Erasable ink composition containing a waterborne polyurethane urea

An erasable ink composition contains a water-insoluble polymeric dye obtained from the polymerization of at least two coreactive polyfunctional monomers with at least one of the monomers possessing a dye moiety covalently bonded thereto. The ink is intended for use in any of a variety of marking instruments, in particular, a ball-point pen.

BACKGROUND OF THE INVENTION 
This invention relates to an erasable ink composition and to a marking 
instrument, e.g., a ball-point pen, containing the composition. More 
particularly, this invention relates to an erasable ink composition 
containing a water-insoluble polymer dye component, i.e., a polymer 
possessing a dye moiety covalently bonded thereto. 
Numerous erasable ink compositions are known, e.g., those described in U.S. 
Pat. Nos. 3,834,823, 3,875,105, 3,949,132, 4,097,290, 4,212,676, 
4,227,930, 4,256,494, 4,297,260, 4,329,262, 4,329,264, 4,349,639, 
4,357,431, 4,367,966, 4,368,076, 4,379,867, 4,389,499, 4,390,646, 
4,391,927, 4,407,985, 4,410,643, 4,419,464, 4,441,928, 4,509,982, 
4,525,216, 4,557,618, 4,578,117, 4,596,846, 4,606,769, 4,629,748, 
4,687,791, 4,721,739, 4,738,725, 4,760,104, 4,786,198, 4,830,670, 
4,954,174, 4,960,464, 5,004,763, 5,024,898, 5,037,702, 5,082,495, 
5,114,469, 5,120,359, 5,160,369 and 5,217,255. These inks are formulated 
by mixing a dye (taken herein to also include "pigment", "colorant", 
"chromophore" and other terms of similar meaning) with a variety of 
polymer and liquid carrier/solvent combinations thereby forming a flowable 
dye/polymer matrix. The polymer component is chosen for its film forming 
properties and its ability to be readily removed from the substrate to 
which it is applied, e.g., cellulosic paper, through the abrasive action 
of an eraser. However, a common problem with these erasable ink 
compositions concerns the residual dye which remains after erasure. 
Incomplete erasure may be attributed to inadequate removal of the 
dye/polymer matrix from the paper substrate and/or migration of dye into 
the pores of the substrate. 
SUMMARY OF THE INVENTION 
In accordance with the present invention an erasable ink composition is 
provided which comprises: 
a) a water-insoluble polymer dye obtained by effecting polymerization of a 
polymer-forming reaction medium containing at least two coreactive 
polyfunctional monomers with at least one of the monomers possessing a dye 
moiety covalently bonded thereto; and, 
b) an evaporable liquid carrier for the polymer dye. 
Since the dye is covalently bonded to the polymer in the erasable ink 
composition of this invention, there is little opportunity for it to 
separate from the polymer and migrate into a porous substrate. Thus, the 
erasable ink composition of this invention is apt to leave significantly 
less residual dye following its erasure than known erasable ink 
compositions in which the dye is merely physically combined with the 
polymer component(s).

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The polymer dye component of the erasable ink composition of this invention 
is prepared by polymerizing at least two coreactive polyfunctional 
monomers with at least one of the monomers possessing a dye moiety 
covalently bonded thereto. At least one of the monomers must be 
sufficiently hydrophobic as to render the resulting polymer dye 
water-insoluble. Part or all of the polyfunctional monomers can be 
oligomeric or polymeric in nature. The expression "polyfunctional monomer" 
characterizes those compounds possessing at least two reactive functional 
groups (not counting any sites of unsaturation that may be present) such 
as, but not limited to, hydroxyl, sulfhydryl, carboxylic acid, amine, 
nitrile, acyl halide and isocyanate groups. The expression also includes 
compounds which, under polymerization reaction conditions, present 
polyfunctionality, e.g., lactones and lactams which on opening of their 
rings are chemically equivalent to .alpha.,.omega.-hydroxy-carboxylic 
acids and .alpha.,.omega.-aminocarboxylic acids, respectively. 
Polymeric dyes of the type that are useful in the erasable ink composition 
of this invention are known (but for applications other than erasable ink 
compositions) or can be prepared by appropriate modification of known 
polymer-forming procedures. Illustrative of such known polymeric dyes are 
those disclosed in U.S. Pat. Nos. 4,778,742, 5,104,913, and 5,194,463, the 
contents of which are incorporated by reference herein. 
In accordance with U.S. Pat. No. 4,778,742, a polymeric dye of the general 
formula 
EQU --)--A--DYE--A--O--B---!.sub.n 
wherein A is selected from the group consisting of alkylene and arylene, B 
is selected from the group consisting of 
##STR1## 
wherein R is an alkylene group, an arylene segment or a polyether segment, 
DYE is a dye moiety and n is from about 2 to about 100 and preferably from 
about 5 to about 35, can be prepared by a solution or interfacial 
polymerization process. In solution polymerization, stoichiometric amounts 
of polyfunctional monomers, specifically, a bisphenoxy-functionalized dye 
and a diacyl halide, are reacted in a suitable solvent medium, e.g., an 
aliphatic halogenated hydrocarbon such as methylene chloride, in the 
presence of an excess amount of a tertiary amine such as triethylamine 
base. Polymerization is then effected at a temperature of from about 
5.degree. C. to about 30.degree. C. and completed in about 0.5 to 3 hours. 
In interfacial polymerization, a bisphenoxy-functionalized dye is 
initially dissolved in an aqueous alkaline solution in the presence of an 
emulsifying agent. Thereafter, the resulting solution is stirred and 
treated with a solution of an appropriate bifunctional monomer such as a 
diacyl chloride or a bishaloformate in a water-immiscible solvent such as 
methylene chloride to obtain, respectively, the polyester dye or the 
polycarbonate dye. The polymeric dyes from the solution polymerization 
process are then further treated by washing the reaction mixture with 
water followed by precipitation of a methylene chloride solution of the 
dyes from a non-solvent such as hexane or methanol. Also, with the 
interfacial process, the polymeric dyes are separated by simple filtration 
followed by washing thoroughly with water. 
Examples of bisphenoxy-functionalized dye monomers that can be used to 
prepare the polymeric dyes of U.S. Pat. No. 4,778,742 include 
1,5-bis(p-hydroxyphenylthio) anthraquinone, 
1,8-bis(p-hydroxyphenylythio)anthraquinone, 
1,5-bis(p-hydroxyphenylthio)-4,8-bis(phenylthio) anthraquinone, 
1,8-bis2-(p-hydroxyphenyl)ethylamino!anthraquinone, 
1,5-bis2-(p-hydroxyphenyl)ethylamino!anthraquinone, 
1,4-bis2-(p-hydroxyphenylamino) anthraquinone, 
1,4-bis2-(p-hydroxyphenyl)ethylamino!anthraquinone, 
1,4-bis2-(p-hydroxyphenylthio) anthraquinone and 
6-phenylthio-1,4-bis2-(p-hydroxy-phenyl)ethylamino!anthraquinone. 
Examples of diacyl halide monomers that can be reacted with the 
bisphenoxy-functionalized dye monomers to provide the polymeric dye of 
U.S. Pat. No. 4,778,742 include succinyl chloride, glutaryl chloride, 
adipoyl chloride, dimethylglutaryl chloride, sebacoyl chloride, phthaloyl 
chloride, isophthaloyl chloride, terephthaloyl chloride, and the like. 
Examples of useful bishaloformates include diethyleneglycol 
bischloroformate, triethyleneglycol bischloroformate, tetraethyleneglycol 
bischloroformate, biphenoxy bischloroformate, propyleneglycol 
bischloroformate, dipropyleneglycol bischloroformate, butyleneglycol 
bischloroformate, ethyleneglycol bisbromoformate, propyleneglycol 
bisbromoformate, and the like. 
The polymeric dye of U.S. Pat. No. 5,104,913 is obtained by polymerizing a 
polyfunctional monomer possessing a dye moiety covalently bonded thereto, 
a terephthalic acid and/or 2,6-naphthalenedicarboxylic acid and a 
branched-chain diol of the general formula 
##STR2## 
wherein R.sup.1 is hydrogen or an unsubstituted or substituted alkyl, 
cycloalkyl or aryl radical and R.sup.2 is an unsubstituted or substituted 
alkyl, cycloalkyl or aryl radical. The dye-containing monomer can be 
selected from anthraquinone, methine, bis-methine, anthrapyridone, 
2,5-diarylamino-terephthalic acid or ester, coumarin, quinophthalone, 
perylene and other thermally-stable dye compounds possessing functional 
groups that are reactive for the carboxylic and/or hydroxyl groups of the 
other monomers, i.e., hydroxyl, carboxyl, ester, amino, alkylamino, etc., 
groups, such that the dye will be incorporated in the resulting polyester. 
Examples of dye-containing monomers include anthraquinone dyes and methine 
dyes possessing two reactive functional groups selected from the 
aforementioned types. 
U.S. Pat. No. 5,194,463 describes a polymer dye which is a polyurethane of 
the general formula 
##STR3## 
wherein R is a divalent radical selected from optionally substituted 
C.sub.2 -C.sub.10 -alkylene, C.sub.3 -C.sub.8 -cycloalkylene, arylene, 
C.sub.1 -C.sub.4 -alkylene-arylene-C.sub.1 -C.sub.4 -alkylene, C.sub.1 
-C.sub.4 -alkylene-C.sub.3 -C.sub.8 -cycloalkylene-C.sub.1 -C.sub.4 
-alkylene or C.sub.1 -C.sub.4 
-alkylene-1,2,3,4,5,6,7-octahydronaphthalene-2,6-diyl-C.sub.1 -C.sub.4 
-alkylene; R.sup.1 is a divalent organic radical comprised of about 1 to 
100 mole percent of the residue of a dye bonded to two hydroxyl groups 
through alkylene moieties with any remainder of R.sup.1 comprised of the 
residue of organic diols of the formula HO--R.sup.2 --OH in which R.sup.2 
is a divalent radical selected from C.sub.2 -C.sub.18 alkylene, C.sub.3 
-C.sub.8 -cycloalkylene, C.sub.1 -.sub.4 
alkylene-1,2,3,4,5,6,7,8-octahydronaphthalen-2,6-diyl-C.sub.1 -C.sub.4 
alkylene, C.sub.1 -.sub.4 -alkylene-C.sub.3 -C.sub.8 
-cycloalkylene-C.sub.1 -C.sub.4 -alkylene, C.sub.1 -.sub.4 
alkylene-arylene-C.sub.1 -C.sub.4 -alkylene, C.sub.2 -C.sub.4 
alkylene-O-C.sub.2 -C.sub.4 alkylene, C.sub.2 -C.sub.4 alkylene-S-C.sub.2 
-C.sub.4 alkylene or C.sub.2 -C.sub.4 alkylene-O-C.sub.2 -C.sub.4 
alkylene-O-C.sub.2 -C.sub.4 alkylene; and n is equal to or greater than 2. 
The dye containing the hydroxyl groups can be selected from a variety of 
chromophoric classes including azo, metallized azo, diazo, methine, or 
arylidene, polymethine, azo-methine, anthraquinone, azamethine, 
anthrapyridone (3H-dibenz f,ij! isoquinoline-2,7-dione), anthrapyridine 
(7H-dibenz f,ij! isoquinoline-7-one), phthaloylphenothiazine (14H-naphtho 
2,3-a! phenothiazine-8,13-dione), benzanthrone (7H(de)anthracene-7-one), 
anthrapyrimidine (7H-benzo e! perimidine-7-one), anthrapyrazole, 
anthraisothiazole, triphenodioxazine, thiaxanthene-9-one, flourindine (5, 
12-dihydroquinoxaline 2,3-b! phenazine), quinophthalone, phthalocyanine, 
naphthalocyanine, nickel dithiolenes, coumarin (2H-1-benzopyran-2-one), 
coumarin imine (2H-1-benzopyran-2-imine), indophenol, perinone, 
nitroarylamine, benzodifuran, phthaloylphenoxazine 
(14H-naphtho2,3-alphenoxazine-8,13-dione), phthaloylacridone 
(13H-naphtho2,3-c! acridine 5,8,14-trione), anthraquinonethioxanthone 
(8H-naphtho2,3-c!thioxanthene-5,8,13-trione), anthrapyridazone, 
naphtho1',2',3':4,5!quino2,1-b! quinazoline-5,10-dione, 
1H-anthra(2,1-b)(1,4) thiazin-7,12-dione, indigo, thioindigo, xanthene, 
acridine, azine, oxazine, 1,4- and 1,5-naphthoquinones, pyromellitic acid 
diimide, naphthalene-1,4,5,8-tetracarboxylic acid diimide, 
3,4,9,10-perylenetetracarboxylic acid diimide, hydroxybenzophenone, 
benzotriazole, naphthotriazole, naphthoquinone, diminoisoindoline, 
naphthopyran (3H-naphtho2,1-b!pyran-3-ones and 3-imines) and 
aminonaphthalimide. 
The polyurethane of U.S. Pat. No. 5,194,463 can be obtained by reacting one 
or more of the dihydroxyl-containing dyes with a diisocyanate and, if 
desired, another diol, employing known procedures. 
Numerous modifications of the foregoing known processes for obtaining a 
polymeric dye that can be utilized in the erasable ink composition of this 
invention are possible. For example, part or all of the 
bisphenoxy-functionalized dye monomer of U.S. Pat. No. 4,778,742, the 
functionalized dye monomer of U.S. Pat. No. 5,104,913 or the 
hydroxyl-containing dye monomer of U.S. Pat. No. 5,194,463 can be replaced 
with a polyfunctional polymer dye monomer of the general formula 
EQU (R.paren close-st..sub.a .paren open-st.P.brket open-st.X!.sub.b).sub.c 
wherein R is a dye moiety covalently bonded to polymer residue P, X is a 
functional group, a, b and c each is at least 1, provided, the product of 
b.times.c is at least 2, when c is at least 2, a is 1 and where there is 
more than one R, P or X, each R, P or X can be the same or different. Dye 
moiety R can be derived from among any of the polyfunctionalized dye 
monomers previously mentioned, polymer residue P can be that of a 
polyether, polyester, polyamide, polycarbonate, or the like, and X can 
include hydroxyl, sulfhydryl, carboxyl, primary amine, secondary amine and 
isocyanate reactive groups. For example, a dihydroxyl-containing dye such 
as one described in U.S. Pat. No. 5,194,463 or some other 
dihydroxyl-containing dye can be reacted with ethylene oxide, propylene 
oxide or a mixture thereof to provide a hydroxyl-terminated liquid 
polyether dye monomer. Polyether dyes of this type are known from U.S. 
Pat. Nos. 3,157,633 and 4,284,729, the disclosures of which are 
incorporated by reference herein. Similarly, the dihydroxyl-containing dye 
can be reacted with an .alpha.,.omega.-hydroxycarboxylic acid or cyclic 
ester analog thereof, for example .epsilon.-caprolactone, to provide a 
hydroxyl-terminated liquid polyester dye monomer. Either the polyether or 
polyester dye monomer can be reacted with a polyisocyanate or an 
isocyanate-terminated prepolymer to provide the water-insoluble polymer 
dye component of the erasable ink composition herein. 
A preferred polymer dye for use herein is one prepared by a waterborne 
process, i.e., a polymerization process in which the resulting polymer is 
provided as an aqueous emulsion or dispersion of polymer dye particles. 
The polymer dye emulsion with or without the addition of other components 
can, if desired, be utilized directly as the erasable ink composition of 
this invention thus eliminating any further manufacturing operations 
(unlike the case of bulk polymer dyes which would require pulverization to 
the desired particle size followed by addition of some suitable evaporable 
liquid carrier). 
A particularly preferred waterborne polymer dye for use herein is a 
waterborne polyurethane-urea prepared by modification of any of the 
polymerization processes described in Frisch et al., ed., "Advances in 
Urethane Science and Technology", Vol. 10, pp. 121-162 (1987), the 
contents of which are incorporated by reference herein. The modification 
referred to involves the substitution of part or all of one or more of the 
polyfunctional reactants employed in these processes with a polyfunctional 
monomer possessing covalently bonded dye in accordance with the present 
invention. Especially suitable are the polyfunctional polymer dye monomers 
of U.S. Pat. No. 5,231,135 which contain a dye moiety covalently bonded 
thereto and at least two groups that are reactive for isocyanate. The 
contents of U.S. Pat. No. 5,231,135 are incorporated by reference herein. 
These processes, respectively, the solvent, melt dispersion, prepolymer 
mixing and ketamine/ketazine processes, can be summarized as follows: 
1. The Solvent Process 
The solvent process involves the steps of: 
a) reacting a polymeric polyol with a diisocyanate to provide an isocyanate 
group-terminated prepolymer possessing or lacking sufficient hydrophilic 
groups to render the prepolymer self-dispersible; 
b) reacting the isocyanate group-terminated prepolymer dissolved in organic 
solvent with an aliphatic diamine chain extender and, where the prepolymer 
lacks sufficient hydrophilic groups to be self-dispersible, an aliphatic 
diamine chain extender possessing at least one hydrophilic group, to 
provide an organic solvent solution of self-dispersible polyurethane-urea; 
and, 
c) adding a sufficient amount of water to the organic solvent solution of 
the polyurethane-urea to form a dispersion of polyurethane-urea particles, 
at least one of said polymeric polyol, diisocyanate and aliphatic diamine 
possessing a dye moiety covalently bonded thereto. 
2. The Melt Dispersion Process 
The melt dispersion process involves the steps of: 
a) reacting a polymeric polyol, an aliphatic diol possessing at least one 
ionic group and a diisocyanate to provide an isocyanate group terminated 
prepolymer possessing ionic groups; 
b) reacting the isocyanate group-terminated prepolymer with a 
formaldehyde-reactive capping agent to cap the isocyanate end groups; 
c) dispersing the capped prepolymer in water; and, 
d) reacting the dispersed capped prepolymer with formaldehyde to provide 
dispersed polyurethane-urea particles, 
at least one of said polymeric polyol, diisocyanate and aliphatic diamine 
possessing a dye moiety covalently bonded thereto. 
3. The Prepolymer Mixing Process 
The prepolymer mixing process involves the steps of: 
a) reacting a polymeric polyol, a carboxylic group-containing diol and an 
aliphatic diisocyanate to provide an isocyanate group-terminated 
prepolymer possessing free carboxyl groups; 
b) reacting the prepolymer with a tertiary amine to convert the carboxyl 
groups to ammonium carboxylate groups and render the prepolymer 
self-dispersible; 
c) dispersing the self-dispersible prepolymer in water; and, 
d) reacting the dispersed prepolymer with a diamine chain extender to 
provide an aqueous dispersion of polyurethane-urea particles, 
at least one of said polymeric polyol, carboxyl group-containing diol, 
aliphatic diisocyanate and aliphatic liquid diamine chain extender 
possessing colorant covalently bound thereto. 
4. The Ketamine/Ketazine Process 
The ketamine/Ketazine process involves the steps of: 
a) reacting a polymeric polyol, a carboxylic group-containing diol and a 
diisocyanate to provide an isocyanate group-terminated prepolymer 
possessing free carboxyl groups; 
b) reacting the prepolymer with a tertiary amine to convert the carboxyl 
groups to ammonium carboxylate groups and render the prepolymer 
self-dispersible; 
c) reacting the self-dispersible prepolymer with at least one member of the 
group consisting of ketimine and ketazine in the presence of water to 
provide an aqueous dispersion of polyurethane-urea particles, 
at least one of said polymeric polyol, carboxyl group-containing diol, 
aliphatic diisocyanate and aliphatic liquid diamine chain extender 
possessing colorant covalently bound thereto. 
In a preferred embodiment of these waterborne processes, the polymeric 
polyol is one of the general formula R.paren open-st.P--OH).sub.2 wherein 
R is a covalently bound dye chromophore and each P is the same or 
different polymer residue. Examples of such polymeric polyols include any 
of the previously mentioned dihydroxyl-terminated liquid polyether or 
polyester dye monomers containing a covalently bonded dye moiety. 
The polymer dye component of the erasable ink composition of this invention 
will generally possess an average particle size of from about 25 to about 
5000 nanometers and preferably from about 50 to about 2000 nanometers. 
Where the polymer dye component is not obtained in a particle size which 
is suitable for use in the erasable ink composition herein, it may be 
reduced to such size by any known or conventional method for obtaining 
polymer powders, for example, by grinding, milling, or by any of several 
"hot water" emulsification processes for producing polymer powders such as 
that described in U.S. Pat. No. 3,586,654, the contents of which are 
incorporated by reference herein. 
The fully formulated erasable ink composition, i.e., the polymeric dye 
component in admixture with the evaporable liquid carrier component and 
any optional component(s), can possess a relatively low viscosity, e.g., 
from about 1 to about 80,000 centipoises and preferably from about 3 to 
about 30,000 centipoises when water is the carrier, or a relatively high 
viscosity, e.g., at least about 100,000 centipoises and preferably at 
least about 500,000 centipoises when the carrier is an organic solvent or 
mixture of organic solvents which swell or dissolve the polymer dye. It 
will, of course, be recognized that when the erasable ink composition 
possesses such a high viscosity that it no longer readily flows solely 
under the influence of gravity, it becomes necessary to provide a 
pressurized delivery system for any marking instrument containing the ink. 
To improve or optimize one or more functional characteristics of the 
erasable ink composition, one or more optional components can be added in 
the usual amounts to the composition, e.g., one or more natural and/or 
synthetic polymer latices, rheological modifiers, suspension agents, 
humectants, emulsifiers, surfactants, plasticizers, spreading agents, 
drying agents, release agents, parting agents, preservatives, 
antimicrobial agents, anticorrosion agents, antioxidants, coalescing aids, 
and the like. 
With or without the addition of any optional component(s), the erasable ink 
composition when applied to a substrate, and particularly a porous 
substrate such as a cellulosic paper, and upon drying thereon must be (1) 
sufficiently adherent to the substrate as to resist flaking therefrom and 
(2) substantially erasable. Thus, the dry erasable ink composition of this 
invention applied to paper and evaluated by the adherency test described 
infra will generally exhibit less than about 30 weight percent flaking, 
preferably less than about 20 weight percent flaking and even more 
preferably less than about 10 weight percent flaking. Erasability values 
delta E*ab of the erasable ink composition herein as measured by ASTM 
D-2244-89 will generally be on the order of less than about 4.0, 
preferably less than about 3.5 and even more preferably less than about 
3.0. 
It is preferred that the erasable ink composition herein when evaluated by 
the smearability test described infra exhibit a subjectively determined 
low level of smear, e.g., a smear value of 2 or less and preferably a 
smear value of 1 (i.e., essentially no smearing). 
The erasable ink composition of this invention is intended to be used in 
any of a variety of marking instruments and in particular, a ball-point 
pen. 
The following examples are illustrative of the erasable ink composition of 
this invention. 
EXAMPLES ILLUSTRATING THE PREATION OF POLYFUNCTIONAL PREPOLYMERS 
POSSESSING COVALENTLY BONDED DYE MOIETY 
Example 1 
Dimethylolpropionic acid (8.25 g) was dissolved in N-methyl pyrollidone 
(13.8 g). To this solution, polytetramethylene glycol (TERETHANE T-2900 
from Dupont) (208.2 g), polyol colorant (15.0 g) corresponding to Colorant 
C from Table I of U.S. Pat. No. 5,231,135, isopherone diisocyanate (42.40 
g) and dibutyltindilaurate catalyst (0.72 g) were added. The solution was 
heated to a temperature of from about 60.degree. to about 70.degree. C. 
for about 3 to about 5 hours under stirring. The color of the resulting 
isocyanate group-terminated prepolymer having dye covalently bonded 
thereto was red. 
Example 2 
Dimethylolpropionic acid (7.37 g) was dissolved in N-methyl pyrollidone 
(12.31 g). To this solution, polytetramethylene glycol (TERETHANE T-2900 
from Dupont) (151.2 g) and polybutylene glycol (BO-4800 from Dow Chemical) 
(84.0 g), polyol colorant (5.0 g) corresponding to Colorant C from Table I 
of U.S. Pat. No. 5,231,135, isopherone diisocyanate (42.40 g) and 
dibutyltindilaurate catalyst (0.48 g) were added. The solution was heated 
to a temperature of from about 60.degree. to about 70.degree. C. for about 
3 to about 5 hours under stirring. The color of the resulting isocyanate 
group-terminated prepolymer having dye covalently bonded thereto was red. 
Example 3 
Dimethylolpropionic acid (3.50 g) was dissolved in N-methyl pyrollidone 
(5.84 g). To this solution, polytetramethylene glycol (TERETHANE T-2900 
from Dupont) (305.9 g), polyol colorant (5.0 g) corresponding to Colorant 
U from Table I of U.S. Pat. No. 5,231,135, polyol colorant (5.0 g) 
corresponding to Colorant G from Table I of U.S. Pat. No. 5,231,135, 
isopherone diisocyanate (42.40 g) and dibutyltindilaurate catalyst (0.12 
g) were added. The solution was heated to a temperature of from about 
60.degree. to about 70.degree. C. for about 3 to about 5 hours under 
stirring. The color of the resulting isocyanate group-terminated 
prepolymer having dye covalently bonded thereto was violet-blue. 
Example 4 
Dimethylolpropionic acid (8.08 g) was dissolved in N-methyl pyrollidone 
(13.5 g). To this solution, polytetramethylene glycol (TERETHANE T-2900 
from Dupont) (184.5 g), polyol colorant (5.0 g) corresponding to Colorant 
C from Table I of U.S. Pat. No. 5,231,135, isopherone diisocyanate (42.40 
g) and dibutyltindilaurate catalyst (0.48 g) were added. The solution was 
heated to a temperature of from about 60.degree. to about 70.degree. C. 
for about 3 to about 5 hours under stirring. The color of the resulting 
isocyanate group-terminated prepolymer having dye covalently bonded 
thereto was red. 
Example 5 
Dimethylolpropionic acid (8.08 g) was dissolved in N-methyl pyrollidone 
(13.5 g). To this solution, polytetramethylene glycol (TERETHANE T-2900 
from Dupont) (174.6 g), polyol colorant (5.0 g) corresponding to Colorant 
C from Table I of U.S. Pat. No. 5,231,135, isopherone diisocyanate (42.40 
g) and dibutyltindilaurate catalyst (0.48 g) were added. The solution was 
heated to a temperature of from about 60.degree. to about 70.degree. C. 
for about 3 to about 5 hours under stirring. The color of the resulting 
isocyanate group-terminated prepolymer having dye covalently bonded 
thereto was red. 
Example 6 
Isopherone diisocyanate (42.40 g) and polytetramethylene glycol (TERETHANE 
T-2900 from Dupont) (174.6 g) were admixed. To this mixture, polyol 
colorant (5.0 g) corresponding to Colorant U from Table I of U.S. Pat. No. 
5,231,135 was added. The mixture was dissolved in methylethylketone (120 
g) and dibutyltindilaurate catalyst (0.24 g) was added to the solution 
which was stirred at room temperature overnight. The color of the 
resulting isocyanate group-terminated prepolymer having dye covalently 
bonded thereto was violet. 
EXAMPLES ILLUSTRATING THE PREATION OF POLYMER DYES 
Example 7 
The prepolymer mixing process was carried out as follows: the prepolymer of 
Example 1 was reacted with triethyl amine (6.22 g) neutralizing agent to 
convert the carboxyl groups in the prepolymer to ammonium carboxylate 
groups and render the prepolymer self-dispersible. Thereafter, the 
self-dispersible prepolymer was dispersed in water (241 g) using an 
impeller-type dispersion blade. The dispersed prepolymer was then reacted 
at room temperature with hydrazine (3.93 g) chain extender to provide a 
dispersion of polyurethane-urea particles of approximately 55.0 weight 
percent solids. 
Example 8 
The prepolymer mixing process was carried out as follows: the prepolymer of 
Example 2 was reacted with triethyl amine (5.60 g) neutralizing agent to 
convert the carboxyl groups in the prepolymer to ammonium carboxylate 
groups and render the prepolymer self-dispersible. Thereafter, the 
self-dispersible prepolymer was dispersed in water (300 g) using an 
impeller-type dispersion blade. The dispersed prepolymer was then reacted 
at about 76.degree. C. with hydrazine (5.76 g) chain extender to provide a 
dispersion of polyurethane-urea particles of approximately 50.7 weight 
percent solids. 
Example 9 
The prepolymer mixing process was carried out as follows: the prepolymer of 
Example 3 was reacted with triethyl amine (2.64 g) neutralizing agent to 
convert the carboxyl groups in the prepolymer to ammonium carboxylate 
groups and render the prepolymer self-dispersible. Thereafter, the 
self-dispersible prepolymer was dispersed in water (436 g) using an 
impeller-type dispersion blade. The dispersed prepolymer was then reacted 
at room temperature with hydrazine (1.49 g) chain extender to provide a 
dispersion of polyurethane-urea particles of approximately 45.9 weight 
percent solids. 
Example 10 
The prepolymer mixing process was carried out as follows: the prepolymer of 
Example 4 was reacted with triethyl amine (6.09 g) neutralizing agent to 
convert the carboxyl groups in the prepolymer to ammonium carboxylate 
groups and render the prepolymer self-dispersible. Thereafter, the 
self-dispersible prepolymer was dispersed in water (300 g) using an 
impeller-type dispersion blade. The dispersed prepolymer was then reacted 
at room temperature with hydrazine (5.82 g) chain extender to provide a 
dispersion of polyurethane-urea particles of approximately 46.4 weight 
percent solids. 
Example 11 
The prepolymer mixing process was carried out as follows: the prepolymer of 
Example 5 was reacted with triethyl amine (6.09 g) neutralizing agent to 
convert the carboxyl groups in the prepolymer to ammonium carboxylate 
groups and render the prepolymer self-dispersible. Thereafter, the 
self-dispersible prepolymer was dispersed in water (300 g) using an 
impeller-type dispersion blade. The dispersed prepolymer was-then reacted 
at room temperature with hydrazine (5.82 g) chain extender to provide a 
dispersion of polyurethane-urea particles of approximately 46.9 weight 
percent solids. 
Example 12 
The solvent process was carried out as follows: the prepolymer of Example 6 
dissolved in methylethylketone was reacted at room temperature with 
hydrazine (2.15 g) chain extender to provide an organic solvent solution 
of polyurethane-urea of approximately 64.9 weight percent solids. 
The properties of the polymer dyes of Examples 7-12 are presented in Table 
I as follows: 
TABLE I 
______________________________________ 
Average Particle 
Size (Dry) T.sub.g 
Example (nm) Color (Dry) 
(.degree.C.) 
______________________________________ 
7 50-500 Red &lt;60 
8 250 Red &lt;60 
9 250-2000 Violet-blue 
&lt;60 
10 150 Red &lt;60 
11 150 Red &lt;60 
12 N/A Violet &lt;60 
(solution) 
______________________________________ 
The polymer dye compositions of Examples 7-12 can be directly employed as 
erasable ink compositions or be combined with one or more optional 
components such as an emulsion prior to being employed as erasable ink 
compositions. 
To further illustrate the erasable ink composition of this invention, the 
polymer dye of Example 7 was combined with a silicone emulsion, i.e., 
SWS-233 Silicone Emulsion from Wacker Chemical Corp., to provide an 
erasable ink composition (Example 13) containing 90 weight percent polymer 
dye and 10 weight percent silicone emulsion. In another example, the 
polymer dye of Example 9 was combined with an emulsion containing 25.0 
weight percent sorbitan sesquaoleate, i.e., Glycomol SOC from Lonza, 1.67 
weight percent sodium dodecylbenzenesulfonate, i.e., Rhodocal DS4 from 
Rhone Poulenc, 1.67 weight percent nonylphenol-ethoxylate sulfate, i.e., 
Abex EP120 from Rhone Poulenc, and 71.66 weight percent water to provide 
an erasable ink composition (Example 14) containing 90 weight percent 
polymer dye and 10 weight percent of the emulsion. 
The properties of the erasable ink compositions of Examples 13 and 14 were 
evaluated. In particular, the color intensity, viscosity, adherency, 
erasability and smearability of the erasable ink compositions were 
evaluated. 
Color intensity was evaluated by a subjective visual comparison of script. 
Adherency was determined by performing a drawdown on preweighed Linetta 
drawdown paper with approximately 0.8 g of sample (spread over an area of 
1/4 inch.times.11/2 inch) and drawn down with a #6 cater-bar. The sample 
was allowed to dry completely (approximately 5 minutes at room 
temperature) and the paper was weighed again. The paper was then crumpled 
by hand, any flakes were blown off and the paper was reweighed. This test 
was also performed with erasable ink made according to U.S. Pat. Nos. 
5,120,359 and 5,203,913 assigned to Sakura Color Products Corporation 
(Comparative Example 1) 
Erasability was determined by performing an actual "WRITE-TEST" (similar to 
a spirograph wherein ink is applied in a circular arrangement on paper 
with some cross-over of ink occurring) with ball-point pens containing the 
erasable ink compositions of Examples 13 and 14 and the following 
commercially available pens which contain erasable ink: 
______________________________________ 
Pen Ink Color 
Comparative Example 
______________________________________ 
Erasermate Blue 2 
Erasermate 2 Blue 3 
Scripto Blue 4 
Scripto Red 5 
______________________________________ 
The "WRITE-TEST" write-downs were then erased and reflectance measurements 
were performed on the erased portion of the paper versus an 
unblemished/untouched portion of the paper. A quantitative value was then 
obtained, i.e., delta E*ab from CIE lab measurement (described in ASTM 
D-2244-89). Lower values indicate more complete erasures. 
Smearability was subjectively evaluated for the erasable ink compositions 
of Examples 13 and 14 and Comparative Examples 2-5 1-2 seconds after 
writing by attempting to smudge the ink with one's fingers. A smear value 
of 1 represents essentially no smearing and a smear value of 5 represents 
such a degree of smearing that legibility of the writing is significantly 
impaired. 
Table II below presents the properties of the erasable ink compositions: 
TABLE II 
______________________________________ 
(Wt. % of 
Dried Ink 
Vis- Composition 
Erasability 
Color cosity Retained on 
Value Smear 
Example 
Intensity (cps) the Paper) 
(delta E*ab) 
Value 
______________________________________ 
13 Comparable to 
.about.3-5 
100% 3.17 1 
Comparative 
Examples 
14 Comparable to 
.about.3-5 
100% 1.44 1 
Comparative 
Examples 
Comp. -- -- 63% -- -- 
Ex. 1 
Comp. -- -- -- 3.3 -- 
Ex. 2 
Comp. -- -- -- 3.63 2 
Ex. 3 
Comp. -- -- -- 5.38 3 
Ex. 4 
Comp. -- -- -- -- 4 
Ex. 5 
______________________________________ 
The data in Table II clearly demonstrate the superiority of the erasable 
ink composition of this invention relative to commercially available 
erasable inks. The erasable ink composition of this invention is highly 
adherent to a substrate as to resist flaking therefrom and substantially 
erasable. 
While this invention has been disclosed herein in connection with certain 
embodiments and certain procedural details, it is clear that changes, 
modifications or equivalents can be used by those skilled in the art. 
Accordingly, such changes within the principles of this invention are 
intended to be included within the scope of the claims below.