Synthesis process of slow-release collapse-preventing agent polycarboxylate water-reducing agent

Abstract

The present invention relates to the technical field of concrete admixtures, and specifically discloses a slow-release slump-preserving polycarboxylate water-reducing agent synthesis process, comprising the following steps: 3600 parts ± 50 parts of isopentanol polyoxyethylene ether and 2800 parts ± 40 parts of deionized water are mixed to form a macromonomer aqueous solution, and an initiator is added to the macromonomer aqueous solution; 180 parts of acrylic acid, 200 parts of hydroxyethyl ester, 30 parts of orthophosphate and deionized water are mixed to prepare aqueous solution A; a chain transfer agent, vitamin C and deionized water are mixed to prepare aqueous solution B; aqueous solution A and aqueous solution B are added dropwise to a reactor at the same time, and the reaction temperature is controlled at 42°C-45°C during the addition process; after the addition of aqueous solution B is completed, the temperature of the reactor is controlled at 42-45°C and kept warm for a period of time, and then liquid alkali is added to the reactor for neutralization. This scheme is used to solve the problem that the water reducer in the prior art can only achieve 2-3 hours of slump without loss and cannot achieve 4-6 hours after the concrete can still meet the use requirements.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, and in particular to a synthesis process of a slow-release collapse-preventing agent polycarboxylate water-reducing agent. Background Art

[0002] With the acceleration of the residential industrialization process and the development of transportation, water and electricity, municipal construction and other construction projects, the requirements for concrete construction performance, strength index and durability are getting higher and higher. Almost all of them require the use of pumped concrete, and high-efficiency water reducer is an indispensable part of the preparation of pumped concrete.

[0003] Pumped concrete requires long-distance transportation and construction work under different ambient temperatures. Both long-distance transportation and construction work under unfavorable temperatures will lead to slump loss of freshly mixed concrete. After the slump loss, the concrete has poor workability, which increases the difficulty of concrete construction and quality control.

[0004] There are many methods in the prior art for reducing the slump loss over time over a long period of time and a long distance, such as directly adding a retarder to the concrete to reduce the initial hydration rate of cement to help solve the problem of large slump loss over time, but this method will affect the setting time of the concrete and affect the construction progress. There are also methods for changing the way of adding the water reducer, such as changing the one-time addition of the water reducer to the method of adding the water reducer in batches, but this method is difficult to control the amount of the water reducer added. Too little addition is difficult to achieve the expected effect, and too much addition will affect the quality of the project. There is also a method of using a slump retaining agent and a polycarboxylate water reducer in combination, and the addition of a slump retaining agent helps solve the problem of large slump loss over time. This method can make the concrete still have a good slump retaining effect in 2-3 hours, but this method requires the addition of both a slump retaining agent and a water reducer to the concrete, which increases the procurement cost of concrete admixtures. In addition, there are a lot of research on slump-retaining polycarboxylic acid water-reducing agents with sustained-release effect. For example, the Chinese invention patent announcement number CN102503226B is a high-slump-retaining polycarboxylic acid water-reducing agent with sustained-release effect and a preparation method thereof. The water-reducing agent prepared by this method has good concrete slump loss control ability. The water-reducing agent configured by this technology shows that it can make the slump of concrete basically not lost within 3 hours, and has no obvious effect on the compressive strength performance of concrete.

[0005] However, in actual applications, traffic jams often occur due to the complexity of urban roads, and the locations that need to be constructed are all in relatively remote places. After the concrete is delivered to the construction site, it may be impossible to construct due to the construction progress or the environmental conditions during construction. As a result, the time from the mixing of concrete with water reducers to the time before construction often exceeds 3 hours, and sometimes even reaches 4-6 hours (which is considered an excessively long time). Under this condition, the current water reducers cannot keep the concrete meeting the use requirements after 4-6 hours. Summary of the invention

[0006] The present invention aims to provide a synthesis process of a slow-release slump-retaining polycarboxylic acid water-reducing agent, so as to solve the problem that the water-reducing agent in the prior art can only achieve slump without loss for 2-3 hours but cannot make the concrete meet the use requirements after 4-6 hours.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme:

[0008] The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent comprises the following steps:

[0009] Primer preparation: add 3600 parts ± 50 parts of isopentanol polyoxyethylene ether and 2800 parts ± 40 parts of deionized water into a reaction container and mix to prepare a macromonomer aqueous solution, the temperature of the macromonomer aqueous solution is controlled at 28°C ± 2°C, and then add 15 parts ± 0.5 parts of initiator into the macromonomer aqueous solution;

[0010] Aqueous solution A is prepared by mixing 180 parts of acrylic acid, 200 parts of hydroxyethyl ester, 30 parts of orthophosphate and 450 parts ± 10 parts of deionized water;

[0011] Aqueous solution B preparation: 14 parts ± 0.5 parts of chain transfer agent, 3.5 parts ± 0.5 parts of vitamin C and 870 parts ± 20 parts of deionized water are mixed to prepare aqueous solution B;

[0012] A / B material dropwise addition: aqueous solution A and aqueous solution B are added dropwise to the reaction container simultaneously, and the reaction temperature is controlled at 42°C-45°C during the dropwise addition process;

[0013] Keep warm, add alkali and replenish water: After the aqueous solution B is added dropwise, the temperature of the reaction container is controlled at 42-45°C and kept warm for a period of time, and then liquid alkali is added into the reaction container for neutralization.

[0014] The principles and advantages of this solution are:

[0015] According to the inventor's research, it is found that under the ingredients of this scheme, the influence of A / B material on the expansion degree is more obvious than the slump. This scheme can maximize the effect of the ingredients of this scheme by reasonably controlling the dropping temperature, so that the slump loss after 4 hours of the test is only 2-2.5cm, and the expansion degree is (470-480)*(480-490); and after 6 hours of the test, the slump can still be 19-20cm, which is only 3-4cm less than the slump loss in the initial situation. At the same time, the expansion degree can also be (410-420)*(420-430), which fully meets the requirements of ultra-long-term use. It can be seen that the water reducer prepared by this scheme achieves a slump-retaining effect of 4h, 5h or even longer, which greatly exceeds the existing technology that the polycarboxylate water reducer can only achieve a slump-retaining effect of 3 hours in the slump-retaining performance, and the scheme adopts fewer ingredients, making the preparation process simple, easy to operate and control.

[0016] In addition, in the present synthesis process, the reaction temperature is relatively low, only 42-45°C. Compared with the conventional reaction temperature of 50°C-60°C, the present solution can reduce energy consumption, and the inventors have also studied the situation at 50°C. At the dropping temperature of 50°C, the expansion degree did not meet the standard after 2 hours of the test, and when the dropping temperature was lower than 40°C, the expansion degree was severely lost after 4 hours of the test and did not meet the use requirements; it can be seen that the dropping temperature has a great influence on the reaction of aqueous solution A and aqueous solution B with the macromonomer aqueous solution, and in conventional tests, the influence of small temperature changes on the final long-term effect is often ignored, which also causes the existing water reducers to be unable to meet the construction requirements of concrete under ultra-long waiting time.

[0017] Preferably, as an improvement, the dropping process is performed at a uniform speed, wherein the aqueous solution A is dropped for 90-120 min, and the aqueous solution B is dropped for 30 min±5 min longer than the aqueous solution A.

[0018] Preferably, as an improvement, during the process of dropwise adding the aqueous solution A and the aqueous solution B into the reaction container, the stirring speed is controlled at 60-65 r / min.

[0019] Beneficial effects: At present, there are many studies on the polymerization technology of ether polycarboxylic acid water reducers at home and abroad, mainly focusing on the influence of the monomer ratio on the corresponding performance, the influence of small monomers and different initiators and chain transfer agents on the final performance, and there is no uniform regulation on the stirring speed in the preparation process of water reducers. For example, the stirring speed is 150-200r / min, 200-300r / min, and there are also faster stirring speeds. This scheme breaks the conventional changes in components and studies the speed process of the reaction process. It is found that at a reactor temperature of 42℃-45℃, too fast stirring speed will destroy the molecular chain and make the final effect worse. If the stirring speed is too slow, the heat release is too large in the early stage, and some components have the phenomenon of stopping polymerization, which also makes the effect worse.

[0020] When the speed is controlled at 60-65r / min, under the control of the reaction temperature of each component, the slump and expansion of the water reducer can still be good after 6 hours, and the initial setting time of the concrete can reach 8.5-9 hours, and the final setting time can reach 11.5-12 hours.

[0021] Preferably, as an improvement, after adding liquid alkali into the reaction container for neutralization, water is added into the reaction container to dilute the solid content to 40%±5%.

[0022] Preferably, as an improvement, the initiator in the primer configuration is an inorganic peroxide initiator.

[0023] Preferably, as an improvement, the chain transfer agent used in the aqueous solution B is any one of mercaptopropionic acid, thioglycolic acid, and mercaptoethanol, or a mixture of several of them. DETAILED DESCRIPTION

[0024] The following is further described in detail through specific implementation methods:

[0025] Example 1

[0026] The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent comprises the following steps:

[0027] Base material preparation: Add 3600 parts of isopentanol polyoxyethylene ether (TPEG) and 2800 parts of deionized water into the reactor and mix to prepare a macromonomer aqueous solution. The temperature of the macromonomer aqueous solution is controlled at 28°C ± 2°C. Then, add 15 parts of an inorganic peroxide initiator (such as hydrogen peroxide) to the macromonomer aqueous solution.

[0028] Aqueous solution A is prepared by mixing 180 parts of unsaturated acrylic acid, 200 parts of hydroxyethyl ester, 30 parts of trisodium phosphate and 450 parts of deionized water to prepare aqueous solution A. In this embodiment, trisodium phosphate can also be replaced by other orthophosphates such as tripotassium phosphate.

[0029] Preparation of aqueous solution B: 14 parts of chain transfer agent, 3.5 parts of vitamin C and 870 parts of deionized water are mixed to prepare aqueous solution B. The chain transfer agent is any one of mercaptopropionic acid, thioglycolic acid and mercaptoethanol or a mixture thereof. In this embodiment, mercaptopropionic acid is used as the chain transfer agent.

[0030] A / B material dropwise addition: aqueous solution A and aqueous solution B were added dropwise to the reactor at the same time, and the reaction temperature was controlled at 44°C during the dropwise addition. The dropwise addition was carried out at a uniform speed, wherein aqueous solution A was added dropwise for 120 min and aqueous solution B was added dropwise for 150 min. The solution was continuously stirred during the dropwise addition, and the stirring speed was controlled at 62 r / min.

[0031] Keep warm, add alkali and make up water: after the aqueous solution B is added, control the temperature of the reactor at 42-45°C and keep warm for 90-120 minutes, then add liquid alkali to the reactor for neutralization until the pH is 6-7, and finally add water to the reactor to dilute it to a solid content of 40%±5%.

[0032] The number of portions indicated above, 1 portion can be 1G, 10G or 1KG.

[0033] In view of the above implementation process, the inventor also conducted the following experiments:

[0034] Comparative Example 1

[0035] The difference from Example 1 is that the amount of acrylic acid in this comparative example is 185 parts.

[0036] Comparative Example 2

[0037] The difference from Example 1 is that the amount of acrylic acid in this comparative example is 175 parts.

[0038] Comparative Example 3

[0039] The difference from Example 1 is that in this comparative example, hydroxyethyl ester is replaced by hydroxypropyl ester.

[0040] Comparative Example 4

[0041] The difference from Example 1 is that in this comparative example, trisodium phosphate is replaced by mercaptopropionic acid.

[0042] Comparative Example 5

[0043] The difference from Example 1 is that this comparative example does not add trisodium phosphate.

[0044] The test results of Example 1 and Comparative Examples 1 to 5 are shown in Table 1 below. The performance tests of the tests were carried out in accordance with GBT50080-2016 “Test methods for properties of ordinary concrete mixtures”.

[0045] Table 1

[0046]

[0047] Note: The unit of expansion in Table 1 is mm.

[0048] From the test results in Table 1 above, it can be seen that the small change in the acrylic acid content in this embodiment has little effect on the slump, but has a very obvious effect on the expansion, especially when the test is tested again after 4 hours, compared with the test of 2 hours, the expansion loss is 130-150mm, which has a very large impact; and at the same time, whether it is changing hydroxyethyl ester or trisodium phosphate, the expansion of the water reducer after adding it to the concrete will be greatly affected, and the slump after 6 hours in particular can no longer meet the use requirements of the concrete. However, this embodiment greatly increases and decreases the slump retention performance through the study of the formula, ensuring that the water reducer of this embodiment can still ensure that the slump reaches 20cm when used in concrete, even if the transportation time is as long as 6 hours, and the expansion can still be 420*430mm.

[0049] Example 2

[0050] The difference from Example 1 is that the temperature of this example is controlled at 42° C. when the A / B material is added dropwise.

[0051] Example 3

[0052] The difference from Example 1 is that the temperature of this example is controlled at 45°C when the A / B material is added dropwise.

[0053] Comparative Example 6

[0054] The difference from Example 1 is that the temperature of this comparative example is controlled at 50° C. when the A / B material is added dropwise.

[0055] Comparative Example 7

[0056] The difference from Example 1 is that the temperature of this comparative example is controlled at 40° C. when the A / B material is added dropwise.

[0057] The test results of Examples 1-3 and Comparative Examples 6-7 are shown in Table 2 below:

[0058] Table 2

[0059]

[0060] Combined with Table 2, it can be seen that Examples 1-3 still have excellent slump and expansion after 6 hours of testing. However, when the temperature is reduced to 40°C of Comparative Example 7, the slump loss over time is large after 2 hours of testing, the slump is poor at 4 hours, and at 6 hours, both the slump and the expansion cannot meet the concrete use requirements.

[0061] Example 4

[0062] The difference from Example 1 is that in this example, the stirring speed during the dropwise addition of the A / B materials is controlled at 60 r / min.

[0063] Example 5

[0064] The difference from Example 1 is that in this example, the stirring speed during the dropwise addition of the A / B materials is controlled at 65 r / min.

[0065] Comparative Example 8

[0066] The difference from Example 1 is that in this example, the stirring speed during the dropwise addition of the A / B materials is controlled at 50 r / min.

[0067] Comparative Example 9

[0068] The difference from Example 1 is that in this example, the stirring speed during the dropwise addition of the A / B materials is controlled at 55 r / min.

[0069] Comparative Example 10

[0070] The difference from Example 1 is that in this example, the stirring speed during the dropwise addition of the A / B materials is controlled at 70 r / min.

[0071] The test results of Example 1, Examples 4 and 5, and Comparative Examples 8-10 are shown in Table 3 below:

[0072] Table 3

[0073]

[0074] According to Table 3 above, when the rotation speed is 60-65r / min, under the control of the reaction temperature of each component, the slump and expansion of the water reducer can be still good after 6 hours, and the initial setting time of the concrete can be 8.5-9 hours, and the final setting time can be 11.5-12 hours; and when the rotation speed is lower than 60r / min, or the rotation speed is higher than 65r / min, the expansion of the concrete obtained by applying the water reducer of this scheme does not meet the use requirements of the concrete after 2 hours or 4 hours of the test. Therefore, when the technical personnel are studying, they often give up the study of the effect of the rotation speed on the performance of the water reducer at this nearby stage. According to the research of the inventor, it is found that at a reaction temperature of 42-45°C, the stirring speed is too fast, which affects the molecular chains that have been generated and destroys the connection between the molecular chains, but the effect is worse; and when the stirring speed is too slow, the reaction is insufficient, and the reaction time is too long, an overreaction will occur, and some components will stop polymerization. Once the stop polymerization occurs, an irreversible process is formed, which also makes the final effect worse. This solution controls the formula and process steps to enable the water reducing agent produced to exceed the performance of conventional water reducing agents and meet the requirements of construction after concrete has been transported for an extremely long time.

[0075] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A synthesis process of a polycarboxylate water-reducing agent for slow-release and collapse-preventing agents, characterized in that: The steps include: Primer preparation: add 3600 parts ± 50 parts of isopentanol polyoxyethylene ether and 2800 parts ± 40 parts of deionized water into a reaction container and mix to prepare a macromonomer aqueous solution, the temperature of the macromonomer aqueous solution is controlled at 28°C ± 2°C, and then add 15 parts ± 0.5 parts of initiator into the macromonomer aqueous solution; Aqueous solution A is prepared by mixing 180 parts of acrylic acid, 200 parts of hydroxyethyl ester, 30 parts of orthophosphate and 450 parts ± 10 parts of deionized water; Aqueous solution B preparation: 14 parts ± 0.5 parts of chain transfer agent, 3.5 parts ± 0.5 parts of vitamin C and 870 parts ± 20 parts of deionized water are mixed to prepare aqueous solution B; A / B material dropwise addition: aqueous solution A and aqueous solution B are added dropwise to the reaction container simultaneously, and the reaction temperature is controlled at 42°C-45°C during the dropwise addition; during the dropwise addition of aqueous solution A and aqueous solution B in the reaction container, the stirring speed is controlled at 60-65r / min; Keep warm, add alkali and replenish water: After the aqueous solution B is added dropwise, the temperature of the reaction container is controlled at 42-45°C and kept warm for a period of time, and then liquid alkali is added into the reaction container for neutralization.

2. The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent according to claim 1, characterized in that: The dropping process was carried out at a uniform speed, wherein the aqueous solution A was added for 90-120 min, and the aqueous solution B was added for 30 min±5 min longer than the aqueous solution A.

3. The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent according to claim 1, characterized in that: After adding liquid alkali into the reaction container for neutralization, water is added into the reaction container to dilute the solid content to 40%±5%.

4. The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent according to claim 1, characterized in that: The initiator in the base material configuration adopts an inorganic peroxide initiator.

5. The synthesis process of the slow-release collapse-preventing agent polycarboxylate water-reducing agent according to claim 1, characterized in that: The chain transfer agent used in the preparation of aqueous solution B is any one of mercaptopropionic acid, thioglycolic acid, and mercaptoethanol, or a mixture of several of them.

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