JPH0143699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a high performance concrete water reducer, in particular:
This invention relates to an improved concrete water reducer that causes less slump reduction after being added to uncured concrete and mixed. Conventionally, sulfonic acid group-containing melamine formaldehyde condensation products have been used as concrete water reducing agents, for example, in Japanese Patent Publications No. 43-21659 and Japanese Patent Publication No. 1982-1999.
It is well known as described in the specification of Japanese Patent No. 13991. This sulfonic acid group-containing melamine formaldehyde condensate is a fluidizing agent in concrete mixing, and in addition to being able to reduce the water mixing ratio, it also has the effect of increasing the initial strength of concrete, so it is gradually becoming popular as a high-performance water reducing agent. However, no one with perfect performance has been proposed yet.
For example, the high concentration solution of the sulfonic acid group-containing melamine formaldehyde condensate described in Japanese Patent Publication No. 52-13991 has considerably improved stability, but when it is added to concrete and kneaded,
It has the disadvantage of poor slump sustainability. The present inventor experimentally manufactured various sulfonic acid group-containing melamine formaldehyde condensates and tested the performance of concrete mixtures, and found that low condensates, high condensates, or mixtures thereof of sulfonic acid group-containing melamine formaldehyde The present invention was based on the discovery of the fact that when mixed with a conventionally known intermediate condensate of melamine formaldehyde containing sulfonic acid groups, when the resulting mixture was added to concrete and kneaded, no significant drop in slump of concrete occurred for a long time. completed. An object of the present invention is to provide a concrete water reducing agent comprising a sulfonic acid group-containing melamine-formaldehyde condensate that has excellent stability during long-term storage and can sustain the slump of concrete for a long period of time. The high-performance concrete water reducing agent of the present invention is the following sulfonic acid group-containing melamine formaldehyde condensate obtained by condensing melamine formaldehyde and sulfite in an aqueous medium at a molar ratio of 1:2.2 to 3.2:0.3 to 1.0. (A), (B)
and (C) so that the weight ratio of (A)/(B) is 1/100 to 100/1 and the weight ratio of the sum of (A) and (B)/(C) is 5/
It is characterized in that it is contained in a ratio of 95 to 50/50. 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 the present invention, formaldehyde is calculated assuming that the amount of the compound that provides 1 mol of CH ₂ O is 1 mol, and sulfite is calculated assuming that the amount of the compound that provides 1 mol of SO ₃ groups is 1 mol, respectively, and the sulfonate used in the present invention is Acid group-containing melamine formaldehyde condensates (A), (B) and (C)
is 1 mol of the above melamine, 2.2 mol of formaldehyde
It is obtained by condensation reaction of these in water at a ratio of ~3.2 mol and 0.3 to 1.0 mol of sulfite.
If the molar ratio is outside the above range, the resulting sulfonic acid group-containing melamine formaldehyde condensate may not have sufficient fluidization ability when added to concrete and may deteriorate during long-term storage. This is not desirable because it easily causes Further, as the reaction medium, an aqueous medium is preferable in order to facilitate adjustment of pH in the condensation reaction. Therefore, the sulfonic acid group-containing melamine formaldehyde condensate used in the present invention is usually obtained as an aqueous solution of about 5 to 40% by weight, and can be used as is, but the concentration may be adjusted as necessary. Furthermore, powder products obtained by dehydrating and drying these may also be used. The sulfonic acid group-containing melamine formaldehyde condensate (A) used in the present invention exhibits a viscosity of less than 5 cp when measured at 20° C. as a 20% by weight aqueous solution of the sulfonic acid group-containing melamine formaldehyde condensate. This condensate (A) is either a resin obtained by first adding the above-mentioned melamine, formaldehyde and sulfite in the above-mentioned molar ratio in water at a pH of about 9 to 12, or a resin which is then subjected to a condensation reaction at a pH of about 5 to 7, followed by cooling, It is a low condensation resin obtained by neutralization. The sulfonic acid group-containing melamine formaldehyde condensate B used in the present invention is a sulfonic acid group-containing melamine formaldehyde condensate containing 20
20 cp when measured at 20°C as a wt% aqueous solution
It shows a viscosity exceeding . This condensate (B) is also a high condensation resin obtained by first carrying out an addition reaction of the above-mentioned melamine, formaldehyde and sulfite at the above-mentioned molar ratio in water at a pH of about 9 to 12, and then carrying out a condensation reaction at a pH of 2.0 to 4.0. It is. A particularly stable condensate can be obtained by adjusting the pH of the liquid after the condensation reaction to about 9 to 12. Sulfonic acid group-containing melamine formaldehyde condensate (C) used in the present invention
shows a viscosity of 5 to 20 cp when measured at 20°C as a 20% by weight aqueous solution of a sulfonic acid group-containing melamine formaldehyde condensate. This condensate (C) is also a medium condensation product obtained by first adding the above melamine, formaldehyde and sulfite at the above molar ratio in water at a pH of about 9 to 12, and then carrying out a condensation reaction at a pH of 3.0 to 6.0. It is resin. This condensate C can also be stabilized by adjusting the pH to 9 to 12, if necessary. These condensates of (A), (B), and (C) above are synthesized by adjusting the temperature and time of the condensation reaction; at the same temperature, (A), (B), and (C) are synthesized in the order of It takes. The pH value in the condensation reaction is an important requirement, and if it is outside the above range, precipitation may occur during the reaction, or an unrealistically long reaction time may be required, or the resulting condensate may deteriorate. This brings about various drawbacks, such as a decrease in concrete fluidization performance and a lack of effect on improving the strength of concrete. The pH in the reaction can be easily adjusted by using a common alkalizing agent, such as caustic soda, or an acidifying agent, such as sulfuric acid. The high-performance concrete water reducer of the present invention includes 5 to 100 parts of the above condensate (A) or (B) in 100 parts by weight of the above condensate C.
It is obtained by blending the above condensate (A) and (B) in a total amount of 5 to 100 parts by weight with 100 parts by weight of the above condensate (C). It will be done. When blending both the above condensates A and B, the weight ratio of (A)/(B) is usually 1/100 to 100/1.
This is done at a rate of . Although the physical analysis of the formation of the preferred concrete water reducing agent of the present invention by such a combination is not yet clear, the above condensate (C)
Although it has a molecular weight distribution, the ratio of low condensates and high condensates is small, and it is understood that the addition and blending of the above condensates (A) and (B) compensate for these. However, by adding and blending a low condensate (A), a high condensate (B), or especially a mixture thereof to a condensate (C), a water reducing agent that can significantly prevent concrete slump is not formed. This is an unexpected and surprising discovery.
When added to concrete, low condensates (A) have poor water-reducing and strength-improving effects, and high condensates (B) are unstable during long-term storage. However, when it is added to concrete and kneaded, the water reduction effect becomes poor even though the strength improvement effect is almost satisfactory.Based on this empirical fact, it is usually
This is because (C) was widely used as a concrete water reducing agent. The concrete water reducer of the present invention exhibits water reduction effect, initial strength and long-term strength improvement effect on concrete, and is also excellent in preventing slump reduction, and can be used for concrete made of any conventionally known sulfonic acid group-containing melamine formaldehyde condensate. It is much better than water reducing agents. In addition to concrete, the water reducing agent of the present invention can also be used as a fluidizing water reducing agent for, for example, mortar. Hereinafter, it will be explained by giving Examples and Comparative Examples.
The technical scope of the present invention is not limited thereto. Example 1 (a) 1 equipped with a reflux condenser, a stirring device and a thermometer
Put 126.0 g (1 mol) of melamine and 225 g (3 mol) of 40% formalin into a four-necked flask, and let them react at pH 7.5 and temperature of 70°C. When the reaction solution becomes clear, immediately heat the mixture to 50°C. cooled to
95 g of sodium pyrosulfite Na ₂ S ₂ O ₅ (1 mole as sulfite), 730 g of water, and sodium hydroxide were added to adjust the pH to 11.0, and the reaction was carried out for about 1 hour at a temperature of 60°C until sulfite was no longer detected. .
Next, the reaction solution was lowered to pH 4.0 with sulfuric acid, condensed at a temperature of 60℃, neutralized with sodium hydroxide to a pH of about 9, and the viscosity at 20℃ and 20% concentration was
The condensation reaction was stopped when 10 cp was obtained, and the condensate (C) was obtained by neutralizing and cooling as described above. (b) Follow the same procedure as in (a) above to determine the pH of the condensation reaction.
3.5, the condensation reaction was stopped when the viscosity at 20°C and 20% concentration showed 25 cp, and the condensate (B) was obtained by neutralization and cooling. (c) The reaction was carried out in the same manner as in (a) above until sulfite was no longer detected, but the subsequent condensation reaction was not carried out to obtain condensate (A). The viscosity at 20°C and 20% concentration was 3 cp. Next, the above sulfone group-containing melamine formaldehyde condensates (A), (B) and (C) were mixed in a solid content ratio of (A)/
By mixing in a weight ratio of (B)/(C)=1/1/8, the concrete water reducing agent of the present invention was obtained. Example 2 The condensate of (A), (B) and (C) prepared above was converted into (A)/(B)/(C)
A concrete water reducing agent was obtained by mixing at a weight ratio of =2/1/7. Example 3 Compounding components Cement: Onoda ordinary cement Fine aggregate: Kinugawa product Coarse aggregate: 〃 (maximum dimension 20 mm) Water reducing agent: Using the prepared products according to Examples 1 and 2 above, and using the concrete mixture described below, a forced mixing mixer was used. (50 volumes) (The water in the water reducing agent was counted as part of the mixing water.) The total kneading time was 2 minutes, and the temperature was 20-23℃.
℃, and the concrete temperature was 18-22℃. The slump over time was measured by stirring with a mixer for 30 seconds every 10 minutes, and then taking a portion of the concrete at regular intervals and measuring the slump according to JIS A-1101.
The results are shown in Table 1. Concrete mix water/cement ratio (W/c) 0.55 Fine aggregate/coarse aggregate ratio (S/a) 0.413 Unit cement amount 307 kg Also, the compressive strength of the above concrete was measured after 28 days of curing and the results are shown in Table 1. The results described were obtained. 【table】

Claims (1)

[Scope of Claims] 1. The following sulfonic acid group-containing melamine formaldehyde condensate (A) obtained by condensing melamine, formaldehyde and sulfite in an aqueous medium at a molar ratio of 1:2.2 to 3.2:0.3 to 1.0. ),
(B) and (C), the weight ratio of (A)/(B) is 1/100 to 100/1
A high-performance concrete water reducing agent characterized in that it is contained in such a manner that the sum of (A) and (B)/(C) is in a weight ratio of 5/95 to 50/50. (A) A 20% by weight aqueous solution exhibits a viscosity of less than 5 cp at 20°C. (B)...A 20% by weight aqueous solution exhibits a viscosity exceeding 20 cp at 20°C. (C)...A 20% by weight aqueous solution exhibits a viscosity of 5 to 20 cp at 20°C.