WO2017072788A1

WO2017072788A1 - Improved optical brightening agent for detergent formulations and a process for preparing the same

Info

Publication number: WO2017072788A1
Application number: PCT/IN2016/050343
Authority: WO
Inventors: Abhay Bhalchandra DESHPANDE; Milind Narayan KOLHE; Dada Sambhaji JADHAV; Hemendra Vasant GANU; Madhukar Sahdeo DUDHANE
Original assignee: Deepak Nitrite Limited
Priority date: 2015-10-07
Filing date: 2016-10-07
Publication date: 2017-05-04
Also published as: WO2017072788A4

Abstract

The present invention relates to a process for preparing disodium 4,4'-bis(4-anilino-6-morpholino-s- triazin-2-ylamino)-2,2'-stilbene disulphonate in the β crystal form, the process comprising subjecting disodium 4,4'-bis (4:anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate in the a crystal form to steam distillation. It also discloses a process to get formulations based on disodium 4,4'-bis(4- anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate, with substantially lower content of the hazardous amines such as aniline and morpholine.

Description

IMPROVED OPTICAL BRIGHTENING AGENT FOR DETERGENT FORMULATIONS AND A PROCESS FOR

PREPARING THE SAME

Field of the invention

The present invention relates to a process to prepare β crystal form of disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate, which is an optical brightening agent used in detergent compositions. It also discloses a process to get formulations based on disodium 4,4'-bis(4- anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate, with substantially lower content of the hazardous amines such as aniline and morpholine.

Background of the Invention

Anilino-substituted bistriazinyl derivatives of 4,4'-diaminostilben-2,2'-disulphonic acid based on cyanuric chloride (CC) and disodium 4,4'-diaminostilbene-2,2'-stilbene disulphonate (Na-DASDA) are an important class of optical brightening agents used for enhancing the whiteness in the applications like paper, paperboard, textile and detergents. Disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate, (CI 71) is an important member of the anilino-substituted bistriazinyl derivatives of 4,4'-diaminostilben-2,2'-disulphonic acid optical brightening agents. It is also one of the most important optical brightening agents incorporated in the detergent compositions to impart enhanced whiteness to the textile goods. Apart from cyanuric chloride and Na-DASDA, the process for the manufacture of CI 71 also uses aniline and morpholineas raw materials at different stages of synthesis.

In the most widely employed process for the manufacture of CI 71, two moles of cyanuric chloride, in the form of aqueous suspension, are reacted with a mole of disodium 4,4'-diaminostilbene-2,2'-stilbene disulphonate followed by two mole of aniline and finally two mole of morpholine at different temperatures and pH conditions. The product is then formulated as per the requirement and finally dried, often using a spray dryer, before being supplied to the detergent industry. This manufacturing process is well known in the art and is followed with some minor modifications by the manufacturers all over the world. It is a common practice to use a little excess of morpholine during the last step of the reactionso as to drive the reaction to completion. Further, the stoichiometric yield of CI 71 by the conventional processes is never 100%. The conventionally known processes for the manufacture of CI 71 therefore inadvertently leave traces of the unreacted amines in the final dried product that is subsequently added in the detergent formulations. Since majority of the detergents available in the market have CI 71 as one of their components, these contaminants find their way to the house-hold clothing and pose a serious health hazard to the end user as the clothes are in intimate contact with the skin of the wearer.

Aniline is severely irritating to mucous membranes and affects the eyes, skin, and upper respiratory tract in humans. (U.S. Environmental Protection Agency. Health and Environmental Effects Profile for Aniline. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1985.). Significant amounts of aniline can be absorbed through the skin. (U.S. Department of Health and Human Services, Hazardous Substances Data Bank, National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.). Environment protection Agency (EPA) considers aniline to be a probable human carcinogen and has ranked it in EPA's Group B2. (U.S. Environmental Protection Agency, Integrated Risk Information System (IRIS) on Aniline, National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999.)

Morpholine is also known to be a hazardous substance. It is highly irritating and airborne exposure to morpholine can cause irritation of the skin and eyes (An assessment of the health risks of morpholine and diethylaminoethanol, National Research Council (U.S.), Committee on Toxicology, National Academies, 1983). It is a primary skin irritant and induces hypersensitive responses. Persons with existing skin disorders may be more susceptible to the effects of this agent (Occupational health guideline for morpholine, U. S. Department of Labor). Morpholine is also known to cause respiratory irritation in animals. In persons with impaired pulmonary function, especially those with obstructive airway disease, breathing of morpholine might cause exacerbation of symptoms due to its irritant properties.

Apart from health hazards, these amines also result in undesirable consequences in the detergent formulation which gives rise to quality concerns in the detergent formulation. The principle undesirable consequences are discolouration and generation of malodour in the detergent formulation on storage. Therefore, it is highly desirable to minimise the level of aniline and morpholine in the final dried form of CI 71. Surprisingly, there is no report in the literature that even takes a note of such concern leave alone a serious effort for the minimisation of these contaminants in the final dried form of this optical brightening agent.

Another important aspect of the optical brightener agents is that the wet cake obtained at the end of synthesis is in the unstable a crystal form, which is in an amorphous or poorly crystallised form and is bright fluorescent yellow in colour. Incorporation of such CI 71 in a crystal form into the detergent formulations results in a noticeable yellowing of the detergent formulation. Thus, in order to improve the whitening efficiency of CI 71, it is desirable to convert the a crystal form into a β crystal form as the β crystal form is white to very slight cream coloured and has a well-defined crystal structure. There are several processes reported in the literature for the transformation of the crystal forms of Anilino-substituted bistriazinyl derivatives of 4, 4'-diaminostilben-2, 2'-disulphonic acid.

US 4549980 discloses a process for the crystal modification of optical brighteners, specially CI 205. It teaches the use of electrolytes to inhibit the water solubility of the brightener during the modification. The quantity of the electrolyte, trisodium phosphate used during the process is fairly high. Furthermore, the downstream processing to recover the product is either by spray drying or by filtration, followed by vacuum drying. It should be noted that the electrolyte used during the process is either released into the effluent during filtration or remains in the dry product obtained at the end of spray drying and finds entry into the detergent formulations only to be released into the effluent during application.

US 4271036 discloses a process for the white modification of a series of optical brighteners including CI 71. The process involves heating a mixture of the optical brightener with oxyalkylate at temperatures ranging from 80°C to 130°C for a period of up to 2 hours to achieve the white modification. The quantity of the oxyalkylate used during the process is substantially high, ranging from 10 to 13 times the quantity of the optical brightener. The final product is recovered by treatment of the waxy mass thus obtained with dry ice and is in the form of a 7.5% mixture with the oxyalkylate. Although the said mixture can be directly incorporated into the detergent formulation, since it is in a substantially diluted form, it calls for significant transportation costs. It also reduces the throughput of the equipment used for the manufacture of the optical brightener. Thus, the disclosed process is not suitable for the manufacture of the optical brighteners in commercially desired concentrated forms apart from being tedious.

US 4326982 discloses a process for the white modification of CI 71 to get the desired β crystal form in the form of fine powder with a particle size of 1μ to 10μ. The process involves the use of a bead mill to grind the optical brightener in the form of a suspension in water along with certain additives with the help of glass beads at 80°C for 5 hours. At the end, the product is recovered by spray drying. Although the process is suitable for the production of the optical brightener in the concentrated form, it requires a bead mill with a low throughput and a substantially high energy cost. CN 101468971 discloses a process for the crystal modification to β crystal form of CI 210 that involves washing of the wet cake of the optical brightener with salt water followed by vacuum drying. There is a generation of significant quantity of effluent during the process, thereby increasing the effluent treatment and disposal cost apart from the need of a vacuum dryer that makes the process even more cost intensive.

US 3951960 and US 4005026 disclose the novel crystalline forms of disodium 4,4'-bis(4-anilino-6- morpholinos-triazin-2-ylamino)-2, 2'-stilbenedisulphonate and disodium 4,4'-bis(4,6-dianilino-s-triazin-2- ylamino)-2,2'-stilbenedisulphonate. The disclosed process involves the use of either aniline or morpholine in quantities as high as 3 mole per mole of the optical brightener. It also involves heating the slurry of the optical brightener along with the added amines to 125°C to 135°C in a pressure reactor for extended time to achieve the white modification. After the desired modification is achieved the product is recovered by filtration and needs extensive washing with hot water with dissolved salt till the filtrate is neutral to Brilliant Yellow indicator and colourless. The process thus inevitably generates a large quantity of wash water that is contaminated with the hazardous amines. Although the quantity of residual amines left over in the final product after filtration, washing and drying is not mentioned in the document, it is expected to be significant.

CN 102504601 discloses a novel process for the production of several optical brighteners, including CI 71 in the desired β crystal form. The process involves the addition of a CI 71 in β crystal form as a slurry in water before the third condensation reaction during the production of CI 71. The quantity of the seed crystal form is up to 20% by weight of the final expected quantity of the product and is added as 10-50% aqueous slurry. The final reaction mass is refluxed for 6hours to complete the process. It is disclosed that the product formed during the process is already in the desired β crystal form and thus does not require an additional processing step for the crystal modification. However, the said process reduces the throughput of the equipment by up to 20% as the seed slurry adds to the volume. Furthermore, the reaction mass at the end of process needs to be filtered to recover the product and the product needs to be dried below 70°C, which takes a long time to get the final dried product.

The average aniline and morpholine content found in the optical brightening formulations based on CI 71 synthesised as per the processes currently known in the art is 30ppm to 40ppm and 20ppm to 50ppm, respectively. Therefore, there is a need for a process to produce disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate (CI 71) in the β crystal form which results in the optical brightening agent formulation with reduced content of amine impurities, particularly reduced content of aniline and morpholine.

Summary of the Invention

An embodiment of the present invention relates to a process for preparing β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate , the process comprising subjecting a crystal form of disodium 4,4'-bis (4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate to steam distillation.

Another embodiment of the present invention relates to a process to prepare β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate having less than 5 ppm of aniline and morpholine, the process comprising successively reacting cyanuric chloride with 4,4'-diaminostilbene-2,2'-disulphonic acid disodium salt followed byaniline to obtain a slurry of disodium 4,4'-bis(4-chloro-6-anilino-s- triazin-2-ylamino)-2,2'-stilbenedisulphonate; treating the slurry with morpholine to obtain a reaction mass comprising of a crystals of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate; subjecting the reaction mass to steam distillation to remove the residual aniline; and wherein mole ratio of cyanuric chloride to aniline and cyanuric chloride to morpholine is reduced.

Detailed Description of the Invention

An embodiment of the present invention relates to a process for preparing β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate , the process comprising subjecting a crystal form of disodium 4,4'-bis (4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate to steam distillation. In the aforesaid embodiment, disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'- stilbene disulphonate in the a crystal form is obtained by sequentially reacting cyanuric chloride with 4,4'-diaminostilbene-2,2'-disulphonic acid disodium salt, aniline and morpholine.

Disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate is represented by the formula mentioned herein below

Another embodiment of the present invention relates to a process to prepare an optical brightening agent formulation of β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)- 2,2'-stilbene disulphonate having less than 5 ppm each of aniline and morpholine, the process comprising successively reacting cyanuric chloride with 4,4'-diaminostilbene-2,2'-disulphonic acid disodium salt followed by the addition of aniline to obtain a slurry of disodium 4,4'-bis(4- chloro-6-anilino-s-triazin-2-ylamino)-2,2'-stilbenedisulphonate; treating the slurry with morpholine to obtain a reaction mass comprising of a crystals of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate; subjecting the reaction mass to steam distillation to remove the residual aniline; and wherein mole ratio of cyanuric chloride to aniline and cyanuric chloride to morpholine is reduced.

In the aforesaid embodiment, a first condensation is carried out by adding a solution of 4,4'- diaminostilbene-2,2'-disulphonic acid disodium salt to the cyanuric chloride suspension in water at temperatures between 0°C to 5°C and at a rate so as to complete the addition in 3 hours. The pH of 4 to 5 is maintained by the simultaneous addition of 25% soda solution. The reaction mass obtained is maintained at a temperatures below 5°C after the addition till 4,4' - diaminostilbene-2,2' - disulphonic acid can no longer be detected, as confirmed by a negative diazo test.

Cyanuric chloride suspension in water used in the aforementioned embodiment is prepared by charging water and crushed ice into the reactor equipped with an efficient agitator, a thermowell and an addition port. The reaction product of dodecyl alcohol and ethylene oxide is added as a wetting agent and the agitation is started. Cyanuric chloride is then introduced into the reactor and the mixture is agitated for approximately 30 minutes to get a fine suspension of cyanuric chloride in water. During this reaction the temperature is maintained between 0°C to 5°C.

The pH of the reaction mass obtained after adding a solution of 4, 4'-diaminostilbene-2, 2'-disulphonic acid disodium salt to cyanuric chloride suspension is then raised to 7 to 7.5 using 30% sodium hydroxide solution. A second condensation is carried out by adding aniline over a period of 30 minutes and the pH of the reaction mass is maintained between at 7 to 8 by simultaneous addition of 30% sodium hydroxide solution to the reaction mass at a temperature of approximately 7°C to 30°C. The temperature of this reaction mass is maintained at this temperature for a further 30 minutes. At the end of the maintenance, the reaction mass is then heated to a temperature of 85°C and maintained for 30 minutes to obtain a white slurry of intermediate disodium 4,4' - bis (4-chloro-6-anilino-s-traizin-2-ylamino)-2,2'- stilbene disulphonate.

The slurry of intermediate disodium 4,4' - bis (4-chloro-6-anilino-s-traizin-2-ylamino)-2,2'-stilbene disulphonate obtained is settled for approximately 30 minutes and the supernatant liquid is discarded to get a slurry of concentration suitable for obtaining 20 to 28%, preferably 22 to 26%, more preferably 24% aqueous suspension of the product at the end of the third condensation. This slurry is then treated with morpholine to obtain a reaction mass comprising of a crystals of disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate.

Alternatively, the slurry of intermediate disodium 4,4' - bis (4-chloro-6-anilino-s-traizin-2-ylamino)-2,2'- stilbene disulphonate is filtered to get a wet cake which is reslurried in water so as to get 20 to 28%, preferably 22% to 26%, more preferably 24% aqueous suspension of the product at the end of the third condensation and then treated with morpholine to obtain a reaction mass comprising of a crystals of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate.

Alternatively, the process can be continued till the end of the third condensation and the yellow slurry of CI 71 in the a cystal form is separated by filteration followed by re-slurry of the wet cake in water to get 20% to 28%, preferably 22% to 26%, more preferably 24% slurry which is then subjected to steam distillation.

Treatment with morpholine is carried outat a temperature of 85 °C to 98°C at a pH of 9.5 to 10.5 which is maintained by the addition of 30% sodium hydroxide solution and once the pH of the reaction stabilizes at pH 10, the reaction mass is then maintained at 98 °C for 1 hour.

In the aforesaid embodiment the mole ratio of aniline to cyanuric chloride is less than 1, preferably 0.95 to 0.98, more preferably 0.95.

In the aforesaid embodiment, the mole ratio of morpholine to cyanuric chloride is less than 1, preferably 0.95 to 0.98, more preferably 0.95 The reaction mass comprising of a crystals of 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'- stilbene disulphonate is then subjected to steam distillation which is carried out either by introducing steam or by the addition of water into the reaction mass for 4 to 6 hours. Thus, the step of steam distillation is carried out for 4-6 hours. Further, introduction of steam or addition of water into the reaction mass is carried out with the simultaneous collection of the condensate. When steam is not used, water is added so as to maintain the water content in the reaction mass. The rate at which the water is added into the reaction mass is at the same rate as collection of the condensate.

During the step of steam distillation, the bright fluorescent yellow slurry of disodium 4,4'bis (4-anilino-6- morpholinio-s-traizin-2-ylamino)-2,2' stilbene disulphonate is transformed into fine crystals of pearl white slurry indicating a transformation of the a crystal form into the β crystal form. Further, steam distillation of the reaction mass removes the residual aniline. Thus, the unreacted aniline in the reaction mass is steam distilled to bring the aniline content in the final dried product formulation to below 5ppm.

The ratio of the quantity of condensate collected to the quantity of the disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate is 6:1 preferably 5:2 more preferably 4:1. The slurry obtained after the steam distillation is then formulated by adding the condensation product of naphthalenesulphonic acid with formaldehyde, and optionally soda ash and common salt so as to get an active content of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate on a dry basis. Total dissolved solids of the slurry is adjusted between 24% to 28% by adding the necessary quantity of water and the slurry is agitated at a temperature of 95°C to 98°C for 30 minutes and subsequently dried either by means of an hot air oven at 105°Cor spray dried to get a dried white free flowing powder.

The final dried powder of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate obtained by the process of the present invention has an aniline and morpholine content of less than 5ppm each. The content of aniline and morpholine in the final formulation is determined by the solvent extraction of the impurities in methanol using a soxhlet extractor, evaporation of methanol to concentrate the extract and finally determining the concentration of aniline and morpholine in the concentrated extract by analytical techniques like gas chromatography using standard solutions with known concentrations of aniline and morpholine in methanol, which is well known in the state of the art.

Another embodiment of the present invention relates to a process to produce disodium 4,4'-bis(4- anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate (CI71) wherein the reduced stoichiometric quantities of aniline and morpholine are used. In the aforesaid embodiment the mole ratio of aniline to cyanuric chloride is less than 1 preferably 0.95 to 0.98 more preferably 0.95. In the aforesaid embodiment, the mole ratio of morpholine to cyanuric chloride is less than 1 preferably 0.95 to 0.98 more preferably 0.95.

An advantage of the process of the present invention is that the optical brightening agent formulations based on disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate (CI 71) obtained by the process of the present invention are in the desired β crystal form and are substantially free from the hazardous residual amine impurities especially aniline and morpholine. Thus, surprisingly, the process used in the present invention results in β crystal form of disodium 4,4'-bis(4- anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate (CI 71) even without the use of extra amines; seed crystals or any other additives or the need to carry out the crystal modification in a pressure reactor. Thus, the process is simple and can be practiced in the conventional industrial atmospheric reactor.

Optionally, the invention can be practiced without any filtration step at any stage of the reaction resulting in the final reaction mass obtained as a 24% to 27% aqueous slurry of disodium 4,4'-bis(4- anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate in β crystal form, which can be dried in a spray dryer directly, optionally after addition of other additives such as the condensation product of naphthalene sulphonic acid with formaldehyde, and optionally soda ash and common salt, thus reducing the effluent generation as well as energy consumption considerably.

Further, the optical brightening agent formulation obtained from the process of the present invention can be incorporated in detergent powders or cakes by any of the process known in the art to enhance the whiteness of the textile materials.

Furthermore, the optical brightening agent formulations obtained by the process of the present invention when used in the detergent formulations do not cause any significant yellowing of the detergent powder and they lead to an excellent improvement in the whiteness of the textile materials with a marked improvement in the light-fastness as described in details in the foregoing examples.

Example 1:

200g water and 400g crushed ice was charged to a 5L glass reactor equipped with an efficient agitator, a thermowei! and an addition port with a dropping funnel. Ig of the reaction product of 1 mole of dodecyl alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started. lOOg (0.54 mole) of cyanuric chloride was introduced into the reactor and the mixture was agitated for 30minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0°C to 5°C during this time by immersing the reactor in an ice bath.

A solution of 4,4'-diaminosti!bene-2,2'-disulphonic acid disodium salt was prepared by neutralizing lOOg (0.27mo!e) 4,4'-diaminostilbene-2,2'-disu!phonic acid suspension in 840g water with 72g of 30% sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3hours. Temperature of the reaction mass was maintained between 0°C to 5°C and H between 4.5 to 5 throughout the addition by simultaneous addition of 25% soda solution. The reaction mass was maintained below 5°C after the addition till 4,4'-diaminosti!bene- 2,2'-disu!phonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The ice bath was removed and 50.3g (0.54 mole) aniline was added over a period of 30mirtutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% sodium hydroxide solution. During this time, the temperature of the reaction mass was increased to 30°C. The reaction mass was then maintained at this temperature for a further SOminutes. At the end of maintenance at 30°C, the temperature of the reaction mass was gradually increased to 85°C and maintained for 30 minutes and at the end of the maintenance, a white easily stirrabie slurry was obtained.

47g (0.54 mole) morphoiine was then added rapidly and the heating was continued till 98°C. During this time the pH of the reaction mass was maintained between 9.5 to 10.5 b the addition of 30% sodium hydroxide solution. After the pH of the reaction mass stabilised at 10, the temperature was then maintained at 98°C for Ihour.

The reaction mass was then cooled to 85°C and filtered using a Buchner funnel. The wet cake was suspended in 670g water to get a slurry and transferred to a 2L stainless steel pressure reactor. 2.5g of the condensation product of naphthalene suiphonic acid with formaldehyde, 17g soda ash and a calculated quantity of common salt was added to the slurry so as to get 67% active content of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate on a dry basis. Total dissolved solid of the slurry was adjusted between 24% to 28% by adding the necessary quantity of water and the reactor was closed. The agitation was started and the contents were heated to 120°C under autogenous pressure. The reaction mass was maintained at this temperature for 2 hours to achieve the transformation of a crystal form into the β crystal form and the mass was cooled to 85°C. The reactor was opened; the pearl white slurry thus obtained was transferred to a glass tray and dried in a hot air oven at 105°C. The dry white free flowing powder had an e-vaiue of 440. The aniline and morpholine content in the final dried product obtained was found to be 247ppm and 104ppm respectively.

Example 2:

200g water and 400g crushed ice was charged to a 5L glass reactor equipped with an efficient agitator, a thermowei! and an addition port with a dropping funnel. Ig of the reaction product of 1 mole of dodecyl alcohol with 5 mole of ethylene oxide was added as a wetting agent and the agitation was started. lOOg (0.54 mole) of cyanuric chloride was introduced into the reactor and the mixture was agitated for 30 minutes to get a fine suspension of cyanuric chloride in water. During this time, the temperature was maintained between 0°C to 5°C by immersing the reactor in an ice bath. A solution of 4,4'-diaminosti!bene-2,2'-disulphoriic acid disodium salt was prepared by neutralizing lOOg (0.27mo!e) 4,4'-diaminostilbene-2,2'-disu!phonic acid suspension in 840g water with 72g of 30% sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. Temperature of the reaction mass was maintained between 0°C to 5°C and pH between 4.5 to 5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained below 5°C after the addition till 4,4'- diaminostilbene-2,2'-disu!phonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The ice bath was removed and 50.3g (0.54 mole) aniline was added over a period of 30 minutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% sodium hydroxide solution. Temperature of the reaction mass increased to 30°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of the maintenance at 30°C, the temperature of the reaction mass was gradually increased to S5°C and maintained for 30 minutes and at the end of the maintenance a white easily stirrable slurry was obtained.

47g (0.54 mole) morpho!ine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9,5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of reaction mass stabilised at 10, the temperature was maintained at 98°C for lhour.

The reaction mass was then cooled to 85°C and filtered using a Buchner funnel. The wet cake was suspended in water so as to get a 22% to 24% slurry and transferred to a 2L glass reactor. 2.5g of the condensation product of naphthalene suiphonic acid with formaldehyde was added to the slurry. The agitation was started and the reaction mass was heated to reflux temperature. The condenser was adjusted to distillation mode and the heating was increased to initiate the water distillation at an approximate rate of 250g/h. Addition of lOOOg water was then started at a rate of 250g/h so as to maintain the water content in the reaction mass. The distillation was complete in 4hours. During this time, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate was transformed in to a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form.

The slurry thus obtained was cooled to 85°C and was formulated by the addition of 17g soda ash and a calculated quantity of common salt so as to get 67% active content of disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate on dry basis. Total dissolved solid of the slurry was adjusted between 24% to 28% by adding necessary quantit of water and the slurry was agitated at a temperature between 95°C to 98"C for 30 minutes; transferred to a glass tray and dried in a hot air oven at 105°C.The dry white free flowing powder had an e-va!ue of 436. The aniline and morphoiine content in the final dried product obtained was found to be 74ppm and 94ppm respectively.

Example 3:

200g water and 400g crushed ice was charged to a 5L glass reactor equipped with an efficient agitator, a thermowei! and an addition port with a dropping funnel. Ig of the reaction product of 1 mole of dodecyl alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started. lOOg (0.54 mole) of cyan uric chloride was introduced into the reactor and the mixture was agitated for 30 minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0°C to 5°C during this time by immersing the reactor in an ice bath. A solution of 4,4'-diaminostilbene-2,2'-disuiphonic acid disodium salt was prepared by neutralizing lOOg (0.27mo!e) 4,4'-diaminosti!bene-2,2'-disulphonic acid suspension in 840g water with 72g 30% sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. Temperature of the reaction mass was maintained between 0°C to 5°C and a pH was maintained between 4.5 to 5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained at a temperature of below 5°C after the addition till 4_/4'-diaminosti!bene-2,2'-disu!phonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The ice bath w/as removed and 47.9g (0.514mole) aniline was added over a period of 30 minutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% sodium hydroxide solution. Temperature of the reaction mass was increased to 30°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of maintenance at 30°C, the temperature of the reaction mass was gradually increased to 85°t and maintained for 30 minutes and at the end of the maintenance a white easily stirrable slurry of intermediate, disodium 4,4' -- bis (4- chloro-6-anilino-s-traizin-2-yla!Tiino)-2,2'-stiibene disulphonate was obtained. The slurry was filtered using a Buchner funnei to get a wet cake with 40% moisture content.

The wet cake was suspended in 670g water in a 2L glass reactor equipped with an efficient agitator, a thermoweil, an addition port with a dropping funnei and a water condenser. 44.8g (0.514 mole) morphoiine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9.5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of reaction mass was stabilized at 10, the temperature was maintained at 98°C for 1 hour.

The condenser was adjusted to a distillation mode and the heating was increased to initiate the water distillation at an approximate rate of 250g/h. Addition of lOOOg water was then started at a rate of 2.50g/h so as to maintain the water content in the reaction mass. The distillation was completed in 4 hours. During the period of dist!!ation, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino- 6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate was transformed in to a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form. The slurry thus obtained was then formulated by the addition of 2.5g of the condensation product of naphthalene sulphonic acid with formaldehyde, 17g soda ash and a calculated quantity of common salt so as to get 67% active content of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'- stilbene disulphonate on a dry basis. Total dissolved solid of the slurry was adjusted between 24% to 28% by the addition of the necessary quantity of water and the slurry was agitated at a temperature between 95"C to 98"C for 30 minutes and finally transferred to a glass tray and dried in a hot air oven at 1Q5°C. The dry white free flowing powder had an e-value of 447.

The aniline and morphoiine content in the final dried product obtained was found to be 1.3ppm and 2.1ppm respectively. Example 4:

200g water and 400g crushed ice was charged to a 5L glass reactor equipped with an efficient agitator, a thermowei! and an addition port with a dropping funnel. Ig of the reaction product of 1 mole of dodecyi alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started, lOOg (0.54 mole) of cyanuric chloride was introduced into the reactor and the mixture was agitated for 30 minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0°C to 5°C during this time by immersing the reactor in an ice bath.

A solution of 4,4'-diaminosti!bene-2,2'-disulphonic acid disodium salt was prepared by neutralizing lOOg (0.27moie) 4,4'-diaminostilbene-2,2'-disu!phonic acid suspension in 840g water with 72g 30% Sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. Temperature of the reaction mass was maintained between 0°C to 5°C and pH between 4.5 to5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained at a temperature of below 5°C after the addition till 4,4'-diaminosti!bene-2,2'-disulphonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The ice bath was removed and 47.9g (0.514moie) aniline was added over a period of 30 minutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% sodium hydroxide solution. Temperature of the reaction mass increased to 3Q°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of maintenance at 3Q°C, the temperature of the reaction mass was gradually increased to 85°C and maintained for 30 minutes and at the end of the maintenance a white easily stirrabie slurry of intermediate disodium 4,4'^" - bis (4-chioro- 6-anilino-s-traizin-2-ylammo)-2,.2 -sti!benedisulphonate wasobtained. The agitation was stopped and the slurry was allowed to settle for 1 hour. lOOOg supernatant dear liquid was decanted carefully and the remaining mass was transferred to a 2L glass reactor equipped with an efficient agitator, a thermowell, an addition port with a dropping funnel and a water condenser. 44. Sg (0.514moie) morphoiine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9.5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of reaction mass was stabilised at 10, the temperature was maintained at 98°C for Ihour.

The condenser was adjusted to a distillation mode and the heating was increased to initiate the water distillation at a rate of 250g,/h. Addition of lOOOg water was then started at a rate of 250g/h so as to maintain the water content in the reaction mass. The distillation was complete in 4hours. During this time, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate was transformed into a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form. The slurry thus obtained was formulated by the addition of 2.5g of the condensation product of naphthalene sulphonic acid with formaldehyde, 17g soda ash and a calculated quantity of common salt so as to get 67% active content of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'- stilbene disulphonate on a dry basis. Total dissolved solid of the slurry was adjusted between 24% to 28% by the addition of the necessary quantity of water and the slurry was agitated at a temperature between 95"C to 98"C for 30 minutes and finally transferred to a glass tray and dried in a hot air oven at 1Q5°C. The dry white free flowing powder had an e-value of 436.

The aniline and morphoiine content in the final dried product obtained was found to be 2.5ppm and l.Sppm respectively. Example 5:

300kg water and 600kg crushed ice was charged to a 5KL reactor. 1.5kg of the reaction product of 1 mole of dodecyi alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started, 150kg cyanuric chloride was introduced into the reactor and the mixture was agitated for 30minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0"C to 5°C during this time by circulating chilled brine through the reactor jacket.

A solution of 4,4'-diaminostilbene-2,2'-disu!phonic acid disodium salt was prepared by neutralizing 150kg (4,4'-diaminosti!bene-2,2'-disulphonic acid suspension in 1300L water with 108kg 30% sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. The temperature of the reaction mass was maintained between 0°C to 5°C and pH between 4.5 to 5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained below a temperature of 5°C after the addition till 4,4'-diaminosti!bene-2,2'-disulphoriic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The cooling was stopped and 72kg aniline was added over a period of 30 minutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% sodium hydroxide solution. Temperature of the reaction mass was increased to 30°C to 35°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of maintenance at 35°C, the temperature of the reaction mass was gradually increased to 85°C and maintained for 30 minutes and at the end of the maintenance a white easily stirrabie slurry of intermediate disodium 4,4' - bis (4-chioro- 6-ani!ino-s-traizin-2-ylamino)-2,2'-stilbenedisuiphonate was obtained. The slurry was filtered using a filter press to get a wet cake. The wet cake was suspended in 1KL water in a 5KL reactor. The agitation was started and the slurry was heated to 85°C. 67kg morpholine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9.5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of reaction mass was stabilised at 10, the temperature was maintained at 98°C for 1 hour.

The system was adjusted to a distillation mode and the heating was increased to initiate the water distillation at an approximate rate of 300L/h. Addition of 1500g water was then started at a rate of 300L/h so as to maintain the water content in the reaction mass. The distillation was complete in 5 to Shours, During this time, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate was transformed in to a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form.

The slurry thus obtained was formulated by the addition of 3.75kg of the condensation product of naphthalene su!phonic acid with formaldehyde, 25kg soda ash and a calculated quantity of common salt so as to get 67% active content of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'- stilbene disulphonate on a dry basis. Total dissolved solid of the slurry was adjusted between 24% to 28% by the addition of the necessar quantity of water and the slurry was agitated at a temperature between 95"C to 98°C for 30 minutes and spray dried to get the dried final product in the form of white free flowing fine granules with an e-vaiue of 448.

The aniline and morpholine content in the final dried product obtained was found to be 2.2ppm and O.Sppm respectively. Example 6:

300kg water and 600kg crushed ice was charged to a 5KL reactor. 1.5kg of the reaction product of 1 mole of dodecyi alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started, 150kg cyan uric chloride was introduced into the reactor and the mixture was agitated for 30 minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0"C to 5"C during this time by circulating chilled brine through the reactor jacket.

A solution of 4,4'-diaminostilbene-2,2'-disu!phonic acid disodium salt was prepared by neutralizing 150kg (4,4'-diaminosti!bene-2,2'-disu!phonic acid suspension in 1300L water with 108kg 30% Sodium hydroxide. This solution was then added slowly to the cyanuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. Temperature of the reaction mass was maintained at a temperature of below 5°C and pH between 4.5 to 5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained at a temperature of below 5°C after the addition till 4,4'-diaminosti!bene-2,2'-disulphonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The cooling was stopped and 72kg aniline was added over a period of SOminutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% Sodium hydroxide solution. Temperature of the reaction mass was increased to 30°C to 35°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of maintenance at 35°C, the temperature of the reaction mass was gradually increased to 85°C and maintained for 30 minutes and at the end of the maintenance a white easily stirrabie slurry of intermediate disodium 4,4' - bis (4-chioro- 6-ani!ino-s-traizin-2-ylamino)-2,2'-stilbene disulphonate was obtained. The slurry was filtered using a filter press to get a wet cake. The wet cake was suspended in 1KL water in a 5 L reactor. The agitation was started and the slurry was heated to 85°C. 67kg morpholine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9.5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of reaction mass was stabilised at 10, the temperature was maintained at 98°C for 1 hour.

The system was adjusted to a distillation mode and the heating was increased to initiate the water distillation at a rate of 300L/h. Addition of 1500g water was then started at a rate of 300L/h so as to maintain the water content in the reaction mass. The distillation was completed in 5 to 6 hours. During this time, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate was transformed in to a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form.

The slurry thus obtained was formulated by the addition of 3.75kg of the condensation product of naphthalene su!phonic acid with formaldehyde, Total dissolved solid of the slurry was adjusted between 24% to 28% by the addition of the necessary quantity of water and the slurry was agitated at a temperature between 95°C to 98°C for 30 minutes and spray dried to get the dried final product in the form of white free flowing fine granules with an e-value of 567.

The aniline and morpholine content in the final dried product obtained was found to be 2.5ppm and 1.2ppm respectively.

Example 1: 300kg water and 600kg crushed ice was charged to a 5KL reactor. 1,5kg of the reaction product of 1 mole of dodecyl alcohol with 5 mole of ethylene oxide was added as wetting agent and the agitation was started. 150kg cyan uric chloride was introduced into the reactor and the mixture was agitated for 30 minutes to get a fine suspension of cyanuric chloride in water. The temperature was maintained between 0°C to 5°C during this time by circulating chilled brine through the reactor jacket.

A solution of 4,4'-diaminostilbene-2,2'-disu!phonic acid disodium salt was prepared by neutralizing 150kg (4,4'-diaminosti!bene-2,2'-disu!phoriic acid suspension in 1300L water with 108kg 30% Sodium hydroxide. This solution was then added slowly to the cya nuric chloride suspension prepared above at a rate so as to complete the addition in 3 hours. Temperature of the reaction mass was maintained at a temperature of below 5°C and pH between 4.5 to 5 throughout the addition by the simultaneous addition of 25% soda solution. The reaction mass was maintained at a temperature of below 5°C after the addition till 4,4'-diaminosti!bene-2,2'-disulphonic acid could no longer be detected, as confirmed by a negative diazo test. pH of the reaction mass was then raised to 7 to 7.5 using 30% sodium hydroxide solution. The cooling was stopped and 72kg aniline was added over a period of 30 minutes and the pH of the reaction mass was maintained between 7 to 8 by the simultaneous addition of 30% Sodium hydroxide solution. Temperature of the reaction mass was increased to 30 to 35°C during this time. The reaction mass was then maintained at this temperature for a further 30 minutes. At the end of maintenance at 35° C, the temperature of the reaction mass was gradually increased to 85°C and maintained for 30 minutes and at the end of the maintenance a white easily stirrable slurry of intermediate disodium 4,4'^" - bis (4-chloro- 6-anilino-s-tra!2!n-2-ylamino}-2,2'-stilbenedisuiphonate was obtained. The slurry was filtered using a filter press to get a wet cake. The wet cake was suspended in 1KL water in a 5 L reactor. The agitation was started and the slurry was heated to 85°C. 67kg morpholine was then added rapidly and the heating was continued till 98°C. pH of the reaction mass was maintained between 9.5 to 10.5 during this time by the addition of 30% sodium hydroxide solution. After the pH of the reaction mass was stabilised at 10, the temperature was maintained at 98°C for Ihour.

The system was adjusted to a distillation mode and steam was introduced into the reaction mass to effect steam distillation. The distillation was completed in 5 to 6 hours. During this time, the bright fluorescent yellow slurry of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate was transformed in to a fine crystalline pearl white slurry indicating the transformation of the a crystal form into the β crystal form.

The slurry thus obtained was formulated by the addition of 3.75kg of the condensation product of naphthalene sulphonic acid with formaldehyde, Total dissolved solid of the slurry was adjusted between 24% to 28% by the addition of the necessary quantity of water and the slurry was agitated at a temperature between 95°C to 98°C for 30 minutes and spray dried to get the dried final product in the form of white free flowing fine granules with an e-vaiue of 564.

The aniline and morpho!ine content in the final dried product obtained was found to be 2.2ppm and 1.4ppm respectively. Example s:

4 pieces of a white 100% cotton bleached fabric weighing 5 ± 0.05g each were used for the exhaust application as per the following process. Three pieces were immersed in three solutions obtained by separately dissolving different quantities of the sample obtained in Example 5 described above in lOOmL distilled water at 85°C to 90°C for 45 minutes. One piece was immersed in distilled water without the optical brightening agent at 85°C to 90°C for 45 minutes as a reference. After 45 minutes, the pieces were taken out and washed with distilled water and air dried at 25°C to 30°C. Whiteness of the fabric was measured using Data Colour Elerpho Brightness Tester. The CIE whiteness value for the blank was found to be 76.9. The results for the exhaust application test for the samples obtained as per different examples are summarised in the following table:

Table 1: Whitening efficiency of the product obtained as per the invention.

Thus, it can be seen from Table 1, the product obtained as per example 5 exhibits an excellent whitening efficiency. There was a substantial increase in the whiteness of the treated fabric pieces as against the blank. Furthermore, the treated fabric pieces indicate a noticeable bluer-redder tone as evidenced by strongly negative 'b*' values and positive 'a*' values as compared to the blank sample.

Example 9; 4 pieces of a white 100% cotton bleached fabric weighing 5 ± 0.05g each were used for the exhaust application. The pieces were immersed in solutions obtained by separately dissolving samples generated as per examples 1, 2, 4 and 5 described above at 85°C to 90°C for 45 minutes. The loading of the product with respect to the weight of the fabric was kept constant at 0.2% in all the tests. One piece was immersed in distilled water without the optical brightening agent at 85°C to 90°C for 45 minutes as a reference. After 45 minutes, the pieces were taken out and washed with distilled water and air dried at 25°C to 30°C. Whiteness of the fabric was measured using Macbeth Spectrophotometer CE 7000. Table 2: Effect of the residual aniline and morpholine on the CIE whiteness.

It can be seen from Table 2 that there was a marked improvement in the whiteness in the case of products obtained as per the present invention, that is with aniline and morpholine content below 5ppm as against as against the products obtained as per the conventional methods, that is with higher aniline and morpholine content.

Example 10:

The treated fabric pieces were exposed to Xenon Arc Lamp for a period of 48 hours to evaluate the effect of residual amino impurities on light fastness. The whiteness/brightness measurements were done using Macbeth Spectrophotometer CE 7000. Table 3 and Table 4 summarise the results of light fastness test in terms of the decrease in the CIE whiteness and the brightness values, respectively.

Table 3 : Results of the lightfastness study in terms of whiteness.

Table 4: Results of the lightfastness study in terms of Brightness.

As can be observed from the results summarised in Table 3 and Table 4, the decrease in the whiteness as well as brightness after exposure to Xenon Arc Lamp for 48h was more pronounced in the case of the products with higher aniline and morpholine content. The products obtained as per the present invention thus exhibit better lightfastness.

Apart from the effect on the whiteness and brightness, there was a marked effect on the tone, especially the blueness (b* values) of the fabric pieces as a result of exposure to Xenon Arc Lamp for 48h as summarised in the Table 5 below. Table 5: Effect of exposure to Xenon Arc Lamp on the tone of the treated fabric pieces.

Thus a significantly higher drop in the B* values in the case of the products obtained as per the conventional process, i.e., with higher aniline and morpholine content as against those obtained as per the process of the present invention.

Claims

Claims :

1. A process for preparing β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate, the process comprising of subjecting a crystal form of disodium 4,4'-bis (4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate to steam distillation.

2. The process as claimed in claim 1, wherein a crystal form of disodium 4,4'-bis(4-anilino-6- morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate is obtained by sequentially reacting cyanuric chloride with 4,4'-diaminostilbene-2,2'-disulphonic acid disodium salt, aniline and morpholine.

3. A process to prepare β crystal form of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2- ylamino)-2,2'-stilbene disulphonate having less than 5 ppm of aniline and morpholine, the process comprising

successively reacting cyanuric chloride with 4,4'-diaminostilbene-2,2'-disulphonic acid disodium salt followed by aniline to obtain a slurry of disodium 4,4'-bis(4-chloro-6-anilino-s- triazin-2-ylamino)-2,2'-stilbenedisulphonate;

treating the slurry with morpholine to obtain a reaction mass comprising of a crystals of disodium 4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate; subjecting the reaction mass to steam distillation to remove the residual aniline;

and wherein mole ratio of cyanuric chloride to aniline and cyanuric chloride to morpholine is reduced.

4. The process as claimed in claim 3, wherein the cyanuric chloride and 4,4-diaminostilbene -2,2'- disulphonic acid disodium salt is reacted at 0°C to 5°C at pH 4-5, followed by the addition of aniline at a temperature of 7°C to 30°C at pH 7 to 8 and morpholine at a temperature of 85°C to 98°C at pH 9.5 to 10.5.

5. The process as claimed in claim 3, wherein the slurry is treated with morpholine after the slurry is settled and the clear supernatant solution is discarded.

6. The process as claimed in claim 3, wherein the slurry is filtered to obtain a wet cake followed by treatment with morpholine.

7. The process as claimed in claim 3, wherein steam distillation is carried out by introducing steam or adding water into the reaction mass.

8. The process as claimed in claim 7, wherein the introduction of steam or addition of water into the reaction mass is carried out with simultaneous collection of condensate.

9. The process as claimed in claim 7 or 8, wherein the rate of adding water into the reaction mass is same as that of the collection of condensate.

10. The process as claimed in 8 or 9, wherein the ratio of the quantity of condensate collected to the quantity of the disodium4,4'-bis(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2'-stilbene disulphonate is 6:1.

11. The process as claimed in claim 3, wherein steam distillation is carried out for 4 to 6 hours.

12. The process as claimed in claim 3, wherein the mole ratio of aniline to cyanuric chloride is less than 1.

13. The process as claimed in claim 3, wherein the mole ratio of morpholine to cyanuric chloride is less than 1.