CA1088711A - Multilevel embossing of sheet foam materials - Google Patents

Abstract

MULTILEVEL EMBOSSING OF SHEET FOAM MATERIALS
Abstract of the Disclosure The process herein is used for achieving multilevel mechanical embossing of an expanded foam in register with a printed design on the foam. The foam is not covered by any fused or cured wear layer. An embossed pattern is provided in register with the printed design on the foam layer. A two-stage embossing is carried out. In the first stage of the embossing, a texturing is placed on the raised areas of the foam layer. The second stage embossing provides deep embossing, which would be in register with the printed design on the foam layer. A wear layer is subsequently applied to the embossed product.

Description

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 process for making a foam vinyl floor covering. A printed color pattern or design is provided between a foam resin layer and a transparent resin wear layer. Embossing is carried out relative to the transparent resin layer and the em-bossing 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. Cooling means are provided to cool either one or both sides of the sheet material prior to embossing.
U.S. Patent No. 3,305,419 is directed to an apparatus for embossing a foamed backed polyurethane sheet.
Surface heating is carried out to heat only the surface to be embossed so that there is no damage to the underlying ,foam layer.
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 foamed thermoplastic resin base and a thermoplastic resin top coating. Surface heating of the thermoplastic resin is carried out just prior to embossing.
Summary of the Invention In the inventive process herein, the expansion of a decorated foam is completed in an earlier step in 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. 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 its high surface temperature, while the backing of the sheet and the foam adjacent thereto may or may not be cooled. Appropriate guide structures and controls feed the backing-foam layer structure into an embossing structure which will place an embossed pattern on the foam layer in registry with a printed design on the surface of the foam layer. The embossing structure has a "bottomless" embossing roll configuration and, therefore, will cause deep embossing in selected areas in registry with the printed design, but will not contact those areas which end up as the raised areas of the finished product.
In order for the raised areas of the finished product to have some embossed effect, an embossed texturing roll is incorporated in the guide apparatus to provide a texturing of the raised areas of the finished product. Consequently, two-stage emboss-ing is carried out with the first stage embossing providing only texturing to the raised areas of the foam, while the second stage embossing provides the deep embossing which forms the embossed configuration of the finished product in register with a printed design of the finished product. After the product has been embossed, it is then provided with a wear layer coat-ing which will be subsequently fused or cured.
Thus, in accordance with the present teachings, a process is provided for embossing a web of material when the material is composed of a carrier and a foamed material

-2-10~1711 layer positioned thereon, the foamed material layer having on the upper surface thereof a decorative pattern printed thereon the composition structure being in the form of a web which is heated to a temperature of about 250F to 350F. The process which is provided comprises deeply embossing in a pattern the embossable foamed material layer of the web with a "bottomless"
embossing means to emboss deeply a portion of the web to form depressed areas therein while at the same time not contacting or embossing the raised areas of the web between the depressed areas of the web. Laterally guiding the web to the embossing means so as to provide a registry of the deeply embossed pattern with the printed pattern in a direction transverse to the direction of the web movement. The registry of the deeply embossed pattern is controlled with the printed pattern of the web so that the two patterns will be in registry and wherein the web, prior to the deep embossing by the "bottomless" embossing means is engaged by another embossing means which embosses a surface texture to a substantial portion of the embossable foamed material layer and particularly those portions of the foamed material layer which will not be engaged by the "bottom-less" embossing means.
This invention permits the manufacture of a laminar-flooring material with the incorporation of designs and/or textures having fine details as well as more rounded - 2a 7~1 and deeply embossed relief areas in register with pre-determined portions of a decorative pattern on a foam layer.
Brief Descrip-tion of the Drawing Fig. 1 of the drawing is a schematic showing of the process for carrying out the invention herein; and, Fig. 2 is a cross-sectional view of an inter-mediate floor covering product made by the process of the invention herein.
Description of the Preferred Embodiments The invention herein is an improvement over the process for the manufacturing of the product of U.S. Patent No. 3,741,851 and U.S. Patent No. 3,655,312 and that set forth in Canadian Patent Application Serial No. 248,946.
In the above-mentioned patents, the oven 18 shown in Fig. 2 of U.S. Patent No. 3,741,851, serves to fuse the resin materials and decompose the blowing agent uniformly throughout the area of the product. Thereafter, the web is passed while still hot, for instance while at a temperature of from about 225F. (107C.) to about 325F. ~167C.), to an embossing structure. The invention herein deals with a -modification of the structure of U.S. Patent No. 3,741,851 in the area between oven 18 and the point where there is the embossing structure of the patent. The invention herein utilizes the inventive apparatus of the abovementioned copending application, but involves the use of that apparatus on a foam material which is not provided with a wear layer coating.
Herein, the warm foam web 2, which would mote from the oven structure 3, passes around a conventional guider structure 4 which maintains the registry of the printed pattern of the web with the embossing roll pattern in a direction transverse to the direction of the 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 face will pass under roll 8, with the roll surface in contact with the surface of the web to be embossed. The surface structure of this roll 8 will be further described below.
This roll 8 is usually maintained at a surface temperature of about 85F. to 125F (29C. to 52C.). The assembly 4 is a commercially available "Xamberoller which i~vo-~es 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 "Kamberol1erTMn structure, and this structure is disclosed in U.S. Patent Nos. 3,024,955 and 2,797,091. The only difference between the guider -structure disclosed in the patents and that of this application is in the surface configuration of roll 8 herein and that point will be discussed below. The transverse guiding is used so that the pattern edge of the sheet will be main-tained in a certain relative position to the embossingroll pattern farther down the processing line to provide registry in a transverse direction of the embossing roll - pattern with a printed pattern on the web 2.
The web may then pass over a roller 10, which may be a back wetting structure such as that set forth in United States Patent~4~076,867 and e~titled "Multilevel Embossing of _ .
Foamed-Sheet Materials". Under some circumstances, the cooling feature of roll 10 may-be utilized, and in other circumstances, the cooling feature of roll 10 is not needed and, therefore, roll lQ need only be a steel transport roller. The particular condition of roll 10 is not eritical to the invention herein. Under some cir-eumstances, a "Teflon eoated roller 12 may be utilized to provide additional heat to the top surface of the web to eompensate for heat loss which may occur as the web~is moving through ambient air from the oven 3 towards the embossing structure 14. It is obvious that the roll 12 must not be heated to the point, nor supply sufficient heat to the upper surface of the web 2, to alter the embossed sur-face configuration of web 2 at the point of engagement byroll 12.
An embossing structure 14, composed of a back-up roll 16 and an embossing roll 18 will engage the web to provide deeply embossed relief areas. The web usually is embossed almost as soon as it comes in contact with the steel back-up roll 16. Under some eircumstances, for example, thiek foam produets, it may be desirable to move the em-- bossing roll 18 to a position underneath of roll 16 (see -18'). Under this set of circumstances, the web will be partially wrapped around the steel back-up roll 16 before the embossing is earried out by the embossing roll 18' in its altered position. When embossing is carried out with the embossing roll 18' underneath of the back-up roll 16, the baek-up roll 16 will be eooled by chilled water to a surfaee temperature of about 75F. to 100F. (24C. to 38C.) and will function to further eool the backside of the web and stabilize the foam prior to the time that embossing is earried out. Therefore, the steel back-up roll 16 is funetioning both as a eooling drum and as a baek-up roll for the embossing roll 18'. The embossing whieh is carried out at this point will be through the use of a "bottomless"

10~il~711 embossinq roll. This structure will be very similar to that structure disclosed in U.S. Patent No. 3,741,851. The embossing roll 18 will contain valleys 19 which are con-siderably deeper than the total thickness of the embossable surface of the web 2, but are usually 0.100 inches (.25 cm.) in depth (see Fig. 2). The embossing roll will be kept at 75F. (24C.) surface temperature.
The web 2, as will be described below, will be composed of a backing of about 0.028 inches (.07 cm.) thick.
Over this will be placed a foam layer of about 0.035 inches thick (.09 cm.) thick. The total thickness of the material being embossed will be 0.063 inches (.16 cm.), which is substantially less than the above-described valley depth of the embossing roll 18. Consequently, when roll 18 is providing the deep embossing on the upper surface of the web 2, only the raised areas of the embossing roll 18 will enaage the web 2. The valley areas 19 of the embossing roll 18 will not contact the upper surface 25 of the web.
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 pro-duct so that it can better serve as a floor covering. Con-sequently, the embossable surface, after embossing, is fed around guide roll 26 to place the embossed surface in a generally 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 coater, a roll coater, spray means, or any other convenient means which will provide a thin wear coating overlying the embossed surface. U.S. ~atent No. 3,828,725 covers a curtain coating method which can be used in the application of a polyurethane coating to a moving embossed foam. The sheet with the wear layer is then passed to a heating 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 of roll 18 with a printed pattern on the web 2, there must be control of the embossing roll pattern relative the printed pattern to get registry between the two patterns.
This will require registration along the machine direction and this registry along the machine direction, which is in the direction longitudinally 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. 3,694,634 and U.S. Patent No.

3,741,851 can be adopted herein for machine direction registry also. 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 printed 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 ~s in the modi-fication of roll 8 of guider structure 4. The surface of roll 8 is provided with a textured or design carrying con-figuration. In e~fect, roll 8 is being used as an embossing roll which will place shallow patterns on the upper surface of the web 2. The pattern placed on roll 8 could be of a certain specific design, or it could simply be an irregular dimpled surface used simply to provide a texturing to the upper surface of the web 2. Roll 8 will have an embossing surface or texturing which will have a difference of 0.015~0.030 inches (.04 cm.-.08 cm.) between the raised 10~711 areas and valley areas of its embossing configuration. This roll 8 will be kept fully impressed against the web surface.
The roll 8 will be kept at a temperature of 85F.-125F.
(29C.-52C.) with the web surface at 275F.-325F. (135C.-163C.). Due to the positioning of rolls 6 and 10 with the web 2 passing thereover, the web 2 will be held tightly in engagement with roll 8 so that roll 8 will be able to provide a textured embossment to the upper surface of web 2.
The depth of embossing typically obtained during this overall embossing step is 0.012 inches (.03 cm.) due to spring-back in the material. As the textured web moves to the embossing means 14, the "bottomless" embossing roll structure 18 will not disturb the texturing on the raised areas of the web wherein deep embossing is not carried out.
Referring now to Fig. 2, there is a cross-sectional view of a portion of web 2. The upper surface of web 2 is to be embossed and this is the upper part of foam layer 22.
Roll 8 will provide surface texturing 24 on the total surface of the embossed product and this appears on the raised areas of the embossed product after the "bottomless"
embossing roll 18 has produced the deep embossing 26. In addition, the deep embossing 26 will be placed on the web without the em~bossing roll 18 disturbing the original texturing 24 that roll 8 had previously placed on the web. The texturing 27 will even appear in the valley areas 26 of . the final embossed product. The areas 26 can be embossed to a depth of 0.020 inches (0.05 cm.) while still retaining the texture 27.
It is possible that the material of U.S. Patent No. 3,741,851, without its wear layer, could come from the oven 18 of that patent and pass through all of the apparatus of that patent with only one slight 108~711 modification in that apparatus to yield the product of Fig. 2 herein. In the structure of U.S. ~atent No.
3,741,851, a "Kamberoller , a lateral guide structure, would be utilized and the second roll thereof would be provided with texturing as roll 8 herein. In the structure of U.S. Patent No. 3,741,851, there is the indication that only 25% of the total sheet area can be embossed, whereas, with the structure herein, it is possible to emboss, by the use of both texturing and deep embossing, the full 100% sheet surface area.

A typical example of a product which may be made by the invention herein is below described. The product will be made by placing a plastisol on a carrier web such as that disclosed in U.S. Patent No. 2,759,813. The following plastisol is prepared by thoroughly mixing the following ingredients:
- Ingredients Parts by Weight 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 having a thickness of about 0.028 inches (.07 cm.).

The plastisol is applied with a reverse roll coater to a wet thickness of 10 mils (.03 cm.). The plastisol-coated 30- backing is gelled in a hot air oven for one minute to an exit temperature of 270F. (132C.).

-_ g _ The sheet is then coo1ed and a printed design isplaced thereoll. The printed design may be of any particular pattern and could be of the same pattern as that shown in Fig. 3 of U.S. Patent No. 3,741,851. Inks are prepared by thoroughly mixing the following ingredients:
Ingredients Parts by ~7eight Vinyl binder 33.0 Pigment 12.8 Cellosolve acetate 1.6 2 Nltropropane 50.0 - Isopropyl acetate 1.0 Alkyl alcohol aryl polyether1.0 Inks of various colors based on the above formula are applied to the gelled plastisol sheet described above utilizing the printlng cylinders of a conventional roto-gravure 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 sheet 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 o~ 375F. (191`C.) 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 temperatu~e of 375F. (191C.) to lOli~711 ~roduce the fully foamed product which would then subsequently be printed. Re~eating for embossing can be done later iust prior to embossing.
After the printing of 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 layer, a foamlayer and a printed design thereon will constitute web 2 of the drawing. The web 2 will then be processed through the apparatus as above described to provide surface texturing with roll 8, to provide deep embossing with roll 18, and then a wear coating through the use of elements 28 and 30.
There is now provided after embossing a product - which is composed of a backing and a foam layer which has embossing therein in register with the design which is 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 had some type of wear layer applied thereto. ~eb 2, now fully embossed, will then pass by a coating apparatus 28 which will provide a wear layer material to the embossed web 2 and then the 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 materials which have been utilized in the floor covering art. About the only limitation that exists relative 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 10~ 7:11 configuration deteriorates. If the fusion or curing of the wear layer is carried out under the 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 the foam. However, these higher temperatures are only utilized for a short period of time and are applied primarily to the wear layer coating and are not permitted to cause a raising of the foam level temperature to a point where the foam will be affected by the temperature.
Example 1 Typical of a clear poly(vinyl chloride) wear layer coating that can be utilized is:
For~ula 1 Ingredi-ents Parts by Weight Poly(vinyl chloride) copolymer100.00 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 curtain coater head cavity described in U.S. Patent 3,828,725 does not ~ontain, 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 10~bt711 embossed, as is shown in Fig. 1, whereby the wear layer is fused utilizing 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 (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 surface and eliminate the need for subsequent waxing by the user of the floor.

Claims (3)

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 composition structure being in the form of a web which is heated to a temperature of about 250°F. to 350°F., the process comprising:
(a) deeply embossing in a pattern the embossable foamed material layer of the web with a "bottomless" em-bossing means to emboss deeply a portion of the web to form depressed areas therein while, at the same time, not con-tacting or embossing the raised areas of the web between the depressed areas of the web, (b) laterally guiding the web to the embossing means so as to provide a registry of the deeply embossed pattern with the printed pattern in a direction transverse to the direction of web movement, (c) controlling the registry of the deeply embossed pattern with the printed pattern of the web so that the two patterns will be in registry, and (d) the improvement in the above process wherein the web, prior to the deep embossing by the "bottomless"
embossing means, is engaged by another embossing means which embosses a surface texture to a substantial portion of the embossable foamed material layer and particularly those portions of the foamed material layer which will not be engaged by the "bottomless" embossing means.

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 for embossing a web of material as set forth in claim 1 wherein there is the further step of:
(a) carrying out the deep embossing without destroying at the point of deep embossing the surface texture previously placed on the web.