OA10241A - Process for manufacturing a porous pipe obtained by said process and use of such a pipe in irrigation - Google Patents

Abstract

A method for making a porous tube for use in irrigation, wherein (a) a uniform mixture (21) of vulcanised rubber particles and a thermoplastic binder is prepared; (b) the mixture (21) is fed through an extruder (30) and heated therein; (c) the mixture (21) is drawn out of the extruder (30) through a die (44) at a linear extrusion speed V1 to form a tube (23); (d) the tube (23) from the die (44) is immersed in a cooling bath (35) in which a percentage linear contraction Ct is caused in the tube (23); (e) the tube (23) from the cooling bath (35) is fed between two feed rollers (27, 28) at a linear withdrawal speed V2; and (f) the tube from the feed rollers (27, 28) is wound onto a spool (25); V1, V2 and Ct being determined by the equation (100-Ct) < 100 V2/V1 < 120.

Description

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METHOD FOR MANUFACTURING A POROUS POROUS PIPE OBTAINED BY SAID METHOD AND USE OF SUCH PIPE IN IRRIGATION

The present invention relates to a method of manufacturing a porous pipe, such pipe being particularly intended for irrigating cultivated land. The irrigation of land cultivated with buried porous pipes has known advantages, particularly in comparison with surface watering: the water is brought near the roots of the plants; less water is necessary because it is not subject to the phenomenon of evaporation; the installation does not obstruct the surface of the ground and this is well suited when, for example, the ground receives a game of pleasure or pleasure. The porous pipes used must be sufficiently flexible to conform to the shapes of the ground and sufficiently rigid transversely, that is to say according to their section, so that they do not sag and keep in shape the passage of the water. Irrigation inside the pipe all along it. Such porous pipes are known; thus, for example, US-A-4,958,770 discloses a method of manufacturing a porous pipe for irrigation, comprising the steps of: a) preparing a homogeneous mixture of vulcanized rubber particles and particulates; a thermoplastic binder: b) passing said mixture through an extruder in which it is heated; C) discharging said mixture from the extruder through a die in the form of a pipe; d) immersing said pipe, at the outlet of the die, in a cooling bath; e) passing the pipe, at the outlet of the cooling bath, between two pulling wheels; f) winding the pipe at the outlet of the pulling wheels.

Of course, the quality of the irrigation obtained by a porous pipe of this type depends on the porosity of the pipe and, especially, on the homogeneity of this porosity all along the pipe, to prevent certain roots from being fed less. in water than others, see very 010 2 41 little or no power. To obtain such a result, the process according to US Pat. No. 4,958,770 provides for using in step a) particles free of moisture, otherwise particles whose moisture content is less than 0.15% by weight. weight, and extracting the pipe according to step e) at a linear extraction speed equal to the linear extrusion speed according to step c), the extruder being without air intake.

However, when the mixture is heated in the extruder, the melting agent melts and coats the vulcanized rubber particles which will then be assembled by bonding with the binder; this collage will be of less intimate and complete autantio that a greater effort is applied on the pipe at the exit of the cooling bath by the wheels of the step IIirirase; it is this collage more or less intimate, more or less complete, which ensures the desired porosity of the pipe.

In fact, other parameters come into play: the proportion of the mixture, i.e. the relative percentages of vulcanized rubber and binder; linear extrusion velocity and linear extraction velocity; the geometric characteristics dutuvau. namely its internal diameter and its radial thickness; the temperature of the barrel of the extruder; the temperature of the cooling bath.

Thus, the method according to US-A-4 958 770 is perhaps well suited to achieve a given pipe, geometric characteristics well defined, but is not suitable for the realization of a range derevaux; furthermore, all the parameters other than the speed must be very finely reduced, which leads to a cost price of the pipe. FR-A-2693401 also describes a process of the above type, in which the extraction rate is equal to 120% extrusion speed and which has the same disadvantages. By numerous tests, the Applicant has found that taking temperatures, extruder and cooling bath into account, in a simple and effective manner, could be carried out taking into account the linear contraction Ct of the pipe in the cooling bath. this contraction acting in the direction of the tension exerted on the pipe during the extraction, generally obtained by the difference of the linear extraction and extrusion speeds. 3 0 1 0 2 4 1

Thus, according to the invention, a method of manufacturing a porous pipe for irrigation, comprising the steps of: (a) preparing a homogeneous mixture of particles, vulcanized rubber and particles of a thermoplastic binder ; B) passing said mixture through an extruder in which it is heated; 1 c) extruding said mixture of Γ extruder through a? die, at a linear extrusion speed Vy, in the form of a pipe · | d) immersing said pipe, at the outlet of the die, in a bath | wherein said pipe is the seat of a linear contraction Ct expressed in percent; e) passing the hose out of the bath | cooling between two draw wheels at a linear speed | extractor Vo; F) winding the hose at the exit of the pulling wheels; is characterized by the fact that Vj, Vo, Ct are linked by the equation

Vo (100-Ct) <100 ~ <120 2 0 Experience has shown that, when this equation is satisfied, on the one hand, the porosity of the pipe is homogeneous over its entire length and, on the other hand, the traction exerted on the pipe during its extraction does not lead to the rupture of the pipe, these two consequences being valid for a wide range of pipes of different geometrical characteristics, such as the internal diameter e? thickness.

The mixture of step a) may contain a stabilizer.

The mixture of step a) can contain 55 to 70% by weight of vulcanized rubber; the thermoplastic binder is preferably low density linear polyethylene. Advantageously, the vulcanized rubber particles have a particle size of between 300 and 600 microns, and preferably between 400 and 500 microns; the particles of the thermoplastic binder have a particle size of between 350 and 1200 microns, and preferably between 650 and 850 microns. 4 010241

It is preferable that during step b) the mixture is maintained in the extruder at a temperature between 90 and 150 ° C; Advantageously, the extruder is divided longitudinally into zones in which the temperature is kept constant, the temperature of the zones increasing from the zone near the introduction of the mixture into the extruder to the zone directly before the head of the extruder. where the pipe is extracted, the temperature of the head being lower than that of this last zone.

The temperature of the cooling bath according to step d) is from 5 to 20 ° C, preferably from 10 to 20 ° C.

For a particularly economical process, the vulcanized rubber is obtained by recovering used tire tapes, or used tires. The invention also relates to a porous pipe obtained by the method defined above, as well as to the use of such a pipe for irrigating cropland, said porous pipe being buried, in which the pipe is supplied with water underwater. a pressure at least equal to 5 meters of water. To better understand the object of the invention will now be described by way of purely illustrative and not limiting, embodiments shown in the accompanying drawings.

In these drawings: FIG. 1 is a general diagram showing an installation example for carrying out the method according to the invention; - Figure 2 is an exploded sectional view showing the main component parts of the head of the extruder ofFigure 1; - Figure 3 is similar to Figure 2, but the parts being assembled; - Figure 4 is a detail, on a larger scale, of Figure 3; - Figure 5 is a view along V-V of Figure 4; FIG. 6 is a view along VI-VI of FIG. 2; the wear 7 is a view along VII-VII of FIG. 2; the wear δ is a section according to VUI-VIII of FIG. 1; Figure 9 is a partial sectional view of a pipe obtained by the process according to the invention.

Referring to Figure 1, we see that the installation,; for the implementation of the process according to the invention, comprises two (5) loops 10, 11 for supplying the constituents of the mixture, namely, vulcanized rubber in the form of particles and thermoplastic alloy, also in the form of particles. Supply pump 14 comprises two suction ducts 15, 16 connected to V tanks 17, 18 each containing one of the two constituents of the mixture I à to be made, and two delivery ducts 12, 13 for feeding the trunking 10, 11 themselves supplying a mixer 9 with a pre-set screw at a constant dosage, the mixer 9, fixed directly to the upper part of a hopper 20, feeds the hopper 20 feeding mixture 21 to the extruder 30, the homogeneity of the mixture 21, in the proportions defined above, is provided by a mixer 19 with a vertical axis, the level 22 of the mixture in the hopper 20 is set a | constant: this is achieved through a detector level 22! not shown, which controls the opening of the hatch 9 mixer! Also a level detector allowing the call of the constituents of the mixture for charging the mixer 9 when its hatch is closed after feeding the hopper 20; this arrangement avoids variations in the static pressure due to the mixture 21 in the shown. The head 40 of the extruder 30 has two hopper zones 20 which do not interfere with the extrusion conditions. The extruder 30 comprises a shaft 36 of horizontal axis in which is rotatably mounted an extrusion screw 31 drivable in rotation by a motor 33: the cask 36 is surrounded by casings 32 distributed longitudinally defining temperature control zones which are maintained at desired values by means of electric heating and air-cooling, non-heating, by means of collars electric, and cooling by air ventilation for the regulation of its temperature; the temperature of the head 40 is thus maintained at a substantially constant temperature of between 85 and 110 ° C. ## EQU1 ## At the outlet of the head 40 of the extruder 30, which forms a pipe 23 and which will be described in more detail below, the pipe 23, emerging from the head 40 at a linear speed Vj, is immersed in unbac 34 containing a coolant 35, such as water for example.

The pipe 23 is pulled out of the tank 34, at a linear speed Vn, by an extractor 24 consisting of two pulling wheels 27, 28 in the form of grooved pulleys whose section is semicircular; the gorgessont bordered by two circular lateral tracks, two tracks 37 for laio draw wheel 27, and two tracks 38 for the draw wheel 28; the two pulling wheels 27, 28 roll one over the other via the circular pathways 37, 38 so that a circular passage 29 (FIG. 7) is defined, the vau 23 passing through the passage 29 with a slight tightening to obtain the drawing of the pipe 23 at the speed Vp; the pipe 23 is then wound on a winder 25.

The head 40 of the extruder 30, better visible in FIGS. 2 to 7, comprises on the side of the barrel 36 of the extruder a decompression stage and on the opposite side a shaping stage; the decompression stage consists of a casing 41 traversed by a frustoconical axial passage 20 whose small base is located on the side of the connection of the casing 41 to the barrel 36 of the extruder, a fixing flange 62 being provided for this purpose . provided with fixing holes 61; the forming stage comprises a hollow die support 43 provided at the end of a threaded unalésaae 66 in which is mounted by screwing the sleeve 65 externally threaded with a die 44 for shaping the pipe; the bore 66 communicates with a cylindrical bore of smaller diameter from which extends a frustoconical Dassaze 67; the sleeve 65 of the die 44 is externally protruded, to the right with respect to the figures, by a shank 56 whose outer surface has a square section to facilitate the screwing operation of the die 44 into the support 43 by means of a corresponding square-shaped key; the die 44 is pierced with a frustoconical channel 45 whose large base is at the right of the outer end of the sleeve 65, the frustoconical channel opening into a cylindrical channel 46 whose diameter is equal to that of the small base 35 of the channel trcncomque 45. 01 0241

The casing 41 of the compression stage and the support 43 of the shaping stage are assembled by means of a flange 42, generally in the form of a disc, provided with an anti-tamper device. turbulence; the casing 41 is provided with a flange 63 in which are | 5 are provided with fixing holes 60 which cooperate with corresponding fixing holes 60 provided in the flange 42; likewise, support | 43 is provided with a flange 64 in which there are provided mounting holes 76 which cooperate with corresponding fixing holes 76! provided in the flange 42 visible in Figure 6. | The flange 42 is traversed by a bore cylindrical cylindrical J axial internally threaded; the bore 59 is intended for assembly by | screwing, on the one hand, on the housing side 41 of a compression cone 51, and, on the other hand, on the side of the die holder 43 of a punch holder 53; for this purpose, the compression cone 51 and the support 53 15 are provided with circular bases, respectively 57 and 58, externally threaded, their threads corresponding to that of the bore 59 of the flange 42.

The base 57 carries a cone 69 whose base is slightly larger than the diameter of the base 57 and defines an annular contact surface 20 with the transverse face facing the flange 42; the base 58 extends in a cylindrical portion 77 of a diameter slightly greater than that of the base 58 also defining an annular contact surface with the transverse face opposite the flange 42: the cylindrical portion 77 serves as a base for a trunk of cone 55 2 5 whose small base extends along a cylindrical nozzle 56 of the same diameter: when the casing 41 and the flange 42 are assembled, as shown in FIG. 3, the frustoconical passage 68 and the cone 69 define between them an annular channel whose section decreases towards the flange 42. the inclination on the axis of the passage 68 being less than the half-angle at the top of the cone 69, so that the mixture is there; subject to compression. The tip 56 of the support 53 is provided with an internally threaded cylindrical bore which receives, as shown in FIG. 4, a threaded rod 50 whose length is greater than the axial length of said bore; the portion of the threaded shank 50 projecting from said bore is for screw mounting a punch 54, the cylindrical end 49 of which is provided with an internally threaded bore at the pitch of the threaded latige 50; the cylindrical end 49 is provided with a flange 74 having radial slots 75 (FIG. 5) facilitating, by means of a suitable key, the gripping of the punch 54 for its screwing onto the threaded rod 50 itself screwed beforehand in the support 53, the cylindrical end 49 extends, on the opposite side to the flange 74, according to a truncated cone 48 itself extended along a cylinder 47, when the flange 42 and the support 43 are assembled, as shown in FIG. 3, the truncated cone 55 and the frustoconical passage 67 defining between them an annular channel whose section tapers toward the thread 44, the corners of the truncated cone 55 and the frustoconical passage 67 having relative values provided accordingly, in so that the mixture is compressed; in the same way, as visible on lafisure 4, the apex angle of the truncated cone 48 is smaller than that of the truncated cone 45 so that the section of the passage defined between the cone rim 48 and the frustoconical channel 45 decreases towards the exit of the sector 44.

Of course, the radial space between the channel 46 of the die 44 and the cylinder 47 of the punch 54 allows the desired thickness E of the pipe 23 to be defined, the outer diameter of the pipe 47 defining the inside diameter D of the pipe 23 (Figure 8): there are several sets of die 44 and punch 54 adapted to different desired values of E and D.

As shown in FIG. 3, the sum of the axial heights of the pedestals 57, 58 is smaller than the axial length of the bore 42 of the flange 42 so that a chamber 74 is defined; the flange 42 is pierced with radial channels 70 (Figure 6) communicatingthechamber 74 with the outside; the flap 42 has axial passages 52 distributed circumferentially, in the form of circular arcs, allowing the mixture to pass through the flange 42 from the decompression stage 41-51 to the shaping stage 43-44-54.

The support 53, the threaded rod 50 and the punch 54 are provided with a central channel respectively 71, 72. 73 of small diameter, of the order of five millimeters for example, so that. when the head 40 is assembled, a channel 71-72-73 communicates the chamber 74

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With the outside, at the exit of the punch 54; the role of channel 71-72-73 will appear below.

Good results are obtained with an extrusion head 40 in which: the frustoconical passage 68 has an axial length of 5 200 mm, the diameters of the bases being 50 and 100 mm; the cone 69 has a length of 110 mm and a base of 70 mm in diameter; the cylindrical portion 77, the cone frustum 55 and the tip 56 have respective lengths of 40 mm, 100 mm and 20 mm, while the diameters of the cylindrical portion 77 and the tip 56 are 70 and 25 mm respectively; the frustoconical passage 67 of the support 43 has a length of 125 mm and bases whose diameters are 110 mm and 30 mm.

In order to obtain a tube 23 in which D = 16 mm and E-2.8 mm, the punch 54 has a cylindrical end 49, a truncated cone 48 and a cylinder 47 whose axial length is respectively 20 mm, 25 mm, 60 mm, the bases of the truncated cone 48 having a diameter of 20 mm and 16 mm; the frustoconical channel 45 of the die 44 has an axial height of 40 mm and the bases of the diameters 45 mm and 22 mm, the axial length of the cylindrical channel 46 being 60 mm.

In order to produce a porous pipe according to the invention, in the installation according to FIG. 1, a vulcanized rubber and a thermoplastic binder are used, both in powder form.

The vulcanized rubber can be of any type; it is preferable, for economic reasons, to grind recovered tires, in particular their treads; the size of the comminuted rubber particles is between 300 and 600 microns, more preferably between 400 and 500 microns.

The thermoplastic binder may also be this type, but polyethylene, in particular linear low density polyethylene, whose density is of the order of 0.9 g / cm 3, is preferred. The mixture produced contains between 55 and 70%. by weight of vulcanized rubber, the corresponding proportion of polyethylene being 45 to 30%; the mixture contains only rubber and binder; indeed, linear low density polyethylene has the advantage that its chains are not destroyed under the conditions of the extrusion operation; of course, if another binder is used, it is possible, in some cases, to add to the mixture a stabilizer preventing destruction of the thermoplastic binder chains.

The level 22 of this mixture in the hopper 20 is regulated, the experiment has shown that a regulation of the level 22 at a height of plus or minus 10 cm is sufficient not to disturb the conditions of extrusion, the total height of the hopper 20 being of the order of 80 cm to 100 cm.

In Figure 1, there is shown three boxes 32defining temperature control zones of the barrel 36; alternatively, there are four wells 32. The regulated temperatures range from 90 to 150 ° C; it increases from the zone near the hopper 20 to the zone near the head 40 of the extruder; a higher temperature of 140 ° C, instead of 150 ° C. has also worked well in some cases. Two temperature control zones are provided for the head 40 of the extruder, the temperature being lower than that of the barrel 36.

Figure 9 shows in section, partly, a pipe 23constimated vulcanized rubber particles 26 covered with polyethylene and more or less agglomerated, shown on a large scale, the pipe 23 having an inner diameter D and a radial thickness E.

The linear velocity V) of extrusion used, expressed in 30 meters per hour, is between 400 and 1000: it is chosen according to D and E desired: for example, if D is 13 mm and E de2 mm it is of the order of 500 meters per hour, the proportion of rubber in the mixture being of the order of 65 f. The extraction vitrine is selected according to the invention, taking into account the linear contraction Ct of the pipe in the cooling bath: according to this example, the bath temperature being 10 ° C, Ct is equal to 12%; Xm is chosen greater than 88% of Vj is here equal to 110% of Vj; under these conditions, the pipe 23 obtained has a uniform porosity over its entire length.

The result according to the invention is obtained for a whole series of pipes; if we define it by the diameter D and the

D ratio - the diameter D can range from 10 mm to 20 mm. see beyond, and $ 35 S- Λ S "

I *; Π 010241, D. the ratio ~ may advantageously be between 0 and 7, but cek. ~ ratio can go down to 2 and go up to 10.

The passage of the pipe 23 in the cooling bath is facilitated when the pipe 23 has a certain stiffness; if it is not the case, it is possible to blow air into the chamber 74 via the radial channels 70; the air thus blown through the conduit 71-72-73 andpénètre inside the pipe 23, out of the punch 54 and enconférant to the pipe 23 a certain holding allows to keep the value of D to the desired value; when no air is blown into the chamber 74, the conduit 71-72-73 and the radial channels 70, to the atmosphere, serve for degassing.

The setting in tension of the pipe 23 during its elaboration, due to the contraction phenomenon in the cooling bath combined with the relative value of the speeds Vj and Vo, requires an adhesion of the pipe 23 at the passage 29 defined by the wheels 27, 28 extractor 24; this adhesion can be obtained by the state of the outer surface of the pipe, relatively rough, especially when the outer diameter of the pipe is large; when this diameter is insufficient, in particular when it is less than 20 mm, it is preferred to provide the diameter of the circular passage 29 slightly less than the outside diameter of the pipe 23 and thus to achieve a clamping of the pipe by the wheels 27. 28; for example, a tightening of a few percent is sufficient, such as 3% for a pipe with an outside diameter of 17 mm. When the pipe 23 is buried in a ground and supplied with water for irrigation thereof, it is necessary, especially when the pipe is of great length. 200 meters, for example, to ensure its filling by controlling the pressure drop due to its porosity and whatever the unevenness of the ground, so that the flow of irrigation water is constant throughout the pipe; this is achieved by feeding the pipe 23 under sufficient water pressure; it is at least equal to 5 meters of water height, and can be between 5 and 10 meters of water height. To fix ideas, feeding under 6 meters of water allows a flow of irrigation water of 3 5 2 liters per minute per meter of pipe.

Claims (12)

mmifiinnrfiWBtâfagii • X I2 010241 CLAIMS 1 - A method of manufacturing a porous pipe for irrigation, comprising the steps of a) preparing a homogeneous mixture (21) composed of vulcanized rubber particles and particles of a thermoplastic binder; b) passing said mixture (21) into an extruder (30) in which it is heated; c) discharging said mixture (21) from the extruder (30) through a die (44) at a linear extrusion velocity Vj in the form of a pipe (23); d) plunging said pipe (23) at the exit of the die (44) into a cooling bath (35) in which said pipe (23) is the seat of a linear contraction expressed in percent; E) passing the pipe (23) at the outlet of the cooling bath (35) between two pulling wheels (27. 28). to a linear extraction line V? ; f) winding the pipe at the exit of the draw wheels (27, 28) into a coil (25); Characterized in that Vj. Vn. Ct are bound by the equation Vo (100-Ct) <100 "<120 2 - Process according to claim 1, characterized in that the mixture (21) of step a) contains a stabilizer. 3 - Method according to one of claims 1 or 2, characterized in that the mixture (21) of step ai contains 55 to 70% by weight of vulcanized rubber. 4 - Process according to one of claims 1 or 3, characterized in that the thermoplastic binder is low density linear polyethylene. 5 - Process according to one of claims 1 to 4, characterized in that the vulcanized rubber particles havean aranulomethane between 300 and 600 microns. 13 01 0241 6 - Process according to claim 5, characterized by the fact that vulcanized rubber particles have a particle size comprise between 400 and 500 microns. 7 - Process according to one of claims 1 to 65 characterized in that the particles of the thermoplastic binder have a particle size of between 350 and 1200 microns. 8 - Process according to claim 7, characterized in that the particles of the thermoplastic binder have a particle sizeecomprise between 650 and 850 microns. to 9 - Process according to one of claims 1 to 8 characterized in that during step b) the mixture is maintained in an extruder (30) at a temperature between 90 and 150 ° C 10 - Process according to claim 9, characterized in that 1 extruder (30) is divided longitudinally into zones (32) 15 in which the temperature is kept constant, the temperature of zones (32) increasing from the zone near the introduction of the mixture in the extruder to the zone directly before the extruder (40) from which the pipe (23) is extracted, the temperature of the head (40) being lower than that of the latter zone. 11 - Method according to one of claims' 1 to 10 characterized in that the temperature of the cooling bath (35) according to step d) is between 10 and 20 ° C. i 1-- Method according to one of claims 1 to 11 1 characterized in that the vulcanized rubber is obtained by recovery of used tires. 1 13 - Porous pipe characterized in that it is obtained by the process according to claims 1 to 12. f 14 - Use of a porous pipe according to claim 13 for the irrigation of cultivated land, said porous pipe being buried characterized by the fact that the pipe (23) is supplied with water under at least one pressure at 5 meters of water. ?