CA1161349A - Color registered decorative laminates - Google Patents

Abstract

27,355 TITLE: IMPROVED COLOR REGISTERED DECORATIVE
LAMINATES
ABSTRACT OF THE DISCLOSURE
The use of a pigmented, fully-hydrolyzed polyvinyl alcohol modified melamine-formaldehyde resin coating in color registered decorative laminates provides improved laminates exhibiting pleasing aesthetics.

Description

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B~CKGROUND
This invention generally relates to decorative lamin-ates and methods of producing the same. More particularly, this invention relates to color registered decorative laminates em-ploying a fully hydrolyzed polyvinyl alcohol modified melamine-formaldehyde resin coating in place of an overlay sheet.
Conventionally, decorative laminates are made of three essential layers: a core layer, a print layer, and a surface layer. The core layer constitutes a bottom or sup-porting layer onto which the other layers are bonded. In normal high-pressure laminate manufacture the core layer consists of a plùrality of cellulosic sheets. The core sheets are generally made from a kraft paper impregnated with a laminating resin. Laminating resins commonly used for the core layer include phenolic, amino, epoxy, polyester, sili-cone, and diallyl phthalate resins to name but a few. The industrially preferred laminating resin for decorative lami-nates appears to be a phenolic resin made from the reaction of phenols with formaldehyde. In low-pressure laminate manufacture the core layer is generally comprised of a sheet of particleboard ranging from 3/8" to 1" in thickness.
Placed above the core layer is the print layer which is generally an alpha cellulose pigmented paper containing a print, pattern, or design that has been impregnated with a melamine-formaldehyde re~in. Typically, the printing is performed prior to impregnation by a high-speed rotogravure.
The cured melamine-ormaldehyde resins are colorless ad rosistant ~o l~ght; they are resistant to a variet~ of solvent~

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and stains; and their heat resistance make~ them immune to burning cigarettes, boiling water and heated containers up to about 325F. Without these melamine-formaldehyde resins the decorative laminate industry would not exist as it is known S tod~y. However~ because these resins are extremely brittle, they sometimes require reinforcement.
The surface layer, or overlay as it iB commonly referred to, is a high-quality alpha cellulose paper impreg-nated with a melamine-formaldehyde resin. This layer protects the print sheet from external abuse such as abrasive wear and tear, harsh chemicals, burns, spill8 and the like. It is primarily the melamine-formaldehyde resin which accounts for these protective properties. The alpha-cellulose paper acts as a tran~lucent carrier for water-thin resin, imparts strength to the rather brittle melamine-formaldehyde resin, maintains a uniform resin thickness in the overlay by acting as a shim, and controls resin flow The core layer, print layer and surface layer are stacked in a superimposed relation~hip, between ~tainless steel plates and subjected to a pressure and temperature for a time sufficiently long enough to cure the laminating resins impregnating the respective layers. The elevated temperatures and pressure actually cause the im-pregnated resins within the sheet~ to flow which con~olidates the whole into an integral mass, known as the laminate.
These laminates find u~e a~ countex tops, table tops, furniture, store fixtures and the like.
For obvious econom~c reason~-, it i~ common practice, when producing the paper supported laminate~, to con~olidate a plurality of these individual laminating assemblies into one 3d,g la~ge assembly, or press pack, said stacks being separated from one another by a release sheet, and then to laminate this pack by heat and pressure application.
In consolidating the laminate components according to most w~dely practiced techniques, an ind~vidual assembly is placed w~th its decorative overlayment surface adjacent to a highly polished stainlesr- steel press plate. The function of the press plate is twofold. First, it provides a smooth, defect-free surface to one side of the laminate. Second, in connection with the paper based supported systems, it serves to separate pairs of back-to-back assemblies, thus permitting a plurality of these assemblies to be consolidated into laminates in one operation, usually in back-to-back relat~onship.
In the earl~e~t day~ of the hi~h pre~ure lam~nat~ng art, the smooth, glo~sy ~urface produced duri`ng the pxessing operatton wa~ somet~mes, upon customer's request, reduced to a matte finish by rubbing the surface ~ith pumice. 5ubsequently, a slightly textured surface was produced by pre~sing the lami-nate ~urface again~t an aluminum foil caul stock, Such a sur-face was described as mini-textured because the hilltop-to-valley bottom depth of such textures was from about 0 5 mil (.0005 in-ches) to about 1.0 mil (.001 inches). These mini-textured laminates met with immediate success and almost totally replaced the glossy ~urface market. Somewhat coar~er textures or three dimen~ional ~urfaces, ~ometime~ called "low~relief" laminate~
were then produced, e.g. by a printing proce~s known as the "heavy ink" method, described in U.S. Patent No. 3,373,068.
These surface~ had hill-to-valley depths o about 3 to 5 mil3.
F~nally, very deep, three dimensional textured sr embos~ed laminates were offered c~mmercially. The~e laminate~

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may be produced by e~g. the methods of U,S. Patent No. 3,860,470, Jaisle et al., 3,718,496, Willard. Here the hill-to-valley depth ~n the sur~ace ls of the order of a~out 20 mils.
The techniques used to produce these deep textured surface~ encompass a design latitude heretofore not achieved by producing simulated patterns such as those occurring in natural materials l~ke sandstone, brick, slate, mosaic, marble, leather, rough or weathered timber; even material like rough wo~en goods such as jute, hemp, etc.
As demands for these new laminates grew, many new designs, such as those slmulating tiles or heavy woven cloth, evolved These designs must have appropriate color contrast and registry with the aurace hill-to-valley con~iguration. Unfor-tunately, the problem of regi~tration of color and embossing has proven very difficult to solve. The problem has plagued the industry, not only rom the ~tandpoint of the appearance of the inished laminate but from the standpoint of the cost of the production of laminatés having a ~ubstantially perfect registry of color and embos~ment, since their inception.
One method of overcoming the above deficiencies i~ set forth in copending application~ Serial Nos. 889,676 and 889,677 filed March 24, 1978, and assigned to the same assignee as this invention. According to these applications, there ia provided a method of consolidating an assembly comprising a rigidity im-parting substrate, a fibrous decor sheet impregnated with a fir~t thermosetting resin, and a second pigmented thermosetting resi~
layer, which method comprises consolidating the as~embly de-scribed above under heat and pres~ure by an embos~ing pre~s plate having a surface with protuberant and valley areas capable of being impressed into the overlay and fibrous decor sheet~, 3~

together, an embossment o the decor sheet and a migratiOn of the p~gmented res~n from the areas of said embossment corresponding to the protu~erant areas o~ the embossed press plates to the valley areas t~ereof.
Employment of the overlay sheet has, however, genera-ted a host of unwanted problems. The overlay contributes sub~
stantial material cost to the manufactured lam~nate, Not only are there raw material costs involved,such as expensive high-quality alpha cellulose paper and melamine--formaldehyde resins, but there exists substantial pro-cessing costs, such as collating sheets, scrap losses generated by the brittle and difficult-to-handle impregnated sheets, as well as the cost of impregnation itself. In addition to these unwanted expen~itures and processing ~teps, the translucent character of the overlay sheet become~ visually distu~bing in decorative laminates when, through the use of more advanced printing technique~, a sharper, more intricate design is employed.
Thus, there exi~t~ the need for sub~titution of the overlay sheet by a tough and transparent thermoset }ayer that will eliminate haze or blur, incur fewer processing steps and lower costs, and yet maintain sufficient resistance to external abuse to be commercially acceptable. The provision for such a layer would fulfill a long-felt need and constitute a significant hdvance in the art.
SUMMARY oP ~HE INVENT~ON
The present invent~on provides a no~el process for obtain;~ng an exact registry of color and embo~mènt in high and low pres~ure laminate production, the assembly for produclng it and the laminate per se, by subst~tuting a ~ully hydrolyzed l 1613~g polyv~nyl alcohol (PVA) modi~ied melamine-formaldehyde resin coat-îng for the convent~onal overlay sheet as the protective surface layer ~n lam~nates. The application of this modified thermoset-t;ng res~n allows ~or the elimlnation of the overlay sheet thereby providing substantial processing and cost savings in the manu-facture of laminates. This method is more commercially signifi-cant than previously known systems ~ecause it is more economical and obviates many of the disadvantages of the prior procedures.
When utilizing the novel process, there is no limit to dimension, design, depth of embossment or color which ca~ be achieved. It avoid~ the mechanical reg~stering of extraneous embossing media with decorative sheetg in the laminates before or after pressing and the application of materials at press time, According to the novel invention one may produce a mar-resistant decorative laminate having on its decorative sur-face, protrusions of any selected design, which protrusions are of a different color from the ~ackground surface of the laminate.
Furthermore, one may produce a mar~resistant decorative laminate in multi-color having protru~ions wh~ch extend outwardly from - 20 the decorative surface of the laminate which protrusions haveon their surface a different color than that of the background material in relief. Finally, the transparent nature of thi~
re~in provides for a clear and undistorted appearance of the pr~nt, pattern or design in the decorat~ve laminate.
DETAILED DESCRIPTION OF THE rNVENTrON
In accordance with the present invention there is provided a heat-and-pressure laminate assembly con~i~t~ng es-~entially of, in super~mposed relationship, a ¢ore layer com-prised of a self-supporting ~ub~trate, a resin impregnated print layer consisting of an opaque alpha cellulose paper ~heet, l 16i3~

a pigmented surface coating of a fully hydrolyzed polyvinyl alco-hol (PV~ modifled melamine-formaldehyde resin wherein the surface coating weight ~s ~rom about 0~5 to about 20 grams per square foot and the amount of fully hydrolyzed PVA in the surface coat-~ng is from about 5 to about 30 percent by weight of the total we~ght of the melamine-formaldehyde reaction product solids, and said pigmented surface coating has a flow sufficient to cause sa~d pigmented surface coating to flow-more than said resin im-pregnating the print layer, and an embossing press plate having a surface with protuberant and valley areas capable of being impressed into the uppermost of said print layer and means for preventing the embossing press plate from sticking to the coated print sheet during lamination.
A method is set forth herein for producing a heat-and-pre~ure con~olidated laminate which comprises aonsolidating the a~embly described above under heat and pressure to thereby ef-fect a lamination of said fibrous ~heets together, an embossment of the uppermost of the print sheet and a migration of the pig-mented res~n from the areas of said embossment corre~ponding to the protuberant area~ F the embos~ed press plates to the valley areas thereof and thereafter removing said embossing press plate from the resultant laminate 80 as to produce a dense laminate having embossed areas of contra~ting color.
Additionally, set forth herein ls a heat~and~pres~ure consolidated laminate of registered embo~ ment and color contrast comprising, in ~uperimposed relationship, a core layer comprised of a self-supporting substrate, a resin impregnated print layer consisting of an opaque alpha cellulose paper sheet, and a pig-mented surface coating of a fully hydrolyzed polyvinyl alcohol (PVA) modified melamine-formaldehyde resin wherein the surface l1~13~

coating weight is fro~ about 0,5 to about 20 grams per square foot ànd the amount o~ fully- hydrolyzed PVA in the sur~ace coating is ~rom about 5 to about 30 percent by weight of the total weight of the melamine-formaldehyde reaction product solids and said pigmented surface coating has a flow sufficient to cause said p~gmented surface coating to flow more than said resin impregna-ting the print layer. The surface of said laminate contains an embossment consisting of protuberances and valleys each of which are of a different color.
The core layer of the laminate may contain either a plurality of sheets impregnated with a laminating resin or a commercially available pressed particleboard. In high-pressure laminates, the core layer is typically provided by a plurality of impregnated sheet~. The~e sheets can be varied in théir nature in accordance w~th the particular properties de~ired in the decorative laminate. Typically, the core layer is made from paper, woven fabrics, mats, felts, or the like. Paper is by far the mo~t widely used and thus constitutes the preferred ~tock for the core layer in high-pressure laminates. More particularly, a kraft paper of about a 60 to about a 130 pound basis weight per 3000 square foot ream is preferred as the stock from which the core layer sheets are prepared for high-pressure laminates because of its strong, cheap and plentiful nature.
In low-pressure laminates, a particleboard of from about 3/8 to about l inch in thickness is preferred a~ the self--supporting substrate compri~ing the core layer. Suitable particleboards are commercially available in plentiful quantities at moderate co~t.

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The laminating resin~ used for impregnating tho sheets of the core layer can be any of those thermosetting resins conventionally used in the production of laminates.
Laminating resins conventionally used include, but are not limited to, phenolic, amino, epoxy, polyester, silicone and diallyl phthalate re~ins. The mo~t commonly employed laminating resin~ and that preferred in the instant invention, is the conden5ation product of a phenol and an aldehyde, generally referred to as a phenolic resin. In particular, it is preferable to employ an alkaline catalyzed phenol--formaldehyde condensation product as the laminating resin employed in the core layer. These resins can be purchased commercially or prepared according to conventional procedures.
When u~ing ~uch a resin, it i~ preferred to impregnate and dry the impregnated ~heets, by method~ known in the art, to a resin content of from about 25% to 45%, and more preferably to a re~in content of about 30~, based on the weight of resin solids in the impregnated sheets. The volatile content of the dried impregnated sheet is preferably between 5% to 10~, more prefer-ablY about 8%, ba~ed on the total weight of the sheet.
The alpha cellulose sheet u~ed in the print lay-r of the laminate generally runs from about S0 to about 120 pound basis weight per 3000 square foot ream. Upon this alpha cellulose sheet i5 di8played a print, pa*tern, ~#dgn or aolor ~uitable for the intended use of the laminate. The decorative print, pattern or design is typically applied by a high-~peed roto-gravure before the sheet is impregnated with the melamine--formaldehyde resin. Recently, photogravure reproduction~ o natural material~ ~uch a~ wood, marble,and leather have been applied to these alpha cellulo~e ~heet~ a~ well. Typi¢ally, 1 16i3~9 a three-ink system is employed with the alpha cellulose sheet itself being highly pigmented to provide a fourth color a~ background and as an opaque base by which the core layer is accordingly obscured. Although printing can be accomplished at any time prior to impregnation of the melamine-formaldehyde resin,printing is often done immediately before the impreg-nation. Printing houses make available, for those laminators not equipped with printing equipment, already printed alpha cellulose paper of various prints, patterns, or designs.
Suitable melamine-formaldehyde resins for impreg-nation of the print layer are prepared by reacting melamine with formaldehyde in an aqueou~ dispersion or solution. The mole ratio o the melamine to formaldehyde may be varied fxom about lsl to about 1:3, re~pectively. It 1~ preferred that thé mole ratio be controlled from about 1:1.3 to about 1:2, mela-mine to formaldehyde, respectively The reaction occurs under alkaline cond~tions at a temperature ranging from about 70 to the reflux temperature until a clear reaction product i~ obtaine~.
When a low pressure decorative laminate i9 being pro-duced, the print layer may also constitute any of the above-described decor sheets. The core, however, as mentioned above, comprises a particleboard ranging in thickness from about 1/8"
to 1" which is produced in a manner known in the art. Medium density, mat formed, wood particleboard and medium den~ity, wood fiberboard substrates are preferred.
The fully hydrolyzed PVA modifled mel~mine-formaldehyde re~in used as a coating over the print layer not only obviate6 the need for an overlay sheet but provides a high-wear, clear, craze-free decorative laminate that i~ ae~thetically mor- plea~-ing. The polyvinyl alcohol i~ employed ~ a pla~ticlzer with ~ 16~

considerable ductility whose particles in the brittle matrix of the melamine-formaldehyde resin provide for a toughening of the thus-modified resin. The one hundred percent or fully hydro-lyzed PVA is required over the partially hydrolyzed PVA for use in the melamine-formaldehyde re~in because the partially hydrolyzed PVA modified melamine-formaldehyde has exhibited too short of a shelf-life (time lapse before gelation) for practical purposes, even when stabilizers such as o,p-toluene sulfonamide have been added. Fully hydrolyzed PVA i8 commercially avail-able for use in the present invention. The fully hydrolyzed PVA employed in the coatlng layer generally will not be prepared by hydrolysis of polyvinyl alcohols in the conventional manner.
Instead, the fully hydrolyzed PVA i~ the produ¢t of fully hydrol-yzing a polyvinyl e~ter, such as polyvinyl acetate or polyvinyl formate This procedure is more efficient and le~s co~tly.
However, the term "fully hydrolyzed PVA" i~ generally recognized in the trade to apply to the fully hydrolyzed polyvinyl ester, and as such will continue to be applied herein.
In preparing the fully hydrolyzed PVA modified mela-mine-formaldehyde re~in of the present invention, the fir~t stage in the preparation of thi~ coating i~ thR reaction between melam~ne and formaldehyde. Although, the fully hydrolyzed PVA
may be added after the reaction of the melamine and formaldehyde, it is preferrable to add the fully hydrolyzed PVA to the initial stage. The mole ratio of melamine to formaldehyde can be varied from about 1:1 to a~out 1:3, respectively. The reaction is to be carried out in an aqueous di~persion or solution. To facili-tate thi~ aqueous pha~e reaction, aqueous formaldehyde solution~
commercially availa~le are usually employed in the preparation of the modified re~in.

The reaction between melamine and formaldehyde should occur under alkaline conditions. The preferred pH range of the reaction is 7.5 to lO. For this purpose, a buffering material to control the pH is traditionally employed. One S guch buffering agent that may be advantageously used is triethanolamine, although the preqent invention is not limited to this particular buffering material. The buffering agent may be employed during the initial ~tage of the roaction, during both the initial stage and the modification stage, or not at all.
During the initial ~tage of the melamine-formaldehyde reaction, the reaction temperature is not critical although lower temperatures, such as room temperature, cause the re-actlon to progre~ rather ~lowly. At th~ po~nt, the iully hydrolyzed PVA is added to the reaction. The amount of fully hydrolyzed PYA to be employed may vary from about 5% to 30% on a weight basi~ of the total weight of the melamine-formaldehyde reaction product solid~ It i~ generally preferred, howéver, that the fully hydrolyzed PVA added be in an amount of from about 10% to 20~ on a weight ba~i~ of the total weight of the melamine-~ormaldehyde re~ction product ~olids. It i~ likewi-e preferred that during the reactîon between the fully hydrolyzed PVA and the melamine~formaldehyde re~in, a reaction temperature ranging from about 70C to the reflux temperature ~hould be main-tained, preferably abo~t 80C to 90C. ~he reaction ~hould con-tinue until the percent water tolerance of the reaction range~
from about 300~ to about 500~ in 5C water. The expre~ion, percent water tolerance, i~ a well-known term in the re~in art and simply means that a ~ample of re~in can be diluted ln a certain percent of its volume without dl~playing any milkin~

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i.e. 300% water tolerance at 5C indicates that the given sample can be diluted in three times its volume of 5C water without displaying any milkiness. After the reaction product has reached the desired endpoint, it is cooled to ambient temperature and S stored for coating use. If the resin produced is not viscous enough for coating purposes and penetrates the print paper dur-ing subsequent coating operations a small amount of a thickening agent, such as carboxyl methyl cellulose, ~odium alginate or the like may be added with the other constituents during the reaction to correct this result. Additionally, stabilizers such a~ o,p-toluene sulfonamide may be added to extend the ~helf life of the resin coating.
To thi~ ~ully hydrolyzed PVA mod~fied melamine-form-aldehyde re~in is added varying amount~ o~ thinners, eolvents, ~iller~, etc ~o a~ to vary its visco~ities and thereby cau~e the pigmented material to flow more than the resin in the decor sheet during the consolidation procedure.
The fully hydrolyzed PVA modif;ed melamine-formaldehyde re~in may be colored by the inclu~ion therein of any one of, or a combination of, inorganic or organic color pigments, extender pigments, metallic pigments, etc. The amount of pigment added to the resin will ~ary from 0.5~ to 20%, based on the ~otal wéight of the resin, and dependent upon the pigment used and resultant color contrast desired. Typical inorganic pigments u~eful ln-clude those iron pigments ranging in color from yellow through red, reddish-brown, brown, brown to black. Such iron pigment~
include yellow ocher, raw and burnt ~ienna, and raw and burnt umber. Other u~eful inorganic color pigment~ include chrome yellow, cadmium sulfide, zinc yellow, cobalt blue, ultramarine blue, iron oxide, chrome green, chromium oxide green, chromlum 3~g hydroxide green, lamp black, and white pigments such as titanium dioxide, t;`tan~um calcium, zi`nc ox~de, zinc sulfide, antimony oxide, lithopone, etc. Although lead pigments may be used, they are preferably avoided because of the safety hazard involved in their use. Organ~c p~gments which may be used include toluidine red, phthalocyan~ne blue and green, Vandyke brown, alizarin, madder lake, lithol red, and the like.
Useful metallic pigments include aluminum powder, copper powder, bronze powders available in various shades depend-ing upon the alloy composition, zinc powder, gold and gold-like powders, and the like. Any of the pigments, and particularly the metallic pigments, may be used alone or in combination with each other or ln com~ination with other pigments.
The ~ully hydrolyzed PVA modi~ied melamine~fôrmaldehyde re~in is coated upon the print layer to a weight of from about 0 5 to about 20 grams per ~quare foot, preferably about 5 to about 10 grams per square foot. The coatlng operation may be performed by a knife coater, reverse roll cohter, or similar techn~que. ~he pre~erred coating proces~ is the knife coater wherein the knife and resln dam are mounted on a roller, adjust-ment of the gap between the print sheet and the knife coater varies the coat~ng thickness to its desired amount. The coating operat~on may be a separate operatisn or p-rt o the impregnation operation. As a ~eparate oper~tion, the print sheet is first impregnated with a melamine-formaldehyde resin and ~ubsequently dried before the coating operation i8 commenced As part of the impregnation operation coating is performed on the wet prin~ sheet immediately subsequent to impregnation on a single apparatus. In the present invention a combination o~
3~ these t~o methods is preferred whereln the entire impregnatlon I~6i3d~

and coating processes are performed on a single apparatus whic~
i5 prov~ded with the means to impart a partial drying to the wet print sheet subsequent to impregnation yet prior to coat-ing, preferably by pas~ing the impregnated print sheet through a hot air oven before the coating operation. After coating, the print sheet undergoes a terminal drying operation in which the coated print sheet is dried to a volatile content of from about 4~ to about 9%, preferably about 6%. The terminal drying imparts upon the coated print sheet the necessary flow characteristics for good bonding to take place in the subsequent heat-pressing operation.
A preferred process for manufacturing a high-pressure laminate of the present invention is one in which 3 to 9 core sheets consisting of 6-20 mil~ kraft paper have been impreg-nated with a 30~ to 60% solution of phenol-formaldehyde re~in ~o that the final re~in ~olids content of the core ~heet~
is about 20~ to about 40% of the total weight of the core.
Typically, these core ~heet~ are oven dried after impregnation for a period of about one to two minutes at températures ranging from ;40C to 170C. The print layer con~i~ting of a 50 to 120 pound ba~is weight per 3,000 quare foot ro~ lph-cellulo~e pigmented sheet optionally di~playing a print, pattern, or design, is impregnated with the melamine--formaldehyde resin ~o that the finàl re~ln ~ol~d8 content of the print sheet i~ from about 10% to about 40% of the print sheet, then partially dried, coated on it~ prlnt bear-ing side with a fully hydrolyzed PVA modified melamine--formaldehyde re~in and then terminally dried, The ~heets are then stacked ~uch that the print ~heet i~ the top mo~t ~heet with it~ print bearing and coated ~ide faclng outward, 1 18~3~g The stacked sheets are placed between embossing press plates.
The embossing press plates used in the novel process of the in-stant invention can be prepared by etching or machining a design on a metal plate. Alternatively, and more preferably, the plate can be prepared as disclosed in United States Patent No.
3,71B,496. Still further, the raised printed design technique, as taught by Grosheim in United States 3,373,068, will also work well as an embossing medium in the instant invention. There is exerted upon these plates a pressure of from 800 to 1600 psi at temperatures from about 120C to 180C for approximately 20 min-utes to effect the cure embossment and thereby provide the high-pressure laminate.
l`he embossed areas of the resultant laminate, i.e.
those formed from the protuberances of the embossing plate and forming the valleys of the final embossment in the finished lam-inate surface should preferably be at least .007 inch deep.
Depths of less than .007 inch are possible but not preferred because the color contrast is not as evident. Laminates of muted color differentials can be produced using embossments of these lesser depths however.
A preferred process for manufacturing a low-pressure laminate of the present invention is one in which a pressed particleboard of from about 3/8 to about 1 inch has stacked above it, in a manner identical to that employed in the high-pressure laminate, the print sheet. The print sheet being identical to the one employed in the high-pressure lam-inate. The stack is placed between polished stainless steel plates upon which there is exerted a pressure of from about 200 to about 600 psi at temperatures from 120C to about 180 C for approximately 20 minutes ,;

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to effect the cure and ther~by provide the low-pree~ure laminate.
The release ~heets used in the pxessing of lam~nate of this ~nvention, ~f necessary, are well known ~n the art and may be any non-adhera~le paper or non-adherable aluminum foil. The non-adherable paper may be a parchment type of paper of which a plurality are ava~lable commercially. The non-adherable metal fo~ls, as well as the lam~nate of paper and the non-adherable foils, are also commercially available. Also suitable for this purpose are papers coated, treated or impregnated with polypro-pylene or the polyfluorocarbons and the like. Films of polypro-pylene may also be used. Silicone oil treated papers may be u~ed and are also commercially a~ailable. Paper~ coated with sodium alginate and other ~alts of alginic acid are also suit-able for this purpo~e and are available commercially. When "low pre~ure" laminate~ are being formed, no relea~e sheet at all is necessary if the press plate has a releasing surface thereon.
The following specific examples illu~trate certain a~pect~ of the present invention and, more particularly, point out methods of evaluating the unique advantages the decorative laminate of the present invention provides. However, the exam-ples are set forth for illustration only and are not to be con-qtrued as limitation~ on the present invention except a~ set forth in the appended claims. All part~ and percentage~ are by weight unle~s otherwise specified.
Example 1 Pa~t A
A pigmented fully hydrolyzed PVA-mod~f;ed melamine-formaldehyde resin is prepared by reacting melamine and form-aldehyde together in a mole ratio of 1:1.8, respectively, ~he 1 16~3~

resin is modified with 10~ fully hydrolyzed PVA on a weight basis of the total weight of the melamine-formaldehyde reaction pro-duct solids and pigmented ~ith 0.5% ~rown iron-oxide, same basis.
-Part B
An alpha cellulose print sheet exhibiting a tawny raw-hide design with a basis weight of 50 pounds per 3000 foot ream is first impregnated with a conventional melamine-formaldehyde resin so that the final resin solids content is 29% of the print sheet. The impregnated sheet is then partially dried by passing through a hot air oven and then coated, on its print bearing ~ide, with the pigmented PVA-modified resin of Part A~ The pig-mented PVA-modified resin of Part A has flow sufficiently great enough to cau~e said pigmented re~in to flow more than the con-ventional melamine-ormaldehyde re~in impregnated print layer.
The coating i~ applied by a knife coater adju~ted to place a coating weight of 6.0 grams per ~quare foot upon the print sheet.
~he coated ~heet is then terminally dried to a 4% volatile con-tent and 16% reain flow.
Part C
Six phenolic impregnated kraft paper sheets having a basis weight of 115 pounds per 3000 foot ream are stacked to-gether. Each kraft sheet is impregnated 80 that the final rè~in solid~ content is 27% of the kraft ~heet. The coated print sheet i~ next placed upon the six assembled kraft ~heet~
such that the print bearing, coated ~ide face~ upward. Upon the print sheet i5 placed a relea~e ~heet and a textured leather embossing ma~ter plate. Thi~ a~embly is pres~ed at 1400 p~i at 145C for 20 minute~, cooled~ trimmed and ~anded.
The resulting laminate give~ a leather-liks appearance displaying variations in color inten~ity - high pre~ure area~

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being l~ghter and low pressure areas being darker.
EXa~ple 2 The procedure of Example 1 is followed in every mater-ial detail except that the amount of fully hydrolyzed PVA em-ployed in Part A i~ 30%, the amount of pigment employed is 18%, the pigment employed ~ 8 Vandyke brown, the coating weight in Part B is 1 0 grams per square foot, and the embossing master employed in Part C is an open weave textured plate. The result-ing laminate is a brown open weave embossed sheet having excellen;:
physlcal and chemical properties.
Example 3 The procedure of Example 1 i~ followed in every mater-ial detail except that the amount of fully hydrolyzed PVA em-ployed in Part A i~ 20%, the amount of pigment empioyed i~ 6%, the pigment employed i~ lamp black, the coating weight in Part B i~ 10 grams per square oot, and the embosfiing master employed in Part C i~ a ~late textured plate. The resulting laminate is a black ~late embossed ~heet exhibiting excellent physical and chemical propertiea, Example 4 The procedure of Example 1 is followed in every ma-terial detaiI except that the amount of fully hydrolyzed PVA
employed in Part A i~ 5~, the amount o pîgment employed i~
the pigment employed i8 titanium dioxide, the coating weight in Part B i~ 18 gram~ per square foot, and the embo~ing ma~ter employed in Part C is a tile textured plate. ~he re~ulting laminate i~ a white tile embo~ed ~heet exhibiting excellent phycical and chemical propertie~.
Example~ 5-8 When the procedure of Examples 1-4 i~ followed in ~ 16~349 eyery ma.terial deta~l except that a 1/2 inch pressed particle-board conRtitutes the core la.yer and the pressure and temperature are 300 p8i and 145C, respect~vely, substantially equivalent re~ults are obtained ~or a low-pressure laminate.

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Claims (13)

CLAIMS:

1. A heat and pressure laminate assembly consisting essentially of, in superimposed relationship, (a) a core layer comprised of a self-supporting substrate;
(b) a resin impregnated print layer consisting of an opaque alpha cellulose paper sheet;
(c) a pigmented surface coating of a fully hy-drolyzed polyvinyl alcohol modified melamine-formaldehyde resin wherein the surface coating weight is from about 0.5 to about 20.0 grams per square foot, the amount of fully hydrolyzed poly-vinyl alcohol in the surface coating is from about 5 to about 30 percent by weight of the total weight of the melamine-form-aldehyde reaction product solids and said pigmented surface coating has a flow sufficient to cause said pigmented surface coating to flow more than said resin impregnating the print layer; and (d) an embossing press plate having a surface with protuberant and valley areas capable of being impressed into the uppermost surface of said print layer and means for preventing the embossing press plate from sticking to the coated print sheet during lamination.

2. The assembly of Claim 1 wherein the core layer comprises a plurality of kraft paper sheets impregnated with an alkaline catalyzed phenol-formaldehyde condensation product.

3. The assembly of Claim 1 wherein the fully hydro-lyzed polyvinyl alcohol modified melamine-formaldehyde resin is the reaction product of melamine, formaldehyde and fully hydro-lyzed polyvinyl alcohol wherein the molar ratio of melamine to formaldehyde is about 1:1 to about 1:3, respectively.

4. The assembly of Claim 4 wherein the amount of form-aldehyde employed in the surface coating is from about 1.3 to about 2.0 moles per mole of melamine employed.

5. The assembly of Claim 1 wherein the amount of polyvinyl alcohol employed is in the range of from about 10 to 20 percent by weight of the total weight of the melamine-form-aldehyde reaction product solids in the surface coating.

6. The assembly of Claim 1 wherein the amount of pigment added to the surface coating resin varies from 0.5 to 20.0 percent by weight of the total weight of the melamine-formaldehyde reaction product solids.

7. The assembly of Claim 1 wherein the coating weight is 5 to 10 grams per square foot.

8. A method for producing a heat-and-pressure con-solidated laminate which comprises consolidating the assembly of Claim 1 under heat and pressure to thereby effect a lamina-tion of said fibrous sheets together, an embossment of the uppermost of the print sheet and a migration of the pigmented resin from the areas of said embossment corresponding to the protuberant areas of the embossed press plates to the valley areas thereof and thereafter removing said embossing press plate from the resultant laminate so as to produce a dense laminate having embossed areas of contrasting color.

9. A heat-and-pressure consolidated laminate of re-gistered embossment and color contrast comprising, in superim-posed relationship, (a) a core layer comprised of a self-supporting substrate;
(b) a resin impregnated print layer consisting of an alpha cellulose paper sheet; and (c) a pigmented surface coating of a fully hydrolyzed poly-vinyl alcohol modified melamine-formaldehyde resin wherein the surface coating weight is from about 0.5 to about 20.0 grams per square foot, the amount of fully hydrolyzed polyvinyl alcohol in the surface coating is from about 5 to about 30 percent by weight of the melamine-formaldehyde reaction product solids and the pigmented surface coating has a flow sufficient to cause said pigmented surface coating to flow more than said resin impregnat-ing the print layer, and the surface of said laminate contains an embossment consisting of protuberances and valleys, each of which are of a different color.

10. The laminate of claim 9 wherein the core layer comprises a plurality of kraft paper sheets impregnated with an alkaline catalyzed phenol-formaldehyde condensation product.

11. The laminate of claim 9 wherein the fully hydrolyzed polyvinyl alcohol modified melamine-formaldehyde resin is the reaction product of melamine, formaldehyde and fully hydrolyzed polyvinyl alcohol wherein the molar ratio of melamine to formaldehyde is about 1:1 to about 1:3, respect-ively.

12. The laminate of claim 11 wherein the amount of formaldehyde employed in the surface coating is from about 1.3 to about 2.0 moles per mole of melamine employed.

13. The laminate of claim 9 wherein the amount of polyvinyl alcohol employed is in the range of from about 10 to 20 percent by weight of the total weight of the melamine-formaldehyde reaction product solids in the surface coating.