Hindered settling of organic pigment dispersions in hydrocarbon liquids

A modified Steinour hindered settling method has been developed for the study of dispersed organic pigment species containing a large proportion of associated immobile liquid. These species are termed flow units with effective volumes and densities different from those of the pigment itself. The effective volume and density are calculated from the final sediment volume fraction after correction (if practicable) by an appropriate packing factor. The mean flow unit diameter (or a size parameter) can then be estimated. The present method has been satisfactorily tested using formalin-fixed yeast cells as model flow units which can be sized readily by optical microscopy. Data for organic pigment dispersions compare well with their appearance under the optical microscope. Various uses of simplified versions of the present technique in studies of dispersibility and dispersion stability of organic pigments are described and exemplified using mainly copper phthalocyanine pigments in hydrocarbon solvents.     

Characteristics of pigments,modification, and their functionalities

Novel treatments of pigments with inorganic materials have tremendous industrial and commercial prospects. Specific treatment of pigment has a marked effect on its behavior during application. The treatment allows a broad modification of the surface characteristics of pigment particles which leads to improved functionalities. Surface modification of pigments is achieved via coating, polymerization with modifying reagent, treatment with derivatives or polymers, which alter either the optical, conductivity or dispersibility during processing and application. These and many other distinguishing factors that affect the characteristics of pigments such as the class, crystal structure, particle morphology, particle size, hiding power, pigment volume concentration, surface character, and surface treatment have been reviewed. Various organic pigments such as those from fungus and bacteria, and the various families of pigment types such as metallic pigment, light interference, and diffractive pigments which presents decorative quality such as leafing, nonleafing, pearlscent, and Fabry‐Perot effects on substrates have also been reviewed in addition to those from inorganic sources with emphasis on the structure and physiochemical modifications using metal and nonmetal Ions.     

Influence of organic pigment particles on millbase flow of nitro-cellulose/alcohol-rich liquid inks

Millbase flow of nitro-cellulose/alcohol-based inks deteriorates above a critical pigment weight fraction in the ink which differs from pigment to pigment. Below this critical concentration the inks are flocculation-resistant by virtue of a stabilizing adsorbed layer of NC resin on the pigment particle surfaces. The pigment particles are large aggregates of crystals, from which additives such as abietyl resin have been shown to dissolve off into the ink medium. The aggregates are associated with liquid medium immobilized within the shear boundary near the pigment/medium interface (includes adsorbed layers and liquid within pores). This results in the effective pigment volume fraction in the ink being higher than that calculated from the weight fraction. When considered in terms of the effective volume fraction, most of the pigments have the same critical concentration of about 0.2–0.25. This indicates that deterioration in flow at higher concentrations is due in the first instance to crowding of particles, rather than to the failure of the mechanism of flocculation resistance per se. The robustness of the flocculation resistance is indicated by a low rate of increase of the strength of the structure with an increase in the effective volume fraction above the critical concentration. Robustness is important in maintaining manageable flow at high concentrations. Increasing the proportion of ethyl acetate in the solvent blend can adversely affect the millbase rheology of dispersions of some pigments in NC ink media due to induced flocculation and structure formation. The improved solvency of the blend for NC resin has been shown to reduce the amount of NC resin adsorbed on the particles of an ester-sensitive pigment. Other pigments give inks with rheology insensitive to ester content. This is attributed to more specific interaction of the NC resin with the pigment particle surfaces. The effect of temperature on flocculation resistance is consistent with these views.     

Synthesis and evaluation of several high absorbance black pigments for spacecraft thermal control coatings

Using black coatings and materials with high light absorbance that are capable of absorbing photons at visible and longer wavelengths is a very effective way to reduce unwanted stray light, also known as optical noise, within optical equipment. These lights can be greatly reduced to a reasonable level by functional and performable black coatings that are modified to absorb incident light as much as possible by their specific pigments. In the present work, several carbonaceous pigments were synthesized for the first time from wasteful materials and their optical properties in the visible and near‐infrared ranges studied. First, MCM‐48 and SBA‐15 were synthesized at different conditions and were then used as templates for carbonaceous products. SSS‐1 (the carbonic pigment synthesized by the mixture of sucrose and sodium silicate), SSS‐2 (the carbonic pigment synthesized by the mixture of sawdust and sodium silicate), and mesoporous carbon pigments (CMK‐3 and CMK‐1 with different levels of saturations) were synthesized. Finally, their structure, morphology, and optical properties were investigated by X‐ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE‐SEM), and Diffuse Reflectance Spectroscopy (DRS). The results indicated that the SSS‐1 pigment had a lower reflectance (below 1%) than carbon black (about 2.5%) in the visible region despite it being more cost‐effective than carbon black. The mesoporous pigments showed very high light absorbance in the visible region (about 2.5%). Compared with other black pigments, the CMK‐1 was the blackest synthesized material with a very low reflectance (about 0.05% in visible region), making it an ideal candidate as a super black pigment for reducing unwanted stray light within optical equipment.     

Challenges of chromate inhibitor pigments replacement in organic coatings

General considerations concerning pigment grade corrosion inhibitors are presented and new characteristic functional parameters proposed. The chemistry, contemporarily practiced for corrosion inhibitor pigment synthesis, as well as known mechanistic considerations relevant to the corrosion inhibitor species available in pigment grades, are reviewed. Inherent limits of chemistry are outlined regarding the feasibility of developing equally effective and versatile non-toxic alternatives for chromates.

Fundamental aspects of corrosion inhibitor pigment behavior are discussed in the context of organic coatings degradation mechanisms. Disclosed experimental data demonstrate that correlation exists between solubility of corrosion inhibitor pigments, leaching from, and osmotic blistering of organic coatings. A mathematical expression is proposed and empirically proven to adequately describe the leaching rate of corrosion inhibitor pigments from organic coatings.

The barrier function of some high performance organic coatings, such as aircraft or coil, is negligible and requires the contribution of an effective corrosion inhibitor pigment, which, typically, is strontium chromate. In this context, the feasibility of replacing chromate inhibitor pigments is assessed and the “gap” observable between the inhibitor performance of chromates and traditional non-chromate pigments is noted.

Experimental data are displayed regarding the corrosion inhibitor performance of a novel, organic–inorganic, hybrid type corrosion inhibitor pigment in typical aircraft primer application on aluminum and plated steel. The presented data demonstrate the feasibility of chromate replacement in this specific case.     

Anticorrosive behaviour of alkyd paints formulated with ion-exchange pigments

Hexavalent chromium compounds (chromates) have been widely used as inhibitive pigments in the formulation of anticorrosive paints. However, their high toxicity and carcinogenic effects are forcing the development of effective chromate-free organic coatings. One such alternative, which is very attractive from a scientific point of view, is the use of ion-exchangeable pigments (IEPs).

The few studies conducted with this type of pigment are not conclusive about their anticorrosive efficiency and controversy surrounds their functioning mechanisms, interchange capacity and anticorrosive performance.

In the present research, which focuses on the anticorrosive protection of this type of pigment, alkyd paint coatings formulated with vanadate-hydrotalcite (HT/V) (anionic) and calcium/silica (Ca/Si) (cationic) IEPs have been applied on low carbon steel specimens. A traditional zinc chromate pigment has also been used for comparative purposes.

The effect of these non-toxic pigments on the protective properties of coatings has been tested by means of natural and accelerated corrosion tests (humidity, salt spray and Kesternich, 0.2 l SO₂) and electrochemical impedance spectroscopy (EIS).

None of the IEPs equalled the anticorrosive behaviour of the zinc chromate in the different tests. The anionic pigment (HT/V) seems to present good behaviour in chloride environments (salt spray, NaCl solutions, etc.) while the cationic pigment (Ca/Si) performs well in the humidity condensation and SO₂ tests.     

世界有机颜料制造工业的发展趋势

阐述了世界有机颜料制造工业的重组和市场对有机颜料需求增长的趋势，以及当前有机颜料行业采取的发展措施。对调整我国有机颜料行业组织结构和发展新颜料具有参考价值。     

Antifouling paints II. A more detailed examination of the effect of pigment volume concentration

The effect of pigment volume concentration upon the leaching of soluble pigments from insoluble binders has been studied and the results used to extend a previously described¹ theoretical treatment. The number of interconnecting holes between the cavities left after solution of the pigment from the insoluble binder is assumed to be related to the pigment volume concentration in a similar way to the number of contacts made by smooth spheres regularly packed at the same solids content. An empirical equation is used to relate the number of contacts made between spheres to their density of packing, and consequently to relate the number of interconnecting holes between cavities to the pigment volume concentration. Predictions based on the resulting relationship are compared with the leaching characteristics measured for three different coating compositions, each made with a range of pigment volume concentrations using two different vinyl resins and two grades of copper (I) oxide pigment. The predicted variations with pigment volume concentration of initial leaching rate, and of initial rates of decrease in leaching rates, hold reasonably well for pigment volume fractions between 0.30 and 0.80, the full range studied. Longer term leaching behaviour appears predictable only for paints of pigment fractions above about 0.45; anomalies below this figure are attributed to lack of pigment solution. Statistical analysis of experimental leaching rate data indicate that the initial leaching rates are unaffected within limits by the type of binder and pigment. The two copper oxide pigments used behaved similarly. However, the kind of binder used does affect the rate of decrease in leaching rate. The experimental data is consistent with the theoretical model employed and with the concept that the thickness of binder separating pigment particles and hence the interconnecting hole size remains approximately constant irrespective of pigment volume concentration.     

细乳液聚合法制备PY-17/PE蜡/PS复合乳胶粒子

通过细乳液聚合法制备彩色墨粉用多组分复合乳胶粒子,即通过细乳液聚合法制备聚苯乙烯包覆有机颜料PY-17和聚乙烯蜡的三元复合乳胶粒子。通过透射电子显微镜、激光粒度仪、紫外可见分光光度计和热失重分析仪对制备的复合乳胶粒子形貌、粒度、热学和光学特性进行表征,着重研究了乳化剂种类及用量、颜料用量和聚乙烯蜡用量对复合乳胶粒子粒径和形貌的影响,并对复合乳胶粒子的热学及光学特性进行了表征。结果表明,使用复合乳化剂,颜料PY-17用量不大于单体量8%、聚乙烯蜡用量占单体量不大于10%时,制备的复合乳胶粒子粒径较小,分布窄,包覆较为完整;并且复合乳胶粒子的热学及光学特性发生了一定的改变。     

Calcium sulphate as pigment for improved functional properties of coated paper

In the last few years, interest and demand of high bright paper have forced paper manufacturers to think new ways to improve brightness and whiteness of coated paper. Pigment coating is widely used to enhance the optical properties such as brightness, whiteness, and gloss of paper and paperboard. These optical properties are the most important for end user and also determine the final cost of coated paper. Calcium sulphate has inherent better optical properties compared to other conventional pigments for example ground calcium carbonate, precipitated calcium carbonate and kaolin clay. The present study was carried out with an aim to synthesize calcium sulphate using waste procured from phosphoric acid industry and to study its impact on the rheology of coating color as well as optical properties of coated paper. Addition of calcium sulphate improved the water retention property of coating color which can be helpful for improving the machine runnability. The results also revealed that calcium sulphate can be used as a pigment to produce coated paper of high brightness and whiteness. The brightness and whiteness of the coated paper were improved 4 and 15 points, respectively by using 50 parts of calcium sulphate as a pigment replacing clay from the coating formulation. The surface strength in terms of IGT pick value of coated sheets was found significantly comparable using calcium sulphate as pigment. The print gloss results were observed analogous with matt grade coated paper.     

Decoloration of vegetable oils and oleoresins with recovery of unaltered pigments

The present study confirms that N,N-dimethylformamide for the extraction of chloroplast pigments from vegetable tissues shows no differences from the usual acetone or methanol. Therefore, it can be applied to fats, as it allows separation of lipids and pigments by means of phase distribution between light petroleum ether and N,N-dimethylformamide. The ether phase retains the decolored fatty matter, and the pigments dissolved in N,N-dimethylformamide can be recovered totally unaltered. This method has been applied to oleoresins and oils from different products and origins. Satisfactory results have been obtained in terms of the degree of decoloration and the percentage of oil recovered. At the same time, the unaltered pigment concentrate obtained from the hypophase could be used as a color enhancer in the chemico-pharmaceutical industry.     

Pigments,Plastics and Progress

The performance of organic pigments in plastics is reviewed briefly. Reference is also made to the newer inorganic pigments. Considerable progress has been made in developing pigments with greatly improved properties, but there are many gaps that need filling before the plastics technologist will have an adequate range of pigments available. A start has been made to develop pigments especially for the plastics industry, either by modifying the surface of the pigment crystals to render them more compatible with the polymer or by enveloping their discrete particles in a medium to prevent agglomeration, but much has still to be done.     

最新一代的Gemini表面活性剂在有机颜料生产中的应用（二）

有机颜料在合成过程,分散过程和表面改性处理中,需要各类具有润湿,分散功能的助剂。由于有机颜料本身的特殊性,对助剂的要求很高,目前市场上供应的助剂不能完全满足要求。Gemini表面活性剂由于独特的性能,优异的表面活性;大大超过传统的表面活性剂,赋予低表面张力,有利于有机颜料的润湿;超低的临界胶束浓度和降低表面张力效力,有利于有机颜料的分散稳定性。它在有机颜料领域的应用正在开始,期待进一步的开发。     

Effect of the milling process on the properties of CoFe2O4 pigment

In this study, CoFe₂O₄ pigments were synthesised using both co-precipitation and conventional ceramic methods. Pigment particles prepared using the conventional ceramic method were subsequently milled to submicron size. The effects of the solvent, dispersant and milling type in the milling process were investigated. This study showed that planetary milling in a diethylene glycol (DEG) medium with sodium tripolyphosphate (STPP) was an effective method for producing submicron-sized pigment powders from pigments synthesised using the conventional method. With this method, submicron-sized pigment particles (approximately 190 nm) were obtained after milling for 4 h. Planetary milling was more efficient in reducing particle size compared to attrition milling. Co-precipitated pigment had a more intense black colour, due to the nanoscale particle size (<100 nm). However, conventional ceramic pigments also had an adequately intense black colour that increased after milling compared to unmilled conventional pigments. When considering production of industrial scale submicron-sized pigments, the milling of these pigments to submicron size can be a good alternative method for the production of ink colourants.     

最新一代的Gemini表面活性剂在有机颜料生产中的应用（一）

有机颜料在合成过程,分散过程和表面改性处理中,需要各类具有润湿,分散功能的助剂。由于有机颜料本身的特殊性,对助剂的要求很高,目前市场上供应的助剂不能完全满足要求。Gemini表面活性剂由于独特的性能,优异的表面活性;大大超过传统的表面活性剂,赋予低表面张力,有利于有机颜料的润湿;超低的临界胶束浓度和降低表面张力效力,有利于有机颜料的分散稳定性。它在有机颜料领域的应用正在开始,期待进一步的开发。     

Synthesis by pyrolysis of aerosols and ceramic application of Cr-doped CaYAlO4 red–orange pigments

The synthesis of red–orange Cr-doped YCaAlO₄ pigments has been improved (softer thermal conditions and lower environmental impact) and optimised by using the pyrolysis of aerosols method. We also study the crystallochemical features of the Cr chromophore with special emphasis on its oxidation state which has not been yet clarified, finding that Cr(III) and Cr(IV) species are present in the octahedral and interstitial tetrahedral sites of the YCaAlO₄ lattice, respectively. Finally, the applicability of this system as ceramic pigment was tested using conventional industrial glazes. A change from orange to pink shades was detected after glaze firing, which is mainly attributed to the Cr³⁺ to Cr⁴⁺ oxidation.     

基料和颜料对乳胶漆光泽的影响

研究了建筑涂料中常用的相同基料、不同颜料,及相同颜料、不同基料时,漆膜光泽随颜料体积浓度（ＰＶＣ）变化的关系。随着ＰＶＣ的增加,漆膜光泽逐渐减弱,但不同的基料及颜料对漆膜光泽的变化影响程度不同。主要探讨了漆膜光泽与基料颜料的折射率、密度、粒径的关系。漆膜的光泽随着基料和颜料折射率的增大、粒径的减小而增大;随着颜料密度增加、颜料分散性降低而减弱。     

Coatings with metallic effect pigments for antimicrobial and conductive coating of textiles with electromagnetic shielding properties

Effect pigments were originally developed to realize advanced optical effects by coating on several types of material surfaces. However, metallic effect pigments are expected to be valuable for many other applications, such as antimicrobial effects, electrical conductive coatings, or shielding against radio waves (electromagnetic shielding). Accordingly, the aim of this article is to evaluate the advanced properties which can be realized by application of coatings containing metallic effect pigments onto textile materials leading to new functional textiles. In total, four different metallic effect pigments were investigated and compared to silver and graphite pigments. By application of coatings with copper- or silver-containing effect pigments significant antibacterial properties against E. coli and S. aureus can be realized. To achieve electric conductive textiles, which also enable effective shielding against radio waves, a copper pigment carrying a silver coating leads to the best properties. Altogether, an effective coating method is presented to achieve functional textiles that offer a broad range of possible applications.     

Associative polymer/particle dispersion phase diagrams III: Pigments

The colloidal interactions of both HEUR and HASE associative polymers with pigments in the presence of dispersant are complicated and subject to a number of variables. The objective of this work was to clarify the conditions needed to achieve good pigment dispersion in associative thickener systems by characterizing particle dispersion behavior. This had previously been done for latex particles, but not for pigments such as TiO₂. Good dispersion leads to optical properties, such as gloss and hiding, that are superior to nonassociative thicknener systems. Pigment dispersion phase diagrams represent a good way to visualize the complex interactions among pigments, dispersant, and thickener. The two most important variables were found to be pigment type (i.e., surface composition) and dispersant composition. Associative thickners can yield good pigment dispersion or flocculation, depending on the correct matching of dispersants and pigment type. Because of the hydrophobic functional groups governing associative thickner behavior, dispersants having some hydrophobic character yielded the best pigment dipersions and optical properties because they could couple the pigment particles with the associative thickener network. Interior-grade TiO₂ tended to yield better dispersions and optical properties than exterior-grade TiO₂. Optimized associative thickner systems generally had improved optical properties over comparable nonassociative systems. Optical properties correlated well with particle dispersion behavior as displayed by the dispersion phase diagrams. Presented at the Tess Symposium of the 230th American Chemical Society National Meeting, Aug. 28–Sept. 1, 2005, in Washington, D.C.     

Dichromatism causes color variations in leaves and spices

Although the color phase (hue) of plants plays fundamental roles in quality of foods and horticultural species, principles of variations in hues of plant materials are neither fully understood nor extensively examined by researchers. This may be partly because plant colors are determined by complex physicochemical factors non‐understandable to most biologists. For example, hue of soluble pigment has been demonstrated to change at different thickness of a layer or pigment concentrations in exceptional substances such as pumpkin seed oil. Such strange effect (dichromatism) of layer thickness on pigment hue was previously explained by application of Beer–Lambert law on absorbance spectra (Naturwissenschaften 2007;94:935–939). In this report, we demonstrate dichromatism in plant leaves and red spices. Dichromatism of these materials can be quite simply observed by extraction and dilution of pigments with dimethylformamide, a scarcely evaporating organic solvent. Hue of pigment solutions gradually changed with dilution from green to yellow‐green for leaves, and from red to yellow for spices. These changes were also explained by changes in absorbance spectra with dilution, nevertheless spectra of absorption coefficient were stable. Dichromatism in leaves caused uniform negative correlation between lightness and hue in any plant species examined. Such correlation was successfully explained by calculation with a normalized RGB color matching function. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 605–611, 2015