Solvent-resistant alkylated melamine cross-linked cellulose ester articles

#This invention relates to the treatment of cellulose ester fibers or filaments to cause surface crosslinking, thereby rendering them resistant to conventional solvents.

#U.S. Pat. No. 3,491,037 discloses that the overall quality and properties of cellulose ester fibers or filaments can be vastly improved without incurring a severe loss in tensile properties. This improved fiber is produced by adding hexamethoxymethylmelamine along with a special "neutral" or "blocked" catalyst to a regular cellulose ester spinning solution. The spinning solution is spun by conventional dry spinning techniques to produce a fiber which is then heated to cause the catalyst to become acidic. The acidic catalyst thus formed causes the hexamethoxymethylmelamine to react with the cellulose ester thereby forming a modified fiber having superior physical and chemical properties.

#This patent also discloses that it is well known that certain synthetic linear condensation polyesters of the cellulose ester class are generally very good fiber forming compositions. However, they are subject to certain inherent disabilities which greatly restrict their utility as general purpose fibers. For example, these cellulose esters and the fibers prepared therefrom do not have a very high elastic recovery capability and are quite susceptible to heat, moisture and photodegradation. In the past many attempts have been made to find some method or means whereby these inherent disabilities of fibers made from cellulose esters could be improved. Means of achieving this goal have usually centered around the addition of an inert or chemically active additive material to either (1) the solution from which the fibers are spun, or (2) to the fibers after they have been woven. The use of additives in the spinning solution has generally been unacceptable, since it usually results in a severe reduction in or complete loss of certain desirable physical properties such as, for example, the tensile strength of the fibers.

#A 15 in. segment of 3.3 denier per filament, 44,000 total denier cellulose acetate tow weighing 5 grams is immersed in a methanol solution containing 10% (by wt.) of Cymel 303 (a highly alkylated melamine manufactured by American Cyanamide) and 0.1% p-toluene sulfonic acid catalyst. The excess solution is removed from the two by compression and the two segment is then allowed to air-dry. The tow is then weighed and based on the weight increase, it is calculated to contain 5.7% Cymel 303 and 0.11% catalyst (p-toluene sulfonic acid). A 10-inch section of the tow is bloomed and sprayed with 8% glyceryl triacetate (which dissolves the surfaces of the fibers and allows them to bond) and then drawn into a hollow tube to form a bonded rod. After about a 2-hour curing period, the bonded rod is heated at 160.degree. C. for 5 min. The rod is then immersed in acetone to test its resistance to solvent action. No dissolution or deformation of the rod occurs indicating the acetate has been crosslinked.

#A 15-inch segment of segment of 3.3 den./fil., 44,000 total denier cellulose acetate two weighing 5 grams is immersed in a methanol solution containing 3% Cymel 303 and 0.1% p-toluene sulfonic acid catalyst. The excess solution is removed by compressing the two and then allowing it to air dry. When dry, the tow is weighed again and was found to contain 2.9% Cymel 303 and 0.1% catalyst. A 10-inch section of the tow is bloomed and sprayed with about 9% glyceryl triacetate, drawn into a hollow tube and allowed to bond. The bonded rod is heated 5 min. at 160.degree. C. to cause crosslinking. The rod is then immersed in acetone to test its resistance to solvent action. The acetate is unaffected by the acetone indicating crosslinking had occurred.

#Example 1 is repeated except that the solvent for the crosslinking agent is composed of 60% ethanol and 40% water. Acetate fibers treated in the water-ethanol solution have solvent resistant properties equally as good as those treated with the methanolic crosslinking solution.