Title of Invention	A NOVEL WATER SOLUBLE SULFONATED MELAMINE FORMALDEHYDE IONIC CONDENSATE AND A PROCESS FOR THE PREPARATION THEREOF
Abstract	The present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate exhibiting the free formaldehyde content in the range of 0.01-0.1%. A process for the preparation of the condensate is also provided whereby polymeric formaldehyde is used under alkaline condition. The product exhibits a storage life of around 6 months and is very effective for different industrial applications. The product finds potential application in leather processing industry as retanning agent.

Title of Invention

A NOVEL WATER SOLUBLE SULFONATED MELAMINE FORMALDEHYDE IONIC CONDENSATE AND A PROCESS FOR THE PREPARATION THEREOF

Abstract

The present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate exhibiting the free formaldehyde content in the range of 0.01-0.1%. A process for the preparation of the condensate is also provided whereby polymeric formaldehyde is used under alkaline condition. The product exhibits a storage life of around 6 months and is very effective for different industrial applications. The product finds potential application in leather processing industry as retanning agent.

Full Text	FIELD OF THE INVENTION The present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate. More particularly, the present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate having general formula (Formula Removed). wherein, R = alkali metal salt of diamino or dihydroxyl sulfonic acid n = any integer between 10 and 100 x = any integer between 2 and 10 The invention further provides a process for the preparation of the novel sulfonated melamine formaldehyde ionic condensate. The product is envisaged to have several industrial applications. It finds potential application in leather processing industry as retanning agent that imparts improved grain tightness and buffing property in the resulting leather. The product may also be used for upgrading inferior quality raw hide/skin, whereby the resulting value added products may be useful for leather products industry. Further, the polymer finds application as polymer additive in the construction industry especially for colourful interior decoration. Background of the Invention Melamine formaldehyde condensates are conventionally prepared by polymerizing melamine with formaldehyde under controlled conditions of temperature, pressure and pH conditions. The hydrophobicity of the resulting condensed polymer restricts its use for aqueous based applications. Hence the product is made water soluble by introducing hydrophilic groups by sulfonation. The commercial demand of water soluble melamine formaldehyde resin is significant primarily because of ease of preparation owing to the abundant availability of raw materials, and economy of production caused by short duration of production of the product to the extent of 6 hours. There have been several reports on the different features of the hitherto known melamine formaldehyde condensate products available in the public domain. Some of these properties which play a crucial role for certain specific industrial applications such as leather processing, are summarized below. Free Formaldehyde content The presence of free formaldehyde in a product to the extent of not less than 0.02% has been considered to be hazardous and even carcinogenic. The major limitation of the hitherto known processes is that the formaldehyde used for the purpose of the reaction results in significant amount of free formaldehyde content in the resulting products. This is an issue of much concern considering the awareness on health hazards arising out of free formaldehyde content in the product, thereby restricting the use of the resulting polymer for consumer products. Hence several attempts are being made by researchers in the present day context to provide products devoid of free formaldehyde or to restrict the free formaldehyde content of any product to the minimum. Aignesberger et al (US Patent No. 3,941,734) prepared sulfite modified melamine formaldehyde resin solution at ordinary atmospheric pressure for 1-3 hours at pH value of 8 - 11. The product was found to exhibit free formaldehyde content to the extent of 0.15%. Reference may be made to Sheldrick (US Patent No. 4,444,945), who prepared an aqueous solution of melamine formaldehyde condensation product having anionic sulfur groups by reacting with sulfate at atmosphere reflux and pH 8 -10 for 1-5 h. The product exhibits free formaldehyde content to the extent of 0.08%. Reference may be made to Dupuis et al (US Patent No. 5,424,390), who provided a process for manufacture of sulfonated melamine formaldehyde resins at super- atmospheric pressure at an elevated temperature of 100-130°C for 1- 5 hours at pH value of 5-7. However, the product exhibited free formaldehyde of 0.08%. This necessitates a requirement of providing a product of melamine formaldehyde resin with a free formaldehyde content not exceeding 0.02%. Particle size This is a very important parameter for chemicals to be used in processing industry. For example, leather processing requires a range of chemicals useful for filling up voids and imparting fullness. While melamine formaldehyde resin is known to be used as synthetic tanning agent in leather industry, bigger particle size of the product, which is not less than 100nm poses as a limitation for its use in leather industry for adequate penetration in the cross section, thereby necessitating additional filling auxiliaries for producing fuller leather, affecting the economy of leather industry adversely. The sulfite modified melamine resin solution provided by Aignesberger et al (US Patent No. 3,941,734) exhibited particle size of 250nm. Dupuis et al (US Patent no. 5,424,390) could reduce the particle size of the melamine formaldehyde condensation product to 200nm. Sheldrick (US Patent No. 4,444,945) provided melamine formaldehyde condensation product exhibiting particle size in the range of 120-140nm. It prompts researchers to explore possibilities to provide a melamine formaldehyde resin having particle size not exceeding 100nm. Free sulfate content Melamine formaldehyde resin finds application in leather as well as construction industries. The major limitation of the conventional products of this kind is that the product is prone to yellowing on ageing because of the presence of free sulfate present in the resin, whereby the sulfate, on ageing, breaks into sulfur that imparts the yellowish tone. In fact, the more the free sulfate content is, the more is the tendency for creating yellowing tone on ageing. Generally, the hithertoknown melamine formaldehyde resins have free sulfate content not exceeding 3.0%. While summarizing the processes for producing the hithertoknown melamine formaldehyde resins, it becomes evident that there is no mechanism available in the art to reduce the free sulfate content of the conventional resin, thereby leading to poor colour retention property. However, the aesthetic aspects of the user industries for this resin demand better colour retention of the polymer, necessitating reduction in the free sulfate content of the resin. Another limitation of the conventional processes is that the reaction temperature usually ranges between 100-130°C, thereby rendering the processes costlier because of the requirement of high temperature monitoring systems. Moreover, the usual reaction period extends upto the extent of 10 hours, resulting in limited productivity. Attempts are therefore being made to reduce the production time to enhance the productivity. Objects of the Invention The main object of the present invention is to provide a novel water soluble sulfonated melamine formaldehyde ionic condensate, which obviates the limitations as stated above. Another object of the present invention is to provide a melamine formaldehyde resin exhibiting free formaldehyde content not exceeding 0.02%. Yet another object of the present invention is to provide a melamine formaldehyde resin exhibiting particle size not exceeding 100nm. Still another object of present investigation is to provide a melamine formaldehyde resin exhibiting free sulfate content less than 3%. Yet another object of the present invention is to prepare a melamine formaldehyde resin by condensation polymerization of melamine and formaldehyde. Still another object of the present invention is to prepare a melamine formaldehyde condensation product under atmospheric conditions. Yet another object of the present invention is to sulfonate the melamine formaldehyde condensate for water solubility. Still another object of the present invention is to use polymeric formaldehyde for preparing the melamine formaldehyde condensate. Yet another object of the present invention is to use Calcium oxide to reduce the free sulfate content of the final polymeric product. Summary of the Invention Accordingly, the present invention provides a novel water soluble sulfonated melamine formaldehyde Sodium-2-[4,4',6,6'-tetrakis(2-hydroxyethylamino)-[1,3,5]triazine-2yl aminoj-methano Sulfonate) ionic condensate having general formula (Formula Removed). wherein, R = alkali metal salt of diamino or dihydroxyl sulfonic acid n = any integer between 10 and 100 x = any integer between 2 and 10 Further, the present invention provides a process for the preparation of sulfonated melamine formaldehyde condensate as claimed in claim 1, wherein the steps comprising: (a) treating melamine having general formula C3N6H3 with 25-30% by weight of (CH20)x, where x is any integer between 2-10 at a pH in the range of 10-14 at a temperature in the range of 40-60°C to obtain clear solution; (b) adding 5-15% w/w, of sulfonating agent such as herein described to the clear solution as obtained in step(a), under continuous stirring at a rate in the range of 5-15 ml per minute to obtain a macromonomer solution of melamine formaldehyde; (c) adjusting the pH of the solution as obtained in step (b), in the range of 2-4 followed by subjecting the resulting solution to a temperature of 50-80°C for a period in the range of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate; (d) adding 1-4 % w/w, of CaO to the polymeric solution as obtained in step (c), under continuous stirring followed by separation of the resulting mixture after a period of not less than 6 hours and subsequent adjusting of pH of the separated mixture in the range of 10-14 to obtain the desired sulfonated melamine formaldehyde ionic condensate. In an embodiment of the present invention, the sulfonating agent used may be selected from sulfonic acid, sulfamic acid, sulfanilic acid, sulfuric acid, sodium meta bisulfate, sodium sulfite, sodium bi-sulfite. In another embodiment of the present invention, known acid used for adjusting pH may be selected from sulfuric acid, hydrochloric acid, perchloric acid. In yet another embodiment of the present invention, the separation process may be such as filtration, sedimentation, settling. In still another embodiment of the present invention, the known alkali used may be selected from sodium hydroxide, sodium bicarbonate, sodium carbonate. In still another embodiment of the present invention, the free formaldehyde content of the condensate may be in the range of 0.01-0.1% by weight on the weight of the condensate. In yet another embodiment of the present invention, the melamine content of the condensate may be in the range of 15-25% by weight on the weight of the condensate. In still another embodiment of the present invention, pH of the condensate may be in the range of 11-14. In yet another embodiment of the present invention, viscosity of the condensate may be in the range of 15-25 mPa.s In still another embodiment of the present invention, the total solid content may be in the range of 15-30% by weight based on the weight of the condensate. In yet another embodiment of the present invention, the free sulfate content of the condensate may be in the range of 0.5-3% w/w. Detailed description of the invention Melamine having general formula C3N6H3 is treated with 25-30% by weight of a polymeric form of formaldehyde, having general formula (CH2O)x, where x is any integer between 2-10, at a pH in the range of 10-14 at 40-60°C to obtain a clear solution of melamine oligomeric formaldehyde condensate. This condensate is sulfonated using 5-10% by weight of a known sulfonating agent, which is added to the clear solution under dynamic condition. The rate of addition of the sulfonating agent is maintained in the range of 5-10 ml per minute. A known acid is then added to the resulting macromonomer solution of melamine formaldehyde to adjust its pH in the range of 2-4. The resulting solution is subjected to a temperature in the range of 50-80°C for a period of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate. 1-5 % by weight of CaO is then added slowly to this polymeric solution under dynamic condition. After a period of not less than 6 hours, the resulting mixture is subjected to conventional separation. Known alkali is used to adjust the pH of the separated mixture in the range of 10-14 to obtain the sulfonated melamine formaldehyde condensate. The inventiveness of the present invention lies in providing a novel water soluble melamine formaldehyde condensate exhibiting a combination of the characteristics comprising 0.08% of free formaldehyde, 100-500nm particle size and 0.5-3% free sulfate, enabled by the use of polymeric formaldehyde. EXAMPLES The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention. Example 1 65ml of (HCHCO)2 was diluted with 50ml of water and heated to a temperature of 70°C in a reaction kettle. pH of the solution was adjusted to 6.0 by adding 1N sodium hydroxide solution. 400g melamine was then added slowly to the formalin solution with continuous stirring. The temperature was allowed to rise to 40-50°C while the melamine reacted in the formalin solution to form a clear solution. The reaction was allowed to proceed for another 10 minutes. pH of the solution was noted to be 5.5. Then 10g of sodium sulphite dissolved in 50ml of water was added to the said solution. This was followed by the addition of 70g of sodium bisulphite for 20-30 min and the solution was further heated to 60°C and continued at the same temperature for 60 minutes. The solution was then cooled rapidly to 40°C. pH of the solution was adjusted to a pH of 2-4 by the addition of 10ml of 30%(w/w) sulfuric acid. The mixture was kept under these conditions for 50 minutes. 10ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 70°C and kept under these conditions for 30 minutes. The reaction was finally cooled to 25°C to obtain sulfonated melamine formaldehyde condensate. The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features. (Table Removed) Example 2 40ml of (HCHO)4 was diluted with 50ml of water and heated to room temperature up to 70°C in the reaction kettle. pH of the solution was adjusted to 9.0 by the addition of 1N sodium hydroxide solution. 450g amount of melamine was added to the formalin solution. The temperature was increased while the melamine dissolved in the formalin solution. After the solution became clear, the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of sulfamic acid dissolved in 10% sodium hydroxide solution in 50ml of water was added maintaining the pH 7.0. 70g of sulfamic acid were then added and further heated to 80'C and continued at the same temperature for 120 minutes. In the third stage of the procedure the solution was cooled rapidly to 55°C. pH of the solution was adjusted to 2 by the addition of 25 ml 30%(w/w) sulfuric acid. The mixture was kept under those conditions for 150 minutes. 25 ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 70°C and kept under these conditions for 180 minutes. The reaction was finally cooled to room temperature and percentage solid content was adjusted using sodium hydroxide. The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features. (Table Removed) Example 3 20 ml of (HCHO)8 was diluted with 50ml of water and heated to room temperature up to 70°C in the reaction kettle. pH of the solution was adjusted to 8.0 by the addition of 1N sodium hydroxide solution. 450g amount of melamine was added to the formalin solution. The temperature was increased while the melamine dissolved in the formalin solution. After the solution became clear, the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of paraformaldehyde dissolved in 250ml of water in 50ml of water was added maintaining the pH 6.0. 70g of paraformaldehyde were then added and further heated to 120°C and continued at the same temperature for 120 minutes. In the third stage of the procedure the solution was cooled rapidly to 50°C. pH of the solution was adjusted to 3.0 by the addition of 15 ml of 30%(w/w) sulfuric acid. The mixture was kept under these conditions for 150 minutes. 15 ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 90°C and kept under these conditions for 180 minutes. The reaction was finally cooled to room temperature and percentage solid content was adjusted using sodium hydroxide. The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features. (Table Removed) Example 4 16ml of (HCHO)io was heated to 55°C in the reaction kettle. pH of the solution was adjusted to 7.0 by the addition of 1N sodium hydroxide. 45g of melamine was added to the polymeric formaldehyde solution at 55°C. The temperature was increased while the melamine dissolved in the solution. After the solution became clear the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of sodium sulphite dissolved in 50ml of water was added thus increasing the pH to 11. Sulfonation was initiated by the addition of 30g of sodium bisulphite dissolved in water. Simultaneously pH of the solution was maintained by the drop wise addition of 30% alkali solution. Temperature of the solution was then raised to 60°C and kept at this temperature for 120 minutes. In the third stage of the procedure the pH of the solution was adjusted to 6.0 by the addition of 20 ml of 30 % (w/w) sulfuric acid. The reaction was stopped and the polymeric condensate was cooled to room temperature. Stirring was continued at room temperature for 24h. Finally the pH of the resin was adjusted to 11.0 with 30% sodium hydroxide. The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features. (Table Removed) Chrome tanned leather weighing 1kg was taken and neutralized to adjust the pH of 5.0 by using the alkali. Then the material was thoroughly washed with 2 liters plain water. The washed material was then treated with the melamine formaldehyde condensate derivative at the level of 30g and agitated in the drum for 40 minutes. Further to the leather, the dye at the level of 10g was added and agitated in the drum for 30 minutes. Finally synthetic fat liquor at the level of 40g was added and agitated in the drum for 40 minutes and the above auxiliaries were fixed by adding formic acid at the level of 10g. Then the leather was dried and the properties were assessed. The leather was assessed for fullness, softness, grain smoothness and dyeing properties. The leather showed improved dyeing properties, softness, grain smoothness and fullness in the resulting leather. The main advantages of the present invention are the following. 1. The product exhibits storage life of 6 months. 2. The product is stable and effective during storage. 3. The product has ample scope for different modifications due to the presence of functional carboxyl group. 4. The product is very economical. 5. The product leads to improved penetration because of the smaller particle size in the range of 40-100 nm of melamine formaldehyde derivative. 6. The novel melamine formaldehyde derivative is able to react with reactive groups of collagen and because of the reactive groups (amino group) present in the product. 7. The novel melamine formaldehyde derivative provides typical interfacial coverage on the polymeric matrix and therefore, exhibits extraordinary stability. 8. The novel melamine formaldehyde derivative improved exhaustion in the post tanning process. 9. The novel melamine formaldehyde derivative used in leather processing results in improved softness, fullness and dye uptake. We Claim : 1. A novel water soluble sulfonated melamine formaldehyde Sodium-2- [4,4',6,6'-tetrakis(2-hydroxyethylamino)-[1,3,5]triazine-2yl amino]- methano Sulfonate) ionic condensate having general formula (Formula Removed). wherein, R = alkali metal salt of diamino or dihydroxyl sulfonic acid n = any integer between 10 and 100 x = any integer between 2 and 10 2. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the free formaldehyde content of the condensate is in the range of 0.01-0.1% by weight on the weight of the condensate. 3. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the melamine content of the condensate is in the range of 15-30% by weight on the weight of the condensate. 4. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the pH of the condensate is in the range of 11-14. 5. A novel water soluble sulfonated melamine formaldehyde ionic condensate, as claimed in claim 1, wherein the viscosity of the condensate is in the range of 15-25 m Pa S. 6. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the total solid content is in the range of 15 - 30% by weight based on the weight of the condensate. 7. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the free sulfate content of the condensate is in the range of 0.5-3% w/w. 8. A process for the preparation of sulfonated melamine formaldehyde condensate as claimed in claim 1, wherein the steps comprising: (a) treating melamine having general formula C3N6H3 with 25-30% by weight of (CH2O)x, where x is any integer between 2-10 at a pH in the range of 10-14 at a temperature in the range of 40-60°C to obtain clear solution; (b) adding 5-15% w/w, of sulfonating agent such as herein described to the clear solution as obtained in step(a), under continuous stirring at a rate in the range of 5-15 ml per minute to obtain a macromonomer solution of melamine formaldehyde; (c) adjusting the pH of the solution as obtained in step (b), in the range of 2-4 followed by subjecting the resulting solution to a temperature of 50-80°C for a period in the range of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate; (d) adding 1-4 % w/w, of CaO to the polymeric solution as obtained in step (c), under continuous stirring followed by separation of the resulting mixture after a period of not less than 6 hours and subsequent adjusting of pH of the separated mixture in the range of 10-14 to obtain the desired sulfonated melamine formaldehyde ionic condensate. 9. A process as claimed in claim 8, wherein the sulfonating agent used is selected from sulfonic acid, sulfamic acid, sulfanilic acid, sulfuric acid, sodium meta bisulfate, sodium sulfite and sodium bi-sulfite. 10. A process as claimed in claim 8, wherein the acid used for adjusting pH is selected from sulfuric acid, hydrochloric acid, perchloric acid. 11. A process as claimed in claim 8, wherein the separation process is such as filtration, sedimentation, settling. 12. A process as claimed in claim 8, wherein the alkali used is selected from sodium hydroxide, sodium bicarbonate, sodium carbonate. 13. A novel water soluble sulfonated melamine formaldehyde ionic condensate and a process for the preparation thereof substantially as described herein with reference to the examples.

Full Text

FIELD OF THE INVENTION
The present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate. More particularly, the present invention relates to a novel water soluble sulfonated melamine formaldehyde ionic condensate having general formula
(Formula Removed).
wherein,
R = alkali metal salt of diamino or dihydroxyl sulfonic acid
n = any integer between 10 and 100
x = any integer between 2 and 10
The invention further provides a process for the preparation of the novel sulfonated melamine formaldehyde ionic condensate.
The product is envisaged to have several industrial applications. It finds potential application in leather processing industry as retanning agent that imparts improved grain tightness and buffing property in the resulting leather. The product may also be used for upgrading inferior quality raw hide/skin, whereby the resulting value added products may be useful for leather products industry. Further, the polymer finds application as polymer additive in the construction industry especially for colourful interior decoration.
Background of the Invention
Melamine formaldehyde condensates are conventionally prepared by polymerizing melamine with formaldehyde under controlled conditions of temperature, pressure and pH conditions. The hydrophobicity of the resulting condensed polymer restricts its use for aqueous based applications. Hence the product is made water soluble by introducing hydrophilic groups by sulfonation. The commercial demand of water soluble melamine
formaldehyde resin is significant primarily because of ease of preparation owing to the abundant availability of raw materials, and economy of production caused by short duration of production of the product to the extent of 6 hours. There have been several reports on the different features of the hitherto known melamine formaldehyde condensate products available in the public domain. Some of these properties which play a crucial role for certain specific industrial applications such as leather processing, are summarized below.
Free Formaldehyde content
The presence of free formaldehyde in a product to the extent of not less than 0.02% has been considered to be hazardous and even carcinogenic. The major limitation of the hitherto known processes is that the formaldehyde used for the purpose of the reaction results in significant amount of free formaldehyde content in the resulting products. This is an issue of much concern considering the awareness on health hazards arising out of free formaldehyde content in the product, thereby restricting the use of the resulting polymer for consumer products. Hence several attempts are being made by researchers in the present day context to provide products devoid of free formaldehyde or to restrict the free formaldehyde content of any product to the minimum.
Aignesberger et al (US Patent No. 3,941,734) prepared sulfite modified melamine formaldehyde resin solution at ordinary atmospheric pressure for 1-3 hours at pH value of 8 - 11. The product was found to exhibit free formaldehyde content to the extent of 0.15%.
Reference may be made to Sheldrick (US Patent No. 4,444,945), who prepared an aqueous solution of melamine formaldehyde condensation product having anionic sulfur groups by reacting with sulfate at atmosphere reflux and pH 8 -10 for 1-5 h. The product exhibits free formaldehyde content to the extent of 0.08%.
Reference may be made to Dupuis et al (US Patent No. 5,424,390), who provided a process for manufacture of sulfonated melamine formaldehyde resins at super- atmospheric pressure at an elevated temperature of 100-130°C for 1- 5 hours at pH value of 5-7. However, the product exhibited free formaldehyde of 0.08%.
This necessitates a requirement of providing a product of melamine formaldehyde resin with a free formaldehyde content not exceeding 0.02%.
Particle size
This is a very important parameter for chemicals to be used in processing industry. For example, leather processing requires a range of chemicals useful for filling up voids and imparting fullness. While melamine formaldehyde resin is known to be used as synthetic tanning agent in leather industry, bigger particle size of the product, which is not less than 100nm poses as a limitation for its use in leather industry for adequate penetration in the cross section, thereby necessitating additional filling auxiliaries for producing fuller leather, affecting the economy of leather industry adversely.
The sulfite modified melamine resin solution provided by Aignesberger et al (US Patent No. 3,941,734) exhibited particle size of 250nm. Dupuis et al (US Patent no. 5,424,390) could reduce the particle size of the melamine
formaldehyde condensation product to 200nm. Sheldrick (US Patent No. 4,444,945) provided melamine formaldehyde condensation product exhibiting particle size in the range of 120-140nm. It prompts researchers to explore possibilities to provide a melamine formaldehyde resin having particle size not exceeding 100nm.
Free sulfate content
Melamine formaldehyde resin finds application in leather as well as construction industries. The major limitation of the conventional products of this kind is that the product is prone to yellowing on ageing because of the presence of free sulfate present in the resin, whereby the sulfate, on ageing, breaks into sulfur that imparts the yellowish tone. In fact, the more the free sulfate content is, the more is the tendency for creating yellowing tone on ageing. Generally, the hithertoknown melamine formaldehyde resins have free sulfate content not exceeding 3.0%.
While summarizing the processes for producing the hithertoknown melamine formaldehyde resins, it becomes evident that there is no mechanism available in the art to reduce the free sulfate content of the conventional resin, thereby leading to poor colour retention property. However, the aesthetic aspects of the user industries for this resin demand better colour retention of the polymer, necessitating reduction in the free sulfate content of the resin.
Another limitation of the conventional processes is that the reaction temperature usually ranges between 100-130°C, thereby rendering the processes costlier because of the requirement of high temperature monitoring systems. Moreover, the usual reaction period extends upto the extent of 10
hours, resulting in limited productivity. Attempts are therefore being made to reduce the production time to enhance the productivity.
Objects of the Invention
The main object of the present invention is to provide a novel water soluble sulfonated melamine formaldehyde ionic condensate, which obviates the limitations as stated above.
Another object of the present invention is to provide a melamine formaldehyde resin exhibiting free formaldehyde content not exceeding 0.02%.
Yet another object of the present invention is to provide a melamine formaldehyde resin exhibiting particle size not exceeding 100nm.
Still another object of present investigation is to provide a melamine formaldehyde resin exhibiting free sulfate content less than 3%.
Yet another object of the present invention is to prepare a melamine formaldehyde resin by condensation polymerization of melamine and formaldehyde.
Still another object of the present invention is to prepare a melamine formaldehyde condensation product under atmospheric conditions.
Yet another object of the present invention is to sulfonate the melamine formaldehyde condensate for water solubility.
Still another object of the present invention is to use polymeric formaldehyde for preparing the melamine formaldehyde condensate.
Yet another object of the present invention is to use Calcium oxide to reduce the free sulfate content of the final polymeric product.
Summary of the Invention
Accordingly, the present invention provides a novel water soluble sulfonated melamine formaldehyde Sodium-2-[4,4',6,6'-tetrakis(2-hydroxyethylamino)-[1,3,5]triazine-2yl aminoj-methano Sulfonate) ionic condensate having general formula
(Formula Removed).
wherein,
R = alkali metal salt of diamino or dihydroxyl sulfonic acid
n = any integer between 10 and 100
x = any integer between 2 and 10
Further, the present invention provides a process for the preparation of sulfonated melamine formaldehyde condensate as claimed in claim 1, wherein the steps comprising:
(a) treating melamine having general formula C3N6H3 with 25-30% by weight of (CH20)x, where x is any integer between 2-10 at a pH in
the range of 10-14 at a temperature in the range of 40-60°C to obtain clear solution;
(b) adding 5-15% w/w, of sulfonating agent such as herein described to the clear solution as obtained in step(a), under continuous stirring at a rate in the range of 5-15 ml per minute to obtain a macromonomer solution of melamine formaldehyde;
(c) adjusting the pH of the solution as obtained in step (b), in the range of 2-4 followed by subjecting the resulting solution to a temperature of 50-80°C for a period in the range of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate;
(d) adding 1-4 % w/w, of CaO to the polymeric solution as obtained in step (c), under continuous stirring followed by separation of the resulting mixture after a period of not less than 6 hours and subsequent adjusting of pH of the separated mixture in the range of 10-14 to obtain the desired sulfonated melamine formaldehyde ionic condensate.
In an embodiment of the present invention, the sulfonating agent used may be selected from sulfonic acid, sulfamic acid, sulfanilic acid, sulfuric acid, sodium meta bisulfate, sodium sulfite, sodium bi-sulfite.
In another embodiment of the present invention, known acid used for adjusting pH may be selected from sulfuric acid, hydrochloric acid, perchloric acid.
In yet another embodiment of the present invention, the separation process may be such as filtration, sedimentation, settling.
In still another embodiment of the present invention, the known alkali used may be selected from sodium hydroxide, sodium bicarbonate, sodium carbonate.
In still another embodiment of the present invention, the free formaldehyde content of the condensate may be in the range of 0.01-0.1% by weight on the weight of the condensate.
In yet another embodiment of the present invention, the melamine content of the condensate may be in the range of 15-25% by weight on the weight of the condensate.
In still another embodiment of the present invention, pH of the condensate may be in the range of 11-14.
In yet another embodiment of the present invention, viscosity of the condensate may be in the range of 15-25 mPa.s
In still another embodiment of the present invention, the total solid content may be in the range of 15-30% by weight based on the weight of the condensate.
In yet another embodiment of the present invention, the free sulfate content of the condensate may be in the range of 0.5-3% w/w.
Detailed description of the invention
Melamine having general formula C3N6H3 is treated with 25-30% by weight of a polymeric form of formaldehyde, having general formula (CH2O)x, where x is any integer between 2-10, at a pH in the range of 10-14 at 40-60°C to obtain a clear solution of melamine oligomeric formaldehyde condensate. This condensate is sulfonated using 5-10% by weight of a known sulfonating agent, which is added to the clear solution under dynamic condition. The rate of addition of the sulfonating agent is maintained in the range of 5-10 ml per minute. A known acid is then added to the resulting macromonomer solution of melamine formaldehyde to adjust its pH in the range of 2-4. The resulting solution is subjected to a temperature in the range of 50-80°C for a period of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate. 1-5 % by weight of CaO is then added slowly to this polymeric solution under dynamic condition. After a period of not less than 6 hours, the resulting mixture is subjected to conventional separation. Known alkali is used to adjust the pH of the separated mixture in the range of 10-14 to obtain the sulfonated melamine formaldehyde condensate.
The inventiveness of the present invention lies in providing a novel water soluble melamine formaldehyde condensate exhibiting a combination of the characteristics comprising 0.08% of free formaldehyde, 100-500nm particle size and 0.5-3% free sulfate, enabled by the use of polymeric formaldehyde.
EXAMPLES
The following examples are given by way of illustration only and therefore should not be construed to limit the scope of the present invention.
Example 1
65ml of (HCHCO)2 was diluted with 50ml of water and heated to a temperature of 70°C in a reaction kettle. pH of the solution was adjusted to 6.0 by adding 1N sodium hydroxide solution. 400g melamine was then added slowly to the formalin solution with continuous stirring.
The temperature was allowed to rise to 40-50°C while the melamine reacted in the formalin solution to form a clear solution. The reaction was allowed to proceed for another 10 minutes. pH of the solution was noted to be 5.5. Then 10g of sodium sulphite dissolved in 50ml of water was added to the said solution. This was followed by the addition of 70g of sodium bisulphite for 20-30 min and the solution was further heated to 60°C and continued at the same temperature for 60 minutes.
The solution was then cooled rapidly to 40°C. pH of the solution was adjusted to a pH of 2-4 by the addition of 10ml of 30%(w/w) sulfuric acid. The mixture was kept under these conditions for 50 minutes. 10ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 70°C and kept under these conditions for 30 minutes. The reaction was finally cooled to 25°C to obtain sulfonated melamine formaldehyde condensate. The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features.
(Table Removed)
Example 2
40ml of (HCHO)4 was diluted with 50ml of water and heated to room temperature up to 70°C in the reaction kettle. pH of the solution was adjusted to 9.0 by the addition of 1N sodium hydroxide solution. 450g amount of melamine was added to the formalin solution. The temperature was increased while the melamine dissolved in the formalin solution. After the solution became clear, the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of sulfamic acid dissolved in 10% sodium hydroxide solution in 50ml of water was added maintaining the pH 7.0. 70g of sulfamic acid were then added and further heated to 80'C and continued at the same temperature for 120 minutes. In the third stage of the procedure the solution was cooled rapidly to 55°C. pH of the solution was adjusted to 2 by the addition of 25 ml 30%(w/w) sulfuric acid. The mixture was kept under those conditions for 150 minutes. 25 ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 70°C and kept under these conditions for 180 minutes. The reaction was finally cooled to room temperature and percentage solid content was adjusted using sodium hydroxide.
The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features.
(Table Removed)

Example 3
20 ml of (HCHO)8 was diluted with 50ml of water and heated to room temperature up to 70°C in the reaction kettle. pH of the solution was adjusted to 8.0 by the addition of 1N sodium hydroxide solution. 450g amount of melamine was added to the formalin solution. The temperature was increased while the melamine dissolved in the formalin solution. After the solution became clear, the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of paraformaldehyde dissolved in 250ml of water in 50ml of water was added maintaining the pH 6.0. 70g of paraformaldehyde were then added and further heated to 120°C and continued at the same temperature for 120 minutes. In the third stage of the procedure the solution was cooled rapidly to 50°C. pH of the solution was adjusted to 3.0 by the addition of 15 ml of 30%(w/w) sulfuric acid. The mixture was kept under these conditions for 150 minutes. 15 ml of 30%(w/w) sodium hydroxide solution was then added. The batch was then heated to 90°C and
kept under these conditions for 180 minutes. The reaction was finally cooled
to room temperature and percentage solid content was adjusted using sodium hydroxide.
The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features.

(Table Removed)
Example 4
16ml of (HCHO)io was heated to 55°C in the reaction kettle. pH of the solution was adjusted to 7.0 by the addition of 1N sodium hydroxide. 45g of melamine was added to the polymeric formaldehyde solution at 55°C. The temperature was increased while the melamine dissolved in the solution. After the solution became clear the reaction was allowed for an additional 10 minutes. In the second stage of the procedure 10g of sodium sulphite dissolved in 50ml of water was added thus increasing the pH to 11. Sulfonation was initiated by the addition of 30g of sodium bisulphite dissolved in water. Simultaneously pH of the solution was maintained by the drop wise addition of 30% alkali solution. Temperature of the solution was then raised to 60°C and kept at this temperature for 120 minutes. In the third stage of the
procedure the pH of the solution was adjusted to 6.0 by the addition of 20 ml
of 30 % (w/w) sulfuric acid. The reaction was stopped and the polymeric condensate was cooled to room temperature. Stirring was continued at room temperature for 24h. Finally the pH of the resin was adjusted to 11.0 with 30% sodium hydroxide.
The melamine formaldehyde ionic condensate product was subjected to characterization study and it exhibited the following features.

(Table Removed)
Chrome tanned leather weighing 1kg was taken and neutralized to adjust the pH of 5.0 by using the alkali. Then the material was thoroughly washed with 2 liters plain water. The washed material was then treated with the melamine formaldehyde condensate derivative at the level of 30g and agitated in the drum for 40 minutes. Further to the leather, the dye at the level of 10g was added and agitated in the drum for 30 minutes. Finally synthetic fat liquor at the level of 40g was added and agitated in the drum for 40 minutes and the above auxiliaries were fixed by adding formic acid at the level of 10g. Then the leather was dried and the properties were assessed. The leather was assessed for fullness, softness, grain smoothness and dyeing properties. The leather showed improved dyeing properties, softness, grain smoothness and fullness in the resulting leather.
The main advantages of the present invention are the following.
1. The product exhibits storage life of 6 months.
2. The product is stable and effective during storage.
3. The product has ample scope for different modifications due to the presence of functional carboxyl group.
4. The product is very economical.
5. The product leads to improved penetration because of the smaller particle size in the range of 40-100 nm of melamine formaldehyde derivative.
6. The novel melamine formaldehyde derivative is able to react with reactive groups of collagen and because of the reactive groups (amino group) present in the product.
7. The novel melamine formaldehyde derivative provides typical interfacial coverage on the polymeric matrix and therefore, exhibits extraordinary stability.
8. The novel melamine formaldehyde derivative improved exhaustion in the post tanning process.
9. The novel melamine formaldehyde derivative used in leather processing results in improved softness, fullness and dye uptake.

We Claim :
1. A novel water soluble sulfonated melamine formaldehyde Sodium-2-
[4,4',6,6'-tetrakis(2-hydroxyethylamino)-[1,3,5]triazine-2yl amino]-
methano Sulfonate) ionic condensate having general formula
(Formula Removed).
wherein,
R = alkali metal salt of diamino or dihydroxyl sulfonic acid
n = any integer between 10 and 100
x = any integer between 2 and 10
2. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the free formaldehyde content of the condensate is in the range of 0.01-0.1% by weight on the weight of the condensate.
3. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the melamine content of the condensate is in the range of 15-30% by weight on the weight of the condensate.
4. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the pH of the condensate is
in the range of 11-14.
5. A novel water soluble sulfonated melamine formaldehyde ionic condensate, as claimed in claim 1, wherein the viscosity of the condensate is in the range of 15-25 m Pa S.
6. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the total solid content is in the range of 15 - 30% by weight based on the weight of the condensate.
7. A novel water soluble sulfonated melamine formaldehyde ionic condensate as claimed in claim 1, wherein the free sulfate content of the condensate is in the range of 0.5-3% w/w.
8. A process for the preparation of sulfonated melamine formaldehyde condensate as claimed in claim 1, wherein the steps comprising:

(a) treating melamine having general formula C3N6H3 with 25-30% by weight of (CH2O)x, where x is any integer between 2-10 at a pH in the range of 10-14 at a temperature in the range of 40-60°C to obtain clear solution;
(b) adding 5-15% w/w, of sulfonating agent such as herein described to the clear solution as obtained in step(a), under continuous stirring at a rate in the range of 5-15 ml per minute to obtain a macromonomer solution of melamine formaldehyde;
(c) adjusting the pH of the solution as obtained in step (b), in the range of 2-4 followed by subjecting the resulting solution to a temperature
of 50-80°C for a period in the range of 1-6 hours to obtain a polymeric solution of sulfonated melamine formaldehyde ionic condensate; (d) adding 1-4 % w/w, of CaO to the polymeric solution as obtained in step (c), under continuous stirring followed by separation of the resulting mixture after a period of not less than 6 hours and subsequent adjusting of pH of the separated mixture in the range of 10-14 to obtain the desired sulfonated melamine formaldehyde ionic condensate.
9. A process as claimed in claim 8, wherein the sulfonating agent used is selected from sulfonic acid, sulfamic acid, sulfanilic acid, sulfuric acid, sodium meta bisulfate, sodium sulfite and sodium bi-sulfite.
10. A process as claimed in claim 8, wherein the acid used for adjusting pH is selected from sulfuric acid, hydrochloric acid, perchloric acid.
11. A process as claimed in claim 8, wherein the separation process is such as filtration, sedimentation, settling.
12. A process as claimed in claim 8, wherein the alkali used is selected from sodium hydroxide, sodium bicarbonate, sodium carbonate.
13. A novel water soluble sulfonated melamine formaldehyde ionic condensate and a process for the preparation thereof substantially as described herein with reference to the examples.

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Patent Number

271025

Indian Patent Application Number

2135/DEL/2008

PG Journal Number

06/2016

Publication Date

05-Feb-2016

Grant Date

29-Jan-2016

Date of Filing

10-Sep-2008

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SELLAMUTHU NAGAPPAN JAISANKAR	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020
2	SIVAGAMA SUNDARI THIRUNAVUKKARASU	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020
3	JAMES KANAGARAJ	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020
4	SANJEEV GUPTA	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020
5	RAMAJEEVAN GANESH JEEVAN	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020
6	GANGA RADHAKRISHNAN	CENTRAL LEATHER RESEARCH INSTITUTE, ADYAR, CHENNAI-600 020

PCT International Classification Number

C14C 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA