Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR FORMING COLORED CELLULOSIC MATERIALS
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority from U.S. Provisional Patent Application
Serial
No. 60/437,978, which was filed on January 3, 2003.
FIELD OF THE INVENTION
The present invention relates to dyeing processes, and more specifically to
methods
for dyeing paper and other cellulosic materials.
BACKGROUND OF THE INVENTION
On many occasions, it is desired to utilize a cellulosic material product,
such as paper,
linerboard, paperboard and/or cardboard, that has a specific color for a
particular use. For
example, when decorating for a special occasion, streamers of various colors
are often
utilized to provide a festive appearance to the location at which the occasion
is being
celebrated.
In order to form products formed of a cellulosic material and having a desired
color,
many different dying techniques have been utilized. While many of these dyeing
techniques
provided adequate color to the cellulosic material being dyed when finished, a
significant
problem remained in that the dye often times washed out or bled from the
cellulosic material
either during the dying process or when the material was contacted by a liquid
or simply
rubbed against another surface.
In order to attempt to overcome the bleeding problem, a number of different
dyeing
compositions and methods were developed. For example, Reinhardt U.S. Patent
No.
4,502,807 discloses a dye stuff that incorporates a thickening mixture
including both a
synthetic thickening agent and a polysaccharide. The presence of the
thickening mixture
with these components enhanced the ability of the dye to remain in the proper
location on the
textile to which the dye was applied. Further, Panto et al. U.S. Patent No.
4,398,915
discloses a method of preparing bleed resistant colored cellulosics utilizing
a colored particle
such as a dye/starch complex formed as a reaction product of a starch with a
reactive dye
compound and a chemical cross-linking agent. Further, Kiesewetter et al. U.5.
Patent No.
5,384,585 discloses the printing of textiles using a dye composition including
a reactive dye
and a methylcarboxymethyl cellulose as a thickener.
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However, these techniques, while initially providing the paper, linerboard,
paperboard or cardboard product with the desired color and an increased level
of resistance to
bleed or color migration, do not achieve the desired level of resistance to
the removal of the
colored dye from the product. As a result, colored products are still produced
in which the
S color bleeds from the product, or in which the color can be removed from the
product by
wetting and/or rubbing a colored surface of the product.
Therefore, it is desirable to develop a method for dying or otherwise coloring
a
cellulosic product in which the dye or color added to the product is highly
resistant to
removal from the product.
SUMMARY OF THE INVENTION
The present invention is an improved method for coloring cellulosic material
products
in which the color is applied to the product such that the color does not
bleed and/or cannot
be easily removed from the product. The method or process involves two
separate steps
which achieve the desired result of applying the color or dye to the product
such that the dye
is highly resistant to removal.
The first step in the method involves applying the colorant to the cellulosic
substrate
in any of a number of well-known application methods. The colorant applied to
the
cellulosic substrate is formed as an aqueous solution of a thickener, a dye,
and water. The
thickener can be virtually any suitable material used to thicken and stabilize
a dye
composition, as will be described. Also, a wide range of dyes can also be used
in forming
the colorant, as will be described. The colorant formed by the dye, thickener
and water can
be any suitable colorant used in the printing or dyeing of cellulosic
materials and/or textiles
that is able to be applied to the substrate in any of a number of conventional
dye application
methods and that resists any spreading or migration on the surface of the
substrate after
application.
In the second step, an overcoat material is applied to the substrate over the
colorant in
order to form a protective film over the colorant on the cellulosic material
and increase the
resistance to removal of the colorant from the substrate. The overcoat
material essentially
provides a barrier between the colorant and any liquid and/or surface that
prevents contact
with the colorant, thereby maintaining the colorant on the substrate.
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DETAILED DESCRIPTION OF THE INVENTION
The present invention is an improved method for applying a colorant to a
cellulosic
substrate in a two-step process which greatly improves the resistance to
removal of the
colorant on the substrate. While the method is applicable to the application
of a colorant or
dye to virtually any number of different substrate types, some of the
preferred substrates
which are capable of being utilized in this method include cellulosic
substrates such as white-
top linerboard, linerboard, and paper, among others.
In a particularly preferred embodiment of the method of the invention, the
substrate is
a white-top linerboard that is defined as a two-ply cellulosic web that has a
basis weight of
20 pounds to 90 pounds per 1000 square feet. The base ply is comprised of a
virgin material,
recycled material or any combination thereof. The top ply of the cellulosic
web is comprised
of bleached or de-inked cellulosic fiber with a GE brightness of at least 60.
Another preferred substrate is linerboard which is defined as a two-ply
cellulosic web
that has a basis weight of 20 pounds to 90 pounds per 1000 square feet. The
base ply is
comprised of virgin material, recycled material, or any combination thereof.
The top ply of
the cellulosic web is comprised of recycled or virgin cellulosic fiber.
Still another preferred substrate is paper which is defined as a cellulosic
web that has
a basis weight of 20 pounds to 160 pounds per 3000 square feet. The web may
also include
filler materials including, but not limited to, clay, calcium carbonate,
titanium dioxide, and/or
sizing agents.
When applying the colorant to the desired substrate, in the first step, the
colorant is
added to the substrate in a suitable printing or dyeing process, such as
either a conventional
off paper machine application, or an on-paper machine application, including
via a size press
or water box. Some suitable off paper machine application processes can
include, but are not
limited to, flexographic application, rod application, and/or processes
utilizing air-knife
waters.
The colorant is most preferably comprised of a solution of a thickener, the
pigment,
and/or dye stuff, and water in the following proportions:
1-30% by weight dye stuff and/or pigment;
1-15% by weight a first thickener;
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1-5% of an optional second thickener (in lieu of or in addition to the first
thickener)
for rheology modification; and
the balance, water.
With particular regard to the dye stuff or pigment, the dye stuff for the
purposes of
this disclosure is defined as any compound within the class of either basic
dyes or anionic
direct or fiber reactive dyes, or a pigment that can impart a color to a
cellulosic material such
as a dry coloring matter, usually an insoluble powder to be mixed with water,
oil or another
base to produce paint in similar products. More particularly, in one aspect of
the present
invention, there is thus provided a colorant comprising, as a direct dye, a
compound
represented by the following formula (1):
w x
wherein, ring A represents a benzene ring which may have a substituent or may
further be
cyclocondensed with another aromatic ring;
B represents an aryl group which may have a substituent or may be coupled with
RZ
to form a heterocyclic structure which will be described later, or a
heterocyclic
group which may have a substituent or may be coupled with RZ to form a
heterocyclic structure which will be described later,
D represents a nitrogen atom or a group CR4 (in which R4 represents a hydrogen
atom
or a C ~ _6 alkyl group);
E represents a group NRS, CR6 R' or CR6=CRS (in which RS represents a C1_6
alkyl
group which may have a substituent, a CZ_6 alkenyl group which may have a
substituent or an aryl group which may have a substituent, or forms, when
taken
together with R2, a ring which will be described later, and R6 and R' each
independently represents a hydrogen atom or a C~_6 alkyl group), an oxygen
atom
or a sulfur atom;
R~ represents a C,_6 alkyl group which may have a substituent, a Cz_6 alkenyl
group
which may have a substituent or an aryl group which may have a substituent;
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RZ represents a divalent group bonded to B or forms, when taken together with
R3 or
R5, a ring which will be described later,
R3 forms, when taken together with R2, a ring which will be described later;
n stands for 0 or 1, with the proviso that when n=0, RZ and R5, when taken
together
with N-CC, form a 5- to 7-membered nitrogen-containing heterocyclic
structure which may have a substituent, or RZ is bonded to B, thereby forming
a 6-
or 7-membered heterocyclic structure which may have a substituent and may
contain a hetero atom other than D and when n=1, Rz and R3, when taken
together
with C=D-N, form a 5- to 7-membered nitrogen-containing heterocyclic structure
which may have a substituent, and
X- represents an anion.
In the formula ( 1 ), examples of the substituent which the ring A may have
include
alkyl groups, aryl groups, alkoxy groups, amino groups, hydroxy groups, cyano
groups, nitro
groups and halogen atoms, more specifically, methyl group, ethyl group,
methoxy group,
ethoxy group, chlorine atom and bromine atoms. Examples of the aromatic ring
with which
the ring A may be cyclocondensed include a benzene ring.
Examples of the aryl group represented by B include phenyl, 1-naphthyl and 2-
naphthyl groups, while those of the heterocyclic group include 2-benzthiazolyl
and 3-indolyl
groups, each of which may be substituted with a chlorine atom, bromine atom,
nitro group,
cyano group, C~_4 alkyl group, phenyl group, benzyl group, Cl~ alkoxy group,
hydroxy
group, phenoxy group, benzyloxy group, Cl_4 alkylsulfonyl group,
phenylsulfonyl group,
benzylsulfonyl group, aminocarbonyl group, mono- or di-(CI_4
alkyl)aminocarbonyl group,
aminosulfonyl group, C,_4 alkylcarbonyl group, C1_4 alkylcarbonylamino group,
benzoylamino group, phenylazo group, and a group NRg R9 (in which R8 and R9
each
independently represents a hydrogen atom, C,_4 alkyl group, aryl group,
aralkyl group,
unsubstituted or mono- or di-(C 1 _4 alkyl)-substituted amino(C ~ ~ alkyl)
group, amino(C 1 ~
alkyl) group substituted by a group of the formula (1) from which one hydrogen
atom has
been removed, or (C1_4 alkoxy) (C~_4 alkyl)amino group). The number of these
substituents is
1 to 3. The cycle-constituting atom may be coupled with the above-exemplified
substituent to
form another cyclic structure.
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Examples of the C1_6 alkyl group represented by R4 in the case where D
represents a
group CR4 or by R6 or R' in the case where E represents a group CR6 R' or
CR6=CRS include
methyl, ethyl, propyl, isopropyl and cyclohexyl groups. Preferred examples of
R4, R6 or R'
include hydrogen atom and methyl groups.
S Examples of the C, _6 alkyl group represented by RS in the case where E
represents a
group NRS include methyl, ethyl, propyl, isopropyl and cyclohexyl groups;
those of the CZ_6
alkenyl group include ethenyl and propenyl groups; and those of the aryl
include phenyl and
naphthyl groups, each of which may be substituted with an aryl, alkoxy, amino,
hydroxy or
cyano group, or a halogen atom.
Examples of the C~ _6 alkyl group represented by R' include methyl, ethyl,
propyl,
isopropyl and cyclohexyl groups, those of the CZ_6 alkenyl group include
ethenyl and
propenyl groups, and those of the aryl group include phenyl and naphthyl
groups, of which
the alkyl group is preferred as R'. Examples of the group which may be a
substituent for
them include aryl groups, cyano group, halogen atoms, hydroxy group, C,~
alkoxy groups,
NR'° R" (in which R'° and R" each independently represents a
hydrogen atom, C,_4 alkyl
group, aryl group, aralkyl group, unsubstituted or mono- or di(CI_4
alkyl)substituted
amino(Cm alkyl) group, or (C,~ alkoxy) (C,~ alkyl)amino group) and a group of
the formula
( 1 ) from which one hydrogen atom has been removed.
Examples of the RS -R2 or RZ -R3 in the case where a 5- to 7-membered nitrogen-
containing heterocyclic structure which may have a substituent is formed by RZ
and RS when
they are taken together with N--C-C at n=0, or by RZ and R3 when taken
together with
C=D N at n=1, include groups represented by - (CR'2 R'3)m - (in which R'2 and
R'3
each independently represents a C1_4 alkyl group and m stands for an integer
of 2 to 4).
Examples of the divalent group, as R2, bonded to B in the case where a 6- or 7-
membered heterocyclic structure which may have a substituent and may have a
hetero atom
other than D is formed by bonding of Rz to B when n=0 include groups -CH=N-
and -
CO-O-.
Examples of the anion represented by X- include chloride ions, bromide ions,
iodide
ions, trichlorozincic acid ions, tetrachlorozincic acid ions, sulfuric acid
ions, hydrosulfuric
acid ions, methyl sulfate ions, phosphoric acid ions, formic acid ions and
acetic acid ions.
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The thickener utilized in the formation of the colorant may be selected from
both
synthetic and natural thickeners. More specifically, the composition of the
thickeners used in
the formation of the colorant can vary between a proportion of 0% for the
synthetic thickener
and 100% by weight for the natural thickener, and vice versa, depending upon
the response
S of the products used to the disburse dye stuffs used. Mixtures which are
more preferable
regarding the dispersion stability of the dye stuffs contain between 1 to 30%
by weight of the
natural thickeners, and most preferably between 1 to 15%, and 1 to 10% by
weight of the
synthetic thickeners, and most preferably between 1 to 5%.
The synthetic thickenings are preferably carboxyl containing synthetic
thickenings
and the natural thickenings are based on polysaccharides in preferred
embodiments of the
invention. Examples of suitable carboxyl-containing synthetic thickenings
which can be
used according to the invention are aqueous solutions or gel-forming
dispersions of
polymerized low molecular weight monoethylenically or polyethylenically
unsaturated
monocarboxylic or dicarboxylic acids, such as polyacrylic acid and its
homologs, for
example products of polymerizing methacrylic acid or crytonic acid, and
polymers of
carboxyalkylderivatives, such as idaconic or teraconic acid, similarly aqueous
solutions of or
dispersions of polymerized malefic acid or its anhydride and fumaric acid and
of its
homologs, such as, for example, citriconic acid or mesaconic acid, further of
copolymers of
olefins, for example, ethylene, propylene or butadiene or of
lowelalkylacrylates, optionally
substituted acrylamids, vinyl alcohols, vinyl ethers, vinyl esthers, vinyl
chloride, vinyl edene
chloride, styrene, acrylonitrile, and analogous alkyl compounds and the above-
mentioned
monomers. These examples also include the reaction products of the polymers
and
copolymers described, with polyhydric alcohols and amines, or amino alcohols,
and
combinations of highly polymerized products with less highly polymerized
products.
The polysaccharides used preferably as the natural thickeners according to the
invention embrace optionally degraded and/or etherified natural products such
as high
molecular weight carob bean flour or guar flour and starch or cellulose
ethers. In a
particularly preferred embodiment, the thickener is formed only of material
thickeners
including carboxymethyl cellulose and starch.
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After the colorant has been formed and applied to the selected surface of the
cellulosic substrate, the substrate may be slightly dried to allow for a
limited set of the
colorant on the substrate and to prevent the smearing of the colorant from the
substrate.
Further, the colorant application rate can vary depending upon the color shade
depth desired
on the surface of the substrate. For example, in a preferred embodiment the
application rate
of the colorant is 1-40% by weight of the substrate and more preferably 1-15%
by weight of
the substrate.
After the application of the colorant to the substrate, in the second step of
the method,
a film of a suitable overcoat material is applied as an overcoat to the
colored cellulosic
substrate to impart the requisite wet and dry rub fastness for the colorant
reacted onto the
substrate. The application methods for the overcoat material are similar to
printing or dyeing
methods used for the application of the colorant and can include, but are not
limited to, off
paper machine application methods, such as flexographic, rod, and/or knife air
coaters.
Further, with regard to the overcoat material the material is a natural or
synthetic rubber
formed from various compounds, including but not limited to polybutadiene,
polyisobutylenes, polystyrenes, polyacrylates and polyurethanes. In a
preferred embodiment
the material is a latex, which for the purposes of this invention is defined
as any material
within the class of modified styrene butadiene-based polymers or modified
styrene acrylate
polymers with provisions for changes in polymer T~ value or polymer
combination. More
preferably, the overcoat may be a 50% solids latex product which is used as a
"varnish" layer
over the substrate, to provide wet and dry rub fastness and to add a gloss or
matte finish to
the substrate. Further, the overcoat application rate to the substrate can
vary depending upon
the level of fastness and the gloss level required for the substrate, with
greater fastness
properties and higher gloss achieved with a higher overcoat application rate.
More
specifically, in a preferred embodiment the application rate for the overcoat
will be within a
range of 1 % to 25% by weight of the substrate and more preferably between 1 %
and 5% by
weight of the substrate.
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Colored linerboard produced as described may be used in any corrugated
application, e.g. point of purchase displays or corrugated containers.
Application of the
overcoat material enhances printability of the material and ensures that the
print medial does
not bleed into the underlying dyed substrate
Various alternatives are contemplated as being within the scope of the
following
claims particularly pointing out and distinctly claiming the subject matter
regarded as the
invention.
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