CN106632881A - Low water-reducing and high slump loss resistant type polycarboxylate superplasticizer master batch - Google Patents

Abstract

The invention discloses a polycarboxylate superplasticizer masterbatch with low water reduction and high slump retention, which is suitable for poor quality materials such as cement, mineral admixtures, and ground materials, and exhibits initial high water reduction and late slump retention strong features. The mass percentage of the mother liquor is limited to 40%, the total mass of synthetic raw materials is 1000, and the dosage ratio is as follows: the dosage of polyether macromonomer is 360~375; the dosage of acrylic acid is 22.0~35.0; 1.25~1.65%; if you choose mercaptopropionic acid MPA, the dosage is 1.37~1.80; the oxidant uses hydrogen peroxide, the dosage is 2.0~3.5%; the reducing agent chooses vitamin C, the dosage is 0.55~0.75; water. The polycarboxylate superplasticizer synthesized by the invention has a moderate molecular weight of about 57,000 to 62,000; the length of the main chain is moderate, the density of the branch chain is relatively large, the water reducing rate is low, and the slump retention is strong, and the effect on poor materials is outstanding.

Description

A kind of low water reduction and high slump retention type polycarboxylate superplasticizer masterbatch

technical field

The invention belongs to the field of cement additives, and relates to a low-water-reducing and high-slump-preserving polycarboxylate superplasticizer masterbatch, which is suitable for poor-quality materials such as cement, mineral admixtures, and gravel floor materials.

Background technique

There are many factors in the process of concrete preparation that will affect the quality of concrete. The strength of the influencing factors is sandstone, cement, and mineral admixtures in order; with the excessive exhaustion of resources or the emergence of protection policies, the use of bad materials leads to the deterioration of fresh concrete. The slump loss is too large, which makes it more and more difficult for polycarboxylate-based water-reducers to be well applied in concrete; in the synthesis of water-reducers, water-reducing and slump-preserving are contradictory designs. The proportion cannot take both into consideration; the initial flow state of the concrete should be properly controlled to ensure the rheological properties over time before construction, and the design of the slump protection factor should be emphasized in the synthesis.

In the case of poor quality materials such as cement, mineral admixtures, and gravel floor materials, the factors affecting the slump retention of concrete depend on the internal factors of concrete raw materials and external factors such as hot environment and long transportation distance. Polycarboxylate superplasticizer with strong slump retention in the late stage of water treatment. This type of water reducer has a relatively large molecular weight, a long main chain length, high branch chain density, low initial water reducing rate, strong slump retention in the later stage, and wide adaptability. Good stability.

CN 105367720 A discloses a water-reducing and slump-retaining polycarboxylate water-reducer and a preparation method thereof, the pH of which is 6.0-7.0, and its raw materials include the following components by weight: isopentenol with a molecular weight of 600-3000 190~200 parts of polyoxyethylene ether, 15~25 parts of acrylic acid, 1~5 parts of hydroxyalkyl acrylate, 0.1~3 parts of unsaturated phosphoric acid ester, 0.5~5 parts of unsaturated alcohol ether, 1.0~3.5 parts of oxidizing agent 0.1-2 parts of reducing agent, 0.1-2 parts of sodium bisulfite formaldehyde, 0.5-2.5 parts of chain transfer agent, 325 parts of water and 30-32% mass concentration of liquid caustic soda. The invention has high active ingredients, good dispersibility and excellent performance.

CN 103450411 A discloses a method for preparing a high-slump polycarboxylate water reducer. Firstly, methoxypolyethylene glycol monomethyl ether of different molecular weights and methacrylic acid are mixed with a polymerization inhibitor, and the mixture is mixed with a polymerization inhibitor at a certain temperature and a catalyst. Carry out esterification for a period of time, then add allyl alcohol at one time, and further esterify under the same conditions to obtain esterified macromonomer MP containing crosslinking monomer allyl methacrylate; then MP, unsaturated sulfonate , (Meth) acrylate unsaturated monomer and chain transfer agent, carry out aqueous solution polymerization under redox initiation system and low temperature conditions, and finally add liquid caustic soda to neutralize to obtain a certain concentration of polycarboxylate water reducer. The high slump retention polycarboxylate water reducer prepared by the invention is designed at low temperature through molecular structure design and has high slump retention, excellent dispersion performance and good adaptability.

CN 105037648 A discloses a slump-retaining water-reducing polycarboxylate water-reducer and a low-temperature rapid preparation method thereof. 100 parts of unsaturated polyoxyethylene ester, 1-10 parts of unsaturated carboxylic acid, 0.05-2 parts of oxidizing agent and Mix 40~90 parts of water, adjust the reaction temperature to 15~60°C and stir to dissolve; first drop solution B containing reducing agent sodium formaldehyde sulfoxylate and solution C containing chain transfer agent at the same time, after 5~30 minutes, Start to add solution A containing unsaturated carboxylic acid dropwise, and the three solutions are added dropwise within 1~3 hours and solution B and solution C are 10~30min later than solution A, keep warm for 30~60min, and then add to the reaction solution Add 1~10 parts of sodium hydroxide to obtain the slump-retaining water-reducing polycarboxylate superplasticizer.

Contents of the invention

The technical problem to be solved by the present invention is to provide a low-water-reducing and high-slump-retaining polycarboxylate superplasticizer masterbatch, which is suitable for poor quality materials such as cement, mineral admixtures, and gravel floor materials.

The present invention can buffer the initial adsorption amount of polycarboxylate superplasticizer molecules under different hydration conditions to a certain extent by rationally designing the length of the main chain of polycarboxylate molecules; increasing the proportion of polyether macromonomers and the amount of vitamin C to control polycarboxylate The high conversion rate of polyether macromonomer in the synthesis of carboxylic acid superplasticizer and the branched chain density of polyether macromonomer grafting ensure that polycarboxylic acid molecules can provide sufficient steric repulsion. The polycarboxylate water-reducer provided by the present invention can stabilize the adsorption-dispersion ability and repellency of polycarboxylate-based water-reducer molecules to the greatest extent under the conditions of different adsorbate capacities and variable quantities.

The low-water-reducing and high-slump-retaining polycarboxylate superplasticizer masterbatch of the present invention is formed by polymerizing the following components, the total mass parts of raw materials are 1000, and each component includes:

Polyether macromonomer: 360~375;

Acrylic acid: 22.0~35.0;

Chain transfer agent: 1.25~1.80;

Hydrogen peroxide: 2.0~3.5;

Vitamin C: 0.55~0.75;

Liquid caustic soda: 10~15;

Water: the rest.

The polyether macromonomer is one or more compositions of methallyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, and isobutenyl alcohol polyoxyethylene ether;

Described hydrogen peroxide is the industrial grade hydrogen peroxide that mass percent is 27.5%;

The chain transfer agent is composed of one or both of mercaptoacetic acid (MSDS) and mercaptopropionic acid (MPA);

The liquid caustic soda is an industrial-grade NaOH solution with a mass percentage of 30-32%.

The synthetic process of a kind of low water reducing high slump retention type polycarboxylate superplasticizer masterbatch described in the present invention is as follows:

Put the polyether macromonomer in the reaction vessel, and keep stirring until the stirred solution has no obvious block or flake material;

Add hydrogen peroxide into the completely dissolved polyether macromonomer solution, and then add the initiator and acrylic acid solution sequentially within 10 minutes. The initiator is an aqueous solution mixture of chain transfer agent and vitamin C; the initiator is added prior to the acrylic acid solution, The priority time is 10 minutes; the time for adding the acrylic acid solution is 1~2.5 hours, the acrylic acid solution is added before the initiator, and the initiator is 10~20 minutes behind the acrylic acid solution before the drop is completed;

Do not turn on the cooling water circulation, put it in the reaction kettle to keep warm for 10~15h automatically, add liquid caustic soda, replenish water, stir evenly and then release.

Judging from the point of view of low water reduction rate, the polyether macromonomer is preferably isopentenol polyoxyethylene ether,

One or two compositions of isobutyl alcohol polyoxyethylene ether;

From the perspective of high slump retention, the polyether macromonomer is preferably isobutylene alcohol polyoxyethylene ether;

Judging from the adaptability point of view, the polyether macromonomer is preferably a polyether with a molecular weight of 2000 or 2400

A mixture of the two macromonomers, the mass ratio is preferably 1:2;

Judging from the perspective of comprehensive factors, the polyether macromonomer is preferably a composition of 2000 molecular weight polyoxyethylene isobutylene ether and 2400 molecular weight isobutylene polyoxyethylene ether with a mass ratio of 1:2;

If the polyether macromonomer is selected as methallyl polyoxyethylene ether, the quality is preferably 370~375;

If the polyether macromonomer is selected to be one or both of isopentenol polyoxyethylene ether and isobutenol polyoxyethylene ether, the quality is preferably 360-370.

When the hydrogen peroxide is added, consider mixing it with water that is 2 to 5 times the mass ratio of hydrogen peroxide, so as to avoid the direct addition of hydrogen peroxide and cause the local concentration to be too high;

When the chain transfer agent is mercaptoacetic acid, the slump retention property is stronger, and the dosage is 1.25 to 1.65;

When the chain transfer agent is mercaptopropionic acid, the water reducing rate is higher, and the dosage is 1.37~1.80;

The amount of vitamin C used is 0.55~0.75, the water reducing rate of the mother liquid of the water reducing agent increases with the amount, first becomes higher and then becomes lower; the slump retention of the mother liquid of the water reducer increases with the amount, first becomes lower and then becomes higher ; The amount of vitamin C is preferably at the point where the slope of the water-reducing rate increasing curve and the slope of the slump-preserving decreasing curve are smooth and coincident;

The amount of the chain transfer agent changes in direct proportion to the amount of acrylic acid, and the range of the amount of the chain transfer agent is determined according to the amount of acrylic acid: the amount of acrylic acid is 22.0~28.5, the amount of the chain transfer agent is 1.25~1.53; the amount of acrylic acid is 28.5~35.0, the chain transfer Dosage is 1.53~1.80;

The dosage of the chain transfer agent can be fine-tuned downward according to the two indicators of mother liquor water-reducing rate and slump retention. The slump property decreases gradually with its dosage, increasing first and then decreasing; the dosage of chain transfer agent is preferably at the point where the slope of the decreasing curve of water reducing rate and the slope of increasing curve of slump retention are smooth and coincident.

The beneficial effects of the present invention are:

1. Appropriately control the amount of chain transfer agent, increase the main chain length of polycarboxylate superplasticizer, and design with low acid-ether ratio, so that the molecular size of the superplasticizer is too large, and absolutely limit the hydration of the superplasticizer molecules in the strong adsorbent Due to the stretching degree in the environment, the initial adsorption of superplasticizer molecules is limited; combined with the design of high branched chain density, the polycarboxylate mother liquor exhibits a low initial water reduction rate (enough to ensure the basic working performance of concrete), and the later water reduction rate gradually increases. feature.

2. In the market, the combination of high water reducing rate water reducing agent and slump retaining agent with no initial water reducing rate is often used to solve the problem of excessive slump loss of concrete. Small monomers such as alkyl acrylates must be introduced into the synthesis of this type of slump-retaining agent. The low-acid-ether ratio, low water-reducing, and high-slump-retaining polycarboxylate water-reducing agent is a common raw material for water-reducing agents, and the mother liquor produced is directly diluted Use, no need to mix other mother liquors, low production requirements, simple and suitable operation.

detailed description

The present invention is further elaborated below by examples, and the following description is only for explaining the present invention, and does not limit the content.

Example 1

A low acid-ether ratio, low water reduction and high slump retention type polycarboxylate water reducer masterbatch, the water reducer is polymerized by the following components by mass percentage, the total mass of raw materials is 1000, each component and process The parameters are as follows:

Primer: methallyl polyoxyethylene ether with a molecular weight of 2400: 372, water: 250;

Hydrogen peroxide solution: 27.5% Industrial grade hydrogen peroxide: 2.5, water: 10;

Add the initiator and the small monomer solution sequentially within 10 minutes after adding the hydrogen peroxide;

Initiator: mercaptopropionic acid: 1.45, vitamin C: 0.65, water: 120;

Small monomer solution: acrylic acid: 23.5, water: 50;

Initiator dropping time: 2.0h;

The small monomer solution dripping time is 1.5h;

Holding time: 2h;

Liquid caustic: 10;

Hydration: 159.9.

Example 2

A low acid-ether ratio, low water reduction and high slump retention type polycarboxylate water reducer masterbatch, the water reducer is polymerized by the following components by mass percentage, the total mass of raw materials is 1000, each component and process The parameters are as follows:

Primer: 2400 molecular weight isopentenol polyoxyethylene ether: 365, water: 250;

Hydrogen peroxide solution: 27.5% Industrial grade hydrogen peroxide: 3.0, water: 10;

Add the initiator and the small monomer solution sequentially within 10 minutes after adding the hydrogen peroxide;

Initiator: thioglycolic acid: 1.57, vitamin C: 0.70, water: 120;

Small monomer solution: acrylic acid: 30.5, water: 50;

Initiator dropping time: 3.0h;

The small monomer solution dripping time is 2.5h;

Holding time: 1.5h;

Liquid caustic: 12;

Hydration: 157.23.

Example 3

A low acid-ether ratio, low water reduction and high slump retention type polycarboxylate water reducer masterbatch, the water reducer is polymerized by the following components by mass percentage, the total mass of raw materials is 1000, each component and process The parameters are as follows:

Primer: isobutylene alcohol polyoxyethylene ether with a molecular weight of 2000: 123, isopentenyl alcohol polyoxyethylene ether with a molecular weight of 2400: 246, water: 250;

Hydrogen peroxide solution: 27.5% Industrial grade hydrogen peroxide: 3.3, water: 12;

Add the initiator and the small monomer solution sequentially within 10 minutes after adding the hydrogen peroxide;

Initiator: mercaptopropionic acid: 1.65, vitamin C: 0.58, water: 120;

Small monomer solution: acrylic acid: 28.7, water: 50;

Initiator dropping time: 2.2h;

The small monomer solution dripping time is 1.8h;

Holding time: 2h;

Liquid caustic: 10;

Hydration: 154.77.

Example 4

A low acid-ether ratio, low water reduction and high slump retention type polycarboxylate water reducer masterbatch, the water reducer is polymerized by the following components by mass percentage, the total mass of raw materials is 1000, each component and process The parameters are as follows:

Primer: 2000 molecular weight isobutyl alcohol polyoxyethylene ether: 362, water: 250;

Hydrogen peroxide solution: 27.5% Industrial grade hydrogen peroxide: 2.2, water: 8;

Add the initiator and the small monomer solution sequentially within 10 minutes after adding the hydrogen peroxide;

Initiator: thioglycolic acid: 1.65, vitamin C: 0.62, water: 120;

Small monomer solution: acrylic acid: 32.4, water: 50;

Initiator dropping time: 3.0h;

The small monomer solution dripping time is 2.5h;

Holding time: 2h;

Liquid caustic: 14;

Hydration: 159.13.

Test the initial fluidity and time-dependent fluidity of the cement paste under the same concentration of the polycarboxylate superplasticizer masterbatch with low acid-ether ratio, low water-reducing and high-slump retention type and common polycarboxylate superplasticizer mother liquor in the above examples. The cement used in the experiment is Huaxin 42.5 ordinary silicate cement, referring to the test standard of GB/8076-2008 "Concrete Admixtures".

Effect of different water reducing agents on the flow of cement slurry

Types of superplasticizers Initial fluidity mm Mobility over time mm Ordinary water reducer 260 220 Example 1 220 260 Example 2 235 250 Example 3 225 265

According to the above-mentioned comparison of the fluidity of the initial slurry and over time, the initial fluidity of examples 1, 2, and 3 of the low water-reducing high-slump polycarboxylate superplasticizer masterbatch are smaller than that of the common water-reducer mother liquor, but after The temporary fluidity is better than the initial fluidity. From the above, the branched chain system of polycarboxylate superplasticizer with low acid ether ratio and low water reduction and high slump retention is more reasonable, which is conducive to improving dispersion stability and ensuring a significant improvement in slump retention performance.

Claims (6)

1. A masterbatch of polycarboxylate superplasticizer with low water reduction and high slump retention, which is formed by polymerization of the following components, the total mass parts of raw materials are 1000, and each component includes: Polyether macromonomer: 360~375; Acrylic acid: 22.0~35.0; Chain transfer agent: 1.25~1.80; Hydrogen peroxide: 2.0~3.5; Vitamin C: 0.55~0.75; Liquid caustic soda: 10~15; water: the rest; The polyether macromonomer is one or more compositions of methallyl polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, and isobutenyl alcohol polyoxyethylene ether; Described hydrogen peroxide is the industrial grade hydrogen peroxide that mass percent is 27.5%; The chain transfer agent is one or both of mercaptoacetic acid and mercaptopropionic acid; The liquid caustic soda is an industrial-grade NaOH solution with a mass percentage of 30-32%. 2. the synthetic method of polycarboxylate superplasticizer master batch described in claim 1 is characterized in that: Put the polyether macromonomer in the reaction vessel, and keep stirring until the stirred solution has no obvious block or flake material; Add hydrogen peroxide into the fully dissolved polyether macromonomer solution, and then add the initiator and acrylic acid solution sequentially within 10 minutes. The initiator is an aqueous solution mixture of chain transfer agent and vitamin C; the initiator is added prior to the acrylic acid solution, The priority time is 10 minutes; the time for adding the acrylic acid solution is 1-2.5 hours, the acrylic acid solution is added before the initiator, and the initiator is 10-20 minutes behind the acrylic acid solution; Do not turn on the cooling water circulation, put it in the reaction kettle to keep warm for 10~15h automatically, add liquid caustic soda, replenish water, stir evenly and then release. 3. The method according to claim 2, wherein the polyether macromonomer is a mixture of polyether macromonomers with molecular weights of 2000 and 2400, and the mass ratio is 1:2. 4. The method according to claim 2, characterized in that, the chain transfer agent is thioglycolic acid, and the consumption is 1.25 ~ 1.65. 5. the method according to claim 2 is characterized in that, described chain transfer agent is mercaptopropionic acid, and consumption is 1.37～1.80. 6. The method according to claim 2, characterized in that, the amount of acrylic acid is 22.0~28.5, and the amount of chain transfer agent is 1.25~1.53; or the amount of acrylic acid is 28.5~35.0, and the amount of chain transfer agent is 1.53~1.80 .