1. Field of the Invention
This invention concerns a new treatment of fabric for imparting wrinkle resistance.
2. Description of the Prior Art
Prior finishing treatments to impart wrinkle resistance to cotton or other cellulosic fabric have employed the products from reaction of formaldehyde and an amido compound as finishing agents. These reaction products are methylol amides. Examples of these compounds are dimethylolurea, dimethylolethyleneurea, dihydroxydimethylolethyleneurea, and alkyl dimethylolcarbamates. These agents are applied to cotton, or other cellulose-containing fabric, with an acidic catalyst, and the fabric is heated. On heating the methylol amide reacts with two or more cellulose molecules forming crosslinks. The crosslinked cellulose makes a more resilient fiber than the untreated cellulose. The fiber is then less prone to suffer permanent deformations that appear in the fabric as wrinkles. To serve as a crosslinking agent the finishing agent must possess two or more methylolamide groups in the molecular structure.
The methylolamide crosslinking agents have been quite effective in producing wrinkle resistance. They do, however, suffer from a number of disadvantages. One disadvantage is that the agent and its reaction product on the fabric tend to decompose and release formaldehyde. Formaldehyde is very irritating and even small amounts are objectionable. It is also possible that even a small amount of free formaldehyde may be a hazard.
Another type of crosslinking treatment employs the application of unsaturated amides, such as acrylamide, with chemical or radiation initiation to promote reation of the amide with cellulose. The fabric with bound amide is then treated with formaldehyde to form chemical links between bound amide groups and thereby crosslink the cellulose. This treatment also suffers from the possibility of releasing free formaldehyde.
Formaldehyde-free finishing agents have been proposed before. One class of such agents is prepared from the reaction of glyoxal with amides. Examples of these reaction products are dihydroxyethyleneurea and dihydroxydimethylethyleneurea. These agents are of their nature formaldehyde-free. However, they suffer from lack of effectiveness, that is, they produce less wrinkle resistance, and also have other disadvantages, such as causing discoloration of the fabric. Still other formaldehyde-free crosslinking agents have been proposed. These contain different groups for reaction with cellulose, such as epoxy, chlorohydrin, isocyanate, and hydroxyethylsulfone. All of these have disadvantages that prevented their wide use in commercial practice.