical pigment dispersion conditions for inkjet inks, and a low amount of phosphorus elution, as shown by the difference before and after dispersion under these conditions, indicates a good inkjet ink with minimal "cogation." The X-ray fluorescence analyzer used in the above measurement method may be either wavelength-dispersive or energy-dispersive; for example, the apparatus used in the present embodiment can be used. The phosphorus content can be determined, for example, by quantifying the phosphorus content in the pigment using an X-ray fluorescence analyzer. The paint conditioner refers, for example, to a paint conditioner type shaker described in JIS 5101-1-2.

[0012] The quinacridone pigment of the present invention has a phosphorus elution amount of 100 ppm or less, preferably 80 ppm or less, and more preferably 60 ppm or less, as measured by the above method. Furthermore, the phosphorus content of the quinacridone pigment of the present invention is 400 ppm or less, preferably 350 ppm or less, more preferably 50 ppm or less, and most preferably 40 ppm or less.

[0013] Examples of quinacridone pigments in the present invention include CI Pigment Violet 19, CI Pigment Red 122, CI Pigment Red 209, CI Pigment Red 202, CI Pigment Orange 48, and CI Pigment Orange 49. The quinacridone pigment in the present invention may also be a pigment containing two or more of the above pigments. Examples of such pigments include solid solution pigments containing CI Pigment Violet 19 and CI Pigment Red 122, which are useful for inkjet magenta inks due to their hue and other factors.

[0014] Furthermore, the quinacridone pigment of the present invention may also contain a quinacridone pigment derivative. By using a quinacridone pigment derivative in combination, higher storage stability can be obtained. The presence of a quinacridone pigment derivative in the quinacridone pigment can be confirmed, for example, by infrared absorption spectroscopy (IR) or mass spectrometry (MS).

[0015] Any known and conventional quinacridone pigment derivative can be used in the present invention. These include quinacridone pigment derivatives in which one or more sulfonic acid residues and their metal salts, dialkylaminoalkylaminosulfamoyl residues, phthalimidomethyl residues, dialkylaminoalkyl residues, etc., are substituted on the skeleton of CI Pigment Violet 19, CI Pigment Red 202, CI Pigment Red 209, and CI Pigment Red 122, for example, quinacridone sulfonic acid, dimethylaminopropylaminosulfamoyl quinacridone, pyrazolyl-methyl quinacridone, dimethylaminopropyl quinacridone monosulfonamide, dimethylaminopropyl quinacridone disulfonamide, and 2-phthalimidomethyl and dimethylaminomethyl quinacridone. Among these, sulfonic acid and its metal salts and dimethylaminopropylaminosulfamoyl derivatives are preferred from the viewpoint of providing better storage stability.

[0016] In the present invention, when a quinacridone pigment derivative is used in combination, it is preferable to use 1 to 10 parts by mass of the quinacridone pigment derivative per 100 parts by mass of the quinacridone solid solution pigment.

[0017] Furthermore, pigment derivatives other than those mentioned above may also be used in combination. These derivatives can utilize not only the skeletons of CI Pigment Violet 19, CI Pigment Red 202, CI Pigment Red 209, and CI Pigment Red 122, but also the skeletons of condensed polycyclic pigments such as CI Pigment Violet 23, CI Pigment Blue 15 (copper phthalocyanine), CI Pigment Red 177, CI Pigment Red 254, and 255.

[0018] <Method for producing quinacridone pigment> Here, we present an example of a method for obtaining the quinacridone pigment of the present invention. The following manufacturing method is a method for obtaining CI Pigment Violet 19 and CI Pigment Red 122 as a solid solution pigment.

[0019] The crude quinacridone pigment used in the present invention is obtained, for example, by dehydrating and cyclizing 2,5-dianilinoterephthalic acid (raw material of C.I. Pigment Violet 19), which is a raw material for the crude quinacridone solid solution pigment, and 2,5-di-p-toluidinoterephthalic acid (raw material of C.I. Pigment Red 122) in polyphosphoric acid, adding them to water, and then filtering and washing the precipitate with water. Here, the mass ratio of 2,5-dianilinoterephthalic acid to 2,5-di-p-toluidinoterephthalic acid is, for example, from 80 / 20 to 20 / 80, and preferably from 70 / 30 to 60 / 40 because crystallites can be formed more uniformly. Usually, the conductivity of the water (industrial water) used for pigment synthesis and water washing, etc. is about 300 to 500 μS / cm. However, in the production method of the present invention, as the water used for dehydration cyclization and subsequent water washing, water with a low ion content (for example, water with a conductivity of 10 μS / cm or less, preferably 5 μS / cm or less, more preferably 3 μS / cm or less, and particularly preferably 2 μS / cm or less) is preferably used. Examples of such water include pure water, ion-exchanged water, RO-treated water, and ultrapure water. By using such water with a low ion content, the phosphorus component in the pigment, particularly on the pigment surface, can be washed away more efficiently.

[0020] The quinacridone pigment of the present invention can be produced by heating the crude quinacridone solid solution pigment obtained above in a large excess of a liquid medium. Here, the liquid medium is selected and used such that it does not dissolve the crude quinacridone solid solution pigment. Also, from the viewpoint of stably controlling crystal formation, it is preferably contained mainly with a water-soluble organic solvent.

[0021] Examples of such water-soluble organic solvents include dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, ethanol, isopropyl alcohol, propanol, isobutanol, ethylene glycol, etc. Considering the heating temperature, price, and safety during production, it is preferable to use dimethylformamide, isopropyl alcohol, or isobutanol. The amount of the water-soluble organic solvent used is not particularly limited, but it is preferably appropriately set within the range of 0.1 to 20 times the equivalent amount by weight. Although a larger amount may be used, it is preferably set within the above range from the perspective of increasing solvent recovery costs.

[0022] The heating temperature can be in the range of 60°C to 150°C, and it is preferably in the range of 70°C to 140°C. The heating time is not particularly limited, but from the perspective of obtaining a pigment with a more uniform particle size, it can be 2 to 10 hours. The obtained quinacridone pigment may be appropriately pulverized and refined.

[0023] In the present invention, when a quinacridone pigment derivative is used in combination, the addition method is not particularly limited. However, when adding the crude quinacridone pigment to the liquid medium, the quinacridone pigment derivative can be further added and then the heating step can be performed to obtain the desired quinacridone pigment. It can also be added to the aqueous dispersion after removing the water-soluble organic solvent from the liquid medium by distillation or the like. Here, the amount of the quinacridone pigment derivative used is as described above.

[0024] Furthermore, for the obtained quinacridone pigment, in order to remove impurities in the pigment, acid washing and water washing using hydrochloric acid, sulfuric acid, nitric acid, etc. may be performed. As the water used for acid washing and water washing, in order to more efficiently wash away the phosphorus component in the pigment, especially on the pigment surface, it is preferable to use water with a low ion content such as ion-exchanged water.

Examples

[0025] Hereinafter, the present invention will be described in more detail using examples and comparative examples. Unless otherwise specified in the following examples and comparative examples, “%” represents “mass %”.

[0026] [Method for measuring phosphorus] For measuring the phosphorus content in the pigments, a PANalytical Epsilon 5 energy-dispersive X-ray fluorescence analyzer (hereinafter referred to as "XRF") was used.

[0027] [Phosphorus extraction method] A pigment that has been previously measured by XRF is added to an aqueous solution (at 20°C) made by mixing IPA and deionized water. After dispersion for 10 minutes with a paint conditioner (vibration frequency 750 rpm), deionized water is added, and dispersion is further carried out with the paint conditioner for another 50 minutes to obtain a slurry.

[0028] [Method for evaluating phosphorus elution] The difference in phosphorus content was determined for the pigments before and after the tests described in the examples and comparative examples. The difference in phosphorus content before and after the test was defined as the amount of phosphorus eluted, and was evaluated according to the following criteria. ○: 0 ppm ≤ (phosphorus elution amount) ≤ 100 ppm ×: 100 ppm < (phosphorus elution amount)

[0029] [Visual evaluation after evaporating the filtrate to dryness] Six g of the filtrate obtained from the tests described in the Examples and Comparative Examples was weighed into an aluminum petri dish and evaporated to dryness at 160°C using an infrared moisture meter (manufactured by Kett Scientific Research Institute Co., Ltd.). The state of the residue after evaporation to dryness was visually evaluated. The evaluation was carried out according to the following criteria. ○: No residue can be observed, or a small amount of white residue can be observed. ×: A large amount of residue was observed, and some parts were discolored yellow.

[0030] [Example 1] 330 g of 85% phosphoric acid was weighed into a 1 L separable flask, and 469 g of anhydrous phosphoric acid was added and stirred to prepare 84% polyphosphate. After the temperature of the polyphosphate decreased to approximately 100°C, 165 g of 2,5-dianilinotephthalic acid, a raw material for CI Pigment Violet 19, and then 110 g of 2,5-di-toluidinoterephthalic acid, a raw material for CI Pigment Red 122, were gradually added. After the addition of the raw materials was complete, a condensation reaction was carried out at 125°C for 3 hours. After the reaction was complete, 5 L of ion-exchanged water (conductivity 10 μS / cm or less) at 30°C was weighed into a 10 L stainless steel cup, and the reaction solution was added to the water while stirring to obtain a solid solution slurry of CI Pigment Violet 19 and CI Pigment Red 122. After filtering this solid solution slurry, it was washed with deionized water (conductivity 10 μS / cm or less) to obtain 465 g of solid solution crude pigment wet cake (solid content 31%). 129 g of solid solution crude pigment wet cake, 129 g of isobutanol, and 174 g of deionized water were placed in a 1 L sealed container and heated at 80°C for 3 hours, then at 135°C for another 3 hours under stirring. The isobutanol was then recovered from the system by distillation to obtain a solid solution pigment slurry. This solid solution pigment slurry was filtered, washed with deionized water (conductivity 10 μS / cm or less), dried at 98°C for 18 hours, and then pulverized to obtain 36 g of solid solution pigments of CI Pigment Violet 19 and CI Pigment Red 122.

[0031] The amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF and found to be 39 ppm. 1.0 g of IPA and 49.0 g of deionized water were weighed into a 110 ml plastic bottle. 10.0 g of the solid solution pigment obtained above was weighed in and dispersed in paint conditioner for 10 minutes. Then 110.0 g of deionized water was weighed in and dispersed in paint conditioner for 50 minutes. The resulting pigment slurry was filtered, and the filtered wet cake was dried at 98°C for 18 hours. The amount of phosphorus contained in the pigment obtained by further grinding was measured by XRF and found to be 39 ppm.

[0032] [Example 2] 511 g of 85% phosphoric acid was weighed into a 2 L separable flask, and 727 g of anhydrous phosphoric acid was added and stirred to prepare 84% polyphosphate. After the temperature of the polyphosphate had decreased to approximately 100°C, 256 g of 2,5-dianilinotephthalic acid, a raw material for CI Pigment Violet 19, and then 170 g of 2,5-di-toluidinoterephthalic acid, a raw material for CI Pigment Red 122, were gradually added. After the addition of the raw materials was complete, a condensation reaction was carried out at 125°C for 3 hours. After the reaction was complete, 7 L of water with a conductivity of 300-500 μS / cm at 30°C was weighed into a 10 L stainless steel cup, and the reaction mixture was added to the water while stirring to obtain a solid solution slurry of CI Pigment Violet 19 and CI Pigment Red 122. This solid solution slurry was filtered and washed with water with a conductivity of 300-500 μS / cm to obtain a solid solution crude pigment wet cake. The same procedure was repeated to obtain 2300 g of solid solution crude pigment wet cake (30% solid content). 2007 g of solid solution crude pigment wet cake, 1940 g of isobutanol, and 2533 g of water with conductivity of 300-500 μS / cm were placed in a 10 L sealed container and heated at 80°C for 3 hours, then at 135°C for 3 hours with stirring. After that, the isobutanol was recovered from the system by distillation, filtered, and washed with water with conductivity of 300-500 μS / cm to obtain a solid solution pigment slurry. This slurry was weighed out to a solid content of 200 g, and ion-exchanged water (conductivity of 10 μS / cm or less) was added to prepare 3200 g of slurry with a solid content of 6%. 3 g of 35% hydrochloric acid was weighed out to this slurry, stirred at 60°C for 1 hour, and then filtered and washed with ion-exchanged water (conductivity of 10 μS / cm or less). The mixture was dried at 98°C for 18 hours and then pulverized to obtain 180 g of solid solution pigments of CI Pigment Violet 19 and CI Pigment Red 122.

[0033] The amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF and found to be 41 ppm. 1.0 g of IPA and 49.0 g of deionized water were weighed into a 110 ml plastic bottle. 10.0 g of the solid solution pigment obtained above was weighed in and dispersed in paint conditioner for 10 minutes. Then 110.0 g of deionized water was weighed in and dispersed in paint conditioner for 50 minutes. The resulting pigment slurry was filtered, and the filtered wet cake was dried at 98°C for 18 hours. The amount of phosphorus contained in the pigment obtained by further grinding was measured by XRF and found to be 22 ppm.

[0034] [Example 3] 330 g of 85% phosphoric acid was weighed into a 1 L separable flask, and 469 g of anhydrous phosphoric acid was added and stirred to prepare 84% polyphosphate. After the temperature of the polyphosphate had decreased to approximately 100°C, 165 g of 2,5-dianilinotephthalic acid, the raw material for CI Pigment Violet 19, and then 110 g of 2,5-di-toluidinoterephthalic acid, the raw material for CI Pigment Red 122, were gradually added. After the addition of the raw materials was complete, a condensation reaction was carried out at 125°C for 3 hours. After the reaction was complete, 5 L of ion-exchanged water (conductivity 10 μS / cm or less) at 30°C was weighed into a 10 L stainless steel cup, and the reaction solution was added to the water while stirring to obtain a solid solution slurry of CI Pigment Violet 19 and CI Pigment Red 122. After filtering this solid solution slurry, it was washed with deionized water (conductivity 10 μS / cm or less) to obtain 465 g of solid solution crude pigment wet cake (solid content 31%). 134 g of solid solution crude pigment wet cake, 129 g of isobutanol, and 168 g of water with a conductivity of 300-500 μS / cm were placed in a 1 L sealed container and heated at 80°C for 3 hours, then at 135°C for another 3 hours under stirring. The isobutanol was then recovered from the system by distillation to obtain a solid solution pigment slurry. This solid solution pigment slurry was filtered and washed with water with a conductivity of 300-500 μS / cm, dried at 98°C for 18 hours, and then pulverized to obtain 36 g of solid solution pigments of CI Pigment Violet 19 and CI Pigment Red 122.

[0035] The amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF and found to be 344 ppm. 1.0 g of IPA and 49.0 g of deionized water were weighed into an 110 ml plastic bottle. 10.0 g of the solid solution pigment obtained above was weighed into this mixture and dispersed in paint conditioner for 10 minutes. Then, 110.0 g of deionized water was weighed in and dispersed in paint conditioner for 50 minutes. The resulting pigment slurry was filtered, and the filtered wet cake was dried at 98°C for 18 hours. The amount of phosphorus contained in the pigment obtained by further grinding was measured by XRF and found to be 304 ppm.

[0036] [Comparative Example 1] The phosphorus content of Hostaperm Pink E (manufactured by Clariant) was measured using XRF and found to be 533 ppm. 1.0 g of IPA and 49.0 g of deionized water were weighed into an 110 ml plastic bottle. 10.0 g of Hostaperm Pink E was added and dispersed in paint conditioner for 10 minutes. Then, 110.0 g of deionized water was weighed and dispersed in paint conditioner for 50 minutes. The resulting pigment slurry was filtered, and the filtered wet cake was dried at 98°C for 18 hours. The phosphorus content of the pigment obtained by further grinding was measured using XRF and found to be 355 ppm.

[0037] [Comparative Example 2] A pigment was prepared by the method described in Japanese Patent Publication No. 2006-96927 (paragraphs 0019-0043 of paragraph 4). At this time, the charging ratio of the quinacridone intermediate was 2,5-dianilinoterephthalic acid:2,5-di-toluidinoterephthalic acid = 20:80, and isobutanol was used as the organic solvent for the heat treatment, and water with a conductivity of 300-500 μS / cm was used as the solvent. The amount of phosphorus contained in this pigment was measured by XRF and found to be 334 ppm. 1.0 g of IPA and 49.0 g of deionized water were weighed into an 110 ml plastic bottle. 10.0 g of this pigment was weighed in and dispersed in paint conditioner for 10 minutes. Next, 110.0 g of deionized water was weighed out and dispersed in paint conditioner for 50 minutes. The resulting pigment slurry was filtered, and the filtered wet cake was dried at 98°C for 18 hours. The amount of phosphorus contained in the pigment obtained by further grinding was measured by XRF and found to be 166 ppm.

[0038] [Table 1]

[0039] Examples 1-3 showed very low phosphorus elution levels, ranging from 0 ppm to 100 ppm. This is presumed to be because, during the pigment manufacturing process, crystal growth was carried out under conditions that made it difficult for phosphorus to be incorporated into the pigment particles, resulting in less phosphorus near the pigment surface (Examples 1 and 3), and because phosphorus near the pigment surface was efficiently eluted beforehand (Example 2). A simple evaluation of whether deposits would form in the ink when it was heated was performed by visually assessing the state of the filtrate after evaporation to dryness. The residues of Examples 1 and 2 were white, but the residues of Comparative Examples 1 and 2 were slightly discolored yellow in some areas, suggesting that charring occurred.

Claims

1. A quinacridone pigment having a phosphorus elution amount of 19 ppm or less and a phosphorus content of 400 ppm or less, as measured by the following method. Measurement method: The quinacridone pigment was measured before and after dispersion under the following dispersion conditions using an X-ray fluorescence analyzer, and the difference between the pre- and post-dispersion measurements was defined as the phosphorus elution amount. Dispersion conditions: Add 0.1 parts by weight of IPA and 15.9 parts by weight of water to 1 part by weight of quinacridone pigment, mix at 20°C, and disperse in a paint conditioner at a vibration frequency of 750 rpm for 1 hour.

2. The quinacridone pigment according to claim 1, wherein the quinacridone pigment comprises C.I. Pigment Violet 19 and C.I. Pigment Red 122.

3. Step 1 involves dehydrating and cyclizing 2,5-dianilinotelephthalic acid and / or 2,5-di-toluidinoterephthalic acid in polyphosphate to obtain a reaction solution. Step 2 involves adding the reaction solution to water to obtain a slurry, Step 3 involves filtering the slurry and then washing the precipitate with water. Step 4 involves heating the water-washed precipitate in a water-soluble organic solvent and water to obtain a slurry. Step 5 involves filtering the slurry and then washing the precipitate with water. A method for producing a quinacridone pigment containing at least the following: The conductivity of the water used in step 2 or 5 is 10 μS / cm or less. A method for producing the quinacridone pigment described above, wherein the amount of phosphorus eluted in the following measurement method is 100 ppm or less and the phosphorus content is 400 ppm or less. Measurement method: The quinacridone pigment was measured before and after dispersion under the following dispersion conditions using an X-ray fluorescence analyzer, and the difference between the pre- and post-dispersion measurements was defined as the phosphorus elution amount. Dispersion conditions: Add 0.1 parts by weight of IPA and 15.9 parts by weight of water to 1 part by weight of quinacridone pigment, mix at 20°C, and disperse in a paint conditioner at a vibration frequency of 750 rpm for 1 hour.

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