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Coloring Finishing And Painting Wood
327. Other Phenol-Formaldehyde Synthetic Resins.— The Paranols, Paraduras, and Esterols form a group of synthetic resins which are modified phenolics that are prepared for use in interior and exterior varnishes. They have high melting points and excellent solubility.
The Durites consist of a pure 100% type of phenolics made from some phenol condensed with formaldehyde and unmodified by any mixture with other resins.
Durez resins are also of the unmodified phenolic type that are oil-soluble in kettle treatments. Varnishes made from Durez resins are said to have high gloss, even tho highly pigmented, and also to possess excellent adhesion to surfaces.
The Beckacites are of the phenol-formaldehyde type of resins that melt at temperatures between 22f>° F. and 275c F., which is a rather low varnish-making temperature. The resins combine easily, especially with China-wood oil, and form varnishes that dry hard with good gloss and make films of good durability.
The Rauzene resins are partly phenolic resins of the modified type and are often combined with fossil resins. Some of them are non-phenolics made especially for lacquers.
328. Alkyd Groups.—Glyptals. These resins, which have been promoted by the General Electric Company, are of the alkyd type. Such resins are highly complex chemically and are formed thru polymerization of glycerine with the mixed esters of phthalic acid and vegetable drying-oil acids, such as are found in linseed oil or China-wood oil. Resins of this type are now preferred for use in certain lacquers, paints, and varnishes. Some of the modified glyptals have been used in insulating varnishes and for a binder for laminated mica.
A resin of the glycerol-phthalate type with China-wood oil and soya-bean oil, a semi-drying oil, is at present used in millions of gallons of enamel now being furnished annually for finishing Ford automobiles in place of lacquer finishes formerly used. The du Pont Company developed the finishes and the Ford Company worked out the technique of application. Finishes of this type are far more durable than were any of the earlier varnish-enamel or lacquer finishes. The coatings are more substantial and require less polishing. It might be added that the automobile trade in general has adopted somewhat similar finishes of spraying enamels for use on all cars.
