Note: Descriptions are shown in the official language in which they were submitted.
10~71Z
Background of the Invention
Field of the invention
The invention is directed to a process for manu-
facturing 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 -foa~bac~-ed 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
material.
Finally, 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 thermo-
plastic resin top coating. Surface heating of the thermo-
plastic resin is carried out just prior to embossing.
- Summary of the Invention
In the inventive process herein, the expansion of a
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decorated foam and the printing of a design thereon are com-
pleted in an earlier step of the same manufacturing process
in which the embossing is to be 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 the design printed thereon. The expanded foam sheet
product is carried on a backing, but does not have any fused
or cured wear layer on the surface of the foam to be
embossed. The surface of the foam to be embossed is maintained
at a high surface temperature while the backing of the sheet
and the foam adjacent thereto is cooled by the combination
steps of back wetting and drum cooling, or simply by back
wetting alone. Appropriate guide structures and controls
feed the combination backing and foam layer into an embossing
structure so that the embossing pattern will be placed on
the foam layer in registry with the printed design on the
surface of the foam. Due to the back wetting and~or cooling,
there will be a ~5F. to 150F. (30C.-65C.) differential between
the surface of the foam being embossed and the back layer of
the foam which is displaced away from the surface being
embossed. After the product has been embossed, it is then
provided with a wear layer coating which will be subsequently
fused or cured.
Utilizing this invention, in conjunction with shallow
embossing rolls having a great area of surface embossing,
mechanical embossing capabilities with controllable embossing
depths and visual end products or foam structures are enhanced
considerably over that found in the prior art. In addition,
the combination of back wetting and drum cooling permits
increased production capacities as well as provides for
multi-level embossing of thick foam products.
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Thus, and in accordance with the present teachings,
an improvement is provided in a process for embossing a rubber
material wherein the material is composed of a carrier and a
foamed material layer positioned thereon with the foamed material
layer having on the upper surface thereof a decorative pattern
printed thereon and the composite structure is in the form of a
web which is heated to a temperature of about 250F to 350F.
The improvement which is provided comprises wetting the carrier
of the web, which is the back surface of the web, so as to
lower the temperature of the back surface of the web approxi-
mately 100 below the top surface of the web, which is the
upper surface of the foamed material. A pattern is embossed
on the upper surface of the foamed material layer and the
registry of the embossed pattern is controlled with the printed
pattern of the web so that the two patterns will be in registry.
The embossed surface of the foamed material is cooled to set
the embossed pattern in the layer. If desired, a wear coat
may be applied to the embossed surface and subsequently fused.
1~
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10l~7~Z
Brief Description of the Draw nq
-
The figure of the drawing is a schematic showing
of the process for carrying out the invention herein.
Description of the Preferred Embodiments
The invention herein is a process for manufacturing
a product similar to that set forth in U.S. Patent No.
3,741,851 and U.S. Patent 4,076,867. In both the above
patents, an oven serves to fuse resin materials and de-
compose a blowing agent uniformly throughout the area of the
product. Thereafter, the web, while still hot, for instance
while at a temperature of about 225F. (107C.) to about
325F. (163C.), is fed to an embossing structure. The
invention herein deals with a modification of the web being
processed in the above-mentioned patents.
The web 2 herein, which will be moving from an
oven structure, will be composed of only a backing layer
and a foam layer. The wear layer, which is disclosed for
the product of the above mentioned patents, will not exist
in the web 2 of the application herein. The warm web
2 passes around a conventional guider structure 4 which
simply maintains the registry of a printed pattern on the
web with the embossing roll pattern in a direction trans-
verse to the directionof 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
foam against the surface of roll 8. This roll 8 is usually
maintained at a surface temperature of 200F. (93C.) to
~- -3-
10~7~;~
250F. (121C.) in order to maintain a hot embossable surface.
The assembly 4 is a commercially available "KamberollerTMn
which involves 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.
The web then passes over a back wetting structure
10 which is preferably a felt-covered roll 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 of the web, that is,
the area of the web not to be embossed, so as to cool the
back side of the web and stabilize the hot thermoplastic foam
next to the back side of the web. The application of the water
and its evaporation from the back side of the web cools the
back side of the web and its adjacent foam layer to 135F.
(57C.) to 200F. ~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 thermo-
plastic 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 210F. (99C.) to 300F. (149C.).
Under some circumstances, a "Teflon " coated roller 16 may
by utilized to provide additional heat to the top surface of
the web to compensate for heat loss which may occur as the
web is moved through ambient air from the oven towards the
embossing structure.
10~1~712
The embossing structure will be composed of a back-
up roll 20 and an embossing roll which may be the embossing
roll 22 positioned as shown in the drawing. In this situation,
the web is embossed almost as SOOII as it comes in contact with
the steel back-up roll 20. Under some circumstances, it may
be desirable to move the embossing roll to the position 24
shown in the drawing. Under this set of circumstances, the
web will be partially wrapped around the steel back-up roll
before the embossing is carried out by the embossing roll 24.
When embossing roll 24 is used in lieu of roll 22, the back-up
roll 20 will be cooled by chilled water to a surface temperature
of about 75F. (24C.) to 100F. (38C.) and will function to
further cool the back side of the web prior to the time that
embossing is carried out. Here, steel back-up roll 20 is
functioning both as a cooling drum and as a back-up roll
for embossing roll 24. Since back wetting is done prior to
embossing, the depth of the embossing roll, as it would be in
either position 22 or 24 can be quite shallow. Embossing rolls
containing engraved designs as shallow as 10 mils in depth
have been used successfully in this invention. Also, a partial
wrap of embossing roll 24 may be needed to impart to the hot
wear layer an intricate and multilevel embossing design.
Since the product that has been embossed is basically
an expanded foam, carried on a backing layer, there is a
need to provide some type of wear surface to the embossed
surface so that it can better serve as a floor covering.
Conseguently, the embossable surface, after embossing, is
fed around guide roll 26 to place the embossed surface in
a general horizontal plane with the embossed surface facing
upward. Means 28 will then provide a wear coating to the
embossed surface. The coating may be applied by a curtain
71;~
coater, a roll coater, spray means, or any other convenient
means which will provide a thin wear coating overlying the
embossed surface. U.S. Patent, 3,828,725 covers ~ curtain
coating method which can be used in the application of a
wet polyurethane coating to a moving embossed foam. The
sheet with the wear layer is then passed to means 30 which
will either fuse or cure the wear layer on the embossed foam
surface.
Since there is a need to register the embossing
pattern with a printed pattern on 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 longitu-
dinally of the sheet movement is maintained in the same manner
as set forth in U.S. Patent No. 3,655,312, Column 5, line 53,
to Column 6, line 43. The technique of U.S. Patent No.
3,698,634 and U.S. Patent No. 3,741,851 can be adopted herein
- for machine direction registr`y 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
"Registron u Dlvision 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
registration between the embossed pattern and the print~d
pattern, but such controls are not a part of the invention
herein since they are conventional in the art. The essence
of the invention herein is in the utilization of the back
wetting with or without a cooled back-up roll for the purpose
of cooling the back side of a web and its adjacent foam while
still permitting the embossable surface of the foam to be
10t~71Z
maintained at a temperature such that embossing can be carried
out in registry with a printed design on the top layer of the
foam. For foam webs having considerable thickness (.100-
.120 inches (.25 cm.-.31 cm.)) and which retain their internal
heat, it has been found that an additional back wetting
structure 10 is needed and will be positioned prior to the
conventional guider structure 4 in order to permit embossing
of these web~ without blistering. Should the material of U.S.
Patent No. 3,741,851, without its wear layer, be utilized
through the apparatus generally described above, and no back
wetting or cooling be carried out, it has been found that the
web will enter the embossing roll nip with a surface temperature
on the embossable surface of 220F. (104C.) and a temperature
on the back of the web, the non-embossed surface, of about
270F. (132C.). Under these conditions, the center of the
foam of the web will be measured at about 300F. (149C.)
and this is an ideal situation for blistering within the foam
layer. Blistering produces an unacceptable product. 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 or 24
herein, both the roll land and valley areas make contact and
emboss the web. This increased area of embossing is a capability
of the structure herein and is not possible in the structure
of U.S. Patent 3,741,851. Also, in the structure of U.S.
Patent No. 3,741,851, the embossing area can only be 25~
of the total sheet area, whereas in the embossing structure
herein, the embossing area can go to 80% to 90% of the total
sheet surface area. Normally, the embossing area covers 30%
to 90% of the total sheet surface area. In operation, the
embossing rolls, either roll 22 or 24, would be maintained
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cold at about 75F. (24C.) to 100~. (38C.) to freeze in
the desired pattern which is being embossed in the web. There
may be partial wrapping of roll 24 if necessary to achieve
the desired pattern effect.
The material described in U.S. Patent No. 3,741,851,
! with the wear coat eliminated, could come from the oven 18
of that patent and pass through appropriate guiding structures
and by back wetter 10 and directly to back-up roll 20 and
embossing roll 22, and can be embossed without any blistering
10, in the end product, with ~e~y good registration between the
embossed pattern and the printed pattern, and with embossing
carried out so that there is bottoming out of the embossing
roll against the embossed surface of the web. Cooling of
the back surface of the web prior to embossing directly
attributes to the lack of blistering and the ability to
carry out a "bottoming out" of the embossing roll while still
maintaining registration.
Even though this invention can provide for unique
embossed designs on wear layers composed of vinyl
formulations as described in U.S. Patent No. 3,741,851, the
embossing of additional materials is possible. ~or example,
a product can be made by placing the following plastisol on
a carrier web such as that disclosed in U.S. Patent No.
2,759,813. The plastisol used is prepared by thoroughly mixing
tbe following ingredients:
Ingredients Parts by We-ight
Poly(vinyl) chloride 100
Dioctyl phthalate (plasticizer) 49,55
Octyl epoxy tallate (stabilizer) 5,0
Titanium dioxide 3.6
Azodicarbonamide ~blowing agent) - 2.3
Talc 0.6
Zinc octoate (blowing agent activator) 1.95
This above plastisol is applied to the above-described
carrier which is a coated beater-saturated asbestos sheet
71;~
having a thickness of about 0.028 inches. The plastisol is
applied with a reverse roll coater to a wet thickness of 10 mils
(.03 cm.). The plastisol-coated backing is gelled in a hot
air oven for one minute to an exit temperature,of 270F.
(132C.).
The sheet is then cooled and a printed design is
placed thereon. The printed design may be of 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 thoroughly
mixing the following ingredients:
Ingr-edients 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 sheets 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.
At this point, the plastisol may be subjected
to further heat in a hot air oven for 1 minute to an exit
temperature of 375F. (191C.) to complete the decomposition
of the blowing agent in the gelled plastisol coat to convert
it to a foamed layer. It is also possible to eliminate
this second heating operation by passing the plastisol coated
backing through a hot air oven and almost completely decompose
71Z
the blowing agent prior to the printing operation. In these
circumstances, the hot air oven would be utilized for 1
minute to an exit temperature of 375F. (191C.) to produce
the fully foamed product which would then subsequently be
printed. Reheating for embossing can be done later just
prior to embossing.
After the printing on the gelled plastisol has been
carried out and this structure has passed through an oven
to complete the decomposition of the blowing agent to convert
the plastisol to a foam layer, embossing can be carried out.
The printed and foamed layer will leave the oven at -
about 300F. (149C.~. Coming from the oven, the above-
described composite sheet composed of a backing sheet, a
foam layer and a printed design thereon would constitute web 2
of the drawing. The web 2 would move past appropriate across-
machine guide structures towards back wetting structure 10.
The backing of the web 2 will be wetted and the evaporation
of the liquid therefrom will cool the backing to a temperature
substantially below that of the foam face of the web 2.
"Teflon " coated heated roll 16 (200F.-250F.) is provided
to engage the upper surface of the sheet and supply heat
thereto if needed and cause the sheet to partially wrap it-
self around back-up roll 20. The web passes on to back-up
roll 20 and embossing roll 22 to be embossed. The embossing
roll would be maintained at about 75F. (24C.) surface
temperature and the back-up 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 roll 22 and roll 20, will
have the top surface of the foam layer at about 250F. (121C.).
The back wetting will have cooled the temperature of the
backlng or carrier and the foam adjacent thereto to a
-- 10 --
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temperature of about 150F. to 200F. (66C. to 93C.). The
cold embossing rolls would immediately freeze the desired
embossed pattern into the foam at the time the embossing
is carried out. The thickness of the web described above
will be about 60 mils (.15 cm.). The embossing pattern on the
embossing roll will comprise 55~ to 60% of the total roll
surface and the depth of pattern on the roll is about 15 mils
(.04 cm.). Full embossing is carried out with both the
land areas and valley areas engaging the web surface.
Due to the spring back of the material, the end product has
an embossed depth of 15 mils (.04 cm.). The foam layer
will be compressed in the valley embossed areas and be un-
cQmpressed in the unembossed areas.
It has been found that with conventional poly(vinyl
chloride) foams of a thickness in excess of 80 mils (.2 cm.),
it may be desirable to move the web partially around the back-
up roll 20 and position the embossing roll at the point of
embossing roll 24. Under this set of circumstances, at the
time of embossing, the surface of the foam to be embossed
will be 200F.-230F. (93C.-110C.), while the back side of
the foam adjacent the carrier or backing will be about 125F.
to 150F. (52C. to 66C.). The wrapping of the web around
the cooled back-up roll 20 will provide this increased reduction
in the temperature of the back of the web as well as prevent
slippage of the web during machine direction registration
o the embossing roll to the printed pattern. The embossing
rolls will have considerable detail and will require the
roll 24 to be partially wrapped to achieve the desired
pattern effect. The partial wrap is accomplished by the
use of roll 26 which causes the web to partially wrap around
roll 24. In all cases, the embossing will be carried out in
register with the printed design on the foam.
1~)i 3~7~
There is now provided a product which is composed
of a backing and a foam layer which has embossing therein
in register with the design which was printed on the foam.
Such a product might be acceptable for use as a wall covering,
but certainly would not work satisfactorily as a floor covering
unless it has some type of wear layer applied thereover. The
web 2 now fully embossed will then pass by a coating apparatus
28 which will apply a wear layer to the embossed web 2 and
then the wet web will pass through heater 30 which will fuse
or cure the wear layer just applied. The wear layer used
may be any of-the conventional wear layer structures
which have been utilized in the floor covering art.
About the only limitation that exists relative to the wear
layer is that the fusion or curing temperature of the wear
layer must be low enough that the temperature utilized will
not cause destruction of the foam layer or relaxation of the
embossed pattern in the foam so that the embossed configuration
deteriorates. If the fusion or curing of the wear layer
is carried out under a circumstance where the total web is
heated, then the temperature of fusing or curing clearly
must be low enough so that deterioration of the foam does
not occur. If the curing or fusion of the wear layer is carried
out by a surface heating which is directed just to the wear
layer, then higher temperatures may be utilized. By higher
temperatures is meant temperatures which would normally be
expected to affect ~he foam. However, these higher temperatures
are only utilized for a short period of time and are applied
primarily to the wear coat and are not permitted to cause a
raising of the foam level temperature to a point where the
foam will be effected by the temperature. --
Example 1
Typical of a clear poly(vinyl chloride) wear layer
- 12 -
~01il8712
coating that can be utilized is:
Formula 1
Ingrèdients Parts by Weight
Poly(vinyl chloride) copolymer 100.00
Dioctyl phthalate (plasticizer) 60.00
Octyl epoxy tallate (stabilizer) 3.00
Barium cadmium zinc (stabilizer) 3.00
This wear layer composition is applied to a fully
embossed web 2, which is 0.060 inches (.15 cm.) in thickness,
by a conventional curtain coating apparatus 28 to a film
thickness of 0.006 inches (0.015 cm.). In this case, the cur-
tain coater head cavity described in U.S. Patent 3,828,725
t
does not contain, when used herein, the flow restricting device
due to the higher viscosity and solids levels of the above
plastisol wear layer formulation. The wet coating can be
applied in a continuous manner after the foam layer is embossed,
as is showr. in Fig. 1, whereby the wear layer is fused utiliz-
ing a hot air heater 30 which is directed towards the top
surface of the web 2. Typical fusing conditions require
hot air impingement for 1/2 minute with the air at 500F.
(260C.). Alternately, the embossed foam 2 can be cooled
by rolls 32, bypassing coater 28 and heater 30 and wound onto
spindle 34. At some future time, and possibly in another
location, the wear layer coating can be applied to the embossed
foam by a similar coating apparatus 28 and fused by similar
types of surface heaters 30. In the case of the clear poly
(vinyl chloride) wear layer applied in the manner as described
above, a resilient floor covering material is produced
which has a depth of embossing of 0.010 inches (.025 cm.)
after the wear layer is fused.
Example 2
Example 1 was repeated wherein a thin adhesive
coating of Formulation 2 below was applied to the 0.006 inch
- 13 -
1()~il~71Z
(0.015 cm.) fused plastisol wear layer of Example 1 and dried
with heater 30 using 140F. (60C.) air. In this case, a
fully embossed 0.080 inch (.203 cm.) foam was used in the
experiment.
Formula 2
.......
Ingredients Parts by Weight
Poly(vinyl chloride) solution grade 30.00
Xylene 21.00
Methyl ethyl ketone 48.64
Thio-tin (stabilizer) (Thermolite-31) 0.36
Onto this layer was applied a clear 2 mil (dry)
coating of a curable polyurethane utilizing the invention
described in U.S. Patent 3,828,725. The polyurethane coating
is a 62.5/37.5 xylene/resin solution containing catalyst.
The polyurethane coating can also be applied by employing
conventional airless spray equipment. Criticality does not
particularly rest in the method by which the wear layer coating
is applied. Heat is applied in the form of hot air impingement
utilizing heater 30 for a period of 3 minutes at 275F.
(149C.) air temperature. 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 surfacè and
eliminate the need for subsequent waxing by the user of the
floor.
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