CN110172128A - A kind of efficient viscosity reduction water-reducing agent of brush-type polycarboxylic acids and preparation method thereof - Google Patents

Abstract

A brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent and its preparation method: the brush-type polycarboxylate high-efficiency viscosity-reducing and water-reducing agent uses ammonium persulfate as an initiator, maleic anhydride, vinyltriethoxysilane, Allyl alcohol polyoxyethylene ether is used as a monomer, and mercaptopropionic acid is used as a chain transfer agent, which is obtained through addition polymerization. The brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention has a good viscosity-reducing effect in gelling materials.

Description

A brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent and its preparation method

technical field

The invention relates to a polycarboxylate water-reducer for concrete and a preparation method thereof, in particular to a polycarboxylate high-efficiency viscosity-reducing water-reducer capable of significantly reducing the viscosity of concrete with low water-binder ratio and multiple gel components and its preparation method.

Background technique

As a key component of concrete, water reducing agent plays a decisive role in the workability of fresh concrete and the performance of hardened concrete.

At present, the most widely used polycarboxylate (PCE) water reducer is 15 to 20 times that of ordinary concrete in low water-binder ratio and complex gelling component systems. However, concrete with low water-binder ratio and complex cementitious component system still has the defects of high viscosity and low fluidity, which have extremely adverse effects on mixing, pumping and molding.

The traditional PCE molecule has a comb-shaped structure, the main chain is connected by C-C bonds, and there are anchor groups such as carboxyl and sulfonic acid groups on the main chain of the molecule, which can be adsorbed on the surface of the gelling component particles, and the long hydrophilic side chain can provide The steric hindrance forms a layer of polymer adsorption layer with a certain thickness. When the particles of the gelling component are close to each other, the steric hindrance effect provided by the side chain will prevent the particles from approaching each other and agglomeration, so as to disperse the particles and reduce the viscosity of the system. According to the action mechanism of comb-type PCE, for low water-to-binder ratio and complex gelling component systems, in order to achieve the purpose of reducing viscosity and improving fluidity, it is necessary to further enhance the adsorption and steric hindrance effect of PCE to prevent the gelling component Agglomeration of particles, especially particles of auxiliary cementitious materials.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the defects of high viscosity and poor workability of concrete with low water-binder ratio and complex gelling component system, and provide a brush-type polymer for concrete with low water-binder ratio and complex gelling component system. Carboxylic acid high-efficiency viscosity-reducing and water-reducing agent and its preparation method, using the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent can significantly reduce the viscosity of ultra-high performance concrete (UHPC), and also has high water-reducing rate and low cost , Simple preparation process and the like.

The technical solution adopted by the present invention to solve the technical problem is a brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent, and its brush-type molecular structure general formula is as follows:

In the formula, a, b, and c respectively represent the degree of polymerization of each monomer in the polymer, wherein, a:b:c=1~5:3~7:1~5.

The weight-average molecular weight Mw of the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent is _6000-18000 (preferably 8000-15000).

The preparation method of the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention uses ammonium persulfate (APS) as the initiator, maleic anhydride (MAH), vinyltriethoxysilane (VTEO), allyl alcohol Polyoxyethylene ether (APEG) is used as a monomer, mercaptopropionic acid is used as a chain transfer agent, and addition polymerization is carried out in deionized water.

Further, the weight ratio of each raw material is: 0.1~10 parts of ammonium persulfate (preferably 0.5~8 parts; more preferably 1.0~6.0; further preferably 2.0~5.0), 3~30 parts of maleic anhydride (preferably 5~ 25 parts; more preferably 8~20; more preferably 10~15), vinyltriethoxysilane 1~20 parts (preferably 2~15 parts; more preferably 4~12; further preferably 6~10), vinyl triethoxysilane 50~200 parts of propanol polyoxyethylene ether (preferably 60~180 parts; more preferably 80~160; further preferably 90~150 parts), 0.1~2 parts of mercaptopropionic acid (preferably 0.3~1.6 parts; more preferably 0.5~1.2 parts ; more preferably 0.7~1.0), 60-80 parts of deionized water (preferably 65~75 parts; more preferably 68-72 parts).

Further, the specific operation steps are as follows:

(1) Dissolve ammonium persulfate in deionized water to prepare an initiator solution;

(2) Dissolve mercaptopropionic acid in deionized water to prepare a chain transfer agent solution;

(3) Put the four-neck flask containing allyl alcohol polyoxyethylene ether, maleic anhydride, vinyl triethoxy silicon, deionized water, and stirrer in an oil bath, heat up to the specified temperature, and use The peristaltic pump starts to evenly add the initiator solution and the chain transfer agent solution dropwise. After the dropwise addition, continue to keep warm for 2~4h to carry out the addition polymerization reaction;

(4) Cool the reaction product to below 40°C, add alkali (preferably NaOH) to adjust the pH value to 6~7 (preferably 7).

Further, in step (1), the drip rate of the initiator solution is 1-2 mL/min.

Further, in step (2), the dropping rate of the chain transfer agent solution is 0.8-1.5 mL/min.

Further, in step (3), the reaction temperature is 60-90°C.

Further, in step (3), the initiator solution and the chain transfer agent solution are added dropwise at the same time.

The technical principle of the present invention is to synthesize a brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent through chemical design.

The applicant found through research that: the degree of dispersion of the cementitious component particles and the surface tension of the liquid phase of the cementitious material are closely related to the viscosity of the concrete. The dispersion degree of the gelling component particles mainly depends on the interaction force and steric hindrance effect between the particles, increasing the electrostatic repulsion and steric hindrance effect between the particles can effectively improve the dispersion degree of the gelling component particles; The surface tension of the liquid phase of the material is directly related to the surface activity of the admixture used.

Based on the above research results, the present invention is based on improving the electrostatic repulsion between the particles of the gelling component, the steric hindrance effect and the surface activity of the water reducer, and through the control of the synthesis process, a brush with a short main chain and a long side chain is prepared. Type polycarboxylate superplasticizer, and by using monomers with high adsorption group density to improve the adsorption of the main chain, using monomers with high surface activity to improve the surface activity of polycarboxylate superplasticizers, further reducing the viscosity of concrete, Improve mobility.

The brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention has an amount of 1% to 3% of the total mass of the gelling material.

The brush-type polycarboxylate high-efficiency viscosity-reducing and water-reducing agent of the present invention can be mixed with at least one admixture known in the prior art, including early-strength agents, air-entraining agents, defoamers, shrinkage reducing agents and expansion agents. agent etc.

The molecular structure of the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention has the structural characteristics of short main chain and relatively long side chain. Part of the pore solution shows a higher degree of molecular freedom, and its molecular chains are stretched to expose more carboxyl groups and silanol groups, which helps PCE to form a dense adsorption layer on the surface of the gelling component and increase the PCE in gelling. The number of adsorption on the surface of the component; and due to the small molecular weight, the brush-type PCE has high surface activity, which can significantly reduce the surface tension of the liquid phase of the gelling material.

The preparation method of the present invention is based on the theory of chemical design and synthesis, and controls the length of the main chain and the density of the side chain; it uses maleic anhydride with high carboxyl density and a silane coupling agent containing silanol to enhance the polycarboxylate water reducer in the gelling component. The amount of adsorption on the surface; the silane coupling agent containing double bonds is introduced into the main chain of the polycarboxylate superplasticizer through addition polymerization to improve the surface activity of the polycarboxylate superplasticizer and significantly reduce the surface tension of the liquid phase of the gelling material system .

Compared with the existing water reducer, the present invention has the following advantages: (1) The water reducer of the present invention has a unique brush structure, which has strong adsorption and steric hindrance; (2) The present invention has a simple synthesis method , strong operability, low production cost, and less environmental pollution; (3) The water reducer prepared by the method of the present invention has the advantages of good viscosity reduction in complex gelling component systems, high water reduction rate, low dosage, Good adaptability and other advantages.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention, it should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, after reading the present invention, those skilled in the art will understand various equivalents of the present invention Modifications in form all fall within the scope defined by the appended claims of this application.

Example 1

1g APS was dissolved in deionized water to make initiator solution, 0.39g mercaptopropionic acid was dissolved in water to make chain transfer agent solution; Place the four-necked flask in an oil bath, and after heating up to 65°C, use a peristaltic pump to start adding the initiator solution and the chain transfer agent solution evenly; the dripping rate of the initiator solution is about 1 mL/min, and the chain transfer agent The dripping rate of the solution is about 0.8 mL/min, and the temperature is continued for 4 hours after the dropping; then, the temperature of the reaction product is lowered to 40°C, and NaOH is added to adjust the pH value to 7 to obtain the high-efficiency viscosity-reducing brush-type polycarboxylic acid of the present invention. Water reducing agent.

Example 2

6.8g APS was dissolved in deionized water to make initiator solution, 1.23g mercaptopropionic acid was dissolved in water to make chain transfer agent solution; 180g APEG, 25g MAH, 8g VTEO, 220g deionized water, stirrer The four-necked flask was placed in an oil bath, and after the temperature was raised to 85°C, the initiator solution and the chain transfer agent solution were evenly added dropwise with a peristaltic pump. The dropping rate of the initiator solution is about 2 mL/min, the dropping rate of the chain transfer agent solution is about 1.2 mL/min, and the temperature is kept for 3 hours after the dropping. Finally, the temperature of the reaction product was lowered to 39°C, and NaOH was added to adjust the pH value to 7 to obtain the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention.

Example 3

Dissolve 4.6g of APS in deionized water to make an initiator solution, and dissolve 0.99g of mercaptopropionic acid in water to make a chain transfer agent solution. Next, put 120g APEG, 17.16g MAH, 1.85g VTEO, 160g deionized water, and a four-neck flask with a stirrer in an oil bath, and after heating up to 75°C, use a peristaltic pump to evenly add the initiator solution and chain transfer agent solution. The dropping rate of the initiator solution is about 1.2 mL/min, the dropping rate of the chain transfer agent solution is about 1.2 mL/min, and the temperature is kept for 2.5 hours after the dropping. Finally, lower the temperature of the reaction product to below 38°C, add NaOH to adjust the pH value to 6.9, and obtain the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent of the present invention.

Comparative Application Example Commercially available Sika ViscoCrete 3301 comb-type polycarboxylate water reducer. The material used is P. I42.5 benchmark cement and silica fume, the water-cement ratio is 0.18, the silica fume content is 20%, and the water reducing agent is 2%. The PCE sample was fully dissolved in 0.1mol/L NaNO ₃ solution and filtered through a 0.22 μm needle filter, and the molecular weight of the water reducer was determined by using a Waters 1515 gel permeation chromatograph from Waters Corporation of the United States; Type automatic control tensiometer to test the surface tension of the water reducer solution with a concentration of 10%; use the Sievers InnovOx total organic carbon analyzer of GE Company in the United States to test the total organic carbon content, and calculate the water reducer in the gelled material according to the test results. Adsorption on the particle surface; fluidity and water reducing rate are carried out in accordance with the relevant provisions of GB8076-2008 "Specification for Concrete Admixtures", and the rheological parameters are tested in the RheoPlus QC coaxial cylinder rheometer of Anton Paar Company in Germany.

Table 1 The physical and chemical property test comparison table of embodiment 1～3 and comparative application embodiment

Table 2 Comparison Table of Basic Performance Tests of Examples 1-3 and Comparative Application Examples

It can be seen from Table 1 that (1) the detected weight-average molecular mass Mw is ₁₀₉₃₃ ~13159, and the molecular weights of the examples are all smaller than those of the comparative examples, which proves that the examples have a brush structure with short main chains and long side chains; (2) implementation The surface tension of the example solution is 29.80~30.18mN·m ^-1 , which is lower than that of the comparative example; (3) The adsorption capacity of the example solution in the low water-binder ratio cement-silica fume system is 4.56~5.33 mg/g, which is significantly greater than that of the comparative example the amount of adsorption. From the results in Table 2, it can be seen that (1) the initial fluidity of the example is significantly increased by about 50 mm compared with the comparison example, showing an excellent water reduction effect; (2) the yield stress of the example is 1.27-1.39 Pa, etc. The effective plastic viscosity is 2.22~2.45 Pa s, compared with the comparative example, the yield stress is reduced by 7.94%~15.89%, and the plastic viscosity is reduced by 59.84%~63.61%. The cement-silica fume system has a significant effect of reducing viscosity and water.

Claims (10)

1. A brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent, characterized in that: its brush-type molecular structure general formula is as follows: In the formula, a, b, and c respectively represent the degree of polymerization of each monomer in the polymer, wherein, a:b:c=1~10:1~5:1~5. 2. A preparation method of brush-type polycarboxylic acid high-efficiency viscosity-reducing water-reducing agent as claimed in claim 1, is characterized in that: with ammonium persulfate as initiator, maleic anhydride, vinyltriethoxysilane, Allyl alcohol polyoxyethylene ether is used as a monomer, mercaptopropionic acid is used as a chain transfer agent, and addition polymerization is carried out in deionized water. 3. the preparation method of brush-type polycarboxylate high-efficiency viscosity-reducing and water-reducing agent according to claim 2, is characterized in that, the weight ratio of each raw material is: 0.1～10 parts of ammonium persulfate, 3～10 parts of maleic anhydride 30 parts, 1-20 parts of vinyl triethoxysilane, 50-200 parts of allyl alcohol polyoxyethylene ether, 0.1-2 parts of mercaptopropionic acid, 60-80 parts of deionized water. 4. the preparation method of brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to claim 3, is characterized in that, the weight ratio of each raw material is: 0.5～8 parts of ammonium persulfate, 5～8 parts of maleic anhydride 25 parts, 2~15 parts of vinyl triethoxysilane, 60~180 parts of allyl alcohol polyoxyethylene ether, 0.3~1.6 parts of mercaptopropionic acid, 65~75 parts of deionized water. 5. the preparation method of brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to claim 4, is characterized in that, the weight ratio of each raw material is: ammonium persulfate 1.0～6.0 parts, maleic anhydride 8～ 20 parts, 4~12 parts of vinyl triethoxysilane, 80~160 parts of allyl alcohol polyoxyethylene ether, 0.5~1.2 parts of mercaptopropionic acid, 68~72 parts of deionized water. 6. according to the preparation method of the described brush-type polycarboxylic acid high-efficiency viscosity-reducing water-reducing agent of one of claim 2-5, it is characterized in that, concrete steps are as follows: (1) Dissolve ammonium persulfate in deionized water to prepare an initiator solution; (2) Dissolve mercaptopropionic acid in deionized water to prepare a chain transfer agent solution; (3) Put the four-neck flask containing allyl alcohol polyoxyethylene ether, maleic anhydride, vinyl triethoxy silicon, deionized water, and stirrer in an oil bath, heat up to the specified temperature, and use The peristaltic pump starts to evenly add the initiator solution and the chain transfer agent solution dropwise. After the dropwise addition, continue to keep warm for 2~4h to carry out the addition polymerization reaction; (4) Cool the reaction product to below 40°C, add alkali to adjust the pH value to 6~7, and it is ready. 7. The method for preparing the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to claim 6, characterized in that: in step (1), the dripping rate of the initiator solution is 1-2 mL/min. 8. The method for preparing the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to claim 6 or 7, characterized in that: in step (2), the dropping rate of the chain transfer agent solution is 0.8-1.5 mL/ min. 9. The method for preparing the brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to any one of claims 6-8, characterized in that: in step (3), the reaction temperature is 60-90 °C. 10. The method for preparing brush-type polycarboxylic acid high-efficiency viscosity-reducing and water-reducing agent according to any one of claims 6-9, characterized in that: in step (3), the initiator solution and the chain transfer agent solution are added dropwise at the same time.