Paints special-effects additives

Special-effects additives. This group of additives include a number of other substances that are added to paint formulation, for example ... 

Core/shell particles have been described that may be used as special effect pigments for use in coatings, paints and inks (16). With respect to their cores, the particles may have a regular arrangement and are based substantially on high molecular polymers. The par-ticulated pigments may be applied to the substrates in the form of solid, liquid or paste preparations with the aid of auxiliary constituents and additives. 

Adhesion promoters are the substances that improve adhesive strength of paints in terms of its resistance against mechanical separation from the painted surface. A large number of different chemical adhesion promoters are available. These include silanes, silicones, titanium compounds, zirconates, amides, imines, phosphates, and specially modified polymers. Furthermore, there are binders, plasticizers, and additives, which have the secondary effect of providing good adhesive strength. Adhesion promoters can be used as additives to the paint formulation, or can be employed in the form of a surface pretreatment. 

Although the formation of surface patterns via the Benard cell may occasionally be useful to form special finishes, usually it is desirable to eliminate the situation. Use of higher boiling solvents will retard evaporation rate and the cooling effect that changes surface tension and propels the vortex action. Increase in paint viscosity will inhibit the action, as will decrease in film thickness. Addition of a surfactant will provide a more uniform value of surface tension and also retard evaporation and thereby help to inhibit the vortex motion in cells. 

All components fulfill special functions in the liquid paint and in the solid coating film. Solvents, binders, and pigments account for most of the material, the proportion of additives being small. Low concentrations of additives produce marked effects such as improved flow behavior, better wetting of the substrate of pigment, and catalytic acceleration of hardening. 

Many effects can be achieved with additives, and not all of their, in some cases, very specific uses can be discussed here. Information on paint additives and their mode of performance is given in the literature and company brochures. There is very little comprehensive literature on additives [5.1], [5.2]. The physical and chemical principles of paint production and application are helpful in understanding their mode of action [5.3], [5.4]. A large-number of paint additives are listed according to areas of use in special tables [5.5]-[5.7]. 

PMA has been used widely as a microbicide for the in-can/in-tank protection of aqueous functional fluids such as latex paints. The ability of PMA to inhibit enzymes that break down cellulosic thickeners was considered a special advantage in that application. At higher addition rates PMA acts also as a paint film fungicide and algicide. However, the duration of activity of PMA in paint films is limited due to volatility and leachability of the active ingredient. Additionally PMA was used extensively in slimicides, algicides, antifouling paints and wood preservatives, where it also exhibited insecticidal effectiveness. 

A low-profile bulk molding compound (BMC) consists of an unsaturated polyester, styrene, poly(vinyl acetate) as the low-profile additive, calcium carbonate, short-cut glass fibers, and various additives, which are contained in minor amounts. Solubility parameters of both key organic components the polyester and poly(vinyl acetate) were determined [129]. The Hansen and the Hildebrand parameters were calculated. They may be used to predict the behavior of those materials in the presence of solvent-containing systems. It was found that the low-profile additive significantly modifies the solubility parameter values. The relationship between morphology and paint solvents interactions of a BMC was studied [237]. The existence of a poly(vinyl acetate)-filler free polyester skin of about 0.1 pm thickness and the existence of heterogeneously distributed porosities were also discussed with special reference to a protective effect towards solvent diffusion. 

Oily additives are used in various technologies (e.g., paper and pulp production, ore flotation, fermentation) and commercial products (detergents, paints, some pharmaceuticals) to avoid the formation of an excessive foam, which would impede the technological process or the product application [1-3]. In other cases (oil recovery and refinement, shampoos, emulsions for metal processing machines) oil drops are present, without being specially introduced for foam control, and can also affect the foamability of the solutions. Small fractions of hydrophobic solid particles of micrometer size, such as hydrophobized silica or alumina, plastic grains, or stearates of multivalent cations, are often premixed with the oil because the solid-oil compounds obtained exhibit a much stronger foam destruction effect than the individual components taken separately [4-8]. Such oily additives are termed antifoams in the literature and can be based on hydrocarbons, poly-dimethylsiloxanes (PDMSs, silicone oil) or their derivatives [1,4]. 

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