Pigments and fillers for powder coatings

Zhu Weibing (Ningbo Chengxiang plastic powder Co., Ltd.) Cheng Dexi (Changzhou Huazhu Pigment Co., Ltd.) Abstract: This paper introduces in detail the application of organic pigments, inorganic pigments, metal powder pigments, functional pigments in powder coatings and the technical parameters of pigment products According to their properties and functions, pigments suitable for powder coatings can be roughly divided into four categories: coloring pigments, metal pigments, functional pigments and physical pigments They are an important part of powder coatings They can give the coating colorful color, improve the mechanical and chemical properties of the coating, or reduce the cost of the coating Pigments can be divided into two categories: organic and inorganic, which can cover almost all the color systems Metal pigments mainly include floating and non floating aluminum powder, copper gold powder and pearlescent pigment of various colors, nickel metal powder and stainless steel powder, etc Functional pigments mainly include fluorescent pigments, luminous pigments, high temperature resistant pigments, conductive pigments, etc Generally speaking, physical pigments include titanium dioxide (anatase and rutile), calcium carbonate (light and heavy), barium sulfate (precipitated and natural barite), talcum powder, bentonite, quartz powder, etc The preparation of high-quality powder coating is inseparable from the selection of high-quality pigments and fillers See Table 1 for the influence of pigments and fillers on powder properties Table 1 Relationship between pigments and fillers and powder coating low pigments and fillers content high gloss flexibility impact strength adhesion coating evenness weather resistance coating pattern powder relative specific gravity powder storage powder relatively high cost powder relatively high sprayability low high; ————————Low high, low high, low high, low low low, high low, high low, high low, high low, high low, high high low, high high high, low low low, high high low, high high low, high high low, high low low, high high low, high high low, high high low, high high low, high high high low, high high high low, high high high low, high low low low, high high high high low, high low low low, high high low low, low low low low, high low low low, high high high, low low low low, high high, high, high, low low low, high, high, high, high, low, high, high, low, high, low, low, low, low, low, low, low, low, high, high, high, high, low, high, low, high, high, low; Some basic principles for the selection of pigments and fillers 2.1 selection of pigments and fillers Due to the special process of powder coating, the following points should be paid attention to when selecting pigment • pigment has good dispersibility, the best dispersing particle size is 0.2-0.9 & micro; m, which is not easy to agglomerate • strong covering and coloring power of pigment • good thermal stability, at least temperature resistance above 160 ℃ • the pigment shall have certain light and weather resistance, such as not easy to fade, anti pulverization, and long-lasting physical properties • the oil absorption of pigment is moderate, and its color resistance is good 2.2 the choice of filler adding a certain amount of filler to the powder coating can increase the hardness and other mechanical properties of the coating, and reduce the cost, which is an effective way to adjust the cost of powder coating The fillers used in powder coatings are mainly calcium carbonate and barium sulfate, while the functional fillers such as bentonite, talcum powder and quartz powder can be seen as successful, and the total amount is very small According to production process and raw materials, calcium carbonate can be divided into light calcium carbonate and heavy calcium carbonate, both of which are used in powder There are also two types of barium sulfate: precipitation type and barite type The former is made by chemical reaction, while the latter is made by grinding natural barite The problems that should be paid attention to in the selection of fillers are: the whiteness of fillers should be high, which can reduce the amount of titanium dioxide • less impurities, considering the particularity of powder coating process, the impurities in the filler will affect the surface decoration of the coating (more particles on the surface of the coating, flow adjustment) • do not select fillers with too coarse particle size, because they are not easy to disperse and wear the screw • the filler should be loose, not agglomerated, and the water content should be low 3 tone color matching tips (1) color can be generally divided into red, orange, yellow, green, blue, purple, black, white and other categories There is a certain relationship between the colors We can use three parameters to represent any color, that is, hue, saturation and lightness Hue is the basic characteristic that distinguishes each color, which is determined by the spectral composition of the light source and the feeling of the reflected light wave on the surface of the object to the human eye, reflecting the "quality" characteristics of color Saturation is the purity of color on the basis of "quality", also known as "chromaticity" Lightness is the feeling of the human eye on the brightness of the object color Everyone has different judgment (2) Red, yellow and blue are three primary colors, which cannot be decomposed The other colors are all made of these three colors (3) The technician shall pay attention to what kind of color is required, which color is the main color, and shall consider the ratio of color base (PVC value), covering power of pigment and cost accounting The content of this aspect will be detailed in another article 4 Brief description of all kinds of pigments 4.1 coloring pigment 4.1.1 inorganic pigment ① carbon black is the most important black pigment Due to different production processes, the color phase, coloring power and dispersion of carbon black are greatly different There are mainly acetylene black, tank carbon black, lamp black, etc Carbon black has good UV resistance For carbon black suitable for powder coating, it is recommended that Regal 330r of Cabot and MA-100 of Mitsubishi of Japan are both blue phase carbon black with pure color phase Refer to table 2 for typical data Table 2 some typical properties of Cabot regal303r particle size (electron microscope method), NM specific surface area (bet-n2 method) m2 / gdbp absorption m3 / 100g coloring power% volatile% density g / l2594651101.0304 domestic carbon black generally presents red phase, with low coloring power and poor dispersion ② Iron oxide pigments are mainly divided into three categories: iron yellow, iron red and iron black (including iron brown) Iron oxide pigments are widely used in powder coatings, which are cheap, nontoxic and easy to disperse Here are the basic performance parameters of a series of iron oxide pigments from Bayer, Germany and a domestic factory (see Table 3 and table 4) Table 3 performance parameters of Bayer iron oxide pigments Product Code: Fe2O3 content% SiO2 &; Al2O3% 1000 ℃ ignition loss oil absorption g / 100gph value density g / cm3 particle size & micro; Basic performance data of pigment product No FeO3 content% water soluble Salt% 1000 ℃ burning loss% oil absorption g / 100gph value 105 ℃ volatile% 0.045mm sieve residue% S120 iron red 950.75253.5-71.00.3 S920 iron yellow 860.514403-61.00.3 S306 iron black 950.56223-71.00.3 s610 iron brown 850.52303.5-71.00.3 ③ chromium series pigments mainly include chrome yellow, molybdenum chrome red, chrome green and so on This kind of pigment has bright color, good acid and alkali resistance, strong coloring power and easy dispersion, which is widely used in the domestic powder industry The heat resistance and weather resistance of chrome pigment are worse than that of iron oxide pigment Chrome yellow can be subdivided into lemon yellow, light chrome yellow, medium chrome yellow, dark chrome yellow, orange chrome yellow, etc according to the color phase It is widely used in lemon yellow and medium chrome yellow See Table 5 for the basic properties of chrome yellow Table 5 basic performance parameters of chrome yellow: lead chromate% oil absorption g / 100g screen residue% pH value water soluble% water content% 501 lemon yellow > 50 < 30 < 0.54-7 < 1 < 3 103 medium chrome yellow > 90 < 22 < 0.55-8 < 1 < 1 124 deep chrome yellow > 55 < 20 < 0.55-8 < 1 < 1 115N orange chrome yellow > 50 < 15 < 0.54-7 < 1 < 1 molybdenum chrome red also has a series of products, among which "107" grade molybdenum chrome red is the most popular (see Table 6) Table 6 performance parameters of molybdenum chromium red series: lead chromate% oil absorption g / 100g screen residue% pH value water soluble% water content% 107 molybdenum chromium Red > 50 < 22 7098.59999.5800 ℃, with excellent weather resistance 4.4.4 fluorescent pigment for the production of fluorescent powder coating, the fluorescent pigment with good temperature resistance shall be selected, and its dispersion and coloring power shall be considered At present, the main fluorescent pigments that can be used in powder coatings are pink and green 4.5 constitution pigment 4.5.1 titanium dioxide is the best white pigment, which is often included in constitution pigment due to its large use For powder coating, the whiteness, brightness and opacity of the coating are given to effectively scatter the visible light It is still chemically inert, insoluble and thermally stable under severe conditions Commercial titanium dioxide usually has two crystal forms, anatase and rutile R-type (rutile type) titanium dioxide is used most in the powder It is not pure titanium dioxide Most of it is precipitated or mechanically mixed with alumina or silica, which makes it adhere to the surface of titanium dioxide particles to improve performance, such as covering power, easy dispersion, weather resistance and fade resistance The commonly used varieties of titanium dioxide in China are zr940 of Zhenjiang titanium dioxide factory, r214 of Gansu Huayuan Nuclear Industry Co., Ltd., r706 and r902 of DuPont company, rcl575 and rcl69 of Meilian, cr828 and cr822 of comeki, etc In order to reduce the cost of powder coating, type A (anatase type) titanium dioxide can also be used in appropriate occasions However, the powder made from it is not resistant to high temperature and light, and its luster is not stable, which must be fully considered 4.5.2 other white pigments mainly include lithopone, zinc sulfide, lead white, zinc oxide, etc They are used less and less in powder coating See table 12 for their performance comparison with titanium dioxide Table 12 comparison of properties of various white pigments optical properties of pigments a-tio2 r-tio2 lithopone zinc oxide lead white zinc sulfide specific gravity 3.94.2-5.66.84.0 refractive index 2.522.71-2.032.092.37 coverage 33341188797 - Ultraviolet (360nm) absorptivity% 67901893-35 reflectivity (400 & micro; m),% 894890817688 reflectivity (500 & micro; m) ,% 949596949095 toner 130017002603001006604.5.3 packing includes barium sulfate and calcium carbonate, see Appendix III Appendix 1 titanium dioxide 1 Technical data cr-828 cr-828 produced by chlorination is a rutile (R-type) titanium dioxide pigment coated with zirconia / alumina See table 13 for product characteristics Table 13 technical index of cr-828: TiO2 content%, density, oil absorption, pH value, minimum resistance, Ω average particle size, durability of & micro; m moisture content%, 934.11187.580000.19 ＜ 0.6, high 2 Rcl-575 technical data of Meilian rcl-575 is produced by chlorination method, and is rutile titanium dioxide pigment after alumina / organic coating treatment See table 14 for main physical properties Table 14 technical index of rcl-575: TiO2 content%, density, oil absorption, pH value, minimum resistance, Ω average particle size, & micro; M water content% durability 944.2118770000.2 ＜ 0.5 high 3 Several problems should be considered when choosing titanium dioxide 3.1 lumps formed in the process of storage or packaging of dispersion pigment can be mixed evenly with other components such as resin after dispersion and agitation Good score