Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVEMTION:
Field Of The Invention:
The present invention relates to carbonless
copying systems and in particular to new improved dual-
walled microcapsules which are useful in connection with
such systems and which comprise minute discrete droplets
of liquid fill matèrial including an initially colorless
chemically reactive color forming dye precursor and a
carrier there~or encapsulated within individual, rupturable,
generally continuous dual-wall shell structures made up of
inner and outer capsule walls. ~:
` '
r~
': ~''
: ~ '
~5'~35
~escrip*ion of The Prior Art:
Impact or pressure sensitive carbonless transfer
papers have recently come into wide usage in the United States
and throughout the world. Ordinarily, such papers are printed
and collated into manifolded sets capable of producing multiple
copies. In this connection, pressure applied to the top sheet
causes a corresponding mark on each of the other sheets of the
set.
The top sheet of paper, upon which the impact or
pressure is immediately applied, ordinarily has its back sur-
face coated with microscopic capsules containing one of the
reactive ingredients which interreact to produce a mark. A
receiver sheet, placed in contact with such back face of the
top sheet has its front surface coated with a material having
a component which is reactive with the contents of the capsule
so that when capsules are ruptured upon impact by stylus or
machine key, the initially colorless or substantially color-
less contents of the ruptured capsules react with a co-reactant
therefor on the receiver sheet and a mark forms on the latter
corresponding to the mark impressed by the stylus or machine
key.
In the art, impa-t transfer papers are designated by
the terms CB, CFB and CF, which stand respectively for "coated
back", "coated front and back", and "coated front". Thus,
the CB sheet is usually the top sheet and the one on which the
impact impression is directly made; the CFB sheets are the
intermediate sheets, each of which have a mark formed on the
front surface thereof and each of which also transmits the
contents of the ruptured capsules from its back surface to the
front surface of the next succeeding sheet; and the CF sheet
is the last sheet and is only coated on its front surface to
have an image formed thereon. The CF sheet is not normally
- 2 -
coated on its back surface as no further transfer is desired.
While it is customary to coat the capsules on theback surface and to coat the co-reactant for the capsule con-
tents on the front surface of each sheet, this procedure could
be reversed if desired. Further, with some systems, coatings
need not be used at all and the co-reactive ingredients may be
carried in the sheets themselves, or one may be carried in one
of the sheets and the other may be carried as a surface coat-
ing. Further, the co-reactive materials may each be micro-
encapsulated. Patents illustrative of many of the various
kinds of systems which may incorporate such co-reactive ingre- ;
dients and which may be used in the production of manifolded
transfer papers include, for example, U. S. 2,~99,694 to Green,
U. S. 2,712,507 to Green, U. ~. 3,016,308 to Macaulay, U. S.
3,42~,827 to Ruus and U. S. 3,720,534 to Macaulay et al.
The most common variety of carbonless impact transfer
paper, and the type with which the present invention is uti-
lized, is the type illustrated, for example, in Green ('507)
and Macaulay ('308) wherein microscopic capsules containing a
liquid fill comprising a solution of an initially colorless
chemically reactive color forming dye precursor are coated on
the back surface of the sheet, and a dry coating of a co-
reactant chemical for the dye precursor is coated on the front
surface of a receiving sheet.
Many color precursors useful in connection with
carbonless copying systems are known to those skilled in the
art to which the present invention pertains. For example,
specific reference is made to the color precursors mentioned
in the patent to Phillips, Jr. et al, U. S. 3,455,721 and par-
t~cularly to those li~ted in the paragraph bridging columns5 and 6 thereof. These materials are capable of reacting
with a CF coating containing an acidic material such as acid-
-- 3 --
1~5;Z~
leached bentonite-type clay or the acid-reactant organic
polymeric material disclosed in the Phillips, Jr. et al '721
patent. Many of the color precursors disclosed in the '721
patent referred to above are capable of undergoing an acid- -`
base type reaction with an acidic material.
Other previously known color precursors are the
spiro-dipyran compounds disclosed in the patent to Harbort,
U. S. 3,293,060 with specific reference being made to the dis-
closure of the '060 patent extending from column 11, line 32,
through column 12, line 21. The color precursors of Harbort,
as well as the color precursors of Phillips, Jr. et al are
initially colorless and are capable of becoming highly colored
when brought into contact with an acidic layer such as an
acid-leached bentonite-type clay or an acid-reacting polYmeric
material, or the like.
Generally speaking, color precursor materials of the
type disclosed by Phillips, JrO et al ('721) and by Harbort
('060) are dissolved in a solvent and the solution is encapsu-
lated. Previously known procedures and processes ~or micro-
encapsulation are described and disclosed in U. S. 3,016,308
to Macaulay, U. S. 2,712,507 to Green/ U. S. 3,429,827 to Ruus
and U. S. 3,578,605 to Baxter.
Solvents known to be useful in connection with dis-
solving color precursors include chlorinated biphenyls. vege-
table oils (castor oil, coconut oil, cotton seed oil, etc.),
esters (dibutyl adipate, dibutyl phthalate, butyl benzyl adi-
pate, benzyl octyl adipate, tricresyl phosphate, trioctyl .
phosphate, etc.), petroleum derivatives (petroleum spirits,
kerosene, mineral oils, etc.), aromatic solvents (benzene,
toluene, etc.), silicone oils, or combinations of the fore-
going. Particularly useful are the alkylated naphthalene
solven~s disclosed in U. S. 3,806,463 to Konishi et al.
-- 4 --
l(~S'~95
.
In the cclor forming systems outlined above, as will
be appreciated by those skilled in the art, the color precur-
sors are conventionally contained in pressure rupturable
microcapsules which are included in the back coatings of the
sheets of carbonless copying manifolded sets. Further, it
will be appreciated that acidic coatings are generally util-- -
ized as front coatings with the color precursor material in a
solvent therefor being transferred from an adjacent back ;~
coating to the acidic layer front coating upon rupture of the
capsules which contain the color precursor materiaL.
Althouqh microcapsules have been extensively used in
connection with carbonless copying systems in the past, those
skilled in this art continue to search for products which are
more durable and better adapted for handling on high speed
processing equipment. U. S. 3,578,605 to Baxter, for example,
discloses dual-walled capsules having an outer shell formed
from a hydrophilic colloid material by coacervation. U. S.
3,429,827 to Ruus discloses dual-walled capsules wherein the
outer shell is applied by spray dryins or coating with a dry
2~ particulate substance. The dual-walled capsules of Jensen
disclosed in U. S. 3,265,629 comprise an inner shell of a waxy
material and an outer wall of a hydrophilic colloid material.
The dual-walled capsules disclosed by Brynko and Scar-
pelli in their patents U. S. 2,969,331 and U. S. 3,190,837
have an outer shell formed from a hydrophilic colloid material
as do the multi-layered capsules of Scarpelli disclosed in U. S. ;~
3,627,693. While the microcapsules disclosed in these refer-
ences generally possess somewhat better properties than single
walled capsules, problems still exist and the search for more ~`~
durable and more easily handled microcapsules continues.
SU~RY OF THE INVENTION:
The present invention provides improved dual-walled
_ 5 _
microcapsules wherein the inner shell is formed by an inter-
facial polycondensation procedure and thereafter the outer
shell is formed thereabout by the polymerization of an initi-
ally water-soluble, low molecular weight aminoaldehyde precon-
densate. In the preferred form of the invention the reaction
leading to the formation of the outer shell is influenced by -
conditions created during the initial interfacial polyconden-~
sation of the inner shell. Thus, microcapsules are produced
which comprise minute, discrete droplets of a liquid fill
material, each surrounded by an individual, rupturable, gener-
ally continuous inner wall of a polycondensate material. The
capsules also each include an individual, rupturable, gener-
ally continuous outer shell of a polycondensate substance encom-
passing the outer surface of each of the inner walls. Prefer-
ably the polycondensate material is a polyamide which has been
formed by interfacial polycondenSation. The preferred poly-
condensate substance for the outer shell is a urea-formaldehyde
polymer.
Broadly, the microcapsules of the invention are pro-
duced by a process which comprises establishing a two-phase
system containing an aqueous continuous phase and a dispersed
discontinuous phase of minute~intended liquid capsule core en-
tities which are substantially insoluble in the cont~nouus
phase. Included in the aqueous continuous phase are a water-
soluble, low molecular weight aminoaldehyde precondensate and
a water soluble first polyfunctional reactant capable of under-
go~ng polycondensation with a second polyfunctional reactant
to produce a polycondensate material. The second polyfunc-
tional reactant is included in the discontinuous phase whereby ;
the first and second polyfunctional reactants condense at the
interface between the phases to thereby encapsulate each core
- 6 -
I
L9~
entity in an individual, generally continuous polycondensate
inner shell. Thereafter the conditions in the continuous -
phase are adjusted to cause polymerization of the preconden-
sate to a water-insoluble polymer which enwraps each encapsu-
lated core entity and forms an individual, generally continu-
ous aminoaldehyde outer shell thereabout. Generally speaking,
the adjustment of the conditions in the continuous phase com-
prises decreasing the pH thereof to about 5.0 or less and
preferably such decrease in the pH of the continuous phase is
caused by the production of an acid such as HCl during the
polycondensation of the first and second reactants. In the
most highly preferred form of the invention, the first poly-
functional reactant is diethylene triamine, the second poly-
functional reactant is terephthaloyl chloride and the aminoal-
dehyde precondensate is a urea-formaldehyde resin.
DETAILED DESCRIPTION OF THE INVENTION:
~roadly, the present invention comprises microcapsules
having an inner wall such as that produced by the interfacial
- polycondensation techniques disclosed in the patent to Ruus,
U. S. 3,429,827 and an outer wall of a hydrophobic, aminoalde-
hyde polymer such as that produced in accordance with the dis-
closure o Macaulay, U. S. 3,016,308, and particularly in accor-
dance with Example IV, beginnin~ at line 17 of column 9 of the
'308 patent. In the preferred method of the present invention,
hydrochloric acid generated by the reaction of terephthaloyl
chloride and diethylene triamine in accordance with the Ruus
interfacial polycondensation procedure is utilized to decrease
the ~H of the system and cause the urea-formaldehyde resin of
Example IV of Macaulay to condense and precipitate to thereby
form the outer shell. -
Usually in interfacial microencapsulation procedures,
_ 7 _
~al5~1~5
an oil containing a diacid chloride, a disulfonyl chloride, a
diisocyanate, etc., is emulsified in an aqueous or polar medium
containing a monomer such as a diamine or a bisphenol or the
like. The condensation reaction takes place at or near the
interface between the dispersed oil phase and the continuous
aqueous phase. The concepts and principles of the instant
invention are attractive because the interfacial polycondensa- -
tion reaction is generally much faster than the acid catalyzed
condensation reaction leading to the formulation of the outer
shell. This minimizes the amount of mixup during shell forma-
tion and protects the capsules from distortion. brea~age. or
the like~caused by de-emulsification and maximizes the devel-
opment of the inner shell wall by interfacial polycondensation.
Hydrochloric acid is a usual by-product of the interfacial
polycondensation reactions by which the inner shell wall is
formed and an acidic condition is required for condensing
conventional aminoaldehyde precondensates. Moreover, an inner
shell formed by an interfacial polycondensation procedure could
be modified to be acidic, basic, reactive, etc., depending on
factors such as the nature and amount of the monomers and the
presence of cross-linking agents or the like during the micro-
encapsulation process. For example, depending on the amount
and nature of the acid chloride and amine used, the end group
of the polymer chain could be acidic or basic. Moreover, the ;
connecting groups could be modified similarly.
Another attractive feature of the present invention ,
is that dual-walled capsules may be formed in a single cbntin-
uous procedure wherein the acid generated by the interfacial
polycondensation is used to cataly~e the condensation of the
aminoaldehyde precondensate. This does not exclude the use
- 8 -
I
~sz~s
of other chemicals, additives, heat, mixing, etc. to enhance
the reaction or improve the quality of the outer shell or
deposit. The dual-walled capsules produced in accordance
with the present invention have improved strength, chemical
resistance, hydrophobicity, etc. when compared with conven-
tional microcapsules. Moreover, microcapsules produced by
conventional interfacial polycondensation procedures are elas-
tic in nature and are not easily separated, dried or filtered
under normal conditions. However, in accordance-with tha
present invention, free flowing dry capsules are quite easily
produced because of the inherent toughness ànd other proper-
ties o~ the cross-linked polycondensate outer shell wàll. `~
The capsules of the present invention are pàrticu-
`:
larly useful in connection with carbonless copying systems;
however, it shou~d be appreciated that other uses for micro-
capsules are well known to those of ordinary skill in this art.
When the capsules are utilized in connection with carbonless
copying systems, the fill material will ordinarily include an
initially colorless chemically reactive color forming dye pre-
cursor and a carrier therefor such as dibutyl phthalate or oneof the alkylated naphthalene solvents disclosed in U. S.
3,806,463 to Konis~i et al.
The inner capsule shell may be any polycondensate
formed by interfacial polycondensation at the interface between
dispersed droplets of fill material and a continuous phase.
For example, various polycondensates are disclosed in U. S.
3,429,827 to Ruus including polyamides, polyurethanes, polysul-
fonamides, polyesters, polyureas, polycarbonates, etc. Par-
ticularly useful in connec'cion with the production of the inner
shell wall by interfacial polycondensation are those reactants
:
~5;~95
which give of~ an acid as a by-product during the condensation.
For example, terephthaloyl chloride and ethylene diamine con-
dense to form a polyamide and hydrochloric acid is produced as
a by-product.
With regard to the outer shell, aminoaldehyde resins
generally are useful. In particular, melamine-formaldehyde,
phenol-formaldehyde, urea-formaldehyde and urea-acetaldehyde
resins are useful. Typically these materials are capable of
existing in a water soluble, low molecular weight preconden-
sate form whenever the pH of the system is greater than a par-
ticular level which is a fwlction of the specific material and
which is generally about 5 or so. However, when the pH of
the system is decreased to such particular level or below, the
precondensate undergoes further polymerization and cross-
linXing to produce a water insoluble polymer which precipi-
tates from solution to enwrap and encapsulate particles which
might be dispersed in the continuous phase. This phenomena
is described in detail in the patent to Matson, U. S. 3,516,941.
This phenomena is also disclosed particularly in Example IV of
the patent to Macaulay, U. S. 3,016,308.
EXAMPLE I
l.00 gm of p-toluene sulfonate of Michler's hydrol
(PTSMH) were admixed with 37.5 gms of dibutyl phthalate (DBP)
and this admixture was warmed slightly on a hot plate until a
clear solution (solution A) was obtained. Thereafter, solu-
tion A was allowed to cool to room temperature. Then 3.26 gms
of terephthaloyl chloride were added to 37.5 gms of dibutyl
phthalate (DBP) and this mixture was also warmed slightly on a
hot plate until a clear solution (solution B) was obtained.
Solution B was then also allowed tQ cool to room temperature.
After solutions A and B were preparea, 89.0 gms of an aqueous
-- 10 --
~5;~ 5
solution containing 1.4 weight percent of the product marketed
under the Trade Mark "~ercules 7Ll" cellulose gum (a commerci-
ally available sodium carboxymethyl cellulose product having a
degree of substitution of approximately 0.~ and a molecular
weight of less than 45,000) and 18.7 gms of the product mar-
keted under the Trade Mark "URAC Resin 180" solution ~a commer-
cial product of American Cyanamide Company which is an unmodi-
fied urea-formaldehyde resin in water solution at approximately
65 weight percent solids) were admixed and were placqd in a one
quart Waring blender. Then solutions A and B were mixed to-
gether at room temperature and the resultant solution was added
to the aqueous solution of URAC 180 and cellulose gum in the
blender. The blender was activated and high shear agitation
was continued for about 45 seconds until an emulsion having a
dispersed phase particle size of about 2 to 10 microns was
obtained. In this emulsion, the aqueous solution containing
the URAC 180 and the cellulose gum formed the continuous phase
and the solution of terephthaloyl chloride and PTSMH in DBP
formed the dispersed phase. 300 gms of water were added to
the emulsion and the diluted emulsion was then transferred to
a suitable container such as a beaker and was stirred with a
variable speed mechanical stirrer at 300 to 500 rpm w~ile an
aqueous solution containing 1.5 gms of diethylene triamine and
10 gms o water was added thereto. Prior to the addition of
the amine solution, the emulsion was examined and the same had
a pH of 6Ø A coating of the emulsion on a paper substrate
was oilish and no writeoff could be produced on a CF paper
coated with a layer of acid-leached bentonite-type clay. This
is an indication that there were no capsules in the emulsion
prior to the addition of the amine. Five minutes after the
amine solution was added thereto, the pH of the mixture was
-- 11 -- I
lOS~,G~5
9.4. A microscopic examination of the mixture indicated that
polyamide capsules had been formed. Stirring of the emulsion
was continued and after 28 hours the pH of the emulsion had
dropped to 2.8. A microscopic examination of the emulsion at
this point indicated the formation of thicker and stronger
urea-formaldehyde walls. The slurry containing the dual-
walled microcapsules, and having the cellulose gum binder in
the continuous phase, was then drawn down on a 12 pound neutral
base continuous bond paper sheet at a coatin~ weight of approx-
imately 2.34 to 3.04 gms per square meter and the coated sheet
was oven dried at a temperature of 110C for about 30 to 45
seconds. The dry coating of microcapsules containing PTSMH
was then brought into contact with an acid-leached bentonite-
type clay coating on the surface of another sheet of paper and
when an impression was made on the rev~rse side of the sheet -~
coated with microcapsules, a corresponding highly colored re-
production of such impression immediately appeared on the acid-
leached bentonite-type clay coating. The remainder of the
slurry which was not utilized Eor coating paper in accordance
with the foregoing was filtered using a Buchner filter. The
filter cake was slurried in 200 ml of distilled water and was
filtered again. The filter cake was air dried and after
drying the same was easily broken. Copious amounts of DBP
were exuded when the dry capsules were squeezed.
EXAMPLE II
In this Example, the procedure was identical with
that set forth in Example I except that in this instance, the
product marXeted under the Trade Mark l'R-300" solvent was util-
ized as the carrier for the dispersed phase rather than aibutyl
phthalate. R-300 solvent is a commercial product of Kureha
Corporation of America which is a mixture of isomeric diisopro-
- 12 -
-
~05~915
pyl naphthaleneS and which is apparently generally disclosed
in U. S. 3,806,463 to Konishi et al. The quantity of R-300
solvent utilized was identical to the quantity of DBP utilized
in Example I and the quantities of all other materials were
identical with Example I. A microscopic examination of the
slurry immediately after the addition of the diethylene tria-
mine solution revealed that microcapsules had been formed and
that the capsule size was within the range of about 3 to about
20 microns. Fifteen minutes after the addition of the di-
ethylene triamine, the pH of the slurry had dropped to 4.2.The slurry containing these microcapsules (which at this point
were mostly single walled capsules with a poly-amide shell),
and having the cellulose gum binder in the continuoùs phase,
was then drawn down on a twelve pound continuous bond paper
sheet at a coating weight of approximately 3.5 gms per square
meter and the coated sheet was oven dried at a temperature of
110C for about 30 to 45 seconds. The dry coating of micro-
capsules containing PTSMH was then brought into contact with
an acid=leached bentonite-type clay coating on the surface of
another sheet of paper and when an impression was made on the
reverse side of the sheet coated with microcapsules, a corres-
ponding blue colored reproauction of such impression immedi-
ately appeared on the acid-leached bentonite-type clay coating.
The mixing of the microcapsule slurry with the mechanical
stirrer was continued for about 5 hours by which time the pH
of the slurry had dropped to approximately 2.3. This illus- ,
trates the effect of the HCl produced by the polycondensation
of the terephthaloyl chloride ana the diethylene triamine. At
this time the microcapsules had become agglomerated and a
microscopic examination of the slurry inaicated that a urea-
- formaldehyae shell wall had formed around the previously formed
- 13 -
~1)5;~5
single wall capsules. After stirring for 24 hours the pH of
the slurry had decreased further to approximately 1.95 and a
microscopic examination of the slurry at this point revealed a
definite urea-formaldehyde wall formation. The slurry con-
taining the dual-walled microcapsules, and having the cellulose
gum binder in the continuous phase, was then drawn down on a 12
pound continuous bond paper sheet at a coating weight of approx-
imately 3.5 gms per square meter and the coated sheet was oven
dried at a temperature of 110C for about 30 to 45 seconds.
The dry coating of microcapsules containing P~SMH was then
brought into contact with an acid-leached bentonite-type clay
coating on the surface of another sheet of paper and when an
impression was made on the reverse side of the sheet coated
with microcapsules a corresponding blue colored reproduction
of such impression immediately appeared on the acid-leached
bentonite-type clay coating. The remainder of the slurry was
filtered with a Buchner funnel and the filter cake was slurried
in 200 ml of water and was filtered again. These microcap-
sules were then air dried. Filtration of the slurry was
easily performed and the dried cake was easy to break. In
this connection it is to be noted that ~singLe walled capsules
having a polyamide shell ~ormed by interfacial polycondensation
are usually quite difficult to filter and if the water is evap-
~orated from the slurry, a rubbery mass is often formed which is
diff.icult to break. This results from the elasticity and the
tackiness of the polyamide films formed by interfacial polycon-
densation. The outer layer of the tough urea-formaldehyde
shell deposited on the inner polyamide wall eliminates problems
such as difficult filtration and/or tacky capsules, and the
dual-walled capsules of the present invention are easily dried
to present a free-flowing powder. When the dry ~apsules pro-
- 14 -
i~5~
duced in accoraance with the present Example were squeezed,
copious amounts of oll were exuded.
- EXAMPLE III
In this Example, the procedures were generally the
same as those of Example I except that in this instance the
diethylene triamine and the URAC Resin 180 were added together.
Solutions A and B were identical with those o Example I. In
this instance, however, 89 gms of 1.4 weight percent solution
of Hercules cellulose gum 7Ll and 36.0 ml of water were placed
in the Waring blender and solutions A and B were admixed and
emulsified therein in the same manner as in Example I. After
emulsification, 200 gms of water were added to the slurry and
the same was placed in a stirred beaker. A solution was
formed from 1.5 gms of diethylene triamine, 18.7 gms of URAC
Resin 180 solution and 50.0 ml of water and this solution was
added to the reaction mixture while the stirring of the same
continued. immediately after the addition of the solution
containing the diethylene triamine and the URAC Resin 180 solu-
tion, the pH of the reaction mixture was within the range of
about 9 to 10. After 24 hours of stirring, the pH had dropped
to 2.3. ~he color of the mixture was blue and a microscopic
examination revealed a definite urea-formaldehyde wall forma-
tion. A portion of the slurry containing the microcapsules,
and having the cellulose gum binder in the continuous phase,
was then drawn down on a 12 pound neutral base continuous bond
paper sheet at a coating weight of approximately 3.5 gms per
square meter and the coated sheet was oven dried at a tempera-
ture of 110C for about 30 to 45 seconds. The dry coating of
microcapsules containing PTSMH was then brought into contact
with an acid-leached bentonite-type clay coating on the surface
of another sheet of paper and when an impression was made on
- 15 -
the reverse side o~ the sheet coated with microcapsules, a
corresponding blue colored reproduction of such impression
immediately appeared on the acid-leached bentonite-type clay
coating. The remainder of the capsule slurry was filtered
washed and air dried in accordance with the procedures set
forth in the previous Examples. The dry capsule mix was
easy to break and copious amounts of liquid fill material
were exuded when the dry capsules were squeezed.
EXAMPLE IV
In this Example the diethylene triamine was added
to the emulsion first and thereafter the URAC 180 resin solu-
tion was added. The emulsion was formed utilizing the same
procedures and quantities of materials outlined in Example III ~`
above. The emulsion was diluted with 250 ml of water and was
placed in a stirred beaker. An aqueous solution containing
1.5 gms of diethylene triamine and 10.0 ml of water were then
added to the stirred emulsion. Immediately after the addi-
tion of the diethylene triamine solution, the pH of the slurry
was approximately 9 to 10. A microsco~ic examination of the
slurry at this point revealed that single walled capsules
having a polyamide shell had been formed by interfacial poly-
condensation. A few minutes after thè diethylene triamine
solution had been added to the slurry, an aqueous solution
containing 18.7 gms of URAC Resin 180 solution and 50 ml of
water were added to the slurry. After 48 hours of stirring,
the pH value of the mix had decreased to approximately 2.1 and
the same had a slight blue coloration. A microscopic examin-
~ation of the slurry revealed that the capsule size ranged from
about 10 to about 100 microns and urea-formaldehyde wall for- -
mation around the polyamide capsules was evident. This slurry
was filtared, washed and dried as outlined above. When the
~15'~ 5
dry capsules were squeezed, copious amounts of liquid fill
material were exuded.
EXAMPLE V
In this Example, the types and quantities of ingre-
dients and the procedures utilized were identical with Example
I except that in this instance, 89 ml of a 0.5% "Elvanol 50-
42" solution ("Elvanol 50-42" being a Trade Mark) were util-
ized in lieu of the 89 ml of 1.4~ Hercules cellulose gum solu-
tion utilized in Example I. Also, 50 gms of URAC Resin 180
solution were utilized. Elvanol 50-42 is a polyvinyl alcohol
with 87 to 89~ hydrolysis and a viscosity of 35 to 45 centi-
poises in a 4% aqueous solution at 20C. The procedures for
producing the dual-walled microcapsuies were identical with
those utilized in Example I. Within a minute after the addi-
tion of the diethylene triamine solution, the pH of the mix-
ture had become approximately 7.0 and the presence of micro-
capsules was apparent. After 2~ hours of mixing the pH of
the slurry had decreased to 1.9 and a microscopic examination
~ of the slurry inaicated that urea-formaldehyde coated cap
sules had been produced. A portion of this slurry was util-
ized to produce coated paper in accordance with the proced-
ures set forth above. Instant blue images were produced
utilizing such paper in conjunction with acid-leached benton-
ite-type clay coated CF paper. A sufficient amount of a 20%
solution of sodium hydroxide was added to the remainder of
the slurry to cure and harden the urea-formaldehyde resin
shells. Paper was coated with these cured capsules and
again instant blue reproductions were created when this
coated paper was utilized in con~unction with acid-leached
bentonite-type clay coated CF paperO The slurry was filtered,
washed and dried in accordance with the procedures set forth
- 17 ~
~ .
~, .
~9~5~5 ~:
a~ove and the dried cake was very easy to break and the dry
capsules were powdery and ~ree flowing. Upon squeezing the
capsules, copious amounts of liquid fill material was exuded.
EXAMPLE VI
1.00 gm of the methyl ether of Michler's hydrol
~MEMH) were admixed with 37.5 gms of xylene and this admixture
was warmed slightly on a hot plate until a clear solution
~solution A) was obtained. Thereafter solution A was allowed
to cool to room temperature. Then, 3.6 gms of terephthaloyl
chloride were added to 37.5 gms of xylene and this mixture was
alqo warmed slightly on a hot plate until a clear solution
(solution B) was obtained. Solution B was then also allowed
to cool to room temperature. After solutions A and B were
prepared, 90.0 ml of 0.5 weight percent ~lvanol 50-42 solution
and 50.~ gms of URAC Resin 180 solution were placed in a one
quart Waring blender and then solutions A and B were mixed to-
gether at room temperature and the resultant solution was
added to the solution containing URAC Resin 180 and Elvanol in
the blender. The blender was activated and high shear agita
tion was continued for about one minute until an emulsion was
obtained. In this emulsion, the aqueous solution containing
the Elvanol and the URAC Resin 180 formed the continuous phase
and the solution containing the xylene solvent, the MEMH and
terephthaloyl chloride formed the dispersed phase. This
emulsion was diluted with 300 ml of water and the diluted
emulsion was then transferred to a suitable container such as
a beaker and was stirred with a variable speed mechanical
stirrer at 300 to 500 rpm while an aqueous solution contain-
ing 1.5 gms of diethylene triamine and 10 ml of water were
added, Immediately upon addition of the di~thylene triamine
solution, the pH of the slurry was in the rangP of from about
`
~ 18 - I
-
~LO S ~ IL9 5
6 to 7 and the formation of single walled capsules having a
polyamide shell formed by interfacial polycondensation became
evident. After ~4 hours of stirring, the pH of the slurry
had decreased to about l.9. Coatings prepared from this
slurry produced an instant blue writeoff on acid-leached
bentonite-type clay coated CF paper. A sufficient amount of
a 20% solution of sodium hydroxide was added to increase the
pH of the slurry to approximately 9Ø The sodium hydroxide
is operable to cure and harden the urea-formaldehyde outer
capsule walls. A portion of this slurry containing the
microcapSules, and having the Elvanol polyvinyl alchohol
binder in the continuous phase, was then drawn down on a 12
pound neutral base continuous bond pàper sheet at a coating
weight of approximately 3.5 gms per square meter and the
coated sheet was oven dried at a temperature of 110C for
about 30 to 45 seconds. The dry coating on the paper sheet
was white. The dry coating of microcapsules containing the
MEMH was then brought into contact with an acid-leached
bentonite-type clay coating on the surface of another sheet
of paper and when an impression was made on the reverse side
of the sheet coated with microcapsules, a corresponding blue
colored reproduction of such impression immediately appeared
on the acid-leached bentonite~type clay coating~ The remainder
of the slurry was then filtered, washed and air dried in
accordance with the procedures set forth above. The dry
cake was easily broken to produce a free flowing powder of
; microcapsules which exuded copious quantities of liquid fill
material whèn squeezed.
EXAMPLE VII ~;
; 30 1.0 gm of PTSMH were admixed with 37.5 gms of DBP
and this admixture was warmed slightly on a hot plate until a
-- 19 -- I
~5'~ 5
clear solution (solution A) was obtained. Thereafter solu-
tion A was allowed to cool to room temperature. Then, 3.6
gms of terephthaloyl chloride were added to 37.5 gms of DBP
and this mixture was also warmed slightly on a hot plate until
a clear solution ~solution B) was obtained. Solution B was
then allowed to cool to room temperature. After solutions A
and B were prepared, 90 ml of an aqueous solution containing
0.5 weight percent Elvanol 50-42 polyvinyl alcohol and 50 ml
of water were placed in a one quart Waring blender and then
solutions A and B were mixed together at room temperature and
the re~ultant solution was added to the Elvanol solution in
the blender, The blender was activated and high shear agita-
tion was continued for about 1 minutè until an emulsion was
obtained. In this emulsion, the aqueous solution containing
the Elvanol polyvinyl alcohol formed the continuous phase and
the solution containing the DBP solvent, the PTSMH and tereph-
thaloyl chloride formed the dispersed phase. The resultant
emulsion was then transferred to a suitable container such as
a beaker and the same was diluted with 200 ml of water. 1.4
gms of 1,2-ethanedithiol were added to 70 ml of water and a
sufficient quantit~ of NaOH was added to the mixture to neu-
tralize the 1,2~ethanedithiol. This mixture was then
warmed slightly to produce a clear solution having a pH of
about 9.O. 50 gms of a ~5 weight percent URAC Resin 180
solution was then added to this clear aqueous solution and the
resultant solution was added to the diluted emulsion while
the latter was stirred with a variable speed mechanical
stirrer at 300 to 500 rpm. Stirring was continued for
approximately 24 hours. Immediately after the addition of
` 30 the ~olution containing the ethanedithiol and the URAC Resin
180, the pH of the slurry was approximately 6 to 7 and the
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formation of single walled capsules having a polythiolester
shell formed by interfacial polycondensation was evident. A
sufficient amount of a20% sodium hydroxide solution was added
to the slurry to increase the pH to approximately 9.0 whereby
the urea-formaldehyde outer ~hells were cured and hardened.
A portion of this slurry containing the hardened microcap6ules,
and having the Elvanol polyvinyl alcohol binder in the contin-
uous phase, was then drawn down on a 12 pound neutral base con-
tinuous bond paper sheet at a coating weight of approximately
3.~ gms per square meter and the coated sheet was then dried
at a temperature of 110C for about 30 to 45 seconds. The
dry coating on the paper sheet was white. The dry coating o
microcapsules containing PTSMH was then brought into contact
with an acid-leached bentonite-type clay coating on the sur-
face of another sheet of paper and when an impression was
made on the reverse side of the sheet coated with microcap-
sules, a corresponding blue colored reproduction of such im-
pression immediately appeared on the acid-leached bentonite-
type clay coating. The remainder of the microcapsules pro-
2~ duced in accordance with this Example were filtered, washedand dried in accordance with the procedures outlined above~
The filter cake was easily broken to present a free flowing
powder of microcapsules. When these microcapsules were
squeezed, copious amounts of the liquid fill material were
exuded.
Although in each of the foregoing Examples a urea-
formaldehyde resin was utilized to form the outer shell, it
should be understood that the present invention contemplates
the utilization of any one of a variety o~ polymers for the
formation of the outer shell wall. Critically, the monomer
for the outer shell must be relatively non-reactive at the
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.
conditions necessary for the formation of the inner wall by
interfacial polycondensation and moreover, th~ monomer for
the outer shell should be water soluble in its monomer form,
whereas the polymer formed therefrom should be water insoluble.
Particularly useful in connection with the present invention
are the two stage resins capable of existing ln a water
soluble, precondensate first stage and in a cross-linked,
water insoluble, higher molecular weight second stage. In
particular, aminoaldehyde resins (or aminoplasts) are useful
in connection with the presentinvention. A discussion of
aminoplasts and aminoplast precursors appears in C. P. Vale's
book "Aminoplasts" published in 1950 by Inter Science Publi-
shers, Inc. The aminoaldehyde resins typically are capable
of existing in a thermoplastic first stage where the same are
in a relatively low-molecular weight, water soluble form.
Upon catalysis with an acid, these precondensates are cross-
linked to present a second stage polymer which is of rela-
tively higher molecular weight and is generally water insol-
uble. As soon as the resin has been converted into its
higher molecular weight, water insoluble form, the same preci-
pitates from water solution and enwraps dispersed particles
present in the system. This phenomena is fully disclosed
and illustrated in U. S. 3j016,308 to Macaulay (see particu-
larly Example IV) and in U. S. 3,516,941 to Matson.
With regard to the inner wall of the dual-walled
microcapsules of the present invention, the present invention
.
contemplate5 the utilization of those polymers which may be
formed by interfacial polycondensation at the interface be-
tween a dispersed phase and a con~inuous phase. Such poly-
mers and processes are fully disclosed in the patent to Ruus,
U. S. 3,~29,827. In this connection, it is pointed out that
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' . I
:llOS'~95
the present invention contemplates the use of any of these
materials; however, those which condense with the evolution
of an acid are particularly preferred 50 that the pH of the
slurry may be autogenously reduced during the interfacial
polycondensation to an extent such that the condensation of
the aminoaldehyde precondensate from its water soluble first
stage to its water insoluble second stage will proceed with-
out further addition of an acid. However, it is pointed out
that the present invention is not predicated upon the auto-
genous generation of acid during the interfacial polyconden-
sation and it is within the broad concepts of the present
invention to add such acid from an outside source.
In connection with the foregoing it is stressed
that the present invention contemplates the production of a
dual-walled microcapsule by polymeri~ation processes which
are carried out seriatum. . That is to say, a first polymeric
shell,is formed about minute, discrete droplets of fill
material by an interfacial polymerization and thereafter the
conditions in the system are altered such that an outer shell `
is formed about the inner wall by a secondary polymerization
reaction~
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