Note: Descriptions are shown in the official language in which they were submitted.
60~; 1
;-45 PLEED RESISTANT COLORED CELLULOSICS
ve AND THE METHOD OF THEIR PREPARATION
I BACKGROUND OF THE INVENTION
-¦l Field OI the Invention
I The invention relates to the coloring of cellulosics,
inclusive of color printing techniques, and more
I particularly relates to the coloring of cellulosics with
¦ chemically reactive dyes to obtain bleed resistant, colored
Il 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 f~st, colored cellulosic articles. In spite of the
I 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. Bv "bleeding" we mean that the
,I color leaches out of the paper and may stain whatever the
20 , ~et paDe- comes into contact with. This effect is
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considered undesirable for many uses of crepe paper.
Apparently the known prior art methods of preparing color
fast dyed cellulosics have not been found practical,
sufficient or efficient for present day practices.
5 I Prior to our invention, a class of dyes (reactive dyes
-ll for cellulosics) were known, which react with free hydroxyl
groups on cellulosic fibers to cause a coloring thereof.
¦¦ However, the fibers must be free of contaminants such as
,' starch, which would also react with the dye to form colored,
10 ~ insoluble particles on the fiber surface. The starch/dye
reaction product is readily washed off of the fiber surface,
resulting in a waste of dye reactant. Another disadvantage
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is found in the long reaction times needed to affect a
,l 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 the
paper pulp in the beater stage to per~it reaction with
cellulose over a prolonged period of time. The dyed pulp is
~ then made into a paper sheet. The resulting colored paper
is color fast (bleed resistant). The disadvantage of this
approach is that a considerable amount of a given colored
paper has to be made at one time (for economic reasons), 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 may
1, be first reacted with a cross-linking agent such as a
Il
¦' melamine-formaldehyde resin. The resulting colorant
compound is then used to impregnate preformed cellulosic
articles such as crepe paper and then further reacted with
the paper to chemically crosslink the dye to the crepe
paper. The result is a colored crepe paper sheet which
resists "bleeding" when placed in contact with water. The
method of the invention is economical and may be used in a
i conventional plant for commercial coloration without
purchasing new equipment or modifying that already in
existence. Reaction times required are relatively short,
which is an unexpected advantage. The method of the
invention may also be carried out at relatively low
temperatures, rapidly. Thus there are operating and
economic advantages. The coloring approach described above
may be used on a wide variety of woven anZ
non-woven disposable cellulosic items where non-bleeding is
2 useful factor (for example, tissue paper, towelling, rayon
~ sheets, crepe paper and the like).
' Our observations made while coloring crepe paper
indicated that the color dispersions used in the method of
the invention can be used for printing on the surfaces of
cellulosic articles. Prior to the invention, a considerable
amount of color printing on low cost substrates was
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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 of highly 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 comprised 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 a substrate. Both of the above described
systems are expensive. For the printing of low cost items
such as paper, paperboard, gift wrapping paper, textiles or
other disposable items, the method of the 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 mav be used to color even more e~:pensive
articles such as textile fabrics, including woven,
non-woven, knitted, pile and velvet fabrics, webs and varns.
By the method of the invention the printing of cotton
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fabrics is particularly advantageous. For example, the
i cotton fabric need not of necessity be pre~washed to remove
starch contaminants.
Il By the method of our invention a particular class of
,' dyes referred to as "reactive dyes for cellulosics", which
',' will react with cross-linker chemicals containing, for
example, amino or hydroxyl groups, are used to form reactive
colorant molecules which may be used as a coloring or a
1 printing medium. The advantages are clear in that the
0 ll water-based system used in the method of the invention has
produced a good definition of print. This is of economic
importance since currently used organic solvent based
systems present occupational and fire hazards and problems
j of environmental pollution.
In addition, an inert flame retardant may be added to
the print pastes or coloring mixtures used in the method of
the invention to render the cellu osic articles
non-fla~mable.
SU~RY OF THE INVENTION
~ The invention comprises a method of coloring preformed
cellulosic articles, which comprises; chemically
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cross-linking a reactive dye molecule to the cellulosic
article. The term "coloring" as used herein includes
printing, i.e.; the coloring of selected areas of a
cellulosic article. More particularly, the invention is
directed to a method of coloring a crepe type paper, which
comprises the steps of:
~a) providing a reactive dye;
(b) mixing the dye with a sufficient proportion of a
cross-linker, to partially cross-link a portion
of the dye molecules, the proportion being in-
sufficient to cross-link all of the dye molecules;
(c) partially cross-linking the portion of dye
molecules;
(d) adding additional cross-linker to the mixture
of partially cross-linked reactive dye;
(e) applying the product of step (d) to the paper;
and
(f) chemically cross-linking the product to the
paper.
Preferably, the cross-linker is a melamine-formal-
dehyde resin or a urea-formaldehyde resin.
The method of the invention enables one to obtain
bleed resistant, colored crepe type paper.
BRIEF DESCRIPTION OF THE DRAWING
The accompanying drawing is a block diagram out-
lining a preferred embodiment method of the invention.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS OF THE 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)
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crepe paper. Although the 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 like
cellulosic articles such as tissue paper, towelling, non-
wovens and like articles.
Cellulosic articles may be colored by the method of
the invention to obtain colored articles which resist color
bleeding upon contact with water. The term "cellulosic
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~~ article" as used herein means natural or synthetic preformed
', articles made from materials such as those containing a
; polymeric structure with repeating moieties of the formula:-
H OH
'' X
; (I)
.,
wherein x is an integer which is an average of about 3,000.Representative of such cellulosic materials are cotton,
paper, rayon and the like. The method of the invention is
particularly advantageous for coloring crepe paper to obtain
a color fast product, i.e.; colored crepe paper resistant to
color bleeding.
The coloring of the cellulosic is carried out by
chemically cross-linking to the cellulosic, through its free
hydroxyl groups, a reactive dye molecule.
As illustrated in the accompanying drawing, the
cellulosic (crepe paper) is impregnated with a mixture of a
reactive dye and a chemical cross-linker. The cellulosic
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can be impregnated with the two reactants separately in any
order or sequence or, preferably, the cross-linker is added
to the dye component and the impregnation carried out in a
single step. In the latter case, the cross-linker is first
added to the dye component and may be partially reacted with
the dye. Impregnation may be carried out by conventional
techniques such as by spraying the impregnants on the
cellulosic, dipplng the cellulosic in a bath of impregnant,
by kiss roll-pad applicators and like techniques. The
impregnants may also include besides the reactive dye and
crosslinker, conventional additives such as wetting agents,
sizes, 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-linkinc reaction is promoted by
heating 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 cellulosics to radiant heaters and like heat
sources.
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The proportion of coloring reactants impregnated into
the cellulosic for reaction 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 of the
cross-linking reagent 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
,, coloring 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 dye component
may be emploved with advantage. If precision is desired~
l the exact quantity of the cross-linking reagent for
accomplishment of the intended purpose can be calculated
using trial and error techniques. For a deeper shade of
dyeing, more than 350 percent (by weight of colorant) of
cross-linker may be employed.
The cross-linking reaction which occurs may be
illustrated in the schematic formula:-
A X + 2 B Z + HO - R
; (II) ~III) (IV)
:,
A M B M R + HX
(V~
wherein ~he compound of formula ~II) is a reactive dye
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(described more fully hereinafter), X being representative
of a halogen; the compound of formula (III) is a
representative polyfunctional cross-linker wherein B is a
' divalent organic moiety and Z is selected from the group
consisting of amino and hydroxyl; and the formula (IV)
represents a hydroxy containing cellulosic material as
, described above wherein R is the residue after removal of a
. hydroxy group. The resulting product of formula (V) is one
, wherein the dye component (II) is chemically bound to the
10 l, cellulosic (IV) so as to be color fast (bleed resistant), M
representing oxygen or a group of formula NH
The cross-linking reagent employed in the method of the
invention may be a di- or polyfunctional compound, provided
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 org~nic, reactive dye
such as that of formula (II) given above. Representative of
such cross-linking reagents are diols and diamines of the
formula (III) given above wherein B is 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,
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(b) the group: - (CH2)m - - Y - - (CH2)n
wherein Y is a divalent radical selected from
the class consisting of straight chain alkylene
groups, branched chain alkylene groups, cyclic
5 . alkylene groups and oxydialkylene groups and
wherein m and n have the value 2 to 4.
~ (c) the group:
,i
., R
,, I
' C3H6 N - C3H6
;;
wherein R is a lower alkyl or phenyl group, and
10 ; ~d) the group:
CH2 _~3 CH2 --
.j The diamines of class (a) above which may be
satisfactorily employed in accordance with the invention are
represented by ethylenediamine, 1,3-propanediamine,
1,2-propanediamine, 1,3-butanediamine, 1,5-hexanediamine,
1,3-diaminecyclohexane, 1,4-diaminocyclohexane,
1,3-cyclohexane-bis (methylamine) and the like.
I I --1 1--
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l~ The diamines of class (b) may be 3,3'-(ethylenedioxy)
,' bis(propylamine), 3,3'-(2,2-dimethyltrimethylenedioxy) bis
; (propylamine), 3,3'-(cyclohexylene-1,4-dimethylenedioxy) bis
~ (propylamine), of the formula:-
S H2N(CH2)3 O 2 4 ( 2)3 NH2
and the like.
Likewise the diamines of class (c) may be
3,3'-ethyliminobis (propylamine) 3,3'-phenyliminobis
; (propylamine) and the like.
Similarly, the diamines of class (d) may be o-, m-, and
o-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 of the class (c) given above are represented by
3,3'-ethyliminobis (propanol~ and the ]ike.
I, Diols of the class (d) given above are represented by
o-, m-, p-xylene diols and the like.
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¦ Preferred cross-linkers (III) of the diol class are
¦~ represented by dimethylol urea, dimethylol melamine,
dimethylol methyltriazine, dimethylol cyclic ethylene urea
l~, (DCEU) and the like. The cross-linking reagents may also be
5 1i represented by polyamines of the formula:-
2 (CNH )n ~H2
wherein G may be any C2 to C10 aliphatic or C6 to C14
Il aromatic radical and n is a whole integer of at least 1.
il Polyamines that may be included in this category include for
~~ example hexamethylene tetramine, diethylene triamine,triethylene tetra~ine 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
Il the like, or a urea-formaldehyde or melamine formaldehyde
polymer condensate of the usual resin precursor varietv,
i.e.; mono-or dimethylolurea and the like. It is generally
desirable to employ as the cross-linking reagent a polvmer
which is a urea-formaldehyde or melamine-formaldehyde
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I 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
~ resin cross-linkers form 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
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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 reactive dye of formula (II) described above is an
acid halide. Reactive dyes o~ the formula (II) are a class
Oc dves having active, functional, halogen groups which will
react with active hydrogen atoms on the cross-linking agents
described above to form chemical bonds between the dye
moiety and the cross-linker. 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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Cl
~C~
N N
S13Na ll ¦
~ r N
S03Na
( Procion Yellow)
,, Cl '.
' C
',', - /~
N N
S03Na H0 NH--C C.Ci
~N= N-- ~ ~I N
.~ So3N a S03Na
(Procion ~ed)
0 A N D
O NH ~ 03Na \ N
( Procion Blu e)
.,
and the li ke .
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An important advantage of the method and the articles
! of the invention is found in their compatibility with the
' presence of conventional, inert flame retardants. Thus,
1, 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 retar~ant" means a flame
, retardant compound or composition which does not enter into
, the above-described cross-linking reaction or otherwise
, adversely affect the desired course of the cross-linking.
The process of the invention as described above may be
used for printing on cellulosics and the coloring
compositions are basically the same as used for dyeing crepe
paper except that alkali such as soda ash is added to the
impregnant 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, the colorants 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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The following examples describe the manner and process
¦ of making and using the invention and set forth the best
mode contemplated by the inventors of 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
tàp water and sandwiching the wet article between a top and
a bottom layer of white tissue paper which layers are
' subsequently saturated with tap water. After a period of
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, about lO minutes the sandwich is opened and the amount of
bleed, i.e.; 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
;
A suitable vessel is charged with 5 gms of a
melamine-formaldehyde resin (Berset 808-B, Bersen Chemical
Co.) in 30 ml of water. The charge is heated with stirring
to a temperature of 140~F. To the heated charge there is
Il added with stirring 4 gms of Procion Blue I~X-2GA (I.C.I.
Z0 Americas Inc., Wilmington, Delaware) dissolved in 20 ml of
hot (140F.) water. The resulting mix,ure is mixed for 30
I minutes while maintaining the temperature of 140~F. At the
end of this period, the mixture is allowed to cool to room
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temperature and then 40 gms of a fire retardant (Apex
Flameproof #736, Apex Chemical Co~) in 10 ml of water is
added with stirring. To the resulting mixture there is
, added an additional 5 gms. of the melamineformaldehyde
~ resin. Crepe paper is immersed in the resulting mixture and
then removed. Excess dye solution is removed by passing the
dye immersed paper between the rolls of a padder. The paper
is cured at a temperature of 300~F. for one minute to obtain
a bleed resistant, colored crepe paper.
EXAMPLE 2
A dye solution is prepared as described in Example 1,
supra. except that the dye solution obtained is not used for
immersion of crepe paper. Instead, there is added to the
dye solution with stirring 0.8 gms. soda ash. The resulting
lS viscous mixture is a printing paste. The printing paste is
ap?lied by screen to paper stock znd the prints are cured by
exposure to radiant heaters (temperature circa 350F.) for
l.S minutes. The resulting print is well defined and is
bleed resistant.
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