Apparatus for and process of treating shrinkable fibers

DETAILED DESCRIPTION What is claimed is: 1.
A process of treating a tow of shrinkable fibers including the steps of: moving the tow in folds through a plug section operatively connected by a restricted opening to a treatment section, said plug section having an entrance opening larger than the restricted opening of the treatment section, and heating the tow with steam in the treatment section wherein sufficient steam migrates through the restricted opening from the treatment section to the plug section to cause shrinkage of the tow in the plug section, and wherein the tow has a cross-sectional area substantially the same as the cross-sectional area of the entrance opening of the plug section as it moves through said opening and wherein the tow has a smaller cross-sectional area as it leaves the plug section and moves through the entrance opening of the treatment section, due to shrinkage, and wherein the cross-sectional area of the shrunken tow as it enters the smaller entrance opening of the treatment section is substantially the same as the cross-sectional area of this opening and wherein the tow moving in folds in the plug section substantially prevents the loss of steam through the entrance opening of the plug section.
2.
The process of claim 1 wherein the tow is an amorphous aromatic polyamide.
3.
The process of claim 2 wherein the aromatic polyamide amide is poly(meta-phenylene isophthalamide).
4.
The process of claim 2 wherein the aromatic polyamide amide has a second order glass transition temperature in steam of above about 150.
degree.
C.
5.
The method of claim 2 including the further step of: padding a water-soluble dye onto the tow prior to the treatment and wherein the tow is heated with steam in such treatment section at a temperature of from about 110.
degree.
C.
to 140.
degree.
C.
for time sufficient to diffuse the dye into pores in the fibers the tow.
6.
The process of claim 5 including the further step of: moving the tow into a second treatment section wherein such tow is heated with steam at a temperature above its glass temperature from about 150