Abstract:
The needlepunched nonwoven synthetic material prevents the insects from burrowing through by presenting the insects with overlapping, randomly placed fiber layers. The insects attack the ends of the fibers, going from fiber to fiber until they are trapped within the fabric layers. Water permeability is enabled while preventing insects from penetrating the material.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]    The present application is a continuation in part of U.S. Ser. No. 09/413,808 filed Oct. 6, 1999, which claims the benefits under 35 U.S.C. 119(e) of provisional patent application serial No. 60/103,285, filed Oct. 6, 1998. This application incorporates by reference, as though recited in full, the disclosure of copending application Ser. No. 09/412,808 and provisional application 60/103,285. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention discloses a geotextile resistant to insect penetration, having application in areas such as yards, playgrounds and home protection.  
           [0004]    2. Brief Description of the Prior Art  
           [0005]    Ants, and other insect, colonies established in lawns, playgrounds and parks, or other recreational areas can cause damage, attack people and animals and make the use of outdoor areas less enjoyable. The imported fire ant has been a problem for years in the southeastern United States and has systematically moved north and west. In an attempt to control their population, fire ants are treated extensively and regularly with various pesticides. Solutions to the problems, which are alternative to pesticide treatment is sought which can reduce or eliminate the problems caused by fire ants and other pests, and which solutions are long term in effect do not have high costs associated with them.  
         SUMMARY OF THE INVENTION  
         [0006]    Because of their lower manufacturing costs, nonwoven fabrics can be economically used as barriers in high value landscapes to keep soil insects within subsurface treatment zones, thereby improving the efficacy of treatments. In addition, subsurface soil barriers may create a non-preferred habitat, which results in the migration of pest to less sensitive areas. For example, fire ants will either build shallower, more easily treated (or easily frozen in frigid weather) nests, or establish nest sites in areas without the fabric. Installing the fabric in playgrounds and schoolyards would reduce insect colonization and pesticide input in these sensitive areas. The fabric placed under mulch in landscape beds and trees or shrubs can have the added benefit of preventing weed emergence.  
           [0007]    The needlepunched nonwoven synthetic material prevents the insects from burrowing through by presenting the insects with overlapping, randomly placed fiber layers. The insects attack the ends of the fibers, going from fiber to fiber until they are trapped within the fabric layers. Water permeability is enabled while preventing insects from penetrating the material. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The advantages of the instant disclosure will become more apparent when read with the specification and the drawings, wherein:  
         [0009]    [0009]FIG. 1 is a chart indicating the various properties of materials for use in the disclosed fabric;  
         [0010]    [0010]FIG. 2 is a cutaway side view of the material being used to cover an area of land;  
         [0011]    [0011]FIG. 3 is a cutaway side view of the material laid out to cover a foundation;  
         [0012]    [0012]FIG. 4 is a cutaway side view of the material covering the foundation and house;  
         [0013]    [0013]FIG. 5 is a flow chart of the method of using the material to wrap a house; and  
         [0014]    [0014]FIG. 6 is a flow chart of them method of using the material to cover an area of land. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Ants and other insect pests that establish nests in lawns, playgrounds and parks, or other recreational areas can cause damage, attack people and animals and make the use of outdoor areas less enjoyable. The imported fire ant has been a problem for years in the southeastern United States and has, recently, moved north info Virginia and west to California. In an attempt to control their population, pesticides have been used extensively and regularly, however affordable alternatives are sought that are long term in effect and environmentally safe. Another pest, termites, which attack wooden structures in most areas of the US, creates extensive damage to public and private property. The termite and the fire ant problem are most severe in the Southeastern US because of weather conditions favorable to their survival. According to Commerce Department statistics, the South is by far the largest market for housing in the US. Although the nesting habits of some insects, including termites and ants, make the application of geotextile technology attractive, the prior art problem lay in finding a mechanism to prevent the insects from eating their way up, through the fabric while maintaining proper water drainage control above the fabric.  
         [0016]    Geotextiles are water permeable textiles frequently used in conjunction with soils or rocks as an integral part of man made projects, providing cost effective substitutes or enhancements to other materials in civil engineering projects. The area of geotextile fabrics has been a strong part of the American textile industry since the 1970&#39;s and few textile markets have recently enjoyed the tremendous growth that the geotextile market has experienced. The nesting habits of insect pests, such as imported fire ants, is now seen to make the application of geotextile technology a logical and useful solution to their control. Application of a successful geotextile material to prevent infestation of pest insects such as ants would be environmentally beneficial by reducing, or eliminating, the need for pesticide use. Although the area of geotextile fabrics offers an environmental acceptable solution to the problem of insect control, such as fire ants, this technology has not, to date, been used to combat infestations of insects in lawns or recreational areas. The primary reason for the absence in this application is the ability of ants, and other insects, to eat through many materials. Therefore, the construction and composition of geotextile required for such an application differs considerably from that previously incorporated in prior art uses.  
         [0017]    Presently geotextiles have been used in the areas of separation, filtration, drainage, and reinforcement. Separation places a geotextile between dissimilar materials so that the integrity and function of both materials can remain intact or be improved. Geosynthetic filtration fabrics allow flow of liquid across the surface while limiting soil loss. The relationship between allowing heavy water flow or limiting soil passage depends on the application and the construction site. The drainage or transmission function refers to passage of water within the plane of the fabric. Geotextiles used for reinforcement improve the structural stability of soil. The textile, in all cases, improves the shear strength of the system and absorbs tensile stresses.  
         [0018]    The use of fabrics in the building and housing construction industry in the US is now limited to house wraps, some soil reinforcement and decoration of housing interiors. Housing contractors use Styrofoam board material or woven steel mesh to line house foundations to prevent termite access to the foundation. Although the woven steel mesh is successful in preventing termites from entering a structure, both production and installation is expensive. Textile use to prevent ant or termite invasion is generally limited to wrapping the root systems of the plant in nursery pots. Textile sheets have also been used to replace plastic for garden and walkway weed prevention, providing the advantage of drainage while reducing the weed growth.  
         [0019]    Depending on the method used to construct the fabric and the intended end use, the geotextile ranges in weight from approximately 3.5 to 60 ounces per square yard. Of the three methods used for fabric construction, weaving is the slowest and most labor intensive, requiring at least four (4) processes to produce the fabric. Knitting is one order of magnitude faster for fabric production, however geotextiles fabrics require the same numbers of processes as are needed in weaving. Nonwoven is two orders of magnitude faster in full-scale production than weaving and needs only two or three processes for fabric production. A nonwoven is as a textile structure consisting of a consolidated mat, or web, of fibers produced by bonding or entangling fibers or filaments through mechanical, chemical or thermal means. The properties of nonwoven fabrics lend themselves most easily to their application for the prevention of ant and other insect infestation in subterranean in the web.  
         [0020]    Needlepunching is the most frequently employed method of nonwoven fabric consolidation, providing a mechanical method of web bonding to interlock fibers and tufts of fibers by entanglement and fiber friction. Entanglement of the fibers occurs as barbed needles in a needlepunch machine (or needle loom) penetrate the fiber batt to carry tufts of fibers from one layer to another without disentangling the fibers when needles are withdrawn. The structure of the needle determines needling efficiency, quality of finished product, and physical characteristics of the fabric. The needle blade penetrates the fiber web and, with the aid of the barbs, entangles the tufts of fibers. The barb transports and entangles tufts of fibers through the batt. To accommodate synthetic fibers, barbs were designed with rounded edges, best suited for products manufactured from delicate or fine fibers, and where excessive fiber damage would be detrimental to the useful life and tensile strength of the felt.  
         [0021]    For a given needlepunch density, a smaller barb size, with less capability for fiber transport, would produce a fabric of greater thickness and loftiness. Such a fabric structure could provide a more difficult barrier for burrowing insects to breach, but the fabric tensile strength suffers as a result. Lowering the amount of barb “kick-up” and increasing the frequency of needle penetrations per square inch achieves higher tensile strengths as well as a smoother fabric surface but it decreases general permeability. Regular barb spacing provides uniform interlocking of the felt from top to bottom while a medium spaced barb, about 0.05 mm per barb closer, can carry more fibers per stroke with a lower penetration depth than the regular spaced barb. Close barb spacing decreases felt thickness.  
         [0022]    The advantage of using close barb spacing is that all the barbs enter the felt with a relatively small amount of penetration depth as compared to a regular spaced barb. Generally, close spaced barbed needles are used for maximizing needling efficiency with minimal needle penetration. Minimal penetration is essential in high throughput loom speeds, where needle deflection is a concern, because less penetration means fewer chances of encountering resistance in the web. Reduced barb spacing produces fiber bundles distributed closer together with a denser felt as the net result.  
         [0023]    Nonwoven fabrics are also unique because their production lines can produce random and more easily controlled void spaces in the fabric. In knits and wovens, voids are determined entirely by the size, and stiffness of the constituent yarns. Further, since nonwovens are produced directly from fibers, they can easily be produced according to the desired thickness. The controllable properties of nonwoven fabrics lend themselves most easily to their application for the prevention of ant and other insect infestation in subterranean environments.  
         [0024]    The most common types of web formation in nonwovens are air-laid, wet-laid, or carded. Wet-laid, or extruded web formation, will not produce maximum results in insect resistance, while air laid and carded both provide optimum prevention. Wet laid nonwovens are very thin and have a tissue-like fabric character and are not as tough as dry formed fabrics. These nonwovens are more easily torn and provide a very flat, relatively uniform surface for the insects to attack by chewing. A web oriented in only one direction will be uniform, but lack strength in other directions because it does not have omnidirectional (isotropic) fiber orientation, as well as eliminate the zigzag fiber orientation to inhibit insect penetration. Fibers in the web are consolidated either by high velocity water jets (hydroentanglement), high temperatures (thermal bonding), barbed needles (needlepunch) or other methods bonding to secure the fibers in the web.  
         [0025]    All geotextiles are characterized by performance and index tests. A performance test attempts to predict geotextile performance in the environment of intended use; an index test measures a physical property of the geosynthetic without consideration of specific intended use. Tensile properties are evaluated in geotextiles to determine effects of stress and strain forces on the fabric. Tensile performance is measured by ASTM specified standards using constant rate of elongation tests including: grab breaking load and elongation test, wide strip test, and performance strength by wide/strip tensile method. Puncture and burst resistance is measured by a rod puncture test and diaphragm-bursting test respectively. Tear resistance can be measured using the trapezoid tear test.  
         [0026]    To examine the feasibility of applying specially constructed nonwoven geotextile fabrics to prevent or inhibit infestation by insects, an initial determination was the most effective, commercially available fiber to use for the construction of the fabric to prevent penetration. This was determined by considering several factors. The minimum threshold level of fabric density for each component fiber type to prevent penetration of the fabric by fire ants was critical. The effects of the number of needle punch density (consolidation technique for fabric production) of a nonwoven fabric on penetration of the fabric by fire ants were then taken into consideration, as well as the fabric degradation caused by soil and mulch. These foregoing factors were considered, along with material cost, to determine the optimum material and cost associated with the construction this fabric.  
         [0027]    Permeability and opening size are important considerations for when using the nonwoven for nesting preventing due to the drainage or filtration considerations. Permeability is defined as the flow rate, under a differential pressure, of a fluid (usually water) through a geotextile. For application to insect penetration inhibiting fabrics, the fabric must have pore (opening) sizes that are too small and too discontinuous to permit penetration by insects such as ants. At the same time, the fabric must allow an acceptable flow rate of water through it to drain standing water from its surface where it is applied. The required permeability will be influenced by the end use and should follow the site required standard industry requirements as known in the geotextile field. Definitions of the types of geotextiles known in the industry are defined in the  Dictionary of Fiber and Textile Technology , Pgs. 71-72, Hoechst Celanese Corporation, 1989, which is incorporated herein as though cited in full.  
         [0028]    The size of openings in a fabric can be compared based on the apparent opening size test (AOS) or by photomicroscopy. The AOS test requires the use of beads of various diameters to be applied to the surface of the fabric to fill pore opening in the fabric surface. AOS is most widely accepted for woven fabric rather than for nonwovens.  
         [0029]    A critical step in manufacturing any fabric is selection of fiber. Some fiber types, which can be considered for such a synthetic geotextile product, are also environmentally desirable because they can be produced wholly or substantially from recycled materials such as plastic soft drink bottles or plastic grocery bags. Polyester, polypropylene, polyethylene and polyamide are example materials for use in the disclosed application and other similar materials, commonly applied to subterranean applications, can also be incorporated herein. The flexible, synthetic materials must be resistance to soil degradation, microorganism growth and have tensile characteristics sufficient to prevent tearing or puncturing during the specific installation. Any of the fibers used should be water resistant and have a long life to make them ideal for insect control application.  
         [0030]    Polypropylene, as is well known in the art, is polymerized from the propylene monomer in the presence of an organo-metallic catalyst. In the reaction, the catalyst breaks the secondary bond and causes a chain reaction to produce the polymer. The properties of polypropylene, such as melting point and density, are dependent on the placement and regularity of placement of the methyl (CH3) groups. Atactic describes the structure in which the placement of methyl groups is irregular. Isotacticity signifies that the methyl groups are on one side of the chain, and syndiotacticity indicates that methyl placement alternates regularly from side to side. The isotacticity index, which is the percentage of isotactic polypropylene in the polymer, is always higher than 90% for commercial polypropylene.  
         [0031]    The chart of FIG. 1, comparing the properties of polypropylene, polyester and polyamide, shows that the melting point of polypropylene is about 150° F. lower than that of polyester. The chart is taken from “ Textile World Manmade Fiber Chart  1994” by McAllister Isaacs III. Textile World, 1994. This means that the energy required to thermally bond polypropylene is less than the energy required to bond the same amount of polyester. Polypropylene is approximately 52% lighter than polyester&#39;s specific gravity of 1.38 g/cc.  
         [0032]    The following tests at Auburn University involving both the Department of Entomology and the Department of Textile Engineering illustrate that certain constructions of nonwoven polyester fabrics are impenetrable by fire ants and that not all nonwoven polyester fabrics will resist penetration by the ants. Imported fire ants were use as the initial test insect, because of the need and interest in controlling this pest, and their ability to breach barriers (e.g. roof linings, electrical insulation).  
         [0033]    The dual tests were performed under identical conditions, with and without water present in the bag. All of the following tests were performed by placing the ants in bags using material described specifically in each Example. The nonwoven fabric was produced using a medium barb and about 550 punches per square inch. Both nonwoven fabrics were made from 1.5 denier polyester fibers, approximately 1½″ in length and needled with a top punch needling process using lightweight felting needles. As no food was placed in the bag during any of the tests, the colony was forced to chew through the bag to get to food. The bags were manufactured to prevent a small colony (&gt;750 worker ants) from escaping.  
       EXAMPLE I  
       [0034]    An extruded nonwoven, such as Tyvek® was used to form a bag which was sealed to prevent the ants escape. The ants penetrated the extruded nonwoven within two (2) hours.  
       EXAMPLE II  
       [0035]    A bag was formed using a nonwoven polyester fabric of 130 g/m 2  (4 oz/yd 2 ) and the ants were placed inside the bag without access to water. The colony was unable to penetrate the 8 oz. fabric and most died within 14 days.  
       EXAMPLE III  
       [0036]    The ants were placed in a duplicate bag of the foregoing 4 oz. with water, although this placed the fabric at a disadvantage. After 23 days, the ants were still unable to chew through the 8 oz. fabric.  
       EXAMPLE IV  
       [0037]    The colony was sealed into a bag of 85 g/m 2  (2.5 oz/yd 2 ) nonwoven polyester without water. The ants were unable to chew through the lighter weight polyester without the presence of water.  
       EXAMPLE V  
       [0038]    The colony was sealed into a bag of 85 g/m 2  (2.5 oz/yd 2 ) nonwoven polyester water. In contrast to the 8 oz. material, the lighter weight polyester fabric was chewed through within six (6) days, which indicates that there is a fabric density threshold above which fire ants cannot penetrate.  
       EXAMPLE VI  
       [0039]    A termite infested small wooden structure was lifted from its resting place to ensure that a termite colony was directly underneath. Several days later the structure was again lifted to ensure that the colony had not left due to the initial disturbance. A sheet of fabric (2.5 oz/yd 2 ) was placed between the termite colony and the base of the wood structure, but did not wrap around the sides. The wood structure was sunken approximately {fraction (1/3)} of the depth of its base. One week later, the colony had left and there was no termite activity.  
         [0040]    Initial test results have shown that the lighter weight material will retard the burrowing of fire ants through the fabric when water is present. In the absence of a water source in the fabric case, however, ants are unable to escape through the lighter, 2.5 oz., fabric. The heavier fabric was impenetrable to the insects even when water was present for them inside the fabric case. The one exception to the results for the heavier fabric sample occurred because of a fabrication defect in the fabric bag side seam. This reinforces the inability of the colony to eat through the 4 oz fabric. The results show that there is a fabric density threshold of about 4 oz. per square yard above which fire ants cannot penetrate a fabric without starving first. This indicates that in earth based colonies, the ants would chose to abandon an attempted nesting site a distance from food or water rather than die of dehydration or starvation. Nesting sites established above the geotextile layer are too shallow to support the colony in extreme heat, cold or temporary flooding from heavy rains. Termite penetration patterns are similar to that of ants.  
         [0041]    To provide new construction with maximum protection against invading insects, once the foundation area  26  is cleared, the nonwoven fabric  20 , as illustrated in FIGS. 3 and 5, is placed within the foundation area  26 . The foundation  24  is then placed on top of the fabric  20  and the house  26  is constructed, as seen in FIG. 4. The fabric is then wrapped over as much of the house  26  as desired and the structure completed. In FIG. 3, the fabric  20  covers only the foundation, while in FIG. 4 additional fabric  20  is added around the house  26 . Although FIG. 3 illustrates the extra fabric pulled away from the foundation  24 , the material can be cut to extend only slightly beyond the foundation  24  and additional added to complete the coverage of the foundation  24 . It should be noted that the disclosed fabric can be used with slab foundation as well as houses having a basement, with any differences in the installation being obvious to those skilled in the art.  
         [0042]    When used to protect yards, playgrounds, etc. from ants, the ground is dug down within the desired periphery and the fabric placed on the cleared surface. The depth to which the soil is removed is a matter of landscaping and/or preferences, with the average being at least 6 to 8 inches below the placement of the surface. In instances where shrubs are being planted, the depth beneath the shrub can be greater, for example 18 inches, with the depth gradually decrease until the it reaches 6 to 8 inches. In applying the fabric  20  to the ground  12 , the strips of fabric  20  must be overlapped to some extent. The overlap can depend upon potential infestation, end use and cost. An overlap must be present to prevent insect penetration and a minimum of ⅛ inch is preferable. Once the excavated ground  12  covered, the topsoil  14  is replaced and/or added.  
         [0043]    The non woven construction of the disclosed fabric prevents root penetration, thereby requiring planning for large trees or shrubs. Since the tree or shrub will die without sufficient root expansion, a hole must be cut within the fabric and a hole dug, beneath the access hole, within which to plan the tree. The area would then need to be treated with insecticides to prevent insect infestation.  
         [0044]    When large areas of land are being protected and the insects trapped beneath the fabric, food deprivation is relied upon to prevent nesting. For the fabric to act as an effective barrier, the viscous energy dissipated by the chewing ant or insect exceeds must energy supply. When the ants must travel too far to transport sufficient food to build the colony, colonies are confined to the periphery of the protected areas, therefore requiring the areas of greatest protection to be along the periphery of the covered area. When covering large areas, such as housing developments, heavier fabric can be used along the periphery while thinner material can be used toward the center of the area. Thus, once the total area is determined  60  and the top soil removed  62 , the area to be covered is divided into two sections; an outer section and an inner section. The outer section, which extends from the outer periphery toward the center a distance greater than the insect would travel to set up a colony is covered with a first, or heavier, fabric  64 . The inner section would cover the remaining interior area and covered with a second, or lighter, fabric  66 . The top soil is then replaced over the entire area  68 . The distance an insect would travel would be known to those versed in entomology. The minimum fabric thickness required is determined by the fracture toughness of the fibers and on the type and thickness of the cross-section.  
         [0045]    When food is not limited, the minimum thickness will depend on the behavior of the insect group, which often emulates the behavior of corrosive viscous liquids. On a micromechanical scale, the length of the mandible moment arm, the acuteness of the mandible bite surface wedge and the fracture toughness of the surface being attacked determine the corrosive action.  
         [0046]    The nonwovens prevent insect penetration due to the insect&#39;s instinct to attack an end of fiber. In a woven, there are viewer ends and a multiple of openings. In a nonwoven the insects see only a multitude of short, jumbled fibers. The each fiber layer forming the nonwoven provides a multiplicity of attack points created by the inherent fiber orientation and characteristics. The insects cannot easily work their way directly through the fabric, but rather travel the zigzag path of the fibers forming the nonwoven and getting lost in the cross laid structure. Since the fiber structure within the material is on a predominately horizontal plane, the insects following the fibers travel horizontally vs. vertically, or from underside to topside, of the material. From an insect perspective, they see only fiber ends, not a flat sheet. Materials, such as Tyveck®, fail to retain insects due to the presentation of a flat sheet rather than the high population, randomly oriented jumbled fiber presentation of the nonwoven. The presentation of a jumble of randomly oriented fibers is eliminated once a bonding material is introduced making it critical, to obtain maximum results, for the material to be only needlepunched. Additional penetration resistance is obtained by increasing the fiber diameters to be equal to, or greater than, the diameter easily accepted by the majority of the insect&#39;s mandibles. The diameter would vary in accordance with the type of insect and can, in some instances realistically, be directed only to the “average”. At some point the diameter sizing would affect adversely the cost and characteristics of the fabric.  
         [0047]    Mathematically, this action can be modeled by the formula used to describe containers for extremely corrosive or hot liquids such as that described by the viscous dissipation formula  
         ρ                          (     u   2     )            t         =         -   u                       ∂   P       ∂   z         +     ρ                   f        (   u   )         -     Q   visc                             
 
         [0048]    Where:  
         [0049]    ρ=liquid/organism density;  
         [0050]    P=pressure;  
         [0051]    D=expression for a first derivative in Calculus;  
         [0052]    u=liquid/organism internal energy;  
         [0053]    Dt=derivative with respect to time;  
         [0054]    □=partial derivative;  
         [0055]    z=fabric thickness direction;  
         [0056]    ρf=ρ times f(u) where f(u) is a function of u;  
         [0057]    Qvisc=viscous dissipation loss  
         [0058]    In cases where Qvisc remains greater than D(u2)/Dt, the insects will not be able to penetrate the fabric before they die.  
         [0059]    Successful use of nonwoven geotextiles as a barrier to imported fire ants, suggests their use in other applications such as termite barriers for structures, confining soil insect pests such as mole crickets and white grubs to treatable subsurface soil zones. Other than prevent fire ant nesting, the geotextile can be used for fire ant proof wraps for root balls for nurseries within the imported fire ant quarantine, and seals for electrical switch boxes. All these applications could reduce or eliminate pesticide applications.