Note: Descriptions are shown in the official language in which they were submitted.
1~10064
Back~round of the Invention
The invention relates to the production of radiation curable microcap-
sular coatin~ coMpositions. In particular, it relates to the production of
microcapsules containing a hydrophilic core by interfacial reaction~ the micro-
capsules being dispersed in a hydrophobic liquid in ~Ihich the hydrophobic
liquid is a radiation curable organic liquid. In a preferred form of this
invention, the encapsulated hydrophilic liquid contains a chromogenic material
soluble in the hydrophilic liquid. The dispersion of microcapsules can be
coated on a substrate and cured by radiation to give a pressure-sensitive
carbonless copy sheet haYing a transfer coating. For purposes of this appli-
cation, the term "chromogenic" shall be understood to refer to materials such
as color precursors, color developers and color ~ormers.
Transfer coatings in which a chromogenic material is dissolved in a
hydrophilic liquid and encapsulated in a hydrophobic liquid by means of ~n
interfacial reaction are described in U.S. Patent No. 3,432,427 to Kan et al.
The process described in this patent, as it pertains to the formation of
microcapsules containing a hydrophilic liquid, involves the incorporation of
one color former or color producing substance of a color producing pair in the
hydrophilic liquid. Also included in this hydrophilic liquid is a wall-formin~
material which reacts with another wall-~ormin~ material present in a hydro-
phobic liquid to form a polymer film insoluble in either the hydrophilic or
hydrophobic liquids. The ~icrocapsules are formed by emulsifyin~ the hydro-
philic liquid into ~he hydrophobic liqllid and allo~ling the t~lo ~Jall-forming
materia1s to react at the interface o~ the hydrophilic and hy~rophobic liquids.
The resultant microcapsules are obtained as a dispers;on of microcapsules in
the hydropho~ic liquid which may be a volatile organic solvent or a non-
Yolatile oil.
Carbonless copy paper, briefly stated, is a standard type o~ paper
wherein during manufacture the back5ide of the paper substrate is coated ~rith
~lhat is reTerred to as a CE3 or trans~er coating, the CE3 coatin~ containing one
or more chromogenic materials, generally in capsular form. ~t the same tiMe
,~
- 1110064
the front sille of the paper substrate is coated during mallufacture with what
is referred to as a CF coating, which contains one or more chromogenic mater-
ials capAble of producing a color with the encapsulated CB chromogenic
material. Both the chromogenic materials remain in the coatings on the re-
spective bac~ and front surfaces of the paper in substantially colorless form.
This is true until the CB and CF coatings are brought into overlying relation-
ship and sufficient pressure, as by a type~lriter, is applied to rupture the
ce coating to release the encapsulated chromogenic material. At this ti~e
the chromogenic material contacts the CF coatin~ and reacts with the chromo-
genic material therein to form a colored irlage. Carbonless copy paper has
proved to be an exceptionally valuable image transfer media for a variety of
reasons, only one of which is the fact that until a ce coating is placed next
to a CF coating both the CB and the CF coatings are in an inactive state as
the co-reactive elements are not in contact with one another. Patents relat-
ing to carbonless copy paper products are:
U.S. Patent 2,712,507 (1955) to Green
U.S. Patent 2,730,456 (1956) to ~reen et al
U.S. Patent 3,455,721 (1969) to Phillips et al
U.S. Patent 3,466,184 (1969) to Bo~ller et al
U.S. Patent 3,672,935 (1972) to ~liller et al
A disadvantage of coated paper products such as carbonless transfer
papers stems from the necessity of applying a liquid coating composition
containing the color forming ingredients during the manufacturing process.
In the application of such coatings, volatile organic solvents are sometimes
used ~Ihich then in turn requires evaporation of e%cess solvent to dry the
coating thus producing volatile solvent vapors. An alternate method of
coating involves the applîcation of the color forming ingredients in an
aqueous slurry, again requiring removal of excess water by drying. eoth
methods suffer from serious disadvantages. In particular, the organic
~lOQ64
solvent coating method necessarily involves the production of generally volatilesol~/ent vapors, creating both a health and a fire ha~ard in the surrounding
environment l~hen using an agueous solvent system the water must be evapo-
rated ~hich involves the expenditure,of significant amounts of energy. Further,
the necessity of a drying s~ep requires the use of complex and expensive ap-
paratus to continuously dry a substrate which has been coated with an aqueous
coating compnund. A separate but related problem involves the disposal of
polluted water. The application of heat not only is expensive, making the
total paper manufacturing operation less cost effective, but also is potenti-
ally damaging to the chromogenic materials which are generally coated onto the
paper substrate during manufacture. High degrees of temperature in the drying
step require specific formulation of coating compositions which permit the use
of excess heat. The problerns encountered in the actual coating step are gen-
erally attributable to the necessity for a heated drying step following the
1~ coating operation.
The novel process and liquid coating composition of this invention
are superior to those used in the prior art microcapsular coating of sub-
strates in that they do not need an organic solvent or water in their coating
composition~ thus avoiding the disadvantages associated ~lith solvellt removal
2~ during dryin~. The liquid radiation curable substance is a solvent for the
wall-forming material in the hydrophobic liquid. The liquid radiation
curable substance cures by radiation to give a tack-free film containing
microcapsules. The cured film acts as a binder to adhere the microcapsules
to the substrate.
In general, patents concerned with the production and application of
liquid resin compositions containing no Yolatile solYent which are subse-
quently cured by radiation to a solid film are:
(! 64
U.S. Patent 3 5~1 235 (1970) to Bassemir et al
U.S. Patent 3 551 246 (1970) to ~assemir et al
U.S. Patent 3 551 311 (1970) ~o Nass et al
U.S. Patent 3 ~58 387 (1971) to Bassemir et al
U.S. Patent 3 661 614 (1972) to ~assemir et al
U.S. Patent 3 720 534 (1973) to Macauley et al
U.S. Patent 3 754 966 (1973) to ~le~lman et al
U.S. Patent 3 772 062 (1973) to Shur et al
U.S. Patent 3 772 171 (1973) to Savageau et al
U S. Patent 3 801 329 (1974) to Sandner et al
U.S. Patent 3 819 496 (1974) to Roskott et al
U.S. Patent 3 847 768 (1974) to Kagiya et al
U.S. Patent 3 847 769 (1974) to Garratt et al
These co~positions generally also contain a pigment or dye. Such resin compo-
lS sitions are useful for protective coatings and fast drying inks. U.S. Pat-
ent 3 754 966 describes the production of an ink releasing dry transfer
element ~hich can be used as a carbon paper or typewriter ribbon. It is sig-
nificant to note here that the particular radiation cured coating must be
compatible with the reaction of CB and CF chromogenic materials to form a
color. Such color forming reactions are generally of a sensitive or delicate
nature and are not generally compatible ~ith the compositions found in the
prior art.
The novel liquid coating coMpositions of this invention contain micro-
capsules having an aqueous core liquid containin~ a chromogenic Material in
addition to a radiation curable hydropnobic liquid Prior to the discovery
of this invention it ~las not known that such microcapsules could be produced
in situ in radiation curable coatin(l compositions and retain their color pro-
ducing properties after the resin is cured by radiation to a tack-free film.
~or pur~oses of this disclosure a tacl;-free film is one which will se~arate
cleanly from a cotton ball li~htly pressed a9ainst the film. The cotton fibers
will not adhere to the film surface.
lllOQ64
An especially preferred application of the process of this inverltion
0uld be in the continuous production of a manifold carbonless form.
As can be appreciated from the above, the continuous production of
a manifold paper product would require simultaneous coatin~, simultaneous
drying, simultaneous printin~, and simultaneous collatin~ and finishing of
a plurality of paper substrates. Thus, Busch in Canadian Patent ~Jo. 945J443
indicates that in order to do so there would be a minimum wettin~ of the
paper ~Jeb by ~later during application of the CB emulsion coat. For that
purpose a high solids content emulsion is used and special driers are described
in Busch. Ho~ever, because of the complexities of the drying-step, this proc-
ess has not been commercially possible to date. ~lore particularly, the
drying step involving solvent evaporation and/or ~later evaporation and the
input of heat does not permit the simultaneous or continuous manufacture of
manifold forms. In addition to the drying step ~Ihich prevents continuous
manifold form production the necessity for the application of heat for solvent
evaporation is a serious disadvantage since aqueous and other liquid coatin~s
require that special grades of generally more expensive paper be employed and
even these often result in buckling, distortion or warping of the paper since
water and other liquids tend to strike through or penetrate thè paper substrate.Additionally, aqueous coatings and some solvent coatings are generally not
suitable for spot application or application to limited areas of one side of
a sheet of paper. They are generally suitable only for application to the
entire surface area of a sheet to produce a con~inuous coating.
Another problem which has been commonly encountered in attempts to
continuously manufacture manifold 'orms has beer the fact that a paper manu-
facturer r!lust design paper from a strength and durability standpoint to be
adequate for use in a large variety of printing and finishin~ machines. This
requires a paper manufacturer to evaluate the coating apparatus o, the forms
manufa~turers he supplies in order that the paper can be designed to aceor,~lo-
date the apparatus and process designed exhibiting the most derllanding condi-
tions. 6ecause of this, a higher long wood fi~er to short wood fiber ratio
~ll()Q64
must be used by the paper manufacturer than is necessary for most coating,
printing or finishin~ machines in order to achieve a proper high level of
strength in his finished pa?er product. This makes the final sheet product
more expensive as the long fiber is ~enerally more expensive than a short
fiber. In essence, the separation of paper manufacturer from forms manu-
facturer, which is now common, requires that the paper manufacturer overdesign
his final product for a variety of machines, instead of s~ecifically desi~n- -
ing the paper product for known machine conditions.
By combining the manufacturing, printing and finishing operations
into a single on-line system a number of advantages are achieved. First,
the paper can be made using ground ~ood and a lower long fiber to short fiber
ratio as was developed supra. This is a cost and potentially a quality
improvement in the final paper product. A second advantage which can be
derived from a combination of manufacturing, printing and finishing is that
waste or re cycled paper hereinafter so~etimes referred to as "hroke" can be
used in the manufacture of the paper since the quality of the paper is not of
an overdesigned high standard. Third and most importantly, several steps in
the normal process of the manufacture of forms can be completely eliminated.
Specifically, drying steps can be eliminated by using a non-agueous, solvent-
free coating system and in addition, the ~Jarehousing and shipping steps can
be avoided, thus resulting in a more cost efficient product.
~dditionally, by using a?~ropriate coating methods, namely radiation
curable coating co~positions and methods, and hy combining the necessary rnanu-
facturing and printing steps, spot printing and spot coating can be realized.
Both of these represent a significant cost savings but neverthe1ess one ~hich
is not generally available ~hen aqueous coatings are used or ~Ihere the rnanu-
facture, printing and finishing of paper are performed as separate functions.
An additional advanta~e of the use of radiation curable coating compositions
and the combination of paper manufacturer, printer and finisher is that ~Jhen
the option of printing follo~led by coating is available significant cost
advanta~es occur.
Q64
Statement of the Invention
In one aspect of the invention, a process is provided for producing
a coating composition containing microcapsules having a hydrophilic core
material for use in the manufacture of pressure-sensitive carbonless transfer
papers comprising the follo~ling steps of preparing a hydroPhobic emulsion
component by dispersing a first wall-forming material in a hydrophilic liquid
containing at least one chromogenic ~aterial, the chromogenic material being
soluble in the hydrophilic liquid, the first wall-forming material being
reactive with a second ~all-forming material to form a polymeric capsule wall,
the capsule ~all bein~ substantially insoluble in the hydrophilic and the
hydrophobic liquids, and mixing the hydrophobic emulsion component with the
hydrophilic emulsion component to form an emulsion containing droplets of the
hydrophilic e~ulsion component dispersed in the hydrophobic emulsion component.
The second wall-formin~ material is then added to the e~ulsion ~ith agitation,
the agitation continu;ng for a period of time sufficient to allow the first
and second wall-forming materials to react to form a dispersion of microcap-
sules in the hydrophobic emulsion component, the microcapsules having cell wallssubstantially impermeable to the hydrophobic and the hydrophilic liquids.
In another aspect of the invention, a process is provided for produc-
ing a pressure-sensitive carbonless transfer paper comprising the further
steps of applying the coating composition to a substrate and curing the coating
composition by subjecting the coating composition on the substrate to radia-
tion ~or a period of time sufficient to cure the radiation curable hydrophobic
liquid, thereby producing a tack-free resinous film on the suhstrate
2~ ~n a further aspect of the invention, a novel coating composition is
produced cor.~prising microcapsules having a hydrophilic core material dispersedin a radiation curable hydrophobic liquid~
g
~llOQ64
In a still further aspect of the invention, a pressure-sensitive
carbonless transfer sheet is produced comprising a substrate having a plur-
ality of surfaces, at least one of the surfaces being coated wi~h a tack-free
resinous film comprising a radiation cured resin having dispersed therein
microcapsules containing a hydrophilic liquid containing at least one chromo-
genic material, the chromogenic material being soluble in the hydrophilic
~iqui~.
~ 10 -
lll~Q64
Detailed Descri~tion of the Invention
The coatin~ composition of this invention is esssentially a dispersion
of microcapsules containing a chromogenic material or materials dissolved in
a hydrophilic liquid in a radiation curahle hydrophobic liquid as a continuous
phase. The dispersion of microcapsules is prepared in situ by inter~acial
reaction of ~lall-~orming material present in droplets of the hydrophilic liquidwith wall-forr,7ing material in the radiation curable hydrophobic liquid.
The coating composition can contain additional materials which func-
tion as photoinitiators. Addition of these materials depends upon the
particular method of curing the microcapsular coating. Filler materials can
also be added to modify the properties of the cured film. The use of non-
reactive solvents for the radiation curable liquid, ~Ihich require heat to re-
move the~ during the drying or curing of the coated film, is avoided. How-
ever, minor amounts of non-reactive solvents can be tolerated without requiring
~ separate step for drying dur;ng any subsequent curing step. Although the
product and process of this invention are useful in the manufacture of a
variety of microencapsulated products, the preferred use of the process and
product of this invention is in the production of a pressure-sensitive car-
bonless transfer sheets such as is described in commonly assigned co-pending
U.S. Application Serial No. 684,462, filed May 7, 1~76.
In general, the hydrophilic liquids known in the art,as illustrated by
those listed in U.S. Patent ~lo. 3,432,427 to Kan et al, can be used in the
practice of this invention. Exa~ples of the preferred hydrophilic liquids
are ~ater, glycerin, 1,4-butanediol, polyethylene glycol, 1,2-propylene
glycol, lg3-butylene glycol, polypropylene glycol, triethylene glycol, tri-
ethylene glycol monomethyl ether, diethylene ~lycol, ethylene diamine,
triethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene
pentamine, polyethylenimine and mixtures thereof.
1110~64
In the preferred use of this invention to prepare pressure-sensitive
transfer sheets, the most preferred hydrophilic liquid is a mixture of water
and glycerin, The hydrophilic liquid also contains at least one chromogenic
material dissolved therein, Besides,bein~ soluble in the hydrophilic liquid,
the chromogenic materials should be essent;ally insoluble in the hydrophobic
liquid and should not be substantially reactive to any appreciable degree ~lith
the other in~redients of the coating composition, such as the hydrophilic ljq_
uid, the radiation curable substance and the wall-forming materials. The
chromogenic Material can be selected fror~ any color-forr~ing pair in which one
chromogenic material reacts ~lith another chromogenic material in the presence
of the hydrophilic liquid to form a color, Follo~,ling are pairs in which the
first mentioned chromogenic rnaterial is particularly useful in the practicin~
of this invention, A most preferred chromogenic material is sodium orthovana-
date,
Color Former Pairs COLOR
Ammoniu~ ferric sulfate ~ Potassium ferrocyanide Blue
An~lonium ~erric sulfate - Potassium r,hiocyanate Red brown
Ammonium ferric sulfate - Salicylaldoxime Brown
Arnmonium ferric sulfate - Gallic acid Black
2Q Ammonium f~rric sulfate - Tannic acid Black
Ammoniurn ferric sulfate - Catechol Black
Ammonium ferric sulfate - 8-~lydroxyquinoline Black
Ferric oleate - Catechol Violet-Black
Ferric oleate - Sodium diethyldithiocarbonate Black
Sodiurn orthovanadate - 2-Ethylhexyl gallate Black
Sodium orthovanadate - Gallic acid Black
Ammonium metavanadate - Gallic acid Black
Ar~lonium metavanadate - rannic acid Black
Ferric sulfate - 2,4-dinitro-1-naphthol 61ack
Cupric sulfate - DithioY~amide Black
Cupric oleate - Dithioxamide Black
lllQQ64
The chromogenic materials are present in the hydrophilic liquid in an
amount from about 0.2~ to 10% based on the weight of the hydrophilic liquid.
The most preferred range is about 0.5,'0 to about 4.0%.
The hydrophilic liquid conta~ns a first wall-forming material which
reacts ~lith a second wall-forming material in the hydrophobic liquid to form
a polymeric capsule wall which is substantially insoluble in both the hydro-
philic and hydrophobic liquids. The first wall-for~ing materials may be solids
which can be dispersed or dissolved in the hydrophilic liquid or they can be
part of the hydrophilic liquid itself. Referring to the examples of the pre-
ferred hydrophilic liquids listed supra, these same co~pounds are the preferred
first wall-forming materials. The preferred second wall-for~ing materials
are the compounds containing polyfunctional isocyanate groups. These
include the diisocyanates, the triisocyanates and other compounds and pre-
polymers containing more than one isocyanate group in each molecule. The
first wall-forming material and second wall-formin~ material are present
in such amounts that there will always be unreacted first wall-forming
material to serve as the hydrophilic liquid of the microcapsules.
The radiation curable liquids useful in the practice of this invention
comprises the free radical polymerizable ethylenically unsaturated organic
compounds. These compounds contain at least one terminal ethylenically unsatu-
rated group per molecule. These compounds are hydrophobic liquids and function
as an inert continuous hydrophobic phase during the in situ preparation of
the microcapsules and as a dispersing media for the microcapsules and other
ingredients of the coating co~position prior to the coating operation. They
2~ are non-reactive ~lith the wall-formin~ materials and they are curable to a
solid resin when exposed to ionizing or ultraviolet radiation. Thus the cured
resin acts as a binder for the microca?sules to a substrate such as paper.
lll~Q64
A group of useful radiation curable compounds are the polyfunctional
ethylenically unsaturated or~anic compounds which have more than one (two
or more) ter~inal ethylenic groups per molecule. Due to the polvfunctional
nature of ~hese compollnds, they cure rapidlv under the influence of radiation
by polymerization, including crosslinking, to form a hard dry tack-free film.
Included in this preferred group of radiation curable compounds are
the polyesters of ethylenically unsaturated acids such as acrylic acid and
methacrylic acids, and a polyhydric alcohol. Examples of some of these poly-
functional compounds are the polyacrylates or methacrylates of trimethylol-
propane, pentaerythritol, dipentaerythritol, ethylene glycol, triethylene
glycol, propylene glycol, glycerin, sorbitol, neopentylglycol and 1,6-hex-
anediol, hydroxy-terminated polyesters, hydroxy-terMinated epoxy resins, and
hydroxy-terminated polyurethanes and polyphenols such as bisphenol A.
Also included in this group are polyallyl and polyvinyl compounds
such as dillayl phthalate and tetrallyloxyethane, and divinyl adipate,
butane divinyl ether and divinylbenzene. ~lixtur~s of these polyfunctional
compounds and their oligimers and prepolymers may be used if desired~
A group of radiation curable compounds which are useful are the mono-
functional ethylenically unsaturated or~anic compounds which have one terminal
ethylenic group per molecule. Examples of such ~onofunctional compounds are
the C2 to C16 alcohol esters of acrylic and methacrylic acid, and styrene,
substituted styrenes, vinyl acetate, vinyl ethers and allyl phenols. In gen-
eral, these compounds are liquid and have a lo~Jer viscosity than the polyfunc-
tional ethylenically unsaturated compounds and thus may be used to reduce the
viscosity of the coating composition to facilitate migration o-f the wall-
forming materials during preparation of the microcapsules. These compounds
are radiation curable and react with the ethylenically unsaturated polyfunc-
tional organic compounds during radiation curin~ to give a dry flexible film
Compounds having only one terrninal ethylenic grou~ may be used alone as the
- ~4 -
Q64
radiation curable substance. However, the resultant radiation cured film ~ay
be rather soft an~ pliable and hence less preferred commercially than other
ethylenically unsaturated compounds.
The preferred ra~iation cura~le hydrophobic liquid is a mixture con-
taining one or more monofunctional compounds and one or more polyfunctional
compounds. The rnonofunctional compounds due to their generally lower viscos-
ity, tend to more easily disperse the hydrophilic liquid into drcplets of the
desired size. The polyfunctional compounds tend to cure rnore rapidly and due
to crosslinking give a harder tougher resin film. This is particularly so
when cor1pounds of higher molecular ~Jeight, such as the oligimers and pre-
polymers of the polyfunctional compounds, are used. In a preferred process
of this invention the lower viscosity monofunctional compounds are used as
the dispersing rnedia ~or the preparation of the microcapsules and the
higher viscosity faster curing polyfunctional compounds, particularly the
oli~imers and prepolymers of these compounds, are added after the micro-
capsules are formed and prior to coating on a substrate.
The radiation curable hydrophobic liquid can be present in the micro-
capsular coating composition in an amount of fro~ about 25% to about 7~% by
weight of the cornposition. The preferred range is from about 35% to about 65%,
and the most preferred range is from about 40% to about 55%.
A photoinitiator is added to the coating co~position if the com-
position is to be cured by ultraviolet radiation. A ~ide variety of
photoinitiators are available ~Ihich serve well in the system described in
B this invention. The preferred photoinitiators are the benzoin al~yl
ethers, such as Vicure 30 (a mixture of alkylbenzoin ethers manufactured
and sold by Stauffer Chemical Co., llestport, Conn.), benzoin butyl ether
(Vicure 10, Stauffer), benzoin rnethyl ether, and ,-diethoxyacetophenone
Other photoinitiators which can be used are benzophenone, 4,4'-bis-
(dirlethylamino)benzophenone, ferrocene, xanthone, thioxanthane,
,-azobisisobut~lnitrile, decabromodiphenyl oxide, pentabromomonochloro-
cylohexane, p~ntachlorobenzene, polychlorinated biphenyls such as the
C 4~ trtLde ~r~ 1
64
Arochlor 1200 series (manufactured and sold by ~lonsanto Chemical Co.,
St. Louis, l~issouri), benzoin ethyl ether, 2-e~hyl anthroquinone,
l~(chloroethyl) naphthalene, desyl chloride, c'nlorendic anhydride,
naphthalene sulfonyl chloride and 2-~roMoethyl ethyl ether. The a~ount
of photoinitiator added can be from about 0.2,' to about 10~ by weight of
the coat;ng composition, with a preferred ran~e being from about 1% to
about g% by ~eight.
Photoinitiation syner~ists can also be added to the ultraviolet
curable coating compositions. Photoinitiation synergists s~rve to enhance
the initiation efficiency of the photoinitiators. The preferred synergists
are the chain transfer agents, such as the tertiary alcoholomines and sub-
stituted morpholines, triethanolamine, N-methyldiethanolamine, ~ di-
methylethanolamine and ~I-methylmorpholine. The a~ount of photoinitiation
synergist added can be fro~ about 0.2% to about 10% by ~leight of the coating
1~ composition, with a preferred ran~e of from about 3% to about 8% by ~leight.
In the preparation of the microcapsules, a hydrophobic emulsion
component is prepared by dissolving or dispersin~ an emulsifier in the
radiation curable hydrophobic liquid. As noted later, the second wall-forming
material may then be added to the radiation curable hydrophobic li~uid if de-
sired. A hydrophilic emulsion component is prepared by dissolviny the chromo-
genic material in ~Jater and adding to this a first ~lall-forming material whichis soluble or miscible in water. Preparation of each of these ernulsion com-
ponents is easily accomplished by stirring together at room temperature the
materials of each component. The Brookfield viscosity of the first emulsion
can be from about 0.5 cps.to about 1000 cps. The preferred viscosity is about
1 cps. to about 500 cps. and the most preferred viscosi~y is from about 1 cps.
to about 50 cps.
c~ ro~e ,~
- 16 -
1110~64
The hydrophobic and hydrophilic emulsion components, ~Ihich are two
inlmiscible liquids, are then mixed together with high agitation to forM
droplets of the hydrophilic emulsion component in the hydrophobic emulsion
componellt. The hydrophilic emulsion component contains a hydrophilic carrier
liquid and dissolved therein the chromogenic material and a first wall-forming
material. The hydrophobic emulsion component contains radiation curable hydro-
phobic liquid and an e~ulsifying agent. At this point the hydrophilic emulsion
component may or may not contain the second wall-for~ing material. As noted
supra, this material can be added to the hydrophobic emulsion component prior
to emulsification or it may be added to the emulsion after emulsification.
To facilitate mixing the second ~all-forming material ~ay be dissolved in
additional radiation curable hydrophobic liquid prior to this addition. In
any event the second wall-forming material must be soluble in the radiation
curable hydrophobic liquid and substantially not soluble in the hydrophilic
emulsion component.
After emulsification, the emulsion is stirred for a period of about
3 hours to about 1~ hours to allo~J the first and second wall-for~ing materials
to react and form a dispersion of microcapsules having cell ~lalls ~Ihich are
substantially impermeable to both the hydrophilic and hydrophobic liquids.
The microcapsules are preferably from about 1 micron to about 30 microns
in diameter.
~n a preferred embodiment of the process of this invention, the radia-
tion curable hydrophobic 1i4u;d is div;ded into two portions and the first
portion is present in the hydrophobic emulsion co~ponent prior to the emulsi-
2~ fication step. A second portion of the radiation curable hydrophobic liquid
containing, in particular, faster curing polyfunctional oligimers and prepoly-
mers may be added after the microcapsules are for~ed At this point, other
materials such as the photoinitiators and photoinitiation synergists may be
added to give a coatable composition Stilt material may be added, if desired,
to prevent pre~ature rupture of the microcapsules.
lllOQ64
The microcapsular coating composition can be added to a substrate,
such as paper or a plastic film by any of the com~on paper coatin~ processes
SUCi1 as roll, air knife, or blade coating, or by any of the common printing
processes, such as offset, gravure, or fleY~o~raphic printing. The rheo-
logical properties, particularly the viscosity, of the coating cornposition,
can be adiusted for each type of application by proper selection of the
type, molecular weight and relative amounts of the liquid radiation curable
co~pounds.
These coating compositions can be cured by any free radical initiated
chain propagated addition polyr,lerization reaction of the terminal ethylenic
groups of the radiation curable compounds. These free radicals can be
pro~uced by several different chemical processes including the therrnal or
ultraviolet induced degradation of a molecular species and any form of
ionizing radiation such as alpha-particles, beta-rays (high-energy electrons),
gamma-rays, X-rays and neutrons.
The preferred curing process is by exposure of the coating composition
to ultraviolet radiation havin~ a wavelength of about 2000 A to about 4000 A.
For curing to occur the cornposition must contain suitable ultraviolet absorb-
ing photoinitiators which will produce polymerization initiating free
radicals upon exposure to the radiation source. A typical ultraviolet source
B suitable for this type of curing process is a Hanovia 230 watt medium pressure
mercury lamp. Curing efficiencies of the coatin~ compos;tion are dependent
on such parameters as the nature of the radiation curable substance, atmos-
phere in contact with ihe coating, quanturn efficiency of the radiation
absorbed, thickness of coating and inhibitory effects of the various materials
in the composition.
In the ionizing radiation induced curins of these coating compositions
a specific radiation absorbiny material (photoinitiator) is not necessary.
Exposure of the coating composition to a source of high energ~ electrons
f rd d ~ ~ G ~ ~i
lll~Q64
results in spontaneous curing of the composition to a tough, tack-free coat-
in~. Any of a number of coRlmercially available high energy electron beam
or linear cathode type high energy electron sources are suitable for curing
these compositions. Parameters such as the atmospheric environment and
inhibitory effects of the various materials in the co~position play an
important role in the determination of the curing efficiency of these
compositions.
The following examples further illustrate but do not limit the
invention.
- 19 -
` ~110Q64
Example 1
In 20 parts of distilled water was dissolved 1.4 parts of
vanadium pentoxide, 2.6 parts of sodium hydroxide, and 40 parts of
glycerin (Liquid A).
S To 100 parts of 2-ethylhexyl acrylate was added 1.0 part
of a mixture of glycerol stearate and polyoxyethylene stearate
(an emulsifying agent sold under the trade mark Arlacel 165 by
I.C.I., Americas, Inc., Wilmingto~, Delaware~ and stirred at
room temperature. A cloudy mixture (Liquid B) was obtained.
The Brookfield viscosity of Liquid B at 25C was 12 centipoise.
A solution of 12 parts of Mondur* CB-75 (a 75~ solution
in ethyl acetate of a prepolymer of toluene diisocyanate and
trimethylolpropane made and sold by Mobay C~.emical Co., Pittsburgh,
Pennsylvania) in 12 parts of n-butyl acetate was added to 50 parts
of 2-ethylhexyl acrylate at room temperature. A clear solution
(Liquid C) was obtained.
Liquid B was placed in a Waring blender. Liquid A was
slowly added to Liquid B in the Waring blender while running at
high speed. The emulsification was continued for 1 minute.
Then Liquid C was slowly added to the Waring blender. After 3
more minutes of emulsification time the mixture was transferred to
a 3-neck glass reactor which was equipped with a condenser and a
mechanical stirrer. The emulsion was stirred overnight
to yield a dispersion of microcapsules.
To 9.7 parts of this microcapsular dispersa~n was ad~ed
0.3 parts of desyl chloride which is a photoinitiator and the
mixture was applied on a sheet of hydroxypropylcellulose base
coated paper with a #19 Mayer* bar. The sheet was finally exposed
to ultraviolet light which was generated by a Hanovia* 200 watts
medium pressure, 4-1/2" mercury arc lamp, 6" from the lamp. The
resulting sheet performed well as the CB part of the Carbonless
copy paper system in which the developer sheet was was coated with
2-ethylhexyl gallate.
*"~londur", "Mayer" and "Hanovia" are trade mar~s
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1:~10064
Example 2
This is an example of the preparation of microcapsules in which
neopentyl glycol diacrylate (a difunctional monomer) was used as one ingredient
of the continuous phase.
The procedure of Example 1 was employed with the exception that
100 parts of 2-ethylhexyl acrylate in Liquid B was replaced by 70 parts of
2-ethylhexyl acrylate and 30 parts of neopentyl glycol diacrylate. ~1icro-
capsules so prepared were suitable for use in making the transfer sheet of
carbonless copy paper systems using a 2-ethylhexyl gallate developer sheet.
Example 3
This is an example of the use of a trifunctional cross-linking
agent. The procedure is the same as Example 2 except that 30 parts of
trimethylol propane triacrylate were used instead of 30 parts of neopentyl
glycol triacrylate. The microcapsules prepared were coated on paper and
performed well as the transfer sheet of a carbonless copy paper system using
a 2-ethylhexyl gallate developer sheet.
Example 4
This is an exa~ple of a higher solids system. The procedure was
~ carried out as in Example l ~ith the exception that double the amounts of
Liquid A, Mondur~CB-75 and n-butyl acetate were employed. The microcapsules
produced were coated on a piece of paper and performed ~lell as the CB part
of a carbonless copy paper system in which the CF sheet was coated with
2-ethylhexyl gallate.
d~r ts ~ ~r~de ~7~rJ~
64
Example 5
In 22.5 parts of distilled water, 1.575 parts of
vanadium pentoxide, 2.925 parts of sodium hydroxide, 45 parts
of glycerin, and 30 parts of sodium bromide were dissolved
(Liquid A). To 150 parts of 2-ethylhexyl acrylate was added
1.5 parts of Arlacel* 165 and stirred at room temperature.
A cloudy mixture (Liquid B) was obtained.
In 75 parts of 2-ethylhexyl acrylate, 5.3 parts of
Desmodur* N-100 and 3.5 parts of Desmodur* E-21 were dissolved
(Liquid C). (Desmodur* N-100 is a liquid biuret made by
reacting hexamethylene diisocyanate with water in a 3 to 1
molar ratio and Desmodur* E-21 is an aromatic polyisocyanate
prepolymer. Both Desmodur* N-100 and E-21 are made and sold
by Mobay Chemical Co~, Pittsburgh, Pennsylvania.) The same
procedure as in Example 1 was repeated except that benzoin
methyl ether replaced desyl chloride as the photoinitiator,
and the microcapsular dispersion was cured by ultraviolet
light which was generated by the Ultraviolet AC 1202 AN
Processor (manufactured and sold by Radiation Polymer Co., a
division of PPG Industries, Pittsburgh, Pennsylvania).
The transfer sheet so produced performed satisfactorily as a
part of a carbonless paper system using a 2-ethylhexyl gallate
coated second sheet.
*"Arlacel" and "Desmodur", are trade marks.
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Q64
Example 6
In 30 parts of distilled water, 2.1 parts of vanadium
pentoxide, 3.9 parts of sodium hydroxide, 60 parts of glycerin,
and 40 parts of sodium bromide were dissolved (Liquid A).
To 175 parts of 2-ethylhexyl acrylate was added 2 parts
of Arlacel* 165. The cloudy mixture resulting was cooled to
about 5C, then 30 parts of Mondur* CB-60 (a 61% solution in
a mixture of xylene and ethyl-glycol acetate of a toluene
diisocyanate-based addent made and sold by Mobay Chemical Co.,
Pittsburgh, Pennsylvania) was dissolved to give Liquid B.
Li~uid A was then emulsified into Liquid B for 4 minutes
in a Waring blender at low speed. This emulsion was then
transferred into a glass reactor to cure overnight at 40C to
46C with mild stirring. The res~ultant mixture was examined
by a microscope. The capsules were good with size of about
7 to 12 microns.
9 parts of this microcapsular dispersion was weighed
out and 0.7 parts of a methyl methacrylate copolymer (Acryloid*
B-82 made and sold by Rohm and Haas Co.) and 0.3 parts Vicure*
30 were dissolved. The mixture was then coated by a ~19 Mayer*
bar onto a polyvinyl alcohol base coated paper and cured by
ultraviolet light which was generated by Ultraviolet QC 1202
AN Processor. This resulting transer sheet was then typed
against a record sheet which was coated with 2-ethylhexyl
gallate to give very good black images.
* "Arlacel", "Mondur", "Acryloid", "Vicure" and "Mayer"
are trade marks.
- 23 -
X
lllOQ64
Examples 7 and 8
The followiny coating formulations ~lere also made, applied to paper
and surface cured by an electron beam unit at Radiation Polymer Co., which
was operated at 5 megarads, 300 KV, and a speed of 30 ft. per min. using
either an air atmosphere or a nitrogen atmosphere:
Example ~lo. 7 8
~icrocapsule tlixture (Example 1) 8 8
B Acryloid B-82(tlethyl methacry-
late copolymer) 1.5 1.5
10Ethyl hydroxyethylcellulose
(L~t ~I) 0.2 0.2
Triethanolamine 0.3 ---
The paper of Example 7 was cured after 2 passes using air. The
paper of example 8 ~tas cured after 1 pass using air and 1 pass using nitrogen.
Both sheets of Examples 7 and 8 performed well as a part of a
carbonless paper system using a 2~ethylhexyl gallate coated second sheet.
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