JPH0627173B2 - Method for producing melamine formaldehyde resin containing sulfonic acid group - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a sulfone group-containing melamine formaldehyde resin. More specifically, it is possible to prevent the deterioration of the workability of concrete or mortar paste with the passage of time, improve the workability and workability of the paste, and have extremely good storage stability. The present invention relates to a method for producing a group-containing melamine formaldehyde resin.

[Conventional technology and its problems]

A cement mixture prepared by mixing cement, water and gravel, an admixture or an admixture, has a physical and chemical agglomeration of the cement with the passage of time after kneading and loses fluidity, resulting in workability and workability. Decreases with time. For example, when pumping cement mixture for pumping for some reason and then restarting pumping, the fluidity of the cement mixture in the pipe decreases, and when pumping is restarted, the pumping pressure rises or is blocked. There is also.

The fluidity is improved by increasing the blending amount of water, but this causes a remarkable decrease in concrete strength.

As a conventional cement water reducing agent to solve these problems,
Lignin sulfonate, oxycarboxylate, naphthalene sulfonate formalin condensate, sulfone group-containing melamine formaldehyde resin, etc. have been proposed. However, it is difficult to say that these conventional techniques sufficiently satisfy the dispersion fluidity, the slump holding power, the storage stability, and the like, which can cope with the recent progress in the construction and civil engineering techniques, and improvements thereof have been strongly desired.

The object of the present invention is to have a long-term storage stability of 18 months or more,
Another object of the present invention is to provide a method for easily and efficiently producing a sulfone group-containing melamine formaldehyde resin having excellent cement water reducing performance and suitable as a high strength concrete water reducing agent aqueous solution.

[Means for solving problems]

The present inventors have conducted intensive studies to improve the storage stability, dispersion fluidity, etc. of sulfo group-containing melamine formaldehyde resin, and the pH of the reaction solution after the condensation reaction and the addition of sulfite after the reaction are the product solutions. The present invention has been completed by finding that it significantly affects the performance as a cement water reducing agent.

That is, the present invention is a method for producing a sulfo group-containing melamine formaldehyde resin, which comprises the following first to fourth reaction steps.

(a) Molar ratio of melamine and formaldehyde in an aqueous medium
1.0: 2.6-3.4, primary reaction step of reacting at pH 3-11, (b) then 0.7-1.3 per mol of melamine with sulfite.
A second reaction step in which the reaction is carried out at a pH of 9 to 13 and a temperature of 50 to 90 ° C for 1 to 5 hours by adding a mole, and (c) then a condensation reaction of 1 to 5 hours at a pH of 3.5 to 6.5 and a temperature of 40 to 90 ° C is performed. Third reaction step, (d) After this, the pH was adjusted to 9-13, and then sulfite was added.
Fourth reaction step in which 0.01 to 0.30 mol is added and the reaction is performed for 0 to 60 minutes.

As the form aldedo used in the present invention, commercially available industrial products such as formalin and paraformaldehyde are sufficient. Also, melamine may be a usual commercial product. Sulfite shall also include bisulfite, commercial industrial products ammonium sulfite,
Examples include sodium sulfite, sodium bisulfite, ammonium bisulfite, sodium pyrosulfite, and the like.

In the present specification, formaldehyde is 1 mol of a compound that provides 1 mol of HCHO regardless of its form, melamine is 1 mol of a compound that provides 1 mol of a triazine ring, and sulfite is 1 mol of SO ₂ The compound providing the group is calculated as 1 mol.

In the method for producing a sulfone group-containing melamine formaldehyde resin of the present invention, first, a primary reaction step of reacting formaldehyde and melamine in an aqueous medium is carried out. The first reaction step is a step of efficiently producing trimethylolmelamine from melamine and formaldehyde. The pH of this reaction is 3-11, preferably 4-9. Below 3,
The methylolation reaction is difficult to proceed, and if it exceeds 11, side reactions are likely to occur. The molar ratio of melamine to formaldehyde is
1.0: 2.6 to 3.4, preferably 1.0: 2.9 to 3.1. When the molar ratio is less than 2.6, methylolation becomes insufficient, and when it exceeds 3.4, free formaldehyde increases and it reacts with sulfite in the sulfonation reaction described below, which is not preferable. The reaction time is 5 to 60 minutes, preferably 15 to 25 minutes. If it is less than 5 minutes, methylolation is insufficient, and if it exceeds 60 minutes, precipitation or the like tends to occur.

Following this first reaction step, a second reaction step is carried out in which sulfite is added to carry out sulfonation. The molar ratio of melamine to sulfite is 1.0: 0.7 to 1.3, preferably 1.0: 0.9 to 1.1.
Is. If it is less than 0.7, the sulfonation becomes insufficient and gelation or abnormal thickening occurs in the condensation reaction described below. If it exceeds 1.3, sulfonation proceeds more than necessary, and the condensation reaction described below becomes difficult to occur, and the resulting sulfo group-containing melamine formaldehyde resin cannot sufficiently improve the fluidity of concrete or the like. The reaction pH is 9-13,
It is preferably 10 to 12. When it is less than 9, sulfonation does not proceed, and when it exceeds 13, it is desulfonated, which is not preferable. The reaction temperature is 50 to 90 ° C, preferably 70 to 80 ° C. If it is less than 50 ° C, a very long reaction time is required, and if it exceeds 90 ° C, it becomes difficult to control the reaction. The reaction time is 1 to 5 hours, preferably 2 to 3 hours. If it is less than 1 hour, the sulfonation reaction is insufficient. Since the sulfonation reaction is almost completed in about 5 hours, it is not necessary to exceed 5 hours. The pH adjustment in the above reaction is easily performed by adding a usual alkaline substance such as caustic soda and caustic potash.

Following this, the third reaction step in which the condensation reaction is performed
Adjust to ~ 6.5, preferably 5-6. When it is less than 3.5, gelation and thickening tend to occur, and when it exceeds 6.5, the condensation reaction hardly proceeds. The reaction temperature is 40-90 ° C, preferably 60-
80 ° C. If the temperature is lower than 40 ° C, the condensation reaction does not proceed, and if it exceeds 90 ° C, it is difficult to control the reaction. The reaction time is 1 to
5 hours, preferably 2-3 hours. If it is less than 1 hour, the condensation reaction will be insufficient to reach the ideal molecular weight, and the storage stability will be significantly deteriorated. Since the condensation reaction is almost completed in about 5 hours, it is not necessary to carry out beyond this. The pH of this reaction can be easily adjusted by adding ordinary mineral acids such as hydrochloric acid and sulfuric acid, and organic acids such as formic acid and acetic acid.

Immediately after the completion of the third reaction step, the pH of the reaction solution was adjusted to 9 to 13 and the sulfite was 0.01 to 0.30 mol, preferably 0.02 to 0.07.
Add moles. If it is less than 0.01 mol, the storage stability cannot be sufficiently improved. If it exceeds 0.30 mol, the durability of concrete is adversely affected, which is not preferable. This pH adjustment is
It is easily done by the addition of normal alkaline substances such as caustic soda. Then, the mixture is cooled to 40 to 70 ° C., aged for 0 to 60 minutes, and then cooled. This aging reaction does not have to be carried out, but it is preferable to carry out the reaction for 20 to 30 minutes. After this, it is possible to further adjust to a predetermined pH.

Finally, a sulfone group-containing melamine-formaldehyde resin having a long-term storage stability of 18 months or more and excellent cement water-reducing performance is obtained by the treatment of adding sulfite.

Further, the sulfone group-containing melamine formaldehyde resin of the present invention can be spray-dried as necessary to obtain a powder.

The addition amount of the sulfone group-containing melamine formaldehyde resin of the present invention is 0.05 to 2.5 with respect to cement as a solid content.
Weight percent is suitable. If it is less than 0.05%, sufficient workability cannot be obtained, and if it exceeds 2.5%, it is economically disadvantageous.

Furthermore, when the sulfone group-containing melamine formaldehyde resin of the present invention is added to cement, a general admixture or admixture, that is, an air entraining agent, an early strengthening agent, a retarding agent, a waterproofing agent, a rust preventive, a water retention agent, a coloring agent. It can be used in combination with a preservative, glass fiber, fly ash, blast furnace slag, silica powder and the like. Further, the sulfone group-containing melamine formaldehyde resin of the present invention is used as a water reducing agent for gypsum as well as concrete.

[Action]

Although the scientific effect of the present invention is unknown, after the condensation reaction,
It is presumed that the re-added sulfite reacts with unreacted methylol groups and free formaldehyde to have a molecular weight distribution related to excellent concrete water-reducing performance and excellent storage stability.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

Examples 1 to 13, Comparative Examples 1 to 6 3 in a reaction vessel equipped with a thermometer, a stirrer, and a condenser.
Add 7% formalin, add 20% caustic soda
After adjusting the pH and adding melamine with stirring, the temperature was raised to a predetermined temperature for reaction to carry out the first reaction step.

Next, 35% sodium bisulfite was added, 20% caustic soda was added to adjust the pH to a predetermined value, and the reaction was carried out at a predetermined temperature to carry out the second reaction step.

Next, the reaction solution was cooled to 40 ° C., 2% sulfuric acid was added to adjust the pH to a predetermined value, and the reaction was carried out at a predetermined temperature to carry out the third reaction step.

Next, 20 caustic soda was added to adjust to a predetermined pH, and 35% sodium bisulfite was added at a predetermined temperature, followed by reaction to carry out a fourth reaction step and cooling. However, in Comparative Example 1, the pH was adjusted to a predetermined value and then cooled as it was without adding 35% sodium bisulfite.

Details of the reaction conditions are shown in Tables 1 to 3.

The performance as a cement water reducing agent was tested for each of the resin liquids obtained in Examples and Comparative Examples according to the method of JIS-R-5201. That is, 260 g of water containing 5 g of sulfonic acid group-containing melamine formaldehyde resin as a solid content was added to 1 kg of ordinary Portland cement, stirred for 3 minutes with a mortar mixer, and the flow value of the cement paste was measured. In Tables 1 to 3, immediately after production and 9 months after production,
The flow value and viscosity after 18 months of production are shown. The flow value of the cement paste without addition was 159.

[Effects of the Invention] From Tables 1 to 3, it is shown that the sulfonic acid group-containing melamine formaldehyde resin according to the present invention is an extremely excellent cement water reducing agent.

Claims (1)

[Claims] 1. A method for producing a sulfo group-containing melamine formaldehyde resin, which comprises the following first to fourth reaction steps. (a) Molar ratio of melamine and formaldehyde in an aqueous medium
1.0: 2.6-3.4, primary reaction step of reacting at pH 3-11, (b) then 0.7-1.3 per mol of melamine with sulfite.
A second reaction step in which the reaction is carried out at a pH of 9 to 13 and a temperature of 50 to 90 ° C for 1 to 5 hours by adding a mole, and (c) then a condensation reaction of 1 to 5 hours at a pH of 3.5 to 6.5 and a temperature of 40 to 90 ° C is performed. Third reaction step, (d) After this, the pH was adjusted to 9-13, and then sulfite was added.
Fourth reaction step in which 0.01 to 0.30 mol is added and the reaction is performed for 0 to 60 minutes.