Note: Descriptions are shown in the official language in which they were submitted.
The present iIIvention relates to laminates and,
2 more particularly, decorative laminates of high abrasion
3 resistance.
4 High pressure decorative lamir~ates are conve~
5 tionalLy produced by stacking and curing under heat and
6 pressure a plurali~y of layers of paper impregnated wi~h
7 variou~ synthetic thermo~etting resin~. In normal practlce
8 ~he assembly, from ~he bottom up, consists of a plurality3
9 e.g. three to eight, core sheets made ~rom phenolic resin :
impre~n~ed kraft paper, abo~e which l~çs a pa~tern or print ;~
11 sheet impregnated with melamine resin; on top o the print.
12 sheet is provided an overlay sheet which, in the laminate9
13 is almo~t transparent and provides pro~ection for ~he
14 pattern sheet.
The core sheets are conventionally made from kraft :
16 paper of about gO-l25 pound ream weight. Ream weight is
17 the weight per ream (500 ~heets) of paper having a sheet size
~8 of 24 x 36 inehes, thus ream weight is pounds per 3000 sq~
19 ft. of paper.
Prior to stacking, the kraft paper is impregna~e~
21 with a water-alcohol solution of phenol-formaldehyde resole
22 resin9 dried and par~lally cured in a hot air o~en, and
23 finally cut into sheets~ The print sheet is a high quality 3
24 50-125 lb. ream weight, pigment filled, alpha cellulose
paper that has been impregnated with a water-alcohol ~olu-
26 tion of meLamine-formaldehyde resin, dried and partially :~
27 cured~ and finally cut into sheets. ~he print sheet, prior
~8 ~o impregnation wi~h ~he resin, usually has beerl printed
29 with a decorative design, or with a photogravure reproduction : ;
of na~ural materials, such as wood,marble, leathe~, etcO
31 An overlay sheet ls almost invariably used when
32 the print or pattern shee~ has a surface printing in order ~o
_
pro~ect ~e printing from abrasive wearO The overlay sheet
2 ls a high quality alpha cellulose paper of aboult 20-30
3 pounds ream weight that is also impregnated with melamlne-
4 formaldehyde resin in a manner similar to that used for t:he
5 print shee~ ~ except that a greater ~nount of resln per ~
6 weight of paper is used~ ~e ind~vidual sheets are s~acked
7 in the manner indicated above and9 i slx sheets of impreg~
8 na~ed core paper are used9 there results ~ flnished lam~nate
9 hav~ng a thickness of about 50 lIlil5~ it being understood
10 that a diferent number of ~heets can be used ~o prov~de
11 ~hicker or thinner l~nlnates~
12 The stack of sh~e~s as described above is placed
13 between ps~lished steel pla~es and sub~ect:ed to about ~30
14 340~F (e.g~ 3005F) at 800~1600 poS~io ~e~g~ 00 poSoi~
1$ :Eor a time sufficient to conso~l.idate the lamlnate ~nd cure
16 the resins ~eOg, about twenty~ive minutes)~ This causes
17 the resln in the paper sheets tb floW9 cure and conso11~ate
18 the sheets in~o a unitary l~minated mass referred to ~n ~he
19 ar~ as a decoratlve h~h~pressure lamlnateO In actual prae~
tice~ ~wo 1aminated staeks are pressed back to baek9 sep~
21 arated by a coated reLe~se sheet that allows ~he ~wo l~L~
22 nates to be peeled apart af~er separatl~n. Also~ a larg~
~3 proportion of the staeks are. laminated wlth an alum~num
24 foil-kraft paper campos~te sheet inserted between the over~
lay and the metal plate~ with the aluminu~ facing ~he over-
26 lay D in order to ob~ain a laminate having a lower gloss and
27 a sllghtly textured surface w~ich is deslrab1e for some
~8 products .
29 At the completion of the laminating operation~ the
backs of ~he lamina~es are sanded to permit gluing ~o partl~
31 cle board~ plywood or other subs~rates~ The glued9 laminate
32 surfaced panel is then f~brica~e~ in~o furni~ure~ kitehen
~ 3 ~
1 counter tops 3 table tops~ store fi~tures and other end-use
2 applications wide~y accepted for the combinatîon of appea~-
3 ance, durability and economyl
4 A number of varla~ions of the above-described
general process are known~ partlcularly those operations de~
6 sign~d to obtain special eff~cts in appearance and textureO
7 Also other curing cycl~s are possible and, in fac~D some~
8 t~mes other resin systems are used as well~
9 Besides decorative high~pressure laminates re~
ferred to-above, there are a~so a n~mber of low-pressure
11 produets whlch have been developed in recent years9 ~nclud~
12 ing low~pressure laminates using either satura~ed polyest~r
13 resins~ or melam~ne~formaldehyde resinO O~e of the fastest
14 growing ma~erials competing with high~pressure laminates in
recent years is a product referred to as lowlpressure mela~
16 mine board w~ich is ~ormally pressed in a shor~ cycle at
17 175~225 po so i at 325~350Fo These l~w~pressure products -
1~ have the advantage of being normally less expensi.ve~ but
19 they cannot be given ~hP title of "high pressure laminates'
beeause in order to be entltled to that designation~ a prod~
21 uct must meet a variety of rigid s~andards promulgated by
22 ~he National Elec~ric Manuacturers Assooiationg NEMA LD3~ ~
23 1975 which incl.udes standards relating to abrasive wear~ ;
24 stain resls~anceg heat re~is~ance~ ~mpact resis~a~ce 3 d~en~
sional stabil~ty~ etcO While varlous other decorativ~
26 printed, surfac m g materials~ such ~s some of the low~
27 pressure laminates~ have certain of the desirable charac~er~
28 ist~cs~ no products other than high~pressure laminates cur~
29 rently avail~ble have all of these proper~ies~
On~ of these properties in particular which is
31 very ;mportant is abrasion resi~tance~ A hlgh-pressure dec~
32 orative læminate must ~ave sufficient abrasion resistanc~ to
~ 4 ~
1 permit use in high exposure areas such as dinette surface
2 ~ops~ check-ou~ coun~ers D et~. The standard N~M~ test for
3 abrasion resistance is NEMA test LD~3,010 In this test a
4 laminate s~mple i~ clamped on a rotatin~ discD over which
5 ride two weighted rubber wheels~ faced wlth calibrated sand~
6 paper strips~ As the laminate ~urfa~e is rotated under the
7 wheels, th~ abrasive action of the sandpaper cuts through
8 ~he surface of the ~mîna~e and gradually through the over~
9 lay until the printed pa~tern is exposed and destroyed~ The
lo NEMA standard for Class I laminate requ~res th~t the l~mi~
ll nate~ after ~our hu~dred rotation cycles~ has no more than
12 S0~/0 of its pattern destroyedO The 50% end point is esti~
13 mated by averaging the number o cycles at w~ich the pattern
l4 shows initial wear~ and ~he number of eycles at wh~c~ the
pattern is completely destroyed.
16 If a high~pressure decorative lam~nate is prepare~
17 iII a con~ren~ional manner3 wi~h a normal 35~40% resin eon~ent
18 in ~he print or pat~ern sheet ~ bu~ withou~ an overlay slhee~: 9
19 the abra~ion resis~Lanee will be orlly ~out 50~75 cyclesO I~
2Q specially form~L~ated melalrline resins ~re usçd in the pat:~ern
21 sheet with a re~in content of 50-55~0~ abras~on resi~tance of
22 up to about 15OD200 cycles are on oceasion obtainable with~
23 out an over~ay ~heet ~ but in ~hi~ latter case the laminates
24 have ~ tendency to develop surface craze and~ furthermore~
they are quite d~fficult to prepare due to the difficulty o~
26 ~mpregnating the print sheet in a unifonm manner, add~tion~
27 ally~ they do not meet the 400 ~ycle minimum required by ~he
23 NEMA standard.
29 Never~heless~ i~ is d~sirable to produce a l~mi~
nate wit~out an overlay ~heet which is capable of attaining
l the perf~rmanee charscteristics of a lamlnate using an o~er~
32 lay~ and~ in part~ cular 9 one tha~ provides a 400 cycle
~~
1 abrasion resistance~ Furthenmore, i~ is d~irable to pro-
2 vide a laminate which, in addit~on ~o ha~ing the 400 cycle
3 abrasion resistance3 has an initial wear point at least
4 equal to the initial wear point of a conventiona~ higho
pressure laminate having overlay~ typically 175-200 cycleq~
6 This is desirable because in actual use ~he la~inate appear- ~;
7 ance becomes unsat1sfactory not when 50% of the pattern is
8 ~estroyed9 but when a much lower percen~age is destroyed3
9 It is well known from many years of ield experience that
0 conv~ntional laminates with overlayg which have 175~200
11 cycle inltial wear point; when used in hard use are~sg will
12 have a satisfactory appearance, at least as long as ~he
13 nonmal replac~ment cyCle9 it being understo~d ~hat replace~
14 ment of most l~minates in c~mmercial use~ is made for style
reasons rather than because of pat~ern wear. There~ore~ a
16 laminate without overlay should meet these same criteria~
17 namely it should have both a NEM~ abrasion resistance of at
18 leas~ 400 cycl~s and ~n ~nitial wear point in the same test
19 of at least 175~00 cycles~ even t~oug~ the latter require~
ment is not part of the N~M~ standardO
21 It ~s desirab~e t~ be able to provi~e these char~ ~
22 acteristic~9 but without usLng an overl~y~ for several r~a~
23 sons~
24 lo ~verlay adds substantial raw ma~erial costs to
the manufacture vf laminatesD both the cost of the overlay
26 paper itself~ the cost of the resin used to ~mpregnate the
27 overl~y paper and t~e in~proeess and handling losses of
23 ~ese materialsO
29 25 The overlay~ by imposing ~n lntermediate l~yer
of su~stantial t~ickness between the print sheet and the
31 eyes o~ the viewer9 detracts sig~i~icantly from the deslred
32 visual rlarity of the pattern~ The cellul~se fibers used to
~ 6 ~
1 make overlay paper have a reractive ~ndex close to that o~
2 cured melæmine~ormaldehyde resinO The flbers are ~herefore
3 almost invisible ln t~e cured lamina~e 7 and penmit the
4 pr~nted patter~ to be seen with very little attenuation~
However, modern printing technique~ ar~ m~king available
~ very accurate reproductions of natural ma~erials, particu-
7 larly various wood veneer species. As these prin~ed repro-
8 ductions approach in appearance ~he na~cural veneerg even
9 small amounts of haze or blur introduced by t~e overlay
paper are disturbing vlsually and des~roy ~ch of the real~
11 lsm desired by the userO
12 3. Furthenmore 9 the overlay contributes to ~he
13 re~ection rate of the lamina~e produc~s produced~ The ~m~
4 pregnated 3 dr~ overlay sheet tends to attract small dirt
partlcles beca~se it de~elops static e~ectricity ch~rges
16 during drying~ This dirt ~s hard to detect and remove be~
17 fore laminating 3 and result~ ~n spoiled laminate shee~s
18 t~at ¢annot be reprocessedO In addl~ion9 the lmpregna~ed
9 d~ied overlay is br~ttle and hard to handle without break~
ageO Broken pieees are accidentally trapped on the surface
21 of the overlay and also result ~n visually defective sheetsO
2~ Additionally~ overlay containi~g laminate, par~
23 t~cularly those hav~g a relatively high surace gloss~
24 have a ~endency ~o become dull very quickly whe~ subje~ted
2S even ~o only moderate abrasive wearO This is und~rstandabl~
26 unacceptable where glossy læmin~tes are desired.
27 The p~oblem of providing improved abrasion resls~
28 ~ance has bçen a long~s~and~ng problem ~n ~he ~ieldO Many
~olutions to t~e problem have been suggested ~nd~ in fact9
some of these ha~e reached commer~ial developmen~ Never~
31 theless~ it has not ~eretofore been possible to provide a
32 lam~nate9 no~ havlng an overlay shee~ but having a NEMA
~ 7 ~
abraslon resistanc2 of at least 400 cycles and an initial
2 wear point in the s~me test of at least 175-200 cyclesO
3 It is well known that small, hard mineral parti~
4 cles dispersed in overlay paper, or in resin mi~tures to
coat the impregnatcd pa~tern sheetl can enhance the abr slon
6 resistance of high-pressure laminates (see, :Eor e~afnple,, ~he
7 patents to M~chl" 33135D643; Fuerst 3~373?O71 and Fuerst
8 3,373,070)0 Tec~niques such ~s these do not eliminate ~e
9 overlay3 but either e~ance lts abrasion resistance~ Qr pro~ ;
vide an alternate form of over~,ay and associ ated resinO
11 For example ~ t~e Barna patent 3~,123DS15 ~, the
12 overlay sheet is ir~pregnated wlth a finely div~ded fritO
13 The overlay is use~ in the normal manner by placing it over
14 the print or pattern sheet~
Ano~er tec~que is tha~ disclosed ln the Larle
16 et al pa~ent 3,,798~111 in w~ich ~her~ is diselo~se~ ~he use
l7 of sm ll m~neral partiel~sD preerably al~mnaa, whieh are
18 incorporated within and near the upper layer o the base
l9 paper during ~ t~ manufacture~ In tests ~, it has been ~own
th~Lt Lamin~te~ made witlh the print paper of Lane et al D
21 without overlay, had ~nitial we~r value~ of under `100
22 cycles S sc~me as low as 35 cyc~sO Furtlhermore in a ru~b~ng
23 test to detennlne initial wear 3 such laminate~ begaLn to s~hGsw
24 pattern des~ruction after only 3,000 rub c~cles~ ~ar less
than necessary.
26 Other prior art paten~s of some in~erest wlth re
27 gard to the background o f the pres ent inventlon ~re ~e
28 paten~s ~o Fuers~ 31445~327; C,ibbons 3$928,,706 ~nd Merril~m
29 3366l ~6730 Of ~mewhat leæs in~ere~t are the Bat~ist:a pat
ents 37259~537 ~nd 3,~57~18, ~ndo e~ al 3~716944û; Power
3 et al 33946~137 and Boen~g 39318,760.
32 Even af ter the considerabl e ac tivi ty in ~e f ield
w ~ .
in order to solve the problems indicated above, these problems
have not been solved until the present time. -~
The present invention provides a high-pressure decorative
laminate that does not contain an overlay sheet, but which ;~
nevertheless meets the requirements of the NEMA abrasion stan-
dard, and furthermore provides an initial wear point of at
least 175-200 cycles in this same test. Specifically the
present invention provides a print sheet for use in the prepara-
tion of decorative laminates of high abraslon resistance,
comprising: a paper sheet substrate having a print design
thereon, and an ultra-thin abrasion resistant porous coating
over said print design, said ultra-thin abrasion resistant
coating comprising a mixture of (l) an abrasion resistant hard
mineral of particle size 20-50 microns ln high concentration
sufficient to provide an abrasion resistant layer without
interfering with visibility and (2) binder material for said
mineral compatible with a thermosetting laminating resin
i selected from the group consisting of melamine-formaldehyde
resin and polyester resin, and being impregnable with said
laminating resin, said binder material being present in an
amount suf~icient to bind and stabilize said abrasion resistant
mineral to the surface of said paper sheet.
Also provided is an abrasion resistant decorative lami-
nate meeting NEMA 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, said
9 --
decorative facing sheet having a print design thereon and an
ultra-thin abrasion resistant coating over said print design,
said ultra-thin abrasion resistant coating comprising a mixture
of (1) an abrasion resistant hard mineral o~ particle size
20~50 microns in high concentration sufficient to provide for
abrasion resistance without interfer.ing with visibility and
(2~ stabilizing binder material for said mineral, said thermo-
set resin bei.ng impregnated throughout said print sheet and
said coating, said binder material not interfering with visibil-
ity, and with said ultra-thin abrasion resistant coating forming
the uppermost layer of said laminate.
These products of the invention are attained by coating
conventional printed or otherwise decorated pattern paper
with an ultra-thin coating containing small mineral particles
immobi.lized in place on the paper sheet by a suitable binder,
and wherein such print sheet is then impregnated in the normal
manner with a suitable thermosetting resin such as melamine
resin, and then using the print sheet in the production of
decorative laminates without an overlay sheet.
; 20 More particuIarly, there is also provided 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 comprîsing:
coating a decorative facing sheet with an ultra-thin
wet layer of a mixture of (1) an abrasion resistant hard
mineral of particle size 20-50 microns ln quantity sufficient
to provide an abrasion resistant layer without interfering
with visibility and (2j binder material for said mineral which
~ 9a -
,, . ",
: i~
binder material has the properties of withstandin~ the
subsequent laminating conditions, being compatible with said
ther~osetting resin, said binder being present in an amount
sufficient to bind said abrasion resistant mineral to the
surface of said decorative fac.ing sheet, and the binder-
mineral layer in the dry state being permeable to said thermo~
setting 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 dxy 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
subjec-ting 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 a method of producing a print sheet com~
prising:
providing a print sheet having a decorative facing and
formed of a porous materiali
coating said print sheet with an ultra~thin wet layer
of a mixture of (1) an abrasibn 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
- 9b -
_J .
has the properties of being capable of withstandiny heat and
pressure, and being compatible ~ith a thermosettable resin,
said binder being present in an amount sufficient to bind said
abrasion resistant mineral to the surface of saicl print sheet,
and the binder-mineral layer in the dry state being permeable ~
to said thermosettable resin; :
drying said coated binder coated material mixture at a
temperature sufficient ~o enhance the bonding of said abrasion
resistant mineral by said binder material to said decorative
print sheet, to provide a porous, ultra-thin, dry layer of said
binder-mineral mixture thereon. ~ : -
The above and other advantages of the instant invention
will be more apparent from the following detailed description of
embodiments ta]cen in conjunction with the drawing wherein~
Fig. 1 is a flow-diagram showing a method of preparing a ~ :
print layer in:accordance with the present invention;
Fig. 2 is a schematic sectional view showing an embodi-
ment of the print sheet in accordance with the present inven-
tion; and
Fig. 3 is a schematic sectional view showing a laminate
in accordance with the present invention.
There has~now been discovered a novel composition, :
`: :
containing small mineral particles, which when coated without
resin over unimpregnated printed pattern paper, provides :
~ :
:~
9c ~,
. .
1 surprlsing and unexpec~ed propertles by p2rm~ tting such
2 paper to be used in the preparation of decorative laminates
3 without an overlay shee~ and whereln ~he re~ultant laminates
4 are highly abrasion resistantD I~ its preferred fonm~ the
coating composition is composed of a mixture of small parti~
6 cles of alumina and a lesser amount of microcrystalline
7 cellulose particles~ bo~h dispersed in a stable~ aqueous
8 slurryO The particles of alumina3 of sma1l ~ize such that
9 they do not interfer~ with the visual efects ~n the final
product~ serve as the abrasion resistant material and the
11 microcrystalline cellulose particles serve as ~he preferred
12 binder. It will be unders~ood ~hat ~he binder must be
13 compatible wi~h ~e resin. system later utilized in ~he l~mi~
14 nating procedureD usually a mel~mine resin or in the case o~
cer~ain low~pressure l~minat~s a polyester resln syst~m~ and
16 the microcrys~alline cellulose serves ~his func~ion as well
17 as stab~lizing the smal~ par~icleæ of al.-~nina on ~he surface
1~ of the print sheetO
19 With reference to ~?igo l g in the preferred oper~
tion a conventional unimpregnated prin~ or patterrl p~per is
21 coated wi~h ~e mixture of h~rd mineral partit~les and bir1Ld~
22 er, preferably alumina and microcryst~ ne cellulose partiG
23 cles in a stable ~queous slurry9 and the coa~ing is dried
24 at an elev~ted ~eDnperature2, such as ~n a hot~a~r o~en9 ~co
produce a thin coa~ing only OaO~ to 0~3 m~ls thicko The
26 resultan~ abrasion resis~n~ coa~ed paper (Fi~. 2) is then
27 impregnated with the melamine or polyester resin and dried
28 in ~ conven~ional way,~ at whi:~ ~oint it is ready for the
29 laminating proceduree
With reference to Figo 3~ it i8 ~een that the
31 abrasion resistant resin impregnated print slheet s, ha~7ing an
32 ultra~thin abrasive reslsl~ant coat:ing on i~s upper surfaee9
~ :10 ao
l is assembled for the- lmainating step in the conventional
2 way, e~cept that no overlay sheet.i$ u~ed. The laminate
3 is then cyred under heat and pressure in the conventional
4 manner. A surprising aharacteristic o~ the u1tra-thin :~
coating is th~t eYen ~hough it is so thin~ it can provide :~
6 abrasion resiætance in the finished lamin~t~ not only meet-
7 ing 400 cycles NEMA Sta~dard, but al3~ providing an lnitlal
8 wear polnt ln e~cess of 175-200 cycle~.
9 It is also surprising tha~ ~his co~ting tightly
adheres to the sur~acq of the printed paper when the paper
is later impregnated with melamine resin9 without significan~
2 amounts of the miner~l particles ei.ther being lost in the
3 impregnating solu~ion or migrat~ng away from the surface of
4 the paperO A ~urther surprising characteristic of th~
coa~ing is that it does not appear to hinder the penetration
l~ of the melamlne-~ormaldehyde resin solut,ion int~ the inter
l7 ior of the paper, during the impregnation stepO Sush pene~
18 tration is essential, or the pattern sheet will be irreg~- :
l9 larly s~arved such as at its center, and could possibly de~
laminate after pressing. A further desirable characteristie :~
2l of the coating is that it does not si~nificantly scatte~ or
2? attenua~e li~h~, resulting In v~ry clear, crisp appearance
23 of the patter~ in the finished laminateO
24 Without bein~ bound ~o the following theory, it is
believed that the improved charac~eristics of the inventio~
26 can be accoun~ed for as follows: Microcrystalline cellulos~
27 particLè~ contain very lar~0 external forces that bindito
28 other polar substances~ suc~ as cellulo~e and aluminaO Thus~
29 an ~que ws slurry o~ microcrys~lline cellulose and alumina
is ~table and does no~ quickly se~tle ou~, even though alum
3l ina particles in wate~ are not ~ble. ~ur~hermore~ when
32 this slurr~ i9 coated on the paper9 ~he microcrys~lline
~¢~
1 cellulose apparently binds the alumina partlcles to the sur-
2 face fibers of the paper, ~nd to the top of the ink pà~ern,
3 preventing migration of the alumi~a partlcle~ to below the
4 surfaceO This may account for the good abrasion resist2nce
developed by ~uch small quantities of alumina. Thus, all
6 or substantially all o~ ~he alumina psrticles stay at the
7 surface where the~ do the most good, rather than becoming
8 dispersed below the surface where they would contribute
9 relatively little initial wear resistance.
As indicated above, the preferred slurry composi-
11 tion contains a mixture of small particles Qf alumina and a
12 lesser amount of microcrystall~ne cellulose particles, both
13 dlspersed in waterO There must be an amount sufficient of
14 the small mineraL particles to provide ~he r~sultant product
with the d~sired abrasion resistance as discussed above9 and
16 there m~st be an amount sufficient of the binder ~o re~ain
17 the mineral particles in place on ~he sur~ce of the print
18 sheet. In general9 it h~s been found that satlsfactory re~
19 sults are attained with about 5 to 10 parts by weight of the
microcrystalline cellulose for about 20-120 par~s by weight
21 of the alumina; it is possible ~o work outside this r~nge :
22 but the~e i5 no advantage doing so and, furthermore, the
23 handling problems become complicate~. The quantity of water
24 in the slurry is also dictated by practical considerations~
since if there i9 too little water the slurry becomes so
26 thick that it is hard to apply; simllarly~ if there is t~o
27 much water the slurry becomes so thin that it ls difficult
28 to maintain a consistent thickness ~uring the coating opera-
29 tion due to run~ing o~ the slurryO Th~s~ a slurry containing
about 200 wt. % microcrystalline cellulose and about 24 w~O
31 % alumina, based on the water, is stable, i.eO the alumina
32 does not settle out; but i~ more than about 3.5 wto % micro
- 12
p~
1 crystalline cellulose and about 24 wt, % alumina, based on
2 the water, ls usedg t~e slurry becomes very thixotropic and
3 difficult to apply.
4 The composition also preferably contains a small
amo~nt of wetting agent, pre~erably a non-ionic wetting
6 agen~, and a silane. The qusntity of wetting agent is not
7 critical, bu~ only a very ~mall amount ls desirable and ex-
8 cess quantities provide no advantage~ If a silane is used
it acts as a coupling agent which rhemically bi~ds alumina
part~cles to the melamine matri~ after impregnation a~d cure,
11 and thls provides bet~er lnitial ~ear ~ince the alumina -
12 particles are chemically bound to the melamlne in addition ;:
13 to being mechanically bound theneto and therefore stay in
4 place longer under abrasive wear. The silane should be se-
` lected from among the group making it compatible with the
16 particular thermosetting laminating resin used, in this re~
7 gard silanes having an amino group~ such as gsmma-aminoprop~
18 ~rimethoxy silane, are partieularly ef~ective ~or use wlth
19 melamine resinsO The quantity of silane ~sed need no~ be
great and, in fact, as little as 0O5% based on the weigh~
21 of the alumina is effective to enhance ~he abrasion ~sist~
22 ance of the inal laminate; a ma~imum quantity of about 2VJo.
23 by weight based on the weight of the alumina is suggested
24 ~ince greater quantitie~ do not lead to any significantly
2s be~ter results and merely ~ncrease the cost of the raw
26 materials
27 It is an important feature of the present inven~ ;
28 ~ion ~ha~ ~he coati~g using microcrystalllne cellulose a~
29 ~he binder must be dried at an elevated temperature before
the prin sheet is impregnated with the melamlne resin. ~;~
31 Thus 7` a minimum drying temperature i~ about l80Fo and the
32 preferred drying temperatures are from 240 270Fo
- 13 -
,f~
1 With regard to the abrasion resistant mineral
2 particles, alumina is the preferred material. Silica~ whi h
3 has been suggested in certain prior ar~ patents a~ an abras
4 ion resistant material, provides considerably inferior re-
sults in the present inventlon compared with alumina. Other
6 minerals of sufficient hardness ~ch as zirconium oxide,
7 cerium oxide, diamond dust, etc. can work9 but ~re ei~her
8 too expensive for prac~ical usage or under certain circum~
9 stanc2~ produce excessive color shl ft . Glass beads have been
tried unsuccessfully. Silicon carbide also was tried, and
while providing good abrasion resistanc~, produced excessive
color shit~
3 An important feature is the size of the alumina
14 particles. Beneath 20 micron particle size3 abrasion re-
5 sistarlce becomes poor, and t~ae preferred minirmlm particle
6 size is about 25 micronsO Maximurn particle size is limitPd
17 by surf~ce :roughness in the article and interference with
18 visual effects~ The preferred maximum si~e o~ the alu~ina
19 particles is about 50 microns,
The n~ture of the binder for the mineral particles
21 is a very important fea~ure in the pre~ent in~ention. O
22 all the materials tried, microcrystalline cellulose is by
23 far the mos~ satisfactory material. The binder must serve
24 not only to maintain the mlneral particles in po~ition on
the surface of t~e print sheet, but should also act as ~ sus~
26 pending agent in the slurry ~otherwise, it would be necessary
27 to add an addi~ional suspending agent)~ The peculiar proper~
28 ty of microcry~talline eellulo~e 15 that it ac~s like a typ-
29 ical suspending binding agent and film former, but unlike
other agents ls ~ot water soluble befor~ or a~ter su~pen-
31 sion and orms a highly porous film through which ~he thermo-
32 set~ing resin can penetra~e. In addi~ion, the binder mus-t
~ 14 -
be compa~ible wi~h the laminating re~in and microcrystalllne
2 cellulose is compatible with both mel~mine resin and poly-
3 e&ter resln~O Furthermore, lt mllst no~ ~ca~er or attenuate
4 light in the thic:knesses ~pplied in the final laminate~ and
microcrystalline ~ellulose is satisactory in this regard
6 as well.
7 Other bindexs w~ich may be usqd, but: which provide
8 inferior results compared with microcrystalline cellulose,
9 are various ~ypical suspendirlg~binding agencs including :~
anionis: acrylic po:Lymer, carbo~y methylcellulo~e and similar .
materi~ls such as hydroxypropyl cellulose, me~hylcellulose,
12 polyvinyl alcohol~ polyvlnyl p~rrolidone, etc~ However, as
13 indicated above, mierocrystalline callulo~e is by far the
14 preferred binder
15 Microcrystalline cellulose is a non-fibrous form `~
16 o~ cellulose in which the cell walls o cellulQse fiber3 have
17 been broken into ragments ranging in leng~h from a few
8 microns to a few tenth~ o a micron~ It is not a chemical
19 ~ derivative but a puri~ied alpha ce~luloseO Microcrystallir~e
cellulose i5 available under the the ~rademark "AVICEL"~ ~he
21 preparation of which is disclosed in the Battista pa~ent
22 NoO 3,2753580, AVICEL Type RC 581 is a white, odorless : .
23 hyg~oscropic powderO It i8 water dispersible and corltains
24 aboat 11% sodium carboxyme~hyl celllllose as a protec~ive
coiloidO Its particle size is le58 than 001% on a 60 meslti
26 screenO
27 Fe~tures and advantages o the instant ixl~ention
28 which are considered ~o be par~icularly ~c~ignlfican~ are aS
2~ f~lows.
(1) The mi~~ure o~ alumirla particles and micrc
31 crystalline cellult)se is deposited from a wa~er slurry,
32 rather than used as illers in a resin solut~onO
~ 15 ~
1 ~2) Such slurry is coated on an unimpregnated
2 printed pa~tern ~hee~, rather than on an lmpregnated pattern
3 sheet.
4 (3~ The coa~ing is dried at an ele~ted tempera-
5 ture of at least about 180F~ :
6 (4) The coating thic~nes~ is 0002-~.2 mils,
7 ra~her than 1-2 mils,
8 (5) After applying the coating ~nd drying i~ the
; 9 pattern sheet is then ~mpregn~ted with the thermosettin~
0 resin, and this co~vent~onal i~pregnation of he pattern
shee~ i~ carried out on conventional equipment, ra~her ~han
12 ~peeial, difficult to control, coating of a thick slurry, ~ ;~
13 t6) The ul~ra-~hin layer provides une~pectedly
; 14 high abrasion re~is~ance.
The desirable character~stics of t~e alumina par-
6 ticle bindlng agent, which charac~eristic~ are all met by
7 microcrystalline cellulose, areo It ac~s as a film former,
8 it acts &s a binding agent for the mineral particle~; lt ac~ -
9 ~s a suspending agent in the sLurr~ for the mineral particles3
20 it is no~ washed off durlng the ~ub~equent thermoset~ing ~ :
~: 21 resin ~mpregnating proca~s9 it is compatible with the sub-
22 sequently applied thermosetting resin, such as melamine
23 resin or polyester r~sln, it is permeable to ~he ~hermose~
24 ting impregnating resin (ind2ed microcrystal~ine cellulose
form~ a porous film~, it is re~ ant ~o the heat generated
26 during the laminating procedure; a~d i~ doqs no~ scatter
27 or attenuate ligh~ in the ~aminateO
28 The following ~x~mples are offere~ illustra~ivelyo
29 EXANPLE 1
Microcry~talline cellulose (AVICEL ~C 581) was
3l added to ætirred water in a Waring blender. Ater 2 to 3
~ 32 minute~ in the blender, ~he AVICEL was comple~ely dispersed
; - 16 -
1 and the aLumin~m o~:ide (Microgrit W~A) W~8 gen~ly stirred
2 in. Finally, three drop~ of TRITON X-l00 (~ non-ionic
3 detergent) was added to promote wetting.
4 The resultant slurry was applied as a coa~ing
to a 65 lb~ream (3000 t2) unimpregnated pattern sheet hav-
6 ing a woodgrain surf~ce print. The coatin~ wa~ dried
7 265F, for 3 minutes. The paper was then satura~ed in ~he
8 normal way using melamine formaldehyde resin and was dried
9 in ~ccordance with normal procedure~O The resin content
was 45-48% and the volatile content wa~s 5-6%. The laminate
11 waæ made up and pr~ssed using a conventional general purpose
12 cycle, viz, about 300F., l000 psi, for about 25 minutes.
13 Formulations and abrasion re~ult~ are lis~ed be-
14 low for a 105 mil wet coating, which calculates to a 0.15
mil thick dry coat.
16 TABLE l
17 l ~ 3 ~ S ~ 7
18 Wa~er (ml) - 250 250 250 250250 ~50
19~ AVTCEI RC 581 ~ 6~5 7.5 7.5 7.57.5 7.
20 (quantity in gms~
2l M~CROGR~T WGA ~ ~ 30 3G 30 60 60
2~ (quan~ity in gms~
23 MICROGRIT WCA - - 20 30 40 9 30
24 ~particle size in :
25 microns) :
26 Abrasion cycles~ ~5 40 l00 400 475775 500
Zt Ini~ial Wear
28 Pattern Destruction~
29 % at 500 cycles 100% 100% 20V/~ 5% 2% 95% ~%
-30 In the above Table, MIC~OGRIT WCA i9 aluminum
31 oxide lapping powder manufac~ured by ~icro Abrasives Corpora=
32 tion of Westfield9 Mas~chuset~s.
33 From the above- comparative trials, it is seen that
~4 the microcry~talline cellulo8e by i~self was not satisf~ctory
:35 ~rial 2); and ~hat the use of alumina having a partlcle
17 -
~4~
size less than 20 micrcsns did not give good results ~trial
2 fj). It is seen that MICROGRIT alumina above 20 micron :~
3 average particle size provided both sa~isfactory initial
4 wear, and NEMA wear resis tance . In addition, the resulting
laminates had clearer pattern appearance ~han conventional
6 laminates having overlay sheets, and such laminates also
7 psssed the other NEMA durability testsc
8 EXAMPLE II
9 Fo~r ~lurrles were prepared as in Example I ~ trial .
0 ~3. Each was used to coat 3 mlls wet onto 65 lb. unimpreg- :
1 na~ed paper, and dried as in Example I to provide a dry coat- ~ :
12 ing thicknesQ of approximately 0~3 milD The dried paper was
13 impregna~ed wi.th melamine resin and assemblecl in a lamlnate
4 stack as shown in Figo 20 Lamination was carried out as
15 described in Example I. The only variation in the four trials ~ :
16 was the avera~e particle size of the alumina. Results were
17 as fvllows:
18TABLE ~
19MICROGRIT Average ParticlePattern Destruction at 500
20Siæ2 ~___
,
21b~0 ~ 1%
2230 ~ ~ 5%
2320 ~ ~20/o
249 ~f 70%
25 EXAMPLE III
26 Example Il was repeated in three trials ~ in each
27 case using alumina particles having an average particle size
28 Of 40 micronsO The only variation. wa~ ~n the we~ coa~ing
29 thicknessO Lamlnates wera compared as in Example II. The
resul~s wereo
1 TABLE 3
2 Pattern Destruc~ion
3 Wet Coat_~g Thickness at 500 cYcles
4 3 mils (0O3 mil dry~ 1%
5 2 mils (002 mil dry) 10% `:
S 1 mil (Ool mil dry) 30~/O
7 E~AMPLE IV
# ~he procedure of Exampls I was repeated using as
g a eoa~ing slurry for the print shee~ the following compo i-
10 ~orl.
11~50 mlO water;
1~705 gmsO microcrystalline ceLlulose;
1360 gmsO of alumlna o~ average particle
14si~e 40 microns; and
151 drop of T~IT0~ X~lOOo
16 Two trials were carried out providing we~ thickne3ses of 1
17 and 2 mils, respectivelyO After lmaination~ abrasion tes~
18 ing produced no i~iti~l pattern destruction at 500 cyclesO
19 EXAMPLE V
. The procedure of E~ample IV was r0peated using the
2~ same coating omposition, exeept tha~ 120 gmsO of alumlna
22 having an average particle size of 30 microns was usedO
~3 Three trials were run with wet coatings o~ 1/2~ l~and 1~5
24 mils, respectivelyO Abrasion resistQnce o~ the ~inal lamln~
~te after-500 cycles gave ~he follQwing resultsO
26 TAKLE 4
27 1~2 m~l ~O05 m~l ~ry) 10% pattern des~ruetion
28 ~ L m~L ~ry3 ~ 1% pattern destruction ::
29 105 ~il (olS mll dry) c 1% pa~tern destruction
3~ The t~ree laminates were highly satisactory in :~
31 all other~respectsO Machineabllity was good wi~h no chip-
32 ping~
33 The physical properties ~f the ~hird sample (pre~
34 pared with ~ol mi~ eoated paper~ te~ted in ~ccordance w~th
~EMA St~ndard LD3-1975~ after impregnation and pressing~
36 were as follows: ~
:,
- :L 9
T'ABLE S ~ ;
2 Wear resistance ~ 500 cyclPs
3 S~ain resistance No effect
4 Moisture absorption 6.5%
Cen~er Swell 8.g%
6 Impact ~un~upported) 36"
7 ~adiant Heat ~un~uppor~d? 185 seconds
8 Hot Water No effec~
9 Hot w~x. No effect
lODi~ensional stability M~Do 0024%
11C~Do Qo56%
12The~e are all satisfactory or superior v~lues a
13 EXAMPLE ~I
14 E~ample IV was repeated in ~wo trials using the
same composition, cxcept tha in the first trial 60 gms~ of
16 MICROG~IT SIC 400 (27 micron silicon carbide) was subs~ituted
17 for ~he alumina and in the secohd trial ~0 gm90 of MICROGRIT
18 SI~ lOOQ ~10 micron silicon carbide) was s~stituted or
19 the aluminaO For each composi~ion, coa~.in~s were deposited
at 1/2, 1 and loS mils ~eto The print sheet had a gen~rally
21 "gray" color due to the color of the ~ilicon c~rbideO Re-
22 sults were as ~ollowso
23 TABLE 6
24
2~1l2 (~05 mil dry) 20 85
271 (.1 mil dry) 5 80
~81.5 (.15 mil dry) ~ 5 70
29As can be seen, while abrasion resistance was sa~=
isfactory, the 10 micr~n silicon carbide gave poorer resul~s
31 than the 27 micron silicon carbideO The poor color can be
32 tolerated in only certain colors o~ print paper~
33 EXAMPLE VII
34 Exampl2 IV was again repea~ed with three composl-
- 20 ~
tions, thls time subst~ tuting 60 gms of glas~ sE~heres (~325
2 screen size), 2~0 gmsO of such glass spheres an~ 60 grns
3 of CABOSIL L~5 (silica aerosil ciE mlllimicroll particle size),
4 respectively, in place of the alumina particles. Each com~
5 position was coated at 1/2, 1 and 1~5 mils wet, The re-
6sults were as follows: -
7 TAsLe 7
8___3~
960 g glass ~qO cycles
lO~40 g glass 200 cycles
160 g Silir~ Aeroæil ~100 cycles
12 * The dev~ce for testing abrasion resistance described at
3 pages 4 and 5 is known as a Taber abraderO
14 None of these samples gave satisfactory abraslQn resisitanceO
E2~AMPLE VIII ,
16 The procedure of Example IV was aga1n repe~ted ex-
17 cept that this time the coatlng compositi~n w~ modified in
18 one sample ~y the substitution ~ 6 gmsO of an anionic acryllc
19 polymer (RETENl~ 4~0 ~Hercules :I?owder Cornpany~ in place o
~he microcrystalline cellulose, and in a seco~d sample by
21 9 gms. of carboxy methyl cellulo~e i~ place of the micrccrys^
22 ~alline celiuloseO For both samples, ~h~ Taber abrasion
23 test showed about 5% wear ~t 500 cycles9 a satisf~c~or~
24 perf~3rmance. However~ the anionic acrylic polymer caused a
slight milkiness in .the laminate ind~ ca~ing that the use cf
26 thiS materiaL would be sa~isactory for only certain colorsO
27 T~e lamlnate in w~ich carboxyl methyl cellulose had been
28 used as the binding agerlt for the alumina had a poo~ boiling
29 water resi~tance and could not mee~ ~he ~E:MA Standard in
this reg~rd; ~his ma~erial could only be u~ed on certain
lower grade low pressure lamina1:e~0
- 21.
1 EXAMPLE IX
2 In order to investig~te ~he ef~ects of silanes,
3 ~he following procedure was carried out~ One gram of
4 gamma-amino propyltrimethoxy sllane was mixed with a 10~/o
wa~er-90% methanol solution until dispersed; a minimum
6 quant~ty of liquid is used sufficient to wet the alumina
7 powderO This dispersion was then added ~o lOO ~msO of
8 alumi~a of 30 micron siæe (MICROGRIT WCA 30) and the alumina
9 was mixed with the soluti~n until thorou~hly wetted. The
0 alumina was then dried~ Example ~V was ~epeated except that
the coating was applied to the pri~t .sheet in a l/4 mil thick
2 wet coating (0O025 ~ils dried), The resul~an~ laminate was
3 compared to Laminates prep~red in accordance with Example
4 IV (without the silane) aLso applied at a thi~kness of l/4
1$ mil wetO All l~minates were pressed to a mirror inishO The
6 results of the abrasion resistant tests are se~ forth in
7 Table 8 below~
18 T~BLE 8
19 No Silane Silane
~ Initial Wear (cycles)300 525
21 Final Wear ~cyeles) 1075 1250
22 Wear Value 687 8~7
23 It is seen from the above results ~ha~ the silane
24 improved the efficlency of the abrasion resis~snt coatingO
EXAYPLE X
26 The present invention was tes~ed to determine it~
27 efficacy in upgrading the performance o low pressure boardO
28 A slurry was prepared ~s i~ Example I with 250 gms water,
29 ~.5 gms. of microcrys~allin~ c~llulo$e, 30 gms of alumin~ of
30 mieron size and 2 drops of TRITON ~lOOo The slurry was
31 coa~ed in ~ l/2 mil we~ layer ~05 mil dry) onto unimpre~-
32 nated printed pattern paper,and dried for 3 minutes at 2~0Fo
2~ -
The shee~ was then impregna~ed and dried ~wice to ensure
2 complete impregnatlon~ The impregn~ted sheet was then placed
3 over a wood particle p~nel and w~s pressed a~ 200 psi at
4 300~F. for 6 minutesO A~ a comE~arisorl, an o~herwise iden-
5 tical low pressure lam~nate was mad~ without providing ~e
6 abrasion resistant coal:ing on the top ~urace of the prirlt
7 shee~ Both samples were sub~ec~e~ ~o the ~EMA Abrasion
8 Test and the results were as follows:
g TABLE 9
~o Abrasion E~esistant
~.~ Coatin~ No Coatl~s~
12 Initial Wear200 cycles nil
13 NEMA Abra~ion 105() cycles 150-200 c ycles
14 From ~he above tests as tabula~ed in Table 9, it
15 is seen that the present inventie~n vastly improves the ~bras
16 ' ic)n reslstance of low pressure laminates as wellO
17 EXAMPLE XI
18 The procedure of E~ample IX was repea~ed and the
19 coatings w~re appl~ed at ~ t~Lickness of 1-1/2 mils wet (OO~LS
20 mil dry)0 Four trlals were run WitXlL ~he quantity of $il~ne
21 being varied~ and t.he resultant laminat~s s~jeeted to the
22 NEMA Abrasi~n Tes~0 The ini~ial wear wan recorded, results
23 being given ln Table 10 below~ :`
24 TABI,E 10
Quantity of Silane-
26 e~/lsG~ Ini ti~l,~,~
~7 0 . 175
28
29 3 510
~ ~
31 The albove ~es~s show the efect o ~he silane ls
32 not subæ~antially enharlced a~er reachin~ a quan~i~y of about
33 2 wt~ % based on the weigh~ of the alumiIla; and9 in fac~c~ in
34 ~his particular ~es~ at 6% silane, the results were poorer
- 23 -
than at 2~/o3 although significan~ly bet~:er ~han the layer
2 containing no silane at all~
3 EXAMPLE XII
4 The procedure of E~ample IX was repeated to der
5 termine initial wear re~istance o the ~al laminate as a
6 func~ion of the ~emperature used to dry the c~atln~ applied
7 over the prin~ sheet~ Thus, ~he pattPrn sheet wa~ coated
8 with ~he coating compasitlon of Example IV at a rate of 8-10
9 pounds per ream ~0~2 mils dry~, excep~ that the co~-ting com-
0 positlon contained silane in accordance with Example IXo The
11 coating was dried for 3 minute~ in each ~ample at the vari
12 ous temper~tures given in Table ll belowO A:~ter drylng the
13 coated sheets were allowed to come to molsture e~ brium
14 with room ~ir at 50% relati~e humldity at 70F; the ~heets
were then impregnated as usual wi~h melamine formaldehyde
16 resln, and were then lamina~ed in the usual way agalnst a
17 sa~in finished plateO The results were as follows-
19~v~ ~ ~ r -u~ ~
20 160 2~
21 180 55Q
22 200 550
23 ~40 575
24 ~65 575
2S. EXAMPLE XIII
26 A slurry o~ lngredients was prepared as disclo~2d
27 in Example I using 6O5 parts by wei~ht of AVICEL microcrys~
28 talline cellulose, 2 parts by welgh~ of carboxymethyl cell-
29 ulose, 30 parts of 30-mioron al.umina~ and 250 par~s by weigh~
3~ of waterO ~ trace quantity of TRITON X l00 was added.
31 The resultant slurry was applled to print she~t
32 using ~ Pleyer rod cvat~ng machine at the r~te of 5~5 pounds
24 -
1 per ream ~0,15 mil dry ~hickness). The prin~ paper was then
2 impregni~ted with melamine formaldehyde resin to provide a
3 resin con~ent of 41~7%, and drying was efec~ed to provide a
4 volatile content of 402%. A laminate was then pressed with
the co~ted print paper using a ~tandard lamlna~ing cycle and
6 a mirr~-finished laminating plate so that the final l~minate
7 had a ~loss surfaceO
8 The laminate so produced was compared with another
4 mirror-finished laminate made in a convention~l w8y using a
20rpound overlay, both laminates being ~ubjected to the
11 "sl~ding can test", described ~n~ra~ The laminate in ~ccord~ : ;
12 ance wi~h the present invention had an initial wear of 325
13 cycles and a NEMA wear value of ~021 cyclesO In the sliding
14 can rub test, the cvmparative results were as ollows:
TABLE 12
16 S~RF~CE DULLI~G
17 Laminate Made ~-
18CYCLES Conventio~al with Coated :
19 ~ 9Y93~V l~in~-- Print Sheet
1500 sLight no efect
21 3000 slight no effect
22 6000(gradually wcrse~ no effect
23 1~000 slight
24 18~00
25 24000extreme wear slight wear
~6 Pattern destruction began at abou~ 30,000 cycles
27 on both samplesl but i~ is seen that t.he conv~n~ional lamin-
28 ate shows gradual surface dulling even at only 1500 rub cyclie.s
29 and, in fact, gr~dua~ surace dulling began almos~ wi~h ~he
fir~t ew hundred rub cyclesO Furthermore, ~he eonven~ion~l
31 laminate is completely dulled well before initial pattern
32 destruction (30jO00 rub cycles~O
33 Compared with the prior a~empts, the presen~ ln-
34 vention provides vastly improved re~ult~ such that the pre~
ent in~en~ion can be truly considered to be a revolu~ionary
- 25 -
" .
5~
l developmen~ in the field o decorative laminate~. Insoar
2 as is known, the present invention provides the first time
3 a laminate without an overlay sheet has been made which is
4 capable of meeting both the N~MA Abrasion Resistance S~an-
dard of at lea~t 400 cycle~, and an initial wear point in
6 this same test of at leas~ 175~200 cycles.
7 There are many use~ o lamlnates in whieh lni~ial
8 pattern wear rather than ~EMA wear vaLue determine the ac-
9 ceptable life of the surface. For example, supermarket
lo check-out counters, food ~ervice counters, cafeteria tables,
11 and other commercial surfaces are exposed to abraslve rub-
12 bing and sliding of un~lazed dinnerw~ar~ canned goods, fiber~
13 glas trays, etc. If small areas of the pattern begin to
14 disappear after a relatively short period of use, p~rticularly
in an irregular pat~ern, the surface will be unacceptabl.e to
16 the owner ~nd will result in an e~pensive replacement. I~
17 the surface we~rs gradu~Lly and evenly over a long period o~
l8 time, the wear out time exceeds the norma:L replacement eycle
l9 due to ~yle changes, approximately 3~5 years~
