PROCESS FOR REMOVING IMPURITIES FROM POLYALKYLENEOXY COLORING AGENTS

Abstract: A process is provided for removing impurities from a polyalkyleneoxy coloring agent, which comprises heating a crude reaction product containing the polyalkyleneoxy color­ ing agent and impurities to a temperature at which the crude reaction product separates into two liquid phases, one phase containing the coloring agent in relatively pure form and the other phase containing the impurities; and separating the phase containing the coloring agent from the phase contain­ ing the impurities.

Description: The present invention relates to a process for purifying polymeric coloring agents. More particularly the present invention relates to a process for separating polymeric alkleneoxy coloring agents from impurities normally present in a crude reaction product by means of the cloud point phenomenon. Polymeric, alkyleneoxy, chromophoric group containing compounds have been known for many years as disclosed in U.S. Patent Slumber 3,157,633 to Kuhn (incorporated by reference). Typically such com- pounds may be water soluble and they have accordingly been used extensively, as disclosed by Kuhn, as fugitive tints in the textile industry because they may be easily removed from textile fibers by scouring with aqueous solutions. Recently, it has been discovered that certain polyalkyleneoxy compounds may advantageously be employed as coloring agents in resin systems where the coloring agent may react with the resin and actually be bound to the resin by covalent bonding. Such coloring agents and. methods for coloring resins are disclosed in U.S. Patent number 4,284,729 filed March 31, 1980 (incorporated by reference) to John P. Cross and George H. Britton, Jr. Unfortunately, however, the methods known in the art for preparing polyalkyleneoxy compounds, as disclosed for instance in the Kuhn patent, have typically resulted in a reaction product being provided in the form of an aqueous solution containing substantial amounts of water soluble impurities, e.g., inorganic salts, which may be detrimental in end use applications of the type disclosed in the Cross et al. application, that is where they are employed as coloring agents. It, therefore, would be higly desirable to remove those impurities from the compositions before they are actually employed for their intended end use applications. Thus, the present invention is directed to a method whereby such impurities may be removed from polymeric, polyalkyleneoxy coloring agents. According to the present invention a process is provided for removing impurities from a polyalkyleneoxy coloring agent, which comprises heating a crude reaction product containing said polyalkyleneoxy coloring agent and impurities to a temperature at which the crude reaction product separates into two liquid phases, one phase containing said coloring agent in relatively pure form and the other phase containing said impurities; and separating the phase containing said coloring agent from the phase containing said impurities. The polyalkleneoxy coloring agents of the present invention may be provided in the liquid or solid phase at ambient conditions of temperature and pressure. Preferred compounds according to the invention may be characterized by the general formula: R-(polymeric constituent-x)n where R is an organic dyestuff radical; the polymeric constituent is selected from polyalkrlene oxides and copolymers of polyalkylene oxides in which the alkarlene moiety of the polymeric constituent contains 2 or more carbon atoms, and such polymeric constituent has a molecular weight of from about 100 to about 10,000; n is an integer of from 1 to about 6; and x is selected from -OH, and and -SH. Preferred amongst the compounds of the above formula are those wherein R is attached by an amino nitrogen to the polymeric constituent. Compounds contemplated within this class are those wherein R is a nitroso, nitro, azo, including monazo, diazo and triazo, diphenylmethane, triarylmethane, zanthene, acridene, methine, thiazole, indamine, azine, oxazine, or anthraquinone dyestuff radical. A preferred method for preparing the polyalkleneoxy coloring agents which may be purified according to the present invention is to first convert a colorless intermediate compound into the corre sponding polyethyleneoxy compound and then employ the resulting compound to produce compounds having chromophoric groups in the molecule. For instance, in the case of azo dyestuffs, this may be accomplished by reacting a primary or secondary aromatic amine, preferably the former with ethyleneoxide, propyleneoxide or mixtures thereof according to procedures well 0Town in the art and then coupling the resulting compound with a diazonium salt of an aromatic amine. Some of the other classes of dyestuffs such as the anthraquinones having chlorine, bromine or iodine attached to the aromatic nucleus, may be reacted with, for instance, excess polyalkylene glycol monoamine to produce the corresponding secondary amine. The polyethyleneoxy group can be introduced in other ways to produce the polyalkyleneoxy coloring agents. For example, anthraquinone-2-carboxylic acid can be reacted with a molar excess of a polyethylene glycol having a molecular weight above about 1350, e.g., in the presence of p-toluene-sulfonic acid in a suitable solvent, e.g., dioxane or nitro-benzene, to produce the corresponding polyethylene glycol monoester of anthraquinone-2carboxylic acid. The reaction can also be conducted on other anthraquinone carboxylic acids containing one or more additional chromophoric or other non-interfering groups in the molecule. An aromatic amine, e.g., aniline or nuclear substituted aniline, can be reacted with a polyethylene glycol as described above under pressure at a temperature of about 220"C to 2300C, preferably in the presence of iodine or a copper or sodium halide as a catalyst. The resulting amine, e.g., the polyethylene glycol substituted aniline, can then be coupled with the usual diazonium salts, e.g., H acid, to produce a diazo polyalkyleneoxy coloring agent. An aromatic bromo compound, e.g., 2-bromoanthraquinone, can be reacted with polyethylene glycol in the presence of sodium at 1500C to produce the corresponding anthraquinone polyethylene glycol ether. A nitrophenol, e.g., p-nitrophenol, can be reacted with polyethylene glycol in the same manner to produce the p-nitrophenol polyethylene glycol ether. This compound can then be reduced by any of the methods well Xnoun in the art for reducing aromatic nitro groups, e.g., zinc and acetic acid, hydrogen and catalyst, to produce the corresponding p-amino compound which can then be diazotized and coupled with a suitable aromatic compound, e.g., "S' acid, to produce a polyalkyleneoxy coloring agent which may be purified according to the present invention. Typically, all of the above procedures for preparing polymeric, alkyleneoxy, chromophoric group containing compounds may result in the compound being produced in a crude reaction mixture containing substantial amounts of impurities in the form of byproducts produced during the synthesis of the desired compound. These materials are generally water soluble, e.g., inorganic salts, as is the chromophoric group containing compound making separation based on differing soltibility quite difficult if not impossible. Their presence, furthermore, is undesirable in a coloring agent product designed, for instance, for incorporation into urethanes by the formation of covalent bonds because they may interfere with the polymerization reaction. Until the present invention, furthermore, no fully satisfactory method has been available for the removal of such impurities from the reaction mixture. It has now been discovered, however, that by making use of a rather unusual property of these compounds a simple, and effective separation of the compounds from impurities present in the crude reaction mixture may be accomplished. The separation is accomplished by simply heating the crude aqueous reaction mixture at least to the cloud point. On passing the cloud point, the crude reaction mixture separates into two phases - one phase containing the colorant and a second aqueous phase containing substantial amounts of impurities such as water soluble salts. The two phases may then be separated by any of the means known in the art. Additional water may be added to the colorant containing phase and the separation may be repeated one or more times to further purify the colorant. The following examples illustrate the invention but are not to be construed as a limitation thereof. The parts and percentages are all by weight unless otherwise specified. PREPARATION I Ethylene oxide was bubbled into warm aniline under nitrogen until two molar equivalents of ethylene oxide were consumed. There was thus produced N,N-dihydroxyethylaniline, which solidified on cooling to room temperature. Similarly, meta-toluidine was treated with ethylene oxide producing N ,N-dihydroxyethyl-m-toluidine. PREPARATION II Five hundred forty-three grams (3moles) of N,N-dihydroxy- ethylaniline and 2.5 grams potasium hydroxide were placed in a 2 liter stainless steel pressure reactor equipped with an agitator gas inlet tube and vent. After purging with nitrogen, the reactor and contents were heated at 100"C under vacuum and held on temperature for 0.5 hours. The vacuum was broken with nitrogen and the reactor was heated to 15O0C. Ethylene oxide was added through the inlet tube until eight equivalents were consumed. After post reacting for 30 minutes, the mixture was subjected to vacuum for 30 minutes, then cooled to room temperature. The thus produced intermediate: EMI6.1 was an amber, freeflowing liquid. PREPARATION III The method of Preparation II was followed, using N,Ndihydroxyethyl-m-toluidine and enough ethylene oxide to add eight moles. The product was the formula: EMI6.2 and was a liquid at room temperature. EXAMPLE I To a 2 liter glass reactor was charged aniline (47.9 grams, 0.52 moles), which was cooled to OOC. Hydrochloric acid (161 grams) was added dropwise with stirring, and the resulting mixture cooled to O OC. Sodium nitrite (40.3 grams, 0.58 moles) was dissolved in water (80 milliliters) and added dropwise to the aniline solution while maintaining the temperature below 50C. B'hen addition wss complete, the mixture was stirred for 30 minutes and excess nitrite was confirmed by starch-iodide paper. Sulfamic acid was added in portions until excess nitrite was consumed. In another reactor, the intermediate of Preparation III (282 grams, 0.52 moles) was charged. A solution of sodium acetate (29.6 grams, 0.36 moles) in water (51 milliliters) was prepared. The previously prepared aniline diazonium solution was added in portions using the sodium acetate solution to maintain the pH of the coupling bath at 4-5. Temperature was maintained below 100C. The mixture was post-stirred for one hour after addition of diazonium salt as complete. The mixture was poured into a beaker and heated to 950C on a steam bath. The colorant formed a layer on top of the solution and was decanted. The thus isolated material, a dark liquid, was treated with an equal volume of water and heated to 950C whereupon the formation of two phases again occurred. This time the colorant formed a layer on the bottom. The aqueous layer was decanted and discarded. The colorant was again treated with water and two phases formed by heating to 95"C. The aqueous layer was decanted and discarded. After removing volatile components at 850C and 2 mmHg vacuum to 99.4 percent nonvolatile, a yellow colorant was obtained: EMI7.1 SAMPLE II In a manner similar to Example I, aniline and the ethoxylated intermediate of Preparation II were coupled giving a yellow colorant of the structure: EMI7.2 EXAMPLE III In a manner similar to Example I, 2-amino-5-nitroanisole and the intermediate of Preparation III were coupled giving a red colorant: EMI8.1 EXAMPLE Iv Using the methods described in U.S. Patent 4,137,243, a colorant was prepared from quinizarin and diamine of molecular weight 230 derived from a polypropylene oxide. The resulting viscous blue colorant has the structure: EMI8.2 EXAMPLE V Using standard procedures, 2-amino-6-methoxybenzothiazole was diazotized with nitrosylsulfuric acid and coupled Bith the intermediate of Preparation III at a pH of 2. After a procedure similar to that of Example I, a red colorant was obtained: EMI9.1 EXAMPLE VI Example of Incorporation into a Flexible Polyester Polyurethane Foam To a mixture of a polyester polyol of hydroxyl number 46 (100 grams), water (3.6 grams), a silicone based emulsifier (1.3 grams), stannous octoate (0.4 grams) and tertiary amine catalyst (0.3 grams) was added 0.1 gram (0.1 php) of the yellow single component liquid reactive coloring agent of Example I. The mixture was stirred for 30 seconds to ensure a homogeneous mixture. Toluene diisocyanate (45.7 grams) was added and mixing continued for 5 seconds whereupon the foam began to rise. After foam rise was completed (about 3 minutes), the foam was postcured for 8 minutes in a 1200C oven. The thus produced foam was butter yellow in color. EXAMPLE VII Incorporation into a Polyurethane Film A urethane prepolymer was prepared from 104 grams of a pol)r- propylene glycol of molecular weight 2000, 22.5 grams of toluene diisocyanate, 3.2 grams of the red coloring agent of Example III. To 30 grams of the prepolymer was added 7 drops of dibutyitin dilaurate and the resulting mixture was cast as a 40 mil film on polytetrafluoroethylene. After curing at room temperature over- night, a tough, flexible, deep red film was obtained. EXAMPLE VIII Incorporation into an Epoxy To a mixture of 68 grams of an epoxy resin derived from bis-phenol A with weight per epoxy of about 185 to 192, 54 grams of methyltetrahydrophthalic anhydride and 0.66 grams of a tertiary amine catalyst was added 1 drop of the blue coloring agent of Example IV. After curing at 1100C, a clear blue resin was obtained. EXAMPLE IX Example of Incorporation into a Polyester Polyurethane Foam A mixture of a polydiethylene adipate (equivalent weight 1066, 50 grams), N-ethylmorpholine (0.9 grams), N,N-dimethylhexadecylamine (0.05 grams), a mixture of nonionic and anionic surfactants and the colorant of Example I (0.25 grams) was blended until the components were homogeneous. To this mixture was added toluene dilsocyanate (22.9 grams) and mixing was continued for 5 seconds. The mixture was poured into a container and allowed to rise forming a yellow flexible urethane foam. EXAMPLE X Example of Incorporation into a Reaction Injection Molding (RIM) Formulation A mixture was prepared of an acrylonitrile and styrene modified polyol (equivalent weight 2000, 42.5 grams), a mixture of short diols (equivalent weight 48, 7.5 grams), methylene chloride (1.0 grams), dibutyltin dilaurate (1 drop) and 0.25 grams of the colorant of Example V. The mixture was blended until homogeneous. To this mixture was added a modified diphenylmethane diisocyanate (equivalent weight 147, 26.6 grams) and blending continued for 5 seconds to ensure homogeneity. After approximately 15 seconds the mixture rapidly tripled its volume and cured. The thus formed polymer was deep violet in color. Upon slicing, it was evident that the color was distributed evenly throughout the structure.

Claims: CLAIMS 1. A process for removing impurities from a polyalkyleneoxy coloring agent, which comprises heating a cnlde reaction product containing said polyalkyleneoxy coloring agent and impurities to a temperature at which the crude reaction product separates into two liquid phases, one phase containing said coloring agent in relatively pure form and the other phase containing said impurities; and separating the phase containing said coloring agent from the phase containing said impurities. 2. The process of Claim 1 wherein said polyalkyleneoxy coloring agent is a reactive coloring agent. 3. The process of Claim 1 wherein said polyalkyleneoxy coloring agent is selected from compounds characterized by the general formula: R-(polymeric constituent-x) where R is an organic dyestuff radical; the polymeric constituent is selected from polyalkylene oxides and copolymers of polyalky- lene oxides in which the alkylene moiety of the polymeric constituent contains 2 or more carbon atoms and such polymeric constituent has a molecular weight of from about 100 to about 10,000; n is an integer of from 1 to about 6; and x is selected from -OH, -NH2, and -SH. 4. The process of claim 2 wherein R is attached by means of an amino nitrogen to the polymeric constituent. 5. The process of Claim 2 wherein R is selected from nitroso, nitro, azo, including monazo, diazo and triazo, di phenylmethane, triarylmethane, zanthene, acridene, methine, thiazole, indamine, azine, oxazine, or anthraquinone dyestuff radical. 6. A process for removing impurities from a polyalkyleneoxy coloring agent, which comprises converting a colorless intermediate compound into the corresponding polyalkyleneoxy compound; employing the resulting compound to produce compounds having chromophoric groups in the molecule in a crude reaction mixture conatining impurities; heating the crude reaction mixture to a temperature at which the crude reaction product separates into two liquid phases, one phase containing said coloring agent in relatively pure form and the other phase containing said impurities; and separating the phase containing said reactive coloring agent from the phase containing said impurities. 7. The process of Claim 6 wherein said polyalkyleneoxy coloring agent contains an azo group as the chromophoric group; said colorless intermediate compound is an aromatic amine selected from primary or secondary amines; said aromatic amine is reacted with an alkylene oxide selected from ethylene oxide; propylene oxide and mixtures of ethylene oxide and propylene oxide; and the resulting compound is coupled with a diazonium salt of an aromatic amine.

Inventors: BRENDLE, RALPH NOBLE, CROSS, JOHN PARSON
Applicants: MILLIKEN RESEARCH CORPORATION
Application year: 1982
Main classification: C09B67
IPC codes: C09B69, C09B1, C08K5, C09B67, C09B29