Source: {"pile_set_name": "USPTO Backgrounds"}

The invention relates to a process for the manufacture of polyester fibers by spinning a polyester mass containing an oxalato complex and drawing of the resulting yarn, followed, as the case may be, by hydrosetting of the same in the presence of liquid water.
A previously developed process is described in U.S. Pat. Nos. 4,307,152 and 4,371,485. The process for the manufacture of hydrophilic polyester fibers described in the above referenced U.S. patents is characterized by the spinning of a polyester mass containing 1 to 20% by weight of one or several oxalato complexes of the general formula EQU Me.sub.n [Z(C.sub.2 O.sub.4)m],
drawing of the resulting yarn and hydrosetting in the presence of liquid water at temperatures within a range from 90.degree. to 170.degree. C., the meaning of the symbols in the formula being:
Me=at least one of the ions Li, Na, K, Rb, Cs or NH; PA0 Z=at least one complex-forming central atom from the group Mg, Ca, Sr, Ba, Zr, Hf, Ce, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Sn, Pb, and Sb; PA0 n=.about.1, .about.2, .about.3 or .about.4, and PA0 m=.about.2, .about.3 or .about.4.
By means of this process, one obtains polyester fibers having outstanding hydrophilic characteristics and excelling through a high moisture uptake and a very favorable water retentivity. In addition, they are flame-resistant. The corresponding hydrophilic characteristics will not come about without hydrosetting. However, in the spinning of such polyester masses, which, as a result of the transesterification of terephthalic esters with ethylene glycol, still contain metal compounds, in particular zinc, calcium, magnesium, or manganese salts, originating from the transesterification catalyst, there is a danger that the melt pressure ahead of the spinning plate will increase relatively rapidly. Thus, in the conventional melt spinning of polyester masses not containing oxalato complexes, the melt pressure ahead of the spinning plate rises only within a period of about 14 days to pressures of about 300 bar. When polyester masses are spun which contain the oxalato complexes referred to above, the time within which such a high pressure is reached is shortened considerably. After only about 60 to 70 hours, a pressure is reached, at which the spinning process has to be terminated. This makes the manufacturing process of the polyester fibers more expensive.
Consequently, there exists a need for an improved process for the manufacture of polyester fibers, in which such disadvantages will not occur.