阅读说明：本技术 具有优良减水性的聚羧酸减水剂及其制备方法 (Polycarboxylate superplasticizer with excellent water reducing property and preparation method thereof ) 是由 马清萍 于 2020-08-28 设计创作，主要内容包括：一种具有优良减水性的聚羧酸减水剂及其制备方法,其由以下单体聚合而成：单体A为不饱和聚醚,单体B为端基含有马来酸酐的多元醇聚合物,单体C为不饱和羧酸；单体D为含有甲基丙烯酸2-乙磺酸酯钠；其中,单体A的分子量为2000-5000,单体B的分子量为1000-4000。本发明通过调整聚合单体的种类获得的聚羧酸减水剂,提高了羧酸基团的含量,协同两种长侧链的空间位阻大大提高了其减水性能。(A polycarboxylic acid water reducing agent with excellent water reducing property and a preparation method thereof are disclosed, which is polymerized by the following monomers: the monomer A is unsaturated polyether, the monomer B is a polyalcohol polymer with a terminal group containing maleic anhydride, and the monomer C is unsaturated carboxylic acid; the monomer D is 2-ethyl sodium sulfonate containing methacrylic acid; wherein the molecular weight of the monomer A is 2000-5000, and the molecular weight of the monomer B is 1000-4000. The polycarboxylic acid water reducing agent obtained by adjusting the types of the polymerization monomers improves the content of carboxylic acid groups, and greatly improves the water reducing performance of the polycarboxylic acid water reducing agent by cooperating with the steric hindrance of two long side chains.)

1. A polycarboxylic acid water reducing agent having excellent water reducing property, characterized in that said water reducing agent comprises the following monomers copolymerized:

the monomer A is unsaturated polyether, wherein the molecular weight of the monomer A is 2000-5000;

the monomer B is a polyalcohol polymer with an end group containing maleic anhydride, wherein the molecular weight of the monomer B is 1000-4000;

the monomer C is unsaturated carboxylic acid;

the monomer D is 2-ethyl sodium methacrylate.

2. The polycarboxylic acid water reducing agent having excellent water reducing property as claimed in claim 1, wherein the molecular weight of said monomer A is 3000-4000; the molecular weight of the monomer B is 1000-2000.

3. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 1, wherein the ratio of monomer A: a monomer B: a monomer C: the molar ratio of the monomer D is 2-10:2-5:5-15: 1-3; preferably, the monomer a: a monomer B: a monomer C: the molar ratio of the monomer D is 5-8:3-4:5-10: 2-3.

4. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 1, wherein said unsaturated polyether is at least one selected from the group consisting of ethylene glycol monovinyl polyoxyethylene ether, allyl polyoxyethylene ether and methacryl polyoxyethylene ether; the polyalcohol polymer with the terminal group containing maleic anhydride is selected from at least one of maleic anhydride polyethylene glycol ester, maleic anhydride polypropylene glycol ester and maleic anhydride polybutylene glycol ester; the unsaturated carboxylic acid is selected from (meth) acrylic acid.

5. The polycarboxylic acid water reducing agent having excellent water reducing property according to any one of claims 1 to 4, characterized in that said water reducing agent further comprises a monomer E, said monomer E being styrene.

6. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 5, wherein the ratio of monomer A: a monomer B: a monomer C: a monomer D: the molar ratio of the monomer E is 5-8:3-4:5-10:2-3: 0.5-2.

7. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 1, characterized in that the method for producing the water reducing agent comprises the steps of:

(1) adding a monomer A into an alkaline aqueous solvent, and uniformly stirring to obtain a first solution; adding the monomer B, the monomer C and the monomer D into water, and uniformly stirring to obtain a second solution; adding a reducing agent and a chain transfer agent into water, and uniformly stirring to obtain a third solution;

(2) under the condition of stirring at the constant temperature of 0-30 ℃, firstly adding an initiator into the first solution, then dropwise adding the second solution and the third solution, and preserving heat for 10-90min to obtain a product solution;

(3) and adding alkali liquor into the product solution to adjust the pH value to 6-7, thereby obtaining the polycarboxylic acid water reducing agent.

8. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 7, wherein in the step (1), the chain transfer agent is a mixture of isopropyl alcohol and mercaptopropanol, wherein the mass ratio of isopropyl alcohol to mercaptopropanol is 1: 1-3.

9. The polycarboxylic acid water reducing agent having excellent water reducing property according to claim 7, wherein in said step (2), the initiator is hydrogen peroxide and ferrous sulfate heptahydrate.

10. A method for preparing a polycarboxylic acid water reducing agent having excellent water reducing property according to any one of claims 1 to 9, characterized by comprising the steps of:

(1) adding a monomer A into an alkaline aqueous solvent, and uniformly stirring to obtain a first solution; adding the monomer B, the monomer C and the monomer D into water, and uniformly stirring to obtain a second solution; adding a reducing agent and a chain transfer agent into water, and uniformly stirring to obtain a third solution;

(2) under the condition of stirring at the constant temperature of 0-30 ℃, firstly adding an initiator into the first solution, then dropwise adding the second solution and the third solution, and preserving heat for 10-90min to obtain a product solution;

(3) adding alkali liquor into the product solution, and adjusting the pH value to 6-7 to obtain a polycarboxylic acid water reducing agent;

wherein:

the monomer A is ethylene glycol monovinyl polyoxyethylene ether, wherein the molecular weight of the monomer A is 3000-4000;

the monomer B is maleic anhydride polyethylene glycol ester, wherein the molecular weight of the monomer B is 1000-2000-;

the monomer C is acrylic acid;

the monomer D is 2-ethyl sodium methacrylate.

Technical Field

The invention belongs to the field of water reducing agents, and particularly relates to a polycarboxylic acid water reducing agent with excellent water reducing property and a preparation method thereof.

Background

The water reducing agent is a concrete admixture capable of reducing the mixing water consumption under the condition of maintaining the slump constant of concrete. The water reducing agent is added into the concrete mixture to disperse cement particles, and the water reducing agent also has the effects of improving the workability of cement, reducing unit water consumption, improving the fluidity of the concrete mixture and the like.

The polycarboxylate superplasticizer comprises a negatively charged hydrophilic group and a hydrophobic long chain. When the polycarboxylic acid water reducing agent is added into a cement dispersion system, a double electric layer is formed on the surface of cement particles by hydrophilic groups, and the double electric layer generates electrostatic repulsion force to play a role in dispersion; one end of the hydrophobic chain is adsorbed on the surface of cement particles to generate steric hindrance effect, thereby playing a role in reducing water. The polycarboxylate superplasticizer serving as a third-generation concrete superplasticizer has the advantages of high water reducing rate, low mixing amount, large freedom degree of molecular structure design, good dispersibility, good slump loss resistance, wide application range, environmental friendliness and the like, and is a research hotspot and development trend in the field of concrete admixtures at the present stage.

At present, polyether macromonomers such as Methoxy Polyoxyethylene Ether (MPEG), allyl Alcohol Polyoxyethylene Ether (APEG), methyl allyl alcohol polyoxyethylene ether (HPEG) and 4-hydroxybutyl Vinyl Polyoxyethylene Ether (VPEG) are commonly used as polycarboxylic acid water reducing agents. However, the water reducing performance of the existing polycarboxylic acid water reducing agent still needs to be improved, and how to improve the water reducing performance is also a research hotspot of researchers at present.

CN109400822A discloses a method for preparing slump-retaining polycarboxylate superplasticizer mother liquor, which comprises the steps of carrying out water-phase free radical polymerization on unsaturated macromonomers and unsaturated acid under the action of an initiator, a reducing agent and a chain transfer agent, and then adding a byproduct epoxy compound in the industrial production process of an organosilane coupling agent for carrying out epoxy ring-opening esterification reaction to obtain the slump-retaining polycarboxylate superplasticizer mother liquor; the slump retaining performance of the polycarboxylic acid is improved by adjusting the length and the density of a side chain of the polycarboxylic acid water reducing agent; however, the water reducing performance of the polycarboxylic acid water reducing agent obtained by the method is not good and still needs to be improved.

CN109970927A discloses a polycarboxylic acid water reducing agent with excellent early strength performance and slump retaining performance, wherein a long side chain is introduced into a molecule of the polycarboxylic acid water reducing agent through free radical polymerization, active groups such as carboxyl, sulfonic group, ester group, phosphate group, amide group and the like are grafted on a main chain, and all the groups have synergistic action, so that the water reducing performance, the slump retaining performance and the early strength of the polycarboxylic acid water reducing agent are improved, but the water reducing performance improving effect is poor.

CN105236803B discloses a novel polycarboxylate water reducer and a preparation method thereof, the polycarboxylate water reducer is prepared from a polyalkoxy alkenyl long-chain unsaturated monomer, unsaturated carboxylic acid, a chain transfer agent, an oxidant, a reducing agent, water and a micro-crosslinking agent, and the obtained polycarboxylate water reducer can effectively reduce the loss of slump with time, but has a limited water-reducing performance improvement effect.

The polycarboxylate water reducer disclosed in CN109575198A introduces amino groups and silane components capable of promoting cement hydration into molecules, so that the polycarboxylate water reducer acts on cement active components from the beginning of adding the water reducer in the application process, the hydration speed of the cement active components is promoted, the hydration degree of the cement active components is improved, and the early strength and the later strength of concrete are improved; but the water reducing performance of the polycarboxylate superplasticizer is not effectively improved.

Disclosure of Invention

Based on the above, the invention provides a polycarboxylic acid water reducing agent with excellent water reducing property, which comprises the following contents:

a polycarboxylic acid water reducing agent having excellent water reducing properties, said water reducing agent comprising monomers copolymerized to form:

the monomer A is unsaturated polyether, wherein the molecular weight of the monomer A is 2000-5000;

the monomer B is a polyalcohol polymer with an end group containing maleic anhydride, wherein the molecular weight of the monomer B is 1000-4000;

the monomer C is unsaturated carboxylic acid;

the monomer D is 2-ethyl sodium methacrylate.

The polycarboxylic acid water reducing agent of the present invention has improved water reducing property by adjusting the kind of the polymerization monomer. The applicant unexpectedly found that the water reducing agent obtained by adding the monomer D sodium 2-ethanesulfonate methacrylate in the polymerization reaction and copolymerizing the monomer D sodium 2-ethanesulfonate with the three monomers A, B and C has an unexpected improvement effect on the water reducing performance. The Applicant speculates that this is related to the narrow molecular weight distribution, the uniform distribution of the long side chains and the carboxyl groups and the density of the copolymers obtained.

The polycarboxylic acid water reducing agent with excellent water reducing property according to the invention is preferably that the molecular weight of the monomer A is 3000-4000; the molecular weight of the monomer B is 1000-2000.

According to the polycarboxylic acid water reducing agent having excellent water reducing property of the present invention, preferably, the monomer A: a monomer B: a monomer C: the molar ratio of the monomer D is 2-10:2-5:5-15: 1-3. More preferably, the monomer a: a monomer B: a monomer C: the molar ratio of the monomer D is 5-8:3-4:5-10: 2-3. According to one embodiment of the invention, the monomer a: a monomer B: a monomer C: the molar ratio of monomer D was 6:3:6: 2.

According to the polycarboxylic acid water reducing agent with excellent water reducing property, preferably, the unsaturated polyether is at least one selected from ethylene glycol monovinyl polyoxyethylene ether, allyl polyoxyethylene ether and methyl propenyl polyoxyethylene ether, more preferably, the unsaturated polyether is ethylene glycol monovinyl polyoxyethylene ether; the polyol polymer with the terminal group containing maleic anhydride is at least one selected from maleic anhydride polyethylene glycol ester, maleic anhydride polypropylene glycol ester and maleic anhydride polybutylene glycol ester, and more preferably, the polyol polymer with the terminal group containing maleic anhydride is maleic anhydride polyethylene glycol ester; the unsaturated carboxylic acid is selected from (meth) acrylic acid, more preferably the unsaturated carboxylic acid is acrylic acid.

The polycarboxylate superplasticizer with excellent water reducing performance provided by the invention preferably further comprises a monomer E, and the monomer E is styrene. Styrene is used as a polymerization monomer to participate in the polymerization reaction, so that the steric hindrance can be increased, and the water reducing property of the polycarboxylic acid water reducing agent can be further improved by cooperating with the long side chain.

According to the polycarboxylic acid water reducing agent having excellent water reducing property of the present invention, preferably, the monomer A: a monomer B: a monomer C: a monomer D: the molar ratio of the monomer E is 5-8:3-4:5-10:2-3: 0.5-2. More preferably, the monomer a: a monomer B: a monomer C: a monomer D: the molar ratio of monomer E was 6:3:6:2: 0.8.

According to the polycarboxylic acid water reducing agent with excellent water reducing property, the preparation method of the water reducing agent preferably comprises the following steps:

(1) adding a monomer A into an alkaline aqueous solvent, and uniformly stirring to obtain a first solution; adding the monomer B, the monomer C and the monomer D into water, and uniformly stirring to obtain a second solution; adding a reducing agent and a chain transfer agent into water, and uniformly stirring to obtain a third solution;

(2) under the condition of stirring at the constant temperature of 0-30 ℃, firstly adding an initiator into the first solution, then dropwise adding the second solution and the third solution, and preserving heat for 10-90min to obtain a product solution;

(3) and adding alkali liquor into the product solution to adjust the pH value to 6-7, thereby obtaining the polycarboxylic acid water reducing agent.

According to the polycarboxylic acid water reducing agent with excellent water reducing property, preferably, in the step (1), the chain transfer agent is a mixture of isopropanol and mercaptopropanol; wherein the mass ratio of the isopropanol to the mercaptopropanol is 1: 1-3. More preferably, the mass ratio of isopropanol to mercaptopropanol is 1: 2.

According to the polycarboxylic acid water reducing agent with excellent water reducing property, in the step (2), preferably, the initiator is hydrogen peroxide and ferrous sulfate heptahydrate. More preferably, the concentration of hydrogen peroxide is 30 wt%.

In the present invention, the reducing agent is at least one of sodium bisulfite and ascorbic acid, and ascorbic acid is preferable.

According to one embodiment of the invention, the reducing agent is ascorbic acid and the chain transfer agent is a mixture of isopropanol and mercaptopropanol in a mass ratio of 1: 2; wherein the mass ratio of the reducing agent, the chain transfer agent, the hydrogen peroxide and the ferrous sulfate heptahydrate to the monomer A is 0.5-3 wt%, 0.2-2 wt%, 1-5 wt% and 3-10 wt%, respectively; preferably, the mass ratio of the reducing agent, the chain transfer agent, the hydrogen peroxide and the ferrous sulfate heptahydrate to the monomer A is 1-2 wt%, 0.5-1 wt%, 2-3 wt% and 4-5 wt%, respectively. Experiments prove that the molecular weight and the distribution of the generated water reducer can be controlled, the water reducing performance is improved, and the slump retaining performance is improved by controlling the proportion of the reducing agent, the chain transfer agent, the initiator and other compounds within the range.

In addition, the invention also discloses a preparation method for preparing the polycarboxylic acid water reducing agent with excellent water reducing property, which comprises the following steps:

(1) adding a monomer A into an alkaline aqueous solvent, and uniformly stirring to obtain a first solution; adding the monomer B, the monomer C and the monomer D into water, and uniformly stirring to obtain a second solution; adding a reducing agent and a chain transfer agent into water, and uniformly stirring to obtain a third solution;

(2) under the condition of stirring at the constant temperature of 0-30 ℃, firstly adding an initiator into the first solution, then dropwise adding the second solution and the third solution, and preserving heat for 10-90min to obtain a product solution;

(3) adding alkali liquor into the product solution, and adjusting the pH value to 6-7 to obtain a polycarboxylic acid water reducing agent;

wherein:

the monomer A is ethylene glycol monovinyl polyoxyethylene ether, wherein the molecular weight of the monomer A is 3000-4000;

the monomer B is maleic anhydride polyethylene glycol ester, wherein the molecular weight of the monomer B is 1000-2000-;

the monomer C is acrylic acid;

the monomer D is 2-ethyl sodium methacrylate.

According to one embodiment of the invention, the preparation method of the water reducing agent comprises the following steps:

(1) adding sodium phosphate into water to obtain an alkaline aqueous solvent, adding the monomer A into the alkaline aqueous solvent, and uniformly stirring to obtain a first solution; adding the monomer B, the monomer C and the monomer D into water, and uniformly stirring to obtain a second solution; adding a reducing agent and a chain transfer agent into water, and uniformly stirring to obtain a third solution;

(2) under the condition of stirring at the constant temperature of 0-30 ℃, firstly adding an initiator into the first solution, then dropwise adding the second solution and the third solution, and preserving heat for 10-90min to obtain a product solution;

(3) adding a sodium hydroxide solution with the mass concentration of 30 wt% into the product solution to adjust the pH value to 6-7, and obtaining a polycarboxylic acid water reducing agent with the solid content of 30-50 wt%;

wherein the monomer A is ethylene glycol monovinyl polyoxyethylene ether, wherein the molecular weight of the monomer A is 3000-4000;

the monomer B is maleic anhydride polyethylene glycol ester, wherein the molecular weight of the monomer B is 1000-2000-;

the monomer C is acrylic acid;

the monomer D is 2-ethyl sodium methacrylate;

monomer A: a monomer B: a monomer C: the molar ratio of the monomer D is 5-8:3-4:5-10: 2-3;

the reducing agent is ascorbic acid, and the chain transfer agent is a mixture of isopropanol and mercaptopropanol in a mass ratio of 1: 2; wherein the mass ratio of the reducing agent, the chain transfer agent, the hydrogen peroxide and the ferrous sulfate heptahydrate to the monomer A is 0.5-3 wt%, 0.2-2 wt%, 1-5 wt% and 3-10 wt%, respectively; preferably, the mass ratio of the reducing agent, the chain transfer agent, the hydrogen peroxide and the ferrous sulfate heptahydrate to the monomer A is 1-2 wt%, 0.5-1 wt%, 2-3 wt% and 4-5 wt%, respectively; more preferably, in the step (1), a monomer E is further added to the second solution, the monomer E is styrene, and the monomer a: a monomer B: a monomer C: a monomer D: the molar ratio of the monomer E is 5-8:3-4:5-10:2-3: 0.5-2.

Advantageous effects

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the polycarboxylic acid water reducing agent is obtained by adjusting the types of the polymerization monomers, so that the content of carboxylic acid groups is increased, and the water reducing performance of the polycarboxylic acid water reducing agent is greatly improved by cooperating with the steric hindrance of two long side chains; furthermore, sulfonic acid groups are introduced into the side long chains to obviously improve the dispersion property of the water reducer; furthermore, the reinforcing effect and slump retention of the water reducing agent can be synergistically improved by adjusting the types and the contents of the monomers;

as a preferable technical scheme of the invention, the steric hindrance is increased by adding the styrene polymerization monomer, so that the water reducing performance of the water reducing agent is further improved.

Detailed Description

In order that the invention may be more fully understood, reference will now be made to the specific embodiments illustrated. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Description of the raw materials

Ethylene glycol monovinyl polyoxyethylene ether with molecular weight of 2000 and 3000, respectively marked as A2000 and A3000; industrial grade.

Maleic anhydride polyethylene glycol esters with molecular weights of 1000, respectively, are designated as B1000; industrial grade.

Acrylic acid; industrial grade.

Sodium 2-ethanesulfonate methacrylate; industrial grade.

Styrene; industrial grade.

Ascorbic acid; industrial grade.

Isopropyl alcohol; industrial grade

3-mercaptopropionic acid; industrial grade.

30 wt% of hydrogen peroxide; industrial grade.

Ferrous sulfate heptahydrate; industrial grade.

Sodium phosphate; industrial grade.

Description of the test methods

Testing of concrete Properties

According to GB8076-2008 'concrete admixture', the concrete base mixing proportion (kg/m)³) Comprises the following steps: m (cement), m (fly ash), m (sand), m (stone), 320:40:800:1050, the slump of the reference concrete is (210 +/-10) mm, the breaking and fixing amount of the fixed water reducing agent is 0.15%, and the water reducing rate, the slump, the expansion and the strength of the concrete are tested. Wherein, the sand used in the test has a fineness modulus of 2.5-3.0 and a mud content of less than 2 wt%; the stone is continuous graded crushed stone with the diameter of 5-20 mm; the cement is flammule P.O42.5R cement; the fly ash is II-grade fly ash; the water reducing agent is a TPEG type common polycarboxylic acid water reducing agent, PCE-1, which is sold in the market.

Molecular weight and distribution test thereof

The molecular weight and the distribution of the water reducing agent are tested by adopting Shimadzu GPC-20A.