JPH0377224B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a technique for manufacturing porous irrigation pipes, and in particular to irrigation pipes manufactured using novel materials. Technical Background As the population increases, water becomes increasingly important, becoming a precious and expensive resource. Agriculture is one of the most common uses of surface water. What is needed is to develop more efficient equipment to transport water to the plants. When water is applied to the earth's surface, it is not absorbed immediately, so it either flows away or evaporates.
Furthermore, even if water is absorbed into the soil, it will not reach the roots of plants unless the surface soil is thoroughly moistened. Therefore, most plants require a water supply facility. After harvesting, when the field is plowed for replanting, if irrigation equipment is on the ground, it must be removed and replaced each time. Irrigation equipment also gets in the way of mechanical mowing operations and requires considerable maintenance. Many plants are susceptible to night-time damage, so above-ground watering usually must be done during the day. Sprinkling water on the ground also interferes with the use of recreational areas such as parks, sports fields, and golf courses. Surface watering is not suitable because crops and grasses are watered equally. Because of the limitations of above-ground irrigation, underground irrigation equipment has been developed that provides water directly to the roots of cultivated crops at a suitable depth underground. The pipes used for this purpose are chemically stable in the soil environment, do not collapse even when encountering hard objects such as rocks, and can withstand hydrostatic pressure.
It is also desirable that the material is not susceptible to brittle failure and is flexible so that it can be bent along the lines along which the crop is planted. Irrigation pipes of various types that allow water to seep out slowly over their entire length and surface are commonly used in agriculture. Such pipes can be buried in the ground at a suitable depth for the crop to grow, where they can provide water directly to the root system. By means of suitable control devices, the amount of water in the soil can be maintained at approximately optimum conditions. By this,
There are reports that it significantly increases the yield of certain crops. Porous irrigation pipes are made from recycled rubber tires mixed with a binder such as polyethylene. When this mixture is used to make a pipe by extrusion molding, the water in the high-temperature extrudate evaporates, at a rate of approximately 0.4 kg/cm ² (several psi).
Pores are formed through which water can seep out under moderate water pressure. Although this pipe can be used effectively for some purposes, it has several drawbacks when used in large-scale, multi-purpose agriculture. The most important problem with this product is that its porosity is not constant. You might end up with areas without pores, but the pores may be too large. The water leaching rate of this product can vary by 50 to 75 percent or more over a length of about 1.5 meters (several feet). If such pipes were used in sugarcane fields where the sugar cane is planted closely and closely together, some areas would have too much water and some areas would be extremely dry. Another problem is that the porosity over the entire length of the pipe cannot be controlled for each lot. If you are planning to install irrigation equipment in a specific area,
This causes serious technical problems. Therefore, many pressure regulators are usually used in this installation. This results in higher costs and
Moreover, the types of materials that can be used for porous pipes are limited. It has been found that the significant variation in the degree of porosity is due to the inability to control the moisture content of the raw materials. Dry powders are somewhat hygroscopic. U.S. Patent No. 4003408 to Turner, no.
In the production methods disclosed in 4110420 and 4168799, blowing agents, ie pore-forming agents, are added depending on the moisture absorption of the strip material. However, the moisture content of each lot or each part of the lot also changes depending on environmental conditions such as humidity and temperature. Since the amount of moisture present in the extrudate is critical to the porosity of the final pipe, variations in the moisture content of the feed can result in a variety of rejects. Turner tried controlling excess moisture by aerating the extrudate, but was unable to change the porosity. The raw material is a mixture of fine powder and a small amount of oil, but such materials do not pass well through a single-screw extruder. Also, if the powder is not supplied uniformly, it will result in uneven density and pipe wall thickness. These requirements are important in maintaining uniform porosity of the wall, so if the extruder is not fed evenly, the amount of water exuded will be uneven. Description of the invention The porous irrigation pipe according to the invention has a uniform porosity throughout. Irrigation systems can be constructed without using as many pressure regulators. Yields are also higher because most crops receive water evenly. The porous pipe of the present invention can be used for drip or continuous underground irrigation for crops that are planted in high density, such as sugar cane. Porous irrigation pipes can be made by precisely controlling the moisture content of the raw materials and shaping them into shapes that feed them uniformly and reliably to the extruder. The moisture content of the high surface area strip or powder mixture varies from about 0.2% to a few percent by weight, even during a unit operation. The moisture content of the material according to the invention does not vary by more than ±10% throughout the unit operation and, by weight,
It ranges from 0.5 to 3%, preferably from 0.75 to 1.5% by weight. The pipe of the present invention is made from raw materials that have been previously processed into pellets. This material is uniformly and reliably fed into any type of single screw extruder. Therefore, porous pipes can be made anywhere using standard extrusion equipment. Therefore, the transportation cost, manufacturing cost, and equipment cost of this porous pipe are also reduced. Furthermore, the moisture content of the pellets can be adjusted to a predetermined value depending on the desired porosity and exudation rate. The pellets are stored in a moisture-free environment, such as in a moisture-proof container. The pellets are less hygroscopic than conventional materials with large surface areas. According to the production method of the present invention, the water content is known and there is no need to pass excessive steam pressure, so it is possible to use a non-porous extruder. Porosity can be controlled by predetermining the moisture content of the pellets, since the parameters of moisture content and feed rate can be controlled, as can the temperature. Also, since all variables can be controlled, the porosity from lot to lot can be controlled by varying the extruder and die temperatures. The present invention is characterized by using a material that can be processed into pellets. The powdered materials conventionally used are difficult to process into pellets. By feeding pellets with controlled moisture content and pelletizing agent to a variety of extruders, highly porous pipes can be used wherever pipes are needed and have a uniform seepage rate. Irrigation pipes can be produced continuously. The porous pipe has sufficient porosity, size, and strength for use. In addition to saving on transportation and manufacturing costs, the porous pipes of the present invention often allow for more precise irrigation cycles, which can increase crop yields. Facilities can be built. The above-mentioned features and other features and advantages of the present invention will become clear from the following detailed description with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION The pelletizable mixture according to the invention is based on a flaky elastomer, which is supplemented with an inorganic material, preferably talc.
It contains 6.0 parts of slip agent and 0.1 to 1.0 part of lubricant such as metal stearate. The elastomer may be a natural rubber based on cis-1,4-polyisoprene, a synthetic homopolymer of butadiene or isoprene, or a butadiene or isoprene containing 0.1 to 20% by weight of a vinyl monomer such as styrene, isobutylene or acrylonitrile. It is a copolymer of Preferably, the elastomer is vulcanized. As an inexpensive and easily available raw material for vulcanized rubber, recycled rubber obtained from automobile tires from which metal tire cords and surface metal reinforcing materials have been removed can be used. The rubber is crushed into pieces large enough to pass through a screen of 10 meshes or less, preferably 20 to 60 meshes. The binder resin is a thermoplastic that can soften at temperatures below 167°C (300°C) so that pores are formed during extrusion. This resin is effective against the soil environment and against fertilizers, herbicides or pesticides that have soaked into adjacent soil or applied in irrigation water. Must be stable even after long-term exposure. The resin must also be inert to other components of the pipe, such as extruded rubber strips. Polyvinyl acetate cannot be used because it reacts with the rubber strips. Styrenic polymers, including high-impact polystyrene copolymers, include various types of nylon,
Useful as linear polyamides such as polyvinyl chloride, polyphenylene oxide, and polyphenylene sulfide polymers. The most preferred group of polymers are polyethylene,
2, such as polypropylene or polybutene
It is a linear polymer consisting of alkenes having 4 to 4 carbon atoms. These polymers have long straight segments that do not react in the soil and in the extrusion barrel and allow crystallization to occur. Polyethylene has a low melting temperature, is strong, and retains its shape well. High density polyethylene is approximately 0.94 to 0.97 gm/
Porous pipes having a density of cc and made using only high density polyethylene binders are somewhat stiff and brittle, and are difficult to extrude. In addition, polyethylene is about 0.90 to 0.93gm/
With densities as low as cc, pipes made using only low-density polyethylene binders are flexible and easy to bend to fit the desired passageway, and are easy to extrude. be. Although these pipes are extremely useful for above-ground irrigation, their walls are insufficiently rigid for underground use. When this pipe is bent, it becomes twisted and cannot maintain its shape. It is not brittle and has appropriate flexibility.
A suitable binder composition for making a porous pipe capable of maintaining its shape is 50 to 80% by weight high density polyethylene, preferably 60 to 70% by weight, and 20% by weight low density polyethylene. ~
50%, preferably 30 to 40%. Any commercially available polyethylene in the form of powder, flakes, or pellets can be used as the polyethylene.
Recycled polyethylene can also be used as a material. In this case, the shape and color of the material have little effect on the product. Slip agents serve to extrude the rubber binder mixture. In addition to talc, finely ground inorganic substances such as clay, silica, carbonate, or mica can be used. The metal stearate lubricant is selected from the group consisting of calcium stearate, magnesium stearate, and zinc stearate. First, FIGS. 1 to 3 will be explained. The strip rubber, additives and binder are dry and thoroughly mixed in a ribbon blender or other suitable mixer 10 to form the material to be fed to the hopper 12 of the extruder 14. This mixture is fed into a diverce pellet system and pelletized. A submersible or water ring pelletizer 16 is shown being fed directly from the extruder. Although single screw extruders with suitable stuffing equipment may be used, rotating screw extruders are preferred. Strand pelletizers do not work well with the rubber binder compositions according to the invention. By means of separate heating devices such as a pair of heating jackets 18, 20 containing separate heat exchange medium heat streams, the extruder can be heated to 178°C (320°C).
At temperatures between 222°C and 400°C, the die is
The temperature is maintained between 139℃ (250〓) and 181℃ (325〓). The extruded strand material has a dry bulk density of at least 0.25 gm/cc and a diameter of 3 to 20 mm, preferably 4 to 10 mm. This strand is cut into lengths of 3 to 20 mm by a mechanical knife 22 in a water tank 24.
The water 28 in this tank is normally between 11°C (20°C) and
It is maintained at 45℃ (80℃). When the extruded strands 26 enter the water 28, they condense and are formed into pellets 32 by a thin layer of air blown out from the nozzle 30. The pellets 32 fall into a collecting section 34 of the water tank 24. An air supply 36 is connected to the nozzle 30 and is periodically activated by a controller 38 . The pellets dispersed in water are fed from the water tank 24 into a separator, such as a cyclone separator 40. The water in the water tank 24 is circulated via pipe 42 while the pellets 32 are transported to the conveyor belt 44.
It is transported to a dehumidifying dryer 46 by the following. The pellets 32 are then dried to a predetermined moisture content ranging from 0.5 to 2.5% by weight, depending on the desired porosity. The conveyor belt 44 conveys the dried pellets 32 into a sealed hopper 48 where the humidity is controlled.
It is fed into a storage container such as a polyethylene bag 50. This bag 50 is sealed with a metal band 52 or the like and a box or barrel 54.
Stored in a protective container such as Dry pellets have a precisely controlled and constant moisture content, which remains stable over long periods of time. The pellets have a lower surface area than conventional powdered materials and therefore do not change their moisture content for short periods of time without special storage. Next, FIG. 4 will be explained. Pellet 32 is transferred to pipe extruder 62
is supplied to the hopper 60 of. The hopper 60 is provided with a lid 61 to prevent objects from entering from around it. The extruder 62 has one low-pressure screw 64. Its length to diameter ratio is at least 24:1, preferably at least 35:1. The compression ratio of the supply section to the metering section is 1.5 to 2.2 times. The diameter of the feed tube 66 is set to an appropriate size according to the outer diameter of the pipe. The outer diameter of the pipe is 5.1cm
(2 inches) to 25.4 cm (10 inches), typically 7.6 cm (3 inches) to 15.2 cm (6 inches).
inch). The use of mixing pins should be avoided as the rubber strips will tangle. The processing is carried out at a temperature high enough to melt the binder resin, but below the melting temperature of the elastomer. The proper temperature of the barrel 54 and especially the die 68 is normally controlled within a range of ±2.8°C (5〓). A more uniformly porous pipe is created by increasing the temperature throughout the length of extruder 62. Separate heating jackets 70, 72, and 74 serve as a supply section, a transfer section, and a transfer section of the feed tube 66 of the extruder.
and the measuring section, respectively. A heat flow of a heat exchange medium circulates through each jacket. Supply section: 189℃ (340〓) to 200℃ (360〓)
(T ₁ ), the transition zone is between 200℃ (360〓) and 206℃
(370〓) (T ₂ ), the measuring section is heated to 203°C (365〓) to 209°C (375〓) (T ₃ ). Die 68 is also provided with a separate temperature control section. A suitable die is shown in FIG. 5 of U.S. Pat. No. 4,168,799. The die 68 has an exit orifice 82 in front of which a mandrel 84 is provided to form the holes 86 of the porous pipe 88 . The mandrel 84 can be used to change the wall thickness of the pipe.
It is removable. The wall thickness depends on the desired flow rate, seepage rate, and wall strength to prevent collapse. This wall thickness is typically 0.25cm
(0.1 inch) to 5.08 cm (2.0 inch). According to the US patent specification, in order to avoid forming an impermeable layer on the surface of the pipe, the die is cooled to between 22°C (40°) and 45°C (80°);
Additionally, the feed tube is vented to eliminate excessive pressure. However, according to the present invention, there is no need for ventilation into the feed tube, and the die can control the porosity of the pipe between 133°C (240〓) and 167°C (300〓).
is heated to a predetermined temperature. A preheated heat exchange medium (T ₄ ) circulates within the annular jacket 90. When the screw 64 is rotated by the motor 92, the supply section begins to move forward and the binder resin begins to melt. Due to the evaporation of the water, expandable bubbles of water vapor form a pore network 96 from the pores 86 to the surface 98 of the porous pipe. Pipe 88 is extruded through die 68 and 14
The film passes through a cooling tank 100 containing water at a temperature of 25°C (25°C) to 50°C (50°C) and is wound onto a winding stand 102. The length of the cooling bath is usually at least
It is 12.2m (40 feet). Next, examples of the method of the present invention will be given. The dry ingredients are mixed in a ribbon blender, then heated to 200°C (360°) to 217°C (390°) with a 5 mm die heated to 167°C (300°) and a twin shaft It was supplied to the hopper of a screw-type extruder. The water bath was kept at 19°C (35°) to 22°C (40°) and the 5 mm strands were cut into pellets approximately 8-9 mm in diameter with a pneumatic knife. The density of the pellet after drying was 0.275 gm/ml. Example 1 The following mixture was pelletized, dried,
The water content was set to 0.75%. Shredded rubber tires (48 pieces)
45,360 g (100 lb.) Low density polyethylene 15,876 g (35 lb.) Finely divided talc 1361 g (3 lb.) Zinc stearate 113 g (0.25 lb.) It was extruded and molded into a 14 mm (0.55 inch) porous pipe with a wall thickness of 5.1 mm (0.2 inch). The temperature of the extruder was as follows. Extruder (all parts) 195℃ (350〓) Gate 189℃ (340〓) Spider 186℃ (335〓) Die 186℃ (335〓) The porosity of porous pipe at 0.703Kg/cm ² (10psi) is , it was as follows. 33.5±2.5cm ³ /min/m (0.27±0.02GPM/100ft.) 44.8±1.2cm ³ /min/ ^m2 (0.11±0.003GPM/100sq.ft.) Example 2 The die temperature was set to 161℃ (290℃) Extrusion molding was carried out under the same conditions as in Example 1, except for the following: and using the same pellet raw material. 0.703Kg/ ^cm2
The porosity of this pipe at (10 psi) was: 23.6±21.1cm ³ /min/m (0.19±0.17GPM/100ft.) 31.0±2.9cm ³ /min/ ^m2 (0.076±0.007GPM/100sq.ft.) Example 3 Instead of low density polyethylene binder, The same procedure as in Example 1 was repeated except that 35 pounds of high density polyethylene was used. The pellets were quite difficult to mold and the pipes were brittle and inflexible. Example 4 Shredded rubber tire (40 mesh)
45360g (100lb.) High density polyethylene 11340g (25lb.) Low density polyethylene 4536g (10lb.) Slip agent - Talc 1361g (3lb.) Lubricant - Calcium stearate
113 g (0.25 lb.) This mixture was processed into pellets and dried to a moisture content of 1.0%. This pellet has a diameter of 6.35 mm.
cm (2.5 inches) and extruded in a Prodex type single screw extruder with a length to diameter ratio of 24:1. This extruder was equipped with a PVC-type screw with a compression ratio of 1.9:1 and a circular pipe die with a land-to-length ratio of 16:1. The temperature of the extruder was maintained between 189°C (340°) and 200°C (360°). Gate, spider, and die temperatures were adjusted to yield extrudates at the temperatures shown below. wall thickness 4.2
A porous pipe with a diameter of 0.165 mm (0.165 inch) and the following properties was created.

[Table] The pellet material was fed smoothly, and the finished porous pipe had excellent compressive strength and flexibility. Weed consistency was measured by determining flow increments of 1 foot over 50 feet of pipe. As a result, the consistency factor C _V which is the ratio of standard deviation to flow
I was able to get it out. The C _V of conventional commercially available porous pipes ranges from 0.25 to
It is 0.5. A _CV of 0.2 is usually preferred for use, and for plants that are planted closely together, such as sugar cane, to ensure that growth is not inhibited if the irrigated area is over-wet or dry. Therefore, 0.1
_CV is required. At 0.703Kg/cm ² (10psi), 124.2cm ³ /min/
A porous pipe of 12.7 mm (0.5 inch) inside diameter according to the present invention having a flow rate of 1 GPM/100 ft.
It has a C _V of 0.1 to 0.15, and 31.0 cm ³ /min/m
The C _V measured for porous pipes with a flow rate of (0.25 GPM/100 ft.) was between 0.05 and 0.1. Although the present invention has been described in detail above with reference to only preferred embodiments, it is possible to make various modifications and variations thereto without departing from the spirit and purpose of the present invention as defined in the claims. It goes without saying that it can be done.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a series of apparatus for producing pellets according to the invention. Second
The figure is an enlarged view of the pellet. FIG. 3 is a partially cutaway front view of the humidity-adjustable storage container. FIG. 4 is a schematic diagram showing an apparatus for extruding a porous pipe according to the invention. Fifth
The figure is an enlarged longitudinal cross-sectional view taken along line 5--5 of FIG. 4. 10...mixer, 12...hopper, 14...
Extruder, 16...Pelletizer, 1
8, 20... heating jacket, 22... knife,
24...Aquarium, 26...Strand, 28...
Water, 30... Nozzle, 32... Pellet, 34...
...Gathering part, 36...Air supply part, 38...Controller, 40...Separator, 42...Pipe, 4
4...Conveyor belt, 46...Dehumidifying dryer,
48...Hopper, 50...Bag, 52...Band, 54...Keg, 60...Hopper, 61...
Lid, 62... Pipe extruder, 64...
Screw, 66...Feed tube, 68...Die, 7
0,72,74...heating jacket, 82...exit orifice, 84...mandrel, 86...
hole, 88...pipe, 90...jacket, 92
... Motor, 96 ... Pore network, 98 ... Surface, 1
00... Cooling tank, 102... Winding stand.

Claims (1)

[Claims] 1. 100 parts by weight of a granular elastomer, and 10 to 10 parts by weight of a granular elastomer.
An extrudable composition comprising 60 parts of a thermoplastic binder, 1.0 to 6.0 parts of a slip agent, and 0.1 to 1.0 parts of a lubricant. 2. The composition according to claim 1, wherein the elastomer is vulcanized rubber. 3. The composition according to claim 2, wherein the elastomer is recycled rubber in the form of strips with a size of 10 to 60 meshes. 4. Composition according to claim 3, characterized in that the binder has a melting temperature lower than 167°C (300°C). 5. The composition according to claim 4, wherein the binder resin is linear polyethylene. 6. The composition according to claim 5, wherein the resin is a mixture of 50 to 80% by weight of high density polyethylene and 20 to 50% by weight of low density polyethylene. 7. The composition according to claim 4, wherein the slip agent is a finely ground inorganic substance, and the lubricant is a metal salt of stearic acid. 8. Claim 7, wherein the slip agent is talc, and the metal salt of stearic acid is selected from the group consisting of calcium stearate, magnesium stearate, and zinc stearate. The composition described in. 9. The composition according to claim 2, characterized in that the water content is 0.5 to 3% by weight. 10. A composition according to claim 9, characterized in that the variation in water content of each lot does not exceed ±10%. 11. The composition of claim 9 in the form of pellets having a bulk density of at least 0.25 gm/cc. 12. The composition of claim 11, wherein the pellets have a diameter of about 3 to 20 mm. 13. A method for producing an extrudable composition, comprising: 100 parts by weight of a particulate elastomer;
preparing a composition containing 60 parts of a thermoplastic binder, 1.0 to 6.0 parts of a slip agent, and 0.1 to 1.0 parts of a lubricant; pelletizing said composition; and determining the water content of said pellets. A method for producing an extrudable composition, comprising the step of adjusting the amount of 14. A method according to claim 13, characterized in that the strands produced by extrusion of the composition are cut into pellets in cold water to form pellets. 15 Porous pipe, comprising 100 parts by weight of granular elastomer and 10 to 60 parts by weight of granular elastomer.
The water content of the composition is adjusted to be between 0.5 and 3.0%, and the composition contains 1.0 to 6.0 parts of a slip agent, and 0.1 to 1.0 parts of a lubricant;
Temperatures range from 178℃ to 222℃ to manufacture pipes.
Extrude the composition using a feed tube extruder maintained at a temperature of (320-400〓) and cool it to a diameter of 5.1-25.4 cm (2-10 inches).
Also, a porous pipe characterized in that it is extruded and has a wall thickness of 0.25 to 5.08 cm (0.1 to 2.0 inches). 16. The porous pipe according to claim 15, wherein the die is heated to a predetermined temperature of 133°C to 211°C (240 to 380°). 17. The porous pipe according to claim 15 or 16, characterized in that the feed tube of the extruder is not ventilated.