Nonaqueous dispersion paints

Application. Emulsion paints can be applied by brush, roller, dipping, inundation, and spraying. A wide range of qualities of emulsion paints with tailor-made properties can be produced from the available binders, thickeners, and auxiliaries. 

Types of Emulsion Paints. The most important types of emulsion paints are the following  

Exterior-use paints have a pigment volume concentration of 30-55%. They may be formulated with all of the aforementioned dispersions. Properties are adapted as appropriate to the substrates, climatic conditions, market circumstances, etc. The most important properties of exterior-use paints are their water and water vapor permeability (moisture balance), chalking resistance, and adhesion to the substrate. Special requirements apply in certain areas of application (e.g., COj protection on reinforced concrete, fungal and algal resistance in moist surroundings, crack bridging on cracked substrates, and alkali resistance on new mineral substrates). 

Interior-use paints have a pigment volume concentration of up to 80% depending on the required surface effects. The gloss, cleaning ability, mechanical strength, washfastness, and abrasion resistance decrease with increasing pigment volume concentration. 

Tinting paints are used to tint and shade emulsion paints. They contain colored pigments and wetting agents to ensure good color development in white emulsion paints. 

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The reaction engineering aspects of these polymerizations are similar. Good heat transfer to a comparatively inviscid phase makes them suitable for vinyl addition polymerizations. Free-radical catalysis is mostly used, but cationic catalysis is used for nonaqueous dispersion polymerization (e.g., of isobutene). High conversions are generally possible, and the resulting polymer, either as a latex or as beads is directly suitable for some applications (e.g., paints, gel permeation chromatography beads, expanded polystyrene). Suspension polymerizations are run in the batch model. Continuous emulsion polymerization is common. 

The preparation of nonaqueous sterically stabilized polymer latices was pioneered by Osmond and coworkers at ICI Paints Division. Their work is summarized in a comprehensive monograph (Barrett, 1975) that provides actual recipes for the successful generation of nonaqueous dispersions. Only the most general considerations need therefore be mentioned here. 

Solvent emission from paints can be reduced without lowering the molecular mass by using nonaqueous dispersions (NAD) (see Section 3.6). Acrylates have been described as binders for NADs, but apart from a low viscosity they offer few advantages over conventional coatings [2.50] and moreover must compete with high-solids paints and powder coatings [2.56]. 

More recently, classification according to the paint or lacquer system has come to be preferred. Here, a distinction is made between solvent paints or lacquers (that is, those with organic solvents), low-solvent systems, water-soluble binders, aqueous dispersions, nonaqueous dispersions, and powder coatings. 

Available Forms. Phthalocyanines are available as powders, in paste, or Hquid forms. They can be dispersed in various media suitable for aqueous, nonaqueous, or multipurpose systems, eg, polyethylene, polyamide, or nitrocellulose. Inert materials like clay, barium sulfate, calcium carbonates, or aluminum hydrate are the most common soHd extenders. Predispersed concentrates of the pigments, like flushes, are interesting for manufacturers of paints and inks (156), who do not own grinding or dispersing equipment. Pigment—water pastes, ie, presscakes, containing 50—75% weight of water, are also available. 

The main use of these clays is to control, or adjust, viscosity in nonaqueous systems. Organoclays can be dispersed in nonaqueous fluids to modify the viscosity of the fluid so that the fluid exhibits non-Newtonian thixotropic behavior. Important segments of this area are drilling fluids, greases (79,80), lubricants, and oil-based paints. The most used commercial products in this area are dimethyl di (hydrogen a ted tallow) alkylammonium chloride [61789-80-8] dimethyl (hydrogen a ted tallow)aLkylbenzylammonium chloride [61789-72-8] and methyldi(hydrogenated tallow)aLkylbenzylammonium chloride [68391-01-5]. 

Lessons learned from paints and inks in achieving complete wetting of powders and separation of particles to micron levels with dispersion stability to forestall settling and caking are quite applicable to aqueous and nonaque-ous flowables. 

The dispersion medium can be aqueous or nonaqueous depending on the application. It consists of a dispersion of the binder in the liquid (which is sometimes referred to as the diluent). The term solvent is fi equently used to include liquids that do not dissolve the polymeric binder. Solvents are used in paints to enable the paint to be made and they enable application of the paint to the surface. In most cases the solvent is removed after application by simple evaporation and if the solvent is completely removed from the pain film it should not affect the paint film performance. However, in the early life of the film, solvent retention can affect hardness, flexibility and other film properties. In water-based paints, the water may act as a true solvent for some of... 

Most paint formulations consist of a mixture of suspension particles (pigments) and emulsion droplets (latex particles that are liquid-like at room temperature) referred to as suspoemulsions. The continuous medium with viscosity Po maybe simply an aqueous phase in which several ingredients are dissolved or could be nonaque-ous (oil) that may consist of two or more miscible oils. For non-Newtonian systems (which is the case with paint systems) some empirical equations can be established to relate the plastic viscosity qpi and yield value Op to the volume fraction of the disperse phase c ) [49]... 

The use of surfactants (ionic, nonionic and zwitterionic) and polymers to control the stability behavior of suspensions is of considerable technological importance. Surfactants and polymers are used in die formulation of dyestuffs, paints, paper coatings, agrochemicals, pharmaceuticals, ceramics, printing inks, etc. They are particularly robust form of stabilization which is useful at high disperse volume fractions and high electrolyte concentrations, as well as under extreme conditions of high temperature, pressure, and flow. In particular, surfactants and polymers are essential for the stabilization of suspensions in nonaqueous media, where electrostatic stabilization is less successful. 

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