Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation of U.S. application Ser. No. 10/060,577, filed Jan. 30, 2002, now abandoned. 

   FIELD OF THE INVENTION 
   This invention relates to the manufacture and use of non-woven materials containing 100% cellulose fiber as a medium for incorporating seeds, fertilizer, moisture absorbing hydrogels and/or herbicides as needed into seedbeds. It is particularly concerned with providing seedbeds having a basic cellulose foundation containing no synthetic material that are entirely biodegradable. 
   BACKGROUND OF THE INVENTION 
   Vegetation has been utilized to provide aesthetic value and soil stabilization for many years. One particular problem with vegetation is the time that it takes for the vegetation to propagate and/or root into the soil. Seed germination suffers from the deficiencies of slow root growth and inadequate water retention. To facilitate vegetation growth, prefabricated seed carriers were developed, such as disclosed in for example, U.S. Pat. No. 2,648,165 to Nestor; U.S. Pat. No. 2,826,865 to Chohamin; U.S. Pat. No. 2,909,003 to Marshall; and U.S. Pat. No. 3,914,901 to Muldner. 
   Seed carriers are well known in the art and often suffer from problems in that they are difficult to handle, contain non-biodegradable components, contain non-homogenous mixtures, suffer poor water retention characteristics, and have a poor shelf life. 
   Many of the seed carriers developed have utilized synthetic nettings, woven and other sheet materials as support media. Nettings often are too weak to provide sufficient soil stabilization, have a tendency to tear during application, and are otherwise generally difficult to handle. The synthetic materials are expensive, and, being non-degradable, tend to be raised by vegetation growing beneath. The netting can become dislodged by increased traffic and high winds. Eventually the netting must be removed by hand and often effective control of erosion ceases. 
   In an effort to expedite the bio-degradation of the support media, seed carriers utilized biodegradable materials such as light paper as backing material, for example, as in U.S. Pat. No. 4,173,844 to Knolle et al.; and U.S. Pat. Nos. 4,190,981 and 4,318,248 to Mulder. 
   U.S. Pat. No. 4,283,880 to Fjeldsa discloses a “peat paper” wherein sphagnum peat moss is utilized as a vector material for seeds. 
   Existing nettings have been employed or suggested for use in applications such as landscaping, highway construction and maintenance, and strip mine recovery. With the possible exception of certain landscaping applications, all such cases require a system needing little maintenance once the area covered by the netting is planted. It would be highly desirable to have a product that would degrade completely, allow full development of vegetation, and provide substantial erosion control. 
   U.S. Pat. No. 4,786,550—McFarland et al.—disclose the use of melt-blown and coform materials to produce an artificial seedbed. The seedbed is comprised of a combination of seeds, fertilizers, herbicides, superabsorbants, and coform, which is the combination of cellulose fibers and a suitable polymer such as polyethylene or polypropylene. While this combination provides for an appropriate seedbed, the biodegradation time remains high due to the polymer contained therein. 
   Cellulose fibers and cellulose-based materials have been used to manufacture artificial seedbeds for some time, while these materials are beneficial, they have always been used with other synthetic materials which lengthen biodegradation or held together by a woven material or web. Therefore, there remains a need for an artificial seedbed that is stable during the time of seeding, degrades within a reasonable time, does not contain synthetic fibers, and provides protection and nourishment to the seed during germination and sprouting. 
   BRIEF SUMMARY OF THE INVENTION 
   An artificial seedbed is disclosed comprising a foundation of virgin, re-processed or waste wood pulp fiber formed by an aqueous-based compression system, a dry non-woven air-blown system containing a cellulose-based binder or adhesive, or a dry non-woven needle punched system containing a cellulose-based binder or adhesive. The seedbed can contain seeds, fertilizers, growth hormones, hydrogels, herbicides, fungicides, insecticides, or any other additive to promote the germination and the growth of the seeds and surrounding landscape. 
   An artificial seedbed includes a carrier media containing 100% biodegradable cellulose fibers, cellulose-based binder, seeds, fertilizer, herbicide, hydrogels, and growth media homogenously mixed and formed into prefabricated seedbeds having an extended shelf life. The method for making a novel seedbed includes the introduction of cellulose fibers, seeds, fertilizer, herbicide, hydrogels, and growth media via the air lay process, wherein the components are bonded together with a biodegradable cellulose-based bonding agent. 
   The subject invention has numerous advantages over the prior art. The artificial seedbed of the present invention provides uniform control of seed dispersal. The seeds will not wash away from the site of the bed as they are embedded in the material. The material is light in weight and is much easier to place for seeding than sod. The invention reduces the necessity for frequent watering and allows the seeding of steep slopes. As compared with the use of sod, the seeding of slopes in shady spots is much improved as sod farm grass does not grow well in shade. The article of the invention does not need additional covering to prevent drying out after seeding. 
   Further, since straw or other material is not necessary, the problem with such materials being unsightly as they are blown around is decreased. A further advantage is that the invention provides protection from birds for the seeds during germination. The material of the invention further will degrade rapidly and its degradation is controllable by the cellulose binding system utilized. 
   The article of the invention further may contain additives such as pesticides or herbicides to inhibit weed growth and may be colored to give the look of grass even prior to the grass growing. By the use of hydrogels in combination with grass seed, the season for growing grass may be extended beyond the normal fall and spring planting times. 
   Accordingly, it is an object of the present invention to overcome disadvantages of prior art materials, processes, and apparatus by providing a low cost biodegradable artificial seedbed. 
   It is a further object of the present invention to provide an artificial seedbed composed of 100% biodegradable cellulosic fiber that requires less watering than prior seedbeds. 
   Further objects and advantages of the present invention will be apparent by reference to the following detailed description of the invention and appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary cross section of an article of the invention. 
       FIG. 2  is a fragmentary cross section of an article of the invention after sprouting. 
       FIG. 3  is fragmentary cross sections of a multilayered seedbed in accordance with the present invention. 
       FIG. 4  is a fragmentary cross section of a multilayered seedbed in accordance with the present invention. 
       FIG. 5  is a schematic illustration of forming apparatus for the article of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1 , a fragmentary cross section of an artificial seedbed in accordance with the invention is shown and generally designated as reference numeral  10 . The seedbed  10  of  FIG. 1  is composed of a network of wood pulp (cellulose) fibers  20  and cellulose-based adhesive (not shown). The seedbed  10  further contains seed  21  and can optionally include fertilizer  23 , hydrogel  22  or other additives beneficial to seed germination and growth such as herbicides, pesticides, insecticides, and growth hormone. The dry hydrogel  22  and seed  21  are securely held within the network of fibers  20 . Fibers  20  are held together by a cellulose-based adhesive during extrusion. The air-formed combination of wood pulp fibers and cellulose adhesive is referred to herein as coform. A system for injection of hydrogels into composite materials is disclosed in U.S. Pat. No. 4,604,313 incorporated herein by reference. 
     FIG. 2  illustrates a seedbed  110  in accordance with the invention. The seeds  121  have grown roots  124  and sprouts  125 . The roots  124  are penetrating the terrain T. The mingled wood pulp fibers  120  and cellulose adhesive (not shown) have not degraded to a significant extent. The hydrogel  122  has absorbed water and expanded and the fertilizer  123  continues to provide nutrition. 
     FIG. 3  is a cross section of a sheet  210  of the invention comprised of layers  230 ,  231 , and  232 . In the embodiment depicted here, sheet  210  is multilayered with each layer containing wood pulp fiber  220 . Particles  222  are of hydrogel in the lower layer  232 . Particles  221  are seeds in the middle layer  231  while particles  223  are fertilizer in the uppermost layer  230 . 
   In the alternative, a two-layer structure can be formed in accordance with the invention. The two-layer structure is formed with an initial layer that is a composite wood pulp fibers and cellulose-based binder. The upper layer contains seeds, fertilizer, and hydrogels. It is noted that some particles such as seed can migrate to the lower level by withdrawal of air through the structure during forming. The structure can be formed either in a two-bank forming system or in a three-bank system with one bank not operating. 
   Referring now to  FIG. 4 , in another alternative embodiment, the seedbed  310  is also multilayered with each layer containing wood pulp fiber  320  and cellulose-based binder (not shown). The upper layer  330  is provided with fertilizer  323 . The middle layer  331  is provided with hydrogels  322  while the bottom layer  332  to be placed next to the terrain T contains only wood pulp fibers  320  and cellulose-based binder (not shown). As shown in the area  340  between upper layer  330  and middle layer  331  and in the area  341  between middle layer  331  and lower layer  332 , seeds  321  or other desirable material may be placed to take advantage of the various properties of the additives. This structure is considered desirable as the seeds  321  are continually kept moist by the above hydrogel  322 . The fertilizer, in a dissolvable form, is provided to the seeds as they grow. In another variation of this form, the pulp can be dyed a certain color prior to application to substantially match the terrain and provide a more pleasing artificial bed prior to sprouting. Other variations of the invention are possible with varying the number of extrusion banks, number of injection nozzles, and variety of additives. 
   Any suitable additive may be provided with the nonwoven meltblown polymer and grass seed composite of the invention. Such additives are color, pesticides such as diazinone, herbicides, fungicides such as copper naphthenate, and rodenticides. Further odor repellents to keep animals such as dogs or cats off new-grown plants can be added. Preferred additives are particularly hydrogels as they provide a moist seedbed for the seeds and fertilizers to provide nutrients. 
   The seeds added to the substrate may be of any desired variety. Typical of seeds suitable for use in ground covers are sedum, clover, ivy, crown vetch, and flowers such as phlox. The preferred material is grass seed as it is widely grown, low in seed size, and may be handled with normal particle delivery systems. Region specific seeds may be utilized to match surroundings and enhance the chances of germination and growth. 
   In addition to the use of the seedbeds to provide ground cover, other seeds can be inserted into the seedbeds. For example, ornamental plots propagated by seeds as is well known in the art, may be included in the artificial seedbed. These seeds nonexclusively include Alyssum, Aster, Baby&#39;s Breath, Bachelors Button, Dosmos, Four O&#39;clock, Marigold, Moonflower, Morning Glory, Daisy, Sunflower, Sweet Pea, Zinnia, Snap Dragons, Forget-Me-Not, Poppy, Wildflower, Black-eyed Susan, and others. 
   Another example of seeds to be placed in the seedbed are those used in the vegetable garden. These seeds nonexclusively include Asparagus, Beans, Beets, Broccoli, Brussels Sprouts, Cabbage, Cantaloupe, Carrots, Cauliflower, Collards, Corn, Cowpeas, Cucumbers, Egg Plant, Endive, Gourds, Herbs, Kale, Kohlrabi, Leeks, Lettuce, Melons, Mustard, Okra, Onions, Parsnips, Peas, Pumpkins, Radish, Rutabaga, Spinach, Squash, Tomato, Turnip, Watermelon, and others. 
   Farmers can also benefit from the use of the instant invention. The ease of use reduces planting time and equipment requirements. Furthermore, farmers in environmentally depressed areas can use cropseed inserted seedbeds to overcome the environmental shortcomings. For example, farmers in arid areas of the world can utilize a seedbed containing cropseeds and hydrogels to reduce the necessity for irrigation and farmers in areas with unfertile soil can include slow release fertilizers in the seedbed to provide the seeds with nutrition throughout germination. Cropseeds which can be included in the seed cover can include corn, barley, wheat, soybean, alfalfa, oats, rye, cotton, sorghum, tobacco, Brassica spp., vetch, silage, and the like. 
   The sheet products of the invention may be further processed after collection by compacting through heat and pressure to control the sheet thickness. Further, the sheet may be embossed to increase its strength, abrasion-resistance, and ease of measurement and separation. 
   The superabsorbant or hydrogel particles preferably are those which rapidly absorb and retain large quantities of liquids. A preferred group of particles comprise modified starches, samples of which are described in U.S. Pat. No. 3,981,100, and high molecular weight acrylic polymers containing hydrophilic groups. A wide variety of water-soluble hydrogel particles are readily commercially available and will absorb more than 20 times their weight in water and preferably more than 100 times their weight in water. The absorbent particles may vary in size, but generally are preferred to be between about 50 microns and about 500 microns for good retention in the seedbed and ease of handling during formation without creation of dust in the atmosphere. 
   The particles of seeds, hydrogels, and other materials may be introduced into the stream of fibers at any convenient point. The seeds may be introduced at a point after the fibers have somewhat bonded such that elevated temperatures do not damage the seeds. However, even if the streams are somewhat hot, the very high rate of cooling during the process will prevent substantial damage to the seeds as cooling will take place before heat can transfer to and damage the seeds which are ordinarily protected by dry insulating husks. The seeds and other particles are sufficiently trapped by mechanical forces that cellulose adhesive bonding is not ordinarily necessary to hold the particles in place. Further, as illustrated in  FIG. 4 , additives too fragile to be blown into the air stream may be deposited between layers. 
   The artificial seedbed of the invention may be combined with other products if desirable. Further, it is possible that it would be formed on a tissue paper base or other biodegradable permeable cellulose-based, or otherwise 100% biodegradable member. Formation on a tissue or permeable base would decrease the likelihood of hydrogel or grass seeds being withdrawn through the forming air system below the foraminous belt. 
   The artificial bed of the invention may be utilized in a variety of ways. Typically, the composite sheets would be placed on the ground and watered until the grass or other seed material sprouted and was rooted. When watered, the seedbed will form to the shape of the terrain and adhere to it thereby reducing the likelihood of movement. The cellulose fibers and binder would then degrade and disperse. Further, it would be possible that entire rolls of the artificial seedbed pre-germinated and then applied to the terrain to provide expedited ground cover. Such a process could be advantageous in seeding areas where fast rooting is particularly desirable. Further, the seedbeds could be applied to special substrate forms to create living sculptures or topiaries. 
   Referring now to  FIG. 5 , the apparatus for the manufacture of the seedbed is illustrated and generally designated by the reference numeral  450 . Materials are fed into an intake  460  and applied along with wood pulp fibers onto a moving belt  461 . Additional intakes (not shown) may be utilized to vary the mixture of the materials or layer the materials throughout the process. As the moving belt  461  proceeds throughout the apparatus  450 , the materials may be compressed by rollers  462  to ensure proper density. Before the materials leave the apparatus  450 , the materials are heated by a heating apparatus  463  to ensure proper activation of the binding material. Once heated, the material cools and can be passed through an embosser  464  where it can be embossed for strength or scored for separation before it exits on an exit belt  465 . 
   While the invention has generally been described with the addition of cellulose binder into wood pulp fibers, it is possible that other sources of cellulose fibers such as peanut seeds, peat moss, and newsprint could be utilized. Other cellulose materials would be suitable for the invention so long as they provide absorbency and strength to the seedbed. 
   Inasmuch as the preceding disclosure presents the best mode devised by the inventor for practicing the invention and is intended to enable one skilled in the pertinent art to carry it out, it is apparent that methods incorporating modifications and variations will be obvious to those skilled in the art. As such, it should not be construed to be limited thereby but should include such aforementioned obvious variations and be limited only by the spirit and purview of this application and the scope of the appended claims.

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