JPH0791101B2 - Method for producing cement dispersant comprising water-soluble vinyl copolymer having sulfonic acid group at terminal of main chain and cement dispersant obtained by the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a cement dispersant comprising a water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain, and a cement dispersion obtained by the method. Regarding agents.

Concrete mixes cement, gravel, sand, etc. with water,
Mortar is a material in which cement, sand and the like are kneaded together with water and hardened by a hydration reaction of cement. At this time, a dispersant is often used as an auxiliary agent. The dispersant improves the workability by facilitating the dispersion flow of the cement particles in the water system, promotes the hydration reaction of the cement, and brings about a water reducing effect, and as a result, improves the strength of concrete and the like. Is. Therefore, as the properties of the cement dispersant, 1) the dispersion fluidity of the cement particles is large, 2) the change of the dispersion fluidity with time is small (the slump loss is small), and 3) the strength of the cured product is reduced. Does not cause excessive entrend air, 4) Has little adverse effect of setting delay,
5) Various characteristics such as good economic efficiency are required.

The present invention meets the above demands.

<Conventional Technology and Its Problems> Conventionally, there are various proposals using a water-soluble vinyl copolymer as a cement dispersant (Japanese Patent Publication No. 59-18338, Japanese Patent Publication No. 2-7).
901, Japanese Patent Publication No. 8983/1989, JP-A No. 1-226757).

As is the case with these conventional proposals, water-soluble vinyl copolymers are usually produced by copolymerizing different vinyl monomers in an aqueous system.

By the way, using a water-soluble vinyl copolymer as a cement dispersant, in order for the water-soluble vinyl copolymer to exhibit sufficient performance, the water-soluble vinyl copolymer has an appropriate molecular weight, Further, it is important to have polar groups in an appropriate ratio so that they are adsorbed to cement particles and give a dispersion flow effect.

Therefore, in the above conventional proposal, in order to obtain a vinyl copolymer in which a vinyl monomer having a polar group is copolymerized at a predetermined ratio, various selection of the copolymerization ratio of the vinyl monomer to be used is performed. Has been.

However, when a water-soluble vinyl copolymer is produced by such a method, it is possible to obtain a water-soluble vinyl copolymer having a structure in which a specific polar group is introduced only at the terminal of the main chain of the copolymer. However, there is a problem that a vinyl monomer having a polar group is randomly bonded to form a water-soluble vinyl copolymer. Water-soluble vinyl copolymer in which vinyl monomers having polar groups are randomly bonded is used as a cement dispersant, and the effect of improving the dispersibility of cement immediately after kneading and the fluidity of the obtained cement composition is obtained. However, there is a large decrease in the fluidity with time (a large slump loss), and the workability is significantly reduced in the field construction of concrete, mortar and the like. Further, if the addition amount is increased in order to reduce the slump loss, the retardation of setting becomes large, and a hardened cement product of desired strength cannot be obtained.

<Problems to be Solved by the Invention, Means for Solving the Problems> The present invention solves the above-mentioned conventional problems and meets the above-mentioned requirements, and is a cement dispersant composed of a water-soluble vinyl copolymer having a regulated structure. And a cement dispersant obtained by the method.

However, the present inventor, as a result of diligent research from the above viewpoint, obtains a water-soluble vinyl copolymer having a structure having a sulfonic acid group as a polar group at the end of the main chain as a polar group by a specific method, and The inventors have found that a water-soluble vinyl copolymer is an excellent one having various properties required as a cement dispersant, and have completed the present invention.

That is, the present invention provides a method for producing a cement dispersant comprising a water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain, which is characterized by undergoing the following first step, second step and third step: , A cement dispersant obtained by the production method.

First step: A vinyl monomer represented by the following formula (1) and a vinyl monomer represented by the following formula (2) are represented by the vinyl monomer represented by the formula (1) / the formula (2). Vinyl monomer = 50
After copolymerizing in the presence of a radical initiator at a ratio of / 50 to 95/5 (molar ratio), radical terminating to obtain a binary copolymer Second step: Binary obtained in the first step Step of adding radical initiator to copolymer to obtain radical-activated binary copolymer Third step: The radical-activated binary copolymer obtained in the second step is represented by the following formula (3). Radical addition of one or more of the vinyl monomers shown to obtain a water-soluble vinyl copolymer having a sulfonic acid group at the end of the main chain Formula (1): Formula (2): Formula (3): [In the formulas (1) to (3), R ^{1 to} R ⁵ and R ⁷ are the same or different at the same time, H or CH ₃ .

R ⁶ is an alkyl group having 1 to 3 carbon atoms.

X and Y are alkali metal, alkaline earth metal, ammonium or organic amine.

n is an integer of 5 to 25. ] The manufacturing method according to the present invention includes a first step, a second step and a third step.
It is roughly divided into processes.

In the first step, after radical-copolymerizing the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2) in a predetermined ratio, radical-termination is carried out, and (1)
Is a step of obtaining a binary copolymer composed of the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2).

Examples of the vinyl monomer represented by the formula (1) include alkali metal salts of acrylic acid, methacrylic acid and crotonic acid, alkaline earth metal salts and alkanolamine salts. Examples of the vinyl monomer represented by the formula (2) include polyalkylene having one terminal alkyl group blocked by methoxy polyethylene glycol, ethoxy polyethylene glycol, propoxy polyethylene glycol, isopropoxy polyethylene glycol, methoxy polyethylene polypropylene glycol or ethoxy polyethylene polypropylene glycol. There is an esterified product of glycol and acrylic acid, methacrylic acid, or crotonic acid, in which the addition mole number of polyalkylene glycol is 5 to 25.

In the first step of the production method according to the present invention, the vinyl monomer represented by the formula (1) / the vinyl monomer represented by the formula (2) =
Both are copolymerized at a ratio of 50/50 to 95/5 (molar ratio), preferably 55/45 to 85/15 (molar ratio). This is because when the finally obtained water-soluble vinyl copolymer is used as a cement dispersant, the water-soluble vinyl copolymer can sufficiently exhibit various properties required as a cement dispersant.

The copolymerization reaction of the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2) is not particularly limited, but may be water or water and a water-soluble organic compound. It is preferable to carry out the aqueous solution polymerization using a mixed solvent with a solvent. The radical initiator used in the copolymerization reaction is not limited to any kind as long as it decomposes at the copolymerization reaction temperature to generate radicals, but a water-soluble radical initiator is used. It is advantageous.

Such water-soluble radical initiators include potassium persulfate, persulfates such as ammonium persulfate, hydrogen peroxide, 2,
2'-azobis (2-amidinopropane) dihydrochloride and the like. These can also be used as a redox initiator in combination with a reducing substance such as sulfite or L-ascorbic acid, as well as an amine. Also, a ceric ammonium salt catalyst such as ceric ammonium nitrate or ceric ammonium sulfate may be used as a strong oxidizing agent. The optimum amount of these water-soluble radical initiators varies depending on the type of the water-soluble radical initiator and the vinyl monomer used for copolymerization, but when ammonium persulfate is used, for example,
It is preferably in the range of 0.2 to 3% by weight based on the total amount of the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2).

In the first step of the production method according to the present invention, in the radical copolymerization of the above-mentioned two kinds of vinyl monomers, radical termination of the reaction system is performed in a timely manner to obtain a binary copolymer. There are roughly two types of methods for stopping such radicals. The first method is a method in which the reaction is continued until radicals completely disappear from the reaction system and the radical copolymerization reaction is substantially stopped. The second method is a method in which a radical terminating agent that forcibly decomposes and eliminates radicals is added to the reaction system.

A conventionally known compound can be used as such a radical terminating agent. Radical terminators that can be used advantageously include 3-mercapto-1,2-propanediol, dithioerythritol, 2-mercaptoethanol, 1,2-
There are compounds having at least two active hydrogen groups such as hydroxyl groups or thiol groups in the molecule such as ethanedithiol. Other radical terminating agents that can be advantageously used are compounds that share a thiol group and an α, β-unsaturated hydrocarbon group in the molecule. More specifically, such compounds include
There are α, β-unsaturated monocarboxylic acid mercaptoalkyl esters such as mercaptoethyl (meth) acrylate and mercaptoethyl crotonic acid ester.

The above-mentioned two kinds of radical terminators, that is, a compound having at least two active hydrogen groups such as hydroxyl groups or thiol groups in the molecule, and a compound sharing a thiol group and an α, β-unsaturated hydrocarbon group in the molecule The advantage of being added to the copolymerization reaction system is that a radical active point in the case of adding a radical initiator in the reaction of the second step described later can be added to the end of the obtained binary copolymer, The point is that the radical addition of the vinyl monomer represented by the formula (3) in the third step described later can be efficiently and selectively performed.

In the first step of the production method according to the present invention, the purpose of adding the radical terminating agent to the copolymerization reaction system is essentially to terminate the copolymerization reaction, but further, the addition of the resulting binary copolymer The point is that the molecular weight can be controlled. From this point of view, the addition of the radical terminating agent can be carried out at any time during the copolymerization reaction, either all at once or in a divided manner. The use of the chain transfer agent, such as mercaptoacetic acid, is not limited. The addition amount of the radical terminating agent is determined depending on the size of the molecular weight of the binary copolymer, the vinyl monomer, the aqueous solvent, and the type of the radical terminating agent. The amount is 0.01 to 5 mol% with respect to the total amount of the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2) that form a united body.

A conventionally known method can be applied to the aqueous solution radical polymerization using the vinyl monomer represented by the formula (1) and the vinyl monomer represented by the formula (2). The method and timing of introducing the vinyl monomer into the copolymerization reaction system are not particularly limited. The entire amount of the vinyl monomer may be introduced into the copolymerization reaction system before the initiation of the copolymerization reaction, or may be divided and introduced into the copolymerization reaction system. The copolymerization reaction temperature may range from room temperature to the boiling point of the aqueous solvent, but is preferably 50 to 80 ° C. The copolymerization reaction temperature when using the above-mentioned redox catalyst as a radical initiator is 10 to 30 than the above temperature.
C can be lowered.

The second step of the production method according to the present invention is a step of adding a radical initiator to the binary copolymer obtained in the first step to obtain a binary copolymer in which the terminal of the main chain is radically activated. is there.

When no unreacted vinyl monomer remains in the reaction solution obtained in the first step, the reaction solution can be directly used in the second step. When the vinyl monomer in the reaction remains, the radical-terminated binary copolymer is separated from the reaction solution, and the separated binary copolymer is subjected to the second step.

The radical initiator used in the second step may be the same as the radical initiator used in the first step.

For the binary copolymer obtained by radically terminating without using a radical terminating agent in the first step, the radical of the vinyl monomer represented by the formula (3) used in the next third step is used. In order to add efficiently and selectively,
It is preferable to add an azovir compound having a hydroxyl group in the molecule as a radical initiator. The application of such an azobis compound is not limited to a binary copolymer obtained by radically stopping with a radical stopper in the first step. Examples of azobis compounds having a hydroxyl group in the molecule include 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] and 2,2'-azobis [2-methyl-N- {1 , 1
-Bis (hydroxymethyl) ethyl} propionamide], 2,2'-azobis [2-methyl-N- {1,1-bis (hydroxymethyl) -2-hydroxyethyl} propionamide] and the like.

In the second step of the production method according to the present invention, the amount of the radical initiator used for radically activating the binary copolymer obtained in the first step depends on the kind of the radical initiator and the following third step. Although it varies depending on the kind of the vinyl monomer represented by the formula (3) used in the step, it is usually in the range of 0.1 to 5% by weight based on the binary copolymer obtained in the first step.

In the third step of the production method according to the present invention, the vinyl monomer represented by the formula (3) is radically added to the binary copolymer obtained by the second step and having the terminal of the main chain radical-activated. ,
This is a step of obtaining a water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain.

Examples of the vinyl monomer represented by the formula (3) include allylsulfonic acid and methallylsulfonic acid alkali metal salts, alkaline earth metal salts, and alkanolamine salts.

The reaction ratio between the binary copolymer obtained by radically activating the terminal of the main chain obtained in the second step and the vinyl monomer represented by the formula (3) is determined by the kind of the radical stopper used in the first step. And the type of radical initiator used in the second step, for example, whether or not an azobis compound having a hydroxyl group in the molecule is used, but usually 1 to 1 mol of the radical-activated binary copolymer. It is 10 mol, preferably 1.5 to 5 mol. The radical addition reaction of the binary copolymer having the terminal of the main chain obtained in the second step with radical activation and the vinyl monomer represented by the formula (3) itself is based on a known method of radical solution polymerization. Can be done.

According to the production method of the present invention, in the radical addition reaction between the binary copolymer having the terminal of the main chain radical-activated and the vinyl monomer represented by the formula (3), radical-activated A product obtained by adding one molecule of (meth) allyl sulfonate per active point of terminal radical of the original copolymer is obtained. When radically adding one molecule of sulfonic acid vinyl monomer per one terminal radical active site, the formula (3)
The (meth) allyl sulfonate represented by is another sulfonic acid vinyl monomer such as styrene sulfonate, 2
-Since it has extremely high reaction selectivity as compared with (meth) acryloxy sulfonates such as (meth) acryloxyethyl sulfonate and (meth) acrylamide sulfonates such as 2-acrylamido-2-methylpropane sulfonate. In addition, the water-soluble vinyl copolymer of the present invention having a regulated terminal structure can be obtained.

The water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain thus obtained is extremely effective as a cement dispersant. When the water-soluble vinyl copolymer is used as a cement dispersant, its number average molecular weight in terms of polyethylene glycol measured by the GPC method is 2000-
It is preferably 15,000, more preferably 3,000 to 10,000.

The cement dispersant according to the present invention is composed of a water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain, which is obtained by the above-mentioned first step, second step and third step, At the time of its use, other agents may be used jointly for the purpose. Such other agents include air entraining agents, antifoaming agents, setting accelerators, setting retarders, rust inhibitors,
Preservatives, waterproofing agents, strength promoters, expansive materials and the like.

The cement dispersant according to the present invention is, relative to cement, in terms of solid content, usually 0.01 to 1.5% by weight, preferably 0.03 to 0.4.
Used in percentage by weight. If the amount used is too small, the dispersion fluidity tends to decrease, and the dispersion fluidity retention effect tends to decrease at the same time, resulting in insufficient workability improving effect. On the other hand, if the amount used is too large, separation will occur and delay in setting will increase, resulting in poor curing.

The cement dispersant according to the present invention can be applied to concrete and mortar prepared by using various Portland cements, fly ash cements, blast furnace cements, silica cements, various mixed cements and the like.

Hereinafter, in order to make the configuration and effects of the present invention more specific,
Examples will be given, but the present invention is not limited to the examples.

<Examples, etc.> Test Category 1 (manufacture of water-soluble vinyl copolymer) -Example 1 (manufacture of water-soluble vinyl copolymer A) Methacrylic acid 60 parts (parts by weight, the same applies hereinafter), methoxy polyethylene glycol (ethylene Oxide addition mole number n
= 9) 150 parts of monomethacrylate, 250 parts of water and 7 parts of 2-mercaptoethanol were charged into a flask, and 58 parts of a 48% (wt%, hereinafter the same) aqueous solution of sodium hydroxide was added thereto to neutralize and uniformly. After the dissolution, the atmosphere was replaced with nitrogen. The temperature of the reaction system was maintained at 65 ° C in a warm water bath, 50 parts of 10% aqueous solution of ammonium persulfate was added to start the polymerization, and the polymerization was continued for 4 hours until almost all the vinyl monomer remaining in the reaction system was consumed. The reaction was continued. Then, 50 parts of a 10% aqueous solution of 2-mercaptoethanol was added to terminate radicals. An aqueous solution of the binary copolymer obtained by stopping the radicals was precipitated and purified in isopropanol and dried to obtain a binary copolymer (molecular weight 3700, sulfur content 1.6%). Next, 200 parts (0.054 mol) of the obtained binary copolymer and water 45
0 part was charged into another flask, and the atmosphere was replaced with nitrogen.
Keep the temperature of the reaction system at 70 ° C in a warm water bath, add 30 parts of 10% aqueous solution of ammonium persulfate to radically activate the binary copolymer, and then add 20% aqueous solution of sodium methallylsulfonate. 80 parts (corresponding to 0.10 mol of sodium methallyl sulfonate) was added and the reaction was continued for 2 hours.
The radical addition reaction was completed.

The product obtained was purified by precipitation as described above and then analyzed. As a result, it had a carboxyl value of 152, a sulfur content of 3.1% and a number average molecular weight of 4000 (GPC method, calculated as polyethylene glycol, the same applies hereinafter). From this result, the product is sodium methallyl sulfonate per one molecule of the binary copolymer copolymerized at a ratio of sodium methacrylate / methoxy polyethylene glycol (n = 9) methacrylate = 70/30 (molar ratio). % (Corresponding to 1.9) was the water-soluble vinyl copolymer A added to the end of the main chain.

Example 2 (Production of water-soluble vinyl copolymer B) Methacrylic acid 70 parts, methoxypolyethylene glycol (n = 9) monomethacrylate 101 parts, water 240 parts and 2
-6 parts of mercaptoethanol was charged into a flask, 67 parts of a 48% aqueous solution of sodium hydroxide was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. The temperature of the reaction system was maintained at 65 ° C in a warm water bath, 30 parts of a 10% aqueous solution of ammonium persulfate was added to start the polymerization, and the polymerization was continued for about 4 hours until the vinyl monomer remaining in the reaction system was almost consumed. The reaction was continued. And 5% of 2-mercaptoethyl acrylate
Radical termination was performed by adding 80 parts of an aqueous solution. An aqueous solution of the binary copolymer obtained by stopping the radical was precipitated and purified in isopropanol and dried to obtain a binary copolymer (molecular weight 5200, sulfur content 1.4%). Next, 150 parts (0.029 mol) of the obtained binary copolymer and 350 parts of water were charged into another flask, and the atmosphere was replaced with nitrogen. After keeping the temperature of the reaction system at 70 ° C in a warm water bath, 23 parts of a 10% aqueous solution of ammonium persulfate was added to radically activate the binary copolymer, and then a 20% aqueous solution of sodium methallylsulfonate was added. 45 parts (corresponding to 0.057 mol of sodium methallylsulfonate) were added and the reaction was continued for 2 hours to complete the radical addition reaction.

The product obtained was purified by precipitation as described above and then analyzed to find that it had a carboxyl value of 221, a sulfur content of 2.5%, and a number average molecular weight of 5,500. From this result, the product is sodium methallyl sulfonate 5.5 molecule per one molecule of the binary copolymer copolymerized at the ratio of sodium methacrylate / methoxy polyethylene glycol (n = 9) methacrylate = 80/20 (molar ratio). % (Corresponding to 1.8) was the water-soluble vinyl copolymer B added to the end of the main chain.

Example 3 (Production of Water-Soluble Vinyl Copolymer C) 50 parts of methacrylic acid, 383 parts of methoxypolyethylene glycol (n = 9) monomethacrylate, 750 parts of water and 4 parts of mercaptoacetic acid were placed in a flask, and sodium hydroxide was added. 48 parts of a 48% aqueous solution was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. The temperature of the reaction system in a warm water bath
After maintaining the temperature at 65 ° C and adding 40 parts of a 10% aqueous solution of ammonium persulfate to start the polymerization, and continuing the polymerization reaction for 5 hours until almost all the vinyl monomer remaining in the reaction system is consumed, a further 90- The radicals were stopped by continuing heating and stirring at 95 ° C. for 1 hour. The aqueous solution of the binary copolymer obtained by stopping the radicals is precipitated and purified in isopropanol and dried,
A binary copolymer (molecular weight 7800, sulfur content 0.3%) was obtained. Next, 400 parts (0.051 mol) of the obtained binary copolymer and 950 parts of water were charged into another flask, and the atmosphere was replaced with nitrogen. Keep the temperature of the reaction system at 70 ° C in a warm water bath,
Azobis [2-methyl-N- (2-hydroxyethyl)
35 parts of a 10% aqueous solution of propionamide was added to radically activate the binary copolymer, and then 100 parts of a 20% aqueous solution of sodium methallylsulfonate (equivalent to 0.13 mol of sodium methallylsulfonate). Was added and the reaction was continued for 2 hours to complete the radical addition reaction.

The product obtained was purified by precipitation as described above and then analyzed to find that it had a carboxyl value of 123, a sulfur content of 0.9% and a number average molecular weight of 8,000. From this result, the product is sodium methallyl sulfonate per molecule of the binary copolymer copolymerized at the ratio of sodium methacrylate / methoxy polyethylene glycol (n = 9) methacrylate = 60/40 (molar ratio). % (Equivalent to 1.6) was the water-soluble vinyl copolymer C added to the end of the main chain.

Hereinafter, water-soluble vinyl copolymers D to H were obtained in the same manner as in Examples 1 to 3. The production conditions of the water-soluble vinyl copolymers A to H are summarized in Table 1, and the analytical values are summarized in Table 2.

Comparative Example 1 (Synthesis of water-soluble vinyl copolymer R-1) 60 parts of methacrylic acid, 150 parts of methoxypolyethylene glycol (n = 9) monomethacrylate, 250 parts of water and 2-
7 parts of mercaptoethanol was charged into a flask, 58 parts of a 48% aqueous solution of sodium hydroxide was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. Keep the temperature of the reaction system at 65 ° C in a warm water bath and use a 10% aqueous solution of ammonium persulfate.
50 parts was added to start the polymerization, and the polymerization reaction was continued for 5 hours to complete the polymerization.

The product obtained was purified by precipitation in isopropanol and then analyzed. As a result, it had a carboxyl value of 175 and a number average molecular weight of 4300. Sodium methacrylate / methoxy polyethylene glycol (n = 9) monomethacrylate = 73
A water-soluble vinyl copolymer R-1 copolymerized at a ratio of / 27 (molar ratio) was obtained.

Comparative Example 2 (Synthesis of water-soluble vinyl copolymer R-2) Methacrylic acid 52 parts, methoxy polyethylene glycol (n = 9) monomethacrylate 129 parts, styrene sulfonic acid sodium salt 48 parts, water 390 parts and 2-mercapto Charge 7 parts of ethanol into a flask and add sodium hydroxide.
After adding 50 parts of 48% aqueous solution to neutralize and dissolve uniformly,
The atmosphere was replaced with nitrogen. The reaction system temperature is 60 ° C in a warm water bath.
Then, 55 parts of a 10% aqueous solution of ammonium persulfate was added to start the polymerization, and the polymerization reaction was continued for 5 hours to complete the polymerization.

The product obtained was purified by precipitation in isopropanol and then analyzed to find that it had a carboxyl value of 140 and a number average molecular weight of 4100, and the copolymerization rate of styrene sulfonic acid sodium salt was 18% by UV absorption (1 molecule of copolymer). Thus, water-soluble vinyl copolymer R-2 in which each vinyl monomer was randomly bonded was obtained.

Comparative Example 3 (Synthesis of Water-Soluble Vinyl Copolymer R-3) 60 parts of methacrylic acid, 150 parts of methoxypolyethylene glycol (n = 9) monomethacrylate and 250 parts of water were charged into a flask, and a 48% aqueous solution of sodium hydroxide was added. After adding 58 parts of the mixture to neutralize and uniformly dissolve it, the atmosphere was replaced with nitrogen. The temperature of the reaction system was kept at 65 ° C in a warm water bath, 40 parts of a 10% aqueous solution of ammonium persulfate was added to initiate polymerization, and 2
The polymerization reaction was continued for an hour. Without performing any operation for terminating the reaction system, 80 parts of a 20% aqueous solution of methallylsulfonic acid sodium salt (0.10 mol equivalent as methallylsulfonic acid sodium salt) was added to the reaction system, The reaction was continued for 3 hours.

The product obtained was purified by precipitation in isopropanol and then analyzed to find that it had a carboxyl value of 171, a number average molecular weight of 9000, a sulfur content of 0.2% or less, and a copolymerization rate of sodium methallylsulfonate of 0.2% (copolymer Water-soluble vinyl copolymer R-3, which is 0.1 per polymer molecule)
Got

Comparative Example 4 (Synthesis of water-soluble vinyl copolymer R-4) 55 parts of methacrylic acid, 160 parts of methoxypolyethylene glycol (n = 9) monomethacrylate, 270 parts of water and 2-
6.5 parts of mercaptoethanol was charged into a flask, and 53 parts of a 48% aqueous solution of sodium hydroxide was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. The temperature of the reaction system was maintained at 65 ° C. in a warm water bath, 50 parts of a 10% aqueous solution of ammonium persulfate was added to initiate polymerization, and the polymerization reaction was continued for 4 hours. And 50% 2-mercaptoethanol 10%
Was added to stop radicals. The aqueous solution of the obtained binary copolymer was precipitated and purified in isopropanol, dried and then analyzed. As a result, the sulfur content was 1.4% and the number average molecular weight was 4,800. Then, the obtained binary copolymer 15
0 part and 350 parts of water were charged into another flask, and the atmosphere was replaced with nitrogen. Keep the temperature of the reaction system at 70 ° C in a warm water bath, add 30 parts of a 10% aqueous solution of ammonium persulfate to radically activate the binary copolymer, and then add a 20% aqueous solution of sodium 2-sulfoethyl methacrylate. Input 100 copies, 2
The reaction was continued for an hour to complete the radical addition reaction.

The obtained product was purified by precipitation in isopropanol and then analyzed to have a carboxyl value of 155, a sulfur content of 1.5% and a number average molecular weight of 4800.
% (Equivalent to 0.2 per 1 molecule of binary copolymer) was added to the end of the main chain to obtain a water-soluble vinyl copolymer R-4.

Comparative Example 5 (Synthesis of water-soluble vinyl copolymer R-5) Methacrylic acid 15 parts, methoxypolyethylene glycol (n = 9) monomethacrylate 327 parts, water 550 parts and 2-
9 parts of mercaptoethanol was charged into a flask, and 15 parts of a 48% aqueous solution of sodium hydroxide was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. Keep the temperature of the reaction system at 65 ° C in a warm water bath and use a 10% aqueous solution of ammonium persulfate.
Polymerization was started by adding 60 parts and the polymerization reaction was continued for 4 hours. Then, 50 parts of a 10% aqueous solution of 2-mercaptoethanol was added to terminate radicals. The resulting aqueous solution of the binary copolymer was precipitated and purified in isopropanol, dried, and analyzed. As a result, the sulfur content was 0.9% and the number average molecular weight was 4,500. Next, the obtained binary copolymer 200
Parts and 450 parts of water were charged into another flask, and the atmosphere was replaced with nitrogen. After keeping the temperature of the reaction system at 70 ° C in a warm water bath and adding 30 parts of 10% aqueous solution of ammonium persulfate to radically activate the binary copolymer, 20% aqueous solution of methallylsulfonic acid sodium salt. 80 parts was added and the reaction was continued for 2 hours to complete the radical addition reaction.

The product obtained was purified by precipitation in isopropanol and then analyzed to find that the carboxyl value was 27 and the sulfur content was
It was 2.0% and the number average molecular weight was 4,800. From this result, the product is sodium methallyl sulfonate per molecule of the binary copolymer copolymerized at the ratio of sodium methacrylate / methoxy polyethylene glycol (n = 9) methacrylate = 20/80 (molar ratio). A water-soluble vinyl copolymer R-5 having 5.4% (corresponding to 1.6 per binary copolymer molecule) added to the end of the main chain was obtained.

Test Category 2 (Concrete Test) Water-soluble vinyl copolymers A to H of the present invention shown in Tables 1 and 2 and comparative water-soluble vinyl copolymers R-1 to R
Using -5 as a cement dispersant, a concrete test was carried out under the following mixing conditions and methods to measure slump, air content, changes with time, compression strength and setting time. The results are summarized in Tables 3 and 4.

・ Mixing conditions 320 kg / m ^{3 of} ordinary Portland cement (equal mixture of ordinary Portland cement made by Onoda and ordinary Portland cement made by Sumitomo), fine aggregate (Oigawa water-based sand, specific gravity 2.6
3) 871kg / m ³ , coarse aggregate (crushed stone from Okazaki, specific gravity 2.66) 979
kg / m ³ (fine aggregate rate 47%) and unit water amount was 160 kg / m ³ (water / cement ratio = 50%).

Cement dispersants have a target slump value of 18 in each case.
It was added to the cement in an amount of 0.60% or less in terms of solid content so that the content would be cm. The air amount was adjusted by using an AE adjusting agent (AE-300 manufactured by Takemoto Yushi Co., Ltd.) so that the target air amount was 4 to 6% in each example.

・ Method All materials (kneading amount 35l) were added to the 60l tilting mixer as shown in Table 3 for the cement dispersant under the above mixing conditions, and kneading was performed for 28r.pm x 3 minutes. , And a uniform state. Immediately after kneading, sampling was performed, and the slump and the amount of air were measured under a humidity condition of 20 ° C. × 80% RH. Continuously, knead for 2r.pm x 60-90 minutes,
Similarly, the slump and the amount of air were measured. For concrete sampled immediately after kneading, 20
The setting time at 0 ° C. and the compressive strength after 7 days and 28 days were measured.

In addition, JIS-A1101, JIS-A1128, JIS-A1108 and JI are used to measure slump, air volume, compressive strength and setting time, respectively.
It was performed in accordance with S-A6204 Appendix 1.

<Effects of the Invention> As is clear from the results of each table, in the present invention described above, a sulfonic acid group as a polar group was introduced only at the terminal of the main chain of the copolymer, and the structure was regulated. A water-soluble vinyl copolymer can be obtained, and when this is used as a cement dispersant, the cement composition can be imparted with excellent fluidity with little deterioration over time, and at the same time, a cement of desired strength with a small delay in setting can be obtained. There is an effect that a cured product can be obtained.

Claims (6)

[Claims] 1. A method for producing a cement dispersant comprising a water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain, which comprises the following first step, second step and third step. First step: A vinyl monomer represented by the following formula (1) and a vinyl monomer represented by the following formula (2) are represented by the vinyl monomer represented by the formula (1) / the formula (2). Vinyl monomer = 50
After copolymerizing in the presence of a radical initiator at a ratio of / 50 to 95/5 (molar ratio), radical terminating to obtain a binary copolymer Second step: Binary obtained in the first step Step of adding radical initiator to copolymer to obtain radical-activated binary copolymer Third step: The radical-activated binary copolymer obtained in the second step is represented by the following formula (3). Radical addition of one or more of the vinyl monomers shown to obtain a water-soluble vinyl copolymer having a sulfonic acid group at the end of the main chain Formula (1): Formula (2): Formula (3): [In the formulas (1) to (3), R ^{1 to} R ⁵ and R ⁷ are the same or different at the same time, H or CH ₃ . R ⁶ is an alkyl group having 1 to 3 carbon atoms. X and Y are alkali metal, alkaline earth metal, ammonium or organic amine. n is an integer of 5 to 25. ] 2. In the first step, the compound having at least two active hydrogen groups such as a hydroxyl group or a thiol group in the molecule is added to terminate the radical, and a sulfonic acid group is present at the terminal of the main chain. A method for producing a cement dispersant comprising a water-soluble vinyl copolymer. 3. In the first step, a compound having a thiol group and an α, β-unsaturated hydrocarbon group in the molecule is added to terminate the radical, and a sulfonic acid group is added to the end of the main chain. Of producing a cement dispersant comprising the water-soluble vinyl copolymer having 4. The sulfonic acid at the end of the main chain according to claim 1, 2 or 3, wherein in the second step, an azobis compound having a hydroxyl group in the molecule is added to obtain a radical-activated binary copolymer. A method for producing a cement dispersant comprising a water-soluble vinyl copolymer having a group. 5. A cement dispersant comprising a water-soluble vinyl copolymer having a sulfonic acid group at the end of the main chain, which is obtained by the method according to claim 1, 2, 3, or 4. 6. The cement dispersant according to claim 5, wherein the water-soluble vinyl copolymer having a sulfonic acid group at the terminal of the main chain has a number average molecular weight of 2000 to 15000.