CA1052026A - Photographic products and processes - Google Patents

Abstract

Abstract of the Disclosure A graft copolymer represented by the formula

Description

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 - ~

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~

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 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 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 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 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 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 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, 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.

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 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 -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 -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 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, 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 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.

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

,.

~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.

~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 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 ~ ~ 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~ , :

. , , ' ~ ' :

' ' ' ' ' : ~ :

f C~2 -CH ~
.~
=C 1~2 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.

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

~ 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 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.

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 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.

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.

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 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 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:

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:

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 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.~ -lOSZOZ6 The following is a tabulation of the permeation times in seconds at various temperatures of each of the various image-receiving elements:

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.

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:

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~-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 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: , 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 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.

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 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.

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:

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.

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.

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.

.
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.

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.

Claims (24)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A graft polymer comprising the structure wherein Z is an organic polymeric backbone selected from the group consisting of cellulosic and vinyl polymers and 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.

2. A graft polymer comprising the structure 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 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.

3. A graft polymer comprising the structure where Z is a polyvinyl alcohol polymeric backbone and 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.

4. A graft polymer of claim 3 where a vinylpyridine and a vinylbenzyl-ammonium halide are grafted to said polyvinyl alcohol backbone.

5. A graft polymer of claim 3 where 4-vinylpyridine and a vinylbenzyl-trialkyl-ammonium chloride are grafted to said polyvinyl alcohol backbone.

6. A graft polymer comprising the following structure where Z is a poly-N-vinylpyrrolidone polymeric backbone and 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.

7. A graft polymer of claim 6 where a vinylpyridine and a vinylbenzyl-ammonium halide are grafted to said poly-N-vinylpyrrolidone backbone.

8. A graft polymer of claim 6 where a 4-vinyl-pyridine and a vinyl-benzyl-trialkyl ammonium chloride are grafted to said poly-N-vinylpyrrolidone backbone.

9. A graft polymer comprising the structure where Z is a polyacrylamide backbone and 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.

10. A graft polymer of claim 9 where a vinylpyridine and a vinylbenzyl-ammonium halide are grafted to said polyacrylamide backbone.

11. A graft polymer of claim 9 where a 4-vinylpyridine and a vinyl-benzyl-trialkyl-ammonium chloride are grafted to said polyacrylamide backbone.

12. A graft polymer comprising the structure where Z is a polymeric backbone comprising a cellulosic polymer and 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.

13. A graft polymer comprising the structure where Z is a hydroxyethylcellulose polymeric backbone and 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.

14. A graft polymer of claim 13 where a vinylpyridine and a vinylbenzyl-ammonium halide are grafted to said hydroxyethylcellulose backbone.

15. A graft polymer of claim 13 where a 4-vinylpyridine and a vinyl-benzyl-trialkyl-ammonium chloride are grafted to said hydroxyethylcellulose.

16. A graft polymer comprising the structure where Z is a methylcellulose polymeric backbone and 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.

17. A graft polymer of claim 16 where a vinylpyridine and a vinylbenzyl-ammonium halide are grafted to said methylcellulose backbone.

18. A graft polymer of claim 16 where a 4-vinyl-pyridine and a vinyl-benzyl-trialkyl-ammonium chloride are grafted to said methylcellulose polymeric backbone.

19. A graft polymer comprising the structure 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 R2 is -(CH2)mCH3, or , and n is a positive integer.

20. A graft polymer comprising the structure where Z is a polyvinyl alcohol 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 R2 is -(CH2)mCH3, or , and n is a positive integer.

21. A graft polymer having 4-vinylpyridine and vinylbenzyl-trialkyl-ammonium chloride grafted to a hydroxyethyl cellulose backbone and wherein the weight ratio of hydroxyethyl cellulose/4-vinylpyridine/vinylbenzyl-trialkyl-ammonium chloride is about 2.2:2.2:1.

22. A graft polymer of claim 21 where said vinylbenzyl-trialkyl-ammonium chloride is vinylbenzyl-trimethyl-ammonium chloride.

23. A graft polymer having 4-vinylpyridine and vinylbenzyl-trialkyl-ammonium chloride grafted to a polyvinyl alcohol backbone and where the weight ratio of polyvinyl alcohol/4-vinylpyridine/vinylbenzyl-trialkyl-ammonium chloride ratio is about 4.4:3.3:1Ø

24. A graft polymer of claim 23 where said vinylbenzyl-trialkyl-ammonium chloride is vinylbenzyl-trimethyl-ammonium chloride.