WO2005041634A1 - Erosion control seed mat - Google Patents

Abstract

In one embodiment, a fibrous mat is provided and includes: (A) a fiber mixture containing: (1) from about 60 to about 90 weight percent thermomechanically produced wood fibers, (2) from about 0.5 to about 5 weight percent binder fiber, (3) optionally, from about 0.1 to about 30 weight percent synthetic staple fiber, and (B) from about 4 to about 15 weight percent of a water soluble polymeric binder, and (C) optionally, a plastic scrim which is from about 2 to about 6 weight percent, where all weight percentages are of the total weight of the mat.

Description

EROSION CONTROL SEED MAT Priority is claimed under 35 U.S.C. 119(e) to U.S. Provisional Application

Serial No. 60/515,181, filed on October 28, 2003 and U.S. Provisional Application Serial No. 60/538,171, filed January 20, 2004. The contents of these provisional applications are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION This invention relates to a fiber mat which can be used as an erosion control device, and more particularly to a fiber mat composed of a thermally bonded mixture of wood fibers or agricultural fibers and synthetic fibers, which provides improved absorption of water and better handling when used to protect or deliver seeds.

BACKGROUND OF THE INVENTION Several products exist in the marketplace to minimize the effects of erosion on bare or newly seeded hillsides. While some are based on straw and others on shredded wood or excelsior, a product with broad use in the landscaping profession is based on refined or ground wood fiber which is thermomechanically processed from either soft hardwoods or softwoods. U.S. Pat. No. 2,008,892, issued July 23, 1935, entitled Method of Manufacture of Pulp discloses a process used to produce wood fibers using thermomechanical defibration. The refined wood fiber is mixed with a synthetic thermoplastic staple fiber and lightly bonded to a plastic webbing to add strength and the ability to be staked to the ground. Profile Products LLC markets one example of this wood fiber material under the trade names Futerra® and Pennington Seed Protector or Seed Starter Mat™. According to U.S. Patents 5,484,501 and

5,330,828, assigned to Conwed Fibers of New York, a Rando® Webber is used to lay down a mat of thermomechanically refined wood fiber pre-mixed with thermoplastic fibers, preferably polypropylene fibers. A preferred wood source is yellow poplar, a soft hardwood. A drawback to this erosion mat is that the lightly bonded wood fiber mat sheds material whenever the product is handled, for example, when unrolled for slitting or applying to the ground. The bonding of the wood fiber is only in an open diamond pattern created by a heated embossing roll. The prior art has numerous disclosures of supports for seeds. Attempts at large scale manufacturing have produced supports for seeds in which many if not all of the seeds have been rendered nonviable because of the manufacturing process.

This is due in large part to the use of binder systems which require heat to activate the binder. The heat also kills the seeds.

SUMMARY OF THE INVENTION This invention provides an erosion mat that can be produced on a conventional modern airlaid machine with homogeneous thermal bonding and the option of an additional sprayed-on binder, which is an improvement over the existing products in the marketplace. In a conventional modern airlaid process, matrix or substrate fiber is air-conveyed to a forming head where it is intimately mixed with synthetic staple fibers including thermoplastic binder fiber, and then is pulled by vacuum onto a continuous moving forming wire or fabric. In the production of various nonwovens, typically, comminuted cellulose pulp fibers are used, but in various embodiments of this invention, any fibrous agricultural material maybe used instead of or in addition to the preferred theraiomechanically refined wood fiber. The web or nonwoven may be consolidated using a compaction roll. Two general types of binders are commonly used in nonwovens such as airlaid nonwovens to provide consolidation and add strength to the nonwoven material, which are a fluid binder, typically an aqueous or synthetic latex or a solution of a polymer, which may be sprayed on the moving web, and bicomponent fiber binders (bico). The typical manufacturing process uses the application of heat in an oven to melt the lower melting sheath component of bico fiber,- or to evaporate the water of an emulsion polymer binder. Since the bonding is throughout the product, web integrity is improved over the partial bonding effected by a heated embossing roll. The sprayed-on binder further aids in dust control and enhances dry tensile strength. In another embodiment of this invention, seeds are included to form an erosion control seed mat. The typical manufacturing process uses the application of heat in an oven to melt the lower melting sheath component of bico fiber, or to evaporate the water of an emulsion polymer binder. In either case, the heat of the oven greatly reduces the viability of the seeds in the support. It is highly desirous to have a production method for seed mats which does not expose the seeds to any heat. This is most conveniently accomplished by depositing the live seeds and other additives on a pre-formed support and using a high solids water-based binder to laminate a second supporting sheet to the first thereby enclosing the seeds and other particulate additives. The increase in moisture level from the water-based binder is negligible and no heated drying step is required. Since the live seeds experience no heat, there is no loss in viability. The moisture content of the final product is low, and, therefore, the seeds do not germinate prematurely. The present invention may be used in a variety of applications involving drainage and erosion control, particularly in regard to facilitating the germination and growth of turf grasses or other vegetation. This improved mat could be used as part of the erosion control system on construction sites, but usually the bare ground is graded, seeded, fertilized, and then covered with an erosion mat or blanket. The erosion-controlling and seed-protecting mat is unrolled over the freshly seeded area where it aids in germination and new shoot growth by holding the seeds in place, maintaining a high moisture level in the soil, and preventing or mitigating the effects of erosion. The wood fiber portion of the mat biodegrades while the plastic mesh portion of the mat photodegrades. The minor amount of synthetic staple fiber in the mat disperses into and becomes a part of the soil. In one preferred embodiment, the erosion control feature is provided by a homogeneously-bonded layer of wood fiber while the seeds and fertilizer or other additives are provided by a second layer laminated to the erosion mat. In practice, the seed layer would be placed against the prepared bare soil. By utilizing conventional airlaid manufacturing equipment and a combination of thermomechanically processed wood fibers or other fibrous materials including refined agricultural waste, sheath-core thermoplastic binder fibers, and, optionally, non-thermoplastic synthetic staple fibers, which do not melt under the conditions of conventional airlaid processing, and applying a water-soluble or dispersible binder, an improved ground covering mat can be produced. This material exhibits far superior dry integrity than a popular product currently in the marketplace, has fewer defects such as large holes or gaps in coverage, is better in absorbing water and preventing erosion, and is effective at a much reduced basis weight in the range of from about 100 grams per square meter (gsm) to about 140 gsm, whereas the current materials in the market range from about 180-225 gsm. Reduced weight per square meter translates into savings on shipping charges since a standard truck load of material would cover more ground. Testing in a certified simulated rainfall facility has shown that the mat of the present invention outperforms the mat cunently on the market by a factor of three in soil erosion control and reduces the water runoff by a third. By conventional airlaid equipment is meant the airlaid technologies developed in Denmark by M & J Fibretech (Horsens) and Dan- Web (Risskov). These high speed state of the art technologies have distinctly different forming heads where the fibers are mixed and deposited on the forming wire, but both utilize through-air ovens to homogeneously evaporate water from applications of emulsion or solution binders and to activate thermoplastic binder fibers. The M&J Fibretech forming head is basically a box with a dispersing fan and a screen. The Dan-Web forming head has two rotating perforated drums with rotating pin rolls inside to mix the fibers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While this invention may be embodied in many different forms, there is described in detail herein specific prefened embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. The wood fibers utilized in a preferred embodiment are processed using a method similar to that disclosed in U.S. Pat. No. 2,008,892, the contents of which are hereby incorporated by reference in its entirety, in which wood chips are fed to a pressurized steam grinding vessel. Any type of wood chip may be used, but wood chips of the soft hardwood variety, such as yellow poplars are preferred. Most generally, the source of the wood chips is scrap material from other forest products industries, such as, for example, knots and shives from wood pulp manufacturing. A defiberator mechanically separates and sizes the steamed and softened chips into individual fiber bundles. The defibrated wood chips are then dried to a moisture level of about 9-20 percent. Optionally, green dye may be added before the drying stage. Other sources of fibers, such as cotton gin byproducts, also know as cotton gin trash, straw including wheat, rice and oat straw, hay, corn shucks, coconut hulls, jute, bamboo, hemp, kudzu, etc may be thermomechanically refined in the same way as wood chips or may be simply mechanically refined or shredded into fibers useful in this invention. For a more detailed discussion of cotton gin byproducts and processing options, which may be useful for fibrous materials from other sources as well, see Characterization of Cotton Gin Byproducts Produced by Various Machinery Groups in the Ginning Operation by G. A. Holt, et al., Transactions of the ASAE, vol. 43(6), 1393-1400, and A Review of Cotton Gin Trash Disposal and Utilization by J Alex Thomasson, USD A, ARS, U. S. Cotton Ginning Laboratory, Stoneville, MS, published in the 1990 proceeding of the Beltwide Cotton Production Research Conferences, and U.S Patent No.'s 6,399,185 and 6,383,548, all of which are hereby incorporated by reference in their entirety. In one embodiment, the erosion-controlling mat of this invention is made of thermomechanically defibrated wood fibers in an amount of from about 75 percent to about 95 percent by weight based on the total weight of the product, bicomponent fiber in an amount from about 1 percent to 5 percent by weight based on the total weight of the product, a second synthetic fiber which is a staple fiber, such as a polyester, which does not melt during the processing of the mat and which serves as a diluent for the bicomponent binder fiber. This enables .the metering of very low levels of the bicomponent fiber and assists through fiber entanglement in giving the web some integrity for processing through the rest of the airlaid machine. The staple fiber content of the mat is from about 10 percent to about 20 percent by weight based on the total weight of the product. A water soluble or dispersible binder polymer, such as a starch, is applied to one or both sides of the product for dust control and to increase dry tensile strength, wherein the total basis weight of the product is from about 100 to about 200 gsm (grams per square meter). In another embodiment of this invention, the erosion and seed-protecting mat of the aforementioned composition is formed on a reinforcing plastic mesh to greatly increase the tensile strength and improve the ability of the product to be staked or stapled to the earth. If a spacer bar is added in the forming head to elevate the mesh above the forming wire, the web can be formed around the mesh effectively embedding the reinforcing mesh in the wood fiber web. Since the mesh provides more than enough tensile strength, the amount of bicomponent fiber and non-melting staple fiber mixed with the wood fiber could be reduced to the minimum necessary for handling the unbonded web. The presence of some small denier staple fiber assists in web formation as thermomechanical wood fiber has little tendency to self-entangle. This amount would vary depending upon the processing characteristics of the particular wood fiber mulch and the nature of the airlaid machine being used to produce the erosion mat. In yet another embodiment of an erosion mat, the web of wood fiber blended with a minor amount of bicomponent binder fiber has a reinforcing mesh formed in situ by discrete placement of an aqueous binder solution or dispersion or even a molten polymer extruded in strands. An overlapping swirl pattern is one execution of the in situ reinforcing mesh. Other patterns are also possible. Any polymer melt, latex, dispersion, or polymer solution capable of forming a strong film would be operable in this method of creating a reinforcing mesh on the airlaid line. The size of an individual strand of the in situ formed mesh could range from as small as 0.1 mm for a molten polymer to as wide as 1.0 cm for a polymer solution or latex. The tensile strength measured on the product would depend on how much of the reinforcing stripe is contained in the cut sample. A refinement of this process would be to reduce the bicomponent fiber in the original composition to about 3 gsm or less and allow the in situ mesh pattern to supply the needed tensile strength for processing, converting, and applying. To control the spreading of the liquid-applied mesh, it may be advantageous to incorporate a suitable thickener or rheo logy-control agent in the formulation. A preferced embodiment of the invention has the erosion mat formed on a special forming wire which creates discrete holes entirely through the mat in a close pattern in which the holes, nominally 5-15 mm across, are approximately 25mm to 100 mm apart across the web. If a pattern of protrusions on the forming wire is used to create the holes,' the pattern should be attached to the forming wire slightly out of parallel to the edges of the wire so that any rolls in contact with the top of the wire would always be in contact with at least one protrusion. This is an engineering practice to minimize vibration and bumping of the equipment as would occur if the protrusions were in parallel lines perpendicular to the machine direction of the forming wire. It is necessary that the lines be offset from perpendicular by about 2 cm per meter in the cross direction of the forming wire. This special forming wire is the subject of US Patent Application No. 60/493,875 filed August 8, 2003, which is hereby incorporated by reference in its entirety. An especially prefened embodiment uses a forming wire with a pattern of occluded spots to block the air flow through the fabric of the forming wire which prevents the deposition of the fibers to create discrete holes in the resulting web while remaining a flat forming wire. The occlusions in the forming fabric can be effected by any means capable of injecting a resin onto and into the fabric or printing a resin on the fabric. Even the application of thin, less than 1.0 mm, self-adhesive dots would accomplish the purpose of this preferred embodiment. The advantage of this approach over adhering protrusions to the wire is that maintenance will be less and wire life will be greater as there are no bumps to wear away. Yet another advantage to modifying the forming wire without raised projections is that the web could be compacted for strength in handling. When the compaction roll presses only on the raised dots, the web itself sees no pressure and transferring the web across an open draw can be problematic necessitating the dependence upon some entanglement from the synthetic fibers in the recipe and the plastic mesh for the required web strength. It is anticipated that the synthetic fiber fraction could be significantly decreased if the web were effectively compacted before transfer from the forming wire. Another especially prefened embodiment of the present invention is having a multi-layer mat in which a seed/fertilizer/additive laminate is topped with an erosion/seed protection layer in a single unitary structure. With one action, a prepared slope can be seeded, fertilized, pre-treated with pesticides or other additives, and protected from erosion. Preferably, the seed laminate contains two or more layers of low wet-strength cellulosic tissue or airlaid. A binder, when present, is preferably biodegradable such as a soluble starch. Of course, a seed mat layer constructed by other means would also be usable in this unitary structure. Although the following working example used an airlaid sheet and then a wet-formed tissue, essentially the same results would be obtained if the seed and fertilizer were deposited on tissue, sprayed with the latex binder and covered with the dispersible airlaid or if the laminate had been made of two sheets of airlaid or two sheets of tissue. The critical parameter is that the upper and lower layers not impede root growth and shoot penetration. In addition to the granular fertilizer, other additives for weed, insect, and disease control could be included in the seed layer. In another embodiment of this invention, the seed mat used in conjunction with the erosion control mat is cellulose support for seed disclosed in US Serial No. 60/426,562 filed November 15, 2002 and PCT/US03/23154 filed August 23, 2003. A further embodiment of the seed mat portion of this invention is that in situations where erosion is not expected to be an issue, the seed mat layer by itself without the overlying wood, fiber erosion layer would be sufficient to treat bare ground so that in a matter of days, under the right conditions of heat, sun, and moisture, the ground would be covered with new grass. In the execution of the erosion mat embodiment of this invention, the thermomechanical wood fibers and the synthetic staple fibers ( bicomponent binder fiber and polyester staple fiber) are opened, weighed, and mixed in a fiber dosing system such as a textile feeder supplied by LAROCHE S.A. of Cours-La Ville, France. From the textile feeder, the fibers are air conveyed to the forming heads of the airlaid machine where they are further mixed and deposited on the continuously moving forming wire. When plastic netting is used, it is unrolled onto the forming wire ahead of the forming section. Vacuum is applied to the bottom of the forming wire within the forming heads of the airlaid machine to cause the dispersed fibers to settle into a uniform mat. After passing under a compaction roll, the airlaid mat of fibers passes under a spray bar where the water-based binder is applied and then the mat is carried into a through air dryer to remove the water from the starch binder and to activate the bicomponent fiber. The dry mat passes over a cooling zone and is slit to width and rolled on cardboard cores. In making the seed mat or seed laminate embodiment of this invention, a water dispersible airlaid sheet is manufactured by comminuting wood pulp fibers with a hammer mill and air conveying the comminuted fibers to the forming heads of the airlaid machine. The fibrous web is compacted, sprayed with a water soluble binder, preferably one based on starch, dried in the through air dryer, and is rolled up. h a second pass through the airlaid machine, the water dispersible airlaid is unwound at the head of the machine and the selected vegetation seeds and other additives are metered onto the moving web. The web passes under a spray system where it is sprayed with a high solids binder, preferably an ethylene vinyl acetate latex at 40 - 55% solids. Immediately after the spray section, another sheet of water dispersible airlaid or even a low wet strength wet laid tissue is unwound onto the slightly tacky airlaid to cover and contain the seeds and other additives. The combination passes through compaction rolls and into the through air dryer which is operated without heating to preserve the viability of the live seeds. The seed laminate is then slit to selected width and rolled on cardboard cores. In making the erosion controlling seed mat of this invention the seed laminate is sprayed with the high solids latex binder and the wood fiber erosion mat is unrolled onto the tacky seed mat and the two pressed together to yield a laminated structure. Alternatively, the erosion mat could be sprayed with binder and the seed mat unrolled onto it. The dry wood fiber and cellulose readily absorb the small amount of moisture from the high solids binder. As with the original manufacturing of the seed laminate, seed viability is preserved since this process does not require a heating step.

EXPERIMENTAL Example 1. Preparation of an airlaid erosion mat 169 grams per square meter (gsm) thermomechanically refined aspen, a relatively soft northern hardwood available from Mat Incorporated, Floodwood, MN as Mat-Fiber and 6 gsm of 2 denier by 6 mm Type T-255 bicomponent fiber with a polyethylene sheath and a polyester core made by Trevira, Bobingen, Germany were blended and airlaid directly on the forming wire of a conventional airlaid machine and compacted. The mat was sprayed with 10 gsm of water soluble starch binder,

Structurecote® 1887 by Vinamul Polymers of Bridgewater, NJ, which had been diluted to 10 percent solids and then passed through a 140°C through-air oven and collected by winding on cardboard cores. The web from the first pass was unwound and the untreated side was sprayed with an additional 10 gsm starch, redried, slit to the final width, and collected on cardboard cores. The mat thickness was approximately 3 mm, and the machine direction (MD) dry tensile ranged from about 400-1000 grams per 25-mm width with the MD wet tensile from 50 to 300 grams per 25 -mm width. When tested on an artificial slope under simulated heavy rain of 20 cm hr (8 in/hr) the product held up for 30 minutes, and then tore at a staple as the underlying mud slid down the hill. Example 2 - Forming Erosion Mat on Forming Wire with Different Rubber Protrusions A. A mat of premium Southern softwood wood fiber mulch from Precision Fibers of Rhonda, NC was formed in a laboratory pad-former on a 36 cm by 36 cm section of forming wire with raised dots made of silicone rubber 4 mm in diameter and 2 mm high, and 6 mm between centers, hereinafter refened to as nubby fonning wire. The density of solid protrusions on the forming wire was approximately 48,000 per square meter. The profiled forming wire was produced by Voith Advanced Concepts, Blackburn, England. The furnish order for the mat was 174 gsm wood fiber, 6 gsm bicomponent binder fiber, 2 denier by 6 mm type T-255 with a polyolefin sheath on a polyester core from Trevira of Bobingen, Germany. The mat was compacted by pressing it with a 12.5 mm thick aluminum plate. Then it was removed from the forming wire and sprayed on each side with 7.5 gsm, solids basis, of water-soluble starch binder, Structurecote® 1887 by Vinamul Polymers of Bridgewater, NJ. The web was heated in a 140°C convection oven to remove the added water and fuse the bicomponent fiber. While the top of the web appeared flat, the forming wire side had a clear pattern of depressions or dimples conesponding to the protrusions on the forming wire. Holding the sample up to the light revealed that the airlaid web was distinctly thinner in the dimpled areas. B. A piece of standard forming wire type ET1035 by Albany International Corp. of Albany NY trimmed to fit in the 36 cm X 36 cm laboratory pad-former was modified by installing self-adhesive clear hemispherical rubber bumpers which were nominally 10 mm diameter by 4.5 mm high and typically used inside cabinet doors. The raised dots were placed in an alternating pattern 20 mm center to center. An mat of wood fiber having the same composition as in Example 2 A was formed on the modified wire and came off the wire with a clear pattern of holes. C. Another similar piece of standard forming wire was modified by adhering 12 mm by 6 mm high tapered square rubber feet of the type typically used on small electronic appliances. Spaced 20 mm apart. As in 2B, the produced web of wood fiber had clearly defined holes. The products of Example 2 are described in Table 1 Table 1- Example 2

The loss of wood dust to the vacuum system during formation of the pads would account for the actual basis weights being below the target of 195 gsm. The forming wire with the 4 mm closely placed raised dots retained more of the fines since there was less open area than in the ^"other forming wires having the applied rubber bumpers. This Example shows that holes could be produced in an airlaid web during formation avoiding the extra step and waste of punching holes in a finished web. Example 3. Erosion Mat with Reinforcing Plastic mesh Example 1 was repeated, except a plastic reinforcing mesh or scrim was unwound at the head of the airlaid machine and the wood fiber web deposited on the mesh, which was carried through the airlaid machine by the moving forming wire. The plastic mesh was type RO 4035 by Conwed Plastics of Minneapolis, MN, and had a basis weight of about 7 gsm. The mesh was made of ultra-violet light- degradable strands of polypropylene fused into a rectangular mesh with openings of 1.9 cm X 3.175 cm (0.75 X 1.25 inches). Soluble starch binder, Stracturecote® 1887 was sprayed on the web at 10 gsm, solids basis, to reduce dusting and on the mesh side for attachment of the mesh. Dry tensile was found to be about 5700 grams per 25 mm and the wet tensile 2900 grams per 25 mm. The thickness was approximately 3 ' mm. Example 4 - Erosion Mat with In situ-formed Mesh In this example, the product of Example 1 was treated with an ethylene-vinyl acetate latex, Airflex® 192 by Air Products of Allentown, PA, applied in a nanow 1.0 cm stripe in swirl or S patterns about 5-10 cm between stripes and dried in the oven. Example 5 - Pilot Trial Nubby Forming Wire For this preparation of erosion mat, the forming wire installed on the airlaid machine had a tight pattern of raised rubber dots 4 mm diameter, 2 mm high, and 6 mm between centers of the dots for approximately 48,000 solid protrusions per square meter. The wire was produced by Voith Advanced Concepts, Blackburn, England. The composition of the airlaid erosion mat was 15 percent by weight synthetic fiber , which was an 80/20 blend of 6 denier by 4 mm polyester fibers available as T224 by KoSa, Salisbury, NC and 2 denier by 6 mm bicomponent fiber available as T255 from Trevira, Bobingen, Germany, 75.5 percent by weight premium Northern hardwood wood fiber mulch, Ecofibre by Canadian Forest Products Ltd. Panel and Fibre Division, New Westminster, BC, Canada, 5.5 percent starch binder, Stracturecote® 1887 by Vinamul Polymers of Bridgewater, NJ, and 4.0 percent by weight plastic reinforcing mesh, 7 gsm polypropylene available as RO 4035 from Conwed Plastics of Minneapolis, MN. The blend of synthetics was necessary with the particular pilot equipment used to get the actual bicomponent fiber content in the product down to about 3 percent by weight of the total mat. The polyester fiber is used as an inert extender so the small amount of bicomponent fiber can be metered more precisely. The starch solution was diluted to 10 percent solids to reduce the viscosity enough for spraying. The through- air oven was adjusted to 140°C to minimize the shrinkage of the plastic netting upon which the mat is fonned. The product was collected and passed through the system a second time to spray binder on the original forming wire side. Three basis weights were produced, 120 gsm, 150 gsm, and 180 gsm. In grass growing trials, the lower basis weights had less evidence of tenting, which is defined as when the grass shoot cannot readily penetrate the mat and actually lifts the mat away from the soil. When subjected to a small-scale simulated 12.7 cm/hr (5 inches/hour) rainfall on a 2/1 slope, horizontal run versus vertical rise, the erosion mat of Example 5 did not allow all the air displaced from the soil to escape and lifted off the slope in several places in blisters. However little actual erosion occurred, which indicates that the deficiency was mainly cosmetic. Example 6 - Pilot Trial Custom Forming Wire The wood fiber feed stock used in Example 5, and the plastic netting from Conwed Plastics was used to form erosion mat on a standard forming wire (Albany International Corp., Albany, NY) modified by sticking on hemispherical 9.5 mm diameter by 3.8 mm high rubber bumpers in an alternating pattern 3.81 cm (1.5 inches) apart in the cross direction and 4.13 cm (1.625 inches) in the machine direction. The button density was approximately 800 per square meter. The rubber bumpers were part number BS-12DCLR obtained from Bumper Specialties Inc. of West Deptford, NJ. In the small-scale simulated 12.7 cm/hr (5 inches/hour) rainfall on a 2/1 slope, the mat from Example 6 performed as well as a commercial product obtained at a home center. Air bubbles and flowing water were able to come out the holes allowing the mat to stay in good ground contact throughout the rainfall test. Example 7 - Pilot Trial Custom Forming Wire The forming wire of Example 6 was modified by extruding drops of silicone caulking compound onto the forming fabric and pressing them into the wire in a small pattern of 18-mm diameter solid circles. The rubber bumpers were removed in the area sunounding the occluded spots making that portion of the web unique and visible during the slitting operation. When a 120-gsm erosion mat was formed on this wire, little or no fiber was deposited on the 18-mm diameter spots. The occluded fabric actually produced holes in the web, which at 10 mm in diameter, were smaller than the size of the occlusion. The product of Example 6 was tested on a 2:1, horizontal run versus vertical rise, test slope and compared to bare dirt and a commercially available embossed mat as control. The results after two 30 minute periods of 12.7 cm/hr (5 in./hr) simulated rainfall are shown in Table 2. Each test plot was 0.61 m (2 feet) by 6.1 meter (20 feet) long by 0.3 meter (1 foot) deep. The erosion mat of Example 6 had less soil loss and less water runoff than the control. Less water runoff means better absorption of rainwater into the soil under the mat. Compared to the bare dirt, the erosion mat of Example 6 had much less soil loss and comparable water runoff. Table 2- Erosion Test

Example 8 - Seed Mat with Erosion/protection Layer To illustrate the preparation of an improved grass seed mat, comminuted Kraft

Southern softwood pulp available as FOLEY FLUFFS® from Buckeye Technologies of Memphis, TN, was airlaid as a 55 gsm web. The web was compacted and sprayed on the topside with 4.2 gsm (grams binder solids per square meter of airlaid web) of a soluble starch binder, Structurecote® 1887 by Vinamul Polymers, Bridgewater, NJ, and dried by passing through a 150°C through-air oven. This starch bonded airlaid was unwound with the original forming wire side, the unbonded side, up at the front of the airlaid machine, and 18 gsm (3.7 lbs/1000 sq. feet) of granular fertilizer,

Miniphos by Simplot of Lanthrup, CA and 22 gsm (4.5 lbs/1000 sq. feet) grass seed, which was a 75/25 mix by weight of S. E. Eagle Blend II Ryegrass and Quality Bluegrass from Lesco, Inc. of Strongsville, OH, were metered onto the moving web.

The metering devices used for grass seed and fertilizer were Drop Spreaders, Scotts® of Marysville, OH, AccuGreen® 1000™, mounted between the forming heads such that the wheels were in contact with and driven by constant speed rolls. The spreaders were set to deliver the prescribed amounts of materials using a stopwatch, catch pan and balance. The airlaid web with its layer of seed and fertilizer was sprayed with 10 gsm solids basis of undiluted, 52 percent solids ethylene- vinyl acetate latex, Airflex® 192 by Air Products Polymers, L.P. of AUentown, PA. A 20 gsm water dispersible tissue having a very low wet strength, Cellu Tissue 1601 by Cellu Tissue Holdings of East Hartford, CT was gently pressed over the seed and fertilizer layer using a rubber- faced roll. The laminate was passed through the unheated through-air dryer and slit to 0.34 meters (13.3 inches). No heat was used to dry the binder, and, therefore, seed viability was not affected. Three lengths of the grass seed laminate were taped edge to edge to make a sheet 1.01 meter wide by 6.1 meter long (40 inches wide by 20 feet long) and sprayed on the tissue side with an ethylene- vinyl acetate latex binder, AF-192, at approximately an add-on of 10 gsm latex solids. A commercial seed protection mat, Pennington Seed Starter Mat™ by Conwed Fibers, a division of Profile Products, LLC of Buffalo Grove, IL, was pressed onto the seed laminate. The seed protection mat had a basis weight of 200 gsm and is a mat of thermomechanically refined wood fiber pre-mixed with thermoplastic fibers as described in U.S. Patents 5,484,501 and 5,330,828. When tested in actual outdoor growing conditions, the material showed high germination and strong shoot growth. The new roots had no difficulty becoming established in the soil as the airlaid separating the seed from the soil lost all integrity when the mat was first soaked with water. Likewise, the low wet strength tissue and porous erosion mat presented no barrier to the emerging grass shoots.

Claims

What is claimed is: 1. A fibrous mat comprising: (A) a fiber mixture containing: (1) from about 60 to about 90 weight percent cellulosic fibers, (2) from about 0.5 to about 5 weight percent binder fiber, (3) optionally, from about 0.1 to about 30 weight percent synthetic staple fiber, and (B) from about 4 to about 15 weight percent of a water soluble polymeric binder, and (C) optionally, a plastic scrim which is from about 2 to about 6 weight percent, where all weight percentages are of the total weight of the mat.

2. The mat of claim 1, wherein the mat has a machine direction and a cross direction defining a longitudinal area of the mat in an XY plane and perpendicular to the XY plane a Z direction conesponding to the thickness of the mat, and wherein the mat defines a plurality of small areas in the XY plane having a basis weight in the Z direction of from 0 to 50 percent of the basis weight of the mat outside the plurality of areas.

3. The mat of claim 2, wherein the plurality of small areas is from about 3 percent to about 20 percent of the longitudinal area of the mat.

4. The mat of claim 2 or claim 3, wherein the basis weight in the Z direction of the plurality of small areas in the XY plane is 0.

5. The mat of one of the previous claims, wherein the binder fiber is a bicomponent fiber with a polyester core and a polyethylene sheath, a polypropylene core and a polyethylene sheath, a polyester core and a polyester sheath, or a mixture thereof.

6. The mat of claim 5, wherein the bicomponent fiber has a length of from about 2 to about 6 mm and a fiber size of from about 1.5 to about 4 denier.

7. The mat of one of the previous claims, wherein the staple fiber is polyester with a length of from about 3 to about 7 mm and a fiber size of from about 4 to about 20 denier.

8. The mat of one of the previous claims, wherein the plastic scrim is made of photodegradable plastic.

9. The mat of one of the previous claims, wherein the water soluble polymeric binder is a polysaccharide, a poly(vinyl alcohol), a poly(lactic acid), or a mixture thereof.

10. The mat of one of the previous claims, wherein the cellulosic fibers are derived from thermomechanically produced wood fibers, cotton gin byproducts, straw, hay, com, coconut, jute, bamboo, hemp, kudzu or a mixture thereof.

11. The mat of claim 10, wherein the cellulosic fibers are thermomechanically produced wood fibers.

12. The mat of claim 10, wherein the cellulosic fibers are derived from cotton gin byproducts.

13. The mat of claim 10, wherein the cellulosic fibers are derived from straw.

14. The mat of one of the previous claims, wherein the mat has a basis weight of from about 80 gsm to about 250 gsm.

15. An erosion control seed mat comprising a seed mat containing: (A) from about 35 to about 60 weight percent cellulosic pulp, (B) from about 2 to about 6 weight percent of a water soluble binder, (C) from about 8 to about 20 weight percent of fertilizer, (D) from about 10 to about 25 weight percent seeds (E) from about 5 to about 15 weight percent latex binder (F) a water dispersible cellulosic tissue which is from about 8 to about 20 weight percent, where all weight percentages are of the total weight of the seed mat, and a fibrous mat comprising: (I) a fiber mixture containing: (1) from about 60 to about 90 weight percent thermomechanically produced wood fibers, (2) from about 0.5 to about 5 weight percent binder fiber, (3) optionally, from about 0.1 to about 30 weight percent synthetic staple fiber, and (II) from about 4 to about 15 weight percent of a water soluble polymeric binder, and (III) optionally, a plastic scrim which is from about 2 to about 6 weight percent, where all weight percentages are of the total weight of the mat.

16. The erosion control seed mat of claim 11, wherein the fibrous mat is laminated to the seed mat by means of a latex binder.

17. A method of manufacturing an erosion control seed mat comprising the steps of: forming a seed mat that contains a fibrous airlaid web and seeds; depositing a high solids binder on the seed mat; forming and depositing a fibrous mat on the seed mat that contains the high solids binder so as to contain the seeds; forming a laminated structure between the fibrous mat and the seed mat with the seeds contained therebetween; and subjecting the laminated structure to a through air dryer which is operated without heating so as facilitate drying of the high solids binder, while preserving viability of the seeds.

18. The method of claim 13, wherein the step of a laminated structure comprises the step of: compacting the fibrous mat and the seed mat in a mam er which ensures that at least a substantial amount of the seeds remain viable.

19. The method of claim 13 or 14, wherein the step of depositing the high solids binder on the seed mat comprises the step of: spraying a latex binder onto the seed mat.

20. The method of claim 15, wherein the latex binder comprises an ethylene vinyl acetate latex at about 40-55% solids.

21. The method of one of claims 13, 14, 15 or 16, wherein the step of depositing the fibrous mat on the seed mat containing the high solids binder comprises the step of: depositing a water dispersible airlaid sheet or a low wet strength wet laid tissue on the seed mat with the seeds being contained therebetween.

22. The method of one of claims 13, 14, 15, 16, or 17, further including the step of: depositing fertilizer on the fibrous airlaid web.

23. The method of one of claims 13, 14, 15, 16, 17 or 18, wherein the step of forming the seed mat includes the step of: forming the fibrous mat with a forming wire that causes the fibrous mat to have a machine direction and a cross direction defining a longitudinal area of the mat in an XY plane and perpendicular to the XY plane a Z direction conesponding to the thickness of the mat, and wherein the mat defines a plurality of small areas in the XY plane having a basis weight in the Z direction of from 0 to 50 percent of the basis weight of the mat outside the plurality of areas.

24. A method of manufacturing an erosion control seed mat comprising the steps of: forming a seed map according to the steps of: forming an airlaid fibrous web; depositing a water soluble binder on the airlaid fibrous web to form a water dispersible airlaid web; drying the water dispersible airlaid web and depositing seeds onto the water dispersible airlaid web to form the seed mat; depositing a high solids binder on the seed mat; forming and depositing a fibrous mat on the seed mat that contains the high solids binder so as to contain the seeds; forming a laminated structure between the fibrous mat and the seed mat with the seeds contained therebetween; and subjecting the laminated structure to a through air dryer which is operated free of heating so as facilitate drying of the high solids binder, while preserving viability of the seeds.