Paint Industries, in this article we will learn about the method and how to make paints, the definition of paints, their types and composition, the chemical foundations of their composition, and their physical properties.
Definition of paints:
Paint is a mixture of insoluble materials suspended in a liquid oil medium, or suspended in an aqueous emulsion. The liquid medium consists of a group of organic or inorganic materials, which, when exposed to air and through polymerization, oxidation or drying reactions, gives a cohesive layer (Film) that has strong adhesion to the painted surface. Paints are classified into two main categories:
Suspended oil paints: The liquid medium in them is a fatty oil that is unsaturated in some of its bonds, and is used to paint all surfaces.
Water-based emulsion paints: Their liquid emulsion medium consists of water, so we cannot use them with metal or plastic surfaces due to the large surface tension factor with water.
Paint composition: The paint consists of:
A- Film components:
These materials play the role of the medium carrying the rest of the paint components, and also play the role of the binding agent, and may be natural or artificial:
Natural film components: including some natural resins such as natural gums, including Madagascar gum, Congo gum, mastic gum, casein, and dry vegetable oils such as linseed oil, soybean oil, coconut oil, and castor oil.
Artificial film components: including synthetic gums, tar, acrylic and urethane gums, alkyd gums, chlorinated rubber, and cellulose derivatives (cellulose esters and ethers).
B - Viscosity reducers:
They are solvents prepared from hydrogen or ketone carbons that are added to paints to reduce their viscosity and thus facilitate their preparation and application processes. Since they evaporate at the end of the process, they must meet a set of specifications:
A relatively low boiling point and a high vapor pressure, provided that they are not volatile quickly so as not to leave behind a rough film or greasy deposits. Inert to other paint components and does not negatively affect the stability of the suspension. Inexpensive, easy to handle, low toxicity, and acceptable odor.
The most common solvents are turpentine (thinner), heavy naphtha (oil), and some organic solvents such as xylol, carbon tetrachloride, methylene chloride, dichlorobenzene, lower alcohols, ethers, and acetone.
As for water-based emulsion paints, water itself is used as a dispersion medium and as a viscosity reducer.
Drying accelerators:
They are a group of materials that accelerate polymerization or oxidation reactions, which speeds up the drying process and the formation of the film carrying the dyes after its application. Among the most important of these materials are some cobalt, manganese and lead salts, some resins and some linseed oil compounds and pentaerythritol (C(CH2OH)4). Each of the aforementioned materials has a special mechanism of action, as pentaerythritol condenses with the carboxyl groups of acids in the oil to link four chains together, strengthening the bonding of the polymerized oil network. As for the oxidation drying accelerators, they are oxygen carriers dissolved in the oil and added at a rate of up to 2% of the weight of the oil.
Plasticizers:
Some types of special oils play an important role in increasing the plasticity of the membranes after drying, and they are especially important for some items that require flexible paints such as some children's toys that may be exposed to pressure and twisting processes, as these additives prevent the paint layer from breaking and peeling, and are added in proportions ranging from 20-70% according to need, and rosin*, castor oil and biphthalates are among the most used materials in this field.
Rosin:
A substance extracted from several types of pine trees that grow in North America and Europe, and its color ranges from light yellow to dark brown and dark red, and there are three main types of this substance:
The resinous gum is produced by distilling the resinous material that is collected from living trees, and the raw resinous material is obtained by making a longitudinal slit in it so that the resin flows from it. The second type is wood resin that is extracted from the tree trunks remaining after cutting using solvents. The third type is sulfur resin, also called resinous pine oil, which is a by-product of the wood pulp industry.
Rolling resin is used for many industrial purposes, and is most commonly used with sodium carbonate in covering paper with a colloidal substance; to prevent the paper from absorbing moisture. It is also used in the preparation of paints, varnishes, adhesives, and sealants for insulation purposes, as well as printing inks.
Fillers: Fillers have very important roles, including:
Giving the paint the ability to cover and resist weather factors and Giving the paint a viscous consistency to control its use. Absorbing and reflecting light rays to protect the oily polymer network after drying. Ultraviolet rays are the most dangerous and most effective of these rays. It often plays the role of a coloring agent. It is also often added to reduce the cost of membrane-forming materials. Some oxides and inorganic compounds are often used as fillers, and they must meet a set of conditions. Low cost and high stability. Not to adversely affect the rate of polymerization, drying or oxidation. To be able to form a suspension with oil or water. The most important of these materials are: kaolin, silica, gypsum, barite (barium sulfate), titanium oxide, asbestos, mica, zinc oxide, lead carbonate and carbide.
