US 6,815,023 B1 · Puncture resistant polymeric films, blends and process

Abstract

A polymer blend and mono-and multilayer films made therefrom suitable for processing or packaging articles which have an improved combination of properties e.g. such as lower tear strength and higher puncture resistance, or higher puncture resistance at both room temperature in air and at elevated temperatures in contact with water wherein the blend preferably has a first copolymer of ethylene and hexene-1 having a copolymer melting point of 80 to 98° C., preferably of 80 to 92° C.; a second copolymer of ethylene and at least one α-olefin having a copolymer melting point of 115 to 128° C.; and a third copolymer of ethylene and a vinyl ester or alkyl acrylate and having a melting point of 60 to 110° C., and a process for making such films, especially shrink films having at least 40% shrink at 90° C. in at least one direction.

Claims105

Dependent claims

A flexible, biaxially stretched, heat shrinkable polymeric film having at least one layer comprising a blend of at least three copolymers comprising:

20 to 85 weight percent of a first polymer having a melting point of 80 to 98° C. comprising at least one copolymer of ethylene and hexene-1;
5 to 35 weight percent of a second polymer having a melting point of 115 to 128° C. comprising at least one copolymer of ethylene and at least one α-olefin;
and
10 to 50 weight percent of a third polymer having a melting point of 60 to 110° C. comprising at least one copolymer of ethylene and a vinyl ester, an alkyl acrylate, acrylic acid, or methacrylic acid;
wherein said first and second polymers have a combined weight percentage of at least 50 weight percent, said weight percentage being based upon the total weight of said first, second and third polymers;
and wherein said film has a maximum ram puncture force of at least 70 Newtons, a ram puncture stress of at least 110 MPa, and a tear propagation strength “x” such that 10≦x≦40 grams per mil in each of the machine and transverse directions or x<25 grams per mil in at least one of the machine and transverse directions.

3 more elements

A process for making biaxially stretched, heat shrinkable film comprising a polymeric blend A comprising:

extruding a melt plastified primary tube comprising 20 to 85 weight percent of a first polymer having a melting point of 80 to 98° C. comprising at least one copolymer of ethylene and hexene-1;
5 to 35 weight percent of a second polymer having a melting point of 115 to 128° C. comprising at least one copolymer of ethylene and at least one α-olefin;
10 to 50 weight percent of a third polymer having a melting point of 60 to 110° C. comprising at least one copolymer of ethylene and a vinyl ester or an alkyl acrylate;
wherein said first and second polymers have a combined weight percentage of at least 50 weight percent, said weight percentage being based upon the total weight of said first, second and third polymers;
cooling said primary tube;
reheating said cooled tube to a draw point temperature of 65 to 88° C.;
biaxially stretching said tube to provide a transverse direction circumference of at least 2½ times the circumference of said primary tube and a machine direction length of at least 2½ times the length of a corresponding segment of said primary tube, and cooling said biaxially stretched tube to form a biaxially stretched, heat shrinkable film having a film thickness less than 10 mil (254 microns);
wherein a multilayer primary tube is made by coextrusion or coating lamination and said resultant biaxially stretched film comprises:
a heat sealing surface layer comprising a polymer selected from the group consisting of:
(a) at least 50% by weight of a copolymer of propene and at least one 0-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a propene content of at least 60 wt. %, and (b) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105° C. and a density of at least 0.900 g/cm3;
an intermediate layer;
a core layer comprising at least 80% by weight, based on said third layer's weight, of at least one copolymer of:
EVOH;
or vinylidene chloride with from 2 to 20 weight percent, based on said copolymer's weight, of vinyl chloride or methyl acrylate;
an outer protective surface layer;
wherein at least one of said intermediate and said outer protective layers comprise said polymeric blend A, and said core layer is disposed between said intermediate and said outer protective layers, and said film has a maximum ram puncture force of at least 100 Newtons, a hot water puncture resistance of at least 100 seconds at 95° C. and a hot water seal strength of at least 200 seconds at 95° C.

13 more elements

A biaxially stretched, heat shrinkable, multilayer film useful for food processing and packaging having at least four layers comprising:

a first heat sealing surface layer comprising a polymer or blend of polymers selected from the group consisting of:
(a) at least 50% by weight of a copolymer of propene and at least one α-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a propene content of at least 60 wt. %, and (b) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105° C. and a density of at least 0.900 g/cm3;
a second polymeric layer comprising (a) from 10 to 85 wt. % of a first copolymer of ethylene and at least one C3-C8 α-olefin, said first copolymer having a melting point of 55 to 98° C.;
(b) from 5 to 60 wt. % of a second copolymer of ethylene and at least one C4-C8 α-olefin, said second copolymer having a melting point of 115° C. to 128° C., (c) from 0 to 50 wt. % of a third copolymer having a melting point of 60 to 110° C. of ethylene with a vinyl ester or alkyl acrylate, wherein said first and second copolymers have a combined weight percentage of at least 50 weight percent, said weight percent being based upon the total weight of said layer;
a third layer comprising at least 80% by weight, based on said third layer's weight, of at least one copolymer of vinylidene chloride with from 2 to 20 weight percent, based on said copolymer's weight, of vinyl chloride or methyl acrylate;
and
a fourth polymeric layer comprising (a) from 10 to 85 wt. % of a first copolymer of ethylene and at least one C3-C8 α-olefin, said first copolymer having a melting point of 55 to 98° C.;
(b) from 5 to 60 wt. % a second copolymer of ethylene and at least one C4-C8 α-olefin, said second copolymer having a melting point of 115° C. to 128° C., and (c) from 0 to 50 wt. % of a third copolymer having a melting point of 60 to 110° C. of ethylene with a vinyl ester or alkyl acrylate, wherein said first and second copolymers have a combined weight percentage of at least 50 weight percent, said weight percent being based upon the total weight of said layer;
and
wherein said film has a shrinkage value at 90° C. of at least 40% in at least one of the machine and transverse directions and said film has a tensile seal strength of at least 400 g/cm at 88° C.

7 more elements

A process for making biaxially stretched, heat shrinkable film comprising:

extruding a melt plastified primary tube comprising a polymeric blend A comprising 20 to 85 weight percent of a first polymer having a melting point of 80 to 98° C. comprising at least one copolymer of ethylene and hexene-1;
5 to 35 weight percent of a second polymer having a melting point of 115 to 128° C. comprising at least one copolymer of ethylene and at least one α-olefin;
and
10 to 50 weight percent of a third polymer having a melting point of 60 to 110° C. comprising at least one copolymer of ethylene and a vinyl ester or an alkyl acrylate;
wherein said first and second polymers have a combined weight percentage of at least 50 weight percent, said weight percentage being based upon the total weight of said first, second and third polymers;
cooling said primary tube;
reheating said cooled tube to a draw point temperature of 65 to 88° C.;
biaxially stretching said tube to provide a transverse direction circumference of at least 2½ times the circumference of said primary tube and a machine direction length of at least 2½ times the length of a corresponding segment of said primary tube, and cooling said biaxially stretched tube to form a biaxially stretched, heat shrinkable film having a film thickness less than 10 mil (254 microns), wherein a multilayer primary tube is made by coextrusion or coating lamination and said resultant biaxially stretched film comprises:
a heating sealing surface layer comprising a polymer selected from the group consisting of:
(a) at least 50% by weight of a copolymer of propene and at least one α-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a propene content of at least 60 wt. %, and (b) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof, said polymer having a melting point of at least 105° C. and a density of at least 0.900 g/cm3;
an intermediate layer,
a core layer comprising at least 80% by weight (based on said third layer's weight) of at least one copolymer of:
EVOH;
or vinylidene chloride with from 2 to 20 weight percent (based on said copolymer's weight) of vinyl chloride or methyl acrylate;
and
an outer protective surface layer;
wherein at lease one of said intermediate and said outer protective layers comprise said polymeric blend A and said core layer is disposed between said intermediate and said outer protective layers, and said film has a maximum ram puncture force of at least 100 Newtons, a hot water puncture resistance of at least 100 seconds at 95° C. and a hot water seal strength of at least 200 seconds at 95° C.

14 more elements

Dependencies are inferred from the claim text.

Puncture resistant polymeric films, blends and process

Life of this patent

Puncture resistant polymeric films, blends and process

Life of this patent

Abstract

Claims105