Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
Field of the Invention
The invention is directed to a process for
manufacturing floor covering material and, more particularly,
to a process for the mechanical embossing of a pattern on
a floor covering material.
Description of the Prior Art
U.S. Patent No. 3,741,851 discloses a product and
process which deals with a foamed vinyl floor covering. A
printed color pattern or design is provided between the foam
resin layer and a transparent resin layer. Embossing is
carried out relative to the transparent resin layer and
the embossing is carried out in register with the printed
pattern.
U.S. Patent No. 3,176,058 is directed to an apparatus
for embossing sheet material. Water cooling means are
provided to cool either one or both sides of the sheet prior
to embossing.
U.S. Patent No. 3,305,419 is directed to an apparatus
for embossing a foamed-back polyurethane sheet. Surface
heating is carried out to heat only the surface to be embossed
so that there will be no damage to the underlying foam layer.
U.S~ Patent No. 3,196,062 is directed to a process
wherein cooled embossing rolls are utilized to provide an
embossed pattern on a sheet material which is composed of
a foamable thermoplastic resin base and a thermoplastic
resin top coating. Surface heating of the thermoplastic
resin is carried out just prior to embossing.
U.S. Patent No. 2,723,937 is directed to a product
for emboss;ng a floor covering material wherein embossing
is carried out by embossing roll 21 in cooperation with
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backup rolls 20 and 23.
U.S. Patent No. 3,776,797 is directed to an
embossing structure wherein embossing is carried out with an
embossing roll 22 and backup rolls 23 and 25.
U.S. Patent No. 3,246,365 is directed to an em-
bossing apparatus using plural embossing rolls and backup rolls.
Finally, U.S. Patent No. 3,338,731 is directed to
a process for embossing poly(vinyl chloride) coatings on a
support base.
Summar of the Invention
y
In the inventive process herein, the expansion of
a decorated foam and the fusion of a wear layer thereover are
completed in an earlier step in the same manufacturing process
in which the embossing is carried out. In other words, the
embossing operation is carried out at the end of the processing
line which forms the expanded foam product with a fused or cured
wear layer. The wear layer is maintained at its high surface
temperature while the foam backing-is cooled on its back side by
the combination steps of back wetting and drum cooling, or simply
by back wetting alone. Appropriate guide structures and
controls feed the combination foam layer-wear layer structure
into an embossing structure so that the embossed pattern will
be placed on the combination wear layer-foam layer web in registry
with the printed design on the surface of the decorated foam.
Due to the back wetting and/or drum cooling, there will be a
100F. to 150F. (38C to 66C.) difference between the surface
of the wear layer being embossed and the back surface of the
foam which is displaced away from the surface being embossed.
The combination foam layer-wear layer web is partially wrapped
around the backup roll of the embossing apparatus prior to the
time the combination layer web is fed into the nip between the
embossing roll and the backup roll of the embossing apparatus.
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After the combination layer web passes through the nip of the
embossing roll and the backup roll, it is wrapped around a
portion of the surface of the embossing roll.
Thus, in accordance with the present teachings, an improve-
ment is provided in a process for embossing a web of material
wherein the material is composed of a composite structure which
has at least a carrier having a foam layer with the foam layer
on the surface thereof adjacent the surface to be embossed having
a decorative pattern printed thereon and wherein the cons~tant
structure is in the form of a web which is heated to a temperature
of about 250F. to 350F. and includes the steps of (a) wetting
the carrier of the web, which is the back surface of the web, the
surface not to be embossed, so as to lower the temperature of the
back surface of the web approximately 100 below the top surface
of the web, which is the surface to be embossed, (b) embossing
the top surface of the web with an embossing roll and backup
roll and tc) cooling the embossed surface of the web to set the
embossed pattern in the web. The improvement which is provided
comprises wrapping the web of material partially around the backup
roll prior to the time that the web passes between the nip of the
backup roll and the embossing roll and wrapping the embossed sur-
face of the web around the embossing roll after it has passed
through the nip between the embossing roll and the backup roll to
partially cool the embossed surface of the web.
Utilizing this invention, in conjunction with shallow
embossing rolls having a greater area of surface embossing,
mechanical embossing capabilities with controllable embossing
depths and visual end products on foam structures are enhanced
considerably over that found in the prior art. In addition, the
combination of back wetting and drum cooling permits increased
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production capabilities, as well as providing for multilevel
Pmbossing of thick foam layers. The wrap around of the combina-
tion layer web around the backup roll provides for a positive
engagement between the backup roll and web, which is actually
driving the combination backup roll and embossing roll. The
wrapping of the combination layer web around the embossing roll
helps to improve the definition of the embossed pattern in the
wear surface, particularly with combination layer webs that have
a thick foam layer.
BRIEF DESCRIPTION OF THE DRAWING
The figure of the drawing is a schematic showing of the
process and apparatus for carrying out the invention herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention herein is an alternate process for the
manufacturing of the product of U.S. Patent No. 3,741,851.
In the above-mentioned patent, the oven 18 shown in
Figure 2 serves to fuse the resin materials and decompose
the blowing agent uniformly throughout the area of the product.
Thereafter, the web is passed while still hot, for instance,
while at a temperature of from about 225F. tlO7C) to about
325F. (163C.) through an embossing structure. The invention
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herein deals with the passing of the web in U.S. Patent 3,741,851
from the oven 18 to and through the inventive embossing roll
structure of the drawing of this disclosure.
The warm web 2, which would move from the oven
structure 3, passes around a conventional guider structure 4
which simply maintains the registry of the printed pattern of
the web with the embossing roll pattern in a direction transverse
to the direction of web movement. The guider structure is
composed of two guide rolls 6 and 8. The back of the web will
pass over roll 6 and then the web will pass under roll 8, with
the roll surface in contact with the surface of the web to be
embossed. This surface will be quite warm, and therefore, roller
8 should be covered with a "Teflon"TM coating to prevent sticking
of the upper embossable surface of the web against the surface
of the roll 8. This roll 8 is usually maintained at a surface
temperature of 200F. to 250F. (93C to 121C) in order to
maintain a hot embossable surface. The assembly 4 is a
commercially available "KamberollerTM" which consists of two
angled guide rolls on a carriage mounted for transverse movement.
The transverse guiding of the sheet is carried out through the
use of the "KamberollerTM". but could equally well be carried
out by simply the use of guide bars which are placed along the
edge of the web and would guide the web edge and, therefore, the
pattern edge relative to the embossing roll farther down the
processing line. U.S. Patents No. 3,024,955 and 2,797,091 show
typical "Kamberoller M" structures.
The web then passes over a back wetting structure
10 which is preferably a felt-covered roller 12 partially immersed
in a bath of liquid 14. The felt-covered roller 12 of the back
wetting structure 10 could be replaced by a steel roller, or
even a water spray system. The back wetting structure applies
water to the back side, the area of the web not to be embossed,
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so as to cool the back side and stabilize the hot thermoplastic
foam next to the back side of the web. The application of the
water and its evaporation on the back side of the web cools the
back side of the web and its ad~acent foam layer to 125F. to
200F. t52C. to 93C.) by the time the web enters the embossing
apparatus. The rate of water application is governed by the
quantity of heat to be removed from the hot thermoplastic foam
next to the back side of the web to keep the printed foam from
distorting and blistering at the embossing nip. Meanwhile, the
upper surface, the embossable surface, of the web is at about
215F. to 300F. (99C. to 149C.). Under some circumstances, a
"TeflonTM" coated roll 16 may be utilized to provide additional
heat to the top surface of the web to compensate for heat loss
which may occur as the web is moving through ambient air from
the oven towards the embossing structure. The roll 16 is also
used to cause wrapping of the web of material around a portion
of the backup roll of the embossing structure to be described
below.
The embossing structure is basically composed of a
backup roll 20, an embossing roll 22, and a guide roll or
definition roll 24. The backup roll and embossing roll can be
driven by separate power sources. However, it is contemplated
according to this invention that they are coupled together
through a power transmission system as described in U.S. Patent
No. 3,741,851. Roll 16 will cause the web to be partially
wrapped around the steel backup roll 20 before embossing is
carried out by the embossing roll 22. The backup roll will be
cooled by chilled water so that the backup roll has a surface
temperature of about 75F. to 100F. (24C. to 38C.) and this
chilled backup roll 20 will function to further cool the back side
of the web prior to the time that embossing is carried out.
Consequently, the steel backup roll 20 is functioning both as
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a cooling drum and as a backup roll for the embossing roll 22. Par-
tial wrapping of the web around the backup roll 20 provides for a
good frictional contact between these two. Pull rolls 28 draw the
web 2 through the processing apparatus. Due to the wrap of the web
on the backup roll 20, a rotational movement of this roll is pro-
vided which is necessary to drive the embossing roll. After the web
of material passes through the nip between embossing roll 22 and
backup roll 20, the definition roll 24 causes the web to partially
wrap around the embossing roll 22. This helps improve the
definition of the pattern being embossed in the web since the
embossing structure is maintained in contact with the web while
the web is chilling to a degree. The web may then move back
into contact with the backup roll 20 and then be directed on
down through further processing by another guide roll 26, or
the web could simply be moved directly to the guide roll 26 with-
out further contact with the backup roll 20.
Since there is a need to register the embossing
pattern with the printed pattern of the web, there must be
control of the embossing roll pattern relative the printed pattern
to get registry between the two patterns. This will require
registry along the machine direction, and this registry along
the machine direction or in the direction longitudinally of the
sheet movement is màintained in the same manner as set forth in
U.S. Patent No. 3,65S,312, Column 5, line 53 to Column 6, line 41.
The technique of U.S. Patent No. 3,694,634 and U.S. Patent No.
3,741,851 can be adopted herein for machine direction registry
also. Finally, registry in the machine direction can be secured
using Model R-500 Digital Control and Model R-425-1 Feathering
Drive Control of "RegistronT " Division of Bobst Champlain, Inc.
At this point, it should be noted that registration controls,
both across the machine direction and along the machine direction,
are necessary to secure a commercially acceptable product with
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registration between the embossed pattern and the printed
pattern, but such controls are not part of the invention herein,
since they are conventional in the art. The essence of the
invention herein is in the utilization of the particular
embossing roll structure shown in the drawing. For thin foam
materials [0.030-0.045 inches (.08-11 cm)], for which the
embossing roll structure herein is particularly adaptable, the
utilization of back wetting for the purpose of cooling the back
side of the web and adjacent foam layer is necessary. For foam
webs having considerable thicknesses [.100-.120 inches (.25 cm
to .3 cm)] which retain their internal heat, it has been found
that the back wetting structure 12 plus drum cooling as supplied
by backup roll 20 is needed. With even thicker foams or
intricate patterns, this may need to be supplemented by even a
further back wetting structure which could be placed before the
"KamberollerT ".
It should be noted that the- embossing rolls of U.S.
Patent No. 3,741,851 have "bottomless" embossing roll valleys and,
therefore, do not emboss the web except with the embossing roll
land areas. In the embossing roll structure 22 herein, both the
roll land and valley areas make contact and emboss the web. This
increased area of embossing is not possible in the structure of
U.S. Patent No. 3,741,851. In the structure of that patent, the
embossing area can only be 25~ of the total sheet area, whereas
in the embossing roll structure herein, the embossing area can
go to 80% to 90% of the total sheet area. Normally, the
embossed area will cover 30% to 90% of the total sheet area. If
the material of U.S. Patent 3,741,851 were utilized through the
embossing apparatus generally described above and no back wetting
or cooling carried out, it has been found that the web will enter
the embossing roll nip with a temperature on the embossing surface
of 220F. (104C.) and a temperature on the back of the web, the
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non-embossed surface, of about 270F. (132C.). Under these
conditions, the center of the foam of the web will be
measured at about 300F. (140C.) and this is an ideal
condition for blistering within the foam layer. Blistering
provides an unacceptable product. The back wetting eliminates
this problem.
In operation, the web to be embossed is wrapped
around the backup roll for about 38% of its surface area, and
can be utilized with a wrap around in a range of 30% to 75%
of the surface area of the backup roll, so as to secure the
necessary drive of the backup roll by the web. The embossing
roll 22 is normally maintained cold at about 75F. to 100F.
(24C. to 38C.), to freeze in the desired pattern which is
being embossed in the web. Due to the use of definition roll 24,
the web will be partially wrapped around the embossing roll 22
to further assist in the freezing of the desired pattern in the
- surface being embossed. The wrap around covers approximately
8.5% of the embossing roll surface and may cover a range of
embossing roll surface ranging from 0% to 20% of the total
embossing roll surface.
The material described in U.S. Patent No. 3,741,851
could come from the oven 18 of that patent and pass through the
appropriate guiding structures by the back wetting roll 10 around
the backup roll 20 and around the embossing roll 22 and be em-
bossed without any blistering in the end product with very good
registration between the embossed pattern and the printed pattern
and with the embossing carried out so that there is "bottoming
out" of the embossing roll against the embossed surface of the
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web. C~)oling of the back surface of the web prior to the
embossing directly attributes to the lack of blistering and
the ability to carry out a "bottoming out" of the embossing
roll while still maintaining registry. Wrapping of the web
around the backup roll provides for good positive drive of the
backup roll plus embossing roll and wrapping of the web around
the embossing roll 22 improves the pattern definition in the
embossed product.
Even though this invention can provide for unique
embossed designs on wear layers composed of vinyl compositions
as described in U.S. Patent 3,741,851, the embossing of additional
non-vinyl wear layers is possible. For example, it is also
possible to emboss a cured thermoset wear layer web which has
a foam underlayer. This particular product will be made by
placing a plastisol on a carrier web such as that disclosed in
U.S. Patent 2,759,813. The following plastisol is prepared by
thoroughly mixing the following ingredients:
Ingredients Parts by Weight
Poly(vinyl chloride~ 100
Dioctyl phthalate (plasticizer) 49.55
20 Octyl epoxy phthalate (stabilizer) 5.0
Titanium dioxide 3.6
Azodicarbonamide (blowing agent) 2.3
Talc 0.6
Zinc octuate (blowing agent activator) 1.95
This above plastisol is applied to the above-
described carrier which is a coated beater-saturated asbestos
sheet having a thickness of about 0.028 inches (.07 cm). The
plastisol is applied with a reverse roll coater to a wet
thickness of 10 mils (.025 cm). The plastisol-coated backing is
gelled in a hot air oven for one minute to an exit temperature
of 270F. (132C.). This sheet is then cooled and a printed
design is placed thereon. The printed design may be any
particular pattern and could be of the same pattern shown in
Figure 3 of U.S. Patent No. 3,741,851. Inks are prepared by
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thoroughly mixing the following ingredients:
Ingredients Parts by Weight
Vinyl binder 33.0
Pigment 12.8
Cellosolve acetate 1.6
2-nitropropane 50.0
Isopropyl acetate 1.0
Alkyl alcohol aryl polyether 1.0
Inks of various colors, based upon the above formula,
are applied to the gelled plastisol sheet described above
utilizing the printing cylinders of a conventional rotogravure
printing press. The printing cylinders are run in a normal
manner, producing the design that is printed in register. The
inks are dried by subjecting the printed sheet to warm air
impingement supplied by the enclosed drying zones of the press.
The inks are not critical to the invention herein, but simply
need be inks which are capable of adhering to and drying on the
plastisol above described.
To the printed gelled plastisol above is applied
a plastisol layer havi~g the f~llowing formula:
Ingredients Parts by Weight
Poly(vinyl chloride) 100
Dioctyl phthalate (plasticizer) 12
2,2,4-trimethyl-1, 3-pentanediol mono
isobutyrate, Nuoplaz 1046, Nuodex
ink (non-staining plasticizer) 27
Barium-cadmium zinc phosphite (stabilizer) 3
2,2,4-trimethyl-1, 3-pentanediol diiso-
butyrate 5
Optical brightener 0.005
The above plastisol was applied to the printed
sheet as a wet film with a thickness of 8.5 mils (.02 cm). It
is fused by being heated to 325F. (163C.) in a hot air
impingement oven for two minutes. This heating step will result
in partial blowing of the azodicarbonamide blowing agent in
the gelled first coat.
To this last-applied fused plastisol there is
applied a clear 2 mil (.005 cm) (dry) coating of a curable poly-
Urethane. The polyurethane coating is a 55:45 xylene/resin
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solution containing catalyst. Heat is applied and the poly-
urethane coating is cured in three minutes' time. The heat
applied will complete the decomposition of the blowing agent in
the gelled first coat to convert it to a foam layer, and will
also cure the polyurethane coating. Heat is applied by passing
the web through a three-stage oven which has the first stage
heated to 270F. (132C.), second stage heated to 380F. (193C.),
and the third stage heated to 340F.(171C.). The last coating
applied is the wear layer surface of the resulting floor product
which will be formed. Polyurethane coatings are applied to
secure a product which will retain a hard, high gloss surface and
eliminate the need for subsequent waxing by the user of the floor.
Again, criticality does not particularly rest in the wear layer
coating. It is only necessary that the coating be embossable
when heated to a range of about 250F. to 350F. (121C. to 177C.).
The invention is particularly applicable to a structure which
constitutes a we~ar layer having thereunder a foam layer, and, it
is desirable to emboss the wear layer without having to o much
heat retained in the foam layer so that the stability of the
printed foam layer is damaged during embossing in registry with
the printed pattern.
The above-described polyurethane coated sheet
would be conveyed from the oven 3, wherein the polyurethane is
cured and the foam is expanded, and directed towards the apparatus
shown in the drawing herein. Coming from the oven, the above-
described composite web composed of the backing sheet, the foam
layer, the vinyl layer and the polyurethane coating would be at
about 270F. (132C.) and would constitute the web 2 of the
drawing. The web 2 would move past appropriate across-machine
and along-machine guide structures towards the back wetting roll
12. Because the polyurethane wear surface would tend to lose
heat a lot faster than a conventional vinyl wear surface, roll
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16 would be provided with heat to engage the upper surface of
the web, the polyurethane wear surface. The roll 16 would be
heated to 200F. to 250F. (93C. to 121C.) to help maintain
the temperature of the polyurethane wear surface to at least
this level. The web would then pass to the backup roll 20 and
embossing roll 22 and would be embossed. The embossing roll
would be maintained at about 75F. (24C.) surface temperature
and the backup roll would also be maintained at about 75F. to
100F. (24C. to 38C.) surface temperature. The product, as
it passes between the nip of the embossing roll, which is the
area between the roll 22 and 20, would have the polyurethane
wear layer, or the top surface of the web, at a temperature of
about 250F. (121C.). The back wetting, plus the cooling action
of the backup roll 20, will have cooled the temperature of the
backing or carrier and the back of the foam layer adjacent
thereto to a temperature of about 125F. to 200F. (52C. to 93C.).
The cool embossing roll will immediately freeze the desired
embossed pattern in the polyurethane wear layer at the time the
embossing is carried out. The thickness of the web described
above will be about 70 mils. The embossing pattern on the
embossing roll comprises 55~ to 60% of the total roll surface -
and the depth of the pattern on the roll is about 60 mils. Full
embossing is carried out with both the land areas and valley
areas engaging the web. Due to spring-back in the material, the
end product has an embossed depth of 15 mils. The foam layer
in the valley embossed areas will be somewhat compressed as
compared to the foam in the non-embossed areas. The wrap
around of the web around the backup roll 20 will constitute
approximately 38% of the total surface area of the backup roll
and the wrap around of the web around the embossing roll 20
will constitute about 8.5% of the total surface area of the
embossing roll.
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It has been found that the conventional poly(vinyl
chloride) wear layers and foams, such as those disclosed in
U.S. Patent 3,741,851, all wor~ equally well in the apparatus
above-described.
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