Dimensionally stable nonwoven fibrous webs and methods of making and using the same

A method of making a nonwoven web comprising:

• forming a molten mixture of one or more thermoplastic polyesters selected from aliphatic polyesters with an antishrinkage additive in an amount greater than 0% and no more than 10% by weight of the mixture;
• wherein the antishrinkage additive is a thermoplastic semicrystalline polymeric additive;
• wherein the thermoplastic semicrystalline polymer has a molecular weight of greater than 20,000 daltons and is selected from the group consisting of polyoxymethylene, poly(vinylidine fluoride), poly(ethylene-chlorotrifluoroethylene), poly(vinyl fluoride), poly(ethylene oxide), polycaprolactone, semicrystalline aliphatic polyamides, and thermotropic liquid crystal polymers;
• simultaneously forming a plurality of fibers from the mixture;
• wherein the fibers exhibit a median fiber diameter of no greater than about 25 μm;
• and
• collecting at least a portion of the fibers to form a nonwoven web, wherein the fibers exhibit molecular orientation and extend substantially endlessly through the web, and further wherein the nonwoven web has at least one dimension which decreases by no greater than 12% in the plane of the web when the web is heated to a temperature above a glass transition temperature of the fibers.

A method of making a nonwoven web comprising:

• forming a mixture of one or more thermoplastic polyesters selected from aliphatic polyesters with an antishrinkage additive in an amount greater than 0% and no more than 10% by weight of the mixture;
• wherein the antishrinkage additive is a thermoplastic semicrystalline polymeric additive;
• wherein the thermoplastic semicrystalline polymer has a molecular weight of greater than 20,000 daltons and is selected from the group consisting of polyoxymethylene, poly(vinylidine fluoride), poly(ethylene-chlorotrifluoroethylene), poly(vinyl fluoride), poly(ethylene oxide), polycaprolactone, semicrystalline aliphatic polyamides, and thermotropic liquid crystal polymers;
• simultaneously forming a plurality of fibers from the mixture;
• wherein the fibers exhibit a median fiber diameter of no greater than about 25 μm;
• and
• collecting at least a portion of the fibers to form a web, wherein the fibers do not exhibit molecular orientation, and further wherein the nonwoven web has at least one dimension which decreases by no greater than 12% in the plane of the web when the web is heated to a temperature above a glass transition temperature of the fibers.

A nonwoven web including a plurality of fibers comprising:

• one or more thermoplastic aliphatic polyesters;
• and
• an antishrinkage additive in an amount greater than 0% and no more than 10% by weight of the web, wherein the antishrinkage additive is a thermoplastic semicrystalline polymeric additive that is mixed within the thermoplastic aliphatic polyester;
• wherein the thermoplastic semicrystalline polymer has a molecular weight of greater than 20,000 daltons and is selected from the group consisting of polyoxymethylene, poly(vinylidine fluoride), poly(ethylene-chlorotrifluoroethylene), poly(vinyl fluoride), poly(ethylene oxide), polycaprolactone, semicrystalline aliphatic polyamides, and thermotropic liquid crystal polymers;
• wherein the fibers exhibit a median fiber diameter of no greater than about 25 μm;
• wherein the fibers do not exhibit molecular orientation;
• and
• further wherein the nonwoven web has at least one dimension which decreases by no greater than 12% in the plane of the web when the web is heated to a temperature above a glass transition temperature but below the melting temperature of the fibers while in an unrestrained condition.