Multilayer packaging structures

Description of the invention

The present invention relates to a thermoformable multi-layer structure in the form of a flexible film for use as packaging films. The invention relates in particular to polyester and nylon structures formed into a packaging film.

Multilayer structures that can be thermoformed in the form of flexible films are used in the packaging of food and medical devices, to protect these products from external contamination and misuse, and to provide an attractive packaging for the product for its possible sale.

There is a great need in the packaging industry for film structures that provide excellent mechanical strength, improved optical and gas barrier properties, and improved heat-formability.

The multi-layer structure in the form of a flexible film according to the invention is characterized in that it comprises:

a) a first polyester layer selected from the group consisting of homopolymers or copolymers of ethylene terephthalate, ethylene naphthalate, and mixtures thereof;

b) a second adhesive layer selected from the group consisting of modified or unmodified ethylene homopolymers or copolymers, alkyl acrylates, vinyl esters, ethylene alpha olefins and mixtures thereof;

c) a third layer comprising nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene nonoanediamide) ), nylon 6.10 (poly (hexamethylene sebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipamide) co-caprolactam)), nylon 11 (polyene decanolactam), nylon 12 (polylauryl lactam) and their alloys or mixtures;

the first layer, the second layer and the third layer are formed into a flexible film by a coextrusion process and the film is non-oriented.

Preferably, the film is produced by slit coextrusion or single blown tube coextrusion.

Preferably, the first layer is the outer surface layer of the film.

Preferably, the second layer is directly adjacent to the first layer.

Preferably, the foil is less than about 0.406 mm thick.

More preferably, the film has a thickness of less than about 0.254 mm.

Most preferably, the film has a thickness from about 0.076 mm to about 0.178.

Preferably, the film has a heat shrinkage amount of less than about 5% in the machine direction at 90 ° C and less than about 5% in the perpendicular direction of the machine at 90 ° C.

More preferably, the film has a heat shrinkage amount of less than about 2% in the machine direction at 90 ° C and less than about 2% in the machine direction at 90 ° C.

Preferably, the foil contains less than 500 ppm of a transition metal salt selected from the group consisting of manganese (II), manganese (III), iron (II), iron (III), cobalt (II), cobalt (III), nickel (II) ), nickel (III), copper (I), copper (II), rhodium (II), rhodium (III), rhodium (IV) and ruthenium.

Preferably, the film has a Gloss Value greater than about 65 Hunter Units (HU).

Preferably, the first layer is selected from the group consisting of homopolymers or copolymers of aromatic esters and mixtures thereof.

Preferably, the film includes processing additives. Preferably, the adhesive is selected from the group consisting of modified or unmodified homopolymers or copolymers of ethylene, methyl acrylate, ethyl acrylate, n-butyl acrylate, ethylene-vinyl acetate copolymers, ethylene-alpha-olefin and mixtures thereof.

Preferably, the third layer is a mixture comprising about 71 wt% to about 100 wt% nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)) , nylon 6.9 (poly (hexamethylene nanediamide)), nylon 6.10 (poly (hexamethylene sebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipamide-co-caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam) and alloys or mixtures thereof and about 0 wt% to about 29 wt% amorphous nylon.

Preferably, the multilayer structure further comprises a fourth oxygen barrier layer or an adhesive layer.

More preferably, the oxygen barrier is selected from the group consisting of ethylene vinyl alcohol, polyvinylidene chloride, polyvinylidene chloride copolymers, polyacrylonitrile, acrylonitrile copolymers, and mixtures thereof.

Most preferably, the oxygen barrier has an oxygen transmission rate of less than about 15.5 cm³/ m² for 24 hours at a pressure of 0.98 x 10⁵ Bye.

More preferably, the adhesive is selected from the group consisting of modified or unmodified ethylene homopolymers or copolymers, alkyl acrylates, vinyl esters or ethylene alpha olefins, and mixtures thereof.

Most preferably, the adhesive is selected from the group consisting of modified or unmodified homopolymers or copolymers of ethylene, methyl acrylate, ethyl acrylate, n-butyl acrylate, ethylene vinyl acetate copolymers, ethylene alpha olefin and mixtures thereof.

Preferably, the multilayer structure further comprises a fifth layer comprising nylon or a mixture of nylons.

More preferably, the fifth layer is nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene adipine diamide) )), nylon 6.10 (poly (hexamethylene sebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipineamide) -caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam) and their alloys or mixtures.

Most preferably, the fifth layer is a mixture comprising about 71% by weight to about 100% by weight of a nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene nonanediamide)), nylon 6.10 (poly (hexamethylene nosebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipineamide-co-caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam), and alloys or mixtures thereof, and between about 0% by weight to about 29% by weight of amorphous nylon.

Preferably, the multilayer structure further comprises a sixth layer of an adhesive.

More preferably, the adhesive is selected from the group consisting of modified or unmodified ethylene homopolymers or copolymers, alkyl acrylates, vinyl esters or ethylene alpha olefin, and mixtures thereof.

Most preferably, the adhesive is selected from the group consisting of modified or unmodified homopolymers or copolymers of ethylene, methyl acrylate, ethyl acrylate, n-butyl acrylate, ethylene vinyl acetate copolymers, ethylene alpha-olefin, and mixtures thereof.

Preferably, the multilayer structure further comprises a seventh heat sealable layer.

More preferably, the heat sealable layer is selected from the group consisting of an ionomer, a heterogeneous ethylene alpha-olefin copolymer, a homogeneous ethylene alpha-olefin copolymer, an ethylene vinyl acetate copolymer, an ethylene-methyl acrylate copolymer, an ethylene-propylene copolymer, a homopolymer or a copolymer. butylene and mixtures thereof.

Preferably, the first layer, the second layer and the third layer form a structural subunit of a coextruded film with a plurality of layers.

Preferably, the film has an elongation at break at room temperature of greater than 250 percent in the longitudinal direction and greater than 250 percent in the transverse direction.

Films that combine the various layers into a single structure can be made by slotted die cast coextrusion or single blown tube coextrusion. The flat die or slotted die pouring method includes extruding the polymeric material through the die onto a cooled roll and winding the film onto the roll prior to further processing. In the single blow-sleeve coextrusion process, the polymer is forced through a die and around a mandrel and then exits into a tube. The tube, or sleeve, is expanded by blowing air through the center of the mandrel to a predetermined thickness followed by rapid cooling or quenching. Films produced with either a pour-through process or a single-sleeve blow molding method as described above are not

Oriented, as opposed to manufacturing methods which achieve a high degree of orientation in the films, such as the double sleeve methods or the tenter frame method.

Optionally, the first and third layers are in direct contact with opposite sides of the second layer.

In one embodiment, the structure with the first, second, and third layers is used to form a flexible seven-layer film.

Suitable films of the present invention may be defined as non-oriented and / or as having an elongation at break at room temperature greater than about 250 percent in both the machine direction (MD) and perpendicular direction (TD) and / or having an amount of shrinkage when exposed to a heat of less than about 5% at 90 ° C (MD and TD).

Fig. 1 is a section view of a multilayer structure comprising three layers according to the present invention.

Fig. 2 is a sectional view of a multi-layer structure comprising seven layers according to the present invention.

Fig. 3 is a sectional view of a multi-layer structure comprising seven alternative layers according to the present invention.

Fig. 4 is a sectional view of a multi-layer structure comprising seven other alternative layers according to the present invention.

Referring now to the drawings, Fig. 1 shows a three-layer multilayer structure 10 having a first layer 11, a second layer 12 and a third layer 13 formed into a film by coextrusion. The first layer 11 of the multi-layer structure 10 comprises polyester, the second layer 12 comprises an adhesive, and the third layer 13 comprises nylon or optionally a nylon blend in which the third layer comprises no more than 25% (by weight) of amorphous nylon.

2, a seven-layer multilayer structure 20 is shown including a first layer 21, a second layer 22, a third layer 23, a fourth layer 24, a fifth layer 25, a sixth layer 26 and a seventh layer 27. The multilayer structure 20 may include a first layer 21 including polyester; a second layer 22 and a fifth layer 25 both comprising adhesive; a third layer 23 and a fifth layer 25 comprising nylon or optionally a nylon blend, the third layer containing no more than 25% (by weight) of amorphous nylon; a fourth layer 24 providing an oxygen barrier layer or optionally an adhesive; and a seventh layer 27 providing a heat sealable layer.

In Fig. 3, a seven-layer multilayer structure 30 is shown including a first layer 31, a second layer 32, a third layer 33, a fourth layer 34, a fifth layer 35, a sixth layer 36 and a seventh layer 37. Structure 30 may include a first layer comprising polyester; a second layer 32, a third layer 3, and a sixth layer 36 each comprising an adhesive; a fourth layer 34 comprising nylon or optionally a nylon blend, the third layer comprising no more than 25% (by weight) of amorphous nylon; a fifth layer 35 comprising an oxygen barrier layer and a seventh heat sealable layer.

4, a seven-layer multi-layer structure 40 is shown including a first layer 41, a second layer 42, a third layer 43, a fourth layer 44, a fifth layer 45, a sixth layer 46 and a seventh layer 47. Structure 40 may include a first layer 41 including polyester; a second layer 42, a fourth layer, and a sixth layer 46 each comprising adhesive; a third layer 43 comprising a polyolefin homopolymer or copolymer; a fifth layer comprising nylon or optionally a nylon blend, the third layer containing no more than 25% (by weight) of amorphous nylon and a seventh layer 47 a heat sealable layer.

The term "polyester as used herein" refers to synthetic homopolymers or copolymers containing ester linkages between the monomer units that may be formed by a condensation polymerization process. Polymers of this type are preferably aromatic polyesters, more preferably homopolymers and copolymers of ethylene terephthalate, ethylene naphthalate, and mixtures thereof. Suitable aromatic polyesters may have an intrinsic viscosity in the range 0.60 to 1.0, preferably 0.60 to 0.80.

In connection with the multilayer structure 10, the first layer 11 provides the film with excellent dimensional stability during the hot-forming process and may serve as a surface layer in the film structure. The thickness of the first layer may be greater than or less than 0.127 mm, or less than 0.076 mm, and is typically from about 0.006 mm to about 0.127 mm.

Preferably about 0.006 mm to about 0.076 mm. Examples of preferred polyesters are available under the trade names EASTAPAK® Polyester 9663, EASTPAK® ​​Polymer 9921, and EASTAR® Copolyester 6763, available from Eastman Chemical Comapany, Kingsport, Tennessee, USA.

The second layer 12 is an adhesive material selected e.g. from the group consisting of modified or unmodified homopolymers or copolymers, especially ethylene copolymers, alkyl acrylates such as methyl methacrylate, ethyl acrylate, n-butyl acrylate or vinyl esters such as vinyl acetate especially ethylene vinyl acetate copolymers, ethylene alpha olefin (EAO), olefins and mixtures thereof.

The term "olefin is used broadly herein, including polymers such as polyethylene, low comonomer ethylene copolymers such as vinyl acetate, ethylene alpha olefin (LLDPE) copolymers, polypropylene, polybutene, and other polymer resins that are classified as fall within the scope of the "olefin.

As used herein, the term "modified" refers to a chemical derivative, e.g., a substance containing any form of anhydride functional group such as maleic anhydride, crotonic acid, citraconic acid, itaconic acid, fumaric acid, etc., which is either grafted onto a polymer, copolymerized with polymer or mixed with one or more polymers, and also includes derivatives of functional groups such as acids, esters, and metal salts derived from these groups.

One of the main functions of the second layer 12 is that of the tie layer, i.e. bonding the first layer 11 to the third layer 13. Preferably, the first and third layers are in direct contact with opposite sides of the second layer, but one or more additional coextruded layers may optionally be present between the first and third layers as long as these intermediate layers in combination with adhesive lamination have sufficient adhesion and adequate resistance to delamination for the intended use, e.g. as a hot-forming foil. The thickness of the second layer is about 0.004 mm to about 0.127 mm, preferably about 0.008 mm to about 0.010 mm. Examples of suitable available industrial adhesives are sold by Rohm and Haas, Philadelphia, Pennsylvania, USA under the tradename TYMOR® 72X06; Mitsui Petrochemical Industries, Ltd. Tokyo, Japan under the trade name ADMER ™ SF700 and DuPont Chemical Company, Wilmington, Delaware, USA under the trade name BYNEL®41E687.

The third layer 13 comprises nylon or a nylon blend. Suitable nylons include nylon homopolymers and copolymers, such as those selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene nanediamide)), nylon 6.10 (poly (hexamethylene nanoamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipine-amide-co-caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam), and alloys or mixtures thereof.

Preferably the third layer comprises about 71 wt% to about 100 wt% nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6 , 9 (poly (hexamethylene nanediamide)), nylon 6.10 (poly (hexamethylene nebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipamide-co-caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam), and alloys or mixtures thereof blended with about 0 wt% to about 29 wt% amorphous nylon.

The generic source nomenclature convention is used in the nomenclature of nylon polymers and copolymers used above. See "Generic Source-Based Nomenclature for Polymers Pure Applied Chemistry, Vol. 73, No. 9, pages 1511-1519 (International Union of Pure and Applied Chemistry / International Union of Pure and Applied Chemistry, 2001).

The third layer typically has a thickness from about 0.013 mm to about 0.102 mm, and preferably makes up about 5% to about 20% of the total thickness of the combined first, second, and third layers. Examples of commercially available nylons are sold under the tradename ULTRAMID® C35 or ULTRAMID® B36 from BASF, Mount Olive, New Jersey, USA and 66 ZYTEL®42A NC010 from DuPont Chemical Company, Wilmington, Delaware, USA. A commercial example of an amorphous nylon is sold under the trade name SELAR® PA 3426 from DuPont Chemical Company, Wilmington, Delaware, USA.

PL 207 071 B1

The term "amorphous nylon" as used herein means nylon that does not contain regular three-dimensional ordered molecular structures or subunits of molecules stretched over a length much greater than its atomic dimensions. However, there is regularity in the structure on a local scale. See, "Amorphous Polymers Encyclopedia of Polymer Science and Engineering, ed. 2nd, pages 789-842 (J. Wiley & Sons, Inc., 1985). In particular, the term amorphous polyamide as used in connection with the present invention refers to a material considered by those skilled in the art of Differential Scanning Calorimetry (DSC) as having no measurable melting point (less than 0.5 calories, g) or no heat of fusion. measured by DSC according to ASTM 3417-83. Such nylons include amorphous nylons produced by the condensation of diamines with dicarboxylic acids. For example, an aliphatic diamine is combined with an aromatic dicarboxylic acid, or an aromatic diamine is combined with an aliphatic dicarboxylic acid to form the corresponding amorphous nylon.

The first, second and third layers are combined into a multilayer film by a single blown sleeve or by casting through a slotted die. When polymers are extruded into monolayer or multilayer films by casting such as slit casting, then there is a tendency to form "beads, which are narrow bands of greater thickness running in a continuous machine direction. “The lumps build up as the film is wound up on the roll, which changes the thickness of the film and eventually produces the wrong film. For this reason, it is preferred that the multilayer structure of the present invention is coextruded into the multilayer film by a single blow sleeve method. As used herein, the term "coextrusion" refers to the process of extruding two or more materials through a single die with two or more openings arranged such that the extruded material fuses and welds together into a film structure prior to cooling and solidification, e.g., by water, metal-cooled or quenching. by air. In accordance with the present invention, the preferred film is non-oriented.

The multilayer structure 10 is formed into a flexible film by a coextrusion process and preferably by a single blown sleeve or cast-through-pour co-extrusion method, most preferably by a single blow tube method.

In accordance with the present invention, the three layer multilayer structure 10 formed into a flexible film has a thickness of less than about 0.406 mm, more preferably less than about 0.254 mm, and most preferably from about 0.076 mm to about 0.178 mm. The seven-layer multilayer structure 20 of the present invention, formed as a flexible film, has a thickness of less than about 0.406 mm, more preferably less than about 0.254 mm, and most preferably from about 0.076 mm to about 0.178 mm.

Further, the multilayer structure 10 formed into a flexible film has a heat shrinkage amount of less than about 5% at 90 ° C, preferably less than about 2% at 90 ° C. The heat shrinkage test determines the amount of shrinkage measured on an unstressed specimen at 90 ° C for 5 seconds. The four samples are cut into 10 cm strips in the machine direction by 10 cm in the perpendicular direction. Each sample is immersed for 5 seconds in a 90 ° C water bath (or other specified non-reactive liquid). The distances between the ends of the shrunken sample are measured. The difference in the distance between the shrunken specimen and the original 10 cm is multiplied by ten to obtain the percentage shrinkage for the specimen in each direction. The MD shrinkage for four samples is averaged for the amount of machine direction shrinkage for a given film sample, and the MD shrinkage is for four samples it is averaged for the amount of shrinkage in the direction perpendicular to the machine operation.

It is also preferred that the multilayer structure 10 formed into a flexible film has a percent elongation at break at room temperature greater than about 250 in both the machine and perpendicular directions. Percentage elongation at break can be measured according to the procedure given in ASTM D-882, method A, which is incorporated by reference.

According to the present invention, the multilayer structure 10 may advantageously be formed into a flexible film containing less than 500 ppm of a transition metal salt selected from the group consisting of manganese (II), manganese (III), iron (II), iron (III), cobalt (II), cobalt (III), nickel (II), nickel (III), copper (I), copper (II), rhodium (II), rhodium (III), rhodium (IV) and ruthenium.

PL 207 071 B1

Minor amounts of additives, such as slip or anti-blocking agents, pigments, processing aids, and the like may be included in any of the layers of the multi-layer structure 10, or in any layers subsequently added to the structure, formed into a flexible film.

One of the noteworthy properties of the flexible films formed from the multilayer structure 10 of the present invention is their excellent optical properties, i.e. high gloss. Gloss can be measured by the test method described in ASTM D-2457 at 45 °, which is hereby incorporated by reference. In the present invention, the multilayer structure 10 formed into a film exhibits a gloss greater than about 65 Hunter units (HU).

The multi-layer structure 10 may be used on its own, i.e. as a three-layer film. For some packaging applications, it may be advantageous to include the three-layer structure 10 as a substructure in a multi-layer film with more layers. In such a configuration, the multilayer multilayer film comprising the structure 10 as a substructure may advantageously exhibit the properties and benefits of the three layer structure 10 as discussed above, but may also exhibit additional properties and benefits of additional layers.

The film structures with more layers into which structure 10 has been incorporated as a sub-structure may have at least one additional layer attached to the structure 10 by various methods known to those skilled in the art, which include heat lamination, adhesive lamination, coextrusion coating, co-extrusion.

Coextrusion by slit casting or coextrusion of a single blown sleeve structure 10 with additional polymer layers results in a multi-layer structure 20. The multi-layer structure 20 formed into a flexible film includes a fourth layer 24, which may be a gas-barrier or a second adhesive layer.

Where the multilayer structure 20 includes a gas barrier as the fourth layer 24, it is preferably an oxygen barrier. Preferred oxygen barriers include ethylene vinyl alcohol, vinylidene chloride copolymers, polyacrylonitrile, acrylonitrile copolymers, and mixtures thereof. A more preferred oxygen barrier is ethylene vinyl alcohol, commercially available under the trade name SOARNOL ET3803 from The Nippon Synthetic Chemical Industry Company, Ltd. (Nippon Gohsei), Osaka, Japan.

A valuable property of the flexible film formed from the multilayer structure 20 in which the fourth layer 24 is an oxygen barrier is its excellent barrier properties. Oxygen permeation resistance or barrier properties can be measured using the procedure of ASTM D-3985, which is hereby incorporated by reference. Accordingly, the multilayer structure 10, formed as a flexible film in which the fourth layer 24 is an oxygen barrier, has an oxygen permeation rate of less than about 15.5 cm.³/ m² for 24 hours under a pressure of 0.98 · 10⁵ Bye.

When the multi-layer structure 20 includes an adhesive as the fourth layer 24, the function of the fourth layer 24 is to bond layer 23 and layer 25 together. Suitable materials that can be used as an adhesive are selected from the group consisting of modified or unmodified alkyl acrylate homopolymers or copolymers such as methyl acrylate, ethyl acrylate, n-butyl acrylate or vinyl esters such as vinyl acetate and are especially ethylene-vinyl acetate (EVA) copolymers, ethylene-alpha-olefin (EAO), olefins, and mixtures thereof. Preferred adhesives are similar to those suitable for the second layer and may include anhydride and / or rubber modified EVA or EAO polymers.

The multilayer structure 20 formed into a flexible film preferably comprises a fifth layer 25 comprising nylon or a mixture of nylons. The fifth layer comprises nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene nonanediamide)), nylon 6.10 (poly (hexamethylene nosebacinamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipamide-co-caprolactam) )), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam) and their alloys or mixtures.

Preferably the fifth layer is a mixture comprising about 71 wt% to about 100 wt% nylon selected from the group consisting of nylon 4.6 (poly (tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6.6 (poly (hexamethylene adipamide)), nylon 6.9 (poly (hexamethylene nanediamide)), nylon 6.10 (poly (hexamethylene nanoamide)), nylon 6.12 (poly (hexamethylene dodecanediamide)), nylon 6/12 (poly (caprolactam-co-dodecanediamide)), nylon 6.6 / 6 (poly (hexamethylene adipineamide-co-caprolactam)), nylon 11 (polyundecanolactam), nylon 12 (polylau8

Of ryllactam) and alloys or mixtures thereof, and about 0% by weight to about 29% by weight of amorphous nylon.

Examples of commercially available nylons are sold under the tradename Ultramid® C35 or Ultramid® B36 from BASF, Mount Olive, New Jersey, USA and 66 Zytel®42A NC010 from DuPont Chemical Company, Wilmington, Delaware, USA. A commercial example of amorphous nylon is sold under the tradename Selar® PA 3426 from DuPont Chemical Company, Wilmington, Delaware, USA.

The multilayer structure 20 formed into a flexible film may also include a sixth layer 26 which is an adhesive. The sixth layer 26 acts as an adhesive to bond layer 25 and layer 27 together. Suitable materials that can be used as an adhesive are selected from the group consisting of modified or unmodified alkyl acrylate homopolymers or copolymers such as methyl acrylate, ethyl acrylate, n-butyl acrylate or vinyl esters such as vinyl acetate, especially ethylene copolymers vinyl acetate (EVA), ethylene alpha olefin (EAO), olefins and mixtures thereof. Preferred adhesives are similar to those suitable for the second layer and may include anhydride and / or rubber modified EVA or EAO polymers.

An example of a commercially available material is that sold under the tradename Bynel® 41E687 from DuPont Chemical Comapany, Wilmington, Delaware, USA. When the layers are laminated together as part of a structure including the required coextrusion, the adhesive for joining the laminate of one or more added layers may also be selected from chemical adhesives such as urethane or isocyanate adhesives.

The multilayer structure 20 formed into a flexible film may further include a seventh heat sealable layer 27. As used herein, the term "heat sealable layer" refers to a layer which is heat sealable to itself, i.e. it is capable of fusing using conventional indirect heating means that generate enough heat on at least one contact surface of the film to conduct it to the continuous contact surface and form an interface therebetween without losing the integrity of the film. Preferably, the bonding interface must be sufficiently heat resistant to prevent leakage of liquid or gas therethrough.

Examples of suitable materials for the seventh layer 27 in the multilayer structure 20 include a heat sealable material selected from the group consisting of an ionomer, a heterogeneous alpha-olefin ethylene copolymer, an ethylene alpha-olefin homogeneous copolymer, an ethylene vinyl acetate copolymer, an ethylene methyl acrylate copolymer, ethylene-propylene copolymer, butylene homopolymer or copolymer, and mixtures thereof.

The invention will now be described in more detail in the following examples.

Examples 1 to 4

It is understood that the scope of the invention is not limited to the following examples.

In all of the examples, all of the film structures were produced using the equipment and method for coextruding a single blown sleeve. The single blow tube extrusion apparatus includes a multi-ring round head with a blown film sleeve die through which the film composition is forced and formed into a round sleeve. The sleeve is directly hardened, e.g. with a cooling water bath, solid surface and / or air, and then finally folded and formed into a film.

Example 1

In Example 1, the first layer 11 comprises polyester and polyester additives that are dried before being mixed together. The polyester comprises a polyester terephthalate copolymer with a declared density of approximately 1.27 g / cm³ and an intrinsic viscosity of 0.70, a gloss 45 of 108 Hunter units (HU), available under the tradename EASTAR Copolyester 6763 from Eastman Chemical Company, Kingsport, Tennessee USA. The second layer 12 is an adhesive resin with a density of 0.941 g / cm³, 5.0 g / 10 minutes melt index, Vicat softening point 48 ° C and available under the tradename TYMOR® 72X06 from Rohm and Haas Company, Philadelphia, Pennsylvania, USA. The third layer is a nylon 6 mixture with a density of 1.12 g / cm³, a melting point of 220 ° C, a recrystallization temperature (measured by Differential Scanning Calorimetry (DSC)) of 176 ° C, available under the trade name ULTRAMID® B36 from BASF Corporation, Mount Olive, New Jersey, USA and a density 1 amorphous nylon 19 g / cm³, glass transition temperature 127 ° C, heat deflection temperature 4.55 · 10⁵ Pa of 126 ° C, sold under the tradename SELAR® PA 3426 by DuPont Chemical Company, Wilmington, Delaware, USA.

PL 207 071 B1

In accordance with the present invention, in example 1, a multilayer structure that can be heat-formed into a film is produced as follows.

Each layer is melt-plasticized in a separate extruder connected to an annular coextrusion die through which the hot-plasticized layers are coextruded to form a tube or sleeve. The sleeve comprises a first layer, a second layer and a third layer. The first layer and the third layer are connected directly to opposite sides of the second core layer.

To produce each of the layers, the resin or resin mixture is fed from a hopper to a connected single screw extruder, where the resin or resin mixture is plasticized by heat and extruded through a three layer coextrusion die into a tube or single sleeve. The extruder body temperature for the first layer is 500 ° F (260 ° C) and for the second and third layers it is approximately 271 ° C (520 ° F). A coffee width of less than 1.35 meters is kept. An extruded multi-layer tubing is hardened by contact with a cold solid surface. The cooled tube is flattened by passing between a pair of pinch rollers, and the resulting film of Example 1 has an average thickness of about 0.127 mm.

Referring to Fig. 1, the multi-layer structure 10 is formed into a film of the present invention having the following three layers:

layer 1: 97.5% poly (ethylene terephthalate) + 1.5% anti-block additive + 1.0% lubricant (20% of the total weight of layers 1-3);

layer 2: adhesive (55% of the total weight of layers 1-3).

layer 3: 85% nylon 6 + 15% amorphous nylon (25% of the total weight of layers 1-3).

Examples 2-4

In Example 2, first layer 21 comprises a polyester terephthalate homopolymer having a declared crystalline density of about 1.4 q / cm.³ and an intrinsic viscosity of 0.80, a gloss at a 45 ° angle of 108 Hunter units (HU), available under the tradename EASTAPAK Polymer 9921 from Eastman Chemical Comapany, Kingsport, Tennessee USA.

In examples 3-4, first layer 21 comprises polyester terephthalate copolymer and polyester additives that are dried before being mixed together. The polyester terephthalate copolymer has a declared density of about 1.27 g / cm³ and an intrinsic viscosity of 0.70, gloss at 45 degrees of 108 Hunter units (HU), and is available under the tradename Eastar Copolyester 6763 from Eastman Chemical Comapany, Kingsport, Tennessee USA.

The second layer 22 and the sixth layer 26 in Examples 2-4 were identical adhesive material with a declared density of 0.88 g / cm.³, a 190 ° C melt index of 1.0 g / 10 minutes, available under the tradename ADMER ™ SF700 from Mitsui Petrochemical Industries, Ltd., Tokyo, Japan. The third layer 23 and the fifth layer 25 were identical nylon mixtures 6 having a density of 1.12 g / cm³, a melting point of 220 ° C, a recrystallization temperature (measured by Differential Scanning Calorimetry (DSC)) of 176 ° C, available under the trade name ULTRAMID® B36 from BASF Corporation, Mount Olive, NJ, USA, and a density 1 amorphous nylon 19 g / cm °, glass transition temperature 127 ° C, heat deflection temperature 4.55 · 10⁵ Pa of 126 ° C, sold under the tradename SELAR® PA 3426 by DuPont Chemical Company, Wilmington, Delaware, USA.

The fourth layer 24 in Examples 2-3 contained ethylene vinyl alcohol (EVOH) with a stated bulk density of 0.64-0.74 g / cm 2.³, specific density 1.13-1.22 g / cm³, a softening point of 164-168 ° C, available under the tradename SOARNOL® ET3803 from Nippon Synthetic Chemical Industry Company, Ltd., (Nippon Gohsei), Osaka, Japan.

The fourth layer 24 in Example 4 was an adhesive material with a density of 0.941 g / cm³, 5.0 g / 10 min melt index, Vicat softening point 48 ° C, available under the tradename Tymor® 72X06 from Rohm and Haas Company, Philadelphia, Pennsylvania, USA.

The seventh layer 27 in Examples 2-4 comprised a partial zinc salt of ethylene methacrylic acid copolymers with a density of 0.940 g / cm 2.³, a 190 ° C melt index of 1.30 g / 10 minutes, a Vicat softening point of 165 ° C (73.9 ° C) available under the tradename SULRYN® 1601 from DuPont Chemical Company, Wilmington, Delaware, USA.

In Examples 2-4, one extruder was used for each layer. Each extruder was connected to an annular coextrusion die through which the heat-plasticized resins were coextruded to form a single tube or sleeve containing seven layers.

The resin or resin mixture is fed from a hopper to a connected single screw extruder where the resin or resin mixture is heat plasticized and extruded

By a seven-layer coextrusion die into a pipe or a single sleeve. The extruder body temperature is 500 ° F (260 ° C) for the first layer, 510 ° F (266 ° C) for the second layer, and 520 ° F (271 ° C) for the third to seventh layers. A sleeve width of less than 1.35 meters is kept. An extruded multi-layer tubing is hardened by contact with a cold solid surface. The cooled tube is flattened by passing between a pair of pinch rollers, and the resulting film of Examples 2-4 has an average thickness of between 0.102 and 0.152 mm.

Referring to Fig. 2, the multilayer structure 20 is formed into a film of the present invention having the following seven layers:

Example 2 layer 21: poly (ethylene terephthalate) (20% of the total weight of layers 1-7); layer 22: adhesive (13% of the total weight of layers 1-7);

layer 23: 85% nylon 6 + 15% amorphous nylon (14% of the total weight of layers 1-7); layer 24: oxygen barrier (9% of the total weight of layers 1-7);

layer 25: 85% nylon 6 + 15% amorphous nylon (14% of the total weight of layers 1-7);

layer 26: adhesive (12% of the total weight of layers 1-7);

layer 27: weldable layer (18% of the total weight of layers 1-7);

The film had a total thickness of about 0.127 mm.

Example 3 layer 21: 98.5% poly (ethylene terephthalate) + 1.0% antiblocking additive + 0.5% lubricant (25% of the total weight of layers 1-7);

layer 22: adhesive (11% of the total weight of layers 1-3);

layer 23: 85% nylon 6 + 15% amorphous nylon (14% of the total weight of layers 1-3); layer 24: oxygen barrier (9% of the total weight of layers 1-7);

layer 25: 85% nylon 6 + 15% amorphous nylon (14% of the total weight of layers 1-7);

layer 26: adhesive (10% of the total weight of layers 1-7);

layer 27: weldable layer (17% of the total weight of layers 1-7);

The film had a total thickness of about 0.102 mm.

Example 4 layer 24: 97.5% poly (ethylene terephthalate) + 1.5% antiblocking additive + 1.0% lubricant (25% of the total weight of layers 1-7);

layer 22: adhesive (11% of the total weight of layers 1-3);

layer 23: 85% nylon 6 + 15% amorphous nylon (9% of the total weight of layers 1-3); layer 24: adhesive (9% of the total weight of layers 1-7);

layer 25: 85% nylon 6 + 15% amorphous nylon (9% of the total weight of layers 1-7);

layer 26: adhesive (21% of the total weight of layers 1-7);

layer 27: heat sealable layer (26% of the total weight of layers 1-7);

The foil had a total thickness of about 0.102 mm.

Table 1 compares the size of the elongation in the machine running direction and the perpendicular direction for films of different thickness with a seven-layer structure. Table 2 shows a comparison of the amount of shrinkage in the running and perpendicular directions for films of different thickness with a seven-layer structure.

Table 1

Comparison of the% elongation value for example 1

<td colspan="2">0.076 mm</td><td colspan="2">0.127 mm</td><td colspan="2">0.254 mm</td>

<td>along</td><td>across</td><td>along</td><td>across</td><td>along</td><td>across</td>

<td> 386,8</td><td> 484,4</td><td> 519,6</td><td> 575,0</td><td> 643,6</td><td> 612,9</td>

<td> 469,1</td><td> 434,1</td><td> 516,8</td><td> 529,8</td><td> 630,8</td><td> 600,4</td>

<td> 412,1</td><td> 459,3</td><td> 513,4</td><td> 579,2</td><td> 615,2</td><td> 599,2</td>

<td> 429,3</td><td> 458,7</td><td> 518,9</td><td> 562,3</td><td> 637,1</td><td> 639,0</td>

<td> 406,1</td><td> 427,1</td><td> 484,0</td><td> 551,8</td><td> 605,1</td><td> 590,2</td>

<td>Medium 420.7</td><td> 452,7</td><td> 510,5</td><td> 559,6</td><td> 626,4</td><td> 608,3</td>

PL 207 071 B1

Table 2

Comparison of the shrinkage in% for example 1

<td>thickness</td><td>in the longitudinal direction</td><td>in the transverse direction</td>

<td>0.076 mm</td><td> 0,0%</td><td> 0,0%</td>

<td>0.127 mm</td><td> 1,5%</td><td> 0,5%</td>

<td>0.254 mm</td><td> 1,0%</td><td> 0,0%</td>

In the examples given above, various embodiments of the present invention have been illustrated; these examples illustrate the scope of protection.