JPS629018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention involves spirally wrapping a plurality of layer-forming tapes around an extruded plastic film tube after the film tube has sufficiently hardened. The present invention relates to a method for manufacturing a layered reinforced film tube, which comprises wrapping the plastic film tube around the plastic film tube and then flattening the plastic film tube.

BACKGROUND OF THE INVENTION Layer-reinforced plastic films, especially in the form of tubular films, are required when producing, for example, very strong packaging films, very strong bags and large-capacity container bags. To produce a film as described above reinforced with inserts, preferably a taut plastic film is used.
Adhere the tape to the support film. However,
Composite films have the desired strength and can be processed further without problems if the connections between the individual layers are good and separation or delamination is prevented, resulting in an unavoidable loss in the strength of the reinforcing layer. Only if individual interlayer connections are not made by heating to a temperature above the stress relaxation temperature of the taut plastic tape layers.

Among the above methods, West German Utility Model Publication No.
No. 1928736 discloses a method for reinforcing core tubes manufactured by extrusion using blown supporting air.
A plurality of reinforcing tapes were wrapped or woven in opposite directions around the core tube at locations spaced from the extrusion nozzle within the cooled mandrel area supporting the tube and then supported on the core of the extrusion nozzle. A protective layer is extruded onto the reinforcing tape layer within the second cooled mandrel area. If the core tube is vertically extruded and pulled out, the strip or tape applied after the extruded tube has sufficiently hardened, i.e. beyond the solidification point, is no longer fixedly supported on the tape. There is no risk of slipping. Furthermore, simply extruding the protective layer onto the reinforcing tape layer does not provide a good connection with the core tube, since the applied coating layer does not exhibit good adhesion due to its weak adhesive strength. There is a risk of peeling, and the load applied to each layer will become uneven. However, the applied tape layer must not slip or peel, since this would significantly reduce the strength of the reinforced film and thus reduce its usefulness.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a reinforced plastic film in which the layers forming a helix are firmly connected to a support film.

According to the present invention, a plurality of layer-forming tapes are spirally wound around the extruded plastic film tube after the film tube has sufficiently solidified, and then the plastic film tube is wrapped around the extruded plastic film tube. A method of manufacturing a layered reinforced film tube comprising flattening, co-extruding a layer of pressure-sensitive adhesive onto the film tube and a reinforcing plastic tape layer wrapped over the film tube. The above-mentioned problems are solved by a method for manufacturing a layered reinforced film tube, which is characterized in that it is formed. Extruding the plastic tube into a tubular shape with an adhesive layer covering it can be carried out using a film blowing head as described in DE-A-2320687. If the tape layer is applied to the adhesive layer in a spiral manner by the method of the present invention after the supporting plastic core film has properly hardened, the tape layer will adhere to the adhesive layer without slipping. Therefore, the tape layer does not become misaligned or loosened, and therefore, a decrease in strength or variation in the strength of the composite film can be avoided.

In addition to the pressure-sensitive adhesive layer covering the entire periphery of the plastic core film, a strip of extruded pressure-sensitive adhesive in the form of an axially extending strip acts as an adhesive force enhancer and is applied. The structure can also be designed to prevent the vertically extruded plastic film from peeling off the extruded plastic film.

After the plastic tube with the pressure-sensitive adhesive layer has properly hardened, multiple pieces of tape forming the layer are wrapped in parallel over the adhesive layer to ensure that the surface of the adhesive layer is not exposed. It can be done. The film thus reinforced by the tape layer can be sent to the next processing step without the need for laminating another protective layer over the tape layer.

If the mesh or roughness of the layers applied in the same or opposite directions is sufficient to provide the desired strength of the tubular film, and a smooth, non-adhesive plastic covering layer is extruded onto the tape layer, A composite film with a smooth surface is obtained. Of course, the tape layers forming the closely aligned surfaces can also be laminated with a smooth surface layer extruded on top.

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

A plastic film tube 1 consisting of a thermoplastic material on the inner surface and a self-adhesive layer of non-crosslinking elastic material on the outer surface is extruded from a film outlet nozzle as described, for example, in DE-A-2320687. . The extrusion nozzle of the film outlet (not shown) is a two-layer annular nozzle in which a passage for delivering the pressure sensitive adhesive layer concentrically surrounds a passage for delivering the thermoplastic material.

The extruded plastic film tube 1 is expanded by blowing cooling/supporting air into the tube in a known manner until it reaches the desired tube diameter. After the tube has sufficiently solidified beyond the solidification point, a plurality of tapes 2 are inserted into the tube. Wrap it in a spiral over 1. Even when the thermoplastic film tube 1 is cooled and sufficiently solidified, the pressure-sensitive adhesive layer does not lose its tackiness, allowing the tape wound on the film tube 1 to be fixed in place.
The reinforced plastic tape is drawn from a supply reel 3 attached to a rotating turret (not shown) surrounding the tube.

Near the turret supporting the supply reel 3,
A support ring with a low friction surface can also be provided to support the tube from the inside.

An annular extrusion nozzle can also be provided above the turret, which surrounds the tube 1 and extrudes a protective layer of thermoplastic material onto the tape layer.

The tube 1, reinforced by the tape layer and preferably also having a protective layer, is then squeezed out and flattened by a pair of rolls 4. The flattened tube can be rolled up or further processed as desired.

The reinforced plastic tape layer may consist of a polyethylene strip that has been made at least ten times stronger by tensioning.

[Brief explanation of the drawing]

The accompanying drawings schematically show a plastic film tube that has been extruded, expanded, wrapped with reinforcing tape and then flattened. 1...Plastic film tube, 2...
... Reinforced plastic tape, 3... Supply reel, 4... Roll pair.

Claims (1)

[Claims] 1. After the extrusion-molded plastic film tube has been sufficiently solidified, a plurality of layer-forming tapes are wound spirally around the extrusion-molded plastic film tube, and then the plastic film tube is flattened. A method of manufacturing a layered reinforced film tube, characterized in that a layer of pressure sensitive adhesive is co-extruded onto the film tube to form a reinforced plastic tape layer wrapped over the film tube. A method for manufacturing a layered reinforced film tube.