Cu—Cr—Zn—O based pigment
11981582 · 2024-05-14
Assignee
Inventors
Cpc classification
C09C3/006
CHEMISTRY; METALLURGY
C01P2002/70
CHEMISTRY; METALLURGY
C01P2002/72
CHEMISTRY; METALLURGY
International classification
C09C1/00
CHEMISTRY; METALLURGY
Abstract
A CuCrZnO based pigment includes a CuCrO based oxide and Zn derived from a zinc oxide added as a modifying oxide and solid-dissolved in the CuCrO based oxide. The CuCrZnO based pigment has a composition formula of aCuO.Math.bCr.sub.2O.sub.3.Math.cZnO (mol %), in which 0.1?c?5, 45?a+c?55, and 45?b?55 (a+b+c=100).
Claims
1. A CuCrZnO based pigment comprising: a CuCrO based oxide; Zn solid-dissolved in the CuCrO based oxide; and the CuCrZnO based pigment having a composition formula of aCuO.Math.bCr.sub.2O.sub.3.Math.cZnO (mol %), in which 0.1?c?5, 45?a+c?55, and 45?b?55 (a+b+c=100).
2. The CuCrZnO based pigment according to claim 1, wherein a by-product CuCrO.sub.2 is not included in an X-ray diffraction pattern.
3. The CuCrZnO based pigment according to claim 1, wherein the CuCrZnO has a spinel structure that is formed by calcining a batch obtained by mixing a copper compound, a chromium compound, and a zinc compound as a starting material by a dry method at a temperature of 800? C. to 1000? C.
4. The CuCrZnO based pigment according to claim 1, which is used as a coloring pigment for a coating material, plastic, and glass.
5. The CuCrZnO based pigment according to claim 1, wherein an eluting amount of hexavalent chromium in a pigment eluate based on an EPA3060A method is 250 ppm or less.
6. The CuCrZnO based pigment according to claim 1, which is used for a glass color, and which does not exhibit red discoloration when the CuCrZnO based pigment is baked on a tin surface of a float plate glass at 500? C. to 700? C.
7. The CuCrZnO based pigment according to claim 1, which is used in a laser direct structuring (LDS).
8. The CuCrZnO based pigment according to claim 1, wherein XRD patterns of the CuCrZnO based pigment include all peaks in XRD patterns of CuCr.sub.2O.sub.4 which is a structure of the CuCrO based pigment.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.
(2)
(3)
(4)
(5)
(6)
DESCRIPTION OF THE EMBODIMENTS
(7) Hereinafter, an embodiment according to the invention will be described in detail.
(8) A CuCrZnO based pigment according to the present invention is formed by solid-dissolving Zn derived from zinc oxide added as a modifying oxide in a CuCrO based oxide having a spinel structure.
(9) Further, the oxides have a composition formula of aCuO.Math.bCr.sub.2O.sub.3.Math.cZnO (mol %), and in the formula, 0.1?c?5, 45?a+c?55, and 45?b?55 (a+b+c=100).
(10) The spinel structure is a kind of a typical crystal structure form generally found in a multiple oxide or a multiple sulfide of a metal element, which is represented by a general formula AB.sub.2X.sub.4. The CuCrO based oxide having the spinel structure has a general formula CuCr.sub.2O.sub.4.
(11) ZnO in an oxide composition of the CuCrZnO based pigment according to the present invention is added as the modifying oxide as described above.
(12) Zinc oxide ZnO is not used as the modifying oxide in the prior art, but when an appropriate amount of zinc oxide ZnO is added during blending of raw materials in a pigment producing process, and a batch obtained through a mixing process based on a dry method is calcined within a predetermined temperature range, reactivity during sintering is improved, and thus both a color characteristic and durability are greatly improved as compared with a CuCrO based pigment in the prior art (that is, a pigment to which the modifying oxide is not added, or a pigment to which another modifying oxide such as manganese oxide MnO.sub.2 or iron oxide Fe.sub.2O.sub.3 is added).
(13) The CuCrZnO based pigment according to the present invention belongs to C.I. pigment black 28 as a pigment component, but is different from the pigment in the prior art in that Mn and Fe are not contained as a metal of the modifying oxide. Based on this difference, the CuCrZnO based pigment according to the present invention is characterized in that the CuCrZnO based pigment has an advantage that, as a color characteristic, a degree of blackness is substantially equal to that of a CuCrMnO based pigment in the prior art, and a degree of redness and a degree of blueness are high.
(14) The oxide composition of the CuCrZnO based pigment according to the present invention preferably consists of 40 to 54.9 mol % of copper oxide (CuO), 45 to 55 mol % of chromium oxide (Cr.sub.2O.sub.3), and 0.1 to 5.0 mol % of zinc oxide (ZnO) which is an additive component. It is found that when oxide composition amounts of the pigment is out of these ranges, a sufficient color characteristic and sufficient durability are not obtained.
(15) Specifically, by using ZnO as the modifying oxide, the color characteristic of the CuCrO based pigment can be greatly improved. Specifically, as compared with the CuCrO based pigment, in the CuCrZnO based pigment in which a composition of three components of CuO, Cr.sub.2O.sub.3, and ZnO and a calcining temperature are optimized, in a color tone obtained when producing an acrylic coating material having a pigment concentration of 10 wt % concentration, and drawing down the coating material at a thickness of 150 ?m, L* decreases by about 2.0 or more, a* increases by about 0.5 or more, and b* decreases by 0.5 or more.
(16) Although it is known that MnO.sub.2 or Fe.sub.2O.sub.3 is used as the modifying oxide in a method for improving the color characteristic in the prior art, the CuCrZnO based pigment using ZnO as the modifying oxide according to the present invention has a more excellent color characteristic in that a* is higher and b* is lower, as compared with the CuCrMnO based pigment using MnO.sub.2 as the modifying oxide, or in that L* is lower and b* is lower, as compared with the CuCrFeO based pigment using Fe.sub.2O.sub.3 as the modifying oxide.
(17) In addition, the durability of the pigment according to the present invention is greatly improved. That is, the CuCrZnO based pigment has acid resistance and alkali resistance, and therefore can prevent hexavalent chromium from being eluted to an outside.
(18) Further, in the pigment according to the present invention, a glass color in which red discoloration is prevented can be provided when the pigment is used for a glass color application.
(19) This effect is obtained by performing the calcining in a temperature range of 800? C. to 1000? C., which is a relatively high range, and at the time of filing of the present invention, it is not clear that the effect is caused by any structure or characteristic of the pigment, and thus it is inevitable to define a scope of the invention of the present application by the temperature range described above.
(20) Next, a method for producing the CuCrZnO based pigment according to the present invention will be described.
(21) Since the pigment according to the present invention contains the CuCrO based oxide as a main component and further contains Zn derived from zinc oxide added thereto as the modifying oxide, a copper compound, a chromium compound, and a zinc compound are prepared as raw materials thereof.
(22) Each of raw materials may be any material as long as each of them contain the metal elements described above and form each of oxides in a production process. Specific examples of these compounds include hydroxides, oxides, carbonates, and the like, and may be used alone or in a combination of a plurality of compounds.
(23) Any method may be used as long as the method is known as a general method for producing a complex inorganic color pigment containing a metal oxide as a main component. Such a production method mainly includes a step 1) of mixing the raw materials, a step 2) of calcining a generated mixture, and a step 3) of milling a calcined product.
(24) The step 1) of mixing the raw materials is limited to the dry method. This is because, when other methods are used, there are problems that the production methods or steps become complicated, a production cost increases, and wastewater treatment equipment is required.
(25) In the step 2) of calcining the obtained mixture, the obtained mixture (batch) is calcined at 800? C. to 1000? C. for about 3 to 6 hours to solid-dissolve and crystallize the components.
(26) It is known that when the calcining temperature is too high, the color characteristic is deteriorated due to formation of a sub-phase, and when the calcining temperature is too low, problems such as insufficient color development, or uneven calcining are caused.
(27) In the present invention, by performing the calcining in the temperature range of 800? C. to 1000? C. described above, an effect that L* decreases, a* increases, and b* decreases can be obtained. In contrast, when MnO.sub.2 or Fe.sub.2O.sub.3 is used as the modifying oxide in the prior art, a sub-phase CuCrO.sub.2 is generated when the calcining is performed at a temperature of 900? C. or higher, and as a result, there is a problem that L* increases.
(28) Finally, the calcined product obtained in the step 2) is subjected to the milling step 3). In the milling step 3), a particle size is generally adjusted by milling, a milling method is not particularly limited as long as a pigment having a desired particle size can be obtained, and a general dry-type milling method or a general wet-type milling method can be applied.
(29) Examples of a mill include an attritor and a jet mill in a case of the dry-type milling, and a ball mill, a vibration mill, and a medium agitation type mill in a case of the wet-type milling. In the case of the wet-type milling, a slurry after the milling is sufficiently dried and crushed to obtain a target product.
(30) According to the production method described above, when the batch is produced by the dry method for the CuCrO based pigment having the spinel structure consisting of Cu and Cr, the color characteristic of the CuCrO based pigment can be greatly improved by adding a predetermined amount of zinc oxide as the modifying oxide.
(31) Though it is known that MnO.sub.2 or Fe.sub.2O.sub.3 is used as the modifying oxide in a method for improving the color characteristic, when ZnO is used as the modifying oxide, the excellent color characteristics are obtained as compared with the case where these modifying oxides are used, and in addition, the durability of the pigment can be greatly improved.
(32) Further, the pigment according to the present invention can be used as a general-purpose product having a simple production process.
EXAMPLES
(33) Then, to specifically describe the present invention, several Examples according to the present invention and Comparative Examples for comparison with Examples will be described.
(34) A pigment composition is represented by aCuO.Math.bCr.sub.2O.sub.3.Math.cX (mol %) (X=ZnO, Mn.sub.2O.sub.3, Fe.sub.2O.sub.3) for convenience.
Examples 1 to 21
(35) In the following Examples 1 to 21, based on a composition formula of aCuO.Math.bCr.sub.2O.sub.3.Math.cZnO (mol %), predetermined amounts of copper oxide, chromium oxide, and zinc oxide were weighed such that a total weight thereof was 100 g to obtain a target pigment composition by variously changing (a, b, and c) in a range satisfying 0.1?c?10, 40?a+b?60, and 40?b?60 (a+b+c=100). Specific values of (a, b, and c) were shown in the following Tables 1a, 1b, and 1c.
(36) Next, these oxides were sufficiently mixed by using a ball mill until a uniform mixture (batch) was obtained.
(37) Next, 30 g of the batch was weighed and put in a mullite crucible and calcined in an electric furnace. A calcining condition was set to three temperatures of 800? C., 900? C., and 1000? C. per composition for 9 hours.
(38) After the batch was calcined, 25 g of the obtained calcined product, 100 g of glass beads having a diameter (?) of 3 mm, and 50 g of distilled water were separately weighed and put in a glass container having a capacity of 140 mL, a lid was closed, and the calcined product was milled for 30 minutes by using a paint conditioner.
(39) After the calcined product was milled, a milled slurry was poured into an aluminum foil container and dried at 120? C. for about 5 hours.
(40) After the milled slurry was dried, a dried product was crushed by using a pestle and a mortar to produce a pigment having the desired composition.
Comparative Examples 1 to 3
(41) Unlike Examples 1 to 21, based on aCuO.Math.bCr.sub.2O.sub.3 (mol %), (a and b) were selected in a range of 45?a?55 and 45?b?55 (a+b=100) to produce a CuCrO based pigment consisting of Cu and Cr and not containing modifying oxide.
(42) A production method was the same as those in Examples 1 to 21 described above.
Comparative Examples 4 to 6
(43) Based on aCuO.Math.bCr.sub.2O.sub.3.Math.cMn.sub.2O.sub.3 (mol %), (a, b, and c) were set in a range of 45?a?55, 40?b?50, and c=5 (a+b+c=100), a CuCrMnO based pigment consisting of Cu, Cr, and Mn which contains a metal element Mn derived from manganese dioxide MnO.sub.2 added as the modifying oxide in the prior art was produced.
(44) A production method of the pigment was the same as those in Examples 1 to 21 described above.
Comparative Examples 7 to 9
(45) Based on aCuO.Math.bCr.sub.2O.sub.3.Math.cFe.sub.2O.sub.3 (mol %), (a, b, and c) were selected in a range of 45?a?55, 40?b?50, and c=5 (a+b+c=100) to produce a CuCrFeO based pigment consisting of Cu, Cr, and Fe which contains a metal element Fe derived from iron oxide Fe.sub.2O.sub.3 added as the modifying oxide in the prior art in the same manner as in Examples 1 to 21 described above.
(46) (Characteristic Evaluation)
(47) ((a) Color Tone)
(48) Into 100 parts by weight of an acrylic resin, 10 parts by weight of each of the multiple oxide pigments obtained in Examples 1 to 21 and Comparative Examples 1 to 9 were dispersed by the paint conditioner.
(49) Next, an obtained coating material was drawn down onto a white paper by using a 150 ?m applicator. After drying, a color of a coating film was measured with a spectrophotometer (standard light source C, 2? field of view).
(50) For a purpose of evaluating a result thereof, a result of colorimetry by a CIELAB color system is shown in Tables 1a, 1b, and 1c below.
(51) ((b) XRD Diffraction Pattern Analysis)
(52) Among each of the CuCrZnO, CuCrO, CuCrMnO, and CuCrFeO based pigments produced in Examples 1 to 21 and Comparative Examples 1 to 9, compositions having a most excellent color characteristic were selected, and XRD diffraction patterns of the pigments produced at the calcining temperatures of 800? C., 900? C., and 1000? C. were compared for each component system, thereby observing changes in crystal structures of the pigments with an increase in the calcining temperature when the pigments were produced.
(53) ((c) Acid and Alkali Resistance Test)
(54) Based on evaluation results of (a) and (b), among each of the produced CuCrZnO, CuCrO, CuCrMnO, and CuCrFeO based pigments, compositions having the most excellent color characteristic and having no heterogeneous phase CuCrO.sub.2 detected in the crystal structure were selected. Specifically, the CuCrZnO based pigment calcined at 1000? C. in Example 10, the CuCrO based pigment calcined at 800? C. in Comparative Example 2, the CuCrMnO based pigment calcined at 800? C. in Comparative Example 5, and the CuCrFeO based pigment calcined at 800? C. in Comparative Example 8 were selected.
(55) Each of the selected pigments was weighed and put in a 5 wt % HCl aqueous solution or a 20 wt % NaOH aqueous solution to have a pigment concentration of 10 wt %, and immersed for 3 days.
(56) After 3 days immersing of the pigments, the eluates were extracted by suction filtration.
(57) A main component amount of the pigment immersed in each of the eluates was measured by high frequency inductively coupled plasma (ICP) chemical analysis, and the durability of the pigment of each component system was compared.
(58) ((d) Evaluation of Eluting Amount of Hexavalent Chromium)
(59) Eluates of hexavalent chromium were produced from the CuCrZnO based pigment at 1000? C. in Example 10, the CuCrO based pigment calcined at 800? C. in Comparative Example 2, the CuCrMnO based pigment calcined at 800? C. in Comparative Example 5, and the CuCrFeO based pigment calcined at 800? C. in Comparative Example 8 by a method based on an EPA3060A (ALKALINE DIGESTION FOR HEXAVALENT CHROMIUM). Concentrations of hexavalent chromium in the eluates were measured by diphenylcarbazide ab sorptiometry. (JISK0102).
(60) ((e) Evaluation of Red Discoloration in Glass Color)
(61) For the CuCrZnO based pigment calcined at 1000? C. in Example 10, the CuCrO based pigment calcined at 800? C. in Comparative Example 2, the CuCrMnO based pigment calcined at 800? C. in Comparative Example 5, and the CuCrFeO based pigment calcined at 800? C. in Comparative Example 8, 1.2 g of each of these pigments and 0.6 g of a vehicle were weighed and sufficiently mixed by using a hoover muller to produce a paste. The produced paste was drawn down on a tin surface of a plate glass by using an applicator having a thickness of 76.2 ?m, and dried in a drying furnace at 120? C. for 30 minutes. Further, the plate glass was baked in the electric furnace at 680? C. for 20 minutes and was sufficiently naturally cooled, followed by washing away the pigment on the plate glass with tap water, and the red discoloration on the tin surface of the plate glass was observed.
(62) Next, results of the tests described above will be described.
(63) With respect to Examples 1 to 20 and Comparative Examples 1 to 9, the color tone at each calcining temperature set during the production of the CuCrZnO, CuCrO, CuCrMnO, and CuCrFeO based pigments are shown in the following Tables 1a, 1b, and 1c.
(64) TABLE-US-00001 TABLE 1a Composition Calcining (mol %) Temperature Color CuO Cr.sub.2O.sub.3 ZnO ? C. L* a* b* Example 39.9 60.0 0.1 800 12.4 ?1.4 ?1.0 1 900 12.7 ?1.5 ?0.7 1000 13.0 ?2.1 0.3 Example 39.0 60.0 1.0 800 13.1 ?1.6 ?1.1 2 900 13.0 ?1.6 ?1.0 1000 12.6 ?2.1 0.1 Example 35.0 60.0 5.0 800 14.5 ?2.2 ?0.5 3 900 13.7 ?2.1 ?0.7 1000 13.2 ?2.4 ?0.2 Example 30.0 60.0 10.0 800 15.6 ?2.7 0.5 4 900 14.8 ?2.5 ?0.4 1000 14.3 ?2.8 ?0.2 Example 44.9 55.0 0.1 800 10.7 0.0 ?2.1 5 900 10.5 0.2 ?2.3 1000 10.9 ?0.1 ?1.9 Example 44.0 55.0 1.0 800 11.4 ?0.4 ?2.0 6 900 11.3 ?0.3 ?2.1 1000 10.6 ?0.7 ?1.4 Example 40.0 55.0 5.0 800 12.2 ?0.9 ?1.7 7 900 12.0 ?0.7 ?2.1 1000 11.5 ?1.0 ?1.6 Example 35.0 55.0 10.0 800 13.5 ?1.5 ?1.0 8 900 12.7 ?1.2 ?1.7 1000 12.3 ?1.2 ?1.8 Example 44.9 50.0 0.1 800 10.4 0.3 ?1.9 9 900 10.8 0.2 ?2.1 1000 11.6 0.2 ?2.4 Example 48.0 51.0 1.0 800 10.2 0.3 ?2.5 10 900 9.8 0.6 ?2.8 1000 9.4 0.8 ?2.8
(65) TABLE-US-00002 TABLE 1b Example 49.0 50.0 1.0 800 9.5 0.5 ?2.7 11 900 9.3 0.7 ?2.8 1000 9.6 0.7 ?2.7 800 10.6 0.1 ?2.5 Example 45.0 50.0 5.0 900 9.6 0.4 ?2.8 12 1000 9.4 0.5 ?2.6 Example 40.0 50.0 10.0 800 11.4 ?0.4 ?1.9 13 900 10.8 ?0.2 ?2.5 1000 9.4 0.2 ?2.5 Example 54.9 45.0 0.1 800 10.5 0.3 ?1.8 14 900 16.5 ?1.1 ?1.6 1000 17.9 ?1.4 ?1.7 Example 54.0 45.0 1.0 800 9.7 0.5 ?2.1 15 900 14.6 ?0.9 ?1.9 1000 16.8 ?1.1 ?2.1 Example 50.0 45.0 5.0 800 10.2 0.1 ?2.2 16 900 15.1 ?1.1 ?1.9 1000 16.1 ?1.3 ?1.9 800 11.0 ?0.3 ?1.7 Example 45.0 45.0 10.0 900 15.7 ?1.4 ?1.6 17 1000 16.1 ?1.6 ?1.6 Example 59.9 40.0 0.1 800 10.9 0.3 ?1.5 18 900 22.4 ?2.8 ?0.1 1000 24.3 ?3.2 0.1 Example 59.0 40.0 1.0 800 10.1 0.5 ?2.1 19 900 21.2 ?2.5 ?0.6 1000 22.5 ?2.8 ?0.4 800 10.4 0.1 ?1.9 Example 55.0 40.0 5.0 900 21.1 ?2.6 ?0.4 20 1000 22.9 ?3.1 0.1 Example 50.0 40.0 10.0 800 11.5 ?0.3 ?1.5 21 900 23.0 ?2.8 0.4 1000 24.3 ?3.3 0.7
(66) TABLE-US-00003 TABLE 1c Composition Calcining (mol %) Temperature Color CuO Cr.sub.2O.sub.3 ? C. L* a* b* Comparative 45.0 55.0 800 11.8 ?0.1 ?1.4 Example 1 900 12.0 ?0.1 ?1.5 1000 12.0 0.2 ?1.8 Comparative 50.0 50.0 800 11.7 0.0 ?1.5 Example 2 900 13.6 ?0.5 ?1.1 1000 13.8 ?0.3 ?1.8 Comparative 55.0 45.0 800 11.7 0.1 ?1.5 Example 3 900 15.3 ?0.9 ?1.1 1000 16.2 ?0.9 ?1.5 Composition Calcining (mol %) Temperature Color CuO Cr.sub.2O.sub.3 Mn.sub.2O.sub.3 ? C. L* a* b* Comparative 45.0 50.0 5.0 800 9.5 0.3 ?1.9 Example 4 900 10.4 0.3 ?1.9 1000 13.0 ?0.1 ?1.6 Comparative 50.0 45.0 5.0 800 9.7 0.3 ?1.6 Example 5 900 11.5 0.3 ?1.6 1000 13.6 0.1 ?1.4 Comparative 55.0 40.0 5.0 800 11.7 0.1 ?1.5 Example 6 900 12.4 0.4 ?1.4 1000 14.5 0.2 ?1.1 Composition Calcining (mol %) Temperature Color CuO Cr.sub.2O.sub.3 Fe.sub.2O.sub.3 ? C. L* a* b* Comparative 45.0 50.0 5.0 800 11.0 0.3 ?0.7 Example 7 900 11.0 0.4 ?0.8 1000 12.2 0.6 ?0.9 Comparative 50.0 45.0 5.0 800 10.8 0.3 ?0.5 Example 8 900 12.0 0.8 ?0.9 1000 13.0 0.9 ?1.0 Comparative 55.0 40.0 5.0 800 11.2 0.3 ?0.5 Example 9 900 12.9 1.3 ?1.0 1000 13.9 1.4 ?1.1
(67) In the tables described above, L* represents a brightness, +a* represents a color tone in a red direction, ?a* represents a color tone in a green direction, +b* represents a color tone in a yellow direction, and ?b* represents a color tone in a blue direction. Regarding a black pigment, a color tone having a high degree of blackness, a strong red color, and a strong blue color is preferred, and it was comprehensively observed and determined that L* is low, a* is high, and b* is low in comparison of a significant difference in a color tone characteristic.
(68)
(69) According to Tables 1a, 1b, and 1c described above, in the CuCrO based pigments to which the modifying oxide was not added, it was observed from Comparative Examples 1 to 3 that L* of the pigments produced at the calcining temperature of 800? C. was 11.7 to 11.8, L* of the pigments produced at the calcining temperature of 900? C. was 12.0 to 15.3, and L* of the pigments produced at the calcining temperature of 1000? C. was 12.0 to 16.2, and in all of the Comparative Examples, the degree of blackness tended to decrease as the calcining temperature increased.
(70) According to the XRD pattern at the calcining temperature of 800? C. for the CuCrO based pigment shown in Comparative Example 2 of
(71) When the CuCrO based pigment consisting of Cu and Cr is produced, it can be said that reactions between copper oxide and chromium oxide used as starting materials during calcining are insufficient in the case of the batch obtained by the dry method even when a composition design is performed so that those used as starting materials theoretically react with each other without excess or deficiency. Further, it is suggested that when the CuCrO based pigment is produced, it is necessary to set an optimum calcining temperature, because, when calcining is performed at a temperature higher than the optimum calcining temperature, in addition to the main phase CuCr.sub.2O.sub.4, the sub-phase CuCrO.sub.2 are formed in the pigment, and as a result, the degree of blackness of the pigment decreases.
(72) Therefore, it can be said that the optimum calcining temperature when the CuCrO based pigment is produced from the batch obtained by the dry method is preferably around 800? C., and it is found that conversely, the pigment should not be calcined at a high temperature of 900? C. or higher.
(73) Regarding the CuCrMnO based pigments to which MnO.sub.2 was added as the modifying oxide, according to Comparative Examples 4 to 6, L* of the pigments produced at the calcining temperature of 800? C. was 9.5 to 11.7, and the degree of blackness was higher, and the color characteristic was more excellent than those of the CuCrO based pigments shown in Comparative Examples 1 to 3. On the other hand, the pigments produced at the calcining temperature of 900? C. or higher had a lower L* than the pigments produced at the calcining temperature of 800? C., and it was observed that in the CuCrMnO based pigments, the degree of blackness decreased as the calcining temperature increased similarly to the CuCrO based pigment.
(74) According to the XRD patterns of the CuCrMnO based pigment shown in Comparative Example 5 in
(75) Regarding the CuCrFeO based pigments to which Fe.sub.2O.sub.3 was added as the modifying oxide, according to Comparative Examples 7 to 9, it was found from the results shown in Table 1c that L* of the pigments produced at the calcining temperature of 800? C. was 10.8 to 11.2, the degree of blackness was higher, and the color characteristic was improved, as compared with the CuCrO based pigments shown in Comparative Examples 1 to 3, but the color characteristic was not improved as much as the CuCrMnO based pigments to which MnO.sub.2 was added as the modifying oxide shown in Comparative Examples 4 to 6.
(76) In addition, according to the XRD patterns of the CuCrFeO based pigment shown in Comparative Example 8 in
(77) In Examples 5 to 7, Examples 9 to 12, and Examples 14 to 16, (a, b, and c) were selected in a range satisfying 0.1?c?5, 45?a+c?55, and 45?b?55 (a+b+c=100) for aCuO.Math.bCr2O3.Math.cZnO (mol %) of the pigments of Examples 1 to 21 to which ZnO is added as the modifying oxide. When CuCrZnO based pigments produced under a calcining temperature condition allowing a highest degree of blackness were selected from the compositions described above, L* was 9.3 to 11.5, and an improvement in the degree of blackness as the pigment characteristic was achieved as compared with the CuCrO based pigments shown in Comparative Examples 1 to 3. Further, in these pigments, a composition having the excellent color characteristic was confirmed based on an aspect that a* was high, and b* was low, that is, the red color was strong, and the blue color was strong as compared with the CuCrMnO based pigments shown in Comparative Examples 4 to 6 to which MnO.sub.2 was added as the modifying oxide.
(78) Further, regarding the CuCrZnO based pigments, a composition in which the color characteristic of the pigment was increased as the calcining temperature was set to be high in the range of 800? C. to 1000? C. during the production of the pigment was also confirmed.
(79) As shown in
(80) Further, based on the XRD patterns of Comparative Example 2, Comparative Example 5, and Comparative Example 8, in the case of CuCrO, CuCrMnO, and CuCrFeO bases, the diffraction peak attributed to the sub-phase CuCrO.sub.2 was detected in all the pigments produced at the calcining temperature of 900? C. or higher, whereas in the case of CuCrZnO based oxide shown in Example 10, the diffraction peak attributed to the sub-phase CuCrO.sub.2 was not detected in the pigment produced at the calcining temperature of 1000? C. Therefore, it can be said that when ZnO is added as the modifying oxide, a higher calcining temperature can be set during the production of the pigment as compared with the case where MnO.sub.2 or Fe.sub.2O.sub.3 known as the modifying oxide is added.
(81) Next, results of (c) acid and alkali resistance test will be described.
(82) Results of the acid resistance test are shown in Table 2 below, and results of the alkali resistance test are shown in Table 3 below.
(83) TABLE-US-00004 TABLE 2 Ion Concentration in Cu Cr Mn Fe Zn 5 wt % HCl Solution ppm ppm ppm ppm ppm CuCrZnO 182 43.7 1.69 (Example 10) CuCrO 2651 44.6 (Comparative Example 2) CuCrMnO 5901 153 285 (Comparative Example 5) CuCrFeO 4317 55.5 110 (Comparative Example 8)
(84) TABLE-US-00005 TABLE 3 Ion Concentration in Cu Cr Mn Fe Zn 20 wt % NaOH Solution ppm ppm ppm ppm ppm CuCrZnO 131 23.4 0.13 (Example 10) CuCrO 212 34.6 (Comparative Example 2) CuCrMnO 314 41.3 1.43 (Comparative Example 5) CuCrFeO 243 29.2 1.07 (Comparative Example 8)
(85) From the results shown in Tables 2 and 3 described above, in terms of the durability of the pigment, the CuCrZnO based pigment according to the present invention has better results in acid resistance and alkali resistance than other pigments.
(86) The pigment is required to have the acid resistance or the alkali resistance depending on usage purposes, and for example, when a pigment is used in an acid-resistant coating material, an acid-resistant rubber, a vinyl chloride resin, or the like, it is necessary to use a pigment having good acid resistance, and when a pigment is used in a coating material for concrete and a mortar, a coating material using a basic compound such as water glass as a vehicle, or the like, it is necessary to use a pigment having good alkali resistance. When the acid resistance and alkali resistance of the pigment are poor, poor dispersion of the pigment in a solvent for a purpose of coloring, and elution of a pigment component or a change in the color tone over time due to decomposition of the pigment occur. In the CuCrO based pigment, the elution of hexavalent chromium in the solvent is concerned. However, the CuCrZnO based pigment according to the present invention has a most excellent durability of the pigment itself as compared with the CuCrO based pigment, the CuCrMnO based pigment, or the CuCrFeO based pigment.
(87) It can be said that the durability of the pigment is influenced by a size of a particle diameter of the pigment because the number of eluted ions decreases as a solid-liquid interface of the pigment to the resin or the coating material becomes smaller regarding, for example, the acid resistance and the alkali resistance, in addition to stability of the crystal structure. In the solid phase reaction in the calcining step during the production of the based pigment, the higher the calcining temperature is, the more promoted a particle growth is and the more coarsened particles are. In the CuCrZnO based pigment, the calcining temperature can be set to a higher temperature. Since the size of the particle diameter of the pigment obtained as a resultant can be easily controlled, it is considered that CuCrZnO based pigment has higher durability of the pigment itself than the CuCrO based pigment, the CuCrMnO based pigment, or the CuCrFeO based pigment.
(88) Next, evaluation results of (d) eluting amount of hexavalent chromium will be described. The present evaluation was performed based on the EPA3060A method.
(89) The evaluation results of the eluting amount of hexavalent chromium based on the EPA3060A method are shown in Table 4 below.
(90) TABLE-US-00006 TABLE 4 Cr.sup.6+ ppm CuCrZnO 250 (Example 10) CuCrO 508 (Comparative Example 2) CuCrMnO 681 (Comparative Example 5) CuCrFeO 312 (Comparative Example 8)
(91) In Table 4 described above, the pigment containing hexavalent chromium in the smallest eluting amount was the CuCrZnO based pigment shown in Example 10, and a numerical value thereof was 250 ppm. The CuCrO based pigment shown in Comparative Example 2, the CuCrMnO based pigment shown in Comparative Example 5, and the CuCrFeO based pigment shown in Comparative Example 8 all contained hexavalent chromium in an eluting amount larger than that in Example 10. Further, in Comparative Example 5, the eluting amount of hexavalent chromium was largest, and a numerical value thereof was 681 ppm. Based on the evaluation results of (a) and (d), it can be said that the method of adding MnO.sub.2 as the modifying oxide to improve the color tone of the CuCrO based pigment is extremely effective, but there is a disadvantage that the durability of the pigment is impaired due to an increase in the eluting amount of hexavalent chromium. In contrast, the CuCrZnO based pigment according to the present invention to which ZnO is added as the modifying oxide has superiority in comparison to the CuCrO based pigment to which the known modifying oxide MnO.sub.2 or Fe.sub.2O.sub.3 is added because the improvement in the color tone and the improvement in the durability of the CuCrO based pigment are achieved at the same time.
(92) Last, an evaluation result of (e) red discoloration test for the glass color will be described.
(93)
(94) As described above, when the CuCrZnO based pigment shown in Example 10 was used to perform the red discoloration test, a glass substrate was hardly discolored, and in all cases where the CuCrO based pigment shown in Comparative Example 2, the CuCrMnO based pigment shown in Comparative Example 5, and the CuCrFeO based pigment shown in Comparative Example 8 were used to perform the red discoloration test, the glass substrate turned red. The red discoloration in the glass color is caused by the reduction of copper as a CuCrO based pigment component by tin on a surface of the plate glass, and generally, the red discoloration in the glass color is more remarkably exhibited as the CuCrO based pigment having lower durability (heat resistance). Therefore, based on the evaluation results of the red discoloration test, it can be said that the CuCrZnO based pigment according to the present invention is excellent in the durability of the pigment itself as compared with the CuCrO based pigment, the CuCrMnO based pigment, or the CuCrFeO based pigment.
(95) From the characteristic tests (a) to (e) described above, the CuCrZnO based pigment according to the present invention has an advantage that the degree of blackness is substantially the same but the redness and the blueness are high in terms of the color characteristic as compared with another CuCrO based pigment such as the commonly used CuCrMnO based pigment, and has an effect that the pigment is clearly excellent in terms of the durability.
(96) Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.