Alkyd-modified siloxane coating

Claim 1

A COATING COMPOSITION PARTICULARLY ADAPTED TO DEPOSIT BAKED FILMS CAPABLE OF ENDURING PROLONGED SERVICE AT ELEVATED TEMPERATURES WITHOUT BECOMING DISCOLORED APPRECIABLY, SAID COMPOSITION COMPRISING A SUBSTANTIAL AMOUNT OF A FILM-FORMING VEHICLE COMPOSED ESSENTIALLY OF AN AROMATIC HYDROCARBON SOLVENT SOLUTION OF A COBODIED INTER-REACTION PRODUCT PREPARED FROM REACTANTS CONSISTING OF: (A) BETWEEN 25 AND 90 PARTS BY WEIGHT OF A THERMALLYEVANESCENT, SUBSTANTIALLY NON-DISCOLORING MONOCARBOXYLICACID-MODIFIED ALKYD HAVING FREE HYDROXYLS AND AN ACID NUMBER BELOW ABOUT 50, SAID ALKYD BEING THE RESINOUS REACTION PRODUCT OF ONLY THE FOLLOWING MATERIALS: (1) ORGANIC ACIDIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF POLYCARBOXYLIC ACIDS AND POLYCARBOXYLIC ACID ANHYDRIDES WHICH BOIL OR SUBLIME ABOVE ABOUT 200* C.; (2) POLYHYDRIC ALCOHOL SELECTED FROM THE GROUP CONSISTING OF GLYCEROL, PENTAERYTHRITOL, TRIMETHYLOL PROPANE AND TRIMETHYOL ETHANE; AND (3) MONOCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF SATURATED ALIPHATIC ACIDS HAVING FROM 6 TO 10 CARBON ATOMS, AND ARYL AND ARALKYL ACIDS HAVING NOT MORE THAN 11 CARBON ATOMS AND FREE OF NON-BENZOID UNSATURATION, SAID MONOCARBOXYLIC ACID BEING PRESENT IN AN AMOUNT SUCH THAT THE TOTAL WEIGHT OF MONOCARBOXYLIC ACID ESTERS IS BETWEEN ABOUT 1/3 AND 1/2 OF THE TOTAL WEIGHT OF THEORETICAL ESTERS IN THE ALKYD; AND (B) BETWEEN ABOUT 75 AND 10 PARTS OF POLYSILOXANE MODIFIED WITH RO- GROUPS AND CHARACTERIZED (1) BY HAVING ITS SILICON ATOMS BONDED TOGETHER BY SI-O-SI LINKAGES, (2) BY HAVING THE REMAINING VALENCES OF ITS SAID SILICON ATOMS SATISFIED BY METHYL, PHENYL AND RO- RADICALS WHERE R IS A HYDROCARBON RADICAL OF 4 UP TO 6 CARBONS SELECTED FROM THE GROUP CONSISTING OF ALKYL AND CYCLOALKYL RADICALS, (3) BY HAVING A TOTAL OF BETWEEN 1 TO 1.7 METHYL AND PHENYL RADICALS PER SILICON ATOM OF WHICH TOTAL BETWEEN 10 AND 90 PERCENT ARE PHENYL RADICALS, (4) BY HAVING BETWEEN ABOUT 0.01 AND 2 RO- GROUPS PER SILICON ATOM AND (5) BY BEING SOLUBLE IN AN AROMATIC HYDROCARBON SOLVENT; SAID FILMI-FORMING VEHICLE BEING PRODUCED BY COBODYING SAID ALKYD AND SAID POLYSILOXANE IN AN AROMATIC HYDROCARBON SOLVENT UNDER REFLUX CONDITIONS WITH SEPARATION OF LIBERATED REACTION PRODUCTS CONTAINED IN THE VAPOR PHASE AND RETURN OF THE HYDROCARBON SOLVENT UNTIL A SUBSTANTIAL INCREASE IN VISCOSITY SHORT OF GELLATION HAS BEEN SECURED IN THE MASS BEING REFLUXED, SAID FREE HYDROXYLS OF SAID MONOCARBOXYLIC-ACID-MODIFIED ALKYD BEING PRESENT IN SUFFICIENT QUANTITY TO REACT WITH AT LEAST A MAJOR PART OF RO- GROUPS OF THE POLYSILOXANE TO LIBERATE ALCOHOLS CORRESPONDING TO THE REACTED ROGROUPS.