WO1994017996A1

WO1994017996A1 - Self-induced tension surface covering having a wear surface face-in roll packaging

Info

Publication number: WO1994017996A1
Application number: PCT/US1994/000605
Authority: WO
Inventors: C. David Wang; Hao A. Chen
Original assignee: Mannington Mills, Inc.
Priority date: 1993-02-08
Filing date: 1994-02-02
Publication date: 1994-08-18
Also published as: AU6124894A

Abstract

A self-induce tension surface covering has a cross-linked, thermoset wear layer and a backing layer. The self-induced tension surface covering is packaged in a roll with the wear surface rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling or decrease post-installation thermal buckling as compared to rolling the surface covering with the wear surface facing outward.

Description

DESCRIPTION

SELF-INDUCED TENSION SURFACE COVERING HAVING A WEAR SURFACE FACE-IN ROLL PACKAGING

Field of the Invention

The present invention relates generally to a self- induced tension surface covering and, more particularly, to a self-induced tension floor covering, which is packaged in a roll with the wear surface facing inward. The present invention also relates to a method for packaging a self- induced tension floor. Description of Related Art

Self-induced tension surface coverings, preferably self-induced tension floor coverings, also known as shrink flooring, are well known in the art. The prior art has recognized that self-induced tension surface coverings, which have stresses built into the surface covering, can be utilized by installing the surface covering to an underlying surface at the perimeter of the surface covering only, so that the tension caused by the stresses in the surface covering create an installed surface product having a self- induced tension built therein.

Shrink flooring has a number of advantageous features including ease of installation, less subfloor preparation than other types of flooring materials, high flexibility, and the ability to maintain a flat, taut surface despite the movement of objects across the outer surface of the shrink floor, such as furniture or people. Examples of self- induced tension floor coverings can be found in U.S. Pat. No. 3,464,178 to Deichert et al.; U.S. Pat. No. 3,990,929 to Evans; U.S. Pat. No. 4,135,675 to Greiner, Jr. et al. ; U.S. Pat. No. 4,159,219 to Evans; U.S. Pat. No. 4,920,720 to LaBianca; and U.S. Pat. Appln. Serial No. 07/758,621 filed September 12, 1991 to Wang et al.

These patents suggest that after manufacturing but prior to installation, a shrink flooring sheet be packaged by rolling it face-out around a core. "Face-out" refers to a sheet being rolled such that the wear surface is facing away from the core or center of the roll. Thus, compared to the backing layer, the wear surface is further away from the core or center of the roll. The term "face-in" is the opposite of "face-out." More particularly, "face-in" refers to a sheet being rolled such that the wear surface is facing the core or center of the roll, that is, the wear surface is closer to the core or center of the roll than the backing layer. It is understood that the sheet is rolled in the machine direction.

The art has rolled face-out to achieve a greater amount of stretch in the outer rolled layers, particularly in the wear layer(s) and possibly the decorative layers. Evans, U.S. Pat. No. 3,990,929, discloses that it is customary during packaging to roll the sheet goods with the vinyl wear layer face-out. This tends to stress the wear layer and, in fact, causes elongation to a limited extent building further stresses into the wear layer. LaBianca, U.S. Pat. No. 4,920,720, discloses that the shrink flooring is rolled face-out around a core. Floor Covering Weekly, June 17, 1991 at page 10, discloses that when handling flex flooring, it must be tightly rolled, face-out, with a 4-inch to 6-inch diameter cardboard tube as a core.

Installation and Cleaning Specialists. January 1992, page 32, discloses that transporting and storing flex floors can be very unforgiving of carelessness and/or neglect. They must always be stored and transported rolled face-out on cores. Additionally, floor covering manufacturers' instruction manuals disclose that the shrink floor must be rolled face-out.

Both Greiner, Jr. et al., U.S. Pat. No. 4,135,675 and Evans, U.S. Pat. No. 4,159,219, which are directed to thermoplastic vinyl resin-containing surface coverings, disclose that the respective layers may be so designed that the sheet may be rolled with the decorative layer facing outward or inward in the roll depending on the elongation and compression characteristics of the layers. However, both Greiner, Jr. et al. '675 and Evans '219 further disclose that when sheet flooring produced in accordance with Examples 1 and 2 of each of those patents were rolled face-in, the sheets grew on unrolling and buckled in a fluctuating environment after installation by securing the sheets at their peripheries over a wooden subfloor. Moreover, neither of these two patents disclose a cross- linked, thermoset wear layer.

The prior art also did not roll shrink floors face-in due to concerns of creating positive edge curl and/or piping or elephant skin wrinkles. In addition, it was more convenient to have the decorative layer facing outward so that it was visually exposed to the retail customer.

The art thus teaches that shrink flooring should be rolled face-out. The art additionally teaches away from rolling face-in due to buckling and other problems.

In order to achieve particular wear layer properties, some shrink flooring materials utilize a cross-linked, thermoset wear layer. As compared to shrink floors not encompassed by the instant invention, shrink floors having a cross-linked, thermoset wear layer tend to have less contractability or a slower rate of contraction to remove any initial installation buckles that are caused by product distortion created during handling, cutting, and fitting. Additionally, shrink floors having a cross-linked, thermoset wear layer tend to buckle as the temperature increases from the installation temperature to a higher in-use temperature. As the in-use temperature increases the buckling increases. This thermal buckling occurs because the cross-linked, thermoset wear layer is more dimensionally s-able than the other layers of the shrink flooring. This wear layer does not shrink as much as the other layers and tends to cause the buckling in the overall shrink floor. Generally, the thermal buckling problem is most pronounced when a shrink floor that has a cross-linked, thermoset wear layer is packaged in a roll with the wear surface facing out, and is subjected to a thermal expansion after installation.

Therefore, there has been a need in the art to overcome the problems experienced with a shrink floor that has a cross-linked, thermoset wear layer, because these shrink floors can manifest an initial installation buckle and can be subjected to a large post-installation temperature increase, which results in unsightly buckling problems.

SUMMARY OF THE INVENTION

One object of the invention is to solve the problems of the prior art, wherein a shrink floor having a cross-linked, thermoset wear layer initially buckles upon installation due to product distortion created during handling, cutting, and fitting.

Another object of the invention is to solve the problems of the prior art, wherein a temperature increase occurring after installation causes a buckling of a shrink floor having a cross-linked, thermoset wear layer.

Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, one embodiment of the invention comprises a self- induced tension surface covering comprising a cross-linked, thermoset wear layer and a backing layer. The self-induced tension surface covering is packaged in a roll with the wear layer rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling or decrease post-installation thermal buckling. Face-in rolling for packaging the shrink floor after manufacturing and prior to installation results in the reduction and/or elimination of initial installation buckling and heat buckling problems in shrink floors of the invention.

Another embodiment of the invention comprises a method for packaging a self-induced tension surface covering. The self-induced tension surface covering comprises a cross- linked, thermoset wear layer and a backing layer. The method comprises the step of rolling said self-induced tension surface covering with the wear layer rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling or decrease post-installation thermal buckling.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying Figures, which are incorporated in and constitute a part of this specification, illustrate several features of the invention and together with the description, serve to explain the principles of the invention.

Figure 1 shows the difference between negative and positive edge curl as discussed herein.

Figure 2 shows the package effect on lay flat property for a shrink floor of one embodiment of the present invention rolled face-in versus face-out at 70°F.

Figure 3 shows the package effect on lay flat property for a shrink floor of one embodiment of the present invention rolled face-in versus face-out at 90°F.

Figures 4A to 7A show the shrinkage after unrolling of the face side of a shrink floor type A, the back side of a shrink floor type A, the face side of a shrink floor type B, and the back side of a shrink floor type B, respectively, for face-in versus face-out rolling and for the machine versus cross machine direction. Figures 4B to 7B show the available shrinkage after installation of the face side of a shrink floor type A, the back side of a shrink floor type A, the face side of a shrink floor type B, and the back side of a shrink floor type B, respectively, for face-in versus face-out rolling and for the machine versus cross machine direction. A three hour period between unrolling and installation was assumed.

Figure 8 shows the structure of one shrink floor embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a self-induced tension surface covering comprising a cross-linked, thermoset wear layer and a backing layer. The self-induced tension surface covering is packaged in a roll with the wear layer rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling and/or decrease post-installation thermal buckling.

Self-induced tension floors are also known as shrink floors. Shrink floors are well known in the art and can be found in, for example, U.S. Patent Nos. 3,464,178; 3,990,929; 4,135,675; 4,159,219; and 4,920,720; and in U.S. Patent Application Serial No. 07/758,621 filed September 12, 1991 and assigned to the assignee of this instant application. U.S. Patent Nos. 3,464,178; 3,990,929; 4,135,675; 4,159,219; and 4,920,720 and U.S. Application Serial No. 758,621 filed September 12, 1991 are all herein incorporated by reference for all of their teachings and particularly for their teachings on the structure and composition of a shrink floor and how to make and use a shrink floor. The terms "self-induced tension floor" and "shrink floor" are used interchangeably herein.

The backing layer, which can also be referred to as the reinforcing layer, of the surface covering of the invention can be of any composition generally used for backing layers in the shrink floor art. The backing layer can be, for example, a non-foamed, non cross-linked or cross-linked, vinyl composition; a felted or matted fibrous sheet of overlapping, intertwined filaments and/or fibers, usually of asbestos, fiberglass, felt, or of natural, synthetic or man- made cellulosic origin, such as cotton or rayon; or a composite material of a polymeric composition in a felted or matted fibrous sheet of overlapping, intertwined filaments and/or fibers; although many other forms of sheets and films or textile materials, fabrics or the like, may be used to provide the desired product reinforcement and shrinkage. Preferably the backing layer is of a vinyl j-^e composition, such as polyvinyl chloride.

More preferably, the backing layer is t. .trengthening layer described in U.S. Patent Application S ιl No. 758,621 filed September 12, 1991, which a non-foamed layer comprising a vinyl resin and a polymerized cross- linked monomer as disclosed as the non-foamable layer in U.S. Patent No. 3,870,591 to Witman, herein incorporated by reference. Even more preferably, this strengthening layer comprises a polyvinyl chloride homopolymer resin and a cross-linking monomer of mono-, di-, tri-, and tetrafunctional acrylates, methacrylates, or blends thereof.

Any cross-linked, thermoset wear layer generally used in the shrink floor ar can serve as the wear layer in the present invention. Preferably, the cross-linked, thermoset wear layer comprises a cross-linked, thermoset composition of (a) polymerized urethane monomers or (b) a polymerized blend of acrylate and urethane monomers.

More preferably, the cross-linked, thermoset wear layer comprises a wear layer as disclosed in U.S. Patent Application Serial No. 758,621, filed September 12, 1991, and described therein as a wear layer base coat. The preferred wear layer base coat as described therein generally comprises a flexible, thermoset, polymeric composition having a flexibility such that the wear layer base coat passes a 1 inch mandrel diameter face out mandrel bend test when applied at a nominal dry film thickness of 1.0 mil over a flexible 80 mil underlying substrate. This wear layer base coat can be, for example, a water based, solvent based, UV-curable or non-UV curable system. This wear layer can comprise, for example, acrylics, acrylates, urethanes, epoxies, vinyls, and other polymerized monomers, and blends thereof, as long as the composition when cured, results in a flexible, thermoset coating with adequate cross-link density. Preferred acrylic or urethane-acrylate monomer blends for use in making this wear layer are PHOTOGLAZE™ U248, PHOTOGLAZE™ U233, and PHOTOGLAZE™ U206, all sold by the Lord Corporation of Erie, PA, USA, and VALRAD™ KKC0047, sold by The Valspar Corporation of Minneapolis, MN, USA. The most preferred composition for this wear layer is PHOTOGLAZE™ U233. The PHOTOGLAZE™ resins comprise blends of cross-linkable UV-curable acrylic monomers. VALRAD™ KKC0047 comprises a cross-linkable UV- curable blend of approximately 20 wt.% of isobornyl acrylate, approximately 25 wt.% of an acrylate ester monomer, specifically 2-propenoic acid, (1-methyl-l,2- ethanediyl)-bis-(oxy-(methyl-2,1-ethanediyl) ester and approximately 55 wt.% of a urethane acrylate oligomer.

Other layer(s) can be optionally incorporated into the shrink floor. These optional layers can be, for example, a strippable substrate layer adhered to the outer face of the backing layer; a foamed layer disposed between the wear layer and backing layer and adhered to the backing layer, such as a foamed polyvinyl chloride plastisol; a design or decorative layer disposed between the wear layer and foamed layer and covering at least a portion of the underlying foamed layer; and/or an initial wear layer, preferably comprising transparent polyvinyl chloride, which is adhered to the cross-linked, thermoset wear layer and to the design layer and in locations where there is no design layer adhered to the foamed layer.

In one embodiment the cross-linked, thermoset wear layer can be an outermost layer. In another embodiment, an additional wear layer coating, such as an additional cross- linked, thermoset wear layer, can be disposed on top of and adhered to the cross-linked, thermoset wear layer. This additional wear layer coating would then be an outermost layer.

The cross-linked, thermoset wear layer, once cured, is preferably from 0.3 mils to 3.0 mils thick and more preferably from 0.9 mils to 1.2 mils. The shrink floor can be of wide range of thickness but is preferably about 80 mils.

Referring now to Figure 8, there is illustrated in cross-section a resilient floor covering which is constructed according to the teachings of one embodiment of the present invention and which is designated generally by reference numeral 11.

Covering 11 has a top surface 13 and a bottom surface 15. Covering 11 includes a resilient support surface 17 and a resilient wear surface 19.

The support surface 17, which is preferably laid out in substantially horizontal condition, is preferably a substrate layer 21, a backing layer 23, a foam layer 25 and a design layer 27.

Layer 21 is a substrate layer. It is useful as a controlled release layer after the structure 11 is stripped from a conventional release carrier in the manufacture of the floor covering of Figure 8 and is also useful to provide improved adhesion in the final product installation. Release carriers are known in the art and can comprise, for example, paper, felt or the machine belt upon which the shrink floor is formed comprising, for example, steel or a teflon coated material.

Layer 21 is a conventional substrate layer known to those in the art. Conventional substrate layer 21 comprises materials typical of substrate layers found in the flooring art, such as a non-foamed, non cross-linked or cross-linked, vinyl composition; a felted or matted fibrous sheet of overlapping, intertwined filaments and/or fibers, usually of asbestos, fiberglass, felt, or of natural, synthetic or man- made cellulosic origin, such as cotton or rayon; or a composite material of a polymeric composition in a felted or matted fibrous sheet of overlapping, intertwined filaments and/or fibers; although many other forms of sheets and films or textile materials, fabrics or the like, may be used. It preferably comprises a polymerized non-cross-linked PVC composition. The thickness of conventional substrate layer 21 is preferably from 2 to 100 mils, more preferably from 5 to 20 mils.

Backing layer or reinforcing layer 23 is either disposed on top of and adhered to substrate layer 21 or is the outermost bottom layer when substrate layer 21 is not used. The backing layer herein is the same backing layer described above. It is preferably a strengthening layer, which is disclosed as a layer intermediate between two foam layers in U.S. patent No. 3,870,591 to Witman, which is incorporated herein by reference.

Disposed on top of and adhered to backing layer 23 is a substantially uniform layer 25 of a liquid or semi-liquid resinous composition which contains a synthetic polymeric material, usually an ungelled poly(vinyl chloride) plastisol and normally containing a blowing or foaming agent. The liquid or semi-liquid plastisol vinyl resin composition of layer 25 after its expansion at the elevated temperature is subsequently firmed or gelled at an elevated temperature to a relatively more stable condition by procedures which are conventional and well-known in the art. The thickness of foam layer 25 after its expansion at the elevated temperature is preferably from 10 to 100 mils, more preferably from 15 to 40 mils.

Layer 27 is a design layer printed on layer 25. The design layer can preferably be a decorative, multicolored pattern or design in which certain predetermined areas may contain a blowing or foaming inhibitor which subsequently modifies or alters the action of the blowing or foaming agent in those certain predetermined areas. Several different printing ink compositions may be used in such procedures. The design layer can preferably be a gravure printed layer.

The design layer 27 is not necessarily a continuous layer. The design may only cover a portion of the underlying layer 25. In locations where there is no design layer, the wear surface 19 will therefore be adhered to foam layer 25.

Wear surface 19, which, as seen in the drawing is applied to the top of and adhered to layer 27, comprises an initial wear layer 29, a cross-linked, thermoset wear layer 31, and a wear layer top coat 33. Initial wear layer 29 is preferably a transparent poly(vinyl chloride) layer. Most PVC wear layers that are known in the art to be formulated for use on PVC resilient flooring products would provide an adequate composition for this layer. The dry film thickness of this PVC layer 29 is preferably from 5 mils to 50 mils and more preferably from 10 mils to 20 mils.

The initial wear layer is preferably used when a foam layer is present to provide adhesion between the foam layer and the cross-linked, thermoset wear layer 31 to provide smoothing of the upper surface of the blown foam layer and to control any chemical embossing. If an initial wear layer is not used, the cross-linked, thermoset wear layer 31 should be adequately adhered to the underlying layer.

A cross-linked, thermoset wear layer 31 is applied to and adhered to initial wear layer 29 and is then cured or partially cured. The cross-linked, thermoset wear layer 31 can be cured by means known to those skilled in the art, such as by ultraviolet light or thermal treatments.

An additional wear layer top coat 33, which can also preferably be a cross-linked, thermoset layer, can be applied to the top of and adhered to the cross-linked, thermoset wear layer 31 and is UV-cured or both layers 31 and 33 are cured by their respective curing methods if the cross-linked, thermoset wear layer 31 was only initially partially cured. To insure that the flooring composite exhibits the desired performance properties for its intended end use, each layer of the composite must exhibit adequate adhesion to the layer below and above it. The layers are generally adhered together by coating and curing each subsequent layer and/or by using an adhesive or bonding agent between layers to increase the adhesion. The initial wear layer 29 should adhere to the support surface 17 without any special treatment, when thermally fused to the support surface under conditions known to those skilled in the art of making PVC resilient floor coverings.

To enhance adhesion of the cross-linked, thermoset wear layer 31 to the initial wear layer 29, it is preferable to treat the initial wear layer 29 with an acid wash/surfactant solution prior to application of the cross-linked, thermoset wear layer 31.

The embodiment represented in Figure 8 is representative of only one aspect of the invention. Only backing layer 23 and the cross-linked, thermoset wear layer 31 are necessary to the invention, while each of the other layers are optional. Each of the optional layers can be present or not present independent of the presence of the other optional layers.

The present invention is also directed to a method for packaging a self-induced tension surface covering. The self-induced tension surface covering comprises a cross- linked, thermoset wear layer and a backing layer. The method comprises the step of rolling the self-induced tension surface covering with the wear layer rolled facing inward and thereby enhance the surface covering contraction property to thereby decrease initial installation buckling and/or decrease post-installation thermal buckling.

An important step in manufacturing and eventual installation of a successful shrink floor is the proper factory roll packaging and any further retailer cut-roll packaging of the flooring material. Because tension floors rely upon a tension system for proper buckle resistance, that tension must be maintained after manufacturing the floor covering and prior to the product's installation. After manufacturing of the tension floor, the tension floor is rolled up in the machine direction around a core. The roll must be tightly rolled with the wear surface facing inward. To maintain the maximum shrinkage of the product, it is preferable to tape the leading edge of the sheet and, if present, the release carrier to a full 12' length 5-ply core, having at least a 4.25 inch inner diameter. If a release carrier is present, the carrier is preferably removed from the tension floor and is preferably reinserted back into the roll between the back and face of the tension floor sheet in the roll. An outer wrapping paper is tucked under the last lap of the tension floor and is tightly rolled with the tension floor. The outer lap of the protective paper is then taped to maintain a tight roll.

As used throughout the Examples, Tables, and Figures, the following terms and abbreviations are used:

MD Machine Direction

CD Cross-Machine Direction

HB Heat Buckling Test

DS Accelerated Dimensional Stability Test.

The heat buckling test ("HB") as used herein determines whether a shrink floor buckles due to the dimensional expansion induced by heat. The heat buckling test procedure that was used is as follows. All samples used for this test were initially maintained tightly rolled on a core. The entire roll of shrink floor was preconditioned at 70°F for 1 hour. If the shrink floor initially contained a strippable release carrier, the strippable release carrier was removed from the shrink floor product, and the entire roll of shrink floor was preconditioned at 70°F for 1 hour. The roll was unwrapped, a 12" x 12" sample was cut, and the sample was immediately stapled at its perimeter on a 12" (L) x 12" (W) x 0.5"(T) lauan board. The sample was placed in a 96°F environment for 4 hours. At the end of 4 hours one observed whether the shrink floor had buckled. The sample was then cooled to 70°F for 20 hours and another 96°F - 4 hour heat cycle was performed. At the end of this second heat cycle, one observed whether the shrink floor sample had buckled. A sample which did not buckle from both the first and second heat cycle tests was reported to have passed the heat buckle test. A sample which buckled on both heat cycles was reported to have failed the heat buckle test. If a sample buckled on only one of the two cycles, a third 96°F - 4 hour heat cycle was repeated. A passing or failing on this third heat cycle then determined whether this particular sample passed or failed the overall heat buckling test.

The accelerated dimensional stability test ("DS") as used herein estimates the shrinkage amount of the shrinkage floor in the machine and cross-machine directions. The procedure for the dimensional stability test that was used herein is as follows. All samples used for this test were initially maintained tightly rolled on a core. The entire roll of shrink floor was preconditioned at 70°F for 1 hour. If the shrink floor initially contained a strippable release carrier, the strippable release carrier was removed from the shrink floor product, and the entire roll of shrink floor was preconditioned at 70°F for 1 hour. The shrink floor roll was then unwrapped and a 12" x 12" sample was cut. Immediately after cutting the sample, the sample was scribed at the 8" mark in the machine direction and cross-machine direction. The sample was then placed in a 120°F oven for 4 hours. The sample was cooled at ambient temperature for 1 hour and rescribed at the 8" mark. A microscope was used to measure the distance in mils between the starting and ending 8" marks, and the percent expansion (denoted as a positive number) or percent contraction (denoted as a negative number) was calculated.

Referring now to the Examples, Tables, and Figures, a surface covering product of one embodiment of the instant invention is denoted as "shrink floor type A" or "shrink floor A. " Shrink floor A is from bottom, which is understood to be the layer nearest to the surface being covered, to top, which is understood to be the layer furthest from the surface being covered, a PVC substrate layer, a backing layer comprising a polyvinyl chloride resin and a polymerized, cross-linked acrylate or methacrylate; a polyvinyl chloride foam layer adhered to the backing layer; a design layer printed on the foam layer; an initial wear layer of polyvinyl chloride adhered to the design layer and adhered to the foam layer where there are areas lacking in design; and an outer wear layer comprising a cross-linked, thermoset polymerized blend of acrylate and urethane monomers sold under the trademark name PHOTOGLAZE™ U233 by the Lord Corporation of Erie, PA, USA. The formulation of shrink floor type A is described in Example 10 below. Shrink floor type A thus corresponds to layers 21, 23, 25, 27, 29, and 31 of Figure 8. "Shrink floor type B" or "shrink floor B" is the same as shrink floor type A except that shrink floor B does not have a cross-linked, thermoset wear layer 31. The polyvinyl chloride wear layer 29 is the outermost top layer for shrink floor B.

EXAMPLE 1 - Edge Curl

Figure 1 shows two different types of edge curls, negative and positive. The X-Y plane represents a flat surface, such as a floor and the ordinate Z represents the direction perpendicular to the X and Y axes. Side views of part of each of two surface coverings are shown at elements 10 and 11. Negative edge curls bow upward in the middle of a surface covering as shown by surface covering 10, whereas positive edge curls bow upward at the edges of the surface covering as shown by surface covering 11. Shrink floor type A has a tendency to display a negative curl, whereas shrink floor type B tends to have a positive curl.

The degree of negative curl of the product is a function of the type of cross-linked, thermoset materials used in the wear layer, the thickness of that wear layer coating, and the formulation and construction of the other layers. A negative curl has the detrimental effect of decreasing the buckle resistance of the surface covering. Because of a negative curl, a shrink floor installer tends to cut the product slightly longer than the size of the room; therefore, a slight buckle already exists when the perimeters are fastened. This fullness fitting cut necessitates about 0.1% of additional dimension to be shrunk away in order to sustain a flat, taut floor.

Samples of shrink floor types A and B were placed in a 120°F oven for four hours and then cooled down to 70°F for one hour. The amount of edge curl was then measured. The measured edge curl was the amount of displacement in the Z or perpendicular direction of the shrink floor from the surface on which the rest of the shrink floor rested. Table 1 lists the degree of negative curl.

Edge Curl Product (Inches )

Shrink Floor A -14/64

Shrink Floor A

0

Shrink Floor B No Cross-Linked, 0

Thermoset Wear Layer

EXAMPLE 2 - Package Effect on Lay Flat Property

A 12" x 12" shrink floor type A sample was rolled face- in and another sample rolled face-out on a 3" outer diameter core and placed in a 70°F room for three days. A second set of the same type samples were prepared but placed in a 90°F room for three days. Then, the samples were unrolled at ambient temperature and the edge curl measured as described in Example 1. The curl was reported in the machine direction. The curl in the cross-direction was negligible. Positive and negative curl in inches corresponds to positive and negative type curls, respectively. In Tables 2 and 3, which are plotted in Figures 2 and 3 respectively, the edge curl vs. relaxation time of a face-in versus face-out packaging of a shrink floor type A at 70°F (Table 2 and Figure 2) and 90°F (Table 3 and Figure 3) are shown.

. TABLE 2

The face-in packaging deformed the shrink floor A into a positive curl and the face-out packaging shrink floor deformed the shrink floor A into a negative curl. The degree of curl and the degree of the relaxation of curl are influenced by the product storage temperature. At 70°F no effect on the curl was seen after relaxation for 40 hours between the face-in and face-out rolling. But at the 90°F storage temperature, less initial and final relaxation curl was found in the face-in product.

Not wishing to be bound by theory, the positive curl created by the face-in packaging is believed to be one reason for improving the buckling problem of shrink floors of the current invention. It is believed that the positive edge curl reduces the buckling because the Z directional displacement is initially eliminated and the resistance to form a Z directional uplifting appears to be much higher for face-in packaging than face-out packing.

EXAMPLE 3 - Total Available Shrinkage of Shrink Floor Types A and B

Shrink floor types A and B were evaluated using the dimensional stability test.

This test thus estimated the amount of shrinkage that a product is capable of contracting from the time of unwinding to 3-4 months after installation. Although there is more available shrinkage in a shrink floor of type B, the strong demands for a surface covering product having the highest standards of stain, mar, scuff and soil resistance necessitates the use of a shrink floor of type A. However, the decrease in shrinkage of shrink floor type A makes it prone to form a buckle or buckles upon installation or after installation if the temperature in the floor environment increases drastically after installation. In addition to the 0.1% shrinkage loss that is necessary to overcome the fullness cut and fitting that results from the negative curl of the shrink floors of the instant invention, the shrinkage must overcome the thermal expansion of the flooring product or else buckling occurs. Typical vinyl resin composition shrink floors of about 80 mils thickness have a 0.008% dimension expansion or contraction per °F of temperature change. Over a 30°F temperature change, which is a likely temperature change in a hot environment, the thermal expansion accounts for 0.24% of expansion of the shrink floor.

For shrink floors of one embodiment of the instant invention, about 0.34% shrinkage is needed to account for both the expansion from thermal conditions and from fullness cutting. These results are achieved and buckling problems are prevented by rolling the shrink floor of the instant invention face-inward.

EXAMPLE 4 - Face-In Versus Face-Out Packaging

Products freshly stripped from release carriers were scribed on the face and back sides with three approximately 21" marks in both the MD and CD at the center of the sheets. The products were wrapped either face-in or face-out on a core and the outer lap was secured with tape. The rolls were then conditioned at 70°F for 5-6 days to simulate roll storage in a warehouse before shipping to an installation site. The sheets were unrolled and the distance between each scribed points in the MD and CD were measured at various times after unrolling.

In Tables 5-8, which are plotted in Figures 4A-7A and 4B-7B, the shrinkage of type A and B shrink floors were measured to study the effect of face-in and face-out packaging. In Tables 5-8, the initial data point value for 0.08 real hours (5 minutes), corresponding to -1.08 log hours, corresponds to the amount of shrinkage during roll storage and the first 5 minutes after unrolling. The shrinkage after unrolling is plotted in Figures 4A- 7A. The data plotted in Figures 4A-7A are based on the amount of shrinkage during roll storage and immediately after unwinding of the shrink floor from the roll. In these figures, a value of zero on the logarithmic scale on the abscissa corresponds to 1 hour after unrolling the shrink floor.

The shrinkage after installation is plotted in Figures 4B-7B. Figures 4B-7B are the same as Figures 4A-7A except that Figures 4B-7B assume a lag time of 3 hours after unrolling the product prior to installation, in order to simulate available shrinkage after installation. In these figures, a value of zero on the logarithmic scale on the abscissa corresponds to 1 hour after installing the shrink floor, which corresponds to 4 hours after unrolling the shrink floor. Three hours after unrolling the packed roll is considered to be a reasonable time for an average installer to complete an installation job that generally includes cutting, fitting, seaming and perimeter gluing of the shrink floor material. The shrinkage lost in the first three hours after the sheet has been unrolled is considered to be irrecoverable. The time required to install a piece of flooring varies for each individual installer. The longer the installer takes before fastening the perimeters of the shrink floor, the greater the loss will be of available self-tension.

TABLE 6

Back Side Of Shrinkage Floor Type A

Product Shrinkage Available Shrinkage After Unrollin After Installation

TABLE 7

Face Side Of Shrinkage Floor Type B

Product Shrinkage Available Shrinkage After Unrollin After Installation

TABLE 8

Back Side Of Shrinkage Floor Type B

Product Shrinkage Available Shrinkage After Unrollin After Installation

The face side of shrink floor type A rolled face-in shows a higher amount of MD shrinkage available for handling dimensional expansion after installation than the same product wrapped face-out. There was no significant difference in shrinkage on the backside between these two types of packagings. The face-in packaging increases the shrinkage of this particular type A shrink floor so that it can handle up to 0.24% of dimensional increase after installation without buckling. This equates to being able to handle as much as a 30°F temperature increase after installation. Conversely, the shrink floor type B had a higher MD shrinkage on both the face and back sides when rolled face-out than face-in. As a result of greater shrinkage capability, less buckling develops for shrink floors of the present invention rolled face-inward.

Not wishing to be bound by theory, it is believed that rolling a shrink floor of type A face-inward results in a positive curl making a buckle more difficult to form in the first place and also results in a slightly higher shrinkage amount available for counteracting the buckling problem.

EXAMPLE 5

Samples of 12" x 12" shrink floor type-A that had previously failed the heat buckle test due to not being tightly wound on the core were wrapped face-in tightly on a 3" core and were stored at 70°F for 5 days to maintain its shrinkage property. The heat buckle was tested again. After the heat buckle test, the panel was cooled down at 70°F for one hour. A six inch long slot was cut in the machine direction and in the cross machine direction. With the upper left corner of the 12" x 12" sample being at coordinates of (machine direction, cross machine direction) of (0, 0) , the two slots were cut in coordinates of machine direction and cross machine direction respectively of (1) machine direction cut at (1 inch, 6 inch) to (7 inch, 6 inch) and (2) cross machine direction cut at (9.5 inch, 3 inch) to (9.5 inch, 9 inch). The panel was then aged for 24 hours and the gaps developed by the tension were measured.

TABLE 9

Samples of shrink floor type A were treated in a 150°F oven for 30 minutes to allow the product to relax and remove its contractibility. The samples were then immediately wound tightly onto a 3" core either face-in or face-out. The samples were stored at 70°F ambient temperature for 3 days. The samples then were tested for heat buckling and accelerated dimensional stability under various elapsed times after unrolling.

TABLE 10A

Samples of shrink floor type A were treated in the same manner as above, except that after heating to 150°F for thirty minutes, the samples were allowed to cool at the room temperature of 70°F for one hour prior to rolling the product face-in or face-out. The samples, as above, were stored for three days at 70°F while wrapped tightly on a core. The samples were again tested for heat buckling and accelerated dimensional stability.

TABLE 10B

Face-in Face-out

Elapsed time D.S. (Z) HB D.S. ( Z ) HB after unroll MD CD MD CD

1 hour -0.10 -0.16 passed 0.00 0.01 failed

As seen in Tables 10A and 10B, the amount of shrinkage is not always indicative of the ability to avoid buckling. The same samples of shrink floor type A, when rolled face- out fail the heat buckling test but when rolled face-in pass the heat buckling test.

EXAMPLE 7

Samples of shrink floor type A were evaluated for buckle resistance under a cold storage condition. The rolls were tightly wound on a 3" core, one rolled face-in, one rolled face-out and then placed in a 40°F environment for one month. The rolls were then taken out of the 40°F room and unrolled at 70°F and allowed to relax for various elapsed times and then tested for heat buckling and accelerated dimensional stability. Elapsed time after unroll

1 hour

2 hours

EXAMPLE 8

Samples of previously stored shrink floor type A having the majority of its contractibility lost were wrapped face- in or face-out tightly on a core in a 70° F environment and were then relaxed at 70°F for various durations. The samples were tested for heat buckling and for accelerated dimensional stability.

The following is an evaluation of the effect of face-in and face-out wrap on the heat buckling and dimensional stability of various commercialized shrink floor products. Three different manufacturers denoted as I-III were tested and a total of seven different products were tested.

Product Structure for Table 13 from the Outermost Wear Layer to the Backing Layer;

1. Cross-linked, thermoset wear layer disposed on decorative color chips or flakes disposed on a PVC base layer.

2. Cross-linked, thermoset wear layer disposed on a PVC wear layer of 10 - 20 mils disposed on roto-gravure printing on a PVC foam layer of 20-50 mils disposed on a PVC base layer of 5-20 mils.

3. Shrink floor type A as specified previously.

4. Same as product structure 2 except that there is no cross-linked, thermoset wear layer. Five out of the 6 shrink floors having a cross-linked, thermoset wear layer failed the heat buckle test when rolled face out. Four of these original five failures passed the heat buckle test when rolled face-in.

EXAMPLE 10

A shrink floor of one embodiment of the present invention was produced as follows. The cross-linkable poly(vinyl chloride) plastisol used to form the backing layer was prepared according to the following formulation:

Coating A Ingredients Parts b wei ht

Dispersion Grade PVC Ho opolymer Blending Grade PVC Homopolymer Secondary Plasticizer-Aliphatic/Aromati

Hydrocarbon Mixture 2,2,4-Trimethyl-l,3-pentanediol diisobutyrate Trimethylolpropane trimethacrylate Calcium/Zinc/Phosphite stabilizer Di-t-butyl peroxide Butyl Benzyl Phthalate Organic arsenical fungicide (2% active) dispersed in Butyl Benzyl Phthalate Titanium Dioxide Calcium Carbonate

This plastisol was prepared by thoroughly mixing the above ingredients in a method known to one of ordinary skill in the art, such as using a Cowles Disperser.

The cross-linkable plastisol may be applied directly to a suitable strippable release carrier. Alternately, a strippable release carrier may be first coated with about 7 mils of a non-foamable uncross-linked coating having the following formulation: Coating B Ingredients Parts by weight

Dispersion Grade PVC Homopolymer 69.7

Blending Grade PVC Homopolymer 30.3

Butyl Benzyl Phthalate 15.4 Secondary Plasticizer-Aliphatic/Aromatic

Hydrocarbon Mixture 6.6 2,2,4-Trimethyl-l,3-pentanediol diisobutyrate 11.5

Naphtha diluent 2.3

Calcium/Zinc/Phosphite stabilizer 5.0

Polyethylene Glycol (400 m.wt. ) 1.3

Calcium Carbonate 12.1 Organic arsenical fungicide (2% active) dispersed in Butyl Benzyl Phthalate 7.1

The coated release carrier was heated at 325°F for 75 seconds to gel the 7 mil uncross-linked PVC plastisol coating B. This gelled coating B was then coated with a thickness of about 37 mils of coating A. After application the wet plastisol was gelled by heating at 325°F for 90 seconds.

The backing layer is now ready to receive additional coatings to prepare a useful resilient floor covering.

The gelled construction described above comprising 7 mils of a substrate coat B and 37 mils of strengthening coat A, was coated with about 10 mils of a foamable PVC plastisol having the following formulation: Coating C Ingredients Parts by weight

Dispersion Grade PVC Homopolymer 70.0

(Foam Type)

Blending Grade PVC Homopolymer 30.0

Di(C7-9-ll-alkyl) Phthalate 28.2

Butyl Benzyl Phthalate 9.0

Aliphatic/Aromatic Hydrocarbon Mixture 9.5 2,2,4-Trimethyl-l,3-pentanediol diisobutyrate 10.5 Dispersing Aid - modified polyester dissolved in naphtha 0.3

Azodicarbonamide 1.1 Organic arsenical fungicide (2% active) in butyl benzyl phthalate 5.4

Zinc Oxide 0.3

Titanium Dioxide 12.0

Calcium Carbonate 15.0 This foamable plastisol was gelled by heating at 325°F for 60 seconds. The surface of the gelled foamable plastisol was then printed with a decorative pattern by gravure printing.

One or more of the inks used may contain a retarder in order to develop a textured relief structure in register with the decorative pattern. The inks used are those customarily used to print decorative patterns on resilient floor coverings. Representative ink formulas may be found in U.S. Patent 3,293,094 and in other references known to those of ordinary skill in the art.

The printed sheet was then coated with about 19-20 mils of an initial wear layer of a clear PVC plastisol having the following formulation: Coating D Ingredients Parts by weight

Dispersion Grade PVC Homopolymer 100.0

(High Clarity Type)

Butyl Benzyl Phthalate 35.3

Aliphatic/Aromatic Hydrocarbon Mixture 6.1 2,2,4-Trimethyl-l,3-pentanediol diisobutyrate 3.4

Naphtha diluent 5.6

Calcium/Zinc/Phosphite Complex Stabilizer 7.6

Polyethylene Glycol (400 m.wt.) 1.4

This coated sheet was then heated at 380°F for 250 seconds to completely fuse the initial wear layer and the other previously gelled PVC layers, blow the foamable plastisol into the foam layer, and form the decorative relief texture if one or more retarders were used in the gravure ink layer.

The initial PVC wear layer was cleaned by washing with an aqueous solution of 1% formic acid (90% strength as received) and 0.4% of a nonionic surfactant.

The washed initial PVC wear layer was dried and then coated with PHOTOGLAZE^® U233 sold by the Lord Corp. The wet coating was distributed over the sample by draw-down with a #30 wire-wound rod. The sample was then passed under an air knife operating at about 4 p.s.i.g. to remove excess coating and distribute the remainder uniformly over the sample surface as a 1.0 - 1.2 mil wet film. This film was cured by passing the sample at 40 ft/min under two medium pressure mercury arc lamps operating at 200 watt/inch in a nitrogen inert atmosphere having less than 2,000 ppm of oxygen.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention and in construction of this invention without departing from the scope or spirit of the invention.

Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A self-induced tension surface covering comprising a cross-linked, thermoset wear layer and a backing layer, wherein said self-induced tension surface covering is packaged in a roll with the wear layer rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling or decrease post-installation thermal buckling.

2. The self-induced tension surface covering as claimed in claim 1, wherein the cross-linked, thermoset wear layer comprises polymerized urethane monomers.

3. The self-induced tension surface covering as claimed in claim 1, wherein the cross-linked, thermoset wear layer comprises a polymerized blend of acrylate and urethane monomers.

4. The self-induced tension surface covering as claimed in claim 1, wherein said cross-linked, thermoset wear layer is an outermost layer.

5. The self-induced tension surface covering as claimed in claim 4, wherein a decorative layer is disposed between said cross-linked, thermoset wear layer and said vinyl backing layer.

6. The self-induced tension surface covering as claimed in claim 5, wherein an initial wear layer comprising polyvinyl chloride is disposed between said decorative layer and said cross-linked, thermoset wear layer.

7. The self-induced tension surface covering as claimed in claim 6, wherein a foamed layer comprising polyvinyl chloride is disposed between said decorative layer and said vinyl backing layer.

8. The self-induced tension surface covering as claimed in claim 1, wherein there is a decrease in post- installation thermal buckling after a post-installation temperature increase of from 1°F to 25°F.

9. The self-induced tension surface covering as claimed in claim 1, wherein there is a decrease in post- installation thermal buckling after a post-installation temperature increase of from 25°F to 30°F.

10. The self-induced tension surface covering as claimed in claim 1, wherein post-installation thermal buckling is eliminated after a post-installation temperature increase of from 1°F to 25°F.

11. The self-induced tension surface covering as claimed in claim 1, wherein post-installation thermal buckling is eliminated after a post-installation temperature increase of from 25°F to 30°F.

12. The self-induced tension surface covering as claimed in claim 1, wherein the initial installation buckling is decreased.

13. The self-induced tension surface covering as claimed in claim 1, wherein the surface covering has at least 0.20% face side available shrinkage after installation.

14. The self-induced tension surface covering as claimed in claim 1, wherein the surface covering has at least 0.24% face side available shrinkage after installation.

15. The self-induced tension surface covering as claimed in claim 1, wherein the self-induced tension surface covering is a perimeter fastened tension floor.

16. A method for packaging a self-induced tension surface covering, said self-induced tension surface covering comprising a cross-linked, thermoset wear layer and a backing layer, comprising the step of rolling said self- induced tension surface covering with the wear layer rolled facing inward to thereby enhance the surface covering contraction property and thereby decrease initial installation buckling or decrease post-installation thermal buckling.