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Preparation method for linear polycarboxylate type water reducing agent special for semi-hydrated gypsum

A technology of linear polycarboxylic acid and hemihydrate gypsum, which is applied in the field of building materials science, can solve the problems of inaccurate representation of molecular structure, poor adaptability, and large loss of fluidity of freshly mixed gypsum slurry over time, achieving excellent Water reduction and retarding effect, obvious dispersion effect and controllable setting time

Active Publication Date: 2014-03-26
CHINA UNIV OF MINING & TECH (BEIJING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] Due to the rapid hydration of building gypsum cementitious materials, the dispersion stability of traditional cement superplasticizers is poor, the fluidity of freshly mixed gypsum slurry is greatly lost over time, and the high ionic strength in gypsum cementitious material slurry will lead to polycarboxylic acid The spatial structure of the water reducing agent is compressed, the volume is reduced, and the steric hindrance effect is reduced, which greatly restricts the application of concrete water reducing agents in gypsum-based cementitious materials.
[0006] Patent CN101619120A discloses a sulfonated polycarboxylate ceramic water reducer and its preparation method, but there will be steric hindrance and selectivity, and the sulfonation reaction is a reversible reaction, so the sulfonation rate cannot reach Expected requirements, and the concentration of concentrated sulfuric acid will destroy the main chain during sulfonation, so the molecular structure is complex, and its molecular structure cannot be accurately expressed
[0007] Patent CN102675504A discloses a polycarboxylate ceramic water reducer synthesized by the RAFT method. The molecular weight distribution of this product is very small, and the adaptability to industrial hemihydrate gypsum with complex phases is not good.
And it does not consider the influence of phosphate and silane capping, which are more adaptable to sulfate, on it, and the latter two are very important for hemihydrate gypsum

Method used

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  • Preparation method for linear polycarboxylate type water reducing agent special for semi-hydrated gypsum
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  • Preparation method for linear polycarboxylate type water reducing agent special for semi-hydrated gypsum

Examples

Experimental program
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Effect test

Embodiment 1

[0051] Add 3.5 g of chain transfer agent sodium methacrylate and 10 g of deionized water into a 100 mL four-necked round bottom flask equipped with a thermometer, a stirrer and a spherical condenser. Stir and heat up to 60°C. After sodium methacrylate is dissolved, use a peristaltic pump to drop a solution consisting of 9g of acrylic acid, 3g of vinyl acetate and 10g of water, and a solution of 0.3g of ammonium persulfate and 5g of water within 1 hour. Add to the four-neck bottle. After the dropwise addition, the reaction was stirred for 4h. After the reaction was completed, the temperature was lowered to below 40°C, and 30% sodium hydroxide was added to neutralize to a pH value of 7 to obtain a light yellow liquid. It is the special linear polycarboxylate high-performance water reducer PC-1 for hemihydrate gypsum of the present invention.

Embodiment 2

[0053] Add 4 g of chain transfer agent sodium bisulfite and 10 g of deionized water into a 100 mL four-necked round bottom flask equipped with a thermometer, a stirrer and a spherical condenser. Stir and heat up to 70°C. After the sodium bisulfite is dissolved, use a peristaltic pump to separate the solution consisting of 8g of acrylic acid, 2g of sodium p-styrene sulfonate and 10g of water, and the solution of 0.8g of potassium persulfate and 10g of water in 0.5h Add dropwise to the four-neck bottle. After the dropwise addition, the reaction was stirred for 4h. After the reaction was completed, the temperature was lowered to below 40°C, and 30% sodium hydroxide was added to neutralize to a pH value of 6 to obtain a brownish-yellow liquid. It is the special linear polycarboxylate high-performance water reducer PC-2 for hemihydrate gypsum of the present invention.

Embodiment 3

[0055] Add 2.1 g of chain transfer agent sodium bisulfite and 10 g of deionized water into a 100 mL four-necked round bottom flask equipped with a thermometer, a stirrer and a spherical condenser. Stir and heat up to 70°C. After sodium bisulfite is dissolved, use a peristaltic pump to prepare a solution consisting of 10g of acrylic acid, 4g of p-styrene sodium phosphate, 1g of hydroxyethyl acrylate and 10g of water, and 0.5g of ammonium persulfate and 5g of water. The solution was added dropwise to the four-neck flask within 0.5h. After the dropwise addition, the reaction was stirred for 3h. After the reaction was completed, the temperature was lowered to below 40°C, and 30% sodium hydroxide was added to neutralize to a pH value of 6 to obtain a light brown liquid. It is the special linear polycarboxylate high-performance water reducer PC-3 for hemihydrate gypsum of the present invention.

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Abstract

The invention discloses a preparation method for a linear polycarboxylate type water reducing agent special for semi-hydrated gypsum. The preparation method comprises the following steps: a chain transfer agent is dissolved with water in a reactor at the temperature of 60-70 DEG C, the aqueous solution of X and the aqueous solution of an initiating agent are dropwise added into the reactor within 0.5-1 h, after the aqueous solution of the X and the aqueous solution of the initiating agent are dropwise added into the reactor completely, stirring is performed for reaction for 3-5 h, the temperature is dropped to be lower than 40 DEG C, and an alkaline solution is used for neutralization until the pH value ranges from 6 to 8, so that light yellow or sandy beige liquid namely the linear polycarboxylate type water reducing agent special for semi-hydrated gypsum is obtained, wherein the X comprises a monomer A, and can further comprise one or more of a monomer B, monomer C and a monomer D. The preparation method for the linear polycarboxylate type water reducing agent is simple in process and short in synthesis cycle, the water reducing agent is good in repeated stability, low in cost, non-toxic and pollution-free, does not contain formaldehyde, and is suitable for popularization and application, and the prepared water reducing agent product special for the semi-hydrated gypsum is high in water-reducing rate and excellent in stability, adaptability and delayed coagulation effect.

Description

technical field [0001] The invention relates to the field of building material science and technology, in particular to a preparation method of a special linear polycarboxylate water reducer for hemihydrate gypsum. Background technique [0002] Natural gypsum is divided into dihydrate gypsum and anhydrous gypsum (anhydrite). Dihydrate gypsum is dehydrated to form hemihydrate gypsum, which is the main raw material for gypsum cementitious materials. Gypsum cementitious material is one of the three traditional cementitious materials. Gypsum cementitious material and its products have light weight, thermal insulation, small expansion and contraction, good fire resistance, low energy consumption for preparation, breathable and breathable functions, and can be recycled. Utilization and other advantages, the gypsum building material based on gypsum cementitious material is a recognized ecological healthy building material. [0003] Hemihydrate gypsum is divided into α and β crysta...

Claims

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Application Information

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IPC IPC(8): C04B24/26C04B24/16C04B103/30
Inventor 王栋民张力冉逄建军王浩张述雄李娟
Owner CHINA UNIV OF MINING & TECH (BEIJING)
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