FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE
Specification
(Section 10; rule 13)
A PROCESS FOR PREPARING A SUITABLE SULFONATED MELAMINE FORMALDEHYDE CONDENSATE SOLUTION (SMF)
GUJARAT STATE FERTILIZERS & CHEMICALS LTD.
of P.O.Fertilizernagar 391 750, Dist.Vadodara
Gujarat, India
an Indian Company

This invention relates to a process for the preparation of a plasticizkig composition.
In particular this invention relates to a process for making a melamine based plasticizing composition.
Still particularly, this invention envisages a process for the preparation of low salt containing, stable aqueous solution of Sulfonated Melamine Formaldehyde Condensate (SMF).
It is already known to prepare Sulfonated Melamine Formaldehyde Condensate (SMF) by several processes.
Thus, in US Patent No. 4677159 dated 30th June 1987 [no Indian equivalent] granted to Kuwait Institute for Scientific Research, SMF is prepared using (1) Melamine or Melamine and Urea which are condensed with Formaldehyde in an aqueous medium at a relative low temperature and pH of 10-13, followed by (2) the addition of a sulfonating agent, such as Sodium Meta bi-sulfite, and the reaction is continued without pH adjustment, followed by (3) lowering the temperature of the reaction medium to 40-60 degreeC, adjusting the pH to 2.5-4 and continuing the reaction for about 5-150 minutes "and finally-followed by (4) adjusting the pH 6.5-9, heating the reaction medium to 70-100 degree C for 30-180 minutes, adjusting the final solid content to a desired level and adjusting the pH to 8-11.
It is also known from US Patent No.3985696 dated 12th October 197& [no Indian equivalent] granted to Suddeutsche Kalkstickstoff - Werke A(G to
2
have a three stage process for preparation of SMF. In the first stage, Melamine, Formaldehyde and alkali metal sulfite are condensed in an aqueous solution at 60-80 degree C and pH 10-13 until the solution is free from readily detectable amounts of sulfite. In the second stage, condensation is continued at pH 3.0 -4.5 and temperature 30-60 degree C for 30-90 minutes. In the third stage, a temperature of 70 - 95 degree C and pH of 7.5 - 9.0 are maintained until a sample of the solution, when diluted to 20% solid by weight has a viscosity of 5 - 40 centipoises at 20 degree C.
Further US Patent No. 4444945 dated 24th April 1984 assigned to Monsanto Company [no Indian equivalent] describes a process wherein a low salt contain] ng aqueous solution of Melamine Formaldehyde condensation product having anionic Sulfo groups is prepared in a two stage process. In the first stage Melamine, Formaldehyde and bi-sulfite are condensed in an aqueous solution at atmospheric reflux and pH 8-10 for 1-5 hours. In the second stage, condensation is continued at pH 6-7 and atmospheric reflux for 2-6 hours. The product is then cooled and adjusted to pH 7-9.
Still further in US Patent No.4,820,766, there is disclosed a highly stable melamine-formaldehyde condensate solution for use as superplasticizer additives for cement or the like is produced by condensing melamine and formaldehyde in an aqueous medium, sulfonating the melamine-formaldehyde condensate, further condensing and stabilizing the aqueous sulfonated melamine-formaldehyde condensate solution. In the said US Patent No.4,820,766, the sulfonating agent quantity used was of a very high order, typically, in the range of 0.8 to 1.2:1 ratio based on sulphite to melamine.
3

It is an object of this invention to provide an improved process for preparation of
SMF using significantly less sulfonating agent and in which effluent/waste
generation is eliminated all together.
It is yet another object of this invention to provide a process, which will ensure
production of a low salt containing, high purity product.
Yet another object of this invention is to provide a process wherein process
conditions are non corrosive and employ commonly used low cost materials of
construction for the apparatus used in the process.
According to this invention there is provided a process for preparing a suitable Sulfonated Melamine Formaldehyde Condensate solution (SMF) which comprises the steps of:
(a) Condensing Melamine and Formaldehyde in an aqueous reaction medium having a Formaldehyde: Melamine ratio of from about 3:1 to 4:1 and pH of from about 10-12, the said condensation being conducted at a temperature: of from about 45 degree C to about 60 degree C for about 10 minutes to about 25 minutes;
(b) Sulfonating the Melamine - Formaldehyde condensate formed in step (a) by adding a sulfonating agent such as Sodium Meta bi-sulfite to the reaction medium obtained in step (a) and heating the said reaction medium to a temperature of from about 75 to 85 degree C for about 30-90 minutes without altering the pH of the reaction medium, the mole ratio of Melamine to sulfonating agent being 1 : 0.5 to 1 : 0.7;
(c) Further condensing the Sulfonated Melamine Formaldehyde condensate formed in step (b) by reducing the temperature of the reaction medium from step (b) to about 50 - 60 degree C, adjusting the pH thereof to about 4 - 5.5 by addition of diluted Sulfuric Acid solution and maintaining said temperature and pH conditions for the period of from about 15 minutes to about 60 minutes
4

followed by adjusting pH of the reaction medium to about 6.5 - 8.5 to step further condensation;
(d) Stabilizing the aqueous Sulfonated Melamine Formaldehyde condensate solution formed in step (c) by heating the reaction mixture to a temperature of from about 80 to 95 degree C for a period of from about 60 minutes to about 120 minutes;
(e) Cooling the reaction mass formed in step (d) to about 40 - 60 degree C and adjusting the pH to about 10.0 - 12.0;
(f) Filtering the reaction mass formed in step (e) under hot condition to remove any suspended impurities, cooling the resulting solution to ambient temperature and diluting the said solution with water to get sulfonated melamine formaldehyde condensate having a solid content ranging between 21 and 4^% of total mass.

Other sulfonating agents which may be used are sulfamic acid and sodium sulfite.

bi

Varying of the final solid content ranging between 21 and 42% of total rrjass gives rise to different grades of SMF.
The invention will now be described in detailed with respect to the following
examples:
Example I
1) In the first step, an aqueous formaldehyde solution was prepared by mixing 313.9 parts of formaldehyde solution having strength of 37.27% with 376.7 parts of water in a jacketed reaction kettle fitted with an agitator and a condenser, equipped with heating cooling system and instrumentation to measure temperature and pH. The pH of the solution was raised by addition
5
of 2 Volumetric parts of Caustic Soda Lye having strength of 47% W/W., The pH of the solution was observed to be 10.5. The reaction mixture was then heated to 45 degree C and 160.1 parts Melamine was added. The temperature of the reaction mixture rose due to addition of Melamine and was observed to be 56 degree C. The reaction medium was then cooled to 50 degree C after ascertaining complete dissolution of Melamine forming homogeneous mixture. The reaction medium was then maintained at 50 degree C for 15 minutes (including the period of cooling) to ensure complete condensation of Melamine with Formaldehyde.
In the second stage, 147.7 parts Sodium Meta bi-sulfite having 97% purity was added to the reaction mass. The temperature of the reaction mass rose by 15 degree C during addition and dissolution of Sodium Metal bi-sulfite. The resultant solution was kept for about 5 minutes under idle stirring. The temperature was then raised to 80 degree C in about 15 minutes period and was maintained at that temperature for another 60 minutes.
In the third stage, the reaction mass was cooled to 55 degree C in about 5
minutes. The pH of the reaction mass was then brought down to 5 by adding
16.4 volumetric parts of 14.5 N Sulfuric Acid. The temperature of the
reaction mixture was maintained at 55 degree C during addition of Sulfuric
Acid through external cooling. After completion of the addition the reaction
mixture was maintained at 55 degree C for another 30 minutes. The pH of
the reaction mass was then adjusted to 7 by addition of caustic soda lye.
Around 11 volumetric parts of caustic soda lye was consumed for the above
pH adjustment.
6

4) In the fourth stage, this reaction mixture was heated to 90 degree C in about 25 minutes and was maintained at that temperature for another 90 minutes. The solution was then cooled to 50 degree C and the pH was raised to 11.5 by adding 1.4 volumetric part of caustic soda lye
5) The reaction mass was finally discharged from the reactor and was filtered through a 50-micron pore size polypropylene filtering medium to remove suspended impurities.
6) The filtered solution was cooled to room temperature.
The solid content of the solution was found to be 42% WAV. The viscosity of the solution at 20 degree C was observed to be 28.7 centipoise.
The said content of above solution was adjusted to 21% WAV by addition of water for evaluation of properties.
The above 21% WAV solution was tested to evaluate its effect on
flowabmty/workability, water cement ratio and compressive strength of M-
30 concrete.
The composition of M-30 concrete used for the evaluation of properties was
as follows:
OPC-53 grade Cement of L&T make 400 parts
Water 188 parts
Sand (Zone-H) 564 parts
10 mm coarse aggregates 504 parts
20 mm coarse aggregates 756 parts
7

For testing purpose, first cement, sand and coarse aggregates were dry mixed thoroughly using a laboratory concrete mixer. Desired quantity of water was then added and ingredients were once again mixed thoroughly for about 1 minute. Finally desired quantity of admixture was added slowly and ingredients were once again mixed for about 1 minute.
The effect on slump, which is a reflection of workability is shown in Table-1 of the accompanying drawings for different does of 21% WAV SMF solution produced in the above example. The slump improvement of 200% was observed over the blank slump with super plasticizer dose of 1.2% VAV of cement.
The reduction in water cement ratio with different doses of super plasticizer was determined through trial and error procedure by observing and achieving near constant slump as per the blank reading. The results are tabulated in Table-2 of the accompanying drawings. It is observed that around 20% water reduction is possible with super plasticizer dose of 3% VAV of cement.
The cubes cast using reduced water cement ratio along with respective doses of super plasticizer as per Table-2 were tested for compressive streng:h at different periods and were compared with compressive strength of cubes cast without addition of any super plasticizer using M-30 concrete as per above formulation (using water/cement ratio of 0.47). The compressive strength comparison is given in the same Table i.e. Table-2.
8

Example II
of then
In the first step, an aqueous formaldehyde solution was prepared by mixing 35 kgs of formaldehyde solution having strength of 37.27% with 42 liters of water in a jacketed reaction kettle fitted with an agitator and a condenser, equipped with heating cooling system and instrumentation to measure temperature and pH. The pH of the solution was raised from an initial pH of 4.27 to 10.52 by addition of 215 ml of Caustic Soda Lye having strength of 47% WAV. The pH of the solution was observed to be 10.52. The reaction mixture was then heated to 52 degree C and 17.85 kg of Melamine was added. The temperature of the reaction mixture rose due to addition of Melamine and was observed to be 60 degree C. The reaction medium was then cooled to 50 degree C after ascertaining complete dissolution Melamine forming homogeneous mixture. The reaction medium was maintained at 50 degree C for 15 minutes (including the period of cooking) to ensure complete condensation of Melamine with Formaldehyde.
In the second stage, 16.45 kg of Sodium Meta bi-sulfite having 97% purity

was added to the reaction mass. The temperature of the reaction mass

rose

by 15 degree C during addition and dissolution of Sodium Metal bi-sulfite. The resultant solution was kept for about 5 minutes under idle stirring. The temperature was then raised to 80 degree C in about 15 minutes period, and was maintained at that temperature for another 60 minutes.
In the third stage, the reaction mass was cooled to 55 degree C in about 5 minutes. The pH of the reaction mass was then brought down to 5.05 by adding 1920 ml of 14.5 N Sulfuric Acid. The temperature of the reaction
9

mixture was maintained at 55 degree C during addition of Sulfuric Acid through external cooling. After completion of the addition the reaction mixture was maintained at 55 degree C for another 30 minutes. The pH of the reaction mass was then adjusted to 7 by addition of 1365 ml of caustic soda lye.
In the fourth stage, this reaction mixture was heated to 90 degree C in about 25 minutes and was maintained at that temperature for another 90 minutes. The solution was then cooled to 50 degree C and the pH was raised to 11.5 by adding 100 ml of caustic soda lye.
The reaction mass was finally discharged from the reactor and was filtered through a 50-micron pore size polypropylene filtering medium to remove suspended impurities.
The filtered solution was cooled to room temperature.
The solid content of the solution was found to be 41.66 % WAV. The viscosity of the solution at 20 degree C was observed to be 33.3 centipoise.
Solution of the SMF obtained was tested for its workability using the mini slump test:
600 gm cement - Vikram 43 grade was mixed with 210 ml of water (water cement ratio of 0.35) and 1.20 gm [0.2 % W/W of cement] of SMF obtained from the above experiment, having the solid content of 41.66% W/W was
10

added/ The mini slump spread area of this mixture was observed to be 606.7 sq. cm as compared to a spread area of 312.4 sq cm without the addition of SMF.
It may be observed that with 3% dose of SMF the rise in early compressive strength (7 days) is more than 41% and the rise in final compressive strength (28 days) is more than 30%.
The process, as developed in accordance with this invention, has following improvements over the process described in the prior art:
In the US Patent No.3985696, the polymerization step is carried out at much lower pH resulting in high corrosivity for the equipment used for manufacturing and also formation of higher quantity of inorganic salt resulting in higher acid alkali consumption and also undesirable effects during application.
In the process in accordance with this invention, polymerization is carried out at 5 pH overcoming the disadvantages mentioned above.
The reaction cycle of the process in accordance with this invention is shorter compared to the one mentioned in US Patent No. 4444945 which will have: advantage of higher production throughput for a given reactor size.
The consumption of Acid Alkali during stage no. 1 & 3 of the process mentioned in US Patent No. 4677159 is much higher compared to the
11
process in accordance with this invention. Besides the use of lime for neutralization results in gypsum formation which is a waste product with disposal problem. Moreover use of lime as a neutralizing agent also involves additional process step of centrifuging and washing which are eliminated in the process in accordance with this invention.
Thus the process described above has several advantages with respect to:
(1) specific consumption of Formaldehyde, Acid and .Alkali,
(2) simplified process steps,
(3) milder and non corrosive operating conditions,
(4) lower reaction cycle period and
(5) elimination of any solid or liquid waste generation.
Upon reading the subject application, various embodiments will become obvious to those skilled in the art. These embodiments are to be considered within the scope and spirit of the subject invention, which is only to be limited by the claims which follow and their equivalents,
12

We Claim:
[1] A process for preparing a suitable Sulfonated Melamine Formaldehyde Condensate solution (SMF) which comprises the steps of:
(a) Condensing Melamine and Formaldehyde in an aqueous reaction medium

pH
having a Formaldehyde: Melamine ratio of from about 3:l to 4:1 Hand
of from about 10-12, the said condensation being conducted at a temperature of from about 45 degree C to about 60 degree C for about 10 minutes to about 25 minutes;
(b) Sulfonating the Melamine - Formaldehyde condensate formed in step (a) by adding a sulfonating agent such as Sodium Meta bi-sulfite to the reaction medium obtained in step (a) and heating the said reaction medium to a temperature of from about 75 to 85 degree C for about 30-90 minutes without altering the pH of the reaction medium, the mole ratio of Melamine to sulfonating agent being 1 : 0.5 to 1 : 0.7;
(c) Further condensing the Sulfonated Melamine Formaldehyde condensate formed in step (b) 'by reducing the temperature of the reaction medium from step(b) to about 50 - 60 degree C, adjusting the pH thereof to about 4 - 5.5 by addition of diluted Sulfuric Acid solution and maintaining said temperature and pH conditions for the period of from about 15 minutes to
_ —about 60. minutes followed by adjusting pH of the reaction medium to about 6.5 - 8.5 to stop further condensation;
(d) Stabilizing the aqueous Sulfonated Melamine Formaldehyde condensate
solution formed in step (c) by heating the reaction mixture to a
temperature of from about 80 to 95 degree C for a period of from about
60 minutes to about 120 minutes;
13

(e) Cooling the reaction mass formed in step (d) to about 40 - 60 degree: C and adjusting the pH to about 10.0-12.0;
(f) Filtering the reaction mass formed in step (e) under hot condition to remove any suspended impurities, cooling the resulting solution to ambient temperature and diluting the said solution with water to get sulfonated melamine formaldehyde condensate having a solid consent ranging between 21 and 42% of total mass.
[2] A process for preparing a suitable Sulfonated Melamine Formaldehyde Condensate solution (SMF) as described herein with reference to the accompanying examples.
Dated this 27th day of August, 2002
Mohan Dewan
Of R K Dewan & Co
Applicants' Patent Attorneys
14
Abstract:
Stable, water soluble and low salt containing, Sulfonated Melamine Formaldehyde resin solution is prepared in a four stage process. In the first
stage Melamine is condensed with Formaldehyde in an aqueous medium at a

relatively low temperature of 45 - 60 degreeC and a pH of 10 - 12. This is

followed by the addition of a sulfonating agent such as Sodium Meta bi-

sulfite to carry out sulfonation reaction at a temperature ranging between 7p-90 degreeC for about 50-90 minutes. The third stage consists of I a polymerization step wherein the pH of the reaction mass is reduced to 4-5.5 along with the temperature to 45-65 degreeC and the reaction is carried out
for about 15-45 minutes. The pH is then adjusted to 6.5 - 8.6 to stop further
i reaction. In the final stage, reaction medium is heated to 80-95 degreeC for
60-120 minutes. The resultant aqueous solution is adjusted for desired solid
content after increasing the pH to 9-12. The resultant aqueous solution is
suitable for use as super plasticizer additive to hydraulically settable
cementitious materials.