2. State of the Art Polyolefin is the general term for any of the largest genus of thermoplastics, which are polymers of simple olefins such as ethylene, propylene, butene, isoprene, and pentene, and copolymers thereof. Two of the more important members of this group are polyethylene and polypropylene, which together account for just under half of all thermoplastics produced in the United States.

In recent years polyolefins and other polymers have been used to create resilient flooring materials for use in athletic arenas such as basketball courts, tennis and racquetball courts, and so forth. An example of such a tile is shown in FIG. 1.

These tiles are typically 10"to 12"square by 3/8"to'/2"thick. Because they are typically configured as interlocking tiles having approximately the same size as traditional floor tiles, these flooring materials are easy to install. However, because of the polymer construction, the resulting floor surface is relatively susceptible to scratches and abrasion, and tends to lose its glossy appearance over time. This is a problem for athletic floors where an attractive, durable, and long lasting high gloss surface is desired.

To solve these problems, some sort of coating of the floor is desirable.

However, due to the chemical structure and simplicity of polyolefins and other polymers, their surfaces are generally resistant to any kind of permanent coating or decorating. Polyolefins, for example, are generally characterized by a nonpolar, nonporous, low-energy surface structure that does not easily bond to inks, lacquers, and other polymers without special oxidative pretreatment. The resistance of polyolefins to coating or decorating is especially problematic when the substance to be bonded is another polymer such as polyurethane. Polyurethane is well known and has many uses in biomedical and other applications. It's suitability to these applications is due in large part to its very low reactivity: polyurethane is very inert, and resists reaction with body fluids and other organic and inorganic chemicals.

Polyurethane would be an excellent coating for a polyolefin floor material because it is scratch and abrasion resistant, and has a long lasting high gloss appearance.

In order to sufficiently bond a coating or decoration to a polyolefin or other polymer, the surface is ordinarily treated in some way, or a secondary adhesion- promoting layer is added to increase the adhesion. There are a number of common methods for doing this, including flame treatment, the use of heat and pressure, chemical treatment, and electron bombardment.

Flame treatment involves the brief application of a flame or heat to the polymer surface. This oxidizes a thin surface layer of the material, creating highly active surface molecules that will bond with inks, dyes and other coatings.

However, not all polymers produce good results with flame treatment. Some polymers do not obtain sufficiently increased surface energy through flame oxidization due to their chemical structure. Other polymers have difficulty withstanding the addition of heat without deforming or changing in clarity or physical structure. Additionally, if excessive heat is applied, the material may soften or warp. Excess heat may also cause accelerated aging by the introduction of heat history to the material. A preferred method of increasing the surface energy in polyolefins and other polymers will increase the surface energy enough to promote bonding, while limiting surface temperature increase to below a level which will deform or significantly damage the material.

The application of pressure and temperature together can cause some coatings and decorations to bond to a polymer surface. An example of this method is hot stamping, which involves the use of a heated applicator and a special ink held by a foil backing. The ink is forced via heat and pressure to transfer to the new substrate. This method works quite well with some small sized parts and certain families of plastics. However, this technique is very sensitive to the size and shape of the objects to be treated. It generally only works well with small or flat surfaces that can be stamped or rolled. Large or convoluted shapes or surfaces that have complex geometric structure or texture are virtually untreatable using heat and pressure. Additionally, this technology requires specialized, stationary equipment.

A preferred method of surface treatment will allow the treatment of large or oddly shaped parts and those with textured surfaces in addition to surfaces that may be

stamped or rolled, and may be accomplished with small, simple equipment that may be easily moved.

Chemical treatment is of two kinds: chemical abrasion, and the application of a secondary'primer'layer. Chemical abrasion involves the activation of the polymer surface with a solvent, and is typically used with polar materials. The solvent chemically'etches'the surface of the polymer, creating an abraded and/or chemically changed surface that is more conducive to bonding. Examples of chemical abrasion are the application of acetone or MEK to acrylic, styrene, PVC, and ABS. The use of a secondary primer layer involves the application of a material that, because of its own high level of chemical activity, will bond to both the polymer substrate and the coating or decoration. An example of such a primer would be a chlorinated compound held in a solvent emulsion.

There are a number of significant drawbacks to chemical treatment. First, if too strong of a chemical solvent is used, or exposure is too prolonged, the polymer will soften or dissolve. There are also significant dangers posed by human exposure to chemical solvents, and the introduction of these chemicals into the environment.

A preferred method of increasing the surface energy of polymers will increase the surface energy enough to promote bonding, while avoiding the possibility of dissolution of the polymer itself, and prevent or limit human and environmental exposure to harmful chemicals.

Electron bombardment involves the direction of a beam or'cloud'of electrons onto a plastic surface to interact with the surface. The free electrons in the cloud or beam act to knock existing electrons out of their orbital positions in the polymer molecules, creating locations on the surface where other chemicals may bond. The electron beam may also cross-link or cut some polymer chains, creating additional locations for chemical bonding. This process is carried out in a vacuum environment to minimize the effects of air molecules. The automotive industry commonly uses electron bombardment to activate bumper fascias and other large parts.

Electron bombardment is a very expensive method of polymer activation because it requires the placement of the object into a closed vacuum chamber.

Moreover, with this method some areas of the surface will receive less treatment

than others. A preferred method of polymer surface activation will treat all areas of a surface equally, will have a reasonable cost, and will not require the placement of the item into a vacuum chamber or other device of a fixed size, allowing the treatment of objects of variable size and shape in a normal human environment.

Another method of treating a polymer surface to increase its surface energy that is superior in many ways to each of the above described methods is corona or plasma treatment. In the discipline of physics, the term"plasma"describes a partially ionized gas composed of ions, electrons, and neutral species. This state of matter may be produced by either very high temperatures, such as exist in celestial bodies or nuclear explosions, or by strong electric arcs or electromagnetic fields. An electric arc plasma may be produced by a pair of electrodes spaced some suitable distance, facing each other. An example of such electrodes is shown in FIG. 3. The electrodes are then given a high voltage charge (AC or DC), which causes electricity to arc across the gap between the electrodes. The distance d between the electrodes primarily depends upon the voltage used. This high energy electric arc produces a plasma in the region immediately around the electrodes.

When a plastic surface is exposed to a high energy plasma produced by a high voltage electric arc, the plasma interacts with the surface molecules, increasing their energy through a variety of mechanisms, depending on the specific polymer involved. In some cases, surface hydrogen molecules are removed, leaving behind active bonding sites. Also, cross-linking or scission can occur in the surface molecules, as in electron bombardment. This will change the surface energy of the material, making it easier for a coating to adhere. Oxides may also form on the surface, as in flame treatment, which are easier to bond to than the actual base polymer. These are just a few of the possible chemical mechanisms which are caused by plasma treatment that increase surface energy. The great benefit of using electric arc plasmas is that they are relatively low temperature, and can be used without damage to the surface of polymers and other relatively delicate materials.

Plasma treatment for the surface modification of polymers including polyolefins is well known in the industry. For example, Roth, et. al. (U. S. Pat. No.

5,387,842) discusses the use of glow discharge plasmas to modify the surface properties of polyolefins. However, the primary applications of this technology have

been for the purpose of improving the wettability of the polymer material (see, e. g., U. S. Pat. Nos. 5,456,972 and 5,403,543 to Roth, et. al.; U. S. Pat. No. 5,518,799 to Finestone, et. al.), and for facilitating printing on these surfaces (see, e. g., U. S. Pat.

No. 5,403,454 to Taniguchi; U. S. Pat. No. 5,695,064 to Huang, et. al.). Other references teach the use of plasma treatment for the purpose of applying a metal coating to a polymer substrate (see, e. g., U. S. Pat. No. 5,462,771 to Motoki, et. al.; U. S. Pat. No. 5,567,490 to Papazian, et. al.), or teach corona treatment of polystyrene for the purpose of causing a polymer contact lens to stick to it temporarily during manufacture (U. S. Pat. Nos. 5,573,715 and 5,679,385 to Adams, et. al.). Many of these also require that the plasma treatment be carried out in an inert gas or other special environment (see, e. g. U. S. Pat. Nos. 5,387,842,5,456,972 and 5,403,543 to Roth, et. al.; U. S. Pat. No. 5,567,490 to Papazian, et. al.; U. S. Pat.

Nos. 5,573,715 and 5,679,385 to Adams, et. al.; U. S. Pat. No. 5,462,771 to Motoki, et. al.), or at very low pressure (see, e. g., U. S. Pat. No. 5,462,771 to Motoki, et. al.; U. S. Pat. No. 5,387,842 to Roth, et. al.).

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a polymeric floor tile which has been coated with a polyurethane surface following plasma treatment of the floor tile.

It is another object of the present invention to provide a method of activating the surface of a polymeric floor tile by means of plasma treatment so as to increase the surface energy enough to promote bonding of a polyurethane coating, without the use of harmful chemicals or the possibility of overheating or damaging the surface of the tile.

It is another object of this invention to provide a method of activating the surface of a polymeric floor tile which will allow treatment to be carried out in a normal human environment without the placement of the tile into a vacuum chamber or other device of a fixed size, allowing the treatment of objects of variable size and shape and those with textured surfaces.

It is another object of this invention to provide a method of activating the surface of a polymeric floor tile which may be accomplished with small, mobile equipment.

It is a further object of the present invention to provide a method of activating the surface of a polymeric floor tile which will have a reasonable cost.

It is a further object of the present invention to provide a method of activating the surface of a polymeric floor tile which will treat all areas of a surface equally.

The above and other obj ects are realized in a polymeric floor tile coated with polyurethane, comprising a polymeric floor tile having a top surface, a region on the top surface of the floor tile that has been activated by plasma treatment, and a polyurethane coating applied over said activated region, so as to produce a bonded attachment at the interface between the polyurethane coating and the top surface of the tile due to the plasma treatment.

These and other objects are also realized in an apparatus for treating, in- place, a polymer based floor material with a high energy plasma jet, comprising a frame, a plasma generator connected to the frame, and control means connected to the frame whereby a user may control the apparatus. The plasma generator comprises downwardly directed electrodes oriented such that when the frame is placed on a floor the electrodes are at a suitable distance from the floor so as to adequately expose it to the plasma.

Some of the above objects are also realized in an apparatus for treating, in- place, a polymer based floor material with a high energy plasma jet, comprising a frame, a plasma generator with downwardly directed electrodes connected to the frame, propulsion means connected to the frame whereby the frame may be propelled across the surface of the floor, and control means connected to the frame whereby a user may control the apparatus.

These and other objects are also realized in a method of treating a polymer based floor system in-place comprising the steps of exposing the floor to a high energy plasma whereby the surface energy of the floor is increased, and applying a polyurethane coating to the surface of the floor while in its energized state. In an alternative embodiment, this method may comprise the additional step of cleaning the floor in the case of dirty or used floors.

Other objects and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 provides a pictorial cut-away representation of a typical polymeric floor tile.

FIG. 2 shows an elevation view of an apparatus according to the present invention for in-place plasma treatment of a polymeric floor system.

FIG. 3 shows a closeup view of a pair of electrodes creating a plasma field.

FIG. 4a shows a frontal view of two staggered rows of electrode pairs arranged side-by-side creating a plasma field.

FIG. 4b shows a top view of two staggered rows of electrode pairs.

FIG. 5 shows a partial cross-sectional view of a polymeric floor tile treated according to the present invention.

FIG. 6 shows a schematic diagram of an assembly line manufacturing process for producing floor tiles according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings: FIG. 1 provides a pictorial cut-away representation of a typical polymeric floor tile, such as is manufactured by Sport Court, Inc. These floor tiles, designated generally at 10, are typically square in plan, with a thickness T that is substantially less than the plan dimension L. A typical Sport Court, Inc. floor tile is approximately 10"to 12"square and 3/8"to l/211 thick. These tiles may be made of many suitable polymer materials, including polyolefins such as polyurethane and polyethylene, and other polymers including nylon. Polyolefins are presently preferred. As shown, the top 12 of the tile is a smooth solid surface, whereas the bottom 14 is comprised of a lattice-type structure 20 which gives strength to the tile while keeping its weight low. The solid top and lattice-type bottom structure are integrally formed of the same material so as to be structurally strong. It will be apparent, however, that the invention described herein is not necessarily limited to floor tiles with a smooth, solid top surface. Tiles having a grid or lattice-type top surface of various configurations may also be coated according to this invention.

The floor tiles 10 typically have loops 16 on two adjacent sides, and pins 18 on the two other adjacent sides as shown. To install the floor, a tile 10 is placed with its top 12 facing up, and its bottom 14 on any suitable subfloor, such as concrete.

A second tile is then placed parallel to and alongside the first tile, oriented such that the pins 18 of one side of the second tile are adjacent the loops 16 of a corresponding side of the second tile. The pins 18 of the second tile are then snapped into the loops 16 of the first tile such that the sides of the two tiles are fitted snugly together. This process is continued until an entire floor is in place.

FIG. 2 shows an elevation view of the apparatus for in-place plasma treatment of a polymeric floor system, which is the subj ect of the present invention.

In this figure the installed polymeric floor system is shown in cross-section, with the top surface of the floor 12 shown above the subfloor 28. The apparatus 30 for treating the floor is generally comprised of a frame 32, a plasma generator 34, electrical power supply connection means 44a and 44b, and control means 40. In the preferred embodiment shown in FIG. 2 the control means is mounted on a handle 42 for operator convenience. The apparatus may also comprise propulsion means 36, such as a motor, which is connected to wheels 38 for the purpose of driving the apparatus across the surface of the floor 12 at a uniform rate. The wheels 38 must have a smooth, relatively soft, non-scuff surface that will not damage the floor surface, nor interfere with the activation process or react chemically with the activated floor. As shown in FIG. 2, the plasma treatment apparatus may also comprise a light 46 to illuminate the path for the operator, and a bumper 48 mounted on the front of the apparatus for preventing damage due to contact with walls. When in use, the apparatus 30 travels in the direction of arrow 54, and the operator walks behind holding handle 42, so as to manipulate the control means 40 which is mounted nearby.

The control means 40 will typically comprise at least an on-off switch for the entire apparatus, means for controlling the power output of the plasma generator, and means for controlling the drive rate of the motor 36 so that the floor surface may be given adequate uniform treatment. It will be apparent that the control means may also include feedback means for indicating desirable treatment parameters, such as

rate of travel and power output, and may also include a power on-off indicator light, various warning lights as desired, and an on-off switch for the light 46.

The plasma generator 34 comprises downwardly directed electrode pairs 50 mounted near the front of the apparatus, and oriented such that when the frame 32 is placed on its wheels 38 on the floor 12 the electrodes 50 are at a height h above the floor. Various alternative electrode configurations are discussed below, and a close-up view of suitable electrodes is given in FIG. 3. The height h is a critical parameter of proper plasma treatment, and is typically less than l/2". It is preferred to have this height as close to 0"as possible in order to improve energy transfer to the flooring material, and also to create a more uniform treatment distribution pattern. It will be apparent to those skilled in the art that to properly treat a polymer floor surface, either the height h is adjusted for a particular power output of the plasma generator, or the power output is adjusted for a given height h.

A suitable plasma generator will typically require 1 to 3 amps per pair of electrodes. It will be appreciated that to practically treat a floor material in place, typically a plurality of electrode pairs must be arranged in some fashion so that a relatively wide swath of floor may be uniformly treated at once. It will also be appreciated that the maximum practical width for the in-place treatment machine may be limited by the power available for the machine, as discussed below. In the preferred embodiment, approximately ten electrode pairs are arranged in two staggered rows so as to treat an area 20"to 24"wide. It will be appreciated that this configuration will thus require 10 to 30 amps of power for the plasma generation, in addition to power required for a self-propelling motor, controls, and other features of the apparatus.

Power for the apparatus may be supplied by any available power source, such as 60 Hz single phase 110-120 v AC, or 220-240 v AC, or 208 v three phase power, or other available sources. Because of its wide availability, the preferred embodiment uses 110-120 v single phase AC power. Because typical circuit breakers for 110-120v wall outlets in buildings where this apparatus is likely to be used are set to allow a maximum of 15 amps per circuit, it will be appreciated that the 30 amp maximum power requirement for this device will typically require the utilization of more than one circuit. For this reason the preferred in-place plasma

treatment apparatus will be provided with more than one power cord, designated by 44a and 44b in FIG. 2, so as to allow the machine to be simultaneously connected to multiple wall outlets on different circuits. It will be appreciated that these cords 44a and 44b must typically be quite long because outlets on different circuits may be relatively remote from each other.

As noted above, the plasma generator 34 may be configured to operate on either direct current (DC) or alternating current (AC). It will be apparent to one skilled in the art that a plasma generator configured to operate on direct current yet connect to a typical electrical power supply as noted above will require power transformation means to transform AC input power into DC. It will be appreciated that the voltage required depends on several parameters, including the spacing of the electrodes 50, their geometry and material of construction, and other factors. When supplied with the proper voltage, an arc of electricity will jump the gap between the electrodes 50, and will produce a corona or plasma field 52 that will activate the polymer floor surface 12. It will also be appreciated that the preferred apparatus as shown in FIG. 2 is shown in a side elevation view, and that while not visible in this view, a number of electrode pairs 50 are mounted across the front of the apparatus in two staggered rows so as to uniformly treat an area approximately as wide as the frame 32 of the apparatus. The frame may be any width, and its size is generally limited only by practical considerations of size, weight, portability, power supply, and so forth. Because athletic floors are generally large, in the range of 2,000 to 100,000 square feet, a preferred machine will cover as much area as possible in a single pass in order to reduce the time and labor required.

FIG. 3 shows a closeup view of a pair of electrodes 50 creating a plasma field. In the depicted embodiment, the electrodes 60a and 60b are elongate with a closed loop on the end, shaped like the letter"b", the pair of electrodes oriented with the loops facing each other. It will be readily appreciated that other electrode configurations may be used in accordance with the present invention, such as straight parallel electrodes, straight parallel electrodes with a ball on the end, electrodes angularly bent toward each other, or electrodes with a hooked"J"shape.

Advantageously, a straight wire electrode oriented parallel to the floor surface and perpendicular to the direction of travel of the machine may also be used for in-place

plasma treatment as well as for the factory treatment embodiment described below.

A preferred material for the electrodes is copper, but other materials known in the art may be used.

When supplied with power, an arc of electricity jumps the distance d between the ends of the electrodes 60. This high voltage electric arc ionizes and energizes the ambient air in the region of the electrodes, and creates a plasma"cloud"52. The "cloud"52 is directed toward the floor surface 12 by a downwardly directed jet of gas forced in the direction of arrow 64 into the region of the electrodes 60 through a nozzle 62 or other means. This gas jet may be compressed air, or may be some inert or other gas such as nitrogen, helium, argon, or carbon dioxide, to name a few.

These other gases are known in the art to vary the activation properties of the plasma cloud in various ways, and may be desirable in certain applications. In the presently preferred embodiment, a jet of compressed air is used because it is the simplest and least expensive method. With the pair of electrodes 50 positioned a distance h above the floor, the plasma"cloud"is thus placed in contact with the floor surface 12. As explained, the plasma interacts with the surface molecules of the polymer flooring, increasing their energy. It has been discovered that this plasma treatment process is surprisingly effective for activating the polymer surface in a manner that a polyurethane coating will adhere.

The ends of the electrodes 60 are separated by a distance d that depends on the voltage and current of the apparatus, and also upon the geometry and material of construction of the electrodes. The plasma"cloud"similarly has a width w in contact with the floor surface 12 that depends upon the power of the plasma generator, and the spacing d of the electrodes 60. The width w represents the area treated by a single pair of electrodes. In the depicted embodiment the distance d between the looped electrodes may vary from'/2"to 2", and the width w may be from 1"to 3". It will be appreciated that the amount of energy in the plasma field, and hence the level of treatment applied to the floor, will vary somewhat within the area w, the plasma field being stronger in the region between and near the electrodes, and somewhat weaker toward the margins.

This variation in the strength of the plasma field 52 leads to the arrangement of FIGS. 4a and 4b. FIG. 4a shows several side-by-side pairs of electrodes arranged

in two staggered rows. In this arrangement the electrode pairs 50 in each row are spaced at a center-to-center distance w, that is greater than the corresponding width of treatment w of a single electrode pair. This arrangement creates a plurality of plasma fields 52 that partially overlap each other, allowing more uniform treatment across the entire width of the machine as it sweeps over the floor surface 12, without unintended arcing, and without leaving"stripes"of relatively untreated surface. It will be appreciated that the electrode pairs must be separated some suitable distance from each other so that electrical arcing will not occur between non-paired electrodes.

The arrangement of FIG. 4a corresponds to a close-up front elevation view of the internal apparatus of the front of the machine shown in FIG. 2. FIG. 4a depicts two pair of electrodes arranged with one pair in front, and the other behind.

The arrangement of FIG. 4a becomes more apparent upon inspecting FIG. 4b, which shows a top view of the two staggered rows of electrode pairs of FIG. 4a. In this view the electrode pairs 50 are arranged such that the corresponding plasma fields 52 overlap to allow treatment of the total width W when the apparatus is moved in the direction of arrow 54. It will be appreciated that any number of electrodes may be so arranged, depending on the size of the machine and the area intended to be treated in a single pass. In any configuration, the total width W that is treated in a single pass is the sum of the electrode pair spacings wl in the row with the greatest number of electrodes.

Alternatively, the electrode pairs 50 of FIG. 4amaybe arranged side-by-side in a single row. In this arrangement, the electrode pairs are spaced at a distance w, so as to create several plasma fields in a single row that partially overlap each other.

It will be appreciated that to provide the appropriate overlap for a given set of power and geometric configurations, the appropriate distance w, will be something less than the total width w of area which would receive some treatment from a single pair of electrodes as in FIG. 3.

It will be appreciated that when using the apparatus as described the floor surface must be very clean in order to promote proper bonding of the coating.

Naturally, cleaning is usually not necessary with newly installed polymeric floors.

However, when the floor to be treated is a previously installed floor that has been in

use for any significant amount of time, cleaning of the floor surface with a chemical solvent may be required before treatment may begin. Additionally, if there has been a previous coating applied, this coating will need to be removed. Similarly, any items that may touch the floor during the process, such as the wheels of the treatment apparatus and the power cords attached to the machine, must also be cleaned in order to maintain a clean surface. Likewise, workers will normally be required to wear some kind of clean protective overshoes when walking on the surface.

FIG. 5 shows an enlarged partial cross-sectional view of a polymeric floor tile before and after treatment according to the present invention. In the left half of the figure, the untreated floor tile 10 has a smooth solid top surface2, and the integrally formed lattice-type structure 20 on the bottom side 14. On either side of the tile are loops 16 and pins 18 which allow the tiles to be interconnected. As shown in the right half of FIG. 5, following treatment by the high voltage electric arc plasma, the top surface 12 is coated with a polyurethane coating 80. Due to the plasma treatment, a bonded attachment forms at the interface 82 between the polyurethane coating 80 and the top surface 12 of the tile.

The polyurethane coating is preferably a two-part aliphatic (solvent based) polyurethane material as is well known in the art, and may be readily obtained from paint and coating retailers, or directly from coating manufacturers. Alternatively, other forms of polyurethane such as water based or water borne polyurethanes may also be used in addition to solvent based forms. It will be appreciated that the specific chemical make-up of the coating to be used may be adjusted for optimum adhesion and other properties depending on the specific polymer substrate and other parameters of the chosen embodiment. Colored coatings of various colors may be used, but for purposes of the present invention the coating is preferably clear (non- pigmented), and is applied in a thickness of from 0.005" to 0.06", with 0.03" preferred.

FIG. 6 shows a schematic diagram of an assembly line manufacturing process for producing floor tiles according to the present invention. An untreated floor tile 90 is placed on a transport means 92 such as a conveyor belt, and is moved in the direction of arrow 94 toward and through a stationary plasma generator mechanism 96. In the preferred embodiment the conveyor belt and corresponding

machines are wide enough to allow the placement of 2 or 3 tiles side by side for simultaneous treatment. While within the plasma generator 96 the tiles are exposed to a plasma field 52 created by electrodes 98. In the preferred embodiment, the electrodes comprise a straight wire 98a, shown here in end view, aligned perpendicular to the direction of travel of the conveyor belt and parallel to its top surface, and a flat metal plate electrode 98b, preferably made of copper, and located immediately beneath and parallel to the conveyor belt, opposite the straight wire.

This straight wire electrode configuration creates an elongated and relatively uniform plasma field across the width of the conveyor belt between the two parallel electrodes. With the belt moving at an optimum rate, the entire surface of a floor tile passing through the field will be uniformly activated.

It will be appreciated that the straight wire and plate electrode configuration of the factory embodiment could also be adapted to the in-place treatment apparatus of FIG. 2. Furthermore, it is known that an effective plasma cloud may be created with a single electrode, whether a wire or other shape, without the need for a second electrode. Such a configuration could be utilized in accordance with the present invention, though it is not presently preferred.

As the factory treatment process continues, after passing through the plasma field within the plasma generator mechanism 96, the activated floor tile 100 moves immediately without stopping toward the polyurethane coating applicator apparatus 102. Therein, the polyurethane material 80 is applied to the top surface of the tile in a spray 106 via a spray apparatus 104, and the coated floor tile 108 emerges. It will be appreciated that for safety reasons the stationary plasma generator mechanism 96 and the polyurethane coating applicator apparatus 102 must be physically separated by a distance sufficient to reduce the risk of fire due to the presence of volatile vapors from the sprayed polyurethane material. It will also be appreciated that the coating process may be performed manually, without the automatic polyurethane coating applicator apparatus 102. In this arrangement a person using a hand-held spray apparatus or other means known in the art for applying polyurethane coatings, manually applies the coating to the activated floor tiles, either continuously or in batches.

Following application of the polyurethane coating, the coating on the tile 108 must be allowed to cure. As will be readily appreciated, the required curing time will depend upon the specific chemical makeup of the polyurethane material used, and may vary from 5 minutes to several days. It will be appreciated that an extremely rapidly curing polyurethane material will be difficult to work with, while a very slowly curing material will tend to unduly impede manufacturing operations.

A preferable coating material will have an unaided curing time of approximately one hour.

Curing of the coating may be hastened by the further provision of a heating station where the tiles are heated to a suitable temperature for a suitable time in order to drive off volatile vapors. As shown in FIG. 6, this process is carried out by the coated tile 108 continuing along the conveyor and through a continuous heating station 110. The heating station comprises heating elements 112 or other means well known in the art for heating the tile as it travels along the conveyor. It will be appreciated that an appropriate temperature for curing will be relatively low, in the range of 140° to 180° f, so as to prevent damage to the tiles. In this temperature range apolyurethane coating with an unaided curing time of approximately one hour may be cured in approximately 10 minutes. The process shown in FIG. 6 will therefore be configured so as to adequately cure the polyurethane coating given the speed of the conveyor and the temperature provided by the heating station. After heat curing, the completed, coated floor tile 114 finally emerges from the process.

As an alternative method, the coated but uncured tiles 108 may be removed from the conveyor and placed into a closed chamber or oven (not shown) for heat curing. Batch curing in an oven is somewhat slower than the process described above, typically taking from 15 to 20 minutes given the same parameters. It will be appreciated that one of the significant advantages of the process depicted in FIG. 6 is that it may be carried out in an ordinary factory environment with no need for vacuum chambers, inert gasses, or other special environments as are required by some of the prior art.

The method and apparatus described herein may be advantageously used to coat a wide array of polymers, including polyolefins such as polyethylene and polypropylene, as well as other polymers such as nylon and even PTFE (teflon) if

desired. The drawings and the foregoing description are not intended to represent the only form of the invention disclosed herein. It will be apparent to one skilled in the art that modifications and variations may be made without departing from the spirit and scope of the present invention. Although specific terms have been employed, they are intended in a generic and descriptive sense only, and not for the purpose of limitation, the scope of the invention being delineated in the claims which follow.