In paints and coatings, solvents are widely used to dissolve or disperse various components used in formulations. Industrial coatings made with solvents dry up to 10 times faster than low-solvent alternatives at room temperature, making painting fast and easy along with other benefits such as long-lasting protection, excellent performance in extreme weather conditions and more.
The main factors to be considered when selecting the right solvent for industrial coating formulations from the range provided by the coatings market. Don't forget, find out the main evaluation of the different solvent groups (hydrocarbons, ketones, esters, alcohols, glycol ethers) and some of the specific solvents within them. Why are solvents needed in paints and coatings?
Solvents are added to paint and coating formulations to dissolve other compounds such as: pigments, additives and binders. Once the paint is applied to a surface, the solvent evaporates, allowing the resin and pigment to set into a layer of paint and dry quickly. Adding solvents to paint formulations helps optimize overall system performance. Even if almost no solvents are present in the final dry coating due to evaporation, their role is very important in coating formulation. the solvent controls the viscosity for the application. The solvent has an important effect on film quality, which is highly dependent on the evaporation rate of the solvent during drying. As a result it can affect properties such as film appearance, adhesion or even corrosion.
Tips on finding a suitable hydrocarbon solvent
Hydrocarbons (molecules consisting only of carbon and hydrogen) can be divided into aliphatic, aromatic, and mixed.
• Aliphatic solvents are linear, branched or cyclic hydrocarbon chains like pure solvents such as hexane.
• Aromatic solvents featuring a benzene group (cyclic 6 carbon structure such as toluene and xylene.
• Mixtures of aliphatic and cyclic hydrocarbons are commonly known as mineral or white spirit and special boiling pound spirit. Aromatic solvent mixtures are also available.
1. Special boiling point spirit (flash point < 21°C) includes different grades with different flash points and a fixed boiling range. They are solvents that evaporate very quickly and are therefore used for fast drying coatings
2. Mineral or white spirit (generally with a flash point > 21°C) is also available in different grades with different flash points and a fixed boiling range. Their names usually refer to their nayal point ((30°C, 40°C, 60°C …). They are commonly used for oil and alkyd based resins.
3. Mixtures of aromatic hydrocarbons (sometimes called naphtha solvents are usually aromatic petroleum fractions (c9 to c13) of varying concentrations that have a fixed boiling point range. They are commonly used in many industrial coatings as part of solvent systems even if they try to avoid them if possible.In general, aromatic solvents have a higher solubility than aliphatic.
4. Toulene and xylene are commonly used with phenolic and amino formaldehyde in hot hardening systems as well as with alkyd resins.
5. Spirits of turpentine is a special solvent made from the distillation of tree resin and is composed of various terpenes. Some are usually used for oil based systems.
Ketones as solvents in paints and coatings
Ketone solvents are considered to have good solubility due to their carbonyl group, a hydrogen acceptor. Small ketones are good for polar resins and because the hydrocarbon chain becomes more important for higher ketones, they become good for non-polar resins only small ketones are water soluble. Ketone solvents can also lower the viscosity of the resin system by avoiding the formation of complexes between polar resins (when hydrogen bonds are formed between the resin molecules).
• Acetone
A fast evaporation solvent used in cellulose coatings.
• Methyl isobutyl ketone (MIBK)
Evaporative media around the solvent are used in many systems.
• Methyl amyl ketone
Low evaporation solvent with good breaking power property.
• Isophorone
Very low evaporation solvent used in heat curing systems. Known to increase surface and pigment wetting.
This type of ester is used as a solvent
Like ketones, esters are also hydrogen acceptors and therefore have similar solubility. If small esters are good solvents for polar resins, their solubility for non-polar materials, such as ketones, increases with the size of the hydrocarbon chain. They usually have very limited miscibility with water but compared to ketones, their usually more "fruity" odor makes them more pleasant. They can also be used to lower the viscosity when polar resin molecules form complexes due to hydrogen bonds.
• Ethyl acetate
A widely used fast evaporation solvent in many rapid drying systems.
• Butyl acetate
It is used widely, its moderate evaporation rate makes it perfect during drying, to avoid film surface defects (redness, craters)
• Propylene glycol mono methyl ether acetate
Moderate evaporation, solvents are also used in many systems. It has greater (but limited) miscibility with water than the other esters.
• Butyl glycol acetate
It is a slow evaporation solvent with excellent solvation making it suitable for increasing the flowability and gloss of coatings cured at high temperatures.
Hope this article is useful!