Note: Descriptions are shown in the official language in which they were submitted.
105ZOZ6
The present invention relates to novel graft copolymers particular-
ly adapted for employment in photography and, more particularly, to processes
for forming photographic diffusion transfer color images.
The present application is divided from apnlication 119,251, filed
July 27, 1~71, the original application.
The original application described and claims an ima~e-receiving
element for use in a photographic diffusion transfer color process including
an alkaline solution permeable and dyeable layer within which a dye image is
adapted to be formed and said layer comprises a graft copolymer wherein thç
grafted moiety provides a mordant capability.
In processes of the type set forth in United States Patent No.
2,983,606, a photosensitive element containing a dye developer and a silver
halide emulsion is exposed and wetted by a liquid processing composition,
for example, by immersion, coating, spraying, flowing, etc., in the dark, and
the exposed photosensitive element is superposed prior to, during, or after
wetting, on a sheetlike support element which may be utilized as an image-re-
ceiving element. In a preferred embodiment, the liquid processing composi-
tion is applied to the photosensitive element in a substantially uniform lay-
er as the photosensitive element is brought into superposed relationship with
the image-receiving layer. The liquid processing composition permeates the
emulsion to initiate development of the latent image contained therein. The
dye developer is immobilized or precipitated in exposed areas as a consequence
of the development of the latent image. This immobilization is, apparently,
at least in part, due to a change in the solubility characteristics of the
dye developer upon oxidation and especially as regards its solubility in al-
kaline solutions. It may also be due in part to a tanning effect on the emul-
sion by oxidized developing agent, and in part to a localized exhaustion of
alkali as a result of development. In unexposed and partially exposed areas
of the emulsion, the dye developer is unreacted and diffusible
- 1 - ~
1052026
and thus provides an imagewise distribution of unoxidized
dye developer dissolved in the liquid processing composi-
tion as a function of the point-to-point degree of exposure
of the silver halide emulsion. At least part of this image-
wise distribution of unoxidized dye developer is transferred,
by imblbition, to a superposed image-receiving layer or
element, said transfer substantially excluding oxidized dye
developer. The image-receiving element receives a depthwise
diffusion from the developed emulsion of unoxidized dye
developer without appreciably disturbing the imagewise
distribution thereof to provide the reversed or positive
color image of the developed image. The desired positive
image is revealed by stripping the image-receiving layer
from the photosensitive element at the end of a suitable
imbibition period.
In accordance with aforementioned U. S. Patent No.
2,983,606, the image-receiving layer need not be separated
from its superposed contact with the photosensitive element,
subsequent to transfer image formation, if the image-receiving
element is transparent and a processing composition containing
a substance rendering the dried processing composition layer
opaque is spread between the image-receiving layer and the
silver halide emulsion layer.
The dye developers, as noted above, are compounds
which contain in the same molecule both the chromophoric
system of a dye and also a silver halide developing function.
By "a silver halide developing function" is meant a grouping
adapted to develop exposed silver halide. A preferred silver
halide development function is a hydroquinonyl group. Other
suitable developing functions include ortho-dihydroxyphenyl
--2~
10520Z6
and ortho- and ~ara-amino substituted hydroxyphenyl groups.
In general, the development function includes a benzenoid
developing function, that is, an aromatic developing group
which forms quinonoid or quinone substances when oxidized.
Multicolor images may be obtained using color
image-forming components such as, for example, the
previously mentioned dye developers, in diffusion transfer
processes. One technique contemplates the use of a
photosensitive silver halide stratum comprising at least
two sets of selectively sensitized minute photosensitive
elements arranged in the form of a photosensitive screen.
Transfer processes of this type are disclosed in U. S.
Patents Nos. 2,g68,554 and 2,983,606. In such an
embodiment, each of the minute photosensitive elements
has associated therewith an appropriate dye developer
in or behind the silver halide emulsion portion. In
general, a suitable photosensitive screen, prepared in
accordance with the disclo~;ures of said patents
comprises minute red-sensitized emulsion elements,
minute green-sensitized emulsion elements and minute
blue-sensitized emulsion elements arranged in side-
by-side relationship in a screen pattern and having
associated therewith~ respectively, a cyan dye developer,
a magenta dye developer and a yellow dye developer.
Another process for obtaining multicolor
transfer images utilizing dye developers employs an integral
multilayer photosensitive element, such as is disclosed
in U. S. Patent No. 3,345,163, issuea October 3, 1967,
wherein at least two selectively sensitized photosensitive
strata are superposed on a single support and are processed,
~OSZOZ6
simultaneously and without separation, with a single, common
image-receiving layer. A suitable arrangement of this
type comprises a support carrying a red-sensitive silver
halide emulsion stratum, a green-sensitive silver halide
emulsion stratum and a blue-sensitive silver halide
emulsion stratum, said emulsions having associated therewith,
respectively, for example, a cyan dye developer, a magenta
dye developer and a yellow dye developer. The dye developer
may be utilized in the silver halide emulsion layer, for
example, in the form of particles, or it may be employed
as a layer behind the appropriate silver halide emulsion
strata.- Each set of silver halide emulsion and associated
dye developer strata may be separated from other sets by
suitable interlayers, for example, by a layer of gelatin or
polyvinyl alcohol. In certain instances, it may be desirable
to incorporate a yellow filter in front of the green-
sensitive emulsion and such yellow filter may be incorporated
in an interlayer. However, where desirable, a yellow dye
developer of the appropriate spectral characteristics and
present in a state capable of functioning as a yellow
filter may be employed. In such instances, a separate
yellow filter may be omitted.
As disclosed in the previously cited patents, the
liquid processing composition referred to for effecting
multicolor diffusion transfer processes comprises at least
an aqueous solution of an alkaline material, for example,
diethylamine, sodium hydroxide or sodium carbonate and the
like, and preferably possessing a p~ in excess of 12, and
most preferably includes a viscosity-increasing compound
constituting a film-forming material of the type which, when
105ZOZ6
the composition is spread and dried, forms a relatively
firm and relatively stable film. The preferred film-forming
materials disclosed comprise high molecular weight polymers
such as polymeric, water-soluble ethers which are inert to
an alkaline solution such as, for example, a hydroxyethyl
cellulose or sodium carboxymethyl cellulose. Additionally,
film-forming materials or thickening agents whose ability
to increase viscosity is substantially unaffected if left
in solution for a long period of time are also disclosed
to be capable of utilization. As statedJ the film-forming
material is preferably contained in the processing composi-
tion in such suitable quantities as to impart to the compo-
sition a viscosity in excess of 100 cps. at a temperature
of approximately 24 C. and preferably in the order of
100,000 cps. to 200,000 Cp5. at that temperature.
U. S. Patent No. 3,362,819, issued January 1, 1968,
discloses image-receiving elements particularly adapted
for employment in the preceding diffusion transfer processes
which elements comprise a support layer possessing on one
surface thereof, in sequence, a polymeric acid layer; an
inert timing or spacer layer; and an image-receiving layer
adapted to provide a visible image upon transfer to said
layer of diffusible dye image-forming substances.
As set forth in the last-mentioned patentJ the
polymeric acid layer comprises polymers which contain acid
groups, such as carboxylic acid and sulfonic acid groups,
which are capable of forming salts with alkali metals, such
as sodium, potassium, etc., or with organic bases, particularly
quaternary ammonium bases, such as tetramethyl ammonium hydroxide,
or potentially acid-yielding groups, such as anhydrides or lac-
tones, or other groups which are capable of reacting with bases
1052026
to capture and retain them. The acid-reacting group i5, of
course, nondiffusible from the acid polymer layer. In
the preferred embodiments disclosed, the acid polymer
contains free carboxyl groups and the transfer processing
S composition employed contains a large concentration of
sodium and/or potassium ions. The acid polymers stated
to be most useful are characterized by containing free
carboxyl groups, being insoluble in water in the free
acid form, and by forming water-soluble sodium and/or
potassium salts. One may also employ polymers containing
carboxylic acid anhydride groups, at least some of which
preferably have been converted to free carboxyl groups
prior to imbibition. While the most readily available
polymeric acids are derivatives of cellulose or of vinyl
polymers, polymeric acids from other classes of polymers
may be used. As examples of specific polymeric acids
set forth in the patent, mention may be made of dibasic
acid half-ester derivatives of cellulose which derivatives
contain free carboxyl groups, e.g., cellulose acetate
hydrogen phthalate, cellulose acetate hydrogen glutarate,
cellulose acetate hydrogen succinate, ethyl cellulose
hydrogen succinate, ethyl cellulose acetate hydrogen
succinate, cellulose acetate hydrogen succinate
hydrogen phthalate; ether and ester derivatives of
cellulose modified with sulfoanhydrides, e.g., with
ortho-sulfobenzoic anhydride; polystyrene sulfonic acid;
carboxymethyl cellulose; polyvinyl hydroqen phthalate;
polyvinyl acetate hydrogen phthalate; polyacrylic acid;
acetals of polyvinyl alcohol with carboxy or sulfo substi-
tuted aldehydes, e.g., o-, m-, or p-benzaldehyde sulfonic
acid or carboxylic acid; partial esters of ethylene/maleic
--6--
105Z02~i
anhydride copolymers; partial esters of methylvinyl
ether/maleic anhydride copolymers, etc.
The acid polymer layer is disclosed to contain
at least sufficient acid groups to effect a reduction in
the pH of the image layer from a pH of about 13 to 14 to
a pH of at least 11 or lower at the end of the imbibition
period, and preferably to a pH of about 5 to 8 within
a short time after imbibition. As previously notedJ the
pH of the processing composition preferably is of the
order of at least 13 to 14.
It is, of course, necessary that the action of
the polymeric acid be so controlled as not to interfere
with either development of the negative or image
transfer of unoxidized dye developers. For this
lS reason, the pH of the image layer is kept at a level of
pH 12 to 14 until the positive dye image has been formed
after which the pH is reduced very rapidly to at least
> about pH 11, and preferably about pH 9 to 10, before
the positive transfer image is separated and exposed to
air. Unoxidized dye developers containing hydroquinonyl
developing radicals diffuse from the negative to the
positive as the quaternary ammonium,sodium or other
alkali salt. The diffusion rate of such dye image-
forming components is at least partly a function of the
alkali concentration, and it is necessary that the p~ of
the image layer remain on the order of 12 to 14 until
transfer of the necessary quantity of dye has been
accomplished. The subsequent pH reduction, in addition
to its desirable effect upon image light stability,
~0 serves a highly valuable photo~rap?lic function by
105;~026 ~
substantially terminating further dye transfer. The
processing technique thus effectively minimizes changes
in color balance as a result of longer imbibition times
in multicolor transfer processes using multilayer negatives.
Where the image-receiving element is maintained in contact
with the photosensitive element, subsequent to dye developer
transfer image formation, and includes the presence of an
alkaline processing composition, necessarily having a pH at
which dye developer, for example, in reduced form, diffuses
to form the dye transfer image, intermediate the elements,
the transfer image thus formed is unstable over an extended
period of time. The dye image instability is due, at least
in part to the presence of what is, in general, a relatively
high pH alkaline composition in intimate contact with the
dye or dyes forming the image. This contact itself provides
instability to the molecular structure of dye by, for example,
catalyzing degradation and undesirable structural shifts
effecting the spectral absorption characteristics of the image
dye. In addition, the presence of an alkaline composition,
possessing a pH at which the dye, for example, in reduced form,
diffuses also provides an integral dynamic system wherein
oxidized dyeJ immobilized in areas of the photosensitive ele-
ment, as a function of its development, with the passage of
time attempts to generate, in such areas, an equilibrium
between oxidized and reduced dye. In that the pH of the
dynamic system is such that diffusion of the reduced form
of the dye will occur, such reduced dye will, at least in part,
transfer to the image-receiving laye~ and the resultant
diffusion will imbalance the equilibrium, in such areas
of the photosensitive element, in favor of additional
105ZOZ6
formation of reduced dye. As a function of the efficiency
of the image-receiving layer, as a dye sink, such nonimage-
wise dyeing of the image-carrying layer still further
imbalances the equilibrium in favor or the additional
formation of dye in reduced, diffusible form. Under such
circumstances, the transfer image definition, originally
carried by the image-receiving layer, will suffer a con-
tinuous decrease in the delta between the image's maximum
and minimum densities and may, ultimately, result in the
'0 image-receiving element's loss of all semblance of image
definition; merely becoming a polymeric stratum carrying
a relatively uniform overall dyeing.
Any attempt to decrease the dye sink capacity
of the image-carrying layer, for example, by reduciion of
its mordant capacity, in order to alleviate, at least to
an extent, the action of the image-receiving layer as a dye
sink, however, will enhance diffusion of the dye, comprising
the transfer image, from the image-carrying layer, to the
remainder of the element due, at least in part, to the
continued presence of the alkaline composition having a
pH at which the reduced form of the dye, forming the trans-
fer image,is diffusible. The ultimate result is substan-
tially the same overall image distortion as occurs when the
image-receiving layer acts as a dye sink, with the exception
that the dye is more extensively distributed throughout the
film unit and the ultimate overall dyeing of the image-
receiving layer itself is of lower saturation.
The problems inherent in fabricating a film unit
of the type wherein the image-receiving element, the alkaline
processing composition and the photosensitive element are
lOSZ026
mai~taincd in contî~uous contact subsequent to dye transfer image formation,
for examplc, a film unit of the typc dcscribed hereinbeforc with reference
to aforementioned U. S. Patent No. 2,983,606, may be effectively ob ~ ated
by fabrication of a film unit in accordance with the physical parameters
specific~ly set forth in U. S. Patents Nos. 3,415,644; 3,415,645 and
3,415,646 as well as those described in U. S. Patent Nos. 3,573,044 filed
December 9, 1969; 3,672,890 filed August 19, 1970 all in the name of Edwin
H. Land; and Patent Nos. 3,594,165 and 3,594,164 of H~ard G. Rogers, filed
May 22, 1970.
Specifically, an integral photographic film unit particularly
adapted for the production of a dye transfer image of unexpectedly impr wed
stability and other properties, by a color dif~usion transfer process will
be constructed, for example, in accordance with aforementioned U. S. Patent
No. 3,415,644, to include a photosensitive element comprising a liminate
having, in sequence, as essential layers, a dimensionally stable opaaue layer;
a photosensitive silver halide emulsion layer having associated therewith
dye image-providing material which is soluble and diff1sible, in alkali,
at a first pH; an alkaline solution permeable polymeric layer dyeable by
the dye image-providing material; a polymeric acid layer such as those
disclosed in aforementioned U. S. Patent No. 3,362,819 containing sufficient
acidifying groups to effect reduction, subsequent to substantial transfer
dye image formation, of a selected processing solution ha~ing the first pH
to a second pH at which said dye image-providing material is insoluble
and nondiffusible; and a dimensionally sta~le transparent layer. In com-
bination with the laminate, a repturable container retaining an aqueous
alkaline processing composition having the first pH ana containing an
opacifying agent, in a quantity sufficient to mask the dye image-providing
material, is fixedly positioned and
-10-
105Z026
extends transverse a leading edge of the laminate whereby
to effect unidirectional discharge of the container's con- -
tents between the alkaline solution permeable and dyeable
polymeric layer and the photosensitive silver halide
emulsion layer next adjacent thereto, upon application of
compressive force to the container.
It will also be recognized that the dimensionally
stable polymeric support layer next adjacent the photosensi-
tive silver halide emulsion layer or layers may be trans-
parent, as disclosed in aforementioned U. S. Patent No.3,415,646, and that in such instance, the opacifying agent
may be initially dispersed in the composite film unit inter-
mediate the dyeable polymeric layer and the silver halide
emulsion layer next adjacent, as disclosed in aforementioned
U. 5. Patent No. 3,415,645.
Employment of the last-mentioned film units,
according to the described color diffusion transfer photo-
graphic process, specifically provides for the production
of a highly stable color transfer image accomplished, at
least in part, by effectively obviating the previously
discussed disadvantages of the prior art products and
processes, by in process adjustment of the environmental
pH of the film unit from a pH at which transfer processing
is operative to a pH at which dye transfer is inoperative
subsequent to substantial transfer image formation by means
of the stated polymeric acid layer. The stab?e color trans-
fer image is obtained irrespective of the fact that the film
unit is maintained as an integral la~inate unit during expo-
sure, processing, viewing, and storage of the unit, which
transfer image exhibits the required maximum and minimum dye
transfer image densities, dye saturation, hues and definition.
lOSZOZ6
In order to prevent premature pH reduction during
transfer processing, as evidenced, for example, by an
undesired reduction in positive image density, the acid
groups of the stated polymeric acid component are disclosed
to be so distributed in the acid polymer layer that the rate
of their availability to the alkali is controllable, e.g.,
as a function of the rate of swelling of the polymer layer which
rate in turn has a direct relationship to the diffusion rate
of the hydroxyl ions. The desired distribution of the acid
groups in the acid polymer layer may be effected by mixing
the acid polymer with a polymer free of acid groups, or lower
in concentration of acid groups, and compatible therewith, or
by using only the acid polymer but selecting one having a rela-
tively lower proportion of acid groups. These embodiments are
illustrated, respectively, in aforementioned U. S. Patent No.
3,362,819, by (a) a mixture of cellulose acetate and cellulose
acetate hydrogen phthalate and (b) a cellulose acetate
hydrogen phthalate polymer having a much lowe~ percentage of
phthalyl groups than the first-mentioned cellulose acetate
hydrogen phthalate.
It is also disclosed that the layer containing
the polvmeric acid may contain a water insoluble polymer,
preferab~y a cellulose ester, which acts to control or
modulate the rate at which the alkali salt of the polymer
acid is formed. As examples of cellulose esters con-
ter.lplated for use, mention is made of cellulose acetate,
cellulose acetate, butyrate, etc. The particular polymers
and combinations of polymers employed in any given embodi-
ment are, of course, selected so as to have adequate wet
and dry strength and when necessary or desirable, suitable
-12-
1052026
subcoats may be employed to help the various polymeric
layers adhere to each other during storage and use.
The inert spacer layer of the aforementioned
patent, for example, a layer comprising polyvinyl alcohol
or gelatin, acts to "time" control the pH reduction by
the polymeric acid layer. This timing is disclosed to
be a function of the rate at which the alkali diffuses
through the inert spacer layer. It was stated to have
been found that the pH does not drop until the alkali
has passed through the spacer layer, i.e., the pH is not
reduced to any significant extent by the mere diffusion
into the spacer layer, but the pH drops quite rapidly
once the alkali diffuses through the spacer layer into
the acid polymer layer.
It has been disclosed in U. S. Patent No.
3,455,686, issued July 15, 1969, that the diffusion rate
of an alkali processing composition through a permeable
inert polymeric spacer layer increases with increased pro-
cessing temperature to the extent, for example, that at
relatively high transfer processing temperature, that is,
transfer processing temperatures above approximately 80 F.,
a premature decrease in the pH of the transfer processing
composition occurs due, at least in part, to the rapid
diffusion of alkali from the dye-transfer environment and its
subsequent neutralization upon contact with the polymeric
acid layer. This was disclosed to be especially true of
alkali traversing an inert spacer layer possessing optimum
alkali-permeability characteristics within the temperature
range of optimum transfer processing. Conversely, at
temperatures below the optimum transfer processing ran~e,
-13-
105Z026
for example, temperatures below approximately 40 F., the
last-mentioned inert spacer layer was found to provide an
effective diffusion barrier timewise preventing effective
traverse of the inert spacer layer by alkali having tempera-
ture depressed diffusion rates. This barrier resulted inmaintenance of the transfe~ processing environment's high
pH for such an extended time interval as to facilitate
formation of transfer imag~ stain and its resultant deg-
radation of the positive transfer image's color definition.
It was further d-sclosed in the last-mentioned
patent, that i~ the inert :,pacer layer of the print-
receiving element is replaced by a spacer layer which
comprises permeable polymeric layer exhibiting perme-
ability inversely dependent: upon temperature, and
specifically a polymeric film-forming material which
exhibits decreasing permeahility to solubilized alkali
derived c3tions such as al~:ali metal and quaternary
ammonium ions under conditions of increasing temperature,
that the positive transfer image defects resultant from
the aforementioned over-extended pH maintenance and/or
premature pH reduction were obviated.
As examples of polymers disclosed in the last-
mentioned patent which exhibit inverse temperature-
dependent permeability to alkali, mention was made of:
hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether,
polyethylene oxide, polyvinyl oxazolidinone, hydroxypropyl
methyl cellulose, partial acetals of polyvinyl alcohol
such as partial polyvinyl butyral, partial polyvinyl formal,
partial polyvinyl acetal, partial polyvinyl propional,
and the like.
-14-
1 0SZOZ6
Addition~l polymers which may be particularly advantagcously
employcd are temperature-invcrting polyvinylamide graft copolymers, as
disclosed in U. S. Patent No. 3,575,701, filed January 13, 1969, in the
name of Lloyd D. T~ylor.
In addition to techniques as described above, alternative dif~usion
transfer color processes kno~m to the photographic art may be employed.
Thus, for example, U.S. Patent No. 3,019,124, issued January 30, 1962, dis-
closes the manufacture of photographic color screen elements; and U.S.
Patent Nos. 2,968,554, issued January 17, 1961 and 2,983,606, issued May
o 9, 1961 disclose diffusion transfer processes wherein a color screen
element is utilized to provide a multicolor positive image to a superposed
image-receiving layer. Also in place of the aforementioned dye developers,
. there may be employed dye image-forming materials such as those described
in U.S. Patent Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735;
3,148,062; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655;
3,347,671, 3,352,672; 3,364,022; 3,443,939; 3,445,228; 3,443,940; 3,443,941;
3,443,943; etc.,wherein color diffusion transfer processes are described
which employ color coupling techniques comprising, at least in part, reacting
one or more color developing agents and one or more color formers or couplers
to provide a dye transfer image to a superposed image-receiving layer and
those disclosed in U. S. Patents Nos. 2,774,668; 2,983,606; 3,087,817; and
3,345,163 wherein color diffusion transfer processes are described which
emploY the imagewise differential trans~er of complete dyes by the mechanisms
therein describea to provide a transfer dye image to a contiguous image-
receiving layer, and thus including the employment of
-15-
105ZOZ6
image-providing materials in whole or in part initially
insolu~le or nondiffusible as disposed in the film unit which
diffuse during processing as a direct or indirect function of
exposure.
As examples of materials which heretofore have béen
found to be useful as image-receiving layers in diffusion
transfer color photographic processes, mention may be made
of solution dyeable polymers such as nylons as, for example,
N-methoxymethyl polyhexamethylene adipamide, partially
hydrolyzed polyvinyl acetate; polyvinyl alcohol with or
without plasticizers: cellulose acetate with fillers as,
for example, one-half cellulose acetate and one-half oleic
acid; gelatin; and other materials of a similar nature. Par-
ticularly useful materials have comprised polyvinyl alcohol or
gelatin, having admixed therewith a dye mordant such as poly-
4-vinylpyridine, as disclosed in U. S. Patent No. 3,148,061,
issued Seotember 8, 1964. However, while image-receiving
layers comprising the aforementioned materials have pro-
vided excellent photographic images, they have nonetheless had
certain inherent drawbacks. Thus, for example, where the
image-receiving layer comprises poly-4-vinylpyridine as dis-
closed in aforementioned U. S. Patent No. 3,148,061, it is
generally necessary to coat the polymer with a small amount of
acid, which is preferably volatile but which is then also
diffusible; any unevaporated acid residue has an adverse
effect on the stability of the photographic unit when the
image-receiving element and the photosensitive element are
stored in face-to-face contact prior to exposure and develop-
ment of the unit. Also, particularly in embodiments where
the image-receiving element is not stripped away but is
~05ZOZ6
maintained in contact with the photosensitive element subsequent to dye
developer transfer image formation, the resulting images have a tendency to
show mottle, and to darken somewhat wi~h the passage of time.
The present invention is a graft copolymer represented by the
formula:
R
Z _-- C (R) 2 ----C--
X
wherein Z is an organic polymeric backbone selected from the group consisting
of cellulosic and vinyl polymers; -C(R)2-C- represents the residue of a
graftable vinyl group wherein each R is the same or different substituent
which will not hinder grafting of the residue to the backbone; M is a moiety
that can provide a mordant capability and X is a positive integer.
Thus in a first embodiment this invention provides a graft polymer
comprising the structure
R
Z ~ C (R) 2 - ---C--_
M
wherein Z is an organic polymeric barkbone selected from the group consisting
of cellulosic and vinyl polymers and
C(R)2 f
~ - 17 -
10520Z6
is a grafted residue of a vinylbenzyl-ammonium halide wherein M represents
a benzylammonium moiety, and each R, which may be the same or different,
represents hydrogen or a substituent which will not hinder grafting of the
residue to the backbone, and n is a positive integer.
In a second embodiment this invention provides a graft polymer
comprising the structure
~ R
Z ~ C~R)2 C----
M n
where Z is a polymeric backbone comprising a vinyl polymer selected from the
group consisting of polyvinyl alcohols, poly-N-vinylpyrollidones and poly-
acrylamides and
~ )2 f
M
is a grafted residue of a vinylbenzyl-ammonium halide wherein M represents a
benzylammonium iety, and each R, which may be the same or different,
represents hydrogen or a substituent which will not hinder grafting of the
residue to the backbone, and n is a positive integer.
In a third embodiment this invention provides a graft polymer com-
prising the structure
_
z C(R)2 f----
_ M
n
- 17a -
lOSZ026
where Z is a polyvinyl alcohol polymeric backbone and
- C(R)2 - C -
represents a grafted residue of a vinyl benzyl-ammonium halide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder grafting
of the residue to the backbone, and n is a positive integer.
In a fourth embodiment this invention provides a graft polymer
comprising the following structure
R
Z C (R) 2 C -
n
where Z is a poly-N-vinylpyrrolidone polymeric backbone and
( )2 IC
M
represents a grafted residue of a vinylbenzyl-ammonium halide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder grafting
of the residue to the backbone, and n is a positive integer.
In a fifth embodiment this invention provides a graft polymer com-
prising the structure
~ - 17b -
lOSZOZ6
r
l 1
T C(R)2
C _
~
M _ n
where Z is a polyacrylamide backbone and
- C(R)2 - I -
represents a grafted residue of a vinylbenzyl-ammonium halide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backbone, and n is a positive integer.
In a sixth embodiment this invention provides a graft polymer
comprising the structure
Rl
Z ~ C~R)2 C-
M n
where Z is a polymeric backbone comprising a cellulosic polymer and
- C(R)2 - C -
M
- 17 c -
lOSZOZ6
is a grafted residue of a vinylbenzyl-amnium ha]ide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backbone, and n is a positive integer.
In a seventh embodiment this invention provides a graft polymer
comprising the structure
r R 1
Z ~ C(R)2 C ~
n
where Z is a hydroxyethylcellulose polymeric backbone and
( )2
represents a grafted residue of a vinylbenzyl-a = nium halide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backbone, and n is a positive integer.
In the eighth embodiment this invention provides a graft polymer
comprising the structure
r 71
Z ~ C(R)2 Cl--
n
17d -
1052026
where Z is a methylcellulose polymeric backbone and
- C(R)2 - C -
M
represents a grafted residue of a vinylbenzyl-ammonium halide wherein M
represents a benzylammonium moiety, and each R, which may be the same or
different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backbone, and n is a positive integer.
In the ninth embodiment this invention provides a graft polymer
comprising the structure
H
Z ----C(R)2 C-
n Cl-
+~(CH2)mCH3
~ 2 1 ~ (CH2)mCH3
where Z is a hydroxyethylcellulose backbone, each R, which may be the same
or different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backbone, m = o - 5, and R is -(CH2)mCH3,
-CH2 ~ or ~ , and n is a positive integer.
In the tenth embodiment this invention provides a graft polymer
comprising the structure
~ - 17e -
lOSZOZ6
Z C(R)2 C~
n Cl-
\ +/( 2)mCH3
~ CH2 ~ N (CH2)mCH3
where Z is a polyvinyl alcohol backbone, each RJ which may be the same or
different, represents hydrogen or a substituent which will not hinder
grafting of the residue to the backboneJ m - o - 5, and R2 is -~CH2)mCH3,
-CH2 ~ or ~ , and n is a positive integer.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed description.
The above graft copolymer of the present invention are useful as
the dyeable stratum of the diffusion transfer products described. The
value of the present invention resides in the unexpected discovery that the
use of a polymeric material, wherein a moiety providing a mordant capability
is grafted to the polymeric chain or backbone as the dyeable stratum of
diffusion transfer color image-receiving elements, provide images exhibiting
excellent dye densities over a wide temperature range, with faster dye
saturation, as compared with compounds described in the prior art. Moreover,
such images are characterized by superior light stability, and reduced degree
of darkening. It has further been discovered that the novel graft polymers
or copolymers of the present invention can be coated from solution at a
higher solids content than the materials or the prior art, resulting in in-
creased coating efficiency; they are coatable at neutral pH and hence their
use can obviate the stability problems inherent in the use of volatile,
diffusible
- 17f -
~"i
10520Z6
acids as coatin~ adjuncts. Moreover, their coatings are molecularly homogen-
ous, resultin~ in more uniform image ~uality and freedom from mottle as com-
pared with prior art image-receiving layers. Additionally the novel graft
polymers and/or copolymers of the present invention exhibit permeability at
least in part inversely dependent upon temperature.
As indicated hereinbefore, polymeric films having inverse tempera-
ture dependence with regard to alkali permeability have been disclosed for
utilization as spacer layers in color diffusion transeer photoRraphic receiv-
ing sheets. Polymers comprising such films generally exhibit the property of
being relatively soluble in cold water, that is, water at a temperature of
less than about 40 to 80C., the precise temperature being dependent upon the
polymer specifically selected for employment; and relatively insoluble in hot
water, that is, water at a temperature about 80C., the precise temperature
being dependent upon the polymer selected. A relatively large number of such
polymers are substantially insoluble in caustic photographic processing media
over the range of photographic diffusion transfer processing. Such polymers,
however, are permeable to photographic alkaline processing composition as a
function of their swelling, which, in turn, is believed to be a function of
the free energy of solution decrease caused, at least in part, by the heat
evolved as a result of the interaction between the polymer and the processing
composition solvent and by an increase of the entropy of the system. This
free energy decrease is believed to lessen with increased temperature of the
environment and result in a decreased swelling, and thus decrease photographic
processing composition permeability with such temperature increase.
Benefits are derived from using a temperature-inverting material in
a process which depends upon permeation of liquids, at a variety of tempera-
tures, since, as the ambient temperature decreases, the polymer tends to form
hydrates and swells, thus facilitating permeation as a function of the degree
of swell of the polymer - deswelling being inherent with an increase in temp-
erature. It is well known that the diffusion rate of a liquid, for example,
-18-
1052026
an alkali, will increase as the temperature increases. Since, in a typical
diffusion transfer ~hotographic process this rate is directly proportional to
the progress of the transfer image formation per unit time, the benefit of de-
vising a mechanism for controlling the diffusion rate inversely with temper-
ature is recognized. The desired result is to have the temperature-inverting
material approximately counteract changes in temperature. Temperature inver-
sion is, therefore, relative, since the precise properties desired would be
dependent upon the response of the whole system to changes in temperature.
Extreme inverse temperature characteristics are ~enerally not par-
ticularly desirable since the development of the photosensitive part of thesystem and the dye transfer are temperature dependent processes and should he
functionally compatible with the temperature-permeation properties of the re-
ceiving sheet. An ideal image-receiving element, therefore, should provide
the system which it comprises with the proper dye permeation-temperature pro-
perties so that dye may diffuse from the photosensitive part of the system to
the receiving sheet, as a function of development, in order to form a positive
image in the receiving sheet within a predetermined time, irrespective of the
processing temperature employed.
It will be obvious that where the image-receiving layer of the image-
receiving element comprises a temperature-inverting polymeric mordant, not
only is the temperature-permeation of the system enhanced, but also a techni-
que is provided for evening out the dye uptake of the layer over an extended
temperature range. Specifically, at lower temperatures where the processing
composition transfer rate is slower, the increased permeability of the layer
renders the mordanting sites more readily available to the diffusing image-
forming components; the increase in processing composition transfer rate which
takes place as the processing temperature is increased is compensated for by
the corresponding decrease in permeability and availability of mordanting
sites in the image-receiving layer. Thus, by means of the present invention,
an image-receiying layer is provided for diffusion transfer color photographic
-19-
lOSZ026
processes wherein mordanting of dye image-forming material
is substantially uniform over a wide range of temperatures.
The temperature-inverting characteristic of members
of the class of graft polymers and/or copolymers of the in-
stant invention is probably attributable to the presence of
a predetermined balance of hydrophobic groups to hydro~hilic
groups in the polymer molecule. The probable mechanism
through which temperature inversion occurs is by the forma-
tion of hydrogen bonds between the hydrophilic portion of the
polymer and the hydrogen of the solvent at low temperatures;
the hydrogen bonding being discouraged as the temperature of
the material is raised due to thermal destruction. The sys-
tem thereupon takes the form of a less-hydrated, less-swollen,
therefore, less-permeable polymer as a function of the increase
in temperature. It may then be said that the preferred poly-
mers useful in the practice of the present invention are those
which con~ain hydrophilic groups which cause swelling as a
function of the solvatability of that group in a given solvent,
and hydrophobic groups which modulate the swelling so that at
some definite ratio of hydrophilic to hydrophobic groups, the
resultant compound will have temperature-inverting properties.
It may further be concluded, that the interactions re-
sponsible for temperature inversion are forces such as hy-
drogen-bonding and hydrophilic-hydrophobic bonding forces.
The graft polymers and/or copolymer~ of the inven-
tion are preferably those wherein Z is an organic polymeric
backbone comprising repeating units comprising structural
units capable of being oxidized by a transition metal ion
catalyst of a first oxidation state;
-20_
lOSZOZ6
said catalyst having an oxidation potential, in acidic solu-
tiont of at least about 1 volt when the transition metal is
reduced to the next lowest acidic solution stable oxidation
state; each R is the same or different substituent'~hich
will not hinder grafting of the mordant through the vinyl
group"such as hydrogen, hydroxy, alkyl radicals, alkanol
radicals, alkoxy radicals and aryl radicals with hydrogen,
hydroxy, lower alkyl or alkoxy, e.g., from 1-4 carbon atoms,
being the preferred substituents; and X is a positive inte-
ger.
With regards to the backbone polymer or copolymer of
the graft polymer, in general, any organic polymer or copolymer
comprising repeating units comprising structural units contain-
ing the -C -H grouping; wherein Y is selected from the group con-
sisting of hydroxyl, amino, mercapto, acyl and aryl, amido are
capable of being oxidized by a transition metal ion catalyst
as stated above, and are therefore useful in the present in-
vention. The terms hydroxyl acyl and aroyl as used above
are intended to encompass partial acetals of these particular
functional group terms. Preferred backbones are substituted
or unsubstituted cellulosic or polyvinyl polymers, and most
preferably, a backbone selected from the group consisting of
polymeric polyols, polyvinyl alcohol, poly-N-vinylpyrrolidone,
gelatin, polysaccharides, polyalkyleneimines, partial acetals
of polyvinyl alcohol, partially hydrolyzed esters of polyvinyl
alcohol such as partially hydrolyzed polyvinyl acetate,
polyaldehydes, polyamides, cellulose, substituted celluloses
such as methyl cellulose, hydroxyethyl cellulose, methyl
hydroxypropyl cellulose, starch, etc.
-21-
105ZOZ6
It is believed that upon oxidation of the - C - H
grouping, a free radical is formed, which attacks the graftable site of the
compound providing the mordant capability thus providing the graft polymer
and/or copolymer.
Graftable compounds which can provide the mordant capability are
those which in their monomeric form, conform to the following formula:
C(R)2 = C(R)
where, as described before, C(R)2 = C(R) - represents a graftable vinyl site
and M is a moiety providing a mordant capability. Compounds of this type
are known to the art and include among others those wherein the M moiety can
conform to the following formulae:
R
N
X
N(~)/
2. _ ~ y (-)
3- CO - O - (CH2)n - N <
R
,.
105ZOZ6
~R
4- ~ON~-(CH2)n - N
5. /N~
Rl/ \ R2 Rl
6. 1_C_(CH ) -N
Il 2 n ~ 1
7. (CH2)n
N
1/ \ 1
R R
S 8. f = N - NH - C - NH
R NH
wherein n is an integer from 1-8; each Rl can be hydrogen, an
alkyl radical an alicyclic radical, an alkoxy radical, a
saturated heterocyclic ring, and an aryl radical or substituted
derivative thereof and each Rl can be the same or different;
X represents an anion such as an aryl sulfonate anion, e.g./
benzenesulfonate, p-toluenesulfonate etc., an alkylsulfonate
anionJ e.g.J methyl sulfate, ethyl sulfate, n-propyl sulfate,
n-butyl sulfate etc.; or X can be a halide ion, e.g., iodide,
chloride bromide or other acid anion radical.
Particular compounds conforming to the above generic
formulae include the vinyl pyridines and salts thereof such as
4-vinylpyridineJ 2-vinylpyridine, 5-vinyl-2 methylpyridine, etc.
-23-
~05ZOZf~
Other compounds include 2-methyl-N-vinylimidizole
B-(trimethyl amino) ethyl methacrylate nitrate, B-(trimethyl
amino) ethyl methacrylate nitrate, B-(trimethyl amino) ethyl
methacrylate methyl sulfate, dimethyl amino ethyl methocrylate
S nitrate, 5-vinyl-2 methyl-N benzyl pyridinium bromide, 4-vinyl
pyridinium tosylate, p-vinyl benzyl triethylammonium chloride,
4 vinylpyridine methyl tosylate, 5-vinyl-2-methyl pyridine
methyl tosylate, vinylbenzyltrimethylammoniumchloride,
vinylbenzyltriethylammoniumchloride, vinylbenzylpyridinium-
chloride, vinylbenzyl-N-methylmorpholiniumchloride,
and the like.
Other details relating to compounds that can provi~e
a mordant capa~y may be found in U. S. Patents 2,537,924,
2,548,S75, 2,564,726, 2,583,076, 2,635,5~5, 2,635,536,
2,753,263, 3,048,487, and 3,075,841.
The graft copolymers of the present invention may be
prepared, in general, by oxidizing an organic polymeric backbone
containing hydroxyl, amino, mercapto, amido, acyl, or aryl groups
with a transition metal ion catalyst, in the presence of the
mordant monomer. Generally, a 1-10%~ by weight, aqueous solution
of the backbone polymer is deaerated for about 30 minutes with
stirring. The monomer is then added and nitrogen is bubbled
through the solution for about one hour. At this point, the
nitrogen is passed over the stirred solution and the pH adjusted
to around 1.5 with concentrated acid. The catalyst is dissolved
in a minimum amount of water, quickly added to the polymerization
mixture and stirring continued under the nitrogen atmosphere
for at least two more hours with stirring times up to 24 hours,
giving no adverse effect to the graft copolymer. The resulting
graft copolymers are obtained from the reaction vessel in the
105ZOZ6
form of aqueous solutions. They may then be coated directly
from solution to provide novel image-receiving layers. However,
in preferred embodiments, the pH is raised, e.g., with NH3, to
a point at which an aqueous emulsion is formed, generally a pH
of around 7, depending at least in part upon the ratio of
catalyst to backbone polymer and backbone polymer to mordant
monomer.
The choice of catalyst is wide ranging, with
particularly good results being obtained when catalysts con-
taining Ce+4, V+5 and Cr+6 are employed in making the graftcopolymers of the present invention.
Although the pH is generally adjusted to around 1.5
with concentrated nitric aeid, pH's of up to about 7 have
proven operative in some instances, depending at least in
part on the ratio of catalyst to backbone polymer.
In some instances, the temperature of the
polymerization mixture can be raised to ar~und 50C. to
, facilitate the reaction.
Examples of novel graft polymers which are found
to be useful in the instant invention are:
(1) 4-vinylpyridine graft on polyvinyl alcohol
OH
r CH2--C ]
CH
1 2 r ~~\
HC ~ ~ h
(2) 5-vinyl-2-methylpyridine graft on polyvinyl
alcohol OH
~CH2--C ] ---
CH
~IC~CH3
lOSZOZ6
~3) 4-vinylpyridine graft on methyl cellulose
H CR20CH H OH
H ~ ~ H ~ \A P~
H ~ O \ ~O ~ H H ~ O C~
~20CH3 -- 7 -- ~2ocH3
HC ~
II I
14) 4-vinylpyridine graft on hydroxyethyl
cellulose
H OH ; CH2C2H4H H ~H
5 H~ H ~ O\ / ~ H
H~o/ \ ~o ~ H H ~ O A
CH20C2H4Cl~ _ ~ _ CH20C2H4H
IS) 4-vinylpyridine graft on gelatin
16) 5-vinyl-2-methylpyridine graft on gelatin
~7) 4-vinylpyridine graft on starch
~8) S-vinyl-2-methylpyridine graft on starch
~9) 4-vinylpyridine graft on poly-N-vinylpyrrolidone
-2~ , :
. , , '
~ '
:
' ' ' ' ' : ~ :
105ZOZ6
f C~2 -CH ~
.~
=C 1~2
-- H C CH2
HC ~
~10) 4-vinyl pyridine graft on hydroxyethylcellulose
(11) 4-vinyl pyridine, vinylbenzyltrimethyl-
ammoniumchloride graft on hydroxyethylcellulose
(12) vinylbenzyltrimethylammoniumchloride graft on
hydroxyethylcellulose
(13) vinylbenzyltrimethylammoniumchloride graft
on polyvinyl alcohol
(14) 4-vinyl pyridine, vinylbenzyltrimethylammonium-
chloride graft n polyvinyl amide
It has been generally found that for any ~iven polymer3
the temperature-permeability characteristics of the layers pre-
pared therefrom can be manipulated by the judicious choice
of backbone/catalyst ratio. In general, any two polymers
having the same backbone, comprised of the same monomers,
and having the same monomer to backbone polymer ratioJ will
result in layers having different diffusion characteristics
if they are prepared in the presence of different backbone/
catalyst ratios. In general, decreasing the amount of
catalyst (and hence increasing the backbone/catalyst ratio)
results in increased impermeability.
As was stated hereinbefore, any transition metal
ion catalyst of a first oxidation state having an oxidation
potential, in acidic solution of at least about 1 volt when
the transition metal is reduced to the next lowest acidic
solution stable oxidation state, is operable in the present
lnvention. As preferred catalysts, mention may be made of
transition metal ion catalysts comprised of a member selected
from the group consisting of V 5, Ce+4 and Cr+6.
1052026
In general, a backbone/catalyst ratio of from
about 10 to about 130 i6 the most useful range, irrespective
of the monomers used.
~rom the foregoing discussion,it will be appreciated
S that employment of the graft copolymers of the present invention,
in addition to providing an e~pecially affective dye mordant
function, can assist in evening out the temperature response
characteristics of the diffusion transfer color photographic
units in which they are emp]oyed, by acting at least in part
as a "timing valve" for the processing composition. Ordinarily,
if the processing temperature is too hot and no temperature
inverting layer is used, poor dye densities and "gappiness"
may be evident in the photographic image, which are believed
to be due to the premature neutralization of the processing
composition; when the temperature i8 cold and no temperature
inverting timing layer is used, the neutralization of the
developing composition is too slow, and may result in the
maintenance of undesirable salts in the top layer of the
photographic image, causing dull, muddy colors.
The present invention will be illustrated in greater
detail in conjunction with the following procedures and pro-
cesses utilized in providing the novel graft copolymers of the
present invention, and which set out representative photo-
graphic products and processes employing the novel graft co-
polymers, which, however, are no~ of limiting effect and are
intended to be illustrative only.
EXAMPLE I
A graft copolymer of 4-vinylpyridine on polyvinyl
alcohol having a polyvinyl alcohol/~-vinylpyridine mole ratio of
2/1 and a polyvinyl alcohol/catalyst mole ratio of 227 was pre-
pared as followY
-2
10520Z6
~ o a dea~rated solution of 2b g. of polyvinyl alcohol
in 500 cc. of water was added 10 g. of 4-vinylpyridine, with
stirring under an atmosphere of nitrogen. Nitrogen was
bubbled through the solution for one hour, after which the
temperature of the solution was raised to 50 C., the pH was
adjusted to 1.5 with concentrated nitric acid, and 1.1 g. of
Ce(NH4)2 (N03)6 in 20 cc. of water was added. Stirring was
continued for two more hours, at the end of which the desired
copolymer was obtained as an aqueou's solution; the pH of the
solution was raised to a point at which an aqueous emulsion
was formed with concentrated NH3. ~he product polymer was
dialyzed to remove any excess ammonium nitrate salt.
EXAMPLE II
A graft copolymer of 4-~inylpyridine on polyvinyl
alcohol having a polyvinyl alcohol/4-vinylpyridine mole ratio of
2/1 and a polyvinyl alcohol/catalyst mole ratio of 57 was prepared
by the procedure of Example I using 4.4 g. of Ce(NH4)2 (N03)6,
except that the reaction was carried out at room temperature
and terminal stirring was continued overnight.
EXAMPLE III
A graft copolymer of 4-vinylpyridine on polyvinyl
alcohol having a polyvinyl alcohol/4-vinylpyridine mole ratio
of 2/1 and a polyvinyl alcohol/catalyst mole ratio of 45 was
prepared by the procedure of Example II, using 5.5 g.
ce(NH4)2 (N3)6
--2
lOSZOZ6
EXAMPLE IV
A graft copolymer of 4-vinylpyridine on polyvinyl
alcohol having a polyvinyl alcohol/vinylpyridine mole ratio
of 1/3 and a polyvinyl alcohol/catalyst mole ratis of 22.5
S was prepared by the procedure as outlined in Example II
using 20 g. of polyvinyl alcohol, 60 g. of 4-vinylpyridine,
and 11.0 g- of Ce(NH4)2 (N03)6 in 25 cc. of water.
EXAMPLE V
Two graft copolymers of 4-vinylpyridine on
hydroxyethyl cellulose were prepared by the procedure
described in Example I, except as follows:
(a) graft copolymer having a hydroxyethyl
cellulose/4-vinylpyridine weight ratio of 2/1 and a
hydroxyethyl cellulose/catalyst weight ratio of 20 was
prepared using 22 g. of hydroxyethyl cellulose, 11 g. of
4-vinylpyridine, and 1.1 g. Ce(NH4)2 (N03)6 in 10 cc. of
' water.
(b) graft copolymer having a hydroxyethyl
cellulose/4-vinylpyridine weight-ratio of 1/3 and a
hydroxyethyl cellulose/catalyst weight ratio of 10 was
prepared using 22g. of hydroxyethyl cellulose, 66 g. of
4-vinylpyridine, and 1.1 g. of Ce~H4)2 (N03)6 in 10 cc.
of water.
-30
105202~;
EXAMPLE ~lI
Graft copolymers of 4-vinylpyridine on methyl
cellulose were prepared as follows:
An aqueous solution of 10 g. of methyl cellulo~e
S in 500 cc. of water (Methocel HG 60, 4000 cps.,available
commercially from Dow Chemical Co. J Midland, Michigan)
was purged with nitrogen for two hours, after which 10 g.
of 4-vinylpyridine was added. The pH was adjusted to l.S
with concentrated nitric acidJ and 0.6 g. of Ce(NH4)2 (N03)6
was added. The mixture was reacted at 30 C. for 1.5 hours
and at 50 C. for l.S hours, after which NH3 was added to
bring the pH to 7. The resulting precipitated polymer
was washed with water and acetone, and recovered as an
off-white powder.
lS A second graft copolymer of 4-vinylpyridine on
methyl cellulose was prepared by the same procedure, but
using a lower viscosity methyl cellulose (Methocel MCJ
400 CPS.J available commercially from Dow Chemical Co.).
Upon addition of NH3J a white latex was obtainedJ which
was dialyzed for two days to yield the product polymer.
A third graft copolymer of 4-vinylpyridine on
methyl cellulose was prepared by dissolving 50 g. of methyl
cellulose (Methocel MC, 10 cps., available commercially
from Dow Chemical Co.) in 500 cc. of hot water. 700 cc.
of cold water and 100 g. of 4-vinylpyridine, and about
100 g. of concentrated nitric acid, to give a pH of 1.5,
were added. After stirring under an atmosphere of
nitrogen at room temperature for two hours, the solution
became cloudy. 300 cc. of water were added, and the
1052026
temperature was raised to 45 C. The mixture was repeatedly
evacuated and vented into nitrogen. Upon addition of 3.0 g.
of Ce(~4)2 (N03)6 in 15 cc. of water, the mixture
gradually became translucent. Stirring was continued
overnight at 45-50 C. after which the reaction product
was recovered as a white latex. The copolymer was purified
by dialysis and centrifugation, yielding a clear 4.4 weight
X aqueous solution.
EXAMPLE VII
A graft copolymer of 5-vinyl-2-methyl pyridine
on gelatin having a gelatin/5-vinyl-2-methyl pyridine
weight ratio of 1/2 was prepared by the procedure of
Example II J using 10 g. of gelatin in 460 cc. of water,
20 g. of 5-vinyl-2-methyl pyridine, and 3.3 g. of
Ce(NH4)2 (N03)6 in 10 cc. of water. The copolymer wa~
recovered in the form of an aqueous emulsion. -
EXAMPLE VIII
A graft copolymer of 4-vinylpyridine on poly-N-
vinylpyrrolidone was prepared by the procedure of Example I,
using 30 g. of poly-N-vinylpyrrolidone in 500 cc. of water,
lS g. of 4-vinylpyridine, and 10.0 g. of Ce(NH4)2 (N03)6 in
20 cc. of water. The copolymer was recovered in the form
of an aqueous emulsion.
EXAMPLE IX
A graft copolymer of 4-vinylpyridine on starch
was prepared by the procedure of Example I, using 20 g. of
solublc starch dissolved in 500 cc. of water, 40 g. of
4_vinylpyridine, and 4.4 g. of Ce(NH4)2 (N03)6 A second
copolymer having a lower starch/catalyst ratio was similarly
prepared, with the exception that B.8 g. of Ce~NH4)2 (N03)6
was employed.
- 32 -
105;~0Z~;
EXAMPI,~ X
To a solution of 11 g. hydroxyethyl cellulose in 250
ml. H20 was added 5.5 g. 4-vinylpyridine, 5.41 g. concentrated
HN03 and 7.6 g. vinylbenzyltrimethylammoniumchloride. Nitrogen
wa~ bubbled through the mixture for one hour and the temperature
was raised to 50C. then 1.1 g. Ce(~H4)2(N03)6 in 10 ml- H20 was
added and stirring continued overnight. The pH of the
polymerization mixture was then adjusted to 7.0 with concentrated
NH40H. The graft copolymer of hydroxyethyl cellulose having 4
vinylpyridine vinylbenzyltrimethylammoniumchloride grafted
thereto was recovered in the form of an aqueous emulsion having
9.1% solids by weight. The mole ratio of hydroxyethyl cellulose
(HEC) to 4 vinylpyridine (4VP) to vinylbenzyltrimethylammonium-
chloride was 2/1/1.4.
EXAMPLE X~
A graft copolymer of vinylbenzyltrimethylammonium-
chloride on hydroxyethyl cellulose was prepared in accordance
with the procedure of Example X but no 4-vinylpyridine was used
' and only 0.5 g. concentrated HN03 was used.
EXAUPLE XII
The following Example illustrates a method for pre-
paring a graft copolymer of p-vinylbenzyltriethylammonium-
chloride on polyvinyl alcohol wherein the mole ratio of
polyvinyl alcohol to p-vinylbenzyltriethylammoniumchloride is
1:1.
To a solution of 11 g. poiyvinyl alcohol in 200 ml.
H20 was added 11 g. vinylbenzyltriethylammoniumchloride.
Nitrogen was bubbled through the mixture for 1 hour and the
temperature raised to 60C. then 0.5 g. concentrated HN03 and
1.6 g. CE(NH4)2(N03)6 in 10 mls. H20 was added. Stirring
continued for 2 1/2 hours and the graft copolymer was recovered
in the form of an aqueous solution having a pH of 5.0 and
containing 9.4% solids by weight.
1052026
The graft copolymer prepared above conforms to the
following structure:
r c _ -
~t
OEI ~
~ (CH2-CH)
~ +
~ 2 ( 2 5)3
EXAMPLE ~III
A graft copolymer of vinylbenzyltrimethylammonium-
chloride, 4 vinylpyridine on polyvinyl alcohol wherein the mole
ratio of polyvinyl alcohol to vinylbenzyltrimethylammonium-
chloride to 4 vinylpyridine was 2h/1 was prepared in accordance
with the procedure of Example XII except that vinylbenzyl-
trimethylammoniumchloride was used together with 5 g. 4-vinyl-
pyridine, 4.8 g. concentrated HN03. 2.2 g. CE(~H4)2 (N03)6 and
the polymerization was run overnight at 60C. The graft
copolymer was recovered as an aqueous emulsion having a pH of
5.0 and containing 11% solids by weight.
EXAMPLE XIV
A series of four image-receiving elements was pre- -
pared as follows:
A cellulose nitrate subcoated baryta paper was
coated with the partial butyl ester of polyethylene/maleic
anhydride copolymer prepared by refluxing, for 14 hours, 300 g.
of a DX-840-31 resin (trade name of Monsanto Chemical Co.,
St. Louis, Missouri, for high viscosity polyethylene/maleic
anhydride), 140 g. of n-butyl alcohol and 1 cc. of 85%
phosphoric acid to provide a polymeric acid layer approxi-
mately 0.7 mils thick. The external surface of said acid layer
was coated with an emulsion comprising a graft copolymer of
-34-
lOSZOZ6
diacetone acryl~nidc ~nd acryl~mide on polyvinyl alcohol at a coverage of
750 mg./ft. to provide a spacer layer. (Spacer laycrs for dif~usion
transfer color image-receiving elements comprising graft vinylamide copoly-
mers and procedures for preparing such polymers are described in U.S.
Patent Nos. 3,575,700 and 3,575,701, both filed January 13, 1969, in the
name of Lloyd D. Taylor.) The first element so prepared was then coated,
on the external surface of the spacer layer, with the vinylpyridine graft
copolymer of Example I at a pH of 7.4, and the second and third elements
were coated at a pH of 6.o with the vinylpyridine graft copolymers of
Examples II and III, respectively, all at coverages of 1000 mg./ft. . The
fourth element was similarly coated at a pH of 4.5 with a 2:1 mixture, by
weight, of polyvinyl alcohol and poly-4-vinylpyridine, to serve as a control.
The thus-prepared image-receiving elements were baked at 180F. for 30
minutes and then allowed to cool.
The negative component of the photographic film distributed by
Polaroid Corporation, Cambriage, Massachusetts, under the trade designat,on
of Polacolor film Type 108, was emplcyed as the photosensitiveelement for
the image-receiving elements prepared above. Such multicolor, multilayer
photosensitive elements may be prepared in a manner similar to that
disclosed in U. S. Patent ~o. 3,345,163, issued October 7, 1967. In general,
the photosensitive elements may comprise a support carrying a red-sensitive
silver hal~de emulsion stratum, a green-sensitive silver halide emulsion
stratum and a blue-sensitive emulsion stratum. In turn, the emulsions may
have dispersed behind them in water-immiscible organic solvents and con-
tained in separate gelatin polymeric layers, respectively, a cyan dye
developer, a magenta dye
-35-
lOSZOZ6
developer, and a yellow dye developer. A gelatin interlayer
may be positioned between the yellow dye developer layer and
the green-sensitive emulsion stratum, and also between the
magenta dye developer layer and the red-sensitive emulsion
stratum. The particular dye developers employed in the
photosensitive element may comprise, for example, l,4-bis-
(~-methyl-~-hydroquinonyl-ethylamino)-5,8-dihydroxyanthra-
quinone ~a cyan dye developer); 2-(p-[2',5'-dihydroxyphenethyl]-
phenylazo)-4-isopropoxy-1-naphthol (a magenta dye developer);
and 1-phenyl-3-n-hexylcarbamyl-4-(p-~hydroquinonyl-ethyll-
phenylazo)-5-pyrazolone (a yellow dye developer). The last-
mentioned yellow and magenta dye developers are disclosed
in U. ~`. Patent No. 3,134,764, issued May 26, 1964, and
the cyan dye developer is disclosed in U. S. Patent No.
3,135,606, issued June 2, 1964.
Each of four photosensitive elements were exposed
and processed at room temperature by spreading an aqueous
liquid processing composition at a pH of not less than about
12 which comprised:
Water 100 cc.
Potassium hydroxide - 11.2 g.
Hydroxyethyl cellulose (high
viscosity) [commercially
available from Hercules Powder
Co., Wilmington, De~aware,
under the trade name
Natrasol 2501 4.03 g.
Potassium thiosulfate 0.5 g.
Benzotriazole 3.5 g.
N-benzyl-~-picolinium bromide 2.3 g.
Lithium hydroxide - 0.3 g.
between each exposed multicolor element and its respective
image-receiving element as they are brought into superposed
relationship. After an imbibition of
approximately 60 seconds, the image-receiving elements
were separated from the remainder of the film assembly.
lOSZOZ6
The following is a tabulation of DmaX values
obtained in the resulting photographic images:
TABLE 1
PVA/catalyst ratio in red green blue
image-receiving layer D D D
max max max
Control 2.47 2.48 2.44
227 (Example I) 2.55 2.55 2.55
57 (Example II) 2.50 2.55 2.5s
45 (Example III) 2.44 2.55 2.55
It can be seen that the novel graft copolymers
of the present invention provide images of excellent dye
density`over a wide polyvinyl alcohol/catalyst ratio range
even when coated at relatively high pH's.
EXAMPLE XV
In order to evaluate the light stability of photo-
graphic images prepared utilizing graft
copolymers of the present invention, a series of four photo-
graphic images were prepared as in Example XIV, except that
the graft copolymers were diluted by half (on
a weight basis) with polyvinyl alcohol prior,to coating. The
images so prepared were subjected to a Xenon arc lamp for
specified periods of time, at the end of which the change in
DmaX (magenta image) was measured. The following is a tabu-
lation of the % change (fading) in each of the test images:
TABLE 2
PVA/catalyst ratio in after after after after
ima~e-receivinq laYer 24 hours 48 hours 9 hours 144 hour~
Control 22 , 36 51 58
227 (Example I) 14 31 41 48
57 (Example II) 14 24 36 43
45 (Example III) 9 23 32 38
105Z026
A series of six image-receiving element~ was pre-
pared, each comprising, in sequence, a transparent cellulose
nitrate-subcoated baryta support, and a polymeric acid layer
and spacer layer as described in Example XIV. A mordant layer
was applied at a coverage of 1000 mg./ft.2 to the first two
elements comprising a graft copolymer of 4-vinylpyridine on
polyvi~yl alcohol having a po~yvinyl alcohol/4-vinylpyridine
mole ratio of 2/1 and a polyvinyl alcohol/catalyst mole ratio
of 45 (prepared in Example III supra and coated at a pH of
6.0); to the second two elements comprising a graft copolymer
of 4-vinylpyridine on polyvinyl alcohol having a polyvinyl
alcohol/4-vinylpyridine mole ratio of 2/1 and a polyvinyl
alcohol/catalyst mole ratio of 76 (prepared by the same
procedure except using 3.3 g. of Ce(NH4)2 (N03)6, and coated
at a pH of 6.0); and to the remaining two elements as controls,
a 2/1 mixture, by weight, of polyvinyl alcohol and poly-4-
vinylpyridine (coated at a pH of 4.5). The thus-prepared
image-receiving elements were baked at 180 F. for 30 minutes
and then allowed to cool.
Each of the above image-receiving elements was pro-
cessed by spreading an agueous liquid processin~J composition at
a p~ of not less than about 12 which comprised water, potassium
hydroxide, hydroxyethyl cellulose thickener, and thymolphthalein,
between each image-receiving element and a superposed stripping
sheet comprising a support having a layer of gelatin coated
thereon at a coverage of 600 mg./ft.2, after which the image-
receiving element and stripping sheet were stripped apart.
In each instance, the permeability of the image-receiving
element was evaluated by visual determination of the length of
time re~uired for the thymolphthalein color to clear tindicating
that a p~ of 10.5 had been reached.~ -
-38-
lOSZOZ6
The following is a tabulation of the permeation
times in seconds at various temperatures of each of the
various image-receiving elements:
TABLE 3
PVA/catalyst ratio in
S imaqe-receivin~ laYer40 ~. 100 F.
Control 340 270
56 39~ 410
76 715 70s
It can be readily seen that the novel graft vinylpyridine
copolymers of the present invention may be used to provide
image-receiving elements having more uniform alkali
permeability over a wide temp~rature range, as compared
with prior image-receiving elements.
A graft copolymer of 4-vinylpyridine on geIatin
having a gelatin/4-vinylpyridine weight rat-io of 1/2 and a
gelatin/catalyst weiyht ratio of 3 was prepared by adding
20 g. of 4-vinylpyridine to a deaerated solution of 10 g.
of gelatin in S00 cc. of water, with stirring under an
atmosphere of nitrogen. Nitrogen was bubbled through the
solution for three hours, after which the pH was adjusted
to 1.5 with concentrated nitric acid, and 3.3 g. of
Ce(NH4)2 (NO3)6 in 20 cc. of water was added. Stirring was
continued overnight, at the end of which the desired copolymer
was obtained as an aqueous solution. The pH was raised to ~7
with agueous NH3, resulting in the fonmation of an aqueous
emulsion. The polymer was dialyzed to remove any excess
ammonium nitrate salt.
-39
lOSZOZ6
Three image-receiving layers were prepared by coating
the thus-prepared copolymer to a thickness of 0~30 mil
on the external surface of a polymeric acid layer as des-
cribed in ExampleXIV, which had been coated on a cellulose
nitrate subcoated baryta paper. Control image-receiving
layers weresimilarly prepared, using a 2/1 mixture, by weight,
of polyvinyl alcohol and poly-4-vinylpyridine (at a thic~ness
of 0.32 mil ) in place of the graft copolymer.
The alkali permeability time (in seconds) of the
respective elements was determined by the same procedure
detailed in Example XVI, with the following results:
TABLE 4
100
Control 33 15.8 8.6
Gelatin/4-vinylpyridine 5 4.5 8
_XAMPLE XVIII
A series of five image-receiving elements was
prepared, each comprising, in sequence, a cellulose-nitrate-
subcoated baryta support, a polymeric acid layer as des-
cribed in Example XIV, and a spacer layer comprising a graftcopolymer of diacetone acrylamide and acrylamide on polyvinyl -
alcohol as described in Example XVI. The image-receiving
layers of the first four elements all comprised a graft
copolymer of 4-vinylpyridine on polyvinyl alcohol having a
polyvinyl alcohol/4-vinylpyridine mole ratio of 2/1 and a poly-
vinyl alcohol/catalyst mole ratio of 46, prepared as in Example
III, and coated at pH's of 4.5, 7.1, 8.3 and 10.0, respec-
tively. The fifth image-receiving element comprised an image-
receiving layer comprising a 2/1 mixture, by weight, of
polyvinyl alcohol and poly-4-vinylpyridine, coated at a pH
of 4.5, as a control.
-4~-
105ZOZ6
Photosensitive elements of the general type des-
cribed with reference to ExampleXIV were provided, with the
major exception that the particular dye developer~ employed
were metal-complexed dye developers of the following formulae:
Cl~3
- NH -25 - ~
N C ~C - ~ 1 3
~IO~,~C~ 1 f ~1 C~l2
NC - NN
~--0~ --502-N~t-It~
t~tO - ~ . CH2
~11
~0--
a cyan dye developer:
~'" ' . . .
~-CH2-cH2~ /=Y
~-S02~_~ =. N ~ -CR3
80-C82-CN2 )l~20~
Jq_C-CH2-C~2~)J
OEt
a magenta dye developer; and
1 0 5ZOZ6
OC3H7 ~2
C3N70 ~----------CNI = N
Cr -- H20
/ \ O OH
b ll_C~2_C~2_
0~
a yellow dye developer. Metallized dye developers of the foregoing types
~re described in U. S. Patent No. 3,402,972, issued December 9, 1969, and
in U. S. Patent Nos. 3,563,739, filed February 11, 1969; 3,551,406, filed
March 4, 1969; and 3,597,200, filed June 4, 1969, all in the name of Martin
Idelson; and in Canadian Appl~cation Serial ~o. 84,717, filed June 4s 1969,
in the names of Arthur B. Goulston and Paul S. Huyfrer.
Each of the photosensitive elements were exposed and processed
at room temperature with one of the above~prepared image-receiving elements.
The follo~ing is a tabulation of the DmaX values obtained in the
resulting photographic images: ,
TABLE 5
red green blue
receiving layer pH D D D
_ max _ max _ _ max
Control 4. 5 2, o8 2.12 2.14
PVA/4-VP graft 4.5 2.55 2.35 2.32
PV ~ 4-VP graft 7.1 2.55 2.53 2.42
PVA/4-VP graft 8.3 2.55 2.35 2.32
PVA/4-VP graft 10.0 2.52 2.24 2.22
-42-
105Z026
It can readily be seen that the graft copolymers
of the present invention can be coated over a wide pH
range without adversely affecting image densities.
EXAMPLE XIX
An image-receiving element was prepared as in
Example XVIII but the image-receiving layer comprised the
graft copolymer of Example X, e.g., a graft copolymer of 4-
vinylpyridine, vinyl benzyl trimethyl ammonium chloride on
hydroxyethyl cellulose. Another image-receiving element
comprised an image-receiving layer comprising a 2/1 mixture by
weight of polyvinyl alcohol and poly-4-vinylpyridine as a
control.
Photosensitive elements of the type used in Example
XVIII, e.g., employing metallized dye developers were exposed
and processed with each of the above prepared image-receiving
elements at room temperature and with the same processing
composition.
The following table presents a comparison of the
d max data after two minutes and after 24 hours.
TABLE 6
receiving layer d max after two minutes
Red Green Blue
control 1.5 1.25 1.4
graft copolymer of Example X 3.1 2.1 2.0
2S d max after 24 hours
control 2.5 2.3 2.15
graft copolymer of Example X 3.0 2.45 2.35
-43-
1052026
EXAMPLE XX
A graft copolymer of 4-vinylpyridine on polyvinyl
alcohol havin~ a polyvinyl alcohol/4-vinylpyridine mole ratio of
1/2 and a polyvinyl alcohol/catalyst mole ratio of 23 was pre-
pared as described in Example II, using 20 g. of polyvinyl
alcohol, 40 g. of 4-vinylpyridine, and 11.0 g. Ce(NH4)2
(N03~6 in 25 cc. of water. The graft copolymer so prepared
was coated at a pH of 5.1 as the image-receiving layer of
an image-receiving element prepared as in Example XVIII.
A photosensitive element substantially identical
to that of Example VIII was employed, and was exposed and
processed with the thus-prepared image-receiving element
as described in Example VIII, resulting in an image having
a red DmaX of 2.50, green DmaX of 2.41 and ~lue D of 2.23
EXAMPLE XXI
A graft copolymer of 5-vinyl-2-methylpyridine on
polyvinyl alcohol having a polyvinyl alcohol~S-vinyl-2-methyl_
pyridine mole ratio of 1/2 and a polyvinyl alcohol/catalyst mole
ratio of 22.5 was prepared by the method of Example I using
20 g. of polyvinyl alcohol, 40 g. of S-vinyl-2-methyl-
pyridine and 1.1 g. of Ce(NH~) 2 (N03) 6 in 10 cc. of water.
The graft copolymer so prepared was coated
as the image-receiving layer of an image-receiving element
comprising a gelatin-subcoated polyester transparent support
and a spacer layer comprising a graft copolymer of diacetone
acrylamidé and acrylamide on polyvinyl alcohol as described
in Example XIV.
-4
lOSZ026
~ II
A graft copolymer of 4-vinylpyridine on hydroxy-
ethyl cellulose having a hydroxyethyl cellulose/4-vinylpyridine
weight ratio of 1/2 and a hydroxyethyl cellulose/catalyst weight
ratio of 10 was prepared by the method of Example I using
llg. of hydroxyethyl cellulose, 22 g. of 4-vinylpyridine,
and 1-1 g. of Ce(NH4)2 (N03)6 in 10 cc. o water. The graft
copolymer so prepared was coated as the
image-receiving layer of an image-receiving element as
described in Example XXI.
EXAMPLE XXIII
A series of three photosensitive elements prepared
as in Example XIV were exposed and processed with, respec-
tively, the image-receiving elements of Example XXI, Example
x~ and a control element identically prepared except that
the image-receiving layer thereof comprised a Z/l mixture,
by weight, of polyvinyl alcohol and poly-4-vinylpyridine.
A processing composition as described in Example XIV was
employed, but which contained additionally a titanium dioxide
reflecting material in sufficient quantity to mask the `
photosensitive element subsequent to exposure and processing;
subsequent to processing, the photosensitive element and
image-receiving element were not stripped apart, but were
maintained in superposed relationship, the final images being
; 25 viewable through the transparent supports of the respective
image-receiving elements. The images resulting from the two
graft copolymer image-receiving layers gave excellent, mottle-
free images of high density as compared with the control.
Moreover, the dye densities were more rapidly achieved with
the former than with the control. It was observed, for
-4~
105Z026 - Y~` -
example, that whil~ the control elemcnt r~quired 7 minutes
to reach a dye density of 2.0, the same dye density wa~
reached in the element comprisi,ng the graft copolymer of
4-vinylpyridine on hydroxyethyl cellulose in less than two
minutes.
The resulting images were examined for darkening
or stain, as determined by
Dmin readings, initially at 24 hours
after processing, and again after 22 day~, with the following ~-
results:
TABLR 7
receiving layerStain Stain ~after 22 days)
red qreen blue red qreen blue
Control 0.22 0.24 0.29 0.20 0.26 0.45
5-vinyl-2-methyl-
pyridine on poly- -
vinyl alcohol 0.20 0.21 0.24 0.21 0.25 0.37
4-vinylpyridine
on hydrox,yethyl
cellulose 0.20 0.21 0.24 0.22 0.27 0.39
It was noted that the Dmin areas in the images prepared with
the graft copolymer image-receiving layers appeared con-
siderably whiter than those of the control emulsion to an
even greater extent than would be expected from the above
Dmin readings.
EXAMPLE XXIV
To a solution of 11 g. polyacrylamide in 250 g.
H2O was added 5.5 g. 4-vinylpyridine, 5.3 g. conc. HNO3
and 2.75 g. vinylbenzyltrimethylammoniumchloride. Nitrogen
was bubbled through the solution for 1 hour; the temperature
raised to 50 C. and 0.55 g. Ce(NH4)2(NO3)6 in 10 cc. H2O was
added. Stirring was continued for 16 hours. The pH of the
mixture was then adjusted to 8.5 with NH3 and dialyzed to remove
ammonium nitrate. An aqueous emulsion is obtained which has a
pH of 8.0 the ratio of polyacrylamide to 4-vinylpyridine to
vinylbenzyltrimethylammoniumchloride is 2:1:0.25 in the graft
copolymer so obtained.
105~026
EXAMPLE XXV
A series of two photosensitive elements were prepared,
exposed and processed in the manner described in Example XXIII.
One element had as the image-receiving layer, a coating of the
graft copolymer of Example XXIV while the other had a coating
of a 2:1:0.25 mixture of polyacrylamide, 4-vinylpyridine,
vinylbenzyltrimethylammoniumchloride as the image-receiving
layer.
The following table presents a comparison of the D
max data for the element having the layer containing the graft
copolymer and the element having the layer containing a mixture
of the ingredients of the graft copolymer composition.
TABLE 8
receiving layer - D max after two minutes
Red Green Blue
graft copoiymer 2.20 2.11 2.11 `
mixtuxe 1.7 1.62 1.88
EXAMPLE XXVI
. . _ .
The procedure of Example XXIV was repeated but 1.2 g.
of Ce(NH4)2(N03)6 were employed as catalyst rather than the
O.55 g. of Example XXIV.
EXAMPLE XXVII
The procedure of Example XXIV was repeated but 2.2 g.
of Ce(NH4)2(NO3)6 were employed as catalyst rather than the
0.55 g. of Example XXIV.
EXAMPLE XXVIII
~ series of two photosensitive elements were prepared,
exposed and processed in the manner described in Example XXIII.
One element had as the receiving layer a coating of the graft
copoly~er of Example XXVI while the other had a coating of the
graft copolymer of Example XXVII.
-4/-
105ZOZ6
The following table presents a comparison of the D
max data for the elements and shows that significant improvements
in D max can be obtained by increasing the catalyst concentration.
TABLE 9
.
receiving layer D max after two minutes
Red Green Blue
graft copolymer of
Example XXVI 1.96 1.74 1.61
graft copolymer of
Example XXVII 2.49 2.13 2.06
In preferred embodiments of this invention wherein
a polymeric acid layer is included as a component of the
novel image-receiving element, the polymeric acid layer
preferably is thicker than the image-receiving layer and has
an appreciably higher mg./ft.2 coverage. The image-receiving
layer is preferably about 0.25 to 0.4 mil. thick, the poly-
meric acid layer is preferably 0.3 to 1.5 mil. thick, and theimage-receiving element spacer layer is preferably about
0.05 tG 0. 5 mils thick.
-48-
105Z026
The support layers referred to may comprise any of the various
types of conventional rigid or flexible supports, for example, glass, paper,
metal, and polymeric films of both synthetic types and those derived from
naturally occurring products. Suitable materials include paper; aluminums;
polymethacryiic acid, methyl and ethyl esters, vinyl chloride polymers;
polyvinyl acetal; polyamides such as nylon; polysters such as polymeric films
derived from ethylene glycol terephthalic acid; and cellulose derivativessuch
as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate-
propionate, or acetatebutyrate.
The graft copolymers of the present invention provide stable aqueous
emulsions having low viscosity and high solids content. The preferred range
is 18-25% solids, with the resulting emulsion having a viscosity of 200-400
centipoises. Depending upon the use, the solids content can vary 10%. They
may be coated at fast coating machine speeds, and result in clear films.
The method of preparation of the graft polymers is generally the
same as that outlined in the hereinbefore stated examples; the pH, however,
may vary from 1.5 to about 7 depending upon the catalyst/backbone polymer ratio.
Although the transition metal ion catalysts hereinbefore described will ini-
tiate homopolymerization of vinylpyridine monomers, for example, the induction
periods are so long and the rates so slow that under grafting conditions, little
or no such polymerization can occur. As a rule, however the vinylpyridine
graft polymers of the present invention are usually obtained in greater than
99% conversion, and most often in the order of 99.9~ conversion, with essent-
ially no residual vinylpyridine homopolymer.
Since certain changes may be made in the above products and processes
without departing from the scope of the invention herein involved, it is
intended that all matter contained in the above description shall be inter-
preted as illustrative and not in a limiting sense.
- 49 -
