Note: Descriptions are shown in the official language in which they were submitted.
1 ~13d~
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~
~ 16:13d~
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~
-- 3 --
1 16ï3~
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
- 5 -
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,
- 6 -
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.
1 16i34~
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
- 10 --
~ 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~
- 12 -
1 16~3~
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
- 13 -
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
- 14 -
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,
- 15 -
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
,;
1 1~13d~
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
- 17 -
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~
- 18 -
1 16134~
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
- 19 -
~ 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.
_ 20 -
