CA1331324C

CA1331324C - Stain and scratch resistant resilient surface coverings

Info

Publication number: CA1331324C
Application number: CA000555034A
Authority: CA
Inventors: Jack Henry Witman
Original assignee: Armstrong World Industries Inc
Current assignee: AWI Licensing LLC
Priority date: 1986-12-23
Filing date: 1987-12-22
Publication date: 1994-08-09
Anticipated expiration: 2011-08-09
Also published as: SE8705116L; NL188912C; GB2200593A; SE8705116D0; GB2200593B; NL188912B; GB8729942D0; NL8703120A; JPS63168345A; JPH0580343B2; DE3743980A1

Abstract

STAIN AND SCRATCH RESISTANT RESILIENT SURFACE COVERINGS
Abstract The present invention relates to surface coverings, and in particular to coverings which comprise treated polyurethane or other wear layers. A coating comprising a urea aminoplast which is at least partially etherified with alkyl groups comprising 4 to 10 carbon atoms, a vinyl modifier resin, a polyol, and an acid catalyst is formed on a release surface and thermally cured. A crosslinkable wear layer composition is then cast on the cured layer and crosslinked, and the composite is transferred to a support surface. Surface coverings are produced which exhibit surprising resistance to common household stains, and also improved scratch resistance.

Description

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STAIN A~D SCRATCH RESISTANT RESILIENT SURFACE COVERINGS
The present invention relate~ to surface coverings, and more particularly to surface covering~
which have i~proved scratch and stain resistance.
Background of the Invention Resilient surface coverings, and in particular resilient floor coverings, are well known in the art. The floor coverings which are in wide u6e today are primarily of vinyl construction and, although they can be con~tructed to have varying degrees of flexibility, they are "resilient~ when co~pared to conventional natural materials, such as ceramic tile. A variety of ~uch products are commercially available and these products have proved to exhibit good wear resistance; however, ~uch coverings are not without certain deficiencies. For example, although vinyl flooring products have proved to be durable and stain resistant, they nevertheless tend to lose their glossy appearance through wear. A high-gloss appearance for a floor covering is often desired.
Accordingly, the manufacturers of such material~ have long sought to find improved floor coverings which exhibit good gloss retention.
One method of providing improved gloss retention i8 through the application of polyurethane or other wear layers to vinyl flooring structures. Such materials are durable and relatively scratch resistant, and they tend to retain their high-gloss appearance over a longer period of time than do vinyl-surfaced flooring 3tructures.
~evertheless, ~hese wear layers, and in particular polyurethane wear layers, also have certain drawbacks.
For example, they are more susceptible to staining. Thu8, when exposed to common household item~ likely to cause : r~

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stains (~uch as ballpoint pen, lipstick, mustard, shoe poliæh and the like), polyurethane coating~ tend to be more easily stained than vinyl coatingæ.
In recent year~, industry has expended considerable effort to develop new and different types of coatings, including coatings ba~ed on aminoplast resins.
Such materials include ureas and ~elamine-formaldehyde resins, such as melamineæ (triaminotriazine6) which have been ~-alkylated with formaldehyde to provide a methylolated or partially methylolated melamine. The methylol group~ are then etherified or partially etherified to provide a crosslinkable material. Such coatingæ are generally fairly rigid, and have found wide use in coatings for automobiles, appli~nces and other fairly rigid types of surfaces. They have al80 been u~ed in coatingæ for ~ertain flexible ~ubstrate6 including paper, paperboard, metal foil~, "Cellophanes"* and the like.
However, Ruch materials have never been ~uccessfully applied to flooring structureæ, and in particular to vinyl flooring Btructures or to vinyl flooring structures comprisin4 polyurethane wear layers.
Accordingly, one objective of the present invention i~ to provide resilient surface coverings with protective coatings two-tenthæ of a mil or greater in thicknesæ which will deform in conjunction with the fiurface coverings, yet which will provide improved scratch - and ætain reæistance.
Another objective of the preæent invention is to provide flooring structure~ comprising composite wear surfaceæ whereby the wear layer material i~ provided with an improved scratch and stain-resistant character.
These and other advantageæ of the present invention will become apparent from the detailed description of preferred embodiments which follows.

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Summary of the Invention The present invention relates to surface coverings, and in particular to floor covering~, which c~mprise polyurethane or ~ther wear layer6 having coatings which ~omprise a urea aminoplast which i~ at least partially etherified with alkyl groups comprising 4 to 10 carbon atoms, a vinyl ~odifier re6in, a polyol, ~nd an acid catalyst. Ihis coating may be formed on ~ release surface and thermally cured. A ~rosslinkable wear layer composition, ~uch a~ a polyurethane composition, may then be cast on the cured layer and crosslinked, and the composite can then be tran~ferred to a support surface.
Surface ~overings are produced which exhibit surpri6ing resi~tance to common hou6ehold ~tains, and also improved 8cratch resistAnce.

. The present invention, then, in one aspect, resides in a resilient surface covering, said covering compris~ng a resilient support and a crosslinked wear layer adhered thereto, the upper surface of said wear layer compr~sing a protective coating derived from a composition comprising:
j (a) a urea aminoplast, ~b) a vinyl modifier resin, $ (c) a polyol, and i (d) -a 6uitable catalyst, said protective coating having the ability to conform to the deflections of said wear layer, yet having improved scratch and stain resistance relative to the untreated vear layer.

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~ ~ r~ ~ 3 2 4 -4a-In another aspect, the present invention resides in a process for providing a wear surface for a resilient surface covering, said process comprising the steps of providinq a release carrler comprising a support surface and a release coating, disposing on said release coating a composition comprising (a~ a urea aminoplast, (b) a vinyl modifier resin, ~c) a polyol, and (d) a suitable catalyst, at least partially thermally curing said composition, disposing a crosslinkable wear layer composition on said aminoplast layer, curing said wear layer, laminating said cured wear layer to a resilient support structure, and ~ eparating ~aid release carrier from said wear layer, whereby said surface covering comprises a wear layer having d protective coating, said protective coating being flexible, and scratch and stain-resistant relative to the untreated wear layer.

~ he present invention further provides a process for forming a resilient surface covering comprising a wear layer, which comprises applying to a free surface of the wear layer a composition comprising (a) a urea aminoplast, (b) a vinyl modifier resin, (c) a polyol, and (d) a catalyst, and forming a protective coating therefrom, or by applying a protective coating derivable from such a composition.

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~'i' -4b- 1~313~4 ~etailed Description of Preferred Embodiments In one embodiment, the preRent invention relates to a resilient surface covering, said covering comprising a resilient ~upport and a crosslinked wear layer adhered thereto, the upper ~urface of ~aid wear layer comprising a protective coating derived from a composition compri~ing (1) a urea aminoplast, (2) a vinyl modifier resin, (3) a polyol, and (4) a suitable cataly~t, 6aid protective coating having the ability to conform to the deflections of ~aid wear layer, yet having improved ~cratch and ~tain resistance relative to the untreated wear layer.
In a second embodiment, the present invention relates to a process for providing a wear ~urface for a resilient 6urface covering, said process comprising the steps of providing a release carrier comprising a support surface and a release coating: disposing on said release - coating a composition comprising (1) an aminoplast, (2) a vinyl =odlfier re~in, (3) ~ polyol, and (4) a euitable ,; . ~
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cataly~t; at least partially thermally curing said composition; disposing a cros~linkable wear layer composition on said aminoplast layer; curing ~aid wear layer; laminating said cured wear layer to a resilient support structure and ~eparating said release carrier from said wear layer, whereby said urface covering comprise~ a wear layer having a protective coating, said protective coating being flexible, and scratch and Rtain-resistant relative to the untreated wear layer.
The resilient surface coverings which may be prepared according to the pre~ent invention are related to ~hoce which are presently well-known in the art. Thus, they may comprise an underlying re3ilient support typical of those used to prepare vinyl flooring structures.
Supports of this type may be derived fro~ backing materials, plastisols, foamed plasti~ols, randomly dispersed vinyl particle~, stencil disposed vinyl particles, and the like, the selection of such ~aterials being well within the skill of an ordinary artisan.
The 6urface covering~ will also comprise compo~ite wear layer compositions. The major portion of the wear layer will compri~e materials which are pre6ently well known in the art. Example~ of such materials are crosslinked wear layers derived from urethanes, acrylated or methacrylated urethanes, unsaturated polyesters, and the like, all of which are well known in the art~ These wear layer~ may be crosslinkable by moisture-curing techniques, thermally induced free radical curing techniques, oxidative curing techniques, radiation-curing techniques, or a combination thereof.
The novelty of the pre~ent invention re~ides in the pre~ence of a ~econd protective layer on the conventional wear layer components. This second material 1~31~2~

i8 derived from urea aminoplast re~in, a polyol, an acid catalyst and a vinyl modifier resin, and provides a flexible, yet 6cratch and ~tain-resistant upper surface.
The resin6 which may be u~ed to practice the pre6ent inven~ion are referred to herein as ~aminoplast6n. With re~pect to melamine-formaldehyde resins, the~e material~ may be partially or sub~tantially methylolated, and ~he methylol group~ may be partially or 6ubstantially etherified with methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl group~, isomer~ o~ these moietie~, and mixtures thereof:
however, these aminoplast~ preferably will be at least partially etherified with a relatively long chain alkyl group having from about 4 to about 10 carbon atoms. These long-chain portion~ of the aminopla~t a38ist in providing fle~ibility to the cured vinyl product.
With respect to urea-based resins, many of these aminopla~ts are commercially available and are ~old, for example, as "Resimene"* resins by Monsanto Company.
The vinyl modifier resins which will be utilized will be one of, or a combination of, resins which are well-known in the art. Examples of such resins are co-polymer ~olution vinyl re6ins derived from vinyl chloride and vinyl acetate. Re6ins ~f this type are sold by ~nion Carbide, and they ~ay or may not contain hydroxyl or other functionality. One ~uch available reEinis sold under the trade designation VAGH*. Other~ ~ight include VAGD*, VROH* nnd VYES* resins. Examples of other resins are specialty re6ins such as the polyvinyl acetals (eg., polyvinylbutyral), either alone or in combination with polyvinyl alcohol and/or polyvinyl acetate, and polyvinyl e6ters such a6 polyvinyl acetate. Such materials are - well-known in the art as being amenable to application 3~ *Trademar~ (each instance).

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l ~31324 from solution; thu~, they are distinguishable from dispersion grade and general purpose resins which are essentially in~oluble in most conventional solvents. In essence, the modifier resins should be suitable to enhance the flexibility and etrength of the cured compo~ition without adversely affec~ing the 6tain resistance.
m e polyols which may be u6ed to practice the present invention are alcohols which comprise two or more alcohol groups. For example, 1,6-hexanediol, 10 1,4-cyclohexane dimethanol, glycerine, neopentyl glycol, tripropylene glycol, 1,4-butanediol, trimethylolpropane, pentaerythritol, and many other polyols or esters of such polyols, such a~ neopentyl glycol ester and the like, may be utilized to prac~ice the present invention, ~aid 15 polyols being well-known in the art.
The ncid catalysts which may be used to catalyze the thermal curing reaction between the vinyl modifier resin, the aminoplast, the polyol and the wear layer ~urface are al~o well-known in the art. Examples of such 20 cataly~ts are ~ulfonic acids, such as methane-sulfonic acid and p-toluenesulfonic acid, and other acids such as citric acia, maleic acid, phthalic acid, etc. The cataly~ts may be used in the free acid form, but they may also be stabilized, such as by the use of an amine to 25 neutralize the acid. E~amples of such amines are ammonia, diisopropanol amine, and 2-amino-2-methyl-1-propanol. The only restriction i8 that the catalysts must be compatible m with the other components of the 6ystem. Because these catalyst~ are all well-Xnown by those skilled in the art, 30 their ~election will be within the capability of an ordinary artisan.
To practice the pre6ent invention, ~ release eurface iB provided for the aminoplast composition. For a , ,, , .. . .
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very smooth surface, a polished chrome plate or a relea~e paper coated with a polyalkylçne material can be used, a particularly good example of the latter being polypropylene, such as polypropylene matted by calendering. For less glossy surfaces, other types of coated papers or belts may be u~ed, examples of which are silicone, complexed chromium and methyl cellulose trea~ed paperc or belt~. The 6election of such materials is well within the skill of an ordinary arti~an.
On to the release paper is cast a layer of aminoplast composition. Although the component ratios of the composition will have sub~tantial variability, the compoqition will u~ually compris2 from about 4 to 1 part~
of modifier resin for every 1 to 4 parts of the aminoplast/polyol mixture. Further, the aminoplast/polyol mi~ture may comprise from about 5 to 1 parts of aminoplaqt fcr every 1 to 5 parts of polyol. Preferably, however, there will be from about 3.5 to 1 parts of modifier for every 1 to 2 parts of aminoplast/polyol having a ratio of from about 3 to 1 parts of aminoplast for evesy 1 to 3 parts of polyol. ~ually this composition will be provided in an organic solvent; however, it i8 al~o pos~ible to apply the compo~ition in aqueous form.
After the aminoplast composition i8 applied to the relea~e paper, it is dried and at least partially cured at about 250-F. Although it is poqsible to form the laminates of the present invention using partially cured aminoplast layers to ohtain a high quality product, it is usually preferable to ensure that the aminoplast layer is fully cured prior to the depo~ition of the urethane layer.
The crosslinkable wear layer coating composition may be disposed directly on the aminoplast layer after the aminoplast layer is cured. It is noted, however, that the artisan may optionally elect to pretreat the ~urface of , , ' , :
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9 133~32~1 the cured aminoplast layer by corona discharge or by applying a key coat compocition 80 as to promote adhe~ion between the layers. The latter compositions, which typically are vinyl lacquers, are in wide use and are well-known to those skilled in the art. Such compo~itions often comprise vinyl chloride copolymer solution resin~
such as the VAGH resin describ2d above.
Corona discharge is also well-known in the art and involves a raising of the surface energy by exposing the æurface to an electrical arc. The amount of energy necessary to promote good adhes~on may be readily deter~ined by standard means. Thu8, the surface tension of the coating composition may be determined according to ASTM D 1331 and the surface energy of the surface to be coated may be determined essentially as described in ASTM
D 2578. The objective is to rais~ the surface energy of the surface to be coated such that it will be wetted by the coating composition. Ideally the surface energy resulting from the corona treatment will be at lea~t about 10 dynes/cm greater than the surface tension of the coating compo~ition.
qhe thicknes3 of application of the wear layer composition can vary from about 1 to about 8 ~il~, but preferably will vary fron about 2.5 to about 4.5 mils.
The composition may be a low solid (e.g. 40~) solution of ~; polyether or polyester-based urethane which is moisture curable, or it may comprise a 2-component system such as a polyester comprising hydroxyl functionality combined with a diisocyanate. Curing of the latter composition occurs by reaction of the diisocyanate with the hydroxyl groups of the polyester, a~ well as with moisture in the air.
Alternatively, radiation curable, or combinea radiation and moisture curable, component~ can be utilized. As with : ,,-.
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the aminopla~t layer, it i8 alBo advisable to en~ure that the urethane layer is fully cured before lamination to ~he xesilient surface covering is achieved.
When fully cured materials are prepared and then laminated to resilient surface covering~, occa~ional poor adherence of the laminate to the surface covering ha~ been encountered. As with the aminoplast layer and wear layer, it has been found desirable to avoid delamination problem3 by providing a key coat between the back (exposed) surface of the wear layer and the resilient layer with which it is interfaced. As an alternative, corona discharge treatment i~ al~o available to facilitate adhesion of the coat~.
The upward facing wear layer i8 interfaced with the resilient ~upport surface layer, with or without an intervening key coat or corona discharge treatment, and the composite material is ~ubjected to heat and pre~sure to en~ure firm adhesion. The composite material may al~o be affixed to granular or consolidated stencil vinyl products in the same manner. After consolidation i8 complete, the release paper i~ ~tripped from the hot sample to provide a decorative ~urface covering which exhibit~ good scratch and ~tain re~i~tance. Thu8 ~ the materials are resistant to staining by household items ~uch as lipstick, mustard, ~hoe polish, food dye and the like.
~he present invention will be better under~tood by reference to the exampl2s which follow, said examples being provided by way of illustration and not limitation.
EXAMPLES ~ -Example 1 Compocition~ were prepared as ~et out in Table 1 compri~ing each of the indicated components in parts by weight.

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Table 1 Component 1-1 1-2 1-3 1-4 Xylol 16.0 16.0 20.0 20.0 Vinyl c~loride/vinyl acetate copolymer (V~GH* from Union Carbide) - - 13.6 13.6 W 6 tabilizer("Uvitex"*
OB; 1% in xylol) 1.0 1.0 1.0 1.0 organotin ~tabilizer ("Thermolite 31" from Metal and Thermit Co.) - - 0.25 0.25 Fluorocarbon 6urfactant (FC-430* from 3-M
Company; 10% in xylol) 1.0 1.0 0.80 0.80 Methyl i60butyl ketone 18.1718.17 22.07 22.07 Diacetone alcohol 8.0 8.0 8.0 8.0 Isopropyl alcohol 3.6 3.6 3.6 3.6 Aminoplast resin "Resimene 980" 15.30 - 5.1 "Resimene 915* (from Monsanto) - 20.4 - 6.8 Cyclohexane dimethanol (90% in water) 5.1 5.1 1.7 1.7 1,6-He~anediol - - - -2~
p-Toluenesulfonic acid (25% in 1:1 xylol/
isopropyl alcohol) 2.9 2.9 0.9 0.9 Vi~cosity, ~2 Zahn*
cup (6econds) 15.0 16.0 - -~3 Zahn* - - 31 30 Total Solids (%) 29.327.17 27.0 26.42 Ratio of vinyl copolymer to total melamine plus diol -- 2:1 2:1 Trademark (each instance).

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Each of a series of polypropylene-coated release papers was provided with a coating of samples 1-1 through 1-5 at a wet thickness of about 2~5 to 3.5 mils using a rever~e roll coater. The coated paper was then passed through a 260F oven such that the coating resided in the oven for 4 minutes.
A moi~ture-curable polyurethane coating compo~ition as set out in Table 2 was prepared for application to the coated relea3e papers.
1~ Table 2 Component Weight (Gram~) Polyetherdiol (Union Carbide LHT 240*) 40.80 Polyetherdiol (Union Carbide LHT 112*) 14.20 Xylene ~olvent 110.00 15 Toluene solvent 46.00 Dimethyltin dineodecanoate ~atalyst ~"Witco UL-28"*) 0-55 Surfactant (Mon~anto"XA-677 Multiflow"*~ 0.30 Light stabilizer (American Cyanamid UV-5411*) 0.20 These components were charged to a stirred, nitrogen-purged glass reactor and heated to 70C for one hour. A~44.90 gram quantity of 4,4'-diisocyanate dicyclohexylmethane was added dropwi6e over a 30 minute period of ti~e at a rate sufficient to maintain the te~perature of the mixture at 70-C. After an additional two-hour period of stirring and heating at 70C, the product was cooled.
To each of the aminopla~t coated relea~e papers wa6 applied a 1 to 2.5 mil wet layer of key coat lacquer compris~ng 18.54 percent ~y weight of VAGH* resin, 0.37 - percent ~nY~m~lite 31~*, 0.0094 penx~t ~Uvitex OB"* and 81.08 percent methyl ~Qobutyl ketone solvent. The coated sample was then dried in ambient air or under low heat to remove the ~olvent. Upon completion of the drying step, each *~rademark (each instance).

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paper was provided with a 5 to 6.5 mil wet coating of the moi~ture curable polyurethane material described above.
The coated samples were then pacsed through a 250F oven to completely dry the sample, the dwell time in the oven being 7 minutes.
Coatings of camples of 1-6 through 1-9 were prepared on polypropylene coated paper uRing a ~30 wire wound rod drawn to obtain coating~ 0.5 mil in thickness when dried. The samples were then cured at 250~F for five minutes. Sa~ple 1-6 delaminated completely and was discarded. The remaining sampleQ were coated with a moisture-curable polyurethane coating composition as given above.
The lamination and consolidation steps for laboratory evaluations involved the use of a 12 inch x 12 inch press to prepare 9 inch ~ 9 inch samples. The top platen of the press was heated at 310-F whereas the bottom platen was heated at 300F. ~he dwell time in the pre~s was 10 seconds at 250 poundQ pressure, followed by 10 seconds at 1,200 pound~ of pre~ure. Following removal of the ~ample from the press, the release paper was stripped from the ~ot ~ample.
Both stencil vinyl and gelled vinyl plastisol resilient support material~ may be used for lamlnation with the above coatings, and stain resistance wa~
evaluated u~ing ordinary household stain~. Although sample 1-7 was clearly more susceptible to ~taining than the other~, all samples showed superior stain resistance a3 compared to the untreated polyurethane material, and also ~howed good scratch resistance.

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Claims

1. A surface covering comprising a resilient support and a crosslinked wear layer adhered thereto, the upper portion of the wear layer being formed from a composition comprising:
(a) an aminoplast, (b) a vinyl resin, (c) a polyol, (d) a catalyst, and (e) a solvent, the solvent comprising at least 64%
by weight of the composition.

2. The surface covering of claim 1 wherein the aminoplast is a melamine.

3. The surface covering of claim 2 wherein the melamine is alkyl etherified with alkyl groups comprising 1 to 10 carbon atoms.

4. The surface covering of claim 3 wherein the melamine is alkyl etherified with alkyl groups comprising 1 to 4 carbon atoms.

5. The surface covering of claim 1 in which the crosslinked wear layer is a composite, the lower portion of the wear layer disposed between the upper portion of the wear layer and the resilient support being derived from material selected from the group consisting of urethanes, acrylated urethanes, methacrylated urethanes and unsaturated polyesters.

6. The surface covering of claim 1 wherein the vinyl resin is a copolymer of vinyl chloride and vinyl acetate.

7. The surface coating of claim 1 wherein the vinyl resin is selected from the group consisting of polyvinyl acetal, polyvinyl ester and a combination of polyvinyl acetal with polyvinyl alcohol or polyvinyl ester.

8. The surface covering of claim 1 wherein the ratio of vinyl resin to aminoplast/polyol mixture is from 4 to 0.25 by weight.

9. The surface covering of claim 1 wherein the ratio of aminoplast to polyol is from 5 to 0.2 by weight.

10. The surface covering of claim 1 wherein the ratio of vinyl resin to aminoplast/polyol is from 3.5 to 0.33 by weight, and the ratio of aminoplast to polyol is from 3 to 0.33 by weight.

11. The surface covering of claim 1 wherein the ratio of vinyl resin to aminoplast/polyol is from 3.5 to 0.5 by weight and the ratio of aminoplast to polyol is from 3 to 0.33 by weight.

12. The surface covering of claim 1 wherein adhesion between the crosslinked wear layer and the resilient support is facilitated by a key coat layer.

13. The surface covering of claim 5 wherein the upper portion of the wear layer receives a corona discharge pretreatment prior to disposition of the lower portion of the wear layer thereto.

14. The surface covering of claim 13 in which a key coat layer is disposed between the wear layer and the resilient support.

15. The surface covering of claim 14 wherein the resilient support comprises a resilient carrier and a decorative layer comprising vinyl resin and pigments.

16. The surface covering of claim 15 wherein the upper portion of the wear layer is 0.2 to 1.5 mil thick and comprises the reaction product of a composition including (a) a melamine aminoplast, (b) a vinyl copolymer resin, (c) a polyol, and (d) p-toluenesulfonic acid catalyst; the lower portion of the wear layer is a moisture cured polyurethane wear layer; the key coat layer comprises a vinyl chloride/vinyl acetate copolymer resin: and the vinyl resin of the decorative layer is a vinyl chloride/vinyl acetate copolymer resin.

17. The surface covering of claim 16 wherein (b) is a vinyl chloride/vinyl acetate copolymer resin.

18. The surface covering of claim 17 wherein the resilient carrier is felt.

19. The surface covering of claim 17 wherein the resilient carrier is foam.

20. The surface covering of claim 17 wherein the polyol is cyclohexane dimethanol.

21. The surface covering of claim 17 wherein the polyol is an esterdiol.

22. The surface covering of claim 1 wherein the aminoplast is a urea resin.

23. The surface covering of claim 1 wherein the upper portion of the wear layer receives a corona discharge pretreatment prior to disposition of the lower portion of the wear layer thereto.

24. A surface covering comprising a resilient support and a crosslinked wear layer adhered thereto, the upper portion of the wear layer being the reaction product of a composition consisting essentially of:
(a) an aminoplast, (b) a vinyl resin, and (c) a polyol.

25. A process for providing a wear surface for a resilient surface covering, said process comprising the steps of providing a release carrier comprising a support surface and a release coating, disposing on said release coating a composition comprising (a) a urea aminoplast, (b) a vinyl modifier resin, (c) a polyol, and (d) a suitable catalyst, at least partially thermally curing said composition, disposing a crosslinkable wear layer composition on said aminoplast layer, curing said wear layer, laminating said cured wear layer to a resilient support structure, and separating said release carrier from said wear layer, whereby said surface covering comprises a wear layer having a protective coating, said protective coating being flexible, and scratch and stain-resistant relative to the untreated wear layer.

26. The process as set forth in claim 25 wherein said wear layer is derived from material selected from the group consisting of urethanes, acrylated urethanes, methacrylated urethanes and unsaturated polyesters.

27. The process as set forth in claim 25 wherein said vinyl modifier resin is a solution vinyl copolymer resin.

28. The process as set forth in claim 27 wherein said resin is derived from vinyl chloride and vinyl acetate.

29. The process as set forth in claim 25 wherein said modifier resin is selected from a polyvinyl acetal, a polyvinyl ester and a combination of a polyvinyl acetal with polyvinyl alcohol or with a polyvinyl ester.

30. The process as set forth in claim 25 wherein said composition comprises, by weight, from 4 to 1 part of modifier resin for every 1 to 4 parts of aminoplast/polyol mixture, said mixture comprising from 5 to 1 part of aminoplast for every 1 to 5 parts of polyol.

31. The process as set forth in claim 30 wherein said composition comprises, by weight, from 5 to 1 part of modifier resin for every 1 to 2 parts of aminoplast/polyol mixture, said mixture comprising from 3 to 1 part of aminoplast for every 1 to 3 parts of polyol.

32. The process as set forth in any one of claims 25-31 wherein a key coat is provided between said wear layer and said aminoplast layer.

33. The process as set forth in any one of claims 25-31 wherein said aminoplast layer is subjected to corona discharge before said wear layer is disposed on said aminoplast layer.

34. The process as set forth in any one of claims 25-31 wherein said aminoplast is fully cured before said wear layer composition is disposed thereon.

35. A process for forming a resilient surface covering comprising a wear layer, which comprises applying to a free surface of the wear layer a composition comprising (a) a urea aminoplast, (b) a vinyl modifier resin, (c) a polyol, and (d) a catalyst, and forming a protective coating therefrom, or by applying a protective coating derivable from such a composition.