JP2535170B2 - Cement dispersant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention increases the fluidity of a cement dispersant, more specifically, cement paste, mortar and concrete, which are cement compositions, and reduces the fluidity over time. The present invention relates to a cement dispersant which is characterized by preventing it, improving its workability and workability, and not delaying the hardening time of the cement composition.

[Conventional technology]

Various types of cement dispersants are known, but as representative ones, β-naphthalenesulfonic acid formalin condensate salt (hereinafter abbreviated as β-NSF) and melaminesulfonic acid formalin condensate salt (hereinafter abbreviated as SMF). ), Lignin sulfonate, etc. are known. Of these, β-NS
F or SMF is called a high-performance water reducing agent, and due to its powerful dispersing action, it has been used mainly for secondary concrete products, but it has also been used in the field of ready-mixed concrete for the purpose of quality improvement in recent years. It's starting to happen.

Due to its strong dispersing action, the superplasticizer can greatly reduce the amount of unit water in the cement composition and improve the quality of the cement composition. However, the cement composition to which the high-performance water reducing agent is added rapidly decreases its fluidity with time. This decrease in liquidity is called slump loss. If this slump loss occurs, for example, when pumping the cement composition in a secondary concrete product factory or the like, the pumping pressure is suddenly increased when the pumping is stopped for some reason and then the pumping is restarted. There was a problem that the pump was blocked. Alternatively, there has been a problem such as defective compaction in centrifugal compaction molding.

Also for ready-mixed concrete, the fluidity decreases during transportation from the concrete manufacturing plant to the setting site, making it difficult to place it on site. In particular, in the case of driving a pump, it causes a blockage of the pipe. For this reason, when a high-performance water reducing agent is used, it is common to add it at the setting site to improve the fluidity and then immediately set it. However, this on-site addition method has various problems. For example, concrete management becomes complicated, that is, it is necessary to manage before and after fluidization, and because the fluidization process is added, the casting efficiency decreases, or the personnel for adding the fluidizing agent is secured. Need of Furthermore, there are pollution problems such as noise and exhaust gas when stirring with a mixer truck. Thus, slump loss has an extremely large impact on concrete management.

Conventionally, the following methods have been proposed as methods for preventing slump loss.

(1) Method of delaying cement hydration by using a setting retarder together (2) Method of repeatedly adding a high-performance water reducing agent (3) Method of granulating the high-performance water reducing agent and gradually dissolving it (4) High performance Method of using lignin sulfonate or special lignin sulfonate together with water reducing agent The method of the above (1) delays the setting time by using a high performance water reducing agent and a setting retarder such as oxycarboxylate. , To maintain fluidity. However, the slump loss prevention effect is not always sufficient.

The method (2) is an effective means to some extent, but has problems such as workability of repeated addition and high cost due to an increase in the addition amount.

With the method (3), it is difficult to control the dissolution rate of the granulated high-performance water reducing agent, and if undissolved portions remain, the quality of concrete deteriorates.

The method (4) is also considered to be an effective practical means to some extent, but it has drawbacks such as an increase in the amount used compared with the conventional high-performance water reducing agent and a delay in setting.

[Problems to be solved by the invention]

All of the conventional slump prevention methods have drawbacks as described above. In other words, it is not practical,
There are problems that the slump loss reducing effect is not sufficient, the water reducing property is reduced, and the composition has a delay in setting. Under such circumstances, an object of the present invention is to provide a cement dispersant characterized by high water-reducing property and preventing slump loss without delaying the curing time.

[Means for solving problems]

The present inventors have conducted extensive studies to improve the problems of the prior art, and as a result, cement containing a water-soluble polymer compound obtained by copolymerization of the following components (a) and (b) as a component. The present inventors have found that the dispersant is a novel dispersant having excellent water-reducing ability and fluidity-retaining ability, and which does not adversely affect the setting delay and other qualities, and has completed the present invention. .

(A) General formula A compound represented by the formula: However, in the formula, n represents 0 or 1, and X represents an alkali metal, an alkaline earth metal, or ammonia.

(B) Maleic acid or salt thereof The present invention is characterized by having excellent water-reducing ability and fluidity-retaining ability, and further, delaying setting and other adverse effects on quality. In order to exert these characteristics, the combination of the molecular weight of the copolymer and the molar ratio of the component (a) and the component (b) in the copolymer is extremely important.

First, the molecular weight of the copolymer will be described. In order to exhibit excellent water-reducing ability and fluidity retention ability, the weight-average molecular weight of the copolymer must be in the range of 1 × 10 ⁴ to 8 × 10 ^4. Is. The weight average molecular weight here is a measured value obtained by GPC measurement using pullulan as a standard substance. When the weight average molecular weight is smaller than the above range, a high water reducing effect cannot be obtained. Further, when the molecular weight is larger than the above range, a high water reducing effect cannot be obtained, and the change in fluidity with time becomes large.

Next, the molar ratio of the component (a) and the component (b) in the copolymer will be described. The relationship of molar ratios mainly affects the change of fluidity with time and the curing time. Therefore, the dispersant of the present invention has a weight average molecular weight of 1 × 10 ⁴ to 8 × 1.
At the same time in 0 ⁴ range, the molar ratio of component (a) and component (b) 1: 0.05 to 1: it is necessary to be in the range of 0.15. If the amount of component (b) is less than the above range, a sufficient fluidity retention effect cannot be obtained. On the other hand, when the amount of the component (b) is more than the above range, the change in fluidity with time becomes large, and the retardation of setting is exhibited.

The reason why the dispersant of the present invention exhibits an excellent slump loss preventing effect is not clear, but one of the reasons is considered as follows. In other words, one of the causes of slump loss is that the dispersant disappears from the particle surface due to the initial hydration reaction of cement, and it does not act effectively on the surface of cement particles. For example, naphthalene sulfonic acid formalin condensate (hereinafter abbreviated as NSF) is adsorbed on cement particles and exhibits a high dispersion effect.
Liquidity decreases over time. As one of the causes of this, the measurement result of the adsorption amount of NSF using Fourier transform infrared spectroscopy (FT-IR) showed that the admixture disappeared from the particle surface due to the hydration of cement. There is. It is considered that this is because NSF is adsorbed on the cement particles by physical adsorption, and is easily desorbed due to the change in phase conditions accompanying the progress of the hydration reaction. On the other hand, in the dispersant of the present invention, the polystyrene sulfonic acid skeleton is copolymerized with a maleic acid component which is a divalent acid to give the dispersant an appropriate chelating property. It is considered that this chelating property makes it difficult to detach from the particle surface even if the hydration reaction proceeds, and effectively prevents slump loss.

Further, those having a structure similar to that of the dispersant of the present invention, which contains a copolymer of p-styrene sulfonate (component (a)) and a monoethylenically unsaturated compound as a main component (JP 57-156355), or a sulfonated styrene-maleic acid copolymer saponified (JP-A-59-156).
-141445). The former is characterized in that it exhibits a high dispersion effect even at low temperatures, and does not mention the slump loss prevention effect. For the latter, the structure is (In the formula, X is any one of Na, K, Ca, and NH _4. ), 1 is an integer of 1 to 5, m is an integer of 1 to 3, and n is
Is an integer of 4 to 10. In other words, l: m is 1.0: 0.2 to 1.0: 3.
It means 0. As described above, when the amount of the maleic acid component exceeds the claimed range, it does not show an effective slump loss preventing effect and, in some cases, causes significant slump loss and retardation of setting. Therefore, the present invention, unlike both dispersants, newly provides a method for effectively preventing slump loss.

The cement dispersant of the present invention is produced by a radical polymerization reaction, and is generally performed in an aqueous phase in an inert gas atmosphere at room temperature to 100 ° C. Commonly used radical polymerization initiators are ammonium persulfate, potassium persulfate, etc.
(II) An aqueous redox initiator that also uses a reducing agent such as a salt is also used. Moreover, the molecular weight of the copolymer can be easily obtained by adjusting the reaction conditions such as the monomer concentration, the initiator concentration, the reaction temperature and the reaction time. The thus obtained cement dispersant of the present invention can be used as it is as an aqueous solution after the polymerization reaction, but it is preferable to use one obtained by dropping it in acetone or methanol to precipitate the copolymer. It is more effective to do it. Furthermore, ultrafiltration or dialysis treatment of the copolymer removes the low polymerized portion, which is more effective. In particular, the dispersion effect is remarkable.

The amount of the cement dispersant of the present invention to be added to cement is generally 0.2 to 1.0% by weight. If it is less than 0.2%, a sufficient dispersing effect and slump loss preventing effect on the cement particles cannot be obtained. When it becomes 1% or more,
Excessive cement dispersion can lead to breathing and paste separation.

Further, the cement dispersant of the present invention is another cement additive as required, for example, an AE agent, an AE water reducing agent such as lignin sulfonate, or a high performance water reducing agent such as a naphthalene sulfonic acid formalin high condensate salt. It can also be used together with.

〔Example〕

The present invention will be specifically described below with reference to examples.
The present invention is not limited to these examples.

(1) Production Example Inventive Example 1 A 5 L four-necked flask equipped with a stir bar, a thermometer, a cooling tube, and a nitrogen introducing tube was charged with sodium p-styrenesulfonate.
Charge 150g, maleic acid 12.7g, and deionized water 3000ml.

Next, nitrogen substitution is performed, and while introducing nitrogen, 10.5 g of ammonium persulfate and 9.0 g of sodium bisulfite are charged,
Adjust temperature to 70 ° C. After continuing the polymerization reaction for 4 hours, it is cooled and neutralized with an aqueous sodium hydroxide solution. Then, the solution is concentrated with an evaporator, and the concentrated solution is dropped into acetone. The precipitated copolymer is filtered, washed with acetone, and dried under reduced pressure.

Invention Example 2 Instead of sodium p-styrenesulfonate, p-chloromethylstyrene (CMS-14, manufactured by Kiyomi Chemical Co., Ltd.)
Was synthesized in the same manner as in Example 1 of the present invention except that 160 g of sodium p-vinyl-toluenesulfonate obtained by sulfonation was used.

Inventive Example 3 A 5 L four-necked flask equipped with a stir bar, thermometer, cooling tube, and nitrogen introducing tube was charged with sodium p-styrenesulfonate.
Charge 167.0 g, maleic acid 10.5 g, and deionized water 4.5.

Next, the atmosphere is replaced with nitrogen, 30.8 g of ammonium persulfate is charged while introducing nitrogen, and the temperature is adjusted to 80 ° C. After continuing the polymerization reaction for 4 hours, it is cooled and neutralized.

The copolymer thus obtained was subjected to ultrafiltration using a membrane having a molecular weight cut off of 5000.

Comparative Example 1 Synthesis was conducted in the same manner as in Example 1 of the present invention except that 300 g of sodium p-styrenesulfonate, 93 g of maleic acid, 21 g of ammonium persulfate and 18 g of sodium bisulfite were charged.

Comparative Example 2 Synthesis was conducted in the same manner as in Example 1 of the present invention except that 600 g of sodium p-styrenesulfonate, 84 g of maleic acid, 8.4 g of ammonium persulfate and 7.2 g of sodium hydrogen sulfite were charged.

Comparative Example 3 Synthesis was performed in the same manner as in Example 1 of the present invention except that 21 g of maleic acid was charged.

Table 1 shows the properties of various dispersants obtained by the production examples.

GPC measurement conditions are as follows: Column: Shodex OH-pak B-803 + B-804 Eluent: 0.05M Borax + 0.3% propanol Temperature: 40 ° C Flow rate: 1 ml / min (2) Concrete test Various cement dispersants shown in Table 1 Using JIS A 62
A concrete test based on 04 was performed to measure the water reduction rate, slump change over time, the amount of air, and the setting time. Table 2 shows the results.

The materials used for the concrete test are as follows.

Cement: Normal Portland (Asano, Onoda, Tokuyama) Fine aggregate: Kashima sand (specific gravity 2.58, F.M2.58) Coarse aggregate: Yamaguchi crushed stone (specific gravity 2.70, F.M6.70) [Effects of the Invention] As is clear from Table 2, the cement dispersant of the present invention is
The water-reducing property of β-NSF is higher than that of β-NSF, and β-NSF has a large slump change over time, whereas the dispersant of the present invention has excellent slump retention ability. Further, dispersants other than those of the examples of the present invention do not have such effects, and it is found that the combination of the molecular weight of the dispersant and the molar ratio of the component (a) and the component (b) is extremely important. .

Therefore, the cement dispersant of the present invention contributes to the improvement of the quality of concrete due to its high water-reducing property, and it is possible to hold the slump without delaying the curing time, so that workability and workability are greatly improved. it can.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigenobu Fujioka 2-8-1, Iida-cho, Iwakuni-shi Sanyo Kokusaku Pulp Co., Ltd. Pulp Co., Ltd. (72) Inventor Masato Tamao 2-8-1, Iida-cho, Iwakuni City Sanyo Kokusaku Pulp Co., Ltd. (56) Reference JP-A-59-141445 (JP, A)

Claims (1)

(57) [Claims] 1. A composition having a molar ratio of the following components (a) and (b) of 1: 0.05 to 1: 0.15 and a weight average molecular weight of 1 × 10 ⁴ to 8 × 10 ⁴ . An anti-slump loss dispersant consisting of a copolymer. (A) General formula A compound represented by the formula: However, in the formula, n represents 0 or 1, and X represents an alkali metal, an alkaline earth metal, or ammonia. (B) Maleic acid or its salt