CA1088712A - Multilevel embossing of a foam sheet - Google Patents

Abstract

MULTILEVEL EMBOSSING OF A FOAM SHEET
Abstract of the Disclosure The process herein is used for achieving multilevel mechanical embossing of an expanded foam in register with a print on the foam. The foam is not covered by any fused or cured wear layer. The expansion of the decorative foam and printing of a design thereon are carried out in conventional apparatus and then the back of the foam is cooled by back wetting with or without drum cooling. The upper embossable surface of the foam is maintained at a high temperature for embossing and is embossed in registry between the embossed pattern and the printed pattern on the foam. A wear layer is subsequently applied to the embossed product.

Description

10~71Z

Background of the Invention Field of the invention The invention is directed to a process for manu-facturing floor covering material and, more particularly, to a process for the mechanical embossing of a pattern on a floor covering material.
Description of the Prior Art U.S. Patent No. 3,741,851 discloses a product and process which deals with a foamed vinyl floor covering. A
printed color pattern or design is provided between the foam resin layer and a transparent resin layer. Embossing is carried out relative to the transparent resin layer and the embossing is carried out in register with the printed pattern.
U.S. Patent No. 3,176,058 is directed to an apparatus for embossing sheet material. Water cooling means are provided to cool either one or both sides of the sheet prior to embossing.
U.S. Patent No. 3,305,419 is directed to an apparatus for embossing a -foa~bac~-ed polyurethane sheet. Surface heating is carried out to heat only the surface to be embossed so that there will be no damage to the underlying foam material.
Finally, U.S. Patent No. 3,196,062 is directed to a process wherein cooled embossing rolls are utilized to provide an embossed pattern on a sheet material which is composed of a foamable thermoplastic resin base and a thermo-plastic resin top coating. Surface heating of the thermo-plastic resin is carried out just prior to embossing.
- Summary of the Invention In the inventive process herein, the expansion of a 71~

decorated foam and the printing of a design thereon are com-pleted in an earlier step of the same manufacturing process in which the embossing is to be carried out. In other words, the embossing operation is carried out at the end of the processing line which forms the expanded foam product with the design printed thereon. The expanded foam sheet product is carried on a backing, but does not have any fused or cured wear layer on the surface of the foam to be embossed. The surface of the foam to be embossed is maintained at a high surface temperature while the backing of the sheet and the foam adjacent thereto is cooled by the combination steps of back wetting and drum cooling, or simply by back wetting alone. Appropriate guide structures and controls feed the combination backing and foam layer into an embossing structure so that the embossing pattern will be placed on the foam layer in registry with the printed design on the surface of the foam. Due to the back wetting and~or cooling, there will be a ~5F. to 150F. (30C.-65C.) differential between the surface of the foam being embossed and the back layer of the foam which is displaced away from the surface being embossed. After the product has been embossed, it is then provided with a wear layer coating which will be subsequently fused or cured.
Utilizing this invention, in conjunction with shallow embossing rolls having a great area of surface embossing, mechanical embossing capabilities with controllable embossing depths and visual end products or foam structures are enhanced considerably over that found in the prior art. In addition, the combination of back wetting and drum cooling permits increased production capacities as well as provides for multi-level embossing of thick foam products.

71~

Thus, and in accordance with the present teachings, an improvement is provided in a process for embossing a rubber material wherein the material is composed of a carrier and a foamed material layer positioned thereon with the foamed material layer having on the upper surface thereof a decorative pattern printed thereon and the composite structure is in the form of a web which is heated to a temperature of about 250F to 350F.
The improvement which is provided comprises wetting the carrier of the web, which is the back surface of the web, so as to lower the temperature of the back surface of the web approxi-mately 100 below the top surface of the web, which is the upper surface of the foamed material. A pattern is embossed on the upper surface of the foamed material layer and the registry of the embossed pattern is controlled with the printed pattern of the web so that the two patterns will be in registry.
The embossed surface of the foamed material is cooled to set the embossed pattern in the layer. If desired, a wear coat may be applied to the embossed surface and subsequently fused.

1~

- 2 a -10l~7~Z

Brief Description of the Draw nq -The figure of the drawing is a schematic showing of the process for carrying out the invention herein.
Description of the Preferred Embodiments The invention herein is a process for manufacturing a product similar to that set forth in U.S. Patent No.

3,741,851 and U.S. Patent 4,076,867. In both the above patents, an oven serves to fuse resin materials and de-compose a blowing agent uniformly throughout the area of the product. Thereafter, the web, while still hot, for instance while at a temperature of about 225F. (107C.) to about 325F. (163C.), is fed to an embossing structure. The invention herein deals with a modification of the web being processed in the above-mentioned patents.
The web 2 herein, which will be moving from an oven structure, will be composed of only a backing layer and a foam layer. The wear layer, which is disclosed for the product of the above mentioned patents, will not exist in the web 2 of the application herein. The warm web 2 passes around a conventional guider structure 4 which simply maintains the registry of a printed pattern on the web with the embossing roll pattern in a direction trans-verse to the directionof web movement. The guider structure is composed of two guide rolls 6 and 8. The back of the web will pass over roll 6 and then the web will pass under roll 8 with the roll surface in contact with the surface of the web to be embossed. This surface will be quite warm and, therefore roller 8 should be covered with a "Teflon TM~ coating to prevent sticking of the upper embossable surface of the foam against the surface of roll 8. This roll 8 is usually maintained at a surface temperature of 200F. (93C.) to ~- -3-10~7~;~

250F. (121C.) in order to maintain a hot embossable surface.
The assembly 4 is a commercially available "KamberollerTMn which involves two angled guide rolls on a carriage mounted for transverse movement. The transverse guiding of the sheet is carried out through the use of the "KamberollerTM", but could equally well be carried out by simply the use of guide bars which are placed along the edge of the web and would guide the web edge and, therefore, the pattern edge relative to the embossing roll farther down the processing line.
The web then passes over a back wetting structure 10 which is preferably a felt-covered roll 12 partially immersed in a bath of liquid 14. The felt-covered roller 12 of the back wetting structure 10 could be replaced by a steel roller, or even a water spray system. The back wetting structure applies water to the back side of the web, that is, the area of the web not to be embossed, so as to cool the back side of the web and stabilize the hot thermoplastic foam next to the back side of the web. The application of the water and its evaporation from the back side of the web cools the back side of the web and its adjacent foam layer to 135F.
(57C.) to 200F. ~93C.) by the time the web enters the embossing apparatus. The rate of water application is governed by the quantity of heat to be removed from the hot thermo-plastic foam next to the back side of the web to keep the printed foam from distorting and blistering at the embossing nip. Meanwhile, the upper surface, the embossable surface of the web, is at about 210F. (99C.) to 300F. (149C.).
Under some circumstances, a "Teflon " coated roller 16 may by utilized to provide additional heat to the top surface of the web to compensate for heat loss which may occur as the web is moved through ambient air from the oven towards the embossing structure.

10~1~712 The embossing structure will be composed of a back-up roll 20 and an embossing roll which may be the embossing roll 22 positioned as shown in the drawing. In this situation, the web is embossed almost as SOOII as it comes in contact with the steel back-up roll 20. Under some circumstances, it may be desirable to move the embossing roll to the position 24 shown in the drawing. Under this set of circumstances, the web will be partially wrapped around the steel back-up roll before the embossing is carried out by the embossing roll 24.
When embossing roll 24 is used in lieu of roll 22, the back-up roll 20 will be cooled by chilled water to a surface temperature of about 75F. (24C.) to 100F. (38C.) and will function to further cool the back side of the web prior to the time that embossing is carried out. Here, steel back-up roll 20 is functioning both as a cooling drum and as a back-up roll for embossing roll 24. Since back wetting is done prior to embossing, the depth of the embossing roll, as it would be in either position 22 or 24 can be quite shallow. Embossing rolls containing engraved designs as shallow as 10 mils in depth have been used successfully in this invention. Also, a partial wrap of embossing roll 24 may be needed to impart to the hot wear layer an intricate and multilevel embossing design.
Since the product that has been embossed is basically an expanded foam, carried on a backing layer, there is a need to provide some type of wear surface to the embossed surface so that it can better serve as a floor covering.
Conseguently, the embossable surface, after embossing, is fed around guide roll 26 to place the embossed surface in a general horizontal plane with the embossed surface facing upward. Means 28 will then provide a wear coating to the embossed surface. The coating may be applied by a curtain 71;~

coater, a roll coater, spray means, or any other convenient means which will provide a thin wear coating overlying the embossed surface. U.S. Patent, 3,828,725 covers ~ curtain coating method which can be used in the application of a wet polyurethane coating to a moving embossed foam. The sheet with the wear layer is then passed to means 30 which will either fuse or cure the wear layer on the embossed foam surface.
Since there is a need to register the embossing pattern with a printed pattern on the web, there must be control of the embossing roll pattern relative the printed pattern to get registry between the two patterns. This will require registry along the machine direction and this registry along the machine direction or in the direction longitu-dinally of the sheet movement is maintained in the same manner as set forth in U.S. Patent No. 3,655,312, Column 5, line 53, to Column 6, line 43. The technique of U.S. Patent No.
3,698,634 and U.S. Patent No. 3,741,851 can be adopted herein - for machine direction registr`y also. Finally, registry in the machine direction can be secured using Model R-500 Digital Control and Model R-425-1 Feathering Drive Control of "Registron u Dlvision of Bobst Champlain, Inc. At this point, it should be noted that registration controls, both across the machine direction and along the machine direction, are necessary to secure a commercially acceptable product with registration between the embossed pattern and the print~d pattern, but such controls are not a part of the invention herein since they are conventional in the art. The essence of the invention herein is in the utilization of the back wetting with or without a cooled back-up roll for the purpose of cooling the back side of a web and its adjacent foam while still permitting the embossable surface of the foam to be 10t~71Z

maintained at a temperature such that embossing can be carried out in registry with a printed design on the top layer of the foam. For foam webs having considerable thickness (.100-.120 inches (.25 cm.-.31 cm.)) and which retain their internal heat, it has been found that an additional back wetting structure 10 is needed and will be positioned prior to the conventional guider structure 4 in order to permit embossing of these web~ without blistering. Should the material of U.S.
Patent No. 3,741,851, without its wear layer, be utilized through the apparatus generally described above, and no back wetting or cooling be carried out, it has been found that the web will enter the embossing roll nip with a surface temperature on the embossable surface of 220F. (104C.) and a temperature on the back of the web, the non-embossed surface, of about 270F. (132C.). Under these conditions, the center of the foam of the web will be measured at about 300F. (149C.) and this is an ideal situation for blistering within the foam layer. Blistering produces an unacceptable product. It should be noted that the embossing rolls of U.S. Patent No.
3,741,851 have "bottomless" embossing roll valleys and, therefore, do not emboss the web except with the embossing roll land areas. In the embossing roll structure 22 or 24 herein, both the roll land and valley areas make contact and emboss the web. This increased area of embossing is a capability of the structure herein and is not possible in the structure of U.S. Patent 3,741,851. Also, in the structure of U.S.
Patent No. 3,741,851, the embossing area can only be 25~
of the total sheet area, whereas in the embossing structure herein, the embossing area can go to 80% to 90% of the total sheet surface area. Normally, the embossing area covers 30%
to 90% of the total sheet surface area. In operation, the embossing rolls, either roll 22 or 24, would be maintained 7~Z

cold at about 75F. (24C.) to 100~. (38C.) to freeze in the desired pattern which is being embossed in the web. There may be partial wrapping of roll 24 if necessary to achieve the desired pattern effect.
The material described in U.S. Patent No. 3,741,851, ! with the wear coat eliminated, could come from the oven 18 of that patent and pass through appropriate guiding structures and by back wetter 10 and directly to back-up roll 20 and embossing roll 22, and can be embossed without any blistering 10, in the end product, with ~e~y good registration between the embossed pattern and the printed pattern, and with embossing carried out so that there is bottoming out of the embossing roll against the embossed surface of the web. Cooling of the back surface of the web prior to embossing directly attributes to the lack of blistering and the ability to carry out a "bottoming out" of the embossing roll while still maintaining registration.
Even though this invention can provide for unique embossed designs on wear layers composed of vinyl formulations as described in U.S. Patent No. 3,741,851, the embossing of additional materials is possible. ~or example, a product can be made by placing the following plastisol on a carrier web such as that disclosed in U.S. Patent No.
2,759,813. The plastisol used is prepared by thoroughly mixing tbe following ingredients:
Ingredients Parts by We-ight Poly(vinyl) chloride 100 Dioctyl phthalate (plasticizer) 49,55 Octyl epoxy tallate (stabilizer) 5,0 Titanium dioxide 3.6 Azodicarbonamide ~blowing agent) - 2.3 Talc 0.6 Zinc octoate (blowing agent activator) 1.95 This above plastisol is applied to the above-described carrier which is a coated beater-saturated asbestos sheet 71;~

having a thickness of about 0.028 inches. The plastisol is applied with a reverse roll coater to a wet thickness of 10 mils (.03 cm.). The plastisol-coated backing is gelled in a hot air oven for one minute to an exit temperature,of 270F.
(132C.).
The sheet is then cooled and a printed design is placed thereon. The printed design may be of any particular pattern and could be of the same pattern shown in Figure 3 of U.S. Patent No. 3,741,851. Inks are prepared by thoroughly mixing the following ingredients:

Ingr-edients Parts by Weight Vinyl binder 33.0 Pigment 12.8 Cellosolve acetate 1~6 2 Nitropropane 50,0 Isopropyl acetate 1.0 Alkyl alcohol aryl polyether 1.0 Inks of various colors based upon the above formula are applied to the gelled plastisol sheet described above, utilizing the printing cylinders of a conventional rotogravure printing press. The printing cylinders are run in a normal manner producing the design that is printed in register. The inks are dried by'subjecting the printed sheets to warm air impingement supplied by the enclosed drying zones of the press. The inks are not critical to the invention herein, but simply need be inks which are capable of adhering to and drying on the plastisol above described.
At this point, the plastisol may be subjected to further heat in a hot air oven for 1 minute to an exit temperature of 375F. (191C.) to complete the decomposition of the blowing agent in the gelled plastisol coat to convert it to a foamed layer. It is also possible to eliminate this second heating operation by passing the plastisol coated backing through a hot air oven and almost completely decompose the blowing agent prior to the printing operation. In these circumstances, the hot air oven would be utilized for 1 minute to an exit temperature of 375F. (191C.) to produce the fully foamed product which would then subsequently be printed. Reheating for embossing can be done later just prior to embossing.
After the printing on the gelled plastisol has been carried out and this structure has passed through an oven to complete the decomposition of the blowing agent to convert the plastisol to a foam layer, embossing can be carried out.
The printed and foamed layer will leave the oven at -about 300F. (149C.~. Coming from the oven, the above-described composite sheet composed of a backing sheet, a foam layer and a printed design thereon would constitute web 2 of the drawing. The web 2 would move past appropriate across-machine guide structures towards back wetting structure 10.
The backing of the web 2 will be wetted and the evaporation of the liquid therefrom will cool the backing to a temperature substantially below that of the foam face of the web 2.
"Teflon " coated heated roll 16 (200F.-250F.) is provided to engage the upper surface of the sheet and supply heat thereto if needed and cause the sheet to partially wrap it-self around back-up roll 20. The web passes on to back-up roll 20 and embossing roll 22 to be embossed. The embossing roll would be maintained at about 75F. (24C.) surface temperature and the back-up roll would also be maintained at about 75F. to 100F. (24C. to 38C.) surface temperature.
The product, as it passes between the nip of the embossing roll, which is the area between roll 22 and roll 20, will have the top surface of the foam layer at about 250F. (121C.).
The back wetting will have cooled the temperature of the backlng or carrier and the foam adjacent thereto to a bl71Z

temperature of about 150F. to 200F. (66C. to 93C.). The cold embossing rolls would immediately freeze the desired embossed pattern into the foam at the time the embossing is carried out. The thickness of the web described above will be about 60 mils (.15 cm.). The embossing pattern on the embossing roll will comprise 55~ to 60% of the total roll surface and the depth of pattern on the roll is about 15 mils (.04 cm.). Full embossing is carried out with both the land areas and valley areas engaging the web surface.
Due to the spring back of the material, the end product has an embossed depth of 15 mils (.04 cm.). The foam layer will be compressed in the valley embossed areas and be un-cQmpressed in the unembossed areas.
It has been found that with conventional poly(vinyl chloride) foams of a thickness in excess of 80 mils (.2 cm.), it may be desirable to move the web partially around the back-up roll 20 and position the embossing roll at the point of embossing roll 24. Under this set of circumstances, at the time of embossing, the surface of the foam to be embossed will be 200F.-230F. (93C.-110C.), while the back side of the foam adjacent the carrier or backing will be about 125F.
to 150F. (52C. to 66C.). The wrapping of the web around the cooled back-up roll 20 will provide this increased reduction in the temperature of the back of the web as well as prevent slippage of the web during machine direction registration o the embossing roll to the printed pattern. The embossing rolls will have considerable detail and will require the roll 24 to be partially wrapped to achieve the desired pattern effect. The partial wrap is accomplished by the use of roll 26 which causes the web to partially wrap around roll 24. In all cases, the embossing will be carried out in register with the printed design on the foam.

1~)i 3~7~

There is now provided a product which is composed of a backing and a foam layer which has embossing therein in register with the design which was printed on the foam.
Such a product might be acceptable for use as a wall covering, but certainly would not work satisfactorily as a floor covering unless it has some type of wear layer applied thereover. The web 2 now fully embossed will then pass by a coating apparatus 28 which will apply a wear layer to the embossed web 2 and then the wet web will pass through heater 30 which will fuse or cure the wear layer just applied. The wear layer used may be any of-the conventional wear layer structures which have been utilized in the floor covering art.
About the only limitation that exists relative to the wear layer is that the fusion or curing temperature of the wear layer must be low enough that the temperature utilized will not cause destruction of the foam layer or relaxation of the embossed pattern in the foam so that the embossed configuration deteriorates. If the fusion or curing of the wear layer is carried out under a circumstance where the total web is heated, then the temperature of fusing or curing clearly must be low enough so that deterioration of the foam does not occur. If the curing or fusion of the wear layer is carried out by a surface heating which is directed just to the wear layer, then higher temperatures may be utilized. By higher temperatures is meant temperatures which would normally be expected to affect ~he foam. However, these higher temperatures are only utilized for a short period of time and are applied primarily to the wear coat and are not permitted to cause a raising of the foam level temperature to a point where the foam will be effected by the temperature. --Example 1 Typical of a clear poly(vinyl chloride) wear layer ~01il8712 coating that can be utilized is:
Formula 1 Ingrèdients Parts by Weight Poly(vinyl chloride) copolymer 100.00 Dioctyl phthalate (plasticizer) 60.00 Octyl epoxy tallate (stabilizer) 3.00 Barium cadmium zinc (stabilizer) 3.00 This wear layer composition is applied to a fully embossed web 2, which is 0.060 inches (.15 cm.) in thickness, by a conventional curtain coating apparatus 28 to a film thickness of 0.006 inches (0.015 cm.). In this case, the cur-tain coater head cavity described in U.S. Patent 3,828,725 t does not contain, when used herein, the flow restricting device due to the higher viscosity and solids levels of the above plastisol wear layer formulation. The wet coating can be applied in a continuous manner after the foam layer is embossed, as is showr. in Fig. 1, whereby the wear layer is fused utiliz-ing a hot air heater 30 which is directed towards the top surface of the web 2. Typical fusing conditions require hot air impingement for 1/2 minute with the air at 500F.
(260C.). Alternately, the embossed foam 2 can be cooled by rolls 32, bypassing coater 28 and heater 30 and wound onto spindle 34. At some future time, and possibly in another location, the wear layer coating can be applied to the embossed foam by a similar coating apparatus 28 and fused by similar types of surface heaters 30. In the case of the clear poly (vinyl chloride) wear layer applied in the manner as described above, a resilient floor covering material is produced which has a depth of embossing of 0.010 inches (.025 cm.) after the wear layer is fused.

Example 2 Example 1 was repeated wherein a thin adhesive coating of Formulation 2 below was applied to the 0.006 inch 1()~il~71Z

(0.015 cm.) fused plastisol wear layer of Example 1 and dried with heater 30 using 140F. (60C.) air. In this case, a fully embossed 0.080 inch (.203 cm.) foam was used in the experiment.
Formula 2 .......
Ingredients Parts by Weight Poly(vinyl chloride) solution grade 30.00 Xylene 21.00 Methyl ethyl ketone 48.64 Thio-tin (stabilizer) (Thermolite-31) 0.36 Onto this layer was applied a clear 2 mil (dry) coating of a curable polyurethane utilizing the invention described in U.S. Patent 3,828,725. The polyurethane coating is a 62.5/37.5 xylene/resin solution containing catalyst.
The polyurethane coating can also be applied by employing conventional airless spray equipment. Criticality does not particularly rest in the method by which the wear layer coating is applied. Heat is applied in the form of hot air impingement utilizing heater 30 for a period of 3 minutes at 275F.
(149C.) air temperature. The last coating applied is the wear layer surface of the resulting floor product which will be formed. Polyurethane coatings are applied to secure a product which will retain a hard, high gloss surfacè and eliminate the need for subsequent waxing by the user of the floor.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for embossing a web of material wherein said material is composed of a carrier and a foamed material layer positioned thereon, said foamed material layer having on the upper surface thereof a decorative pattern printed thereon, said above composite structure being in the form of a web which is heated to a temperature of about 250°F
to 350°F the improvement comprising:
(a) wetting the carrier of the web, which is the back surface of the web, so as to lower the temperature of the back surface of the web approximately 100° below the top surface of the web, which is the upper surface of the foamed material layer, (b) embossing a pattern on the upper surface of the foamed material layer, (c) controlling the registry of the embossed pattern with the printed pattern of the web so that the two patterns will be in registry, and (d) cooling the embossed surface of the foamed material layer to set the embossed pattern in said layer.

2. The process for embossing a web of material as set forth in Claim 1 wherein there are the further steps of (a) applying a wear coat to the embossed surface, and (b) fusing or curing the wear coat.

3. The process of Claim 1 wherein:
(a) a heating means heats the embossing top surface of the web just prior to embossing.

4. The process of Claim 1 wherein:
(a) the embossing step is carried out by an embossing means with both the land areas and valley areas of the embossing means contacting and impressing a pattern on the top surface of the web.

5. The process of Claim 1 wherein:
(a) the web of material, after back wetting, is passed partially around a cooled drum which engages the carrier or back surface of the web to cool said surface of the web prior to the time that the embossing step is carried out.

6. The process of Claim 1 wherein:
(a) the embossing step is carried out with a cold embossing roll and the web of material is wrapped partly around the embossing roll.

7. The process of Claim 2 wherein:
(a) the wear coat which is applied to the embossed surface of the web is placed on the web in such a manner as to maintain the embossed configuration of the web, yet cover the total web surface, and said wear surface is subsequently solidified to provide the web with a composite structure consisting of a carrier, a wear coat, and there-between an embossed foamed material layer with the embossing thereon in registry with the printed pattern on the foamed material layer.