U.S. patent application number 10/364853 was filed with the patent office on 2003-06-26 for method for producing a deep embossed tile design postformable high pressure decorative laminate.
Invention is credited to Fairbanks, Robert Paul, Nilsson, Kenneth Allan, O'Brien, Kevin Francis.
Application Number | 20030116261 10/364853 |
Document ID | / |
Family ID | 23643661 |
Filed Date | 2003-06-26 |
United States Patent
Application |
20030116261 |
Kind Code |
A1 |
O'Brien, Kevin Francis ; et
al. |
June 26, 2003 |
Method for producing a deep embossed tile design postformable high
pressure decorative laminate
Abstract
A method of producing a deep embossed tile design postformable
high pressure decorative laminate by first preparing artwork having
a first layer of fibrous sheets impregnated with a thermosetting
resin, a second layer having a plurality of adjacent tiles
comprising a plurality of fibrous sheets impregnated with a
thermosetting resin, wherein the tiles were previously pressed and
heated, and a third layer having a plurality of shims. The assembly
is then pressed and heated against a rigid substrate whereby the
second layer forms a substantially convex shape on the upper
surface of each tile, thus imparting substantially concave
impressions on the first layer. The first layer is subsequently
removed from the second and third layers, and grooves are formed in
the first layer, preferably by machining. The method also includes
forming a negative image texturing plate from the artwork and then
forming the embossed laminate from the texturing plate.
Inventors: |
O'Brien, Kevin Francis;
(Cincinnati, OH) ; Fairbanks, Robert Paul;
(Cincinnati, OH) ; Nilsson, Kenneth Allan;
(Cincinnati, OH) |
Correspondence
Address: |
Douglas M. Eveleigh
Mayer, Brown, Rowe & Maw
P.O. Box 2828
Chicago
IL
60690-2828
US
|
Family ID: |
23643661 |
Appl. No.: |
10/364853 |
Filed: |
February 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10364853 |
Feb 10, 2003 |
|
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09414937 |
Oct 9, 1999 |
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6551678 |
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Current U.S.
Class: |
156/219 ;
156/222 |
Current CPC
Class: |
Y10T 428/24479 20150115;
B44C 5/0469 20130101; B44C 1/24 20130101; Y10T 428/16 20150115;
Y10T 428/161 20150115; Y10T 156/1044 20150115; Y10T 428/24537
20150115; Y10T 428/24521 20150115; Y10T 428/2457 20150115; Y10T
156/1039 20150115 |
Class at
Publication: |
156/219 ;
156/222 |
International
Class: |
B32B 003/10 |
Claims
We claim:
1. A method of forming image artwork for use in producing an
embossed laminate comprising: A. assembling in a stack from the top
down: a first layer comprising a plurality of fibrous sheets
impregnated with a thermosetting resin; a second layer comprising a
plurality of adjacent tiles comprised of a plurality of fibrous
sheets impregnated with a thermosetting resin, wherein said tiles
were previously heated and pressed; a third layer comprising a
plurality of shims of decreasing dimensions below each tile of said
second layer; B. applying to the upper and lower surfaces of said
assembly sufficient heat and pressure to cure said thermosetting
resin, wherein upon applying heat and pressure to said assembly,
said second layer forms a substantially convex shape on an upper
surface of each tile, thus imparting concave impressions on said
first layer. C. removing said first layer from said assembly; and
D. forming grooves in said first layer.
2. The method in accordance with claim 1, wherein said fibrous
sheets are kraft paper, and wherein said thermosetting resin is
phenolic resin.
3. The method in accordance with claim 1, wherein said shims are
substantially squire and comprise phenolic resin treated kraft
paper filler.
4. The method in accordance with claim 1, wherein forming grooves
comprises machining said first layer at the thickest portions of
said first layer.
5. The method in accordance with claim 4, wherein said machining
creates a grout pattern in said first layer, thereby defining a
plurality of substantially rectangular tiles.
6. The method in accordance with claim 5, wherein said method
further includes filling said grout pattern with grouting
compound.
7. The method in accordance with claim 4, wherein said machining
includes cutting in said first layer individual tiles of
substantially rectangular dimensions.
8. The method in accordance with claim 1, wherein said second layer
is textured on said upper surface, and said second layer imparts
said texture to said first layer upon said application of heat and
pressure.
9. The method in accordance with claim 1, wherein said tiles of
said second layer are of particular dimensions to account for
shrinkage coefficients of at least the final high pressure laminate
article.
10. The method in accordance with claim 1, wherein said assembly is
pressed at approximately 1400 psi and is heated to approximately
150 degrees Celsius.
11. A method of forming image artwork for use in producing an
embossed laminate comprising: A. assembling from the top down: a
first layer comprising a plurality of adjacent tiles comprised of a
plurality of fibrous sheets treated with a thermosetting resin,
wherein said tiles were previously heated and pressed; a second
layer comprising a deformable plate; a third layer comprising a
grid of substantially incompressible material attached to said
second layer, wherein said grid corresponds substantially to the
edges of said adjacent tiles of said first layer; B. applying to
the upper and lower surfaces of said assembly heat and pressure,
wherein upon applying heat and pressure to said assembly, said
second layer forms substantially concave shapes on an upper surface
thereof, which causes said first layer to follow the contour of the
second layer, thus producing concave impressions on the upper
surface of said first layer; and C. forming grooves in said first
layer.
12. The method in accordance with claim 11, wherein said fibrous
sheets are kraft paper, and wherein said thermosetting resin is
phenolic resin.
13. The method in accordance with claim 11, wherein said second
layer comprises a cold rolled mild carbon steel plate
14. The method in accordance with claim 11, wherein said forming
grooves comprises machining said first layer where the edges of
said tiles meet.
15. The method in accordance with claim 11, wherein said machining
creates a grout pattern in said first layer.
16. The method in accordance with claim 15, wherein said method
further includes filling said grout pattern with grouting
compound.
17. The method in accordance with claim 11, wherein first layer is
textured on an upper surface thereof.
18. The method in accordance with claim 11, wherein said tiles of
said first layer are of particular dimensions to account for
shrinkage coefficients of at least the final high pressure laminate
article.
19. The method in accordance with claim 11, wherein said assembly
is pressed at approximately 1400 psi and is heated to approximately
150 degrees Celsius.
20. The method in accordance with claim 11, wherein said
substantially incompressible material comprises ceramic shot.
21. A method of manufacturing an embossed laminate having tiles
with a desired shape comprising: forming positive image artwork,
wherein shape of said artwork takes into account at least the
shrinkage that occurs in said embossed laminate when said embossed
laminate is formed, so that said embossed laminate will maintain
said desired shape; forming a negative image texturing plate from
said artwork; forming said embossed laminate from said texturing
plate.
22. The method according to claim 21, wherein said positive image
artwork comprises kraft paper impregnated with phenolic resin.
23. The method according to claim 22, wherein said negative image
texturing plate comprises kraft paper impregnated with phenolic
resin.
24. The method according to claim 21, wherein said desired shape of
said tiles is substantially a square.
25. The method according to claim 21, wherein said shape of said
artwork is substantially rectangular.
26. The method according to claim 21, wherein said artwork further
takes into account the shrinkage that occurs in said texturing
plate when said texturing plate is formed.
Description
[0001] This is a divisional of application Ser. No. 09/414,937,
filed on Oct. 9, 1999.
FIELD OF THE INVENTION
[0002] This invention relates generally to high pressure decorative
laminates and methods for producing same, and more specifically,
laminates having a deeply textured surface displaying a tile
design.
BACKGROUND OF THE INVENTION
[0003] Typically deeply textured embossed high pressure decorative
laminates are produced with an overall thickness greater than those
with more planar textures, such that the areas of deepest
embossment have a thickness about the same as that for
conventionally textured high pressure decorative laminates. While
this avoids the problem of texture embossment punch-through and
weakening of the laminate structure, with associated breakage,
etc., the necessary increased thickness of such laminates detracts
from their postformability. As such, it is often not possible to
postform these laminates to the relatively tight radii of
conventional kitchen countertop profiles, or other demanding
postforming applications, and therefore restricting their use to
either general purpose flatstock applications, or postforming
applications with less aesthetically pleasing larger radii bends.
For the aforementioned reasons, a deeply embossed tile design high
pressure decorative laminate, with commercially acceptable physical
properties and postforming characteristics, has been heretofore
precluded.
[0004] High pressure decorative laminates have been used as a
surfacing material for many years, in commercial and residential
applications, where pleasing aesthetic effects, in conjunction with
functional behavior, such as superior wear, heat and stain
resistance compared to alternative surfacing materials, have been
desired. Typical applications include, but are not limited to,
furniture, kitchen countertops, table tops, store fixtures,
bathroom vanity tops, cabinets, wall paneling, partitions, and the
like. However, historically, high pressure decorative laminates
have not been successfully used to replace "natural" ceramic tile
for applications such as kitchen countertops, bathroom vanity tops,
or shower and tub surrounds, where the "real" tile look is desired,
even though high pressure decorative laminate offers several
distinct advantages over ceramic tile, including a naturally
antibacterial, antifungal and mold resistant surface, ease of
installation, ease of cleaning, lower cost, warmth to the touch,
and more forgiveness with breakable objects such as glassware and
dinnerware. A natural ceramic tile installation consists of 5% or
more porous grout area, which is easily stained and readily
promotes bacterial, fungal and mold growth, which is becoming ever
more of a household and business concern. Therefore, the need
exists for a postformable, high pressure decorative laminate with a
pleasing, deep textured tile design simulating the look and feel of
natural ceramic tile without the deficiencies noted above.
[0005] High pressure decorative laminates can generally be
classified by their decorative surface design as being either a
uniform solid color, or a printed pattern, whether a woodgrain,
stone-like or abstract design. Each type of high pressure
decorative laminate can also be classified as to its surface
finish, which in conjunction with its color or pattern, contributes
to the overall decorative surface design, structure and aesthetics,
as will be discussed in more detail below. High pressure decorative
laminates can also be classified by their intended application as
defined by the industry's governing body, the National Electrical
Manufacturers Association (NEMA) in there standards publication LD
3-1995. Of particular interest is the "postforming type", which is
defined as "a high pressure decorative laminate (HPDL) similar to
the general-purpose type, but is capable of being thermoformed
under controlled temperature and pressure" after its initial
manufacture, which is well understood by those versed in the
art.
[0006] High pressure decorative laminates are generally comprised
of a decorative sheet layer, which is either a solid color or a
printed pattern, over which is optionally placed a translucent
overlay sheet, typically employed in conjunction with a print sheet
to protect the print's ink line and enhance abrasion resistance,
although an overlay can also be used to improve abrasion resistance
of a solid color as well. A solid color sheet typically consists of
alpha cellulose paper containing various pigments, fillers and
opacifiers, generally with a basis weight of about 50 to 120 pounds
per 3000 square foot ream. Similarly, print base papers are also
pigmented and otherwise filled alpha cellulose sheets, usually
lightly calendered and denser than solid color papers, and lower in
basis weight at about 40-75 pounds per ream, onto which surface is
rotogravure or otherwise printed a design using one or more inks.
Conversely, overlay papers are typically composed of highly pure
alpha cellulose fibers without any pigments or fillers, although
they can optionally be slightly dyed or "tinted", and are normally
lighter in weight than the opaque decorative papers, in the range
of 10-25 pounds per ream.
[0007] Typically, these overlay and decorative print and solid
color surface papers are impregnated, or "treated", with a
melamine-formaldehyde thermosetting resin, which is a condensation
polymerization reaction product of melamine and formaldehyde, to
which can be added a variety of modifiers, including plasticizers,
flow promoters, catalysts, surfactants, release agents, or other
materials to improve certain desirable properties, as will be
understood by those versed in the art. As with
melamine-formaldehyde resin preparation and additives thereto,
those versed in the art will also appreciate that other
polyfunctional amino and aldehydic compounds can be used to prepare
the base resin, and other thermosetting polymers, such as
polyesters, may be useful as the surface resin for certain
applications, but use of a melamine-formaldehyde resin is
preferred. Optionally, an untreated decorative paper can be used in
conjunction with a treated overlay, if the overlay contains
sufficient resin, such that during the laminating process heat and
pressure consolidation, there is adequate flow of the resin from
the overlay to contribute to the adjacent decorative layer, so as
to effect sufficient interlaminar bonding of the two, as well as
bonding of the decorative layer to the core. The equipment used to
treat these various surface papers is well known to those versed in
the art. The papers are normally treated to controlled,
predetermined resin contents and volatile contents; the optimum
levels will be well understood by those versed in the art, with
typical resin contents in the ranges of 64-80%, 45-55% and 35-45%
for overlay, solid color and print (unless used untreated) papers
respectively, and all with volatile contents of about 5-10%.
[0008] The surface paper of a high pressure decorative laminate is
simultaneously bonded to the core, which usually is comprised of a
plurality of saturating grade kraft paper "filler" sheets, which
have been treated or impregnated with a phenol-formaldehyde resin,
which also simultaneously fuse and bond together during the
laminating process, forming a consolidated, multi-lamina integral
assembly. Again, those versed in the art will appreciate that a
variety of modifiers such as plasticizers, extenders and flow
promoters can be added to the phenol-formaldehyde resin, that other
phenolic and aldehydic compounds can be used to prepare the base
resin, or other types of thermosetting resins such as epoxies or
polyesters may be used, although a phenol-formaldehyde resin is
preferred. In addition, other materials such as linerboard, fabric,
glass, or carbon fiber may be used for the filler plies, but a
saturating grade kraft paper and other modified kraft papers are
presently preferred, typically with a basis weight of about 70-150
pounds per ream. The resin preparation and filler treating
methodologies are also well known to those versed in the art.
[0009] During the laminating or pressing operation, the various
surface and filler sheets are cured under heat and pressure, to
fuse and bond them together, consolidating them into an integral
mass. Typically, this process is accomplished in a multi-opening,
flat bed hydraulic press between essentially inflexible, channeled
platens capable of being heated and subsequently cooled. While
other types of press equipment can be used to produce high pressure
decorative laminates, for example a continuous double belt press, a
single or limited opening "short cycle" press, or an isothermal
"hot discharge" press, a conventional multi-opening press is most
suited to the practice of the present invention.
[0010] Typically, back-to-back pairs of laminate assemblies,
consisting of a plurality of filler sheets and one or more surface
sheets, are stacked in superimposed relationship between rigid
press plates, with the surfaces adjacent to the press plates. Such
press plates are typically made of a stainless steel alloy such as
AISI 410, and can have a variety of surface finishes, which they
either impart directly to the laminate surface during the pressing
operation, or they are used in conjunction with a non-adhering
texturing/release sheet between the laminate surface and the plate,
which will impart a finish to the laminate surface as well. Such
texturing/release sheets, for example paper backed aluminum foil,
or a variety of polymer coated papers, are commercially available
from a variety of suppliers.
[0011] Several pairs of laminate assemblies are usually interleaved
between several press plates to form a press pack (or book), which
is then inserted, by means of a carrier tray, into an opening or
"daylight" between two of the heating/cooling platens of the
multi-opening, high pressure flat bed press. The press platens are
typically heated by direct steam, or by high pressure hot water,
the latter usually in a closed-loop system, and water cooled. The
laminate pairs between the press plates are usually separated from
each other by means of a non-adhering material such as a wax coated
paper, or biaxially oriented polypropylene film, which are
commercially available, or the backmost face of one or both of the
laminates' opposed filler sheets in contact with each other is
coated with a release material such as a wax or fatty acid salt. In
either case, after the pressing operation has been completed and
the press pack removed from the press, the press plates are removed
sequentially from the press pack build-up, and the resultant
laminate doublets separated into individual laminate sheets. In a
separate operation, these must then be trimmed to the desired size,
and back sanded so as to improve adhesion during subsequent bonding
to a substrate and other fabrication.
[0012] A typical press cycle, once the press is loaded with one or
more packs containing the laminate assemblies and press plates,
will consist of closing the press to develop a specific pressure of
about 1000-1500 psig, heating the packs to about 130-145 C.,
holding at that temperature for a predetermined time, and then
cooling the packs to or near room temperature before discharging
the packs from the press for separation. Those versed in the art
should have a detailed understanding of the overall pressing
operation, and will recognize that careful control of the degree of
the laminate's cure, as well as its cure temperature, are critical
in achieving the desired laminate properties, particularly its
postformability, as are selection of the proper
melamine-formaldehyde and phenol-formaldehyde surface and filler
resins respectively, as well as the surface and filler paper
properties.
[0013] Many types of press plates and texturing/release materials
have been used to manufacture high pressure decorative laminate
products with a wide variety of surface finishes. Historically, the
earliest manufacture was confined to a smooth, reasonably glossy
surface finish produced directly from a polished and buffed
stainless steel press plate. This finish was sometimes reduced to a
dull, essentially smooth, flat finish by rubbing the pressed
laminate surface with a slurry of fine pumice. Later on, a lightly
textured surface finish was produced by pressing the laminate
surface against paper backed aluminum foil "caul stocks", e.g.,
kraft paper backed foil Caulstock #6 or litho paper backed foil
Caulstock #13, placed between a flat stainless steel backing plate
and the laminate, and later stripped off the laminate after the
pressing operation. For economic reasons, the aluminum foils were
subsequently replaced with specially coated texturing/release
papers, usually with proprietary coating formulations based on
substituted melamine resins and/or alkyd resins, such as St. Regis'
(now Ivex) LC-55 and LC-58, and S. D. Warren's Transkote ETL, which
produced essentially the same type finish and texture as did the
aluminum foils, with a peak-to-valley depth of about 0.0005-0.001
inches. These types of textured finishes became extremely popular,
nearly annihilating the glossy finish market, and are still
produced in large quantity today, but now most commonly by the use
of direct release shot peened or chemically etched stainless steel
texturing plates.
[0014] Eventually, "low relief" embossed finishes were introduced,
for example using the "heavy ink" method of U.S. Pat. No. 3,373,068
Grosheim et al., with peak-to-valley depths of about 0.003-0.005
inches. Still later, three-dimensional, deep textured or embossed
laminates were manufactured, with peak-to-valley depths of
0.010-0.020 inch or more, for example by the methods of U.S. Pat.
No. 3,718,496 issued to Willard and U.S. Pat. No. 3,860,470 issued
to Jaisle et al., which are preferred and are incorporated herein
by reference. Such laminates, of necessity to retain their
mechanical strength, were usually produced substantially thicker
than those with conventional "smooth" finishes, which adversely
affected their postforming capability and often relegated such
products to general purpose "flat stock" applications. This is
especially true as the extent of embossing increased in
severity.
[0015] Finally, the deep textured laminate technology evolved into
efforts to faithfully simulate "natural" materials such as slate,
marble, sandstone, pebbles, brick, cane, woven jute and hemp,
leather, rough hewn and weathered timber, woodgrains, tile, and the
like. To do so properly, and create a truly natural appearance and
texture, registered embossed methods were developed in which the
design color contrasts are in register with the peak and valley
topography of the texture embossment itself. The earliest "overlay
methods" of U.S. Pat. No. 4,092,199 issued to Unger, et al. and
U.S. Pat. No. 4,093,766 issued to Scher, et al. relied on use of a
pigmented, high flow melamine-formaldehyde resin impregnated
overlay placed over a conventional solid color or printed pattern
sheet to achieve the registered embossed effect. The later methods
of U.S. Pat. No. 4,374,866 issued to Raghava and U.S. Pat. No.
4,376,812 issued to West replaced the pigmented
melamine-formaldehyde resin treated overlay with a pigmented
melamine-formaldehyde resin coating directly on the treated
decorative paper of choice. However in the practice of the instant
invention, for the manufacture of a registered embossed, deep
grout, tile design high pressure decorative laminate, the method of
U.S. Pat. No. 4,092,199 issued to Ungar, et al. is preferred and is
incorporated herein by reference.
[0016] Over the ensuing years since development of the deep
textured embossed and registered embossed high pressure decorative
laminate technologies noted above, there have been encountered
heretofore insurmountable difficulties in producing a suitable deep
textured tile design laminate, particularly one with commercially
acceptable postforming properties, because of both the unique
geometry of the tile profile itself, and the materials used in its
manufacture. Most of the "natural material" deep embossed designs,
whether registered or non-registered, such as a slate or leather
pattern, have a random texture with relatively gradual
peak-to-valley texture gradients. Conversely, a tile design, and
particularly its grout lines, have steep, nearly perpendicular
profiles, which with a desirably deep grout, would make the
laminate very difficult to handle during processing and
fabrication, and in the worse case, the grout could actually punch
through the back of the laminate, resulting in shearing and
breakage in the press.
[0017] Another difficulty in producing an acceptable tile design
heretofore is that traditional ceramic tiles are square, and the
consumer's expectation of a tile texture laminate would be that it
have square tiles as well. Use of the conventional texturing
process of U.S. Pat. No. 3,718,496 issued to Willard, which is
widely practiced in the industry, to produce such tile textured
laminate, where a real ceramic tile and cementaceous grout artwork
master would most likely be used to produce a phenolic resin/kraft
paper negative image texturing plate laminate, which in turn could
be used to produce the final decorative laminate product, would
result in smaller, rectangular tiles. During each step in such a
process, i.e., during preparation of the phenolic/kraft texturing
plate, during repeated usage of said plate, and during press curing
of the final laminate product itself, cumulative asymmetric
shrinkage occurs, with shrinkage about twice that in the less paper
fiber reinforced crosswise direction of the laminate compared to
the more highly reinforced lengthwise direction, due to the paper's
directionality. Of particular concern is the progressive shrinkage
of the phenolic/kraft texturing plate with repeated usage,
resulting in variable, rectangular tile dimensions, which would
make butt joining and mitering of laminates pressed from such
texturing plates of differing ages impossible without grout line
misalignment.
[0018] U.S. Pat. No. 3,860,470 issued to Jaisle et al. recognized
the propensity for such phenolic/kraft texturing plates to shrink,
and taught preshrinking them with exposure to heat in an oven to
stabilize them prior to trimming to plate size and use. This was
done strictly to reduce shrinkage during subsequent repeated press
use, and therefore increase their useful life before being retired
as undersized. With random textures such as a slate or leather
design, the fact that the texture itself was also shrinking and
changing along with the plate's overall dimensions was of little
consequence in terms of significantly affecting the design
aesthetics, joinery capability, etc., as would be the case with a
tile design. While such a method of preshrinking would largely
resolve the plate age variability problem, it could not resolve the
out-of-squareness issue if starting with real ceramic tile
artwork.
[0019] Thus, for example, a stable, slightly rectangular tile
design stainless steel texturing plate with the requisite negative
image of the final laminate tile design, which would compensate for
the shrinkage of the final laminate product, would be effective in
preventing the above-described problems. However, producing such
plates, with a raised grout pattern and tile face texture design as
well, by mechanical machining, chemical etching or some other
method, would be extremely difficult and expensive to accomplish,
particularly in any large quantity required to satisfy the capacity
of a conventional multi-opening laminating press.
[0020] Thus, there is a need for a deep embossed tiled design high
pressure decorative laminate that has the characteristics that have
not heretofore been achieved. There is also a need for a method of
producing such a deep embossed tiled design high pressure
decorative laminate. Other needs will become apparent upon a
reading of the following detailed description, taken in conjunction
with the drawings.
SUMMARY OF THE INVENTION
[0021] The aforementioned needs are fulfilled by a deep embossed
high pressure decorative laminate having a plurality of integral
tiles with various surface textures bordered by deep embossed
portions. Each tile of the laminate has a peripheral thickness
greater than the thickness of the non-peripheral portions of the
tile. Preferably, each tile has a concave profile along its upper
surface when viewed in cross section. A method of producing artwork
necessary for the deep embossed high pressure decorative laminate
of the present invention comprises assembling a first layer of
fibrous sheets impregnated with a thermosetting resin, a second
layer comprising a plurality of adjacent tiles comprising a
plurality of fibrous sheets impregnated with a thermosetting resin,
wherein the tiles were previously pressed and heated, and a third
layer comprising a plurality of shims. The assembly is then pressed
and heated against a rigid substrate whereby the second layer forms
a substantially convex shape on the upper surface of each tile,
thus imparting substantially concave impressions on the first
layer. The first layer is subsequently removed from the second and
third layers, and grooves are formed in the first layer, preferably
by machining.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a partial cross-sectional elevational view of a
deep embossed postformable high pressure decorative laminate
according to the present invention.
[0023] FIG. 2 is a cross-sectional exploded view of an assembly
used to prepare artwork of the present invention.
[0024] FIG. 2A is a cross-sectional view of a layer of FIG. 2 after
it has been pressed and heated in the assembly of FIG. 2.
[0025] FIG. 2B is a cross-sectional view of another layer of FIG. 2
after it has been pressed and heated in the assembly of FIG. 2.
[0026] FIG. 3 is a cross-sectional exploded view of another
assembly used to prepare artwork of the present invention.
[0027] FIG. 3A is a cross-sectional view of a layer of FIG. 3 after
it has been pressed and heated in the assembly of FIG. 3.
[0028] FIG. 3B is a cross-sectional view of another layer of FIG. 3
after it has been pressed and heated in the assembly of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0029] While the present invention is capable of embodiment in
various forms, there is shown in the drawings and will be
hereinafter described a presently preferred embodiment with the
understanding that the present disclosure is to be considered as an
exemplification of the invention, and is not intended to limit the
invention to the specific embodiment illustrated.
[0030] As discussed above, there are many deficiencies with the
prior art, that heretofore precluded manufacture of a commercially
acceptable postforming, high pressure decorative laminate with a
deep, well defined grout line and square tile design, and with
consistent three-dimensional texture dimensions, i.e., the tile
size, grout width and grout depth. The starting artwork used to
prepare a suitable textured phenolic/kraft press plate according to
the method of U.S. Pat. No. 3,718,496 Willard, previously
incorporated herein by reference, can not be made from commercially
available square ceramic tiles, for the reasons previously
delineated. It was found, however, that phenolic/kraft paper
laminates shrink predictably with repeated or continual exposure to
heat: the rate of shrinkage being a function of the temperature and
thickness of the laminate, and the final degree of shrinkage being
a function of the resin content of the phenolic resin treated kraft
paper "filler" used in its construction, and the temperature.
Shrinkage is initially the result of removal of residual moisture
contained within the laminate, and then continuation of the
crosslinking, condensation polymerization reaction cure of the
laminate, where pendant hydrophilic methylol groups on the phenolic
nuclei crosslink to form hydrophobic ether and methylene bridges,
and as the cure is advanced further, residual ether linkages are
converted to the shorter bond length methylene bridges. This
process pulls the three dimensional, polymeric phenolic lattice
together, resulting in shrinkage of the entire laminate mass. The
curing chemistry for phenolic resins is well understood by those
versed in the art.
[0031] With temperature and resin content of the filler held
constant (as well as the phenolic resin formulation and grade of
kraft paper used), the times required to preshrink various
thickness press cured phenolic resin/kraft paper laminates was
established, and found to be predictable and repeatable. As long as
the subsequent press cure temperature for final decorative laminate
manufacture does not exceed that of the conditioning temperature of
the preshrunk phenolic/kraft textured laminate plate used to
produce it, the latter will be stable and no further significant
shrinkage will occur. As such, the phenolic/kraft texturing plate
should be preshrunk at a higher temperature than the press cycle
top cure temperature used for the manufacture of the final
decorative laminate product. The phenolic/kraft laminate shrinks
asymmetrically, with the cross direction (width) shrinking about
twice that of the length direction on a percentage basis, since in
the cross direction, the shrinkage is not restrained as much by the
directionality of the paper fibers, i.e., the laminate has a lower
compressive strength in the cross direction than in the length
direction. The length direction fully shrinks about 0.4-0.6%,
whereas the cross direction shrinks about 0.7-0.9%, depending on
the above mentioned variables. Hence, rectangular tiles will be
produced after repeated pressings if starting with a square tile
artwork.
[0032] Therefore, the key to obtaining square tiles of the desired
dimensions in the final laminate product, is to begin the process
with stable rectangular tiles in the starting artwork, where said
tiles are properly sized, being slightly wider than they are long.
How oversized the tiles in the beginning artwork should be is
dependent on the established length and width shrinkage
coefficients, as well as the number of pressing steps, or
replications, required between the artwork (or its precursor
"pre-artwork", which will be described below) and the final
decorative laminate pressing, which also shrinks about 0.10% in the
length direction and 0.15% in the cross direction out-of-press,
relative to the dimensions of the texturing plate it was pressed
against, as tensile stresses relax.
[0033] It is preferred to use the method of U.S. Pat. No. 3,718,496
issued to Willard for the preparation of the texturing plate,
wherein the texturing plate used to produce the final decorative
laminate is obtained directly from an original artwork. More
complicated replication processes have evolved, designed to
preserve, protect and extend the life of the original artwork, for
example, where a phenolic/kraft negative image "supermaster" is
prepared from the artwork, which is then used to produce a
phenolic/kraft positive image "copymaster", which in turn is used
to generate a phenolic/kraft negative image texturing plate, which
is then finally used to manufacture the decorative laminate.
[0034] While such a process does better protect the artwork, there
would be more shrinkage steps involved, and more importantly, with
each replication step, about 10% of the overall texture depth and
fidelity is lost. While this may be acceptable for a slate or
leather texture, it is not preferred in the practice of the present
invention, where sharp, well defined grout lines are desired, and
texture loss is even greater in those areas. The only requisite
with use of the simpler Willard process is that the artwork not be
too delicate or irreplaceable, i.e., that duplicate artworks can be
produced relatively easily and inexpensively, which this invention
also embodies. As will be described in more detail below, by
preshrinking the phenolic/kraft laminate used for the pre-artwork,
artwork and texturing plate, and compensating for the decorative
laminate shrinkage as well, the exact rectangular dimensions for
the tiles in the starting pre-artwork can be determined, such that
the tiles in the final decorative laminate will have the desired
dimensions, as will the width of the grout lines.
[0035] A typical postforming laminate, used for kitchen countertops
and the like applications, has a thickness of about 0.036 inch
(NEMA grade HGP), and is expected to postform to a 5/8 inch surface
outside radius of curvature or better. In reality, a typical
postformed countertop profile includes a 3/4 inch surface outside
radius bull nose bend, a {fraction (3/16)} inch surface inside
radius cove bend, and a 3/4 inch surface outside radius backsplash
bend, which must be met consistently, without cracking or
blistering, if the postformable high pressure decorative laminate
of the present invention is to be commercially viable. With a
desired grout line depth of about 0.012 inch, the resultant
laminate would only have a sanded thickness of about 0.024 inch in
the grout line areas, which is too thin for everyday handling of
the laminate during manufacture and fabrication, without
experiencing excessive breakage at the grout lines. With this grout
line depth, punch-through of the grout lines and fracture of the
laminate during pressing can also occur.
[0036] To resolve this dilemma, rather than using conventional flat
tiles, the tiles of the present invention were designed with their
periphery or edges (adjacent to the grout lines) raised about half
the desired depth of the grout line above the plane of the tile
face itself, i.e., tiles with a quasi-concave or dished profile. To
accomplish this profiling, a negative image phenolic resin/kraft
paper "pre-artwork" was used to prepare the artwork laminate, as
will be described in detail below. In such a manner, the resultant
laminate will actually have the desired grout line depth of about
0.012 inch, but the grout line will only penetrate into the
laminate below the elevation of the tile face about 0.006 inch.
This novel method and structure therefore allows for the
manufacture of a 0.036 inch thick postforming laminate with a
thickness of about 0.030 inch at the grout line areas, rather than
only about 0.024 inch thick in those areas and being much more
fragile, as would otherwise be the case using conventional flat
tiles.
[0037] This concept is illustrated in FIG. 1, which shows a
cross-sectional elevation view, roughly to scale, of the tile
design, high pressure decorative laminate of the present invention
2, in the area of a grout line 4, where the tile edges 6, adjacent
to the grout line 4, are dished upwards relative to the essentially
planar faces of the rest of the tile bodies 8, whether the tile
faces have a smooth or rough texture therein. Although tiles having
dished edges or concave shapes are discussed herein, those skilled
in the art will recognize that a multitude of other tile shapes may
be used to perform the present invention, such as stepped shapes or
other graduated shapes.
[0038] Referring to FIG. 2, the pre-artwork tiles 10 were prepared
by first pressing 32 plies of phenolic resin treated 115 pounds per
ream kraft paper filler against a rigid, heat stable material with
the desired positive image surface texture, whether a smooth plate
or some other relatively subtle texture, with a polypropylene
release film in-between, resulting in a nominal 1/4" thick
phenolic/kraft laminate with the negative image of the tile texture
of choice imparted to it. This pre-artwork stock was sanded on the
back side, then baked in an oven for 4 days at 135 C. to preshrink
the material. The pre-artwork laminate was then accurately cut into
individual rectangular tiles 10 of predetermined dimensions, based
on the lengthwise and crosswise shrinkage coefficients of the
subsequent artwork, texturing plate and final decorative laminate
article. To the backside of each individual tile 10 was then "spot
welded", with isocyanurate glue, nominally square shims 12 of
decreasing dimensions to form a step-wedge effect, said shims 12
being comprised of phenolic/kraft filler. On top of a press carrier
tray 14 were placed in ascending superimposed relationship several
plies of untreated kraft paper "cushion" 16, a nominal 0.100" thick
steel plate 18, an epoxy film adhesive sheet 20, and four plies of
115 lb. basis weight phenolic/kraft filler 22. The preferred
adhesive sheet is CyTec Fiberite Inc.'s FM 300-2M epoxy film, with
a tensile shear strength of approximately 3200 psi at 250 F. (120
C.) and 2000 psi at 300 F. (150 C.), and with a continuous service
temperature rating of 275 F. (135 C.).
[0039] The tiles 10, with the shims 12 attached and facing the
filler 22, were then butt joined by gluing them to the topmost ply
of filler 22 by means of an epoxy resin (Gougeon Brothers, Inc's
West System 105) applied to the backside perimeter of each tile.
The tiles 10 were weighted and allowed to sit 12 hours while the
epoxy cured. The pack build-up was then completed by placing, in
ascending superimposed relationship on top of the tiles 10, a sheet
of 1 mil (0.001" thick) high softening point biaxially oriented
polypropylene film (BOPP) 24, 32 more plies of the 115 lb. basis
weight phenolic/kraft filler 22, which during pressing will mold
into a nominal 1/4" thick positive image artwork sheet 26 (FIG.
2B), another sheet of 1 mil BOPP 24, 16 additional plies of kraft
cushion 16, another steel plate 18, and finally several more plies
of kraft cushion 16 on the top of the pack. It should be understood
that, as previously discussed, the filler may be formed of other
materials, such as linerboard, fabric, glass, or carbon fiber. The
BOPP, commercially available from many suppliers, was used as a
two-sided separator sheet for the phenolic resin based laminate
surfaces, as will be appreciated by those versed in the art.
[0040] After loading into a high pressure flat bed hydraulic press,
the pack was heated to about 150 C., held at that temperature for 1
hour to insure full cure of the epoxy film, and then cooled to near
room temperature, all under a specific pressure of 1400 psig. At
that pressure, the edges of the individually shimmed pre-artwork
tiles 10 deflected downward to form a substantially convex shape on
the top surface thereof, as shown in FIG. 2A, and the artwork 26 on
top of the individually shimmed pre-artwork tiles 10 was molded and
cured to a reverse of that shape, i.e., a concave shape, as shown
in FIG. 2B. Upon cooling and removal from the press, the artwork 26
was separated from the bonded pre-artwork 10, 12, 22, 20, and 18,
and consisted of a unified, 1/4" thick phenolic/kraft laminate with
the positive image of the final tile face texture, with raised
crisscross pattern ridge lines 27 corresponding to where the grout
lines would be located, and sunken "square" areas corresponding to
the resultant tile locations. The newly formed artwork 26 was then
baked in an oven for 4 days at 135 C. to effect full shrinkage.
[0041] The next step in preparing the artwork 26 was to machine in,
along the tile ridge lines 27, the desired grout design using a
router. The type of router bit and guide employed will determine
the general shape, width and depth of the grout lines and tile edge
profile, with position, alignment and "squareness" of the grout
lines critical to obtaining the desired final decorative laminate
design. Many grout line/tile edge design options are possible,
including square, rounded or beveled tile edges; straight, "craggy"
or chipped tile sides; square or rounded tile corners; and with a
flat or rounded grout bottom. For a craggy tile edge look, a
randomly uneven router guide "wobble board" was used, and fine
detail tile edge work for edge chipping, corner rounding, etc. was
accomplished with a Dremel MultiPro rotary tool and appropriate
bit. Optionally, the grout depth can be over-routed too deep, and
subsequently back-filled with a suitable grouting compound that
will be capable of withstanding the laminating press temperatures
it will be exposed to. The grouting compound can be course or
smooth, depending on the final design sought. Grouting compounds
that have been used include China clay filled epoxy resin, PVA, a
PVA/fine sand/cement mixture, furnace cement and Omega
Engineering's CC [ceramic cement] High Temperature Cement. Each
material has its own distinct shrinkage characteristics during its
initial cure and final press cure, as well as its own unique
compressibility characteristics under pressure in the press. These
properties must be predetermined to establish how much to fill the
grout channel in the artwork. It is important to establish the
proper grout depth in the cured artwork if the desired grout depth
is to be achieved in the final decorative laminate, since the grout
depth will decrease about 25% with each replication step in the
process. The reason for the loss of the grout depth/height
reproducibility is primarily due to the need to use a separator
film between the two articles, with secondary effectors being that
the "parent" expands slightly in the z-direction (thickness) during
pressing, and the "child" contracts slightly in the z-direction
upon cooling in the press, and during the preshrink baking
operation thereafter.
[0042] One particularly useful grouting compound was developed,
consisting of a mixture of the West System 105 epoxy resin, Dualite
hollow composite microsphere filler (Pierce & Stevens Corp.),
and SEPR's Zirblast Grade B60 ceramic shot (0.125-0.250 mm
diameter). This material exhibits very predictable, one time,
irreversible compaction or compression, with collapse of the
microspheres during the initial pressing, and the degree of
compression can be varied with the ratio of the components. A
mixture by volume of 1 part epoxy resin, 3 parts microspheres, and
2 parts ceramic shot will compress about 50% during the initial
pressing, and will not change substantially thereafter. Based on
the above, to obtain a final decorative laminate grout depth of
about 0.012 inch, the artwork grout channel was routed to a depth
of 0.042 inch, the grout channel was then filled with the above
proportioned grouting compound mixture to the top edge of the
tiles, and the grout was allowed to cure 12 hours at room
temperature prior to pressing. During pressing to produce the
negative image texturing plate, the grout will collapse to a depth
of about 0.021 inch, and impart a grout height of about 0.016 inch
to the texturing plate. This plate, in turn, will produce an
embossed decorative laminate with a grout depth of about 0.012
inch.
[0043] A variation of the above artwork preparation process was
developed to further improve the dimensional stability of the
entire artwork plate. Rather than machining the grout lines into
the full size preshrunk artwork sheet 26, the preshrunk artwork
sheet 26 was first cut into individual tiles of predetermined
dimensions. This process requires that the pre-artwork, and the
individual tiles 10 thereon forming the pre-artwork, be larger than
for the "full sheet artwork" method discussed above, to allow and
compensate for the saw kerfs when cutting the tiles. Optionally,
the pre-dished tiles can then either be butt joined and bonded to a
steel plate prior to machining the grout and tile edges, and
filling the grout, as above, or the tiles can first be individually
machined, with grout cut-outs, etc., prior to butt joining and
bonding to a steel plate or other suitable base. In this manner, if
there should be any dimensional movement of the tiles due to slight
continued shrinkage of the tiles even after preshrinking, each tile
will move individually and the grout centerline design will be
preserved.
[0044] It will be appreciated by those versed in the art that other
pre-dished tiles can be used in the practice of this invention; for
example, machined or drop forged metal tiles, molded high
temperature plastic tiles, or cast ceramic tiles, whose edge and
grout treatments can optionally be machined prior to adhering them
to a steel sheet or other suitable substrate.
[0045] A second method of creating dished tiles in the positive
image artwork, without the need of first creating a pre-artwork,
was also developed. Referring to FIG. 3, a crisscross lattice work
grid, comprised of strips of the Cytec Fiberite FM 300-2M epoxy
adhesive film 20, was laid down on the back side of a nominal 0.100
inch (12 gauge) cold rolled mild carbon steel plate 28 conforming
to ASTM A366 specifications. The centerlines of the grid strips
corresponded exactly to the edges of butt joined preshrunk tiles 32
of predetermined, slightly rectangular dimensions. The epoxy
adhesive strips 20 were then heated momentarily with a heat gun
until soft and tacky, and Zirblast B60 ceramic shot 30 was spread
over the lattice work strips and gently patted into them. After
removing the excess shot with a vacuum cleaner, there results a
near-continuous "film" of ceramic shot 30 stuck in the adhesive
film strips 20. The plate, with the lattice work adhered to it on
its upper side, was then placed in a flat bed laminating press and
baked for 1 hour at about 150 C., with the press only partially
closed, to set and cure the epoxy/ceramic shot strips 20, 30.
Afterwards, in superimposed ascending order on a press carrier tray
14 were placed first a ply of BOPP separator/release film 24, and
then the mild steel plate 28 with the adhesive/ceramic shot strips
20, 30 face down against the BOPP film 24 and the carrier tray 14.
On top of the steel plate 28 was then placed in superimposed
ascending relationship first a continuous film of the CyTec
Fiberite FM 300-2M epoxy adhesive 20, and then 4 plies of phenolic
resin/kraft paper filler 22.
[0046] In a separate operation using essentially the method of U.S.
Pat. No. 3,718,496 Willard referenced herein, 16 plies of phenolic
resin treated 115 pounds per ream kraft filler were pressed against
a rigid, heat stable material with the desired positive image
surface texture, resulting in a nominal 1/8 inch thick
phenolic/kraft laminate with the negative image of the texture of
choice imparted to it. After trimming off the excess filler
"flash", this texturing plate was then used in the same manner to
produce another 1/8 inch thick phenolic/kraft laminate with the
positive image of the chosen texture imparted to it. This second
replication laminate, with the positive texture image, was then
baked in an oven at 135 C. for 3 days to preshrink it. After
shrinking, the sheet was cut into tiles 32 of predetermined
dimensions.
[0047] Still referring to FIG. 3, the preshrunk tiles 32 were
placed on top of and glued to the filler 22 with West System 105
epoxy resin applied to the bottom side perimeter of each tile,
being butt joined such that the joints were exactly centered over
the center lines of the epoxy adhesive/ceramic shot shim strips
20,30 underneath the filler 22, adhesive film 20, and mild steel
plate 28. The tiles were weighted and allowed to sit 12 hours for
the epoxy resin to cure. Then, in ascending superimposed
relationship were placed on top of the tiles a sheet of BOPP film
24, and finally 16 plies of cushion 16. After this assembly was
loaded into a flat bed, high pressure laminating press and
pressurized to 1400 psig specific pressure, the pack was heated to
about 150 C., held at that temperature for one hour to achieve full
cure of the epoxy film and bond to the steel plate, and then cooled
to near room temperature. At this press pressure, the mild carbon
steel plate 28 was deflected on the top surface in a concave manner
as shown in FIG. 3A, with permanent deformation around the
incompressible ceramic shot 30 supported lattice work shims 20,30,
thereby causing the bonded tiles 32 to also deflect and form a
generally concave shape on the upper surface thereof, with raised
areas 33 at the butt joints where the grout lines would be
machined, as shown in FIG. 3B. With use of the B60 ceramic shot,
the amount of dishing was about 0.008 inches, which was more than
adequate to allow for a 0.012 inch grout depth in the final
decorative laminate. The amount of dishing can be easily controlled
by the grade (diameter) of the ceramic shot used, the thickness of
the lattice work shims, which can be built up systematically with
more than one layer of adhesive film strips and ceramic shot
application, and by the thickness of the tiles themselves, where
thinner tiles are more easily deflected than are thicker ones.
[0048] After the novel artwork is prepared by any of the methods of
this invention described above, a flat backed, negative image,
single-sided texturing plate can next be prepared, essentially in
accordance with the methods of U.S. Pat. No. 3,718,496 issued to
Willard and U.S. Pat. No. 3,860,470 issued to Jaisle et al.
previously referenced. Specifically, in ascending superimposed
relationship on a press carrier tray were placed 8 plies of 115
pound basis weight kraft cushion, the tile artwork, texture side
facing up, 1 sheet of BOPP separator/release film, 8 sheets of 115
pound per ream phenolic resin treated kraft filler, another sheet
of BOPP film, a smooth steel backing plate, and finally 8 more
plies of cushion on top of the pack build-up.
[0049] This assembly was loaded into a flat bed hydraulic
laminating press. After closing and pressurizing the press to 1400
psig specific pressure, the pack was heated to about 135 C. in
about 20 minutes, held at that temperature for about another 20
minutes, and then cooled to near room temperature. The pack was
then removed from the press, and the newly formed phenolic/kraft
texturing plate, approximately {fraction (1/16)} inch thick,
separated from the artwork. The texturing plate was then baked in
an oven for 3 days at 135 C. to preshrink it. It will be
appreciated by those versed in the art that the thickness of the
phenolic/kraft texturing plate can be varied simply by altering the
basis weight of the filler or the number of filler plies used in
the build-up, but a nominal {fraction (1/16)} inch plate is
preferred for its intended application within the scope of the
present invention. Thinner plates will be more fragile and easily
damaged, and thicker plates will adversely affect heat transfer,
press cycle time, press pack capacity and productivity.
[0050] After preshrinking, the texturing plate was very brittle and
could be easily broken, and as such, was unsuitable for
manufacturing use as is. This deficiency can be corrected to some
extent by producing a substantially thicker texturing plate,
bonding two plates back-to-back with a suitable adhesive, thus
producing a double sided texturing plate, or bonding it to a flat
sanded phenolic/kraft laminate sheet (also preshrunk) to produce a
thicker one sided texturing plate while avoiding the longer
preshrinking time required when producing a thicker texturing plate
directly in the press, albeit with the penalties previously noted.
However, the preferred method to improve the durability of the
working texturing plate and its heat transfer properties is to bond
the nominal {fraction (1/16)} inch phenolic/kraft texturing plate
to a sheet of cold rolled carbon steel using a suitable,
temperature resistant adhesive.
[0051] Specifically, in ascending superimposed relationship were
placed on a press carrier tray 16 plies of 115 pounds per ream
kraft cushion, 1 sheet of BOPP film, the preshrunk {fraction
(1/16)} inch phenolic/kraft texturing plate face down with the
textured side towards the cushion, a continuous CyTec Fiberite FM
300-2M epoxy adhesive film, a sheet of 12 gauge cold rolled carbon
steel suitably prepared by sanding and degreasing of its bonding
face, another ply of BOPP film, and finally 6 plies of kraft
cushion on top of the pack. This assembly was loaded into a flat
bed hydraulic laminating press, pressurized to 1000 psig specific
pressure, heated to about 150 C. and held at that temperature for 1
hour to fully cure the adhesive sheet and insure good bonding of
the phenolic/kraft texturing plate to the steel, and then cooling
the pack to near room temperature.
[0052] The tile texturing plate composite, or template, thus
obtained after the edges were trimmed of excess phenolic/kraft
flash, was essentially flat. Optionally, the steel core template
can be simultaneously balanced with another preshrunk
phenolic/kraft texturing plate, or a preshrunk flat phenolic sheet,
on the other side, but it is not necessary to do so since the
coefficients of thermal expansion of the two materials are quite
similar. It will be understood by those versed in the art that
other core materials, such as a stainless steel or suitable
aluminum alloy, e.g. AISI 410 and 6061 T6 respectively, can be used
effectively, but use of mild carbon steel is preferred due to its
substantially lower cost and ready availability, as well as its
compatible thermal expansion characteristics.
[0053] The durable steel backed, tile design texturing template
described above is suitable for the manufacture of a postformable,
deep grout textured, registered embossed, tile design, high
pressure decorative laminate by conventional laminating techniques
as will be described in detail in the following example. It should
be appreciated that the scope of this instant invention is not
limited in any way by the description of the preferred embodiments
set forth above. The following specific examples are provided to
illustrate further aspects and unique advantages of the present
invention, and other features and embodiments should become
apparent to those skilled in the art. The example is set forth for
illustration only, and should not be construed as limitations on
the scope of the present invention.
EXAMPLE
Part A
[0054] It was considered aesthetically desirable to produce a
two-color, gray-on-white, registered embossed, high pressure
decorative laminate with a 4 inch square "tumbled" tile design, and
with uneven {fraction (3/16)}" wide "craggy" grout lines 12 mils
(0.012") deep, wherein the 4 inch tile repeat would include both
the tile face and half of each adjacent grout line. A
65".times.150" (oversize 5'.times.12") artwork plate was produced
in accordance with the first method (second option) of this
invention, described above, utilizing a pre-artwork plate to dish
the artwork tiles, with one minor process modification.
[0055] The material chosen to provide the tile texture was a
Homopal GmbH metal clad decorative laminate with a relatively
small, random, bumpy texture, the inverse or negative of which was
judged would be suitable for providing small craters for the tile's
uneven, tumbled look. Therefore, a phenolic/kraft laminate for the
pre-artwork could not be pressed directly from the Homopal
laminate, since it would have the inverse symmetry needed, i.e., in
this case, the Homopal laminate was considered to possess the
tile's negative design, such that a laminate pressed directly off
it would have the tile's positive design. However, the pre-artwork
must have the tile negative design, such that the artwork produced
from it has the tile positive design. Therefore, the phenolic/kraft
laminate pressed directly off the Homopal laminate was trimmed to
remove edge flash, and then used as a texturing plate to press an
additional 1/4 inch thick phenolic/kraft laminate having the same
texture as the original Homopal laminate, i.e., the tile's negative
texture. This 1/4 inch thick phenolic/kraft laminate with the
tile's negative texture image was then baked in an oven at 135 C.
for 4 days to preshrink the material.
[0056] After the preshrinking process was completed, and the
material allowed to cool to room temperature, it was carefully cut
into rectangular tiles with predetermined dimensions of 4.269
inches in the width (cross) direction and 4.246 inches in the
length direction, using a caliper to insure the accuracy of the
tile dimensions. The dimensions were determined using length and
width shrinkage coefficients for the positive image artwork and
negative image texturing plate of 0.55% and 0.80% respectively, and
for the final decorative laminate of 0.10% and 0.15% respectively,
a saw kerf width for each tile of 5 mm (0.1969"), and with a square
tile dimension for the finished decorative laminate of 3.8125
inches for the tile face plus 0.1875 inch for the grout, or 4.0000
inches total. The calculation for the cross direction dimension was
therefore 4.0/(0.992)(0.992)(0.9985)+0.1969/0.992=4.269 inches, and
for the length direction
4.0/(0.9945)(0.9945)(0.999)+0.1969/0.9945=4.246 inches. The second
term is not required if the "full sheet artwork" method is to be
used, and additional shrinkage factors would be required in the
first term denominator if more replication steps than the preferred
method are planned in the process.
[0057] After the pre-artwork tiles were cut to size, they were
shimmed on the backside with 31/4-, 23/4" and 21/4 squares of
phenolic resin treated 115 pound per ream kraft filler, in
superimposed relationship centered on the individual tiles. The
pre-artwork and artwork plates were then prepared by the prescribed
method of this invention detailed above, with a grout centerline
tile layout. After preshrinking the 1/4" thick phenolic/kraft
positive artwork sheet obtained in an oven for 4 days at 135 C., it
too was accurately cut into individual tiles along the grout area
ridge witness lines on a table saw with a 5 mm kerf blade. After
gluing them in place by the prescribed method of this invention
detailed above, {fraction (3/16)}" wide grout channels were routed
with a straight flute bit to a depth of 0.042". The edges of the
grout channels were then machined with a different router bit,
using a wobble board guide to create a randomly uneven, wavy
effect, and afterwards, the top edges were randomly chipped with a
Dremel tool. The grout lines were then filled with the "50%
collapsible" epoxy resin, microspheres and ceramic shot grouting
compound previously discussed. From this prepared artwork, by the
methods prescribed above, a nominal {fraction (1/16)}" thick,
negative image phenolic/kraft texturing plate was produced, which
after preshrinking for 3 days at 135 C., was adhered to a
621/4".times.147" sheet of 12 gauge cold rolled carbon steel.
Several additional, identical cold rolled carbon steel backed
texturing templates were then prepared from the original artwork in
a like manner.
EXAMPLE
Part B
[0058] A light weight, 14 pound per 3000 square foot ream, clear
overlay paper was treated to 71-73% resin content (the difference
between the treated weight and the untreated weight, divided by the
treated weight) and 8-9% volatile content (the difference between
the treated weight and bone dry treated weight, divided by the
treated weight) with a high flow, pigmented melamine-formaldehyde
resin; said resin being plasticized and suitable for postforming
applications. The resin blend was comprised of (by weight) 81% of
the melamine base resin (50% solids content), 10% 2-phenoxyethanol
flow promoter, 7% gray ink, and 2% alumina grit (50:50 5 and 15
micron diameter particle sizes) to enhance abrasion resistance,
wherein the ink formulation consisted of 0.035% black ink and
99.965% white (titanium dioxide based) ink, both with aqueous
solvated, melamine resin compatible vehicles.
[0059] Additionally, a 75 pound per ream, white pigmented solid
color decorative paper was treated with the same unpigmented and
otherwise unmodified melamine-formaldehyde base resin to 48%-50%
resin content and 7-9% volatile content.
[0060] Furthermore, 115 pound per ream saturating kraft paper was
treated with a postforming type phenol-formaldehyde resin to a
resin content of 26-28% and a volatile content of 8-10%.
[0061] In addition, the same phenolic resin used to treat the kraft
filler, was also used to treat 115 pound per ream bleached kraft
"barrier" paper to 27-29% resin content and 7-9% volatile content.
This paper forms an optical barrier between the light color
decorative paper and the dark phenolic/kraft filler, so as to
prevent show-through of the laminate's dark core to its optical
surface.
[0062] Finally, 75 pound per ream stresskraft (Tolko Paper Company,
Canada) was treated to a 27-29% resin content and 7-9% volatile
content with the same phenolic resin as used for the above kraft
filler. The stresskraft is an extensible paper used as the backmost
plies to enhance formability, and particularly cove forming, where
the back of the laminate is in tension and requires some
extensibility during the forming operation.
[0063] Formulations for suitable postforming melamine and phenolic
resins are well known by those versed in the art, as are the
treating methods used for the various types of papers, and the
roles of each of the various treated materials contained in the
decorative laminate's construction. As such, further details will
not be delineated herein.
EXAMPLE
Part C
[0064] Deep grout, registered embossed, tumbled tile design,
postformable grade high pressure decorative laminates, with the
prerequisite perfectly square tile configuration, were produced
using the tile texturing templates from Part A, and treated
materials from Part B, of this example. The tumbled tile laminates
themselves had a construction consisting of, in descending
superimposed relationship, 2 plies of stresskraft, 2 plies of the
standard kraft filler, 1 ply of barrier, 1 ply of the white solid
color decorative paper (felt side facing down), and 1 ply of the
pigmented overlay. The actual press pack assembly was comprised of,
in ascending superimposed relationship on top of a press carrier
tray, 1 sheet of untreated kraft "cushion", 1 flat, hard AISI 410
stainless steel "backing plate" (with a Rockwell C hardness of
about 40-42), 2 plies of cushion, one of the tile templates
textured side facing up, 2 sheets of LC-59 texturing/release paper
(Ivex, Inc.), with the coated side of one sheet facing the
texturing template and the coated side of the other sheet facing
up, one of the tile laminate assemblies described above, with the
pigmented overlay against the coated side of the second, uppermost
sheet of LC-59, 2 plies of a wax separator paper (with their coated
release sides facing away from each other), 3 sheets of kraft
cushion, and 2 more sheets of wax separator paper.
[0065] This sequence of tile texturing template (face up), tile
decorative laminate assembly (face down), and cushion, with the
appropriate sheets of LC-59 release/texturing papers and wax
separator papers interleaved as described above, was repeated four
additional times. The pack construction was then completed with
another stainless steel backing plate, and finally, 3 kraft cushion
on the top of the pack. As such, the completed press pack consisted
of five tile texturing templates with their design facing up, and
five laminate assemblies with their decorative surfaces pressed
against them and separated from the templates by means of
texturing/release sheets, which also serve to impart a subtle
secondary texture to, and control the final gloss level of, the
surface of the laminates so produced. The function of the
interleaved cushion was to prevent "shadowing" of the deep grout
texture from one template/laminate pair to the adjacent laminates,
where the high flow, pigmented melamine resin in the overlay is
sensitive to pressure differentials induced by the texturing
template's grout lines. Optionally, rather than use of internal
cushion for this purpose, several plies of phenolic/kraft filler
can be used in its place to simultaneously produce backers, for
example NEMA grades BKV or BKL.
[0066] As will be appreciated by those versed in the art, other
suitable decorative postforming laminate constructions, and pack
build-ups, can alternatively be used that would not circumvent the
spirit and scope of the present invention. Additional optimization
is still required to improve the pack build-up productivity, i.e.,
increase the number of sheets per pack of tile laminate that can be
produced, for example by reducing the amount of cushioning, or
possibly with use of double-sided rather than single-sided tile
texturing templates, or other like process improvements. It should
also be appreciated that the color combinations of pigmented
overlay and decorative underlayment sheet are essentially
limitless, and that the underlay is not restricted to a solid color
decorative sheet, in that a print sheet can also be employed with
pleasing results. Furthermore, other methods of registered
embossing, and non-registered embossing, are also suitable in the
practice of the present invention.
[0067] After inserting the above described pack into a nominal
5'.times.12" flat bed, multi-opening, high pressure hydraulic
laminating press, the press was closed and pressurized to 1400 psig
specific pressure. The pack, along with other packs of conventional
postforming laminate to fill the press, was heated to 132 C. in
about 20 minutes, held at that temperature for another 20 minutes,
and then cooled to near room temperature. After discharge from the
press, and separation of the registered embossed tile design
decorative laminates from the tile texturing plates, the laminates
were then trimmed to about 611/4".times.1451/2" and back sanded on
conventional equipment. The decorative laminate sheets were then
split lengthwise, along the center grout line, to about
301/2".times.1451/2" size using an SCMI traveling undercut saw. The
pressing procedure was repeated several more times to obtain enough
nominal 21/2'.times.12' splits to conduct a reasonably thorough
postforming trial. The laminates obtained were all about 0.036 inch
thick after sanding, with about a 0.011-0.013 inch average grout
line depth.
EXAMPLE
Part D
[0068] A kitchen countertop postforming trial was conducted using a
Midwest Automation/Bechtold Engineering Roll-A-Matic postforming
machine, with in-line parabolic infrared radiant heaters, for the
simultaneous forming of the outside radii bull nose and backsplash
bends, with the particleboard blanks radiused to 3/4" with a router
for both, and a Midwest Automation cove forming machine with an
electrically heated {fraction (3/16)}" radius cove bar. Those
versed in the art should be familiar with typical postforming
equipment, such as the above, and their operations.
[0069] Thirty-six twelve foot long countertops were postformed
without encountering any crack failure for either the outside bends
or at the cove. Blister resistance was also acceptable, as was
surface cure, previously measured by the widely used "tea pot" test
(NEMA Test Method LD 3-3.5 Boiling Water Resistance), with no
adverse effects noted. The registered embossed, deep grout tile
textured laminates of this invention, and the kitchen countertops
thus prepared and surfaced therewith, were extremely pleasing in
terms of the tile face tumbled appearance, the color variation with
the registered embossing, and the pronounced grout lines, with the
distinctive relief and feel thereof.
[0070] A 90 degree mitering trial with the above postformed, tile
design kitchen countertops was also conducted at the postformers
shop. When the 45 degree cuts were made arbitrarily, the grout
lines for the two halves did not match up properly, which detracted
from the overall "real" tile effect. However, when the 45 degree
cuts were made diagonally through the grout line intersections,
with the aid of a laser guide, the grout lines matched very well,
and the real tile look was preserved.
[0071] The foregoing description of a preferred embodiment of the
invention has been presented for purposes of illustration and
description, and is not intended to be exhaustive or to limit the
invention to the precise form disclosed. The description was
selected to best explain the principles of the invention and their
practical application to enable others skilled in the art to best
utilize the invention in various embodiments and various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention not be limited by the
specification, but be defined by the claims set forth below.
* * * * *