Viscosity alkyd

The time that is required to produce a homogeneous suspension of particles in the dispersion medium using an oscillatory shaking machine equipped with several containers is measured. Not only can small quantities of the millbase with the same composition be tested (as with other types of apparatus), but various millbases can also be tested under the same conditions. A low-viscosity alkyd resin system of the stoving or oxidatively drying type can be used as a test medium. For standards, see Table 1.1 ( Ease of dispersion Oscillatory shaking machine ). 

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. 

Mliphatic dibasic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acids have also been used to make alkyd resins. Their linear chain stmcture lends higher flexibiUty and lower viscosity to the resin as compared to the rigid aromatic rings of phthaUc acids. 

Process Control. The progress of the alkyd reaction is usually monitored by periodical deterrninations of the acid number and the solution viscosity of samples taken from the reactor. The frequency of sampling is commonly every half-hour. Deterrnined values are plotted against time on semi-1 ogarithmic coordinates, as shown in Figure 4. 

The product is a mistuie of various polyoxyethylene chain lengths (29—31). Glycol diesters ate used as vinyl plasticizers the monoesters as surface-active agents and viscosity modifiers for alkyd resins (qv). 

Low viscosity cellulose propionate butyrate esters containing 3—5% butyryl, 40—50% propionyl, and 2—3% hydroxyl groups have excellent compatibihty with oil-modified alkyd resins (qv) and are used in wood furniture coatings (155). Acetate butyrate esters have been used in such varied apphcations as hot-melt adhesive formulations (156), electrostatically spray-coated powders for fusible, non-cratering coatings on metal surfaces (157—159), contact lenses (qv) with improved oxygen permeabiUty and excellent wear characteristics (160—162), and as reverse-osmosis membranes for desalination of water (163). 

C H NO, and drying oil acid amides with hexamethoxymethylmelamine [3089-11-OJ, C H qN O, (23,24), and trimethylolpropane triacrylate [37273-47-17, been recommended. Such reactive diluents give solutions of higher viscosity, ie, lower alkyd concentration at the same... 

An appHcation where latex paints show outstanding performance is over masonry such as stucco or ciader block constmction. This performance results from saponification resistance ia the preseace of the alkaH from the cement. Furthermore because masoary surfaces are porous, having both small and large pores, the low viscosity external phase of a latex paint can penetrate rapidly iato the small pores, causiag a rapid iacrease ia the viscosity of the remaining paiat. The bulk paiat, ia turn, sinks iato the larger holes more slowly than a solution-based paint. Thus less latex paint is required to cover the same surface area as compared to alkyd paints. 

The products of these reactions with maleic anhydride, termed maleated oils, react with polyols to give moderate mol wt derivatives that dry faster than the unmodified oils. For example, maleated, esterified soybean oil is a drying oil with a drying rate comparable to that of a bodied linseed oil with a similar viscosity. Maleated linseed oil can be converted to a water-dilutable form by hydrolysis with aqueous ammonium hydroxide to convert the anhydride groups to ammonium salts of the diacid. Such products have not found significant commercial use, but similar reactions with alkyds and epoxy esters are used on a large scale to make water-dilutable derivatives. 

A wide range of polyurethane-type products has become available in recent years for coating applications. These include simple solutions of linear polyurethanes, two-pot alkyd-isocyanate and polyether-isocyanate systems and a variety of prepolymer and adduct systems. The coatings can vary considerably in hardness and flexibility and find use mainly because of their toughness, abrasion resistance and flexibility. Uses include metal finishes in chemical plant, wood finishes for boats and sports equipment, finishes for rubber goods and rain-erosion-resistant coatings for aircraft. One type of coating is potentially competitive with PVC leathercloth. Both alkyd-di-isocyanate and adduct-diisocyanate compositions may be coated on to fabrics from solutions of controlled viscosity and solids content. Such coated fabrics are soft, flexible and, unlike PVC leathercloth, free from plasticisers. 

Alkyds These are the most widely used of all air-oxidizing coatings and have the broadest use both industrially and domestically. They are usually classified according to the proportion of drying oil to synthetic resin (known as oil length ). The oil length influences all properties (e.g. chemical resistance, viscosity, flexibility and hardness). 

These are the most important components of paint. Coatings can be either clear or opaque (containing pigments) and either solvent- or water-based. With solvent-based paints, after application, most of the solvent is lost through evaporation. These solvent-based coatings are mostly alkyds (name derived from alkyl/acid) or modified alkyd resins. Normally they contain 30% polymer solids higher solids content is limited by the increasing viscosity of the system. 

Decreasing the viscosity of the currently applied synthetic alkyd resins reduces the amount of organic solvent that is needed in these paints for optimal performance. This could either be accomplished by decreasing the molecular weight of the applied alkyd resin, or by using polymers having a narrower... 

The dilution properties of hyperbranched polymers also differ from those of linear polymers. In a comparison between two alkyd resin systems, where one was a conventional high solid alkyd and the other based on a hyperbranched aliphatic polyester, the conventional high solid alkyd was seen to exhibit a higher viscosity [113]. A more rapid decrease in viscosity with solvent content was noted for the hyperbranched alkyd when the polymers were diluted. 

Fig. 13. Comparison between a conventional high solid alkyd coating ( ) and an alkyd based on a hyperbranched aliphatic polyester ( ). Viscosity as a function of molar mass [123]...

Pettersson and Sorensen have described a number of different thermoset resin structures based on hyperbranched aliphatic polyesters [123]. Their results can best be exemplified by a study on hyperbranched alkyd coating resins. A comparative study was performed between an alkyd resin based on a hyperbranched aliphatic polyester and a conventional high solid alkyd, which is a less branched structure. The hyperbranched resin had a substantially lower viscosity than the conventional resin of comparable molecular weight, that is, less solvent was needed to obtain a suitable application viscosity. The hyperbranched resin also exhibited much shorter drying times than the conventional resin, although the oil content was similar. These achievements would not have been possible without a change in architecture of the backbone structure of the resins (Figs. 12,13). 

A combination of enhanced reactivity and reduced viscosity for alkyd resins has been achieved by using hyperbranched polyester structures as discussed in Sect. 4.2.3 [ 123]. This study clearly showed the benefits of using highly branched structures in coating applications to obtain improved properties. 

At least one study has compared vemonia oil to partially epoxidized soybean and linseed oils, to investigate claims that vemonia oil is advantaged due to inherently lower viscosity. Authors conclude that partially epoxidized soybean and linseed oils have viscosity and reactivity that are similar to vemonia oil in formulated coating systems, and provide improvements to viscosity, content of volatile organic compounds (VOCs), and curing time in alkyd coatings when compared to conventional formulations and formulations containing fully epoxidized soybean oil [116]. 

Another resin application based on the same hyperbranched polyester structure described herein is low-VOC alkyds, which have very low viscosity and high reactivity compared to conventional high-solid alkyds. Other resin structures are unsaturated polyesters, polyurethane dispersions, and epoxides. ... 

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