Method of making a reusable, tear-resistant polyolefin-paper laminate

Claim 2

A PROCESS FOR PREPARING A BONDED POLYMONOOLEFIN-PAPER LAMINATE COMPRISING IN ORDER A POLYMONOOLEFIN FILM, A POLYMONOOLEFIN BONDING LAYER, AND A FIBROUS CELLULOSIC SUPPORT SHEET, AND SUITED TO REPEATED REUSE, WHICH COMPRISES: A. CONTACTING A MOVING CONTINOUS POLYMONOOLEFIN FILM, AND A MOVING CONTINOUS POLYMONOOELFIN FILM, B. CONTINOUSLY EXTRUDING A HOT MELT OF A POLYMOONELFIN TO THE AREA OF CONTACT BETWEEN SAID SHEET AND SAID FILM WHEREIN SAID FILM AND SAID MELT EACH ARE POLYMONOOLEFIN POLYMERS CONTAINING AS A MAJOR COMPONENT A COMMON 1-MONOOLEFIN MONOMER, AND C. PRESSING TOGETHER BY SAID ROLLER MEANS SAID SHEET, MELT AND FILM, AND THEREBY FORMING SAID LAMINATE; WHEREIN SAID POLYMONOOLEFIN OF SAID FILM IS CHARACTERIZED BY A MELT FLOW OR INDEX OF 0.2 TO 20, AND SAID POLYMONOOLEFIN OF SAID MELT IS CHARACTERIZED BY A MELT FLOW OR INDEX HIGHER THAN THAT OF SAID FILM AND FURTHER IN THE RANGE 20 TO 100.

Claim 3

A process according to claim 1 wherein each said polymonoolefin is a polymer of at least one monoolefin of 2 to 8 carbon atoms per molecule and 0 to 25 weight percent of a monomer copolymerizable therewith.

Claim 4

A process according to claim 2 wherein said film has a thickness of 0.2 to 5 mils and is prepared from a polymonoolefin with a density of 0.89 to 0.97 gms/cc; wherein said melt polymonoolefin is applied at a melt temperature of 350* to 700* F., and at a rate of 3 to 16 pounds per ream of paper; and wherein said sheet is a Kraft paper weighing 25 to 100 pounds per 3,000 square foot-ream.

Claim 5

A process according to claim 3 wherein said paper is preheated and said melt temperatuure is above 600* F.

Claim 6

A process according to claim 3 wherein said film is an oriented film.

Claim 7

A process according to claim 5 wherein said polyolefins are polymers of propylene; said film is biaxially oriented; said Kraft paper is pretreated with polyalkylene prior to said step (a); said film M.F. is about 1 to 6, and said melt M.F. is about 50 to 80; and said process includes the further step of applying a curable organopolysiloxane release coating onto at least one of the outer surface of said film and the outer surface of said sheet.

Claim 8

A process for preparing at high line speeds a polymonoolefin-substrate laminate suited to repeated reuse which comprises laminating a polymonoolefin film to a fibrous cellulosic substrate by means of a polymonoolefin melt, which process comprises: a. continuously contacting a moving web of said substrate and a moving polymonoolefin film, b. continuously extruding a polymonoolefin melt bonding layer at elevated temperature to the area of said contact between said substrate and said film, c. pressing together said substrate, said bonding layer melt, and said film, thereby forming said polymonoolefin-substrate laminate, wherein said polymonoolefin bonding layer and said polymonoolefin film each contain as a major component a common 1-monoolefin monomer of 2 to 8 carbon atoms per molecule, and each can contain up to 25 weight percent of monomer copolymerizable therewith, wherein said polymonoolefin of said bonding layer is characterized by melt flow of about 50 to 80, and said polymonoolefin of said film is characterized by melt flow of about 1 to 6.

Claim 9

A process for preparing at high line speeds a polymonoolefin-substrate laminate suited to repeated reuse which comprises laminating a polymonoolefin film to a fibrous cellulosic substrate by means of a polymonoolefin melt, which process comprises: a. continuously contacting a moving web of said substrate and a moving polymonoolefin film, b. continuously extruding a polymonoolefin melt bonding layer at elevated temperature to the area of said contact between said substrate and said film, c. pressing together said substrate, said bonding layer melt, and said film, thereby forming said polymonoolefin-substrate laminate, wherein said polymonoolefin bonding layer and said polymonoolefin film each contain as a major component a common 1-monoolefin monomer of 2 to 8 carbon atoms per molecule, and each can contain up to 25 weight percent of monomer copolymerizable therewith, wherein said polymonoolefin of said bonding layer is characterized by melt flow of about 50 to 80, and said polymonoolefin of said film is characterized by melt flow of about 1 to 6.

Claim 10

The process according to claim 7 wherein said polyolefin film further is characterized by a density of about 0.89 to 0.97 gm/cc.

Claim 11

A process according to claim 7 wherein said film has a thickness of about 0.2 to 5 mils.

Claim 12

The process according to claim 7 wherein said film is an oriented film.

Claim 13

The process according to claim 7 wherein said substrate or said film or both are release coated on the exposed outer surface thereof, and said release coating is an organopolysiloxane applied in an amount so as to provide about 0.03 to 0.4 pounds per ream on a dry basis.

Claim 14

The process according to claim 7 wherein said substrate is preheated to a temperature below a loss of strength stage for said substrate.

Claim 15

The process according to claim 7 wherein said polymonoolefin bonding melt is melt extruded at a melt temperature of about 350* to 700* F., and applied in a range of about 3 to 16 pounds of said melt per 3000 square foot-ream of said substrate.

Claim 16

The process according to claim 13 wherein said substrate is pretreated with a polyalkyleneimine at a rate of about 0.5 to 5 pounds per ream employing said polyalkyleneimine as a hydrocarbon solution thereof, so as to apply about 0.01 to 0.1 pound per ream on a dry solids basis.

Claim 17

The process according to claim 14 wherein said subStrate is a Kraft paper, said film is a biaxially oriented polypropylene film, said melt flow bonding is a polypropylene.

Claim 18

The process of claim 7 wherein each said polymonooolefin is selected from homopolymers of propylene and copolymers of ethylene-propylene.

Claim 19

The process of claim 1 wherein said sheet is conveyed by a first roller means; said film is conveyed by a second roller means; said first and second roller means define or nip area therebetween, and said area of contact is defined by said nip area.