Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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L26-41 BLEED RESISTANT COLORED CELLULOSICS
rE:ve AND THE METHOD OF THEIR PREPARATION
BACKGROUND OF THE INVENTION
Field of the Invention
S The invention relates to the coloring of
cellulosics, inclusive of color printing techniques, and
more particularly relates to the coloring of cellulosics
with chemically reactive colorants to obtain bleed
resistant, colored, cellulosic articles.
. Brief Description of the Prior Art
The U.S. Patents 1,732,540; 1,805,013; 1,863,813;
1,871,647; and 1,871,769 are representative of descriptions
of prior art methods and practices for preparing so-called
color fast, colored cellulosic articles. In spite of the
known art for preparing colored cellulosic articles, there
is a considerable amount of commercially available articles
such as crepe paper, colored with dyes, that "bleed" when
: put into contact with water. By "bleeding" we mean that the
i colcr leaches out of the papers with water and may stain
whatever the wet paper comes in contact with. This effect
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is considered undesirable for many uses of crepe paperO
Apparently, the known prior art methods OI preparing color
fast dyed cellulosics have not been found practical,
sufficient or efficient for present day practices and needs.
Prior to our invention, a class of dyes (reactive dyes
for cellulosics) were known, which react with free hydroxvl
groups on cellulosic fibers to cause a coloring thereof.
However, the fiber must be free of contaminants, such as
starch, which would also react with the dye to form colored
1 insoluble particles on the fiber surface. These color
particles will subsequently wash off the fiber surface and
represent a waste of dye component. ~nother disadvantage is
found in the long reaction times needed to affect
coloration, i.e.; 20 to 30 minutes at elevated temperatures.
In another way, to use such dyes (to dve paper for example),
this class of reactive dye may be added to paper pulp in the
beater stage to permit reaction with the cellulose over a
prolonged period of time. The dyed pulp is then made into a
paper sheet. The resulting colored pa?er is color fast
~o (bleed resistant). The disadvantage o. this approach is
that a considerable amount of a given colored paper has to
~e made at one time (for economic reasors), and thus an
inventory must be maintained until demand depletes it. This
is a costly procedure.
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!~ By the method of this invention the reactive dyes are
first reacted with an organic polymer such as starch and the
resultin~ dye-starch ~colorant) particles are then used to
' impregnate preformed cellulosic articles such as crepe
paper. A cross-linking agent is then used to chemically
crosslink the dye-starch colorant particles to the crepe
paper. The result is a colored crepe paper sheet which
resists "bleeding" when placed in contact with water. There
is an efficiency in the amount of dye effectively coupled to
the cellulosic. The method of the invention is economical
and may be used in a conventional plant for commercial
coloration, without purchasing new equipment or modifying
that already in existence. Reaciion times required are
relativelv short, an unexpected advantage. The method of
the invention may also be carried out rapidly at relatively
low temperatures. Thus there are operating and economic
advantages. The coloring approach described above may be
used on a wide variety of woven anc non-woven disposable
cellulosic items where non~bleeding is a useful factor (for
eY.ample tissue paper, towelling, crepe paper, rayon sheets
and the like).
Our observations made while coloring crepe paper
indicated that the colorant dispersions used in the method
of the invention can be used for printing on sur~aces of
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cellulosic articles. Prior to the invention, a considerable
amount of colox printing on low cost substrates was
accomplished with either resin bonded pigments or solvent
'~ based inks. Both of these systems operate on a common
principle, that is, attachment of the colorant to a
substrate using a binder. Resin bonded systems are
comprised OI hi~hly dispersed water insoluble pigments in
water based emulsions. An acrylic emulsion is most commonly
, used in such systems. Preparation of the print paste
,; involves addition of suitable thickeners to achieve good
definition of the print, then drying to coalesce and adhere
the pigment particles to the substrate. Solvent based
systems are compris~d of solvated dyes and lacquers.
Preparation of the print paste involves addition of suitable
~ thickeners to achieve good definition of print, then drying
to evaporate the solvent and permit the lacquer to hold the
colorant on the substrate. Both of ~he above described
prior art systems are expensive. For the printing OI low
cost items such as non-wovens,paper, paperboard, gift
wrapping paper, textiles or o,her disposable items, the
method of our invention is advantageous since it adds little
to the overall cost of manufacture. The method of the
invention is not limited however to the coloring or printing
of low cost disposable cellulosics but may be used to color
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even more expensive articles such as textile fabrics
including woven, non-woven, knitted, pile and velvet
fabrics, ~ebs and yarns. By the method of the invention the
printing of cotton fabrics is particularly advantageous.
For example, the cotton fabric need not of necessity be
pre-washed to remove starch contaminants as described above.
By the method of our invention a particular class of
; dyes referred to as "reactive dyes for cellulosics", which
- will react with starch or other organic polymers containing
hydroxyl groups, are used to form insoluble colorant
; particles which may be used as a coloring or a printing
medium. Due to the nature of the dyes' reactivity with
starch, it has been found that upward adjustment of pH will
cause an increase in viscosity. This eliminates the need
for thickeners to achieve good definition of the print. A
cross-linking agent is used to crosslink the dye-starch
(colorant) particles to the cellulosic surface and render
the printing "non-bleeding". The advantages are clear in
that the water-based sys.em used in the method of the
invention produces a good print definition. This is of
economic importance since currently used organic solvent
based systems present occupational and fire hazards and
problems of environmental pollution.
In addition, an inert flame retardant can be added to
the print pastes or coloring mixtures used in the method of
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121~56(~
the invention to render cellulosic articles non-flammable.
An "inert flame retardant" is one which does not enter 1nto
or adversely affect the desired course of the chemical
reaction which comprises the method of the invention.
SU~ARY OF THE INVENTION
The invention comprises a method of coloring preformed
cellulosic materials, which comprises; chemically
cross-lin~ing a water-insoluble colorant particle to the
cellulosic material, said colorant particle being the
reaction product OI an organic polymer bearing substituent
groups which are reactive with acid halides, and a reactive
dye compound. The term "coloring" as used herein includes
printing i.e.; the coloring of selected areas of a
~cellulosic article. The invention also comprises the bleed
resistant colored products of the method of the invention
and intermediate coloring materials used in their
preparation.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing is a block diagram outlining a
preferred embodiment method of the invention.
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DETAILED DESCRIPTION OF THE PREFERRED
EM~ODIMENTS OF TH~ INVENTION
In the accompanying diagram, there is illustrated
schematically an embodiment method of the invention for
, coloring crepe paper to obtain a color-fast (bleed
resistant) crepe paper. Although he method is described in
regard to the coloring of crepe paper, it will be
appreciated that the method of the invention applies to the
coloring of any cellulosic article such as tissue paper,
~ towelling and like articles.
Cellulosic articles may be colored by the method of the
invention to obtain colored articles ~hich resist color
bleeding upon -contact with water. The term "cellulosic
article" as used herein means natural or synthetic preformed
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articles made ~rom materials such as those containing a
polymeric structure with repeating moieties of the formula:-
H OH
OH ~ ~ O
H ~ O
CH20H _ ,
x (I)
wherein x is an integer which is an average of about 3000.
Representative of such cellulosic materials are cotton,paper, rayon and the like. The methoà of the invention is
particularly advantageous for colorins crepe paper to obtain
a color fast product, i.e.; colored crepe paper resistant to
color bleeding.
The coloring of the cellulosic article is carried out
by chemically cross-linking to the cellulosic, through its
free hydroxyl groups, a water-insoluble colorant particle.
As illustrated in the accompanying drawing, the
cellulosic (crepe paper) is impregnated with a
water-insoluble colorant particle such as a dye/starch
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complex and the cellulosic bound to the colorant with a
chemical cross-linker. The cellulosic can be impregnated
with the other reactants separately in any order or sequence
of addition or, preferably, the cross-linker is added to the
mixture of the dye/starch component and the impregnation
carried out in a single step. Impregnation may be carried
out by conventional techniques such as by spraying the
impregnants on the cellulosic, dipping the
cellulosic in a bath of impregnant, kiss roll-pad
application and like techniques. The impregnants may also
include besides the colorant and/or cross-linking agent
conventional additives such as stabilizers, wetting agents,
sizes, surfactants, anti-migration agents, fire retardants
and the like commonly used in the art to dye or color
~ cellulosic materials.
- Following impregnation of the cellulosic, such as crepe
paper, the desired cross-linking reaction is promoted by
heatins the impregnated cellulosic to a cross-linking
temperature. In general, a cross-linking temperature is one
within the range of from about 150F. to 500F. for periods
of time between 10 seconds or less and an hour or more,
depending on the particular heating techniques that are
involved and the heat exchanging efficiencies that are
realized. Heating may be carried out by exposure of the
impregnated paper to radiant heaters and like heat sources.
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The proportion of coloring reactants impregnated into
the cellulosic for reac,ion therewith are important in
' regard to the degree of color fast coloration to be
, achieved. If a relatively light shade of coloration is
desired, only a relatively small proportion OI the
cross-linking reagen~ is necessary to provide the
cross-linked product. Thus, from 5 to 350 percent by weight
of the cross-linking reagent, based on the weight of the
colorant component, is generally adequate for the
cross-linking purpose. Frequently, an amount of the
cross-linking reagent that is between about 100 and 275
percent by weight, based on the weight of the colorant
component may be employed with advantage. If precision is
desired, the exact quantity of the cross-linking reagent for
accomplishment O,c the intended purpose can be determined by
~trial and error technique. For a deeper shade of dyeing,
more than 350 percent (by weight of dye) of cross-linker may
be employed.
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The cross-linking reaction which occurs may be
iilustrated in the schematic formula:-
A OH + Z B Z + H0 R
(II) (III) (IV)
A - - M - B M - R + 2H20
,. (V)
~ wherein the compound of formula ~II) is a hydroxy
containing, water-insoluble dye particle (described more
fully hereinafter) where A is the residue after removal of
the hydroxy group; the compound or rormula (III) is a
representative polyfunctional cross-linker wherein Z
represents one of a hydroxyl grou? or an amino group and B
- represents a divalent organic moiety and the formula (IV)
represents a hydroxy containing cellulosic material as
described above; R being the residue of the cellulosic after
removal of the hydroxyl group. The resultins product of
formula (V) wherein M represents oxygen or the divalent
group N is one wherein the d~e compound (II) is
H
chemically bound to the cellulosic (IV) so as to be color
fast (bleed resistant).
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The cross-linking reagent employed in the method of the
invention may be a di- or polyfunctional compound, provlded
i the functional groups are capable of a cross-linking
. reaction between the free hydroxyl groups on the cellulosic
(see for example the formula (I) given above) and the
: reactive, functional groups on the organic polymer/dye
j~ comple~ such as that of formula (II) given above.
;' Representative of such cross-linking reagents are diols and
: diamines of the formula:-
Z B - Z
~III)
wherein B and Z are as defined above. B may be more
specifically represented by organic mo~eties selected from
the group consisting of
(a) a straight chain, branched chain or cyclic
alkylene radical containing from 2 to 12
carbon atoms and in which one or both of the
Z groups may be present on a secondary carbon
, atom,
(b) the group: - (CH2)m - - Y - - (CH2)n -
wherein Y is a divalent radical selected from
the class consisting of str~ight chain alkylene
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groups, branched chain alkylene groups, cyclic
alkylene groups and oxydialkylene groups and
wherein m and n have the value 2 to 4.
: lc) the group:
I R'
- C3H6 - N - C3~6 -
wherein R' is a lower alkyl or phenyl group, and
' (d) the group:
2 ~ 3
. The diamines of class (a) above which may be
satisfactorily employed in accordance with the invention are
represented by-ehtylenediamine, 1,3-propanediamine,
1,2-propanediamine, 1,3-butanediamine, 1,5-hexanediamine,
-1,3-diaminocyclohex~ne, 1,4-diaminocyclohexane,
1,3-cyclohexane~bis (methylamine) and the like.
The diamines of class (b) may be
3,3'-~ethylenedioxy) bis(propylamine),
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3,3'-(2,2-dimethyltrimethylenedioxy) bis (propylamine),
3,3'-(cyclohexylene-1,4-dimethylenedioxy)bis (propylamine),
of the ~ormula:-
. ~ .
2 ( 2)3 C2H4 - - (CH2)3 - NH
,
! and the like.
Likewise the diamines of class (c) may be
3,3-'-ethyliminobis (propylamine) 3,3'-phenyliminobis
(propylaminej and the like.
Similarly, the diamines of class (d) may be o-, m-, and
~0 p-xylene-diamines and the like.
Diols of class (a) above are represented by ethylene
glycol, 1,3-propanediol, 1,3-butanediol,
1,4-dihydroxycyclohexane and the like.
The diols of class (b) above may be a poly (alkylene
oxide) glycol or the like.
Diols OL the class (c) given above are represented b~
3,3'-ethyliminobis (propanol) and the like.
Diols of the class (d) given above are represented by
~~ O-, m~, p- xylene diols and the like.
Preferred cross-linkers (III) OL the diol class are
represented by dimethylol urea, dimethylol melamine,
dimethylol methyltriazine, dimethylol cyclic ethylene urea
(DCEU) and the like.
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The cross-linking reagents may also be represented by
polyamines of the formula: -
H2N - (GNH - ~ G)n NH2
` wherein G may be any C2 to C10 aliphatic or C6 to C14
aromatic radical and n is a whole integer of at least 1.
Polyamines that may be included in this category include for
example hexamethylene tetramine, diethylene triamine,
triethylene tetramine and the like. Other functionally
- equivalent polyamine compounds such as piperazine and the
various substituted piperazines and melamine, in which the
nitrogen atoms are part of a heterocyclic molecular
structure, may also be utilized as cross-linking reagents in
the method of the invention.
Advantageously, the cross-linking reagent may be an
aldehyde type of material such as furfural or glyoxal and
the like, or a urea-formaldehyde or melamine formaldehyde
polymer condensate of the usual resin precursor variety,
i.e, mono or dimethylolurea and the like. It is generally
desirable to employ as the cross-linking reagent a polymer
which is a urea-formaldehyde or melamine-formaldehyde
polymer condensate such as those which have been previously
used in the treatment of paper to increase or impart wet
strength to the paper fibers. It is believed that such
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resin cross-linkers may ~orm hydrogen bonds between the
polymer chains, thereby increasing further the chemical bond
strength; see Kirk Othmer, Encyclopedia of Chemistry, Vol.
2, pages 254-255. These urea-formaldehyde and
melamine-formaldehyde polymer condensates contain
(generally) both free hydroxyl and free amino groups which
may function in the desired cross-linking reaction.
Although we are not to be bound by any theory of the
mechanism involved, it is believed that the free hydroxyl
, groups predominate in the cross-linking reaction.
The colored cellulosic of formula (V) is bleed
resistant.
The water-insoluble colorant particle of formula (II)
- described above is the reaction product of a polymer having
substituent grollps which are reactive with acid halides, and
-a reactive dye. The reaction may be represented
schematically by the formula: -
( E ta-1 D ( E ) + a tX-J) --~ ( E ~-a-_lD -J + E-X
(VI) (VII) (VIII)
wherein D represents the residue of an organic polymer
I following removal of substituent groups E; E representing a
chemical yroup which will react with an acid chloride.
Representative Ol E are amine and hydroxyl groups. The
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symbol "a" represents an integer of at least 1, preferably 1
to 25. In the formula (VII), X represents halogen such as
chlorine and bromine and J represents the residue of a
reactive dye compound upon removal of the moiety X (the
compound of formula (~II) being representative of a reactive
dye). The product dye/insoluble polymer complex of formula
(VTII) is representative of water insoluble dye particles of
the formula (II) described above.
Representative of the organic polymer of the formula
, (VI) are naturally occurring or synthetic polymers having
for example substituent amine and/or hydroxyl groups.
Preferably hydroxyl groups are present. Among the natural
polymers carrying hydroxyl groups may be mentioned
cellulose, starch, dextrin and the like, and their partial
esters and ethers as long as they still possess in their
-structure a substan-ial amount of free hydroxyl groups
capable of reacting ~ith acid chlorides, such as the
hydroxyethyl and hyaroxypropyl derivatives of cellulose and
starch.
Cellulose derivatives such as carboxymethyl cellulose,
phosphocellulose, sulfomethyl cellulose, sulfoethyl
cellulose, para-aminobenzyl cellulose, aminoethyl cellulose,
diethylaminoethyl cellulose, triethylaminoethyl cellulose;
cross-linked gels of dextran-epichlorohydrin (hereinafter
referred to for convenience as "dextran gel"); dextran gel
,
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derivatives such as carboxymethyl dextran gel and the like
are also representative of the polymers of formula (VI)
given above.
Synthetic condensation polymers (VI) carrying free
hydroxyl groups are for instance polyamides carrying
hydroxymethyl or hydroxyethyl substituents, and epoxy resins
such as the polyether obtained by the polycondensation of
2,2-bis(4-hydroxyphenyl)-propane with epichlorohydrin.
Most preferred as the organic polymers of formula (VI)
, are the naturally occurring starches.
Starch, 2S the term is used herein, means the
polysaccharide consisting of about 27 percent linear polymer
of the formula: -
- CH20H
H / ¦ O H
~ H
OH ~ o
H OH
m (X)
; wherein m is an integer of from about 70 to about 2100; and
73 percent of a branched polymeric moiety made up of
branched units of the formula (X) above, wherein m is an
in.eger of 25 or less joined together in such a way that the
free reducing group of a glucose unit of formula (X) at the
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~Z056~
end of one branch is glucosidically linked thrcugh the sixth
carbon of a glucose unit (not an end one) in an adjoining
chain.
, Reactive dyes for cellulosics of the formula (VIII) are
a class of dyes having active, functional, halogen groups
which will react with active hydrogen atoms on, for example,
starch, to form chemical bonds between the dye moiety and
the starch substrate. Representative of reactive dyes are
those described in U.S. Patents 3,290,282 and 3,503,953
which also describe their preparation. Preferred reactive
dyes are those of the formulae: -
. .
. .
.
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~20S~iiL)6
C
, . ~C~
., N N
S03Na
;~--N = N 1 N
S03Na
( Procion Yellow)
C~ .
/1~
N N
S03~ a H0 NH--C C.C~
~N= N~ N
S03N a~J S03Na
( Proci on Red~
O AND
~i~so3
O NH ~NH--C\ C.C
(Procion Blue)
and the like.
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I
In the above-described reaction scheme between the
organic polymer of formula (VI) and the reactive dye
compound of formula (VII), a by-product of the formula (IX),
i.e., for example a hydrogen halide may be formed. This
~ acid by-product is advantageously neutralized by the
presence of an alkali. Any alkali may be used, which will
provide the desired neutralization. Representative of such
alkali compounds are sodium hydroxide, lithium hydroxide,
sodium triphosphate, sodium carbonate (soda ash) and the
liXe.
The reaction between the organic polymer (VI) and the
reactive dye (VII) may be carried out at room temperatures
but is advantageously promoted by heating the reaction
mixture, preferably within a range of from about 100F. to
1 about 200F., most preferably circa 140F., after admixture
of the reactants (VI) and (VII). Admixture may be carried
out by conventional technique, employing conventional
reaction apparatus.
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In the drawing of the accompanying figure, it is shown
that in the preferred embodiment method of the invention, a
reactive dye is reacted with starch in the presence of
alkali to obtain the preferred dye/starch colorant particle.
The colorant particles obtained are impregnated in a
cellulosic for coloring as described previously. The same
colorant particles prepared as described above may be used
for printing on cellulosics and are basically the same as
used for dyeing crepe paper except that more alkali ~soda
ash) is used to produce a desired viscosity. Any desired
viscosity can be achieved by varying the proportion of
alkali, as those skilled in the art will appreciate
(viscosity increases as the pH is raised). In printing
operations, these dyes are very suitable for use in the
thermal process wherein the printing paste contains both the
colorant and alkali and the print is cured by heating above
270C. for 30 seconds or more. Thermal printing is a well
known process and the techniques and apparatus are known and
readily available.
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An important advantage of the method and the articles
of the invention is found in their compatability with the
presence of conventional, inert flame retardants. Thus,
inert flame retardants conventionally used to impregnate
cellulosic articles may be added to the coloring
compositions used to color cellulosics in the method of the
invention. The term "inert flame retardant" means a flame
retardant compound or composition which does not enter into
the above-described cross-linking reaction or otherwise
i adversely affect the desired course of the cross-linking.
The following examples describe the manner and process
of making and using the invention and set forth the best
mode contemplated by the inventors oî carrying out the
invention, but are not to be construed as limiting. Bleed
resistance is determined by immersing a representative
.portion of the colored cellulosic article ~crepe paper) in
tap water and sandwiching the wet article between a top and
bottom layer of white tissue paper which layers are
~ subsequently saturated with tap water. After a period of
about 10 minutes the sandwich is opened and the amount of
i, bleed, ie; migration of colorant from the colored article to
the upper and lower tissue layers noted. The article is
deemed "bleed resistant" if no color migration is seen.
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EXAMPLE 1
Ten grams of Clearfilm starch (thin cooking,
noncongealing starch; National Starch and Chemical Corp.) is
~ added to 50 ml of water and heated to 180F. to dissolve the
starch. The starch is cooked at a temperature of 180F. for
10 minutes. Four grams of Procion Red MX-GBA (I.C.I.
Americas, Inc., Wilmington, Delaware) and 0.2 gram of soda
ash are each separately dissolved in warm water and then
added to the dissolved starch solution. The temperature o~
' the starch-dye-soda ash mixture is then allowed to remain at
180F. for 30 minutes while undergoing constant stirring.
The mixture is then cooled to 140F.
Twenty grams of Apex Flameproof #736 (Apex Chemical
Co.) is dissolved in water at 140F. This dissolved product
is then added to the cooled starch-dye-soda ash mixture.
Finally 10 grams of melamine-formaldehyde type resin ~Parez
613 resin; American Cyanamid Co.) is added to the above
~mixture with stirring and maintained at 140F. to obtain a
dye mixture, red in color. Cellulosic paper is then dipped
in the prepared dye mixture and then passed between squeeze
rolls to remove excess dye. The impregnated colored sheet
is then cured for 1.5 minutes at 350F. The dry, colored
cellulosic paper sheet is found to be resistant to colored
bleeding.
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EXAMPLE 2
Similarly, repeating the procedure of Example 1,
supra., but replaciny the Procion Red MX-GBA as used therein
with an equal proportion of Procion Blue MX-2 GA (I.C.I.
Americas Inc., supra) and increasing the proportion of soda
ash to 0.6 gms, there is obtained a color fast, blue colored
paper which is bleed resistant.
; EXAMPLE 3
i'
Similarly, repeating the procedure of Example 1, but
replacing the Procion Red MX-GBA as used therein with an
equal proportion of Procion Yellow MX-3 RA (I.C.I. Americas
Inc., supra) there is obtained a yellow colored paper which
is bleed resistant.
EXAMPLE 4
Ten grams of Clear film starch (National Starch and
Chemical Corp., supra) is first dissolved in 40 ml of water
at a temperature of 180F. Then after cooking at this
temperature for 5 to 10 minutes, there is added four grams
of Procion Yellow MX-3RA (I.C.I. Americas Inc., supra) and
0.6 gram soda ash (each separately dissolved in warm water).
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There is thus obtained a viscous mixture. Twenty grams of
the fire retardant ammonium sulfamate (CM, E.I. DuPont de
Nemours and Co; is dissolved in water at 140F. This
dissolved product is then added to the starch-dye-soda ash
mixture. aThe addition causes a decrease in viscosity.
Finally, 10 grams of Parez 613 (supra) is added to the
print paste and allowed to cool to room temperature. The
product mixture is useful as a printing paste of yellow dye
color. The print pastes are applied with a screen to paper
l stock. The prints are then cured at 350F. for 1.5 minutes.
'l The results show that the print pastes produce good
coloration on the paper stock and that the cured printed
stock does not color bleed when tested.
,
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