CN102173638A - Polycarboxylate water reducer and preparation method thereof - Google Patents

Abstract

The invention discloses a polycarboxylate water-reducer and a preparation method thereof. The water-reducer has a molecular weight of 20,000 to 60,000, and methoxypolyethylene glycol is prepared by reacting itaconic acid with methoxypolyethylene glycol. Itaconic acid monoester, and then copolymerized with unsaturated carboxylic acid or its derivatives to form a polycarboxylate superplasticizer containing carboxyl, ester and polyoxyethylene side chains. The present invention introduces one more carboxyl group on the polymerized macromonomer, which increases the carboxyl group density, thereby increasing the water reducing rate, and the present invention also has the advantage of maintaining good slump.

Description

A kind of polycarboxylate superplasticizer and preparation method thereof

technical field

The invention relates to a concrete admixture, in particular to a polyether itaconate monoester polycarboxylate water reducer and a preparation method thereof.

Background technique

Concrete is one of the most important civil engineering materials today. Concrete admixtures are the fifth component of concrete except cement, water, sand, and stones, and occupy a very important position in high-performance concrete.

The development of water reducing agent has a long history. In 1935, E.W. Scrapture of the United States first developed lignosulfonate water reducer with lignosulfonate as the main component, which is widely used in C20-C40 concrete. The water reducing rate of this series of water reducers is low, but It is still used because of its low price. In the 1960s, Japan successfully developed a high-efficiency water reducer for naphthalenesulfonic acid formaldehyde condensate, and Germany successfully developed a high-efficiency water reducer for sulfonated melamine formaldehyde condensate. These two types of water reducers are widely used in C30-C60 concrete. It has the advantages of low production cost and good water reduction effect. From the 1960s to the early 1980s, it was the development stage of high-efficiency water reducers. At this stage, the water reducers were mainly represented by naphthalene series. The water rate is higher, but the concrete slump loss is faster, and it needs to be compounded to meet different construction requirements, but the compounded water reducing agent has an impact on the development of the early strength of concrete. In addition, this product uses a large amount of formaldehyde and concentrated sulfuric acid to synthesize, and the production causes serious pollution to the environment.

In 1995, Japan successfully developed a polycarboxylic acid-based high-performance water reducer by copolymerizing olefins and unsaturated carboxylic acids. The polycarboxylate water reducer is characterized in that the link between the main chain and the branch is an ester bond. The polycarboxylate water reducer is suitable for preparing high fluidity and self-compacting concrete due to its high water reducing rate of over 30%, low dosage, good slump retention and moderate air-entrainment. Moreover, no formaldehyde is used in the synthesis, which is harmful to the environment. Pollution is small, which has been widely promoted. Japan is the country with the most research and application of polycarboxylate water reducers and the most successful country. After 1995, the amount of polycarboxylate water reducers used in Japanese commercial concrete exceeded that of naphthalene water reducers. In Japan, the earliest carboxylic acid-based water reducer is a copolymer of olefin and unsaturated carboxylic acid, and then there are breakthroughs in performance improvement and copolymerization technology, and the performance is becoming more and more perfect.

In recent years, the research and production of concrete admixtures in the world tend to develop in the direction of high performance and no pollution. Copolymerized polycarboxylate admixtures have high water-reducing rate, good slump-retaining performance, and large strength increase in the later stage. They are suitable for the preparation of high-strength, ultra-high-strength concrete, high-fluidity and superplasticized concrete, self-compacting concrete, etc., and thus are favored at home and abroad. extensive attention.

In the patent CN101357833A, a kind of slump retention type polycarboxylic acid superplasticizer using itaconic acid as a small monomer is disclosed, which is copolymerized by polyether macromonomer, unsaturated monobasic acid and itaconic acid, Obtain polycarboxylic acid slump retaining agent. However, the polycarboxylate superplasticizer prepared by this method has a low water-reducing rate and needs to be improved.

Contents of the invention

The object of the present invention is to provide a polycarboxylate water reducer and its preparation method, the water reducer has high water reducing rate and good slump retention.

A kind of polycarboxylate water-reducer provided by the present invention, first use itaconic acid and polyether macromonomer methoxypolyethylene glycol ester to synthesize macromonomer, then and water-soluble unsaturated acid and/or The derivative is copolymerized under the condition of aqueous solution, its weight-average molecular weight is 20000-60000, and its structural formula is:

In the formula: R ₁ represents a hydrogen atom or a carboxyl group

R ₂ represents a hydrogen atom, a methyl group or a carboxyl group

M represents a hydroxyl group, an amino group or an ether group with 1 to 5 C atoms

a=5-60, b=5-60, n=10-120.

A kind of preparation method of polycarboxylate water reducer provided by the invention comprises the following steps:

(1) Esterification reaction: take p-toluenesulfonic acid as a catalyst, and toluene as a water-carrying agent, through methoxypolyethylene glycol and itaconic acid at toluene reflux temperature for 6 hours, remove the water-carrying agent by distillation under reduced pressure Impurities such as agent, get the mixture of methoxypolyethylene glycol itaconic acid monoester and remaining itaconic acid; Raw material ratio: methoxypolyethylene glycol: itaconic acid=1: 1.2～1.5 (molar ratio) The consumption of p-toluenesulfonic acid is 4%～6% of the total mass of methoxypolyethylene glycol and itaconic acid, and the consumption of toluene is 50%～80% of the total mass of methoxypolyethylene glycol and itaconic acid; The formula is as follows:

In the formula: n=10-120, preferably 10-50.

(2) Copolymerization reaction: with persulfate as initiator, the mixture of methoxy polyethylene glycol itaconic acid monoester and remaining itaconic acid obtained in step (1) and water-soluble unsaturated acid and / or its derivatives are copolymerized at 60-85°C for 3-5 hours to obtain a polycarboxylate water reducer; raw material ratio: a mixture of methoxy polyethylene glycol itaconic acid monoester and the remaining itaconic acid: water soluble Reactive unsaturated acid and/or derivative=1～1.5: 4; Initiator consumption is 6%～10% of the total mass of polymerized monomers; Reaction formula is as follows:

In the formula: R ₁ represents a hydrogen atom or a carboxyl group

R ₂ represents a hydrogen atom, a methyl group or a carboxyl group

M represents a hydroxyl group, an amino group or an ether group with 1 to 5 C atoms

a=5-60, b=5-60; n=10-120, n is preferably 10-50.

The initiator of the radical copolymerization reaction is ammonium persulfate, potassium persulfate or sodium persulfate and the like.

If the water-soluble unsaturated acid has a high polymerization activity, a chain transfer agent, such as thioglycolic acid, needs to be added to the polymerization reaction.

After repeated experiments, it is known that the water reducing rate and slump retention capacity of polycarboxylate superplasticizers are closely related to the adsorption of superplasticizers in cement systems, and the adsorption of polymers to cement can be changed by changing the structure of polymers. Performance, polycarboxylate superplasticizer with high carboxyl density has more initial adsorption and can provide high concrete water reducing rate. The present invention introduces one more carboxyl group on the polymerized macromonomer, which increases the carboxyl group density, thereby increasing the water reducing rate. The invention also has the advantage of good slump retention.

Detailed ways

In order to simplify the expression, MPEG is used to represent methoxypolyethylene glycol below;

Example 1:

In a 250mL three-neck flask equipped with a thermometer, a stirrer, and a water separator, add 60g of MPEG (molecular weight: 1000), 9.4g of itaconic acid, 2.7g of catalyst p-toluenesulfonic acid, and 34.7g of toluene with water agent, heat and stir Uniformly dissolve the reactants completely, raise the temperature to continuously reflux the toluene, and keep the temperature at 110-120°C. After 6 hours of esterification reaction, carry out vacuum distillation to remove the solvent to obtain methoxypolyethylene glycol itaconate monoester and the remaining mixture of itaconic acid.

In a 250ml flask equipped with a thermometer and a stirrer, add 40g of the obtained methoxypolyethylene glycol itaconate monoester and the remaining itaconic acid mixture, raise the temperature to 50°C, and after the mixture dissolves, add 51.9g Distilled water, 11.9g maleic anhydride, stir evenly, add 2.0g ammonium persulfate, control the temperature at 70-75°C, react for 4 hours, lower the temperature to below 40°C, add NaOH aqueous solution to neutralize to get a pH value of about 7, solid It is a yellow-brown transparent liquid with a content of 40%.

Example 2:

In a 250mL three-neck flask equipped with a thermometer, a stirrer, and a water separator, add 60g of MPEG (molecular weight: 1200), 7.8g of itaconic acid, 3.4g of catalyst p-toluenesulfonic acid, and 33.9g of toluene with water agent, heat and stir Uniformly dissolve the reactants completely, raise the temperature to continuously reflux the toluene, and keep the temperature at 110-120°C. After 6 hours of esterification reaction, carry out vacuum distillation to remove the solvent to obtain methoxypolyethylene glycol itaconate monoester and the remaining mixture of itaconic acid.

In a 250mL four-necked flask equipped with a thermometer and a stirrer, add 40g of the obtained methoxypolyethylene glycol itaconate monoester and the remaining itaconic acid mixture, raise the temperature to 50°C, and after the mixture dissolves, add 20g of distilled water, 0.01mL of chain transfer agent mercaptoacetic acid, stir evenly, dropwise add 8.8g of acrylic acid, and dropwise add 34g of potassium persulfate solution with a mass percentage of 6%, control the dropping speed, add dropwise of acrylic acid solution for 3h, initiator persulfate Add the ammonium solution dropwise for 3.5 hours, keep the temperature at 60-65°C, keep the temperature for 0.5 hours after the dropwise addition, and add NaOH aqueous solution to neutralize after cooling to obtain a yellow-brown transparent liquid with a pH of about 7 and a solid content of 40%.

Example 3:

The preparation of methoxy polyethylene glycol itaconate monoester is the same as in Example 1

In a 250ml flask equipped with a thermometer and a stirrer, add 40g of the obtained methoxypolyethylene glycol itaconate monoester and the remaining itaconic acid mixture, raise the temperature to 50°C, and after the mixture dissolves, add 51.9g Distilled water, maleic anhydride 6.3g, acrylamide 1.7g, stir evenly, add 2.8g sodium persulfate, control the temperature at 70-75°C, react for 4 hours, lower the temperature to below 40°C, add NaOH aqueous solution to neutralize the pH value It is a yellow-brown transparent liquid with a solid content of about 7 and a solid content of 40%.

Example 4:

The preparation of itaconate monoester was the same as in Example 2.

In a 250mL four-necked flask equipped with a thermometer and a stirrer, add 40g of the obtained methoxypolyethylene glycol itaconate monoester and the remaining itaconic acid mixture, raise the temperature to 50°C, and after the mixture dissolves, add Distilled water 20g, hydroxyethyl methacrylate 3.3g, chain transfer agent mercaptoacetic acid 0.01mL, stir evenly, while adding acrylic acid 5.5g dropwise, while adding dropwise 32g of ammonium persulfate solution with a mass percentage of 10%, control the dropping speed, acrylic acid The solution was added dropwise for 3 hours, the initiator ammonium persulfate solution was added dropwise for 3.5 hours, and the temperature was kept at 60-65°C. After the dropwise addition, the temperature was kept for 0.5 hours. After cooling, NaOH aqueous solution was added for neutralization to obtain a pH value of about 7. The solid content was 40% yellowish brown transparent liquid.

Comparative example:

In the 250mL there-necked flask equipped with thermometer, stirrer, water separator, add MPEG (molecular weight is 1000) 60g, catalyst p-toluenesulfonic acid 3.1g, water-carrying agent toluene 38.6g, heat and stir to make reactant dissolve completely, Raise the temperature to continuously reflux the toluene, keep the temperature at 110-120°C, and at the same time add 17.3 g of acrylic acid dropwise, and the dropwise addition is completed within 2 hours. After 6 hours of esterification, the solvent was distilled off under reduced pressure to obtain methoxypolyethylene glycol acrylate.

In a 250ml flask equipped with a thermometer and a stirrer, add 40g of the obtained methoxypolyethylene glycol acrylate and raise the temperature to 50°C. After the mixture is dissolved, add 20g of distilled water and 0.01mL of chain transfer agent mercaptoacetic acid in sequence, and stir Evenly, while adding 13.3g of acrylic acid dropwise, dropwise add 32g of ammonium persulfate solution with a mass percentage of 10%, control the dropping speed, add dropwise of acrylic acid solution for 3h, add dropwise of initiator ammonium persulfate solution for 3.5h, keep the temperature at 60～ 65°C, keep warm for 0.5h after the dropwise addition, and add NaOH aqueous solution to neutralize after cooling to obtain a yellow-brown transparent liquid with a pH of about 7 and a solid content of 40%.

The water reducer of the present invention is evaluated according to the GB8076-2008 standard, and the dosage is 0.2%. The test results are shown in Table 1 and Table 2:

Table 1 Fluidity test of cement slurry

Table 2 Concrete slump test

Example Initial slump/mm 30min slump/mm 60min slump/mm 1 220 195 160 2 195 170 150 3 225 215 220 4 210 205 210 comparative example 195 155 130

It can be seen from the data in Table 1 and Table 2 that the performance of the water reducer of the present invention is better.

Claims (4)

1. a polycarboxylate dehydragent is characterized in that, weight-average molecular weight is 20000～60000, and structural formula is:

In the formula: R ₁Show hydrogen atom or carboxyl; R ₂Show hydrogen atom, methyl group or carboxyl; M represents the ether of hydroxyl, amido or C atomicity 1～5; A=5～60, b=5～60, n=10～120.

2. the preparation method of a kind of polycarboxylate dehydragent as claimed in claim 1 is characterised in that to comprise the steps:

(1) esterification: with the tosic acid is catalyzer, toluene is the band aqua, by methoxy poly (ethylene glycol) and methylene-succinic acid esterification 6 hours under the refluxing toluene temperature, impurity such as band aqua are removed in underpressure distillation, the mixture of methoxy poly (ethylene glycol) methylene-succinic acid monoesters and residue methylene-succinic acid; Proportioning raw materials: methoxy poly (ethylene glycol): methylene-succinic acid=1: 1.2～1.5 (mol ratio); The tosic acid consumption is 4%～6% of methoxy poly (ethylene glycol) and a methylene-succinic acid total mass, and the consumption of toluene is 50%～80% of methoxy poly (ethylene glycol) and a methylene-succinic acid total mass;

(2) copolyreaction: with the persulphate is initiator, the mixture of the methoxy poly (ethylene glycol) methylene-succinic acid monoesters of gained in the step (1) and remaining methylene-succinic acid and water miscible unsaturated acid and/or its derivative at 60～85 ℃ of following copolymerization 3～5h, are obtained polycarboxylate dehydragent; Proportioning raw materials: methoxy poly (ethylene glycol) methylene-succinic acid monoesters and the mixture that remains methylene-succinic acid: water miscible unsaturated acid and/or derivative=1～1.5: 4; Initiator amount is 6%～10% of a polymerization single polymerization monomer total mass.

3. the preparation method of a kind of polycarboxylate dehydragent as claimed in claim 2 is characterised in that the persulphate in the described step (2) is ammonium persulphate, Potassium Persulphate or Sodium Persulfate.

4. the preparation method of a kind of polycarboxylate dehydragent as claimed in claim 2 is characterised in that to add the chain-transfer agent Thiovanic acid in the step (2).