CA1245965B

CA1245965B - Abrasion-resistant laminate

Info

Publication number: CA1245965B
Application number: CA000486192A
Authority: CA
Inventors: Herbert I. Scher; Israel S. Ungar
Original assignee: Nevamar Corp
Current assignee: Nevamar Corp
Priority date: 1977-01-10
Filing date: 1985-06-28
Publication date: 1988-12-06
Also published as: IL53694A; FR2530534A1; CA1104051A; GB1591954A; IL53694A0; JPS6335419B2; JPS59106961A; DE2800762C2; FR2530534B1; JPS6240191B2; DE2800762A1; BR7800068A; IT1091960B; JPS5392875A; IT7819087A0; DE2858182C2; FR2376746B1; FR2376746A1

Abstract

ABSTRACT

A method of producing an abrasion resistant decorative laminate from at least one backing layer and a thermosetting resin impregnated decorative facing sheet, said laminate having enhanced abrasion resistance without an overlay layer, the method comprising:
coating a decorative facing sheet with an ultra-thin wet layer of a mixture of (1) an abrasion resistant mineral of fine particle size in a quantity sufficient to provide an abrasion resistant layer without interfering with visibility and (2) a stabilizing binder material for the mineral having the properties of withstanding the subsequent laminating conditions and being compatible with the thermosetting resin, the binder being present in an amount sufficient to bind said abrasion resistant mineral to the surface of said decorative facing sheet, and the binder-mineral layer in the dry state being permeable to said thermosetting resin;
drying said coated binder-mineral mixture at a temperature sufficient to enhance the bonding of said abrasion resistant mineral by said binder material to said decorative facing sheet, to provide an ultra-thin dry porous layer of said binder-mineral mixture thereon;
impregnating said coated facing sheet with said thermosetting resin;
assembling said resin impregnated and coated facing sheet over said backing layer; and subjecting said assembly to heat and pressure sufficient to effect consolidation of said backing layer and said facing sheet to thereby provide said abrasion resistant decorative laminate. Also provided is an abrasion resistant decorative laminate, a decorative sheet, and a method for making the latter.

Description

` ` ~ ;2~5~36~

The present invention relates to laminates and, more particulnrly, decorative laminates of high abrasion resistance.
High pressure decorative laminates are conventionally produced by stacking and curlng under heat and pressure a plurality of layers Df paper lmpre~nated with various synthetic thermosetting resins. In norm~l practice the assembly, from the bottom up, consists of a plurality, e.~. three to eight, core shaets made from phenolic resin impregnated kraft paper, above which lies a pattern or print sheet impregnated with melnmine resin; on top of the print sheet is provided an overlay sheet which, in the laminate, is almost trnnsparent and provides protection for the pattern sheet.
The core sheets are conventionally made from kraft paper of about 90-125 pound ream weight. Ream weight ls the weight per ream (S00 sheets) of paper having a sheet size of 24 x 36 inches; thus ream weight is pounds per 3000 sg.
ft. of paper.
Prior to stackin~, the kraft paper is impregnsted with a water-alcohol solution of phenol-formaldehyde resole resin, dried and partially cured in a hot air oven, Qnd finally cut into sheets. The print sheet is a high quallty, 50-125 lb. ream weight, pigment filled, alpha cellulose paper that has been impregnated with a water-alcohol solution of melamine-formaldehyde resin, drisd and partially cured, and finally cut into sheets. The print sheet, prior to impregnstion with the resin, usually has been printed with a deGorative design, or with a photogravure reproduction of natural materials, such as wood, marble, leather, etc.
~ n overlay sheet is almost invariably used when the print or pattern sheet has A surface printing in order to protect the printing from abrasive wear.
The overla~ sheet i6 a high quality alpha cellulose paper of about 20-30 pounds ream weight that is also impresnated with melamine-formaldehyde resin in a manner similar to that used for tha print sheet, e~cept that a 8reater amount of resin per unit waight of paper is used. The individual sheets are stacked in the manner indicated above and, if si~ sheets of impragnated core paper are used, there results a finished laminate having a thickness of about S0 mils, it being understood that a dieferent number of sheets can be used to provide thicker or thinner laminates.
The stack of sheets as described abova is placed between polished steel plates and subjected to about 230-340 F (e.g. 300 F) at 800-1600 p.s.i.

5~

(~.g. 1000 p.s.i.) for a time sufficient to consolidate the l~inate and cure the resins (e.g. about twenty-five minutes~. This causes the resin in the paper sheets to flow, cure and consolidate the sheets into a unitary laminated mass referred to in the art as a decorative high-pressure laminate. In actual practice, two laminated stacks are pressed back to back, separated by a coated release sheet that allows the two laminates to be peeled apart after separation. Also, a large proportion of the stacks are laminated with an aluminum foil-kraft paper composite shee~ inserted between the overlay and the metal plate, with the sluminum facing the overlay, in order to obtain a laminate having a lower gloss and a slightly textured surface which is desirable for some products.
At the completion of the laminating oper~tion, the backs of the laminates are sanded to permit gluing to particle board, plywood or other substrates.
The glued, l~minate surfaced panel is then fabricated into furniture, kitchen counter tops, table tops, store fi~tures and other end-use applications widely accepted for the combin~tion of appearance, durability and econ~my.
A number of VQriatiOnS of the above-described general process are ~nown, particularly those operations designed to obtain special effects in appearance and te2ture. Also other curing cycles are possible and, in fact, sometimeg other resin systems are used as well.
Besides decorative high-pressure laminates referred to above, there are also a number of low-pressure products which have been developed in recent years, including low-pressure laminates using either sntur~ted polyester resins, or melamine-formaldehyde resin. One of the fastest growing materials competin~ with high-pressure laminates in recent years is a product referred to as low-pressure melamine board which is normally pressed in a short cycle at 175-225 p.s.i. at 325-350 F. These low-pressure products have the advantage of bein~ normally less e~pensive, but they cannot be given the title of "high pressure laminates" because in order to be entitled to that designation, a product must meet a variety of rigid standards promulgated by the National Electric Manufacturers Association, NEMA LD3-1975 which includes standards relating to abrasive wear, stain resistance, heat resistance, impact resistance, dimensional stability, etc. While various other decorative printed, surfacing materials, such as some of the low-pressure laminates, have certain of the desirable characteristicsl no products other than high-pressure `\ ~ s lamiaates currently available have all of these properties.
One of these properties in particular which i5 Yery important is abrasion r~sistance. A high-pressure decorative laminate must have sufficient abraslon resistanee to permit use in high exposure areas such as dinette surface tops, check-out counters~ etc. The standard NEMA test for abrasion resistance is NEMA test LD-3.01. In this test a laminate sample is clamped on a rotating disc, over which ride two weighted rubber wheels, faced with calibrated sandpaper strips. As the laminate surface is rotated under the wheels, the abrssive action of the sandpaper cuts through the surface of the laminate and gradually throu&h the overlay until the printed pattern is exposed and destroyed. The NEHA standard for Class I laminate requires that the laminate, after four hundred rotation cycles, has no more than 50% of its pattern destroyed. The 50% end point is estimated by averaging the number of cycles at which the pattern shows initial wear, and the number of cycles at which the pattern is completely destroyed.
If a high-pressure decorative laminate is prepared in a conventional manner, with a normal 35~40~ resin content in the print os pattern sheet, but without an overlay sheet, the abrasion resistance will be only about 50-75 cycles. If speciall~ formulated melamine resins are used in the pattern sheet with a resin content of 50-55%, abrasion resistance of up to abo~t 150-200 cycles are on occssion obtainable without ~n overlay sheet, but in this latter case tha laminates have a tendency to develop surface craze and, furthsrmore, they ~re quite difficult to prepare due to the difficulty of impregnating the print sheet in a uniform manner; additionally, they do not meet the 400 cycle minimum required by the NEMA standard.
Nevertheless, it is desirable to produce a laminate without an overlay sheet which is capable of attaining the performance characteristics of a laminate using an overlay, and, in particular, one that provides a 400 cycle abrasion resistance. Further~ore, it is desirable to provide a laminate which, in addition to having the 400 cycle abrasion resistance, has an initial wear point at least equal to the initial wear point of a conventional high-pressure laminate having overlay, typically 175-200 cycles. This is desirable because in actual use the laminate appearance becomes unsatisfactory not when 50~ of the pattern is destroyed, but when a much lower psrcentage is destroy~d. It is well known from many years of field experience that 96~6-1 ~2~ 5 conventional laminates with overlay, which have 175-200 cycle initial wear point, when used in hard use areas, will have a ~atisfactory appearance, at lea~t as long as the norm~l replacement cycle, it being understood that replacement of most lam;nQtes in commercial uses is made for style reasons rather thnn because of pattern wear. Therefore, a laminate ~ithout overlay should meet these same criteria, namely it should have both a NEMA abraslon resistance of at least 400 cycles and an initial wear point in the same tast of at least 175-200 cycles, even though the latter requirement is not part of the NEHA standard.
It is desirable to be able to provide these characteristics, but without using an ovarlay, for several reasons:
1. Overlay adds substantial raw material costs to the manufacture of laminates, both the cost of the overlay paper itself, the cost of tha resin used to impregnate the overlay paper and the in-process and handling losses oP
these materials.

2. The overlay, by imposing an intermediate layer of substantial thickness between the print sheet and the eyes of the viewer, detracts significQntly from the desired visual clarity of the pattern. The cellslose fibers used to make overlay paper have a refractive inde~ close to that of cured melamine-formaldehyde resin. The fibers are therefore almost invi3ibl~
in the cured l~minate, and permit the printed pattern to be seen with vary little attenuation. However, modern printing techniques are making available vsrg accurate reproductions of natural materials, particularly various wood veneer species. As these printed reproductions approach in appearance the natural veneer, even small amounts of haze or blur introduced by the overlay pRper are disturbing visually and destroy much of the realism desired by the user .

3. Furthermore, the overlay contributes to the rejection rate of tha laminate products produced. The impregnated, dry overlay sheet tends to attract small dirt particles because it develops static electricity charges during drying. This dirt is hard to detect and remove before laminating, and results in spoiled laminate sheets that cannot be reprocessed. In addition, the impregnated dried overlay is brittle and hQrd to handle without breakage.
Broken pieces are accidentally trapped on the surface of the overlay and also result in visually defective sheets.

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Additionally, overlay containing laminate, particularly those having A
relatively high surf~ce gloss, have a tendency to become dull very quickly when subjected even to only moderate abrasive wear. This is understandably unacceptable where glossy laminates are desired.
The problem of providing improved abrasion resistance has been a long-standing problem in the field. Many solutions to the problem have been su~gested and, in fact, some of these have reached commercial development.
Nevertheless, it has not heretofore been possible to provide a laminate, not having an overlay sheet, but h~ving a NEMA abrasion resistance of at least 400 cycles and an initial wear point in the same test of at least 175-200 cycles.
It i8 well known that small, hard mineral particles dispersed in overlay paper, or in resin mixtures to cost the impregnated pattern sheet, csn enhance the nbrasion resistance of hi~h-pressure laminates (see, for example, the patents to ~ichl, 3,135,643; Fuerst 3,373,071 and Fuerst 3,373,070).
Techniques such ~s these do not eliminate the ovarlay, but either enhance its abrasion resistance, or provide an alternate form of overlay and associated resin.
For e~ample in the Barna patent 3,123,515, the overlay sheet is impregnated with a finely divided frit. The overlay is used in the normal manner by placing it over the print or pattern sheet.
Another technique is that disclosed in the L~ne et al paten~ 3,798,111 in which there is disclosed the use of smA11 mineral particles, preferably alumina, which are incorpor~ted within and near the upper layer of the base paper during its m~nufacture. In tests, it has been shown thst laminates made with the print paper of Lane et al, without overlay, hnd initial wear values of under 100 cycles, some as low as 35 cycles. Furthermore in a rubbing test to determine initial wear, such laminates be~an to show pattern destruction after only 3~000 rub cycleE, far less than necessary.
Oth~r prior art patents of some interest with regard to the background of the present invention are the patents to Fuerst 3,445,327; Gibbons 3,928,706 ~nd Merriam 3,661,673. Of somewhat less interest are the Battista patents 3,259,537 and 3,157,518; Ando et al 3,716,440; Power et al 3,946,137 and soeni~ 3,318,760.
Even after the considerable activity in the field in order to solve the problems indicated ~bove, these problems have not been solved until the present time.
The prasent invention provides d method of producing an abrasion resistant decorative laminate from at least one backing layer and a thermo~etting resln impregnated decorntive facing sheet, said laminate having enhanced abrasion resistance without an overlay layer, the method comprising:
coating a decorative facing sheet with an ultra-thin wet layer of a mixture of ~l) an abrasion resistant mineral of fine particle size in a quantity sufficien~ to provide an abrasion resistant layes without interferinB
with visibility and (2) a stabilizine binder material for the mineral having the properties of withstanding the subsequent laminating conditions and being compatible with the thermcsetting resin, the binder beine present in an amount sufficient to bind said abrasion resistant mineral to the surface of said decorative facing sheet, and the binder-mineral layer in the dry state bein~
permeable to said thermosetting resin;
drying said coated binder-mineral mixture at a temperature sufficient to enhance the bonding of said abrasion resistant mineral by said binder material to said decorative facing sheet, to provide an ultra-thin dry porous layer of said binder-mineral mixture thereon;
impreenating said coated facing sheet with said thermosetting resin;
assembling said resin impregnated and coated facing sheet over said backin~ layer; and subjecting said assembly to heat and pressure sufficient to effect consolidation of said backing layer aDd s~id facing sheet to thereby provide said abrasion resistant decorative laminate.
Also provided is an abrasion resistant decorative laminate meeting NEHA
abrasion resistance standards and also capable of withstanding 175-200 cycles of initial wear in the same test, comprising:
a backing layer and laminated thereto a thermoset laminating resin impregnated decorative facing sheet, the decorative facing sheet having an ultra-thin, abrasion resistant coating over the upper surace thereof, sald ultra-thin, abrasion resistant coating comprising a mi~ture of (1) an abrasion resistant mineral in fine particle size and quantity sufficient to provide for abrasion resistance without int~rferinB with visibility and (2) a stabilizin~
binder material for the mineral which binder is compatible with the thermoset resin impregnated throughout said facing sheet, the binder not interferinB

with visibility, and wlth the ultra-thin, abrasion resistant co~ting forming the uppermost layer of the laminate.
These products of the invention nre attained by coatin~ conventional printed or otherwise decorated pattern paper with an ultra-thin coating containing small mineral particles immobilized in place on the paper shest by a suitable binder, and wherein such sheet is then impregnated ln the normal manner with a suitable thermosetting resin such as melamine resin, and then using the sheet in the production of decorative laminates without an overlay sheet. It should be noted that both solid coloured and patterned decorative sheets or print sheets are envisaged for use in the present invention.
In another aspect, the invention provides a decorative sheet for use in the preparation of decorative laminates of high abrasion resistance comprisin~
a decorative paper sheet, the surface of which has an ultra-thin, abrasion resistant porous coating which comprises (1) an abrasion resistant hard mineral of fine particle size in a quantity sufficient to provide abrasion resistance without interfering with visibility snd (2) a binder material for said mineral compatible with a thermosettable laminating resin selected from melamine-formaldehyde resin and polyester resin; the coated substrate being impregnable with said laminatin~ resin and the binder material being present in an amount sufficient to bind and stabilize said abrasion reslstant mineral to the surface of said decorative paper sheet substrQte.
Also provided is a method of producing a decorative sheet comprising:
praviding a tecorative sheet havin~ a decorative fncin~ and formed of B
porous material;
coatinS said decorative sheet with an ultra-thin wet layer of a mixture of (1) an abrasion resistant hard mineral of particle si~e 20-50 microns in quantities sufficient to provide an abrasion resistant layer without interferlng w;th visibility, and (2) binder material for said mineral, which binder material has the properties of beine capable of withstanding heat and pressure, and being compatible with a thermosettable resin, said binder being present in an amount sufficient to bind said abrasion resistant mineral to the surface of said decorative sheet, and the binder-mineral layer in the dry state being permeable to said thermosettable resin;
drying said coated binder-mineral material mixture at a temperature sufficient to enhance the bonding of said abrasion resistant nineral by said binder material to s~id decorative sheet, to provide a porous, ultra-thin, dry layer of said binder-mineral mixture thereon.
In one of its most preferred for~s, the invention provides an abrasion resistant ds~orative laminate having superior NEMA abrhsion resistance, superior initial wear resistance in the same test, and superior wear resistance in the Sliding Can Test comprising:
a backine layer and laminated thereto a thermoset laminating resin impregnated decorative facin~ sheet, said decorative facing sheet having an ultra-thin abrasion resistant coating thereo~er, said ultra-thin abrasion resistant coating having a thickness of up to about 0.3 mils comprising a mi~ture of (1) an abrasion resistant hard mineral of particle size 20-50 microns in high concentration sufficient to provide for abrasion resistance without interering with visibility, and (2~ stabilizing binder materi~l for said mineral, said thermoget resin being impregnated throu~hout said decorative sheet and said coating, said binder material not interfering with visibility, and with said ultra-thin abrasion resistant coating forming the uppermost layer of said laminate.
The above and other advantages of the instant invention will be more apparent from the following detailed description of embodiments taken in conjunction with the drawin~ wherein:
~ ig. 1 is a ~low-diagram showing a method of preparing a print layer in accordance with the present invention;
Fig. 2 is a ichematic sectional view showing an embodiment of the print sheet in accordnnce with the present invention; and Fig. 3 is a schematic sectional view showine a laminate in accordance with the present invention.
There has now been discovered a novel composition, containing small mineral p~rticles, which when coated without resin over unimpregnated printed pattern psper, provides surprising and unexpected properties by permitting such paper to be used in the preparation of decorative laminates without an overlay sheet and wherein the resultant laminates are highly abrasion resistant. In its preferred form, the conting composition is composed of a mixture of small particles of alumina and a less0r amount of microcrystalline cellulose particles, both dispersed in a stable, aqueous slurry. The particles of alumina, of small size such that they do not interfere with the ~2~5~6~i visual effects in the fin~l product, serve as the abr~sion resistant material and the microcrystalline cellulose particles BerVe as the preferred binder.
It will be understood that th0 binder must be ~ompatible with the resin system layer utilized in the laminsting procedure, usuQlly a melamine resin or in the case of certain ~ow-pre~sure laminates a polyester resin system9 and the microcrystalline cellulose serves this function as well as stabilizing the small particles of alumina on the surface of the print sheet.
With reference to Fig. 1, in the pr~ferred operation a conventional unimpregnated print or pattern pBper is coated with the mi~ture of h&rd mineral particles and binder, preferably alumina and microcrystallin0 cellulose particles in a stable, aqueous slurry, and the coating is dried at an elevated temperature, such ~s in a hot-air ovsn, to produce a thin coating only 0.02 to 0.3 mils thick. The resultant abrasion resistant coated p~per (Fig. 2) is then impregnated with the melamine or polyest~r resin and dried in a conventional way, at which point it is ready for the laminating procedure.
With reference to Fig. 3, it is seen that the abrasion resistant rcsin impregnated print sheet, having an ultra-thin abraeive resistant coating on its upper surface, is ~ssembled for the laminating step in the conventional w&y, except that no overlay sheet is used. The laminate is then cured under heat and pressure in the conventional manner. A surprising characteristic of the ultra-thin coating is that even thoueh it is so thin, it can provide ~brasion resistance in the finished laminate not only meeting 400 cycles NEMA
Standard, but also providing an initial wear point in sxcess of 175 200 cycles.
It is also surpriYing that this coating tightly adheres to the surf~ce of the printed paper when the paper is later impregnated with melamine resin, without significant amounts of the mineral particles either being lost in the impregnating solution or migrating away from the surface of the paper. A
further surprising characteristic of this coating is that it does not appear to hinder the penetration of the melamine-formaldehyde resin solution into the interior of the paper, during the impregnation step. Such penetration is essential, or the pattern sheet will be irregularly starved such as at its center, and could possibly delaminate after pressing. A further desirnble characteristic of the coating is that it does not significantly scatter or attenuate light, resulting in very clear, crisp appear~nce of the p~ttern in the finished laminate.

_ 9 _ Without being bound to the followin~ theory, it i5 believed that the improved chPracteristics of the invention can be accounted for ns follows:
~icrocrystslline cellulose particles contain very large external forces that bind to other polar substance , such as cellulose and alumina. Thus, an aqueous slurry of microcrystQlline cellulose and alumina is stable ~nd does not quickly settle out, even though alumina particles in water sre not stable. Furthermore, when this slurry is coated on the paper, the microcrystalline cellulose apparently binds the alumina partlcles to the surface fibers of the paper, and to the top of the ink pattern, preventing migration of the alumina particles to below the surface. This may account for the good abrasion resistance developed by such small quantities of alumina.
Thus, all or substantially all of the alumina particles stay at the surface where they do the most good, rather than becoming dispersed below the surface where they would contribute relatively little initial wear resistance.
As indicated above, the preferred slurry composition contains a mixture of ~mall particles of alumina and a lesser amount of microcrystslline cellulose particles, both dispersed in water. There must be an amount sufficient of the small mineral particles to provide the resultant product with the desired abrnsion resistance as discussed above, and there must be an smount sufficient 20 of the binder to retain the mineral particles in place on the surface of the print sheet. In general, it has been found that satisfactory results are attained with about 5 to 10 parts by weight of the microcrystalline cellulose for about 20-120 parts by weight of the alumina; it is possible to work outside this rnnge but there is no ad~antage doing so and, furthermore, the handling problems become quite complicated. The quantity of water in the slurry is also dict~ted by practical considerations, since if there is too little water the slurry becomes so thick that it is hard to apply; similarly, if there i5 too much water the slurry becomas so thin that it is difficult to maintain a consistent thlckness during the coating operation due to running of the slurry. ~hus, a slurry containing about 2.0 wt.% microcrystalline cellulose and about 24 wt.% alumina, based on the water, is stable, i.e. the alumina does not settle out; but if more than about 3.5 wt.% microcrystalline cellulose and about 24 wt.% alumina, based on the water, is used, the slurry becomes ~ery thixotropic and difficult to apply.
The composition also preferable contains a sm~ll amount of wetting agent, 5~

pLeferably a non-ionic wetting agent, snd a silane. The quantity of wetting agent is not critical, but only Q very small amount i~ desirable and excess quantlties provide no advanta~e. ~f a sllane is used, it acts R5 a ~ouplln~
agent which chemically binds alumina particles to the melamine matrix after impregnation and cure, and this provides better initial wear since the alumina particles are chemically bound to the melamine in ~ddition to being mechanically bound thereto and therefore stay in place longer under abrasive wear. The silane should be selected from among the group making it compatlble with the particular thermosetting laminating resin used; in this r~gard silanes having an amino group, such as gamm~-aminopropyl trimethoxy silane, are particularly effective for use with melamine resins. The quantity of silane used need not be grest and, in fact, as little as 0.5~ based on the weight of the alumina is effective to enhance the abrasion resistanse of the final laminate; a maximum quantity of about Z% by weight based on the weight of the alumina is suggested since greater quantities do not lead to ~ny significantly better results and merely increase the cost of the raw materials.
It is an important feature of the present invention that the coating using microcrystalline cellulose as the binder must be dried at an elevated tamperature before the print sheet is impregnated with the melamine resin.
Thus, a minimum drying temperature is about 180 F and th~ preferred drying temperatures are from 240-270 F.
With regard to the abrasion resistant mineral particles, aluminQ is the preferred material. Silica, which has been suggested in certain prior art patents as an abrasion resistant material, provides considerably inferior results in the present invention compared with alumina. Other minerals of sufficient hardness such as zirconium oxide, cerium oxide, diamond dust, etc.
can work, but are either too expensive for practical usage or under certain circumstances produce excessive color shift. Glass beads have been tried unsuccessfully. Silicon carbide also was tried, and while providing good abrasion resistance, produced axcessive color shift.
An important feature i5 the size of the alumina particles. Beneath 20 micron particle size, abrasion resistance becomes poor, ~nd the pr~ferr~d minimum particle size is about 25 microns. Maximum particle size is limited by surface roughness in the article and interference with visual effects. The preferred maximum size of the alumina particles is about 50 microns.

It should be understood that acceptable products and methods of the invention which fall outside this particle size rangs can be obtained. It is possible to employ particles which ~re below the 20 micron particle size.
Although particles as small as 9 microns have proven unsatisfactory, this is particularly so when the decorative sheet substrate is a solid color as opposed to one with a printed pattern. The major improvement in abrasion resistance for such products is observed in the sliding can test. Abrasion resistant mineral particles of size somewhat below 20 microns ~ill give satisfactory results for this test.
1~ The nature of the binder for the mineral particles is a very important feature in the present invention. Of all the materials tried, microcrystalline cellulose is by far the most satisfactory material. ~he binder must serve not only to maintain the mineral particles in position on the surface of the print sheet, but should also act as a suspending agent in the slurry (otherwise, it would be necessary to add an additional suspendin~
agent). The peculiar property of microcrystalline cellulsse is thst it acts like a typical suspending binding agent 6nd film former, but unlike other a~ents is not water soluble before or after suspension and forms a highly porous film throu~h which the thermosetting resin can penetrate. In addition, the binder must be compatible with the laminating resin and microcrystallin0 cellulose is compatible with both melamine resin and polyester resins.
Furthermore, lt must not scatter or attenuate light in the thicknesses applied in the final laminate, and microcrystalline cellulose is s~tisfactory in this regard as well.
Other binders whach may be used, but which provide inferior results compared with microcrystalline cellulose, aLe various typical su6pending-binding agents including anionic acrylic polymer, carboxymethyl-cellulose and similar materials such as hydroxypropyl cellulose, methylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, etc. However, as indicated above, microcryst~lline cellulose is by far the preferred binder.
Microcrystalline cellulose is a non-fibrous form of cellulose in which the cell walls of cellulose fibers have been broken into fragments ranging in length from a few microns to a few tenths of a micron. It is not a chemical derivative but a purified alpha cellulose. ~icrocrystalline cellulose is available under the trade mark "AVICEL", the preparation of which is disclosed ~L2~5~

in the Battists patent No. 3,275,580. AVICEL Type ~C 581 is a white, odorless hy~roscropic powder. It is wQter dispersible and cont~ins about 11% sodi~
csrboxrmethyl-cellulose as a protective colloid. Its particle size is less than 0.1% on a 60 mesb screen.
Features and Qdvantages of the instant invention which are considered to be particularly significant are as follows:
~ 1) The mixture of alumina particles and microcrystalline cellulose is deposited from a water slurry, rather than used as fillers in a resin solution.
(2) Such slurry is coated on an unimpregnated printed pattern sheet, rather t~an on an impregnated pattern sheet.
(3) The coating is dried at an elevated temperature of at least about 180F .

(4) The coating thickness is 0.02-0.2 mil5, rather than 1-2 mils.

(5) After applying the coating and drying it, the pattern sheet is then impregnated with the thermosetting resin, and this conventional impre~nation of the pattern sheet is carried out on conventional eguipment, rather than special, difficult to control, coating of a thick slurry.

(6) The ultra-thin layer provides une~pectedly high abrasion resistance.
The desirable characteristics of the alumina particle binding agent, which characteristics are all ~et by microcrystalline cellulose, are: It acts as a film former; it acts as a binding agent for the ~ineral pRrticles; it ~cts as a ~uspending agent in the slurry for the mineral particles; it is not washed off durin~ the subse~uent thermosetting resin impregnating process; it is compatible with the subsequently applied thermosettin~ resin, such as melamlne resin or polyester resin; it is permeable to the thermosetting impregnQting resin (indeed microcrystalline cellulose forms a porous film); it is resistant to the heat generated during the laminating procedure; Qnd it does not scatter or attenuate li~ht in the laminate.
The following examples are offered illustratively:
FXA~PLE I
Microcrystalline cellulose (A~ICEL RC 581) was added to stlrred water in a WaringX blender. After 2 to 3 minutes in the blender, the AVICEL was completely dispersed and the aluminum oxide (Microgrit* WCA) WQS fiently stirred in. Finally, three drops of TRITON~ X-100 (a non-ionic detergent) was added to promote wetting.

Trade Mar~

L~ 59 ~ S

The resultant slurry was applied as a coating to a 65 lb./ream (3000 ft. ~ unimpregnated patterD sheet havin~ a wood~rain surf~ce print. The coatin~ was dried at 265 F for 3 minutes. The paper was then satur~ted in th0 normal way using melamine-formaldehyde resin and was dried in accordance with normal procedures. The resin content w8s 45-48% and the volatile content was 5~6%. The laminate was made up and pressed usin~ a conventional general purpose cycle, viz. about 300 F, lOOO p.s.i., for about 25 minutes.
Formulations and abrasion results are listed below for a 1.5 mil wet coating, which calculates to a 0.15 mil thick dry coat.

l 2 3 4 5 6 7 _ Water tml) - 250 250 250 250 250 250 AVICEL RC 581 - 6.5 7.5 7.5 7.5 7.5 7.5 ~quantity in gms.) ~ICROGRIT WCA - - 30 30 30 60 60 ~quantity in gms.) ~particle size in microns) Abrasion cycles, 2540 lOO 400 475 75 500 Initial ~ear Pattern Destruotion, % Qt 500 cycles ~00% 100% 20% 5% 2% 95~ 0%
In the above Table, ~ICROGRIT WCA is sluminum 02ide lapping powder manufactured by Micro Abrasives Corporation of Westeield, Hassachusetts.
From the above comparative trials, it is seen that the microcrystalline cellulose by itself was not satisfactory (trial 2); and that the use of alumina havin~ a particle size less than 20 microns did not give good rQsults (trial 6). It is seen that MICROG~IT alumina above 20 micron average psrticle size provided both satisfactory initial wear, and NEMA wear resistance. In addition, the resulting laminates had clearer pattern appearance than conventional laminates having overlay sheets, and such laminates also passed the other NEMA durability tests.
EXAM_LE II
Four slurries were prepared as in Example I, trial #3. Each was used to 9686-l 5~5 coat 3 mils wet onto 65 lb. unimpregnated paper, and dried as in Example I to provide 8 dry coating thickness of ~pproximately 0.3 mil. The dried paper wa~
impregnated with melamine resin and assembled in a laminate stack as shown in Fig. 2. Lamination was carried out as described in Example I. The only varistion in the four trials was the av~rage particle size of the al~mina.
Results were as follows:

MICR0GRIT ~vera~,e Particle Size Pattern Destruction at 500 CVC1QS

9 70%
EXAMPLE III
Example II was repeated in three trials, in each case using alumina particles having an average particle size of 40 microns. The only variation wa5 in the wet coating thickness. Laminates were compared as in Example II.
The results were:

Wet Coatin~ ThicknessPattern Destruction at 500 Cvcles 203 mils (0.3 mil dry) 1%
2 mils (0.2 mil dry) 10~
1 mil (~.1 mil dry) 30%
EXA~PLE IV
The procedure of Example I was repeated using as a coating slurry for the print sheet the following composition:
250 ml. water;

7.5 gms. microcrystalline cellulose;
60 ~ms. of alumina of average particle size 40 microns; and 1 drop of TRITON X-100.
Two trials were carried out providing wet thicknesses of 1 and 2 mils, respectively. After lamination, abrasion testing produced no initial pattern destruction at 500 cycles.
EXANPLE V
The procedure of Example IV was repeated using the same coatin~
composition, except that 120 gms. of alumina having an average particle size g686-1 of 30 microns wns used. Three trials were run with wet costings of 1/2, 1 and 1.5 mils, respectiuely. Abrasion resistancs of the final laminate after 500 cycles gave the following results:
TA~LE 4 1/2 mil (.05 mil dry) 10% pattern destruction 1 mil (.1 mil dry~ 1~ pattern destruction 1.5 mil ~.15 mil dry) 1~ pattern destr~ction The three laminates were highly satisPsctory in all other respects.
~achinability was goot with no chipping.
The physical properties of the third sample (prepared with 0.1 mil coated paper) tested in accordance with NEMA Standard LD3-1975, after impregnation and pres~ing, were as follows:

Wear resistance 500 cycles Stain resistance No effect ~oisture ~b~orption 6.5%
Center Swell 8.9%
Impact (unsupported) 36"
Radiant Heat (unsupported) 185 seconds Hot Water No effect ~ot wax No effect Dimensionnl stability ~.D. 0.24%
C.D. 0.56%
These are all satisfactory or superior -~alues.
EXAMPLE VI
Example IV was repeated in two trials using the same composition, except that in the first trial 60 gms. of HICROGaIT SIC 400 (27 micron silicon carbide) was substituted for the alumina and in the second trial 60 gms. of MICROGRIT SIC 1000 (10 micron silicon carbide) was substituted for the alumina. For each composition, coatings were deposited at 1/2, 1 and 1.5 mils wet. The print sheet had a generally "gray" color due to the color of the silicon carbide. Results were as follows:

Coat~n~~ Pattern De~truction at 500 Cycles 1~2 ~0.5 mil dry) 20 85 1 (.1 mil dry) 5 80 1.5 (.15 mil dry) 5 70 As c~n be seen, while abrasion ~esistance was satisfactory, the 10 micron silicon carbide gave poorer results than the 27 micron silicon carbide. The poor color can be tolerated in only certain colors of print paper.
E~AMPLE YII
E~ample IV was again repeat0d with three compositions, this time substituting 60 gms. of glass spheres (-3Z5 screen size) 9 240 gms. of such glass sphares and 60 gms. of CABOSIL~ L-5 ~silica aerosil of millimicron particle size), respectively, in place of the alumina particles. Each composition was coated at lt2, 1 and 1.5 ~ils wet. The results were as follows:
TABL~ 7 TYPE FULLY WOaN ON TABE:R*
~0 g glass 200 cycles 240 g glass 290 cycles 60 ~ Silica Aerosil 100 cycles ~The device ~or testing Rbrasion resistance described at pages 4 and 5 is ~nown as a Tabe~ abrader.
None of these samples gave sutisfactory abrasion resistance.
EXAMPLE VIII
The procedure of Example IV ~ras again repeated except that this time the coating composition was modified in one sample by the substitution of 6 gms.
of an anionic acrylic polymer (aETENE* 420 - Hercules Powder Company) in place of the microcrystalline cellulose, and in a second sample by 9 gms. of carboxymethyl-cellulose in place of the microcrystalline cellulose. For both samples, the Taber abrasion test showed about 5% wear at 500 cycles, a satisfactory performance, however, the anionic acrylic polymer caused slight milkiness in the laminate indicuting that the use of this material would be satisfactory for only certain colors. The laminate in which Trade Mark ~2~

carboxymethyl-cellulose had been used as the binding sgent for the slumina had A poor boiling water resistance and could not meet the NEMA Standard in this re~ard; this material could only b0 used on certain lower grade low pressure laminates.
E~A~PL~ I~
In order to investi~ate the effects of silanes, the following procedure was carried out. One ~r~m of ~amma-amino propyltrimethoxy silane was mixed with a 10% water-90~ methanol solution until dispersed; a minimum qusntity of liquid is used sufficient to wet the al~mina powder. This dispersion was then added to 100 gms. of alumina of 30 micron size (MICROGRIT WCA 30) and the alumina was mixed with the solution until thoroughly wetted. The alumina was then dried. E~ample IV was repeated e~cept that the coating was appli~d to the print sheet in a 1/4 mil thick wet coatin~ (0.025 mils dried). The resultant laminate was compared to laminates prepared in accordance with e~ample IV (without the silane) also applied at a thickness of 1/4 mil wet.
All laminates were pressed to a mirror finish. The results of the abrasion resistant tests are set forth in Table 8 below:

No Silane Silane Initial ~ear (cycles~ 300 525 Finsl Wear ~cycles) 1075 1250 Wear ~alue 687 8B7 It is seen from the above results that the silane improvad the efficiency of the abrasion resistant coating.
EXAMPLE X
The present invention was tested to determine its efficacy in upgrading the performance of low pressure board. A slurry was prepared as in Example I
with 250 gms. water, 6.5 gms. of microcrystalline cellulose, 30 gms. of alumina of 30 micron size and 2 drops of TRITON X-100. The slurry was coated in lt2 mil wet layer (.05 mil dry) onto unimpregnated printed pattern paper, and dried for 3 minutes at 260F. The sheet was then impregnated and dried twice to ensure complete impregnation. The impregnated sheet was then placed over a wood particle panel and was pressed at 200 p.s.i. at 300F for 6 minutes. As a comparison, an otherwise identical low pressure laminnte was made without providing the abrasion resistant coating on the top surface of ~.2gL~

the print sheet. Both samples were subjected to the NEMA Rbrasion Test and the results were as follows:

Abrasion Resistant Coatin~ No Coatin~
Initial Wear 200 Cycles nil NEHA Abrasion1050 Cycles 150-200 cycles From the above tests as tabulated in Table 9, it is seen that the present invention vastly improves the abrasion resistance of low pressure laminates ns w~ll.
E~AMPLE XI
The procedure of Example IX was repPated and the coatings were applied at a thickness of 1-1/2 mils wet (0.15 mil dry). Four trials were run with the quantity of silane being varied, and the resultant laminate subjected to the NEHA Abrasion Test. The initial wear was recorded, results being ~iven in Table 10 below.

Quantity of Silane-~ms./100 ~ms. alumina Initial Wear, CYcles ~ 475 The above tests show the effect of the silane is not substantially enhanced after reaching a quantity of about 2 wt.~ based on the weight of the alumina; and, in fact, in this particular test at 6~ silane, the results were poorer than at 2~, although significantly better than the layer containing no silane at Qll.
E~AMPLE XII
. _ _ The proccdure of Example IX was repeated to determine initial wear resistance of the ~inal laminate as a function of the temperature used to dry the coating applied over the print sheet. Thus, the pattern sheet was coated with the coatinG composition of Example IV at a rate of 8-10 pounds per ream (0.2 mils dry), except that the coating composition contained silane in accordance with Example IX. The coatin~ was dried for 3 minutes in each sample at the various temperatures given in Table 11 below. After drying the coated sheets were allowed to come to moisture equilibrium with room air at 50~ relative humidity at 70 F; the sheets were then impregnated as u~ual with ~elamine-formaldehyde resin, and were then laminated i~ the usual way n~sinst a satin finished plate. The results ~ere as follows:

Oven TemPerature. Initial Wear, Crclss 2~5 575 EXAMPLE XIII
A slurry of in~redients was prepared as disclosed in ~xample I using 6.5 parts by weight of A~ICEL microcrystalline cellulose, 2 parts by weizht of carbo~ymethyl-cellulose, 30 parts of 30-micron alu~ina, and 250 parts by weight of water. A trace quantity of TRITON X-100 was added.
The resultant slurry WAS applied to print sheet using a ~eyer rod coating machine at the rate of 5.5 pounds per ream (0.15 mil dry thic~ness). The print paper was then impregnated with mel~mine-formaldehyde resin to pr~vide n resin content of 41.7~, and drying was effected to provide a volatil2 content of 4.2%. A l~minate was then pressed with the coated print paper using a standard laminatin~ cycle and a mirror-finished laminating plate so that the inal laminate had a gloss surface.
The laminate so produced was compared with another mirror-finished laminate made in a conventional way usin~ a 20-pound overlay, both laminates bein~ subjected to the "sliding can test", described infra. The laminate in accordance with the present invention had an initial wear of 325 cycles and a NEMA wear value of 1021 cycles. In the sliding csn rub test, the comparative results were as follows:

TABLE 1, ?
SURFACE DULLING
La~inate Made With CYCLESConventional Overlay Laminate Coated Print Sheet 1500 slight no effect 3000 slight no effect 6000(~,radually worse) no effect 12000 slight 24000 extreme wear slight w0ar Pattern destruction began at about 30,000 cycles on both samples, but it i8 seen that the conventional laminate shows gradual surface dulling even at only 1500 rub cycles and, in fact, ~radual surface dullin~ began almost with the first few hundred rub cycles. Furthermore, the conventional laminate is completely dulled w011 before initial pattern destruction t30,000 rub cycles).
Compared with the prior attempts, the present invention provides vnstly improved results such that the present invention can be truly considered to be a revolutionary development in the field of decorative laminates. Insofar as is known, the present invention provides the first time n laminate without an overlay sheet has been made which is capable of meeting both the NEM~ Abrasion ~esistance Standard of at least 400 cycles, and an initial wear point in this same test of at least 175-200 cycles.
There are many uses of laminates in which initial pattern wear rather than NEMA wear value deter~ine the acceptable life of the surface. For example, supermar~et check-out counters, food service counters, cafeteria tables, and other commercial surfaces are exposed to abrasive rubbing and sliding o un~lazed dinnerwear, canned goods, fiberglas tray~, etc. If small areas of the pattern be~in to disnppear after a relatively short period of use, particularly in an irregular pattern, the surface will be unacceptable to the owner and will result in an expensive replacement. If the surface wears gradually and evenly over a lon~, period of time, the wear out time exceeds the normal replacement cycle duc to style chan~,es, approximately 3-5 years.

Claims

1. A method of producing an abrasion resistant decorative laminate from at least one backing layer and a thermosetting resin impregnated decorative facing sheet, said laminate having enhanced abrasion resistance without an overlay layer, the method comprising:
coating a decorative facing sheet with an ultra-thin wet layer of a mixture of (1) an abrasion resistant mineral of fine particle size in a quantity sufficient to provide an abrasion resistant layer without interfering with visibility and (2) a stabilizing binder material for the mineral having the properties of withstanding the subsequent laminating conditions and being compatible with the thermosetting resin, the binder being present in an amount sufficient to bind said abrasion resistant mineral to the surface of said decorative facing sheet, and the binder-mineral layer in the dry state being permeable to said thermosetting resin;
drying said coated binder-mineral mixture at a temperature sufficient to enhance the bonding of aid abrasion resistant mineral by said binder material to said decorative facing sheet, to provide an ultra-thin dry porous layer of said binder-mineral mixture thereon;
impregnating said coated facing sheet with said thermosetting resin;
assembling said resin impregnated and coated facing sheet over said backing layer; and subjecting said assembly to heat and pressure sufficient to effect consolidation of said backing layer and said facing sheet to thereby provide said abrasion resistant decorative laminate.

2. A method in accordance with claim 1 wherein the abrasion resistant mineral is of particle size of 20-50 microns.

3. A method in accordance with claim 1 or 2 wherein the decorative facing sheet substrate has a pattern printed thereon.

4. A method in accordance with claim 1 wherein the decorative facing sheet substrate is solidly colored.

5. A method in accordance with claim 1 wherein said binder material is microcrystalline cellulose and said thermosetting resin is melamine-formaldehyde resin, and said drying is carried out at a temperature of at least about 140 F.

6. A method in accordance with claim 5 wherein said abrasion resistant mineral is alumina, silica or a mixture thereof.

7. A method in accordance with claim 6 wherein said binder-mineral mixture comprises 5-10 parts by weight of microcrystalline cellulose for about 20-120 parts by weight of alumina, along with sufficient water to facilitate the coating operation, and wherein said coating is carried out at such a rate as to provide an ultra-thin coating, after drying, of thickness from 0.2 to about 0.3 mils thick.

8. A method in accordance with claim 6 wherein said binder-mineral mixture further contains a small quantity of non-ionic wetting agent.

9. A method in accordance with claim 1 wherein said binder-mineral mixture further comprises a silane compatible with said thermosetting resin, said silane being present in an amount sufficient to chemically bond said abrasion resistant mineral to said thermosetting resin.

10. A method in accordance with claim 7 wherein said binder mineral mixture further comprises about 0.5% to about 2% by weight of an amino silane based on the weight of the alumina.

11. A method in accordance with claim 6 wherein said drying is carried out at a temperature of 240-270°F.

12. A method of producing an abrasion resistant, high-pressure decorative laminate in accordance with claim 1 wherein said backing layer comprises a plurality of phenolic resin impregnated kraft paper sheets, and said thermosetting resin comprises melamine-formaldehyde resin, the heat and pressure to which said assembly is subjected to effect consolidation being about 230-340°F and 800-1600 p.s.i.

13. A method in accordance with claim 12 wherein said binder material comprises predominantly microcrystalline cellulose and said abrasion resistant mineral is alumina, said mixture comprising about 5-10 parts by weight of said microcrystalline cellulose for about 20-120 parts by weight of said alumina, and wherein said binder material is applied so as to provide a dry, ultra-thin layer of about 0.02 to about 0.3 mils thick.

14. A method in accordance with claim 13 wherein said binder-mineral mixture further comprises 0.5 to about 2% by weight, based on the weight of said alumina, of an amino silane.

15. A method of producing an abrasion resistant low-pressure decorative laminate in accordance with claim 1, wherein said thermosetting resin is selected from the group consisting of melamine-formaldehyde resin and polyester resin.

16. A method in accordance with claim 15 wherein said backing layer comprises a wood particle panel, said thermosetting resin is melamine-formaldehyde resin, said laminating is carried out at a temperature of about 325-350°F and a pressure of about 175-225 p.s.i., and wherein said abrasion resistant mineral is alumina, silica or a mixture thereof, and said binder material comprises predominantly microcrystalline cellulose, said microcrystalline cellulose being present in an amount of about 5 to about 10 parts by weight per about 20-120 parts by weight of said mineral, said mixture being applied to provide a dried coating of 0.02 to 0.1 mils thickness, said drying being carried out at a temperature of at least 180°F.

17. A method in accordance with claim 7, 12 or 16 wherein the mineral is of particle size 20-50 microns.

18. A method in accordance with claim 1, 5 or 7 wherein the binder material comprises a mixture of microcrystalline cellulose and carboxymethyl-cellulose.

19. A method in accordance with claim 13 or 16 wherein the binder material comprises a mixture of microcrystalline cellulose and carboxymethyl-cellulose.

20. A method in accordance with claim 16 wherein said composition further comprises 0.5-2% by weight of an amino silane based on the weight of said alumina.

21. A decorative sheet for use in the preparation of decorative laminates of high abrasion resistance comprising a decorative paper sheet the surface of which has an ultra-thin abrasion resistant porous coating having a thickness of 0.02 to 0.3 mils which comprises (1) an abrasion resistant hard mineral of fine particle size in a quantity sufficient to provide abrasion resistance without interfering with visibility, and (2) a binder material for said mineral compatible with a thermosettable laminating resin selected from melamine formaldehyde resin and polyester resin; the coated sheet being impregnable with said laminating resin and the binder material being present in an amount sufficient to bind and stabilize said abrasion resistant material to the surface of said decorative paper sheet substrate.

22. A decorative sheet in accordance with claim 21 wherein said thermosetting laminating resin is a melamine-formaldehyde resin.

23. A decorative sheet in accordance with claim 21 wherein said binder material comprises predominantly microcrystalline cellulose.

24. A decorative sheet in accordance with claim 21 wherein said abrasion resistant mineral is alumina, silica or mixtures thereof.

25. A decorative sheet in accordance with claim 21 impregnated with melamine-formaldehyde resin, wherein said abrasion resistant mineral is alumina particles, said binder material comprises predominantly microcrystalline cellulose, said ultra-thin coating having a thickness of 0.02-0.2 mils and comprising 5 to 10 parts by weight of said microcrystalline cellulose for about 20-120 parts by weight of said mineral.

26. A decorative sheet as claimed in claim 21, 23 or 25 wherein said binder material comprises a mixture of microcrystalline cellulose and carboxymethyl-cellulose.

27. A decorative sheet in accordance with claim 25 wherein said coating further comprises a silane for binding the alumina to the melamine-formaldehyde resin.

28. A decorative sheet in accordance with claim 27 wherein the silane comprises from 0.5 to 2.0% by weight based on the weight of said mineral.

29. A decorative sheet for use in the preparation of decorative laminates of high abrasion resistance, comprising a paper sheet having a print design thereon, and an ultra-thin abrasion resistant coating over said print design, said ultra-thin abrasion resistant coating having a thickness on the order of 0.02-0.3 mils and comprising a mixture of (1) abrasion resistant hard mineral of small particle size and quantity sufficient to provide an abrasion resistant layer without interfering with visibility, and (2) binder material for said mineral, said binder being present in an amount sufficient to bind and stabilize said abrasion resistant mineral to said paper sheet so as to provide abrasion resistance without the necessity of an overlay sheet, said coating being impregnable by a laminating resin selected from the group consisting of melamine-formaldehyde resin and polyester resin.

30. A decorative sheet for use in the preparation of decorative laminates of high abrasion resistance in which a thermosetting laminating resin selected from the group consisting of melamine-formaldehyde resin and polyester resin is employed, said decorative sheet comprising a paper sheet substrate unimpregnated with laminating resin having a print design thereon, and an ultra-thin abrasion resistant coating having a thickness on the order of 0.02-0.3 mils and comprising a mixture of (1) abrasion resistant hard mineral of small particle size and quantity sufficient to provide an abrasion resistant layer without interfering with visibility, and (2) binder material for said mineral, said binder material being present in a lesser amount than said mineral but sufficient to bind and stabilize said abrasion resistant mineral over said paper sheet, said decorative sheet including said coating being impregnable with said laminating resin.

31. A decorative sheet in accordance with claim 21 wherein said binder material comprises a mixture of microcrystalline cellulose and carboxymethyl-cellulose.

32. A decorative sheet in accordance with claim 21 wherein the quantity by weight of said binder material in said abrasion resistant coating is no greater than the quantity by weight of said mineral therein.

33. A decorative sheet in accordance with claim 1 or 21 which is impregnated with the thermosettable resin.

34. A decorative sheet in accordance with claim 1 wherein the thermosettable resin is a melamine-formaldehyde resin or a polyester resin.

35. A decorative sheet in accordance with claim 1 wherein the thermosettable resin is a melamine formaldehyde resin.

36. A method of producing a decorative sheet in accordance with claim 21 comprising:
providing a decorative sheet having a decorative facing and formed of a porous material coating said decorative sheet with an ultra-thin wet layer of a mixture of (1) an abrasion resistant hard mineral of particle size 20-50 microns in quantities sufficient to provide an abrasion resistant layer without interfering with visibility, and (2) binder material for said mineral, which binder material has the properties of being capable of withstanding heat and pressure, and being compatible with a thermosettable resin, said binder being present in an amount sufficient to bind said abrasion resistant mineral to the surface of said decorative sheet, and the binder-mineral layer in the dry state being permeable to said thermosettable resin;

drying said coated binder mineral material mixture at a temperature sufficient to enhance the bonding of said abrasion resistant mineral by said binder material to said decorative sheet, to provide a porous, ultra-thin, dry layer of said binder-mineral mixture thereon.

37. A method in accordance with claim 36 wherein the decorative sheet is impregnated with the thermosettable resin.

38. A method in accordance with claim 37 wherein the resin is a melamine-formaldehyde resin or a polyester resin.

39. A method in accordance with claim 34 wherein the resin is a melamine-formaldehyde resin.

40. An abrasion resistant decorative laminate meeting NEMA abrasion resistance standards comprising:
a backing layer and laminated thereto a thermoset laminating resin impregnated decorative facing sheet, the decorative facing sheet having an ultra-thin, abrasion resistant coating over the upper surface thereof, said ultra-thin abrasion resistant coating having a thickness of 0.02 to 0.3 mils, and comprising a mixture of (1) an abrasion resistant mineral in fine particle size and quantity sufficient to provide for abrasion resistance without interfering with visibility, and (2) a stabilizing binder material for the mineral which binder is compatible with the thermoset resin impregnated throughout said facing sheet, the binder not interfering with visibility, and with the ultra-thin abrasion resistant coating forming the uppermost layer of the laminate.

41. An abrasion resistant decorative laminate comprising:
a backing layer and laminated thereto a thermoset laminating resin impregnated decorative facing sheet, the decorative facing sheet having an ultra-thin, abrasion resistant coating over the upper surface thereof and having a thickness of 0.02 to 0.3 mils, said ultra-thin abrasion resistant coating comprising a mixture of (1) an abrasion resistant mineral in fine particle size and quantity sufficient to provide for abrasion resistance without interfering with visibility, and (2) a stabilizing binder material for the mineral which binder is compatible with the thermoset resin impregnated throughout said facing sheet, the binder not interfering with visibility, and with the ultra-thin abrasion resistant coating forming the uppermost layer of the laminate.

42. A decorative laminate in accordance with claim 40 or 41 wherein said thermoset resin is melamine-formaldehyde resin.

43. A laminate in accordance with claim 40 or 41 wherein said thermoset resin is melamine-formaldehyde resin and said binder comprises predominantly microcrystalline cellulose.

44. A laminate in accordance with claim 40 or 41 wherein said thermoset resin is melamine-formaldehyde resin and said binder comprises a mixture of microcrystalline cellulose and carboxymethyl-cellulose.

45. A laminate in accordance with claim 40 or 41 wherein said abrasion resistant mineral particles constitute alumina, silica or mixtures thereof.

46. A laminate in accordance with claim 40 or 41 wherein said ultra-thin abrasion resistant coating is directly over the upper surface of the decorative facing sheet and has a thickness of 0.02-002 mils.

47. A laminate in accordance with claim 40 or 41 wherein said abrasion resistant mineral is of particle size 20-50 microns.

48. A decorative, high-pressure laminate in accordance with claim 40 wherein said backing comprises a plurality of phenolic impregnated paper sheets and said facing sheet comprises a paper sheet impregnated with melamine-formaldehyde resin, said abrasion resistant particles comprising alumina particles, said binder material comprising microcrystalline cellulose, said abrasion resistant coating comprising about 5-10 parts by weight of said microcrystalline cellulose for about 20-120 parts by weight of said alumina, the thickness of said coating being about 0.02-0.2 mils.

49. A decorative, high-pressure laminate in accordance with claim 41 wherein said backing comprises a plurality of phenolic impregnated paper sheets and said facing sheet comprises a paper sheet impregnated with melamine-formaldehyde resin, said abrasion resistant particles comprising alumina particles, said binder material comprising microcrystalline cellulose, said abrasion resistant coating comprising about 5-10 parts by weight of said microcrystalline cellulose for about 20-120 parts by weight of said alumina, the thickness of said coating being about 0.02-0.2 mils.

50. A laminate in accordance with claim 48 or 49 wherein said alumina is bonded to said melamine-formaldehyde resin with a silane.

51. An abrasion resistant decorative laminate having superior NEMA abrasion resistance, superior initial wear resistance in the same test, and superior wear resistance in the Sliding Can Test comprising:

a backing layer and laminated thereto a thermoset laminating resin impregnated decorative facing sheet, said decorative facing sheet having an ultra-thin abrasion resistant coating thereover, said ultra-thin abrasion resistant coating having a thickness of up to about 0.3 mils comprising a mixture of (1) an abrasion resistant hard mineral of particle size 20-50 microns in high concentration sufficient to provide for abrasion resistance without interfering with visibility, and (2) stabilizing binder material for said mineral, said thermoset resin being impregnated throughout said decorative sheet and said coating, said binder material not interfering with visibility, and with said ultra-thin abrasion resistant coating forming the uppermost layer of said laminate.

52. A decorative laminate in accordance with claim 51 wherein said thermoset resin is melamine-formaldehyde resin.

53. A laminate in accordance with claim 52 wherein said binder comprises predominantly microcrystalline cellulose.

54. A laminate in accordance with claim 53 wherein said abrasion resistant mineral particles constitute alumina, silica or mixtures thereof.

55. A laminate in accordance with claim 52 wherein said abrasion resistant mineral is alumina, and wherein said alumina is chemically bound to said melamine resin with a silane.

56. A laminate in accordance with claim 51 wherein said ultra-thin abrasion resistant coating has a thickness of 0.02-0.2 mils.

57. A decorative, high-pressure laminate in accordance with claim 51 wherein said backing comprises a plurality of phenolic impregnated paper sheets and said facing sheet comprises a paper sheet impregnated with melamine resin, said abrasion resistant particles comprising alumina particles, said binder material comprising microcrystalline cellulose, said abrasion resistant coating comprising about 5-10 parts by weight of said microcrystalline cellulose for about 20-120 parts by weight of said alumina, the thickness of said coating being about 0.02-0.2 mils.

58. A laminate in accordance with claim 57 wherein said alumina is bonded to said melamine resin with a silane.

59. A laminate in accordance with claim 51 wherein said ultra-thin abrasion resistant coating has a thickness no greater than 0.3 mils.

60. A laminate in accordance with claim 41 or 51 wherein the quantity by weight of said binder material in said abrasion resistant coating is no greater than the quantity by weight of said mineral therein, and said binder material constitutes a mixture.

61. An abrasion resistant decorative laminate having superior NEMA abrasion resistance, superior initial wear resistance in the same test, and superior wear resistance in the Sliding Can Test comprising:
a backing layer and laminated thereto a thermoset laminating melamine-formaldehyde resin impregnated decorative facing sheet, said decorative facing sheet having an ultra-thin abrasion resistant coating thereover, said ultra-thin abrasion resistant coating having a thickness of up to about 0.3 mils comprising a mixture of (1) an abrasion resistant hard mineral having a minimum average particle size of about 20 microns in high concentration sufficient to provide for abrasion resistance without interfering with visibility, and (2) stabilizing binder material for said material, said thermoset resin being impregnated throughout said decorative sheet and said coating, said binder material not interfering with visibility, and with said ultra-thin abrasion resistant coating forming the uppermost layer of said laminate.