Name | C.I. Pigment Yellow 37 |
Synonyms | C.I. Pigment Yellow 37 Pigment yellow 37 (C.I. 77199) C. I. Pigment Yellow 37 (77199) |
CAS | 68859-25-6 |
Molecular Formula | CdS·ZnS |
Melting Point | 1405℃ |
Physical and Chemical Properties | The chemical composition of pure cadmium yellow is a solid solution of cadmium sulfide or cadmium sulfide and zinc sulfide. The color of cadmium yellow is bright and full (saturation up to 80% ~ 90%), and its chromatographic range can be from light yellow, through yellow to red and yellow. The yellow degree of cadmium yellow containing zinc sulfide becomes shallow with the increase of solid solution amount of zinc sulfide until it is light yellow. Industrial production of cadmium yellow light yellow (primrose yellow), bright yellow (lemon yellow), yellow (yellow), dark yellow (golden) and orange and so on several. Cadmium sulfide can also be mixed with cadmium carbonate to form a mixture of orange, but not a solid solution. The color of cadmium yellow depends on the secondary factors associated with the colloidal aggregates of the pigment and to a large extent on the valence of the condensed anion. The cadmium yellow particles have a spherical shape or an aggregate thereof. The particle size of yellow cadmium is 0.04~0.4 μm, the pore radius is 20~200 nm, and the specific surface is 7~8 m2/g. cadmium sulfide yellow has two stable forms at room temperature: one is β-CDs, which belongs to cubic crystal form; The other is α-CDs, which belongs to hexagonal crystal form. The former is called low temperature stable, heat resistance is less than or equal to 500 deg C; The latter is called high temperature stable, melting point of 1405 deg C, heat resistance is greater than or equal to 600 deg C. At room temperature and 500 deg C range, two kinds of crystal forms of cadmium yellow can be stable coexistence. The single grain size of the cubic crystal is less than or equal to 100, while the single crystal grain of the six crystal is in the range of ~ 280nm. Cadmium sulfide yellow at more than 700 deg C to Brown, at 980 deg C in nitrogen atmosphere sublimation but does not decompose, if the presence of air is completely oxidized to CdSO4 and CdO. Under the combined action of humidity and air, cadmium yellow can be oxidized to toxic cadmium sulfate. cadmium yellow is insoluble in water, alkali, organic solvents and oils, slightly soluble in 5% dilute hydrochloric acid, soluble in concentrated acid, dilute nitric acid and boiling dilute sulfuric acid (1:5). Cadmium yellow is not affected by hydrogen sulfide. The relative density of cadmium yellow is 4.5~5.9, and the secretion of light yellow is smaller than that of dark yellow. The β-form is more lipophilic than the α-form. Cadmium yellow grinding is good, easy and adhesive research and, but poor wear resistance. In the dry state long grinding color darkening, heat treatment can make the discoloration of cadmium yellow to restore the original state. Cadmium yellow color strength is strong, light resistance, excellent weather resistance, no migration, no bleeding. Cadmium yellow is safe in colored products because of its insolubility, but it is still a toxic pigment. |
Use | cadmium yellow is widely used in the coloring of enamel, glass and ceramics. It is also used in coating and plastic industries, and is also used as an electronic fluorescent material. Cadmium yellow is suitable for the coloring of almost all resins and is translucent in plastics. Light-colored cadmium yellow containing zinc sulfide used in polyethylene, should try to shorten the molding processing time, because zinc sulfide will promote polyethylene plastic decomposition and green. The stability of cadmium yellow in the chamber is not as good as cadmium red, and it is used for indoor plastic products. Cadmium Yellow should not be used in combination with pigments containing copper or copper salts to avoid the formation of black copper sulfide or green copper sulfate. Cadmium yellow can be mixed with a blue pigment to obtain a green color. |
Raw Materials | Zinc oxide Zinc sulphate Cadmium oxide ARSENIC (III) SULFIDE CADMIUM CARBONATE Dark chrome yellow Cadmium sulfide |
The industrial production of general-purpose cadmium yellow generally adopts calcination method or precipitation-calcination method.
Calcination method. Calcinate cadmium carbonate and sulfur at high temperature to produce cadmium yellow. Add zinc oxide or zinc sulfate to produce light-tone cadmium yellow. Reaction equation:
CdCO3→CdO+CO2↑
2CdO+S→SO2↑+Cd
Cd+S→CdS
ZnO+S→ZnS+SO2↑
CdS + ZnS & rarr;CdS · ZnS operation method: the cadmium oxide generated during combustion is in an activated state and immediately reacts with sulfur to generate cadmium sulfide. The released carbon dioxide can prevent the premature combustion of sulfur caused by oxygen in the air. However, some sulfur is still oxidized to sulfur dioxide, so the sulfur in the charge should be more than the theoretical calculation, such as 1.2 ~ 1.5mol of sulfur per mole of cadmium carbonate. The proportion of charge for calcination of cadmium yellow is cadmium carbonate: zinc oxide: sulfur is 100;15:50 (light yellow), 100:5:47 (normal yellow), 100:0:50 (deep yellow). Before calcination, the charge is placed in a ball mill and mixed evenly. The calcination temperature is generally 500~600 ℃, and the calcination time is 1~2h. If the temperature is too high or the time is too long, the generated cadmium sulfide may be oxidized to cadmium sulfate. If the temperature or time is insufficient, there will be reddish brown or black cadmium oxide. A converter or muffle furnace with uniform heat transfer should be used for calcination. During calcination, sampling and observation are required at any time to control the color of the pigment. After calcination, rinse the pigment with water to remove cadmium sulfate or zinc sulfate impurities, then filter and dry below 250 ℃ to obtain cadmium yellow product. The calcination method is not suitable for large-scale production.
Precipitation-calcination method. According to the different raw materials used, the method is divided into cadmium carbonate method and cadmium sulfate method.
Cadmium carbonate method. Reaction equation: CdCO3 + Na2S & rarr;CdS↓ + Na2CO3
Operation method: The preparation method of cadmium chloride and cadmium carbonate can be found in "Cadmium Red" and related literature. Industrial sodium sulfide removes impurities from it by recrystallization. After the purified sodium sulfide is dissolved in steam, the density is adjusted to 1.134~1.143g/cm3, and the sodium sulfide tank is sucked into the pump for later use. The sodium sulfide solution is measured and sent to the synthesis kettle equipped with coil heating, and at the same time, it is stirred and added with the prepared cadmium carbonate slurry, and the temperature is increased to 70~80 ℃. After 1h of reaction, yellow cadmium sulfide precipitate was obtained. The sediment is rinsed with water to remove soluble salts, measured as neutral with test paper, and sent to a filter press for filtration. The filter residue is sent to a drying oven and dried below 120 ℃ for 24 hours. When the moisture content is less than 0.4%, the package is the finished product. This uncalcined cadmium yellow can be used as enamel or glass pigment, because glass products still need to be fired at high temperature when coloring. If cadmium yellow needs to be calcined, it will be carried out according to the post-stage process of cadmium carbonate method "cadmium red. The calcination temperature is 450~600 ℃. Cadmium sulfate method. Cadmium sulfate is a water-soluble salt. There are usually two kinds of cadmium yellow produced with it as the starting material. One is the reaction of cadmium sulfate with sodium sulfide, namely: CdSO4 + Na2S & rarr;CdS↓ + Na2SO4
The other is the reaction of cadmium sulfate with sodium thiosulfate. Also known as sodium thiosulfate method. In order to prevent the formation of sulfuric acid and produce double salt (CdS · nCdSO4), an appropriate amount of neutralizer (such as sodium carbonate) needs to be added to strictly control the pH value. At this time, the reaction is as follows:
CdSO4+Na2S2O3+Na2CO3→CdS↓+2Na2SO4+CO2↑
If you want to make light-colored cadmium yellow, add zinc oxide to the reaction mixture. In this case, the sulfuric acid produced in the reaction reacts with zinc to form a salt, so there is no need to add a neutralizer, CdSO4 + Na2S2O3 + H2O & rarr;CdS↓ + Na2SO4 + H2SO4
ZnO+H2SO4→ZnSO4+H2O
Znso4+Na2S2O3+H2O→ZnS↓+Na2SO4+H2SO4
In the finished product, the total molar ratio of cadmium and zinc to sulfur is 1:(0.98~0.99). When preparing different cadmium yellow products, the ratios of sodium thiosulfate (Na2S2O3 · 5H2O), cadmium sulfate (CdSO4 · 8/3H2O), zinc oxide (ZnO) and sodium carbonate (Na2CO3) are 150:100:18:0 (lemon yellow), 150:100:12:0 (light yellow), 150:100:0:21 (normal yellow), respectively. The process of cadmium sulfate method is similar to cadmium carbonate method. First, the cadmium sulfate solution (concentration of 200g/L) is sent to the synthesis kettle, heated to 70~80 ℃, and then added with the indication of sodium carbonate or zinc white (ZnO). Crystal sodium thiosulfate is then added under stirring. The generated precipitate is filtered and dried, and then calcined for 1~2h. The calcination temperature of lemon yellow and light yellow is 550~600 ℃, and that of normal yellow is about 400~500 ℃. Calcination is usually in a reducing or inert atmosphere.