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What are the common pigments for paints?

Sep 17, 2019

1. White pigment.
1.1 Titanium dioxide.
The chemical name of titanium dioxide is titanium dioxide, which is one of the best white pigments at present and is widely used in architectural coatings. Titanium dioxide not only has good whiteness, coloring power and hiding power, but also has high chemical stability, heat resistance and weather resistance. The coating prepared with titanium dioxide has bright color and long film life.
Titanium dioxide has two crystal forms:
One is anatase (type A) and the other is rutile (type R). Rutile titanium dioxide has dense lattice, stable, good weather resistance and not easy to pulverize, so it is suitable for the preparation of exterior wall coatings and high-grade coatings. Anatase titanium dioxide has large lattice space, instability and poor weather resistance, so it is suitable for the preparation of interior wall coatings and low-grade coatings.
1.2 Zinc oxide.
Zinc oxide, commonly known as zinc white, the covering power is less than titanium dioxide and Lithopone, so it is rarely used alone, usually combined with titanium dioxide or Lithopone to improve the light resistance and pulverization resistance of the film, and increase the mildew resistance of the film.
At present, zinc oxide is mainly used as antirust pigment in coating industry, but not as coloring pigment.
1.3 Lithopone.
Lithopone, also known as zinc barium white, is a compound formed by the interaction of zinc sulfide and barium sulfate. Lithopone is stable to alkalinity and released hydrogen sulfide from acid decomposition. Its most serious disadvantage is that it is not resistant to light and darkens when exposed to light.
The coating prepared with Lithopone has poor weather resistance and easy pulverization after film formation, so it is not suitable to be used outdoors. In addition, Lithopone makes the coating easy to thicken after the problem. Therefore, it has been rarely used in architectural coatings, especially in exterior wall coatings. However, because of its good alkali resistance, it can be used as an interior wall coating to give the coating a better covering power.
2. Red pigment.
2.1 Iron oxide red.
The chemical composition of iron oxide red is iron oxide, referred to as iron red, its light resistance, weather resistance and chemical stability are very good, the hiding power is the best of red pigments, but the acid resistance is poor. The hue of iron red is black in red, not bright enough.
Toluidine red, also known as scarlet, Turudine red, is the best fastness red pigment, with bright red tones. It has high water resistance, oil resistance, acid and alkali resistance. The texture is soft and easy to grind. It is not easy to disperse in waterborne coatings, and it is beneficial to improve the dispersibility after surface treatment.
2.2 Big Red Powder.
Dahong powder is a kind of azo pigment with good fastness, bright tone, loose texture and easy dispersion, acid and alkali resistance, light resistance and heat resistance. Compared with toluidine red, the price is lower, so it is more used in architectural coatings.
2.3 cadmium red.
Cadmium red is a complex of cadmium sulfide and cadmium selenide, which has good coloring power, covering power, light resistance and weather resistance. The color light changes with the content of cadmium selenide. The more cadmium selenide content is, the stronger the red color light is. It is a kind of red pigment with very bright color. However, due to the high price, it is less used in ordinary architectural coatings.
3 orange and yellow pigments.
3.1 Molybdenum Chrome Orange.
Molybdenum chromium orange, also known as lead molybdenum chromium orange, is composed of lead chromate, lead molybdate and lead sulfate. Molybdenum chromium orange color is very bright, the tone changes from light orange to red orange, with a high root luster. High coloring power, good stability, light resistance, heat resistance, chemical resistance are good, is the main pigment for the production of orange-red and orange-yellow coatings.
3.2 Chrome Yellow.
Chrome yellow, also known as lead chrome yellow, the chemical composition is lead chromate, or a mixture of lead chromate and lead sulfate. With the increase of the proportion of lead chromate, the color is from light to dark, which can be divided into lemon yellow, light chrome yellow, medium chromium yellow, dark chromium yellow and orange chrome yellow. Chrome yellow has bright color, strong coloring power and covering power, and is poisonous. The hiding power, coloring power and weather resistance decreased with the increase of lead sulfate content. The acid and alkali resistance is poor, and the light resistance is not good enough. The hue turns green or even black under the action of light. The suspension and light resistance of chrome yellow can be improved by surface treatment.
3.3 Iron oxide yellow.
Iron oxide yellow is referred to as iron yellow, and its chemical composition is iron trioxide hydrate. Earth yellow, the color light changes between light yellow and brown yellow. When heated, it is dehydrated and gradually transformed into iron oxide red. Covering power is one of the best yellow pigments, light resistance, weather resistance, alkali resistance are very excellent, but not acid resistance. It is widely used in architectural coatings.
3.4 Sun resistant Yellow G.
Sun-resistant yellow G has a pure yellow, bright color, high hiding power, light resistance, heat resistance, acid and alkali resistance are very good. Non-toxic, can replace toxic chrome yellow. The color is red at high temperature, and the solvent resistance is poor.
4. Green pigment.
4.1 lead Chrome Green.
Lead-chromium green is a green pigment made of lead-chromium yellow and iron blue by coprecipitation method, which can also be mechanically mixed, but its performance is not as good as that of coprecipitation method. The color depends on the proportion of the two, which can be divided into three kinds: light chromium green, medium chromium green and dark chromium green. Bright hue, excellent light resistance, weather resistance, strong hiding power and coloring power. However, the acid and alkali resistance is poor, the color will become dark for a long time, and less used in architectural coatings.
4.2 Chrome oxide Green.
The chemical name of chromium oxide green is chromium trioxide, which has olive green, gray green, tea green and grass green. Chromium oxide green has very good stability, excellent acid and alkali resistance, high temperature resistance, light resistance and weather resistance. The hiding power is second only to lead-chrome green, but the color is not bright enough. Poor dispersibility, when using, we should pay great attention to avoid the coating flowering phenomenon caused by poor dispersion, which is a commonly used green pigment for exterior wall coatings.
4.3 phthalein green.
Phthalein green is the most commonly used green pigment in architectural coatings because of its bright tone, coloring power, light resistance, heat resistance, weather resistance, acid and alkali resistance, solvent resistance and insolubility in water and organic solvents.
5. Blue pigment.
5.1 Iron Blue.
Iron blue, also known as Hua blue, Prussian blue, hue for dark blue. The color varies from blue to red or from blue to red depending on the water content. Strong coloring power, poor hiding power, good light resistance, weak acid resistance, but poor alkali resistance, so it is rarely used in architectural coatings.
5.2 Qunqing.
Qunqing, also known as Foqing, Yunqing, foreign blue, is containing sodium polysulfide and has a special structure of aluminum silicate powder, colorful and translucent. The hiding power and coloring power are very low. Heat resistance, alkali resistance is better, but not acid resistance. It is less used alone, but because the green group has the effect of eliminating or weakening the yellow color, a little is usually added to the latex paint to increase the whiteness of the white paint.
5.3 phthalocyanine blue.
Phthalocyanine blue is a kind of organic pigment with bright color, strong coloring power, light resistance, weather resistance and chemical resistance. The colors range from blue to red and blue.
Phthalocyanine blue is prone to flocculation and thickening in waterborne coatings, which is related to binders, auxiliaries and dispersion methods. It is not easy to disperse in water and is widely used in architectural coatings.
6. Black pigment.
6.1 Iron Black.
The chemical name of iron black is ferric oxide, which has saturated blue black light and strong coloring power, but the covering power is small. Stable to light and atmosphere, resistant to alkali but not acid.
6.2 carbon black.
Carbon black has high coloring power and covering power, light resistance, weather resistance, chemical stability, acid resistance, alkali resistance and high temperature resistance. It is difficult to disperse in water and needs to be ground in the presence of dispersant and transferred into the coating. The anti-thickening phenomenon is easy to appear in the process of coating storage. It is widely used in architectural coatings.