Лако-красочные материалы — производство

Waxes based on polyolefin chemistry are also used as anti-settling and sag control agents in high-solid coatings. They are supplied as fine powders or as pastes in solvent. They must be activated by a combination of heat and shear. During this process of activation, their coiled crystalline matrix becomes extended into a straight chain configuration, […]

One of the important classes of organic thickeners used in solvent — based coatings is based on hydrogenated castor oil and its modified amide, ether, and ester derivatives. The hydrogenated castor oil thi­ckener molecule, due to its three-dimensional structure and hydroxyl functionality, can form hydrogen bonds to another thickener molecule or with the solvent. This […]

Though inorganic thickeners are efficient thickeners for solventba — sed coatings, their major limitation is that they must be incorpora­ted at the grinding stage of paint manufacturing. It is quite often necessary to optimize the rheological properties of solventborne coating materials during the let-down stage, and organic thicke­ners are important in such instances due to […]

Another class of thickeners for solventborne coatings is the overba­sed calcium sulfonates. They contain acicular microcrystals (0.5 to 3 pm) of calcium carbonate associated with the long chain sulfonate by adsorption through the sulfonate group. The non-polar hydro­carbon chains (typically C12 to C30) form intermolecular bonds through weak van der Waals forces, producing a stable […]

Metal soaps such as aluminum stearate have been used as thi­ckening agents for a long time in systems rich in hydrocarbon solvents such as alkyd-based systems. As a result of intermolecular hydrogen bonding, they behave as high MW compounds and conse­quently increase the viscosity, but under the effect of shear force, the hydrogen bonds break […]

Very finely divided fumed silica (pyrogenic silica) is another important inorganic thickener used in the coating industry that possesses surface hydroxyl groups (silanols) capable of forming a three-dimensional structure via hydrogen bonding to yield incre­ased viscosity. Depending on the system, the thickening effect is determined mainly by the grade and concentration of the pyrogenic silica, […]

A wide range of rheology modifier additives is commercially availa­ble for solventborne coatings. Some important classes are discussed in the following chapters. 1.3.1.1 Organoclays Organoclays are the most widely used inorganic thickeners in the paint and coating industry. They are derived by modification of naturally occurring laminar silicates (clays) such as hectorite and bentonite. They […]

1.3.1 Rheology and its role in coatings Rheology is the science of deformation and flow behavior of materi­als under the influence of parameters such as shear rate and time. Liquids with viscosity not dependent on shear rate are termed New­tonian liquids while non-Newtonian liquids exhibit changes in viscosity depending on shear rate. Most paints exhibit […]

The classical deflocculating additive has a typical structure with one or more closely spaced pigment affinic groups and a number of resin-like chain structures extending in the vehicle, as described in Figure 5.2. Such additives are low MW polymers that can be adsor­bed strongly on the pigment surface and provide sufficient steric stabilization to give […]

Most inorganic pigments have surfaces sufficiently polar to have strong adsorption of dispersing agents. On the other hand, many organic pigments and carbon blacks have less polar surfaces, which leads to difficulty in having sufficient coverage of the sur­face by adsorption of the dispersing agent. In addition, they are very small in particle size compared […]