Acrylic fibers with improved brightness and process for producing the same

Abstract

Abstract An acrylic fiber with a triangular cross-section wherein the curved peripheral edge thereof is defined in accordance with formulas discussed herein. Also provided is a process for preparing these fibers, which exhibit improved brightness, by extruding a spinning solution through Y-shaped orifices into a coagulating bath, the inorganic salt concentration in the spinning solution and coagulating bath being within defined ranges, maintaining the delivery ratio within the range 0.5-3.0 and subjecting the filament to a series of stretching steps which include cold-stretching, primary hot-stretching and secondary stretching such that 16X1 + 2.5X2 - 3X3 < OR = 31 where X1 is the cold-stretching ratio, X2 is the primary hotstretching ratio and X3 is the secondary stretching ratio. This invention relates to acrylic fibers with improved brightness and a process for producing the same. There have been already made many attempts to improve the brightness of synthetic fibers by forming their cross-section in a noncircular shape (known as fibers of differently shaped crosssections). For example, in the U.S. Pat. No. 2,939,201 or No. 2,939,202, it is mentioned that a textile filament of a crosssection having substantially symmetrical three lobes has an excellent brightness. However, the technique disclosed therein is directed solely to a melt-spinning system which can maintain a comparatively high degree of correlativity between the crosssectional shape of the spinning orifice and that of the spun fiber, but has not been applicable in fact to a wet-spinning system wherein the cross-sectional shape of the fiber is determined by the correlation between the desolvating velocity when the spinning solution is extruded into the coagulating bath and the diluting velocity of the solvent and by the mechanism of the formation of a skin-core structure. As a result of researches to impart a silky brightness to acrylic fibers obtained by a wet-spinning method and to improving their esthetic value, we have found that the brightness of acrylic fibers represented quantitatively as the later mentioned 60-degree mirror-surface luster degree and contrast index is not to be determined on such individual factors as the solvent concentration and streching ratio in the coagulating bath, but can be attained only by adopting limited spinning conditions in a series of fiber producing steps from the extrusion of the spinning solution into the coagulating bath to the steam heat stretching. A principal object of the present invention is to provide a special form peculiarity of acrylic fibers remarkably improved in the brightness. A second object of the present invention is to provide a new process to obtain acrylic fibers having a remarkably improved brightness represented quantitatively as a correlation with the 60-degree mirror-surface luster degree and contrast index.

Inventors

• 👤 Keitaro Shimoda
• 👤 Nobuhiro Tsutsui
• 👤 Hideto Sekiguchi
• 👤 Masao Sone

Bibliographic Details