Quinacridone pigment

Abstract

To provide a quinacridone pigment which cannot only reduce a phosphorus content in total pigment but also suppress elution of phosphorus from a pigment surface and which is useful for use in inkjet printing.SOLUTION: There is provided a quinacridone pigment which shows a phosphorus elution amount of 100 ppm or less according to the following measurement method and a phosphorus content of 400 ppm or less. Measurement method: quinacridone pigments before and after dispersion under the following dispersion condition are subjected to measurements by an X-ray fluorescence analyzer and a difference in phosphorus contents is taken as a phosphorus elution amount. Dispersion condition: to 1 pt.wt of quinacridone pigment are added 0.1 pt.wt of IPA and 15.9 pts.wt of water, and the mixture is agitated at 20°C and is dispersed by a paint conditioner at a vibration 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 often 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 the ink to foam, and the ink is ejected by the pressure. As a phenomenon peculiar to this thermal method, there is adhesion of deposits, so-called "cog," to the surface of the heater for applying thermal energy to the inkjet recording ink. This "cog" is also called "cogation," and 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 to form 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 are generated by the adhesion of the char of phosphorus and calcium to the heater, and the sudden decrease in the ejection amount occurs when carbon char enters there. Therefore, in the ink described in Patent Document 1, in order to suppress cogation, the concentration of phosphorus in the pigment used is set to 500 ppm or less, and the amount of phosphorus in the whole pigment is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] As described above, quinacridone pigments with a low phosphorus content are highly desired as an inkjet ink. The inventors have found that merely reducing the phosphorus content in the pigment as in Patent Document 1 does not necessarily reduce the phosphorus content in the ink. When the amount of phosphorus eluted from the pigment surface is large, particularly in the case of quinacridone pigments, cogelation may occur. Therefore, the problem to be solved by the present invention is to provide a quinacridone pigment that can not only reduce the phosphorus content in the entire pigment but also suppress the elution of phosphorus from the pigment surface, which is particularly useful for inkjet applications. Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the inventors have found that quinacridone pigments with a specific surface structure not only have a low phosphorus content in the entire pigment but also have low phosphorus elution from the pigment surface, thus completing the present invention.

[0007] That is, the present invention relates to "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 following measurement method. Measurement method: The quinacridone pigment before and after dispersion under the following dispersion conditions was measured with a fluorescent X-ray analyzer, and the difference before and after was taken as the phosphorus elution amount. Dispersion conditions: 0.1 part by weight of IPA and 15.9 parts by weight of water were added to 1 part by weight of the quinacridone pigment, mixed at 20°C, and dispersed with a paint conditioner at a vibration frequency of 750 rpm for 1 hour. Item 2. The quinacridone pigment according to Item 1, wherein the quinacridone pigment contains C.I. Pigment Violet 19 and C.I. Pigment Red 122." Advantages of the Invention

[0008] According to the quinacridone pigment of the present invention, since the phosphorus content in the whole pigment is low and phosphorus is hardly eluted from the pigment surface, in the inkjet ink used in the thermal method, the adhesion of "cogging" to the ink nozzle, that is, "cogging" can be suppressed. That is, according to the quinacridone pigment of the present invention, it is difficult to generate a phosphorus compound by phosphorus and calcium during ink formation, and it is possible to produce a good inkjet ink with less occurrence of "cogging".

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail.

[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 following measurement method. Measurement method: The quinacridone pigment before and after dispersion under the following dispersion conditions was measured with a fluorescent X-ray analyzer, and the difference before and after was taken as the phosphorus elution amount. Dispersion conditions: 0.1 part by weight of IPA (= isopropyl alcohol) and 15.9 parts by weight of water were added to 1 part by weight of the quinacridone pigment, mixed at 20 ° C., and dispersed with a paint conditioner at a vibration frequency of 750 rpm for 1 hour.

[0011] The above dispersion conditions mimic the general pigment dispersion conditions in inkjet ink. The fact that the phosphorus elution amount indicated by the difference before and after dispersion under these conditions is small means that it is a good inkjet ink with less occurrence of "cogging". The fluorescent X-ray analyzer used in the above measurement method may be either a wavelength dispersive type or an energy dispersive type. For example, the apparatus used in the examples of the present application can be used. In addition, the above phosphorus content can be obtained, for example, by quantifying the phosphorus content in the pigment using a fluorescent X-ray analyzer. The above paint conditioner indicates, for example, a paint conditioner type shaker described in JIS5101-1-2.

[0012] The quinacridone pigment of the present invention has a phosphorus elution amount of 100 ppm or less, preferably 80 ppm or less, more preferably 60 ppm or less, as measured by the above method. Further, the phosphorus content in 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 the quinacridone pigment in the present invention include C.I. Pigment Violet 19, C.I. Pigment Red 122, C.I. Pigment Red 209, C.I. Pigment Red 202, C.I. Pigment Orange 48, and C.I. Pigment Orange 49. The quinacridone pigment in the present invention may be a pigment containing two or more of the above pigments. Examples of such pigments include solid solution pigments containing C.I. Pigment Violet 19 and C.I. Pigment Red 122, which are more useful for magenta ink for inkjet in terms of hue and the like.

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

[0015] In the present invention, any known and commonly used quinacridone pigment derivatives can be used. Quinacridone pigment derivatives substituted with one or more of a sulfonic acid residue and its metal salt, a dialkylaminoalkylaminosulfamoyl residue, a phthalimidomethyl residue, a dialkylaminoalkyl residue, etc. on the skeletons of C.I. Pigment Violet 19, C.I. Pigment Red 202, C.I. Pigment Red 209, and C.I. 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, etc. may be mentioned. Among them, from the viewpoint of imparting more excellent storage stability, sulfonic acid and its metal salt, dimethylaminopropylaminosulfamoyl derivatives are preferable.

[0016] In the present invention, when using a quinacridone pigment derivative in combination, it is preferably used in an amount of 1 to 10 parts by mass of the quinacridone pigment derivative with respect to 100 parts by mass of the quinacridone solid solution pigment.

[0017] Also, pigment derivatives other than the above-mentioned derivatives may be further used in combination. As the structure, not only the skeletons of C.I. Pigment Violet 19, C.I. Pigment Red 202, C.I. Pigment Red 209, and C.I. Pigment Red 122, but also the skeletons of condensed polycyclic pigments such as C.I. Pigment Violet 23, C.I. Pigment Blue 15 (copper phthalocyanine), C.I. Pigment Red 177, C.I. Pigment Red 254, and 255 can be used.

[0018] <Method for producing quinacridone pigment> Here, an example of a method for obtaining the quinacridone pigment of the present invention is shown. The following production method is a method for obtaining C.I. Pigment Violet 19 and C.I. 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 of a crude quinacridone solid solution pigment, and 2,5-di-p-toluidinoterephthalic acid (raw material of C.I. Pigment Red 122) in polyphosphoric acid, pouring the mixture into 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 more uniform crystallites can be formed. Usually, the conductivity of water (industrial water) used for pigment synthesis, washing, etc. is about 300 to 500 μS / cm. However, in the production method of the present invention, it is preferable to use water with a low ion content (for example, water having 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) as the water used for dehydration cyclization and subsequent washing. 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 surface of the pigment, 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 so that it does not dissolve the crude quinacridone solid solution pigment. Further, from the viewpoint of stably performing crystal control, it is preferable to contain a water-soluble organic solvent as a main component.

[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 set appropriately within the range of 0.1 to 20 times the equivalent weight by mass. Although it may be used in a larger amount, 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, by further adding the quinacridone pigment derivative and then performing the heating step, a desired quinacridone pigment can be obtained. 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, particularly 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] [Phosphorus measurement method] For the measurement of phosphorus contained in the pigment, an energy-dispersive X-ray fluorescence analyzer Epsilon 5 manufactured by PANalytical (hereinafter referred to as "XRF") was used.

[0027] [Phosphorus extraction method] The pigment that has been previously measured by XRF is added to an aqueous solution (temperature 20°C) mixed with IPA and ion-exchanged water. After dispersing for 10 minutes with a paint conditioner (vibration frequency 750 rpm), ion-exchanged water is added, and further dispersion is carried out with a paint conditioner for 50 minutes to obtain a slurry.

[0028] [Evaluation method for phosphorus elution amount] For the pigments before and after the tests described in the examples and comparative examples, the difference in phosphorus content was determined. The difference in phosphorus content before and after the test was defined as the phosphorus elution amount, and the evaluation was carried out according to the following criteria. ○: 0 ppm ≤ (phosphorus elution amount) ≤ 100 ppm ×: 100 ppm < (phosphorus elution amount)

[0029] [Visual evaluation when the filtrate is evaporated to dryness] 6 g of the filtrate obtained by conducting the tests described in the examples and comparative examples was weighed into an aluminum petri dish and evaporated to dryness under the condition of 160°C using an infrared moisture meter (manufactured by Kett Science Laboratory Co., Ltd.). The state of the residue after evaporation to dryness was visually evaluated. At this time, the evaluation was carried out according to the following criteria. ○: No residue can be confirmed or a small amount of white residue can be confirmed. ×: A large amount of residue can be confirmed and part of it has changed color to yellow.

[0030] [Example 1] Weighed 330 g of 85% phosphoric acid into a 1 L separable flask, added 469 g of phosphoric anhydride, and stirred to prepare 84% polyphosphoric acid. After the temperature of the polyphosphoric acid dropped to about 100 °C, 165 g of 2,5-dianilinoterephthalic acid, which is a raw material of C.I. Pigment Violet 19, and then 110 g of 2,5-di-p-toluidinoterephthalic acid, which is a raw material of C.I. Pigment Red 122, were gradually added. After the addition of the raw materials was completed, a condensation reaction was carried out at 125 °C for 3 hours. After the reaction was completed, 5 L of ion-exchanged water (conductivity 10 μS / cm or less) at 30 °C was weighed into a 10 L stainless steel cup. While stirring this water, the reaction solution was poured into the water to obtain a solid solution slurry of C.I. Pigment Violet 19 and C.I. Pigment Red 122. After filtering this solid solution slurry, it was washed with ion-exchanged water (conductivity 10 μS / cm or less) to obtain 465 g of a solid solution crude pigment wet cake (solid content 31%). 129 g of the solid solution crude pigment wet cake, 129 g of isobutanol, and 174 g of ion-exchanged water were charged into a 1 L sealed container, heat-treated with stirring at 80 °C for 3 hours and then at 135 °C for 3 hours, and then isobutanol was recovered from the system by distillation to obtain a solid solution pigment slurry. After filtering this solid solution pigment slurry and washing it with ion-exchanged water (conductivity 10 μS / cm or less), it was dried at 98 °C for 18 hours and further pulverized to obtain 36 g of a solid solution pigment of C.I. Pigment Violet 19 and C.I. Pigment Red 122.

[0031] When the amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF, it was 39 ppm. Weighed 1.0 g of IPA and 49.0 g of ion-exchanged water into a 110 ml poly bottle. Weighed 10.0 g of the solid solution pigment obtained above and dispersed it for 10 minutes with a paint conditioner. Then weighed 110.0 g of ion-exchanged water and dispersed it for 50 minutes with a paint conditioner. The pigment slurry thus obtained was filtered, and the wet cake after filtration was dried at 98 °C for 18 hours and further pulverized. When the amount of phosphorus contained in the obtained pigment was measured by XRF, it was 39 ppm.

[0032] [Example 2] Weighed 511 g of 85% phosphoric acid into a 2 L separable flask, added 727 g of phosphoric anhydride, and stirred to prepare 84% polyphosphoric acid. After the temperature of the polyphosphoric acid decreased to about 100 °C, 256 g of 2,5-dianilinoterephthalic acid, which is a raw material of C.I. Pigment Violet 19, and then 170 g of 2,5-di-p-toluidinoterephthalic acid, which is a raw material of C.I. Pigment Red 122, were gradually added. After the addition of the raw materials was completed, a condensation reaction was carried out at 125 °C for 3 hours. After the reaction was completed, 7 L of water with a conductivity of 300 - 500 μS / cm at 30 °C was weighed into a 10 L stainless steel cup. While stirring this water, the reaction solution was poured into the water to obtain a solid solution slurry of C.I. Pigment Violet 19 and C.I. Pigment Red 122. This solid solution slurry was filtered and washed with water having a conductivity of 300 - 500 μS / cm to obtain a wet cake of the solid solution crude pigment. The same operation was performed once again to obtain 2300 g (30% solid content) of the wet cake of the solid solution crude pigment. 2007 g of the wet cake of the solid solution crude pigment, 1940 g of isobutanol, and 2533 g of water with a conductivity of 300 - 500 μS / cm were charged into a sealed container with an internal volume of 10 L, and heat-treated with stirring at 80 °C for 3 hours and then at 135 °C for 3 hours. After that, isobutanol was recovered from the system by distillation, and filtration and washing with water having a conductivity of 300 - 500 μS / cm were carried out to obtain a solid solution pigment slurry. This slurry was weighed so that the solid content became 200 g, and ion-exchanged water (conductivity 10 μS / cm or less) was added to prepare 3200 g of a slurry with a solid content of 6%. 3 g of 35% hydrochloric acid was weighed into this slurry, stirred at 60 °C for 1 hour, and then filtered and washed with ion-exchanged water (conductivity 10 μS / cm or less). It was dried at 98 °C for 18 hours and further pulverized to obtain 180 g of a solid solution pigment of C.I. Pigment Violet 19 and C.I. Pigment Red 122.

[0033] When the amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF, it was 41 ppm. Weigh 1.0 g of IPA and 49.0 g of ion-exchanged water into a 110 ml poly bottle. Weigh 10.0 g of the solid solution pigment obtained above into it and disperse it with a paint conditioner for 10 minutes. Then weigh 110.0 g of ion-exchanged water and disperse it with a paint conditioner for 50 minutes. The pigment slurry thus obtained was filtered, and the wet cake after filtration was dried at 98 °C for 18 hours and further pulverized. When the amount of phosphorus contained in the obtained pigment was measured by XRF, it was 22 ppm.

[0034] [Example 3] Weigh 330 g of 85% phosphoric acid into a 1 L separable flask, add 469 g of phosphoric anhydride and stir to prepare 84% polyphosphoric acid. After the temperature of the polyphosphoric acid drops to about 100 °C, 165 g of 2,5-dianilinoterephthalic acid, which is a raw material of C.I. Pigment Violet 19, and then 110 g of 2,5-di-p-toluidinoterephthalic acid, which is a raw material of C.I. Pigment Red 122, are gradually added. After the addition of the raw materials is completed, a condensation reaction is carried out at 125 °C for 3 hours. After the reaction is completed, weigh 5 L of ion-exchanged water (conductivity 10 μS / cm or less) at 30 °C into a 10 L stainless steel cup, and while stirring this water, pour the reaction solution into the water to obtain a solid solution slurry of C.I. Pigment Violet 19 and C.I. Pigment Red 122. After filtering this solid solution slurry, it was washed with ion-exchanged water (conductivity 10 μS / cm or less) to obtain 465 g of a solid solution crude pigment wet cake (solid content 31%). Charge 134 g of the solid solution crude pigment wet cake, 129 g of isobutanol and 168 g of water with a conductivity of 300 - 500 μS / cm into a sealed container with an internal volume of 1 L, heat-treat it with stirring at 80 °C for 3 hours and further at 135 °C for 3 hours, and then recover the isobutanol from the system by distillation to obtain a solid solution pigment slurry. This solid solution pigment slurry was filtered and washed with water having a conductivity of 300 - 500 μS / cm, dried at 98 °C for 18 hours, and further pulverized to obtain 36 g of a solid solution pigment of C.I. Pigment Violet 19 and C.I. Pigment Red 122.

[0035] When the amount of phosphorus contained in the solid solution pigment obtained above was measured by XRF, it was 344 ppm. Weigh 1.0 g of IPA and 49.0 g of ion-exchanged water into a 110 ml plastic bottle. Weigh 10.0 g of the solid solution pigment obtained above and disperse it with a paint conditioner for 10 minutes. Then weigh 110.0 g of ion-exchanged water and disperse it with a paint conditioner for 50 minutes. The pigment slurry thus obtained was filtered, and the wet cake after filtration was dried at 98 °C for 18 hours and further pulverized. When the amount of phosphorus contained in the obtained pigment was measured by XRF, it was 304 ppm.

[0036] [Comparative Example 1] When the amount of phosphorus contained in Hostaperm Pink E (manufactured by Clariant) was measured by XRF, it was 533 ppm. Weigh 1.0 g of IPA and 49.0 g of ion-exchanged water into a 110 ml plastic bottle. Weigh 10.0 g of Hostaperm Pink E and disperse it with a paint conditioner for 10 minutes. Then weigh 110.0 g of ion-exchanged water and disperse it with a paint conditioner for 50 minutes. The pigment slurry thus obtained was filtered, and the wet cake after filtration was dried at 98 °C for 18 hours and further pulverized. When the amount of phosphorus contained in the obtained pigment was measured by XRF, it was 355 ppm.

[0037] [Comparative Example 2] The pigment was prepared by the method described in JP-A-2006-96927 (paragraph numbers 0019 to 0043 of claim 4). At this time, the charging ratio of the quinacridone intermediate was 2,5-dianilinoterephthalic acid:2,5-di-p-toluidinoterephthalic acid = 20:80, isobutanol was used as the organic solvent for the heat treatment, and water having a conductivity of 300 to 500 μS / cm was used as the solvent. When the amount of phosphorus contained in this pigment was measured by XRF, it was 334 ppm. Weigh 1.0 g of IPA and 49.0 g of ion-exchanged water into a 110 ml poly bottle. Weigh 10.0 g of this pigment there and disperse it with a paint conditioner for 10 minutes. Then weigh 110.0 g of ion-exchanged water and disperse it with a paint conditioner for 50 minutes. The thus-obtained pigment slurry was filtered, and the wet cake after filtration was dried at 98°C for 18 hours and further pulverized. When the amount of phosphorus contained in the obtained pigment was measured by XRF, it was 166 ppm.

[0038]

Table 1

[0039] In Examples 1 to 3, the phosphorus elution amount was very small, 0 ppm or more and 100 ppm or less. This is presumably because in the process of manufacturing the pigment, crystal growth was carried out under conditions where phosphorus was difficult 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 in advance (Example 2). By visually evaluating the state when the filtrate was evaporated to dryness, it was simply evaluated whether deposits would form in the ink when the ink was heated. The residues of Examples 1 and 2 were white, but the residues of Comparative Examples 1 and 2 were partially slightly discolored to yellow, and it was considered that charring occurred.

Claims

1. A quinacridone solid solution pigment having a phosphorus elution amount of 19 ppm or less and a phosphorus content of 400 ppm or less in the following measurement method. Measurement method: The quinacridone pigment before and after dispersion under the following dispersion conditions was measured with a fluorescent X-ray analyzer, and the difference before and after was taken as the phosphorus elution amount. Dispersion conditions: 0.1 part by weight of IPA and 15.9 parts by weight of water were added to 1 part by weight of quinacridone pigment, mixed at 20 °C, and dispersed for 1 hour at a vibration frequency of 750 rpm with a paint conditioner.

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

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