JPH0442844A - Additive for cement - Google Patents

Abstract

PURPOSE:To provide a cement additive composed of a sulfonated copolymer of indene and maleic anhydride or its salt, free from air-entraining property, having suppressed slump loss and giving a cement having improved and stable workability. CONSTITUTION:The objective cement additive is composed of a sulfonated copolymer of indene and maleic anhydride or its salt. All benzene rings of indene in the above sulfonate or its salt are not necessarily sulfonated and the above effect can be attained by sulfonating >=20% of the benzene ring. The salt is e.g. alkali metal salt, alkaline-earth metal salt or ammonium salt and it is not necessary to convert the sulfonic acid completely to salt. The additive does not cause the entrainment of air compared with conventional similar additives, gives a cement composition free from lowering of fluidity with time and prevents the lowering of the strength of cement composition, which is the objective function of cement additives.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cement additive, and more particularly, it improves the fluidity of cement mixtures such as cement paste, mortar, or concrete, and improves the fluidity over time. The purpose of the present invention is to provide a cement additive that prevents a decrease in properties and improves workability and workability.

[Conventional technology]

Fluidity and workability (
If you increase the unit amount of water to improve workability, the strength will decrease and you will not be able to obtain a cement mixture with the desired strength.On the other hand, if you decrease the unit amount of water in the cement mixture, the strength will decrease. This does not occur and the desired strength is achieved, but workability is significantly reduced.

Therefore, various cement additives have been used to reduce the unit water volume and improve workability while maintaining the desired strength. A typical example is β−
Naphthalene sulfonic acid formaldehyde condensates or salts thereof, melamine sulfonic acid formaldehyde condensates or salts thereof, lignin sulfonates, and the like are known. The amount of these cement additives to be added is determined by considering their type and desired fluidity. Seed cement additives are used in considerable amounts. However, lignin sulfonate has the disadvantage that it cannot be added in large amounts due to negative effects such as low dispersibility, setting retardation, and air entrainment.
- Naphthalenesulfonic acid formaldehyde condensates or their salts, melaminesulfonic acid formaldehyde condensates or their salts have excellent dispersion effects, and can be used up to high loadings without adverse effects such as delayed condensation or air entrainment; It is known that there is a noticeable problem in that it is extremely difficult to maintain the temperature for a long period of time. This is because after mixing, physical and chemical agglomeration of cement particles progresses over time due to hydration reactions between cement and water, causing the blend to gradually lose its fluidity, resulting in so-called slump loss. This is a major drawback of cement additives.

Various measures have been taken to solve this problem. For example, according to JP-A No. 54-139929, cement additives are powdered and the active ingredients are gradually dissolved to maintain their effect, and according to JP-A No. 51-15856, cement additives are repeatedly applied in small amounts. It is said that when added to cement mixtures, it is effective in preventing a decrease in slump.

Although the effectiveness of these measures has been well recognized, in the former case, cement additives are added in the form of powder, so local residuals are unavoidable, resulting in local bleeding. In addition, the latter method requires time and labor to be added repeatedly, and is not industrially desirable. Moreover, it has the drawback that the addition equipment is expensive.

[Problem to be solved by the invention]

The problem to be solved by the present invention is to solve the drawbacks of this kind of conventional cement additives, namely, to reduce the strength of the cement mixture, which is the original function of the additive, regardless of the amount added. The objective is to develop a cement additive that can improve and sustain workability without causing any problems, that is, has a small slump loss and is free from air entrainment and setting retardation.

[Means to solve the problem]

As a result of intensive research in order to achieve the intended purpose, the present inventors have found that the above-mentioned It was found that the purpose was achieved.

That is, the present invention relates to a cement dispersant comprising a sulfonated indene-maleic anhydride copolymer or (and) a salt thereof. This has never been used in this type of field.

[Function and structure of the invention]

In the sulfonated indene-maleic anhydride copolymer or (and) salt thereof used in the present invention, it is not necessary that all of the benzene rings of indene are sulfonated, and 20% or more, more preferably 60% of the benzene rings are sulfonated. If the above is sulfonated, the effect will be fully exhibited. Furthermore, as the salt thereof, alkali metals, alkaline earth metals, ammonia, etc. can be used. As for salts, there is no No. 1λ, in which all sulfonic acids are salts. The manufacturing method itself is not limited in any way, and any product manufactured by various methods can be used. For example, indene-maleic anhydride copolymer may be mixed with sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, sulfuric anhydride, etc. Specific examples of salts prepared by conventional methods using a curing agent include not only alkali metals or alkaline earth metals such as sodium, potassium, and calcium, but also ammonia and the like, with sodium being particularly preferred. Inden here
The copolymerization ratio of maleic anhydride copolymer is usually indene/
The molar ratio of maleic anhydride is 2/1 to 2/3, preferably about 1/1 of the alternating copolymer. In addition, the weight average molecular weight of the copolymer is 1000 or more, more preferably 6000 to 6000.
20000 is used.

The additive of the present invention has a solid content of 0.0 compared to cement.
A suitable amount is 5 to 1.5% by weight, more preferably 0.08 to 0.3% by weight. The amount added to cement is 0.0
If it is less than 5% by weight, no improvement in the fluidity of cement can be expected. On the other hand, if it exceeds 1.5% by weight, it not only causes aggregate separation but also tends to extremely slow down setting.

The cement additive of the present invention can be added to a cement mixture in the form of an aqueous solution or a powder, and can be added during or after kneading the cement mixture, or can be added publicly. In addition to the cement additive of the present invention, various conventionally used cement additives such as water reducing agents,
Air entraining agents, set retarders, accelerators, etc. may also be added.

〔Effect of the invention〕

According to the present invention, compared to conventional additives of this type, there is no air entrainment, and it is possible to significantly suppress slump loss, which causes a decrease in fluidity over time, and to maintain the original function of the additive. Workability can be improved and sustained without reducing the strength of certain cement formulations.

Therefore, regardless of the proportion of its use, it is extremely effective industrially.

〔Example〕

Hereinafter, the present invention will be explained with reference examples and examples as production examples of the sulfonated indene-maleic anhydride copolymer or its salt used in the present invention, but the present invention is not limited to these examples. It's not something you can do.

Reference Example 1 Indene-maleic anhydride copolymer having a molecular weight of 16,000 (copolymerization ratio +Ql: l T"h3.) 20 was placed in a flask equipped with a dropping funnel, a stirrer, a thermometer, and a reflux condenser.
0 g and nitromethane If were charged and dissolved.

Next, 87 g of chlorosulfonic acid was added over 1 hour while adjusting the temperature to 30-40°C, and the copolymer was then reacted at 50"C for 21 hours to sulfonate the copolymer. The degree of sulfonation was 71. Ta.

After the reaction was completed, nitromethane was removed, water was added to the reaction product, and the pH was adjusted to 7 to 8 with a 20% aqueous sodium hydroxide solution to obtain a sulfonated salt of an indene-maleic anhydride copolymer.

Reference Example 2 In Reference Example 1, chlorosulfonic acid! 87g to 55g
A salt of an indene-maleic anhydride copolymer sulfonate was obtained in the same manner as in Reference Example 1 except that

Reference Example 3 200 g of indene-maleic anhydride copolymer (copolymerization ratio 1it:IT'Tf) S) having a molecular weight of 5.500 was placed in a flask equipped with a dropping funnel, a stirrer, a thermometer, and a reflux condenser.
and nitromethane 11 were charged and dissolved.

Next, 298 g of fuming sulfuric acid (containing 25% sulfuric anhydride) was added over 1 hour while adjusting the temperature to 30 to 40°C, and the copolymer was then reacted at 50°C for 11 hours to sulfonate the copolymer. The degree of sulfonation is <1'l l
It was Erita ζ-ci 2 bio.

After the reaction was completed, nitromethane was removed, water was added to the reaction mixture, and the waste sulfuric acid was neutralized with calcium hydroxide until the aqueous solution reached pH 7.0. After separating the gypsum, 148 g of sodium carbonate was added to the neutralized product, and the resulting calcium carbonate was filtered to obtain a sulfonated salt of an indene-maleic anhydride copolymer.

Reference Example 4 A sulfonated salt of an indene-maleic anhydride copolymer was obtained in the same manner as in Reference Example 3 except that the amount of fuming sulfuric acid was changed from 298 g to 149 g.

Example 1 (1) Concrete mix and materials used Table 1 Cement (C): Ordinary Portland cement Fine aggregate (
S): Kuzuryu sand (specific gravity 2.57) coarse aggregate (G):
Rikuhori Gyokusai (specific gravity 2.64) water produced for Kuzuryu
Tap water fine aggregate ratio (A): Fine aggregate coarse aggregate (by volume) (2) Concrete mixing method Cement additives obtained under the conditions in Table 2 below are mixed in advance and dissolved in water. 30 with tiltable mixer at 20°C! The concrete shown in Table 1 was obtained by mixing. Further, the mixture was kneaded at a rotational speed of 3 r, p, m for a predetermined period of time, and the slump and air amount changes over time were measured. Note that a natural resin acid-based AE agent (air entrainment agent) was used to adjust the amount of air. Slump here,
Air volume and compressive strength are JISA-1101 and JI, respectively.
It was conducted in accordance with SA-1128 and JIS A-1108. The results are shown in Table 3.

Comparing the present invention and comparative examples, it is clear that the additive of the present invention has an excellent slump loss prevention effect, and of course has low air entrainment and setting retardation.

(Hereafter Up)

Claims (1)

[Claims] A cement additive comprising a sulfonated indene-maleic anhydride copolymer or (and) a salt thereof.