JPS6337058B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing a highly concentrated concrete water reducing agent aqueous solution consisting essentially of a sulfonic acid group-containing melamine formaldehyde resin. Sulfonic acid group-containing melamine formaldehyde resin is known as a water reducing agent that exhibits high dispersion performance for hydraulic inorganic materials such as cement and gypsum in mixing water. is desired to be provided. Furthermore, in this aqueous solution product, a product with a high concentration is desired because if the concentration of the water reducing agent component is low, the cost of unnecessary water for transportation and other handling will be increased. However, this aqueous solution of sulfonic acid group-containing melamine formaldehyde resin has the property of becoming more susceptible to deterioration during storage as its concentration increases, so high concentration products with different storage periods are used in concrete. In this case, not only is it not possible to set the water reduction rate constant, but also the hardening time of the concrete, the strength after curing, etc. become values that deviate from the target values, leading to serious practical problems. As a method for producing a concrete water reducing agent aqueous solution made of a highly concentrated and highly stable sulfonic acid group-containing melamine formaldehyde resin, melamine, formaldehyde and alkali sulfite are mixed in a molar ratio of 1: 2.7～
3.2: In aqueous solution at 0.9-1.1, temperature 60-80℃ and PH
After reacting until the sulfite disappears at 10 to 13,
After setting the pH to 3.0 to 4.5 and carrying out the condensation reaction at a temperature of 30 to 60°C for 30 to 90 minutes, and further adjusting the resulting liquid to pH 7.5 to 9.0, the viscosity at 20°C and solid content of 20% was 5. ~
A method has been proposed in which the pH of the produced liquid is adjusted to 10.5 to 11.5 after heating to 70 to 95°C until it reaches 40 cp. According to this proposed method, the solids concentration
A 30-50% aqueous solution product can be produced, but after the condensation reaction as described above, the pH is 7.5-9.0.
It requires a heat treatment step of, for example, 60 minutes at a temperature of 70 to 95°C, which is not only not an efficient and simple process, but also makes it difficult to control the performance of the manufactured product to a constant level. The present invention aims to solve such problems by using a high-performance concrete water reducing agent aqueous solution consisting essentially of a sulfonic acid group-containing melamine formaldehyde resin with a solid content concentration of 30 to 50% by weight. The object of the present invention is to provide a manufacturing method that enables the production of a concentrated product, which has such high stability that no deterioration occurs even after long-term storage, for example, one year or more, and which can produce a product of constant quality. The method for producing a highly concentrated concrete water reducing agent aqueous solution of the present invention involves mixing melamine, formaldehyde and sulfite in an aqueous medium in a molar ratio of 1:2.7 to 3.3:0.9 to 1.2.
In the method for producing an aqueous concrete water reducing agent solution substantially containing a sulfonic acid group-containing melamine formaldehyde resin, the method comprises a first reaction step of heating in an alkaline solution and a second reaction step of heating the resulting solution in an acidic state. The first stage reaction was carried out for 20 to 60 minutes at a pH of 10 to 13 and a temperature of 60 to 80°C, and then the second stage reaction was carried out at a pH of 5 to 6 and a temperature of 40 to 60°C for 30 to 150 minutes.
By immediately adjusting the pH of the second reaction process product liquid to 12 to 13.5 and cooling it at the same time, the solid content derived from the raw materials charged into the reaction system can be removed without a water removal process. It is characterized by producing an aqueous solution containing 30 to 50% by weight of The melamine used in the present invention may be an ordinary commercially available industrial product, and as the formaldehyde, commercially available industrial products such as formalin and paraformaldehyde are sufficient. Furthermore, as sulfites,
Examples include commercially available industrial products such as sodium sulfite, ammonium sulfite, sodium bisulfite, ammonium bisulfite, and sodium pyrosulfite. In some cases, instead of the above melamine, specifically for melamine
In a proportion of 20% by weight or less, amino group-containing compounds other than melamine, such as urea, guanamine compounds,
Mixtures of dicyandiamide, thiourea, etc. with melamine may also be used. The above melamine has an average of 6
It is calculated assuming that the amount of the compound containing mol of active hydrogen is 1 mol, and the above formaldehyde is CH ₂ O1
The amount of the compound that provides 1 mole of SO 3 groups is 1 mole, and the amount of the compound that provides 1 mole of SO ₃ groups is 1 mole.
Each is calculated as a mole. The first stage reaction according to the present invention can be easily carried out under stirring by charging a reaction medium of water, melamine, formaldehyde, sulfite, and an alkaline substance for adjusting the pH in a conventional reactor. The melamine, formaldebide and sulfite may be added in any order, but a simultaneous method is convenient. Usually, the addition of an alkaline substance for pH control is carried out immediately before the start of the reaction. This first
In the reaction step, melamine, formaldebide and sulfite are mixed in a molar ratio of 1:2.7-3.3:0.9-1.2.
By heating for 20 to 60 minutes at a pH of 10 to 13 and a temperature of 60 to 80°C, an aqueous solution of methylolmelamine containing a sulfonic acid group is generated, which can be used in the subsequent second reaction step. The pH in the above reaction can be easily adjusted by adding a common alkaline substance such as caustic soda. In the second reaction step following this first reaction step, a condensation reaction proceeds. Adjustment of the pH to 5 to 6 in order to proceed with this reaction can be easily carried out by adding ordinary mineral acids such as hydrochloric acid and sulfuric acid, preferably sulfuric acid, as an aqueous solution to the liquid produced in the first stage reaction step. This second stage reaction takes place at a temperature of 40 to 60°C.
This is done by heating under stirring for ~150 minutes. In the method of the present invention, immediately after completing this second stage reaction, a normal alkaline substance is added to the product liquid.
Preferably, the pH is adjusted to 11.5 to 13.5, preferably 12 to 13, by adding an aqueous solution such as caustic soda, and at the same time, the product is cooled to a room temperature product. Therefore, the production method of the present invention does not include a step of removing water from the reaction system before obtaining the product. The solid content concentration of the product according to the invention is usually 30~
The concentration is as high as 50% by weight, but this concentration is the same as that in the first reaction step, second reaction step, and final pH of 11.5.
13.5 from the raw materials used during the adjustment. This final pH adjustment is usually performed by adding an aqueous solution of caustic soda, so the second stage reaction is usually carried out at a high concentration of solids exceeding 30% by weight, for example about 50% by weight. This second stage reaction is a reaction in which a condensation reaction proceeds, and it has been found that the PH value in this second stage reaction step has a significant effect on the performance of the product as a water reducing agent for an aqueous solution. Although it is difficult to explain this effect physically, if the concentration in this second stage reaction where the condensation reaction progresses is high, even a slight change in the pH value will result in the formation of sulfonic acid group-containing melamine. It is thought that the molecular structure and molecular weight of formaldehyde resin, as well as their distribution, etc., tend to fluctuate, and the production ratio of resin components that do not function as a preferred water reducing agent tends to fluctuate. If the pH of the liquid in the second stage reaction step is 5 or less,
As the reaction progresses, the viscosity of the liquid increases dramatically, making it difficult to stop the reaction at a desired point, and even if the pH of the resulting liquid is adjusted to 11.5 to 13.5, the storage stability of the liquid is poor. This tends to be insufficient, and furthermore, the viscosity of the cement paste obtained by adding this increases, reducing the water-reducing effect. In contrast to the above, if the pH of the liquid in the second reaction step is 6 or higher, the reaction will hardly proceed or it will take a significant amount of time to proceed, which is not preferable. At the above specific pH, the reaction temperature is 40-60℃, and
By setting the reaction time to 30 to 150 minutes, a preferable water reducing agent aqueous solution of the present invention can be obtained. Immediately after the completion of the second stage reaction, the alkali added to the product liquid acts to stop the further progress of the second stage reaction, and for particular stabilization of the resulting aqueous product solution, It has been found that a pH of 11.5 or higher, preferably 12 or higher is required, and that it is also necessary to cool the produced liquid to room temperature at the same time as adjusting the pH. Even if a large amount of alkali is added to this product aqueous solution so that its PH value exceeds 13, the stability will not be improved. It is preferable to avoid adding alkali and add alkali so that the pH value is about 12 to 13. Thus, according to the method of the present invention, the manufacturing process is simple and efficient, and the product aqueous solution obtained has a high concentration of 30 to 50% by weight, but exhibits extremely high stability, and concrete using the same gives high fluidity and high strength to cured concrete. Example 1 675 parts by weight of 40% formalin was charged into a reactor equipped with a thermometer, a stirrer, and a condenser.
378 parts by weight of melamine, 286 parts by weight of sodium pyrosulfite under stirring
parts by weight and about 210 parts by weight of a 10% aqueous solution of caustic soda were added to adjust the pH to 11.0. The reaction mixture was heated to 75°C over 20 minutes with stirring, continued to react for 30 minutes, and then cooled to 45°C. The pH was adjusted to 5.0 by adding approximately 550 parts by weight of 10% sulfuric acid, and the temperature of the reaction solution was maintained at 45°C while stirring for approximately 60°C.
Immediately after partial condensation, 10% caustic soda aqueous solution of approx.
330 parts by weight was added to adjust the pH to 12.5 and cooled.
The resulting liquid was transparent, contained 40.5% nonvolatile content, had a viscosity of 270 cp at 20°C, and exhibited a pH of 13.2 at 20°C. Moreover, when this product liquid was stored at room temperature under closed conditions, no deterioration was observed for more than one year and it was extremely stable. Example 2 In the same manner as in Example 1, 378 parts by weight of melamine,
40% formalin 675 parts by weight, 35% acidic sodium sulfite aqueous solution 891 parts by weight and 30% caustic soda aqueous solution 70 parts by weight
% by weight was charged into the reactor and the pH was adjusted to 11.0.
The reaction mixture was heated to 75°C over 20 minutes with stirring, and then allowed to react for 30 minutes, and then cooled to 50°C. Add 438 parts by weight of pure water and further add 25% sulfuric acid aqueous solution to adjust the pH to 5.01. While keeping the temperature of the reaction solution at 50°C, condensation reaction was carried out for 90 minutes with stirring, and immediately after that, 30% caustic soda aqueous solution was added. plus
The pH was adjusted to 12.0 and cooled. The resulting liquid was transparent, contained 34.8% nonvolatile content, had a viscosity of 86 cp at 20°C, and exhibited a pH of 12.5. When this product liquid was stored at room temperature under closed conditions, no deterioration was observed for more than one year and it was extremely stable. Comparative Example 1 Example 2 except that the pH was adjusted to 6.5 during the condensation reaction
When a resin solution was prepared in the same manner as above, the resulting liquid was transparent, contained 35% nonvolatile content, and had a pH of 12.0, but the viscosity at 20°C was only 12 cp, as shown in Table 1 below. It was acknowledged that the water reducing agent performance was inferior. Comparative example 2 Example 2 except that the PH during the condensation reaction was adjusted to 3.8
When a resin solution was prepared in the same manner as above, the resulting liquid was transparent, contained 34.2% nonvolatile content, and had a pH of 12.0, but the viscosity at 20°C was as high as 550 cp, and it did not last for 6 months when stored at room temperature under closed conditions. gelatinized.
The water reducing agent performance of the product immediately after preparation is shown in Table 1. Comparative Example 3 The reaction temperature during the condensation reaction was 30°C, and the reaction time was 150°C.
A resin solution was prepared in the same manner as in Example 2 except that the temperature was changed to
It contained 35.5% and showed a pH of 12.0, but the viscosity at 20°C was only 7 cp, and as shown in Table 1 below, it was recognized that the water reducing agent performance was poor. Comparative Example 4 A resin solution was prepared in the same manner as in Example 2 except that the reaction temperature during the condensation reaction was 70°C and the reaction time was 30 minutes. The resulting liquid was transparent and had a nonvolatile content of 35.1
%, and the pH was 12.0, but the viscosity at 20°C was as high as 480 cp, and when stored at room temperature under closed conditions, it gelled in 2 months. The water reducing agent performance of the freshly prepared product is shown in Table 1. Comparative Example 5 A resin solution was prepared in the same manner as in Example 2, except that the pH after the completion of the condensation reaction was adjusted to 11.0. It gelled in 6 months. Example 3 In the same manner as in Example 1, 675 parts by weight of 40% formalin, 378 parts by weight of melamine, 891 parts by weight of 35% acidic sodium sulfite aqueous solution, and 30% caustic soda aqueous solution were prepared.
70 parts by weight was charged into a reactor, and the pH was adjusted to 11.0. The reaction mixture was heated to 75°C over 20 minutes with stirring, and then allowed to react for 30 minutes, and then cooled to 50°C. By adding 438 parts by weight of pure water and further adding 25% sulfuric acid aqueous solution, the pH was adjusted to 5.01.
Immediately after the partial condensation reaction, a 30% aqueous sodium hydroxide solution was added to adjust the pH to 13.0, and the mixture was cooled. The resulting liquid was transparent, contained 34.9% nonvolatile content, had a viscosity of 78 cp at 20°C, and exhibited a pH of 13.2. When this product liquid was stored at room temperature under closed conditions, it remained stable for more than one year without any change in quality. Example 4 Regarding the resin solutions obtained in Examples 1 to 3 and Comparative Examples 1 to 4, the performance of the water reducing agent was evaluated according to JIS-R-
Tested according to the method of 5201. That is, 520 parts by weight of ordinary Portland cement and 1040 parts by weight of Toyoura standard sand.
parts by weight and 286 parts by weight of water were mixed, and each resin solution was internally added to 286 parts by weight of the above mixed water and mixed. Table 1 shows the amount of resin solution added, mortar flow value, and compressive strength after 28 days. The amount of the resin solution added is expressed in parts by weight relative to the cement, and the weight ratio of the resin solid content to the cement was constant at 1/100. still,
An example in which no resin solution was added was also tested and the results are shown in Table 1. The table shows that the sulfonic acid group-containing melamine formaldehyde resin solution prepared by the method of the present invention is an extremely excellent water reducing agent.

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【table】

Claims (1)

[Claims] 1 A first reaction step in which melamine, formaldehyde and sulfite are heated in an alkaline molar ratio of 1:2.7 to 3.3:0.9 to 1.2 in an aqueous medium, and a second reaction step in which the resulting solution is heated in an acidic state. In the method for producing an aqueous concrete water reducing agent solution containing substantially sulfonic acid group-containing melamine formaldehyde resin, the first stage reaction is carried out at a pH of 10 to 13 and a temperature of
The second stage reaction was carried out at 60 to 80°C for 20 to 60 minutes, and then the second stage reaction was carried out at a pH of 5 to 6 and a temperature of 40 to 60°C for 30 to 150 minutes.
By adjusting the temperature to 12 to 13.5 and cooling at the same time, an aqueous solution containing 30 to 50% by weight of solids derived from the raw materials charged into the reaction system is produced without a water removal step. A method for producing a highly concentrated concrete water reducing agent aqueous solution.