Effect of ultrasonic treatment on structure and properties of ethylhydroxyethylcellulose polymer adsorption layer on inorganic pigments in aqueous dispersion

The course and the result of the surface modification of titanium dioxide and ferrous oxide pigments in aqueous dispersion by ethylhydroxyethylcellulose (EHEC) without and with mechanical treatment of the dispersion by ultrasonic power was studied by the electrokinetic sonic amplitude (ESA) method. The evaluation of the ESA data showed that the ultrasonic treatment causes a significant thickness increase of the EHEC layer on the pigment which is primarily attributed to the ultrasonically induced activation of the pigment surface. The thickness of the polymer adsorption layer derived from ESA measurements was confirmed by TEM investigations. The ultrasonic treatment leads to significant changes of the properties of the adsorption layers and is a promising method for the surface modification of pigments with regard to dispersion stability.     

TiO2 pigment structure and kinetics of PVC weathering

The influences of doping the core of TiO₂ pigments with Al₂O₃ and of various inorganic surface modifications on the rate of poly(vinyl chloride) (PVC) weathering are investigated. The kinetics of loss of gloss are transformed into photooxidation rates by using Weibull statistics of failure, and a scheme of two consecutive reactions is fitted to the intermediate losses of brightness observed for the most photoactive pigments. When Ca/Zn stabilizers in PVC are exchanged for Pb stabilizers, gloss degradation rate doubles, and the energetic spread of irradiation defects broadens. No indications for specific interactions between pigment and stabilizer are found.     

Hybrid coating pigments of poly(styrene-co-maleimide)/kaolin/alumina trihydrate for paper coating

Novel organic–inorganic hybrid pigments were prepared by in situ imidization of poly(styrene-co-maleic anhydride) (SMA) aqueous dispersion with ammonia in the presence of inorganic pigments, i.e. kaolin (K) or a mixture of kaolin (K)/alumina trihydrate (ATH). The objective was to allow the organic nano-particles of poly(styrene-co-maleimide) (SMI) to precipitate during their formation onto the surface of the inorganic pigment(s) and to investigate their potential in paper coatings. The produced hybrid pigments were characterized by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT-FTIR), scanning electron microscopy (SEM), wide-angel X-ray diffraction (WXRD) spectroscopy and their particle sizes were determined by dynamic light scattering technique. By FTIR measurements the formation of maleimide was confirmed and the existence of strong hydrogen bonding between organic and inorganic components could also be detected. Whereas, the SEM images revealed that the surface of silicate layers had successfully been to a large extent covered by the organic nano-particles to give raise to novel hybrid particles. In addition, the particle size measurements support the observation that the organic nanoparticles for the most part had been chemically or physically attached to the larger inorganic particles. Thus, this in situ imidization process in the presence of clay particles provides a neat method of dispersing the formed nanoparticles onto the inorganic surface through hydrogen bonding. The produced hybrids were applied as auxiliary pigments in paper coating where they improved gloss without roughening the paper surface.     

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.     

Use of poly(2-vinylpyridine)-b-poly(?-caprolactone) copolymers as pigment stabilizers in powder coatings

Four poly(2-vinylpyridine)-b-poly(ɛ-caprolactone) copolymers, differing in buoy block length and anchor/buoy block length ratio, have been used as TiO₂ pigment dispersants in a polyester powder coating resin. When the TiO₂ surface was fully covered with the block copolymers, the colloidal stability of the TiO₂ dispersions at typical curing temperatures was significantly improved because of the formation of a steric layer around the pigment particles. As a result, powder coatings with excellent flow, high gloss, and low haze values were obtained. Because of the high affinity of the dispersants for the TiO₂ surface, pretreatment of the pigments with the block copolymers was not necessary. At full pigment surface coverage, the chain length of the stabilizing polymer had little effect on the performance of the dispersants used. Dept. of Polymer Chemistry and Coatings Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.     

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.     

Surface modification of organic pigment particles for microencapsulated electrophoretic displays

The surface modification of Pigment Yellow 13, Pigment Red 254 and Pigment Blue 15 to improve their electrophoretic properties in electrophoretic suspension were studied. The particle size distribution and the surface morphology of the modified pigments were determined, the presence of the functional groups on the surface of pigments was confirmed, and the dispersion stability and chargeability of pigments suspended in electrophoretic slurry were characterized. For the application of microencapsulated electrophoretic displays, the colored microcapsules containing the modified organic pigments were prepared and spread on an ITO coated conducting film. A working prototype of electrophoretic display was successfully fabricated in this approach.     

Research on the Influence of the Type of Surfactant and Concentrator in Aqueous Dispersion of Pigments

This work reports tests performed to evaluate the stability of aqueous dispersions of inorganic oxide pigments with different specific surface areas, with the use of anionic and non-ionic surfactants and concentrators. Color mixtures of oxide compounds of blue, green, olive and brown with the unit cell spinel structure were used as pigments. The sodium salt of sulfosuccinic acid monoester, oxyethylenated nonylphenol and ethoxylated derivatives of lauryl alcohol, fatty alcohol and fatty amine were used as surfactants. The concentrators used were: poly(vinyl alcohol), the sodium salt of carboxymethyl cellulose as well as a water-based polyurethane oligomer. The highest dispersion efficiency was found for dispersed systems in which surfactant and concentrator were incorporated in the formula. The one containing the sodium salt of carboxymethyl cellulose or polyurethane oligomer with ethoxylated saturated fatty alcohol or fatty amine was found to be the most efficient. It was discovered that a higher dispersion efficiency corresponds to pigments with larger specific surface. The efficiency is also found to improve when the concentrator is an acrylic polymer or copolymer made up of two acrylic species. In this case, the concentrator interaction with the surfactant is more effective if the value of its boundary viscosity number is higher. This observation confirms the existence of interactions between macro-chains of the concentrator and surfactant molecules forming micelles with the pigment particles.     

分散剂对红色颜料分散体系稳定性的影响及其在白板笔墨水中的应用

以高分子化合物——聚乙烯醇缩丁醛(PVB)、聚氧乙烯聚氧丙烯嵌段共聚物(F68)、聚乙烯吡咯烷酮(PVP)及其分别与非离子型表面活性剂脂肪醇聚氧乙烯醚(AEO-6)复配作为分散剂,研究不同分散剂对醇溶性白板笔墨水红色颜料分散体系稳定性的影响。通过离心分离-吸光度测试、粒径分析判断其稳定性;通过流变性测试探究高分子化合物与AEO-6之间的作用关系。将稳定性好的分散剂用于制备红色白板笔墨水,并通过流变性测试、粒径分析表征墨水的稳定性能。结果表明,采用3种高分子分散剂的红色颜料分散体系稳定性好,且添加质量分数为1%PVB的体系稳定性最佳。在高分子分散剂与AEO-6复配分散的颜料体系中,高分子分散剂对体系稳定性起主导作用,AEO-6并没有起到明显的作用。在红色白板笔墨水中,PVB分散的墨水体系稳定性最佳,此结果与红色颜料分散体系相一致。     

TiO2对聚氯乙烯紫外光稳定与催化降解的影响

综述了普通和纳米TiO_2对聚氯乙烯(PVC)的紫外光稳定和催化降解的机理及研究进展,以及包覆和掺杂改性对TiO_2光稳定和光催化性能的作用。金红石型纳米TiO_2具有优异的紫外光稳定特性,锐钛型纳米TiO_2表现出极强的光催化活性。无机包覆过的金红石型TiO_2对PVC有明显的保护作用。有机改性则能提高锐钛型TiO_2的分散性,从而提高其对聚合物的光催化效率。过渡金属离子掺杂可在TiO_2晶格中引入缺陷位置或改变结晶度,从而改变PVC的光降解速率。     

聚氯乙烯树脂的物理共混增韧改性研究新进展

综述了近年来国内外对聚氯乙烯（PVC）物理共混改性研究的方法及其增韧机理。重点介绍了弹性体增韧、有机刚性粒子增韧、无机刚性粒子增韧及纤维状填料增韧的研究进展,并对目前物理共混改性增韧PVC所存在的主要问题进行了分析,展望了其发展趋势。     

Stability of pigment and resin dispersions in waterborne paint

The stability of a colloidal dispersion in a waterborne paint system, which consists of dispersed pigment and polymeric particles (dispersion or emulsion) along with a water-soluble acrylic polymer, was investigated. It was found that adsorption of appropriate ultrafine particles to the relevant particles could stabilize these particles against flocculation, leading to lower viscosity and yield value. The gloss and smoothness of the resultant films are notably improved. As the stability of the colloidal particles in an aqueous system is strongly dependent on the electrostatic effect, the effect was evaluated by measuring the ζ-potentials of the relevant colloidal particles. The ζ-potential is the electric potential on the outside of the surface layer, which includes the counterions around the particle. The ζ-potentials of a series of pigments in a solution of a water-soluble polymer were determined. By arranging the pigments according to their ζ-potentials, an order of basicity-acidity was established for pigments in a waterborne system, and the order was found to be different from that of solventborne systems, thought to be due to adsorbed counterions. After dispersing the pigment sufficiently with an appropriate polymer dispersant, ultrafine particles (of size under 0.05 μm) of lower refractive indexes were adsorbed to the surface of the pigments and polymeric particles. The adsorption layer of ultrafine particles can modulate the ζ-potentials of various colloidal particles to bring them into a certain range, so that the co-flocculation tendency between different colloids is remarkably diminished providing quite stable paint compositions by both electrostatic and steric hindrance effects.     

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.     

有机颜料与无机颜料电子墨水稳定性研究

电泳显示型电子纸的主要性能由电子墨水的性能决定,电子墨水的稳定性又是影响图像显示的重要参数。本研究选择该领域比较成熟的有机颜料电子墨水和无机颜料电子墨水配方,通过放置观察,乳液稳定性测试,密度计测试电泳图像密度等方法,对2类电子墨水的稳定性做了对比,结果显示有机颜料电子墨水稳定性要优于无机颜料电子墨水。     

Uses of electron‐beam irradiation to prepare pH‐ and temperature‐sensitive hydrogels from reactive poly(vinyl alcohol) grafts

Thermosensitive poly(vinyl alcohol)‐graft‐(maleic anhydride), PVA‐MA, and poly(vinyl alcohol)‐graft‐(N‐isopropylacrylamide maleic anhydride) (PVA‐MA‐NIPAAm) copolymers containing carboxyl groups were prepared using electron beam irradiation at dose 80 kGy. The swelling ratios of the cross‐linked gels were measured at various temperatures. The LCST values were measured using DSC technique. The temperature dependence of the swelling ratios of the cross‐linked copolymers and terpolymers were measured at different temperatures. The swelling ratios of copolymers increased with increasing temperature up to 25–38°C, then decreased. The swelling behavior of both copolymers and terpolymers was referred to formation of hydrogen bonds between amide group of NIPAAm moieties and carboxyl group in MA moieties and to hydrophobic interaction due to methyl groups of NIPAAm. The swelling behaviors of these gels were analyzed in buffer solution at various pH. Swelling ratios of all gels were relatively high and they showed reasonable sensitive to pH. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

有机颜料商品化及表面改性(修饰)技术

本文讨论了有机颜料商品化剂型的重要特性,颜料的表面改性(修饰)技术的基本原理,主要改性工艺技术的类型,诸如以经典表面活性剂改性(阴离子、阳离子、两性及非离子表面活性剂,松香酸、松香胺及有机烷胺等);颜料衍生物改性技术,(添加方式及处理过程中生成);研磨,溶剂处理及酸溶与酸胀;聚合物处理(制备物,高分子分散剂与包膜技术)及以无机化合物实施改性(包核、表面键合及低温离子溅射)。并对偶氮、酞菁及杂环三大类别主要颜料品种的商品化与改性实例进行了介绍。     

Synthesis and properties of hydrophobically modified water-borne polymers for pigment stabilization

Some aspects of the molecular design of pigment stabilizers are discussed. The approach of employing copolymers with pigment-affine segments and matrix-affine segments will be particularly addressed. First experimental results obtained with amphiphilic block copolymers and amphiphilic graft copolymers with similar overall composition with regard to polar and relatively non-polar blocks of, e.g. polar backbone and relatively non-polar grafts will be presented. The comparison between the poly(acrylic acid)-polystyrene block copolymer and the graft copolymer with poly(acrylic acid) backbone and polystyrene grafts showed a similar stabilization of TiO₂ in water.     

Design of polymeric dispersants for waterborne coatings

Block and random copolymers of ammonium methacrylate and dimeth-ylaminoethyl methacrylate have been synthesized and tested as dispersants of various organic and inorganic pigments in formulations for waterborne paints. Blockiness of the co-monomer distribution is a prerequisite for good color characteristics in the final paint. It is however noteworthy that a tapered diblock (one-step anionic synthesis), a diblock copolymer with a regular change in composition from one block to the other one, has an interfacial activity quite comparable to the parent “pure” diblock copolymer (two-step anionic synthesis). The most interesting observation is that the poly(dimethylaminoethyl methacrylate) anchoring block can impart stability to dispersions of pigments as different as iron oxide, a blue Cu-phthalocyanine pigment, and a red organic pigment based on pyrrole in representative aqueous paint formulations. This type of diblock copolymer is promising for the design of universal dispersants. Center for Education and Research on Macromolecules (CERM), Sart-Tilman, B6, 4000 Liège, Belgium. Rijksstraatweg 31, P.O.Box 3, 2170 BA Sassenheim, The Netherlands.     

Weather stabilization and pigmentation of UV-curable powder coatings

A UV-curable powder coating based on an unsaturated polyester binder and a vinyl ether crosslinker has been tested for weathering resistance. Accelerated and outdoor weathering demonstrate the combined protective action of a UV absorber and a hindered amine light stabilizer (HALS). Successful coatings cure of various colors and shades from organic and inorganic pigments is also reported in this study. Curing performance mainly depends on pigment absorption and particle size. A combination of a bis-acylphosphineoxide and an α-hydroxy-acetophenone photoinitiator overcomes limitations imposed by filtering of UV radiation by the pigments and provides balanced cure. Ciba Specialty Chemicals Inc., 4002 Basel, Switzerland. DSM Resins bv. P.O. Box 615, 8000 AP Zwolle, The Netherlands.     

Mathematical modeling of pigment dispersion taking into account the full agglomerate particle size distribution

The purpose of this work is to develop a mathematical model that can quantify the dispersion of pigments, with a focus on the mechanical breakage of pigment agglomerates. The underlying physical mechanism was assumed to be surface erosion of spherical pigment agglomerates. The full agglomerate particle size distribution was simulated. Data from two previous experimental investigations were used for model validation. The first concerns two different yellow organic pigments dispersed in nitrocellulose/ethanol vehicles in a ball mill and the second a red organic pigment dispersed in a solvent-based acrylic vehicle in a three-roll mill. When the linear rate of agglomerate surface erosion was taken to be proportional to the external agglomerate surface area, simulations of the volume-moment mean diameter over time were in good quantitative agreement with experimental data for all three pigments. The only adjustable parameter used was an apparent rate constant for the linear agglomerate erosion rate. Model simulations, at selected values of time, for the full agglomerate particle size distribution were in good qualitative agreement with the measured values. A quantitative match of the experimental particle size distributions could be obtained using time-dependent fragment distributions, but this resulted in a very slight improvement in the simulated transient mean diameter only. The model provides a mechanistic understanding of the agglomerate breakage process that can be used, e.g., in the development of novel dispersion principles and for analysis of dispersion failures. The general applicability of the model, beyond the three pigments considered, needs to be confirmed.