CN113087858A

CN113087858A - Shrinkage-reducing polycarboxylate superplasticizer and preparation method thereof

Info

Publication number: CN113087858A
Application number: CN202110519952.4A
Authority: CN
Inventors: 陈凤琪; 任建波; 杨文杰; 罗紫隆; 田静; 陈志明; 郑永超; 田玲香
Original assignee: Beijing Jinyu Concrete Co ltd; Tangshan Jidong Cement Admixture Co ltd; Bbmg Cement Co ltd; Beijing Building Materials Academy of Sciences Research
Current assignee: Beijing Jinyu Concrete Co ltd; Tangshan Jidong Cement Admixture Co ltd; Bbmg Cement Co ltd; Beijing Building Materials Academy of Sciences Research
Priority date: 2021-05-12
Filing date: 2021-05-12
Publication date: 2021-07-09

Abstract

The application relates to the field of polycarboxylate superplasticizers, and particularly discloses a reduction type polycarboxylate superplasticizer and a preparation method thereof. The shrinkage-reducing polycarboxylic acid water reducing agent comprises, by weight, 10-25 parts of sodium methallylsulfonate, 10-20 parts of distilled water, 15-30 parts of ethylene glycol polymer, 20-40 parts of acrylic acid compound and 20-40 parts of polyborate; the preparation method comprises the following steps: s1, mixing sodium methacrylate and distilled water to obtain a mixed solution; and S2, introducing nitrogen into the mixed solution, heating to 70-90 ℃, simultaneously adding the ethylene glycol polymer, the acrylic compound, the polyborate and the initiator into the mixed solution, keeping the temperature at 70-90 ℃ for 2-3h, cooling, and adjusting the pH value to obtain the shrinkage-reducing polycarboxylic acid water reducer. The application can improve the reduction effect of the reduction type polycarboxylate water reducer and enhance the stability of the reduction type polycarboxylate water reducer.

Description

Shrinkage-reducing polycarboxylate superplasticizer and preparation method thereof

Technical Field

The application relates to the field of polycarboxylic acid water reducing agents, in particular to a reduction type polycarboxylic acid water reducing agent and a preparation method thereof.

Background

Modern concrete is gradually developed towards high strength and high performance based on high requirements on modern buildings, however, due to the inherent structure of concrete, excessive shrinkage of concrete is one of important factors influencing the quality of concrete engineering. Excessive shrinkage of the concrete may cause cracks to occur in portions thereof, which may not only cause a decrease in strength of the concrete but also result in a decrease in the lifespan of the concrete.

In order to reduce the shrinkage of concrete and effectively control the generation of internal defects of concrete so as to reduce the risk of cracking of concrete, various water reducing agents have been developed. The polycarboxylic acid type water reducer has the advantages of good water reducing effect, high fluidity, environmental protection, designable structure and the like, and is one of the most common water reducers for the current concrete. The reduction type polycarboxylate superplasticizer can graft a reduction group on a side chain of a molecular structure of the reduction type polycarboxylate superplasticizer, so that the reduction type polycarboxylate superplasticizer has a higher water reduction rate and a reduction effect, and therefore, the research on the reduction type polycarboxylate superplasticizer is more and more at present.

For example, chinese patent with an authorization publication number of CN103193410B proposes a preparation method of a shrinkage-reducing polycarboxylic acid water reducer, which is prepared by using sodium methallylsulfonate, allyl polyethylene glycol, methacrylic acid, diethylene glycol dimethyl monobutyl ether maleic anhydride monoester as a comonomer.

In view of the above-mentioned related art, the inventors found in practical use that: in the method, the activities of the sodium methallylsulfonate, the allyl polyethylene glycol, the methacrylic acid and the diethylene glycol dimethyl monobutyl ether maleic anhydride monoester are different greatly, and the copolymerization activity of the allyl polyethylene glycol and the diethylene glycol dimethyl monobutyl ether maleic anhydride monoester is low, so that the prepared shrinkage reducing polycarboxylic acid water reducing agent is unstable in shrinkage reducing performance, and the concrete is poor in durability.

Disclosure of Invention

In order to solve the problem of poor durability of concrete, the application provides a shrinkage-reducing polycarboxylic acid water reducing agent and a preparation method thereof.

In a first aspect, the application provides a shrinkage-reducing polycarboxylic acid water reducing agent, which adopts the following technical scheme:

a shrinkage-reducing polycarboxylic acid water reducing agent comprises, by weight, 10-25 parts of sodium methallylsulfonate, 10-20 parts of distilled water, 15-30 parts of ethylene glycol polymer, 20-40 parts of acrylic acid compound and 20-40 parts of polyborate.

By adopting the technical scheme, the polyborate is adopted, and can act synergistically with sodium methallylsulfonate, glycol polymer and acrylic acid compound, so that the compatibility of the sodium methallylsulfonate, the glycol polymer and the acrylic acid compound is greatly improved, the copolymerization activity of the glycol polymer is improved, the water loss rate and the bleeding rate of the surface of concrete tend to be balanced, the shrinkage reducing effect of the shrinkage reducing polycarboxylic acid water reducing agent is greatly improved, and the shrinkage reducing effect and the stability of the water reducing effect of the shrinkage reducing polycarboxylic acid water reducing agent are improved.

Preferably, the glycol-based polymer is a mixture of polyethylene glycol and allyl polyethylene glycol.

By adopting the technical scheme, the compatibility of the raw materials is further improved by compounding the polyethylene glycol and the allyl polyethylene glycol, the copolymerization activity of the polyethylene glycol and the allyl polyethylene glycol is further enhanced by the synergistic effect of the polyethylene glycol and the allyl polyethylene glycol, and the surface tension of water in capillary pores of concrete is reduced by the interaction of the polyethylene glycol and the allyl polyethylene glycol with the rest raw materials, so that the shrinkage effect of the shrinkage-reducing polycarboxylic acid water reducer is improved, and the stability of the shrinkage-reducing polycarboxylic acid water reducer is enhanced.

Preferably, the weight ratio of the polyethylene glycol to the allyl polyethylene glycol is (0.1-0.2): 1.

by adopting the technical scheme, the compatibility between the allyl polyethylene glycol and the polyethylene glycol can be improved by controlling the proportion of the allyl polyethylene glycol and the polyethylene glycol, and the copolymerization reaction of the raw materials is promoted, so that the shrinkage reducing effect and the stability of the shrinkage reducing polycarboxylate superplasticizer are improved.

Preferably, the hydroxyl value of the allyl polyethylene glycol is 27 to 63 mgKOH/g.

By adopting the technical scheme, the synergistic effect between the allyl polyethylene glycol and the polyethylene glycol can be promoted by controlling the hydroxyl value of the allyl polyethylene glycol, the compatibility among the raw materials is further improved, and the stability of the shrinkage-reducing and water-reducing performance of the shrinkage-reducing polycarboxylic acid water reducing agent is improved.

Preferably, the acrylic compound is a mixture of acrylic acid and methacrylic acid.

By adopting the technical scheme, acrylic acid and methacrylic acid have synergistic effect, so that the groups of the prepared reduction type polycarboxylate water reducer have carboxylic acid, methyl, ether bond and other groups, and the reduction type polycarboxylate water reducer generates a large space obstruction effect, thereby obviously improving the reduction and water reducing performances of the reduction type polycarboxylate water reducer and improving the stability of the reduction type polycarboxylate water reducer.

Preferably, the weight ratio of acrylic acid to methacrylic acid is 1: (0.1-0.35).

By adopting the technical scheme, the copolymerization activity of the ethylene glycol polymer is promoted by controlling the proportion of the acrylic acid and the methacrylic acid, the space barrier effect of the reducible polycarboxylate superplasticizer is improved, and the reduction and water reduction performances of the reducible polycarboxylate superplasticizer are improved.

Preferably, 8 to 10 parts by weight of fumed silica is also included.

By adopting the technical scheme, the fumed silica has a strong dispersing effect, the compatibility among the raw materials is improved, and the fumed silica can act with the glycol polymer in a synergistic manner, so that the copolymerization activity of polyethylene glycol is improved, and the possibility of agglomeration of the fumed silica is reduced, thereby further balancing the water loss rate and the bleeding rate of the surface of concrete, and enhancing the shrinkage reducing effect of the shrinkage reducing polycarboxylate superplasticizer.

In a second aspect, the application provides a preparation method of a shrinkage-reducing polycarboxylic acid water reducing agent, which adopts the following technical scheme:

a preparation method of a shrinkage-reducing polycarboxylate superplasticizer comprises the following preparation steps:

s1, mixing sodium methacrylate and distilled water to obtain a mixed solution;

and S2, introducing nitrogen into the mixed solution, heating to 70-90 ℃, simultaneously adding the ethylene glycol polymer, the acrylic compound, the polyborate and the initiator into the mixed solution, keeping the temperature at 70-90 ℃ for 2-3h, cooling, and adjusting the pH value to obtain the shrinkage-reducing polycarboxylic acid water reducer.

By adopting the technical scheme, the initiator is adopted to promote the copolymerization reaction among the raw materials, and the compatibility among the raw materials is improved, so that the shrinkage-reducing polycarboxylate water reducer with stable performance is prepared.

Preferably, the initiator is an inorganic peroxy initiator.

In summary, the present application has the following beneficial effects:

1. according to the application, the polyborate is adopted, and can act synergistically with sodium methallylsulfonate, ethylene glycol polymer and acrylic acid compound, so that the water loss rate and the bleeding rate of the surface of concrete tend to be balanced, the shrinkage reducing effect of the shrinkage reducing polycarboxylate water reducer is greatly improved, and the shrinkage reducing effect and the stability of the water reducing effect of the shrinkage reducing polycarboxylate water reducer are improved;

2. in the application, the polyethylene glycol and the allyl polyethylene glycol are preferably compounded, the copolymerization activity of the polyethylene glycol and the allyl polyethylene glycol is further enhanced under the synergistic effect of the polyethylene glycol and the allyl polyethylene glycol, and the surface tension of water in capillary pores of concrete is reduced under the interaction of the polyethylene glycol and the allyl polyethylene glycol and other raw materials, so that the shrinkage reducing effect of the shrinkage reducing polycarboxylic acid water reducing agent is improved, and the stability of the shrinkage reducing polycarboxylic acid water reducing agent is enhanced;

3. according to the method, the initiator is adopted to promote the copolymerization reaction among the raw materials, and the compatibility among the raw materials is improved, so that the shrinkage-reducing polycarboxylate water reducer with stable performance is prepared.

Detailed Description

The present application is further illustrated in detail by the following combinations and examples, the sources of the raw materials for each example being shown in Table 1.

TABLE 1 example sources of raw materials

The polyborate used in each example is self-made, and the preparation method comprises the following steps:

pretreatment of borate ester: dissolving 20g of borate monomer in 50mL of acetone, refrigerating at-10 ℃ for 12h, taking out the frozen acetone dissolved with borate, carrying out suction filtration, adding 20mL of acetone refrigerated at-10 ℃ for 12h into the liquid obtained by suction filtration, stirring for 10min, and carrying out vacuum drying at 40 ℃ to remove acetone;

preparation of polyborate: uniformly mixing 10g of acrylamide and 3g of pretreated borate with 20mL of benzene, heating to 60 ℃ under a nitrogen atmosphere, reacting for 10min, adding 0.006g of azobisisobutyronitrile, preserving heat at 60 ℃ for 3h, heating to 75 ℃ for curing for 3h, distilling the cured material at 60 ℃ under 50kPa under reduced pressure to remove the solvent, dispersing the product after the solvent is removed in 50mL of acetone, filtering to obtain a polymerization product, and drying the polymerization product at 40 ℃ under vacuum to obtain white solid powder, namely the polyborate.

The borate is self-made, and the preparation method comprises the following steps: mixing 0.02mol of N, N-dihydroxyethyldodecylamine, 0.02mol of triethyl borate and 40mL of benzene, refluxing at 60 ℃ and 0.04MPa to remove ethanol, stirring for 1h, adding 0.02mol of N-hydroxymethyl acrylamide and 20mg of phenothiazine, refluxing at 60 ℃ and 0.04MPa for 1.5h, distilling the refluxed product at 80 ℃ and 0.8MPa, dissolving in 30mL of acetone, filtering to remove precipitate, and vacuum-drying the liquid without precipitate at 40 ℃ to obtain the finished product of the borate.

The N, N-dihydroxyethyl dodecyl amine is self-made, and the preparation method comprises the following steps: mixing 0.1mol of bromododecane with 50mL of absolute ethanol, heating the absolute ethanol mixed with the bromododecane to 90 ℃, adding 0.11mol of diethanolamine into the absolute ethanol, stirring the mixture at 90 ℃ for 0.5h, adding 0.105mol of sodium hydroxide solution, reacting the mixture for 5h, pouring the mixture into a separating funnel, standing the mixture for 2h, separating and removing dark yellow liquid impurities insoluble in the absolute ethanol to obtain a crude product of N, N-dihydroxyethyl dodecylamine, and then carrying out vacuum distillation at 60 ℃ to obtain a finished product of the N, N-dihydroxyethyl dodecylamine.

Examples

Example 1

A shrinkage-reducing polycarboxylate superplasticizer is prepared by the following preparation steps:

s1, mixing 10g of sodium methacrylate and 20g of distilled water to obtain a mixed solution;

s2, introducing nitrogen into the mixed solution, heating to 70 ℃, simultaneously adding 20g of PEG-2000, 40g of methacrylic acid, 35g of polyborate and 3g of ammonium persulfate into the mixed solution, keeping the temperature at 80 ℃ for 2h, cooling to 25 ℃, and adjusting the pH value to 7 to obtain the shrinkage-reducing polycarboxylic acid water reducer.

Examples 2 to 5

Examples 2 to 5 are based on example 1 and differ from example 1 only in that: the raw materials are different in type and dosage, and are shown in Table 2.

TABLE 2 raw material compositions and amounts of examples 1-5

Example 6

Example 6 is based on example 1 and differs from example 1 only in that: the ethylene glycol polymer is a mixture of PEG-2000 and APEG-700, and the weight ratio of the PEG-2000 to the APEG-700 is 1: 1.

examples 7 to 8

Examples 7 to 8 are based on example 6 and differ from example 6 only in that: the weight ratio of PEG-2000 to APEG-700 was varied, as shown in Table 3.

TABLE 3 examples 7-8PEG-2000 to APEG-700 weight ratios

Examples 9 to 11

Examples 9 to 11 are based on example 8 and differ from example 8 only in that: the hydroxyl number of the allyl polyethylene glycol used varies and is shown in Table 4.

TABLE 4 examples 9-11 allyl polyethylene glycol hydroxyl numbers

Examples	Example 9	Example 10	Example 11
				Allyl polyethylene glycol	APEG-2000	APEG-900	APEG-1000
Hydroxyl value (mgKOH/g)	27-30	53-63	50-55

Examples 12 to 15

Examples 12 to 15 are based on example 11 and differ from example 1 only in that: the acrylic compound used was a mixture of acrylic acid and methacrylic acid, with different weight ratios of acrylic acid to methacrylic acid, as specified in table 5.

TABLE 5 examples 12-15 weight ratio of acrylic acid to methacrylic acid

Examples	Example 12	Example 13	Example 14	Example 15
					Acrylic acid: methacrylic acid (weight ratio)	1：0.5	1：0.1	1：0.2	1：0.35

Example 16

Example 16 is based on example 15 and differs from example 15 only in that: in the step S1, 10g of sodium methacrylate, 8g of fumed silica and 20g of distilled water were mixed to obtain a mixed solution.

Example 17

Example 17 is based on example 15 and differs from example 15 only in that: in the step S1, 10g of sodium methacrylate, 10g of fumed silica and 20g of distilled water were mixed to obtain a mixed solution.

Comparative example

Comparative example 1

Comparative example 1 is based on example 2 and differs from example 2 only in that: the sodium methallylsulfonate was replaced by the same amount of polyborate.

Comparative example 2

Comparative example 2 is based on example 2 and differs from example 2 only in that: the polyethylene glycol was replaced by the same amount of sodium methallylsulfonate.

Comparative example 3

Comparative example 3 is based on example 2 and differs from example 2 only in that: methacrylic acid was replaced by the same amount of sodium methallylsulfonate.

Comparative example 4

Comparative example 4 is based on example 2 and differs from example 2 only in that: the anhydride monoester was obtained in the same amount as diethylene glycol methyl monobutyl ether.

Detection method

The following performance tests were conducted on the reduction type polycarboxylic acid water reducing agents obtained in examples 1 to 17 and comparative examples 1 to 4.

And (3) testing the net slurry fluidity: according to GB/T8077 + 2000 concrete admixture homogeneity experiment method, the cement paste fluidity is measured on the shrinkage-reducing type polycarboxylate superplasticizers prepared in examples 1-17 and comparative examples 1-4, the mixing amount of the shrinkage-reducing type polycarboxylate superplasticizer is 0.2 wt%, the fixed water-cement ratio is 0.29, the cement paste fluidity after mixing the cement paste and 1 hour is measured, the cement used in the test is P.II 42.5R cement of Guangzhou Guangxue cement production plant, and the test results are shown in Table 6.

And (3) dry shrinkage test: the dry shrinkage of cement mortar doped with the shrinkage-reducing polycarboxylic acid water reducing agents of examples 1 to 17 and comparative examples 1 to 4 was tested according to JC/T603-plus 2004 cement mortar test method, wherein the weight ratio of cement to sand was kept at 1: 2, the mixing amount of the shrinkage-reducing polycarboxylate superplasticizer is 0.2 wt%, the fluidity of the mortar is kept to be 140 +/-5 mm, the cement used in the test is P.II 42.5R cement of Guangzhou Guangxouxiu cement manufacturing plants, and the test results are shown in Table 7.

Shrinkage ratio relative percent fluctuation: under the above conditions of the dry shrinkage test, 400 cement mortar preparations were carried out and tested in each of examples 1 to 17 and comparative examples 1 to 4, and the shrinkage ratio was recorded as a₁、a₂……a₄₀₀The average shrinkage ratio was calculated as a₀(ii) a Percent shrinkage relative fluctuation (a)₁/a₀+a₂/a₀+……a₄₀₀/a₀) The calculated results are shown in Table 7, where,/400X 100%.

TABLE 6 neat paste fluidity for examples 1-17, comparative examples 1-4

TABLE 7 shrinkage ratios and relative percent variation of shrinkage ratios for examples 1-17 and comparative examples 1-4

Analyzing the data to know that:

comparing comparative examples 1-4 and example 2, it can be seen that the polyborate can act synergistically with sodium methallylsulfonate, glycol polymer and acrylic acid compound, greatly improve the compatibility among three raw materials of sodium methallylsulfonate, glycol polymer and acrylic acid compound, and improve the copolymerization activity of glycol polymer, so that the water loss rate and the bleeding rate of the surface of concrete tend to be balanced, the shrinkage reducing effect of the shrinkage reducing polycarboxylate water reducer is greatly improved, and the shrinkage reducing effect and the stability of the water reducing effect of the shrinkage reducing polycarboxylate water reducer are improved.

Comparing example 1, example 4 and example 6, it can be seen that the compatibility between the raw materials can be further improved by compounding polyethylene glycol and allyl polyethylene glycol, the copolymerization activity of the polyethylene glycol and allyl polyethylene glycol is further enhanced by the synergistic effect of the polyethylene glycol and the allyl polyethylene glycol, and the surface tension of water in concrete pores is reduced by the interaction of the polyethylene glycol and the other raw materials, so that the shrinkage reducing effect of the shrinkage reducing polycarboxylic acid water reducer is improved, and the stability of the shrinkage reducing polycarboxylic acid water reducer is enhanced.

It is understood from comparative examples 9 to 11 and example 8 that by controlling the hydroxyl value of allyl polyethylene glycol, the synergistic effect between allyl polyethylene glycol and polyethylene glycol can be promoted, the compatibility between the raw materials can be further improved, and the stability of the shrinkage reducing and water reducing performance of the shrinkage reducing polycarboxylic acid water reducing agent can be improved.

It is understood from the comparison of examples 4, 5 and 12 that acrylic acid and methacrylic acid act synergistically to provide groups such as carboxylic acid, methyl group, ether bond and the like on the groups of the obtained reduction type polycarboxylate water reducer, so that the reduction type polycarboxylate water reducer generates a large steric hindrance effect, and the reduction and water reducing performances of the reduction type polycarboxylate water reducer are remarkably improved, and the stability of the reduction type polycarboxylate water reducer is improved.

Comparing examples 16-17 with example 15, it is known that the fumed silica can improve the compatibility between the raw materials, and the fumed silica can act synergistically with the ethylene glycol polymer, so that the copolymerization activity of polyethylene glycol is improved, and the possibility of self-agglomeration is reduced, thereby further balancing the water loss rate and the bleeding rate of the concrete surface, and enhancing the shrinkage reducing effect of the shrinkage reducing polycarboxylic acid water reducer.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. The shrinkage-reducing polycarboxylate water reducer is characterized by comprising, by weight, 10-25 parts of sodium methallylsulfonate, 10-20 parts of distilled water, 15-30 parts of glycol polymer, 20-40 parts of acrylic compound and 20-40 parts of polyborate.

2. The reduction type polycarboxylate superplasticizer according to claim 1, characterized in that: the ethylene glycol polymer is a mixture of polyethylene glycol and allyl polyethylene glycol.

3. The reduction type polycarboxylate superplasticizer according to claim 2, characterized in that: the weight ratio of the polyethylene glycol to the allyl polyethylene glycol is (0.1-0.2): 1.

4. the reduction type polycarboxylate superplasticizer according to claim 2, characterized in that: the hydroxyl value of the allyl polyethylene glycol is 27-63 mgKOH/g.

5. The reduction type polycarboxylate superplasticizer according to claim 1, characterized in that: the acrylic compound is a mixture of acrylic acid and methacrylic acid.

6. The reduction type polycarboxylate water reducer according to claim 5, characterized in that: the weight ratio of the acrylic acid to the methacrylic acid is 1: (0.1-0.35).

7. The reduction type polycarboxylate superplasticizer according to claim 1, characterized in that: also comprises 8-10 parts by weight of fumed silica.

8. The preparation method of the reduction type polycarboxylate superplasticizer according to any one of claims 1 to 7 is characterized by comprising the following preparation steps:

s1, mixing sodium methacrylate and distilled water to obtain a mixed solution;

9. The preparation method of the reduction type polycarboxylate superplasticizer according to claim 8, characterized by comprising the following steps: the initiator is an inorganic peroxy initiator.