CN101717220B - A kind of polycarboxylate water reducing agent and preparation method thereof - Google Patents

Abstract

The invention discloses a polycarboxylic acid water-reducing agent and a preparation method thereof. The polycarboxylic acid water-reducing agent has the molecular weight between 1,000 and 100,000, and has the structure composition shown in (7), wherein X represents polyether groups, and M is Na or K. The polycarboxylic acid water-reducing agent is prepared by the method comprising the following steps: subjecting polyether X-H and excessive unsaturated fatty acid to esterification so as to obtain esterified substances; subjecting the esterified substances and remaining unsaturated fatty acid to copolymerization so as to obtain carboxylic acid polymer; and neutralizing the obtained carboxylic acid polymer with alkali solution so as to obtain the polycarboxylic acid water-reducing agent. The polycarboxylic acid water-reducing agent has high plastic-retaining property, low fluidity loss of cement paste, high water-reducing rate, low production cost and other excellent performance.

Description

A kind of polycarboxylate water reducing agent and preparation method thereof

(1) Technical field

The invention relates to a concrete admixture, in particular to a polycarboxylate water reducer with high plasticity retention and a preparation method thereof.

(2) Background technology

With the development of concrete technology, higher requirements are put forward for the performance of water reducing agents. In the past, traditional water reducing agents have their own shortcomings and deficiencies, such as low water reducing rate, poor plasticity retention, and poor adaptability to cement. etc. Since the 1990s, polycarboxylic acid has developed into a new type of high-efficiency water reducer. It has high strength and excellent properties such as heat resistance, durability and weather resistance. At present, the methods for preparing polycarboxylate superplasticizers from unsaturated carboxylic acids mainly include acrylic acid method, methacrylic acid method, maleic anhydride method, etc.

In the patent CN1636922, a preparation method of polycarboxylate concrete water reducer is disclosed. Polyethylene glycol and acrylic acid are catalyzed by a catalyst to synthesize an esterified product, and then copolymerized with sodium methacrylate and acrylic acid to form a water reducer. Aqua. Although the acrylic acid in this method is cheap, the characteristics of the molecular structure of its monomer itself make the plastic retention performance of its product can not be improved all the time.

In the patent CN101353404, a preparation method of a polycarboxylate-based high-efficiency water reducer is disclosed. Polyether and methacrylic acid are esterified in the presence of a polymerization inhibitor and a catalyst to obtain an esterified product, and then the esterified The product is polymerized with mercaptopropionic acid and an initiator to obtain a polycarboxylate water reducer. Although the plasticity retention of the water reducing agent prepared by this method is improved compared with the acrylic method, the water reducing rate is low, and the production cost is relatively high.

Disclosed in the patent CN1948209B is a kind of method that prepares polycarboxylate water reducing agent with maleic anhydride, obtains polyethylene glycol maleic anhydride ester and remaining maleic anhydride through the esterification reaction of polyethylene glycol and maleic anhydride mixture, and then this mixture of acrylic acid and sodium methacrylate sulfonate is copolymerized to obtain a polycarboxylate water reducer. In this method, although maleic anhydride is easy to undergo esterification reaction with alcohols, the polymer with other monomers cannot achieve the effect of normal water reducer, so it can only be added in a small amount as a raw material to reduce costs. And maleic anhydride is difficult to participate in the polymerization reaction as a polymerization monomer.

(3) Contents of the invention

One of the technical problems to be solved by the present invention is to provide a new polycarboxylate superplasticizer, which has high plastic retention performance, better steric hindrance effect, and less loss of cement paste over time, which can overcome the existing technology. The water reducing agent can not control the plasticizing effect of cement well, and the water reducing rate is not high.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A polycarboxylate water reducer with a molecular weight of 1,000 to 100,000 and a structure as shown in (7):

In formula (7), R ⁴ is selected from C ₁ -C ₃ alkylene, R ⁵ is selected from hydrogen or C ₁ -C ₃ alkyl, M is Na or K; a, b, c, d are all integers, Wherein a is 1-80, b is 0-300, c is 0-80, d is 1-200; when c=0, b=0; wherein X represents a polyether group, and the polyether group in each structural unit The ether groups X are each independently selected from one of the groups shown in the following formula (8-1), formula (8-3), and formula (8-3):

In formula (8-1), formula (8-2) or formula (8-3), R ¹ is selected from C ₁ to C ₃ alkyl, R ² and R ³ are independently selected from C ₁ to C ₃ alkylene , m, n, p, and q are natural numbers, wherein m takes a value of 8 to 72, preferably 18 to 56; n takes a value of 5 to 35; p takes a value of 1 to 71, and q takes a value of 1 to 71, And p+q=8-72, preferably p+q=18-56.

Further, preferably, the molecular weight of the polyether group is 600-3000.

It should be noted that the formula (7) represents the composition of the structural units of the polycarboxylate superplasticizer, and does not represent the actual ordering of the structural units.

Another technical problem to be solved by the present invention is to provide a preparation method of the above-mentioned polycarboxylate water reducer, which has high esterification rate, simple synthesis process and easy control of reaction conditions under the premise of ensuring the water reducing performance of the polymer , and can also reduce the production cost of polycarboxylate superplasticizer.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A method for preparing said polycarboxylate water reducer, comprising the steps of:

Step A: In the presence of a polymerization inhibitor and a catalyst, polyether X-H and excess unsaturated fatty acid are subjected to an esterification reaction at 120-140°C for 3-7 hours to obtain an esterified product; the unsaturated fatty acid is of formula (2 ) shown in the unsaturated dibasic acid, or a mixed acid composed of the unsaturated dibasic acid shown in the formula (2) and the unsaturated monobasic acid shown in the formula (3); the polyether X-H is selected from the formula One or any combination of compounds shown in (1-1), formula (1-2), and formula (1-3);

In formula (1-1), formula (1-2) or formula (1-3), R ¹ is selected from C ₁ to C ₃ alkyl, R ² and R ³ are independently selected from C ₁ to C ₃ alkylene , m, n, p, and q are natural numbers, where m takes a value from 8 to 72; n takes a value from 5 to 35; p takes a value from 1 to 71, q takes a value from 1 to 71, and p+q=8 ~72;

In formula (2) or formula (3), R ⁴ is C ₁ -C ₃ alkylene, R ⁵ is hydrogen or C ₁ -C ₃ alkyl;

Step B: In an aqueous solution, under the action of an initiator, carry out a copolymerization reaction of the esterified product prepared in step A and the remaining unsaturated fatty acid at 55-100°C for 2-5 hours to obtain the carboxylic acid of formula (6) polymer;

In formula (6), a, b, c, and d are all integers, wherein a is 1-80, b is 0-300, c is 0-80, and d is 1-200; when c=0, b= 0; the definitions of R ⁴ , R ⁵ , and X are the same as above;

Step C: neutralize the carboxylic acid polymer prepared in step B with an alkali solution, and control the pH to 6-8 to obtain a polycarboxylate water-reducer product; the alkali solution is sodium hydroxide solution or potassium hydroxide solution.

Further, when the unsaturated fatty acid described in step A is an unsaturated dibasic acid, the present invention specifically recommends that the mass ratio of the polyether to the unsaturated dibasic acid be: 65-96%: 35-4%, preferably 70% ~90%: 30~10%.

Further, when the unsaturated fatty acid described in step A is a mixed acid of unsaturated dibasic acid and unsaturated monobasic acid, the present invention specifically recommends that the mass ratio of polyether to unsaturated dibasic acid and unsaturated monobasic acid is 55% ~96%: 35~1.5%: 33~1%. Preferably, the mass ratio of polyether to unsaturated dibasic acid and unsaturated monobasic acid is 65-95%: 30-3%: 30-2%.

It should be noted that the feed ratio of the above polyether and unsaturated fatty acid is based on the total mass of polyether and unsaturated fatty acid as 100%.

The molecular weight of the polyether of the present invention is preferably 600-3000, preferably one or any combination of the following: methoxypolyethylene glycol, ethoxypolyethylene glycol, propoxypolyethylene glycol, structure such as The compound shown in formula (9-2), the compound shown in structure as formula (9-3), wherein in formula (9-2) or formula (9-3), ^R is selected from methyl, ethyl or Propyl. The polyether is more preferably one or any combination of methoxypolyethylene glycol, the compound shown in formula (9-2) and the compound shown in formula (9-3) , wherein in formula (9-2) or (9-3), R ¹ is a methyl group.

The unsaturated dibasic acid represented by the formula (2) is preferably methylene succinic acid (itaconic acid).

The unsaturated monobasic acid represented by the formula (3) is preferably acrylic acid or methacrylic acid.

The present invention specifically recommends that the catalyst described in step A is concentrated sulfuric acid or p-toluenesulfonic acid, and the added weight of the catalyst is recommended to be 0.5-5.0%, preferably 0.5-3.5%, of the total weight of polyether and unsaturated fatty acid.

The present invention specifically recommends that the polymerization inhibitor described in step A is one or both of phenothiazine and hydroquinone, and its dosage is recommended to be 0.05-0.5% of the total weight of unsaturated fatty acids, preferably 0.1-0.5% %.

The initiator described in step B of the present invention can be selected from one of ammonium persulfate, potassium persulfate, sodium persulfate, sodium percarbonate, azobisisobutyronitrile, azobisisobutylamidine hydrochloride or There are several kinds, and its addition amount is recommended to be 0.1-10% of the total weight of polyether and unsaturated fatty acid, preferably 1-6%.

In the copolymerization reaction described in step B, when the mass concentration of the reaction system is higher than 25%, in order to prevent crosslinking reaction, the present invention recommends adding a chain transfer agent to adjust the molecular weight of the polymer. The recommended amount of chain transfer agent is 0.2-1.5% of the total weight of polyether and unsaturated fatty acid; the chain transfer agent can be selected from mercaptopropionic acid, mercaptoethanol, n-butylmercaptan, isopropanol, 2-mercaptoethanol , 3-mercaptopropionic acid, and one or more of thioglycolic acid. If the concentration of the reaction solution is lower than 25%, there is no need to add a chain transfer agent.

The polymer product of the present invention can be used in combination with the existing carboxylic acid-based water reducer and sulfamic acid-based water reducer, which not only effectively improves the slump loss of new concrete, but also improves the dispersion performance and increases the water reducing rate . In addition, the water reducer prepared by the present invention can also be used in combination with other air-entraining agents, retarders, early strength agents, defoamers, etc., to improve the overall performance of the product.

The polycarboxylate water reducer described in the present invention can be used as an important component of high performance concrete, high slump retaining concrete, high fluidity concrete, and anti-corrosion concrete, and is widely used in construction engineering, water conservancy, marine engineering, bridges, etc. In concrete projects such as tunnels and tunnels, it has significant economic benefits and promotion value.

Compared with the prior art, the present invention has the following advantages:

1. The present invention adopts unsaturated dibasic acid and polyether to carry out esterification reaction, and in the macromolecule esterification product of generation, both contain ester group, can provide polycarboxylic acid macromolecule long chain branch, mainly play steric hindering effect in application, It also contains carboxyl groups, which play a plastic-retaining role in application, and can also improve the slump retention effect of polycarboxylate superplasticizers; and the unsaturated dibasic acid used in the present invention is cheap and contains double carboxyl groups, which is more conducive to combining with Polyether undergoes esterification reaction to achieve a higher esterification rate.

2. The present invention uses unsaturated monobasic acid and unsaturated dibasic acid to synthesize together. In terms of molecular structure, it considers increasing the density of carboxyl groups on the main chain in the product molecule and adjusting the length of the branch chain, which can make the water reducing agent The rate and plasticity performance are greatly improved.

3. The polycarboxylate superplasticizer in the present invention does not contain chloride ions, is non-corrosive to steel bars, and has strong adaptability. It can be applied to cement of various specifications and types, and it will not be stratified or precipitated for long-term storage.

4. The unsaturated dibasic acid of general formula (2) is used in the esterification of the present invention, and nitrogen gas is fed in the process, which not only protects the reaction system but also plays the role of carrying water, and improves the esterification rate of the product.

The polycarboxylate water reducer of the present invention has excellent performances such as high plastic retention, small loss of cement paste over time, high water reducing rate, and low production cost.

(4) Specific implementation methods

Hereinafter, the present invention will be described in more detail with reference to examples, the purpose of which is only to illustrate the present invention, but not to limit the present invention in any way.

Example 1

Take 150g of methoxypolyethylene glycol with a molecular weight of 1500 and melt it and put it into a 500mL four-necked flask, add 0.12g of hydroquinone, 22.12g of itaconic acid, and 1.53g of 98% sulfuric acid under stirring, and then blow in nitrogen and heat up , react at 125-128°C for 6 hours; cool down to below 50°C, add 89g of water and 1.01g of chain transfer agent mercaptoethanol and stir well as the dripping solution (1); take 2.74g of ammonium persulfate and 48g of deionized water, and prepare into a solution as the dropping solution (2); add 89g of deionized water into a 500mL four-neck flask, raise the temperature to 95°C, start adding the above dropping solutions (1) and (2) dropwise at the same time, and drop them at a constant speed at this temperature Add for 1.5 hours to complete the addition, keep warm at 96-98° C. for 1 hour, cool, neutralize with 10% sodium hydroxide solution, adjust the pH to 7, and finally obtain the polycarboxylate superplasticizer of the present invention.

Example 2

Take 100 g of methoxypolyethylene glycol (0.1 mol) with a molecular weight of 1000 and melt it into a 500 mL four-neck flask, add 0.1 g of hydroquinone, 0.04 g of phenothiazine, 6.51 g of itaconic acid, and acrylic acid 23.06g, 1.55g p-toluenesulfonic acid, feed nitrogen and raise the temperature, react at 125-128°C for 5 hours; cool down to below 50°C, add 131.5g water and stir well as drop solution (3); take 2.92g persulfuric acid Ammonium and 97g of deionized water were made into a solution as the dripping solution (4); 263g of deionized water was added to a 1000mL four-neck flask, the temperature was raised to 65°C, and the above dropping solutions (3) and (4) were started to be added dropwise at the same time , and added dropwise at this temperature for 3 hours to complete the addition, kept at 68 to 70° C. for 1 hour, cooled, neutralized with 10% sodium hydroxide solution, adjusted to a pH of 7, and finally obtained the present invention polycarboxylate superplasticizer.

Example 3

Take 120g of methoxy polyethylene glycol with a molecular weight of 1200 and melt it into a 500mL four-neck flask, add 0.12g of hydroquinone, 13.2g of itaconic acid, 34.5g of methacrylic acid, and 1.22g of 98% sulfuric acid under stirring , feed nitrogen and heat up, and react at 122-125°C for 6 hours; cool down to below 50°C and add 165g of water and stir well as the dripping liquid (5); take 7.4g of ammonium persulfate and 124g of deionized water to make a solution As the dripping solution (6); add 332g deionized water into a 1000mL four-neck flask, heat up to 95°C, start adding the above dropping solutions (5) and (6) dropwise at the same time, and add 4 drops at a constant speed at this temperature Add it within 1 hour, keep it warm at 96-98° C. for 1 hour, cool, neutralize with 10% sodium hydroxide solution, adjust the pH value to 7, and finally obtain the polycarboxylate superplasticizer of the present invention.

Comparative Example 4

Take 155g of methoxypolyethylene glycol with a molecular weight of 1200 and melt it into a 500mL four-neck flask, add 0.21g of hydroquinone, 42.61g of methacrylic acid, and 1.53g of 98% sulfuric acid while stirring, and then blow in nitrogen and heat up , reacted at 122-125°C for 6 hours; cooled to below 50°C, added 155g of water and 1.55g of chain transfer agent mercaptoethanol and stirred evenly as the dripping solution (7); took 5.83g of ammonium persulfate and 94g of deionized water, and prepared into a solution as the dropping solution (8); add 355g of deionized water into a 1000mL four-neck flask, heat up to 65°C, start adding the above dropping solutions (7) and (8) dropwise at the same time, and drop them at a constant speed at this temperature Add for 3 hours to complete the addition, keep warm at 68-70°C for 1 hour, cool, neutralize with 10% sodium hydroxide solution, adjust the pH to 7, and finally obtain a conventional polycarboxylate water reducer.

Example 5

According to GB/T8077-2000, the polycarboxylate water-reducer prepared in Examples 1-4 was tested for cement slurry fluidity and mortar water-reducing rate. The test cement is local conch 42.5R, the water-cement ratio is 0.29, and the dosage of water reducer is 0.25% dry. The measurement results are shown in Table 1:

Table 1

Above data shows, use itaconic acid and polyether to carry out esterification alone in embodiment 1, and the plastic retaining performance of its product is better, sees from the pure pulp plastic retaining test that the loss over time is a negative value; in embodiment 2 Using acrylic acid and itaconic acid to carry out esterification reaction with polyether jointly, the initial slurry dispersibility of the product is better, but the loss is relatively large; in embodiment 3, use methacrylic acid and itaconic acid to carry out esterification with polyether Chemical reaction, the product has very little net pulp loss and high water reducing rate; comparative example 4 is a currently recognized preparation method, and its product has poor clean pulp retention and relatively low water reducing rate.

Claims (10)

1. polycarboxylate water-reducer, its molecular weight is 1000～100000, structure is formed shown in (7):

In the formula (7), R ⁴Be selected from C ₁～C ₃Alkylidene group, R ⁵Be selected from hydrogen or C ₁～C ₃Alkyl, M are Na or K; A, b, c, d are integer, and wherein a is 1～80, and b is 0～300, and c is 0～80, and d is 1～200; When c=0, b=0; Wherein X represents polyether group, and the polyether group X in each structural unit independently is selected from shown in following formula (8-1), formula (8-2), the formula (8-3) a kind of in the group separately:

In formula (8-1), formula (8-2) or the formula (8-3), R ¹Be selected from C ₁～C ₃Alkyl, R ², R ³Independently be selected from C ₁～C ₃Alkylidene group, m, n, p, q are natural number, wherein the m value is 8～72; The n value is 5～35; The p value is 1～71, and the q value is 1～71, and p+q=8～72.

2. polycarboxylate water-reducer as claimed in claim 1, the molecular weight that it is characterized in that described polyether group is 600～3000.

3. the preparation method of a polycarboxylate water-reducer as claimed in claim 1 comprises the steps:

Steps A: in the presence of stopper and catalyzer, polyethers X-H and excessive unsaturated fatty acids carried out esterification 3～7 hours in 120～140 ℃, obtained carboxylate; Described unsaturated fatty acids is the unsaturated dibasic acid shown in the formula (2), perhaps is the mixing acid that the unsaturated monoprotic acid shown in unsaturated dibasic acid shown in the formula (2) and the formula (3) is formed; Described polyethers X-H is selected from a kind of or any several kinds combination in the compound shown in formula (1-1), formula (1-2), the formula (1-3);

In formula (1-1), formula (1-2) or the formula (1-3), R ¹Be selected from C ₁～C ₃Alkyl, R ², R ³Independently be selected from C ₁～C ₃Alkylidene group, m, n, p, q are natural number, wherein the m value is 8～72; The n value is 5～35; The p value is 1～71, and the q value is 1～71, and p+q=8～72;

In formula (2) or the formula (3), R ⁴Be C ₁～C ₃Alkylidene group, R ⁵Be hydrogen or C ₁～C ₃Alkyl;

Step B: in the aqueous solution, under action of evocating, carboxylate that steps A is made and remaining unsaturated fatty acids carried out copolymerization 2～5 hours in 55～100 ℃, made the carboxylic acid polyalcohol of formula (6);

In the formula (6), a, b, c, d are integer, and wherein a is 1～80, and b is 0～300, and c is 0～80, and d is 1～200; When c=0, b=0; R ⁴, R ⁵, X definition the same;

Step C: the carboxylic acid polyalcohol that step B is made neutralizes with alkaline solution, and control pH is 6～8, gets the polycarboxylate water-reducer product; Said alkaline solution is sodium hydroxide solution or potassium hydroxide solution.

4. the preparation method of polycarboxylate water-reducer as claimed in claim 3 it is characterized in that described unsaturated fatty acids is a unsaturated dibasic acid, and the mass ratio that feeds intake of polyethers and unsaturated dibasic acid is: 65～96%: 35～4%.

5. the preparation method of polycarboxylate water-reducer as claimed in claim 3; It is characterized in that described unsaturated fatty acids is unsaturated dibasic acid and unsaturated monacid mixing acid, polyethers and unsaturated dibasic acid and the unsaturated monacid mass ratio that feeds intake are 55～96%: 35～1.5%: 33～1%.

6. like the preparation method of the described polycarboxylate water-reducer of one of claim 3～5, it is characterized in that said polyethers is selected from following a kind of or any several kinds mixing: methoxy poly (ethylene glycol), oxyethyl group polyoxyethylene glycol, propoxy-polyoxyethylene glycol, structure suc as formula the compound shown in (9-2), structure suc as formula the compound shown in (9-3); Its Chinese style (9-2) or (9-3) in, R ¹Be selected from methyl, ethyl or propyl group;

7. like the preparation method of the described polycarboxylate water-reducer of one of claim 3～5; It is characterized in that the catalyzer described in the steps A is the vitriol oil or tosic acid, the adding weight of described catalyzer is 0.5～5.0% of polyethers and unsaturated fatty acids gross weight.

8. like the preparation method of the described polycarboxylate water-reducer of one of claim 3～5, it is characterized in that the stopper described in the steps A is one or both in thiodiphenylamine, the Resorcinol, its consumption is 0.05～0.5% of a unsaturated fatty acids gross weight.

9. like the preparation method of the described polycarboxylate water-reducer of one of claim 3～5; It is characterized in that the initiator described in the step B is selected from one or more in ammonium persulphate, Potassium Persulphate, Sodium Persulfate, SPC-D, Diisopropyl azodicarboxylate, the azo-bis-isobutyrate hydrochloride, its add-on is 0.1～10% of polyethers and a unsaturated fatty acids gross weight.

10. like the preparation method of the described polycarboxylate water-reducer of one of claim 3～5; It is characterized in that in the described copolymerization of step B; The reaction system mass concentration is higher than at 25% o'clock, adds chain-transfer agent, and its add-on is 0.2～1.5% of polyethers and a unsaturated fatty acids gross weight; In said chain-transfer agent selected from mercapto propionic acid, mercaptoethanol, n-butyl mercaptan, Virahol, 2 mercapto ethanol, 3-thiohydracrylic acid, the Thiovanic acid one or more.