Liquid Polyisocyanate Adduct Mixtures Possessing Good Compatibility With Apolar Solvents

In the examples which follow, adducts were prepared from DES N 100 (a commercially available biuret of hexamethylene diisocyanate prepared in accordance with U.S. Pat. No. 3,903,127) and various monohydroxy alcohols. The polyisocyanate was first introduced into the reaction vessel and then the monohydroxy alcohol was added dropwise with stirring at room temperature. After the addition of the alcohol was complete and while maintaining stirring, the mixture was heated to between 60.degree. and 70.degree. C. for three hours. After completion of the reaction, the mixture was cooled to room temperature. Xylene was then added until a 40 weight percent solids content was obtained. The previously discussed Cold Cycle Test was then conducted.

The compatibility of the adduct mixtures with apolar solvents was then determined by titrating heptane into solutions of the polyisocyanate adduct mixture in xylene (the Heptane Tolerance Test). Heptane was chosen as the titrant because it is readily available in reagent purity and it is believed to be fairly representative of apolar solvents. All tests were conducted with the polyisocyanate adduct mixtures at a 40 weight percent solids content using 50 g specimens. Good compatibility of these adduct mixtures with apolar solvents may be obtained when the amount of heptane titrated, before a 40 weight percent solution of the adduct mixture in xylene turns cloudy, is greater than or equal to 6 ml, however, amounts greater than about 9 ml are preferred with amounts greater than about 15 ml being most preferred. Subsequent testing with commercially available alkyd systems (resin and solvents) verified the compatibility results of the heptane titrations.

Especially preferred monohydroxy alcohols are those which achieve Heptane Tolerance values in accordance with the previously described test of at least 9 ml, preferably at least 12 ml, when reacted to form adducts at a ratio of 0.2 moles of the alcohol per equivalent of isocyanate. This is not to say that the alcohols can only be used in this amount, but merely that when they are used in this amount, they achieve these Heptane Tolerance values. These especially preferred monohydroxy alcohols should also be able to pass the Cold Cycle Test when used to prepare adducts at a ratio of 0.2 moles of the alcohol per equivalent of isocyanate.

The following Table sets forth the monohydroxy alcohol, the number of equivalents of the modifier based on 1 equivalent weight of the biuret (approximately 195 g), whether the mixture passed the Cold Cycle Test (CCT) and the amount of heptane titrated in milliliters before the mixture turned cloudy in accordance with the Heptane Tolerance Test (HTT).

Although the invention has been described in detail in the foregoing for the purposes of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.