CN109970931A - A shrinkage-reducing polycarboxylic acid-based superplasticizer, preparation method and application thereof - Google Patents

Abstract

The invention discloses a shrinkage-reducing polycarboxylic acid-based superplasticizer, a preparation method and an application thereof. The monomer A (5-50 parts), the monomer B (1-60 parts) and the monomer C (20- 100), monomer D (10～60 parts) and monomer E (1～20 parts), carry out free radical copolymerization in the presence of initiator and chain transfer agent, and finally add alkali to neutralize to make PH=7～ 8; Monomer A is acrylic acid, acrylate, acrylate or acrylate salt; Monomer B is methacrylic sulfonic acid or methacrylic sulfonate; Monomer C is polyether monoacrylate or alkoxy polyether Monoacrylate; monomer D is maleic anhydride polyether ester, maleic anhydride half ester, maleic anhydride polyether ester salt or maleic anhydride half ester salt; monomer E is polysiloxane and acrylic acid modified polyether copolymer. The invention has wide raw material sources, mature production technology, high water reduction rate, obvious enhancement effect, excellent air entrainment effect, good slump retention performance, shrinkage resistance and dry crack resistance.

Description

A shrinkage-reducing polycarboxylic acid-based superplasticizer, preparation method and application thereof

technical field

The invention belongs to the technical field of concrete structures and concrete engineering, relates to the technical field of concrete admixture synthesis, and belongs to the technical field of synthesis of polycarboxylic acid-based superplasticizer active organic monomers and polycarboxylic acid-based superplasticizers. The invention relates to a shrinkage-reducing polycarboxylic acid-based superplasticizer, a preparation method and an application thereof.

Background technique

In recent decades, concrete has developed into the most important contemporary structural engineering material. According to data released by the National Bureau of Statistics, the national cement output in 2016 was 2.4 billion tons, a year-on-year increase of 2.5%. The dosage is in the leading position in the world. With the rapid advancement of my country's urbanization, the establishment of the Asian Infrastructure Investment Bank is bound to promote the modernization of infrastructure projects. Due to the different environments and different infrastructure projects, most of them use concrete as the engineering structural material, which is bound to accelerate the progress of concrete technology.

As the basic material of construction engineering, concrete cracking has become a common problem in civil engineering. When the relative humidity (RH) < 65%, the crack width is less than 0.5mm, and when the RH> 65%, the crack width is less than 0.3mm. Although this will not bring great harm to the concrete structure, after the concrete structure is loaded, the crack will widen, harmless or less harmful cracks will become harmful cracks. Harmful cracks not only affect the safety of concrete structures, but also shorten the service life of concrete structures and bring huge economic losses.

The main measures to improve the durability of concrete and ensure its service life can be divided into two aspects: first, to ensure that the concrete is dense enough to reduce penetration and delay corrosion of steel bars; second: to reduce various cracks, especially early cracks. Once cracks appear in concrete, it will greatly increase the permeability of concrete, aggravate the corrosion of steel bars and the degree of freeze-thaw damage of concrete. How to take effective measures to reduce or even eliminate various shrinkage has always been a problem that engineers strive to explore. The most commonly used expansion agent is to use ettringite to compensate for shrinkage, but the dosage is large (10-15% of the cement dosage), which pollutes the environment during production; and the maintenance is difficult; in addition, in the concrete with high water-to-binder ratio. Adding an expansion agent can reduce the early expansion, but the concrete shrinkage is larger in the later stage, while the expansion effect of low water-binder ratio concrete is poor, and it can basically not compensate for the shrinkage. The new shrinkage reducer developed by BENTZ D P, HANSEN KK and ENGSTRAND J. can effectively reduce the shrinkage of concrete, but its dosage is high (2% to 3% of the mass of the cementitious material), the cost is high, and it has no water-reducing function. It is popularized in a large amount of medium and low strength concrete. In addition, because the water reducing rate of the polycarboxylate superplasticizer is much higher than that of the traditional naphthalene superplasticizer, the flow retention performance is better, and it has a certain shrinkage reduction function, it is suitable for formulating a large amount of fly ash. Or large-volume slag concrete, sprayed superplasticized concrete, fiber-reinforced fluid concrete and high-strength and high-fluidity concrete, the successive development and application of new special concrete make polycarboxylate superplasticizers very popular and attractive. Attention. At the same time, many new types of concrete have been widely used in high-rise buildings, long-span bridges, offshore drilling platforms, tunnels and other projects. The research and development of polycarboxylate superplasticizers has attracted more and more attention at home and abroad. The research on polycarboxylate superplasticizers has represented the main direction of concrete chemical admixture research.

CN200510037872.6 reported a multifunctional carboxylic acid type comb-shaped graft copolymer retarder superplasticizer, which has the functions of dispersion, slump retention, reinforcement and shrinkage reduction, but the effect is far from enough.

JP8268741 reported a multifunctional admixture with allyl alcohol ether-maleic anhydride copolymer as the main component, which has the functions of water reduction and shrinkage reduction. When mixed with 0.2%, the water reduction rate is 18%, and the 28d drying shrinkage ratio benchmark The cement is reduced by about 35%, which still has a certain gap compared with the effect of shrinkage reducer. In addition, such copolymers are expensive and have poor dispersing properties for cement.

US2005/0096413 reported a multifunctional admixture, the main component of which is a copolymer of α-allyl alcohol-ω-methyl polyether-maleic anhydride, using ordinary Portland cement (W/C=0.3), 24h Compared with the common polycarboxylate water reducer Chupol HP-11, the drying shrinkage is reduced by 15%-25%, and there is a certain difference compared with the effect of shrinkage reducer.

CN200610040089.X discloses a shrinkage-reducing and anti-cracking graft copolymer concrete superplasticizer. When the dosage is 0.2%, the water reduction rate reaches more than 25%, and the 28d drying shrinkage is reduced by 40- 50%, which is 30-50% lower than the benchmark concrete; but the oily system used in the synthesis is easy to cause pollution, and it also needs to raise the temperature to recover the organic solvent, resulting in energy waste, which is not in line with the modern development of environmental protection and energy saving.

To sum up, there are still obvious deficiencies in the current multifunctional admixtures, including high price of main raw materials, poor dispersion performance, insufficient water reduction rate, environmental pollution, and energy consumption.

The above search found that the above technical solutions do not affect the novelty of the present invention; and the mutual combination of the above patents cannot destroy the inventive step of the present invention.

SUMMARY OF THE INVENTION

Aiming at the defects and deficiencies in the prior art, the first object of the present invention is to provide a shrinkage-reducing polycarboxylic acid-based superplasticizer, which has high water-reducing rate, good enhancement effect, and air-entraining effect. Excellent, good slump retention performance, anti-shrinkage, anti-dry cracking and low price.

The second object of the present invention is to provide a method for preparing a shrinkage-reducing polycarboxylic acid-based superplasticizer, to provide a variety of organic monomers for synthesizing polycarboxylic acid-based high-performance water-reducing agents, and the raw materials used in the preparation. The source is abundant, the price is cheap, and the preparation process is simple.

The third object of the present invention is the application of the shrinkage-reducing polycarboxylic acid-based superplasticizer for preparing concrete, and the prepared concrete has high water-reducing rate, good reinforcement effect, excellent air-entraining effect, good slump retention performance, and high resistance to slump. Shrinkage resistance to dry cracking and low price.

Following the above-mentioned three purposes of the present invention, the technical scheme of the present invention is as follows:

In order to achieve the first object of the present invention, a shrinkage-reducing polycarboxylic acid-based superplasticizer, the chemical structural formula of the superplasticizer is:

In the formula, EO represents an ethylene oxide unit, PO represents a propylene oxide unit, R ₁ and R ₄ are alkoxy groups or hydroxyl groups, respectively, R ₂ , R ₃ and R ₅ are respectively hydrogen, monovalent metal or ammonium group, a and c are integers from 0 to 50 respectively, b and d are integers from 0 to 150 respectively, e is an integer from 0 to 30, x and y are integers from 0 to 50 respectively, m and n are integers from 0 to 50 respectively integer;

And the molecular weight of the shrinkage-reducing polycarboxylic acid-based superplasticizer is 5,000-50,000.

Optionally, combine monomer A (5-50 parts), monomer B (1-60 parts), monomer C (20-100 parts), monomer D (10-60 parts) and monomer E (1-60 parts) 20 parts), carry out free radical copolymerization in the presence of initiator and chain transfer agent, and finally add alkali to neutralize to make PH=7～8;

Monomer A is acrylic acid, acrylate, acrylate or acrylate salt; Monomer B is methacrylic sulfonic acid or methacrylic sulfonate; Monomer C is polyether monoacrylate or alkoxypolyether monoacrylic acid Ester; monomer D is maleic anhydride polyether ester, maleic anhydride half ester, maleic anhydride polyether ester salt or maleic anhydride half ester salt; monomer E is polysiloxane and acrylic acid modified polyether copolymer .

Optionally, the initiator is a water-soluble free radical initiator, and the water-soluble free radical initiator is selected from potassium persulfate K ₂ S ₂ O ₈ , ammonium persulfate (NH ₄ ) ₂ S ₂ One or more mixtures of O ₈ , sodium persulfate Na ₂ S ₂ O ₈ , hydrogen peroxide H ₂ O ₂ , ferrous salt, sulfite and thiosulfate;

The amount of the initiator accounts for 0.1% to 10.0% of the total mass of the reaction monomer;

The reaction temperature of the free radical copolymerization reaction is 70～130℃;

Described chain transfer agent includes but is not limited to one or more mixtures in isopropanol, mercaptoethanol, mercaptopropanol, mercaptoacetic acid and mercaptopropionic acid;

The amount of the chain transfer agent is 0.1% to 5% of the total mass of each monomer.

Optionally, the monomer A can be represented by the following general formula (1):

In formula (1), R ₅ represents hydrogen, a monovalent metal or an ammonium group.

Optionally, the monomer B can be represented by the following general formula (2):

In formula (2), R ₂ represents hydrogen, a monovalent metal or an ammonium group.

Optionally, the monomer C can be represented by the following general formula (3):

In formula (3), R ₁ is an alkyl group, an allyl group or a hydroxyl group of 1 to 4 carbon atoms, and x and y are an integer of 0 to 50 respectively;

The preparation method of the monomer C: the acrylic acid and the following (4) polyether are added in a solvent-free condition in a molar ratio of 1:1.0 to 4.5, and a polymerization inhibitor and a catalyst are added to undergo an esterification reaction;

In (4), x and y are integers from 0 to 50, respectively, and R ₁ is an alkyl group or a hydroxyl group with 1 to 5 carbon atoms;

The catalyst is selected from one or more mixtures of concentrated sulfuric acid, p-toluenesulfonic acid, phosphorous acid, solid superacid, boron trifluoride, aluminum trichloride, Lewis acid and amine substances. The dosage is 0.1% to 5.0% of the mass of polyether;

Described polymerization inhibitor is selected from one or more mixtures in hydroquinone, phenothiazine, hydroquinone-methyl ether and di-tert-butyl-p-cresol, and its consumption is acrylic acid. 0.01%～5.0% of the mass;

The temperature of the esterification reaction is 75～140℃, and the reaction time is 3～15h.

Optionally, the monomer D can be represented by the following general formula (5):

In formula (5), R ₃ represents hydrogen, a monovalent metal or an ammonium group; R ₄ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms; x and y are an integer of 0 to 10 respectively;

The preparation method of the monomer D: an esterification reaction occurs under the catalysis of a catalyst from maleic anhydride and the following (6) polyether in a molar ratio of 1:1.0 to 5.0;

In formula (6), x and y are each an integer of 0 to 10; R ₄ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms.

The catalyst is selected from one or more mixtures of concentrated sulfuric acid, p-toluenesulfonic acid, phosphoric acid and solid super acid, and the amount of the catalyst is 0.01% to 5.0% of the mass of the polyether;

The temperature of the esterification reaction is 80-150 DEG C, and the reaction time is 3-15h.

Optionally, the monomer E can be represented by the following general formula (7):

In formula (7), x, y, m and n are integers from 0 to 50 respectively;

The preparation method of the monomer E: from the low-hydrogen silicone oil PHMS as follows (9) Si-H-based polydimethylsiloxane and polyethylene glycol diacrylate are as follows (8) The molar ratio is 1:0.1～4.0 and prepared by addition reaction under the action of catalyst;

where x and y are integers from 0 to 50 respectively; m and n are integers from 0 to 30 respectively and m≥1;

The catalyst is selected from one or more mixtures of H ₂ PtCl ₆ , (Ph ₃ P) ₄ Pd, [RhCl(CO) ₂ ] ₂ and (Ph ₃ P) ₂ NiCl ₂ , and the amount of the catalyst is PHMS and 1～100ppm of the total mass of allyl polyether;

The temperature of the addition reaction is 70-140 DEG C, and the reaction time is 3-15h.

In order to achieve the second object of the present invention, the preparation method of the shrinkage-reducing polycarboxylic acid-based superplasticizer of the present invention, the synthesis process of the polycarboxylic acid-based superplasticizer includes:

Step 1, the monomer C and the monomer E are mixed to prepare the first monomer aqueous solution, the mass of the first monomer aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, and the mass of the monomer C in the first monomer aqueous solution The percentage is 10% to 40%, and the mass percentage of the monomer E in the first monomer aqueous solution is 0 to 10%;

In step 2, monomer A, monomer B and monomer D are mixed to prepare a second monomer aqueous solution, the second monomer aqueous solution accounts for 10% to 40% of the total mass of the reaction raw materials, monomer A, monomer B and monomer The mass percentages of D in the second monomer aqueous solution are respectively 20% to 50%, 5% to 20% and 0% to 10%; the initiator and the chain transfer agent are mixed to prepare the initiator mixed aqueous solution, and the initiator mixed aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, the mass percentages of the initiator and the chain transfer agent in the initiator mixed aqueous solution are respectively 0% to 10% and 0% to 10%; the second monomer aqueous solution and the initiator mixed aqueous solution Add dropwise to the first monomer aqueous solution respectively within 3-5h to carry out the reaction and keep the temperature for 1-2h to obtain the reactant;

In the third step, the reactant obtained in the second step is neutralized with an alkaline solution, and the mass concentration of the obtained solid is 20%-30%.

The shrinkage-reducing polycarboxylic acid-based superplasticizer of the present invention is used for the preparation of concrete, and the shrinkage-reducing polycarboxylic acid-based superplasticizer accounts for 0.1% to 0.3% of the total mass of the concrete.

The advantages of the present invention are:

The invention provides a shrinkage-reducing polycarboxylic acid-based superplasticizer, a preparation method and an application thereof. The production technology is mature and simple, and has high water-reducing rate, good reinforcement effect, excellent air-entraining effect, good slump retention performance, shrinkage resistance and dry crack resistance. Inexpensive. In addition, a variety of organic monomers for synthesizing the polycarboxylic acid-based high-performance water reducing agent are provided, the raw materials used in the preparation are rich in sources, the price is low, and the preparation process is simple.

Detailed ways

When the applicant investigated the literature, it was found that during the hydration process of concrete, water loss was the main cause of drying shrinkage. The applicant also found that the mechanism of reducing the interfacial tension is the main reason for the shrinkage-reducing and anti-cracking superplasticizer (the research results of Ran Qianping, Miao Changwen and others). The applicant also found that the chemical composition of concrete anti-shrinkage agents can be divided into three categories, which are small molecular fatty polyols, alkyl ether polyoxyethylene or polyoxypropylene monohydric alcohols, and polyoxyethylene or polyoxypropylene. Polycarboxylate graft copolymer. Therefore, grafting a polyether with a certain molecular weight into the main chain of a polycarboxylate superplasticizer can not only reduce shrinkage, but also have water retention and dispersibility.

In the formula, EO represents ethylene oxide unit, PO represents propylene oxide unit, R ₁ , R ₄ represent alkoxy group or hydroxyl group, R ₂ , R ₃ , R ₅ represent hydrogen or monovalent metal or ammonium group. Monovalent metals are Na ⁺ , K ⁺ etc., where a, b, c, d and e represent the number of different units in the main chain and are integers, where a and c are integers from 0 to 50 respectively, b and d They are integers from 0 to 150 respectively, e is an integer from 0 to 30; x and y represent the number of ethylene oxide and propylene oxide in the side chain and are integers, and x and y are integers from 0 to 50 respectively; m and n It represents the number of siloxane chain units in the side chain and is an integer, and m and n are integers from 0 to 50 respectively;

The present invention consists of monomer A: 5-50 parts of acrylic acid or acrylate or its salt, monomer B: 1-60 parts of methacrylic sulfonic acid and its salt, monomer C: polyether monoacrylate or alkoxy polyether 20-100 parts of monoacrylate, monomer D: maleic anhydride polyether ester or maleic anhydride half-ester or its salt 10-60 parts, monomer E: polysiloxane and acrylic modified polyether copolymer 1- 20 parts are prepared by free radical polymerization and neutralization with alkali to convert it into a salt form.

Among the above-mentioned monomers A, B, C, D and E, monomers A and B are known substances, wherein:

Monomer A can be represented by the following general formula (1):

In the formula, R ₅ represents hydrogen, a monovalent metal (Na ⁺ , K ⁺ etc.) or an ammonium group and the like. Carboxylate is beneficial to improve water-reducing performance and slump retention performance, and at the same time, it also has a certain retarding effect. It mainly provides adsorption points and electric repulsion.

Monomer B can be represented by the following general formula (2):

In the formula, R ₂ represents hydrogen, a monovalent metal (Na ⁺ , K ⁺ etc.) or an ammonium group and the like. Sulfonate is beneficial to produce high-efficiency dispersion properties and improve water-reduction rate. It mainly provides adsorption points and electric repulsion.

Monomer C can be represented by the following general formula (3):

In the formula, R ₁ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms, and x and y are respectively integers of 0 to 50;

The preparation method of monomer C: the esterification reaction occurs directly from acrylic acid and the following (4) polyether in a molar ratio of 1:1.0-4.5 under solvent-free conditions and adding a polymerization inhibitor and a catalyst;

In formula (4), x and y are integers from 0 to 50 respectively, R ₁ is an alkyl group or a hydroxyl group of 1 to 5 carbon atoms; EO represents an ethylene oxide unit, and PO represents a propylene oxide unit, which can be Linear or branched polymers, homopolymers, block copolymers, etc. These polyether group grafts and copolymers provide certain dispersing ability and water retention performance, and at the same time provide certain steric hindrance ability.

The catalyst mentioned above can be concentrated sulfuric acid, p-toluenesulfonic acid, phosphorous acid and solid super acid, etc., and Lewis acids such as boron trifluoride, aluminum trichloride and ferric sulfate, and amines such as ethylenediamine and triethylamine can also be used. They can be used alone or in combination, and the amount of the catalyst is 0.1% to 5.0% of the mass of the polyether;

The aforementioned polymerization inhibitor is selected from hydroquinone, phenothiazine, hydroquinone-methyl ether, di-tert-butyl-p-cresol, etc., and the amount thereof is 0.01% to 4.0% of the mass of acrylic acid; The main function is to prevent the self-polymerization of acrylic acid or the premature polymerization of acrylic acid and the resulting unsaturated ester;

The temperature of the esterification reaction is 80-85°C, and the reaction time can reach the required esterification rate in 5-7h, and a brown-red transparent liquid, namely monomer C, is obtained. There is no need for separation and removal, and it can directly participate in the next step of polymerization.

Monomer D can be represented by the following general formula (5):

In formula (5), R ₃ represents hydrogen, monovalent metal (Na ⁺ , K ⁺ etc.) or ammonium group; R ₄ is an alkyl group or allyl group or hydroxyl group of 1 to 4 carbon atoms; x and y are respectively 0 An integer of ~10.

The preparation method of monomer D: it is produced by the direct esterification reaction of maleic anhydride and the following (6) polyether in a molar ratio of 1:1.0-5.0 in the absence of a solvent and the presence of a catalyst. It is grafted into the polymer superplasticizer, which can not only reduce the shrinkage of concrete, but also have a certain steric hindrance and improve the dispersion performance at the same time.

In formula (6), x and y are each an integer of 0 to 10; R ₄ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms.

The aforementioned catalyst is selected from concentrated sulfuric acid, p-toluenesulfonic acid, phosphoric acid and solid super acid, etc., which can be used alone or in combination, and the amount of the catalyst is 0.1% to 5.0% of the mass of the polyether;

The temperature of the esterification reaction is 130-140°C. If the temperature is too high, the side reactions will increase, which will affect the formation of half-esters, and finally affect the performance of the product; The brown transparent solution is monomer D. After the esterification reaction is completed, it is sealed and stored, and the excess maleic anhydride does not need to be separated and removed, and can directly participate in the next step of polymerization.

Monomer E can be represented by the following general formula (7):

In formula (7), x, y, m and n are integers from 0 to 50 respectively;

Preparation method of monomer E: from low hydrogen-containing silicone oil PHMS as follows (9) (Si-H group polydimethylsiloxane) and polyethylene glycol diacrylate as follows (8) molar ratio is 1:0.1～4.0 and prepared by addition reaction under the action of catalyst;

In formulas (8) and (9), x and y are respectively integers from 0 to 50; m and n are integers from 0 to 30 respectively, and m≥1;

The aforementioned catalysts are selected from H ₂ PtCl ₆ ·6H ₂ O, (Ph ₃ P) ₄ Pd, [RhCl(CO) ₂ ] ₂ , (Ph ₃ P) ₂ NiCl ₂ and the like, which can be used alone or in combination. The dosage is 1～100ppm of the total mass of PHMS and allyl polyether;

The temperature of the addition reaction is 70-100 DEG C, and the reaction time is 3-8h, the desired conversion rate can be achieved, and a yellow or light yellow liquid, namely the monomer E, is obtained, which is sealed and stored.

The mass ratio of monomer A, monomer B, monomer C, monomer D, and monomer E is (5-50):(1-60):(20-100):(10-60):(1 ~20) Under the action of initiator chain transfer agent, carry out radical polymerization at 70-90 ° C, and add alkali to neutralize, and adjust the pH to 7-8 (high or low pH will affect its storage stability) That is, a reddish-brown polycarboxylic acid-based superplasticizer product is obtained, and the solid content is 20%-30%.

The initiator is a water-soluble free radical initiator and a mixture thereof, including potassium persulfate K ₂ S ₂ O ₈ , ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ , sodium persulfate Na ₂ S ₂ O ₈ , persulfate Hydrogen oxide H ₂ O ₂ and ferrous salts, sulfites, thiosulfates, etc. The amount thereof accounts for 0.1% to 10.0% of the total mass of the reaction monomers.

The reaction synthesis device of the polycarboxylic acid-based superplasticizer includes a heater, a magnetic stirrer, a thermometer, a peristaltic pump and a 500ml three-necked flask.

The molecular weight of the polycarboxylic acid superplasticizer copolymer is controlled by an alkyd chain transfer agent, which includes but is not limited to isopropanol, mercaptoethanol, mercaptopropanol, mercaptoacetic acid and mercaptopropionic acid, etc. The dosage is 0.1% to 5% of the total mass of each monomer.

The synthesis process of polycarboxylate superplasticizer is generally carried out in three steps:

Step 1, the monomer C and the monomer E are mixed to prepare the first monomer aqueous solution, the mass of the first monomer aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, and the mass of the monomer C in the first monomer aqueous solution The percentage is 10% to 40%, and the mass percentage of the monomer E in the first monomer aqueous solution is 0 to 10%;

In step 2, monomer A, monomer B and monomer D are mixed to prepare a second monomer aqueous solution, the second monomer aqueous solution accounts for 10% to 40% of the total mass of the reaction raw materials, monomer A, monomer B and monomer The mass percentages of D in the second monomer aqueous solution are respectively 20% to 50%, 5% to 20% and 0% to 10%; the initiator and the chain transfer agent are mixed to prepare the initiator mixed aqueous solution, and the initiator mixed aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, the mass percentages of the initiator and the chain transfer agent in the initiator mixed aqueous solution are respectively 0% to 10% and 0% to 10%; the second monomer aqueous solution and the initiator mixed aqueous solution Add dropwise to the first monomer aqueous solution respectively within 3-5h to carry out the reaction and keep the temperature for 1-2h to obtain the reactant;

In the third step, the reactant obtained in the second step is neutralized with an alkaline solution, and the mass concentration of the obtained solid is 20%-30%.

Example 1: Preparation process of superplasticizer

Monomer C preparation process:

In a 500ml glass reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, under solvent-free conditions, add an appropriate amount of polyether (the following formula, where x=23, y=0, R ₁ is hydroxyl), the temperature was raised to 50 °C, and after the polyether was completely melted, acrylic acid (the molar ratio of acrylic acid to polyether was 3:1), a polymerization inhibitor (hydroquinone, and hydroquinone accounted for acrylic acid) was added. 2% of the total mass) and a catalyst (concentrated sulfuric acid, and the concentrated sulfuric acid accounts for 1.0% of the total mass of the polyether), gradually warming up to 80-85 ° C and continuously reacting for 5h to obtain the monomer C crude product, which can be directly used. In the synthesis of shrinkage-reducing polycarboxylate superplasticizers;

Monomer D preparation process:

Without adding any catalyst, add an appropriate amount of maleic anhydride into a 500ml glass reactor equipped with a thermometer, agitator, nitrogen introduction tube and reflux condenser, and raise the temperature to 55°C until the maleic anhydride is completely melted. Then, add diethylene glycol monobutyl ether (the following formula, wherein x=2, y=0, R ₁ is butyl group, -C ₄ H ₉ ) (wherein the molar ratio of maleic anhydride and diethylene glycol monobutyl ether is 3:1), gradually heat up to 130°C, and keep a constant temperature, and after esterification for 4.5 hours, the shrinkage-reducing active monomer diethylene glycol monobutyl ether maleic anhydride monoester, namely monomer D, is obtained.

Monomer E preparation process:

In a 500ml glass reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, an appropriate amount of hydrogen-containing silicone oil PHMS (the following Si-H-based polydimethylsiloxane (where m=1, n= 10～20)) and polyethylene glycol diacrylate (the following formula (where x=20～30, y=0)), according to the molar ratio of hydrogen-containing silicone oil and polyethylene glycol diacrylate is 1:1, in Catalyst H ₂ PtCl ₆ (the amount of catalyst used is 20 ppm of the total mass of PHMS and allyl polyether;), and the temperature is gradually increased to 80-85°C for continuous reaction for 7 hours to obtain a yellow or pale yellow liquid, namely monomer E.

Superplasticizer preparation process:

In a 500ml glass reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 90g of water was added, the reactor was purged with nitrogen while stirring, and the temperature was raised to 75°C, and 25g of monomer C ( Wherein, x=23, y=0, R ₁ is hydroxyl) and 3g monomer E (wherein, x=20～30, y=0, m=1, n=10～20) were added into the three-necked flask, and stirred into a Uniform monomer aqueous solution; then 40g monomer A (wherein, R ₅ is hydrogen), 12g monomer B (wherein, R ₂ is sodium), 5g monomer D (wherein, R ₃ is hydrogen, x=2, y=0, R ₄ is butyl) and 60g of water are mixed to prepare a uniform active monomer aqueous solution; then, 4.5g of initiator ammonium persulfate and 2.0g of mercaptopropionic acid chain transfer agent are added to 90g of water and prepared into a uniform initiator mixed solution; finally, the initiator mixed solution and the active monomer aqueous solution were added dropwise to the three-necked flask reactor through a peristaltic pump at a certain speed, the dropwise addition time was 3h, after the dropwise addition was completed, the temperature was kept for 2h, cooled to room temperature, and the use concentration It is neutralized with 30% NaOH solution to a pH value of about 7.5 to obtain a brown-red transparent solution with a solid content of 25.5% and a molecular weight range of 5000-20000.

Example 2: Concrete mixed with superplasticizer

The superplasticizer used in this example is the superplasticizer prepared in Example 1. Calculate the mass according to the solids in the superplasticizer:

By mass percentage, cement 15.119%, sand 35.067%, 5-10mm pebble 17.135%, 10-20mm pebble 25.702%, water 6.929%, superplasticizer 0.048%; The method is to mix and mix (the slump is controlled at 21±1cm), put it on the vibrating table and vibrate for 30s and then form it. Before the initial setting of the concrete, the surface is plastered. After 24h, the formwork is removed and sent to the curing room for standard curing.

According to GB8076-2008 "Concrete Admixtures" specification, the plasticizer meets the requirements of standard high-performance water reducer, and its performance indicators meet the requirements of the specification. When the content of superplasticizer is 0.32% of the cement quality, the product index reaches: water reduction rate 25%, slump 21.5cm, 1h slump loss 3cm, 2h slump loss 7cm, gas content 4.5%, The bleeding rate ratio was 10%.

When the dosage is 0.32%, the effect of superplasticizer on concrete shrinkage is shown in Table 1. The shrinkage rate of concrete mixed with superplasticizer is 0.044043%, and the reference concrete shrinkage rate is 0.051915%. The 28d shrinkage ratio is 85%, which meets the requirement of 28d shrinkage ratio ≤ 110%; when the dosage is 0.32%, the effect of superplasticizer on concrete strength is shown in Table 2. The 28d compressive strength of the agent concrete is 43.35MPa, the 28d compressive strength of the benchmark concrete is 28.02MPa, and the 28d compressive strength ratio is 155%, which meets the requirement of 28d compressive strength ratio ≥ 140%.

Table 1

Table 2

Example 3: Concrete mixed with superplasticizer

The superplasticizer used in this example is the superplasticizer prepared in Example 1. Calculate the mass according to the solids in the superplasticizer:

By mass percentage, cement 15.121%, sand 35.072%, 5-10mm pebble 17.137%, 10-20mm pebble 25.706%, water 6.930%, superplasticizer 0.033%; according to SL352-2006 "Hydraulic Concrete Test Regulations" The method is to mix and mix (the slump is controlled at 21±1cm), put it on the vibrating table and vibrate for 30s and then form it. Before the initial setting of the concrete, the surface is plastered. After 24h, the formwork is removed and sent to the curing room for standard curing.

According to GB8076-2008 "Concrete Admixtures" specification, its performance indicators meet the requirements of the specification. When the content of superplasticizer is 0.22% of the cement quality, the product indicators reach: water reduction rate of 25%, slump of 21cm, slump loss of 6cm in 1h, slump loss of 8cm in 2h, gas content of 4%, and slump loss of 6cm. The water ratio is 25%.

When the dosage is 0.22%, the effect of superplasticizer on concrete shrinkage is shown in Table 3. The shrinkage rate of concrete mixed with superplasticizer is 0.049362%, and the reference concrete shrinkage rate is 0.051915%. The 28d shrinkage ratio is 95%, which meets the requirement of 28d shrinkage ratio ≤ 110%; when the dosage is 0.22%, the effect of superplasticizer on concrete strength is shown in Table 4. The 28d compressive strength of the agent concrete is 39.39MPa, the 28d compressive strength of the benchmark concrete is 28.02MPa, and the 28d compressive strength ratio is 141%, which meets the requirement that the 28d compressive strength ratio is greater than or equal to 140%.

table 3

Table 4

The preferred embodiments of the present disclosure are described above in detail, but the present disclosure is not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure. These simple modifications All belong to the protection scope of the present disclosure.

In addition, it should be noted that the various specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner unless they are inconsistent. In order to avoid unnecessary repetition, the present disclosure provides The combination method will not be specified otherwise.

In addition, the various embodiments of the present disclosure can also be arbitrarily combined, as long as they do not violate the spirit of the present disclosure, they should also be regarded as the contents disclosed in the present disclosure.

Claims (10)

1. a shrinkage-reducing type polycarboxylic acid superplasticizer, is characterized in that, the chemical structural formula of described superplasticizer is: In the formula, EO represents an ethylene oxide unit, PO represents a propylene oxide unit, R ₁ and R ₄ are alkoxy groups or hydroxyl groups, respectively, R ₂ , R ₃ and R ₅ are respectively hydrogen, monovalent metal or ammonium group, a and c are integers from 0 to 50 respectively, b and d are integers from 0 to 150 respectively, e is an integer from 0 to 30, x and y are integers from 0 to 50 respectively, m and n are integers from 0 to 50 respectively integer; And the molecular weight of the shrinkage-reducing polycarboxylic acid-based superplasticizer is 5,000-50,000. 2 . The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 1 , wherein the monomer A (5-50 parts), the monomer B (1-60 parts), the monomer C (20 parts) ～100), monomer D (10～60 parts) and monomer E (1～20 parts), carry out free radical copolymerization reaction in the presence of initiator and chain transfer agent, and finally add alkali to neutralize to make PH=7 ~8; Monomer A is acrylic acid, acrylate, acrylate or acrylate salt; Monomer B is methacrylic sulfonic acid or methacrylic sulfonate; Monomer C is polyether monoacrylate or alkoxypolyether monoacrylic acid Ester; monomer D is maleic anhydride polyether ester, maleic anhydride half ester, maleic anhydride polyether ester salt or maleic anhydride half ester salt; monomer E is polysiloxane and acrylic acid modified polyether copolymer . 3. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2, wherein the initiator is a water-soluble free radical initiator, and the water-soluble free radical initiator is selected from the group consisting of Potassium persulfate K ₂ S ₂ O ₈ , ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ , sodium persulfate Na ₂ S ₂ O ₈ , hydrogen peroxide H ₂ O ₂ , ferrous salts, sulfites and sulfur One or more mixtures of sulfites; The amount of the initiator accounts for 0.1% to 10.0% of the total mass of the reaction monomer; The reaction temperature of the free radical copolymerization reaction is 70～130℃; Described chain transfer agent includes but is not limited to one or more mixtures in isopropanol, mercaptoethanol, mercaptopropanol, mercaptoacetic acid and mercaptopropionic acid; The amount of the chain transfer agent is 0.1% to 5% of the total mass of each monomer. 4. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2 or 3, wherein the monomer A can be represented by the following general formula (1): In formula (1), R ₅ represents hydrogen, a monovalent metal or an ammonium group. 5. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2 or 3, wherein the monomer B can be represented by the following general formula (2): In formula (2), R ₂ represents hydrogen, a monovalent metal or an ammonium group. 6. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2 or 3, wherein the monomer C can be represented by the following general formula (3): In formula (3), R ₁ is an alkyl group, an allyl group or a hydroxyl group of 1 to 4 carbon atoms, and x and y are an integer of 0 to 50 respectively; The preparation method of the monomer C: the acrylic acid and the following (4) polyether are added in a solvent-free condition in a molar ratio of 1:1.0 to 4.5, and a polymerization inhibitor and a catalyst are added to undergo an esterification reaction; In (4), x and y are integers from 0 to 50, respectively, and R ₁ is an alkyl group or a hydroxyl group with 1 to 5 carbon atoms; The catalyst is selected from one or more mixtures of concentrated sulfuric acid, p-toluenesulfonic acid, phosphorous acid, solid superacid, boron trifluoride, aluminum trichloride, Lewis acid and amine substances. The dosage is 0.1% to 5.0% of the mass of polyether; Described polymerization inhibitor is selected from one or more mixtures in hydroquinone, phenothiazine, hydroquinone-methyl ether and di-tert-butyl-p-cresol, and its consumption is acrylic acid. 0.01%～5.0% of the mass; The temperature of the esterification reaction is 75～140℃, and the reaction time is 3～15h. 7. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2 or 3, wherein the monomer D can be represented by the following general formula (5): In formula (5), R ₃ represents hydrogen, a monovalent metal or an ammonium group; R ₄ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms; x and y are integers of 0 to 10 respectively; The preparation method of the monomer D: an esterification reaction occurs under the catalysis of a catalyst from maleic anhydride and the following (6) polyether in a molar ratio of 1:1.0 to 5.0; In formula (6), x and y are each an integer of 0 to 10; R ₄ is an alkyl group or an allyl group or a hydroxyl group of 1 to 4 carbon atoms. The catalyst is selected from one or more mixtures of concentrated sulfuric acid, p-toluenesulfonic acid, phosphoric acid and solid super acid, and the amount of the catalyst is 0.01% to 5.0% of the mass of the polyether; The temperature of the esterification reaction is 80-150 DEG C, and the reaction time is 3-15h. 8. The shrinkage-reducing polycarboxylic acid-based superplasticizer according to claim 2 or 3, wherein the monomer E can be represented by the following general formula (7): In formula (7), x, y, m and n are integers from 0 to 50 respectively; The preparation method of the monomer E: from the low-hydrogen silicone oil PHMS as follows (9) Si-H-based polydimethylsiloxane and polyethylene glycol diacrylate are as follows (8) The molar ratio is 1:0.1～4.0 and prepared by addition reaction under the action of catalyst; where x and y are integers from 0 to 50 respectively; m and n are integers from 0 to 30 respectively and m≥1; The catalyst is selected from one or more mixtures of H ₂ PtCl ₆ , (Ph ₃ P) ₄ Pd, [RhCl(CO) ₂ ] ₂ and (Ph ₃ P) ₂ NiCl ₂ , and the amount of the catalyst is PHMS and 1～100ppm of the total mass of allyl polyether; The temperature of the addition reaction is 70-140 DEG C, and the reaction time is 3-15h. 9. the preparation method of the described shrinkage-reducing type polycarboxylic acid-based superplasticizer of any one of claims 1-8, is characterized in that, the synthesis process flow of polycarboxylic acid-based superplasticizer comprises: Step 1, the monomer C and the monomer E are mixed to prepare the first monomer aqueous solution, the mass of the first monomer aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, and the mass of the monomer C in the first monomer aqueous solution The percentage is 10% to 40%, and the mass percentage of the monomer E in the first monomer aqueous solution is 0 to 10%; In step 2, monomer A, monomer B and monomer D are mixed to prepare a second monomer aqueous solution, the second monomer aqueous solution accounts for 10% to 40% of the total mass of the reaction raw materials, monomer A, monomer B and monomer The mass percentages of D in the second monomer aqueous solution are respectively 20% to 50%, 5% to 20% and 0% to 10%; the initiator and the chain transfer agent are mixed to prepare the initiator mixed aqueous solution, and the initiator mixed aqueous solution accounts for 20% to 40% of the total mass of the reaction raw materials, the mass percentages of the initiator and the chain transfer agent in the initiator mixed aqueous solution are respectively 0% to 10% and 0% to 10%; the second monomer aqueous solution and the initiator mixed aqueous solution Add dropwise to the first monomer aqueous solution respectively within 3-5h to carry out the reaction and keep the temperature for 1-2h to obtain the reactant; In the third step, the reactant obtained in the second step is neutralized with an alkaline solution, and the mass concentration of the obtained solid is 20%-30%. 10. The application of the shrinkage-reducing polycarboxylic acid-based superplasticizer according to any one of claims 1-8 for preparing concrete, and the shrinkage-reducing polycarboxylic acid-based superplasticizer accounts for 0.1% to 0.3% of the total mass of the concrete %.