Emulsions alkyd

Both regulatory limits on the amount of organic solvents allowed in paints and advancements in alkyd resin technology have resulted in the development of higher soHds alkyd resins that requke less solvent for dilution and viscosity reduction. In addition, developments of water-reducible alkyds and alkyd emulsions have resulted in alkyd-based paints that requke less organic solvent in thek formulations. 

A separate approach to the problem of VOC release during film formation is the use of polymer films cast from aqueous emulsions. Alkyd emulsions in particular have been proposed as new environmentally friendly paints and have therefore... 

Bergenstahl B, Ostberg G. Alkyd emulsion instability and drying properties. In Ref. 1 327-341. 

Other water-borne coatings include water-soluble emulsions, dispersions, and latex resins. Water-soluble resins are rare because most resins derived from vegetable oils are insoluble in water. The true emulsions are based on the emulsification of the oil or alkyd through either the action of a surfactant or a resin that has a surfactantlike character. The alkyd emulsions are readily prepared and can be used for OEM coatings and architectural applications. The submicron size droplets are stabilized by the thickeners (El-Aasser Sudol, 2004 Landfester, 2005 Landfester et al., 2004 Tsavalas et al., 2004 Weissenborn Motiejauskaite, 2000a,b). In dispersions, the resin is a solid and is dispersed in water. The latex resin is usually vinyl acetate, styrene, acrylates, or methacrylates radically copolymerized in a micelle to form particles 0.1 pm in diameter (Bloom et al., 2005 Brister et al., 2000 Jiratumnukul Van De Mark, 2000 Thames et al., 2005). 

Weissenborn, P.K. A. Motiejauskaite. Drying of alkyd emulsion paints./. Coating. Technol. 2000a, 72, 65-74. 

The stability improvement of Ti02 suspensions is important not only for water-based paints, but also for paints based on non-polar or low-polar solvents. It is shown in [208] that Ti02 powders modified with an anionic surfactant, e.g. sodium dodecyl sulphate, are dispersed to smaller sizes, and their sedimentation stability increases. The production of water-alkyd emulsions is inhibited due to low mechanical stability. These emulsions can easily break when exposed to shear forces such as those produced by pumps, and when intensively agitated during dispersion. [209] demonstrates that most stable emulsions can be obtained with alkyds showing high acid numbers, as well as with highly polymerised alkyds of low viscosities. 

Ostberg et al. [210] have investigated in detail the influence of the emulsifier type and alkyd properties on droplet size and stability of alkyd emulsions. Alkyd S-68 (Bergvik Kemi AB, Sweden) was mainly used as an alkyd resin, containing 67.8% of oil, acid value=10.6, viscosity=680 mPa s. Other oils were also used, with acid values 8-9 and viscosities from 180 to 970 mPa s. The surfactants used were ... 

Data on the preparation of alkyd emulsions by the phase inversion technique were presented in [211]. This technique is accomplished by adding water to an alkyd/surfactant mixture under formation of a stable emulsion. The determination of surfactant s solubility in water and alkyd phases allows to calculate the quantity of water required for phase inversion. Effective emulsifiers are ethoxylated sulphates (2-3 EO groups) of C12 - Ch and C16 - Cig higher alcohols. With these surfactants, the emulsification becomes less dependent on the temperature than with nonionic surfactants. 

Chem. Descrip. Surfactant consisting of ethxoylated partially unsat. fatty acid monoethanolamide Uses Emulsifier for alkyd emulsions... 

Chem. Descrip. Sec. short oil alkyd emulsion in Dl water, EGMBE Uses Alkyd for air-dry maintenance enamels and primers, baked and air-dty metal protective coatings... 

Uses Detergent, emulsifierfor oils, fats and waxes stabilizer in latex and alkyd emulsions emulsion polymerization asphalt scouring textile operations... 

Figure 6.10. Concentration of cobalt in the alkyd and water phases as a function of pH. Cobalt 2-ethylhexanoate was used in an amount of 0.2% of alkyd. The oil-in-water alkyd emulsions were made without emulsifier. (From G. Ostberg et aL, Prog. Org. Coatings, 24, 281 (1994) Reprinted with permission of Elsevier Science)...

Alkyd emulsions are also of interest in the industrial coatings market. The alkyds used for such applications, so-called short oil alkyds, have a much higher viscosity and are most conveniently emulsified in a phase-inversion process. The emulsifier, which can either be a nonionic surfactant, an anionic surfactant or a combination of these, is dissolved in the alkyd at high temperature and water is added under low shear so that a water-in-oil emulsion is formed. For alkyds of very high viscosity, the process must be performed in pressurized vessels to prevent boiling of the water. By adding more water and/or lowering the temperature, the emulsion is made to invert and form an oil-in-water emulsion. 

The use of water in place of organic solvents as a paint thinner has obvious attractions. The first important commercial product of this type was the oil-bound water paint, the vehicle being an emulsion of oil or varnish in an aqueous solution of gelatine. The preferred white pigment was lithopone (zinc sulphide/ barium sulphate), and a high ratio of pigment to binder was used. This product was eventually replaced by the emulsion paint (known as latex paint in USA and dispersion paint on the continent of Europe). It used a synthetic vinyl polymer as a binder, mainly a co-polymer of vinyl acetate with either vinyl versatate or butyl acrylate, with titanium dioxide as the white pigment. Attempts to use an alkyd emulsion based on oil as the vehicle were commercially unsuccessful. The droplet size of the dispersion at emulsion is normally about 0.2-1 //m. 

Rubber seed oils (RSO) have also been used to prepare alkyd emulsions after their modification with MAA and PA, which produced wate-soluble alkyd materials [86]. 

Alkyd emulsions are made by dispersing a liquid alkyd resin in water by mechanical means. Alkyds are polyester resins modified with fatty acids. They are produced by reacting fatty acids with a polyol such as glycerol (1,2,3-trihydroxypropane) and a dibasic acid such as orthophthalic acid... 

The latest alkyd emulsions contain only resin, water, and nonionic srufactant. High shear rates are used to disperse the resin so that high acid values and amines are not required. Drying is still inhibited to some extent as some of the cobalt resides in the aqueous phase. For this reason more dryer is required than for solvent-based systems. 

Uradil AZ516Z is a 63% OL tall oil alkyd emulsion provided at 60% in water. It is amine and solvent free, and supplied by DSM Resins bv. 

SYNTHESIS OF AMPHIPHILIC COPOLYMERS BASED ON ACRYLATES BY FREE-RADICAL POLYMERIZATION AND THEIR APPLICATION IN ALKYD EMULSIONS... 

Alkyds are among the first water-based coatings. An alkyd emulsion is a dispersion of an alkyd resin in water. Unfortunately, almost all dispersions are unstable from the thermodynamic point of view - droplets will coalesce together in an irreversible way once they come too close to each other. In order to assure that all the particles repel each other strongly enough to withstand all the external influences, the mechanism called electrostatic repulsion or the steric (osmotic) repulsion is used. A fundamental study [77] on alkyd emulsion paints has arrived at the following conclusions ... 

A recent study [84] regarding the application to wood of this group of coatings, shows that the adhesion values of alkyd emulsion paints were much lower than the values of the acrylic dispersion paints under dry conditions. The adhesion was much higher for small particle dispersion paint, due to the improved penetration of the small acrylic particles into wood and/or to an increased contact area between this paint and the wood substrate due to a more packaging of the particles. Under high moisture conditions the adhesion values of the acrylic dispersion paints decreased to a high extent. 

As with almost all other resin classes, work has been done to make alkyd resins for coatings that can be reduced with water. One approach that has been more extensively studied in Europe than in the United States is the use of alkyd emulsions (25,26). The emulsions are stabilized with surfactants and can be prepared with little, if any, volatile solvent. Some problems limit use of alkyd emulsions (27). Coatings prepared using alkyd emulsion loose dry time on storage because of absorption of cobalt drier on the surface of pigments and precipitation of cobalt hydroxide. Best results were obtained with a combination of cobalt neodecanoate... 

---