JP2664899B2 - Cement dispersant - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a dispersant for cement or cement blends. More specifically, a cement dispersing agent which can improve the workability of concrete, mortar or paste which is a hydraulic cement compound, and can improve its workability and workability, or reduce the unit water amount to a high degree. And a cement dispersant which makes it possible to obtain high strength. [Related Art] Naphthalenesulfonic acid formalin condensate is generally used as a high-performance water reducing agent. Separation operation to improve the dispersibility of this high-performance water reducing agent (Japanese Patent Laid-Open No. 58-17 / 1983)
No. 6158) and a method of oxidation treatment (JP-A-60-33239). [Problems to be Solved by the Invention] However, removing a high molecular weight portion and / or a low molecular weight portion by a fractionation method is effective for improving dispersibility, but requires treatment of the substance removed by the method. It is economically disadvantageous. Introducing a carboxyl group into a sulfonic acid compound by an oxidation treatment is one effective method for improving dispersibility, but it is not possible to prepare a molecular weight distribution particularly effective in the field of secondary concrete products. [Means for Solving the Problems] As a result of intensive studies, the present inventors have conducted a dispersing process by an economically advantageous method of only performing a chemical reaction under limited conditions without performing the separation operation as described above. It has been found that an excellent cement dispersant in which the molecular weight distribution that has the greatest influence on the improvement of the property and the carboxyl group can be suppressed as much as possible can be obtained, and the present invention has been completed. That is, the present invention is obtained by subjecting a naphthalene-based sulfonic acid formalin polycondensate or a salt thereof to an oxidative polymerization reaction with hydrogen peroxide at a pH of 2 or less, or after the reaction, further performing an oxidative polymerization reaction with a hydrogen peroxide at pH 3 to 6. A cement dispersant comprising a product having a molecular weight characteristic of F470-26500 of 89% or more and a carboxyl group concentration of 0.1 mol / kg or less. Examples of the naphthalene sulfonic acid formalin polycondensate or a salt thereof according to the present invention include a naphthalene sulfonic acid formalin polycondensate, an alkyl naphthalene sulfonic acid formalin polycondensate, and salts thereof. A formalin co-condensate of naphthalene sulfonic acid, a co-condensate with lignin sulfonic acid, or a salt thereof may be contained. or,
Examples of naphthalene sulfonic acid and alkyl naphthalene sulfonic acid include creosote oil, naphthalene oil, broth residue, purge naphthalene, components such as pitch generated in the process of coking coal, and sulfones such as coal liquefied oil containing these components. Compounds can also be used. Further, a compound which is not partially sulfonated may be contained as naphthalenesulfonic acid or alkylnaphthalenesulfonic acid. Although the oxidative polymerization reaction in the present invention reacts without adding a metal ion as a catalyst, it is preferable to add a metal ion in view of the reaction rate. As the metal ion, a transition metal ion is preferable, for example, silver, cobalt, cerium,
Ions such as manganese, iron, copper, molybdenum, tungsten, vanadium, titanium, chromium, lead, thallium, mercury, nickel, platinum, selenium, osmium, and zinc can be used. These transition metal ions are preferably used as salts or complexes or oxides. As used herein, the term `` F4
"70-26500" represents a value obtained by the following method. That is, in gel permission chromatography (GPC) measurement using a combination of gel permission chromatography columns TSKgel G4000SW and TSKgel G2000SW (manufactured by Toyo Soda Kogyo Co., Ltd.), a sodium polystyrene sulfonate standard sample (NaSS) for GPC (Showa Denki) A calibration curve is prepared in advance using Kogyo Co., Ltd.). In addition, the retention time of the fraction containing the naphthalene-based sulfonic acid polycondensate salt monomer and the dimer and the naphthalene-based disulfonic acid salt is determined in advance and converted to the molecular weight of NaSS. Since the retention time may change every measurement day, it is necessary to determine the relationship between these three components and the retention time for each measurement. In this specification, a molecular weight of 470 in terms of NaSS is specified as a typical retention time including these three components. There is almost no change in the molecular weight of 26500 in terms of NaSS on the high molecular weight side. This NaSS equivalent molecular weight 4
The fraction from 70 to 26500 was expressed as the area percentage of GPC by the term molecular weight distribution characteristic F470-26500. In the present invention, the concentration of the carboxyl group was determined by changing the reaction product to an acid state with a cation exchange resin, and titrating with a 0.1 N aqueous ammonia solution using a conductivity meter. Conventional oxidation treatment with hydrogen peroxide (JP-A-60-33239)
In this publication, the pH of the reaction solution is not controlled because the aim is to increase the amount of carboxyl groups. However, the present inventors have found that the reaction can be selectively performed by controlling the pH. That is, the reaction of a naphthalene-type sulfonic acid formalin polycondensate or a salt thereof with hydrogen peroxide under a strong acid having a pH of 2 or less, preferably 1 or less selectively causes cleavage of a methylene chain to reduce the molecular weight. Further, the carboxyl group generated is decarboxylated. From these facts, it is considered that it seems that only the cleavage of the methylene chain proceeds with almost no apparent carboxyl group formation. In the pH range of 3 to 6, the cleavage of the methylene chain and the opening of the naphthalene ring occur almost at the same time, and the carboxyl group formed remains almost without decarboxylation. In addition, a low molecular component of 1 to 3 mer causes a polymerization reaction. All of these reactions occur in this pH range. The above reaction can be selected by controlling the pH, and the molecular weight distribution can be adjusted narrowly without introducing a carboxyl group. What molecular design is required for naphthalene cement dispersants?
The purpose is to adjust the molecular weight to around 10 to 20 mer and to increase the anion charge (sulfone group + carboxyl group). However, these two factors have different effects depending on the unit cement amount of the concrete mixture. That is, whereas in the case of high cement content of the unit cement content 350~500kg / m ³ is almost solely governed by factors of molecular weight, in the case of 250 kg / m ³ or lower cement content molecular weight and functional groups, especially carboxyl It is affected by two factors, base amount. Therefore, the technology of the present invention is effective in the field of high cement content. Although the cement dispersant of the present invention can be used in the form of an acid, it is generally preferred to use it in the form of a salt. Examples of the cation to be formed include sodium, potassium, calcium, ammonium, alkanolamine, N-alkyl-substituted polyamine, ethylenediamine, polyethylenepolyamine, polyethyleneimine, and alkylene oxide adducts thereof. The addition amount of the cement dispersant of the present invention is preferably 0.1 to 1.5 solid content% by weight based on the cement of the hydraulic cement composition. If it is less than 0.1% by solid content, a sufficient dispersing effect on the cement particles cannot be provided. On the other hand, if the content exceeds 1.5% by weight of the solid content, the dispersion of the cement particles becomes excessive, causing paste separation or bleeding. The method of adding the cement dispersant according to the present invention to the segment composition can be in the form of an aqueous solution or a powder, or in the form of granules.
It is also possible to dissolve in the kneading water or to start kneading the cement composition, that is, simultaneously with or immediately after pouring water into the cement and from the time of the completion of the kneading of the cement composition to the cement composition once kneaded. Can also be added. It is also possible to add the dispersant of the present invention all at once or to add it in several divided portions. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the present invention, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Examples 1 to 3 Using the dispersants of the present invention and the comparative dispersants of product numbers 1 to 8 shown in Table 1, experiments were conducted on the dispersibility of concrete and the effect on compressive strength. Concrete was manufactured by using the following materials and by mixing shown in Table 2. Dispersibility measurement is based on JIS A 1101 slump test and JIS A 11
28 air volume test. ASTM C 4 for setting time measurement test
03-65T and JIS A 1108 for the compressive strength test.
Table 3 shows the test results. Material used Cement (C): Normal Portland cement (specific gravity 3.1
7) Fine aggregate (S): Kinokawa-produced river sand (specific gravity 2.57) Coarse aggregate (G): Takarazuka-produced crushed stone (specific gravity 2.59) Water (W): Kneading method of tap water concrete Kneading a cement dispersant beforehand Dissolved in water and kneaded 50 concrete for a total of 3 minutes at 20 ° C. using a 100 forced mixer. The charging sequence and mixing time of the materials are as follows. Production Example of Cement Dispersant (Production Example of Product No. 1) 50 g of naphthalenesulfonic acid 250 g, 98% sulfuric acid 10 g, and water 50 g
Placed in a 0 ml flask and warmed to 80 ° C. Then 80-90 ° C
140 g of 37% formalin was added dropwise over 5 hours. Thereafter, the pH of the reaction solution was adjusted to 1.0 with an aqueous sodium hydroxide solution. 1.3 g of ferrous sulfate is added, and 25 g of 60% hydrogen peroxide at 60 ° C. (5% based on the formalin polycondensate of naphthalenesulfonic acid)
Was added dropwise, the pH was further adjusted to 3.5, and 25 g of 60% hydrogen peroxide (5% with respect to the naphthalenesulfonic acid formalin polycondensate) was added dropwise. Thereafter, the mixture was weakly alkaline with caustic soda and filtered to obtain a cement dispersant of the present invention. 95% molecular weight characteristics F470-26500, carboxyl group concentration
It was 0.0 mol / kg. The dispersants of Product Nos. 2 to 5 and 7, 8 are the above product No. 1
It was manufactured according to the manufacturing example of No. Product No. 5 was reacted only under the conditions of pH 2 or less, hydrogen peroxide 5% and naphthalenesulfonic acid formalin condensate, and then made weakly alkaline with caustic soda. The analytical values are shown in Table 1. From the results shown in Table 3, it is clear that the dispersant of the present invention exerts extremely excellent effects in terms of dispersing effect, setting time, air entrainment and compressive strength.

Claims (1)

(57) [Claims] A product obtained by subjecting a naphthalene sulfonic acid formalin polycondensate or a salt thereof to an oxidative polymerization reaction with hydrogen peroxide at a pH of 2 or less, or an oxidative polymerization reaction with hydrogen peroxide at a pH of 3 to 6 after the reaction. , Molecular weight characteristics F470-26500: 89% or more, carboxyl group concentration: 0.1%
A cement dispersant comprising a product having a mol / kg or less. 2. 2. The cement dispersant according to claim 1, wherein the amount of hydrogen peroxide added is 15% by weight or less based on the naphthalene sulfonic acid formalin polycondensate or a salt thereof.