Note: Descriptions are shown in the official language in which they were submitted.
CA 02332142 2001-O1-25
MECHANICAL AND CHEMICAL EMBOSSED SURFACE COVERING
FIELD OF THE INVENTION
This invention relates generally to surface coverings. In particular, this
invention relates to a mechanical and chemical embossed surface covering and a
method of making same.
BACKGROUND OF THE INVENTION
Decorative laminate surface coverings having textured surfaces and the
methods of making such surface coverings are known. For example, such surface
coverings are commonly patterned to duplicate a look of actual wood, tile,
brick,
stone, and other such products. Typically, the texture is either mechanically
embossed by pressing a pattern into the surface covering or chemically
embossed into
an expanded foam layer disposed within the structure of the surface covering
by foam
retarding agents. Although these methods provide attractive decorative surface
coverings, they are limited in their capability to replicate the appearance of
the actual
product. Examples of mechanical embossing methods are discussed in U.S. Patent
Nos. 3,655,312, 3,887,678, and 3,953,639. Chemical embossing methods are, for
example, discussed in U.S. Patent Nos. 3,293,108 and 5,643,677.
There has been and continues to be a demand by consumers for surface
coverings that have a "more realistic" appearance to the actual product. In
response,
the manufacturers combined both techniques of chemical embossing and
mechanical
embossing to produce a surface covering. For example, U.S. Patent No.
4,022,643 to
Clark ("Clark") discloses using a chemically embossed vinyl structure (with or
without a wear layer attached) as a continuous embossing belt to mechanically
texture
a chemically embossed product with a wear layer. Clark indicates that there is
a need
for sharper embossing (achieved by mechanical embossing rolls) on chemically
embossed products, but a lower embossing tooling cost. Clark discloses using a
continuous chemically embossed embossing belt to texture the wear layer of a
flooring product as an economical alternative to etched embossing rolls.
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Eby et al. ("Eby") in U.S. Patent No. 5,961,903 disclose a method of making a
surface covering which is both chemically and mechanically embossed. In this
method, a backing layer is coated with a foamable layer, and the foamable
layer then
receives a print layer thereon. Eby states that the print layer forms a design
and a
portion of the design is formed with a retarder composition. A thermoplastic
wear
layer is applied onto the print layer and cured by heat at a temperature
sufficiently
high to expand the foamable layer. The areas of the design layer where the
retarder
composition is applied are also chemically embossed during such curing.
Thereafter,
Eby requires that this chemically embossed structure cool to ambient
temperature
before any further handling. Upon reaching ambient temperature, the cured
thermoplastic wear layer is softened by heating. The wear layer is then
mechanically
embossed to have a surface texture. Optionally, a top coat, also known as a
wear layer
top coat, is applied to and adhered to the mechanically embossed wear layer.
Despite existing methods of making chemically and mechanically embossed
surface coverings, there is a need for a surface covering which has a
chemically
embossed foam layer and a mechanically embossed top coat wear layer. Further,
there remains a need for a method of making such a surface covering.
Additionally,
there remains a need for a method of making such a surface covering which does
not
require cooling a preform comprising a substrate, a chemically embossed foam
layer,
and a wear layer to ambient temperature prior to mechanically embossing the
wear
layer. Still, there remains a need for a method of making such a surface
covering
which does not require cooling a preform comprising a substrate, a chemically
embossed foam layer, a wear layer, and a top coat wear layer to ambient
temperature
prior to mechanically embossing the top coat wear layer. It is to the
provision of a
mechanical and chemical embossed surface covering and method of making the
same
that meets these needs that the present invention is primarily directed.
SUMMARY OF THE INVENTION
Briefly described, the present invention comprises a method of manufacturing
a mechanical and chemical embossed surface covering. In one embodiment of the
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present invention, a web is formed comprising a substrate, a curable wear
layer, an
expandable foam layer between the substrate and the wear layer, and at least
one
inhibitor composition disposed as a pattern proximate the foam layer. The wear
layer
is coated with a cross-linkable top coat to form a coated web and then heated
to a
temperature at which the top coat is substantially cross-linked and cured, the
wear
layer is substantially cured, the foam layer substantially expands, and the
pattern is
chemically embossed to form a surface covering. Thereafter, the surface
covering is
tempered to a temperature above ambient temperature. The top coat is then
heated
and at least one surface texture is mechanically embossed onto the top coat.
Upon
setting the at least one surface texture, the mechanical and chemical embossed
surface
covering is formed. In addition, mechanical embossing includes mechanical
embossing in register with a printed or chemically embossed pattern of the
surface
covering.
Another aspect of the present invention relates to a method of manufacturing a
mechanical and chemical embossed surface covering that has a mechanically
embossed wear layer. In this embodiment, a web is formed comprising a
substrate, an
expandable foam layer operably connected to the substrate, and at least one
inhibitor
composition disposed as a pattern proximate the foam layer. The foam layer is
coated
with a wear layer to form a coated web and then heated to a temperature at
which the
wear layer is substantially cured, the foam layer substantially expands, and
the pattern
is chemically embossed to form a surface covering. Thereafter, the surface
covering
is tempered to a temperature above ambient temperature. The wear layer is then
heated and at least one surface texture is mechanically embossed onto the wear
layer.
Upon setting the at least one surface texture, the mechanical and chemical
embossed
surface covering is formed. In addition, mechanical embossing includes
mechanical
embossing in register with a printed or chemically embossed pattern of the
surface
covering.
Yet, another aspect of the present invention relates to a chemically and
mechanically embossed surface covering comprising a substrate; a foam layer
disposed on the substrate, wherein the foamed layer has a chemically embossed
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pattern imposed therein; a wear layer disposed on the foam layer; and a
mechanically
embossed, cross-linked top layer disposed on the wear layer.
A significant advantage of the present invention over existing surface
coverings is that the mechanical and chemical embossed surface covering can be
manufactured without cooling the expanded foam layer to ambient temperature at
any
stage of production. Further, a top coat comprising a cross-linkable resinous
composition on a chemically embossed structure can be mechanically embossed.
Also, a chemically embossed structure can be mechanically embossed in register
with
a printed and/or chemically embossed pattern to provide more than one
mechanically
embossed surface texture.
In one embodiment, a first mechanically embossed texture is applied to a first
region of the top coat or wear layer and a second mechanically embossed
texture
applied to a second region of the top coat or wear layer.
Thus, a unique mechanical and chemical embossed surface covering and
1 S method of manufacturing such surface covering is now provided that
successfully
addresses the shortcomings of and provides distinct advantages over existing
surface
coverings and their methods of manufacture. Additional obiects, features. and
advantages of the invention will become more apparent upon review of the
detailed
description set forth below when taken in conjunction with the accompanying
drawing
figures, which are briefly described as follows.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view of an embodiment of a process for manufacturing a
mechanical and chemical embossed surface covering of the present invention.
Fig. 2 is a schematic view of another embodiment of a process for
manufacturing a mechanical and chemical embossed surface covering of the
present
invention.
Fig. 3 is a partial cross sectional and elevation view of an embodiment of a
mechanical and chemical embossed surface covering made in accordance with the
process of Fig. I .
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Fig. 4 is a partial cross sectional and elevation view of an embodiment of a
mechanical and chemical embossed surface covering made in accordance with the
process of Fig. 2.
Fig. 5 is a partial cross sectional and elevation view of another embodiment
of
a mechanical and chemical embossed surface covering made in accordance with
the
process of Fig. 2.
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DETAILED DESCRIPTION OF THE INVENTION
For a more complete understanding of the present invention, reference should
be made to the following detailed description taken in connection with the
accompanying drawings, wherein like reference numerals designate corresponding
parts throughout the several figures.
Referring first to Figs. 1 and 3, there is shown a schematic view of an
embodiment of a process generally indicated at 8 for producing a mechanical
and
chemical embossed surface covering 10. In this embodiment, a web 19 is formed
comprising a substrate 12, a curable wear layer 18, an expandable foam layer
14
between the substrate 12 and the wear layer 18, and at least one inhibitor
composition
disposed as a pattern proximate the foam layer 14. The wear layer 18 is coated
with a
cross-linkable top coat 20 to form a coated web 21 and then heated to a
temperature at
which the top coat 20 is substantially cross-linked and cured, the wear layer
18 is
substantially cured, the foam layer 14 expands to some extent, and the pattern
is
chemically embossed to form a surface covering 11. Thereafter, the surface
covering
11 is tempered to a temperature above ambient temperature. The top coat 20 is
then
heated and at least one surface texture is mechanically embossed onto the top
coat 20.
Upon setting the at least one surface texture, the mechanical and chemical
embossed
surface covering 10 is formed. In addition, mechanical embossing includes
mechanical embossing in register with a printed or chemically embossed pattern
of the
surface covering 11.
As indicated in Fig. 1, the substrate 12 is removed from an appropriate unwind
roll 22 and fed past a pinch roll structure 24, which is nothing more than the
feed
structure for pulling the substrate 12 off the unwind roll 22 and pushing it
partly
through the processing operation. The substrate 12 then passes through a
dancer roll
structure 26 which is conventional in the art and simply functions to take up
slack in
the feed of the substrate 12 and aids in tension control. Optionally, the
substrate 12
can then pass around an appropriate guider structure (not shown), which
maintains the
registry of the substrate 12 in a direction transverse to the direction of
substrate
movement.
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The expandable foam layer 14 comprises a resinous composition containing a
chemical blowing agent and is applied to a surface of the substrate 12 to form
a coated
substrate 13. In one embodiment, the expandable foam layer 14 has a
substantially
uniform thickness. The expandable foam layer 14 is coated onto the substrate
12 by
any suitable conventional coating apparatus 28 such as a reverse roll coater,
a doctor
blade, an air knife, or other similar coating apparatus. The coated substrate
13 is then
passed through a heating unit generally indicated at 30 which supplies
sufficient heat
to at least partially gel the resinous coating, for example, a thermoplastic
resinous
coating, without decomposing the blowing agent. Any conventional heating unit
such
as a bank of radiant heaters, an oven, a heated drum, and the like may be
utilized.
The gelled foam layer 14 and substrate 12 are then passed to a printing unit
32
which places the print layer 16, which in one embodiment includes a printing
ink
composition, onto the jelled foam layer 14. Any conventional printing
apparatus such
as a silk screen apparatus, a flat bed printing machine, an ink jet printer,
or a
conventional gravure or rotogravure press which is etched to print a design
with a
suitable ink can be utilized to print on the surface of the gelled foam layer
14. The
print layer 16 is conventionally dried in the printing unit 32. One or more of
the
printing ink compositions, which may be either pigmented or transparent,
contain an
inhibitor or an accelerator for the blowing agent in the foamable layer 14.
Further,
concentrations of inhibitor or accelerator can differ from one printing ink
composition
to another. Accordingly, the print layer 16 can be printed wherein the
printing ink and
inhibitor or accelerator composition vary from one portion or area to another.
Alternatively or in addition to the inhibitor or accelerator present in the
print
layer 16, the inhibitor or accelerator can be printed or otherwise applied to
the
substrate 12 and then the foam layer 14 applied over the inhibitor or
accelerator.
Accordingly, the inhibitor or accelerator composition can be a pigmented
composition, for example, the aforementioned printing ink composition, which
can be
visible from the surface of the mechanical and chemical embossed surface
covering
10. The pigmented composition is visible if substantially complete inhibition
of the
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blowing agent is obtained and the non-foam areas of the foam layer 14 and any
subsequent layers disposed thereon are at least translucent or substantially
clear.
The wear layer 18 comprises a coat of a resinous composition, such as a
polyvinyl chloride plastisol or organosol, and is applied over the print or
foam layers
16 and 14 by another conventional coating apparatus 28' such as to a reverse
roll
coater, a doctor blade, an air knife, or other similar coating apparatus.
Optionally, the
wear layer can be applied by melt coating or film lamination techniques. In
one
embodiment, the wear layer 18 has a substantially uniform thickness across the
coated
substrate 13. The wear layer 18 can be transparent, translucent or pigmented
opaque.
If the wear layer 18 is opaque, the inks will not be visible from the surface
of the
mechanical and chemical embossed surface covering 10. After applying the wear
layer 18, the composite structure is passed through another heating unit 36
which
supplies sufficient heat to at least partially gel the wear layer 18 without
decomposing
the blowing agent to form a web 19. Again, any conventional heating unit such
as a
bank of infra-red heating lamps, an oven, a heated drum, and the like may be
utilized.
Thereafter, a print layer 16 can be optionally printed onto the jelled wear
layer 18 in
addition to or as an alternative to the print layer 16 on the foam layer 14.
However,
for chemical embossing of the foam layer 14, an inhibitor and/or accelerator
must be
able to interact with the foam layer 14 for the areas in which non-foaming is
desired.
As previously discussed, the foam and wear layers 14 and 18 are formed into a
coating having the desired thickness and then heated to gel the composition to
provide
a suitable surface for application of the inhibitor, the print layer 16,
and/or other layers
or coatings. The term "gel" includes both the partial solvation to the
elastomeric point
of the resinous composition and complete solvation of the resin or resins with
the
plasticizer to fuse the layers and top coat. For example, the temperature is
raised to
between about 275° F and 325° F, in one embodiment, about
300° F, to gel the
preferred polyvinyl chloride resinous compositions.
The top coat 20, also known as an extended wear layer, is applied over the
jelled wear layer 18 to form the coated web 21. In one embodiment, the top
coat 20
comprises a coat of a cross-linkable resinous composition, such as a cross-
linkable
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polyurethane, epoxies, melamines, and other cross-linkable resins.
Thermoplastic
resins, such as thermoplastic polyurethane and acrylics can also be employed.
The
top coat 20 is applied by another conventional coating apparatus 28" such as a
reverse
roll coater, a doctor blade, an air knife, or other similar coating apparatus
to form a
coated web. Similar to the wear layer 18, the top coat 20 can be transparent,
translucent, or pigmented opaque and, in one embodiment, has a substantially
uniform
thickness across the wear layer 18. Again, if the top coat 20 is opaque, the
inks will
not be visible from the surface of the mechanical and chemical embossed
surface
covering 10.
The coated web 21 is then passed through a fusion oven 40 to fuse, cure, and
expand the coated web 21, thereby forming a surface covering 11. The fusion
oven 40
can be any heating apparatus such as a hot air impingement oven or infra-red
heat
lamps. In one embodiment, the fusion oven 40 heats both surfaces of the coated
web
21. The fusion oven 40 raises the temperature of the resinous compositions on
the
substrate 12 sufficiently high to cause the selective decomposition of the
blowing
agent contained in the foam layer 14 and to completely solvate and fuse all
resinous
layers on the substrate 12. If the substrate 12 comprises a resinous
composition, the
substrate 12 is fused to an adjacent resinous layer, such as the foam layer
14. The
cellular foam areas not in contact with or exposed to any inhibitor
composition can
reach their maximum expansion or blow. The portion of foam layer 14 in contact
with any area or composition having a concentration of inhibitor will have
little or no
foam structure or expansion. However, as indicated above, those foam areas
exposed
to a portion of the print layer 16 having smaller concentrations of inhibitor
can have
more foam structure or expansion than those areas having a greater
concentration of
inhibitor.
Upon exiting the fusion oven 40, the surface covering 11 is tempered to at
least a temperature where the surface 12 covering resists blistering or
separation
between the substrate and layers thereof upon application of an external
stress, such as
a mechanical embossing procedure. Tempering is accomplished in the present
invention by temperature reduction of the surface covering. This is
particularly
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important since any premature handling of the surface covering 11 immediately
after
foaming might cause partial collapse and distortion of the foam structure.
Importantly, although permissible, it is not necessary to reduce the
temperature of the
surface covering 11 to ambient. In one embodiment, the temperature is reduced
to
between about 125 and 300° F for tempering the surface covering 11. In
another
embodiment, the tempering is performed at a temperature between about
240°F and
300° F. Because the surface covering 11 does not need to be reduced to
ambient
temperature, the process of the present invention reduces energy demands in
any
heating requirement following tempering, permits a continuous process which
reduces
handling requirements by the manufacturer, and reduces space requirements for
either
storage or process line length.
Tempering can be accomplished through various methods. For example,
tempering can be accomplished by allowing the surface covering to sufficiently
cool
to the desired temperature through atmospheric radiant heat transfer as it
moves along
the process line prior to engaging any device following the fusion oven. A
blowing
device (not shown), such as a fan or an air conditioning unit, may be employed
to
assist in this tempering technique. In one embodiment, a tempering unit 42 is
utilized
to temper the surface covering. Depending upon line speed, surface covering
composition, and surface covering temperature exiting the fusion oven 40, a
conventional back wetter 46 may be included with or utilized as an alternative
to the
tempering unit 42 for additional tempering of the surface covering 11. The
back
wetter 46 applies water to the substrate of the surface covering 11, which
assists in
cooling.
In the present invention, the tempering unit 42 comprises at least one surface
cooled tempering roller 44 having a relatively smooth contact surface. In the
preferred embodiment, the tempering unit 42 has two water-cooled, chrome-
plated
steel tempering rollers 44. As illustrated in Fig. 1, the tempering rollers 44
are
positioned so that the surface covering 11 is fed through the tempering
rollers in an
"S" configuration and passes around and is maintained in contact with between
from
about 180° to about 200° of the circumference of each tempering
roller 44 (about 180°
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CA 02332142 2001-O1-25
to about 200° of wrap). In this configuration, the substrate 12 of the
surface covering
11 initially contacts one tempering roller 44, and the other tempering roller
44
contacts the top coat 20. To avoid incidental mechanical embossing of the top
coat
20, the tempering roller 44 contacting the top coat 20 should have a surface
roughness
no greater than 32 microinch (10-b inch) root-mean squared (32 RMS). The
surface
smoothness of the tempering roller 44 contacting the substrate 12 is not as
critical.
Clearly, the tempering rollers 44 can have any desired outside diameter, more
than
two tempering rollers 44 may be utilized, and the amount of wrap about the
tempering
rollers 44 can be more or less than that mentioned above.
Optionally, a breaking mechanism 48 is operably connected to the tempering
rollers 44. By applying rotational resistance to the tempering rollers 44, the
breaking
mechanism 48 isolates the relatively high tension that is applied to the
surface
covering 11 during mechanical embossing from the respectively lower tension
applied
to the substrate 12 during the chemical embossing stage of the process. This
is
particularly useful when the substrate 12 has a hot melt calendered layer 6
disposed
thereon, which is described below. The breaking mechanism 48, such as a motor,
disc
break, and the like, maintains a back tension on the surface covering 11 as it
enters an
embosser nip 52 and provides the ability to control the tension on the
substrate 12 to
prevent breakage or tearing while in the fusion oven 40.
Thereafter, the surface covering is heated by a high temperature heater 50
which rapidly heats the top coat 20, but does not heat the total surface
covering 11
thickness to a uniform temperature. Importantly, the top coat 20 is heated to
a
sufficient degree to allow it to be mechanically embossed without fracture,
cracking,
or structural failure, such as de-lamination. That is, the top coat 20 is
heated to a
sufficient temperature for a sufficient time in order to soften or even
further soften the
top coat 20. The amount of heat to be applied and the duration of such
application
depends upon, among other things, the temperature of the surface covering 11
exiting
the tempering unit 42, the composition of the top coat 20, the thickness of
the top coat
20, the speed of the moving surface covering 11, the color of the printed
design under
the wear layer 18 surface, and the color of the resinous layers. For example,
a cross-
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linked polyurethane top coat 20 is heated to a temperature from about
250° F to about
350° F. To further enhance heating of the top coat 20, the resinous
layers can
comprise a resin or contain agents which absorb energy from a desired
frequency of
the infra-red spectrum.
For example, a surface covering 11 has a top coat 20 approximately 1 mil
thick, a wear layer 18 approximately 10 mils thick, a foam layer 14
approximately 35
mils thick, and a substrate 12 approximately 30 mils thick. The temperature at
the
interface between the wear layer 18 and the foam layer 14 is only about
220° F. At
the interface between the foam layer 14 and the substrate 12, the temperature
is
approximately 150° to 170° F. On the back side of the substrate
12 at the point
farthest from the high temperature heater 50, the temperature is only about
150° F.
Optionally, the high temperature heater 50 may be a burner, such as a gas
burner. One example is the "Blu-Surf ' burner sold by the Blu-Surf Division of
I-ayes-Albion Corporation of Parma, Michigan. This is a burner structure which
operates with a very short flame coming off an air-gas manifold. The hot gases
from
the flame are directed by a nozzle structure towards the top coat of the
surface
covering. The surface covering is moved at approximately 200 feet per minute
past
two heaters which are spaced approximately 12 inches from the top coat
surface. The
length of the enclosed heating area is only about 40 inches, and the heaters
put out
approximately 10,000-14,000 Btu's per square inch per hour. During the short
time
(approximately 1 second) that the surface covering 11 passes by the burners,
the
surface of the top coat 20 facing the burners is heated to about 320°
F. It is known
that the above heating can be carried out at a temperature range of
250° F to 350° F.
for a time span of about 0.6 to about 6 seconds to secure the desired results.
In one embodiment, the high temperature heater SO comprises a bank of infra-
red heaters. Suitable infra-red heaters are 10.1 kW RADPLANE SERIES 81 infra-
red
heaters manufactured by Glenro, Inc., Patterson, New Jersey. The high
temperature
heater 50 should extend beyond the respective edges of the surface covering 11
to
assist in heating the portions of the top coat 20 proximate the edges. Top
coat edge
temperature and heating are further discussed below.
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From the high temperature heater 50, the surface covering moves directly to
the embosser nip 52 which comprises a conventional engraved steel embossing
roll 54
and a back-up roll 56. In one embodiment, the embossing roll 54 is water
cooled and
servo-driven, and the back-up roll is a steel back-up roll 56. Upon engaging
the
embosser nip 52, the steel back-up roll 56 contacts the substrate 12 and the
embossing
roll 54 contacts the hot top coat 20 of the surface covering 11. In the
present
invention, the embossing roll 54 is approximately 22.8 inches in outside
diameter, and
the back-up roll 56 is approximately 24 inches in outside diameter. If the
back-up roll
56 is a rubber back-up roll, the rubber back-up roll can be provided with a
steel
support roll (not shown) to counteract any tendency of the rubber roll to
"bow"
downward. In the present invention, the surface covering 11 wraps the
embossing roll
54 between about 85° to about 90° by means of an articulatable
idler roll 58.
However, the amount of wrap of the surface covering 11 on the embossing roll
54
depends upon the temperature and the speed of the surface covering 11 through
the
embosser nip 52 and can be more or less than between about 85° to about
90°. Wrap
should be sufficient to cool the mechanical and chemical embossed surface
covering
11 to a temperature below about 250° F. In one embodiment, the
embossing roll 54
has substantially the same temperature across its surface. This contact with
the cooled
embossing roll surface removes heat from the top coat 20 of the surface
covering 11
by heat transfer from the surface covering 11 to the water-cooled, steel
embossing roll
54, and thus "sets" the embossing to form the mechanical and chemical embossed
surface covering 10. Dwell time of the surface covering on the embossing roll
54 is
dependent on exact embossing roll circumference and line speed, which can be
determined by one skilled in the art. The preferred line speed or rate of the
surface
covering 11 through the embosser nip 52 is between about 65 feet per minute to
about
100 feet per minute.
The embosser nip 52 or gap can float against a fixed pressure or, in one
embodiment, can be adjustably fixed. Adjustment to the embosser nip 52 can be
made, for example, by adjustable steel wedge blocks (not shown) or, in one
embodiment, by a jack screw (not shown). However, when the embosser nip 52 is
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fixed, consistent caliper of the surface covering 11 prior to entry into the
mechanical
embossing section of the process needs to be monitored and maintained. The
preferred starting point of the fixed gap is between from about 0.010 inch to
about
0.020 inch less than the specific product thickness or caliper. Fine-tuning
adjustments
thereafter are made to achieve the desired appearance. Furthermore, in order
to
maintain consistent reproduction of the embossing roll pattern in the top coat
20 of the
surface covering 11, positive tension should be maintained on the surface
coating 11
as it enters the embosser nip 52. This tension also helps to keep the surface
coating
tracking straight.
The mechanical embossing of the top coat 20 can be achieved in such a
manner that the wear and foam layers 18 and 14 beneath the top coat 20 may or
may
not be mechanically embossed. Importantly, the portion of the foam layer 14
either
overlayed or in contact with the inhibitor composition, for example, the print
layer 16,
is not mechanically embossed. And, the depth of the embossing into the
portions or
areas of the foam layer 14 beneath the areas or portions of the top coat 20
that are
mechanically embossed is controlled by the pattern protruding from the
embossing
roll 54. For purposes of the present invention, in addition to the engraved
steel
embossing roll 54 and the steel back-up roll 56 discussed above, any
mechanical
embossing technique known to those skilled in the art can be used.
During mechanical embossing, the embossing roll 54 can, although not
required, bottom out against the top coat surface. That is, not only the
raised areas,
but also the depressed areas of the embossed pattern on the embossing roll 54
substantially engage the top coat 20 of the surface covering 11. Consequently,
both
the raised and depressed areas of the embossing roll 54 can provide a pattern
effect
directly on the top coat 20 of the surface covering 11. By the time the now
chemically
and mechanically embossed surface covering 10 is able to leave the embossing
roll
54, it has cooled to below about 240° F on the surface of the top coat
20. The
mechanical and chemical embossed surface covering 10 is then optionally
wrapped on
a second cooled roll (not shown) for further cooling.
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As indicated above, the embossing roll 54 is a steel roll with the appropriate
embossing pattern thereon. Further, the surface and pattern of the embossing
roll 54
can be coated with a non-stick or friction reducing material, for example, a
tetrafluoroethylene fluorocarbon polymer, a diamond-like carbon and silicon
material,
and the like. The embossing roll 54 is a cooled roll, and when in operation
with the
embossing pattern engaging the surface covering 11, it is operated at a
surface
temperature of about 140° F or below, in one embodiment at about
90° F. The
embosser nip 52 can fixably range from zero to 250 plus mils during operation.
This
distance is measured from the raised area of the embossing roll 54 to the
surface of the
back-up roll 56. Although not required, a gap setting can be used which
bottoms out
the embossing roll 54 onto the top coat 20. For purposes of mechanical
embossing,
generally, the pressure applied to the top coat 20 is sufficient to create an
embossing
of, for example, from about 4 mils to about 12 mils. Depending upon the
desired
visual effects of the mechanical embossing the embossing can be more or less
than 4
mils to 12 mils depth. As indicated earlier, the chemical embossing portion is
generally deeper than that of the portions of the surface covering 11 which
have only
been mechanically embossed. However, it is possible to mechanically emboss in
register and provide mechanically embossed portions which are deeper than the
chemically embossed portions. This process, which does not create the
mechanically
embossed surface texture in the deep, essentially unblown chemically embossed
portion, although it could, imparts to the mechanical and chemical embossed
surface
covering 10 the appearance of mechanical embossing in register. If desired,
the
chemically embossed portion, the raised, non-chemically embossed portions
and/or
the pattern can be mechanically embossed in register with a different surface
texture
as well by using the patterned embossing roll 54.
The mechanical and chemical embossed surface covering 10 then passes to a
tension control device 60, such as a dancer structure, a load cell roll, and
the like,
which maintains tension control in the process line, particularly the
mechanical
embossing section. At about this point, the mechanical and chemical embossed
surface covering 10 has been cooled to approximately 75° F-100°
F (ambient
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temperature). The mechanical and chemical embossed surface covering is then
wound or rolled on an appropriate winding structure 62.
As indicated above, a critical feature of the invention is the surface
temperature of the surface covering 11 as it enters the embosses nip 52. In
addition to
the factors mentioned above, this temperature is also dependent on the
position where
the measurement is taken. However, this position may not be readily accessible
for
temperature measurements because of the diameter of the embossing roll 54.
Normally, therefore, the reading is taken from the mid-point of the distance
between
the end of the high temperature heater 50 and the embosses nip 52. The actual
temperature as the surface covering 11 enters the embosses nip 52 will be
lower than
this reading because of heat loss from the top coat 20 of the surface covering
11 as it
moves through the space between the measurement point and the embosses nip 52.
The faster the line speed, the less opportunity for heat loss and the closer
the actual
temperature will be to the measured temperature at the embosses nip 52. It is
desirable for the top surface 20 to have substantially the same temperature
across the
surface covering as the surface covering enters the embosses roll nip 52.
However,
heat loss is greater along side edges of the surface covering 11. To
compensate for
this heat loss, portions of the top coat 20 along the side edges, for example,
respective
portions approximately 4 inches wide from either edge of the surface cooing,
are
subjected to further heating. This additional heating assists in maintaining a
temperature profile across the top coat 20 that, at least in one embodiment,
does not
deviate more than about 5° F. As discussed above, the high temperature
heater SO
extends beyond the respective edges of the surface covering 11 to provide
thorough
heating of these portions of the top coat 20.
It is certainly within the bounds of the present invention to use several
devices
to mechanically emboss different textures onto the top coat 20. Examples of
patterns
which can be mechanically embossed onto the surface covering 11 include
patterns
that simulate the surface texture of wood, stone, marble, granite, brick,
tile, or any
other desired covering material.
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Referring now to Figs. 2 and 4, there is shown a schematic view of another
embodiment of a process generally indicated at 8', for producing a mechanical
and
chemical embossed surface covering 10'. This embodiment is substantially
similar to
the embodiment discussed above, except that the top coat 20, if present, is
not
mechanically embossed. Accordingly, the previous discussion of like components
and apparatus are applicable to this embodiment. Here, the web 19 is formed
comprising the substrate 12, the expandable foam layer 14 operably connected
to the
substrate 12, and at least one inhibitor composition disposed as a pattern
proximate
the foam layer 14. The foam layer 14 is coated with a wear layer 18 to form a
coated
web 21 and then heated to a temperature at which the wear layer 18 is
substantially
cured, the foam layer 14 substantially expands, and the pattern is chemically
embossed to form a surface covering 11. Thereafter, the surface covering 11 is
tempered to a temperature above ambient temperature. The wear layer 18 is then
heated and at least one surface texture is mechanically embossed onto the wear
layer
1 S 18. Upon setting the at least one surface texture, the mechanical and
chemical
embossed surface covering 10 is formed. As previously indicated, mechanical
embossing includes mechanical embossing in register with a printed or
chemically
embossed pattern of the surface covering.
As indicated in Fig. 2, the substrate 12 is removed from an appropriate unwind
roll 22 and fed past the pinch roll structure 24 to pull the substrate 12 off
the unwind
roll 22 and push it partly through the processing operation. The substrate 12
then
passes through the dancer roll structure 26 to take up slack in the feed of
the substrate
12 and aid in tension control. Optionally, the substrate 12 can then pass
around the
appropriate guider structure (not shown), which maintains the registry of the
substrate
in a direction transverse to the direction of substrate movement.
The expandable foam layer 14 comprises a resinous composition containing a
chemical blowing agent and is applied to a surface of the substrate 12 to form
the
coated substrate 13. In one embodiment, the expandable foam layer 14 has a
substantially uniform thickness. The expandable foam layer 14 is coated onto
the
substrate 12 by of the any conventional coating apparatus 28 previously
discussed.
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The coated substrate 13 is then passed through heating unit 30 which supplies
sufficient heat to at least partially gel the resinous coating without
decomposing the
blowing agent. As discussed above, heating unit 30 may be utilized to jell the
foam
layer 14.
The gelled foam layer 14 and substrate 12 are then passed to the printing unit
32 which places the print layer 16, that in one embodiment includes a printing
ink
composition, onto the jelled foam layer 14. The print layer 16 is
conventionally dried
in the printing unit 32. One or more of the printing ink compositions, which
may be
either pigmented or transparent, contain the inhibitor or the accelerator for
the
blowing agent in the foamable layer 14. Further, concentrations of inhibitor
or
accelerator can differ from one printing ink composition to another.
Accordingly, the
print layer 16 can be printed wherein the printing ink and inhibitor or
accelerator
composition vary from one portion or area to another.
As before, the inhibitor or the accelerator can be printed or otherwise
applied
to the substrate 12, and then the foam layer 14 applied over the inhibitor or
the
accelerator alternatively or in addition to the inhibitor or accelerator
present in the
print layer 16. Accordingly, the inhibitor or accelerator composition can be a
pigmented composition, for example, the aforementioned printing ink
composition,
which can be visible from the surface of the mechanical and chemical embossed
surface covering 10. The pigmented composition is visible if substantially
complete
inhibition of the blowing agent is obtained and the non-foam areas of the foam
layer
14 and any subsequent layers disposed thereon are at least translucent or
substantially
clear.
The wear layer 18, which comprises a coat of a resinous composition, such as
a polyvinyl chloride plastisol or organosol, is applied over the print layer
16 by any
conventional coating apparatus 28 previously discussed to form the web 19. In
one
embodiment, the wear layer 18 has a substantially uniform thickness across the
coated
substrate 13. The wear layer 18 can be transparent, translucent or pigmented
opaque.
If the wear layer 18 is opaque, the inks will not be visible from the surface
of the
mechanical and chemical embossed surface covering 10.
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After applying the wear layer 18, the web 19 is passed through the fusion oven
40, which is discussed above, to fuse, cure, and expand the web 19 and form
the
surface covering 11. In one embodiment, the fusion oven 40 heats both surfaces
of the
web 19. The fusion oven 40 raises the temperature of the resinous compositions
on
S the substrate 12 sufficiently high to cause the selective decomposition of
the blowing
agent contained in the foam layer 14 and to completely solvate and fuse all
resinous
layers, including the substrate if comprising a resinous composition, on the
substrate.
The cellular foam areas not in contact with or exposed to any inhibitor
composition
can reach their maximum expansion or blow. The portion of foam layer 14 in
contact
with or exposed to any area or composition having a concentration of inhibitor
will
have little or no foam structure or expansion. However, as indicated above,
those
foam areas exposed to a portion of the print layer 16 having smaller
concentrations of
inhibitor can have more foam structure or expansion than those areas having a
greater
concentration of inhibitor.
Upon exiting the fusion oven 40, the surface covering 11 is tempered to at
least a temperature where the surface covering resists blistering or
separation between
the substrate 12 and layers thereof upon application of an external stress.
Again,
tempering is accomplished in the present invention by temperature reduction of
the
surface covering 11. However, although permissible, it is not necessary to
reduce the
temperature of the surface covering 11 to ambient. In one embodiment, the
temperature is reduced to between about 125° F to 300° F for
tempering the surface
covering 11. In another embodiment, the tempering is performed at a
temperature
between about 240° F to 300° F.
Tempering can be accomplished through the various methods previously
discussed. In one embodiment, the tempering unit 42 is utilized to temper the
surface
covering 11. As before, the conventional back wetter 46 may be included with
or
substituted for the tempering unit 42.
Again, the tempering unit 42 comprises at least one surface cooled tempering
roller 44 having a relatively smooth contact surface. In the preferred
embodiment, the
tempering unit 42 has two water-cooled, chrome-plated steel tempering rollers
44. As
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illustrated in Fig. 2, the tempering rollers 44 are positioned so that the
surface
covering 11 is fed through the tempering rollers 44 in an "S" configuration
and passes
around and maintains a wrap from about 180° to about 200°. In
this embodiment, the
substrate 12 initially contacts one tempering roller 44, and the other
tempering roller
44 contacts the wear layer 18. To avoid incidental mechanical embossing, the
tempering roller 44 contacting the wear layer 18 should have a surface
roughness no
greater than 32 microinch (10-6 inch) root-mean squared (32 RMS). The surface
smoothness of the tempering roller 44 contacting the substrate 12 is not as
critical.
Clearly, the tempering rollers 44 can have any desired outside diameter, more
than
two tempering rollers 44 may be utilized, and the amount of wrap about the
tempering
rollers 44 can be more or less than that mentioned above. As previously
indicated, the
breaking mechanism 48 may optionally be operably connected to the tempering
rollers 44 to maintain a back tension on the surface covering 11 as it enters
the
embosser nip 52. Again, the breaking mechanism 48 isolates the relatively high
tension associated with mechanical embossing from the respectively lower
tension
associated with chemical embossing. This is particularly useful when the
substrate 12
is the hot melt calendered substrate.
Thereafter, the surface covering 12 is heated by the previously described high
temperature heater 50 to rapidly heat the wear layer 18. Importantly, the
total surface
covering thickness is not heated to a uniform temperature. The wear layer 18
is
heated to a sufficient degree to allow it to be mechanically embossed without
fracture,
cracking, or structural failure, such as de-lamination. In one embodiment, the
wear
layer 18 is heated to a sufficient temperature for a sufficient time in order
to soften or
even further soften the wear layer 18. If the wear layer 18 is a thermoplastic
resinous
composition, it should be heated to at least the glass transition temperature.
Again,
the amount of heat to be applied and the duration of such application depends
upon,
among other things, the temperature of the surface covering 11 exiting the
tempering
rollers 44, the composition of the wear layer 18, the thickness of the wear
layer 18, the
speed of the moving surface covering 11, the color of the printed design under
the
wear layer 18 surface, and the color of the resinous layers. To further
enhance heating
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of the wear layer 18, the resinous layers can comprise a resin or contain
agents which
absorb energy from a desired frequency of the infra-red spectrum.
From the high temperature heater 50, the surface covering 11 moves directly
to the embosser nip 52. As previously discussed, the embosser nip 52 can float
against a fixed pressure or, in one embodiment, can be adjustably fixed.
Again, the
embossing roll 44 can be water cooled and servo-driven. In one embodiment, the
back-up roll 46 is a steel back-up roll, however, in other embodiments, other
back-up
rolls, such as rubber back-up rolls, may be used. Upon engaging the embosser
nip 52,
the steel back-up roll 46 contacts the substrate 12 and the embossing roll 44
contacts
the hot wear layer 18. In one embodiment, the embossing roll 44 is
approximately
22.8 inches in outside diameter, and the back-up roll 46 is approximately 24
inches in
outside diameter. Embossing and back-up rolls 44 and 46 having outside
diameters
larger or smaller may also be employed. The preferred wrap on the embossing
roll 44
is between about 85° to about 90° and can be accomplished by
articulatable idler roll
58. Wrap should be sufficient to set the embossing on the wear layer 18. In
one
embodiment, the mechanical and chemical embossed surface covering 10 is cooled
to
a temperature below about 250° F. Again, the embossing roll 44 should
have
substantially the same temperature across its surface. Again, dwell time of
the surface
covering 11 on the embossing roll 44is dependent on exact embossing roll
circumference and line speed, which can be determined by one skilled in the
art.
Furthermore, in order to maintain consistent reproduction of the embossing
roll pattern in the wear layer 18, positive tension should be maintained on
the surface
coating 11 as it enters the embosser nip 52. This tension also helps to keep
the surface
coating 11 tracking straight.
The mechanical embossing of the wear layer 18 can be achieved in such a
manner that the foam layer 14 beneath the wear layer 18 may or may not be
mechanically embossed. Importantly, the portion of the foam layer 14 either in
contact with or exposed to the inhibitor or the accelerator composition, for
example,
the print layer 16, is not mechanically embossed. And, the depth of the
embossing
into the portions or areas of the foam layer 14 beneath the areas or portions
of the
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wear layer 18 that are mechanically embossed is controlled by the pattern
protruding
from the embossing roll 44. For purposes of the present invention, in addition
to the
engraved steel embossing roll 44 and the steel back-up roll 46 discussed
above, any
mechanical embossing technique known to those skilled in the art can be used.
As with the embodiment discussed above, the embossing roll 54 can
substantially bottom out against the wear layer surface during mechanical
embossing.
By the time the now chemically and mechanically embossed surface covering is
able
to leave the embossing roll, it has cooled to below about 240° F on the
surface of the
wear layer. The mechanical and chemical embossed surface covering is then
optionally wrapped on a second cooled roll for further cooling.
As indicated above, the embossing roll is a steel roll 44 with the appropriate
embossing pattern thereon. It has been discovered, however, it is difficult to
slip the
wear layer 18 on the embossing roll 44, which is important for mechanical
embossing
in register. To assist in slipping the surface covering 11 of this embodiment,
the
surface and pattern of the embossing roll 44 can be coated with a non-stick or
friction
reducing material, for example, a tetrafluoroethylene fluorocarbon polymer, a
diamond-like carbon and silicon material, and the like. The embossing roll 44
is a
cooled roll, and when in operation with the embossing pattern engaging the
surface
covering 11, it is operated at a surface temperature of about 140° F or
below, in one
embodiment at about 90° F. The embosser nip 52 can fixably range from
zero to 250
plus mils during operation. This distance is measured from the raised area of
the
embossing roll 54 to the surface of the back-up roll 56. In one embodiment, a
gap
setting is used which bottoms out the embossing roll 54 onto the wear layer.
As
indicated earlier, the chemical embossing portion is generally deeper than
that of the
portions of the surface covering 11 which have only been mechanically
embossed. It
is possible for the mechanically embossed portion to be deeper than that of
the
portions of the surface covering 11 which are chemically embossed. This
process,
which does not create the mechanically embossed surface texture in the deep,
essentially unblown chemically embossed portion, although it could, imparts to
the
mechanical and chemical embossed surface covering 10 the appearance of
mechanical
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CA 02332142 2001-O1-25
embossing in register. If desired, the chemically embossed portion or pattern
can be
mechanically embossed in register with a different surface texture as well by
using the
patterned embossing roll 54.
The mechanical and chemical embossed surface covering 10 then passes to the
tension control device 60, discussed above, which maintains tension control in
the
process line, particularly the mechanical embossing section. At about this
point, the
mechanical and chemical embossed surface covering 10 has been cooled to
approximately ambient temperature. The mechanical and chemical embossed
surface
covering 10 is then wound or rolled on an appropriate rewind structure 62.
As indicated above, a critical feature of the invention is the surface
temperature of the surface covering 11 as it enters the embosser nip 52, and
the
discussion above is likewise applicable. Again, for convenience, the
temperature
reading is normally taken from the mid-point of the distance between the end
of the
high temperature heater 50 and the embosser nip 52. The actual temperature as
the
1 S surface covering 11 enters the embosser nip 52 will be lower than this
reading because
of heat loss from the wear layer 18 of the surface covering 11 as it moves
through the
space between the measurement point and the embosser nip 52. It is desirable
for the
wear layer 18 to have substantially the same temperature across the surface
covering
11 as the surface covering enters the embosser nip 52. As discussed above, the
high
temperature heater SO extends beyond the respective edges of the surface
covering 11
to provide thorough heating of these side edges of the wear layer 18 so that
the
temperature profile across the wear layer 18 does not deviate more than about
5°F.
It is certainly within the bounds of the present invention to use several
devices
to mechanically emboss different textures onto the wear layer 18. Examples of
patterns which can be mechanically embossed onto the surface covering include
patterns that simulate the surface texture of wood, stone, marble, granite,
brick, tile, or
any other desired covering material.
It is also possible to mechanically emboss in register (MEIR) the surface
covering 11 produced by either embodiment of the process 8 and 8' of the
present
invention. That is, the surface covering 11 can be mechanically embossed in
register
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whether or not the top coat 20 is present. Mechanical embossing in register
imparts
surface textures that vary from one area to another. For example, one area of
the top
coat 20 or the wear layer 18 over the expanded foam layer 14 can be
mechanically
embossed with one surface texture while an adjacent area is embossed with
another
S surface texture. It is also possible to mechanically emboss more than two
surface
textures in register to the surface covering 11. Further, such variations in
surface
texture can be mechanically embossed in register with the printed pattern of
the print
layer 16. One option is to emboss different textures to two or more up areas
of the
printed design. For example, if the design is composed of tiles or stones with
grout
surrounds, the faces of different tiles/stones can be mechanically embossed
with
different textures. Another option is to mechanically emboss the chemically
embossed grout areas to impart a texture different from the texture embossed
on the
tile/stones. The MEIR embossing capability allows for maximum design
flexibility
because it allows selective texturing of chemically embossed and non-
chemically
1 S embossed regions.
To mechanically emboss in register, it is necessary to provide transverse
guiding of the surface covering as it enters the embossing nip. Transverse
guiding can
be conducted with a structure as simple as a guide edge (not shown) or a
"Kamberoller" which is a commercially available structure involving an angled
guide
roll on a carriage mounted for transverse movement. The Kamberoller can form a
part
of the tempering unit 42. Registry along the machine direction (MD) or in the
direction longitudinally of the surface covering movement can be maintained in
the
same manner as set forth in U.S. Patent No. 3,655,312 to Erb et al., column 5,
line 53,
to column 6, line 43. The technique of U.S. Patent No. 3,694,634 can be
adopted
herein for machine direction registry. Both U.S. Patent Nos. 3,655,312 and
3,694,634
are incorporated herein in their entirety.
Registry can also be maintained with a servo controller 64 which phase shifts
the embossing roll 54 by periodic rotational speed increase or decrease with
nominal
effect on the surface covering 11 speed. Typically, such phase shift occurs
upon each
complete revolution of the embossing roll 54. Contemporaneously, the servo
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controller 64 matches the embossing roll 54 rotational speed with the average
process
speed of the surface covering 11 through the embosser nip 52. Phase shift
realigns the
embossing pattern on the embossing roll 54 with the printed pattern of the
print layer
16 by slipping the surface covering 11 on the embossing roll 54. In one
embodiment,
the servo controller 64 is a positional control servo which self rotates the
embossing
roll 54. Such a servo is manufactured by Allen-Bradley (Milwaukee, WI) and
referred
to as a 1394 DRIVE SYSTEM. An alternative to the positional control servo for
controlling the embossing roll 54 rotation is a combination of a Model R-S00
Digital
Control (provides phase shift) (not shown) and a Model R-425-1 Feathering
Drive
Control System (provides speed matching) (not shown) of Registron Division of
Bobst Champlain, Inc.
Mechanical embossing in register with the printed pattern of the print layer
16
can be maintained as long as the surface covering 11 is capable of being
slipped or
stretched on the embossing roll 54 without fading, which is insufficient
setting of the
1 S mechanically embossed pattern on the top coat 20 or the wear layer 18.
That is, the
rate of movement of the surface covering 11 through the embosser nip 52 either
in
across machine, machine, and/or longitudinal direction is temporarily
different with
respect to the rotation rate of the embossing roll 54, whereby the surface
covering 11
slips on the surface of the embossing roll 54. Yet, sufficient wrap must be
maintained
to set the embossed pattern during the slip adjustment to avoid fade. If the
surface
covering 11 can not be slipped, it can tear as register adjustments with the
embossing
roller 54 are made. It has been discovered that the cured top coat 20,
although in a
softened state as it enters the embossed nip 52, is sufficiently "slick" or
has a
coefficient of friction sufficiently low to allow slip as the aforementioned
adjustments
are made. As indicated above the embossing roll 54 can be coated with a
friction
reducing coating to enhance the slipping of the surface covering on the
embossing roll
54, which is useful with thermoplastic resinous coatings. Accordingly, the
mechanical and chemical embossed surface covering 10 can be slipped during
mechanical embossing to produce in register surface textures.
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MD or phase register can also be maintained by stretching the surface covering
11 as it enters the embosser nip 52, if the composition of the surface
covering permits
stretching without structural failure thereof. Stretching occurs by holding a
back
tension on the surface covering 11 as it enters the embosser nip 52. Back
tension can
be maintained by the breaking mechanism operably connected to the tempering
unit.
Skew register can be maintained by adjusting the angle at which the surface
covering enters the embosser nip 52. In the present invention, this is
accomplished by
squaring the tempering unit 42 with the production line. That is, the
tempering unit
42 is positioned substantially perpendicular to the direction of surface
covering 11
movement. The back wetter 46 comprises a roll 46 which is pivotally mounted so
that
it is capable of pivoting with respect to the embosser nip 52. A proximal end
of the
back wetter roller 46 is pivotally mounted to a mount (not shown) so that its
distal end
moves forwardly or rearwardly along an arc. In one embodiment, the surface
covering
11 has a wrap between about 40° to about 90° wrap, in one
embodiment, about 80°,
on the back wetter roll 46. As the back wetter 46 is pivoted in an appropriate
direction, the surface covering 11 entry angle or skew realigns so that the
surface
covering enters the embosser nip 52 substantially parallel to the embosser
roll 54.
Across machine direction (AMD) register is be maintained by moving the
surface covering 11 with respect to the embosser nip 52 from one side of the
embossing roll 54 toward the other side until the embossing pattern
appropriately
aligns with the printed pattern along the surface covering edges. Although
this can be
accomplished by laterally moving the surface covering 11 with respect to a
stationary
embossing roll 54, it is preferred to laterally shift and slip the embossing
roll 54 with
respect to the moving surface covering 11. The embossing roll 54 is rotatably
mounted to a frame 66 which is laterally movable with respect to the surface
covering
11. The back-up roll 56, however, remains stationary with respect to lateral
movement. To adjust AMD register, the embossing roll 54 is moved laterally in
the
appropriate direction to align the embossing pattern with the printed pattern
on the
surface covering 11.
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Further, it is important during any slipping operation to maintain constant
and
sufficient tension on the surface covering 11 as it feeds into the embosser
nip 52.
Absent constant and sufficient tension, the surface covering 11 is unlikely to
properly
slip, if at all, resulting in damage to the surface covering. For example, if
too much
tension is placed on the surface covering 11 and the rotation rate of the
embossing roll
54 is increased, the surface covering 11 can tear. On the other hand, if too
little
tension is maintained on the surface covering 11 and the rotation rate of the
embossing roll 54 is decreased, wrinkles or other similar defects can appear
in the
surface covering 11. Tension is maintained on the surface covering 11 by the
tension
control device 60 mentioned above. The appropriate amount of tension to be
applied
to the surface covering 11 is dependent upon surface covering temperature and
composition, particularly the top coat 20, if present, or the wear layer 18
composition,
the embosser nip 52 gap and pressure, embosser roll 54 wrap, and overall
tension on
the surface covering 11 throughout the process, among other things. Thus, the
1 S appropriate amount of tension is generally specific for the mechanical and
chemical
embossed surface covering 10 being then produced and must be determined by
"fine
tuning" the process.
As a result of passing the surface covering 11 through the embodiments of the
process of the present invention, there is formed a mechanical and chemical
embossed
surface covering 10 with a cross section such as that respectfully shown in
Figs. 3 and
4. Refernng to Fig. 3, one embodiment of the mechanical and chemical embossed
surface covering 10 comprises the substrate 12, an optional hot melt
calendered layer
6, the chemically embossed foam layer 14, the print layer 16, the wear layer
18, and
the mechanically embossed top coat 20. Referring to Fig. 4, another embodiment
of
the mechanical and chemical embossed surface covering 10 comprises the
substrate
12, an optional hot melt calendered layer 6, the chemically embossed foam
layer 14,
the print layer 16, and the mechanically embossed wear layer 18. Now referring
to
Fig. 5, another embodiment of the mechanical and chemical embossed surface
covering 10 comprises the substrate 12, an optional hot melt calendered layer
6, the
chemically embossed foam layer 14, the print layer 16, and the mechanically
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embossed wear layer 18, where the mechanical embossing extends into the
chemically
embossed area 70. With reference to both Figs 3-5, the chemically embossed
pattern
70 is deeply embossed. Embossed region 72, located on one side of the
chemically
embossed pattern 70, is similarly deeply embossed, however, region 72 is
mechanically embossed. Likewise, embossed region 74, which is disposed on the
other side of the chemically embossed pattern is mechanically embossed, but
not as
deep as region 72. Although the top coat 20, as shown in Fig. 3, and the wear
layer,
as shown in Fig. 4, has been depressed in region 72 below the normal plane of
the
respective coat or layer surface, the foam layer 14 retains its cellular
structure and the
respective coat or layer 18 or 20 retains substantially the same thickness as
the
respective non-embossed coat or layer. However, the cell structure has been
somewhat compressed and reduced in size. The substrate 12 and the hot melt
calendered layer 6 appear to be unaffected by the embossing operation. Should
this
particular mechanical and chemical embossed surface covering 10 be heated
again, the
1 S stress in the respective coat or layer 18 or 20 as a result of the
mechanical embossing
may or may not be relieved, depending upon the resinous composition selected
for the
respective coat or layer 18 or 20. The foam cells may have sufficient
resiliency to
cause the mechanical embossing to relax. That is, heating of the foam material
could
possibly cause the depressed areas created by mechanically embossing to raise
back to
their normal position, and consequently, the resulting mechanical and chemical
embossed surface covering 10 could appear only as a chemically embossed
surface
covering. This is a clear indication that the foam material under the
mechanically
embossed regions can have the foam regions unaffected or virtually undamaged
by the
embossing operation. Consequently, these regions retain a substantial degree
of
resiliency. Because the embossing nip 52 gap is adjustable, it is possible to
mechanically emboss in register with the printed pattern of the print layer 16
and
provide multiple surface textures to the raised areas which coincide with such
printed
pattern. As indicated in Figs. 3 and 4, it is possible to mechanically emboss
one
region, for example, region 72, with a surface texture having a visual effect
and
another region, for example, region 74, with a respectively different surface
texture,
28
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CA 02332142 2001-O1-25
thereby creating a distinctively different surface texture. Also, a matte
finish and/or
other minute texture can be applied to portions of the chemically embossed
pattern 70.
As shown in Fig. 5, it is possible to emboss the bottom of the chemically
embossed
section. The mechanical embossing overlying the chemically embossed areas can
be
performed, for example, with an embossing roll with grout texture, tile
texture and/or
stone texture. Such mechanical embossing will provide the chemically embossed
areas with grout, tile and/or stone texture.
The combination of chemical embossing and mechanical embossing in register
permits the formation of designs such as grout lines without having to crush
selected
expanded foam areas. Crushing selected areas, in contrast to mechanically
embossing
chemically embossed areas, displaces air from the foam and creates "blisters"
in the
final product. Accordingly, the combination of chemical and mechanical
embossing
improves yields of acceptable products.
In the present invention, for purposes of creating the chemically embossed
foam layer, the web 19 comprises a substrate 12 and the expandable and
resinous
foam layer 14 containing a foaming or blowing agent. The print layer 16, which
can
form a printed pattern design, is provided over at least a portion of the
expandable
foam layer 14. A plurality of print layers 14 can be disposed on the substrate
12, the
foam layer 14 and/or the wear layer 18. The print layer 16 can comprise an
inhibitor
or an accelerator composition. Additionally, the inhibitor or the accelerator
composition can be printed onto or proximate the foam layer 14 to provide a
chemically embossed pattern. As described above, once the wear layer 18 and
the top
coat 20 are applied on top of the foam layer 14, the expandable foam layer 14
is then
subjected to a sufficient temperature for a sufficient time to expand such
layer. As a
result, the chemically embossed region or pattern proximate the portion of the
printed
design containing the foaming or blowing agent inhibitor or accelerator is
formed.
Generally, a sufficient temperature is from about 350° F to about
400° F and for a
time of from about 0.8 minute to about 3 minutes to expand the foam layer 14.
It
should be understood, however, that the inhibitor or the accelerator can be
applied at
29
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random rather than as an exact reproducible design. Further, it is not
required for the
' inhibitor or the accelerator to be directly applied to the expandable foam
layer 14.
The substrate 12 of the present invention can be any conventional substrate,
earner, or backing layer used in surface coverings. Its selection depends in
large
measure on the product to be produced. For example, in one embodiment of the
invention, the substrate 12 remains as a part of the mechanical and chemical
embossed
surface covering 10. Accordingly, the substrate 12 can be formed of a resinous
composition, a woven, knitted, or non-woven fabric, a paper product, a felted
or
matted fibrous sheet of overlapping, intertwined natural, synthetic, or man-
made
cellulosic filaments and/or fibers, and other forms of sheets, films, textile
materials,
fabrics, and the like. In addition, any thermoplastic or elastomeric resinous
composition which can be formed into a sheet may be utilized as the substrate
12.
These resins typically can be compounded with plasticizers and fillers and
sheeted to
form a substrate. Such resins include, but are not limited to, butadiene-
styrene
copolymers, polymerized chloroprene, and the like. Also, the substrate 12 can
be a
non-foamed, non-crosslinked vinyl composition such as polyvinyl chloride,
polyvinyl
acetate, and vinyl chloride-vinyl acetate copolymers. Additional substrates 12
useful
with the present invention are also discussed in U.S. Patent No.3,293,108 to
Nairn et
al., which is incorporated herein in its entirety. The thickness of the
substrate 12 is
generally not critical and it is from about 5 to about 150 mils. In one
embodiment, the
thickness is from about 10 mils to about 80 mils.
The substrate 12 can be further coated with the hot melt calendered ("HMC")
layer 6 manufactured by a HMC process. HMC refers to the process of
formulating a
homogeneous mixture containing a hot melt processable resin and, in various
embodiments, plasticizer, stabilizer, filler, and/or other ingredients,
heating the
mixture, and delivering the heated mixture to a calender where the mixture is
applied
in a precisely controlled thickness to the substrate 12 to form a laminated
substrate.
Although the substrates 12 mentioned above are suited for the HMC process, the
preferred substrates 12 are felt or polyester sheet. Such melt processable
resins
include, but are not limited to, polyvinyl chloride (including general purpose
RTP 35096v1
CA 02332142 2001-O1-25
polyvinyl chloride as defined in ASTM Standard D1755-92), polyethylene,
polypropylene, polystyrene, and copolymers thereof. The HMC layer should
comprise less than 30 percent by weight of plasticizer, in one embodiment,
less than
percent by weight. Fillers can include mineral fillers, such as clay, talc,
dolomite,
S and limestone, and in some embodiments comprise at least about 60 percent by
weight of the HMC layer.
The constituents of the HMC layer 6 are mixed in a mixer (not shown), and
fed into a calender (not shown) at a desired mix temperature. The calender nip
(not
shown) opening of the calender is adjusted to the desired thickness of HMC
layer 6
10 and the HMC layer 6 is melt-coated directly onto the substrate 12 by
bringing the
substrate 12 into contact with a calender transfer roll (not shown) in a
continuous
process to form a laminated HMC substrate. The HMC substrate can also be
produced by bringing the HMC layer 6 into contact with the heated substrate 12
downstream from the calender.
In one embodiment, the foam layer 14 is applied to a substrate 12 and gelled
as
described above. The constituents of the HMC layer 6 are processed in a high
intensity mixer (not shown). The HMC layer 6 is calendered to the desired
thickness,
brought into contact with one side of the substrate 12, and coated thereon to
form a
HMC substrate. Thereafter, the foam layer 14, an inhibitor or an accelerator
composition, which can be disposed within a print layer 16, the wear layer 18,
and top
coat 20, if desired, can be coated onto either the HMC layer 6 or the exposed
substrate
12 as previously described. Thus, the substrate 12 can either be exposed or an
internal
structure not visible to the customer.
If the backing is to be removable, the substrate 12 can be, for example, a
release paper. Such paper conventionally has a coating on its surface to allow
the
plastic sheet to be easily stripped from the paper. Typical coatings used are
clays,
silicone compositions, polyvinyl alcohol, and similar compositions known in
the art.
The foam layer 14 of the present invention can be any conventional foam layer
used in surface coverings, such as a foam layer used in flooring. In
particular, the
foam layer 14 can be any suitable material known in the art for producing foam
layers
31
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such as a fluid or semi-fluid plastisol or organosol composition. Generally,
the
composition of the foam layer 14 is (i) a plastisol or organosol composition
of a
homopolymer of polyvinyl chloride, or a copolymer of polyvinyl chloride and
one or
more other co-polymerizable resins such as vinyl acetate, vinyl propionate,
vinyl
butyrate, vinylidene chloride, alkyl acrylates and alkyl methacrylates, a
graft polymer
of polyvinyl chloride and one or more other co-polymerizable resins, or blends
thereof, or (ii) melt-processable resins that include a polyvinyl chloride, a
polyamide,
a polyester, a polyolefin, a polystyrene, a polyacrylic homo- or copolymer, or
blends
thereof. These and other such materials may be used to form the foam layer 14
of the
present invention. Additionally, a cross-linked resin system may be employed
as long
as such resin system can be chemically embossed and cured.
In one embodiment, the foam layer 14 is a resilient, cellular foam layer
formed
from a resinous composition containing a foaming or blowing agent that causes
the
composition to expand on heating. It is also known in the art that foamable,
resinous
sheet material can be selectively embossed by controlling the decomposition
temperature of a catalyzed blowing or foaming agent in the heat-expandable
composition. For example, by applying a reactive chemical compound referred to
in
the art as an inhibitor, regulator, retarder, or accelerator to the heat-
expandable
composition, it is possible to modify the decomposition temperature of the
catalyzed
foaming or blowing agent in the area of application of the reactive compound.
It is
thus possible to produce sheet materials having surface areas that are
depressed with
inhibitor application and raised proximate the area without inhibitor
application.
In one embodiment, the foam layer 14 is applied as a coating to the substrate
12. In other embodiments, the foam layer 14 is applied as a preformed sheet or
the
composition is molded, extruded, calendered, or otherwise formed into any
desired
shape depending on the ultimate use of the product.
As indicated above, the expandable resinous composition comprising the foam
layer 14 includes an effective amount of a foaming or blowing agent. The
larger the
amount of blowing agent within practical limits used, the greater is the
expansion of
the foam. Foaming or blowing agents are well known in the art and the
particular
32
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CA 02332142 2001-O1-25
blowing agent selected usually depends on such matters as cost, resin, and
desired
foam density. Complex organic compounds which, when heated, decompose to yield
an inert gas and have residues which are compatible with the resin are
preferred as
foaming or blowing agents. Such materials should have the property of
S decomposition over a narrow temperature range which is particularly
desirable to
obtain a good foam structure. Examples of typical foaming or blowing agents
include
without limitation substituted nitroso compounds substituted hydrazides,
substituted
azo compounds, acid azides, and guanyl compounds, to name only a few. Foaming
or
blowing agents for use in the present invention must be decomposed an
effective
amount at a temperature below the decomposition temperature of the resinous
compositions and substrate of the mechanically and chemically embossed surface
covering. The preferred foaming or blowing agents are those that decompose
above
the elastomeric point of the resin composition of the foam layer 14 since this
enables
at least partial gelling of the foam layer 14 so that a design can be printed
on its
surface. Additionally, accelerators or catalysts can be added to the resinous
composition of the foam layer 14 to accelerate the decomposition of the
blowing
agents, reduce the decomposition temperature, act as stabilizers for the
resinous
composition, and/or narrow the decomposition temperature range. Such
accelerators
and catalysts are known in the art. Further discussion of foaming or blowing
agents is
provided in U.S. Patent No. 3,293,108, column 11, line 37-column 12, line 24.
Further, the resinous composition can include solvents, viscosity modifiers,
color and
UV stabilizers, and the like.
The inhibitor can be conveniently incorporated in an inhibitor composition, in
one embodiment incorporated in the printing ink composition to form a foam-
retarding, printing ink composition, which is printed over the heat-expandable
resinous composition. Such compositions are well-known in the art and are
generally
based on an organic solvent carrier or vehicle system. Foaming or blowing
agent
inhibitors or modifiers include but are not limited to tolyltriazole,
benzotriazole,
fumaric acid, malic acid, hydroquinone, dodecanethiol, succinic anhydride, and
adipic
acid. Examples of printing ink compositions useful with the present invention
are
33
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described in U.S. Patent No. 5,169,435 to Sherman et al., U.S. Patent Nos.
4,191,581
and 4,083,907 to Hamilton, U.S. Patent No. 4,407,882 to Houser, and U.S.
Patent No.
5,336,693 to Frisch. Further discussion of inhibitors is also provided in U.S.
Patent
No. 3,293,108 to Nairn et al., column 14, line 38-column 17, line 47.
The print layer 16 is formed from the printing ink composition. As indicated
above, the printing ink composition may or may not include at least one
inhibitor or
accelerator composition. The area or portions of the print layer comprising
the
printing ink composition without inhibitor will not inhibit expansion of the
foam
layer. Printing ink compositions usually comprise resins, plasticizers,
solvents,
pigments, stabilizers, dyes, accelerators, promoters, kickers, and the like.
They are
applied by the conventional printing apparatus discussed above and are usually
very
thin, only a fraction of a mil. To inhibit or promote expansion of the foam
layer, the
blow or foam modifying agents, such as inhibitors, regulators, retarders,
suppressants,
accelerators, and the like, are added to the printing ink composition. Drying
is usually
1 S conducted within the printing unit 32 and can be accomplished by exposure
to air or
by conventional heating and drying procedures. An example of such an ink
composition contains an acrylic resin, water, alcohol, and one or more
pigments.
In forming a design having both an inhibitor composition and one not
containing a inhibitor composition, such a design can be done in register
using
multiple station rotogravure printing, as described in U.S. Patent No.
3,293,108. For
example, the print layer 16 can form a pattern of joint or grout lines which
are created
with at least one inhibitor composition. Upon expansion of the foam layer 14,
these
portions will be chemically embossed and will visually form joint or grout
lines to
simulate such lines which exist with natural wood, stone, marble, granite,
brick, or tile
surfaces. The joint or grout lines created with the inhibitor composition
generally will
have a width of, for example, from about 0.125 inch to about 0.25 inch.
The wear layer 18 is usually a clear, unpigmented resinous composition, which
provides the mechanical and chemical embossed surface covering 10 improved
wearing or in-use qualities. Any suitable material known in the art for
producing
such wear layers 18 can be utilized with the present invention. The fluid or
semi-fluid
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CA 02332142 2001-O1-25
thermoplastic and thermoset plastisol or organosol compositions utilized to
form the
foam layer 14 may likewise be utilized to form the wear layer 18. However, the
wear
layer 18 does not include the blowing or foaming agents. In one embodiment,
the
wear layer 18 is a polyvinyl chloride plastisol composition. The dry film
thickness of
the wear layer 18 is not critical. In one embodiment, the thickness is from
about 5
mils to about 30 mils, and in another embodiment, from about 10 mils to about
20
mils.
As indicated, the wear layer 18 may be applied to and adhered to either the
foam layer 14 or the print layer 16. The wear layer 18 can be applied by any
conventional coating apparatus 28 known in the art, such as a reverse-roll
coater, an
air knife coater, knife coater, and any other coater known in the art. Once
the wear
layer 18 is applied, the wear layer 18 is jelled. Jelling can be accomplished
by
subjecting the wear layerl8 along with the foam layer 14 and substrate 12 to a
sufficient temperature, for example, by heating, to jell the wear layer 18. If
the
mechanical and chemical embossed surface covering 10 being produced does not
include the top coat 20, the foam layer 14 can be expanded and cured and the
wear
layer cured by the fusion oven 40, as discussed above.
Optionally, besides the layers discussed above, one or more additional layers
can be present, such as the layers described in U.S. Pat. No. 5,458,953,
incorporated
herein in its entirety by reference. Such additional layers include
strengthening layers,
additional foamable layers, and a wear layer base coat. The composition of
these
layers and their locations are described in U.S. Pat. No. 5,458,953 and can be
used in
the mechanical and chemical embossed surface covering of the present
invention.
The top coat 20, if present, is deposited or applied on top of the wear layer
18
to form the coated web 21. The coated web 21 is then subjected to heat or
curing
which cures the top coat 20 and wear layer 18, expands and chemically embosses
the
foam layer, and fuses all resinous layers to one another, as described
earlier. For
purposes of curing the top coat 20 and the wear layer 14, a sufficient
temperature for a
sufficient time is utilized. Typically, this temperature is from about
350° F to about
400° F for a time of from about 0.8 minute to about 3 minutes, in one
embodiment,
RTP 35096v1
CA 02332142 2001-O1-25
from about 1 minute to about 1.5 minutes. Alternatively, the top coat can be
applied
to the mechanically embossed wear layer by any of the conventional coating
apparatus
and conventionally cured by heat, ultraviolet light, and the like.
FXAMPT .F~
F~rer~rnr ~ i
A felt substrate having a thickness of approximately 25 mils is substantially
uniformly coated with an expandable foam layer of a polyvinyl chloride
plastisol
containing a blowing agent with a reverse roll coater. The expandable foam
layer has
a wet applied average thickness of about 10 mils. Thereafter, the expandable
foam
layer is jelled to a relatively firm condition by heating to a temperature of
approximately 300° F for approximately 17 seconds on heated drum
without
expansion of the foam layer. A print ink composition containing an inhibitor
consistent with those described herein is printed and dried on the jelled
expandable
foam layer by a conventional rotogravure printing apparatus to form a print
layer. The
print layer is printed in a pattern design. A clear, non-foaming polyvinyl
chloride
plastisol wear layer having an applied thickness of approximately 10 mils is
coated
onto the print layer by a reverse roll coater. The wear layer is jelled on a
heated drum
at a temperature of approximately 300° F for approximately 10 seconds
to a relatively
firm condition without expansion of the foam layer. A top coat of a cross-
linkable
polyurethane-melamine resin having a wet applied average thickness of
approximately
1 mil is coated onto the jelled wear layer by a reverse roll coater to form a
coated web.
The coated web is passed through a fusion oven at a temperature of
approximately
380° F for approximately 1 minute to expand and cure the foam layer,
cure the wear
layer, cure the top coat, and fuse all resinous layers to form a surface
covering. The
portions of the foam layer in contact with the printed pattern of the print
layer did not
expand, thereby chemically embossing the printed pattern into the foam layer.
Immediately upon exiting the fusion oven, the surface covering is tempered to
approximately 250° F by passing the surface covering in an "S"
configuration of
36
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CA 02332142 2001-O1-25
between two water cooled tempering rollers with a wrap on each tempering
roller is
approximately 180°, substantially as described above. The top coat of
the surface
coating is then heated in a high temperature oven of a bank of infra-red
radiant heaters
to a substantially uniform surface temperature of approximately 350° F,
while the
temperature of the substrate as the surface covering exits the high
temperature oven is
approximately 290° F Immediately thereafter, the surface covering
enters the
embosser nip, which is spaced from the high temperature oven so that the top
coat has
substantially no temperature drop. The embosser nip is formed by the water
cooled
chrome plated steel embosser roll having a pattern on the surface thereof and
the
chrome plated steel back-up roll described herein and has a gap of
approximately SO
mils. Upon entering the embosser nip, the pattern of the embossing roll
mechanically
embosses the top coat of the surface covering. Embossing roll surface
temperature is
maintained at approximately 80° F, thereby setting the mechanically
embossed pattern
and forming the mechanical and chemical embossed surface covering. Upon
cooling
to ambient temperature, the mechanical and chemical embossed surface covering
is
found to be acceptably and permanently embossed.
nor a ~~rnr ~ ~
The mechanical and chemical surface covering of Example 1 is mechanically
embossed in register as follows. Phase registration is conducted by reducing
the
rotation rate of the embossing roll with respect to the surface covering rate
through the
embosser nip. The top coat slipped on the embossing roll without either damage
to
the surface covering or fading of the embossed pattern on the top coat. As a
result the
mechanically embossed pattern is placed in phase with the printed pattern of
the
surface covering.
EXAMPLE 3
A felt substrate having a thickness of approximately 10 mils is substantially
uniformly coated with a polyvinyl chloride HMC layer of approximately 25 mils,
which is applied by a calender as substantially described above. The substrate
and
37
RTP 35096v1
CA 02332142 2001-O1-25
HMC layer are tempered to approximately 75° F. An expandable foam
layer of a
polyvinyl chloride plastisol containing a blowing agent is applied with a
blade coater.
The expandable foam layer has a wet applied average thickness of about 10
mils.
Thereafter, the expandable foam layer is jelled to a relatively firm condition
by
heating to a temperature of approximately 300° F for approximately 6
seconds on
heated drum without expansion of the foam layer. A print ink composition
containing
an inhibitor consistent with those described herein is printed and dried on
the jelled
expandable foam layer by a conventional rotogravure printing apparatus to form
a
print layer. The print layer is printed in a pattern design. A clear, non-
foaming
polyvinyl chloride plastisol wear layer having an applied thickness of
approximately
10 mils is coated onto the print layer by a blade coater to form the coated
web. The
coated web is passed through a fusion oven at a temperature of approximately
400° F
for approximately 1 minute to expand and cure the foam layer, cure the wear
layer,
cure the top coat, and fuse all resinous layers to form a surface covering.
The portions
of the foam layer in contact with the printed pattern of the print layer did
not expand,
thereby chemically embossing the printed pattern into the foam layer.
Immediately
upon exiting the fusion oven, the surface covering is tempered to
approximately 240°
F by passing the surface covering in an "S" configuration of between two water
cooled tempering rollers with a wrap on each tempering roller is approximately
200°,
substantially as described above. The wear layer of the surface coating is
then heated
in a high temperature oven of a bank of infra-red radiant heaters to a
substantially
uniform surface temperature of approximately 275° F, while the
temperature of the
substrate as the surface covering exits the high temperature oven is
approximately
265° F. Immediately thereafter, the surface covering enters the
embosser nip, which
is spaced from the high temperature oven so that the wear layer has
substantially no
temperature drop. The embosser nip is formed by the water cooled chrome plated
steel embosser roll having a pattern on the surface thereof and the chrome
plated steel
back-up roll described herein and has a gap of approximately 42 mils. Upon
entering
the embosser nip, the pattern of the embossing roll mechanically embosses the
wear
layer of the surface covering. Embossing roll surface temperature is
maintained at
38
RTP 35096v1
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approximately 80° F, thereby setting the mechanically embossed pattern
and forming
the mechanical and chemical embossed surface covering. Upon cooling to ambient
temperature, the mechanical and chemical embossed surface covering is found to
be
acceptably and permanently embossed.
Although the invention has been described in detail for the purpose of
illustration, it is understood that such detail is solely for that purpose,
and variations
can be made therein by those skilled in the art without departing from the
spirit and
scope of the invention which is defined by the following claims.
39
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