DE2620263A1 - Large dia. pipe made from thermoplastics - where plastic flows along heated bore of rotating pipe mould - Google Patents

Abstract

An externally heated, rotating metal cylinder is used in which grains of plastic are heated to above their m.pt. by the hot inner wall of the cylinder and form the pipe. A cooled metal tube or core is pref. located concentrically in the metal cylinder; this tube is stationary, or may be rotated and is provided with a screw thread via which the plastic pipe is extracted; the thread is followed by a conical zone used to smooth and compact the pastic. The metal cylinder pref. contains an oil cavity ensuring uniform distribution of heat provided by electricity fuel-gas or -oil. The cylinder is followed by a concentric, double-walled cooling cylinder used to cool the plastic pipe. The plastic grains are pref. heated to >50 degrees C before entering the rotating cylinder. Used for mfg. pipe, 500-1000 mm dia. or more from practically all thermoplastics, e.g. PVC, polythene, polypropylene, polystyrene, polyamide. A simple plant with lower investment- and prodn. costs than conventional plant.

Description

Method and device for the production of plastic pipes

large diameter.

The production of large diameter plastic pipes, so-called Large plastic pipes are still associated with problems today. In the production these large plastic pipes, with diameters of 500-100 mm and more according to the known manufacturing processes in which the plastics are melted in extruders and homogenized, formed in the pipe head and in the subsequent cooling and transport facilities are manufactured, almost insurmountable difficulties arise today. The required throughput of the extruder is in the production of large pipes so high that the material overheats and the plastic becomes homogeneous is no longer achieved, so that irregularities and blockages result are. The investment costs of such systems are very high and the generation the large pipes becomes uneconomical.

A new process has been found that enables the production of large plastic pipes, with diameters of 500-100 mm and more, permitted in a simple manner and opposite the known methods in investment and generation costs significant savings permitted.

In the method according to the invention are in one from the outside on the Melting point of the plastic heated, rotating metal cylinder, plastic granules introduced, which melt together on the hot inner wall of the cylinder to form a tube. The rotating cylinder wall takes the plastic grains, through centrifugal force and friction, in the direction of rotation upwards with until they are attracted again by gravity roll down. During these rolling movements, the plastic grains are the over exposed to the temperature of the inner wall of the cylinder, which is the melting point of the plastic, they melt and thus form the plastic tube in the metal cylinder. The outside diameter of the plastic pipe is given by the inner diameter of the metal cylinder and the wall thickness is determined by the heating power and the pipe wall temperature.

The plastic pipe produced is when it reaches the thickness, by a piece of metal pipe arranged concentrically inside the metal cylinder Via a thread provided on its circumference, through the relative movement between the rotating metal cylinder and the stationary pipe section from the metal cylinder pulled out. The pipe section has 3 or more evenly distributed around the circumference Arms provided that extend axially into the space in which the plastic pipe The arms are provided with the same thread as the pipe section and are indirectly cooled with cooling water. If the plastic pipe reaches the between the metal cylinder and the wall thickness formed on the arms of the pipe section, the plastic solidifies on the cold thread of the arms, the formed plastic tube is screwed on and becomes slowly discharged axially from the metal cylinder to the rear via the pipe section. Further plastic grains melt on the hot cylinder wall thus exposed and so an endless plastic tube with a large diameter is continuously formed.

Following the thread of the pipe section is a smooth "light" arranged ascending cone, which smooths the thread grooves formed and that The structure of the pipe wall formed is compressed. The indirectly cooled inside and outside Plastic pipe is placed in between the metal cylinder and the inner pipe section The ring cross-section formed is calibrated and then by direct water cooling Cooled inside and outside to room temperature and sawn to the desired length.

The metal cylinder is advantageously heated on the circumference applied heating rods, which are supplied with electrical current via slip rings. The metal cylinder is used to achieve a uniform temperature over the entire circumference designed as a double jacket in which a heat transfer oil circulates. The heating can in this case also as resistance heating, radiant heating and gas or oil heating are executed. ft a heat connection to the heating zone of the metal cylinder01s # against drainage well-insulated cooling zone, in which in a double jacket in-cooling water, for direct cooling of the emerging plastic pipe, circulates. To increase the heat transfer, the cooling water is advantageous against the D # direction of the metal cylinder by headed the double jacket. Depending on the type of plastic it can be for a mild or spicy Cooling: * the cooling water flows axially through the double jacket in cocurrent or countercurrent.

The metal cylinder is on the front face with a cover provided, which is driven by a hollow shaft and a worm drive. In the lid provided openings allow the introduction of the plastic granules into the metal cylinder, which are evenly distributed by blades arranged on the circumference.

Alternatively, the inner metal pipe section can also be driven WillSn, dXlse discharge speed of the plastic pipe due to changes in the number of revolutions can be regulated. Also an opposite rotation of the two Cylinder is possible; it allows the plastic pipe to be discharged very quickly.

To discharge the plastic pipe, this can be done inside the metal cylinder arrangedp pipe section alternatively arranged displaceably in the axial direction will. A lever arranged outside the cylinder is used to initiate the discharge of the plastic pipe the pipe section with its thread against this pressed. Anjkalten thread solidifies the formed plastic pipe and is over the thread carried out to the rear.

The cooling water supply for cooling the outer metal cylinder and of the inner pipe section is advantageously carried out via an axially arranged water supply pipe. For the rotating metal cylinder, the cooling water is connected to the cylinder rotating stuffing box on the water supply pipe. removed and through in the cover and Cable attached to the jacket is routed into the rotating cooling jacket. For the interior Pipe section, the cooling water is supplied from the supply pipe via a stuffing box through the hollow shaft provided to the distributor pipes in the cylinder of the pipe section.

The plastic grains can before being introduced into the system, for example by blowing hot inert gases into the plastic layer. The output increases by this amount of heat introduced outside the system on molten plastic and generated plastic pipe.

The storage of the system takes place advantageously over 2 nested Hollow shafts, which are stored separately, one for the necessary flying arrangement, solid Allow execution.

The production of large plastic pipes with different diameters can take place in the same system if, according to the invention, the one arranged at the front Lid is designed with a large diameter. Depending on the diameter of the to generating tube is then the corresponding metal cylinder on the large cover screwed on and the required piece of metal pipe for the required wall thickness used. With this version, most of the system, from the cover, can with it the hollow shaft of the bearing with the drive, the plastic feed, the connecting lines for electricity and water, including base and foundations, for all to be generated Large plastic pipes are used.

In the method according to the invention, a granular plastic is therefore used placed on the face of a rotating and externally heated metal cylinder, which fuses to a plastic tube on the heated inner jacket of the cylinder. This large plastic pipe is arranged in the interior of the metal cylinder and cooled tubing, circumferentially threaded, from the metal cylinder pulled out, cooled to room temperature by direct cooling and on its Cut length.

The method and the device are shown in Figure 1.

The metal cylinder 1 is over the cover arranged on the end face 2 and the hollow shaft 3, which rests in the bearing 4, connected to the worm wheel 5 and is driven electrically via the worm shaft 6. The metal cylinder 1 is electrically heated by the heating rods 7 and transfers the heat to the double jacket 88 circulates in the heat transfer oil, so that on the entire circumference of the metal cylinder 1 an even temperature is guaranteed. Following the heatable Double jacket 8, the metal cylinder 1 is equipped with a cooling cylinder 9 in the, in a double jacket 10, cooling water for indirect cooling of the plastic pipe produced 2727, circulates. The two double jackets 8 and 10 and the cover 2 are for prevention from Heat flows against each other with good asbestos seals 50 isolated. The cylinder cover 2 is inside with a larger number of baffles 26 for even distribution of the plastic grains.

Inside the metal cylinder 1, a pipe section 11 is arranged, which is connected to a hollow shaft 13 via the web and hub 12, which is located in the bearing 14 rests. The cylindrical part of the pipe section 11 has a screw thread on the circumference 15 provided, with the direction of rotation towards the open side of the Netall cylinder 1 increases. In the front part, the pipe section 11 is uniform with 3 or more distributed arms 17, which are provided with the same thread 15 and come close to the cylinder cover 2. Following the thread 15 of the pipe section 11, the diameter increases conically to then into a cylinder pass over which forms the inner diameter of the plastic pipe 27.

The cooling of the metal cylinder 9 takes place, for example, via the Fresh water supply line 28 through - the double stuffing boxes 29,30 and line 31, which rotates with the cover 2. In the cover 2 'is the cooling water through a hole forwarded and then flows via the line 32 into the double jacket 10. Here internals 51 are provided, which the cooling water in spiral paths on the entire Lead the circumference of the double jacket 10 along. The heated cooling water leaves the Double jacket 10 via line 52.

in a similar way.

For the cooling of the inner pipe section are from the fresh water pipe starting from the stuffing box 33 and the collecting vessel 34 provided on the hollow shaft 13 is attached, a pipe 35 leads from the vessel 34 in the hollow shaft 13 to the distribution lines 36, 37 and 38 in the circumference of the pipe section 11 and in the arms 17 the cooling water spread evenly. The plastic pipe 27 produced is cooled directly Via the tube 45 arranged in the hollow shaft 13, the distribution piece 46 to the ring 47 the nozzle 48 ç 49 distributed around the circumference is supplied with cooling water. The direct external cooling takes place via the fixed cooling water supply line 39 in the outer ring 40 to the spray nozzles 41 and 42. The tub 43 with the drain pipe is for the water drainage 44 provided.

FIG. 1 shows a system for producing a large plastic pipe with a certain diameter and the same wall thickness. When generating of large pipes with different diameters and the desired wall thickness the cover 2 can be made so large in diameter, for example 1600mm.

Then you can use metal cylinders of different diameters, for example 1a and all large pipes up to diameters of 1500mm are produced will. A corresponding piece of pipe must be installed for the desired wall thickness will.

Most of the system starts from the cover 2a, the infeed device24 with the bunker 23, all facilities for the drive 5 and 6 and the storage of Annex 4, 14 and '21 as well as all foundations can be used for the production of the Large pipes with different diameters can be used.

For the production of these large plastic pipes according to the process of the invention can practically all thermoplastics such as high and low pressure polyethylene, Polypropylene, polyvinyl chloride, palystyrene, polyamide 6 and 66, polycarbonate and others find more application. They must be in the usual granular form or in Spherical shape are available. The performance of the plant is essentially through the heat transfer through the metal that determines the KunsYstUff. This transferred Heat must be the specific heat for heating up the plastic grains on the Melting temperature and the heat of fusion cover itself. According to the invention it is for Increasing the power advantageously the plastic grains before they are introduced To heat the system, for example, depending on the type of plastic, to 60-1000C. she can by blowing heated inert gases into or outside the bunker. the The level of the heating temperature depends on the plastic and is determined by the sticking together the plastic grains are limited.

The following examples are the application of various arts and crafts The production of large-scale fuel for various orurc knives, and thicknesses shown: 1.) The system is with a metal cylinder 750mm inner diameter and an inner pipe section with the largest outer diameter of 690mm. As plastic polyethylene grains with a melting point of l200C, a heat of fusion of of 35 kcal / kg and a specific heat of 0.5 kcal / kg, ° C are used. The hourly Heat output of the plant is about 40,000 kcal and this results in an hourly plastic processing of 470kg. The generated pipe length of 750mm diameter and 25mm wall thickness is determined at 8.3m per hour.

2.) For a large PVO pipe with a diameter of 1 m and a wall thickness of 30mm, a metal cylinder with an inner diameter of 100mm and a piece of pipe used with an outer diameter of 940mm. The plastic has a temperature of 200C, a melting point of 160 and a specific heat of 0.35 kcal / kg, oC. The hourly The output of the plant is 70,800kcal and the plastics processing results at 950kg / hour. The pipe length of the large plastic pipe with a diameter of 1 m and 30mm wall thickness is 5.8m. The trigger thread has at 75 revolutions of the metal cylinder a pitch of 1.3mm.

3.) To generate the same PV0 pipe, preheated to 8000 PVC grains used. With the same performance of the system of 70,800 kcal / hour the hourly plastic processing is 1240kg and a plastic grossr Pipe with a diameter of 1 m, a wall thickness of 30 mm and a length of 7.8 m. The increase in performance is 33. Blank page

Claims (14)

Claims: 1. Method and device for producing plastic pipes rs eat diameter characterized in that in a rotating metal cylinder Plastic grains on the outside heated above the melting point of the plastic fuse the inner cylinder wall to a plastic tube. 2.) Method according to claim 1, characterized. that the formed plastic tube on a concentric inside the rotating metal cylinder arranged, fixed and cooled pipe section, which is evenly distributed around the circumference distributed arms is equipped, screwed on the provided on the circumference of both threads and is discharged axially from the metal cylinder. 3.) The method according to claim 1 and 2, characterized in that the The pipe section is provided with a conical expansion following the thread, through which the thread grooves inside the plastic pipe are smoothed and the structure is compressed. 4.) The method according to claim 1-3, characterized in that the # metal cylinder is heated from the outside with electricity, heating gas or heating oil and with a Double jacket is provided in the heat transfer oil to even out the wall temperature circulates. 5.) Method according to claims 1-4, characterized in that the metal cylinder in connection with the heating zone there is a cooling zone in which the generated Plastic pipe is cooled indirectly via a double jacket. 6.) Method according to claims 1-5, characterized. that the cooling water flows on the circumference against the direction of rotation and axially directed in cocurrent or countercurrent will. 7.) Method according to claims 1-6, characterized in that the introduction the plastic grains in the rotating metal cylinder through openings on the front Cover takes place. 8.) Method according to claim 1-7, characterized in that the inner Pipe section is also driven and in or against the direction of rotation of the Metal cylinder can be rotated. 9.) The method according to claim l-dMduzbrgcC alternatively shifted in the axis can be. lO.) Method according to claims 1-9 characterized in that the cooling water Via an axially arranged cooling water line and corresponding stuffing bags to the rotating metal cylinder and passed through a hollow shaft to the inner pipe section will. ll.) Method according to claims 1-10, characterized in that the Plastic grains before being introduced into the metal cylinder to temperatures above 5000 can be heated up. 12.) Device according to claim 1-11 characterized # ekzeich.dass a Metal cylinder that is driven by a worm gear and a hollow shaft, in the first part it is heated from the outside and in the subsequent part it is cooled, in the frontal part arranged lid has openings for the plastic introduction and inside Equipped with one piece of pipe, the one on the front side has several with discharge threads provided and circumferentially arranged arms and at the cylinder end with the metal cylinder forms the ring cross-section for the plastic tube. 13.) Device according to claim 12, characterized in that the Storage and drive via two hollow shafts arranged one inside the other, which are separated are stored, e # follows. 14.) Device according to claim 12, characterized in that the frontally arranged cover of the metal cylinder made so large in diameter is that all pipe diameters in the plant, hureh-unscrewing the corresponding Metal cylinder and arrangement of the inner pipe section can be carried out.