[0001] This invention relates generally to the production of decorative plastics laminates,
which are extensively used in making furniture, counter tops, paneling and other decorative
or functional surfaces.
[0002] The art of making such laminates is well known. A plurality of sheets σf resin impregnated
kraft paper are stacked together to form a core or backing. The resin employed is
a heat curable type such as phenol formaldehyde. A decorative sheet of paper having
a printed design or solid color and impregnated with a melamine resin is laid over
the core, and an overlay sheet, usually melamine impregnated alpha cellulose paper,
is superimposed over the decorative sheet. In some instances, especially where the
final product is of solid color, the overlay sheet may be omitted. A panel of particle
board may be substituted for the core sheets.
[0003] The foregoing assembly of resin impregnated sheets is subjected to heat and compression
by confining the same between heated press plates or molding cauls such that the sheets
become firmly adhered to one another as the resin cures. A release sheet composed
of relatively non-adhereable paper, plastics film or aluminum foil is interposed between
the decorative surface and the caul to prevent adhesion between the caul and the decorative
surface.
[0004] Various techniques have been developed for applying a textured surface to the decorative
surface of such laminates. U.S. Patent No. 1,742,516 describes a process wherein a
design or letter is embossed in a laminabe by using an engraved caul having the design
deoossed therein. U.S. Patent No. 1,997,358 and No. 2,133,081 descrioe the texturizing
of plastics laminates utilizing an embossed metal caul.
[0005] Inasmuch as engraved or embossed metal cauls are expensive to proauce and have a
short life span, subsequent efforts have been directed primarily toward substitute
methods. U.S. Patent No. 2,606,355 discloses a process of using a master to make a
number of textured .caul plates from a stack of resin impregnated paper. Similar techniques
utilizing emoossed or debossed plastics laminates as molding cauls are described in
U.S. Patent No. 3,303,081 and No. 3,311,5<0. U.S. Patent No. 3,373,068 describes the
use of particulate matter on the decorative sheet to impart texture thereto.
[0006] In U.S. Patent No. 3,616,011 there is described another method for making a textured
molding caul wherein a textured original is sandwiched between a pair of thin flexible
resin impregnated sheets. The sheets are forced intimately into the surface recesses
of the original and the resin is cured. Thereafter, the resin- .set sandwich of the
original and the sheets are used as a master molding caul.
[0007] Often it is desirable to produce a laminate that simulates another product, a good
example being a wood grained surface. In such a case, it has been possible to use
a decorative sheet having a colored wood grain printed thereon, and the decorative
surface may also be textured during the subsequent molding process. It is not usually
possible or convenient, however, to impart a texture conforming to the print pattern,
and the resulting product does not have the combined texture and appearance of a'naturally
stained wood wherein the grain is highlighted by differential absorption of the stain
into the grain, saw marks or depressed areas of the wood.
[0008] The present invention represents a further improvement in the production of textured
decorative laminates, which allows for greater realise, warmth and a contrasting textural
quality heretofore not attainable.
[0009] In the production of a textured decorative laminate, a release sheet having a coating
of pigment thereon is applied over the decorative surface before the-laminate* is
pressurized against a textured molding caul. The release sheet may be composed, for
example, of a.sheet of polymeric material having a thin layer of ink applied substantially
uniformly on the surface against which the panel or laminate is to be-molded.
[0010] As the laminate is pressurized and heated, the pigment is uniformly transferred to
the texturized surface, the color of the pigment being selected so as to contrast
with the color of the decorative sheet.
[0011] After the lamination has been completed, the release sheet is removed to expose a
textured surface that is substantially uniformly colored by the pigment. The decorative
surface is then subjected to surface rubbing, brushing or light abrasion to the extent
necessary to remove color from the raised or embossed portions while allowing more
color to remain in the depressed or debossed areas, thus highlighting or shadowing
the texture and providing added visual dimension to the appearance of the textured
surface.
[0012] It is believed that a portion of the transferred pigment is absorbed into the decorative
surface during the application of heat and pressure, particularly into the debossed
areas, and any pigment not removed by the subsequent rubbing has a high degree of
adherence to the product. Equivalent results are not achieved by the application of
liquid pigment to the relatively non-porous surface of a finished laminate followed
by surface rubbing.
[0013] In order to carry out the process of the present invention, any of the well known
methods of making textured laminates may be employed. A variety of textures are possible,
such as wood grain, fabric, decorative objects, writing or printing, as well as many
others. The process of making the textured laminate from a textured caul is conventional,
and the present invention resides in imparting color highlights to the textured surface.
[0014] The core sheets or other suitable backing, decorative sheet and overlay sheet, as
well as the resins used to impregnate such sheets and the processing conditions, follow
conventional practices such as described in the foregoing patents, which are incorporated
herein by reference. In the conventional process, the core is made up from a plurality
of resjn impregnated kraft'sheets. These sheets are normally impregnated with a phenolic
resin, allowed to at least partially dry, and then stacked in a superimposed relation.
The number of sheets utilized may vary and ordinarily the number will vary between
three and six. Other core materials, such as particle board, may be used. Immediately
above the core sheet assembly or backing there is positioned a resin impregnated decorative
sheet, which in the case of the preferred embodiment will be a sheet having color,
printing, or other decoration thereon, for example, printing that resembles a grained
wood panel. Superimposed above the print sheet in many cases is a protective overlay
sheet of fine paper such as alpha cellulose. The overlay and print sheet are impregnated
with a heat curable resin, preferably with a noble thermosetting resin such as melamine
formaldehyde resin or the like. Alternatively, the decorative sheet may be replaced
by metal foil.
[0015] In accordance with conventional practices, the sandwich of the aforesaid materials
is placed between a pair of rigid caul plates. The caul plate facing the decorative
sheet is provided with a desired textured surface by any of the well known and conventional
methods, and a release sheet is placed between the caul and the outer sheet of the
laminate. The assembly is placed in a heated press, and the sandwich is subjected
to heat and pressure for a time sufficient to cure the resin in the laminate, i.e.
typically 500 to 2,000 p.s.i. (3,447 x 10
3 to 13,790 x 10
3 Pa), 200° to 400°F (93.30 to 204.4°C), and 15 to 60 minutes. The resulting product
is a rigid laminate having a hard, durable decorative and textured surface.
[0016] In the preferred embodiment, the textured caul is prepared by any suitable method.
For example, the caul plate may be a rigid metal plate with any desired texture etched
thereon by conventional methods.
[0017] Another suitable method for preparing a textured caul plate is described in U.S.
Patent No. 3,616,011. As .described in this patent, a consumable original textured
panel or sheet is sandwiched between a pair of resin impregnated or resin containing
overlay sheets of a size slightly larger than the original. The overlay sheets and
the curable resin therein may be of any of a wide variety of acceptable materials,
such as various heat curable resins, such as melamine, phenolic, epoxy, urea formaldehyde
and others. Each of the overlay sheets-is covered by a release sheet, and the release
sheets in turn may be backed by a stack of padding sheets, such as sheets of kraft
paper.
[0018] The resulting assembly is then placed in a molding press between a pair of cauls,
and the assembly is heated and compressed between the cauls in a conventional manner
until the resin is cured. Upon curing, the overlay sheets bond to the textured core
and assume the texture of the core. The resulting laminate, which may be textured
on one or both sides, is used as a molding caul to make textured decorative laminates,
as hereinbefore described.
[0019] It should be understood that the method of imparting color highlights in accordance
with the present invention is carried out as part of the formation of the textured
decorative laminate. Color is applied to the decorative surface during the pressure
molding procedure, and any excess color is removed from the textured surface after
completion of the molding operation.
[0020] In carrying out the process of the present invention, a special release sheet is
used and is an important feature of the invention. The release sheet to be used is
first coated on one side with a pigment, and the pigmented side is placed against
the decorative surface prior to the pressure forming of the textured laminate. The
color of the pigment is preferably selected to be darker than the color of the decorative
sheet or in any event is preferably of a contrasting or highlighting color.
[0021] Although any forms of pigment may be employed, the form of pigment used must lend
itself to application to the release sheet. For this purpose, therefore, pigments
carried in a solvent and binder system capable of being coated onto the release sheet
and dried after application are preferred, such as printing inks. It is not necessary
to apply tne ink to the release sheet in accordance with any pattern, and in fact,
a substantially uniform and unpatterned application is preferred to assure complete
coverage of the decorative surface. Uniform coating of the ink onto the release sheet
by conventional rotogravure methods has been found suitable for this purpose.
[0022] . The material for the release sheet may be selected from any of the materials in
common use and include foil, polymer films and treated paper films. Polypropylene
film is especially preferred due to its ability to release the ink when placed under
the heat and_pressure conditions used in the laminating process.
[0023] The components of the decorative laminate, pigmented release sheet and textured caul
are then assembled as a sandwich as aforesaid and are compressed in the aforesaid
manner at sufficient pressures and temperatures to cause curing and bonding of the
resin impregnated sheets. During the laminating process, the textured surface of the
caul is imparted to the decorative surface, and at the same time, the release sheet
conforms to the irregular surfaces and transfers pigment thereon substantially uniformly
onto the decorative surface of the laminate. Upon curing, the release sheet is stripped
away from the textured decorative surface, which is now substantially uniformly coated
with the pigment.
[0024] Under high volume production conditions, it is preferable to use a caul plate having
a textured surface on both sides, since-an assembly of caul plates and resin impregnated
paper assemblies may be compressed and heated simultaneously. For example, five cauls
can be used in a single molding operation to produce ten decorative panels.
[0025] In the production of a simulated wood panel, wood grain print sheet is utilized,
and a wood grain texture is imparted to the laminate. The pattern of the print sheet
need not coincide with the texture pattern to'produce the desired results, thus eliminating
the problem or bringing the patterns into exact, register.
[0026] The pigmented textured surface of the laminate is now subjected to an operation in
which some or all of the pigment remaining on the mebossed areas is removed from such
areas of the surface while allowing a greater amount of pigment to remain in the debossed
areas. This operation may be accomplished by surface rubbing or brushing, exposing
the lighter shades of the raised grain or texture and enhancing a three dimensional
shadow effect. A suitable procedure is to brush the textured surface with rotary bristle
or tampico brushes, preferably in the direction of the grain pattern. Such apparatus
is conventionally used in a dull rubbing operation to reduce the gloss of the decorative
surface of laminates,'and any equivalent procedure for mechanically removing the pigment
from the high spots would be effective.
[0027] The. pigment used preferably will be one having high adherence properties, but in
any event it is believed that some of the pigment migrates into the resinous surface,
partiularly in the debossed areas which are subjected to the greatest molding pressure,
and becomes bonded therein as the resin is cured.
[0028] The resulting laminate will thus have a textured surface with a greater concentration
of pigment in the debossed areas than in the embossed areas. By means of the present
invention, therefore, it is possible to create a variety of effects, particularly
with the use of contrasting colors in the decorative surface and pigment.
1. A method of imparting highlights or shadows to a decorative laminate comprising
the steps of preparing a textured decorative laminate by compression molding utilizing
a pigmented release sheet to cause transfer of pigment to said laminate, and then
rubbing the surface. of the pigmented textured laminate to the extent necessary to
remove some of the applied pigment, with more pigment being removed from the raised
areas of the textured laminate than from the depressed areas thereof.
2. A method of imparting color highlights or shadows to a textured decorative laminate,
which comprises the steps of making an assembly of heat curable resin impregnated
sheets, placing a release sheet having a pigmented surface against an outer surface
of said assembly wherein the pigmented surface is facing said outer surface, compressing
and heating said assembly and release sheet under conditions to cure said resin and
bond said assembly into a laminate while imparting texture to said outer surface and
while causing transfer of pigment from the release sheet to the outer surface, and
upon completion of the compression and heating operation, removing said release sheet
from the cured laminate to expose the textured, pigmented surface, and then rubbing
said surface to the extent necessary to remove more pigment from the raised areas
than the depressed areas of said surface.
3. A method as claimed in claim 2, wherein the release sheet is polypropylene film.
4. A method as claimed in claim 2 or claim 3, wherein said pigment is liquid ink applied
to said release sheet and dried thereon.
5. A method as claimed in claim 4, wherein said ink is applied substantially uniformly
to said release sheet.
6. A method as claimed in any of claims 2 to 5, wherein rubbing the textured, pigmented
surface comprises brushing with a rotary brush.
7. A method as claimed in any of claims 2 to 6, wherein said outer surface has a wood
grain pattern printed thereon and said pigment is of a shade which contrasts with
said outer surface.
8. In conjunction with the production of a decorative laminate having a textured outer
surface wherein the laminate is formed by making an assembly comprising resin impregnated
sheets, applying a release sheet over an outer surface of said assembly, and forming
a laminate by heating and compressing said assembly between a pair of molding cauls,
wherein one of said cauls has a textured surface facing said release sheet and serving
- to impart a textured finish to said outer surface, a method of imparting color higahlights
or shadows to the outer textured surface of said laminate, said method comprising
the steps of providing said release sheet with a pigment coating facing said outer
surface such that pigment is transferred from said release sheet to said outer surface
during said heating and compressing step and while texture is being imparted to said
outer surface, and upon formation of said laminate, removing the release sheet to
expose the outer pigmented, textured surface, and rubbing said textured surface-such
that pigment is removed more from the raised areas than the depressed areas thereof.