Trimellitic alkyd

TrimeUitic anhydride is converted to PVC plasticizers, polyesters, water-soluble alkyd coatings, and polyamide—imide resias. The trimellitate plasticizers have a lower volatility than those derived from phthaUc anhydride (see Plasticizers). 

The oleoresinous, trimellitic anhydride-based alkyd was also obtained commercially it is a 46% oil length safflower oil resin. In addition to the trimellitic anhydride the resin also contains hydrogenated bis-phenol-A and isophthalic acid (5). 

Trimellitic Alkyd. Methyl isobutyl ketone was ruled out for poor aqueous solubility characteristics. 2-Ethoxyethanol and 2-(2-butoxyeth-oxy) ethanol were chosen in keeping with the selection for the other two... 

Solvents for the Trimellitic Alkyd. The four solvents evaluated with this resin were the 2-butoxyethanol control, 2-ethoxyethanol, 2-(2-butoxy-ethoxy) ethanol, and hexylene glycol. This alkyd displayed a pronounced tendency to sag. It is suspected that the viscosity of the neat resin is somewhat lower than desired from the standpoint of film forming characteristics. By contrast the wet film resistances observed were an order of magnitude higher than those obtained with either of the other two resins. It would be interesting to know what effect this has on throwing power. 

Table V. Rupture Voltages of Trimellitic Alkyd Solutions...

Trimellitic Based Alkyd and Formulation. The trimellitic based alkyd was supplied as 100% non-volatile material. The acid number as received was 43.2. Calculation showed (see below) that the degree of base neutralization recommended was 85% of theory. The typical charge for resin preparation was described as (5) ... 

This formulation, typical of all the combinations, consists of trimellitic alkyd, grams 105.0 triethylamine, grams 8.16... 

Figure 15. Trimellitic alkyd-2-butoxyethanol effect of voltage and solids on...

Two solvents used in this evaluation, 2-butoxyethanol and 2-(2-butoxyethoxy) ethanol, were the most versatile. Except for the film appearance of the trimellitic alkyd, satisfactory coating systems could be made with each of the three resins. The 2-butoxyethanol has slightly lower viscosity and lower cost. On the other hand 2-(2-butoxyethoxy)-ethanol gave slightly higher rupture voltages. With the acrylic resin and... 

Figure 17. Trimellitic alkyd-2-butoxyethanol voltage vs. wet film resistance...

Hexylene glycol was better than 2-butoxyethanol as a solvent for the trimellitic alkyd. It may also be of value with the acrylic resin, but high solution viscosity could be a problem. 

Sec-butyl alcohol offered some promise with the trimellitic alkyd and the epoxy ester vehicles, judging from the preliminary phase of the investigation. Further work is needed to establish this fact. An approach involving mixed solvent systems is suggested. With the acrylic resin, the solution properties and deposition characteristics were poor. Isopropyl alcohol offered some promise with the alkyd and the acrylic resin, but further tests are needed to determine its ultimate utility. Diacetone alcohol may be of value with the alkyd and the acrylic. With these resins it... 

Amoco WS-3823 is a short oil tall oil/isophthalic acid/neopentyl glycol/trimellitic anhydride alkyd of acid value 36, which is at 80% solids in butyl Cellosolve. TTie formulation is available from Amoco Chemicals. Cymel 301 is an HMMM resin supplied at 100% solids by American Cyanamid. 

Preparation of a Trimellitic Anhydride-Based Alkyd Resin No. 3712NT. . 179... 

In recent years the availability of several aromatic polycarboxylic acids has been exploited in specialty alkyd resin preparations [57, 58]. For example, trimellitic acid-based alkyds are used in alkyd-melamine enamels and acrylic lacquers [57]. Isophthalic acid can be used alone or in conjunction with trimellitic anhydride or phthalic anhydride [59]. Pyromellitic acid and pyromellitic anhydride have also been suggested as partial replacements for phthalic anhydride in long or short oil alkyds to give more water-resistant (also caustic- and gasoline-resistant) coatings [60]. 

Other dibasic acids used in alkyds to impart special properties are adipic acid, azelaic acid, sebacic acid, tetrachlorophthalic anhydride, chlorendic anhydride, dimerized fatty acids, and trimellitic anhydride. Adipic, azelaic, and sebacic acids impart flexibility in the alkyd structure and are primarily used in alkyds designed for application as plasticizers. Tetrachlorophthalic anhydride and chlorendic anhydride are used to impart fire-retardant properties to the resin system. 

Conventional air drying paints usually comprise alkyd oligomers as binders. These alkyds used in coating formulations are suitable for application at ambient temperature and are synthesised by a polycondensation reaction of polycarboxylic acids, polyhydric alcohols and unsatura fatty acids or oils (Figure 4). Highly suitable polycarboxylic acids include phthalic acid anhydride, terephthalic acid anhydride, trimellitic acid, adipic acid and maleic acid. 

Although phthalic anhydride is the most common dibasic acid for producing alkyd resins, isophthalic acid, terephthalic acid, trimellitic anhydride and maleic anhydride are also used. Isophthalic and terephthalic acid are often used in exterior coatings where improved hydrolitic stability is required. Maleic anhydride is used with other polybasic acids as a modifier to increase viscosity and film hardness. Trimellitic anhydride is used in making water soluble alkyds for specific applications. 

---