GB1562182A - Horticultural capillary substrate - Google Patents

Description

(54) HORTICULTURAL CAPILLARY SUBSTRA (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by wnich it Is to be performed, to be particularly described in and by the following statement:- The invention relates to horticultural capillary substrates.

According to the invention there is provided a horticultural capillary substrate comprising a laminate of a water impermeable sheet and a textile fabric (as herein defined) capable of transporting and retaining an aqueous liquid in the interstices between its fibres and having a wicking (as herein defined) which is greater than 100 mm and a water absorption (as herein defined) in excess of 8.0 grams.

The expression "textile fabric" is defined as a manufactured assembly of fibres and/or yarns which has substantial surface area in relation to its thickness and sufficient mechanical strength to give the assembly inherent cohesion. (Textile Terms and Definitions, 7th Edition, Published by The Textile Institute, Manchester).

Such substrates may be used as capillary mats, whereby water may be caused to wick through the textile fabric from a reservoir to a plant container placed on the fabric.

Alternatively, strips of the substrate may be formed into channels, with the textile fabric lining the inner face of the channel, through which water and solutions of nutrients may flow for uptake of plants contained in the channel. Such channels are thus particularly suitable for use in the so-called Nutrient Film Technique (NFT) of hydroponic growing, described inter alia in the Grower, January 25, 1975. For NFT use, the plastics sheet of the laminate of the invention is conveniently formed of a mouldable, rigid material such as poly vinyl chloride or polypropylene, whereby a self-supporting channel or trough is provided. Alternatively flexible plastics material may be used such as 500 gauge polythene and the edges of the laminate strip may be provided with means such as press studs to secure them to each other at spaced intervals.

Preferably the plastics sheet does not transmit light, so that the roots of plants growing and cultivated in the channel are not exposed to light The textile fabric employed is preferably a non-woven material composed of synthetic thermoplastic fibres which are non-toxic and will not rot in the liquid medium to which they are exposed. In the context of the present invention, the manufactured sheet, web or bath of directional or random fibres held together through mechanical and/or physical and/or chemical methods and/or a combination of these various methods. The fibres are bonded together to provide a dimensionally stable fabric which allows easy handling before lamination in addition to being more robust in operation.It is preferred that inter-fibre bonding is autogeneous in nature, that is, adhesives are not used, since the latter may contain materials which pollute the liquid growing medium. Likewise, lamination between textile fabric and plastics sheet, which is preferred, should also be autogeneous. Conveniently, a melded fabric (as defined in U.K. patent specification 1,269,934) formed of conjugate fibres may be used, the fibres having a component forming part at least of the periphery of the fibre which can be rendered adhesive by a treatment which leaves the other component or components unaffected. Suitable fibres are bicomponent fibres having a nylon 66 core and a nylon 66.6 copolymer sheath, or those having a polyethylene terephthalate core and a copolymer of ethylene terephthalate and ethylene isophthalate sheath.In both of these examples the sheath component may be rendered adhesive by a heat treatment at a temperature above the softening point of the copolymer sheath but below the softening point of the core component and under such conditions contiguous filaments bond together. Heat may be supplied throughout and over all an assembly comprising such fibres in an oven or alternatively at discrete points by processing the assembly by passage through a calender press, at least one roller of which is heated and provided with a pattern of projections on its surface.

'1'he preferred laminate of the invention, i.e. when the textile fabric and water impermeable sheet are secured together, may be made by any known method, but we find that extrusion laminating, wherein the textile fabric is pressed into contact with a freshly extruded hot plastics sheet by calender rollers is particularly convenient.

The laminate may be moulded to a preferred shape if desired after the lamination step.

The laminate (or more strictly the textile fabric) should also possess good wicking and water absorption characteristics, i.e.

wicking (as defined below) should be greater than 100 mm. and water absorption (measured by the WIRA Shower Test: B.S.

5066) in excess of 8.0 gms. In most horticultural end uses it is desirable that these figures should be as high as possible and from substrates similar to that exemplified below a wicking of 250 mm. and a water absorption of 20.0 gms. may be obtained.

Wicking is a measure of the capability of the laminate to transport an aqueous liquid and is determined by vertically suspending a 25 mm. wide strip of the laminate and immersing the lower end of the strip in a reservoir of water. The vertical height in mm. which is reached by moisture transported by the laminate in 30 minutes is then described as the wicking of the laminate.

The invention is further described with reference to the following example which refers to the drawing accompanying the provisional specification in which Figure 1 is an illustration of a method of forming the preferred laminate of the invention.

Figure 2 represents the preferred laminate of the invention in cross-section.

Figure 3 is a perspective view of a channel employing the preferred laminate of the invention for use in the cultivation of plants by hydroponic techniques.

EXAMPLE A melded non-woven textile fabric was made as follows: Polyamide bicomponent filaments having a core of polv(hexamethylene adipamide) surrounded by a sheath of poly(epsilon caprolactam), the components being present in equal volumes, were melt spun, drawn to a decitex of 3.3, mechanically crimped in a stuffer box crimper to 6 crimps per cm at a crimp ratio of 20% and cut into 5ü mm lengths. The staple fibres thus produced were formed into a web, weighing 150 gm m2, by means of conventional airdeposition equipment (Rando-Webber manufactured by Curlator Corporation); The web was consolidated by a light needle-punching with 36 gauge 5 barb needles, arranged in a random pattern in a needle board, the needles penetrating the web to a depth of 10 mm.The web was passed through the needle loom at a rate which ensured about 46 needle penetrations per square centimetre.

The consolidated web was subsequently treated by heat and pressure in a nip between rollers of a calender. The upper roller was a rigid steel tube and the lower roller was a thin walled steel tube with an outer diameter of 5.020 inches and an inner diameter of 4.498 inches which could conform to localised and transistory variations in the nip pressure to ensure the nip pressure was maintained at a substantially uniform level as disclosed in published West German appliction 2A02, 140.

The lower roller had a planar surface and the upper roller had a pattern of protrusions on its surface, the protrusions measuring 0.012" in one direction and 0.1" in the other direction. The protrusions were arranged in columns in the circumferential direction around the roller, the long dimension being in the circumferential direction. Adjacent columns were staggered one from the other. There were 14 protrusions per inch measured axially and 6.5 protrusions per inch measured circumferentially. The "valleys" between the protrusions were 0.065'' deep. The area of the tips was thus about 10.9% of the total area.The calender roller was heated internally to give a surface temperature of about 218 C and the surface of the backing roller was maintained at 21 20C. The calender roller and backing roller were urged together to give a nip pressure of 100 lbs/linear inch of nip.

When the fibrous assembly was passed through the nip under the influence of heat and pressure the sheath component of the fibres softened and bonds formed in discrete area (points) corresponding to the tips of the protrusions.

The point bonded melded fabric so formed was wound up as a roll, which was subsequently used as supply roll 10 in Figure 1.

Referring to Figure 1, polyethylene granules (preferably coloured black to minimise the growth of algae) were fed from hopper 12 to screw extruder 14. The polymer had a Melt Flow Index of 7. The molten polymer was extruded through a slot die 15, measuring 2 metres length with a width of 1 mm at an extrusion temperature of 300 C. The curtain of polyethylene, indicated by reference number 16, was cooled to solidification and was passed between chilled calender rollers 18, 20 situated vertically below die 15 where it was combined with the melded fabric 22 passing from supply roll 10. Rollers 18, 20 were urged together at a pressure of 10 lbs/linear inch of nip. The conditions in the nip caused the fabric to adhere to the hot polyethylene sheet, by virtue of the tackiness of the latter.

The laminate was then wound up on roll 24.

Preferably the final thickness of the polyethylene sheet is of the order of 0.0030.005 inches. The wicking and water absorption properties of this laminate were 205 mm and 12.0 gms respectively.

Figure 2 shows a cross-section through the preferred laminate of the invention, with plastics sheet 26 and fabric 28.

Figure 3 illustrates the use of the preferred laminate of the invention in the nutrient film technique of hydroponic cultivation. A trough 30 is formed of a strip of the laminate, having the fabric layer 28 on its inside. Plant containers 32 stand within the trough and the edRes of the strip of laminate are joined together at spaced intervals by means of connectors 34 which may be for example press-studs or staples. The trough 30 is stood on an inclined plane and water containing appropriate nutrients is allowed to flow down the trough, any excess being recirculated. The fabric layer of the laminate provides an anchorage for the plant roots and stagnant pools are prevented from forming by capillary action within the fabric.

In bright sunlight where it may be necessary to keep the laminate cool an impermeable plastic sheet with a metallic coating may be used.

WHAT WE CLAIM IS: 1. A horticultural capillary substrate comprising a laminate of a water impermeable sheet and a textile fabric (as herein defined) capable of transporting and retaining an aqueous liquid in the interstices between its fibres and having a wicking (as herein defined) which is greater than 100 mm and a water absorption (as herein defined) in excess of 8.0 grams.

2. A substrate according to claim 1 in which the water impermeable sheet comprises a mouldable rigid material.

3. A substrate according to claim 2 in which the water impermeable sheet is made from polyvinyl chloride.

4. A substrate according to claim 1 in which the water impermeable sheet comprises a flexible material.

5. A substrate according to claim 4 in which the water impermeable sheet is made from polyethylene.

6. A substrate according to any one of the preceding claims in which the water impermeable sheet is coloured black.

7. A substrate according to any one or the preceding claims in which the water impermeable sheet possesses a metallic.

coating.

8. A substrate according to any one of the preceding claims in which the fabric comprises a non-woven (as herein defined) material.

9. A substrate according to any one of the preceding claims in which the fibres of the fabric are derived from synthetic thermoplastic material.

10. A substrate according to claims 8 or 9 in which the material comprises a melded (as herein defined) fabric.

11. A substrate according to claims 9 or 10 in which the fibres of the fabric are sheath/core conjugate fibres.

12. A substrate according to any one of the preceding claims in which the impermeable sheet and fabric are secured together.

13. A horticultural capillary substrate comprising a laminate of a water impermeable sheet and a textile fabric (as herein defined) capable of transporting and retaining an aqueous liquid in the interstices between its fibres and having a wicking (as herein defined) of from 100 mm to 250 mm and a water absorption (as herein defined) of from 8 gm to 20 gm.

14. A horticultural capillary substrate.

substantially as hereinbefore described with reference to the Example.

15. A horticultural capillary substrate substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. width of 1 mm at an extrusion temperature of 300 C. The curtain of polyethylene, indicated by reference number 16, was cooled to solidification and was passed between chilled calender rollers 18, 20 situated vertically below die 15 where it was combined with the melded fabric 22 passing from supply roll 10. Rollers 18, 20 were urged together at a pressure of 10 lbs/linear inch of nip. The conditions in the nip caused the fabric to adhere to the hot polyethylene sheet, by virtue of the tackiness of the latter. The laminate was then wound up on roll 24. Preferably the final thickness of the polyethylene sheet is of the order of 0.0030.005 inches. The wicking and water absorption properties of this laminate were 205 mm and 12.0 gms respectively. Figure 2 shows a cross-section through the preferred laminate of the invention, with plastics sheet 26 and fabric 28. Figure 3 illustrates the use of the preferred laminate of the invention in the nutrient film technique of hydroponic cultivation. A trough 30 is formed of a strip of the laminate, having the fabric layer 28 on its inside. Plant containers 32 stand within the trough and the edRes of the strip of laminate are joined together at spaced intervals by means of connectors 34 which may be for example press-studs or staples. The trough 30 is stood on an inclined plane and water containing appropriate nutrients is allowed to flow down the trough, any excess being recirculated. The fabric layer of the laminate provides an anchorage for the plant roots and stagnant pools are prevented from forming by capillary action within the fabric. In bright sunlight where it may be necessary to keep the laminate cool an impermeable plastic sheet with a metallic coating may be used. WHAT WE CLAIM IS:

1. A horticultural capillary substrate comprising a laminate of a water impermeable sheet and a textile fabric (as herein defined) capable of transporting and retaining an aqueous liquid in the interstices between its fibres and having a wicking (as herein defined) which is greater than 100 mm and a water absorption (as herein defined) in excess of 8.0 grams.

2. A substrate according to claim 1 in which the water impermeable sheet comprises a mouldable rigid material.

3. A substrate according to claim 2 in which the water impermeable sheet is made from polyvinyl chloride.

4. A substrate according to claim 1 in which the water impermeable sheet comprises a flexible material.

5. A substrate according to claim 4 in which the water impermeable sheet is made from polyethylene.

6. A substrate according to any one of the preceding claims in which the water impermeable sheet is coloured black.

7. A substrate according to any one or the preceding claims in which the water impermeable sheet possesses a metallic.

coating.

8. A substrate according to any one of the preceding claims in which the fabric comprises a non-woven (as herein defined) material.

9. A substrate according to any one of the preceding claims in which the fibres of the fabric are derived from synthetic thermoplastic material.

10. A substrate according to claims 8 or 9 in which the material comprises a melded (as herein defined) fabric.

11. A substrate according to claims 9 or 10 in which the fibres of the fabric are sheath/core conjugate fibres.

12. A substrate according to any one of the preceding claims in which the impermeable sheet and fabric are secured together.

13. A horticultural capillary substrate comprising a laminate of a water impermeable sheet and a textile fabric (as herein defined) capable of transporting and retaining an aqueous liquid in the interstices between its fibres and having a wicking (as herein defined) of from 100 mm to 250 mm and a water absorption (as herein defined) of from 8 gm to 20 gm.

14. A horticultural capillary substrate.

substantially as hereinbefore described with reference to the Example.

15. A horticultural capillary substrate substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.