| abstract |
A method for forming a biodegradable polylactic acid suitable for use in the fibers is provided. Specifically a polylactic acid is a processed melt or a water content to initiate the hydrolysis reaction. Without attempting to be bound by a theory, it is believed that the hydroxyl groups present in the water are capable of attacking the ester bond of polylactic acids, thus leading to the chain incision or "depolymerization" of the polylactic acid molecule in one or more shorter ester chains. Shorter chains may include polylactic acids as well as minor parts of lactic acid monomers or oligomers and combinations of any of the foregoing. By selectively controlling the hydrolysis conditions (for example the humidity and polymer concentrations, the temperature, the cutting rate, etc.), a hydrolytically degraded polylactic acid can be achieved having a lower molecular weight than the starting polymer. . Such lower molecular weight polymers have a higher melt flow rate and lower apparent viscosity which is useful in a wide variety of fiber forming applications such as meltblown in nonwoven fabrics. |