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Selection of dispersant for Waterborne Coatings

2020-09-10 14:28:23

1. Dosage and development trend of dispersant for Waterborne Coatings

Waterborne coatings are environment-friendly coatings, with a market share of more than 60% in Japan, Europe and the United States, while the proportion in China is obviously low, less than 4%, and there is a large space for development. From 2011 to 2016, the market scale of China's waterborne coatings increased from 35.3 billion yuan to 54 billion yuan, with an average annual compound growth rate of about 9%. Some organizations predict that the average growth rate of waterborne coatings in the next five years will be 23%; by 2020, the output of waterborne coatings in China will reach 6.34 million tons. From the investment projects in 2016, water-based coating projects accounted for the majority.

According to the latest research report released by zon market research, the global market size of waterborne coatings in 2015 was US $58.39 billion, and it will reach US $78.24 billion by 2021, with a compound annual growth rate of 5%.

In recent years, with the continuous improvement of China's environmental protection laws and regulations and the enhancement of consumers' awareness of environmental protection, the paint market tends to be healthy and safe, and the comprehensive "oil to water" plan is becoming more and more intense. In the context of "oil to water" policy, the pace of China's paint industry reshuffle accelerated.

2. Price analysis of dispersant for Waterborne Coatings

"Natural selection". In today's competitive society, as long as any industry introduces competition, consumers will certainly benefit. Either improve the quality of service, or reduce the price of products. Water based coatings are no exception. As far as I know, the price of dispersants for waterborne coatings has been relatively stable, but there is a downward trend from time to time, especially for imported additives. Unless they have special properties, other products cannot be replaced. Otherwise, the pressure on their sales department will be very heavy, mainly because the price war is starting. Due to the rise of raw materials, the compression of market profit and the hostile suppression of price by competitors, coating manufacturers are constantly trying to reduce costs. Therefore, we think: the price fluctuation of waterborne coating dispersant will not be great, but there is still a great possibility of price competition in the future.

3. Classification of waterborne dispersants

There are many kinds of dispersants. It is estimated that there are more than 1000 dispersants in the world. According to its structure, it can be divided into three parts

① They are anionic, cationic, nonionic, amphoteric, electronegative and macromolecular hyperdispersants.

① Anionic surfactants: mostly composed of nonpolar, negatively charged lipophilic hydrocarbon chains and polar hydrophilic groups. These two groups are located at both ends of the molecule, forming an asymmetric hydrophilic lipophilic molecular structure. Its varieties are: sodium oleate, carboxylate, sulfate (r-o-so3na), sulfonate (r-so3na), etc. Anionic dispersants are widely used because of their good solubility.

② Cation type: it is a kind of nonpolar base band positive charge compound. This variety has octadecylamine acetate. Cationic surfactants such as alkyl quaternary ammonium salt, aminopropylamine dioleate, quaternary ammonium salt and specially modified polyamine phosphate have strong adsorption capacity and good dispersion effect on carbon black, various iron oxides and organic pigments. However, attention should be paid to the chemical reaction between cationic surfactant and carboxyl group in the substrate, which can not be used together with anionic dispersant.

③ Non ionic type: cannot ionize, not charged. Pigment surface adsorption is weak, mainly used in water-based coatings. Varieties include C17H33COO (CH2CH2O) NH, polyethylene glycol polyols and polyethyleneimine derivatives. Their function is to reduce surface tension and improve wettability. Adding appropriate amount of organosiloxane can prevent halo and floating color and improve leveling effect.

④ Amphoteric: a compound consisting of anions and cations. Typical applications are phosphate polymers. This polymer has a high acid value, which will affect the adhesion between layers. It is worth noting that.

⑤ Electronegativity: the organic groups of cation and anion in the molecule are basically equal in size, and the whole molecule is neutral but polar. Varieties are: Oil amino oleate

⑥ Polymer type (including high, medium and low molecular weight). Among them, the advanced and stable ones belong to polymer type, such as: A. block copolymer of polycaprolactone and polyethylenimine; B. reaction of polycaprolactone and triethylenetetramine; C. acrylate polymer prepared by group transfer polymerization, first adding methyl methacrylate, then adding dehydrated glyceryl methacrylate. d. Low molecular weight polyesters were prepared from polyhydroxystearic acid. Polyurethane and polyacrylate were prepared by introducing anchoring groups. Because one end of the anchoring group is entangled with the resin, the other end is wrapped by pigment particles. Therefore, the storage stability is relatively good. Of course, we should also pay attention not to use too strong solvent, because the solvent is too strong, in the case of high shear force, it will dissolve the anchor chain of these polymer super dispersants, and then cause the coarsening and flocculation of the pigment.

4. Principle of dispersant for Waterborne Coatings

Most dispersants disperse pigments and fillers by wetting, grinding and dispersing, coupling and wrapping. However, due to cost control, expensive dispersants can not be used in waterborne coatings. At present, anionic and nonionic wetting dispersants are commonly used. The principle is low surface tension, fast wetting pigment particles, and then through high shear force, such as disperser, grinder, etc., the pigment particles form semi flocculation (or controlled flocculation) dispersion. If the viscosity of the coating is relatively high at this time, there will be no coarsening resistance and serious flocculation phenomenon of the pigment, but if the viscosity is not well controlled, there will be long-term problems; some use coupling agent as dispersant to couple two different substances through hydrophilic group and sulfur water group. Like the bridging method, this method has the advantages of good comprehensive performance, good dispersion, less dosage and increased adhesion of the coating, but the disadvantage is that it is not a deflocculating group and is not suitable for the coating with high color development requirements. Through research and practice, it is suggested to use dispersant which can play a role of dewetting in waterborne coatings. Because the advantages are: good color rendering, high brightness and good luster.





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