GB1592796A

GB1592796A - Composition for preparing flexible coatings

Info

Publication number: GB1592796A
Application number: GB4186377A
Authority: GB
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1976-10-08
Filing date: 1977-10-07
Publication date: 1981-07-08
Also published as: FR2367099A1; JPS6049299B2; DE2745287A1; JPS5346018A; CA1116004A; DE2745287C2; FR2367099B1

Description

(54) COMPOSITION FOR PREPARING FLEXIBLE COATINGS (71) We, EASTMAN KODAK COMPANY, a Company organised under the Laws of the State of New Jersey, United States of America of 343 State Street, Rochester, New York 14650, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a composition for the preparation of flexible coatings.

More particularly, the invention relates to a composition comprising an aqueous dispersion of a hydrophilic colloid and a sulphonate-containing copolymer.

In accordance with the invention, it has been found that certain sulphonatecontaining latex copolymers of the acrylic type may be used to improve the physical properties of photographic layers containing hydrophilic colloids.

Proteinaceous hydrophilic colloids are known to be useful in many connections, particularly those of a photographic nature, due to the optical clarity of attenuated products which may be prepared therefrom. Gelatin or gelatin derivatives, for example, are typical of the hydrophilic colloids which have been found to be useful in this respect.

However, these colloids exhibit physical properties which are objectionable in certain applications. Many of these objections have been met by mixing or "extending" the colloid with one or more synthetic materials such as synthetic polymers.

Many latex polymers which are used as gelatin extenders are susceptible to gelatin-latex agglomeration and coagulation caused by salts and organic solvents.

This agglomeration in coating melts leads to limited melt stability, excessive filter plugging and coating defects commonly referred to as "double-ended comets".

Further, due to this agglomeration, partially-used melts cannot be sent to storage for reuse at a later time. The result is considerable waste and less than optimum flexibility in preparing melts and scheduling emulsion coating machines.

Hence, there is a continuing search for latex polymers which can be used as gelatin extenders which are not susceptible to the problems disclosed hereinabove.

These polymers must be stable to organic solvents and dissolved salts normally used in photographic emulsions.

In accordance with this invention, it has been found that particular sulphonate-containing latex copolymers are more stable in the presence of organic solvents or dissolved salts when used with hydrophilic colloids to prepare flexible coatings than polymers previously used in the art for this purpose. In addition, the copolymers surprisingly impart a highly desirable increase in photographic speed and an improvement in contrast, as well as dye hue shifts in color photographic materials.

In one aspect of the present invention, there is provided a composition for the preparation of flexible coatings which comprises an aqueous dispersion of a hydrophilic colloid and a copolymer having a glass transition temperature less than or equal to 600 C, wherein the copolymer comprises: A. from 50 to 70 percent by weight of a polymerized ethylenically unsaturated carboxylic acid ester monomer; B. from 2 to 18 percent by weight of a polymerized ethylenically unsaturated carboxylic acid amide monomer free from carboxylic acid ester groups and sulphonate groups; C. from 10 to 30 percent by weight of a polymerized vinyl benzene monomer; and D. from 2 to 18 percent by weight of a polymerized sulphonate monomer having, prior to polymerization, the formula (I):

wherein R is a hydrogen atom or an alkyl group; R' is an alkylene group or a

group; R2 is a divalent amino group substituted with an alkyl group or a hydrogen atom, or a sCH2+0 group wherein n is 0 or an integer of from 1 to 5; m is either 0 or 1; and X is a hydrogen atom or a monovalent cation, the total amount of the polymerized amide monomer and the polymerized sulphonate monomer being less than 20 percent by weight of the total copolymer weight.

In another aspect of the present invention, there is provided a photographic element comprising a support having thereon at least one layer of a composition of the invention.

The sulphonate monomer used in the preparation of the copolymers described herein has the formula (I)

wherein m is 0 or 1; R is a hydrogen atom or an alkyl group, preferably having from 1 to 10 carbon atoms, i.e. methyl, ethyl, propyl, butyl, pentyl, hexyl. heptyl, octyl, nonyl, decyl or an isomer thereof; and R' may be an alkylene group preferably having from 1 to 10 carbon atoms, i.e. methylene ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene or an isomer thereof and may be substituted with a variety of substituents. Alternatively, R' may be a

group wherein R2 is an amino group having the formula

wherein R3 is a hydrogen atom or a branched or linear alkyl group having from I to 10 carbon atoms, such as described above for R, and R4 is a branched or linear alkylene group having from 1 to 10 carbon atoms, such as described above for R'.

Alternatively, R2 may be a mCH240 group wherein n is 0 or an integer of from 1 to 5.

X is a hydrogen atom or a monovalent cation, such as the cation of an alkali metal e.g. lithium, sodium, potassium or rubidium; or the cation of copper (1), or others known to those skilled in the art.

Exemplary of sulphonate monomers used in the preparation of the copolymers described herein are sodium 2 - acrylamido - 2 - methylpropane sulphonate.

sodium 2 - acrylamido - 2,2 - dimethylpropane sulphonate, sodium 2 methacrylamido - 2 - methylpropane sulphonate, sodium 2 - methacrylamido 2,2 - dimethylpropane sulphonate, 2 - acrylamido - 2 - methylpropane sulphonic acid, 2 - acrylamido - 2 - ethylpropane sulphonic acid, sodium 2 - acrylamido 2 - ethylpropane sulphonate, sodium vinyl sulphonate, potassium vinyl sulphonate sodium 2 - propenyl sulphonate and

As noted above, the copolymer comprises from 50 to 70 percent by weight of an ester of an ethylenically unsaturated carboxylic acid. As exemplary of such monomers may be listed: methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and other alkyl acrylates; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and other hydroxyalkyl acrylates; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and other alkyl methacrylates; 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and other hydroxyalkyl methacrylates; esters of (m- and p-vinylphenyl) acetic acid, mand p-vinylbenzoic acid, 3-acrylamido-3-methylbutanoic acid and other ethylenically unsaturated carboxylic acids.

Preferred monomers include alkyl esters of acrylic acid such as methyl acrylate, ethyl acrylate, propyl acrylate and n-butyl acrylate.

In addition, the copolymer comprises from 2 to 18 percent by weight of an amide of an ethylenically unsaturated carboxylic acid free from carboxylic acid ester groups and sulphonate groups. Exemplary of such monomers are; acrylamide, methacrylamide, N - isopropylacrylamide, N - (1,1 - dimethyl - 3 dimethylaminopropyl)acrylamide, N - t - butylacrylamide and diacetoneacrylamide.

Further, the copolymer comprises from 10 to 30 percent by weight of a vinyl benzene. Such monomers include styrene, vinyltoluene, a - methylstyrene, p bromostyrene, p - t - butylstyrene, styrene sulphonic acid, the sodium salt thereof, and other substituted styrenes.

Examples of copolymers useful herein include a copolymer of n-butyl acrylate (4060 weight percent), methacrylamide (415 weight percent), styrene (130 weight percent) and sodium 2 - acrylamido - 2 - methylpropane sulphonate (2-18 weight percent); poly(butyl acrylate - co - styrene - co - sodium vinyl sulphonate - co - methacrylamide) (58.8:25.2:8:8 weight ratio); and poly(methyl acrylate - co - styrene - co - sodium 2- acrylamido - 2 - methyl propane sulphonate - co - methacrylamide) (58.8:25.2:8:8 weight ratio).

The sulphonate monomers useful in preparing the copolymers of the present invention can be obtained from commercial sources or prepared by the techniques disclosed in U.S. Patents Nos. 2,983,712; 3,332,904 and 3,506,707. The other monomers useful in preparing the copolymers described herein are either commercially available or prepared by methods known to those skilled in the art.

The glass transition temperatures (Tg), as used in this invention and set forth in this specification, unless otherwise specified, can be determined by differential scanning calorimetry as disclosed in "Techniques and Methods of Polymer Evaluation", Vol. 2, Marcel Dekker, Inc., N.Y. 1970. The glass transition temperatures of the copolymers described herein are less than or equal to 600 C, and preferably from -200C to +100C.

The molecular weights of the copolymers useful in the present invention are subject to wide variation, but are often in the range of from 104 to 106. These copolymers preferably have inherent viscosities (0.25 g polymer in 100 ml acetic acid at 25"C) of from 0.3 to 0.9, and more preferably from 0.4 to 0.6. As used herein, the term "inherent viscosity" is determined by the formula 2.30 log ,u rel ,u inh= C wherein u inh is the inherent viscosity, u rel is the relative viscosity of acetic acid solution of the polymer and C is the concentration in grams (0.25) of polymer per 100 cc of solution.

The latex copolymers useful in the present invention can be prepared by well known polymerization techniques. The preferred methods include variations of emulsion polymerization such as batch, semi-continuous and continuous polymerization methods. Preparation I shows one semi-continuous method of making the latex copolymer by premixing the monomers in a head tank with a suitable surface active agent to make a fairly homogeneous monomer mixture. This mixture is then added to an aqueous solution of surface active agent and catalyst in a reactor vessel. The time period for addition can be from 10 to 120 minutes, preferably 30 minutes, and is varied to produce different physical properties in the interpolymer, such as molecular weight.

The temperature at which the copolymers described herein are prepared is subject to wide variation since this temperature depends upon such variable features as the specific monomers used, the duration of heating and the pressure employed. However, the polymerization temperature generally does not exceed about 110 C, and most often it is in the range of 50 to 1000C. The pressure employed in the polymerization is usually only sufficient to maintain the reaction mixture in liquid form, although either superatmospheric or subatmospheric pressures can be used where such is advantageous. The concentration of polymerizable monomers in the polymerization mixture may be varied widely with concentrations up to about 100% by weight and preferably from 20 to 70% by weight based on the weight of the polymerization mixture, being satisfactory.

Suitable catalysts for the polymerization reaction include, for example, from 0. I to 2.0 percent by weight, based on the total monomer weight, of a free radical catalyst, such as hydrogen peroxide, a salt of peroxydisulphate, cumene hydroperoxide or a water soluble azo type initiator. In redox polymerization systems conventional ingredients can be employed, such as potassium persulphate and potassium meta bisulphite. If desired, the polymer can be isolated from the reaction medium by freezing, salting out, precipitation or any other procedure suitable for this purpose.

In some instances it may be advantageous to include from 0.5 to 4 percent by weight, based on the total monomer weight, of a surface active agent or compatible mixtures of such agents in the preparation of the copolymers of the present invention. Suitable wetting agents include the non-ionic, ionic and amphoteric types as exemplified by the polyoxyalkylene derivatives and amphoteric amino acid dispersing agents, including sulphobetaines. Such wetting agents are disclosed in U.S. Patents Nos. 2,600,831; 2,271,623; 2,275,727; 2,787,604; 2,816,920 and 2,739,891.

Commercially-available surfactants such as DuPont's Duponol ME and Olin Mathieson's Surfactant 10G are also useful.

The compositions of the present invention comprise an aqueous dispersion of a copolymer as described hereinabove and a hydrophilic colloid, preferably a proteinaceous colloid. Exemplary of such colloids include: gelatin, protein derivatives, such as carboxymethylated proteins, colloidal albumin, cellulose derivatives, poly(vinyl pyrrolidones) and other water soluble polymers. The colloid usually comprises from 10 to 90 weight percent of the total composition weight.

In a preferred embodiment of the present invention, the composition additionally comprise from 30 to 70 weight percent of the total composition weight of a light sensitive silver halide, such as silver chloride, silver bromide, silver chlorobromide, silver iodide, silver bromoiodide, or a mixture thereof. Dispersions of the photographic silver halide and the sulphonate copolymers described herein in combination with a hydrophilic colloid, such as gelatin, can be made in a variety of ways. For example, an aqueous gelatin dispersion of the photographic silver halide can be mixed with an aqueous dispersion or solution of the sulphonate copolymer. Alternatively, the photographic silver halide can be precipitated in an aqueous dispersion or solution of the copolymer with or without another colloid, depending upon the dispersion characteristics of the copolymer. In this case, a water-soluble salt such as silver nitrate is admixed with a water-soluble halide such as potassium bromide in the presence of the mixture. In still another procedure, the photographic silver halide is precipitated in an aqueous gelatin solution and digested in the conventional manner known to the art. After digestion, but prior to coating there is added to the emulsion an aqueous dispersion of the copolymer. The bulk of the resulting dispersion can be increased by the addition of more of the copolymers and/or natural or synthetic colloids or other binding agents suitable for use in photographic silver halide emulsions. Generally, the concentration of the copolymers described herein in the compositions of the present invention will be in the range of from 10 to 90 percent by weight, more preferably in the range of 30 to 60 percent weight, based on the total composition weight.

Where the compositions are used in photographic elements in layers other than the silver halide emulsion layers, for example, in filter layers, antihalation layers, antiabrasion layers, antistatic layers, barrier layers or receiving layers for diffusion transfer processes, they can be used as the sole vehicle or in admixture with natural or synthetic colloids such as are mentioned hereinbefore.

The compositions described herein can be coated on a wide variety of supports, including film bases such as polyethylene terephthalate, cellulose acetate butyrate, polycarbonate and polyolefins (e.g., polyethylene, polypropylene). When such film bases are used, the photographic product obtained can be used, for example, as a transparency. If desired, the compositions may be coated on an opaque support such as paper, polyolefin coated paper such as polyethylene or polypropylene coated paper which can be pigmented, with TiO2, for example, the electron bombarded or exposed to a corona discharge to promote emulsion adhesion. When such supports are used, a colour photographic print may be obtained.

The emulsions containing the copolymers described herein may be chemically sensitized with compounds of the sulphur group, noble metal salts such as gold salts, reduction sensitized with reducing agents, and combinations of these. The emulsion layer and other layers present in photographic elements made according to this invention can be hardened with any suitable hardener. Useful concentrations of hardeners are related to the amount of binder used and are known to those skilled in the art. Such hardened layers will have a melting point in water greater than about 65"C and preferably greater than 90"C.

The emulsion can also contain additional additives, particularly those known to be beneficial in photographic emulsions, including for example, water-miscible and water-immiscible organic solvents, stabilizers or antifoggants, speed increasing materials, soluble inorganic salts, absorbing dyes and plasticizers. Sensitizers which give particularly good results in the photographic compositions disclosed herein are the alkylene oxide polymers which can be employed alone or in combination with other materials, such as quaternary ammonium salts, as disclosed in U.S.

Patent No. 2,886,437 or with mercury compounds and nitrogen containing compounds, as disclosed in U.S. Patent No. 2,751,299.

The compositions of the invention may be used in various kinds of photographic compositions and elements, including direct positive silver halide emulsions, x-ray and other non-spectrally sensitized emulsions as well as in orthochromatic, panchromatic and infrared sensitive emulsions, particularly those sensitized with, for example, merocyanine dyes, cyanine dyes and carbocyanine dyes. Furthermore those compositions may be used in emulsions comprising colour forming materials or emulsions developed by solutions containing couplers or other colour generating materials. In addition, they may be used in photographic emulsions containing developers, e.g., polyhydroxybenzenes, as well as in emulsions intended for use in diffusion transfer processes which utilize the nondeveloped silver halide in the non-image areas of the negative to form a positive by dissolving the underdeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in U.S. Patents Nos. 2,352,014; 2,543,181 and 3,020,155.

The sulphonate copolymers disclosed herein are useful in photographic imagetransfer film units such as in image-transfer film units as described, for example, in U.S. Patents Nos. 2,543,181; 2,983,606; 3,227,550; 3,227,552; 3,415,695; 3,415,644; 3,415,646 and 3,635,707; Canadian Patent No. 674,082; Belgian Patent Nos. 757,959 and 757,960; British Patent Nos. 904,364 and 840,731; and German Patent No.

2,242,762.

The compositions of the present invention may be used in individual layers of a multilayer photographic element over a broad range of coating coverages, e.g., from 0.001 g/m2 to 0.5 g/m2 of support, and preferably from 0.05 g/m2 to 0.3 g/m2 of support.

These compositions are particularly useful in colour reversal-type photographic elements because the latex sulphonate copolymers incorporated therein impart a desirable decrease in the brittleness of the layers and a hue shift of the dyes in the elements. By hue shift is meant that the intensity and absorption maxima of the imaging dyes in the multilayers of photographic elements are shifted with a concurrent increase in speed and contrast relative to an element having the same multilayers but with no sulphonate copolymer.

The following examples are included for a further understanding of the present invention.

Preparation 1 Poly(butyl acrylate-co-styrene-co-sodium-2-acrylamido-2-methylpropanc sulphonate co-methacrylamide) (58.8:25.2:8.0:8.0 weight ratio) This polymer latex was prepared by the following procedure: Distilled water (528 kg) and Duponol ME* (sodium lauryl sulphate surface active agent) (1.7 kg) were added to a reactor vessel. This solution was thoroughly purged with nitrogen and heated to about 90"C with a slight nitrogen purge.

A 10 /, by weight aqueous solution of sodium 2-acrylamido-2-methylpropane Sulphonate (132 kg); surfactant Duponol ME* (1.7 kg); and methacrylamide (13.3 kg) were added to a head tank with moderate stirring. Butyl acrylate (100 kg) and styrene (42.5 mg) were then added to this and the monomer emulsion in the head tank was continuously stirred for 20 minutes.

Potassium persulphate catalyst (0.85 kg) was added to the contents in the reactor vessel and the addition of the emulsion in the head tank was begun within 2 minutes following the catalyst addition. The emulsion was added to the reactor continuously over a 30 minute period. The reactor vessel contents were kept at 92--95"C during this time. Following reaction of the monomer emulsion, the reactor contents were cooled to 850C and polymerization was allowed to proceed for 30 minutes.

After reaction, the temperature was further lowered to 75"C and residual monomer was removed by vacuum distillation. The resulting latex was cooled to room temperature and more distilled water (538 kg) was added with stirring. The latex was discharged through cheesecloth into storage containers.

The resulting latex had a percent solids of 12.2. The isolated polymer had an inherent viscosity of 0.78 measured in acetic acid; and a glass transition temperature of +2"C.

Preparation 2 Poly(butyl acrylate-co-styrene-co-sodium vinyl sulphonate-co-methacrylamide) (58.8:25.2:8:8 weight ratio) This copolymer was prepared in a similar fashion as the copolymer of preparation 1 except that sodium vinyl sulphonate was used as the sulphonate monomer instead of sodium 2-acrylamido-2-methylpropane sulphonate. The isolated polymer had an inherent viscosity of 0.49 measured in acetic acid and a glass transition temperature of -1"C.

Preparation 3 Poly(Methyl acrylate-co-styrene-co-sodium 2-acrylamido-2-methylpropane sulphonate-co-methacrylamide) (58.8:25.2:2:8:8 weight ratio) The copolymer was prepared in a similar fashion as the copolymer of Preparation 1 except that methyl acrylate was used instead of butyl acrylate. The isolated polymer had an inherent viscosity of 0.72 measured in acetic acid, and a glass transition temperature of 60"C.

Example 1 Stability of a Composition Comprising Gelatin and Poly(butyl acrylate-co-styrene co-sodium 2-acrylamido-2-methylpropane sulphonate-co-methacrylamide) (58.8:25.2:8.0:8.0 weight ratio) This is a comparative example showing the improved stability of a composition of the present invention over a composition outside the teaching of this invention.

Table I shows typical latex properties and stability test results of a composition comprising the sulphonate copolymer of Preparation I compared to the latex properties and test results of a control latex composition comprising poly(butyl acrylate-co-styrene-co-methacrylamide) (58.8:25.2:16 weight ratio) prepared in accordance with the teaching of U.S. Patent No. 2,739,137.

Light scatter was measured by diluting each of the latex copolymers 1:10 with distilled water, placing the diluted latex in a I cm cell and measuring the apparent absorbance in a Beckman DU spectrophotometer at 546 nm.

Tolerance of the gelatin-latex compositions to a typical organic solvent used in photographic compositions, such as methanol, was measured by incubating a *Trademark of E. I. DuPont de Nemours, Inc.

mixture of 5 g gelatin, 70 ml water, 20 ml methanol and 4.3 ml latex for 4 hours at 40"C and microscopically evaluating the simulated melt for polymer coagulation at 645x magnification. A microscopic field with a clear to fine background and few visible coagulum particles is desired. A tolerance of 20 percent or more alcohol is acceptable.

Tolerance of the compositions to dissolved inorganic salts was measured by the light scatter technique after the specified room temperature incubation of samples made up of 97.5 g latex and. 2.5 g of a typical salt, such as potassium bromide. Acceptable salt tolerance is indicated by an increase in apparent absorbance of less than 50 /" with no caking.

TABLE I Polymer Control Example 1 20 /n Alcohol Tolerance < 20 > 20 Background Fine Clear Agglomerates Loaded, 0.5-1.5 u Few, 0.5-1.0 u 2.5 KBr Tolerance (apparent absorbance) 0.5 hr 0.72 0.35 4 hr 1.5 0.4 6 hr 2 0.4 22hr caked 0.44 46hr caked 0.44 75 hr caked 0.44 99 hr caked 0.44 In addition, similar tests applied to poly(butyl acrylate - co - styrene - co 3 - acryloyloxypropane - I - sulfonic acid, sodium salt - co - methacrylamide) (58.8:25.2:8:8 weight ratio), which is similar to the copolymers taught in U.S. Patent No. 3,411,911 showed that that prior art polymer was rapidly coagulated by a KBr solution. Other copolymers which were unstable to the KBr solution include poly(butyl acrylate - co - styrene - co - styrenesulphonic acid, sodium salt - co methacrylamide) (58.8:25.2:8:8 weight ratio) and poly(butyl methacrylate - co sodium 2 - acrylamido - 2 - methylpropane sulphonate) (84:8:8 weight ratio).

These results show that the composition of the present invention comprising a sulphonate copolymer has improved stability to alcohols and dissolved salts over the latex compositions taught in the art.

Examples 24 Compositions Comprising Latex Polymers Having Varying Amounts of Sodium 2-Acrylamido-2-Methylpropane Sulphonate Monomer These are comparative examples.

Latex polymers were prepared having varying amounts of sodium 2 acrylamido - 2 - methylpropane sulphonate and methacrylamide according to the procedure of Preparation 1. Compositions comprising each copolymer were evaluated for alcohol and potassium bromide tolerance using the techniques of Example I and compared to a control latex composition using a copolymer taught in U.S. Patent No. 2,739,137, notably poly(butyl acrylate - co - styrene - co methacrylamide) (58.8:25.2:16 weight ratio). The results are shown in Table II.

TABLE II Example Control 2 3 4 Wt. percent sodium 2-acrylamido-2-methyl propanesulfonate 0 3.1 4.7 8.0 Wt. percent methacrylamide 16 12.9 11.3 8.0 20% Alcohol Tolerance 20 > 20 > 20 > 20 Background Fine Very Fine Clear Clear Agglomerates (0.5-1.0 u) Loaded Loaded Some Few 2.5% KBr Tolerance (apparent absorbance) 0.5 her 1.70 0.79 0.56 0.35 4 hr 2.0 0.92 0.65 0.40 6 hr 2.0+ 0.94 0.67 0.40 22 hr caked 1.2 0.72 0.45 46 hr caked 1.1 0.73 0.45 75 hr caked 1.2 0.79 0.47 99 hr caked 1.2 0.79 0.48 Again, these examples show the improved stability to alcohol and dissolved salt of the compositions of the present invention over the control composition taught in the art. Even small amounts of sodium 2-acrylamido-2-methylpropane sulphonate in the latex produce a marked increase in the composition stability. Salt tolerance improves with increasing amounts of the sulphonate monomer in the interpolymer as indicated by lower absorbances and no caking.

Example 5 Stability Tests for the Copolymer of Preparation 3 This is a comparative example.

The copolymer of Preparation 3 exhibited improved tolerance to alcohol and salt solutions over a control copolymer composition of poly(butyl acrylate - co styrene - co - sodium 2- acrylamido- 2 - methylpropane sulphonate) (58.8:25.2:16 weight ratio) not containing methacrylamide, as indicated by the test results in Table III (the lower the absorbance, the greater the stability). The control copolymer had unacceptable tolerance to the KBr solution, i.e., an increase in absorbance > 50 /n.

TABLE III Control Example 5 20"/, Alcohol 20 > 20 Tolerance Background clear clear Agglomerates (0.5-l.0u) many none 2.5 /n KBr Tolerance (apparent absorbance) initial 0.20 0.19 0.5 hr 0.38 0.25 4.0 hr 0.63 0.26 8.0 hr 0.80 0.26 24 hr 1.30 0.26 48 hr 1.60 0.26 76hr 1.70 0.26 WHAT WE CLAIM IS: 1. A composition for the preparation of flexible coatings which comprises an aqueous dispersion of a hydrophilic colloid and a copolymer having a glass transition temperature less than or equal to 600 C, wherein the copolymer comprises: A. from 50 to 70 percent by weight of a polymerized ethylenically unsaturated carboxylic acid ester monomer;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

TABLE II Example Control 2 3 4 Wt. percent sodium

2-acrylamido-2-methyl propanesulfonate 0 3.1 4.7 8.0 Wt. percent methacrylamide 16 12.9 11.3 8.0 20% Alcohol Tolerance 20 > 20 > 20 > 20 Background Fine Very Fine Clear Clear Agglomerates (0.5-1.0 u) Loaded Loaded Some Few 2.5% KBr Tolerance (apparent absorbance) 0.5 her 1.70 0.79 0.56 0.35 4 hr 2.0 0.92 0.65 0.40 6 hr 2.0+ 0.94 0.67 0.40 22 hr caked 1.2 0.72 0.45 46 hr caked 1.1 0.73 0.45 75 hr caked 1.2 0.79 0.47 99 hr caked 1.2 0.79 0.48 Again, these examples show the improved stability to alcohol and dissolved salt of the compositions of the present invention over the control composition taught in the art. Even small amounts of sodium 2-acrylamido-2-methylpropane sulphonate in the latex produce a marked increase in the composition stability. Salt tolerance improves with increasing amounts of the sulphonate monomer in the interpolymer as indicated by lower absorbances and no caking.

Example 5 Stability Tests for the Copolymer of Preparation 3 This is a comparative example.

The copolymer of Preparation 3 exhibited improved tolerance to alcohol and salt solutions over a control copolymer composition of poly(butyl acrylate - co styrene - co - sodium 2- acrylamido- 2 - methylpropane sulphonate) (58.8:25.2:16 weight ratio) not containing methacrylamide, as indicated by the test results in Table III (the lower the absorbance, the greater the stability). The control copolymer had unacceptable tolerance to the KBr solution, i.e., an increase in absorbance > 50 /n.

TABLE III Control Example 5 20"/, Alcohol 20 > 20 Tolerance Background clear clear Agglomerates (0.5-l.0u) many none 2.5 /n KBr Tolerance (apparent absorbance) initial 0.20 0.19 0.5 hr 0.38 0.25 4.0 hr 0.63 0.26 8.0 hr 0.80 0.26 24 hr 1.30 0.26 48 hr 1.60 0.26 76hr 1.70 0.26 WHAT WE CLAIM IS: 1. A composition for the preparation of flexible coatings which comprises an aqueous dispersion of a hydrophilic colloid and a copolymer having a glass transition temperature less than or equal to 600 C, wherein the copolymer comprises: A. from 50 to 70 percent by weight of a polymerized ethylenically unsaturated carboxylic acid ester monomer;

B. from 2 to 18 percent by weight of a polymerized ethylenically unsaturated carboxylic acid amide monomer free from carboxylic acid ester groups and sulphonate groups; C. from 10 to 30 percent by weight of a polymerized vinyl benzene monomer; and D. from 2 to 18 percent by weight of a polymerized sulphonate monomer having, prior to polymerization, the formula (I):

wherein R is a hydrogen atom or an alkyl group; R' is an alkylene group or a

group; R2 is a divalent amino group substituted with an alkyl group or a hydrogen atom, or a SCH2+0 group wherein n is 0 or an integer of from I to 5; m is either 0 or 1; and X is a hydrogen atom or a monovalent cation, the total amdunt of the polymerized amide monomer and the polymerized sulphonate monomer being less than 20 percent by weight of the total copolymer weight.
2. A composition as claimed in claim 1 wherein the hydrophilic colloid is gelatin.
3. A composition as claimed in claim 1 or claim 2 wherein the ester is an alkyl ester of acrylic acid.
4. A composition as claimed in claim 1 or claim 2 wherein the ester is butyl acrylate.
5. A composition as claimed in any one of the preceding claims wherein the amide is an amide of methacrylic acid.
6. A composition as claimed in any one of the preceding claims wherein the vinyl benzene is styrene.
7. A composition as claimed in any one of the preceding claims wherein the sulphonate has the formula:

wherein R is a hydrogen atom or an alkyl group; R2 is an amino group substituted with an alkyl group or a hydrogen atom; and X is a hydrogen atom or an alkali metal cation.
8. A composition as claimed in any one of claims 1 to 7 wherein the sulphonate is sodium 2-acrylamido-2-methylpropane sulphonate.
9. A composition as claimed in any one of the preceding claims wherein the copolymer has a glass transition temperature of from -20 C to +10 C.
10. A composition as claimed in any one of the preceding claims wherein the copolymer has an inherent viscosity of from 0.3 to 0.9.
II. A composition as claimed in any one of claims 1 to 9 wherein the copolymer has an inherent viscosity of from 0.4 to 0.6.
12. A composition as claimed in any one of the preceding claims wherein the copolymer is present in an amount of from 10 to 90 percent by weight based on the total weight of the composition.
13. A composition as claimed in any one of claims I to 11 wherein the copolymer is present in an amount of from 30 to 60 percent by weight based on the total weight of the composition.
14. A composition as claimed in any one of the preceding claims further comprising a light sensitive silver halide.
15. A composition as claimed in claim 14 wherein the silver halide is present in an amount of from 30 to 70 percent by weight based on the total weight of the composition.
16. A composition as claimed in claim I substantially as hereinbefore described in any one of Examples 1 to 5.
17. A photographic element comprising a support having thereon at least one layer of a composition as claimed in any one of the preceding claims.
18. An element as claimed in claim 17 comprising at least one silver halide emulsion layer.
19. An element as claimed in claim 17 or claim 18 wherein the coating coverage of the layer of the composition is from 0.001 to 0.5 g/m2 of support.
20. An element as claimed in claim 17 or claim 18 wherein the coating coverage of the layer of the composition is from 0.05 to 0.3 g/m2 of support.
21. A method of making a photographic element which method comprises forming a layer of a composition as claimed in any one of claims I to 16 on a support.
22. A photographic element whenever made by a method as claimed in claim 21.
23. A method of producing a silver image which method comprises exposing to a light image a photographic element as claimed in claim 18 and developing the latent image so formed.
24. A silver image which has been produced by a method as claimed in claim 23.