Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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POLYMERIC SHEET
This invention relates to a polymeric sheet having an
inco~patible ink permanently bonded thereto. Specifically,
the inver.tion includes a floor covering having a
lithographic ink or electrographic toner bonded to a primer
which is bonded to the floor covering.
The term incompatible refers to the inability of the
ink system to directly and permanently ~ond to a polymeric
sheet only through solvent or carrier evaporation. An
example of a compatible system would be the case in a
typical rotogravure vinyl ink system when it is printed onto
a rigid polyvinyl chloride (PVC) film.
To create a high quality colored (nearly photographic)
decorative design on surfaces of tile products, the
rotogravure printing technique is the state of the art
technique most often selected. While this printing
technique is relatively easy to operate, it has some
drawbacks. It is capital intensive, in that new designs
require new printing cylinders prior to printing. It
requires long lead times to prepare the cylinders for
printing. In addition, this technique is geared to high
volume printing and usually on relatively thin webs, i.e.,
0.04 to 0.25 mm in thickness. Clean up of the printing
cylinders is more time consuming than most of the actual
print run, resulting in potentially high labor costs
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2~57~17
associated wlth the actual ~ob, and a natural tendency to
make the runs longer than are necessary.
In order to provide a lower cost, short run, and
faster turnaround printing system, a departure was made from
the current rotogravure printing system. Two hi~h quallty
four color printing techniques, lithographic and
e'ectrographic printing, offered these opportunities.
However, it became obvious that the conventional ink systems
used in these techniques were not compatible with the
polymeric films that are used in the manufacture of
polymeric sheet products.
In the lithographic process, which can be a sheet-fed
printing process, the inks cure by oxidation. After
printing on riqid polyvinyl chloride (PVC) film, the ink
will still be soft after drying. The image will readily
smud~e and result in an unacceptable print. This actually
occurs to some extent in normal conventional lithographic
printing of paper today if one were to examine a four color
process-printed page in a magazine or on an advertising
poster. It has been found that when a
conventional-lithographic printed PVC 'ilm is bonded
conventionally to a floor tile base, the ink layer will not
impart the proper adhesion requirements after lamination for
an adequately performing product.
The same is true of the electro~raphic printing systems
where the colored images are formed on the film using both
liquid and dry toners. Even, when the electrographic
printing (e.g., from a color copying machine) is done on
specially treated papers and films, the ink layer which is
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actually to act 2S the adhesive layer between the clear
protective ilm and base or substrate after lamination is
not strong enough to prevent delamination in use.
The present invention provides a polymeric sheet having
an incompatible ink permanently bonded thereto, the ink
being bonded to the polymeric sheet by a first primer layer,
the primer layer being interposed between the polymeric
sheet and the ink, the primer being compatible with the
polymeric sheet, and wherein, during application of the
primer, the primer comprises a solvent selected from the
group consisting of benzene derivatives, ketones, acetates,
nitroparaffins, pyrrolidones, piperidones and acetamides.
In an organic solvent based primer system, the solvent
system preferably includes toluene, methyl isobutyl ketone,
methyl ethyl ketone, propyl acetate or isopropyl acetate.
The binding materials of the same system may include resin
such as a polyvinyl resin, acrylic resin, polyurethane resin
or polyester resin, and optionally a pigment. To deter
smudging of the ink, ths primer should have a glass
transition temperature (Tg) of at least about 60C, and
preferably at least about 100C.
An aqueous based primer system preferably includes an
aqueous colloidal dispersion of one of the above-listed
polymers. Also, the aqueous primers include a solvent or
film former. The solvents or film formers preferably
include pyrrolidones, piperidones and acetmides.
~ f the polymeric sheet is used in a floor covering,
performance of the floor covering and adhesion of the ink is
improved by encapsulating the ink in the primer. The ink
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may be interposed between two layers of primer. In a
preferred embodiment using a clear film which is
backprinted, the primer layer, interposed between the ink
and pol~meric sheet, is clear and the other primer layer may
be white or colored. Other options include any combination
of clear and colo-ed films and primers.
The floor covering preferably includes a polymeric wear
layer such as clear polyvinyl, acrylic, polyurethane or
polyester. The wear layer may be crosslinked.
A p-imer containing certain resins and solvents, in
either a solution or dispersion form (if water is the
vehicle of preferred choice), is interposed between the
polymeric sneet and incompatible ink or encapsulates the
ir.compatible ink system and bonds it to the polymeric film.
After solvent removal from the primer, permanent adhesion is
achieved between the film and ink layer in the form of a
scratch resistant image. Through additional post lamination
steps the encapsulated ink layer can be directly bonded to
other substrates to result in decorative products such as
floor, wall, ard ceiling tile products. This i9 achieved by
conventional lamination with heat and pressure.
The primer described in this invention consists of an
orqanic resin binder and an organic solvent or blend of
solvents. In the vinyl polymer family, the organic resins
can comprise polyvinyl chloride, polyvinyl acetate,
carboxyl-modified vinyl chloride/vinyl acetate copolymers
hydroxy-modified vinyl chloridetvinyl acetate copolymers, a
blend of vinyl chloride/vinyl acetate/maleic acid, and vinyl
chloride/vinyl acetate/hydroxy alkyl acrylate. In addition,
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orsanic resins that will work include polymers and
copolymers of acrylic and methacrylic acids and their
esters, polyes~ers, polyurethanes, and vinyl butyral.
The solvents of this invention do nGt interact in any
way chemically or physically with the ink system to cause
adverse effects such as color bleed, image distortion, and
milkiness in the polymeric film prior to or after
lamination. The solvents may include methyl isobutyl ketone
(MIBK), methyl ethyl ketone (MEK), isopropyl acetate,
n-propyl acetate, propylene glycol monome~hyl ether acetate,
and 1-nitropropane. Singular solvents can be used in the
application of the encapsulating medium. However, the
solvent system sometimes needs to be modified in practice in
order to achieve optimum balance between the application
metnod of the primer, penetration of these materials into
the film and zround the ink layers, and drying.
The film may come from the polyvinyl, acrylic,
polyester, and polyurethane families or copolymers thereof.
The polymeric 'ilm is usually a clear film which is
backprinted. ~ypically, for a decorative surface product
fcr floors, walls and furniture, the film is a clear rigid
PVC film which becomes the wear surface. Also, the film may
consist o' two layers in which one of the layers is
crosslinked. ~or ceiling products, the fiim may be white,
both primer layers are clear, and the printed image would be
encapsulated and permanently bonded to the white film.
The primer resin should be compatible with the
polymeric sheet. Typically polyvinyl, acrylic, polyurethane
and polyester primer resins may be used with either PVC or
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acrylic sheets~ Polyurethane and polyester primer resins
may be used with polyurethane and polyester sheets.
While using primer resins of the same family as the
polymeric sheet (e.g., a polyvinyl primer on a PVC sheet)
will insure that the primer and sheet are compatible, as
demonstrated by Examples 1 and 2, infra, the primer and
sheet are not identical. The polymers have different
molecular wei~hts, glass transition temperatures and
moieties attached to the backbone. Further, the primers are
dissolved or dispersed in a solvent, whereas the sheet is
not.
The ink systems which are used in this invention and
are incompatibie with the po~ymeric film include
lithographic inks (conventional drying and W cure) and
electrographic toners. They may be classified as either dry
or wet in their i~aging form, i.e., the printinq process.
Neither ink system without the use of this invention will
adhere by itself to a rigid PVC film after evaporation of
zheir respective carriers. In addition to providing an
excellent color gamut, they must be heat and light stable as
weli as resistant to alkali.
The base may be another film, a primed paper or board
containing cellulosic and/or man-made fibers, a filled
thermoplastic tile composition, a tile composition
containing a filled (white) latex topcoat, and other base
structures as well.
The use of these two imaqing systems in making
decorative surface covering products necessarily requires
that the colored pigment system adheres well to the
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protective wear layer as well as the base structure. In
floor and wall products, the base structure often is
composed of plasticlzed polyvinyl chloride resins and
inorganic fillers (such as limestone and silica). The wear
layer can be a clear polymeric film such as PVC, polyester,
acrylic, polyurethane, or combinations thereof. When the
inks cf these imaging systems are printed directly onto
tAese types of films, and subsequently laminated onto a PVC
floor base structure using conventional flooring laminating
conditions, the lamination is not successful. The adhesion
of the pisment/resins used in both of these imaging systems
between itself, the wear layer, and base, is unacceptable.
Tn order to guarantee the permanent adhesion required
for performance, a primer is applied first to the polymeric
film and then to the back of the decorated image. Thus, the
image becomes encapsulated between the primers on the
polymeric film. It remains stable while it is either in a
stack of films or wound up within a roll of film. It will
not block in either case and can be reactivated at any time
the correct lamination conditions are present.
In the second preferred embodiment, the resin sy~tem
used in the two primer layers will crosslink at temperatures
typically at 80C to 140C to further enhance smudge
resistance, e.g., improve resistance to dot distortion.
This is especially valuable during subsequent operations
where heat and pressure may otherwise distort the image.
The primer in an aqueous based system preferably
includes an aqueous colloidal dispersion of the polymer
resins identified with respect to the organic solution
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primers above. Pre~erably the resins lnclude acrylics,
urethanes and polyvinyl acetates. Examples of the
dispersion resins include S 575, a polyvinyl acetate
dispersion (Armstrong World Industries); Tredfast 108, an
acrylic dispersion (Tetrabond PLC); Permuthane UE-40-570,
Permuthane UE-41-510 and Permuthane UE-41-512, urethane
dispersions (Permuthane Ccatings); Aquathane 60, a urethane
dispersion ~Peerless Emulsions); NeoRez XR-9409 and NeoRez
XR-9679, urethane dispersions (ICI Resins); and combinations
thereof.
The preferred dispersion has about 30~ to 45% solids
and an organic solvent. The preferred solvents which may be
used to improve the performance of the dispersed resins
include about 5% to about 15% by weight of N-methyl-
2-pyrrolidone solvent and about 0.5% to about 2.0% by weight
of N,N-diethylethanamine. Other solvents include N-methyl
piperidone and N,N-dimethyl acetamide.
Optional surfactants include an ethylene glycolJethyl
alcohol mixture such as Permuthane KM-10-1610 (Permuthane
Coatings). Such surfactants may be added up to 2% or as
needed.
The aqueous based primer also preferably includes a
crosslinking catalyst to enhance smudge resistance. The
catalysts include isocyanate, e.g., KM-10-1880 ~Permuthane
Coatlngs); carbodimide, e.g., KM-10-1869 (Permuthane
Coatings); aziridine, e.g., KM-10-1703 (Permuthane
Coatings); and hexamethoxylated melamine resins, e.g.,
Resimene R475 (Monsanto).
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Example l - Lithoqraphic_printinq system
A 0.5 mm thick clear rigid PVC film in sheet form was
gravure-coated with a clear primer made according to Formula
1, below.
Formula 1
20% by weight VAGH, a hydroxy-modified polyvinyl
chloride/vinyl acetate copolymer (Union Carbide Corp.)
80% by weight methyl isobutyl ketone
The coating was done with a 150 line overall knurl
cylinder with two passes through the coater. The coating
was air-dried to remove the carrier solvent. The amount of
primer applied was 3-4 grams/square meter dry. The coating
was p_inted with conventional air-dry lithographic inks (R.
W. Rexford Company). The inks were printed onto the dry
clear primer according to the following sequence: black,
cyan, magenta, and yellow. The design was a four color
process print representing a ceramic floor tile
configuration. After overniqht drying, the white primer of
Formula 2 below was applied over the dried lithographic inks
at the dry weight rate of 7-9 grams/square meter and
zir-dried.
Formula 2
20% by weight TiO2 pigment
80% by weight Formula l
The back-printed 0.5 mm thick clear rigid PVC sheet was
then post-laminated to a limestone-filled tile base
formulation to make a floor tile product. The conditions of
lamination in a two-stage press were as follows: 163C, 20
seconds, 100 psi for heating, and 38C, 20 seconds, 100 psi
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for cooling. By placing different texturing means against
the unprinted side of the film, various textural surface
fea~ures were imparted to the face of the product during the
lamination operation. A smooth and overall finely textured
surface having depth of 0.025 mm was produced as well as a
more deeply embossed-in-register product where the depths
were measured as much as 0.38 to 0.635 mm in depth.
Adhesion between the 0.5 mm wear layer film and the floor
tile base was excellent and found to be better than the
adhesion when roSogravure inks are used as the ink layer.
Exam~le 2 - Electroaraphic Printin~ SYstem
The same primer Formula 1 was applied to a 0.075 mm
clear rigid PVC film. In this case, the primer was applied
by a knife blade coater and air-dried. The same application
rate was applied as in Example 1.
To the dried surface was applied colored llquid toners
(Hilord Chemical Corporation). The toners that were applied
seguentially were cyan, magenta, and yellow. The toners
were applied using a modified electro~raphic imaging and
developing system. The electrostatic imaging was provided
by an ionographic deposition technique. After evaporation
of toner carrier, another thickness of Formula 1 was applied
and dried in the same manner. The post lamination and
texturing steps of Example 1 were used with a filled PVC
tile base formulation to make a conventional floor tile
product. The resulting PVC surface contained an embossing
texture that was 0.15 to 0.25 mm deep and the adheslon
between the protective film, toned image, and the tile base
was permanent.
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Example 3 - Hi~her Tg Primer
While the above inks were permanently bonded to the
polymeric sheet, they did have a tendency to distort in the
post laminating and embossing steps. This tendency to
distort was reduced by increasing the Tg of the primer resin
from the 68C of Examples 1 and 2 to 105C by substituting a
methyl methacrylate polymer, Acryloid A-21 (Rohm and Haas)
for the VAGH of Formula 1 and a solvent comprising methyl
ethyl ketone/isopropyl acetate/propyl acetate in a ratio of
1:1:1 for the MIBK of Formula 1.
ExamPle 4 - Aqueous Based Litho~raPhic Svstem
A 0.5 mm thick clear rigid PVC film in sheet form was
blade coated with a dispersion consisting of Permuthane
UE-40-570 having a solids content of 33~ by weight. The
water based dispersion was applied at 0.001 inch wet
thickness by hand drawdown to a thickness of 0.025 mm. The
amount of coating applied was 3-4 grams/square meter dry.
The coating was then printed via a hand rubber roller
with a conventional air dry lithographic ink (R. W. Rexford
Company). After drying overnight, the Permuthane UE-40-570
was applied over the dried lithographic inks at the dry
weight rate of 3-4 grams/square meter and post-laminated to
a limestone-filled tile base formulation to make a floor
tile product using the same technique as described in
Example 1. Adheslon between the O.S mm wear layer film and
the floor tile base was excellent.
Though the inventors do not wish to be limited to the
following explanation, they believe the improved adhesion
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results from the solvents of the primer diffusing into the
lithograp~,ic ink layers or electrographic toner layers
carryin~ the VAGH or A-21 resin with it. Then when the
layers are laminated, the resins in the ink fuse with the
resins in the primer and polymeric sheet.
The preferred application rate of the clear backcoated
primer layer is three to four grams/square meter dry.
However, the application rate could be as low as two
grams/square meter dry and obtain adequate adhesion. The
upper limit to the application rate depends merely on the
cost of the applied primer.
For use in floor coverings, the preferred application
rate of the white primer which is interposed between the
base sheat and ink is seven to nine grams/square meter dry.
However, the application rate could be as low as about six
grams/square meter dry, particularly if there are open areas
in the ink layer. The upper limit to the application rate
depends merely on the cost of the applied primer.
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