CN107556440B - Maleate polycarboxylic acid concrete slump retaining agent and preparation method thereof - Google Patents
Maleate polycarboxylic acid concrete slump retaining agent and preparation method thereof Download PDFInfo
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Abstract
The invention provides a maleate polycarboxylic acid type concrete slump retaining agent and a preparation method thereof, and aims to solve the problem that the conventional polycarboxylic acid slump retaining agent has large loss when applied to concrete. A maleic acid ester polycarboxylic acid concrete slump retaining agent has the molecular weight of 8000-15000 and the molecular formula:
Description
Technical Field
The invention relates to the field of concrete admixtures, in particular to a maleate polycarboxylic acid type concrete slump retaining agent and a preparation method thereof.
Background
With the rapid development of economy and the improvement of building level in China, the requirement on the quality of concrete is higher and higher. As a novel high-performance water reducing agent, the polycarboxylate water reducing agent has been widely applied to the fields of municipal administration, railways, highways, airports, ports, bridges, hydropower and the like due to a series of outstanding performances of low mixing amount, high water reducing rate, good flowability and slump retaining property of fresh concrete, low shrinkage, large reinforcing potential, environmental friendliness and the like.
However, the quality of domestic cement is very variable and the quality of concrete gravel is poor due to a plurality of domestic cement varieties. For example, the gas content and stone dust content are high, and the quality of some machine-made sands is poor. There are also problems associated with concrete formulated with common polycarboxylic acid water reducing agents of the general type, of which excessive slump loss over time is the most common major problem. Particularly, long-time long-distance transportation can cause the slump loss of concrete to be very fast, which not only influences construction, but also greatly influences the performance and quality of the concrete, thereby restricting the popularization of the polycarboxylic acid water reducing agent to a certain extent.
The main domestic methods for solving the problems are as follows: (1) compounding a retarder; (2) adding the water reducing agent for two or more times; (3) improving initial fluidity and even initial bleeding segregation to ensure pumping performance over time. Although the three methods can solve the problem of slump loss to some extent, each method has certain limitations and cannot fundamentally solve the problem of slump loss. Therefore, the slow release of the water reducing agent by using the reactive polymer is an effective method for solving the problem of concrete slump loss. However, at present, domestic water reducing agent mother liquor products are single, mainly comprising high water reducing type and common slump retaining type polycarboxylic acid mother liquor, while the common slump retaining type polycarboxylic acid mother liquor is developed on the basis of high water reducing type polycarboxylic acid, concrete initially has larger fluidity, but still has certain loss after time, and the water reducing agent mother liquor still can not meet the engineering which has special requirements on long-time long-distance transportation or slump retaining. Therefore, the polycarboxylate superplasticizer for controlling the concrete slump loss is urgently needed, and the problem of the slump loss within 2-4 hours or even longer time is fundamentally solved, so that the additive quality is widened to meet the requirements of different projects.
At present, the production process of the polycarboxylic acid slump retaining agent is generally more than 5 hours, the polycarboxylic acid slump retaining agent needs to be synthesized by heating to the temperature of 40-80 ℃, and the polycarboxylic acid slump retaining agent is synthesized by adopting various dropping modes, and has the current situations of more synthetic raw materials, complex process and the like.
In addition, the existing raw materials for synthesizing the polycarboxylic acid slump retaining agent are limited, are purchased from the existing raw materials in the market, and have high price, narrow selection range, high cost of the synthesized polycarboxylic acid slump retaining agent, and low adaptability of concrete, and the market use of the product is seriously influenced.
Disclosure of Invention
The invention provides a maleate polycarboxylic acid type concrete slump retaining agent and a preparation method thereof, and aims to solve the problem that the conventional polycarboxylic acid slump retaining agent has large loss when applied to concrete.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a maleic acid ester polycarboxylic acid concrete slump retaining agent has the molecular weight of 8000-15000 and the molecular formula:
wherein a =1 ~ 3, b =2 ~ 5, c =10 ~ 15, d =2 ~ 5, n =50 ~ 60.
The preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent sequentially comprises the following steps:
esterification reaction:
(1) mixing maleic anhydride and methanol, and after the maleic anhydride is completely dissolved in the methanol, carrying out exothermic reaction for 60-100 min, and raising the temperature to 60-75 ℃ to obtain the monomethyl maleate.
(2) Adding catalyst, and heating at 0.9-1.1 deg.C/5 min.
(3) After the temperature rises to 96-98 ℃, the temperature rises at the speed of 0.9-1.1 ℃/20min, and the temperature rises to 100-104 ℃, and then the temperature is preserved for 58-62min, so as to obtain the maleic acid dimethyl ester. Then cooling to room temperature to obtain a maleic ester mixture.
Polymerization reaction:
(4) uniformly mixing and fully dissolving the mixture of the maleic acid esters, the large monomer isopentenol polyoxyethylene ether and the deionized water.
(5) Adding an oxidant, stirring for 5min, and then dropwise adding a reducing agent for reaction.
(6) Adding an alkali solution to adjust the pH value to 6.0-8.0 to obtain the maleic ester polycarboxylic acid type concrete slump retaining agent.
Further, in step (1), maleic anhydride and methanol are mixed in a molar ratio of 1: 1. In the step (1), the exothermic reaction is carried out for 75min-100min, and the temperature is raised to 60-75 ℃.
Further, in step (1), maleic anhydride and methanol are mixed in a molar ratio of 2: 1. In step (3), the temperature is maintained at 102 ℃ for 60 min.
Further, in the step (2), the catalyst is at least one of concentrated sulfuric acid, p-toluenesulfonic acid and boron trifluoride.
Further, after the temperature rises to 96-98 ℃, nitrogen gas is started to be introduced, and then the temperature rises at the speed of 0.9-1.1 ℃/20 min.
Furthermore, in the step (4), the mass ratio of the mixture of the large monomer isopentenol polyoxyethylene ether and the maleic acid ester is 1: 0.2-0.5.
Further, in the steps (4) to (6), the adding amount of the oxidant is 0.3 to 0.5 percent of the total mass of the mixture of the large monomer prenyl alcohol polyoxyethylene ether and the maleic acid ester. The addition amount of the reducing agent is 0.3 to 0.8 percent of the total mass of the maleate mixture. The alkaline solution is 30% by mass, and the addition amount of the alkaline solution is 30% -45% of the total mass of the maleate mixture. The addition of deionized water is 30-65% of the total reactants.
Further, the oxidizing agent is at least one of hydrogen peroxide, potassium persulfate and ammonium persulfate.
Further, the reducing agent is L-ascorbic acid.
Compared with the prior art, the invention has the advantages that:
1. simple preparation process, simple equipment, normal-temperature polymerization reaction and low energy consumption.
2. Short polymerization reaction time, high production efficiency and no pollution.
3. The prepared maleate polycarboxylic acid type concrete slump retaining agent is compounded with a common polycarboxylic acid slump retaining agent to be used in cement paste, can keep the fluidity within 3h without loss or even increase, and can obviously reduce the slump loss of concrete when being applied to common concrete.
4. The small monomer monomethyl maleate and dimethyl maleate are esterified and synthesized by the simple process, the raw materials are easy to obtain, the price is low, and the method is suitable for industrial mass production.
Detailed Description
Example 1:
a maleic acid ester polycarboxylic acid concrete slump retaining agent has the molecular weight of 8000-15000 and the molecular formula:
wherein a =1 ~ 3, b =2 ~ 5, c =10 ~ 15, d =2 ~ 5, n =50 ~ 60.
Example 2:
the preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent in the embodiment 1 sequentially comprises the following steps:
esterification reaction:
(1) adding 630 parts of maleic anhydride and 360 parts of methanol into a four-neck flask provided with a thermometer and a stirrer in parts by mass, mixing, and reacting at 10-75 ℃ for 75-100 min after the maleic anhydride is completely dissolved in the methanol to raise the temperature to 75 ℃ to obtain monomethyl maleate. The reaction formula is as follows:
(2) 7 parts of boron trifluoride etherate catalyst are added and the mixture is heated to 97 ℃ within 120 min.
(3) After the temperature rises to 97 ℃, introducing nitrogen for protection, slowing down the temperature rise rate, raising the temperature to 102 ℃ at the rate of 1 ℃/20min, and preserving the temperature for 60min to obtain the dimethyl maleate. The reaction formula is as follows:
cooling to room temperature to obtain a maleic ester mixture. The resulting mixture of esters of maleic acid comprises monomethyl maleate, dimethyl maleate and residual maleic acid. Wherein the molar ratio of monomethyl maleate to dimethyl maleate is 1: 3.
Polymerization reaction:
(4) adding 240 parts of macromonomer isopentenol polyoxyethylene ether, 80 parts of maleic acid ester mixture and 300 parts of deionized water in parts by mass into a three-neck flask, and stirring for 30min for full dissolution.
(5) Adding 1.3 parts of 30% hydrogen peroxide solution, stirring for 5min, then beginning to drop 100 parts of 3% L-ascorbic acid, finishing dropping for 120min, and keeping the temperature for reaction for 30 min.
(6) And adding 30% of alkali solution to adjust the pH value to 6.0-8.0, and adding certain water to dilute until the solid content is 40% to obtain the maleic ester polycarboxylic acid concrete slump retaining agent.
The reaction formula of the polymerization reaction is:
example 3:
the preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent in the embodiment 1 sequentially comprises the following steps:
esterification reaction:
(1) adding 600 parts by mass of maleic anhydride and 390 parts by mass of methanol into a four-neck flask with a thermometer and a stirrer, mixing, and reacting at 10-75 ℃ for 75-100 min after the maleic anhydride is completely dissolved in the methanol to increase the temperature to 75 ℃ to obtain monomethyl maleate. The reaction formula is as follows:
(2) 7.5 parts of concentrated sulfuric acid as catalyst were added and heated to 97 ℃ within 120 min.
(3) After the temperature rises to 97 ℃, introducing nitrogen for protection, slowing down the temperature rise rate, raising the temperature to 102 ℃ at the rate of 1 ℃/20min, and preserving the temperature for 60min to obtain the dimethyl maleate. The reaction formula is as follows:
cooling to room temperature to obtain a maleic ester mixture.
Polymerization reaction:
(4) 255 parts of macromonomer isopentenol polyoxyethylene ether, 85 parts of maleic acid ester mixture and 300 parts of deionized water are added into a three-mouth flask according to the mass parts, and stirred for 30min for full dissolution.
(5) Adding 1.4 parts of 30% hydrogen peroxide solution, stirring for 5min, then beginning to drop 100 parts of 3% L-ascorbic acid, finishing dropping for 120min, and keeping the temperature for reaction for 30 min.
(6) And adding 30% of alkali solution to adjust the pH value to 6.0-8.0, and adding certain water to dilute until the solid content is 40% to obtain the maleic ester polycarboxylic acid concrete slump retaining agent.
The reaction formula of the polymerization reaction is:
example 4:
the preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent in the embodiment 1 sequentially comprises the following steps:
esterification reaction:
(1) 650 parts of maleic anhydride and 340 parts of methanol are added into a four-neck flask with a thermometer and a stirrer in parts by mass and mixed, after the maleic anhydride is completely dissolved in the methanol, the mixture reacts at 10-75 ℃ for 75-100 min, and the temperature is raised to 75 ℃ to obtain monomethyl maleate. The reaction formula is as follows:
(2) 7 parts of p-toluenesulfonic acid were added as catalyst and heated to 97 ℃ within 120 min.
(3) After the temperature rises to 97 ℃, introducing nitrogen for protection, slowing down the temperature rise rate, raising the temperature to 102 ℃ at the rate of 1 ℃/20min, and preserving the temperature for 60min to obtain the dimethyl maleate. The reaction formula is as follows:
cooling to room temperature to obtain a maleic ester mixture.
Polymerization reaction:
(4) adding 250 parts of macromonomer isopentenol polyoxyethylene ether, 75 parts of maleic acid ester mixture and 300 parts of deionized water in parts by mass into a three-neck flask, and stirring for 30min for full dissolution.
(5) Adding 1.3 parts of 30% hydrogen peroxide solution, stirring for 5min, then beginning to drop 100 parts of 3% L-ascorbic acid, finishing dropping for 120min, and keeping the temperature for reaction for 30 min.
(6) And adding 30% of alkali solution to adjust the pH value to 6.0-8.0, and adding certain water to dilute until the solid content is 40% to obtain the maleic ester polycarboxylic acid concrete slump retaining agent.
The reaction formula of the polymerization reaction is:
example 5:
the preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent in the embodiment 1 sequentially comprises the following steps:
esterification reaction:
(1) and adding 640 parts of maleic anhydride and 350 parts of methanol into a four-neck flask provided with a thermometer and a stirrer in parts by mass, mixing, and reacting at 10-75 ℃ for 75-100 min after the maleic anhydride is completely dissolved in the methanol to raise the temperature to 75 ℃ to obtain monomethyl maleate. The reaction formula is as follows:
(2) 7 parts of a mixture of boron trifluoride and methanol were added as catalyst and heated to 97 ℃ within 120 min.
(3) After the temperature rises to 97 ℃, introducing nitrogen for protection, slowing down the temperature rise rate, raising the temperature to 102 ℃ at the rate of 1 ℃/20min, and preserving the temperature for 60min to obtain the dimethyl maleate. The reaction formula is as follows:
cooling to room temperature to obtain a maleic ester mixture.
Polymerization reaction:
(4) 235 parts of macromonomer isopentenol polyoxyethylene ether, 90 parts of maleic acid ester mixture and 300 parts of deionized water are added into a three-mouth flask according to the mass parts, and stirred for 30min for full dissolution.
(5) Adding 1.4 parts of 30% hydrogen peroxide solution, stirring for 5min, then beginning to drop 100 parts of 3% L-ascorbic acid, finishing dropping for 120min, and keeping the temperature for reaction for 30 min.
(6) And adding 30% of alkali solution to adjust the pH value to 6.0-8.0, and adding certain water to dilute until the solid content is 40% to obtain the maleic ester polycarboxylic acid concrete slump retaining agent.
The reaction formula of the polymerization reaction is:
the maleic ester polycarboxylic acid type concrete slump retaining agent prepared in the embodiment 2-5 of the invention adopts reference cement, and the fluidity of cement paste is tested according to GB/T8077-2012. The results are shown in Table 1:
TABLE 1-fluidity of standard Cement paste with time (test temperature 33 ℃ C., humidity 85%)
TABLE 2-fluidity of neat paste with time (test temperature 33 ℃ C., humidity 85%) when Standard Cement is compounded
Note: 101A is a standard polycarboxylic acid water reducing agent which is a product sold by novel Sichuan iron building materials, 101C is a common slump retaining agent sold by novel Sichuan iron building materials, and 301C-1 is a maleic acid ester polycarboxylic acid concrete slump retaining agent.
As can be seen from Table 1, when the mixing amount is 0.25%, the fluidity of the cement paste of 301C-1, 301C-2, 301C-3 and 301C-4 of the invention is continuously increased along with the prolonging of time, the cement paste has the maximum fluidity when reaching 3 hours, and the cement paste can still maintain the fluidity when reaching 4 hours; the fluidity of the common slump retaining agent 101C cement paste begins to increase along with time, has the maximum fluidity when reaching 2h, and then begins to decrease; the reduced water 101A cement paste initially has the greatest fluidity, but gradually decreases over time. As can be seen from Table 2, the 101A and 301C-1 compound and the 101A and 101C compound are used in the cement paste, the 101A and 301C-1 compound can keep the fluidity not lost or even increased within 3h, the fluidity can still be kept not lost within 4h, and the change amount of 4h is very small with the passage of time. Whereas the 101A:101C formulation had the maximum fluidity at 1h and began to decrease at 2 h. Therefore, the maleic ester polycarboxylic acid type concrete slump retaining agent prepared by the invention has ultrahigh later slump retaining performance compared with the common slump retaining agent 101C.
The 301C-1 maleate polycarboxylic acid concrete slump retaining agent obtained in the example 2 is compounded with a 101A water reducing agent, and is compounded with 101C and 101A to compare the concrete test performances:
the slump constant and the time-dependent slump of the concrete mixture are tested according to GB/T50080-2002 Standard test method for the Performance of common concrete mixtures. The cement is Czochralski PO42.5, the mixing amount is 0.25%, and the detection formula is as follows 3:
TABLE 3 concrete mix proportion (kg/m dry)
| C | F | S | G | W | WJ |
| 312 | 78 | 796 | 1109 | 165 | 0.78 |
TABLE 4 concrete slump loss behavior results
As is apparent from Table 4, the slump retaining agent of the present invention has a long slump retaining ability, hardly loses slump for 3 hours, and has workability for 4 hours.
In addition to the above examples, the following schemes may also be employed:
in the step (1), maleic anhydride and methanol are mixed according to a molar ratio of 1:1 or 2: 1; the exothermic reaction is carried out for 75min-100min, and the temperature is increased to 60-75 ℃ or not.
In the step (2), the catalyst may be at least one of concentrated sulfuric acid, p-toluenesulfonic acid, and boron trifluoride.
In the step (4), the mass ratio of the mixture of the macromonomer prenyl polyoxyethylene ether and the maleate is 1: 0.2-0.5.
In steps (4) to (6), the mass can be realized in any one of the following ratios: the adding amount of the oxidant is 0.3 to 0.5 percent of the total mass of the mixture of the large monomer prenyl alcohol polyoxyethylene ether and the maleic ester; the addition amount of the reducing agent is 0.3 to 0.8 percent of the total mass of the maleate mixture; the alkaline solution is 30% by mass, and the addition amount of the alkaline solution is 30% -45% of the total mass of the maleate mixture; the addition of deionized water is 30-65% of the total reactants.
The oxidizing agent may be at least one selected from hydrogen peroxide, potassium persulfate, and ammonium persulfate.
The above description is only an embodiment of the present invention, but the technical features of the present invention are not limited thereto, and any changes or modifications within the technical field of the present invention by those skilled in the art are covered by the claims of the present invention.
Claims (7)
1. A maleate polycarboxylic acid concrete slump retaining agent is characterized in that: the molecular weight is 8000-15000, and the molecular formula is:
wherein a is 1-3, b is 2-5, c is 10-15, d is 2-5, and n is 50-60;
the preparation method of the maleic ester polycarboxylic acid concrete slump retaining agent sequentially comprises the following steps:
esterification reaction:
(1) mixing maleic anhydride and methanol, and carrying out exothermic reaction for 60-100 min after the maleic anhydride is completely dissolved in the methanol, so that the temperature is raised to 60-75 ℃ to obtain monomethyl maleate;
(2) adding a catalyst, and starting heating at the speed of 0.9-1.1 ℃/5min to raise the temperature;
(3) after the temperature rises to 96-98 ℃, the temperature rises at the speed of 0.9-1.1 ℃/20min, and the temperature rises to 100-; then cooling to room temperature to obtain a maleic ester mixture;
polymerization reaction:
(4) uniformly mixing and fully dissolving a maleate mixture, a macromonomer isopentenol polyoxyethylene ether and deionized water;
(5) adding an oxidant, stirring for 5min, and then dropwise adding a reducing agent for reaction;
(6) adding an alkali solution to adjust the pH value to 6.0-8.0 to obtain a maleic ester polycarboxylic acid concrete slump retaining agent;
in the step (4), the mass ratio of the mixture of the macromonomer prenyl polyoxyethylene ether and the maleate is 1: 0.2-0.5;
in the steps (4) to (6), the adding amount of the oxidant is 0.3 to 0.5 percent of the total mass of the mixture of the large monomer prenyl alcohol polyoxyethylene ether and the maleate; the addition amount of the reducing agent is 0.3 to 0.8 percent of the total mass of the maleate mixture; the alkaline solution is 30% by mass, and the addition amount of the alkaline solution is 30% -45% of the total mass of the maleate mixture; the addition of deionized water is 30-65% of the total reactants.
2. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: in the step (1), maleic anhydride and methanol are mixed according to a molar ratio of 1: 1; in the step (1), the exothermic reaction is carried out for 75min-100min, and the temperature is raised to 60-75 ℃.
3. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: in the step (1), maleic anhydride and methanol are mixed according to a molar ratio of 2: 1; in step (3), the temperature is maintained at 102 ℃ for 60 min.
4. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: in the step (2), the catalyst is at least one of concentrated sulfuric acid, p-toluenesulfonic acid and boron trifluoride.
5. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: in the step (3), after the temperature is raised to 96-98 ℃, nitrogen gas is started to be introduced, and then the temperature is raised at the speed of 0.9-1.1 ℃/20 min.
6. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: the oxidant is at least one of hydrogen peroxide, potassium persulfate and ammonium persulfate.
7. The maleate polycarboxylic acid concrete slump retaining agent as claimed in claim 1, wherein: the reducing agent is L-ascorbic acid.
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