GB2096266A - Improvements in or relating to pipes for irrigation and other uses - Google Patents

Abstract

A flexible fluid-pervious pipe for use in irrigation and similar applications comprises two tubular members 1, 2 one within the other. The inner tubular member 1 is formed from a sheet of permeable material such as non-woven polyolefinic film- fibril material and the outer tubular member 2 is made from a needled impermeable material such as an unwoven, flocked polyester. The inner tubular member controls the egress of fluid from the pipe and the outer tubular member protects the inner member from attack by insects. The tube may be made by joining the edges of the inner member 1, wrapping the outer member 2 thereabout to leave a gap between its edges and sealing the two members lengthwise by application of welding material 5 in the region of the gap. <IMAGE>

Description

SPECIFICATION Improvements in or relating to pipes for irrigation and other uses This invention relates to tubing or pipes for use in irrigation and similar applications.

An object of this invention is to improve plantation irrigation conditions by means of underground irrigation systems on a drip or stream basis, with the use of a fibrous polyolefinic film-fibril material which is joined and spun but not woven.

A variety of articles have been proposed for use in irrigation systems.

There are many references in the literature to the development of irrigation systems. The first kinds of pipework used in such systems consisted of cheap plastics tubing formed with small orifices at appropriate intervals. Other systems for underground irrigation and drip or stream irrigation have complete emitters. Both systems have the disadvantage that the orifices or emitters can become blocked by earth or by earth-borne organisms or by particles, such as sediment, weeds and so on, suspended in the feed water.

The first experiments were carried out using porous pipework made of long plastics fibres and formed with thousands of small apertures varying in size from approximately 1 to 5 microns and sometimes more. For instance, United Kingdom Patent Specification No. 1 290 847 describes the use of a porous and fibrous tubing made of woven or non-woven structures of natural fibres or regenerated natural fibres or synthetic fibres.

Conventional tubing is pervious to fluids and not likely to be blocked by the earth or the organisms thereof or by particles in the supply water. They also have considerable tensile strength to withstand the internal water pressure necessary for underground and drip or stream irrigation systems.

They also have high strength in the joint between the edges of the article, such joints being produced, for instance, by heat sealing. They also withstand attack by soil insects. They are cheap and have long underground life since the polyolefinic film-fibril material is not biodegradable.

According to one aspect of the present invention there is provided a process for the production of tubing for use in irrigation and similar applications characterised in that a permeable sheet of appropriate dimensions is shaped using a tubular former so that its edges can be joined longitudinally to form a tube of indefinite length which is wrapped, using an appropriate former, in another sheet of mechanically needled impermeable material to provide a tubular envelope having a longitudinal gap defined between spaced apart edges of the other sheet and sealing said two sheets lengthwise in the region of said gap by the application of an appropriate welding material.

According to another aspect of the present invention there is provided a tubular article for use in irrigation and similar applications, said article comprising a pair of substantially concentric tubular members, the inner tubular member being formed from a sheet of permeable material and the outer tubular member being formed from a sheet of mechanically needled, impermeable material.

The present flexible fluid-pervious tubing article thus comprises two independent sheets each made of a different material and forming a tube with two concentric walls. The sheet forming the inner wall and serving to control the egress of fluids can be made of a nonwoven polyolefinic film-fibril material having a porosity of from 0.5 to 0.7, a contact angle of more than 850 and a Gurley-Hill porosity within the range of from 4 to 70 seconds/100 cc. The tubing formed by two separate elongate members placed one above another whose lateral ends terminates in a plane and waterproofed projection.

The film-fibril sheet material used for the tubing articles may be that disclosed in United States Patent Specification No. 3 442 740. As stated therein, an appropriate polyolefinic film-fibril sheet material can be prepared from strands/fibres prepared from a high-molecular-weight polymerisable fibre.

Hydrophobic polymers are particularly preferred because of their water-repellent properties. They can be considered as having the property of not being wetted by the water. The polymers which can be used are those within the class of addition polymers. Among them the preference is for polyhydrocarbons, more particularly linear polyethylene. Other suitable polymers are mixtures of linear polyethylene with small quantities of branched polyethylene, polypropylene, polybutene, polyisobutylene, polybutadiene and mixtures thereof.

The sheet material made from the polymers just mentioned is in the form of an integral network of strip-like fibre elements whose cross-sections vary along the elements. This structure can actually be identified by splitting the sheet and thus exposing a number of fibrous elements, removing one or more therefore and examining consecutive cross-sections with a magnification of 450.

These delicate membrane-like strip-like elements have a normal size of less than 4 microns.

The polymeric material forms overlapping and intersecting layers in the sheet structure. The superimpositioning is apparent in the sheet structures because substantial quantities of fibrous elements are aligned transversely relatively to one another. This can be determined by the splitting of the sheet in the manner described above. Some fibrous elements extending in a direction crossing the split are exposed. The split part is then broken in a direction extending transversely at 900 to the original split. The fibrous filaments crossing the split are observed again. These elements extend transversely to determine the shape of intersection and superimpositioning of the layers.Without such superimpositioning, the fibrous elements would appear to go generally in the same direction, as they do in the finished film-fibril spinning material disclosed by Belgian Patent Specification No 568 524.

One characteristic of the sheet material which makes it suitable for use in the present tubing articles can be defined as the absence of a straight parallel paralielizer extending through continuous apertures or tunnels of the sheet material. This feature can be oserved with a 450 magnification of the sheet surface. In this observation it can be seen that the sheet material has pockets or voids with irregular communications between them in the form of sinuously extending passages. These passages give the fluid permeability feature necessary for the transmission of water at a controllable rate through the wall of tubing made of the sheet material. This sinuosity of the sheet material is described in "flow of Gases in Porous Media", Carman, Academic Press, New York (1 956).

The polyolefinic film-fibril sheet material used for the present tubing would not be readily wetted with water, for instance, the contact angle should be more than 850, as can be seen in the method described in "Surface Chemistry; Theory and Applications", Bikerman, Academic Press 2nd Ed., New York, (1958).

The Gurley-Hill porosity of the material should be within the range of 4-70 seconds/100 cc, preferably in the range of 6-30 seconds/100 cc; the Gurley-Hill porosity is defined as the time required for 100 cc of air to pass through 1 square inch of the material at a pressure of 1.25 pounds per square inch (psi).

The material suitable for the purposes of this invention can have a basic weight of from 1.3 to 3.5 ounces per square yard and a thickness of from 4 to 12 thousandths of an inch.

The sheet which forms the outer wall and whose function is to protect the inner wall from attack by soil insects is made of a porous fibrous nonwoven mechanically needled flocked polyester fibre fabric and finished with a styrene butadiene material.

The articles in accordance with this invention can be produced by the two sheets of different material being passed through two concentric formers. The sheet of polyolefinic film-fibril material passes through the inner former and is given thereby a tube shape by its overlapping edges being joined together. The sheet of flocked polyester nonwoven passes through the outer shaper and is given the same shape thereby as the inner sheet but without its edges being joined together and engaging most of the way round the film-fibril tube except at its top over a width equal to twice the overlap.

After two sheets have passed through the former, they are sealed and welded together to form the tubing, molten polyethylene being added to them. The sheets can then be passed over compressing and cooling rollers.

The invention will be described now by way of example only with particular reference to the accompanying drawings. In the drawings: Figure 1 is a plan view of sheet material for making tubing in accordance with the present invention; Figure 2 is a side view of the tubing; Figure 3 is a cross-sectional view of the tubing, and Figure 4 is a plan view of the tubing.

Tubing for use in irrigation is prepared by the present process from a sheet of unspun polythene film-fibril material 1, which is, therefore, pervious and which is of appropriate length and width. The sheet material is passed through a tubular forming device so that its appropriately overlapping edges 4 (Figure 3) are joined together longitudinally. The permeable tubular sheet is wrapped within a second sheet 2 made of a mechanically needled unwoven flocked polyester material and finished with a styrene butadiene material. The second sheet 2 is formed into a tube by means of an external shaper which imparts to the second sheet 2 the same shape as that applied to the first sheet 1 but without its edges being joined. Thus the inner tube 1 has the outer tube 2 extending most of the way around its surface except in a region at its top having a width of approximately twice the overlap 4.Formation is completed by sealing and welding 5 the sheets 1 , 2 in the joint zone by the addition of molten polythene.

The resulting tubing is then treated by compressing and cooling rollers to give it a flat strip-like structure which can be expanded into the tubular shape shown in Figure 3 when the tube is filled with a fluid, such as water, at an appropriate working pressure.

Consequently, in a complete irrigation installation the permeable material of the inner sheet 1 permits the passage of water which finally issues to the outside through the outer needled sheet 2. The sheet 2 is provided to protect the inner sheet 1 , which is the actual irrigation dispenser, from attack by insects and other agents.

Other desirable qualities in the tubing for use in underground and drip or stream irrigation systems are high seal strength, a long working life and a uniform flow. These qualities are essential if the tubes are to operate in a very long irrigation system of, for instance, 500 feet in an independent teminal irrigation system and 1000 feet in a system of two fronts of equal ends; they are also essential for uniform distribution of water to the earth along lengths of tubing of this order. the seals must be of high strength along the heat seals of the tubing to withstand the pressure of e.g. from 5 to 8 psi used in irrigation systems where various quantities of water are supplied to vary the water pressure and differences of head above a field may require pressures greater than 2 or 3 psi to overcome the effect of gravity on the flow in the irrigation system.

Other requirements are rapid build-up to a balanced flow throughout the length of the pipework to ensure uniform distribution of water to the earth from the tube sections furthest from the water source.

Another requirement is high resistance to attack by soil insects. Also, the tubing must retain these qualities over long periods underground and must be able to withstand the on-off irrigation system cycle.

Tubing of this kind is of use for other purposes such as soil ventilation, fertilizer application, the aeration of fish ponds or sewage and the separation of organic solvents from water.

The properties of the tubing are shown in the following comparative examples, described hereinafter to give an indication of their qualities.

EXAMPLE 1 In a laboratory test, tubing in accordance with the present invention was made with a rated internal diameter of 3/8" by the method previously described. The material used was polythene filmfibril sheet and a porous non-woven flocked polyester fibre prepared by the process disclosed by United States Patent Specification No. 3 442 740. The sheet material has a basic density of 1.6 ounces/square yard, a porosity of 0.6, a contact angle of 990 and a Gurley-Hill porosity of 10 seconds/100 cc. The strength of the joint was measured to determine the adhesion of the film of the heat seal on each side of the tubing in a recorder at 0.1"/minute. 1M samples of tubing were cut and folded to measure the strength of more than one seal. The strength of that seal was 1 6-1 8 pounds/inch.

The flow in the tubing of this example was studied by placing 4' long sections of the tubing in crystal tubes slightly inclined so that the water filtering through the tubing walls could be collected and measured. Unfiltered water was used and the initial flow, at 2.5 psi, was 3.6 cu. ft. after 1 hour. The balanced flow of approximately 2.6 cu. ft./day was obtained within approximately 10 hours and remained nominally at this rate for more than 10 000 hours.

An accelerated aging test of the tubing was carried out at various pressures using a 12" length of tubing. The results are shown in Table 1. A 16 psi the tubing ruptured after 280 hours. A semilogarithmic extrapolation of the data of Table 1 indicates a probable life of approximately 2000-400 hours with underground irrigation tubing operating in a pressure range of 5-2 psi.

TABLE I Pressure Rupturing Time (psi) (hours) 26 42.5 18 190 16 280 EXAMPLE II Tubing was prepared and tested in the same way as in Example I, the polythene film-fibril sheet having a basic weight of 2.2 ounces/sq yard, a rated thickness of 7.5 thousandth of an inch, a porosity of 0.6, a contact angle of 1140 and a Gurley-Hill porosity of 12 seconds/100 cc. The strength of the seals, determined by the film adhesion test, was 20-25 psi.

The flow was studied by the process of Example I and showed a nominal rate of flow of 2 cu. ft./day at a pressure of 2.5 psi, approximately 20 hours being taken to reach a balanced flow.

Accelerated aging tests were carried out in the same way as in Example I and are listed in Table II. The tubing ruptured at 1 6 psi in 710 hours. A semi-logarithmic extrapolation of this data indicates an accelerated life of approximately 6400-4500 hours as underground irrigation tubing when used in a pressure range of 2-5 psi.

A UV radiation test was made of the tubing to demonstrate its suitability for use in a surface drip or stream irrigation system. The tubing was given UV radiation using an Xenotester with a quartz filter.

The strength of the seals was tested after 100-200 hours exposure by means of the film adhesion test. The strength was initially 20.6 psi. After 100 hours exposure the strength of the seals was 1 6.2 psi and after 200 hours 6.4 psi. 100 hours' exposure in the Xenotester is the equivalent of 4 months in regions of the world where there is a high level of UV radiation, such as in Arizona in the summer. This shows that these tubings would have a useful life of at least one cultivation season in a system of drip or stream irrigation.

TABLE II Pressure Rupturing Time (psi) (hours) 49 18 40 54 36 86 31 160 26 361 22 430 16 710 Irrigation tubing of the prior art described herein, made of a long-fibre porous plastics, was tested by the methods explained in Example I. The strength of its seals, as determined by the film adhesion test, was 6-8 psi. The initial rate of flow at 2 psi was more than 25 cu. ft. daily and the rate of flow took 200-300 hours until balance conditions were reached at 3.5 cu. ft. daily. An accelerated aging test, as shown in Table Ill, resulted in the tubing rupturing after 2.5 hours at 16 psi. A semilogarithmic extrapolation of these data indicates an antIcipated life of less than 50 hours at 2 psi.

TABLE ill Pressure Rupturing Time (psi) (hours) 16 2.5 12 6 10 10 8 12.3 The polyolefinic film-fibril material of this tubing had a contact angle of 540. The material had thousands of undeflected straight orifices of from 10 to 1 5 microns in diameter. The low contact angle, the poor strength of the seal, the likelihood of a short working life and the long time taken to reach balance flow conditions appear to be connected with processing of the material by coronary discharge and with antistatic agents and make it unsuitable for use in the irrigation system mentioned.

The process can be carried out in any sizes and materials which are appropriate and can be modified in detail subject to its essence not being altered.

EXAMPLE lil Tubing was prepared as in the previous examples in which the porous nonwoven mechanically needled flocked polyester fibre sheet material was 1 mm thick and weighed 230 grams/m2.

The ability of this tubing to withstand attack by soil insects was studied by putting it in a field where insects were known to be active. A number of tubings consisting just of a single sheet of polythene-film fibril material were also placed in the same field, such other tubings having previously been treated by immersion in specific soil insect pesticides and then, when placed in the soil given further treatment by pouring on them a mixture of the insecticide with water along each tube in a 12' strip. Tubing consisting only of the sheet of polythene film-fibril material but completely untreated against soil insects was also installed as a reference.

All the tubes were buried at a depth of 4-5". 7 different insecticides were used and were tagged in the experiment with the following numbers: No. 1 Dynfonato No,2 Mocap No. 3 Dasinit No. 4 Euradan No. 5 Diazinon No. 6 Rotenona No. 7 Clordano.

No. 8 was the tube consisting of a single untreated sheet of polythene film-fibril material and No. 9 was the double-sheet tubing in accordance with the present invention.

All the tubes were 200' long.

The field was arranged so that there were 4 repetitions.

The result of this experiment is described in the following table: Duration Repetition Treatment Installed Completed Weeks No. of Holes Average Tubing 1 Sheet No.1 Dytonato 18/5/80 16/9/80 17 22 27,5 62 12 14 Tubing 1 Sheet No. 2 Mocap 18/5/80 16/9/80 17 8 19 48 4 16 Tubing 1 Sheet No. 3 Dasinit 18/5/80 16/9/80 17 20 24 56 14 6 Tubing 1 Sheet No. 4 Euradan 18/5/80 16/9/80 17 14 14 12 22 8 Tubing 1 Sheet No. 5 Diazinon 18/5/80 16/9/80 17 6 7,5 4 12 8 Tubing 1 Sheet No. 6 Rotenona 18/5/80 16/9/80 17 16 7,5 4 2 8 Duration Reptition Treatment Installed Completed Weeks No. of Holes Average Tubing 1 Sheet No. 7 Clordano 18/5/80 16/9/80 17 1 4,5 4 10 3 Tubing 1 Sheet No. 8 Testigo 18/5/80 16/9/80 47 34,75 24 29 39 Tubing 2 Sheets No.9 18/5/80 16/9/80 0 0 Subject of the Patent O 0 0 Now that the nature of the invention and the practical embodiment thereof has been described, it merely remains to add that both as a whole and as regards its constituent independent elements, there can be modifications and alterations of materials, shapes and arrangement subject to such modifications not departing from the essence of the invention.

Claims (13)

1. A process for the production of tubing for use in irrigation and similar applications characterised in that a permeable sheet of appropriate dimensions is shaped using a tubular former so that its edges can be joined longitudinally to form a tube of indefinite length which is wrapped, using an appropriate former, in another sheet of mechanically needled impermeable material to provide a tubular envelope having a longitudinal gap defined between spaced apart edges of the other sheet and sealing said two sheets lengthwise in the region of said gap by the application of an appropriate welding material.

2. A process according to claim 1, characterised in that the tubing thus prepared is passed between rollers which compress and cool it and give it a flat strip-like structure which can expand into a tubular form when fluid flows therethrough at an appropriate pressure.

3. A process according to claim 1 or claim 2, characterised in that the permeable sheet comprises an unwoven film-fibril polyolefinic material having a porosity of from 0.5 to 0.7, a Gurley-Hill porosity of from 4-70 seconds/cc and a contact angle greater than 850.

4. A process according to claim 3, characterised in that the polyolefinic film-fibril material has a basic weight of between 1.3 and 3.5 ounces/sq. yard and a thickness of from 0.004 to 0.012".

5. A process according to any preceding claim, characterised in that the impermeable sheet comprises an unwoven mechanically needled, flocked, polyester material which is finished with a styrene-butadiene material.

6. A process according to claim 5, characterised in that the polyester material weighs between 200/m2 and 230/m2 and is from 1 to 1.5 mm thick.

7. A tubular article for use in irrigation and similar applications, said article comprising a pair of substantially concentric tubular members, the inner tubular member being formed from a sheet of permeable material and the outer tubular member being formed from a sheet of mechanically needled, impermeable material.

8. A tubular article as claimed in claim 7 wherein the permeable sheet comprises an unwoven film-fibril polyolefinic material having a porosity of from 0.5 to 0.7, a Gurley-Hill porosity of from 4-70 seconds/cc and a contact angle greater than 850.

9. A tubular article as claimed in claim 8 wherein the polyolefinic film-fibril material has a basic weight of between 1.3 and 3.5 ounces/sq. yard and a thickness of from 0.004 to 0.012".

10. A tubular article as claimed in any one of claims 7 to 9 wherein the impermeable sheet comprises an unwoven mechanically needled, flocked, polyester material which is finished with a styrene-butadiene material.

11. A tubular article as claimed in claim 10 wherein the polyester material weighs between 200/m2 and 230/m2 and is from 1 to 1.5 mm thick.

12. A process for producing tubing substantially as hereinbefore described.

13. A tubular article substantially as hereinbefore described with reference to and as shown in the accompanying drawings.