Process for stretching incremental portions of an orientable thermoplastic substrate and product thereof

Claim 2

A process for longitudinally stretching incremental portions of a film of synthetic thermoplastic material selected from the group consisting of a thermoplastic orientable polymer or a blend of thermoplastic orientable polymers in which there is admixed an incompatible second phase material selected from the group consisting of an incompatible polymer or inorganic material which comprises: (a) introducing said film into a nip of interdigitating rollers having grooves substantially parallel to the axis of said rollers; (b) controlling the velocity of introduction of said film into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent slipping of said film and thereby longitudinally stretch incremental portions of said film by a deflection of said film into the shape of said grooves; and (c) collecting the thus formed sheet.

Claim 3

The process as defined in claim 1 wherein the withdrawal velocity is not greater than a factor of the draw ratio of said nip of interdigitating rollers.

Claim 4

The process as defined in claim 2 wherein steps (a) and (b) are repeated to a point below the break point of said film.

Claim 5

The process as defined in claim 3 wherein the resulting product is cut into strips and subjected to agitation to form fibers.

Claim 6

The process as defined in claim 1 wherein said incompatible phase is contacted with a selective solvent to dissolve said phase.

Claim 7

The product produced by the process of claim 4.

Claim 8

A process for bi-axially stretching incremental portions of a film formed of synthetic thermoplastic material selected from the group consisting of a thermoplastic orientable polymer or a blend of thermoplastic orientable polymers in which there is admixed an incompatible second phase material selected from the group consisting of an incompatible polymer or inorganic material which comprises: (a) introducing said film into a nip of interdigitating rollers having grooves parallel to the axis of said rollers; (b) controlling the velocity of introduction of said film into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent slipping of said film and thereby longitudinally stretch incremental portions of said film by deflection of said film into the shape of said grooves; (c) withdrawing said film from said rollers at a velocity greater than the rotational velocity of said rollers; (d) introducing said film into a nip of interdigitating rollers having grooves substantially perpendicular to the axis of said rollers; (e) controlling the velocity of introduction of said web into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent narrowing of said film prior to introduction into said nip thereby to laterally stretch incremental portions of said web by deflection of said film into shape of said grooves; (f) withdrawing said web from said rollers at a velocity substantially corresponding to the velocity of introduction and; (g) collecting the thus stretched film.

Claim 9

A process for bi-axially stretching incremental portions of a film formed of synthetic thermoplastic material selected from the group consisting of a thermoplastic orientable polymer or a blend of thermoplastic orientable polymers in which there is admixed an incompatible second phase material selected from the group consisting of an incompatible polymer or inorganic material which comprises: (a) introducing said film into a nip of interdigitating rollers having grooves parallel to the axis of said rollers; (b) controlling the velocity of introduction of said film into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent slipping of said film and thereby longitudinally stretch incremental portions of said film by deflection of said film into the shape of said grooves; (c) withdrawing said film from said rollers at a velocity greater than the rotational velocity of said rollers; (d) introducing said film into a nip of interdigitating rollers having grooves substantially perpendicular to the axis of said rollers; (e) controlling the velocity of introduction of said web into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent narrowing of said film prior to introduction into said nip thereby to laterally stretch incremental portions of said web by deflection of said film into shape of said grooves; (f) withdrawing said web from said rollers at a velocity substantially corresponding to the velocity of introduction and; (g) collecting the thus stretched film.

Claim 10

The process as defined in claim 7 wherein the steps (a) to (f) are repeated prior to step (g).

Claim 11

The process as defined in claim 7 wherein steps (d) to (f) are affected prior to steps (a) to (c).

Claim 12

The process as defined in claim 7 including the steps of selecting said incompatible polymer as said incompatible phase and contacting said stretched film with a selective solvent to dissolve said incompatible phase.

Claim 13

The opaque, low density, porous film produced by claim 10.

Claim 14

The process as defined in claim 7 including the steps of selecting said inorganic material as said incompatible material and contacting said stretched film with a solvent to dissolve said inorganic material.

Claim 15

The opaque, low density, porous film produced by the process of claim 12.

Claim 16

The process as defined in claim 1 wherein said film is withdrawn from said interdigitating rollers at a velocity greater than the surface velocity of said rollers to pull said film away from said interdigitating rollers.

Claim 17

A process for stretching incremental portions of a film formed of synthetic thermoplastic material selected from the group consisting of a thermoplastic orientable polymer or a blend of thermoplastic orientable polymers in which there is admixed an incompatible second phase material selected from the group consisting of an incompatible polymer or inorganic material which comprises: (a) introducing said film into a nip of interdigitating rollers having grooves substantially perpendicular to the axis of said rollers; (b) controlling the velocity of introduction of said film into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent narrowing of said film prior to introduction into said nip thereby to laterally stretch incremental portions of said film by deflection of said film into the shape of said grooves; and (c) collecting the thus laterally stretched film.

Claim 18

A process for stretching incremental portions of a film formed of synthetic thermoplastic material selected from the group consisting of a thermoplastic orientable polymer or a blend of thermoplastic orientable polymers in which there is admixed an incompatible second phase material selected from the group consisting of an incompatible polymer or inorganic material which comprises: (a) introducing said film into a nip of interdigitating rollers having grooves substantially perpendicular to the axis of said rollers; (b) controlling the velocity of introduction of said film into said nip to assume and maintain the velocity substantially identical to the surface velocity of said rollers to prevent narrowing of said film prior to introduction into said nip thereby to laterally stretch incremental portions of said film by deflection of said film into the shape of said grooves; and (c) collecting the thus laterally stretched film.

Claim 19

The process as defined in claim 15 wherein said stretched film is laterally extended prior to step (c).