Stretch-oriented porous films and preparation and use thereof

Claim 2

A stretch-oriented, elastomeric, porous polyurethane film less than 80 mils in thickness having a void volume of about 5 -60 volume percent, said void volume being in the form of an interconnecting network of voids, said voids averaging about 3 -250 microns in their longest dimension, said polyurethane film having been stretch-oriented at a stretch ratio of at least 1.5:1 in at least one direction, thereby being enlarged in area to at least 1.5 times as large as the original area and thereby being decreased in thickness, said polyurethane film containing 5 to 60 percent by volume of an inorganic water insoluble pore nucleating agent distributed throughout said interconnecting network of voids and being smaller in average size than the said average size of said voids, said polyurethane film having a moisture vapor transmission value of at least 500 microgram/cm2 hr for a relative humidity difference on opposite sides of said polyurethane film of no less than 100/60 percent.

Claim 3

A STRETCH-ORIENTED, ELASTOMERIC, POROUS POLYURETHANE FILM LESS THAN 80 MILS IN THICKNESS HAVING A VOID VOLUME OF ABOUT 5 - 60 VOLUME PERCENT, SAID VOID VOLUME BEING IN THE FORM OF AN INTERCONNECTING NETWORK OF VOIDS, SAID VOIDS AVERAGING ABOUT 3 - 250 MICRONS IN THEIR LONGEST DIMENSION, SAID POLYURETHANE FILM HAVING BEEN STRETCH-ORIENTED AT A STRETCH RATIO OF AT LEAST 1.5*1 IN AT LEAST ONE DIRECTION, THEREBY BEING ENLARGED IN AREA TO AT LEAST 1.5 TIMES AS LARGE AS THE ORIGINAL AREA AND THEREBY BEING DECREASED IN THICKNESS, SAID POLYURETHANE FILM CONTAINING 5 TO 60 PERCENT BY VOLUME OF AN INORGANIC WATER INSOLUBLE PORE NUCLEATING AGENT DISTRIBUTED THROUGHOUT SAID INTERCONNECTING NETWORK OF VOIDS AND BEING SMALLER IN AVERAGE SIZE THAN THE SAID SAID AVERAGE SIZE OF SAID V OIDS, SAID POLYURETHANE FILM HAVING A MOISTURE VAPOR TRANSMISSION VALUE OF AT LEAST 500 MICROGRAN/CM2HR FOR A RELATIVE HUMIDITY DIFFERENCE ON OPPOSITE SIDES OF SAID POLYURETHANE FILM OF NO LESS THAN 100/60 PERCENT.

Claim 4

A STRETCH-ORIENTED, ELASTOMERIC, POROUS POLYURETHANE FILM LESS THAN 80 MILS IN THICKNESS HAVING A VOID VOLUME OF ABOUT 5 - 60 VOLUME PERCENT, SAID VOID VOLUME BEING IN THE FORM OF AN INTERCONNECTING NETWORK OF VOIDS, SAID VOIDS AVERAGING ABOUT 3 - 250 MICRONS IN THEIR LONGEST DIMENSION, SAID POLYURETHANE FILM HAVING BEEN STRETCH-ORIENTED AT A STRETCH RATIO OF AT LEAST 1.5*1 IN AT LEAST ONE DIRECTION, THEREBY BEING ENLARGED IN AREA TO AT LEAST 1.5 TIMES AS LARGE AS THE ORIGINAL AREA AND THEREBY BEING DECREASED IN THICKNESS, SAID POLYURETHANE FILM CONTAINING 5 TO 60 PERCENT BY VOLUME OF AN INORGANIC WATER INSOLUBLE PORE NUCLEATING AGENT DISTRIBUTED THROUGHOUT SAID INTERCONNECTING NETWORK OF VOIDS AND BEING SMALLER IN AVERAGE SIZE THAN THE SAID SAID AVERAGE SIZE OF SAID V OIDS, SAID POLYURETHANE FILM HAVING A MOISTURE VAPOR TRANSMISSION VALUE OF AT LEAST 500 MICROGRAN/CM2HR FOR A RELATIVE HUMIDITY DIFFERENCE ON OPPOSITE SIDES OF SAID POLYURETHANE FILM OF NO LESS THAN 100/60 PERCENT.

Claim 5

A polyurethane film according to claim 1 wherein said film is coated with a pressure-sensitive adhesive.

Claim 6

A film according to claim 2 wound upon itself to form a roll comprising a plurality of convolutions.

Claim 7

A film according to claim 1 laminated to a nonadherent, moisture-transmissive burn covering material.

Claim 8

A film according to claim 4 wound upon itself to form a roll comprising a plurality of convoluTions.

Claim 9

A FIRST AID DRESSING COMPRISING A FILM ACCORDING TO CLAIM 1 LAMINATED TO AN ABSORBENT PAD.