Process for the preparation of a branched phosphorus-containing liquid retarder

Abstract

The application discloses a preparation method of a branched phosphorus-containing liquid retarder, and comprises the following steps: (1) mixing a catalyst, a solvent, a water-carrying agent, a polyhydric alcohol compound and a silane coupling agent aqueous solution to perform a condensation reaction, so as to obtain a condensation product; (2) adding a phosphoric acid compound aqueous solution dropwise into the condensation product to perform an addition polymerization reaction, so as to obtain a polymerization product; and (3) adding liquid alkali into the polymerization product to adjust the pH value to 7-7.5, and then performing a reduced-pressure distillation, so that the branched phosphorus-containing liquid retarder is obtained. The branched phosphorus-containing liquid retarder prepared by the method has a good retarding effect when being compounded with a polycarboxylic acid water reducing agent, does not affect the water reducing rate and stability of the water reducing agent, has no influence on the later strength of concrete, is not easy to rot in summer high temperature, and can effectively prolong the operation time of concrete.

Description

Technical Field

[0001] This invention belongs to the field of building admixture technology, specifically relating to a method for preparing a branched phosphorus-containing liquid retarder. Background Technology

[0002] As the most widely used building material today, concrete faces increasing demands for environmental friendliness and efficiency, leading to higher performance requirements. During the pouring of fresh concrete, a suitable setting time must be ensured. Too short a setting time results in excessive heat of hydration due to rapid hydration, causing problems such as poor bonding and temperature cracks in certain areas, affecting the later strength and durability of the concrete and creating quality and safety hazards. Conversely, too long a setting time hinders construction progress. The application of retarders can effectively extend the initial setting time of concrete.

[0003] A retarder is an admixture that slows down the hydration rate of cement. Currently, the main concrete retarder types can be divided into inorganic and organic retarder. There are various types of inorganic retarders, among which phosphate and metaphosphate retarders are more commonly used in recent years. Sodium fluorosilicate, zinc chloride, zinc carbonate, and sulfates of zinc, iron, and copper also have some retarding effect, but due to the instability of their retarding effect, they are not frequently used. Organic retarders include hydroxycarboxylic acids, aminocarboxylic acids, polyols, and their derivatives. Retarders can delay the hydration rate of cement, prolong the setting time of concrete, maintain the plasticity of concrete for a longer period, facilitate pouring, and do not adversely affect the later properties of the concrete.

[0004] Currently, the most commonly used retarders in engineering are sodium gluconate, white sugar, sodium citrate, and tartaric acid, which can control the initial setting time of fresh concrete to within 20 hours. However, sodium gluconate and white sugar are white solid powders. During the compounding process, powdered retarders dissolve slowly in polycarboxylate superplasticizers. Moreover, the superplasticizer solution after compounding may exhibit stratification, sedimentation, spoilage, and foul odor in the high temperatures of summer, resulting in unstable product performance. Therefore, there is an urgent need to develop a retarder with good retarding effect, easy solubility in polycarboxylate superplasticizers, stable performance of the superplasticizer after compounding, and resistance to spoilage in the high temperatures of summer. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing a branched phosphorus-containing liquid retarder.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a branched phosphorus-containing liquid retarder, characterized by comprising the following steps:

[0008] (1) A condensation reaction is carried out by mixing a catalyst, solvent, dehydrating agent, polyol compound and silane coupling agent aqueous solution to obtain a condensation product;

[0009] (2) Add an aqueous solution of a phosphoric acid compound to the above condensation product to carry out an addition polymerization reaction to obtain a polymer product;

[0010] (3) Add liquid alkali to the above polymerization product to adjust the pH to 7-7.5, and then perform vacuum distillation to obtain the branched phosphorus-containing liquid retarder.

[0011] The specific reaction principle is as follows:

[0012]

[0013] In a preferred embodiment of the present invention, the catalyst is p-toluenesulfonic acid.

[0014] In a preferred embodiment of the present invention, the solvent is DMAc.

[0015] In a preferred embodiment of the present invention, the dehydrating agent is toluene.

[0016] In a preferred embodiment of the present invention, the polyol compound is at least one selected from glycerol, pentaerythritol, xylitol, and sorbitol.

[0017] In a preferred embodiment of the present invention, the silane coupling agent is at least one selected from vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, KH-550, KH-560, KH-570 and KH-792.

[0018] In a preferred embodiment of the present invention, the phosphoric acid compound is at least one selected from phosphorus trioxide, phosphorus pentoxide, hypophosphoric acid, phosphoric acid, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphite, hydroxyethylidene diphosphonic acid, diethylenetriaminepentamethylidene phosphate, and aminotrimethylidene phosphate.

[0019] In a preferred embodiment of the present invention, the polyol is glycerol or pentaerythritol, the silane coupling agent is vinyltriethoxysilane or KH-570, and the phosphoric acid compound is phosphorus pentoxide or hydroxyethylidene diphosphonic acid.

[0020] More preferably, the polyol is glycerol, the silane coupling agent is vinyltriethoxysilane, and the phosphoric acid compound is phosphorus pentoxide.

[0021] More preferably, the catalyst is p-toluenesulfonic acid, the solvent is DMAc, and the dehydrating agent is toluene.

[0022] The beneficial effects of this invention are:

[0023] 1. Based on molecular construction and organic synthesis technology, this invention prepares a branched phosphorus-containing liquid retarder. Its molecular structure contains phosphate functional groups, and a silane coupling agent is added to connect organic and inorganic substances, so that the branched phosphorus-containing liquid retarder can better combine with cement particles and play a greater role.

[0024] 2. The branched phosphorus-containing liquid retarder prepared by this invention, when combined with polycarboxylate superplasticizer, has a good retarding effect, does not affect the water reduction rate and stability of the superplasticizer, has no effect on the later strength of concrete, is not easily corroded in the high temperature of summer, and can effectively extend the working time of concrete. Attached Figure Description

[0025] Figure 1 The infrared spectrum of the branched phosphorus-containing liquid retarder prepared in Example 1 of this invention.

[0026] Figure 2 This is a comparison chart of the color changes of the water-reducing agent in Example 8 of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0028] Example 1

[0029] Using a condensation reaction, with 0.5g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 25g of pentaerythritol was weighed and added to a four-necked flask. Then, 17.5g of 5wt% vinyltriethoxysilane aqueous solution was added dropwise to initiate the reaction. The temperature was raised to 120℃, and the reaction was carried out for 6-8 hours. Then, 25g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to initiate addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0030] Example 2

[0031] Using a condensation reaction, with 0.25g of p-toluenesulfonic acid as a catalyst, DMAc as a solution and toluene as a dehydrating agent, 15g of glycerol was weighed and added to a four-necked flask, followed by the dropwise addition of 10.5g of 5wt% vinyltriethoxysilane aqueous solution. The reaction was carried out at 120℃ for 6-8 hours, and then 10g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to initiate addition polymerization. The reaction was stirred for 8 hours, and finally the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution. The mixture was then distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0032] Example 3

[0033] Using a condensation reaction, with 0.5g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 25g of glycerol was weighed and added to a four-necked flask. Then, 17.5g of 5wt% KH-570 aqueous solution was added dropwise to initiate the reaction. The temperature was raised to 120℃, and the reaction was carried out for 6-8 hours. Then, 25g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to initiate addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0034] Example 4

[0035] Using a condensation reaction, with 0.25g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 25g of glycerol was weighed and added to a four-necked flask. Then, 17.5g of 5wt% vinyltriethoxysilane aqueous solution was added dropwise to carry out the reaction. The temperature was raised to 120℃ and the reaction was carried out for 6-8 hours. Then, 20g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to carry out addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0036] Example 5

[0037] Using a condensation reaction, with 0.5g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 17.5g of glycerol was weighed and added to a four-necked flask. Then, 20g of 5wt% KH-570 aqueous solution was added dropwise to initiate the reaction. The temperature was raised to 120℃, and the reaction was carried out for 6-8 hours. Then, 25g of 5wt% hydroxyethylidene diphosphonic acid solution was added dropwise to initiate addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0038] Example 6

[0039] Using a condensation reaction, with 0.5g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 25g of glycerol was weighed and added to a four-necked flask. Then, 15.5g of 5wt% vinyltriethoxysilane aqueous solution was added dropwise to carry out the reaction. The temperature was raised to 120℃ and the reaction was carried out for 6-8 hours. Then, 15g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to carry out addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0040] Example 7

[0041] Using a condensation reaction, with 0.5g of p-toluenesulfonic acid as a catalyst, DMAc as a solution, and toluene as a dehydrating agent, 25g of glycerol was weighed and added to a four-necked flask. Then, 17.5g of 5wt% vinyltriethoxysilane aqueous solution was added dropwise to carry out the reaction. The temperature was raised to 120℃ and the reaction was carried out for 6-8 hours. Then, 15g of 5wt% phosphorus pentoxide aqueous solution was added dropwise to carry out addition polymerization. The reaction was stirred for 8 hours. Finally, the pH was adjusted to 7-7.5 with 40% sodium hydroxide solution, and then the mixture was distilled under reduced pressure to obtain a branched phosphorus-containing liquid retarder.

[0042] The branched phosphorus-containing liquid retarder prepared in the above embodiments was subjected to performance testing. The specific testing methods are as follows:

[0043] 1. Infrared spectroscopy: Infrared spectroscopy can identify organic functional groups and provide a preliminary assessment of whether the structure of the compound matches the expected structure based on the information provided by the spectrum.

[0044] 2. Setting Time: The concrete mixture is sieved through a 5mm (round hole) vibrating sieve to obtain mortar. After thorough mixing, it is placed into a rigid, impermeable metal cylinder with an upper inner diameter of 160mm, a lower inner diameter of 150mm, and a net height of 150mm. The sample surface should be slightly below the cylinder opening by about 10mm. The cylinder is then vibrated for approximately 3-5 seconds and placed in an environment of (20±2)℃ with the container covered. Measurements are taken 4-6 hours after setting, and then every 0.5 or 1 hour thereafter. However, the interval can be shortened when approaching initial and final setting. Each measurement point should avoid the previous measurement location, with a net distance of twice the needle diameter, but not less than 15mm. The distance between the needle and the edge of the container should not be less than 25mm. A 100mm² cross-sectional area is used to determine the initial setting time. 2 The test needle was used to determine the final setting time using a 200mm needle. 2 The test needle was used. Based on the calculation results, a curve was plotted with the penetration resistance value on the ordinate and the test time on the abscissa to determine the relationship between the penetration resistance value and time. The time corresponding to a penetration resistance value of 3.5 MPa was taken as the initial setting time, and the time corresponding to a penetration resistance value of 28 MPa was taken as the final setting time. The setting time was calculated from the moment the cement came into contact with water.

[0045] 3. Flexural Strength: Prepare prismatic specimens with dimensions of 40mm × 40mm × 160mm. The mortar is mixed using a planetary mixer, molded on a vibratory compaction table, and the specimens, still in their molds, are cured in moisture for 24 hours. Then, they are demolded and cured in water until the strength test is completed. The standard requires that three specimens under identical conditions be tested in each group of tests, and the average value is taken as the final result.

[0046] 4. Compressive Strength: Standard cubic specimens with dimensions of 150mm × 150mm × 150mm were prepared. The concrete was manually compacted into the molds and allowed to stand for 48 hours. The concrete specimens were then numbered, demolded, and transferred to a standard curing room (temperature 20±2℃, relative humidity ≥95%) for curing. The compressive strength was then tested using a universal testing machine at curing times of 7 days and 28 days. The standard requires that three specimens under identical conditions be tested in each group of tests, and the average value is taken as the final result.

[0047] Figure 1 The infrared spectrum of the branched phosphorus-containing liquid retarder prepared in Example 1 is shown, with the peak value at 3650 cm⁻¹. -1 Strong hydroxyl absorption peaks were observed at all locations, indicating that the synthesized sample contains a large number of hydroxyl functional groups. (2937 cm⁻¹) -1 The absorption peaks at 1652 cm⁻¹ belong to -CH₃ and -CH₂-. -1 The absorption peak at 1404 cm⁻¹ is due to the carbon-oxygen bond in the ester group; at 1404 cm⁻¹... -1 The peak appearing at 1016 cm⁻¹ is the -CC- absorption peak of the sample; at 1016 cm⁻¹... -1 The peak appearing at 694 cm⁻¹ is the absorption peak of the C-Si bond in the silane coupling agent; at 694 cm⁻¹... -1 The peak observed is the -PC- absorption peak at the end of the sample. Analysis of the infrared spectrum shows that the measured functional groups are identical to those of the expected molecule, indicating that this invention successfully synthesizes a branched phosphorus-containing liquid retarder.

[0048] The blank experiments in Table 1 below represent the workability of concrete without the addition of this type of retarder, while Comparative Example 1 represents the workability of concrete with the same amount of sodium gluconate added.

[0049] Table 1. Setting time difference of phosphorus-containing retarder

[0050]

[0051]

[0052] As can be seen from the cement setting time, the branched phosphorus-containing liquid retarder prepared in the embodiments of the present invention has excellent retarding effect. Compared with concrete without branched phosphorus-containing liquid retarder, the retarding time is significantly extended. Compared with the most widely used retarder on the market (sodium gluconate), the retarding effect is also significantly better.

[0053] The branched phosphorus-containing liquid retarder prepared in Example 2 was compounded with LQ-909M, and the mixture was placed in a stoppered graduated cylinder to observe its changes. The color change was as follows: Figure 1 As shown in the figure, the specific experimental results are shown in Table 2.

[0054] Table 2 Static Experiment of Water-Reducing Agent

[0055] label sample Color change, mold spots ① White sugar Mold spots appear in 5 days, the color darkens in 1 month, and the layers separate in 45 days. ③ Sodium Gluconate Mold spots appear after 20 days, the color darkens after 2 months, and the layers separate after 3 months. ⑤ Branched phosphorus-containing liquid retarder Mold spots appeared after 35 days, and the color changed slightly after 3 months. ② Sugar + retarder Mold spots appear after 5 days, the color darkens after 1 month, and the layers separate after 2 months. ④ Sodium gluconate + retarder Mold spots appeared after 25 days, and the color darkened after 2 months.

[0056] Through static experiments, the changes in the water-reducing agents were observed. It was found that the color of the water-reducing agents darkened over time until they separated into layers. The water-reducing agent with added sugar deteriorated earlier, with mold spots appearing in just five days. The time for mold spots to appear with sodium gluconate was 20 days, and the time for mold spots to appear with the branched phosphorus-containing liquid retarder was 35 days. This indicates that the branched phosphorus-containing liquid retarder prepared in Example 2 has a better anti-corrosion effect.

[0057] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a branched phosphorus-containing liquid retarder, characterized in that: Includes the following steps: (1) A condensation reaction is carried out by mixing a catalyst, a solvent, a dehydrating agent, a polyol compound and a silane coupling agent aqueous solution to obtain a condensation product; the catalyst is p-toluenesulfonic acid, the solvent is DMAc, the dehydrating agent is toluene, the polyol compound is at least one of glycerol, pentaerythritol, xylitol and sorbitol, and the silane coupling agent is at least one of vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, KH-550, KH-560, KH-570 and KH-792; (2) Add an aqueous solution of a phosphoric acid compound to the above condensation product to carry out an addition polymerization reaction to obtain a polymer product. The phosphoric acid compound is at least one of phosphorus trioxide, phosphorus pentoxide, hypophosphoric acid, phosphoric acid, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphite, hydroxyethylidene diphosphonic acid, diethylenetriamine pentamethylidene phosphate and aminotrimethylidene phosphate. (3) Add liquid alkali to the above polymerization product to adjust the pH to 7-7.5, and then perform vacuum distillation to obtain the branched phosphorus-containing liquid retarder.

2. The preparation method according to claim 1, characterized in that: The polyol is glycerol or pentaerythritol, the silane coupling agent is vinyltriethoxysilane or KH-570, and the phosphoric acid compound is phosphorus pentoxide or hydroxyethylidene diphosphonic acid.

3. The preparation method according to claim 2, characterized in that: The polyol is glycerol, the silane coupling agent is vinyltriethoxysilane, and the phosphoric acid compound is phosphorus pentoxide.

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