DE4430038A1 - Double-walled plastic tube with a low-grade foam interlayer - Google Patents

Abstract

A recycled softened thermoplastic, which may be polyethylene or polypropylene, is extruded from an annular nozzle. The inner dia. is sized by a cooled inner mandrel. The tube passes through a former, extending over the length of the mandrel, and consisting of a pair of converging, floating die halves, lying closely together. The tube is coated by a pressed profile of encircling ridges. A transverse injection head completes the tube, covering the ridges with an outer casing of recycled plastic. Finally, the outer surface of the composite tube is sized and smoothed. A tube made in the manner described, is also claimed.

Description

The invention relates to a method for producing double-walled ger pipes made of plastic.

Large quantities fall within the framework of environmentally conscious waste management of recyclable plastics, but their use causes increasing problems. There are already numerous Proposals have been made to find a reusable plastic as far as possible also profitable, economically reasonable recycling supply.

The object of the invention is therefore to produce a method double-walled pipes made of recyclable thermoplastic propose plastic.

According to the invention this object is achieved in that rever valuable thermoplastic plasticized in an extruder Plastics from a spray head with an annular nozzle gap ex that the inner diameter of the extruded raw res calibrated on a cooled inner mandrel and the jacket of the tube in a substantially the length of the Dor Nes extending molding line, which consists of pairs of rings  merged and close together mold halves consists, with a pressed profile from circumferential ribs ver will see and that with a crosshead on the ribs Sheathing tube extruded from recyclable plastics and the outer surface of the jacket tube by a potash calibrating device is calibrated and smoothed. After the invent The process according to the invention can be used to recycle handsome pipes ten plastics, for example recycled bulk plastics such as PE and PP, because they are also plastic have poorer quality processed. After the invention Pipes manufactured according to the method have a smooth upper surface of the inner wall because the inner tube from one cooled mandrel is calibrated. Such a chilled potash brier-Dorn is known from DE-PS 35 13 708. Continue to point the tubes produced by the process according to the invention a smooth and appealing outer surface because of this calibrated and smoothed in appropriate calibration facilities tet and thereby ironed out as it were. Such potash briereinrichtung for the outer jacket of the tube are as Vacuum calibrators or calibration tanks known from a water-cooled vacuum sleeve exist and also when used of lower material qualities the creation of im allow essential non-porous smooth surfaces.

To profile the jacket of the inner tube, the ex truded tube or the extruded plastic or melt liquid tubing used with migratory shapes, as in for example from DE-PS 43 18 514 for the production of corrugated pipes are known. According to the inventive method, the Pro However, fil is not shaped by injected compressed air, but as it were by compression molding, the mold cavity between the Mandrel and the moving molding line under pressure with the extru dated plastic is filled, so that there is a possible bla  Sen-free profiled inner tube results.

On this inner tube is then formed with egg extruded a jacket tube on a crosshead. Such Crossheads are also of a known type Process according to the invention poorer material qualities surface, the surfaces will be reduced accordingly Quality concealed by facing each other in the Inside the double-walled jacket of the tube, while the inner and outer walls of the double-walled tube through the corresponding calibration has been smoothed.

The pipe manufactured by the method according to the invention comes out through an inner tube with smooth walls used plastic, which on its outer jacket with circumferential ribs is provided with an outer jacket tube also made of recycled plastic with a smoother External wall are connected.

According to a development of the method according to the invention provided that the plastics consist of a spray head and two concentric, annular nozzle columns, which are two from each other the separate extruders are fed, extruded, and that extruded from the outer annular die gap Plastic a blowing agent is added so that in the mold stretch ribs made of foamed plastic the. According to this variant of the method according to the invention an inner smooth-walled inner tube and a con centric outer tube with smooth outer wall made of reusable Produce hard plastic, in which in the annular space between the inner and outer tubes have a circumferential ribs the pipe made of foamed plastic is arranged.  

According to the method according to the invention, primarily re processed plastics. According to the Ver Of course, higher quality plastics can also be driven work when pipes are to be manufactured for higher demands len.

Are double-walled tubes according to the inventive method Made from recycled plastics, these can be for example as pressure-free pipes, such as cable protection pipes or Use drainage pipes.

The sheathing tube is expediently held by a vacuum Calibrator calibrated. The one calibrating the jacket tube Calibrator can also be from a water-cooled calibration tank stand.

To ensure a good connection between the casing tube and the profiler To reach the inner tube, the outer ones are expedient Areas of the circumferential ribs in the housing or body of the Crosshead melted so that this with the extrusion weld the coated jacket.

The inner and outer tube can be round or in polygonal shape can be extruded. The ribs can run all the way around or be spiral and any cross-section, before but preferably have rectangular cross sections.

Embodiments of the invention are described below with reference to the Drawing explained in more detail. In this shows

Fig. 1 is a plan view of a plant for the production of DOP-walled tubes in a schematic representation;

Fig. 2 is an enlarged view of the Vakuumkalibrators the plant according to Fig. 1,

Fig. 3 is a side view of the tube produced by the first variant of the method according to the invention, cut in half, and

Fig. 4 is a side view of the tube produced by the second variant of the method according to the invention, cut in half.

A plant for the production of the tube of FIG. 3 consists of a so-called axial extrusion head (1) gap with an annular nozzle, which is fed by an axial extruder (2) having a plastifying th plastic or plastic melt, whose axis coincides with the axis of the axial spray head is aligned.

The extruded tubular plastic strand extruded from the axial spray head runs into a corrugated tube device which consists of a cooled inner mandrel and a molding section which forms the outside of the jacket and is formed from ring-shaped merging and closely adjacent mold halves. The inner tube emerging from the corrugated tube device and provided with a profiled jacket produced by pressing then enters a jacketing spray head ( 4 ) of a known type, which is fed with a plasticized or molten plastic mass by a transverse extruder arranged approximately at right angles to the production line. A sheathing tube is extruded through the sheathing or cross-molding head ( 4 ) onto the ribbed profile of the inner tube, the inner wall of which is welded to the fins. The double-walled tube emerging from the jacket spray head is then calibrated in a vacuum calibrator, by means of which the tube is calibrated and provided with a smoothed surface. The vacuum calibrator ( 6 ) is also of a known type and can be seen in more detail in FIG. 2. The vacuum tank 15 is an airtight room with spray cooling or full flooding, which can be evacuated to an adjustable vacuum (absolute 0.3 - 0.5 bar). The calibrators used are slotted calibration sockets made of non-ferrous metal, which are followed by calibration plate packs in the manner shown. The double-walled tube produced in this way is then cooled in a cooling section ( 7 ) in a spray cooling bath. The tube is then cut to a suitable length using a separating saw ( 8 ) and deposited using a tilting channel ( 9 ).

A section of the pipe made by the method according to the invention can be seen in FIG. 3. The tube ( 10 ) be consists of an inner tube ( 11 ) with a smoothed inner wall ( 12 ) made by a cooled mandrel and outer spaced circumferential annular ribs ( 13 ) with a rectangular cross-section. A jacket tube ( 14 ) is extruded onto these circumferential ribs and is welded to the outer peripheral surfaces of the ribs ( 13 ).

The tube shown in Fig. 4 is also made of reusable plastics according to the second variant of the inventive method. The tube 21 differs from the tube 10 of FIG. 3 in that between the inner tube 22 and the outer tube 23, a tube 24 made of foamed plastic with circumferential ribs 25 is arranged. In order to extrude the tube 24 made of foamed plastic with circumferential ribs onto the tube 22 , a spray head must be used instead of an axial extruder with an axial spray head, in which the two concentric, annular die gaps are fed with plastic from two separate extruders, the one from which a blowing agent is added to the outer, annular die gap extruded plastic, so that the plastic tubing extruded from this foams in the molding section. The reusable plastics for the manufacture of the tube according to FIG. 4 can also consist of PE or PP.

Claims (10)

1. A process for the production of double-walled plastic pipes, characterized in that
that reusable thermoplastic plastics plastified in an extruder are extruded from a spray head with a ring-shaped nozzle gap,
that the inner diameter of the extruded tube calibrated on a cooled inner mandrel and the jacket of the tube in a substantially over the length of the mandrel he stretching molding line, which consists of a pair of ring-shaped together and closely adjoining moving mold halves, with a pressed profile is provided around the ribs and
that with a crosshead on the ribs a sheathing tube made of recyclable plastics extruded and the outer surface of the sheathing tube is calibrated and smoothed by a calibrating device. 2. The method according to claim 1, characterized in that the Plastics from a spray head with two concentric, annular nozzle columns separated by two ten extruders are fed, extruded and that the Art extruded from the outer, annular die gap a blowing agent is added so that in the mold stretch formed from foamed plastic ribs become. 3. The method according to any one of claims 1 or 2, characterized records that the jacket tube by a vacuum potash brator is calibrated. 4. The method according to any one of claims 1 to 3, characterized records that the jacket tube by a water-cooled cal calibration tank is calibrated. 5. The method according to any one of claims 1 to 4, characterized records that the outer areas of the circumferential ribs in melted on the housing or body of the crosshead be so that this with the extruded casing weld pipe. 6. The method according to any one of claims 1 to 5, characterized records that the inner and outer tube extru in a round shape is dated.   7. The method according to any one of claims 1 to 6, characterized records that the inner and outer tube in polygonal shape is extruded. 8. The method according to any one of claims 1 to 7, characterized records that the ribs from annular webs rightly square cross section. 9. Pipe, produced by a method according to one of the claims che 1 and 3 to 8, marked by an internally smooth-walled inner tube made of recyclable Plastic attached to its outer jacket with all-round rip pen is provided, which also with an outer casing tube made of re-used plastic with a smooth outer wall are bound. 10. Pipe, produced by a method according to one of the claims che 2 to 8, characterized by an internally smooth-walled inner tube and an outer tube concentric to it with smooth outer wall made of reusable plastic, the one in the annulus between the inner and outer Pipe with a circumferential ribbed pipe Plastic is arranged.