To provide a multilayer film that enables easy opening of a packaging material manufactured by deep draw forming. A multilayer film for deep draw forming, including: a vinylidene chloride copolymer resin layer as a middle layer; a crosslinked olefin resin layer as a first surface layer; and an ethylene/vinyl acetate copolymer resin layer as a second surface layer; where the ethylene/vinyl acetate copolymer resin layer is further provided either at least between the vinylidene chloride copolymer resin layer as the middle layer and crosslinked olefin resin layer as the first surface layer, or between the vinylidene chloride copolymer resin layer as the middle layer and ethylene/vinyl acetate copolymer resin layer as the second surface layer.

The invention relates to a calibrating device and to a method for calibrating a film tube. An elastically deformable element (704) is secured to the sleeve (703) such that a fluid, in particular a gas, preferably air, can be introduced or discharged via a fluid connection such that a specific pressure P1 and/or a specific volume V1 is set in an area (708) enclosed by the sleeve and the elastically deformable element at a given temperature. Annular bodies (706) and (707) are arranged within the area (708), and a surface section of each annular body (706), (707) supports a respective region of the elastically deformable element (704). The elastically deformable element (704) regions which are supported by the annular bodies are located in the inlet region (711) and the outlet region (712) of the calibrating device for the film tube (713).

The invention relates to a calibrating device and to a method for calibrating a film tube. An elastically deformable element (704) is secured to the sleeve (703) such that a fluid, in particular a gas, preferably air, can be introduced or discharged via a fluid connection such that a specific pressure P1 and/or a specific volume V1 is set in an area (708) enclosed by the sleeve and the elastically deformable element at a given temperature. Annular bodies (706) and (707) are arranged within the area (708), and a surface section of each annular body (706), (707) supports a respective region of the elastically deformable element (704). The elastically deformable element (704) regions which are supported by the annular bodies are located in the inlet region (711) and the outlet region (712) of the calibrating device for the film tube (713).

A method of producing a blown film with a controlled thickness profile, comprises the steps of: extruding molten plastic through an annular extrusion die; cooling the molten plastic using an annular blower around the extrusion die, positioning one or more sources of supplemental air at one or more desired circumferential positions about the annular extrusion die and adjacent to the extruded molten plastic, the annular blower and the one or more sources of supplemental air being operated to supply cooling air to the molten plastic between the annular extrusion die and the frost line where the molten plastic solidifies; and controlling the one or more sources of supplemental air to form one or more areas of increased thickness along a circumferential thickness profile of the blown film, the one or more areas of increased thickness having a thickness that is greater than an average thickness of the circumferential profile.

A method of producing a blown film with a controlled thickness profile, comprises the steps of: extruding molten plastic through an annular extrusion die; cooling the molten plastic using an annular blower around the extrusion die, positioning one or more sources of supplemental air at one or more desired circumferential positions about the annular extrusion die and adjacent to the extruded molten plastic, the annular blower and the one or more sources of supplemental air being operated to supply cooling air to the molten plastic between the annular extrusion die and the frost line where the molten plastic solidifies; and controlling the one or more sources of supplemental air to form one or more areas of increased thickness along a circumferential thickness profile of the blown film, the one or more areas of increased thickness having a thickness that is greater than an average thickness of the circumferential profile.

An apparatus includes an upper lip positioned with respect to an air flow passage. The upper lip is to direct air flow from the air flow passage around a bubble of blown film. The apparatus further includes a Venturi ring movably mounted with respect to the upper lip and adjustable in position with respect to the upper lip. The Venturi ring is to adjustably lock the bubble of blown film.

In the case of a device to permit the monoaxial length change of film webs in machine direction, which comprises at least one processing gap delimited by two rolls via which a film web is routed in machine direction, whereby the first roll in film transport direction exhibits a first peripheral speed and the second roll in film transport direction exhibits a second peripheral speed, in order to produce film webs with low transverse neck-in as well as reduced edge build-up and to improve the flatness of the film web.

In the case of a device to permit the monoaxial length change of film webs in machine direction, which comprises at least one processing gap delimited by two rolls via which a film web is routed in machine direction, whereby the first roll in film transport direction exhibits a first peripheral speed and the second roll in film transport direction exhibits a second peripheral speed, in order to produce film webs with low transverse neck-in as well as reduced edge build-up and to improve the flatness of the film web.

A blown-film extrusion apparatus for manufacturing a tubular polymer film comprises an extruder; a solidification ring for solidifying a tubular element produced by the extruder and for forming the film by delivering cooling air on the tubular element at a given cooling height, and a film conveyor for conveying the film upwards. The apparatus also comprises a delivery device for projecting correction air on the tubular element, in order to locally correct the thickness of the film, comprising a distribution chamber; a plurality of air delivery members with delivery channels whose delivery mouths are arranged about said axis of the apparatus for projecting correction air partial streams on respective angular correction positions, between the die and the cooling height; flow control elements between the distribution chamber, and the inlet of respective air delivery members, configured for adjusting the flowrate of the respective correction air stream according to an adjustment signal. According to an aspect of the invention, a plurality of separate radial ducts is provided defining respective delivery channels and spaced apart, at an own end portion, by separation spaces, so that the correction air partial streams, after hitting the tubular element in the respective angular correction positions, can flow away from the tubular element through said separation spaces. According to another aspect of the invention, the distribution chamber is defined by an upper ring and by a lower ring connected to each other by means of tight fixed joints with a first substantially cylindrical wall and with a second substantially cylindrical wall arranged around the first cylindrical wall, wherein possible separate radial ducts of the air delivery members protrude from the first cylindrical wall.

A blown-film extrusion apparatus for manufacturing a tubular polymer film comprises an extruder; a solidification ring for solidifying a tubular element produced by the extruder and for forming the film by delivering cooling air on the tubular element at a given cooling height, and a film conveyor for conveying the film upwards. The apparatus also comprises a delivery device for projecting correction air on the tubular element, in order to locally correct the thickness of the film, comprising a distribution chamber; a plurality of air delivery members with delivery channels whose delivery mouths are arranged about said axis of the apparatus for projecting correction air partial streams on respective angular correction positions, between the die and the cooling height; flow control elements between the distribution chamber, and the inlet of respective air delivery members, configured for adjusting the flowrate of the respective correction air stream according to an adjustment signal. According to an aspect of the invention, a plurality of separate radial ducts is provided defining respective delivery channels and spaced apart, at an own end portion, by separation spaces, so that the correction air partial streams, after hitting the tubular element in the respective angular correction positions, can flow away from the tubular element through said separation spaces. According to another aspect of the invention, the distribution chamber is defined by an upper ring and by a lower ring connected to each other by means of tight fixed joints with a first substantially cylindrical wall and with a second substantially cylindrical wall arranged around the first cylindrical wall, wherein possible separate radial ducts of the air delivery members protrude from the first cylindrical wall.