The Paint & Coatings manufacturing market consists of both waterborne and solvent-borne producers. For the sake of understanding where certain pumps fit into the production of paint and coatings, we will segment the market into categories. Either type of paint-and-coating producer may use the same binders, pigments and additives, but the main difference is finding the right pump to do the job right in a “mostly water” or “mostly solvent” process.
There are generally three ways to categorize paint and coatings:
1. End Use Characteristics
2. Binder Type
3. The Physical Makeup (Water-borne or solvent-borne) of the paint or coating
According to the National Paint & Coatings Association, paint is a term used to describe a group of emulsions generally consisting of pigments suspended in a liquid medium (such as oil or water) for use as decorative or protective coatings.
Paints Generally Fall into two basic Categories:
Waterborne Paint (35% of Global Production)
• Water-based emulsion paints are made with synthetic binders such as 100% acrylic, vinyl acrylic, terpolymer or styrene acrylic, providing a stable emulsion of polymers and pigment in water.
Solvent-Borne Paint (55% of Global Production)
• Oil and/or alkyd-based paints containing drying oil, oil varnish or oil-modified resin as the film-forming ingredient.
The manufacture of paint and coatings includes four basic components:
The Coalesence Process
Film formation of latex paint occurs when the paint is applied and the water evaporates. During this process, the particles of pigment and binder come closer together. As the last vestiges of the liquid evaporate, capillary action draws the binder particles together with great force, causing them to fuse and bind the pigment into a continuous film in a process called coalescence.
The binder is the most important component of the paint. A binder is the liquid resinous part of a paint that holds all of the paint’s constituents into a solution which, after application onto a surface, enables the paint to cure into a film. Binders “bind” the pigment together, providing adhesion, integrity and toughness to the dry paint film. A paint-and-coating manufacturer will usually buy a binder polymer material that is already in vehicle form. The many types of film forming polymer resins used in binders include acrylics, alkyds, aminoplasts, cellulosics, epoxies, chloro- and fluorocarbons, natural plant oils, phonetics, polyesters, polyurethanes, silicones and vinyls.
Water / Solvents
Liquid, also called the “carrier”, is the portion of the paint that provides a medium to get the pigment and binder from the container onto the surface that is to be painted. A solvent is a liquid that is able to lower the viscosity of a binder sufficiently to allow application onto a substrate and then evaporate to permit the formation of a paint film.
A "true solvent" can rapidly dissolve the viscosity of the binder. Within limits, a "diluent" solvent is able to reduce viscosity, but it simultaneously weakens the solvent powder of the true solvent. Various solvents can function as true solvents or diluents, depending on the particular type of binder (resin). The terms "thinner" and "reducer" are inexact and refer to any liquid used in mixing paints.
Selecting a solvent involves many parameters. The two most important are solubility and evaporation rate. The solubility is the ability to dissolve a binder. The evaporation rate is of crucial importance because the solvent needs to leave the paint at an ideal rate to allow the paint film to form properly. When paint is applied at a given thickness and then dries, the proportion of solids and liquid determines how thick the dried paint film will be. Thus, a higher solids content can provide a thicker dry paint film, which results in better hiding and durability.
Pigments are tiny solid particles that are used to enhance the appearance by providing color and/or to improve the physical (functional) properties of the paint. Pigments used to provide color generally range from 0.2 to 0.4 microns in diameter. Functional pigments are typically 2-4 microns in diameter, but they may be as large as 50 microns.
There are two primary categories of pigments: prime and extender pigments
• Prime pigments provide whiteness and color while also being the main source of hiding capability.
• Titanium dioxide is the predominant white pigment due to its exceptional ability to scatter light and provide whiteness and hiding in flat or glossy paint, whether it is wet, dry or rewetted.
• Color pigments provide color by selective absorption of light and fall into two main types
Organic pigments - include the brighter colors but are not highly durable in exterior use.
Inorganic pigments - are not as bright as organic colors but are the most durable exterior pigments.
• Color pigments are compounded into liquid dispersions called colorants, which are added at the point of sale to tint bases, and to white paints designed for tinting. In the factory, color pigments are used as dry powders and in liquid colorant form to make prepackaged color paints.
• Provide bulk at a relatively low cost.
• Possess less hiding capability than titanium dioxide, but they positively impact other properties, such as sheen, scrub resistance and exterior color retention.
• Some commonly used extenders are clay, silica and silicates, diatomaceous silica, calcium carbonate, talc and zinc oxide.
• Clays, or aluminum silicates, are used mainly in interior paints.
• Calcined clay provides added hiding capabilities.
• Delaminated clay enhances stain resistance.
• Silica and silicates provide scrub and abrasion resistance, key characteristics needed in exterior paints.
• Diatomaceous silica—a form of hydrous silica—is used to control sheen.
• Calcium carbonate, also called chalk, is a general-purpose pigment used in all types of paint.
• Talc is a soft general-purpose extender used in interior and exterior paints.
- Zinc oxide is a reactive pigment helpful with mildew resistance, corrosion inhibition and stain-blocking. A heavy concentration of zinc particles allows them to touch each other, thereby providing continuous conductivity in order to provide sacrificial cathodic protection.
Additives are defined as low-level ingredients that provide specific paint properties such as mildew resistance, defoaming, and good flow and leveling.
A list of additives used in the manufacture of latex paints includes:
Thickeners or Rheology Modifiers
• Rheology is the science of how a liquid tends to flow. These additives provide adequate viscosity so the paint may be applied properly, and they impact how thick the paint goes on, and how well it flows when applied.
• Modern rheology modifiers help latex paints resist splattering, flow out smoothly and resist spoilage.
• These specialized soaps stabilize the paint so that it will not separate or become too thick to use.
• Keep pigments dispersed for maximum gloss and hiding.
• Help “wet” the surface being painted so the paint won’t move about when it is applied.
• Provide compatibility with tinting colorants so that the correct color will be obtained.
Biocides– Two types are used in latex paints:
• Preservative - keeps bacteria from growing in the paint.
• Mildewcide - discourages mildew from growing on the surface of the paint after it has been applied.
• Additives that break bubbles as they are formed in the paint when the paint is mixed in a factory, stirred or applied to a surface.
Co-Solvents (Most co-solvents are volatile organic compounds)
• Additional liquids, other than water, that aid the binder in forming a good film when applied down to the minimum application temperature.
• Help the liquid paint resist damage if frozen.
• Enhance brushing properties, including flow and the time the paint can be applied and worked before it sets up, known as “open time.”
Other additives produce certain desired characteristics in paint, such as the thixotropic agents that give paint its smooth texture, driers, anti-settling agents, anti-skinning agents, defoamers, and others that enable paint to cover well and endure. Additives can also include antifloating agents, antimicrobial agents, antioxidants, catalysts, flame retardants, friction reducers, plasticizers and thickeners.