Reinforced Foam Anti-Fatigue Floor Tile Module and Method of Making Same

Foam-type mats are commonly employed to provide cushioning and shock-absorbing surfaces for objects or people. Vinyl-foam anti-fatigue mats are often used as free lay mats employed as a standing or floor-type surface for those personnel who must stand for considerable periods of time in a confined area during the normal work periods.

A flame-resistant, vinyl-foam gasket material, particularly for use in and around electrical outlets or switchboxes has been disclosed in U.S. Pat. No. 4,447,484, issued May 8, 1984, which patent is hereby incorporated by reference in its entirety. This patent discloses the employment of dimensionally stable glass fiber issue sheet material inwardly positioned and secured within a gasket foam layer, so as to meet particular flame test standards. Such foam gasket material is a very low density-type soft foam and quite resilient, since it must conform to irregular surfaces and is not subject to or need have abrasion-resistant properties, shock absorbing or cushioning properties. The dimensionally stable gasket material resists or prevents melting in the vinyl-foam gasket when exposed to an open flame, and therefore such gasket foam is described as a flame-resistant vinyl-foam gasket material. The fibrous tissue sheet material employed in the vinyl-foam gasket material is generally positioned anywhere within 20% to 80% of the thickness or depth of the foam material and is positioned by permitting the tissue material to penetrate to a desired level into the liquid vinyl plastisol layer prior to heating and expanding the plastisol layer to form the vinyl-foam gasket material.

The invention relates to dimensionally stable, anti-fatigue foam floor tile modules, to the method of manufacturing such floor tile modules, and to the method of using such floor tile modules, particularly when used in a complete, integrated anti-fatigue floor system comprising a plurality of the anti-fatigue floor modules or in combination with conventional carpet tiles.

A reinforced vinyl-foam, anti-fatigue floor module has been discovered which comprises a resilient foam layer having a face surface and a back surface. Typically, the foam layer has a foam density of over 20 pounds per cubic foot, such as for example, 20 to 40 pounds per cubic foot, and sufficient thickness to provide adequate cushioning, shock-absorbing and anti-fatigue properties, such as for example, 250 to 600 mils. The foam layer generally comprises a substantially closed cell foam layer, that is over about 80%, e.g. 90%, closed cells, so as to prevent the absorption of water into the vinyl foam layer and to provide for better cushioning. The vinyl-foam layer has a top and back surface very thin-skin layer. Generally, the top face surface of the anti-fatigue module has been embossed under heat and pressure so as to provide a decorative or a non-slip or other distinctive friction or design pattern thereon.

The anti-fatigue module contains a dimensionally stable reinforcing sheet material, such as scrim, or particularly a fibrous tissue sheet material comprised of glass fibers or polyester fibers or other polymeric or a combination, between the first and second foam layers to provide high dimensional stability with time to the module after production and embossing.

In one embodiment, the anti-fatigue foam floor module may comprise a first foam layer having a face surface and a second foam layer having a back surface with the first and second foam layers integrally and directly bonded to each other with a reinforcing material carefully positioned and bonded in between to impart a high degree of dimensional stability to the floor module.

The high degree of dimensional stability in a floor tile module is essential to the proper function and performance of the module while a high dimensional stability in a vinyl-foam, free lay mat or runner or a soft vinyl-foam gasket material is not a critical factor. Mats and runners used for floor surfaces are generally and merely placed on the floor as a free-laying mat and runner in areas where required. Unlike floor tile modules, which require careful and controlled edge matching with adjoining floor modules or with conventional carpet tiles, the mat and runner does not require edge match ups, since mats and runners are normally used alone. Furthermore, a vinyl-foam mat or runner normally will shrink with time, for example, up to about one percent or more, both in length and width. However, shrinkage in such mats and runners is not an essential factor because of the lack of need of edge match up and also because the mats and runners are fairly large and loosely laid on the floor, so minor variations are not noticed and do not affect the anti-fatigue mat or runner performance.

It has been discovered, both unexpectedly and surprisingly, that the employment of a reinforcing material within the foam layer of a floor module and its positioning is critical in order to provide a floor tile module of very high dimensional stability, and which floor tile module may be employed with other same or similar floor tile modules or in combination with other conventional carpet tiles. Further, surprisingly, it has been discovered that the reinforcing material cannot be merely placed in dead center in the anti-fatigue foam layer floor module. Rather, it has been discovered that the exact position and location of the reinforcing material is essential and critical to the dimensional stability and performance of the floor tile module, and that it is necessary to place the reinforcing and fibrous sheet material in a position of from 55% to 65% of the depth or thickness of the anti-fatigue foam floor tile module as measured from the back surface of the module in order to provide a module which lies flat after production and does not curl with time even through the floor tile module has had the face surface embossed which creates further stresses in the floor tile module.

The purpose of the reinforcing materials, such as the fiberglass scrim, or particularly the non-woven tissue material, is to stabilize the anti-fatigue foam module so that the shrinkage is controlled, typically to less than one-tenth of one percent, upon aging. The shrinkage control of the floor module is also important in that it allows the floor module to be accurately die cut and to obtain a floor module which will retain its dimensions when installed in a floor surface system. Obviously, anti-fatigue floor modules which are employed in a floor system with a shrinkage as high as one percent as runners and mats results in gaps and openings and would be totally unacceptable commercially. Therefore, the simple cutting up of normal foam anti-fatigue mats or runners into a floor tile module would not provide for a commercially acceptable product.

Normal vinyl-foam, anti-fatigue mats and runners, without the employment of a reinforcing material therein, do not exhibit a curl problem, but merely exhibit a shrinkage problem, which is not an essential factor for such mats and runners, since such mats and runners merely lay very flat on the floor. It has been found that when a reinforcing material such as a glass fiber sheet material is positioned within the foam layer of the foam module in order to provide dimensional stability, that is to prevent shrinkage, the exact position and location of the reinforcing sheet becomes very critical. For example, in the unembossed floor tile product, if the reinforcing material is placed closer to the face than to the back surface, then the floor tile material would dome, or curl downwardly. While if the reinforcing material is placed closer to the back than the face surface, an upward curl is exhibited upon shrinkage. Therefore, there is a need to balance the natural shrinkage of the vinyl-foam in the proper location of the reinforcing material. However, another factor is that the embossing of the face surface or the back surface of the floor tile module creates further stresses. Thus, it has been discovered that the position of placing the reinforcing material from 55% to 65% from the back surface of the floor tile module balances the effect both of the embossing and provides a dimensionally stable floor tile module which does not curl, with a dimensional stability when employing a fiberglass scrim or tissue material as a reinforcing material of less than from about one-tenth of one percent or less.

The principal application for the floor tile modules of the invention would be in those areas where a person is standing, such as a cashier, where a carpet tile can be replaced with the anti-fatigue floor tile modules. Obviously, a complete floor system could be made employing a plurality of the anti-fatigue floor tile modules placed together in an edge-matching relationship to cover the designated area. Also, the floor tile modules, because of the high dimensional stability, may be employed in combination with conventional carpet tiles replacing carpet tiles in a particular area where anti-fatigue properties are more desirable, such as for example, in convention booths, showrooms and in other places and areas where a high degree of floor comfort is needed, particularly where the floor system is or has to be removable. Generally, the dimensions of the tiles in the United States will be 18 inches by 18 inches which are the same size as the United States carpet tiles, while in Europe and in other areas, the conventional size of the floor tile modules would match that of the carpet tiles and would be 50 centimeters by 50 centimeters, representing the European and world-wide size standard.

Typically, the anti-fatigue module is embossed on one surface, such as the face surface, by passing the module under a roller with heat and pressure to impart an embossing on the surface. The embossed pattern may take various forms which may be decorative, non-slip or a combination. However, on embossing, the foam layer immediately under the face skin layer is densified due to such embossing.

It has been found that the employment of the reinforcing fibrous sheet material in the designated position causes the module to lie flat even through the module has been subject to additional strains through embossing on the face surface. When the embossing occurs on the back surface only to provide, for example, anti-friction propeties to the back surface, then the reinforcing material should be positioned 55% to 65% from the unembossed face surface.

The anti-fatigue module may also be an anti-static module where an electrically conductive module having an electrical resistivity of 1.times.10.sup.9 ohm-square or less is desirable. Such modules are useful in static-free environments and usually areas where electronic components such as microchips and integrated circuits are subject to damage by static electricity. Anti-static modules are prepared by incorporating one or more anti-static agents into the vinyl-foam layer in an amount sufficient to lower the electrical conductivity of the vinly-foam and without reducing the cushioning properties of the module or abrasion-resistant characteristic of the face surface.

Suitable anti-static agents comprise, but are not limited to: carbon black particles such as furnace black particles; metal particles; polyalkylene glycols, such as polyethylene and polypropylene glycols; quaternay ammonium compounds such as di-alkyl benzyl, fatty or long-chain hydrocarbon quaternary ammonium halides; and particularly long-chain fatty acids and fatty acid esters and half esters of polyols, e.g. alkylene polyol, such as lauryl, oleate and other fatty or long-chain esters of polyethylene glycol and combinations thereof. The anti-static aqents are employed typically in an amount of from 1 to 20 parts, e.g. 2 to 10, per 100 parts of the vinyl resin.

The invention also concerns a method of preparing a foam anti-fatigue module. The reinforcing material may be positioned in the foam layer by a number of techniques, such as permitting the reinforcing material to penotrate a liquid, foamable plastisol layer to the desired location before heating, which creates difficulty in the exact positioning of the reinforcing material. The reinforcing material may be positioned by laminating two vinyl-foam layers, or a liquid, foamable plastisol layer, to a vinyl-foam layer with the reinforcing material therebetween.

One preferred method comprises forming a first layer of an expandable liquid vinyl plastisol composition by casting, e.g. 50 to 70 ounces per square yard, onto a support surface, such as a releasable paper sheet or a fluorocarbon-coated, teflon, fiberglass or stainless steel endless belt. A fibrous reinforcing sheet material, such as a glass fiber tissue (of non-woven glass fiber with a strengthening resin binder), is placed onto the top surface of the first plastisol layer permitting the glass fiber tissue to be wet by the plastisols or face. If desired, and optionally, the first layer may be heated to gel the layer or the top surface to control the position of the reinforcing sheet material.

This technique avoids the difficulties associated with trying to position accurately a fibrous sheet material by permitting penetration of a single layer of an expandable liquid vinyl resin plastisol. It is essential in the practice of the invention and to achieve the objects and results thereof to position accurately the fibrous sheet material.

A second layer of an expandable liquid vinyl resin plastisol, e.g. 30 to 40 ounces per square yard, which may be of the same density of same characteristics or different than the first layer is then formed by casting over the fibrous tissue sheet material on the first layer. Thereafter, the first and second foam layers containing the fibrous tissue sheet material are heated typically in an hot air oven or heated platens to gel the first and second layer, to expand the first and second layer and to form a substantially closed cell, integrally bonded, cushioning-type foam layer having a top and back surface thin-skin layer and having a foam density of 20 to 40 pounds per cubic foot and with the foam layer having a thickness of 250 to 600 mils, for example, 300 to 500 mils.

The fibrous sheet material is positioned in the foam layer at a position of 55% to 65% of the thickness of the layer from the back surface. Thereafter, the foam layer containing the fibrous tissue material embedded therein is embossed by passing over or through a heat and pressure roller so as to emboss the face surface of the foam layer which densifies the underlining foam beneath the embossed area, the embossed area generally ranging from about 10 to 150 mils in thickness. Thereafter, the embossed foam layer containing the fibrous, dimensionally stable sheet material therein is cut, usually by die cutting, into modules of desired size.

The vinyl resin plastisol or organosol compositions used in preparing the anti-fatigue floor modules generally comprise a vinyl-chloride, dispersion-type resin together with appropriate plasticizers, cell control agents, stabilizers, activators, chemical blowing agents, flame retardants, pigments, anti-static agents and the like and, optionally, solvents or diluents.

The fibrous reinforcing sheet material employed for preventing curl of the modules generally is composed of an open, very fibrous-type material, typically of a glass fiber or other inorganic or polymeric, such as polyester, olefins like polypropylene nylon and blends and combinations thereof. There are glass fiber scrims where there are regular and uniform openings of larger size as a woven glass fiber scrim, or more particularly and preferred is a glass fiber tissue composed of non-woven glass fibers and wherein both in the tissue and in the scrim are small amounts of a thermo-setting resin or other binders which are used to retain the glass fibers in place.

The invention will be described for the purposes of illustration only in connection with a particular embodiment of a vinyl-foam, reinforced anti-fatigue floor module. However, it is recognized that various changes and modifications and improvements may be made in the invention as illustrated, all falling within the spirit and scope of the invention as described and illustrated.

FIG. 1 is a perspective view of the vinyl-foam, anti-fatigue module of the invention, and

FIG. 2 is a perspective view of a flooring system showing the use of the modules of FIG. 1.

Plastisol formulation for use in preparing standard, i.e. non-anti-static and anti-static, anti-fatigue floor modules in accordance with the invention are as follows:

A first layer of the plastisol formulation is cast onto a release surface endless belt travelling at 13 feet per minute in an amount of 60 ounces per yard.sup.2, a non-woven glass fiber tissue as a reinforcing sheet is laid onto the top surface of the first plastisol layer, a second plastisol layer is cast over the glass fiber tissue in an amount of 40 ounces per yard.sup.2, and the plastisol layer heated in an oven set at 490.degree. F. to provide a foamed, anti-fatigue sheet. The sheet is then heat-pressure embossed by passing over a roller to impart an anti-friction embossed surface to the face or top surface. Thereafter, on cooling, the foam material is die cut into floor modules of 18 inches by 18 inches. An anti-static floor module may be prepared by employing the anti-static plastisol formulation on the first, second, or typically to form both foam layers.

The vinyl-foam anti-fatigue modules prepared as described after production and after embossing, with time, lie flat and exhibit, with aging, about one-tenth of one percent, or less, shrinkage. It has been found that the vinyl-foam module is prepared in the same manner, however with the fibrous tissue material placed higher or lower than 55% to 65% permits curl and therefore is not acceptable.

FIG. 1 illustrates a reinforced, vinyl-foam, anti-fatique module 10 of the invention and comprises a first top vinyl-foam layer 12, a second bottom vinyl-foam layer 14 integrally and directly bonded to the front layer 12 with a glass fiber tissue sheet material integrally bonded with the top 12 and bottom 14 foam layers and positioned 60% of the depth from the back surface of the module 10. The module 10 has a striated, non-slip-type embossed area 18 with a densified foam area 20 directly under the embossed area 18 with the vinyl-foam module having a thin back surface skin 22 and a front surface skin 24 formed of a thin, solid vinyl layer during manufacture.

FIG. 2 illustrates a flooring system 30 wherein a plurality of conventional fibrous-face carpet tiles 32, e.g. tufted nylon face bitumen or polyvinyl chloride-backed carpet tiles, of conventional 18-inch-by-18-inch size are positioned edge-to-edge to form a flooring system to cover a defined floor area. A portion of the carpet tile system has been replaced with the anti-fatigue floor modules of FIG. 1 in an edge-to-edge relationship within the flooring system 30 to provide an anti-fatigue or also an anti-static area in the flooring system 30.

The anti-fatigue, dimensionally stable floor modules of the invention permit edge-to-edge matching with the modules or with conventional carpet tiles without curl or excess shrinkage.