Acylthiourea and polyethylene polyamine condensation compound, phosphorus-free corrosion and scale inhibitor and preparation method of phosphorus-free corrosion and scale inhibitor

Abstract

The invention provides an acylthiourea and polyethylene polyamine condensation compound, a phosphorus-free corrosion and scale inhibitor and a preparation method, and relates to the technical field of industrial water treatment.The acylthiourea and polyethylene polyamine condensation compound contains amide, amino and other polar groups, the electrostatic attraction force and the chelation process of the acylthiourea and polyethylene polyamine condensation compound and zinc ions and calcium ions in water are enhanced, the scale inhibition efficiency is improved, and the corrosion and scale inhibitor has the advantages of being environmentally friendly and free of pollution. The phosphorus-containing corrosion and scale inhibitor has the effect similar to that of phosphorus, can achieve the effect similar to that of a phosphorus-containing corrosion and scale inhibitor through compounding and synergism with other raw materials, can completely replace phosphorus, and meets the environment-friendly requirement; the phosphorus-free corrosion and scale inhibitor provided by the invention does not contain phosphorus, causes little pollution to the environment after being discharged and is easy to biodegrade in a water body, and in the corrosion and scale inhibitor provided by the invention, all the components have a synergistic effect, so that stable storage of the product can be ensured, and the product also can be ensured to have good corrosion and scale inhibition performance; and a new thought is developed for development, design and application of non-phosphorus products.

Description

Technical Field

[0001] The invention relates to the technical field of industrial water treatment, and in particular to an acylthiourea and polyethylene polyamine condensate, a phosphorus-free corrosion and scale inhibitor and a preparation method thereof. Background Art

[0002] Circulating cooling water is indispensable in modern industry, and the two major drawbacks of corrosion and scaling must be solved. The effective way to solve corrosion and scaling is to add corrosion and scale inhibitors to the circulating water. Currently, the most widely used corrosion and scale inhibitors are phosphorus-based agents. Although phosphorus is non-toxic, it acts as a nutrient source for microorganisms and promotes the over-growth of microorganisms, especially algae, causing lake blooms, red tides in seawater and other hazards. Therefore, phosphorus-free corrosion and scale inhibitors are an inevitable trend for future development.

[0003] In recent years, researchers have begun to explore phosphorus-free corrosion and scale inhibitors. Among them, inorganic or organic heterocyclic compounds have the disadvantage of high cost and are rarely used in practice. Polycarboxylic acid or sulfonate copolymers such as polyaspartic acid, polyepoxysuccinic acid, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer only have certain scale inhibition performance, no obvious corrosion inhibition performance, and the corrosion inhibition performance cannot be comparable to that of phosphorus-containing corrosion and scale inhibitors.

[0004] In view of the above problems, the present invention proposes a condensation product of acyl thiourea and polyethylene polyamine, a phosphorus-free corrosion and scale inhibitor and a preparation method. The new phosphorus-free corrosion and scale inhibitor product not only has the characteristics of green and environmental protection, but also has good corrosion and scale inhibition performance, and can replace the mainstream phosphorus-containing corrosion and scale inhibitors in the current market. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a condensation product of acyl thiourea and polyethylene polyamine, a phosphorus-free corrosion and scale inhibitor and a preparation method, which can replace the mainstream phosphorus-containing corrosion and scale inhibitors in the current market and are widely used in metal corrosion protection in industrial circulating water systems and other water treatment processes.

[0006] The first aspect of the present invention provides a condensation product of acylthiourea and polyethylene polyamine, the structural formula of which is as follows:

[0007] ,

[0008] Wherein, R1 is a C1-C20 alkyl group; n and m are integers between 1 and 10.

[0009] Preferably, the alkyl group is any one of methyl, ethyl, propyl, butyl, pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, undecyl, dodecyl, pentadecyl or octadecyl.

[0010] The second aspect of the present invention provides a phosphorus-free corrosion and scale inhibitor, which is composed of the following components in parts by weight per 100 parts by weight: 20 to 30 parts of acyl thiourea and polyethylene polyamine condensate, 10 to 15 parts of a polycarboxylic acid mixture, 15 to 20 parts of a low molecular weight anionic polymer, 5 to 10 parts of a water-soluble zinc salt and 30 to 50 parts of deionized water.

[0011] Preferably, the polycarboxylic acid mixture comprises a mixture consisting of at least any one of hydrolyzed polymaleic anhydride, polyacrylic acid, polyepoxysuccinic acid, polyaspartic acid, itaconic acid polymers and their corresponding water-soluble salts.

[0012] Preferably, the low molecular weight anionic polymer includes a mixture of at least any one of maleic acid-acrylic acid copolymer, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid and hydroxypropyl acrylate copolymer, acrylic acid / acrylic acid ester copolymer, acrylic acid / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid / acrylic acid ester / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid-acrylic acid ester-sulfonate copolymer, acrylic acid-acrylic acid ester-phosphonic acid-sulfonate tetrapolymer and their corresponding water-soluble salts.

[0013] Preferably, the water-soluble zinc salt is a water-soluble inorganic zinc salt.

[0014] The third aspect of the present invention provides a method for preparing a phosphorus-free corrosion and scale inhibitor, which is used to prepare the above-mentioned phosphorus-free corrosion and scale inhibitor, and is characterized in that it comprises the following steps:

[0015] S1, preparing condensation products of acyl thiourea and polyethylene polyamine;

[0016] S2, adding weighed acylthiourea and polyethylene polyamine condensate, polycarboxylic acid mixture, low molecular weight anionic polymer and deionized water into the reaction kettle in sequence and stirring evenly;

[0017] S3. At room temperature, add the weighed water-soluble zinc salt into the reactor and stir for 30 to 60 minutes to obtain a phosphorus-free corrosion and scale inhibitor.

[0018] Preferably, the preparation of the condensation product of acyl thiourea and polyethylene polyamine specifically comprises:

[0019] S101, accurately weighing organic acid chlorides in sequence into a four-necked bottle equipped with a thermometer and a stirrer, adding the organic acid chlorides to the first acetone solution containing potassium thiocyanate, controlling the reaction temperature at 9.5 to 36.8° C., controlling the reaction time at 36 to 77 min, and filtering and desalting to obtain acyl isothiocyanate after the reaction is completed;

[0020] S102, controlling the reaction temperature at 10-20°C, adding the acyl isothiocyanate obtained in S1 dropwise to the second acetone solution in which polyethylene polyamine is dissolved, and controlling the dropping time to be 28-56 min. After the dropwise addition is completed, removing the solvent by distillation under reduced pressure to obtain a condensation product of acyl thiourea and polyethylene polyamine.

[0021] Preferably, in step S101, the molar ratio of the organic acid chloride to potassium thiocyanate is 1:0.83 to 1:1.27, and in the first acetone solution, the mass ratio of potassium thiocyanate to acetone is 1:1.1 to 1:2.3; in step S102, the molar ratio of polyethylene polyamine to the organic acid chloride in step S101 is 1:1.06 to 1:2.18, and in the second acetone solution, the mass ratio of polyethylene polyamine to acetone is 1:1.13 to 1:2.27.

[0022] Preferably, the polyethylene polyamine includes at least any one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine or polyethyleneimine.

[0023] Through the above technical solution, the present invention has the following technical effects:

[0024] (1) The condensation product of acyl thiourea and polyethylene polyamine provided by the present invention contains polar groups such as amide and amino groups, which enhances its electrostatic attraction and chelation process with zinc ions and calcium ions in water. It forms a stable chelate in water, reduces the formation of deposits, and thus improves the scale inhibition efficiency; the condensation product of acyl thiourea and polyethylene polyamine contains electron donor sites (O, N, S heteroatoms), which can coordinate with metal ions such as zinc, calcium, magnesium and iron to form a three-dimensional network structure chelate protective film that is chemically adsorbed on the metal surface, so that other corrosive ions are prevented from reaching the metal surface, thereby improving the corrosion inhibition efficiency;

[0025] (2) The acylthiourea and polyethylene polyamine condensate provided by the present invention has similar effects to phosphorus. By compounding with other raw materials, it can achieve effects similar to those of phosphorus-containing corrosion and scale inhibitors, and can completely replace the use of phosphorus to meet environmental protection requirements.

[0026] (3) The corrosion and scale inhibitor provided by the present invention does not contain phosphorus, causes little pollution to the environment after discharge, and is easily biodegraded in water bodies. In the corrosion and scale inhibitor provided by the present invention, the various components have a synergistic effect, which can not only ensure the stable storage of the product, but also ensure that the product has good corrosion inhibition and scale inhibition properties, opening up new ideas for the development, design and application of phosphorus-free products.

[0027] (4) Compared with traditional phosphorus-containing products, the corrosion and scale inhibitor provided by the present invention does not have the problem of significantly increased cost and will not increase the user's cost of use. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0029] In recent years, researchers have begun to explore phosphorus-free corrosion and scale inhibitors. Among them, inorganic or organic heterocyclic compounds have the disadvantage of high cost and are rarely used in practice. Polycarboxylic acid or sulfonate copolymers such as polyaspartic acid, polyepoxysuccinic acid, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer only have certain scale inhibition performance, no obvious corrosion inhibition performance, and the corrosion inhibition performance cannot be comparable to that of phosphorus-containing corrosion and scale inhibitors.

[0030] The present invention proposes a condensation product of acyl thiourea and polyethylene polyamine, a phosphorus-free corrosion and scale inhibitor and a preparation method. The novel phosphorus-free corrosion and scale inhibitor product not only has the characteristics of being green and environmentally friendly, but also has good corrosion and scale inhibition performance, and can replace the mainstream phosphorus-containing corrosion and scale inhibitors in the current market.

[0031] First, the present invention discloses a condensation product of acylthiourea and polyethylene polyamine, the structural formula of which is as follows:

[0032] ,

[0033] Wherein, R1 is a C1-C20 alkyl group; n and m are integers between 1 and 10.

[0034] Preferably, the alkyl group is any one of methyl, ethyl, propyl, butyl, pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, undecyl, dodecyl, pentadecyl or octadecyl.

[0035] The invention also discloses a phosphorus-free corrosion and scale inhibitor, which is composed of the following components in parts by weight based on 100 parts by weight: 20 to 30 parts of acyl thiourea and polyethylene polyamine condensate, 10 to 15 parts of a polycarboxylic acid mixture, 15 to 20 parts of a low molecular weight anionic polymer, 5 to 10 parts of a water-soluble zinc salt and 30 to 50 parts of deionized water.

[0036] Preferably, the polycarboxylic acid mixture comprises a mixture consisting of at least any one of hydrolyzed polymaleic anhydride, polyacrylic acid, polyepoxysuccinic acid, polyaspartic acid, itaconic acid polymers and their corresponding water-soluble salts.

[0037] The number average molecular weight of the polycarboxylic acid and its salts is 1500-2000, and the molecular weight distribution index is less than 2.0.

[0038] Preferably, the low molecular weight anionic polymer includes a mixture of at least any one of maleic acid-acrylic acid copolymer, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid and hydroxypropyl acrylate copolymer, acrylic acid / acrylic acid ester copolymer, acrylic acid / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid / acrylic acid ester / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid-acrylic acid ester-sulfonate copolymer, acrylic acid-acrylic acid ester-phosphonic acid-sulfonate tetrapolymer and their corresponding water-soluble salts.

[0039] The number average molecular weight of the low molecular weight anionic polymer and its salts is 1800-2200, and the molecular weight distribution index is less than 2.5.

[0040] Preferably, the water-soluble zinc salt is a water-soluble inorganic zinc salt.

[0041] Wherein, the above-mentioned water-soluble inorganic zinc salt can be zinc chloride or zinc sulfate.

[0042] The present invention also provides a method for preparing the above-mentioned phosphorus-free corrosion and scale inhibitor, which is used to prepare the above-mentioned phosphorus-free corrosion and scale inhibitor, comprising the following steps:

[0043] S1, preparing condensation products of acyl thiourea and polyethylene polyamine;

[0044] S2, adding weighed acylthiourea and polyethylene polyamine condensate, polycarboxylic acid mixture, low molecular weight anionic polymer and deionized water into the reaction kettle in sequence and stirring evenly;

[0045] S3. At room temperature, add the weighed water-soluble zinc salt into the reactor and stir for 30 to 60 minutes to obtain a phosphorus-free corrosion and scale inhibitor.

[0046] Preferably, the preparation of the condensation product of acyl thiourea and polyethylene polyamine specifically comprises:

[0047] S101, accurately weighing organic acid chlorides in sequence into a four-necked bottle equipped with a thermometer and a stirrer, adding the organic acid chlorides to the first acetone solution containing potassium thiocyanate, controlling the reaction temperature at 9.5 to 36.8° C., controlling the reaction time at 36 to 77 min, and filtering and desalting to obtain acyl isothiocyanate after the reaction is completed;

[0048] The reaction temperature fluctuation range in S101 is controlled to be ±0.1°C.

[0049] Temperature selection and stability control are key factors in ensuring the structure and purity of the target product. Reasonable control of the reaction time can effectively avoid the production of by-products. In step S101, the molar ratio of the organic acid chloride to potassium thiocyanate is 1:0.83 to 1:1.27, and in the first acetone solution, the mass ratio of potassium thiocyanate to acetone is 1:1.1 to 1:2.3, which can effectively ensure the purity of the acyl isothiocyanate.

[0050] S102, controlling the reaction temperature at 10-20° C., adding the acyl isothiocyanate obtained in S1 dropwise to the second acetone solution in which polyethylene polyamine is dissolved, and controlling the dropping time to be 28-56 min. After the dropwise addition is completed, removing the solvent by distillation under reduced pressure to obtain a condensation product of acyl thiourea and polyethylene polyamine.

[0051] The molar ratio of polyethylene polyamine to the organic acid chloride in step S101 is 1:1.06 to 1:2.18, and the mass ratio of polyethylene polyamine to acetone in the second acetone solution is 1:1.13 to 1:2.27.

[0052] The polyethylene polyamine includes at least any one of diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine or polyethylene imine.

[0053] The technical solution of the present invention is described in detail below through specific embodiments:

[0054] Example 1

[0055] Preparation of condensation products of acylthiourea and polyethylene polyamine

[0056] S101: Into a four-necked bottle equipped with a thermometer and a stirrer, lauroyl chloride (43.75 g, 0.20 mol) was accurately weighed in sequence, and at a temperature of 30°C, a mixed solution of potassium thiocyanate (19.44 g, 0.2 mol) and acetone (50.00 g) was added and reacted for 40 minutes to prepare acyl isothiocyanate.

[0057] S102: Add diethylenetriamine (20.63 g, 0.2 mol) and acetone (40.00 g) to a new four-necked bottle equipped with a thermometer and a stirrer. Add the acyl isothiocyanate (36.21 g, 0.15 mol) prepared in S1 dropwise to the system at 20°C. After 30 minutes of dropwise addition, remove the solvent by vacuum distillation to obtain the condensation product A1 of acylthiourea and polyethylene polyamine.

[0058] Example 2

[0059] Preparation of condensation products of acylthiourea and polyethylene polyamine

[0060] S101: Into a four-necked bottle equipped with a thermometer and a stirrer, lauroyl chloride (43.75 g, 0.20 mol) was accurately weighed in sequence, and at a temperature of 10°C, a mixed solution of potassium thiocyanate (19.44 g, 0.2 mol) and acetone (50.00 g) was added and reacted for 70 min to prepare acyl isothiocyanate.

[0061] S102: Add triethylenetetramine (29.25 g, 0.2 mol) and acetone (40.00 g) to a new four-necked bottle equipped with a thermometer and a stirrer. Add the acyl isothiocyanate (36.21 g, 0.15 mol) prepared in S1 dropwise to the system at 10°C. After 50 minutes of dropwise addition, remove the solvent by vacuum distillation to obtain the condensation product A2 of acyl thiourea and polyethylene polyamine.

[0062] Example 3

[0063] Preparation of condensation products of acylthiourea and polyethylene polyamine

[0064] S101: Into a four-necked bottle equipped with a thermometer and a stirrer, lauroyl chloride (43.75 g, 0.20 mol) was accurately weighed in sequence, and at a temperature of 10°C, a mixed solution of potassium thiocyanate (19.44 g, 0.2 mol) and acetone (50.00 g) was added and reacted for 70 min to prepare acyl isothiocyanate.

[0065] S102: Tetraethylenepentamine (75.72 g, 0.4 mol) and acetone (100.00 g) were added to a new four-necked bottle equipped with a thermometer and a stirrer. Acyl isothiocyanate (36.21 g, 0.15 mol) prepared in S1 was added dropwise to the system at 10°C. After 50 minutes of dropwise addition, the solvent was removed by vacuum distillation to obtain acylthiourea and polyethylene polyamine condensate A3.

[0066] Example 4

[0067] A method for preparing a phosphorus-free corrosion and scale inhibitor:

[0068] S1: preparing acylthiourea and polyethylene polyamine condensate A1 according to Example 1;

[0069] S2: 20 kg of the acylthiourea and polyethylene polyamine condensate A1 prepared in Example 1, 10 kg of polyaspartic acid, 20 kg of acrylic acid-2-acrylamide-2-methacrylic acid copolymer, and 40 kg of deionized water were weighed and added into the reaction kettle in sequence, and stirred evenly;

[0070] S3: Add 10 kg of anhydrous zinc chloride at room temperature and stir for 30 minutes to obtain the phosphorus-free corrosion and scale inhibitor H1.

[0071] Example 5

[0072] A method for preparing a phosphorus-free corrosion and scale inhibitor:

[0073] S1: preparing condensation product A2 of acylthiourea and polyethylene polyamine according to Example 2;

[0074] S2: 20 kg of acylthiourea and polyethylene polyamine condensate A2 prepared in Example 2, 10 kg of polyaspartic acid, 20 kg of acrylic acid-2-acrylamide-2-methacrylic acid copolymer, and 40 kg of deionized water were weighed and added into the reaction kettle in sequence, and stirred evenly;

[0075] S3: Add 10 kg of anhydrous zinc chloride at room temperature and stir for 30 minutes to obtain the phosphorus-free corrosion and scale inhibitor H2.

[0076] Example 6

[0077] A method for preparing a phosphorus-free corrosion and scale inhibitor:

[0078] S1: preparing condensation product A3 of acylthiourea and polyethylene polyamine according to Example 3;

[0079] S2: 20 kg of the acylthiourea and polyethylene polyamine condensate A3 prepared in Example 3, 10 kg of polyacrylic acid, 20 kg of maleic acid-acrylic acid copolymer, and 40 kg of deionized water were weighed and added to the reaction kettle in sequence, and stirred evenly;

[0080] S3: Add 10 kg of anhydrous zinc chloride at room temperature and stir for 30 minutes to obtain the phosphorus-free corrosion and scale inhibitor H3.

[0081] Example 7

[0082] A method for preparing a phosphorus-free corrosion and scale inhibitor:

[0083] S1: preparing acylthiourea and polyethylene polyamine condensate A1 according to Example 1;

[0084] S2: 20 kg of the acylthiourea and polyethylene polyamine condensate A1 prepared in Example 1, 10 kg of hydrolyzed polymaleic anhydride, 20 kg of maleic acid-acrylic acid copolymer, and 40 kg of deionized water were weighed and added to the reaction kettle in sequence, and stirred evenly;

[0085] S3: Add 10 kg of anhydrous zinc chloride at room temperature and stir for 30 minutes to obtain phosphorus-free corrosion and scale inhibitor H4.

[0086] Example 8

[0087] A method for preparing a phosphorus-free corrosion and scale inhibitor:

[0088] S1: preparing condensation product A3 of acylthiourea and polyethylene polyamine according to Example 3;

[0089] S2: 20 kg of the acyl thiourea and polyethylene polyamine condensate A3 prepared in Example 3, 10 kg of hydrolyzed polymaleic anhydride, 20 kg of maleic acid-acrylic acid copolymer, and 40 kg of deionized water were weighed and added to the reaction kettle in sequence, and stirred evenly;

[0090] S3: Add 10 kg of anhydrous zinc chloride at room temperature and stir for 30 minutes to obtain the phosphorus-free corrosion and scale inhibitor H5.

[0091] Comparative Example 1

[0092] The preparation method of the phosphorus-free corrosion and scale inhibitor composition for cooling water is basically the same as that in Example 4, except that in step S2, 20 kg of the acyl thiourea and polyethylene polyamine condensate A1 prepared in Example 1 is replaced with 20 kg of polyepoxysuccinic acid to obtain the phosphorus-free corrosion and scale inhibitor H6.

[0093] Comparative Example 2

[0094] The preparation method of the phosphorus-free corrosion and scale inhibitor composition for cooling water is basically the same as that in Example 5, except that in step S2, 10 kg of polyaspartic acid is replaced with 10 kg of acrylic acid-acrylate-sulfonate copolymer to obtain the phosphorus-free corrosion and scale inhibitor H7.

[0095] Comparative Example 3

[0096] The preparation method of the phosphorus-free corrosion and scale inhibitor composition for cooling water is basically the same as that in Example 6, except that in step S2, 20 kg of maleic acid-acrylic acid copolymer is replaced with 20 kg of hydrolyzed polymaleic anhydride to obtain the phosphorus-free corrosion and scale inhibitor H8.

[0097] Comparative Example 4

[0098] The preparation method of the phosphorus-free corrosion and scale inhibitor composition for cooling water is basically the same as that of Example 7, except that in step S2, 20 kg of maleic acid-acrylic acid copolymer is replaced by 20 kg of acyl thiourea and polyethylene polyamine condensate 1. Thus, the phosphorus-free corrosion and scale inhibitor H9 is obtained.

[0099] Comparative Example 5

[0100] The preparation method of the organic phosphorus corrosion and scale inhibitor composition for cooling water is basically the same as that in Example 8, except that in step S2, 20 kg of the acyl thiourea and polyethylene polyamine condensate A3 prepared in Example 3 is replaced by 20 kg of 2-phosphoric acid-1,2,4-tricarboxylic acid butane to obtain the phosphorus-free corrosion and scale inhibitor H10.

[0101] Corrosion and scale inhibition performance evaluation test requirements and standards:

[0102] The raw water quality of the experiment was prepared according to GB / T 18175-2014. The calcium ion concentration in the standard experimental raw water was 200.4 mg / L, the magnesium ion concentration was 48.52 mg / L, the chloride ion concentration was 399.1 mg / L, and the bicarbonate ion concentration was 122.0 mg / L. The dosing concentration during the test was 20 mg / L, and the standard corrosion coupon material was 20# carbon steel.

[0103] The corrosion inhibition performance was evaluated using a rotating corrosion coupon instrument. The corrosion rate was expressed in mm / a and the calculation formula was shown in (1):

[0104] (1)

[0105] Where:

[0106] m: the value of the mass loss of the test piece, in g

[0107] m0: average mass loss of the blank test of the test piece in pickling, unit: g

[0108] s: surface area of ​​the test piece, in cm 3

[0109] ρ: Density value of the test piece, in g / cm 3

[0110] t: test time value, unit is h

[0111] 8760: Hours per year, in h / a

[0112] 10: The number of millimeters equivalent to 1 cm, the unit is mm / cm

[0113] The static scale inhibition method is used to evaluate the scale inhibition performance. The scale inhibition rate is expressed in %, and the calculation formula is shown in (2):

[0114] (2)

[0115] Where:

[0116] C: Remaining Ca in water after cooling 2+ Concentration, in mg / L

[0117] C1: Ca in blank sample 2+ Concentration, in mg / L

[0118] C0: Ca in experimental raw water 2+ Concentration, in mg / L

[0119] Experimental method for evaluating corrosion and scale inhibition performance:

[0120] Scale inhibition experiment: The test water with the agent added in each implementation case was placed in a constant temperature water bath at 80±1℃ using a volumetric flask for 10 hours, and then sampled and analyzed for residual Ca in the water after cooling and filtration. 2+ concentration, and make a blank sample at the same time to calculate the scale inhibition rate.

[0121] Corrosion inhibition experiment: Fix the 20# carbon steel test piece on the rotating corrosion coupon instrument and put it into the test water with the reagent added in each implementation case. Keep the temperature at 45±1℃ and rotate at 100rpm for 72h. Record the weight of the coupon before and after the experiment and calculate the corrosion rate.

[0122] The experimental results are shown in Table 1:

[0123] Table 1 Corrosion and scale inhibition results of various examples and comparative examples

[0124]

[0125] As shown in the above table, the corrosion rates of Example 8 and Comparative Example 5 are close, and it can be seen that the condensation product of acyl thiourea and polyethylene polyamine has similar effects as phosphorus; the corrosion rate of Comparative Example 1 is much higher than that of the embodiment, and it can be seen that the condensation product of acyl thiourea and polyethylene polyamine has a crucial influence on the corrosion and scale inhibition performance; the corrosion rates of Comparative Examples 2, 3, and 4 are higher than those of the embodiment, and it can be seen that the components of the phosphorus-free corrosion and scale inhibitor composition, acyl thiourea and polyethylene polyamine condensation product, polycarboxylic acid mixture and low molecular weight anionic polymer have a synergistic effect and are indispensable.

[0126] In the synergistic effect of each component, the special structure of acyl thiourea and polyethylene polyamine condensate can combine with zinc ions to form a three-dimensional network chelate, and can also form a three-dimensional network chelate with zinc ions, calcium ions, magnesium ions, etc. at the same time. The chelate can form a stable protective film on the metal surface, effectively inhibiting the anode electron loss reaction and cathode oxygen absorption reaction on the metal surface, thereby reducing the electrochemical corrosion rate and protecting the metal surface from corrosion. At the same time, acyl thiourea and polyethylene polyamine condensate chelate hard water ions such as calcium and magnesium, which reduces the scaling risk of the metal surface to a certain extent. Therefore, acyl thiourea and polyethylene polyamine condensate are the main components of the corrosion inhibition performance of the product in the present invention, and have certain scale inhibition performance.

[0127] In the synergistic effect of each component, the polycarboxylic acid mixture plays a good scale inhibition role, and its scale inhibition performance has a high requirement on molecular weight. The number average molecular weight is 1500-2000, and the molecular weight distribution index is less than 2.0, which is an ideal selection range. If the number average molecular weight is too large or too small, the scale inhibition performance will be reduced. Scaling on the metal surface will reduce the film-forming properties of the acyl thiourea and polyethylene polyamine condensation chelate, resulting in severe under-scale corrosion. Therefore, the selection and synergistic coordination of acyl thiourea, polyethylene polyamine condensation product and polycarboxylic acid mixture is the key to the product of the present invention being able to exert good corrosion inhibition and scale inhibition performance.

[0128] In the synergistic effect of each component, the low molecular weight anionic polymer plays a key role in the stability of zinc in the composition. It can make the zinc and acylthiourea and polyethylene polyamine condensate exist stably in the form of chelate without precipitation, thus ensuring the quality of the product. In addition, the low molecular weight anionic polymer has a good scale inhibition performance, which can effectively improve the solubility of hard water ions such as calcium and magnesium and prevent scale formation.

[0129] As described above, the present invention provides a phosphorus-free corrosion and scale inhibitor, in which the condensate of acylthiourea and polyethylene polyamine is used as a substitute for the core components of organic phosphine or inorganic phosphorus in conventional products, and its three-dimensional network structure is also a key factor in forming a special chelate protective film. In addition, the present invention also provides a preparation method of the condensate of acylthiourea and polyethylene polyamine, and the difference in the control conditions in the preparation method will lead to changes in its three-dimensional network structure, and ultimately lead to differences in corrosion inhibition performance.

[0130] As described above, the present invention provides a phosphorus-free corrosion and scale inhibitor, which is not a simple physical compound, but a new product with coordinated synergistic effect obtained by comprehensive design from the perspectives of the three-dimensional network structure of acyl thiourea and polyethylene polyamine condensate, the type, molecular weight, and dosage optimization of polycarboxylic acid mixture, and the type, molecular weight, and dosage optimization of low molecular weight anionic polymer. Acyl thiourea and polyethylene polyamine condensate are combined with zinc ions in water-soluble zinc salts to obtain a three-dimensional network structure chelate, which can form a protective film that effectively prevents electrochemical corrosion processes. The selection of polycarboxylic acid mixtures, through strong scale inhibition performance, avoids under-scale corrosion, and provides favorable conditions for the formation of corrosion-inhibiting protective films on metal surfaces. Low molecular weight anionic polymers ensure that zinc ions are stably present in the product system without precipitation, providing a guarantee for the chelation of acyl thiourea and polyethylene polyamine condensate with zinc ions.

[0131] The acylthiourea and polyethylene polyamine condensate and phosphorus-free corrosion and scale inhibitor disclosed in the present invention have the following technical effects:

[0132] (1) The condensation product of acyl thiourea and polyethylene polyamine provided by the present invention contains polar groups such as amide and amino groups, which enhances its electrostatic attraction and chelation process with zinc ions and calcium ions in water. It forms a stable chelate in water, reduces the formation of deposits, and thus improves the scale inhibition efficiency; the condensation product of acyl thiourea and polyethylene polyamine contains electron donor sites (O, N, S heteroatoms), which can coordinate with metal ions such as zinc, calcium, magnesium and iron to form a three-dimensional network structure chelate protective film that is chemically adsorbed on the metal surface, so that other corrosive ions are prevented from reaching the metal surface, thereby improving the corrosion inhibition efficiency;

[0133] (2) The acylthiourea and polyethylene polyamine condensate provided by the present invention has similar effects to phosphorus. By compounding with other raw materials, it can achieve effects similar to those of phosphorus-containing corrosion and scale inhibitors, and can completely replace the use of phosphorus to meet environmental protection requirements.

[0134] (3) The corrosion and scale inhibitor provided by the present invention does not contain phosphorus, causes little pollution to the environment after discharge, and is easily biodegraded in water bodies. In the corrosion and scale inhibitor provided by the present invention, the various components have a synergistic effect, which can not only ensure the stable storage of the product, but also ensure that the product has good corrosion inhibition and scale inhibition properties, opening up new ideas for the development, design and application of phosphorus-free products.

[0135] (4) Compared with traditional phosphorus-containing products, the corrosion and scale inhibitor provided by the present invention does not have the problem of significantly increased cost and will not increase the user's cost of use.

[0136] In the present invention, the term "comprises", "includes" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of more restrictions, the elements defined by the sentence "includes..." do not exclude the presence of other identical elements in the article or device including the elements.

[0137] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0138] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include these modifications and variations.

Claims

1. A condensation product of acylthiourea and polyethylene polyamine, characterized in that: The structural formula is as follows: ， Wherein, R1 is a C1-C20 alkyl group; n and m are integers between 1 and 10.

2. The condensation product of acyl thiourea and polyethylene polyamine according to claim 1, characterized in that: The alkyl group is any one of methyl, ethyl, propyl, butyl, pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, undecyl, dodecyl, pentadecyl or octadecyl.

3. A phosphorus-free corrosion and scale inhibitor, characterized in that: The invention is composed of the following components in parts by weight based on 100 parts by weight: 20-30 parts of acylthiourea and polyethylene polyamine condensate, 10-15 parts of polycarboxylic acid mixture, 15-20 parts of low molecular weight anionic polymer, 5-10 parts of water-soluble zinc salt and 30-50 parts of deionized water.

4. A phosphorus-free corrosion and scale inhibitor according to claim 3, characterized in that: The polycarboxylic acid mixture comprises a mixture consisting of at least any one of hydrolyzed polymaleic anhydride, polyacrylic acid, polyepoxysuccinic acid, polyaspartic acid, itaconic acid polymer and their corresponding water-soluble salts.

5. The phosphorus-free corrosion and scale inhibitor according to claim 3, characterized in that: The low molecular weight anionic polymer includes a mixture of at least any one of maleic acid-acrylic acid copolymer, acrylic acid-2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid and hydroxypropyl acrylate copolymer, acrylic acid / acrylic ester copolymer, acrylic acid / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid / acrylic ester / 2-acrylamide-2-methylpropane sulfonic acid copolymer, acrylic acid-acrylic ester-sulfonate copolymer, acrylic acid-acrylic ester-phosphonic acid-sulfonate tetrapolymer and their corresponding water-soluble salts.

6. The phosphorus-free corrosion and scale inhibitor according to claim 3, characterized in that: The water-soluble zinc salt is a water-soluble inorganic zinc salt.

7. A method for preparing a phosphorus-free corrosion and scale inhibitor, for preparing the phosphorus-free corrosion and scale inhibitor as claimed in claim 3, characterized in that: The steps include: S1, preparing condensation products of acyl thiourea and polyethylene polyamine; S2, adding weighed acylthiourea and polyethylene polyamine condensate, polycarboxylic acid mixture, low molecular weight anionic polymer and deionized water into the reaction kettle in sequence and stirring evenly; S3. At room temperature, add the weighed water-soluble zinc salt into the reactor and stir for 30 to 60 minutes to obtain a phosphorus-free corrosion and scale inhibitor.

8. The method for preparing a phosphorus-free corrosion and scale inhibitor according to claim 7, characterized in that: The preparation of the condensation product of acylthiourea and polyethylene polyamine specifically comprises: S101, accurately weighing organic acid chlorides in sequence into a four-necked bottle equipped with a thermometer and a stirrer, adding the organic acid chlorides to the first acetone solution containing potassium thiocyanate, controlling the reaction temperature at 9.5 to 36.8° C., controlling the reaction time at 36 to 77 min, and filtering and desalting to obtain acyl isothiocyanate after the reaction is completed; S102, controlling the reaction temperature at 10-20° C., adding the acyl isothiocyanate obtained in S1 dropwise to the second acetone solution in which polyethylene polyamine is dissolved, and controlling the dropping time to be 28-56 min. After the dropwise addition is completed, removing the solvent by distillation under reduced pressure to obtain a condensation product of acyl thiourea and polyethylene polyamine.

9. The method for preparing a phosphorus-free corrosion and scale inhibitor according to claim 8, characterized in that: In step S101, the molar ratio of the organic acid chloride to potassium thiocyanate is 1:0.83 to 1:1.27, and in the first acetone solution, the mass ratio of the potassium thiocyanate to acetone is 1:1.1 to 1:2.3; In step S102, the molar ratio of the polyethylene polyamine to the organic acid chloride in step S101 is 1:1.06 to 1:2.18, and in the second acetone solution, the mass ratio of the polyethylene polyamine to acetone is 1:1.13 to 1:2.

27.

10. The method for preparing a phosphorus-free corrosion and scale inhibitor according to claim 8, characterized in that: The polyethylene polyamine includes at least any one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine or polyethyleneimine.

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