Basic knowledge of water-based coating formulation

 Water-based coatings, including water-based wood paints, are water-dispersed media and thinners, but not commonly used solvent-based coatings, and their formulation system is a more complex system. The formulation is designed not only to pay attention to the type of polymer, emulsion and dispersant performance, but also to select various additives and take into account the interaction between the components to make a reasonable match. Sometimes, we also have to select special additives for special requirements, and eventually form the applicable formula
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. Because the content of combing is also quite detailed, so the author organized into (top), (middle), (bottom) three series with you to explore, welcome guidance!
basic composition of the formula:
1) water-based resin: This is the substing of the film, determines the main function of the paint film.
2) Membrane additives: After water evaporation, the emulsion or dispersion particles form a uniform dense film, and improve the film-forming at low temperature conditions.
3) Anti-foaming agents and de-foaming agents: inhibit the bubbles produced in the lacquer liquid during production and allow the resulting bubbles to escape from the surface and break the bubbles.
4) leveling agent: improves the construction performance of the paint to form a flat, smooth coating.
5) Wetting agent: improve the wetting performance of the lacquer liquid to the substrate, improve the leveling, increase the adhesion of the lacquer film to the substrate.
6) Dispersant: Promotes the dispersion of pigments in the paint solution.
7) Fluidizer: Provides good fluidity and leveling of paint materials, reducing the disadvantages of the coating process.
8) Thickener: Increases the viscosity of the lacquer liquid, increases the thickness of the wet film that is applied once, and has anti-precipitation and anti-layering effects on putty and solid paint.
9) Preservatives: Prevents mold in lacquer during storage.
10) Flavors: Make lacquer liquid have a pleasant odor.
11) Colorant: Mainly for color paint, so that water-based paint has the desired color. Colorants include pigments and dyes, pigments for solid paint (painting without exposing wood grain) and dyes for transparent paint (painting that reveals wood grain).
12) Fillers: Mainly used in putty and solid paint to increase solids and reduce costs.
13) pH regulator: Adjust the pH of the lacquer liquid to stabilize it.
14) Wax lotion or wax powder: improves the scratch resistance of the paint film and improves its feel.
15) Special additives: additives added to the special requirements of water-resistant paints, such as rust inhibitors (iron tank packaging to prevent premature rust), hardeners (to improve the hardness of the paint film), anti-lighting agents (reduced paint film gloss), anti-scratching agents, slippers (improved paint film hand) anti-adhesive agent (prevents coating lamination adhesion), crosslinker (made into two-component paint to improve comprehensive performance), water repugnant agent (makes the coating have a lotus leaf effect), wear inhibitor (increases the wear resistance of the coating), UV absorbent (outdoor paint anti-aging, prevent yellowing) and so on.
16) Ionized water: The formula is often designed with a small amount of deionized water added for painting.
water-based resin
-based paint formulation, the substation is the key part to form the paint film and determine the performance of the paint film. Formula design should try to improve the amount of water-based resin, accounting for 60-70% of the volume ratio, so that the effective film content in the lacquer liquid as much as possible, so as to ensure that the paint made of a coated paint film thicker, high plumpness. Among its main components of water-based resins, stability, weather resistance, light resistance, corrosion resistance and other performance is very good is water-based acrylic resin. Water-based acrylic resin made of water-based coating film-forming performance is good, color preservation is also very good, and both non-polluting, good construction performance and so on.
water-based acrylic resin is polymerized from acrylic emulsions. Acrylic emulsions, due to their versatility, weather resistance and diversity, have been widely used in various fields of the coating industry. Water-based acrylic emulsions are made from acrylic monosome-based vinyl monosomes polymerized by emulsions. Various additives such as emulsifying agents, stabilizers and pH regulators have been added to the polymerization process, and the system is quite complex. Water-based acrylic emulsion made of paint film has good weather resistance, not easy yellow hair, high hardness, good gloss. In recent years, with the continuous development of water-based acrylic emulsion polymerization technology, multiphase polymerization, nuclear shell technology, self-linking technology and the application of polymer surfactants, and nuclear shell polymerization and other technologies to further improve and improve the nature of water-based acrylic emulsion, so that water-based acrylic emulsion to adapt to different construction and use conditions of the needs of the use of continuous expansion. Today, the application of water-based acrylic emulsions has been extended to industrial applications where performance requirements are higher.
polyurethane dispersion
polyurethane material is a class of large molecular compounds in molecular structure with urethane structure, usually made of isocyanate and polyols by polygasing reaction. Polyurethane polymers have both polar and flexible chain segments that make them physically cross-linked. When used well, its polar tube energy group can also be further chemically interlinked. These molecular properties give polyurethane materials high strength, toughness and solvent resistance. Polyurethane, as a high strength, good weather resistance, strong adhesion of high-quality materials, has been widely used in the field of coatings.
according to the type of isocyanate used in the preparation of polyurethane, polyurethane emulsion and the corresponding paint can be divided into two categories: fat family type and aromatic family type. The paint film of the fat family has excellent weather resistance and yellow degeneration; Aromatic aquatic polyurethane is mostly used to make interior decoration paint. The resulting particle sizes by polymerization are polyurethane emulsions and polyurethane dispersions (Polyurethane Dispersions PUD). Water-based polyurethane dispersion, the use of a unique process to disperse polyurethane particles in the water, so as to achieve water-based film-forming effect. Similar to other emulsion film-forming processes, the effect of film-forming depends on the ability of polymers to penetrate each other between particles. In order to increase penetration, on the one hand, the polyurethane molecular chain should be soft enough, good mobility, on the other hand, emulsion particles should be as small as possible, which can increase the contact area between particles, reduce the distance of polymer movement. Water-based polyurethane dispersions usually have nanoscale particle sizes, translucent appearance and even complete transparency, and are one of the best water-based paint substrates. Water-based polyurethane dispersions are sometimes referred to as nano-emulsions to distinguish them from ordinary emulsions that appear white.
water-based acrylic emulsion
water-based acrylic emulsion formulation needs to be considered: water-based acrylic resin composition in the modulation of water-based paint formula, the choice of emulsion raw materials is the most important decision of engineers. The main properties of coatings are determined by resins. A wide variety of water-based acrylic emulsions, including polystyrene-acrylic emulsions, are mixed with fish on the market. The composition of different water-based acrylic resins has a great influence on the film-forming nature and cost of water-based paint. Here's a brief discussion of a few factors.
1) Styrene
polyacrylate emulsions are introduced into the monomer mainly because they provide a higher glassy forwarding temperature (Tg), thereby increasing the hardness of the film, and another reason is cost. Styrene is used in the packaging industry is very large, is the oil industry's most important, mature downstream products, low prices but by the macro-economic impact. However, the introduction of styrene, especially when its content is more than 15% of the total monosome, will also bring many negative effects on water-based paint film. First of all, the polymer chain segment containing styrene lacks flexibility, the macro performance is water-based paint film hard and not tough, and styrene contains benzene ring, is the absorption of ultraviolet light, the monomer content is high, ultraviolet light through the adjacent benzene ring will be polymer Chain has shear reaction, so that the water-based paint film brittle, gloss decreased, life is reduced, styrene structure also determines that it has affinity for many organic solvents, water-based paint film solvent resistance is not other resins have a significant gap.
2) Acrylic monosomes
acrylic monosomes, performance and price vary greatly. The most commonly used in China is acrylate butyl, the lowest cost of changing the unit, is most emulsion manufacturers used with styrene matching, the manufacture of cheap wall paint emulsion monosomy. Its function is to provide the flexibility of water-powered paint film. Since the acrylic polymer main chain does not contain a substrate other than ester-based, the main chain and ester-based side chain flexibility are good, so that the water-based paint film lack of hardness. Although this type of polyacrylate emulsion is the choice of interior and exterior wall coatings, but as a hardness and toughness requirements are high wood paint, performance is not enough.
3) Methyl acrylates monosomes
methyl acrylates monosomes, than acrylates monosomes on the performance of another step. Due to the addition of methyl on the main chain of methyl acrylic polymers, the activity of its main chain is limited, the main chain steel is enhanced, while the ester-based sidechain provides flexibility, making methyl acrylates monomer with the best balance of hardness and toughness, such as polymethyl Acrylates (methylate) is commonly known as lyphosate, methyl acrylates monoidos, because they do not contain benzene rings, so that they are more resistant to ultraviolet erosion, durability, and solvent resistance than styrene has a clear advantage.
, water-based acrylic resin manufacturers have many choices for monosomes, which can not only change their types, but also change their relative proportions and compositions. Water-based paint manufacturers in the selection of water-based acrylic emulsions, can not only consider "pure propylene" or "phenyl" these empty conceptual terms, should be water-based acrylic resin and the actual performance of its formulation as a measure.
When choosing a water-based acrylate emulsion, you should not only consider the empty conceptual terms "pure propylene" or "phenylpropyl" and should be measured by the actual performance of the water-based acrylic resin and its formulation!
film additives,
that make up emulsions or dispersions, usually have a glassy temperature higher than room temperature. In order for the emulsion particles to blend well into a uniform paint film, the minimum film-forming temperature (MFFT) must be reduced using film-forming additives. Film-forming additives are a class of small molecular organic compounds, which are present in lacquer film and eventually escape and evaporate.
film additives are an important part of coating organic volatiles (VOCs), so the less film additives should be used, the better. The choice of film-forming additives should give priority to compounds that do not fall within the scope of VOC restrictions, but are not too volatile and have high film-forming efficiency. The amount of film-forming additives depends on the amount of emulsion or water dispersion in the formulation and the glassing temperature. Large amount of emulsion or water dispersion and high Tg of polymer, membrane additives should also be large, the reverse amount is less, formula design, first consider film additives accounted for about 3%-5% of emulsion or water dispersion, or accounted for 5% to 15% of emulsion or dispersion solids. However, the amount of polymer emulsion with Tg exceeding 35 degrees C may need to be increased to ensure the reliability of membrane additives at low temperature, and the dosage of film additives should be gradually increased until the low temperature (around 10 degrees C or less) coating can form a uniform paint film without cracking and powdering, to find out the minimum dosage of film additives.
it is not desirable to use film-forming additives up to 15% or higher of emulsions or dispersants, consideration should be given to replacing other film-forming aids for retesting. In addition to reducing the minimum film temperature and increasing the density of the paint film, film-forming additives can also improve the performance of the paint, increase the leveling of the paint, extend the opening time, improve the storage stability of the paint, especially low temperature antifreeze.
film-forming additives of water-based coatings are generally alcohol ether-type solvents, the most commonly used are diethanol ethers, propylene glycol ethers and N-methyl propranone and other film-forming additives, and has a high and low boiling point. Water-based coatings in the summer construction, moisture volatile faster, that is, the table dry relatively fast, some of the moisture may be closed in the coating film before not drying out, resulting in the coating of the film whitening or leveling the disadvantages of bad. Therefore, by adding a small amount of appropriate and suitable high boiling point solvent to slow down the drying speed of the coating film, extend the opening hours of the coating film, improve its construction performance and coating appearance. In winter, due to the low temperature, water-based coating drying speed is slower, that is, water evaporation is slower, but film-forming additives are relatively faster than water evaporation, perhaps part of the water evaporation together, so that water-based coating can not form a dense coating, resulting in water-based coating film whitening and cracking phenomenon. Therefore, when adding film additives, we must consider overcoming the construction of water-based coatings in different seasons, but also consider that it is as fast as possible drying speed, which is also the most difficult technical points of water-based coatings, especially Tg higher acrylic dispersion is difficult to solve the problem. Therefore, a variety of film-forming additives to match is the best choice.
film additives have a non-resin system compatible problem, in one system a good film additives in another water-based wood paint may cause system instability, or serious, or poor re-painting. The formulation should be designed with this in full consideration, and the best film-forming additives and their dosages have been tested.