Breathable non-woven composite barrier fabric and fabrication process

A non-woven composite fabric comprising:

• a polypropylene microporous film having at least one film surface bonded to a layer of non-woven thermoplastic polymer, said film and layers being bonded at multiple spaced-apart locations;
• said layers and microporous film being joined by ultrasonic point bonding;
• said composite fabric providing a barrier to passage of biological liquid as defined when the composite fabric is subjected to contact with synthetic blood at zero psi for five minutes followed by synthetic blood contact at 2 psi for one minute followed by zero psi synthetic blood contact for fifty-four minutes, said composite fabric exhibiting no visible penetration of the synthetic blood;
• said composite fabric having a moisture or vapor transmission rate of greater than about 450 grams per square meter for twenty-four hours at about 75.degree. F. and about 65% relative humidity;
• and
• said woven composite fabric having a breaking strength of at least about 14 pounds.

A process for forming a thermally bonded non-woven composite fabric having a moisture or vapor transmission rate of greater than about 450 grams per square meter for 24 hours at about 75.degree. F. and about 65% relative humidity, said fabric providing a barrier to passage of biological liquid when the composite fabric is subjected to contact with synthetic blood at 0 psi for 5 minutes followed by synthetic blood contact at 2 psi (13.6 kpa) for 1 minutes followed by synthetic blood contact at 0 psi for 54 minutes, said composite fabric exhibiting no visible penetration of the synthetic blood;

• and said composite fabric having a breaking strength of at least 14 pounds per inch;
• comprising:
• unwinding and contacting at least one continuous thermoplastic non-woven web to at least one side of a continuous polypropylene microporous film;
• continuously transporting said contacted web and film through an ultrasonic point bonding zone;
• thermally bonding the webs and film at multiple spaced-apart locations;
• said bonding having a dwell time sufficient to thermally bond while avoiding burn-through degradation of the film and webs;
• and forming the thermally bonded non-woven composite fabric.