2,4,6-Tri-(6-aminocaproic acid)-1,3,5-triazine: Synthesis, and Phosphate-Free Scale Cont，and Corrosion Inhibition

Introduction

2,4,6-Tri-(6-aminocaproic acid)-1,3,5-triazine is a very important water-based rust inhibitor. It has superior performance, mainly including: it can be used to protect various metals from rusting, and it works better with Irgamet 42; excellent hard water stability; extremely low foaming tendency, good air release; its triethanolamine sodium salt will not affect the performance of extreme pressure antiwear agent. 

Synthesis of 2,4,6-Tri-(6-aminocaproic acid)-1,3,5-triazine

The present invention provides a one-pot method for producing 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine, and the specific technical scheme is as follows: (1) Dissolve caprolactam in water. (2) Add sodium hydroxide to the solution in step (1), continuously stirring vigorously during the adding process, and refluxing for 2-4 hours to obtain 6-aminocaproic sodium salt aqueous solution. (3) Add cyanuric chloride to the 6-aminocaproic sodium salt aqueous solution in step (2), stir for 1-3h, heat up to 80-100°C, and react for 3-5h. (4) The solution in step (3) is cooled to room temperature, acidified by adding acid, filtered, washed, and dried to obtain the target product. [1]

In the production process of the reaction one-pot method, the whole process is completed in one kettle. After the product is generated, it only needs to perform a simple filtration operation to carry out the production of the next pot. At this time, the crude product can be filtered and washed, and dry. The whole process is convenient and fast, and the production can be realized without turning the material into the kettle, which greatly facilitates the production process. [1]

Formulation of Phosphate-Free Scale Inhibitor

Composed of 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine, disodium tartrate dihydrate, zinc sulfate heptahydrate, Benzotriazole( BTA) , polyepoxysuccinic acid ( PESA) and acrylic acid - 2 - acrylamide - 2 - methylpropane sulfonic acid copolymer ( AA / AMPS), an effective phosphate-free scale inhibitor can be formulated. [2]

During the operation of industrial circulating water systems, the continuous accumulation of ions in water can cause corrosion and scaling, threatening system safety. In industry, corrosion and scale inhibitors are commonly added to address such issues. However, conventional commercial inhibitors are mostly low-phosphorus formulations. Although these agents exhibit strong corrosion inhibition and good performance, their phosphorus content, even at low levels, may still contribute to eutrophication when discharged into natural waters. To overcome this problem, 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine, sodium tartrate, and zinc salts were employed as the main corrosion-inhibiting components. From a molecular perspective, 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine contains multiple nitrogen atoms, whose lone-pair electrons can coordinate and adsorb onto the Fe surface of carbon steel. Through the synergistic effect of its branched chains and cyclic structure, a three-dimensional protective film is formed. Orthogonal experiments determined the optimal formulation ratio as 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine : sodium tartrate : PESA : AA/AMPS : zinc sulfate heptahydrate (calculated as Zn²⁺) : BTA = 15 : 14 : 7 : 8 : 3 : 1. Further optimization and performance validation established the best dosage at 48 mg/L, achieving a corrosion inhibition rate of 88.99%, a scale inhibition rate of 81.24%, and a transmittance of 60.5%. Experimental results indicate that this composite inhibitor exhibits excellent corrosion inhibition, scale inhibition, and dispersion properties. Mechanistic studies suggest that the formulation components contribute to the formation of a composite protective film on the metal surface, suppressing carbon steel corrosion. Meanwhile, its strong lattice distortion effect reduces the crystallinity of calcium scale, resulting in a loose and irregular structure that is less prone to adhesion. [2]

Formulation of Water-Based Rust Inhibitor

An aqueous rust inhibitor comprising 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine, organic base, urea and its derivatives, surfactant and water, 2,4, The mass fraction of 6-tris(aminocaproic acid group)-1,3,5-triazine is 1-2%, the mass fraction of organic base is 3%-4%, the mass fraction of urea and its derivatives is 0.1%- 1%, the mass fraction of surfactant is 0.1%-3%, and the balance is water. In the rust inhibitor, the water component accounts for more than 90%, and the main components are 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine and organic base. The organic base makes the rust inhibitor Alkaline, making the metal in a relatively stable environment. Apply rust inhibitor to metal surface, 2,4,6-tri-(6-aminocaproic acid)-1,3,5-triazine has polar functional group and long hydrocarbon chain, in which polar functional group relies on intermolecular The acting force (Coulomb force or hydrogen bond) can be directionally adsorbed on the metal interface to form a protective film, thereby preventing oxygen and moisture from immersing into the metal surface, which can greatly reduce the generation of rust. [3]

References:

[1] Nanjing Tech University. (2020, September 29). One-pot method for producing 2,4,6-tri(aminocaproic acid)-1,3,5-triazine: CN201910202007.4 [Patent].

[2] Yang, B., Chen, K., & Chen, Q. (2022). Formulation and performance of phosphate-free corrosion andscaleinhibitors. Water PurificationTechnology, 41(4), 86–92.

[3] Nanjing Tech University. (2019, July 23). Aqueous rust inhibitor and its preparation method: CN201910438844.7 [Patent].

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