JP3823368B2 - Method for producing water reducing agent aqueous solution - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a method for producing a sulfonated melamine formaldehyde resin aqueous solution used as a water reducing agent.
[0002]
[Prior art]
The purpose of reducing the amount of water in the uncured compound such as cement, mortar, concrete, etc., prepared to obtain a cured product of hydraulic cement, and improving the fluidity and workability of the compound Therefore, a sulfonated melamine formaldehyde resin is added as a so-called water reducing agent. In the case of obtaining a cured product of gypsum, a sulfonated melamine formaldehyde resin is similarly added to an uncured compound containing hemihydrate gypsum.
[0003]
  Several proposals relating to the improvement of the method for producing a sulfonated melamine formaldehyde resin as a water reducing agent have been disclosed. Japanese Patent Publication No. 63-37058 discloses that 1 mole of melamine, 2.7 to 3.3 moles of formaldehyde, and 0.9 to 1.2 moles of sulfite in water at a pH of 10 to 13 and a temperature of 60 to 80 ° C. The first step of heating for 60 minutes, followed by the second step of heating the product solution of the first step at a pH of 5-6 and a temperature of 40-60 ° C. for 30-150 minutes, and immediately the product solution of the second step of 12-12 A method comprising a third step of adjusting to a pH of 13.5 and cooling at the same time, having a solids content of 30-50% by weight directly without removing water during these steps and having high stability A method for producing an aqueous agent solution is disclosed.
[0004]
  Japanese Patent Publication No. 1-40850 discloses 1 mol of melamine, 3.5 to 6 mol of formaldehyde, and 0.5 to 1 mol of compound-1 (wherein compound-1 is an alkali sulfite, an alkaline earth sulfite, an alkali And at least one selected from the group consisting of sulfate, alkaline earth sulfate, aminosulfonic acid, amino acid, aminodicarboxylic acid, hydroxycarboxylic acid, hydroxycarboxylic acid lactone and sulfamic acid). Reacting at a temperature of 75 to 90 ° C. in an alkaline medium having a pH of 9.0 to 13.0, the mixture obtained in step (a) is 0.1 to 0.1 mol per 1 mol of melamine used in step (a). 3 moles of compound-2 (wherein compound-2 is an amino acid, aminocarboxylic acid, aminodicarboxylic acid, carboxylic acid, hydroxycarboxylic acid, hydroxycarboxylic acid lactone, sulfamine) (B) at least one selected from the group consisting of acids, aminosulfonic acids, polyhydroxycarboxylic acids and polyhydroxycarboxylic acid lactones) at a pH of 5.5 to 6.5 and 75 to 90 ° C. , Basic compound-3 (however, basic compound-3 is amine, polyamine, alkali oxide, alkali hydroxide, ammonium hydroxide, alkaline earth oxide, alkali) to the resin solution obtained in step (b). PH of the solution by adding at least one selected from earth hydroxide, monoethanolamine, diethanolamine, triethanolamine, basic salts of transition metals, and basic salts of zinc or aluminum. The method for producing an aqueous solution of melamine / aldehyde resin is developed by cooling the solution obtained in step (C) and adjusting the pH to 8.0 to 13.0, and in step (C). It is shown.
[0005]
  Japanese Examined Patent Publication No. 6-21173 discloses a first step in which 1 mol of melamine and 2.6 to 3.4 mol of formaldehyde are reacted at a pH of 3 to 11 in water, preferably for 15 to 25 minutes, and then 1 mol of mol. The second step of adding 0.7-1.3 moles of sulfite to melamine and reacting at 9-13 pH and 50-90 ° C. for 1-5 hours, then at 3.5-6.5 pH and 40-90 ° C. The third step of the condensation reaction for 1 to 5 hours, and then the pH is adjusted to 9 to 13, then cooled to 40 to 70 ° C., and further 0.01 to 0.30 mol of sulfite is added, preferably for 20 to 30 minutes. The manufacturing method of the sulfone group containing melamine formaldehyde resin which consists of a 4th process to make is disclosed.
[0006]
[Problems to be solved by the invention]
The aqueous solution of water reducing agent by the method described in the above Japanese Patent Publication No. 63-37058 has excellent water reducing agent performance, but contains formaldehyde derived from the raw material in about 0.3% by weight with respect to the solid content in the water reducing agent. There are many. Since ordinary cement, mortar, concrete, and other compounds containing a sulfonated melamine formaldehyde resin water reducing agent solution are gradually dried and hardened, the formaldehyde that gradually evaporates from the water reducing agent with this drying is reduced in the workplace. It is rare to reach high concentrations in the working environment to the extent that it harms the surroundings. However, as the placement of high-strength concrete by increasing the amount of water-reducing agent has gradually increased, the problem of contamination around the workplace due to volatilized formaldehyde has been newly pointed out. Yes. The water reducing agent according to the method described in the above Japanese Patent Publication No. 1-40850 often contains formaldehyde exceeding 1.0% by weight with respect to the solid content in the water reducing agent, and has the same problem as described above. Since hydraulic gypsum formulations generally have a high water reducing agent content and are often dried in a dryer, the problem of contamination of the work environment by volatilized formaldehyde is even more serious.
[0007]
  The water reducing agent described in the above Japanese Patent Publication No. 6-21727 has improved storage stability, but its production method is such that the melamine and formaldehyde are first reacted in the first step, and then the second step. It is a simple method in that it takes 1 to 5 hours to add sulfite, and it is necessary to add sulfite in the fourth step, and it takes a long time to measure and react the raw material three times. Absent. In this method, the sulfite added in the fourth step reacts with unreacted formaldehyde immediately after the addition, and the amount of formaldehyde in the water reducing agent is reduced. Since the amount of formaldehyde in the water reducing agent increases to the original amount, it is difficult to provide as a product containing formaldehyde at a certain low value.
[0008]
  The present invention provides a water reducing agent aqueous solution of a sulfonated melamine formaldehyde resin having excellent water reducing agent performance and extremely low content of formaldehyde, for example, 0.05% by weight or less based on the solid content in the water reducing agent. An object of the present invention is to provide a method for producing efficiently.
[0009]
[Means for Solving the Problems]
  Of the present inventionThe method for producing the sulfonated melamine formaldehyde resin water reducing agent aqueous solution includes the following steps (a), (b), (c) and (d):
(A) In an aqueous medium, at least one sulfonate group-containing compound selected from the group consisting of an alkali metal sulfite, a sulfamate, and a sulfanilate, melamine, formaldehyde, and alkali are added to 1 mol of melamine. Formaldehyde is added in a ratio of 2.0 to 5.0 moles and the sulfonate group-containing compound is added in a ratio of 0.5 to 1.5 moles to form a reaction mixture having a pH of 9.0 to 13.5, and the reaction mixture is mixed with 50 to 95 moles. A step of producing a transparent solution by heating at 0 ° C. until none of the sulfonate group-containing compound and the addition reaction product of formaldehyde with formaldehyde is detected in the reaction mixture;
(B) The transparent solution produced in step (a) is heated at 80 to 95 ° C. for 10 to 120 minutes while maintaining the pH in the range of 11.0 to 13.5 as it is or by adding alkali to the solution. Process,
(C) An acidic solution having a pH of 4 to 7 is formed by adding an inorganic acid to the solution obtained by heating in step (b), and the acidic solution is heated at 50 to 95 ° C. for 10 to 10 ° C. Producing an aqueous solution of a sulfonated melamine formaldehyde resin by heating for 300 minutes; and
(D) A strongly alkaline aqueous solution of a sulfonated melamine formaldehyde resin having a pH of 13.0 to 14.0 is formed by adding an alkali to the aqueous solution of the sulfonated melamine formaldehyde resin produced in the step (c), and the strong alkaline aqueous solution Is heated at 80 to 95 ° C. for 10 to 180 minutes.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Of the present invention(A)The melamine, formaldehyde and sulfonate group-containing compounds used in the process may be ordinary industrial products and can be obtained as commercial products. Examples of formaldehyde industrial products include formalin, paraformaldehyde, and examples of sulfonate group-containing compounds include sulfites such as sodium sulfite and potassium sulfite, sulfamic acids such as sodium sulfamate and potassium sulfamate. Examples thereof include salts, sulfanilates such as sodium sulfanilate and potassium sulfanilate. Examples of preferable alkali added for pH adjustment include sodium hydroxide and potassium hydroxide.
[0011]
  (A)As the reaction mixture formed in the process, amino group-containing compounds other than melamine, such as urea, guanamine, dicyandiamide, thiourea, etc., are added in an amount of 0.2 mol of amino groups of these amino group-containing compounds with respect to 1 mol of amino groups of melamine. You may contain in the ratio to. The reaction mixture comprises medium water, melamine, formaldehyde, and a sulfonate group-containing compound in a ratio of 2.0 to 5.0 moles, preferably 2.2 to 4.5 moles of formaldehyde per mole of melamine, and a sulfonate group-containing compound. Is added in a ratio of 0.5 to 1.5 moles, preferably 0.7 to 1.3 moles per mole of melamine, and an amount of alkali is added such that the reaction mixture exhibits a pH of 9.0 to 13.5, preferably 10.0 to 13.5. Can be formed. The amount of these substances added to the medium water to form the reaction mixture is preferably based on about 5 to 70 parts by weight of melamine per 100 parts by weight of water in the reaction mixture.Any step of (a) to (d)In addition, although concentration by vacuum concentration or dilution by addition of water can be performed, it is preferable to produce a water reducing agent aqueous solution without performing concentration in any step,(D) ProcessIn the reaction mixture such that the solid content concentration of the aqueous solution of the water reducing agent obtained in is 20 to 60% by weight, preferably 30 to 50% by weight(A) ProcessIt is preferable to start.
[0012]
  (A) ProcessThen, the reaction mixture formed is heated at 50-95 ° C., preferably 70-90 ° C., preferably with stirring. It is preferred to keep the reaction mixture at a pH of 9.0 or higher during this heating. This heating is performed until neither the sulfonate group-containing compound added to the reaction mixture nor the addition reaction product of the sulfonate group-containing compound and formaldehyde is detected, and usually ends in about 10 to 120 minutes. Can be made. this(A) ProcessAs a result, sulfonated methylol melamine is produced in the liquid.(A) ProcessThe finished product is a clear solution and usually has a pH above 9.0.
[0013]
  Aqueous solution of sulfonated melamine formaldehyde resin with low formaldehyde contentIt can be produced by a method comprising the steps (a) to (d).in this way(A) ProcessIs first started. In the step (b), after the completion of the step (a), it is preferably heated immediately. However, when the transparent solution generated in the step (a) has a pH outside the range of 11.0 to 13.5, the solution is alkalinized. Alternatively, an acid is added to form a solution having a pH of 11.0 to 13.5, preferably 11.5 to 13.0. As this added alkali,Step (a) aboveIt may be the same as that used in the above example. The solution is then heated at 80-95 ° C, preferably 85-90 ° C for 10-120 minutes, preferably 20-90 minutes. The end-of-heating solution has a pH lower than that before the heating, but is still alkaline.
[0014]
  In step (c), after completion of step (b), preferably immediately after adding an inorganic acid to the solution formed in step (b), a pH of 4 to 7, preferably 4.5 to 6.5 is obtained. An acidic solution is formed. Preferable examples of the inorganic acid to be added include mineral acids such as hydrochloric acid, sulfuric acid and nitric acid, and sulfamic acid. The solution adjusted to be acidic in this manner is heated at 50 to 95 ° C., preferably 60 to 90 ° C., for 10 to 300 minutes, preferably 30 to 240 minutes. If necessary, the inorganic acid may be added during the heating in order to maintain the pH in the above range. However, it is not usually necessary, and the aqueous solution of the sulfonated melamine formaldehyde resin still having an acidic pH is not necessary. Produces.
[0015]
  In step (d), after completion of step (c), preferably immediately after adding alkali to the solution produced in step (c), it has a pH of 13.0 to 14.0, preferably 13.2 to 13.8. A strongly alkaline aqueous solution is formed. As the added alkali, the above(A) ProcessIt may be the same as that used in the above example. The solution thus adjusted to be strongly alkaline is heated at 80 to 95 ° C., preferably 85 to 90 ° C., for 10 to 180 minutes, preferably 20 to 150 minutes. If necessary, the alkali may be added during the heating in order to maintain the pH in the above range. However, it is usually not necessary, and the heating does not require 0.01% by weight or less of formaldehyde with respect to the solid content in the liquid. An aqueous solution of a sulfonated melamine formaldehyde resin showing the content is obtained.
[0016]
  (A) ProcessIn the case of changing the ratio of formaldehyde to melamine and using less than 2 moles of formaldehyde per mole of melamine,Solid melamine remains in the liquid.And if you use more than 5 moles of formaldehyde per mole of melamine,(A) ProcessThe amount of formaldehyde remaining in the product liquid increases.(A) ProcessIn the above, when the ratio of the sulfonate group-containing compound to melamine is changed, and the sulfonate group-containing compound is used in an amount of less than 0.5 mol per mol of melamine,(D) ProcessThis product liquid does not have sufficient stability. And when the above sulfonate group-containing compound is used in an amount of more than 1.5 mol per mol of melamine,(A) ProcessA large amount of this sulfonate group-containing compound remains in the product solution, or(D) ProcessIn the product liquid, undesirable by-products are contained.(A) ProcessWhen the pH of the reaction mixture is changed to a pH lower than 9.0, the formation reaction of the sulfonated methylol melamine is slowed down, and even when adjusted to a pH higher than 13.5, the formation rate of the sulfonated methylol melamine is no longer increased. Without this, unnecessary alkali is consumed.(A) ProcessIn this case, when the heating temperature is changed and the heating is performed at a temperature lower than 50 ° C., the production rate of the sulfonated methylol melamine is lowered, so that such a low temperature is not suitable for the production method for industrial production. When heated at temperatures above 95 ° C, the stirred reaction mixture may boil, requiring additional equipment to operate safely, or special equipment to heat under pressure. Necessary.(C) ProcessIf the pH of the solution is changed to a pH lower than 4, gelation tends to occur during heating, and if the pH is higher than 7, it takes a long time to produce a sulfonated melamine formaldehyde resin.(C) ProcessIn the case of heating at a temperature lower than 50 ° C by changing the heating temperature, it takes a long time to produce a sulfonated melamine formaldehyde resin, and when heated at a temperature higher than 95 ° C under normal pressure,(A) ProcessAs in the case of, additional equipment and special equipment are required.(C) ProcessIn, when changing the heating time and stopping the heating within 10 minutes,(D) ProcessA water reducing agent having high performance cannot be obtained by heating in the same manner as in the above. And300 Min or moreFurther, when heated, gelation occurs during the heating, or a water reducing agent having high performance cannot be obtained.
[0017]
  (D) ProcessSignificantly reduces the formaldehyde content in the resulting water reducing agent aqueous solution.(D) ProcessIf the pH of the solution is changed to a pH lower than 13.0, a water reducing agent aqueous solution with a sufficiently low formaldehyde content cannot be obtained, and a solution to which an alkali is further added after reaching a pH of 14.0 can be prepared. The formaldehyde content in the water reducing agent aqueous solution is not further reduced.(D) ProcessIn this case, if the heating time is changed and heating is stopped within 10 minutes, the formaldehyde content in the liquid cannot be sufficiently reduced, and even if heated for 180 minutes or more, the formaldehyde content in the liquid is no longer reduced. It cannot be further reduced.
[0018]
  In the method comprising the steps (a) to (d), the step (b) significantly reduces the formaldehyde content in the water reducing agent aqueous solution produced in the step (d). In step (b), if the pH of the solution is changed to a pH lower than 11, in the step (d), the formaldehyde content in the aqueous solution of the water reducing agent produced in step (d) is not sufficiently lowered and adjusted to a pH higher than 13.5. Even if, the formaldehyde content rate in the water reducing agent aqueous solution produced | generated at (d) process does not fall further. In the step (b), if the heating temperature is changed and the heating is performed at a temperature lower than 80 ° C., heating for a long time exceeding 120 minutes is required, which is not preferable. And when heated at a temperature higher than 95 ° C under normal pressure,(A)As in the process, additional equipment and special equipment are required. In the step (b), when the heating time is changed and heating is stopped within 10 minutes, the formaldehyde content in the resulting water reducing agent aqueous solution is not sufficiently lowered even if the heating is performed in the same manner as in the step (d). And even if it heats for 120 minutes or more, when it heats similarly to (d) process, the formaldehyde content rate in the water reducing agent aqueous solution to produce | generate does not fall further.
[0019]
【Example】
referenceExamples 1, 2, 5 and 6 are examples showing the production of a water reducing agent aqueous solution by steps (A) to (C) and the formaldehyde content of the obtained water reducing agent aqueous solution. Example 3 is an example showing the production of a water reducing agent aqueous solution by steps (a) to (d) and the formaldehyde content of the obtained water reducing agent aqueous solution.
[0020]
  Example 4referenceIt is the example which added the water reducing agent obtained in Example 1 and Example 3 to concrete, and tested the water reducing agent performance.
The formaldehyde content rate of the water reducing agent aqueous solution was measured by the following formaldehyde measurement method.
[0021]
  Method for measuring formaldehyde: 1 g of the sample is taken from the aqueous solution of water reducing agent, and 19 g of isopropanol is added thereto to precipitate the resin component. Then, the precipitate is filtered off while washing with isopropanol, and the entire filtrate is collected. The amount of formaldehyde is measured by the acetylacetone method described in JIS A 5908 5.8.2.
[0022]
  referenceExample 1
In this example, the following water reducing agent aqueous solution P₁~ P₁₄Was prepared. P₁~ P₉IsreferenceExamples and P_Ten~ P₁₄IsreferenceIt is a comparative example.
Water reducing agent aqueous solution P₁ Preparation of (A): Formalin 365 g having a formaldehyde concentration of 37 wt%, 446 g of 35 wt% sodium hydrogen sulfite aqueous solution, 189 g of melamine powder of industrial products, 28 g of 32 wt% sodium hydroxide aqueous solution, A reaction mixture having a pH of 11.5 was formed by adding 60 g of water with stirring. The reaction mixture was heated to 80 ° C. with stirring, and the heating was continued while maintaining this temperature, and a detection test for sulfite ions and hydroxymethanesulfonate ions in the reaction mixture was carried out by liquid chromatography analysis every 10 minutes. went. When the final sulfite ion and hydroxymethanesulfonate ion were no longer detected in the reaction mixture, the heating was stopped and cooled to obtain 1088 g of a clear solution. This solution exhibited a pH of 12.8.
[0023]
  Step (B): Immediately after the end of step (A), an acidic solution having a pH of 5.5 was formed by adding 195 g of water and 45 g of sulfamic acid to the total amount of the above clear solution with stirring. . The acidic solution was then kept under stirring at 70 ° C. and heating was continued for 180 minutes, at which point heating was stopped. A portion of the resulting aqueous solution was sampled and the viscosity of the solution adjusted to pH 12 was measured and found to be 55 mPa · s at 20 ° C.
[0024]
  Step (C): Immediately after completion of Step (B), a 32% by weight aqueous sodium hydroxide solution is added to the aqueous solution obtained in Step (B) to form a strongly alkaline aqueous solution having a pH of 13.5. It was. Next, the strongly alkaline aqueous solution was heated at 90 ° C. for 60 minutes and then immediately cooled to obtain a water reducing agent aqueous solution (P₁) This aqueous water reducing agent solution had a viscosity of 50 mPa · s and a pH of 12.0 at 20 ° C. and contained 50 ppm by weight of formaldehyde relative to its solid content.
[0025]
  Water reducing agent aqueous solution P₂~ P₁₄Preparation: Water reducing agent aqueous solution P₁(C) except that the process (C) was changed as shown in Table 1.₁The amount of formaldehyde in the aqueous solution of the resulting water reducing agent was measured. The weight ratio of formaldehyde to its solids is shown in Table 1.
〔table 1〕
                            Table 1
―――――――――――――――――――――――――――――――――――
Water reducing agent(C) Process       Formaldehyde amount
Aqueous solution pH Temperature (℃) Heating time (min) (ppm)
―――――――――――――――――――――――――――――――――――
P₁ 13.5 90 60 50
P₂ 13.5 80 60 210
P_Three 13.5 95 60 50
P_Four 13.2 90 60 220
P_Five 13.8 90 60 50
P₆ 13.5 90 10 200
P₇ 13.5 90 180 50
P₈ 13.5 80 180 50
P₉ 13.5 95 10 130
P_Ten 13.5 70 0 3000
P₁₁ 11.1 90 60 3000
P₁₂ 12.8 90 60 900
P₁₃ 13.5 70 180 700
P₁₄ 13.5 90 5 600
―――――――――――――――――――――――――――――――――――
referenceExample 2
In this example,referenceExcept that the steps (A), (B) and (C) in Example 1 were changed as shown in Table 2.referenceIn the same manner as in Example 1, the following water reducing agent aqueous solution P₁₅~ P₁₉Was prepared. P₁₅~ P₁₈Is an example and P₁₉Is a comparative example. In Table 2, the (A) step molar ratio F / M value represents the molar ratio of formaldehyde to melamine, the S / M value represents the molar ratio of sulfite to melamine, and T represents the temperature, t represents time, and the amount of HCHO represents the weight ratio of formaldehyde to solid content in the water reducing agent.
(Table 2)
                            Table 2
―――――――――――――――――――――――――――――――――――――
Water reducing agent(A) Process molar ratio    ( B ) Process      ( C ) Process     HCHO
Aqueous solution F / M S / M pH T (° C) t (min) pH T (° C) t (min) Amount (ppm)
―――――――――――――――――――――――――――――――――――――
P₁₅ 2.2 1.0 4.5 70 180 13.2 90 60 40
P₁₆ 4.5 1.0 5.5 70 180 13.8 90 60 400
P₁₇ 3.0 1.3 4.5 70 180 13.5 90 60 50
P₁₈ 3.0 0.6 6.0 70 180 13.5 90 60 80
P₁₉ 6.0 1.0 5.5 70 180 13.8 90 60 5000
―――――――――――――――――――――――――――――――――――――
Also in this example, the water reducing agent of the present invention showed a remarkably low formaldehyde content.
[0026]
  Example 3
In this example, the following water reducing agent aqueous solution P₂₀~ P₂₇Was prepared.
[0027]
  Water reducing agent aqueous solution P₂₀ Preparation of:
(A) Process: 365 g of formalin having a formaldehyde concentration of 37 wt%, 446 g of 35 wt% aqueous sodium hydrogen sulfite solution, 189 g of melamine powder as an industrial product, 28 g of 32 wt% sodium hydroxide aqueous solution, and 60 g of water Were added with stirring to form a reaction mixture having a pH of 11.5. The reaction mixture was heated to 80 ° C. with stirring, and the heating was continued while maintaining this temperature, and a detection test for sulfite ions and hydroxymethanesulfonate ions in the reaction mixture was carried out by liquid chromatography analysis every 10 minutes. went. Stop heating and cool down when the last sulfite and hydroxymethanesulfonate ions are no longer detected in the reaction mixturethingGave 1088 g of a clear solution. This solution exhibited a pH of 12.8.
Step (b): Immediately after the end of step (a), a solution having a pH of 13.0 was formed by adding 32% by weight aqueous sodium hydroxide solution to the total amount of this transparent solution. The solution was then heated at 90 ° C. for 60 minutes to obtain a solution having a pH of 9.5.
Step (c): Immediately after completion of Step (b), add 195 g of water and 45 g of sulfamic acid to the total amount of the solution obtained in Step (b) with stirring to add an acidic solution having a pH of 5.0. A solution was formed. The acidic solution was then kept under stirring at 70 ° C. and heating continued for 180 minutes, at which point heating was stopped.
Step (d): Immediately after completion of step (c), a 32% by weight aqueous sodium hydroxide solution is added to the aqueous solution obtained in step (c) to form a strongly alkaline aqueous solution having a pH of 13.5. It was. Next, the strongly alkaline aqueous solution was heated at 90 ° C. for 60 minutes and then immediately cooled to obtain a water reducing agent aqueous solution (P₂₀) This aqueous solution of water reducing agent contained 38% by weight of solid, showed a viscosity of 40 mPa · s and a pH of 12.4 at 20 ° C., and no formaldehyde was detected by the above measurement method.
[0028]
  Water reducing agent aqueous solution P_{twenty one}~ P₂₇Preparation of:
For pH adjustment in the steps (a) and (b), the addition amount of the 32 wt% sodium hydroxide aqueous solution is increased or decreased. For pH adjustment in the step (c), the addition amount of sulfamic acid is increased or decreased. Other than changing to the steps (a) and (b) described in Table 3, P₂₀The amount of formaldehyde in the aqueous solution of the resulting water reducing agent was measured. In Table 3, T represents temperature, t represents time, and the amount of HCHO represents the weight ratio of formaldehyde to solid content in the water reducing agent.
(Table 3)
                          Table 3
――――――――――――――――――――――――――――
Water reducing agent(a) Process    ( b ) Process     HCHO
Aqueous solution pH pH T (° C) t (min) Amount (ppm)
――――――――――――――――――――――――――――
P_{twenty one} 11.5 13.0 80 120 No detection
P_{twenty two} 11.5 13.0 80 30 40
P_{twenty three} 11.5 13.0 90 120 No detection
P_{twenty four} 11.5 13.0 95 10 40
P_{twenty five} 11.5 12.0 90 120 No detection
P₂₆   9.0 13.0 90 60 Not detected
P₂₇  9.0 10.0 90 60 50
――――――――――――――――――――――――――――
The results in Table 3 also show that the water reducing agent according to the present invention has a significantly lower formaldehyde content.
[0029]
  Example 4
As a water reducing agent,referenceExample P₁, P_Three,ExampleP_{twenty one} , P_{twenty three} as well asreferenceComparative Example P_Ten Prepared. 320kg / m^ThreeThree kinds of mixed ordinary Portland cement and 0.4% by weight of water reducing agent P in terms of solid content with respect to this cement₁180kg / m^ThreeOf 40 liters of concrete by blending crushed stone 2005 as coarse aggregate and 48% by volume of Kinugawa river sand from the coarse aggregate and fine aggregate as fine aggregate. Object C₁Was prepared. Similarly, P_ThreeConcrete compound with addition of C_Three, P_{twenty one} Concrete compound with addition of C_{twenty one} , P_{twenty three} Concrete compound with addition of C_{twenty three} And P_Ten Comparative concrete mix C with added_Ten Was prepared.
[0030]
  Subsequently, the slump value (cm) and the amount of air (%) were measured for these concrete blends according to JISA 1101 and 1128, and the results shown in Table 4 were obtained.
[Table 4]
              Table 4
――――――――――――――――――――――
Concrete slump value Air volume
    Compound (cm) (%)
――――――――――――――――――――――
  C₁             18.0 1.5
  C₃             18.5 1.7
  C₂₁            18.0 1.4
  C₂₃            18.0 1.8
  C₁₀            18.0 1.7
――――――――――――――――――――――
The results in Table 4 show that the water reducing agent according to the present invention has the same or better performance than the conventional water reducing agent.
referenceExample 5
In this example, sodium sulfamate was used as the sulfonate group-containing compound.
Step (A): 365 g of formalin having a formaldehyde concentration of 37 wt%, 510 g of 35 wt% sodium sulfamate aqueous solution, 189 g of melamine powder of industrial products, 28 g of 32 wt% sodium hydroxide aqueous solution, and 26 g of water Were added with stirring to form a reaction mixture having a pH of 13.0. The reaction mixture was heated to 80 ° C. with stirring, and the heating was continued while maintaining this temperature, and by addition of sulfamic acid and sulfamic acid and formaldehyde in the reaction mixture every 10 minutes by liquid chromatography analysis An object detection test was conducted. When the final sulfamic acid and addition reaction product of sulfamic acid and formaldehyde were no longer detected in the reaction mixture, the heating was stopped and cooled to obtain 1118 g of a clear solution. This solution exhibited a pH of 12.5.
[0031]
  Step (B): Immediately after completion of step (A), an acidic solution having a pH of 6.0 was formed by adding 195 g of water and 40 g of sulfamic acid with stirring to the total amount of the above clear solution. . The acidic solution was then kept under stirring at 70 ° C. and heating was continued for 180 minutes, at which point heating was stopped. A portion of the resulting aqueous solution was sampled and the viscosity of the solution adjusted to pH 12 was measured and found to be 65 mPa · s at 20 ° C.
[0032]
  Step (C): Immediately after completion of Step (B), a 32% by weight aqueous sodium hydroxide solution is added to the aqueous solution obtained in Step (B) to form a strongly alkaline aqueous solution having a pH of 13.5. It was. Next, this strongly alkaline aqueous solution was heated at 90 ° C. for 60 minutes and then immediately cooled to obtain a water reducing agent aqueous solution. This aqueous reducing agent solution contained 39% by weight solids, exhibited a viscosity of 60 mPa · s and a pH of 12.1 at 20 ° C., and contained 60 ppm by weight of formaldehyde relative to the solids.
[0033]
  referenceExample 6
In this example, sodium sulfanilate was used as the sulfonate group-containing compound.
Step (A): To 365 g of formalin having a formaldehyde concentration of 37% by weight, 976 g of a 20% by weight sodium sulfanilate aqueous solution, 189 g of an industrial product melamine powder, and 28 g of a 32% by weight sodium hydroxide aqueous solution are stirred. Was added to form a reaction mixture having a pH of 13.0. The reaction mixture was heated to 80 ° C. with stirring, and heated while maintaining this temperature, and an addition reaction of sulfanilic acid and sulfanilic acid and formaldehyde in the reaction mixture was carried out every 10 minutes by liquid chromatography analysis. An object detection test was conducted. When no last sulfanilic acid or addition product of sulfanilic acid and formaldehyde was detected in the reaction mixture, the heating was stopped and cooled to obtain 1558 g of a clear solution. This solution exhibited a pH of 12.5.
Step (B): Immediately after the end of step (A), an acidic solution having a pH of 6.0 was formed by adding 40 g of sulfamic acid to the total amount of the transparent solution with stirring. The acidic solution was then kept under stirring at 70 ° C. and heating was continued for 210 minutes, at which point heating was stopped. A part of the produced aqueous solution was collected, and the viscosity of the liquid whose pH was adjusted to 12 was measured and found to be 25 mPa · s at 20 ° C.
Step (C): Immediately after completion of Step (B), a 32% by weight aqueous sodium hydroxide solution is added to the aqueous solution obtained in Step (B) to form a strongly alkaline aqueous solution having a pH of 13.5. It was. Next, this strongly alkaline aqueous solution was heated at 90 ° C. for 60 minutes and then immediately cooled to obtain a water reducing agent aqueous solution. This aqueous water reducing agent solution contained 31 wt% solids, exhibited a viscosity of 22 mPa · s and a pH of 12.1 at 20 ° C., and contained 80 ppm by weight of formaldehyde relative to the solids.
[0034]
【The invention's effect】
According to the present invention, a sulfonated melamine formaldehyde resin water reducing agent aqueous solution having a remarkably low formaldehyde content can be efficiently produced as a water reducing agent aqueous solution having a concentration as high as 30 to 50% by weight as desired. And(B) Process and (d) ProcessSince both are efficient methods comprising pH adjustment and heating, the method of the present invention including such steps is suitable for industrial production of a water reducing agent aqueous solution.
[0035]
  The water-reducing agent aqueous solution produced by the method of the present invention exhibits high water-reducing agent performance and can be applied to various uncured compounds such as cement, mortar, concrete, etc. It can be used by adding to the cured formulation.

Claims (1)

The following steps (a), (b), (c) and (d):
(A) In an aqueous medium, at least one sulfonate group-containing compound selected from the group consisting of an alkali metal sulfite, a sulfamate, and a sulfanilate, melamine, formaldehyde, and alkali are added to 1 mol of melamine. Formaldehyde is added in a ratio of 2.0 to 5.0 moles and the sulfonate group-containing compound is added in a ratio of 0.5 to 1.5 moles to form a reaction mixture having a pH of 9.0 to 13.5, and the reaction mixture is mixed with 50 to 95 moles. A step of producing a transparent solution by heating at 0 ° C. until none of the sulfonate group-containing compound and the addition reaction product of formaldehyde with formaldehyde is detected in the reaction mixture;
(B) The transparent solution produced in step (a) is heated at 80 to 95 ° C. for 10 to 120 minutes while maintaining the pH in the range of 11.0 to 13.5 as it is or by adding alkali to the solution. Process,
(C) An acidic solution having a pH of 4 to 7 is formed by adding an inorganic acid to the solution obtained by heating in step (b), and the acidic solution is heated at 50 to 95 ° C. for 10 to 10 ° C. A step of producing an aqueous solution of a sulfonated melamine formaldehyde resin by heating for 300 minutes, and adding an alkali to the aqueous solution of the sulfonated melamine formaldehyde resin produced in steps (d) and (c), thereby providing a pH of 13.0 to 14.0. A method for producing a sulfonated melamine formaldehyde resin water reducing agent aqueous solution comprising the steps of: forming a strongly alkaline aqueous solution of a sulfonated melamine formaldehyde resin having a temperature of 10 to 180 minutes at 80 to 95 ° C.