0 Introduction Automotive coatings are highly decorative and highly protective coatings. As an important component of film-forming substances, pigments, especially pigments for automotive finishes, play an important role in ensuring high decorativeness and high durability of automotive coatings. With the modern exterior design, bright or elegant colors are an effective means for automakers to attract customers and generate high quality intrinsic performance. With the development of paint and coating industry and the strengthening of environmental protection regulations, the recommendation and adoption of pigments for automotive finishes are constantly changing. The emergence of some high-performance pigments and their popularity due to the expiration of patents (such as DPP red) have made pigments, which are less cost-effective, fade out of the market. From the standpoint of toxicity, some inexpensive pigments such as chromium yellow and molybdenum chromium are no longer used in automotive coatings. This article will introduce the current pigments recommended and used in automotive finishes based on the use of pigments in European automotive finishes that I learned in my work in recent years and the recent product introductions by some pigment companies. Inaccurate, please correct knowledge.
1 Performance requirements of automotive paint pigments Automotive paint pigments should have the following four properties:
(1) Excellent chemical stability.
The excellent chemical stability not only means that the pigment has good fastness to various chemicals such as gasoline, lubricant, acid, alkali, solvent (anti-bleed), salt fog, water, and resistance Hot and humid, and in a variety of climatic conditions outdoor long-term use has a good resistance to sun and rain, UV, sulfur dioxide resistance, that is, excellent light retention, color retention, resistance to outdoor durability of powder. In addition, considering the over-bake test when the automotive paint is cured, there should also be a higher heat-resistant temperature (180°C).
(2) Excellent color performance.
The color, hue, and saturation of the pigment in a well-dispersed state should meet the user's requirements. Usually have high coloring power and film gloss. Opaque pigments should have high hiding power, and transparent pigments should have good transparency. In addition, the color reproducibility of the pigment is better, that is, different batches of the same brand of pigment should have a narrow main color, hue, tinting strength and other color indicators of the allowable range.
(3) Good application performance.
In grinding, dispersing and blending paints, the pigments must have good dispersion, flocculation resistance and storage stability, and the resulting colorants must have good fluidity to meet the process requirements of computer automatic color matching in the manufacture of modern automotive paints.
(4) Low toxicity.
2 Main types of paints for automotive finishes 2.1 Inorganic pigments Inorganic pigments currently used in automotive finishes include titanium dioxide, carbon black, iron oxide pigments, bismuth vanadate, metal oxide miscible pigments, and flash aluminum as effect pigments. Powder and mica pearl powder etc. This article is not prepared to discuss two effect pigments, aluminum powder and pearl powder. Lead chrome yellow (PY34) and molybdenum chrome red (PR104), which have improved light and weather resistance by surface treatment such as coating, are suitable for automotive coatings in terms of properties other than toxicity, but are no longer in use because of toxicity. Used in automotive coatings. Cadmium red is also banned for the same reason. Bismuth vanadate is an inorganic yellow pigment (PY 184) commercialized in the 1980s. Its chemical composition is BiVO4/nBi2MoO4, a two-phase pigment of vanadium bismuth and bismuth molybdate, with a hue similar to lemon yellow. In the chemical formula n=0.2-2, the green phase increases as the value of n increases. Its greatest feature is extremely low toxicity, bright and clean colors, excellent heat resistance, weather resistance, light resistance, chemical resistance and solvent resistance. Its hiding power is very good, similar to titanium white and high coloring power, is an ideal non-toxic alternative to chrome yellow pigments. The disadvantage is the high density (around 7), which is prone to precipitation. Metal oxide mixed phase pigments are a class of inorganic pigments with excellent chemical stability. In the crystal structure of a stable metal oxide, colored metal ions can exhibit their color. Miscible pigments can be regarded as solid solutions of metal oxides. The composition of different oxides can produce different colors, such as titanium nickel yellow (PY53, NiO · Sb2O3 · 20TiO2), chrome tantalum titanium (PBr24, Cr2O3 · Sb2O3 · 31TiO2), cobalt blue (PB28, CoO · Al2O3) and Copper chrome black (PBk28, CuO·Cr2O3) and so on. Such pigments are characterized by good high temperature resistance, acid resistance, alkali resistance, light resistance, and weather resistance. The disadvantage is that the coloring power is low, and the dispersion of some varieties is not good enough. Their main use is coloring of ceramics and enamels, and in coatings they are mainly used for high temperature and coil coatings. Can be used for light-colored metallic flash primer in automotive finishes.
2.2 Organic pigments 2.2.1 Azo pigments Azo pigments have a bright color, strong coloring power, and a wide spectrum of chromatograms, mainly yellow, orange, red and brown. However, the conventional monoazo and disazo pigments have poor light fastness, heat resistance, solvent resistance and migration resistance, and are not suitable for use in automotive finishes. The chemical structure modification of azo pigments can improve their various fastness properties. There are two main directions for modification: one is to introduce groups that increase chemical stability, and the other is to increase the relative molecular mass and increase the amide groups in the molecule accordingly. The former modified successful variety is a benzimidazolone azo pigment. Their performance is very good, to meet the requirements of automotive finishes. Benzimidazolone can be considered as a cyclic amide structure. Pigment researchers have discovered that the more amide groups in the molecular structure of azo pigments, the better their light, heat, and solvent resistance properties. For example, in the naphthol AS red monoazo pigment, in addition to the original amide group in the molecule, an amide group (such as PR170 and PR188) is introduced, so that the performance of the modified pigment can basically reach the automotive finish. The requirements, in view of the cost-effectiveness, can be used in automotive finishes. The latter representative method of increasing the relative molecular mass is a condensed azo pigment. This azo pigment combines two monoazo pigments by condensation, which increases the relative molecular mass and increases the number of amide groups in the molecule, thereby improving the performance. Condensed azo pigments have good heat resistance and migration resistance, and can meet the requirements of automotive finishes, but their coloring power is relatively low. Currently used mainly in plastics and synthetic fibers, it is no longer recommended in automotive finishes.
2.2.2 Phthalocyanine Pigments Phthalocyanine pigments are a class of high-performance, cost-effective pigments with blue and green chromatograms. The phthalocyanine pigments used in coatings can meet the requirements of automotive topcoats in terms of resistance to light, heat and solvents. Anti-flocculation types are usually recommended in automotive finishes such as PB15:2, PB15:4, PB15:6, PG36 and some PG7.
2.2.3 Fused and Heterocyclic Pigments (1) Quinacridone Pigments This is a class of pigments with very good overall properties and is suitable for automotive finishes. According to the different substituents and crystal forms, the colors are blue phase red (such as R122 and γ type PV19) and red phase purple (β type PV19).
(2) Anthraquinone Pigment Anthraquinone pigment is a pigment converted from a vat dye. The chromatograms are mainly red, red and purple, and brown (PBr26) and black (PBk32). Lanthanide pigments are also high-performance pigments, and their overall performance is also good, but some early products have poor light fastness at low concentrations. In recent years, through improvement, many products no longer have this problem and can be highly diluted and still maintain good light fastness, and can be used as a color match or in a metallic glitter paint.
(3) DPP pigment DPP, pyrrolopyrrolidione, is a red color pigment with high color saturation and good overall performance introduced by Ciba in 1986. In addition to the red color in the chromatogram, there are orange and purple, which are determined by different substituents. The earliest of these pigments was the opaque red PR254 (DPP Red BO), which now also has a highly transparent blue-red PR264. With the expiration of patents for DPP pigments in 2003, the production and application of these pigments have gradually increased.
(4) The best known diazine pigment diazine pigment is carbazole diazide violet PV23. Its coloring power is very high, it has good light fastness at very low concentrations, and other properties are also good. The disadvantage is that it is not easy to deflocculate during dispersion. Although deflocculation-type products were also available, the results of the anti-floating-fat color test (wiping test) mixed with white paint were still difficult to satisfy. In recent years, a new breed of PB80 has appeared in diazine pigments. The chemical name is benzimidazolone dizine. It combines the chemical stability of the benzoimidazolone structure and the dioxine structure. It has excellent properties, and has a higher coloring power than PV23. The hue is red phase blue.
(5) Isoindoline and quinophthalone pigments The isomorpholine pigments are PY109 (green phase yellow) and PY110 (red phase yellow) and isoporphyrin PY139 (red) in tetrachloroisoindolinone. Yellow) is more commonly used. This is also a class of pigments that are suitable for automotive finishes. In addition to yellow color, there are orange, red, brown and so on. Quinone is also a very good pigment. At present, only BASF's PY138 (Green Phase Yellow) is still recommended for use in automotive finishes.
(6) Anthraquinone Pigments Anthraquinone pigments are also developed from vat dyes. The most commonly used in automotive finishes are eosin PR177 and indanthone blue PB60, in addition to the presence of dibromoindone red PR168. In the anthraquinone pigments, flavanone PY24 (red phase yellow) and pyrimidine PY108 (green phase yellow) are often mentioned in the past. Since the performance is not very prominent, it is no longer recommended in automotive finishes. In addition to lanthanum and lanthanum, other reduced pigments include fluorenone and sulfonium. The performance of perinone pigments is similar to that of lanthanide pigments, of which PO43 performance is better. The former commonly recommended in thionine pigments is PR88, a red-purple violet, which is no longer present in the catalogue of automotive finish pigments.
2.2.4 Metal complexing pigments If complex metal atoms are present in the structure of organic pigments, the properties of heat resistance, solvent resistance and light fastness are greatly improved. In fact, the phthalocyanine pigment is a complex pigment of copper. Because it is a large category, it is listed separately. Among other metal complex pigments, nickel azo complexes (represent green and yellow phase green PY150 and yellow phase green PG10) and metal dimethyl amine complexes (such as methyl amine) have been used in automotive topcoats. Copper complex PY129, Methyl amine nickel complex PY153 and PR257). In addition to PR257, the remaining metal complex pigments are no longer recommended in automotive finishes for various reasons.
3 Overview of colored pigments 3.1 White pigments The white pigments used in automotive finishes are essentially titanium white. A suitable type is the fourth category in the ASTM D476 classification, namely high durability (high resistance to chalking) rutile titanium dioxide, such as Kronos 2310 commonly used in European formulations. Different brands of titanium dioxide due to its surface treatment and the different resin systems used, applicable wetting and dispersing agents are also different. It is usually appropriate to determine which of the three dispersants is acidic (eg DISPERBYK-110), basic (eg DISPERBYK-161) and neutral (eg DISPERBYK-180) by experimentation. The wetting and dispersing agent of a particular brand of titanium dioxide in a particular binder system, once selected, cannot be easily modified. Because the dispersion stability of titanium dioxide on the color of the complex paint float color phenomenon. The amount of dispersant is about 2% (the active ingredient of the additive is based on the mass of the pigment, the same below). Nano-scale titanium dioxide, also known as transparent titanium dioxide, often used in the metal flash primer with aluminum powder or pearl powder, is an auxiliary effect pigment. Because of its small particle size, large specific surface area, the amount of dispersant should be higher. A suitable dispersant is DISPERBYK-180 in an amount of 10% to 15%.
3.2 Black Pigment The black pigment used in automotive finishes is basically carbon black. For full black paint, high-pigment carbon blacks such as Raven 5000 Ultra II, Monarch 1400, and FW200 are used. For use as a color match, low-pigment carbon blacks, such as Tec 100 or medium-pigment carbon blacks, such as Teha 4 can be used. After surface treatment, carbon black with a pH of less than 7 is easily dispersed and stabilized; carbon black with a pH of more than 7 is more difficult to disperse and stabilize. Dispersion stability of carbon black should use high molecular weight deflocculation type wetting and dispersing agent, such as DISPERBYK-161, DISPERBYK-2000, -2001, -2025, etc., and the amount is 30% to 90% of the specific surface area. between. PBk10 graphite and PBk34 molybdenum disulfide in black pigments are silvery-gray flake pigments that can be used in conjunction with aluminum powder or pearl powder in metallic glitter paints, resulting in satin-like effects. Graphite is used in dark grey, molybdenum disulfide for light grey basecoats.
3.3 Blue pigment Blue pigment is mainly phthalocyanine blue. Among the phthalocyanine blue pigments, α-type has red light (PB15:1, PB15:2), β-type has blue light (PB15:3, PB15:4), and ε-type (PB15:6) has stronger red light. PB15:2, PB15:4 and PB15:6 are deflocculating pigments and are preferred in automotive finishes. However, after using BYKS-2100, a synergist with 3% to 5% of PB15:1 and PB15:3, its deflocculation resistance can be greatly improved and it can be used in automotive finishes. These phthalocyanine blues are copper complexes of phthalocyanine. PB16 is a phthalocyanine blue containing no metal atoms. It is a greenish slightly fluorescent blue, slightly inferior to copper-containing phthalocyanine blue, but has better durability in light-colored metallic paints. In addition to phthalocyanine blue, indanthrone blue PB60 is also used in automotive finishes. PB60 is also a kind of red light blue, also has very good light resistance and other properties. The more reddish phase than PB60 is a new breed of benzimidazolone diazide PB80 with excellent properties and high tinctorial strength as mentioned above. For organic pigments, whether blue or other colors, high molecular weight deflocculation wetting and dispersing agents should generally be used in automotive finishes. For solvent-based systems, unless otherwise noted, DISPERBYK-161, -2000, -2001, -2025, -2163, etc. are generally used, and the amount is generally 15% to 30%. For the aqueous system, DISPERBYK-184, -190, -2010, -2015, etc. can be used, and the amount is generally 20% to 40%.
3.4 Green Pigment Phthalocyanine Blue In the molecule, when the 16 H atoms on the four benzene rings are replaced with Cl and Br atoms, the color changes from blue to green. The more Cl atoms that are substituted, the greener the color, and the more Br atoms, the greener the yellow phase. There are two main types of phthalocyanine green pigments used in automotive finishes: one is PG7, and about 13 to 15 H atoms in each copper phthalocyanine molecule are replaced by Cl atoms. The copper phthalocyanine substituted with 10 Cl atoms is called PB76 and the color is between blue and green, and it is cyan. The other is PG36, which is a mixture of Cl atoms and Br atoms, and the number of substitutions is 12-15, wherein the number of Br atoms is 4-10. PG36 is yellow phase green, its dispersion stability is better than PG7, it is deflocculation type. Some PG7s have poor deflocculation resistance. Like PB15:1 and PB15:3, while using dispersants, 3% to 5% of synergist BYKS-2100 is still needed to make the colorants have better dispersion. Effects (transparency, fluidity, coloring, etc.).
3.5 Yellow pigments For yellow inorganic pigments, bismuth vanadate yellow and iron oxide yellow are currently suitable, the latter being opaque and transparent. Opaque yellow iron oxide is usually used only for color matching, while transparent iron oxide yellow is used in metallic base paint. The wetting and dispersing agents suitable for iron oxide yellow are DISPERBYK-110 and -180, and the amount is 7% for the opaque type and 25% for the transparent type. The wetting and dispersing agent suitable for bismuth vanadate is DISPERBYK-110 in an amount of 10%. Benzimidazolone azo pigments, such as PY151, PY154 and PY175, are useful in yellow organic pigments. In recent years, Clariant has introduced the disazo pigment PY219, whose specific chemical structure has not been disclosed and it is presumed to be a bis-benzimidazolone-modified disazo pigment. It is a very green yellow pigment with excellent properties, good hiding power and tinting strength, high gloss and color saturation, and is an ideal companion for use with bismuth vanadate. Another high-performance yellow pigment Clariant has introduced in recent years is PY213, a benzoquinolinone dione modified azo pigment. The chemical structure of benzoquinolinedione is very similar to benzimidazolone, which is a cyclic amide group containing one carbonyl group (-NH-CO-NH-), while the former is a cyclic amide containing two carbonyl groups. Base (-NH-CO-CO-NH-), so it has good performance. Isopininone yellow PY109 and PY110, isoindoline yellow PY139, PY185 and quinophthalone yellow PY138 are other yellow organic pigments that can be used in automotive finishes. As mentioned earlier, some yellow pigments used in automotive finishes a few years ago are no longer recommended for various reasons.
3.6 Orange pigments Orange pigments include benzimidazolone azo pigments PO36 and PO62, DPP pigments PO73, co-crystallized products of DPP and isoindoline Iragzin Orange 2037 (without CI name) and fluorenone PO43. PO43 has a good variety of fastnesses, high saturation and high tinting strength, but when used as a full-color paint, it tends to have a dark tendency outdoors, so it is mainly used for color matching and can be imitated in a metallic background paint. Copper effect.
3.7 Red Pigments Red inorganic pigments used in automotive finishes are currently limited to red iron oxide. Like iron oxide yellow, iron oxide red is also available in both opaque and transparent types, the latter being used in metallic base paints. The wetting and dispersing agent and the amount used for red iron oxide are similar to that of iron oxide yellow. Suitable red organic pigments are azo, quinacridone, anthraquinone, DPP and quinones. As mentioned earlier, the azo red pigments are mainly benzimidazolone modified, such as PR176 and PBr25, and the amide-modified monoazo pigments PR170 and PR188. PBr25 is a very transparent brown-paste red pigment commonly used in metallic base paints. Among the quinacridone reds are PR122, PR202, PR207, PR209, gamma PV19 and Ciba's RT-355-D (a yellowish yellow with good clarity and saturation) that has no CI pigment name. The γ-type PV19 is a blue-phase red. There are PR178 (mainly opaque type), PR179 (mainly transparent type), PR224 and so on. The most famous DPP red is PR254 (DPP-BO), in addition there are PR255 (scarlet), PR264 (transparent bluish red) and co-crystallized products of DPP and quinacridone. There is no CI pigment name RT-380 -D (blue transparent red) and RT-390-D (highly saturated transparent scarlet). When DPP pigments are stable in dispersion, besides __ is used with a high molecular weight deflocculation type wetting dispersant, 3% to 5% of synergist BYKS-2105 should be added. There are PR177 and PR168 (dibromoanthranone) in eosin. Ciba's PR177 has two grades, A2BN and A3B. A2BN has good transparency and colorant fluidity and is suitable for automotive finishes, but A3B has poor color flow and is mainly used in inks. Clariant's PR168 Scarlet has two kinds of opaque (GO) and transparent (GOTrans), is Huang Guanghong. PR168 has good light and weather resistance, and it has good fastness even at low concentrations. However, in some paints, the recoating fastness is not the best.
3.8 Purple Pigments The purple pigments for automotive finishes are mainly carbazozine violet PV23 and β-quinacridone PV19, the latter being a red-phase violet. In addition there are also purple PV29 and nickel complex PR257. PV29 is a high-saturation purple pigment with good transparency. PR257 is also a red-phase violet. Apart from satisfying the lightfastness and weatherability of automotive finishes, Clariant's PR257 3RL has excellent hiding power, dispersibility and deflocculation properties. The representative products of various colors of pigments suitable for automotive topcoats are shown in Tables 1 to 6 for the reader's reference when selecting pigments.
1 Performance requirements of automotive paint pigments Automotive paint pigments should have the following four properties:
(1) Excellent chemical stability.
The excellent chemical stability not only means that the pigment has good fastness to various chemicals such as gasoline, lubricant, acid, alkali, solvent (anti-bleed), salt fog, water, and resistance Hot and humid, and in a variety of climatic conditions outdoor long-term use has a good resistance to sun and rain, UV, sulfur dioxide resistance, that is, excellent light retention, color retention, resistance to outdoor durability of powder. In addition, considering the over-bake test when the automotive paint is cured, there should also be a higher heat-resistant temperature (180°C).
(2) Excellent color performance.
The color, hue, and saturation of the pigment in a well-dispersed state should meet the user's requirements. Usually have high coloring power and film gloss. Opaque pigments should have high hiding power, and transparent pigments should have good transparency. In addition, the color reproducibility of the pigment is better, that is, different batches of the same brand of pigment should have a narrow main color, hue, tinting strength and other color indicators of the allowable range.
(3) Good application performance.
In grinding, dispersing and blending paints, the pigments must have good dispersion, flocculation resistance and storage stability, and the resulting colorants must have good fluidity to meet the process requirements of computer automatic color matching in the manufacture of modern automotive paints.
(4) Low toxicity.
2 Main types of paints for automotive finishes 2.1 Inorganic pigments Inorganic pigments currently used in automotive finishes include titanium dioxide, carbon black, iron oxide pigments, bismuth vanadate, metal oxide miscible pigments, and flash aluminum as effect pigments. Powder and mica pearl powder etc. This article is not prepared to discuss two effect pigments, aluminum powder and pearl powder. Lead chrome yellow (PY34) and molybdenum chrome red (PR104), which have improved light and weather resistance by surface treatment such as coating, are suitable for automotive coatings in terms of properties other than toxicity, but are no longer in use because of toxicity. Used in automotive coatings. Cadmium red is also banned for the same reason. Bismuth vanadate is an inorganic yellow pigment (PY 184) commercialized in the 1980s. Its chemical composition is BiVO4/nBi2MoO4, a two-phase pigment of vanadium bismuth and bismuth molybdate, with a hue similar to lemon yellow. In the chemical formula n=0.2-2, the green phase increases as the value of n increases. Its greatest feature is extremely low toxicity, bright and clean colors, excellent heat resistance, weather resistance, light resistance, chemical resistance and solvent resistance. Its hiding power is very good, similar to titanium white and high coloring power, is an ideal non-toxic alternative to chrome yellow pigments. The disadvantage is the high density (around 7), which is prone to precipitation. Metal oxide mixed phase pigments are a class of inorganic pigments with excellent chemical stability. In the crystal structure of a stable metal oxide, colored metal ions can exhibit their color. Miscible pigments can be regarded as solid solutions of metal oxides. The composition of different oxides can produce different colors, such as titanium nickel yellow (PY53, NiO · Sb2O3 · 20TiO2), chrome tantalum titanium (PBr24, Cr2O3 · Sb2O3 · 31TiO2), cobalt blue (PB28, CoO · Al2O3) and Copper chrome black (PBk28, CuO·Cr2O3) and so on. Such pigments are characterized by good high temperature resistance, acid resistance, alkali resistance, light resistance, and weather resistance. The disadvantage is that the coloring power is low, and the dispersion of some varieties is not good enough. Their main use is coloring of ceramics and enamels, and in coatings they are mainly used for high temperature and coil coatings. Can be used for light-colored metallic flash primer in automotive finishes.
2.2 Organic pigments 2.2.1 Azo pigments Azo pigments have a bright color, strong coloring power, and a wide spectrum of chromatograms, mainly yellow, orange, red and brown. However, the conventional monoazo and disazo pigments have poor light fastness, heat resistance, solvent resistance and migration resistance, and are not suitable for use in automotive finishes. The chemical structure modification of azo pigments can improve their various fastness properties. There are two main directions for modification: one is to introduce groups that increase chemical stability, and the other is to increase the relative molecular mass and increase the amide groups in the molecule accordingly. The former modified successful variety is a benzimidazolone azo pigment. Their performance is very good, to meet the requirements of automotive finishes. Benzimidazolone can be considered as a cyclic amide structure. Pigment researchers have discovered that the more amide groups in the molecular structure of azo pigments, the better their light, heat, and solvent resistance properties. For example, in the naphthol AS red monoazo pigment, in addition to the original amide group in the molecule, an amide group (such as PR170 and PR188) is introduced, so that the performance of the modified pigment can basically reach the automotive finish. The requirements, in view of the cost-effectiveness, can be used in automotive finishes. The latter representative method of increasing the relative molecular mass is a condensed azo pigment. This azo pigment combines two monoazo pigments by condensation, which increases the relative molecular mass and increases the number of amide groups in the molecule, thereby improving the performance. Condensed azo pigments have good heat resistance and migration resistance, and can meet the requirements of automotive finishes, but their coloring power is relatively low. Currently used mainly in plastics and synthetic fibers, it is no longer recommended in automotive finishes.
2.2.2 Phthalocyanine Pigments Phthalocyanine pigments are a class of high-performance, cost-effective pigments with blue and green chromatograms. The phthalocyanine pigments used in coatings can meet the requirements of automotive topcoats in terms of resistance to light, heat and solvents. Anti-flocculation types are usually recommended in automotive finishes such as PB15:2, PB15:4, PB15:6, PG36 and some PG7.
2.2.3 Fused and Heterocyclic Pigments (1) Quinacridone Pigments This is a class of pigments with very good overall properties and is suitable for automotive finishes. According to the different substituents and crystal forms, the colors are blue phase red (such as R122 and γ type PV19) and red phase purple (β type PV19).
(2) Anthraquinone Pigment Anthraquinone pigment is a pigment converted from a vat dye. The chromatograms are mainly red, red and purple, and brown (PBr26) and black (PBk32). Lanthanide pigments are also high-performance pigments, and their overall performance is also good, but some early products have poor light fastness at low concentrations. In recent years, through improvement, many products no longer have this problem and can be highly diluted and still maintain good light fastness, and can be used as a color match or in a metallic glitter paint.
(3) DPP pigment DPP, pyrrolopyrrolidione, is a red color pigment with high color saturation and good overall performance introduced by Ciba in 1986. In addition to the red color in the chromatogram, there are orange and purple, which are determined by different substituents. The earliest of these pigments was the opaque red PR254 (DPP Red BO), which now also has a highly transparent blue-red PR264. With the expiration of patents for DPP pigments in 2003, the production and application of these pigments have gradually increased.
(4) The best known diazine pigment diazine pigment is carbazole diazide violet PV23. Its coloring power is very high, it has good light fastness at very low concentrations, and other properties are also good. The disadvantage is that it is not easy to deflocculate during dispersion. Although deflocculation-type products were also available, the results of the anti-floating-fat color test (wiping test) mixed with white paint were still difficult to satisfy. In recent years, a new breed of PB80 has appeared in diazine pigments. The chemical name is benzimidazolone dizine. It combines the chemical stability of the benzoimidazolone structure and the dioxine structure. It has excellent properties, and has a higher coloring power than PV23. The hue is red phase blue.
(5) Isoindoline and quinophthalone pigments The isomorpholine pigments are PY109 (green phase yellow) and PY110 (red phase yellow) and isoporphyrin PY139 (red) in tetrachloroisoindolinone. Yellow) is more commonly used. This is also a class of pigments that are suitable for automotive finishes. In addition to yellow color, there are orange, red, brown and so on. Quinone is also a very good pigment. At present, only BASF's PY138 (Green Phase Yellow) is still recommended for use in automotive finishes.
(6) Anthraquinone Pigments Anthraquinone pigments are also developed from vat dyes. The most commonly used in automotive finishes are eosin PR177 and indanthone blue PB60, in addition to the presence of dibromoindone red PR168. In the anthraquinone pigments, flavanone PY24 (red phase yellow) and pyrimidine PY108 (green phase yellow) are often mentioned in the past. Since the performance is not very prominent, it is no longer recommended in automotive finishes. In addition to lanthanum and lanthanum, other reduced pigments include fluorenone and sulfonium. The performance of perinone pigments is similar to that of lanthanide pigments, of which PO43 performance is better. The former commonly recommended in thionine pigments is PR88, a red-purple violet, which is no longer present in the catalogue of automotive finish pigments.
2.2.4 Metal complexing pigments If complex metal atoms are present in the structure of organic pigments, the properties of heat resistance, solvent resistance and light fastness are greatly improved. In fact, the phthalocyanine pigment is a complex pigment of copper. Because it is a large category, it is listed separately. Among other metal complex pigments, nickel azo complexes (represent green and yellow phase green PY150 and yellow phase green PG10) and metal dimethyl amine complexes (such as methyl amine) have been used in automotive topcoats. Copper complex PY129, Methyl amine nickel complex PY153 and PR257). In addition to PR257, the remaining metal complex pigments are no longer recommended in automotive finishes for various reasons.
3 Overview of colored pigments 3.1 White pigments The white pigments used in automotive finishes are essentially titanium white. A suitable type is the fourth category in the ASTM D476 classification, namely high durability (high resistance to chalking) rutile titanium dioxide, such as Kronos 2310 commonly used in European formulations. Different brands of titanium dioxide due to its surface treatment and the different resin systems used, applicable wetting and dispersing agents are also different. It is usually appropriate to determine which of the three dispersants is acidic (eg DISPERBYK-110), basic (eg DISPERBYK-161) and neutral (eg DISPERBYK-180) by experimentation. The wetting and dispersing agent of a particular brand of titanium dioxide in a particular binder system, once selected, cannot be easily modified. Because the dispersion stability of titanium dioxide on the color of the complex paint float color phenomenon. The amount of dispersant is about 2% (the active ingredient of the additive is based on the mass of the pigment, the same below). Nano-scale titanium dioxide, also known as transparent titanium dioxide, often used in the metal flash primer with aluminum powder or pearl powder, is an auxiliary effect pigment. Because of its small particle size, large specific surface area, the amount of dispersant should be higher. A suitable dispersant is DISPERBYK-180 in an amount of 10% to 15%.
3.2 Black Pigment The black pigment used in automotive finishes is basically carbon black. For full black paint, high-pigment carbon blacks such as Raven 5000 Ultra II, Monarch 1400, and FW200 are used. For use as a color match, low-pigment carbon blacks, such as Tec 100 or medium-pigment carbon blacks, such as Teha 4 can be used. After surface treatment, carbon black with a pH of less than 7 is easily dispersed and stabilized; carbon black with a pH of more than 7 is more difficult to disperse and stabilize. Dispersion stability of carbon black should use high molecular weight deflocculation type wetting and dispersing agent, such as DISPERBYK-161, DISPERBYK-2000, -2001, -2025, etc., and the amount is 30% to 90% of the specific surface area. between. PBk10 graphite and PBk34 molybdenum disulfide in black pigments are silvery-gray flake pigments that can be used in conjunction with aluminum powder or pearl powder in metallic glitter paints, resulting in satin-like effects. Graphite is used in dark grey, molybdenum disulfide for light grey basecoats.
3.3 Blue pigment Blue pigment is mainly phthalocyanine blue. Among the phthalocyanine blue pigments, α-type has red light (PB15:1, PB15:2), β-type has blue light (PB15:3, PB15:4), and ε-type (PB15:6) has stronger red light. PB15:2, PB15:4 and PB15:6 are deflocculating pigments and are preferred in automotive finishes. However, after using BYKS-2100, a synergist with 3% to 5% of PB15:1 and PB15:3, its deflocculation resistance can be greatly improved and it can be used in automotive finishes. These phthalocyanine blues are copper complexes of phthalocyanine. PB16 is a phthalocyanine blue containing no metal atoms. It is a greenish slightly fluorescent blue, slightly inferior to copper-containing phthalocyanine blue, but has better durability in light-colored metallic paints. In addition to phthalocyanine blue, indanthrone blue PB60 is also used in automotive finishes. PB60 is also a kind of red light blue, also has very good light resistance and other properties. The more reddish phase than PB60 is a new breed of benzimidazolone diazide PB80 with excellent properties and high tinctorial strength as mentioned above. For organic pigments, whether blue or other colors, high molecular weight deflocculation wetting and dispersing agents should generally be used in automotive finishes. For solvent-based systems, unless otherwise noted, DISPERBYK-161, -2000, -2001, -2025, -2163, etc. are generally used, and the amount is generally 15% to 30%. For the aqueous system, DISPERBYK-184, -190, -2010, -2015, etc. can be used, and the amount is generally 20% to 40%.
3.4 Green Pigment Phthalocyanine Blue In the molecule, when the 16 H atoms on the four benzene rings are replaced with Cl and Br atoms, the color changes from blue to green. The more Cl atoms that are substituted, the greener the color, and the more Br atoms, the greener the yellow phase. There are two main types of phthalocyanine green pigments used in automotive finishes: one is PG7, and about 13 to 15 H atoms in each copper phthalocyanine molecule are replaced by Cl atoms. The copper phthalocyanine substituted with 10 Cl atoms is called PB76 and the color is between blue and green, and it is cyan. The other is PG36, which is a mixture of Cl atoms and Br atoms, and the number of substitutions is 12-15, wherein the number of Br atoms is 4-10. PG36 is yellow phase green, its dispersion stability is better than PG7, it is deflocculation type. Some PG7s have poor deflocculation resistance. Like PB15:1 and PB15:3, while using dispersants, 3% to 5% of synergist BYKS-2100 is still needed to make the colorants have better dispersion. Effects (transparency, fluidity, coloring, etc.).
3.5 Yellow pigments For yellow inorganic pigments, bismuth vanadate yellow and iron oxide yellow are currently suitable, the latter being opaque and transparent. Opaque yellow iron oxide is usually used only for color matching, while transparent iron oxide yellow is used in metallic base paint. The wetting and dispersing agents suitable for iron oxide yellow are DISPERBYK-110 and -180, and the amount is 7% for the opaque type and 25% for the transparent type. The wetting and dispersing agent suitable for bismuth vanadate is DISPERBYK-110 in an amount of 10%. Benzimidazolone azo pigments, such as PY151, PY154 and PY175, are useful in yellow organic pigments. In recent years, Clariant has introduced the disazo pigment PY219, whose specific chemical structure has not been disclosed and it is presumed to be a bis-benzimidazolone-modified disazo pigment. It is a very green yellow pigment with excellent properties, good hiding power and tinting strength, high gloss and color saturation, and is an ideal companion for use with bismuth vanadate. Another high-performance yellow pigment Clariant has introduced in recent years is PY213, a benzoquinolinone dione modified azo pigment. The chemical structure of benzoquinolinedione is very similar to benzimidazolone, which is a cyclic amide group containing one carbonyl group (-NH-CO-NH-), while the former is a cyclic amide containing two carbonyl groups. Base (-NH-CO-CO-NH-), so it has good performance. Isopininone yellow PY109 and PY110, isoindoline yellow PY139, PY185 and quinophthalone yellow PY138 are other yellow organic pigments that can be used in automotive finishes. As mentioned earlier, some yellow pigments used in automotive finishes a few years ago are no longer recommended for various reasons.
3.6 Orange pigments Orange pigments include benzimidazolone azo pigments PO36 and PO62, DPP pigments PO73, co-crystallized products of DPP and isoindoline Iragzin Orange 2037 (without CI name) and fluorenone PO43. PO43 has a good variety of fastnesses, high saturation and high tinting strength, but when used as a full-color paint, it tends to have a dark tendency outdoors, so it is mainly used for color matching and can be imitated in a metallic background paint. Copper effect.
3.7 Red Pigments Red inorganic pigments used in automotive finishes are currently limited to red iron oxide. Like iron oxide yellow, iron oxide red is also available in both opaque and transparent types, the latter being used in metallic base paints. The wetting and dispersing agent and the amount used for red iron oxide are similar to that of iron oxide yellow. Suitable red organic pigments are azo, quinacridone, anthraquinone, DPP and quinones. As mentioned earlier, the azo red pigments are mainly benzimidazolone modified, such as PR176 and PBr25, and the amide-modified monoazo pigments PR170 and PR188. PBr25 is a very transparent brown-paste red pigment commonly used in metallic base paints. Among the quinacridone reds are PR122, PR202, PR207, PR209, gamma PV19 and Ciba's RT-355-D (a yellowish yellow with good clarity and saturation) that has no CI pigment name. The γ-type PV19 is a blue-phase red. There are PR178 (mainly opaque type), PR179 (mainly transparent type), PR224 and so on. The most famous DPP red is PR254 (DPP-BO), in addition there are PR255 (scarlet), PR264 (transparent bluish red) and co-crystallized products of DPP and quinacridone. There is no CI pigment name RT-380 -D (blue transparent red) and RT-390-D (highly saturated transparent scarlet). When DPP pigments are stable in dispersion, besides __ is used with a high molecular weight deflocculation type wetting dispersant, 3% to 5% of synergist BYKS-2105 should be added. There are PR177 and PR168 (dibromoanthranone) in eosin. Ciba's PR177 has two grades, A2BN and A3B. A2BN has good transparency and colorant fluidity and is suitable for automotive finishes, but A3B has poor color flow and is mainly used in inks. Clariant's PR168 Scarlet has two kinds of opaque (GO) and transparent (GOTrans), is Huang Guanghong. PR168 has good light and weather resistance, and it has good fastness even at low concentrations. However, in some paints, the recoating fastness is not the best.
3.8 Purple Pigments The purple pigments for automotive finishes are mainly carbazozine violet PV23 and β-quinacridone PV19, the latter being a red-phase violet. In addition there are also purple PV29 and nickel complex PR257. PV29 is a high-saturation purple pigment with good transparency. PR257 is also a red-phase violet. Apart from satisfying the lightfastness and weatherability of automotive finishes, Clariant's PR257 3RL has excellent hiding power, dispersibility and deflocculation properties. The representative products of various colors of pigments suitable for automotive topcoats are shown in Tables 1 to 6 for the reader's reference when selecting pigments.
Dongfeng Fast Gearbox Parts,Separation Fork,Worm Gear Gearbox,Worm Speed Gearbox
Dongfeng Truck Engine Parts Co., Ltd. , http://www.ochoasautoparts.com