GB1566948A

GB1566948A - High purity polymeric water soluble colourants and their production

Info

Publication number: GB1566948A
Application number: GB39575/77A
Authority: GB
Original assignee: Dynapol Corp
Current assignee: Dynapol Corp
Priority date: 1976-09-27
Filing date: 1977-09-22
Publication date: 1980-05-08
Also published as: MX4915E; IL52987A0; BE859079A; FR2365610B1; IT1089899B; AU515797B2; IL52987A; DE2743451A1; AU2902177A; FR2365611A1; JPS5359724A; NL7710379A; FR2365610A1; FR2365611B1; CA1107888A; ZA775619B

Description

(54) HIGH PURITY POLYMERIC WATER SOLUBLE COLORANTS AND THEIR PRODUCTION (71) We, DYNAPOLL, a Corporation of the State of California, of 1454 Page Mill Road, Palo Alto, California, 94304, U.S.A., 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:- Recent patents and articles, such as USP 3,920,855 issued Nov. 18, 1975 to Dawson et al and Yakugaku Zasshi 89(4) 524 (1969) have shown the advantageous use of polymeric colorants in food systems. It is pointed out that polymeric colorants of suitably large molecular size are not absorbed through the walls of the gastrointestinal tract, while their smaller counterparts do pass through these walls.

If a molecule can not pass through the walls of the gastrointestinal tract it does not enter the body. Thus, any risk of systemic toxicity to the body should be eliminated.

As a general rule, polymeric colorants having a molecular size and a molecular weight above about 1000 Daltons do not pass through the GI tract walls, while polymeric colorants and/or contaminants having a molecular weight below about 500 Daltons do pass through these walls. The degree of transport of compounds having weight in the 5001000 Dalton range depends upon the shape and chemical character of the molecules. Thus, if absorption of a polymeric colorant is to be minimized, it follows that the amount of material in such a colorant having a molecular weight below 500 Daltons, and preferably below about 1000 Daltons must be minimized.

In theory, one approach to minimizing low molecular weight materials wound be to carefully control reaction conditions and feedstock composition to assure that the formation of feeding of light impurities is minimized. In practice, however, this does not work. When polymeric colors are prepared under reaction conditions which eliminate essentially all light impurities from the products, the final products are of too high an average molecular weight. This can lead to viscosity and solubility problems.

Another possible solution to the problem of low molecular weight components is to isolate and recover the correctly sized polymeric colorants from their preparative media. Many of the most commonly employed procedures are unavailable, however. Distillation, for example, cannot be employed since the polymeric colors and many impurities are essentially non-volatile salts.

Precipitation and/or extraction can be used but generally result in unacceptably high yield losses. Dawson et al in the above-noted patent disclose dialysis as a laboratory purification step, but this method is not usually employed on an industrial scale. Similarly, to my knowledge, ultrafiltration has never been employed in purification of polymeric colors. A separation of the type contemplated is a complex one for ultrafiltration. High molecular weight colorant is to be separated from low molecular weight polymers and from nonpolymeric ionics, i.e.: salts if a satisfactory final product is to be achieved. Thus, two separations are taking place at once. One use of ultrafiltration in a "color setting" has been reported in USP 3,758,405. In this Patent, colored bodies are removed from kraft pulp waste streams. This in the direct contrast to the present process where salts and the like are removed from colour streams.

The product of an ultrafiltration like the crude reaction product is a liquid (aqueous) solution. While colors are sometimes marketed as aqueous solutions, more commonly they are sold as dry solids. The conversion of an aqueous solution of polymeric color to a dry solid requires special consideration. The colors are often hygroscopic so that precipitation, filtration and conventional drying yield a caked or paste-like product. The colors, being polymers, can break down to undesired low molecular weight fragments if they are heated to very high temperatures for very long periods, such as might be experienced in a shelf drier or the like. As can be appreciated, it is necessary to convert the solution to a solid powder a a way which prevents such breakdown if the desired nonabsorption property is to be achieved. This means that the backbones should not cleave at the conditions of polymeric colorant preparation or a polymeric dye use. In the case of polymeric food colorants, use conditions where stability is required include the conditions of the gastrointestinal tract.

According to the present invention there is provided a water soluble polymeric colorant having an average molecular weight of greater than 5,000 Daltons comprising optically chromophoric organic groups covalently bonded to a nonchromophoric organic backbone said colorant being further characterized as containing not more than 1.0% by weight, basis total organics, of total polymeric colorant, polymeric colorant precursors, and degradation products having a molecular weight of less than 1,000 Daltons and as containing not more than 3% by weight, basis total solids, of inorganic or organic salts.

According to another aspect of the present invention there is provided a process for separating a water-soluble polymeric colorant of average molecular weight greater than 5,000 Daltons from a mixture containing said polymeric colorant and polymeric colorants of molecular weight less than 1,000 Daltons which comprises (i) forming an aqueous feed solution of said mixture and not containing less than 0.5% by weight, basis solution, of an alkali metal ionic compound selected from the soluble inorganic salts and hydroxides of the alkali metals; and (ii) subjecting said aqueous feed solution to ultrafiltration to form an aqueous filtrate containing said polymeric colorants of molecular weight less than 1,000 Daltons and a retentate containing polymeric colorant of average molecular weight greater than 5,000 Daltons and not more than 1.0% by weight, basis total polymeric colorant of polymeric colorant, precursors or degradation products thereof of molecular weight less than 1,000 Daltons and hot more than 3% by weight, basis total solids of inorganic or organic salts.

According to a further aspect of the present invention, there is provided the process for preparing a dry particulate water-soluble polymeric colorant suitable for use as a nonabsorbable food colorant and having a molecular weight greater than 1000 Daltons which comprises: (i) forming a feed solution comprising an aqueous solvent, from 0.1 to 20% by weight (basis solution) of polymeric watersoluble colorant having a molecular weight above 1000 Daltons, from 0.1 to 20% by weight (basis solution) of water-soluble polymeric colorant plus monomeric organic chromophore having a molecular weight below 1000 Daltons, and from 0.1 to 20% by weight (basis solution) of inorganic salts; (ii) contacting said feed solution with an anisotropic semipermeable polymeric membrane at an upstream pressure of from 25 to 200 psig thereby forming an aqueous ultrafiltrate phase which passes through said membrane comprising solvent, water-soluble polymeric colorant plus monomeric organic chromophore having a molecular weight of less than 1000 Daltons, and inorganic salts; and a retentate phase which does not pass through said membrane comprising aqueous solvent, water-soluble polymeric colorant having a molecular weight greater than 1000 Daltons, and not more than 1%, basis polymeric colorant having a molecular weight greater than 1000 Daltons, of water-soluble polymeric colorant and monomeric organic chromophore having a molecular weight below 1000 Daltons and not more than 2% of inorganic or organic salts; (iii) recoverying said retentate phase; and (iv) subjecting the recovered retenate phase to spray-drying to remove aqueous solvent as a vapor phase and form a particulate solid phaue consisting essentially of polymeric nonabsobable water-soluble polymeric colorant of molecular weight greater than 1000 Daltons.

Such colorants may be isolated and recovered from an aqueous crude reaction medium by the process comprising 1. Subjecting the aqueous reaction medium to ultra-filtration thereby forming an ultrafiltrate containing salts, monomers and polymeric colorants having a molecular weight below about 1000 Daltons, and a retentate comprising an aqueous solution of polymeric colorant having a molecular weight above about 1000 Daltons; and 2. Spray drying the retentate thereby forming an aqueous vapor phase and a solid particulate colorant phase which solid phase is recovered.

In accord with this invention a water-soluble polymeric dye in a high purity solid particulate form is recovered from a crude liquid reaction mixture. A suitable crude reaction mixture has the following properties and composition.

Solvent-water with up to 15% w of organic solvents. Preferably water with from 0 to 10% w of organic solvents.

Polymeric Dye-having a molecular weight above 1000, % w (basis total solution), 0.1 to 20%, preferably 0.5 to 15%, more preferably 1 to 10%.

Organic impurities-Polymeric dye having a molecular weight below 1000 plus monomeric organic dye species and organic molecular fragments, % w (basis total solution), 0.1 to 20%, preferably, 0.1 to 15%, more preferably, 0.5 to 15%.

Inorganic salts w (basis total solution), 0.1 to 20%, preferably, 0.5 to 15%, more preferably, 1 to 10%.

Such a reaction mixture may result from either of two general preparative methods. In the first, a monomeric dye containing a polymerizable group, such as a vinyl group, is polymerized into a polymer via covalent chemical bonds. In the second, a preformed polymer backbone having active sites is reacted with a chromophore under conditions such that the chromophore is covalently bonded to the polymer.

The first process may be shown as follows:

wherein n is a number greater than 1, PG is a polymerizable group and Ch is a chromophoric group or chromophoric group precursor.

Polymerizable group, PG, is an organic group which can undergo polymerization in an aqueous medium and does not degrade under conditions of use of the final colorant. The ability of the group PG to undergo polymerization in an aqueous medium may be a function of its solubility in the aqueous medium.

Such solubility will in turn be in part dependent upon the solubility properties of the chromophore or chromophore precursor, Ch.

Examples of suitable polymerizable groups, PG, include olefinic double bonds, especially in a vinyl configuration, unsaturated acids, unsaturated esters, the epoxy groups, halohydrins, acid halides, ketenes, acid azides, acid amides, urethanes, and the like.

Attached to the polymerizable group, PG, by means of a covalent link, is a chromophoric group or chromophoric group precursor, Ch.Ch is an optical chromophore or precursor thereof. An "optical chromophore" is an organic group which produces a color which may be detected by the human eye. There is no limitation on the type of chromophore employed so long as the resulting polymeric colorant product is water soluble. The term "water soluble" as used herein is defined to be a solubility in room temperature neutral water of not less than 500 parts per million. Chromophores useful as Ch may be selected from the art-known classes of chromophores including the azo chromophores, anthraquinone chromophores, xanthene chromophores, triphenylmethane chromophores, indigoid chromophores and the like. These classes of chromophores are merely representative-other similar materials also being usable. Among these chromophores special preferences are given to azo chromophores, because of the great variety of technically important clear intense red to yellow colors which they enable and to anthraquinone chromophores because of their great stability under stressful conditions of heat and light and the wide range of colors wijich they permit. Typical monomer

units and the units they form in polymers and copolymers include, for example, Monomer Polymer unit Anthraquinones

wherein R is a lower alkyl

wherein R is a single bond or a 1--3 carbon alkyt any of these anthraquinones may also contain up to three additional substituents such as sulfonyls, lower alkyl amines, benzoyl amines, hydroxyls, nitros or halo groups.

Triphenylmethanes (shown in nonoxidized form)

wherein R1, R2, R5 are hydrogens or lower alkyls, R3 is OH or hydrogen and R4 is -NHC, phenylene, -COO- or -0-, Xanthenes

wherein R, and R3 are H, a halogen or a lower alkyl and R2 is an alkyl amino group and the like.

The crude reaction mixtures of this general preparation route will contain as organic impurities-unreacted

almers and tnmers of

unreacted solubilizer comonomers (if any) as well as degradation products and coproducts which will have formed during the reaction. Polymerization catalyst, which may be an inorganic or an organic material, depending upon the particular preparation process employed will also be present along with salts of mineral acids and the like resulting from pH adjustments during preparation.

In the second major preparative method for polymeric colorants, a preformed backbone is covalently bonded to an attachable chromophore. This process is depicted as

wherein AS is an attachable site, B is a preformed organic polymer backbone, preferably a carbon-carbon backbone, and Ch and n are as already defined.

Exemplary AS sites are amines, acids, halides, cyanos and the like. Exemplary backbones, B, include olefinically saturated hydrocarbon backbones, preferably essentially linear hydrocarbons and polymeric ethers such as result when epichlorohydrin is polymerized.

Such backbones may carry amine AS groups. Structurally, these backbones may be depicted as linear

chains, wherein R, is hydrogen or a lower saturated alkyl of up to 4 carbon atoms, i.e., methyl, ethyl, propyl or butyl; R2 is hydrogen, a lower saturated alkyl of up to 4 carbon atoms or an aromatic hydrocarbon of about 6 carbon atoms, i.e., phenyl; R3 is most commonly a simple carbon to nitrogen single covalent bond but also may be a 1 to 4 carbon lower saturated alkyl bridge, or a 6 carbon aromatic (phenylene) bridge; and n is an integer greater than 1 and m is at least such that not more than 1/2 the backbone carbons carry an amine group. In one other embodiment, R3 is a methylene bridge which joins together with an adjacent R3 into a repeating

i.e., a "cyclodiallylamine" configuration. Generally, R1 is preferred to be hydrogen or methyl and R2 is preferred to be hydrogen or methyl. The backbone may comprise added copolymeric units as well. These units need not be solely hydrocarbons but should only add hydrocarbon to the structural chain of the backbone. The added units include, for example the hydrocarbons

wherein R4 is hydrogen, a 1 to 4 carbon alkyl or an aryl, alkaryl or aralkyl of from 6 to8 carbons; the oxyhydrocarbons

wherein R5 is hydrogen, a 1 to 4 carbon alkyl, a -O-CH3 group, or an -NH2 group; and the nitrilohydrocarbon

As illustrated by these formulae, the sole contribution made to the backbone chain by these materials is hydrocarbon.

The following is a list of exemplary homopolymeric backbones for use in this invention. It will be appreciated that the aforementioned copolymeric groups could be incorporated also. Suitable backbones include poly(vinylamine),

poly(N-methylvinylamine),

poly(cr-methylvinylamine)

poly(p-methylvinylamine),

poly(a-ethyl-, a-propyl, or a-butylamine),

and the like. Preferred homopolymer amine backbones include poly(vinylamine), poly(N-methylvinylamine), and poly(a-methylvinylamine). Nonamine homopolymeric backbones include polyacrylic acid, polyepichlorhydrin and the like.

Typical copolymeric backbones include linear copolymers made up of repeating ethylsulfonate and alkylamine groups, The sulfonate component is represented by the formula

wherein M+ is an alkali metal cation, especially Na+, K+, or Li+. It is referred to herein as ethylsulfonate. The term "vinyl sulfonate" is used to refer to its precusor,

which is commercially available material which is formed into these copolymers.

The other component of these backbones is generally a single alkylamine group. Of course, a plurality of amines could be used, but for simplicity, a single amine is generally preferred. These alkylamines are lower alkylamines, that is, amines having from 2 to about 6 carbons per amine group. They will normally be olefinically saturated when present in the copolymer. The amine groups are joined into the backbone through carbon-carbon single bonds, not through amine links.

Suitable amines m their combined forms include ethyl-amine, Nmethylethylamine, a-methylethylamine, 3-methylpiperidine, p-methylethylamine, butylamine and the like. These suitable amines can be represented structurally by the formula:

wherein each of R1 and R2 are independently selected from the group consisting of hydrogen and lower saturated alkylas of up to 4 carbon atoms, R3 is a branched or linear lower saturated alkyl of from 1 to 4 carbon atoms, and R4 is a carbonnitrogen single bond or a 1 to 4 carbon alkyl subject to the limitation that the total number of carbon atoms in R1, R2, R3 and R4 is not greater than 5. R2 and R3 can be joined into a single lower alkyl such as occurs with 3-methylpiperidine.

These copolymer backbones are represented by the structural formula:

wherein n and m are integers greater than 1.

Yet another typical backbone is polyacrylic acid and its esters and copolymers resulting from the partial conversion of acrylic polymers to amines.

Chromophores for attaching to these preformed backbones can be chosen from a wide range of materials that include for example, the azo chromophores, antraquinone chromophores, xanthene chromophores, triphenylmethane chromophores, indigoid chromophores, and the like.

Preferred anthraquinone chromophores in their unattached state have a leaving group such as a -Cl, -Br, -I, -SO3Na, -NCl-, or -NO2 group attached to their aromatic ring. This permits the chromophore's facile attachment to the backbone via for example amine group by known techniques such as the Ullmann reaction wherein copper is used to catalyze the leaving groups' displacement by amines. In many cases, no catalyst is required to effect the desired displacement. Representative classes of useful anthraquinone chromophores include: Aminoanthraquinone chromophores of the structure of Formula I;

formed by coupling the monomer IA wherein R1 is a hydrogen or a lower saturated alkyl of up to four carbon atoms, R2 is hydrogen, a lower saturated alkyl or up to four carbon atoms or an alyl or alkaryl of from six to eight carbons and X is a leaving group. These are useful to give the range of blue colorants listed in Table I.

TABLE I Compound R, R2 Color hydrogen hydrogen purplish blue hydrogen methyl greenish blue hydrogen ethyl, propyl or butyl greenish blue hydrogen aryl navy blue Anthrapyridones of the structure of Formula II;

formed by coupling the corresponding monomer, wherein X is a leaving group, R, is hydrogen, a lower saturated alkyl of from 1 to 4 carbon atoms inclusive, or an aryl grouping of about 6 carbons, R2 is a 1 to 4 carbon lower saturated alkyl, a 1 to 4 carbon lower saturated alkoxy, or an aryl grouping of about 6 carbon atoms, and R3 is hydrogen or a I to 4 carbon lower saturated alkyl. These chromophores are rich reds. Preferred among the anthrapyridones are these according to Formula II wherein R1, R2 and R3 are shown by Table II.

TABLE II R1 R2 R3 hydrogen 1,4 carbon alkyl l carbon alkyl hydrogen methyl hydrogen methoxy 1 carbon hydrogen methoxy 1-4 carbon alkyl hydrogen methoxy methyl hydrogen ethoxy 1-4 carbon alkyl hydrogen ethoxy methyl hydrogen phenyl methyl methyl methyl hydrogen methyl phenyl hydrogen ethyl methyl hydrogen methyl methoxy hydrogen ethyl methoxy hydrogen Anthrapyridines of the structure of Formula III:

which are formed by coupling the corresponding monomeric chromophore

wherein X is a leaving group, 4 is a 1 to 4 carbon lower alkyl group or an aryl group of about 6 carbons and R2 is hydrogen or a 1 to 4 carbon lower alkyl, and R3 is a 1 to 4 carbon alkyl group or aryl group of about 6 carbons. These colorants range in hue from yellow to red. Preferably R2 is hydrogen or methyl. Other typical anthraquinone chromophores include the pyridinoanthrones, anthrapyrimidines and anthrapyrimidones.

Other chromophores include azo chromophores, such as those having monomeric forms containing sulfonyl halide groups since they can join to the amine backbone via the well-known Schotten-Baumann reaction. Exemplary azo chromophores and representative halo precursors include: Chromophore Precursor

Ct SO, SO, Lil H II /(orange) (OA OAc slO2 Ct ty SO2 N 1.

N N HO II N AcO HO 0 (Bu-gundy) AcO 0 The Schotten-Baumann reaction also functions with sulfonyl halidecontaining nonazo chromophores such as:

0 1 0 sO2 I 502 0 0 0 (Yellow C <

Ct 5 2 sO2 NH2 0 NHAc oO oO WA lYettow} WX The attachment of these or other chromophores to backbones may be carried out by any of the methods for joining a chromophore to a polymer through an amine link known in the art.

The reaction product of this general reaction would contain unreacted Ch, fragments of

and various degradation products. In both of these general preparation processes, the crude reaction product may also contain up to about 10% of organic solvents.

These materials may be present to enhance its solubility of products, feedstocks, etc. Typical added organic solvents include lower alkanols such as methanol, ethanol and isopropanol, glycols of up to 3 carbon atoms such as ethylene or propylene glycol, lower alkanones such as acetone, and methylethyl ketone and the like.

In accordance with the present invention a high purity polymeric colorant is achieved by recovery of said colorant from the crude reaction mixtures which have been described. These high purity colorants can be characterized as follows: They have an average molecular weight of not less than 5000 Daltons. They comprise a plurality, preferably from 10 to 5000, more preferably 20 to 1000 units, of optical chromophore attached to a nonchromophoric backbone. They are particulate solids. They are more particularly characterized by their purity. Not less than 99.0, preferably 99.3, and more preferably 99.5% w of the colorants (basis organics) has a molecular weight above 1000 Daltons. They may additionally contain minor amounts of inorganic salts, such as NaCI, and the like up to a maximum of 3.0% w of their total solids, preferably they contain not more than 2.0% w and more preferably from 0 to 1% w of inorganic salts, basis total solids. These products are hygroscopic and generally contain from about 1 to about 15% w, preferably 2 to 12% water. The inorganic salts and organic materials of molecular weight below 1000 Daltons are the same types of materials described as present in the crude reaction mixture.

The hirh purity colorant product may be obtained from a crude reaction product by the process which comprises subjecting the reaction product to ultrafiltration to form an aqueous permeate containing inorganic salts and organic materials having a molecular weight below 1000 Daltons and an aqueous retentate containing polymeric colorant having a molecular weight above 1000, recovering the retentate and subjecting it to spray drying to form an aqueous vapor phase and a separate particulate solid phase which is the desired colorant product.

Additional optional pretreatment steps may be added to the process prior to the ultrafiltration step. These include bulk (nonmolecular) filtration to remove any solids in the reaction mixture which might foul the ultrafiltration unit or contaminate the final product and extraction or ion exchange as needed to remove dissolved catalysts. Ion exchange or the like can be carried out as well intermediate ultra-filtration 9nd spray drying. Such filtration may employ any conventional filter means including the rotary vacuum type, gravity type, or the like.

Ultrafiltration, one process suitable for removing salts and organic colorant fragments of molecular weight below 1000 is a membrane process of growing commercial importance. In this process, a semipermeable membrane is used as the separating agent and pressure is used as the driving force. In an ultrafiltration step the feed solution is introduced into a membrane unit or cell water, inorganic salts and low molecular weight organics pass through pores of the membrane under an applied hydrostatic pressure. Colorant molecules whose sizes are greater than the pore size of the membrane are retained and concentrated. The pore structure of the membrane is asymetric and acts as a molecular filter, passing the smaller solutes but retaining the larger solutes, which in this case are the desired molecules of polymer dye.

Any asymetric ultrafiltration membrane which can effect the desired separation may be used, these include membrane having pore diameters of from about 1 to about 500 millimicrons. Excellent results are obtained with anisotropic membranes such as developed by Amicon Corporation, and marketed under the Tradenames PM-10 and PM-30. Other suitable membranes include asymetric ultrafiltration membranes having an upper limit of exclusion of not less than 5000 nor more than 150,000 Daltons such as marketed by ABCOR, T. J. Engineering and Union Carbide. The conditions employed in the ultrafiltration are preferably a pressure of from about 25 psig to 200 psig, preferably 50 to 150 psig and more preferably 75 to 125 psig, and usually near room temperature, i.e., 1545 C, although higher and lower temperatures-say from 10--750C can also be used. The ultrafiltration may be carried out in continuous mode, with either a controlled recycle to a plurality of ultrafiltration cells in series used to attain the required degree of purification.

The retentate which results from ultrafiltration is essentially an aqueous solution of polymeric colorant having a molecular weight above 1000. This retentate usually contains from 1 to 20% w of colorant, preferably 2 to 18% w of colorant and more preferably contains 4 to 15% w of colorant.

Following ultrafiltration, the polymeric colorant-rich retentate is recovered.

Water and any other solvents are removed. The method of choice for this water removal is spray drying. This may be carried out in conventional spray drying apparatus. Useful conditions for spray drying are as follows: Inlet temperature 100--400"C preferably 1137.5"C more preferably 1 5350dC Outlet temperature 75-2500C preferably 100--240"C more preferably 110--225"C The pressure drop across the dryer should be about 5-12 inches of water.

The feed rate should be such as will result in the above-noted inlet and outlet temperature. In a 30- or 36-inch diameter unit feed rates of from 4 to 30 liters of liquid per hour are suitable. Larger, industrial scale units would have proportionately higher feed rates.

The product of this spray drying is a particulate solid. Its water content will vary from about 1 to about 15% w depending upon the drying conditions and the degree of care used to exclude water from the product after drying.

Following is a description by way of example only of methods of carrying the invention into effect.

EXAMPLE I This example illustrates the production of a high purity yellow orange azo dye of the formula:

This material is formed by the genera Parts G and H relate to the purification and isolation of the desired purified colorant in solid form. Part I illustrates the utility of this purified product.

A. Preparation of Vinylacetamide To 462 g of acetamide (technical) is added 12.45 ml of 6M aqueous sulfuric acid followed immediately by 168 ml (3 moles) of acetaldehyde (99+%). This mixture is stirred and heated until the internal temperature reaches 70"C (9 minutes). After another minute of heating, the 95"C clear solution spontaneously crystallizes, causing a temperature rise to 1060 C. The reaction product, ethylidenebis-acetamide, is not separated. Heating and stirring are continued for another 5 minutes and a mixture of 60 g calcium carbonate (precipitated chalk) and 30 g soft glass powder is added. The resulting mixture is heated to cracking temperature and distilled at 40 mm Hg (2000C bath temperature). When the internal temperature reaches 160"C (0.5 hr.), the receiver is changed. After another 1.7 hr. the distillation is almost over, the stirrer is stopped and the heating continued. Slow distillation continues for another hour and is then stopped. The first distillation fraction is 95.9 g of water and acetamide. The second fraction is 466 g of orange oil and crystals. NMR indicates this mixture to contain 195 g vinylacetamide (76 yield) 217 g acetamide, and 54 g ethylidene-bis-acetamide.

B. Polymerization of Vinylacetamide A red-brown solution of 460 g of vinylacetamide, 557 g acetamide, and 123 g ethylidene-bis-acetamide, (one-half of five combined vinylacetamide preparations in accord with part A) in 570 ml methanol is filtered through 250 g of AmerliteR IRC-50 ion exchange resin over an eight hour period. The column is rinsed with 1,000 ml methanol. The combined column eluant is stripped to its original volume of 1,667 ml, treated with 7.75 g of AIBN polymerization catalyst (1 mole %) deoxygenated and stirred under Argon at 650C for 15 hours to polymerize. Solid polymer is precipitated from the resulting very thick solution by addition to 15 liters of acetone. The polymer is collected by filtration, washed with acetone and dried in a vacuum oven (800 C) for two days to afford 459 g of crude poly(vinylacetamide) contaminated with acetamide as a yellow, semigranular solid having molecular weight of of 200,000 as determined by Gel Permeation Chromatography, using demethylformamide is eluent and polystyrene as standards.

C. Hydrolysis of Poly(vinylacetamide) to Poly(vinylamine Hydrochloride).

The crude poly(vinylacetamide) obtained in Part B (459 g) is dissolved in 1,000 ml water with heating. Concentrated hydrochloric acid (1,000 ml) is added and the resulting dark brown solution is stirred and heated at a gentle reflux (97-1060C) for 19 hours. A precipitate forms and is redissolved by addition of 200 ml water.

Reflux is continued and over the next 8 hours 1,000 ml water is added in several portions to maintain solubility of the polymer. After a total of 27 hours at reflux, the polymer is precipitated by the addition of 1,000 ml concentrated hydrochloric acid. The mixture is cooled to 180C and the thick polymeric gum isolated by decantation and dried under vacuum at 50-750C with occasional pulverization for 40 hours to give 332 g of poly(vinylamine hydrochloride) as a brown granular solid (77% yield from vinylacetamide, 59% from acetaldehyde). Steps B and C are repeated and the products are pooled.

D. Conversion of Poly(vinylamine Hydrochloride) to Sulfonamido Adduct.

125 g of the poly(vinylamine hydrochloride) of Part C is added with 1.0 liters of water to a 12 liter stirred flask. The pH is raised from 2.5 to 10.0 by addition of 0.8 N NaOH. Then 350 ml of tetrahydrofuran is added to yield a solution of the free amine.

Next, 404 g of N-acetylsulfanilyl chloride is added slowly, pH being controlled at 9.09.5 by NaOH addition. 1250 ml of THF is added to maintain a solution.

Additional NaOH is added to carry the pH to l0.t 1.0. THF is stripped off under vacuum. A precipitate forms and is collected and found to be the polymer.

This reaction is repeated five times.

E. Hydrolysis The individual products of the six runs of Part D are hydrolyzed.

To a flask is added one of the reaction products, 2.9 liters of water, and 786 ml of concentrated hydrochloric acid. The mixture is refluxed for six hours to yield a solution of the amine:

(This reaction is repeated with each product of Part D).

F. Diazotization and Coupling One of the solutions of PartE containing 1.6 equivalents of polymer is cooled to 20"C; 377 ml of 5 N NaNO2 is added with stirring. The mixture is stirred for 30 minutes. The solution is then transferred to a solution of 484 g (1.15 equivalents) of Schaeffer's salt in 4.5 liters of water and 12.8 equivalents of NaOH at a temperature of about 5--10"C (maintained by ice addition). This solution is stirred for 45-60 minutes. NaOH is added to pH 12. About 18 liters of crude reaction product containing about 4% w yellow-colored dye is obtained.

This product, additionally, contains sodium hydroxide, sodium chloride, unreacted Schaeffer's salt and monomeric sunset yellow. The amount of organic impurities is about equal to the amount of polymeric colorant. The amount of inorganic salts is also about this level.

G. Purification The solutions of Part F are ultrafiltered using a Romicon Hollow Fiber ultrafiltration cell. This cell contains 25 square feet of Romicon PM-30A membrane, an anisotropic membrane having a molecular weight cut off of 30,000.

This membrane is a thin channel membrane with an I.D. of 0.40 mm. Inlet pressure is 88-110 psi. pH of the solutions was high (pH 12.5). The ultrafiltration is conducted at somewhat elevated temperature 3(50C. Each product of Part F has a pH of about 12 and a volume of about 35 liters. The solutions are pre-filtered through a 25y filter and introduced into the ultrafiltration retentate tank. The material is first concentrated to a volume of about 10 liters in the ultrafiltration unit. The remainder of the separation is carried out in a diafiltration made using deionized water as make up to maintain the retentate volume at 10 liters. Sodium chloride, other inorganic impurities and low molecular weight colored impurities are removed in the ultrafiltrate. Ultrafiltration is stopped when no appreciable color or salt appears in the ultrafiltrate. The retentate is brought to pH 7 and concentrated to 4 liters. This concentrate is removed and filtered through a coarse sintered glass filter. This process is repeated for each product of Part F.

H. The concentrates ol rart G are spray-dried. A Nichols Niro laboratory spray drier is employed. This drier has an inner drying cylinder which is 31 inches in diameter and an atomizer which is run at 38,000 rpm. Inlet temperature is 200"C.

Collector outlet temperature is 11W120 C. The feed concentration is W6%. The liquid feed rate is .791.3 liters per hour. A 5--50 micron particulate solid product in accord with this invention results. This colorant is water soluble and has a "Sunset Yellow" color. It contains less than 1% (basis colorant) of organics of molecular weight below 1000 Daltons and less than 3% of organic salts.

I. When 100 ppm wt of this colorant is dissolved in sweetened orangeflavored carbonated water an orange soda results. When 500 ppm wt (basis dry powder) of the colorant is added to a gelatin dessert powder, a product results which yields orange gelatin dessert when mixed with water and gelled. When an aqueous solution of 1000 ppm wt of this colorant is formed and cotton fiber and paper are dipped in it an orange color is imparted to the cotton fiber and paper.

EXAMPLE II This example illustrates the production of a high purity yellow orange colorant of the formula

A. Colorant Precursor Preparation A 5% solution in dry DMF of polyepichlorohydrin (HydrinTM-100) is prepared.

An amount of this solution to provide 287 g of polyepichlorohydrin is stirred at 18"C while 922 g of solid salt,

is added. The mixture is heated gradually to about 109"C over a 5 hour period. The mixture is heated at 100"C overnight. The next morning the product is dumped into pH 10 water to precipitate. The very wet solid is collected and dried in a 40"C vacuum oven to give 770 g of a polymeric colorant precursor of the formula

B. Colorant Production The polymer of Part A (602 g) is dissolved in 2250 ml of concentrated hydrochloric acid at 500C. About 1-1/2 liters of water is added and the mixture is refluxed for two hours to yield the polymeric amine,

The solution is cooled to e5"C and 178 g of sodium nitrite is added in a liter of water to diazotize the amine group and yield a solution of

This solution is slowly run into 38 liters solution of Schaeffer's salt (628 g) of pH 1W13. Aqueous base is added along with the acidic polymer solution to maintain this pH. The resulting product is 84 liters of a solution of the polymeric colorant,

This solution contains appreciable NaCI, base, other inorganic salts, Shaeffer's salt and other low molecular weight organic impurities.

C. Ultrafiltration The solution of Part B is filtered through a 25 micron filter to remove solids.

The solution is then ultrafiltered.

This ultrafiltration is carried out using the apparatus of Example I and two thin channel membrane modules-one holding an Amicon PM-10 anisotropic ultrafiltration membrane, the second holding an Amicon PM-30 anisotropic ultrafiltration membrane. The solution pH is adjusted to about 12 and placed in the retentate tank and ultrafiltered with an inlet pressure of 85 psig and an outlet pressure of 15 psig. Operating conditions are varied as shown in Table I.

TABLE I Ultrafiltration Operating Conditions Yield Diafiltra Aug of Overall of Diafiltra- tion conc.

Run Flux Time Product tion temp. Polymer No. Membrane MVsec Mins. g "C. g/100 ml Gl PM30 9.3 315 194 40 1.3 when G3 PM10 7.3 700 112 40 0.75w% G5 PM30 10.1 160 33 32 0.22w% G6 PM10 6.7 315 44 43 0.29w% G9 PM30 9.8 203 120 36 1.2 w% G10 PM30 9.9 240 115 35 1.2 w% Gll PM30 8.7 180 190 36 1.9 w% G12 PM30 8.0 135 176 36 1.8 w% G13 PM30 7.5 240 insoluble 36 Water is removed initially and later low molecular weight organic and inorganic impurities are taken out. The two membranes effect the required separation. The PM-30 membrane is somewhat more efficient than the PM-10 membrane giving somewhat higher flux rates and achieving the separation in about 1/2 the total number of diafiltrations. The products are essentially clean of materials below 1000 Daltons by GPC analyses. The solutions are neutralized to pH 7 while ultrafiltering. About 7-10% of the total fed material is removed via ultrafiltration.

D. Spray Drying The retentate products of Part C are spray dried in the apparatus set out in Example I. The spray drying operating conditions and product properties are set forth in Table II.

TABLE II Spray Drier Operating Conditions Run Number Gl-G6 G9 G10 G11 G12 Temperature inlet air ("C) 170 205 208 207 202 Temperature exit air ("C) - 104 100 111 93 Flow rate (liters/hr) - 1.26 1.49 1.28 2.03 Feed concentration (w%) - 6.3 5.5 9.0 8.0 Yield(g) 112 120 115 190 176 % Moisture 11.4 7.9 5.9 7.4 9.1 Particle size (flu) 5-25 5-26 4-30 5-35 5-25 The products are very hygroscopic and quickly become damp when exposed to the atmosphere, as can also be seen in Table II. They are, however, solid particulate products in accord with the invention. They contain less than 1% of polymeric colorant monomers, salts or other nonwater compounds having a molecular weight below 1000.

EXAMPLE III A. Preparation of Copolymer Backbone To 2304 g of acetamide (technical) in a 12 liter reaction flask is added 62.2 ml of 6M aqueous sulfuric acid followed immediately by 661 g of acetaldehyde (99+ x). 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 5 minutes to a temperature of 107"C and a mixture of 150 g calcium carbonate (precipitated chalk) and 150 g of CeliteR 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 1850C. A fraction made up of vinylacetamide and acetamide is taken overhead, analyzed by NMR and found to contain 720 g of vinyl-acetamide and 306 g of acetamide. A portion of this pooled material is dissolved in isopropanol, cooled, and filtered to yield a stock solution This stock solution is analyzed and found to be 4.1 molar in vinylacetamide.

Into a five liter flask is added 505 ml (272 g) of a vinylacetamide solution obtained by stripping isopropanol from 900 ml of the above stock solution (containing 3.69 moles of vinylacetamide). AIBN (15 g) in 1500 ml of water is added followed by 1279 g of 25% W sodium vinyl sulfonate in water (Research Organic Corporation) and a liter of water. This is 3 equivalents of sulfonate per 2 equivalents of vinylacetamide. Following deoxygenation, the mixture is heated to 65"C and there maintained with stirring for 3 hr. This reaction mixture is then reduced to 2/3 volume, solid AIBN is removed and the liquid added to 8 gallons of isopropanol. The copolymer precipitate is collected and dried in vacuum to yield 865 g of solid copolymer (MW 6.6xl04). Whenever an experimental molecular weight is given in this specification it is derived by gel permeation techniques. In the primary technique, a silanized porous glass support is used with a 0.01 M LiBr in DMF eluent. Detection is by refractometer with standarization being based on suitable purchased poly(styrene) or poly(styrene sulfonate) standards.

Into a two liter flask is added 863 g of the just-noted solid product, 2.5 liters of water and a liter of concentrated hydrochloric acid. The mixture is refluxed (99 110"C) for about 24 hours and cooled, the solid precipitate is washed, and dissolved in 3 liters of 10% NaOH.Tliis mixture is added to about twelve liters methanol to give 400 g of fine solid precipitate.

B. Preparation of Chromophore Into a 5 liter kettle is charged 750 g of l-amino-2-methyl-4-bromoanthraquinone (Sandoz AMBX), 1550 g of ethyl acetoacetate, 580 g of nitrobenzene, and 196 g of sodium acetate. The mixture is deoxygenated and heated to 150+ over about 4 hr. During the last 2-1/2 hours, 385 ml of distillate is collected. The product is cooled, collected on a filter and washed with acetone and water and dried to yield 830 g of the chromophore

C. Attachment of Chromophore 300 g of the copolymer of Part A is dissolved in 4.2 liters of 1 normal NaOH and the mixture is heated to 900C. Then 480 g of the chromophore of Part B and 20 g of CuCl2 catalyst are added. The mixture is heated at 90--1010C for 3-1/2 hours, while an addition 4 liters of NaOH and an addition 20 g of catalyst are added. The mixture is cooled by adding 10.7 kg of ice. HCI, NaOH and acetic anhydride are added to buffer the solution at pH 10.

D. Ultrafiltration Five gallons of the solution of Part C is prefiltered three times with a 0.25 micron filter to remove solids. This material contains an estimated 412 g of polymeric colorant of the formula,

It also contains unreacted chromophore, chromophore degradation products, salts, organic solvents and other impurities. To the filtered material is added 660 ml of 19.1 N NaOH and 2.2 liters of pyridine.

This material is charged to an ultrafiltration unit similar to the device set forth in Example I. This unit however, has two parallel filtration cells with a total membrane area of 47 sq. ft. The membrane is PM-10.

The mixture is first concentrated to four gallons. Then ten diavolumes of diafiltration are carried out using the following make up solvent: 10 gal. H2O, 1 gal.

pyridine, 800 ml of 19.1 N NaOH. This removed the colorant impurities. Then 7 diavolumes of diafiltration are performed with a water make up. Next, the solution is brought to pH 7 with HCI and 5 additional diavolumes of water are passed to remove neutralization products.

The retentate is then passed over a 50 cm by 1.2 cm diameter bed of 4.5 kg of macroporous strong acid ion exchange resin, A 6 MP50, from Bio-Rad Laboratories, to remove copper. The resin bed is rinsed with 3 liters of water. The rinse is added to the product.

E. Spray Drying.

The combined solution of Part D (6.8 gallons) is spray dried in a Bowen Spray AireR dryer. Inlet temperature is 265"C, outlet is 147"C; 100 ml/minute is fed. The resulting final product is a dry solid having the following analysis: Water 7.5 Insolubles 0.02% Salt 0.073 E Monomers and materials less than 1000 mw 0.24% Polymeric colorant with molecular wt. above 1000 92.2% We are aware of the "Colorants in Food Regulatlons" No 1t40, of 1973 and make no claim to the use of the invention in contravention of these regulations; subject to this disclaimer.

WHAT WE CLAIM IS: 1. A water-soluble polymeric colorant having an average molecular weight of greater than 5,000. Daltons comprising optically chromophoric organic groups covalently bonded to a non-chromophoric organic backbone said colorant being further characterized as containing not more than 1.0% by weight, basis total organics, of total polymeric colorant, polymeric colorant precursors, and degradation products having a molecular weight of less than 1,000 Daltons and as containing not more than 3% weight, basis total solids, of inorganic or organic salts.

2. A polymeric colorant as claimed in Claim 1, wherein said optically chromophoric organic group is an azo chromophoric group.

3. A polymeric colorant as claimed in Claim 1, wherein said optically chromophoric group is an anthraquinone chromophoric group.

4. A polymeric colorant as claimed in any preceding claim, wherein said nonchromophoric organic backbone is polyaminoethylene, or is a copolymeraof aminoethylene and ethylenesulfonate.

5. A polymer colorant as claimed in Claim 1 and substantially as described in any one of the specific examples herein before set forth.

6. A process for separating a water-soluble polymeric colorant of average molecular weight greater than 5,000 Daltons from a mixture containing said polymeric colorant and polymeric colorants of molecular weight less than 1,000 Daltons which comprises (i) forming an aqueous feed solution of said mixture and not containing less than 0.5% by weight, basis solution, of an alkali metal ionic compound selected from the soluble inorganic salts and hydroxides of the alkali metals; and (ii) subjecting said aqeous feed solution to ultrafiltration to form an aqueous filtrate containing said polymeric colorants of molecular weight less than 1,000 Daltons and a retentate containing polymeric colorant of average molecular weight greater than 5,000 Daltons and not more than 1.0% by weight, basis total polymeric colorant of polymeric colorant precursors or degradation products thereof of molecular weight less than 1,000 Daltons and not more than 3% by weight, basis total solids of inorganic or organic salts.

7. A process as claimed in Claim 6 wherein said ultrafiltration is effected through an anisotropic microporous polymer membrane.

8. A process as claimed in Claim 6 or 7 wherein said ultrafiltration is effected

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. It also contains unreacted chromophore, chromophore degradation products, salts, organic solvents and other impurities. To the filtered material is added 660 ml of 19.1 N NaOH and 2.2 liters of pyridine. This material is charged to an ultrafiltration unit similar to the device set forth in Example I. This unit however, has two parallel filtration cells with a total membrane area of 47 sq. ft. The membrane is PM-10. The mixture is first concentrated to four gallons. Then ten diavolumes of diafiltration are carried out using the following make up solvent: 10 gal. H2O, 1 gal. pyridine, 800 ml of 19.1 N NaOH. This removed the colorant impurities. Then 7 diavolumes of diafiltration are performed with a water make up. Next, the solution is brought to pH 7 with HCI and 5 additional diavolumes of water are passed to remove neutralization products. The retentate is then passed over a 50 cm by 1.2 cm diameter bed of 4.5 kg of macroporous strong acid ion exchange resin, A 6 MP50, from Bio-Rad Laboratories, to remove copper. The resin bed is rinsed with 3 liters of water. The rinse is added to the product. E. Spray Drying. The combined solution of Part D (6.8 gallons) is spray dried in a Bowen Spray AireR dryer. Inlet temperature is 265"C, outlet is 147"C; 100 ml/minute is fed. The resulting final product is a dry solid having the following analysis: Water 7.5 Insolubles 0.02% Salt 0.073 E Monomers and materials less than 1000 mw 0.24% Polymeric colorant with molecular wt. above 1000 92.2% We are aware of the "Colorants in Food Regulatlons" No 1t40, of 1973 and make no claim to the use of the invention in contravention of these regulations; subject to this disclaimer. WHAT WE CLAIM IS:

1. A water-soluble polymeric colorant having an average molecular weight of greater than 5,000. Daltons comprising optically chromophoric organic groups covalently bonded to a non-chromophoric organic backbone said colorant being further characterized as containing not more than 1.0% by weight, basis total organics, of total polymeric colorant, polymeric colorant precursors, and degradation products having a molecular weight of less than 1,000 Daltons and as containing not more than 3% weight, basis total solids, of inorganic or organic salts.

at a temperature of from 150C to 75QC and a~pressure upstream df the polymer membrane of from 25 psig to 200 psig.

9. A process as claimed in Claim 8 wherein said aqueous feed solution contains from 0.5 to 15 by weight, basis feed solution, of polymeric colorant of molecular weight greater than 1,000 Daltons.

10. A process as claimed in Claim 9 wherein during ultrafiltration the volume of retentate is maintained by addition of water.

11. A process as claimed in Claim 10 wherein following ultrafiltration, water is removed from said retentate.

12. The process for preparing a dry particulate water-soluble polymeric colorant suitable for use as a nonabsorbable food colorant and having a molecular weight greater than 1000 Daltons which comprises: (i) forming a feed solution comprising an aqueous solvent, from 0.1 to 20% by weight (basis solution) of polymeric water-soluble colorant having a molecular weight above 1000 Daltons, from 0.1 to 20% by weight (basis solution) of water-soluble polymeric colorant plus monomeric organic chromophore having a molecular weight below 1000 Daltons, and from 0.1 to 20% by weight (basis solution) of inorganic salts; (ii) contacting said feed solution withan anisotropic semipermeable polymeric membrane at an upstream pressure of from 25 to 200 psig thereby forming an aqueous ultrafiltrate phase which passes through said membrane comprising solvent, water-soluble polymeric colorant plus monomeric organic chromophore having a molecular weight of less than 1000 Daltons, and inorganic salts, and a retentate phase which does not pass through said membrane comprising aqueous solvent, water-soluble polymeric colorant having a molecular weight greater than 1000 Daltons, and not more than 1%, basis polymeric colorant having a molecular weight greater than 1000 Daltons, of water-soluble polymeric colorant and monomeric organic chromophore having a molecular weight below 1000 Daltons and not more than 2% of inorganic or organic salts; (iii) recovering said retentate phase; and (iv) subiecting the recovered retentate phase to spray-drying to remove aqueous solvent as a vapor phase and form a particulate solid phase consisting essentially of polymeric nonabsorbable water-soluble polymeric colorant of molecular weight greater than 1000 Daltons.

13. A process as claimed in Claim 12 wherein said step (ii) is effected at a temperature of from 15"C to 750C.

14. A process as claimed in Claim 12 or 13 wherein the aqueous solvent in the feed solution in step (i) consists essentially of water and up to 15% by weight of organic solvents.

15. A process as claimed in Claim 6 or Claim 12 and substantially as described in any one of the specific examples herein before set forth.