WO2010088478A2

WO2010088478A2 - Water retaining membrane

Info

Publication number: WO2010088478A2
Application number: PCT/US2010/022529
Authority: WO
Inventors: Patrick J. Mcgroarty
Original assignee: Tegraseal Products, Llc
Priority date: 2009-01-30
Filing date: 2010-01-29
Publication date: 2010-08-05
Also published as: WO2010088478A3

Abstract

Water retaining membranes are described that can be placed in the soil to hydrate plants. The water retaining membranes include a super absorbent polymers (SAPs) on or within substrate material that absorb significant amounts of water to retain water for use by plants. The absorbed water can be accessed by the plants as the soil dries out. The present disclosure also includes methods of making the water retaining membranes and methods of hydrating plant roots.

Description

WATER RETAINING MEMBRANE

BACKGROUND OF THE INVENTION

[0001] It has long been known that super absorbent polymers (SAPS) have the capacity to absorb large quantities of water in relation to their weight. Certain SAPs are known to speed the growth of commercially valuable plants through improved water management. Some types of polymers used for that purpose include polyacrylate, polyvinyl alcohol, starch-based copolymers and cross-linked polyacrylamides.

[0002] Polyacrylamides (PAMs) are monomers of acrylamide water soluble polymers that are a subset of the SAPs (super absorbent polymers) and have been used, for example, as soil amendments for various agricultural purposes. PAMs are also used for mineral and coal processing, petroleum production, paper production and water treatment. PAM has been used for soil structure improvement since the 1940s and in agriculture since the 1960s. These early generations of PAMs were low molecular weight molecules and were applied to soil at high rates. PAMs that have been used more recently have a higher molecular weight and are generally more stable and absorb much more water then earlier forms.

J0003] Generally, SAPs (super absorbent polymers) can be granular material that, when wetted, convert to a gel form and can absorb up to six hundred times their weight in water. Furthermore, SAPs can repeatedly absorb and release water for as long as a decade. When properly applied, SAPs can reduce the amount of water lost through percolation and evaporation, reduce the leaching of soil nutrients, pesticides, or herbicides into ponds, lakes streams, rivers and/or ground water.

[0004] In order to maximize the effectiveness of the SAP installation, it is important that the SAP layer be uniform in concentration, depth, and dispersment. This invention relates to all of these issues,

[0005] Current practice of using SAPs involves distributing a layer of SAP directly to the soil and raking it in. This, however, has a number of drawbacks including difficulty in uniform application. Once applied, the SAP layer can be easily disturbed and damaged. For example, it is tedious to achieve the desired level, smooth surface and also to rake SAP into the soil to a uniform depth. Since SAPs are fine powders, applications are generally limited to being carried out on calm, non-windy days. Heavy foot traffic or lawn equipment over the treated area can result in displacement of the SAP. Another complication is the formation of a uniform gel layer that may form an impervious layer to water and thus lead to ponding in the event of a heavy rain.

SUMMARY OF THE INVENTION

[0006] In one aspect, the present invention includes a water saver membrane. The water saver membrane includes a base sheet, super absorbent polymers (SAPs) held in place on the base sheet. The water saver membrane absorbs water during wet (hydrating) conditions and releases water under dry conditions.

[0007] The base sheet may be biodegradable and the SAPs may be adhered to the base sheet by using an adhesive. The water saver membrane may include a tackified adhesive film on its lower side.

[0008] In another aspect, the present invention includes a method of manufacturing a water saver membrane. The method includes creating a semi permeable sheet that includes a base sheet with SAPs entrapped within the base sheet matrix. The base sheet comprises a low melting point plastic. The method also allows the SAPs to be entrapped in the base sheet without the use of additional adhesives. The method includes creating the permeable base sheet by combining particles of the low melting point plastic with the particles of SAPs₉ applying the mixture of low melting point plastic particles and SAP particles onto a coated conveyor belt and heating the mixture to form a semi permeable sheet.

[0009] In yet another aspect, the present invention includes a method of keeping a plant hydrated. The method includes providing a soil retaining wall defining a root holding enclosure. The method also includes adhering a water retaining membrane on the soil retaining wall. The water retaining membrane comprising a base sheet adhered to the soil retaining wall and a super absorbent polymer adhered to a side of the base sheet opposite from the soil retaining wall. The method further includes positioning roots of the plant along with soil within the root holding enclosure wherein the roots when positioned in the root holding enclosure defining a bottom portion, and side portion above the bottom portion of the root enclosure. The water retaining membrane being disposed along the side portion thereby providing hydration to the roots.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is a schematic representation of an overhead view of a base sheet with SAP nodes.

[0011] Fig. 2 is a schematic representation of an overhead view of a base sheet with SAPs deposited by a transverse hopper.

[0012] Fig. 3a is a schematic representation of a side view of an apparatus for manufacturing the water saver of the present invention.

[0013] Fig. 3b is a schematic representation of a side view of an apparatus for manufacturing a water saver of the present invention after the nodes of SAPs are deposited. [0014] Fig. 4a is a perspective view of an apparatus for manufacturing a water saver of the present invention.

[0015] Fig. 4b is a schematic representation of a side view of an apparatus depositing a cover screen on the water saver of the present invention.

[0016] Fig. 5 is a perspective view of an apparatus to manufacture pressure sensitive sheet with SAPs adhered.

[0017] Fig. 6 is a side view of an apparatus for manufacturing the water saver of the present invention with a single thru-put system that simultaneously creates the permeable base sheet, the SAP holding matrix and a premeasured amount of SAP.

[0018] Fig. 7 is a sectional view of the water retaining membrane adhered to the inside surfaces of a pot.

[0019] Fig. 8 is a view of the water retaining membrane within a burlap or fabric wrap of the roots of a plant. [0020] Fig. 9 is a schematic side view illustrating the placement of SAP/Matrix in the lower quadrant of a holding device in a manner which supplies vital water while allowing drainage of the surplus water and continuous soil aeration.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0021] The present invention includes a water saver that can be used as an aid in keeping plants hydrated for long periods of time. The water saver may be used, for example, in the soil underneath sod, in pots and/or with burlap or similar fabric wrapped around roots. "Water saver" as used herein refers to the semi-permeable water saving membrane/sheet of the present invention. This water saver increases the water holding capacity of the soil by creating water reservoirs in the proper location in the subsoil under the plants. The water saver is a semipermeable membrane adhered in place, that when moistened, absorbs and retains a significant amount of water. Water that is not absorbed is allowed to percolate through the soil reducing the possibility of ponding or flooding. The absorbed or retained water in the water saver membrane can be accessed by the plants as needed, i.e. as the soil dries out.

[0022] The water saver can advantageously reduce the frequency of watering and improve the ability of plants to tolerate drought conditions. In addition, the water saver membrane can trap fertilizers and such to reduce the runoff of applied chemicals and nutrients into area lakes and ponds. The location of water saver above the bottom and on the side of the plant containers and shipping sacks is important because the roots of most plants should not be subjected to continuous immersion in water.

[0023] The water savers of the present invention include a base sheet and one or more super absorbent polymers (SAPs) on or within the base sheet. The water savers may include an adhesive to substantially hold the SAPs in place. The water savers may also, optionally, include a cover screen. In some embodiments, the base sheet is premanufactured and the water savers are made by depositing SAPs on the base sheet and using adhesives to hold the SAPs in place. In alternative embodiments, the base sheet of the water saver is created simultaneously along with the deposition of the SAPs during the manufacturing process. In these embodiments, the SAPs are entrapped within the base sheet matrix, thus eliminating the need for additional adhesives or additional processing. In addition to the SAPs, fillers, fertilizers, pesticides and weed controls may be incorporated into the water saving membranes. The incorporation of fillers can alter the permeability rate of the water through the water saver.

[0024] The present invention also includes methods of making the water saver. In some embodiments, a base sheet can travel on a conveyor and pass under a series of spray bars and hoppers which apply premixed or alternate layered materials to form a pre-determined thickness of SAPs, adhesive and any desired fillers. In some alternative embodiments, particles of low melting point plastic are premixed with a selected amount of SAP particles. The mixture of low melting point plastic and SAP particles is deposited onto a conveyor belt and then heated. This results in a water saver in which the base sheet, formed from the melted low melting point plastic particles, has SAPs entrapped within the base sheet matrix forming a permeable membrane. The present invention also includes methods of keeping plants hydrated and of conserving water by installing a water saver membrane underneath plants.

[0025] The water saver of the present invention can be used in conjunction with a variety of greenery including plants, sod and other foliage. These include trees, shrubs, flowering and non- flowering plants. The plants may be confined to containers or planted into the ground. A particularly useful application of the water saver is under grass or sod in a residential or a public setting such as golf courses, public boulevards and parks. Golf courses, for example, can benefit from the use of the water saver placed in the subsoil under the grass or sod to reduce the number of waterings and retain the nutrients in fertilizers, thus realizing considerable cost savings. "Plants" as used herein refer to all plants and plant like materials described above including grass, sod, flowering and non-flowering plants, trees, shrubs and the like.

(0026) Sandy or highly permeable soils under a cultivated area are particularly prone to drying out because water from irrigation or rainfall percolates through the soil quickly. Maintaining plants, in dry, arid environments with sandy soil is challenging, costly and labor intensive. The water saver of the present invention can be advantageously used in these environments to capture and fully utilize any water from rainfall or irrigation and to drastically reduce the amount of water and nutrient runoff.

[0027] The water savers of the present invention include a base sheet made from a variety of substrate materials. The base sheet may be a biodegradable sheet or a non-biodegradable sheet. Biodegradable base sheets may be made- from substrate materials such as paper, cotton, burlap, hemp and such, hi a preferred embodiment, degradation of the biodegradable sheet under sod facilitates root passage and aeration. Substrate materials for non-biodegradable sheets can include, for example, woven rayon, nylon and polyesters. The base sheet may be a premanufactured base sheet such that the SAPs are placed on the base sheet and held in place using any of the methods described herein.

[0028] Alternatively, the water saver can include a base sheet that is simultaneously created in the manufacturing process of the semi permeable membrane with the SAPs in place. In these embodiments, the substrate materials are low melting point plastic particles that are combined with a predetermined amount of the particles of SAPs. The low melting point plastic can be, for example, ethylene vinyl acetate (EVA) and the like. The mixture of particles are evenly dispersed and heated to form a semi-permeable membrane that includes a base sheet that is formed by the melting of the low melting plastic particles. Without being bound to any particular theory, it is believed that the heating of the low melting point plastic particles such as EVA melts the particles and forms a microcell structure or a foam structure that partially surrounds the SAPs and entraps the SAPs within the base sheet matrix. EVA is preferred because of its ability when melted, to produce microcell (foam) which partially surrounds each particle of SAP to form a soft, pliable and permeable sheet. Such microcells increase the capillary draw of water into the mesh for better and more efficient activation of the SAP. As the structure cools, a soft, pliable semi-permeable membrane is formed in which SAPs are entrapped within the plastic matrix of the base sheet. The hollow spaces in the matrix that do not contain SAPs can allow subsequent root growth through the sheet. These water savers generally do not require any additional adhesives to hold the SAPs in place. However, the use of adhesives in these water savers is also within the scope of the invention.

[0029] The water savers of the present invention include SAPs placed on or within the base sheet. SAPs can include, for example, polyacrylamides, polyacrylates, polyethylene oxides, polyvinyl alcohol copolymers, starch grafted copolymers of polyacrylonitrile. In preferred embodiments, polyacrylamides (PAMs) are used as the SAPs. SAPs are manufactured in a variety of particle sizes ranging from fine powder to granules. Any of these particle sizes may be used in a water saver of the present invention. Preferably, the SAPs used have a particle size such that the particles can pass through a screen of about 20 mesh but retained by a screen of about 200 mesh. Particles outside of this range are also within the scope of this invention. [0030] The SAPs generally absorb large amounts of water. The SAPs used in the present invention can absorb at least about 100 times their weight in water. Preferably, the SAPs can absorb at least about 300 times their weight in water and more preferably, at least about 500 times their weight in water,

[0031] The water saver may include an adhesive that holds the SAPs in place on the base sheet. A variety of adhesives can function in the present invention. Adhesives can be emulsion adhesives, hot melt adhesives, solvent based adhesives, reclaimed low density polyolefin film particles and the like. The adhesives can be, for example, acrylics, urethanes and silicones, acetates and butyls.

[0032] In some preferred embodiments, emulsion adhesives such as acrylics are used. Emulsion adhesives are particularly amenable for use in the present invention because breaking the emulsion results in almost instant adhesion. Emulsion adhesives upon contact with the SAPs lose their water to the SAP due to the hydrophilic nature of the SAPs. The SAPs, thus, supersaturate and break the emulsion freeing the adhesive. The choice of a paper backing can further assist the breaking of the emulsion.

[0033] Reclaimed low density polyolefin particles, preferably, reclaimed low density polyethylene (LDPE) a linear low density PE (LLDPE) film particles may also be used as an adhesive. LDPE film particles and SAPs, for example, may be placed on a base sheet. Heat may be applied until the LDPE particles soften and the polyethylene can flow around the SAPs. Upon cooling, the LDPE film particles can unite and fuse to form a loose matrix around the SAPs and hold the SAPs in place. The LDPE matrix, thus, acts as an adhesive in the water saver.

[0034] Hot melt adhesives generally include granules of polymer adhesives such as ethylene vinyl acetate, polyethylene, polypropylene and the like. Hot melt adhesives suitable for use are described in U.S. Patent Number 5,041,482 which is herein incorporated by reference in its entirety. In an exemplary embodiment, SAPs are premixed with hot melt adhesives in a predetermined ratio. The premix can be applied to the base sheets and transported on a conveyor through hot zones that can melt the hot adhesive and adhere the SAPs to the base sheet upon cooling.

[0035] Additional materials such as fillers, fertilizers, insecticides, pesticides and weed control substances may also be placed on the base sheet in addition to the SAPs. Fillers can include, for example, sand, loam, peat and the like. Any of the fertilizers, pesticides, insecticides and herbicides known in the art may be used and are all within the scope of this invention. The amount of the fillers incorporated in the water saver can determine the permeability of the water saver. Generally, the permeability of the water saver membrane increases as the amount of filler increases. The amount of a particular filler used in this invention is an amount that is sufficient to be effective for its purpose. For example, sufficient pesticides would be added to be effective against the intended pest. The amounts of fertilizer, insecticide or herbicide added would also be determined on a similar basis.

[0036] In preferred embodiments, water saver membranes include fillers scattered throughout the water saver membrane in order for excess water to drain through the water saver. The sections of the water saver containing the SAPs act as water reservoirs and the sections of the water saver containing the fillers allow excess water to drain. In some embodiments, the fillers are spaced at regular intervals throughout the water saver. In other embodiments, the fillers and other additives such as fertilizers, pesticides and the like can be mixed with the SAPs into a premix and the premix is then placed onto the base sheet as described below. In alternative embodiments, fillers are not included in the water saver and in these embodiments, the water saver membranes include holes that are punched out or cut out of the membrane to allow for excess water drainage.

[0037] A cover screen, preferably biodegradable, may also be placed over the SAPs. The cover screen is generally a permeable layer and, if used, can further aid in holding the SAPs in place on the base sheet. One exemplary embodiment uses cheesecloth as a cover screen. [0038] Other suitable materials for use as a cover screen include filtered fabric, other natural or synthetic fibers, fire retardant woven and non-woven fabrics (such as fabrics used in curtains and bedding that are fire retardant). Such a cover screen can be placed on top and/or the bottom of the low melt polymer/SAP matrix. In one embodiment, the result would be a multiple layer product having a woven or non-woven layer, a lofted/entangled fused filament layer, the low melt polymer/SAP matrix layer, a lofted/entangled fused filament layer, and then a woven or non-woven layer. The cover screen can be attached to the filament layer by hot melting, sewing, quilting or needle punching the layers together.

[0039] The water saver of the present invention may also include a pressure sensitive adhesive on one side of the water saver. The pressure sensitive adhesive is preferably on the side opposite from the SAPs. This pressure sensitive adhesive can be useful for holding the water saver in place, particularly in pots. A release paper may be place over the pressure sensitive adhesive during manufacturing. The water saver can be manufactured and transported with the release paper. This release paper can then be removed before using the water saver in the desired setting.

[0040] The thickness of the water saver can vary depending on the specific SAPs used, the end use and the methods employed to manufacture the water saver. Generally, the thickness of the water saver is at least about l/32^nd inches. Preferably, the thickness of the water saver is between about l/32^πd inches and about 1/8 inches. Water saver membranes can be of variable length and width depending on the manufacturing equipment used and the end use. They may be cut to predetermined lengths in order to control the ease of handling, packaging and shipping. [0041] Methods of manufacturing the water saver will vary and can depend, for example, on the type of adhesive used and the end use. SAPs are generally deposited on the base sheet by any known dispensing techniques. SAPs can be deposited on the base sheet, for example, by hoppers, preferably metering hoppers. Hoppers and metering hoppers are well known in the art and a number of different types of hoppers can be functional in the present invention. Figures. 1- 6 illustrate some exemplary hoppers and methods of manufacturing water savers and are described in detail below.

[0042] In alternative embodiments, the water saver can be made by simultaneously creating the base sheet with the SAPs fully entrapped within the base sheet. This method advantageously does not require the use of additional adhesive to keep the SAPs in place. Low melting point plastic particles are mixed with particles of SAPs. These premixed particles can be placed in a dispenser such as a metered hopper. Measured amounts of the mixture is deposited onto a moving conveyor belt, preferably coated with Silicone or Teflon. When heat is applied to the mixture of particles on the conveyor belt, the low melting point plastic particles melt to produce a microcell (foam) structure that partially surrounds the SAP particles to form a soft, pliable and permeable sheet upon cooling. The hollow spaces that do not contain the SAP particles can allow subsequent root growth through the sheet. The permeable sheet acts as a water saver and can be used in embodiments described herein. Water saver sheets made in this manner have a fixed amount of SAPs and are permeable to water. A suitable range of SAP in the premixed particles is approximately 10% to 60% by weight.

[0043] Water savers that are generally placed under sod have SAPs distributed in a noncontiguous manner. By non-contiguous, it is meant that the SAPs do not form a continuous surface coating over the base sheet. In other words, there are spaces or gaps between the deposits of SAP particles. In some embodiments, the spaces/gaps may contain fillers as described above. Alternatively, water savers that are placed in confined areas such as pots or containers may have a base sheet that is coated with the SAPs in a contiguous manner, i.e. without gaps. Although the use of water savers with gaps within pots is within the scope of this invention. The base sheet may have a bottom side coated with pressure sensitive adhesives and a release paper over the pressure sensitive adhesive as described above,

[0044] The SAPs are applied to a base sheet in such a manner so as to distribute and separate the SAPs to prevent a continuous layer of gel formation after total hydration. Distribution of SAPs in a non-contiguous manner creates a non-slip plane that is particularly advantageous in water saver membranes placed in the subsoil underneath sod. This is important when applying under sod in order to allow free passage of excess moisture after trapping and storing a portion thereof. Most lawn or golf course areas are subject to equipment travel creating horizontal and vertical shear that could rip or indent the sod. Areas in the water saver membranes devoid of SAPs can act as a non-slip or support area for the sod. In preferred embodiments, the SAPs are adhered to the base sheet by the adhesive sufficiently to prevent the particles from moving and thus establishing and maintaining a predetermined space between each group that can act as a non-slip and support area for the sod.

[0045] In some embodiments, as shown in Fig. 1, metering hoppers can place mounds of SAPs, referred to as nodes 11, on base sheet 13. The SAP nodes 11 are preferably, distributed in a non-contiguous manner on base sheet 13. The spacing between the SAP nodes may be uniform or non-uniform. In another exemplary embodiment, as shown in Fig. 2, a transverse moving hopper that moves back and forth in the direction of arrow 15 disperses SAPs 17 such that a curvy line of SAPs are formed on base sheet 13.

[0046] The method of making the water savers of the present invention can also include incorporation of adhesive to substantially hold the SAPs in place on the base sheet and minimize the movement of SAPs in the water saver. Adhesives can be incorporated in a variety of ways depending on the specific type of adhesive used. In one embodiment, for example, an adhesive may be sprayed onto the base sheet, preferably in areas where the SAPs will be deposited. In an alternative embodiment, an adhesive, such as a hot melt adhesive, may be in particulate form and mixed in along with the SAPs. The SAPs and the adhesive are deposited together onto the base sheet. The hot melt adhesive is activated by passing through a hot zone. If a solvent adhesive is used, methods to reclaim the solvent are generally included in the procedure. Additional types and methods of incorporating adhesives that are functional in holding SAPs in place in the water saver are also within the scope of this invention.

[0047] In producing the water saver, a suitable substrate material such as polyethylene or ethylene vinyl acetate can be ground to a particular size and mixed with the SAP. When visually viewed, the plastic film is in the form of granules or dust. Particle size may be variable, and for the most part, can be between a range of about 10 mesh size to about 300 mesh size. Reclaimed and/or virgin polyethylene or ethylene vinyl acetate film particles can be mixed with the SAPs at a selected concentration to form a pre-mix. A suitable range of SAP in the prernix is approximately 10% to 60% SAP by weight. The pre-mixed particles are placed on the surface, such as a surface of a conveyor belt. The conveyor belt surface is generally a non-stick silicone or Teflon surface that allows the water saver membrane, once formed, to be removed. Generally, heat is applied to the pre-mix on a conveyor belt to soften the plastic film particles sufficiently to permit the plastic particles to melt sufficiently so that the SAP particles are embedded therein. As the particles are permitted to cool, the plastic particles fuse to form a lattice or a type of matrix with the SAP embedded therein. After cooling, the sheet can be removed from the conveyor belt.

[0048] Once formed, the product has some porosity which permits water to enter the matrix. Once the SAP has absorbed water to its fullest extent, excess water may then flow through the matrix of the water retaining membrane. This process is described in more detail in a provisional patent application 61/148,447 entitled "Water Containment and Inclusion Product", which is incorporated by reference in its entirety. The water saver membrane resulting thickness once water has been absorbed can be up to an inch thick or more.

[0049] In embodiments in which an adhesive is used to secure the SAPs onto the base sheet, hoppers generally contain the selected SAPs. In some embodiments, the hopper may also include, in addition to the SAPs, adhesives, fillers and other materials such as weed controls such as herbicides, fertilizers and the like. Alternatively, a series of hoppers and spray bars may be used each containing one or more of the materials mentioned above.

[0050] In an exemplary embodiment shown in Fig. 3a, metered hopper 10 contains SAPs 12 in bin 14. SAPs 12 in bin 14 fill the rotary dispenser IS in the "up" position. The rotary dispenser 18, as it turns downward empties into chute 22 and transfers the contents downward through chute 22 to base sheet 26. The chute 22 of metered hopper 10 in Fig. 3a is positioned above base sheet 26. Base sheet 26 is placed flat over conveyor belt 30. Conveyor belt 30 moves base sheet 26 past metered hopper 10 at a set speed. As shown in Fig. 3b, conveyor belt 30 moves base sheet 26 underneath chute 22. Rotary dispenser 18, in the "down" position, empties into chute 22. SAPs 12 move downward through chute 22 and are placed as nodes 34 on base sheet 26. The space between nodes 34 is dependent on the speed of conveyor belt 30 and the speed of rotary dispenser 18.

[0051] Fig. 4a illustrates yet another embodiment of the present invention in which a proportionate dispensing hopper works in conjunction with an interruptible adhesive spray system to sequentially apply adhesive and SAPs to a base sheet. Metering hopper 110 contains SAPs 112 in bin 114. SAPs 112 from bin 114 fill rotary dispenser 118 in the "up" position. Rotary dispenser 118 extends transversely across base sheet 140 on conveyor belt 144. Conveyor 148 is generally indicated and includes drive roller 152. Rotary dispenser 118 has rod 122 inserted through transverse aperture 124 through dispenser 118. Rod 122 is rotatably engaged with dispenser 118 and rotated by pulley system 126. Pulley system 126, when turned on, rotates rod 122, at a set speed, engaging rotary dispenser 118 and thus, rotating dispenser 118 between "up" and "down" positions. As rotary dispenser 118 moves into the "down" position SAPs 62 are transferred into one of chutes 160a, 160b, 160c or 160d traversing the width of base sheet 140. SAPs 112 are deposited from chutes 160a-d onto base sheet 140 as nodes 170 across base sheet 140. Prior to deposition of nodes 170 from chutes 160a-d, base sheet 140 is intermittently coated with adhesive 180 that is sprayed in a thin layer on base sheet 140 by spray bar 184 that extends transversely across the width of base sheet 140. Spraying of adhesive 180 from spray bar 184 is interruptible and is coordinated with rotary dispenser 118 such that nodes 170 are placed on sections of base sheet 140 covered with adhesive 180.

[0052] Fig. 4b illustrates the use of cover screen 200 placed over nodes 170 on base sheet 140. Cover screen 200 traverses across the width of base sheet 140 and guided onto base sheet 140 containing nodes 170 by guide roller 190. Screen roll 192 threads cover screen 200 into guide roller 190. Cover screen 200 traps and protects SAPs of nodes 170. [0053] Fig. 5 illustrates another exemplary embodiment of the present invention in which manufacture of a pressure sensitive water saver with adhered SAPs is shown. Base sheet 300 is covered with SAPs 304 from hopper 308 that traverses the width of base sheet 300. Adhesive 320 is sprayed from spray bar 324 traversing the width of base sheet 300. Base sheet 300 is a biodegradable sheet that is fed from roll 330 onto conveyor belt 340 with a pressure sensitive adhesive on the bottom, i.e. the side placed on the conveyor belt side. Additional hoppers and spray bars may be incorporated in series to produce multiple layers of SAPs and adhesive until a desired water saver is produced.

[0054] Fig. 6 illustrates another exemplary embodiment of the present invention. Fig. 6 shows a side view of an apparatus for manufacturing the water saver with a single thru-put system that simultaneously creates a base sheet with the SAPs entrapped in base sheet matrix. Hopper 414 contains a premix of particles containing SAPs 412 and low melting point plastic particles 410. Particles 410 and 412 are deposited onto a Teflon coated conveyor belt 400. As particles 410 and 412 pass underneath infra-red heaters 420 particles 410 melt and form a matrix around SAPs 412. The heated mixture cools as it travels conveyor belt 400 past heaters 420. Semi-permeable sheet 430 can be removed from conveyor belt 400 and formed into a roll. Semipermeable sheet 430 may also be cut into strips.

[0055] The present invention also includes a method of growing plants by placing a water saving membrane in the ground below the surface, in pots or burlap cloth wrapped around roots. Preferably, the surface is a smooth surface. Alternatively, the water saving membrane may also be placed on non-smooth surfaces. When placed in the ground, the water saver membrane can be easily spread out in the selected area. If a large surface is to be covered such as underneath an area of sod, the water saver membrane may be in a large roll and simply unrolled at the selected location. After unrolling the water saver, soil may be added on top of the water saver. The soil may be dirt, mulch and the like. Additionally, the soil may contain fertilizers, fillers, mulch and other additives. The desired plants may be placed into or on top of the soil and the water saver. If desired, the sod may be placed directly on the water saver. The plants may be hydrated after planting by irrigation or rainfall. Some of the water can be absorbed by the plant and some can be absorbed by the water saver as it percolates past the sod and water saver. Excess water that can not be absorbed by the water saver membrane percolates through the membrane into the strata below.

[0056] The present invention also includes a method of conserving water by installing a "water saver" membrane and maintaining it in the "proper location" relative to the plants root system. This ability to be properly located and remain so during the "potting" or "bagging" process assures that the plant will maintain proper moisture levels without the possibility of drowning. The proper location of the water reservoir is especially important in "bagging" (wrapping) of nursery trees or foliage because the horizontal root system of the excavated vegetation is often sheared off in the process. This damage increases the need to provide a continuous moist environment if the plant is to survive transportation (often transcontinental.) The "tacky" undersurface of the invention allows the water saver to be located and bonded to the potting container or the wrapping around a root system. Later, as the plant is watered the water saver absorbs up to 400% of its weight and holds it in reserve for the plants use in time of stress (drought). The location of the "water saver" reservoir is vital because although the plant must maintain proper moisture levels, it must not be continuously flooded as would be the case if the bottom of the holding container included a water reservoir. This is a problem whenever SAPs are randomly mixed within the potting soil. The water saver is preferably held in an area of the planter (pot or root bag) elevated from the base which allows the roots to tap the water trapped in the hydrated SAPs and yet, does not flood or drown the plant by totally immersing the root system.

[0057] The water retaining membrane embodiment made through the use of particulate polyethylene is also particularly useful as a water saver or water retaining membrane in relation to plants. For example, it is useful in a plant container. For example, a base layer of soil is placed in the pot, such as a one inch layer and a small strip of the membrane may be placed along the interior wall of the pot and the remaining soil placed in the pot along with the plant. A strip of the water retaining membrane may be for example be 1 inch by 4 inches in dimension and may expand to 1 inch in thickness, once water is introduced to the plant within the pot. Water absorbed by the water retaining membrane can then be used by the plant as needed. [0058) The water saver membrane may be produced in various lengths and widths so that selected sizes and pre-determined concentrations may be removed from a roll or sheet and adhered to the inside of a flowerpot or shipping container including being adhered to the interior portion of "root wrapping" material such as burlap or similar fabric. The size and shape, for example, may be dependent on the size and type of plant container. In one exemplary embodiment, a 2 inch by 4 inch piece may be used for potted plants and placed over one inch layer of potting soil and then covered with remainder of potting soil. In another exemplary embodiment, 4 inch by 6 inch wide strips of various lengths may be placed inside the burlap of trees or shrub root balls and then watered before transporting.

[0059] Similarly, the water retaining membrane may also be used in a similar fashion for burlap wrapped or fabric wrapped plants during transport. The water retaining membrane can be wrapped around the roots of the plant, the burlap or fabric can then be wrapped around the roots and the burlap is then watered. The SAP within the matrix absorbs the water and retains the water for use by the plant during transport. Such a method is also useful for potted plants for transport.

[0060] Fig. 7, 8 and 9 illustrate embodiments of the use of the water savers of the present invention. Fig. 7 shows a sectional view of the water retaining membrane adhered to the inside 47-

surfaces of a pot. Pot 506 is lined with water saver membrane 500 on the vertical inside surfaces of pot 506. Roots 502 of plant 504 are exposed to membrane 500 on the sides but roots 502 are not soaking in a reservoir of water at the bottom of pot 506 due to aperture 508 at the bottom of pot 506 to drain excess water. Fig. 8 shows burlap 520 wrapped around root bundle 522 of tree 530. Root bundle 522 includes roots 524 and soil 526. Water. saver membrane 540 is placed on the inside surface of burlap 520 such that membrane 540 is wrapped around root bundle 522. Fig. 9 shows a side view of water saver membrane 600 in pot 610. Approximately 2 inches of potting soil 614 is placed in pot 610 and membrane 600 is placed above soil 614. Additional potting soil 614 and plant 620 with roots 624 are placed in pot 610 that also includes aperture 630 at the bottom for drainage of excess water. Membrane 600 includes permeable plastic matrix 634 having SAP particles 636 embedded within matrix 634.

[0061 J The water retaining membranes of the present invention are also useful in preventing structures such as houses from catching on fire during forest or brush fires. Large sheets of the membrane may be placed over the house that is in imminent danger of fire, and water such as via a garden hose is sprayed on the membrane to activate the membrane. The SAP within the membrane absorbs and retains the water. The water within the membrane then acts as a shield absorbing heat from the fire thereby eliminating heat buildup within the structure and preventing combustion of the structure. The fire retardant membrane can also be used as a fire break by rolling the membrane out and hydrating the membrane with water.

[0062] The water retaining membrane is also useful in curing concrete in a hot, low humidity environment such as in the summer. On hot, low humidity days, and especially slim/flat slabs of concrete poured on grade, the concrete dries too quickly, gets hot, curls and cracks. In addition, concrete that cures too quickly is not as strong as concrete that cures slowly. For example, concrete that cures for 7 days is about 50% stronger than concrete that cures quickly. A typical solution is to keep spraying the concrete with water and/or sometimes covering the concrete with sand, canvas, burlap or straw which may retain some water. A plastic sheet is sometimes used, but of course, plastic does not retain water. To further exacerbate the curing problem, concrete generates heat (heat of hydration) when it cures, thereby accelerating the evaporation of water particularly at the surface or near the corner or edges of the poured concrete slab. Placing the water retaining membrane over newly poured concrete, and watering the membrane slows the evaporation/curing of the concrete. The water retaining membrane holds considerably more water than the typically used coverings mentioned above. When the concrete is cured, the membrane can be rolled up and reused again to cure another poured concrete slab. [0063] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A water saver membrane comprising: a base sheet comprising a super absorbent polymer (SAP) held in place on or within the base sheet wherein the water saver membrane absorbs water during hydrating conditions and releases water under dry conditions, said membrane being semi permeable.

2. The water saver membrane of claim 1 and further comprising a pressure sensitive adhesive layer disposed on one side of the base sheet.

3. The water saver membrane of claim 2 and further comprising a release layer disposed on the pressure sensitive adhesive layer for removal and exposure of the pressure sensitive adhesive layer.

4. The water saver membrane of claim 1 further comprising an adhesive that adheres the SAP in place on the base sheet.

5. The water saver membrane of claim 4 wherein the adhesive is an emulsion adhesive, a hot melt adhesive or a polyethylene matrix.

6. The water saver membrane of claim 1 further comprising a cover screen placed over and/or under the base sheet and the SAP.

7. The water saver membrane of claim 1 wherein the SAP is in granular form between about 20 and about 200 mesh.

8. The water saver membrane of claim 1 wherein the SAP comprises polyacrylamides, polyethylene oxide, polyvinyl alcohol, polyacrylontrile, bentonite and starch-based super absorbents.

9. The water saver membrane of claim 1 further comprising fillers, fertilizers, water soluble pesticides or weed controls.

10. The water saver membrane of claim 1 wherein the water saver membrane can retain water of at least about 200 times the weight of the SAP.

11. The water saver membrane of claim 1 wherein the water saver membrane can retain water up to about 500 times the weight of the SAP.

12. The water saver membrane of claim 1 wherein the base sheet is biodegradable or nonbiodegradable.

13. The water saver membrane of claim 1 wherein the SAP is placed as nodes on the base sheet.

14. The water saver membrane of claim 1 wherein the base sheet comprises a low melting point plastic.

15. The water saver membrane of claim 14 wherein the low melting plastic is ethylene vinyl acetate, and wherein the ethylene vinyl acetate is in the form of a porous mesh.

16. The water saver membrane of claim 1 wherein the base sheet comprises a low melting point plastic with the SAPs. entrapped within the base sheet.

17. A method of manufacturing a water saver membrane compri sing: creating a semi permeable sheet comprising a base sheet with SAPs entrapped within the base sheet matrix and wherein the base sheet comprises a low melting point plastic.

18. The method of claim 17 wherein the SAPs are entrapped in the base sheet without the use of additional adhesives.

19. The method of claim 17 wherein the low melting point plastic is ethyl vinyl acetate.

20. The method of claim 17 wherein the creating comprises combining particles of the low melting point plastic with the particles of SAPs prior to forming the semi permeable sheet.

21. The method of claim 20 further comprising applying the mixture of low melting point plastic particles and SAP particles onto a coated conveyor belt and heating the mixture.

22. A method of keeping a plant hydrated, the method comprising: providing a soil retaining wall defining a root holding enclosure; adhering a water retaining membrane on the soil retaining wall, the water retaining membrane comprising a base sheet adhered to the soil retaining wall and a super absorbent polymer adhered to a side of the base sheet opposite from the soil retaining wall; positioning roots of the plant along with soil within the root holding enclosure, roots when positioned in the root holding enclosure defining a bottom portion, and side portion above the bottom portion of the root enclosure, the water retaining membrane being disposed along the side portion thereby providing hydration to the roots.

23. The method of claim 22 wherein the soil retaining wall is part of a pot for holding the plant.

24. The method of claim 22 wherein the soil retaining wall is burlap or a synthetic based fabric.

25. The method of claim 22 wherein the water retaining membrane can retain water at least 200 limes the weight of the SAP.

26. The method of claim 22 wherein the water retaining membrane can retain water up to 500 times the weight of the SAP.