JPS605051A - Cement dispersant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement dispersant, and more particularly to a water reducing agent and a slump loss inhibitor used in cement compositions such as cement paste, mortar, and concrete.

Various types of cement dispersants are known, but representative ones include β-naphthalenesulfonic acid formaldehyde condensate (hereinafter abbreviated as β-KF3F) salt,
Melamine sulfonic acid formaldehyde condensate salts and lignin sulfonic acid (hereinafter abbreviated as L8) salts are known. These are used when kneading cement compositions, thereby reducing the amount of water used and improving workability. However, all of these known dispersants have a common drawback: a decrease in fluidity over time (hereinafter referred to as slump loss).
is known to be extremely large.

In general, in hydraulic cement compositions, after mixing, chemical and physical aggregation of cement particles progresses over time, gradually losing fluidity and causing problems in workability during construction. In particular, concrete to which a high-performance water reducer such as β-N8F has been added is compared to when no concrete admixture is used or when conventional admixtures such as AH agent, water reducer, and AE water reducer are used. , the slump loss is significant due to the high rate of water reduction.

When such a slump loss occurs, for example, when pumping cement composition at a concrete 2 fractured product factory, the pumping is temporarily interrupted during a lunch break or during a tossible, and then when the pumping is restarted, the pumping pressure suddenly increases. If the cement composition is poured into the formwork and compaction or other forming is delayed for any reason, problems such as non-filling may occur.

For ready-mixed concrete, slump loss occurs during the process from the concrete manufacturing plant to the pouring site, resulting in a significant decrease in work efficiency, blockage of pumps, and
This may cause problems such as non-filling during molding. Although the cause of such slump loss is not clear,
After the cement particles in the cement paste come into contact with water, coagulation due to chemical hydration reaction and/or physical aggregation due to interparticle attraction progresses, and the fluidity of the cement paste and thus the hydraulic cement composition decreases over time. This is thought to be due to a decrease in Especially β-NSF-? When a concrete water reducer (cement dispersant) such as L8 is added, the water reducer adsorbs to the Minato cement particles, increases the zeta potential of the cement particles, and its electrical repulsion disperses the cement particles, resulting in hydraulic cement. Although it is possible to improve the fluidity of the composition (armpit, Concrete Engineering Vol. 14 No. 3, 1
See pp. 2-19, March 1976 issue. It is thought that over time, the water reducing agent is stored in the hydrated precipitated minerals of cement, and its electrical repulsion is no longer expected, resulting in a decrease in fluidity. Therefore, if a water reducing agent that disperses cement particles can be continuously supplied in some way, the cement particles can always be dispersed in the form of primary particles, and slump loss of the hydraulic cement composition can be prevented. It seems possible.

The following methods have been discovered as countermeasures against slump loss based on this idea. Namely, 1) the concrete admixture is made into powder or granules, or encapsulated in a carrier, and the active ingredient is gradually released into the system to maintain its effect (for example, JP-A-54-159929).

1i) Repeatedly adding a concrete admixture to a hydraulic cement composition by mechanical force (e.g.
15856).

etc.

However, in case 1), although the effect of preventing slump loss is well recognized, the cement dispersant remains locally in the cement mixture even after the purpose of maintaining slump has ended, causing local bleeding. generation, which in turn leaves negative effects such as a decrease in strength. In II), the effect of preventing slump loss is also recognized, but if the concrete after being discharged from the mixer is in the pressure-feeding piping or formwork, it becomes difficult to add the cosicrete admixture.

In addition, as a measure to prevent slump loss, in order to suppress chemical coagulation of cement particles, substances such as oxycarboxylate or genin sulfonate are added or used in combination to delay the initial hydration reaction of cement (for example, Kosho 52
-24555 Publication, Special Publication No. 52-13853,
JP-A-54-17918) has also been found, but although this method suppresses chemical coagulation of cement particles to some extent, the effect is not sufficient. Also, in order to increase the effect, the amount added is increased (if this happens, the initial slump will become too large and there is a risk of causing aggregate separation, causing an increase in setting time and causing a major problem in pleating and initial strength.

As described above, each method has its own drawbacks and poses practical problems.

The present inventors have discovered that the dispersant is not in a solid state such as a powder or granules as in the method I) above, and that it is not applied by mechanical force as in the method I), but is in the usual form of a concrete mixer. The present invention was completed by researching methods for preventing slump loss using agents.

That is, the present invention provides a slump which contains as an essential component a compound containing 0.5 molar equivalent or more of carboxyl group per 1 kg of solid content by subjecting a formalin cocondensate of the following components (a) and (b) to an oxidation reaction. A loss-preventing cement dispersant is provided.

(,) One or more of the following compounds (11, +21, and (3)) (1) Naphthalenesulfonic acid or alkylnaphthalenesulfonic acid (2) One or more formalin of the above (1) Condensate or co-condensate (3) Said fl) or salt of (2) (b)') Geninsulfonic acid or (a) of its basic invention
) As the naphthalene sulfonic acid and alkylnaphthalene sulfonic acid, components containing these components such as creosote oil, naphcrene oil, pitch produced in the process of coking coal, or sulfonated products such as coal liquefied oil can also be used. Ru. Further, a partially unsulfonated compound such as naphthalene sulfonic acid or alkylnaphthalene sulfonic acid may be included. Also, before co-condensation with the valence component,
The (-) component itself may be subjected to formalin condensation or formalin co-condensation in advance.

As the component (b) of the present invention, geninsulfonic acid and soybean paste commonly used as cement dispersants are used, and among them, those with low air entrainment and low setting retardation are preferred.

For this reason, it is preferable to remove sugar content and low molecular weight components by ultrafiltration or the like. These ligogeninsulfonic acids include c he m lc IL I Admi
xturesf'or 0onorete (M,R,
RIXOM, E&F, N, 5pon Ltd.)
Analysis values as described on pages 5 to 9 of
Purellgnosulf with properties similar to molecular weight distribution
onate acid is typical. Additionally, partially modified materials such as desulfonation may also be used. The present invention (
A reaction similar to the formalin cocondensation reaction of components a) and (b) is described in Japanese Patent Publication No. 52-24553, and a cocondensate can be obtained by a similar method. However, in Japanese Patent Publication No. 52-24555, desulfonated ligninsulfonic acid obtained by subjecting ligninsulfonic acid to an alkaline treatment such as air oxidation is used as the component (b), but in the present invention, ( b) Component lignin sulfonic acid or lignin sulfonate is used without limitation. Particularly when the proportion of component (b) is large, insoluble precipitates are likely to form, so to prevent this, component (b) is preferably one whose low molecular weight has been removed by ultrafiltration or the like.

The reason for this is thought to be that the low molecular weight component has many reaction points for the formalin cocondensation reaction and is therefore three-dimensionally crosslinked to form an insoluble precipitate. Of course, even if an insoluble precipitate is formed,
Since the precipitate is reduced by the subsequent oxidation reaction, there is often no problem in practical use.

The oxidation reaction product of the formalin cocondensation reaction product of component (a) and component (b) of the present invention can be obtained by a known method.

For example, oxidation reaction with metal oxides such as permanganates under alkaline conditions, oxidation with oxygen or air using transition metals such as vanadium compounds or palladium compounds, metal salts or metal complexes as catalysts, oxidation with oxygen or air using alkaline catalysts. Oxidation reactions include hydrogen peroxide or oxidation reactions with water-soluble peroxides such as persulfates such as ammonium persulfate.

The structure of these oxidation reaction products is not clear, and various bonds are oxidized depending on the oxidation reaction conditions. Typical reaction formats among these reactions are (a) component side: oxidation of naphthalene rings, oxidation of methylol groups generated during formalin condensation, and oxidation of alkyl groups such as methyl groups bonded to naphthalene rings. In particular, regarding the oxidation of naphthalene rings, fucuric acid is produced from naphthalene on an industrial scale. On the component (b) side, hydroxyl groups, benzylic carbons, etc. may be considered. Regarding the oxidation reaction on the component side (b), it is also described in Japanese Patent Publication No. 5-40106.These oxidation reactions produce compounds containing 0.5 molar equivalent or more of carboxyl groups per 1 kg of solid content. You can get it.

It is important that the amount of carboxyl groups exists in an amount of 0.5 molar equivalent or more per 1 solid content; if it is less than 0.5 molar equivalent, it is not effective in preventing slump loss, and is 0.8 mol per 1 kP solid content. Equivalent or more is desirable.

The reason why the compound of the present invention is extremely effective as a cement dispersant for preventing slump loss is not clear, but it is thought to be as follows.

That is, although it is known that the formalin condensate or formalin cocondensate of component (a) of the compound of the present invention exhibits high dispersibility, the carboxyl group present in the compound of the present invention is It is thought that the sulfone groups present in the compound are arranged outward, increasing the charge on the cement particles, suppressing the accumulation of charge due to the hydration reaction of the cement, and preventing slump loss. (a)
The ratio of component to component (b) is preferably 9515 to 2.
0/80. More preferably, it is 90/10 to 25/75. If this ratio is too large, the oxidation reaction rate will be low. Moreover, if this ratio is too small, it becomes difficult to control the oxidation reaction and also causes a delay in setting.

Although the cement dispersant of the present invention can be used as an acid, it is generally preferable to use it in the form of a salt. Examples of cations that form salts include Na.

Examples include K, Ca, NH4t alkanolamine, N-alkyl substituted polyamine, ethylene diamine, polyethylene polyamine, polyethylene imine, or a fullylene oxide adduct thereof.

The amount of the cement dispersant of the present invention added is 0.25% by weight of solid content with respect to the cement of the hydraulic cement composition.
~2.5 is good. If it is less than 0.25%, sufficient dispersion effect and slump loss prevention effect on cement particles cannot be obtained. Moreover, if it exceeds 2.5%, it may be economically disadvantageous, or the dispersion of cement particles may become excessive, causing pleating or paste separation.

The cement dispersant formulation according to the present invention is most preferably added to the hydraulic cement composition in the form of an aqueous solution, but the slump loss prevention effect can also be obtained in the form of powder or granules. In addition, the timing of its addition can be determined by dissolving the compound in mixing water, adding it at the same time as mixing water, adding it to the mixed hydraulic cement composition, or adding it to the cement composition in powder form. be. Furthermore, it is also possible to add the dispersant of the present invention in portions at each stage.

In addition to the cement dispersant of the present invention, other cement dispersants, water-soluble polymer compounds, etc. can also be used in combination.

Other cement dispersants include formalin condensates of naphthalenesulfonic acid, ligninsulfonic acid salts, formalin condensates of melaminesulfonic acid, polycarboxylate salts, etc. Among these, formalin condensates of naphthalenesulfonic acid, ligninsulfone Particularly preferred are acid salts. In addition, as the lignin sulfonate, Chemical Ac1
m1Xture8 for 0oncrete (M,
R.

RIXOM, E&F, N, 5pon Ltd)
Pure lignosulfo with analysis values and molecular weight distribution similar to those described on page 9
The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

The concrete formulations and materials used in the Examples and Comparative Examples are shown in Table 1 below.

Table 1 Cement (C): Ordinary Portland cement (Onoda Cementon fine aggregate (S): Industrial sand from Kiku (specific gravity 2.58.FM2.9)
1) Coarse aggregate (G): Crushed stone from Takarazuka (specific gravity 2.61, F
M75.98) Water (W) (Note) * Add an appropriate amount of Mighty AE-05 (product name manufactured by Kako Soap Co., Ltd.), or add the cement dispersant and mix the concrete using the following methods 1 and 1. I did either of the 2.

Method 1: Knead the cement dispersant in advance and dissolve it in water, mix 404 in a tilting mixer at 25°C to obtain the concrete shown in Table 1, and continue kneading at a rotation speed of 2 rpm for a predetermined period of time. Changes in slump and air volume over time were measured. Measurements of slump, air volume, pressure and linear strength, and collection of strength specimens were all carried out in accordance with JI and El.

Method 2: The same procedure as Method 1 was carried out except that the cement dispersant was added at the same time as the mixing water.

Reference example naphthalene sulfone! (208,9), 98% concentrated sulfuric acid (
75I! Heat water and water (45J9) to 80-90°C, add 37% formalin (1551I) to the flask,
Warm to 80°C. Next, at 80-90°C, 37% formalin (14011) was added dropwise over 0.5 hours, followed by reaction at the same temperature for 1 hour, and then ultrafiltrated to obtain geninsulfonic acid (45,1 and 37% formalin (859
) was added in 4 portions at 1 hour intervals until 95~
The reaction was carried out at 100° C. for 18 hours with stirring. The formalin cocondensate thus obtained was adjusted to pH 12 with sodium hydroxide and oxidized with 30% hydrogen peroxide (SO, P) at 60-70°C. The carboxyl group content of the obtained product was 1.1 molar equivalent (solid content 1k)
per gram). Table 2 shows the compositions and carboxyl group contents of the products of the present invention and comparative products obtained in the same manner.

Examples 1 to 8 and Comparative Examples 1 to 4 A mixing test into concrete was conducted using the products of the present invention and comparative products obtained in the above reference example, as well as a commercially available cement dispersant, as dispersants. Test conditions are shown in Table 3.

Also, the results of the mixing test for concrete are shown in Tables 4 and 5.
Shown in the table.

Table 4 Note Residual Ramp Residual Rate = (Slan 7 after a certain period of time / (Initial Slanka x 100 (%)) Table 5 Note) Standard curing (kg/ha 2) Based on the results of Tables 4 and 5, the present invention It is clear that the product has an extremely superior effect in terms of slump survival rate.

Applicant's agent Kaoru Furutani

Claims (1)

[Scope of Claims] 1. A formalin cocondensate of the following components (a) and (b) is subjected to an oxidation reaction to remove carboxyl groups with a solid content of 1 kg.
A cement dispersant containing as an essential component a compound containing 0.5 molar equivalent or more. (a) One or more compounds selected from the following compounds (1), +21, and (3), (1) Naphthalenesulfonic acid or alkylnaphthalenesulfonic acid, (2) One or two of the above (1). Formalin condensate or co-condensate of the above, (3) Salt of the above (11 or (2)), (b) IJ geninsulfonic acid or its salt 2 The oxidation reaction is carried out under alkaline conditions with air, oxygen or peroxide. 1
The cement dispersant according to claim 1, which comprises one or more species. 3. The cement dispersant according to claim 1 or 2, wherein the oxidation reaction is carried out by oxygen or air using an alkaline earth metal or metal salt as a catalyst. 4. The cement dispersant according to claim 1, wherein the oxidation reaction is caused by an alkaline earth metal oxide. 5. The cement dispersant according to claim 2, wherein the peroxide is hydrogen peroxide or a water-soluble peroxide. 6 (a) component and (bl component weight is 9515 ~ 20/8
The cement dispersant according to claim 1, wherein the cement dispersant is 0.