阅读说明：本技术 一种制备淀粉基高性能减水剂的方法及其产品 (Method for preparing starch-based high-performance water reducing agent and product thereof ) 是由 王万金 赖振峰 黄靖 冷发光 丁印 王浩 于 2021-03-05 设计创作，主要内容包括：本发明公开了一种制备淀粉基高性能减水剂的方法及其产品,该方法以淀粉基功能大单体为主链骨架,通过不饱和聚醚、不饱和羧酸接枝到淀粉基主链骨架上,形成旋转梳型结构分子形式。本发明还公开了上述淀粉基高性能减水剂的制备方法,主要包括可控的酸降解淀粉原料的制备,淀粉基功能大单体的制备,自由基共聚反应。该工艺简单,制备过程中不产生废液、废气和废渣,为绿色低碳合成工艺。本发明的淀粉基高性能减水剂可以有效解决聚羧酸减水剂在掺量的敏感性、适应性问题,提高混凝土和易性、粘聚性等工作状态,降低混凝土收缩开裂。对于不同的水泥、掺合料、机制砂、尾矿砂、环境温度及混凝土配合比波动都有着优异的适应性。(The invention discloses a method for preparing a starch-based high-performance water reducing agent and a product thereof. The invention also discloses a preparation method of the starch-based high-performance water reducing agent, which mainly comprises the steps of preparing the controllable acid-degraded starch raw material, preparing the starch-based functional macromonomer and carrying out free radical copolymerization reaction. The process is simple, does not produce waste liquid, waste gas and waste residue in the preparation process, and is a green low-carbon synthesis process. The starch-based high-performance water reducing agent can effectively solve the problems of sensitivity and adaptability of a polycarboxylic acid water reducing agent in the mixing amount, improves the working states of workability, cohesiveness and the like of concrete, and reduces shrinkage cracking of the concrete. The concrete admixture has excellent adaptability to different cements, admixtures, machine-made sands, tailing sands, environmental temperatures and concrete mixing ratio fluctuation.)

1. The method for preparing the starch-based high-performance water reducing agent is characterized in that the starch-based high-performance water reducing agent takes a starch-based functional macromonomer as a main chain framework, and is grafted to the starch-based main chain framework through unsaturated polyether and unsaturated carboxylic acid to form the starch-based high-performance water reducing agent in a rotating comb-shaped structure molecule form, wherein a starch-based glucose unit chain is taken as a main chain, and the unsaturated polyether and the unsaturated carboxylic acid are taken as side chains;

the preparation method of the starch-based high-performance water reducing agent comprises the following steps:

preparing a controllable acid-degraded starch raw material: preparing 20-90% of starch mixture by mass percent from starch by using water as a reaction medium, and adding an acidolysis catalyst with the use amount of 1-15% of the mass of the starch mixture and an oxidant with the use amount of 1-10% of the mass of the starch mixture to react to obtain a controllable acid-degraded starch raw material;

preparation of starch-based functional macromonomer: mixing the controllable acid-degraded starch raw material with unsaturated carboxylic acid or acid anhydride with the amount of 3-30% of the mass of the controllable acid-degraded starch raw material, and adding an esterification catalyst with the amount of 1-5% of the mass of the controllable acid-degraded starch raw material and a polymerization inhibitor with the amount of 0.02-0.2% of the mass of the controllable acid-degraded starch raw material to perform esterification reaction to obtain a starch-based functional macromonomer;

free radical copolymerization: mixing (5-20) starch-based functional macromonomer, unsaturated polyether and deionized water: (5-15): (65-85) adding an initiator with the mass of 0.2% -1.5% under stirring for prepolymerization reaction to obtain a first solution, and then respectively mixing the monomer A, the monomer B and the chain transfer agent in the ratio of (75-90): (5-20): (1-5) mixing the two solutions in a mass ratio to form a second solution, wherein the mass ratio of the first solution to the second solution is (90-99): (1-10), dropwise adding the second solution into the first solution, stirring to fully react to obtain a mixed solution, and neutralizing the mixed solution with an alkaline solution until the pH value is 5-7 to obtain a starch-based high-performance water reducing agent;

the monomer A is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid or maleic anhydride, and sodium salt, potassium salt or ammonium salt of maleic acid; the monomer B is one or more of sodium allyl sulfonate, sodium methallyl sulfonate and sodium styrene sulfonate.

2. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the starch is one or more of corn starch, tapioca starch, sweet potato starch, wheat starch, bean starch or modified starch.

3. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the acidolysis catalyst is one or more of sulfuric acid, nitric acid, sodium bisulfate, sulfamic acid or p-toluenesulfonic acid.

4. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the oxidizing agent is one or more of potassium permanganate, hydrogen peroxide, ammonium persulfate, potassium persulfate or periodic acid.

5. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the controllable acid-degradable starch is glucose unit, the polymerization degree of the glucose unit is 10-150, and the weight average molecular weight Mw is 1600-25000.

6. The method for preparing the starch-based high performance water reducing agent according to claim 1, wherein the unsaturated carboxylic acid is one or more of methacrylic acid, acrylic acid or maleic acid, and the anhydride is maleic anhydride.

7. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the esterification catalyst is one or more of concentrated sulfuric acid, p-toluenesulfonic acid, sulfonic acid type strong acid cation exchange resin, and tetrachloroaluminum ether complex.

8. The method for preparing the starch-based high performance water reducing agent according to claim 1, wherein the polymerization inhibitor is one or more of tert-butyl catechol, hydroquinone, methylaniline or benzidine.

9. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the weight average molecular weight Mw of the starch-based functional macromonomer is 1800-30000, wherein the proportion of the starch-based functional macromonomer Mw in the distribution range of 1800-5000 is 35% -55%, and the proportion of the starch-based functional macromonomer Mw in the distribution range of 5000-30000 is 45% -65%.

10. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the unsaturated polyether is one or more of polyoxyethylene methacrylate, allyl polyoxyethylene ether, methallyl polyoxyethylene ether, isopentenyl polyoxyethylene ether and vinyl polyglycol ether, and the weight average molecular weight Mw of the unsaturated polyether is 1000-5000.

11. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the initiator is one or more of ferrous ammonium sulfate, cerium ammonium nitrate, potassium persulfate, ammonium persulfate and hydrogen peroxide.

12. The method for preparing the starch-based high-performance water reducing agent according to claim 1, wherein the chain transfer agent is one or more of 2-mercaptoethanol, 2-mercaptoacetic acid, 3-mercapto-1-propanol, 3-mercaptopropionic acid, 1-hexanethiol and dodecyl mercaptan.

13. A starch-based high performance water reducer prepared by the method for preparing a starch-based high performance water reducer according to any one of claims 1 to 12.

Technical Field

The invention relates to the field of concrete admixtures, in particular to a method for preparing a starch-based high-performance water reducing agent and a product thereof.

Background

Concrete admixtures are the core materials for preparing and influencing the performance of modern concrete. The development of the preparation and application technology of the high-performance green additive is beneficial to ensuring the quality of concrete and promoting the development of green buildings and durable buildings. Along with the increase of environmental protection force in China, the exploitation of natural resources for concrete is limited, a large amount of materials such as machine-made sand, tailing sand, recycled aggregate, artificial composite admixture and the like are used, and due to factors such as material variety change, grain type change, unreasonable grading, quality fluctuation and the like, the wrapping property and the workability of slurry of freshly mixed concrete are greatly different, the problems of segregation, bleeding, bottom grabbing, pump blockage and the like easily occur, and the problems of construction and engineering quality are seriously influenced.

The water reducing agent applied in the engineering of China mainly comprises polycarboxylic acid series, naphthalene series, aliphatic series, sulfamate series and other water reducing agent varieties. However, these water reducers are prepared from chemical raw materials obtained from petrochemical industry and coal chemical industry, and have the characteristics of high emission and high energy consumption, and some varieties release harmful substances in the preparation process, so that the environment is polluted, and the degradability is poor. And with the gradual attention on environmental protection, people also care about the safety problems of self and environment while pursuing the performance of building materials, so that new raw materials and a synthesis method are urgently needed to be explored, and a green low-carbon high-efficiency water reducing agent is researched and developed.

Starch is a renewable resource of biomass, and has the advantages of complete degradability, no pollution to the environment, low price and the like. Under the pressure that petrochemical resources are reduced day by day and the cost of petrochemical raw materials is rapidly increased at present, the concrete admixture prepared by effectively utilizing starch has wide development prospect. The water reducer prepared by using starch as a raw material meets the national low-carbon policy and the market demand, but the research on the aspect is still in the research and development stage of a laboratory and does not enter the engineering application stage.

The molecular formula of the starch is (C)₆H₁₀O₅)_nIt is a polysaccharide comprising a plurality of glucose units connected to each other by glycosidic bonds to form a long chain, and can be regarded as a high polymer of glucose. The chemical properties of the nucleoside bond and the hydroxyl in the molecular structure of the modified starch polymer are active, and an anionic group is introduced into the molecular structure of the starch by a chemical modification means to form the modified starch polymer with the function of the water reducing agent. In recent years, starch water reducing agents have been paid attention to by broad scholars as green and environment-friendly water reducing agents. For example, the prior art discloses a test research on a corn starch modified polycarboxylic acid water reducer, oxidized starch is used for partially replacing TPEG polyether, and the starch modified polycarboxylic acid water reducer is synthesized by free radical copolymerization. Due to the low activity of oxidized starch, the reaction efficiency is relatively low in the radical copolymerization reaction. And a small amount of oxidized starch is used as a side chain to replace polyether, so that the defects of the existing polycarboxylic acid water reducer are only overcome, the main raw material is still a polycarboxylic acid raw material, the starch consumption is low, and the water reducer is not a real water reducer taking starch as the main raw material. Schaffer et al disclose a novel starch-based polycarboxylic acid water reducing agent and a preparation method thereof, which comprises the steps of reacting starch with an oxidant, an esterifying agent and an etherifying agent in sequence, and then carrying out free radical polymerization to obtain the water reducing agent by taking the starch as a branched chain macromonomer in the synthesis of polycarboxylic acid. The method has the advantages of low starch consumption, complex treatment process and more post-treatment procedures, and is only used as branched chains to replace partial polyether, thereby being difficult to realize industrial production. The method develops an organic silicon and saccharide co-modified polycarboxylate water reducer and a preparation method thereof by Zengxiajun and the like, wherein the polycarboxylate water reducer is co-modified by saccharide modified (methyl) acrylate macromonomer, organic silicon modified macromonomer and polyether macromonomer, and the adopted saccharide modifier is glucose, fructose and lactoseAnd small molecules such as xylose or starch hydrolysis sugar, and the like, and the water reducing agent is not prepared by directly utilizing starch.

Therefore, how to use starch as the main raw material of the water reducer in a large amount, improve the efficiency of starch graft copolymerization reaction and be capable of industrially producing and preparing the high-performance water reducer is still a challenge. If the key technology in the aspect is broken through, the method can play a great promoting role in the water reducing agent industry and the starch industry.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preparing a starch-based high-performance water reducing agent and a product thereof. The raw materials are wide in source, low in cost and excellent in performance; the preparation method has simple production process, does not generate waste liquid, waste gas and waste residue in the preparation process, and is a green synthesis process. The starch-based high-performance water reducing agent provided by the invention effectively solves the problems of sensitivity and adaptability of a polycarboxylate water reducing agent in the mixing amount, improves the working states of workability, cohesiveness and the like of concrete, and reduces the shrinkage cracking of the concrete. The mortar has excellent adaptability to different cement, admixture, machine-made sand, tailing sand, environment temperature and concrete mixing ratio fluctuation, and is more favorable for solving the workability problems of segregation, bleeding and the like of concrete caused by using the machine-made sand, the tailing sand, recycled aggregate and poor gradation.

In order to solve the technical problems, the invention provides the following technical scheme:

the invention provides a method for preparing a starch-based high-performance water reducing agent, which takes a starch-based functional macromonomer as a main chain skeleton, and is grafted to the starch-based main chain skeleton through unsaturated polyether and unsaturated carboxylic acid to form the starch-based high-performance water reducing agent in a rotating comb-shaped structure molecular form, wherein a starch-based glucose unit chain is taken as a main chain, and the unsaturated polyether and the unsaturated carboxylic acid are taken as side chains;

the preparation method of the starch-based high-performance water reducing agent comprises the following steps:

preparing a controllable acid-degraded starch raw material: preparing 20-90% of starch mixture by mass percent from starch by using water as a reaction medium, and adding an acidolysis catalyst with the use amount of 1-15% of the mass of the starch mixture and an oxidant with the use amount of 1-10% of the mass of the starch mixture to react to obtain a controllable acid-degraded starch raw material;

preparation of starch-based functional macromonomer: mixing the controllable acid-degradable starch raw material with unsaturated carboxylic acid or anhydride with the amount of 3-30% of the mass of the controllable acid-degradable starch raw material, and adding an esterification catalyst with the amount of 1-5% of the mass of the controllable acid-degradable starch raw material and a polymerization inhibitor with the amount of 0.02-0.2% of the mass of the controllable acid-degradable starch raw material to perform esterification reaction to obtain a starch-based functional macromonomer;

free radical copolymerization: mixing (5-20) starch-based functional macromonomer, unsaturated polyether and deionized water: (5-15): (65-85) adding an initiator with the mass of 0.2% -1.5% under stirring for prepolymerization reaction to obtain a first solution, and then respectively mixing the monomer A, the monomer B and the chain transfer agent in the ratio of (75-90): (5-20): (1-5) mixing the two solutions in a mass ratio to form a second solution, wherein the mass ratio of the first solution to the second solution is (90-99): (1-10), dropwise adding the second solution into the first solution, stirring to enable the second solution to react fully to obtain a mixed solution, and neutralizing the mixed solution with an alkaline solution until the pH value is 5-7 to obtain the starch-based high-performance water reducing agent.

Wherein the starch is one or more of corn starch, cassava starch, sweet potato starch, wheat starch, bean starch or modified starch.

Wherein, the acidolysis catalyst is one or more of sulfuric acid, nitric acid, sodium bisulfate, sulfamic acid or p-toluenesulfonic acid.

Wherein the oxidant is one or more of potassium permanganate, hydrogen peroxide, ammonium persulfate, potassium persulfate or periodic acid.

The controllable acid-degradable starch is a glucose unit, the polymerization degree of the glucose unit is 10-150, and the weight average molecular weight Mw of the glucose unit is 1600-25000.

Wherein the unsaturated carboxylic acid is one or more of methacrylic acid, acrylic acid or maleic acid, and the anhydride is maleic anhydride.

Wherein the esterification catalyst is one or more of concentrated sulfuric acid, p-toluenesulfonic acid, sulfonic acid type strong acid cation exchange resin and tetrachloroaluminum ether complex.

Wherein the polymerization inhibitor is one or more of tert-butyl catechol, hydroquinone, methylaniline or benzidine.

Wherein the weight average molecular weight Mw of the starch-based functional macromonomer is 1800-30000, the proportion of the starch-based functional macromonomer Mw in the 1800-5000 distribution interval is 35-55%, and the proportion of the starch-based functional macromonomer Mw in the 5000-30000 distribution interval is 45-65%.

The unsaturated polyether is one or more of methacrylic acid polyoxyethylene ester, allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, isopentene polyoxyethylene ether and vinyl polyglycol ether, and the weight average molecular weight Mw of the unsaturated polyether is 1000-5000.

Wherein the initiator is one or more of ferrous ammonium sulfate, ammonium ceric nitrate, potassium persulfate, ammonium persulfate and hydrogen peroxide.

Wherein the monomer A is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid or maleic anhydride, and sodium salt, potassium salt or ammonium salt of maleic acid.

Wherein the monomer B is one or more of sodium allyl sulfonate, sodium methallyl sulfonate and sodium styrene sulfonate.

Wherein the chain transfer agent is one or more of 2-mercaptoethanol, 2-mercaptoacetic acid, 3-mercapto-1-propanol, 3-mercaptopropionic acid, 1-hexanethiol and dodecyl mercaptan.

Wherein, the preparation of the controllable acid-degraded starch raw material comprises the following steps: preparing 20-90% of starch mixture by mass percent by using water as a reaction medium, adding an acidolysis catalyst with the amount of 1-15% of the mass of the starch mixture, uniformly mixing, heating to 50-80 ℃, hydrolyzing for 2-10 h, then adding an oxidant with the amount of 1-10% of the mass of the starch mixture, uniformly mixing, vacuum drying, and reacting for 1-5 h at 80-150 ℃ to obtain the controllable acid-degraded starch raw material.

Wherein, the preparation of the starch-based functional macromonomer: adding the controllable acid-degradable starch raw material and unsaturated carboxylic acid or anhydride with the amount of 3-30% of the mass of the controllable acid-degradable starch raw material into a reactor, adding an esterification catalyst with the amount of 1-5% of the mass of the controllable acid-degradable starch raw material and a polymerization inhibitor with the amount of 0.02-0.2% of the mass of the controllable acid-degradable starch raw material, stirring and heating to 60-130 ℃ for esterification reaction, wherein the reaction time is 2-10 hours, and thus the starch-based functional macromonomer is obtained.

Wherein the free radical copolymerization reaction: mixing (5-20) starch-based functional macromonomer, unsaturated polyether and deionized water: (5-15): (65-85), heating to 50-95 ℃, adding an initiator with the mass of 0.2-1.5% under stirring to perform prepolymerization for 0.5-2 h to obtain a first solution, and then adding the monomer A, the monomer B and the chain transfer agent according to the weight ratio of (75-90): (5-20): (1-5) mixing the two solutions in a mass ratio to form a second solution, wherein the mass ratio of the first solution to the second solution is (90-99): (1-10), dropwise adding the second solution into the reaction kettle within 0.5-2 h, stirring and reacting for 1-5 h after dropwise adding, cooling to 25-50 ℃ after reaction, and neutralizing the solution in the reaction kettle with an alkaline solution until the pH value is 5-7 to obtain the starch-based high-performance water reducer.

The invention provides a starch-based high-performance water reducing agent, which is prepared by using any one of the methods.

In conclusion, the invention takes starch as a main raw material, and prepares the functional macromonomer of starch molecules connected by ester groups and having reactive double bond groups through continuous multi-step reaction under acidolysis catalyst, oxidant and specific reaction conditions. The starch-based high-performance water reducing agent takes a starch-based functional macromonomer as a main chain framework, and is grafted to the starch-based main chain framework through unsaturated polyether and unsaturated carboxylic acid to form the starch-based high-performance water reducing agent in a rotating comb-shaped structure molecule form, wherein a starch-based glucose unit chain is taken as a main chain, and the unsaturated polyether and the unsaturated carboxylic acid are taken as side chains. The main chain of the water reducing agent is a special modified starch structure, has a molecular conformation with a rotating comb structure, and has a better steric hindrance effect, so that the fluidity of a system is improved. Meanwhile, the main chain of the starch-based glucose unit contains a large amount of hydroxyl, so that the starch-based glucose unit has strong water molecule hydrogen bond complexing capability, can enhance the binding force between cement particles attached with water reducing agent molecules and water, is favorable for improving the workability of concrete and reducing segregation and bleeding phenomena.

By adopting the technical scheme, the invention at least has the following beneficial effects:

1. the water reducing rate of the water reducing agent prepared by the preparation method disclosed by the invention is up to 25-35%, and the requirement of a high-performance water reducing agent is met; the polycarboxylic acid water reducer has good matching property with the polycarboxylic acid water reducer, can greatly improve the adaptability of the polycarboxylic acid to various cement and sand, and reduces the sensitivity of the mixing amount;

2. the water reducing agent disclosed by the invention has excellent adaptability to different cements, admixtures, machine-made sand, tailing sand, environmental temperature and concrete mixing ratio fluctuation. The concrete has the advantages of improving the workability and cohesiveness of the concrete, preventing bleeding and reducing the shrinkage and cracking of the concrete.

3. The invention has simple production process, does not generate waste liquid, waste gas and waste residue in the polymerization process, is a green synthesis process and is suitable for industrial production.

The key technical points of the invention are as follows: (1) and (3) carrying out acid degradation modification on the starch by adopting inorganic acid and an oxidant, and breaking the original deoxyglucose long chain of the starch molecule to obtain the modified degraded starch with different molecular weights. Through multi-step control of feeding sequence and proportion, reaction temperature and time, the purpose of controlling acid degradation and section cutting of starch molecules is achieved, and finally the starch molecule chain segment with the polymerization degree of glucose units of 10-150 and the weight average molecular weight Mw range of 1600-25000 is obtained. Preferably, unsaturated carboxylic acid and unsaturated anhydride are subjected to esterification reaction with the segmented starch to form double bond groups which take segmented starch molecules as a main chain framework and are connected by ester groups and have reactivity, the main chain framework functional macromonomer for the starch-based high-performance water reducing agent is prepared, and the Mw range is 1800-30000. (2) In the aqueous solution free radical copolymerization reaction of a starch functional macromonomer containing an active double bond group, unsaturated polyether and unsaturated small monomers (monomer A and monomer B), the graft copolymerization reaction of the starch main chain monomer and the unsaturated polyether with moderate reaction activity is controlled by design, and then the unsaturated small monomer is slowly dripped in a feeding mode, and the conditions such as reaction temperature, reaction time and the like are controlled, so that the unsaturated small monomer is grafted to the starch-based main chain skeleton functional macromonomer to form a rotating comb-type structure molecular form taking a starch-based glucose unit chain as a main chain and polyether and unsaturated carboxylic acid as side chains.

Detailed Description

The foregoing is merely an overview of the technical solutions of the present invention, and the present invention is described in further detail below in order to make the technical means of the present invention more clearly understood.

The invention provides a method for preparing a starch-based high-performance water reducing agent and a product thereof, wherein the starch-based high-performance water reducing agent takes a starch-based functional macromonomer as a main chain skeleton, and is grafted to the starch-based main chain skeleton through unsaturated polyether and unsaturated carboxylic acid to form the starch-based high-performance water reducing agent in a rotating comb-shaped structure molecule form, wherein a starch-based glucose unit chain is taken as a main chain, and the unsaturated polyether and the unsaturated carboxylic acid are taken as side chains;

the preparation method of the starch-based high-performance water reducing agent comprises the following steps:

preparing a controllable acid-degraded starch raw material: preparing 20-90% starch mixture from starch by using water as a reaction medium, and adding an acidolysis catalyst and an oxidant to react to obtain a controllable acid-degraded starch raw material; preferably, the starch is one or more of corn starch, tapioca starch, sweet potato starch, wheat starch, bean starch or modified starch; in addition, the acidolysis catalyst is one or more of sulfuric acid, nitric acid, sodium bisulfate, sulfamic acid or p-toluenesulfonic acid, and the amount of the acidolysis catalyst is 1-15% of the mass of the starch; and the oxidant is one or more of potassium permanganate, hydrogen peroxide, ammonium persulfate, potassium persulfate or periodic acid, and the using amount of the oxidant is 1-10% of the mass of the starch.

Preparation of starch-based functional macromonomer: mixing the controllable acid-degraded starch raw material with unsaturated carboxylic acid or anhydride, and adding an esterification catalyst and a polymerization inhibitor to perform esterification reaction to obtain a starch-based functional macromonomer; the controllable acid-degradable starch is a glucose unit, the polymerization degree of the glucose unit is 10-150, and the weight average molecular weight Mw of the glucose unit is 1600-25000. Preferably, the unsaturated carboxylic acid is one or more of methacrylic acid, acrylic acid or maleic acid, the anhydride is maleic anhydride, and the amount of the unsaturated carboxylic acid or the anhydride is 3-30% of the mass of the starch; the esterification catalyst is one or more of concentrated sulfuric acid, p-toluenesulfonic acid, sulfonic acid type strong acid cation exchange resin and tetrachloroaluminum ether complex, and the using amount of the esterification catalyst is 1-5% of the mass of starch; the polymerization inhibitor is one or more of tert-butyl catechol, hydroquinone, methylaniline or benzidine, and the using amount of the polymerization inhibitor is 0.02-0.2% of the mass of starch; in addition, the weight average molecular weight Mw of the starch-based functional macromonomer is 1800-30000, wherein the proportion of the starch-based functional macromonomer Mw in a distribution range of 1800-5000 is 35-55%, and the proportion of the starch-based functional macromonomer Mw in a distribution range of 5000-30000 is 45-65%.

Free radical copolymerization: mixing (5-20) starch-based functional macromonomer, unsaturated polyether and deionized water: (5-15): (65-85) adding an initiator with the mass of 0.2% -1.5% under stirring for prepolymerization reaction to obtain a first solution, and then respectively mixing the monomer A, the monomer B and the chain transfer agent in the ratio of (75-90): (5-20): (1-5) mixing the two solutions in a mass ratio to form a second solution, wherein the mass ratio of the first solution to the second solution is (90-99): (1-10), dropwise adding the second solution into the first solution, stirring to enable the second solution to react fully to obtain a mixed solution, and neutralizing the mixed solution with an alkaline solution until the pH value is 5-7 to obtain the starch-based high-performance water reducing agent. Preferably, the unsaturated polyether is one or more of methacrylic acid polyoxyethylene ester, allyl polyoxyethylene ether, methyl allyl polyoxyethylene ether, isopentenyl polyoxyethylene ether and vinyl polyethylene glycol ether, and the weight average molecular weight Mw of the unsaturated polyether is 1000-5000; the initiator is one or more of ferrous ammonium sulfate, ammonium ceric nitrate, potassium persulfate, ammonium persulfate and hydrogen peroxide; the monomer A is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid or maleic anhydride, and sodium salt, potassium salt or ammonium salt of maleic acid; the monomer B is one or more of sodium allylsulfonate, sodium methallylsulfonate and sodium styrene sulfonate; in addition, the chain transfer agent is one or more of 2-mercaptoethanol, 2-mercaptoacetic acid, 3-mercapto-1-propanol, 3-mercaptopropionic acid, 1-hexanethiol and dodecyl mercaptan.

Specifically, the preparation of the starch-based high-performance water reducing agent of the invention may comprise the following steps:

the preparation of the controllable acid-degraded starch raw material comprises the following steps: preparing 20-90% of starch mixture by mass percent by using water as a reaction medium, adding an acidolysis catalyst with the amount of 1-15% of the mass of the starch mixture, uniformly mixing, heating to 50-80 ℃, hydrolyzing for 2-10 h, then adding an oxidant with the amount of 1-10% of the mass of the starch mixture, uniformly mixing, vacuum drying, and reacting for 1-5 h at 80-150 ℃ to obtain the controllable acid-degraded starch raw material. The step mainly achieves the purpose of controlling the weight-average molecular weight of the starch after acid degradation by controlling the factors such as the use amount of sulfuric acid, the reaction temperature, the reaction time and the like.

The preparation of the starch-based functional macromonomer comprises the following steps: adding the controllable acid-degradable starch raw material and unsaturated carboxylic acid or anhydride with the amount of 3-30% of the mass of the controllable acid-degradable starch raw material into a reactor, adding an esterification catalyst with the amount of 1-5% of the mass of the controllable acid-degradable starch raw material and a polymerization inhibitor with the amount of 0.02-0.2% of the mass of the controllable acid-degradable starch raw material, stirring and heating to 60-130 ℃ for esterification reaction, wherein the reaction time is 2-10 hours, and thus the starch-based functional macromonomer is obtained.

The free radical copolymerization reaction: mixing (5-20) starch-based functional macromonomer, unsaturated polyether and deionized water: (5-15): (65-85), heating to 50-95 ℃, adding an initiator with the mass of 0.2-1.5% under stirring to perform prepolymerization for 0.5-2 h to obtain a first solution, and then adding the monomer A, the monomer B and the chain transfer agent according to the weight ratio of (75-90): (5-20): (1-5) mixing the two solutions in a mass ratio to form a second solution, wherein the mass ratio of the first solution to the second solution is (90-99): (1-10), dropwise adding the second solution into the reaction kettle within 0.5-2 h, stirring and reacting for 1-5 h after dropwise adding, cooling to 25-50 ℃ after reaction, and neutralizing the solution in the reaction kettle with an alkaline solution until the pH value is 5-7 to obtain the starch-based high-performance water reducer.

The invention provides a starch-based high-performance water reducing agent, which is prepared by using any one of the methods.

The present invention is illustrated in detail by the following examples. They are preferred embodiments of the present invention, and the present invention is not limited by these examples.

Examples 1,

The embodiment of the invention provides a starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same, which comprises the following specific steps:

(1) weighing 40g of corn starch and 60g of water to prepare a starch mixture with the concentration of 40%, slowly adding 1.2g of sulfuric acid, uniformly stirring, heating to 60 ℃, hydrolyzing for 6h, then adding 3.4g of hydrogen peroxide, uniformly mixing, drying in vacuum at 55 ℃ for 2h, and reacting at 110 ℃ for 2h to prepare the controllable acid-degraded starch (the weight average molecular weight Mw is 2500-17800).

(2) Adding 40g of controllable acid-degraded starch and 3.6g of methacrylic acid into a reactor, adding 0.6g of p-toluenesulfonic acid and 0.05g of methylaniline, stirring and heating to 120 ℃ for esterification reaction, and reacting for 3h to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 2800-19200, wherein the proportion of the Mw of the starch-based functional macromonomer in a 1800-5000 distribution interval is 37%, and the proportion of the Mw of the starch-based functional macromonomer in a 5000-30000 distribution interval is 63%).

(3) Adding 40g of starch-based functional macromonomer, 25g of methallyl polyoxyethylene ether (Mw = 2400) and 265g of deionized water into a reaction kettle, heating to 85 ℃, adding 2.8g of ammonium persulfate under stirring to perform prepolymerization for 1h, dropwise adding aqueous solutions of 8.6g of acrylic acid, 1.5g of sodium methallyl sulfonate and 0.16g of mercaptopropionic acid into the reaction kettle within 1.5h, stirring and reacting for 3h after dropwise adding, cooling to 45 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH value is 5.8 to obtain the starch-based high-performance water reducer.

Examples 2,

The embodiment of the invention provides a starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same, which comprises the following specific steps:

(1) weighing 35g of corn starch, 15g of potato starch and 50g of water to prepare a 50% starch mixture, slowly adding 1.2g of sulfuric acid, uniformly stirring, heating to 60 ℃, hydrolyzing for 8 hours, then adding 5.6g of hydrogen peroxide, uniformly mixing, drying in vacuum at 55 ℃ for 2 hours, and reacting at 115 ℃ for 2 hours to prepare the controllable acid-degraded starch (the weight average molecular weight Mw is 2680-17400).

(2) Adding 50g of controllable acid-degraded starch and 3g of maleic anhydride into a reactor, adding 0.7g of p-toluenesulfonic acid and 0.03g of tert-butyl catechol, stirring and heating to 115 ℃ for esterification, and reacting for 4h to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 3150-18820, wherein the proportion of the Mw of the starch-based functional macromonomer in a 1800-5000 distribution interval is 42%, and the proportion of the Mw of the starch-based functional macromonomer in a 5000-30000 distribution interval is 58%).

(3) Adding 50g of starch-based functional macromonomer, 28g of isopentenyl polyoxyethylene ether (Mw = 2400) and 305g of deionized water into a reaction kettle, heating to 80 ℃, adding 2.5g of initiator (ammonium ceric nitrate: potassium persulfate =1: 1) while stirring to perform prepolymerization reaction for 0.5h, then respectively dropwise adding 9g of methacrylic acid, 1.8g of sodium allylsulfonate and 0.15g of aqueous solution of thioglycolic acid into the reaction kettle within 2h, stirring to react for 2h after dropwise adding is finished, cooling to 50 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH is 6.2 to obtain the starch-based high-performance water reducer.

Examples 3,

The embodiment of the invention provides a starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same, which comprises the following specific steps:

(1) weighing 40g of corn starch, 20g of cassava starch and 40g of water to prepare a 60% starch mixture, slowly adding 4.8g of sulfamic acid, uniformly stirring, heating to 55 ℃, hydrolyzing for 7h, then adding 2.5g of potassium permanganate, uniformly mixing, drying in vacuum for 2h at 60 ℃, reacting for 4h at 90 ℃, and thus obtaining the controllable acid-degraded starch (with the weight average molecular weight Mw of 2820-19060).

(2) Adding 50g of controllable acid-degraded starch and 3.5g of acrylic acid into a reactor, adding 0.7g of concentrated sulfuric acid and 0.08g of hydroquinone, stirring and heating to 125 ℃ for esterification reaction, and reacting for 3h to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 2500-20080, wherein the proportion of the Mw of the starch-based functional macromonomer in a distribution range of 1800-5000 is 48%, and the proportion of the Mw of the starch-based functional macromonomer in a distribution range of 5000-30000 is 52%).

(3) Adding 50g of starch-based functional macromonomer, 24g of vinyl polyglycol ether (Mw = 3000) and 300g of deionized water into a reaction kettle, heating to 70 ℃, adding 2.3g of initiator (ammonium ceric nitrate: ammonium persulfate =1: 1) under stirring to perform prepolymerization reaction for 0.5h, then respectively dropwise adding aqueous solutions of 6.5g of acrylic acid, 2.1g of itaconic acid, 1.6g of sodium styrene sulfonate and 0.18g of mercaptopropionic acid into the reaction kettle within 1h, stirring to react for 3h after dropwise adding, cooling to 40 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH is 6 to obtain the starch-based high-performance water reducer.

Examples 4,

The embodiment of the invention provides a starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same, which comprises the following specific steps:

(1) weighing 60g of corn starch, 20g of cassava starch and 20g of water to prepare a starch mixture with the concentration of 80%, slowly adding 12.4g of sulfamic acid, uniformly stirring, heating to 50 ℃, hydrolyzing for 3h, then adding 6.3g of hydrogen peroxide, uniformly mixing, drying in vacuum for 1h at 60 ℃, reacting for 2h at 105 ℃, and preparing the controllable acid-degraded starch (the weight average molecular weight Mw is 2873-16810).

(2) Adding 50g of controllable acid-degraded starch and 10.3g of maleic anhydride into a reactor, adding 0.9g of concentrated sulfuric acid and 0.1g of hydroquinone, stirring and heating to 110 ℃ for esterification, and reacting for 4 hours to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 2935-17480, wherein the proportion of the Mw of the starch-based functional macromonomer in the 1800-5000 distribution range is 39%, and the proportion of the Mw of the starch-based functional macromonomer in the 5000-30000 distribution range is 61%).

(3) Adding 50g of starch-based functional macromonomer, 10g of methallyl polyoxyethylene ether (Mw = 2400), 15g of vinyl polyglycol ether (Mw = 3000) and 290g of deionized water into a reaction kettle, heating to 78 ℃, adding 2.5g of initiator (ammonium ceric nitrate: ammonium persulfate =1: 2) under stirring to perform prepolymerization for 1h, then respectively dropwise adding aqueous solution of 6.8g of acrylic acid, 1.8g of sodium methallyl sulfonate, 1.1g of sodium styrene sulfonate and 0.16g of mercaptoethanol into the reaction kettle within 1.5h, stirring and reacting for 2.5h after dropwise adding is finished, cooling to 45 ℃ after the reaction is finished, and neutralizing with alkaline solution to pH 6.5 to obtain the starch-based high-performance water reducer.

Examples 5,

The embodiment of the invention provides a starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same, which comprises the following specific steps:

(1) weighing 25g of cassava starch and 75g of water to prepare a 25% starch mixture, slowly adding 10.5g of nitric acid, uniformly stirring, heating to 45 ℃, hydrolyzing for 4h, then adding 2.8g of potassium persulfate, uniformly mixing, drying in vacuum for 4h at 60 ℃, reacting for 5h at 90 ℃, and preparing the controllable acid-degraded starch (with the weight average molecular weight Mw of 2880-14050).

(2) Adding 50g of controllable acid-degraded starch and 8.5g of methacrylic acid into a reactor, adding 1.5g of p-toluenesulfonic acid and 0.08g of tert-butyl catechol, stirring and heating to 115 ℃ for esterification reaction, and reacting for 3h to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 2650-14600, wherein the proportion of the Mw of the starch-based functional macromonomer in a distribution range of 1800-5000 is 53%, and the proportion of the Mw of the starch-based functional macromonomer in a distribution range of 5000-30000 is 47%).

(3) Adding 50g of starch-based functional macromonomer, 22g of isopentenyl polyoxyethylene ether (Mw = 2400) and 310g of deionized water into a reaction kettle, heating to 80 ℃, adding 2.1g of initiator (ammonium ceric nitrate: potassium persulfate =2: 1) while stirring to perform prepolymerization reaction for 0.5h, then respectively dropwise adding aqueous solutions of 6g of acrylic acid, 2.4g of methacrylic acid, 1.2g of sodium methallyl sulfonate and 0.2g of mercaptopropionic acid into the reaction kettle within 2h, stirring to react for 2h after dropwise adding is finished, cooling to 40 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH is 7 to obtain the starch-based high-performance water reducer.

Comparative examples 1,

A starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same are disclosed, and the method comprises the following specific steps:

(1) weighing 40g of corn starch and 60g of water to prepare a 40% starch mixture, heating to 60 ℃, hydrolyzing for 6h, adding 2.4g of hydrogen peroxide, mixing uniformly, drying in vacuum for 2h at 55 ℃, and reacting for 2h at 110 ℃ to obtain the controllable acid-degraded starch (the weight average molecular weight Mw is 55640-98200).

(2) Adding 40g of controllable acid-degraded starch and 3.6g of methacrylic acid into a reactor, adding 0.6g of p-toluenesulfonic acid and 0.05g of hydroquinone, stirring and heating to 120 ℃ for esterification reaction, and reacting for 3h to obtain the starch-based functional macromonomer (with the weight average molecular weight Mw of 58720-100360).

(3) Adding 40g of starch-based functional macromonomer, 25g of methallyl polyoxyethylene ether (Mw = 2400) and 265g of deionized water into a reaction kettle, heating to 85 ℃, adding 2.8g of ammonium persulfate under stirring to perform prepolymerization for 1h, dropwise adding aqueous solutions of 8.6g of acrylic acid, 1.5g of sodium methallyl sulfonate and 0.16g of mercaptopropionic acid into the reaction kettle within 1.5h, stirring and reacting for 3h after dropwise adding, cooling to 45 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH value is 5.8 to obtain the starch-based water reducer.

Comparative examples 2,

A starch-based functional macromonomer and a method for preparing a starch-based high-performance water reducing agent by using the same are disclosed, and the method comprises the following specific steps:

(1) weighing 40g of corn starch and 60g of water to prepare a starch mixture with the concentration of 40%, slowly adding 1.2g of sulfuric acid, uniformly stirring, heating to 60 ℃, hydrolyzing for 6h, then adding 2.4g of hydrogen peroxide, uniformly mixing, drying in vacuum at 55 ℃ for 2h, and reacting for 2h at 110 ℃ to prepare the controllable acid-degraded starch (the weight average molecular weight Mw is 3820-17350).

(2) Adding 40g of controllable acid-degraded starch into a reactor, adding 0.6g of p-toluenesulfonic acid and 0.05g of hydroquinone, stirring and heating to 120 ℃ for esterification reaction, and reacting for 3h to obtain the starch-based functional macromonomer (the weight average molecular weight Mw is 3160-19080).

(3) Adding 40g of starch-based functional macromonomer, 25g of methallyl polyoxyethylene ether (Mw = 2400) and 265g of deionized water into a reaction kettle, heating to 85 ℃, adding 2.8g of ammonium persulfate under stirring to perform prepolymerization for 1h, dropwise adding aqueous solutions of 8.6g of acrylic acid, 1.5g of sodium methallyl sulfonate and 0.16g of mercaptopropionic acid into the reaction kettle within 1.5h, stirring and reacting for 3h after dropwise adding, cooling to 45 ℃ after the reaction is finished, and neutralizing with an alkaline solution until the pH value is 5.8 to obtain the starch-based water reducer.

Application example

The starch-based high performance water reducing agents obtained in examples 1, 2, 3, 4, 5, comparative examples 1, 2 were subjected to concrete tests: machine-made sand with mud content and stone powder content of 1.5 percent and 5 percent respectively and fineness modulus of 3.3 and continuous graded broken stones with nominal grain diameter of 5-10 mm and 10-20 mm and mud content of 0.6 percent are adopted as materials. The water reducing rate, the bleeding rate, the compressive strength, the shrinkage ratio and other index test methods are executed according to relevant regulations of GB 8076-. The specific test results are shown in table 1 below:

TABLE 1 Water reducing agent Performance test results

The results of the performance tests in table 1 show that: although the water reducing rate of the commercial polycarboxylate superplasticizer can meet the requirement, the bleeding rate and the 28d shrinkage rate of the commercial polycarboxylate superplasticizer are relatively high, the 7d compressive strength is relatively low, the workability is general, and the sensitivity is relatively high, namely, concrete doped with the commercial polycarboxylate superplasticizer is easy to separate and bleed, and the shrinkage cracking condition of the concrete cannot be improved. The water reducing rate of the starch-based high-performance water reducing agent (as in examples 1-5) prepared by the method is up to 25-35%, the requirement of the high-performance water reducing agent is met, the bleeding rate and the 28d shrinkage ratio of the starch-based high-performance water reducing agent are both obviously reduced (particularly the bleeding rate is obviously reduced) compared with those of a commercial polycarboxylic acid water reducing agent, the sensitivity and the workability are obviously improved compared with those of the commercial polycarboxylic acid water reducing agent, and the 7d compressive strength ratio is also obviously improved. In addition, the invention also provides comparative examples 1 and 2, compared with example 1, the comparative example 1 lacks an acidolysis catalyst when preparing the controllable acid-degraded starch, the weight average molecular weight Mw of the prepared controllable acid-degraded starch is obviously larger, mainly in that the starch molecule is incompletely degraded by acid, and compared with example 1, the comparative example 2 lacks unsaturated carboxylic acid or anhydride when preparing the starch-based functional macromonomer, the prepared starch-based functional macromonomer does not have reactive double bond groups, so that unsaturated polyether and unsaturated carboxylic acid are difficult to graft on the starch-based main chain skeleton; and as can be seen from the table 1, the water reducing rate of the water reducing agent prepared in the comparative examples 1 and 2 can not meet the requirements of the starch-based high-performance water reducing agent, and although the bleeding rate is obviously reduced, the 7d compressive strength ratio, the 28d shrinkage ratio, the workability and the sensitivity of the water reducing agent can not meet the requirements. Therefore, as can be seen from comparison of each example in the table 1 with each comparative example and the performance of a commercial polycarboxylate water reducer, when the starch-based high-performance water reducer disclosed by the invention is used for preparing cement, the adaptability of the cement can be greatly improved, the workability of concrete can be improved, segregation bleeding can be reduced, and the shrinkage cracking of the concrete can be reduced.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention in any way, and it will be apparent to those skilled in the art that the above description of the present invention can be applied to various modifications, equivalent variations or modifications without departing from the spirit and scope of the present invention.