GB1592006A - Water-soluble polymeric colourants - Google Patents

Description

(54) WATER-SOLUBLE POLYMERIC COLOURANTS (71) We, DYNAPOL, a corporation of the State of California, United States of America, of 1454 Page Mill Road, Palo Alto, California 94304, 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 new polymeric colorants which find especial utility as yellow food colors.

The monoazo dye of the formula

commonly known as tartrazine, has a "lemon yellow" hue which has placed it among the three most widely used colors in foods, drugs and cosmetics. It finds use alone in gelatin desserts, jellies, beverages and the like and as a component of orange through green blends for use in both edibles and nonedibles.

The past decade has seen a sustained attack on the general class of monoazo food colors. A number of these materials, most notably Reds have been found to be unsafe and banned from food use by governmental action. There is continuing questioning of the safety of the monoazo colorants which is causing a search to be made for properly hued, safe replacements. In the case of tartrazine, certain natural carotinoid colors can function as replacements. However, the carotinoids are relatively very expensive. The present invention seeks to provide a nonazo color replacement for the yellow colorant tartrazine. This invention concerns a limited class of polymeric nitroaniline colorants. The advantages of polymeric colorants in food coloring applications is disclosed in general terms in British Patent 1,485,846, issued November 18, 1975 to Dawson et al. These references show that when colorants are employed in polymeric form having a molecular size exceeding a certain limit -- usually a molecular size of greater than 1,000 or 2,000 Daltons -- and if the color compounds do not break down in use, and thus maintain this size, the polymeric colorants are not absorbed through the walls of the gastrointestinal tract. This means that when such colorants are ingested, they pass essentially directly through the gastrointestinal tract. They are not taken through the tract walls into the body or its systemic circulation. Thus, risk of systemic toxicity is reduced or eliminated. The present invention is an extension of these prior art disclosures and involves a family of polymeric colorants having particularly attractive color properties.

The new and useful polymeric colorants of this invention are characterized as having a nonchromophoric organic backbone of molecular weight 1,000 to 200,000 to which is covalently attached through pendant amine groups a plurality of chromophore units of the formula

wherein M+ is a monovalent ion selected from K+, Na+ and NH4+. The pendant amine group is immediately adjacent to the chromophore aromatic ring and bonded thereto with a carbon-nitrogen single bond, thus achieving a nitroaniline structure

The preparation and use in food of these materials is also shown herein.

The colorant compositions of this invention comprise a plurality of units of a particular chromophore unit covalently bonded to a polymer backbone through amine groups pendant from the backbone.

The Chromophore The chromophore employed in the colorant materials of this invention is a

group, that is a 2-nitrobenzene-4-sulfonic acid sodium, ammonium, or potassium salt. As in demonstrated in the comparative experiments which accompany the examples, the placement of the nitro and sulfonic acid groups in the 2 and 4 positions, respectively, is critical to the color desired of these materials. Reversing these positions of substituting other electronically similar groups interferes with the clear yellow color achieved with the materials of this invention. The presence of a sulfonate group on the chromophore assures that the polymeric colorants of this invention are water soluble, that is, that they have a solubility in room temperature pH 7 water of not less than 1,000 ppm by weight.

The chromphores are linked into polymeric form via a non-chromophoric organic backbone, that is, a backbone which itself does not present visual colors to the human eye. These backbones are defined as having essentially no crosslinks and as containing only covalent bonds which are stable under the acidic, basic, and enzymatic conditions of passage through the mammalian G.I. tract. This stability is required to assure that the polymeric colorants retain their nonabsorbable size during G.I. tract passage.

Preferred backbones are carbon-oxygen aliphatic ether backbones and essentially linear alkyl carbon-carbon backbones having molecular weights of from 2,000 to 100,000.

Pendant from the backbones are primary or lower secondary amine groups. At least a portion these amine groups are used to join the chromophore units to the backbone via a chromophore aromatic carbon to amine nitrogen single covalent bond. Such a bond is shown structurally as

Backbone N-R uNOZ S03 ! so3 M wherein R2 is hydrogen or a lower alkyl, preferably hydrogen, methyl or ethyl. The amine groups are usually bonded directly to a backbone carbon, but it is also suitable (but less preferred) to have a methylene link in between the backbone and the amine. Thus, the structure is

wherein -C- is a backbone carbon and R, is a C to N single covalent bond or methylene.

The backbones may contain other chemical entities as well. For example, they may contain lower alkyl (methyl or ethyl) substituents; residual amine groups, that is, amine groups which do not carry a chromophore substituent; and/or polar groups such as carboxylic acid, sulfonic acid or phosphonic acid K+ or Na+ salt groups. The polar groups, if present, can increase the water-solubility of the colorant. The residual amine groups can be present as amines or as acetylated amines-i.e., amides. The acetylation of residual amines is of advantage to assure good solubility in acidic environments and is described more fully in copending British Patent Application Number 4,6468/77 (Serial No. 1,592,005).

Among the colorants, those having a carbon-carbon backbone are preferred.

These are most commonly formed by polymerizing vinylamine or a substituted 'vinylamine as protected precursors or polymerizing with vinyl sulfonate, acrylic acid or vinylphosphate. These preferred backbones yield colorants of the structure shown in Formula I.

wherein R, and R2 are as already defined; R3 and R4 are hydrogen, methyl or ethyl, and preferably hydrogen and A, A' and A" are independently selected from among the materials listed in Table I.

TABLE 1 Residual amines Acetylated residual amines Sulfonic acid salts Carboxylic acid salts Phosphoric acid salts

One or more of A, A' and A" may be chromphore units,

as well. n, m, p and q are numbers defined as follows: n+m+p+q=40-8000; no0.2 (m+p+q).

Preferably, R2, R3 and R4 are hydrogens and R, is a carbon to nitrogen single bond. In one most preferred of these colorants, A" is residual amine, and A and A' are chromophore with n+m+p equal to from 0.3 to 10 (preferably I to 7 and most preferably 1.25 to 4) times q and preferably with n+m+p+q equal to 500 to 7,000.

In a second most preferred of these colorants, A" is residual amine, A' is acetylated amine and A is chromophore wherein n+m=(0.3 to 10) times, preferably I to 7 and more preferably 1.25 to 4 times p+q and q may be from 0.01 to 0.4 times p. Preferably, the sum of n+m+p+q equals 500 to 7,000. This latter colorant may be shown more clearly as:

wherein M+ is as defined, preferably Na+, a is 9003500, b is 6002000-; c is 10- 100, with a:b:c about 6:4:0.1, i.e., 5.5-6.5:3.54.5:0.03-0. 15.

In other preferred colorants shown by Formula I, A" is residual amine, A' is a polar group, and A is acetylated residual amines or chromophore. When A is chromophore, n+m+p+q is 40 to 4,000, preferably 80 to 2,000, n+m+q is from 0.15 to 7, preferably 0.5 to 4 times p and n+m equals 0.3 to 10, preferably 1 to 7 times q.

Preparation The preparation of colorants of this invention is generally carried out as follows: A preformed amine containing polymer, such as, in the case of the preferred colorants, polyvinylamine or a vinylamine copolymer is used as backbone and as the source of the amine groups. Representative Vinyl-amine polymers are described and claimed in British Patent No. 1,550,498. Their preparation and the preparation of other backbones is also shown herein in the Examples. The chromophore is coupled to the amine backbone. This is effected very simply by employing a derivative of the chromophore having a leaving group para to the sulfonic acid salt, and displacing the leaving group with an amine backbone nitrogen. Leaving groups known in the art may be used, with halos, especially chloro, bromo or iodo being preferred.

This displacement reaction is carried out in liquid phase. When, as in the preferred case where the backbone is a vinylamine polymer or copolymer, water dissolves both the chromophore and the backbone, it is an ideal solvent. If desired, water/organic mixed solvents may be used.

The displacement is carried out in a basic environment. Base in an amount adequate to neutralize any residual acids or acidic groups on the backbone is added at the outset of the reaction, followed by about 1 equivalent, i.e., 0.5 to 10.0 equivalents, of base per equivalent of amine present in the polymer backbone.

Greater excesses of base may be used, but are not seen to offer advantage. Use of 1.0 to about 5.0 equivalents of base per equivalent of amine is preferred. Any pharmacologically acceptable base which can achieve a pH of about 12 or greater may be used. KOH and NaOH, and K2CO3 and Na2CO3 and mixtures thereof give good results. Preferred bases are NaOH and mixtures of NaOH and Na2CO3 containing up to 3:1 molar Na2CO3 to NaOH.

The concentration of reactants is most easily expressed in terms of a molarity of polymeric amine and the number of equivalents of chromophore present based on the amine. Polymer concentrations as low as about 0.05 molar or as great as about 5 molar may be used. Lower concentrations might be used, but are uneconomical. Preferably, the polymer is 0.2 to 2 molar. The chromophore is present in an amount of from about 0.2 to about 3.0 equivalents, basis amine, with amounts of from about 0.5 to about 1.5 equivalents being preferred. Clearly, the amount of chromophore employed should not be lower than the degree of substitution desired.

The reaction is carried out at elevated temperatures such as reflux (100- 1200C) with temperautres of from 70"C to as high as 200"C being useful. The higher temperatures necessitate the use of suitable superatmospheric pressure equipment.

Reaction times range from as little as about 0.25 hours at the highest temperature to as much as 48 hours. Degree of substitution increases with reaction time with 5 to 24 hours giving good reactions at 101200C. Following the coupling reaction, it is often of interest to acetylate residual amines such as by contacting the reaction mixture with from 1 to 5 equivalents (basis amines) of acetic anhydride for a few minutes at a pH of 11-13 and a temperature of 0 C to 10 C.

Following reaction (and, if used, acetylation), the polymeric colorant is recovered and purified, such as by precipitation in a nonaqueous nonsolvent or by ultrafiltration to remove low molecular weight species. Thereafter, the colorant material is often isolated via spray-drying or the like as a powder.

The colorants of this invention are excellent yellow colors. They are excellent matches for tartrazine. When added in coloring amounts, such as from 10 to 10,000 ppm wt, they color fibers and other substrates. They are especially advantageous as colorants for edibles since when their molecular weights are above 1,000 daltons, they are not absorbed through the walls of the G.I. tract. In edible applications, the colorants are dissolved in beverages and syrups, dry-mixed into powdered drink mixes and cake mixes and otherwise conventionally admixed with food beverages, pharmaceuticals and cosmetics. The amount of color used in these applications usually ranges from 10 ppm wt to 1,000 ppm wt, basis finished food, beverage or pharmaceutical.

The invention is further illustrated by the following Examples. These are given to exemplify the invention only.

Example I In section A, acetamidoethylene monomer is prepared.

In Section B, the monomer is formed into a poly(vinylamine) hydrochloride polymer.

In Section C, the polymer of B is used as backbone to form one polymeric colorant of this invention.

In Section D, the colorant of C is acetylated to yield a second polymeric colorant of this invention.

A. To 2304 g of acetamide (technical) in a 12 liter reaction flask is added 62.2 ml of 6 m aqueous sulfuric acid followed immediately by 661 g of acetaldehyde (99+van). This mixture is stirred and heated until the internal temperature reaches 78"C (11 minutes) at which point the clear solution spontaneously crystallizes, causing a temperature rise to 950C. The reaction product, ethylidene-bisacetamide, is not separated. Heating and stirring are continued for another five minutes to a temperature of 107"C and a mixture of 150 g calcium carbonate (precipitated chalk) and 150 g of Celite (Registered Trade Mark) diatomaceous earth powder is added. A first distillate fraction of water and acetamide is removed.

The remaining materials are cracked at 35 mm Hg and 185"C. A fraction made up of vinylacetamide and acetamide is taken overhead, analyzed by NMR and found to contain 720 g of vinylacetamide and 306 g of acetamide. A portion of this pooled material is dissolved in isopropanol, cooled, and filtered to yield a stock solution.

B. An acetamidoethylene solution (8.0 moles) of Part A and 2,2'-azobis-(2methylpropionitrile) AIBN (13.3 g, 0.08 moles) in 2.13 liters isopropanol is deoxygenated 3x 1 Ar and refluxed for two hours. The isopropanol is removed by distillation and the polymer is then purified of monomeric impurities and formed into an aqueous solution. The polymer solution is concentrated to 30o/ w. The peak molecular weight (ups) is determined by gel permeation chromatography and found to be 6.0+1.5x104 (polystyrene reference in DMF with porous glass beads support). A 300/ aqueous polymer solution (1558 g, 505 moles) and 755 mls of 20".Be aqueous hydrochloric acid (7.6 moles) are refluxed for 20 hours under Argon. The resulting polyaminoethylene-hydrochloride solution contains 2.05 meq/g amine and 1.05 meq/g HCl (5.15 meq/g total titratable acids).

C. An aqueous solution of the polymer of Part B (4.5 moles), 3-nitro-4chlorobenzenesulfonic acid-sodium salt (Mobay Chemical60V paste) (4.5 moles) and enough 50 w NaOH to neutralize the amine hydrochloride and residual acids (total titratable acid) is deoxygenated 3 X /Ar, then heated to reflux (1 100C). After one hour, 50% w NaOH (396 g, 4.5 moles) is slowly added at reflux over a six-hour period. The total time for refluxing is eight hours.

The reaction mixture is cooled by adding 8 liters cool H2O. One-half of the solution is purified by dialysis to remove salts and low molecular weight contaminants, concentrated and lyophilized to yield the polymeric colorant

wherein N+m=100--170 and n=1.3--1.7(m).

D. The remaining one-half of the reaction product solution of Part C. is further cooled to -50C by the addition of 3kg of ice. Then, the coolant in solution is acetylated over a 15-minute period with acetic anhydride (106 mls, 1.13 moles).

Enough 25V w NaOH is gradually added with stirring to keep the pH=I I for the first two-thirds of the acetylation, and pH=12 for the last third. This yields the acetylated colorant

wherein n+m+p=100--170 and n=1.3--1.7 (m+p). Exact values for p or n cannot be determined. Best values for these numbers indicate that the great maiority of the amines have been acetylated, i.e., m is only from .01 to 0.2 times p.

Both of these colorants (of Part C. and Part D.) are polymeric yellow colorants. Each is useful as a substitute for FD & C Yellow No. 5 in edible systems.

Their large polymeric size precludes their absorption through the walls of the gastrointestinal tract. Thus, the chance of systemic toxicity is substantially reduced.

The two colorants are water-soluble. The acetylated colorant has better solubility properties in acidic aqueous systems.

Example II A smaller scale preparation of polymeric colorant is carried out. A poly(vinylamine)hydrochloride backbone having a 5.3x104 molecular weight is prepared for use as backbone using the technique of Part B of Example I.

Into a round-bottomed flask equipped with stirrer, argon bleed and condenser is charged 1.0 g of the polymer, 10 mls of 1N NaOH, 1.06 g of Na2CO3 and 2.2 g of 3nitro-4-chlorobenzenesulfonic acid. The molar amounts are: Polymer 10 mmol NaOH 10 mmol Na2CO3 10 mmol Sulfonic Acid (As Na Salt) 5 mmol The mixture is refluxed at 1500C for three hours and gradually cooled by dilution to 60 mls. If the colorant were recovered, it would be

wherein n+m=670; n=0.31 (n+m), i.e., 31 /" of the amines are substituted.

Instead, the colorant is acetylated by cooling to 50C and gradually adding 5 mls of acetic anhydride and 5 mls of 50% NaOH over ten minutes. The product is purified by ultrafiltration using an Amicon PM-10 membrane in a lab scale ultrafiltration unit. This yields a solution of the product

wherein n+m+pr660; n=0.31 (n+m+p); p-0.l(m). The value of p is an estimate.

Some unacetylated amine is detected, but an exact number for its small value is not obtainable.

Example III The reaction of Example II is repeated in principle with variation of a number of reaction parameters.

In one repeat, about 1.4 equivalents of sulfonic acid are used and the reaction is continued for 22 hours. This gives very complete substitution of the backbone amines - 90% are substituted. The remaining 10 /,, are presents amines or as acetylated amines.

In a second repeat, only 1.0 equivalent of the sulfonic acid is employed along with 1.0 equivalent of each of Na2CO3 and NaOH. An eight-hour reaction time is used to yield a final product having 58 /n of its amines substituted with chromophores. The remaining amines are present as amines or acetylated amines.

Example IV A. Acetamidoethylene solution (250 g, 1.025 moles), prepared as in Example 1, Part A, is stripped to 133 mls. This material is charged to a 2 liter flask equipped with stirrer, condenser and heater along with 230 mls of a 25 /n solution (in water) of sodium vinyl sulfonate (0.552 moles), 400 mls of water and 4 g of AIBN polymerization catalyst. The mixture is heated with stirring. After about 40 minutes, it reaches 670"C where it is maintained for 24 hours. An additional gram of AIBN is added and the mixture is heated for an additional 12 hours to yield a product which is precipitated in 30 volumes of IPA and dried in a vacuum oven at 1250C for four hours. This product has a formula

and a molecular weight of about 36,000, i.e., the polymer contains on average about 225-250 units of amide and about 12(if130 units of sulfonate; (It is referred to herein at times as PAE-SES after hydrolysis with 4 equiv. acid at 100--110"C.) B. Into an egg-shaped flask equipped with stirrer, reflux condenser, argon bleed and oil bath heater, is added 1.3 g (10 mmol of amine) of the copolymer of Part A and 10 mls (10 mmol) of IN NaOH. After the polymer dissolves, 2.12 g (20 meq) of Na2CO3 and 4.5 (10 mmol) of 3-nitro-4-chloro-benzenesulfonic acid are added, the mixture is deoxygenated thrice and heated to 100C (reflux). After 24 hours, the reaction is cooled. The colorant is separated by removing impurities via ultrafiltration and lyophilizing the retentate to yield 1.8 g of product of the structure.

wherein n=0.40 (n+m+p); m=0.35 (n+m+p); p=0.23 (n+m+p).

C. A 0.5 g portion of the colorant of Part B is dissolved in 25 ml of water. At 0--5"C, 2 mls of acetic anhydride is gradually added with stirring along with IN NaOH in an amount to hold the pH at 11-12. This forms acetylated product of the formula

wherein n=0.40 (n+m+p+q); m=0.35 (n+m+p+q); p=0.24; us0.03, which is then recovered.

Example V A. The preparation of poly(n-methylvinylamine) is begun by adding 500 g of Nmethylaminoethanol to 1380 g (2.20 equivalents) of acetic anhydride at 115 1200C. The reaction is exothermic (cooling required) and is complete by the time the addition is concluded. The bis-acetylated product,

is isolated by vacuum distillation (bp 95--98"/0.1 mm) as a colorless oil in about 93 /" yield.

The bis-acetylated product is pyrolyzed by passing 642 g of this material at a rate of 1.17 g/min through a Pyrex (Registered Trade Mark) helices-packed quartz tube (3.5 cm diameter, 40 cm length), maintained at 4800. A 400 ml/min Argon stream is employed. The crude pyrolysate is a dark orange oil weighing 1350g. The crude mixture containing the desired N-methyl-vinylacetamide is distilled (72"C/20 mm) to afford 250 g of purified N-methylvinylacetamide.

Polymerization of 225 g of purified N-methylvinylacetamide is carried out in 500 ml of methanol at 700C in the presence of 4 mol /^ of AIBN. The polymerization is complete within 12 hours and affords 200 g yield of poly(Nmethylvinyl-acetamide).

The polymeric amide is hydrolysed with 6 N HCI at 1250 to yield poly(Nmethylvinylamine) as the hydrochloride. This material has a molecular weight of about 20,000 as determined by gel permeation chromatography comparisons to standards. The hydrolysis is monitored by NMR and requires roughly 40 hours to go to completion. The product is isolated in essentially quantitative yield by precipitation of the partially evaporated reaction mixture from isopropanol.

B. Into a round bottomed flask, equipped with stirrer, argon bleed and condenser, is charged 1.1 g of the polymer (10 mmole), 10 mls of I N NaOH, 2.l2g of Na2CO3 and 2.2 g of 3-nitro-4-chlorobenzenesulfonic acid. The mixture is refluxed at --1500C for six hours. One-half of the mixture is cooled, diluted, ultrafiltered and lyophilized to yield the solid colorant

The remaining half is cooled to 0--50C with ice addition. Gradually, 3 ml of acetic anhydride and 3 mls of 50 /n NaOH are added to acetylate the residual amines. The product is isolated by ultrafiltration and lyophilization. It has the structure

Example VI The preparation of Example IV is repeated substituting an equimolar amount of acrylic acid for the vinyl sulfonate in the preparation of the polymer backbone.

A 1:1 ratio of acrylic acid to amine is employed. This product would have a molecular weight of from 1.0x104 to 5.0x104 Daltons. This product could be employed as a backbone for a polymeric colorant of this invention, prepared in accord with Example IV, having a structure

with acetylation, the residual amines could be converted in 90+", efficiencv. to acetamides.

Example VII The preparation of Example IV is repeated. A different ratio of amine to sulfonate in the polymer backbone is achieved by adding vinyl sulfonate and acetamidoethylene in a 1:3 molar ratio. The resulting polymer is a PAE--SES copolymer having a 3 to I molar ratio and a molecular weight of 2.0 2.(5.0x l0 Daltons. When this material is substituted in the colorant preparation of Example IV a similar product, with similar chromophore substitution, results. Residual amine groups can be acetylated, if desired.

Example VIII In Examples 1-VI, all salts are sodium salts, since the bases used in their preparation are sodium bases. It will be appreciated that by substituting corresponding potassium bases in the preparations, potassium salts could be formed. Similarly, ammonium cations can be substituted in the products.

Comparative Experiments A. A polymeric colorant is prepared using as chromophore a positional isomer of the material used in the present invention. Into a 50 ml flask, equipped with stirrer and argon bleed, is placed 0.9 g (9.5 mmol) of poly(aminoethylene) as used in Example I, 10 mls of water and 2.65 g (25 mmol) of Na2CO,. After deaerating the mixture. it is stirred and heated to 700C. The chromophore,

is added (1.19 g, 5.0 mmol) and the mixture is kept at 9 & 1000.C for about 18 hours. Three drops of 50% NaOH and 10 ml of water are added during the reaction.

The product is removed and ultrafiltered. A portion is acetylated and ultrafiltered, as shown in Example I.

This product (acetylated) has a structure very close to that of the colorants of the invention, i.e.,

When the color of this material is evaluated, it is seen to be unacceptable as a replacement for existing food colors. It has a very brownish cast which cannot yield true oranges, yellows or greens. Colors of this invention. such as produced in Example 1, do not have this failing.

B. A second similar colorant is produced. A 50 ml flask, equipped with stirrer and argon bleed and condenser, is charged with 1.0 g (7.7 mmol) of PAE-SES copolymer such as shown in Example IV. Na2CO3 (3.25 g, 31 mmol) and 20 ml water are added. The mixture is heated to 950C and 1.55 g (7.7 mmol) of chromophore

is added with 10 ml of water. The mixture is refluxed -100"C for about 20 hours, cooled, filtered through glass filter A, ultrafiltered and lyophilized to yield

This product is evaluated as a yellow colorant. It is observed to have a very low coloring power (tinctorial strength). This property is quantitized by the color's extinction coefficient. The material has an extraction coefficient of 3.9.

Compounds of the invention are unexpectedly higher, having extinction coefficients of 13-16 in most cases.

We are aware of "The colouring Matter in Food Regulation 1973" and make no claim to the use of any material in contravention of those Regulations.

WHAT WE CLAIM IS: 1. A water-soluble polymeric yellow colorant comprising a nonchromophoric organic backbone as herein defined of molecular weight of from 1000 to 200,000 having covalently attached thereto through the nitrogens of the pendant amine groups a plurality (n) of chromophore units of the structure

wherein M+ is Na+K+ or NH+4, and wherein each nitrogen is directly attached to the aromatic ring of the chromophore group.

2. The colorant of Claim I wherein said organic backbone has a carbon-carbon linked structure.

3. The colorant of Claim 1 wherein n is between 10 and 2000.

4.The colorant of Claim 3 being further characterized as being of a size that precludes the colorant's transport across the walls of the mammalian gastrointestinal tract.

5. The colorant of Claim 4 wherein M+ is Na+.

6. A water-soluble polymeric yellow colorant according to claim I and of the formula

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

Claims (24)

**WARNING** start of CLMS field may overlap end of DESC **. B. A second similar colorant is produced. A 50 ml flask, equipped with stirrer and argon bleed and condenser, is charged with 1.0 g (7.7 mmol) of PAE-SES copolymer such as shown in Example IV. Na2CO3 (3.25 g, 31 mmol) and 20 ml water are added. The mixture is heated to 950C and 1.55 g (7.7 mmol) of chromophore is added with 10 ml of water. The mixture is refluxed -100"C for about 20 hours, cooled, filtered through glass filter A, ultrafiltered and lyophilized to yield This product is evaluated as a yellow colorant. It is observed to have a very low coloring power (tinctorial strength). This property is quantitized by the color's extinction coefficient. The material has an extraction coefficient of 3.9. Compounds of the invention are unexpectedly higher, having extinction coefficients of 13-16 in most cases. We are aware of "The colouring Matter in Food Regulation 1973" and make no claim to the use of any material in contravention of those Regulations. WHAT WE CLAIM IS:

1. A water-soluble polymeric yellow colorant comprising a nonchromophoric organic backbone as herein defined of molecular weight of from 1000 to 200,000 having covalently attached thereto through the nitrogens of the pendant amine groups a plurality (n) of chromophore units of the structure

wherein M+ is Na+K+ or NH+4, and wherein each nitrogen is directly attached to the aromatic ring of the chromophore group.

2. The colorant of Claim I wherein said organic backbone has a carbon-carbon linked structure.

3. The colorant of Claim 1 wherein n is between 10 and 2000.

4.The colorant of Claim 3 being further characterized as being of a size that precludes the colorant's transport across the walls of the mammalian gastrointestinal tract.

5. The colorant of Claim 4 wherein M+ is Na+.

6. A water-soluble polymeric yellow colorant according to claim I and of the formula

wherein Rl is selected from a carbon-nitrogen single covalent bond and methylene, R2 R3 and R4 are independently selected from hydrogen, methyl and ethyl; A, A' and A" are independently selected from

I I COO-+M and PO3=2M+; and n m,p and q are numbers such that the sum of n,m,p and q is from 40 to 8000, n is not less than 0.2 times the sum of m+p+q, and m is as defined in Claim 1.

7. The colorant of Claim 6 wherein R2, R3 and R4 are hydrogen.

8. The colorant of Claim 7 wherein R1 is a carbon-nitrogen covalent bond.

9. The colorant of Claim 8 wherein A" is

{$ 1 R, N'RZ 2 N-R2 and A' and A are Q H H S03 M and wherein n+m+p is from .3 to 10 times q.

10. The colorant of Claim 9 wherein n+m+p+q is from 500 to 7000 and n+m+p is from I to 7 times q.

Il. The colorant of Claim 10 wherein n+m+p is from 1.25 to 4 times q.

12. The colorant of Claim 8 wherein A" is

R1 N-R R1 R1 H N-R2 A' is N-R2 and A is Q202 H H3CCO o3 M and wherein n+m is from 0.3 to 10 times p+q and q is from 0.01 to 0.4 times p.

13. The colorant of Claim 12 wherein n+m+p+q equals 500 to 7000 and n+m equals from I to 7 times p+q.

14. The colorant of Claim 13 wherein n+m equals from 1.25 to 4 times p+q.

15. The colorant of Claim 8 wherein A" is

A' is selected from among SO3- M+, COO-M+ and P03=2M+; A is

and n+m+p+q equals 40 to 4000, n+m+q equals from 0.-15 to 7 times p and n+m equals from 0.3 to 10 times q.

16. The colorant of Claim 15 wherein n+m+p+q equals 80 to 2000, n+m+q equals from 0.5 to 4 times p and n+m equals from 1 to 7 times q.

17. The colorant of Claim 15 wherein A' is S13-M+.

18. The colorant of Claim 16 wherein A' is SO3-M+.

19. The colorant of Claim 17 wherein n equals from 0.3 to 10 times m+q, and q equals 0.01 to 0.4 m.

20. The colorant of Claim 19 wherein n+m+p+q equals 80 to 2000, n+m+q equals 0.5 to 4 times p and n equals 1 to 7 times m+q.

21. The colorant of Claim 20 wherein n+m+q equals 1 to 3 times p, n equals 1.25 to 4 (m+q), and q equals (0.03 to 3) times m.

22. A polymeric colorant according to Claim 1 and consisting essentially of material of the formula

wherein n is a number from 900 to 3500, m is a number from 600 to 2000, and p is a number from 10 to 100, n, m and p being further defined as being in a ratio of about 6 to 4 to 0.1.

23. A colored edible product comprising an edible material having admixed therewith from 10 ppm wt to 1,000 ppm wt of the colorant of Claim 22.

24. A water-soluble polymeric colourant as claimed in claim l and substantially as described in any one of the specific examples hereinbefore set forth.