JPH02212343A - Cement additive - Google Patents

Abstract

PURPOSE:To obtain the cement additive capable of imparting high fluidity to a cement mixture for a long time and capable of enhancing the mechanical strength after setting by incorporating a sulfonated styrene-maleic acid copolymer and a polyacrylate into the additive. CONSTITUTION:The cement additive contains a sulfonated styrene-maleic acid copolymer and a polyacrylate, and is capable of imparting high fluidity to a cement mixture and capable of keeping the fluidity over a long period. Consequently, the long-distance transportation of the cement mixture is made possible. A copolymer having about 20-85%, especially about 30-70%, molar fraction of the sulfonated styrene unit and having about 500-50,000 number-average mol.wt. is preferably used as the sulfonated styrene-maleic acid copolymer. A polyacrylate having about 500-1,000,000 number-average mol.wt. is ordinarily used as the polyacrylate. One hundred pts.wt. of the copolymer is appropriately used with 10-300 pts.wt. of the polyacrylate. Meanwhile, a nonionic and/or anionic surfactant can be added to the additive to improve its dispersibility, and about 0.01-1.00wt.% of the additive based on cement is appropriately used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an additive for cement, and more specifically, to an additive for cement that can impart excellent fluidity to a cement mixture and maintain this fluidity constant over a long period of time. The present invention relates to an additive for cement that can increase the mechanical strength of concrete after hardening.

[Prior art and problems to be solved by the invention] Conventionally, in cement mixtures containing cement paste, mortar, concrete, etc., the cohesive force of cement particles is strong, so it is difficult to work with the unit amount of water required to harden the cement. It was not possible to obtain a cement mixture with good properties. Therefore, in order to improve the workability of cement mixtures, it was necessary to use more water than the unit amount of water required for curing.

However, simply increasing the amount of water leads to a decrease in the strength of concrete after hardening, so it was necessary to increase the amount of cement per unit in order to obtain concrete with the same strength. However, when the unit amount of cement is increased, the curing calorific value increases.

Therefore, there was an inconvenience that cracks were likely to occur.

Furthermore, after mixing the various ingredients, cement mixtures are often transported to the pouring site by mixer trucks, etc., but the time required for transportation varies depending on factors such as the distance of transportation and the degree of traffic congestion. It is usual. For this reason, at the pouring site, the fluidity of the cement mixture differs depending on the lot being transported, making it difficult to obtain consistent workability. Furthermore, while the cement mixture was being pumped, the pumping was interrupted for some reason.
If it is then pumped again, the fluidity of the cement mixture in the pipe has decreased.

There were problems such as the need to increase the pumping pressure after restarting, or the piping being partially blocked.

As mentioned above, the simplest way to improve the fluidity of a cement mixture is to increase the amount of water in the mixture, but such an increase in water amount can cause problems such as cracking and flaking after construction. known to be the cause.

Therefore, there is a need for an additive that has a water-reducing effect, improves the dispersibility of cement particles, provides suitable fluidity, and can maintain this fluidity constant over a long period of time. Ta.

As an additive for such cement, salts of sulfonated styrene-maleic acid copolymers (Japanese Patent Application Laid-Open No. 59-141
445) and polyacrylates (Japanese Unexamined Patent Application Publication No. 49-1989)
No. 117519 and JP-A-61-141! (see Publication No. i52) is known.

However, when using the salt of the sulfonated styrene-maleic acid copolymer, although the level of fluidity is almost satisfactory,
The disadvantage is that the fluidity cannot be maintained constant over a long period of time, and when the polyacrylate is used, sufficient fluidity cannot be imparted, which is unsatisfactory.

[Means for Solving the Problem] In order to solve the problem, the inventors have conducted extensive research and have developed an additive using a mixture of a salt of a specific polymer and a salt of a specific compound. However, they discovered that it is possible to impart fluidity to a cement mixture and maintain that fluidity for a long period of time, leading to the completion of this invention.

That is, the present invention is a cement additive characterized by containing a salt of a sulfonated styrene-maleic acid copolymer and a polyacrylate.

This invention will be explained in more detail below.

(1) Cement additive (a) component The cement additive of the present invention basically contains a salt of a sulfonated styrene-maleic acid copolymer and a polyacrylate as essential components, and further includes: contains a nonionic surfactant and/or anionic surfactant.

The salt of the sulfonated styrene-maleic acid copolymer used as an essential component of the cement additive of the present invention is represented by the general formula shown below (wherein XI is Na, l/ 2Ca
, N ) (representing either 4 or an organic amino group) and a maleate unit represented by the following general formula, (wherein X2.X3 is tSotLzotLNa,K,1/2
(representing either Ca, NH4 or an organic amino group) in a molar ratio of 0.
Random copolymers of these, having maleate units which may be replaced with maleic anhydride units represented by the general formula R shown below in a proportion of 1 to 1;
Examples include block copolymers and alternating copolymers.

Among these various sulfonated styrene-maleic acid copolymer salts, the molar fraction of sulfonated styrene units is 20
Preferably, the content is between 85% and 30% to 70%.

Such a salt of a sulfonated styrene-maleic acid copolymer can be prepared, for example, by the following general formula % formula % () (where xl, Xff1 and x2 each have the same meaning as above, The integer 1m of 20 can be expressed as an integer of 1 to 3, and n is an integer of 4 to 100.

Note that the formula (m) does not indicate that it is a block copolymer, but conceptually indicates the type of repeating unit and the number of repeating units.

Such a salt of a sulfonated styrene-maleic acid copolymer can be prepared by sulfonating a styrene-maleic acid copolymer by a conventional method, removing the unreacted copolymer, and removing the remaining sulfuric acid by a conventional liming process. It can be manufactured by performing a treatment such as removing it as gypsum by sodation.

Here, the styrene-maleic acid copolymer as a raw material may be a random copolymer, a block copolymer, or an alternating copolymer, but the number average molecular weight is 500 to s.
o, ooo, particularly preferably from 1.000 to 20,000.

Further, the sulfonation rate of the salt of the copolymer represented by general formula (m) [the number of sulfone groups (SO, X') introduced per styrene unit multiplied by 100] is 30% or more, Preferably it is 50% or more.

The polyacrylic acid salt used as an essential component of the cement additive of the present invention is one in which the carboxyl group of polyacrylic acid has been neutralized with an alkaline substance. This neutralization may be to completely neutralize the carboxylic acid in polyacrylic acid, or may be to partially neutralize it.

The polyacrylic acid includes homopolymers of acrylic acid, homopolymers of methacrylic acid, and monomers copolymerizable with acrylic acid or methacrylic acid, such as maleic acid, fumaric acid, itaconic acid, or These esters, esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate,
It may also be a copolymer with monomers such as allyl alcohol, vinyl ether, styrene, styrene sulfonic acid, or acrylamide.

The molecular weight of this polyacrylic acid is not particularly limited, but usually has a number average molecular weight of 500 to t, ooo, ooo.

Such polyacrylic acid can be produced, for example, by polymerizing acrylic acid using a solution polymerization method or a suspension polymerization method.

The solvent used in such a polymerization method is usually water or an organic solvent (for example, n-hexane, toluene,
hydrocarbons such as ethylbenzene).

As a specific method for polymerizing acrylic acid, acrylic acid is added to the solvent, and a polymerization initiator is further added to perform radical polymerization.

As the polymerization initiator, most water-soluble and alcohol-soluble radical initiators can be used, such as persulfates such as ammonium persulfate and potassium persulfate, azobisisobutyronitrile, and azobisaminodipropane. Azo compounds such as hydrochloride, hydroperoxide compounds such as cumene hydroperoxide, diacyl peroxide compounds such as lauroyl peroxide and benzoyl peroxide, alkyl perester compounds such as t-butylperoxy-2-ethylhexoxide. or can be used. It is also possible to use a redox initiator consisting of a combination of a reducing agent such as acidic sodium sulfite or sodium thiosulfate and concentrated sulfuric acid.

The polymerization temperature when performing the radical polymerization differs depending on the type of polymerization initiator, but a relatively high temperature is preferable because it lowers the degree of polymerization and shortens the polymerization time.
The polymerization temperature is preferably 30 to 95°C, and it is particularly preferable to carry out the polymerization under reflux.

The molecular weight of the produced polymer can be controlled by controlling the amount of polymerization initiator, polymerization temperature, solvent temperature, and polymerization regulators (such as mercaptans, methanol, ethanol, isopropanol,
(lower alcohol such as tert-butanol).

The polyacrylic acid thus obtained is used after being roughly neutralized with an alkaline substance.

Examples of the alkaline substance include aqueous compounds, chlorides, or carbonates of -valent metals or divalent metals, ammonia, or organic amines.

It is preferable to mix a nonionic surfactant and/or anionic surfactant in the cement additive of the present invention, thereby improving the dispersibility of the cement mixture.

Examples of the nonionic surfactants include polyethylene glycol alkyl ether, polyethylene glycol alkyl phenyl ether, polyethylene glycol fatty acid ester, polyethylene glycol fatty acid amide, N-polyethylene glycol alkylamine, polyethylene glycol sorbitan fatty acid ester, polypropylene glycol polyethylene glycol ether, and polyethylene glycol. And so on.

Examples of the anionic surfactants include polyoxyethylene alkyl ether sulfate salts, polyoxyethylene alkyl phenyl ether am ester salts, polyoxypropylene alkyl phenyl ether sulfate salts, polyoxyethylene alkyl ether phosphorus sulfate salts, and polyoxyethylene alkyl ether phosphorus sulfate salts. Examples include styrene alkyl phenyl ether phosphate salts.

(b) Amount ratio The mixing ratio of the salt of the sulfonated styrene-maleic acid copolymer and the polyacrylate in the cement compounding agent is not particularly limited, but is usually 100 parts of the salt of the copolymer.
The polyacrylate may be blended in an amount of 10 to 300 parts by weight, preferably 30 to 100 parts by weight.

Further, the blending ratio of the nonionic surfactant and/or anionic surfactant as a surfactant is usually 0 to 100 parts by weight of the copolymer.
．． The amount may be 0.01 to 200 parts by weight, preferably 0.05 to 150 parts by weight.

The cement additive of the present invention contains a salt of the sulfonated styrene-maleic acid copolymer and a polyacrylate, or a nonionic surfactant and/or anionic surfactant is added to these components. It basically consists of at least three or four components added, but other known fluidizing agents such as naphthalene sulfonic acid formalin condensate salts, melamine sulfone It can be used in appropriate combination with a salt of an acid-formalin condensate, a salt of ligninsulfonic acid, or the like.

(2) Cement mixtures Cement mixtures to which the above cement additives are mixed include Portland cements such as ordinary Portland cement, early-strength Portland cement, and white Portland cement, as well as blast furnace cement, silica cement, and fly ash cement. Cement selected from mixed cement, special cement such as alumina cement and expanded cement, water, aggregate such as sand, gravel, crushed sand, crushed stone, etc.
Lightweight aggregates such as pumice, volcanic ash, expanded slag, coal debris, AE agents, water reducing agents, retarders, curing accelerators, air entraining agents,
Cement paste, mortar or mortar containing admixtures such as air-entraining water reducer, cement particle dispersant, anti-freezing agent, anti-corrosion agent, wear-resistant agent, waterproofing agent, swelling agent, foaming agent, blowing agent, coloring agent, etc. concrete, etc.

(3) Addition amount The amount of the cement additive of the present invention to be added to the cement mixture is not particularly limited, but it is 0.000% in terms of solid content relative to cement. O1 to 1.00% by weight, preferably 0.05 to 0.70% by weight is suitable.

[Examples] In order to more specifically explain the cement additive of the present invention, Examples are given below, but the present invention is not limited thereto.

(Examples 1 to 6 and Comparative Examples 1 to 5) Sulfonated styrene-maleic acid copolymer number average molecular weight 1,900. Manufactured by ARCO Chemica1, rsM
A-3000'') was dissolved in 90% concentrated sulfuric acid, 80 g of fuming sulfuric acid was added over 1 hour while adjusting the temperature to 30-40°C, and the reaction was then carried out for 3 hours to form the above-mentioned compound. The polymer was sulfonated.

After the completion of the reaction, water is added to one reactant and the unreacted styrene-maleic acid copolymer is filtered off.Then, the remaining sulfuric acid is removed as a gypsum component by a normal liming sodation method at 70°C. Salt of union (sodium salt) 138g
I got it.

嘗＾の２ 500 parts of a 50% isopropyl alcohol aqueous solution was placed in a 21-volume glass reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, and the internal temperature was brought to 8 by purging with nitrogen while stirring.
Acrylic acid aqueous solution 4 with a concentration of 50% at zero temperature raised to 0°C
00 parts were added dropwise over 4 hours. Meanwhile, in parallel with this, 270 parts of 3% potassium persulfate was added dropwise over 4.5 hours to cause a reaction.

After the polymerization was completed, the isopropyl alcohol was removed, and 270 parts of 40% caustic soda was added to neutralize it.The concentration was adjusted to a solid content of 30% and a viscosity of 30 cps.
(25°C) 850 parts of an aqueous polymer solution was obtained.

B-3 In Production Example 2, except for using methacrylic acid,
Polymerization was carried out in the same manner as in Production Example 2.

After the polymerization was completed, the isopropyl alcohol was removed, and 230 parts of 40% caustic soda was added to neutralize.
s (25°C) was obtained.

A cement additive was prepared by blending a sulfonated styrene-maleic acid copolymer of cement, a polyacrylate, a surfactant, and an air-entraining water reducer in the ratios shown in Table 1.

Using a forced kneading mixer with an internal capacity of 60 grams of cement, 30 grams of cement mixture were prepared by mixing according to the mixing methods 1 and 2 shown below in the proportions shown in Table 1.

The obtained cement mixture was evaluated by measuring the air content, slump value, and compressive strength after hardening.

The results are shown in Table 1.

Cement method-1: After kneading and dissolving the air-entraining water reducing agent in water, predetermined amounts of cement, sand, pebbles and mixing water were added and kneaded at 20°C for 1 minute. After that, the specified amount of cement additive shown in Table 1 was added.

The cement mixture was prepared by kneading for an additional 30 seconds.

Method-2: After mixing cement additives in advance and dissolving them in water, add a predetermined amount of cement, sand, pebbles, and mixing water.
The cement mixture was prepared by kneading for 2 minutes at 0°C.

(Hereinafter, blank spaces) Request l...Made by Tokuyama Sodasu, ordinary Portland cement book 2...Produced in Nagahama, Shikoku Omishima, surface dry specific gravity 2.52 Coarse particle ratio 2
．． 34 Meaning 3... Crushed stone from Suohanaoka 1 surface dry specific gravity 2.70 Coarse particle ratio 6
．． 48, Maximum dimension 20mm Book 4... Manufactured by Hozoris Bussan ■, air-entraining water reducer Bozoris No. 70 (sodium lignin sulfonate) Attack 5... Displayed as solid content weight % based on cement weight Car 6... Polyoxy Ethylene monolaurate C01lt
iCOO(CHtCHJ)i. 11 7... Sodium polyoxyethylene nonyl phenyl ether sulfate Book 8... Conforms to JISA-1128 Heat 9... Conforms to JISA-1101 Clothing 10 - Conforms to JISA-1108 (compressive strength after curing) Moreover, the fluidized cement mixture can be maintained as it is for a long period of time. Therefore, by using this additive for cement, even when the cement is transported to the casting site by mixer truck, there is no fluctuation in the fluidity of the cement due to traffic congestion or distance of transportation, and consistent construction can be performed.

Furthermore, even if the pumping is interrupted when pumping the cement mixture, the fluidity will not decrease, so the pumping pressure will not increase or the piping will not be blocked.

[Effect of the invention]

Claims (2)

[Claims] (1) A cement additive characterized by containing a salt of a sulfonated styrene-maleic acid copolymer and a polyacrylate. (2) The cement additive according to claim 1, which contains a nonionic and/or anionic surfactant.