Common knowledge of coatings: basis and nomenclature of Waterborne Coatings

Core tip: 0 Preface Emulsion (Emulsion) and latex (latex) are both emulsions, but literally they can be very different The emulsion refers to the emulsion dispersed by the liquid, and the latex is the solid emulsion dispersed in the water Emulsion polymerization is an example of changing emulsion into latex First, the liquid monomer is emulsified into emulsion, then polymerized under the action of initiator, and the liquid particles are transformed into solid polymer particles, and the resulting products are latex However, the raw material of latex paint is called emulsion in our national standard What is added to the emulsion? 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 News: 0 Introduction emulsion (Emulsion) and latex (latex) are both emulsions, but literally they can be very different The emulsion refers to the emulsion dispersed by the liquid in the water, and the latex is a solid emulsion dispersed in the water Emulsion polymerization is an example of changing emulsion into latex First, the liquid monomer is emulsified into emulsion, then polymerized under the action of initiator, and the liquid particles are transformed into solid polymer particles, and the resulting products are latex However, the raw material of latex paint is called emulsion in our national standard What is the reason why latex additives are added to the emulsion and paint becomes latex? If it's just a matter of appellation, it doesn't matter much, because it's conventional, but here it's conceptual confusion, which can cause great confusion for beginners, and this confusion will affect the thinking of those who are considering how to further improve the coating performance At present, the development of water-based coatings is very fast In addition to latex paint, various kinds of water-based coatings have entered the market one after another, and the relevant terms are also very different There is a so-called water-soluble coating that appears in reports and literatures in large quantities The so-called water-soluble coating refers to the material can exist in the water medium in molecular form, and the polymer compound must have a large number of hydrophilic groups and hydrophilic groups to dissolve in water In addition, as a polymer solution, its viscosity and concentration are closely related The higher the molecular weight is, the higher the viscosity is In order to make the film have better physical and mechanical properties, the higher the molecular weight is If the film is not reactive, the concentration of the polymer solution used in the coating cannot be very high, that is, the solid content is very low As mentioned above, the performance of water-soluble coating is generally not good But many so-called water-soluble coatings have good performance Why? In fact, the so-called water-soluble coating is water diluble coating, which is the manufacturer's brand reduction The appearance of polymer aqueous solution and water diluable resin dispersion is very similar, both of them are transparent liquid Due to the lack of basic understanding of water-based coating, the two similar substances are confused Now, several basic concepts of waterborne coatings are put forward for discussion with you The purpose is to avoid similar problems of conceptual confusion when experts formulate relevant standards or noun standards for the country 1 Types of water-based coatings water-based coatings can be divided into two categories: water solubility and water dispersion according to their resin status The dispersibility of water can be divided into emulsion type, latex type, water soluble type, and so on Especially, the water thinning coating has different appellations according to the different preparation methods, such as water dispersions, self emulsifying coatings and so on The film-forming substance in water-soluble coating should exist in water in molecular form, but the polymer solution is different from the general small molecule solution, it has high viscosity and some fluorescence phenomenon The film formation of water dispersive coatings is in the form of molecular aggregate, usually with emulsifier or self emulsifiable group Water dispersible coatings, whose resin dispersions are usually prepared in organic solvents and then diluted by water, are commonly prepared by emulsion polymerization of microemulsions The particles of film-forming substances in water dilutive coatings and microemulsion latex particles are all in the nano scale range, which are different from latex with larger particles They are stable systems and transparent in visible light They are similar in appearance and water solubility, and easy to be confused with water-soluble resins 2 water soluble coating As mentioned before, there must be enough hydrophilic groups, such as hydroxyl group, amino group, ethoxyl group, etc too many hydrophilic groups make the coating film performance lose water resistance Therefore, except for some cases, generally, water-soluble resin is not used as the main film-forming material, but as the auxiliary agent of coating, such as polyvinyl alcohol as protective colloid, polyacrylic acid and water-soluble polyurethane As thickener, etc In China, polyvinyl alcohol or its derivatives have been used as the main film-forming materials of coatings, such as 106 coatings, which have lost market due to their poor performance, especially water resistance 3 water emulsion paint water emulsion is generally used as film forming liquid emulsifier directly emulsified However, the emulsion can only form a liquid film after coating To be a solid coating, there is a reactive film forming process Therefore, only the liquid or liquid film that can be dried can react with the water curing agent The alkyd emulsion can be obtained by emulsifying the alkyd resin of the liquid, and the alkyd emulsion coating can produce liquid film which can be cross-linked into solid film under the action of oxygen The alkyd emulsion has good fluidity, it is easy to infiltrate into the rust layer and the gap of the substrate, which is beneficial to the adhesion of the coating The emulsion of the alkyd resin or the dry oil is often mixed with latex to overcome the poor permeability of the latex paint Shortcomings Liquid epoxy resin can also be emulsified into emulsion, coated with water soluble or emulsified amine, and can be cross-linked and cured after film forming 4 water emulsion paint most of the water emulsion paint, including the so-called micro latex coating film is prepared by emulsion polymerization, such as various acrylic latex paint The monomer is emulsified and then polymerized into emulsion Emulsion polymerization has a characteristic that polymerization is carried out in micelles, and polymers with high molecular weight can be obtained Latex has another characteristic as a dispersion, that is, its viscosity and molecular weight are independent, but only related to the size and shape of solid content particles Therefore, even if the molecular weight is very high, the viscosity of the system is not necessarily high Because of these two characteristics, emulsion polymerization can obtain latex with high solid content and high molecular weight, so that high performance latex paint can be obtained The latex is a solid, and the solid film can be obtained without further reaction However, when the vitrification temperature of solid particles is very high, it is very difficult for particles to fuse into a film In order to overcome the difficulties of film formation, film-forming AIDS should be added in the preparation of latex paint The film-forming aids can be considered as a temporary plasticizer, which can evaporate after the film-forming of latex, and finally a solid solid film can be obtained It is not a rigorous argument that latex paint has the characteristics of fast drying in the relevant article In fact, it has the common disadvantages of water-based paint, and the drying speed is slow, even compared with alkyd paint The emulsion paint can be dried on the surface after 1-2 hours, but it takes more than 1 day to dry This is because the viscosity of the emulsion paint rises very fast in the dehydration process, which can quickly meet the surface drying requirements, but the film-forming process is not completed at this time, and the residual water and film-forming AIDS need a long time to escape, unlike alkyd resin film-forming process, Although the surface drying time is long, once the reaction glass transition temperature occurs, it will rise rapidly and reach real drying soon There are many kinds of water thinkable coatings, including water-based acrylic coating, water-based polyurethane coating, water-based epoxy resin coating and water-based alkyd resin coating The general preparation method of the matrix resin dispersion of the water diluble coating is as follows: polymerize or modify the resin in the water miscible cosolvent such as acetone, glycol ether and butanol, introduce carboxyl group (or amino group) into the resin structure, and obtain the organic solvent solution with high solid content, the general acid value is 40-60, Use amine (or carboxylic acid) to neutralize the carboxyl group (or amino group) in the solution, make the carboxyl group on the resin molecule salt, then dilute to a certain concentration with water to obtain water diluble dispersion, sometimes the solvent in the dispersion can be removed In water dispersible dispersions, water is not a solvent, the real solvent is organic solvent, and the resin molecules exist in the form of aggregates The resin molecules curl together into small particles The base is oriented towards water to form a particle protective layer similar to emulsifier Because it is a dispersion like latex (or emulsion), the viscosity of the system is independent of molecular weight In order to prove the difference between water-soluble dispersions and water-soluble resins, Professor cainowicks did the following experiments: free radical polymerization of butyl acrylate and acrylic acid in butanol, the ratio of the two substances was 90:10 When the organic solution was diluted with water, the viscosity change of the system was found to be abnormal, as shown in Figure 1, curve 1 Set the viscosity of polymer organic solution at point a in the figure When diluted with water, the viscosity will decrease rapidly For example, in the case of general solution dilution, continue to dilute, and the viscosity will not decrease slowly For example, in the case of general solution dilution, it is similar (curve 2 in Figure 1), but the viscosity will increase inversely when adding water, until it reaches a maximum value At this time, it may even make mixing difficult After adding water, the viscosity decreased rapidly, and the trend was similar to that of emulsion dilution (curve 3 in Figure 1) The home of viscosity coatings with n (BMA): n (AA) = 90:10 copolymer solution focuses on coatings, diatom mud, paint coatings, coating technology, news and coating of fire retardant coatings, diatom mud, paint coatings, coating technology, decoration knowledge and decoration effect map of fire retardant coatings,