IL32994A - Molded thermoplastic artificial sod having backing material integral therwith - Google Patents

Description

MOLDED THERMOPLASTIC AETIFICIAL SOD H VING BACKING MATERIAL INTEGRAL THEREWITH MOLDED THERMOPLASTIC ARTIFICIAL SOD HAVING BACKING MATERIAL INTEGRAL THEREWITH Molded, synthetic sod or grass has recently found some acceptance for use in place of natural grass in areas where grass is difficult to grow or maintain. In the copending application of Doleman and Hills, S.N. 650 , 986 , filed July 3 , 19 7 , there is disclosed and claimed a type of synthetic sod which is a continuously molded thermoplastic material comprising a matrix having projections therefrom.

The matrix also contains opening.: for drainage, etc. French Patent No. 1 , 314 , 933 discloses another but similar type of molded grass product which Is produced in squares or blocks with means for connecting one to the other. U. S. Patent 3 , 157 , 557 discloses yet another type of molded grass product made of synthetic thermoplastic material.

While synthetic, thermoplastic, molded grass products are relatively inexpensive and do have a certain aesthetic appeal, certain difficulties have been encountered in their use. Since these synthetic grass products are made of thermoplastic materials, e.g. polyolefins, they possess the disadvantage of extremely poor dimensional stability, i.e., they tend to expand and contract in response to temperature changes. Obviously this is undesirable when, for example, the product is used as a lawn surface, since contraction will leave openings at the seams and expansion will cause unsightly buckling.

SUMMARY OF THE INVENTION In accordance with this invention, these disadvantages are overcome by providing a three-dimensional, molded, grass-like product comprising a relatively flat thermoplastic matrix having projections extending therefrom and integral therewith. The projections are shaped to simulate natural grass, and the matrix is . rovided with openings over its surface area. On the bottom side of the matrix, in accordance with this invention, there is provided a synthetic, porous, fibrous or an fabric/open mesh metallic screen which is bonded thereto.

The matrix and projections thereon^are molded, as an integral unit, from a thermoplastic material . Because of its availability and performance qualities, polyethylene is preferred, but other materials such as polypropylene, nylon, polyesters and like thermoplastic materials may be employed. Thermoplastic copolymers or blends are also satisfactory.

The integrally molded matrix and projections may be produced by a batch process, i.e., one sheet at a time, or by a continuous process as described in said copending S.N. 550,986, filed July 3, 1967. Obviously, for economic reasons a continuous process is preferred. Regardless of how the integrally molded material is made, it is necessary that the matrix be provided with openings for water drainage .

In a continuous molding process for molding three- dimensional materials described in said S.N. 650, 86, openings in the matrix occur as a natural result of * the process. In that process, the projections occur- in clusters, which clusters are connected by paralled" strips of thermoplastic material. Since the clusters do not abut each other, the openings occur between the clusters. The projections which extend from the matrix are essentially vertical after being molded. In order to impart the appearance of natural grass, it is necessary to texture the molded material to disperse the tips of the projections randomly, much in the manner of natural grass. This may be conveniently done by applying a heated pressure roll to the top of the molded material, i.e., the side from which the projections extend. If the thermoplastic material is hot enough, e.g., if it retains heat from the molding operation, the pressure roll need not be heated. This texturing imparts a permanent crimp in the projections whereby they remain flattened down with the tips dispersed randomly over the surface.

The important feature of this invention is the provision of a backing material of synthetic, porous, fibrous fabric or of an open mesh metallic . screen bonded to the back of the matrix which seems to overcome the disadvantage mentioned above. The use of backing material serves to impart dimensional stability to the artificial sod.

Since the products of this invention find application in out-of-doors uses, it is desirable that the backing material be one which has resistance o weathering. In event the backing material selected is a synthetic, porous, fibrous material, suita le materials are polyole ins, such as polypropylene; nylon, polyester and other like synthetic fiber-forming materials. The synthetic, fibrous material is bonded to the underside of the molded thermoplastic in the form of a fabric which may be woven but preferably is a non-woven fabric. The fabric backing must be porous to allow drainage of water and yet must be strong enough to provide a substantial bond to he molded thermoplastic. Non-woven fabrics have been found to be particularly suitable for this purpose .

The synthetic fabric is preferably bonded to the molded thermoplastic matrix by heating the thermoplastic followed by contacting the heated portion of the matrix with the synthetic fabric and applying sufficient pressure such as, for example, squeeze rolls, to embed the fabric into the molded article. Heat bonding is preferred since it does not introduce any foreign materials and, also, does not appreciably effect the strength of either the molded thermoplastic or the fabric. If desired, however, other methods of bonding may be employed, e.g., solvent bending or adhesives, when the product is to be used for those specific purposes in which the disadvantages are not objectionable.

As an additional feature of this invention, a thin synthetic, cellular foam may be bonded to the underside of the synthetic fabric. When the synthetic sod of this invention is to be used for a purpose in which slipping of the sod is undesirable, e.g., as a door mat, the use of the foam as an additional backing has been found to prevent slipping. Any synthetic foam material may be used for this purpose. Polyurethane foam has been found particularly suitable but other foams such as polyvinyl chloride foams and the like may be used. The foam may be applied to the fabric with an adhesive or any other suitable bonding means. It should be relatively thin, since this is all that is required for the non-skid characteristic .

In event the backing material selected is an open porous metallic screen, aluminum in preferred, but other metals such as steel, stainless steel, iron, lead and other like metals may also be used.

The metal screen is preferably bonded to the thermoplastic matrix by heating the matrix, contacting the heated portion of the matrix with the screen and applying pressure, e.g., squeeze rolls, to firmly embed the screen into the matrix. This type of bonding, i.e., heat bonding, is preferred since no foreign substances are introduced into the product. However, other bonding methods, e.g., adhesive bonding, may be employed for those p r oses in which the disadvantages are not objectionable.

While the bonding of the metal screen to the thermoplastic matrix serves to Impart dimensional stability to the synthetic sod of this invention, it may also be found desirable to bond an additional backing onto the matrix, For example, since the screen is open mesh and since the- matrix is provided with openings to permit drainage, there is a tendency for weeds to grow up through the openings. Such weed growth can be retarded by bonding a synthetic, porous, fibrous, backing oni:o the matrix which can readily be applied to the matrix in which the metal screen is already embedded cr bonded. Since the metal screen is open mesh, there is a substantial area of uncovered thermoplastic to which the fibrous material may be bonded. Again, while other methods . of bonding may be used, it is preferred that the synthetic, porous, fibrous backing bp heat bonded to the matrix through the holes in the open mesh metallic screen. This bonding can even bs done concurrently with the bonding of the metal screen.

Thus, the metal screen can be contacted to the matrix with the synthetic fabric on top of the metal screen, the matrix is heated and the entire assembly passed through pressure rolls. Such bonding has been found very satisfactory.

It is to be understood that, if desired, a thin synthetic foam nay also be bonded to the underside of the synthetic fabric bonded to the metallic screen.

DESCRIPTION OF THE DRAWINGS With reference to the drawings, Figure 1 shows an illustrative cut-away view of the product of this invention. As shown therein, the molded product comprises thermoplastic blades, 1, which are preferably crimped, or bent, to simulate natural grass. Preferably, the blades are in clusters having a base, 2. The blade clusters form an integral part of the synthetic sod and are arranged between parallel strips, 3, composed of the same thermoplastic material. The thermoplastic matrix has. a backing, 4, bonded thereto which is a metallic screen or synthetic, porous fibrous material. Figure 2 is a view of an additional embodiment of this invention and shows a foam material, 5» bonded to the underside of the metallic screen or porous fabric, or a synthetic porous, fibrous fabric bonded to the open mesh metallic screen.

PREFERRED EMBODIMENTS EXAMPLE I This example illustrates a preferred method of producing synthetic molded sod with a non-woven fabric bonded to its lower surface by means of a continuous process. The apparatus used to mold the synthetic grass of this example is fully described in U. S. Patent Application 650,986, filed July 3, 1967* and is shown in Figures 1, 15 and 16 of said application.

Before the molded product being discharged from the aforesaid apparatus cools, non-woven polyester of mass equal width with the molded product and of low »j&ije:g¾ifcx The linear feed rate of the fabric is about equal to the peripheral speed of the drum and is controlled by drum speed. While the fabric is fed from the roll, it is held under tension by a tension gate; it then travels under a pressure roll which embeds the fabric into the curvi -linear surface of the molded grass.

The tension on the fabric is sufficient to give a stretch to the fabric of 1% which is the amount by which the thermoplastic material shrinks upon cooling. In this way will lay f3at without curling or buckling when being used at ambient temperatures. The pressure roll is held against the surface of the product by a force of about 600 lbs. at the point of contact. Simultaneously, external heat is applied to the molded product before it makes contact with the fabric. This is done to maintain the polymer surface in a molten state and thereby allow polymer to flow into the interstices of the non-woven fabric and effect a perfect bond between fabric and molded product. The external heat that is supplied to the polymer immediately following injection molding is preferably radiant heat. In this example, one 2,000 watt infra-red lamp, placed about 1 to 2 inches above the mold drum, is sufficient to maintain the polymer surface in a molten state satisfactory for fabric bonding. During processing, the synthetic grass product is cooled by feeding water at about 70°F. to the interior of the drum at a rate of about 35 gals./min. As the molded grass is cooled to about 175 F., it is stripped fron> the drum and textured by passing it under a pair of heated metal rolls and wound on a mandrel to form large rolls of synthetic grass suitable for future handling and storage. The product of this example has the form depicted in Fig. 1 and has broad use as an outdoor artificial grass capable of preventing the growth of weeds on the ground beneath it and allowing water drainage such that the result is an aesthetically pleasing grass-like area requiring none of the maintenance of natural turf.

EXAMPLE II This example illustrates a method whereby synthetic molded sod can be manufactured with a non-skid material bonded to its lower surface.

When it is desired to produce a synthetic molded grass-like product having a non-skid surface, another material is first adhered to the non-woven fabric.

Subsequent steps and processing conditions in molding the thermoplastic product and in bonding the fabric are the same as those in Example I.

As an illustration, a 1/8 inch thick poly-urethane foam sheet was flame-laminated to a polyester non-woven fabric using conventional methods. Foam sheet width and fabric width were about 36 Inches. Th laminated pad is then rolled onto a spool for use as the fabric supply roll in bonding molded grass by a continuous process. The laminated fabric is then directed onto the molten surface of the molded, product with' the ol ester fabric face toward the molded The resulting product is depicted in Figure 2 and can be made into rectangles, or other shapes, for use as door mats cr non-skid carpets in play areas and the like .

EXAMPLE III SYNTHETIC SOD WITH A METALLIC SCREEN BONDED TO ITS LOWER SURFACE Before the molded product be.&ng discharged from the aforesaid apparatus cools, a 36" width of 8 x 8 woven aluminum wire screen/is fed to the flat surface of the molded synthetic sod from a supply roll " above the apparatus . The linear feed rate of the screen is about equal to the peripheral speed of the drum and is controlled by drum speed. While the screen is fed from the supply roll it is held under tension by a tension gate; it then travels under a pressure roll which embeds the screen into the curvilinear surface of the molded grass. The pressure roll is held against the surface of the product by a force of about 600 lbs. at the point of contact.

Simultaneously, external heat is applied to the molded product before it makes contact with the screen. This is done to maintain the polymer surface in a semi-molten state and thereby allow the screen to be embedded into the matrix and effect a perfect bond between screen and molded product. The external heat that is supplied to the polymer immediately following injection molding is preferably radiant heat. In this example, one 2,000 watt infra-red lamp, placed about 1 to 2 inches above the mold drum, is sufficient to maintain the During processing the synthetic grass product is cooled by feeding water at about 70°F. to the interior of the drum at a rate of about 35 gais/min. As the molded grass is cooled to about 175°F.» it is stripped from the drum and textured by passing it under a pair of heated metal rolls and wound on a mandrel to form large rolls of synthetic grass suitable for future handling and storage.

EXAMPLE IV The procedure described in Example III was repeated with the exception that a 36" width of non-woven polyester (1-2 os./yd, 2) is fed to the flat surface of the molded sod on top of the aluminum screen from a supply roil. The feed rate of the fabric is about equal to the feed rate of the screen. When the sod, screen and fabric are passed under the pres ure roll, the fabric is embedded into the surface of the matrix between the holes in the screen, thus, forming a bond. The subsequent processing and stripping of the sod off the mold is as described in Example I.

EXAMPLE V The procedure described in Example IV is repeated with the exception that a non-skid material is bonded to its lower surface as set forth in Example II. The resulting product is metallic screen reinforced synthetic sod.

Claims (16)

E-P- /4A What is claimed is:

1. A three-dimensional, molded grass-like product characterized by comprising (a) a relatively flat, thermoplastic matrix having projections extending therefrom on the upper side thereof, said projections being integral therewith and being shaped to simulate natural grass, said matrix having openings dispersed over its surface area; and (b) a backing material bonded to the underside of said matrix.

2. A product according to claim 1 characterized in that said backing material is heat bonded to the matrix.

3. A product according to claim 1 characterized in that said thermoplastic material is a polyolefin.

4. A product according to claim 3 characterized in that said polyolefin is polyethylene.

5. A product according to claim 3 characterized in that said backing material is a synthetic, porous, fibrous fabric.

6. A product according to claim 5 characterized in that . said fibrous fabric is a polyester.

7. A product according to claim 5 characterized in that said fibrous fabric is nylon.

8. A product according to claim 1 characterized in that said projections are in the form of clusters.

9. A product according to claim 8 characterized in that said matrix is composed of parallel strips spaced between the clusters and integral thereto.

10. A product according to claim 5 characterized in that there is a relatively thin synthetic foam bonded to the underside of the fabric.

11. A product accordin to claim 3 characterized in that there is a relatively thin synthetic foam bonded to the underside of the said backing material.

12. A product according to claim 3 characterized in that said backing material is an open mesh metallic screen.

13. A product according, to claim 12 characterized in that said screen is aluminum wire.

14. A product according to claim 13 characterized in that there is a relatively thin synthetic, fibrous, porous fabric bonded to the underside of the matrix through the openings in the screen.

15. A product according to claim Ik characterized in that said fabric is a non-woven polyester sheet.

16. A product according to claim 15 characterized in that there is a relatively thin synthetic foam bonded to underside of said non-woven polyester sheet. P. 0. Box 1169, ') el ■ vi Attorneys for. Applicant