Thixotropic alkyd resins

Thixotropic Alkyd Resins. Thixotropic flow is always associated with structural... 

Thermoplastic polyamides are used in coatings to modify alkyd resins (qv) in thixotropic systems (238) and to plasticize nitroceUulose lacquers (239). DETA-taH oil fatty acid-based polyamides are suggested for use as corrosion inhibitors in alkyd paints (240). Printing inks for fiexo-gravure appHcation on certain paper, film and foil webs rely on EDA- and PDA-based polyamides for their specific performance (241). 

The most important coating appHcation for the nonreactive polyamide resins is in producing thixotropy. Typical coating resins such as alkyds, modified alkyds, natural and synthetic ester oils, varnishes, and natural vegetable oils can be made thixotropic by the addition of dimer acid-based polyamide resins (see Alkyd resins). Specialty high performance coating appHcations often requite the properties imparted by dimer acid components. 

Chemical reactions with alkyd resins can take place via their hydroxyl or carboxyl groups as well as via the double bonds of the unsaturated fatty acids. Isocyanates, epoxy resins, or colophony, for example, may be reacted with the hydroxyl groups. The carboxyl groups can be reacted with polyamidoamines (reaction products formed from dimerized linoleic acid and ethylenediamine) to form thixotropic resins, or can react with hydroxy-functional silicone precondensates. The double bonds of the unsaturated fatty acids permit copolymerization with vinyl compounds [e.g., styrene or (meth)acrylic acid derivatives]. 

Thixotropic air-drying and oven-drying alkyd resins with low oil contents are used as binders for one-coat industrial paints with a high dry-film thickness of 50-75 pm. In special-effect paints (e.g., hammer finishes, soft-feel coatings, textured finishes) they facilitate fixation of the desired effect and prevent smudging. 

Another modification involves treating prepared long oil alkyd with polyamide resin (p. 212) while still hot. Providing this is done carefully, a thixotropic alkyd is obtained which may be used as a rheology control additive, as described in Chapter 10. 

Polyamide-modified alkyds are nsed as thixotropic agents to increase the low shear viscosity of alkyd resin based paints. Topically, abont 10% of a polyamide resin made from diamines snch as 1,2-ethanediamine (ethylenediamine) with dimer acids is reacted with an alkyd resin. High sohds thixotropic alkyds based on polyamides made with aromatic diamines have been developed, which give superior performance in high sohds alkyd coatings (36). 

The modifications with urethane and silicone are discussed in Section 2.11.3.2 and 2.12.5 respectively. Alkyd resins are modified by reacting them with polyamide resins to achieve special rheological properties (Section 5.3.2.5) and are called thixotropic alkyds. Although epoxy esters are a class of epoxy resin, they are frequently considered alkyds rather than epoxies. They are also ester-based... 

Solvent system thickeners - Hydrogenated eastor oil is used as a thixotropic thickener in paints based on nonpolar aliphatie solvents. Hydroxyl groups on the fatty acid chains of the eastor oil triglyeeride structure enable the formation of a colloidal network via hydrogen bonds. Polar attraction among fimctional groups accoimts for the ability of polyamide-alkyd resins to fimction as thixotropic thickeners in nonpolar solvents. 

Chem. Descrip. Resin Uses Thixotrope in sag-resist, alkyd paints Features Develops true thixotropic gel structure Properties Vise. 4 poise (120 C) soften, pt. 115 C... 

Includes some water-based resins and some resins modified to obtain thixotropic properties(typically, these alkyds contain 1-2% polyamide resin). 

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