Process for forming film from low strain hardening polymers

Claim 2

A process for forming a blown film from a normally solid thermoplastic resin having an extensional viscosity index of less than about 6 which comprises extruding said resin through the die lips of a tubular film die to form a molten tube, expanding said molten tube radially at an angle of at least 45° as measured from the longitudinal axis of said expanding film bubble, said angle being substantially maintained at at least 45° for a distance of at least one inch along the longitudinal cross-section taken through the longitudinal axis of said expanding film bubble and thereafter contacting said film bubble with a primary cooling stream.

Claim 3

A process according to claim 1 wherein said film bubble is expanded until said film bubble is at least 1.5 times the diameter of said molten tube leaving said die lips, prior to contact with said primary cooling stream.

Claim 4

A process according to claim 1 wherein said film bubble is reduced in thickness to at least about 30% of the initial thickness of the tube leaving said extrusion die prior to contact with said primary cooling stream.

Claim 5

A process according to claim 1 wherein said film bubble is expanded radially at an angle of at least 55°.

Claim 6

A process according to claim 1 wherein said film bubble is expanded radially at an angle of from about 65° to about 85°.

Claim 7

A process according to claim 1 wherein each discharge orifice has a diameter equal to or greater than 1.6 times the die diameter.

Claim 8

A process according to claim 1 wherein said normally solid thermoplastic resin has an extensional viscosity index of from about 2 to about 4.5.

Claim 9

A process according to claim 7 wherein said normally solid thermoplastic resin is a low pressure-low density ethylene polymer.

Claim 10

A process according to claim 8 wherein said low pressure-low density ethylene polymer is a copolymer of not more than 15 mole percent of at least one C 3 to C 8 alpha-olefin hydocarbon comonomers, said polymer having a density of about 0.91 to about 0.94 g/cc.

Claim 11

A process according to claim 1 wherein said normally solid thermoplastic resin is a low pressure-high density ethylene polymer.

Claim 12

A process according to claim 1 wherein said primary cooling stream comprises air.

Claim 13

A process according to claim 1 wherein the die rate is greater than about 5 lb./hr.-in.

Claim 14

A process according to claim 1 wherein films are produced having a haze of less than 8.5 percent.

Claim 15

An improvement in the process for forming a blown film from a normally solid thermoplastic resin having an extensional viscosity index of less than about 6 wherein said resin is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said resin, allowing said molten tube to expand to form a film bubble, directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream the improvement which comprises expanding said film bubble radially at an angle of at least 45° as measured from the longitudinal axis of said expanding film bubble said angle being substantially maintained at at least 45° for a distance of at least one inch along a longitudinal cross section taken through the longitudinal axis of said expanding film bubble prior to contact with said primary cooling stream.

Claim 16

An improvement in the process for forming a blown film from a normally solid thermoplastic resin having an extensional viscosity index of less than about 6 wherein said resin is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said resin, allowing said molten tube to expand to form a film bubble, directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream the improvement which comprises expanding said film bubble radially at an angle of at least 45° as measured from the longitudinal axis of said expanding film bubble said angle being substantially maintained at at least 45° for a distance of at least one inch along a longitudinal cross section taken through the longitudinal axis of said expanding film bubble prior to contact with said primary cooling stream.

Claim 17

The improvement according to claim 14 wherein said film bubble is expanded until said film bubble is at least 1.5 times the diameter of said molten tube leaving said die lips, prior to contact with said primary cooling stream.

Claim 18

The improvement according to claim 14 wherein said film bubble is expanded until said film bubble is at least 1.7 times the diameter of said molten tube leaving said die lips, prior to contact with said primary cooling stream.

Claim 19

The improvement according to claim 14 wherein said film bubble is expanded until said film bubble is from about 1.8 to about 6 times the diameter of said molten tube leaving said die lips, prior to contact with said primary cooling stream.

Claim 20

The improvement according to claim 14 wherein said film bubble is reduced in thickness to at least about 30% of the initial thickness of the tube leaving said extrusion die prior to contact with said primary cooling stream.

Claim 21

The improvement according to claim 14 wherein said film bubble is reduced in thickness to from about 5% to about 20% of the initial thickness of the tube leaving said extrusion die prior to contact with said primary cooling stream.

Claim 22

The improvement according to claim 14 wherein said primary cooling stream is directed against said film bubble in a manner such as to create said reduced pressure zone.

Claim 23

The improvement according to claim 14 wherein said film bubble is expanded radially at an angle of at least 55°.

Claim 24

The improvement according to claim 14 wherein said film bubble is expanded radially at an angle of from about 65° to about 85°.

Claim 25

The improvement according to claim 14 wherein said discharge orifice has a diameter equal to or greater than 1.6 times the die diameter.

Claim 26

The improvement according to claim 14 wherein said discharge orifice has a diameter equal or greater than 1.8 times the die diameter.

Claim 27

The improvement according to claim 14 wherein said discharge orifice has a diameter of from about 1.9 to about 6.1 times the die diameter.

Claim 28

The improvement according to claim 14 wherein said normally solid thermoplastic resin has an extensional viscosity index of from about 2 to about 4.5.

Claim 29

The improvement according to claim 26 wherein said normally solid thermoplastic resin is a low pressure-low density ethylene polymer.

Claim 30

The improvement according to claim 27 wherein said low pressure-low density ethylene polymer is a copolymer of not more than 15 mole percent of at least one C 3 to C 8 alpha-olefin hydrocarbon comonomers, said polymer having a density of about 0.91 to about 0.94 g/cc.

Claim 31

The improvement according to claim 14 wherein said normally solid thermoplastic resin is a low pressure-high density ethylene polymer.

Claim 32

The improvement according to claim 14 wherein said primary cooling stream comprises air.

Claim 33

The improvement according to claim 14 wherein the die rate is greater than about 5 lb./hr.-in.

Claim 34

The improvement according to claim 14 wherein the die rate is from 7 to 12 lb./hr.-in.

Claim 35

The improvement according to claim 14 wherein films are produced having a haze of less than 8.5%.

Claim 36

The improvement according to claim 14 wherein films are produced having a haze of from about 1 to 6%.

Claim 37

An improvement in the process for forming a blown film from a normally solid thermoplastic resin having an extensional viscosity index of from about 2 to about 4.5 wherein said resin is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said resin, allowing said molten tube to expand to form a film bubble by directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream the improvement comprising (a) expanding said film bubble radially at an angle of at least 55° as measured from the longitudinal axis of said film bubble towards the film surface, (b) substantially maintaining said film bubble at said angle for a distance of at least one inch along said expanding film bubble (c) expanding said film bubble until said film bubble is at least 1.5 times the diameter of said molten tube leaving said die lips, and (d) reducing the thickness of said film bubble to about 30% of the initial thickness of said molten tube leaving said die lips, each of (a) through (d) being performed prior to contact with said primary cooling stream.

Claim 38

An improvement in the process for forming a blown film from a normally solid thermoplastic resin having an extensional viscosity index of from about 2 to about 4.5 wherein said resin is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said resin, allowing said molten tube to expand to form a film bubble by directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream the improvement comprising (a) expanding said film bubble radially at an angle of at least 55° as measured from the longitudinal axis of said film bubble towards the film surface, (b) substantially maintaining said film bubble at said angle for a distance of at least one inch along said expanding film bubble (c) expanding said film bubble until said film bubble is at least 1.5 times the diameter of said molten tube leaving said die lips, and (d) reducing the thickness of said film bubble to about 30% of the initial thickness of said molten tube leaving said die lips, each of (a) through (d) being performed prior to contact with said primary cooling stream.

Claim 39

The improvement according to claim 35 wherein in (a) said film bubble is expanded radially at an angle of from about 65° to about 85° and wherein in (b) the angle is maintained at from 65° to about 85°.

Claim 40

The improvement according to claim 35 wherein in (c) said film bubble is expanded until said film bubble is at least 1.7 times the diameter of said molten tube leaving said die lips.

Claim 41

The improvement according to claim 35 wherein in (c) said film bubble is expanded until said film bubble is from about 1.8 to about 6 times the diameter of said molten tube leaving said die lips.

Claim 42

The improvement according to claim 35 wherein (d) said film bubble is reduced in thickness to from about 5% to about 20% of the initial thickness of the molten tube leaving said die lips prior to contact with said primary cooling stream.

Claim 43

The improvement according to claim 35 wherein said primary cooling stream is directed against said film bubble in a manner such as to create said reduced pressure zone.

Claim 44

The improvement according to claim 35 wherein said discharge orifice has a diameter equal to or greater than 1.6 times the die diameter.

Claim 45

The improvement according to claim 35 wherein said discharge orifice has a diameter equal to or greater than 1.8 times the die diameter.

Claim 46

The improvement according to claim 35 wherein said discharge orifice has a diameter of from about 1.9 to about 6.1 times the die diameter.

Claim 47

The improvement according to claim 35 wherein said normally solid thermoplastic resin is a low pressure-low density ethylene polymer.

Claim 48

The improvement according to claim 44 wherein said low pressure-low density ethylene polymer is a copolymer of not more than 15 mole percent of at least one C 3 to C 8 alpha-olefin hydrocarbon comonomer, said polymer having a density of about 0.91 to about 0.94 g/cc.

Claim 49

The improvement according to claim 35 wherein said normally solid thermoplastic resin is a low pressure-high density ethylene polymer.

Claim 50

The improvement according to claim 35 wherein said primary cooling stream comprises air.

Claim 51

The improvement according to claim 35 wherein the die rate is greater than about 5 lb/hr-in.

Claim 52

The improvement according to claim 35 wherein the die rate is 7 to 12 lb/hr-in.

Claim 53

The improvement according to claim 35 wherein films are produced having a haze of less than 8.5%.

Claim 54

The improvement according to claim 35 wherein films are produced having a haze of from about 1 to 6%.

Claim 55

An improvement in the process for forming a blown film from a low pressure-low density ethylene polymer wherein said polymer is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said polymer, allowing said molten tube to expand to form a film bubble by directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream, the improvement comprising (a) extruding said polymer at a die rate of about 7 to about 12 lb/hr-in. (b) expanding said film bubble radially at an angle of at least 55° as measured from the longitudinal axis of said film bubble towards the film bubble surface, (c) substantially maintaining said angle of at least 55° for a distance of at least one inch along a longitudinal cross section taken through the longitudinal axis of said expanding film bubble (d) expanding said film bubble until said film bubble is at least 1.7 times the diameter of said molten tube leaving said die lips, and (e) reducing the thickness of said film bubble until said film bubble is reduced in thickness to from about 5% to about 20% of the initial thickness of said molten tube leaving said die lips, each of (a) through (e) being performed prior to contact with said primary cooling stream.

Claim 56

An improvement in the process for forming a blown film from a low pressure-low density ethylene polymer wherein said polymer is extruded through the die lips of a tubular film die under conditions and in a manner such as to form a molten tube of said polymer, allowing said molten tube to expand to form a film bubble by directing a flow of fluid from at least one discharge orifice in a manner such that a reduced pressure zone is created outside said film bubble and wherein said film bubble is cooled by a primary cooling stream, the improvement comprising (a) extruding said polymer at a die rate of about 7 to about 12 lb/hr-in. (b) expanding said film bubble radially at an angle of at least 55° as measured from the longitudinal axis of said film bubble towards the film bubble surface, (c) substantially maintaining said angle of at least 55° for a distance of at least one inch along a longitudinal cross section taken through the longitudinal axis of said expanding film bubble (d) expanding said film bubble until said film bubble is at least 1.7 times the diameter of said molten tube leaving said die lips, and (e) reducing the thickness of said film bubble until said film bubble is reduced in thickness to from about 5% to about 20% of the initial thickness of said molten tube leaving said die lips, each of (a) through (e) being performed prior to contact with said primary cooling stream.

Claim 57

The improvement according to claim 52 wherein in (b) said film bubble is expanded radially at an angle of from about 65° to about 85° and wherein in (c) the angle is maintained at from about 65° to about 85°.

Claim 58

The improvement according to claim 52 wherein in (d) said film bubble is expanded until said film bubble is from about 1.8 to about 6 times the diameter of said molten tube leaving said die lips.

Claim 59

The improvement according to claim 52 wherein said primary cooling stream is directed against said film bubble in a manner such as to create said reduced pressure zone.

Claim 60

The improvement according to claim 52 wherein said discharge orifice has a diameter equal to or greater than 1.8 times the die diameter.

Claim 61

The improvement according to claim 52 wherein said discharge orifice has a diameter of from about 1.9 to about 6.1 times the die diameter.

Claim 62

The improvement according to claim 52 wherein said low pressure-low density ethylene polymer is a copolymer of not more than 15 mole percent of at least one C 3 to C 8 alpha-olefin hydrocarbon comonomer said polymer having a density of about 0.91 to about 0.94 g/cc.

Claim 63

The improvement according to claim 52 wherein said primary cooling stream comprises air.

Claim 64

The improvement according to claim 52 wherein films are produced having a haze of less than 8.5%.

Claim 65

The improvement according to claim 52 wherein films are produced having a haze of from about 1 to 6%.

Claim 66

Films produced according to the process of claim 1.

Claim 67

Films produced according to the improvement of claim 14.