Coating classification: new wetting agent for architectural coatings

Core tip: Introduction: Most architectural coatings consist of the following basic components: latex or latex, pigments and additives (see Fig 1) Each material plays an important role in the overall performance of the final coating, so the selection of raw materials is very important Any incorrect selection of materials may have a great impact on the performance of the coating For example, choosing the wrong paint base may result in poor durability, long drying time or poor adhesion to the substrate Similarly, choosing inappropriate wetting agent or surfactant will lead to poor dispersion of pigment, which will make the paint film dull or unsightly For building Application scope and advantages of roller ceramic coating Recommended introduction: the surface of ceramic rubber plate used for roller ceramic coating is cast into durable rubber plate by hundreds of independent small ceramic pieces Each ceramic piece has raised characteristics Under general conveyor belt pressure, thousands of unique cast bumps can produce positive traction, prevent slipping and extend the service life of conveyor belt roller At the same time, the bottom layer adopts high-quality rubber, which has strong elasticity and can play a good impact resistance role The scope of application of roller ceramic coating is one three six 83857180 (the same as V) 1 Roller coating in extremely harsh working environment 2 The belt joint is not suitable for fixing with iron buckle; 3 It is suitable for leather Paint Home: Introduction: most architectural coatings are made up of the following basic components: latex or latex, pigment and additives (see Figure 1) Each material plays an important role in the overall performance of the final coating, so the selection of raw materials is very important Any incorrect selection of materials may have a great impact on the performance of the coating For example, choosing the wrong paint base may result in poor durability, long drying time or poor adhesion to the substrate Similarly, choosing inappropriate wetting agent or surfactant will lead to poor dispersion of pigment, which will make the paint film dull or unsightly For architectural coatings, surfactants are usually used to reduce the free energy of the surface or interface of the aqueous phase, so that the pigment can be well wetted and effectively ground, and the base material can be uniformly wetted to form a defect free coating The good wettability of these applications has been confirmed by the fact that the surfactant can rapidly migrate into the new interface due to the low dynamic surface tension value during production and construction Low dynamic surface tension can promote all kinds of surfaces to be well wetted and pigments to be effectively ground, which leads to the increase of coverage and adhesion, the reduction of grinding times and the promotion of color formation Wetting process refers to the process that one fluid is replaced by another from the solid surface or solid-liquid interface Surfactant: a surfactant is a chemical that can be adsorbed to a surface or system interface Surfactants have characteristic molecular structure, including hydrophilic and hydrophobic groups Because of its amphoteric structure, at low concentration, the surfactant will agglomerate at the air / water interface and reduce the surface or interface tension Traditional surfactants connect a hydrocarbon tail (hydrophobic part) to the polar or ionic head (hydrophilic part) On the contrary, there are two hydrophobic and two hydrophilic ends in the same molecule One half of the double surfactant composed of a hydrophobic end and a hydrophilic end is connected to the spacer, and then connected to the other same parts of the molecule to form the double surfactant structure, as shown in Fig 2 Because of its unique molecular structure, double surfactants usually have more active surfaces than corresponding traditional surfactants Alkyne diols double double surfactants (2,4,7,9- four methyl -5- decyne -4,7- glycol and its ethoxy ester) are widely used in architectural coatings to improve wetting and foam control The transformation of solvent based coatings to water-based systems makes the manufacturers of additives face various challenges The surface tension of solvent-based systems is usually in the range of 25-35 Mn / m, mostly due to the solvents used in these systems On the other hand, the surface tension value of waterborne coatings is usually 50 Mn / m or higher, which is mainly due to the high surface tension value of water, which is 72 Mn / m It is necessary to reduce the surface tension of the coating when the substrate with surface energy of 35-45 Mn / M is coated with water-based system As shown in Fig 3, surface spontaneous wetting occurs only when the surface tension of the liquid is lower than the surface energy of the substrate In order to do this, surfactants or wetting agents are usually used in waterborne coatings Pigment dispersion: the process of preparing pigment dispersion is usually defined as the addition of three independent processes The first process is to wet the dry pigment to replace the air or other impurities on the surface of the pigment Once the pigment particles are fully wetted outside, they can be ground to make the large pigment aggregates and agglomerates become their original size particles The last step is to make the dispersion stable and improve the stability of color and viscosity, as well as the impact resistance and relaxation compatibility For waterborne coatings, the dispersion process faces some challenges For example, the high surface tension of water and the high interfacial tension between the continuous aqueous phase and the pigment must be reduced to sufficiently low to wet the pigment particles, as shown in Figure 4 In order to reduce the interfacial and surface tension, the surfactant which makes the pigment wet should be used These additives adsorbed on the surface of pigment reduce the interfacial tension In order to form stable molecules, pigments need to further adsorb surfactants When the surface and interface tension decrease, the grinding efficiency increases This results in shorter grinding time, lower energy required to form particles of original size, lower grinding temperature and lower viscosity of grinding slurry, which can increase the amount of pigment added The traditional wetting agents are alkylphenol ethoxylates (apes), which have excellent ability to wet the outer surface of pigment Due to the adverse effects of apes on endocrine system and health, there is an increasing trend to replace these materials in coating field Because of its hydrophilicity, APEs can stabilize foam and cause water sensitivity of the final film The use of these surfactants will also lead to the use of strong defoamer to control the formation of foams, which will eventually lead to defects in the final film Choosing suitable wetting agents for wetting can not only provide the most effective grinding and color formation, but also help prevent foam formation during production and construction Once the pigment aggregate is broken to the original size particles, the particles must be stabilized to prevent re aggregation or flocculation As shown in Fig 5, this stability can usually be obtained by potential resistance or electrostatic stability Electrostatic stability is achieved by a double layer, which is formed by molecules adsorbed on the surface of particles Steric stability is achieved by the interaction of hydrophilic segments of molecules adsorbed on the surface of particles in the aqueous phase These stable hydrophilic segments usually come from surfactants containing alkylphenol ethoxylates, neutralized alkylphenol sulfonates, or polymer molecules such as polyacrylic acid copolymers neutralized by amines According to the formula, an additive can be used for both wetting and stabilization processes Pigment type, construction parameters and cost are all factors to be considered when choosing dispersant combination The development of new surfactants: the auxiliaries used in building coatings are used not only for wetting pigments and substrates, but also for controlling foam It also improves durability, adhesion resistance, color formation, washability or scrub resistance, and helps to reduce VOCs A new type of surfactant without ape was developed to improve these properties in the most cost-effective way, at the same time, the VOV content of the final formula was minimized Application test: three types of coating formulations were prepared to evaluate the performance of this new type of wetting agent without ape See table 1-3 for the formula The new surfactant (Code: e2010) was compared with two kinds of surfactants (named low foam surfactant (lfape) with ape and hydrophobically modified ape (hmape), which were sold in the market Use all of these additives in the amounts recommended in the starting formula The physical properties of these surfactants to be tested are shown in Table 4 Performance characteristics: during the grinding process, it can effectively wet titanium dioxide pigment, improve the freeze-thaw stability and viscosity stability of the coating, control the formation of foam well, have better scrubbing resistance, improved fluidity and leveling, and will not add extra PVCs to the coating formula Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,